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Layered Transmissions over Decode-and-Forward Wireless Relay Networks


In this dissertation, we consider a wireless relay network with a single source, a single destination, and multiple relays. The relays are half-duplex and use the decode-and- forward protocol. In the first part, we consider the layered transmission using an information-theoretic approach, where a successively refinable Gaussian source is transmitted using superposition coding. In the second part, we consider the layered transmission using a communication-theoretic approach, where a layered video- encoded bitstream is transmitted using hierarchical modulation. In both cases, we assume the transmitted source can be partitioned into a base layer (BL) and an enhancement layer (EL). The BL is more important than the EL, and the source cannot be reconstructed without the BL. It takes two time slots for each transmission. In the first time slot, the source broadcasts a message that consists of a BL and an EL to all the relays and the destination. The relays detect the transmitted message individually. Each relay detects the BL first, and, if successful, then it detects the EL. Unlike other cooperation techniques, we assume the relays are not able to communicate with each other, and that there is no feedback channel from the destination to the relays, or from the relays to the source. Hence, a given relay does not know if any other relay successfully decodes a specific layer. Rather, we assume that, in the second time slot, each relay will forward all its successfully decoded layers to the destination. That is, a relay can transmit either only the BL or both the BL and the EL to the destination (or not transmit at all)

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