LTE handoff

I was reading LTE specs for a while now. I am more interested in core network of LTE. Well, iam an IP guy so my interests are in EPC. The pic below describes the LTE handoff scenario where source eNodeB knows the target eNodeB. I with my friend tried to simulate some LTE request responses. We are more interested in control plane signalling. So we picked up this call flow, removed the air interface portion and wrote a small client server programs for the rest.

This particualr call flow has both X2 and S1 interface control plane signalling. So after reading the X2AP(TS 36423-840) and S1AP(TS 36413-840) protocol specs for hours, i could finally figure out the packet structures. Then, we had to figure out SCTP stack. Since all the controlling is done on SCTP. Some google search and some test programs told me that Linux kernel version 2.6 and above have SCTP stack built in. I got the lksctp stack from source forge, complied the kernal and zoom. God, I love linux. Well you can get SCTP for Mac too and i got it in my mac. Thanks NKE SCTP!

Well we had everything in hand, SCTP sockets up and running, S1 AP and X2AP request response packets and nice ubuntu and mac pc's to write and test scripts. After couple of hours of colourful C, we had our test programs ready. Hurray!! Below is what we implemented

Next aim to implement GTP-U header!! Will take some time and lot of reading. Office is pretty relaxing these days, might help in speeding up things.

New Blog to My List

I was browsing about 3G 4G today, well i do it everyday and i landed up at a beautiful blog by Martin Sauter. He is a telecom researcher, consultant, book author and off-course a blogger based in Europe I suppose. He had written some wonderful blogs about wireless in there. Well, office was not that busy today and i could squeeze in couple of hours to read his entries. I was particularly overwhelmed with one of his post where he described all the events related wireless which happened in 2008.

Next i went on reading about LTE, which is my hot favourite these days. I am reading about X2 and S1 interfaces of LTE. Good news is that me and my friend have come with a small program which performs a handoff signalling in LTE. Its a very basic simulation. How ever we are happy that we implemented it over SCTP transport. I will post more about it soon.

I was never much into phones and stuff. I own a ipod touch , which is just brilliant. I always thought phones were just meant for talking and messaging. Just recently i have changed my mind. I had a look at Nokia N97 today. The very first look of it made me go crazy. I decided then and there, it is going to be my next phone. Well i need to wait for couple of months before i squeeze in budget for that, hopefully i will do it.

And with a beautiful kiss, movie, "The Mummy" comes to an end in HBO and i feel like lying on my bed now.