CN102612076B - High speed media access control - Google Patents

Abstract

Techniques for MAC processing for efficient use of high throughput systems that is backward compatible with various types of legacy systems are disclosed. In one aspect a first signal is transmitted according to a legacy transmission format to reserve a portion of a shared medium, and communication according to a second transmission format transpires during the reserved portion. In another aspect, a communication device may contend for access on a legacy system, and then communicate according to a new class communication protocol with one or more remote communication devices during the access period. In another aspect, a device may request access to a shared medium according to a legacy protocol, and, upon grant of access, the device may communicate with or facilitate communication between one or more remote stations according to a new protocol.

Description

High speed media access control

Priority is required according to 35U.S.C § 119

Patent application claims enjoys the priority of following U.S. Provisional Patent Application:

On October 15th, 2003 submits to, exercise question is the provisional application No.60/511 of " Method and Apparatus forProviding Interoperability and Backward Compatibility in WirelessCommunication Systems ", 750;

On October 15th, 2003 submits to, exercise question is the provisional application No.60/511 of " Method, Apparatus, and Systemfor Medium Access Control in a High Performance Wireless LANEnvironment ", 904;

On October 21st, 2003 submits to, exercise question is the provisional application No.60/513 of " Peer-to-Peer Connections inMIMO WLAN System ", 239;

On December 1st, 2003 submits to, exercise question is the provisional application No.60/526 of " Method, Apparatus, and Systemfor Sub-Network Protocol Stack for Very High Speed Wireless LAN ", 347;

On December 1st, 2003 submits to, exercise question is the provisional application No.60/526 of " Method; Apparatus; and Systemfor Multiplexing Protocol data Units in a High Performance WirelessLAN Environment ", 356;

On December 23rd, 2003 submits to, exercise question is the provisional application No.60/532 of " Wireless CommunicationsMedium Access Control (MAC) Enhancements ", 791;

On February 18th, 2004 submits to, exercise question is the provisional application No.60/545 of " Adaptive Coordination Function (ACF) ", 963;

On June 2nd, 2004 submits to, exercise question is the provisional application No.60/576 of " Method andApparatus for RobustWireless Network ", 545;

On July 8th, 2004 submits to, exercise question is the provisional application No.60/586 of " Method and Apparatus forDistribution Communication Resources Among Multiple Users ", 841; And

On August 11st, 2004 submits to, exercise question is the provisional application No.60/600 of " Method, Apparatus, and Systemfor Wireless Communications ", 960;

Above-mentioned provisional application all transfers the assignee of the application, therefore is incorporated to herein with way of reference clearly.

Invention field

The present invention relates generally to communication, particularly relate to medium education.

Technical background

In order to provide such as speech to communicate with the various of data and so on, widespread deployment wireless communication system.Typical radio data system or network provide the access to one or more shared resource for multiple user.A kind of system can use multiple access technology, as frequency division multiplexing (FDM), time division multiplexing (TDM), code division multiplexing (CDM) etc.

Exemplary wireless network comprises the data system based on honeycomb.Some such examples are as follows: (1) " TIA/EIA-95-B Mobile Station-B ase Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System " (IS-95 standard); (2) standard (W-CDMA standard) provided by " 3rd Generation Partnership Project " (3GPP) by name, it is included in one group of document 3G TS 25.211,3GTS 25.212,3G TS 25.213 and 3G TS 25.214; (3) standard (IS-2000 standard) provided by " 3rdGeneration Partnership Project 2 " (3GPP2) by name, during it is included in " TR-45.5 Physical Layer Standard for cdma2000 SpreadSpectrum Systems "; (4) high data rate (HDR) system of TIA/EIA/IS-856 standard (IS-856 standard) is followed.

Other examples of wireless system comprise WLAN (wireless local area network) (WLAN), as IEEE 802.11 (i.e. 802.11 (a), (b) or (g)).What employing comprised OFDM (OFDM) modulation technique enters to have more (MIMO) WLAN more, can realize the improvement to these networks.In order to improve some shortcomings of standard before 802.11, introduce IEEE 802.11 (e).

Along with the development of wireless system design, more high data rate can be provided.More high data rate creates possibility for advanced person applies, as speech, video, high speed data transfer and other application various.But different application has different requirements for its respective transfer of data.Numerous types of data has time delay and throughput demands, or needs certain service quality (QoS) to ensure.When there is no resource management, the capacity of system may be reduced, and system possibly cannot work efficiently.

Medium education (MAC) agreement is generally used for distributing the shared communication resource between a plurality of users.The high-rise physical layer with being used for transceiving data is joined together by MAC protocol usually.Benefit in increasing from data rate, MAC protocol must be designed to utilize shared resource efficiently.Under normal circumstances, preferably interoperability is kept with interchangeable or traditional communication standard.Therefore, the MAC process utilizing high throughput systems is efficiently needed in this area.In this area, also this needs MAC process and various types of legacy system to keep backward compatibility.

Summary of the invention

Embodiment disclosed herein solves can utilizing high throughput systems efficiently and can keeping the demand of the MAC process of backward compatibility with various legacy system.In an aspect, a kind of data transmission structure comprises gathering and gathers poll frame described in poll frame and one or more basis and the frame sent.In another aspect, a kind of time division duplex (TDD) data transmission structure comprises: pilot frame; Gather poll frame; The access point of poll frame is gathered to distant station frame described in zero or multiple basis.

In an aspect, multiple frame sends when not having frame pitch or frame pitch obviously reduces.In another aspect, protection frame pitch can be introduced between the frame sent out from various information source or the visibly different frame of power level.In another aspect, single lead code and one or more frame are sent explicitly.In another aspect, after the one or more sequenced frame of transmission, send a block and confirm.In another aspect, send one and gather poll frame, and send one or more frame associated with itly.Give other aspects various.

Accompanying drawing explanation

Fig. 1 is a kind of exemplary embodiment of system, and it comprises high speed WLAN;

Fig. 2 gives an exemplary embodiment of radio communication device, and it can be configured to access point or user terminal;

Fig. 3 shows 802.11 frame pitch parameters;

Fig. 4 gives exemplary physical layer (PHY) span line, uses DIFS to add back off time to access for illustration of according to DCF;

Fig. 5 gives exemplary physical layer (PHY) span line, uses SIFS for illustration of before ACK, and it has the priority higher than DIFS access;

Fig. 6 shows and large packet fragmentation is become little fragment, and the latter has the SIFS be associated;

Fig. 7 gives exemplary physical layer (PHY) span line, has the TXOP of confirmation for illustration of every frame;

Fig. 8 shows the TXOP having block and confirm;

Fig. 9 gives exemplary physical layer (PHY) span line, for illustration of the poll TXOP using HCCA;

Figure 10 is an exemplary embodiment of TXOP, and it comprises the multiple continuous transmission without any gap;

Figure 11 is an exemplary embodiment of TXOP, for illustration of the required preamble transmissions amount of reduction;

Figure 12 shows an exemplary embodiment of the method being integrated with various aspects, and it comprises and gather lead code, deletes the gap of such as SIFS and so on and inserts GIF as required;

Figure 13 gives exemplary physical layer (PHY) span line, for illustration of gathering poll frame and corresponding TXOP;

Figure 14 gives an illustrative methods for gathering poll frame;

Figure 15 gives an exemplary mac frame;

Figure 16 gives an exemplary MAC PDU;

Figure 17 gives an exemplary point to point link;

Figure 18 shows the physical layer bursts of a prior art;

Figure 19 gives an exemplary physical layer bursts, and it can be used for point to point link;

Figure 20 gives an exemplary embodiment of mac frame, and it comprises optional self-organizing section;

Figure 21 gives an exemplary physical layer bursts;

Figure 22 shows an exemplary point-to-point data transmission method;

Figure 23 gives an exemplary point to point link method;

Figure 24 gives an illustrative methods for providing Rate Feedback in point-to-point connection;

The managed point-to-point that Figure 25 shows between two stations and an access point connects;

The point-to-point that Figure 26 shows based on competition (or self-organizing) connects;

Figure 27 gives an exemplary mac frame, for illustration of the managed point to point link between station;

Figure 28 shows and support tradition and novel station on identical parallel compensate;

Figure 29 shows and tradition and new media access control is combined;

Figure 30 gives a kind of illustrative methods getting transmission opportunity;

Figure 31 gives a kind of illustrative methods sharing single FA with multiple BSS;

Figure 32 shows the overlapping BSS using single FA;

Figure 33 give with traditional B SS interoperability while perform a kind of illustrative methods of high speed point to point link;

Figure 34 shows the point to point link using MIMO technology, and it is contention access on traditional B SS;

Figure 35 shows and is encapsulated in an aggregate frame by one or more mac frame (fragment);

Figure 36 shows a traditional mac frame;

Figure 37 shows an exemplary decompressed frame;

Figure 38 gives an exemplary condensed frame;

Figure 39 gives another exemplary condensed frame;

Figure 40 gives an exemplary polymerization stem;

Figure 41 gives an exemplary embodiment of the scheduled access period frame (SCAP) used in ACF;

Figure 42 shows how SCAP and HCCA and EDCA is combined use;

Figure 43 shows beacon interval, comprises multiple SCAP, inserts the access period based on competition therebetween;

Figure 44 shows and adopts the low delay of a large amount of MIMO STA to operate;

Figure 45 gives an exemplary SCHED message;

Figure 46 gives an exemplary power management field;

Figure 47 gives an exemplary MAP field;

Figure 48 gives the exemplary SCHED control frame distributed for TXOP;

Figure 49 shows a traditional 802.11PPDU;

Figure 50 gives an exemplary MIMO PPDU for transfer of data;

Figure 51 gives an exemplary SCHED PPDU;

Figure 52 gives an exemplary FRACH PPDU; And

Figure 53 show can with another embodiment of the method for legacy system interoperability.

Embodiment

The very high bit rate physical layer of combining wireless LAN (or, use the similar application of emerging transmission technology), discloses the embodiment of the present application supporting efficient operation.This exemplary WLAN supports the bit rate more than 100Mbps (MBPS) in 20MHz bandwidth.

Various exemplary embodiment remains simplicity and the robustness of the distributed collaboration operation of conventional WLAN system, and such as, they are 802.11 (a-e).The advantage of various embodiment can be realized, keep the backward compatibility with these legacy systems simultaneously.(it should be noted that in the following description, 802.11 systems are described as exemplary legacy system.Those skilled in the art will find, these improve same and other system and operating such.)

A kind of exemplary WLAN can comprise Subnetwork protocol stack.Subnetwork protocol stack can support the physical layer transmission mechanism of high data rate, high bandwidth usually, including, but not limited to: based on the mechanism of OFDM modulation; Single carrier modulation technique; Use the system of multiple transmitting and multiple reception antenna (enter to have more (MIMO) system more, comprise and enter singly to go out (MISO) system more), for the operation of unusual high bandwidth efficiency; Multiple transmitting and receiving antenna to be combined with space multiplexing technique thus to multiple user terminal to transmit data or the system receiving data from multiple user terminal within the identical time interval; Employing code division multiple access (CDMA) technology realizes the system that multiple user is transmitted simultaneously.Other example comprises singly entering to have more (SIMO) and singly entering singly to go out (SISO) system.

One or more exemplary embodiment given here is launched for wireless data communication system environment to introduce.Although preferably use in this context, also different embodiments of the invention can be applied to different environment or configuration.Under normal circumstances, various system described herein can realize with the processor of software control, integrated circuit or discrete logic.Run through the data of the application, instruction, order, information, signal, symbol and chip preferably to represent with voltage, electric current, electromagnetic wave, magnetic field or particle, light field or particle or its combination.In addition, the module shown in every width block diagram can represent the step of hardware or method.When not departing from scope, the step of method can be exchanged." exemplary " used herein one word mean " as example, illustration or explanation ".Here be described to any embodiment of " exemplary " or design should not be interpreted as than other embodiments or design more preferably or have more advantage.

Fig. 1 is an exemplary embodiment of system 100, and it comprises an access point (AP) 104, and this access point 104 is connected to one or more user terminal (UT) 106A-N.Consistent with 802.11 terms, in this article, AP and UT is also referred to as station, or STA.AP with UT communicates via WLAN (wireless local area network) (WLAN) 120.In this illustrative embodiment, WLAN 120 is high speed MIMO ofdm systems.But WLAN 120 also can be any WLAN.Access point 104, via network 102, communicates with any amount of external equipment or process.Network 102 can be the Internet, Intranet or any other wired, wireless or optical-fiber network.Connect 110 and physical layer signal is sent to access point 104 from network.Equipment or process can be connected to network 102, or, as the UT (or via the connection with it) on WLAN 120.The example of the equipment that can be connected with network 102 or WLAN 120 comprises: phone; Personal digital assistant (PDA); Various types of computer (terminal of laptop computer, PC, work station, any type); Video equipment, as camera, video camera, network camera; And, the data equipment of any other type.Process can comprise sound, video, data communication etc.Various data flow may have different transmission requirements, and these can be met by using different service quality (QoS) technology.

System 100 can be disposed with a centralized AP 104.In an exemplary embodiment, all UT 106 communicate with this AP.In another embodiment, direct point to point link can be carried out between two UT, and without the need to revising system, this is apparent to those skilled in the art, will be described its example below.Access can be managed by AP, or (that is, based on competition) of self-organizing, will be described in detail below to this.

In one embodiment, AP 104 provides Ethernet adaptive capacity (adaptation).In this case, except AP, an ip router can also be disposed, to be provided to the connection (not showing its details here) of network 102.Ethernet frame can pass through WLAN subnet, between router and UT 106, transmit (will describe in detail) below.It is known technology in this area that Ethernet adapts to being connected.

In another embodiment, AP 104 provides IP to adapt to.In this case, for the set (not showing its details) connecting UT, AP serves as a gateway router.In this case, IP datagram can be sought footpath to UT 106 by AP 104, and, footpath is sought to the IP datagram from UT 106.It is known technology in this area that IP adapts to being connected.

Fig. 2 gives an exemplary embodiment of Wireless Telecom Equipment, and this Wireless Telecom Equipment can be configured to access point 104 or user terminal 106.Fig. 2 shows access point 104 and configures.Transceiver 210, according to the physical layer requirement of network 102, connection 110 receives and sends signal.From or the data that are sent to equipment or the application be connected with network 102 be delivered to mac processor 220.These data are called as stream 260 here.Stream may have different characteristics, and, based on the type of the application be associated with this stream, different process may be needed.Such as, video or speech can be called as low delay stream (video has higher throughput demands than speech usually).A lot of market demand is not too responsive to time delay, but may have higher data integrity requirement (that is, some loss of dividing into groups can be tolerated in speech, but file transfer can't stand the loss of grouping usually).

Mac processor 220 receives stream 260, and processor they so that transmit on a physical layer.Mac processor 220 also receives physical layer data, and processes this data, to form the grouping of output stream 260.Internal control and signaling is also transmitted between AP and UT.Medium Access Control (MAC) Protocol Data Unit (MAC PDU), be also referred to as physical layer (PHY) protocol Data Unit (PPDU) or frame (sayings according to 802.11), wireless LAN transceiver 240 is delivered to by connecting 270, further, them are received from wireless LAN transceiver 240.Convert MAC PDU to and convert from MAC PDU the example technique flowed and order to will be described in detail below from stream and order.Other embodiments can adopt any switch technology.The feedback 280 corresponding with various MAC ID can turn back to mac processor 220, for various object from physical layer (PHY) 240.Feedback 280 can be any physical layer information, and what comprise channel (comprising Multicast Channel and unicast tunnel) can supporting rate, modulation format and other parameters various.

In one exemplary embodiment, adaptation layer (ADAP) and data link control layer (DLC) perform in mac processor 220.Physical layer (PHY) performs on wireless LAN transceiver 240.One skilled in the art will appreciate that the segmentation can carrying out various function under arbitrary configuration.Mac processor 220 can perform part or all of physical layer process.Wireless LAN transceiver can comprise a processor, for performing MAC process or its part.Any amount of processor, specialized hardware or its combination can be adopted.

Mac processor 220 can be general purpose microprocessor, digital signal processor (DSP) or application specific processor.Mac processor 220 can be connected with specialized hardware, to assist each task (not showing its details here).Various application may operate on the processor of outer company, as the computer of outer company or connected by network, may operate on the Attached Processor in access point 104 (not shown), or, operate in it mac processor 220.Shown mac processor 220 is connected with memory 255, and the latter can be used to store data and instruction, so that perform various progresses and methods described herein.It will be appreciated by those skilled in the art that memory 255 can comprise one or more various types of memory member, can embed in whole or in part in mac processor 220.

Except storing the instruction and data for performing function described here, memory 255 also can be used to store the data be associated with individual queue.

Wireless LAN transceiver 240 can be the transceiver of any type.In an exemplary embodiment, wireless LAN transceiver 240 is OFDM transceivers, and it can utilize MIMO or MISO interfaces.To those skilled in the art, OFDM, MIMO and MISO are known.On August 27th, 2003 submits to, title is the co-pending United States Patent application No.10/650 of " FREQUENCY-INDEPENDENT SPATIAL-PROCESSING FORWIDEBAND MISO AND MIMO SYSTEMS ", in 295, describe OFDM, MIMO and MISO transceiver of various exemplary, this part of application has transferred assignee of the present invention.Other embodiment can comprise SIMO or SISO system.

Shown wireless LAN transceiver 240 is connected with antenna 250A-N.In various embodiments, any amount of antenna can be supported.Antenna 250 can be used to carry out sending and Received signal strength on WLAN 120.

Wireless LAN transceiver 240 can comprise the spatial processor be connected with one or more antenna 250.This spatial processor can process the data that each antenna will send independently, or, Combined Treatment is carried out to the signal that all antennas receive.The example of independent process can based on channel estimating, the feedback from UT, channel reversion (channel inversion) or multiple other technologies as known in the art.This process uses one of any in multiple spatial processing technique execution.Multiple such transceiver can use Wave beam forming, beam conduct (beam steering), feature to guide (eigen-steering) or other space technologies, improves the throughput that is sent to a given user terminal and the throughput from a given user terminal.Wherein send in the exemplary embodiment of OFDM symbol at one, this spatial processor can comprise multiple subspaces processor, is used for processing each OFDM subchannel or frequency range.

In one exemplary embodiment, this AP has N number of antenna, and an exemplary UT has M antenna.Therefore, MxN paths is had between this AP and antenna of this UT.In the art, described mulitpath is used to be all known to improve the various space technologies of throughput.In a kind of space-time emission diversity (STTD) system (here, being also referred to as " diversity "), transmission data carry out formaing and encoding, and then, flow through all antennas send as individual data.Use M transmitting antenna and N number of reception antenna, the individual independent channel of MIN (M, N) can be formed.Spatial reuse utilizes these independent pathways, and can send different data on these independent pathways, thus improves transmission rate.

Various technology for the characteristic of channel learning and adapt between AP and UT are known.Unique pilot signal can be sent from each transmitting antenna.Receive at each reception antenna place and measure these pilot signals.Then, information feedback can be returned to transmitter, for use in transmission.The feature decomposition measuring channel matrix can be performed, to determine channel characteristics pattern.Another kind avoids the technology of the feature decomposition of carrying out channel matrix in receivers, uses the feature guiding of pilot signal and data, carrys out the spatial manipulation in simplified receiver.

Therefore, according to current channel status, for the transmission to each user terminal in system, different data rates can be provided.Specifically, the concrete link between AP and each UT has superior performance than multicast link or broadcasting link, and multicast link or broadcasting link can be shared from AP to more than one UT.Further the example of this respect is described in detail below.Use which kind of spatial manipulation based on the physical link between AP and each UT, wireless LAN transceiver 240 can determine supported speed.This information can be feedbacked by connection 280, for MAC process.

The quantity of antenna can be disposed according to the demand data of UT and size and form factor.Such as, due to the bandwidth requirement that it is higher, high definition video display can comprise, such as, and four antennas; And PDA can have two antennas.An exemplary access point can have four antennas.

By the mode similar to the access point 104 shown in Fig. 2, user terminal 106 can be disposed.Not allow stream 260 be connected to LAN transceiver (although UT can comprise such transceiver, wired or wireless), stream 260 normally receives from the one or more application or process that are attached thereto the equipment that connects or UT work, or is delivered to one or more application or process that the equipment or UT that are attached thereto and connect work.The high level be connected with AP 104 or UT 106 can be any type.Layer described herein is only illustrative.

traditional 802.11MAC

As mentioned above, in order to keep compatible with legacy system, various embodiment described herein can be adopted.IEEE 802.11 (e) function set (keeping backward compatibility with 802.11 standards comparatively early) comprises in this section the various functions that will sum up, and in the function comparatively introduced in standard morning.For the detailed description of these functions, please refer to corresponding IEEE 802.11 standard.

Basic 802.11MAC comprises the carrier sense multiple/conflict avoidance (CSMA/CA) based on distributed coordination function (DCF) and some collaboration feature (PCF).DCF can access media when not having center-control.In AP, use PCF, thus centralized control is provided.In order to avoid conflict, DCF and PCF utilizes the various gaps continuously between transmission.Transmission is called as frame, and the gap between frame is then called as frame pitch (IFS).Frame can be user data frame, control frame or management frames.

The frame pitch duration changes according to the type in inserted gap.Fig. 3 shows 802.11 frame pitch parameters: short frame pitch (SIFS), some frame pitch (PIFS) and DCF frame pitch (DIFS).Note that SIFS < PIFS < DIFS.Therefore, with must wait for the transmission of long period before attempting to access channel compared with, the transmission be positioned at after the shorter duration will have higher priority.

