Collaborative Techniques for Enhancing Spatial Diversity

移动通信和计算的融合导致了从传统（2G）移动电话到支持新宽带数据和多媒体应用的所谓智能电话的大规模迁移。这些新的应用程序需要大量的电力，并不总是与移动设备的尺寸兼容，因为新服务的电力消耗的增长已经超过了电池技术的进步。多输入多输出（MIMO）是利用空间分集来提高网络容量的一种有效技术。研究表明，在许多网络中，MIMO的空间分集增益可以通过协作实现，而不需要多个天线。我们的团队在以前的资助下，已经为中继网络开发了几种协作通信策略和代码设计指南。我们还表明，在多址信道中，使用非正交传输以及由无速率码（如Raptor码）辅助的干扰消除可以导致接近信息理论界限的和速率。使用无速率码还会产生不需要事先知道信道状态信息就能适应信道条件的方案。我们打算通过考虑更复杂的网络场景来扩展我们的研究，包括具有多个源、中继和目的地的中继网络。在理论方面，我们将致力于寻找各种网络配置的可实现速率的信息理论界限。在实践方面，我们将为不同信道实现下的特定网络配置开发编码方案，并根据理论界限衡量所开发技术的性能。本课题的主要工作包括：1)推导了复合多址信道和中继信道等几种感兴趣的网络的可达速率的理论边界。2)开发利用网络编码、嵌套代码和Raptor代码的协作技术。3)已开发方案对3GPP LTE-Advanced （Long Term Evolution-Advanced）、IEEE 802.16 （WiMax）等无线通信标准的适应性评估。

Convergence of mobile communications and computing has resulted in a massive migration from legacy (2G) mobile phones to so called Smart Phones that support new broadband data and multimedia applications. These new applications require a large amount of power not always compatible with the size of the mobile devices since the increase in power consumption for new services has outpaced the advances in battery technology. Multiple Input Multiple Output (MIMO) is an efficient technique for increasing the network capacity through utilization of spatial diversity. It has been shown that in many networks, spatial diversity gains typical of MIMO can be achieved through cooperation, without the need for multiple antennas. Our team, under previous grants, has developed several collaborative communication strategies and code design guidelines for relay networks. We have also shown that in multiple access channels the use of non-orthogonal transmission together with interference cancellation aided by rateless codes such as Raptor codes can result in sum rates close to information theoretic bounds. Using rateless codes also results in schemes that adapt to the channel condition without prior knowledge of the channel state information. We intend to expand our research by considering more elaborate network scenarios including relay networks with multiple sources, relays and destinations. On the theoretical side, we will aim at finding information theoretic bounds on the achievable rates for various network configurations. On the practical side, we will develop coding schemes for particular network configurations under different channel realizations and to gauge the performance of the developed techniques against the theoretical bounds. The main tasks under this research project include: 1) Derivation of theoretical bounds on the achievable rate of several networks of interest including compound multiple access channels and relay channels. 2) Development of collaboration techniques utilizing network coding, nested codes and Raptor codes. 3) Assessment of adaptability of the developed schemes for wireless communication standards such as 3GPP's LTE-Advanced (Long Term Evolution-Advanced) and IEEE's 802.16 (WiMax).