In the evolving landscape of Fifth-generation (5G) and beyond, Integrated Access and Backhaul (IAB) networks have emerged as a promising solution to extend coverage and enhance capacity without additional wired infrastructure. However, the dynamic allocation of radio resources on the shared access-backhaul spectrum in IAB networks presents challenges, particularly in meeting the diverse Quality of Service (QoS) requirements of today's services such as voice, video, and data. This paper introduces a heuristic-based, QoS-aware downlink scheduler specifically designed for radio resource scheduling in IAB networks. The proposed scheduler aims to enhance users' satisfaction by meeting users' delay requirements. We evaluate its performance using discrete-event simulations, demonstrating that our scheduler ensure the best Packet Delay Outage Ratio (PDOR) and the highest percentage of satisfied users compared to other tested schedulers.

Currently, the Open Radio Access Network (O-RAN) architecture is the best solution for deploying Radio Access Network (RAN). This architecture presents several challenges, i.e., function splitting, function placement and energy consumption. The aim of this study is to satisfy user demand while minimizing costs. In this work we combine the O-RAN architecture and the multiband system. We consider that the RAN network load varies during the day and we study the optimal placement of the Distributed Unit (DU) function and switch off unnecessary frequency bands. First, we propose an algorithm to find the number of frequency bands needed to satisfy user demand for different smoothing periods. Based on these results, we formulate the problem of DU placement and frequency band switch-off as an Integer Linear Programming (ILP) whose objective is to minimize computing and routing cost while respecting delay and capacity constraints. Evaluation of our model on real topology has shown that our model with frequency band extinction has a much lower system cost than our model without band extinction.

The Industrial Internet of Things (IIoT) covers a wide range of use cases with different requirements. Among them, critical use case are distinguished by their need for extremely low latency and high reliability. Similarly, 5G networks are designed to support diverse use cases that meet the requirements of IIoT applications. However, achieving ultra-low latency remains a challenge. On the other hand, the Static Context Header Compression (SCHC) mechanism, designed to address the issue of large protocol overhead in IoT, has demonstrated its effectiveness in reducing latency by compressing the packet header across various LPWAN technologies. Consequently, integrating SCHC into 5G networks will enhance the low-latency capabilities necessary to effectively support these critical IIoT use cases. This paper proposes an integration architecture of SCHC compression mechanisms within the 5G core network. Based on 3GPP specifications, the proposed solution ensures compatibility with existing 5G standards while optimizing communication efficiency and reducing protocol over-head for IIoT applications in 5G networks.

Ensuring both reliable and low-latency communications over 4G or 5G Radio Access Network (RAN) is a key feature for services such as smart power grids and the metaverse. However, the lack of appropriate security mechanisms at the lower-layer protocols of the RAN–a heritage from 4G networks–opens up vulnerabilities that can be exploited to conduct stealthy Reduction-of-Quality attacks against the latency guarantees. This paper presents an empirical assessment of a proposed time-delay attack that leverages overshadowing to exploit the reliability mechanisms of the Radio Link Control (RLC) in Acknowledged Mode. By injecting falsified RLC Negative Acknowledgements, an attacker can maliciously trigger retransmissions at the victim User Equipment (UE), degrading the uplink latency of application flows. Extensive experimental evaluations on open-source and commercial off-the-shelf UEs demonstrate the attack’s effectiveness in increasing latency, network load, and buffer occupancy. The attack impact is quantified by varying the bitrate representing different applications and the number of injected negative acknowledgments controlling the attack intensity. This work studies a realistic threat against the latency quality of service in 4G/5G RANs and highlights the urgent need to revisit protocol security at the lower-RAN layers for 5G (and beyond) networks.

The 3rd Generation Partnership Project (3GPP) has proposed recently the Integrated Access and Backhaul (IAB) to simplify the deployment of new base stations, where the connection between the User Equipment (UE) and the Core Network (CN) is provided by a multi-hop 5G wireless connection between the IAB nodes. The main contribution of this paper is to propose a cell selection policy specific to IAB, that aims to guarantee the lowest possible total transmission bandwidth cost (including the backhaul cost which is a significant factor in an IAB context) while respecting the base stations capacities, in order to boost IAB network capacity. In this context, a comparative performance study is performed between our proposed policy and state-of-the-art policies. System level simulation results show that our solution provides the best system capacity via a trade-off between spectral efficiency and load balancing.

Mobile traffic classification is a topic of interest for researchers focused on improving the network capacity or for those seeking to identify potential risks to users’ privacy. In recent years, traffic classification accuracy has significantly improved thanks to machine learning techniques. These techniques allow traffic identification even if it is encrypted, as in mobile networks. In this paper, we show that it is feasible to classify mobile traffic applications with high accuracy using downlink control information (DCI) messages and machine learning. The DCI messages are collected using a sniffer located near the base station. Then we extract the statistical features of the bursts and inter-burst periods of the traffic generated by mobile applications at the physical layer. This strategy uses few features and does not require a big dataset. We have tested our approach on a 4G cellular network testbed and a commercial 4G cellular network. The results show an accuracy greater than 92% and 95% for application and category classification, respectively.

