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A combination of market forces, including the growing number of mobile phone subscribers and the popularity of data applications, are creating a substantial need for capacity within wireless communications networks. Subscribers use their phones everywhere, and so a significant amount of the traffic carried on wireless networks now comes from inside buildings. As 3G services are launched, the maximum data rate of 2 MB/s will be achievable only in low-mobility, mainly indoor situations. With service availability and quality becoming competitive issues, wireless service providers have many reasons to ensure that they are providing adequate coverage and capacity for indoor applications.

Whether an indoor network is cellular, PCS, 3G, or even a wireless LAN, testing plays a crucial role at all stages of network build-out, from determining that some type of indoor system is needed to ensuring that the system meets the service provider’s ongoing quality of service requirements.

The network coverage and capacity needs of a small office building, a busy airport, a subway system, and a metropolitan high rise are all different, and service providers have to evaluate the RF characteristics of each unique indoor setting. This process may begin with a competitive analysis, in which test equipment similar to the receiver- and phone-based systems used for drive testing are carried through the hallways and into the rooms of a building. This is done to actively test how well the macro network performs indoors. A service provider can compare his network’s coverage to that of the competition and, based on the test results, decide whether or not it is necessary to invest in indoor wireless infrastructure.

If test results indicate that the outdoor (macro) network cannot provide a strong enough signal to adequately cover the indoor location, the service provider can simply boost power at the outdoor cell site to increase signal penetration inside the building. This solution does not add capacity, however, and it can create greater interference with other outdoor sites and path imbalance. More likely, the service provider will choose to deploy some type of indoor network equipment.

An indoor system of repeaters is a simple and inexpensive way to boost coverage. Similarly, a directional antenna coupled with a bi-directional amplifier can be used to extend the outdoor cell site’s coverage into a specific location. To increase network capacity in areas of heavy usage generally requires the addition of one or more micro cells or pico cells inside the building.

All of these solutions can be used to feed a distributed antenna system (DAS), which offers the greatest flexibility in adding coverage and capacity. A DAS also allows for technology expansion and migration. In traffic hot spots, such as airports, distributed antenna systems are popular because multiple service providers can share the same equipment. Technology is developing multiband indoor antennas (at 800, 1900, and 2400 MHz or at 900, 1800, 2200, and 2400 MHz, for example), which support combinations of cellular, personal communications systems (PCS), 3G, Bluetooth and wireless local area networks (W-LAN) applications.

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