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Train-to-wayside (T2W) and train-to-train (T2T) communication modes may coexist in future train-centric communication-based train control (CBTC) systems. The feasibility of T2T communication in urban rail transit is analyzed first. Referring to the device-to-device (D2D) communication scenario in the general cellular network, this paper establishes a radio resource optimization model for the coexistence of train-to-train communication and train-to-wayside communication. With the aim of more efficient scheduling of radio time-frequency resources in the dedicated frequency band, we propose a Stackelberg game-based radio resource management algorithm based on the consideration of different service priorities of trains. The analysis and simulation results show that the proposed algorithm can effectively guarantee the performance of the system and improve the reliability of the CBTC system. [ABSTRACT FROM AUTHOR]

Pattern division multiple access (PDMA) is a new non-orthogonal multiple access (NOMA) technology. It is proposed to meet the challenge of 5G large-scale connectivity and high-frequency spectral efficiency. Compared with traditional orthogonal multiple access (OMA), PDMA can support more users through the allocation of non-orthogonal resources. Due to perfect aperiodic correlation, complete complementary sequence (CCS) greatly improves the spectrum efficiency of the system. It has been widely used in wireless communication and radar sensing, and it still has research value in 5G. In order to apply the advantages of CCS to NOMA communication system, this paper proposes a system model of CCS spread spectrum coding based on PDMA. CCS is used as spread spectrum code to improve the performance of PDMA communication system. At the same time, on the basis of spread spectrum technology, this paper analyzes the average power allocation algorithm and water-filling power allocation algorithm, and a dynamic power allocation algorithm based on the transmission rate and practical application is proposed. The simulation results show that the system model can effectively improve the performance of the system. [ABSTRACT FROM AUTHOR]

Mobile services differ from other services because of their temporal and spatial attributes. Mobile services additionally differ from each other in their value-added to the end-user. Some services—such as emailing and voice—are more business oriented. On the other hand, various free-time oriented services are provided in new smartphones, such as imaging and music playback. The present paper studies how mobile services are used in different contexts. For this, the paper develops a specialized algorithm that can be used with handset-based usage data acquired straight from end-users in an established panel study process. Educated guesses can be drawn on the user context based on the developed algorithm. In the present exercise usage contexts were divided into home, office and “on the move”. The algorithm is used with exemplary data from Finland and the UK covering 324 consumers in 2006. More than 70% of contextual use cases are correctly classified based on raw data. According to exemplary results particularly multimedia services are used “on the move”, whereas legacy mobile services experience more evenly distributed usage across all contexts. The algorithm that identifies context based on raw data provides a new angle to mobile end-user research. In the future, the accuracy of the algorithm will be improved with the integration of seamless cell-id logging and GPS data. [ABSTRACT FROM AUTHOR]

In this paper, we study the application of non-monotone derivative-free optimization algorithms to wireless local area networks (WLAN) planning, which can be modeled as an unconstrained minimization problem. We wish to determine the access point (AP) positions that maximize coverage in order to provide connectivity to static and mobile users. As the objective function of the optimization model is not everywhere differentiable, previous research has discarded gradient methods and employed heuristics such as neighborhood search (NS) and simulated annealing (SA). In this paper, we show that the model fulfills the conditions required by recently proposed non-monotone derivative-free (DF) algorithms. Unlike SA, DF has guaranteed convergence. The numerical tests reveal that a tailored DF implementation (termed "zone search") outperforms NS and SA. [ABSTRACT FROM AUTHOR]

Intelligent reflecting surfaces (IRSs) are considered one of the core technologies in sixth-generation (6G) mobile communication. In this paper, we investigate an aerial IRS (AIRS)-enhanced cell-free (CF) massive multiple-input-multiple-output (MIMO)system where multiple APs serve a high-speed mobile user simultaneously. The mobility of the user leads to fast time-varying and nonnegligible Doppler frequency offsets (DFOs), which cause a serious threat to link performance. To overcome the influence of the Doppler effect and reduce the energy consumption of the system, we propose a Doppler compensation and transmission method by using the AIRS. Specifically, we divide the AIRS reflection phase shift vector into two parts: one part is used for Doppler compensation, and the other is used for transmission. First, we propose an angle-sensing algorithm to obtain the user angle in each coherent time (CT) and use it to design a Doppler compensation vector. Then, we propose an angle information-aided transmission strategy to design the transmission reflecting vector, the beamforming vector, and the power allocation coefficient of each AP to minimize the transmission power of all APs at a required achievable rate. The simulation results show that we can significantly reduce the total transmission power by using the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, the secure transmission for high-speed railway (HSR) communication system is studied. The considered HSR wireless communication system consists of a macro base station, B roadside base stations, and K vehicle stations (VSs) on the top of the train, and the eavesdropping user is a mobile unmanned aerial vehicle (UAV). We consider maximizing the sum of the minimum security rate of each time slot as the objective function, and the constraint conditions contain the quality of service (QoS), switch requirements and the total power constraint. The original optimization problem is mixed-integer and non-convex, it is intractable to solve directly. The block coordinate descent (BCD) method is applied, and the original problem can be decoupled into two sub-problems. The one is the joint BS-VS association problem, and the other is the power control problem. The first sub-problem of optimizing BS-VS association can be solved by the successive convex approximation (SCA) algorithm, and the second one of optimizing transmit power can be solved by the lagrangian dual method. Simulation results show that the proposed algorithms have good convergence. [ABSTRACT FROM AUTHOR]

