U.S. patent application number 14/219263 was filed with the patent office on 2014-07-24 for method and arrangement in a telecommunication system.
This patent application is currently assigned to Unwired Planet, LLC. The applicant listed for this patent is Unwired Planet, LLC. Invention is credited to Walter MULLER.
Application Number | 20140204787 14/219263 |
Document ID | / |
Family ID | 40579751 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140204787 |
Kind Code |
A1 |
MULLER; Walter |
July 24, 2014 |
METHOD AND ARRANGEMENT IN A TELECOMMUNICATION SYSTEM
Abstract
In a cell of a cellular wireless telecommunication system, a low
interference time period is predefined for transmissions from the
cell. For at least one user equipment served by the first cell, it
is determined whether the user equipment should be scheduled for
the low interference time period. This determination may be based
on a determination as to whether the user equipment is located in
the interior or exterior parts of the cell. The low interference
time period may be determined based on a timing of transmissions
from at least one neighbouring cell. In the case of a synchronized
system, a low interference time period may be defined for each
cell, such that a reuse distance between low interference time
periods is maximized. In the case of an unsynchronized system, a
user equipment that is close to a particular neighbour cell may be
scheduled to avoid the low interference time period defined for
that neighbour cell.
Inventors: |
MULLER; Walter; (Upplands
Vasby, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Unwired Planet, LLC |
Reno |
NV |
US |
|
|
Assignee: |
Unwired Planet, LLC
Reno
NV
|
Family ID: |
40579751 |
Appl. No.: |
14/219263 |
Filed: |
March 19, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12739322 |
Apr 22, 2010 |
8681745 |
|
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PCT/SE07/50777 |
Oct 25, 2007 |
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14219263 |
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Current U.S.
Class: |
370/252 ;
370/336 |
Current CPC
Class: |
H04W 24/08 20130101;
H04W 16/02 20130101; H04L 5/0073 20130101; H04W 16/10 20130101;
H04W 72/082 20130101; H04L 5/0028 20130101; H04W 72/048
20130101 |
Class at
Publication: |
370/252 ;
370/336 |
International
Class: |
H04L 5/00 20060101
H04L005/00; H04W 24/08 20060101 H04W024/08 |
Claims
1. A method of controlling a wireless communication network, the
method comprising: receiving, from at least one user equipment,
data relating to a signal strength of a signal from a first node
and a signal strength of a signal from at least one neighboring
node of the first node; and determining based on the received data
whether the at least one user equipment should be scheduled for a
low interference time period during which interference in relation
to the at least one neighboring node is reduced.
2. The method of claim 1, wherein the at least one neighboring node
is configured to reduce interference in relation to the first node
during the low interference time period.
3. The method of claim 1, comprising comparing the signal
strengths.
4. The method of claim 1, comprising transmitting an instruction to
the at least one user equipment to perform signal strength
measurement.
5. The method of claim 1, wherein said determining depends on the
signal strength of the signal from the first node relative to the
signal strength of the signal from the at least one neighboring
node.
6. The method of claim 1, wherein said determining depends on
whether the signal strength of the signal from the first node
exceeds the signal strength of the signal from the at least one
neighboring node by a threshold value.
7. The method of claim 6, wherein the threshold value is 3 dB.
8. The method of claim 1, comprising scheduling the at least one
user equipment for the low interference time period if the signal
strength of the signal from the first node does not exceed the
signal strength of the signal from the at least one neighboring
node by a threshold value.
9. The method of claim 1, wherein the data relates to the signal
strength of the signal from the first node and the signal strengths
of signals from a plurality of neighboring nodes of the first
nodes, and wherein said determining comprises determining whether
the at least one user equipment should be scheduled for a low
interference time period during which interference in relation to a
particular neighboring node of the plurality of neighboring nodes
is reduced depending on the signal strength of the signal from the
first node relative to the signal strength of the signal from the
particular neighboring node.
10. The method of claim 1, comprising performing resource
allocation for the at least one user equipment based on a result of
said determining.
11. The method of claim 1, wherein the data comprises the signal
strength of the signal from the first node and the signal strength
of the signal from the at least one neighboring node.
