TE contention is therefore rather more proactive than present wire line or wireless systems in terms of real-time bandwidth reallocation, although work is still needed on realising power- efficient voice over IP. Wire line ADSL provides a baseline model. With ADSL a number of users coshare line bandwidth with other users, the number being described as the contention ratio. Higher contention ratios will reduce single-user data rates but very high contention ratios will also reduce multiple-user throughput rates as there will be a substantial number of failed access and retry attempts that will translate into a loss of throughput. This can be both bandwidth inefficient and power inefficient. Interrelationship of the Physical Layer with Other Layers of the OSI Model Table 3.9 802.11 e QOS and prioritisation Bandwidth management/Parametised QOS Traditional CSMA/CA PCF/PC Extended data channel access Background Best Effort Video TXOP Voice TXOP Wireless media extension (Replaces Video Voice transmission transmission opportunity opportunity Hybrid Controlled Channel HCCA establishes 8 queues in the Access Point (AP) Access Point co-coordinator designated by their traffic specification (PC) replaced with a hybrid coordinator (HC) ADSL is increasingly used for voice and real time video exchanges SO the need to arbitrate between traffic with different latency requirements has increased over time. WiFi contention protocols are similar to ADSL. The channel will be inherently less variable than wide-area LTE, though will still exhibit fast and slow fading and as with ADSL there is an end-user expectation that simultaneous voice and video calls can coexist with best-effort data both between two users and/or a multiple users including conversational conferencing. 802.11 has always traditionally been a connectionless contention-based access protocol. The traditional bandwidth allocation mechanisms, primarily the distributed coordination function and point coordination (PC) functions are not well adapted to and were never intend