U.S. patent application number 14/303952 was filed with the patent office on 2014-10-02 for base station, method and computer program product.
This patent application is currently assigned to ALCATEL LUCENT. The applicant listed for this patent is Imran Ashraf, Holger Claussen. Invention is credited to Imran Ashraf, Holger Claussen.
Application Number | 20140295846 14/303952 |
Document ID | / |
Family ID | 41623307 |
Filed Date | 2014-10-02 |
United States Patent
Application |
20140295846 |
Kind Code |
A1 |
Ashraf; Imran ; et
al. |
October 2, 2014 |
BASE STATION, METHOD AND COMPUTER PROGRAM PRODUCT
Abstract
A base station, a method and a computer program product are
disclosed. The base station is operable, in concert with other base
stations within a group, to support wireless communications with
user equipment. The base station comprises: transmission logic
operable to generate a cell having a coverage area supporting
wireless communications with user equipment; reception logic
operable to receive load information indicative of a user equipment
communications load experienced by base stations within said group;
and coverage area adjustment logic operable to determine changes
required to said coverage area to change a user equipment
communications load experienced by at least one base station within
said group. In this way, it can be seen that each base station
within the group may receive information about the user loading on
other base stations within that group and is able to adjust its
coverage area to cause that communications loading to be rebalanced
to enable efficient use of resources and optimise the overall
performance of each of the base stations within the group. The
group of base stations with co-ordinated and optimised coverage can
achieve higher end user data rates and improved quality of service
than would otherwise be possible.
Inventors: |
Ashraf; Imran; (Wiltshire,
GB) ; Claussen; Holger; (Co. Kildare, IE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ashraf; Imran
Claussen; Holger |
Wiltshire
Co. Kildare |
|
GB
IE |
|
|
Assignee: |
ALCATEL LUCENT
PARIS
FR
|
Family ID: |
41623307 |
Appl. No.: |
14/303952 |
Filed: |
June 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13394836 |
Jul 23, 2012 |
|
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|
PCT/EP2010/004585 |
Jul 22, 2010 |
|
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14303952 |
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Current U.S.
Class: |
455/436 |
Current CPC
Class: |
H04W 16/32 20130101;
H04W 16/26 20130101; H04W 84/045 20130101; H04W 16/08 20130101 |
Class at
Publication: |
455/436 |
International
Class: |
H04W 16/26 20060101
H04W016/26 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2009 |
EP |
09360041.9 |
Claims
1. A base station operable, in concert with other base stations
within a group, to support wireless communications with user
equipment, said base station comprising: transmission logic
operable to generate a cell having a coverage area supporting
wireless communications with user equipment; reception logic
operable to receive load information indicative of a user equipment
communications load experienced by base stations within said group;
and coverage area adjustment logic operable to determine changes
required to said coverage area to change a user equipment
communications load experienced by at least one base station within
said group; wherein said coverage area adjustment logic is
configured, when said user equipment communications load
experienced by said base station is above an average user equipment
communications load for said group and exceeds a predetermined
maximum user equipment communications load supportable by said base
station, to decrease said coverage area to decrease said user
equipment communications load experienced by said base station.
2. The base station as claimed in claim 1, wherein said coverage
area adjustment logic is operable to determine changes required
said coverage area within a predetermined range bounded by an upper
and lower threshold.
3. The base station as claimed in claim 2, wherein said coverage
area adjustment logic is operable, when said user equipment
communications load supported by said base station is below an
average user equipment communications load for said group but fails
to exceed a predetermined maximum user equipment communications
load supportable by said base station, to increase said coverage
area to no more than a maximum coverage area defined by said upper
threshold of said predetermined range to increase said user
equipment communications load experienced by said base station.
4. (canceled)
5. The base station as claimed in claim 1, wherein said coverage
area adjustment logic is operable, when said decrease in said
coverage area is to below said lower threshold, to reduce said
lower threshold.
6. The base station as claimed in claim 2, wherein said coverage
area adjustment logic is operable, when said user equipment
communications load experienced by said base station is above an
average user equipment communications load for said group but fails
to exceed a predetermined maximum user equipment communications
load experienced said base station and when base stations
identified from said load information as being candidates to
support user equipment communications load which would no longer be
supported by said base station fail to exceed a predetermined
maximum user equipment communications load supportable by those
base stations, to decrease said coverage area to no less than a
minimum coverage area defined by said lower threshold of said
predetermined range to decrease user equipment communications load
experienced by said base station.
7. The base station as claimed in claim 6, wherein said reception
logic is operable to receive receiver sensitivity information
indicative of a sensitivity of receivers of user equipment
supported by base stations within said group and said coverage area
adjustment logic is operable to determine from said receiver
sensitivity information whether said decrease to said coverage area
would cause user equipment communications load to no longer be
supported by said base stations within said group and, if so, to
prevent said decrease.
8. The base station as claimed claim 1, wherein said load
information indicative of a user equipment communications load
experienced by base stations within said group comprises
information indicative of numbers of user equipment supported by
said base stations within said group and said coverage area
adjustment logic is operable to determine changes required to said
coverage area by changing its pilot channel transmission power to
change said user equipment communications load experienced by at
least one base station within said group by changing numbers of
users supported by said at least one base station within said
group.
9. The base station as claimed in claim 8, wherein said
predetermined range bounded by an upper and lower threshold
comprises a predetermined pilot channel transmission power range
bounded by an upper pilot channel transmission power threshold and
a lower pilot channel transmission power threshold.
10. The base station as claimed in claim 8, wherein said coverage
area adjustment logic is operable, when said number of user
equipment supported by said base station is below an average number
of user equipment supported by base stations within said group but
fails to exceed a predetermined maximum number of user equipment
supportable by said base station, to increase said coverage area to
no more than a maximum coverage area defined by said upper
threshold of said predetermined range to increase said number of
user equipment supported by said base station.
11. The base station as claimed in claim 8, wherein said coverage
area adjustment logic is operable, when said number of user
equipment supported by said base station is above an average number
of user equipment supported by base stations within said group and
exceeds a predetermined maximum number of user equipment
supportable by said base station, to decrease said coverage area to
decrease said number of user equipment supported by said base
station.
12. The base station as claimed in claim 8, wherein said coverage
area adjustment logic is operable, when said number of user
equipment supported by said base station is above an average number
of user equipment supported by base stations within said group but
fails to exceed a predetermined maximum number of user equipment
supportable said base station and when base stations identified
from said information indicative of numbers of user equipment
supported by said base stations as being candidates to support user
equipment which would no longer be supported by said base station
fail to exceed a predetermined maximum number of user equipment
supportable by those base stations, to decrease said coverage area
to no less than a minimum coverage area defined by said lower
threshold of said predetermined range to decrease said number of
user equipment supported by said base station.
