WO2002096036A1 - Procede et appareil d'arbitrage pour l'acces a un canal partage d'un systeme de communication en reseau a jeton - Google Patents

Procede et appareil d'arbitrage pour l'acces a un canal partage d'un systeme de communication en reseau a jeton Download PDF

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Publication number
WO2002096036A1
WO2002096036A1 PCT/EP2002/005563 EP0205563W WO02096036A1 WO 2002096036 A1 WO2002096036 A1 WO 2002096036A1 EP 0205563 W EP0205563 W EP 0205563W WO 02096036 A1 WO02096036 A1 WO 02096036A1
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WIPO (PCT)
Prior art keywords
token
nodes
counters
priority
node
Prior art date
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PCT/EP2002/005563
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English (en)
Inventor
Jacobus Haartsen
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Telefonaktiebolaget L M Ericsson (Publ)
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Application filed by Telefonaktiebolaget L M Ericsson (Publ) filed Critical Telefonaktiebolaget L M Ericsson (Publ)
Publication of WO2002096036A1 publication Critical patent/WO2002096036A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/42—Loop networks
    • H04L12/427—Loop networks with decentralised control
    • H04L12/433—Loop networks with decentralised control with asynchronous transmission, e.g. token ring, register insertion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/535—Allocation or scheduling criteria for wireless resources based on resource usage policies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H04L47/13—Flow control; Congestion control in a LAN segment, e.g. ring or bus
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/56—Allocation or scheduling criteria for wireless resources based on priority criteria
    • H04W72/566—Allocation or scheduling criteria for wireless resources based on priority criteria of the information or information source or recipient
    • H04W72/569—Allocation or scheduling criteria for wireless resources based on priority criteria of the information or information source or recipient of the traffic information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

Definitions

  • the present invention relates to communication networks, and more particularly, to bandwidth allocation in a network with distributed control.
  • Radio Local Area Networks typically cover an area of technology where the computer industry and the wireless communications industry merge.
  • Conventional computer networking has relied on wired LANS, typically packet- switched and targeted for data transfer.
  • wired LANS typically packet- switched and targeted for data transfer.
  • wireless networking and in
  • the wired medium can range from a simple twisted pair to an optical
  • the medium constitutes a single channel, which is used by only a single one of a number of different users at any given time.
  • Time-division multiplexing TDM
  • the protocols for accessing wired media have been standardized by the IEEE in its 802 series.
  • multiple access reservation techniques like carrier-sensing (e.g., Ethernet,
  • CSMA/CD Carrier-Sense Multiple Access/Collision Detect
  • 802.4 token buses, or 802.5 token rings are used to gain access to the medium.
  • These protocols can be used in a distributed sense in that the user occupying the channel reserves the medium by its present transmission or by its token.
  • every user can hear all traffic. That is, in a single LAN, all users share not only the channel, but also all of the information carried on that channel.
  • the LAN can be divided into smaller LANs or segments, which channels operate independently.
  • LANs can be interconnected via bridges or routers, which form interfaces between the different local networks.
  • the LAN typically provides a connectionless packet-switched service. Each packet has a destination address (and usually a source address as well) so that each user can determine whether the packet that passes by is intended for him or not. It will be understood that the net throughput per user in a single LAN is determined by the peak data rate on the channel and by the number of users that share this channel. Even if the peak data rate is very high due to the wide bandwidth of the wireline medium, the effective user throughput can be low if the channel has to be shared among many users.
  • the worldwide Internet is based on a peer-to-peer protocol.
  • the channel is the key element of the network.
  • Communication units that are added to the network may gain access to the channel by distributing the channel access control.
  • the concept of distributed control and the peer concept goes against the usage of priority traffic in which certain communication units (providing delay-sensitive traffic) should have priority over other communication units.
  • prioritization has become essential.
  • a different distributed protocol was proposed that is based on a Ping-Pong protocol that involves a virtual token distribution. This is described in "Method and apparatus for medium access on a radio channel" by J. C. Haartsen, U.S.
  • each packet transmission coincides with a token exchange.
  • Communication unit A owning the token, can send a packet to communication unit B.
  • Communication unit B receiving the packet, also receives the token and is therefore allowed to transmit as soon as the packet from communication unit A has been received.
