Proposed Joint Scheme Research Articles

Energy Efficient Resource Allocation for Uplink RIS-Aided Millimeter-Wave Networks With NOMA

In this paper, energy efficiency (EE) is maximized for the reconfigurable intelligent surface (RIS) aided millimeter-Wave (mmWave) networks with non-orthogonal multiple access (NOMA) and multiple mobile devices. To this end, we first propose the EE optimization, under the constraints of maximum power, minimal rate of devices and constant modulus of beamforming (BF) vectors. Then, the joint resource allocation scheme of power allocation (PA) and BF is designed. Specifically, given PA, an effective iterative algorithm based on the majorizationminimization, concave-convex procedure and block coordinate descent (BCD) is presented to obtain closed-form solutions of suboptimal passive BF (PBF) and analog BF (ABF) for each iteration. Then, given PBF and ABF, an effective iterative algorithm based on the successive convex approximation, BCD and Dinkelbach methods is derived to achieve suboptimal closedform PA for each iteration. By incorporating these two algorithms into the BCD method, a joint optimization algorithm for EE maximization is presented. As a result, joint resource allocation of PA, PBF and ABF is attained. Besides, the convergence and complexity of the algorithms are analyzed. For comparison, the benchmark scheme based on the multidimensional search method and artificial bee colony algorithm is also presented. Simulation results show that the proposed joint scheme is effective and higher EE can be obtained with lower complexity.

On solving the cross-dock door assignment problem

A class of strong lower bounds on the solution value of a Linearised Integer Programming reformulation is introduced for the binary quadratic optimisation model to assign origin and destination nodes to strip and stack doors, resp., in a cross-dock infrastructure. The goal is to minimise the transportation cost of the commodities to be handled at the cross-dock. Strip- and stack-related decomposition submodels are developed by taking benefit of the Integer Linearisation Property that appears in the new model. A linear search heuristic is also provided for obtaining feasible solutions by exploiting the special structure of the problem. We present an extensive computational study on a testbed of 55 instances to show that the proposed joint scheme for lower bounding and feasible solution providing is very efficient. The results obtained by our proposal are similar to those obtained by CPLEX in the 50 instances taken from the literature, but usually the time is much smaller for the large instances. The comparison with CPLEX is particularly good for the new five largest instances, which make it very promising for its application in real-life cases.

User Grouping, Precoding Design, and Power Allocation for MIMO-NOMA Systems

In this paper, we study user grouping, precoding design, and power allocation for multiple-input multiple-output (MIMO) nonorthogonal multiple access (NOMA) systems. An optimization problem is formulated to the maximize the sum rate under a transmit power constraint at a base station and rate constraints on users, which are nonconvex and combinatorial and thus very challenging to solve. To tackle this problem, we carry out the optimization in two steps. In the first step, exploiting the machine learning technique, we develop an efficient iterative algorithm for user grouping and precoding design. In the second step, we develop a power-allocation scheme in closed form by recasting the original problem into a useful and tractable convex form. The numerical results demonstrate that the proposed joint scheme, including user grouping, precoding design, and power allocation, considerably outperforms the existing schemes in terms of sum rate maximization, which increases the sum-rate up to 8–18%. In addition, the results show the larger the number of antennas or users, the bigger the performance gap, at the cost of less computational complexity.

Throughput Maximization in Cloud-Radio Access Networks Using Cross-Layer Network Coding

Cloud radio access networks (C-RANs) are promising paradigms for the fifth-generation (5G) networks due to their interference management capabilities. In a C-RAN, a central processor (CP) is responsible for coordinating multiple Remote Radio Heads (RRHs) and scheduling users to their radio resource blocks (RRBs). In this paper, we develop a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cross-layer network coding (CLNC)</i> approach that proposes to optimize RRH’s transmit powers and user’s rates in making the coding decisions. As such, cross-layer throughput of the network is maximized. The joint user scheduling, file encoding, and power adaptation problem is solved by designing a subgraph for each RRB, in which each vertex represents potential user-RRH associations, encoded files, transmission rates, and power levels (PLs) for one RRB. It is then shown that the C-RAN throughput maximization problem is equivalent to a maximum-weight clique problem over the union of all such subgraphs, called herein the CRAN-CLNC graph. Numerical results revealed that the proposed joint and iterative schemes offer improved throughput performances as compared to the existing algorithms in the literature. Compared to our proposed joint scheme, our proposed iterative scheme has a certain degradation, roughly in the range of 9%–14%. This small degradation in the throughput performance of the iterative scheme comes at the achieved low computational complexity as compared to the high complexity of the joint scheme.

