Showing papers presented at "IFIP Wireless Days in 2013"

WiFi Direct and LTE D2D in action

Abstract: With the evolution of high-performance multi-radio smartphones, Device-to-Device (D2D) communications became an attractive solution for enhancing the performance of cellular networks. Although D2D communications have been widely studied within past few years, the majority of the literature is confined to new theoretical proposals and did not consider implementation challenges. In fact, the implementation feasibility of D2D communications and its challenges are still a relevant research question. In this paper, we introduce a protocol that focuses on D2D communications using LTE and WiFi Direct technologies. We also show that currently available WiFi Direct features permits to deploy the D2D paradigm on top of the LTE cellular infrastructure, without requiring any fundamental change in LTE protocols.

Experimenting opportunistic networks with WiFi Direct

Abstract: WiFi Direct introduces new opportunities to deploy real opportunistic networks through users' mobile devices. However, its original specification does not take into account all the parameters that can emerge from an opportunistic network scenario, not only in terms of technical requirements (e.g., available resources and connectivities) but also of users characteristics and profiles, which can heavily influence the system's performances and devices' interactions. In this work we investigate the feasibility of creating opportunistic networks on top of WiFi Direct framework by analyzing the protocol's performances in real scenarios with a variable number of mobile devices. Experimental results show the times required to form a group of variable size and the best configurations to support opportunistic networking operations and upper layer applications.

Named Data Networking: A natural design for data collection in Wireless Sensor Networks

Abstract: Named Data Networking (NDN) is a promising paradigm for the future Internet architecture that also opens new perspectives in the way data can be retrieved in Wireless Sensor Networks (WSNs). In this paper, we explore the potentialities of the NDN paradigm applied to WSNs and propose enhancements to the NDN forwarding strategy by including principles inspired by traditional data-centric routing schemes. Results achieved through the ndnSIM simulator confirm the viability and effectiveness of the proposal.

Cyber Physical System: Architecture, applications and research challenges

Abstract: Cyber world and physical world were considered as two different entities in the past decade. However, researchers have found that these two entities are closely correlated with each other after integration of sensor/actuators in the cyber systems. Cyber systems became responsive to the physical world by enabling real time control emanating from conventional embedded systems, thus emerging a new research paradigm named Cyber Physical System (CPS). In this article, we investigate major challenges in the integration of cyber world with physical world and its applications. In addition, we propose an architecture which contains several modules supporting the CPS. We found that every module in our proposed architecture has its own significance and can be applied to various applications.

An insight into Decentralized Congestion Control techniques for VANETs from ETSI TS 102 687 V1.1.1

Abstract: Many cooperative applications designed to improve road safety rely on the frequent exchange of awareness messages among vehicles. Therefore, under high vehicle density, the channel medium is expected to get congested. To tackle this situation, the European Telecommunications Standards Institute (ETSI) specified a set of Decentralized Congestion Control (DCC) mechanisms that adapt the transmission parameters based on channel load measures. Due to some concerns about its effectiveness and stability, DCC and its overall philosophy are currently being revised and extended: all in all, DCC deserves additional investigations. For this purpose, in this paper a simulation analysis is presented, aiming at enriching the insight into the DCC behaviour, under a variety of channel load conditions and through the definition of both link- and application-layer performance metrics. Achieved results show that the DCC techniques are not really effective with the currently specified parameters settings; hence some hints are given to improve their performance.

V2X-d: A vehicular density estimation system that combines V2V and V2I communications

Abstract: Road traffic is experiencing a drastic increase, and vehicular traffic congestion is becoming a major problem, especially in metropolitan environments throughout the world. Additionally, in modern Intelligent Transportation Systems (ITS) communications, the high amount of information that can be generated and processed by vehicles will significantly increase message redundancy, channel contention, and message collisions, thus reducing the efficiency of message dissemination processes. In this work, we present a V2X architecture to estimate traffic density on the road that relies on the advantages of combining V2V and V2I communications. Our proposal uses both the number of beacons received per vehicle (V2V) and per RSU (V2I), as well as the roadmap topology features to estimate the vehicle density. By using our approach, modern Intelligent Transportation Systems will be able to reduce traffic congestion and also to adopt more efficient message dissemination protocols.

