Radio Resource Management Scheme Research Articles

Exploiting context, profiles, and policies in dynamic sub-carrier assignment algorithms for efficient radio resource management in OFDMA networks

Dynamic sub-carrier assignment (DSA) is considered as one of the most important aspects for achieving efficient spectrum utilization in orthogonal frequency division multiple access (OFDMA) based networks. Most of well-known DSA algorithms operate in a best effort manner, where the full set of sub-carriers is used in order to achieve the maximum possible quality of service level per user. However, in a real network environment, there are several management aspects to be considered such as context information (users, services, and radio environment conditions), user profiles, and network operator policies. In the context of OFDMA networks management, DSA algorithms should be extended incorporating such aspects in order to introduce fairness in the assignment of sub-carriers as well as to improve the overall system performance. In this paper, an efficient radio resource management scheme that incorporates a new DSA algorithm which exploits context profiles and policies information is presented. Results showcase the benefits that the proposed approach brings in terms of fairness on sub-carriers assignment and overall system performance.

Opportunities and Challenges in OFDMA-Based Cellular Relay Networks: A Radio Resource Management Perspective

The opportunities and flexibility in relay networks and orthogonal frequency-division multiple access (OFDMA) make the combination a suitable candidate network and air-interface technology for providing reliable and ubiquitous high-data-rate coverage in next-generation cellular networks. Advanced and intelligent radio resource management (RRM) schemes are known to be crucial toward harnessing these opportunities in future OFDMA-based relay-enhanced cellular networks. However, it is not very clear how to address the new RRM challenges (such as enabling distributed algorithms, intra-cell/inter-cell routing, intense and dynamic co-channel interference (CCI), and feedback overhead) in such complex environments comprising a plethora of relay stations (RSs) of different functionalities and characteristics. Employment of conventional RRM schemes in such networks will highly be inefficient if not infeasible. The next-generation networks are required to meet the expectations of all wireless users, irrespective of their locations. High-data-rate connectivity, mobility, and reliability, among other features, are examples of these expectations. Therefore, fairness is a critical performance aspect that has to be taken into account in the design of prospective RRM schemes. This paper reviews some of the prominent challenges involved in migrating from the conventional cellular architecture to the relay-based type and discusses how intelligent RRM schemes can exploit the opportunities in relay-enhanced OFDMA-based cellular networks. We identify the role of multiantenna systems and explore the current approaches in literature to extend the conventional schedulers to next-generation relay networks. This paper also highlights the fairness aspect in such networks in the light of the recent literature, provides some example fairness metrics, and compares the performances of some representative algorithms.

Performance analysis of multi-user diversity in heterogeneous cooperative communication systems

The heterogeneous cooperative relaying technique can be utilized to complete the hierarchical convergence for the multi-radio access networks, where the single heterogeneous cooperative relay is selected and the maximal-ratio combining (MRC) scheme is utilized to achieve the cooperative diversity gain. In order to evaluate performances of the hierarchical convergence mechanism, this paper theoretically investigates the key factors of the multi-user diversity (MUD) gain, the heterogeneous cooperative diversity gain and the large scale fading of the first and second links. The tight closed-form expressions in terms of the outage probability and the average symbol error rate are derived for evaluating how and with what factors impact on the system performance. The analytical and simulation results show that the number of heterogeneous cooperative relay nodes (HCRNs)M and the number of destination stations (DSs)K have great impacts on performances, and the order of outage probability is (M + 1)K. The large scale fading ratio of the first hop to the second hop also has a big impact on performances. Thus in the real network, we can utilize advanced radio resource management schemes to achieve a high multi-user diversity, instead of configuring too many HCRNs for the heterogeneous cooperative diversity gain. Furthermore, we can guarantee the transmission quality between the BS and HCRNs via the network planning to optimize the overall network performance.

