Subject: Re: [MOBILE-IP] 3G RAN and IP mobility

From: "Andras G. Valko" <[email-masked]>
Date: Mon, 6 Sep 1999 18:05:05 +0200

Guilhem,

There seems to be some misunderstanding concerning the difference
between 3G cellular systems and IP-based approaches such as Cellular IP
and Hawaii. GSM, GPRS and UMTS are primarily designed to provide full
coverage over very large geographical areas, such as a state. Most
operators even have legal commitment to guaranteeing a certain level of
availability in the entire service area. In these systems the single
most important design consideration is efficient use of the scarce radio
spectrum. I am not an expert in radio technology, but as far as I
understand accurate synchronization/resource management of base stations
is needed to make use of every bit over the air. This motivates tight
control over the wireless interface which is supported by a hierarchical
system and a signalling network.

Cellular IP, a research project at Columbia University (supported by
Ericsson among other industrial partners) is focused on wireless
Internet access in a different environment. A fundamental assumption
behind Cellular IP is that the requirement of tightly controlled radio
interface can be relaxed in exchange for simplicity, lower equipment
cost and increased flexibility. This means that instead of designing the
entire system around the radio interface, as is the case in existing
cellular systems, one can build a distributed system on IP principles
where the radio is just another link layer. For most current cellular
operators this is not yet an alternative, but one can imagine, for
example, wireless Internet access service in a hot spot area where the
operator can afford a best effort type approach to the radio resources.

The bottom line is that Cellular IP and Hawaii are not IP based
solutions for the same 3G problem that one could have thought of before.
They are systems built around assumptions that do not characterize
current operators today but may become realistic for some future
operators.

Regards/Andras