Open Radio Access Network (O-RAN) is very promising for flexible and efficient 5G and 6G wireless networks. The O-RAN architecture consists of three main units: Radio Unit (RU), Distributed Unit (DU), and Centralized Unit (CU). In this paper, we study the placement of virtualized DUs. This placement has strong consequences on cost and delay, among others, and is thus an important challenge. First, we analyze the throughput between the O-RAN interfaces. Based on our analysis, we propose an efficient Integer Linear Programming (ILP) model. The objective is to minimize the O-RAN cost depending on the DU placement while respecting the delay and capacity constraints. We evaluate our model on a real topology. Our results provide interesting insights into the cost savings with regard to a legacy architecture. Moreover, the proposed model provides solutions in a configuration where a fully centralized Cloud RAN architecture would not. We also estimate the limits of capacity of a given configuration.

Reducing mobile network and device energy consumption is one of the main objectives of the fifth and future sixth-generation (5G and 6G) cellular networks. This paper studies the Base Station (BS) and User Equipment (UE) energy consumption in scenarios where many users demand the same content and broadcast transmission might be used. We present analytical models to calculate the energy consumption in uni-cast, Multicast Broadcast Single Frequency Network (MBSFN), and Single-Cell Point-to-Multipoint (SC-PTM). Furthermore, we calculate the number of users per cell from which SC-PTM or MBSFN help to reduce BS and UE energy consumption compared to unicast.

The ever increasing demand for high quality multimedia content in mobile networks requires the implementation of techniques for efficient spectrum management. Broadcast transmission is the preferred solution for scenarios in which the same content is transmitted to many users at the same time. The objective of this study is to propose an analytical method to calculate the user threshold to switch from unicast to broadcast in order to reduce radio resource utilization. We compute the probability of coverage of a given location in a Multicast Broadcast Single Frequency Network (MBSFN) area using tools from stochastic geometry. This expression is general and valid for a point not necessarily in the center of the MBSFN area. We use it to develop a method to calculate the user threshold analytically.

In LTE and 5G mobile networks, radio resources are dynamically allocated. In the uplink, the Base Station (BS) needs to know how much data each User equipement (UE) has in its butter to properly share the resource among the different UEs. In this paper, using a simple scenario and measurements made on an operational network, we show that the BS works on systematically outdated information about the butter size, which generates delay spikes. We thus propose to add a predictive estimation of the butter size, called enhanced Buffer Status Report (eBSR). It works with off-the-shelf UE and is incorporated in BS at the Medium Access Control (MAC) layer without changes in scheduling algorithm. We evaluated it on a lab testbed with various traffic profiles. Results show a clear improvement on uplink latency and jitter, together with a limited impact on radio resource usage efficiency.

In this paper, we investigate downlink interference management schemes for future railway communications that avoid channel state information (CSI) knowledge at the transmitter side. Assuming reconfigurable antennas at both ends of each train, we apply the dark-blind interference alignment principle. Simulations show that compared to considered orthogonal multiple access techniques, the proposed scheme achieves an efficient trade-off between maximum achievable throughput and error rate.

In fifth generation (5G) wireless technology, the centralization of some base station functions will be possible using the new radio access network (RAN) architecture: centralized-RAN (C-RAN). The most challenging type of service to be served by 5G is ultra reliable low latency communication (URLLC), which requires high reliability and low latency simultaneously. In this paper, we compare three RAN architectures. The first has all the processing close to the user and involves single reception. The second and the third architectures, have some centralized BS functions, allowing multiple-cell coordination and thus multiple reception points. We study the impact of architecture and macro-diversity both on the reliability of uplink (UL) packet transmission and on latency.

Radio resource allocation is a major research field in wireless networks. The main challenge is to find the most suitable user for each time and frequency resource to ensure the Quality of Service (QoS) requirements. The use of Massive Multiple-Input-Multiple-Output (MIMO) makes it possible to simultaneously schedule several users on the same time and frequency resources. This is a new paradigm for resource scheduling. In this context, resource allocation algorithms have to account for the choice of users served on the same time and frequency resource in their decision mechanism. In this paper we analyze the impact of different group sizes on system capacity using several user selection algorithms and we propose a new user selection algorithm which performs closer to the optimal algorithm proposed in the literature.

In wireless networks, the transmission efficiency is highly impacted by attenuations such as: path-loss, shadowing, multi-path fading and interference. At cell edges, mobiles are far from their access point and close to neighboring cells, leading to high path-loss and high magnitude of interference. Consequently, ensuring high spectral efficiency is necessary to guarantee an appropriate Quality of Service (QoS), especially at edges. To cope with this crucial issue, this work investigates the benefits of the Joint Transmission Coordinated Multi-Point (JT-CoMP) clustering to mitigate Inter Cell Interference (ICI). This paper proposes the Hybrid Joint-Transmission Coordinated MultiPoint algorithm (H-JT-CoMP). This solution dynamically performs its ICI management according to the Chanel State Information (CSI). This allows to make a wise CoMP usage according to the magnitude of interference received. Performance evaluation highlights an increased QoS and system capacity with a better fairness between inner and edges of the cell.

Amongst the appealing features of 5G, ultra low latency is perhaps the most attractive one, as it unleashes a wealth of disruptive services. However, meeting such a challenging goal requires a thorough understanding of latency in the 5G prevailing bottleneck, that is, the Base Station. For this purpose, we propose LatSeq, an open-source tool for fine-grained analysis of latency inside a software Base Station (BS), and implement it on the OpenAirInterface platform. LatSeq tackles each packet's sequence of successive delays across the layers of a Base Station, which reveals enlightening causal links.This paper discusses LatSeq's design choices and evaluates its fitness for purpose in a first baseline usage scenario. We demonstrate the low impact of LatSeq on the observed system, and the relevance of statistics based on individual packet tracing inside the base station.

