Subspace Projection in the Time and Frequency Domain for Time-Variant Multi-User MIMO OFDM Channel Estimation

Description

This paper describes an iterative time-variant channel estimation scheme for a multi-user multi-input multi-output (MIMO) system that is based on orthogonal frequency division multiplexing (OFDM). Due to OFDM the time-variant channel can be estimated individually for every frequency-flat subcarrier. We use an appropriately designed subspace projection in the time and frequency domain, thus allowing for noise suppression and complexity reduction. The subspace in the time domain is spanned by the discrete prolate spheroidal (DPS) sequences. The DPS sequences are designed according to two system parameters, the maximum Doppler bandwidth and the block length. The correlation between the individual subcarriers can be exploited by a subspace projection in the frequency domain using so called shifted DPS sequences. The shifted DPS sequences are designed according to the maximum essential support of the channel impulse response and the number of subcarriers. Due to the subspace projection in the frequency domain the presented channel estimation scheme is able to deal with realistic channels that have non sample-spaced path delays. We validate the channel estimation scheme with a geometry based stochastic channel model according to the COST 259 recommendations.

Period	20 Sept 2004 → 22 Sept 2004
Event title	Cost 273 - 11th Meeting of the Management Committee
Event type	Other
Degree of Recognition	International