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To maximize the throughput of wireless powered communication (WPC), it is critical for the device to decide when to harvest energy, when to transmit data and what transmit power to use. In this paper, we consider a WPC system with a single device using harvest-store-transmit protocol and aim to maximize the longterm average throughput with optimal allocation of the energy harvesting time, data transfer time and the device’s transmit power. With the consideration of many practical constraints including finite battery capacity, time-varying channels and non-linear energy harvesting model, we propose both deep Q-learning (DQL) and actor-critic (AC) approaches to solve the problem and obtain fully online policies. Simulation results show that the performance of our proposed AC approach comes close to that achieved by value iteration and is superior to DQL and other baseline algorithm. Meanwhile, its space complexity is 2-3 orders of magnitude less than that required by value iteration.

With the promising technology of far-field wireless power transfer, wearable devices are able to harvest radio frequency (RF) energy from RF-based chargers and thus operate continuously. Rational planning of the quantity and positions of the chargers provide an effective way to improve the recharging efficiency and save the charger deployment budget. Existing work on RF-based charger placement mainly considers the situation where the devices are static, or adopt very simple mobility model. In this paper, we consider wireless charging service provision for wearable devices worn by users in a two-dimensional area, with users having a specific stay–move behavior pattern characterized by the trajectories, stay points, and stay time distribution. Based on this mobility pattern, we formulate the problem as how to find a charger placement to minimize the charging service budget, subject to the power non-outage probability requirement of the wearable devices. We further transform this problem to several equivalent problems for easier tractability and prove that it is NP-complete. Both greedy heuristic and particle swarm optimization (PSO) based solutions are proposed to solve the problem with certain approximation ratio. Finally, performances of the proposed solutions are compared with exhaustive search and existing point provisioning algorithm through extensive simulations. Simulation results show that both greedy heuristic and PSO-based solutions outperform the baseline algorithms, while PSO-based solution requires least number of chargers and thus is the most cost-effective.

International audience; The 3D indoor positioning and indoor navigation (IPIN) system is of great significance for promoting and ex- panding indoor intelligent services and applications. The rapid development of unmanned aerial vehicles (UAVs) has provided new opportunities in this field. However, in contrast to their outdoor applications, IPIN for UAVs is more challenging since the Global Positioning System (GPS) is in general inaccessible in indoor environments. In this work, we propose a UAV-enabled 3D IPIN system based on visible light communication (VLC). Firstly, a novel VLC-based indoor positioning scheme is developed using a fusion algorithm based on the dynamic time warping (DTW) method with visible light intensity sequence (VLIS) and inertial measurement unit (IMU) data. To reduce the workload of fingerprint measurements, we propose to modularize a floor site using a standard symmetric structure for VLC positioning. In this manner, the navigation can be achieved by recognizing the edge of each module. Furthermore, since the sampling frequency of IMU is much higher than that of VLIS, discrete Kalman filter (KF) is introduced to correct the location measured by IMU when VLIS is unavailable. A proof-of-concept IPIN prototype is constructed. Field experiments confirm the effectiveness of our proposed IPIN system.

This paper investigates the platoon control problem for vehicular cyber physical systems (VCPSs) subject to Denial-of-Service (DoS) attacks which often cause significant transmitted data packet delay or dropout by jamming the communication channels among vehicles. As a result, the VCPSs may contain isolated vehicles which cannot receive information from others. This in truth can lead to performance degradation, or even collisions of vehicles. To mitigate such adverse effects of DoS attacks on VCPSs, this paper proposes a distributed control protocol for each vehicle to track the leading vehicle. In order to guarantee asymptotic tracking performances under both DoS attacks and the existing recovery mechanism, this paper characterizes the upper bounds of the time duration rate and the frequency of the communication network being in the state of containing no spanning tree, respectively, by using a state transformation method and multiple Lyapunov functions. The controller gains are also jointly designed in association with the parameters of the upper bounds. Numerical results show the effectiveness of the derived theoretical results.

Motivated by the needs of health monitoring at home (or a senior center) using a sensor network system, we study the problem of how to place the relay nodes so that the data collection and localization requirements of the monitoring system can be satisfied. By exploiting the inherent nature of the problem, we model it as finding a minimum connected k-dominating (k ≥ 3) set. Instead of using an idealistic disk radio model, we explicitly take into account the obstacles’ effect on the radio propagation in an indoor environment. We prove that the problem is NP-hard and propose an efficient greedy algorithm ORPA (Optimal Relay Placement Algorithm) to compute in polynomial time the best locations to place the relays. Results of extensive simulations have shown that by using our proposed algorithm ORPA, the number of relays required can be substantially reduced in comparison to the random placement and two-stage placement strategies. We also study the impact of the transmission power and the grid size on the algorithm and system performance. The result and method presented in the paper is useful to today’s indoor deployment of practical WSN-based monitoring system and to ensure network connectivity with minimal relay nodes.

