Enhanced MAC proposal for high throughput Tohoku University

Enhanced MAC proposal for high throughput. Tohoku University Hiroyuki Nakase and Hiroshi Oguma Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 1

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 Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 2

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 100 Mbps. → New PHY and MAC proposal is needed Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 3

Background • MAC throughput using conventional MAC Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 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, Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 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 Aggregation Header Sub. Header Data Body Frame 1 Sub. Header Frame 2 FCS Sub. Header Frame n Less than 9000 bytes Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 6

Throughput with frame aggregation • Simulation results • • 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 180 Mbps was obtained Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 7

Throughput using aggregation 324 Mbps (54 x 6 ch) 274. 8 Mbps (84. 8%) 216 Mbps (54 x 4 ch) 191. 2 Mbps (88. 5%) 162 Mbps (54 x 3 ch) 142. 9 Mbps (88. 2%) AP-STA Point-to-Point UDP packet ACK : 54 Mbps SIFS: 16 usec DIFS: 32 usec Frame aggregation is effective to improve MAC throughput in the case of P-P connection. Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 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 Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 9

System throughput using EDCF • PHY data rate of 216 Mbps and 324 Mbps • CW setting of AP and STA is the same. • Frame aggregation was employed. 6 Ch, 4000 Byte/CH Throughput: 32. 4 Mbps Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 4 Ch, 4000 Byte/CH Throughput: 28. 4 Mbps 10

System throughput using EDCF • Unfair CW setting for advantage of AP – CWmin_AP=15 6 Ch(324 Mbps), 4000 Byte/CH 50. 8 Mbps (Downlink : 49 Mbps , Uplink: 1 Mbps) at CWmin_STA=255 Improvement of Throughput : 157% 4 Ch(216 Mbps), 4000 Byte/CH 47. 8 Mbps (Downlink : 47 Mbps , Uplink: 0. 3 Mbps) at CWmin_STA=255 Improvement of Throughput : 168% Usage efficiency of PHY data rate is less than 60% Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 11

Proposal of Enhanced PCF • Three Types of MAC procedure 1) Static Beacon Timing HCF ① Individual polling ② MAC frame aggregation for multicast polling 2) 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 Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 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 Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 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 is started from Beacon signal from AP. STA-STA communication is also controlled by AP EDCF duration Beacon PCF Data Poll-request CF-end DCF Data Poll-accept Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 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, Vo. IP, 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. Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 15

Simulation results of EPCF • Scenario 1 • 10 msec Beacon interval is assumed. – HDTV, SDTV, Vo. IP, MP 3, Video. Phone 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 81 Mbps. • MAC efficiency is more than 96%. Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 16

Problem • Waste duration of PHY preamble and SIGNAL field of 16+4 usec in low data rate frame. – Ex: 0. 096 Mbps (Vo. IP) • Preamble and SIGNAL: 20 usec • MAC Header + Data + FCS @ 216 Mbps: 16 usec » (36 Byte + 120 Byte + 4 Byte)/(216 Mbps) • Solution : Reduce the number of PHY preamble – Merging downstream for low data rate!! • MAC frame Aggregation for low data stream of < 1 Mbps Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 17

Enhanced PCF with MAC frame aggregation • • • 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 Guard duration Beacon PCF Data Poll-request CF-end DCF Data Poll-accept Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 18

Frame format Preamble SIGNAL Aggregation MAC Header MAC Sub. Header 1 Body + FCS MAC Sub. Header 2 MAC Sub. Header 3 Frame Control 2 Duration 2 Source Address 6 Body + FCS FCS BSSID 6 • Aggregation header has four fields of Frame Control, Duration, Source Address, BSSID and Sequence Control 1 Duration 2 Destination Address 6 • MAC Sub. Header has fields of Sequence Number, Duration and Destination Address Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 19

Control Field Definition • Frame Control Field – First 1 Byte is the same as conventional MAC header. – Number of aggregated MAC frames is represented. Protocol Version 2 Type Subtype Number of Aggregation Researved 2 4 4 4 • Sequence Control Field – Sequence number for identification – MAC information for individual terminal Sequence Number Retry 4 1 Pwr Mgt 1 WEP Order 1 1 Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 20

Throughput Estimation (Scenario 1) • 10 msec Beacon interval is assumed. – HDTV, SDTV, Vo. IP, MP 3, Video. Phone 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 82 Mbps. • MAC efficiency is more than 98%. Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 21

Dual PHY communication • IFS for ACK, low rate AP-STA are wasted duration for 11 n. – 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 11 a/b/g – Ack, low rate packet for STA-AP connection Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 22

Dual PHY protocol stack • Definition of MAC sub-layer for merging different PHY MAC STA-AP AP-STA MAC 11 b/g/n MAC 11 n PHY 11 b/g/n PHY 11 n Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 23

Dual PHY communication • Employment of 11 b/g/n PHY for low data rate traffic of less than 1 Mbps • High data rate of 11 n 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 Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 24

PHY and MAC implementation • We have a national project to implement 5 GHz high throughput WLAN terminal. – Development with Mitsubishi Electric Co. and Net. Cleus Systems Co. • Band expansion based on 11 a PHY format. – 6 channels expansion available – Xillinx Vertex. IIPro was used for MAC implementation. Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 25

Block diagram of implemented modem Wireless LAN Gbit Ethernet 14 bit 160 Msps TX RF/IF DAC Modulation MAC RX RF/IF ADC MAC PHY LSI RJ 45 Demodulation 12 bit 160 Msps Implemented on Virtex 2 Pro With dual processor of Power. PC 450 Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 26

Implementation of 5 GHz modem Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 27

Implementation of modem • MAC board : throughput of more than 100 Mbps Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 28

Conclusion • New MAC Proposal with effective polling procedure is indispensable for high system throughput using 11 n. • 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. Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 29

Enhanced Mac proposal for High throughput by Hiroyuki Nakase, Tohoku University, 13 -17, Sep. 2004 30