This paper develops a novel approach to green spectrum management for 6G Non-Terrestrial Networks (NTNs) using Large Language Models (LLMs). An intelligent system is proposed, which dynamically allocates and shares spectrum resources between terrestrial and non-terrestrial networks while optimizing energy efficiency. The system employs adaptive licensing schemes that can adjust to varying network loads and environmental conditions. The proposed LLM-based system uses real-time analysis of network states and user demands, facilitating more efficient spectrum utilization across diverse geographical regions and orbital layers of NTNs. Simulation results demonstrate significant improvements in both spectrum utilization efficiency and energy consumption compared to conventional methods. This research offers new perspectives on green communications for the 6G era and how dynamic spectrum assignment policies will impact future regulatory approaches and technological development in the evolving telecommunications landscape.

The Internet of Things (IoT) plays a critical role in enabling the seamless integration of disparate devices. Future IoT will rapidly expand its coverage to offer future worldwide omnipresent applications and services by merging communications in diverse spatial domains to build the space–air–ground–ocean-integrated network (SAGOI-Net). SAGOI-Net will include a significant number of battery-powered network nodes, such as satellites, unmanned vehicles, and underwater devices, due to the extremely vast geographic reach and dynamics in free space. Given the battery limitations, high-energy-efficiency communications and networking will be critical to the future system. Green SAGOI-Net seeks to not only bring ubiquitous connectivity to every corner of the globe but also to deliver more data with the same amount of energy.

With the acceleration of a new round of global scientific, technological, and industrial revolution, the next generation of information and communication technology, i.e., 6G, will inject new momentum into industry transformation and upgrading, as well as into economic innovation and development.This will subsequently promote a global industrial integration.Wireless communication will be ubiquitous in all areas of future society, supporting novel applications with various performance requirements, such as immersive-or interactive-experience applications requiring a large bandwidth, autonomous driving and vehicle-to-everything applications requiring ultrahigh reliability and ultra-low latency, and applications for industrial Internet requiring massive machine-type connectivity.Facing the challenges of the post-Moore and post-pandemic era, wireless communication needs breakthroughs in network architecture to improve the intelligence, security, robustness, bandwidth, and heterogeneity.With this background, several important tendencies have emerged in the development of 6G wireless communications

Mobile edge computing (MEC) is envisioned as re- expanded cloud compared to fog computing. As making mobile services computing sank to the edge of network further, performance improvement can be got on time aspect. Therefore, MEC is seemed as a potential technology for delay-sensitive applications. Based on that, a reasonable computation offloading strategy would reduce system consumption for MEC further and release its computational capability. In view of resource shortage, especially bandwidth competition problem among Small Cells and edge computational requirements of HetNet, we focus on distributed uplink offloading for MEC in macro-micro coordination scene. It mainly contains two steps. First, based on Lyapunov to solve offloading decision-making problem for users in each Small Cell. Second, complete offloading update order- making of Small Cells in Macro Cell with proposed deviation update decision algorithm (DUDA). Our strategy makes up for the lack of system stability and uplink analysis in existing research. Numerical results demonstrate the effectiveness of our strategy.

The increasing traffic puts high demands on capacity for the next generation mobile networks. The millimeter-Wave (mmWave) communication system offers new opportunities to meet this requirement due to the tremendous amount of avail- able spectrum. However, the massive non-line-of-sight (NLOS) transmissions and the site constraints in urban environment are severely challenging the conventional way of deploying terrestrial low power nodes (LPNs). To address these problems, we introduce the mmWave aerial base station (mAeBS) in next generation mobile networks, which can be quickly and flexibly deployed to enhance the capacity in data traffic bursting areas. To maximize the enhancing effects, an ergodic capacity analytical model of mAeBS is proposed, considering both user distribution and environment conditions. Then an mAeBS 3D placement method based on the model is given. Simulation results show that the proposed method can achieve considerable capacity enhancement and supplement regional coverage as well.

This paper investigates the application of 5G wireless multicast to the big data system. In particular, we propose a hybrid unicast/multicast transmission scheme using 3D massive multi-input multi-output (MIMO) technique. The proposed scheme employs multicast beamforming in the multicast group and multi-user MIMO (MU-MIMO) linear precoding in the unicast group. It also applies the null space based interference cancellation to eliminate the signal leakage generated by other groups. Simulation results show that the proposed system can significantly improve the system throughput with an antenna array configuration, precoding/beamforming schemes and user grouping strategies.