According to carrier sense (CSMA) function of CSMA/CA, detecting that stand (STA) can obtain the access right of channel for time idle at least one DIFS duration of channel.(term " STA " used here can refer to an access any station of WLAN, and can comprise access point and user terminal).In order to avoid conflict, except DIFS, each STA also waits for the back off time (backoff) of a Stochastic choice, then could access channel.The STA with longer back off time will be noted that when high priority STA starts to send on channel, therefore avoids and conflicts with this STA phase.(its corresponding back off time can be reduced it and listen to the time quantum that this channel is waited for before other transmission by the STA of each wait, thus the priority keeping it relative).Therefore, according to conflict avoidance (CA) function of this agreement, STA keeps out of the way a random time section between [0, CW], wherein selects CW to be CWmin at first, increases the factor 2, until maximum CWmax during each conflict.

Fig. 4 gives exemplary physical layer (PHY) span line 400, is used for illustrating how using DIFS to add back off time to access according to DCF.Existing transmission 410 busy channel.In this embodiment, when transmission 410 stops, there is not the access of higher priority, so, after DIFS with the back off time be associated, start new transmission 420.In the following discussion, think that the STA carrying out transmission 420 has obtained this transmission opportunity by competition in this case.

Only expecting that a specific STA makes in the frame sequence of response to current transmission, use SIFS.Such as, when sending one acknowledgement frame (ACK) in response to the Frame received, this ACK can be sent immediately after receiving data and adding SIFS.Other transfer sequence also can use SIFS between frames.When a request sends SIFS after (RTS) frame, can be followed by one and permit sending (CTS) frame, then, can send data during SIFS after CTS, after this, SIFS after the data can be followed by an ACK.As mentioned above, these frame sequences are all interspersed with SIFS.The SIFS duration can be used for: (a) detects the energy on channel, and judges whether energy exhausts (that is, channel clear); B () is free decodes to preceding one and judges whether ACK frame shows that transmission is correctly received; C () STA transceiver switches to from reception if having time launches and switches to reception from transmitting.

Fig. 5 gives exemplary physical layer (PHY) span line 500, is used for illustrating how before ACK, to use SIFS, and it has higher priority than DIFS access.An existing transmission 510 takies this channel.In this embodiment, when transmission 510 stops, ACK 520 is followed by when transmission 510 terminates a rear SIFS.Note that ACK 520 started before DIFS at the expiration, so any other STA attempting to win transmission opportunity can not be successful.In this embodiment, there is not the access of higher priority after terminating in ACK 520, so, after DIFS with the back off time be associated, start new transmission 530, if any.

RTS/CTS frame sequence (except providing flow control function) can be used to improve the protection to data frame transfer.RTS and CTS comprises the Duration Information of subsequent data frame and ACK and any middle SIFS.The STA listening to RTS or CTS marks the shared duration on their network allocation vector (NAV), and is considered as by media busy within this duration.Usually, utilize RTS/CTS, the frame longer than designated length can be protected, and shorter frame is sent out away in unprotect situation.

PCF can be used to make AP provide the centralized control of channel.Media detected for time idle within the PIFS duration, AP can obtain the control to these media.PIFS is shorter than DIFS, therefore has higher priority than DIFS.Compared with DCF, once AP obtains the access right to channel, it just can provide uncompetitive access chance to other STA, thus improves MAC efficiency.Note that SIFS has higher priority than PIFS, so PCF must wait for before control channel, until all SIFS EOSs.

Once AP uses the access right of PIFS acquisition to media, it just can establish a uncontended periods (CFP), and within this cycle, AP can provide polling type to access to the STA be associated.Uncompetitive poll frame (CF-Poll), or be simply referred to as poll frame, sent by AP, what it was followed below is from the transmission by poll STA to AP.Equally, STA must wait for the SIFS duration after CF-Poll, although need not wait for DIFS or any back off time by poll STA.802.11 (e) introduces various enhancing, comprises the enhancing of polling mechanism, below in conjunction with Fig. 9, such example is described in further detail.

The beacon that AP sends establishes the duration of CFP.This is similar to and uses RTS or CTS to prevent contention access.But some terminal cannot hear this beacon, but its transmission may cause interference to the transmission of being dispatched by AP, so hidden terminal problem still there will be.The each terminal starting in the cfp to transmit, by using CTS-to-self, can realize further protection.

ACK and CF-Poll can be included in a frame, and together with can containing with data frame packet, thus improve MAC efficiency.Note that SIFS < PIFS < DIFS closes is that channel access provides a kind of certainty priority mechanism.In DCF, the contention access between STA is probabilistic based on avoidance mechanism.

802.11 early stage standards also specify and large packet fragmentation is become less fragment.An advantage of this segmentation is: the mistake in a fragment needs less re-transmission than the mistake in a larger grouping.In these standards, a shortcoming of segmentation is: for the transmission of confirmation type, needs for each fragment sends an ACK, and wherein, additional SIFS corresponds to additional ACK transmission and fragments for transport.Fig. 6 shows this point.This exemplary physical layer (PHY) span line 600 gives N number of section and the corresponding transmission confirmed.An existing transmission 610 is sent out away.At the end of transmission 610, a STA waits for DIFS 620 and back off time 630, to obtain the access right to channel.One STA sends N number of fragment 640A-640N to the 2nd STA, must to have thereafter the delay of N number of corresponding SIFS 650A-650N respectively.2nd STA sends N number of acknowledgement frame 660A-660N.Between each fragment, a STA must wait for SIFS, so, there is N-1 SIFS 670A-670N-1.Therefore, divide into groups with transmission one, an ACK compares with a SIFS, a grouping through segmentation needs the identical transmitted in packets time, but has N number of ACK and 2N-1 SIFS.

802.11 (e) standard with the addition of enhancing function, so that improve the former MAC in 802.11 (a), (b) and (g).802.11 (g) and (a) is all ofdm system, and they are very similar, but work in different frequency bands.The various functions of the low speed MAC protocol of such as 802.11 (b) and so on pass on to forward the system with more high bit rate, thus introduce poor efficiency, after will be described in detail to this.

In 802.11 (e), DCF obtains enhancing, therefore is called as enhancing distributed channel access (EDCA).Main quality of service (QoS) enhancing of EDCA is the introduction of arbitration frame spacing (AIFS).AIFS [i] is associated with the type of service (TC) identified with numbering i.AP can use AIFS [i] value different from the AIFS that other STA can use [i] value.Only have AP can use AIFS [i] value equal with PIFS.In other cases, AIFS [i] is more than or equal to DIFS.Under default condition, for " speech " and " video " type of service, select the AIFS equaling DIFS.If AIFS comparatively greatly, is then indicated as type of service " best endeavors " and " background " have selected lower priority.

The size of competition window is also the function of TC.Limit priority type allows to arrange CW=1, that is, do not have back off time.For other TC, different contention window size provides probabilistic relative priority, but can not be used for reaching delay guaranteed.

802.11 (e) introduces transmission opportunity (TXOP).In order to improve MAC efficiency, when STA is by EDCA or when getting media by the polling type access in HCCA, STA can send more than one frame.The one or more frame is called as TXOP.In the media, the maximum length of TXOP depends on type of service, and is determined by AP.In addition, for the TXOP by poll, AP indicates the allowance duration of TXOP.During TXOP, STA can send a series of frame, is embroidered with ACK and SIFS from destination party therebetween.Except waiting for that DIFS adds except back off time to each frame, the STA having won a TXOP can know, it can occupy this channel for subsequent transmission.

During TXOP, can be every frame (the same in the 802.11MAC comparatively early that coexists) from the ACK of destination party, or, can use at once or the block ACK that postpones, as described below.In addition, for specific Business Stream, as broadcast or multicast, the strategy without ACK is allowed.

Fig. 7 gives exemplary physical layer (PHY) span line 700, for illustration of having the TXOP confirmed frame by frame.An existing transmission 710 is sent out away.After transmission 710 and after waiting for DIFS 720 and back off time 730, if any, STA gets TXOP 790.TXOP 790 comprises N number of frame 740A-740N, follows N number of corresponding SIFS 750A-750N after each frame.The STA carrying out receiving makes response with N number of corresponding ACK760A-760N.ACK 760 follows N-1 SIFS 770A-770N-1 below.It should be noted that each frame 740 comprises lead code 770, and stem and grouping 780.The following detailed description of exemplary embodiment greatly can be reduced to the reserved transmission time amount of lead code.

Fig. 8 shows the TXOP 810 having block and confirm.TXOP 810 can be won by competition or poll.TXOP 810 comprises N number of frame 820A-820N, follows N number of corresponding SIFS 830A-830N after each frame.After the transmission of frame 820 and SIFS 830, send a block ACK and ask 840.The STA carrying out receiving will make response in a certain moment in future to this block ACK request.This block ACK immediately following after frame Bulk transport terminates, or can be able to postpone, to allow the software process of receiver.

The following detailed description of exemplary embodiment can greatly reduce transmission time amount (in this embodiment for SIFS) between frame.In some embodiments, there is no need between transmission (i.e. frame) continuously to postpone.

It should be noted that for specific transformat, define a kind of signal extension (Signal Extension), it increases additional delay in the end of every frame in 802.11 (a) and other standards.Although be not included in technically in the definition of SIFS, the following detailed description of each embodiment also can remove signal extension.

Block ACK function can be raised the efficiency.In one example in which, STA can send maximum 64 MAC service data units (SDU) corresponding with 1024 frames (each can also be divided into 16 fragments), and destination party STA can provide single response in the end of frame block, to show the ACK state of this 1024 frame.Under normal circumstances, during speed height, MAC SDU can not carry out segmentation, and for low delay, before needing the block ACK from destination party, can send and be less than 64 MAC SDU.In this case, in order to send M frame, total time reduces to M frame+M SIFS+ block ACK from M frame+M SIFS+M ACK+M-1 SIFS.The following detailed description of embodiment improve the efficiency of block ACK further.

The direct link agreement (DLP) that 802.11 (e) introduces enables STA be directly transmitted to by frame to be in another the destination party STA (being controlled by identical AP) in a set of basic (BSS).AP can provide the TXOP of poll for this direct frame transmission between STA.Before this function of introducing, in polling type access procedure, from the destination party of frame by poll STA, always these frames are transmitted to destination party STA by AP, AP.Forwarded by the frame eliminating double bounce, media efficiency is improved.The embodiment further described below is that DLP transmission increases obvious efficiency.

802.11 (e) also introduces in-dash computer F, is called as mixing collaboration feature (HCF).In the channel access (HCCA) that HCF controls, AP can access channel at any time, thus sets up controlled access phase (CAP), and this is similar to CFP, transmission opportunity is provided for any time within the competitive stage, instead of only immediately following after beacon.AP waits for PIFS when not having back off time, then accesses media.

Fig. 9 gives exemplary physical layer (PHY) span line 800, for illustration of use HCCA by ask TXOP.In this embodiment, AP competes this poll.An existing transmission 910 is sent out away.After transmission 910, AP waits for PIFS, then sends the poll frame 920 of a sensing STA.It should be noted that other STA of this channel of competition must wait at least DIFS, because the poll 920 sent causes this there will not be, as shown in the figure.The STA ask sends the TXOP940 ask after poll frame 920 and SIFS 930.AP can continue poll, is respectively waiting for PIFS by asking between TXOP 940 and poll frame 920.In another kind of situation, AP can wait for PIFS from transmission 910, thus establishes CAP.AP can send one or more poll frame during CAP.

mAC improves

As mentioned above, the various poor efficiency functions of former MAC also pass in version later on.Such as, be the 11Mbps relative with 64Mbps and the very long lead code that designs can cause poor efficiency.Along with the increase of speed, Medium Access Control (MAC) Protocol Data Unit (MPDU) constantly reduces, so, make various frame pitch and/or lead code keep the constant corresponding reduction just meaning channel utilization.Such as, the length that high data rate MIMO MPDU transmits may only have a few microsecond, and by contrast, 802.11 (g) has the lead code of 72 μ s.Eliminate or reduce and postpone, as SIFS, signal extension and/or lead code, throughput and channel utilization will be improved.

Figure 10 is an exemplary embodiment of TXOP 1010, and it comprises multiple continuous print transmission frame, and without any gap.TXOP 1010 comprises N number of frame 1020A-1020N, and they are when without any (being compared by SIFS required in the TXOP 810 shown in this and Fig. 8) of transmitting in an orderly manner when gap.The quantity of the frame in this TXOP is only limited to buffer and the decoding capability of receiver.When STA sends successive frame together with block ACK in TXOP 1010, the SIFS duration need not be inserted, because between successive frame, do not have other STA to need to obtain the access right to media.After N number of frame, add an optional block ACK ask 1030.The business of some type may not need to confirm.After TXOP, response can be made to a block ACK request, or, can send after a while.Frame 1020 undesired signal is expanded.TXOP 1010 can be used for any embodiment described in detail here, as long as wherein need TXOP.

As shown in Figure 10, when sending all frames by same STA, SIFS need not be sent between the successive frame of TXOP.In 802.11 (e), remain these gaps, so that in the limit complexity requirement of receiver place.In 802.11 (e) standard, the SIFS period of 10 μ s and the ofdm signal of 6 μ s expand to receiver and provide 16 μ s altogether, for the treatment of the frame received (comprising demodulation code).But if PHY speed is very large, this 16 μ s can lower efficiency significantly.In some embodiments, by introducing MIMO process, even if 16 μ s have also been not enough to process.And in this exemplary embodiment, from STA a to AP or to another STA continuous transmission, do not need SIFS and ofdm signal expansion (use direct link agreement).Therefore, if a receiver needs additional period for MIMO receiver process and channel-decoding (such as, turbo/ convolution/LDPC decoding) after the end of transmission, then can perform these functions, these media are used for additional transmitted stream simultaneously.After a while, an acknowledgement frame can be sent, (such as, use block ACK) as mentioned above.

Due to the different propagation delays between STA; different STA between transmission can separate with protective time slot; to avoid these media collide at receiver place (Figure 10 does not show, but will be further described in detail below) from the continuous transmission of different STA.In one exemplary embodiment, protective time slot (4 μ s) all working environment for 802.11 of an OFDM symbol is all enough.Do not need to separate (as shown in Figure 10) with protective time slot from same STA to the transmission of different destination party STA.Also will further describe below, these protective time slots can be called as guard band frame pitch (GIFS).

Do not use SIFS and/or signal extension, by using the ARQ mechanism (rollback N or selectively repetition) based on window, can provide required receiver processing time (such as, for MIMO process and decoding), these technology are known for those skilled in the art.Stop-and-wait (stop-and-wait) the MAC layer ACK of tradition 802.11 has been enhanced to the mechanism of window type in 802.11 (e), in this embodiment, reaches at most 1024 frames and block ACK.Preferred introducing is based on the ARQ mechanism of normal window, but not the self-organizing block ACK mechanism of design in 802.11 (e).

The maximized window allowed depends on receiver process complexity and buffering.Transmitter can according to transmitter-receiver between accessible peak value PHY speed, send enough data to fill up receiver window.Such as, because receiver process possibly cannot get caught up in PHY speed, so receiver may need to store soft (soft) decoder and export, until they can be decoded.Therefore, during peak value PHY speed, the buffer requirement of physical layer process can be used to the maximized window determining to allow.

In one exemplary embodiment, receiver can notice it can when not making its physical layer buffers overflow with the maximum permission PHY block size of a specific PHY rate processing.Or receiver also can notice it can when not making its physical layer buffers overflow with the maximum permission PHY block size of maximum PHY rate processing.When PHY speed is lower, longer block size can be processed when not having buffer to overflow.According to the maximum permission PHY block size noticed during maximum PHY speed, transmitter can use known formula to calculate the maximum permission PHY block size for specific PHY speed.

If the maximum PHY block size noticed is a static parameter, is then known at transmitter place and is also known receiver parameters at scheduler place can process physical layer buffers and receiver to get out the time quantum received before next PHY happens suddenly be another.Or take situation according to physical layer buffers, the maximum PHY block size noticed can dynamically change.

Receiver processing delay can be used to determine that come and go (round-trip) of ARQ postpones, and the latter can be used to the delay determining that application program is observed.Therefore, in order to support low delay service, the PHY block size of permission can be limited.

Figure 11 gives an exemplary embodiment of TXOP 1110, for illustration of the preamble transmissions amount needed for reduction.TXOP 1110 comprises lead code 1120, and that follow below is N number of continuous transmission 1130A-1130N.An optional block ACK can be added and ask 1140.In this embodiment, transmit 1130 and comprise a stem and a grouping.By TXOP 1110 compared with the TXOP 790 of Fig. 7, except stem and grouping, each frame 740 also comprises a lead code.For the transmission data of identical amount, by sending single lead code, required preamble transmissions is only a lead code, instead of N number of lead code.

Therefore, lead code 1120 can exclude from transmit continuously.Receiver can use initial preamble 1120 to obtain signal and to obtain for the fine frequency of OFDM.Compared with current OFDM lead code, for MIMO transmission, initial preamble 1120 can be expanded, to enable receiver estimation space channel.But the subsequent frame in same TXOP can not need the lead code of adding.Pilot tone in OFDM symbol is enough to carry out signal trace usually.In another embodiment, additional symbol (being similar to lead code) periodically can interlock at TXOP 1110.But, obviously can reduce total lead code expense.Only just can send lead code where necessary, and, based on the time quantum of having passed since the last lead code sent, differently lead code can be sent.

It should be noted that TXOP 1110 also can combine with the function of legacy system.Such as, block ACK is optional.Also the ACK of higher frequency can be supported.Even so, less gap, as GIFS, can replace longer SIFS and (add signal extension, if you are using).Continuous transmission 1130 can also comprise multiple sections of larger grouping, as mentioned above.Should also be noted that the stem of the continuous transmission 1130 of mailing to same recipient STA can be compressed.Also in detail an example of compressed header will be described below.

Figure 12 gives an exemplary embodiment of method 1200, and it is combined with above-mentioned each side, comprises and gathers lead code, removes the gap of such as SIFS and so on and insert GIF as required.This flow process starts from frame 1210, and wherein, use any technology described in detail here, a STA has won a TXOP.In frame 1220, as required, a lead code is sent.Equally, existing lead code is longer than or is shorter than to this lead code can, and can change according to various parameter (such as, the time passed since last transmission lead code), estimates MIMO space channel to enable recipient STA.In frame 1230, STA sends one or more grouping (or, more generally, the continuous transmission of any type) to destination party.It should be noted that and do not need to send additional lead code.In other embodiments, one or more additional lead code also can be sent, or, as required, the symbol of similar lead code can be inserted.In frame 1240, STA sends signal to an additional recipient STA alternatively.In this case, insert GIFS as required, and, one or more continuous transmission can be sent to additional recipient STA.Then, flow process can terminate.In other embodiments, STA can continue to send signal to plural STA, and the GIFS inserted needed for estimated performance grade and/or lead code.

Therefore, as mentioned above, by the transmission from a STA to multiple destination party STA is aggregated into continuous transmission, MAC efficiency can be improved further, thus save a lot of or whole protective time slot, and, reduce lead code expense.For the multiple continuous transmission from same STA to different destination party STA, single lead code (or, pilot transmission) can be used.

Gathered by poll frame, extra high efficiency can be obtained.In one exemplary embodiment, multiple poll frame can be aggregated in a control channel, its example will be described in detail below.In one example in which, AP can send signal, comprising the polling message for distribution T XOP to multiple destination party STA.By contrast, in 802.11 (e), before each TXOP, have the CF-Poll from AP, after have SIFS.When multiple such CF-Poll message being aggregated into single control channel message (in the exemplary embodiment be discussed in more detail below, being referred to as SCHED message) to be used for distributing multiple TXOP, can raise the efficiency.In a common embodiment, section can distribute to the poll frame after gathering and corresponding TXOP thereof any time.Below in conjunction with Figure 15, an exemplary embodiment is described, and, also comprise other examples herein.

In order to raise the efficiency further, can encode to control channel (i.e. SCHED) message with the rate architecture of layering.Correspondingly, the polling message mailing to any STA can be encoded according to the channel quality between AP and STA.The order of transmission of polling message needs not to be the order of institute distribution T XOP, but can be ranked according to coding robustness.

Figure 13 gives exemplary physical layer (PHY) span line 1300, for illustration of gathering poll frame and corresponding TXOP thereof.Gather poll frame 1310 to be sent out away.Can use the control channel structure described in detail here, or can use various other technologies, send these poll frames, to those skilled in the art, these are apparent.In this embodiment, in order to not use frame pitch between poll frame and any forward link TXOP, after gathering poll frame 1310, directly send forward link TXOP 1320.After forward link TXOP1320, send various reverse link TXOP 1330A-1330N, wherein can insert GIFS 1340 as required.It should be noted that when carrying out order transfer from a STA, GIFS (forward link transmissions be similar to for being sent to different STA from AP does not need GIFS) need not be comprised.In this embodiment, reverse link TXOP comprises the TXOP (such as, using DLP) of STA to STA (that is, point-to-point).It should be noted that shown order of transmission is illustrative.Forward direction and reverse link TXOP (comprising point-to-point transmission) can exchange, or, intert mutually.The number of gaps that some configuration is eliminated may be different from the number of gaps that other configurations are eliminated.By the disclosure of the application, those skilled in the art can design multiple interchangeable embodiment easily.

