U.S. patent application number 11/410327 was filed with the patent office on 2006-08-31 for handover between mobile communication networks.
This patent application is currently assigned to NEC Corporation. Invention is credited to David Cooper.
Application Number | 20060194582 11/410327 |
Document ID | / |
Family ID | 10854881 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060194582 |
Kind Code |
A1 |
Cooper; David |
August 31, 2006 |
Handover between mobile communication networks
Abstract
The invention provides a method of handover from an active
network to a selected one of a plurality of potential other
networks. In addition to the overall solution, the solution
proposed has several individual aspects. All subsidiary aspects are
related to the common problem mentioned above and sharing the
underlying common solution concept of implementing a system in
which selective handover is possible and in which a list of
available other networks provided by an active network can be
handled and selection made by a terminal, so that neighbor cell
information can be transmitted based on expressed terminal
preferences.
Inventors: |
Cooper; David; (Surrey,
GB) |
Correspondence
Address: |
SCULLY SCOTT MURPHY & PRESSER, PC
400 GARDEN CITY PLAZA
SUITE 300
GARDEN CITY
NY
11530
US
|
Assignee: |
NEC Corporation
Tokyo
JP
|
Family ID: |
10854881 |
Appl. No.: |
11/410327 |
Filed: |
April 24, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09589217 |
Jun 7, 2000 |
|
|
|
11410327 |
Apr 24, 2006 |
|
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Current U.S.
Class: |
455/436 |
Current CPC
Class: |
H04W 36/0061 20130101;
H04W 8/205 20130101; H04W 36/14 20130101 |
Class at
Publication: |
455/436 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 1999 |
GB |
9913218.5 |
Claims
1. A method of facilitating handover from an active network with
which User Equipment is in communication to another network, the
method comprising the steps of: providing a list of available other
networks to said User Equipment via the active network; in the User
Equipment, selecting among the available networks based on
preference information and signalling to said active network at
least one preferred other network; and providing neighbor cell
information for the at least one preferred other network to said
User Equipment via the active network.
2. A method of facilitating handover from an active network with
which User Equipment is in communication to another network, the
method comprising a step of providing to User Equipment
communicating via the active network a list of available other
networks.
3. (canceled)
4. A method of operating User Equipment capable of handover between
an active network and another network comprising a step of storing
in the User Equipment a list of available networks based on
information supplied by the active network with which the User
Equipment is in communication.
5. (canceled)
6. A method according to claim 2 further comprising a step of
sending a message to the User Equipment containing information for
incrementally adding to or subtracting from the list of available
networks.
7. A method of operating an active network to facilitate handover
to another network comprising a step of providing to User Equipment
communicating via the active network a message containing
information for incrementally adding to or subtracting from a
stored list of available networks.
8-10. (canceled)
11. A method of operating an active network with which User
Equipment is in communication comprising a step of sending neighbor
cell information to User Equipment based on network preferences
communicated by the User Equipment.
12. A method according to claim 11 comprising a step of sending
mutually different neighbor cell information to mutually different
User Equipments based on mutually different network
preferences.
13. A method according to claim 1, wherein the preferred other
network is selected based on information stored in the User
Equipment, preferably in a SIM card.
14. A method according to claim 1, wherein the active network is a
UMTS network and the other network is selected from available GSM
networks.
15. A method according to claim 1, wherein the active network is
provided by an active network provider and the other network is
selected from networks provided by other network providers.
16-18. (canceled)
19. User Equipment for a mobile communications system capable of
handover from an active network with which User Equipment is in
communication to another network comprising means for signalling a
preferred other network to the active network during a call.
20-21. (canceled)
22. A mobile communications network or component thereof including
means for communicating to User Equipment communicating with the
network a list of available other networks.
23. A mobile communications network or component thereof according
to claim 22 having means for sending a message to me User Equipment
containing information for incrementally adding to or subtracting
from the list of available networks.
24. A mobile communications network or component thereof including
means for sending a message to User Equipment containing
information for incrementally adding to or subtracting from a list
of available networks stored in the User Equipment.
