Despite their widespread adoption, cellular networks face growing vulnerabilities due to their inherent complexity and the integration of advanced technologies.One of the major threats in this landscape is Voice over IP (VoIP) to GSM gateways, known as SIMBox devices.These devices use multiple SIM cards to route VoIP traffic through cellular networks, enabling international bypass fraud with losses of up to $3.11 billion annually.Beyond financial impact, SIMBox activity degrades network performance, threatens national security, and facilitates eavesdropping on communications.Existing detection methods for SIMBox activity are hindered by evolving fraud techniques and implementation complexities, limiting their practical adoption in operator networks.This paper addresses the limitations of current detection methods by introducing SigN , a novel approach to identifying SIMBox activity at the cellular edge.The proposed method focuses on detecting remote SIM card association, a technique used by SIMBox appliances to mimic human mobility patterns.The method detects latency anomalies between SIMBox and standard devices by analyzing cellular signaling during network attachment.Extensive indoor and outdoor experiments demonstrate that SIMBox devices generate significantly higher attachment latencies, particularly during the authentication phase, where latency is up to 23 times greater than that of standard devices.We attribute part of this overhead to immutable factors such as LTE authentication standards and Internet-based communication protocols.Therefore, our approach offers a robust, scalable, and practical solution to mitigate SIMBox activity risks at the network edge.

Low earth orbit (LEO) satellite based non-terrestrial networks are a key theme of the upcoming 6G networks. These space networks are proposed to be used for high-mobility use-cases like airplanes and vehicles. The initial access process between a base station (BS) and a user equipment (UE) involves timing advance (TA) value computation at the BS, requiring precise BS location information at the UE. It becomes more challenging in LEO satellite networks due to the fast moving LEO satellites and large pathloss, in addition to the mobile UE. This paper aims to compute the TA and Doppler shift experienced at the UE by modeling the joint system dynamics in a LEO satellite-mobile UE network through an extended Kalman filter (EKF) based recursive Bayesian framework. The framework accurately models the joint system dynamics by considering the LEO satellite acceleration. It constructs the Jacobian to linearize the inherent non-linearities present in the motion. Probabilistic insights regarding the state-update and propagation are also provided. The analytical framework factors in the limited satellite visibility at the UE and the satellite-UE geometry w.r.t. the earth center. The proposed framework is also useful when the satellite and UE clocks are not in sync, with the corresponding clock drift a function of the measured time difference of arrivals. Our results showcase the efficacy and robustness of the proposed EKF framework to estimate the TA and Doppler shift, even at very high UE speeds. The work is expected to be extremely useful in realizing LEO satellite based non-terrestrial networks.

In recent years, with the widespread adoption of 5G Standalone (SA) technology in mobile networks, there has been an increasing need to address the complex and data-intensive nature of 5G SA traffic classification. Building upon previous research, this paper enhances the performance of the Light Gradient Boosting Machine (LGBM) for classifying 5G SA traffic, using physical channel records as input. This approach helps reduce dataset dimension and addresses user privacy concerns. The paper also focuses on mitigating overfitting—ensuring the model’s generalization ability—and incorporates zero-shot transfer learning techniques. We have refined LGBM by integrating dropout, regularization, and specialized feature engineering, which significantly boosts the model’s performance on unseen data. Validated on a comprehensive dataset designed to reflect real-world 5G traffic scenarios, our optimized model achieves an overall accuracy of 89% in multi-class classification on unseen data across four classes and eleven different case scenarios, markedly improving upon the baseline accuracy of 66% observed with other methods.

The classification of fifth-generation New-Radio (5G-NR) mobile network traffic is an emerging topic in the field of telecommunications. It can be utilized for quality of service (QoS) management and dynamic resource allocation. However, traditional approaches such as Deep Packet Inspection (DPI) can not be directly applied to encrypted data flows. Therefore, new real-time encrypted traffic classification algorithms need to be investigated to handle dynamic transmission. In this study, we examine the real-time encrypted 5G Non-Standalone (NSA) application-level traffic classification using physical channel records. We generate a noise-limited 5G NSA trace dataset with traffic from multiple applications. We develop a new pipeline to convert sequences of physical channel records into numerical vectors. We propose our solution based on Light Gradient Boosting Machine (LGBM) due to its advantages in fast parallel training and low computational burden in practical scenarios. Our experiments demonstrate that our algorithm can achieve 95% accuracy on the classification task with a state-of-the-art response time as quick as 10ms.

The fifth-generation (5G) of mobile networks and beyond is to host a variety of services for industry verticals with a diverse range of requirements. Network slicing (NS) is considered to be the fundamental enabling technology to address legacy networks’ shortcoming, by tailoring logical virtual networks, called network slices, over the same infrastructure. Adopting the concepts of virtualization and open interfaces, Virtual radio access networks (vRAN) and Open RAN (ORAN) are two of the most promising architectures proposed for slicing radio access networks. To realize the efficient deployment (i.e. increase flexibility, scalability, and decreased CAPEX and OPEX) of these architectures, a proper network planning approach is essential. This paper introduces a novel approach to planning and design of the ORAN architecture that takes into account QoS, CAPEX, OPEX and the transport network, simultaneously. The ORAN slice planning and design is formulated as a multi-objective optimization with binary variables and solved by simulated annealing. This paper provides a comprehensive discussion of the results. The proposed approach can be used in designing 5G ORAN network slices but also can be used as a transition network solution to integrate the 4G tier together with 5G for enabling a smooth and less costly transition.

