Impact of CSI latency on HF multi-carrier communications for delay-sensitive applications

Multi-carrier modulations are widely used in HF communications, and particularly OFDM. Delay-sensitive applications can make use of spreading schemes such as OFDM-CDM in order to cope with deep nulls in the channel. If CSI is known at transmitter, it is possible to improve performance using a bit-loading algorithm for OFDM and channel matrix SVD decomposition for OFDM-CDM. If a source of non-ideality in CSI due to latency is taken into consideration, it is shown how performance decreases. A receiver-side technique is applied to OFDM-CDM communications to compensate for delay-incurred matrices mismatch.