A Simple OFDM-Based Multiple Access System with Super-Orthogonal Convolutional Codes and Golay Sequence

Orthogonal frequency division multiplexing (OFDM) based multiple access systems have found their applications in many wireless communication systems. However, similar to conventional OFDM systems, they have a major drawback that their signal waveforms have a large peak-to-average power ratio (PAR). The resulting systems have low power amplifier efficiency, which is prohibitive for battery driven terminals. In this paper, we propose a simple OFDM-based multiple access system that combines low-rate super-orthogonal convolutional codes (SOCC) and Golay complementary sequences with applications to the uplink of low-cost wireless communication systems such as sensor networks. The proposed system has a PAR as low as 3 dB and can also achieve a frequency diversity gain due to the spreading of sequences in the frequency domain similar to a conventional coded OFDM architecture. The use of differential encoding with differential detection at the receiver further simplifies the overall system.