MOBILE COMMUNICATION DEVICE AND METHOD FOR ALLOCATING RESOURCES OUTSIDE OF A VIRTUAL CARRIER
BASED ON UE CAPABILITIES
TECHNICAL FIELD OF THE DISCLOSURE
The present disclosure relates to communications devices, and methods of communicating
using mobile communications devices, infrastructure equipment for mobile communications networks,
mobile communications networks and systems and methods of communicating using mobile
communications networks.
BACKGROUND OF THE DISCLOSURE
Mobile communications systems continue to be developed to provide wireless
communications services to a greater variety of electronic devices. In more recent years, third and
fourth generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS
and Long Term Evolution (LTE) architectures have been developed to support more sophisticated
communications services to personal computing and communications devices than simple voice and
messaging services offered by previous generations of mobile telecommunication systems. For
example, with the improved radio interface and enhanced data rates provided by LTE systems, a user
may enjoy high data rate applications such as mobile video streaming and mobile video conferencing
that would previously only have been available via a fixed line data connection. The demand to deploy
third and fourth generation networks is therefore strong and the coverage area of these networks, i.e.
geographic locations where access to the networks is possible, is expected to increase rapidly.
More recently it has been recognised that rather than providing high data rate communications
services to certain types of electronics devices, it is also desirable to provide communications services
to electronics devices that are simpler and less sophisticated. For example, so-called machine type
communication (MTC) applications may be semi-autonomous or autonomous wireless communication
devices which may communicate small amounts of data on a relatively infrequent basis. Some
examples include so-called smart meters which, for example, are located in a customer's house and
periodically transmit information back to a central MTC server data relating to the customer's
consumption of a utility such as gas, water, electricity and so on.
Whilst it can be convenient for a communications device such as an MTC type device to take
advantage of the wide coverage area provided by a third or fourth generation mobile
telecommunication network there are at present disadvantages. Unlike a conventional third or fourth
generation communications device such as a smartphone, an MTC-type device is preferably relatively
simple and inexpensive. The type of functions performed by the MTC-type device (e.g. collecting and
reporting back data) do not require particularly complex processing to perform.
As will be appreciated, there may be a desire for many types of communications devices to
conserve power. However this may be particularly applicable to MTC type devices, which are
arranged to operate with a less sophisticated transceiver and may for example be low power and
battery operated and for example may be deployed for a significant time before the batteries are to be
replaced. Accordingly there is a desire to provide arrangements in which a power of all types of
communications devices operating with a mobile communications networks can be conserved.
SUMMARY OF THE DISCLOSURE
Embodiments of the present disclosure can provide in one example a communication device
for transmitting data to and receiving data from a mobile communications network. The mobile
communications network includes one or more network elements providing a wireless access interface
for the communications devices. The wireless access interface provides a plurality of communications
resource elements across a host frequency range which is for example a full or host bandwidth
available for the mobile devices to communicate via the mobile communications network. A full
bandwidth may correspond to the uplink or the downlink of the mobile communications network. The
mobile communications network is adapted to provide a wireless access interface to include within the
host frequency bandwidth a first section of communications resource elements within a first frequency
bandwidth for allocation preferably to reduced capability devices forming a first virtual carrier. The
reduced capability devices each have a receiver bandwidth which is greater than or equal to the first
frequency bandwidth but less than the host frequency bandwidth. The mobile communications
network preferably allocates the communications resources to the reduced capability devices in the
sense that the reduced capability devices are given priority to the communications resources of the first
section of communications resources over the allocation of the communications resources to
communications devices which are able to communicate using the full bandwidth of the host carrier of
the mobile communications network. In one example, the first section of the communications
resources forming the first virtual carrier is reserved for allocation to the reduced capability devices
only, but in other examples, some of the communications resources of the first section of the first
virtual carrier may be allocated to the full capability communications devices, if a demand for the
communications resources from the reduced capability devices leaves some of the communications
resources un-allocated.