  • priority or recovery slots are defined, which give a communication unit unconditional access to the channel. For example, when a priority slot associated with communication unit A arrives, communication unit A is allowed to transmit regardless of whether it received the token by means of a previous packet transmission; that is, at a priority slot, the token is given unconditionally to the communication unit associated with the priority slot.
  • the token Ping-Pong protocol as described in U.S. Patent Application No. 60/180,095 does not describe how the token is distributed among the communication units in the interval in between the priority slots.
  • a communication unit that receives the token can send the token (along with its transmission) to any unit, but there are no rules governing to which communication unit the token should be sent. Therefore, when two communication units exchange information continuously, they keep exchanging the token between themselves while other communication units are starved (apart from the communication units that have priority slots that receive the token unconditionally some of the time). Yet, if a token distribution strategy is to be considered, the bandwidth requirements of the participants should be taken into account. Thus, there is a need in the art for a token distribution scheme that enables the token to circulate between the communication units participating on the channel, while at the same time taking into account the bandwidth requirements of the participants.
  • the present invention is directed to a method and apparatus for network token distribution that substantially obviates one or more of the shortcomings or problems due to the limitations and disadvantages of the related art.
  • a method of arbitrating access to the shared channel includes assigning a priority level to each of the M counters, such that the assigned priority level for a respective one of the M counters among all of the L nodes is the same and at least two of the M counters are assigned a different priority level.
  • the method also includes assigning a corresponding initial count value to each of the M counters.
  • a token-possessing one of the N nodes identifies one of a remaining number of other nodes of the N nodes for receiving the token based, at least in part, on at least one of relative count values of the M counters in the token possessing node and the assigned priority levels of the M counters in the token possessing node.
  • the token- possessing node explicitly or implicitly transfers the token to the identified node, and the count value of the counters associated with each of the M nodes in each of the L nodes are adjusted each time the token is transferred.
  • a system for arbitrating access to a shared channel in a token-based communication network includes a plurality of nodes sharing a channel.
  • the system is capable of implicitly or explicitly passing a token, thus permitting the token-receiving node access to the shared channel.
  • the system includes a shared channel medium and a number, N, of nodes that are capable of communicating with one another along the shared channel medium.
  • Each of a number, L, of the N nodes in the system is associated with a token machine for tracking and passing the token, where L ⁇ N.
  • Each token machine includes a number, M, of counters that are respectively associated with a corresponding one of a number, M, of the N nodes, where M ⁇ L. These M counters also are assigned a priority level such that at least two of the M nodes have a different priority level.
  • each of the counters Upon formation of the channel, each of the counters is set to their respective initial count value.
  • the token machine also includes a processor for monitoring and controlling the counters. The processor is configured to select one of the N nodes to transfer the token.
  • Figure 1 is a diagram showing a channel configuration of a peer network with several participants
  • Figure 2 is a diagram illustrative of a typical packet format on a peer channel
  • FIG. 3 is a block diagram of an exemplary token machine in accordance with an embodiment of the present invention.
  • Figure 4a is an exemplary first process diagram for token distribution in accordance with the present invention.
  • Figure 4b is an exemplary second process diagram for token distribution in accordance with the present invention.
  • Figure 4c is an exemplary third process diagram for token distribution in accordance with the present invention.
  • Figure 4d is an exemplary process diagram for token distribution in accordance with the present invention.
  • the present invention is useful for allowing nodes connected within a network environment to share access to a common channel by way of a token distribution method and apparatus.
  • the method and apparatus of the present invention provide an efficient allocation of effective channel bandwidth to nodes (e.g., communication units) on the common channel that may require transmission of priority services involving delay-sensitive information (e.g., voice, video).
  • nodes e.g., communication units
  • delay-sensitive information e.g., voice, video
  • unit(s) may include computers, portable computers, printers, and/or other peripheral devices such as a headset or a mouse, and/or radio connectable devices, such as PDAs, mobile phones and the like.
  • the channel may include wired and/or wireless links, for example, cable, fiber, and/or radio links. Radio links used to transmit on the channel may be established with portable radio communication equipment.
  • portable radio communication equipment includes all equipment such as mobile telephones, pagers, communicators (e.g., electronic organizers, smartphones) and the like.
