Downlink scheduling and resource management for best effort service

Abstract. Throughput performance and geographical service fairness of best effort service used for downlink of a 802.16e based TDD-OFDMA sectored cellular networks are evaluated in conjunction with different scheduling schemes and frequency reuse plans. The OFDM systems are based on two multiple access schemes, which are the OFDM-TDM and OFDMA, and considered scheduling schemes are round robin, max C/I, PF and G-fair schedulers with adaptive rate control. The 3-sectored 1 FA, 3-sectored 3 FA, and 6-sectored 3 FA plans are compared in terms of throughput, capacity, and geographical service fairness, which assist in determining the choice of a scheduling and frequency reuse plan

Policy-Based Radio Resource Management in Multicast OFDMA Systems

Η ασύρματηφασματική αποδοτικότητα είναι ένας, όλο και περισσότερο, σημαντικός παράγοντας εξαιτίας της ταχείας ανάπτυξης των ασύρματων υπηρεσιών ευρείας ζώνης. Η σχεδίαση ενός συστήματος με πολλά φέροντα, όπως είναι ένα σύστημα OFDMA,επιτρέπει στα συστήματα να έχουν υψηλή χωρητικότητα για να ικανοποιήσουν τις απαιτήσεις των υπηρεσιών ευρείας ζώνης.Αυτή η αυξημένη χωρητικότητα των συστημάτων μπορεί να βελτιστοποιηθεί περαιτέρω εκμεταλλευόμενοι καλύτερα τα χαρακτηριστικά των ασύρματων καναλιών. Ηθεμελιώδηςιδέα ενός σχήματος κατανομής πόρων είναι η αποτελεσματική κατανομή των διαθέσιμων ασύρματων πόρων, όπως είναι οι υποφορείς και η ισχύς εκπομπής, μεταξύ των χρηστών του συστήματος. Σχετικά με τα προβλήματα της κατανομής πόρων σε ασύρματα συστήματα τηλεπικοινωνιών βασισμένα στην τεχνική OFDMA, η περισσότερη έρευνα επικεντρώνεται στην αναζήτηση πολιτικών ανάθεσης υποφορέων και ισχύος. Οι διαθέσιμες τεχνικές της βιβλιογραφίας δεν μπορούν να εφαρμοστούν όπως είναι σε συστήματα πολυεκπομπής. Επιπλέον, οι υπάρχουσες τεχνικές δεν μπορούν να εφαρμοστούν αμετάβλητες σε πραγματικά συστήματα στα οποία υπάρχει μεγάλος αριθμός OFDMυποφορέων, καθώς η υπολογιστική πολυπλοκότητα είναι πολύ μεγάλη. Ο βασικός στόχος της παρούσας διπλωματικής εργασίας είναι η πρόταση ικανών μηχανισμών κατανομής των διαθέσιμων υποφορέων σε ασύρματα συστήματα πολυεκπομπής χρησιμοποιώντας την τεχνολογία OFDMA. Πιο συγκεκριμένα, σχετικά με τα συστήματα πολυεκπομπής, θεωρούμε ότι τόσο ο σταθμός βάσης όσο και κάθε χρήστης είναι εφοδιασμένοι με μοναδική κεραία και η μονάδα κατανομής δεν είναι ο υποφορέας, όπως στα συμβατικά συστήματα OFDMA, αλλά μία ομάδα γειτονικώνυποφορέων, η οποία ονομάζεται τεμάχιο, με σκοπό τη μείωση της μεγάλης υπολογιστικής πολυπλοκότητας. Ένας αποτελεσματικός αλγόριθμος προτείνεται του οποίου ο στόχος είναι η μεγιστοποίηση του συνολικού ρυθμού μετάδοσης δεδομένων με περιορισμούς στη συνολική διαθέσιμη ισχύ, στο BERανά τεμάχιο και στους αναλογικούς περιορισμούς μεταξύ των ρυθμών μετάδοσης δεδομένων των ομάδων χρηστών. Η προσομοίωση και η ανάλυση της πολυπλοκότητας που παρουσιάζονται, υποστηρίζουν τα πλεονεκτήματα της κατανομής πόρων σε συστήματα πολυεκπομπήςOFDMA τα οποία βασίζονται σε κατανομή τεμαχίων και έχουν ως στόχος την εξασφάλιση της αναλογικότητας μεταξύ των ρυθμών μετάδοσης δεδομένων των ομάδων χρηστών.Wireless spectral efficiency is increasingly important due to the rapid growth of demand for high data rate wideband wireless services. The design of a multi-carrier system, such as an OFDMA system, enables high system capacity suited for these wideband wireless services. This system capacity can be further optimized with a resource allocation scheme by exploiting the characteristics of the wireless fading channels. The fundamental idea of a resource allocation scheme is to efficiently distribute the available wireless resources, such as the subcarriers and transmission power, among all admitted users in the system. Regarding the problems of resource allocation in OFDMA-based wireless communicationsystems, much of the research effort mainly focuses on finding efficient power controland subcarrier assignment policies. With systems employing multicast transmission,the available schemes in literature are not always applicable. Moreover, the existing approachesare particularly inaccessible in practical systems in which there are a large numberof OFDM subcarriers being utilized, as the required computational burden is prohibitivelyhigh. The ultimate goal of this Thesis is therefore to propose affordable mechanisms toflexibly and effectively share out the available resources in multicast wireless systems deployingOFDMA technology. Specifically, according to multicast system, it is assumed thatboth the BS and each user are equipped witha single antenna and the allocation unit is not the subcarrier,as in conventional OFDMA systems, but a set of contiguoussubcarriers, which is called chunk, in order to alleviate the heavy computational burden. An efficient algorithmis proposed whose aim is to maximize the total throughput subject to constraints on totalavailable power,BER over a chunk, and proportional data rates constraints among multicast groups. Simulation and complexity analysis are provided to support thebenefits of chunk-based resource allocation to multicast OFDMA systems with targeting proportional data rates among multicast groups

