U.S. patent application number 14/126075 was filed with the patent office on 2014-09-18 for assigning licensed and unlicensed bandwidth.
This patent application is currently assigned to Neul Ltd.. The applicant listed for this patent is William Webb. Invention is credited to William Webb.
Application Number | 20140269550 14/126075 |
Document ID | / |
Family ID | 50825403 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140269550 |
Kind Code |
A1 |
Webb; William |
September 18, 2014 |
ASSIGNING LICENSED AND UNLICENSED BANDWIDTH
Abstract
A controller for assigning bandwidth to communications made over
a communication network, the communication network having available
to it a first type of bandwidth, which is not available to other
users, and a second type of bandwidth, which is available to other
users, the controller being configured to assign a communication
the first type of bandwidth or the second type of bandwidth in
dependence on an overall bandwidth available to the communication
network.
Inventors: |
Webb; William; (Cambridge,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Webb; William |
Cambridge |
|
GB |
|
|
Assignee: |
Neul Ltd.
Cambridge
GB
|
Family ID: |
50825403 |
Appl. No.: |
14/126075 |
Filed: |
June 13, 2012 |
PCT Filed: |
June 13, 2012 |
PCT NO: |
PCT/EP2012/061147 |
371 Date: |
June 2, 2014 |
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 28/20 20130101;
H04W 88/06 20130101; H04W 72/1289 20130101; H04W 72/1215 20130101;
H04W 72/0446 20130101; H04W 72/1257 20130101; H04W 28/0236
20130101; H04W 28/065 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 28/20 20060101
H04W028/20; H04W 28/02 20060101 H04W028/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2011 |
GB |
1109829.0 |
Jun 13, 2011 |
GB |
1109830.8 |
Jun 13, 2011 |
GB |
1109836.5 |
Jun 13, 2011 |
GB |
1109837.3 |
Jun 13, 2011 |
GB |
1109840.7 |
Jun 13, 2011 |
GB |
1109848.0 |
Jun 13, 2011 |
GB |
1109850.6 |
Jun 13, 2011 |
GB |
1109853.0 |
Jun 13, 2011 |
GB |
1109854.8 |
Jun 13, 2011 |
GB |
1109863.9 |
Jun 13, 2011 |
GB |
1109867.0 |
Jun 13, 2011 |
GB |
1109874.6 |
Sep 30, 2011 |
GB |
1116910.9 |
Mar 14, 2012 |
GB |
1204494.7 |
Claims
1. A controller for assigning bandwidth to communications made over
a communication network, the communication network having available
to it a first type of bandwidth, which is not available to other
users, and a second type of bandwidth, which is available to other
users, the controller being configured to assign a communication
the first type of bandwidth or the second type of bandwidth in
dependence on an overall bandwidth available to the communication
network.
2. A controller as claimed in claim 1, configured to assign the
communication the first type of bandwidth or the second type of
bandwidth in dependence on a relative split in the overall
bandwidth between the first type of bandwidth and the second type
of bandwidth.
3. A controller as claimed in claim 1 or 2, configured to assign
the communication the first type of bandwidth or the second type of
bandwidth in dependence on a type of data comprised in the
communication.
4. A controller as claimed in any preceding claim, configured to
assign bandwidth to communications to be made over the
communication network such that communications via the first type
of bandwidth and the second of type bandwidth occur simultaneously
over the network.
5. A controller as claimed in any preceding claim, configured to
preferentially assign the first type of bandwidth to communications
to be made over the communication network.
6. A controller as claimed in any preceding claim, configured to
only assign a communication to the second type of bandwidth if
there is insufficient of the first type of bandwidth to accommodate
that communication.
7. A controller as claimed in any preceding claim, configured to
control the operation of one or more base stations comprised in the
communication network, the controller being configured to control a
base station to operate in a first mode when communicating via the
first type of bandwidth and in a second mode when communicating via
the second type of bandwidth.
8. A controller as claimed in claim 7, configured to control the
base station to, when operating in the first mode, disable one or
more functions that are part of its second mode.
9. A controller as claimed in claim 8, configured to control the
base station to disable one or more functions that enable the base
station to communicate via bandwidth that is subject to
interference.
10. A controller as claimed in claim 8 or 9, configured to control
the base station to disable one or more of: antenna nulling,
frequency hopping and communicating via narrow bandwidth
channels.
11. A controller as claimed in any preceding claim, configured to,
when assigning a communication the second type of bandwidth,
schedule that communication so as to avoid interference and/or
frequency masking.
