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Cellular networks are increasingly densified to deal with the fast growing wireless traffic. Interference mitigation plays a key role for the dense cellular networks. Successive interference cancellation (SIC) and fractional frequency reuse (FFR) are two representative inter-cell interference (ICI) mitigation techniques. In this paper, we study the application of both SIC and FFR for LTE uplink networks, and develop an analytical model to investigate their interactions and impact on network performance. The performance gains with FFR and SIC are related to key system functionalities and variables, such as SIC parameters, FFR bandwidth partition, uplink power control and sector antennas. The ICIs from individual cell sectors are approximated by log-normal random variables, which enables low complexity computation of the aggregate ICI with FFR and SIC. Then, network performance of site throughput and outage probability is computed. The model is fast and has small modeling deviation, which is validated by simulations. Numerical results show that both SIC and FFR can largely improve network performance, but SIC has a stronger impact than FFR. In addition, most of the network performance gains with SIC could be obtained with a small number of SIC stages applied to a few sectors. [ABSTRACT FROM AUTHOR]

In millimeter wave (mmWave) communication systems, hybrid analog/digital precoding with single-carrier transmission and time delay compensation is a promising technique for realizing the cost-effective large-scale multiple-input multiple-output (MIMO) communications with limited radio frequency (RF) chains. This paper studies the mmWave downlink with fully connected MIMO architecture system for the general frequency-selective channels. By leveraging the fact that the mmWave channels are likely to be sparse in the directions and the signal propagation is usually dominated by the line of sight path, we investigate the low-complexity single-carrier transmission scheme with time delay precompensation applied at the base station (BS). The resulting signal-to-interference-plus-noise ratio (SINR) is derived in terms of the precoding vectors by taking into account both the residual intersymbol interference and interuser interference. Based on the derived SINR expression, we first propose a codebook based precoding scheme, then develop an effective joint codeword selection and precoding algorithm by utilizing the group sparse approaches to accommodate a limited number of RF chains at the BS. Numerical results are provided to validate the effectiveness of the proposed schemes, showing that the proposed scheme achieves a performance close to the fully digital system. [ABSTRACT FROM AUTHOR]

This paper considers a multicell downlink (DL) massive MIMO system operating over Ricean fading channels in which each base station (BS) is equipped with a massive antenna array, while each user has a single antenna. We explore equal-gain transmission (EGT), line-of-sight (LOS) component-based EGT (LOS-EGT) and maximum-ratio transmission (MRT) under imperfect channel state information. Closed-form expressions for lower bounds of the achievable rates are derived for EGT over Ricean and Rayleigh fading channels, and for LOS-EGT and MRT over Ricean fading channels. With the obtained closed-form expressions, various power scaling laws concerning DL data transmit power and uplink (UL) pilot transmit power are established and discussed. In particular, it is found that, as the number of BS antennas $M$ grows unlimited, the lower bounds on the rates achieved with EGT, LOS-EGT and MRT schemes approach infinity and are not affected by pilot contamination, while the DL data transmit power and UL pilot transmit power can be scaled down proportionally to ${M^{ -a}}$ and ${M^{ - b}}$ (where $0 \leq a < 1$ and $b > 0$), respectively. Numerical results corroborate the tightness and accuracy of these closed-form expressions and they also show that, when the number of antennas and intercell interference level are large, compared to the MRT, EGT and LOS-EGT are more resistant to intercell interference and pilot contamination. [ABSTRACT FROM AUTHOR]

This paper studies the beamforming design for the multiple-input multiple-output (MIMO) multiway relay channel with clustered full data exchange. We formulate the linear signal alignment in the model under a rank-constrained rank-minimization (RCRM) framework. Our contribution is twofold. We decompose the RCRM problem into independent rank-minimization subproblems and put forth an iterative algorithm for the beamforming design. For symmetric antenna setups, our approach advances the state of the art by expanding the achievable degree of freedom (DoF) region, and for asymmetric antenna setups, our approach can be directly applied while prior approaches are not readily applicable. [ABSTRACT FROM AUTHOR]

Aiming at the problem of high detection complexity at the base station in massive multiuser multiple-input multiple-output system, this paper proposes a low complexity variable node full information Gaussian message passing iterative detection based on forced convergence (VFI-GMPID-FC) algorithm. First, the traditional GMPID algorithm is improved to get the VFI-GMPID algorithm. The detection performance of the VFI-GMPID algorithm approaches the minimum mean square error (MMSE) detection algorithm, but the complexity is much lower than that of the MMSE algorithm. Combined with the idea of forced convergence and VFI-GMPID, the VFI-GMPID-FC algorithm is proposed to further reduce the complexity of the algorithm and improve the detection efficiency. Finally, the simulation results show that the proposed algorithm can effectively reduce the complexity of the algorithm while ensuring improved detection performance. [ABSTRACT FROM AUTHOR]

This paper presents a single-inductor multiple-input single-output (SI-MISO) boost converter with a deadbeat-based control method. The proposed deadbeat-based control has the capability to simultaneously conduct the power regulation from multiple inputs and the output voltage regulation for the SI-MISO boost converter. The advantages of the proposed method are less component count, lower system cost, compatibility for arbitrary number of inputs, fast response, and simplicity for implementation. Hence, the SI-MISO boost converter is a promising interface for the regulation of multiple energy sources as a standalone power system, which can be utilized in electric vehicle applications. To verify the performance of the proposed deadbeat-based control method, a laboratorial prototype of the SI-MISO boost converter is built. The steady-state and dynamic operations are investigated based on the prototype. The experimental results demonstrate that input power and output voltage of the SI-MISO boost converter can be effectively regulated by the proposed control method. The comprehensive comparison with the existing methods is conducted to further illustrate the advantages of the proposed deadbeat-based method. [ABSTRACT FROM AUTHOR]

One of the main goals of the future wireless networks is improving the users’ quality of experience (QoE). In this paper, we consider the problem of the QoE-based resource allocation in the downlink of a massive multiple-input multiple-output heterogeneous network. The network consists of a macrocell with a number of small cells embedded in it. The small cells’ base stations (BSs) are equipped with a few antennas, while the macro BS is equipped with a massive number of antennas. We consider the two services Video and Web Browsing and design the beamforming vectors at the BSs. The objective is to maximize the aggregated mean opinion score (MOS) of the users under constraints on the BSs’ powers and the required quality of service of the users. We also consider extra constraints on the QoE of users to more strongly enforce the QoE in the beamforming design. To reduce the complexity of the optimization problem, we suggest suboptimal and computationally efficient solutions. Our results illustrate that increasing the number of antennas at the BSs and also increasing the number of small cells’ antennas in the network leads to a higher user satisfaction. [ABSTRACT FROM AUTHOR]

