No description available.

In this thesis, we proposed a call admission control algorithm (CAC) and an adaptive allocation of resource algorithm (AAR) for 3G wireless multimedia data transmission. The proposed CAC algorithm uses a measurement-based method by measuring real-time network load to modulate the parameters of the CAC algorithm and to decide whether to accept a call or not. When a call is admitted, the proposed AAR algorithm uses a low complexity algorithm to adaptively allocate bandwidth for the call to improve resource utilization. Taking advantages of the proposed CAC and AAR algorithms, the desired quality of service (QoS) can be maintained, the call forced termination probabilities can be reduced, and the call completion probabilities can be increased. In addition, there are a variety of types of data in 3G wireless communication networks. To set a proper priority for different data to maintain a desired QoS is important. Therefore, we also proposed a scheme to set priority for each call. On the basis of this scheme, simulation results show that the proposed CAC algorithm and the AAR algorithm can forward the call with higher priority to get relative higher QoS, and guarantee that an emergency call can go through and complete at any time in a normal situation.

An overwhelming number of models in the literature use average inter-cell interference for the calculation of capacity of a Code Division Multiple Access (CDMA) network. The advantage gained in terms of simplicity by using such models comes at the cost of rendering the exact location of a user within a cell irrelevant. We calculate the actual per-user interference and analyze the effect of user-distribution within a cell on the capacity of a CDMA network. We show that even though the capacity obtained using average interference is a good approximation to the capacity calculated using actual interference for a uniform user distribution, the deviation can be tremendously large for non-uniform user distributions. Call admission control (CAC) algorithms are responsible for efficient management of a network's resources while guaranteeing the quality of service and grade of service, i.e., accepting the maximum number of calls without affecting the quality of service of calls already present in the network. We design and implement global and local CAC algorithms, and through simulations compare their network throughput and blocking probabilities for varying mobility scenarios. We show that even though our global CAC is better at resource management, the lack of substantial gain in network throughput and exponential increase in complexity makes our optimized local CAC algorithm a much better choice for a given traffic distribution profile.

We propose a novel call admission control which makes use of ratio-based traffic measurement to estimate the required bandwidth when a new call is issued. Existing approaches fail to estimate properly the required bandwidth. To alleviate the problem, we calculate the ratio between the measured mean rate and the mean rate declared by UPC parameters. The ratio and the target cell loss rate are used to estimate the required bandwidth to make decision if a new call is accepted or rejected. Because of more accurate estimation of required bandwidth, our method can provide a better control on quality of service.

ATM (Asynchronous Transfer Mode) networks were deemed the best choice for multimedia communication. The traditional mode was replaced because ATM can provide varied traffic types and QoS (quality of service). Maintaining QoS, however, requires a flexible traffic control, including call admission control and congestion control. Traditional approaches fail to estimate the required bandwidth and cell loss rate precisely. To alleviate these problems, we employ AI methods to improve the capability of estimated bandwidth and predicted cell loss rate. This thesis aims to apply neural network techniques to ATM traffic control and consists of two parts. The first part concerns a neural-based call admission control, while the second part presents an intelligent congestion control for ATM networks. In the first part, we focus on the improvement of RBF (Radial basis function) networks and the design of a neural-based call admission control. RBF networks have been widely used for modeling a function from given input-output patterns. However, two difficulties are encountered with traditional RBF networks. One is that the initial configuration of a RBF network needs to be determined by a trial-and-error method. The other is that the performance suffers from some difficulties when the desired output has abrupt changes or constant values in certain intervals. We propose a novel approach to overcome these difficulties. New kernel functions are used for hidden nodes, and the number of nodes is determined automatically by an ART-like algorithm. Parameters and weights are initialized appropriately, and then tuned and adjusted by the gradient descent method to improve the performance of the network. Then, we employ ART-RBF networks to design and implement a call admission control. Traditional approaches fail to estimate appropriately the required bandwidth, leading to a waste of bandwidth or a high cell loss rate. To alleviate the problem, we employ ART-RBF networks to estimate the required bandwidth, and thus a new connection request can then be accepted or rejected. Because of the more accurate estimation on the required bandwidth, the proposed method can provide a better control on quality of service for ATM networks. In the second part, we propose a neural-fuzzy rate-based feedback congestion control for ATM networks. Traditional methods perform congestion control by monitoring the queue length. The source rate is decreased by a fixed rate when the queue length is greater than a predefined threshold. However, it is difficult to get a suitable rate according to the degree of traffic congestion. We employ a neural-fuzzy mechanism to control the source rate. Through learning, cell loss can be predicted from the current value and the derivative of the queue length. Then an explicit rate is calculated and the source rate is controlled appropriately. In summary, we have proposed improvements on architecture and performance of neural networks, and applied neural networks to traffic control for ATM networks. We have developed some control mechanisms which, through simulations, have been shown to be more effective than traditional methods.

