Impact of cooperative space–time/frequency diversity in OFDM-based wireless sensor systems over mobile multipath channels

摘要

Cooperative linear dispersion coding (LDC) can support arbitrary configurations of source nodes and destination nodes in virtual multi-input-multi-output systems. In this study, the authors investigate two spatial diversity applications of cooperative LDC for orthogonal frequency division multiplexing (OFDM)-based wireless sensor systems in order to achieve space-time/frequency (ST/SF) diversity gains when transmitting over time-/frequency-selective fading channels. Cooperative LDC-aided ST-/SF-OFDM is flexible in configuring various numbers of cooperative source nodes and time-slots or frequency-tones. Their results show that the ST-OFDM scheme is sensitive to exploiting diversity gains, subject to the impact of varying channel Doppler spreads; while the performance of SF-OFDM is mainly subject to delay spread. Specifically, when the system involves more than two cooperative nodes, the cooperative LDC-aided ST-/SF-OFDM outperforms the cooperative orthogonal block codes (e.g. Tarokh's codes) aided ST-/SF-OFDM, when communicating over a higher Doppler/delay spread.