Subject: [MOBILE-IP] Some novice questions!!!

From: opamps cybernetics <[email-masked]>
Date: Fri, 4 Aug 2000 16:19:03 EST

Hi Gurus,

Sorry for asking these stupid questions:

1) What is soft handoff, hard handoff and fast handoff?

2) Is the mobile-ip already implemented in present-day consumer networks or
it is still a proposition?

3) Cellular-ip, HMIP and UMIP: Which one is better and why?

Thank you very much in advance...

Opamps

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From: Mika Ylianttila <[email-masked]>
Date: Fri, 4 Aug 2000 15:02:12 +0300

>1) What is soft handoff, hard handoff and fast handoff?

Soft and hard handoff are concepts of connection oriented (cellular)
networks. Hard handoff refers to brake-before-make type of procedure,
typical in TDMA systems. In hard handoff there is a slight gap in the
communication during handoff when the connection to old BS is closed and
the connection to new BS is established. As on opposite, soft handoff is an
make-before-brake type of procedure, typical in CDMA systems. In soft
handoff MH establish connection to new BS before braking the previous
connection.

Seamless handoff is a concept of connectienless packet networks, such as
Internet. While there can be handoffs between access points inside one
network (=micro-mobility), seamless handoff is typically used as a concept
of macro-mobility where MH moves between subnetworks. If the subnets use
same technology, handoff is referred as intra-technology (horizontal)
handoff, and when subnets have different technology, handoff is referred as
inter-technology (vertical) handoff. Micro-mobility takes usually place in
layer 2, whereas macro-mobility takes usually place in layer 3 or above.
However, current trend has been to bring micro-mobility functions to layer
3 (e.g. micro-mobility with extended Mobile IP).

Term "seamless" refers to the fact that handoff does not cause any
noticeable gap to the packet based communications (especially to real-time
communications such as Voice over IP). I guess term "fast handoff" is
basicly the same thing, meaning that he handoff happens fast enough that
the user does not notice any gap.

I hope this clariefies these concepts to you and others. I noticed that
there was a little bit confusion and mixing of concepts of soft and
seamless handoff in the Mobile IP WG sessions in Pittsburgh.

--
Mika Ylianttila
M.Sc., Research Scientist
Centre for Wireless Communications
PL 4500, Tutkijantie 2 E, FIN-90014
University of Oulu, Finland

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From: John Emmert <[email-masked]>
Date: Fri, 4 Aug 2000 09:59:09 -0500

>it is still a proposition?

Yes. Nextel offers it in the plus line of subscribers as their Nextel
Online product.

Some examples of consumer products already on the market that implement it
can be found at:

http://commerce.motorola.com/consumer/QWhtml/multi_cat.html

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From: Brijesh Kumar <[email-masked]>
Date: Fri, 4 Aug 2000 10:49:10 -0400

Hi,

A little addition to Mika Ylianttila excellent explanation.

Soft Hand off is a basic property of the CDMA systems as there is no
channel to be acquired when a device moves from one cell area to
another cell area. The actual algorithm is a lot more complex than
this simple description as the device and base stations need to
organize when it is appropriate to effect this hand over - remember
you don't have definitive road signs saying "Welcome to area XX" in
the wireless world. A device can hear from three cell controllers at
the same time each saying "Welcome to area XX". And you get into all
power computation and control algorithms in the system. In hard hand
off the device needs to acquire the new RF channel (as in CDMA or GSM
systems) and relinquish the current one. There are many techniques to
do it efficiently in cellular systems. And Hard hand off doesn't mean
that the user is going to notice it. Read any text book on wireless
systems to know more on this.

Fast handoff is a meaningless term like fast computer. What is fast?
Such wonderful terms are coined by  "Internet Experts" trying to be
"Wireless specialists". Or is it other way - I don't know ;-).

Cheers,

--brijesh
Ennovate Networks Inc.

> -----Original Message-----
> From: IP Routing for Wireless/Mobile Hosts (mobile-ip)
> [mailto:[email-masked]]On Behalf Of Mika
> Ylianttila
> Sent: Friday, August 04, 2000 8:02 AM
> To: [email-masked]
> Subject: Re: [MOBILE-IP] Some novice questions!!!
>
>