Faster Than Nyquist Transmission With Multiple Turbo-Like Codes

The performance of turbo-like codes highly depends on their frame size and thus, the bit error rate (BER) performance of turbo-like codes can be improved by increasing the frame size. Unfortunately, increasing the frame size induces some drawbacks such as the increase of transmission and decoding latencies. On the other hand, faster than Nyquist (FTN) transmitter transmits modulated symbols at a rate higher than the Nyquist rate and thus, inter-symbol interference (ISI) is introduced. In this letter, we propose an FTN system with multiple turbo-like codes. In the proposed scheme, an information frame is divided into subframes and the subframes are encoded independently by multiple turbo-like encoders before being presented at an FTN modulator. Due to the ISI induced within the FTN modulator, the code frames generated by the multiple turbo-like encoders are combined and act as a larger code frame. Compared with conventional coded FTN schemes, the proposed scheme not only improves the BER performance but also reduces the decoding latency.