Practical design of optimal wireless metropolitan area networks: model and algorithms for OFDMA networks

A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Ph.D.This thesis contributes to the study of the planning and optimisation of wireless metropolitan area networks, in particular to the access network design of OFDMAbased systems, where different parameters like base station position, antenna tilt and azimuth need to be configured during the early stages of the network life. A practical view for the solution of this problem is presented by means of the development of a novel design framework and the use of multicriteria optimisation. A further consideration of relaying and cooperative communications in the context of the design of this kind of networks is done, an area little researched. With the emergence of new technologies and services, it is very important to accurately identify the factors that affect the design of the wireless access network and define how to take them into account to achieve optimally performing and cost-efficient networks. The new features and flexibility of OFDMA networks seem particularly suited to the provision of different broadband services to metropolitan areas. However, until now, most existing efforts have been focused on the basic access capability networks. This thesis presents a way to deal with the trade-offs generated during the OFDMA access network design, and presents a service-oriented optimization framework that offers a new perspective for this process with consideration of the technical and economic factors. The introduction of relay stations in wireless metropolitan area networks will bring numerous advantages such as coverage extension and capacity enhancement due to the deployment of new cells and the reduction of distance between transmitter and receiver. However, the network designers will also face new challenges with the use of relay stations, since they involve a new source of interference and a complicated air interface; and this need to be carefully evaluated during the network design process. Contrary to the well known procedure of cellular network design over regular or hexagonal scenarios, the wireless network planning and optimization process aims to deal with the non-uniform characteristics of realistic scenarios, where the existence of hotspots, different channel characteristics for the users, or different service requirements will determine the final design of the wireless network. This thesis is structured in three main blocks covering important gaps in the existing literature in planning (efficient simulation) and optimisation. The formulation and ideas proposed in the former case can still be evaluated over regular scenarios, for the sake of simplicity, while the study of latter case needs to be done over specific scenarios that will be described when appropriate. Nevertheless, comments and conclusions are extrapolated to more general cases throughout this work. After an introduction and a description of the related work, this thesis first focuses on the study of models and algorithms for classical point-to-multipoint networks on Chapter 3, where the optimisation framework is proposed. Based on the framework, this work: - Identifies the technology-specific physical factors that affect most importantly the network system level simulation, planning and optimization process. - It demonstrates how to simplify the problem and translate it into a formal optimization routine with consideration of economic factors. - It provides the network provider, a detailed and clear description of different scenarios during the design process so that the most suitable solution can be found. Existing works on this area do not provide such a comprehensive framework. In Chapter 4: - The impact of the relay configuration on the network planning process is analysed. - A new simple and flexible scheme to integrate multihop communications in the Mobile WiMAX frame structure is proposed and evaluated. - Efficient capacity calculations that allow intensive system level simulations in a multihop environment are introduced. In Chapter 5: - An analysis of the optimisation procedure with the addition of relay stations and the derived higher complexity of the process is done. - A frequency plan procedure not found in the existing literature is proposed, which combines it with the use of the necessary frame fragmentation of in-band relay communications and cooperative procedures. - A novel joint two-step process for network planning and optimisation is proposed. Finally, conclusions and open issues are exposed

