1. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 1 Enhanced MAC proposal for high throughput. Tohoku University, Japan Hiroyuki Nakase and Hiroshi Oguma

2. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 2 Outline Background Frame aggregation for high throughput single link using UDP – Simulation – New MAC procedure –Polling with MAC frame aggregation of different IP link –Dual PHY method Development of WLAN terminal

3. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 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

4. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 4 Frame aggregation Frame format for aggregation –Aggregation of MAC frame to send same destination STA. –Aggregation Header is defined in addition to MAC header. –Subheader is attatched to each frame.

5. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 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 MAC Header Aggregation Header SubHeader Frame 1 FCS Data Body SubHeader Frame2SubHeader Frame n Less than 9000 bytes SIGNALFrame BodyPreamble

6. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 6 Throughput with frame aggregation Simulation results –Network Simulator II – Frame size of 1500 x 6 = 9,000 Byte by aggregation Point-to-point connection using UDP packet Wireless data rate is 324 Mbps Throughput of more than 185 Mbps was obtained. (~57%)

7. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 7 AP-STA Point-to-Point UDP packet ACK : 54Mbps SIFS: 16usec DIFS: 32usec Throughput using aggregation Frame aggregation is effective to improve MAC throughput in the case of P-P connection. 324Mbps (54 x 6ch) 216Mbps (54 x 4ch) 162Mbps (54 x 3ch) 274.8Mbps (84.8%) 191.2Mbps (88.5%) 142.9Mbps (88.2%) Aggregation size per channel [Byte] MAC Throughput [Mbps]

8. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 8 System throughput using DCF Scenario 1 of usage model PHY data rate of 324Mbps and 216Mbps 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

9. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 9 System throughput using EDCF Unfair CW setting for advantage of AP –CWmin_AP=15 50.8Mbps (Downlink : 49Mbps, Uplink: 1Mbps) at CWmin_STA=255 47.8Mbps (Downlink : 47Mbps, Uplink: 0.3Mbps) at CWmin_STA=255 6Ch(324Mbps), 4000Byte/CH 4Ch(216Mbps), 4000Byte/CH Improvement of Throughput : 157% Improvement of Throughput : 168% Usage efficiency is less than 60% Polling is needed to increace system throughput

10. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 10 Proposal of Enhanced PCF MAC PCF procedure with Static Beacon Timing ① Individual polling ② MAC frame aggregation for multicast polling Concept Improvement of system throughput All traffics of STAs are controlled by AP in BSS Suppression of overhead in low data rate traffic

11. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 11 Enhanced PCF with static beacon timing AP sends broadcast information for EPCF using Beacon packet Beacon interval is fixed. (Ex. 10 msec) : Easy control for power saving Transmission available by only AP in guard duration Duration of EPCF and EDCF are alternated Length of frame for each STA is defined by AP due to request All STAs are controlled by AP even if STA adhoc communication

12. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 12 PCF duration DCF duration Example procedure Guard duration Beacon CF-end PCF Data Poll-request Poll-accept DCF Data EPCF durationEDCF duration STA-STA streaming is also controlled by AP During DCF duration, STAs are operated as standard DCF mode. Polling request is transmitted on the rule of DCF. EPCF duration is switched to DCF by CF- end packet from AP. AP STA1 STA2 STA3 STA4 EPCF duration is started from Beacon signal from AP. AP-STA communication is carried out by TDD scheme

13. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 13 Definition for EPCF 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 the polling sequence number 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.

14. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 14 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 : 4.56 msec Without re-transmission for packet error Usage bandwidth for PCF is 98.5Mbps @ 216Mbps. PCF efficiency is 84% when the offered load of 83Mbps

15. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 15 Problem Wasted duration of PHY preamble and SIGNAL field of 16+4  sec in low data rate frame. –Ex: 0.096Mbps (VoIP) Preamble and SIGNAL: 20  sec MAC Header + Data + FCS @ 216Mbps: 8  sec (36Byte + 120Byte + 4Byte)/(216Mbps) Solution :Reduce the number of PHY preamble –Aggregation of downstream for low data rate!! MAC frame Aggregation for low data stream of < 1Mbps

16. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 16 PCF duration DCF duration Enhanced PCF with MAC frame aggregation Guard duration Beacon CF-end PCF Data Poll-request Poll-accept DCF Data MAC frame aggregation is employed for AP-STA. STA-AP frame is sending during reserved slot. DCF duration is extended by PCF suppression.

17. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 17 Frame format (Example) Aggregation header has four fields of Frame Control, Duration, Source Address, and BSSID. PreambleSIGNALAggregation MAC Header MAC SubHeader 1 Body + FCSMAC SubHeader 2 Body + FCS MAC SubHeader 3 Body + FCSFCS Frame Control 2 Duration 2 Source Address 6 BSSID 6 MAC SubHeader has fields of Sequence Number, Duration and Destination Address Duration 2 Destination Address 6 Sequence Control 1

18. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 18 Control Field Definition 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 Protocol Version 2 Type 2 Subtype 4 Sequence Number 4 Retry 1 Pwr Mgt 1 Order 1 WEP 1 Number of Aggregation 4 Researved 4

19. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 19 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 : 4.43 msec Without re-transmission for packet error Usage bandwidth for PCF is 95.7 Mbps PCF efficiency is 87%. (3% reduction) Improvement is depend on the number of low rate traffic

20. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 20 Scenario configuration HDTV, gaming ~30Mbps FTP ~2Mbps Video streaming ~2Mbps Video Phone ~500kbps VoIP, MP3 ~100kbps 100Mbps throughput is needed for HDTV streaming on AP-STA connection HDTV stream (>20Mbps) VoIP stream (<100kbps)

21. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 21 Is it needed over 100Mbps for VoIP? Comparison between 11n and 11a –VoIP stream every 10msec : 960 bit DIFS(32usec)+Backoff(0usec)+preamble(20usec)+MAC(240bit)+Body +FCS(32bit) +SIFS(16usec)+preamble+MAC+Body+FCS –VoIP on 11n (216Mbps): 88usec + 8 usec =96 usec 32+20+(240+960+32)/216+16+20+(240+960+32)/216 –VoIP on 11a (54Mbps): 88usec + 24 usec = 112 usec 32+20+(240+960+32)/216+16+20+(240+960+32)/216 If there are some MIMO trainig symbols, duration for VoIP is the same between 11n and 11a. It is not efficient usage of 100Mbps.

22. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 22 Proposal: Dual PHY communication All packet of STA-AP connection are small size. IFS and preamble for ACK and low rate packet in STA-AP connection 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-to-AP connection : Employment of Freqency Division Duplex (FDD) using 11a/b/g –Ack, low rate packet for STA-AP connection

23. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 23 Dual PHY protocol stack Definition of MAC sub- layer for using different PHY For AP-STA, legacy devices is used. For AP-STA connection, 11n is used. PHY 11n PHY 11a/b/g/n MAC 11a/b/g/n MAC 11n MAC STA-AP AP-STA

24. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 24 Dual PHY communication Employment of regacy devices for STA-AP connection AP-to-STA streaming without IFS to achieve higher throughput. Simulation results are shown lator. IFS is not needed for AP-STA ACK is transmitted immediately from STA PCF duration DCF duration

25. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 25 WLAN terminal implementation We have a national project to implement 5GHz high throughput WLAN terminal. –Project was started in 2002. –Budget of Ministry of Education, Culture, Sports, Science and Technology, JAPAN –Development with Mitsubishi Electric Co. and NetCleus Systems Co. Band expansion based on 11a PHY format. –6 channels expansion available –FPGAs of Xillinx and Altera were used for implementation.

26. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 26 Block diagram of implemented modem Gbit Ethernet PHY LSIMAC Wireless LAN MAC Modulation Demodulation TX RF/IF RX RF/IF DAC ADC RJ45 Implemented on Virtex2Pro With dual processor of PowerPC405 14bit 160Msps 12bit 160Msps 5.47-5.59 GHz 23dBm

27. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 27 Implementation of 5GHz modem License for radio transmission measurement is available.

28. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 28 Implementation of modem MAC board : throughput of more than 100Mbps

29. doc.: IEEE 802.11-04/1032r3 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 29 Conclusion MAC proposal MAC frame aggregataion of multi-destination in PCF duration. FDD mode using 11n and regacy devices Every proposal has improvement of MAC throughput superior to conventional MAC procedure.