WO2000059260A1 - Procede de communications de donnees et signaux de donnees - Google Patents

Procede de communications de donnees et signaux de donnees Download PDF

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Publication number
WO2000059260A1
WO2000059260A1 PCT/GB2000/001125 GB0001125W WO0059260A1 WO 2000059260 A1 WO2000059260 A1 WO 2000059260A1 GB 0001125 W GB0001125 W GB 0001125W WO 0059260 A1 WO0059260 A1 WO 0059260A1
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WIPO (PCT)
Prior art keywords
data
channel
wherem
remote
nodes
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Application number
PCT/GB2000/001125
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English (en)
Inventor
John David Porter
Walter Charles Vester
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Adaptive Broadband Ltd.
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Publication date
Application filed by Adaptive Broadband Ltd. filed Critical Adaptive Broadband Ltd.
Priority to AU34442/00A priority Critical patent/AU3444200A/en
Publication of WO2000059260A1 publication Critical patent/WO2000059260A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • H04Q11/0478—Provisions for broadband connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5603—Access techniques
    • H04L2012/5604—Medium of transmission, e.g. fibre, cable, radio
    • H04L2012/5607—Radio
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5603—Access techniques
    • H04L2012/5609—Topology
    • H04L2012/561—Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5629—Admission control
    • H04L2012/563—Signalling, e.g. protocols, reference model
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5629—Admission control
    • H04L2012/5631—Resource management and allocation
    • H04L2012/5632—Bandwidth allocation

Definitions

  • the present invention relates to a data communications method and a data signal for use m a data network where access to a common communications channel must be controlled
  • the present invention provides a bandwidth efficient and highly integrated method of performing robust data transfer and bandwidth allocation m a pomt-to-multipomt data network m which bandwidth is a scarce resource bemg managed
  • the advantages of the present invention over other similar implementations are that it provides the ability to dynamically assign bandwidth to multiple network terminals and multiple types of traffic BACKGROUND OF THE INVENTION
  • Data networks can be classified m many ways, but for the purpose of the present invention, it is useful to classify them by their means of accessmg the medium over which data is communicated
  • the relevant classifications are broadcast and non-broadcast
  • Ethernet Ethernet uses broadcast medium access All network nodes sharing the network medium hear all traffic bemg passed over the medium Traffic is directed to mdividual network nodes via physical layer addresses that are attached to the data packets bemg sent over the medium When multiple network nodes attempt to transmit data simultaneously there is the possibility for contention among the nodes for access to the medium
  • a modification to the broadcast network is the broadcast network with hidden terminals In this network, all termmals share the same medium. however it cannot be guaranteed that all terminals can hear each other All that can be guaranteed is that all termmals can hear the central network node, referred to herein as the access pomt For this reason, it is not enough for each terminal simply to momtor the channel m order to detect contentions Feedback on success or failure of network contention must also be commumcated back to the network terminals by the access pomt
  • a non-broadcast network can be provided using connection-oriented protocols such as, for example, asynchronous transfer mode (ATM) ATM provides for the reservation of channel bandwidth by network nodes by the defmition of virtual channels within the medium More generally within a non-broadcast network, the medium that connects a network node to the rest of the network can only be accessed by two devices the network node itself, and the network switch to which it is attached The medium itself is full duplex. so there is no possibility for contention
  • ATM asynchronous transfer mode
  • Broadcast networks require some mechanism for distributing access to the medium This is because as network loading mcreases. the non-determmistic nature of random attempts at accessmg the medium causes the throughput and efficiency of the network to fall off catastrophically The uncertainty of the loadmg or the potential success of the medium contention results m non- determmistic transit times for traffic bemg passed across networks with broadcast medium access Furthermore, each node on the network is a peer, meaning it has equal priority when attempting access to the medium
  • non-broadcast networks gracefully approach maximum capacity until they reach very high medium loadmg Because there is no contention, traffic can be passed over the medium with known absolute limits to propagation delay time and bit error rate Network transfer efficiency can therefore be mamtamed. and m particular under conditions of high network loadmg
  • the problem of poor performance of networks usmg a broadcast medium at hi ⁇ h network loadmg can be solved bv emulating non-broadcast networks This is achieved by assigning fixed time slots to all nodes of the network, and restricting the transmissions of each node to its particular assigned time slot Such an arrangement is known as Time Division Multiple Access (TDMA) While such time-slot arrangements allow the network to operate well when at high levels of loadmg and with equal data loads from each network terrmnaL at low network loadmg the efficiency of medium utilisation is very poor, as each node must wait for its assigned time slot before transmitting SUMMARY OF THE INVENTION
  • the present invention provides for dynamic time slot assignment via centralised control of medium access In order for a network node to gam access to the medium it must first be granted permission by the access pomt The grant to a particular node of permission to access the medium is commumcated by the access pomt to all network nodes, so that each node has substantially full a priori knowledge
  • a data communications method for use m a pomt-to-multipomt network comp ⁇ smg a central control node and one or more remote subsc ⁇ ber nodes, said network having a bi-directional commumcations channel accessible to all network nodes, said method comp ⁇ smg the steps of a) transmitting a first data portion mcludmg control data onto the channel from the central control node exclusively within a first time penod, b) receiving said first data portion mcludmg control data at each of said remote subsc ⁇ ber nodes.