Figure 14 shows an exemplary embodiment of the method 1400 for gathering poll frame.Flow process starts from frame 1410, wherein, by channel resource allocation in one or more TXOP.Any scheduling feature can be used, make this TXOP Decision of Allocation.In frame 1420, the poll frame carrying out distribution T XOP according to this assignment information is gathered.In frame 1430, by one or more control channel, this is gathered poll frame and send to one or more STA (that is, in the exemplary embodiment be discussed in more detail below, the CTRLJ section of SCHED message).In an interchangeable embodiment, any message delivery techniques can be used, send and gather poll frame.In frame 1440, STA gathers the poll assignment information in poll frame according to this, sends TXOP.Then, flow process can terminate.The method can use in conjunction with gathering between poll frame of any length, gathers poll frame and can comprise all or part of of system localizer interval.As mentioned above, gather poll can off and on for based on competition access or traditional poll.In one exemplary embodiment, can periodically, or, according to other parameters, as system load or data transportation requirements, repeat method 1400.

Below in conjunction with Figure 15 and 16, describe an exemplary embodiment of MAC protocol in detail, so that various aspects to be described.Submit to the application simultaneously, exercise question is the co-pending United States Patent application XX/XXX of " WIRELESS LANPROTOCOL STACK ", XXX, XX/XXX, XXX and XX/XXX, in XXX (file number is respectively 030428,030433 and 030436), this MAC protocol has been described in further detail, these three sections applications have transferred the assignee of the application.

An exemplary TDD mac frame interval 1500 has been shown in Figure 15.Term " TDD mac frame interval " used in this case refers to a period of time, wherein, defines the various span lines be described below in detail.TDD mac frame interval 1500 is different from the general term " frame " used, so that the transmission in 802.11 systems of description.In 802.11 terms, TDD mac frame interval 1500 is similar to the sub-fraction of beacon interval or beacon interval.The parameter described in detail in conjunction with Figure 15 and 16 is only illustrative.Use some or all and various parameter value of described parts, those of ordinary skill in the art can make this example be adapted to other embodiments multiple easily.MAC function 1500 is distributed between following transmission channel section: broadcast, control, forward business and reverse traffic (being called as downlink phase and uplink phase respectively) and Stochastic accessing.

In this exemplary embodiment, TDD mac frame interval 1500 is time division duplex (TDD) within the time interval of 2 milliseconds, is divided into five transmission channel section 1510-1550, as shown in the figure.In other embodiments, other order and different frame sizes can be used.The duration of the dispensing section on TDD mac frame interval 1500 can be quantized into a certain mini-bus time interval.

These five in TDD mac frame interval 1500 exemplary transmission channels comprise: (a) broadcast channel (BCH) 1510, and it transmits Broadcast Control Channel (BCCH); (b) control channel (CCH) 1520, it transmits frame control channel (FCCH) and Stochastic accessing feedback channel (RFCH) on the forward link; (c) Traffic Channel (TCH), it transmits user data and control information, and is further subdivided into the forward traffic channel (F-TCH) 1530 on (i) forward link and the reverse traffic channel (R-TCH) 1540 on (ii) reverse link; D () Random Access Channel (RCH) 1550, it transmits access request channel (ARCH) (for UT access request).Pilot beacon also sends in section 1510.

The downlink phase section of the comprising 1510-1530 of frame 1500.The uplink phase section of comprising 1540-1550.Section 1560 represents the beginning at next TDD mac frame interval.Further describe another embodiment comprising point-to-point transmission below.

Broadcast channel (BCH) and beacon 1510 are sent by AP.The Part I of BCH 510 comprises common physical layer expense, as pilot signal, comprises sequential and frequency acquisition pilot signal.In an exemplary embodiment, beacon comprises 2 short OFDM symbol, is used for frequency and time obtains by UT, after be 8 short OFDM symbol of public MIMO pilot tone, by UT for estimating channel.

The Part II of BCH 1510 is data divisions.BCH data division defines transmission channel section CCH 1520, F-TCH 1530, R-TCH 1540 and RCH 1550 distribution condition in TDD mac frame interval, also defines the combination of CCH sub-channels.In this embodiment, BCH 1510 defines the coverage of WLAN 120, so, send under available most robust data transmission mode.The length of whole BCH is fixing.In an exemplary embodiment, BCH defines the coverage of MIMO-WLAN, and, under space-time emission diversity (STTD) pattern, use the binary phase shift keying (BPSK) of 1/4 rate coding to send.In this embodiment, the length of BCH is fixed as 10 short OFDM symbol.In other embodiments, other different signaling technologys can be used.

The control channel (CCH) 1520 sent by AP defines the combination of the remainder at TDD mac frame interval, and shows how to use and gather poll frame.CCH 1520 sends in multiple subchannel by very strong transmission mode, and each subchannel has different data rates.First subchannel is the most strong, and expection can be decoded by all UT.In an exemplary embodiment, the BPSK of 1/4 rate coding is used for a CCH subchannel.Additionally provide the subchannel that other robustnesss reduce (efficiency rising).In one exemplary embodiment, maximum three additional subchannels are used.Each UT in order, decodes to all subchannels, until decode unsuccessfully as possible.CCH transmission channel section in each frame has variable length, and this length depends on the quantity of CCH message in every sub-channels.The confirmation of reverse link Stochastic accessing burst transmits on the most strong (first) subchannel of CCH.

CCH comprises physical layer bursts assignment information on the forward and reverse links (be similar to gather poll frame in TXOP).Assignment information is used in forward direction or reverse link transmitting data.Usually, physical layer bursts assignment information comprises: (a) MAC ID; B () value, represents the time started (in F-TCH or R-TCH) of dispensing section in this frame; The length of (c) dispensing section; The length of (d) special physical layer overhead; (e) transmission mode; F () is for the coding of physical layer bursts and modulation scheme.

The assignment information of CCH other exemplary types upper comprises: for transmitting the assignment information of the dedicated pilot from UT on reverse link; For transmitting the assignment information of buffer from UT and link-state information on reverse link.CCH can also define the reservation unused portion of frame.These unused portions of this frame can be used for carrying out noise floor (and interference) by UT and estimate, and, measure adjacent system beacon.

Random Access Channel (RCH) 1550 is reverse chain channels, and UT can send Stochastic accessing burst by it.For each frame, in BCH, specify the variable-length of RCH.

Forward traffic channel (F-TCH) 1530 comprises one or more physical layer bursts sent from AP 104.The specific MAC ID shown in CCH assignment information is pointed in each burst.Each burst comprises special physical layer overhead, such as, and the pilot signal (if any) that sends and MAC PDU according to the transmission mode shown in CCH assignment information and coding and modulation scheme.F-TCH has variable length.In an exemplary embodiment, special physical layer overhead can comprise a special MIMO pilot tone.Figure 16 set forth in detail an exemplary MAC PDU.

The physical layer bursts that reverse traffic channel (R-TCH) 1540 comprises from one or more UT 106 is transmitted.Each burst is sent by one that shows in CCH assignment information specific UT.Each burst can comprise a dedicated pilot lead code (if any) sending and a MAC PDU according to the transmission mode shown in CCH assignment information and coding and modulation scheme.R-TCH has variable length.

In this exemplary embodiment, F-TCH 530, R-TCH 540 or the two, can the multiplexing or CDMA (Code Division Multiple Access) of usage space, realize and transmit while MAC PDU that different UT is associated.The field comprising the MAC ID (that is, the transmit leg in up link, or the expection recipient on down link) be associated with MAC PDU can be included in MACPDU stem.These can with all addressing uncertain problems that may occur when solving the multiplexing or CDMA of usage space.In other embodiments, when multiplexing strictly based on time division technique time, do not need MAC ID in MAC PDU stem, because addressing information is included in CCH message, the specific time period in TDD mac frame interval is allocated to a concrete MAC ID by CCH message.The combination of spatial reuse, code division multiplexing, time division multiplexing and any other technology known in the art can be adopted.

Figure 16 shows an exemplary MAC PDU 1660 from a grouping 1610, and in this embodiment, it can be IP datagram or ethernet segment.Described exemplary fields type and size are illustrative.One skilled in the art will recognize that in protection scope of the present invention, other sizes various, type and configuration also can be imagined and obtain.

As shown in the figure, packet 1610 carries out segmentation in adaptation layer.Each adaptation sublayer PDU 1630 one of to carry in these sections 1620.In this embodiment, packet 1610 is divided into N number of section of 1620A-N.Adapt to sublayer PDU 1630 and comprise load 1634, load 1634 comprises corresponding section 1620.Type field 1632 (being a byte in this embodiment) is attached to and adapts in sublayer PDU 1630.

Logical links (LL) stem 1642 (being 4 bytes in this embodiment) is added in load 1644, and load 1644 comprises adaptation layer PDU 1630.The exemplary information of LL stem 1642 comprises flow identifier, control information and sequence number.For stem 1642 and load 1644, calculate CRC 1646, and affix it, to form logical links sublayer PDU (LL PDU) 1640.Logic link control (LLC) and wireless spread-spectrum technology (RLC) PDU can be formed by similar fashion.LL PDU 1640 and LLC PDU and RLC PDU is placed on (such as, high QoS queue, best endeavors queue or control message queue) in queue, to be used by MUX functional section.

MUX stem 1652 is attached on each LL PDU 1640.An exemplary MUX stem 1652 can comprise length and type (in this embodiment, stem 1652 is two bytes).For each control PDU (that is, LLC and RLC PDU), similar stem can be formed.LL PDU 1640 (that is, LLC or RLC PDU) forms load 1654.Stem 1652 and load 1654 form MUX sublayer PDU (MPDU) 1650 (MUX sublayer PDU is also referred to as MUX PDU here).

In this embodiment, the communication resource on shared medium is distributed in a series of TDD mac frame interval by MAC protocol.Below by other embodiments of describing in detail, the TDD mac frame interval of these types can insert other MAC functional sections various, comprise based on competition or poll, and comprise and use the access protocol of other types and legacy system to carry out alternately.As mentioned above, scheduler can determine the size (being similar to the TXOP gathering poll) distributing to the physical layer bursts of one or more MAC ID in each TDD mac frame interval.It should be noted that not each MAC ID having data to send can be assigned to the space in any specific T DD mac frame interval.In protection scope of the present invention, any access control or scheduling scheme can be used.When distributing for MAC ID, the corresponding MUX functional section of this MAC ID will form MAC PDU 1660, and it comprises one or more MUXPDU 1650, so that be included in this TDD mac frame interval.One or more MUX PDU 1660 for one or more MAC ID distributed will be included in (that is, TDD mac frame interval 1500, is described in detail in conjunction with Figure 15) in a TDDMAC frame period above.

In one exemplary embodiment, an aspect makes it possible to transmission part MPDU1650, thus realizes efficient package in MAC PDU 1660.In this embodiment, all part MPDU 1650 remaining byte that do not send in front once transmission can be included, and is identified by part MPDU 1664.In the current frame, these bytes 1664 will send before all new PDU 1666 (that is, LL PDU or control PDU).Stem 1662 (being 2 bytes in this embodiment) comprises MUX pointer, and it points to the beginning of first new MPDU (being MPDU 1666A in this embodiment) that will send in present frame.Stem 1662 also comprises MAC Address.

MAC PDU 1660 comprises the possible part MUXPDU 1664 (remaining after front primary distribution) in MUX pointer 1662, beginning, zero or multiple complete MUX PDU 1666A-N and possible part MUX PDU 1668 (from current primary distribution) below, or other filling informations, for filling up the distribution portion of physical layer bursts.MAC PDU 1660 is carried in the physical layer bursts distributing to this MAC ID.

Therefore, this exemplary MAC PDU 1660 shows a transmission (or, be frame by 802.11 terms), and it can be sent to another STA from a STA, comprises the data division from the one or more streams pointing to this destination party STA.By using part MUX PDU alternatively, efficient package can be realized.What comprise at CCH gathers the time shown in poll frame, and each MAC PDU can send in a TXOP (using 802.11 terms).

The exemplary embodiment described in detail in Figure 15 and 16 lists various aspects, comprises by sending physical layer bursts in an orderly manner from each STA (comprising AP) thus gathering poll frame, minimizing preamble transmissions and eliminate gap.These aspects are also applicable to any MAC protocol, comprise 802.11 systems.Provide other embodiments further below, other various technology are described, these technology can realize the high efficiency of MAC, and, support point-to-point transmission, and existing legacy protocol or system can combine and/or cooperate.

As mentioned above, the various embodiments described in detail here can adopt channel estimating and strict speed to control.By making the unnecessary transmission on media minimize, MAC efficiency can be improved, but in some cases, insufficient rate control feed back will reduce overall throughput.Therefore, for channel estimating and feedback, can provide enough chances, to make the transmission rate under all MIMO mode maximize, thus prevent the throughput caused due to insufficient channel estimating from reducing, throughput reduction can offset any MAC efficiency to be increased.Therefore, can the MAC embodiment of design example, to provide enough preamble transmissions chances, and, allow receiver have an opportunity to provide rate control feed back to transmitter, above this is introduced, also will further describe below.

In one example in which, AP periodically inserts MIMO pilot tone (at least every TP millisecond, wherein, TP can be fixing or variable parameter) in its transmission.Each STA can start it by asking TXOP by a MIMO pilot tone, and this MIMO pilot tone can be used for estimating channel by other STA and AP.For the transmission using direct link agreement (will further describe) to mail to AP or another STA below, MIMO pilot tone can be steered reference signal (steeredreference), to contribute to simplifying the receiver process in destination party STA.

AP can offer an opportunity to destination party STA, to allow it provide ACK to feed back.Destination party STA also can use these feedback chances, provides the rate control feed back of available MIMO mode to transmit leg STA.Such rate control feed back does not define in 802.11 traditional systems, comprises 802.11 (e).Introduce the total amount (for often kind of MIMO mode) that MIMO can improve rate control information.In some cases, in order to the effect improved be maximized in MAC efficiency, by strict rate control feed back, these can be imagined and obtain.

Here by the agency of and be storage level (backlog) information and the scheduling of STA below by the another aspect of further description.Each STA can start its TXOP by a lead code, after request duration of and then next TXOP.This information object points to AP.AP collects next request TXOP for information about from multiple different STA, and, for next TDD mac frame interval, determine TXOP duration distribution condition in the media.AP can use different priority or QoS rule, determine how shared medium, or it can use very simple rule, according to the request from STA, and proportional ground shared medium.Any other dispatching technique can also be adopted.The TXOP dispensing section at next TDD mac frame interval distributes in from a rear control channel message of AP.

the access point of specifying

In embodiment described herein, operation when network can be supported real access point or not have real access point.When there is real AP, such as, it can be connected to wired pipeline connection (that is, cable, optical fiber, DSL or T1/T3, Ethernet) or home entertainment server.In this case, this real AP can be information source and the stay of two nights of most of data of equipment room flowing in network.

When there is not real AP, multiple station still can use the technology such as the distributed coordination function (DCF) of 802.11b/g/a or the enhanced distributed channel access of 802.11e, mutually communicates, above to these techniques have been description.Below also by further description, when needs additional resource, adopt centralized scheduling scheme, more efficiently can use media.Such as, this network architecture may occur in the family, and wherein, a lot of distinct device (that is, DVD-TV, CD-Amp-Speaker etc.) needs mutually to communicate.In this case, these network stations specify a station to serve as AP automatically.It should be noted that as described below, self adaptation coordination function (ACF) can use by specifying access point, and can adopt when centralized scheduling, Stochastic accessing, ad hoc communication or its combination in any.

Some non-AP equipment but not every non-AP equipment, have the MAC ability of enhancing, therefore be suitable for as appointment AP and work.It should be noted that not all equipment all needs to be designed to have to specify AP MAC ability.When QoS (such as, secure time delay), high-throughput and/efficiency are very important, an equipment in network must can support the operation of specifying AP.

This means, specify the ability of AP to be usually associated with the equipment possessing high ability, such as, there is one or more attribute, as line power (line power), a large amount of antennas and/or transmit/receive chains, or high-throughput requirement.(additive factor for selecting to specify AP will be described in further detail below).Therefore, low side devices, as low side camera or phone, does not need to possess the ability of specifying AP, and high-end equipment, as high-end video source or high definition video display, the ability of specifying AP can be possessed.

In the network not having AP, the AP specified plays the effect of real AP, and or can not have less function.In various embodiments, the AP specified can perform following function: (a) establishes network basic service set and close (BSS) ID; B (), by sending beacon and broadcast channel (BCH) network configuration information (BCH defines the media synthesis before next BCH), arranges network sequence; C () uses forward control channel (FCCH), dispatch the transmission at the station in network, thus management connects; (d) management association (association); E () provides call access control for QoS flow; And/or (f) other functions various.Specify AP can realize complicated scheduler, or, the dispatching algorithm of any type.Simple scheduler can be adopted, its example is described in further detail below.

Below in conjunction with point to point link, describe physical layer convergence protocol (PLCP) stem improved in detail, this is also applicable to specify AP.In one embodiment, the PLCP stem of all transmission sends with the master data speed can being undertaken decoding by all stations (comprising the AP specified).PLCP stem from the transmission at multiple station comprises the data reserve amount at the station place be associated with certain priority or stream.Or it comprises a Duration Request of the rear launching opportunity for certain priority or stream.

By " pry (snooping) ", the AP specified can determine by the storage level of these station requests or transmission opportunity duration in the stem of all stations transmission.Based on load, conflict or other congestion metric, the AP specified can determine portion of time to distribute to (distributed access) based on EDCA, portion of time is distributed to uncompetitive poll (centralized) access.The AP specified can run a basic scheduler, and it distributes the bandwidth proportional with request, and dispatches it in uncontended periods.The scheduler strengthened also is fine, but is not necessary.Pass through the transmission of scheduling by specifying AP at the enterprising announcement that works of CCH (control channel).

The AP specified does not need the transmission of standing to forward (echo) to another station (that is, serving as springboard), but this function is also permit.Real AP possesses transfer capability.

When selecting to specify access point, a kind of hierarchical system can be created, determine which equipment should serve as access point.When selecting to specify access point, admissible example factors comprises following: (a) user configures (over-ride); B preference gradations that () is higher; (c) safe class; (d) ability: line power; (e) ability: antenna amount; (f) ability: maximum transmission power; G () is based on the additional consideration (break a tie) of other factors: medium education (MAC) address; H first equipment that () is started shooting; (i) any other factor.

In fact, the AP specified preferably is positioned at center, and has best total Rx SNR CDF (that is, can receive all stations when good SNR).Usually, the antenna that station has is more, and receiving sensitivity is better.In addition, the AP specified can have higher transmitting power, thus the AP that this is specified can be listened to by a large amount of stations.When adding station and/or when station is mobile, these attributes can be assessed, and utilize them, dynamically reconfiguring to enable network.

If the AP that network configuration has a real AP or to specify, then can support that point-to-point connects.Next joint will be described point-to-point in detail and connect.In one embodiment, can support that the point-to-point of two types connects: the point-to-point connection that (a) is managed, wherein, AP dispatches the transmission that each station participates in; B the connection of () self-organizing, wherein, AP does not participate in management and the scheduling of station transmission.

The AP specified can set mac frame interval, and sends a beacon when frame starts.Broadcast and control channel can specify the duration of having distributed in the frame allowing station send.Request for those and transmit concerning point-to-point the station (for AP, these requests are known) distributed, AP can provide the dispensing section that have passed through scheduling.AP can notice these dispensing sections in control channel, such as, in each mac frame.

AP can also be included in A-TCH (self-organizing) section in this mac frame (will be described in detail to this) below.Whether there is A-TCH in mac frame to indicate in BCH and FCCH kind.In A-TCH, stand and CSMA/CA process can be used to perform point to point link.The CSMA/CA process of IEEE Wireless LAN standard 802.11 can be revised, to get rid of the requirement of ACK at once.When a station rob account for channel time, this station can send a MAC-PDU (protocol Data Unit), and it comprises multiple LLC-PDU.One stands in A-TCH the maximum duration that can take and provides in BCH.For the LLC through confirming, can, according to required application delay, postpone to hold consultation to window size and maximum confirmation.Describe the mac frame of improvement in detail below in conjunction with Figure 20, it has A-TCH section, the AP that can be used for real AP He specify.

In one embodiment, uncontrolled (unsteered) MIMO pilot tone can make all stations understand channel between their self and dispatching stations.In some cases, this is useful.In addition, the AP specified can use uncontrolled MIMO pilot tone, so that carry out the demodulation of channel estimating and PCCH, then therefrom can derive dispensing section.Once the AP specified receives all requested dispensing sections in the frame of a special MAC, then it can be dispatched them for follow-up mac frame.It should be noted that rate control information need not be included in FCCH.

In one embodiment, scheduler can perform following operation: first, and for next mac frame, all requested dispensing sections collected by scheduler, and calculate total requested dispensing section (Total Requested).The second, scheduler calculates the total available resources (Total Available) can distributing to F-TCH and R-TCH.3rd, if Total Requested is greater than TotalAvailable, then use the factor determined by Total Available/Total Requested, all requested dispensing sections are carried out convergent-divergent.4th, for dispensing section after any convergent-divergent being less than 12 OFDM symbol, these dispensing sections are increased to 12 OFDM symbol (like this in this exemplary embodiment, but other embodiments can use different parameters).5th, in order to provide the dispensing section of gained in F-TCH+R-TCH, by reducing all dispensing sections being greater than 12 OFDM symbol in a looping fashion, from maximum, next symbol, can provide any extra OFDM symbol and/or guard time.