Strong Coordination Over Noisy Channels

We study the problem of strong coordination of the actions of two nodes $X$ and $Y$ that communicate over a discrete memoryless channel (DMC) such that the actions follow a prescribed joint probability distribution. We propose two novel random coding schemes and a polar coding scheme for this noisy strong coordination problem, and derive inner bounds for the respective strong coordination capacity region. The first scheme is a joint coordination-channel coding scheme that utilizes the randomness provided by the DMC to reduce the amount of local randomness required to generate the sequence of actions at Node $Y$. Based on this random coding scheme, we provide a characterization of the capacity region for two special cases of the noisy strong coordination setup, namely, when the actions at Node $Y$ are determined by Node $X$ and when the DMC is a deterministic channel. The second scheme exploits separate coordination and channel coding where local randomness is extracted from the channel after decoding. The third scheme is a joint coordination-channel polar coding scheme for strong coordination. We show that polar codes are able to achieve the established inner bound to the noisy strong coordination capacity region and thus provide a constructive alternative to a random coding proof. Our polar coding scheme also offers a constructive solution to a channel simulation problem where a DMC and shared randomness are employed together to simulate another DMC. Finally, by leveraging the random coding results for this problem, we present an example in which the proposed joint scheme is able to strictly outperform the separate scheme in terms of achievable communication rate for the same amount of injected randomness into both systems. Thus, we establish the sub-optimality of the separation of strong coordination and channel coding with respect to the communication rate over the DMC.

A Joint Symbol-Detection, Channel-Estimation and Decoding Scheme under Few-Bit ADCs in mmWave Communications.

Few-bit analog-to-digital converter (ADC) is regarded as a promising technique to greatly reduce power consumption of Internet of Things (IoT) devices in millimeter-wave (mmWave) communications. In this work, based on the recently proposed parametric bilinear generalized approximate message passing (PBiGAMP), we propose a new scheme to perform joint symbol detection, channel estimation and decoding. The proposed scheme is flexible to deal with discrete prior on symbols, Gaussian mixture prior on channels and quantized likelihood on observations. Furthermore, we introduce doping factor to control the portion of “extrinsic” and “posterior” information with negligible complexity increase. Since this joint scheme can be implemented via fast Fourier transformation (FFT), the complexity grows only logarithmically. Compared to the benchmark algorithms, numerical results show that the proposed joint scheme can achieve significant performance gain, and demonstrate the effectiveness in dealing with the nonlinear distortion from few-bit ADC.

Joint image compression–encryption scheme using entropy coding and compressive sensing

Recently, compressive sensing (CS)-based joint compression–encryption schemes have been widely investigated due to their high efficiency and good security for images. However, the existing schemes typically have a lower compression ratio (CR), and there may be a flaw during their compression processes. Therefore, in this paper, according to the intrinsic features of images, we propose a novel compression architecture to enhance the CR. Meanwhile, based on this architecture, a joint image compression–encryption scheme using entropy coding and CS is designed to implement a complete compression and encryption process. In this joint scheme, a presented bit-level lossless compression–encryption algorithm based on entropy coding for the higher bit-planes is incorporated to improve the quality of the reconstructed image and ensure the security. Alternately, this joint scheme also contains an improved CS-based lossy compression–encryption algorithm for the lower bit-planes, which can guarantee the efficiency and security. Through the cooperation between the proposed lossless and lossy coding, the higher reconstruction performance can be achieved. SHA-256 is combined with all initial keys in the proposed joint scheme to generate the updated keys for chaos cryptosystem to maintain high security and resist some common attacks. Experimental and analytical results illustrate the superiority of the proposed joint scheme compared with the existing compression–encryption schemes and JPEG, as well as good encryption performance.