4G Technology Features and Evolution towards IMT-Advanced

Kiinteiden- ja mobiilipalveluiden kysyntä kasvaa nopeasti ympäri maailmaa. Älykkäiden päätelaitteiden, kuten iPhone:n ja Nokia N900:n markkinoilletulo yhdistettynä näiden korkeaan markkinapenetraatioon ja korkealuokkaiseen käyttäjäkokemukseen lisäävät entisestään palveluiden kysyntää ja luovat tarpeen jatkuvalle innovoinnille langattomien teknologioiden alalla tavoitteena lisäkapasiteetin ja paremman palvelunlaadun tarjoaminen. Termi 4G (4th Generation) viittaa tuleviin neljännen sukupolven mobiileihin langattomiin palveluihin, jotka International Telecommunications Union:in Radiocommunication Sector (ITU-R) on määritellyt ja nimennyt International Mobile Telecommunications-Advanced (IMT-Advanced). Nämä ovat järjestelmiä, jotka pitävät sisällään IMT:n ne uudet ominaisuudet, jotka ylittävät IMT-2000:n vaatimukset. Long Term Evolution-Advanced (LTE-Advanced) ja IEEE 802.16m ovat IMT-A sertifiointiin lähetetyt kaksi pääasiallista kandidaattiteknologiaa. Tässä diplomityössä esitellään kolmannen sukupolven järjestelmien kehityspolku LTE:hen ja IEEE 802.16e-2005 asti. Lisäksi työssä esitetään LTE-Advanced:n ja IEEE 802.16m:n uudet vaatimukset ja ominaisuudet sekä vertaillaan näiden lähestymistapoja IMT-A vaatimusten täyttämiseksi. Lopuksi työssä luodaan katsaus LTE ja IEEE 802.16e-2005 (markkinointinimeltään Mobile WiMAX) -järjestelmien markkinatilanteeseen.The demand for affordable bandwidth in fixed and mobile services is growing rapidly around the world. The emergence of smart devices like the iPhone and Nokia N900, coupled with their high market penetration and superior user experience is behind this increased demand, inevitably driving the need for continued innovations in the wireless data technologies industry to provide more capacity and higher quality of service. The term "4G" meaning the 4th Generation of wireless technology describes mobile wireless services which have been defined by the ITU's Radiocommunication Sector (ITU-R) and titled International Mobile Telecommunications-Advanced (IMT-Advanced). These are mobile systems that include the new capabilities of IMT that go beyond those of IMT-2000. Long Term Evolution-Advanced (LTE-Advanced) and IEEE 802.16m are the two main candidate technologies submitted for IMT-Advanced certification. This thesis reviews the technology roadmap up to and including current 3G systems LTE from the 3rd Generation Partnership Project (3GPP) and IEEE 802.16e-2005 from the Institute of Electrical and Electronics Engineers (IEEE). Furthermore, new requirements and features for LTE-Advanced and IEEE 802.16m as well as a comparative approach towards IMT-Advanced certification are presented. Finally, the thesis concludes with a discussion on the market status and deployment strategies of LTE and IEEE 802.16e-2005, or Mobile WiMAX as it is being marketed

