Application of Multicarrier Techniques for 4th Generation Telecommunications Systems
The observed trend radio systems lead to the finding of the need for convergence between different wireless systems. The wireless networks adapt to support ever higher data rates. The radio transmission channel, consisting of multipath, is very restrictive. A high speed in mono-carrier modulation causes a low symbol duration. The channel time sprawl causes problems of interference between symbols. In addition, when the channel is frequency selective, the signal undergoes attenuation which varies with frequency. To overcome these difficulties, multi-carrier modulations have been introduced. It is frequency multiplexing techniques which modulate the signal to a large number of carriers at once. These techniques are useful for high-speed transmissions over a multipath and frequency selective channel. On each subcarrier, the transmission rate is thus low. The inter-frequency space is less than the channel coherence bandwidth.
Keywords - AWGN, BER, OFDM, OFDMA, QAM, Uplink