U.S. patent application number 14/263739 was filed with the patent office on 2015-04-16 for method and apparatus for deriving signal strength attenuation characteristic values.
This patent application is currently assigned to JDSU UK Limited. The applicant listed for this patent is JDSU UK Limited. Invention is credited to Michael Joseph Flanagan, Peter Kenington, Gareth Smith, Stefan Thiel.
Application Number | 20150103681 14/263739 |
Document ID | / |
Family ID | 52809564 |
Filed Date | 2015-04-16 |
United States Patent
Application |
20150103681 |
Kind Code |
A1 |
Thiel; Stefan ; et
al. |
April 16, 2015 |
METHOD AND APPARATUS FOR DERIVING SIGNAL STRENGTH ATTENUATION
CHARACTERISTIC VALUES
Abstract
A method of deriving signal strength attenuation characteristic
values for cells within a wireless communication network. The
method for determining a set of cells for which signal strength
attenuation characteristic values are to be derived, and using a
genetic algorithm to derive signal strength attenuation
characteristic values for the set of cells based at least partly on
signal strength information for signal strength measurements
obtained by wireless communication subscriber units within the
wireless communication network.
Inventors: |
Thiel; Stefan; (Newbury,
GB) ; Kenington; Peter; (Chepstow, GB) ;
Smith; Gareth; (Berkshire, GB) ; Flanagan; Michael
Joseph; (Chester, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JDSU UK Limited |
Hampshire |
|
GB |
|
|
Assignee: |
JDSU UK Limited
Hampshire
GB
|
Family ID: |
52809564 |
Appl. No.: |
14/263739 |
Filed: |
April 28, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61891800 |
Oct 16, 2013 |
|
|
|
61894781 |
Oct 23, 2013 |
|
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Current U.S.
Class: |
370/252 |
Current CPC
Class: |
H04W 64/00 20130101;
G01S 5/0252 20130101; H04W 16/22 20130101; H04W 24/02 20130101 |
Class at
Publication: |
370/252 |
International
Class: |
H04W 24/08 20060101
H04W024/08 |
Claims
1. A method of deriving signal strength attenuation characteristic
values for cells within a wireless communication network; the
method comprising: determining a set of cells for which signal
strength attenuation characteristic values are to be derived; and
using a genetic algorithm to derive signal strength attenuation
characteristic values for the set of cells based at least partly on
signal strength information for signal strength measurements
obtained by wireless communication subscriber units within the
wireless communication network.
2. The method of claim 1, wherein the method comprises: determining
a set of cells for which signal strength attenuation characteristic
values are to be derived; generating a first generation of
chromosome strings, each chromosome string comprising at least one
signal strength attenuation characteristic value for each cell
within the determined set of cells; calculating a fitness score for
each chromosome string within the first generation of chromosome
strings based at least partly on signal strength information for
signal strength measurements obtained by wireless communication
subscriber units within the wireless communication network;
generating at least one further generation of chromosome strings;
calculating a fitness score for each chromosome string within the
at least one further generation of chromosome strings based at
least partly on signal strength information for signal strength
measurements obtained by wireless communication subscriber units
within the wireless communication network; and deriving signal
strength attenuation characteristic values for the set of cells
based at least partly on the calculated fitness scores for the
first and at least one further generation of chromosome
strings.
3. The method of claim 2, wherein the first generation of
chromosome strings comprises random signal strength attenuation
characteristic values.
4. The method of claim 2, wherein calculating a fitness score for a
chromosome string comprises: defining a plurality of signature
points, each signature point representing a geographical location;
calculating an expected signal strength measurement value for at
least one cell at each signature point; matching each of a
plurality of signal strength measurement reports received from
wireless communication subscriber units to one of the signature
points based at least partly on the expected signal strength
measurement values for the signature points; calculating a fitness
score for each signal strength measurement report based at least
partly on the or each expected signal strength measurement value
for the respective signature point and corresponding signal
strength information from the signal strength measurement report;
and calculating the fitness score for the chromosome string based
at least partly on the calculated fitness scores for the plurality
of signal strength measurement reports.
5. The method of claim 4, wherein the method comprises calculating
the fitness scores for the chromosome string by summing the fitness
scores for the signal strength measurement reports.
6. The method of claim 2, wherein generating at least one further
generation of chromosome strings comprises: deriving parent
chromosome strings to form part of the at least one further
generation of chromosome strings; and performing a crossover
between parent chromosome strings to generate child chromosome
strings to form part of the at least one further generation of
chromosome strings.
7. The method of claim 6, wherein generating at least one further
generation of chromosome strings further comprises performing
mutation of the child chromosome strings.
8. The method of claim 6, wherein generating at least one further
generation of chromosome strings comprises identifying at least one
chromosome string from a current generation of chromosome strings
comprising a highest fitness score and including the identified at
least one chromosome string from the current generation of
chromosome strings in the at least one further generation of
chromosome strings.
9. The method of claim 2, wherein the method comprises generating
further generations of chromosome strings until at least one
chromosome string comprising a suitable solution for signal
strength attenuation characteristic values for the set of cells is
found.
10. The method of claim 9, wherein a chromosome string comprising a
suitable solution for signal strength attenuation characteristic
values for the set of cells is found when no chromosome string in a
succeeding generation of chromosome strings comprises a higher
fitness score than that chromosome string.
11. The method of claim 1, wherein the method comprises deriving
signal strength attenuation characteristic values comprising slope
and intercept values.
12. The method of claim 1, wherein determining the set of cells for
which signal strength attenuation characteristic values are to be
derived comprise: taking an initial cell ID referenced within cell
measurement reports; and adding to the initial cell ID with further
cell IDs referenced within the same measurement reports as the
initial cell ID to form the set of cells for which signal strength
attenuation characteristic values are to be derived.
13. The method of claim 1, wherein the method further comprises
storing the derived signal strength attenuation characteristic
values within at least one data storage device.
14. A method of generating a signal strength contour model for at
least one cell within a wireless communication network, the method
comprising: deriving at least one signal strength attenuation
characteristic value for the at least one cell within the wireless
communication network in accordance with the method of claim 1; and
generating a signal strength contour model for the at least one
cell based at least partly on the at least one derived signal
strength attenuation characteristic value.