The diffusion of Device-to-Device (D2D) communications opens the door to exploit the contributions of multiple Mobile Devices (MDs) to accomplish collaborative tasks. In this paper a speaker recognition algorithm for MDs based on a multiple-observations approach is presented. We propose various fusion and clustering algorithms aimed at efficiently exploiting data coming from MDs. Numerical results show that in many cases our multiple-observation approach is able to significantly improve the accuracy of the considered speaker recognition algorithm. [ABSTRACT FROM AUTHOR]

It is expected that next-generation wireless networks will provide a plethora of mobile wireless services to users and ubiquitous network coverage at all times. Meeting these expected goals requires that new and existing networks be seamlessly integrated together to form Heterogeneous Wireless Networks (HWNs). Thus, seamless and efficient handover mechanisms are pertinent for optimal network performance in HWNs; so that the mobile user can switch from one access network to another, in search of the best connection for the demanded services. The HWNs' performance can be reduced, if efficient network selection is not achieved. In HWNs, network-selection decisions can be evaluated by using multi-criteria, or a single criterion. However, network selection and decision-making in HWNs often involves taking into account a large number of complex and conflicting network-decision factors, or criteria. Thus multi-criteria decision-making techniques are more efficient than single-criterion techniques. Multi-Criteria Decision-Making (MCDM) techniques comprise of a developed branch of operational research for assisting in the resolution of complex decision-making problems. MCDM is an important tool that has been used to model and analyze handover-decisions and network-selection problems in HWNs. This paper reviews and classifies the most significant MCDM algorithms that have been used to address the network decision-making problems in HWNs in terms of algorithmic approach, the type of calls, the cardinality of decision criteria employed, handover-control points and the types of network utilities. Comprehensive step-wise mathematical implementations of the reviewed MCDM schemes are presented, while pointing out their strengths and limitations. This paper review fills a research gap in the investigation on network-selection criteria's interdependence and interactions, and their effects on criteria's weight of importance. It then provides an insight into the importance of network-criteria weighting and the current research trend in the application of MCDM algorithms to network-selection problems in HWNs. [ABSTRACT FROM AUTHOR]

Random interleavers are the most preferred interleavers utilized in digital and cellular communication systems for burst errors control. Fisher-Yates shuffling algorithm and its several modified versions offer alternate techniques of generating random permutations popularly employed in the areas of computer programming, information theory and cryptography for data security purposes. In this short paper, Modern Fisher-Yates shuffling algorithm, also known as Durstenfeld's algorithm, has been explored to generate random interleavers and further applied in single carrier frequency division multiple access based interleave division multiple access (SCFDMA-IDMA) systems. The results show that random interleavers generated by applying this algorithm are suitable enough to be employed in SCFDMA-IDMA system without compromising its performance. [ABSTRACT FROM AUTHOR]

Mobility with high degree of network-facility is a mandatory attribute for better QoS in cellular networks, but it leads to a huge increment in energy consumption, a significant fraction of which related to the base stations within the service area. In this paper, we are introducing a base station cooperation technique for energy efficiency in mobile communication networks, and it is based on nature-inspired computing, especially the Bee system. All serving base stations within a given geographical area will work together to provide a better network experience to the mobile subscriber. In order to achieve this, base stations will check for availability of unutilized (or underutilized) bandwidth and if it is over a certain threshold, all base stations perform a re-reunion procedure to provide a uniform distribution of the consumed bandwidth (bandwidth load), thereby providing better service to users. We have formulated the proposed technique to determine the effectiveness, efficiency and scalability of work. Further we create a simulation setup for proposed algorithm using OPNET to implement a real time cellular networks. It has been observed that results of proposed work have sufficient improvement in energy efficiency at the base station with respect to traditional schemes. [ABSTRACT FROM AUTHOR]

The identification of cohesive communities is a key process in social network analysis. However, the algorithms that are effective for finding communities do not scale well to very large problems, as their time complexity is worse than linear in the number of edges in the graph. This is an important issue for those interested in applying social network analysis techniques to very large networks, such as networks of mobile phone subscribers. In this respect, the contributions of this paper are twofold. First, we demonstrate these scaling issues using a prominent community-finding algorithm as a case study. Then, we show that a two-stage process, whereby the network is first decomposed into manageable subnetworks using a multilevel graph partitioning procedure, is effective in finding communities in networks with more than 10 nodes. [ABSTRACT FROM AUTHOR]

Vehicular Ad hoc NETworks (VANET) is emerging as a highly promising technology, which aims to provide road safety, environment protection and personal-oriented services. The vehicle ad hoc wireless communications form an indispensable part of truly ubiquitous communications networking. VANET is formed by spontaneously moving autonomous vehicles with the self-organization and self-management capability. In this paper, we focus on the decentralized coordination of multiple unmanned vehicles such that they can freely move and adaptively cooperate in a complex environment. During this procedure, flocking is one of the key operations and requirements. Here, flocking refers to the formation and maintenance of a desired pattern by a group of mobile vehicles without collision during movement. We propose a resilient and scalable flocking scheme for a group of vehicles, which follows the leader–followers moving pattern. In the absence of obstacles, a collision avoidance algorithm is presented to maintain a desired distance among vehicles. This will ensure information completeness and is significant in certain mission critical situations without collision between a unmanned vehicle and its neighboring vehicles. In the presence of obstacles in an environment, this algorithm is able to avoid collision between a vehicle and its neighbor (either a neighboring vehicle or a neighboring obstacle). Theoretical proof has been presented to demonstrate the effectiveness and correctness of the algorithm to guarantee collision-free. In addition, with increasing number of vehicles, the performance of the proposed flocking scheme performs without increasing the processing overhead, which demonstrates the desirable scalability. [ABSTRACT FROM AUTHOR]