13. The base station as claimed in claim 2, wherein said reception
logic is operable to receive an indication of quality of service
provided to user equipment supported by said base station and said
coverage area adjustment logic operable to adjust said lower
threshold of said predetermined range to vary said minimum coverage
area definable by said predetermined range in response to said
indication.
14. The base station as claimed in claim 13, wherein said coverage
area adjustment logic is operable to perform at least one of: when
said indication of quality of service indicates that less than or
equal to a predetermined quality of service is being provided to
user equipment supported by said base station, to increase said
lower threshold of said predetermined range by a first
predetermined amount; and when said indication of quality of
service indicates that greater than a predetermined quality of
service is being provided to user equipment supported by said base
station, to decrease said lower threshold of said predetermined
range by a second predetermined amount.
15. A method, comprising: generating a cell having a coverage area
supporting wireless communications with user equipment; receiving
load information indicative of a user equipment communications load
experienced by base stations operating in concert with other base
stations within a group to support wireless communications with
user equipment; determining changes required to said coverage area
to change a user equipment communications load experienced by at
least one base station within said group; and decreasing said
coverage area to decrease said user equipment communications load
experienced by said base station when said user equipment
communications load experienced by said base station is above an
average user equipment communications load for said group and
exceeds a predetermined maximum user equipment communications load
supportable by said base station.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a base station, a method
and a computer program product.
BACKGROUND
[0002] In a cellular wireless telecommunications system, radio
coverage is provided by areas known as cells. A base station is
located in each cell to provide the radio coverage area.
Traditional base stations provide coverage in relatively large
geographical areas and these cells are often referred to as macro
cells. It is possible to provide smaller sized cells, often within
a macro cell. Such smaller sized cells are sometimes referred to as
micro cells, pico cells or femto cells. Such small cells are
typically established by providing a small cell base station that
provides radio coverage having a relatively limited range within
the radio coverage area of a macro cell. The transmission power of
the small cell base station is relatively low and, hence, each
small cell provides a smaller coverage area compared to that of a
macro cell and covers, for example, an office or a home. A group of
such small cell base stations may together provide a wireless small
cell network.
[0003] Such small cells are typically provided where the
communications coverage provided by the macro cell is poor or where
a user wishes to use an alternative communications link provided
locally, by the small cell base station, to communicate with the
core network. Such a situation might arise where, for example, a
user has a pre-existing communications link and the user wishes to
utilise that link in preference to that provided by a macro cell
network provider to communicate with the core network. The group of
small cell base stations providing the wireless small cell network
can together provide extended local coverage to user equipment
throughout, for example, a home or an office building by using
multiple small cell base stations distributed throughout those
buildings which enables each of those base stations to transmit at
a lower power than would otherwise be necessary if coverage was to
be provided by a single small cell base station.
[0004] However, the proliferation of the deployment of base
stations makes the control of base stations difficult to
achieve.
[0005] Accordingly, it is desired to provide an improved technique
for controlling base stations.
SUMMARY
[0006] According to a first aspect there is provided a base station
operable, in concert with other base stations within a group, to
support wireless communications with user equipment, the base
station comprising: transmission logic operable to generate a cell
having a coverage area supporting wireless communications with user
equipment; reception logic operable to receive load information
indicative of a user equipment communications load experienced by
base stations within the group; and coverage area adjustment logic
operable to determine changes required to the coverage area to
change a user equipment communications load experienced by at least
one base station within the group.
[0007] The first aspect recognises that radio coverage optimisation
of base stations is an important element in improving the overall
performance of each of the base stations within a group. A group of
base stations with co-ordinated and optimised coverage can achieve
higher end user data rates and improved quality of service than
would otherwise be possible. However, the first aspect also
recognises that achieving optimised coverage requires careful
trade-offs to be made in order to accommodate conflicting
objectives. Furthermore, since the network provider may have little
or no control over the exact locations of each individual base
station, the first aspect recognises that coordinating the coverage
areas becomes difficult to achieve.
[0008] Existing techniques for coverage optimisation generally
utilise centralised computation approaches to determine base
station configurations for the network. However, the first aspect
recognises that utilising such an approach would require each base
station to communicate with a central entity which would
significantly increase the amount of signalling data being
transmitted throughout the network. Also, such an approach would
require either accurate information on the location and
configuration of the base stations to be provided by the installer
of that base station or complex functionality to be provided in the
base stations to enable those base stations to provide that
information automatically. However, if that information is
inaccurate or incomplete, then optimisation of coverage areas may
not be possible to achieve. Accordingly, a technique is provided
where distributed joint coverage optimisation is achieved between
base stations. Although this technique has particular utility to
base stations deployed in wireless small cell networks, it will be
appreciated that similar functionality would also be beneficial in
other base stations or network nodes such as, for example, macro
base stations.
[0009] Hence, a base station is provided which may operate together
with other base stations within a group such as, for example, a
wireless small cell network, to support wireless communications
with user equipment. Transmission logic is provided which may
generate a cell such as, for example, a macro cell, micro cell,
pico cell or femto cell which has a coverage area which supports
wireless communications with user equipment. Reception logic is
provided which may receive information regarding the communications
load being experienced by other base stations within the group.
Coverage area adjustment logic is provided which may determine
those changes required to the coverage area to vary the
communications load experienced by base stations within the group.
In this way, it can be seen that each base station within the group
may receive information about the user loading on other base
stations within that group and is able to adjust its coverage area
to cause that communications loading to be rebalanced to enable
efficient use of resources and optimise the overall performance of
each of the base stations within the group. By co-ordinating within
the group, the need to obtain and communicate accurate
configuration and location information to a central entity is
obviated. Instead, optimised coverage can be achieved through
trade-offs made locally to accommodate conflicting local
objectives. It will be appreciated that the load information may be
obtained from neighbouring base stations within the group either
directly or via another network node such as, for example, a
gateway or may be obtained from measurement reports communicated by
the user equipment. The group of base stations with co-ordinated
and optimised coverage can achieve higher end user data rates and
improved quality of service than would otherwise be possible.
[0010] In one embodiment, the coverage area adjustment logic is
operable to determine changes required the coverage area within a
predetermined range bounded by an upper and lower threshold. Hence,
the extent to which changes can be made may generally be restricted
to within a particular range to help improve the stability and
convergence of the overall system.