To adapt with the frequent link failures in mobile ad-hoc networks, the routing protocols shall catch more than one route, at least two routes. In case of two routes, the first route can be used as the main route; while the other one can be used as a standby route used upon the detections of link failures. If this is the case, the packet losses are virtually decreased to zero, and seamless multimedia communications can be supported over mobile ad-hoc networks. To ensure the existence of two routes between any randomly chosen two nodes, the node density in terms of the number of neighbors must be above a certain threshold. In this paper, we propose a mathematical model to find such node density, and propose some solutions in case the node density is below the required density in order to increase it to the required node density. Our results show that the probability to have two routes rapidly increases with node density till it reaches the saturation region, where the increase of node density has negligible improvement in terms of network availability. This paper shows that the network nodes must have at least 16 neighbors in order to ensure the existence of two routes between any randomly chosen source and destination pair.

This paper concentrates on the multicast service in the next generation (5G) communications system, and develops an opportunistic massive MIMO-NOMA scheme. The proposed scheme superimposes the signal of Non-orthogonal Multiple Access (NOMA) users on the multicast signal, and employs successive interference cancellation (SIC) to separate the signal of NOMA users from the multicast signal. This scheme also applies null space based interference cancellation to eliminate the signal leakage generated by other groups. And multi-user MIMO (MU-MIMO) linear precoding is employed in the unicast group. Numerical results revealed that opportunistic massive MIMO-NOMA system significantly satisfies the requirement of high peak spectral efficiency in typical massive MIMO scenarios.

This work focuses on the analysis for multicast services in fifth-generation (5G) wireless communication system. We investigate the physical- layer wireless multicast technology in massive multi-input multi-output (MIMO) mutual coupling channel model, and proposed the hybrid unicast/multicast transmission system. The mutual coupling channel model is adopted to describe the channel characteristics under the linear antenna array scenario and the rectangular antenna array scenario. The proposed hybrid transmission scheme adopts multicast beamforming in the multicast groups as well as multi-user MIMO (MU-MIMO) linear precoding in the unicast group to increase system throughput. The null-space method based interference cancellation is further performed between each group to eliminate signal leakage generated from each group. Comparisons between two types of antenna array configurations, different channel models, linear precoding as well as multicast beamforming, and user grouping strategies for multicast services are presented and analyzed by simulation.

With the deployment of small cell networks, low-cost backhaul schemes for small cell base stations (SBSs) have attracted great attentions. Self-backhaul using cellular communication technology is considered as a promising solution. Although some excellent works have been done on self-backhaul in small cell networks, most existing works do not consider the recent advances of full-duplex (FD) and massive multiple-input and multiple-output (MIMO) technologies. By jointly considering them, we propose a novel self-backhaul scheme for small cell networks in this paper, where the macro base station is equipped with massive MIMO antennas, and the SBSs have the FD communication capability. Then, we can achieve the simultaneous transmissions of the access link of users and the backhaul link of SBSs in the same frequency and then spectrum efficiency is improved. Furthermore, we formulate the power allocation problem of the MBS and SBSs as an optimization problem. Because the formulated power allocation problem is a non-convex problem, we transfer the original problem into a difference of convex program by using successive convex approximation method and variable substitution, and then solve it using a constrained concave convex procedure based iterative algorithm. Finally, extensive simulations are conducted to verify the effectiveness of the proposed scheme.

In this paper, we aim at green small cell networks by jointly achieving self-backhaul and energy harvesting. We study full duplex (FD) technology and massive multiple-input and multiple-output (MIMO) technology to enhance the performance. In order to improve the energy efficiency (EE) further, we design a precoding scheme to eliminate the inter-tier interference. Moreover, we formulate the cell association and power allocation problem as an optimization problem to optimize the EE of the considered network with considering the energy arrival rate and remainder battery energy in SBSs. The formulated optimization problem implies a sleep mechanism to control the on/off of SBSs, which will reduce the energy consumption of small cell networks. Considering the high computation complexity for solving the non-convex optimization problem, we transform the original problem into a difference of convex program, which can be efficiently solved by using a constrained concave convex procedure based algorithm. Extensive simulations are conducted with different system configurations to verify the effectiveness of the proposed scheme.

