| Ad Hoc Network is a kind of peer-to-peer networks which is of no infrastructure, self-organized and fast-configurated. It consists of a great deal of self-organized nodes that cooperate with each other in creating and managing the network. In addition to the functions which nodes usually have in traditional networks, nodes in Ad Hoc networks have their exclusive capabilities of packeting and forwarding information as routers and spatial multiplexing of wireless resources. With rapid development and wide application of wireless network technologies, it has become a great demand for more and more real-time multimedia services such as voice and video service in wireless networks to support high QoS as that in wired networks. However, due to the property of being communicated in wirelesss channels and being multi-hop during communication, architecture and main technologies deployed in Ad Hoc networks are quite different. Traditional protocols and techniques which are used in guaranteeing QoS can no longer be used directly in Ad Hoc networks. It is quite necessary to design new protocols and technologies for Ad Hoc networks.According to the characters of Ad Hoc networks, key technologies which can be used to improve quality of service (QoS) are being discussed, including MAC access technologies, network topology management, routing algorithms and network resource allocation schemes.In aspect to MAC access technology, IEEE 802.11DCF protocol, widely applied in Ad Hoc network, has been studied. To solve the problem of serial unfairness in congestion environment with 802.11DCF, a new self-adaptive back-off algorithm (LDBSB) based on load detection is proposed. A new index indicating the degree of congestion of the channel is introduced in the new algorithm. According to this index, the proposed algorithm is able to adjust the contest windows to reduce original problem of unfairness, and to improve the channel access efficiency and network transmission performance.Based on a comprehensive study and a critical comparison of many topology control algorithms, a topology control algorithm named MABCLTC, which mainly meets large-scale wireless sensor network application requirements, is proposed. Details of topology establishing, data transmission and final topology maintenance in MABCLTC are also given. MABCLTC can reduce cluster head's communication energy consumption by collecting data using two tire mobile agents. In addition, MABCLTC keeps the network topology and upper level protocols stable, and avoids much energy consumption of changing other upper protocols.With respect to features of Ad Hoc routing, layered routing protocols are also discussed. A novle method PSBA(Pre-Select Based Approach)is introduced. With a threshold being set suitable, some working nodes will be selected to manage the nodes in Ad Hoc network before the cluster construction begins for all nodes. Using the PSBA, the network nodes can use the energy efficiently, and reduce data redundancy. With an appropriate threshold value, the additional cost of pre-select cluster heads can be reduced, and the lifetime of nodes is prolonged.Finally, characters of network resource allocation schemes are analyzed. Auction mechanism based on microeconomics is chosed as first mechanism to allocate network resources efficiently, and the method of using utility function as a tool to evaluate the users'satisfaction had been discussed. Based on Progressing Second Price model in microeconomics, an auction scheme using variety reserve price to allocation bandwidth resource in wirelesss network is proposed. With limited wireless bandwidth, the scheme can realize the goal of maximizing the number of satisfied the QoS of users and the throughput of network.
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