CN101496350A - MAC protocol for centrally controlled multichannel wireless local area networks - Google Patents

Abstract

A wireless system and method of wireless communication are described, which method comprises: providing a plurality of code channels in a single frequency channel; allocating at least one contention free period in at least one of the code channels; and allocating at least one contention period in another code channel commencing concurrently with the contention free period.

Description

The media access control protocol of central controlled multichannel wireless local area networks

Background technology

Along with the progress of channel modulation techniques, wireless communication bandwidth is significantly increased, and makes wireless medium become wired and the feasible alternative scheme optical fiber solution.Equally, the use of the wireless connections in data and the voice communication continues to increase.These equipment comprise portable computer in mobile phone, the wireless network (for example, wireless lan (wlan)), the stationary computer in the wireless network, portable earphone or the like.

Every kind of wireless network comprises many layers and sublayer.Medium access control (MAC) sublayer and physics (PHY) layer are two layers wherein.In the OSI(Open Systems Interconnection) stack, the MAC layer is lower sublayer in two sublayers of data link layer.The MAC layer provides the coordination between many users that need visit identical wireless medium simultaneously.

Mac-layer protocol comprises many rules that management conducts interviews to the broadcast medium of being shared by each user in the network.As everyone knows, some different multiple access technologies (being commonly called the MAC agreement) have been defined, under each agreement of managing MAC layer, to work.These multiple access technologies include but not limited to carrier wave divide multiple access (Carrier Division Multiple Access, CDMA), carrier sense multiple access (CSMA), frequency division multiple access (FDMA) and time division multiple access (TDMA).

As everyone knows, especially have among the WLAN of concentrated MAC agreement, access point (AP) provides control for the distribution of other wireless station (STA) access system of visited WLAN.AP is used to reduce between STA and the AP and the conflict of the communication packet between each STA self to the control of WLAN.By suitably controlling visit to medium, avoided conflict, reduce the grouping of losing, and increased the throughput of WLAN.

As everyone knows, many WLAN comprise multichannel (or multicarrier) MAC (MC-MAC).Although MC-MAC allows bigger STA medium access, provide control by needs to multichannel more, to the also further increase of demand of AP.In known WLAN, this may cause the increase of " expense " or system requirements, and these may influence the complexity of system and the cost that system realizes unfriendly.

Summary of the invention

According to representative embodiment, a kind of method of wireless communication comprises: a plurality of yards channels (cch) are provided in the single-frequency channel; In at least one described sign indicating number channel, distribute at least one uncontested period (CFP); And in another yard channel, distribute at least one the competition period (CP) that begins simultaneously with described CFP.

According to another representative embodiment, a kind of wireless network comprises: a plurality of wireless stations (STA); Access point (AP), it can be operated and authorize the visit of described STA to wireless medium; The superframe that in the single-frequency channel, has a plurality of yards channels (cch); At least one uncontested period (CFP) at least one described sign indicating number channel; And at least one competition period (CP) that begins simultaneously with described CFP in another yard channel.

Description of drawings

When read in conjunction with the accompanying drawings, will be understood best by following detailed the present invention.It is emphasized that various features needn't draw in proportion.In fact, for discuss clear for the purpose of, can increase or reduce size arbitrarily.

Fig. 1 is the rough schematic view according to the WLAN of representative embodiment.

Fig. 2 is the concept map according to the superframe structure with competition period (CP) and uncontested period (CFP) of representative embodiment.

Fig. 3 is the concept map that sends application of frame (RTSapp) form according to the request of representative embodiment.

Fig. 4 is the concept map according to clear to send accumulation (CTScum) frame of representative embodiment.

Fig. 5 is the concept map according to the sequential chart of example embodiment.

Embodiment

In the following detailed description, the unrestricted purpose for explanation has been set forth the example embodiment of open specific detail, so that the complete understanding to example embodiment is provided.Yet,, will be conspicuous with other embodiment that specific detail disclosed herein deviates from mutually for the those of ordinary skills that have been benefited from the disclosure.In addition, can omit the description of well-known equipment, method, system and agreement, fuzzy to avoid description of the invention.Yet,, can use in those of ordinary skills' such equipment within the vision, method, system and agreement according to example embodiment.At last, no matter actual conditions how identical reference number refer to the feature of system.