12. A controller as claimed in any preceding claim, configured to,
when assigning a communication the first type of bandwidth, not
schedule that communication so as to avoid interference and/or
frequency masking.
13. A controller as claimed in any preceding claim, configured to
schedule a communication in dependence on the type of bandwidth it
assigns to that communication.
14. A controller as claimed in any preceding claim, configured to
assign a communication an amount of bandwidth in dependence on the
overall bandwidth available to the communication network.
15. A controller as claimed in any preceding claim, configured to
assign a communication an amount of bandwidth in dependence on
whether that communication is assigned the first type of bandwidth
or the second type of bandwidth.
16. A controller as claimed in any preceding claim, configured to
control the operation of one or more base stations comprised in the
communication network, the controller being configured to control a
base station to communicate at a data rate that is dependent on the
amount of bandwidth the controller has assigned to that
communication.
17. A controller as claimed in any preceding claim, configured to
determine a frequency hopping sequence comprising the first type of
bandwidth and the second type of bandwidth for communicating over
the network.
18. A controller as claimed in claim 17, configured to determine
the frequency hopping sequence to use the first type of bandwidth
for one hop and the second type of bandwidth for the following
hop.
19. A controller as claimed in claim 17 or 18, configured to assign
the communication the first type of bandwidth or the second type of
bandwidth by allocating that communication a time slot on a hop in
the frequency hopping sequence that uses that respective type of
bandwidth.
20. A method for assigning bandwidth to communications made over a
communication network, the communication network having available
to it a first type of bandwidth, which is not available to other
users, and a second type of bandwidth, which is available to other
users, the method comprising assign a communication the first type
of bandwidth or the second type of bandwidth in dependence on an
overall bandwidth available to the communication network,
21. A communication network having available to it a first type of
bandwidth, which is not available to other users, and a second type
of bandwidth, which is available to other users, the communication
network being configured to, if it determines that the first type
of bandwidth available to it is insufficient to accommodate data to
be communicated over the network, communicate at least some of that
data using the second type of bandwidth.
22. A controller as claimed in any of claims 1 to 19, a method as
claimed in claim 20 and a communication network as claimed in claim
21, in which the communication network is configured for machine
communication.
23. A controller as claimed in any of claims 1 to 19, a method as
claimed in claim 20 and a communication network as claimed in claim
21, in which the communication network is configured to operate in
accordance with the Weightless protocol.
24. A controller as claimed in any of claims 1 to 19, a method as
claimed in claim 20 and a communication network as claimed in claim
21, in which the first type of bandwidth is licensed to the
communication network.
25. A controller as claimed in any of claims 1 to 19, a method as
claimed in claim 20 and a communication network as claimed in claim
21, in which the second type of bandwidth is unlicensed.
26. A controller substantially as herein described with reference
to the accompanying drawings.
27. A method substantially as herein described with reference to
the accompanying drawings.
28. A communication network substantially as herein described with
reference to the accompanying drawings.
Description
[0001] The invention relates to a controller configured to assign
bandwidth to communications sent via a communication network.
[0002] A wireless network may be configured to operate without
having been specifically allocated any part of the electromagnetic
spectrum. Such a network may be permitted to operate in so-called
white space: a part of the spectrum that is made available for
unlicensed or opportunistic access. Typically white space is found
in the UHF TV band and spans 450 MHz to 800 MHz, depending on the
country. A large amount of spectrum has been made available for
unlicensed wireless systems in this frequency range.
[0003] A problem with operating in white space is that the
available bandwidth is variable and cannot be guaranteed. These
limitations are well-matched to the capabilities of
machine-to-machine networks in which there is no human interaction.
Machine-to-machine networks are typically tolerant of delays,
dropped connections and high latency communications.
[0004] Any network operating in the UHF TV band has to be able to
coexist with analogue and digital television broadcast
transmitters. The density of the active television channels in any
given location is relatively low (resulting in the availability of
white space that can be used by unlicensed systems). The FCC has
mandated that systems operating in TV white space must reference a
database that determines which channels may be used in any given
location. This is intended to avoid interference with the TV
transmissions and certain other incumbent systems such as wireless
microphones.
[0005] For TV receivers (including those for digital TV (DTV)),
there will inevitably be adjacent channels on which a strong
transmission close to the TV receiver will interfere with TV
reception. For example, the TV receivers may have image frequencies
and poor adjacent channel rejection (ACR) on certain frequencies
due to spurs on their local oscillators and limitations in their
receive filters. These frequencies are often dependent on the
specific receiver implementation.
