demodulation scheme to a particular type of data. Thirdly, having multiple narrowband sub-carriers instead of one wideband carrier simplifies the equalization² process that operates upon a signal at the receiving end. Beside the advantages, FDM does have some drawbacks, in particular the requirement of a guard band between modulated sub-carriers to prevent the spectrum of one subcarrier from interfering with another. Each sub-carrier is separated by a guard band to ensure that they do not overlap. These sub-carriers are then demodulated at the receiver by using filters to separate the bands (as shown in Figure 2.1). These guard bands lower the system's effective information rate when compared to a single carrier system with similar modulation. OFDM is a well known multi carrier modulation scheme used in 3GPP 3G-LTE, Wireless LANs, WiMAX and has been specified for 3GPP2 UMB and IEEE 802.20 MobileFi networks. Multi-carrier modulation is a method of transmitting data by splitting it into several components, and sending each of 2 Equalization is the process of using passive or active electronic elements or digital algorithms for the purpose of altering (originally flattening) the frequency response characteristics of a system. An equalization filter is a filter, usually adjustable, meant to compensate for the unequal frequency response of some other signal processing circuit or system [1]. OFDM and OFDMA 7 subcarriers Frequency Figure 2.1 FDM with seven sub-carriers using filters these components over separate carrier signals. The individual carriers have narrow bandwidth, but the composite signal can have broad bandwidth. A functional block diagram of multi carrier modulation is shown in Figure 2.2. First, the serial data bits carrying information are converted to parallel bit streams. This simply means that a stream of data elements received in time sequence, that is, one at a time, are converted into a data stream consisting of multiple data elements transmitted simultaneously. Then, every block of N data bits ent