How to Measure Spectrum Efficiency

n the ’70s fixed-to-fixed microwave links were developed and deployed. Wireless local loop (WLL) systems could also have been implemented in the ’70s in U.S. rural areas, but were not. The cost justifications at that time for WLL were: For the Near Term — Using the radio link for WLL was the solution because the cost of laying a long wire cable to connect to a remote point was very high. For the Long Term — Using the wire link was the solution. Although the cost of laying a long wire cable was high in the beginning, adding more users along the wire link later on would drive the cost per user down as the years went by. Nevertheless, when the network layout reached its limit, WLL was the solution. For an Urban Situation — In New York City, laying additional wire cables was very costly. Therefore, WLL was the solution. In the meantime, in the ’70s Advanced Mobile Phone System (AMPS) was developed and could have been applied in wireless local loop systems to gain two advantages: • It could have been easier to acquire the spectrum from the FCC for WLL in the ’70s. • WLL services could have been deployed first; then we could have gone into cellular markets using bundled services, that is, providing wireless local loop and cellular together using the same spectrum and operating the same wireless communication network. By taking this approach, both wireless local loop and cellular operations would have taken place in the ’70s. Since telephone companies did not take advantage of this opportunity in the ’70s, wireless operators were busy developing cellular systems in the ’80s. Now, in the ’90s, we are starting to look at the domestic and international markets for WLL.