  • fair token distribution does not necessarily mean that a token is distributed equitably among participating nodes on a shared channel, although a fair token distribution scheme in accordance with the invention may be configured to and/or may operate such that equitable token distribution is substantially allowed or approximated.
  • Nodes participating in fair token distribution in accordance with the invention are generally nodes sending best-effort (asynchronous) data traffic, so-called “best-effort nodes.” However, every node sharing a channel may not necessarily be a best-effort node. Nodes carrying delay-sensitive traffic, such as priority or "real-time" (asynchronous or isochronous) data traffic, also may be sharing a common channel with nodes carrying best-effort data.
  • Token distribution schemes described herein include strategies that allow a token to circulate between the best-effort nodes participating on a shared channel in a "fair" way (e.g., to reduce or eliminate occurrences when nodes are starved of the token) while coping with bandwidth requirements of all channel participants, which may include nodes carrying delay-sensitive or other priority type data traffic.
  • FIG. 1 shows a general system 100 in which the token distribution scheme of the present invention may be used.
  • a single channel 110 is shared by participating communication units 120 (communication unit A), 122 (communication unit B) and 124 (communication unit C), however, it is to be understood that single channel 110 may be shared by a larger or smaller number of participants.
  • the channel 110 may be any medium that can support a signal transmission between the participating communication units 120-124 (A-C), such as cable, fiber, and/or air (e.g., in the case of radio transmission). To avoid collisions on the channel 110, only a single one of the communication units A-C can access the channel and transmit data at any moment in time.
  • FIG. 1 shows the participating communication units A-C of system 100 to be separately arranged (e.g., physically separated communication units) for purposes of illustration
  • participants in fair token distribution of the present invention may, in a more general sense, include other types of logical links having start and end points (i.e., nodes) between which a token may be distributed.
  • participants may include a plurality of nodes (points) that reside in a single physical device.
  • there may be more participating nodes than there are separate physical communication devices on the channel.
  • TDM time division multiplexing
  • MAC multiple access control
  • a widely-used protocol is based on CSMA (carrier-sense multiple access), which is also called listen-before-talk.
  • CSMA carrier-sense multiple access
  • MAC protocols are less suitable for delay sensitive traffic, or when priorities in traffic streams have to be made, because they are, to a large extent, peer protocols. This is a particular concern in multimedia services because delay sensitive information like voice or video has to have priority over other services, such as best effort services.
  • peer-to-peer protocols are less suitable for supporting multimedia traffic cases.
  • FIG. 2 shows a typical packet format in simplified block form.
  • the packet format includes a header section 210 and a payload section 220.
  • the header section 210 is divided to include several subsections 212-218 that provide the network with information that is necessary to handle the packet.
  • Subsection 212 contains information relating to the length of the packet
  • subsection 214 contains information relating to the source address identifying the sender of the packet
  • subsection 216 contains information relating to the destination address identifying the intended recipient of the packet
  • subsection 218 contains information used in an optional acknowledgment protocol (described below).
  • Data is transmitted in payload section 220, which is divided into segments 222a-222n. Each segment 222a-222n may optionally be checked for errors, for example, by adding a Cyclic Redundancy Check (CRC) portion 224a-224n to respective packet segments 222a- 222n, or by including a number of parity bits.
  • CRC Cyclic Redundancy Check
  • the packet overhead also may include additional information, such as information relating to segment interleaving or latency requirements, for example.
  • ARQ Automatic Retransmission Query
  • Ping Pong Protocol U.S.
  • priority allocation may be divided among priority times, which are fixed time positions at which the token is unconditionally passed. While the following description assumes a slotted channel, it is to be understood that utilizing priority times instead of priority slots would be a straightforward application of the principles set forth by the exemplary embodiments described herein.
  • the token can freely circulate among the participants in between the priority slots.
  • a method of passing the token is not trivial.
  • a bandwidth allocation scheme designed for a central control scheme is described in U.S. Provisional Application No. 60/271,715 entitled “Method and Apparatus for Dynamic Bandwidth Allocation in Bluetooth Piconets,” filed on Feb. 28, 2001, and hereby incorporated herein by reference in its entirety. That document describes a piconet based on a master and several slaves.
  • the master allocates bandwidth between the slaves according to a specific polling scheme.