On the feasibility of WiFi offloading in urban areas: The Paris case study

Abstract: With the increasing number of users subscribing to mobile Internet such as 3G and 4G networks, the Wireless Internet Services providers (WISP) aim to offer a good service for customers while elevating the number of clients. Several proposals to offload the traffic of 3G networks have been made in the past few years, including the use of femtocells,WiFi offloading and more recently mobile-to-mobile opportunistic offloading. In this paper, we measure the public WiFi hotspots provided by the government and private WiFi access points (AP) scanned during several bus routes in Paris in order to evaluate the feasibility of offloading data traffic through WiFi. We compare the AP positions with the positions of mobile clients provided publicly in Location Sharing Services, such as Foursquare. Our main findings are that, on average, an access point is available up to 60m of range, during 30 seconds, and the already deployed WiFi infrastructure could offload up to 30% of mobile traffic in the scenario analyzed.

Vehicle-to-infrastructure messaging proposal based on CAM/DENM specifications

Abstract: The European Telecommunications Standards Institute (ETSI) has proposed a middleware solution (called facility) to support vehicular safety and traffic efficiency services needing continuous status information about surrounding vehicles or wanting to send asynchronous warning notifications to vehicles. The former capability is offered by the Cooperative Awareness Basic Service, while the latter is provided by the Decentralized Environmental Notification Basic Service. Reference packet formats for both the Cooperative Awareness Message (CAM) and Decentralized Environmental Notification Message (DENM) have been specified by ETSI, together with the general message dissemination guidelines. This paper presents an implementation prototype that has been developed to validate both CAM and DENM messaging capabilities. We provide implementation decisions and demonstrate the usefulness of these facilities through two reference services which provide a way to third-party services to gather tracking and tracing information, and send asynchronous road events to drivers within a specific area.

Self-organized neighborhood mobility load balancing for LTE networks

Abstract: This paper investigates mobility load balancing (MLB) in a hexagonal LTE (Long Term Evolution) macro cellular deployment. Gain and cost of MLB is evaluated by downlink (DL) system simulations in terms of quality of service (QoS) enhancement versus increased resource expenses. A novel distributed SON (self-organizing network) algorithm, termed as neighborhood mobility load balancing (NMLB) algorithm, is presented which also includes non-adjacent neighborhood cells in the optimization area as compared to the classical approach in which only adjacent neighbor cells are considered in the optimization area. The simulation results show that NMLB gives a significant gain w.r.t. the traffic throughput as compared to the classical MLB in complex load scenarios where the capacity is not available in the adjacent neighbor cells but further away in the neighborhood cells.

A naming scheme to represent geographic areas in NDN

Abstract: Vehicular networks are intended to support a safer and more comfortable driving experience both through vehicle-to-infrastructure communication and, even more interesting, vehicle-to-vehicle ad-hoc networking. In the latter case, the focus will be on getting a content of interest from a specific geographic region, rather than communicating to a predetermined host. As current IP-based protocols are specifically designed for conversations between hosts, innovative solutions have to be devised. To this aim, we consider the Named Data Networking paradigm and propose a named-data approach efficiently mapping bi-dimensional geographic areas into a uni-dimensional naming scheme.

A comparison study of 2D and 3D ITU channel model

Abstract: Recently there has been strong interest in extending MIMO signal processing from the azimuth dimension to include the elevation plane. However, many channel models, such as the 3GPP/ITU model, focus on two dimensional propagation, i.e. propagation in the azimuth plane only. The assumption of 2D propagation may lead to inaccurate estimation of channel capacity, spatial correlation and system level performance in environments where the distribution of the elevation angles is significant. In this paper, we implement a 3D extension of the 3GPP/ITU 2D channel model by adding elevation angle statistics generated by a state-of-the-art 3D ray tracer. The paper also presents a comparison study between the implemented 3D 3GPP/ITU model and the ray tracer channel statistics. We also show the impact of considering 3D components on the channel ergodic capacity, antenna spatial correlation and large/small scale parameters (total received power, delay spread, angular spread, and K-factor).

