Abstract
Space-time coded orthogonal frequency division multiplexing (OFDM) transmitter diversity techniques have been shown to provide an efficient means of achieving near optimal diversity gain in frequency-selective fading channels. For these systems, knowledge of the channel parameters is required at the receivers for diversity combining and decoding. In this paper, we propose a low complexity, bandwidth efficient, pilot-symbol-assisted (PSA) channel estimator for multiple transmitter OFDM systems. The pilot symbols are constructed to be nonoverlapping in frequency to allow simultaneous sounding of the multiple channels. The time-varying channel responses are tracked by interpolating a set of estimates obtained through periodically transmitted pilot symbols. Simulations are used to verify the effectiveness of the propsed estimator and to examine its limitations. It is also shown decision-directed minimum mean square error MMSE channel estimator for OFDM transmitter diversity systems.
Highlights
The mobile wireless channel suffers from multipath fading that severely attenuates the received signal during periods of deep fades
Transmitter diversity techniques are, very suitable for paging, cellular, and portable wireless data services, where a small number of base stations serve a large number of mobile users and where spatially separated antennas can be implemented at the base stations
Instead of explicitly tracking the multiple time-varying channel impulse response (CIR) using a continuous decision-directed algorithm that would require the minimum mean square error (MMSE) solution as in [12], we propose to track the multiple CIRs by interpolating a set of estimated channel responses hm(n) obtained from periodically transmitted pilot symbols PSm(n), that is, the insertion of one pilot symbol every N transmitted orthogonal frequency division multiplexing (OFDM) symbols
Summary
The mobile wireless channel suffers from multipath fading that severely attenuates the received signal during periods of deep fades. The channels over which these high data rate mobile communications systems operate are generally frequency-selective, so transmitter diversity techniques that are effective in frequency-selective fading channels are of special interest. A number of space-time coded orthogonal frequency division multiplexing (OFDM) transmitter diversity techniques have recently been proposed for frequency-selective fading channels [1, 2, 3, 4]. These techniques are capable of achieving near optimal diversity gain when the receivers have perfect knowledge of the channels. Simple interpolation filters are used to update the estimates during the data transmission mode
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