- This topic has 7 replies, 1 voice, and was last updated 10 years, 1 month ago by bill.
1st October 2010 at 05:08 #64486FedGuest
Hey guys, i have a little query, in GPRS/EDGE network if you calculate the payload at Gn layer and RLC layer we observe quite a lot of difference in the values, though the payload trend remains the same but the values differ, why their is a difference in values at Gn and RLC layers? i understand that the values cannot be same but why ??1st October 2010 at 08:17 #64487pixGuest
could you please share the values ?
RLC payload includes Gn payload + Gn header + Gb header.
On top of that, I don’t know how you compute the payload, but RLC has a retransmission mechanism. Beware not to take that into account, otherwise you would be counting twice 1 payload.
pix1st October 2010 at 13:37 #64488FedGuest
Thanks for your reply pix. Let me share that we calculate RLC payload using RLC data blocks multiplied with the block size (i hope you know the complete details, its just to give you some idea), yes we consider the retransmissions but the retransmission rate in our network is very minimal, so even if we just compare the transmitted payload (excluding retransmissions) even then it doesn’t match the Gn payload values (RLC remains higher then Gn). And can you please clarify on “RLC payload includes Gn payload + Gn header + Gb header”, you know that RLC block structure is something like RLC header + RLC data + Spare bits, so how your equation fits in this structure? i hope you got my query… i am a little new to GPRS domain so plz tolerate any stupid question 🙂1st October 2010 at 14:05 #64489pixGuest
well, could you please share the numerical values ?
you know that the PCU (equipment between the SGSN and the BSC) is segmenting the frames from the SGSN into RLC blocks.
The frames from the SGSN looks like :
Gn header + Gb header + user payload
n “RLC blocks” = n*[(Gn header + Gb header + user payload)/n]
Gn header = GTP header
Gb header = LLC hedaer
user payload = the whole IP datagram, including the IP header.
Well, just have a look to the protocol stacks of the GPRS, you’ll see all the headers 🙂
pix4th October 2010 at 08:05 #64490FedGuest
Thanks pix for your reply, numeric values are like 300MB at Gn layer and ~400MB at RLC layer… didn’t get your n formula again 🙂24th February 2011 at 11:38 #64491billGuest
u said not to incorporate retransmissions in the payload. Why is that so? the network is bearing this much of traffic? In our case we report the ‘total payload’ as ‘the payload’ and include retransmissions in it too! We have around 8% of retransmission in either direction?
regards.24th February 2011 at 18:50 #64492pixGuest
i said that if you want to know the Gn load, and if your only input is the RLC data, then….
look at the RLC volume which is transmitteed (not re-transmitted) and apply a factor to take into account all headers that were added on the path.
The RLC retransmissions were not carried over the Gn interface, so there is no reason to take them into account.
RLC retransmissions would only increase the volume carried over Ater-PS, Abis and radio interfaces.
pix28th February 2011 at 05:13 #64493billGuest
thanks, got it 🙂