  • control data indicates to each of said remote subsc ⁇ ber nodes those particular of the nodes which are permitted to transmit at step c) whereby access to the channel can be dynamically controlled by the central control node
  • the control data can mdicate to each of the remote subsc ⁇ ber nodes the structure of the remamder of the first data portion, and also mdicate to each of the remote subsc ⁇ ber nodes the expected content and/or structure and/or timing of the further data portions to be transmitted from the remote nodes to the central control node at step c)
  • the method mcludes the further steps of generating a channel reservation request requesting permission to transmit onto the channel, transmitting the channel reservation request onto the channel within a contention pe ⁇ od defined by said control data, said contention pe ⁇ od bemg a pe ⁇ od within said second time pe ⁇ od when the further data portions are not bemg transmitted, and receiving said channel reservation
  • a time-division duplex data signal for transmission onto a channel for use m a pomt-to-multipomt data network comp ⁇ smg a central control node and one or more remote subsc ⁇ ber nodes, said signal comp ⁇ smg a) a first data portion mcludmg a control data portion for transmission from the central control node over the channel to each of the remote subsc ⁇ ber nodes, and b) further data portions for transmission from particular of the remote subsc ⁇ ber nodes over the channel to the central control node in response to the control data portion.
  • said control data portion mdicates to each of the remote subscnber nodes the particular of those nodes which are permitted to transmit one or more further data portions, wherem access to the channel can be dynamically controlled by the central control node
  • the control data portion may further compnse a downstream structure data portion indicating the structure of the remamder of the first data portion and an upstream structure portion mdicatmg the expected contents and/or structure and/or timing of each of the further data portions
  • the signal may further mclude a channel reservation request portion for transmission from particular of the remote subsc ⁇ ber nodes over the channel to central control node, said channel reservation request portion comp ⁇ smg one or more channel reservation requests each generated by a smgle remote subsc ⁇ ber node in response to a requirement to transmit data traffic to the central control node, wherem each of the channel reservation requests are transmitted by the respective remote subsc ⁇ ber nodes onto the channel du ⁇ ng the channel reservation request portion, wherem each of the channel reservation requests is m contention with one another for channel capacity
  • the central control node has the ability to throttle any subsc ⁇ ber terminal ' s access to the medium
  • the present invention allows persistent bandwidth allocations for support of constant bit rate traffic, and by virtue of dynamic bandwidth allocation also enables statistical multiplexing, which mcreases the number of subsc ⁇ bers that can be provisioned service from a smgle access pomt It is a further advantage of the present invention that it provides high efficiency of medium utilization during pe ⁇ ods of high network loadmg and provides low latency medium access du ⁇ ng pe ⁇ ods of low network loadmg
  • each network node has the ability to e ⁇ or check each data cell of each received data portion mdependently, thus allowing implementation of a selective repeat automatic repeat query m a point-multipoint network.
  • position of data within a portion conveys mformation. More specifically, acknowledgements of the receipt of data bursts are ordered the same as the bursts themselves, therefore the acknowledgement does not require an additional identifier to be transmitted over the air. This mcreases bandwidth efficiency BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the present invention will become apparent from the following detailed desc ⁇ ption of a particularly preferred embodiment thereof, presented by way of example only, and by reference to the accompanying drawings, m which:-
  • Figure 1 shows the overall frame structure of the time division duplex data signal of the present invention
  • Figure 2 shows the frame structure of the control data portion used in the present invention
  • Figure 3 shows the frame structure of a smgle reservation request acknowledgement cell of the present invention
  • Figure 4 shows the frame structure of a smgle downstream acknowledgement cell of the present invention
  • Figure 5 illustrates the structure of a single downstream payload cell of the present invention
  • Figure 6 shows the structure of a smgle subsc ⁇ ber reservation request cell of the data signal of the present invention
  • Figure 7 shows the frame structure of a smgle upstream acknowledgement cell of the present invention
  • Figure 8 illustrates the frame structure of an upstream payload cell with reservation request of the present invention
  • Figure 9 illustrates the frame structure of a smgle upstream payload cell without reservation request
  • Figure 10 demonstrates the sequence of messages mvolved in remote subsc ⁇ ber terminal registration m the present invention
  • Figure 11 shows the sequence of messages mvolved in transmitting a smgle payload cell from upstream to the central access pomt from a remote subscriber terminal;
  • Figure 12 shows the sequence of messages mvolved m transmitting multiple payload cells upstream to the central access pomt from a remote subscriber terminal
  • FIG. 13 shows a schematic representation of the wireless access network within which the present invention is employed.