Joint Sub-Nyquist Spectrum Sensing Scheme With Geolocation Database Over TV White Space

To maximize spectrum access opportunities for white space devices, incorporating real-time spectrum sensing with geolocation database is a promising approach to enhance detection resolution with reduced computation complexity. Advanced spectrum sensing techniques are needed to quickly and accurately identify spectrum occupancy over a wide frequency range. However, the stringent requirements from wideband signal acquisition and processing pose a major implementation challenge in compact devices with limited energy storage and computation capabilities. In this paper, a hybrid scheme of sub-Nyquist wideband spectrum sensing with geolocation database is proposed to achieve accurate detection of the surrounding spectrum with reduced number of required measurements and computation complexity. Two iterative algorithms are modified to incorporate a priori information from geolocation database, therefore enabling spectrum sensing to be performed only on a limited number of potentially vacant channels over TV white space. Theoretical analyses and simulation results show that the proposed joint scheme speeds up the sensing process with enhanced detection performance and smaller required sampling rate, whereas the updated channel information from wideband spectrum sensing reduces the risk of interferences to the dynamic incumbent users.

Separable authentication in encrypted HEVC video

A joint encryption and authentication scheme for HEVC compressed video is proposed in this work. It produces a HEVC format compliant video stream that permits the authentication process to be carried out irregardless of the video being in the encrypted or plaintext (i.e., decrypted) form. To achieve this separable property, one set of syntax elements within the HEVC standard is utilized to achieve authentication, while another set is exploited for encryption. Specifically, for authentication, information such as coding unit size in each video slice is utilized to generate the authentication code, which is then embedded into each video slice to detect the tampered regions. A two-level authentication method is implemented to facilitate the legitimacy verification process. On the other hand, for video encryption, syntax elements in the HEVC standard including Sign Bins, Transform Skip Bins and Suffix Bins are randomized to perceptually distort the video. Experiment results show that by using the proposed encryption modules, the perceptual quality of the plaintext video can be distorted, and the distorted video can be restored to the original HEVC compressed video. Furthermore, the proposed joint scheme is verified to be viable in detecting and localizing the tampered regions. Finally, a pragmatic comparison among the proposed and conventional joint schemes is performed.

A Joint SMSE Waveform Design and Blind Cyclostationary Based Sensing for Cognitive Radios

Cognitive Radio (CR) presents a lot of challenges with regard to developing the techniques and methodologies to dynamically utilize the unused or underused spectrum. The issue of efficient utilization of radio resources can be implemented unitedly through dynamic waveform design and an efficient spectrum sensing. In this paper, waveform design using spectrally modulated spectrally encoded (SMSE) framework is conjoined with the cyclostationary based sensing technique (CSS) for CR. To identify the free spectrum, an analytical expression of waveform design variables in terms of sensing parameters has been derived. Further, to find the channel occupancy/spectrum holes, a joint CSS and SMSE based test stat has been proposed. The joint test stat offers a better and clear decision by providing a large gap between test stat and the required threshold setting. Finally, to evaluate the receiver performance, receiver operating characteristic (ROC) curves have been plotted which show that the proposed joint scheme achieves a significant performance improvement at lower SNR values when compared with traditionally available detectors.

Joint Design of Massive MIMO Precoder and Security Scheme for Multiuser Scenarios under Reciprocal Channel Conditions

The exploration of the physical layer characteristics of the wireless channel is currently the object of intensive research in order to develop advanced secrecy schemes that can protect information against eavesdropping attacks. Following this line of work, in this manuscript we consider a massive MIMO system and jointly design the channel precoder and security scheme. By doing that we ensure that the precoding operation does not reduce the degree of secrecy provided by the security scheme. The fundamental working principle of the proposed technique is to apply selective random rotations in the transmitted signal at the antenna level in order to achieve a compromise between legitimate and eavesdropper channel capacities. These rotations use the phase of the reciprocal wireless channel as a common random source between the transmitter and the intended receiver. To assess the security performance, the proposed joint scheme is compared with a recently proposed approach for massive MIMO systems. The results show that, with the proposed joint design, the number of antenna elements does not influence the eavesdropper channel capacity, which is proved to be equal to zero, in contrast to previous approaches.

