Simulation is a technique of growing importance and is becoming an indispensable tool applied in various academic industries, including packet networks. Simulation provides an alternative research approach to implementing a real environment, owing to its features of scalability, exibility and ease of setup. However, simulating large-scale networks can be very time and resource consuming. It can take several days to run one long simulation experiment, which may be expensive or even unaffordable. Therefore, planning simulation is important. This research proposes to plan simulation run length through predicting the required shortest run length that approximates steady-state, in the form of mathematical and logical expressions, i.e. building an analytical model. Previously related research always focused on classical models, such as the M/M/1 queue model, M/G/1 queue model, and so on. This research expands the research base to include a packet multiplexing model of homogenous sources which is widely accepted and used. This thesis investigates different traffic types (Markovian/Pareto) and different QoS parameter (delay/losses), as well as applying them to end-to-end networks. These scenarios are analysed and expressed, in terms of different desired precision level. Final results show that run length time is well predicted using the developed analytical model, which can be a guide for simulation planning in packet networks of the present and the future. This can be of great significance for performance evaluation studies.

Cooperation is seen as a means to improve the signal in OFDMA wireless networks by overcoming the inter-cell interference. Such co-operation can be deployed in both the physical layer and the MAC layer. In this thesis, a cross-layer cooperation strategy is considered. Firstly, in the physical layer, a cooperative coding scheme with private information sharing is proposed based on dirty paper coding; this is analyzed in a scenario with two transmitters and two receivers. To implement the cooperation, a rate limited link is deployed at the transmitters’ side in order to share the information. A new achievable rate region is established in both strong interference regime and weak interference regime. Secondly, in the MAC layer, a graph-based dynamic coordinated clustering scheme is proposed. An interference weighted graph is constructed to assist dynamic coordinated clustering for inter-cell interference mitigation and to improve the cell-edge user performance. Only 2 bits are allowed for the signalling exchange between transmitters and this reduces the overhead of the approach. The system throughput and cell-edge throughput with different user distributions are used to evaluate the performance. Thirdly, a transmit antenna selection algorithm is presented to optimize system performance with the constraint of fairness. A graph is generated by using the channel condition between the transmit antennas and Mobile Stations. Based on the graph, a heuristic algorithm is proposed to choose the transmit antenna for each user in order to improve the system performance and guarantee the user fairness. Finally, combining the cooperative coding scheme and cooperative clustering scheme, a cross-layer cooperation scheme is presented. In the physical layer, the cooperation coding scheme mitigates the interference and increases the transmission rate; in the MAC layer, the cooperative clustering scheme provides efficient cooperative transmission. Simulation results show that the proposed scheme can effectively increase both the system throughput and cell-edge throughput.

Mobile ad hoc networks are of growing interest because of their unique characteristics and advantages in many practical applications. QoS provision acts as a major challenge in the routing protocol design in the real-world mobile ad hoc networks, especially for the real-time services. OFDM is a new technology which has many advantages over the other modulation schemes. Because of its prominent features, many popular wireless standards have adopted it as physical layer modulation, such as IEEE 802.11 series, WiMAX, 3GPP LTE etc, and it is extended to multiuser environment known as OFDMA. So far none of the existing ad hoc routing protocols fully account for the OFDMA based mobile ad hoc networks. In this thesis, a QoS routing protocol is proposed for OFDMA based mobile ad hoc networks. A signal strength-based sub-channel allocation scheme is proposed in the routing protocol aiming to reduce the signalling overhead and cochannel interference. The performance of the proposed routing protocol is compared with other alternative proposals through simulations using OPNET simulator. Moreover, a partial time synchronization and a null subcarrier based frequency synchronization algorithms are also proposed for OFDMA based ad hoc network to further support and facilitate the proposed sub-channel allocation scheme and routing protocol.

The problem of finding a shortest TDMA is formally described as anInteger Program (IP). A brief user manual explains how the attached implementation can be used to find an optimal size TDMA for any givenWSN and routing table, fulfilling the validity criteria.

Future generation wireless networks are envisioned to provide ubiquitous networking to a wide number of mobile users, promising them the ability to access the various data networks anywhere and anytime. Such networks have motivated the research into efficient management and allocation of the wireless network's limited resources. Heterogeneity also exists amongst the subscribers, i.e. there are those who are willing to spend a little extra on their subscriptions in the prospect of obtaining a better level of service. This work proposes a framework for efficient resource management, while satisfying the heterogeneous QoS demands of the different subscribers. Part of the proposed framework was used to generate mathematical models for the purpose of analyzing the behavior of the system under two different resource management schemes. / February 2006