[0011] In one embodiment, the coverage area adjustment logic is
operable, when the user equipment communications load supported by
the base station is below an average user equipment communications
load for the group but fails to exceed a predetermined maximum user
equipment communications load supportable by the base station, to
increase the coverage area to no more than a maximum coverage area
defined by the upper threshold of the predetermined range to
increase the user equipment communications load experienced by the
base station. Accordingly, should it be determined that the load
currently being supported by the base station is less than the
maximum load which the base station can support and is also less
than the average load for base stations within that group, then
this is likely to indicate that that the base station still has
capacity to take on more load and that other base stations are
carrying more than their fair share of load. Hence, the coverage
area of that base station may be increased. Increasing the coverage
area is likely to cause user equipment which currently exerts a
communications load on a neighbouring base station to handover to
this base station thereby rebalancing the load on base stations
within the group. Also, by ensuring that the increase in coverage
does not exceed the maximum threshold, the maximum coverage area of
that base station can be restrained to prevent any one base station
unnecessarily dominating an area which may otherwise cause a
detrimental effect on the overall performance of the network.
[0012] In one embodiment, the coverage area adjustment logic is
operable, when the user equipment communications load experienced
by the base station is above an average user equipment
communications load for the group and exceeds a predetermined
maximum user equipment communications load supportable by the base
station, to decrease the coverage area to decrease the user
equipment communications load experienced by the base station.
Accordingly, should it be determined that the load currently being
supported by the base station exceeds the maximum load which the
base station can support and is also above the average load of base
stations within the group, then this is likely to indicate that
that the base station still has no capacity to take on more load
and that other base stations are carrying less than their fair
share of load. Hence, the coverage area of that base station is
decreased. Decreasing the coverage area of the base station is
likely to cause user equipment exerting a load on that base station
to handover to another base station within that group, again
rebalancing the load between base stations within the group.
[0013] In one embodiment, the coverage area adjustment logic is
operable, when the decrease in the coverage area is to below the
lower threshold, to reduce the lower threshold. It will be
appreciated that if the decreased coverage area provides a coverage
area which is less that the lower threshold, then it is likely that
the lower threshold may be too high for the currently loading since
that base stations is exceeding its capacity and supporting more
user load than others within the group. By reducing the lower
threshold, the coverage area may be reduced to an amount which
enables reasonable operation of that base station and helps to
rebalance the loading.
[0014] In one embodiment, the coverage area adjustment logic is
operable, when the user equipment communications load experienced
by the base station is above an average user equipment
communications load for the group but fails to exceed a
predetermined maximum user equipment communications load
experienced by the base station and when base stations identified
from the load information as being candidates to support user
equipment communications load which would no longer be supported by
the base station fail to exceed a predetermined maximum user
equipment communications load supportable by those base stations,
to decrease the coverage area to no less than a minimum coverage
area defined by the lower threshold of the predetermined range to
decrease user equipment communications load experienced by the base
station. Accordingly, it is determined whether the current loading
on the base station is less than the maximum loading for that base
station but exceeds the average loading for the group, thereby
indicating that the base station is more heavily loaded than it
need be. However, rather than simply decrease its coverage area, a
further determination is made as to whether those base stations
which would experience an increase in load should be coverage area
of this base station be reduced have the capacity to take on that
additional load. Only if those base stations do have the capacity
to take the additional load may the coverage area be decreased.
Otherwise, no changes in the coverage area may be made since the
base station still has sufficient capacity to accommodate the
additional loading. In this way it can be seen that a decrease in
coverage area may only occur when it is not overly detrimental to
do so to other base stations within the group.
[0015] In one embodiment, the reception logic is operable to
receive receiver sensitivity information indicative of a
sensitivity of receivers of user equipment supported by base
stations within the group and the coverage area adjustment logic is
operable to determine from the receiver sensitivity information
whether the decrease to the coverage area would cause user
equipment communications load to no longer be supported by the base
stations within the group and, if so, to prevent the decrease.
Accordingly, information regarding the sensitivity of receivers of
the user equipment being supported by base stations within the
group may be provided. It will be appreciated that this information
may be provided by the user equipment themselves and communicated
to base stations either directly, via the base stations to which
the user equipment are attached, or via some other network node. A
decrease in the coverage area of the base station may be prevented
should it be determined from the receiver sensitivity information
that doing so would cause user equipment to no longer be supported
by the base stations within the group. It will be appreciated that
if that would be allowed to occur, then either the user equipment
would experience a dropped call or this may cause the user
equipment to be handed back to any overlying cell such as, for
example, a macro cell within which the group is located.
[0016] In one embodiment, the load information indicative of a user
equipment communications load experienced by base stations within
the group comprises information indicative of numbers of user
equipment supported by the base stations within the group and the
coverage area adjustment logic is operable to determine changes
required to the coverage area by changing its pilot channel
transmission power to change the user equipment communications load
experienced by at least one base station within the group by
changing numbers of users supported by the at least one base
station within the group. Accordingly, the number of user equipment
supported by the base stations may be provided. Changes in the
pilot transmission power level may be utilised to vary the coverage
area. It will be appreciated that increasing or decreasing the
pilot channel transmission power may cause the number of user
equipment being supported by base stations to be increased or
decreased.
[0017] In one embodiment, the predetermined range bounded by an
upper and lower threshold comprises a predetermined pilot channel
transmission power range bounded by an upper pilot channel
transmission power threshold and a lower pilot channel transmission
power threshold. Accordingly, upon receiving user load information
from each of its neighbouring base stations, the base station may
compute the average user load shared by all base stations. The
difference between the base station's current load and the average
load shared by all the base stations represents a target number of
users to be adjusted within its coverage area. The base station may
then adjust its pilot transmission power (and consequentially its
coverage) within the threshold of the minimum pilot transmission
power and the maximum transmission power to acquire or handover the
desired number of users to or from other base stations. The maximum
pilot transmission power threshold is typically fixed and depends
on how much of the total base station transmission power is
allocated to the pilot channel by the network operator, whereas the
lower threshold may be varied to suit the individual operating
conditions of that base station.
[0018] In one embodiment, the coverage area adjustment logic is
operable, when the number of user equipment supported by the base
station is below an average number of user equipment supported by
base stations within the group but fails to exceed a predetermined
maximum number of user equipment supportable by the base station,
to increase the coverage area to no more than a maximum coverage
area defined by the upper threshold of the predetermined range to
increase the number of user equipment supported by the base
station. By increasing the pilot channel transmission power it is
likely that user equipment which are currently being supported by
other base stations within the group may handover to that base
station, thereby reducing the number of user equipment being
supported by those other base stations and increasing the number or
user equipment being supported by this base station. Also, by
increasing the pilot channel transmission power any coverage holes
which may otherwise exist can be filled.