Secretly Pruned Convolutional Codes: Security Analysis and Performance Results

Constructions of secure channel encoders, based on secret pruning, are considered in this paper. The key defines how pruning is applied on a mother convolutional code. This results in a secret subspace that legitimate users are using to perform decoding, in contrast to an eavesdropper that employs the mother code. Both reliability and security aspects of the joint scheme are treated. We derive the expected weight enumerating function of the secret subcode and show that the legitimate users achieve a better performance (that depends on the pruning rate) in terms of word and bit error rate compared with the eavesdroppers. The security relies on the notion of indistinguishability against chosen plaintext attacks. The security proofs are given in the random oracle model, and it is shown that a randomized version of the proposed joint scheme is semantically secure by relying on the hardness of the learning parities with noise problem. The above-mentioned results are achieved by introducing a new model for physical encryption to consider the contribution of the channel noise to the system’s security.

Low-complexity joint symbol synchronization and sampling frequency offset estimation scheme for optical IMDD OFDM systems.

A low-complexity joint symbol synchronization and SFO estimation scheme for asynchronous optical IMDD OFDM systems based on only one training symbol is proposed. Numerical simulations and experimental demonstrations are also under taken to evaluate the performance of the mentioned scheme. The experimental results show that robust and precise symbol synchronization and the SFO estimation can be achieved simultaneously at received optical power as low as -20dBm in asynchronous OOFDM systems. SFO estimation accuracy in MSE can be lower than 1 × 10-11 under SFO range from -60ppm to 60ppm after 25km SSMF transmission. Optimal System performance can be maintained until cumulate number of employed frames for calculation is less than 50 under above-mentioned conditions. Meanwhile, the proposed joint scheme has a low level of operation complexity comparing with existing methods, when the symbol synchronization and SFO estimation are considered together. Above-mentioned results can give an important reference in practical system designs.

Joint QoS provisioning and congestion control for multi-hop wireless networks

The capability of quality-of-service (QoS) provisioning is of particular importance for multi-hop wireless networks when the real-time applications boost in current days. The scheduling and delivery of data packets in a deficient method may probably cause network congestion, which will in turn decrease the capability of QoS provisioning in the network. To this end, we propose a joint QoS provisioning and congestion control scheme for multi-hop wireless network in this paper based on our previous works of Differentiated Queueing Service (DQS) and Semi-TCP, which provide per-packet granular QoS and carry out efficient hop-by-hop congestion control, respectively. While DQS and Semi-TCP are studied separately, we investigate the arising issues in the joint scheme and propose possible solutions accordingly, including a fast estimation of the latest departure time, a method to handle overdue packets, and an adaptive ACK scheme, as well as the design of a shared database cross-layer architecture for the implementation in the protocol stack. Simulation results show that our proposal improves the network performance in terms of goodput, delivery ratio, and end-to-end delay significantly, particularly in the scenario of mobile users. Our discussion and simulation results both indicate that the proposed joint scheme is flexible and adaptive to the dynamic multi-hop wireless network environment.

