An Interleave-Division multiplexing (IDM) based modulation for 3GPP LTE downlink

Interleave-division multiple-access (IDMA) is an efficient multiple access technique to improve high spectrum efficiency for cellular communications. In this paper IDM-based modulation (called layered modulation (LM)) is proposed for OFDM systems. The idea of LM is to multiplex multiple parallel layers of data streams by performing repetition and layer-specific interleaver on each layer. Since LM code bits are fully distributed in time-frequency plane, by the aid of low-complexity chip-by-chip interference cancellation time-frequency diversity can be well exploited in LM. Applying LM to 3GPP LTE downlink, we compare LM to M-PSK/QAM modulation. Numerical results show that the LM can achieve superior performance over M-PSK/QAM. The performance gain over QPSK, 8PSK and 16QAM is 1.1 dB, 2.2 dB and 0.6 dB, respectively.