4G and 5G cellular traffic pattern recognition and prediction are key objectives for network optimization. They also are becoming of fundamental importance for the next-generation cellular network. Recognizing mobile traffic patterns and proactively knowing the user behaviors allow the operator to optimize the resource allocation. On the other hand, it is a complex problem due to the diverse set of applications behind the traffic. Most traffic prediction problems focus on capturing the dynamic of traffic and enhancing the performance. In this paper, we design a deep learning model for traffic pattern recognition and prediction of the type of arrival packet using Long Short-Term Memory (LSTM) neural networks. The mobile traffic information is collected from the Downlink Control Information (DCI) using the Amarisoft software. The learning phase of the model relies on a well-known traffic pattern simulated on Amarisoft 4G and 5G testbed.

Network slicing is an important feature introduced by 5G. It enables an operator to deploy multiple independent end-to-end virtual networks, called network slices, on top of a common physical infrastructure. Network slices require the allocation of resources at different levels of the system, among which power budget is of upmost importance at RAN level. This work proposes a new power allocation algorithm for 5G network slicing. Network slices are introduced as a set of five parameters that reflect slices capacity, latency and reliability requirements. Simplicial homology is used to analyse network coverage. Reliability is then defined in terms of a multiple network connectivity criteria. The performances of the proposed algorithm are evaluated by simulations for a scenario with three different network slices: eMBB, uRLLC and mMTC. This method can be used to determine the required power budget at RAN level for different 5G network slices deployment scenarios.

5G technology has been designed with flexibility and software reusability in mind. In this context, open-source developments are critical enablers for mastering software architecture and associated codes, which are of the utmost importance for all technology stakeholders (ranging from manufacturers to operators and service users). free5GRAN is a new open-source 5G development framework. It focuses on research and education. It provides a modular architecture and a set of well-documented APIs, which enable easy experiment reproduction. free5GRAN aims at easing the understanding of 5G standards and the development of new technology components. The global objective is to be as modular as GnuRadio project [1], but with full system implementation. It has not been designed with performances in mind, unlike other open-source projects such as srsLTE [2] and OpenAirInterface [3]. The current release implements a significant part of the PHY layer on the receiver side, and the MAC layer will be part of a future release. Its architecture, which is composed of a library and an implementation part, is described. Moreover, RAN components are explained, and custom implementation methods are provided. It has been tested and validated against a commercial Amarisoft 5G SA gNodeB in a Faraday Cage.

This work derives a numerical dimensioning model for the downlink of a multi-cell Narrow-band Internet of things (NB-IoT) network. In such a system, the number of resource blocks (RBs) that a user requires depends on the SINR value which is a function of user position and the fading model. A network outage happens when the number of resource blocks available in the network is smaller than the one required by the user. In this paper, we propose a model to calculate the number of resource blocks needed in the NB-IoT network to guarantee the target outage probability, taking into account the repeated transmission feature of NB-IoT.

We focus on the full coverage hole problem in the context of Cloud Radio Access Networks while considering joint holes detection and cells interferences minimization. We propose a Branch and Cut algorithm describing the convex hull of this NP-Hard problem. New valid inequalities based on chordless cycles detection and network connectivity are added to this formulation to accelerate convergence time and detect rapidly coverage holes. Our Branch and Cut algorithm finds optimal solutions in acceptable times even for large problem instances. Simulation results and comparison to the state of the art highlight the efficiency and the usefulness of our approach.

NB-IoT has been defined in 3GPP release 13. It modifies LTE radio access procedures and protocols to fulfill energy consumption, low data rate and latency requirements associated with IoT applications. One of the major issues of NB-IoT deployment is the design of performance evaluation models that make it possible to plan and dimension this new system. This work proposes a new analytical model based on stochastic geometry. It provides a closed form expression of the successful transmission of an NB-IoT system in the uplink for a given sensor spatial intensity. The accuracy of the proposed analytical model is validated by simulation.

In this paper, a novel resource allocation scheme based on discrete Cournot-Nash equilibria and optimal transport theory is proposed. The originality of this framework lies in the joint optimization of downlink bandwidth allocation and cooperation between base stations. A tractable formalization is given in the form of a quadratic optimization problem. A low complexity approximate solution is derived and theoretically characterized. Simulations highlight the existence of an optimal working point, that maximizes user satisfaction ratio and network load. The impact of the network deployment on the optimum is numerically investigated, thanks to the β-Ginibre model. Indeed, base stations are assumed to be drawn according to β-Ginibre point processes. Numerical analysis shows that the network performance increases with β going to one.

In this paper, we introduce a distributed load balancing algorithm for cellular networks. Traffic load in cellular networks is sometimes unbalanced. Some cells are overloaded, while others remain free. Simplicial homology is a tool from algebraic topology that allows to compute the coverage of a network by using only simple matrix computations. Our algorithm, which is based on simplicial homology, controls the transmission power of each cell in the network, not only to satisfy the coverage constraint, but also to redirect users from the overloaded cells to the underloaded ones. As a result, the traffic load of the cellular network is more balanced. The simulation results show that this algorithm improves the capacity of the whole network by 2.3% when the user demand is fast varying.