Joint inversion of Rayleigh-wave dispersion data and vertical electric sounding data: synthetic tests on characteristic sub-surface models

In the traditional inversion of the Rayleigh dispersion curve, layer thickness, which is the second most sensitive parameter of modelling the Rayleigh dispersion curve, is usually assumed as correct and is used as fixed a priori information. Because the knowledge of the layer thickness is typically not precise, the use of such a priori information may result in the traditional Rayleigh dispersion curve inversions getting trapped in some local minima and may show results that are far from the real solution. In this study, we try to avoid this issue by using a joint inversion of the Rayleigh dispersion curve data with vertical electric sounding data, where we use the common-layer thickness to couple the two methods. The key idea of the proposed joint inversion scheme is to combine methods in one joint Jacobian matrix and to invert for layer S-wave velocity, resistivity, and layer thickness as an additional parameter, in contrast with a traditional Rayleigh dispersion curve inversion. The proposed joint inversion approach is tested with noise-free and Gaussian noise data on six characteristic, synthetic sub-surface models: a model with a typical dispersion; a low-velocity, half-space model; a model with particularly stiff and soft layers, respectively; and a model reproduced from the stiff and soft layers for different layer-resistivity propagation. In the joint inversion process, the non-linear damped least squares method is used together with the singular value decomposition approach to find a proper damping value for each iteration. The proposed joint inversion scheme tests many damping values, and it chooses the one that best approximates the observed data in the current iteration. The quality of the joint inversion is checked with the relative distance measure. In addition, a sensitivity analysis is performed for the typical dispersive sub-surface model to illustrate the benefits of the proposed joint scheme. The results of synthetic models revealed that the combination of the Rayleigh dispersion curve and vertical electric sounding methods in a joint scheme allows to provide reliable sub-surface models even in complex and challenging situations and without using any a priori information.

A Novel Low-Complexity Joint User-Relay Selection and Association for Multi-User Multi-Relay MIMO Uplink

In this work, we study joint user-relay selection and association in multi-user multi-relay cooperative wireless relay uplinks with multi-antenna nodes. For non-regenerative and altruistic relays we propose a low-complexity joint scheme, which simultaneously selects multiple relays and users for cooperation as well as assigns the selected users to different selected relays for service. The proposed scheme is sub-optimal and utilizes only the channel gains between the nodes, which leads to reduced feedback and overhead in comparison to schemes that require full channel knowledge. Furthermore, the complexity of the scheme scales linearly as the product of the total number of relays, the total number of users and the number of selected users. Simulation results demonstrate the superiority of the proposed joint scheme compared to a scheme with neither user-relay selection nor user-relay association and another scheme with user-relay association, but no user-relay selection. The favorable performance and low-complexity of the proposed scheme make it very attractive for possible implementation in emerging broadband wireless relay networks (e.g., LTE-Advanced).

A Novel Joint Method for Frequency Offset Estimation and Peak-to-Average Power Ratio Reduction in OFDM Systems Using Null Subcarriers

Orthogonal frequency division multiplexing (OFDM) is a spectral efficient multi-carrier modulation technique which offers many advantages in wireless as well as wired communication systems. Major issues of OFDM implementation are its high peak to average power ratio (PAPR) and extreme sensitivity to carrier frequency offset (CFO). In this paper, we propose a new scheme named optimum null swapping for combined PAPR reduction and CFO estimation in OFDM systems by using one training symbol (pilot) with some null subcarriers embedded in it. We exploit certain number of nulls in the pilot symbol for swapping with some data subcarriers of the data block in such a way as to reduce PAPR. By the proper allocation of null subcarriers based on some specific sequences at the transmitter, CFO is estimated at the receiver using the same pilot OFDM symbol. The computational complexity of the new objective function for the proposed joint optimum null swapping scheme is made significantly low by using the Tabu search algorithm. Moreover, the proposed method demands less side information to be send to the receiver for the reverse swapping of nulls in order to retrieve original data symbols. Simulation results show that the proposed joint scheme offers substantial reduction in PAPR apart from CFO estimation without any additional bandwidth overhead.

