U.S. patent application number 11/616409 was filed with the patent office on 2007-05-10 for device and method for forming a set of cells for time difference measurements and for measuring time differences for locating a user of a mobile terminal.
This patent application is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Allan Madsen.
Application Number | 20070105553 11/616409 |
Document ID | / |
Family ID | 32668960 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070105553 |
Kind Code |
A1 |
Madsen; Allan |
May 10, 2007 |
DEVICE AND METHOD FOR FORMING A SET OF CELLS FOR TIME DIFFERENCE
MEASUREMENTS AND FOR MEASURING TIME DIFFERENCES FOR LOCATING A USER
OF A MOBILE TERMINAL
Abstract
A method and device are provided, for locating a user of a
mobile terminal, for forming a set of cells for time difference
measurements for a mobile terminal camped on a first cell of a
cellular network and being in idle mode, the method including the
steps of: receiving a first set of cell identifiers of neighboring
cells for the first cell, with each of the neighboring cells
sending a radio signal on synchronization channels; and measuring
the received signal strength for cells having identifiers which are
included in the first set, with a number N of cells having a signal
strength exceeding a predefined threshold constituting a set of
available cells; wherein the improvement includes the steps of:
reading the synchronization channels for the set of available
cells, thereby measuring time differences for the set of available
cells; and selecting a second set from the set of available cells
using a predefined selection rule, the second set including M<N
cells, thus forming a new set of cells for time difference
measurements.
Inventors: |
Madsen; Allan; (Aalborg,
DK) |
Correspondence
Address: |
BELL, BOYD & LLOYD, LLP
P.O. BOX 1135
CHICAGO
IL
60690
US
|
Assignee: |
Siemens Aktiengesellschaft
Muenchen
DE
|
Family ID: |
32668960 |
Appl. No.: |
11/616409 |
Filed: |
December 27, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10777880 |
Feb 11, 2004 |
|
|
|
11616409 |
Dec 27, 2006 |
|
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Current U.S.
Class: |
455/434 |
Current CPC
Class: |
H04W 64/00 20130101 |
Class at
Publication: |
455/434 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 11, 2003 |
EP |
03002992.0 |
Claims
1. A method for locating a user of a mobile terminal, the method
comprising the steps of: providing that the mobile terminal be
camped on a first cell of a cellular network and is in idle mode;
receiving, at the mobile terminal, a first set of cell identifiers
respectively associated with neighboring cells of the first cell,
with each of the neighboring cells sending a radio signal;
measuring, at the mobile terminal, received signal strengths of the
neighboring cells having identifiers which are included in the
first set of cell identifiers, with a number N of cells having a
signal strength exceeding a predefined threshold constituting a set
of available cells; reading, at the mobile terminal, a
synchronization channel for the set of available cells, thereby
measuring time differences for the set of available cells;
selecting, at the mobile terminal, a second set of cells from the
set of available cells using a predefined selection rule, the
second set of cells including M<N cells, wherein the predefined
selection rule causes a non-selection of a cell having a same cell
identity as another cell in the set of available cells if it is
probable that the cell which is not selected and the another cell
belong to one sectorized base station; reading, at the mobile
terminal, a synchronization channel for the second set of cells,
thereby measuring time differences for the second set of cells; and
using the time difference measurements to obtain the location of
the user.
2. A method for locating a user of a mobile terminal as claimed in
claim 1, wherein locationing is performed on the cellular network
side in response to a transfer of the time difference
measurements.
3. A method for locating a user of a mobile terminal as claimed in
claim 2, wherein the transfer is performed in response to a call
which is one of originated by the user and terminated to the
user.
4. A method for locating a user of a mobile terminal as claimed in
claim 3, wherein the call is an emergency service call.
5. A mobile terminal, comprising: parts for receiving a first set
of cell identifiers respectively associated with neighboring cells
of a first cell of a cellular network on which the mobile terminal
is camped, the mobile terminal being in idle mode, with each of the
neighboring cells sending a radio signal; parts for measuring
received signal strengths of the neighboring cells having
identifiers which are included in the first set of cell
identifiers, with a number N of cells having a signal strength
exceeding a predefined threshold constituting a set of available
cells; parts for reading a synchronization channel for the set of
available cells, thereby measuring time differences for the set of
available cells; parts for selecting a second set of cells from the
set of available cells using a predefined selection rule, the
second set of cells including M<N cells, wherein the predefined
selection rule causes a non-selection of a cell having a same cell
identity as another cell in the set of available cells if it is
probable that the cell which is not selected and the another cell
belong to one sectorized base station; parts for reading a
synchronization channel for the second set of cells, thereby
measuring time differences for the second set of cells; and parts
for using the time difference measurements to obtain a location of
the user.
