Heterogeneous wireless networks will be dominant in the next-generation wireless networks with the integration of various wireless access networks. Wireless mesh networks will become to a key technology as an economically viable solution for wide deployment of high speed, scalable and ubiquitous wireless Internet services. In this thesis, we consider an interworking architecture of wireless mesh backbone and propose an effective vertical handoff scheme between 802.11 and 802.16 wireless access networks. The proposed vertical handoff scheme aims at reducing handoff signaling overhead on the wireless backbone and providing a low handoff delay to mobile nodes. The handoff signaling procedure in different scenarios is discussed. Together with call admission control, the vertical handoff scheme directs a new call request in the 802.11 network to the 802.16 network, if the admission of the new call in the 802.11 network can degrade quality-of-service (QoS) of the existing real-time traffic flows. Simulation results demonstrate the performance of the handoff scheme with respect to signaling cost, handoff delay, and QoS support.

In recent years, the applications of wireless mesh network in the embedded systems have become more widely. It's an important issue that how to consume lower energy and transfer data stably based on energy considerations. The embedded systems must have the appropriate routing protocol for low power consumption and stable long-distance data transmission. In this paper, a routing protocol is proposed with sequential repair and backup routing protocol(Ad Hoc On-Demand Distance Vector Routing-Sequential Repair and Backup Routing Protocol, AODV-SRBR Protocol), that can reduce the number of transceivers and have a stable connection. In the proposed routing protocol, the node of network can create multi-route message through decoding the path information of packets. Using a complete routing information can reduce the number of route request packets efficiently. when the link is broken, the proposed protocol can repair the data transmission by sequential repair or select backup routing. In this paper, we implement the routing protocol to verify a multi-hop connection and data transfer in the general environment. The performance of AODV-SRBR and AODV is compared and simulated by NS2. The proposed routing protocol can achieve same transmission efficiency in the fewer route request packets, fewer maintance packets and fewer transmit and receive times according to the simulation result. By stable connection¡Blow power consumption and multi-hop data transfer, we expect that the proposed routing protocol on the embedded systems platform can be extended in large sensor mesh network.

abstract: A Fiber-Wireless (FiWi) network integrates a passive optical network (PON) with wireless mesh networks (WMNs) to provide high speed backhaul via the PON while offering the flexibility and mobility of a WMN. Generally, increasing the size of a WMN leads to higher wireless interference and longer packet delays. The partitioning of a large WMN into several smaller WMN clusters, whereby each cluster is served by an Optical Network Unit (ONU) of the PON, is examined. Existing WMN throughput-delay analysis techniques considering the mean load of the nodes at a given hop distance from a gateway (ONU) are unsuitable for the heterogeneous nodal traffic loads arising from clustering. A simple analytical queuing model that considers the individual node loads to accurately characterize the throughput-delay performance of a clustered FiWi network is introduced. The accuracy of the model is verified through extensive simulations. It is found that with sufficient PON bandwidth, clustering substantially improves the FiWi network throughput-delay performance by employing the model to examine the impact of the number of clusters on the network throughput-delay performance. Different traffic models and network designs are also studied to improve the FiWi network performance. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2015

It is well known that TCP performs poorly in wireless mesh networks. There has been intensive research in this area, but most work uses simulation as the only evaluation method; however, it is not clear whether the performance gains seen with simulation will translate into benefits on real networks. To explore this issue, we have implemented ATP (Ad-hoc Transport Protocol), a transport protocol designed specifically for wireless ad hoc networks. We have chosen ATP because it uses a radically different design from TCP and because reported results claim significant improvement over TCP. We show how ATP must be modified in order to be implemented in existing open-source wireless drivers, and we perform a comprehensive performance evaluation on mesh testbeds under different operating conditions. Our results show that the performance of ATP is highly sensitive to protocol parameters, especially the epoch timeout value. To improve its performance we design an adaptive version that utilizes a self-adjustable feedback mechanism instead of a fixed parameter. A comprehensive measurement study demonstrates the advantages of our adaptive ATP under various operating conditions. For networks with high bit-rate, low quality links, our adaptive version of ATP demonstrates an average of more than 50% gain in goodput over the default ATP for a single flow case. With respect to fairness, the adaptive ATP generally outperforms the default ATP by an order of magnitude in most results.