  • the master contains a polling machine which includes several counters, each counter being associated with a slave.
  • the counters are initialized with begin values that represent the polling intervals for the slaves and are derived from the bandwidth requirements of the slaves.
  • the counters are periodically decremented. If a counter reaches zero or becomes negative, the associated slave is polled. If more than one counter reaches zero or are negative, the slave with a counter highest on the counter list is served first. Slaves with counters higher on the list therefore have priority over slaves lower on the counter list.
  • a distributed control mechanism is used with token machines distributed among some or all of the participating nodes on the shared channel.
  • counters in the token machine are associated with nodes carrying best-effort traffic (best-effort nodes).
  • Each best-effort node partaking in a token passing scheme according to this embodiment is therefore associated with a counter in each token machine of each node participating in the scheme.
  • the token machine concept of the present invention discussed later in detail, provides a fair token passing between the best-effort nodes. Nodes carrying real-time or priority traffic, so-called priority nodes, do not necessarily have an associated counter in the token machine.
  • priority nodes may have token machines that at least include counters associated with the best-effort nodes sharing the channel.
  • the latter embodiment provides a method of passing the token from one of the priority nodes to a best-effort node that is identified by a token passing scheme of the present invention as the next node for receiving the token.
  • a priority node may have an associated counter in each of the token machines.
  • the counters in the token machine correspond to source nodes (start points) that have best-effort data to send.
  • the number of counters in use equals the number of nodes on a shared channel that are participating in a fair token passing scheme in accordance with the invention.
  • Each of these nodes has the same token machine.
  • “same token machine,” as used herein, means nodes have either identical token machines or token machines that function identically to one another. If several best-effort nodes reside in a same physical device, each of these nodes may use (share) a same token machine that is associated with the device.
  • a same physical device may include several nodes, each having their own associated token machine, and/or combinations of nodes in which some share same token machines, some are associated with their own respective token machine, and some that are not associated with any token machine.
  • the token machine includes a list of counters.
  • the list of counters on each token machine is prioritized such that best-effort nodes carrying traffic with higher priority are higher in the list.
  • the counters may be numbered to indicate their relative priority with respect to one another. For example, the counters may be numbered consecutively, like 1, 2, . . . , M, where, for example, the counter with the lowest number has the highest priority and the counter with the highest number has the lowest.
  • counter 1 is associated with, for example, a communication unit having the highest priority
  • counter 2 is associated with a communication unit having the second-highest priority
  • the above-described order of priority may be reversed such that the counter with number M is the highest priority and counter number 1 is the lowest priority.
  • the counter list may include any type of symbol that can be associated with a counter and designate a relative priority level for that counter.
  • the counters are initialized with certain begin values, as will be discussed later.
  • Figure 3 shows an exemplary token machine 300 in accordance with an embodiment of the present invention.
  • the token machine 300 includes a list of counters 310-1, 310-2, . . .
  • Selection/Control unit 320 includes a clock line 330 controlling each of the counters 310-1 to 310-M. The clock line in each token machine 300 is synchronized, such that after each token passing event, each of the counters is enabled to activate the counter for one counting cycle. Selection/control unit 320 also includes initializing control lines 340-1 to 340-M respectively connected with each counter 310-1 to 310-M.
  • Initializing control lines 340-1 to 340-M operate independently to perform an adjusting function on one of the counters 310-1 to 310-M after its associated node receives the token.
  • the output 350 of control/selection unit 320 is a node destination address (DST) that corresponds to the present destination of the token.
  • DST node destination address
  • any one of the communication units 120-124 would include a counter associated with itself and each of the other communication units.
  • the counter list would be prioritized in accordance with the type of traffic transferred on each communication unit 120-124.
  • one or more of the units 120-124 may be carrying delay-critical traffic and assigned a priority slot, in which case it is unconditionally passed the token during the priority slot.
  • a node assigned to a priority slot does not necessarily (but may) include a token machine.
  • the number, M, of nodes partaking in a best-effort token passing scheme in accordance with the invention may be less than or equal to the total number of network nodes N.
  • M may take on any value from 1 (only one node is partaking in best-effort token passing) to N (all nodes are partaking in best-effort token passing).
