This work investigates high-SNR outage behavior of slow fading channels with quantized feedback and partial power control, when feedback indices are error-prone. We propose a quantizer structure with continuous Voronoi regions and derive its optimality conditions using probability analysis. Our design involves construction of a novel bit-mapping scheme. The optimized power control codebook resembles channel optimized scalar quantizers (COSQs). Also, the diversity gain of the communication system under study is characterized with both nonzero and vanishing feedback error probabilities.

We design a conceptual transmission scheme that adjusts rate and power of data codewords to send them over a slowly fading channel, when quantized and possibly erroneous channel state information (CSI) is available at the transmitter. The goal is to maximize the data throughput or the expected data rate using a multi-layer superposition coding technique and temporal power control at the transmitter. The main challenge here is to design a CSI quantizer structure for a noisy feedback link. This structure resembles conventional joint source and channel coding schemes, however, with a newly introduced quasi-gray bit-mapping. Our results show that with proper CSI quantizer design, even erroneous feedback can provide performance gains. Also, with an unreliable feedback link, superposition coding provides significant gains when feedback channel is poorly conditioned and channel uncertainty at the transmitter is severe, whereas power control is more effective with more reliable feedback.

The goal of combining beamforming and spacetime coding is to obtain full-diversity order and to provide additional received power (array gain) compared to conventional space-time codes. In this work, a class of code constellations is proposed, called generalized partly orthogonal designs (PODs) and both high-rate and low-rate feedback information is incorporated with possible feedback errors. A binary symmetric channel (BSC) model characterizes feedback errors. Two cases are studied: first, when the BSC bit error probability is known a priori to the transmission ends, and second, when it is not known exactly. Based on a minimum pairwise error probability (PEP) design criterion, we design a channel optimized vector quantizer (COVQ) for feedback information and a precoder matrix codebook to adjust the transmission codewords. The attractive property of our combining scheme is that it converges to conventional space-time coding with low-rate and erroneous feedback and to directional beamforming with high-rate and error-free feedback. This scheme also shows desirable robustness against feedback channel modeling mismatch.

We combine space-time coding and transmit beamforming over multiple-antenna quasi-static fading channels using limited-rate channel state information at the transmitter (CSIT). The combining is performed using a class of constellation sets inspired from orthogonal designs and directional beamforming or in general, unitary preceding with quantized feedback. This constellation class is called partly orthogonal designs (PODs). The conventional way of combining coding and quantized feedback beamforming is through precoded space-time block codes (PSTBCs) that provide full-diversity order with all system configurations in terms of the number of feedback regions and the number of transmit antennas. PODs maintain the same advantage. However, they require less decoding and quantization complexity compared to PSTBCs. We develop POD structures, analyze their performance, and optimize them based on pairwise error probability analysis. PODs create a larger combining space compared to PSTBCs. We can show that with certain system configurations, PODs outperform PSTBCs. Using PODs, we also propose a combined coding, beamforming, and spatial multiplexing scheme over multiple-antenna multi-user channels that enables a low-complexity joint interference cancellation scheme.

We study the problem of maximizing the expected rate over a slowly fading channel with quantized channel state information at the transmitter (CSIT). This problem has been recently studied in the literature assuming a noiseless feedback link. In this work, we consider a more realistic model, where the feedback link suffers from fading, as well as the limited power allocated to the feedback signals. Our scheme considers a finite-state model to capture the fading in the feedback link. We solve the rate maximization problem with different power control strategies at the transmitter. A channel optimized sealer quantizer (COSQ) is designed to incorporate feedback in our transmission scheme. Unlike the conventional COSQs where the objective is to reconstruct the source, our proposed quantizer is designed to optimize the expected rate of the forward link. For a high quality feedback channel, the proposed system performs close to the noiseless feedback case, while its performance converges to the no-feedback scenario as the feedback channel quality degrades

We investigate the outage behavior of multiple-antenna slowly fading channels with resolution constrained feedback and partial power control. A fixed-rate communication scheme is considered. It is known from the literature that with error-free feedback, the power control codebook that minimizes the outage probability with an average power constraint at the transmitter has a circular quantizer structure. Moreover, the diversity gain of the system increases polynomially with the cardinality of the power control codebook. Here, we study a similar system, but within a noisy feedback channel framework. We show that the optimal quantizer structure in this scenario is still circular. Furthermore, the optimal quantization codebook resembles a channel optimized scalar quantizer (COSQ). With noisy feedback, using the new power control codebook, the outage performance of the system is superior to that of a no-feedback system. However, we show through asymptotic analysis that the diversity gain is the same as a no-feedback scheme.

Combining the benefits of diversity/coding gain from space-time coding and array gain from beamforming over quasi-static block fading channels is accomplished in a suitable way for erroneous feedback conditions. For this purpose, we utilize multi-dimensional space-time constellation sets or vector codes combined with linear precoders which are designed to minimize the error probability. Furthermore, the design of a feedback link based on maximum received signal-to-noise ratio criterion is considered. In practice, the transmitter channel state information is degraded by several factors in the feedback link, e.g. bandwidth limitation, delay, and noise which is the main problem. The defective information at the transmitter leads to drastic performance degradation unless the system is robustly designed against the feedback errors and mismatches. Therefore, we employ quantized feedback strategies optimized for noisy channels. The most attractive property of our scheme is that it converges to space-time coding in extremely poor feedback cases and to pure beamforming in relatively high quality feedback situations. Simulation results confirm the good performance of our scheme.

In this paper, we first introduce a quasi-orthogonal space-time block coding scheme over multiple antenna block fading channels. The proposed code exploits temporal diversity due to the mobile nature of the block fading channel as well as spatial diversity due to multiple antennas. We then propose a beamforming strategy over temporally correlated channel blocks. It is assumed that the channel undergoes Doppler frequency shift and an AR1channel model is adopted to track the channel temporal correlation coefficients at the transmitter. Using the combination of transmit beamforming and quasi-orthogonal block coding over adjacent channel blocks, we accomplish to achieve the available array gains on top of notable diversity gains and coding gains, compared to the standard solutions in the conventional wireless communication schemes. In our model, the knowledge of the channel statistics at the transmitter side is based on the approximation of the Jakes' model and does not require frequent feedback updates from the receiver. Simulation results show the superiority of our scheme to the existing coding schemes with knowledge of the channel statistics at the transmitter

In this article, we introduce a novel group of space-time-frequency codes based on multiple trellis coded modulation (MTCM). These codes are originally designed without accounting for the channel spectral and temporal correlation conditions. We improve the code performance by utilizing an augmented distance spectrum enhancement technique to serve for the wireless channels that undergo mobility and multi path fading. The performance of the new group of codes, with enhanced distance spectrum characteristics is investigated though numerical simulations

In this paper, we present a novel power loading scheme for several existing space-time trellis codes (STTCs). These STTCs are originally designed for the open loop systems where no channel state information is available at the transmitter. To further enhance the performance of these STTCs, we assume that the scalar quantized channel magnitude information is available at the transmitter through a feedback channel. Therefore, the error performance of these STTCs is improved through proper power loading on the different transmit antennas. To calculate the power loading parameters, we derive the distance spectrum of these STTCs based on the channel magnitude information. We also use a novel transfer function analysis to optimize the overall distance spectrum. The proposed power loading algorithm is flexible enough to be applied for various kinds of existing STTCs and it also enjoys easy implementation at the transmitter. Finally, numerical simulations show that the new power loading scheme accomplishes superior performance compared to several widely used open loop algorithms as well as some popular closed loop algorithms in the literature.