LTE planning for Soft Frequency Reuse

Abstract: Future 4G cellular systems will address the need of capacity increase for the support of diverse Internet services. This article deals with cell capacity issues and cell planning for LTE technology. The Soft Frequency Reuse (SFR) scheme is considered here as an interesting approach to efficiently utilize the bandwidth in LTE systems. With SFR, a cell is divided into two parts (the central part and the external part) using different reuse schemes. On the basis of a suitable path loss model, we have been able to characterize the Signal to Interference plus Noise Ratio (SINR) and the probability to use different transmission modes in a cell with SFR. This has allowed us to evaluate the capacity of a cell that can be achieved with SFR. Finally, a cell capacity optimization has been carried out by means of extensive numerical results in order to select both the radius of the cell-center region and the border-to-center power ratio of SFR.

Analysis of hybrid relaying in cooperative WLAN

Abstract: An ever-growing demand for higher data-rates has facilitated the growth of wireless networks in the past decades. Nevertheless, wireless technologies face performance limitations due to unstable wireless conditions and mobility of devices. In face of multi-path propagation and low data-rate stations, cooperative relaying promises gains in performance and reliability. However, cooperation procedures are unstable and introduce overhead that can endanger performance. In this paper we analyze the performance of a hybrid relaying protocol build based on the combination of opportunistic and broadcast-based relaying approaches. Hybrid relaying aims to increase the transmission capacity of wireless networks (proactive operation) when compared to proactive opportunistic and broadcast-based approaches due to rectifying the setbacks involved in those approaches, while adding a reactive approach to recover from failed transmissions.

Efficient coverage through inter-operator infrastructure sharing in mobile networks

Abstract: Herein, we study efficient coverage provisioning in mobile networks under an inter-operator infrastructure sharing regime which we call Networks without Borders. For the purpose of the study, we derive general formulations of the full and partial coverage provisioning problem. Based on these formulations, we assess the efficiency of coverage provisioning over shared multi-operator infrastructure for two datasets: randomly generated deployment and a real network deployment from Poland. In the paper we report over 90% cost efficiency between shared and non-shared networks for dense deployments with both homogeneous and heterogeneous power allocations, and a divergence in the efficiency between real and random deployments for low deployment density case.We consider this work as a first tractable attempt to describe large-scale inter-operator infrastructure sharing which may be the key to enabling appropriate coverage in currently under-served areas, with effects on the digital divide.

Evaluating HEVC video delivery in VANET scenarios

Abstract: Video delivery over VANETs is a difficult task. On the one hand, video streaming is a demanding application, where big deals of data need to be processed and transmitted. On the other hand, VANETs are error prone networks due to the high mobility of the nodes and the wireless channel. The sum of these two factors makes video transmission a hard to manage task. In this paper we evaluate the new emerging video coding standard HEVC and how it behaves under packet losses conditions in a VANET.

Modeling of interference maps for Licensed Shared Access in LTE-advanced networks supporting Carrier Aggregation

Abstract: Cognitive Radio based Dynamic Spectrum Access (CR-DSA) has been envisaged as the foremost solution to eliminate the impending false scarcity of the radio frequency spectrum and to combat the dramatic surge in mobile data traffic. Furthermore, the revolutionary concepts - Carrier Aggregation (CA) and Licensed Shared Access (LSA) - have been conceived to support higher data rates by aggregating bandwidth from different parts of the spectrum, and to provide for a predictable Quality of Service (QoS) through spectrum sharing, respectively, so as to enhance the performance of the current generation mobile communication systems. However, an inevitable consequence of spectrum sharing is the interference induced upon the incumbent user. In this work, the prime focus of attention is on the mitigation of the interference caused by an LSA-licensed LTE-Advanced Radio Access Network (RAN) in the uplink (UL). To this end, we propose an interference management scheme based on Radio Environment Maps (REMs). Different approaches have been considered for the modeling of the requisite maps and a performance comparison between them by means of detection theory is presented. In conclusion, we prove the superior performance of the kriging spatial interpolation technique over the other approaches.