International audience; Non-Orthogonal Multiple Access (NOMA) is a candidate channel access technique for the future generation wireless communication systems. It exploits the power domain to enable simultaneous access for multiple users. In this paper, a NOMA system with a base station (BS) and two users is studied. A novel scheme where the near user (UE 1) harvests energy from the signals sent from BS and relays the previously decoded message of the far user (UE 2) is proposed. It includes two common energy harvesting schemes, namely, power splitting and time switching, as special cases. The performance is evaluated by the achievable data rate of UE 2 under different requirements on the data rate of UE 1. Numerical simulations and analysis reveal that when the channel conditions between BS and UE 1, and between UE 1 and UE 2 are good, while that between BS and UE 2 is bad, the proposed scheme works the best and has a significant gain over the conventional NOMA scheme without cooperation. In addition, for the sake of simplicity, the power splitting scheme can be used to replace the generalized scheme for energy extraction without jeopardizing the performance gain much.

International audience; Non-orthogonal multiple access (NOMA) is an effective means to improve the spectral efficiency of a wireless communication system. When applied to cellular networks, cell edge users may suffer from low bit rate, or the associated base stations may need to use excessively high power to serve those users. In order to alleviate the problem, this paper considers the integration of NOMA with coordinated transmission techniques. A two-cell system is considered, in which there are two users near their associated base stations and a cell edge user served by both base stations. It is assumed that each user has a data rate requirement , and the system objective is to minimize the total transmit power. With a formal problem formulation, the feasibility of the problem is characterized by using Helly's theorem. When the problem is feasible, we design both centralized and distributed algorithms to solve it. Numerical results show that NOMA can significantly outperform an orthogonal multiple access scheme in terms of power consumption and outage probability. Index Terms: Non-orthogonal multiple access (NOMA), coordinated multipoint (CoMP), power control, power domain multiplexing.

International audience; In a visible light communications system (VLC), light sources are responsible for both illumination, communications and positioning. These light sources inevitably interfere each others at the receiver. To retain the appealing advantage that VLC systems can reuse existing lighting infrastructure, using an extra network to control or synchronize the light sources should be avoided. This paper proposes an uncoordinated multiple access scheme for VLC systems with positioning capability. The proposed scheme does not require a central unit to coordinate the transmission of the transmitters. Transmitters can be asynchronous with one another and with the receiver. Each transmitter is allocated a unique codeword with L chips for a system with up to (L-1)/2 transmitters where L is prime. Due to the linear growth in complexity with respect to number of transmitters, our proposed scheme is feasible for systems with large numbers of transmitters. Our novel decoder can minimize the effect of additive Gaussian noise at the receiver side. Simulation results show that the proposed decoder outperforms zero-forcing decoder.

International audience; Cloud Radio Access Network (C-RAN) is becoming more than ever timely in 5G for dense network deployments, but its design has to be adapted to 5G requirements. To ensure high uplink throughput in cell-edge regions affected by inter-cell interference, C-RAN enables multiuser reception techniques among cells. In this paper, we propose an efficient end-to-end uplink transmission scheme dealing with implementation and deployment constraints on both communication interfaces in C-RAN, i.e., the wireless one between the users and the Remote Radio Heads (RRHs), and the fronthaul links between the RRHs and the central processing unit. Multi-cell non-orthogonal multiple access (NOMA) can improve spectral efficiency and cell-edge throughput, but its design needs to fit requirements regarding receiver complexity and delay. Optimizing the fronthaul rate allocation to maximize the benefit of the transmissions allows to exploit the fronthaul links effectively. Our model considers the throughput of NOMA transmissions in C-RAN and the expense related to fronthaul usage in various deployment scenarios. When the available fronthaul rate allows accurate transmission, optimizing fronthaul rate allocation results in 10% higher transmission benefit than uniform allocation. It also makes possible to involve less users in NOMA while keeping the benefit. The proposed strategy enables uplink multi-cell multiuser processing in a cost-effective manner in 5G C-RAN deployments.

International audience; Software defined networking (SDN) and network function virtualization (NFV) are the embraced technologies for the backhauling of future 5G networks. Virtual Machine (VM) and Docker container based deployments have received much attention. This paper presents the virtualization of a prototyped software defined radio access network (RAN) architecture by using VMs and Docker containers. In addition, it provides an analytical model for the generalized software defined RAN architecture with the practice of VM based and Docker container based implementations. Using measurements obtained from the two testbeds and the introduced queuing model, we compare their performances and analyze the two different architectures. Results verify the superiority of the Docker technology. Some observations from the behavior of the testbeds are concluded for a better understanding of the VM and Docker container based technologies for the future development of 5G SDN controller.

