In a WiMAX network, four traffic types with different priorities are defined. They are Unsolicited Grant Service (UGS), real-time Polling Service (rtPS), non-real-time Polling Service (nrtPS), and Best Effort (BE). In this thesis, we propose a Dynamic Bandwidth Allocation (DBA) scheme for BS to schedule the four above-mentioned traffic types. By adopting Deficit Round Robin (DRR) scheduling, DBA first assigns minimum quantum to each traffic type for transmission. When rtPS packets exceed their delay constraints, without sacrificing the minimum requirements of nrtPS and BE traffic, DBA borrows some quantum from nrtPS and BE to satisfy the delay requirements of rtPS traffic. When nrtPS packets can not reach the minimum transmission rate, without starving the BE traffic, DBA borrows some quantum from BE to support the required throughput of nrtPS traffic. According to the history record of borrowed quantum, DBA dynamically adjusts the assigned quantum for the three traffic types. For the purpose of evaluation, we use NS-2 to simulate the proposed DBA. We adjust the traffic load to analyze the performance in terms of average packet delay, average throughput, and average packet loss ratio. The simulation results show that the DBA, in comparison to a previous work, can promise the delay constraints of rtPS, maintain the average throughput of nrtPS, and avoid the starvation of BE, when the traffic load is high.

WiMAX (Worldwide Interoperability for Microwave Access) provides wide transmission range and broadband network services. However, in IEEE 802.16 standard, there is no specific definition for SS (Subscriber Station) to select an optimal route in a mesh-based WiMAX network. In this thesis, we propose an Optimal Route Selection Scheme (ORSS) for SS to select a route to its BS (Base Station). ORSS basically considers three influential factors, the bandwidth SS to be assigned, the number of interference nodes around SS, and the hop counts to BS. We also investigate QoS (Quality of Service) issue in a mesh-based WiMAX network; an SS transferring the rtPS traffic type will share bandwidth with the neighboring SS of the same level that transmit the same traffic type. To ensure the selected route that can meet the bandwidth requirements of rtPS and the delay constraints, we estimate the average transmission delay from SS to BS. For the purpose of evaluation, we establish a mathematical model to analyze the proposed ORSS and discuss the impact of varying network parameters on the successful rate of route selection. Through the Matlab simulation, we validate our mathematical model. The simulation results demonstrate that our ORSS, in comparison to a previous work, is more effective in ensuring the delay constraints when selecting a route to transfer rtPS traffic.

WiMax or the IEEE 802.16 standard is one of the most promising broadband wireless technologies nowadays. It is characterized by its high data rates, large coverage area, flexible design and QoS support. The standard defines two modes of operation: Point-to- Multi-Point (PMP) and the Mesh Mode. In the first mode, all nodes are connected directly to the base station and communication is not allowed amongst nodes. In the mesh mode, nodes are placed in an ad hoc manner communicating to neighbors and relaying the traffic of other nodes. The goal of this thesis is to design a partitioning scheme for the frame structure of the Mesh mode. Increasing the frame utilization would result in better support for QoS applications and optimized resource allocation, and thus revenue increase from the service provider’s perspective. The mesh frame is divided into control and data, which are further divided into centralized and distributed portions. We propose a novel and efficient scheme for partitioning the data subframe between the two schedulers. We use a Markovian model that studies the system behavior in the long run, and provides predictions based on analysis of previous window of frames. We further enhance the decision by tuning the partitioning through statistical analysis of smaller windows to accommodate demand changes. Our simulations show that the proposed scheme achieves high utilization under different network and traffic conditions and decreases the packet overflow. / Thesis (Master, Computing) -- Queen's University, 2008-10-02 18:41:36.551

In this thesis we investigate the performance of spatial reuse in wireless networks. More specifically, we investigate the performance of location-based spatial reuse built upon the identification of links in the network that form Collision-Free Sets (CFSs). We develop algorithms that efficiently find such CFSs. The main focus of this thesis is the application of our CFS-based algorithms to emerging WiMAX (Worldwide Interoperability for Microwave Access) networks. However, we will also apply our CFS-based algorithms to smaller scale networks, as well as to the issue of QoS routing. This thesis makes several contributions. We first show how CFSs can be found within polynomial time in small scale wireless networks. We then probe how CFSs can be used to enhance network efficiency when location is available. We also explore how CFS determination is affected by location error, determining what level of location error renders the use of CFSs ineffective. In this context, we discuss the density of access points required to ensure CFS-based spatial reuse remains effective. We then focus on the use of CFSs in emerging multihop WiMAX networks, showing in detail how enhanced spatial reuse is delivered. The spatial reuse gains are probed both in the presence of realistic channel conditions and realistic location errors. Within the context of the IEEE 802.16 standard we show how CFSs can enhance, by factors of two, the VoIP capacity of multihop WiMAX networks. We also discuss how our CFS algorithms can be applied to other ongoing efforts aimed at improving VoIP capacity in WiMAX networks. Finally, an application of our CFS algorithms in the context of QoS routing is studied. Specifically, we develop a two-hop QoS routing protocol that guarantees QoS specifications by securing higher bandwidth for the chosen routes.

