Adaptive Transmission Scheme Research Articles

A novel adaptive event‐triggered scheme for network descriptor systems with randomly occurring uncertainties and nonlinearities

SummaryThis article investigates the problem of event‐triggered control for network descriptor systems with randomly occurring uncertainties and nonlinearities. First, a novel adaptive event‐triggered scheme (AETC) is introduced to save more limited network resource. Second, by considering the network‐induced delay, randomly occurring uncertainties and nonlinearities, and the adaptive transmission scheme, a delay system method is used to build a novel time‐varying delay system model. Based on this model and Lyapunov function technology, sufficient stability conditions to verdict admissible and stabilization conditions to codesign the controller gain and the weighting matrix of the adaptive transmission scheme are obtained in terms of linear matrix inequalities. Finally, a numerical simulation example and a comparing example are employed to illustrate the effectiveness and the advantageous performances of the proposed AETC.

Adaptive Transmission Design for Rechargeable Wireless Sensor Network With a Mobile Sink

In this article, we aim at maximizing the data gathering performance of the rechargeable wireless sensor network, where a mobile sink moves along the predefined path to charge sensor nodes through a wireless energy transfer technique and gather data from them. First, we show how to transform the original time-average optimization problem into a queue stability one by using the Lyapunov optimization framework, then we show how to decompose it into multiple subproblems by using the optimization decomposition. A distributed speed control and routing algorithm was proposed to reduce the computing load of the mobile sink and to obtain the near-optimal solution for data collection. Our analysis shows that there is an inherent tradeoff between the network utility and the average data queuing size, and the proposed adaptive transmission scheme can achieve the near-optimal network utility when a certain queueing delay can be tolerated.

An Optimum Transmission Distance and Adaptive Clustering Based Routing Protocol for Cognitive Radio Sensor Network

Adaptive transmission strategies for cognitive radio sensor network provide flexibility to the nodes based on data packets. In this paper, an optimum transmission distance is formulated by considering the energy consumption in the inter-cluster and intra-cluster data forwarding. The nodes are arranged in the clustered form and the size of cluster is adaptable with respect to the number of packets in the cluster. Furthermore, due to cognitive capability of sensor node, it is possible to calculate the residual time of unused licensed channels by taking into consideration the primary users activity. The proposed routing protocol uses the concept of optimal transmission distance and cognitive technique for data forwarding and the objective of the routing protocol is to forward the data packets through energy efficient paths. The comparison with other state-of-the-art algorithm validates that the proposed routing protocol improves the network performance.

Data-Rate Driven Transmission Strategies for Deep Learning-Based Communication Systems

Deep learning (DL) based autoencoder is a promising architecture to implement end-to-end communication systems. One fundamental problem of such systems is how to increase the transmission rate. Two new schemes are proposed to address the limited data rate issue: adaptive transmission scheme and generalized data representation (GDR) scheme. In the first scheme, an adaptive transmission is designed to select the transmission vectors for maximizing the data rate under different channel conditions. The block error rate (BLER) of the first scheme is 80% lower than that of the conventional one-hot vector scheme. This implies that higher data rate can be achieved by the adaptive transmission scheme. In the second scheme, the GDR replaces the conventional one-hot representation. The GDR scheme can achieve higher data rate than the conventional one-hot vector scheme with comparable BLER performance. For example, when the vector size is eight, the proposed GDR scheme can double the date rate of the one-hot vector scheme. Besides, the joint scheme of the two proposed schemes can create further benefits. The effect of signal-to-noise ratio (SNR) is analyzed for these DL-based communication systems. Numerical results show that training the autoencoder using data set with various SNR values can attain robust BLER performance under different channel conditions.