Massive machine-type communications (mMTC) is one of the main services delivered by the fifth Generation (5G) mobile network. The traditional cellular architecture where all devices connect to the base station is not energy efficient. For this reason, the use of device-to-device (D2D) communications is considered to reduce the energy consumption of mMTC devices. The main idea is to use nearby user equipment (UE) as a relay and establish with it D2D communication. However, the relay selection process also consumes energy, and this consumption can be significant compared to the energy consumed during the data transmission phase. In this paper, we propose a distributed energy-efficient D2D relaying mechanism for mMTC applications. This mechanism favors the selection of the UEs with low path loss with the mMTC device. Through mathematical analysis and simulations, we show that our mechanism allows a reduction of the total energy consumption of mMTC devices (up to 75% compared to direct transmission) when they have an unfavorable link budget. Moreover, our mechanism achieves almost constant energy consumption for a large range of UE densities and distances between the mMTC device and the base station.

Many use cases are meant to be supported by the fifth generation (5G) wireless technology. The one which is occupying the research area for its challenging requirements is the Ultra Reliable Low Latency Communications (URLLC). Hybrid Automatic Repeat reQuest (HARQ) protocol is used to ensure reliability but it induces delay. Furthermore, the transmission in the Radio Access Network (RAN) should be taken into account in the delay budget. In this paper, we jointly analyze the reliability and the delay with two RAN architectures: the legacy one where only one radio unit receives the packet from a terminal and a Centralized-RAN (C-RAN) architecture where several radio units can decode a packet. We propose to combine these approaches in a flexible architecture. The observed enhancement is a division by 850 of the packet erasure rate compared to the legacy architecture with a latency of 3 milliseconds.

In this paper, we consider the uplink of a railway communication system with onboard mobile relays. Each onboard relay communicates with two cooperating base stations at the ends of the section along which the train is moving. Each carriage is equipped with two distinct antenna arrays. We design transmit coding schemes distributed between the antenna arrays and we apply receive macrodiversity. Simulations show that the proposed schemes enable to maintain transmission quality and throughput as the carriage moves along the section.

Video is an important factor of the load in cellular networks due to the growing popularity of streaming and linear services. In unicast transmission mode, the same data is transmitted as many times as the number of receivers demanding the same video content. Conversely, in broadcast transmissions using the Single Frequency Network (SFN) technique, a set of base stations perform synchronized transmission of the same waveform to a potentially infinite number of users. The objective of this study is to compare the performance of unicast and broadcast. More precisely, we determine the minimum number of users downloading the same data from which a broadcast transmission is more efficient than multiple unicast transmissions. In this paper, a model to calculate the Signal-to-Interference-plus-Noise Ratio (SINR) in unicast and broadcast modes is presented, considering Poisson distributed base stations, path loss, fading, shadowing, trisectored antennas, SFN with a different number of base stations and beamforming in unicast mode. Results show that even when an SFN is formed by just 2 base stations and unicast transmissions are performed using beamforming with 8 antennas per sector, broadcast outperforms unicast when there are at least 8 users per cell demanding the same content.

Heterogeneous Network (HetNet) is among the most important challenges for the upcoming cellular wireless networks. In this paper, we propose a method to optimize the Radio Access Technologies (RATs) selection and resource allocation in multitechnology wireless networks during a time period. We optimized on a realistic topology of Base Stations (BS) with overlaps of the cellular coverage and dynamic users traffic (arrival and departure). The optimization takes into account the requested services, different users' contract, and user satisfaction. Furthermore, in the proposed approach, we add constraints to ban the session drops and handovers for static users. For each instance, we formulate the problem as a linear optimization problem and we optimize it successively. The aim of the optimization is to jointly maximize the overall user satisfaction and the number of users connected. Compared with a legacy approach, numerical results show that our solution outperforms in terms of user satisfaction.

Even with dense base station deployments, public transport users often have a low quality for mobile services. Due to the insulation of the vehicle, passengers experience little to no connectivity on their end devices and low data bitrate. We thus propose a mobile relay architecture based on two imbricated levels of LTE networks and adapted to public transport systems. This architecture is evaluated on an actual LTE test-bed, consisting in standard radio interfaces, off-the-shelf terminals and the Amarisoft software suite. One of the specifics of a mobile relay is the use of a radio link between the core network and the base stations, with all the limitations of this medium. This work therefore evaluates the impact on data rate of signaling mechanisms and of tunneling in that context.

Centralized/Cloud Radio Access Network (C-RAN) separates Baseband Units (BBUs) away from Remote Radio Heads (RRHs) and centralizes BBUs into a BBU pool. This new architecture can facilitate the cooperation between different cells. We apply zero-forcing (ZF) for joint transmission in a C-RAN downlink system. A number of User Elements (UEs) are assigned to be served into different subframes for serving. This paper proposes two user grouping algorithms denoted Global Greedy User Grouping Algorithm (GGUGA) and User Division Algorithm (UDA) to maximize the average achievable sum rate. GGUGA is a typical greedy algorithm. UDA restricts the random selection of UEs groupings into a certain region which increases the chance to make a good choice. GGUGA achieves a similar performance compared to exhaustive enumeration of all possible UEs groupings. The complexity of UDA is much less than the one of GGUGA when the number of UEs for grouping is large at the expense of a small loss in performance.