[0019] In one embodiment, the coverage area adjustment logic is
operable, when the number of user equipment supported by the base
station is above an average number of user equipment supported by
base stations within the group and exceeds a predetermined maximum
number of user equipment supportable by the base station, to
decrease the coverage area to decrease the number of user equipment
supported by the base station. By decreasing the pilot channel
transmission power it is likely that user equipment which are
currently being supported by that base station may handover to
other base stations within the group, thereby reducing the number
of user equipment being supported by that base station and
increasing the number or user equipment being supported by other
base stations within the group. Also, decreasing the pilot channel
transmission power helps to minimise any coverage overlap which may
exist between neighbouring base stations.
[0020] In one embodiment, the coverage area adjustment logic is
operable, when the number of user equipment supported by the base
station is above an average number of user equipment supported by
base stations within the group but fails to exceed a predetermined
maximum number of user equipment supportable the base station and
when base stations identified from the information indicative of
numbers of user equipment supported by the base stations as being
candidates to support user equipment which would no longer be
supported by the base station fail to exceed a predetermined
maximum number of user equipment supportable by those base
stations, to decrease the coverage area to no less than a minimum
coverage area defined by the lower threshold of the predetermined
range to decrease the number of user equipment supported by the
base station.
[0021] In one embodiment, the reception logic is operable to
receive an indication of quality of service provided to user
equipment supported by the base station and the coverage area
adjustment logic is operable to adjust the lower threshold of the
predetermined range to vary the minimum coverage area definable by
the predetermined range in response to the indication. By utilising
a measured coverage metric such as, for example, the quality of
service, over a specified amount of time, an assessment can be made
of the overall coverage provided by the base stations within the
group to help minimise coverage holes and/or overlap.
[0022] In one embodiment, the coverage area adjustment logic is
operable to perform at least one of: when the indication of quality
of service indicates that less than or equal to a predetermined
quality of service is being provided to user equipment supported by
the base station, to increase the lower threshold of the
predetermined range by a first predetermined amount; and when the
indication of quality of service indicates that greater than a
predetermined quality of service is being provided to user
equipment supported by the base station, to decrease the lower
threshold of the predetermined range by a second predetermined
amount. Accordingly, the threshold may be incremented to help to
remove coverage holes whilst the threshold may be decremented to
help to minimise any coverage overlap. It will be appreciated that
a base station's coverage area may typically be the geographical
region where its transmitted signal can be received by user
equipment at a signal strength that is greater than some specified
threshold. A coverage gap represents the area where the received
base station signal is typically below the specified threshold,
whereas a coverage overlap denotes the region where two or more
base stations signals are received by user equipment above the
specified threshold.
[0023] In one embodiment, the first predetermined amount is greater
than the second predetermined amount. Setting the decrement step to
be much lower than the increment step helps to ensure that the
coverage is dominated by the increment step and that coverage is
decreased gradually. Accordingly, the base station may monitor the
value of a coverage metric (for example a metric incorporating the
users call drop probability or a coverage overlap coefficient) over
a specified amount of time. If the measured value of the specified
metric exceeds a corresponding maximum allowable threshold, then
the base station's minimum pilot transmission power threshold may
be increased typically by a fixed step size. However, if the
measured metric value is less than the maximum allowable threshold,
then the base station's minimum pilot transmission power threshold
may be reduced gradually.
[0024] In one embodiment, the coverage area adjustment logic is
operable to assess whether changes are required to the lower
threshold based on the indication of quality of service less
frequently than whether changes are required to the coverage area
based on the load information. Accordingly, the rate at which the
lower threshold is assessed may be much lower that the rate at
which the coverage area is assessed to help improve convergence of
the system. Accordingly, the minimum pilot transmission power
threshold is set adaptively by the algorithm which runs
individually on each base station and consists of two update
cycles, a more frequent pilot transmission power update, which
achieves user load balancing, and a less frequent minimum pilot
transmit power threshold update to minimise coverage holes and
overlap.
[0025] According to a second aspect of the present invention, there
is provided a method, comprising the steps of: generating a cell
having a coverage area supporting wireless communications with user
equipment; receiving load information indicative of a user
equipment communications load experienced by base stations
operating in concert with other base stations within a group to
support wireless communications with user equipment; and
determining changes required to the coverage area to change a user
equipment communications load experienced by at least one base
station within the group.
[0026] In one embodiment, the step of determining comprises:
determining changes required the coverage area within a
predetermined range bounded by an upper and lower threshold.
[0027] In one embodiment, the step of determining comprises: when
the user equipment communications load supported by the base
station is below an average user equipment communications load for
the group but fails to exceed a predetermined maximum user
equipment communications load supportable by the base station,
increasing the coverage area to no more than a maximum coverage
area defined by the upper threshold of the predetermined range to
increase the user equipment communications load experienced by the
base station.
[0028] In one embodiment, the step of determining comprises: when
the user equipment communications load experienced by the base
station is above an average user equipment communications load for
the group and exceeds a predetermined maximum user equipment
communications load supportable by the base station, decreasing the
coverage area to decrease the user equipment communications load
experienced by the base station.
[0029] In one embodiment, the step of determining comprises: when
the decrease in the coverage area is to below the lower threshold,
reducing the lower threshold.
[0030] In one embodiment, the step of determining comprises: when
the user equipment communications load experienced by the base
station is above an average user equipment communications load for
the group but fails to exceed a predetermined maximum user
equipment communications load experienced the base station and when
base stations identified from the load information as being
candidates to support user equipment communications load which
would no longer be supported by the base station fail to exceed a
predetermined maximum user equipment communications load
supportable by those base stations, decreasing the coverage area to
no less than a minimum coverage area defined by the lower threshold
of the predetermined range to decrease user equipment
communications load experienced by the base station.
[0031] In one embodiment, the step of receiving comprises:
receiving receiver sensitivity information indicative of a
sensitivity of receivers of user equipment supported by base
stations within the group and the step of determining comprises:
determining from the receiver sensitivity information whether the
decrease to the coverage area would cause user equipment
communications load to no longer be supported by the base stations
within the group and, if so, to prevent the decrease.
[0032] In one embodiment, the load information indicative of a user
equipment communications load experienced by base stations within
the group comprises information indicative of numbers of user
equipment supported by the base stations within the group and the
step of determining comprises: determining changes required to the
coverage area by changing its pilot channel transmission power to
change the user equipment communications load experienced by at
least one base station within the group by changing numbers of
users supported by the at least one base station within the
group.
[0033] In one embodiment, the predetermined range bounded by an
upper and lower threshold comprises a predetermined pilot channel
transmission power range bounded by an upper pilot channel
transmission power threshold and a lower pilot channel transmission
power threshold.
