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Enhanced MAC proposal for high throughput.

Enhanced MAC proposal for high throughput. Tohoku University Hiroyuki Nakase and Hiroshi Oguma. Outline. Background Frame aggregation for high throughput single link using UDP – Simulation – New MAC procedure EDCF with CW definition for AP Polling with static frame control

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Enhanced MAC proposal for high throughput.

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  1. Enhanced MAC proposal for high throughput. Tohoku University Hiroyuki Nakase and Hiroshi Oguma Hiroyuki Nakase, Tohoku Univ.

  2. Outline • Background • Frame aggregation for high throughput single link using UDP – Simulation – • New MAC procedure • EDCF with CW definition for AP • Polling with static frame control • Polling with MAC frame aggregation of different IP link • Dual PHY method • Development of PHY Hiroyuki Nakase, Tohoku Univ.

  3. Introduction • Throughput of MAC SAP was limited by connection procedure based on CSMA/CA. • SIFS, DIFS and backoff for every packet • 802.11 task group n is aiming to high throughput of more than 100Mbps. → New PHY and MAC proposal is needed Hiroyuki Nakase, Tohoku Univ.

  4. Proposal 1: Frame aggregation • Frame format for aggregation • Aggregation of MAC frame to send same destination STA. • Aggregation Header is defined in addition to MAC header. • Aggregation header has informations of number of aggregation, Hiroyuki Nakase, Tohoku Univ.

  5. Frame structure • Aggregation flag is defined in subtype field of MAC header. • Aggregation header is defined. • Number of aggregation frames • Subheader is added to each aggregated frame. • Length of frame Preamble SIGNAL Frame Body MAC Header Data Body FCS Aggregation Header SubHeader Frame 1 SubHeader Frame2 SubHeader Frame n Less than 9000 bytes Hiroyuki Nakase, Tohoku Univ.

  6. Throughput with frame aggregation • Simulation results • Frame size of 1500x6 = 9,000 Byte by aggregation • Point-to-point connection using UDP packet • Wireless data rate is 324 Mbps • Throughput of more than 180 Mbps was obtained Hiroyuki Nakase, Tohoku Univ.

  7. Throughput using aggregation 324Mbps (54 x 6ch) 274.8Mbps (84.8%) 216Mbps (54 x 4ch) 191.2Mbps (88.5%) 162Mbps (54 x 3ch) 142.9Mbps (88.2%) AP-STAPoint-to-Point UDP packet ACK : 54Mbps SIFS: 16usec DIFS: 32usec Frame aggregation is effective to improve MAC throughput in the case of P-P connection. Hiroyuki Nakase, Tohoku Univ.

  8. MAC throughput using Scenario • Scenario 1 of usage model • Conventional DCF • Enhanced DCF with unfair contention window setting • Proposal of employment of polling connection • Proposal of FDD mode using dual PHY Hiroyuki Nakase, Tohoku Univ.

  9. System throughput using EDCF • PHY data rate of 216Mbps and 324Mbps • CW setting of AP and STA is the same. • Frame aggregation was employed. 6Ch,4000Byte/CH Throughput: 32.4 Mbps 4Ch,4000Byte/CH Throughput: 28.4 Mbps Hiroyuki Nakase, Tohoku Univ.

  10. System throughput using EDCF • Unfair CW setting for advantage of AP • CWmin_AP=15 6Ch(324Mbps),4000Byte/CH 50.8Mbps (Downlink : 49Mbps , Uplink: 1Mbps) at CWmin_STA=255 Improvement of Throughput : 157% 4Ch(216Mbps),4000Byte/CH 47.8Mbps (Downlink : 47Mbps , Uplink: 0.3Mbps) at CWmin_STA=255 Improvement of Throughput : 168% Usage efficiency of PHY data rate is less than 60% Hiroyuki Nakase, Tohoku Univ.

  11. Proposal of Enhanced PCF • Three Types of MAC procedure • Static Beacon Timing HCF • Individual polling • MAC frame aggregation for multicast polling • Advanced HCF with dual PHY • Concept Improvement of system throughput AP acts full traffic control in BSS Suppression of overhead in low data rate traffic Hiroyuki Nakase, Tohoku Univ.

  12. Enhanced PCF with static beacon timing • Beacon interval is fixed. (Ex. 10 msec) : Easy control with power saving • Transmission available by only AP in guard duration • Duration of alternate EPCF and EDCF • Length of EPCF is defined by AP due to request • AP broadcast information for EPCF using Beacon packet • All STAs are controlled by AP even if STA adhoc communication Hiroyuki Nakase, Tohoku Univ.

  13. Example procedure Guard duration During EDCF duration, STAs are operated as standard DCF mode. Polling request is transmitted on the rule of DCF. EPCF duration EDCF duration STA-STA communication is also controlled by AP EPCF duration is started from Beacon signal from AP. Poll-request Beacon PCF Data DCF Data Poll-accept CF-end Hiroyuki Nakase, Tohoku Univ.

  14. Definition of frame format (I) • Polling request and accept • STA sends a request frame to AP during DCF when STA has an application with fixed data rate streaming. • EX: HDTV, SDTV, VoIP, etc. • AP assigns on the polling list table for the STA, and send a acceptance frame to the SAT. • Polling List Table • AP has a polling list table for management of PDF duration. • Data rate, sequence number, STA’s address, etc. Hiroyuki Nakase, Tohoku Univ.