With the successful deployment of the fourth-generation cellular networks around the world, long-term evolution (LTE) and LTE-advanced (LTE-A) have become key technologies to enable Internet of Things (IoT) applications. To accommodate various streaming data of IoT applications, LTE/LTE-A standards have defined several quality-of-service (QoS) classes for different traffic characteristics, in terms of traffic bit-rate, tolerable delay, and packet loss rate. Moreover, to meet the stringent power-saving requirements for IoT devices, LTE/LTE-A standards also have defined the discontinuous reception/transmission (DRX/DTX) mechanism to allow devices to turn off their radio interfaces and go to sleep when no data need to be received or transmitted from/to the evolved Node B (eNodeB).

With the dense deployment of small cell networks, the powering and backhaul problem of small cell base stations (SBSs) has attracted great attention, and energy harvesting technology and self-backhaul technology have been proposed as promising solutions. Although some excellent works have been done on energy harvesting and self-backhaul in small cell networks, most existing works do not consider them jointly. In this paper, we aim at green small cell networks by jointly achieving self-backhaul and energy harvesting. In addition, full-duplex and massive multiple-input and multiple-output technologies are also exploited to enhance the system performance. In order to improve the energy efficiency (EE) further, a novel precoding scheme is designed to eliminate both the inter-tier and multi-user interference. Based on the proposed precoding scheme, we formulate the cell association and power allocation problem as an optimization problem to optimize the system EE performance, with the energy arrival rate and remaining battery energy in SBSs involved. The formulated optimization problem implies a sleep mechanism to control the ON/OFF of SBSs, which will further reduce the energy consumption of small cell networks. In addition, to reduce the computation complexity to solve this non-convex problem, we propose to transform the original problem into a difference of convex program, which can be efficiently solved via a constrained concave convex procedure-based algorithm. Extensive simulation results are presented to justify the effectiveness of the proposed scheme with different system configurations.

Abstract This paper addresses the audio piracy problem over Internet by tweaking data redundancy of host media signal for optimized embedding and extraction of spread spectrum watermarking. In particular, we take into account a special feature that host audio signals have the short‐time stationary property and their major power can be removed using linear prediction filter. By combining the redundancy removing and the improved spread spectrum modulation, host interference is canceled with minimized embedding distortion to the host audio. The data redundancy removing is also applied at the receiver to achieve matched filtering and improved performance. Experiments based on real audio signals show that our proposed scheme performs robustly against various kinds of channel attacks while maintaining high extraction performance. Copyright © 2016 John Wiley & Sons, Ltd.

Cellular relaying architecture is in an early stage for development and deployment. A restricted number of deployment scenarios are addressed in the LTE-A relay standard, though different design options in alternative deployment scenarios do potentially exist. Presently, the LTE-A relay standard is restricted to a single-hop relaying. The principal reason for opting for this architecture is to minimize system complexity. Nonetheless, multi-hop relay architecture could potentially provide greater capacity and coverage, in the future, particularly for urban sparse area deployment scenarios. However, many problems involving the complexity of multi-hop relaying paradigm need to be resolved, specifically resource management. In this paper, we focus on the resource management problem, and we propose a new resource allocation framework to overcome the additional challenges introduced by the multi-hop relay stations. Numerical results are presented to demonstrate the validity of the proposed framework.

Future heterogeneous networks (HetNets) will have to face a great challenge of overwhelming demand of spectrum resource, due to the exponential increase in mobile internet traffic driven by a new generation of wireless devices. In this paper, we propose a spectrum sensing and scheduling scheme for circular array, in order to make better use of the spectrum resource and improve the performance of multi-user MIMO (MU-MIMO) in HetNets. The proposed scheme can effectively detect the users and frequency use based on angles, and schedule the users with optimized codebook. Simulation results show that our proposed scheme can achieve considerable gain in terms of throughput and users' data rate, with significantly reduced system complexity and increased efficiency.

Heterogeneous network (HetNet) is a promising technology to improve the capacity of future generations of cellular network, in which a mobile station can be served by multiple base stations (BSs) with different scales of coverage range, including short range low power nodes (LPNs). In HetNet, a major challenge is how to provide guaranteed quality-of-service (QoS) for all users. To address this issue, we investigate a practical scenario in which the massive multiple-input multiple-output (MIMO) technology is adopted by the cooperation of one macro-cell BS and several LPNs. Furthermore, we provide a lightweight channel state information (CSI) acquisition scheme for the implementation. Numerical simulation results demonstrate that the signal-to-interference-and noise ratio (SINR) of intended users in LPNs covered with small cells can be significantly increased by this proposed massive MIMO precoding scheme, whereas oppressing the impact on neighboring victim users.

