U.S. patent application number 12/320049 was filed with the patent office on 2009-07-30 for communication systems.
Invention is credited to Saied Abedi.
Application Number | 20090191813 12/320049 |
Document ID | / |
Family ID | 39186451 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090191813 |
Kind Code |
A1 |
Abedi; Saied |
July 30, 2009 |
Communication systems
Abstract
A method of controlling spectrum use in a first wireless
communications system, the first wireless communications system
being operable to take part in a spectrum assignment process
involving at least the first wireless communications system and one
or more other wireless communications systems, the method
comprising in a single instance of the spectrum assignment process,
exchanging a first portion of spectrum for a second, different
portion of spectrum, by assigning the first portion of spectrum
from the first wireless communications system to the one or more
other wireless communications systems and accepting the assignment
of the second portion of spectrum from the one or more other
wireless communications systems to the first wireless
communications system.
Inventors: |
Abedi; Saied; (Reading,
GB) |
Correspondence
Address: |
HANIFY & KING PROFESSIONAL CORPORATION
1055 Thomas Jefferson Street, NW, Suite 400
WASHINGTON
DC
20007
US
|
Family ID: |
39186451 |
Appl. No.: |
12/320049 |
Filed: |
January 15, 2009 |
Current U.S.
Class: |
455/62 |
Current CPC
Class: |
H04W 16/14 20130101 |
Class at
Publication: |
455/62 |
International
Class: |
H04W 72/00 20090101
H04W072/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2008 |
GB |
0801535.6 |
Claims
1. A method of controlling spectrum use in a first wireless
communications system, the first wireless communications system
being operable to take part in a spectrum assignment process
involving at least the first wireless communications system and one
or more other wireless communications systems, the method
comprising in a single instance of the spectrum assignment process,
exchanging a first portion of spectrum for a second, different
portion of spectrum, by assigning the first portion of spectrum
from the first wireless communications system to the one or more
other wireless communications systems and accepting the assignment
of the second portion of spectrum from the one or more other
wireless communications systems to the first wireless
communications system.
2. The method of claim 1 comprising controlling one or both of the
first and second portions to substantially equalise operational
parameters of the first wireless communications system with
equivalent operational parameters of the second wireless
communications system.
3. The method of claim 1 comprising selecting one or both of the
first and second portions of spectrum to reduce a level of
interference in at least one of the first wireless communications
system and the other wireless communications systems, based on
levels of interference in the first and second portions.
4. The method of claim 1 comprising assigning the first portion of
spectrum from the first wireless communications system to a second
wireless communications system amongst the one or more other
wireless communications systems, and accepting the assignment of
the second portion of spectrum from the second wireless
communications system to the first wireless communications
system.
5. The method of claim 1 comprising assigning the first portion of
spectrum from the first wireless communications system to a second
wireless communications system amongst the one or more other
wireless communications systems, and accepting the assignment of
the second portion of spectrum from a third wireless communications
system amongst the one or more other wireless communications
systems to the first wireless communications system, the second and
third wireless communications systems being different.
6. The method of claim 1 comprising, before the exchange,
identifying a high-interference portion of spectrum to serve as the
first portion of spectrum.
7. The method of claim 6 comprising analysing interference levels
in each of a plurality of sub-chunks of spectrum used by the first
wireless communications system before the exchange, and identifying
the high-interference portion of spectrum by selecting a said
sub-chunk associated with a level of interference which is higher
than levels of interference associated with other said
sub-chunks.
8. The method of claim 7 wherein analysing the interference levels
comprises each of a plurality of network elements of the first
wireless communications system analysing the interference levels in
each of a plurality of sub-chunks of the spectrum used by the first
wireless communications system before the exchange, and each of the
network elements identifying a said sub-chunk associated with a
level of interference which is higher than levels of interference
associated with other said sub-chunks.
9. The method of claim 8 wherein identifying the high-interference
portion of spectrum comprises, in the case that the network
elements all identify the same sub-chunk, selecting that sub-chunk
as the high-interference portion, and, in the case that the network
elements identify different sub-chunks, determining a region of
spectrum which has the greatest degree of overlap with all of the
different sub-chunks and selecting that region as the
high-interference portion.
10. The method of claim 1 comprising transmitting outgoing
signalling specifying the first portion of spectrum as an exchange
candidate.
11. The method of claim 10 wherein transmitting the outgoing
signalling comprises transmitting an exchange request specifying
the first portion of spectrum as an exchange candidate in order to
trigger the instance of the spectrum assignment process.
12. The method of claim 10 comprising transmitting the outgoing
signalling following the receipt of an exchange request specifying
the second portion of spectrum as an exchange candidate.
13. The method of claim 1 comprising receiving incoming signalling
specifying the second portion of spectrum as an exchange
candidate.
14. The method of claim 1 comprising comparing the first and second
portions of spectrum before the exchange, and proceeding only if
the first portion of spectrum is different to the second portion of
spectrum.
15. The method of claim 1 comprising, before the exchange,
analysing an expected level of interference associated with the
second portion of spectrum.
16. The method of claim 1 comprising, following the exchange,
operating the first wireless communications system to use the
second portion of spectrum and to avoid using the first portion of
spectrum.