6. A mobile terminal as claimed in claim 5, wherein the mobile
terminal is a GSM terminal.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a divisional of U.S. application
Ser. No. 10/777,880, filed on Feb. 11, 2004.
BACKGROUND
[0002] 1. Field of Technology
[0003] The present invention relates to forming a set of cells for
time difference measurements and, more specifically, to measuring
such time differences for locating a user of a mobile terminal.
[0004] 2. Background
[0005] If someone is in trouble or notices something alarming
happening and dials an emergency number, such as 112 in Europe or
911 in the US, the emergency services (police, ambulance, fire
department) need to know where the help is needed. A caller may,
especially under difficult circumstances, such as at night or in a
location not known to the caller, find it extremely difficult to
give route guidance for the emergency services.
[0006] Mobile terminals are widely used. Their penetration has in
many countries reached and exceeded 900 of the total population. As
a consequence, most people are carrying a mobile terminal with
themselves while being away from home.
[0007] Cellular networks can be arranged to measure the coordinates
of a mobile terminal of a subscriber under network coverage. One of
the straightforward solutions then is to use this location
information of the mobile terminal for locationing the subscriber
who is calling an emergency number.
[0008] In the US, each cellular carrier is required to implement
the E911 service as required by the Federal Communications
Commission (FCC) in its order FCC 02-283 which, at the time of
writing (Feb. 3, 2003), can be found on the Internet at the
address: http:/hraunfoss.fcc.gov/edocs
public/attachmatch/FCC-02283A1.pdf.
[0009] Originally, the locationing accuracy in the so-called Phase
II was first specified to 100 meters for 670 of calls and 300
meters for 95% of calls. From early October 2003, however, the
locationing accuracy will be enhanced to 50 meters for 67% of calls
and 150 meters for 95% of calls, which can be found at.
http://www.fcc.gov/Bureaus/wireless/News Releases/2001/nw1012
7a.pdf.
[0010] For the Global System for Mobile communications (GSM), the
locationing is usually performed by using the so-called Enhanced
Observed Time Difference E-OTD method.
[0011] It is possible to make the locationing measurements in idle
mode, this kind of approach being used by some manufacturers.
Typically, the locationing interval is approximately 10 seconds.
Then, the locationing history is already known by the mobile
terminal MS when it enters dedicated mode. Not only the location
but also speed and direction, if any, can be determined.
[0012] Other manufacturers do not use idle mode measurements.
Rather, the location of the mobile terminal is found out only at
the beginning of each 911 or 112 call. Presently, such
manufacturers have at least some problems in obtaining the desired
accuracy. According to some opinions, in order to achieve the
accuracy requirements it is necessary to execute idle mode
measurements for neighboring cells.
[0013] The problem with the state-of-the-art solutions is that the
continuously performed measurement of time differences consumes a
great deal of power, significantly reducing the standby time of the
mobile terminal. As such, the battery of the mobile terminals needs
to be recharged quite often. This is an undue burden for most
mobile subscribers because the mobility of the user is, obviously,
substantially limited while the battery of the mobile terminal is
being recharged.
[0014] One solution for channel measurements, as disclosed in
international patent application WO 2001/58201, is for the mobile
terminal to receive a neighbor cell list f from a base station.
Channel quality measurements are performed for the cells on the
list based on the location of the mobile device. This is performed
in order to reduce the power consumption in the terminal.
[0015] The solution proposed in WO 2001/582-1 is, however, far from
optimal for locationing measurements. It cannot be used if the
location of the mobile station is not known. Further, it has turned
out to be extremely difficult to construct neighbor cell lists in
such a manner that they would not only provide enough cell
reselection possibilities but also enable good enough quality for
time difference measurements still saving power in the mobile
terminal.