Physical layer security has drawn significant attention in recent years because of its advancement in preventing confidential information leakage to eavesdroppers. In this paper, we focus on secure beamformer designs in multiuser multi-input multi-output (MU-MIMO) systems with a multi-antenna eavesdropper attempting to overhear the confidential information of a particular user. Unlike the existing work, we aim to exploit the inherent multi-user interference to disrupt the reception of the eavesdropper and enhance the security of wireless communications. Particularly, utilizing practical signal-to-interference-noise metrics, the objective of the secure beamformer design is to minimize the eavesdropper's SINR, while providing legitimate users with required prespecified SINRs to guarantee the qualify of service. We propose secure beamformer designs for both downlink and uplink transmissions, under the conditions of known and unknown eavesdropper's channels, respectively. With the proposed secure beamformers, the multiuser signal behaves like the artificial noise or distributed friendly jamming, which can further degrade the reception of the eavesdropper. Extensive simulation studies confirm our analytical performance predictions and illustrate the advantages of proposed beamformer designs for secure MU-MIMO transmissions. [ABSTRACT FROM AUTHOR]

Diagnosis and troubleshooting are critical to efficiently detecting the imperfections and improving the radio frequency designs for wireless systems in the research and development stage. For achieving these, this paper proposes a decomposition method for the measurement of multi-input multi-output (MIMO) devices’ over-the-air (OTA) performance. By using the proposed method, the antenna active envelope correlation coefficient, the radiated sensitivity of each receiver, the total isotropic sensitivity, the self-interference, and the desensitization can all be achieved separately, and in the OTA working mode. In consideration of the MIMO system's complex array antennas and radio frequency receivers, the parameters obtained by this decomposition method are significant for discovering the imperfections, for debugging, and for improving the design of the devices. It is a valuable tool to raise the debugging efficiency of MIMO systems. [ABSTRACT FROM AUTHOR]

This paper considers a multi-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay network. In the multi-hop AF MIMO relay network, the performance deteriorates as the number of hops increases because the effect of noise is enhanced. To suppress the effect of noise, this paper proposes the two beamforming schemes using channel state information (CSI) for the transmit beamforming at the source, relay beamforming at the relay, and receive beamforming at the destination. The forward-and-backward-CSI based beamforming and all-CSI based beamforming schemes are designed at each node based on the minimum mean square error criterion under the source and relay transmit power constraint. The forward-and-backward-CSI based beamforming scheme is designed by using the two matrices, forward channel, and backward channel. The two matrices are designed by using the beamforming matrices and channels from the previous nodes. Unlike the forward-and-backward-CSI based beamforming scheme, the all-CSI based beamforming scheme is designed by using all channels and an iterative algorithm. In terms of the complexity, the forward-and-backward-CSI based beamforming scheme is superior to the all-CSI based beamforming scheme. However, the all-CSI based beamforming scheme has advantage over the forward-and-backward-CSI based beamforming scheme in terms of the performance. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the performance of a wireless relay network with each of its nodes equipped with N antennas and the same orthogonal space–time block coding (OSTBC) scheme adopted at its destination and relays for transmission. By deriving the performance expressions for a single-relay system, we obtain the maximum diversity order achievable by the channel-state information (CSI)-assisted amplify-and-forward (CAF) protocol. Then, by focusing on CAF multirelay systems subject to a total power constraint, we derive a simple approximate symbol error rate (SER) expression for the multiple-relay channels with and without relay selection revealing a higher achievable diversity order by using relay selection than its counterpart with fixed relay configuration. [ABSTRACT FROM PUBLISHER]

This paper investigates the network resource allocation in multiuser downlink wireless systems where the base station and the mobile stations are equipped with multiple antennas to provide fair and efficient transmission services to the mobile users. We focus on packet scheduling, given that it has a significant impact on the overall performance of a multiple-input-multiple-output (MIMO) system. Most previous schedulers designed at the packet level do not take into account the traffic characteristics (different packet lengths and the arrival process parameters); consequently, they fall short of simultaneously providing fairness and a low average packet transmission delay. We are making use of a flexible packet transmission algorithm at the medium access control (MAC) layer to develop and propose a novel scheduler, which is referred to as MIMO packet-based proportional fairness (MP-PF). The new scheduler is designed with the goal of providing high performance in terms of a low average packet transmission delay and time and service fairness among the users based on the concept of proportional fairness. The scheduler also conserves work and takes into consideration the packet length, the user queue length, the user transmission rate (related to its channel quality), and the service guarantees for heterogeneous users. The well-known ideal service fair scheduler called max-min can also significantly be improved using our framework by taking into consideration the traffic characteristics. We also provide an analysis for the fairness of the new scheduler in terms of time and service allocation, which is the key contribution of this paper. Simulations that consider the traffic characteristics and the mobility of users show the relatively low average packet transmission delay and demonstrate the time and service fairness capabilities of MP-PF, compared with other well-known MIMO schedulers. [ABSTRACT FROM AUTHOR]

Based on the basic principle of spread spectrum systems, this paper proposes a hybrid automatic-repeat-request (HARQ) scheme with interference mitigation for multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. The proposed hybrid media access control (MAC) and physical layer (PHY) design orthogonally spreads signals in the transmission domain to separate the desired signals from interferences. It not only improves the signal-to-noise ratio (SNR) but also suppresses intercarrier interference (ICI) and interantenna interference (IAI). Almost without increasing complexity, mathematical analyses and numerical simulations show that the proposed scheme outperforms the conventional Chase combining HARQ. [ABSTRACT FROM AUTHOR]

This paper investigates the transmission scheduling of users under spatially correlated multiple-input-multiple-output (MIMO) channels. By maximizing an upper bound of the sum capacity, we propose a scheduling scheme that requires only scalar feedback from each receiving user. To simplify user information feedback and better exploit the spatial channel correlation, we further develop a more efficient scheduling method that only requires a 1-bit indicator from each user and selects users based on the MIMO channel correlation information. Additionally, we then extend the proposed scheduling schemes for the system with imperfect (finite-rate) channel information feedback. Numerical results finally show that the proposed scheduling schemes can effectively improve the system sum capacity performance by exploiting the statistic channel-correlation information. [ABSTRACT FROM AUTHOR]