[0034] In one embodiment, the step of determining comprises: when
the number of user equipment supported by the base station is below
an average number of user equipment supported by base stations
within the group but fails to exceed a predetermined maximum number
of user equipment supportable by the base station, increasing the
coverage area to no more than a maximum coverage area defined by
the upper threshold of the predetermined range to increase the
number of user equipment supported by the base station.
[0035] In one embodiment, the step of determining comprises: when
the number of user equipment supported by the base station is above
an average number of user equipment supported by base stations
within the group and exceeds a predetermined maximum number of user
equipment supportable by the base station, decreasing the coverage
area to decrease the number of user equipment supported by the base
station.
[0036] In one embodiment, the step of determining comprises: when
the number of user equipment supported by the base station is above
an average number of user equipment supported by base stations
within the group but fails to exceed a predetermined maximum number
of user equipment supportable the base station and when base
stations identified from the information indicative of numbers of
user equipment supported by the base stations as being candidates
to support user equipment which would no longer be supported by the
base station fail to exceed a predetermined maximum number of user
equipment supportable by those base stations, decreasing the
coverage area to no less than a minimum coverage area defined by
the lower threshold of the predetermined range to decrease the
number of user equipment supported by the base station.
[0037] In one embodiment, the step of receiving comprises:
receiving an indication of quality of service provided to user
equipment supported by the base station and the step of determining
comprises: adjusting the lower threshold of the predetermined range
to vary the minimum coverage area definable by the predetermined
range in response to the indication.
[0038] In one embodiment, the step of determining comprises at
least one of: when the indication of quality of service indicates
that less than or equal to a predetermined quality of service is
being provided to user equipment supported by the base station,
increasing the lower threshold of the predetermined range by a
first predetermined amount; and when the indication of quality of
service indicates that greater than a predetermined quality of
service is being provided to user equipment supported by the base
station, decreasing the lower threshold of the predetermined range
by a second predetermined amount.
[0039] In one embodiment, the first predetermined amount is greater
than the second predetermined amount.
[0040] In one embodiment, the step of determining comprises
assessing whether changes are required to the lower threshold based
on the indication of quality of service less frequently than
whether changes are required to the coverage area based on the load
information.
[0041] According to a third aspect of the present invention, there
is provided a computer program product operable, when executed on a
computer, to perform the method steps of the second aspect.
[0042] Further particular and preferred aspects are set out in the
accompanying independent and dependent claims. Features of the
dependent claims may be combined with features of the independent
claims as appropriate, and in combinations other than those
explicitly set out in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] Embodiments of the present invention will now be described
further, with reference to the accompanying drawings, in which:
[0044] FIG. 1 illustrates the main components of a
telecommunications network according to one embodiment;
[0045] FIG. 2 illustrates a general femto cell deployment within
one macro cell shown in FIG. 1;
[0046] FIG. 3 illustrates in more detail a specific femto cell
deployment within the wireless communications network of FIG.
1;
[0047] FIG. 4 illustrates schematically the update cycles;
[0048] FIG. 5 is a flowchart illustrating the main processing steps
of the load balancing updates; and
[0049] FIG. 6 is a flowchart illustrating the main processing steps
of the coverage updates.
DESCRIPTION OF THE EMBODIMENTS
[0050] FIG. 1 illustrates a wireless communication system,
generally 10, according to one embodiment. User equipment 44 roam
through the wireless communication system 10. Base stations 22 are
provided which support respective macro cells 24. A number of such
base stations are provided, which are distributed geographically in
order to provide a wide area of coverage to the user equipment 44.
When user equipment 44 is within a macro cell 24 supported by the
base station 22 then communications may be established between the
user equipment 44 and the base station 22 over an associated radio
link. Each base station typically supports a number of sectors.
Typically, a different antenna within a base station supports an
associated sector. Of course, it will be appreciated that FIG. 1
illustrates a small subset of the total number of user equipment
and base stations that may be present in a typical communications
system.
[0051] The wireless communication system 10 is managed by a radio
network controller 170. The radio network controller 170 controls
the operation of the wireless communications system 10 by
communicating with the base stations 22 over a backhaul
communications link 160. The network controller 170 also
communicates with the user equipment 44 via their respective radio
links in order to efficiently manage the wireless communication
system 10.
[0052] The radio network controller 170 maintains a neighbour list
which includes information about the geographical relationship
between cells supported by base stations. In addition, the radio
network controller 170 maintains location information which
provides information on the location of the user equipment within
the wireless communications system 10. The radio network controller
170 is operable to route traffic via circuit-switched and
packet-switched networks. Hence, a mobile switching centre 250 is
provided with which the radio network controller 170 may
communicate. The mobile switching centre 250 then communicates with
a circuit-switched network such as a public switched telephone
network (PSTN) 210. Likewise, the network controller 170
communicates with service general packet radio service support
nodes (SGSNs) 220 and a gateway general packet radio support node
(GGSN) 180. The GGSN then communicates with a packet-switch core
190 such as, for example, the Internet.
[0053] As shown in more detail in FIG. 2, there are provided small
cell base stations, in this example femto cell base stations
F.sub.Ato F.sub.C, each of which provides a femto cell A to C in
the vicinity of a building within which the associated femto cell
base station is installed. The femto cells A to C provide local
communications coverage for a user in the vicinity of those
buildings. Each femto cell base station F.sub.A to F.sub.C
communicates via a femtocell controller/gateway 230. A handover or
camping event occurs between the base station 22 and the femto cell
base stations F.sub.A to F.sub.C when the femto base stations
F.sub.A to F.sub.C detect that user equipment comes within range.
The femto cell base stations F.sub.Ato F.sub.C typically utilise
the user's broadband Internet connection 240 (such as ADSL, Cable,
Ethernet, etc.) as a backhaul.
[0054] Femto cell base stations F.sub.A to F.sub.C are lower-power,
low-cost, user-deployed base stations that provide a high cellular
quality of service in residential or enterprise environment. In
contrast to current macro cell approaches where complex and highly
reliable base stations are deployed to strategic locations decided
by the network owner, the femto cell base stations F.sub.A to
F.sub.C are provided locally by customers. Such femto cell base
stations F.sub.A to F.sub.C provide local coverage in areas of the
macro network where quality of service may be low. Hence, the femto
cell base stations F.sub.Ato F.sub.C provide for improved quality
of service in areas which are difficult for network operators. To
reduce the cost of the femto base stations F.sub.Ato F.sub.C and to
reduce complexity and interference effects of the femto cell on
other user equipment within the macro cell, the transmission power
of the femto cell base station F.sub.A to F.sub.C is relatively low
in order to restrict the size of the femto cell to a range of tens
of metres or less. The femto cell base stations F.sub.A to F.sub.C
have extensive auto-configuration and self-optimisation capability
to enable a simply plug-and-play deployment. As such, they are
designed to automatically integrate themselves into an existing
macro cellular wireless network 10.