The work in this thesis concerns the use of reinforcement learning solutions to re-source allocation problems in channelised cellular networks. The methodology of re-inforcement learning techniques was chosen for application to these problems due to its capability of finding efficient policies in a fully on-line, adaptable manner, without requiring specific environment models. All of the presented agent architectures are assumed to simultaneously learn and perform network control functions in a totally on-line and unsupervised manner, and agents are developed with a view to real-world implementability by focussing on techniques that have low resource requirements and make use of only local system information.

An adaptive resource reservation and handoff priority scheme, which jointly considers the characteristics from the physical, link and network layers, is proposed for a packet switching Multicode (MC)-CDMA cellular network supporting multimedia applications. A call admission region is derived for call admission control (CAC) and handoff management with the satisfaction of quality of service (QoS) requirements for all kinds of multimedia traffic, where the QoS parameters include the wireless transmission bit error rate (BER), the packet loss rate (PLR) and delay requirement. The BER requirement is guaranteed by properly arranging simultaneous packet transmissions, whereas the PLR and delay requirements are guaranteed by the proposed packet scheduling and partial packet integration scheme. To give service priority to handoff calls, a threshold-based adaptive resource reservation scheme is proposed on the basis of a practical user mobility model and a proper handoff request prediction scheme. The resource reservation scheme gives handoff calls a higher admission priority over new calls, and is designed to adjust the reservation-request time threshold adaptively according to the varying traffic load. The individual reservation requests form a common reservation pool, and handoff calls are served on a first-come-first-serve basis. By exploiting the transmission rate adaptability of video calls to the available radio resources, the resources freed from rate-adaptive high-quality video calls by service degradation can be further used to prioritize handoff calls. With the proposed resource reservation and handoff priority scheme, the dynamic properties of the system can be closely captured and a better grade of service (GoS) in terms of new call blocking and handoff call dropping probabilities(rates) can be achieved compared to other schemes in literature. Numerical results are presented to show the improvement of the GoS performance and the efficient utilization of the radio resources.