Maximum-likelihood (ML) detection for higher order multiple-input-multiple-output (MIMO) systems faces a major challenge in computational complexity. This limits the practicality of these systems from an implementation point of view, particularly for mobile battery-operated devices. In this paper, we propose a modified approach for MIMO detection, which takes advantage of the quadratic-amplitude modulation (QAM) constellation structure to accelerate the detection procedure. This approach achieves low-power operation by extending the minimum number of paths and reducing the number of required computations for each path extension, which results in an order-of-magnitude reduction in computations in comparison with existing algorithms. This paper also describes the very-large-scale integration (VLSI) design of the low-power path metric computation unit. The approach is applied to a 4 x 4, 64-QAM MIMO detector system. Results show negligible performance degradation compared with conventional algorithms while reducing the complexity by more than 50%. [ABSTRACT FROM AUTHOR]

This paper proposes a stochastic multipath model that is useful for generating multiple-input-multiple-output (MIMO) channel matrices in time-variant environments. The multipath model is developed by first extracting the relevant multipath cluster characteristics from measured indoor channel data and subsequently capturing these characteristics in an autoregressive stochastic model. This model is then used to generate channel matrices whose space-time characteristics closely match those of realistic scenarios, particularly when birth and death of multipath clusters-are included in the stochastic representation. Computational examples reveal the applicability and the accuracy of the approach. While the current implementation is based on data taken assuming that propagation is confined to the horizontal plane, this paper also discusses the extension of the model to describe 3-D propagation, enabling its application to a wide range of physical scenarios and antenna characteristics. [ABSTRACT FROM AUTHOR]

Thanks to the short wavelength at high frequency (HF), it is promising to combine massive multiple-input and multiple-output (MIMO) with HF communications. In particular, HF massive MIMO differs from the conventional MIMO in array structure and radio propagation. In this paper, we investigate the HF massive MIMO system with a compact planar array (CPA) deployed at the base station (BS) in the presence of electromagnetic mutual coupling (MC) for the asymptotic case under unlimited antenna elements assumption. Specifically, the HF sparse channel is analyzed asymptotically to show that the randomness characteristic of channel decreases in the asymptotic regime, which is conducive to the design of communication systems. Moreover, on the basis of the asymptotic analysis results, the optimal beamforming to maximize the minimum user signal-to-interference-plus-noise ratio (SINR) is derived by applying random matrix theory. Numerical results verify the accuracy of the asymptotic analysis, indicate the performance superiority of the proposed scheme to the traditional minimum mean squared error (MMSE) and maximum ratio transmission (MRT) schemes, and reveal the robustness of the proposal to electromagnetic MC. [ABSTRACT FROM AUTHOR]

This paper studies the sum spectral/energy efficiency (SE/EE) of a full-duplex (FD) cell-free (CF) massive multiple-input multiple-output (MIMO) system with low-resolution analog-to-digital converters (ADCs) at the access points (APs) and the downlink (DL) users. We characterize the joint impact of the residual self-interference, inter-AP interference, uplink (UL)-to-DL interference, pilot contamination and quantization noise (QN) by deriving closed-form solutions for the UL/DL SE. It is shown that the UL SE loss due to the QN can be compensated by increasing the receiving antenna arrays. By contrast, in the DL, increasing the transmit antennas is ineffective in compensating for the DL SE loss. Furthermore, the analysis shows that the operating region of the FD CF massive MIMO is reduced as the ADCs’ resolution declines. We investigate the EE/SE trade-offs. [ABSTRACT FROM AUTHOR]

In this paper, a generalized uplink cell-free massive multiple-input multiple-output (mMIMO) system with hardware imperfections is investigated. Specifically, the hardware impairments consist of multiplicative phase drifts, additive distortion, and amplified thermal noise. Leveraging on a generic hardware impairment model, closed-form expressions for the channel estimation and achievable rate are presented. Based on these tractable results, we explore the uplink achievable rate surrounding the key design parameters, i.e., the channel estimation error, the number of antenna arrays, the local oscillator (LO) setup, and the variance of phase drifts. Aside from this, we also design a power optimization algorithm to maximize the sum-rate under variant channel use. The weighted minimum mean square error (MMSE) methodology is introduced to iteratively determine the solution in closed form. Numerical simulations validate the analytical analyses and examine the effectiveness of the proposed power control algorithm. [ABSTRACT FROM AUTHOR]

Free-space optics (FSO) communication is often unreliable, especially for long distances, as it suffers from attenuation due to foggy weather, atmospheric turbulence, and pointing errors. To avoid communication link failure, radio frequency (RF) communication, which is unaffected from these effects, is utilized when FSO communication is in outage. Diversity is known to counteract the adverse fading effects, therefore, this paper presents a transmit aperture/antenna selection (TAS) and selection combining (SC)-based multiple-input-multiple-output (MIMO) hybrid FSO/RF system. The proposed system consists of a MIMO FSO and RF sub-systems. The MIMO FSO sub-system is given higher priority to transmit and receive using the selected best link. The best link of the MIMO RF sub-system is used when the FSO sub-system is in outage. The probability density function (PDF) and cumulative distribution function (CDF) expressions for TAS/SC-based MIMO FSO and RF sub-systems are derived. The derived PDF and CDF expressions are used further to derive the exact and asymptotic expressions for outage probability, average symbol error rate (SER), and capacity of the hybrid system. From the asymptotic SER expressions, the diversity order of the proposed system is determined. The optimum values for the threshold SNR and transmit beam waist, which minimize the average SER, are obtained. Further, the obtained optimal values using analytical expressions are verified using numerical optimization technique. The effect of multiple apertures/antennas, pointing errors, and atmospheric attenuation over the system performance is analyzed extensively by varying the FSO and RF channel parameters. The results show that the proposed hybrid FSO/RF system is more reliable compared to the individual MIMO FSO and RF systems and achieves higher capacity compared to the MIMO RF system. [ABSTRACT FROM AUTHOR]

This paper presents a non-orthogonal multiple access (NOMA) scheme with group detection for uplink multiple-input multiple-output (MIMO) systems, for which an effective precoder design is developed. In the scheme, users are divided into groups in accordance with their locations for detection at the base station. The inter- and intra-group interferences are mitigated by successive interference cancellation (SIC) and transceivers, respectively. Based on a derived approximate signal-to-interference-plus-noise ratio (SINR) for using zero-forcing detection, an iterative power and beamforming update procedure is developed for obtaining the user precoders. The precoder design effectively mitigates the intra-group-inter-user correlation making the adopted approximate SINR represent the original SINR accurately. The proposed multi-group MIMO-NOMA scheme can work under more practical transmit-receive antenna configurations and is shown to outperform upon existing cluster-based MIMO-NOMA schemes in terms of total transmit power for various system configurations. The impact of SIC residuals on the multi-group MIMO-NOMA scheme is investigated. Feasibility conditions for the design under imperfect SIC based on the fractional cancellation error model are developed. [ABSTRACT FROM AUTHOR]