The development of the IEEE wireless technologies is promising the ultimate Internet service deployment on wireless and mobile infrastructures since they would offer larger bandwidth at cheaper price. However, it is disquieting to see that the different control algorithms supposed to be the heart of the wireless deployment are not evolving as fast as the wireless technologies do. Here we come up with the hard question: how to pilot these control algorithms? This paper is proposing a revolutionary tyre where all control algorithms are fed in a concerted manner by a self-steering system. In network terms, this paper is proposing a definitely new technology that will permit to optimize, secure, manage and control the wireless devices using an automatic pilot system. [ABSTRACT FROM AUTHOR]

Today, mobile and smart phones are often viewed as enablers of pervasive computing systems because they provide anytime and anywhere access to information services and computational resources. However, mobile devices are inherently constrained in their computational power and battery capacity making them mere “dumb terminals” connected to a resource-rich pervasive environment. If they are ever to play a more prominent role as true elements of a pervasive environment, mobile devices must be able to embed more application logic and delegate processing requests to pervasive infrastructure. In this paper we discuss distribution and offloading of computationally intensive tasks in pervasive environments populated by mobile devices. This approach is illustrated by experimenting with a distributed version of iterative deepening A* search algorithm. In our approach, the solution space of a problem being solved is partitioned and distributed among heterogeneous mobile devices, which yields a significant increase in the time of finding an optimal solution. Distributed IDA* search algorithm does not require any coordination or communication between mobile devices, but added inter-processor communication through shared memory further increases the efficiency of the algorithm. This paper presents the results of our experiments with the algorithm and discusses a number of issues related to its implementation. [ABSTRACT FROM AUTHOR]

High Altitude Platforms (HAPs) are currently experiencing a great interest as potential solutions for the growing demand of wireless broadband applications, but their rapid motion and the characteristics of the stratospheric channel, which may cause strong attenuation, multipath fading and Doppler shift, can strongly impact their performances. The described scenario requires the use of beamforming techniques, able to provide medium to high gains in a mobile environment. Given these premises, this paper discusses the conjugation of OFDM techniques with smart antennas for HAP-based communications, stressing the need for integration of the different functional blocks of an OFDM receiver. In fact, in order to face a time varying scenario, adaptive techniques are needed, and only a careful joint design of time and frequency synchronization with beamforming algorithms can guarantee reliable communication. The detailed and integrated receiver design described in the paper is based on the OFDM version of the IEEE 802.16a transmission standard. [ABSTRACT FROM AUTHOR]

Abstract Service discovery is an integral part of constructing self-configuring Mobile Ad Hoc Networks (MANETs). While several service discovery protocols have been developed, most of them are designed for infrastructure-based networks and thus not suitable to be used in MANETs. Due the volatile nature of MANET, service discovery protocols designed for MANETs often suffer from problems. Firstly, they have limited scalability due to the extensive use of broadcast communication. Secondly, they usually lack context-aware selection mechanisms and feature only reduced interaction standards. This paper proposes a network layer supported comprehensive service discovery solution that addresses the above issues and provides a solution in two parts. First it discusses a location-aware network layer routing protocol that groups mobile nodes into clusters while a gateway in each cluster is responsible for routing. Secondly, this paper proposes a service discovery protocol that utilizes directories for service discovery that interact with lower network layer gateway configurations. In this architecture, gateways are also used as directories for service discovery to improve performance. In doing so, we improve the systems overall efficiency by eliminating the use of complex graph-based algorithms for maintaining clusters and establishing virtual backbones. Furthermore, this service discovery solution includes an agent-based context-aware service selection, and provides standard mechanisms for different types of service interaction. [ABSTRACT FROM AUTHOR]

In this paper, we present an iterative technique for sequential mobile power updates in wireless CDMA networks based on Gauss-Seidel iterations. The obtained algorithm is distributed and has the same complexity as the popular DPC (distributed power control) algorithm, which is based on Jacobi iterations and which assumes simultaneous power updates for all mobiles that use the same frequency channel. The paper demonstrates that the newly presented algorithm converges faster than the DPC algorithm. The constrained version of the new algorithm is also presented indicating that it has the same complexity as the constrained DPC algorithm, known as DCPC, but its speed of convergence is superior over the convergence speed of DCPC algorithm. [ABSTRACT FROM AUTHOR]

The device-to-device (D2D) communication, as a high-speed communication from device to device, has attracted large researchers' attention recently. Namely, by using the D2D communication in the cellular networks, mobile users can transmit data to the adjacent users at a faster rate. As a result, a large part of cellular data traffic can be diverted, reducing the overhead of data transmission from the base station and saving the energy as well as improving the spectrum efficiency. However, in the heterogeneous networks where cellular and D2D communication coexists when the D2D devices are connected to the network, the network performance is not only affected by the slow and fast fading factors, but also by the access network selection strategy and network switching factors. With the aim to improve the network performance, this paper proposes a game theory-based D2D network access algorithm for heterogeneous networks. The proposed algorithm can adapt to the dynamic changes of the network environment while avoiding unnecessary switching by considering the properties of the user equipment and network utilization, and thus improving the network throughput and reducing the delay. The experimental results demonstrate that the proposed algorithm has better performance than the flow algorithm. [ABSTRACT FROM AUTHOR]