12. The method of claim 1, wherein the first node is a serving node
of the at least one user equipment.
13. The method of claim 1, wherein the network comprises an
unsynchronized network.
14. The method of claim 1, wherein the network comprises a
synchronized network.
15. The method of claim 1, comprising determining a timing of
transmissions from the at least one neighboring node relative to a
timing of transmissions from the first node.
16. A network node configured to determine whether at least one
user equipment should be scheduled for a low interference time
period during which interference in relation to least one
neighboring node of a first node is reduced based on data received
from the at least one user equipment, the data relating to a signal
strength of a signal from a first node and a signal strength of a
signal from at least one neighboring node of the first node.
17. A network node configured to: allocate resources for at least
one user equipment during a low interference time period in
relation to at least one neighbor cell of a first cell based at
least in part on data received from the at least one user
equipment, the data relating to a signal strength for the first
cell and a signal strength for the at least one neighbor cell.
Description
PRIORITY APPLICATIONS
[0001] This application is a continuation application claiming
priority from U.S. application Ser. No. 12/739,322, filed Apr. 22,
2010, which is the U.S. national phase of International
[0002] Application No. PCT/SE2007/050777, filed 25 Oct. 2007, which
designated the U.S., the entire contents of each of which are
hereby incorporated by reference.
TECHNICAL FIELD
[0003] The technology relates to wireless telecommunication
systems, and in particular to resource allocation in wireless
telecommunication systems.
BACKGROUND
[0004] Many wireless telecommunication systems are cellular. That
is, the coverage area is divided into cells, and each mobile
device, or other user equipment, communicates with a base station
in the cell in which it is located. In order to achieve such
communication, a communication resource must be allocated to the
mobile device. The available communication resources include the
available communication bandwidth and the available time. Thus, in
a TDMA (Time Division Multiple Access) system, the available
communications channel is allocated to different users at different
times, while, in a FDMA (Frequency Division Multiple Access)
system, different communications frequencies are allocated to
different users.
[0005] Many cellular wireless telecommunication systems use a
combination of TDMA and FDMA, in that the communication resource
allocated to a user comprises a particular bandwidth allocation
during a specified time period.
[0006] One issue in cellular wireless telecommunication systems
concerns interference. That is, where for example a mobile device
is located between a base station to which it is transmitting and
another base station that is also receiving signals transmitted on
the same frequency, there is a danger that the signals transmitted
from that mobile device will erroneously be received, and/or will
cause interference at the other base station.
[0007] One way to solve this issue is to allocate the available
transmission frequencies to different cells, in such a way as to
reduce the probability of such interference. For example, if a
transmission frequency is allocated for use by mobile devices
within a particular cell of the system, then it may advantageously
not be allocated for use by mobile devices within any other cell
that neighbours that particular cell. This step reduces the
probability that the signals transmitted from that mobile device
will erroneously be received, or will cause interference at any
other base station that is receiving signals on that transmission
frequency.
SUMMARY
[0008] In example aspects, transmission times in different cells
are controlled in such a way as to reduce the probability of
interference with transmissions in neighbouring cells.
[0009] More specifically, one example embodiment provides a method
of controlling a cellular wireless telecommunication system, in
which data is transmitted in frames, and wherein, for a first cell
of said system, there is semi-statically defined at the same time
position in a plurality of consecutive time intervals a low
interference time period for transmissions in the first cell, each
of said time intervals comprising an equal number of frames, and
the low interference time period being a time period during which
neighbouring cells are configured to minimize interference in the
first cell; [0010] the method comprising, for at least one user
equipment served by the first cell: [0011] receiving signal
strength measurements; and [0012] based on the signal strength
measurements, determining whether the user equipment should be
scheduled for the low interference time period.
[0013] This has the advantage that the probability of interference
may be reduced, and hence that the overall capacity of the cell can
be used with high efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 illustrates a wireless communication network
according to an aspect.
[0015] FIG. 2 illustrates a division of a network coverage area
into cells in the network.
[0016] FIG. 3 is a flow chart, illustrating a method according to
an aspect.
[0017] FIG. 4 is a flow chart, illustrating a second method
according to an aspect.