An example can illustrate above-described embodiment.Consider following distribution request: 20,40,12,48.So, Total Requested=120.Suppose Total Available=90.Suppose that required guard time is 0.2 OFDM symbol again.Therefore, as described in the 3rd operation above, the dispensing section after convergent-divergent is: 15,30,9,36.As described in the 4th operation above, dispensing section 9 is increased to 12.According to the 5th operation, amended dispensing section and guard time are added, total allocation section is 93.8.This means, dispensing section will reduce by 4 symbols.From maximum, once remove a symbol, thus determine that final dispensing section is 14,29,12,34.(that is, altogether 89 symbols and 0.8 symbol for the protection of the time)

In one exemplary embodiment, when there is appointment AP, it can be set up the beacon of BSS and arrange network sequence.Multiple equipment is associated with the AP that this is specified.When needing a QoS to be connected with two equipment of specifying AP to be associated, such as, have the HDTV link of low delay and high-throughput requirement, so, they provide operational indicator to this appointment AP, to carry out call access control.This appointment AP can receive or refuse this connection request.

If media utilance is enough low, then can use CSMA/CA, reserve the media whole duration between the beacons, operate for EDCA.If EDCA operation runs smooth and easy, such as, do not have excessive conflict, keep out of the way and postpone, then this appointment AP need not provide coordination function.

The PLCP stem that the AP specified is transmitted by monitoring station, can continue to monitor media utilance.According to the observation to media, and storage level or transmission opportunity Duration Request, specify AP can determine when the dissatisfied required QoS permitting stream of EDCA operation.Such as, it can the storage level of observation station's report and the trend of duration of asking, and based on the stream of permitting, itself and desired value are compared.

When determining when specifying AP not meet required QoS in distributed access situation, the operation transformation on media can be become to have the operation of poll and scheduling by it.The latter provides the throughput efficiency having more deterministic time delay and Geng Gao.The example of this operation will be described in detail below.

Therefore, by observation media utilance, conflict, congested and observation from the transmission opportunity request of dispatching station with request and allowance QoS flow are compared, scheduling (centralized) operation can be converted adaptively to from EDCA (distributed access mechanism).

As previously mentioned, in any embodiment that the application describes in detail, which describing access point, it will be appreciated by those skilled in the art that this embodiment can adapt to work when having real access point or appointment access point.Just as described in detail here, can adopt and/or select one to specify access point, this appointment access point according to any protocols work, can comprise any combination of agreement or the various protocols do not mentioned in the application.

point-to-point transmission and direct link agreement (DLP)

As mentioned above, point-to-point (or referred to as " some point ") transmission enables a STA send data directly to another STA, and first need not send the data to AP.Here the various aspects described in detail go for point-to-point transmission.In one embodiment, direct link agreement (DLP) can be revised, as described below.Figure 17 shows an exemplary point to point link in system 100.System 100 in this example is similar to the system 100 shown in Fig. 1, and it is through amendment, (can in this embodiment, show the transmission between UT 106A and UT 106B) realize directly transmitting from a UT to another UT.UT 106 can pass through WLAN 120, directly communicates, will be described in greater detail here with AP 104.

In various exemplary embodiment, can support that the some point of two types connects: the some point connection that (a) is managed, wherein, AP dispatches the transmission that each STA participates in; B the some point of () self-organizing connects, wherein, AP does not participate in management or the scheduling of STA transmission.An embodiment can comprise these the two kinds one or both connected.In one exemplary embodiment, the signal sent can comprise: a part, and it comprises the public information that can be received by one or more station (also may comprise access point); And, to carry out specially formaing so that the information that received by Dian Dian receiving station.Public information can be used for scheduling and (such as, as shown in figure 25), or by various neighbor station keeps out of the way (such as, as shown in figure 26) for competition.

The closed loop rate that the various exemplary embodiment introduction point points be described below in detail connect controls.This speed can be adopted to control, make full use of available high data rate.

For ease of illustrating, in exemplary embodiment, do not describe various function (that is, confirming) in detail.It will be recognized by those skilled in the art, function disclosed herein can combine, thus forms set or the subclass of any amount in various embodiments.

Figure 18 shows the physical layer bursts 1800 of prior art.Can first send lead code 1810, after and then physical layer convergence protocol (PLCP) stem 1820.A kind of PLCP stem of 802.11 traditional system definitions, comprises rate type and modulation format, for the data transmitted as data symbol 1830.

Figure 19 gives an exemplary physical layer bursts 1900, and it can be used for a some transmission.As Figure 18, lead code 1810 and PLCP stem 1820 includable, follow below be marked as P2P 1940 some point transmission.P2P 1940 can comprise the MIMO pilot tone 1910 used by recipient UT.MIMO Rate Feedback 1920 is also includable, so that used in the future transmission sending back to transmit leg UT by recipient UT.Rate Feedback can generate in response to last transmission from receiving station to dispatching station.Then, data symbol 1930 can send according to a selected rates of some connection and modulation format.It should be noted that physical layer bursts, as PHY burst 1900, the some point that can be used for AP management connects, and the some point transmission of self-organizing.The following detailed description of exemplary Rate Feedback embodiment.Also comprise other embodiments of the physical layer transmission burst comprising these aspects below.

In an exemplary embodiment, AP sets TDD mac frame interval.Broadcast and control channel can be used to indicate the duration of having distributed in TDD mac frame interval.For requesting a STA (being known for AP) for some transmission dispensing section, AP can provide the dispensing section through scheduling, and in control channel, notices them in each TDD mac frame interval.Figure 15 above gives an exemplary system.

Figure 20 shows an exemplary embodiment at TDD mac frame interval 2000, and it comprises an optional self-organizing section, is identified as A-TCH 2010.The part identical with numbering described in conjunction with Figure 15 above can be comprised in TDD mac frame interval 2000.Can show in BCH510 and/or CCH 520 in TDD mac frame interval 2000 and whether there is A-TCH 2010.During A-TCH 2010, STA can use any competition process, performs point to point link.Such as, 802.11 technology can be used, as SIFS, the DIFS, back off time etc. that describe in detail above.Also QoS technology can be used, as those (that is, the AIFS) technology introduced in 802.11 (e).Other schemes various based on competition can also be used.

In one exemplary embodiment, for the CSMA/CA process of competing, such as, the process be defined in 802.11, can revise as follows.Do not need ACK at once.When rob account for channel time, a STA can send and comprise multiple PDU (that is, LLC-PDU) at interior Medium Access Control (MAC) Protocol Data Unit (MAC-PDU).The maximum duration that STA is shared in A-TCH can be shown in BCH.When the transmission of hope through confirming, according to required application delay, window size and maximum confirmation delay can be consulted.

In this embodiment, F-TCH 530 is the parts at TDD mac frame interval, for the transmission from AP to STA.In A-TCH 2010, the point to point link between STA can be performed.In R-TCH 540, the scheduling point to point link between STA can be performed.Any one in these three sections can be set to sky.

Figure 21 gives an exemplary physical layer bursts 2100, is also referred to as " PHY burst ".PHY burst 2100 can be used for dispatching point point connect, such as, during R-TCH 540, or such as A-TCH 2010 and so on self-organizing connect during, above in conjunction with Figure 20 to this has been detailed description.PHY burst 2100 comprises uncontrolled MIMO pilot tone 2110, reciprocity Common Control Channel (PCCH) 2120 and one or more data symbol 2130.Uncontrolled MIMO pilot tone 2110 can receive at one or more station place, and, can by receiving station's respective channel estimated between dispatching station and receiving station for referencial use.This exemplary PCCH comprises fields: (a) destination party MAC-ID; B () is for the distribution request of the expection transmitting continuous time at next TDD mac frame interval; C () transmission rate designator, is used to indicate the transformat of current data grouping; D () control channel (that is, CCH) subchannel, for receiving any dispensing section from AP; (e) CRC.PCCH 2120 and uncontrolled MIMO pilot tone 2110 are common segment, therefore can be received by various monitoring station (comprising access point).Can insert in PCCH and distribute request, connect so that realize managed some point in the TDD mac frame interval in future.Such PHY burst can be included in self-organizing connection, and, still can connect by the point-to-point of request scheduling in following TDD mac frame interval.In this exemplary embodiment, uncontrolled MIMO pilot tone is 8 OFDM symbol (in the following detailed description of in other embodiments, less symbol is just enough to realize channel estimating), and PCCH is two OFDM symbol.After common segment (comprising uncontrolled MIMO pilot tone 2110 and PCCH 2120), use the spatial reuse and/or higher modulation form determined by each STA in a some connection, send one or more data symbol 2130.This part of transmission is encoded according to the rate control information embedded in the data division of transmission.Therefore, a part for PHY burst 2100 can be received by multiple periphery stations, and the data of reality have passed through special finishing, so that high efficiency of transmission is to the station of one or more specific connection or AP.Data 2130 can carry out sending as access point distributes or, connect according to self-organizing and carry out sending (that is, based on the process of CSMA/CA competition).

An exemplary embodiment of PHY burst comprises a lead code, and it is made up of 8 OFDM symbol of uncontrolled MIMO reference.Equity Common Control Channel (PCCH) MAC-PDU stem is included in 2 follow-up OFDM symbol, employs STTD pattern, encodes with R=1/2BPSK.MAC-ID is 12 bits.Also comprise the distribution request of 8 bits, so that receive (therefore, largest request is 256 short OFDM symbol) by the expected duration of AP in next TDD mac frame interval.TX speed is 16 bits, for identifying the speed used in current group.FCCH subchannel preference is two bits, and corresponding to the preference between maximum four sub-channels, based on this, AP makes any applicable distribution.CRC is 10 bits.Other fields any amount of and/or field size can be included in other PHY and happen suddenly in embodiment.

In this embodiment, remaining MAC-PDU transmission uses the modulation of spatial reuse and the Geng Gao determined by each STA in a some connection.This part of this transmission carries out encoding according to the rate control information embedded in the data division transmitted.

Figure 22 gives an illustrative methods 2200 for point data transmission.In frame 2210, flow process starts, and wherein, a station sends uncontrolled MIMO pilot tone.In frame 2220, this station sends the information that can jointly decode.Such as, uncontrolled MIMO pilot tone 2110 and PCCH2120 are as an example of the mechanism of request dispatching in managed connection, and AP or other control stations need to decode to the signal section comprising this request.Those skilled in the art can recognize, also have other countless request mechanisms, dispatch for connecting a point on a shared channel.In frame 2230, according to the transformat consulted, data are sent to another station from a station.In this embodiment, controlled data sends with according to the determined speed of measurement result of uncontrolled MIMO pilot tone 2110 and parameter.Those skilled in the art can recognize, also have other means multiple to can be used to be sent as specific some channel and the data of repairing especially.

Figure 23 shows a kind of illustrative methods 2300 of point to point link.This illustrative methods 2300 gives many aspects, and a part for these aspects can be used in any specific embodiment.In decision block 2310, flow process starts.In decision block 2310, if there are data that STA-STA transmission will be carried out, then enter decision block 2320.If no, then enter frame 2370, perform the communication of any other type, comprise other access styles, if any.After entering frame 2360, flow process can return decision block 2310 and carry out repetition, or flow process can terminate.

In decision block 2320, if there are STA-STA data to transmit, then judging that this some point connects is scheduling type or self-organizing.If this transmission is scheduling type, then enter frame 2320, and the dispensing section of a TXOP is won in request.It should be noted that in the Stochastic accessing part at TDD mac frame interval, can send and distribute request, as mentioned above, or it can be included in self-organizing transmission.Once make distribution, so, in frame 2350, just can send a STA-STA physical burst.In one exemplary embodiment, method 2200 can be used for a class STA-STAPHY burst.

In decision block 2320, if do not wish that the some point of scheduling type connects, then enter in frame 2340, so that contention access power.Such as, the A-TCH 2010 sections at TDD mac frame interval 2000 can be used.When by after compete and successfully winning access right, enter frame 2350, and send a STA-STAPHY and happen suddenly, as mentioned above.

Enter decision block 2360 from frame 2350, wherein, flow process can repeat, as mentioned above, or, can stop.

Figure 24 shows a kind of illustrative methods 2400 providing Rate Feedback, connects for a point.Other steps that the figure shows various transmission and can be performed by two station STA 1 and STA 2.STA 1 sends a uncontrolled pilot tone 2410 to STA 2.STA 2, while the uncontrolled pilot tone 2410 of reception, measures channel 2420.In one exemplary embodiment, what STA 2 determined measured channel carries out to transmit can supporting rate.Using this speed determination result as Rate Feedback 2430, be sent to STA 1.In other embodiments various, other parameters can be transmitted, so that make Rate Feedback decision-making in STA 1.In 2440, STA 1 receives the dispensing section through scheduling, or contention transmission opportunities, such as, in A-TCH.Once win transmission opportunity, in 2450, STA 1 just with according to the determined speed of Rate Feedback 2430 and modulation format, sends data to STA2.

Can promote the use of in various embodiment by the method shown in Figure 24, this is apparent to those skilled in the art.To describe in further detail below and be integrated with some point velocity feedback and more otherwise examples.

The managed some point that method 2500 in Figure 25 shows between two station STA 1 and STA 2 and access point (AP) connects.In 2505, STA 1 sends uncontrolled pilot tone, and distributes request.Also can send data according to dispensing section comparatively early and previous Rate Feedback, will be explained below.In addition, according to from the previous managed Rate Feedback connecting or come the ad hoc communication that free STA 1 or STA 2 initiates, any such data can be sent.STA 2 and access point all can receive uncontrolled pilot tone and transmission request (can being received by other stations various in this region).

Access point receives transmission request, and according to the one in multiple dispatching algorithm, determines when and whether make the distribution for point to point link.STA 2 measures channel, and simultaneously in 2505, uncontrolled pilot tone is sent out away, thus STA 2 can determine to carry out with STA 1 point to point link can supporting rate.Alternatively, STA 2 also once can transmit according to front, receives the feedback from STA 1 and/or data.

In this embodiment, access point has been determined to provide allocative decision for asked transmission.In 2515, a dispensing section is transferred to STA 1 from access point.In this embodiment, the dispensing section on R-TCH540 transmits in control channel (CCH 520 described above).Equally, in 2520, for STA 2, make the allocative decision on R-TCH.In 2525, STA 1 receives the dispensing section from access point.In 2530, STA 2 receives the dispensing section from access point.

In 2535, feed back according to dispensing section 2520, STA 2 transmission rate.Alternatively, can comprise as above for dispatching the request of type transmission, and, any data that will send according to last request.As mentioned above, the Rate Feedback of transmission is selected according to channel measurement 2510.The PHY burst of 2535 also can comprise uncontrolled pilot tone.In 2540, STA 1 measures the channel from STA 2, receives feedback, and can receive optional data.

In 2545, send data according to dispensing section 2515, STA 1 according to the rate feedback information received.In addition, for the dispensing section in future, can request be made, and according to the channel measurement in 2540, provide Rate Feedback.The concrete channel measurement that data are believed according to click-through sends.In 2550, STA 2 receives data, and any speed sent alternatively controls.STA 2 also can measure channel, so that provide Rate Feedback for future transmission.

It should be noted that transmission 2535 and 2545 all can be access in a little to receive, is at least that non-controlled components can be received, as mentioned above.Therefore, for any request comprised, access point can provide the additional allocation section for future transmission, is represented respectively by the dispensing section 2555 and 2560 mailing to STA 1 and STA2.In 2565 and 2570, STA 1 and STA 2 receives respective dispensing section.Then, this flow process ad infinitum repeats, and wherein, the access on access point management shared medium, STA 1 and STA 2 is according to selected speed supported on a some channel and modulation format, directly sending point point communication mutually.Note that in other embodiments, also can perform self-organizing click-through letter, also perform managed click-through letter as shown in figure 25 simultaneously.

(that is, self-organizing) some point that Figure 26 shows based on competition connects.STA 1 communicates mutually with STA 2.Other STA also can be in range of receiving, and can access shared channel.In 2610, there are data that the STA 1 of STA 2 will be sent to monitor shared channel, and contention access power.Once win transmission opportunity, just send to STA 2, PHY burst 2615 also may be received by other STA a point PHY burst 2615.In 2620, monitor that other STA of shared channel may receive the transmission from STA 1, old friend avoids in road accessing this channel.Such as, above-described PCCH can be included in transmission 2615.In 2630, STA 2 to happen suddenly 2615 pilot tones according to PHY, measures channel, and competes the return access on shared channel.STA2 also can send data as required.Note, the competition time can change.Such as, in traditional 802.11 systems, after sifs, an ACK can be returned.Because SIFS priority is the highest, so STA 2 can make response when not losing channel.Other embodiments can reduce delay, and can provide high priority for return data.

In 2635, STA 2 is to STA 1 transmission rate feedback and optional data.In 2640, STA 1 receiving velocity feeds back, and competes the access right to shared channel again, and in 2645, according to the Rate Feedback received, sends signal to STA 2.In 2640, STA 1 can also measure channel, so that be provided for the Rate Feedback of future transmission to STA 2, and can receive any optional data sent out by STA 2.In 2650, the speed that STA 2 determines according to measured channel conditions and modulation format, receive transfer of data 2645.STA 2 also can feed back, for returning a transmission to STA 1 by receiving velocity.STA 2 also can measure channel, to provide following Rate Feedback.Therefore, get back in 2635, allow STA 2 return Rate Feedback and data, this flow process can repeat.

Therefore, two stations can be weighed by contention access and bidirectionally perform ad hoc communication.By the transmission using Rate Feedback and special finishing to mail to receiving station, make a some connection itself very efficient.When use PHY burst public can receiving unit (as PCCH) time, so, as shown in 2620, other STA can access this information, and avoid on channel, causing interference in the known holding time that shows in PCCH.As shown in figure 25, before the step shown in Figure 26, click-through letter that is managed or self-organizing can initiate transfer of data, and, can be used for proceeding click-through letter subsequently.Therefore, any combination that the click-through of scheduling type and self-organizing can be used to believe.

Figure 27 gives an exemplary TDD mac frame interval 2700, for illustration of the managed click-through letter between station.In this embodiment, F-TCH and the A-TCH duration is all set as 0.Beacon/BCH 510 and CCH 520 transmission the same as before.Beacon/BCH 560 represents the beginning of next frame.CCH 520 indicates the dispensing section for click-through letter.According to these dispensing sections, during the burst 2710 distributed, STA 1 sends signal to STA 2.Note that, in identical TDD mac frame interval, STA 2 distributes the section of obtaining 2730, for making response to STA 1.Above-mentioned various compositions can be comprised, as Rate Feedback, request, controlled and/or uncontrolled pilot tone, controlled and/or uncontrolled data in the burst of arbitrary specific some PHY layer.In dispensing section 2720, STA 3 sends signal to STA 4.In dispensing section 2740, STA 4 in a similar manner, sends signal to STA 3.Other rl transmission various can be comprised in R-TCH, comprise non-dots point and connect.Provide the additional exemplary embodiment that these and other aspects are described below further in detail.

Note that in figure 27, as required, can the protection interval between section be dispatched.A major issue about click-through letter is, under normal circumstances, the path delay between two STA is unknown.To this, a kind of processing method is, allows each STA keep its transmitting time to fix, thus makes the clock of they and AP synchronizedly arrive AP.In this case, AP can provide guard time at the two ends of each point-to-point dispensing section, to compensate the unknown path delay between the STA in two communication.Under many circumstances, Cyclic Prefix will be enough, and need not adjust in STA receiving area.Then, STA must determine their respective time deviations, so that know the transmission when receiving other STA.STA receiver may need maintenance two receive clocks: one for AP frame sequential, another connects for some point.

Described by various embodiments above, receiver can be confirmed and channel feedback in its dispensing section, and feeds back to transmitter.Even if total Business Stream is unidirectional, receiver also can send reference and request, to obtain dispensing section.AP scheduler ensures feedback to provide enough resources.

interoperability is carried out with conventional stations and access point

Just as described in detail here, described various embodiments provide the improvement relative to legacy system.But because legacy system extensively existed already, a system preferably can keep backward compatibility with existing legacy system and/or legacy user terminals.Term used herein " novel " is used for distinguishing with traditional system.The system of newtype can be integrated with the one or more aspect or feature described in detail here.An exemplary novel system describes MIMO ofdm system below in conjunction with Figure 35-52.In addition, be described below in detail for making the aspect of novel system and legacy system interoperability also be applicable to other systems still leaved for development, and no matter whether comprise any particular refinement described in detail here in this system.

In an exemplary embodiment, by using different parallel compensate (FA), backward compatibility can be kept with other system, thus a novel system is worked on the FA different from legacy user.Therefore, novel system can search for the available FA worked thereon.Dynamic frequency selection (DFS) algorithm can be implemented in this New WLAN, to realize this function.Preferably adopt the AP of multicarrier.

The traditional STA attempting to access WLAN can adopt two kinds of scan methods: active scan and drive sweep.When drive sweep, by scanning work frequency band, STA obtains the list of the feasible set of basic (BSS) near it.When active scan, STA sends a query messages, to ask the response from other STA in BSS.