When the wireless communication system evolves to massive multiple-input multiple-output (MIMO) system, the system becomes more and more complex. Hybrid beamforming architecture provides excellent trade-off between the system performance and the complexity for the massive MIMO system. Hybrid beamforming architecture can be classified as fully-connected (FC) and sub-connected (SC) architecture. Existing studies on the system performance comparison of the two architectures are limited. In this paper, we investigate the performance of the FC and SC architecture in the multi-user multiple-input single-output (MU-MISO) system. We derive the closed-form sum rate of two architectures under the same total transmission power constraint. From the results, we conclude that the system performance of FC architecture is always better than that of SC architecture. When the number of users is small or the signal noise ratio (SNR) is low, the performance difference between the FC and SC architecture is small. Our analysis can serve as a guideline of choosing hybrid beamforming architectures. [ABSTRACT FROM AUTHOR]

The number of commercial and civilian vehicles equipped with automotive radars is expected to rise rapidly in the forthcoming years and with that comes the problem of increased mutual interference between the radar sensors, which can result in severely reduced radar sensitivity and increased false alarm rates. The difficulty and complexity of the problem increase with MIMO radar systems and multiply even further with a growing number of vehicles present on the scene. A system of connected vehicles can efficiently address this problem by sharing information amongst themselves. In this paper, we propose an efficient waveform design algorithm that seeks to minimize a collective cross-ambiguity function. Vehicles that can talk to each other, can perform the design online in a collaborative manner, or offline, in which case the radar codes can be designed and stored in a codebook for future use. The proposed coding scheme is computationally efficient for practical use and the incorporation of such schemes requires only a slight modification of the existing systems. Our numerical examples indicate that the proposed scheme can significantly reduce the interference power level in a desired area of the radar cross-ambiguity functions. [ABSTRACT FROM AUTHOR]

In this paper, a novel differential space-time block coded spatial modulation (differential STBC-SM) is proposed for uplink multi-user massive multiple-input multiple-output (MIMO) communications, which combines the concept of differential coding and STBC-SM to enhance the diversity benefits in the absence of the channel state information (CSI). The transmission structure of the proposed system is on a block basis, where each block contains two sub-blocks. More specifically, the first sub-block only conveys amplitude and phase modulation (APM) symbol bits, since its transmit antennas (TAs) obey a pre-designed activation pattern, which do not carry any information bit. For the second sub-block, the input bits are modulated to STBC-SM matrices, which are then differentially coded between two adjacent sub-blocks. Moreover, a novel block-by-block based non-coherent detector is presented. Finally, we derive an upper bound on the average bit error probability (ABEP) by using the moment generating function (MGF). Our simulation results show that the proposed differential STBC-SM transmission structure is able to acquire considerable bit error rate (BER) performance improvements compared to both the conventional differential spatial modulation (DSM) and differential Alamouti schemes. [ABSTRACT FROM AUTHOR]

Practical data detectors must achieve low error-rate at low-complexity for massive multiple-input multiple-output (MIMO) wireless systems. Since near-optimal minimum mean square error (MMSE) detection exhibits high computational complexity for such wireless systems, various iterative methods as well as their enhanced variants have been proposed. The efficiency of iterative approaches, however, is not satisfying due to slow convergence rate and reduced accuracy. This paper proposes a novel semi-iterative data detection algorithm for massive MIMO systems that simultaneously achieves a large improvement in convergence and accuracy with respect to the corresponding iterative method. We provide a general three-term recurrence expression for semi-iterative detection and incorporate it with Richardson method as a show case. To further improve the convergence rate of the proposed technique, a new trace-diagonal based low-complexity initial method is developed. A sufficient condition for convergence of the proposed method is also provided. We analyze the associated complexity of semi-iterative detector, and provide numerical results which demonstrate that the proposed detector is superior to recently introduced iterative detectors in terms of both the error-rate performance and computational complexity. [ABSTRACT FROM AUTHOR]

This paper gives an insight on the performance of mixed dual-hop radio-frequency (RF)-underwater optical wireless communication (UOWC) systems. The system consists of multiple-input multiple-output (MIMO) RF hop employing Nakagami- $m$ fading channel on the source ($S$) node communicating with a destination node ($D$) considered as the legitimate receiver via an amplify-and-forward (AF) relay ($R$) node equipped with multiple RF antennas for reception. It considers transmit antenna selection (TAS) scheme for communication in the MIMO RF hop while the information is transmitted from the $S$ node to the $D$ node, i.e. submarine etc., via the UOWC hop. Specifically, the $R$ node receives incoming information messages from $S$ node via MIMO RF links, applies maximal-ratio combining (MRC) technique, amplifies the output combined signal, and subsequently forwards it to the destination utilising a variable gain relaying (VGR) via an UOWC link. We derive exact closed-form expressions for the system's end-to-end (E2E) statistical channel characteristics. Our derived analytical expressions present an efficient technique to depict the impact of our system and channel parameters on the performance, namely the varying number of increasing antennas $N_t=N_r=2,3,4$ or more from the $S$ node towards $R$ node and the involvement of underwater detection techniques of $r = 1$ for heterodyne detection and $r = 2$ for intensity modulation/direct detection (IM/DD) in the underwater turbulence severity of the UOWC link. Outage probability (OP) and average bit error rate (BER) closed-form expressions for the varying bubble levels (BL) (L/min) for different scenarios, varying temperature gradients (TG) (°C cm−1), different fresh and saline waters, and various binary modulation techniques have been accurately validated for the E2E system presented in this work along with the tightness of their respective high-end asymptotes. [ABSTRACT FROM AUTHOR]

