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Enhanced Contention Period Proposal for QoS and Throughput Enhancements - Summary. Sid Schrum, Donald P. Shaver, Jin-Meng Ho, Khaled Turki and Matthew B. Shoemake Texas Instruments Incorporated 12500 TI Blvd. Dallas, Texas 75243
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Enhanced Contention Period Proposal for QoS and Throughput Enhancements -Summary Sid Schrum, Donald P. Shaver, Jin-Meng Ho, Khaled Turki and Matthew B. Shoemake Texas Instruments Incorporated 12500 TI Blvd. Dallas, Texas 75243 (214) 480-4349 (Shaver), (214) 480-1994 (Ho), (919) 463-1043 (Schrum), (214) 480-6908 (Turki) (214) 480-2344 (Shoemake) shaver@ti.com, jinmengho@ti.com, sschrum@ti.com, khaled@ti.com, shoemake@ti.com Sid Schrum et. al ,Texas Instruments
Key Features • Contention–Free Access during Contention Period • EAP / HC CF Access in CP • Poll / Ack CF exchange sequences (CFP-like) • ESTA to ESTA Contention Free Burst • Poll Request: STA request for CF access • Contention Access • Probabilistic Access Mechanism • Adaptive Contention Sid Schrum et. al ,Texas Instruments
Contention-Free Access • New use of existing timing hierarchy (SIFS, DIFS, etc.) allows for contention free access during contention period • Different primary access mechanism vs. CFP, similar function • Positive benefits of contention free access and CFP-like exchange sequences without access delay of CFP • Allows EAP to transmit QoS traffic to STAs without contention • Allows EAP to initiate Poll-Ack-w/data sequences, and for ESTAs to respond without contention • Allows for piggybacked Acks • Mitigates inter-BSS interference • Improves channel reuse • Offers opportunity to consolidate Level 1 and Level 2 QoS Sid Schrum et. al ,Texas Instruments
CF Access Extensions • ESTA to ESTA contention free exchange • Benefits of contention free access • Better utilization of available channel vs. STA to AP to STA transfer • Poll Request allows ESTA to request contention free access via EAP initiated Poll / Ack sequence • Reduces contention when a burst of frames is available for transmission Sid Schrum et. al ,Texas Instruments
Probabilistic Access Method • Utilizes Permission Probabilities to determine when to transmit • Similar to current backoff scheme in that current timing hierarchy applies (use of slot times), and collisions result in backoff • Compatible with CC/RR which also contends by probability • Different method of picking which slot to use for transmission. • Results in improved channel access characteristics and enables immediate application of updated access parameters to contending traffic Sid Schrum et. al ,Texas Instruments
Adaptive Contention • EAP / HC updates permission probabilities based upon detected channel load • Utilizes lessons learned from Ethernet • Simulation results show Probabilistic Access + Adaptive Contention results in improved channel access characteristics and throughput • Delivery delay mean and variance key metrics Sid Schrum et. al ,Texas Instruments