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In this paper, we first derive the channel capacity of the full-duplex spatial modulation (FD-SM) system and its upper and lower bounds. Furthermore, different from the traditional optimization-driven decision, we use the data-driven prediction method to solve the transmit antenna selection (TAS) problem in the FD-SM system. Specifically, two novel TAS methods based on the support vector machine (SVM) and deep neural network (DNN) are proposed for reducing the effect of residual self-interference (RSI) on the FD-SM system performance. In our design, we propose a novel feature extraction method based on the principal component analysis (PCA) to help the proposed classifiers improve training. Our simulation results show that our data-driven TAS schemes can approach the optimal performance achieved by exhaustive search while significantly reducing complexity. [ABSTRACT FROM AUTHOR]

Compact MIMO systems often suffer from degraded channel capacity due to spatial correlation. To overcome this issue, we propose a formulation for the channel capacity of a compact MIMO system that directly links it to the geometry of a pixelated surface embedded into the MIMO system. This formulation allows us to maximize the channel capacity of the MIMO system and straightforwardly obtain the optimum geometry for the pixelated surface that reduces spatial correlation. The key step in obtaining the formulation is to link the pixelated surface geometry to an impedance matrix that allows us to obtain an expression for the systems channel capacity. The formulation is general and can be applied to a wide variety of MIMO antenna systems and geometries. To demonstrate the versatility of the approach, we include a design for a compact 4-port planar inverted-F antenna (PIFA) array integrated with a pixelated surface. Simulations and experiments are provided to evaluate the performance of the compact MIMO system with and without optimization of the surface. It is shown that optimizing the geometry of the pixelated surface can increase channel capacity by 13% and energy efficiency by 19.9% compared to the system without optimization. The importance of the approach is that it provides a link between communication and electromagnetic formulations of MIMO antenna systems. [ABSTRACT FROM AUTHOR]

In this correspondence, we consider an amplify-and-forward relay network in which relayed information is overheard by an eavesdropper. In order to confound the eavesdropper, a wireless-powered jammer is also considered which harvests energy from a multiple-antenna source. We proposed a new secure beamforming scheme in which beamforming vector is a linear combination of the energy beamforming (EB) and information beamforming (IB) vectors. In particular, we present a new closed-form solution for the proposed beamforming vector which is shown to achieve a near-optimal secrecy capacity for asymptotic regime of a large number of antennas at the source. Moreover, it is also demonstrated that the proposed beamforming vector achieves significantly higher secrecy rate as compared to the trivial EB and IB vectors. A tight closed-form approximation for the ergodic secrecy rate is also derived for a large number of antennas. Finally, numerical examples and simulations are provided which validate our analytical results. [ABSTRACT FROM AUTHOR]

This paper analyses the experimentally-assessed dual-polarized (DP) mobile channel in a tunnel environment at 1.35 GHz under traffic conditions. We investigate the impact of antenna polarization and radiation pattern on the non-stationary vehicle-to-infrastructure (V2I) channel. Basic channel evaluation metrics are examined including path gain, co-polarization ratio (CPR), and cross-polarization discrimination (XPD). In addition, the stationarity region is estimated using the channel correlation function approach, and used to calculate the time-varying delay and Doppler power profiles. Statistical models are presented for parameters like CPR, XPD, RMS delay and Doppler spreads, where the lognormal distribution provides the best fit. The polarization and the opening angle of the antennas into the propagation channel are found to strongly influence the observed non-stationarity of the channel. They impact the degree of multipath richness that is captured, thus providing different path gain, delay and Doppler spreads. Based on our analysis, the directional antenna with vertical polarization provides the longest stationarity time of 400 ms at 90 km/h, as well as the highest path gain and lowest dispersion. Furthermore, the DP channel capacity is calculated and its dependence on different normalization approaches is investigated. We propose a more accurate normalization for the DP channels that takes the conservation of energy into account. Moreover, the subchannels correlation coefficients are determined. While the condition number is found to be low on average, the correlation results show high correlation among the DP subchannels. As conclusion, we show how the CPR and XPD play the main role in providing multiplexing gain for DP tunnel channels. [ABSTRACT FROM AUTHOR]

