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Synchronous Collision Resolution A New Technology Proposal

Synchronous Collision Resolution A New Technology Proposal. Date: 2010-March-16. Authors:.

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Synchronous Collision Resolution A New Technology Proposal

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  1. Synchronous Collision ResolutionA New Technology Proposal Date: 2010-March-16 Authors: John Stine is employed by The MITRE Corporation but represents himself in this presentation. The MITRE Corporation is a not for profit company and has no economic interest in the outcome of the 802 standards process. The author's affiliation with The MITRE Corporation is provided for identification purposes only, and is not intended to convey or imply MITRE's concurrence with, or support for, the positions, opinions or viewpoints expressed by the author. MITRE Public Release #10-0877 John A. Stine, Self

  2. Abstract • Synchronous Collision Resolution (SCR) is an approach to medium access control. This presentation proposes a design of SCR for use by TGad. This design provides • A foundation for coexistence and technology evolution • Support for beamforming (SDMA) • Quality of service differentiation • Contention-based reservations for streaming • Support for channelization (CDMA or FDMA) • Multiple energy conservation techniques • SCR makes the MAC evaluation criteria easy to achieve • The deterministic nature of SCR allows evaluation without simulation John A. Stine, Self

  3. Scope • Synchronous Collision Resolution is used for arbitrating access through the use of a common timing structure and signals • This proposal makes no requirements for or restrictions on the messaging portions of the MAC protocol Involves the exchange of management frames Messaging Involves the transmission and detection of RF energy Signaling Some 802.11 management frames and fields in those frames will become obsolete John A. Stine, Self

  4. Framing, Timing, and Signaling Broadcast Priority/QoS 4 1 2 3 5 CBR C E C E C E C E C E C E C E C E Contention Phases Priority Phases Packet Transmissions CR Signaling Transmission Slot … … … 1 2 3 4 m-1 m 1 2 3 4 m-1 m 1 2 CBR Epoch CBR Epoch w 2 1 w-1 Synchronization Epoch John A. Stine, Self

  5. Proposed Design Parameters Contention Design 16 signaling slots for contention 4 priority levels CBR Broadcast Priority/QoS Routine (= no signals in the priority phase) n = 5 Contention Phases (Design density, k = 5) p1 = 0.26, p2 = 0.34, p3 = 0.42, p4 = 0.46, p5 = 0.48 Transmission Slot Size Signaling duration = 16  9 msec = 144 msec Slot duration = 333 msec Slot duration (first slot of an epoch) = 358 msec Epoch Design m = 75 transmission slots per epoch y = 3 contention only transmission slots Synchronization Epoch Design w = 10 CBR epochs per synchronization epoch 4 synchronization epochs per second Rationale John A. Stine, Self

  6. Specialized Signaling for Contiguous Slot Reservations • After reserving contiguous slots, a contention in the first transmission slot reserves them all in subsequent epochs CBR Bit 1 Bit 0 Bit 6 After the CBR priority phase the remaining phases are used to send a binary number indicating the number of reserved slots … C E C E C E C E Number of reserved slots … CR Signaling Space for multiple consecutive frames Multiple Transmission Slots … … … 1 2 3 4 m-1 m 1 2 3 4 m-1 m 1 2 CBR Epoch CBR Epoch John A. Stine, Self

  7. Specialized Signaling for Synchronization Designated and Ad Hoc Reference • Type of Reference • 00 – A stations between two references assisting their time shift • 01 – A station that is the source to a device • 10 – A station that takes on the role of an ad hoc • 11 – A station that is configured to be a designated reference • Type of Shift • 00 – Transmission slot 2 will be skipped this epoch • 01 – Transmission slot 2 will be skipped every other epoch • 10 – Transmission slot 2 will be skipped every epoch • 11 – Epoch 2 will be skipped this synchronization epoch • Reference Quality • 00 – Internal clock only • 01 – Synchronized to multiple peer references • 10 – Neighbor to a reliable reference • 11 – Reliable reference at this station (e.g. GPS) • Shift Type • 00 – Tenths of microseconds • 01 – Microseconds • 10 – Transmission slots • 11 – Epochs • Shift Size: 28 possible shifts, (27 signed shifts for microseconds) • Device ID: 210 possible IDs Arbitrating Reference Device Reference John A. Stine, Self