15. A method of geolocating a wireless communication subscriber
unit comprising: deriving signal strength attenuation
characteristic values for cells within a wireless communication
network in accordance with the method of claim 1; receiving signal
strength measurement information for a set of cells within the
wireless communication network obtained by the wireless
communication subscriber unit; determining a distance between the
wireless communication subscriber unit and an antenna for each cell
within the set of cells based at least partly on: (i) the derived
signal strength attenuation characteristic values for the set of
cells; and (ii) the received signal strength measurement
information for the set of cells within the wireless communication
network obtained by the wireless communication subscriber unit; and
determining a geolocation of the wireless communication subscriber
unit based at least partly on the determined distance between the
wireless communication subscriber unit and an antenna for each cell
within the set of cells.
16. A non-transitory computer program product having executable
program code stored therein for performing a method of deriving
signal strength attenuation characteristic values for cells within
a wireless communication network, the program code operable for:
determining a set of cells for which signal strength attenuation
characteristic values are to be derived; and using a genetic
algorithm to derive signal strength attenuation characteristic
values for the set of cells based at least partly on signal
strength information for signal strength measurements obtained by
wireless communication subscriber units within the wireless
communication network.
17. The non-transitory computer program product of claim 16,
wherein the non-transitory computer program product comprises at
least one of: a hard disk, a CD-ROM, an optical storage device, a
magnetic storage device, a Read Only Memory (ROM), a Programmable
Read Only Memory (PROM), an Erasable Programmable Read Only Memory
(EPROM), an Electrically Erasable Programmable Read Only Memory
(EEPROM), and a Flash memory.
18. A geolocation system comprising at least one signal strength
attenuation characteristic value derivation component arranged to:
determine a set of cells for which signal strength attenuation
characteristic values are to be derived; and use a genetic
algorithm to derive signal strength attenuation characteristic
values for the set of cells based at least partly on signal
strength information for signal strength measurements obtained by
wireless communication subscriber units within the wireless
communication network.
19. The geolocation system of claim 18, wherein the at least one
signal strength attenuation characteristic value derivation
component is arranged to: determine a set of cells within a
wireless communication network for which signal strength
attenuation characteristic values are to be derived; generate a
first generation of chromosome strings, each chromosome string
comprising at least one signal strength attenuation characteristic
value for each cell within the determined set of cells; calculate a
fitness score for each chromosome string within the first
generation of chromosome strings based at least partly on signal
strength information for signal strength measurements obtained by
wireless communication subscriber units within the wireless
communication network; generate at least one further generation of
chromosome strings; calculate a fitness score for each chromosome
string within the at least one further generation of chromosome
strings based at least partly on signal strength information for
signal strength measurements obtained by wireless communication
subscriber units within the wireless communication network; and
derive signal strength attenuation characteristic values for the
set of cells based at least partly on the calculated fitness scores
for the first and at least one further generation of chromosome
strings.
20. The geolocation system of claim 18, wherein the at least one
signal strength attenuation characteristic value derivation
component is arranged to store the derived signal strength
attenuation characteristic values within at least one data storage
device.
Description
PRIORITY CLAIM TO RELATED APPLICATIONS
[0001] This U.S. patent application claims the benefit of, and
priority under .sctn..sctn.119(e) and 120, to U.S. Provisional
Application No. 61/891,800 filed Oct. 16, 2013, and U.S.
Provisional Application No. 61/894,781 filed Oct. 23, 2013, the
disclosures of which are all incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The field of the invention relates to a method and apparatus
for deriving signal strength attenuation characteristic values, and
in particular to a method and apparatus for deriving signal
strength attenuation characteristic values for cells within a
wireless communication network.
BACKGROUND OF THE INVENTION
[0003] Wireless communication networks, such as the 3.sup.rd
Generation (3G) and 4.sup.th Generation (4G) of wireless telephone
standards and technology, are well known. Examples of such 3G and
4G standards and technology are the Universal Wireless
Telecommunications System (UMTS.TM.) and the Long Term Evolution
(LTE) respectively, developed by the 3.sup.rd Generation
Partnership Project (3GPP.TM.) (www.3gpp.org).
[0004] These 3.sup.rd and 4.sup.th generations of wireless
communications, have generally been developed to support macro-cell
wireless phone communications, and more recently femto-cell
wireless phone communications. Here the `phone` may be a smart
phone, or another wireless or portable communication unit that is
linked wirelessly to a network through which calls etc. are
connected. Henceforth all these devices will be referred to as
wireless communication units. Calls may be data, video, or voice
calls, or a combination of these.
[0005] Typically, wireless communication units, or User Equipment
(UE) as they are often referred to in 3G parlance, communicate with
a Core Network of the 3G or 4G wireless communication network. This
communication is via a Radio Network Subsystem. A wireless
communication network typically comprises a plurality of Radio
Network Subsystems. Each Radio Network Subsystem comprises one or
more cells, to which wireless communication units may attach, and
thereby connect to the network. A base station may serve a cell.
Each base station may have multiple antennas, each of which serves
one sector of the cell.
[0006] Geolocation is the real-world geographical location of
objects, and geolocation of wireless communication units is an
increasingly important and desirable service. There are many
mechanisms by which users of a wireless communication network may
be located, whilst they are using the system. These include use of
the global positioning system (GPS), if the wireless device is
equipped with a GPS receiver and the user has enabled this on
his/her device. However, many users do not enable GPS on their
devices as it is typically a significant power drain on the
device's battery.
[0007] Alternative known techniques for geo-locating a wireless
communication unit within a wireless communication network use
timing information. Wireless communication networks fall into two
broad categories: [0008] (i) Synchronous networks, such as Code
Division Multiple Access systems, e.g. CDMA 2000. In synchronous
networks, the timing offset between different base stations is
constant. The amount of the offset is known to wireless mobile
communication units that are using the network. In the example of
CDMA2000, the timing offset is both known and constant, because
each base station's timing is locked to a Global Positioning System
satellite. [0009] (ii) Asynchronous networks, such as the Universal
Mobile Telephone System (UMTS). In asynchronous networks, the
timing offset between different base stations is not constant.
Wireless mobile communication units in asynchronous networks are
not provided with information about the timing offset between base
station timing references. In addition, these references drift over
time, relative both to absolute timing references, as well as to
each other.
[0010] In a synchronous wireless communication network, the known
timing offset information makes it relatively straight forward to
derive a measurement of the location of a wireless communication
unit from signal timing information. However, in an asynchronous
network, it is much more difficult to derive a measurement of the
location of a wireless communication unit from signal timing
information.
[0011] Furthermore, although LTE networks comprise synchronous
networks, not every LTE network reports timing advance/offset
information, and without this information the accurate judgement of
distance from a cell site can be difficult. It is therefore
necessary/desirable to utilise alternative geolocation techniques
within LTE (and asynchronous) networks.