Notice that in the illustrative embodiment of Miao Shuing, network can be the wireless network with centralized architecture here.Described wireless network comprises (newer) modulation with renewal and wireless station (STA) and traditional STA of frame format.Illustrative ground, the network that described network can move under (traditional) IEEE 802.11 standards, and comprise one or more wireless station with the MAC layer that meets IEEE 802.11n or its spawn.As recognizing that the MC-MAC of described illustrative embodiment is based on the system of CDMA from summary of the present disclosure.Yet this instruction is not limited to the MAC layer by IEEE 802.11 consultative managements, and can be expected at this instruction of application in other networks/protocols.These networks include but not limited to: cellular network; Wireless lan (wlan); Time division multiple access (TDMA) agreement; CSMA; Has the CSMA (CSMA/CA) that conflict is avoided; And frequency division multiple access (FDMA).It is emphasized that these agreements only are illustrative, and under the situation that does not deviate from example embodiment, can use the agreement except the agreement that these are specifically mentioned.In addition, example embodiment may be used on being included in the various centralized networks of the STA that moves under the modulation of renewal and the frame format and traditional STA.

Fig. 1 is the schematic diagram according to the wireless network 100 of example embodiment.Wireless network 100 comprises the concentrated MAC layer in the AP (main frame) 102, and as example, this AP (main frame) 102 is according to an agreement operation in above-mentioned a plurality of illustrative agreements.AP 101 is a plurality of STA (wireless device) 101 services according to selected agreement.Illustrative ground, network 100 is WLAN, wide area network (WAN) or mobile telephone network, and STA (equipment) the 102nd, computer, mobile phone, PDA(Personal Digital Assistant) or the similar devices that typically moves in such network.As by four-headed arrow indication, but equipment 101 two-way communications; And AP 102 and equipment 101 can two-way communications.

Notice that according to certain mac-layer protocol, the communication from the equipment of STA to another equipment of STA is not direct; But such communication is through main frame 102, and main frame 102 (use known scheduling method) then arrives correct receiver equipment 101 with communications.

Also be appreciated that although some STA 101 only are shown, this is just for for the purpose of simplifying discussion.Obviously, can use many other equipment 101.At last, notice that each equipment 101 needs not to be identical.In fact, in network 100, can use the many different equipment that under selected agreement, moves.

Fig. 2 is the timetable 200 according to example embodiment, and shows the essential characteristic of dividing according to the time among the WLAN of representative embodiment.When looking back, will understand timetable 200 best in conjunction with the illustrative embodiment of Fig. 1.Begin and its duration equals the interval of target beacon transmit time (TBTT) and is defined as superframe 201 with the transmission of beacon 201, and comprise the basic element of hubbed mode.

The superframe of Fig. 2 illustrates the allocated bandwidth of a frequency channels.Naturally, this principle is applied to effectively by the AP 102 of WLAN 100 and a plurality of frequency channels of MC-MAC control.Only gone through a channel, to avoid the making description of illustrative embodiment fuzzy.This channel is divided into each subchannel by time and sign indicating number, and subchannel is called as a yard channel (cch), as shown in Figure 2.The time of sign indicating number channel divides CP and CFP is provided.During CP, the rule of the C-DCF that describes is obeyed in the network operation in " MC-CDMA based IEEE 802.11wireless LAN " (meeting summary of IEEE MASCOTS 2004, in the October, 2004) of G.Orfanos, J.Habetha, L Liu; And during CFP, AP 102 controls are as the network by 802.11a/e provided.The IEEE publication of being quoted is herein incorporated by reference especially.

As will be recognized, during CP, STA 101 fundamental freedom accessing subchannels or sign indicating number channel (cch); And during CFP, the cch visit is distributed by AP 102.The division of available resources is carried out in time domain and sign indicating number territory according to the broadcast message that comprises in beacon.It should be noted that the allocated frequency band of example shown in Fig. 2, wherein in 60% of the superframe duration, CP moves in sign indicating number channel (cch) 3 and cch4.