[0016] EP 0 930 513 A2 presents a cellular radio network based
positioning system for determining the position of a mobile
station. For each base transceiver station or cell of the network,
a fixed list of base transceiver stations is stored by a mobile
positioning center. Each list identifies those base transceiver
stations which enable the position of a mobile station served by
the corresponding base transceiver station to be optimally
determined. The list is transmitted to the mobile station via the
serving base transceiver station and the mobile station determines
an observed time difference for each of the listed base transceiver
stations, relative to the serving base transceiver station, from
signals broadcast by the listed base transceiver stations. The
observed time differences are transmitted from the mobile station
to the serving base transceiver station and are used by the network
to compute the position of the mobile station.
SUMMARY
[0017] Accordingly, the present invention proposes a method and a
device with which it is possible to form a set of cells for time
difference measurements and to perform the measuring of time
differences and the locationing of a user of a mobile terminal more
economically; thus, using less power in the mobile terminal.
[0018] A prior art method for forming a set of cells for time
difference measurements for a mobile terminal camped on a first
cell of a cellular network and being in idle mode includes the
steps of: 1) receiving a first set of cell identifiers of
neighboring cells for the first cell, with each of the cells
sending a radio signal; and 2) measuring received signal strength
for cells, the identifiers of which are included in the first set,
with a number N of cells having a signal strength exceeding a
predefined threshold constituting a set of available cells.
[0019] This prior art method can be improved upon by further
performing the steps of: 3) reading a synchronization channel for
the set of available cells, thereby measuring time differences for
available cells; and then 4) selecting a second set from the set of
available cells using a predefined selection rule, the second set
including M<N cells and thus forming a new set of cells for time
difference measurements. The advantage obtained by the improvement
is that the resulting second set is more compact than the set of
available cells.
[0020] The enhanced method for forming a second set of cells for
time difference measurements for a mobile terminal camped on a cell
of a cellular network and being in idle mode can be used for
enhancing the efficiency of measuring of time differences for the
mobile terminal camped on the cell measuring time differences for
cells in the second set only. In this manner, the mobile terminal
saves energy and the standby time is prolonged.
[0021] In particular, a cell from the set of available cells is
selected to the second set whenever: 1) a base station identity
code of the cell is not equal to a base station identity code of
any other cell available; or 2) a base station identity code of the
cell is equal to a base station identity code of any other cell
available, and 2a) its measured time difference deviates from
measured time differences for other cells sharing the same base
station identity code more than a predefined threshold, or 2b) it
has the largest signal strength among all cells sharing the same
base station identity code and has a measured time difference
deviating less than or equal to the predefined threshold. The
advantage of such a mapping rule is that, in particular, cells
having same base station identity code need not be measured if it
is very probable that the cells belong to one sectorized base
station. Using all such cells for obtaining more time differences,
especially for locationing purposes, would only consume more energy
without bringing much detailed positioning information.
[0022] According to one embodiment of the present invention, the
location of a user can be obtained using time differences obtained
in accordance with other aspects of the present invention. One
advantage from this is that the positioning system may be
compatible with the mobile terminal, and can handle a smaller
number of time differences than expected, for example.
[0023] Additional features and advantages of the present invention
are described in, and will be apparent from, the following Detailed
Description and the Figures.
BRIEF DESCRIPTION OF THE FIGURES
[0024] FIG. 1 shows a typical cellular network, such as a GSM
network.
[0025] FIG. 2 shows exemplary cells of the cellular network from
FIG. 1.
[0026] FIG. 3 shows how E-OTD measurements are performed in prior
art solutions.
[0027] FIG. 4 is a flow chart showing an algorithm using which a
set of cells is selected and then further used for measuring time
differences.
[0028] FIG. 5 is an example showing some aspects of cell selection
performed according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0029] FIG. 1 shows a typical cellular network 100, such as a GSM
network. Characteristic for the cellular network 100 is that it
includes a number of base stations 104. Each of these base stations
104 forms a cell 103a, 103b, 103c. FIG. 1 shows only a small
proportion of cells 103 for the sake of clarity. A mobile station
101 camps on one of the cells 103a, 103b, 103c. In other words,
when the mobile station 101 is camping on cell 103a, it is under
radio coverage of base station 104a.
