Re: ip in the ran

[James Kempf <James.Kempf@Sun.COM>]

Tim,

>from the misp reqts doc
>
>>The ideal  IP access infrastructure is one where the RAN is an IP network
>where
>>base stations, base station controllers, and mobile terminals communicate
>via IP
>>protocols. There is considerable ongoing work in this area (e.g., the Open
>RAN
>>work within the MWIF). Initially, the RAN will be implemented as a link
>layer
>>between mobile terminals and the core access network; as a second stage the
>RAN
>>will become an IP-routed network
>
>Has anyone thought about routing and route table convergence in this
>scenario?  I've spoken to some colleagues that come from the legacy Internet
>space and we discussed the apparent implication of the "edge" of the routed
>cloud (from the core perspective) extending out to, say, the BTS.  It seems
>implied that one's interior routing protocol must now handle a much larger
>domain of addresses.  While I'm sure there are ways to introduce hierarchy
>into this picture and make the routing more palatable, I don't believe such
>an infrastructure has been contemplated on the legacy internet side.
>

I'm not exactly sure what the problem is here, but I don't think
this has anything to do with whether the RAN uses IP or not. 

Basically, you should be able to configure your subnet topology on
the edge with a wireless network just like you do with a wired network.
You group all radio access points under an access router and that
becomes the edge subnet for the mobiles. Whether the radio access points are 
WLAN boxes or BTSs for CDMA/GSM is not relevant. During the network
configuration, you need to arrange the mapping between access
routers and radio access points so that routing convergence is
not adversely affected.

IP RAN is strictly an L2 issue between the access router and the
radio access points. In networks that run protocols such as
wCDMA and GSM, IP acts as transport between the BTSs and the
access routers. It is possible to push IP protocols deeper
into these networks than the 3Gs currently are discussing. It
is even possible to do "smart BTSs" where the BTS does macrodiversity
resolution, but even then the stacks on the connections from the other soft
handoff legs look like:

		application IP
		wCDMA/cdma2000
		RAN IP
		
The exact implications of smart BTSs are still a research topic,
as is micromobility in this scenario. Perhaps, in the end, the smart
BTS becomes simply a transparent bridge between both the radio
and the radio frames over IP on the wire from other smart handoff 
legs.

		jak