Correlated Scrambling Scheme for Time-Frequency Diversity in OFDM Single-Frequency-Network Systems

For orthogonal frequency division multiplexing- based single frequency network systems, such as the terrestrial digital broadcasting systems, the performance of a static/quasi- static receiver at cell edge can be severely degraded by the slow and flat fading effect due to a destructive combination of signals from adjacent transmitters. Recently, the cyclic delay diversity (CDD) and group-wise scrambling diversity (GSD) schemes have been presented to address this issue. However, both the CDD and GSD schemes provide no time diversity against the slow fading nature. Moreover, discontinuities of composite channel responses inherent in the GSD scheme make channel estimation even more difficult. In this paper, a new correlated scrambling diversity (CSD) scheme is proposed that introduces both time and frequency diversities via the time-frequency scrambling independently among transmitters. Continuity of composite channel responses resulting from utilization of correlated scrambling patterns further makes channel estimation easy for receivers.