Cell-free massive multiple-input multiple-output (MIMO) is considered as a promising technology for satisfying higher rate requirement of users in beyond-5G networks. This paper investigates the impact of phase noise on the performance of cell-free MIMO systems which employ a large number of multi-antenna access points (APs). For both downlink and uplink transmissions, we derive the tractable closed-form achievable rate expressions when signal detection with channel state information (CSI) and channel distribution information (CDI), respectively, by utilizing the extended deterministic equivalence method in random matrix theory. The closed-form achievable rate expressions provide efficient evaluation for the impact of phase noise on system performance. The analytical results indicate that the phase noise influences the power of the desired signal, the beamforming uncertainty gain, and the inter-user interference increment caused by the pilot contamination. In addition, the special cases that only APs have phase noise and only users have phase noise are discussed. It is found that the impact of phase noise at users is more severe than that at APs. Besides, we discuss the system performance at low and high SNR regimes. It demonstrates that the phase noise is the major limitation of the system performance in high SNR regime while it can be neglected in low SNR regime. Furthermore, we formulate the max-min power control problem for both downlink and uplink transmissions to guarantee the users’ fairness and prove that the downlink max-min problem is a quasi-concave problem while the uplink max-min problem is a geometric programming (GP) problem. Then, the phase noise-aware max-min power control schemes for both downlink and uplink transmissions are proposed to ensure the users’ fairness. Finally, numerical results are provided to validate the analytical results and the proposed phase noise-aware power control scheme. [ABSTRACT FROM AUTHOR]

Intelligent reflecting surface (IRS) has recently emerged as a promising technology for 6 G wireless systems, due to its capability to reconfigure the wireless propagation environment. In this paper, we investigate a Rate-Splitting Multiple Access (RSMA) for IRS-assisted downlink system, where the base station (BS) communicates with single-antenna users with the help of an IRS. RSMA relies on rate-splitting (RS) at the BS and successive interference cancellation (SIC) at the users and provides a generalized multiple access framework. We derive a new architecture called IRS-RS that leverages the interplay between RS and IRS. For performance analysis, we utilize an on-off control technique to control the passive beamforming vector of the IRS-RS and derive the closed-form expressions for outage probability of cell-edge users and near users. Moreover, we also analyze the outage behavior of cell-edge users for a sufficiently large number of reflecting elements. Additionally, we also analyze the outage performance of cooperative RS based decode-and-forward (DF)-assisted framework called DF-RS. Through simulation results, it is shown that the proposed framework outperforms the corresponding DF-RS, RS without IRS and IRS-assisted conventional non-orthogonal multiple access (NOMA) schemes. Furthermore, the impact of various system's parameters such as the number of IRS reflecting elements and the number of users on the system performance is revealed. [ABSTRACT FROM AUTHOR]

For large-scale antenna array multiple-input multiple-output (MIMO) systems, a typical solution often put forward for uplink detection consists in applying low-complexity linear receivers such as zero-forcing (ZF) and minimum mean-square error (MMSE) combiners. In this paper, the performance of uplink MMSE detection has been analyzed in the context of a multi-cell multiuser MIMO system. An approximate expression for the signal-to-interference-plus-noise ratio (SINR) is proposed, which is in simple form and becomes exact in the low SNR regime. This approximate SINR applies to systems where the base station (BS) has the statistical information of the out-of-cell interfering signals, and systems where the BS ignores the presence of such interfering signals. This approximate SINR is tight for arbitrary user powers, arbitrary number of antennas at the base station, and arbitrary channel correlation matrix associated with any particular user. Approximate expressions for capacity and bit-error rate/symbol-error rate have also been derived. Particularly, it can be proven that, when the MMSE receiver ignores the presence of out-of-cell interfering signals, the performance gap between ZF and MMSE vanishes in the high SNR regime. [ABSTRACT FROM AUTHOR]

In this paper, we propose a three-dimensional (3D) cluster-based model for the fifth generation (5G)/beyond 5G (B5G) vehicle-to-vehicle (V2V) massive multiple-input multiple-output (MIMO) wideband channels. It is the first cluster-based irregular shaped geometry-based stochastic model (IS-GBSM) to distinguish the dynamic clusters and static clusters in vehicular massive MIMO communication scenarios. This model not only considers the high time-variance, the time non-stationarity, and the vehicular traffic density (VTD) of V2V channels, but also models the massive MIMO channel characteristics, such as spherical wavefronts by 3D vector calculation and space non-stationarity. Meanwhile, this model for the first time integrates the VTD into birth-death process to model the channel characteristics of V2V and massive MIMO jointly and deeply, where a novel VTD-combined time-array cluster evolution algorithm for 5G/B5G V2V massive MIMO channel model is developed. Based on the proposed model, we derive some expressions of channel statistical properties, including time-space-frequency correlation function (STF-CF) and Doppler power spectral density (DPSD). The influence of several parameters, e.g., VTDs, vehicle moving directions, and antenna spacings, on the channel characteristics are sufficiently explored, which can provide assistance for the design of vehicular massive MIMO communication systems. Finally, the utility of the proposed model is verified by the close agreement between simulation results and measurement data. [ABSTRACT FROM AUTHOR]

This paper considers the secure transmission in a cell-free massive MIMO system with imperfect radio frequency (RF) chains and low-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) at both access points (APs) and legitimate users, where an active eavesdropper attempts to wiretap the confidential data. The Gaussian RF impairment model (GRFIM) and additive quantization noise model (AQNM) are used to evaluate the impacts of the RF impairments and low resolution ADCs/DACs, respectively. The analytical results of the linear minimum mean square error (MMSE) channel estimation show that there is nonzero floor on the estimation error with respect to the RF impairments, ADC/DAC precision and the pilot power of the eavesdropper which is different from the conventional case with perfect transceiver. Then, a tractable closed-form expression for the ergodic secrecy rate is obtained with respect to key system parameters, such as the antenna number per AP, the AP number, user number, quality factors of the ADC/DAC and the RF chain, pilot signal power of the eavesdropper, etc. Moreover, a compensation algorithm between the imperfect RF components and the inexpensive coarse ADCs/DACs is also presented. Finally, numerical results are provided to illustrate the efficiency of the achieved expressions and the devised algorithm, and show the effects of RF impairments and low resolution ADC/DAC on the secrecy performance. [ABSTRACT FROM AUTHOR]

In this paper, an iterative design method for beamformers is proposed for multiple-input multiple-output (MIMO) two-way relay networks with multiple pairs of source nodes. It is known that the joint beamformer design problem based on the minimum mean-square-error (MMSE) is known to be nonconvex, and it cannot be analytically solved. To manage this difficulty, a novel iterative algorithm is proposed, which uses duality relationships. First, the MSE duality for MIMO two-way relay networks with multiple pairs of nodes is presented. Moreover, the optimization problem is divided into three subproblems, which can be separately solved; then, the duality is applied to the proposed iterative algorithm, which provides closed-form solutions for all subproblems. The numerical results demonstrate that the proposed method improves network performance and can be applied to various communication systems that use the two-way relay network. [ABSTRACT FROM AUTHOR]