17. The method of claim 1 comprising selecting one or both of the
first and second portions of spectrum to reduce the number of
separate, continuous regions of spectrum used by at least one of
the first wireless communications system and the other wireless
communications systems.
18. Apparatus for controlling spectrum use in a first wireless
communications system, the first wireless communications system
being operable to take part in a spectrum assignment process
involving at least the first wireless communications system and one
or more other wireless communications systems, the apparatus
comprising spectrum assignment circuitry configured to exchange a
first portion of spectrum for a second, different portion of
spectrum, in a single instance of the spectrum assignment process,
by assigning the first portion of spectrum from the first wireless
communications system to the one or more other wireless
communications systems and accepting the assignment of the second
portion of spectrum from the one or more other wireless
communications systems to the first wireless communications
system.
19. A computer program storage medium comprising a computer
readable storage medium and computer program instructions, recorded
on the computer readable storage medium, for controlling spectrum
use in a first wireless communications system, which, when run on a
computer comprising a processor and a memory storing the computer
program instructions and forming part of a network element or an
external controlling element, causes the computer to perform a
method of controlling spectrum use in a first wireless
communications system, the first wireless communications system
being operable to take part in a spectrum assignment process
involving at least the first wireless communications system and one
or more other wireless communications systems, the method
comprising in a single instance of the spectrum assignment process,
exchanging a first portion of spectrum for a second, different
portion of spectrum, by assigning the first portion of spectrum
from the first wireless communications system to the one or more
other wireless communications systems and accepting the assignment
of the second portion of spectrum from the one or more other
wireless communications systems to the first wireless
communications system.
Description
[0001] The invention relates to a method of, and apparatus for,
controlling spectrum use in a wireless communications system.
BACKGROUND
[0002] Recent studies worldwide indicate that while some systems
and mobile operators are in desperate need for more efficient
utilization of spectrum resources, most of the radio spectrum
resources remain underutilized or unused most of the time. The
increasing demand for flexible use of the radio spectrum for
emerging new services and applications is the motivation behind
numerous research activities worldwide. Efficient access to radio
spectrum resources will generate new sources of revenues for
worldwide vendors and wireless network operators.
[0003] Four different levels of spectrum management techniques have
been introduced in three different time scales: Spectrum Sharing
and Coexistence (couple of hours or days), Long Term Spectrum
Assignment (couple of minutes), Short Term Spectrum Assignment (1
sec or tens of ms) and fast dynamic spectrum allocation (10 ms time
scale or even below).
[0004] However, due to the heavy traffic load, multiple negotiating
parties involved in a Short Term Spectrum Assignment process might
not be able to provide free spectrum to other parties, for the
simple reason that they themselves require the spectrum.
SUMMARY
[0005] According to a first aspect, there is provided a method of
controlling spectrum use in a first wireless communications system,
the first wireless communications system being operable to take
part in a spectrum assignment process involving at least the first
wireless communications system and one or more other wireless
communications systems, the method comprising
[0006] in a single instance of the spectrum assignment process,
exchanging a first portion of spectrum for a second, different
portion of spectrum, by assigning the first portion of spectrum
from the first wireless communications system to the one or more
other wireless communications systems and accepting the assignment
of the second portion of spectrum from the one or more other
wireless communications systems to the first wireless
communications system.
[0007] The method may provide for a different type of spectrum
exchange process under which the parties involved do not lose
spectrum to other parties, and instead exchange a sub-chunk of
spectrum (which is troubled in terms of the currently inflicted
interference or which has been troubled in terms of interference,
say for the past couple of transmission attempts) with a better
sub-chunk of spectrum in terms of the interference they suffer.
[0008] The invention may improve the spectral efficiency by
exploiting the availability of spectrum on a short-term basis based
on cluster-wise negotiations. It may provide a further fine tuning
to long-term spectrum assignment (when performed as a short-term
spectrum assignment) and to short-term spectrum assignment,
improving the QoS and SIR ratio, the overall network coverage,
throughput, and the revenue for the borrowing party by making sure
that the radio resource is available when needed at peak times. An
extra source of income for operators as the lending party may be
provided by making sure that the redundant radio spectrum is not
wasted and employed in an efficient way. The method may reduce the
potential call blockage by providing better and more efficient
access to more radio resources.
[0009] The term "wireless communications system" may relate to a
wireless access network, for example a radio access network (RAN),
including all of the elements of the network, for example base
stations. The radio access network may be a metropolitan-area
network or a wide-area network, for example. In another
arrangement, it may relate to an RFID tag reader, to a sink or
wireless sensor network base station, or to a group of such readers
forming a network, possibly including other equipment, e.g. control
circuitry. It may also relate to a WiMAX network. A wireless
communications system may be a macro network or a micro
network.