This paper develops a novel scheme of game theory based spectrum sharing to mitigate the inter-cell interference in LTE-A heterogeneous networks (HetNets). In particular, we first assume that the macro-cell protects itself by pricing the bandwidth allocated to small-cells. We then employ the Stackelberg game to jointly consider the utility maximization of macro-cell and small-cells. During game formulation, our scheme takes the advantage of LTE-A standards, such as almost blank sub-frames (ABS) for enhanced inter-cell interference coordination (eICIC) and cell range expansion (CRE) for small cell. Simulation results justify that our approach can significantly improve the throughput of multi-tier cellular network as well as leverage the spectral efficiency of the macro-users in the vicinity of small-cells.

The next generation cellular networks target significant capacity improvements and require dense frequency reuse of the scarce radio spectrum, resulting in a danger of severe interference. Fractional frequency reuse (FFR) techniques have been proposed for macro-cell networks to mitigate interference. However, these static schemes are not adaptive to meet the traffic demand changes from mobile users, and thus inefficient with respect to power consumption in many scenarios. This paper starts with the basic soft fractional frequency reuse (SFFR) framework and proposes a traffic demand orientated green power control scheme that can make power allocation by considering different traffic demands. Afterwards, this green concept is extended to heterogeneous network (HetNet) for the power control strategies in low-power nodes (LPNs). Numerical results show that our proposed schemes can achieve considerable improvement in terms of throughput and power consumption, as well as extra rewards of high flexibility and low complexity.

Abstract Multiple‐input multiple‐output orthogonal frequency division multiplexing has become an attractive air‐interface solution for the next generation wireless networks because of its high spectrum efficiency. This paper addresses the security concern and proposes to achieve covert orthogonal frequency division multiplexing transmission using cyclic delay diversity featured multiple‐input multiple‐output technology. Particularly, our physical layer security scheme takes the advantage of cyclic delay diversity formed periodical frequency selective channel and utilizes uneven comb pilots to confuse unauthorized receivers and benefit authorized receivers. We conduct simulation study to evaluate the impact of different cyclic delay, antenna number, and interpolation algorithms on our scheme. Numerical results show that our scheme can provide authorized users with significant advantage over eavesdroppers without complicated upper‐layer encryption and decryption. Moreover, the scheme has flexible choice of parameters and thus can be easily deployed in a variety of wireless networks with different requirements. Copyright © 2014 John Wiley & Sons, Ltd.

This paper presents a novel scheme of adaptive self-organization network (SON) by integrating cognitive radio (CR) with inter-cell interference coordination (ICIC) for LTE-A heterogeneous networks (HetNets). Particularly, we take advantage of the spectrum sensing function from CR and the radio resource layering function from ICIC. Our work addresses the issues of smart low-power node (SLPN) development, which associates appropriate sectorization with radio resource allocation during the self-organization process. We further develop a Hungary algorithm based self-organization strategy to improve the SLPN adaptive optimization. Simulation results show that our proposed scheme can achieve considerable gain in terms of throughput and coverage, with extra rewards of high flexibility and low complexity in HetNet SON.

Orthogonal Frequency Division Multiplexing (OFDM) has become an increasingly common technique in communication systems and raised tremendous security concerns recently. This paper proposes to achieve covert OFDM transmission with cyclic delay diversity (CDD) featured multiple input multiple output (MIMO) technology. Particularly, our physical layer security scheme takes the advantage of CDD formed frequency selective channel and addresses uneven comb pilots to confuse unauthorized receivers and benefit authorized receivers. Numerical results justify that, with our design, the CDD paradigm can efficiently safeguard OFDM system, and the performance can be further optimized by fine tuning channel estimation for authorized users.

