The True Cost of Bandwidth
Bandwidth is another big factor in any wireless decision, yet it's hard to find straight bandwidth figures on a lot of radio products, notably what is referred to as "unlicensed" or "license-free" wireless. Product descriptions that dance around the bandwidth issue are substituting posturing for performance. Why else would you get all that double-talk about "aggregate" or "dynamic" throughput. If you're seeing that, then "54 Mbps" isn't anywhere near to what you're going to get in real life. Did I mention that I jumped six feet off the floor today? Sure, three feet up and in compliance with gravity, another three down. Someone call the Celtics.
I'm often asked to recommend bandwidths and my advice is that you should consider the nature of your business as well as your network traffic. I say be more or less aggressive on bandwidth based on the extent that productivity effects your profits. Too conservative in the wrong setting and while you might be controlling your department's budget by keeping a reign on bandwidth, you could inadvertently be adding a whole lot more to your employer's cost. Productivity requires that you keep the digital engines humming so that users can do their jobs without blaming the network (they will anyway). Efficiency = profit, as much for the network as an assembly line, and that's a perfect argument for justifying your budget.
No term is as misapplied or over generalized as "wireless". Now let's get specific. Wireless is either for personal (lap top, cell phone, PDA) or enterprise use. It can be for indoor or building to building applications. It can transmit point-to-point or omnidirectional (point-to-multipoint).
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Our focus is point-to-point wireless for enterprise connections between buildings, whether for WAN (wide area network), last-mile or backup applications. Point-to-multipoint radios are excluded because they deliver dynamic slices of shared traffic that works fine for hot-spots, but falls short of enterprise needs.
Glancing at a color coded chart of the radio spectrum, you can see all the frequencies that are allocated in the U.S. to some particular purpose (e.g., maritime mobile, satellite, broadcasting, etc.). You'll immediately notice that the chart is divided by kilohertz (kHz), megahertz (MHz) and gigahertz (GHz). Point-to-point wireless operates in the gigahertz part of the spectrum which represents "microwave" frequencies. Accordingly, when you see or hear "wireless" in connection with point-to-point corporate or enterprise applications it specifically means "microwave radio".
As you read further you'll understand that one wireless medium can be as different to another as a Focker Triplane to a space shuttle. Also, microwave covers a wide range of frequencies on the radio spectrum. One microwave radio can vary greatly in characteristics from another depending on whether it transmits in the low or high end of the frequency range. So if someone makes a statement like: "You can't get microwave frequencies in Manhattan" or "Microwave is effected by rain" then tune them out because such generalizations are patently false.
Point-to-Point Wireless Solutions
Point-to-point microwave is classified as licensed or unlicensed ("license-free"). This is the main distinction. Unlicensed wireless also includes optical solutions, which use lasers instead of radio signals.
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