[0010] A spectrum assignment may comprise the re-assignment of at
least a portion of a spectrum band which has been pre-assigned to
one wireless communications system from that wireless
communications system to another wireless communications system. In
other words, where a first spectrum band has been pre-assigned to a
first wireless communications system, and a second spectrum band
has been pre-assigned to a second wireless communications system,
the spectrum assignment process may comprise (for example during
negotiations between the first and second wireless communications
systems) re-assigning, from one of the first and second wireless
communications systems to the other of the first and second
wireless communications systems, some or all of the respective
first or second pre-assigned spectrum band. By "pre-assigned" it
may be meant that the wireless communications system to which the
spectrum band has been pre-assigned is licensed for operation
within that spectrum band. The act of assigning a portion of
spectrum from one system to another may comprise the one system
giving permission to the other system to use the assigned portion
of spectrum, whereafter the one system ceases to operate using the
assigned portion, while the other system may choose to operate
using the assigned portion if desired. The spectrum assignment
process may relate in particular to a short-term spectrum
assignment process (1 sec or 10 s of milliseconds timescale)
forming part of a larger spectrum sharing scheme further including
at least a long-term spectrum assignment process. The spectrum
assignment process may involve at least three wireless
communications systems including the first and the other wireless
communications systems. The term "instance" when used in relation
to the spectrum assignment process may refer to a single run of the
spectrum assignment process, i.e. spectrum use (including a
spectrum configuration) may change only once during the process. A
wireless communications system which assigns spectrum to another
system may be referred to as an assignor, whereas a system which
accepts the assignment of spectrum from another system may be
referred to as an assignee.
[0011] By "spectrum" there may be meant radio frequencies or any
other range of frequencies of electromagnetic radiation suitable
for communication. For example, the first and second wireless
communications systems may be radio access networks (RANs)
operating within the radio frequency range of the electromagnetic
spectrum. Additionally or alternatively, the wireless
communications systems may operate within a microwave frequency
range, for example.
[0012] The terms "portion" or "band" when used in relation to
spectrum may relate to a particular range of frequencies, which may
consist of a single, continuous range of frequencies, or two or
more separate, continuous ranges. The terms "chunk" and "sub-chunk"
may also refer to portions or bands of spectrum.
[0013] The term "spectrum configuration" may relate to an
arrangement of one or more portions of spectrum, and may specify
one or both of the amount of spectrum in each portion and/or its
position in relation to other portions of spectrum in the spectrum
configuration. For example, by defining each portion of spectrum
with reference to its upper and lower limits, it is possible to
indicate both the size of the portion and its position in relation
to other portions of spectrum. A portion of spectrum may also be
identified by reference to its size and/or a spectrum ID. A
spectrum ID may be a number assigned to each sub-chunk, selected
from a range of possibilities. The arrangement whereby sub-chunks
are given spectrum IDs may be decided before or during the spectrum
assignment process. A spectrum configuration may comprise one or
more guard bands, and one or more regions of licensed/unlicensed
spectrum. In addition, the spectrum configuration may comprise
information which associates each portion of spectrum with a
respective entity, which may be a wireless communications system
(e.g. a radio access network) or part thereof, a cell or base
station or a group of cluster thereof, or an uplink or downlink
belonging to any such entity.
[0014] Preferably, the method may comprise performing the exchange,
i.e. completing both the assignments from and to the first wireless
communications system, in the same instance of the spectrum
assignment process, before operating the first wireless
communications system to use the new (altered) spectrum
configuration.
[0015] The first wireless communications system and one or more of
the other wireless communications systems may form part of a
hierarchical overlaid cellular network. Additionally or
alternatively, the first wireless communications system may have
substantially no geographical overlap with the other wireless
communications systems.
[0016] Any number of wireless communications systems may be
involved in the exchange, with portions of spectrum being exchanged
for example in a reciprocal fashion (between two systems) or in a
circular fashion (between three or more systems) in order to
benefit one or more, and preferably all, of the systems. For
example, in a reciprocal exchange, the method may comprise
assigning the first portion of spectrum from the first wireless
communications system to a second wireless communications system
amongst the one or more other wireless communications systems, and
accepting the assignment of the second portion of spectrum from the
second wireless communications system to the first wireless
communications system. Alternatively, the method may comprise
assigning the first portion of spectrum from the first wireless
communications system to a second wireless communications system
amongst the one or more other wireless communications systems, and
accepting the assignment of the second portion of spectrum from a
third wireless communications system amongst the one or more other
wireless communications systems to the first wireless
communications system, the second and third wireless communications
systems being different. Thus, a two-way, three-way, four-way (or
more) exchange may be provided. Additionally, one system may act as
a relay or broker between two or more other systems.
[0017] The first and second portions of spectrum comprise any
chunks of spectrum the exchange of which benefits one or more of
the wireless communications systems, and preferably all of the
systems. The benefit of the exchange to the wireless communications
systems may take any appropriate form, including reduced levels of
interference. In this regard, the method may comprise selecting one
or both of the first and second portions of spectrum to reduce a
level of interference in at least one of the first wireless
communications system and the other wireless communications
systems, based on levels of interference in the first and second
portions. Preferably, the selection is made to reduce a level of
interference in all of the wireless communications systems involved
in the exchange. The selection may be done by the first wireless
communications system, one or more of the other wireless
communications systems, or by an external controller. The levels of
interference may be measured, estimated or expected levels of
interference.