In this paper, we introduce a distributed algorithm to compute the Čech complex. This algorithm is aimed at solving the coverage problems in self organized wireless networks. The complexity to compute the minimal Čech complex that gives information about coverage and connectivity of the network is O(n2), where n is the average number of neighbors of each cell. An application based on the distributed computation of the Čech complex, which is aimed at optimizing the wireless network for energy saving, is also proposed. This application also has polynomial complexity. The performance of the proposed algorithm and its application are evaluated. The simulation results show that the distributed computation of the Čech complex provides a consistent outcome with the one obtained by the centralized computation that is introduced in [6], while requires a much shorter calculation time. The optimized coverage saves 65% of the total transmission power, while also keeps the maximal coverage for the network.

Base station cooperation is a promising scheme to improve network performance for next generation cellular networks. Up to this point research has focused on station grouping criteria based solely on geographic proximity. However, for the cooperation to be meaningful, each station participating in a group should have sufficient available resources to share with others. In this work we consider an alternative grouping criterion based on a distance that considers both geographic proximity and available resources of the stations. When the network is modelled by a Poisson Point Process, we derive analytical formulas on the proportion of cooperative pairs or single stations, and the expected sum interference from each of the groups. The results illustrate that cooperation gains strongly depend on the distribution of available resources over the network.

Cooperation in cellular networks has been recently suggested as a promising scheme to improve system performance. In this work, clusters are formed based on the Mutually Nearest Neighbour relation, which defines which stations cooperate in pair and which do not. When node positions follow a Poisson Point Process (PPP) the performance of the original clustering model can be approximated by another one, formed by the superposition of two PPPs (one for the singles and one for the pairs) equipped with adequate marks. This allows to derive exact expressions for the network coverage probability under two user-cluster association rules. Numerical evaluation shows coverage gains from different signal cooperation schemes that can reach up to 15% compared to the standard non- cooperative network coverage. The analysis is general and can be applied to any type of cooperation or coordination between pairs of transmitting nodes.

Dimensioning the LTE maritime Mobile Ad-hoc Networks relies essentially on the accuracy of the channel propagation path-loss model. The maritime ITU-R path-loss is computed based on empirical field strength measures that statistically capture, depending on the weather condition, the behavior of the wireless channel over a certain percentage of time. In this paper, we provide an analytical method to linearly adjust the required number of radio resource blocks (RBs) computed in [1] in function of the channel fluctuations. Based on a reference path-loss model, we compute the variation in the number of RBs required to achieve the same target resource outage probability as a function of the path-loss exponent and attenuation factor variations.

In this paper, we introduce a centralized algorithm which constructs the generalized Cech complex. The generalized Cech complex represents the topology of a wireless network whose cells are different in size. This complex is useful to address a wide variety of problems in wireless networks such as: boundary holes detection, disaster recovery or energy saving. We have shown that our algorithm constructs the minimal generalized Cech complex, which satisfies the requirements of these applications, in polynomial time.

Simplicial homology is a tool that provides a mathematical way to compute the connectivity and the coverage of a cellular network without any node location information. In this paper, we use simplicial homology in order to not only compute the topology of a cellular network, but also to discover the clusters of nodes still with no location information. We propose three algorithms for the management of future cellular networks. The first one is a frequency auto-planning algorithm for the self-configuration of future cellular networks. It aims at minimizing the number of planned frequencies while maximizing the usage of each one. Then, our energy conservation algorithm falls into the self-optimization feature of future cellular networks. It optimizes the energy consumption of the cellular network during off-peak hours while taking into account both coverage and user traffic. Finally, we present and discuss the performance of a disaster recovery algorithm using determinantal point processes to patch coverage holes.

Homology theory provides new and powerful solutions to address the coverage problems in wireless sensor networks (WSNs). They are based on algebraic objects, such as Čech complex and Rips complex. Čech complex gives accurate information about coverage quality, but requires a precise knowledge of the relative locations of nodes. This assumption is rather strong and hard to implement in practical deployments. Rips complex provides an approximation of Čech complex. It is easier to build and does not require any knowledge of nodes location. This simplicity is at the expense of accuracy. Rips complex cannot always detect all coverage holes. It is then necessary to evaluate its accuracy. This work proposes to use the proportion of the area of undiscovered coverage holes as performance criteria. Investigations show that it depends on the ratio between communication and sensing radii of a sensor. Closed-form expressions for lower and upper bounds of the accuracy are also derived. For those coverage holes that can be discovered by Rips complex, a homology-based distributed algorithm is proposed to detect them. Simulation results are consistent with the proposed analytical lower bound, with a maximum difference of 0.5%. Upper-bound performance depends on the ratio of communication and sensing radii. Simulations also show that the algorithm can localize about 99% coverage holes in about 99% cases.

In this paper, we proposed a general analytical model for mobile relay scenario using stochastic geometry approach. By applying different parameters into this general model, the Cumulative Distribution Function of the SINR and the average achievable rate on different links in both traditional mode and relay mode can be obtained. According to numerical results, we observed that penetration loss between outdoor and in-vehicle is a key factor to decide whether mobile relay could bring data rate gain into the system. When penetration loss is large, mobile relay could bring considerable data rate gain to embedded UEs inside the bus.