How STA being determined to add which BSS, traditional standard is kept silent, but, once make a decision, just can attempt associating.If unsuccessful, STA will be moved by its BSS list, until success.When a traditional STA cannot understand sent beacon message, this STA can not attempt to be associated with a New WLAN.But as a kind of method maintaining single WLAN type on single FA, novel AP (and UT) can ignore the request from traditional STA.

Another kind of technology is, allows new A P or New type of S TA use effective tradition (that is, 802.11) message delivery techniques, refuses the request of any traditional STA.If a legacy system supports this message delivery techniques, then can provide redirect message for this STA of tradition.

The obvious drawback be associated is from working on different FA, supports that the STA of two types needs additional frequency spectrum.A benefit is, is convenient to manage different WLAN, and retains as functions such as QoS.But, just as described in detail in the application, for the high data rate that novel system is supported, traditional CSMA MAC protocol (as, those agreements described in detail in tradition 802.11 standards) usually efficient not, as the mimo system embodiment described in detail here.Therefore, preferably adopt the mode of operation of backward compatibility, coexist on identical FA with traditional MAC to make novel MAC.Several exemplary embodiments are described below, and wherein, tradition and novel system can share identical FA.

Figure 28 shows method 2800, for supporting tradition and novel both stations on identical parallel compensate.In this embodiment, for ease of illustrating, suppose that BSS works isolatedly (that is, less than cooperating between the BSS of multiple overlap).Flow process starts from frame 2810, uses traditional signaling to establish a uncontended periods.

Here is the several illustrated examples for traditional 802.11 systems, and wherein, New WLAN AP can use hook built-in in traditional 802.11 standards, the reserved time special by novel station.In addition, for various types of legacy system, other signaling technologys any amount of can be used, establish a uncontended periods.

A kind of technology is under PCF/HCF pattern, establish uncontended periods (CFP).AP can establish a beacon interval, and notices a uncontended periods in this beacon interval, and wherein, it can in the polling mode for novel and traditional STA provides service.This makes all traditional STA that its network allocation vector (NAV) is arranged to the duration of noticed CFP, and network allocation vector is used to the counter following the tracks of CFP.So in CFP, the traditional STA receiving this beacon must not use channel, unless by AP poll.

Another kind of technology be by RTS/CTS and duration/id field, establish CFP and NAV be set.In this case, this new A P can send the specific RTS that has reserved address (RA), shows this AP this channel reserved to all New type of S TA.This RA field is resolved to the specific STA of sensing one by traditional STA, and does not make response.A novel STA specific CTS makes response, thus, CTS/RTS message pair duration/id field in remove BSS in time period of providing.At this point, novel station freely can use channel within the reservation duration, and does not conflict.

In frame 2820, the traditional STA having received the signal for establishing uncontended periods waits for, until polled or uncontended periods terminates.Like this, access point is successfully assigned with shared medium, uses for novel MAC protocol.In frame 2830, new STA can access according to this agreement.Any set of the aspect described in detail here or subset may be used in so a kind of novel MAC protocol.Such as, forward direction and the rl transmission of scheduling type can be adopted, and, managed some point transmission, self-organizing or based on the communication (comprising a point) of competition, or, the combination in any of above-mentioned transmission.In frame 2840, use any one in multi-signal type, terminate novel access period, signal type can change according to adopted legacy system.In this exemplary embodiment, a uncontended periods end signal is sent.In another embodiment, in uncontended periods, also can poll tradition STA.Such access can after novel access, or, can intert wherein.

In frame 2850, if define a competing cycle for legacy system, then all STA can contention access power.Like this, the legacy system that can not carry out communicating in uncontended periods just can send request and/or attempt to send signal.In decision block 2860, this flow process can be continued by turning back to frame 2810, or, also can stop.

Figure 29 shows the combination of tradition and new media access control.Novel protocol 2930 gives traditional MAC protocol 2910, when both combines, just defines a MAC protocol, as the MAC protocol 2950 after combination.In this embodiment, for purpose of explanation, 802.11 traditional signaling message are employed.It will be recognized by those skilled in the art, technology disclosed herein is also applicable to any one in multiple legacy system and the novel MAC protocol of any one, comprises the combination of function disclosed herein.

Traditional MAC protocol 2910 comprises beacon 2902, and it identifies beacon interval.Traditional beacon interval comprises uncontended periods 2904, and what follow below is competing cycle 2906.Various contention free-poll frame 2908A-N can produce in uncontended periods 2904.Uncontended periods 2904 terminates 2910 by means of uncontended periods and stops.In 802.11 exemplary embodiments, each beacon 2902 was sent out away in target beacon transmitting time (TBTT) time.Novel MAC protocol 2930 comprises mac frame 2932A-N.

Beacon interval 2950 after merging describes tradition and the interoperability of novel MAC protocol in uncontended periods 2904.Comprising novel TDD mac frame interval 2932, what follow below is traditional poll, CF poll frame 2908A-N.Uncontended periods ends at CFPEND 2910, and what follow below is competing cycle 2906.Novel TDD mac frame interval 2932 can be any type, comprises the various aspects described in detail alternatively here.In one exemplary embodiment, novel TDD mac frame interval 2932 comprises various sections, as those sections described in conjunction with Figure 20 above.Therefore, in this embodiment, novel TDD mac frame interval comprises pilot tone 510, control channel 520, fl transmission channel 530, self-organizing point point part (A-TCH) 2010, reverse link traffic channel 540 and Random Access Channel 550.

Note that in CFP 2904, traditional STA should not disturb any New WLAN to transmit.AP can in CFP any traditional STA of poll, thus allow in this paragraph to carry out mixed mode operations.In addition, AP can reserve whole CFP 2904 for novel use, and pushes all traditional businesses to competing cycle (CP) 2906 at the end of beacon interval.

These exemplary 802.11 traditional standards need CP 2906 to look to be enough to the exchange between support two conventional terminals.So, can beacon be adopted, but this can cause the time jitter (time jitter) in system.If necessary, in order to reduce shake, CFP interval can be shortened, thus keep fixing beacon interval.Timer for establishing CFP and CP can be set, to make CFP (that is, about 1.024 seconds) longer than CP (that is, being less than 10 milliseconds).But if AP poll conventional terminal during CFP, then the duration of their transmission may be unknown, and may cause extra time jitter.Therefore, when being contained on identical FA by traditional STA, must be noted that the QoS keeping New type of S TA.802.11 traditional standard synchronisation are to the time quantum (TU) of 1.024 milliseconds.In this embodiment, adopt the mac frame duration of 2TU or 2.048 millisecond, novel MAC can be designed to synchronous with legacy system.

In some embodiments, preferably guarantee to make novel mac frame synchronous.That is, the mac frame clock of system can be continuous, and when sending, this mac frame border starts from the integral multiple of 2.048 milliseconds of frame periods.Like this, the sleep pattern keeping STA is easy to.

Novel Delivery does not need with conventional transmission compatible.Stem, lead code etc. can be distinctive for novel system, and their example runs through in the application and has been described in detail.Tradition STA can attempt its demodulation, but cannot correctly decode.Traditional STA under sleep pattern can not be affected usually.

Figure 30 shows the method 3000 obtaining transmission opportunity.Method 3000 can be used as the frame 2830 in an exemplary embodiment of method 2800, as mentioned above.This flow process starts from decision block 3010, and wherein, access can be scheduling type, or non-scheduled type.It will be recognized by those skilled in the art, although this is illustrated the access of two types, in any specific embodiment, can to support in these two kinds of access styles one or both of.In decision block 3010, if expect the access of non-scheduled type, then enter frame 3040, thus contention access power.Any amount of access technology based on competition can be used.Once obtain transmission opportunity (TXOP), then send according to this transmission opportunity in frame 3050.Then, flow process can terminate.

In frame 3010, if expect the access of scheduling type, then enter frame 3020, to ask access.This access request can be made on a random access channel during Self-organizing Competition, or, use any other technology disclosed herein.In frame 3030, after this access request goes through, a dispensing section will be received.Enter in frame 3050, according to the dispensing section received, send TXOP.

In some cases, preferably use overlapping traditional B SS, in identical parallel compensate, between new A P and the BSS that is associated thereof, realize interoperability.Under traditional B SS can be operated in DCF or PCF/HCF pattern, so between novel B SS and traditional B SS may not be synchronously to reach.

If under traditional B SS is operated in PCF or HCF pattern, then new A P can attempt to be synchronized to TBTT.If this is possible, then new A P can use various mechanism to occupy channel in competing cycle, has made description to its example above, so that be operated in overlapping BSS region.If under traditional B SS is operated in DCF, then new A P also can attempt to occupy channel, and notices a CFP, to remove channel.

In some cases, some or all STA in traditional B SS may can not receive new A P transmission.In this case, these traditional STA may disturb the operation of New WLAN.In order to avoid this interference, novel station can be given tacit consent to based on CSMA operation, and relies on some point transmission (also being described in further detail it by composition graphs 33-34) below.

Figure 31 shows a kind of exemplary method 3100, shares single FA to make multiple BSS.In frame 3110, conventional access points sends a beacon.The novel access point sharing identical frequency assignments can be synchronized to the TBTT (optionally) be associated with this beacon.In frame 3120, if traditional uncontended periods specifies according to this beacon, then perform it.Once uncontended periods (if any) terminates, then all STA just can weigh by contention access in the competing cycle of regulation.In frame 3130, novel access point is contention access power in competing cycle.In frame 3140, New type of S TA has competed in the time of access right can access shared medium at novel access point.Access style during this novel access can comprise to be described in detail in any one here.The multiple technologies as described in detail can being used above, indicating the time quantum of this access point channel reservation to traditional STA.In frame 3150, once this end cycle, then traditional STA just can compete.In decision block 3160, this flow process can continue by turning back in frame 3110, or, can terminate.

Figure 32 shows the overlapping BSS using single FA.Legacy system 3210 sends beacon 3205 (there is shown 3205A and 3205B, TBTT and total beacon interval for illustration of legacy system).Beacon 3205A identifies uncontended periods 3210 and competing cycle 3215.In uncontended periods 3210, can perform traditional contention free-poll frame 3220A-N, what follow below is the end indicator 3225 of uncontended periods.

Station monitoring channel in New WLAN 3240, receives beacon 3205, and gains control of oneself and do not access media, until the chance of contention access power is arrived.In this embodiment, chance is the earliest in uncontended periods.After PIFS 3230, novel access point sends a classical signal 3245 to conventional stations, to indicate the time quantum of busy channel.Multiple symbol can be used to perform this function, and their example has been described in detail above.Can adopt other signals various, this depends on expects which legacy system to realize interoperability with.Traditional STA in the range of receiving of classical signal 3245 can avoid accessing channel, until novel access period 3250 terminates.Cycle 3250 comprises one or more TDD mac frame interval 3260 (in this embodiment, being 3260A-N).TDD mac frame interval 3260 can be any type, and its example comprises the one or more aspects described in detail here.

In an exemplary embodiment, new A P occupies channel (that is, in every 40 milliseconds, new A P busy channel 20 milliseconds) in the interval of fixed length.New A P can maintain a timer, to guarantee its only busy channel in expected duration, thus ensures the fairness of Channel Sharing.In the process seizing channel, new A P can use any signaling technology.Such as, CTS/RTS or conventional beacon can be sent, notice new CFP.

In novel interval 3250, exemplary TDD mac frame interval can as given a definition: first, send a beacon and add F-CCH, will UT in current MAC frame on polling list to indicate.After F-CCH, broadcast one section of MIMO pilot tone, obtain mimo channel to make STA and form the accurate measurement results of mimo channel.In one exemplary embodiment, each antenna 2 short OFDM symbol, can realize fabulous performance.This means, the F-TCH in initial mac frame comprises 8 MIMO frequency pilot signs substantially.The R-TCH part of the first mac frame can so construct: to make the STA on polling list send uncontrolled MIMO pilot tone and rate indicator (for down link) to AP, and confirm.In this embodiment, at this point, under all terminals on polling list prepare to be operated in normal consistency type mode in next TDD mac frame interval.After this, under the coordination of AP, use any one technology disclosed herein, the TDD mac frame interval after a TDD mac frame interval can be used for swap data.

As mentioned above, under specific circumstances (such as, when some or all STA in traditional B SS can not receive new A P transmission), novel station acquiescence based on the operation of CSMA, and relies on the transmission of some point.Now, above-described on/off cycling may not have advantage, or, or even impossible.In these cases, a point operation can be given tacit consent in novel station.

Figure 33 gives a kind of illustrative methods 3300, and it uses various technology disclosed herein, performs high speed click-through letter, simultaneously with traditional B SS interoperability.Flow process starts from frame 3310, wherein, has data will issue a STA contention access power of the 2nd STA.In frame 3320, after successful contention to access right, this station uses classical signal, as described above those signals, cleaning media.In frame 3330, a STA sends a request (together with pilot tone) to the 2nd STA.2nd STA according to sent pilot tone, can measure channel.Channel feedback is sent to a STA by the 2nd STA.Therefore, in frame 3340, first stop receives the response with channel feedback (such as, Rate Feedback).In frame 3350, according to this feedback, a STA sends pilot tone and controlled data to second station.In frame 3360, the 2nd STA can send to a STA and confirm, and can send follow-up Rate Feedback, for other transmission.The classical signal being used for clearing up media makes: use any one high speed technology and the improvement relative to legacy system, as disclosed herein those technology, performs frame 3330 to 3360.In protection scope of the present invention, once STA has cleared up media, any some point MAC protocol just can be used.Flow process returns frame 3310 and can be continued, as shown in decision block 3370 or, flow process can terminate.

In one exemplary embodiment, adopt some dot pattern, seize channel and work according to the traditional rule of CSMA.In this embodiment, do not adopt PCF and HCF, and a centralized network architecture need not be had.When a New type of S TA wishes to communicate with another New type of S TA (or AP), this STA seizes channel.First transmission comprises enough MIMO pilot tones, adds the message that a certain request connects.CTS and RTS can be adopted to carry out cut-back region and set aside some time.Requesting party STA message must comprise STA BSS ID, STA MAC ID and target STAMAC ID (if knowing).Response should comprise the BSSID of responder STA.Like this, these STA just can judge that they correct, if employ guiding (steering) the need of performing the receiver launching guiding (transmitsteering) vector.Note that not use in this embodiment and launch guiding, but to do like this be advantageous, if STA has used the appointment AP that coordinates BSS and calibrated.

As shown in figure 33, response can comprise MIMO pilot tone (if employed, being controlled), adds speed instruction.Once this exchange occurs, just can carry out on each link guiding (steering).But if these STA belong to different BSS, then the first controlled transfer between the STA initiating this connection can comprise steered mimo pilot signal, correct phase difference value between different B SS to enable the receiver of responder STA.

In this exemplary embodiment, once there occurs initial exchange, just can guide.These exchanges should follow the SIFS interval between down link and ul transmissions.Owing to calculating the potential processing delay for carrying out in the characteristic vector guided, this may need STA to use least mean-square error (MMSE) process, instead of characteristic vector process.Once calculate steering vector, STA just can start at launch party's use characteristic vector, and recipient can continue to adopt MMSE process, changes towards optimal spatial matched filter solution.Periodic feedback between two STA contributes to carrying out tracking and speed control.SIFS interval can be followed, so that allow STA keep control to channel.

Figure 34 shows click-through letter, its operation technique MIMO technology, contention access power (that is, managed) on traditional B SS.In this embodiment, initiator 106A contention access power on channel.When it successfully rob account for channel time, send MIMO pilot tone 3405, after and then request 3410 again.This message can comprise BSS ID, the MAC ID of initiator STA and the MAC ID of target STA, if known words.Other signalings, as CTS and RTS, can be used to clear up channel further.Responder STA 106B sends controlled pilot 3420, after and then confirm and Rate Feedback 3425.Send during the SIFS 3415 of controlled pilot 3420 after request 3410.In this exemplary embodiment, conventional access points is 802.11 access points, and SIFS has limit priority, and therefore, response station 106B keeps the control to channel.The various transmission that Figure 34 describes in detail can phase mutual edge distance SIFS and sending, thus keeps the control to channel, until click-through letter terminates.

In one exemplary embodiment, the maximum duration of channel occupancy can be determined.Controlled pilot 3430 after Rate Feedback 3425 and data 3435, according to this Rate Feedback, are sent to response station STA 106B from initiator STA 106A.After data 3435, responder STA 106B sends controlled pilot 3440 and confirms and speed control 3445.Responsively, initiator 106A sends controlled pilot 3450, after then data 3455.

This flow process can ad infinitum continue, or reaches at most the maximum time that channel access allows, and this depends on deployment cycle.Although not display in Figure 34, responder STA also can send data, and initiator also can sending rate control.These data segments can combine with those sections shown in Figure 34, to make maximizing efficiency (that is, SIFS need not be inserted between these transmission).

When two or more BSS is overlapping, preferably adopting can with the mechanism of cooperation mode shared channel.Provide several exemplary mechanism and exemplary operational process associated with it below.These mechanism can combine use.

The first exemplary mechanism is dynamic frequency selection (DFS).Before establishment BSS, WLAN needs to search for this wireless medium to determine best parallel compensate (FA), so that establish the operation of BSS.In the process of search candidate FA, AP also can create neighbor list, so that carry out being redirected and switching between AP.In addition, mac frame sequential can be carried out synchronous (will further illustrate below) with neighbours BSS by WLAN.DFS can be used to distribute BSS, thus synchronisation requirement between BSS is minimized.

The exemplary mechanism of the second is synchronous between BSS.In DFS process, AP can obtain the sequential of neighbours BSS.Usually, preferably make all BSS (in one embodiment, on single FA, or, in another embodiment, stride across multiple FA) synchronous, so that carry out switching between BSS.But, adopt this mechanism, at least work on identical FA and those BSS approximating its mac frame synchronous.In addition, if altogether channel BSS overlap (that is, AP can listen to the other side each other), then can be there is situation and informed original AP in newly arrived AP, and formulate Resource Sharing Protocol as follows.

The third exemplary mechanism is Resource Sharing Protocol.BSS overlapping on same FA can shared channel coequally.Mac frame can be made to replace between BSS according to certain predetermined way, thus realize this point.Like this, the business in each BSS just can use channel, and can not emit the risk disturbed by other BSS.Like this shared can be implemented between two overlapping BSS.Such as, when 2 BSS overlaps, an AP uses the mac frame of even-numbered, and another AP uses the mac frame of odd-numbered.When three BSS overlaps, sharing can with 3 for mould realizes.Other embodiments can adopt the shared mechanism of any type.Control field in BCH Overhead Message can show the type whether can carrying out resource-sharing and shared cycle.In this embodiment, in BSS, the sequential of all STA adjusts to the suitable shared cycle.In this embodiment, when BSS overlap, time delay will increase.

4th kind of exemplary mechanism is auxiliary synchronous again of STA.This situation may be there is: two BSS can't hear the other side each other, but a new STA in overlapping region can hear they two.This STA can determine the sequential of these two BSS, and this is reported to them.In addition, this STA can determine time deviation, and indicates which AP should change its frame sequential and change how many.This information must propagate into all BSS be connected with this AP, and they all must re-establish frame sequential, synchronous to realize.Synchronously can noticing in BCH again of frame.This algorithm can be applied to process more how unconscious overlapping BSS.

The example process that can be used for one or more mechanism above-mentioned is described below in detail.

AP or can realize synchronous when powering up in other fixed times.By system near search in all FA, can the certainty annuity time.For ease of synchronously, one group of orthogonal code can be used for assisting to distinguish different AP.Such as, AP has the known beacon of repetition in each mac frame.These beacons can use Walsh sequence (such as, length is 16) to cover.Therefore, the equipment of such as AP or STA and so on can perform the pilot frequency intensity measuring (PSM) of local AP, to determine overlapping BSS.To further describe below, the movable STA be associated with an AP can send echo, synchronous to assist.These echoes can use the sequential corresponding with AP overlay code (cover) and soverlay technique (covering).Therefore, when BSS is overlapping but these BSS AP separately cannot detect the signal from the other side, STA echo can be received by neighbor AP, thus provide its AP for information about and neighbor AP can be synchronous signal.Note that and can reuse orthogonal overlay code on different FA.

Based on the set of undetected Walsh overlay code, can complete to certainty the selection (that is, selecting a Walsh overlay code do not detected in neighbor AP) of Walsh overlay code.If all overlay codes all exist, then corresponding with the most weak received signal level (RSL) code can be reused by new AP.Otherwise, in one embodiment, can select to make the maximized code in the working point of AP (refer to the reusable structuring power compensated mechanism of self adaptation, also will be described in detail to this) below.

In this embodiment, the frame counter sent by each AP is interlaced with each other to come.The interlace mode adopted corresponds to Walsh overlay code label.Therefore, AP0 uses Walsh code 0.As AP0 frame counter=j, APj uses Walsh overlay code j, and its frame counter equals 0.

When powering up or will perform the synchronous any time, AP monitors neighbor AP beacon and/or STA echo.If neighbor system do not detected, then AP establishes its time reference.This can be arbitrary, or relevant to GPS, or any other local time reference.If individual system detected, then correspondingly establish local zone time.If AP detects two or more system done with different time lineman, then AP can carry out synchronous with the system with peak signal.If these system works are on identical parallel compensate (FA), then AP can attempt to be associated with more weak AP, thus inform that it is operated on independent clock other near AP.This new AP attempts the time deviation needed for synchronous Liang Ge AP district to inform more weak AP.More weak district AP can adjust its sequential.For multiple neighbor AP, this can repeat.With the synchronous sequence of two or more system, new AP can establish its sequential.If all neighbor AP all can not be synchronized to single sequential (no matter being what reason), then this new AP can be synchronized to any one neighbor AP.