[0055] FIG. 3 illustrates a cluster or group of femto base stations
F.sub.A to F.sub.C jointly providing coverage in an intended
geographical area. The group of femto base stations form a wireless
small cell network. The wireless small cell network is provided
typically within an underlying macro cell 24. The underlying macro
cell 2 is intended to cater for high mobility users and a wide
geographical coverage area. The group of femto base stations
forming the wireless small cell network is intended to provide
local coverage to user equipment. When user equipment move between
the different femto cells A to C forming the wireless small cell
network, it is desired that the user equipment remains supported by
those femto base stations and avoids being handed over to the
underlying macro cell 24.
[0056] Each base station's coverage area is the geographical region
where the transmitted signal can be received by a user equipments
receiver at a signal strength which is greater than some specified
threshold. Of course, the coverage will depend on may factors such
as, for example, the transmission strength of the signal, the
sensitivity of the receiver at the user equipment, the attenuation
between the transmitter and the receiver, as well as any other
noise or interference experienced. Hence, the area 11 is a coverage
gap or hole where the received signal from each of the femto base
stations is below that specified threshold. The overlap areas 8, 9,
10 denote those regions where the signal strength from two base
stations in that region is greater than the specified
threshold.
[0057] The technique disclosed herein seeks to perform optimisation
within the wireless small cell network by varying the coverage area
provided by each base station in a way which seeks to meet the
following objectives. The first is to balance the user load amongst
the co-located base stations to enable efficient utilisation of
radio resources. The second is to minimise any radio coverage holes
or gaps within the wireless small cell network. The third is to
minimise any coverage overlap between neighbouring base stations;
in other words to achieve the first two objectives with a minimum
possible transmission power. Local status information available to
each base stations is used to perform this optimisation. This
information is obtained from measurement reports communicated back
to the base stations by connected user equipment and/or from
information provided by neighbouring base stations either directly
or via a central node such as, for example, the femto
controller/gateway 230. Each base station then makes use of this
information and, based on predefined algorithms, makes a local
decision to help the wireless small cell network collectively to
better achieve those objectives. In particular, each base station
performs frequent updates to its pilot channel transmission power
to vary the coverage area of that base station, thereby adjusting
the load on that base station and/or on neighbouring base
stations.
[0058] Each base station stores thresholds for maximum pilot
channel transmission power and minimum pilot channel transmission
power. The maximum pilot channel transmission power threshold is
fixed and depends on how much of the total base station
transmission power is allocated to the pilot channel by the network
designer. The minimum pilot power transmission threshold is set
adaptively by the predefined algorithms. Pilot channel transmission
power updates occur more frequently and adjust the level of the
pilot channel transmission power within these two thresholds.
Minimum pilot channel transmission power threshold updates occur
less frequently, as illustrated schematically in FIG. 4.
[0059] Each base station, upon receiving user load information
relating to neighbouring base stations, computes the average user
load shared by those base stations. The difference between the base
stations current load and the average load shared by the
neighbouring base stations represents the target number of users to
be adjusted within the base stations coverage area. The base
station then, if appropriate, adjusts its pilot channel
transmission power, and consequently its coverage, within the
thresholds to acquire or handover the desired number of users to a
neighbouring base station in order to rebalance the load, as will
be described in more detail below.
[0060] Each base station also monitors the value of the coverage
metric such as a metric incorporating a call drop probability
and/or a coverage overlap coefficient and/or another quality of
service metric over a specified amount of time. If the measured
value of the specified metric exceeds a corresponding maximum
allowable threshold, the base station's minimum pilot channel
transmission power threshold is increased by a particular step size
because exceeding the desired threshold indicates inadequate
coverage. However, if the measured metric is less than the maximum
allowable threshold, the base station's minimum pilot channel
transmission power threshold is reduced gradually since greater
than an adequate quality of service is being provided to user
equipment and it may be that the base station can reduce its
transmission power.
[0061] As shown in FIG. 3, each base station F.sub.A, F.sub.B,
F.sub.C is operable to communicate and/or sense the neighbouring
base stations within the group. To improve clarity of the following
description and by way of example, the base station F.sub.A will be
referred to as the "local" base station. The neighbouring base
station F.sub.B and F.sub.C will the referred to as neighbouring
base stations. The local base station F.sub.A is operable to
perform pilot channel signal measurements to detect the
neighbouring base stations that are located nearby either directly
or through measurement reports. The local base station F.sub.A can
also perform query and respond procedures over the backhaul network
to obtain information about its neighbours either directly from
those neighbouring base stations or from information stored
centrally by the femto cell controller/gateway 230. In any event,
the neighbouring base stations are those whose pilot channel power
changes can have a significant impact on the local base station
performance and visa versa.
[0062] As mentioned above, each base station periodically gathers
information from supported user equipment and neighbouring base
stations the base station then periodically adjusts its pilot
channel transmission power lower threshold periodically to minimise
coverage holes and any overlaps. Each base station also performs
more frequently changes to its pilot channel transmission power
within the set upper and lower thresholds to balance the load
experienced between neighbouring base stations within the wireless
small cell network, as will now be described in more detail.
[0063] FIG. 5 is a flow chart illustrating the operation of each
base station when performing load balancing updates. As mentioned
previously, these load balancing updates occur relatively
frequently compared to the coverage updates illustrated in FIG.
6.
[0064] At step S10, the local base station determines the current
user load L.sub.0,k (typically the number of active users being
supported by the base station, but may also include other load
metrics such as, for example, the transmission bandwidth being
demanded by the supported users) in the current update slot, K.
[0065] At step S20, the local base station determines the loads
L.sub.i,K of each of the neighbouring base stations, where i=1 to
N-1, and N is the total number of base stations in a neighbour
cluster or group (for example N is 3 in the example shown in FIG.
3).
[0066] At step S30, the local base station then calculates a base
station target load in accordance with the algorithm
L T , k = min ( C , i = 0 N - 1 l i , k N ) , ##EQU00001##
where L.sub.T,k is the target load for the local base station being
currently updated in the slot K, C is the local base station
capacity (typically the maximum number of active users supportable
by that base station or some other load metric such as the maximum
communications bandwidth supportable by that base station). This
target load can then be used to provide an indication of whether
the local base station is supporting more or less than the average
load being supported by other base stations within the group.