Multi-cell Coordination Techniques for DL OFDMA Multi-hop Cellular Networks

The main objective of this project is to design coordinated spectrum sharing and reuse techniques among cells with the goal of mitigating interference at the cell edge and enhance the overall system capacity. The performance of the developed algorithm will be evaluated in an 802.16m (WiMAX) environment. In conventional cellular networks, frequency planning is usually considered to keep an acceptable signal-to-interference-plus noise ratio (SINR) level, especially at cell boundaries. Frequency assignations are done under a cell-by-cell basis, without any coordination between them to manage interference. Particularly this approach, however, hampers the system spectral efficiency at low reuse rates. For a specific reuse factor, the system throughput depends highly on the mobile station (MS) distribution and the channel conditions of the users to be served. If users served from different base stations (BS) experience a low level of interference, radio resources may be reused, applying a high reuse factor and thus, increasing the system spectral efficiency. On the other side, if the served users experience large interference, orthogonal transmissions are better and therefore a lower frequency reuse factor should be used. As a consequence, a dynamic reuse factor is preferable over a fixed one. This work addresses the design of joint multi-cell resource allocation and scheduling with coordination among neighbouring base stations (outer coordination) or sectors belonging to the same one (inner coordination) as a way to achieve flexible reuse factors. We propose a convex optimization framework to address the problem of coordinating bandwidth allocation in BS coordination problems. The proposed framework allows for different scheduling policies, which have an impact on the suitability of the reuse factor, since they determine which users have to be served. Therefore, it makes sense to consider the reuse factor as a result of the scheduling decision. To support the proposed techniques the BSs shall be capable of exchanging information with each other (decentralized approach) or with some control element in the back-haul network as an ASN gateway or some self-organization control entity (centralized approach)

