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Response to Call For Proposal for P802.11n

Response to Call For Proposal for P802.11n. Hervé Bonneville, Bruno Jechoux Mitsubishi ITE 1, allee de Beaulieu, 35700 Rennes, France e-Mail: {bonneville,jechoux}@tcl.ite.mee.com. Our vision. Ethernet: Topology had to change for 100 Mbit/s and above No more a shared bus

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Response to Call For Proposal for P802.11n

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  1. Response to Call For Proposal for P802.11n Hervé Bonneville, Bruno Jechoux Mitsubishi ITE1, allee de Beaulieu, 35700 Rennes, Francee-Mail: {bonneville,jechoux}@tcl.ite.mee.com H.Bonneville, B.Jechoux, Mitsubishi ITE

  2. Our vision • Ethernet: • Topology had to change for 100 Mbit/s and above • No more a shared bus • Collisions shall be avoided to get performances • Physical layer enhancements might be sufficient to compensate MAC lack of efficiency on TGn simulation scenarios • but at which cost in terms of complexity? • AND Customers and applications evolution are not limited to IEEE simulation scenarios! • Let’s anticipate these needs right now! H.Bonneville, B.Jechoux, Mitsubishi ITE

  3. System Objectives • QoS support • Efficient resource usage • Compatibility • Versatile and Flexible • No added complexity H.Bonneville, B.Jechoux, Mitsubishi ITE

  4. Flow differentiation Centralised on-demand resource allocation Buffer management MAC features for QoS support Guaranteed Throughput Delay constraints Heterogeneous traffic support Multi-environment support H.Bonneville, B.Jechoux, Mitsubishi ITE

  5. Flow differentiation Centralised on-demand resource allocation Buffer management Inclusion in 802.11e superframe MAC features for Compatibility Delay constraints Guarantied Throughput Backward compatibility Heterogeneous traffic support Multi-environment support H.Bonneville, B.Jechoux, Mitsubishi ITE

  6. Flow differentiation Centralised on-demand resource allocation Buffer management Inclusion in 802.11e superframe Short MAC PDU Fast selective repeat ARQ IFS Suppression MAC Header compression Aggregation @ PHY MAC features for Efficient resource usage Delay constraints Guarantied Throughput Capacity to sustain high load Backward compatibility Heterogeneous traffic support Multi-environment support MAC efficiency Bad channel resistance H.Bonneville, B.Jechoux, Mitsubishi ITE

  7. Flow differentiation Centralised on-demand resource allocation Buffer management Inclusion in 802.11e superframe IFS Suppression MAC Header compression Aggregation @ PHY Fixed size MAC PDU Efficient with simple scheduler Resource announcement MAC features for Low cost implementation Delay constraints Guarantied Throughput Capacity to sustain high load Backward compatibility Short MAC PDU Fast selective repeat ARQ Heterogeneous traffic support Multi-environment support MAC efficiency Bad channel resistant Low consumption Low complexity H.Bonneville, B.Jechoux, Mitsubishi ITE

  8. Derived MAC enhancements • TDMA frame embedded in 802.11e superframe • Centralised on demand resource allocation with Resource announcement, • efficient even with simple Round Robin scheduler per priority • Fast selective repeat ARQ with Buffer management • Short and fixed size MAC-PDU with MAC Header compression • Aggregation at PHY level (1 to several destination) H.Bonneville, B.Jechoux, Mitsubishi ITE

  9. Stack overview • MAC layer is enhanced with the “Extended Centralised Coordination Function” mode (ECCF). • Functions are distributed over 4 sub-layers 802.2 LLC 802.2 LLC ECCF MAC Legacy 802.11 MAC Packet Sequence Number Assignments MAC Header Compression LLCCS Sequence Number Assignments Fragmentation Encryption MDU Header + CRC SAR Segment Sequence Number Assignments Segmentation/Re-Assembly Error and Flow Control MIS Encryption MPDU Header Signalling Insertion MLS PHY PHY H.Bonneville, B.Jechoux, Mitsubishi ITE

  10. Frame structure and timing • 802.11 MAC Super Frame & Beacon kept for compatibility. • A part of the Contention Free Period (CFP) divided into MAC Time Frame (MTF) of fixed duration (for example 2 ms). • Resource scheduling performed on a per MTF basis. Time Intervals (TI) of variable duration dynamically allocated to STAs within an MTF. 802.11 MAC Super Frame CFP CP CFP MTF Period for ECCF Period for PCF/HCCA access Period for DCF/EDCA access Period for ECCF Beacon Beacon Beacon Information CF Parameter Set ECCF Parameter Set H.Bonneville, B.Jechoux, Mitsubishi ITE