[0006] In addition, some channels that the data base indicates are
available to unlicensed networks will be subject to interference
that makes them practically unusable. For example, a network
operating in the UHF TV band may have to contend with interference
from other unlicensed users, such as neighbouring communication
networks or incumbent systems such as wireless microphones. A
network may also suffer interference from cellular systems and
emergency service communications at the band edges.
[0007] Another issue with which an unlicensed network must contend
is that the bandwidth available to it will tend to vary with time.
For example, a channel that the data base indicates should be
available for use may be subject to intermittent interference from
another user. Therefore, the network may find without warning that
it has less bandwidth available to it than expected.
[0008] Therefore, there is a need for greater flexibility in
allocating bandwidth.
[0009] According to a first embodiment of the invention, there is
provided a controller for assigning bandwidth to communications
made over a communication network, the communication network having
available to it a first type of bandwidth, which is not available
to other users, and a second type of bandwidth, which is available
to other users, the controller being configured to assign a
communication the first type of bandwidth or the second type of
bandwidth in dependence on an overall bandwidth available to the
communication network.
[0010] The controller may be configured to assign the communication
the first type of bandwidth or the second type of bandwidth in
dependence on a relative split in the overall bandwidth between the
first type of bandwidth and the second type of bandwidth.
[0011] The controller may be configured to assign the communication
the first type of bandwidth or the second type of bandwidth in
dependence on a type of data comprised in the communication.
[0012] The controller may be configured to assign bandwidth to
communications to be made over the communication network such that
communications via the first type of bandwidth and the second of
type bandwidth occur simultaneously over the network.
[0013] The controller may be configured to preferentially assign
the first type of bandwidth to communications to be made over the
communication network.
[0014] The controller may be configured to only assign a
communication to the second type of bandwidth if there is
insufficient of the first type of bandwidth to accommodate that
communication.
[0015] The controller may be configured to control the operation of
one or more base stations comprised in the communication network,
the controller being configured to control a base station to
operate in a first mode when communicating via the first type of
bandwidth and in a second mode when communicating via the second
type of bandwidth.
[0016] The controller may be configured to control the base station
to, when operating in the first mode, disable one or more functions
that are part of its second mode.
[0017] The controller may be configured to control the base station
to disable one or more functions that enable the base station to
communicate via bandwidth that is subject to interference.
[0018] The controller may be configured to control the base station
to disable one or more of: antenna nulling, frequency hopping and
communicating via narrow bandwidth channels.
[0019] The controller may be configured to, when assigning a
communication the second type of bandwidth, schedule that
communication so as to avoid interference and/or frequency
masking.
[0020] The controller may be configured to, when assigning a
communication the first type of bandwidth, not schedule that
communication so as to avoid interference and/or frequency
masking.
[0021] The controller may be configured to schedule a communication
in dependence on the type of bandwidth it assigns to that
communication.
[0022] The controller may be, configured to assign a communication
an amount of bandwidth in dependence on the overall bandwidth
available to the communication network.
[0023] The controller may be configured to assign a communication
an amount of bandwidth in dependence on whether that communication
is assigned the first type of bandwidth or the second type of
bandwidth.
[0024] The controller may be, configured to control the operation
of one or more base stations comprised in the communication
network, the controller being configured to control a base station
to communicate at a data rate that is dependent on the amount of
bandwidth the controller has assigned to that communication.
[0025] The controller may be configured to determine a frequency
hopping sequence comprising the first type of bandwidth and the
second type of bandwidth for communicating over the network.
[0026] The controller may be configured to determine the frequency
hopping sequence to use the first type of bandwidth for one hop and
the second type of bandwidth for the following hop.
[0027] The controller may be configured to assign the communication
the first type of bandwidth or the second type of bandwidth by
allocating that communication a time slot on a hop in the frequency
hopping sequence that uses that respective type of bandwidth.
[0028] According to a second embodiment of the invention, there is
provided a method for assigning bandwidth to communications made
over a communication network, the communication network having
available to it a first type of bandwidth, which is not available
to other users, and a second type of bandwidth, which is available
to other users, the method comprising assign a communication the
first type of bandwidth or the second type of bandwidth in
dependence on an overall bandwidth available to the communication
network.
[0029] According to a third embodiment of the invention, there is
provided a communication network having available to it a first
type of bandwidth, which is not available to other users, and a
second type of bandwidth, which is available to other users, the
communication network being configured to, if it determines that
the first type of bandwidth available to it is insufficient to
accommodate data to be communicated over the network, communicate
at least some of that data using the second type of bandwidth.