International audience; Aiming to throughput enhancement in future mobile networks, dense deployment of wireless access points (APs) is intended. Spectral efficiency on the uplink can be improved via joint processing of users located in areas covered by several APs. Thanks to centralized processing of such users enabled by Cloud Radio Access Network (C-RAN) architecture, low-latency multi-cell cooperation becomes possible. However, the price to pay to benefit from its advantages is the cost of transferring data from distributed access points to the data center through limited-capacity fronthaul links. A mobile network operator using C-RAN would have the objective to maximize data transmission rates with lowest possible fronthaul rate. We consider in this work the optimal tradeoff between the amount of fronthaul allocated and the sum rate of each user group in a multiple access scheme, where the wireless resource is reused among the user groups. By performing low-complexity joint reception of signals quantized according to attributed fronthaul rate, we can maximize the benefit of uplink transmission in C-RAN despite constrained fronthaul links. With optimal fronthaul allocation, the net benefit of the uplink transmission improves by 10% in a usual configuration.

International audience; Coordination between neighboring cells is intended to be implemented in future mobile networks, since it promises significant performance gains. Despite low-latency cooperation made possible by Cloud Radio Access Networks (C-RAN), practical feasibility and improvements brought to a real system were still to be evaluated. We define in this paper an architecture based on the abstraction and scalability provided by Software Defined Networking (SDN) enabling multi-cell coordination both on the uplink and downlink. We also evaluate gains offered by the proposed coordination algorithms under practical conditions. The described proof-of-concept platform shows not only why multi-cell cooperation is useful, but also how to make it happen.

International audience; Software Defined Networking (SDN) has attracted tremendous interest in the telecommunication industry due to its ability to abstract, manage and dynamically re-configure end-to-end networks from a centralized controller. Though SDN is considered to be a suitable candidate for various use cases in mobile networks, none of the work so far has discussed its advantages and actual realization for Train-to-Wayside Communication System (TWC). In this paper, for the first time, the architecture and use cases of SDN controlled mobile backhauling framework for TWC is proposed. We discuss how our proposed architecture can efficiently handle mobility management and also provide dynamic quality-of-service (QoS) for different services on board. As a first step, a software prototype is developed using industrial standard OpenDayLight SDN controller to have our architecture evaluated. Since the automotive sector is being considered to be an important driver for 5G network, our SDN based mobile backhauling solution can be positioned in 5G where SDN plays an important role.

International audience; 5G is envisioned to support scalable networks and improved user experience with virtually zero latency and ultra broad-band service. Supporting unlimited seamless mobility is one of the key issues and also for network resource utilization efficiency. In this paper, we focus on mobility management and user equipment (UE) speed class estimation, also known as mobility state estimation (MSE). We propose a method for estimating the UE mobility which is compliant with UE history information specifications by 3GPP (3rd Generation Partnership Project). We also exploit the impact of the environment on the UE trajectory and speed when determining UE mobility state. We evaluate the effectiveness of our algorithm using realistic mobility traces and network topology of the city of Cologne in Germany provided by the Kolntrace project [1]. Results show that the speed classification of UEs can be achieved with much higher accuracy compared to existing legacy 3GPP LTE MSE procedures.

Software Defined Networking (SDN) has generated tremendous interest in the telecommunication industry due to its ability to abstract, manage and dynamically re-configure end-to-end networks from the centralized controller. In this poster, for the first time, the architecture of SDN controlled wireless backhauling framework for Train to Ground communication system is proposed. We demonstrate how our architecture can efficiently handle mobility management and also provide dynamic quality-of-service (QoS) for different services on board.

International audience; Due to Orthogonal Frequency Division Multiple Access (OFDMA) mechanism adopted in LTE cellular networks, intra-cell interference is nearly absent. Yet, as these networks are designed for a frequency reuse factor of 1 to maximize the utilization of the licensed bandwidth, inter-cell interference coordination remains an important challenge. In both homogeneous and heterogeneous cellular networks, there is a need for scheduling coordination techniques to efficiently distribute the resources and mitigate inter-cell interference. In this paper, we propose a dynamic solution of inter-cell interference coordination performing an optimization of frequency sub-band reuse and transmission power in order to maximize the overall network utility. The proposed framework, based on game theory, permits to dynamically define frequency and transmission power patterns for each cell in the coordinated cluster. Simulation results show significant benefits in average throughput and also cell edge user throughput of 40% and 55% gains when performing the frequency sub-band muting and power control. Furthermore, we also obtain a meaningful improvement in energy efficiency.

