In the random acccess procedure of LTE, to mitigate the congestion in physical random access channel, the standard adopts the Uniform backoff scheme. The backoff window size is indicated by Backoff Indicator, which is a system parameter broadcasted by eNodeB.
My question is: How does eNodeB select Backoff Indicator? Does the standard give any scheme to select Backoff inidcator?
It's a combination of busyness at eNodeB and latency in the UE signal reaching eNobeB. Here are some interesting answers:
http://tech.queryhome.com/108619/lte-what-the-back-off-indicator-there-any-significance-this
This is an interesting explanation too, giving you a scenario of three UEs simultaneously attempting to establish comms through eNobeB:
http://www.eventhelix.com/lte/random-access-procedure/lte-random-access-procedure.pdf
Also interesting is that LTE places the responsibility for determining the best backoff on the eNobeB, whereas the original shared Ethernet CSMA/CD protocol places the responsibility on the client (equivalent of LTE UE).
Dear,
Back-Off indicator field indicates time delay between PRACH and next PRACH. Based on the value received in back-off indicator sub header field, UE performs random access procedure, at times where eNB suffers from lot of traffic,at that instance if a new UE sends a preamble but enb cant give any resources then eNB ask the UE to perform the RACHing after some time.this is informed to the UE in the form of Back off indicator.based on it UE has to wait for next RAChing procedure.
- Badges
- Science topic