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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 |