[0018] To promote a fair exchange, in one arrangement, the method
comprises controlling one or both of the first and second portions
to substantially equalise operational parameters of the first
wireless communications system with equivalent operational
parameters of the second wireless communications system. The
operational parameters may include any one or more of the size of
the first or second portion of spectrum, a level of interference in
the respective wireless communications system, the amount of a
reduction in a level of such interference, the bandwidth of a
channel belonging to the respective wireless communications system,
the bit rate capacity of such a channel, a range of frequencies of
the first or second portion of spectrum, or a change in data
throughput capacity. In particular, in one arrangement, the first
portion of spectrum may be substantially equal in size to the
second portion of spectrum. However, even if it is not possible for
some systems to have exactly equal sizes of exchanged portions of
spectrum, it may be possible to have similar ones in terms of size.
Each system may exchange a bad chunk of spectrum with a better
chunk of spectrum, in terms of the interference being inflicted,
although the exchanged values might not be exactly the same in some
cases.
[0019] The method may comprise, before the exchange, identifying a
high-interference portion of spectrum (i.e. a `red` chunk) to serve
as the first portion of spectrum. In this regard, the method may
comprise analysing interference levels in each of a plurality of
sub-chunks of spectrum used by the first wireless communications
system before the exchange, and identifying the high-interference
portion of spectrum by selecting a said sub-chunk associated with a
level of interference which is higher than levels of interference
associated with other said sub-chunks. By "associated with" there
may be meant a current level of interference, a recent level of
interference (for example in terms of interference for the past
couple of transmissions, e.g. a level of interference which has
been above a threshold for the last couple of transmissions), a
running average of the level of interference, or any other
appropriate measure.
[0020] The method may involve a simultaneous exchange of more than
one portion of spectrum between (e.g. first and second) systems.
Multiple sub-chunks of spectrum may be exchanged for example on a
fair basis that would improve the performance of the systems
involved to a certain level.
[0021] Analysing the interference levels may comprise each of a
plurality of network elements of the first wireless communications
system analysing the interference levels in each of a plurality of
sub-chunks of the spectrum used by the first wireless
communications system before the exchange, and each of the network
elements identifying a said sub-chunk associated with a level of
interference which is higher than levels of interference associated
with other said sub-chunks. In this case, identifying the
high-interference portion of spectrum may comprise, in the case
that the network elements all identify the same sub-chunk,
selecting that sub-chunk as the high-interference portion, and, in
the case that the network elements identify different sub-chunks,
determining a region of spectrum which has the greatest degree of
overlap with all of the different sub-chunks and selecting that
region as the high-interference portion.
[0022] The method may comprise transmitting outgoing signalling
specifying the first portion of spectrum as an exchange candidate,
the signalling being transmitted for example to one or more of the
other wireless communications systems (e.g. the one assigning
spectrum to, or accepting spectrum from, the first wireless
communications system) or to an external controller. Transmitting
the outgoing signalling may comprise transmitting an exchange
request specifying the first portion of spectrum as an exchange
candidate in order to trigger the instance of the spectrum
assignment process. The outgoing signalling may be transmitted from
time to time, e.g. periodically, or in response to unusually high
interference levels or traffic loads. The exchange request may
request the exchange of the first portion of spectrum for
unspecified portion, or it may specify a particular portion of
spectrum in which an expected level of interference is low.
Alternatively, the method may comprise transmitting the outgoing
signalling following the receipt of an exchange request specifying
the second portion of spectrum as an exchange candidate.
[0023] The method may comprise receiving incoming signalling
specifying the second portion of spectrum as an exchange candidate.
The incoming signalling may be received from the one or more
wireless communications systems or from an external controller, for
example. Receiving the incoming signalling may comprise receiving
an exchange request specifying the second portion of spectrum as an
exchange candidate in order to trigger the instance of the spectrum
assignment process. The exchange request may request the exchange
of the second portion for an unspecified portion, or a portion of
spectrum in which an expected level of interference is low.
Alternatively, the method may comprise receiving the incoming
signalling following the transmission of an exchange request
specifying the first portion of spectrum as an exchange
candidate.
[0024] The method may comprise comparing the first and second
portions of spectrum before the exchange, and proceeding (for
example with the exchange, or with any of the steps following the
comparison and prior to the exchange) only if the first portion of
spectrum is different to the second portion of spectrum. By
"different" there may be meant that the portions occupy completely
separate frequency ranges, or that the frequency ranges partially
overlap, i.e. the portions are completely or partially different,
with one portion including a range of frequencies not present in
the other portion. (In the case that the systems are located
sufficiently far from one another that the interference from one
system does not have a major impact on the other system.)
[0025] The method may comprise, before the exchange, analysing an
expected level of interference associated with the second portion
of spectrum, in order to determine its suitability as an exchange
candidate.