<p>When using Voice over IP (VoIP) in Wireless Mesh Networks the overhead induced by the IEEE 802.11 PHY and MAC layer accounts for more than 80% of the channel utilization time, while the actual payload only uses 20% of the time. As a consequence, the Voice over IP capacity is very low. To increase the channel utilization efficiency and the capacity several IP packets can be aggregated in one large packet and transmitted at once. This paper presents a new hop-by-hop IP packet aggregation scheme for Wireless Mesh Networks.</p><p>The size of the aggregation packets is a very important performance factor. Too small packets yield poor aggregation efficiency; too large packets are likely to get dropped when the channel quality is poor. Two novel distributed protocols for calculation of the optimum respectively maximum packet size are described. The first protocol assesses network load by counting the arrival rate of routing protocol probe messages and constantly measuring the signal-to-noise ratio of the channel. Thereby the optimum packet size of the current channel condition can be calculated. The second protocol, which is a simplified version of the first one, measures the signal-to-noise ratio and calculates the maximum packet size.</p><p>The latter method is implemented in the ns-2 network simulator. Performance measurements with no aggregation, a fixed maximum packet size and an adaptive maximum packet size are conducted in two different topologies. Simulation results show that packet aggregation can more than double the number of supported VoIP calls in a Wireless Mesh Network. Adaptively determining the maximum packet size is especially useful when the nodes have different distances or the channel quality is very poor. In that case, adaptive aggregation supports twice as many VoIP calls as fixed maximum packet size aggregation.</p>

Context: Wireless Mesh Network (WMN) is a form of ad-hoc network with flexible backhaul infrastructure and configuration, provides adaptive wireless internet connectivity to end users with high reliability. WMN is a wireless network consisting of mesh clients, mesh routers and gateways which are organized in a mesh topology with decentralized nature can consume more energy for data transmission. The networking performance of WMNs can be degraded due to the fact of high energy consumption for data transmission. Therefore, energy efficiency is the primary factor for attaining eminent performance. Organizing efficient routing and proper resource allocation can save huge amount of energy. Objectives: The main goal of this thesis is to reduce the energy consumption in WMNs. To do this, a new energy efficient routing algorithm is suggested. Adaptive rates based on rate allocation strategy and end to end delay metric are used mainly for optimal path selection in routing, which may in turn reduces the resource utilization and energy consumption. Method: An energy efficient routing algorithm is implemented by using the Ad hoc OnDemand Distance Vector (AODV) routing protocol. The RREQ packet in AODV is modified by adding a new field known as delay parameter which measures end to end delay between nodes. Adaptive rates obtained from Rate allocation policy are considered in the routing process to reduce energy consumption in the network. Energy measurement of the WMN and its performance is evaluated by measuring the metrics such as Throughput, End-to-End delay, Packet Delivery Ratio (PDR). For performing the simulation process, in this thesis, Network Simulator - 3 (NS-3) which is an open source discrete-event network simulator in which simulation models can be executed in C++ and Python is used. Using NetAnim-3.107 animator in NS-3-25.1, traffic flows between all the nodes are displayed. Results: The results are taken for existing algorithm and proposed algorithm for 25,50,75 and 100 nodes. Comparison of results shows that the total energy consumption is reduced for proposed algorithm for in all four scenarios. Conclusion: Energy efficient routing algorithm is implemented in different scenarios of radio access networks and energy is saved. Due to this algorithm even the performance metrics, Throughput, End-to-End delay, Packet Delivery Ratio (PDR) have shown eminent performance.

The ongoing Smart Grid (SG) initiative proposes several modifications to the existing power grid in order to better manage power demands, reduce CO2 emissions and ensure reliability through several new applications. One part of the SG initiative that is currently being implemented is the Advanced Metering Infrastructure (AMI) which provides two-way communication between the utility company and the consumers' smart meters (SMs). The AMI can be built by using a wireless mesh network which enables multi-hop communication of SMs. The AMI network enables collection of fine-grained power consumption data at frequent intervals. Such a fine-grained level poses several privacy concerns for the consumers. Eavesdroppers can capture data packets and analyze them by means of load monitoring techniques to make inferences about household activities. To prevent this, in this dissertation, we proposed several privacy-preserving protocols for the IEEE 802.11s-based AMI network, which are based on data obfuscation, fully homomorphic encryption and secure multiparty computation. Simulation results have shown that the performance of the protocols degrades as the network grows. To overcome this problem, we presented a scalable simulation framework for the evaluation of IEEE 802.11s-based AMI applications. We proposed several modifications and parameter adjustments for the network protocols being used. In addition, we integrated the Constrained Application Protocol (CoAP) into the protocol stack and proposed five novel retransmission timeout calculation functions for the CoAP in order to increase its reliability. Upon work showing that there are inconsistencies between the simulator and a testbed, we built an IEEE 802.11s- and ZigBee-based AMI testbed and measured the performance of the proposed protocols under various conditions. The testbed is accessible to the educator and researchers for the experimentation. Finally, we addressed the problem of updating SMs remotely to keep the AMI network up-to-date. To this end, we developed two secure and reliable multicast-over-broadcast protocols by making use of ciphertext-policy attribute based signcryption and random linear network coding.

