| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 50-55 |
| Abstraksi Narasi | : | A very important problem in fade countermeasure systems is the need to detect signal quality quickly and accurately. In fact, the countermeasure has to be initiated before the signal degradation effect on the bit error rate is detected by the user. This article presents an overview of different methods to evaluate signal quality, which are based on the availability of soft quantized levels of PSK demodulated signals at the receiver. It is shown that this class of methods hs a good thereotical performance. Also, an innovative procedure is presented which adapts one of the methods to some existing hardware, and tunes up a set of parameters in order to compensate for the fact the hardware is to some extent impaired. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 56-65 |
| Abstraksi Narasi | : | This article describes a proposed network architecture for both the ground and space segments of a satellite network supporting multimedia services with quality of service (QoS) guarantees. The space segment proposal is geared toward a TDMA-based satellite network comprising many nongeostationary satellites, while the ground segment proposal does not put any restriction on the satellite network. The ground segment proposal is based on the new ATM adaption layer 2 (AAL2) which we consider to have a major role to play in offering an efficient way to provide multimedia services over ATM networks. Indeed, it allows easy encapsulation of the complete set of media component sessions which forms a multimedia transaction into a single ATM virtual channel connection. An additional advantage of AAL2 is that it can run over any arbitrary slotted access system independent of the ATM format (i.e., whithout transporting the ATM cell headers). This is important for efficient interfacing of the and space segments. The space segment proposal aims at providing a robust, easily managed and controlled architecture to guarantee QoS by using a combination of connectionless and connection-oriented techniques. This is achieved by: defining a fixed logical network architecture (i.e., independent of the motion of the satellites); limiting the functionality of the switches in the sky; using adequate addresing and routing procedures. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 110-111 |
| Abstraksi Narasi | : | The intent of this article is to first present the formulation for computing the optimum soft decision metrics for decoding of convolutional codes on fading channels and then demonstrate the performance gains achieved in using optimum soft decision metrics. The optimum soft decision metrics use channel state information to account for signal strength variations due to fading. The formulation for computing the optimum soft decision metrics is given for the general case in which the statistics of the additive noise on the channel is nonstationary. However, the formulation is applied to a more simple case in which the noise is assumed to be stationary. The results indicate that at moderate signal-to-noise ratios, the 2 dB advantage usuaaly claimed for soft decision decoding over hard decision decoding on Gaussian channel is achievable on fading channels, with the rate 3/4 code used, if channel state information is incorporated in the soft decision metrics. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 66-70 |
| Abstraksi Narasi | : | This article presents an architecture for onboard ATM switching. The constraints of the space environment and the associated delays (especially with geostationary) create often conflicting requirements for the implementation of ATM via satellite. These requirements must be considered when designing onboard equipment. The article suggest that the use of MF-TDMA framing and of physical-layer scheduling as a preswitching stage for the use of standard switch fabrics onboard with additional fault tolerance and buffer mechanisms. The details of the scheduler and of the RF front end, including demodulation and demultiplexing, are presented as well as suitable switch fabrics and their performance/implementation impact. ATM is now widely consider the delivery medium for the broadband services of the future. This fact has recently attracted the attention of the satellite community. Current satellite ATM trials [1] have concentrated on trunking applications using available broadcast satellites. However, the recent U.S. FCC filings for Ka band satellites, as well as Canadian [2] and European initiatives [3], have focused on a new generation of digital regenerative multibeam onboard processing satellites. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 44-49 |
| Abstraksi Narasi | : | The exponential growth of Internet use may result in reduction of the grade of service of telecommunication networks. Capacity increase is the challenge to telecom operators. Communication satellites `see` a large customer population and provide a large amount of-mainly entertainment-information. Interactive services are possible with enhanced communication satellite systems. Such satellite concepts and technologies are the subject of this article. |
| Nama Pengarang | : | Ian F. Akyildiz, Keith L. Bernhardt, Manfred Wittig, Jim Gilderson, Jafaar Cherkaoui, Moe Rahnema, Yezdi Antia, Roy Mauger, Catherine Rosenberg, Nedo Celandroni, Erina Ferro, Francesco Potorti, Bernard Sklar, Bernard Sklar, Ian F. Akyildiz, Seong-Ho Jeong, Abdelnaser Adas, Koichi Asatani, Shinya Nogami |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 72-80 |
| Abstraksi Narasi | : | There is increasing interest in deploying ATM technology in local or campus networks. ATM is an ideal technology to overcome many of the limitations of today`s LAN technologies. This article focuses on the application of ATM in the LAN environment to interconnect high-end host computers and on the interworking of ATM-based LANs with legacy LANs. In this article, the authors introduce ATM LAN requirements, followed by a discussion of possible ATM LAN architectures to support these requirements. The article then covers standards and their relation to the possible architectures, and concludes with a discussion of current ATM LAN issues and directions. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 170-178 |
| Abstraksi Narasi | : | The Internet has fallen prey to its most succesful service, the World Wide Web. The networks do not keep up with the demands incurred by the huge amount of Web surfes. Thus, it takes longer and longer to obtain the information one wants to access via the World Wide Web. Many solutions to the problems of network congestion have been developed in distributed systems research in general and distributed file and database systems in particular. The introduction of caching and replication strategies has proven to help in many situations; therefore, these techniques are also applied to the Web. Although most problems and associated solutions are known, some circumstances are different with the Web, forcing the adaptation of known strategies. This article gives an overview about these differences and about currently deployed, developed, and evaluated solutions. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 136-140 |
| Abstraksi Narasi | : | Relativity few databases are accessible over the Internet. With today`s technology one would like to encapsulate a database and make it available over the Internet. A client using such databases would browse an old census database, look up references in an object-oriented database system, access descriptions and pictures over the Internet, or combine different information using NCSA Mosaic, Web, or back-end database middleware that enables users to effectively search, update, and combine information in distributed, heterogeneous environments. The DOK system uses security agents to maintain a DOK federation in a secure state. Different types of security agents are involved in the enforcement of security policies. Coordination agents are responsible for managing the whole federation, and delegate functions to more specific agents, called task agents. By delegating the access to information of local databases to database agents, task agents are able to control any access to a federation by using specifically designed security procedures. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 104-112 |
| Abstraksi Narasi | : | Competition in deregulated telecommunication market forces network operators to modernize their access networks-often called the `last mile` to the customer-to provide a mix of multimedia and traditional telecommunication services. Economics necessitate an evolutionary, step-by-step approach to migrate from the present access infrastructure-composed mainly of existing telephone networks and cable TV networks-to the ultimate information superhighway. At the end of the day, however, networks of different operators should provide interconnectivity for the same set of services. In this article a system concept is described that drives access network technology toward a common platform` with generic access methods, cognate routing and switching, and common, standardized communication protocols. Simulation results show some performance figures of the common platform concept. An implementation on a CATV network is presented as well. |
| Nama Pengarang | : | - |
| Nama Majalah/Jurnal | : | IEEE Communications Magazine |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 96-103 |
| Abstraksi Narasi | : | The article presents risk and techno-economic analyses of broadband access network upgrade strategies for public network operators and cable operators in a competitive environment in the residential and small business market. The effect of uncertainties in predictions of critical parameters such as demand forecast and market shares are analyzed. The assessed technology options include broadband twisted pair moderns, hybrid fiber coax networks, and ATM-based passive optical networks. |
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