International audience; Estimating mobile user speed is a problematic issue which has significant impacts to radio resource management and also to the mobility management of Long Term Evolution (LTE) networks. This paper introduces two algorithms that can estimate the speed of mobile user equipments (UE), with low computational requirement, and without modification of neither current user equipment nor 3GPP standard protocol. The proposed methods rely on uplink (UL) sounding reference signal (SRS) power measurements performed at the eNodeB (eNB) and remain efficient with large sampling period (e.g., 40 ms or beyond). We evaluate the effectiveness of our algorithms using realistic LTE system data provided by the eNB Layer1 team of Alcatel-Lucent. Results show that the classification of UE’s speed required by LTE can be achieved with high accuracy. In addition, they have minimal impact to the central processing unit (CPU) and the memory of eNB modem. We see that they are very practical to today’s LTE networks and would allow a continuous and real-time UE speed estimation.

International audience; Software defined networking (SDN) is growing rapidly in telecommunications due to its capability to efficiently manage end-to-end networks by decoupling control plane and data plane. The scalability and flexibility can bring benefits to network management and maintenance. However, it has yet to happen for wireless networks since there is a lack of practical solutions for migrating Radio Access Networks (RAN) to software defined wireless networks. Here, we design a wireless SDN controller based on OpenDayLight (ODL). We show how our framework can support typical use case and Self-Optimized Network algorithm. The design is highly flexible and can be leveraged for future wireless networks such as C-RAN and 5G.

International audience; With the widely use of smart devices and rapid development of communication technologies, it becomes easier for base stations to obtain the context information of users. The context information can be utilized to optimize system resource allocation. This paper focuses on context-aware unicast cellular networks. Assuming that some channel state information (CSI) can be predicted based on user context such as user location and moving pattern, joint power control and transmission scheduling is applied to minimize the transmission energy consumption. By reducing the energy minimization problem to a semi-assignment problem, our proposed algorithm can find the optimal solution in polynomial time. Simulation results show that the proposed context-aware scheme outperforms the traditional round-robin scheduler and opportunistic scheduler, which do not consider the feature of context-awareness.

International audience; To meet quality of service requirements on the uplink of future cellular networks, we need to exploit inter-cell interference among users eligible for cooperation. Cloud Radio Access Network (C-RAN) architecture is particularly favorable to realize cooperation between users in neighboring cells, since signal detection is realized in the same processing unit. The novel technology of Software Defined Networking (SDN) increases the flexibility of network optimization and scalability of computational resources. We propose a C-RAN based architecture and a practical scheme of realizing uplink joint processing in critical scenarios where strong interference would affect cell-edge users. We consider characteristics of a real network and novel technological solutions necessary for reliable transmission over the radio access network. The central idea is to split the physical layer processing between Remote Radio Heads (RRHs) and the central processing unit only for selected users in enabling cooperation and maintaining affordable fronthaul transport infrastructure. In practice, the joint detection for selected few co-channel users would simplify the required multiuser channel estimation while improving overall performance and cell-edge users' quality-of-service (QoS).

Due to the increasing need of health monitoring at home or in senior center, we study the optimal relay node placement problem for wireless sensor networks with data collection and localization requirements. The problem can be modeled as finding a minimum connected k-dominating set. We consider realistic indoor wireless environment and explicitly take into account the effect of obstacles to the radio coverage, instead of using idealistic disc model. We prove the problem is NP-hard and propose an efficient greedy method called optimal relay placement algorithm (ORPA) to derive the best network setup. Results show that by using the proposed method, the number of relays required can be significantly reduced in comparison to two baseline algorithms. The method presented would be also relevant to other systems of similar network connectivity and relay deployment criteria.

Background: Earlier research suggested female predominance in adult conversion disorder, and the strong association between conversion disorder and experiences of being abused is well known. However, the data for child and adolescent populations are limited. In Taiwan, the dramatic increase in child abuse may have some impact on the features of child and adolescent conversion disorder. This study aimed to compare the demographic characteristics, psychiatric comorbidity, and experiences of being abused in Taiwanese children and adolescents diagnosed with conversion disorder in psychiatric consultations across 2 decades. Methods: Retrospective and consecutive chart reviews were conducted for child and adolescent patients (< 20 years old) who were newly diagnosed with conversion disorder in psychiatric consultations at Taipei Veterans General Hospital from 1987 to 2006. The first group included patients who were diagnosed between 1987 and 1996 (the first decade), and the second group included patients who were diagnosed between 1997 and 2006 (the second decade). Results: A total of 42 patients diagnosed with conversion disorder were included in this study. Nineteen of the 42 subjects were diagnosed in the first decade (from 1987 to 1996), and 23 in the second decade (from 1997 to 2006). There existed among patients a tendency toward an increasing number of male subjects (p < 0.05), suffering more abuse (p < 0.05), and higher prevalence rates of depression and dysthymia comorbidity (p < 0.05) in the second decade compared to the first. Conclusion: The sex distribution in conversion disorder might have significantly changed over the past 2 decades. There is an increasing need for screening and interventions for psychiatric comorbidity and experiences of being abused in children and adolescents with conversion disorder. Because of the small sample size of our study, further studies that include multiple study sites and a larger number of patients are needed before a firm conclusion can be drawn. [J Chin Med Assoc 2009;72(9):471–477]