[0012] Alternative known techniques for geo-locating a wireless
communication unit within a wireless communication network use
signal strength measurements for cells visible to the wireless
communication to determine the approximate distance of the wireless
communication unit from the respective basestation for each of the
cells. This distance information may then be used in conjunction
with the known location for the basestations to estimate the
location of the wireless communication unit.
[0013] FIG. 1 illustrates the decay of signal strength with
increasing distance from a basestation site. The rate of decay
varies depending upon the environment in which the basestation is
placed. For example, in a city with many structures to attenuate
the signal, the rate of decay of signal strength with distance will
typically be relatively high, perhaps decaying at a rate
proportional to 1/r.sup.4, where r is the radial distance from the
basestation site. Conversely, in the countryside where there are
fewer structures etc. to attenuate the signal, the rate of decay of
signal strength with distance will typically be lower than in a
city, for example reduced to a rate proportional to 1/r.sup.2.
[0014] Whilst these general values for signal strength decay rates
may be used as a guide or a starting point for estimating the
distance between a wireless communication unit and a basestation
site, they will typically vary significantly from site to site,
even within a given (e.g. urban) environment. Clearly, if this
variation is known accurately for a given base-station, at a given
receive location, then it is possible to utilise signal strength
alone (e.g. in the absence of timing information etc.) to provide a
distance estimate between a wireless communication unit and a
basestation site. If accurate distance estimates can be determined
for a number of cell sites (e.g. a minimum of three), the
intersection of signal strength contours (defined by the distance
estimates) can be used to determine the likely location of the
wireless communication unit. This situation is shown in FIG. 2. In
practice, using a larger number of cell sites is beneficial, since
this provides a greater number of sample points and minimises the
impact of a gross error arising from measurements based on a
particular cell-site.
[0015] In FIG. 2, three contours are shown 210, 220, 230, one for
each of the three base-stations. In a perfect system, with
perfectly circular contours (as shown), the intersection of the
contours 210, 220, 230 at a single point would provide a precise
location. In a real scenario, however, the modelled signal strength
contours will be far from accurate and the measured vs modelled
values will lead to a gap (as shown), within which the wireless
communication unit is likely to be located. So long as this `gap`
is sufficiently small, a sufficiently accurate location estimate
may be obtained.
[0016] Thus, there is a need for a method and apparatus for
enabling signal strength contours for cells within wireless
communication networks to be accurately modelled.
SUMMARY OF THE INVENTION
[0017] Accordingly, the invention seeks to mitigate, alleviate or
eliminate one or more of the abovementioned disadvantages singly or
in any combination.
[0018] According to a first aspect of the present invention, there
is provided a method of deriving signal strength attenuation
characteristic values for cells within a wireless communication
network. The method comprises determining a set of cells for which
signal strength attenuation characteristic values are to be
derived, and using a genetic algorithm to derive signal strength
attenuation characteristic values for the set of cells based at
least partly on signal strength information for signal strength
measurements obtained by wireless communication subscriber units
within the wireless communication network.
[0019] In this manner, signal strength attenuation characteristic
information may be derived on a per cell basis from signal strength
measurement information provided by wireless communication units,
enabling signal strength contours for cells within wireless
communication networks to be accurately modelled.
[0020] In some optional embodiments, the method may comprise:
[0021] determining a set of cells for which signal strength
attenuation characteristic values are to be derived; [0022]
generating a first generation of chromosome strings, each
chromosome string comprising at least one signal strength
attenuation characteristic value for each cell within the
determined set of cells; [0023] calculating a fitness score for
each chromosome string within the first generation of chromosome
strings based at least partly on signal strength information for
signal strength measurements obtained by wireless communication
subscriber units within the wireless communication network; [0024]
generating at least one further generation of chromosome strings;
[0025] calculating a fitness score for each chromosome string
within the at least one further generation of chromosome strings
based at least partly on signal strength information for signal
strength measurements obtained by wireless communication subscriber
units within the wireless communication network; and [0026]
deriving signal strength attenuation characteristic values for the
set of cells based at least partly on the calculated fitness scores
for the first and at least one further generation of chromosome
strings.
[0027] In some optional embodiments, the first generation of
chromosome strings may comprise random signal strength attenuation
characteristic values.
[0028] In some optional embodiments, calculating a fitness score
for a chromosome string may comprise: [0029] defining a plurality
of signature points, each signature point representing a
geographical location; [0030] calculating an expected signal
strength measurement value for at least one cell at each signature
point; [0031] matching each of a plurality of signal strength
measurement reports received from wireless communication subscriber
units to one of the signature points based at least partly on the
expected signal strength measurement values for the signature
points; [0032] calculating a fitness score for each signal strength
measurement report based at least partly on the or each expected
signal strength measurement value for the respective signature
point and corresponding signal strength information from the signal
strength measurement report; and [0033] calculating the fitness
score for the chromosome string based at least partly on the
calculated fitness scores for the plurality of signal strength
measurement reports.
[0034] In some optional embodiments, the method may comprise
calculating the fitness scores for the chromosome string by summing
the fitness scores for the signal strength measurement reports.
[0035] In some optional embodiments, generating at least one
further generation of chromosome strings may comprise: [0036]
deriving parent chromosome strings to form part of the at least one
further generation of chromosome strings; and [0037] performing a
crossover between parent chromosome strings to generate child
chromosome strings to form part of the at least one further
generation of chromosome strings.
[0038] In some optional embodiments, generating at least one
further generation of chromosome strings may further comprise
performing mutation of the child chromosome strings.
[0039] In some optional embodiments, generating at least one
further generation of chromosome strings may comprise identifying
at least one chromosome string from a current generation of
chromosome strings comprising a highest fitness score and including
the identified at least one chromosome string from the current
generation of chromosome strings in the at least one further
generation of chromosome strings.
[0040] In some optional embodiments, the method may comprise
generating further generations of chromosome strings until at least
one chromosome string comprising a suitable solution for signal
strength attenuation characteristic values for the set of cells is
found.
[0041] In some optional embodiments, a chromosome string comprising
a suitable solution for signal strength attenuation characteristic
values for the set of cells may be found when no chromosome string
in a succeeding generation of chromosome strings comprises a higher
fitness score than that chromosome string.
[0042] In some optional embodiments, the method may comprise
deriving signal strength attenuation characteristic values
comprising slope and intercept values.
[0043] In some optional embodiments, determining the set of cells
for which signal strength attenuation characteristic values are to
be derived may comprise: [0044] taking an initial cell ID
referenced within cell measurement reports; and [0045] adding to
the initial cell ID with further cell IDs referenced within the
same measurement reports as the initial cell ID to form the set of
cells for which signal strength attenuation characteristic values
are to be derived.