Low-complexity linear precoders are known to be close to optimal for massive multiple-input multiple-output (M-MIMO) systems. However, the large number of antennas at the transmitter imposes a high computational burden and high hardware overloads. In line with this, in this paper, we propose a low-complexity antenna selection (AS) scheme that selects the antennas that maximize constructive interference between the users. Our analyses show that the proposed AS algorithm, in combination with a simple matched-filter (MF) precoder at the transmitter, is able to achieve better performances than systems equipped with a more complex channel inversion (CI) precoder and computationally expensive AS techniques. First, we give an analytical definition of constructive and destructive interference, based on the phase of the received signals from phase-shift-keying-modulated transmissions. Then, we introduce the proposed AS algorithm, which identifies the antenna subset with the highest constructive interference, maximizing the power received by the user. In our study, we derive the computational burden of the proposed technique with a rigorous and thorough analysis, and we identify a closed-form expression of the upper bound received power at the user side. In addition, we evaluate in detail the power benefits of the proposed transmission scheme by defining an efficiency metric based on the achieved throughput. The results presented in this paper prove that AS and green radio concepts can be jointly used for power-efficient M-MIMO, as they lead to significant power savings and complexity reductions. [ABSTRACT FROM AUTHOR]

This paper proposes an amplify-and-forward-based massive multiple-input–multiple-output full-duplex relaying (AF-MM-FDR) protocol, where multiple source–destination pairs communicate simultaneously with a common full-duplex relay. A zero-forcing (ZF)-based relay transceiver design with semiblind gain control is presented, considering the problem of relay oscillation. The asymptotic expression of end-to-end signal-to-interference-plus-noise power (SINR) is derived under the general power scaling scheme. The scaling behaviors of echo interference (EI) and effective channel estimation error are determined. Scaling results show that the deployment of very large antenna arrays at the relay has the potential to eliminate the effect of EI due to the full-duplex operation, if the power scaling scheme is selected properly. Moreover, based on the asymptotic analysis, a low-complexity power control scheme is proposed to optimize the spectral efficiency of AF-MM-FDR. Simulation results show that the proposed power control scheme improves the spectral–energy efficiency tradeoff of AF-MM-FDR significantly. [ABSTRACT FROM AUTHOR]

This paper considers the 3-D spatial fading correlation (SFC) resulting from an angle-of-arrival (AoA) distribution that can be modeled by a mixture of Fisher–Bingham distributions (FB-distributions) on the sphere. By deriving a closed-form expression for the spherical harmonic transform for the component FB-distributions, with arbitrary parameter values, we obtain a closed-form expression of the 3-D SFC for the mixture case. The 3-D SFC expression is general and can be used in arbitrary multiantenna array geometries and is demonstrated for the cases of a 2-D uniform circular array (UCA) and a 3-D regular dodecahedron array (RDA). In computational aspects, we use recursions to compute the spherical harmonic coefficients and give pragmatic guidelines on the truncation size in the series representations to yield machine precision accuracy results. The results are further corroborated through numerical experiments to demonstrate that the closed-form expressions yield the same results as significantly more computationally expensive numerical integration methods. [ABSTRACT FROM AUTHOR]

In this paper, we consider the low-cost design for point-to-point millimeter-wave (mmW) multiple-input–multiple-output (MIMO) systems in rainfall environments. We first show that rain does not always have a negative impact on system performance, provided that accurate instantaneous channel state information (CSI) is available at both the transmitter and receiver. In addition, we propose a practical and low-cost transmission scheme, referred to as hardware-constrained statistical precoding (HC-SP), for mmW MIMO systems in rainfall environments. This scheme only requires statistical channel information at the transmitter and takes into consideration the hardware constraints on transceiver imposed by the high radio-frequency chain cost. Simulation results demonstrate that the HC-SP scheme allows the mmW MIMO system to have near-optimal performance. [ABSTRACT FROM AUTHOR]

For millimeter-wave (mmWave) massive multiple-input–multiple-output (MIMO) systems, codebook-based analog beamforming (including transmit precoding and receive combining) is usually used to compensate the severe attenuation of mmWave signals. However, conventional beamforming schemes involve complicated search among predefined codebooks to find out the optimal pair of analog precoder and analog combiner. To solve this problem, by exploring the idea of turbo equalizer together with the tabu search (TS) algorithm, we propose a Turbo-like beamforming scheme based on TS, which is called Turbo-TS beamforming in this paper, to achieve near-optimal performance with low complexity. Specifically, the proposed Turbo-TS beamforming scheme is composed of the following two key components: 1) Based on the iterative information exchange between the base station (BS) and the user, we design a Turbo-like joint search scheme to find out the near-optimal pair of analog precoder and analog combiner; and 2) inspired by the idea of the TS algorithm developed in artificial intelligence, we propose a TS-based precoding/combining scheme to intelligently search the best precoder/combiner in each iteration of Turbo-like joint search with low complexity. Analysis shows that the proposed Turbo-TS beamforming can considerably reduce the searching complexity, and simulation results verify that it can achieve near-optimal performance. [ABSTRACT FROM AUTHOR]

In this paper, we study the transmission of orthogonal space–time block codes (OSTBCs) over a shadowed Rician (SR) land mobile satellite (LMS) link. Specifically, we derive the symbol error rate (SER), diversity order, and the average capacity of the OSTBC-transmission-based scheme over the SR fading LMS communication systems. First, we consider the independent and identically distributed (i.i.d.) SR fading channels and derive the expressions of moment-generating function (mgf) in terms of the Meijer-G function. By substituting the Meijer-G function in terms of hypergeometric function and then by considering the asymptotic approximation of hypergeometric function, the analytical diversity order of the scheme is obtained. The ergodic capacity of the scheme is derived by using the mgf-based approach. The effect of elevation angles over the SER performance of the scheme is analyzed, and it is observed that the performance of the system is improved with increasing values of elevation angles. Next, we consider the OSTBC transmission over correlated SR fading channels and derive the expressions of mgf, SER, diversity order, and average capacity of the considered setup. In particular, it is demonstrated in this paper that, by employing an additional transmit antenna at the satellite along with Alamouti code, the error rate of the LMS communication system can be significantly improved. It is also shown that the correlation has no impact on the diversity order of the system, but it adversely affects the capacity of the system. [ABSTRACT FROM AUTHOR]

