Power allocation approaches for combined positioning and communications OFDM systems

The design of pilot and data power allocations for multicarrier OFDM signals is a key aspect in the development of combined positioning and high-data-rate communications systems. Previous work has investigated the capacity-maximizing pilot and data power allocation when only taking into account the effect of channel estimation accuracy on capacity. Results have shown that distributions with equi-spaced and equi-powered pilot structures are optimal. In this paper, we consider a formulation based on the CRB of the joint time-delay and channel estimation, which allows us to study the design of signals for combined positioning and communications OFDM systems. We compare the performance of capacity-maximizing pilot and data power distributions with unstructured pilots, with respect to distributions that use equi-spaced and equi-powered pilot structures. Numerical results show that the constraint of equi-spaced and equi-powered pilot structures has an important impact on both the achievable capacity and the positioning capabilities of the designed signals.