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To access the contents, click the chapter and section titles.
Wireless Networking Handbook
Sensitivity determines the amount of time the mobile station will spend in cell search mode and when the mobile station will switch to another WavePOINT. Sensitivity parameters set the values of the Cell Search Thresholds, which determine when the mobile station starts or stops looking for another WavePOINT. These thresholds are related to the level of communications quality. There are three Cell Search thresholds:
In cell search mode, a mobile station has to interpret beacons and network broadcast messages transmitted by different WavePOINTs. If sensitivity is too high, a station is likely to spend more time in cell search mode than needed. This will cause unnecessary use of the processing capacity from the mobile station. A mobile station requires network overhead to switch between two WavePOINTs. WaveAROUND roaming functionality enables a mobile station to detect an out-of-range situation and reestablish a lost connection. The combined characteristics of applications and the NOS, however, may pose problems for network operations because most of todays applications are not designed for use in a wireless mobile environment. Future developments of applications should allow for temporarily working offline. When a connection is lost, the application must be able to synchronize files as soon as the connection becomes available again. Radio-based Wireless LAN PerformanceRadio-based wireless LANs offer performance similar to ethernet networks. Figure 2.11 compares the performance of WaveLAN versus ethernet. The figure shows the response time of performing a DOS file copy for several different size files between a 80386/25 MHz server and 80386sx/16 MHz workstation via WaveLAN NICs. For file sizes of less than 100 KB, ethernet and WaveLAN performance is nearly the same. For larger files, though, ethernet takes the lead. The actual performance will depend on the applications file sizes and frequency of network use. In addition, radio-based wireless bridges were designed to operate within a typical LAN environment. WavePOINT, for example, was designed to operate under the following assumptions:
This allows the bridge to keep up with typical ethernet traffic.
Infrared Light-based Wireless LANsInfrared light is an alternative to using radio waves for wireless LAN interconnectivity. The wavelength of infrared light ranges from about 0.75 to 1,000 microns, which is longer (lower in frequency) than the spectral colors but much shorter (higher in frequency) than radio waves. Under most lighting conditions, therefore, infrared light is invisible to the naked eye. Infrared light LAN products operate around 820 nanometer wavelengths because air offers the least attenuation at that point in the infrared spectrum.
In comparison to radio waves, infrared light offers higher degrees of security and performance. These LANs are more secure because infrared light does not propagate through opaque objects, such as walls, keeping the data signals contained within a room or building. Also, common noise sources such as microwave ovens and radio transmitters will not interfere with the light signal. In terms of performance, infrared light has a great deal of bandwidth, making infrared light possible to operate at very high data rates. Infrared light, however, is not as suitable as radio waves for mobile applications because of its limited coverage. An infrared light LAN consists mainly of two componentsan adapter card or unit and a transducer. The adapter card plugs into the PC or printer via an ISA or PCMCIA slot (or connects to the parallel port). The transducer, similar to the antenna with a radio-based LAN, attaches to a wall or office partition. The adapter card handles the protocols needed to operate in a shared medium environment, and the transducer transmits and receives infrared light signals. There are two types of infrared light LANs:
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