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MIMO-OFDM Speeds Raise Backhaul Questions

Two days ago, Nortel announced extremely high throughput speeds in an experimental MIMO-OFDM system of ???37 Mbps over a standard 5 MHz PCS mobility band, taking into account noise and fading conditions found on a real-world cellular network.??? This is significantly higher than what is being achieved today with 3G systems. MIMO-OFDM is also the basis of 802.11n, which promises throughput rates in excess of 100 Mbps for WLANs. I???ll have more to say about the evolution of 3G systems in subsequent blogs as this is an area I have been actively studying and reporting on over the last six months, but right now I want to raise an interesting problem, mentioned to me by a network architect yesterday who works for a major cellular operator. The problem is backhaul. As throughput rates increase with faster cellular air links, there is a fundamental problem connecting base stations to the infrastructure network. It used to be that a T1 (1.5 Mbps) would do the job, but now we???re looking at fiber rates (10 Mbps or greater), and fiber simply does not pass most cell sites. What to do? There are currently no good affordable answers for systems that are faster than the current 3G systems being deployed.