This thesis contributes toward the design of a quality-of-service (QoS) aware network layer for wireless ad hoc networks. With the lack of an infrastructure in ad hoc networks, the role of the network layer is not only to perform multihop routing between a source node and a destination node, but also to establish an end-to-end connection between communicating peers that satisfies the service level requirements of multimedia applications running on those peers. Wireless ad hoc networks represent autonomous distributed systems that are infrastructure-less, fully distributed, and multi-hop in nature. Over the last few years, wireless ad hoc networks have attracted significant attention from researchers. This has been fueled by recent technological advances in the development of multifunction and low-cost wireless communication gadgets. Wireless ad hoc networks have diverse applications spanning several domains, including military, commercial, medical, and home networks. Projections indicate that these self-organizing wireless ad hoc networks will eventually become the dominant form of the architecture of telecommunications networks in the near future. Recently, due to increasing popularity of multimedia applications, QoS support in wireless ad hoc networks has become an important yet challenging objective. The challenge lies in the need to support the heterogeneous QoS requirements (e.g., data rate, packet loss probability, and delay constraints) for multimedia applications and, at the same time, to achieve efficient radio resource utilization, taking into account user mobility and dynamics of multimedia traffic. In terms of research contributions, we first present a position-based QoS routing framework for wireless ad-hoc networks. The scheme provides QoS guarantee in terms of packet loss ratio and average end-to-end delay (or throughput) to ad hoc networks loaded with constant rate traffic. Via cross-layer design, we apply call admission control and temporary bandwidth reservation on discovered routes, taking into consideration the physical layer multi-rate capability and the medium access control (MAC) interactions such as simultaneous transmission and self interference from route members. Next, we address the network-layer resource allocation where a single-hop ad hoc network is loaded with random traffic. As a starting point, we study the behavior of the service process of the widely deployed IEEE 802.11 DCF MAC when the network is under different traffic load conditions. Our study investigates the near-memoryless behavior of the service time for IEEE 802.11 saturated single-hop ad hoc networks. We show that the number of packets successfully transmitted by any node over a time interval follows a general distribution, which is close to a Poisson distribution with an upper bounded distribution distance. We also show that the service time distribution can be approximated by the geometric distribution and illustrate that a simplified queuing system can be used efficiently as a resource allocation tool for single hop IEEE 802.11 ad hoc networks near saturation. After that, we shift our focus to providing probabilistic packet delay guarantee to multimedia users in non-saturated IEEE 802.11 single hop ad hoc networks. We propose a novel stochastic link-layer channel model to characterize the variations of the IEEE 802.11 channel service process. We use the model to calculate the effective capacity of the IEEE 802.11 channel. The channel effective capacity concept is the dual of the effective bandwidth theory. Our approach offers a tool for distributed statistical resource allocation in single hop ad hoc networks, which combines both efficient resource utilization and QoS provisioning to a certain probabilistic limit. Finally, we propose a statistical QoS routing scheme for multihop IEEE 802.11 ad hoc networks. Unlike most of QoS routing schemes in literature, the proposed scheme provides stochastic end-to-end delay guarantee, instead of average delay guarantee, to delay-sensitive bursty traffic sources. Via a cross-layer design approach, the scheme selects the routes based on a geographical on-demand ad hoc routing protocol and checks the availability of network resources by using traffic source and link-layer channel models, incorporating the IEEE 802.11 characteristics and interaction. Our scheme extends the well developed effective bandwidth theory and its dual effective capacity concept to multihop IEEE 802.11 ad hoc networks in order to achieve an efficient utilization of the shared radio channel while satisfying the end-to-end delay bound.

An adaptive resource reservation and handoff priority scheme, which jointly considers the characteristics from the physical, link and network layers, is proposed for a packet switching Multicode (MC)-CDMA cellular network supporting multimedia applications. A call admission region is derived for call admission control (CAC) and handoff management with the satisfaction of quality of service (QoS) requirements for all kinds of multimedia traffic, where the QoS parameters include the wireless transmission bit error rate (BER), the packet loss rate (PLR) and delay requirement. The BER requirement is guaranteed by properly arranging simultaneous packet transmissions, whereas the PLR and delay requirements are guaranteed by the proposed packet scheduling and partial packet integration scheme. To give service priority to handoff calls, a threshold-based adaptive resource reservation scheme is proposed on the basis of a practical user mobility model and a proper handoff request prediction scheme. The resource reservation scheme gives handoff calls a higher admission priority over new calls, and is designed to adjust the reservation-request time threshold adaptively according to the varying traffic load. The individual reservation requests form a common reservation pool, and handoff calls are served on a first-come-first-serve basis. By exploiting the transmission rate adaptability of video calls to the available radio resources, the resources freed from rate-adaptive high-quality video calls by service degradation can be further used to prioritize handoff calls. With the proposed resource reservation and handoff priority scheme, the dynamic properties of the system can be closely captured and a better grade of service (GoS) in terms of new call blocking and handoff call dropping probabilities(rates) can be achieved compared to other schemes in literature. Numerical results are presented to show the improvement of the GoS performance and the efficient utilization of the radio resources.

