A comment on the bandwidth expansion of Data Dependent Superimposed Training

This paper clarifies the issue of bandwidth expansion of Data Dependent Superimposed Training (DDST) schemes. It has previously been claimed that DDST schemes have the benefits of both Time Division Multiplexed (TDM) training and Superimposed Training (ST) based schemes without any of their respective drawbacks. That is, that channel estimation can be done without interference from the super imposed data as in a TDM scheme, while at the same time transmit data in all timeslots and hence not have the bandwidth increase associated with TDM, where a number of time-slots are dedicated strictly to training. While the estimation accuracy claim is valid we show that the bandwidth expansion claim is not. It is instead shown that the bandwidth expansion of a DDST system is identical to that of a TDM based system.