25. (canceled)
26. A mobile communications network or component thereof including
means for sending neighbor cell information to User Equipment based
on network preferences communicated by the User Equipment.
27. A mobile communications network or component thereof according
to claim 26 arranged to send mutually different neighbor cell
information to mutually different User Equipments based on mutually
different network preferences.
28. A system for facilitating handover from an active network with
which User Equipment is in communication to another network, the
system comprising: means for providing a first list including at
least one unique network identifier to a user equipment via an
active network; and means for comparing the provided first list
with a second list internally stored in the user equipment, the
second list containing at least one unique network identifier, and
the comparing means being provided in the user equipment.
29. A method for facilitating handover from an active network with
which User Equipment is in communication to another network, the
method comprising: providing a first list including at least one
unique network identifier to a user equipment via an active
network; and comparing the provided first list with a second list
internally stored in the user equipment, the second list containing
at least one unique network identifier, and the comparing being
performed in the user equipment.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is concerned with handover of a call
between mobile communication networks. The present invention is
particularly concerned with handover between UMTS networks and GSM
networks but is also applicable to handover between different GSM
networks and different cellular mobile communication networks
generally.
[0003] 2. Description of the Related Art
[0004] In current GSM systems, it is possible for a user to select
manually among a plurality of available GSM networks when a mobile
device (User Equipment) is off line. It is also possible for the
User Equipment to select a network automatically from among the
available networks based on preferences stored in the User
Equipment, normally in the SIM card. However, when a call is in
progress, this selection is not possible. In the present
specification, the term User Equipment is intended to encompass any
equipment capable of communicating with a network; this will
typically be a mobile telephone, but may be, for example, a
dedicated data, facsimile, E-mail or video communication device or
combination device.
[0005] During call progress, the majority of the User Equipment's
radio resource are involved in the active call and so it is not
possible to scan broadly for available networks. To enable a mobile
device to move between cells, while a call is in progress, the
network supplies a limited list of adjacent cells, normally
confined to cells provided by the same network provider and permits
the mobile device to make limited investigation of signal strength
from the neighboring cells. In the event that the mobile device
finds a stronger signal from another cell, it can signal a change
to the other cell.
[0006] According to above prior method, it is not impossible to
hand over between mobile communication networks while call is in
progress.
[0007] It has been appreciated that it would be desirable to enable
User Equipment to select a preferred one of a plurality of
available networks while a call is in progress. This would be
particularly beneficial when handing over from a UMTS network to a
selected GSM network', but would also be useful, particularly when
traveling outside the User Equipment's home network territory, to
enable handover between preferred "foreign" networks.
[0008] It has been appreciated that, although this is not normally
done, it would be possible for an active network to supply a list
of cells not only belonging to the active network, but also
including cells of other network providers. This potentially offers
a solution to the problem mentioned above, and may be provided
independently in an aspect of the invention.
[0009] However, to implement the system, the network provider would
have to supply a significant amount of information concerning other
network providers' cells. Therefore, the above mentioned potential
solution has the attendant problem that the list of available cells
may become too large in practical terms for the User Equipment
to
investigate during an active call, and this may degrade performance
of the network. This solution may therefore be undesirable for many
network providers.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention is to provide a
method capable of handing over between mobile communication
networks while call is in progress.
[0011] Pursuant to the invention, an improved solution has been
proposed. According to the first main aspect of the invention, the
invention provides a method of facilitating handover from an active
network with which User Equipment is in communication to another
network. According to the present invention, the active network
provides a list of available other networks to the User Equipment.
User Equipment selects among the available networks based on
preference information and signals to the active network at least
one preferred other network. The active network provides neighbor
cell information for the at least one preferred other network to
the User Equipment.
[0012] In this way, the User Equipment may signal a preferred
network to the active network and then the active network may
transmit cell information for only the preferred network(s) to that
User Equipment.
[0013] The preference information may be stored in the User
Equipment, preferably in the SIM card. The preference information
may include a list of networks which are "black listed" with which
the User Equipment is not able to connect. The preference
information may also include a list of networks which are "white
listed" with which communication is preferred. The white list may
include partner networks of the home network provider. The
preference information may include an explicit "gray list" of
networks which are to be tried in the absence of a "white listed"
network; alternatively, networks which are not explicitly in the
white list or black list may be deemed to be in the gray list.
