An OFDM-based wireless ATM transmission system assisted by acyclically extended PN sequence for future broad-band mobile multimediacommunications

摘要

An orthogonal frequency division multiplexing (OFDM)-basednwireless asynchronous transfer mode (ATM) transmission system isndescribed that is suitable for the future broad-band mobile multimediancommunications. In the proposed system, guard symbols, which arencyclically extended by repeating the information symbols, are insertednbefore and after serial-to-parallel converted wireless ATM data symbolsnfor OFDM transmission. These symbols are used for both wireless ATMnframe synchronization and deciding the discrete Fourier transformationn(DFT) start point at the receiver. A cyclically extended pseudorandomnnoise (PN) sequence is inserted into some of the OFDM transmissionnsubchannels at fixed intervals and used to estimate the phase rotation,nfrequency offset, and delay characteristics. The proposed system doesnnot use "symbol-by-symbol" guard-interval insertion or removal circuits,nas do conventional OFDM systems. With this system, it is easy tonestimate the phase rotation, frequency offset, and delay characteristicsnand to synchronize wireless ATM cells. Computer simulation showed thatnthe bit error rate (BER) performance of the proposed system is betternthan that of a conventional "symbol-by-symbol" OFDM system