Performance of SDMA Systems Using Transmitter Preprocessing Based on Noisy Feedback of Vector-Quantized Channel Impulse Responses

Abstract

Abstract-In this contribution we investigate the performance of Spatial Division Multiple Access (SDMA) multiple-input multiple-output (MIMO) systems using transmitter preprocessing, when the channel knowledge required for preprocessing is acquired by the receiver and conveyed to the transmitter via noise feedback channels that may also conflict fading. Specifically, in our system the MIMO channel impulse responses (CIRs) are vector quantized. Then, the CIR magnitudes and phases are conveyed to the transmitter via a feedback channel, which is noise contaminated and may also experience Rayleigh fading. At the transmitter, the CIRs used for transmit preprocessing are recovered using a soft estimator, which is optimum in the minimum mean-square error (MMSE) sense, and is implemented based on the so-called Hadamard soft-decoding principles. Our study and simulation results demonstrate that vector quantization combined with soft-decoding constitutes an efficient technique of feeding back the CIRs from the receiver to the transmitter. However, it is also known that the performance of the zero-forcing (ZF) or MMSE transmit preprocessing schemes is highly sensitive to the effect of quantization errors as well as to the feedback channel induced errors.

Collaborative Transmission in Wireless Sensor Networks by a (1 + 1)-EA

“…In order to synchronise signals at the receiver, we propose the use of channel feedback as, for example, detailed in [45,28,44] to guide this synchronisation. The received sum-signal is analysed at the receiver and a feedback describing the state of the optimisation is created and transmitted back to the sensor nodes.…”

“…Solutions to providing receiver-based channel feedback are presented in [45,28,44]. The authors utilise long-term prediction at the transmitter in order to estimate the channel state evolution.…”

Particle Swarm Optimisation Aided MIMO Multiuser Transmission Designs

“…In order to facilitate the employment of a low-complexity, high-powerefficiency single-user receiver, the transmitted multiuser downlink signals may be pre-processed at the BS, leading to the appealing concept of MUT. 33,34 More explicitly, the MUT requires the knowledge of each user's unique channel impulse response (CIR) for differentiating the different users' transmissions. For time division duplex systems, the uplink CIRs measured at the BS may be exploited for subsequent downlink pre-processing owing to the channel's reciprocity.…”

Downlink MBER Transmit Beamforming Design Based on Uplink MBER Receive Beamforming for TDD-SDMA Induced MIMO Systems

“…The assumption that the downlink channel impulse response (CIR) is known at the BS is valid for time division duplex (TDD) systems due to the channel reciprocity. However, for frequency division duplex systems, where the uplink and downlink channels are expected to be different, CIR feedback from the MT's receivers to the BS transmitter is necessary [13]. Many research efforts have been made to discover the equivalent relationship between the MUD and MUT [14][15][16][17][18][19].…”

“…The Tx beamforming design based on the MMSE criterion is popular owing to its appealing simplicity [13,21]. Since the bit error rate (BER) is the ultimate system performance indicator, research interests in MBER based Tx beamforming techniques have intensified recently [22][23][24][25].…”