The S-ALOHA (i.e. slotted-ALOHA) protocol is recently regaining interest in Lower Power Wide Area Networks (LPWAN) handling M2M traffic. Despite intensive studies since the birth of S-ALOHA, the special features of M2M traffic and requirements highlight the importance of analytical models taking into account performance-affecting factors and giving a thorough performance evaluation. Fulfilling this necessity is the main focus of this paper: we jointly consider the impact of capture effect, diversity of transmit power levels with imperfect power control. We propose a low-complexity but still accurate analytical model capable of evaluating S-ALOHA in terms of packet loss rate, throughput, energy-efficiency and average number of transmissions. The proposed model is able to facilitate dimensioning and design of S-ALOHA based LPWAN. The comparison between simulation and analytical results confirms the accuracy of our proposed model. The design guides about S-ALOHA based LPWAN deduced from our model are: the imperfect power control can be positive with capture effect and appropriate transmit power diversity strategy. The transmit power diversity strategy should be determined by jointly considering network charges level, power control precision and SINR threshold to achieve optimal performance of S-ALOHA.

In this paper, we tackle the problem of access point selection and resource allocation in heterogeneous networks including 3G/4G and Wi-Fi. We study the user satisfaction optimization in terms of throughput and blocking rate. More precisely, the aim is to associate users with the optimal Radio Access Technology (RAT) and to allocate them the optimal number of Resource Units (RUs) based on their requested services and contracts. Starting with a non-linear problem, we re-formulate it into a Mixed Integer Linear Programming (MILP) and assess it on a realistic network configuration. We also compare it with a legacy strategy of selection and allocation. We show that our approach improves the user satisfaction while maintaining a reasonable blocking rate.

The tremendous increase of mobile data traffic pushes operators to find quick and efficient solutions in order to avoid an overload on their networks. Using WiFi to offload a part of the traffic is interesting for the operators as they can take advantage of the unlicensed bands and high bit rates. Moreover, thanks to the convergence of fixed and cellular networks, it is possible to connect WiFi access points to the LTE eNodeBs in order to have Very Tight Coupling between LTE and WiFi. Thus, the different flows are merged at the link layer (i.e. PDCP) and share the same IP instance. This allows the terminal to have a unique IP address, ensuring a seamless experience when using WiFi and LTE simultaneously. However, both networks can have different delays. In this paper, we investigate the impact of such differences in the delay by means of a real implementation of very tight coupling on an open test bed. We show that aggregation of LTE and WiFi is beneficial only when the delays are similar.

In this paper, we present experimental results on WebRTC voice quality as a function of LTE radio coverage. Different LTE radio conditions were tested by varying the radio path loss (with fast fading) in controlled test lab conditions. Voice quality was evaluated at different speech coding bit rates in terms of POLQA score and mouth-to-ear delay. Results show that, with acknowledged mode (AM) data transmission over LTE, degraded radio coverage translate essentially into increased end-to-end delay and jitter, with virtually no packet loss up to the coverage limit. Voice quality is analyzed by studying the influence of the specific jitter buffer used in WebRTC endpoints.

Inter-Cell Interference Coordination (ICIC) techniques are proposed as solutions to alleviate the negative impact of interference on system performance, while enhancing the provided Quality of Service (QoS). Typically, the available bandwidth is divided into inner and edge sub-bands. Users are also classified into interior and edge users. The available resources in each zone are exclusively allocated to users belonging to this zone. Mobile users classification is usually based on a threshold that can be either a given mean SINR value or a given distance. However, ICIC approaches based on these static parameters cannot efficiently manage non-homogeneous distribution of users. In this paper, we introduce a dynamic handoff algorithm that aims to adapt static ICIC schemes to uneven distribution of users. Our new solution dynamically computes the classification of active users into interior and edge users, based on a heuristic load balancing algorithm. In our proposal, each cell autonomously reconfigures its bandwidth allocation constraints without modifying bandwidth repartition across the cellular network. This makes the solution well adapted to the non-uniform repartition of users at the multicell scale. Simulation results show that the proposed scheme improves bandwidth usage, reduces packet delay, and increases user satisfaction compared to state-of-the-art ICIC techniques.

This paper aims at characterizing the energy efficiency (EE)-area spectral efficiency (ASE) tradeoff in random geometry networks with multiple-antenna arrays at base stations (BSs). In particular, ASE and EE are studied with respect to the transmit power when BSs use a signal-to-leakage-plus-noise ratio (SLNR) precoder. When the static power consumption cannot be neglected, EE behaves linearly with respect to ASE before a sharp decreasing of EE due to the interference-limited characteristic of the network. Our contribution relies on the derivation of a closed-form expression for ASE with SLNR precoder in the asymptotic regime, i.e., when the number of antennas and users grows to infinity, using stochastic geometry. We derive EE from a linear power consumption model afterwards. Unlike conventional SLNR precoders, the average signal-to-interference-plus-noise ratio and the leakage to other cells are considered in a geometry-dependent network. Extensive Monte Carlo simulations show that despite the asymptotic nature of the theoretical analysis, the closed-form expressions are tight with respect to simulations even for the moderate number of antennas and users. Hence, the analysis can be used for realistic network performance analysis.

Apart from its tremendous enhanced transfer performances, the LTE/EPC mobile network is intended to distinguish itself from previous mobile technologies as an all-IP system. Nevertheless, far from usual IP QoS management policies, its QoS model inherits many characteristics of circuit oriented model of legacy standards. Additional signalling procedures are required in order to establish an end-to-end dedicated bearer for each desired QoS level. A major issue of this QoS model is the management load related to contexts and bearers established by each user equipment. This paper proposes an analytical model to evaluate the impact of this standard QoS model in terms of Context Load, Processing Load and Memory Access Rate in various LTE/EPC network elements. Simulation results are then presented to evaluate the impact of different realistic scenarios of QoS deployment.