Operation of full-duplex systems requires efficient mitigation of the self-interference signal caused by the simultaneous transmission/reception. In this paper, we propose a maximum-likelihood (ML) approach to jointly estimate the self-interference and intended channels by exploiting its own known transmitted symbols and both the known pilot and unknown data symbols from the other intended transceiver. The ML solution is obtained by maximizing the ML function under the assumption of Gaussian received symbols. A closed-form solution is first derived, and subsequently, an iterative procedure is developed to further improve the estimation performance at moderate-to-high signal-to-noise ratios (SNRs). We establish the initial condition to guarantee the convergence of the iterative algorithm to the ML solution. In the presence of considerable phase noise from the oscillators, a phase noise estimation method is proposed and combined with the ML channel estimator to mitigate the effects of the phase noise. Illustrative results show that the proposed methods offer good cancelation performance close to the Cramer–Rao bound (CRB). [ABSTRACT FROM AUTHOR]

This paper proposes a linear interference alignment (IA) scheme, which can be used for uplink channels in a general multicell multiuser multiple-input-multiple-output (MIMO) cellular network. The proposed scheme aims to align interference caused by signals from a set of transmitters into a subspace that is established by the signals from only a subset of those transmitters, thereby effectively reducing the number of interfering transmitters. The total degrees of freedom (DoF) achievable by the proposed scheme is given in closed-form expression, and a numerical analysis shows that the proposed scheme can achieve the optimal DoF in certain scenarios and provides a higher total DoF than other related schemes in most cases. [ABSTRACT FROM AUTHOR]

This paper considers an online multiantenna precoder design for energy harvesting transmitter based on finite-alphabet inputs and statistical channel state information (CSI). It formulates the problem by maximizing the sum of average mutual information (AMI) of multiple time slots in one channel frame with causal energy constraint. The formulated problem is a \mbox2Nt^2- dimensional stochastic dynamic programming (SDP) problem with a nonconcave objective function, where Nt is the number of transmit antennas. The \mbox2Nt^2- dimensional SDP problem is prohibitively complex and prevents the development of online algorithm for multiantenna systems. We provide equivalence between the multidimensional SDP problem and a one-dimensional power choice problem. Solving the one-dimensional equivalence decreases the computational burden extraordinarily without loss of optimality. We separate the one-dimensional problem into two cases: 1) the discrete-battery-state–discrete-power-choice (DBDP) problem and 2) the continuous-battery-state–continuous-power-choice (CBCP) problem. We also develop numerical algorithms to solve them, respectively. We further analyze the computational complexity of the developed algorithms and demonstrate the significant performance gains offered by the proposed method when compared with other methods. [ABSTRACT FROM AUTHOR]

We propose a statistical information-based approach to enhance the performance of the noniterative quasi-maximum-likelihood (QML) receiver (detector plus decoder) recorded at the output of the channel decoder for coded multiple-input–multiple-output (MIMO) systems. As an illustrative example, the QR decomposition with an $M$-algorithm (QRD-M)-based noniterative QML receiver is employed in this paper. We first illustrate that there is a large discrepancy between the amplitude of the raw log-likelihood ratio (LLR) generated by the complexity-constrained QRD-M detector and its reliability, particularly for LLRs with high amplitudes. The discrepancy is shown to be the main underlying cause of degraded performance in coded MIMO systems. Then, we propose a reliability-aware transformation technique, which exploits the statistical relationship between the raw LLR's amplitude and its reliability to adjust the raw LLR's amplitude to a level commensurate with its reliability. By using the proposed statistical knowledge-based technique, the performance of the receiver (detector plus decoder) recorded at the output of the channel decoder is significantly enhanced for high-order modulations. The extension of the proposed method to other QML receivers such as the list sequential (LISS) detector and list sphere detector (LSD)-based receivers is straightforward. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of massive multiple-input multiple-output (MIMO) cellular systems with pilot contamination. We derive a closed-form approximation of the area spectral efficiency (ASE) for uplink multicell multiuser massive MIMO systems by using a uniformly distributed user location model. Considering a practical power consumption model, we obtain the area energy efficiency (AEE) in a cell. The theoretical results of ASE and AEE can be used to investigate some system parameters of massive MIMO cellular systems, such as the number of antennas at the base station, the number of users, and the number of symbols over which the channel remains constant. We also study the optimal pilot-to-data power ratio for both ASE maximization and AEE maximization. [ABSTRACT FROM AUTHOR]

In this paper, we study resource allocation for multiuser multiple-input–single-output secondary communication systems with multiple system design objectives. We consider cognitive radio (CR) networks where the secondary receivers are able to harvest energy from the radio frequency when they are idle. The secondary system provides simultaneous wireless power and secure information transfer to the secondary receivers. We propose a multiobjective optimization framework for the design of a Pareto-optimal resource allocation algorithm based on the weighted Tchebycheff approach. In particular, the algorithm design incorporates three important system design objectives: total transmit power minimization, energy harvesting efficiency maximization, and interference-power-leakage-to-transmit-power ratio minimization. The proposed framework takes into account a quality-of-service (QoS) requirement regarding communication secrecy in the secondary system and the imperfection of the channel state information (CSI) of potential eavesdroppers (idle secondary receivers and primary receivers) at the secondary transmitter. The proposed framework includes total harvested power maximization and interference power leakage minimization as special cases. The adopted multiobjective optimization problem is nonconvex and is recast as a convex optimization problem via semidefinite programming (SDP) relaxation. It is shown that the global optimal solution of the original problem can be constructed by exploiting both the primal and the dual optimal solutions of the SDP-relaxed problem. Moreover, two suboptimal resource allocation schemes for the case when the solution of the dual problem is unavailable for constructing the optimal solution are proposed. Numerical results not only demonstrate the close-to-optimal performance of the proposed suboptimal schemes but unveil an interesting tradeoff among the considered conflicting system design objectives as well. [ABSTRACT FROM AUTHOR]

In this paper, we consider time-domain vector perturbation (TDVP) in a large-system limit when channel state information (CSI) is imperfect due to pilot contamination, and we derive the system's achievable sum rate per cell. We use random matrix methods to avoid time-consuming Monte Carlo simulations. Numerical results show that, in general, linear precoding ensures a higher sum rate than TDVP in the massive multiple-input–multiple-output (MIMO) regime. [ABSTRACT FROM AUTHOR]

