Enhanced-DCF Wireless MAC Protocol: Some Simulation Results doc.: IEEE 802.11-00/457 January 2001 Enhanced-DCF Wireless MAC Protocol: Some Simulation Results Mathilde Benveniste AT&T Labs, Research Mathilde Benveniste, AT&T Labs - Research

Simulation Study Overview January 2001 Simulation Study Overview TCMA and V-DCF are compared for two network configurations and various traffic loads Three priority classes are considered: High, Medium, and Low Packets from legacy stations are treated the same as medium priority packets The following statistics are plotted for stream aggregates referred to as “calls”: Total throughput for all calls (bits per sec) Goodput by call (bits per sec) Goodput/Application load by call Data sent by call (bits per sec) Dropped traffic by call (bits per sec) Media access delay (queueing plus contention time) by call (sec) Retransmissions by call (packets per sec) Mathilde Benveniste, AT&T Labs - Research

Compared Features January 2001 Features simulated for TCMA doc.: IEEE 802.11-00/457 January 2001 Compared Features Features simulated for TCMA Differentiation by UAT (urgency arbitration time) … by backoff parameters (offset and contention window) used on first transmission attempt … by persistence coefficient used on retrial Absent from simulation ‘Slow’ adaptation to traffic (initial and retrial backoff parameters) ‘Fast’ adaptation to traffic (during backoff) Differentiation by contention time limit Urgency class upgrade Differentiation by limit on queueing time Refs: IEEE 802.11-00/375; -00/456; -00/457; -01/002; -01/003 Features simulated for VDCF Differentiation by backoff offset* used on first transmission attempt … by backoff contention window Absent from simulation ‘Slow’ adaptation to traffic (initial and retrial backoff parameters) Refs: IEEE 802.11-00/398; -00/399; -00/412r1; -00/429; -01/011 *Offset can be used only for priorities below legacy-equivalent Mathilde Benveniste, AT&T Labs - Research

Class Description January 2001 doc.: IEEE 802.11-00/457 *Factor multiplying contention window following collision Mathilde Benveniste, AT&T Labs - Research

OPNET Simulations Network Configuration WLAN Parameters doc.: IEEE 802.11-00/457 January 2001 OPNET Simulations Network Configuration Pairs of stations generate bi-directional traffic streams One direction generates twice the volume of the other Note: Under certain scheduling assumptions, a node with streams destined to different stations can be modeled approximately as a cluster of stations WLAN Parameters DS, 11 Mbps channel rate Buffer size -- 2,024,000 bits RTS/CTS suppressed Maximum retry limit -- 7 [See Notes below for OPNET Model settings] Traffic Statistics Frames of fixed size -- 1504 bytes Inter-arrival times exponentially distributed Packet arrival rate determined from scenario traffic load Adjustment for PHY overhead of 192 microsecs must be made OPNET Simulation Assumptions Specified on Transmitter: Modulation bpsk Transmission delay model dra_txdel Receiver Group Model wlan_rxgroup Closure Model dra_closure_all Channel Match Model wlan_chanmatch Transmission Gain Model dra_tagain Propagation Delay Model wlan_propdel Specified on Receiver Modulation bpsk Noise figure 1.0 ECC Threshold 0. Receiver Gain Model dra_gain Receiver Power Model wlan_power Background Noise Model dra_bkgnoise Interference Noise Model dra_noise Signal to Noise Ratio Model dra_snr Bit Error Rate Model dra_ber Error Model dra_error Error Correction Control Model wlan_ecc __________________ dra_ are OPNET default radio models. wlan_ are 802.11 specific models. Mathilde Benveniste, AT&T Labs - Research

Network Configuration A doc.: IEEE 802.11-00/457 January 2001 Network Configuration A Traffic 8 stations generate 4 bi-directional streams; stream load split 1-to-2 between two directions WLAN Parameters DS, 11 Mbps channel buffer size=2.024 Mbits; no fragmentation RTS/CTS suppressed; max retry limit=7 Mathilde Benveniste, AT&T Labs - Research

Legacy Only Traffic Loading January 2001 30 90 5.0 Mbps 2.5 Mbps 150 doc.: IEEE 802.11-00/457 January 2001 Legacy Only Time (sec) 30 90 5.0 Mbps 2.5 Mbps 150 Traffic Loading BL2 Mathilde Benveniste, AT&T Labs - Research

Legacy Only Traffic Loading January 2001 30 90 5.0 Mbps 2.5 Mbps 150 doc.: IEEE 802.11-00/457 January 2001 Legacy Only Time (sec) 30 90 5.0 Mbps 2.5 Mbps 150 Traffic Loading BL2 Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 5.0 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 5.0 Mbps 2.5 Mbps 150 Priority QoS-Enhanced MAC TCMA TCMA A7 VDCF B7 V-DCF Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 5.0 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 5.0 Mbps 2.5 Mbps 150 Priority QoS-Enhanced MAC TCMA TCMA A7 VDCF B7 V-DCF Mathilde Benveniste, AT&T Labs - Research

Network Configuration B January 2001 Network Configuration B Traffic 60 stations generate 30 bi-directional streams; stream load split 1-to-2 between two directions WLAN Parameters DS, 11 Mbps channel buffer size=2.024 Mbits; no fragmentation RTS/CTS suppressed; max retry limit=7 Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 3.2 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 3.2 Mbps 1.6 Mbps 150 Priority QoS-Enhanced MAC TCMA TCMA D4a VDCF E4 V-DCF Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 3.2 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 3.2 Mbps 1.6 Mbps 150 Priority QoS-Enhanced MAC TCMA TCMA D4a VDCF E4 V-DCF Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 3.2 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 3.2 Mbps 1.6 Mbps 150 Priority QoS-Enhanced MAC Goodput / Application Load 0.2 0.4 0.6 0.8 1 1.2 1.4 20 40 60 80 100 Time (s) Call 1 Call 2 Call 3 Call 4 Percent Retransmissions 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 20 40 60 80 Time Call 1 Call 2 Call 3 Call 4 TCMA TCMA D4a VDCF E4 Goodput / Application Load 0.2 0.4 0.6 0.8 1 1.2 1.4 20 40 60 80 100 Time (s) Call 1 Call 2 Call 3 Call 4 Percent Retransmissions 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 20 40 60 80 Time Call 1 Call 2 Call 3 Call 4 V-DCF Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 3.0 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 3.0 Mbps 1.5 Mbps 150 Priority QoS-Enhanced MAC TCMA TCMA D3 VDCF E3 V-DCF Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 3.0 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 3.0 Mbps 1.5 Mbps 150 1.0 Mbps Priority QoS-Enhanced MAC TCMA TCMA D3 VDCF E3 V-DCF Mathilde Benveniste, AT&T Labs - Research

QoS-Enhanced MAC Priority TCMA V-DCF January 2001 30 90 3.0 Mbps doc.: IEEE 802.11-00/457 January 2001 Time (sec) 30 90 3.0 Mbps 1.5 Mbps 150 1.0 Mbps Priority QoS-Enhanced MAC TCMA TCMA D4a VDCF E4 V-DCF Mathilde Benveniste, AT&T Labs - Research

Comparison of TCMA and VDCF doc.: IEEE 802.11-00/457 January 2001 Comparison of TCMA and VDCF Similarities Both protocols differentiate between different priorities Both protocols transmit comparable amounts of low priority traffic Differences TCMA transmits more of the high priority traffic TCMA causes lower delay to the high priority traffic TCMA results in fewer collisions Mathilde Benveniste, AT&T Labs - Research