ferenced in Chapter 2 was free-space optics at 800 nm or 1550 nm with 1550 nm being the preferred option for safety reasons. These systems can support high bandwidth but are subject to scintillation and fog attenuation that precludes their use in many more mainstream applications. 13.5 Summary - Backhaul Options Economic Comparisons In a voice-centric network a single T1 (1.544 Mbps) or E1 2 Mbit/s backhaul connection would have been sufficient to support a moderate size cell. Simplistically, an LTE channel with a peak data rate of 150 Mbit/ with three sectors needs up to 450 Mbit/s of capacity. Cell geometry reduces this. Adding channels per sector and/or implementing neutral host networks with shared backhaul increases this. Gigabit rather than megabit backhaul requirements are therefore at least plausible. Practical limits with copper are presently of the order of 100 Mbits but essentially this is a bandwidth-limited medium with propagation limitations and significant interference constraints (crosstalk). It is usually very fully amortised but lease costs, for example, for an E1 or T1 line can be substantial both in terms of a set up charge and monthly rental and this cost increases linearly with capacity - you don't get a discount for multiple T1/E1 lines, which means that 10 Mbps of bandwidth cost ten times as much as 1 Mbps. So, for example, a T1/E1 circuit in 2008 would cost anywhere between $150 and $750 per month with a set up charge of over $500 dollars. Making Telecoms Work Fibre using higher-order modulation can deliver multigigabit throughput but is often not available as a legacy installation and therefore has to be aggressively amortised. A leased fibre capacity of 155 Mbps would be in the region of between $4000 and $7500 dollars per month and a set up charge of around $7000 dollars, assuming of course that the fibre is available, which it may not be. The T1/E1 costs and bandwidth limitations and fibre cost and availability limitations together determine the market share of microwave systems in ba