Adaptive Communications for Next Generation Broadband Wireless Access Systems

Un dels aspectes claus en el disseny i gestió de les xarxes sense fils d'accés de banda ampla és l'ús eficient dels recursos radio. Des del punt de vista de l'operador, l'ample de banda és un bé escàs i preuat que s´ha d'explotar i gestionar de la forma més eficient possible tot garantint la qualitat del servei que es vol proporcionar. Per altra banda, des del punt de vista del usuari, la qualitat del servei ofert ha de ser comparable al de les xarxes fixes, requerint així un baix retard i una baixa pèrdua de paquets per cadascun dels fluxos de dades entre la xarxa i l'usuari. Durant els darrers anys s´han desenvolupat nombroses tècniques i algoritmes amb l'objectiu d'incrementar l'eficiència espectral. Entre aquestes tècniques destaca l'ús de múltiples antenes al transmissor i al receptor amb l'objectiu de transmetre diferents fluxos de dades simultaneament sense necessitat d'augmentar l'ample de banda. Per altra banda, la optimizació conjunta de la capa d'accés al medi i la capa física (fent ús de l'estat del canal per tal de gestionar de manera optima els recursos) també permet incrementar sensiblement l'eficiència espectral del sistema.L'objectiu d'aquesta tesi és l'estudi i desenvolupament de noves tècniques d'adaptació de l'enllaç i gestió dels recursos ràdio aplicades sobre sistemes d'accés ràdio de propera generació (Beyond 3G). Els estudis realitzats parteixen de la premissa que el transmisor coneix (parcialment) l'estat del canal i que la transmissió es realitza fent servir un esquema multiportadora amb múltiples antenes al transmisor i al receptor. En aquesta tesi es presenten dues línies d'investigació, la primera per casos d'una sola antenna a cada banda de l'enllaç, i la segona en cas de múltiples antenes. En el cas d'una sola antena al transmissor i al receptor, un nou esquema d'assignació de recursos ràdio i priorització dels paquets (scheduling) és proposat i analitzat integrant totes dues funcions sobre una mateixa entitat (cross-layer). L'esquema proposat té com a principal característica la seva baixa complexitat i que permet operar amb transmissions multimedia. Alhora, posteriors millores realitzades per l'autor sobre l'esquema proposat han permès també reduir els requeriments de senyalització i combinar de forma óptima usuaris d'alta i baixa mobilitat sobre el mateix accés ràdio, millorant encara més l'eficiència espectral del sistema. En cas d'enllaços amb múltiples antenes es proposa un nou esquema que combina la selecció del conjunt optim d'antenes transmissores amb la selecció de la codificació espai- (frequència-) temps. Finalment es donen una sèrie de recomanacions per tal de combinar totes dues línies d'investigació, així con un estat de l'art de les tècniques proposades per altres autors que combinen en part la gestió dels recursos ràdio i els esquemes de transmissió amb múltiples antenes.Uno de los aspectos claves en el diseño y gestión de las redes inalámbricas de banda ancha es el uso eficiente de los recursos radio. Desde el punto de vista del operador, el ancho de banda es un bien escaso y valioso que se debe explotar y gestionar de la forma más eficiente posible sin afectar a la calidad del servicio ofrecido. Por otro lado, desde el punto de vista del usuario, la calidad del servicio ha de ser comparable al ofrecido por las redes fijas, requiriendo así un bajo retardo y una baja tasa de perdida de paquetes para cada uno de los flujos de datos entre la red y el usuario. Durante los últimos años el número de técnicas y algoritmos que tratan de incrementar la eficiencia espectral en dichas redes es bastante amplio. Entre estas técnicas destaca el uso de múltiples antenas en el transmisor y en el receptor con el objetivo de poder transmitir simultáneamente diferentes flujos de datos sin necesidad de incrementar el ancho de banda. Por otro lado, la optimización conjunta de la capa de acceso al medio y la capa física (utilizando información de estado del canal para gestionar de manera óptima los recursos) también permite incrementar sensiblemente la eficiencia espectral del sistema.El objetivo de esta tesis es el estudio y desarrollo de nuevas técnicas de adaptación del enlace y la gestión de los recursos radio, y su posterior aplicación sobre los sistemas de acceso radio de próxima generación (Beyond 3G). Los estudios realizados parten de la premisa de que el transmisor conoce (parcialmente) el estado del canal a la vez que se considera que la transmisión se realiza sobre un sistema de transmisión multiportadora con múltiple antenas en el transmisor y el receptor. La tesis se centra sobre dos líneas de investigación, la primera para casos de una única antena en cada lado del enlace, y la segunda en caso de múltiples antenas en cada lado. Para el caso de una única antena en el transmisor y en el receptor, se ha desarrollado un nuevo esquema de asignación de los recursos radio así como de priorización de los paquetes de datos (scheduling) integrando ambas funciones sobre una misma entidad (cross-layer). El esquema propuesto tiene como principal característica su bajo coste computacional a la vez que se puede aplicar en caso de transmisiones multimedia. Posteriores mejoras realizadas por el autor sobre el esquema propuesto han permitido también reducir los requisitos de señalización así como combinar de forma óptima usuarios de alta y baja movilidad. Por otro lado, en caso de enlaces con múltiples antenas en transmisión y recepción, se presenta un nuevo esquema de adaptación en el cual se combina la selección de la(s) antena(s) transmisora(s) con la selección del esquema de codificación espacio-(frecuencia-) tiempo. Para finalizar, se dan una serie de recomendaciones con el objetivo de combinar ambas líneas de investigación, así como un estado del arte de las técnicas propuestas por otros autores que combinan en parte la gestión de los recursos radio y los esquemas de transmisión con múltiples antenas.In Broadband Wireless Access systems the efficient use of the resources is crucial from many points of views. From the operator point of view, the bandwidth is a scarce, valuable, and expensive resource which must be exploited in an efficient manner while the Quality of Service (QoS) provided to the users is guaranteed. On the other hand, a tight delay and link quality constraints are imposed on each data flow hence the user experiences the same quality as in fixed networks. During the last few years many techniques have been developed in order to increase the spectral efficiency and the throughput. Among them, the use of multiple antennas at the transmitter and the receiver (exploiting spatial multiplexing) with the joint optimization of the medium access control layer and the physical layer parameters.In this Ph.D. thesis, different adaptive techniques for B3G multicarrier wireless systems are developed and proposed focusing on the SS-MC-MA and the OFDM(A) (IEEE 802.16a/e/m standards) communication schemes. The research lines emphasize into the adaptation of the transmission having (Partial) knowledge of the Channel State Information for both; single antenna and multiple antenna links. For single antenna links, the implementation of a joint resource allocation and scheduling strategy by including adaptive modulation and coding is investigated. A low complexity resource allocation and scheduling algorithm is proposed with the objective to cope with real- and/or non-real- time requirements and constraints. A special attention is also devoted in reducing the required signalling. However, for multiple antenna links, the performance of a proposed adaptive transmit antenna selection scheme jointly with space-time block coding selection is investigated and compared with conventional structures. In this research line, mainly two optimizations criteria are proposed for spatial link adaptation, one based on the minimum error rate for fixed throughput, and the second focused on the maximisation of the rate for fixed error rate. Finally, some indications are given on how to include the spatial adaptation into the investigated and proposed resource allocation and scheduling process developed for single antenna transmission

