With the gradual implementation of three-network combination policy in past two years, service types and quantities carried by CATV network increase fast, and users’ demand of network bandwidth and availability is becoming higher and higher. This article analyzes the service demand and key method to improve CATV network reliability, and network availability influence factors and network construction model.

Key words: MTTR CATV network, Reliability, Availability, MTBF, MTTR

Fast Increase of Service Types and Numbers Carried by CATV Network Guarantees Reliable Running of Service to Be More and More Important.

In past two years, with the development of three-network combination, users of digital network modification have been over 50%, and users of bidirectional coverage have been over 33%. Besides traditional TV and broadcasting service, CATV network carries plenty of new services, such as DTV/HDTV/Ultra HD TV, broadband data and so on. Based on above services, CATV network develops telecom value-added service, such as interactive TV (VoD, etc.) and VoIP. According to SARFT's plan, CATV network will transfer hundreds of SD, 100 sets of HD, 10 sets of 3D and tens of stereo programs in late ‘twelve five years’, which requires higher demand of network reliability and network maintenance level.

LUSTER has studied international and domestic development of network and service of Telecom and CATV for years, and presents the goal that plans, constructs, operates and maintains Telecom-level 99.99% reliability FTTx/H CATV network to fulfill service experience of users.

Competition Between Telecom Operators and CATV Operators Is Not Only the Competition of Service, But Also the Competition of Network.

High Availability and Management of Network are Extremely Important.

Compared with CATV network, Telecom network has the advantages of high quality, high reliability, wide coverage and carefully managed network. Port to port availability reaches 98% and port to port availability of optical nodes reaches 99.99%. In the planning, construction, operation and maintenance of network, there are complete standards and specifications, which guarantee open and stable operation of service and good user experience. Based on users’ demand, Telecom provides SLA (service level agreement) service, meets customers' requirements for quality level of network service and guarantees service performance and network reliability provided. For example, in dedicated access service provided by Telecom, it has defined availability, time delay, packet loss, utilization rate of bandwidth of dedicated line in SLA, which requires operators to have high level of network management and optimization.

CATV is now constructing digital and bidirectional network. CATV must seize key links of network planning and maintenance, emphasize planning and construction of network high availability and manageability, build good foundation of high-quality HD video communication service, voice service and build solid – bandwidth Internet service.

Availability Analysis of Several CATV Network Models

• Network structure is star – star – tree. No network equipment management system is adopted. Main trunk fiber has only one router. Optical node is in the field. Cable network has two-level electric amplifier.

No redundant backup in each link sets. System structure is shown as below picture.

• Optical transmission and optical amplifier both realize 1 : 1 hot backup, using optical switch to switch. Meanwhile, network structure uses loop – star – tree structure to realize main trunk router redundant backup. No network management system is adopted. System structure is shown as below picture.

• The third model adds network system and cooperating operation and maintenance system based on second model. Once fault appears, network management can find and locate timely, help operation and maintenance staff repair and recover service. Based on our assessment, by adding network management system, MTTR time of equipment and circuit can be reduced half and availability from port to port can fulfill the requirement of 99.99%.

LUSTER’s Key Measures to Realize High-reliability CATV Network

According to above analysis of network availability, CATV operators must seize below key measures, planning, constructing and maintaining 99.99% high-reliability FTTx/H network.

Network design structure: adopting FTTH or FTTB network structure, avoiding active equipment and cable being exposed outdoor.

Fiber double-router structure is adopted from headend to sub-headend. Prepare 1 + 1 hot backup for important transmitter, splitter and optical switch. Highly increase reliability of equipment and network.

In equipment's tender selection, pay attention to MTBF index of equipment and choose high-reliability equipment.

Network must have network equipment management system, cooperating with high-level operation and maintenance team, to help find, locate and clean fault timely, and decrease mean time to repair (Mean Time to Repair).