Wireless user cooperation strategies, coding schemes, and applications

In modern wireless systems, the key challenge is multipath fading which causes fluctuations in the received signal power. Cooperative networks, also ask known as user cooperations, is an emerging technique to combat multipath fading by engaging distributed wireless nodes in assisting each other to exploit spatial diversity. Since the impairment of the multipath fading can be effectively compensated by cooperative networks, faster and more reliable communication, larger coverage ranges, and more accurate position tracking can be achieved.;The first contribution of this dissertation involves decode-amplify-forward(DAF), an efficient data forwarding scheme which combines the merits of decode-forward(DF) and amplify-forward(AF). Theoretical analysis for the capacity bounds are conducted and practical simulation based on turbo codes and LDPC codes are performed. Both of them show that DAF can effectively improve the data rate and reduce outage probability, especially when the relay node can not decode the data from source node successfully.;The second contribution focuses on an efficient space-time-coding design for the three-node user cooperation model, termed double space time coded cooperation. This strategy operates by separating the space-time coding into an AF part and a DF part, and transmitting them through the broadcasting phase and relaying phase respectively. The AF part brings additional space-time diversity even before the two users decode each other's data correctly, while the DF part in the relaying phase attains helpful space-time coding gain.;The third contribution of this dissertation is motivated by the recent advances in network coding. We first propose the framework of adaptive network coded cooperation (ANCC), which dynamically encodes all data packets from all the distributed users into a large network code by accounting for the fact that the inter-user channels may experience random outages. The key idea is to match dynamical codes-on-graph with network-on-graph. We next extend the strategy to include the joint channel and network coded cooperation, generalized adaptive network coded cooperation (GANCC), which integrates channel codes as a seemless part of network codes by a simple and elegant operation of circulant interleaving.;The fourth contribution of this dissertation focuses on the design of a class of an efficient rateless erasure codes, called dynamical degree distribution (DDD) codes. These codes are designed for a special form of wireless network codes, which exploit a different way to construct rateless codes by optimizing both the left and right degree distributions progressively layer by layer. Both theoretical analysis and computer simulation show that the DDD codes can achieve better bandwidth efficiency than the existing rateless codes.;The final contribution addresses the application of user cooperation on wireless localizations. A distributed space-time coding localization strategy is firstly suggested, where different reference nodes transmit simultaneously using distributed space-time block codes, and each target node estimates the time difference of arrival(TDOA) using a clever synchronization and decoding technique matched to the space-time codes. This scheme effectively combats the multipath fading and helps distinguish the line-of-sight(LOS) path, and thus significantly enhances the localization accuracy. We also propose a cooperative time-difference-of-arrival (TDOA) and received-signal-strength (RSS) localization scheme. The novelty is to exploit TDOA to give rough estimations and the RSS between neighboring sensor nodes to refine their location estimates. A joint TDOA and RSS maximum likelihood (ML) algorithm to estimate the positions of the cooperating nodes is derived. Analysis and simulation show that the new algorithm can significantly reduce the position estimation error under multi-path fading and non-line-of-sight (NLOS) conditions, an is particularly useful for mobile tracking in indoor environment and urban area.