The authors consider collision channel without feedback in which collided packets are considered unrecoverable. For each user, the transmission of packets follows a specific periodical pattern, called the protocol sequence. Due to the lack of feedback, the beginning of the protocol sequences cannot be synchronized and nonzero relative offsets are inevitable. It results in variation of throughput. In this paper, we investigate optimal protocol sequence sets, in the sense that the throughput variance is zero. Such protocol sequences are said to be shift-invariant (SI). The characterizing properties of SI protocol sequences are presented. We also prove that SI sequences are identifiable, meaning that the receiver is able to determine the sender of each successfully received packet without any packet header. A general construction of SI sequences that meets the lower bound on sequence length is given. Besides, we study the least periods of SI sequences, and show that the least periods must be distinct in some cases. The throughput performance is compared numerically with other protocol sequences.

International audience; A two-hop neighborhood information-based routing protocol is proposed for real-time wireless sensor networks. The approach of mapping packet deadline to a velocity is adopted as that in SPEED; however, our routing decision is made based on the novel two-hop velocity integrated with energy balancing mechanism. Initiative drop control is embedded to enhance energy utilization efficiency, while reducing packet deadline miss ratio. Simulation and comparison show that the new protocol has led to lower packet deadline miss ratio and higher energy efficiency than two existing popular schemes. The result has also indicated a promising direction in supporting real-time quality-of-service for wireless sensor networks.

International audience; In this paper, a class of periodic unipolar binary sequences are investigated for their potential applications in defining new protocols for distributed wireless multiple access. Based on linear congruence sequences, one can show that for any finite subset of these sequences with total proportional rate not exceeding a specific threshold, there cannot be enough collisions to completely block any particular sequence, no matter how they are shifted with respect to one another. This property can be exploited in certain applications such as wireless sensor and ad hoc networks. A further investigation on how to enhance the allowable rate sum is carried out. New protocol sequences with interesting and useful properties are designed accordingly.

International audience; The co-existence of small cells and macro cells is a key feature of 4G and future networks. This heterogeneity, together with the increased mobility of user devices can generate a high handover frequency that could lead to unreasonably high call drop probability or poor user experience. By performing smart mobility management, the network can pro-actively adapt to the user and guarantee seamless and smooth cell transitions. In this work, we introduce an algorithm that takes as input sounding reference signal (SRS) measurements available at the base station (eNodeB in 4G systems) to estimate with a low computational requirement the mobility level of the user and with no modification at the user device/equipment (UE) side. The performance of the algorithm is showcased using realistic data and mobility traces. Results show that the classification of UE speed to three mobility classes can be achieved with accuracy of 87% for low mobility, 93% for medium mobility, and 94% for high mobility, respectively.

The co-existence of small cells and macro cells is a key feature of 4G and future networks. This heterogeneity, together with the increased mobility of user devices can generate a high handover frequency that could lead to unreasonably high call drop probability or poor user experience. By performing smart mobility management, the network can pro-actively adapt to the user and guarantee seamless and smooth cell transitions. In this work, we introduce an algorithm that takes as input sounding reference signal (SRS) measurements available at the base station (eNodeB in 4G systems) to estimate with a low computational requirement the mobility level of the user and with no modification at the user device/equipment (UE) side. The performance of the algorithm is showcased using realistic data and mobility traces. Results show that the classification of UE speed to three mobility classes can be achieved with accuracy of 87% for low mobility, 93% for medium mobility, and 94% for high mobility, respectively.

International audience; In this paper we propose a distributed algorithm for jointly optimizing almost blank subframe (ABS) and cell selection bias (CSB) patterns in Long Term Evolution-Advanced (LTE-A) heterogeneous networks (HetNets). We formulate the optimization problem as an exact potential game, where a Nash equilibrium point is guaranteed to be achieved within finite number of plays. Through simulations, we are able to demonstrate the fast convergence of the algorithm, an increase in average user rate, and a tremendous improvement on the service fairness of the users.

International audience; The major issue of indoor localization system is the trade-off between implementation cost and accuracy. A low-cost system which demands only few hardware devices could save the cost but often it turns out to be less reliable. Aiming at improving classical triangulation method that requires several reference points, this paper proposes a new method, called Two-Step Movement (2SM), which requires only one reference point (RP) by exploiting useful information given by the position change of a mobile terminal (MT), or the user movement. This method can minimize the number of reference points required in a localization system or navigation service and reduce system implementation cost. Analytical result shows that the user position can be thus derived and given in simple closed-form expression. Finally, simulation is conducted to demonstrate its effectiveness under noisy environment.