  8. Contention Behaviors • Contention Rules • Priority phase signaling • Contention phase signaling • Using directional antennas in signaling • Reserving capacity and CBR Signaling • Energy conservation • Retry rules Arrows are hyperlinks to descriptions John A. Stine, Self

  9. Timing and Network Entry Behaviors • Network participation • Network entry and reference selection • Possible coexistence procedure • Selecting the best synchronization reference • Ad hoc reference selection • Ad hoc reference maintenance • Reference directed time adjustments • Device synchronization • Arbitrating synchronization of references • Reference signaling for a device Arrows are hyperlinks to descriptions John A. Stine, Self

  10. Features John A. Stine, Self

  11. Coexistence Non-cooperative design Cooperative design • A design to rules approach • Uses the simplest transmissions as the foundation of coexistence (signaling using tones, chirps, etc.) • After resolving space, time and frequency allows any technology to be used • The point • A commitment in the near term to a physical layer technology does not preempt future use of another • Enables evolution of technology with fewer legacy constraints Technologies Strategies Targeted cooperation Design to rules John A. Stine, Self

  12. Spectrum Reuse • Signaling uses the propagation of the signals to orchestrate the reuse of spectrum • Signaling can support the arbitration of multiple frequency channels for variable bandwidth John A. Stine, Self

  13. Fairness • Stations with equivalent priority packets have an equal chance of gaining access with > 94% probability only one gains access • SCR eliminates • Hidden node effects • Exposed node effects • Muteness • Deafness Deaf Node Mute Node Hidden Node John A. Stine, Self

  14. Beamforming Support • Signaling works with any sort of radiation pattern • Allows the use of permanently pointed antennas • Allows the integration of omni, directional, & adaptive antennas • If stations are equipped with adaptive antennas that can adapt within the parameters of signaling • Signaling can resolve the pointing of antennas • Signaling can resolve greater channel reuse • The synchronous nature of access allows the use of handshakes within the slots to create full adaptation • Receivers – beams toward their sources and nulls toward other active transmitters • Transmitters – beams toward destinations and nulls toward other active receivers John A. Stine, Self

  15. Quality of Service Broadcast • Priority phase supports • Four levels of precedence • Constant Bit Rate to support streaming • Broadcast for packets being transmitted to multiple destinations • Two levels of best effort access • Guarantees stations with highest priority packets get access • Contention is always with neighbors using the same priority for access Priority/QoS 4 1 2 3 5 CBR C E C E C E C E C E C E C E C E Contention Phases Priority Phases John A. Stine, Self

  16. Reservations for Streaming  • Two step reservation process • Special signaling for contiguous reservations     Bit 0 Bit 1 Bit 6 CBR … C E C E C E C E Number of reserved slots John A. Stine, Self

  17. Channelization Broadcast Priority/QoS 4 1 2 3 5 • Priority signaling reveals whether a point-to-point transmission or a broadcast transmission follows CBR C E C E C E C E C E C E C E C E Contention Phases Priority Phases John A. Stine, Self

  18. Energy Conservation - 1  • Periodic Opportunistic Dozing Inactivity indicates a low load so doze Recall there is no delay for contention, stations with packets contend in every slot Sync Signaling Transmission Slot … … … 1 2 3 4 m-1 m 1 2 3 4 m-1 m 1 2 CBR Epoch CBR Epoch CBR Epoch Start dozing as soon as possible  9 8 7 6 w 4 2 3 5 1  Synchronization Epoch Doze until the last transmission slot of epoch w of the synchronization epoch, wakeup and wait for the synchronization signal Duty cycles as low as 0.3% are possible John A. Stine, Self

  19. Energy Conservation - 2 Wakeup just prior to the end of the exchange If exchange is not for this node, doze until the end • Default Mode • Periodic Coordinated Dozing (requires messaging)   A station coordinates a dozing period with another “supporting” station (A number of synchronization epochs) The station dozes while the supporting station collects traffic for the dozing station The dozing station awakens prior to the start of a synchronization epoch    I want to doze until x OK The dozing station returns to the doze state when routine priority is used or when no stations contend The supporting station uses the “priority” priority phase in contentions to transmit the accumulated packets for the dozing station   Duty cycles are selectable John A. Stine, Self