In order to cope with the dramatic growth of cellular data traffic, mobile operators should find cost-effective and easily deployable solutions of capacity increase of their networks. One of these solutions is to use WiFi networks to offload the cellular network. One question when using WiFi networks beside cellular is how they are integrated. Several degrees of integration exist, one of them is to connect the WiFi Access Points (APs) directly to the cellular Base Stations (BSs). This is known as very tight coupling. In this paper, we study the performance of such an architecture. We define a model that takes into account the fluctuation of the coverage (shadowing) and compute how much bandwidth can be saved on the cellular network.

Centralized/Cloud Radio Access Network (C-RAN) is a promising future mobile network architecture, which can potentially increase the capacity of mobile network meanwhile reducing operators' cost. In standard C-RAN, frequency shifting is made in Remote Radio Heads (RRHs), which are close to the antennas. Signal processing and upper layers are made in Baseband Unit (BBU) pool for multiple base stations. However, this results in high burden on the optical transport network between RRHs and BBU pool. This paper investigates new functional split architectures between RRH and BBU, to reduce the transmission throughput between RRHs and BBUs. Two new architectures are proposed and modeled for the uplink. We propose to move part of physical layer functions of the BBU to the RRH. For the proposed architectures, the transmission rate between RRHs and BBUs depends on the mobile network load, while that of current architecture is constant. Simulation results illustrate that 30 to 40 percent bandwidth can be saved when all the radio channel capacity is used, and up to 70 percent bandwidth when half of the radio channel capacity is used.

In order to face the continuous increase of the data traffic on the cellular network, using WiFi to offload the LTE network can be an interesting solution for the operators. The convergence between fixed and mobile access allows the WiFi access points to be connected to the cellular eNodeBs. This is known as very tight coupling between LTE and WiFi. WiFi and LTE flows are merged just bellow the IP layer which allows faster attachment procedures to WiFi access points and dual WiFi/LTE transmission while providing a seamless experience to the end user. However, WiFi networks are very different from LTE in terms of delays and loss rates which may have a bad impact on higher layers such as TCP. In this paper, we study the performance of TCP with Very Tight Coupling. We perform experimentation on a real testbed based on the Open Air Interface framework.

Machine-to-machine (M2M) communication is expected to enable billions of devices to be connected by the cellular networks in the near future. The large number of devices involved in M2M will create a huge market potential but at the same time pose some challenges for 3GPP cellular networks. The challenges include massive access management, QoS provisioning, energy/power efficiency, etc. Nowadays, energy-related issues are deemed as the key problems in cellular M2M communications. In this paper, we extend the research framework of [1] by taking into account some important issues that were not yet addressed, mainly the existence of machines with different packet lengths and the effect of imperfect power control. With the proposed system model, we evaluate the power efficiency, energy efficiency and system capacity for uncoordinated CDMA and coordinated FDMA. Through numerical results, we conclude that coordinated FDMA is more resistant to various packet lengths of M2M devices packets in terms of power efficiency and is not influenced by imperfect power control. Thus coordinated multiple strategies, especially FDMA, are more suitable for the future M2M-included cellular networks and deserve further optimization works. With respect to uncoordinated CDMA, although its performance is affected by BS load intensity and power control, it is still a considerable choice due to its simplicity and no signaling overhead, when the BS load intensity is not high and the power control policy is suitable.

With the introduction of smartphones and tablets and the dramatical increase of the data traffic on the cellular network, operators are seeking for new solutions to provide the users with continuous connectivity while preserving a good quality of service. Since most of current user terminals are equipped with multiple interfaces, one solution is to take advantage of the different access networks. However, with the current network architectures and user application, it is not possible to use both accesses at the same time or even to switch from one to another without loosing current sessions. In this paper, we present and analyse the main mechanisms of the literature that allow a user to use multiple access networks at the same time or to move between the different networks. We show how a converged network can permit the deployment of new solutions and present some of them accompanied by use cases.

With the popularity of smart phones and tablets, people make intensive use of these devices on public transport. It is thus interesting to deploy mobile relays in public transportation with the aim of offering high-quality services. In LTE Rel 10 fixed relays are specified. Although mobile relays have been considered by 3GPP, no protocol stack is specified yet. In this paper, we propose to keep the same protocol stack as for fixed relays but introduce the concept of global tunnel, which gathers several tunnels. We analyze the main signaling procedures and show that the proposed solution dramatically reduces the number of messages that each network node should process.

This paper deals with the energy-efficiency spectralefficiency (EE-SE) tradeoff in regular hexagonal interference-limited networks. We aim to characterize the EE-SE region when non negligible static circuitry power consumption is assumed and when several frequency reuse factors as well as shadowing are taken into account. Our contribution is three-fold: a parametric expression of the interference to signal ratio, a.k.a. fparameter, obtained with a curve fitting approach is proposed, the EE-SE tradeoff is then studied when several frequency reuse factors are considered and a new characterization, called the c-EE-SE tradeoff, is proposed when shadowing is considered. This definition relies on the outage capacity achievable and its corresponding EE and remains particularly useful when longterm fading is present.