Hybrid RF/FSO Backhaul Networks With Statistical-QoS-Aware Buffer-Aided Relaying

We investigate adaptive transmission schemes over a hybrid radio frequency (RF)/free space optical (FSO) backhaul network for connecting macro-cell base station with small-cell base station through multiple parallel buffer-aided relay nodes. The proposed adaptive transmission schemes improve delay-throughput trade-off of backhaul network by exploiting the degrees-of-freedom over both RF and FSO links and capturing quality-of-service (QoS) requirements. We study two different system configurations, namely, single-carrier and multi-carrier hybrid RF/FSO systems. Our goal is to maximize the constant data arrival rate to the network such that the total queue occupancy in the network is bounded with certain acceptable queue-length bound violation probability. Towards this goal, we formulate novel optimization problems in order to maximize the end-to-end effective capacity over RF and FSO links of both system configurations. Efficient solutions are derived by employing the Lagrangian optimization technique. Some interesting insights are also revealed by considering special cases on link conditions and QoS requirements. Simulation results provide the following two observations: (i) the proposed adaptive transmission scheme outperforms the conventional switch-over hybrid RF/FSO transmission, especially in clear to moderately harsh weather conditions; and (ii) compared to several non-buffer-aided and buffer-aided relaying with non-adaptive transmission schemes, the proposed adaptive transmission scheme substantially improves the supportable data arrival for the hybrid RF/FSO backhaul network.

Dual-Hop Relaying Communications Over Fisher-Snedecor F-Fading Channels

In this paper, we present a comprehensive framework for the performance analysis of dual-hop relaying communications with variable gain amplify-and-forward (AF) relays and operating in the presence of both multipath fading and shadowing, modeled by the Fisher-Snedecor $\mathcal {F}$ -distribution. Novel closed-form expressions for the probability density function (PDF) and the cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) of the considered system subject to hardware impairments are first derived. Single-integral expressions for the numerical evaluation of the $n$ -th moment of the end-to-end SNR, the outage probability (OP), the ergodic capacity under different adaptive transmission schemes, the effective capacity and the average bit error rate (ABER) of $M$ -ary modulation schemes are further presented. The proposed analytical expressions are valid for most of the well-known fading distributions, provided that the moment generating function (MGF) of the inverse SNR of each hop is readily available. For the special case of ideal hardware, it is shown that the above performance metrics can be expressed in closed-form. It is worth pointing out that the proposed analysis is valid even when the destination node is equipped with multiple antennas and maximal ratio combining (MRC) is employed. The correctness of the proposed mathematical analysis is validated through extensive numerically evaluated results accompanied with Monte-Carlo simulations.

Adaptive Secure MIMO Transmission Mechanism against Smart Attacker

The MIMO transmission against a smart attacker has recently been formulated as a noncollaborative game, in which both the MIMO transmitter and the malicious attacker try to maximize their predefined utilities. In this paper, by carefully analyzing the Nash Equilibrium (NE), we focus on the conditions, in which the gaming results incline to the malicious attacker instead of the MIMO transmitter. In this adverse case, it is highly desirable to develop an effective mechanism to suppress the attack intention by the attacker for better secure communication. Motivated by this, an adaptive secure MIMO transmission scheme was proposed to make the MIMO transmitter better resist malicious attackers in adverse channel conditions. Compared with the existing gaming-based strategy, not only the transmit power of the MIMO transmitter but also the transmission probability will be adjusted in the proposed adaptive secure transmission scheme. Our analysis results show that the proposed scheme can be regarded as a generalized adaptive transmission one, i.e., when the adaptive transmit power policy is enough to suppress the attack motivation, the proposed scheme will be reduced to the adaptive power control scheme; otherwise, both the adaptive transmit power and the adaptive probabilistic transmission can be employed to suppress the attack motivation. The analysis results confirm us that the proposed adaptive transmission scheme provides us a choice to enhance the secure MIMO transmission performance in adverse conditions.

Capacity analysis of free space optical communication system under atmospheric turbulence

In this paper, the analytical channel capacity of the free space optical (FSO) system under weak, moderate and strong turbulence is derived. The FSO channel statistics follows the log-normal distribution under weak turbulence and follows the Gamma–Gamma distribution under moderate and strong turbulence. The three generally used adaptive transmission schemes in FSO communication system are as follows (1) optimal simultaneous power and rate adaptation, (2) optimal rate adaptation with constant transmit power, and (3) truncated channel inversion with a fixed rate. The closed-form approximations for the average ergodic channel capacity for these adaptive transmission schemes under different atmospheric turbulence without any pointing error are derived. Simulation results depict the excellent agreement of the proposed analytical models with the Monte Carlo simulation.

Capacity of Adaptive Transmission Schemes over FTRF Channels

The study of channel capacity is essential to assure the quality of service and to measure spectral efficiency for designing a wireless system. In this paper, a simple probability density function (PDF) expression for fluctuating two ray fading (FTRF) channels is developed. Capacity analysis for various adaptive transmission schemes such as channel inversion with fixed-rate, the truncated channel inversion with fixed-rate, and optimal rate adaptation are evaluated using the PDF expression. The FTRF channel is the best statistical model of fifth-generation millimeter-wave communication. A comparison of the capacity among the adaption schemes over the FTRF channel is also presented.