The rapid development of mobile broadband services with continuously increasing traffic volumes has resulted in a number of challenges, including ubiquitous network coverage, high bandwidth, and reliable services for reasonable price, etc. To address these challenges, evolved packet system (EPS) is proposed as the evolution of the packet core network. While resource management and load balancing issues in EPS are discussed in 3GPP standardization, relatively few research works consider mechanism design for load information monitoring and evaluation. Furthermore, even though some load balancing algorithms have been proposed for integrated networks, the load balancing scheme design which achieves the optimization of joint system performance has not been extensively studied. In this paper, an inter-access system anchor based load balancing mechanism is introduced which performs load monitoring and evaluation for access gateways and networks, and an optimal load balancing algorithm is proposed for heterogeneous integrated networks. To characterize the performance of integrated networks, the concept of utility function is introduced and the comprehensive performance of integrated networks which support both single type service and multimedia service is modeled mathematically. Applying vertical handoff as an efficient mechanism for achieving load balancing, the optimal number of handoff users is obtained through solving the optimization problem. Numerical results demonstrate that load balancing between access networks can be achieved, and the optimal number of handoff users corresponding to the maximal joint network utility can be obtained. [ABSTRACT FROM AUTHOR]

Femtocells are considered as a solution for indoor high data rate demands. Interference mitigation is a fundamental challenge in two-tier femto-macrocell networks. In this paper, we consider six-sector macrocell layout for reducing the co-tier interference in the macrocell network and cross-tier interferences from macrocell to femtocell network. As interference reduces, the whole of available spectrum can be used in each macrocell which increases the spectrum efficiency. We also consider interference-level algorithm to allocate resource for femtocell in which macrocell uses the whole of spectrum. In the coverage area of each sector, femtocell uses a portion of the spectrum that is not used by the macrocell users. This approach ignores the high co-channel interference from the macrocell network to the femtocell network and vice versa in each sector. Simulation results show that the proposed layout and interference management scheme reduce the downlink interference and increase the efficiency of the orthogonal frequency division multiple access (OFDMA)-based femtocell and macrocell. Consequently, system throughput and outage probability are improved significantly. [ABSTRACT FROM AUTHOR]

In this paper, the well-known network backbone formation problem is modeled as the stochastic min-degree constrained minimum spanning tree (md-MST) problem, where the link duration is associated with the edge weight. Then, a decentralized learning automata-based algorithm is proposed to form the most stable backbone of the wireless mobile ad hoc network (MANET) by finding a near optimal solution to the stochastic md-MST problem of the network topology graph. The proposed method significantly decreases the network overhead and shortens the network delay by reducing the number of intermediate forwarding hosts. It also extends the backbone lifetime by selection of the links with the maximum expected duration. The convergence of the proposed algorithm to the most stable network backbone is proven on the basis of the Martingale theorem. Several simulation experiments are conducted to investigate the efficiency of the proposed backbone formation algorithm. Numerical results show the superiority of the proposed method over the existing methods in terms of the backbone lifetime, end-to-end delay, backbone size, packet delivery ratio, and control message overhead. [ABSTRACT FROM AUTHOR]

QR-decomposition with M-algorithm (QRDM) achieves quasi-ML performance in multiple-input multiple-output (MIMO) multiplexing systems. Nevertheless, QRDM performs avoidable computations because of its systematic search strategy and its failure to consider the channel and noise conditions. Another drawback is that QRDM is sequential, which limits pipelining capabilities. In this paper, we propose quasi-ML adaptive parallel QRDM (APQRDM) and adaptive iterative QRDM (AIQRDM) algorithms based on set grouping. In set grouping, the tree-search stage of the QRDM algorithm is divided into partial detection phases (PDPs). These are processed in parallel and iteratively in the proposed APQRDM and AIQRDM algorithms, respectively. Therefore, when the tree-search stage of the QRDM algorithm is divided into G PDPs, the latency of the proposed APQRDM algorithm and the hardware requirements of the proposed AIQRDM algorithm are reduced by a factor of G compared to the QRDM algorithm. Moreover, simulation results show that in 4 × 4 MIMO system, and at E/ N of 12 dB, APQRDM decreases the average computational complexity to approximately 43% that of the conventional QRDM. Also, at E/ N of 0 dB, AIQRDM algorithm reduces the computational complexity to about 54%, and the average number of metric comparisons to approximately 10%, compared to the conventional QRDM. [ABSTRACT FROM AUTHOR]

Mobile social networks, which consist of mobile users who communicate with each other using cell phones, are reflections of people's interactions in social lives. Discovering typed communities (e.g., family communities or corporate communities) in mobile social networks is a very promising problem. For example, it can help mobile operators to determine the target users for precision marketing. In this paper we propose discovering typed communities in mobile social networks by utilizing the labels of relationships between users. We use the user logs stored by mobile operators, including communication and user movement records, to collectively label all the relationships in a network, by employing an undirected probabilistic graphical model, i.e., conditional random fields. Then we use two methods to discover typed communities based on the results of relationship labeling: one is simply retaining or cutting relationships according to their labels, and the other is using sophisticated weighted community detection algorithms. The experimental results show that our proposed framework performs well in terms of the accuracy of typed community detection in mobile social networks. [ABSTRACT FROM AUTHOR]

One of the important issues of green mobile networking is the low energy consumption for either mobile devices or transmissions. To adapt this, a low-cost Inter frame mode decision (MD) algorithm is proposed for H.264/AVC encoder to reduce the computational complexity of the original encoding procedure in this paper. The information extracted from macroblock (MB), such as energy, temporal domain mode similarity and so on, which can be used to pre-estimate the optimal mode of the MB is investigated and utilized to eliminate the redundant mode candidates. The performance evaluations including quantitative analysis and PC simulations show that the proposed algorithm is an energy-efficient source coding because it can reduce around 85% Inter frame encoding time with little quality loss. It can be widely implemented in green mobile networking systems with H.264/AVC standard to realize the real-time video signal coding. [ABSTRACT FROM AUTHOR]