In this paper, three power allocation (PA) schemes for distributed antenna (DA) systems with orthogonal frequency division multiplexing over multipath fading channels are presented. Unlike the conventional total power constraint, power constraints for individual antenna ports are considered. By maximizing the channel capacity of the system subject to per-antenna maximum power constraints, the optimization problem for the PA design is formulated. Based on the block coordinate descent method, an optimal PA scheme to the optimization problem is derived. Considering that the optimal scheme is an iterative algorithm, a suboptimal PA scheme is derived by maximizing an upper bound of the channel capacity, which provides a closed-form PA procedure. Interestingly, this suboptimal scheme can obtain almost the same performance as the optimal one for large number of subcarriers, low maximum power, and/or small number of DA ports. To reduce the performance loss, a modified suboptimal scheme with closed-form PA is developed, and it has the capacity performance very close to the optimal scheme. Computer simulations verify the effectiveness of the three proposed schemes. [ABSTRACT FROM AUTHOR]

Array beamforming (BF) has received considerable attention as a means of anti-jamming by combining desired signals constructively and jamming signals destructively. However, even with BF, the state-of-the-art reactive jammer (RJ) can easily detect the target channels from the leakage of the transmit power and concentrate its own power to the detected band to degrade communication performance. In this paper, we attempt to mitigate this problem by exploiting fake information, the so-called decoy signal, and proper BF at the transmitter and the receiver, and show that it is possible to deceive the RJ into allocating a large portion of its own power to the decoy signal. In this regard, we attempt to maximize the signal-to-jamming-plus-noise power ratio (SJNR) at the receiver and the signal-to-leakage power ratio at the transmitter by optimizing the BF strategy. Through numerical simulations measuring the SJNR and the channel capacity, we demonstrate the effectiveness of the proposed BF scheme, especially in high-power RJ environments. [ABSTRACT FROM AUTHOR]

In space modulation techniques (SMTs), data bits are transmitted through modulating spatial and signal symbols. Signal symbols are ordinary complex symbols drawn from an arbitrary constellation diagram, such as quadrature amplitude modulation. Yet, spatial symbols represent the different channel paths from multiple transmit antennas to all receive antennas in a multiple-input multiple-output (MIMO) system. At each particular time instant, one or more of these channel paths is used to transmit the signal symbol and all other paths remain inactive. The receiver jointly determines the transmitted symbol and the considered channel paths to retrieve the information bits. This is unlike any conventional wireless communication technique, and special information-theoretic treatment is needed. In this paper, the theoretical channel capacity of SMTs is deduced. The conditions under which such capacity can be achieved are derived and discussed. Mutual information results for space shift keying, spatial modulation, generalized spatial modulation, and quadrature spatial modulation, as illustrative examples of SMTs, over several fading channels are reported and thoroughly discussed. The obtained Monte Carlo simulation results validate the accuracy of the conducted analysis. It is demonstrated that SMTs can achieve substantial gains as compared to the conventional MIMO systems. Such gains are attainable with proper design of signal symbols for each specific fading channel. [ABSTRACT FROM AUTHOR]

Given the increased amount of data traffic in in-vehicle networks with more systems now included in vehicles, enormous amounts of research have recently focused on providing reliable and inexpensive quality of service for in-vehicle communication systems. To support high-speed data processing while maintaining backward compatibility with controller area network (CAN) for in-vehicle communication systems, the turbo controller area network (TURBO CAN) was proposed, combining the standard baseband CAN signal with a passband modulated signal. In this paper, we demonstrate both an improvement in the performance and the validity of the backward compatibility of the TURBO CAN system. To be specific, we provide passband channel modeling of the CAN system based on the channel gain and the noise characteristics as measured in an actual vehicle environment. Using these measurements, we also provide proper criteria for determining the power constraint of the passband signal to achieve a highly compatible system by analyzing the channel capacity of TURBO CAN as well as the bit error rate of a standard CAN receiver. [ABSTRACT FROM AUTHOR]

