Improved channel access during CFP, and the ability to retain polling for backward compatibility, result in more efficient polling. The ability to schedule transmissions and chain a sequence of polls in a single command is included.
These mechanisms provide for maximum efficiency for high-bandwidth streams, power-management friendly implementations, and poled-style access for variable bit rate and bursty streams.
The centralized scheduler used in the QoS Baseline guarantees collision avoidance and, therefore, improved ability to deliver time-critical payloads. The ability to honor critical QoS contracts such as latency, jitter and bandwidth is much improved. Channel access is tied to the allocations made by subnet bandwidth manager –like higher layer protocols and mechanisms so system reliability is achieved.
Channel robustness in wireless systems is an important consideration because noise, interference and multipath effects lead to degraded channel throughput in the 2.4GHz and 5.xGHz bands, adversely affecting the ability to reliably transmit latency-sensitive or high-bandwidth traffic such as voice and video.
Special attention was paid to improving channel robustness. The proposed schemes include FEC and selective retransmission. These mechanisms include the ability to specify the correction, the ability to specify the correction, acknowledgement and retransmission policy on per-stream basis, thereby accommodating a range of traffic types with policies designed specifically for each.
Channel throughput is improved through FEC, delayed acknowledgements with selective retransmissions and dynamic channel change.
The Baseline enhancements support QoS even when wireless subnets are deployed densely, as in enterprise environments. In such environments, multiple IEEE802.11e subnets could be located within radio range of each other, which would cause interference and/or collisions during the communications by devices in different subnets.
The QoS Baseline has not been approved yet. The next steps in the process are the approval of a draft specification, followed by the approval of the final specification.
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