In this paper, we propose an auto-tuning of mobility algorithm in the mobile communication systems as a load balancing self-optimization use case. This paper presents a distributed approach in which the traffic load can be balanced systematically by utilizing the effective load information of neighboring cells. The proposed load balancing scheme detects a load imbalance in the network and resolves the problem automatically by controlling the handover parameter as a nonlinear function of the load difference. Based on control theory, we analyze the adaptive behavior of the proposed controller and derive condition for system stability. Results from asymptotic analysis and simulation indicate that the proposed local controller of each individual cell effectively achieves the global properties, such that the load difference in the network is stabilized globally within a predetermined threshold. Extensive simulation results also show that the proposed scheme outperforms the existing methods by reducing call blocking rate of the overloaded cells. [ABSTRACT FROM AUTHOR]

Media delivery, especially video delivery over mobile channels may be affected by transmission bitrate variations or temporary link interruptions caused by changes in the channel conditions or the wireless interface. In this paper, we present the use of Priority-based Media Delivery (PMD) for Scalable Video Coding (SVC) to overcome link interruptions and channel bitrate reductions in mobile networks by performing a transmission scheduling algorithm that prioritizes media data according to its importance. The proposed approach comprises a priority-based media pre-buffer to overcome periods under reduced connectivity. The PMD algorithm aims to use the same transmission bitrate and overall buffer size as the traditional streaming approach, yet is more likely to overcome interruptions and reduced bitrate periods. PMD achieves longer continuous playback than the traditional approach, avoiding disruptions in the video playout and therefore improving the video playback quality. We analyze the use of SVC with PMD in the traditional RTP streaming and in the adaptive HTTP streaming context. We show benefits of using SVC in terms of received quality during interruption and re-buffering time, i.e. the time required to fill a desired pre-buffer at the receiver. We present a quality optimization approach for PMD and show results for different interruption/bitrate-reduction scenarios. [ABSTRACT FROM AUTHOR]

Flooding is one of the most essential and commonly used operations in mobile ad hoc networks. Different sender-based and receiver-based flooding algorithms have been presented separately in the literature. To integrate the advantages of sender-based and receiver-based flooding algorithms, this paper proposes a novel joint 1-hop neighbor information-based flooding scheme that consists of two sub-algorithms: the sender-phase algorithm and the receiver-phase algorithm. The sender-phase algorithm of our flooding scheme helps a node select a subset of its 1-hop neighbors to forward the flooding message. Based on the convex-hull concept, this algorithm selects forwarding nodes with the highest contribution to flooding message dissemination. On the other hand, the receiver-phase algorithm complements the sender-phase algorithm, allowing our flooding scheme to guarantee full delivery. We prove that our flooding scheme requires lower time complexity O( n log h), where h is the number of forwarding nodes, than the best known 1-hop neighbor information-based flooding algorithms proposed by Liu et al. and Khabbazian et al. Additionally, to alleviate the local optimal problem caused by sender-based flooding algorithms, we relax the full delivery requirement and modify our flooding scheme to discard more redundant rebroadcasting operations. Simulation experiments are conducted to compare the performance of our flooding schemes with those of Liu et al.'s and Khabbazian et al.'s flooding algorithms. The simulation results show that our flooding schemes accomplish a lower ratio of broadcasting nodes and a higher message delivery ratio simultaneously under various network conditions. Moreover, since our flooding schemes have lower ratios of broadcasting nodes, they incur fewer packet collisions on the network. Consequently, message disseminations applying our flooding schemes have a smaller effect on other transmissions of different message types. [ABSTRACT FROM AUTHOR]

Clustering in mobile ad hoc network (MANET) play a vital role in improving its basic network performance parameters like routing delay, bandwidth consumption and throughput. One-hop clustering scheme adopts the simple mechanism to make the logical partition of the dynamic network where the network topology changes constantly resulting an unstable clustering. This paper makes a comprehensive survey of some bench-mark one-hop clustering algorithms to understand the research trends in this area. The literature provides the logic of cluster formation for different algorithms in achieving a linked cluster architecture and an intensive simulation survey of their performance on the cluster maintenance aspects such as cluster density, frequency of cluster reelection, frequency of cluster changes by the nodes and the granularity of cluster heads. This paper should facilitate the researchers as well as practitioners in choosing a suitable clustering algorithm on the basis of their formation and maintenance overhead, before any routing scheme is adopted in the mobile ad hoc network. [ABSTRACT FROM AUTHOR]

Abstract  The autoconfiguration algorithm of the mobile node addresses is important in the practical usage of most mobile ad hoc networks (MANETs). The passive Duplicate Address Detection (PDAD) protocols can detect address conflicts in a passive manner and thus have very low protocol overhead. However, the blindly random assignment algorithm used in PDAD leads to a high initial conflict probability. In this paper, we propose a novel concept of address agent, based on which arises a novel autoconfiguration approach, to obtain the least address conflict probability. Most features of PDAD are inherited, e.g., address conflicts are still detected in a passive manner based on anomalies in routing protocol traffic. Analysis and simulation show that our algorithm outperforms existing methods. [ABSTRACT FROM AUTHOR]