The ongoing increasing traffic in the era of big data yields unprecedented demands in user experience and network capacity expansion. The users of next generation mobile networks (5 G) should be able to use 3GPP, IEEE, and other technologies simultaneously. The integration of multiple radio access technologies (RATs) of licensed or unlicensed bands has been widely deemed as a cost-efficient way to greatly increase the network capacity. In this paper, we propose a smart aggregated RAT access (SARA) strategy with aim of maximizing the long-term network throughput while meeting diverse traffic quality of service (QoS) requirements. We consider the scenario that users with different QoS requirements access to a heterogeneous network with coexisting cellular-WiFi. In order to maximize system throughput while meeting diverse traffic QoS requirements in such a complex and dynamic environment, we exploit multiagent reinforcement learning to perform RAT selection in conjunction with resource allocation for individual user access requests, through sensing dynamic channel states and traffic QoS requirements. In SARA, we first use Nash Q-learning to provide a set of feasible RAT selection strategies while decreasing the strategy space in learning process, and then employ Monte Carlo tree search (MCTS) based Q-learning to perform resource allocation. Numerical results reveal that the network throughput can be maximized while meeting various traffic QoS requirements with limited number of searches by using our proposed SARA algorithm. For bulk arrival access requests, a suboptimal solution can be obtained as high computational complexity is incurred for achieving global optimality. Another attractive feature of SARA is that a tradeoff between the solution optimality and learning time can be readily made by terminating the search of MCTS according to the time constraint. Compared with traditional WiFi offloading schemes, SARA can significantly improve network throughput while guaranteeing traffic QoS requirements. [ABSTRACT FROM PUBLISHER]

Device-free wireless localization and activity recognition is an emerging technique, which could estimate the location and activity of a person without equipping him/her with any device. It deduces the state of a person by analyzing his/her influence on surrounding wireless signals. Therefore, how to characterize the influence of human behaviors is the key question. In this paper, we explore and exploit a radio image processing approach to better characterize the influence of human behaviors on Wi-Fi signals. Traditional methods deal with channel state information (CSI) measurements on each channel independently. However, CSI measurements on different channels are correlated, and thus lots of useful information involved with channel correlation may be lost. This motivates us to look on CSI measurements from multiple channels as a radio image and deal with it from the two-dimensional perspective. Specifically, we transform CSI measurements from multiple channels into a radio image, extract color and texture features from the radio image, adopt a deep learning network to learn optimized deep features from image features, and estimate the location and activity of a person using a machine learning approach. Benefits from the informative and discriminative deep image features and experimental results in two clutter laboratories confirm the excellent performance of the proposed system. [ABSTRACT FROM PUBLISHER]

Small cells deployment is one of the most significant long-term strategic policies of the mobile network operators. In heterogeneous networks (HetNets), small cells serve as offloading spots in the radio access network to offload macro users (MUs) and their associated traffic from congested macrocells. In this paper, we perform analytical analysis and investigate how the radio channel propagation impairments such as multipath fading, shadowing, and small cell base station density affect MUs’ offloading to small cells network (SCN). In particular, we exploit composite fading channels in our evaluation when an MU is offloaded to SCN with varying small cell base station density in the stochastic geometry HetNets framework. We derive the expressions for service outage probability (equivalently service coverage probability) of the MU in macro cell network and SCN under two different composite fading scenarios, viz., Nakagami-Lognormal channel fading and time-shared (combined) shadowed/unshadowed channel fading. We propose efficient approximations for the probability density functions of the channel fading (power) for the aforementioned composite fading distributions that do not have closed-form expressions employing Gauss–Hermite integration and finite exponential series, respectively. Finally, the service outage probability performance of MU with and without offloading services is analyzed under various system parameters and channel fading conditions. [ABSTRACT FROM PUBLISHER]

