Channel Aware Uplink Scheduler for a Mobile Subscriber Station of IEEE 802.16e

The scheduling part of the IEEE 802.16 (WiMAX) standards is kept as an open issue to provide differentiation among equipment manufacturers and operators. The uplink scheduling is very significant and more complex compared to downlink scheduling. Uplink scheduling is divided into two parts; one is scheduling the resources among many users from a base station (BS) and the other is sharing the resources among its services in a single user. BS uplink scheduling has been given more attention compared to subscriber station (SS) uplink scheduling. SS scheduler plays a significant role in providing the quality of service (QoS) among its services. The channel status awareness is vital in designing the SS scheduler as the channel conditions vary for a mobile user. This work proposes a scheduling algorithm for SS, which utilizes the channel information and queue length variation for the reallocation of received aggregated bandwidth grant to optimize the QoS parameters. The performance of the proposed algorithm is studied by conducting simulations using QualNet 5.0.2 simulation tool. Simulation results demonstrate the effectiveness of the proposed algorithm to improve the QoS

Algoritam alokacije resursa s dinamičkim pridruživanjem podnosioca u bežičnim mrežama zasnovanim na OFDMA-u

The allocation of available resources is one of the main issues in multi-user systems. Dependence of system capacity on radio link quality is an additional obstacle of efficient resource allocation in wireless networks. Combinations of two opposite approaches -- fair resource allocation and system capacity maximization are used to solve this problem in practice.This paper proposes a resource allocation method that is primarily based on assigning almost an equal bandwidth to all users. System capacity maximization is achieved by selecting the subcarriers with the best SNR values. This algorithm was developed for orthogonal frequency division multiple access (OFDMA) wireless systems. Resource allocation is done at the subcarrier level according to the weight factor that had been calculated for each user. Frequency hopping was used to increase frequency diversity and to make the system more robust to disturbance. Frequency hopping pattern is determined dynamically on the basis of SNR value of each subcarrier.The results of the proposed algorithm are compared with the water filling (WF) and proportional fairness (PF) methods. The influence of various data traffic classes on system throughput and resource allocation is also described.U sustavima s više korisnika jedno od glavnih pitanja je kako podijeliti raspoložive resurse. Kod radio mreža dodatni otežavajući faktor predstavlja promjenjivost kapaciteta sustava ovisno o kvaliteti radio veze. U praksi se za raspodjelu resursaobično koriste algoritmi koji su kombinacija dvaju oprečnih pristupa, fer raspodjele resursa i maksimizacije kapaciteta sustava.U ovom radu predložena je metoda primarno bazirana na fer raspodjeli resursa. Maksimizacija kapaciteta sustava ostvarena je odabirom podnosilaca s najboljim mogućim SNR-om. Algoritam je razvijen za sustave bazirane na OFDMA. Dodjela resursa korisnicima vrši se na razini pojedinog podnosioca prema izračunatom težinskom faktoru za svakog korisnika posebno. Kako bi se povećao frekvencijski diverziti i sustav učinio otpornijim na smetnje, uvedeno je frekvencijsko skakanje prema dinamički određenom predlošku. Predložak se formira na osnovu SNRvrijednosti određene po svakom podnosiocu. Rezultati predloženog algoritma uspoređeni su s WF (water filling) i PF(proportional fairness) algoritmima. Prikazan je utjecaj različitih klasa prometa na prijenosni kapacitet i raspodjelu resursa sustava

