When decision-directed channel estimation is used for QAM-OFDM systems, the optimal filter shape depends on the amplitudes of the modulated symbols as well as the channel characteristics. In this letter we propose a s...
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When decision-directed channel estimation is used for QAM-OFDM systems, the optimal filter shape depends on the amplitudes of the modulated symbols as well as the channel characteristics. In this letter we propose a simple channel estimation method for multi-level-amplitude-modulated systems, which can effectively suppress the estimation variances with a small filter. Using the proposed method the implementation cost can be reduced and possibly better results might be obtained by avoiding the estimation bias due to large-sized filtering.
In this paper, the IEEE 802.11 multiple access control (MAC) protocol was modified for use in multi-channel, multi-hop ad hoc networks through the use of a new channel-status indicator. In particular, in the modified ...
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In this paper, the IEEE 802.11 multiple access control (MAC) protocol was modified for use in multi-channel, multi-hop ad hoc networks through the use of a new channel-status indicator. In particular, in the modified protocol, the RTS/CTS dialogue is exchanged on the common access control channel and data packets are transmitted on a selected traffic channel. We have evaluated the improvement due to the multi-channel use and we report in this paper on the results of the per-node throughput and the end-to-end delay for different network sizes. Using these results, we were able to propose a number of per-node throughput scaling laws. Our simulation results show that the per-node throughput with multiple channels for the fully connected, the line, and the grid ad hoc network topologies increases by 90% to 253%, by 47%, and by 139% to 163%, respectively, for networks with 16 to 64 nodes, as compared with that of a single channel.
Web-based applications are being more and more widely used, and electronic document safety technology is considered as an important technique to ensure the integrity of data. The traditional approaches are either inef...
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Web documents are increasingly playing an important role in our daily life, as the Internet has become a new medium for communication and commerce. So internet training become popular now and it is important to build ...
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ISBN:
(纸本)0964345692
Web documents are increasingly playing an important role in our daily life, as the Internet has become a new medium for communication and commerce. So internet training become popular now and it is important to build a web document for learning course. In this paper, we propose not only a Web document developing paradigm as well as a CSCW(computer Supported Collab.rative Works) environment with distributed course database support for instructors of a virtual university to develop and test their course materials but also a virtual course DBMS supporting the paradigm.
Due to the development of Internet, many human behaviors were adapted to the virtual world, such as commerce, education, and entertainment, etc. Distance learning will play an important role in the near future. The co...
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ISBN:
(纸本)0964345692
Due to the development of Internet, many human behaviors were adapted to the virtual world, such as commerce, education, and entertainment, etc. Distance learning will play an important role in the near future. The concepts of 3A's, which are Administration, Awareness, and Assessment, are the basic guidelines of virtual university operations. As another factor, "Authoring", is very important as well. This paper provides an E-Notebook authoring tool used by students in a virtual university environment. The E-Notebook was developed on the Web and user can do the dynamic scratching. We design a schedule-oriented methodology to achieve the utility of mobile storage. Therefore, students can edit or read their notebook anywhere any time. User can design his/her schedule on the Web to describe his/her event, time, position, and action. An agent can monitor the schedule and perform the action, such as transferring data to the indicated position. The mobile agent will choose the shortcut such as a smart message to carry user's data according to the schedule. User can read his/her data without going through a long-distance network transfer.
The signaling traffic between access managers (AMs) and home location register (HLR) are SS7 signaling messages in the personal access communication system (PACS) system. These signaling messages are for the transport...
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ISBN:
(纸本)0780336925
The signaling traffic between access managers (AMs) and home location register (HLR) are SS7 signaling messages in the personal access communication system (PACS) system. These signaling messages are for the transportation of subscriber unit (SU) registration, call origination, and call delivery, and also for authentication in these procedures. The signaling traffic is referred to mobility management traffic. In addition, the performance of mobility management traffic plays an essential role in the performance of the whole PACS system network. In this paper, we propose an M/G/1 traffic analysis on the PACS mobility traffic between AMs and HLR by using the mobile, business, and residential subscriber profiles. In addition, four performance metrics are investigated to observe the mobility characteristics with various subscriber profiles, which include waiting times at the AM and HLR average query response times, average update response times, and the expected numbers of messages per second exchanged between the AM and HLR. Finally, some observations and comments are made for the PACS system.
This volume contains the proceedings of UIC 2009, the 6th International C- ference on Ubiquitous Intelligence and Computing: Building Smart Worlds in Real and Cyber Spaces. The UIC 2009 conference was technically co-s...
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ISBN:
(数字)9783642028304
ISBN:
(纸本)9783642028298
This volume contains the proceedings of UIC 2009, the 6th International C- ference on Ubiquitous Intelligence and Computing: Building Smart Worlds in Real and Cyber Spaces. The UIC 2009 conference was technically co-sponsored by the IEEE and the IEEE computer Society Technical Committee on Scalab.e Computing. The conference was also sponsored by the Australian Centre of - cellence in information and Communication Technologies (NICTA). UIC 2009 was accompanied by six workshops on a variety of research challenges within the area of ubiquitous intelligence and computing. The conference was held in Brisbane, Australia, July 7–9, 2009. The event was the sixth meeting of this conference series. USW 2005 (First International Workshop on Ubiquitous Smart World), held in March 2005 in Taiwan, was the ?rst event in the series. This event was followed by UISW 2005 (Second International Symposium on Ubiquitous Intelligence and Smart Worlds) held in December 2005 in Japan. Since 2006, the conference has been held annually under the name UIC (International Conference on Ubiquitous Intelligence and Computing). UIC 2006 was held in September 2006 in Wuhan andThreeGorges,China,followedbyUIC2007heldinJuly2007inHongKong, and UIC 2008 held in June 2008 in Oslo, Norway. Ubiquitous sensors,computers, networksand informationare paving the way towardasmartworldinwhichcomputationalintelligenceisdistributedthrou- out the physical environment to provide reliable and relevant services to people.
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