This paper investigates the slow fading single-antenna wiretap channel with imperfect channel state information (CSI) and studies an on–off transmission scheme with fixed communication rate, secrecy rate, and transmit power for maximizing the secrecy throughput under the constraints of secrecy outage probability (SOP) and reliability outage probability (ROP). We first solve this problem in a special case without ROP constraint for which the optimal secrecy throughput is obtained under SOP constraint. The result for the special case gives us an upper bound for the secrecy throughput with imperfect CSI. With the help of this special case, a general case with ROP constraint is studied. In this case, the problem is transformed into a one-dimensional (1-D) search problem on a finite interval, which can be solved either by the exhaustive 1-D search to obtain the optimal solution or by the golden search method (GSM) to obtain a suboptimal solution. Simulation results are finally presented to validate the theoretical analysis and show that the performance obtained by using the GSM based 1-D search is very close to that of exhaustive 1-D search. [ABSTRACT FROM PUBLISHER]

Leaky coaxial (LCX) cable is widely used in wireless communication systems as an antenna, especially for a long and narrow area called the linear-cell environment. The general usage of LCX cable is that it can be treated as one antenna. To configure a multiple-input–multiple-output (MIMO) system, it requires more than one LCX cable. In this paper, we propose a simple design in which one single LCX cable can be used as two antennas. Therefore, the proposal reduces the cost and spacing requirement and releases the space requirement of MIMO deployment for wireless application over linear-cell environments. We will study the capacity of the proposed LCX–MIMO system using equal power (EP) allocation and water-filling power allocation and compare its capacity with the conventional MIMO system using monopole antennas. The capacity results over the 2.4 GHz band and the 5 GHz band show that the proposed LCX–MIMO channel has better capacity than that of using monopole antennas over linear-cell environments. In particular, it can achieve more capacity improvement than that of channel using monopole antennas with the simple EP allocation. The throughput experiments over 5 GHz also show that our proposal can achieve the higher and stable throughput over the radiation coverage of LCX cable. [ABSTRACT FROM AUTHOR]

Efficient utilization of wireless communication resources and increases in the capacity of the communication networks have become very crucial claims for next-generation cellular networks. Full-duplex (FD) is a very promising technique that allows for the efficient use of wireless communication resources, given that the self-interference level can be suppressed to an acceptable level. In this paper, we consider a simple FD communication system, consisting of one FD access point (AP) and two half-duplex (HD) mobile users, and investigate when it is more advantageous for the communication network to operate in FD or HD multiuser multiple-input multiple-output (MIMO) mode. Since FD transmission is degraded by self-interference while HD suffers from spatial correlation between MIMO antennas, which causes rate loss, we study the effect of both the self-interference cancelation parameter at the FD AP and the mutual distance between the HD users on FD performances and the effect of the spatial correlation coefficient on HD MIMO. Afterward, a switching criterion is proposed, which chooses the operation mode that maximizes the downlink channel capacity while maintaining the uplink channel capacity at a certain level. Subsequently, based on our study of the system's parameters that affect the performance of both FD and HD, theoretical thresholds for these parameters are derived. Finally, numerical analysis is presented, verifying the validity of the optimization problem solution and the derived thresholds. [ABSTRACT FROM PUBLISHER]

In this paper, analytical expressions for the channel capacity, channel cutoff rate, and achievable bandwidth efficiency associated with $M$-ary signaling and Joint Fading Two-path Shadowing (JFTS) fading/shadowing channel model that characterize mobility-constrained indoor propagation scenarios are derived. Expressions for the bandwidth efficiency of a JFTS fading channel involve infinite-series summation since the probability density function of the JFTS signal-to-noise ratio (SNR) contains infinite series. We derive lower and upper bounds on the errors resulting from truncating the infinite series in the bandwidth efficiency expression. The cutoff rate and bandwidth efficiency analysis can be used to demonstrate how much throughput can be practically achieved when $M$-ary signaling techniques are implemented over indoor composite fading/shadowing channel conditions. Simulation results show that in order to achieve 3 bits/symbol, the average SNR for a 16-quadrature-amplitude-modulation (16-QAM) system requires almost 10 dB more for a JFTS channel model compared with a traditional Rayleigh channel model, thus reinforcing the necessity of using proper channel models for indoor communication systems. [ABSTRACT FROM PUBLISHER]