  11. Frame structure and timing (cont.) • ECCF insertion into CAP: CAP generated by the HC using CF-Poll data frame as defined in the 802.11e extension. • CF-Poll contains the RRM MAC address (HC and RRM can be distinct) as destination address, and allocates a reserved time period for ECCF. • CAP is split by the RRM into successive MTFs of fixed duration, each being described by a PGPM broadcast at the beginning of the MTF. SIFS PIFS MTF DIFS CF-Poll PGPM PGPM Data Data CAP Legacy MAC frame ECCF MAC frame H.Bonneville, B.Jechoux, Mitsubishi ITE

  12. Frame structure and timing (cont.) • TI constituted of one MPDU = data unit exchanged with the PHY layer as in legacy 802.11 • MPDU contains two parts: signalling and data • contents defined by the emitter (source STA) • data and signalling can be intended for one or more destination STAs • Possible long PHY bursts • MTF composition defined in a specific MPDU = PGPM MTF MPDU MPDU MPDU MPDU PGPM Data Data Data Data PGPM TI#0 TI#1 TI#2 TI#3 TI#4 H.Bonneville, B.Jechoux, Mitsubishi ITE

  13. PGPM PGPM Header Signalling TID STA#1 ->STA#2 TID STA#4 ->RRM,STA#3 HSCS RR ->RRM FB ->STA#3 MPDU MPDU MPDU Header DPD STA#2 Signalling HSCS Data Block to STA#2 Data MPDU Header Signalling HSCS STA#1 STA#4 STA#2 RRM, STA#3 ... MIS-PDU MIS-PDU HDR CRC HDR CRC Fixed size segments (2 possible lengths) MTF structure (detailed) • An MPDU may aggregate all data blocks sent by a station • MPDU signalling part (variable length): • Has a dedicated protection (HSCS) • Includes resource requests, Error Control signalling,... • Includes description of data blocks (if any) MTF structure example Sent by RRM All (TI #0) (TI #1) (TI #2) H.Bonneville, B.Jechoux, Mitsubishi ITE

  14. PGPM MPDU PGPM Header TID STA#1 ->STA#2;#3 Signalling HSCS MPDU Header Signalling DPD STA#2 DPD STA#3 HSCS Data Data Block to STA#2 Data Block to STA#3 STA#1 STA#2,#3 STA#2 STA#3 ... ... MIS-PDU MIS-PDU MIS-PDU MIS-PDU HDR CRC HDR CRC HDR CRC HDR CRC Fixed size segments (2 possible lengths) Fixed size segments (2 possible lengths) MTF structure (cont.) • MTF structure example with flow aggregation: • Station 1 transmits data to stations 2 and 3 in one MPDU (PHY burst) only • PHY mode may be different for each pair Sent by RRM Received by All (TI #0) (TI #1) H.Bonneville, B.Jechoux, Mitsubishi ITE

  15. HDR HDR MIS-PDU MIS-PDU CRC CRC Data Segmentation • Short and fixed-size segments • better robustness against errors remaining above PHY layer • Segmentation and Re-assembly (SAR) sub-layer introduced to perform adaptation between LLC and MAC. • Simulations have been made with two segment sizes (Long and Short, 128 and 61 octets of payload). Good trade-off between: • MAC signaling overhead added to each segment • Segmentation overhead due to padding added to reach a predetermined size in the last segment LLC Long Short Segmentation overhead MAC signalling overhead SAR Sub-Layer (MAC) SAR-SDU Data Segment Segment Segment MIS (MAC) HDR MIS-PDU CRC H.Bonneville, B.Jechoux, Mitsubishi ITE

  16. Power Saving • Inherent power saving facilities • An active STA doesn’t need to listen to all MPDUs • Only resource grants announcements and traffic it is destined to • STA may be on a low power scheme otherwise • Long-term power saving: • RRM allows an STA to enter sleep mode when it has no more traffic to schedule for it • RRM will grant resource to that STA after the sleeping period • During sleep mode, traffic is buffered in any source STA as there is no resource granted for it • Compatible with direct link communication H.Bonneville, B.Jechoux, Mitsubishi ITE