[0018] FIG. 5 is a timing diagram, illustrating operation of a
first network in accordance with the method of FIG. 4.
[0019] FIG. 6 is a timing diagram, illustrating operation of a
second network in accordance with the method of FIG. 4.
DETAILED DESCRIPTION
[0020] FIG. 1 shows a wireless communication network, in which
there are a number of base stations 10, 12, 14, located within a
coverage area of the network such that they can provide mobile
communication services to user equipments active within the
coverage area. FIG. 2 shows four such user equipments, in the form
of mobile phones 20, 22, 24, 26, but it will be appreciated that
any suitable type of user equipment can be used in the network.
[0021] As is conventional, the base stations 10, 12, 14 have
connections to a core network (not shown) of the wireless
communication network, and each have radio transceiver circuitry
for communicating with the user equipments. The coverage area of
the network is divided into cells, as described in more detail
below, with each base station providing service to the user
equipments located within the corresponding cell.
[0022] The user equipments are similarly conventional, and also
have radio transceiver circuitry, for communicating with the base
stations.
[0023] The description is provided with reference to an example
wireless communication network operating on the OFDMA (Orthogonal
Frequency Division Multiple Access) principle, in which the whole
of the available frequency bandwidth is used in each of the cells.
This available bandwidth is divided into sub-channels, and one or
more of these sub-channels can be allocated for communications with
any particular user equipment.
[0024] Although FIG. 1 shows only a small number of base stations
and user equipments, it will be appreciated that a practical
network is likely to include large numbers of base stations and
user equipments.
[0025] FIG. 2 illustrates schematically the division of the
coverage area into cells. More specifically, FIG. 2 shows a part of
the network coverage area being divided into three cells 100, 120,
140, served respectively by the base stations 10, 12, 14. The base
stations are not shown in FIG. 2 although it will be recognized
that one common arrangement involves the definition of each cell in
the area surrounding the respective base station. It will also be
recognized that the division shown in FIG. 2 is purely
illustrative, and that the shape of cells is not regular as shown
in FIG. 2, but rather is defined by the radio frequency properties
of the environment, and the signal strengths employed by the base
stations, as well as by the positions of other surrounding base
stations.
[0026] Each user equipment can be instructed by its serving base
station to make measurements relating to the signals transmitted by
that serving base station and by other base stations. One of the
purposes of such measurements is to allow the network to determine
the nearby cells that should be considered to be neighbouring
cells, it being recognized that the arrangement of base stations
and cells will likely be less regular in practice than that shown
in FIG. 2.
[0027] As is conventional, the cells 100, 120, 140 define the areas
served respectively by the base stations 10, 12, 14. That is, a
mobile device within the cell 100 will have a connection to the
base station 10, etc. In preferred example embodiments, the cells
are subdivided, and the service provided to a user equipment
depends on the part of the cell in which it is located.
[0028] FIG. 3 is a flow chart, illustrating a method for
determining a part of the serving cell in which a user equipment is
located.
[0029] In step 160, the user equipment measures the strength of
signals received from its serving cell. Techniques for measuring
signal strength are well known to the person skilled in the art,
and will not be described further. An illustrative example refers
to a user equipment that is located within the cell 100, and so in
step 160 the user equipment measures the strength of signals
received from the cell 100.
[0030] In step 162, the user equipment measures the strength of
signals received from the neighbouring cells. Again, techniques for
determining the neighbour cell list, and for making the signal
strength measurements, are well known to the person skilled in the
art, and will not be described further. In the case of the user
equipment that is located within the cell 100, in step 160 the user
equipment measures the strength of signals received from the cells
120 and 140, as well as other neighbouring cells not shown in
detail in FIG. 2.
[0031] In step 164, a comparison is made, for example within the
base station 10 or elsewhere in the network, between the signal
strength measurements made in steps 160 and 162. Based on these
comparison results, the cell 100 is logically subdivided into
regions, and the location of the user equipment within one of those
regions is determined
[0032] FIG. 2 shows a part of the logical subdivision of the cell
100, based on the comparison of the signal strength
measurements.
