Abstract-We propose an efficient centralized scheduling algorithm in IEEE 802.16 based Wireless Mesh Networks (WMN) to provide high qualified wireless multimedia services. Our algorithm takes special attention on the relay function of the mesh nodes in a transmission tree which is seldom studied in previous research. Some important design metrics, such as fairness, channel utilization and transmission delay are considered in this scheduling algorithm. IEEE 802.16 employs TDMA and the selection policy for scheduled links in a time slot will definitely impact the system performance. We evaluated the proposed algorithm with four selection criteria through extensive simulations and the results are instrumental for improving the performance of IEEE 802.16 based WMNs in terms of link scheduling. I.

Wireless mesh networks are a recent architecture for multihop wireless networks. Also, standards for realizing mesh networks are being actively developed, especially in the IEEE working groups. In contrast with mobile ad hoc networks, mesh networks consist of static nodes communicating with each other over wireless links. The static nodes are essentially wireless routers. Such networks can be used, for example to provide a cost effective alternative to a wireline Internet access network. As opposed to the nodes in mobile ad hoc networks, the nodes in mesh networks are not energy constrained and node mobility is not a concern in protocol scalability. Instead, the main technical problems relate to achieving high user data rates over multihop wireless paths by using advanced MAC/routing layer solutions. This report presents a state-of-the-art analysis of wireless mesh networks, both from the point of view of standardization and academic research activities. In the standardization, we focus on the recent developments on defining new physical layer and MAC layer standards for mesh network in the IEEE 802.11 and 802.16 working groups. At the IP layer, in addition to routing, mobility management is a key issue, and these are reviewed from the point of view of recent IETF activities in the field. In academic research, the emphasis has been on identifying feasible mechanisms that can be used to mitigate the impact of interference

Abstract—In wireless mesh networks, the end-to-end throughput of traffic flows depends on the path length, i.e., the higher the number of hops, the lower becomes the throughput. In this paper, a fair end-to-end bandwidth allocation (FEBA) algorithm is introduced to solve this problem. FEBA is implemented at the medium access control (MAC) layer of single-radio, multiple channels IEEE 802.16 mesh nodes, operated in a distributed coordinated scheduling mode. FEBA negotiates bandwidth among neighbors to assign a fair share proportional to a specified weight to each end-to-end traffic flow. This way traffic flows are served in a differentiated manner, with higher priority traffic flows being allocated more bandwidth on the average than the lower priority traffic flows. In fact, a node requests/grants bandwidth from/to its neighbors in a round-robin fashion where the amount of service depends on both the load on its different links and the priority of currently active traffic flows. If multiple channels are available, they are all shared evenly in order to increase the network capacity due to frequency reuse. The performance of FEBA is evaluated by extensive simulations. It is shown that wireless resources are shared fairly among best-effort traffic flows, while multimedia streams are provided with a differentiated service that enables quality of service. Index Terms—Access protocols, packet reservation multiaccess, scheduling, wireless LAN. I.

Current and future wireless standards use TDMA to provide guaranteed Quality-of-Service (QoS) in the network. While these standards specify how transmissions should occur, they do not discuss scheduling algorithms to find when transmissions should oc-cur (transmission schedules). Despite the technological advances, the question of finding transmission schedules has existed for the past twenty years without a satisfactory an-swer. This thesis presents a new class of scheduling algorithms for Time Division Mul-tiple Access (TDMA) wireless multihop networks. These algorithms have three major advantages. First, they take into account overhead and delay. With reduced overhead, transmission schedules have much higher throughput than what is possible with previous approaches. The algorithms can also be customized to produce schedules with specific delay properties. Scheduling to achieve a specific delay opens up a new dimension in wireless scheduling that was previously not possible. Second, the algorithms provide a simple and computationally efficient way to specify exact constraints on end-to-end flows in the network. These constraints provide us with a way to solve two important cross-layer design problems in TDMA wireless multihop networks. Third, the algorithms

the popularization rate of the wireless communication equipment is higher and higher. However, WiMax is the one of new broadband wireless technologies. It can provide high data rate, large network coverage, and different application services. When large amount of users use these applications, the network may occur transmission collision and broadcast storm. The most important factor to cause this problem is the competition of communication bandwidth by different service requests. However, due to the limitation of communication channel, the OFDMA is used in this research to divide the channel into several sub-channels and those sub-channels can be provided for different users. In this research, a channel allocation mechanism is proposed. The channel is divided into reservation and dynamic by the allocation mechanism to enhance the utilization of channel and shorten the length of minislot.

IEEE 802.16 protocol [1,2] specifies two different modes of operation. The first mode of operation is the point-to-multipoint (PMP) mode. In the PMP mode, each 802.16 access point has a dedicated broadband connection to the Internet. Wireless terminals connect to the access points on their first hop and their traffic goes to the

In this thesis proposal, we discuss the current limitations and challenges in wireless networks, especially in rural, remote or areas with rough terrains. Although traditional wireless networking technologies have already provided communication services in urban areas, they cannot satisfy the communication demands in the rural environment very well. Therefore, two new technologies—WiMAX and VANET— are proposed to solve the problems. The relay technique will be used extensively in rural networks to provide better service while keep the cost low. We show resource allocation problems in the WiMAX relay and VANET networks and the importance to solve these problems. We analyze the actual problems and propose abstract models for them. With some assumptions, we mathematically formalize some of the problems, show the hardness of the problems and suggest ideas to solve them. We also show some of our preliminary results and some other ideas for the future research. The expected research achievements are discussed for both WiMAX and VANET problems.

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Abstract — We consider the problem of centralized routing and scheduling for IEEE 802.16 mesh networks so as to provide Quality of Service (QoS) to individual real and interactive data applications. We first obtain an optimal and fair routing and scheduling policy for aggregate demands for different sourcedestination pairs. We then present scheduling algorithms which provide per flow QoS guarantees while utilizing the network resources efficiently. Our algorithms are also scalable: they do not require per flow processing and queueing and the computational requirements are modest. We have verified our algorithms via extensive simulations.

New wireless Internet applications such as telephony and video have forced the introduction of Time Division Multiple Access (TDMA) technologies (802.16 and 802.11s) that provide high reliability and guaranteed access to the wireless channel. While the wireless network technology is providing deterministic end-to-end service, the analysis tools have not matched the new technological developments. In this paper we bridge the gap. We use bottom-up analysis of spatial TDMA, starting with a given TDMA schedule, to show that spatial TDMA systems are stop-and-go queuing systems, which can be analyzed in the network calculus framework. In particular, we take advantage of the fact that stop-and-go queuing systems have relatively easy to derive service curves and derive an endto-end service curve for spatial TDMA networks. We then analyze the performance of two 802.16 mesh scheduling algorithms, by comparing the end-to-end service curves offered to their connections. With the service curve framework, the challenge becomes in the top-down analysis of wireless networks, towards scheduling algorithms that generate specific end-to-end service curves.