In this paper, the mobile deployment and subchannel number distribution are estimated for different values of Anisotropy Ratio (AR) and Mean Building Block Area (MBBA) pairs. This work proposes to model city maps with a particular family of random tessellations: Crack STIT tessellation to generate realistic city maps with a reduced number of parameters: i.e., AR and MBBA. The model is used to compute the received power map and further identify the impact of terrain topology parameters on wireless propagation. Simulations results show that mean mobile number and mean sub-channel number (SCN) both decrease with increasing MBBA following a power law dependency. The variance of SCN distribution increases with increasing MBBA by a potential exponential law. However, AR does not show obvious and strong impact on mobile and SCN. For different value of MBBA, AR leads to different mobile number and sub-channel evolutions gradually. Furthermore, the evolution of SCN does not monotonically decrease with increasing MBBA at 95% cumulative density function (CDF) bound of SCN distribution. Unlike the mean value (50% CDF bound), the SCN at 95% bound increases back for very large MBBA. The results are particularly promising for providing a parametric relation between mobile deployment/SCN and terrain topology. This considerably simplifies the radio estimation and planning of wireless networks.

Considering a damaged wireless network, presenting coverage holes or disconnected components, we propose a disaster recovery algorithm repairing the network. It provides the list of locations where to put new nodes to patch the coverage holes and mend the disconnected components. In order to do this we first consider the simplicial complex representation of the network, then the algorithm adds supplementary nodes in excessive number, and afterwards runs a reduction algorithm in order to reach a unimprovable result. One of the novelty of this work resides in the proposed method for the addition of nodes. We use a determinantal point process: the Ginibre point process which has inherent repulsion between vertices, which simulation is new in wireless networks application. We compare both the determinantal point process addition method with other vertices addition methods, and the whole disaster recovery algorithm to the greedy algorithm for the set cover problem.

This work proposes to model city maps with a particular family of random tessellations: Crack STIT tessellations. This family of tessellations allow the generation of realistic city maps with a reduced number of parameters: the Anisotropy Ratio (ξ) and the Mean Building Block Area (MBBA). These city models are then used as input to a 3D ray tracing simulator to compute received power distributions. The objective of this investigation is to identify the impact of random tessellation parameters on wireless propagation. For this purpose, path loss exponent γ is estimated from received power distributions obtained by simulation for different values of ξ and MBBA pairs. Simulations results clearly show a linear dependency between path loss γ, ξ and MBBA. Path loss γ increases with ξ while it decreases with MBBA. Furthermore the evolution of the surface occupation ratio between outdoor and overall surface is also investigated. This ratio is named Free Area Ratio (FAR) in the sequel. It decreases with MBBA according to a power law. The results obtained are particularly promising as they provide a parametric relation between path loss exponent γ and terrain topology. This considerably simplifies the radio planning and dimensionning process of cellular networks.

In this study, the authors propose a low complexity user scheduling for multi‐antenna broadcast systems with a large number of users with diverse delay‐quality of service (QoS) assurances. Owing to the exclusive user scheduling constraints, the optimisation is combinatorial. Furthermore, by adopting effective capacity and effective bandwidth to illustrate the behaviours of different traffic characteristics such as different source statistics and queue dynamics, the delay‐bound violation probability constraints can be converted into equivalent minimum data rate constraints. To reduce the computational complexity, they use genetic algorithm (GA) to perform scheduling, instead of a brute‐force exhaustive search (ES) over all possible user subsets. By comparing the complexity of GA and ES, they show that GA is a rapid, although suboptimal, option of performing user scheduling optimisation. Simulation results show that the proposed algorithm can not only maximise the achievable user sum data rate, but also keep the delay‐bound violation probability of each user below a given threshold.

Homology theory has attracted great attention because it can provide novel and powerful solutions to address coverage problems in wireless sensor networks. They usually use an easily computable algebraic object, Rips complex, to detect coverage holes. But Rips complex may miss some coverage holes in some cases. In this paper, we investigate homology-based coverage hole detection for wireless sensor networks on sphere. The case when Rips complex may miss coverage holes is first identified. Then we choose the proportion of the area of coverage holes missed by Rips complex as a metric to evaluate the accuracy of homology-based coverage hole detection approaches. Closed-form expressions for lower and upper bounds of the accuracy are derived. Asymptotic lower and upper bounds are also investigated when the radius of sphere tends to infinity. Simulation results are well consistent with the analytical lower and upper bounds, with maximum differences of 0.5% and 3% respectively. Furthermore, it is shown that the radius of sphere has little impact on the accuracy if it is much larger than communication and sensing radii of each sensor.

ABSTRACT Next generation mobile networks will provide seamless mobility between existing cellular systems and other wireless access technologies. To realize a seamless vertical handover (inter‐radio access technology handover) among these different access technologies, a multi‐interfaced mobile station (i.e., multihomed) is a good approach to provide better handover performance in terms of packet loss rate and handover latency. In this article, we propose a novel layer 2 multihoming approach for inter‐radio access technology handover between Universal Mobile Telecommunications System (UMTS) and Worldwide Interoperability for Microwave Access (WiMAX) in both integrated and tight coupling architectures. This layer 2 multihoming approach has the ability of enabling either soft handover or make‐before‐break handover to adapt to mobility scenarios for the sake of a lossless and short latency handover procedure. Our simulation results show that, in case of handover from UMTS to WiMAX for transmission control protocol (TCP) traffics, the layer 2 multihoming approach can achieve a lossless and zero latency handover procedure by enabling soft handover. In case of handover from WiMAX to UMTS, because of the fact that the performance gain of soft handover is more affected by the differences of bandwidth and transmission delay between these wireless links, the make‐before‐break handover is preferred to achieve lossless and short latency handover procedure. Copyright © 2012 John Wiley & Sons, Ltd.