Access selection and mobility management in a beyond 3G RAN: The WINNER approach

Next generation communications will be composed of flexible, scalable and context-aware, secure and resilient architectures. The technologies will allow full mobility of the user and enable dynamic management policies that ensure end-to-end secure transmission of data and services across heterogeneous infrastructures and networks. The concept of ubiquitous and scalable system is applied in the IST WINNER II project to deliver optimum performance for different deployment scenarios from local area to wide area wireless networks. The integration of cellular and local area networks in a unique radio system will provide a great advantage to final users and operators, compared with the nowadays situation, where there are many standalone systems and users equipped with different subscriptions, radio interfaces and terminals. To this issue, the IST project WINNER II has defined three system modes suited to local, metropolitan and wide area respectively. This paper describes the mobility management and access selection schemes that are proposed for the WINNER system that is designed as a candidate Beyond 3G type of system. A radio resource management (RRM) architecture that fully enables the functionality of these schemes will also be presented. The RRM schemes are based on specially designed cooperation RRM algorithms for the successful coexistence and handover of WINNER with new and legacy systems. The paper describes the cooperation architecture and mobility management functionalities and the rules that are applied for the support of mobility within the above scenarios.

Radio resource management strategy for VoIP service in TD-HSDPA system

In this article, the performance of a novel radio resource management (RRM) strategy for voice over IP (VoIP) service will be evaluated in low code rate (LCR) time duplex high speed downlink packet access (TD-HSDPA) system. This novel RRM strategy is studied from the aspects of scheduling algorithm and time slot assignment algorithm. As VoIP is delay sensitive service, the delay based proportional fair (DBPF) scheduler is proposed in this article. Smart antenna (SA), which is adopted in LCR TD-HSDPA, can obtain spatial information from the direction of arrival (DOA) estimation. To exploit this spatial information further, a dynamic time slot allocation (DTA) algorithm is introduced to cooperate with the DBPF scheduler. The performance of the round robin (RR), proportional fair (PF) with the random time slot allocation (RTA) algorithm will be given to demonstrate the benefits of this novel DBPF with DTA RRM strategy. The system level simulation results prove that the performance of this novel RRM strategy is the best of all the RRM strategies.

Enhancing interoperability in heterogeneous mobile wireless networks for disaster response

Efficient communications are crucial for disaster response and recovery. However, most current public safety land mobile radio (LMR) networks only provide narrowband voice service with limited support of low-speed data services. In this paper, we study to enhance the interoperability of LMR with commercial wireless cellular networks, by which a wide variety of benefits can be offered to disaster responders, including new multimedia services, increased data rates and low cost devices. Our approach is based on Session Initiation Protocol (SIP) and a joint radio resource management framework. We use a novel SIP- based seamless handoff scheme to support the interoperability between cellular and LMR networks. In addition, an optimal radio resource management scheme is proposed to maximize the overall radio resource utilization and at the same time guarantee service availability and continuity quality of service (QoS) for disaster responders. The effectiveness of the proposed schemes is illustrated by numerical examples.

A TDMA MAC protocol for multiservice wireless ad hoc networks

AbstractQuality of Service (QoS) provision in wireless ad hoc networks requires the support of efficient MAC protocols and Radio Resource Management strategies to efficiently handle the access process and to achieve a high resource reuse. In this context, we present in this paper a MAC proposal capable of providing resource reservation and service differentiation in the medium access level as a basis for guaranteeing end‐to‐end QoS support in higher levels. We propose a TDMA MAC structure based on a frame subdivision consisting of a broadcast control phase and a data phase. We have designed an adaptive strategy to share the resources between both control and data services and a resource reservation strategy for data services that solves the problems stemmed from the contention for the medium, also adding a service differentiation mechanism based on priorities. In addition, we evaluate the impact of a realistic propagation channel considering multipath fading and users interference on the performance of this scheme. In this scenario, we propose modifications to guarantee the reliability and efficiency of both broadcast control and data services, including power control techniques. Copyright © 2009 John Wiley & Sons, Ltd.