  17. Simulations • Unique MAC configuration (no knob activation nor parameter tuning depending on the context or scenario) • Simulation conditions: • MAC, EC and segmentation overhead fully taken into account • Dynamic resource allocation based on requests from STA • Simple Round Robin scheduler (per priority level), 2 priority classes • No contention period, 2 ms long MTF • PHY modes • SISO in 20 MHz or 40 MHz (up to 108 Mbit/s) • MIMO (2x2 up to 3x3), 20 or 40 MHz (from 54 Mbit/s up to 405 Mbit/s) • PHY abstraction in system simulation (preliminary configuration) • Uniform PER in the BSS (all the STA see the same PER) • Simulated PER: 0, 3.10-2, up to 1.5 10-1 (equivalent to 0; 3.10-1; 8.5 10-1 for 1500 bytes packets) H.Bonneville, B.Jechoux, Mitsubishi ITE

  18. ECCF Scalability • Goodput at MAC SAP vs PHY data rate (point-to-point scenario) • linear variation • Slight impact of the PER on MAC efficiency • retransmission with low signalling SR-ARQ • MAC efficiency: • Constant vs PHY rate • High level: [76% ; 86%] • Fully scalable for high bit rates Results valid whatever the application packet size (c.f.segmentation) H.Bonneville, B.Jechoux, Mitsubishi ITE

  19. Mixed traffic handling • Capacity usage at MAC-SAP vs. Number of VoIP sessions • 1 TCP data flow transmitted using MIMO 126Mbit/s • VoIP: 120-byte packets emitted every 10 ms (2x96kbit/s) • n VoIP sessions, using MIMO or SISO • 30 VoIP sessions + at least 70 Mbit/s of TCP traffic H.Bonneville, B.Jechoux, Mitsubishi ITE

  20. Delay performances • IEEE TGn Usage models : Scenario I (Home) • Traffic classification based on priority level (VoIP > TCP) • Delay comparison for different error rate [cdf(d>D)] • Strong QoS constraints of VoIP reached: • with a simple centralised scheduling • an efficient ARQ • Max delay below 20 ms for QoS traffic H.Bonneville, B.Jechoux, Mitsubishi ITE

  21. Simulation results for Scenario 1 • Scenario 1: • all data flow transmitted using 40 MHz 64QAM 2/3 SISO • Modified scenario 1bis: • Infinite TCP sources + Multiple PHY modes (24 - 405 Mbit/s) • QoS requirements can be achieved with 105 Mbit/s at PHY • > 75% MAC efficiency • 148 Mbit/s available at MAC-SAP (198 Mbit/s avg at PHY) H.Bonneville, B.Jechoux, Mitsubishi ITE

  22. Simulation results for Scenario 4 • Scenario 4: • all data flow transmitted using 40 MHz 64QAM 3/4 SISO • Modified scenario 4bis: • Infinite TCP sources + Multiple PHY modes (24 - 405 Mbit/s) • QoS requirements can be achieved with 106 Mbit/s at PHY • > 67% MAC efficiency • 229 Mbit/s available at MAC-SAP (341 Mbit/s avg at PHY) H.Bonneville, B.Jechoux, Mitsubishi ITE

  23. Simulation results for Scenario 6 • Scenario 6: • all data flow transmitted using 40 MHz 64QAM 3/4 SISO • Modified scenario 6bis: • Infinite TCP sources + Multiple PHY modes (24 - 405 Mbit/s) • QoS requirements can be achieved with 93 Mbit/s at PHY • > 67% MAC efficiency • 79 Mbit/s available at MAC-SAP (185 Mbit/s avg at PHY) H.Bonneville, B.Jechoux, Mitsubishi ITE

  24. Results conclusion • QoS requirements supported (throughput and delay) • High level MAC efficiency for all scenarios • Flexibility ensured, without context-dependent tuning • Overall support of 11n simulations scenarios with a 120 Mbps PHY layer H.Bonneville, B.Jechoux, Mitsubishi ITE

  25. Feasibility • Nothing futuristic • TDMA has been used for 20-30 years • Present in many systems (GSM, 802.15, 802.16…) • Just one step further than HCCA • Proven technologies • Centralised RRM • Simple scheduler • Classical ARQ • Moderate complexity implementation • not more complex than 802.11e (HCCA) H.Bonneville, B.Jechoux, Mitsubishi ITE

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