[0046] In some optional embodiments, the method may further
comprise storing the derived signal strength attenuation
characteristic values within at least one data storage device.
[0047] According to a second aspect of the present invention, there
is provided a method of generating a signal strength contour model
for at least one cell within a wireless communication network. The
method comprises deriving at least one signal strength attenuation
characteristic value for the at least one cell within the wireless
communication network in accordance with the first aspect of the
present invention, and generating a signal strength contour model
for the at least one cell based at least partly on the at least one
derived signal strength attenuation characteristic value.
[0048] According to a third aspect of the present invention, there
is provided a method of geolocating a wireless communication
subscriber unit. The method comprises deriving signal strength
attenuation characteristic values for cells within a wireless
communication network in accordance with the first aspect of the
present invention, receiving signal strength measurement
information for a set of cells within the wireless communication
network obtained by the wireless communication subscriber unit,
determining a distance between the wireless communication
subscriber unit and an antenna for each cell within the set of
cells based at least partly on: [0049] (i) the derived signal
strength attenuation characteristic values for the set of cells;
and [0050] (ii) the received signal strength measurement
information for the set of cells within the wireless communication
network obtained by the wireless communication subscriber unit; and
[0051] (iii) determining a geolocation of the wireless
communication subscriber unit based at least partly on the
determined distance between the wireless communication subscriber
unit and an antenna for each cell within the set of cells.
[0052] According to a fourth aspect of the present invention, there
is provided a non-transitory computer program product having
executable program code stored therein for performing a method of
deriving signal strength attenuation characteristic values for
cells within a wireless communication network. The program code
operable for determining a set of cells for which signal strength
attenuation characteristic values are to be derived, and using a
genetic algorithm to derive signal strength attenuation
characteristic values for the set of cells based at least partly on
signal strength information for signal strength measurements
obtained by wireless communication subscriber units within the
wireless communication network.
[0053] In some optional embodiments, the non-transitory computer
program product may comprise at least one of: a hard disk, a
CD-ROM, an optical storage device, a magnetic storage device, a
Read Only Memory (ROM), a Programmable Read Only Memory (PROM), an
Erasable Programmable Read Only Memory (EPROM), an Electrically
Erasable Programmable Read Only Memory (EEPROM), and a Flash
memory.
[0054] According to a fifth aspect of the present invention, there
is provided a geolocation system comprising at least one signal
strength attenuation characteristic value derivation component
arranged to determine a set of cells within a wireless
communication network for which signal strength attenuation
characteristic values are to be derived, and use a genetic
algorithm to derive signal strength attenuation characteristic
values for the set of cells based at least partly on signal
strength information for signal strength measurements obtained by
wireless communication subscriber units within the wireless
communication network.
[0055] In some optional embodiments, the at least one signal
strength attenuation characteristic value derivation component may
be arranged to store the derived signal strength attenuation
characteristic values within at least one data storage device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] Embodiments of the invention will be described, by way of
example only, with reference to the accompanying drawings, in
which:
[0057] FIG. 1 illustrates the decay of signal strength with
increasing distance from a basestation site.
[0058] FIG. 2 illustrates the intersection of signal strength
contours for a plurality of cells within a wireless communication
network.
[0059] FIG. 3 illustrates a simplified flowchart of an example of a
method of deriving signal strength attenuation characteristic
values for cells within a wireless communication network.
[0060] FIG. 4 illustrates an example of such a chromosome
string.
[0061] FIG. 5 illustrates a simplified flowchart of an example of a
method for calculating a fitness score for a generation of
chromosome strings.
[0062] FIG. 6 illustrates an example of a grid of signature
points.
[0063] FIG. 7 illustrates a simplistic two dimensional
visualisation of finding a closest matching signature point for a
measurement report.
[0064] FIG. 8 illustrates a simplified example of calculating a
fitness score for a match between a selected measurement report and
a closest matching signature point.
[0065] FIG. 9 illustrates a simplified flowchart of an example of a
method of generating a next generation of chromosome strings.
[0066] FIG. 10 illustrates an example of selecting individuals for
parent chromosome strings.
[0067] FIG. 11 illustrates an example of performing crossover
between two parent chromosome strings.
[0068] FIG. 12 illustrates a simplified flowchart of an example of
a method of geolocating a wireless communication subscriber
unit.
[0069] FIG. 13 illustrates a simplified block diagram of an example
of a geolocation system.
[0070] FIG. 14 illustrates a typical computing system that may be
employed to implement data processing functionality in embodiments
of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0071] Examples of the invention will be described in terms of a
system and a method for deriving signal strength attenuation
characteristic values for cells within a wireless communication
network, such as a network implemented in accordance with the
3.sup.rd Generation (3G) and/or 4.sup.th Generation (4G) of
wireless telephone standards and technology. Examples of such 3G
and 4G standards and technology is the Universal Wireless
Telecommunications System (UMTS.TM.) and Long Term Evolution (LTE),
developed by the 3.sup.rd Generation Partnership Project (3GPP.TM.)
(www.3gpp.org).
[0072] In order to accurately model signal strength contours for
cells within wireless communication networks, it is necessary to
ascertain accurate attenuation characteristic values such as the
slope of the signal attenuation with distance from the basestation
sites for the cells, as well as the `starting point` for the graph,
known as the intercept point. Determining these slope and intercept
attenuation characteristic values for base-stations within a
network (and refining the values with time, as the network or
environment evolves) allows accurate position estimates to be
determined purely from received signal strength information (such
as: Reference Signal Received Power (RSRP) and/or Received Signal
Strength Indicator (RSSI) in LTE parlance) and a knowledge of the
basestation's identity (and hence location).
[0073] In accordance with some examples of the present invention
there is provided a method and apparatus therefor, the method
comprising deriving signal strength attenuation characteristic
values for cells within a wireless communication network. The
method comprises determining a set of cells for which signal
strength attenuation characteristic values are to be derived,
generating a first generation of chromosome strings, each
chromosome string comprising at least one signal strength
attenuation characteristic value for each cell within the
determined set of cells, calculating a fitness score for each
chromosome string within the first generation of chromosome strings
based at least partly on signal strength information for signal
strength measurements obtained by wireless communication subscriber
units within the wireless communication network, generating at
least one further generation of chromosome strings, calculating a
fitness score for each chromosome string within the at least one
further generation of chromosome strings based at least partly on
signal strength information for signal strength measurements
obtained by wireless communication subscriber units within the
wireless communication network, and deriving signal strength
attenuation characteristic values for the set of cells based at
least partly on the calculated fitness scores for the first and at
least one further generation of chromosome strings.
