.11 k below). 3.5.3 802.11 h Power Control If measurement reporting is used then it makes sense to introduce power control. Power control improves the battery life/duty cycle of the user device and should generally help to reduce the noise floor, which in turn should deliver some capacity and coverage benefits. Power control, however, implies a rework of the beacon structure (see 802.11k below). 3.5.4 802.11 i Authentication and Encryption 802.11 i (ratified in June 2004) addresses the replacement of the existing (semisecure) authen- tication and encryption procedures known as wireline equivalent privacy (WEP) with WiFi protected access (WPA). This adds in the user authentication missing in WEP and makes it easier to implement SIM-based access - effectively bringing WiFi together with existing cellular authentication procedures. 802.i also describes a temporal key integrity protocol, a combination of WPA and AES, the American encryption standard for streamed media. The challenge here is to keep the configuration simple and to minimise any impact on header overheads and end-to-end latency budgets. 3.5.5 802.11 j Interworking Originally established to address issues of 802.11a and Hiperlan interworking, additional work items include handover between 802.11 b, g and a and in the longer term, handover between WiFi and cellular (or alternative 802.16/802.20 wide-area systems.) 3.5.6 802.11 k Measurement Reporting 802.11k measurement reporting introduces many of the techniques presently used in cellular (including GSM MAHO mobile-assisted handoff). Measurements collected and sent to the MIB Management Information Base) would include data rate, BER, SNR and a neighbour graph. One proposal is to use beacon compression to take out redundant information in persistent sessions and therefore release beacon bandwidth for measurement reporting. This would be known as a radio resource management beacon (RRM beacon). 3.5.7 802.11 n Stream Multiplexing 802.11n is intended as a protocol for managing multiple HDTV channel streams w