Investigation of capacity and call admission control schemes in TD‐SCDMA uplink systems employing smart antenna techniques

AbstractDue to the TDMA (time division multiple access)/time division duplex (TDD) specialization in the uplink (UL) of code division multiplex access (CDMA) systems, some advanced techniques, such as smart antenna (SA) and multi‐user detection (MUD), are utilized conveniently in time division‐synchronous code division multiplex access (TD‐SCDMA) systems. These advanced techniques have great impacts on the capacity and radio resource management (RRM) schemes. In this paper, the UL capacity and load models specified for TD‐SCDMA systems are proposed, in which the impacts from SA and MUD techniques are considered, and the UL load can be estimated based on the total received power in the base station. According to the proposed theoretical capacity and load evaluation models, the call admission control (CAC) strategies suitable for TD‐SCDMA systems are presented. Since there are two kinds of SA schemes (i.e., tracking beam antenna (TBA) and switched beam antenna (SBA)) utilized in TD‐SCDMA systems, the efficient CAC algorithms suitable for these two SA schemes are designed and evaluated, which are based on principles of the interference increase estimation. All simulation results show that the proposed CAC strategies can work efficiently and improve performances of TD‐SCDMA systems dramatically. Copyright © 2009 John Wiley & Sons, Ltd.

Downlink Scheduling With Economic Considerations for Future Wireless Networks

Future wireless cellular systems, i.e., high-speed downlink packet access (HSDPA) and 1x EVolution Data Optimized Revision A (1xEV-DO Rev A), promise to revolutionize the mobile users' wireless experience by offering high data rates that are beyond the capabilities of third-generation (3G) systems. These systems, however, require proficient radio resource management schemes to provide the high data rates that they promise. A key component of radio-resource management is packet scheduling, which is responsible for distributing the shared radio resources among the mobile users. In this paper, we propose a novel centralized downlink packet scheduler (CDPS) scheme to be implemented at the base stations of future wireless cellular systems. CDPS is designed to balance between the requirements of connections (e.g., throughput, fairness, etc.) and the requirements of service providers (e.g., revenues). CDPS aims at maximizing the system capacity while ensuring a fair distribution of the wireless resources. To achieve its objective, CDPS employs a flexible utility function that competently incorporates the channel quality conditions of the mobile users, as well as a unique fairness measure. In addition, CDPS utilizes an opportunity cost function that allows service providers to control its degree of fairness and hence control the system capacity. We analytically show that CDPS can be configured to reduce to the maximum carrier-to-interference ratio (Max CIR) and proportional fairness (PF) schemes, hence providing service providers the flexibility to choose between different scheduling schemes. Simulation results and comparisons with existing schemes show the effectiveness and strengths of the CDPS scheme.

Cooperative load-balancing strategy based on N-hops routing algorithm of ad hoc network in heterogeneous overlapping networks

A major challenge of the heterogeneous wireless networks is how to jointly utilize the resources of different radio access technologies in an efficient manner. In this paper, system performance, such as the block probability and throughput, was investigated in communication hot spots overlapped by heterogeneous networks: cellular, WLAN, and WiMax networks. Two cooperative load-balancing strategies based on hops-limited routing algorithm of ad hoc network are proposed in order to raise the resource utilization of the whole overlapping heterogeneous networks. They both firstly make a decision whether to admit a new call or not based on common radio resource management strategies, and in overloaded condition, select certain traffic to transfer into targeted BS/AP according to minimum price strategy or minimum load BS/AP and nearest traffic strategy, which take into account these factors such as load index, number of hops, traffic prediction, cost, etc. An analytical model is used to compute the call block probability and throughput performance for two different traffic models. Simulation results show that the proposed load-balancing strategies can distribute traffics to the whole heterogeneous wireless networks, decrease the call block probability, improve system throughputs efficiently, and obviously outperform HM-MACA and HS-TC load-balancing strategies.