This work gives an analytical model for the radio dimensioning of uplink Long Term Evolution (LTE) systems. It relies on the computation of an upper bound of the outage probability, the outage being defined by an insufficient number of Resource Blocks (RBs) for serving all the users in the network. The number of RBs, that has to be dedicated to each communication in order to ensure its Quality of Service (QoS), depends on the transmitting users random positions and their radio conditions. Throughout this paper, this number of RBs is assimilated as a marked Poisson point process. The upper bound of the outage probability is computed for different service classes according to the users throughput requirements, for the fair and the opportunistic RB allocation algorithms. Once validated by Monte-Carlo simulations, it estimates the necessary cells bandwidth. Finally, we apply these results to LTE standard bandwidths and give the associated resulting outage probabilities. Our work shows that the analytical upper bound of the outage probability helps the radio system planners to decrease the networks outage probability to a desired threshold at the price of a slight and controlled radio over dimensioning.

In this paper, we aim at reducing power consumption in wireless sensor networks by turning off supernumerary sensors. Random simplicial complexes are tools from algebraic topology which provide an accurate and tractable representation of the topology of wireless sensor networks. Given a simplicial complex, we present an algorithm which reduces the number of its vertices, keeping its homology (i.e. connectivity, coverage) unchanged. We show that the algorithm reaches a Nash equilibrium, moreover we find both a lower and an upper bounds for the number of vertices removed, the complexity of the algorithm, and the maximal order of the resulting complex for the coverage problem. We also give some simulation results for classical cases, especially coverage complexes simulating wireless sensor networks.

In this paper, we propose a transceiver structure for the multi-user MIMO uplink channel of the Long Term Evolution (LTE) networks. This transceiver structure is based on the use of an adequate encoder at the transmitter side, to take advantage of the multiple transmit antenna diversity, and a combination of a joint zero forcing (ZF) and a maximum likelihood (ML) decoder at the receiver side. Based on this transceiver design, we show how to extend an opportunistic multiuser spatial multiplexing allocation to the whole LTE bandwidth with respect to Single Carrier Frequency Division Multiple Access (SC-FDMA) constraints. The evaluated rate performances of the proposed transceiver in a scheduling uplink LTE context outperform the ones of other well known decoders.

This work proposes two new Resource Block (RB) allocation algorithms for the LTE uplink. They take into account the RB adjacency constraint and update the allocation metric. Two different heuristics are proposed: an Opportunistic and Efficient RB allocation Algorithm (OEA) and a Quality of Service based Opportunistic and Efficient RB allocation Algorithm (QoS based OEA). Both algorithms seek to maximize the aggregate throughput and avoid RB wastage unlike other algorithms in the literature. The complexity of the proposed algorithms are also computed analytically and compared to other well known heuristics.

Homology theory provides new and powerful solutions to address the coverage problems in wireless sensor networks (WSNs). They are based on algebraic objects, such as Cech complex and Rips complex. Cech complex gives accurate information about coverage quality but requires a precise knowledge of the relative locations of nodes. This assumption is rather strong and hard to implement in practical deployments. Rips complex provides an approximation of Cech complex. It is easier to build and does not require knowledge of nodes location. This simplicity is at the expense of accuracy. Rips complex can not always detect all coverage holes. It is then necessary to evaluate its accuracy. This work proposes to use the area of undiscovered coverage holes per unit of surface as performance criteria. Investigations show that it depends on the ratio of communication and sensing ranges of each sensor. Closed form expressions for lower and upper bounds of the accuracy are also derived. Simulation results are consistent with the proposed analytical lower bound, with a maximum difference of 0.4%. Upper bound performance depends on the ratio of communication and sensing ranges.

This paper addresses a power control and Inter-Cell Interference (ICI) estimation problem in uplink Single Carrier Frequency Division Multiple Access (SC-FDMA) networks. We consider a power control based on Signal to Interference plus Noise Ratio (SINR) target to be achieved, which requires knowledge of the interference level. We propose a simple method to estimate ICI in uplink SC-FDMA networks, less greedy than the classical Monte Carlo method which has higher computation complexity. Numerical results validate the new method in multiple environments even after adding fast fading and shadowing effect. Moreover, it shows robustness against variation of above mentioned parameters.

Abstract In this paper, we present an analytical model for determining the optimal number of clusters, with the objective of minimizing the communication costs in a clustered wireless sensor network (WSN). Sensor nodes are located randomly and distributed according to a homogeneous two‐dimensional Poisson point process. Overall communication costs in the network are calculated analytically based on a practical energy consumption model at node level. The optimal probability of being a cluster head (CH) for each node is deduced by minimizing a cost function taking into account the energy dissipation of nodes. The scenarios with single‐hop and multi‐hop clustered networks are investigated. Simulation results show the existence of the optimum number of clusters which improves the energy efficiency of clustering schemes. We also verify by simulations that the analytical optimal probability of being a CH can provide a good approximation of the actual optimum probability, regardless of the different densities of nodes in the network. Copyright © 2010 John Wiley & Sons, Ltd.

Coverage is considered as an important measure of quality of service provided by a wireless sensor network (WSN). Yet, coverage holes may appear in the target field due to random deployment, depletion of sensor power or sensor destruction. Discovering the boundaries of coverage holes is important for patching the sensor network. In this paper, we adopt two types of simplicial complexes called Cech complex and Rips complex to capture coverage holes and classify coverage holes to be triangular and non-triangular. A distributed algorithm with only connectivity information is proposed for non-triangular holes detection. Some hole boundary nodes are found first and some of them initiate the process to detect coverage holes. Simulation results show that the area percentage of triangular holes is always below 0.03% when the ratio between communication radius and sensing radius of a sensor is two. It is also shown that our algorithm can discover most non-triangular coverage holes.