In wired network, there are many researches about scheduling algorithm. As for wireless network, the scheduling algorithm is not maturer than wired network. And there are some following characteristics of wireless network that we can not make use of wired scheduling algorithm directly:(1)Less bandwidth in wireless network;(2)Location dependent errors;(3)Higher error rate and bursty error. So when we design the wireless scheduling algorithm, there are some important issues we should take into account¡G (1)Fairness ; (2)QOS ; (3)Whether the overall throughput rises or not; (4)Whether the bandwidth is best utilized or not In this paper, we introduce the wired and wireless scheduling algorithm separately and discuss the advantage and disadvantage of these methods first. And we propose a scheduling algorithm which is based on WFQ [1] and dynamically adjusts weights according to the error rate of each flow. In this method, the base station will allocate the bandwidth by calculating the weight of mobile hosts and the proportion of error rates to the whole body. And during the process of adjusting, we will prevent the weight of a certain channel from increasing or decreasing excessively which might lead to unfair phenomenon. Under this adjustment, we will raise the whole throughput and maintain the fairness of all users.

Future generation wireless networks are envisioned to provide ubiquitous networking to a wide number of mobile users, promising them the ability to access the various data networks anywhere and anytime. Such networks have motivated the research into efficient management and allocation of the wireless network's limited resources. Heterogeneity also exists amongst the subscribers, i.e. there are those who are willing to spend a little extra on their subscriptions in the prospect of obtaining a better level of service. This work proposes a framework for efficient resource management, while satisfying the heterogeneous QoS demands of the different subscribers. Part of the proposed framework was used to generate mathematical models for the purpose of analyzing the behavior of the system under two different resource management schemes.

Future generation wireless networks are envisioned to provide ubiquitous networking to a wide number of mobile users, promising them the ability to access the various data networks anywhere and anytime. Such networks have motivated the research into efficient management and allocation of the wireless network's limited resources. Heterogeneity also exists amongst the subscribers, i.e. there are those who are willing to spend a little extra on their subscriptions in the prospect of obtaining a better level of service. This work proposes a framework for efficient resource management, while satisfying the heterogeneous QoS demands of the different subscribers. Part of the proposed framework was used to generate mathematical models for the purpose of analyzing the behavior of the system under two different resource management schemes.

Next generation wireless networks are expected to provide high data rate and satisfy the Quality-of-Service (QoS) constraints of the users. A significant component of achieving these goals is to increase the effi ciency of wireless networks by either optimizing current architectures or exploring new technologies which achieve that. The latter includes revisiting technologies which were previously proposed, but due to a multitude of reasons were ignored at that time. One such technology is relaying which was initially proposed in the latter half of the 1960s and then was revived in the early 2000s. In this dissertation, we study relaying in conjunction with resource allocation to increase the effi ciency of wireless networks. In this regard, we differentiate between conventional relaying and relaying with buffers. Conventional relaying is traditional relaying where the relay forwards the signal it received immediately. On the other hand, in relaying with buffers or buffer-aided relaying as it is called, the relay can store received data in its buffer and forward it later on. This gives the benefit of taking advantage of good channel conditions as the relay can only transmit when the channel conditions are good. The dissertation starts with conventional relaying and considers the problem of minimizing the total consumed power while maintaining system QoS. After upper bounding the system performance, more practical algorithms which require reduced feedback overhead are explored. Buffer-aided relaying is then considered and the joint user-and-hop scheduler is introduced which exploits multi-user diversity (MUD) and 5 multi-hop diversity (MHD) gains together in dual-hop broadcast channels. Next joint user-and-hop scheduling is extended to the shared relay channel where two source-destination pairs share a single relay. The benefits of buffer-aided relaying in the bidirectional relay channel utilizing network coding are then explored. Finally, a new transmission protocol for overlay cognitive radios is derived. This protocol utilizes relays with buffers, requires only causal knowledge of the primary's message at the secondary and incentivizes the primary to cooperate with the secondary and share its codebook.

This thesis describes simulation models for Local Multipoint Distribution Service (LMDS) systems, and uses simulation to examine the performance of two different multiple access schemes and two different duplexing schemes. LMDS is a broadband wireless point-to-multipoint access network that aims to improve network access capacity for end-users by solving the "last mile" problem. This study involves building a parameterized simulation model for symmetric LMDS systems and comparing performance of the systems for different multiple access and duplexing schemes. The report describes the LMDS system and briefly discusses other broadband access networks. Objectives of this study are discussed and methodology is chosen. The simulation model design is explained. Further, the experimental design is discussed. The simulation results are presented and discussed, and conclusions are drawn. The multiple access schemes under study are Time Division Multiple Access (TDMA), and Frequency Division Multiple Access (FDMA). The duplexing schemes under study are Time Division Duplexing (TDD), and Frequency Division Duplexing (FDD). For the system under study, it was observed that TDMA results in lower end-to-end (ETE) delay per packet, but higher jitter, than FDMA. In addition, TDD results in lower ETE delay per packet than FDD. Specifically, TDMA in conjunction with TDD was found to result in lowest ETE delay per packet among the configurations under study. In addition, FDMA in conjunction with FDD was found to result in lowest jitter among the configurations under study. / Master of Science