Complementary M ‐ary orthogonal spreading OFDM architecture for HF communication link

A complementary M ‐ary orthogonal spreading (CMOS) architecture with orthogonal frequency division multiplexing (OFDM) is proposed to improve performance of bit‐error rate (BER) and spectrum efficiency for high frequency (HF) communications. The CMOS‐OFDM architecture is based on orthogonal complementary pairs with their central elements being zero. It is well known that complementary pairs theoretically reduce peak‐to‐mean envelope power ratio (PMEPR) of OFDM due to their ideal aperiodic auto‐correlation properties. However, many practical OFDM applications, such as HF OFDM and IEEE 802.11, require that no data should be modulated to direct current (DC) subcarrier, which will destroy ideal properties of traditional complementary pairs and hence increase their PMEPRs. Compared with traditional complementary pairs, the proposed zero‐centre complementary pairs (ZCCPs) in CMOS‐OFDM architecture may maintain ideal properties and hence be more suitable for OFDM systems as long as zero element in the centre is modulated to DC subcarrier. The corresponding simulation results and numerical analyses over the HF fading channel modelled by ITU‐R F.1487 are provided. Different from the previous researches on HF OFDM systems, the proposed HF CMOS‐OFDM architecture using the constructed ZCCPs not only possesses excellent BER performance, but also may firmly resist PMEPR to 3 dB or near to 3 dB.