Sum of Fisher-Snedecor F Random Variables and Its Applications

The statistical characterization of a sum of random variables (RVs) is useful for investigating the performance of wireless communication systems. We derive exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of a sum of independent but not identically distributed (i.n.i.d.) Fisher-Snedecor F RVs. Both PDF and CDF are expressed in terms of the multivariate Fox's H-function. Besides, a simple and accurate approximation to the sum of i.n.i.d. Fisher-Snedecor F variates is presented using the moment matching method. The obtained PDF and CDF are used to evaluate the performance of wireless communication applications including the outage probability, the effective capacity, and the channel capacities under four different adaptive transmission strategies. Moreover, the corresponding approximate expressions are obtained to provide useful insights for the design and deployment of wireless communication systems. In addition, we derive simple asymptotic expressions for the proposed mathematical analysis in the high signal-to-noise ratio regime. Finally, the numerical results demonstrate the accuracy of the derived expressions.

Energy-Efficient and QoS-Aware Link Adaptation With Resource Allocation for Periodical Monitoring Traffic in SmartBANs

Limited energy resources of sensors and stringent quality-of-service (QoS) constraints in biomedical applications raise serious concerns when utilized in Wireless Body Area Networks (WBANs). The European Telecommunications Standards Institute (ETSI) Smart Body Area Network (SmartBAN) represents a standardized communication interface and protocol between a hub coordinator and a set of sensors, that has been designed with simplicity and low power in mind. This work presents an ETSI SmartBAN PHY and MAC configuration framework that remarkably lengthens sensors battery lifespan through reducing transceivers consumed energy. To that end, and taking into account the channel quality and packet error rate requisites of sensors, a mechanism to select between the different PHY transmission modes of the standard is proposed. This link adaptation scheme is combined with a resource allocation algorithm that derives the duration of the inter-beacon intervals and the transmission periods of sensors, while fulfilling traffic delay constraints and minimizing sensors transceivers energy consumption. Analytical expressions for packet error rate of all available PHY transmission modes, as well as for traffic delay, transceivers energy savings of hub and sensor nodes, and battery duration, are derived. Computer simulation results substantiate the efficacy of both, the presented QoS-aware adaptive transmission scheme and the resource allocation algorithm, in fulfilling the target packet error rate and delay requirements, while significantly expanding the battery duration, specially for sensors with long elapsed times between successive sensing intervals (up to a 515% increase and a 960% increase are obtained for the two considered simulation scenarios).

EAAT: Environment-Aware Adaptive Transmission for Split-Screen Video Streaming

With the tremendous growth of video contents and mobility demands, there is a need to develop more personalized video services. Split-screen services, such as picture in picture become more and more popular. Furthermore, the user’s viewing environment affects the user’s quality of experience (QoE). Therefore, video transmission of split-screen services face several major challenges, such as to quantify the impact of environmental factors on user’s QoE; how to assess the user’s QoE of the split-screen services; how to choose the bit-rate of each video stream to maximize user’s QoE of the split-screen services. To address these challenges, in the paper, an environment-aware adaptive transmission (EAAT) scheme for split-screen video streaming is first presented. Then, we introduce a mathematical model for characterizing user’s QoE to be affected by environmental factors in the proposed EAAT. In the model, the QoE of user’s relationship with the viewing environment is proposed. Based on the model, a problem of maximizing user’s QoE is formulated, and we develop a heuristic algorithm to solve the optimization problem. In addition, we conduct various trace-bandwidth experiments to rigorously evaluate the proposed EAAT scheme in different network environments, and show that EAAT can enrich the video quality while saving network resources.

Hybrid Satellite-Terrestrial Relay Networks With Adaptive Transmission

Hybrid satellite-terrestrial relay network (HSTRN) has been viewed as a flexible and promising solution to be developed with heterogeneous devices and integrated infrastructures for improved coverage and reduced latency. Taking the requirements of overall spectral and power efficiency into account, we consider different adaptive transmission schemes for the hybrid architecture oriented to potential applications in practical scenarios, and obtain the analytical expressions for the achievable channel capacity with respect to different schemes, i.e., optimal power and rate adaptation, and truncated channel inversion and fixed rate. Numerical simulations confirm the validity of the derived theoretical results, and provide useful guidance for emerging applications in HSTRN that are under various fixed/adaptive transmit power or rate requirements.