[0030] Typically, base stations 104 are adapted to form cells in
such a manner that some cells 103 overlap with each other. Such a
construction enables a flexible changing from one cell 104 to
another. When the mobile station 101 is in a dedicated mode, such
as when there is an ongoing phone call, the changing from one cell
104 to another is called handover. When the mobile station 101 is
in idle mode, the changing from one cell 104 to another is called
cell reselection. Typically, cell reselection or handovers are
performed when the mobile terminal 101 has moved so that the
quality of the radio connection between the base station 104 and
the mobile station 101 starts to degrade. When the cell reselection
includes changing a location area, this is reported to the BSC.
[0031] In order to decide whether a handover or cell reselection is
necessary, and to which cell the handover or cell reselection
should be made, the mobile station 101 continuously measures
received signal strength of its S neighboring cells.
[0032] Usually, in order to avoid interference, each cell has a
frequency different than its neighboring cell. There are also more
than one cellular network 100 overlapping, such that a subscriber
roaming under network 100 may not be able to use a different
network geographically covering the same area. This is one of the
reasons why each cell 103 has a so-called neighbor list, sometimes
referred to as the BA list. The neighbor list is a cell-based list
which includes identifiers of such closest neighbors for the cell
103 which belong to the same cellular network 100. The mobile
terminal 101 therefore measures the signal strengths of only the
cells 103 having identifiers which were included in the neighbor
list.
[0033] The cellular network 100 knows the location of mobile
terminal 101 in accuracy of a location area LA. Typically, an LA
includes several cells 103a, 103b, 103c. Visitor Location Register
110 knows which LA the mobile terminal 101 is under and when a call
is terminating to the mobile terminal 101. It is paged via a Base
Station Controller BSC 106. BSC is the element which controls a
number of the base stations 104. Usually, a cellular network 100
also includes a number of BSCs. The Mobile Switching Center MSC 108
coordinates the different BSCs 106 and then takes care of switching
of the traffic to and from different mobile terminals 101. The MSC
108 is usually connected via a Gateway MSC 112 to other cellular
networks 100B having a similar structure.
[0034] This kind of hierarchy and operational model enables the
roaming of mobile station 101, originally coming from another
cellular network 100B, under cellular network 100. The cellular
network 100B has its own subscribers, the data about whom is stored
in Home Location Register HLR 114. The HLR 114 includes all
services, etc., which are provided for a given subscriber of the
cellular network 100B. In general, in order to reach a subscriber,
the HLR 114 knows the VLR 110 address which the subscriber is
under.
[0035] For locationing purposes, there are Location Services
Centers LCS 109 connected into cellular network 100. AN LCS 109 is
used, for example, when a subscriber is missing. As explained
above, the cellular network 100 knows within the accuracy of a
location area LA where the user is, whereas the other cellular
network 100B knows only in the accuracy of a VLR 110 area where the
user is. Basically, the locationing of the user or mobile terminal
101 can be performed from LCS 109B from cellular network 100B as
well, if the operators of cellular networks 100 and 100B have
agreed as such.
[0036] Because of some legislative considerations, there are
usually no problems for an authorized user making a query to LCS
109B if the subscriber is roaming under his/her home cellular
network 100B. If the authorities are looking for the user in the
geographical area of his/her own cellular network 100B but he/she
is roaming under cellular network 100, the authorities need to
collaborate with authorities authorized in making LCS inquiries for
LCS 109.
[0037] FIG. 2 shows exemplary cells of a cellular network 100. The
mobile terminal 101 is camping on cell A having dimensions denoted
by curve C.sub.A. The cell A has neighboring cells B, C, and D.
Cell C is a sectorized cell, so that it includes three sectorized
transmitter/receiver units TRX. The sectors C1, C2, and C3 have
dimensions denoted by curves C.sub.C1, C.sub.C2, C.sub.C3,
respectively. Cells B and D have dimensions denoted by curves CB
and CD. The position of the mobile station 101 is denoted by point
P.
[0038] FIG. 3 shows the principle of how state-of-the-art
locationing measurements are performed. Typically, such
measurements are used to produce Enhanced Observed Time Difference
E-OTD information, which then can be used to interpret the quite
accurate location of the user.