Multiple levels of preference may be stored. Preferably, the method
includes storing in the User Equipment a list of available networks
based on information supplied by the active network. This feature,
using information supplied by a network rather than that obtained
by a (relatively lengthy) search performed by the User Equipment,
offers advantages.
[0014] The method may include incrementally adding to or deleting
from the list of available networks stored in the User Equipment.
This feature avoids the need to re-transmit a complete list,
thereby allowing shorter messages to be used.
[0015] Using the method of claim 1, it becomes possible for a
network to send different neighbor cell information to different
terminals (User Equipment), based on preferences expressed by the
terminals and not solely dependent on the area in which the
terminals are located.
[0016] The signalling of available networks by an active network,
the first step in the method of claim 1, is of itself a useful step
as it provides a terminal with information concerning available
networks without the terminal having to search.
[0017] The signalling by a terminal to an active network with which
the terminal is in communication of a preferred (other) network
(effectively the second step in the method of claim 1) in itself
provides useful information to the active network.
[0018] The invention extends to methods of operating terminals and
to methods of operating networks, terminals and network for
implementing any the above aspects.
[0019] In a first preferred implementation, the active network is a
UMTS network and the list of available networks comprises a list of
available GSM networks. This implementation facilitates handover
from UMTS to a selected GSM network.
[0020] In a second implementation, the active network is a GSM
network (or a UMTS network) provided by an active network provider
and the list of available networks comprises a list of other GSM
networks (or UMTS networks) provided by other network providers.
This facilitates handover within a communication system between
network providers.
[0021] The above and other objects, features and advantages of the
present invention will become apparent from the following
description with reference to the accompanying drawings which
illustrate examples of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a flowchart showing a processing of the first
embodiment according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] An embodiment of the invention will now be described, by way
of example.
[0024] By way of explanation, we will describe in general terms,
the elements of a practical implementation of a handover system
embodying several of the above aspects and advantageous features.
The following applies to both handover between networks of a
similar type (e.g. GSM) belonging to different network providers,
or between networks--of differing types (e.g. UMTS to GSM), unless
otherwise stated. Indeed, in certain applications it may be
possible to select between multiple networks of multiple types, for
example GSM 900, GSM 1900, UMTS and local coverage networks.
[0025] Features of User Equipment
[0026] In addition to "standard" user equipment features, for
communicating with the networks between which handover is to be
performed (for a UMTS to GSM handover, this requires a dual mode
terminal), the user equipment should ideally have the following
components:--
[0027] A store for a list of network preferences.
[0028] This may be based on an existing store, preferably in the
SIM card (which term as used in this specification is intended to
encompass any removable device which is used to configure a
standard handset), and will normally be at least partially
pre-programmed by the home network provider. The equipment may be
configured to allow the user to edit at least part of this list,
for example by adding networks or modifying preference levels.
[0029] In particular, where a network provider has two or more
partner networks in a given (foreign) country and the charges vary
(either permanently or from time to time) between networks, the
user (or the network provider) may update the preference list so
that the cheaper network is always preferred. The preference list
may simply be binary, 0 for never use ("blacklisted"), 1 for use if
possible ("white listed"), unlisted networks being used if a
network annotated 1 is not found. Alternatively, multiple levels
may be stored; this facilitates differentiation on the basis of
pricing. If multiple levels are used, the home network may be given
a unique, highest, preference. If only two or a few levels are
provided, the home network may nonetheless be specifically marked,
if desired. Although it is greatly preferred to store the
preferences, the user may be prompted to select all alternative
network on demand; this will normally be inconvenient during a
voice call, but may be more acceptable in a data communication
application. The order in which the networks are listed may or may
not be significant; if it is, even in a binary system, the order of
networks within the stored list may be used to designate preference
and all white listed networks may be ranked in order. Thus, in the
selecting step, the User Equipment may be arranged to find the
first white listed available network.
[0030] Means for Receiving and Interpreting a Message Specifying
Available Networks.