This thesis contributes toward the design of a quality-of-service (QoS) aware network layer for wireless ad hoc networks. With the lack of an infrastructure in ad hoc networks, the role of the network layer is not only to perform multihop routing between a source node and a destination node, but also to establish an end-to-end connection between communicating peers that satisfies the service level requirements of multimedia applications running on those peers. Wireless ad hoc networks represent autonomous distributed systems that are infrastructure-less, fully distributed, and multi-hop in nature. Over the last few years, wireless ad hoc networks have attracted significant attention from researchers. This has been fueled by recent technological advances in the development of multifunction and low-cost wireless communication gadgets. Wireless ad hoc networks have diverse applications spanning several domains, including military, commercial, medical, and home networks. Projections indicate that these self-organizing wireless ad hoc networks will eventually become the dominant form of the architecture of telecommunications networks in the near future. Recently, due to increasing popularity of multimedia applications, QoS support in wireless ad hoc networks has become an important yet challenging objective. The challenge lies in the need to support the heterogeneous QoS requirements (e.g., data rate, packet loss probability, and delay constraints) for multimedia applications and, at the same time, to achieve efficient radio resource utilization, taking into account user mobility and dynamics of multimedia traffic. In terms of research contributions, we first present a position-based QoS routing framework for wireless ad-hoc networks. The scheme provides QoS guarantee in terms of packet loss ratio and average end-to-end delay (or throughput) to ad hoc networks loaded with constant rate traffic. Via cross-layer design, we apply call admission control and temporary bandwidth reservation on discovered routes, taking into consideration the physical layer multi-rate capability and the medium access control (MAC) interactions such as simultaneous transmission and self interference from route members. Next, we address the network-layer resource allocation where a single-hop ad hoc network is loaded with random traffic. As a starting point, we study the behavior of the service process of the widely deployed IEEE 802.11 DCF MAC when the network is under different traffic load conditions. Our study investigates the near-memoryless behavior of the service time for IEEE 802.11 saturated single-hop ad hoc networks. We show that the number of packets successfully transmitted by any node over a time interval follows a general distribution, which is close to a Poisson distribution with an upper bounded distribution distance. We also show that the service time distribution can be approximated by the geometric distribution and illustrate that a simplified queuing system can be used efficiently as a resource allocation tool for single hop IEEE 802.11 ad hoc networks near saturation. After that, we shift our focus to providing probabilistic packet delay guarantee to multimedia users in non-saturated IEEE 802.11 single hop ad hoc networks. We propose a novel stochastic link-layer channel model to characterize the variations of the IEEE 802.11 channel service process. We use the model to calculate the effective capacity of the IEEE 802.11 channel. The channel effective capacity concept is the dual of the effective bandwidth theory. Our approach offers a tool for distributed statistical resource allocation in single hop ad hoc networks, which combines both efficient resource utilization and QoS provisioning to a certain probabilistic limit. Finally, we propose a statistical QoS routing scheme for multihop IEEE 802.11 ad hoc networks. Unlike most of QoS routing schemes in literature, the proposed scheme provides stochastic end-to-end delay guarantee, instead of average delay guarantee, to delay-sensitive bursty traffic sources. Via a cross-layer design approach, the scheme selects the routes based on a geographical on-demand ad hoc routing protocol and checks the availability of network resources by using traffic source and link-layer channel models, incorporating the IEEE 802.11 characteristics and interaction. Our scheme extends the well developed effective bandwidth theory and its dual effective capacity concept to multihop IEEE 802.11 ad hoc networks in order to achieve an efficient utilization of the shared radio channel while satisfying the end-to-end delay bound.