Impact of Channel Estimation Errors on the Capacity of Space Modulation Techniques

Abstract

Capacity analysis of space modulation techniques (SMTs) multiple–input multiple–output (MIMO) systems were recently derived and significant enhancements were reported assuming perfect channel knowledge at the receiver. It was illustrated that SMTs achieve higher theoretical capacity than spatial multiplexing (SMX) MIMO system, which can be attained through designing signal symbols such that their distribution multiplied by the channel distribution leads to complex Gaussian distribution. Yet, perfect channel knowledge is impractical and channel estimation techniques must be considered, which cause channel estimation errors (CSE). Such errors are shown in previous literature to severely impact the performance of SMX MIMO system and prevent achieving the theoretical capacity of these systems. Therefore, the impact of CSE on the capacity of SMTs are studied in this paper. It is shown that Space modulation techniques (SMTs), and unlike SMX, can achieve the capacity in the presence of CSE and the conditions under which this can be obtained are derived over variant fading channels. Also, the impact of CSE on the overall capacity is discoursed. Validating the derived theoretical capacity formula through Monte Carlo simulation of the mutual information are presented over wide range of system and channel parameters.