Wireless Mesh Networks are increasingly becoming popular as low cost alternatives to wired networks for providing broadband access to users (the last mile connectivity). A key challenge in deploying wireless mesh networks is designing networks with sufficient capacity to meet user demands. Accordingly, researchers have explored various schemes in an effort to build high throughput mesh networks. One of the key technologies that is often employed by researchers to build high throughput wireless mesh networks (WMN) is equipping nodes with smart antennas. By exploiting the advantages of reduced interference and longer transmission paths, smart antennas have been shown to significantly increase network throughput in WMN. However, there is a need to identify and establish an upper-bound on the maximum throughput that is achievable by using smart antennas equipped WMN. Such a bound on throughput is important for several reasons, the most important of which is identifying the services that can be supported by these technologies. This thesis begins with a focus on establishing this bound. Clearly, it is evident that smart-antennas cannot increase network throughput beyond a certain limit for various reasons including the limitations imposed by existing smart an- tenna technology itself. However with the spiralling demand for broadband access, schemes must be explored that can increase network throughput beyond the limit imposed by smart antennas. An interesting and robust method to achieve this increased throughput is by en- abling multiple gateways within the network. Since, the position of these gateways within the network bears a significant influence on network performance, techniques to “opti- mally” place these gateways within the network must be evolved. The study of multiple gateway placement in multi-hop mesh networks forms the next focus of this study. This thesis ends with a discussion on further work that is necessary in this domain.

Wireless Mesh Networks are increasingly becoming popular as low cost alternatives to wired networks for providing broadband access to users (the last mile connectivity). A key challenge in deploying wireless mesh networks is designing networks with sufficient capacity to meet user demands. Accordingly, researchers have explored various schemes in an effort to build high throughput mesh networks. One of the key technologies that is often employed by researchers to build high throughput wireless mesh networks (WMN) is equipping nodes with smart antennas. By exploiting the advantages of reduced interference and longer transmission paths, smart antennas have been shown to significantly increase network throughput in WMN. However, there is a need to identify and establish an upper-bound on the maximum throughput that is achievable by using smart antennas equipped WMN. Such a bound on throughput is important for several reasons, the most important of which is identifying the services that can be supported by these technologies. This thesis begins with a focus on establishing this bound. Clearly, it is evident that smart-antennas cannot increase network throughput beyond a certain limit for various reasons including the limitations imposed by existing smart an- tenna technology itself. However with the spiralling demand for broadband access, schemes must be explored that can increase network throughput beyond the limit imposed by smart antennas. An interesting and robust method to achieve this increased throughput is by en- abling multiple gateways within the network. Since, the position of these gateways within the network bears a significant influence on network performance, techniques to “opti- mally” place these gateways within the network must be evolved. The study of multiple gateway placement in multi-hop mesh networks forms the next focus of this study. This thesis ends with a discussion on further work that is necessary in this domain.

When using Voice over IP (VoIP) in Wireless Mesh Networks the overhead induced by the IEEE 802.11 PHY and MAC layer accounts for more than 80% of the channel utilization time, while the actual payload only uses 20% of the time. As a consequence, the Voice over IP capacity is very low. To increase the channel utilization efficiency and the capacity several IP packets can be aggregated in one large packet and transmitted at once. This paper presents a new hop-by-hop IP packet aggregation scheme for Wireless Mesh Networks. The size of the aggregation packets is a very important performance factor. Too small packets yield poor aggregation efficiency; too large packets are likely to get dropped when the channel quality is poor. Two novel distributed protocols for calculation of the optimum respectively maximum packet size are described. The first protocol assesses network load by counting the arrival rate of routing protocol probe messages and constantly measuring the signal-to-noise ratio of the channel. Thereby the optimum packet size of the current channel condition can be calculated. The second protocol, which is a simplified version of the first one, measures the signal-to-noise ratio and calculates the maximum packet size. The latter method is implemented in the ns-2 network simulator. Performance measurements with no aggregation, a fixed maximum packet size and an adaptive maximum packet size are conducted in two different topologies. Simulation results show that packet aggregation can more than double the number of supported VoIP calls in a Wireless Mesh Network. Adaptively determining the maximum packet size is especially useful when the nodes have different distances or the channel quality is very poor. In that case, adaptive aggregation supports twice as many VoIP calls as fixed maximum packet size aggregation.