  • these nodes still may include a respective token machine including counters associated with best- effort nodes that are participating in fair token distribution.
  • any node having a token machine is aware of which best-effort node is identified for next receiving the token, whether or not the node is participating in the fair token passing scheme.
  • a number, L, of the N network nodes sharing the channel may be defined as the number of nodes having token machines, where L is > M.
  • L may be equal to N (in which case every node has a token machine), L may be equal to M (e.g., when only nodes participating in a fair token passing scheme include a respective token machine), or L may reside between M and N (e.g. , in a case when some, but not all of the priority nodes on the channel have respective token machines without a counter associated with themselves).
  • M ⁇ L ⁇ N.
  • a one-time initial offset, ⁇ k can optionally be added to stagger individual token distribution schemes (e.g., to prevent two communication units with the same ⁇ k from simultaneously having zero or negative counter values; however, this is not mandatory since the priority of the counters will solve distribution if multiple counters become zero or negative).
  • the token is (virtually) passed to the node k with the lowest counter value Ck. If there are multiple counters with this same minimum value, the counter highest on the counter list is selected. The node receiving the token is then allowed to transmit a packet. For each new slot (or each token passing event if there are no slots), all counters are decreased by one. This node k will transmit its packet to a new node m. The selection of node m may be based on a number of factors, including:
  • Token transfer between nodes k and m may be either an explicit token transfer or an implicit token transfer. For example, if a token possessing node has something to transfer to another node, the token possessing node may send a packet including an information data payload. This type of packet transfer is referred to in this disclosure as an implicit token transfer, since mere receipt of this packet allows the recipient to respond.
  • the node has no information to send to another node, it occasionally has to send a packet without a payload, just to enable the other node access to the channel (e.g., to send something).
  • This type of packet transfer without a payload is referred to in this disclosure as an "explicit token transfer.”
  • the amount by which a counter is adjusted may be changed in a dynamic way. For example, if a node repeatedly receives the token, but has no data to transmit, a counter begin (initial) value, or other value by which this token receiving node is adjusted, may be increased in each token machine in each node active in the network.
  • the frequency at which the token is passed to this node decreases, and thus reduces the bandwidth allocated to that node (and correspondingly increases bandwidth for other nodes).
  • the amount by which counters are incremented/decremented may be modified.
  • a packet header also may contain information that may be used to dynamically adjust counter values according to the bandwidth and/or priority requirements of the payload information. Another way to change the effective bandwidth for a node would be, for example, to change its counter priority in a priority list of the token machines.
  • this may be accomplished by a node broadcasting a message to each of the other nodes, wherein the reinitializing message is in turn broadcast by nodes in rotating or random order.
  • one node may be designated to periodically broadcast a reinitialization message to each of the other nodes.
  • the logical connections between the nodes on the channel can (but do not necessarily need to) include an Automatic Retransmission Query (ARQ) scheme which forces the recipient to acknowledge the received information.
  • ARQ Automatic Retransmission Query
  • a recipient responds with an ACKNOWLEDGMENT (ACK) if the information was received correctly or with an NAK if it was not received correctly.
  • ACK/NAK information 218 can conveniently be carried (i. e. , piggybacked) in the header 210 of a return packet.
  • communication unit A If communication unit A has to send something to communication unit B, it can at the same time in the header confirm the reception of data received from B. If communication unit A has no data to send to communication unit B, but unit A wants to acknowledge data received from unit B, it only sends the (short) packet header. Since the ARQ protocol, as described in U.S. Provisional Application No. 60/180,095, adapts to the packet sizes and introduces no extra overhead due to short packets, errors introduced into transmitted packets may be detected and the correct data retransmitted efficiently to conserve the effective channel bandwidth.
  • the counter value Ck of node k may be adjusted by resetting Ck to its initial value ⁇ k (now without offset ⁇ k) in each token machine in each of the L nodes (t.e., nodes with token machines).
  • Ck may be adjusted in other ways. For example, instead of resetting CA: to be its initial value TA:, an alternative adjustment may include making C : equal to a value that is a function of its initial value, such as by adding the initial value TA: to a current CA; value.
  • CA equal to an amount, or equal to a function of a value included within information data (e.g., a packet header) waiting in node k, indicating a required bandwidth. It is preferable that the adjustment of CA: is carried out identically in all token machines (/. e. , in each token machine of all L nodes).