[0030] The communication network may be configured for machine
communication.
[0031] The communication network may be configured to operate in
accordance with the Weightless protocol.
[0032] The first type of bandwidth may be licensed to the
communication network.
[0033] The second type of bandwidth may be unlicensed.
[0034] For a better understanding of the present invention,
reference is made by way of example to the following figures, in
which:
[0035] FIG. 1 shows an example of a communication network;
[0036] FIG. 2 shows an example of a controller and associated
radio;
[0037] FIG. 3 shows an example of a process for allocating
bandwidth in a communication network;
[0038] FIG. 4 shows examples of how bandwidth might be reduced;
[0039] FIG. 5 shows an example of scheduling a communication to
avoid a particular frequency;
[0040] FIG. 6 shows an example of antenna nulling; and
[0041] FIG. 7 shows an example of a controller.
[0042] The following description is presented to enable any person
skilled in the art to make and use the system, and is provided in
the context of a particular application. Various modifications to
the disclosed embodiments will be readily apparent to those skilled
in the art.
[0043] The general principles defined herein may be applied to
other embodiments and applications without departing from the
spirit and scope of the present invention. Thus, the present
invention is not intended to be limited to the embodiments shown,
but is to be accorded the widest scope consistent with the
principles and features disclosed herein.
[0044] A communication network may comprise a controller for
allocating bandwidth to communications to be made over the network.
The network may have two different types of bandwidth available to
it: one type which is not available to other users and another
which is available to other users. The controller may assign a
communication to either type of bandwidth, depending on the overall
bandwidth available to the communication network.
[0045] The first type of bandwidth may be bandwidth that is
licensed to the communication network. This bandwidth is
specifically assigned to the communication network and may not be
used by users operating outside of the network. Typically this type
of bandwidth is assigned by some government body responsible for
regulating spectrum usage. The second type of bandwidth may be
unlicensed bandwidth. This bandwidth is open to all, and any
network operating using unlicensed bandwidth has to deal with users
operating outside of the network using the same frequency space.
The bandwidth will usually have been opened to unlicensed users by
the government body responsible for regulating spectrum usage.
[0046] Wireless systems tend to operate either in licensed spectrum
or in unlicensed spectrum. For example, cellular systems operate
solely in licensed spectrum, whereas WiFi networks operate solely
in unlicensed spectrum. However, there may be benefits in combining
operation in the two different types of spectrum and the respective
modes of operation they require of the network devices.
[0047] An example of a network in which licensed and unlicensed
spectrum might be beneficially employed is one that is configured
to operate in white space. Such a network might be configured to
operate in accordance with the Weightless protocol for machine
communications. Such networks typically require around four 8 MHz
channels to operate effectively, although they can cope with fewer
channels by reducing data rates. Usually there will be more than
four channels available in white space for the network to use.
However, sometimes the number of available channels may fall below
four. For example, congestion caused by other unlicensed users
might render one or more channels unusable. For an operator that
wants to provide a high quality of service to customers, the risk
of having to reduce data rates due to congestion can be
unacceptable.
[0048] An alternative is to acquire licensed bandwidth that the
network alone would be permitted to use. There would be no risk of
congestion from other users because no other users would be
entitled to use that part of the spectrum. However, spectrum
purchase is often expensive. Typically, an operator would want to
keep the amount of spectrum it buys to a minimum.
[0049] A suitable compromise is to purchase a minimal amount of
licensed bandwidth for the network. A suitable amount might be, for
example, two channels. The purchased bandwidth will typically not
be sufficient on its own to meet the traffic requirements of the
network. It may, however, be sufficient to maintain a minimally
acceptable level of service when none of the unlicensed bandwidth
available to the network is usable. The network is preferably able
to use both licensed and unlicensed bandwidth simultaneously. If
the network has two channels of licensed spectrum available to it,
this should result in at least four channels being available to the
network, even when the unlicensed part of the spectrum is subject
to congestion. When congestion is severe enough for none of the
unlicensed channels to be available, the network would still have
the licensed channels available to it. Even two channels would
allow some level of service to be provided.
[0050] The licensed and unlicensed spectrum could come from many
sources. The preferred part of the unlicensed spectrum is TV white
space. However, unlicensed access to other bands might be possible
in future, including e.g. VHF bands, military bands below 1 GHz, or
selected bands above 1 GHz. The preferred part of the licensed
spectrum is that which is close to, or interleaved with, the TV
bands. However, any licensed part of the spectrum is suitable,
including e.g. 900 MHz, 1.8 GHz and other bands.
