Key Support Technologies Study On HFC Network Interactive Service System

HFC network is the important infrastructure in national broadcasting television transmission. With the trend of network business integration, the use of HFC network to transmit multimedia and broadband data and carry out two-way interactive personalized business has become the urgent demand of broadcasting television area. The State Administration of Broadcasting Television opened up specialized projects to research the interactive business support technologies of HFC network, and deployed the interactive business demonstration system.Based on "design and development of Hainan two-way HFC interactive business demonstration network and terminal" project, this dissertation focused on the research of HFC network interactive business support key technologies and the main work and innovation are as follows:(1) A HFC network interactive video business traffic analysis based on Erlang B rejected model was proposed. Based on the model, Erlang formula can be used to calculate the actual bandwidth number of the interactive business, which guides the network design and reaches the lowest of the network deployment costs.(2) Multi-dimensional state space was proposed to describe network traffic when multi-service program streams converge at the network edge. Through Kaufman-Roberts recursive algorithm, multiple businesses blocking rate were calculated under bandwidth sharing circumstance. Theoretical analysis showed that the multi-service bandwidth sharing could increase bandwidth utilization by 10%.(3) A unified bandwidth allocation model was proposed through the combination of unicast and multicast technologies. Based on the model, a unicast and multicast bandwidth allocation algorithm was proposed, which adopted current network load and program popularity as determined parameters. The simulation results show that the model and algorithm can achieve a dynamic balance between bandwidth utilization and business interaction performance. In the demand peak, multicast bandwidth increases the throughput of the system. And in the low demand period, unicast bandwidth achieves the users' interaction.(4) A terminal addressing method based on the directional stream was proposed to effectively solve access problem in a real-time, stable, and easy expansion way for large-scale terminals. By combining HFC network MPEG2 protocol and IP network RTP protocol, a program flow time distribution method was proposed based on private MPEG2 table. The distribution of program flow time was applied to provide VCR operations of interactive terminal.(5) A time-shift television system terminal software module was proposed. Based on the existed MPEG2 decoder, the time-shift terminal can be implemented by software only. The software approach eliminates the hardware dependency and lowers the cost of set-top-box, and the time-shift software module can easily be integrated into any third-party set-top-box and compatible with already deployed set-top-box through a software upgrade manner. The software module has been successfully integrated into Broadcom and Philips dual-mode set-top-box.The above (1), (2), (4), (5) methods and mechanisms have been deployed in Hainan two-way HFC network interactive business model networks.