[0026] It may be assumed that base stations have the capability to
measure/predict/estimate the interference that they inflict on
other base stations (and/or generally on the cells of those base
stations) for each possible spectrum assignment, and are also
capable of determining/measuring/estimating (or obtaining relevant
information regarding) the interference received from such other
base stations (and/or from the cells of those other base stations)
for each such spectrum assignment. Radio transmissions occupying
the same frequency allocations (i.e. the same parts of the shared
communication spectrum) can interfere with one another. The level
of interference will depend on a number of factors, for example on
the power levels of the respective transmissions, and on the
relative locations of the transmitters. In fact, many factors have
impact on interference. Considering a mobile telecommunications
system comprising base stations as an example, these factors
include antenna orientation in the base stations, transmission
schemes employed (say FDD or TDD) by the base stations, the nature
of sectorisation within the cells of the base stations, the power
control schemes employed, the handover schemes employed, the nature
of traffic being handled by the base stations at each point in
time, and the number of active subscribers (e.g. mobile stations)
assigned to each base station at each point in time. The smart
antenna scheme employed in the base stations may also affect
interference. Considering the impact of transmission power on
interference, it is possible that a base station may be assigned a
number of separate spectrum sub-chunks or sub-bands and that it may
use different transmission power levels per sub-chunk. These
different power levels can affect interference. Another important
factor is the interference leakage between two adjacent sub-bands.
Although in telecommunications systems the practical solution is to
introduce guard bands to reduce such leakage, the arrangements of
sub-bands assigned to a base station can nevertheless affect
interference. Other important factors regarding interference may
be, for example, surrounding atmospheric conditions and the
presence or absence of obstructions to signal propagation. The
effect of interference can be signal degradation and an overall
drop in system performance as a whole, as compared to that in an
"interference-free" system.
[0027] Analysing the expected level of interference associated with
the second portion of spectrum may comprise each of a plurality of
network elements of the first wireless communications system
analysing the expected level of interference associated with the
second portion of spectrum (and may comprise the network elements
reporting to an apparatus which performs the remainder of the
method, for example a lead network element of the first wireless
communications system, or an external controller).
[0028] In order to determine the suitability of the second portion
of spectrum as an exchange candidate, the method may comprise
comparing the expected level of interference associated with the
second portion of spectrum with a level of interference associated
with the first portion of spectrum. Furthermore, the method may
comprise transmitting confirmatory signalling to request or confirm
the exchange of the first portion of spectrum for the second
portion of spectrum, if the result of the comparison shows that the
expected level of interference associated with the second portion
of spectrum is lower than the level of interference associated with
the first portion of spectrum. The method may comprise receiving
confirmation of the exchange from one or more of the other wireless
communications systems of from an external controller before
performing the exchange.
[0029] As a final step, the method may comprise, following the
exchange, operating the first wireless communications system to use
the second portion of spectrum and to avoid using the first portion
of spectrum (to the extent that the first and second portions do
not overlap).
[0030] The method may comprise selecting one or both of the first
and second portions of spectrum to reduce the number of separate,
continuous regions of spectrum used by at least one of the first
wireless communications system and the other wireless
communications systems, in order to improve the layout of a
spectrum configuration and potentially to reduce leakage.
[0031] The method of the first aspect may be performed by the first
wireless communications system, an external controller, or both,
for example.
[0032] According to a second aspect, there is provided apparatus
for controlling spectrum use in a first wireless communications
system, the first wireless communications system being operable to
take part in a spectrum assignment process involving at least the
first wireless communications system and one or more other wireless
communications systems, the apparatus comprising
[0033] spectrum assignment circuitry configured to exchange a first
portion of spectrum for a second, different portion of spectrum, in
a single instance of the spectrum assignment process, by assigning
the first portion of spectrum from the first wireless
communications system to the one or more other wireless
communications systems and accepting the assignment of the second
portion of spectrum from the one or more other wireless
communications systems to the first wireless communications
system.
[0034] The spectrum assignment circuitry may be configured to
control one or both of the first and second portions to
substantially equalise operational parameters of the first wireless
communications system with equivalent operational parameters of the
second wireless communications system.
[0035] The spectrum assignment circuitry may be configured to
select one or both of the first and second portions of spectrum to
reduce a level of interference in at least one of the first
wireless communications system and the other wireless
communications systems, based on levels of interference in the
first and second portions.
[0036] The spectrum assignment circuitry may be configured to
assign the first portion of spectrum from the first wireless
communications system to a second wireless communications system
amongst the one or more other wireless communications systems, and
to accept the assignment of the second portion of spectrum from the
second wireless communications system to the first wireless
communications system. Alternatively, the spectrum assignment
circuitry may be configured to assign the first portion of spectrum
from the first wireless communications system to a second wireless
communications system amongst the one or more other wireless
communications systems, and to accept the assignment of the second
portion of spectrum from a third wireless communications system
amongst the one or more other wireless communications systems to
the first wireless communications system, the second and third
wireless communications systems being different.
[0037] The spectrum assignment circuitry may be configured to
identify a high-interference portion of spectrum to serve as the
first portion of spectrum. The spectrum assignment circuitry may be
configured to analyse interference levels in each of a plurality of
sub-chunks of spectrum used by the first wireless communications
system before the exchange, and to identify the high-interference
portion of spectrum by selecting a said sub-chunk associated with a
level of interference which is higher than levels of interference
associated with other said sub-chunks.
