Research And Design Of The Narrowband Return-Path Technology Base On Wired Television Network

With the process of information technology, the function of DVB which is used as a media information terminal in family is more and more important, and now DVB is toward the development of bidirectional interactive communication. Traditional bidirectional DVB sends signal back in PSTN or Ethernet network, but the disadvantages of both measures get increasing. And new bidirectional DVB sending signal back with Cable Modem technology is too expensive to use widely.Therefore, there are scholars who claim that narrowband return-path technology should be developed, and the pivot is to reconstruct HFC as a bidirectional communication network. The fact of the reconstruction work is to change the upstream channel, especially the distributing arithmetic of the upstream channel resources of HFC. And the difficulties of the reconstruction work are to implement multi-access and to deal with "the funnel noise".This paper uses the Token technology of computer local area network for reference, and designs a Token HFC network to solve both difficulties, and the tokens in this paper are divided into competitive tokens and business tokens. The first type token is used to join the virtual ring and an improved ALOHA arithmetic is proposed to deal with collisions happened when users joining the virtual ring. The second token is used to send interactive information back and an arithmetic assigning token in advance is designed after studying the characteristic of HFC, and the arithmetic can reduce the max user delay time.The performance of the token HFC network is analyzed at the end of the paper. First, it simulates and analyzes traditional ALOHA and ameliorated ALOHA and compares the simulating and analyzing result, and then the similar simulation and analysis is compared between two pre-assigning token model. The conclusion that can be educed is the token HFC network with pre-assigning token model demands band is rather narrow and the delay of user node is in a reasonable range, so the token HFC network is can be used for bidirectional DVB.