International audience; This paper proposes two novel and practical designs of angle diversity receivers to achieve multiple-input-multiple-output (MIMO) capacity for indoor visible light communications (VLC). Both designs are easy to be constructed and suitable for small mobile devices. By using light emitting diodes for both illumination and data transmission, our receiver designs consist of multiple photodetectors (PDs) which are oriented with different inclination angles to achieve high-rank MIMO channels and can be closely packed without the requirement of spatial separation. Due to the orientations of the PDs, the proposed receiver designs are named pyramid receiver (PR) and hemispheric receiver (HR). In a PR, the normal vectors of PDs are chosen the same as the normal vectors of the triangle faces of a pyramid with equilateral N-gon base. On the other hand, the idea of HR is to evenly distribute the PDs on a hemisphere. Through analytical investigation, simulations and experiments, the channel capacity and bit-error-rate (BER) performance under various settings are presented to show that our receiver designs are practical and promising for enabling VLC-MIMO. In comparison to induced link-blocked receiver, our designs do not require any hardware adjustment at the receiver from location to location so that they can support user mobility. Besides, their channel capacities and BER performance are quite close to that of link-blocked receiver. Meanwhile, they substantially outperform spatially-separated receiver. This study reveals that using angle diversity to build VLC-MIMO system is very promising.

International audience; Indoor positioning system is a key component for developing various location based services such as indoor navigation in large complex buildings (e.g., commercial center and hospital). Meanwhile, it is challenging to design a cost effective solution which is able to provide high accuracy. A new method, namely Two-Step Movement (2SM), was proposed in [1] to demonstrate how to build a positioning system which requires only one Reference Point (RP) by exploiting user movement. The method can offer good precision and minimize the number of RPs required so as to reduce system implementation cost. Built on 2SM, here we first improve the positioning performance through multi-sampling technique to combat measurement noise. Secondly, we propose the Generalized Two-Step Movement (G2SM) method for device-to-device (D2D) systems in which both the mobile terminal (MT) and RP can be mobile device. The mobile user's position can be derived analytically and given in simple closed-form expression. Its effectiveness in the presence of noise is shown in simulation results.

International audience; This paper considers the energy minimization problem for wireless broadcast networks. One important feature is that user context is taken into consideration, integrated with network coding technique. Assuming that the user context, i.e., channel state information (CSI) can be predicted or estimated by using user location and moving pattern, power allocation is optimized to minimize energy consumption. It is proved NP-hard to find the optimal solution. By formulating the minimization problem into a binary integer programming (BLP) problem, the optimal solution can be obtained. Considering the high complexity of BLP, a heuristic algorithm is also proposed. Simulation results show that the proposed context-aware algorithms can reduce energy consumption up to 98%, compared with the scheme without using context information.

This paper deals with a class of power control problems where the system link gains are assumed to be time varying and the signal-to-interference ratio (SIR) estimates are allowed to be corrupted with bounded noises. A simple control algorithm is devised by applying a distributed, fixed step approach. It is a feedback algorithm that requires only local information. By modifying the distributed, fixed step power control algorithm proposed by Sung and Wong, we obtain here a more robust version that can handle time varying link gains and measurement noises. The convergence property of the new algorithm is established and simulation studies were carried out to show that it is effective.

In integrated wireless multimedia service, isochronous traffic of different connections can be scheduled by using a most regular binary sequence (MRBS). Such a sequence schedules traffic in an evenly spaced manner to achieve any arbitrary rate asymptotically and while avoiding excessive delay or buffering requirement. Flexible slot assignment that can match requests exactly improves bandwidth efficiency in multirate operations. The most regular binary sequence provides a distributed solution for multiaccess control that is based on limited information exchange. As a generalization, the concept of a most regular code sequence (MRCS) is proposed to support variable rate transmission in wideband code division multiple access (CDMA) systems and to provide spreading factor (SF) optimization. This scheme improves channel utilization efficiency in supporting traffics of various classes and hence results in an overall capacity gain.

Heterogeneous network (HetNet) is considered as an energy efficient system structure to alleviate the problem of rapidly increasing power consumption in the wireless communication system. Significant research on HetNet energy efficiency has been conducted. However, most of them only consider power consumption of Base Stations (BSs) while ignoring influence on energy efficiency of Mobile Devices (MDs) brought by new BSs deployment. In this work, we propose a novel energy efficiency metric for HetNet, which considers the energy efficiency of both BSs and MDs. Under the coexisting scenario of a single macrocell and a single microcell, we analyze the changes in power consumption at both the BSs side and the MDs side with the deployment of a micro BS. Optimum microcell radii for maximum power saving at the MDs sides and for highest network energy efficiency are obtained through analytical studies. It is found that total power saving for microcell MDs is close to 18% with a proper deployment of a microcell. Finally, extensive simulations have been provided to establish the accuracy of our theoretical analysis.