At selected interval, the AP 102 transmission beacons of (centralized) network 100.As everyone knows, the period between each beacon 202 is commonly called superframe.In the scope of network 100, receive beacon.In example embodiment, STA 101 asks service in network 100.For example, STA 101 can move under 802.11 agreements.Such agreement often is called as " listem-before-talk (listen before talk) " agreement.Equally, the request that may occur after receiving beacon between STA101 and the AP 102 sends (RTS) and clear to send (CTS) exchange.Can recognize that when one or more equipment were retained in the scope of main frame 101, this process continued.After first superframe interval stops, transmit another beacon, indicate the beginning of second superframe interval.

Transmission (first) beacon during the beacon period 202 of AP 102 after being right after its initialization, and to network signal transmission operation characteristic.The information that comprises in IEEE 802.11a beacon, AP 102 statement is for the duration of the CFP 204 of as shown in Figure 2 each cch.Thisly between each cch, carry out different CFP/CP and be assigned as network and increased flexibility.The STA that starts new connection transmits for the first time for it and can use CP, thereby reduces its delay till it is by the resource of mutatis mutandis CFP.In addition, the STA with low load or Best-Effort service can move under CP continuously.The total duration that have to be noted that CFP depends on Internet traffic, and can adjust each cch in each superframe by AP.

When the beacon period stops and after protection interval (not shown) stops, AP 102 accumulates CTS (CTScum) 203 transmission.In representative embodiment, CTScum 203 transmission provide all CTS orders to all STA 101 of network 100.For this reason, the one or more RTS of each STA 101 transmission are to AP 102.CTScum 203 transmits in all cch, and comprises and be used for information transmitted on the horizon during the CFP of each cch, thereby provides medium access grant to the STA of needs.Each access authorization (CFP) comprises the corresponding transmit leg that connects and recipient's address.Alternately, access authorization comprises connection identifier (CID.

As example, the CTScum of extra byte represents that the periodicity of the access authorization of (signal) previous statement repeats till the end of superframe, so that reduce expense.Equally, notify CFP among each cch to each STA 102.Each STA 101 stores time of being distributed and the subchannel that is used for access medium from this broadcasting.Advantageously, CTScum 203 has reduced the expense of MC-MAC, and has therefore improved service quality (QoS).

After the termination of CTScum 203, each cch is in CFP 205 separately.CFP 205 need move under the IEEE 802.11x or under the instruction of the IEEE publication of being quoted that as above merges.During this period, AP 102 keeps the control to medium, wherein the visit of described medium is authorized during beacon period 202 or CTScum 203.AP 102 also states the duration of CFP 205 to each cch.

After the termination of CFP 205, each cch enters one of CP in period 206 of superframe 201 or CFP.During this part of superframe 201, some cch restriction STA 101 carries out the CFP visit, and some cch allows STA 101 free access channels.After the termination of period 206, as shown in Figure 2, along with the next beacon period begins next superframe.

Some overviews are worth discussing.At first, the order of CFP period 205 and period 206 only is illustrative.Time sequencing that it should be noted that these periods can be put upside down with time sequencing shown in Figure 2.In addition, AP 102 radio slots 205 and 206 distribution, and particularly in the period 206 by control (CP) respectively with allow number, sign and the timing of the cch of free access (CFP).AP 102 determines demand based on the RTS grouping that receives from STA 101 during superframe before, and attempts correspondingly assigns access, asks and provide appropriate QoS to satisfy except that other known benefits.

As one of skill in the art will recognize that of being benefited from the disclosure, distributing CFP/CP in the period 206 between each cch is that network 100 has increased flexibility.For example, start between STA101 self and the AP 102 and each STA 101 self between the STA 101 of new connection can transmit for the first time it and use CP, thereby reduce the delay till it is by the resource of mutatis mutandis CFP.In addition, the STA with low load or Best-Effort service can move under CP continuously.The total duration that have to be noted that CFP depends on Internet traffic, and can adjust each cch in each superframe by AP.

