1. Token-DCF, COMSNET(2013) -> MOBICOM(2014)

2. Introduction ▣ To improve standard MAC protocol of IEEE 802.11 for WLAN. ▣ S-MAC, A-MAC, SPEED-MAC, and etc are for WSN.  Close to 802.15.4  Energy Consumption is the main issue.  Duty Cycling ▣ Whereas, Throughput & Latency is of most important factor for WLAN.

3. Motivation ▣ 802.11a, b(1999), 802.11g(2003), 802.11n(2009), 802.11ac,ad(2013)  Basic CSMA/CA being improved ▣ Problems of CSMA/CA  unnecessarily long idle time –channel access delay, low channel utilization  High collision rate –Still possibe to collide even with big CW size ▣ The paper is for reducing idle time and collision rate to get better throughput and latency.

4. Related Works ▣ Many researches for improving CSMA/CD  Optimal CW size –Set optimal CW size immediately considering network status –optimal backoff distribution  802.11e,n –Transmit Opportunity (TXOP) – multiple frames –Reverse Direction (RD) – burst response

5. Related Works (cont.) ▣ Wireless Token Passing Protocols  Token Passing is a medium access method where a short packet called token is passed between stations to authorize a station for transmission.  To send data frame, it needs to possess token.  No collision. ▣ Issues  connectivity loss, network partitioning, token loss & duplication, network connectivity change.  Round Robin Passing

6. Main Idea  not round robin scheduling.  Privilege (Token) Scheduling with neighbor nodes’ queue length >0. 2. implicit scheduling.  Queue length information of source and token are collected by each neighbor node by overhearing through MAC header.  Node with same Id can transmit next.

7. ad hoc mode / infrastructure mode

9. Evaluation  Compared to 802.11g in NS-2  Wireless adhoc/infra network  RTS/CTS turned off  Each simulation – 30 seconds/10seconds. Averaged over 20 runs.  Packet payload size – 1500 B  P

10. Results – ad hoc

11. Results - infra

12. Ad hoc – detailed

13. Ad hoc – detailed (cont.)