A multi-code space-frequency RAKE receiver

We present a linear receiver structure for spatial multiplexing with NTx transmit and NRx receive antennas based on multi-carrier code division multiplex. We consider optimal symbol-by-symbol decision based on the space-frequency (SF-) RAKE and operate the system with multiple codes. It is found that the inter-code interference after the RAKE can be predicted when the channel coefficients and the spreading sequences are known at the receiver. Hence, all the spatial and code interference can be removed by a joint space-code post-processing. Results indicate that most of the spatial and multi-path diversity can already be achieved with a linear MMSE detection. At up to 80% system load, the SNR degradation is below 3 dB.