  • node k As a result of node k receiving a packet, it also receives the token and has the right to send on the channel. In response to receipt of the token, node k first determines whether the counter values in the token machine are all positive. If one of the counters Cm is negative, it sends a packet to the associated node m. If several nodes have a negative counter value, the node m that is associated with the highest priority counter in the counter list of these several nodes is selected. Alternatively, if several counter values are negative, the node m with the most negative counter value is selected. If node k has information to send to node m, it will append a payload to the packet. If not, it only sends a header, including possible
  • the node k preferably sends a packet back (and with it the token) to the sender to ACK or NAK the received data. If there is no data to acknowledge, it may send a packet to a node m for which node k has information waiting to be sent. If no data is waiting, node k may send a packet (header only if no data is available) to that node m corresponding to the counter having the lowest (but positive) value in the counter list. After each slot (or after each transmission in case there are no slots) all counter values CA: in every token machine are decremented by 1.
  • the token circulation can be overruled by the priority (reserved) slots.
  • priority slots may be provided to meet throughput, latency, and/or quality of service requirements of a node (e.g., for meeting requirements of nodes carrying delay-critical synchronous or isochronous traffic, such as voice, video or multimedia).
  • the token is unconditionally passed to the node that owns this priority slot. As the owner of the priority slot obtains the token, it has the right to send.
  • a channel may include nodes owning priority slots that are either participants of a token distribution scheme or part of a scheme in which best-effort services are separated from priority services.
  • the node has an associated counter included among the M counters of each token machine and that counter is placed at a high priority level.
  • priority slots would not strictly be required since their high priority level counters in the token machines will automatically provide a priority service.
  • use of priority slots within a token distribution scheme are still preferred to allow for recovery from an error condition.
  • a node owning a priority slot can re- inject the token into the system after a token-losing event, such as when a packet fails.
  • Priority slots also may re-inject the token into the system, for example, in a scenario involving a nonparticipating node (i.e., a node that does not track counter values of the nodes participating in the token distribution scheme) that receives the token, but does not have information for transmission to another node.
  • a nonparticipating node i.e., a node that does not track counter values of the nodes participating in the token distribution scheme
  • receives the token but does not have information for transmission to another node.
  • FIGS. 4a-4d show first through fourth exemplary token distribution processes in accordance with the present invention. Same reference characters in Figures 4a-4d are intended to represent same or like processes.
  • a complete exemplary token distribution process is summarized in a process flow diagram 400. It is assumed that the token resides with communication unit x, obtained either by a priority slot or by a previous reception of a packet.
  • a number, M, of communication units are sharing a common channel.
  • Each communication unit, m, of the M communication units includes number of counters (also equal to M) in the token machine of the unit m, and each of these counters is associated with a respective one of the M communication units and has a counter number (also indicated as m for an associated communication unit m) in a counter list.
  • a counter number also indicated as m for an associated communication unit m
  • nodes may be sharing the channel without participating in token distribution for best-effort traffic.
  • the communication unit m owning the overlapping slot and having the lowest value o ⁇ m (i.e., highest priority) receives the token. If there is no priority slot, communication unit x checks in process 440 to determine whether any of the counters have reached zero or a negative value. If the answer is "yes,” then in process 470 unit x identifies a highest-priority one of those communication units whose counter is equal to or smaller than zero. In the exemplary embodiment, the counter number, m, indicates priority, with relative priority decreasing as m increases. [0058] In process 480, communication unit x sends a packet to communication unit m.
  • Communication unit m thus receives the token and, in process 490, its counter value Cm in all communication units is adjusted based on Ym. [0059] If no counter has reached zero ("no" path out of process 440), communication unit x next determines whether there is ACK/NAK information waiting for transmission in process 450. If so, in process 476 it selects the communication unit m with the lowest m for which ACK/NAK is waiting and transmits a packet to this communication unit m in process 480. [0060] If no ACK/NAK is waiting ("no" path out of process 450), communication unit x determines, in process 460, whether data is waiting to be transmitted. If yes, then the communication unit m with the lowest m for which data is waiting is selected in process 472 by communication unit x and communication unit x sends a packet to communication unit m in process 480.
