This paper considers the channel-assignment and scheduling in wireless mesh networks that employ multiple radios and multiple channels. In contrast to the various algorithms available in the literature, we explicitly model the delay overhead that is incurred during channel switching, and use that delay in the design of algorithms. We prove that the well known Greedy Maximal Scheduling (GMS) algorithm does not have any provable efficiency ratio when the switching overhead is considered. We present a centralized algorithm (CGSSO), and a dynamic algorithm (DMSSO), both of which consider switching overhead. Simulation results show that the proposed algorithms significantly outperform other algorithms in packet throughput and average packet delay metrics. Results also show that the improvements in performance become more pronounced as the switching delay increases.

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ABSTRACT:Smartphone can not only be operated under 3G network environment anytime and anyplace but also cost less than the existing photogrammetric UAV since it provides high-resolution image, 3D location and attitude data on a real-time basis from a variety of built-in sensors. This study is aimed to assess the possibility of smartphone as a payload for photogrammetric UAV system. Prior to such assessment, a smartphone-based photogrammetric UAV system application was developed, through which real-time image, location and attitude data was obtained using smartphone under both static and dynamic conditions. Subsequently the accuracy assessment on the location and attitude data obtained and sent by this system was conducted. The smartphone images were converted into ortho-images through image triangulation. The image triangulation was conducted in accordance with presence or absence of consideration of the interior orientation (IO) parameters determined by camera calibration. In case IO parameters were taken into account in the static experiment, the results from triangulation for any smartphone type were within 1.5 pixel (RMSE), which was improved at least by 35% compared to when IO parameters were not taken into account. On the contrary, the improvement effect of considering IO parameters on accuracy in triangulation for smartphone images in dynamic experiment was not significant compared to the static experiment. It was due to the significant impact of vibration and sudden attitude change of UAV on the actuator for automatic focus control within the camera built in smartphone under the dynamic condition. This cause appears to have a negative impact on the image-based DEM generation. Considering these study findings, it is suggested that smartphone is very feasible as a payload for UAV system. It is also expected that smartphone may be loaded onto existing UAV playing direct or indirect roles significantly.

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Abstract-Increasing demand for high data-rate multimedia services has led to the emergence of high-speed data transfer features such as High-Speed Downlink Packet Access (HSDPA) for WCDMA networks. The role of the MAC-hs scheduler is vital in HSDPA in improving overall system performance. Using Opportunistic scheduling to exploit multi-user diversity for efficient transmission of best effort services or considering user fairness constraints has been the main focus of most scheduling algorithms. However the need for strict QoS support for services such as streaming, gaming, and VoIP is growing. Service operators can enforce their own policies in meeting these QoS requirements. In this paper we introduce two QoS-aware policy driven scheduling algorithms. We developed an HSDPA system in OPNET, and implemented our scheduling algorithms along with other well-known algorithms. OPNET simulations show that unlike other schedulers, our Strict and Loose Policy Scheduling (SPS and LPS) algorithms comply with the policy constraints if allowed by radio conditions and cell capacity.

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