Q&A: The Evolution of Wireless Webinar #All-DigitalSolution
Q. How do you address latency & redundancy issues?
A. For latency, the maximum distance is determined by the modulation technology. With 4G, the maximum distance is around 20km with no loss using a digital solution over fiber. With Dali’s all-digital and software-configurable platform, the optical delay is measured and the compensation is calculated in real time. Then the delay is normalized automatically across all fibers with just a click of a button to synchronize transmission from multiple simulcast antennas. This is really important where we are trying to equalize two or more carriers in a MIMO mode to get the theoretical doubling of throughput. The 3GPP spec requires equalization to be within 65 nanoseconds, and Dali Wireless can meet this specification.
We have a number of redundancy options, because we use digital data packet. With its all-digital nature, it can provide a range of redundancy features including hot-standby host, hot-standby RF modules inside the host, hot-standby remote, secondary fiber optic link, and automatic equipment failure detection and switchover. The intelligence is incorporated in the FPGAs at the heart of our equipment.
Full redundancy is achieved by deploying a secondary host in hot-standby mode and the same can be accomplished at the remote site by deploying a secondary remote unit with optical and RF bypass kit. Fiber diversity can be implemented by deploying a secondary fiber that runs on a different path from the host to the remote unit.
Another feature that is unique to Digital DAS is the automatic equipment failure detection and switchover. In the case of primary host failure, and/or primary fiber failure, the intelligent remote unit(s) will detect a loss of signal and automatically switch to the secondary optical link and standby host. In addition, Digital DAS will automatically measure and compensate for changes in delays in the fiber connected to the remotes caused by the introduction of the secondary optical link.
Dali can incorporate all of these features in system using our hdBBI16 CPRI switch to provide a system that is tolerant of multiple faults not just single fault tolerant.
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