[0038] Each of a plurality of network elements of the first
wireless communications system may be configured to analyse the
interference levels in each of a plurality of sub-chunks of the
spectrum used by the first wireless communications system before
the exchange, and to identify a said sub-chunk associated with a
level of interference which is higher than levels of interference
associated with other said sub-chunks. In this regard, the spectrum
assignment circuitry may be configured to receive signalling from
each of the network elements indicating the respective sub-chunk.
The spectrum assignment circuitry may be configured to identify the
high-interference portion of spectrum, in the case that the network
elements all identify the same sub-chunk, by selecting that
sub-chunk as the high-interference portion, and, in the case that
the network elements identify different sub-chunks, by determining
a region of spectrum which has the greatest degree of overlap with
all of the different sub-chunks and selecting that region as the
high-interference portion. The spectrum assignment circuitry may be
configured to compare and analyse the sub-chunks in order to
identify the high-interference portion.
[0039] The spectrum assignment circuitry may be configured to
transmit outgoing signalling specifying the first portion of
spectrum as an exchange candidate. The spectrum assignment
circuitry may be configured to transmit an exchange request
specifying the first portion of spectrum as an exchange candidate
in order to trigger the instance of the spectrum assignment
process. The spectrum assignment circuitry may be configured to
transmit the outgoing signalling following the receipt of an
exchange request specifying the second portion of spectrum as an
exchange candidate.
[0040] The spectrum assignment circuitry may be configured to
receive incoming signalling specifying the second portion of
spectrum as an exchange candidate. The spectrum assignment
circuitry is configured to receive an exchange request specifying
the second portion of spectrum as an exchange candidate in order to
trigger the instance of the spectrum assignment process. The
spectrum assignment circuitry may be configured to receive the
incoming signalling following the transmission of an exchange
request specifying the first portion of spectrum as an exchange
candidate.
[0041] The spectrum assignment circuitry may be configured to
compare the first and second portions of spectrum before the
exchange, and to proceed only if the first portion of spectrum is
different to the second portion of spectrum.
[0042] The spectrum assignment circuitry may be configured to
analyse an expected level of interference associated with the
second portion of spectrum.
[0043] Each of a plurality of network elements of the first
wireless communications system may be configured to analyse the
expected level of interference associated with the second portion
of spectrum. In this regard, the spectrum assignment circuitry may
be configured to receive signalling indicating the expected levels
of interference from each of the network elements.
[0044] The spectrum assignment circuitry may be configured to
compare the expected level of interference associated with the
second portion of spectrum with a level of interference associated
with the first portion of spectrum.
[0045] The spectrum assignment circuitry may be configured to
transmit confirmatory signalling to request or confirm the exchange
of the first portion of spectrum for the second portion of spectrum
in response to the result of the comparison showing that the
expected level of interference associated with the second portion
of spectrum is lower than the level of interference associated with
the first portion of spectrum.
[0046] The spectrum assignment circuitry may be configured to
operate the first wireless communications system to use the second
portion of spectrum and to avoid using the first portion of
spectrum.
[0047] The spectrum assignment circuitry may be configured to
select one or both of the first and second portions of spectrum to
reduce the number of separate, continuous regions of spectrum used
by at least one of the first wireless communications system and the
other wireless communications systems.
[0048] The apparatus of the second aspect may be located at one or
more of the network elements of the first wireless communications
system or at another part of that system, or at an external
controller, for example.
[0049] According to a third aspect, there is provided a computer
program which, when run on a computer (perhaps forming part of a
network element or an external controlling element), causes the
computer to perform the method of the first aspect.
[0050] According to a fourth aspect, there is provided a computer
program which, when loaded into a computer (perhaps forming part of
a network element or an external controlling element), causes the
computer to become the apparatus of the second aspect.
[0051] According to a fifth aspect, there is provided a computer
program of the third or fourth aspect, carried by a carrier medium,
which may be a recording medium and/or a transmission medium.
[0052] According to a sixth aspect, there is provided a computer
program which, when run on a computer, causes the computer to
perform a method of controlling spectrum use in a first wireless
communications system, the first wireless communications system
being operable to take part in a spectrum assignment process
involving at least the first wireless communications system and one
or more other wireless communications systems, the method
comprising
[0053] in a single instance of the spectrum assignment process,
exchanging a first portion of spectrum for a second, different
portion of spectrum, by assigning the first portion of spectrum
from the first wireless communications system to the one or more
other wireless communications systems and accepting the assignment
of the second portion of spectrum from the one or more other
wireless communications systems to the first wireless
communications system.
[0054] According to a seventh aspect, there is provided a computer
program for controlling spectrum use in a first wireless
communications system, the first wireless communications system
being operable to take part in a spectrum assignment process
involving at least the first wireless communications system and one
or more other wireless communications systems, the computer program
comprising
[0055] spectrum assignment code configured to exchange a first
portion of spectrum for a second, different portion of spectrum, in
a single instance of the spectrum assignment process, by assigning
the first portion of spectrum from the first wireless
communications system to the one or more other wireless
communications systems and accepting the assignment of the second
portion of spectrum from the one or more other wireless
communications systems to the first wireless communications
system.
[0056] Any circuitry may include one or more processors, memories
and bus lines. One or more of the circuitries described may share
circuitry elements.