We study secure transmission considering the practical scenario in which only outdated knowledge of the legitimate receiver's channel and statistical knowledge of the eavesdropper's channel are available at the transmitter. Conditioned on the limited channel knowledge, we adopt an on–off secure transmission scheme and propose a versatile strategy to determine the codeword transmission rate. We first analyze the outage performance of the system and then provide the design of optimal wiretap code parameters maximizing the secrecy throughput. Compared with the existing solution in the literature, the proposed secure transmission design enlarges the achievable reliability–security region and increases the maximum secrecy throughput. [ABSTRACT FROM PUBLISHER]

This paper shows that the recently proposed $\kappa$– $\mu$ shadowed fading model includes, besides the $\kappa$– $\mu$ model, the $\eta$– $\mu$ fading model as a particular case. This has important relevance in practice, as it allows for the unification of these popular fading distributions through a more general, yet equally tractable, model. The convenience of new underlying physical models is discussed. Then, we derive simple and novel closed-form expressions for the asymptotic ergodic capacity in $\kappa$– $\mu$ shadowed fading channels, which illustrate the effects of the different fading parameters on the system performance. By exploiting the unification here unveiled, the asymptotic capacity expressions for the $\kappa$– $\mu$, $\eta$– $\mu$, and Rician shadowed fading models are also obtained in closed form as special cases. [ABSTRACT FROM PUBLISHER]

A polar coding scheme is proposed for reliable communication over channels with bit-interleaved coded modulation (BICM). In an ideal information-theoretic model, BICM schemes are modeled as a set of multiple binary-input channels that experience different reliabilities. This model is referred to as multichannel. The conventional scheme for encoding information over multi-channels is to encode separately across the individual constituent channels, which requires multiple encoders and decoders. As opposed to the conventional scheme, we take advantage of the recursive structure of polar codes to construct a unified compound polar code. The proposed scheme has a single encoder and decoder and can be used over multi-channels, in particular over channels with BICM. We prove that the scheme achieves the multi-channel capacity with the same error decay rate as in Arıkan's polar codes. Furthermore, due to more levels of channel polarization, we obtain a better finite block length performance compared with the separated polarization scheme. This is confirmed through various simulations over the binary erasure channel and with transmissions over additive white Gaussian noise (AWGN) and fast fading channels with BICM and different modulation orders. [ABSTRACT FROM AUTHOR]

This paper investigates the scenario in which a weak desired signal reaches a poorly selective receiver along with a high-powered pulsed radar occupying a neighboring channel. Traditionally, an automatic gain control (AGC) is used to fit the high-powered radar into the dynamic range of the receiver. However, this approach desensitizes the receiver because it also sacrifices the signal-to-noise ratio (SNR) of the desired signal. We propose the use of an auxiliary receive path to address this problem of strong neighboring channel signals. In this method, receiver gain is not lowered to avoid clipping. Instead, the strong signal is allowed to clip and distort the desired signal. This paper shows that only a subset of the symbols contained in the desired signal will be distorted; hence, redundancy within the desired signal (due to forward error correction) can be exploited to “fill the gaps” created by the distortion. The auxiliary path samples the envelope of the strong neighboring-channel signal and informs the decoder about which symbols are distorted (or “bad”) and which symbols are not distorted (or “good”). This additional information is shown to improve the estimation performance of the decoder in the presence of high-powered neighboring-channel radar. Using simulation and hardware-based experiments, it is shown that auxiliary-path-based receivers can obtain a significantly better throughput performance than AGC-based receivers. [ABSTRACT FROM AUTHOR]