[0051] One or more embodiments of the invention will now be
described with specific reference to a wireless network in which
the controller is part of a base station controller. This is for
the purposes of example only and it should be understood that the
mechanisms for allocating bandwidth described herein may be
implemented in any suitable network device, irrespective of what
particular role that device plays within the network.
[0052] An example of a wireless network is shown in FIG. 1. The
network, shown generally at 104, comprises one or more base
stations 105 that are each capable of communicating wirelessly with
a number of terminals 106. Each base station may be arranged to
communicate with terminals that are located within a particular
geographical area or cell. The base stations transmit to and
receive radio signals from the terminals. The terminals are
suitably entities embedded in machines or similar that communicate
with the base stations. Suitably the wireless network is arranged
to operate in a master-slave mode where the base station is the
master and the terminals are the slaves.
[0053] The base station controller 107 is a device that provides a
single point of communication to the base stations and then
distributes the information received to other network elements as
required. That is, the network is based around a many-to-one
communication model. The network may be arranged to communicate
with a client-facing portion 101 via the Internet 102. In this way
a client may provide services to the terminals via the wireless
network.
[0054] Other logical network elements shown in this example are:
[0055] Core network. This routes traffic information between base
stations and client networks. [0056] Billing system. This records
utilisation levels and generates appropriate billing data. [0057]
Authentication system. This holds terminal and base station
authentication information. [0058] Location register. This retains
the last known location of the terminals. [0059] Broadcast
register. This retains information on group membership and can be
used to store and process acknowledgements to broadcast messages.
[0060] Operations and maintenance centre (OMC). This monitors the
function of the network and raises alarms when errors are detected.
It also manages frequency and code planning, load balancing and
other operational aspects of the network. [0061] White space
database. This provides information on the available white space
spectrum. [0062] Client information portal. This allows clients to
determine data such as the status of associated terminals, levels
of traffic etc.
[0063] In practice, many of the logical network elements may be
implemented as databases running software and can be provided on a
wide range of platforms. A number of network elements may be
physically located within the same platform.
[0064] A network such as that shown in FIG. 1 may be used for
machine-to-machine communications, i.e. communications that do not
involve human interaction. Machine-to-machine communications are
well-matched to the limitations of operating in white space, in
which the bandwidth available to the network may vary from one
location to another and also from one time instant to the next.
Machines are able to tolerate the delays and breaks in
communication that can result from these varying communication
conditions. Services can be provided in non real-time; low latency
is not important as long as data is reliably delivered.
[0065] The communication network shown in FIG. 1 is configured to
operate in an unlicensed part of the spectrum. The network may
benefit from also having licensed bandwidth available to it. The
network is therefore preferably configured to be able to operate
using both unlicensed and licensed bandwidth. Devices operating in
the network (such as base stations, base station controllers,
terminals etc.) are preferably able to switch between licensed and
unlicensed modes of operation. For most devices, this may primarily
involve disabling specific functions designed to address the
challenges of operating in an unlicensed part of the spectrum (more
details of this are given below).
[0066] The communication network preferably comprises a controller
for allocating communications to either licensed or unlicensed
bandwidth. The controller may be a stand-alone device or form part
of another device, such as a base station. In a preferred
embodiment, the controller is implemented by a base station
controller. The base station controller may assemble frames. It may
also make scheduling decisions and plan radio-related resources,
including bandwidth allocation, frequency planning, code assignment
synchronisation word planning and load balancing. Base stations may
be simple devices that take pre-formatted frames of information and
transmit them under the control of their respective base station
controller.
[0067] An example of a controller (e.g. a base station controller)
together with an associated radio (e.g. a base station) is shown in
FIG. 2. The controller (or at least part of it) is shown at 201.
The controller comprises a network layer 203 and a control layer
204, both of which are implemented in software. The control layer
is configured to format the data to be transmitted over the network
into frames. The frames are suitably entire frames, including
control and header information. These frames may then be passed,
e.g. via an Ethernet connection, to the radio 202. The radio
comprises a thin layer of embedded firmware 206 for presenting the
formatted data to the MAC 207 and a physical layer 208 for
transmitting signals over the air interface.
[0068] The result is an architecture in which a simple physical
device acts as the "base station" in the conventional sense, by
transmitting and receiving signals over the air interface. The
"base station controller" controls the operation of the "base
station". Moving more of the intelligence into the software renders
the controller readily transferrable to different physical
devices.
