Factors in Cable Choice
There are many characteristics that separate the cable types and wireless technology from each other. Some of the more important ones are maximum cable length, bandwidth, bend radius, cost, and interference susceptibility. Depending on the needs of the network, some characteristics will be emphasized over others. For example, if cost is no factor, the contractor will put in the cable with the highest performance.
All cable types and wireless devices have a maximum range. Beyond this range the signal starts to degrade significantly and performance falls rapidly. The range is not set in stone and can be played with a small amount. For example, if the range of a cable is 100 meters it should still work if the two computers it is connecting are 102 meters apart, but the range should not be gone over too much or network performance will start to degrade.
Bandwidth is the amount of data that can be transferred by a cable. It is usually measured in bits per second. Bits are the most basic unit of computer storage. Bits per second is usually abbreviated as bps. It should not be confused with Bps which is bytes per second. (A byte is made up of eight bits. Consequently the Bps number will be eight times smaller than the bps number, even though they represent the same speed.) Metric prefixes can be added to increase the bandwidth number by powers of one thousand. For example, Mbps (Megabits per second) and Gbps (Gigabits per second) represent one million and one billion bits per second respectively. For comparison, the bandwidth of the average home modem is forty to fifty Kbps (Kilobits per second-forty to fifty thousand bits per second). A larger bandwidth is beneficial because it can transfer more data in a given amount of time.
The bend radius of a cable describes how much a cable can be safely bent without damaging the cable. Fiber optic cable, for example, has a bend radius of only 30 degrees/foot. To make a 180 degree turn, six feet of cable must be used. If the cable is bent too much, the glass or plastic core may be broken. This obviously affects the ability of the cable to transmit data. Twisted pair cable on the other hand has an unlimited bend radius as long as there is no kink in the cable. With a kink there is the risk of breaking the copper conductor.
Cost is a very important factor when making a cable or wireless choice. The initial cost of the cable is obvious when it is purchased. However, some types of cable are much harder to install than others. The installation costs of cables or wireless must be considered. Lastly, it is usually a good idea to buy a cable or wireless option with room for growth in the future. While a higher performance cable may be more expensive now, it will nearly always be cheaper than having to rewire the entire network in a year.
The last factor to remember when choosing a cable or wireless technology option is its susceptibility to electromagnetic interference (EMI). An example of EMI is the static on a television screen. If something is affected little by EMI, its interference rating is low. EMI can come from many sources. Power lines and the electrical wires in a building are the most obvious sources of EMI. Cable should not come within six to eight inches of electrical lines. When the proximity must be closer than this, the cable should cross the electrical line perpendicular to it to minimize the distance they run beside each other. Fluorescent lights also generate EMI. Coaxial cable, being shielded, has a low interference rating. UTP has a high interference rating. Fiber optic cable has an interference rating of zero. This is because the data is transferred by light and is unaffected by EMI. Another factor to remember is that if cables are susceptible to EMI, they also generate EMI. This EMI can be decoded to discover what data the cable is carrying. This is electronic eavesdropping. Places that transmit confidential data, such as financial institutions, must consider the possibility of electronic eavesdropping.