A Survey on Scheduling in IEEE 802.16 Mesh Mode

Cataloged from PDF version of article.IEEE 802.16 standard (also known as WiMAX) defines the wireless broadband network technology which aims to solve the so called last mile problem via providing high bandwidth Internet even to the rural areas for which the cable deployment is very costly. The standard mainly focuses on the MAC and PHY layer issues, supporting two transmission modes: PMP (Point-to-Multipoint) and mesh modes. Mesh mode is an optional mode developed as an extension to PMP mode and it has the advantage of having an improving performance as more subscribers are added to the system using multi-hop routes. In 802.16 MAC protocol, mesh mode slot allocation and reservation mechanisms are left open which makes this topic a hot research area. Hence, the focus of this survey will mostly be on the mesh mode, and the proposed scheduling algorithms and performance evaluation methods

Efficient design of WIMAX/802.16 mesh networks

Broadband wireless networks are becoming increasingly popular due to their fast and inexpensive deployment and their capabilities of providing flexible and ubiquitous Internet access. While the majority of existing broadband wireless networks are still exclusively limited to single hop access, it is the ability of these networks to forward data frames over multi-hop wireless routes which enabled them to easily extend the network coverage area. Unfortunately, achieving good multi- hop throughput has been challenging due to several factors, such as lossy wireless links caused by interference from concurrent transmissions, and intra-path interference caused by transmissions on successive hops along a single path. A wireless mesh network WMN consists of a number of stationary wireless mesh routers, forming a wireless backbone. The wireless mesh routers serve as access points (APs) for wireless mobile devices, and some of them also act as gateways to the Internet via high speed wireless links. Several technologies are currently being considered for mesh (multi-hop) networks, including, IEEE 802.11 (both single channel and multi-channel), IEEE 802.16/WiMAX, and next generation cellular networks (LTE). In this work, we focus on the IEEE 802.16. To maximize the network performance of mesh networks (e.g., throughput), it is essential to consider a cross-layer design, exploiting the dependency between protocol layers such as the routing network layer and the scheduling resource allocation MAC layer. Therefore this PhD thesis considers a cross-layer design approach for designing efficient wireless mesh networks; we first develop mathematical models (link-based and path-based) for the problem of joint routing tree construction and link scheduling in WiMAX-based mesh networks with the objective of minimizing the schedule length to satisfy a set of uplink and downlink demands. This is achieved by maximizing the number of concurrent active transmissions in the network by efficiently reusing the spectrum spatially. Second, we exploit the broadcasts nature of the wireless medium and enhance our design models by incorporating opportunistic network coding into the joint routing tree construction and link scheduling problem. Identifying coding-aware routing structures and utilizing the broadcasting feature of the wireless medium play an important role in realizing the achievable gain of network coding. Last, the uprising mobile WiMAX (802.16e amendment) has introduced more difficulties and challenges into the network design problem; thus, ensuring larger connection lifetime and better routing stability become of greater interest for the joint routing and scheduling problem. This is addressed by augmenting the previously designed models. Throughout this thesis, we assume centralized scheduling at the base station (BS) and we develop, for the joint problems, integer linear programming (ILP) models which require the enumeration of all feasible solutions to reach the optimal solution. Given their complexities, we rely on optimization decomposition methods using column generation for solving each model in an efficient way