[0033] Where the signal strength measured in step 160, i.e. the
signal strength from the serving cell 100, is greater than any of
the signal strengths measured in step 162, i.e. the signal
strengths from the neighbouring cells, by a margin that exceeds
some threshold value, such as 3 dB, then the user equipment is
determined to be in an interior region 101 of the cell 100, and the
user equipment (UE) is referred to as an interior UE.
[0034] By contrast, where the signal strength from the serving cell
100 does not exceed all of the signal strengths from the
neighbouring cells by a margin that exceeds the threshold value,
such as 3 dB, then the user equipment is determined to be in an
exterior region of the cell 100, and the user equipment is referred
to as an exterior UE.
[0035] More specifically, where the signal strength from the
serving cell 100 does not exceed the signal strength from the
neighbouring cell 120 by a margin that exceeds the threshold value,
but where the signal strength from the serving cell 100 does exceed
the signal strength from all of the other neighbouring cells by a
margin that exceeds the threshold value, then the exterior UE is
determined to be in the exterior region 102 that borders the
neighbouring cell 120.
[0036] Similarly, where the signal strength from the serving cell
100 does not exceed the signal strength from the neighbouring cell
140 by a margin that exceeds the threshold value, but where the
signal strength from the serving cell 100 does exceed the signal
strength from all of the other neighbouring cells by a margin that
exceeds the threshold value, then the exterior UE is determined to
be in the exterior region 104 that borders the neighbouring cell
140.
[0037] Where the signal strength from the serving cell 100 does not
exceed the signal strength from the neighbouring cell 120 by a
margin that exceeds the threshold value, and also does not exceed
the signal strength from the neighbouring cell 140 by a margin that
exceeds the threshold value, but where the signal strength from the
serving cell 100 does exceed the signal strength from all of the
other neighbouring cells by a margin that exceeds the threshold
value, then the exterior UE is determined to be in the exterior
region 103 that borders both of the neighbouring cells 120,
140.
[0038] Similar exterior regions 106, 107 are defined, with the
exterior region 106 bordering the neighbouring cell 120 and one
other neighbouring cell not shown in detail in FIG. 2, and the
exterior region 107 bordering the neighbouring cell 140 and a
different neighbouring cell not shown in detail in FIG. 2. Other
exterior regions are also defined, bordering other neighbouring
cells, but are not shown in FIG. 2.
[0039] Thus, any user equipment in the interior region 101 can be
regarded as an interior device, while other user equipments can be
regarded as exterior devices. Then, exterior devices in the regions
106, 102 and 103 that border the first neighbouring cell 120 can be
regarded as having a higher risk of interference with that first
neighbouring cell, while exterior devices in the regions 103, 104
and 107 that border the second neighbouring cell 140 can be
regarded as having a higher risk of interference with that second
neighbouring cell, it being noted of course that exterior devices
in the region 103 that borders the first and second neighbouring
cells 120, 140 can be regarded as having a higher risk of
interference both with the first and with the second neighbouring
cell.
[0040] FIG. 4 is a further flow chart, illustrating a further
method whereby a degree of coordination is achieved between the
cells.
[0041] In step 180, the timing of the transmissions from one or
more neighbouring cells is determined, relative to the timing of
the transmissions from the cell under consideration. This
determination may be made in the base station serving that cell, or
may be made elsewhere in the network and communicated explicitly or
implicitly to the cell, as required.
[0042] The methods described herein can be applied either to
synchronized networks or to unsynchronized networks. In the case of
synchronized networks, each of the base stations starts the
transmission of a new frame of data simultaneously. Therefore, in
this case, it can readily be determined that there is no time
difference between the transmissions from each base station.
[0043] In the case of an unsynchronized network, the frames
transmitted by the different base stations begin at times that are
effectively random. Therefore, in this case, each base station
instructs the devices within its cell to make measurements relating
to the timing of the transmissions from the neighbouring cells,
relative to the timing of its own transmissions. For example, the
relative timings can be determined with reference to the system
frame numbers of the respective transmissions.
[0044] These measurements can be made at regular periodic
intervals, or when initiated by the network or the base station in
response to a specified condition occurring.