Frequency assignments in IEEE 802.11 WLANs with efficient spectrum sharing

AbstractAs the number of WLAN users grows, the need to perform efficient radio resource management strategies becomes essential due to the fact that most popular technologies, those based on IEEE 802.11 standards, use unlicensed frequency bands. A good channel assignment improves the network performance, producing benefits that are perceived by the users and also by the network administrators. In this paper, we present a new frequency management scheme for IEEE 802.11 WLANs in the 2.4 GHz ISM band that minimizes interference to increase the throughput available to client stations by adapting a weighted DSATUR algorithm for graph coloring. The algorithm takes both co‐channel and adjacent channel interference into account, and makes use of all available channels instead of the traditional non‐overlapping three. In this way, collisions as well as transmission errors are minimized, thus improving the network capacity and the user experience. Different architectures are discussed for the implementation of our approach, including the possibility to incorporate client stations into the management system. Copyright © 2008 John Wiley & Sons, Ltd.

Analysis of Common Radio Resource Management Scheme for End-to-End QoS Support in Multiservice Heterogeneous Wireless Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Future-generation wireless networks will consist of heterogeneous radio access technologies (RATs) with Internet Protocol-based infrastructure and support multiple bearer services having different quality-of-service (QoS) requirements. However, a major issue is how to jointly utilize the resources in the different RATs in an efficient manner while simultaneously achieving the desired QoS and minimizing the service cost from both the user and service provider perspectives. To resolve this issue, this paper proposes an adaptive common radio resource management (CRRM) scheme in the context of CDMA2000 and IEEE 802.11 wireless technologies, which are examples of today's wireless wide-area network (WWAN) and wireless local area network (WLAN) RATs, respectively. The key parameters of the scheme, i.e., service type, user mobility and location information, and service cost, are described. The effectiveness of the proposed CRRM scheme is analytically assessed using the theory of Markov chains. Numerical results show that the proposed CRRM scheme minimizes the rate of unnecessary vertical handoffs, thereby providing stable communication without degrading call-blocking probabilities in all mobility and loading scenarios considered. The proposed CRRM scheme also minimizes service cost, which makes it attractive for implementation in heterogeneous wireless networks. </para>

Power control in distributed cooperative OFDMA cellular networks

This paper addresses downlink cooperation at a system level. Cooperation between base stations is an alternative to macrodiversity to provide QoS continuity in case of mobility. We propose a radio resource management strategy for the relay channel, made of relayed users identification, resource allocation and power control in an OFDMA-based system. Four scheduling methods are tested for power allocation in inter-cell interference environment: globally optimal, proportional fair, harmonic mean fair and max-min fair. Cooperation brings additional gain, both in terms of throughput and fairness, with all fair schedulers.

Esquema eficiente de administración de la calidad de serviciopara el sistema de telecomunicaciones móviles universales

ESTE TRABAJO DE INVESTIGACION PROPONE UN NUEVO ESQUEMA ADMINISTRADOR DE RECURSOS DE RADIO (RRM), PARA LLEVAR A CABO LA ADMINISTRACION DE LA CALIDAD DE SERVICIO (QOS) EN EL SISTEMA DE TELECOMUNICACIONES MOVILES UNIVERSALES (UMTS). EL PLANTEAMIENTO DE SOLUCION QUE SE PRESENTA ESTA BASADO EN LA ESTANDARIZACION DE UMTS Y SE PRESENTA UNA EVALUACION DE DESEMPENO PARA DEMOSTRAR SU EFICIENCIA.

Analytical approach to the optimal adaptation rate of reconfigurable radio networks

AbstractFlexible radio resource management schemes are nowadays used within a wide range of systems. However, the optimal selection for their adaptation rate is still an open research issue. This paper presents an analytical approach to such problem, which consists in a combined analysis of the dynamics of the session‐arrival process and the estimation of the mean traffic load from network measurements. From this study, it is concluded that both aspects pose an upper limit on the optimal system adaptation rate, being the most restrictive the one depending on the mean traffic load estimation. A specific procedure for deriving such limit on adaptation rate is provided. It is shown that the derived value directly depends on the mean service duration. The application of the whole analysis is illustrated with an example based on a set of measurements from a live network. Copyright © 2008 John Wiley &amp; Sons, Ltd.