  • the method of data communication and data signal of the present mvention are chiefly for use within a wireless access network, although it will be readily apparent to those skilled m the art that the said method and signal may equally be employed within a wired network Within the particularly preferred embodiment to be desc ⁇ bed herem.
  • Each cell 102 consists of a central access pomt 104 and multiple subscnber units 106 Subsc ⁇ ber units communicate to the network only through the access pomts, makmg the network a pomt-multipomt architecture
  • Each access pomt is the center of all wireless network communication for the particular cell, and thus is the locus of control of access to the wireless medium for the cell
  • Each access pomt is connected to a wide area network 120 via a respective backhaul link 108
  • Higher layer network functions are provided by means of a network server 110
  • Figure 13 shows multiple cells and access pomts fo ⁇ ning the network
  • the following desc ⁇ ption concentrates on the operation of the present mvention m a smgle cell only
  • FDD frequency division duplexing
  • TDD time division duplexing
  • each cell to which the mvention is applied is composed of multiple switches On one end, co ⁇ esponding to an access pomt 104.
  • Each subscnber terminal has a smgle wireless port and a smgle physical wired port
  • the network model is complicated by the fact that a subsc ⁇ ber termmal can be powered on and off at will, thus there are tunes that the subsc ⁇ ber termmal switches are not accessible to the network This gives ⁇ se to the concept of subscnber termmal registration, the procedure for which will be desc ⁇ bed m detail later Du ⁇ ng the registration process, a subsc ⁇ ber termmal negotiates with an access pomt to be assigned a temporary port identifier, referred to as a subsc ⁇
  • the present mvention is directed towards controlling access of the subscnber termmals to the wireless medium through central control of the subsc ⁇ ber termmals by the access pomt
  • the access pomt is provided with a medium access controller (MAC) which administers the medium control
  • MAC medium access controller
  • each remote subscnber termmal is also provided with a compatible medium access controller for respondmg to the central MAC m a master-slave manner the subsc ⁇ ber terminals request access to the medium and the access pomt has the ability to grant access or fail to grant access based on the current level of network utilisation
  • Access to the network is granted m the form of time slots - when a subsc ⁇ ber termmal is granted the ability to access the wireless network medium, it is granted one or more time slots m which it can transmit Within the granted time slot the entire medium capacity is available to the subscnber node to transmit its payload data
  • a medium access controller it is
  • the MAC operates by controlling transmissions on the medium by the definition of a MAC frame, bemg the framework m which data transmissions take place
  • a MAC frame which data transmissions take place
  • Figure 1 shows the overall structure of a smgle MAC frame
  • the MAC frame consists of a downstream portion, generated by the access pomt and broadcast to all subsc ⁇ ber termmals. and an upstream portion, which consists of a contention interval and all data bursts bemg sent from subsc ⁇ ber termmals back to the access pomt
  • the downstream portion consists first of a downstream preamble (2)
  • the preamble is a Physical layer synchronization sequence of fixed length, used for frame acquisition and channel estimation. Only one downstream preamble may occur per MAC frame Immediately following the preamble is the frame desc ⁇ ptor header (FDHDR) (4) The FDHDR desc ⁇ bes the complete contents of the remainder of the MAC frame The size of the FDHDR may varv although only one FDHDR may occur per frame
  • the FDHDR contains a map of all traffic upstream and downstream, to occur within the MAC frame m both the remamder of the downstream and the complete upstream directions .
  • subsc ⁇ ber termmals demodulate the FDHDR and from that gam complete knowledge of the traffic that will occur within the remamder of the frame Only one FDHDR may occur per MAC frame The precise contents of the FDHDR are shown m Figure 2 and descnbed m detail m Table 1 below Field Tag Description
  • Pomt ID Identifies the access pomt that ongmated the frame desc ⁇ ptor header
  • Downstream Identifies the subscnber units bemg sent cells. 16 Map the number of cells to be sent, and the traffic type bemg sent
  • Upstream Identifies the subscnber units that have been 16 Map granted reservations, the number of cells to be sent by each, and the traffic type allowed Field Tag Description No. of Bits
  • the downstream map in the FDHDR consists of respective one or more data sequences to identify each SU to which data traffic is to be sent and to inform the SU of the number of cells bemg sent and the traffic type.
