Collaborative Research: Low Peak to Average Power Multicarrier Signals via Coding: Fundamental Limits and Algorithms

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One of the most important obstacles in deployment of high data rate, low cost, and power efficient multicarrier communication systems is the cost of front-end RF amplifiers. Multicarrier modulations offer the promise of low complexity equalization, adaptability to frequency selectivity of the channel, and efficient use of available bandwidth in cognitive networks. However, multicarrier signals consist of linear superposition of many subcarriers leading to large peak to average power ratio (PAPR) and implying the need for highly linear power amplifier. In particular, RF power amplifier becomes substantially power inefficient and expensive when its linearity region increases to accommodate signals with large PAPR. Any nonlinearity introduced by the power amplifier can cause large out-of-band leakage and reduce the transmit range of the link.While the worst case PAPR is quite large, it has been established by the investigators that the likelihood of having large peaks is small and there exist codes of almost full rate with PAPR bounded by a constant. Existing coding schemes, however, provide low PAPR and large minimum distance at the cost of substantially reducing the transmission rate. This research involves addressing both existential and algorithmic aspects of coding schemes for PAPR reduction. This research develops both probabilistic techniques and new algorithms to prove the existence and to construct pragmatic codes that not only provide low PAPR and high rate but also lead to optimizing other parameters such as capacity loss, minimum distance and out-of-band leakage.