In this paper, we consider a spatial modulation (SM)-based multiple-input–single-output (MISO) system relying on a single radio-frequency chain equipped with a finite-rate feedback channel to provide quantized channel state information (CSI) to the transmitter. First, under the assumption of Rayleigh flat-fading channels and perfect CSI at the transmitter (CSIT), we analyze the symbol error probability (SEP) of an SM scheme, which perfectly compensates the channel phase and employs constellation rotation at the different transmit antennas (TAs). Then, we consider a more practical scenario, where scalar quantization of the channel phase angles is employed, and the quantized CSI is made available to the transmitter via a finite-rate feedback channel. We analyze the SEP reduction, i.e., Pe_L, relative to perfect CSIT, imposed by the quantized CSIT (Q-CSIT). We show that at a high feedback rate, Pe_L varies as C^\prime\mbox2^-2B, where each channel phase angle is quantized to B bits, and C^{\prime} is a constant. Furthermore, based on the rotational symmetry of the M-ary phase-shift keying ( M-PSK) signal constellation, we propose a novel feedback scheme, which requires (n_t-\mbox{1})\log_2(M) fewer bits of feedback with any performance erosion, where n_t$ is the number of TAs. We characterize the performance of the SM-MISO system with finite-rate feedback and validate our analysis through Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

This paper introduces a novel transmission design for antenna beam pattern modulation (ABPM) with a low-complexity decoding method. The concept of ABPM was first presented with optimal maximum-likelihood (ML) decoding. However, an ML detector may not be viable for practical systems when the constellation size or the number of antennas is large, such as in massive multiple-input–multiple-output (MIMO) systems. Linear detectors, on the other hand, have lower complexity but inferior performance. In this paper, we present the antenna pattern selection with a lattice-reduction-aided linear detector for ABPM to reduce the detection complexity with the bit error rate (BER) performance approaching that of ML while conserving low complexity. Simulation results show that even with this suboptimal detection, performance gain is achieved by the proposed scheme compared with different spatial modulation techniques using ML detection. In addition, to validate the results, an upper bound expression for the BER is provided for ABPM with ML detection. [ABSTRACT FROM AUTHOR]

The coordinated multipoint transmission/reception aided collocated antenna system (CoMP-CAS) and the mobile relay assisted fractional frequency reuse distributed antenna system (MR-FFR-DAS) constitute a pair of virtual-MIMO-based technical options for achieving high spectral efficiency in interference-limited cellular networks. In practice, both techniques have their respective pros and cons, which are studied in this paper by evaluating the achievable cell-edge performance on the uplink of multicell systems. We show that, assuming the same antenna configuration in both networks, the maximum available cooperative spatial diversity (or the multiplexing gain) inherent in the MR-FFR-DAS is lower than that in the CoMP-CAS. However, when the cell-edge mobile stations (MSs) have a low transmission power, the lower complexity MR-FFR-DAS relying on the simple single-cell processing may outperform the CoMP-CAS by using the proposed soft-combining-based probabilistic data association (SC-PDA) receiver, despite the fact that the latter scheme is more complex and incurs a higher cooperation overhead. Furthermore, the benefits of the SC-PDA receiver may be enhanced by properly selecting the MRs' positions. Additionally, we show that the performance of the cell-edge MSs roaming near the angular direction halfway between two adjacent remote antennas (i.e., the “worst-case direction”) of the MR-FFR-DAS may be more significantly improved than that of the cell-edge MSs of other directions by using multiuser power control, which also improves the fairness among cell-edge MSs. Our simulation results show that, given a moderate MS transmit power, the proposed MR-FFR-DAS architecture employing the SC-PDA receiver is capable of achieving significantly better bit error rate (BER) and effective throughput across the entire cell-edge area, including even the worst-case direction and the cell-edge boundary, than the CoMP-CAS architecture. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of amplify-and-forward (AF) relaying for multiple-input–multiple-output (MIMO) multiuser relay networks, where each source transmits multiple data streams to its corresponding destination with the assistance of multiple relays. Assuming realistic imperfect channel state information (CSI) of all the source–relay and relay–destination links, we propose a robust optimization framework for the joint design of the source transmit precoders (TPCs), relay AF matrices and receive filters. Specifically, two well-known CSI error models are considered, namely, the statistical and the norm-bounded error models. We commence by considering the problem of minimizing the maximum per-stream mean square error (MSE) subject to the source and relay power constraints (min–max problem). Then, the statistically robust and worst-case robust versions of this problem, which take into account the statistical and norm-bounded CSI errors, respectively, are formulated. Both of the resultant optimization problems are nonconvex (semi-infinite in the worst-case robust design). Therefore, algorithmic solutions having proven convergence and tractable complexity are proposed by resorting to the iterative block coordinate update approach along with matrix transformation and convex conic optimization techniques. We then consider the problem of minimizing the maximum per-relay power subject to the quality-of-service (QoS) constraints for each stream and the source power constraints (QoS problem). Specifically, an efficient initial feasibility search algorithm is proposed based on the relationship between the feasibility check and the min–max problems. Our simulation results show that the proposed joint transceiver design is capable of achieving improved robustness against different types of CSI errors when compared with nonrobust approaches. [ABSTRACT FROM AUTHOR]

This paper studies the optimal transmission of multimedia progressive sources, which require unequal target error rates in their bitstream, over multiple-input–multiple-output (MIMO) channels. First, we derive the information outage probability expression of a space–time code for an arbitrarily given piecewise-linear diversity–multiplexing tradeoff (DMT) function and the conditions for the existence of a crossover point of the information outage probability curves of the space–time codes. We prove that as long as the crossover point of the outage probabilities exists, as spectral efficiency increases, the crossover point in the signal-to-noise ratio (SNR) monotonically increases, whereas that of the outage probability monotonically decreases. This analysis can be applied to any space–time code, receiver, and propagation channel with a given DMT function. As a specific example, we analyze the two-layer diagonal Bell Labs space–time architecture (D-BLAST) with a group zero-forcing receiver, the vertical BLAST (V-BLAST) with a minimum mean-square error receiver, and orthogonal space–time block codes (OSTBCs), and prove the monotonic behavior of the crossover point for those codes. Based on that, with respect to D-BLAST, V-BLAST, and OSTBC, we derive a method for the optimal space–time coding of a sequence that contains numerous progressive packets. We show that by employing the optimization method rather than exhaustive search, the computational complexity involved with optimal space–time coding can be exponentially reduced without losing any peak SNR performance. [ABSTRACT FROM AUTHOR]