A communications device is configured to transmit to the mobile communications network a
relative capability of the communications device to transmit or receive the data via the wireless access
interface, the relative capability comprising at least an indication of a relative bandwidth of the
receiver to receive signals within the host frequency range greater than or equal to the first bandwidth.
The mobile communications device is configured to receive an allocation of communications
resources outside the the first virtual carrier in response to the indication of the relative capability of
the device indicating that the communications device can receive radio signals outside the first virtual
carrier.
According to the present technique communications devices of different capabilities can be
allocated communications resources within different frequency ranges according to their capability,
which can relieve congestion on a centre frequency of communications resources in which
communications devices with a minimum bandwidth capability receive communications resources for
receiving down link signals. This is because in some examples the centre frequencies include control
channels which may be required to receive system information for communicating via the mobile
communications network, such as synchronisation signals and cell parameters etc.
It is expected in the future that there may be many devices which have a reduced capability
and which may be required to communicate within a virtual carrier bandwidth which may be less than
the host bandwidth of a mobile communications network such as a 4G or LTE network. Since the
number of devices may be relatively large, a technical problem exists because the number of
communications devices wishing to communicate via the virtual carrier may produce congestion on,
for example, a control channel or shared communications resources which are provided within the
virtual carrier.
Embodiments of the present disclosure are therefore directed to address a technical problem of
reducing an amount of congestion which may occur in a virtual carrier particularly in regard to a
capacity of the communications channel. According to the embodiments of the present disclosure, a
capacity of the virtual carrier is increased by providing a wireless access interface, which can
exchange communications signals with a communications device in which the communications device
informs the mobile network of its capability. Thus a communications device may have a different
capability from other communications devices, and although operating in accordance with a reduced
bandwidth capability mode, may be able to communicate that it has a capability to transmit and to
receive radio signals outside a virtual carrier which is provided by the mobile communications
network. Accordingly, if the communications device is capable of transmitting data to or receiving
data from the mobile communications network outside the virtual carrier then the mobile network may
allocate communications resources outside the virtual carrier for this communications device.
According to this present technique therefore, communications devices may be determined as
belonging to different classes corresponding to different capabilities for transmitting or receiving data.
The capabilities may include one of a radio frequency bandwidth of a transmitter or a receiver or a
base band bandwidth of a transmitter or a receiver to the effect that depending upon the capability of
the device, a mobile communications network may allocate resources for communicating via the
wireless access interface in accordance with the relative capability of the device.
Further aspects and features of the present disclosure are defined in the appended claims,
including but not limited to, a mobile communications device, a method of communicating, a network
infrastructure element, a communications network and the method of communicating via a wireless
access interface.
Various further aspects and embodiments of the disclosure are provided in the appended
claims, including but not limited to, an infrastructure equipment, an infrastructure equipment, a
communications device and method of receiving data from a mobile communications network
element.
BRIEF DESCRIPTION OF DRAWINGS
Embodiments of the present disclosure will now be described by way of example only with
reference to the accompanying drawings in which like parts are provided with corresponding reference
numerals and in which:
Figure 1 provides a schematic diagram illustrating an example of a conventional mobile
communications system;
Figure 2 provides a schematic diagram illustrating an arrangement of channels of a wireless
access interface for ten down-link sub-frames of a conventional LTE wireless access interface;
Figure 3 provides a schematic diagram illustrating a conventional LTE downlink radio subframe;
Figure 4 provides a schematic diagram illustrating an LTE downlink radio sub-frame arranged
to provide a narrow band virtual carrier including communications resources within a bandwidth
which is narrower than a bandwidth of a host system;
Figure 5 provides a schematic diagram illustrating an LTE downlink radio sub-frame arranged
to provide a narrow band virtual carrier which provides for an allocation of communications resources