[0057] The present invention includes one or more aspects,
embodiments or features in isolation or in various combinations
whether or not specifically stated (including claimed) in that
combination or in isolation.
[0058] The above summary is intended to be merely exemplary and
non-limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] A description is now given, by way of example only, with
reference to the accompanying drawings, in which:
[0060] FIG. 1 illustrates a wide-area base station sending a
trigger for a spectrum exchange process, and includes a spectrum
diagram indicating a high-interference sub-chunk of spectrum;
[0061] FIG. 2 illustrates base stations measuring interference in
the sub-chunk of spectrum suggested by the wide-area base
station;
[0062] FIG. 3 illustrates base stations of the metropolitan-area
network informing a leader base station of a sub-chunk with a
maximum level of interference;
[0063] FIG. 4 illustrates the leader base station of the
metropolitan-area network informing the wide-area base station of a
suggested sub-chunk for exchange;
[0064] FIG. 5 illustrates the wide-area base station confirming the
spectrum exchange, and includes a spectrum diagram illustrating a
comparison of the interference in sub-chunks of spectrum;
[0065] FIG. 6 illustrates spectrum configurations for the wide- and
metropolitan-area networks following the spectrum exchange;
[0066] FIG. 7 shows a protocol for the spectrum exchange
process;
[0067] FIG. 8A shows the result of a simulation of the impact of
the spectrum exchange process on a level of interference,
immediately before the exchange of spectrum;
[0068] FIG. 8B shows the result of a simulation of the impact of
the spectrum exchange process on a level of interference, after
completion of the spectrum exchange process;
[0069] FIG. 9 shows the impact of the invention on the stages of
spectrum assignment.
DETAILED DESCRIPTION
[0070] Embodiments of the invention relate to methods for
short-term spectrum exchange in wireless networks.
[0071] FIGS. 1 to 6 relate to the exchange of spectrum between a
base station BS1 of a cell WA1 of a wide-area network (WAN) and
three cells MA1-3 of a metropolitan-area network (MAN), grouped as
a cluster located within the WA cell WA1. The cell MA1 acts as a
leader of the cluster of MA cells MA1-3.
[0072] The following steps describe a short-term spectrum exchange
process.
[0073] In step 1, the spectrum is divided into sub-chunks. On a
short-term basis, the base station BS1 of cell WA1 measures the
interference in different sub-chunks of spectrum, as shown in the
spectrum diagrams to the right-hand side of FIG. 2, in which the
sub-chunk being analysed is shown in dark. Sub-chunks are
preferably completely separate, but may partially overlap, as
shown. If the interference is above a specific threshold, the base
station BS1 identifies the specific sub-chunk of spectrum as `red`
or high temperature, as shown in the spectrum diagram at the top of
FIG. 1, in which the arrow indicates the `red` sub-chunk. In that
case, the base station BS1 signals the leader base station in cell
MA1 a trigger for the exchange of the high temperature sub-chunk of
spectrum with a low interference sub-chunk of spectrum from the
MAN, if available. Within the trigger, the exact ID of the specific
red spectrum chunk is sent to the base station of cell MA1. The red
spectrum sub-chunk can be a sub-chunk which has been troubled in
terms of interference for the past couple of transmissions (e.g.
the total interference has been above a threshold for the past
couple of transmissions). Alternatively, it can be a sub-chunk
which is currently experiencing a high level of interference.
[0074] In step 2, in response, the leader base station in cell MA1
asks all the MA base stations (in cells MA2 and MA3) to scan all
the possible sub-chunks, again in the manner shown in the spectrum
diagrams to the right-hand side of FIG. 2, to identify the one with
the maximum interference level. It also asks them to scan the red
sub-chunk suggested by the base station BS1 of cell WA1, which is
indicated by the arrow in the spectrum diagram at the bottom-left
corner of FIG. 2.
[0075] In step 3, the leader base station of cell MA1 itself also
carries out the scan and identification process.
[0076] In step 4, the base stations of cells MA2 and MA3 inform the
leader base station in cell MA1 of the sub-chunk they identified to
have the maximum interference level, as shown in the spectrum
diagrams in FIG. 3, in which the sub-chunk having the maximum
interference level for each of cells MA2 and MA3 is shown in
dark.
[0077] In step 5, if all the MA cells MA1-3 have identified the
same sub-chunk with maximum interference (and the identified
sub-chunk is different from the one suggested by the WA base
station BS1) and if the interference they experience in this
sub-chunk is below the interference of the red sub-chunk suggested
by the WA base station BS1, the leader base station in cell MA1
informs the WA base station BS1 about the potential for exchange
and availability of sub-chunk of spectrum selected by all the MA BS
as shown in FIG. 4, in which the spectrum diagram indicates in dark
the sub-chunk selected by the MA cells.
[0078] In step 6, in response, the WA base station BS1 measures the
interference at the sub-chunk of spectrum suggested by the cell
MA1. If its interference is below the current troubled sub-chunk in
the cell WA1, the WA base station BS1 informs the leader cell MA1
that it is happy to go ahead with the exchange, as shown in FIG. 5.
The spectrum diagram at the top of FIG. 5 shows the WA base station
BS1 comparing the interference levels in the sub-chunks.