A Channel based Fair Scheduling Scheme for Downlink Data Transmission in TD-CDMA Networks

High speed data transmission in wireless networks demands better radio resource management schemes. A fair packet scheduling is proposed for downlinks of a cellular TD-CDMA system for delay-tolerant applications. It is based on the combined consideration of channel conditions, required throughput and achieved average throughput. A system dependent parameter is introduced to control the maximum achievable date rate as well as the degree of fairness. Through analysis and simulation, we study the tradeoff between system throughout (i.e., efficiency) and individual throughput (i.e., fairness). The relative performance between the proposed scheme and the traditional schemes is evaluated through simulation to confirm the analytical observations. The sensitivity of the system tolerance factor towards efficiency and fairness is also investigated.

A Study on RAT Selection Algorithms in Combined UMTS/GSM Networks

The future wireless network is expected to be a heterogeneous system, which integrates different Radio Access Technologies (RATs) through a common platform. A major challenge arising from this heterogeneous network is Radio Resource Management (RRM) strategy. Common RRM (CRRM) has been proposed in the literature to jointly manage radio resources among a number of overlapped RATs in an optimized way. Currently, the RAT selection algorithm is one of the key research areas of CRRM. This paper studies RAT selection algorithms in co-located UMTS/GSM networks. In this paper, a three complex algorithm called IN*VG*Load is proposed based on improvements on the IN*VG algorithm. The simulation results show that the IN*VG*Load algorithm can optimize the system performance in highly loaded combined UMTS/GSM networks. A new algorithm suitable for low to medium loaded UMTS/GSM networks is also proposed and simulation results are presented in this paper.

A novel approach to smart multi-cell radio resource management based on load gradient calculations

This paper presents a novel methodology for capturing the coupling between the different cells in both the uplink and downlink directions in a Wideband Code Division Multiple Access (WCDMA) scenario. It is based on the definition and computation of the gradient of the uplink cell load factor and the downlink transmitted power, which are the two main parameters that reflect the actual cell load in the two link directions. The paper shows that the gradient is able to capture the relevant information about the spatial distribution of traffic, which has an impact on cell performance. The proposed methodology is also used as the basis for defining and evaluating new Radio Resource Management (RRM) strategies that operate at a multi-cell level.

On the Optimum Traffic Allocation in Heterogeneous CDMA/TDMA Networks

This paper presents the optimum user allocation in heterogeneous scenarios with CDMA and TDMA technologies in order to minimize the total outage probability in the uplink. An analytical model reflecting the different nature of the two access technologies is presented in order to formulate the optimization procedure. It is shown how the optimum allocation depends on the specific parameters of the two technologies, as illustrated with some representative results. The proposed optimization methodology is claimed to have applicability in the field of common radio resource management strategies for beyond 3G networks.

A Cross-Layer Packet Scheduling Scheme for Multimedia Broadcasting via Satellite Digital Multimedia Broadcasting System [Advances in Mobile Multimedia

In recent years, multimedia content broadcasting via satellite has attracted increased attention. The satellite digital multimedia broadcasting (S-DMB) system has emerged as one of the most promising alternatives for the efficient delivery of multimedia broadcast multicast service (MBMS). The design of an efficient radio resource management (RRM) strategy, especially the packet scheduling scheme, becomes a key technique for provisioning multimedia services at required quality of service (QoS) in S-DMB. In this article, we propose a novel cross-layer packet scheduling scheme that consists of a combined delay and rate differentiation (CDRD) service prioritization algorithm and a dynamic rate matching (DRM)-based resource allocation algorithm. The proposed scheme considers multiple key factors that span from the application layer to the physical layer, aiming at simultaneously guaranteeing diverse QoS while utilizing radio resources efficiently under the system power and resource constraints. Simulation results demonstrate that the proposed cross-layer scheme achieves significantly better performance than existing schemes in queuing delay, jitter, and channel utilization.