  15. Numerical results of EPCF • Scenario 1 • 10msec Beacon interval is assumed. • HDTV, SDTV, VoIP, MP3, VideoPhone is communicated under polling streaming. • Internet file transfer is under DCF. • Necessary duration for polling : 4.8 msec • Without re-transmission for packet error • Estimated throughput more than 81Mbps. • MAC efficiency is more than 96%. Hiroyuki Nakase, Tohoku Univ.

  16. Problem • Waste duration of PHY preamble and SIGNAL field of 16+4usec in low data rate frame. • Ex: 0.096Mbps (VoIP) • Preamble and SIGNAL: 20usec • MAC Header + Data + FCS @ 216Mbps: 16usec • (36Byte + 120Byte + 4Byte)/(216Mbps) • Solution :Reduce the number of PHY preamble • Merging downstream for low data rate!! • MAC frame Aggregation for low data stream of < 1Mbps Hiroyuki Nakase, Tohoku Univ.

  17. Enhanced PCF with MAC frame merging Guard duration • Employment of MAC frame aggregation of AP-to-STAs frame during EPCF • STA-to-AP frame is sending by reserved slot in Poll-accept packet • Expansion of duration for EDCF due to suppression of EPCF overhead Poll-request PCF Data Beacon Poll-accept DCF Data CF-end Hiroyuki Nakase, Tohoku Univ.

  18. Frame format Preamble SIGNAL Merging MAC Header MAC SubHeader 1 Body + FCS MAC SubHeader 2 Body + FCS • Merge header has four fields of Frame Control, Duration, Source Address, BSSID and Sequence Control. MAC SubHeader 3 Body + FCS FCS Frame Control 2 Duration 2 Source Address 6 BSSID 6 Sequence Control 1 Duration 2 Destination Address 6 MAC SubHeader has fields of Sequence Number, Duration and Destination Address Hiroyuki Nakase, Tohoku Univ.

  19. Frame Control Field First 1 Byte is the same as conventional MAC header. Number of aggregated MAC frames is represented. Sequence Control Field Sequence number for identification MAC information for individual terminal Control Field Definition Protocol Version 2 Type 2 Subtype 4 Number of Aggregation 4 Researved 4 Sequence Number 4 Retry 1 Pwr Mgt 1 WEP 1 Order 1 Hiroyuki Nakase, Tohoku Univ.

  20. Throughput Estimation (Scenario 1) • 10msec Beacon interval is assumed. • HDTV, SDTV, VoIP, MP3, VideoPhone is communicated under polling streaming. • Internet file transfer is under DCF. • Necessary duration for polling : 4.4 msec • Without re-transmission for packet error • Estimated throughput more than 82Mbps. • MAC efficiency is more than 98%. Hiroyuki Nakase, Tohoku Univ.

  21. Dual PHY communication • IFS for ACK, low rate AP-STA are wasted duration for 11n. • AP-STA and STA-AP connection are used the same frequency band : Time Division Duplex (TDD) • In order to increase throughput, different band is used for STA-AP connection : Employment of Freqency Division Duplex (FDD) using 11a/b/g • Ack, low rate packet for STA-AP connection Hiroyuki Nakase, Tohoku Univ.

  22. Dual PHY protocol stack • Definition of MAC sub-layer for merging different PHY MAC STA-AP AP-STA MAC 11n MAC 11b/g/n PHY 11b/g/n PHY 11n Hiroyuki Nakase, Tohoku Univ.

  23. Dual PHY communication • Employment of 11b/g/n PHY for low data rate traffic of less than 1 Mbps • High data rate of 11n PHY for large streaming such as HDTV, Gaming, etc. • AP-to-STA streaming without IFS to achieve higher throughput. IFS is not needed for AP-STA ACK is transmitted immediately from STA Hiroyuki Nakase, Tohoku Univ.

  24. PHY and MAC implementation • We have a national project to implement 5GHz high throughput WLAN terminal. • Development with Mitsubishi Electric Co. and NetCleus Systems Co. • Band expansion based on 11a PHY format. • 6 channels expansion available • Xillinx VertexIIPro was used for MAC implementation. Hiroyuki Nakase, Tohoku Univ.

  25. Block diagram of implemented modem Wireless LAN Gbit Ethernet 14bit 160Msps TX RF/IF DAC Modulation MAC MAC PHY LSI RJ45 RX RF/IF ADC Demodulation 12bit 160Msps Implemented on Virtex2Pro With dual processor of PowerPC450 Hiroyuki Nakase, Tohoku Univ.

  26. Implementation of 5GHz modem Hiroyuki Nakase, Tohoku Univ.

  27. Implementation of modem • MAC board : throughput of more than 100Mbps Hiroyuki Nakase, Tohoku Univ.

  28. Conclusion • New MAC Proposal with effective polling procedure is indispensable for high system throughput using 11n. • Our proposals are based on 1 Enhanced DCF with unfair contention window setting 2 Proposal of employment of polling connection 3 Proposal of FDD mode using dual PHY Every proposal has improvement of MAC-SAP throughput superior to conventional MAC procedure. Hiroyuki Nakase, Tohoku Univ.

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