Asynchronous system provides great performance improvement for wireless ad hoc networks, such as anti-jamming, collision reduction and device simplification. Nevertheless, new media access and routing protocols are required to assist the asynchronous system, e.g., a neighbor discovery algorithm, which is the first step in the initialization of wireless ad hoc networks. In the past few years, a number of algorithms have been proposed for neighbor discovery. However, most of them only consider synchronous system and cannot work efficiently in asynchronous system. In this paper, firstly, we propose an analytical model for an 1-way asynchronous system in wireless ad hoc networks with directional antennas. Then, we compare the time-slot consumption in asynchronous system to complete the neighbor discovery process with that in synchronous system. Finally, in order to improve the performance of the neighbor discovery process, we extend the 1-way asynchronous discovery algorithms to a 2-way asynchronous discovery algorithm. To the best of our knowledge, this is the first practical analytical model of 2-way asynchronous neighbor discovery algorithm with directional antennas.

This paper presents a novel multi-layer iterative decoding scheme using deterministic bits to lower the decoding threshold of LDPC codes in wireless multimedia communication systems. These deterministic bits serve as known information in the LDPC decoding process to reduce the redundancy during data transmission. Unlike the existing work, our proposed scheme addresses the controllable deterministic bits, such as MPEG null packets, rather than the widely investigated protocol headers. In particular, our multi-layer scheme integrates deterministic bit identification into LDPC decoding process. This integration is able to make significant performance improvement if adequate deterministic bits are discovered. We find that the length of deterministic bits may vary from time to time, and the exploring of deterministic bits is associated to a series of shortened parity matrices during the decoding iterations. Accordingly, we develop a recursive LDPC shortening algorithm to match the dynamic length and facilitate the iterative identification of deterministic bits. Simulation results show that our proposed scheme can achieve considerable gain in today's most popular broadband wireless access networks such as WiMAX.

This paper proposes an algorithm of data subcarrier designing to apply the tone reservation(TR) peak-to-average power ratio (PAPR) reduction algorithm in OFDM-based wireless communication systems and overcome the high computational cost issue. Different from the existing works, the proposed algorithm focuses on designing data subcarriers, controlling both the iteration times and the number of subcarriers. The new algorithm exhibits similar performance as the traditional TR algorithm with lower computational complexity and the ability to control the number of used subcarriers. Simulation results show that the proposed algorithm can significantly reduce the PAPR by only 2 or 3 iterations.

Node clustering has been considered as a promising approach in ad hoc networks, where the inter cluster routing is limited to some special nodes called cluster head (CH). In practice, the performance of data transmission often degrades with the increase of distance between neighboring CHs. This paper proposes a new scheme that employs intermediate nodes as relays between neighboring CHs. Particularly, we develop both feedback and non-feedback fountain coded cooperative communications to improve reliability and robustness. It is observed that the number of relays plays a significant role in our scheme. Accordingly, we design a rateless coded relay selection (RCRS) algorithm to guarantee the required data rate with a minimum cost. Simulation results show that feedback based protocol outperforms its non-feedback counterpart in terms of end to end rate and throughput.

Low-density parity-check (LDPC) codes are playing an important role in modern wireless communication systems such as WiMAX due to their Shannon limit approaching error correction performance. To lower the decoding threshold of LDPC codes, this paper develops a novel multi-layer iterative decoding scheme using deterministic bits for multimedia communication systems. These deterministic bits serve as known information in the LDPC decoding process to reduce the redundancy during data transmission. Unlike the existing work, our proposed scheme addresses the controllable deterministic bits, such as MPEG null packets, rather than the widely investigated protocol headers. Simulation results show that our proposed scheme can achieve considerable gain in WiMAX networks.

Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique for high speed data transmission over multipath fading channels. In an MIMO-OFDM system, cyclic delay diversity (CDD) serves as a simple and elegant solution to exploit transmit diversity. This paper investigates the uneven comb pilots based channel estimation for CDD-OFDM system with periodical frequency selective channel. Our study reveals that uneven comb pilots outperform their even counterpart in complicated channel conditions, such as adaptive CDD, where cyclic delay parameters may change from time to time. Furthermore, we identify the interpolation as a key problem in uneven-pilot based OFDM system and study several scattered data interpolation algorithms. Simulation results show that radial basis function (RBF) interpolation has the best tradeoff in terms of accuracy and computational complexity.

Fitting noisy measurements to a circle is a classic statistical estimation problem. In this paper, we make two contributions to the study of this problem. First, we propose a novel formulation of the maximum likelihood (ML) estimator for identifying the center and radius of the circle from noisy measurements. This new estimator uses the unknown true values of the measurement points as the nuisance parameter to obtain an exact ML formulation. We then examine the Karush-Kuhn-Tucker (KKT) conditions for the optimum solution to the ML estimator. We show analytically that this new estimator is in fact equivalent to the well-known least squares (LS) form of the circle fitting problem. Second, from the insights gained in deriving the optimum solution, a computationally simple circle fitting algorithm based on greedy search is proposed. Performance results are given to illustrate the performance of the proposed algorithm.