  • the token When there is no data waiting, the token is passed to the communication unit m with the lowest counter value Cm (Cm being bigger than zero though) (processes 474 and 480).
  • Cm Counter Value
  • the token when there is no data waiting the token may be "killed" (i.e., the token is not sent at all). Circulating the token when there is no data to send needlessly consumes power, so during these times the system can enter into a low-power mode. All units can sleep until the next priority slot in which the token is again injected into the channel. The present alternative embodiment would therefore require the existence of priority slots.
  • the unit owning the token decides to which other unit the token is transmitted (unless there is a priority slot and the token resides at the priority unit without explicit token/packet transmission).
  • the counter of the communication unit that gets possession of the token is adjusted in every token machine based on its associated token interval (process 490). Then the counters of all the communication units are decremented in every token machine (process 420) and the entire procedure repeats.
  • Figure 4b shows a second exemplary process diagram 402 in accordance with the present invention.
  • Process diagram 402 differs from comprehensive process diagram 400 of Figure 4a in that counters are ignored (i.e., not adjusted) during a priority slot occurrence. In Figure 4b, this is represented by the "yes" path out of process 430 that returns to the same decision process 430.
  • Figure 4c shows a third exemplary process diagram 404 in accordance with the present invention.
  • Diagram 404 is similar to diagram 400 of Figure 4a except that a default process (i.e., process 474 of Figure 4a) into which the "no" path out of decision process 460 has been eliminated and "no" path is fed back to the counter decrementing process 420.
  • a default process i.e., process 474 of Figure 4a
  • FIG. 404 shows a fourth exemplary process diagram 406 in accordance with the present invention.
  • Process diagram 406 is essentially the same as process diagram 400, but without priority slots in the distribution scheme. Priority slots still may be defined, but only used to re-inject the token if it becomes lost.
  • the token machines and priority slots provide a convenient access technique in which multimedia traffic with different priorities can be supported.
  • the TA values on which the nodes agree determine the access opportunities each node obtains. If the TA: is lower, a node obtains access to the channel more frequently.
  • the nodes can agree on a maximum size SA: of the packet each node k is allowed to transmit.
  • SA controls the latency
  • SA controls the instantaneous bandwidth usage.
  • TA: and SA determine the average bandwidth allocated to node k.
  • each data packet includes a header 210 that may include a source address 214 and a destination address 216. Because each node sharing the channel can monitor transmissions from any other node, the value m may be derived from the destination address of a packet transmitted on the channel in process 480. For example, each of the N nodes listens for header information corresponding to the destination (and the source) as well as the length of a packet being transmitted. Each node therefore knows where the token is being sent and the length of time needed for the packet transmission. The destination node determines that it is the intended recipient and receives the packet (and thus the token).
  • nodes not involved in the transmission may "sleep" (e.g., enter into a low power mode) until the transmission is complete.
  • many aspects of the invention have been described in terms of sequences of actions to be performed by elements of a computer system. It will be recognized that in each of the embodiments, the various actions could be performed by specialized circuits (e.g. , discrete logic gates interconnected to perform a specialized function), by program instructions being executed by one or more processors, or by a combination of both.
  • the invention can additionally be considered to be embodied entirely within any form of computer readable carrier, such as solid-state memory, magnetic disk, optical disk or carrier wave (such as radio frequency, audio frequency or optical frequency carrier waves) containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.
  • computer readable carrier such as solid-state memory, magnetic disk, optical disk or carrier wave (such as radio frequency, audio frequency or optical frequency carrier waves) containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.
  • any form of embodiments may be referred to herein as "logic configured to" perform a described action, or alternatively as “logic that" performs a described action.
  • adjustment of the counter has been illustrated as a "decrement by 1" operation.
  • adjusting the counter need not be in the form of a decrementing operation; the counter could alternatively be adjusted by adding a value to the counter.
  • the amount of counter adjustment need not be a value of 1 in all embodiments. It could alternatively be any value.
  • the identified unit (or node) m alternatively may be selected based on a node m having a lowest or most negative counter value Cm (in the case in which counter values are decremented (process 420) after a token-passing event).
  • Cm a lowest or most negative counter value
  • node x token possessing node
  • the node selected for receiving the packet is the highest priority level one among the several nodes having met the criteria.