[0074] Referring first to FIG. 3, there is illustrated a simplified
flowchart 300 of an example of a method of deriving signal strength
attenuation characteristic values for cells within a wireless
communication network. The method starts at 310, and moves on to
step 320 where cell measurement data measured by wireless
communication units, or User Equipment (UEs) in 3G/4G parlance, is
obtained. For example, such cell measurement data may comprise, or
be obtained from, measurement report messages provided by UEs over
a period of time, for example as part of a cell
selection/reselection process or otherwise. Such cell measurement
data comprises cell IDs (a cell ID comprising a unique identifier
for a particular cell) for cells visible to the respective UEs
along with measurement data for the strength of signals from the
respective cells as measured by the respective UEs. Each such
measurement report typically comprises signal strength data for
cells measured by the respective UE at substantially the same time.
As such, the signal strength measurement data provided within a
measurement report will relate to substantially the same location
for the UE (i.e. the location of the UE at the time the signal
strength measurements were taken).
[0075] Having obtained the cell measurement data at step 320, the
method of the illustrated example moves on to step 330, where a set
of cells for which attenuation characteristic values (e.g. slope
and intercept values in the illustrated example) are to be derived
is determined. For example, such a set of cells may be determined
by taking an initial cell ID referenced within the obtained cell
measurement data. This initial cell ID may then be added to with
further cell IDs that are also referenced within the same
measurement report messages as the initial cell ID to form the set
of cells for which attenuation characteristic values are to be
derived. In this manner, all of the cell IDs within the set of
cells are linked by at least one common cell ID with which they are
referenced in a particular measurement report message.
[0076] In some examples of the present invention, given a set of
measurement report messages for an entire wireless communication
network (for example a whole day's worth of measurement report
messages for the entire wireless communication network), all cell
IDs referenced within the set of measurement report messages may be
identified. A `bucket` may then be created for each referenced cell
ID, and each measurement report message referencing the respective
cell ID can then be placed within the corresponding bucket. The
measurement reports within a bucket may then be used to determine a
set of cells for which signal strength attenuation characteristic
values are to be derived, with the cell ID for which the bucket was
initially created comprising the initial cell ID and further cell
IDs within the set being extracted from the message report messages
within the bucket.
[0077] Determining a set of cells in this manner enables the
wireless communication network to be partitioned into manageable
`chunks` to reduce the number of cells (and thus the number of
varying parameters) to a manageable amount from a processing
perspective. Repeating the method of FIG. 3 for different sets of
cells enables the complete network to be covered over a number of
iterations. It is contemplated that sets of, say, approximately 20
cells are created, although this is only an approximate target size
and is for the most part dependent on the processing resource
available etc.
[0078] Referring back to FIG. 3, having determined the set of cells
for which slope and intercept values are to be derived, the method
moves on to step 340 where a first generation of `chromosome`
strings are generated, each chromosome string comprising the signal
strength attenuation characteristic values (i.e. slope and
intercept values in the illustrated example) for each cell within
the determined set of cells.
[0079] FIG. 4 illustrates an example of such a chromosome string.
As illustrated in FIG. 4, each chromosome string is made up of
`candidate solutions` for the signal strength attenuation
characteristic values (i.e. the slope and intercept values in the
illustrated example) for the set of cells. Each candidate solution
for the signal strength attenuation characteristic value(s) of a
particular cell is referred to as an `individual`. Each generation
of chromosome strings may comprise, say, between 50 and 200
individual chromosome strings, each chromosome string comprising a
different population of candidate solutions for the signal strength
attenuation characteristic values. In the illustrated example of
FIG. 3, the individuals within the first generation of chromosome
strings comprise random signal strength attenuation characteristic
values.
[0080] Referring back to FIG. 3, having generated the first
generation of chromosome strings for the determined set of cells,
the method moves on to 350 where the current (i.e. first in this
instance) generation of chromosome strings are evaluated and given
a fitness score. Such a fitness score for each chromosome string
may be calculated based on signal strength information for signal
strength measurements obtained by wireless communication subscriber
units within the wireless communication network.
[0081] In some examples, calculating a fitness score for a
chromosome string may comprise defining a plurality of signature
points, each signature point representing a geographical location.
FIG. 5 illustrates a simplified flowchart 500 of an example of a
method for calculating a fitness score for a generation of
chromosome strings, such as may be implemented within step 350 of
FIG. 3. The method of FIG. 5 starts at 505 and moves on to 510
where a set of signature points for the set of cells within the
chromosome strings is defined, each signature point representing a
geographical location.
[0082] For example, and as illustrated in FIG. 6, a grid 600 of
signature points 610 may be defined. The grid 600 may be limited to
being within the bounds 620 of the combined coverage areas for the
set of cells to which the chromosome string relates. In the
illustrated example, the signature points 610 are spaced 50 metres
apart.
[0083] Referring back to FIG. 5, having defined the set of
signature points, the method moves on to step 515 where a first
chromosome string from the generation of chromosome strings is
selected. Next, at step 520, an expected signal strength for each
cell within the set of cells is then calculated at each signature
point based on the known locations of the respective basestations
for the cells (e.g. as defined within network configuration data
for the wireless communication network) and, in the illustrated
example, the slope and intercept values for the respective cells as
defined in that particular chromosome string.
[0084] Having calculated the expected signal strength value for
each cell at each signature point, the method moves on to step 525
where, in the illustrated example, a first measurement report is
selected from a set of measurement reports corresponding to the set
of cells to which the chromosome string relates. For example, in
the example where the set of cells is determined by way of creating
a `bucket` for a particular (initial) cell ID and each measurement
report message referencing the respective cell ID is placed within
the corresponding bucket, the set of measurement reports may
comprise the measurement reports within the respective bucket.
[0085] Having selected the first measurement report, the method
moves on to step 530 where a closest matching signature point is
found for the selected measurement report. For example, FIG. 7
illustrates a simplistic two dimensional visualisation of finding a
closest matching signature point for a measurement report. In this
illustrated example, the signal strength measurements within the
selected measurement report are compared to the expected signal
strength values at each signature point 610 (as calculated at step
520). The closest matching signature point, e.g. such as indicated
at 710 in FIG. 7, may be determined based on, say, the signature
point for which the measurement report comprises the largest number
of Cell IDs matching the ten nearest cells/basestations to the
signature point, the closest match between measured and expected
signal strength values, etc.