Network coding based joint signaling and dynamic bandwidth allocation scheme for inter optical network unit communication in passive optical networks

As an innovative and promising technology, network coding has been introduced to passive optical networks (PON) in recent years to support inter optical network unit (ONU) communication, yet the signaling process and dynamic bandwidth allocation (DBA) in PON with network coding (NC-PON) still need further study. Thus, we propose a joint signaling and DBA scheme for efficiently supporting differentiated services of inter ONU communication in NC-PON. In the proposed joint scheme, the signaling process lays the foundation to fulfill network coding in PON, and it can not only avoid the potential threat to downstream security in previous schemes but also be suitable for the proposed hybrid dynamic bandwidth allocation (HDBA) scheme. In HDBA, a DBA cycle is divided into two sub-cycles for applying different coding, scheduling and bandwidth allocation strategies to differentiated classes of services. Besides, as network traffic load varies, the entire upstream transmission window for all REPORT messages slides accordingly, leaving the transmission time of one or two sub-cycles to overlap with the bandwidth allocation calculation time at the optical line terminal (the OLT), so that the upstream idle time can be efficiently eliminated. Performance evaluation results validate that compared with the existing two DBA algorithms deployed in NC-PON, HDBA demonstrates the best quality of service (QoS) support in terms of delay for all classes of services, especially guarantees the end-to-end delay bound of high class services. Specifically, HDBA can eliminate queuing delay and scheduling delay of high class services, reduce those of lower class services by at least 20%, and reduce the average end-to-end delay of all services over 50%. Moreover, HDBA also achieves the maximum delay fairness between coded and uncoded lower class services, and medium delay fairness for high class services.

Joint Topology-Transparent Scheduling and QoS Routing in Ad Hoc Networks

This paper considers the problem of joint topologytransparent scheduling (TTS) and quality-of-service (QoS) routing in ad hoc networks and presents a joint scheme for the problem. Due to its ability to guarantee single-hop QoS support, TTS is chosen as the underlying medium-access-control (MAC) protocol. By being built on top of TTS, this paper first designs methods for bandwidth estimation and allocation (BWE and BWA, respectively) to provide QoS support without knowledge of slot status information, and then, estimates and allocates nonassigned eligible bandwidth for best effort (BE) flows. With these bandwidth management methods, this paper proposes a QoS routing protocol for a mixture of QoS and BE flows. Idealized simulation results based on the standard radio model, which ignores external sources of radio interference and protocol inefficiencies, reveal that the proposed joint scheme can provide a reduction of at least 93% in QoS violation rates and a reduction of 78%-89% in control overhead compared with the conventional dynamic source routing (DSR)/IEEE 802.11 technique. A comparison with another conventional technique, i.e., DSR/carrier sense multiple access (CSMA), also reveals that the proposed joint scheme can reduce QoS violation rates by at least 93%. In addition, the proposed joint scheme can provide an increase of 31%-104% in aggregate throughput over two representative QoS routing protocols while achieving a reduction of approximately 93% in QoS violation rates. The performance improvement to be achieved under a realistic radio model is yet to be determined.

Adaptive Quality of Service Provisioning in IEEE 802.11 Wireless Local Access Network

–This paper provides a cross-layer Quality of Service (QoS) provisioning scheme for IEEE 802.11 Wireless Local Area Network (WLAN). Specifically, we develop a new scheduling algorithm in link layer and a call admission control mechanism in network layer to support multimedia services. Instead of using a single coordination function in link layer, we adopt polling scheme to support real-time (RT) services while using EDCF contention-based function for nonreal- time (NRT) services, based on wireless channel condition and service fairness. The proposed polling algorithms search idle system time and use it to reduce average packet loss of RT variable-bit-rate (VBR) services, as well as satisfying transmission delay and bandwidth requirements of all RT services. The admission control mechanism provides long-term quality for both RT and NRT services by ensuring low average packet loss ratio for RT services and acceptable minimum throughput for NRT services. Service priority and fairness are achieved by assigning VBR bursts higher priority for resource allocation based on their weighting values. Fairness is also implemented by reserving resource for NRT to avoid possible starvation. Rate allocation for VBR connections are adaptively adjusted with sliding window measurement. Detailed analysis is given by taking into account several key statistical factors, such as service traffic model, the ratio between the polling period and the contention period (CP), burst generation probabilities, and wireless propagation model. Performance is evaluated through OPNET simulation. Both numerical and simulation results demonstrate that our proposed joint scheme is effective in terms of both system resource utilization and QoS provisioning.