[0045] In step 182, there is defined for the cell a first time
period, which is advantageously a time period during which there is
a lower probability of interference from neighbouring cells. This
will be discussed in more detail below.
[0046] In step 184, there is defined for that cell one or more
second time periods, which correspond to the first time periods
defined in neighbouring cells, and during which there may be a
higher probability of interference from neighbouring cells. Again,
this will be discussed in more detail below.
[0047] The operation of the method is illustrated, firstly with
reference to its application in a synchronized network, in FIG. 5.
As is well known, communications networks that use time division
duplexing (TDD) are usually synchronized, to allow for the
possibility that a device will handover from one cell to another
and retain the same timings.
[0048] Similarly, systems that use frequency division duplexing
(FDD) need to be synchronized if they are to allow the transmission
of multicast messages. Thus, the system illustrated in FIG. 5 may
arise in such networks but will not arise exclusively in such
networks.
[0049] In FIG. 5, there are shown the timings of transmissions from
the three cells 100, 120, 140 described above. As mentioned
previously, the transmissions from the three cells are divided into
frames, as specified by the relevant OFDMA communication system.
The available communication resources are then the available
sub-channels into which the bandwidth is divided, and the available
fractions of each frame. In one example embodiment, each active
user equipment may be allocated all of the available sub-channels
for some fraction of each frame. In other embodiments, an active
user equipment may be allocated only a fraction of the available
sub-channels for some fraction of each frame.
[0050] Aspects relate primarily to the way in which the fraction of
the frame is allocated to a particular user equipment.
[0051] In this example embodiment, each frame is divided into three
sections, each of equal length. Thus, a first frame transmitted
from the cell 100 is divided into sections t.sub.A0-t.sub.A1,
t.sub.A1-t.sub.A2, t.sub.A2-t.sub.A3, while a second frame is
divided into sections t.sub.A3-t.sub.A4, etc. Similarly, a first
frame transmitted from the cell 120 is divided into sections
t.sub.B0-t.sub.B1, t.sub.B1-t.sub.B2, t.sub.B2-t.sub.B3, while a
second frame is divided into sections t.sub.B1-t.sub.B4, etc, and a
first frame transmitted from the cell 140 is divided into sections
t.sub.C0-t.sub.C1, t.sub.C1-t.sub.C2, t.sub.C2-t.sub.C3, while a
second frame is divided into sections t.sub.C3-t.sub.C4, etc.
[0052] Within each of the cells 100, 120, 140, a time period is
defined, during which there is a lower probability of interference
from neighbouring cells. In one example embodiment, these time
periods may be determined by network planning and the relevant base
station may be informed which time period to adopt. In another
embodiment, the time period may be determined by the base station
on the basis of measurements made by user equipments within the
cell. The time differences between the serving cell and the
neighbouring cells may be determined by knowledge of the network
planning in the case of synchronized cells, or may be determined by
the base station on the basis of measurements made by user
equipments within the cell or by the base station itself.
[0053] In either case, the time period is defined at least
semi-statically, i.e. on a static or semi-static basis. That is,
after the time period has been defined for a cell, it occurs at the
same time position for a significant period of time, and in
particular for the duration of a large number of frames, for
example until measurements suggest that the radio environment has
changed, or the timing relations between cells have changed. Again,
the radio environment or the timing relations can be monitored
using UE measurements or measurements made by the base station
itself.
[0054] For example, as shown in FIG. 5, and referring to FIG. 2,
the cell 100 may adopt the time period t.sub.A from
t.sub.A0-t.sub.A1 as its less interfered time period, the cell 120
may adopt the time period t.sub.B from t.sub.B1-t.sub.B2 as its
less interfered time period, and the cell 140 may adopt the time
period t.sub.C from t.sub.C2-t.sub.C3 as its less interfered time
period. In this embodiment, there are only three time periods that
are available for selection by each of the cells in the system.
Preferably, these time periods are selected by the different cells
such that no time period is adopted as the less interfered time
period by any two adjacent cells. Even if this is not possible
then, in any event, steps are preferably taken to ensure the
maximum average reuse distance between cells that share a time
period as the less interfered time period.