This paper discusses over-the-air (OTA) testing for multiple-input–multiple-output (MIMO) capable terminals with emphasis on wideband MIMO channel capacity analysis in a multiprobe anechoic chamber setup. In the literature, the spatial correlation simulation accuracy at the receiver (Rx) side has been used to determine the test area size for a limited number of probes. However, it is desirable that the test area size is defined in terms of data rate deviation of the simulated channel in the laboratory from that of the target channel model. This paper reports MIMO capacity analysis results for wideband spatiotemporal channel models, with emphasis on the impact of the spatial correlation at the transmit (Tx) side, the channel model, and the spatial correlation at the Rx side on the capacity simulation accuracy. Simulation results show that the number of probes is irrelevant to capacity simulation accuracy when the spatial correlation at the Tx side is in the high region (e.g., \rho > \mbox0.7). Furthermore, when correlation at the Tx side is low, the spatial correlation accuracy is less critical with small correlation at the Rx side. The simulation results are further supported by measurements in a practical multiprobe anechoic chamber setup. The capacity simulation accuracy is shown to be a valid measure to determine the test area size. [ABSTRACT FROM AUTHOR]

The ergodic and outage channel capacity of different optimal and suboptimal combinations of transmit power and modulation rate adaptation strategies over a joint fading and two-path shadowing (JFTS) fading/shadowing channel is studied in this paper. Analytically tractable expressions for channel capacity are obtained, assuming perfect channel side information (CSI) at the receiver and/or the transmitter with negligible feedback delay. Furthermore, the impacts of the JFTS parameters on the channel capacity achieved by these adaptive transmission techniques are determined. [ABSTRACT FROM PUBLISHER]

Hierarchical modulation (HM), which is also known as layered modulation, has been widely adopted across the telecommunication industry. Its strict backward compatibility with single-layer modems and its low complexity facilitate the seamless upgrading of wireless communication services. The potential employment of HM in cooperative communications has the promise of increasing the achievable throughput at low power consumption. In this paper, we propose a single-relay-aided hierarchical-modulation-based cooperative communication system. The source employs a pair of turbo trellis-coded modulation (TTCM) schemes relying on specially designed HM, whereas the relay invokes the decode-and-forward (DAF) protocol. We have analyzed the system's achievable rate, as well as its bit error ratio (BER), using Monte Carlo simulations. The results demonstrate that the power consumption of the entire system is reduced to 3.62 dB per time slot (TS) by our scheme. [ABSTRACT FROM PUBLISHER]

An analytical study of selection combining (SC) diversity under \eta-\mu multipath fading is presented, considering that the $\mu$ parameter takes integer values. Closed-form expressions are derived for the statistics of the signal-to-noise ratio (SNR) at the combiner output and for the error rate of some relevant $M$-ary modulation schemes. Additionally, closed-form expressions are also derived for the channel capacity, considering different adaptive transmission policies. It is shown that, if the number of receive branches is high enough, severe fading may result in an increased channel capacity for all the considered transmission strategies due to the branch selection and the higher channel variability. This is in sharp contrast to the behavior of capacity in single-channel reception schemes. Monte Carlo simulations have been carried out to validate the derived analytical expressions. [ABSTRACT FROM PUBLISHER]

Multimedia encoders typically generate symbols having a wide range of legitimate values. In practical mobile wireless scenarios, the transmission of these symbols is required to be bandwidth efficient and error resilient, motivating both source coding and channel coding. However, separate source and channel coding (SSCC) schemes are typically unable to exploit the residual redundancy in the source symbols, which cannot be totally reduced by finite-delay finite-complexity schemes, hence resulting in a capacity loss. Until recently, none of the existing joint source and channel codes (JSCCs) were suitable for this application since their decoding complexity rapidly increases with the size of the symbol alphabet. Motivated by this, we proposed a novel JSCC referred to as the unary error correction (UEC) code, which is capable of exploiting all residual redundancy and eliminating any capacity loss, while imposing only a moderate decoding complexity. In this paper, we show that the operation of the UEC decoder can be dynamically adapted to strike an attractive tradeoff between its decoding complexity and its error correction capability. Furthermore, we conceive the corresponding 3-D EXtrinsic Information Transfer (EXIT) charts for controlling this dynamic adaptation, as well as the decoder activation order, when the UEC code is serially concatenated with a turbo code. In this way, we expedite iterative decoding convergence, facilitating a gain of up to 1.2 dB compared with both SSCC and to its nonadaptive UEC benchmarkers, while maintaining the same transmission bandwidth, duration, energy, and decoding complexity. [ABSTRACT FROM PUBLISHER]