from a frequency range which is outside that of the narrow band virtual carrier of Figure 4;
Figure 6 provides a schematic diagram of an LTE downlink radio sub-frame which illustrates
a wireless access interface provided by a mobile communications network which includes allocating
communications resources outside the narrow band virtual carrier for three possible bandwidths
including the narrow band virtual carrier;
Figure 7 provides a schematic diagram of an LTE downlink radio sub-frame which illustrates
a wireless access interface provided by a mobile communications network which includes allocating
communications resources for two classes of communications devices and includes a down-link
control channel;
Figure 8 is an example diagram representing a message exchange during an attach procedure
according to the present technique;
Figure 9 provides a schematic diagram of an LTE downlink radio sub-frame which illustrates
a wireless access interface provided by a mobile communications network which includes allocating
communications resources for primary and secondary virtual carriers, which may be aggregated;
Figure 10 provides a schematic diagram of an LTE downlink radio sub-frame which illustrates
a further example of wireless access interface provided by a mobile communications network for the
example shown in Figure 9 in which a down-link control channel is provided for only the primary
virtual carrier;
Figure 11 provides a schematic diagram of an LTE downlink radio sub-frame which illustrates
a further example of wireless access interface provided by a mobile communications network which
includes allocating communications resources from an extended bandwidth where these resources are
accessible to a communications device;
Figure 12 provides a schematic diagram of an LTE downlink radio sub-frame which illustrates
a further example of wireless access interface provided by a mobile communications network which
includes allocating communications resources for primary and secondary virtual carriers;
Figure 13 provides a schematic diagram of an LTE downlink radio sub-frame which illustrates
a further example of wireless access interface provided by a mobile communications network which
includes allocating communications resources for primary and secondary virtual carriers and in which
only the primary virtual carrier includes a downlink control channel resource;
Figure 14 is a schematic block diagram of a mobile communications system according to one
example of the present technique;
Figure 15 is a flow diagram illustrating the operation of a communications device (UE)
according to the present technique; and
Figure 16 is a flow diagram illustrating the operation of a mobile communications network
according to the present technique.
DESCRIPTION OF EXAMPLE EMBODIMENTS
Example Network
Figure 1 provides a schematic diagram illustrating the basic functionality of a conventional
mobile communications system.
The network includes a plurality of base stations 101 connected to a core network 102. Each
base station provides a coverage area 103 (i.e. a cell) within which data can be communicated to and
from communications devices 104. Data is transmitted from a base station 101 to a communications
device 104 within a coverage area 103 via a radio downlink. Data is transmitted from a
communications device 104 to a base station 101 via a radio uplink. The core network 102 routes data
to and from the base stations 104 and provides functions such as authentication, mobility management,
charging and so on.
The term communications devices will be used to refer to a communications terminal or
apparatus which can transmit or receive data via the mobile communications system. Other terms may
also be used for communications devices such as personal computing apparatus, remote terminal,
transceiver device or user equipment (UE) which may or may not be mobile.
Mobile telecommunications systems such as those arranged in accordance with the 3GPP
defined Long Term Evolution (LTE) architecture use an orthogonal frequency division multiplex
(OFDM) based radio access interface for the radio downlink (so-called OFDMA) and the radio uplink
(so-called SC-FDMA). Data is transmitted on the uplink and on the downlink on a plurality of
orthogonal sub-carriers. Figure 2 shows a schematic diagram illustrating an OFDM based LTE
downlink radio frame 201. The LTE downlink radio frame is transmitted from an LTE base station
(known as an enhanced Node B) and lasts 10 ms. The downlink radio frame comprises ten sub-frames,
each sub-frame lasting 1 ms. A primary synchronisation signal (PSS) and a secondary synchronisation
signal (SSS) are transmitted in the first and sixth sub-frames of the LTE frame, in the case of
frequency division duplex (FDD) system. A physical broadcast channel (PBCH) is transmitted in the
first sub-frame of the LTE frame. The PSS, SSS and PBCH are discussed in more detail below.
Figure 3 provides a schematic diagram providing a grid which illustrates the structure of an
example of a conventional downlink LTE sub-frame. The sub-frame comprises a predetermined
number of symbols which are transmitted over a 1ms period. Each symbol comprises a predetermined
number of orthogonal sub-carriers distributed across the bandwidth of the downlink radio carrier.