[0086] Referring back to FIG. 5, having found the closest matching
signature point for the selected measurement report, a fitness
score is then calculated for the match between the selected
measurement report and the closest matching signature point. For
example, and as illustrated in FIG. 8, the selected measurement
report 810 comprises a signal strength value (e.g. a Reference
Signal Received Power (RSRP) in LTE parlance) corresponding to each
of one or more cell IDs, the signal strength value representing a
measured signal strength for respective cells visible to the UE at
the time. Similarly, the closest matching signature set 820
comprises an expected signal strength value corresponding to each
of one or more cell IDs, as calculated at step 520 in FIG. 5. In
the example illustrated in FIG. 8, a score 830 is determined for
each signal strength measurement within the measurement report 810
based on a comparison with corresponding expected signal strength
values of the signature point for the respective cell IDs. In some
examples, the comparison may be limited to, for example, the ten
cell IDs for the signature point comprising the highest expected
signal strength values. In the illustrated example, where no
expected signal strength value is available for comparison with a
measured signal strength value in the selected measurement report,
such as the signal strength measurement value indicated at 840 in
FIG. 8, the score for that measured signal strength value may be
heavily penalised. The individual scores 830 for the measured
signal strength values may then be added together to provide a
fitness score 850 for the match between the selected measurement
report and the closest matching signature point.
[0087] Referring back to FIG. 5, having calculated the fitness
score for the match between the selected measurement report and the
closest matching signature point, the method moves on to step 540,
where it is determined whether a fitness score has been calculated
for each measurement report (in the set of measurement reports). If
it is determined that a fitness score has not been calculated for
each measurement report, the method moves on to step 545 where the
next measurement report is selected, and the method loops back to
step 530 so that a fitness score for that measurement report can be
calculated. Conversely, if it is determined that a fitness score
has been calculated for each measurement report, the method moves
on to step 550 where in the illustrated example the individual
measurement report scores are summed to obtain a fitness score for
the chromosome string. The method then moves on to step 555, where
it is determined whether a fitness score has been calculated for
each chromosome string (in the current generation of chromosome
strings). If it is determined that a fitness score has not been
calculated for each chromosome string, the method moves on to step
560 where the next chromosome string is selected, and the method
loops back to step 520. Conversely, if it is determined that a
fitness score has been calculated for each chromosome string, the
method ends at 565.
[0088] Referring back to FIG. 3, having evaluated and scored the
current (first) generation of chromosome strings, the method moves
on to step 360 where it is determined whether a suitable solution
has been found for the signal strength attenuation characteristic
values (i.e. slope and intercept values in the illustrated example)
for the set of cells. For example, it may be determined that a
chromosome string comprising a suitable solution for signal
strength attenuation characteristic values for the set of cells has
been found when no chromosome string in a succeeding generation of
chromosome strings comprises a higher fitness score than that
chromosome string.
[0089] In this instance, since the current generation of chromosome
strings comprises the first generation of chromosome strings, it
may be assumed that a suitable solution has not been found in this
instance. Accordingly, the method moves on to step 370 where a next
generation of chromosome strings is generated.
[0090] FIG. 9 illustrates a simplified flowchart 900 of an example
of a method of generating a next generation of chromosome strings.
The method starts at 910, and moves on to step 920 where, in the
illustrated example, chromosome strings from the most recent
generation of chromosome strings comprising the highest fitness
scores are identified and added to (i.e. to begin) a set of
chromosome strings to comprise the next generation of chromosome
strings. For example, the two highest scoring chromosome strings
from the previous (i.e. most recent) generation of chromosome
strings may be identified and added to the set of chromosome
strings to comprise the next generation of chromosome strings. In
this manner, the `best` chromosome strings from the previous
generation survive into the next generation. The method then moves
on to step 930, where in the illustrated example individuals (i.e.
candidate solutions for the signal strength attenuation
characteristic values for the set of cells) are selected for parent
chromosome, and such parent chromosome strings are generated from
the selected individuals. For example, and as illustrated in FIG.
10, a set of individuals may be randomly selected from a
`population` 1010 of individuals comprising the set of individuals
corresponding to a particular cell from all chromosome strings
within the previous (most recent) generation of chromosome strings.
In this manner, a randomly selected set of individuals
corresponding to a particular cell is obtained from the respective
population of individuals for that cell. From this randomly
selected set of individuals, the individual comprising the best
fitness score (e.g. based on the fitness score for the chromosome
string from which the individual has come) may then be selected as
the individual for the respective cell within a parent chromosome
string. This may be repeated until an individual has been selected
for all cells within the parent chromosome string, and thus a
parent chromosome string may be generated. This may be repeated to
generate (at least) two parent chromosome strings.
[0091] Referring back to FIG. 9, having generated a pair of parent
chromosome strings, one or more genetic algorithms may then be used
to generate child chromosome strings from the parent chromosome
strings. For example, and as illustrated in FIG. 9, the method may
comprise performing `crossover` between the parent chromosome
strings, at step 940. FIG. 11 illustrates an example of performing
crossover between two parent chromosome strings 1110, 1120 to
generate two child chromosome strings 1130, 1140 therefrom. In the
illustrated example, a random crossover point 1150 within the
parent chromosome strings is determined. The individuals `below`
this crossover point 1150 within the parent chromosome strings are
swapped such that the individuals below the crossover point 1150
within the first parent chromosome string 1110 become the
individuals below the crossover point 1150 within the second
`child` chromosome string 1140, and the individuals below the
crossover point 1150 within the second parent chromosome string
1120 become the individuals below the crossover point 1150 within
the first `child` chromosome string 1130.
[0092] Referring back to FIG. 9, having performed the crossover to
generate the child chromosome strings, mutation of the generated
child chromosome strings is then performed in the illustrated
example, at step 950. Mutation is a genetic operator used to
maintain genetic diversity from one generation of a population of
genetic algorithm chromosome strings to the next. It is analogous
to biological mutation. Mutation alters one or more gene values
(individuals) in a chromosome string from its initial state. Such,
mutation occurs according to a chosen mutation probability, and any
such chosen mutation probability may be used to provide a suitable
genetic diversity between parent and child chromosome strings.
[0093] The parent and mutated chromosome strings are then added to
the set of next generation chromosome strings, at step 960. The
non-mutated child chromosome strings may also be added to the set
of next generation of chromosome strings.
[0094] The method then moves on to step 970, where it is determined
whether a required population size for the next generation of
chromosome strings has been reached. Such a required population
size may be in the range of, say, 50 to 100 chromosome strings. If
it is determined that the required population size has not been
reached, then the method loops back to step 930. Conversely, if it
is determined that the required population size has been reached,
the method ends at 980.