This paper investigates the capacity of radio channels when iterative channel estimation, data detection, and decoding are employed. Knowing the capacity gain from iterative detection versus purely pilot-based channel estimation helps a designer compare the performance of an iterative receiver against a noniterative receiver and select the best balance between performance and cost. A bound is put on the linear minimum mean square error (LMMSE) channel estimation error, based on which a bound on the capacity is obtained. The attainable capacity is related to the channel estimation error of the receiver. The bounds take into account the uncertainty in symbol detection on channel estimation and incorporate the effect of channel estimation error on channel capacity. The interaction between the symbol detector and the decoder is analytically characterized and depicted in an extrinsic information transfer (EXIT) chart, where a bound on the detector curve is found. With optimal LMMSE pilot-based channel estimation, the results of this paper demonstrate that iterative channel estimation provides insignificant capacity advantage at fading rates below 1% of the symbol rate, although a computational-cost gain is still available. Iterative channel estimation provides a capacity benefit if suboptimal pilot signaling is used to provide initial channel estimates. [ABSTRACT FROM PUBLISHER]

An orthogonal frequency-division multiple access (OFDMA)-based cognitive radio network (CRN) is considered where cognitive radio users (CRUs) can only access the frequency bands not being occupied by primary users (PUs) while keeping the cross-channel interference to each PU under a specified threshold. In this paper, we investigate the ergodic sum capacity of all CRUs in OFDMA-based networks and consider the constraints on the long-term transmit power of all CRUs, the long-term interference thresholds of PUs, and the statistical proportional fairness of all CRUs. In OFDMA-based CRNs, the number of available subchannels is smaller than that of CRUs in some OFDM symbol durations. To deal with this time-varying nature of available spectrum resource and achieve the ergodic sum capacity of all CRUs, we propose an optimal resource-allocation algorithm under the given constraints. Simulation results show that the proposed algorithm can achieve substantial capacity gains for CRUs over the traditional resource-allocation algorithm and maintain the statistical proportional rate constraints of all CRUs. [ABSTRACT FROM AUTHOR]

In this paper, we present a two-phase cooperative transmission and relay scheme between a primary network and a secondary network to address spectrum underutilization and spectrum inefficiency. By placing orthogonally dual-polarized antennas (ODPAs) and enabling polarization signal processing functionalities at secondary users (SUs), the cochannel interference caused by multiple independent transmissions from primary and secondary networks can be mitigated. A framework design, including system description, signaling plan, and key enabling techniques, is studied to perform Polarization Enabled Active CoopEration (PEACE) between primary users (PUs) and SUs. In the presented PEACE framework, polarization zero forcing and oblique projection polarization filtering are utilized to address interference from SUs to the primary network and to separate SUs signals, respectively. We provide theoretical analysis to maximize the sum achievable channel capacity under certain transmission rates and power constraints to evaluate PEACE performance. To solve the original nonconvex optimization problem, it is effectively approximated to a convex problem, which can be tackled quite efficiently. Closed-form solutions to optimal power allocation of SUs are, respectively, obtained by a centralized algorithm and a distributed algorithm. Extensive numerical results are given to illustrate the performance and to examine the features of the PEACE framework and the proposed algorithms. [ABSTRACT FROM PUBLISHER]