Cooperative multihop connectivity performance in visible light communications

Abstract: In this work, we have studied the cooperative multi-hop communication using relays to increase the connectivity in visible light communications (VLC). Short transmission range, narrow field of view and occlusion/obstruction by object are limiting the user connectivity to the access point in VLC. The connectivity performance of such cooperative communications is characterized by taking into account optical line-of-sight (LOS) channel model, relay selection algorithm, velocity of user, semi-angle at half power of the light emitting diode (LED) and the field of view (FOV) of the photo detector. Simulations have been performed to evaluate the connectivity performance of such networks with and without relays. In user connectivity performance several simulation parameters are considered: user density, coverage range ratio of multi-hop region (MR), relay probabilities. Simulation results reveal that in case of all considered simulation parameters user connectivity increases using relays in comparison to without relays.

Mobile Cloud based architecture for Device-to-Device (D2D) communication underlying cellular network

Abstract: Device-to-Device communication (D2D) allows User Equipment's (UE's) in the close vicinity to communicate directly by exploiting the cellular resources. The benefit of such communication paradigm results in an increase bit rate. Mobile Cloud (MC) is D2D based architecture of closely located multi-standard wireless devices connected to the cellular network as well as with each other through short-range links. In this way, MC assists other UE's in the network for data delivery. Traditionally, a Cluster Head (CH) is employed for such MC based architectures. The homogeneous data distribution in to such network has many challenges such as, the selection of the best possible CH. This paper presents a novel architecture of MC where UE's compete for Cluster Heads (CH's) based on the residual energy and Signal to Interference and Noise (SINR). The proposed architecture comprises of multiple logical regions (clusters) having multiple CH's. Simulation results shows about 25% increase in throughput and bandwidth efficiency as compared to classical mobile communication.

Improvement of IEEE 802.15.4a IR-UWB for time-critical industrial wireless sensor networks

Abstract: Wireless sensor networks for industrial factory automation require high reliability and low latency. Since state of the art wireless sensor networks do not entirely meet these requirements, novel system approaches need to be developed. In this regard, ultra wideband communication systems seem to be a promising approach due to their high bandwidth and robustness against frequency selectivity. This paper analyzes the feasibility of the IEEE 802.15.4a impulse-radio ultra-wideband physical layer in the application domain of factory automation. The IEEE 802.15.4e media access control layer which is specified to meet the requirements of industrial applications is included in the analysis. Based on a realistic network and application scenario, the resulting system latency is examined. Parameter adaptions and system enhancements for latency reduction considering both physical and media access control layers are given. As a result, the performance investigation serves as a guide for selecting a suitable wireless system for the establishment of a wireless sensor network. A lower bound of resulting latency is presented.

End-to-end delay estimation using RPL metrics in WSN

Abstract: Critical monitoring applications can use wireless sensor networks to transport delay sensitive data. This data may demand bounded delays in order to be considered useful by the receiver. In these cases, an accurate and real-time estimation of the end-to-end delay could be used to anticipate the data usefulness prior to sending it. A novel real-time and end-to-end delay estimation mechanism is proposed in this paper, which considers processing times and two new RPL metrics. Results show that our proposal is more accurate than the ETT-based solution for delay estimation, and it does not significantly degrade the network performance.

Combining fractional frequency reuse with coordinated multipoint transmission in MIMO-OFDMA networks

Abstract: This paper presents a systematic comparative study involving two fundamental mechanisms envisaged to play a crucial role in 4G networks, namely, fractional frequency reuse (FFR) and coordinated multipoint transmission (CoMP). A simulation framework is developed to assess the performance of the most relevant coordination schemes under different user scheduling policies while also revealing what are the corresponding optimum settings for the FFR component. Moreover, for one particularly interesting CoMP technique, namely, zero-forcing (ZF) precoding, a novel power allocation strategy is proposed that is shown to significantly enhance its performance. Simulation results serve to confirm the benefits of combining both techniques, FFR and CoMP, in comparison to non-coordinated architectures.