AP can perform dynamic frequency selection when powering up.As mentioned above, under normal circumstances, preferably select to make BSS overlap minimum by DFS, thus the quantity of the BSS making needs synchronous and any delay associated with this locking phase or throughput reduce and minimize (namely, compare and must share the BSS of these media with one or more neighbours BSS, the BSS that a FA can access whole media is more efficient).After synchronous, new AP can select the FA (that is, when measuring neighbor AP, or during echo) with minimum RSL.AP periodically can inquire STA, so that carry out AP pilot measurement.Equally, AP can dispatch silence period, to assess the level of interference that AP place is caused by the STA from other districts (i.e. neighbor bss S).If this RSL grade is excessive, then AP can attempt finding another FA within the non-scheduled cycle, and/or braking power compensation policy, as described below.

As mentioned above, according to pilot tone overlay code, AP can be organized.In this embodiment, each AP can use length be 16 Walsh sequential covering code.The code of a different length arbitrarily can be used.Pilot tone overlay code is used for the signal at a super frame period internal modulation beacon.In this embodiment, super frame period equals 32 milliseconds (that is, 16 continuous N AC frame beacons).Then, STA can in superframe interval coherently integration, to determine and the pilot power that a specific AP is associated.As mentioned above, AP can select its Walsh code from undetected multiple available Walsh code.If all codes (on identical FA) detected, then AP can according to the most weak secondary ordered pair, they be ranked from the strongest.AP can reuse the Walsh code corresponding with the most weak Walsh code detected.

For ease of identifying neighbor AP, STA can be used for sending echo, to identify their corresponding AP.Therefore, as mentioned above, do not detect that an AP of neighbor AP may detect corresponding STA echo, thus identify this AP and sequential thereof.Each AP can send configuration information in its beacon, and each STA can serve as repeater, so that resend AP configuration information and sequential to the neighbor AP of any reception.

When receiving the order from AP, the pattern that movable STA needs transmission one predetermined, detects the existence of this neighbor system to make to be operated in AP near on identical FA.A kind of simple method defines an observation interval (such as, between FCH and RCH) in mac frame, and it is not used for any business by AP.The duration of observation interval can be defined as long enough, with process maximum different propagation delay between STA that this AP is associated and the STA that neighbor AP is associated (such as, 160 chips, or, 2 OFDM symbol).Such as, the STA using the AP of Walsh overlay code j to be associated can send echo when its mac frame counter=0.On this echo, coding has and makes neighbor AP detect existence and to coexist efficiently necessary information with the STA in adjacent AP district.

The reusable structuring power back-off (backoff) of self adaptation can be adopted.When system is crowded must reuse near another AP to each FA time, preferably can apply a kind of structurized power compensated mechanism, with the terminal in Shi Liangge district all with maximal efficiency work.When detecting crowded, power can be used to control, improve the efficiency of system.That is, be not whenever all send with total power, AP can use the structurized power compensated mechanism of one with their mac frame counter synchronisation.

Such as, suppose that two AP are operated on identical FA.Once these AP detect this situation, they will work out known power back-off strategy.Such as, two AP use a kind of compensation mechanism, and it makes: total power Ptot on mac frame 0, Ptot (15/16) on mac frame 1 ..., Ptot/16 on mac frame 15.Due to AP be synchronous and they frame counter interlock, so, do not have AP district to use total power simultaneously.This target is the compensation model selecting the STAs in each AP district is worked with highest-possible throughput.

Specific AP compensation model used can be the function of the degree of disturbance detected.In this embodiment, specific AP can use maximum 16 known compensation models.AP in BCH and in the echo of the STA transmission be associated by AP, can transmit compensation model used.

Walton etc. make, exercise question is the United States Patent (USP) 6 of " Method and apparatus for controllingtransmissions of a communications systems ", 493, describe a kind of exemplary compensation mechanism in 331 in detail, this patent has transferred assignee of the present invention.

Figure 53 shows and can carry out another exemplary embodiment of the technology of interoperability with legacy system.There is shown an exemplary mac frame 1500, in conjunction with Figure 15, it is elaborated above.Also introduce a kind of time slotted pattern, wherein, define slot time 5310.Slot time 5310 comprises MIMO pilot interval 5315 and time slot gap 5320.As shown in the figure, insert pilot tone 5315, with this channel reserved, make it from the impact at other stations (comprising AP) of the Rules according to such as EDCA and so on.The mac frame 5330 improved consists essentially of mac frame 1500, wherein inserts pilot tone 5315, so that keep the control to media.Figure 53 is illustrative, and to those skilled in the art, this is apparent.Time slotted pattern can combine with the mac frame of any type, describes its various example here in detail.

In this embodiment, for ease of illustrating, suppose that the mac frame of 802.11 traditional systems uses is integral multiples of 1.204 milliseconds.Mac frame can be set to 2.048 milliseconds, so that synchronously.At target beacon transmitting time (TBTT), notice the CFP duration, its NAV is set to make STA.During CFP, the STA in BSS should not send signal, unless polled.As previously mentioned, AP also can send RTS, and allows STA respond an identical CTS, to clear up BSS further.This CTS can be the synchronous transmission from all STA.In this embodiment, by guaranteeing that mac frame always starts from 2.048 milliseconds of borders, shake can be eliminated.Like this, even if when TBTT shortens, also hold time between adjacent/overlapping BSS synchronous.Above-described various other technologies can be got up with combine with technique described below.Once reserve media for amended mac frame 5330, just can use any techniques available, adopt time slotted pattern to keep the right of possession corporeal right to media, the transmission being subject to dispatch is disturbed to prevent traditional STA, thus (namely the throughput reducing novel system potentially increases, use mechanism shown in Figure 15 or Figure 53, or other mechanism described in detail here).

In this embodiment, new A P follows CSMA rule to seize channel.But before this, it or should listen to beacon, or other STA, attempt to determine whether there is another BSS.But, in order to realize fair resource-sharing, do not need synchronous.

Once neighbours BSS be detected, this new A P just can seize channel by sending its beacon.In order to stop (lock out) other users, this new A P sends the pilot tone with a certain frequency, thus prevents other STA from using this channel (that is, not having idling cycle to be longer than PIFS=25usec).

This new A P can arrange one can make it at the timer determining to take in the fair fixing duration this channel.Like this can roughly with the Beacon Period Synchronization of traditional AP, or asynchronous (that is, every 200 milliseconds in 100 milliseconds).

This new A P can seize channel by any point in the interval that it allows, and this can be postponed by traditional B session service user.If do not have business to serve, this new A P can abandon channel before its time expires.When this new A P occupies channel, it is used to be restricted to just time period.In addition, the sequential that this new A P establishes can be consistent with original mac frame sequential.That is, novel beacon appears on 2.048 milliseconds of borders of new A P clock.Like this, New type of S TA by observing these specific intervals, can judge whether HTAP occupies channel, thus keeps synchronous.

This new A P can notice its frame parameter in a beacon.A part for frame parameter can comprise pilot interval spacing, for representing the frequency of pilot transmission in this mac frame.Note that this new A P can dispatch STA, overlapping with periodic burst pilot to make it transmit.In this case, the STA of dispensing section overlap knows this point, and ignores pilot tone within this cycle.Other STA do not know this point, therefore use a threshold supervision device, confirm what whether pilot tone sent in predetermined distance.

This situation may be there is: the moment that STA will undertaken sending by AP originally have sent pilot signal, or AP sends controlled pilot signal to STA in this interval.Worsen its channel estimating to prevent other STA from using this pilot signal, AP pilot signal can use the Walsh overlay code mutually orthogonal with public guide frequency Walsh overlay code.The structure for distributing Walsh overlay code can be adopted.Such as, when STA and AP uses different Walsh overlay codes, Walsh space can comprise 2N overlay code, N number of overlay code wherein for AP reserve, and other overlay code to be STA for being associated with a specific AP reserved, the overlay code that these STA use associates with the Walsh overlay code of corresponding AP in a known way.

When this new A P sends assignment information to a STA, it expects that this STA sends to it in predetermined distance.This STA may not receive this assignment information, and in this case, channel may be longer than PIFS by the interval used.In order to prevent this situation, AP can detect channel in t < SIFS, and judges that whether it is occupied.If unoccupied, then AP by sending the pilot tone of corresponding phasing, can seize channel immediately.

Novel channel allocation section time slot can be changed into the interval (16usec) of SIFS.Like this, channel occupancy just can be protected, thus refuses legacy user within the new exclusive cycle.

RCH must be designed to support interoperability, this is because the duration of RCH may more than 16usec.If this RCH can not be provided easily In a particular embodiment, so, when novel MAC does not have channel control weight (that is, coexisting under traditional mode), can distribute under this RCH is operated in traditional mode.By allowing any time of STA after pilot transmission (that is, wait for 4 microseconds, and send 8 microseconds) to send access request, F-RCH can be provided, as shown in Figure 53.

exemplary embodiment: 802.11 MIMO WLAN of enhancing

The exemplary embodiment be described below in detail illustrates above-mentioned various aspects and other aspects.In this embodiment, the enhancing 802.11WLAN using MIMO is shown.Various MAC will be described in detail strengthen, and, be used in the corresponding data in MAC layer and physical layer and messaging structure.It will be recognized by those skilled in the art, disclose only a part for WLAN feature, and they can make content disclosed herein be applicable to 802.11 legacy system interoperability, and, with the interoperability of various other system.

The exemplary embodiment be described below in detail is characterised in that: can with traditional 802.11a, 802.11g STA interoperability, and, can with the ultimate criterion interoperability of 802.11e draft and expection.This exemplary embodiment comprises MIMO OFDMAP, and so name is to distinguish with traditional AP phase.Also will describe in detail below, due to backwards compatibility, traditional STA can be associated with MIMO OFDM AP.But MIMO OFDM AP can refuse the association request from traditional STA clearly, if necessary.DFS process can be directed to unaccepted STA the AP (can be traditional AP or another MIMO OFDMAP) that another supports traditional operation.

MIMO OFDM STA can be associated with wherein not having 802.11a or the 802.11g BSS of AP or independent BSS (IBSS).Therefore, for this operation, such a STA will realize all necessary functions of 802.11a, 802.11g and 802.11e expection final version.

In BSS or IBSS, when tradition and MIMO OFDM STA share identical RF channel, support various function.The spectral mask of the MIMO OFDM PHY spectral mask advised and existing 802.11a, 802.11g is compatible, thus, additional adjacent-channel interference can not be introduced to traditional STA.PLCP stem (the following detailed description of) in extended signal field with tradition 802.11 signal field backward compatibility.Rate value non-in legacy signal field is configured to define new PPDU type (will describe in detail) below.Adaptive cooperation function (ACF) (will describe in detail below) can make the media between tradition and MIMO OFDM STA realize sharing arbitrarily.The cycle of 802.11e EDCA, 802.11e CAP and SCAP can insert arbitrarily any beacon interval, and this is determined by AP scheduler.

As mentioned above, the high data rate effectively realizing the support of MIMO WLAN physical layer with high-performance MAC is needed.Each attribute of this exemplary MAC embodiment is described below in detail.Here is some exemplary attributes:

The self adaptation of PHY speed and transmission mode, effectively utilizes the capacity of mimo channel.

The low delay service of PHY provides low end-to-end delay, to solve the demand that high-throughput (such as, multimedia) is applied.The MAC technology based on competition is adopted when low load, or, use centralized or distributed scheduling when heavy duty system, low delay operation can be realized.Low delay has a lot of benefit.Such as, low delay can realize quick self-adapted, thus physical layer data rate is maximized.Low delay can realize cheap MAC with minibuffer device, and need not stop ARQ.For multimedia and high-throughput application, low delay also makes end-to-end delay minimize.

Another attribute is high MAC efficiency and low competition expense.In the MAC based on competition, during data rate height, the time shorten that useful transmission takies, and the incremental portion of this time is wasted in expense, conflict and idling cycle.By scheduling, and, by being aggregated in single mac frame by multiple high layer packets (such as, IP datagram), the time wasted in the media can be reduced.Also can form aggregate frame, thus reduce lead code and training expense.

The high data rate that PHY supports can realize the QoS process simplified.

The following detailed description of exemplary MAC strengthen and to keep the mode of backward compatibility with 802.11g and 802.11a, above-mentioned performance issue can be solved.In addition, as mentioned above, support and the improvement of the function comprised in draft standard 802.11e comprise following functions, as TXOP and direct link agreement (DLP), and, optional block affirmation mechanism.

In order to describe the following examples, for some concepts presented hereinbefore, use new term.The mapping of new terminology is as shown in table 1:

Table 1, term mapping table

frame aggregation flexibly

In this embodiment, frame aggregation is flexibly easy to realize.Figure 35 shows and encapsulate one or more mac frame (or segment) in an aggregate frame.Frame aggregation can be encapsulated in an aggregate frame 3520 one or more mac frame (or segment) 3510, wherein can add header compressed, will be described in detail below to this.Polymerization mac frame 3520 forms PSDU 3530, can be used as a PPDU and sends.Aggregate frame 3520 can containing type be frame (or segment) 3510 after the encapsulation of data, management or control.When needs privacy, can be encrypted frame load.The mac frame stem of encrypted frame is that " be in expressly state under (in the clear) " transmits.

Frame when not having IFS or BIFS (burst frame spacing will further describe) below, can be transferred to identical recipient STA by this frame aggregation of MAC layer as above.In some applications, preferably making AP when there is no IFS by multiple frame or aggregate frame, being sent to multiple recipient STA.By using SCHED frame, can this point be realized, also will discuss to this below.The time started of the multiple TXOP of SCHED frame definition.When AP to multiple recipient STA carry out back-to-back (back-to-back) transmit time, can without lead code and IFS.This is called as PPDU polymerization, to be different from the frame aggregation of MAC layer.

Exemplary polymerization mac frame transmission (i.e. PPDU) beginning is lead code, then be that MIMO OFDM PLCP stem (comprises signal field, this signal field can comprise signal 1 and signal 2), then be MIMO OFDM training symbol (if any) below.Exemplary PPDU form is further described below in conjunction with Figure 49-52.Polymerization mac frame has been polymerized one or more frame or segment that will be sent to identical recipient STA neatly.(the following detailed description of SCHED message allow be polymerized from AP to the TXOP of multiple recipient STA).For the quantity of polymerisable frame and segment, not restriction.Full-size for the aggregate frame of establishing through consultation can be restricted.Usually, first frame in aggregate frame and last frame may be the segments created in order to efficient package.When the Frame after multiple encapsulation is included in an aggregate frame, MAC stem and the QoS data frame of data can compress, as described below.

By using frame aggregation flexibly, transmit leg MAC can reduce PHY and PLCP expense and idling cycle as possible.Frame can be polymerized, to eliminate frame pitch and PLCP stem, and frame segmentation flexibly, to take the free space in TXOP completely, realizes this point.In a kind of example technique, based on current data rate and distribute or based on duration of TXOP of competition, MAC first calculates the byte number that will be supplied to PHY.Then, the mac frame after complete and segmentation can be packed, to take whole TXOP.

If a complete frame can not be contained in the remaining space in TXOP, then next frame can be carried out segmentation by MAC, to take remainder bytes as much as possible in TXOP.In order to package efficiently, segmentation can be carried out to frame.In one exemplary embodiment, this any segmentation will be subject to the restriction of maximum 16 segments of every frame.In other embodiments, this restriction can not be needed.The residue segment of mac frame can send in follow-up TXOP.In follow-up TXOP, MAC can give higher priority the frame of non-complete transmission, if desired.

The following detailed description of polymerization stem (being 2 bytes in this embodiment) be inserted into the MAC stem of each encapsulated frame (or segment), encapsulated frame (or segment) is inserted in aggregate frame.Length field in polymerization stem represents the length (unit is byte) of the rear mac frame of encapsulation, and is used for from aggregate frame, extract frame (and segment) by receiver.PPDU size field in the signal field advised specifies the size (quantity of OFDM symbol) that MIMO OFDM PPDU transmits, and the length of mac frame after each encapsulation indicates by being polymerized stem.

encapsulated frame header compressed

Figure 36 shows a traditional mac frame 3600, it comprises MAC stem 3660, what follow below is frame entity 3650 (can comprise the N number of byte of variable number) and frame check symbol (FCS) 3655 (in this embodiment, being 4 bytes).The prior art mac frame form is described in detail in 802.1 le.MAC stem 3660 comprises: frame control field 3610 (2 bytes), duration/id field 3615 (2 bytes), sequence control field 3635 (2 bytes) and QoS control field 3645 (2 bytes).In addition, four address fields are also comprised: address 13620, address 23625, address 33630 and address 43640 (each is 6 bytes).Also these addresses can be called TA, RA, SA and DA.TA is transmitter station address, and RA is destination address, and SA is source station address, and DA is address, point of destination.

When comprising multiple encapsulation of data frame in an aggregate frame, the MAC stem of data and QoS data frame can be compressed.Such as, Figure 37-39 shows the MAC stem after compression and QoS data frame.Note that FCS calculates according to the MAC stem after compression and (encryption or unencrypted) load.

As shown in figs. 37-39, when with MIMO data PPDU (type 0000) transmission frame, in the MAC stem 3660 of mac frame 3600, introduce a polymerization header field, thus create the mac frame after encapsulation, namely 3705,3805 or 3905.MAC stem, comprises polymerization header field, is called as the MAC stem (namely 3700,3800 or 3900) of expansion.Management after one or more encapsulation, control and/or Frame (comprising QoS data) can be aggregated in the mac frame after polymerization.When usage data privacy, can be encrypted data payload or QoS data frame.

For each frame (or segment) be inserted in aggregate frame (being respectively 3705,3805 or 3905), insert polymerization stem 3710.The header compressed polymerization first portion type field by being described below in detail indicates.Frame stem and the QoS data frame of data can compress, to eliminate redundant field.The aggregate frame 3705 provided in Figure 37 shows a kind of unpressed frame, it comprise all four addresses and duration/id field.

After sending a unpressed aggregate frame, other aggregate frame just need not identify dispatching station and destination address, because they are identical.Therefore, address 13620 and address 23625 can be omitted.For the subsequent frame in aggregate frame, need not comprise duration/id field 3615.Duration is for setting NAV.Duration/id field is determined on a case-by-case basis.In polling message, it comprises access ID (AID).In other message, identical field indicates the duration for setting NAV.Corresponding frame 3805 has been shown in Figure 38.

When source address and address, point of destination comprise identical information, further compression can be provided.In this case, address 33630 and address 43640 also can be omitted, thus obtain the frame 3905 shown in Figure 39.

When field is removed, in order to decompress, the respective field from last stem (after decompression) can be inserted in aggregate frame by receiver.In this embodiment, the first frame in an aggregate frame always uses unpressed stem.The deciphering of load needs some fields from MAC stem, and these fields may for ease of header compressed and be removed.After the decompression of frame stem, these fields can be supplied to decryption engine.Length field is used for from aggregate frame, extract frame (and segment) by receiver.Length field indicates the length (unit is byte) of the frame with compressed header.

After extracting, remove polymerization header field.Then, the frame after decompression is delivered to decryption engine.In decrypting process, the field in (after decompression) MAC stem needs to carry out message integrity verification.

Figure 40 gives an exemplary polymerization stem 3710.For the one or more frames sent in MIMO data PPDU (encryption, or unencrypted), be that each frame (or segment) stem adds polymerization stem.This polymerization stem comprise 2 bits polymerization first portion type field 4010 (for represent whether have employed header compressed, and which kind of type) and the length field 4030 of 12 bits.Type 00 frame does not adopt header compressed.Type 01 frame eliminate duration/ID, address 1 and address 2 field.Class1 0 frame has the removal field identical with type 01 frame, eliminates address 3 and address 4 field in addition.Length field 4030 in polymerization stem indicates the length of the frame with compressed header, and unit is byte.2 bits 4020 are reserved.Polymerization first category type is summarized in table 2.

Table 2, polymerization first category type

In this exemplary embodiment, all management frames encapsulated in aggregate frame and control frame adopt unpressed frame stem, and its polymerization first category type is 00.Management frames below can be encapsulated in aggregate frame together with Frame: associate request, associated response, again associate request, again associated response, probe requests thereby, probe response, disassociation, certification and releasing certification.Control frame below can be encapsulated in aggregate frame together with Frame: BlockAck (block confirmation) and BlockAckRequest (block confirms request).In other embodiments, the frame of any type can be encapsulated.

adaptive cooperation function

Adaptive cooperation function (ACF) is the extended version of HCCA and EDCA, and it can realize flexibly, the operation of efficient, low delay scheduling, is suitable for the operation of the high data rate supported by MIMO PHY.Figure 41 gives an exemplary embodiment of the scheduled access period frame (SCAP) used in ACF.Use SCHED message 4120, AP can dispatch one or more AP-STA, STA-AP or STA-STA TXOP within the cycle of scheduled access period 4130 by name simultaneously.These transmission through scheduling are identified as scheduled transmission 4140.SCHED message 4120 instead of the traditional HCCA poll frame described in detail above.In this exemplary embodiment, the maximum permissible value of SCAP is 4 milliseconds.

