文档介绍：March 2011 James Wang et al ( MediaTek ) doc.: IEEE -11/0350-r0 Submission Discussion on 11ah MAC and PHY Issues and Enhancements ? Date: 2011-03-13 Authors: March 2011 James Wang et al ( MediaTek ) Slide 2 doc.: IEEE -11/0350-r0 Submission Abstract ? Issues for works are discussed ? Some possible MAC enhancements are presented Slide 2 March 2011 James Wang et al ( MediaTek ) doc.: IEEE -11/0350-r0 Submission Issues with Outdoor Wide work ? Uplink – Large AP footprint and large number of STAs in some usage models – Hidden nodes between non-AP STAs due to structural blockage – Increased chances of uplink collision for contention access 3 March 2011 James Wang et al ( MediaTek ) doc.: IEEE -11/0350-r0 Submission Issues with Outdoor Wide work ? Downlink – Large number of OBSSs due to large footprint; deployment of APs is not well-planed – APs and pete for channel access – petes for channel access 4 March 2011 James Wang et al ( MediaTek ) doc.: IEEE -11/0350-r0 Submission Controlled Access ? To avoid the uplink collision issue, use controlled access as the primary mode access for STAs ? Two controlled access modes are available in .11 – Contention Free Access Period (CFP) – Controlled Access Period (CAP) ? Both controlled access modes use PIFS priority access to channel ? PIFS access can subject to OBSS collision, some improvement is required 5 March 2011 James Wang et al ( MediaTek ) doc.: IEEE -11/0350-r0 Submission Controlled Access ? CFP and CAP Operation in 11 6 Beacon D1+poll SIFS U1+Ack SIFS CF-END D2+Ack +poll D3+poll SIFS PIFS U1+Ack SIFS PIFS Contention-Free Period (CFP) Contention Period (CP) NAV CFPMaxDuration NAV Reset No Response to CF- Poll Beacon PIFS Contention Period (CP) NAV ACK QOS+CF-poll U1+ ACK ACK Controlled Access Period (CAP) PIFS QOS+CF-poll TXOPLimit U1 SIFS SIFS SIFS SIFS PIFS SIFS March 2011 James Wang et al ( MediaTek ) doc.: IEEE -11/0350-r0 Submission Contention Access ? Cont