  • the selection criteria e.g., a set of several counters having an identical value equal to a predetermined threshold or equal values corresponding to a distance past the predetermined threshold.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)

Abstract

L'invention porte sur un procédé et sur un appareil de distribution de jetons comprenant un ou plusieurs noeuds d'une pluralité de noeuds avec une machine (300) comportant des compteurs associés à chacun des autres noeuds de réseau possédant une machine à jetons. Chaque fois qu'un noeud de réseau possédant un jeton passe de manière implicite ou explicite le jeton à un autre noeud de réseaux possédant une machine à jetons, on ajuste les valeurs de chacun des compteurs associés à chaque noeud possédant une machine à jetons. Lorsqu'un jeton est passé, la valeur du noeud récepteur est ajustée, au moins en partie, sur la base d'une valeur initiale d'intervalle de jeton, et les valeurs associées à d'autres noeuds sont ajustées par rapport à une valeur de seuil. La décision selon laquelle le jeton est passé peut être basée, au moins en partie, sur la valeur d'un compteur et/ou d'un niveau de priorité attribué au compteur. Ce système et ce procédé peuvent comporter des fentes de priorité dans lesquelles le jeton est passé de manière inconditionnelle à un noeud attribué à le fente de priorité et une logique ARQ pour l'accusé de réception des informations transférées.
PCT/EP2002/005563 2001-05-22 2002-05-21 Procede et appareil d'arbitrage pour l'acces a un canal partage d'un systeme de communication en reseau a jeton WO2002096036A1 (fr)

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WO2004051960A1 (fr) * 2002-12-04 2004-06-17 Koninklijke Philips Electronics N.V. Procede de limitation du nombre de dispositifs de reseau dans un reseau de communications
WO2008156458A1 (fr) * 2007-06-22 2008-12-24 Thomson Licensing Procédé et appareil permettant un accès au support dans des réseaux basés sur la contention
WO2012047924A1 (fr) * 2010-10-06 2012-04-12 Qualcomm Incorporated Procédés et appareil permettant de supporter le partage des privilèges dans un système de poste à poste
US20140068700A1 (en) * 2012-08-31 2014-03-06 Motorola Solutions, Inc. Prioritized token based arbiter and method
US9113492B2 (en) 2011-11-07 2015-08-18 Qualcomm Incorporated Method and apparatus for transmit priority determination within a link

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US5631906A (en) * 1993-03-11 1997-05-20 Liu; Zheng Medium access control protocol for single bus fair access local area network
US5566177A (en) * 1994-10-09 1996-10-15 International Business Machines Corporation Priority-based arbitrator on a token-based communication medium
EP0836296A2 (fr) * 1996-08-22 1998-04-15 AT&T Corp. Appareil et procédé d'accès dynamique par répartition dans le temps
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004051960A1 (fr) * 2002-12-04 2004-06-17 Koninklijke Philips Electronics N.V. Procede de limitation du nombre de dispositifs de reseau dans un reseau de communications
WO2008156458A1 (fr) * 2007-06-22 2008-12-24 Thomson Licensing Procédé et appareil permettant un accès au support dans des réseaux basés sur la contention
KR101365435B1 (ko) 2007-06-22 2014-02-19 톰슨 라이센싱 회선 쟁탈 기반의 네트워크들에서 매체 액세스를 위한 방법 및 장치
US8737425B2 (en) 2007-06-22 2014-05-27 Thomson Licensing Method and apparatus for media access in contention-based networks
WO2012047924A1 (fr) * 2010-10-06 2012-04-12 Qualcomm Incorporated Procédés et appareil permettant de supporter le partage des privilèges dans un système de poste à poste
US8938509B2 (en) 2010-10-06 2015-01-20 Qualcomm Incorporated Methods and apparatus for supporting sharing of privileges in a peer to peer system
US9113492B2 (en) 2011-11-07 2015-08-18 Qualcomm Incorporated Method and apparatus for transmit priority determination within a link
US20140068700A1 (en) * 2012-08-31 2014-03-06 Motorola Solutions, Inc. Prioritized token based arbiter and method
US9043865B2 (en) * 2012-08-31 2015-05-26 Motorola Solutions, Inc. Prioritized token based arbiter and method

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