[0039] When the mobile terminal camps on cell A, it receives the
neighbor list from cell A. The neighbor list includes Absolute
Radio Frequency Channel Number ARFCN of the Broadcast Control
Channel BCCH. The ARFCN is used to select the right frequency from
the multitude of different frequencies. The synchronization channel
of all the cells in the neighbor list is read before their base
station identity codes BSIC can be obtained. BCCH is used to send
controlling information to downlink direction, such controlling
information including synchronization frames which are sent in the
part of the BCCH known as the Synchronization Channel SCH.
[0040] The mobile terminal measures received signal strength for
the cells included in the neighbor list. It then decides to read
the SCH for those cells having a signal strength exceeds a
predefined threshold; i.e., which are available. The moment at
which the receiving of a data frame in the synchronization table
begins is marked as Time of Arrival TOA for the cell.
[0041] In this simple example, cell A has a Base Station Identifier
Code BSIC "A." BSIC is "B" for cell B, "C" for sectors C1 and C2,
and "D" for cell D. Sector C3 is below the predefined threshold;
i.e., mobile terminal 101 cannot hear it well enough.
[0042] Cell A has BCCH "a." For B, the BCCH is "b," for sector C1
and C2 "c1" and "c2", respectively, and for D the BCCH is "d."
[0043] TOA of A is T.sub.A, of B T.sub.B, of C1 T.sub.c1, of C2
T.sub.c2, and of D T.sub.D.
[0044] As such, the OTD is T.sub.B-T.sub.A for cell B,
T.sub.c1-T.sub.A for sector C1, and T.sub.c2-T.sub.A for sector C2.
For cell D, the OTD is T.sub.D-T.sub.A. The principle thus is that
the time difference is computed as the difference from the serving
cell A.
[0045] The mobile station 101 keeps on measuring all the OTDs
periodically. The measurement period depends on the particular
implementation, but a 10 second interval between measurements is
sufficiently satisfactory for locationing purposes.
[0046] FIG. 4 shows one particular aspect of the present invention.
In step L11, mobile terminal 101 camps on cell A. In step L13 it
receives a neighbor list of cell A, the neighbor list being
referred to as the first set.
[0047] In step L15 the mobile terminal 101 measures the received
signal level for each cell having an identifier which was in the
neighbor list; i.e., in the first set. In step L17, the mobile
station 101 defines the set of available cells. As described above,
a cell is determined to be available if the received signal
strength is above a predefined threshold value. In some
implementations, only a limited number (such as 6) of the strongest
neighbor cells are selected, whereas for some other implementations
all cells for which the received signal strength exceed some value
characteristic for 5 the mobile station are selected.
[0048] In step L19, the synchronization channel SCH is read for
cells available. In step L21, the mobile station 101 timer value at
the beginning of each synchronization frame is stored, this
corresponding to measuring time differences for available cells. It
is not necessary to read the SCH for measuring the time differences
on all occasions. Depending on the cellular network structure, the
timing also can be measured in some other way.
[0049] According to another aspect of the present invention, the
second set is, in step L23, selected from the set of available
cells using a predefined selection rule. Then in step L25,
synchronization channel SCH could be read for the cells which
belong to the second set.
[0050] In step L27 the time differences are measured for cells
having identifiers which are included in the second set only. The
timer value at the beginning of each synchronization frame is
stored, this corresponding to measuring time differences for the
cells in the second set.
[0051] According to a further aspect of the present invention, a
predefined mapping rule reads, at least partially, that a cell from
the set of available cells is selected to the second set
whenever:
[0052] 1) a base station identity code of the cell is not equal to
a base station identity code of any other cell available; or 2) a
base station identity code of the cell is equal to a base station
identity code of any other cell available, and 2a) its measured
time difference deviates from measured time differences for other
cells sharing the same base station identity code more than a
predefined threshold, or 2b) it has the largest signal strength
among all cells sharing the same base station identity code and has
a measured time difference deviating less than or equal to the
predefined threshold.
[0053] In step L29, it is checked whether or not the
synchronization channel has to be read for all cells in the
neighbor cell list; i.e., the cells in the first set. This has to
be performed occasionally. Specification 3GPP TS 05.08 V7.7.0
defines (clause 6.6.1) that "The mobile station shall attempt to
check the BSIC for each of the 6 strongest non-serving cell BCCH
carriers at least every 30 seconds, to confirm that it is
monitoring the same cell. If a change of BSIC is detected, then the
carrier shall be treated as a new carrier and the BCCH data
re-determined."
