doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 1 Enhanced MAC proposal for high throughput. Tohoku University Hiroyuki Nakase and Hiroshi Oguma

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 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

doc.: IEEE /1032r1 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 task group n is aiming to high throughput of more than 100Mbps. New PHY and MAC proposal is needed

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 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. –Subheader is attatched to each frame.

doc.: IEEE /1032r1 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

doc.: IEEE /1032r1 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%)

doc.: IEEE /1032r1 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]

doc.: IEEE /1032r1 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

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 9 System throughput using EDCF Unfair CW setting for advantage of AP –CWmin_AP= Mbps (Downlink : 49Mbps, Uplink: 1Mbps) at CWmin_STA= Mbps (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%

doc.: IEEE /1032r1 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

doc.: IEEE /1032r1 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 with 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

doc.: IEEE /1032r1 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 communication is also controlled by AP During EDCF duration, STAs are operated as standard DCF mode. Polling request is transmitted on the rule of DCF. EPCF duration is started from Beacon signal from AP.

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 13 Definition of frame format 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.

doc.: IEEE /1032r1 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 Bandwidth for DCF is 117.5Mbps.

doc.: IEEE /1032r1 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 + 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

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 16 PCF duration DCF duration Enhanced PCF with MAC frame merging 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 Expantion of duration for EDCF due to suppression of EPCF overhead Guard duration Beacon CF-end PCF Data Poll-request Poll-accept DCF Data

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 17 Frame format (Example) Merge header has four fields of Frame Control, Duration, Source Address, BSSID and Sequence Control. PreambleSIGNALMerging 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

doc.: IEEE /1032r1 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

doc.: IEEE /1032r1 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 Bandwidth for DCF is Mbps Improvement is depend on the number of low rate traffic

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 20 Careful consideration of throughput Why the throughput is limited? –Collision, backoff (contention window) –Ack packet –Preamble, IFS Solution : Frame aggregation and Polling

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 21 Is it needed over 100Mbps for VoIP? 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 ( )/ ( )/216 –VoIP on 11a (54Mbps): 88usec + 24 usec = 112 usec ( )/ ( )/216 HDTV stream (>20Mbps) VoIP stream (<100kbps)

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 22 Dual PHY communication IFS, ACK and low rate packet of AP-STA 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-AP connection : Employment of Freqency Division Duplex (FDD) using 11a/b/g –Ack, low rate packet for STA-AP connection

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 23 Dual PHY protocol stack Definition of MAC sub- layer for using different PHY For low rate packet, legacy devices is used. For high rate 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

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 24 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 PCF duration DCF duration

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 25 MIMO and band expantion MIMOBand expantion Merit20MHz bandwidthNo overhead Single RF/IF DemeritAntenna Multi RF/IF Overhead for training Complex processing Wide baseband High speed ADC/DAC

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 26 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.

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 27 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 GHz 23dBm

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 28 Implementation of 5GHz modem

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 29 Implementation of modem MAC board : throughput of more than 100Mbps

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 30 Conclusion New MAC Proposal with effective polling procedure is indispensable for high system throughput using 11n. Our proposals are based on Enhanced DCF with unfair contention window setting Proposal of employment of polling connection Proposal of FDD mode using dual PHY Every proposal has improvement of MAC-SAP throughput superior to conventional MAC procedure.