[0069] The controller may be implemented as a virtual machine
running on a PC. Preferably the controller can be moved to a new
machine without having to be adapted to the particular physical
attributes of that machine. The radio might be implemented by a
modem. The PC might be connected to a modem over an Ethernet
connection.
[0070] An example of a process for assigning bandwidth to a
communication is shown in FIG. 3. The process starts in step 301.
In step 302, the controller may determine whether the communication
is subject to any time constraints, as this may affect the amount
and type of bandwidth available. In step 303, the controller
determines what bandwidth will be required to transmit the
communication. In this example the controller is arranged to
preferentially assign licensed bandwidth, as it is less likely to
suffer from interference. The controller determines in step 304
whether there is sufficient licensed bandwidth available to
accommodate the communication. If yes, the controller may cause the
base station to enter the licensed mode of operation (step 305).
The communication is scheduled to be sent using licensed bandwidth
in step 306. If the answer at step 304 is no, the controller may
cause the base station to enter its unlicensed mode of operation
(step 307). The communication is then assigned the required
unlicensed bandwidth in step 308. The process terminates in step
309.
[0071] The controller may consider a relative split between the
licensed and unlicensed bandwidth available to a base station when
deciding what type if bandwidth to assign to a particular
communication. The controller might also consider the type of data
being transmitted. For example, some data may be associated with a
time limit or a particular quality of service requirement that
requires it to be transmitted more quickly or via bandwidth that is
more likely to result in a successful transmission. Some data may
have intrinsic qualities that make it more suitable for being
transmitted via one type of bandwidth over the other. For example,
voice data might be better suited to being transmitted via licensed
bandwidth. The controller might also be configured to prefer one
type of bandwidth over the other. For example, the controller might
be configured to only assign a communication to the unlicensed
bandwidth if there is not enough licensed bandwidth available to
accommodate it. Licensed bandwidth may be preferred because it is
less subject to interference. If there is a cost associated with
using licensed bandwidth, e.g. under a "pay per use" scenario, then
the controller may prefer unlicensed bandwidth.
[0072] The bandwidth available to the network may be divided into
channels. Channels may have different bandwidth depending on which
part of the spectrum they come from. For example, TV bands tend to
use 6 MHz or 8 MHz channels, while some cellular spectrum is
configured on a 5 MHz bandwidth and other spectrum on a narrower
band than this. In this example the unlicensed channels are wider
than the licensed channels; the reverse may also be true.
[0073] The network may be configured to use frequency hopping.
Suitably the controller is arranged to determine a frequency
hopping sequence for the base stations it controls. The controller
may obtain a list of channels that are available to each base
station from the network's white space database. The controller may
reject one or more channels from the list if it has determined that
those channels are practically unusable because of interference.
The controller may generate a hopping sequence for each base
station to include the remaining channels. Suitably the hopping
sequences are arranged so that neighbouring base stations use
different frequencies at any one time.
[0074] The controller may generate a frequency hopping sequences to
include both licensed and unlicensed channels. Each base station
may only communicate on one channel at a time. Each base station
may only communicate via unlicensed or unlicensed bandwidth at any
one time. The network as a whole, however, will be able to
communicate via both types of bandwidth simultaneously since at any
given moment one base station may be communicating via licensed
bandwidth while another is communicating via unlicensed bandwidth.
For each base station, the type of bandwidth can change from one
hop to the next. The width of a channel may also change from one
hop to the next.
[0075] The controller may generate a series of frames for
communication by a base station. The controller may instruct the
base station to transmit each frame at a particular time and on a
particular frequency in the hopping sequence. Each frame may be
communicated on a different frequency in the hopping sequence.
Consequently, one frame may be allocated a different type and
amount bandwidth from the one preceding it.
[0076] Each frame may comprise uplink and downlink sections.
Frequency hopping may occur at the frame rate, so that both uplink
and downlink sections of a frame use the same channel. In one
example each frame is 2 seconds long. The controller suitably
assigns bandwidth to both whole frames and individual
communications within those frames. Preferably the uplink and
downlink portions of each frame are divided into a series of time
slots that the controller can assign to communications between the
base station and terminals. The controller may divide the overall
bandwidth between different communications by assigning each
communication a time slot in a frame to be transmitted on a
particular hop in the frequency hopping sequence. If access to
unlicensed access is good, the number of unlicensed channels in the
frequency hopping sequence may be relatively high and the
controller will be more likely to assign a communication to an
unlicensed channel. The reverse is also true. If performance on
some of the unlicensed channels worsens, the controller may remove
one or more of those channels from the hopping sequence, thereby
shifting the balance towards licensed channels.
