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If the results of the latest studies for Internet usage are to be believed, worldwide 12 million TV consumers will be using Internet protocol TV (IPTV) instead of the traditional TV broadcasting by the year 2010. These figures were published by ABI Research in 2006. Furthermore, analysts of Informa Telecoms & Media are forecasting the worldwide grow in revenue of IPTV to be ten billion dollar...
Fast lightweight encryption algorithms must be developed to satisfy the level of security and the real time constraints. However the proposed lightweight MPEG video encryption algorithms that have been proposed in the past suffer from certain drawbacks. While some of them require hardware support, the others are weak or reduce the MPEG compression ratio. The lightweight encryption algorithm called...
In this paper, we propose a QoS-promoted dynamic bandwidth allocation (Q-DBA) method to support quality-of-service (QoS) requirement services for Ethernet passive optical networks (EPON). The Q-DBA method classifies the three types of services: voice, video, and data into six priorities. It can not only satisfy QoS requirements of real-time service and but also improve the QoS of non-real-time packets...
Tuning latency and scheduling latency are two major overheads when designing medium access control (MAC) protocols for single hop passive star-coupled WDM optical network. Some schemes proposed so far has considered these two overheads, however, they cannot remove these two overheads completely, especially the overhead caused by receiver. To reduce the negative impact of tuning latency and scheduling...
Wireless local area networks (WLAN) are increasingly deployed because of the freedom wireless communications afford and the decreasing costs of the underlying technology. Together with its higher and higher popularity, the Internet has also shown more and more weakness of wireless protocols that lead to attacks. There are a lot of efforts to improve the security of wireless network (from IEEE 802...
In order to support quality of service (QoS) in 802.11 wireless LAN, current research work as well as the enhanced DCF (EDCF) defined in 802.11e standard, tends to provide differentiated services by varying the parameters of MAC protocol. In this paper, we present an analytical model for performance evaluation of these service differentiation schemes in non-saturated traffic conditions. The analytical...
We consider the provision of access point buffers in WLANs. We first demonstrate that the default use of static buffers in WLANs leads to either undesirable channel under-utilisation or unnecessary high delays, which motivates the use of dynamic buffer sizing. Although adaptive algorithms have been proposed for wired Internet, a number of fundamental new issues arise in WLANs which necessitates new...
Business models involving buyers of digital goods in the distribution process are called superdistribution schemes. We review the state-of-the art of research and application of superdistribution and propose systematic approach to market mechanisms using super-distribution and technical system architectures supporting it. The limiting conditions on such markets are of economic, legal, technical, and...
In this paper, we propose to use high altitude platforms (HAPs) for providing wireless broadband communication services in suburban and rural areas, which usually require a cost-effective and economical delivery of telecommunication services. Architectures for HAP communication systems are discussed in terms of service applications and cooperation with terrestrial and satellite systems. WiMax broadband...
In severe time dispersive channel, channel shortening equalization enables short cyclic prefix to effectively combat the inter-symbol interference, thus improving the bandwidth efficiency of OFDM system. However, for practical OFDM systems, the transmission powers of all the subcarriers may be different due to either transmission arrangement or power allocation scheme. We propose a new MMSE channel...
To realize secure access to multimedia anywhere, anytime, and with any devices, we need efficient authentication mechanisms suitable for resource-limited environments. Password authentication is regarded as one of the most widely used authentication mechanisms for its convenience, easy implementation, and user-friendliness. Up to now, many verifier-free password authentication schemes that can resist...
Recently, mobile communication system has been required to provide quality of service and multimedia service. Since the radio frequency spectrum is a precious resource, wireless radio networks need to make efficient use of it by providing high capacity for the system of interest. Time-domain and Frequency-domain spread MC DS-CDMA (TF-domain spread MC DS-CDMA) is a capacity improvement transmission...
We propose in this paper a near-optimal and reduced-complexity turbo multiuser receiver for space-time block-coded (STBC) multi-carrier code division multiple access (MC-CDMA) uplink systems over frequency selective multi-input multi-output (MIMO) fading channels. Since optimal soft-in soft-out (SISO) multiuser detector based on a posteriori probability (APP) algorithm has an exponential computational...
Spectrum sensing is crucial for the success of cognitive radio because it will guarantee service improvement to unlicensed users and avoidance of interference to licensed users. However this new radio functionality will place severe sensitivity requirement on individual radio. Local decision fusion as a low complexity method can improve the detection performance by simply increasing the number of...
In cognitive networks, power control is commonly applied to limit the interference caused by the cognitive radio to the primary userpsilas communication, while rate control seeks the way of rate adaptation that achieves the highest spectrum efficiency. In this paper, we combine these two techniques and jointly consider power and rate control in fading channels. In particular, we propose our joint...
Delay tolerant networks (DTNs) provide a promising solution to support delay tolerant applications in areas where end-to-end network connectivity is not available. In DTNs, the intermediate nodes on a communication path are expected to store, carry and forward the in-transit messages (bundles) in an opportunistic way, which is also named as opportunistic data forwarding. Opportunistic data forwarding...
Traditional backoff algorithms in WLAN extend their contention windows to resolve collisions. However, collisions may still occur due to intersecting windows among contending stations. Based on such observation, this paper puts forward a collision classification model to classify collisions into two categories and proposes an algorithm featuring collision classification resolution (CCR) to resolve...
In this paper, we present an event based visually monitoring system in a kitchen environment. The system architecture is designed for average users to access the coffee availability as well as for administrators to effectively manage and monitor the coffee pot via a web site. We capture the visual information using web cameras, detect events from the picture sequence and store these events in the...
Cognitive radio systems offer the opportunity to improve spectrum utilization while avoiding the interference to primary users. On the one hand, secondary users must be aware of the interference caused to primary users. Therefore, cognitive radio network should control their transmission power. On the other hand, the interference from primary network may degrade the performance of cognitive network...
In this paper, we analyze the allowable transmission power of cognitive radios when used as secondary users in a dynamic spectrum access network. Closed-form upper and lower bounds are derived, while accurate solutions to transmission power are available through numerical evaluation. The transmission power depends on the distance between primary and secondary transmitters as well as the number of...
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