Abstract
Network coding allows to exploit spatial diversity naturally present in mobile wireless networks and can be seen as an example of cooperative communication at the link layer and above. Such promising technique needs to rely on a suitable physical layer in order to achieve its best performance. In this paper, we present an opportunistic packet scheduling method based on physical layer considerations. We extend channel adaptation proposed for the broadcast phase of asymmetric two-way bidirectional relaying to a generic number of sinks and apply it to a network context. The method consists of adapting the information rate for each receiving node according to its channel status and independently of the other nodes. In this way, a higher network throughput can be achieved at the expense of a slightly higher complexity at the transmitter. This configuration allows to perform rate adaptation while fully preserving the benefits of channel and network coding. We carry out an information theoretical analysis of such approach and of that typically used in network coding. Numerical results based on nonbinary LDPC codes confirm the effectiveness of our approach with respect to previously proposed opportunistic scheduling techniques.
Highlights
Intensive work has been devoted the field of network coding (NC) since the new class of problems called “network information flow” was introduced in the paper of Ahlswede et al [1], in which the coding rate region of a single source multicast communication across a multihop network was determined and it was shown how message mixing at intermediate nodes allows to achieve such capacity
In this paper we proposed a new approach for rate adaptation in opportunistic scheduling
Such approach applies channel adaptation techniques originally proposed for asymmetric two-way relay channel (TWRC) communication to a network context
Summary
Intensive work has been devoted the field of network coding (NC) since the new class of problems called “network information flow” was introduced in the paper of Ahlswede et al [1], in which the coding rate region of a single source multicast communication across a multihop network was determined and it was shown how message mixing at intermediate nodes (routers) allows to achieve such capacity. Considering the problem in a wireless multihop scenario, each of the potential receivers will experiment different channel conditions due to fading and different path losses At this point, a scheduling problem arises: which packets must be combined and transmitted? In [10], a solution based on information theoretical considerations is described, that consists of combining and transmitting, with a fixed rate, packets belonging only to nodes with highest channel capacities The number of such nodes is chosen so as to maximize system throughput.
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