[0077] The long term balance between licensed and unlicensed
spectrum might change over time. For example, an operator might
progressively acquire more spectrum and shift usage towards
licensed access. Alternatively, experience may develop an
operator's confidence in unlicensed spectrum. Such an operator may
decide to use their licensed spectrum for activities such as
transmitting voice and shift other communications (e.g. machine
communications) towards greater use of unlicensed spectrum.
[0078] The scheduling system (which may be implemented by the
controller) is preferably able to manage any degradation in data
rates as the network moves between licensed and unlicensed access,
and between different channel bandwidths. For example, lower data
rates may have to be implemented when operating in an unlicensed
part of the available spectrum, in order to accommodate additional
spreading or error control coding to deal with potential
interference. Data rates may also have to be adjusted to account
for different channel widths. The controller may control the base
station to use a particular data rate. The terminals may be
instructed to use a particular data rate by the base station
(acting under the control of the controller).
[0079] Operating in licensed and unlicensed parts of the spectrum
is different, mainly because extra functions may be required to
successfully use unlicensed spectrum. Therefore, the network is
preferably one that is designed to work using unlicensed
frequencies. The network may have two modes of operation: licensed
and unlicensed. Certain features of unlicensed mode may be disabled
when operating in licensed mode. The disabled features may
particularly be intended to address interference problems that a
network might encounter in an unlicensed part of the spectrum. Some
examples are given below.
Using a Reduced Bandwidth
[0080] One in way in which the controller may control a base
station to address problems with interference is by limiting the
bandwidth that the base station and its associated terminals are
permitted to use. The controller may detect that a particular
channel is subject to interference, characterise the nature of that
interference and determine a reduced channel bandwidth accordingly.
This can enable the base station to use a channel that would
otherwise not be practicably usable. It also assists the network to
meet the stringent adjacent channel protection requirements for
white space.
[0081] The communication device may have a variety of different
options at its disposal for communicating over part of the
bandwidth of an available channel. Some of these options are
illustrated in FIGS. 4(a) to (d). In the most straightforward case,
the communication device may simply use only part of the channel,
leaving the centre frequency unchanged. For example, in FIG. 4(a)
the channel bandwidth b.sub.ch is defined by the boundary
frequencies 401 and 402. The communication device has determined,
however, that only a portion of the channel bandwidth should be
used, and so it transmits on a reduced bandwidth b.sub.u
(represented as cross-hatched portion 403 in the figure). Such a
configuration might, for example, be suitable when there are
incumbents on both adjacent channels. This situation is shown in
FIG. 4(b), in which there are incumbents 404 and 405 in both
adjacent channels, causing the communication device to use much
reduced portion 406 of the available channel. As an example, with
incumbents on both sides of the channel, the bandwidth used by the
communication device might be divided by a factor of 4 but left
centred on the channel's centre frequency.
[0082] In addition to scaling the bandwidth, a further option
available to the communication device is to shift the centre
frequency so it is offset within the whitespace channel. An example
is shown in FIG. 4(c), in which the transmit bandwidth 407 has been
shifted from the centre frequency of the channel to provide an
additional frequency guard between the transmission and the
neighbouring incumbent 408. As a practical example, a communication
device might halve the signal bandwidth from 5 MHz to 2.5 MHz and
shift it by say 2 MHz away from the adjacent incumbent. A further
option is to utilise the frequency guard band at the edges of a
channel being used by a distant DTV transmitter. This is
illustrated in FIG. 4(d), with the communication device using one
of the two guard bands 409, 410 to avoid distant incumbent 411. In
this example, the communication device uses guard band 409. Using a
guard band might typically give a bandwidth reduction factor of 16
(giving a 3 dB bandwidth of 312.5 kHz). The frequency offset may
approach 4 MHz (with an 8 MHz channel), or may be exactly 4 MHz in
the case that two adjacent channels have DTV interference well
above the noise floor.