  20. Performance John A. Stine, Self

  21. General Assumptions for Analysis Sequence for multiple packet transmissions • Packets no larger than 1500 bytes, otherwise fragmented • Packets sent at specified data rate • Fixed times of 4 msec preambles, 8 msec interframe spaces Sequence for streams across multiple contiguous transmission slots • Packets the size of slices and transmitted at the specified data rate • Fixed times of 4 msec preambles, 8 msecinterframe spaces, 1 msecinterslice spaces John A. Stine, Self

  22. Uncompressed Video • Recall, up to 72 x 333 msec slots can be reserved per epoch • The table provides the bit rate required to support uncompressed video for the specified number of slots reserved per epoch & the efficiency John A. Stine, Self

  23. Lightly Compressed Video • Tables show required slots and efficiency for different data rates Bit Rates Very high efficiencies John A. Stine, Self

  24. Local File Transfer • All packets in the transfers would take one slot for all data rates 100 Mbps and above • There are >2960 slots available per second and transmission slots occur every 333 msec • Peak rate of packet exchanges are consecutive packet-acknowledgement • The following table shows the delay between packets based on the number of simultaneous contenders and desired confidence Bit Rate Well within 50 msec criteria for max ACK delay John A. Stine, Self

  25. First Packet of Session Reading Time Reading Time Last Packet of Session Web Browsing Focus on the burst • Here we consider the contribution of SCR (The user experience is likely dominated by the rest of the network and the competing traffic) • Observations • All MSDUs can fit within a transmission slot, four 1500 byte MSDUs at 1 Gbps • >2960 transmission slots available per second • 267 slots to download a 2 MB embedded object (<10% of slots in a second) • SCR provides statistical multiplexing of traffic • Most exchanges are downlink (i.e. access point to station) • Expected access delays are within a few milleseconds for most likely number of contenders (see previous slide) John A. Stine, Self

  26. Hard Disk File Transfer • Worst case of model proposes download will average 30 Mbps • Observations • SCR supports device synchronization so direct transfers between hard drives and computers • Can exploit CBR reservations for large file downloads • At 1Gbps data rate • Pure contentions can support up to 17 Mbps average download rates • Less than 1 msec response • Creating a recurring reservation of contiguous slots for higher download rates • A reservation of 6 slots is only 8% of the available time and provides >30 Mbps • A maximum of 25 msec from request to start of download John A. Stine, Self

  27. References – Previous Presentations John A. Stine, Self

  28. References • J. A. Stine, “Exploiting processing gain in wireless ad hoc networks using synchronous collision resolution medium access control schemes,” Proc. IEEE WCNC, Mar 2005. • J.A. Stine, “Cooperative contention-based MAC protocols and smart antennas in Mobile Ad Hoc Networks,” Chapter 8 in Distributed Antenna Systems: Open Architecture for Future Wireless Communications, Auerbach Publications, Editors H. Hu, Y. Zhang, and J. Luo. 2007. • K. H. Grace, J. A. Stine, R. C. Durst, “An approach for modestly directional communications in mobile ad hoc networks,” Telecommunications Systems J., March/April 2005, pp. 281 – 296. • J. A. Stine, “Modeling smart antennas in synchronous ad hoc networks using OPNET’s pipeline stages,” Proc. OPNETWORK, 2005. • J. A. Stine, “Exploiting smart antennas in wireless mesh networks,” IEEE Wireless Comm Mag. Apr 2006. • J. M. Peha, “Sharing Spectrum through Spectrum Policy Reform and Cognitive Radio,” TBP Proc. of the IEEE, 2009. • J. A. Stine, “Enabling secondary spectrum markets using ad hoc and mesh networking protocols,” Academy Publisher J. of Commun., Vol. 1, No. 1, April 2006, pp. 26 - 37. • J. Stine, G. de Veciana, K. Grace, and R. Durst, “Orchestrating spatial reuse in wireless ad hoc networks using Synchronous Collision Resolution,” J. of Interconnection Networks, Vol. 3 No. 3 & 4, Sep. and Dec. 2002, pp. 167 – 195. • J.A. Stine and G. de Veciana, “A paradigm for quality of service in wireless ad hoc networks using synchronous signaling and node states,” IEEE J. Selected Areas of Communications, Sep 2004. • J. A. Stine and G. de Veciana, “A comprehensive energy conservation solution for mobile ad hoc networks,” IEEE Int. Communication Conf., 2002, pp. 3341 - 3345. • K. Grace, “”SUMA – The synchronous unscheduled multiple access protocol for mobile ad hoc networks,” IEEE ICCCN, 2002. John A. Stine, Self