Iterative equalization using optimal multiuser detector and optimal channel decoder in coded CDMA systems improves the bit error rate (BER) performance tremendously. However, given large number of users employed in the system over multipath channels causing significant multiple-access interference (MAI) and intersymbol interference (ISI), the optimal multiuser detector is thus prohibitively complex. Therefore, the sub-optimal detectors such as low- complexity linear and non-linear equalizers have to be considered. In this paper, a novel low- complexity block decision feedback equalizer (DFE) is proposed for the synchronous CDMA system. Based on the conventional block DFE, the new method is developed by computing the reliable extrinsic log-likelihood ratio (LLR) using two consecutive received samples rather than one received sample in the literature. At each iteration, the estimated symbols by the equalizer is then saved as a priori information for next iteration. Simulation results demonstrate that the proposed low-complexity block DFE algorithm offers good performance gain over the conventional block DFE. [ABSTRACT FROM AUTHOR]

Abstract??This paper investigates the power saving mechanism of Universal Mobile Telecommunications System (UMTS). UMTS discontinuous reception (DRX) is exercised between the network and a mobile station (MS) to save the power of the MS. The DRX mechanism is controlled by two parameters: the inactivity timer thresholdtIand the DRX cycletD. Analytic analysis and simulation model are proposed to study the optimaltIandtDselections that maximize the MS power saving under the given mean packet waiting time constraint. We also devise an adaptive algorithm called dynamic DRX (DDRX). This algorithm dynamically adjusts thetIandtDvalues to enhance the performance of UMTS DRX. Our study quantitatively shows how to select the best inactivity timer and DRX cycle values for various traffic patterns. We also show that DDRX nicely captures the user traffic patterns, and always adjusts thetIandtDclose to the optimal values. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new empirical formula for handover rate as a function of base stations separation, standard deviation of shadow fading, path loss exponent, averaging distance, and correlation distance. The handover initiation algorithm is based on averaged signal strength measurements using relative signal strength with hysteresis margin approach. We generate the data through computer simulations for the average number of handovers referred to as handover rate, for the practical range of path loss exponent and standard deviation of shadow fading. The proposed formula provides for a practical design tool to optimize the handover initiation performance under varied propagation environments. [ABSTRACT FROM AUTHOR]

Abstract In mobile computing environments, vital resources like battery power and wireless channel bandwidth impose significant challenges in ubiquitous information access. In this paper, we propose a novel energy and bandwidth efficient data caching mechanism, called GreedyDual Least Utility (GD-LU), that enhances dynamic data availability while maintaining consistency. The proposed utility-based caching mechanism considers several characteristics of mobile distributed systems, such as connection-disconnection, mobility handoff, data update and user request patterns to achieve significant energy savings in mobile devices. We develop an analytical model for energy consumption of mobile devices in a dynamic data environment. Based on the utility function derived from the analytical model, we propose algorithms for cache replacement and passive prefetching of data objects. Our comprehensive simulation experiments demonstrate that the proposed caching mechanism achieves more than 10% energy saving and near-optimal performance tradeoff between access latency and energy consumption. [ABSTRACT FROM AUTHOR]

The accommodation of various traffic load situations in W-CDMA-based cellular systems requires the engineering of the allowed interference levels per cell. This paper presents functionality that can complement the design and management as well as the mechanisms required. The overall scheme is called Interference Level Configuration (ILC). It relies on the solution of problems, which will be concisely defined, optimally formulated and solved by computationally efficient algorithms. The proposed herewith algorithms are also able to co-operate with soft computing (SC) methods to the solution of problems in the power control domain. Numerical results will be presented. [ABSTRACT FROM AUTHOR]

In cellular mobile communication systems, radio channels are repeatedly used in order to efficiently use assigned frequency bands. The computation time for the optimization of channel assignment increases with the increase of cell number. This paper presents a group channel assignment method for the optimization and its simulation results. This method utilizes the genetic algorithm (GA). Prior to the optimization calculation, whole channel cells are divided into subgroups and then, each subgroup is optimized. Using this result, the whole cells are further optimized. This process enables an efficient calculation to optimize the channel assignment. The results of simulation shows that the proposed method gives a shorter computation time compared with the method called as the individual assignment. [ABSTRACT FROM AUTHOR]

As devices become smaller and wireless networking technologies improve, the popularity of mobile computing continues to rise. In today's world, many consider devices such as cell phones, PDAs, and laptops as essential tools. As these and other devices become increasingly independent of the wired infrastructure, new kinds of applications that assume an ad hoc network infrastructure are being deployed. Their development forces software engineers to revisit well understood problems in a setting in which existing solutions are no longer working. This paper illustrates one such attempt by focusing on an important problem in distributed computing, termination detection in diffusing computations, in an ad hoc network environment. We formulate an algorithmic solution amenable to usage in mobile ad hoc networks. Along the way, we highlight several important software engineering concerns one must address and design strategies one might employ in a mobile setting. [ABSTRACT FROM AUTHOR]

In this paper we propose a Connection Admission Control (CAC) algorithm to provide Quality of Service (QoS) in UMTS Terrestrial Radio Access Networks (UTRAN). In UTRAN, the main QoS requirement is to ensure low packet delays. The CAC algorithm works with priority scheduling, which is used for QoS differentiation. We give a detailed investigation on the performance implications of applying priority scheduler. We provide novel closed-form formulae which are fast, simple and accurate enough for practical implementation of the CAC. A comprehensive performance evaluation study with illustrative numerical examples is also presented. The results are validated by simulations. [ABSTRACT FROM AUTHOR]

Abstract Link Adaptation (LA) has been proposed in the literature as a means of increasing the throughput obtained by each user in wireless communication systems. Due to its significant simplicity, LA has even been adopted as the standard adaptive coding technique for the next generation mobile communication system known as EDGE. In this paper, we present a novel link adaptation technique, valid for use in the case of Rayleigh fading wireless channels. The new technique is based on the blind channel estimation algorithm usually used for combating inter-symbol interference (ISI). The algorithm is presented and its efficiency in providing the maximum available throughput is illustrated by means of computer simulations. [ABSTRACT FROM AUTHOR]