[0067] At step S40, a determination is made as to whether the
current user load L.sub.0,k on the base station is greater than the
target load L.sub.T,k for that base station. If the current user
load L.sub.0,k is less than the target load L.sub.T,k (meaning that
the current user load is less than the maximum capacity of the base
station C), then processing proceeds to step S45. At step S45, a
determination is made as to whether the current user load L.sub.0,k
on the base station equals the target load L.sub.T,k for that base
station. If the current user load L.sub.0,K equals the target load
L.sub.T,K, then no changes to the pilot channel transmission power
and processing proceeds to step S90. If the current user load
L.sub.0,k is less than but not equal to the target load L.sub.T,k
(meaning that the current user load is less than the maximum
capacity of the base station C), then processing proceeds to step
S50 where routine 3: Inc_Pwr_Underloaded (shown below) occurs
because the base station is operating at less than the target level
meaning that other base stations within the group are supporting a
greater load and the local base station still has capacity to
accept more load; the coverage area of the local base station is
then increased by increasing the pilot channel transmission power
to cause user equipment to handover from the more heavily loaded
base stations within the group to the local base station, and
processing proceeds to step S90. If the current user load L.sub.0,K
is greater than the target load L.sub.T,K, indicating that the base
station is supporting greater than its share of load then
processing proceeds to step S60.
[0068] At step S60, a determination is made of whether the current
user load L.sub.0,K is greater than the capacity C of the local
base station. If the current user load L.sub.0,K is greater than
the capacity C of the local base station, then this indicates that
the local base station is overloaded and needs to reduce its
loading by handing-off user equipment; processing then proceeds to
step S70 where routine 1: Dec_Pwr_Overloaded occurs. If the user
load L.sub.0,K is less than or equal to the capacity C of the local
base station then processing proceeds to step S80 where routine 2
Dec_Pwr_Underloaded occurs whereby the local base station seeks to
reduce its transmission power, but only when it is possible to do
so; accordingly a determination is made of whether other base
stations within the group are able to carry that load before any
power reduction occurs.
[0069] At step S90, processing returns to step S10 to calculate the
user load in the next slot.
[0070] Routine 1: Dec_Pwr_Overloaded
TABLE-US-00001 1: For each connected mobile receiver, calculate its
RPSS difference, i.e. P.sub.rx.sup.diff . 2: Sort, in ascending
order, the calculated P.sub.rx.sup.diff of all mobile receivers. 3:
Store the sorted P.sub.rx.sup.diff in an array . 4: Decrease base
station pilot transmission power by P.sub.tx = P.sub.tx - MEAN[
(L.sub.0 - C), (L.sub.0 - C + 1)]. 5: if P.sub.tx <
P.sub.tx,min.sup.thr then 6: P.sub.tx,min.sup.thr = P.sub.tx 7: end
if 8: Go to Routine 2: Dec_Pwr_Underloaded.
[0071] Routine 2: Dec_Pwr_Underloaded
TABLE-US-00002 1: for i = 1 to (L.sub.0 - L.sub.T ) do 2: For each
connected mobile receiver, calculate its RPSS difference i.e.
P.sub.rx.sup.diff . 3: Sort, in ascending order, the calculated
P.sub.rx.sup.diff of all mobile receivers. 4: Store the sorted
P.sub.rx.sup.diff in an array . 5: Pick the mobile receiver R.sub.1
with the lowest P.sub.rx , i.e. P.sub.rx,L . 6: Pick the mobile
receiver R.sub.2 with the lowest P.sub.rx.sup.diff , i.e.
P.sub.rx,L.sup.diff . 7: Calculate pilot power update as P.sub.tx,u
= P.sub.tx - min(P.sub.tx,min.sup.thr,Mean[ (1), (2)]). 8: if
(R.sub.1 is the same as R.sub.2) then 9: Pick the mobile receiver
R.sub.3 with the second lowest P.sub.rx , i.e. {circumflex over
(P)}.sub.rx,L . 10: if (({circumflex over (P)}.sub.rx,L -
P.sub.tx,u) > .eta. then 11: For R.sub.2, check the following:
12: if (its next best base station is not a Macro) AND (its next
best base station is not fully loaded) AND (P.sub.rx.sup.NB >
.eta.) then 13: P.sub.tx = P.sub.tx - P.sub.tx,u . 14: else 15:
Break. 16: end if 17: else 18: Break. 19: end if 20: else 21: if
((P.sub.rx,L - P.sub.tx,u) > .eta. then 22: For R.sub.2, check
the following: 23: if (its next best base station is not a Macro)
AND (its next best base station is not fully loaded) AND
(P.sub.rx.sup.NB > .eta.) then 24: P.sub.tx = P.sub.tx -
P.sub.tx,u 25: else 26: Break. 27: end if 28: else 29: Break. 30:
end if 31: end if 32: end for
[0072] Routine 3 Inc_Pwr_Underloaded
TABLE-US-00003 1: For each neighbour-connected mobile receiver,
calculate its RPSS difference, i.e. P.sub.rx.sup.diff between the
own pilot signal and the neighbour BS's pilot signal. 2: Sort, in
ascending order, the above-calculated RPSS differences, and store
in an array . 3: Increase base station pilot transmission power by
P.sub.tx = min(P.sub.tx,max.sup.thr,P.sub.tx + MEAN[ (L.sub.T -
L.sub.0), (L.sub.T - L.sub.0 + 1)].
[0073] Hence, it can be seen that a local base station employs
algorithms to adjust its user load to that of the calculated mean
of all N neighbouring base stations. Given the current user load of
the local base station, it collects via backhaul the user loads of
its neighbours. It then computes the average load of the neighbour
set (including its own load. Next, the local base station compares
its current user load against the average load of the neighbour
set, and decreases or increases its pilot transmission power to
handover or acquire desired users, respectively. If the current
user load is greater than its capacity (L0>C; the overloaded
case), it employs the routine Dec_Pwr_Overloaded to drop the extra
users. For the case (C, L.sub.0>L.sub.T), the local base station
uses the routine Dec_Pwr_Underloaded, which drops a user only if it
can be picked up by another femtocell. For the underloaded case
(L.sub.0<L.sub.T), the routine Inc_Pwr_Underloaded increases the
BS's pilot transmission power to acquire the required number of
users (L.sub.T-L.sub.0).
[0074] As mentioned above, periodically, the minimum pilot channel
transmission power threshold P.sub.tx,min.sup.thr is varied to help
minimise coverage holes and any overlaps. A coverage metric is
measured over a certain predetermined amount of time and the base
station compares the measured metric against a predetermined
threshold and decides to increase or decrease the minimum pilot
channel transmission power threshold accordingly. An increase in
the minimum pilot channel transmission power threshold
P.sub.tx,min.sup.thr helps to remove coverage holes whilst a
decrease in the minimum pilot channel transmission threshold
P.sub.tx,min.sup.thr helps to minimise any coverage overlaps.
