Network coding: literature review

Communication networks are a prevalent component of the modern connected times. Everywhere around us people and machines exchange information at various scales and throughputs. The network is everywhere: from the analog voice communication that the phone company offers to the vast expanse of connectedness built upon TCP/IP passing by all the mobile communication devices that literally make a network out of thin air. The information technology we have today is the product of successive improvements in the physical layer of our communication networks and the invention of new protocols and standards that make inter-operation possible. Without a doubt, one important evolutionary leap for the development of communication technologies was the transition from circuit switching to packet switching networks. Unlike an analog voice connection that physically connects pairs of wires at the phone company’s central office, packet communication don’t require an end-to-end channel from sender to receiver. Instead, the information is packaged into packets which can be concatenated, split, multiplexed, encapsulated and in general transmitted in a very efficient manner. Using this low level packet sending protocol as a building block we can build higher level protocols that provide us with end-to-end channels. Recently, a new communication paradigm called network coding has emerged in which the intermediary relay stations are allowed to perform encoding/decoding operations on the information they receive. Network coding protocols are more powerful than the current packet protocols where relay stations are only allowed to forward the packets. The question that we would like to pose here is whether network coding is the next big evolutionary step for the development of communication protocols. What kind of benefits does network coding offer for throughput, code construction, delay and robustness? This literature review is an attempt to answer these questions. While it may be too early to give a final verdict about the usefulness of network coding, there is a considerable body of theoretical work that can inform us about what we can and cannot accomplish. The structure of this review is as follows. In section 2 we will present some background material. Next in section 3 we present a simple example of a network where network coding is used. The main content of this review are contained in sections 4 and 5 which deal with theoretical and practical aspects of network coding respectively.