The research issue of broadcasting has attracted a considerable amount of attention in a mobile computing system. By utilizing broadcast channels, a server continuously and repeatedly broadcasts data to mobile users. These broadcast channels are also known as “broadcast disks” from which mobile users can retrieve data. Using broadcasting, mobile users can obtain the data of interest efficiently and only need to wait for the required data to present on the broadcast channel. The issue of designing proper data allocation in the broadcast disks is to reduce the average expected delay of all data items. We explore in this paper the problem of generating hierarchical broadcast programs with the data access frequencies and the number of broadcast disks in a broadcast disk array given. Specifically, we first transform the problem of generating hierarchical broadcast programs into the one of constructing a channel allocation tree with variant-fanout. By exploiting the feature of tree generation with variant-fanout, we develop a heuristic algorithm VFK to minimize the expected delay of data items in the broadcast program. In order to evaluate the solution quality obtained by algorithm VFK and compare its resulting broadcast program with the optimal one, we devise an algorithm OPT based on a guided search to obtain the optimal solution. Performance of these algorithms is comparatively analyzed. Sensitivity analysis on several parameters, including the number of data items and the number of broadcast disks, is conducted. It is shown by our simulation results that by exploiting the feature of variant-fanout in constructing the channel allocation tree, the solution obtained by algorithm VFK is of very high quality and is in fact very close to the optimal one resulted by algorithm OPT. Moreover, algorithm VFK is of very good scalability which is important for algorithm VFK to be of practical use to generate hierarchical broadcast programs dynamically in a mobile computing environment. [ABSTRACT FROM AUTHOR]

The 5G wireless communication system supports varied applications, making the uplink/downlink traffic asymmetry more and more serious. Dynamic time division duplex (TDD) technique has become a key technology of 5G networks due to its flexibility to support asymmetric services. In this paper, we study dynamic TDD sub-frame reconfiguration algorithm based on shifting. Firstly, we define cell shifting priority considering both traffic and interference. Then, we perform cell shifting-based TDD sub-frame reconfiguration following cell shifting priority. Simulation results show that the proposed dynamic TDD algorithm can guarantee high data rate and low interference, thus effectively increases the network throughput. [ABSTRACT FROM AUTHOR]

In this paper we propose a noisy Multivariate Autoregressive (MVAR) process for modeling and estimating the correlated fading channels. The method can estimate joint MVAR processes and model parameters from noisy received signal. The proposed method is based on serial connection of two algorithms. In the first algorithm, we estimate MVAR model parameters. For this purpose, a combination of Yule-Walker equations is used. This combination is considered as a generalized eigenvalue problem; an estimate for receiver noise variance is obtained by solving this eigenvalue problem then Least-Squares method is used to estimate the MVAR model parameters. In the second algorithm, the fading process is estimated by using Kalman filter. Simulation results show that the proposed method has good performance compared with other existing methods. [ABSTRACT FROM AUTHOR]

With the rapid growth in cellular user quantity and quality of service demand, the resource allocation in device-to-device communication system significantly affects the overall efficiency and user experience. In this study, the resource allocation for large-scale device-to-device communication system is modelled as a constrained optimization problem with thousands of dimensionalities. Then, the variable-coupling relationship of the developed model is analysed and the mathematical proof is firstly provided, and a novel algorithm namely multi-modal mutation cooperatively coevolving particle swarm optimization is developed to optimize the ultra-high dimensional model. Finally, efficacy of the developed method is verified by a comprehensive set of case studies, some famous algorithms for the specialized literature are also employed for comparison. Experimental results shown that the developed algorithm can obtain accurate and robust optimization performance for different system scales. In addition, when the system scale increases to 1000 cellular users and 300 D2D-pair users, the developed method can still outperform the compared algorithms and output accurate resource allocation solution. [ABSTRACT FROM AUTHOR]

The Orthogonal Frequency Division Multiplexing (OFDM) method provides effective bandwidth utilization and straightforward Frequency Domain Equalization (FDE). The OFDM system can be applied without a group of modulators and demodulators by using the Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT). The Fast Walsh Hadamard Transform (FWHT) and Inverse Fast Walsh Hadamard Transform (IFWHT) can also be used to build the OFDM system. In this work, we employ the IFWHT and FWHT to build the OFDM. This is followed by a proposal for a Joint Low-Complexity Regularized Zero Forcing-Successive Interference Cancellation (JLCRZF-SIC) equalizer with respect to various linear and nonlinear equalizers at various antenna configurations. A closed form for arithmetic operation count for the proposed equalizer is proposed. The proposed equalizer executes the equalization process more accurately than other schemes with low-complexity deployments. The analysis results show that the proposed equalizer outperforms the conventional one. [ABSTRACT FROM AUTHOR]

Currently, mobile devices are becoming the popular instrument for accessing the cloud environment. Mobile devices are resource and energy limited; they can rely on cloud computing resource to perform computationally intensive operations such as data mining and multimedia processing. This paper presents the cost and energy aware service provisioning scheme for mobile client in mobile cloud, which includes two-stage optimization process. In the first-stage optimization process, the mobile cloud user gives the unique optimal payment to the cloud provider under the cost and energy constraint and optimizes its benefit. In the second-stage optimization process, mobile cloud provider runs multiple VMs to execute the jobs for mobile cloud users; the cloud providers also need to maximize the revenue. The cost and energy aware service provisioning algorithm in mobile cloud is proposed. The proposed algorithm is involved with the cloud datacenter provider's optimization and mobile cloud user's optimization, which are conducted by two routines. In the simulation, the proposed cost and energy aware mobile cloud service provisioning algorithm is compared with other related algorithm. [ABSTRACT FROM AUTHOR]