LTE/EPC is an all-IP mobile system which provides higher data rates and lower latency. Nevertheless guaranteeing the QoS is a real challenge since the LTE/EPC QoS model inherits many characteristics of circuit oriented legacy standards. Contrary to usual QoS models of the fixed internet (IP networks), additional signalling procedures are required in order to establish a dedicated bearer for each desired QoS level. This paper introduces an analytical model to evaluate the impact of such a QoS model in terms of Processing Load. Simulation results are then presented to evaluate the impact of different scenarios of QoS deployment.

Machine Type communication (MTC) in LTE networks is expected to gain a great popularity in the next decade. Due to different traffic characteristics, it poses some challenges for traditional random access procedure and resource allocation algorithm in LTE network. We propose a polling service that avoids contention. This service is integrated into LTE access network, fully compatible with the standard access mechanism and able to manage a large range of polling periods (typically from 1 minute to 28 days). This proposed service reduces the transmission overhead and thus improves the energy efficiency for MTC devices. It also reduces access network overload in radio access network by avoiding random access. Compared with traditional random access mechanism, numerical results show that with proposed service one eNodeB (eNB) can easily support up to 15000 MTC devices without network access collision.

In this paper, we analyze whether mobile relay could bring capacity gain to a LTE-Advanced network. The analysis is based on the Shannon formula modified for LTE. The Spatial Poisson Process is used to model the distribution of terminals and mobile relays in the cell. We consider two relay modes in the study: pure-relay mode and femto-like mode. Through the analysis we get the conclusion that penetration loss is a key factor to decide whether mobile relay can bring considerable capacity gain into the system. When penetration loss is 25 dB, pure-relay mode can bring about +30% capacity gain compared with traditional mode, femto-like mode can bring almost +100% capacity gain compared with traditional mode.

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.

We propose a new lightweight mechanism called Forwarding By Retransmission, that allows 802.11 stations to opportunistically relay overheard frames toward a destination. When a destination does not receive a frame, any other receiver that has better radio conditions than the source of the frame could participate in the retransmission process along with the source. This reduces the number of retransmissions made by stations with poor connectivity. We show by NS-2 simulations that our mechanism allows to fairly share the bandwidth among stations, even for those with poor radio quality and high packet error rates. Our solution comes with only a few modifications to the frame structure and a change in the acknowledgement semantic.

The advancements in the field of Digital Video Broadcasting (DVB) have enabled very wide coverages and high capacities in the DVB networks. The advent of Single Frequency Networks (SFN) has played a primary role in making it possible. In this paper we study the distribution of the Signal to Interference Noise Ratio (SINR) for a DVB - 2ndgeneration Terrestrial (DVB-T2)SFN. We also study the relationship of SINR with the distance and the DVB cell size for both indoor and outdoor scenarios. In the end, we demonstrate that the handheld receivers are not properly covered in a DVB-T2 SFN. To highlight the DVB handheld coverage issue, we estimate the handheld receivers' coverage in a SFN designed to cover fixed users.

Recent technical breakthroughs in wireless communications have facilitated significantly increased data rates and reduced end-to-end latency in cellular networks. Higher throughputs however lead to increase traffic loads on cellular networks and require mechanisms to mitigate such traffic loads on the cellular networks. In this paper, we introduce a host-based distributed mobility management protocol supporting selective traffic offloading for the evolution of the 3GPP core network architecture. Unlike the current approach of 3GPP, traffic offloading is achieved based on IP flow mobility in a distributed manner. The offloading point is thus also distributed. We show how the proposed host-based distributed mobility management protocol alleviates the high traffic loads in the evolution of the 3GPP core network architecture.

Traditionally cellular networks have been dimensioned for providing seamless coverage and meeting the user demand with little regard to their energy consumption. Recently, the focus has been moved to seeking ways to increase the energy efficiency by better adapting to the existing users behaviors. In this paper, we are going a step further in studying a new type of disruptive service by trying to answer the question “What are the potential energy efficiency gains if some of the users are willing to tolerate delays?”. We present an analytical model of the energy usage of LTE base stations, which provides lower bounds of the possible energy gains under a decentralized, non-cooperative setup. The model is analyzed in six different scenarios (such as micro-macro cell interaction and coverage redundancy) for varying traffic and user-tolerable delays. We show that it is possible to reduce the power consumption by up to 30%.

The world is entering a post-PC era in which more real-time entertainment traffic is delivered to mobile devices than to PCs. The unprecedented expansion of mobile Internet traffic has resulted in the development of distributed mobility management (DMM) at the IETF. In this paper, we introduce a dynamic tunneling scheme for network-based DMM, in which mobility anchors are distributed at an access network level while tunnels for data packets are dynamically configured taking into account of both session and mobility status. We illustrate the proposed scheme's initial attachment and handover procedures step-by-step in an environment where network-based DMM is coexisted with Proxy Mobile IPv6. To justify the effectiveness of the proposed scheme, we develop an analytical cost model that is used to compare the performance of the proposed scheme with existing ones in terms of signaling and packet delivery costs. Our analysis shows that the proposed scheme optimizes packet delivery paths and thus provides a cost reduction during the packet delivery compared to the existing schemes. We also describe possible performance extensions to the proposed scheme.

Mobile Internet relies on global mobility management protocols in order to provide reachability and session continuity for mobile nodes. This paper presents a comparative analysis on the global mobility management schemes MIPv6, SIP and their integration. For each scheme, analytical models are developed for mobility costs taking into consideration all the related aspects. We consider the signaling, data packet delivery, tunneling, and processing costs. The impacts of several parameters on the mobility costs are then investigated. Following the analysis, conclusions and perspectives are drawn out paving the way for enhancing the mobility management performance.