In this paper, we address the issue of multicast cooperative communications over WMNs. Specifically, we propose a new framework where mesh router is in charge of the cooperation of mesh clients during a multicast session. Under this framework, we identify the selection of relaying nodes as a critical step to success. To solve above problem, we further develop the concept of in/out-group cooperation as well as the heuristics to find the optimal relay solution. Extensive simulation results show that our approach can considerably mitigate the transmission errors in wireless multicast environment with high efficiency.

In this paper, we propose a modification to Belief Propagation (BP) decoding algorithm for LDPC codes. The modification is to attenuate the check to bit extrinsic logarithm likelihood ratio by a factor α, when sudden sign change happens. This modification can be applied to both the standard BP algorithm and the joint row and column (JRC) BP algorithm. Simulation results show that the BER and WER performance of both traditional BP and JRC BP algorithms is improved by this method. The expense of the proposed modification is a slight increase in the average number of decoding iterations.

This paper investigates the design of LDPC codes over mobile DTV multipath channels. Most of the existing LDPC codes are optimized for additive white Gaussian noise (AWGN) channel, and not feasible to encounter the long burst error occurring in mobile DTV channel. Accordingly, we study the error propagation statistics of decision feedback equalizer (DFE) and formulate it into a gated noise model. To achieve good error correction in burst error channel, we proposed a class of dual-degree IRA codes to balance the metrics of decoding threshold and robustness. Extensive simulation results are presented in this paper to justify the performance of dual-degree IRA codes over gated noise model.

This paper investigates the use of ATSC M/H digital television (DTV) signal for location finding. In comparison to satellite based location finding system, DTV signals have higher field strength, wider bandwidth, lower frequency band, and DTV transmission towers are pervasively available everywhere. They can be used for indoor and mobile location finding in major cities where satellite based system might not function well. The ATSC receiver can obtain the multiple transmitter impulse responses and signal arrival times using the embedded RF watermark (RFWM) signal, and then derives its geographic coordinates based on the position of ATSC transmitters. As a critical step of this process, the transmitter identification in mobile environment has significant impact on the overall accuracy of location finding. In this paper, we present extensive analytical and simulation results to demonstrate the performance of RFWM technology over mobile channels.

In the past few years, wireless mesh networks (WMNs) have drawn significant attention from academia and industry as a fast, easy, and inexpensive solution for broadband wireless access. In WMNs, it is important to support video communications in an efficient way. To address this issue, this paper studies the multipath routing for multiple description (MD) video delivery over IEEE 802.11 based WMN. Specifically, we first design a framework to transmit MD video over WMNs through multiple paths; we then investigate the technical challenges encountered. In our proposed framework, multipath routing relies on the maximally disjoint paths to achieve good traffic engineering performance. However, video applications usually have strict delay requirements, which make it difficult to find multiple qualified paths with the least joints. To overcome this problem, we develop an enhanced version of Guaranteed-Rate (GR) packet scheduling algorithm, namely virtual reserved rate GR (VRR-GR), to shorten the packet delay of video communications in multiservice network environment. Simulation study shows that our proposed approach can reduce the latency of video delivery and achieve desirable traffic engineering performance in multipath routing environment.

In this paper, we investigate how Multiple Description Coding (MDC) can improve the user's satisfaction for a group of heterogeneous destinations for video multicast over wireless ad hoc networks. Specifically, we explore the independent-description property of MDC with multiple paths to improve the user's satisfaction. In our approach, the assignment of multiple description (MD) video is randomly done by a multicast source node. Based on the assignment of MD video, the multicast source constructs multiple multicast trees accordingly. Simulation results demonstrate that our approach can achieve higher user's satisfaction regardless of the multicast group size.