[0054] The exit criteria, for LOOP2 to be tested in step L29 may
include any or a number of the following: i) LOOP2 has been
executed a predetermined number of times (1, 2, 3, 4, 5, . . . )
after performing step L15 (counter expiry); ii) the mobile terminal
101 is changing from idle mode to dedicated mode; iii) the step L25
(i.e., reading the synchronization channel SCH for cells in the
second set) has failed; iv) timer expiry, cell reselection; or v)
neighbor list changed.
[0055] Option iii) corresponds to the case that the subscriber is
moving and the synchronization channel of at least some of the
cells in the second set cannot be received without errors.
[0056] If none of the exit criteria for LOOP2 is met, the execution
of LOOP2 is continued; i.e., steps L25, L27, and L29 are repeated.
If any of the exit criteria for LOOP2 is met, the LOOP1 is
executed; i.e., the mobile terminal measures received signal level
in step L15 and so on. However, if a new neighbor cell list is
being received, then the LOOP1 extends to step L13.
[0057] FIG. 5 shows some further considerations relating to the
present invention. The contents of FIG. 5 include substantially
everything from FIG. 3. In addition, the column "COMPUTE
.DELTA..sub.jk" includes logical values "yes" and "no." The
contents of the column are decided based on the base station
identifier code BSIC. If BSIC is identical for any two cells, the
COMPUTE .DELTA..sub.jk is set to a true value. In the opposite
case, it has a false value.
[0058] Observed Time Difference OTD.sub.i for an i:th entry is
defined as follows: OTD.sub.i=TOA.sub.i-TOA.sub.i,
[0059] for all 1<i<n+1; where TOA.sub.i is the measured time
of arrival i.e. the beginning of the synchronization frame for the
i:th entry, and the serving cell is the first entry.
[0060] The contents of one of the preferred mapping rules included
the condition "a cell is selected when its measured time difference
deviates from measured time differences for other cells sharing the
same base station identity code more than a predefined threshold".
In FIG. 5 terms this can be put into the following context: .DELTA.
jk = OTD j - OTD k = TOA j - TOA k ##EQU1##
[0061] for all j.noteq.k; and 1<j, i<n+1.
[0062] So now
.DELTA..sub.23=.DELTA..sub.32=.parallel.T.sub.c1-T.sub.c2.parallel..
If this is below a predefined threshold, say .epsilon., where
.epsilon./T.sub.c1 can be any relatively small value, say 2.5%-25%,
it can be deduced with relative certainty that sectors C1 and C2
belong to the same cell with only one of them being selected.
[0063] As a consequence, only one of the sectors C1, C2 is selected
to the second set in step L23 and the measurement of the sector not
selected can be avoided. The selection rule "the cell having the
largest signal strength among all cells sharing the same base
station identity code and having a measured time difference
deviating less than or equal to the predefined threshold" allows
the received signal strength RXLEV in the mobile terminal to be
used to select the stronger cell or sector.
[0064] One of the main reasons behind this solution is that now the
consecutive measurements of sectorized Base Stations 104 can be
avoided. The comparison of the time differences is included in some
embodiments of the present invention, because some operators are
using base station identifiers repetitively. It would then endanger
the success of the locationing if the observed time difference OTD
for such a cell would not be measured.
[0065] Using a 10 second measurement interval, the standby time of
a test mobile phone was reduced from 270 hours to roughly 90 hours.
It is clear that the 180 hour reduction in the standby time is
highly significant for the user. If an operator chooses to
repeatedly use sectorized cells, the savings obtained by performing
step L23 and repeating steps L25 and L27 instead of steps L19 and
L21 saved, in our example, 25% of OTD measurements. As such,
depending on the cellular network 100 structure, it is possible to
obtain significantly better improvement in the standby time because
of smaller energy consumption in the mobile terminal 101.
[0066] Although the present invention was described above with
reference to specific embodiments, it should be clear that the
present invention is not limited to these but may be modified by
those skilled in the art without departing from the spirit and
scope of the present invention as set forth in the hereafter
appended claims. For example, any cellular network having similar
neighbor list and base station identifier structure as described
can be used. Such networks includes, for example, most GSM, GPRS
and UMTS/WCDMA networks.
* * * * *
References