For ease of illustrating, Figure 41 gives exemplary scheduled transmissions 4140, and it comprises AP to STA transmission 4142, STA to AP transmission 4144 and STA to STA transmission 4146.In this embodiment, AP sends 4142A to STA B, then, sends 4142B to STA D, then sends 4142C to STA G.Note that and need not introduce gap between these TXOP, because for each frame, information source (AP) is identical.When information source changes, show the gap (exemplary gap clearance is described in further detail) between TXOP below.In this embodiment, after AP to STA transmission 4142, STA C sends 4144A to AP, and then, behind a gap, STA G sends 4144B to AP, then through a gap, STAE sends 4144C to AP.Then, a point-to-point TXOP 4146 is dispatched.In this case, STA E is information source (sending to STA F), so, if STA E transmitting power is constant, then do not need to introduce gap, otherwise, BIFS gap can be used.Can dispatch other STA to STA transmission, but not show these in this embodiment.According to any order, can dispatch any combination of TXOP.The order of shown TXOP type just for purpose of explanation.In order to reduce required gap number, preferably can dispatch TXOP, but this not necessarily.

Scheduled access period 4130 also can comprise: the FRACH cycle 4150, is exclusively used in quick Random Access Channel (FRACH) transmission (wherein, STA can send and distribute request); And/or in MIMO OFDM EDCA 4160 cycle, wherein MIMO STA can use EDCA process.These access periods based on competition are subject to as SCAP and the protection of NAV that sets.Within MIMO OFDM EDCA 4160 cycle, MIMO STA uses EDCA process to access media, and need not be at war with traditional STA.Transmission in each shielded competing cycle uses MIMO PLCP stem (below further describe).In this embodiment, AP does not provide TXOP to dispatch in shielded competing cycle.

When only there is MIMO STA, the NAV of SCAP can be set by the Duration field in SCHED frame (also SCHED frame can be described in further detail below).If wish the protection affected from traditional STA, AP also can arrange CTS-to-Self4110 before SCHED frame 4120, thus was the SCAP establishment NAV at all STA places in BSS.

In this embodiment, MIMO STA observes SCAP border.In SCAP, carry out last STA of sending must its TXOP of at least PIFS expires before SCAP terminates.MIMO STA also observes the TXOP border through scheduling, and before distributed TXOP terminates, complete its transmission.Like this, the follow-up STA that is scheduled just can start its TXOP when detecting channel and be idle.

SCHED message 4120 defines dispatch list.The assignment information (AP-STA, STA-AP and/or STA-STA) of TXOP is included in the CTRLJ item interior (be described below in detail, be 4515-4530 in Figure 45) in SCHED frame.SCHED message also can define: a part of SCAP4100, is exclusively used in FRACH 4150, if any; And, the protected part of EDCA operation 4160, if any.If do not comprise in SCHED frame through scheduling TXOP assignment information, be then SCAP and the NAV that sets reserves whole SCAP for EDCA transmission (comprising any FRACH), to protect it from the impact of traditional STA.

The maximum length based on the TXOP dispatched or based on competition allowed in SCAP can be shown in ACF ability item.In this embodiment, the length of SCAP does not change in a beacon interval.This length may be displayed in ACF ability item.An exemplary ACF item comprises: SCAP length (10 bit), maximum SCAP TXOP length (10 bit), protection IFS (GIFS) duration (4 bit) and FRACH respond (4 bit).SCAP length represents the length of SCAP in current Beacon Interval.This field is encoded in units of 4 μ s.Maximum SCAP TXOP length represents the maximum permission TXOP length in SCAP.This field is encoded in units of 4 μ s.The GIFS duration be continuous through scheduling STA TXOP between protection interval.This field is encoded in units of 800ns.FRACH response represents in units of SCAP.AP must use FRACH PPDU, by providing the TXOP through scheduling to STA in FRACH RESPONSE SCAP, makes response to the request received.

Figure 42 gives example SCAP and HCCA and EDCA being combined use.In any beacon interval (representing with beacon 4210A-C), together with AP can intert with 802.11e CAP, MIMOOFDM SCAP completely flexibly, adaptively by the access duration of competing based on EDCA.

Therefore, use ACF, AP can work as in HCCA, but it can also be SCAP assignment period.Such as, AP can use CFP and CP as in PCF, for polling operation distributes CAP as in HCCA, or, SCAP can be distributed for scheduling operation.As shown in figure 42, in a beacon interval, AP can use any combination in the cycle of access (EDCA) 4220A-F, CAP 4230A-F and the SCAP 4100A-I based on competition.(example for the sake of simplicity, in Figure 42 does not show any CFP.) AP based on its dispatching algorithm and to the observed result that media take, adjust the ratio of the media taken by dissimilar access mechanism.Any dispatching technique can be adopted.AP determines whether received QoS flow is satisfied with, and can use other observed results, comprises the media measured and takies situation, adjust.

Described above is the CAP of HCCA and association thereof.An illustrative CAP 4230 is given in Figure 42.That AP TXOP 4232 follows below is poll frame 4234A.HCCATXOP 4236A follows after poll frame 4234A.Send another poll frame 4234B, that it is followed below is another corresponding HCCA TXOP 4236B.

Described above is EDCA.An illustrative EDCA 4220 is given in Figure 42.Show various EDCA TXOP 4222A-C.CFP is eliminated in this example.

The form that SCAP 4100 as shown in figure 42 can adopt Figure 41 to describe in detail, comprises optional CTS-to-Self 4110, SCHED 4120 and scheduled access period 4130.

AP uses 802.11 business transferring Indication message (DTIM) message, instruction scheduling operation, as described below.DTIM comprises the bitmap of access ID (AID), and another STA in this AP or BSS has laid in data for it.Use DTIM, notify that the STA of all MIMO of possessing abilities keeps wake-up states after beacon.In the BSS that tradition and MIMO STA all exist, immediately following after beacon, first dispatch traditional STA.After conventional transmission, send SCHED message immediately, it shows the composition of scheduled access period.The STA possessing MIMO ability be not scheduled in particular schedule access period can sleep in remaining SCAP, then wakes up and monitors follow-up SCHED message.

Adopt ACF, other operator schemes various can be realized.Figure 43 shows an exemplary operation, and wherein, each beacon interval comprises multiple SCAP 4100, is wherein interspersed with the access period 4220 based on competition.In such a mode, can shared medium liberally, wherein, dispatch during SCAP to MIMO QoS flow, the non-QoS flow of MIMO (if present) together with traditional STA uses competing cycle simultaneously.The cycle of inserting realizes low delay service to MIMO and traditional STA.

As mentioned above, in SCAP, a CTS-to-Self can be had before SCHED message, for the protection of the impact from traditional STA.If there is no traditional STA, then do not need CTS-to-Self (or other traditional cleaning signals).Beacon 4210 can set a long CFP, to protect all SCAP from the impact of any arrival tradition STA.CP at the end of beacon interval makes newly arrived traditional STA to access media.

Using the exemplary operation shown in Figure 44, when there being a large amount of MIMO STA, the optimization of low delay operation can be realized.In this embodiment, suppose that traditional STA (if any) only needs limited resource.AP sends a beacon, thus sets up long CFP 4410 and short CP 4420.Any broadcast/multi broadcast message that what beacon 4210 was followed below is for traditional STA.Then, lean against and privately SCAP 4100 is dispatched.This operator scheme can realize the power management optimized, because STA needs periodically to wake up to listen to SCHED message, and, if be not scheduled in current SCAP, then can sleep in SCAP interval.

By FRACH or the MIMO EDCA cycle that the scheduled access period 4130 of SCAP 4100 comprises, provide for MIMO STA based on protected contention access.In CP 4420, traditional STA can to media carry out based on competition access.

After the transmission of SCHED frame, can the continuous scheduling type transmission from AP be dispatched.SCHED frame can send together with lead code.The follow-up AP transmission that is scheduled can send when not having lead code.(can send for representing the designator whether comprising lead code).An exemplary PLCP lead code is described in further detail below.In this exemplary embodiment, the STA transmission be scheduled starts when there being lead code.

fault recovery

Recover to receive in mistake from SCHED, AP can use various process.Such as, if a STA cannot decode to a SCHED message, then it can not utilize its TXOP.If the TXOP that is scheduled did not start in the distributed time started, then by not with scheduling TXOP start after PIFS time send, AP can start recovery.AP can use the non-scheduling TXOP cycle, as a CAP.In this CAP, AP can send signal to one or more STA, or poll STA.Poll frame can mail to the STA or another STA that lost the TXOP that is scheduled.Before next is scheduled TXOP, this CAP terminates.

At the end of the TXOP that is scheduled is too early, also can use identical process.Send by during PIFS after last end of transmission be scheduled in TXOP, AP can start to recover.AP can use that the TXOP's that is scheduled do not use the cycle, as CAP, as mentioned above.

shielded competition

As mentioned above, SCAP also can comprise: the part and/or the MIMO STA that are exclusively used in FRACH transmission can use the part of EDCA process wherein.These access periods based on competition can be protected by the NAV set for SCAP.

Shielded competition allows STA to indicate TXOP request, so that assist AP in scheduling, thus supplements low delay scheduling operation.Within the shielded EDCA cycle, MIMOOFDM STA can use the access (avoiding competing with traditional STA) based on EDCA to carry out transmission frame.Use conventional art, STA can indicate TXOP Duration Request or buffer state in 802.11e QoS control field in MAC stem.But FRACH is to provide the one more efficient means of identical function.Within the FRACH cycle, STA can use the competition of the Aloha formula in gap, in the FRACH time slot of fixed dimension, access channel.FRACH PPDU can comprise TXOP Duration Request.

In this exemplary embodiment, the transmission of MIMO frame uses MIMO PLCP stem, will be described in detail below to this.When there is non-MIMO STA; because traditional 802.11b, 802.11a and 802.11g STA can only decode to signal 1 field (being described in detail below in conjunction with Figure 50) of MIMO PLCP stem; so MIMO frame must send when there being protection.When tradition and MIMO STA exist, use the STA of EDCA access procedure can use traditional RTS/CTS sequence, protect.Tradition RTS/CTS refers to and uses legacy preamble code, PLCP stem and mac frame form to transmit RTS/CTS frame.

The protection mechanism that MIMO transmission also can use 802.11e HCCA to provide.Therefore, use and control access period (CAP), the transmission from AP to STA, the polled transmission (using direct link agreement) from STA to AP or from STA to STA can be protected.

AP also can use traditional CTS-to-Self, and protection MIMO scheduled access period (SCAP) is from the impact of traditional STA.

When an AP determines that all STA existed in BSS can both decode to MIMO PLCP stem, in its MIMO ability item in a beacon, indicate this point.Such BSS is called as MIMO BSS.

In MIMO BSS, under EDCA and HCCA, according to the aging rule of MIMO OFDM training symbol, frame transmission uses MIMO PLCP stem and MIMO OFDM training symbol.Transmission in MIMO BSS uses MIMO PLCP.

the frame pitch reduced

Describe the various technology being generally used for reducing frame pitch above in detail.Here the example of the frame pitch in this exemplary embodiment of several reduction is provided.For scheduled transmission, the time started of TXOP indicates in SCHED message.The accurate start time that launch party STA can indicate in SCHED message, starts its scheduling TXOP, and need not determine that media are idle.As mentioned above, during SCAP, continuous print scheduling AP transmission is what to send when not having minimum IFS.

In this exemplary embodiment, continuous print be scheduled STA transmission (from different STA) be when IFS at least one protect IFS (GIFS) send.The default value of GIFS is 800ns.Larger value can be selected, reach at most the value of the burst IFS (BIFS) defined below.The value of GIFS can indicate in ACF ability item, as mentioned above.Other embodiments can adopt any value of GIFS and BIFS.

Continuous N IMO OFDM PPDU from identical STA transmits (TXOP burst) and separates with BIFS.When being operated in 2.4GHz frequency band, BIFS equals 10 μ s, and MIMO OFDM PPDU does not comprise the ofdm signal expansion of 6 μ s.When being operated in 5GHz frequency band, BIFS is 10 μ s.In another embodiment, BIFS can be set to comparatively large or smaller value, comprises 0.In order to make recipient STA automatic growth control (AGC) change between transmissions, when the transmitting power of launch party STA changes, the gap being greater than 0 can be used.

The frame at once responded from recipient STA is needed not use MIMO OFDMPPDU to send.On the contrary, they use conventional P PDU to send, that is, the clause 19 in 2.4GHz frequency band or the clause 17 in 5GHz frequency band.Provide several example below, illustrate and how tradition and MIMO OFDM PPDU are multiplexed on media.

First, consider a traditional RTS/CTS, after it, and then MIMO OFDM PPDU happens suddenly.This transfer sequence is as follows: traditional RTS-SIFS-traditional CT S-SIFS-MIMOOFDM PPDU-BIFS-MIMO OFDM PPDU.In 2.4GHz, traditional RTS or CTS PPDU uses ofdm signal expansion, and SIFS is 10 μ s.In 5GHz, do not have OFDM to expand, but SIFS is 16 μ s.

Secondly, an EDCA TXOP using MIMO OFDM PPDU is considered.This transfer sequence is as follows: MIMO OFDM PPDU-BIFS-traditional B lockAckRequest-SIFS-ACK.For suitable access style (AC), use EDCA process, obtain EDCA TXOP.As mentioned above, the access style of EDCA definition can use different parameters to each AC, as AIFS [AC], CWmin [AC] and CWmax [AC].Traditional BlockAckRequest sends when having signal extension or 16 μ s SIFS.If sent in the aggregate frame of BlockAckRequest in MIMO OFDM PPDU, then there is no ACK.

3rd, consider that continuous print is scheduled TXOP.Transfer sequence is as follows: STA A MIMOOFDM PPDU-GIFS-STAB MIMO OFDM PPDU.If the maximum permission TXOP time that PPDU transfer ratio is distributed is short, so, after STA A MIMO OFDMPPDU transmits, one period of free time may be had.

As mentioned above, the decoding of coded OFDM transmissions and demodulation impose extra processing demands at recipient STA place.In order to solve this point, 802.11a and 802.11g allows recipient STA to have the additional time before must sending ACK.In 802.11a, the SIFS time is set to 16 μ s.In 802.11g, the SIFS time is set to 10 μ s, but is the introduction of 6 additional μ s ofdm signal expansions.

According to identical logic, because the decoding of MIMO OFDM transmission and demodulation can cause more processing load, so can design the embodiment that is improved SIFS or ofdm signal expansion, this can lower efficiency further.In this exemplary embodiment, by expanding the block ACK of 802.11e and delay block affirmation mechanism, for all MIMO OFDM transmission, not necessarily ACK at once.SIFS or signal extension do not increase, and also eliminate signal extension, and for a lot of situation, the required frame spacing continuously between transmission obtains and reduces or eliminate, thus raises the efficiency.

sCHED message

Figure 45 shows SCHED message, introduces it above in conjunction with Figure 41, also will be described in further detail it below.SCHED message 4120 is polling messages more than, within the duration of scheduled access period (SCAP), distributes one or more AP-STA, STA-AP and STA-STA TXOP.Use SCHED message, poll and competition expense can be reduced, and, eliminate unnecessary IFS.

SCHED message 4120 defines the dispatch list of SCAP.SCHED message 4120 comprises MAC stem 4510 (in this exemplary embodiment, being 15 bytes).In this exemplary embodiment, CTRL0, CTRL1, CTRL2 and CTRL3 section (is typically expressed as CTRLJ here, J can be 0 to 3, respectively represent section 4515-4530) in each be elongated, their (when it is present) can be sent with 6,12,18 and 24Mbps respectively.

This exemplary MAC stem 4510 comprises: frame controls 4535 (2 bytes), duration 4540 (2 bytes), BSSID 4545 (6 bytes), power management 4550 (2 bytes) and MAP 4555 (3 bytes).The bit 13-0 of Duration field 4540 indicates the length of SCAP, and unit is microsecond.Duration field 4540 is used for setting NAV within the duration of SCAP by the STA that can carry out MIMO OFDM transmission.When there is traditional STA in BSS, AP can use other means, protects SCAP, such as, and traditional CTS-to-Self.In this exemplary embodiment, the maximum of SCAP is 4 milliseconds.BSSID field 4545 identifies AP.

Power management field 4550 has been shown in Figure 46.Power management 4550 comprises: SCHED counting 4610, reserved field 4620 (2 bits), transmitting power 4630 and received power 4640.AP transmitting power and AP received power show in power management field, and STA received power level is measured in STA.

SCHED counting is a field (being 6 bits in this embodiment) all increased progressively when each SCHED transmission.SCHED counting resets when each beacon sends.SCHED counting can be used for various object.Such as, the electricity-saving function using SCHED counting is described below.

Transmitting power field 4630 represents the transmitted power level that AP is used.In this exemplary embodiment, this 4 bit field is encoded as follows: for the channel indicated in the item of information of beacon, and this value represents the quantity of transmitted power level lower than the 4dB stride of maximum transmit power level (unit is dBm).

Received power field 4640 represents the received power level that AP place is expected.In this exemplary embodiment, this 4 bit field is encoded as follows: this value represents the quantity of received power level higher than the 4dB stride of minimum receiver sensitivity level (-82dBm).Based on the received power level at STA place, STA can calculate its transmitted power level as follows: STA transmitting power (dBm)=AP transmitting power (dBm)+AP received power (dBm)-STA received power (dBm).

In this exemplary embodiment, be scheduled in STA-STA transmitting procedure, control section sends with the launching electrical level that can carry out decoding at AP and recipient STA place.From the power control report of AP, or the power management field 4550 in SCHED frame, enable STA determine can to decode to control section at AP place needed for transmitted power level.This general aspect is described above in conjunction with Figure 22.For the STA-STA transmission be scheduled, when the power needed for decoding at AP place is different from the power needed for decoding in recipient STA place, send PPDU with the higher person in these two power levels.

MAP field 4555 shown in Figure 47 represents the access period and duration thereof that whether to exist during SCAP based on protected competition.MAP field 4555 comprises: FRACH counting 4710, FRACH skew 4720 and EDCA skew 4730.It is offset at FRACH the quantity (10 bits) that 4720 places start the FRACH time slot dispatched that this exemplary FRACH counts 4710 (4 bits).Each FRACH time slot is 28 μ s.If FRACH count value is 0, then represent in current scheduled access period there is no the FRACH cycle.EDCA skew 4730 is the beginnings in protected EDCA cycle.It is 10 bits that this exemplary EDCA offsets 4730.FRACH skew 4720 and EDCA skew 4730 be all from SCHED frame transmission in units of 4 μ s.

SCHED message 4120 is sent out away as a special SCHED PPDU 5100 (type 0010), is described in detail below in conjunction with Figure 51.CTRL0 4515, CTRL1 4520, CTRL2 4525 and CTRL34530 section and length thereof whether is there is, display in the signal field (5120 and 5140) of the PLCP stem of SCHED PPDU 5100 in SCHED message 4120.

Figure 48 shows the SCHED control frame distributed for TXOP.Each in CTRL0 4515, CTRL1 4520, CTRL2 4525 and CTRL3 4530 sections has variable length, and each comprises 0 or multiple assignment item (being respectively 4820,4840,4860 and 4880).Each CTRLJ section is added with FCS (being respectively 4830,4850,4870 and 4890) and 6 tail bits (not shown)s of 16 bits.(so, show, before MAC stem is added on CTRL0 4515 in Figure 48) is calculated for MAC stem 4510 and all CTRL0 assignment item 4820 for CTRL0 section 4515, FCS.In this exemplary embodiment, even if do not comprise assignment item in CTRL0 section, also comprise the FCS 4830 of CTRL04515.

Just as described in detail herein, AP sends the assignment information of AP-STA, STA-AP and STA-STA transmission be used in SCHED frame.Assignment item to different STA sends in CTRLJ section, is represented by the STA in the SCHED speed field of the PLCP stem of its transmission.Note that CTRL0 to CTRL3 is corresponding to the robustness of successively decreasing.Each STA starts to decode to the PLCP stem of SCHED PPDU.Signal field indicates existence and the length thereof of CTRL0, CTRL1, CTRL2 and CTRL3 section in SCHED PPDU.Decode to MAC stem and CTRL0 section when STA receiver starts, decode, then decode to FCS to each dispensing section, it continues decode CTRL1, CTRL2 and CTRL3 subsequently, cannot be stopped at FCS by the CTRLJ section place of checking.

As shown in table 3, define five kinds of assignment item.Several assignment item can be bundled in each CTRLJ section.Each assignment item indicates transmit leg STA and accesses ID (AID), recipient STAAID, the time started of the TXOP that is scheduled and the maximum permission length of the TXOP that is scheduled.

Table 3, assignment item type

From in the continuous transmission of AP, lead code can be eliminated.If AP not for scheduling type AP transmit and send lead code, then be there is bit in lead code and is set to 0.Such as, eliminating the benefit of lead code is, when AP has low bandwidth, low delay stream to multiple STA, such as, has multiple transmission by IP in the BSS that speech (VoIP) flows.Therefore, SCHED frame can realize the polymerization (that is, above-mentioned PPDU polymerization) from AP to the transmission of multiple recipient STA.Above-mentioned frame aggregation allows the frame mailing to a recipient STA to be polymerized.

Start offset field is the integral multiple of 4 μ s, is to obtain from the time started of SCHED message lead code.AID be distribute the access ID of (multiple) STA.

For all assignment item types except the STA-STA transmission that is scheduled, TXOP Duration field is the maximum permission length of TXOP of being scheduled, and is the integral multiple of 4 μ s.The actual PPDU size of the PPDU sent shows (will further describe) below in signal 1 field of PPDU.