Wireless mesh networks (WMNs) have attracted increasing attention from the research community as a high-performance and low-cost solution to last-mile broadband Internet access. However, it remains an open challenge to provide mesh clients with efficient handoff among different mesh routers. In this paper, we address channel switching efficiency and load balancing capability during the handoff process. More specifically, (1) we introduce the concept of clique into WMNs to handle channel conflicts among neighboring mesh routers and thus achieve scalability; and (2) we propose a dynamic load balancing strategy for the handoff process, which integrates the mechanisms of mesh router selection and traffic admission control. Simulation results show that our proposed approach achieves significant gain in the handoff delay. Moreover, it provides good performance in terms of load balancing, loss rate and overall throughput.

Recently, wireless mesh networks (WMNs) have drawn significant attention from academia and industry as a fast, easy, and inexpensive solution for broadband wireless access. In WMNs, many important applications, such as mobile TV and video/audio conferencing, require the support of multicast. In this paper, we address the issue of multicast cooperative communications over WMN. Specifically, we identify the selection of relay nodes as a critical step to the success of cooperative multicast. To solve this problem, we develop the concept of in-group/out-group cooperation as well as a distributed relay selection algorithm for the mobile computing environment. Extensive simulation results show that our approach can efficiently mitigate the multicast transmission errors in wireless mesh networks.

Code-division multiple access (CDMA) technology has been applied to many wireless communication systems. CDMA system suffers from both multiple access interference (MAI) and inter-symbol interference (ISI) over a multipath channel. To suppress MAI and ISI, this paper proposes the spreading codes with interference free windows. In particular, we will develop several upper bounds on the efficiency of generalized spreading codes (for both unitary and complementary codes) in terms of the width of their interference free windows.

In wireless mesh network (WMN), it is important to provide an efficient handoff scheme, due to the frequent user mobility. To address this issue, we propose a mobile agent (MA) based handoff approach, where each mesh client has a MA residing on its registered mesh router. To guarantee quality of service (QoS) and achieve differentiated priorities during the handoff, we develop a proportional threshold structured optimal effective bandwidth policy for call admission control (CAC) on the mesh router. Simulation study shows that our proposed CAC scheme can obtain satisfying tradeoff between differentiated priorities and statistical effective bandwidth in WMN handoff environment.

Abstract In this paper, we investigate optimal key management design for secure and survivable heterogeneous wireless sensor networks (HWSNs). In particular, we formulate the key management problem as a multi‐objective optimization problem, in which the cost of the sensor network, and the security and survivability metrics of the sensor network are taken into account. To solve the multi‐objective optimization model, we develop a genetic algorithm (GA)‐based approach that can efficiently obtain near‐optimal solutions. We show the performance of our scheme through extensive numerical results. With a small amount of powerful sensor nodes in HWSN, we can balance the cost of the sensor network and the resilience of the sensor network with the required security constraint in different hostile environment. Copyright © 2008 John Wiley & Sons, Ltd.

Wireless mesh network (WMN) has recently emerged as a promising technology for next-generation wireless networking. In WMNs, many important applications, such as mobile TV and video/audio conferencing, require the support of multicast communication with quality-of-service (QoS) guarantee. In this paper, we address the QoS multicast routing issue in WMNs. Specifically, we propose a novel network graph preprocessing approach to enable traffic engineering and enhance the performance of QoS multicast routing algorithms. In this approach, we employ prioritized admission control scheme and develop a utility-constrained optimal priority gain policy. Extensive simulation results show that our approach can significantly improve the performance of QoS multicast routing in WMNs.

In this paper, we investigate optimal key management design for secure and survivable heterogeneous wireless sensor networks. In particular, we formulate the key management problem as a multi-objective optimization problem, in which the cost of the sensor network, and the security and survivability metrics of the sensor network are taken into account. To solve the multi-objective optimization model, we develop a genetic algorithm (GA) based approach that can efficiently obtain near- optimal solutions. We show the performance of our scheme through extensive numerical results. With a small amount of powerful sensor nodes in heterogeneous wireless sensor network, we can balance the cost of the sensor network and the resilience of the sensor network with the required security constraint in different hostile environment.

WiMAX (Worldwide Interoperability for Microwave Access) is a promising technology for last-mile broadband Internet access. In multiservice WiMAX networks, call admission control (CAC) plays a critical role. In this paper, we address CAC problem from the perspectives of both WiMAX service providers and subscribers. Specifically, we formulate CAC as an optimization problem, in which the demands of service providers and subscribers are taken into account. To solve the optimization problem, we develop a utility and fairness constrained greedy revenue algorithm. Simulation results show that the proposed approach has satisfying performance.