The cognitive cooperative system with coexisting scenario of multiple primary users and one secondary capable of relaying is considered in this study. The primary users transmit packets in orthogonal subchannels. According to the cognitive principle, the secondary activity cannot interfere with the primary performance. Therefore in this study, the secondary user makes use of the spectrum when sensed idle. Based on the proposed media access control (MAC) protocol, the authors derive the stable throughput and delay slots expressions of each primary user with secondary relaying. They also achieve the stable network constraints of relaying probability ɛ, the feasible range of primary arrival rates and the maximum allowed secondary transmitting power which is to make a tradeoff between the stable throughput of the primary and secondary user. Simulation results show that secondary relaying can increase the primary and secondary throughput and also reduce the delay slots when designing an appropriate ɛ.

The concept of cognitive radio is to exploit efficiently the spectrum resources by allowing the coexistence of the primary and secondary users in the same bandwidth without interfering the performance of primary users. Three coexisting models (overlay, underlay and interleave) were presented in recent literature. In this study, the authors propose a hybrid cognitive network model with overlay and underlay models, whereby a primary link leases its fractions of transmission time to the secondary users for their cooperation (i.e. these nodes form as a virtual multiple input multiple output (VMIMO) group) under the outage constraints of the primary and secondary systems. A new cooperative protocol between primary and secondary users is presented. The authors attempt to achieve the maximum transmission capacity of the secondary users under the primary and secondary outage constraints, which depend on the secondary density in the cognitive network. This study gives the upper bound density of the secondary transmitters that are modelled as a homogeneous marked Poisson point process. The maximum density is achieved by computing an optimal set of system parameters such as power control factor of the secondary user and the dirty paper coding (DPC) parameter. Simulation results illustrate that the maximum secondary density obtained using VMIMO is superior to that obtained by direct primary transmission.

The cognitive cooperative system with coexisting scenario of multiple primary users and one secondary capable of relaying is considered. The primary users transmit packets in orthogonal sub-channels. According to the cognitive principle, the secondary activity cannot interfere with the primary performance. Therefore, in this paper, the secondary user makes use of the spectrum when sensed idle. Based on the proposed MAC protocol, we derive the stable throughput expressions of each primary user with secondary relaying. We also achieve the stable network constraints of relaying probability ε, the feasible range of primary arrival rates and the maximum allowed secondary transmitting power which is to make a tradeoff between the stable throughput of the primary and secondary user. Numerical simulations show that secondary relaying can increase the primary and secondary throughput when designing an appropriate ε.

This paper proposes the utilization of GSM logical channels (RACH, AGCH and TCH) and UMTS signaling (MIB and SIBs) of the Broadcast Channel to transmit a Cognitive Beacon Channel (CBC). The CBC will help to improve spectrum awareness by conveying signalization to mobile users in a multi-Radio Access Technology (RAT) environment (e.g. 3GPP, Wi-Fi, WiMAX and future cognitive radio systems). Taking advantage of this spectrum knowledge, the purpose of the CBC is to transmit the necessary information to allow Dynamic Spectrum Access (DSA) using a centralized architecture. The principal motivation of this proposition is to obtain benefit from existing 3GPP technologies proved to be efficient and accepted. Simulation results show that our proposals, using logical channels of GSM and UMTS outperform, respectively, the On-demand and the Broadcast CPC implementations of the E2R II project.

One of main feature of next generation of mobile networks is an integration of existing cellular systems with other wireless access technologies. In order to realize a seamless vertical handover (inter-RAT handover) among these different access technologies, a multi-interfaced mobile station is expected to communicate simultaneously on various network interfaces (i.e. to be multihomed) to achieve best handover performance gain, such as low packet losses and short handover latency. Unfortunately, the conventional multihoming schemes are almost realized at IP layer or above and the handover performance gains are limited. Moreover, these multihoming schemes are not applicable to integrated and tight coupling architectures. In this article, a novel layer 2 multihoming approach is proposed for inter-RAT handover between UMTS and WiMAX in the integrated and tight coupling architectures. This layer 2 multihoming approach has the ability of enabling either soft handover or make-before-break handover in order to adapt to handover scenarios, and can achieve a lossless and short latency handover procedure. The simulation results show that, in case of TCP traffics for handover from UMTS to WiMAX, the layer 2 multihoming approach can achieve a lossless and zero latency handover procedure by enabling soft handover. For handover from WiMAX to UMTS, due to the fact that the performance gain of soft handover is more affected by the difference of bandwidth and transmission delay between these wireless links, the make-before-break handover is preferred and it can achieve lossless and short latency handover procedure.

In this paper, a contention model for the IEEE 802.16e is first proposed to analyze the frame-based behavior of contention resolution in 802.16e network. Then a waiting-time dependent increasing rate adapted backoff (WDIA) algorithm is proposed to improve the contention efficiency. We introduce the concept of reduced overlapping between back-off windows of contending stations and we adopt an adapted increasing rate of the back-off window. The simulation results show that the WDIA algorithm achieves better performance in terms of number of retransmissions, access delay and resource utilization.