Broadband access technology has significant influences in the telecommunication industry. Worldwide interoperability for microwave access (WiMAX) is a broadband wireless technology which brings broadband experience to a wireless context. There are two different types of broadband wireless services. One is fixed wireless broadband which is similar to the traditional fixed line broadband access technology like DSL or cable modem but using wireless as a medium of transmission. Another type is broadband wireless known as mobile broadband which has additional functionality of portability, mobility and nomadicity. The IEEE 802.16 family WiMAX is designed to accommodate both fixed and mobile broadband application. WiMAX promises to solve the last mile problem which refers to the expense and time needed to connect individual homes and offices to trunk route for communications. WiMAX also offer higher peak data rates and greater flexibility than 3G networks and Wi-Fi. This thesis is provides the analysis of the broadband wireless access (BWA) technology with a focus on WiMAX and compare it with the other wireless technology like Wireless Fidelity (Wi-Fi) and third-generation (3G).

No description available.

Approved for public release; distribution is unlimited. / The major driver for broadband wireless communications has been reliable, high-data rate services. In wireless communication, the multipath fading constitutes a bottleneck for increasing data rates and causes performance degradation. To combat fading, we can use diversity. Wireless systems with multiple antennas at the transmitter and receiver have much larger capacity in fading channels than standard wireless systems. The objective of this thesis is to investigate the transmission scheme provided by matrix A and B in the 802.16 standard and show how it can be implemented. The research focuses on using maximal-ratio combining (MRC) to demodulate the transmitted symbols. Modifications to the existing matrix by using more frequency bands were introduced; this reduces the number of transmitting antennas and uses fewer time slots to transmit the same number of symbols. The modulator and demodulator design is also discussed. The performance of orthogonal and non-orthogonal space time codes (STC) are evaluated. / Civilian

In mobile communication channels information symbols are transmitted through a communication channel that is prone to fading and multipath propagation. At the receiver, the effect of multipath propagation is reduced by a process called channel equalization. Channel equalization relies on an accurate estimate of the channel state information (CSI). This estimate is obtained using a channel estimation algorithm. Mobile WiMAX is a recently released technology that makes use of an orthogonal frequency division multiplexing (OFDM) based physical layer to transmit information over a wireless communication channel. In this dissertation, frequency and time domain channel estimation methods typically used in classical OFDM systems, using block and comb type pilot insertion schemes, were analyzed and adopted for mobile WiMAX. Least squares (LS) and linear minimum mean square error (LMMSE) channel estimation methods were considered in the case of block type pilot insertion. In the case of comb type pilot insertion, piecewise constant, linear, spline cubic as well as discrete Wiener interpolation methods were considered. A mobile WiMAX simulation platform was developed as part of the dissertation to evaluate and compare the performance of these different channel estimation methods. It was found that the performance of the channel estimation methods, applied to a real world mobile WiMAX simulation platform, conforms to the expected performance of the corresponding classical OFDM channel estimation methods found in literature. / Dissertation (MEng)--University of Pretoria, 2009. / Electrical, Electronic and Computer Engineering / unrestricted

Aim of thesis was to acquaint with architecture and process of signal in systems using broadband LTE wireless technology. Thesis in detail is described physical layer of system. Next there is described comparison of LTE and WiMAX and table with all present systems. Thesis also is contained information about tested LTE system in real traffic. Next aim was created simulation of LTE system in downlink and uplink. Interface was created for easier configuration of each characteristics of transfer and type of interference of useful signal. This interface is contained control of whole simulation and presentation of measured values. Measured data were processed into graphs, which show dependence of error rate BER on C/N of useful and interference signal.

This paper provides theoretical analysis of LTE network and Femto cells. Its presents their modulation and transition techniques, their performance and of course implementation of Femto cells into LTE macro-layer. It also describes potential risk of interference between LTE macro-layer and Femto cells and provides the way how to solve and simulate interference. Finally it states simulation and analysis of model situations.