  • the data sequence is repeated for each SU to which data is bemg sent m the present MAC frame, with the appropriate SU_AID at the start of each sequence and traffic information in the form of a Cell_cnt value and a TRjype flag.
  • the downstream burst maps therefore communicate to all of the sus which of the SUs are to be sent downstream bursts in the present MAC frame, and it should be understood that multiple downstream bursts may be sent to multiple different SUs in the same MAC frame.
  • the upstream map m the FDHDR takes the same form, that is one or more respective data sequences to identify those SUs which have been allocated a transmission slot (i.e. allocated an upstream burst) and which are therefore expected to transmit in the upstream portion of the present MAC frame, the number of cells they are to transmit and the traffic type.
  • the data sequence is repeated for each SU which is expected to transmit with the approp ⁇ ate change in SU_ALD at the start of the sequence, Cell_cnt value, and TR_type flag.
  • the upstream burst maps therefore communicate to all of the SUs which of the SUs have been allocated an upstream burst slot m the upstream portion of the present MAC frame, and it should be understood that multiple upstream bursts may be received from multiple different SUs m the same MAC frame.
  • the format of the upstream and downstream maps in the FDHDR is also shown m Figure 2, and given m detail m Table 1 1 below -
  • TRjype Traffic pnonty type (allowed values 0 to 3) 4
  • the RRA acknowledges a request by a subsc ⁇ ber for upstream time slots and can also commumcate signal propagation delay
  • RRA reservation request acknowledgement
  • the precise contents of the RRA are shown m Figure 3 and desc ⁇ bed m detail m Table 2 below
  • RTRN Return Code Communicates reservation status 4 to SUs and SU_AID status to SUs performing registration Field Tag Description No. of Bits
  • DELAY Delay compensation bits These bits are 12 assigned during subscnber unit registration and cause a shift m subscnber unit timing.
  • DACK Downstream Acknowledgement
  • Each DACK cell contams a downstream ack or nack of a smgle upstream burst from a previous MAC frame
  • the precise contents of a DACK cell are shown in Figure 4 and described in detail in Table 3 below.
  • the MAC operates on a principle of cell bursts for communicating payload data between the access pomt and the subscnber termmals by allowing multiple cells of data to be sent to or from a particular subscnber unit at a time
  • a burst must always consist of at least one cell.
  • this smgle cell must be an upstream cell with reservation request (UCELLR)
  • Additional cells m the upstream burst are m the format of a UCELL - an upstream cell without reservation request (20)
  • Upstream cells are discussed m more detail later Downstream bursts can also consist of multiple cells, but there is oniy one type - the downstream cell (DCELL) 10.
  • DCELLs there can be many DCELLs per frame - either several directed to a smgle subscnber termmal, or several directed to several subsc ⁇ ber termmals.
  • Each DCELL contains one ATM cell of payload data.
  • the MAC allows bursts to have a maximum size of six cells, although more or less cells may be designated per burst if required m a future implementation without departing from the scope of the present mvention.
  • the structure of a DCELL is shown m more detail m Figure 5, and desc ⁇ bed m Table 4 below
  • SEQ Sequence number Used by the MAC to resequence cells that get out of sequence due to cell loss and subsequent cell repetition
  • VPI Virtual Path Identifier
  • VCI Virtual 24 ATM Header Channel Identifier
  • Traffic Type Traffic Type
  • CRC Cyclic redundancy code Used to verify 16 co ⁇ ect receipt of the downstream cell.
  • the downstream burst concludes the downstream portion transmitted by the access point and received at all subsc ⁇ ber termmals. There then follows a slight delay due to subscriber turnaround time (STT) 12.
  • STT subscriber turnaround time
  • the STT vanes with distance to the farthest subscriber umt A typical maximum distance to a subscriber unit could be , for example, 5km, although this obviously depends on the network configuration and the size of each network cell.
  • the Upstream Portion of the MAC frame being data transmitted from the subscriber units to the access point.
  • the entire expected structure of the upstream portion has already been commumcated to each and every subscriber terminal in the FDHDR transmitted in the downstream portion. Therefore, each subscriber terminal knows whether or not it is permitted to transmit in the upstream portion, what data it is to transmit and when it is to transmit this data. In this way absolute control of the contents of the upstream portion can be controlled by the access point. With such a mechanism, however, it becomes necessary to define a period in which subscriber terminals can first communicate a request for transmission permission to the access point without which no subsequent permission would ever be granted. This period forms the first part of the upstream portion, being the subscriber reservation request (SRR) portion 14.