Effective Capacity of $L_p$ -Norm Diversity Receivers Over Generalized Fading Channels Under Adaptive Transmission Schemes

This paper presents novel moment generating function (MGF)- and characteristic function (CHF)-based frameworks for the EC performance analysis of a generic L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -norm diversity combining scheme under adaptive transmission policies. The considered system operates over generalized fading channels, a maximum delay constraint and under various channel state information (CSI) conditions. Depending upon the operational CSI, four policies are studied, namely: i) Constant power with optimal rate adaptation (ORA); ii) Optimal power and rate adaptation (OPRA); iii) Channel inversion with fixed rate (CIFR); and iv) Truncated CIFR (TIFR). The L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -norm diversity is a generic diversity structure which includes as special cases various well-known diversity schemes, such as equal gain combining (EGC), maximal ratio combining (MRC) and amplify-and-forward (AF) relaying. Under the ORA and OPRA policies, we derive single integral expressions for evaluating the EC of L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -norm diversity reception directly from the MGF or the incomplete MGF of the Signal-to-Noise-Ratio (SNR) at the receiver, respectively. For the EC performance evaluation of the EGC and AF relaying systems operating under the OPRA policy, a CHF-based approach, which is computationally more efficient as compared to the MGF-based approach, is further presented. It is shown that the EC for the CIFR and TIFR policies can be directly evaluated from the MGF or the CHF of the SNR at the receiver, respectively. For the ORA policy, a novel analytical approach for the asymptotic EC performance analysis is also developed and evaluated, revealing how important system operation parameters affect the overall system performance. The mathematical formalism is validated with selected numerical and equivalent simulation performance evaluation results, thus confirming the correctness of the proposed analytical methodology.

Design of a Physical Layer Encryption Scheme for Rate Compatible Modulation

Spectral efficiency and transmission security are both essential metrics for wireless communication. Rate compatible modulation (RCM) is an adaptive transmission scheme to improve the spectral efficiency. However, the mapping matrix of RCM is fixed. Once the mapping matrix is known to eavesdroppers, information will be leaked. Physical layer encryption (PLE) is a secure approach to enhance the security using encryption at physical layer. In this paper, we propose a secure transmission scheme for RCM, namely, secure RCM (S-RCM). The construction method of RCM mapping matrix is of great random. Combined with PLE, S-RCM mainly uses the secret key extracted from the channel information to generate mapping matrix. Due to the randomness of channel, the mapping matrix will also be random. Security analysis shows that the demapping of S-RCM must be based on the right mapping matrix. It also shows that S-RCM owns extremely large cipher mapping matrix space, which makes it impossible for eavesdropper to guess the mapping matrix. Furthermore, known-plaintext attack (KPA) is hardly impossible to get the mapping matrix due to the high calculations and multiple possibilities. Simulation result shows that the S-RCM have the same throughput performance and bit error rate (BER) performance as RCM. In addition, the simulation results also show that eavesdropper faces extremely high complexity, which is thought safe.

Exploiting Interference for Intelligent Relaying in Integrated Space and Terrestrial Networks Based on PNC and SIC

The integrated space and terrestrial networks which incorporate various satellite systems and ground networks could provide a wide variety of services and global seamless network access. The integrated network is composed of multiple heterogeneous nodes and sub-networks which requires intelligent and efficient physical layer transmission techniques to maintain high-speed links between these subsystems. As a traditional technology in satellite communications, relay could still work as an important part in these heterogeneous and complex networks. In this paper, two interference exploitation schemes, i.e., physical-layer network coding (PNC) and successive interference cancellation (SIC) which can efficiently increase data exchange rate for relay systems are studied, and an intelligent relaying scheme combining both the advantages of these two schemes is proposed. Simulation results show the proposed adaptive transmission scheme achieves a smoother sum-rate gain while being more robust to dynamic topologies.

