by a factor equal to the number of transmit- ting antennas (e.g., using four antennas increases the data rate by four times). In the ideal case, the throughput will be increased n-fold, where n represents the number of spatial channels in use. In addition, because all data is transmitted both in the same frequency band and with separate spatial signatures, this technique uses spectrum very efficiently. MIMO can be combined with Orthogonal Frequency Division Multiplexing (OFDM; discussed later in this chapter) to take advantage of the multipath proper- ties of environments by using base station antennas that do not have line-of-sight (LOS) functionality. MIMO-OFDM allows service providers to deploy a broadband wireless access (BWA) system that has non-line-of-sight (NLOS) functionality, which is a tremendous benefit for wireless communications. Chapter 13 Wireless Communications Basics Wireless Bandwidth Bandwidth is determined by the range of frequencies that can be carried on a facility or the range of radio frequencies that a signal will occupy. Bandwidth refers to the amount of spectrum available to transport information. Narrowband, also referred to as baseband, implies a single channel. Wideband, also referred to as broadband, implies the use of multiple channels. It is important to note that bandwidth is most often limited by regulation rather than technology. That is, the politics and business of spectrum allocation- rather than the physical attributes of a given frequency band-often determine which frequencies are made available and who obtains the licenses to use them. The maximum physical capacity of a transmission channel can be determined by using Shannon's Law, which describes the relationship between the primary lim- iting factors in a transmission channel-bandwidth and noise. This formula is C = log, (1+S/N) where C is the capacity of a channel (in bits per second), W is the bandwidth of the channel (in Hertz), and S/N is the signal-to-noise ratio. The more bandwidth there is available, the more bi