  • SRR subscriber reservation request
  • the SRR is a contention based reservation request interval. If a subscriber terminal has been sitting idle with empty data queues, the arrival of a burst of data on its physical port will force it to request a time slot reservation from the access pomt. Because the subscriber terminal has no active reservations, and because it is believed that at any given time the number of termmals makmg initial bandwidth requests will be small, it is reasonable to force the subsc ⁇ ber terminals to contend for reservations. This contention window is kept as small as possible while still allowing reasonable success probability by employmg a novel implementation of aloha contention control schemes.
  • the subscriber terminal ceases requesting bandwidth in the contention slots, allowing other terminals access to the contention interval.
  • the number of SRR's that may occur m one MAC frame is commumcated to the subsc ⁇ ber termmals m the FDHDR. Multiple slots can be made available during times of heavy request traffic.
  • the start of the contention interval can be calculated by the subscriber termmals by virtue of the FDHDR indicating to each terminal the number of RRAs, DACKs and the structure of the downstream burst in the subsequent downstream portion of the MAC frame.
  • the contention interval then begins immediately after the end of the downstream burst, allowing for the STT.
  • the structure of a single SRR to be transmitted during the contention interval is shown in Figure 6, and described in detail in Table 5 below
  • the upstream acknowledgement portion 16 Following the contention interval comes the upstream acknowledgement portion 16 . containing upstream acknowledgement (UACK) cells of each downstream burst received du ⁇ ng the downstream portion Each UACK indicates upstream ack or nack of a smgle downstream burst from a previous MAC frame As many UACKs may be transmitted m each upstream acknowledgement portion as there were downstream bursts m the the downstream portion The structure of each UACK cell is shown m Figure 7, and descnbed m detail below m Table 6
  • the upstream burst portion 22 Following the upstream acknowledgement portion comes the upstream burst portion 22. containing cell bursts from subsc ⁇ ber units which were granted permission m the FDHDR to transmit payload data to the access pomt
  • the FDHDR from the downstream portion contams the instructions to the subsc ⁇ ber terminals on when to transmit a burst m the upstream burst portion, and what the burst is expected to contam
  • Each upstream burst contams one or more data cells with the same traffic type bemg sent from a particular subscnber terminal
  • Each upstream burst made m the upstream burst portion may be from a different subscnber unit, or alternatively may be from the same subscnber unit depending upon the channel allocations granted to the subscnber units In this way channel allocations can be dynamically arranged between the subscnber terminals from MAC frame to MAC frame, depending on the network traffic loadmg and the traffic pno
  • VPL VCI Traffic Type
  • Cell Loss 24
  • ATM Header Pnonty Payload Payload data 48*8 CRC Cyclic redundancy code Used to venfy 16 co ⁇ ect receipt of the downstream cell
  • SEQ Sequence number Used by the MAC to 8 resequence cells that get out of order due to cell loss and retransmission.
  • VPI Condensed Includes VPI, VCI. Traffic Type, Cell Loss 24
  • CRC Cyclic redundancy code Used to venfy 16 co ⁇ ect receipt of the downstream cell.
  • Channel access information for a particular MAC frame is communicated to all network termmals by the access pomt by virtue of the FDHDR
  • the MAC is fundamentally dependent on the subsc ⁇ ber termmals ' knowledge of the timing of all network traffic from the FDHDR. All traffic over the wireless network medium must therefore be contamed within the MAC frame, whose contents, size, and time ahgnment are determmed by the MAC at the access pomt. This requires that subsc ⁇ ber termmals have the ability to synchromse to the traffic m the network before they can transmit within the contention interval defined by the access pomt.
  • Subscnber termmals therefore achieve physical layer synchronisation by monitoring the channel for the 32 symbol correlation sequence refened to as the PREAMBLE m figure 1 They then acquire MAC frame synchronisation by searching for the 8 bit frame synchronisation sequences located at the start of each transmitted cell.