  29. Conclusion • This SCR design provides • A foundation for coexistence and technology evolution • Support for beamforming (SDMA) • Quality of service differentiation • Contention-based reservations for streaming • Support for channelization (CDMA or FDMA) • Multiple energy conservation techniques • SCR will deliver performance that meets all of the MAC related evaluation criteria • SCR’s signaling only design • Allows all physical layers to coexist • Will enable easier evolution of the physical layer John A. Stine, Self

  30. Strawpoll 1 • Do you support the inclusion of the technique- Synchronous Collision Resolution MAC as described in 10/0255r2 in the TGad draft amendment? • Yes – • No – • Abstain – John A. Stine, Self

  31. Strawpoll 2 • Do you have sufficient information to understand the features of the technique - Synchronous Collision Resolution MAC as described in 10/0255r2? • Yes – • No – • Abstain – John A. Stine, Self

  32. Strawpoll 3 • Do you have sufficient information on the claims made about the performance of the technique- Synchronous Collision Resolution MAC as described in 10/0255r2? • Yes – • No – • Abstain – John A. Stine, Self

  33. Backup John A. Stine, Self

  34. Slot and Epoch Design Rationale • Contention design • 5 phases provide best throughput for transmission slot durations • Design density of 5 provides good balance of performance for most anticipated contender densities • Four priority levels supports all the unique functions of SCR: channelization, reservations, & energy conservation • Transmission slot design • Sized to support for a 1500 byte packet at 100 Mbps and a 4-way handshake (assumes 8 msec interframe space, 4 msec preamble, 120 bit control pkts) • Epoch design • Repetition rate to avoid waste in supporting CBR voice (25 msec accumulation time = 200 samples for 64 kbps voice) • Signaling slot duration (Assumptions next slide) Return John A. Stine, Self

  35. Assumptions on Signaling Capability Modem Capabilities and Physics Return John A. Stine, Self

  36. Timing Parameters Table 1. Design Choices Table 2. Modem Capabilities and Physics Return John A. Stine, Self

  37. Collision Resolution Signaling Performance • Our 5 phase design has been optimized for 5 simultaneous contenders • The contention probabilities p1 = 0.26, p2 = 0.34, p3 = 0.42, p4 = 0.46, p5 = 0.48 Return John A. Stine, Self

  38. Behavior details John A. Stine, Self

  39. Contention Rules • Stations with packets to send contend in every slot until they are successful • If a stations survives a contention but fails to exchange a packet follow the retry rules John A. Stine, Self

  40. Rules of Collision Resolution Signaling (CRS) Broadcast Priority/QoS 4 1 2 3 5 CBR C E C E C E C E C E C E C E C E Contention Phases Priority Phases • Rules for the priority phases • Determine the priority of the content and then the slot to use • A routine packet – do not signal • A high priority packet or the first packet of a stream – use the Priority/QoS phase • A packet destined for more than one station – use the Broadcast phase • A packet from a stream in a previously reserved slot – use the CBR phase • If the node hears a signal in an earlier phase echo the signal and defer from contending and echo all subsequent “C” signals heard • If the node hears an echo in an earlier phase defer from contending and echo all subsequent C signals heard • If still a contender at the selected phase this nodes survives the priority phase - signal in the “C” slot of that phase unless a routine priority John A. Stine, Self

  41. Rules of Collision Resolution Signaling (CRS) Broadcast Priority/QoS 4 1 2 3 5 CBR C E C E C E C E C E C E C E C E Contention Phases Priority Phases • Rules for the contention phases • At the beginning of a contention phase a contending node determines if it will signal in the “C” slot. A contending node signals with the probability assigned to that phase. • Any node that does not signal in the “C” slot but hears a signal echoes the signal in the “E” slot. • A contender survives the phase by signaling in the “C” slot or by not signaling and not hearing another signal in the “C” slot nor an echo in the “E” slot. A contender that does not signal and hears either a “C” or “E” signal loses the contention and defers from contending any further in that transmission slot John A. Stine, Self