Adaptive Channel Coding and Power Control for Practical FSO Communication Systems Under Channel Estimation Error

Adaptive channel coding and power control for practical free-space optical communication systems are proposed in this paper. Particularly, we first assume that the channel state information (CSI) is perfectly known at the transmitter, and propose adaptive transmission schemes in which coding rate is adjusted either independently or jointly with transmit power according to the channel conditions. Moreover, an optimization problem is developed to attain power consumption minimization under free space optical (FSO) practical constraints, i.e., target bit-error rate, target outage probability, and maximum transmit power. We then solve the optimization problem and derive closed-form expressions for throughput and average transmit power for both adaptive schemes over the Gamma–Gamma atmospheric turbulence channels. Our results demonstrate the superiority of the proposed adaptive schemes over non-adaptive schemes, especially under strong turbulence conditions. In the second part of this paper, we move toward a more realistic scenario where the channel is not perfectly known to Tx/Rx and is estimated by the sequence of received signals. Therefore, we investigate the effect of channel estimation inaccuracies on the performance of the proposed schemes and show that the accuracy of the channel estimator depends on the length of the sequence and, for a sufficiently large length of the observation window, it achieves performance close to the receiver with known CSI. Extensive analytical derivations are provided to investigate the performance of the proposed adaptive schemes under channel estimation error. Our analytical results can be used for calculating and tuning of the optimum length of the observation window without resorting to Monte Carlo simulations.

Online Adaptive Transmission Strategy for Buffer-Aided Cooperative NOMA Systems

This paper investigates a buffer-aided cooperative NOMA system, where a source is connected to multiple destinations through a buffer-aided NOMA relaying. We aim to maximize a long-term average network utility by jointly optimizing working mode selection, admission control, and power allocation in each time slot, subject to queue stability constraints and both the peak and average power constraints at the relay. To solve this problem, by leveraging the recently-developed Lyapunov optimization framework, we design an Online Adaptive Transmission (OAT) strategy, which converts the original long-term optimization problem into a series of online admission control and power allocation subproblems in each time slot, without loss of optimality. By considering the fact that the power allocation problem is non-convex in nature and thus cannot be solved with a standard method, we transform it into an equivalent convex optimization based on the specific feature of the formulation, and then propose a Fast Decision Criteria (FDC) based algorithm to derive the optimal solution with high computational efficiency. Extensive simulation results are provided to evaluate the performance of the proposed OAT strategy with FDC based power allocation for the buffer-aided cooperative NOMA system, and demonstrate that the proposed strategy can significantly outperform multiple benchmark schemes.

How Much of Wireless Rates Can Smartphones Support in 5G Networks?

Due to the higher wireless transmission rates in the 5G cellular networks, higher computation overhead is incurred in smartphones, which can cause the wireless transmission rates to be limited by the computation capability of wireless terminals. In this case, is there a maximum receiving rate for smartphones to maintain stable wireless communications in 5G cellular networks? The main objective of this article is to investigate the maximum receiving rate of smartphones and its influence on 5G cellular networks. Based on Landauer's principle and the safe temperature bound on the smartphone surface, a maximum receiving rate of the smartphone is proposed for 5G cellular networks. Moreover, the impact of the maximum receiving rate of smartphones on the link adaptive transmission schemes has been investigated. Numerical analyses imply that the maximum receiving rate of smartphones cannot always catch up with the downlink rates of future 5G cellular networks. Therefore, the link adaptive transmission scheme for future 5G cellular networks has to take the maximum receiving rate of smartphones into account.

Secure Transmission in mmWave Wiretap Channels: On Sector Guard Zone and Blockages

Millimeter-wave (mmWave) communication is one of the key enabling technologies for fifth generation (5G) mobile networks. In this paper, we study the problem of secure communication in a mmWave wiretap network, where directional beamforming and link blockages are taken into account. For the secure transmission in the presence of spatially random eavesdroppers, an adaptive transmission scheme is adopted, for which sector secrecy guard zone and artificial noise (AN) are employed to enhance secrecy performance. When there exists no eavesdroppers within the sector secrecy guard zone, the transmitter only transmits information-bearing signal, and, conversely, AN along with information-bearing signal are transmitted. The closed-form expressions for secrecy outage probability (SOP), connection outage probability (COP) and secrecy throughput are derived under stochastic geometry. Then, we evaluate the effect of the sector secrecy guard zone and AN on the secrecy performance. Our results reveal that the application of the sector secrecy guard zone and AN can significantly improve the security of the system, and blockages also can be utilized to improve secrecy performance. An easy choice of transmit power and power allocation factor is provided for achieving higher secrecy throughput. Furthermore, increasing the density of eavesdroppers not always deteriorates the secrecy performance due to the use of the sector secrecy guard zone and AN.