Japanese incumbent NTT announced it has developed and trialed low-latency optical access technology that helps reduce the number of optical fibers needed to accommodate base stations, especially as 5G mobile systems are rolled out.
NTT says the technology reduces data transmission latency – which is an issue when applying optical access systems to a mobile network – by making optical line terminals in the optical access system operate in coordination with the signal control by the base station aggregation unit.
The basic issue NTT is addressing here is that 5G networks will require new frequency bands and greater cell densification, resulting in an increase in the amount of fiber needed to connect base stations to base station aggregation units, as well as the number of ports in each base station aggregation unit. That’s expected to complicate network operations, including fault recovery and maintenance, which is why base stations need to be connected and operated efficiently.
According to NTT, a conventional optical access system cannot satisfy the low latency requirement demanded by the mobile network.
For conventional optical access systems, when an optical network unit receives data from a user terminal, it notifies the optical line terminal of the volume of data that it will transmit. It sends data to the optical line terminal only after it has received transmission permission. This results in higher latency.
When NTT’s low-latency optical access technology is applied, the base station aggregation unit is notified by the user terminal in advance of the volume of data that it will send. The aggregation unit in turn provides advance notification to the optical line terminal of the data volume to be sent by the user terminal. This coordination between the optical access system and the mobile system makes it possible to omit the round trip procedures used in the conventional system, thus reducing latency.
NTT says it has initiated discussions with the ITU-T about this technology for possible standardization.