Network Coded Modulation for Next Generation Wireless Access Networks

In view of the rapid increase in demand for mobile data services, next generation wireless access networks will have to provide greatly increased capacity density, up to 10 Gbps per square kilometre. This will require a much larger density of very small, cheap and energy-efficient base stations, and will place increasing demand on the bandwidth and energy efficiency of the network, and especially the backhaul network. Recent work on network MIMO, or coordinated multipoint (CoMP) has shown that by ensuring base stations cooperate to serve users, especially those close to cell edge, rather than interferring with one another, inter-user interference can be effectively eliminated, greatly increasing the efficiency of the network, in terms of both spectrum and energy. However this tends to greatly increase the backhaul load.

This work proposes a form of wireless network coding, called network coded modulation, as an alternative to conventional CoMP. This also enables base station cooperation, but instead of sending multiple separate information flows to each base station, flows are combined using network coding, which in principle allows cooperation with no increase in backhaul load compared to non-cooperative transmission, while gaining very similar advantages to CoMP in terms of bandwidth and energy efficiency.

The objective of the proposed work is to establish the practical feasibility of this approach, and evaluate its benefits, as applied to next generation wireless access networks. To this end it will develop practical signalling schemes, network coordination and management protocols, and, with the help of industrial collaborators, will ensure compatibility with developing wireless standards.

Access to the Internet via high-speed communications links, especially mobile access, has many times been identified by Government as a major driver of economic growth. Moreover the lack of this in sections of the population, often described as "digital exclusion", is recognised as a cause of persistent poverty. The demand for mobile data is known to be increasing at a rate between 70 and 100% per year, and it is important for networks to keep pace with this demand to avoid congestion which might stifle growth.

In this context the proposed programme has the potential to impact significantly upon all users of mobile communications - that is, nearly everyone, in this country and worldwide. By enabling cost-effective access networks with greatly increased capacity density it will enable much wider access to existing Internet services, and also stimulate the growth of new services which cannot even be envisaged at present.

This will be achieved via a more immediate impact on industry, specifically upon mobile equipment manufacturers and network operators. (It may also enable entry to the market of new types of network operator, providing services on a smaller geographical scale in a more heterogeneous form of network). By enabling wireless backhaul on a much larger scale than at present it will reduce costs for operators to install new capacity, and by displacing many of the higher layer functions towards the physical layer it may reduce the energy required to provide this additional capacity, also providing environmental benefits. In turn it will create new markets for equipment providers.

However, because wireless network coding constitutes an important part of a new paradigm for wireless networks in general, it has the potential to improve efficiency across a much wider range of applications, including, for example, the "Internet of Things", "smart grid" networks, transportation and other "smart city" applications, etc. These applications will give rise to many societal benefits, including improved healthcare, more efficient and reliable energy supply, safer and more efficient transport systems, improved security and wider participation in the digital economy.

Our collaborators include network operators and equipment manufacturers, who will have an opportunity to benefit directly from the new techniques developed in providing new products and services and in improving the efficiency of their networks. This is expected to involve contributing to global standards activities, by which the impact will be greatly expanded.