[0031] The User Equipment must be able to interpret a special
message sent during an active call from the active network listing
possible handover networks. This may be based on existing
facilities for interpreting messages during a call, the special
message being identified by a special prefix or identifier agreed
with the network. It is to be noted that it may only be possible to
perform preferential handover from certain networks but not others,
particularly where certain networks are not configured to provide
special messages identifying neighboring networks. For example, in
the case of UMTS to GSM handover, the UMTS network may be arranged
to provide a list of candidate GSM networks, but, when attempting
to hand back to UMTS from a GSM network, or when attempting to hand
over between at least certain GSM networks, this may not be
possible as the GSM network(s) may not be adapted to provide lists
of candidate networks.
[0032] Means for Maintaining List of Available Networks.
[0033] Preferably, the User Equipment is able, in addition to (or
instead of) receiving a complete list of available networks, to
receive and interpret messages specifying incremental addition or
deletion of networks from the current list of available networks.
In this way, a complete list of available networks may be built up
in the User Equipment by a series of "ADD" messages, rather than by
transmitting a complete list. This feature is particularly
desirable in regions where there are a number of networks from
which to choose and the availability of each network changes from
place to place frequently, as it avoids the need to re-transmit a
long list each time one network becomes or ceases to be
available.
[0034] Means for Requesting a List of Available Networks.
[0035] The network may be arranged to transmit available network
information regularly or when the network determines that handover
is desirable (for example when the received signal becomes weak).
However, preferably, the User Equipment is able specifically to
request this information; this may be achieved in a similar manner
to the conventional manner for User Equipment to send a handover,
but using a message identifier agreed with the network as
signifying a request for available networks.
[0036] Means for Comparing the List of Available Networks to the
List of Preferences and Selecting a Network.
[0037] This may be achieved simply by searching for each available
network in the list of preferences and returning the one (or top
several) with the highest preference. Where more than one available
network has an equal top preference, the User Equipment may select
several in turn and then, following receipt of radio cell
information, select the network with the strongest signal.
Alternatively, other criteria may be provided.
[0038] Means for Signalling the Preferred Network.
[0039] This may be achieved simply by sending a message with an
identifier agreed with the network to signify a network
selection.
[0040] Thereafter, the network would supply neighbor cell
information for the selected network(s) in a similar manner to that
presently used to enable cell-to-cell handover and the User
Equipment would treat this cell information (radio frequencies,
time slots codes, etc.) in the same way to find the most suitable
handover candidate.
[0041] Features of Network
[0042] In addition to "standard" network parameters, a network
should implement the following features:-- [0043] Store of list of
available other networks.
[0044] This list varies from point to point, so it is conveniently
stored at each base station or radio access point. This may be
based on stored information, obtained either based on knowledge of
other networks in the area and predicted coverage, or based on
empirical data, for example obtained by scanning for radio coverage
throughout he region covered by a cell, or by fixed receivers
located at the access point and surrounding access points. Normally
the network will not know the position of the User Equipment to
much better than 1 cell accuracy (although, by triangulation from
other cells in the network, accurate positioning is possible;
alternatively, a rough idea of direction within the cell may be
obtained), so the list of potentially available networks may
include all networks receivable at any point within the cell. If
the list omits certain networks which are in fact available, then
handover to those networks will not be possible, so it is desirable
to include more rather than fewer in the list. However, where too
many networks are included, efficiency will be degraded, as the
User Equipment may be instructed to search for an "available"
network which is in fact not available. It may be possible to
update the list dynamically, based on information returned from
User Equipment concerning availability of networks.
[0045] For each available network, corresponding neighbor cell
information (frequencies, time slots etc.) should be stored.
[0046] The network is configured to send and respond to messages
described above in relation to the User Equipment. Thus, in a
practical example, processing steps and exchange of messages are
shown in FIG. 1. At step 101, User Equipment determines handover
required and request available networks. At step 102, the active
network looks up list of available networks and transmits the list
to the User Equipment. At step 103, User Equipment compares the
list to preferences, selects preferred network and signals the
preferred network to the active network. At step 104, the active
network looks up cell information for preferred network and signals
neighbor cell information to the User Equipment. At step 105, the
User Equipment searches for cell availability, determines cell and
network and signals handover to specific cell. Finally, at step
106, handover to new network is implemented.