[0055] Although the description makes reference to a situation
where there is a less interfered time period during each frame, it
is also possible to define a time interval that is equal to a
plurality of frames, with the less interfered time period then
occurring at the same time position in each time interval.
[0056] Further, although an example in which each frame is divided
into three sections is described with the less interfered time
period being equal to one third of one frame, it is also possible
to divide each frame or other time interval into a different number
of sections, such that the less interfered time period is equal to
some different fraction of one frame or time interval.
[0057] When a first, less interfered, time period has been defined
in each cell, one or more second time periods are also defined, in
which there is a specific risk of interference from one or more
respective other cell.
[0058] Thus, in this case, exterior user equipments in each cell,
which would tend to have a greater risk of interference with other
cells because they are closer to the cell boundaries, are
preferably allocated resources during the less interfered time
periods. Specifically, in this example, exterior user equipments in
the cell 100 are preferably allocated resources during the time
period t.sub.A, exterior user equipments in the cell 120 are
preferably allocated resources during the time period t.sub.B, and
exterior user equipments in the cell 140 are preferably allocated
resources during the time period t.sub.C.
[0059] However, if no such resources are available, an exterior
user equipment may instead be allocated resources outside the less
interfered time period of that cell, provided that it avoids the
use of a second time period during which there is a particular risk
of interference with a specific neighbouring cell.
[0060] Thus, considering cell 100, the time period t.sub.B may be
regarded as such a second time period concerning interference from
the cell 120, since exterior user equipments in that cell will
preferentially be transmitting during that time period, while the
time period t.sub.C may be regarded as such a second time period
concerning interference from the cell 140, since exterior user
equipments in that cell will preferentially be transmitting during
that time period.
[0061] Therefore, for an exterior user equipment in the cell 100
that is in the region 102 bordering the cell 120, if that user
equipment cannot be allocated resources in the less interfered time
period t.sub.A, it can instead be allocated resources during the
time period t.sub.C, in preference to the time period t.sub.B.
Similarly, for an exterior user equipment in the cell 100 that is
in the region 104 bordering the cell 140, if that user equipment
cannot be allocated resources in the less interfered time period
t.sub.A, it can instead be allocated resources during the time
period t.sub.B, in preference to the time period t.sub.C.
[0062] As described above, it is exterior user equipments in a cell
that are preferentially allocated resources in the less interfered
time period defined for that cell. However, alternatively or
additionally, other user equipments that require low interference
conditions may be preferentially allocated resources in the less
interfered time period.
[0063] The operation of the method is further illustrated with
reference to its application in an unsynchronized network, in FIG.
6.
[0064] In FIG. 6, there are again shown the timings of
transmissions from the three cells 100, 120, 140 described above.
As mentioned previously, the transmissions from the three cells are
divided into frames, as specified by the relevant OFDMA
communication system. The available communication resources are
then the available sub-channels into which the bandwidth is
divided, and the available fractions of each frame. In one example
embodiment, each active user equipment may be allocated all of the
available sub-channels for some fraction of each frame. In other
embodiments, an active user equipment may be allocated only a
fraction of the available sub-channels for some fraction of each
frame.
[0065] Again, in this example embodiment, each frame is divided
into three sections, each of equal length, although the frames may
be divided in any convenient way. Thus, a first frame transmitted
from the cell 100 is divided into sections t.sub.A5-t.sub.A6,
t.sub.A6-t.sub.A7, t.sub.A7-t.sub.A8, while a second frame is
divided into sections t.sub.A8-t.sub.A9, etc. Similarly, a first
frame transmitted from the cell 120 is divided into sections
t.sub.B5-t.sub.B6, t.sub.B6-t.sub.B7, t.sub.B7-t.sub.B8, while a
second frame is divided into sections t.sub.B8-t.sub.B9, etc, and a
first frame transmitted from the cell 140 is divided into sections
t.sub.C5-t.sub.C6, t.sub.C6-t.sub.C7, t.sub.C7-t.sub.C8, while a
second frame is divided into sections t.sub.C8-t.sub.C9, etc.