Mechanisms for quality of service provision in IEEE 802.16 networks

Orientador: Nelson Luis Saldanha da FonsecaTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: O padrão IEEE 802.16 para acesso sem fio em banda larga, também conhecido como WiMAX (Worldwide Interoperability for Microwave Access Forum), é uma solução de baixo custo para o acesso à Internet em áreas metropolitanas e rurais. Outro atrativo desta tecnologia está no fato de incluir uma arquitetura para provisão de Qualidade de Serviço (QoS) para aplicações de tempo real e aplicações que demandam altas taxas de transmissão. Esta arquitetura de QoS inclui um mecanismo de sinalização entre a estação base e as estações cliente, cinco níveis de serviço, para priorização e diferenciação do tráfego, um mecanismo de escalonamento e um mecanismo de controle de admissão de novas conexões. Entretanto, as políticas que devem ser utilizadas na implementação dos mecanismos de escalonamento e controle de admissão não foram definidas pelo padrão. O mecanismo de escalonamento tem como objetivo garantir a banda passante requisitada pelas estações cliente bem como promover o uso eficiente do enlace sem fio, equanto o mecanismo de controle de admissão restringe o número de conexões simultaneamente presentes na rede, de forma a evitar a saturação do enlace sem fio e, conseqüentemente, a violação dos requisitos de QoS. Esta tese propõe políticas para os mecanismos de escalonamento e de controle de admissão para a provisão de QoS em redes baseadas no padrão IEEE 802.16. A política de escalonamento proposta nesta tese é compatível com as especificações do padrão IEEE 802.16 e é capaz de atender os cinco tipos de serviço bem como o conjunto de parâmetros de QoS a eles associado. Requisitos de latência máxima e taxa mínima são garantidos para cada conexão aceita na rede, sem que os limites impostos pelos requisitos de taxa máxima e tamanho máximo da rajada sejam violados. Cinco soluções são propostas para o mecanismo de controle de admissão. Estas soluções visam atingir três objetivos principais: restringir o número de conexões simultaneamente presentes na rede para que o escalonador tenha recursos suficientes para atender os requisitos de QoS de cada conexão, atender as expectativas do provedor de serviço através da maximização do lucro e maximizar a satisfação dos usuários através da disponibilização de recursos extras. As soluções propostas foram avaliadas através de experimentos de simulação, utilizando um módulo para simulação de redes IEEE 802.16 desenvolvido para conduzir esta pesquisaAbstract: The IEEE 802.16 standard for broadband wireless access, also known as WiMAX (Worldwide Interoperability for Microwave Access Forum), is a low cost solution for Internet access in metropolitan and rural areas. Another advantage of this technology is the fact that it includes an architecture for the provision of Quality of Service (QoS) for real time and bandwidth demanding applications. This QoS architecture includes a signaling mechanism between base station and subcriber stations, five types of service, for traffic priorization and differentiation, a scheduling mechanism and a connection admission control mechanism. However, policies for the implementation of these mechanisms are not defined by the standard. The scheduling mechanism aims at guaranteeing the bandwidth required by the subscriber stations as well as enabling the efficient wireless link usage, while the connection admission control restricts the number of users simultaneously present in the network so as to avoid the wireless link saturation and, consequently, violation of QoS contracts. This theses proposes policies for scheduling and connection admission control mechanisms for the provision of QoS in IEEE 802.16 networks. The proposed scheduling policy is standard compliant and supports the five types of service as well as the QoS parameters associated with them. Maximum latency and minimum rate requirements are guaranteed without violating maximum rate and maximum traffic burst requirements. Five solutions are proposed for the connection admission control mechanism. These solutions aim to support three main goals: to restrict the number of simultaneous connections in the system so that the resources available to the scheduler are sufficient to guarantee the QoS requirements of each connection, to support the service provider expectations by maximizing the revenue, and to maximize the users satisfaction by providing extra resources. The proposed solutions were evaluated through simulation experiments using a module for the simulation of IEEE 802.16 networks developed to conduct this researchDoutoradoRedes de ComputadoresDoutor em Ciência da Computaçã

Quality of service and channel-aware packet bundling for capacity improvement in cellular networks

Title from PDF of title page, viewed on May 26, 2011VitaIncludes bibliographical references (p. 76-84)Thesis (Ph.D.)--School of Computing and Engineering. University of Missouri--Kansas City, 2011We study the problem of multiple packet bundling to improve spectral efficiency in cellular networks. The packet size of real-time data, such as VoIP, is often very small. However, the common use of time division multiplexing limits the number of VoIP users supported, because a packet has to wait until it receives a time slot, and if only one small VoIP packet is placed in a time slot, capacity is wasted. Packet bundling can alleviate such a problem by sharing a time slot among multiple users. A recent revision of cdma2000 1xEV-DO introduced the concept of the multi-user packet (MUP) in the downlink to overcome limitations on the number of time slots. However, the efficacy of packet bundling is not well understood, particularly in the presence of time varying channels. We propose a novel QoS and channel-aware packet bundling algorithm that takes advantage of adaptive modulation and coding. We show that optimal algorithms are NP complete and recommend heuristic approaches. We also show that channel utilization can be significantly increased by slightly delaying some real-time packets within their QoS requirements while bundling those packets with like channel conditions. We validate our study through extensive OPNET simulations with a complete EV-DO implementation.Introduction -- Related work -- Background on wireless systems -- Multiple packet bundling -- Evaluation -- Conclusion