Abstract-Multiuser diversity refers to a type of diversity present across different users in a fading environment. This diversity can be exploited by scheduling transmissions so that users transmit when their channel conditions are favorable. Using such an approach leads to a system capacity that increases with the number of users. However, such scheduling requires centralized control. In this paper, we consider a decentralized medium access control (MAC) protocol, where each user only has knowledge of its own channel gain. We consider a variation of the ALOHA protocol, channel-aware ALOHA; using this protocol we show that users can still exploit multi-user diversity gains. First we consider a backlogged model, where each user always has packets to send. In this case we show that the total system throughput increases at the same rate as in a system with a centralized scheduler. Asymptotically, the fraction of throughput lost due to the random access protocol is shown to be 1/e. We also consider a splitting algorithm, where the splitting sequence depends on the users' channel gains; this algorithm is shown to approach the throughput of an optimal centralized scheme. Next we consider a system with an infinite user population and random arrivals. In this case, it is proved that a variation of channel-aware ALOHA is stable for any total arrival rate in a memoryless channel, given that users can estimate the backlog. Extensions for channels with memory are also discussed.

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In this paper, we develop distributed approaches for power allocation and scheduling in wireless access networks. We consider a model where users communicate over a set of parallel multi-access fading channels, as in an OFDM or multi-carrier system. At each time, each user must decide which channels to transmit on and how to allocate its power over these channels. We give distributed power allocation and scheduling policies where each user's actions depend only on knowledge of their own channel gains. We characterize an optimal policy which maximizes the system throughput and also give a simpler sub-optimal policy which is shown to have the optimal scaling behavior in several asymptotic regimes.

Abstract-Uncompressed HD (high-definition) video delivery over wireless personal area networks (WPANs) is a challenging problem because of the limited bandwidth and variations in channel. The 60GHz millimeter-wave (mmWave) band has recently drawn much interest because of the huge bandwidth that it can provide from 57-66 GHz unlicensed spectrum available worldwide. However, to date a system design supporting uncompressed HD video over WPAN is still lacking.In this paper, we develop, simulate, and evaluate an mmWave system for supporting Uncompressed Video streaming over Wireless (UVoW). New features of the UVoW system incorporates: (i) UEP (unequal error protection) where different video bits (MSBs and LSBs) are protected differently, (ii) a multi-CRC to determine whether MSB or/and LSB portions are in error, (iii) UV-ARQ, uncompressed video retransmission protocol which allows the receiver to request only those portions of a video packet which have high importance. Simulations indicate that the UVoW system achieves significantly higher video quality than normal systems under various wireless channel conditions. This shows that UVoW is a promising wireless system supporting uncompressed HD video.Index Terms-Uncompressed high-definition (HD) video, Gigabit WPAN, 60GHz mmWave, UEP, Network simulator (ns2).