  • the wireless medium over which the data is sent is by nature unreliable
  • the wireless network operates at a speed that prohibits the use of forward error correction (FEC) to improve the raw channel bit error rate
  • FEC forward error correction
  • ARQ selective repeat automatic repeat query
  • the present mvention therefore has the ability to perform quick turnaround automatic repeat query while still satisfying quality of service commitments of the wired network beyond the access pomt
  • the retry mechanism relies on the upstream and downstream acknowledgements of the MAC (UACK and DACK), which contam bit maps co ⁇ esponding to mdividual cells m an upstream or downstream burst
  • Each network node has the ability to detect bit errors usmg the CRC codes at the end of each cell
  • the recipient of a burst then conveys the success or failure of the a ⁇ ival of a particular cell by setting the corresponding bit of the burst map contained m the ACK
  • the onginal sender of the burst reads the bitmap m the ACK and then re-sends the cells that were lost
  • the bit map is arranged so that the position of a bit m the bit map corresponds to the order m which a burst was received In this way the bit position conveys information m itself and therefore the acknowledgement does not require an additional identifier to be transmitted
  • the subsc ⁇ ber umt Upon power up, the subsc ⁇ ber umt (SU) generates an autho ⁇ sation initiation cell which must be sent to the access pomt It is placed m a traffic queue, which causes the MAC to proceed through the process of requesting a reservation
  • the SU searches for the preamble sequence (30) of the downstream portion of the MAC frame (see figure 1)
  • the SU demodulates the frame desc ⁇ ptor header (32) From the contents of the frame desc ⁇ ptor header, the SU knows exactly the framing and timing of the remamder of the MAC frame, and thus the exact location of the contention interval for its reservation request (SRR m figure 4)
  • the SU transmits a reservation request for a one-cell reservation (34) Smce the subsc ⁇ ber umt has not yet been granted an SU_AID, m this reservation request the SU_AID will be set to zero Because only a smgle cell is
  • the access pomt If the access pomt receives the reservation request error free, it will send a reservation request acknowledgement (RRA) m the next MAC frame (36) Contained within the RRA will be the SU_ALD assigned by the access pomt to the subscnber umt The subsc ⁇ ber termmal will now use this SU AID m all future upstream bursts As a result of the reservation acknowledgement, the subscnber termmal now has knowledge that its reservation request has been received by the access pomt It waits an mdetermmate amount of time (38) to be granted a timeslot in which to transmit the authentication initiation cell The SU continues to demodulate FDHDRs that are sent out by the AP Eventually, an FDHDR (40) will be sent out with an upstream burst map (Upstream Map m figure 2) that mcludes the SU's SU_AID This indicates to the SU that it must transmit its cell within the upstream portion of the current MAC frame (42)
  • RRA
  • successful cell arnval at the access pomt causes a downstream cell acknowledgement to be generated for transmission du ⁇ ng the downstream portion of the next MAC frame (44)
  • the authentication initiation cell is routed (46) to the access network control server (110), which generates a challenge message and routes it back to the subsc ⁇ ber termmal
  • This cell enters one of the access pomt's traffic queues When a time slot is available for sendmg traffic, it is sent downstream to the SU by the AP (48)
  • a radio control application that executes on the SU receives the challenge cell and generates the authentication response This cell is placed m one of the subsc ⁇ ber terminal' s traffic queues, which causes the MAC to generate another SRR -After the AP has granted the reservation, the SU sends the cell upstream Acknowledgement of cell arnval by the AP, and passage of additional access network signalling between the SU and the AP m the manner desc ⁇ bed above, completes the registration and authentication process (52)
  • the SU While sitting idle, the SU continuously momtors the downstream bursts (60) from the AP m order to demodulate the FDHDR and thus have full knowledge of the remamder of the MAC frame
  • a smgle payload cell (62) ar ⁇ ves at the MAC of the SU, it enters the queue co ⁇ espondmg to its traffic type
  • the SU MAC then generates an SRR(64) and transmits it during the reservation contention interval of the next MAC frame If the SRR is received conectly.
  • the AP generates a reservation request acknowledgement (66) and transmits it m the downstream portion of the next MAC frame
  • the SU receives the acknowledgement and continues to momtor the downstream portion and demodulate the FDHDRs
  • the AP grants a time slot to the SU (68)
  • the grant is commumcated via the FDHDR. which mcludes burst maps for each burst to be sent m the remamder of the MAC frame
  • the SU detects its SU_ALO m one of the burst maps of the FDHDR.
  • the number of cells granted is also part of the burst map, m this example only one cell was requested so only one cell will be granted
  • the SU generates an upstream cell (UCELLR) which, m addition to the payload data, mcludes a reservation request that mdicates to the AP whether the reservation is to be maintained or released In this case, smce the traffic to be sent consists of only one cell, the reservation request will request 0 cells (the Cells field of the UCELLR m figure 8 is set to 0)
  • the UCELLR (70) is then sent upstream during the time slot assigned to it by the AP
  • the same time slot m which the SU's burst map appeared m the FDHDR is the same time slot m which the UCELLR is to appear m the upstream portion of the MAC frame
  • the AP MAC granted a reservation to the SU m the downstream portion of the current frame, it is expecting to receive the cell m the upstream portion of the same frame, and is expecting to send a DACK in the subsequent MAC frame.
