What makes cellular communication standout from other wireless technologies is its roaming ability. No matter in which country you are just dial the number and talk. This makes mobile communication truly mobile. But the technology behind is not that simple.
I was wondering how difficult will it get for an operator to maintain so many roaming agreements. A given operator may have to maintain like, say, 100 roaming agreements. Well considering LTE a given MME will have to talk to 100 different HSSs and SGW will have to communicate to 100 different PGWs. Whoa!
There is a nice way to maintain the list of PGWs based on the various APNs. MME informs the SGW which PGW it has to contact for which IMSI. The S8 interface is UDP based and DNS maintains detailed records of APN to PGW mappings. So its relatively easy to fetch a PGW and establish a tunnel for the user. But for HSS its little complicated. Now that HSS runs on diameter, there are several solutions proposed to reach home hss from visiting network. Also diameter runs on tcp or sctp which means there is always a connection established. This is quite difficult as the MME has to reach several HSS across the world. Looking forward to some interesting solutions here. Diameter relays, proxies ?
Wednesday, August 25, 2010
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For data it is very easy using IPX GR.37. for Diameter IPX providers can provide Proxy/replay functions same as used for CDMA where AAA is required unlike GPRS.
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