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Technology Stocks : Spectrum Signal Processing (SSPI) -- Ignore unavailable to you. Want to Upgrade?

To: pat mudge who wrote (2101)	12/30/1998 6:56:00 AM
From: nord	Read Replies (1) \| Respond to of 4400

comsoc.org Digital microcellular technology holds forth the promise of an alternative wireless infrastructure with more distributed intelligence and lower cost elements; The base stations are now computers, which are interconnected via fiber-optic or high-bandwidth microwave radio networks. The network provides both high bandwidth and a low-cost method of broadcast or multicast. The network switch connects the local cells into a wide-area/metropolitan-area computer network. With the arrival of asynchronous transfer mode (ATM) networking, this figure is not too far removed from the general direction in which both computer networking and digital telephony are evolving. It will be used first for in-building wireless systems, and may eventually find application in wireless extensions to fiber-to-the-curb (FTTC) telephony deployments. This alternative architecture has several advantages over the existing cellular system outlined above. These include the following characteristics. * Inexpensive switches: the switches are based on microprocessor technology and are designed to route short packets with low latency through the network. * Smart base stations: the base stations also contain microprocessors and work with nearby base stations in a distributed fashion to decide how to control power and when to trigger handoffs. * Small antennas: the usual description of a microcellular system places the base stations on top of existing utility poles. Along with reduced size comes reduced site preparation costs. * 100-m radius: the use of lower transmission power will reduce the effective radius of the cells. This also makes possible greater frequency reuse to meet increasing demand for spectrum. * Extensive handoff capability: with a more distributed control algorithm, the bottleneck in effecting handoff is no longer the central switch, but rather the capacity of the network to transmit the protocol messages. * Optimized for data channels: the system is designed from the ground up for data transmission. Voice data is only one of the many possible forms of encoded data streams that require real-time delivery guarantees. * High bandwidth (> 1 Mb/s): because of the smaller cell radii and greater frequency reuse, it should be possible to support higher data transmission rates. With spread spectrum techniques, the available bandwidth can be allocated based on the needs of particular terminals: low bandwidth for text data and high bandwidth for audio/ video data. * Digital design: a complete digital design makes it possible to embed error detection and correction capabilities throughout the system. * Dedicated control signaling: with greater terminal intelligence, the control signaling will be performed either "out of band," in dedicated control signals, or as embedded control packets within the allocated data channels. Enjoy, Norden