Phil,
all,
I believe that we
can go into two possible directions here:
- Either well define the
terminology, which I believe Phil did well (although some additions are
required).
- Acknowledge the fact the some
terminology is used in other standards, reuse their meaning (like soft
handoff) and define new scenarios special to .16
networks.
I think that both
approaches will reduce possible ambiguity. The advantage of the second
approach is that people coming from different mobile world and skip the
definitions part, will not misinterpret our
terminology.
Don't know what
option is better.
Itzik.
-----Original
Message-----
From:
owner-stds-802-16-mobile@LISTSERV.IEEE.ORG
[mailto:owner-stds-802-16-mobile@LISTSERV.IEEE.ORG] On Behalf Of Phillip Barber
Sent: Monday, June 07, 2004 2:22
PM
To:
STDS-802-16-MOBILE@LISTSERV.IEEE.ORG
Subject: Re: [STDS-802-16-MOBILE]
[Handoff] Virtual Soft Handoff (Soft Switching)
This is the
mechanism I originally envisioned when devising HO methodology language and
structure in the document. Supporting this mechanism would be much
easier than re-writing the document to support a macrodiversity/synchronized
transmission Soft HO mechanism. But we should be aware that any
macrodiversity benefit will be lost using this
mechanism.
On a related note,
this is what I was talking about when discussing differentiating concept
('Soft Handoff') from the specific mechanism used to achieve that concept or
enhance reliability (pre-HO context transfer, fast-switching,
macrodiversity, etc...). The EVDO mechanism is referred to as 'Virtual
Soft Handoff' yet has no element of macrodiversity--the primary criteria
cited by the group on the June 3 conference call as defining 'Soft Handoff'
(by the way, we should be using 'handover' here, not
'handoff').
I once again
reiterate these definitions:
Hard-handover: a
handover occuring without transfer of MSS service and operating context
prior to MSS network re-entry at the new attachment
point
Soft-handover: a
handover occuring with transfer of MSS service and operating context prior
to network re-entry at the new attachment point such that the MSS
enjoys persistent context and continuity of service across
handover
Soft-handover with
macrodiversity: a handover occuring with transfer of MSS service and
operating context prior to MSS network re-entry at the new attachment point,
with two or more BS providing synchronized transmission of MSS downlink data
during the handover interval, such that the MSS enjoys persistent context
and continuity of service across handover
----- Original
Message -----
Sent:
Sunday, June 06, 2004 10:51 PM
Subject:
[STDS-802-16-MOBILE] [Handoff] Virtual Soft Handoff (Soft
Switching)
Hi,
Soft Handoff
provides gains for real-time transmission application, thus, we strongly
support it being accepted in the standard.
However, system
complexity may increase dramatically and H-ARQ may need to be turned off
to support Soft Handoff. For non-real-time transmission, the loss may
outweigh the benefit by using soft Handoff.
Therefore, in
cdma2000 1XEV-DO system, virtual soft handoff (or soft switching) is used
instead of Soft Handoff.
In virtual soft
handoff (or soft switching), only one BS in the active list with the best
pilot strength transmits at any moment.
We think it will
provide the following benefit:
1. It provides
diversity gain by allowing fast switching of data transmission from
BS to another BS.
2. It can fit
into both OFDM and OFDMA PHY layer without much
change
3. Since only BS
is transmitting at any given time, the schedule of the BS can be more
flexible and optimized than in SHO (no data synchronization issue to
worry about)
4. It can easily
support data connection with H-ARQ
5. It won't take
up additional air link capacity/resource as in SHO
case.
We would like to
propose the virtual soft handoff coexist with soft handoff in the standard
to provide more flexibility.
Any
opinion?
Best
regards,
Irving
Wang, Ph.
D.
Director,
Standards
& 3G
Technologies
ZTE San
Diego