[0079] In step 7, the exchange takes place and part of the WA
spectrum (i.e. the exchanged sub-chunk) is exchanged for part of
the MA spectrum, as shown in FIG. 6. The lighter-coloured portion
of spectrum in the spectrum diagram at the top of FIG. 6 has been
gained by the WA base station BS1 from the MA cells, while the
darker-coloured portion of spectrum in the spectrum diagram at the
right-hand side of FIG. 6 has been gained by the MA cells from the
WA base station BS1.
[0080] The figures, especially FIGS. 5 and 6, shows there to be a
small degree of overlap between the portions of spectrum exchanged
by the MA cells and the WA cell. As mentioned above, this is
preferably not the case, but is allowable if the systems are
located far enough away from each other such that interference from
one system does not have a major impact on the other system.
[0081] FIG. 7 shows a protocol for the spectrum exchange process. A
macro-cell base station (BS) (e.g. the WA base station BS1)
periodically measures interference in sub-chunks of spectrum and,
if the interference for a particular sub-chunk is above a specific
threshold for the past couple of transmissions, the sub-chunk is
identified as a high-interference sub-chunk. The macro-cell BS
sends a message to a micro-cell BS leader (e.g. the base station of
cell MA1), the message being a spectrum exchange request including
the spectrum ID and the interference value of the exchange
candidate sub-chunk (the high-interference sub-chunk). The
micro-cell BS leader requests measurements of interference in all
sub-chunks from the micro-cell BSs (the other micro-cell BSs). The
micro-cell BSs measure interference in all sub-chunks and identify
the one with the maximum interference level. At the same time, the
micro-cell BS leader measures interference in all sub-chunks and
identifies the one with the maximum interference level. Each
micro-cell BS sends IDs and interference values of the sub-chunk
experiencing the highest interference, and reports on the
interference value in the exchange candidate sub-chunk, to the
micro-cell BS leader. If the interference experienced in the
exchange candidate sub-chunk at the micro-cell BSs is lower than at
the macro-cell BS, the micro-cell BS leader reports the exchange
availability to the macro-cell BS. The micro-cell BS leader also
reports on the availability and ID of the potential swap candidate
(the candidate sub-chunk referred to above). The macro-cell BS
measures interference in the swap candidate. If the interference in
the swap candidate is less than the exchange candidate sub-chunk,
then the macro-cell BS informs the micro-cell BS leader by sending
a request to proceed with the spectrum exchange to the micro-cell
BS leader, which sends a similar request to the micro-cell BSs. The
micro-cell BSs send acknowledgements to the micro-cell BS leader,
which sends an acknowledgement to the macro-cell BS. Finally, each
of the micro-cell BSs, the micro-cell BS leader and the macro-cell
BS adopts the new spectrum configuration.
[0082] The following disclosure relates to a performance evaluation
and simulation results. For the purposes of the simulation, it is
assumed that three MA BSs are present within a WA cell. The bit
error rate (BER) requirements selected for simulations is
10.sup.-3, and it is assumed that a Reed-Muller channel code
RM(1,m) is used. Adaptive channel coding rates for a data packet
and radio node have been considered to enable the radio nodes to
adjust their transmission rates and consequently the target SIR
values. The presented SIR results in Table 1 can be employed to
obtain the equivalent throughput results.
TABLE-US-00001 TABLE 1 Code Rates of Reed-Muller Code RM (1, m) and
Corresponding SIR Requirements for Target BER m Code Rate SIR (dB)
2 0.75 6 3 0.5 5.15 4 0.3125 4.6 5 0.1875 4.1 6 0.1094 3.75 7
0.0625 3.45 8 0.0352 3.2 9 0.0195 3.1 10 0.0107 2.8
[0083] FIG. 8A shows the result of a simulation of the impact of
the spectrum exchange process on a level of interference,
immediately before the exchange of spectrum, while FIG. 8B shows
the result of a simulation of the impact of the spectrum exchange
process on a level of interference, after completion of the
spectrum exchange process. It can be seen that, after a successful
negotiation between the leader MA base station of the WA base
station, the interference was reduced.
[0084] FIG. 9 shows the impact of the invention on the stages of
spectrum assignment, the major impact being on short-term spectrum
assignment and on inter-cell resource partitioning.
[0085] It will be appreciated that the aforementioned circuitry may
have other functions in addition to the mentioned functions, and
that these functions may be performed by the same circuit.
[0086] Although embodiments of the invention have been described
with reference to a hierarchical overlaid cellular network, it will
be appreciated that the invention is applicable to other networks,
including non-hierarchical, non-overlaid networks.
[0087] The applicant hereby discloses in isolation each individual
feature described herein and any combination of two or more such
features, to the extent that such features or combinations are
capable of being carried out based on the present specification as
a whole in the light of the common general knowledge of a person
skilled in the art, irrespective of whether such features or
combinations of features solve any problems disclosed herein, and
without limitation to the scope of the claims. The applicant
indicates that aspects of the present invention may consist of any
such individual feature or combination of features. In view of the
foregoing description it will be evident to a person skilled in the
art that various modifications may be made within the scope of the
invention.
* * * * *