  42. Directional Signaling Broadcast Priority/QoS 4 1 2 3 5 CBR • Rules for when to signal do not change • Objectives • Increase spatial reuse and enable SDMA • Allow beamforming using the signals • Support contention among stations with different antenna technologies • Rules for using directionality in signaling • Contenders send priority signals in all directions they might possibly receive • Contenders may send contention phase signals in the direction of their destinations • All stations listen and transmit echoes in all directions they might possibly receive • Contenders may defer directionally after receiving echoes (assuming they can) C E C E C E C E C E C E C E C E Contention Phases Priority Phases Anticipates most stations can commit to directional signaling to one other station John A. Stine, Self

  43. Rules for Reserving Slots • Stations wanting to reserve slots may attempt to reserve any of the slots except those set aside for synchronization purposes • Reservations are made using contention and require two steps • Reservations start with a contention using the QoS priority • After a successful exchange, the station that won the contention may use the CBR priority for subsequent contentions in the same ordinal slot of subsequent CBR epochs • Contentions using the CBR priority transmit only the CBR signal unless contending for contiguously reserved slots • A slot must be reserved in the two step process above before it can be included in the count of contiguous slots • Reservations are use it or lose it, “use-it” means contend for the transmission slot John A. Stine, Self

  44. Energy Conservation Rules • Default Mode • A conserving station enters a low energy state during a transmission slot or through an exchange it is not party but must wake up prior to the next contention • Periodic Opportunistic Mode • Stations enter a low energy state when no contentions are occurring • Stations must wakeup prior to the next quarter second synchronization signaling • Stations waking up cannot contend until they re-synchronize • Periodic Coordination Mode (Requires Messaging) • A station coordinates its dozing period (some number of synchronization epochs) with a supporting station (e.g. access point) and enters the low energy state • The station wakes up just prior to the synchronization signaling of the synchronization epoch and stays awake so long as a priority phase signal is used in contention and returns to dozing after a contention without priority phase signaling • The supporting station downloads all of the accumulated packets for the dozing station contending in the priority phase with the priority signaling slot John A. Stine, Self

  45. Retry Rules • Observations • A try occurs when a node survives signaling but fails to exchange a packet • On account of energy conservation, some contention failures may result from stations dozing • When opportunistic periodic dozing is used • Retries should occur in multiple epochs • Example: After two retries in three consecutive synchronization epochs drop the packet • When opportunistic periodic dozing is not used • Drop that packet after some number of retries, or • Drop the packet after trying for some number of epochs after there have been some number of retries John A. Stine, Self

  46. Network Participation • A station may participate in a network if it is a reference or is synchronized to a reference • A station may only contend if it has synchronized itself to a reference station in the current synchronization epoch • It can always receive packets • A station exiting a low energy state must synchronize itself to a reference signal prior to participating in the network • A station that does not hear a reference for r epochs must execute the procedure for network entry and reference selection • All stations should be either a reference or a direct one-hop neighbor to a reference John A. Stine, Self

  47. Network Entry and Reference Selection • Begin searching for a synchronization reference • If multiple references are found, synchronize to the best reference • If none found, perform coexistence procedures, and if the channel is free • If this station is a designated reference • After finding the best reference (it could be the station itself if it has access to GPS) synchronize to that reference • If neighboring references conflict first serve as an arbitrating reference until neighboring references are synchronized • Begin serving as a reference in the same slots as the best reference • If no reference is found, begin serving as a reference • If this station is not a designated reference and no reference is found, follow ad hoc reference procedures John A. Stine, Self

  48. Possible Coexistence Procedure • At startup, if a station does not identify another reference signal it will sense for known users of the band and if any are identified it either precludes their directions from its antenna pointing or chooses another channel John A. Stine, Self

  49. Selecting the Best Synchronization Reference • Given a choice of references a station will prefer references by the following criteria • Stations not designate as a reference prefer references from which the station can receive packets • The reference with the highest quality in the order • Reliable reference at the reference station (e.g. GPS) • Neighbor to a reliable reference • Synchronized to multiple peer references • Internal clock only • The reference more advanced in time John A. Stine, Self

  50. Ad Hoc Reference Selection • After a station fails to find a neighboring designated or ad hoc reference initiate process to become an ad hoc reference • Randomly select a time within the window of x seconds to become a reference • While waiting to become a reference continue to search for a reference and if found end this process and synchronize to that reference • If no reference is found in the wait • If within two hops of a reference synchronize to the best two hop reference (Used to support mesh or ad hoc networking) • Start sending an ad hoc reference signal • Execute the ad hoc reference maintenance procedure John A. Stine, Self

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