[0047] 2nd Embodiment;
[0048] The first embodiment above deals with transmission of a
complete list of available networks in response to a specific
request. The following second embodiment deals in particular with
incremental updating of the list of available networks, and these
details may be used in other contexts (not only in the UMTS to GSM
handover case in which it is explained), for example in GSM to GSM
handover.
[0049] Application to UMTS to GSM Handover
[0050] Three novel signaling procedures arc proposed as below. All
these procedures rely on local interaction between the dual mode
terminal and the UTRAN, with no involvement of the VLR or core
network.
[0051] We will assume that while a dual mode terminal has a call in
progress, it maintains a list of potential GSM handover candidates
{G1, G2, G3, . . . } (which may contain no entries if no potential
GSM handover candidate is available). At any time it also has a
preferred candidate Gpref which is a member of {G1, G2, G3, . . .
}. This proposal describes signalling means whereby this list is
maintained.
[0052] Signalling the Availability of Candidate GSM Networks
[0053] At any time during a call the serving UMTS network U can
signal to the dual mode terminal the identity of one or more GSM
network that are available, {Gi.} for potential handover. This
signal contains the unique network identifier of each potential GSM
network. This message would typically be used when the terminal
first enters the coverage area of a potential candidate GSM network
while a call is active, or sets up a call while within its coverage
area,
[0054] The terminal records the identity of the GSM networks, and
compare it with internally stored information (for example a
network preference list stored on the SIM and the identity of other
available GSM networks previously signalled to it) and signals its
preference Gpref back to the serving network, if it can identify a
suitable network.
[0055] After this the serving network provides neighbor cell
information relating to network Gpref until such time as the call
ends, the terminal leaves the network or the terminal indicates a
new value of Gpref.
[0056] Signalling the Non-Availability of an Existing Candidate GSM
Network
[0057] When the terminal leaves the coverage area of a potential
candidate GSM network during a call, the serving radio network U
can signal to the terminal at any time the identity of GSM
networks, {Gi.} that are now unavailable. This signal contains the
unique network identifier of the GSM network which is no longer
available.
[0058] The terminal can note that this GSM network is no longer
available, and using internally stored information (for example a
network preference list stored on the SIM and the identity of
remaining available GSM networks) signals its preference Gpref back
to the serving network, if a suitable network is identified.
[0059] After this the serving network provides neighbor cell
information relating to network Gpref until such time as the call
ends, the terminal leaves the network or the terminal indicates a
new value of Gpref.
[0060] Terminal Network Preference
[0061] At any time the terminal can signal a new preference Gpref
back to the serving network, which would be chosen from the list of
available networks. After this the serving network provides
neighbor cell information relating to network Gpref until such time
as the call ends, the terminal leaves the network or the terminal
indicates a new value of Gpref.
[0062] Typically this signal would be sent if the list of available
GSM network changed in such a way that the preferred network needed
to be re-evaluated.
[0063] In the above described second embodiment, the mobile device
always has a preferred other network stored and is therefore
regularly updated with neighbor cell information for that preferred
network. This is particularly useful in the case of a dual mode
terminal (the case of UMTS, to GSM handover being one example, GSM
900 to GSM 1900 being another example) where the "unused" mode
components can be kept up dated and ready to change as soon as
required.
[0064] To summarize, the above embodiments provide the following
novel features, each of which may be independently provided:--
[0065] The signalling of available GSM candidate network
information.
[0066] The maintenance in the terminal of a list of available
networks.
[0067] The possibility of incremental addition and deletion of
elements of that list.
[0068] The ability of the terminal to indicate the preferred
network.
[0069] The ability to send selective neighbor cell information to
different dual mode terminals, so that dif3ferent terminals within
the same area may receive different neighbor cell information.
[0070] While preferred embodiments of the present invention have
been described using specific terms, such description is for
illustrative purposes only, and it is to be understood that changes
and variations may be made without departing from the spirit or
scope of the following claims.
* * * * *