IP mobility management has a key role in wireless networking and mobile Internet. The existing IP mobility protocols are deployed generally in a centralized manner. All the data traffic passes through a centralized entity and all the bindings are managed at this entity as well. Recently, various efforts from both industry and academia are being performed on specifying Distributed Mobility Management (DMM). DMM is considered as a promising approach and is expected to enhance significantly the mobility management performance. In this paper, we propose a novel DMM scheme based on Mobile IPv6 (MIPv6) that provides local and global mobility support in a distributed and dynamic manner, named Distributed Dynamic MIPv6 (DDM). Then, we carry out a performance analysis in terms of mobility costs. The results show that DDM outperforms MIPv6 significantly in optimizing the network resources and their consumption.

It is expected that the upcoming DVB-NGH (Digital Video Broadcasting-Next Generation Handheld) shall be based on the existing DVB-T2 technology. Also DVB-NGH enabled Handheld receivers are going to work with the existing DVB infrastructure. In this paper we model the link budget deficits of the Handheld DVB receivers as additional power losses for a typical fixed roof-top DVB-T2 receiver. Because of those additional losses Handhelds get a reduced coverage. The attrition in coverage is especially dramatic for the indoor Handheld receivers. We analyze coverage for two different models of the Population density, i.e. Clark's and Smeed's.

Mobile ad hoc networks (MANETs) are self-organized and dynamically reconfigurable wireless networks. It is a promising technology for emergency scenarios where communication systems should be able to operate in potentially adverse environments. However, MANETs experience severe impairments because of node motion or scarce node density yielding network partitioning. Satellite communications may help in this respect by setting up recovery links. In this article, we study the problem of selecting for each network partition a MANET node called gateway that will provide access to the satellite capacity. A key challenge is that nodes are mobile resulting in frequent topology changes. We address this challenge by re-using the mechanisms of clustering techniques initially designed to solve scalability issues in MANETs.

In this paper, we investigate different HARQ strategies with unreliable feedback channel. In classical approaches, retransmitted packets are different versions of the same user data. In order to improve HARQ performance, we propose to construct redundancy packets by jointly encoding several data packets. This strategy is referred to as HARQ Multiple Packet Incremental Redundancy (MP-IR). It can eliminate imperfect feedback effect on performance at medium to high Signal to Noise Ratio (SNR) values. On the other hand, classical HARQ Single Packet Incremental Redundancy (SP-IR) strategy is more robust at low SNR. This motivates us to introduce a hybrid SP-IR and MP-IR strategy. This strategy can benefit from SP-IR performance at low SNR and MP-IR performance at medium to high SNR. The throughput of the different schemes is analyzed using renewal theory and an appropriate Markov model representation. Simulation results confirming the proposed throughput analysis are also presented.

The recent explosion of mobile Internet traffic has resulted in an evolution of mobile network architectures. Mobile network architectures are being flattened to cope with the recent traffic growth. Existing IP mobility support protocols relying on centralized mobility anchors are thus required to be adopted in the evolution of mobile network architectures. In this paper, a new IP mobility support protocol is presented: a new host-based distributed mobility management support protocol designed for the current evolution of mobile network architectures. Mobility anchors are distributed at an access network level and a mobile node is served by a close-by mobility anchor. While the mobile node changes its point of attachment to the Internet, it keeps previous IP address(es) for continuous communications established with the previous IP address(es). The detailed protocol operation is explained with discussion for operational considerations. The performance of the proposed protocol is compared with Mobile IPv6 in terms of handover latency and throughput.

One of the primary mechanisms to mitigate idling energy consumption and reduce communication activities in Wireless Sensor Networks (WSNs) is to put nodes to low duty cycle operation as long as possible. Keeping a small time window (the listen period) is a challenging task, and thus requires appropriate tailoring of duty cycle so as not to compromise network performance. In this work, we explore an adaptive duty cycle mechanism for scheduling a node to sleep mode using node density. A forwarding candidate assesses its vicinity and adaptively adjusts its duty cycle. We show via simulation that the adaptive duty cycle mechanism can reduce the energy usage and prolong the network lifetime for the data delivery toward the sink.

WiMAX/IEEE 802.16 Broadband Wireless Access (BWA) is a very open technology with various possible services. While different technical aspects of that technology have been addressed, the pricing of WiMAX has received little attention until now. In this paper, we analyze the performance of a WiMAX pricing scheme that we proposed in previous works. Through extensive simulations, we evaluate the importance of a well-planned WiMAX pricing framework by comparing our proposed scheme with a basic one. Then, we study the sensitivity of the proposed pricing scheme with regard to the parameters values choices. We show that our proposed pricing scheme still provides better revenue than a basic one for a difference up to 30% more or less than the best values chosen.

This paper targets multicast packet scheduling over cellular networks like High Speed Downlink Packet Access (HSDPA). The salient benefit of multicast is to avoid clogging up the air interface with redundant data transmissions. When allocating resources to users of a system, it should be aimed at fulfilling QoS requirements instead of only providing fairness or maximizing the system throughput. This paper addresses QoS-based scheduling for multicast video streaming for which minimum bitrate requirements are particularly stringent. Hence, we adapt Minimum Guaranteed Bit Rate (Min GBR) scheduler by Hosein (2002) to multicast. In this context, we introduce different versions, namely the cluster-size agnostic and the cluster-size aware. Solutions are tested with homogeneous clustering and mixed clustering. These proposals offer different trade-offs between QoS guarantees and the overall diversity gain.