According to illustrative embodiment, in many parallel cch, carry out channel width and divide the parallel running that has realized concentrated and decentralized model, this is very important to the different communication flow characteristic in the network enabled.In system with variable spread spectrum coefficient (SF), can keep a cch for signalingization during CP and transmission, wherein spread spectrum coefficient will define its capacity.At least for following reason, such channel is useful:

1. because any STA 101 can use this cch to be used for sending at any time the access request of CFP, so reduced access delay.

2. can more easily avoid deriving from the beacon delay that to expect and the conflict of the operation of CP on the same channel and CFP, this is because yard territory that is separated in of two transmission periods takes place, rather than the Time Division Multiplexing method of common IEEE 802.11a/e.

3. the STA 101 (for example, employed STA in medical treatment or emergency application) that has high quality-of-service (QoS) demand can transmit in the entire CF P time, thereby can guarantee transmission delay.

In addition, this instruction also considers according to the broadcast message that comprises in the beacon, in time domain and sign indicating number territory, and division of available resources between CP and CFP.In each superframe, CP in the sign indicating number territory the position and the duration of CP can change.In addition, by the transmission of RTSapp frame, transmit the data volume that will send to any other controlled entity or reciprocity recipient's signaling of AP or network.The RTSapp frame comprises wants data quantity transmitted, or according to the transmission request of traffic class.And also (for example, CTScum) middle signaling is transmitted down link, up link, direct link, the forwarding traffic that will transmit during CFP at control frame.This frame comprises and is used for information transmitted on the horizon during the CFP of each cch, promptly so-called access authorization.Each medium access grant comprises the corresponding transmit leg that connects and recipient's address.

Alternately, access authorization comprises connection identifier (CID.The periodicity of the access authorization of statement repeated before the CTScum of extra byte represented, up to the end of superframe.In addition, for connecting last time, AP can dispatch the transmission of all jumpings in its control range in the CTScum frame, thus the delay and the quantity of medium access trial when being reduced in multi-hop and connecting.And, if each MAC entity is given unique ID by AP during getting in touch, then can realize header-compressed.Can distinguish each MAC entity by given ID and AP MAC Address then.The hardware device that uses said method is also disclosed.

Fig. 3 is the concept map that sends application of frame (RTSapp) form according to the request of representative embodiment.The CFP resource of STA by asking to AP transmission RTSapp frame to be used to transmit.This frame is sent out with obeying the C-DCF access rule during CP, and comprises and want data quantity transmitted or according to the transmission request of traffic class.The latter defines the transmission rate that guiding AP suitably dispatches the transmission that is used for this MS.At S.Heier.Leistungsbewertung der UMTSFunkschnittstelle.Dissertation, Aachen University, 2003, can find its further details among the ISBN3-86073-167-9.In addition, can be according to for example IEEE802.11e/D9: " Wireless LAN Medium Access Control (MAC) andphysical layer (PHY) specifications:Medium Access Control (MAC) Enhancements for Quality of Service (QoS); TechnicalSpecification; IEEE LAN/MAN Standard Committee.IEEE, in August, 2004." maximum allowable delay is provided.The disclosure of described paper and ieee specification merges therewith especially by reference.

Fig. 4 is the concept map according to clear to send accumulation (CTScum) frame of representative embodiment.After beacon transmissions, after the protection at interval of a for example time slot, and then transmit clear to send accumulation (CTScum) frame.As previously mentioned, similar beacon, CTScum is transmitted in all cch, and comprises and be used for information transmitted on the horizon during the CFP of each cch, promptly so-called access authorization.Each access authorization comprises the corresponding transmit leg that connects and recipient's address.Alternately, access authorization comprises connection identifier (CID.The periodicity of the access authorization of statement repeated the end up to superframe before the CTScum of extra byte represented, so that reduce expense.