For STA-STA transmission (assignment item type 011 and 100) be scheduled, maximum PPDU size field is also the maximum permission length of TXOP of being scheduled, and is the integral multiple of 4 μ s, but, also can use other rules.In this exemplary embodiment, for the STA-STA transmission that is scheduled, TXOP only comprises a PPDU.Recipient STA uses the maximum PPDU size shown in assignment item, determines the quantity (because PPDU size field is replaced by the request field in signal 1, describing in detail below in conjunction with Figure 51) of OFDM symbol in PPDU.If STA-STA flows the OFDM symbol that use has standard protection interval (GI), then the PPDU size of the TXOP that is scheduled is set to the maximum PPDU size shown in assignment item by recipient STA.If STA-STA stream uses the OFDM symbol having and shorten GI, then recipient STA is by being undertaken amplifying and rounding up by the maximum PPDU size field factor 10/9, determines PPDU size.Transmit leg STA can send the PPDU shorter than distributed maximum PPDU size.The length of mac frame after PPDU size does not provide polymerization to receiver.The length of encapsulated frame is included in the polymerization stem of each mac frame.

Launch party and recipient STA are included in assignment item, the not predetermined STA power saving sending or receive in SCAP can be made.Recall the SCHED count area of mistake presented hereinbefore.The each dispensing section being undertaken dispatching by SCHED message indicates transmit leg STA AID, recipient STA AID, the time started of the TXOP that is scheduled and the maximum permission length of the TXOP that is scheduled.SCHED counting increases progressively when each SCHED transmission, and resets when each beacon transmissions.STA can indicate power-save operation to AP, thus provides concrete SCHED count value, and during this period, they can be assigned to by AP the transmitting or reception TXOP that are scheduled.Then, STA can periodically wake up, and just monitors the SCHED message with suitable SCHED counting.

pPDU form

Figure 49 shows traditional 802.11PPDU 4970, and it comprises PLCP lead code 4975 (12 OFSM symbols), PLCP stem 4910, the afterbody 4950 of elongated PSDU 4945,6 bit and elongated filling information 4955.A part 4960 of PPDU 4970 comprises: signal field (1 OFDM symbol), sends with speed=1/2 with BPSK; Elongated data field 4985, sends by the modulation format indicated in signal 4980 and speed.PLCP stem 4910 comprises the service field 4940 (be included in data 4985, send according to this form) of signal 4980 and 16 bit.Signal field 4980 comprises: speed 4915 (4 bit), reserved field 4920 (1 bit), length 4925 (12 bit), parity bit 4930 and afterbody 4935 (6 bit).

Extended signal field (describing in detail below) in this exemplary PLCP stem keeps backward compatibility with the signal field 4980 of tradition 802.11.What arrange the speed field 4915 in traditional signal field 4980 does not use value, to define new PPDU type (being described below in detail).

Introduce multiple new PPDU type.In order to keep backward compatibility with traditional STA, the speed field in the signal field of PLCP stem is revised as speed/type field.Speed be not designated as PPDU type by value.PPDU type also represents whether signal field expansion specification signal 2 exists and length.The new value of speed/type field is defined in table 4.For traditional STA, these values of speed/type field define.Therefore, traditional STA, after successfully decoding to signal 1 field and find the undefined value in speed field, can abandon the decoding to PPDU.

Or, the reserved bit in legacy signal field can be set to 1, to represent the MIMO OFDM transmission mailing to a New type of S TA.Recipient STA can ignore reserved bit, and continues to attempt decoding to signal field and remaining transmission.

Receiver cannot based on the length of PPDU type determination signal 2 field.FRACHPPDU only occurs once in the specified portions of SCAP, and only needs to be decoded by AP.

Table 4, MIMO PPDU type

Figure 50 shows the MIMO PPDU form 5000 for transfer of data.PPDU 5000 is called as PPDU type 0000.PPDU 5000 comprises: PLCP lead code 5010, signal 15020 (1 OFDM symbol), signal 25040 (1 OFDM symbol), training symbol 5060 (0,2,3 or 4 symbol) and elongated data field 5080.In this exemplary embodiment, PLCP lead code 5010 (if present) is 16 μ s.Signal 15020 and signal 25040 is sent with PPDU control section speed and modulation format.Data 5080 comprise: service 5082 (16 bits); Feedback 5084 (16 bits); Elongated PSDU5086; Afterbody 5088 (each stream has 6 bits), wherein, the convolution chnnel coding different to each stream application; Elongated filling information 5090.Data 5080 are sent with PPDU control section speed and modulation format.

The MIMO PLCP stem of PPDU type 0000 comprises: signal (comprising signal 15020 and signal 25040), service 5082 and feedback 5084 fields.Compared with traditional 802.11, service field is constant, and sends with this data segment speed and form.

Feedback fields 5084 sends with data segment speed and form.This feedback fields comprises: ES field (1 bit), data rate vector feedback (DRVF) field (13 bit) and power control field (2 bit).

ES field represents preferred guidance method.In this exemplary embodiment, when the set of ES bit, select characteristic vector guiding (ES), otherwise, select spatial spread (SS).

Data rate vector feedback (DRVF) field provides feedback to peer station, about in maximum four spatial models can supporting rate.

Clear and definite Rate Feedback enables station make its transmission rate maximize fast and exactly, thus greatly improves system effectiveness.The feedback of low delay is desirable.But feedback chance needs not to be synchronous.Transmission opportunity can be obtained, such as, based on (i.e. the EDCA) that compete, (i.e. the HCF) of poll or (i.e. ACF) mode of scheduling by any mode.Therefore, variable time amount can be transmitted between transmission opportunity and Rate Feedback.Based on the age of Rate Feedback, transmitter can apply avoidance mechanism, to determine transmission rate.

For the transport stream of the B from STAA to STA, PPDU data segment rate adaptation depends on the feedback (being previously description, such as, see Figure 24) provided to STA A by STA B.For ES or SS operator scheme, when STA B receives MIMOOFDM training symbol from STAA, it all will estimate attainable data rate on each spatial flow.From in any subsequent transmission stream of STA B to STA A, this estimated value is included in the DRVF field of feedback 5084 by STA B.DRVF field sends with data segment 5080 speed.

When sending signal to STAB, the DRVF that STAA receives from STAB based on it, determines to use which kind of transmission rate, and avoidance mechanism also can be adopted if desired to consider time delay.Signal field (the following detailed description of) comprise the DRV field 5046 of 13 bits, to enable recipient STAB, the frame sent from STA A is decoded.DRV 5046 sends with control section speed.

Encode to DRVF field, it comprises: STR field (4 bit), R2 field (3 bit), R3 field (3 bit) and R4 field (3 bit).STR field represents the speed of stream 1.Be the STR value shown in table 5 by this code field.R2 represents the difference between the STR value of stream 1 and the STR value of stream 2.R2 value " 111 " represents that stream 2 turns off.R3 represents the difference between the STR value of stream 2 and the STR value of stream 3.R3 value " 111 " represents that stream 3 turns off.If R2=" 111 ", be then set to R3 " 111 ".R4 represents the difference between the STR value of stream 3 and the STR value of stream 4.R4 value " 111 " represents that stream 4 turns off.If R3=" 111 ", be then set to R4 " 111 ".

As ES=0, namely during spatial spread, the another kind coding of DRVF is as follows: the speed (4 bit) of fluxion amount (2 bit), each stream.The speed field of each stream is encoded as above-mentioned STR value.Remaining 7 bits retain.

Table 5, STR encode

Except DRVF, STAB also provides continuous power-control feedback to transmit leg STAA.This feedback is included in power control field, and also sends with data segment speed.This field is 2 bits, and represents increase power or reduce power or keep power constant.The transmitted power level obtained is designated as data segment transmitted power level.

Table 6 shows exemplary power control word segment value.Other embodiment can adopt the power control field of different size, and other power adjustment.

Table 6, power control word segment value

Power control field	Implication
		00	Unchanged
01	Power is increased 1dB
		10	By power reduction 1dB
11	Retain

For whole PPDU, transmitted power level remains unchanged.When data segment transmitted power level and open loop STA transmitting power (that is, AP above-mentioned transport stream decoded needed for power level) different time, send PPDU with the maximum in these two power levels.That is, PPDU transmitted power level is the maximum in open loop STA transmitting power (dBm) and data segment transmitting power (dBm).

In this exemplary embodiment, in the first frame of any Frame switch sequence, power control field is set to " 00 ".In a subsequent frame, its expression increases according to the step-length of 1dB or reduces power.Recipient STA uses this feedback information by all subsequent frame transmission of mailing to this STA.

Signal 15020 comprises: the afterbody 5030 of speed/type field 5022 (4 bit), reservation bit 5024, PPDU size/request 5026 (12 bit), parity bit 5028 and 6 bit.Signal 1 field 5020 sends (in this exemplary embodiment, being 6Mbps) with control section speed and form.Speed/type field 5022 is set as 0000.Reservation bit 5024 can be set to 0.

PPDU size/request 5026 has two effects, and this depends on transmission mode.In the STA based on competition transmits and all AP transmit, this field represents PPDU size.In a first mode, bit 1 represents that PPDU employs the OFDM symbol of expansion, and bit 2 represents that PPDU uses the OFDM symbol having and shorten GI, and bit 3-12 represents the quantity of OFDM symbol.

In the non-AP STA be scheduled transmits, PPDU size/request 5026 represents request.In the second mode, bit 1-2 represents SCHED speed.The SCHED field of SCHED rate representation numbering the highest (0,1,2 or 3), can be used to send a dispensing section to STA.Between the training symbol transmission period from AP, each non-AP STA estimates that it can receive the speed of SCHED frame transmission steadily from AP.From in the subsequent scheduled transmissions of STA, the maximum rate of permission is included in SCHED speed field.This field is decoded by AP.AP uses this information, dispatches the follow-up TXOP of STA, and determines CTRLJ (0,1,2 or 3), sends these dispensing sections for STA.

In the second mode, bit 3-4 represents qos field, a part (being the multiple of 1/3rd) (that is, 0%, 33%, 67%, 100%) for the request of its mark TC 0 or 1.Bit 5-12 represents the request length integral multiple of 16 μ s (in this exemplary embodiment, be) of TXOP.

Signal 1 field 5020 is verified by parity bits 5028, is 6 bit tail 5030 for convolution coder at the end of it.

Whether signal 2 field 5040 exists and length is indicated by the speed/type field 5022 in signal 15020.Signal 2 field 5040 sends with control section speed and form.Signal 25040 comprises: reservation bit 5042, training type 5044 (3 bit), data rate vector (DRV) 5046 (13 bit), parity bit 5048 and afterbody 5050 (6 bit).The training type field of 3 bits indicates length and the form of MIMO OFDM training symbol.Bit 1-2 represents the quantity (0,2,3 or 4 OFDM symbol) of MIMO OFDM training symbol 5060.Bit 3 is training type fields: 0 represents SS, and 1 represents ES.DRV5046 provides the speed of maximum four spatial models.DRV 5046 is identical with the coded system that DRVF adopts (to be included in feedback 5084, as mentioned above).Signal 2 field 5040 is verified by 1 parity bit 5048, terminates as 6 bit tail 5050 for convolution coder.

Figure 51 shows SCHED PPDU 5100 (speed/type=0010).SCHEDPPDU 5100 comprises: PLCP lead code 5110, signal 15120 (1 OFDM symbol), signal 25140 (1 OFDM symbol), training symbol 5160 (0,2,3 or 4 symbol) and elongated SCHED frame 5180.In this embodiment, when PLCP lead code 5110 exists, be 16 μ s.Signal 15020 and signal 25040 send with PPDU control section speed and modulation format.SCHED frame 5180 can comprise the above-mentioned various speed described in conjunction with ACF.

Signal 15120 comprises: speed/type 5122 (4 bit), reservation bit 5124, CTRL0 size 5126 (6 bit), CTRL1 size 5128 (6 bit), parity bit 5130 and afterbody 5132 (6 bit).Speed/type 5122 is set to 0010.Reservation bit 5124 can be set to 0.CTRL0 size 5126 indicates the segment length of the SCHED PPDU sent with minimum speed limit (in this embodiment for 6Mbps).This section comprises: the service field of PLCP stem, MAC stem and CTRL0 section 5126.In this embodiment, this value carries out encoding with the integral multiple of 4 μ s.CTRL1 size 5128 represents the segment length of the SCHED PPDU sent with next higher rate (in this embodiment for 12Mbps).In this embodiment, this value carries out encoding with the integral multiple of 4 μ s.CTRL1 size is that " 0 " represents: there is not corresponding CTRL1 section in SCHED PPDU.Signal 1 field 5120 is verified by parity bit 5130, terminates as 6 bit tail 5132 for convolution coder.

Signal 25140 comprises and retains position 5142, training type 5144 (3 bit), CTRL2 size 5146 (5 bit), CTRL3 size 5148 (5 bit), FCS 5150 (4 bit) and afterbody 5152 (6 bit).Retain position 5142 and can be set to 0.Training type 5144 and the same (the training type 5044) of specifying for PPDU type 0000.

CTRL2 size 5146 represents the segment length of the SCHED PPDU that the following flank speed (being 18Mbps in this embodiment) sends.In this embodiment, this value carries out encoding with the integral multiple of 4 μ s.CTRL2 size is that " 0 " represents: there is not corresponding CTRL2 section in SCHED PPDU.CTRL3 size 5148 represents the segment length of the SCHED PPDU sent with flank speed (in this embodiment for 24Mbps).In this embodiment, this value carries out encoding with the integral multiple of 4 μ s.CTRL2 size is that " 0 " represents: there is not corresponding CTRL3 section in SCHED PPDU.

FCS 5150 calculates according to whole signal 1 and signal 2 field.Be 6 bit tail 5152 for convolution coder at the end of signal 2 field 5152.

Figure 52 shows FRACH PPDU 5200 (speed/type=0100).FRACHPPDU 5200 comprises: PLCP lead code 5210, signal 15220 (1 OFDM symbol) and signal 25240 (2 OFDM symbol).In this exemplary embodiment, PLCP lead code 5210 (when it is present) is 16 μ s.Signal 15220 and signal 25240 send with PPDU control section speed and modulation format.During the FRACH cycle in MIMO scheduled access period, STA sends FRACH PPDU 5200.The FRACH cycle is established by AP, therefore is known (as mentioned above) for it.

Signal 15220 comprises: speed/type 5222 (4 bit), reservation position 5224, request 5226 (12 bits), parity bit 5228 and afterbody 5230 (6 bit).Speed/type 5222 is set as 0100.Retain position 5224 and can be set to 0.Request field 5226 is designated as PPDU type 0000 (5000), as mentioned above.Signal 1 field 5220 is tested by parity bit 5228, terminates as 6 bit tail 5230 for convolution coder.

Signal 25240 comprises and retains position 5242, source AID 5244 (16 bit), object AID5246 (16 bit), FCS 5248 (4 bit) and afterbody 5250 (6 bit).Retain position 5242 and can be set to 0.Source AID 5244 identifies the STA that FRACH sends.Object AID5246 identifies the object STA that TXOP asks.In this exemplary embodiment, if destination party is AP, then the value of object AID field 5246 is set as 2048.The FCS 5248 of 4 bits calculates according to whole signal 1 and signal 2 field.Before convolutional encoding, add the afterbody 5250 of 6 bits.

In this exemplary embodiment, STA can use time slotted Aloha to access channel, and sends a request message in FRACH.If successfully received by AP, then AP provides one through the TXOP of scheduling to requesting party STA in a rear scheduled access period.The FRACH timeslot number of current scheduling access period indicates in SCHED message, N_FRACH.

STA can also maintain a variable B_FRACH.After transmission on FRACH, if STA receives the TXOP assignment information from AP, then its reset B_FRACH.If STA does not receive the TXOP assignment information from AP in the SCHED transmission of predetermined quantity (FRACH_RESPONSE), then B_FRACH is increased by 1, reach at most maximum 7.Parameter FRACH_RESPONSE is included in the ACF item of beacon.In any FRACH, STA is (N_FRACH) at probability ^-1* 2 ^-B_FRACHwhen choose a FRACH time slot.

If AP does not dispatch any FRACH cycle, then MIMO STA can use EDCA rule, is at war with in the protected competing cycle in SCAP.

It will be appreciated by those skilled in the art that and can use multiple different technologies and method representation information and signal.Such as, the data mentioned in the description on run through, instruction, order, information, signal, bit, symbol and chip can represent with voltage, electric current, electromagnetic wave, magnetic field or particle, light field or particle or above-mentioned combination in any.

Those skilled in the art also can understand, various exemplary box, module, circuit and the algorithm steps that describe in conjunction with the disclosed embodiments here all can realize in electronic hardware, computer software or the combination of the two.In order to be clearly shown that the interchangeability between hardware and software, above to various exemplary assembly, frame, module, circuit and step all with the description that its functional form is carried out generally.This functional be depend on hardware implementing or with software simulating the design constraint that specific application and whole system apply.Those skilled in the art can realize described functional in many ways for each specific application, but the result of this realization should not be construed as and causes deviating from scope of the present invention.

Utilize general processor, digital signal processor (DSP), application-specific integrated circuit (ASIC) (ASIC), field programmable gate array (FPGA) or other programmable logical device, discrete gate or transistor logic, discrete hardware components or the combination in any among them, can realize or perform various exemplary logic diagram, module and the circuit that describe in conjunction with embodiment disclosed herein.General processor may be microprocessor, but in another scenario, this processor may be the processor of any routine, controller, microcontroller or state machine.Processor also may be implemented as the combination of computing equipment, such as, and the combination of DSP and microprocessor, multi-microprocessor, the one or more microprocessor in conjunction with DSP core or any other this kind of structure.

Step in conjunction with the method described by embodiment disclosed herein or algorithm directly can be presented as hardware, the software module performed by processor or the combination of both.Software module may be present in the storage media of RAM memory, flash memory, ROM memory, eprom memory, eeprom memory, register, hard disk, mobile disk, CD-ROM or any other form well known in the art.A kind of exemplary storage medium is coupled with processor, thus make processor can from this storage media read message, and can to this storage media write information.In replacement example, storage media is the part of processor.Processor and storage media may be present in an ASIC.This ASIC may be present in a subscriber station.Replace in example at one, processor and storage media can exist as the discrete assembly in subscriber station.

The title comprised herein for reference to and contribute to locating each joint.These titles are not the protection ranges wanting to be limited in concept described thereafter.These concepts go in full.

There is provided the foregoing description of described disclosed embodiment that those skilled in the art can be made can to realize or use the present invention.To those skilled in the art, the various amendments of these embodiments are apparent, and the general principles defined here also can be applied to other embodiments not departing from the scope of the present invention on the basis with purport.Therefore, the present invention is not limited to shown here embodiment, but consistent with the widest scope meeting principle disclosed herein and novel feature.

Claims (12)

1. a method for transfer of data, comprising:

Transmission gathers poll frame, described in gather poll frame and divide the multiple transmission opportunitys being used in multiple distant station; And

Poll frame is gathered, via forward link and reverse link and described multiple distant station swap data frame according to described.

2. a method for TDD transfer of data, comprising:

Send pilot frame;

Transmission gathers poll frame, described in gather poll frame and divide the multiple transmission opportunitys being used in multiple distant station; And

Gather poll frame according to described, zero or multiple Frame are sent to described multiple distant station from access point.

3. the method for TDD transfer of data as claimed in claim 2, also comprises:

Gather poll frame according to described, receive zero or multiple Frame from described multiple distant station.

4. the method for TDD transfer of data as claimed in claim 2, wherein, gathers poll frame according to described, exchanges zero or multiple Frame via between at least two distant stations of reverse link in described multiple distant station.

5. the method for TDD transfer of data as claimed in claim 2, also comprises:

Gather poll frame according to described, receive zero or multiple Stochastic accessing section.

6. the device for transmitting and receive data on shared medium, comprising:

Receiver, for receiving one or more message from one or more distant station, every bar message comprises the instruction of the data from each remote station; And

Transmitter, poll frame is gathered for what send transmission time that each indicating in one or more distant station carries out sending on described shared medium and transmitting continuous time, the described poll frame that gathers is in response to described one or more message received and generates, and described transmitter be further used for according to described in gather poll frame to the one or more Frame of remote station.

7. a device for transfer of data, comprising:

Receiver, gathers poll frame for receiving, described in gather poll frame and divide the multiple transmission opportunitys being used in multiple distant station;

Processor, for gathering the transmission opportunity of poll frame determination distant station described in basis; And

Transmitter, for sending one or more Frame during the described transmission opportunity of described distant station.

8. a device for transfer of data, comprising:

For sending the module of pilot frame;

For sending the module gathering poll frame, described in gather poll frame and divide the multiple transmission opportunitys being used in multiple distant station; And

The module of one or more Frame is sent for gathering poll frame described in basis.

9. a method for transfer of data, comprising:

Send pilot frame;

Transmission gathers poll frame, described in gather poll frame and divide the multiple transmission opportunitys being used in multiple distant station; And

Gather poll frame according to described, send one or more Frame.

10. method as claimed in claim 9, wherein, sends one or more Frame from an access point to one or more distant station respectively.

11. methods as claimed in claim 9, wherein, send one or more Frame from one or more distant station to an access point respectively.

12. methods as claimed in claim 9, wherein, from the first distant station to the one or more Frame of the second remote station.