传输重要比特和航行高无线电波：一种分散的跨层协作视频传输方法
Transmitting important bits and sailing high radio waves: a decentralized cross-layer approach to cooperative video transmission
摘要：
我们研究了协作中继对上行链路和下行链路多用户（MU）无线视频传输的影响。我们的目标是最大限度地提高效用的长期总和在一个分散的方式，通过联合优化的数据包调度，资源分配，和合作的决定，假设一些节点愿意作为合作的中继。采用基于定价的分布式资源分配框架，其中价格反映了网络中预期的未来拥塞。具体来说，我们制定的无线视频传输问题作为一个MU马尔可夫决策过程（MDP），明确考虑在物理层和媒体访问控制子层，视频用户的异构流量特性，动态变化的网络条件，以及用户之间的耦合的传输策略跨时间由于共享的无线资源的合作。虽然MDP臭名昭著地遭受维数灾难，我们的研究表明，通过适当的简化和近似，MU-MDP的复杂性可以显着减轻。我们的仿真结果表明，集成合作决策的MU-MDP优化可以增加资源价格的网络，只支持低传输速率，可以降低价格的网络，支持高传输速率。此外，我们的研究结果表明，合作允许用户与微弱的直接信号，以实现改善视频质量的顺序为5-10 dB的峰值信噪比（PSNR），与小于0.8 dB的质量损失的用户与强直接信号，并且总网络能量消耗的适度增加显著小于远距离节点实现等效网络所需的能量PSNR而不利用协作分集。
英文摘要：
We investigate the impact of cooperative relaying on uplink and downlink multi-user (MU) wireless video transmissions. The objective is to maximize the long-term sum of utilities across the video terminals in a decentralized fashion, by jointly optimizing the packet scheduling, the resource allocation, and the cooperation decisions, under the assumption that some nodes are willing to act as cooperative relays. A pricing-based distributed resource allocation framework is adopted, where the price reflects the expected future congestion in the network. Specifically, we formulate the wireless video transmission problem as an MU Markov decision process (MDP) that explicitly considers the cooperation at the physical layer and the medium access control sublayer, the video users' heterogeneous traffic characteristics, the dynamically varying network conditions, and the coupling among the users' transmission strategies across time due to the shared wireless resource. Although MDPs notoriously suffer from the curse of dimensionality, our study shows that, with appropriate simplications and approximations, the complexity of the MU-MDP can be significantly mitigated. Our simulation results demonstrate that integrating cooperative decisions into the MU-MDP optimization can increase the resource price in networks that only support low transmission rates and can decrease the price in networks that support high transmission rates. Additionally, our results show that cooperation allows users with feeble direct signals to achieve improvements in video quality on the order of 5-10 dB peak signal-to-noise ratio (PSNR), with less than 0.8 dB quality loss by users with strong direct signals, and with a moderate increase in total network energy consumption that is significantly less than the energy that a distant node would require to achieve an equivalent PSNR without exploiting cooperative diversity.
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