Higher order statistics (HOS) of the channel capacity provide useful information regarding the level of reliability of signal transmission at a particular rate. In this paper, we propose a novel and unified analysis, which is based on the moment-generating function (MGF) approach, to efficiently and accurately compute the HOS of the channel capacity for amplify-and-forward (AF) multihop transmission over generalized fading channels. More precisely, our easy-to-use and tractable mathematical formalism requires only the reciprocal MGFs of the transmission hop signal-to-noise ratio (SNR). Numerical and simulation results, which are performed to exemplify the usefulness of the proposed MGF-based analysis, are shown to be in perfect agreement. [ABSTRACT FROM PUBLISHER]

Cooperative communications enhance the performance of wireless networks by allowing nodes to cooperate with each other to achieve spatial diversity gains. To obtain cooperation gains, appropriate relay node(s) should be selected according to network topology and channel state information (CSI). However, in ad hoc wireless networks, the CSI is random, and the network topology is dynamic. This complicates relay selection, and in turn, makes it difficult to implement cooperative communications in ad hoc wireless networks. To tackle the issue, this paper proposes blind cooperative communications (BCC) for multihop ad hoc wireless networks. In BCC, intermediate nodes and the destination node in a multihop path first listen and cache the data from two-hop-away upstream nodes, and then combine the cached data with the data forwarded by the upstream to obtain diversity gains. The performance of BCC is evaluated by analysis and simulations to show that BCC can significantly increase the packet delivery ratio (PDR) and the average end-to-end throughput (AET). Compared with existing cooperation methods, BCC requires neither CSI and topology information nor additional signaling overheads, making it extremely easy to implement in dynamic multihop ad hoc wireless networks. [ABSTRACT FROM AUTHOR]

It has been shown that adaptive power allocation can provide a substantial performance gain in wireless communication systems when perfect channel state information (CSI) is available at the transmitter. In the case when only imperfect CSI is available, the performance may significantly degrade, and robust power-allocation schemes are developed to save this kind of degradation. In this paper, we investigate power-allocation strategies for multicarrier systems, in which each subcarrier employs single amplify-and-forward (AF) relaying scheme. Optimal power-allocation schemes are proposed by maximizing the approximated channel capacity under an aggregate power constraint (APC) and a separate power constraint (SPC). By comparison with the uniform power-allocation (UPA) scheme and the best channel power-allocation (BCPA) scheme, we confirm that both the APC and SPC schemes achieve a performance gain over benchmark schemes. In addition, the impact of channel uncertainty is also considered in this paper by modeling the uncertainty regions as bounded sets, and results show that the uncertainty can degrade the worst case performance significantly. [ABSTRACT FROM AUTHOR]

In this paper, the capacity of orthogonal frequency-division multiple-access (OFDMA) networks is evaluated when serving mobile TV traffic. To introduce the service within the network, we develop analytical cross-layer models to assess the performance of the system when carrying TV calls over unicast connections. The presented cross-layer analysis is general and can be adapted to all types of multimedia services. We then focus on a TV-specific capacity analysis, exploiting the possibility of broadcasting TV channels over point-to-multipoint (PtM) connections. This includes investigating an enhanced broadcast solution where the modulation is dynamically adapted to the radio conditions of connected TV users. The more complete broadcast solution over single-frequency networks (SFNs) is then evaluated, based on a novel physical-layer model integrating the combined signal gain from neighboring cells. We finally show how to maximize the system capacity through a secondary usage of the SFN resources by elastic traffic. The presented models are evaluated using numerical applications and further validated through network simulations. [ABSTRACT FROM PUBLISHER]

In this paper, we extend the interference channel with degraded message sets model by introducing multiple secondaries. The new model allows for multiple concurrent transmissions in a wireless network by employing dirty paper and superposition coding. We apply the proposed scheme to the communication between nodes in a wireless mesh network (WMN). The cases of different WMN. topologies are analyzed, and numerical results show that considerable capacity gains are achieved when using the proposed model with multiple secondaries. [ABSTRACT FROM AUTHOR]