• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1252-1260
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• 1999

The HFC network has a architecture of a star topology in fiber optic trunks, and tree and branch topology is used in the part of coaxial cable. It is well known that the HFC upstream channel is noisy. Ingress, common mode distortion and impulse noise exist in the upstream channel. In order to provide Quality of Service(QoS) to users with real-time data such as voice, video and interactive services, the evolving IEEE 802.14 standard for HFC networks must include an effective priority scheme. The scheme separates and resolves collisions between stations in a priority order. It is important to simulate protocols under a practical environment. The proposed algorithm in this paper is simulated with the assumption that the collision detector made certain mistake due to noises. Simulation results show that the proposed algorithm is more efficient than existing tree-based algorithm under practical environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.1004-1013
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• 2012

The legacy voice broadcast systems are used to broadcast the voice over an entire space or a specific zone. these broadcast systems generate unnecessary noise and waste of resources. In this paper, we propose a ubiquitous voice message broadcast system called uPaging, by combining the technique of location-awareness and the voice message delivery service in ubiquitous sensor network environment. In uPaging system, the wire/wireless hybrid network is used to implement the network system. Also, in order to actualize the location-awareness service, we use the Bidirectional Location ID-Exchange protocol was suggested by our previous research. the uPaging system can deliver the voice to a selected user or the location in which the user is present by this location awareness.