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The timing and headers overheads of IEEE 802.11 PHY and MAC layers consume a large part of the channel time leading to performance degradation especially at higher data rates. Several enhancements at both the PHY and MAC layers have been proposed in order to reduce these overheads and increase the channel utilization. A key enhancement is frame aggregation in which the timing and headers overheads are reduced by aggregating multiple frames into a single large frame and then transmit it in a single channel access. This paper addresses the frame aggregation techniques that have been proposed for the next generation wireless networks and the aggregation techniques that are adopted by IEEE 802.11n standard. It also highlights the aggregation issues that need to be investigated in order to further enhance the frame aggregation performance.

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A body area network is a wireless network of biomedical sensors that are attached to a human body. The aim of wireless body area network (WBAN) is to facilitate continuously recording and monitoring of a person's health condition, if needed, over a long-distance communication network. A sensing system is to be worn by the individual for a long duration. The hardware must be compact and light. This limits the size of the battery. These factors have made energy the most critical resource in WBAN and extending system lifetime has become a priority to fully realize the capabilities of WBAN. This paper presents design and system integration of WBAN technology along with issues and technical challenges of WBAN.

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Cloud computing amplifies computer security issues that have proliferated with the growth of the Internet. A broad range of security research is being applied to cloud computing. This paper gives a description of cloud computing followed by a general description of information security issues and solutions, and a brief description of issues linking cloud computing with information security. Security solutions must make a trade-off between the amount of security and its performance cost and impact on the end-user experiences. This is accentuated in a cloud computing environment where users desiring different levels of security share the same resources. An essential issue for cloud computing is the perception of security, which is beyond the simple technical details of security solutions. This paper includes a list of a few key information security challenges that also present significant research opportunities. Solving these key problems will encourage the widespread adoption of cloud computing.

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Electric Power Wheelchairs (EPWs) are becoming increasingly important in assistive technology and rehabilitation devices. Normally EPWs are controlled by a joystick. However, this may not be suitable for disabled people who lack full control of their upper-limbs. Recent advances in the control of EPWs based on electromyography (EMG) signals are able to meet the needs of users with restricted limb movement and provide high performance control. Hence, EPWs controlled by EMG signals are highly appropriate for ­elderly and disabled users. The purpose of this article is to review the state-of-the-art of EMG controlled EPWs and to present the achievements so far in this technology. A study of a variety of methods for EMG-based control in literature was studied here. Two types of control methods for EPWs, pattern recognition and hybrid recognition systems are discussed. Four major criteria are applied to compare the quality of control resulting from the use of these control methods: Accuracy of control, response time or real-time operation, robustness, and intuitiveness of control. Based on these four criteria, the use of the support vector machine classifier using features based on the time domain such as mean absolute value, waveform length, and zero crossing are suggested for the pattern recognition method. Furthermore, a combination of the pattern recognition and non-pattern recognition methods is recommended in order to increase the control commands by use of a small number of muscle positions.

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As the technology evolves, end-users are stuffed with many kinds of handheld devices along with an enormous number of interactive multimedia applications and communication functionalities. These devices consume much power, especially for displaying their services or functions. In contrast, the battery, which is the main power supplier for such devices, has a much lower capacity growth compared to the power demands. This gap has inspired many researchers to study low-power display techniques. In the mean time, there came the invention of a light emitting diode (LED) as a new backlight source for a display panel. LEDs have been adopted in the most widely used Liquid Crystal Display (LCD) system. This paper focuses on recent noticeable low-power display techniques based on LCD systems, especially associated with an LED backlight unit as its light source. We categorize these techniques into four groups: 1) low-power techniques with backlight dimming, 2) low-power techniques with dynamic voltage scaling, 3) software-based low-power techniques, and 4) hardware-based low-power techniques, and review the core of each technique briefly. Among many techniques, concurrent brightness and contrast scaling technique in a color sequential LED-backlit display system achieved the largest power saving ratio by up to 90% of the total system power with a small distortion level. As future research, it is one of important methods to combine the pros from each beneficial technique into one synergistically in the aspect of the whole system power.

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Super Junction Lateral Double-diffused MOSFET (SJ-LDMOS) is one of the important attractive devices in high-voltage integrated circuit and power integrated circuit. However, the SJ-LDMOS is generally implemented on a low-resistance substrate, which always suffers from substrate-assisted depletion (SAD) effect, which thus degrades the performance of devices. A number of literatures have been published to solve the SAD effect and improve performance. This review summarizes the developments made in SJ-LDMOS based on bulk silicon, silicon on insulator, and silicon on sapphire in the last 10 years. Finally, the future work what researchers can do on the SJ-LDMOS also has been proposed.

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Many signal processing algorithms have been proposed to enhance the quality and/or intelligibility of speech degraded by the additive background noise. In all speech enhancement algorithms the improvement in the quality and intelligibility are of utmost importance for ease and accuracy of information exchange. The speech quality and intelligibility can be quantified using subjective and objective measures. Subjective speech quality measures are obtained using listening tests in which human participants rate quality of the speech in accordance with a predetermined opinion scale. Objective quality measures predict perceived speech quality based on a computation of the numerical distance or distortion between the original and the processed speech. In this paper, several subjective and objective quality measures that determine the speech quality will be briefly discussed.

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Transactional memory (TM) is being viewed by researchers as a suitable mechanism to perform shared-memory synchronization on upcoming many-core systems. This paper provides an introductory material on TM, followed by a background of important historical work on synchronization leading to current TM research. The paper reviews recent pure hardware and hardware-software TM design proposals, and finally brings out a list of interesting open problems in this field.

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