SmartAP: Practical WLAN backhaul aggregation

Abstract: In light of the growing disparity between residential broadband and 802.11 speeds, Access Point (AP) backhaul aggregation has been proposed by the research community as a service whereby residential customers may enjoy higher throughput when in range of participating 802.11 APs. The fundamental assumption of these works is that 802.11 clients can be modified at driver level. However, due to the high diversity of 802.11 chipsets and drivers in the market, the cost of modifying any WiFi driver for any operating system is prohibitive, which in turn makes the solution unpractical for commercial deployment. In this paper, we propose a WLAN backhaul aggregation scheme that works with unmodified 802.11 clients. We introduce SmartAP, a single-radio 802.11 AP, that can deliver higher throughput to its off-the-shelf clients by aggregating the backhaul capacity of APs in range, even if these APs are in different radio channels. SmartAP reaches this goal without adding new radio hardware to the network. We build SmartAP with off-the-shelf hardware and evaluate its performance in a network testbed of 6-nodes with unmodified smartphones and laptops as clients. We evaluate the conditions under which SmartAP leads to gains comparable to state-of-the-art approaches with client-side modifications and we demonstrate that using a two-hop transmission to access additional backhaul capacity yields substantial benefits.

On the impacts of distributed and Dynamic Mobility Management strategy: A simulation study

Abstract: The explosive increase in Internet traffic definitely requires operators to turn their eyes to a flat-based mobile architecture, providing scalable and reliable mobility solutions for future evolved mobile networks. Distributed and Dynamic Mobility Management (DMM) is one of the main enablers to implement the flat-based mobile architecture, placing anchor functions at the edges and providing dynamic mobility activation. In this paper, we perform a simulation study to assess the impact of the DMM strategy, focused on the data plane, in mobile networks. The main objective of this paper is to identify how much DMM can be effective in reducing network stresses imposed on the mobile backhaul and core networks, compared to Proxy Mobile IPv6 (PMIPv6) having excellent handover performance among centralized mobility protocols. Simulation results demonstrate that DMM is effective to improve packet delivery efficiency and to mitigate the network stresses due to IP mobility support by distributing anchoring burdens and eliminating the need of packet anchoring.

Ad hoc network QoS architecture for cooperative Unmanned Aerial Vehicles (UAVs)

Abstract: New trends in cooperative human-machine system use in the domain of transportations are rising. These systems rely on a powerful interaction, or collaboration between humans and machines. This collaboration is made possible by an exchange of information between actors (humans or machines, commonly referred to as agents) in the transport of good or people. Cooperation in such a dynamic environment implies that the actors may have varying roles and/or tasks assigned to them, thus leading to changes in their communication needs. This paper presents an ad hoc network QoS architecture oriented toward cooperation between agents, called DAN. This architecture is aware of agents needs in term of communication and is able to provide, or inform of the impossibility to provide, a quality of service in accordance to those needs.

A collision-aware backoff mechanism for IEEE 802.15.4 wireless sensor networks

Abstract: The IEEE 802.15.4 standard uses carrier sense multiple access with collision avoidance (CSMA/CA) as the medium access mechanism. This mechanism employs a binary exponential backoff (BEB) algorithm to control the access of nodes to the wireless medium. The main drawbacks of this algorithm are that the range of the backoff exponent is very small and it updates the length of the backoff period in a deterministic manner without taking into consideration the actual state of the communication channel. These inefficiencies degrade the system performance when the network has many nodes and the collision probability is large. We address these problems by proposing a novel collision-aware backoff algorithm (CABEB) which can dynamically select a suitable backoff period according to the collision probability of the nodes. The simulation results verify the efficiency of the proposed algorithm.