The example sub-frame shown in Figure 3 comprises 14 symbols and 1200 sub-carriers
spaced across a 20MHz bandwidth. The smallest unit on which data can be transmitted in LTE is
twelve sub-carriers transmitted over one sub-frame. For clarity, in Figure 3, each individual resource
element is not shown, but instead each individual box in the sub-frame grid corresponds to twelve subcarriers
transmitted on one symbol.
Figure 3 shows resource allocations for four LTE devices 340, 341, 342, 343. For example,
the resource allocation 342 for a first LTE device (UE 1) extends over five blocks of twelve subcarriers,
the resource allocation 343 for a second LTE device (UE2) extends over six blocks of twelve
sub-carriers and so on.
Control channel data is transmitted in a control region 300 of the sub-frame comprising the
first n symbols of the sub-frame where n can vary between one and three symbols for channel
bandwidths of 3MHz or greater and where n can vary between two and four symbols for channel
bandwidths of 1.4MHz. The data transmitted in the control region 300 includes data transmitted on the
physical downlink control channel (PDCCH), the physical control format indicator channel (PCFICH)
and the physical HARQ indicator channel (PHICH).
The PDCCH contains control data indicating which sub-carriers on which symbols of the subframe
have been allocated to specific LTE devices. Thus, the PDCCH data transmitted in the control
region 300 of the sub-frame shown in Figure 3 would indicate that UEl has been allocated the first
block of resources 342, that UE2 has been allocated the second block of resources 343, and so on. In
sub-frames where it is transmitted, the PCFICH contains control data indicating the duration of the
control region in that sub-frame (i.e. between one and four symbols) and the PHICH contains HARQ
(Hybrid Automatic Request) data indicating whether or not previously transmitted uplink data has
been successfully received by the network.
In certain sub-frames, symbols in a central band 310 of the sub-frame are used for the
transmission of information including the primary synchronisation signal (PSS), the secondary
synchronisation signal (SSS) and the physical broadcast channel (PBCH). This central band 310 is
typically 72 sub-carriers wide (corresponding to a transmission bandwidth of 1.08 MHz). The PSS
and SSS are synchronisation signals that once detected allow the LTE device 104 to achieve frame
synchronisation and determine the cell identity of the enhanced Node B transmitting the downlink
signal. The PBCH carries information about the cell, comprising a master information block (MIB)
that includes parameters that the LTE devices require to access the cell. Data transmitted to individual
LTE devices on the physical downlink shared channel (PDSCH) can be transmitted in the remaining
blocks of communications resource elements of the sub-frame. Further explanation of these channels
is provided in the following sections.
Figure 3 also shows a region of PDSCH containing system information and extending over a
bandwidth of R344. Thus in Figure 3 the central frequency carries control channels such as the PSS,
SSS and PBCH and therefore implies a minimum bandwidth of a receiver of a communications
device.
The number of sub-carriers in an LTE channel can vary depending on the configuration of the
transmission network. Typically this variation is from 72 sub carriers contained within a 1.4MHz
channel bandwidth to 1200 sub-carriers contained within a 20MHz channel bandwidth as shown in
Figure 3. As is known in the art, subcarriers carrying data transmitted on the PDCCH, PCFICH and
PHICH are typically distributed across the entire bandwidth of the sub-frame. Therefore a
conventional LTE device must be able to receive the entire bandwidth of the sub-frame in order to
receive and decode the control region.
Virtual Carrier
Certain classes of devices, such as MTC devices (e.g. semi-autonomous or autonomous
wireless communication devices such as smart meters as discussed above), support communication
applications that are characterised by the transmission of small amounts of data at relatively infrequent
intervals and can thus be considerably less complex than conventional LTE devices. Communications
devices may include a high-performance LTE receiver unit capable of receiving and processing data
from an LTE downlink frame across the full carrier bandwidth. However, such receiver units can be
overly complex for a device which only needs to transmit or to receive small amounts of data. This
may therefore limit the practicality of a widespread deployment of reduced capability MTC type
devices in an LTE network. It is preferable instead to provide reduced capability devices such as MTC
devices with a simpler receiver unit which is more proportionate with the amount of data likely to be
transmitted to the device. Furthermore, as explained above it is desirable to include features in a
mobile communications network and/or communications devices which can conserve power
consumption of the communications devices.