International audience; In indoor visible light communication systems, transmitters are usually within the line of sight of the receiver. In order to enjoy the benefits of using multiple-input-multiple-output (MIMO) system, the technique for reducing channel correlation is important. This paper proposes a MIMO system using an angle diversity receiver (ADR) to achieve high spatial multiplexing gain. In our proposed system, receiver consists of multiple photodetectors (PDs) whose normals are pointing toward different directions. As a result, the incident angles from the same light emitting diode (LED) are different for different PDs and hence, channel correlation can be reduced. The spatial separation among PDs is small and no imaging lens is required. The proposed receiver is suitable for mounting on small devices like smartphones. Performance comparisons, in terms of analytical, simulated and experimental bit error rates (BER), are carried out for a MIMO system with 4 LED transmitters and 5 PD receivers. Results show that the proposed receiver performs better than other existing non-imaging receiver designs. Our proposed MIMO system is a practically feasible solution to enjoy low channel correlation and support mobility at receiver.

Heterogeneous cellular networks are composed of a mixture of macro and small (pico) cells embedded in the macro network. A greedy strategy is proposed to maximize network capacity. Picos placement and either macro or pico transmit power are optimized jointly, as picos are deployed. The scaling of area spectral efficiencies (ASE) as pico densities are increased is studied. Median ASEs grow linearly with density and are comparable to cell-splitting given fixed pico power -20dB EIRP relative to the macro. The effectiveness of the pico at such low power is due in part to the improvement in area coverage of an omni vs. a 3 sectored antenna.

International audience; Small cell techniques are recognized as the best way to deliver high capacity for broadband cellular communications. Femtocell and distributed antenna systems (DAS) are important components in the overall small cell story, but are not the complete solution. They have major disadvantages of very limited cooperation capability and expensive deployment cost, respectively. In this article, we propose a novel mobile-over-FTTx (MoF) network architecture, where a fiber-to-the-x (FTTx) network is enhanced as an integrated rather than a simple backhauling component of a new mobile network delivering low-cost and powerful small cell solutions. In part, the MoF architecture combines the advantages of femtocell and DAS, while overcoming their disadvantages. Implementation challenges and potential solutions are discussed. Simulation results are presented and demonstrate the strong potential of the MoF in boosting the capacity of mobile networks.

International audience; Small cell network is designed to provide mobile services to hot spots by deploying a large number of small access points (APs). As traditional network deployment requires costly AP location acquisition, cost-effective network deployment is necessary for small cell networks. We investigate this question by studying the network performance in terms of spatial outage and throughput of a completely random topology in comparison to that of a perfectly regular topology. Using a stochastic geometry model of user SINR in a random topology, our results show that the performance gap in terms of user SINR guarantee becomes narrow when the network density increases during the network densification. By a massive deployment, the loss is about 1 dB. Besides, it is at about 18% loss in user average throughput. These comparative results would provide helpful information to choose an appropriate deployment. In particular, as far as this relatively small performance loss can be compensated by other network control algorithms, the massive random deployment of a small cell network becomes attractive considering the cost reduction by the given deployment freedom.

International audience; We consider the problem of LTE network self organization and optimization of resource allocation. One particular challenge for LTE systems is that, by applying OFDMA, a transmission may use multiple resource blocks scheduled over the frequency and time. There are three key components involved in the resource allocation and network optimization: resource block scheduling, power control, and client association. We propose a distributed protocol that aims to achieve weighted proportional fairness (WPF) among clients by jointly consider them. The cross-layer design includes: (i) an optimal online policy for resource block scheduling, (ii) a heuristic for transmit power control, and (iii) a selfish strategy for client association. The proposed scheme only requires limited local information exchange and thus can be easily implemented for large networks. Simulation results have shown its effectiveness in both the system throughput and user fairness.

International audience; We consider coordination in a multi-user multiple input single output cellular system. In contrast with existing base station cooperation methods that rely on sharing CSI with or without user data to manage interference, we propose to share user data only. We consider a system where blind interference alignment (BIA) is applied to serve multiple users in each cell. We apply interference coordination through data sharing to mitigate other-cell interference at the cell-edge users. While BIA mitigates intra-cell interference in MU-MISO systems, it does not address the problem of inter-cell interference. We apply interference coordination through data sharing to mitigate inter-cell interference at the cell-edge users. We propose a new cooperative BIA scheme that takes into account the users whose data is being shared between adjacent base stations. We derive the achievable sum rate with interference mitigation and we compare it to achievable rates with the original BIA strategy. Numerical results show that the achievable sum rate of the cell-edge users with data sharing decreases with increasing number of served users in each cell and increasing number of antennas at the base stations.