[0095] Referring back to FIG. 3, having generated the next
generation of chromosome strings, the method loops back to step 350
where the newly generated generation of chromosome strings are
evaluated and given a fitness score. The method then moves on again
to step 360 where it is determined whether a suitable solution has
been found for the signal strength attenuation characteristic
values for the set of cells in this next generation of chromosome
strings. In this manner, the method comprises generating further
generations of chromosome strings until at least one chromosome
string comprising a suitable solution for signal strength
attenuation characteristic values for the set of cells is
found.
[0096] Once it is determined that a suitable solution for signal
strength attenuation characteristic values for the set of cells is
found, the method moves on to 380, where the signal strength
attenuation values (i.e. slope and intercept values in the
illustrated example) from the suitable solution are stored within
one or more data storage devices, at step 380, and the method ends
at 390.
[0097] Thus, an exemplary method of deriving signal strength
attenuation characteristic information for cells within a wireless
communication network has been described based on the use of a
genetic algorithm. Advantageously, the use of genetic algorithms in
this manner enables signal strength attenuation characteristic
information to be derived on a per cell basis from signal strength
measurement information provided by wireless communication units,
and also to enable such information to be repeatedly derived using
continuously received signal strength measurement data. As a
result, the specific and ever changing environmental influences for
individual cells can be taken into consideration to enable a more
accurate modelling of signal strength contours for individual cells
to be achieved. Furthermore, any changes over time to the signal
strength attenuation characteristics for cells within the network
can be identified and taken into consideration. For example, in
more rural environments, changes in plant and tree foliage due to
changes in season may be modelled. Furthermore, changes in
urban/suburban environments due to new buildings etc. being
constructed can also be adapted for.
[0098] FIG. 12 illustrates a simplified flowchart 1200 of an
example of a method of geolocating a wireless communication
subscriber unit. The method starts at 1205, and moves on to step
1210 where a measurement report from the wireless communication
unit (UE) is received comprising signal strength measurement data
for a set of cells. Next, at step 1215, a cell from the set of
cells for which the measurement report comprises signal strength
measurement data is selected. Signal strength attenuation
characteristic information (which in the illustrated example
comprises slope and intercept values) is then retrieved from a data
storage device at step 1220. In particular, signal strength
attenuation characteristic information derived by way of a genetic
algorithm based on signal strength measurement information received
from wireless communication units, such as the method of FIG. 3, is
retrieved. A signal strength model is then generated for the
selected cell based on the retrieved signal strength attenuation
characteristic information at step 1225. For example, the slope and
intercept values for the illustrated example may be used to derive
radial distance values for signal strength contours relative to a
basestation antenna of the selected cell. The signal strength
measurement data within the receive measurement report for the
selected cell is then applied to the generated signal strength
model to estimate a distance between the wireless communication
unit and the basestation/antenna for the selected cell, at step
1230. Having estimated the distance between the wireless
communication unit and the selected cell basestation/antenna, the
method moves on to step 1235 where it is determined whether the
selected cell is the last cell in the measurement report. If it is
determined that the selected cell is not the last cell in the
measurement report, the method loops back to step 1215, where the
next cell in the measurement report is selected. Conversely, if it
is determined that the selected cell is the last cell in the
measurement report, the method moves on to step 1240, where
location data for the basestations/antennas of the set of cells is
obtained, for example from a network configuration database or the
like. A geolocation estimate for the wireless communication unit is
then generated at step 1245 based on locations of the
basestations/antennas of the set of cells and the estimated
distances between the wireless communication unit and the
basestations/antennas of the set of cells. The method then ends at
1250.
[0099] Referring now to FIG. 13, there is illustrated a simplified
block diagram of an example of a geolocation system 1300. The
geolocation system 1300 may be implemented in any suitable manner.
For example, and as illustrated in FIG. 13, the geolocation system
1300 may be implemented at least in part by way of one or more
processing modules 1305 arranged to execute computer program code.
The computer program code may be stored within one or more
non-transitory computer program products, for example such as one
or more memory element(s). Such memory element(s) may comprise any
form of computer-readable storage device, such as a hard disc, a
CD-ROM, an optical storage device, a magnetic storage device, a
Read Only Memory, ROM, a Programmable Read Only Memory, PROM, an
Erasable Programmable Read Only Memory, EPROM, an Electrically
Erasable Programmable Read Only Memory, EEPROM, and a Flash
memory.
[0100] In particular, the geolocation system 1300 illustrated in
FIG. 13 comprises a signal strength attenuation characteristic
derivation component 1320 (in the form of computer program code
executing on the processing module(s) 1305), the signal strength
attenuation characteristic derivation component 1320 being arranged
to implement a method of deriving signal strength attenuation
characteristic values for cells within a wireless communication
network, such as the method hereinbefore described with reference
to FIGS. 3 to 11. In the illustrated example, the geolocation
system 1300 is operably coupled to a data storage device 1310 in
which cell measurement data received from wireless communication
units is stored, and is arranged to receive cell measurement data
from the data storage device 1310. The geolocation system 1300 is
further operably coupled to a data storage device 1330 within which
the signal strength attenuation characteristic derivation component
1320 is arranged to store signal strength attenuation
characteristic values. In some examples, the data storage device
1320 and the data storage device 1330 may be realised by way of a
single data storage device.
[0101] In the illustrated example, the geolocation system 1300
further comprises a geolocation module 1340 (in the form of
computer program code executing on the processing module(s) 1305),
arranged to perform geolocation of wireless communication units,
such as the method hereinbefore described with reference to FIG.
12. In the illustrated example, the geolocation module 1340
comprises a signal strength contour model generator component 1345
arranged to generate signal strength contours for cells within a
wireless communication network based on signal strength attenuation
characteristic data derived by the signal strength attenuation
characteristic derivation component 1320, and stored within the
data storage device 1330.
[0102] Referring now to FIG. 14, there is illustrated a typical
computing system 1400 that may be employed to implement signal
processing functionality in embodiments of the invention. For
example, a computing system of this type may be used within the
geolocation system 1300 of FIG. 13. Those skilled in the relevant
art will also recognize how to implement the invention using other
computer systems or architectures. Computing system 1400 may
represent, for example, a desktop, laptop or notebook computer,
hand-held computing device (PDA, cell phone, palmtop, etc.),
mainframe, server, client, or any other type of special or general
purpose computing device as may be desirable or appropriate for a
given application or environment. Computing system 1400 can include
one or more processors, such as a processor 1404. Processor 1404
can be implemented using a general or special-purpose processing
engine such as, for example, a microprocessor, microcontroller or
other control module. In this example, processor 1404 is connected
to a bus 1402 or other communications medium.
