ckhaul provision. After factoring in hardware costs, cable costs and licensing costs the payback for microwave compared to multiple T1/E1 lines is somewhere in the order of 4 to 12 months The availability of 10-Mbps Ethernet over copper over distances of up to 1.5 miles has changed this trade off point in some markets, but these services do not support TDM services. The microwave versus fibre economics calculation is very much determined by distance and population density with the cost of digging the trench directly dependent on distance. The capex cost for fibre is definitely higher, up to about 2 Gbps, but the exact crossover point will be dependent on local factors. If the fibre can be shared amongst multiple operators the cost per bit will of course be substantially lower. 13.6 Other Topics So now I have noticed that I had also said I would address core network hardware, router hardware, server hardware and cost and energy economics in this chapter. I am going to offer several excuses for not doing this at this point Core network hardware has already been addressed in 3G Handset and Network Design and subsequently in more extensive and accurate detail by other more technically liter- ate authors including Harri Holma and Antti Toskala's LTE for UMTS book (John Wiley ISBN 978 0 470 66000-3) My own take on the changing shape of core network architecture eight years ago was that the overall complexity would increase rather than decrease over time but would become distributed and that cost would shift to routers that would be surprisingly hardware centric in order to realise throughput and latency metrics. Lots of high-performance memory would also be needed in each router. The ability to buffer at router nodes meant that network bandwidth utilisation could be substantially increased but there were two associated costs, the memory and the bandwidth occupied by the signalling needed to avoid buffer overflow that would result in packet loss. The section on deep packet examination (Chapter 18 page 406, has proved pa