When comparing wireless equipment for use in your network, be sure to consider these variables:
- Interoperability. Will the equipment you are considering work with equipment from other manufacturers? If not, is this an important factor for this segment of your network? If the gear in question supports an open protocol (such as 802.11b/g), then it will likely interoperate with equipment from other sources.
- Range. Range is not something inherent in a particular piece of equipment. A devices range depends on the antenna connected to it, the surrounding terrain, the characteristics of the device at the other end of the link, and other factors. Rather than relying on a semifictional “range” rating supplied by the manufacturer, it is more useful to know the transmission power of the radio as well as the antenna gain (ifan antenna is included). With this information, you can calculate the theoretical range.
- Radio sensitivity. How sensitive is the radio device at a given bit rate? The manufacturer should supply this information, at least at the fastest and slowest speeds. This can be used as a measure of the quality of the hardware, as well as allow you to complete a link budget calculation.
- Throughput. Manufacturers consistently list the highest possible bit rate as the “speed” of their equipment. Keep in mind that the radio symbol rate (eg. 54Mbps) is never the actual throughput rating of the device (eg. about 22Mbps for 802.11g). If throughput rate information is not available for the device you are evaluating, a good rule of thumb is to divide the device “speed” by two, and subtract 20% or so. When in doubt, perform throughput testing on an evaluation unit before committing to purchasing a large amount of equipment that has no official throughput rating.
- Required accessories. To keep the initial price tag low, vendors often leave out accessories that are required for normal use. Does the price tag include all power adapters? (DC supplies are typically included; power over Ethernet injectors typically are not. Double-check input voltages as well,
as equipment is often provided with a US-centric power supply). What about pigtails, adapters, cables, antennas, and radio cards? If you intend to use it outdoors, does the device include a weatherproof case? - Availability. Will you be able to easily replace failed components? Can you order the part in large quantity, should your project require it? What is the projected life span of this particular product, both in terms of useful running time in-the-field and likely availability from the vendor?
- Other factors. Be sure that other needed features are provided for to meet your particular needs. For example, does the device include an external antenna connector? If so, what type is it? Are there user or throughput limits imposed by software, and if so, what is the cost to increase these limits? What is the physical form factor of the device? How much power does it consume? Does it support POE as a power source? Does the device provide encryption, NAT, bandwidth monitoring tools, or other features critical to the intended network design?