[0103] Computing system 1400 can also include a main memory 1408,
such as random access memory (RAM) or other dynamic memory, for
storing information and instructions to be executed by processor
1404. Main memory 1408 also may be used for storing temporary
variables or other intermediate information during execution of
instructions to be executed by processor 1404. Computing system
1400 may likewise include a read only memory (ROM) or other static
storage device coupled to bus 1402 for storing static information
and instructions for processor 1404.
[0104] The computing system 1400 may also include information
storage system 1410, which may include, for example, a media drive
1412 and a removable storage interface 1420. The media drive 1412
may include a drive or other mechanism to support fixed or
removable storage media, such as a hard disk drive, a floppy disk
drive, a magnetic tape drive, an optical disk drive, a compact disc
(CD) or digital video drive (DVD) read or write drive (R or RW), or
other removable or fixed media drive. Storage media 1418 may
include, for example, a hard disk, floppy disk, magnetic tape,
optical disk, CD or DVD, or other fixed or removable medium that is
read by and written to by media drive 1412. As these examples
illustrate, the storage media 1418 may include a computer-readable
storage medium having particular computer software or data stored
therein.
[0105] In alternative embodiments, information storage system 1410
may include other similar components for allowing computer programs
or other instructions or data to be loaded into computing system
1400. Such components may include, for example, a removable storage
unit 1422 and an interface 1420, such as a program cartridge and
cartridge interface, a removable memory (for example, a flash
memory or other removable memory module) and memory slot, and other
removable storage units 1422 and interfaces 1420 that allow
software and data to be transferred from the removable storage unit
1418 to computing system 1400.
[0106] Computing system 1400 can also include a communications
interface 1424. Communications interface 1424 can be used to allow
software and data to be transferred between computing system 1400
and external devices. Examples of communications interface 1424 can
include a modem, a network interface (such as an Ethernet or other
NIC card), a communications port (such as for example, a universal
serial bus (USB) port), a PCMCIA slot and card, etc. Software and
data transferred via communications interface 1424 are in the form
of signals which can be electronic, electromagnetic, and optical or
other signals capable of being received by communications interface
1424. These signals are provided to communications interface 1424
via a channel 1428. This channel 1428 may carry signals and may be
implemented using a wireless medium, wire or cable, fiber optics,
or other communications medium. Some examples of a channel include
a phone line, a cellular phone link, an RF link, a network
interface, a local or wide area network, and other communications
channels.
[0107] In this document, the terms `computer program product`
computer-readable medium' and the like may be used generally to
refer to media such as, for example, memory 1408, storage device
1418, or storage unit 1422. These and other forms of
computer-readable media may store one or more instructions for use
by processor 1404, to cause the processor to perform specified
operations. Such instructions, generally referred to as `computer
program code` (which may be grouped in the form of computer
programs or other groupings), when executed, enable the computing
system 1400 to perform functions of embodiments of the present
invention. Note that the code may directly cause the processor to
perform specified operations, be compiled to do so, and/or be
combined with other software, hardware, and/or firmware elements
(e.g. libraries for performing standard functions) to do so.
[0108] As used herein, the expression non-transitory will be
understood to refer to the non-ephemeral nature of the storage
medium itself rather than to a notion of how long the stored
information itself may persist in a stored state. Accordingly,
memories that might otherwise be viewed, for example, as being
volatile (such as many electronically-erasable programmable
read-only memories (EPROM's) or random-access memories (RAM's)) are
nevertheless to be viewed here as being "non-transitory" whereas a
signal carrier in transit is to be considered "transitory"
notwithstanding that the signal may remain in transit for a lengthy
period of time.
[0109] In an embodiment where the elements are implemented using
software, the software may be stored in a computer-readable medium
and loaded into computing system 1400 using, for example, removable
storage drive 1422, drive 1412 or communications interface 1424.
The control module (in this example, software instructions or
computer program code), when executed by the processor 1404, causes
the processor 1404 to perform the functions of the invention as
described herein.
[0110] Furthermore, the inventive concept can be applied to any
signal processing circuit. It is further envisaged that, for
example, a semiconductor manufacturer may employ the inventive
concept in a design of a stand-alone device, such as a
microcontroller, digital signal processor, or application-specific
integrated circuit (ASIC) and/or any other sub-system element.
[0111] It will be appreciated that, for clarity purposes, the above
description has described embodiments of the invention with
reference to different functional units and processors. However, it
will be apparent that any suitable distribution of functionality
between different functional units or processors may be used
without detracting from the invention. For example, functionality
illustrated to be performed by the same processor or controller may
be performed by separate processors or controllers. Hence,
references to specific functional units are only to be seen as
references to suitable means for providing the described
functionality, rather than indicative of a strict logical or
physical structure or organization.
[0112] Because the illustrated embodiments of the present invention
may for the most part, be implemented using electronic components
and circuits known to those skilled in the art, details will not be
explained in any greater extent than that considered necessary as
illustrated above, for the understanding and appreciation of the
underlying concepts of the present invention and in order not to
obfuscate or distract from the teachings of the present
invention.
[0113] In the foregoing specification, the invention has been
described with reference to specific examples of embodiments of the
invention. It will, however, be evident that various modifications
and changes may be made therein without departing from the broader
spirit and scope of the invention as set forth in the appended
claims. Other modifications, variations and alternatives are also
possible. The specifications and drawings are, accordingly, to be
regarded in an illustrative rather than in a restrictive sense.
[0114] In the claims, any reference signs placed between
parentheses shall not be construed as limiting the claim. The word
`comprising` does not exclude the presence of other elements or
steps then those listed in a claim. Furthermore, the terms "a" or
"an," as used herein, are defined as one or more than one. Also,
the use of introductory phrases such as "at least one" and "one or
more" in the claims should not be construed to imply that the
introduction of another claim element by the indefinite articles
"a" or "an" limits any particular claim containing such introduced
claim element to inventions containing only one such element, even
when the same claim includes the introductory phrases "one or more"
or "at least one" and indefinite articles such as "a" or "an." The
same holds true for the use of definite articles. Unless stated
otherwise, terms such as "first" and "second" are used to
arbitrarily distinguish between the elements such terms describe.
Thus, these terms are not necessarily intended to indicate temporal
or other prioritization of such elements. The mere fact that
certain measures are recited in mutually different claims does not
indicate that a combination of these measures cannot be used to
advantage.
* * * * *