3 ms·
When you send packets of data out of your phone, there are several layers that are added onto your IP packet. Here is a basic diagram of the different nodes in
by grogers 16y ago
When you send packets of data out of your phone, there are several layers that are added onto your IP packet. Here is a basic diagram of the different nodes in the RAN and CN and which layers they operate on:
UE<->NodeB (Uu): <your data> | PDCP | RLC | MAC | <L1 radio stuff>
NodeB<->RNC (Iub): <your data> | PDCP | RLC | MAC | FP | <L2 stuff depending on IP/ATM/etc>
RNC <-> SGSN (Iu): <your data> | GTP | UDP | IP | <L2 stuff>
SGSN <-> GGSN (Gn): <your data> | GTP | UDP | IP | <L2 stuff>
GGSN <-> Internet (Gi): <your data> (finally!)
At some points your data's UDP/TCP headers might be compressed/uncompressed but thats the basic idea. Something needs to perform the functions performed by all these nodes. "Traditionally" the femtocell is a combination of the RNC/NodeB (aka the Radio Access Network).
Clearly it is possible to add core network functionality to the femtocell, but not only is it probably not worth it, the security implications are tricky (you would have to expose your HLR directly to the internet to be able to talk to the femtocell - instead of just your SGSN, which you would likely have special CN nodes for talking to femtocells).
So it is almost guaranteed to be the former. And it makes AT&T's recommendations make alot more sense. You don't even need to assume any malice in them.
- jonah 16y agoGoogling madly ... http://en.wikipedia.org/wiki/GPRS_Core_Network http://en.wikipedia.org/wiki/GPRS_Core_Network http://en.wikipedia.org/wiki/Network_switching_subsystem http://en.wikipedia.org/wiki/Network_switching_subsystem ... OK, makes some sense now. Their recommendations make sense. It's actually nice of them to recommend using WiFi where available (though you'd hope people would be smart enough to figure that out on their own.) Looking at it from a bottleneck/financial perspective I wonder where the constraints are that cause them to want/need to limit data usage. If it's just the UE<->NodeB (Uu) bandwidth, then the femtocell addresses that and maybe they could prorate the data coming through it, if it's farther up the string then it's understandable.
- jboydyhacker 16y agoHi Grogers- Let me give a shot at paraphrasing what you just said. Essentially the data packets on your phone have routing info that requires data packets to route back to AT&Ts core network rather than going directly to the internet. For it to occur otherwise, the femtocell would have to change the routing and that would be expensive and impractical. Is that accurate? If so I'm going to update the post with that.