Clustered OFDM with transmitter diversity and coding

Multipath delay spread in a radio environment can severely limit the maximum transmission rate. Multicarrier transmission, in particular OFDM, and a single-carrier system with equalization, often proposed as techniques for overcoming these limitations, present practical difficulties which can restrict their application. In a wireless LAN/ATM application, the desire to transmit short packets requires fast start-up, so the potentially long time required to train an equalizer could limit its usefulness. On the other hand, while OFDM requires very little training, it is burdened with a large peak-to-average power ratio which requires the use of highly linear amplifiers. In this paper, we describe a new approach to OFDM where subchannels are clustered into several smaller blocks and transmitted over separate (ideally, independent) antennas. A single receive antenna is used to demodulate the entire OFDM signal. This approach reduces the peak-to-average power ratio, minimizes the receiver training required, and increases the effectiveness of coding across frequencies.