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From: Liang Chen
[mailto:leo.liang.chen@gmail.com] Dear Gupta, The enhanced management and regulation to the 802.11 APs could help
operators construct a more accurate map for the wireless network. [Vivek G Gupta] Yes enhanced management of 802.11 could help. But from
heterogeneous network handovers perspective one needs to think about optimal management
and selection from all radios/networks and overall benefits to users, network
operators and other players in ecosystem. That’s what 802.21 is trying to
address from handover perspective. But it might introduce extra difficulites when 802.21 systems are
widely deployed. [Vivek G Gupta] Why? Can you elaborate on these
difficulties? Sincerely yours, Liang On 11/9/05, Gupta,
Vivek G <vivek.g.gupta@intel.com>
wrote: From: stds-802-21@ieee.org
[mailto:stds-802-21@ieee.org]
On Behalf Of Liang Chen Dear all, 802.21/D00.01
draft describes an mechanism for the vertical handover decision in Sec.
6.3. With the help of networking location information boardcast in
any medium supported by 802.21, STA could aware the surrounding networks before
handover. However, I guess there are some problems in the real scenarios.
1. Due to
the cheap deployment cost of 802.11 AP, users may want to deploy the
802.11 hot-spot in their office or home independently and without the notification
to the WWAN operators. When a user moves to their home/office from
outsides, how user's STA know there is a 802.21 supporting WiFi AP from
the location information boardcast by WWAN. [Vivek G
Gupta] You are right! WiFi is a
network operating in unlicensed band and there can be many ad hoc unmanaged
installations. It's going to
be quite challenging (almost impossible) to cover all of these installations
through the Information service. However in
cases of more more managed WiFi installations, a multi-network operator, or a
multi-network IT administrator in an enterprise may be able to provide more
reliable and up to date information about public hot-spots and in general more
managed WiFi installations…ones that provide more compelling services with certain
degree of reliability etc. The user in such cases could get updates from
network operator through other wider coverage area radios and take advantage of
more opportunistic handovers to networks such as WiFi. Over a period of time
the service could cover a large number of such managed installations and some
of the other ones as well. For ad hoc unmanaged WiFi installations that are not
covered by this service the user may still have to resort to traditional
probe/scan and discover type access network specific mechanisms. Do you still
see such a service being useful? 2. How
STA locates itself in the wireless networks map? GPS may not work in-door
and increase the cost. [Vivek G
Gupta] Yes this
service does rely on location information, but believe there are several ways
of tackling this even indoors. Also emerging devices are starting to
incorporate and take advantage of "presence" in many different ways. Moreover,
I am a little confused on the different benefits of network-initiated and
MN-initiated handover mentioned in Set. 5.2. [Vivek G
Gupta] WiMax and Cellular networks support network initiated handovers wherein
the network operator may influence network selection due to a variety of
reasons in a multi-radio environment. 802.21 handover mechanisms support
co-operation between client devices and network in promoting the selection of
the most appropriate network at different times. Best
regards, -Liang
Chen
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