Slot Scheduling
[0083] If a terminal is subject to localised interference on a
particular frequency, the controller may schedule future
communications with that terminal to avoid the problematic
frequency. If those future communications have yet to be scheduled,
the controller can simply allocate future communications with the
terminal to time slots within the frequency hopping sequence that
are on frequencies other than the interfered frequency. The
controller may be constrained by a time period within which a
particular communication needs to be scheduled. For example, in
FIG. 4 a communication with a particular terminal should occur
between t.sub.1 and t.sub.2. There are two frequencies available
during this time period: frequency 1 and frequency 3. So if, for
example, the terminal is subject to localised interference on
frequency 3, the controller may select the time slot on frequency 1
for a communication with the terminal. If there are no time slots
within the predetermined time period that will occur on a
non-interfered frequency, the controller may be configured to not
allocate a time slot for communication with the terminal in that
time period. Instead, the controller may schedule a time slot
outside the predetermined time period, or may wait to schedule a
time slot until the next predetermined time period within which it
should communicate with that terminal.
Antenna Nulling
[0084] Another option for addressing interference is for the
network to determine the direction from which an interfering signal
originates and for the base station to form a null in its antenna
radiation pattern in that direction. An example is illustrated in
FIG. 6, which shows a base station having 12 available channels.
Channels 1 to 4 (C1-4) suffer interference from TV transmitter
T.sub.A, channels 5 to 8 (C5-8) from transmitter T.sub.B and
channels 9 to 12 (C9-12) from transmitter T.sub.c. BS is a white
space network base station and all circles marked with lowercase Ts
are white space network terminals. The shaded areas represent nulls
with respect to the groups of frequencies marked. While effective
at combating interference, the nulls will also reject signals at
their respective frequencies from wanted devices in the same
direction. Therefore, in the cell shown in FIG. 6, t.sub.A cannot
communicate effectively with the base station over C1-4, t.sub.B1
and t.sub.B2 cannot communicate effectively with the base station
over C5-8 and t.sub.C cannot communicate effectively with the base
station over C9-12. t.sub.A, t.sub.B1, t.sub.B2 and t.sub.C are all
partially or wholly masked by the antenna nulls.
[0085] If the controller determines that a terminal is subject to
antenna null masking on a particular frequency, it may schedule
future communications with that terminal to avoid the problematic
frequency. This may be achieved in the same way as slot scheduling
to avoid an interferer (as described above). The controller selects
a time slot that avoids the masked frequency.
[0086] A diagram showing the functional blocks that may be
comprised within a controller is shown in FIG. 7. This figure is
not intended to supersede or contradict FIG. 2. The two figures
show the same controller but just from different perspectives. FIG.
2 illustrates the division of communication layers between the
controller and a radio; FIG. 7 shows the functional blocks that may
be implemented by the communication layers working together.
[0087] The controller of FIG. 7 is shown generally at 701. The
controller comprises two interfaces with which it can communicate
with the network core (702) and one or more base stations (703).
The controller may communicate with the network core and the base
stations via either wired or wireless links. The controller further
comprises a receiving unit 704 for receiving data to be
communicated to the terminals by the base stations. The amount of
data and any timeliness or quality of service constraints are
preferably communicated by the receiving unit to the scheduling
unit 706, which is responsible for scheduling time slots (and
thereby allocating bandwidth) to the data to be communicated. The
data and the associated allocations are preferably passed to a
frame generation unit 705, which generates the frames to be
communicated to each base station. These frames may then be passed
to a control unit 707, which passes the frames to the base stations
for transmission and controls the operation of the base stations in
accordance with the allocated bandwidth, appropriate data rate,
mode of operation etc.
[0088] The controller may also comprise appropriate functional
blocks for receiving data transmitted from the terminals to the
base stations, processing that data and passing it to the core
network. These are not shown in FIG. 7 for clarity, but it should
be understood that suitable receiving and processing units will
also form part of the controller.
[0089] The apparatus in FIG. 7 is shown illustratively as
comprising a number of interconnected functional blocks. This is
for illustrative purposes and is not intended to define a strict
division between different parts of hardware on a chip. In
practice, the controller preferably uses a microprocessor acting
under software control for implementing the methods described
herein. In some embodiments, the algorithms may be performed wholly
or partly in hardware.
[0090] The controller, other network devices described herein and
the communication network as whole may be configured to operate in
accordance with a protocol for machine communications, such as
Weightless or any other suitable protocol.
[0091] Although one or more embodiments of the invention have been
described above with specific reference to networks configured for
machine communications, it should be understood that the mechanisms
described above may be advantageously implemented in any type of
network.
[0092] The applicants hereby disclose 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 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 discloses herein, and
without limitation to the scope of the claims. The applicants
indicate that aspects of the present invention may consist of any
such 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.
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