How to Look at Specs

Perhaps the most important spec to consider when looking for wireless equipment is receive sensitivity. This is signal strength required for the card to overcome channel noise. Better receiving (a lower dB number) sensitivity means less signal is needed to acquire a signal. For example, a receive sensitivity of 86 dBm may be all right, but a receive sensitivity of 91 dBm is better. Usually this figure is part of the specifications. If it is not listed, then usually it's not worth bragging about.

The next figure to look for is transmitter output. This spec is expressed in mW or in dBm. Typically, a transmitter will have an output between 20 mW (or 13 dBm) and 100 mW (or 20 dBm). It is desirable to be able to control the output power so that interference issues can be mitigated. The combination of receiver sensitivity and transmitter are major contributors to range.

The WAN/MAN Connection

The Internet backbone and the WiMAX BSs have plenty of bandwidth, but the WAN connection to the Internet is bandwidth-limited. The choices currently available are as follows:

• DS3 or Fractional DS3

• T1

• Frame Relay

• Cable

• DSL

• ISDN

• Wireless

Basically, you get what you pay for. DS3 or Fractional DS3, T1, and Frame Relay are point-to-point services that are also provided by the LECs...