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Because the bandwidth usage of wireless transmission is limited, one of the major research topics in this field is to improve system throughput by supporting multiple users with limited bandwidth resources. Although there are several studies on cross-layer designs for improving system throughput, previous research on quality-of-service guarantee and fairness are relatively rare. This study proposes a cross-layer subcarrier permutation (CLSP) mechanism that uses cross-layer strategies to select suboptimal subcarriers. Service flows simulations in the IEEE 802.16e system indicate that CLSP achieved a lower delay time and a long-term fairness among multiple users. Experimental results further show that the throughput of CLSP is 28 percent higher than that of the partial usage of subchannels model using the orthogonal frequency division multiple access technique.

Mobile Worldwide Interoperability for Microwave Access networks usually provide flexible sleep-mode operations that allow mobile stations to conserve energy during sleep or active mode. For example, the IEEE 802.16e/m standard presents three power-saving classes that can be associated with different types of network connections to decrease the power consumption of mobile stations. However, previous studies failed to fully use the sleep-mode features to save energy of a mobile station while simultaneously maintaining unicast and multicast/broadcast connections. This study proposes an energy-efficient packet scheduling algorithm for both multicast and broadcast services that does not violate the QoS requirements of real-time connections. The proposed activity aggregation selection mechanism approach can minimize total power consumption of mobile stations in one cell and simultaneously satisfy the QoS of real-time connections. This method improves energy efficiency for IEEE 802.16e/m and the activity aggregation selection mechanism approach can optimize sleeping mode features to save the energy of mobile stations with overlapping connection packets The simulations in this study verified the proposed approach.(1) Default listening window: length of the default listening window.(2) Initial sleep cycle: length of the initial sleep cycle.

By referring to the object‐oriented efforts of the Multimedia and Hypermedia information coding Expert Group (MHEG), and the augmented Petri net model, we present a formal definition of the multimedia hypermedia Petri net (MHPN) model. Through this proposed model, issues of authoring, rendering and synchronization of multimedia information (i.e. structure authoring, spatial temporal relationships, user interaction, etc.) can all be laid to rest. We have implemented a testbed system, the Petri net object information system (POIS), which offers considerable potential for the development of distributed hypermedia applications. The testbed has been implemented on an IBM‐PC486 under Windows 3.1. We are now in the process of porting the testbed model to Windows NT.

In dense sensor networks, there are a large number of low-power, short-lived, low cost and unreliable sensors. A major challenge in constructing dense sensor networks is to prolong network lifetime as well as to keep low sensing coverage loss ratio. To prolong network lifetime, it is necessary to turn off redundant nodes to save energy. Moreover, to obtain low sensing coverage loss ratio is an important issue in dense sensor networks. We propose a cluster-based algorithm that can present a flexible, adjustable and energy-efficient scheme to identify redundant nodes for different requirements of network lifetime and low sensing coverage loss ratio. This algorithm needs without additional GPS and directional antennas support to identify redundant nodes. Our simulation results show that the cluster-based algorithm could save energy consumption under the process of determining redundant nodes for prolonging network lifetime, and achieve low sensing coverage loss ratio.

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