Coupling sensors in a sensor network with mobility mechanism can boost the performance of wireless sensor networks (WSNs). In this paper, we address the problem of self-deploying mobile sensors to reach high coverage. The problem is modeled as a multi-objective optimization that simultaneously minimizes two contradictory parameters; the total sensor moving distance and the total uncovered area. In order to resolve the aforementioned deployment problem, this study investigates the use of biologically inspired mechanisms, including evolutionary algorithms and swarm intelligence, with their state-of-the-art algorithms. Unlike most of the existing works, the coverage parameter is expressed as a probabilistic inference model due to uncertainty in sensor readings. To the best of our knowledge, probabilistic coverage of mobile sensor networks has not been addressed in the context of multi-objective bio-inspired algorithms. Performance evaluations on deployment quality and deployment cost are measured and analyzed through extensive simulations, showing the effectiveness of each algorithm under the developed objective functions. Simulations reveal that only one multi-objective evolutionary algorithm; the so-called multi-objective evolutionary algorithm with decomposition survives to effectively tackle the probabilistic coverage deployment problem. It gathers more than 78 % signals from all of the targets (and in some cases reaches 100 % certainty). On the other hand, non-dominated sorting genetic algorithm II, multi-objective particle swarm optimization, and non-dominated sorting particle swarm optimization show inferior performance down to 16-32 %, necessitating further modifications in their internal mechanisms. [ABSTRACT FROM AUTHOR]

This paper considers the self-deployment of wireless sensor networks. Conventional deployment problem usually focuses on enhancing the coverage, while the conditions for network connectivity are largely simplified. We present a deployment scheme to enhance the coverage while keeping the network connected at each step of the deployment. Our scheme contains two parts. The coverage improvement part proposes an improved force-based mechanism. A limit is provided to determine the sensors which should attractive each other, so the wasted overlap and communication resource can be reduced. The connectivity preservation part provides constrains for the movement distance of each sensor, in order to take account of both connectivity and coverage enhancement. Some simulation results are presented to show the connectivity preservation and coverage maximization properties of our mechanism. [ABSTRACT FROM AUTHOR]

In view that authentication has made a significant determinant in handover delay, this paper presents a fast authentication mechanism for mobile stations roaming within a WiMAX-WLAN interconnected environment. Incorporating a key reuse design that prevents repeated transactions at a remote server, our mechanism distributes security contexts ahead of handover to a local trusted key holder which manages several sites. A target site, upon receiving a mobile station, retrieves the contexts locally for authentication purpose and thus completes handover efficiently. While employing a target prediction algorithm as an option, our mechanism distributes the contexts to target candidates as dictated, which further improves handover performance if target prediction hits and maintains its advantage even in a miss. In addition, the handover optimization design specified in WiMAX is extended to support WiFi-to-WiMAX handovers. We reason that the proposed mechanism does not compromise the system in any sense as well. Analytical and simulation results show that, despite key pre-distribution misses, our mechanism leads to marked improvement over counterpart schemes in terms of handover delay and packet loss, meeting delay-sensitive application requirements. [ABSTRACT FROM AUTHOR]

In this paper, we propose a range-free cooperative localization algorithm for mobile sensor networks by combining hop-distance measurements with particle filtering. In the hop-distance measurement step, we design a differential-error correction scheme to reduce the positioning error accumulated over multiple hops. We also introduce a backoff-based broadcast mechanism in our localization algorithm. It efficiently suppresses redundant broadcasts and reduces message overhead. The proposed localization method has fast convergence with small location estimation error. We verify our algorithm in various scenarios and compare it with conventional localization methods. Simulation results show that our proposed method has similar or superior performance when compared to other state-of-the-art localization algorithms. [ABSTRACT FROM AUTHOR]

As mobile nodes roam in a wireless network, they continuously associate with different access points and perform handoff operations. Frequent handoffs performed by a mobile device may have undesirable consequences, as they can cause interruptions for interactive applications and increase the energy usage of mobile devices. While existing approaches to this issue focus entirely on improving the latency incurred by individual handoffs, in this paper, we initiate a novel approach to association control of mobile devices with the goal of reducing the frequency of handoffs for mobile devices. We study the handoff minimization problem across multiple dimensions: offline versus online where the complete knowledge of mobility patterns of users is known in advance or unknown respectively; capacity constrained versus unconstrained access points, which imposes limits on the number of mobile devices which could be associated with a given access point at any given point in time; group mobility versus arbitrary mobility of users, which are contrasting ways to model the mobility patterns of the mobile users. We consider various combinations of the above dimensions and present the following: (1) optimal algorithms, (2) provably-good online and offline approximation algorithms, (3) complexity (NP-Completeness) results, and (4) a practical heuristic which is demonstrated to work well on real network traces. [ABSTRACT FROM AUTHOR]

The authors propose a novel method to evaluate the interference conditions in a cellular network. The method takes advantage of the signal strength and quality measurements available at a Base Station. Measurements from both up-link and down-link are jointly processed to remotely detect the presence of a medium-range frequency jammer and other situations involving abnormal interference levels, as a malfunctioning of the power control algorithm, a bad radio optimization and planning or an outer interference, among others. The proposed method can be adapted to any cellular system. In this paper we focus on its application to GSM/GPRS system. We include some experiments where real cell data recordings were analyzed. [ABSTRACT FROM AUTHOR]