International audience; In this paper, we propose an autonomous radio resource allocation and optimization scheme that chooses the transmit power and precoding vector among codebooks for multiple antennas transmitters to improve spectral and power efficiency and provide user fairness. Network self-optimization is an essential feature for supporting the cell densification in future wireless cellular systems. The proposed self-optimization is inspired by Gibbs sampler. We show that it can be implemented in a distributed manner and nevertheless achieves system-wide optimization which improves network throughput, power utilization efficiency, and overall service fairness. In addition, we extend the work and include power pricing to parametrize and enhance energy efficiency further. Simulation results show that the proposed scheme can outperform today's default modes of operation in network throughput, energy efficiency, and user fairness.

This paper deals with the handover measurement in cellular networks. The work is dedicated to network modeling and performance evaluation. The exposition concentrates on temporal evolution of the scanning process with key events: (i) a suitable handover target found, (ii) call drop or service failure, and (iii) scan withdrawal. By observations on the stochastic properties of best signal quality and minimum-duration outage, we determine the probability of the key elements and provide a generalized framework for network design and analysis such as in scanning failure probability and target cell expected quality. Results obtained with LTE have also shown its effectiveness.

International audience; In this work, we develop mathematical and algorithmic tools for the self-optimization of mobile cellular networks. Scalable algorithms which are based on local measurements and do not require heavy coordination among the wireless devices are proposed. We focus on the optimization of transmit power and of user association. The method is applicable to both joint and separate optimizations. The global utility minimized is linked to potential delay fairness. The distributed algorithm adaptively updates the system parameters and achieves global optimality by measuring SINR and interference. It is built on Gibbs' sampler and offers a unified framework that can be easily reused for different purposes. Simulation results demonstrate the effectiveness of the algorithm.

Protocol sequences are used for channel access in the collision channel without feedback. Each user is assigned a deterministic zero-one pattern, called protocol sequence. The zeros and ones in a protocol sequence are read out periodically, and a packet is sent if and only if it is one. A collision occurs if two or more users transmit at the same time. Due to the lack of feedback from the receiver and cooperation among users, the beginning of the protocol sequences cannot be synchronized and relative delay offsets are incurred.We study the design of protocol sequences from two different perspectives. Under the first one, called shift invariance, we aim at minimizing the fluctuation of throughput due to relative delay offsets. As for the second one, called user irrepressibility, we want to guarantee that each user can send at least one packet successfully in each period. For both design criteria, we derive a lower bound on sequence period and give an optimal construction that achieves this lower bound.

A revisit of the model of collision channel without feedback (CCw/oFB) has motivated some interesting designs on periodic binary sequences. The protocol and system simplicity is particularly favorable for applications in certain wireless sensor and ad hoc networks. User unsuppressibility for individual service guarantee is desirable and emphasized here. We review some protocol sequences that are user unsuppressible (UU). Lower bounds of sequence length are obtained. Some corresponding sequence sets are identified.

We explore the asymptotic performance of existing geographic routing with a utilization of k-hop neighborhood information. The reachability from source to sink improves as we integrate more information into the routing decision. It is observed that the average number of hops required decreases significantly from the 1-hop to 2-hop based searching. This indicates an attractive tradeoff between the performance enhancement and system complexity. As simple greedy forwarding is insufficient in lossy wireless environment, we propose a new metric incorporating advance in distance and link quality to handle unreliable communication links. Simulation result has verified its effectiveness and superiority over the conventional simple greedy method. Besides, a generalization to k-hop based routing and the resulting performance are presented. Results show that with the multi-hop based searching, in both the deterministic and probabilistic lossy radio models, there is a good improvement in the number of transmissions required from end to end, which can indicate potential improvement in the routing delay and energy efficiency in transmissions.

International audience; A two-hop neighborhood information based routing protocol is proposed for real-time wireless sensor networks. The approach of mapping packet deadline to a velocity is adopted as SPEED; however, our routing decision is made based on the novel 2-hop velocity. Energyefficient probabilistic drop is embedded to enhance energy utilization efficiency while reducing packet deadline miss ratio. In case packet deadline requirement is not stringent, a new mechanism is included to release nodes which are frequently chosen as forwarders. Improvement on energy consumption balance throughout the network is observed. The true characteristics of physical and MAC layers are captured in the simulation. A real lossy link model is drawn from extensive experiments through Mica2 Motes. Simulation results show that the new protocol has achieved lower packet deadline miss ratio and higher energy efficiency.

In this paper, we analyze the sum rate maximization problem in a two-cell wireless system under peak power and minimum service rate constraints. The optimal power allocation is found to be binary, in the sense that each base station power will have one out of only two possible discrete levels, and the result can greatly reduce the optimization and power control complexity required. A closed-form solution of the optimal assignment is reported. The new result provides a generalization of the binary power control (BPC) proposed in. It is possible to apply the new result under the two-cell structure when clustering a larger network into groups of two cells. In a comparison with the full power transmission, it is shown that the proposed scheme outperforms in both the outage probability and sum rate performance generally.