Publication IX

2015 IEEE Globecom Workshops (GC Wkshps), 2015

Device-to-Device (D2D) communication underlying 5G cellular networks enable using direct communication between devices as a relay strategy for coverage extension. We consider such a D2D-relaying approach in a scenario where there are multiple candidate devices to be selected as relays. Both backhaul and D2D transmissions are performed in uplink cellular resources, and are subject to cellular uplink power control. We investigate the relay selection and resource allocation problem for D2D-relaying in a multiuser , multi-carrier and multi-cellular network. For this purpose, we formulate a joint optimization problem and propose a simplified relay selection and resource allocation scheme. Using this scheme in a system simulation, we demonstrate that D2D-relaying under uplink power control increases the throughput of cell-edge users significantly.

Journal of Communications

Mobile cell is a new area emerging from the small cell technology that will dominate future networks. Mobile relay plays a major role in mobile cells allowing mobile user equipment (UE) to maintain network connectivity with good quality of experience to the macrocell base station during high speed vehicular movement. Group handover is an excellent solution to handle huge number of handovers associated with moving UEs in the mobile cell. In this paper, an efficient group handover strategy for mobile cell in LTE-Advanced system have been proposed. With the proposed group handover strategy, mobile relay node (MRN) attached to a high-speed train handover all UEs related communication from the source donor eNB (DeNB) to the target DeNB. In addition, unlike most work that uses fixed relay architecture, mobile relay architecture has been used in this work. By applying the proposed group handover strategy to the mobile cell, the number of handovers and call dropping probabilities in the system have been greatly reduced.

Journal of Electrical and Computer Engineering, 2010

Decode-and-forward relaying is a promising enhancement to existing radio access networks and is currently being standardized in 3GPP to be part of the LTE-Advanced release 10. Two inband operation modes of relay nodes are to be supported, namely Type 1 and Type 1b. Relay nodes promise to offer considerable gain for system capacity or coverage depending on the deployment prioritization. However, the performance of relays, as any other radio access point, significantly depends on the propagation characteristics of the deployment environment. Hence, in this paper, we investigate the performance of Type 1 and Type 1b inband relaying within the LTE-Advanced framework in different propagation scenarios in terms of both coverage extension capabilities and capacity enhancements. A comparison between Type 1 and Type 1b relay nodes is as well presented to study the effect of the relaying overhead on the system performance in inband relay node deployments. System level simulations show that Ty...

Proceedings of the 12th ACM international symposium on Mobility management and wireless access - MobiWac '14, 2014

Multi-hop relay technology is one of the most promising candidate technologies to overcome the coverage and capacity problem in LTE-Advanced networks. Currently 3GPP is considering the incorporation of multi-hop relays into Release 12 of LTE-A standards. However, many issues remain to be resolved due to the complexity of multi-hop relaying paradigm, specifically resource allocation and mobility management. In this work we focus on the relay selection problem, where a user may have in his range several relay nodes to choose. The conventional selection scheme is based on the channel condition between the relay and the user, such that the user will achieve a high level of throughput. Alternatively we propose in this paper a novel relay selection strategy taking handoff into account over LTE-A multi-hop relay networks. Our goal is to achieve significant performance improvement against legacy centralized resource allocation and handoff algorithms such as disjoint path relay selection. Simulation results show that our design has the advantage of reducing inter-cell handoff frequency and lowering handoff failure ratio.

International Journal of Computer Applications

Long Term Evaluation (LTE) Advanced networks are popular due to very high data rates with ultra-wide bandwidth spectrum, and broad coverage and are currently adopted as 4G standard. In spite of vast benefits of LTE Advanced, the propagation loss occurs due to low signal-to-noise-ratio (SNR) and results in low coverage and channel capacity at the cell boundaries. To overcome these problems, cooperative communication network is used by deploying relay nodes. In this paper, we conduct the performance analysis of LTE Advanced relay system on WINNER channel model with various communication scenarios. The simulations environment for the LTE Advanced network and WINNER channel models is created using Matlab. For easiness, only one base station and user equipment are used in the simulation setup. We observe the effect on LTE performance using one or two relay nodes in the LTE network. We conduct the experiments for four different environments and six scenarios. We analyze the performance using symbol-error-rate for different SNR. The results show that LTE Advanced network using relay nodes performs much better than other environments. It also provides least latencies, even wider coverage, and higher data rate with minimum outage.

