SENIOR MEMBER, IEEE, AND SESHADRI MOHAN, MEMBER, IEEE Absrracr-The cost of a number of sequential coding search algorithms is analyzed in a systematic manner. These algorithms search code trees, and find use in data compression, error correction, and maximum likelihood sequence estimation. The cost function is made up of the size of and number of accesses to storage. It is found that algorithms that utilize sorting are much more expensive to use than those that do not; metric-first searching regimes are less efficient than breadth-first or depth-first regimes. Cost functions are evaluated using experimental data obtained from data compression and error correction studies.
We propose an auxiliary strategy, called per-user caching, for locating users who move from place to place while using Personal Communications Services (PCS). The caching strategy augments the basic location strategy proposed in existing standards such as GSM and IS-41, with the objective of reducing network signaling and database loads in exchange for increased CPU processing and memory costs. Since technology trends are driving the latter costs down, the auxiliary strategy will become increasingly attractive. The idea behind caching is to reuse the information about a called user's location for subsequent calls to that user, and is useful for those users who receive calls frequently relative to the rate at which they change registration areas. This idea attempts to explqit the spatial and temporal locality in calls received by users, similar to the idea of exploiting locality of file access in computer systems. We use a reference PCS architecture and the notion of a user's local call-to-mobility ratio (LCMR) to quantify the costs and benefits of using caching and classes of users for whom it would be beneficial. We also present two simple algorithms for estimating users' LCMR and the situation in which each is preferable. We show that under a variety of assumptions caching is likely to yield significant net benefits in terms of reduced signaling network traffic and database loads.
Using a combination of empirical data and theoretical models, this paper develops a model of user behavior for a personal communications system environment. This model is used to analyze a mobility management strategy that combines automatic updates by the users-either when they make significant moves or when they go extended periods without network interaction; multiple hysteresis in the form of dynamic registration areas and delayed updates; and a focused paging strategy that minimizes the number of pages given a constraint on the time allowed to page. Over a range of system and user parameters, the total paging and update traffic can be kept below 1 per 2000 user seconds. The impact on the user's handset is less than 10 brief updates per day. The total traffic is only a factor of three more than the minimum, immobile users case.
Source and channel coding : an algorithmic approach / by John B. Anderson, Seshadri Mohan.p. cm. --(The K1uwer international series in engineering and computer science ; SECS 150. Communications and information theory)Includes bibliographical references and index.
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