Typically, the decrease step size {circumflex over (P)}.sub.step
will be set to be much lower than the increment step size
P.sub.step to ensure that the base station coverage decreases
gradually and that the coverage is dominated by the increment step.
This is because coverage overlaps are less likely to adversely
affect user equipment quality of service than coverage holes.
[0075] Turning now to FIG. 6, at step S100, the coverage metric
.zeta..sub.0,k is measured.
[0076] At step S110, a determination is made as to whether the
measured coverage metric .zeta..sub.0,k exceeds the predetermined
threshold .zeta..sub.0.sup.thr or not. If the measured coverage
metric .zeta..sub.0,k does exceeds the threshold
.zeta..sub.0.sup.thr, indicating that an inadequate service is
being provided to the user equipment, then the minimum pilot
channel transmission power threshold P.sub.tx,min.sup.thr is
increased by a predetermined step P.sub.step as step S120. If it is
determined at step S110 that the measured coverage metric
.zeta..sub.0,k is less than or equal to the threshold
.zeta..sub.0.sup.thr, then processing proceeds to step S130.
[0077] At step S130, a determination is made of whether the current
transmission power P.sub.tx equals the minimum pilot channel
transmission power threshold P.sub.tx,min.sup.thr. If it does not,
then no changes are made and processing proceeds to step S150. If
it is determined that the pilot channel transmission power P.sub.tx
equals the minimum pilot channel transmission power threshold
P.sub.tx,min.sup.thr then, at step S140, the minimum pilot channel
transmission power threshold P.sub.tx,min.sup.thr is reduced by a
predetermined step {circumflex over (P)}.sub.step. Thereafter,
processing proceeds step S150.
[0078] At step S150, further processing is suspended until the next
update slot in B time periods.
[0079] Hence, it can be seen that In contrast to centralized
approaches, decentralized/distributed algorithms are utilised which
allow base stations to take local decisions to achieve a global
objective. A decentralized joint coverage optimisation algorithm
runs individually in each femtocell base station and works towards
achieving user load balancing and minimization of coverage holes
and overlap. Each base station stores thresholds for maximum pilot
transmission power and minimum pilot transmission power. The
maximum pilot power threshold is fixed and depends upon how much of
the total base station transmission power is allocated to the pilot
channel by the network designer. The minimum pilot power threshold
is set adaptively by the algorithm. The algorithm, which runs
individually at each base station, consists of two update cycles; a
more frequent pilot power transmission update to achieve user load
balancing and an infrequent minimum pilot transmission threshold
update to handle coverage hole and overlap minimization. The reason
for more frequent load balancing updates is to cater for the
mobility of the users and to converge to a balanced load before the
users' positions change.
NOMENCLATURE
[0080] N--The total number of base stations in a neighbor cluster,
such that each base station has N-1 neighbors.
[0081] C--Base station capacity (e.g. maximum number of active
users).
[0082] .eta.--mobile receiver's receiver sensitivity.
[0083] L.sub.0--User load (number of active users) for the base
station currently updating.
[0084] L.sub.T--Target user load for the base station currently
updating.
[0085] P.sub.tx,min.sup.thr--Base station minimum pilot power
threshold (adaptive).
[0086] P.sub.tx,min.sup.thr--Base station maximum pilot power
threshold (fixed).
[0087] .zeta..sup.thr--Threshold for the coverage holes metric
[0088] P.sub.rx--Received Pilot Signal Strength (RPSS).
[0089] P.sub.rx,L--Lowest Received Pilot Signal Strength.
[0090] P.sub.rx.sup.B--Received Pilot Signal Strength from the best
base station.
[0091] P.sub.rx.sup.NB--Received Pilot Signal Strength from the
next best base station.
P.sub.rx.sup.diff=P.sub.rx.sup.B-P.sub.rx.sup.NB.
[0092] P.sub.rx,L.sup.diff--Lowest P.sub.rx.sup.diff.
[0093] A person of skill in the art would readily recognize that
steps of various above-described methods can be performed by
programmed computers. Herein, some embodiments are also intended to
cover program storage devices, e.g., digital data storage media,
which are machine or computer readable and encode
machine-executable or computer-executable programs of instructions,
wherein said instructions perform some or all of the steps of said
above-described methods. The program storage devices may be, e.g.,
digital memories, magnetic storage media such as a magnetic disks
and magnetic tapes, hard drives, or optically readable digital data
storage media. The embodiments are also intended to cover computers
programmed to perform said steps of the above-described
methods.
[0094] The functions of the various elements shown in the Figures,
including any functional blocks labelled as "processors" or
"logic", may be provided through the use of dedicated hardware as
well as hardware capable of executing software in association with
appropriate software. When provided by a processor, the functions
may be provided by a single dedicated processor, by a single shared
processor, or by a plurality of individual processors, some of
which may be shared. Moreover, explicit use of the term "processor"
or "controller" or "logic" should not be construed to refer
exclusively to hardware capable of executing software, and may
implicitly include, without limitation, digital signal processor
(DSP) hardware, network processor, application specific integrated
circuit (ASIC), field programmable gate array (FPGA), read only
memory (ROM) for storing software, random access memory (RAM), and
non volatile storage. Other hardware, conventional and/or custom,
may also be included. Similarly, any switches shown in the Figures
are conceptual only. Their function may be carried out through the
operation of program logic, through dedicated logic, through the
interaction of program control and dedicated logic, or even
manually, the particular technique being selectable by the
implementer as more specifically understood from the context.
[0095] It should be appreciated by those skilled in the art that
any block diagrams herein represent conceptual views of
illustrative circuitry embodying the principles of the invention.
Similarly, it will be appreciated that any flow charts, flow
diagrams, state transition diagrams, pseudo code, and the like
represent various processes which may be substantially represented
in computer readable medium and so executed by a computer or
processor, whether or not such computer or processor is explicitly
shown.
[0096] The description and drawings merely illustrate the
principles of the invention. It will thus be appreciated that those
skilled in the art will be able to devise various arrangements
that, although not explicitly described or shown herein, embody the
principles of the invention and are included within its spirit and
scope. Furthermore, all examples recited herein are principally
intended expressly to be only for pedagogical purposes to aid the
reader in understanding the principles of the invention and the
concepts contributed by the inventor(s) to furthering the art, and
are to be construed as being without limitation to such
specifically recited examples and conditions. Moreover, all
statements herein reciting principles, aspects, and embodiments of
the invention, as well as specific examples thereof, are intended
to encompass equivalents thereof.
* * * * *