  • the AP MAC has assembled most of the bits compnsmg the DACK, minus the bit map containing the acknowledgements of the mdividual cells
  • the AP receives the smgle upstream cell correctly (verified usmg its CRC)
  • it sets the co ⁇ esponding bit m the DACK (72)
  • the SU receives the DACK m the downstream portion of the subsequent MAC frame, it will know that both the upstream data cell and the attached reservation request were received conectly by the AP
  • the request for 0 additional cell reservations by the SU is received by the AP MAC and processed accordmgly At this pomt the SU has completed the process of cell transfer It sits idle, continumg to momtor the downstream bursts and awaiting the arnval of data from its external port
  • Thisnach ⁇ o differs from the previous strig ⁇ o m that it demonstrates the MAC ' s combination of payload data ARQ and reservation request acknowledgement mto a smgle message
  • the MAC is able to use the payload cell acknowledgement for both the reservation request acknowledgement and the payload cell acknowledgement Because cell acknowledgement and retry is handled at the MAC layer, it is possible for the wireless access network to maintain short cell latencies even during retries
  • the payload data (80) ar ⁇ ves at the SU's MAC layer, it is put mto the approp ⁇ ate traffic queue for transmission
  • the arnval of the data causes the SU to initiate the reservation request process
  • the SU waits for the next downstream burst (82), then demodulates the FDHDR to determine the location of the contention interval within the current MAC frame 0
  • the SU can request a maximum of six slots
  • the SU generates an SRR (84) and transmits it during the contention interval Smce the number of cells to be transmitted m this example is greater than the maximum number that can be requested, the SU requests six slots
  • the SU generates the request and transmits it du ⁇ ng the contention window
  • the AP receives the SRR, it acknowledges 5 the request by placmg an RRA (86) m the downstream portion of the next MAC frame
  • the .AP grants time slots to the SU (88)
  • the grant is commumcated via the FDHDR. which mcludes burst maps for each burst to be sent m the remamder of the MAC frame
  • the SU detects its SU_AT-D m one of the 0 burst maps of the FDHDR, and takes that as an mdication that it is to send some of its traffic upstream
  • the number of cells granted is also part of the burst map.
  • the access pomt could grant anywhere from one to six cells In this example six cells are granted to the subsc ⁇ ber terminal
  • the SU generates an upstream cell (UCELLR) which, m addition ⁇ ⁇ ; to the payload data, mcludes a reservation request that mdicates to the .AP that it is requesting time slots for four additional cells
  • UELLR upstream cell
  • the SU also generates cells to fill the remainmg five slots that it has been granted for the current burst
  • remainmg cells need not contam reservation requests - they follow the format of the UCELL (see figure 9)
  • the burst of six cells is then sent upstream (90) during the time slots allocated to the SU m the upstream portion of the MAC frame
  • the AP MAC expects the first cell of the burst to contam a reservation request In this case, it finds that the SU has requested four additional time slots As mentioned m the previous strigno. the DACK also acts as an acknowledgement of the reservation request The AP therefore grants four time slots m the upstream burst portion of the present MAC frame (92) The SU generates its UCELLR plus three UCELLs. and places a reservation request of 0 slots m UCELLR The upstream burst is sent as before (94)
  • the .AP has now updated the number of reservations bemg maintained for the SU However, if any of the four cells that the .AP expected is received m error, the SU will need to retransmit it It is not practical to require the SU to request a reservation and await the reservation grant m order to re-send the single cell that was m error Rather, any time the AP receives a cell m error, it mcrements the number of slots reserved for the particular SU In this example, the AP had received a UCELLR with a reservation request of 0 cells (94) However.
  • the SU receives the FDHDR and the DACK of the next MAC frame, it will know that it has one slot reserved for it and it will know which cell to re-transmit from the position of the nack m the DACK map If the .AP verifies correct reception of the four cells, it sets the conesponding bits in the DACK. Smce the UCELLR contamed a reservation request for 0 slots, no further reservations are needed and the transfer of cells from SU to AP is complete upon downstream receipt of the DACK (96) by the SU.
  • va ⁇ ous of the data cells and in particular various of the data payload cells as bemg ATM cells
  • the data cells need not be ATM cells exclusively, but may mstead be data cells of a different structure which still satisfy and support ATM quality of service requirements. In this case, such data cells of a different structure are ATM compatible data cells.
