Making DOCSIS Suitable for LTE Backhaul
Cable Labs and Cisco are exploring ways to reduce DOCSIS latency so it can become a suitable backhaul for LTE. One trick is parallelism:
We found that traditional cable equipment suppliers were also innovating in this space and working on enabling DOCSIS to provide better mobile backhaul. Together with my colleague John Chapman, Cisco Fellow and CTO Cable Access, we came up with a simple solution that reduces the DOCSIS upstream latency to 1-2 ms consistently. We developed a proof-of-concept (PoC), each supplying expertise and resources in the mobile and CMTS space.
Looking closely, LTE and DOCSIS are two independent systems – their operations occur in serial. The overall latency is the sum of the two system latencies. The two technologies have similar mechanisms to access the channel, and that is through a request-grant-data transfer loop.
Here comes the lightbulb moment: The LTE loop is much longer than DOCSIS, resulting in much higher latency than DOCSIS. This presents a hidden opportunity for DOCSIS. Rather than waiting for the LTE transaction to complete and then start the request process on the DOCSIS side as it is today, we proposed that LTE tell DOCSIS about the data that is on its way so that the DOCSIS request process can start earlier and in parallel with the LTE transaction. This will lead to much lower overall system latency.
Read the whole thing: Powering the Future of Mobile Backhaul – CableLabs