In future mobile networks, different radio access technologies, such as GSM, UMTS, WiMAX, WIFI, will coexist. In order to realize a seamless vertical handover (inter-RAT handover) among these technologies, a variety of interworking architectures and inter-RAT handover mobility managements have been proposed. Based on an integrated coupling architecture, we propose a novel common interworking sublayer (IW sublayer) at layer 2 on RNC and UE to provide a seamless PS inter-RAT handover between UMTS and WiMAX systems. This IW sublayer scheme focuses on eliminating packet loss and reducing handover latency which are common problems for most inter-RAT handover scenarios. In addition, an enhanced TCP proxy, which interacts with the IW sublayer, is also introduced to RNC to resolve other two typical inter-RAT handover problems of TCP traffics: BDP mismatch and spurious RTO. Compared with other vertical handover solutions, our novel inter-RAT scheme has the merits of keeping existing TCP protocol stacks unchanged and is robust to different handover scenarios. The simulation results show our total solution not only achieves a lossless and prompt handover procedure, but also accommodates BDP mismatch and prevents spurious RTO of TCP sender.

The fast handover for mobile IPv6 (FMIPv6) (Koodli, 2005) aims at reducing the long handover latency in mobile IPv6 (Johnson, 2004) by fast movement detection and fast binding update. Furthermore, it also reduces packet loss by buffering before the real link layer handover takes place. Due to uncertain link layer trigger time, however, the buffering mechanism sometimes introduces unacceptable handover latency for real-time traffics such as voice over IP (VoIP). In addition, if itpsilas the mobile node that makes the handover decision, FMIPv6 also suffers from uncertainty of handover target, which is unfavorable to TCP traffics such as FTP. In order to eliminate these negative effects, we propose that FMIPv6 should operate in predictive mode under the control of network if possible for TCP traffics. As to the VoIP traffic, in terms of the handover latency and packet loss requirements, a proposed hybrid mode is chosen adaptively. Numerical simulation results for the VoIP traffic demonstrate obvious performance improvement in terms of call drop rate and a new performance metric called packet cost.

The future B3G or 4G mobile networks will consist of heterogeneous networks, including GSM, UMTS, and WiMAX. In order to realize a seamless vertical handover (inter-RAT handover), a variety of interworking architectures and inter-RAT handover mobility managements have been proposed. In this paper we consider the tight coupling architecture to achieve the interconnection between UMTS and WiMAX systems. A novel common interworking sublayer (IW sublayer) is proposed at layer 2 on RNC, W-RNC and UE to provide a seamless PS inter-RAT handover between UMTS and WiMAX. This IW sublayer scheme, which features SR ARQ mechanism, focuses on eliminating packet loss and reducing handover latency that are common problems for most inter-RAT handover scenarios. The simulation results of the tight coupling architecture show that, compared with other context transfer schemes like buffering-and-forwarding of FMIPv6, the IW sublayer solution can achieve a lossless and prompt handover.

The future B3G or 4G mobile networks will consist of heterogeneous networks, including GSM, UMTS, WiMAX and WIFI. In order to realize a seamless vertical handover (inter-RAT handover), a variety of interworking architectures and inter-RAT handover mobility managements have been proposed. Based on the integrated coupling architecture, we propose a novel common interworking sublayer (IW sublayer) at layer 2 on RNC and UE to provide a seamless PS inter-RAT handover between UMTS and WiMAX systems. This IW sublayer scheme focuses on eliminating packet loss and reducing handover latency which are common problems for most inter-RAT handover scenarios. Compared with other context transfer schemes, the simulation results show the IW sublayer with ARQ mechanism can achieve a lossless and prompt handover procedure. In addition, this IW sublayer scheme can eliminate false fast retransmit of TCP traffics which is usually caused by packet losses or out-of-order packet arrivals.

In this paper, the problem of subchannel composition and allocation for the downlink of an OFDMA system is investigated. The subchannelization mode FUSC adopted in 802.16 is described and compared with dynamic subcarrier allocation algorithms. Performances are evaluated regarding spectral efficiency and complexity. Both single cell and multi-cell scenarios are considered.

Next generation wireless networks will take advantage of the popularity and the data rates offered by unlicensed wireless networks such as WiFi (WirelessFidelity) or WiMAX (WorldwideInteroperabilityforMicrowaveAccess) to enhance cellular services Le. UMTS (Universal Mobile Telecommunication System). Although currently exist approaches that provide service mobility, they rely on the assumption that cellular operators also own or manage the WiFi/WiMAX networks. Nevertheless, in spite of the business-related and technical differences of network operators/service providers we consider that service mobility between cellular and independent unlicensed wireless networks is feasible. In this article we present the SIP embedded Attribute Certificates to enable service mobility in heterogeneous multi- operator wireless networks.

In this paper, we investigate packet scheduling and radio resource allocation in orthogonal frequency division multiple access (OFDMA) wireless networks. Each subchannel is a Rayleigh fading channel modeled by a finite state Markov channel (FSMC). The wireless fair service (WFS) packet scheduler is modified for a multi carrier and multi rate context. The proposed algorithm, named opportunist wireless fair service (OWFS), copes with both real time (RT) and non real time (NRT) traffic constraints. For both traffic classes, specific criteria of performance are compared with PLFS, a scheduler recently proposed for OFDMA.