In order further to reduce expense, this instruction is considered to carry out address compression with hubbed mode.For this reason, STA 101 is storing a unique byte long address that is used as its identifier with AP 102 related backs, and 6 non-standard byte long addresses.One byte is enough to support 255 STA in the subnet, and provides unique address with subnet identifier for each STA.In addition, be obviously to distinguish each STA, needed MAC Address number can (from 4 bytes) be reduced to minimum three bytes, and it comprises source, destination and subnet address.In IEEE 802.11 WLAN medium access control (MAC) and physical layer (PHY) standard: Wireless LAN Medium Access Control (MAC) and physical layer (PHY) specifications, TechnicalSpecification, IEEE LAN/MAN Standard Committee.IEEE, in July, 1999; With WLAN medium access control (MAC) and physical layer (PHY) standard: WirelessLAN Medium Access Control (MAC) and physical 1ayer (PHY) specifications, Technical Specification, IEEE LAN/MAN StandardCommittee.IEEE can find further details in 1999 7 months.The disclosure of the ieee specification of being quoted is incorporated herein by reference especially.

According to access authorization, STA is with the transmission among the predefined procedure startup cch.Come the correct reception of data grouping is replied with (ACK) frame of replying that transmits after the time at short interFrameGap (SIFS).Because SIFS is mainly by transmit leg turnaround time definition, so identical distance separates ACK with next Frame, so that allow to carry out from identical MS the continuous transmission of packet.In Fig. 5, provide example.

As shown in Figure 5, in two cch, the superframe duration 40% after, CFP expires.In cch2 and cch4, allow the CP operation then.According to the statement of the TBTT in the last beacon frame, AP begins beacon transmissions sense channel idle in concentrated coordination function interFrameGap (PIFS) after.For fear of with the conflicting of beacon, the resource authorization of CFP is considered TBTT, and when arriving TBTT, the STA of the previous beacon of reception that moves under CP should abandon transmitting.

At the disclosure, notice that the whole bag of tricks described herein and equipment can be realized in hardware and software.In addition, only by example but not under any limitation, comprise described the whole bag of tricks and parameter.At the disclosure, those skilled in the art can realize various example apparatus and method when the required equipment of the technology of determining themselves and these technology of realization, and still within the scope of the appended claims.

Claims (13)

1. method of wireless communication, described method comprises: a plurality of yards channels (cch) are provided in the single-frequency channel; In at least one described sign indicating number channel, distribute at least one uncontested period (CFP); And in another yard channel, distribute at least one the competition period (CP) that begins simultaneously with described CFP.

2. the method for claim 1, also being included in provides a plurality of competition periods that begin simultaneously in each yard channel.

3. method as claimed in claim 2 also is included in beacon accumulation clear to send (CTScum) was provided after the period.

4. the method for claim 1 wherein is provided in superframe by described providing and described distribution.

5. the method for claim 1 also comprises: will be to the transmission of access point (AP) signaling by wireless station (STA) data quantity transmitted, or the request of wanting data quantity transmitted or being used for failing according to the traffic class supplementary biography.

6. method as claimed in claim 5, wherein said signaling transmission also comprises the transmission of RTSapp frame.

7. the method for claim 1 also comprises: the traffic that the signaling transmission will be transmitted during described CFP in control frame.

8. method as claimed in claim 7, wherein said frame comprise for information transmitted on the horizon during the CFP in each described sign indicating number channel.

9. method as claimed in claim 8 also comprises the corresponding transmit leg that connects and recipient's address are provided.

10. method as claimed in claim 8 also comprises connection identifier (CID.

11. a wireless network comprises: a plurality of wireless stations (STA); Access point (AP), it can be operated and authorize described STA visit wireless medium; The superframe that in the single-frequency channel, has a plurality of yards channels (cch); At least one uncontested period (CFP) at least one described sign indicating number channel; And at least one competition period (CP) that begins simultaneously with described CFP in another yard channel.

12. wireless network as claimed in claim 11, wherein said superframe also are included in a plurality of competition periods that begin simultaneously in each yard channel.

13. wireless network as claimed in claim 11, wherein said superframe also comprise the accumulation clear to send (CTScum) of beacon after the period.

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