Market
Many different services, including digital television, mobile TV and radio need highly accurate time distribution in order to operate efficiently. They use the same frequency for all transmitters in the system in order to preserve frequency spectrum and increase transmitter density for optimum coverage. In mobile TV, SFN operation is mandatory since the transmitters are closely spaced. In order to work, however, SFN requires that the transmitters be synchronized. The traditional approach has relied on costly GPS receivers co-located with every transmitter. This works, but at a very high cost in terms of many additional points of failure plus the capital cost for the GPS equipment. A better solution is to distribute time signals that are even more accurate than GPS through the same network that transports the content.
Challenges
Distributing accurate time signals to multiple locations makes SFN systems work but it’s not easy:
- GPS signals are weak and are therefore sensitive to atmospheric disturbances
- Using GPS means that the distribution of for example TV depends on a system controlled by a foreign nation which is sensitive to some countries
- Troubleshooting problems is difficult since there are two parallel systems: the content distribution system and the GPS systems. Figuring out what’s wrong with these parallel systems requires specialized expertise and uses up valuable time during network failures
- If the GPS system is knocked out there are no redundant system that can take over as backup for the time distribution
Net Insight offering
The Nimbra platform has built-in network-based time distribution system that helps you improve the reliability of your network and reduce costs at the same time. Nimbra distributes time signals at 1 pulse per second at 10 MHz to every network node. The time signals are carried with the content. You can also configure the system to broadcast time signals from multiple locations in the network to provide redundancy. It’s just as accurate as GPS but less expensive and more reliable.
The Net Insight time distribution system configures itself automatically. In the event of a network failure, it reroutes the signals as needed. If the central clock fails, it automatically fails over to a new central clock. It’s a robust, elegant solution for any SFN operator.
Network-based time distribution is available in the Nimbra 360, our compact 2U edge network chassis for multi-service implementations. The 360 supports a wide range of interfaces, including 10/100/1000 Base-T, Gigabit Ethernet, ASI, SDI, AES/EBU, E1/T1, E3/T3 and STM-1/OC3 for clients and 10/100/1000 Base-T and STM-1/4/16 for networks.
Key benefits
The major benefits of the Nimbra platform for network based time distribution are:
- Higher network reliability
- Built-in redundancy for network and central clock failures
- Eliminate multiple points of failure by removing GPS units from the picture
- Lower capital costs
- Faster and easier troubleshooting of system problems
- Easy management with automatic configuration and reconfiguration functions