Multistreaming and multihoming SCTP features give better performance than TCP for the transport of signaling in wired networks. More recently, some solutions have been defined for wireless environment (Xing et al., 2002), mobile SCTP (mSCTP) is a wireless extension that was proposed to take benefit from the multihoming feature for hand off. In this paper we use SCTP's multihoming feature and define a new type of control chunk in order to retrieve radio information from mobile and to use this information to improve the performance of SCTP in handoff situation. We propose modifications of the SCTP congestion control algorithms to take into account information sent by mobile to the network (GGSN) via QoS_Measurement_Chunk. This new mechanism is useful to perform inter RAT handover for data. The example studied here is between EGPRS and WLAN. The results obtained are compared with the standard SCTP and present an improvement of performance especially in terms of throughput

SCTP is a transport protocol that is used in wired networks to transport PSTN signaling. It provides interesting features (namely multihoming and multistreaming) to enhance the performances of information transport over cellular networks air interfaces (S. Kang and M. Fields, 2003). Some additional extensions have been defined to adapt SCTP in a wireless context (mSCTP) (W. Xing et al., 2002). However current approaches do not take into account radio information in cell reselection/handover process. This study proposes a new extension for the SCTP protocol which aims at improving the transport performance in wireless environments. We define for that purpose a new control chunk (named Qos_measurement_chunk). It allows the emission of radio information from the mobile to the SCTP peer in the network. These information can be used by the SCTP layer to adapt the transmission rate to the current radio transmission conditions (particularly useful in handover/reselection situation). The combined use of Qos_measurement_chunk and of the multihoming feature provide a data handover with a performance improvement. The obtained simulation results are compared with the standard SCTP and present better performance in terms of data throughput in the access network

Dual transfer mode (DTM) has been defined by 3GPP for EGPRS networks. It provides simultaneous usage of GSM and GPRS services without requiring a full fledged GPRS class A terminal. DTM relies on the usage of half rate coders that make it possible to share a timeslot between a voice call and a data session. The data session can be extended to more time slots if necessary. This work examines an optimal policy adapted for resource allocation in a cell providing DTM capability. At the end of one part of a DTM call, the policy decides whether the released half slot should be reallocated to an existing data session or not. In earlier work, this optimal policy was proven to be a threshold strategy. The optimal policy is compared with the two policies where the same decision is taken regardless of the state of the system. Its performance is evaluated with respect to system load and configuration parameters

This paper is part of an ongoing effort for the standardization of a new APCO Project 25 air interface for professional mobile radio. It describes the structure of the control channel for the 2-slot TDMA air interface. It presents the types of signaling messages involved, the structure of the multiframe and the priority scheduling algorithm for signaling messages on the common control channel CCH. The performance of the algorithm is analyzed in terms of signaling message delays

In this paper, the downlink of a multi-cell OFDMA system is considered. Rate adaptive optimization is investigated with minimum rate requirement and in presence of co-channel interference. A low-complexity subcarrier allocation scheme is proposed. A particular procedure provides limitation of co-channel interference by dynamically adapting the subcarrier reuse factor. A rate requirement violation (RRV) threshold is introduced to decide whether or not the interference limitation procedure is to be used. The performance is evaluated for variant user's rate requirement. The evaluation includes comparison of the cell global rate and the outage probability with existing heuristics

B3G networks will provide seamless data handover between different radio access technologies (RAT). In a near future, the WLAN access will be integrated in GPRS and UMTS radio access networks (RAN). During their communications, the subscribers will be able to switch automatically between the two technologies. In that case, their previous data transfer need to be re-established in the new RAT. This process must be carried out while minimizing the breakdown time and the data loss. This paper intends to evaluate the performances of handover policies between GPRS/UMTS and WLAN RAT and to propose adapted data handover strategies at layer two

In this paper, the rate adaptive optimization (RA) problem, which maximizes the sum of user data rates subject to total power constraint and individual guaranteed rates, is considered. Two tasks are commonly examined: bandwidth allocation and specific subcarrier assignment. A mechanism to provide a degree of fairness among users is coupled with the first task. Considering the second task, a novel algorithm, rate profit optimization algorithm (RPO), is defined to assign specific subcarriers to different devices of a multiuser downlink OFDM system. In RPO, a new approach is proposed to assign a conflicting subcarrier (best subcarrier for several users). This algorithm is shown to exhibit good results regarding spectral efficiency and fairness with a complexity significantly lower than the Hungarian algorithm.

This paper analyzes a TCP connection over UMTS radio access bearer in RLC acknowledged mode. The stacking of RLC and TCP protocols is highly beneficial for the global system behavior. Protocol mechanisms used by RLC are well adapted to wireless constraints and the ARQ function implemented by RLC hides the wireless channel unreliability to TCP. However, RLC protocol parameters have to be carefully tuned otherwise the TCP performance can degrade due to RLC. One of the factors that can influence the TCP performance is the RLC buffer size. We analyzed some of factors that affect the RLC buffer occupancy and we show that an insufficient buffer size degrades the TCP performance.

Integration of cellular networks into the existing Internet world gives rise to some problems, mainly for the reason that protocol mechanisms defined and optimized for wired networks do not perform well when they are directly applied in wireless networks. In this paper we study an uplink TCP connection over the UMTS radio interface, when using a RLC entity in acknowledged mode. We suggest the introduction between TCP and RLC protocols of a specific mechanism called early error notification. Via this mechanism, a TCP sender is informed whenever a data segment is virtually discarded at the RLC level. Thus, a TCP sender detects in advance a segment loss at the RLC level without waiting for three duplicated acknowledgments or a timeout event.