QoS investigation of proportional fair scheduling in LTE networks

Abstract: In this paper, the quality of service in a Long Term Evolution (LTE) network with respect to the employed scheduling strategy and the cell-load is investigated. Considering a traffic-mix with services that have different requirements, the scheduler needs to be aware of the type of data to be scheduled and of the state of each user, e.g., the availability of user-data for transmission or how long a packet of a user has been in the queue already. Classical schedulers are not designed for such scenarios. To overcome this situation, we propose two new scheduling strategies based on proportional fair scheduling since the metric for proportional fair scheduling is already well suited for the kind of traffic-mix that we assume in our network. We compare the performance of the classical scheduling strategies to the new approaches in terms of average-delay but also throughput by applying them in traffic-situations, where various services are used under different load-situations.

Propagation model alternatives for outdoor Wireless Sensor Networks

Abstract: Modeling propagation in Wireless Sensor Networks (WSNs) is a vital issue in system design and analysis. Energy efficiency, routing performance, Quality-of-Service, coverage and almost all aspects of WSNs are inherently related with the employed propagation model. Yet, in WSN research, even after more than a decade long continuing and widening research history, very simplistic and impractical propagation models are still utilized. In this paper, we briefly provide the necessary background on propagation modeling and concisely overview experimentally verified propagation models for WSNs.

Highly accurate evaluation of GPS synchronization for TDOA localization

Abstract: Clock synchronization is critical for the operation of a distributed wireless network system. In this paper we investigate on a method able to evaluate in real time the synchronization offset between devices down to nanoseconds (as needed for positioning). The method is inspired by signal processing algorithms and relies on fine-grain time information obtained during the reconstruction of the signal at the receiver. Applying the method to a GPS-synchronized system show that GPS-based synchronization has high accuracy potential but still suffers from short-term clock drift, which limits the achievable localization error.

Foresighted delayed CSIT feedback for finite rate of innovation channel models and attainable NetDoFs of the MIMO interference channel

Abstract: Channel State Information at the Transmitter (CSIT) is of utmost importance in multi-user wireless networks, in which transmission rates at high SNR are characterized by Degrees of Freedom (DoF, the rate prelog). In recent years, a number of ingenious techniques have been proposed to deal with delayed and imperfect CSIT. In this paper we consider Finite Rate of Information (FRoI) channel models (CM) introduced earlier, which captures the DoF of the channel coefficient time series. Both the block fading model and the stationary bandlimited channel model are special cases of the FRoI CM. However, the fact that FRoI CMs model stationary channel evolutions allows to exploit one more dimension: arbitrary time shifts. In this way, the FroI CM allows Foresighted Channel Feedback (FCFB) which provides CSIT at all times, even in the presence of CSIT FB delay, by increasing the FB rate. DoF-optimal schemes in the presence of perfect CSIT then maintain optimal DoF when combined with FCFB. This is applicable to any multi-user network. In this paper we analyze NetDoFs, which account for training overhead and FB DoF consumption on the reverse link. We provide attainable NetDoF expressions in the MIMO Interference Channel (IC) with linear transceivers for the DoF-optimal schemes of Interference Alignment (IA) with FCFB and several simpler schemes. Numerical evaluations show that the attainable NetDoF may be far away from the DoF and that simpler schemes may be close to optimal in terms of NetDoF.

A new application for enhancing VANET services in emergency situations using the WAVE/802.11p standard

Abstract: Car-to-car communication (C2C) makes possible offering many services for vehicular environment, mainly to improve the safety. The decentralized kind of these networks requires new protocols to distribute information. The V2X communication requires On-Board Units (OBUs) in the vehicles, and Road-Side Units (RSUs) on the roads. The proposed application uses the peculiarities of the VANETs to advise danger or emergency situations with V2V and V2I message exchange. IEEE 802.11p is the standard on which the communication is based, that provides the PHY and MAC layers. The performance of the application will be evaluated through many simulations executed in different scenarios, to provide general data independent from them.