Abstract-Two types of noise-free relay cascades are investigated. Networks where a source communicates with a distant receiver via a cascade of half-duplex constrained relays, and networks where not only the source but also a single relay node intends to transmit information to the same destination. We introduce two relay channel models, capturing the half-duplex constraint, and within the framework of these models capacity is determined for the first network type. It turns out that capacity is significantly higher than the rates which are achievable with a straightforward time-sharing approach. A capacity achieving coding strategy is presented based on allocating the transmit and receive time slots of a node in dependence of the node's previously received data. For the networks of the second type, an upper bound to the rate region is derived from the cut-set bound. Further, achievability of the cut-set bound in the single relay case is shown given that the source rate exceeds a certain minimum value.
Abstract-The focus is on noise-free half-duplex line networks with two sources where the first node and either the second node or the second-last node in the cascade act as sources. In both cases, we establish the capacity region of rates at which both sources can transmit independent information to a common sink. The achievability scheme presented for the first case is constructive while the achievability scheme for the second case is based on a random coding argument.
Abstract-The problem of maximizing the n-letter mutual information of the trapdoor channel is considered. It is shown that 1 2 log 2 5 2 ≈ 0.6610 bits per use is an upper bound on the capacity of the trapdoor channel. This upper bound, which is the tightest upper bound known, proves that feedback increases the capacity.
Abstract-We show that the broadcast capacity of an infinite-depth tree-structured network of error-free half-duplexconstrained relays can be achieved using constrained coding at the source and symbol forwarding at the relays.
Network coding allows nodes in a network to combine different packets using linear operations. In most instances, the encoding coefficients are chosen randomly and placed in the packet header. The ability to correct errors and erasures is critical, because a single malicious packet injected by a misbehaving node or the deletion of a single packet can corrupt multiple packets and jeopardize the entire information flow. Building on Kötter and Kschischang's theoretical work on subspace network codes, we propose a practical network coding protocol with in-built resilience against faults and active attacks. Also included is a low-complexity extended code construction for high-rate subspace Reed-Solomon like codes. The code maintains the distance properties that are key for error and erasure correction. Performance results show that throughput gains can be achieved with lower complexity and smaller field sizes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.