  • the present mvention presents a data communications method and system and a data signal wherein dynamic time va ⁇ able time-division duplexing can be achieved by virtue of control data in the form of a frame desc ⁇ ptor header providing full a pno ⁇ knowledge to every subscnber termmal in a cell of the expected contents, structure and/or timing of the remamder of the data to be transmitted onto a common channel m both the downstream and subsequent upstream direction m the remamder of the frame.
  • the provision of this is a p ⁇ ori knowledge to each subscnber termmal via the frame descnptor header facilitates the many advantages of the present mvention as desc ⁇ bed earlier.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention concerne un procédé de communications de données et un signal de données dans lesquels le duplexage dynamique variable temps et division dans le temps peut être réalisé grâce à des données de contrôle sous forme d'en-tête de description de trame, apportant une connaissance complète à priori de chaque terminal d'abonné dans une cellule des contenus attendus, la structure et/ou la synchronisation du reste des données devant être transmises via un canal commun dans les deux directions montante et descendante dans le reste de la trame. Cette invention présente l'avantage de maintenir une haute efficacité d'utilisation du canal sans tenir compte de la symétrie du trafic montant et descendant.
PCT/GB2000/001125 1999-03-31 2000-03-24 Procede de communications de donnees et signaux de donnees WO2000059260A1 (fr)

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AU34442/00A AU3444200A (en) 1999-03-31 2000-03-24 Data communications method and data signal

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GB9907481A GB2348581B (en) 1999-03-31 1999-03-31 Data communications method and data signal

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Publication number Priority date Publication date Assignee Title
WO2002073898A2 (fr) * 2001-03-12 2002-09-19 Hrl Laboratories, Llc Procede d'attribution dynamique des ressources fonde sur la priorite et dispositif pour systemes d'offre et de demande
WO2004010652A1 (fr) * 2002-07-19 2004-01-29 Xtremespectrum, Inc. Dispositif de commande d'acces medias presentant des intervalles de temps garantis pseudo-statiques
US6980541B2 (en) 2002-01-03 2005-12-27 Freescale Semiconductor, Inc. Media access controller having pseudo-static guaranteed time slots
US7593422B2 (en) 2002-01-03 2009-09-22 Freescale Semiconductor, Inc. Method of operating a media access controller having pseudo-static guaranteed time slots

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EP0713347A2 (fr) * 1994-11-17 1996-05-22 AT&T Corp. Méthode et appareil permettant l'accès en mode STM ou en mode paquet sur un réseau de communication à large bande

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GB9602807D0 (en) * 1996-02-12 1996-04-10 Northern Telecom Ltd A bidirectional communications network
US5787080A (en) * 1996-06-03 1998-07-28 Philips Electronics North America Corporation Method and apparatus for reservation-based wireless-ATM local area network
FR2767620B1 (fr) * 1997-08-25 1999-09-24 Alsthom Cge Alcatel Procede d'exploitation d'un lien de transmission numerique partage temporellement par plusieurs unites et unite pour la mise en oeuvre d'un tel procede
JP2003518335A (ja) * 1998-09-11 2003-06-03 シェアウェーブ・インコーポレーテッド コンピュータ・ネットワーク通信チャネルにアクセスするための方法および装置

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Publication number Priority date Publication date Assignee Title
EP0713347A2 (fr) * 1994-11-17 1996-05-22 AT&T Corp. Méthode et appareil permettant l'accès en mode STM ou en mode paquet sur un réseau de communication à large bande

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002073898A2 (fr) * 2001-03-12 2002-09-19 Hrl Laboratories, Llc Procede d'attribution dynamique des ressources fonde sur la priorite et dispositif pour systemes d'offre et de demande
WO2002073898A3 (fr) * 2001-03-12 2003-11-20 Hrl Lab Llc Procede d'attribution dynamique des ressources fonde sur la priorite et dispositif pour systemes d'offre et de demande
US7054936B2 (en) 2001-03-12 2006-05-30 Hrl Laboratories, Llc Priority-based dynamic resource allocation method and apparatus for supply-demand systems
US6980541B2 (en) 2002-01-03 2005-12-27 Freescale Semiconductor, Inc. Media access controller having pseudo-static guaranteed time slots
US7450558B2 (en) 2002-01-03 2008-11-11 Freescale Semiconductor, Inc. Method for controlling operation of a child or neighbor network
US7593422B2 (en) 2002-01-03 2009-09-22 Freescale Semiconductor, Inc. Method of operating a media access controller having pseudo-static guaranteed time slots
WO2004010652A1 (fr) * 2002-07-19 2004-01-29 Xtremespectrum, Inc. Dispositif de commande d'acces medias presentant des intervalles de temps garantis pseudo-statiques

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GB2348581B (en) 2004-02-18
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AU3444200A (en) 2000-10-16

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