2009

The Third Generation Partnership Project's Long Term Evolution-Advanced is considering relaying for cost-effective throughput enhancement and coverage extension. While analog repeaters have been used to enhance coverage in commercial cellular networks, the use of more sophisticated fixed relays is relatively new. The main challenge faced by relay deployments in cellular systems is overcoming the extra interference added by the presence of relays. Most prior work on relaying does not consider interference, however. This paper analyzes the performance of several emerging half-duplex relay strategies in interference-limited cellular systems: one-way, two-way, and shared relays. The performance of each strategy as a function of location, sectoring, and frequency reuse are compared with localized base station coordination. One-way relaying is shown to provide modest gains over singlehop cellular networks in some regimes. Shared relaying is shown to approach the gains of local base station coordination at reduced complexity, while two-way relaying further reduces complexity but only works well when the relay is close to the handset. Frequency reuse of one, where each sector uses the same spectrum, is shown to have the highest network throughput. Simulations with realistic channel models provide performance comparisons that reveal the importance of interference mitigation in multihop cellular networks.

2014

Relay based cooperative spectrum sensing elevates the spectrum sensing problems in harsh propagation conditions if the relay nodes are positioned suitably for the dynamic spectrum access systems. This article investigates the performance of relay based spectrum sensing (energy detection based) in myriad fading environments using the area under the receiver operating characteristic curve (AUC) performance metric. AUC is a single statistical parameter, which provides better insight of detection probability compared to the receiver operating characteristic curve (ROC). The article includes the performance analysis of two-hop multi-relay amplify-and-forward (AF) relay network with channel state information (CSI) assisted relaying (variable relay gain) and blind (fixed) relay gain. A unified model is also investigated to describe the relay network for variable and fixed relay gain. Various fading and relay configurations are illustrated to show the efficacy of the energy detection based collaborative spectrum sensing in AF relay configuration using the AUC performance metric. Performance of the variable and fixed relay gain based AF relay network are analysed and compared considering different factors affecting energy sensing such as the per-hop signal-to-noise ratio (SNR), fading index, and the timebandwidth product. The results can be readily used for the design of the cognitive relay network.

In this paper, we propose an energy-efficient scheduling algorithm for a relay-aided shared LTE network using CoMP and LB. A new complex scenario has been considered using a combination of the aforementioned four techniques. More explicitly, relay and LTE technologies are employed. In order to provide highthroughput for users at anywhere and anytime, we combine the relaying, the cooperative multipoint and the load balancing techniques in this paper, so as to increase the cell-edge users' throughput. Moreover, the interested area is jointly covered by two operators, who have an agreement in sharing their resources. For such a complicated relay-aided shared LTE network, we propose an energy efficient scheduling algorithm, whose objective is increase significantly the throughput and energy efficiency in the two operators' network sharing environment. Results have show meaningful increase up on the cell edge throughput when compared to conventional single cell. More specifically, the combined cooperative techniques, including single cell, relaying and CoMP scenario show significant improvement in throughput and energy consumption in the transmission stage, and in general a meaningful throughput improvement in the two LTE operators network sharing environment were achieved. 5 4 1 10 to 3.5 10 J J and draw the overall energy consumption in Fig. 3, where we see clearly that, compared with direct communication scheme, cooperative communication achieves significant energy savings. For example, when 4 max 1 10 E J the

IEEE Transactions on Vehicular Technology, 2015

This paper studies the performance of two traditional schedulers, Proportional Fair (PF) and Round Robin (RR), in the context of relay-enhanced LTE-A networks. These two schedulers are indeed natural candidates for implementation in relays nodes (RN) and, following the results obtained in singlehop networks, mobile operators could be tempted to adopt PF because of the good trade-off it offers between cell capacity and fairness. Based on a statistical throughput evaluation model, we show that this is not necessarily the right option. The number of RNs, their locations in the cell, and the backhaul link quality have indeed a decisive influence on the scheduler choice. In some scenarios, it is even not desirable to deploy relays as they degrade the network performance compared to the no relay case. For the purpose of performance evaluation, we develop a realistic and computationally tractable statistical network model that takes into account fast fading, multiple interferers, cell range expansion bias, backhaul link quality, and traffic load. We also propose an optimization of the radio frame structure and a sub-optimal RN placement scheme in order to fairly compare RR and PF. .sg). M. Minelli is also with Télécom ParisTech and CNRS LTCI, 46, rue Barrault, Paris, France.

IEEE Transactions on Wireless Communications, 2000

We investigate bandwidth allocation in next generation cellular systems employing relays similar to LTE advanced systems with type-I relays. We jointly optimize the bandwidth and power usage under constraints on required rate, bandwidth and transmit power. We study scenarios wherein, the relay acts as a forwarder for multiple User Equipments (UEs/users) in both uplink and/or downlink. This includes scenarios when the relay has its own data to send along with forwarding the data of other users. We examine the weighted power minimization problem for relaying with multiple users. We also show specific results with user scenario and also single user case in order to understand how the bandwidth and power are allocated. Numerical evaluations with users on a three sector LTE-A cell employing Fractional Frequency Reuse (FFR) indicate that power savings of at least 3 dB can be achieved by optimizing over both bandwidth and power.