Packet scheduling is one of the key features in data-oriented radio interfaces of cellular networks like HSDPA (High Speed Downlink Packet Access). It has been primarily designed for unicast applications. Nevertheless, unicast may not optimise the resource usage when the same content has to be transmitted to several users in the same cell. In this paper, we compare the performance of multicast and unicast scheduling considering both a theoretical generic system and an HSDPA system. We prove the benefit of deploying multicast which is found to have merits when the average channel quality is good enough. Results show that the better the average channel quality is, the more users are allowed to receive the service simultaneously.

The combination of the TDD mode and the TDMA technique in WCDMA systems engenders a new degree of flexibility that can increase system capacity and QoS levels of active channels if efficient slot allocation techniques are used. These techniques allow the system to control the allocation of slots to users, and thus lead to relevant reduction in interference levels. In order to study slot allocation performance, it is important to define a reference performance that gives adequate approximation of system maximum capacity. In this paper, we propose a novel formulation to the computation of system maximum capacity using a set of combinatorial optimization problems. Furthermore, we propose meta-heuristic algorithms that give satisfactory approximations for each combinatorial problem

Although a single carrier frequency is usually considered in wideband code division multiple access (WCDMA) systems, each operator has more than one carrier frequency in practical 3G systems. Moreover, QoS levels and the throughput within a given frequency highly depend on interference patterns, which are mainly related to cell-frequency allocation. Therefore, frequency management plays a key role in WCDMA network planning. However, the frequency management problem has not been in the center of attention for WCDMA systems so far due to the fact that WCDMA has not yet been implemented in wide range with all possible services. Nevertheless, the arrival of multimedia services will emphasize the critical importance of a smart frequency allocation. In this context, the presence of several frequencies for each operator (typically 2 or 3 in Europe) manifests itself as a fertile dimension of flexibility to be exploited. This paper introduces a novel frequency management methodology based on coupling matrices that reflects the interaction between cells for a given interference pattern. The proposed methodology is implemented as an integral task of the planning tool and has lead to better results than the frequency allocation in the classical hierarchical cell structure.

Adaptive power control algorithms has been widely studied for interference reduction, base station radiation decrease and terminal battery saving in 3G cellular systems. We study some of the existent adaptive power control algorithms and we propose an evolution of these algorithms in the forward link. In the proposed algorithm, we try to maintain the intercell interference stable and to reduce intracell interference when it is possible. Therefore, the power control steps of mobiles requesting a power increase may be reduced to limit the total power increase if some constraints are verified. The proposed algorithm uses an adaptive step, which is updated using the instantaneous mobile power control command and the command history. Moreover, a stabilization zone above the SIR target is used to limit oscillations. The proposed algorithm has been compared to the 3GPP standardized power control and to a recently proposed adaptive power control. Simulation results has shown that the proposed algorithm decreases slightly the outage probability as the already proposed adaptive power control and reduces the power consumption.

The issue of power control (PC) in the downlink of a cellular CDMA network is studied. Two approaches are discernible. The first uses the base-to-mobile-distance in order to allocate transmitted powers while the other is based on closed-loop control. The best achievable performance of a PC is evaluated for the downlink of a CDMA network. This paper then studies an almost optimal downlink power control. Numerical examples are presented in order to discuss the downlink PC performance.

Power control is a very important feature of CDMA systems and it dramatically impacts the cellular capacity. The UTRA-TDD (Universal Terrestrial Radio Interface with Time Division Duplex) adopted for third generation systems is a hybrid radio interface, which mixes TDMA and CDMA schemes. Therefore, power control and slot allocation must be optimised jointly. In this paper, we introduce two slot allocation methods combined with optimal power control. In the first method, we calculate the mean normalized path loss of mobile stations and try to obtain for each cell an allocation with the same mean normalized path loss on all time slots. In another way, we try to obtain the same signal to interference ratio in all cells. The principle of the second method is to group mobile stations with close path loss values on the same slot for each cell and associate a set of high-gain mobile stations of a cell with sets of low-gain mobile stations from neighbouring cells in the same time slot. The second method performs better than the first one and gives very close results to the optimal ones.

For third generation mobile systems, the benefit of locally centralized architectures for resource allocation and management should be investigated in the micro-cellular environment. In this paper the concept of bunch defined as a group of base stations strongly interconnected is investigated. An interference-matrix based scheme (i.e. best packing strategy) for resource allocation is used and its performance in presence of location errors is evaluated through simulations.

We present an architecture for a system with multi-cell centralized packet access. In micro- or pico-cellular environments, the coverage overlap by adjacent antenna units arises naturally, which means that a signal emitted by a mobile terminal is multiple received. The whole service area of the system is parceled out into small coverage zones, to which channels are dynamically allocated. For such a dynamic channel allocation to be effective, the system has to attach the mobile terminals to the zones of allocation, based on the strength of the received signal. We study the problem of this fine-localization of the mobile terminals in the presence of fast fading.

Studies a mutual synchronisation technique between base stations (BSs) which operates over the air. First, the different possible structures for broadcast control channels (BCCHs) are presented with their main functionalities. A structure of a common BCCH for a group of BSs sharing the same carrier with time multiplexing is proposed. This common BCCH may be used to provide synchronisation. Existing mutual synchronisation algorithms are then reviewed. For such algorithms, each BS combines measurements (estimated time offset) from neighbouring BSs to determine its own time phase. Computer simulations based on a TDMA system are used to evaluate stability and convergence speed of the algorithm.>