[0066] Within each of the cells 100, 120, 140, a time period is
defined, during which there is a lower probability of interference
from neighbouring cells. In some situations, these time periods may
be determined by the cell itself to be the first section of each
frame. In other situations, the time period in one cell may be
adjusted, based on reported timing measurements relating to other
cells, such that the time periods become the same in all cells.
This will tend to reduce the number of timing reports that are
needed in the network.
[0067] In an unsynchronized system, the relative timings of the
frames in the different cells are arbitrary, as shown in FIG. 6
and, furthermore, these relative timings may change. In any event,
the time period is defined on a static or semi-static basis. That
is, after the time period has been defined, it occurs at the same
time position for a significant period of time, and in particular
for the duration of a large number of frames, for example until
measurements suggest that the radio environment has changed.
However, the cell may set its own first time period based on the
present conditions, and in particular based on the measurements of
the timings in other cells. The cell can monitor the timing
relations with the neighbouring cells on the basis of measurements
made by the user equipments in the cell, or measurements made by
the base station itself
[0068] For example, as shown in FIG. 6, the cell 100 may adopt the
time period t.sub.A from t.sub.A5t.sub.A6 as its less interfered
time period, the cell 120 may adopt the time period t.sub.B from
t.sub.B5-t.sub.B6 as its less interfered time period, and the cell
140 may adopt the time period t.sub.C from t.sub.C5-t.sub.C6 as its
less interfered time period.
[0069] As before, although the description refers to a situation
where there is a less interfered time period during each frame, it
is also possible to define a time interval that is equal to a
plurality of frames, with the less interfered time period then
occurring at the same time position in each time interval.
[0070] Further, although the description refers to an example in
which each frame is divided into three sections, and the less
interfered time period is equal to one third of one frame, it is
also possible to divide each frame or other time interval into a
different number of sections, such that the less interfered time
period is equal to some different fraction of one frame or time
interval.
[0071] When a first, less interfered, time period has been defined
in each cell, one or more second time periods are also defined, in
which there is a specific risk of interference from one or more
respective other cell.
[0072] Thus, in this case, exterior user equipments in each cell,
which would tend to have a greater risk of interference with other
cells because they are closer to the cell boundaries, are
preferably allocated resources during the less interfered time
periods. Incidentally, although specific reference is made to the
allocation of resources for exterior user equipments, which are
likely to cause interference with user equipments in neighbouring
cells as well as being more vulnerable to interference from user
equipments in neighbouring cells, the methods described are
applicable to any user equipments that require lower interference,
such as interior user equipments having coverage problems or user
equipments requiring particularly high data rates.
[0073] Specifically, in this example, exterior user equipments in
the cell 100 are preferably allocated resources during the time
period t.sub.A, exterior user equipments in the cell 120 are
preferably allocated resources during the time period t.sub.B, and
exterior user equipments in the cell 140 are preferably allocated
resources during the time period t.sub.C.
[0074] However, this is also subject to the condition that an
exterior user equipment in a region bordering one or more
particular neighbouring cell should preferably not be allocated
resources during respective second time periods corresponding to
the less interfered time periods of that one or more neighbouring
cell.
[0075] Thus, considering cell 100, the time period t.sub.B may be
regarded as such a second time period concerning interference from
the cell 120, since exterior user equipments in that cell will
preferentially be transmitting during that time period, while the
time period t.sub.c may be regarded as such a second time period
concerning interference from the cell 140, since exterior user
equipments in that cell will preferentially be transmitting during
that time period.
[0076] Therefore, for an exterior user equipment in the cell 100
that is in the region 102 bordering the cell 120, that user
equipment can be allocated resources at any time during the less
interfered time period t.sub.A, because there is no overlap with
the time period t.sub.B. However, for an exterior user equipment in
the cell 100 that is in the region 104 bordering the cell 140, that
user equipment should preferentially be allocated resources in that
part of the less interfered time period t.sub.A that does not
overlap with the time period t.sub.C.
[0077] There is thus disclosed a system for minimizing
interference, based on the allocation of resources to user
equipments, at times when there is a reduced possibility of such
interference, as a result of some predetermined definition of a
less interfered time period.
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