Interference Study
Although the unlicensed spectrum offers the benefit of no licensing fees, users pay a penalty in terms of interference. There are no restrictions on the types of devices that operate in these bands, provided that they all conform to a common set of rules. Although the 5-GHz band is less crowded than the 2.4-GHz band today, over time the 5-GHz band will likely become equally crowded with more and more interference-causing devices.The Industrial, Scientific, and Medical (ISM) frequencies can contain emissions from microwave ovens, heaters, plywood laminators, medical diathermy, and other noncommunication devices. Although most of these types of devices usually pose no threats of interference to bridge links (because they are low-power, indoor devices), the engineer must be aware that the possibility exists of some industrial high-power system (such as a 10-kilowatt industrial oven next door) that wipes out any attempted communications use of that band. Equipment operating in this type of environment is subject to FCC rules and regulations as well.Amateur radio operators are also licensed to use parts of the bands in which bridge products are designed to be used. Although not many amateurs use these bands, a few full-time (on the air continually) point-to-point amateur microwave links operate in this band.There is also the possibility of interference from other data systems in the same bands. In any case, it is necessary to do an interference analysis using a spectrum analyzer to make sure you have an interference-free radio link. |
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