In this paper, we propose a novel downlink resource management framework for multiservice WiMAX (worldwide interoperability for microwave access) networks. Our framework consists of two major components: adaptive power allocation (APA) and call admission control (CAC). We formulate each of them as an optimization problem, where the demands of both WiMAX service providers and subscribers are taken into account. To solve the optimization problems, we develop a fairness-constrained greedy revenue algorithm for downlink APA optimization and a utility-constrained greedy approximation algorithm for downlink CAC optimization. Our simulation results show that, when combining the APA and CAC optimization methods together, the proposed resource management framework can meet the expectations of both service providers and subscribers

For deploying wireless group-oriented applications in an adversarial environment such as battlefield or disaster rescue cases, it is necessary to provide support for secure multicast communication. In this paper, pyramidal security model is proposed to safeguard a special multicast scenario of multi-security- level information broadcast in an information sharing domain of mobile ad hoc network. In order to give an efficient key management solution to the pyramidal security model, we propose an integrated tree key graph scheme. Performance comparison proves that this scheme possesses many advantages over its counterparts.

The main concerns of network performance are throughput, end-to-end packet delay and packet loss. A high-performance network is characterized by high throughput, small delay, and low packet loss. In this paper, a theoretical model to analyse the one hop throughput with regular structure operating under the CSMA/CA access protocol in wireless ad hoc networks is proposed. Numerical results show that we can find an optimal transmission range to achieve the highest throughput. An optimal transmission range is essential to limit the energy dissipation on the mobile devices

The rapid growth of multimedia group-based applications motivates research into QoS guaranteed multicast network. In the multicast network carrying traffics of different QoS requirements, bandwidth fragmentation is considered as a bottleneck for traffic admission fairness and efficient usage of bandwidth resource. When the bandwidth fragmentation happens, the chance of accepting high-bandwidth flows is greatly decreased. To prevent bandwidth fragmentation in multicast network, we propose a new approach of bandwidth fragmentation avoided QoS multicast routing in this paper. In our new approach, we integrate active admission control into traditional QoS multicast routing algorithms to gain bandwidth fragmentation immunity. Moreover, an algorithm named dynamic bandwidth allocation with adaptive constraint is proposed and investigated as an example of active admission control algorithm in this paper. Because this algorithm is nonlinear and unsolvable by analytical approach, we employ OPNET simulation to study its performance.

The next generation communication system will provide high quality multimedia service in a more flexible and intelligent manner. In this paper, we propose a new SIP over MPLS network architecture to achieve this goal. To integrate SIP protocol with the traffic engineering (TE) function of MPLS network seamlessly and facilitate SIP call setup, the SIP-MPLS traffic aggregation server (TA server) is highlighted in this new architecture. Furthermore, the call admission and bandwidth renegotiation algorithms running on the TA server are investigated carefully. We rely on OPNET simulation to assess the performance of our network architecture and the capability of different call admission and bandwidth renegotiation algorithms. The simulation results show that the algorithm of TBCA-BP is a suitable candidate for accomplishing the call admission and bandwidth renegotiation task due to its satisfying performance, and our network architecture is able to shorten the SIP call setup delay greatly by using the TA server.

In order to provide high quality multimedia service in a flexible and intelligent manner, future wired and wireless networks will employ SIP as the call control protocol and MPLS as the core network packet switching technology. In this paper, we propose a traffic aggregation based SIP over MPLS network architecture to integrate SIP protocol with the traffic engineering (TE) function of MPLS network seamlessly. Furthermore, the call admission and bandwidth prediction/re-negotiation algorithms running in this new network architecture are investigated intensively. We rely on OPNET simulation to assess the performance of different call admission and bandwidth prediction/re-negotiation algorithms. The simulation results show that the algorithm of FCFS-LMS-BPR is an eligible candidate for achieving the designated goals.

To make the best use of network resources across a QoS guaranteed multicast network, it is urgent to add a traffic engineering mechanism to the existing QoS multicast routing protocols. We propose a new approach of integrating QoS multicast routing with TE-oriented admission control to offer a traffic engineering function. Moreover, a TE-oriented admission control algorithm, namely dynamic bandwidth allocation with adaptive constraint (DBA-AC), is suggested to make the best use of resources across the entire multicast network by distributing traffic over different paths. Because this admission control algorithm is nonlinear and unsolvable by an analytical approach, we employ OPNET simulation to study its performance.