In conventional mobile telecommunication networks, data is typically transmitted from the
network to the communications devices in a frequency carrier (first frequency range) where at least
part of the data spans substantially the whole of the bandwidth of the frequency carrier. Normally a
communications device cannot operate within the network unless it can receive and decode data
spanning the entire frequency carrier, i.e. a maximum system bandwidth defined by a given
telecommunication standard, and therefore the use of communications devices with reduced
bandwidth capability transceiver units is precluded.
However, as disclosed in co-pending International patent applications numbered
PCT/GB2012/050213, PCT/GB2012/050214, PCT/GB2012/050223 and PCT/GB2012/051326, the
contents of which are herein incorporated by reference, a subset of the communications resource
elements comprising a conventional carrier (a "host carrier") are defined as a "virtual carrier", where
the host carrier has a certain bandwidth (host frequency bandwidth) and where the virtual carrier has a
reduced bandwidth (virtual carrier frequency bandwidth) compared to the host carrier's bandwidth.
Data for reduced capability devices is separately transmitted on the virtual carrier set of
communications resource elements. Accordingly, data transmitted on the virtual carrier can be
received and decoded using a reduced complexity or capability transceiver unit.
Devices provided with reduced complexity or capability transceiver units (hereafter referred to
as "reduced capability devices") could operate by using a part of its full capability (i.e. reduced
capability set of its full capability) or they could be constructed to be less complex and less expensive
than conventional LTE type devices (onwards referred to generally as LTE devices). Accordingly, the
deployment of such devices for MTC type applications within an LTE type network can become more
attractive because the provision of the virtual carrier allows communications devices with less
expensive and less complex transceiver units to be used.
Dynamic Allocation of Resources to Different Capability Receivers
Embodiments of the present technique can provide an arrangement in which a mobile
communications network is configured to allocate communications resources which are outside a
certain core frequency range, which forms a virtual carrier for reduced capability devices. However
according to the present technique different classes of mobile communications devices are configured
to communicate using the mobile communications network. As explained above, the mobile
communications network including one or more network elements provides a wireless access interface
for the communications devices. The wireless access interface provides a plurality of communications
resource elements across a host frequency range, and at least one section of frequency resources
within the host frequency band within a first frequency band, which forms a virtual carrier for reduced
capability devices. The virtual carrier provides a plurality of communications resources for preferable
allocation to the communications devices for receiving signals transmitted or received within the first
frequency band.
According to the present technique, the communications device is configured to transmit to
the mobile communications network a relative capability of the communications device to transmit or
receive data via the wireless access interface, the relative capability comprising at least an indication
of a bandwidth of the receiver. The mobile communications network responds by allocating
communications resources outside the first virtual carrier in response to an indication that the relative
capability of the device is such that the device can receive or transmit via the wireless access interface
in communications resources which are outside the frequency range of the virtual carrier.
Embodiments of the present technique are therefore configured to provide an arrangement in
which a communications device can select a supporting virtual carrier bandwidth which is less than the
full bandwidth of the host system, but maybe different per communications device, according to its
complexity and capability, data rate, etc. From the network side, an infrastructure element such as an
eNodeB can be arranged to allocate communications resources within the wide system bandwidth
according to the supported bandwidth signalled from the communications terminals. Accordingly, the
present technique can provide for a flexible selection of supporting bandwidth for communications
devices so that these devices can:
• Enable the reuse of the PSS/SSS/PBCH in the host carrier for MTC devices
· Provide more resource to MTC devices outside centre frequency, so as to reduce congestion
on the centre frequencies;
• Reduce the cost of MTC devices compared to legacy communications devices by reducing the
supported RF/Baseband bandwidth (basic merit of a virtual carrier arrangement)
Figure 4 provides an example illustration which corresponds to that shown in Figure 3 but
with the virtual carrier forming a centre frequency of the wireless access interface and in which the
sub-frame comprises two time slots delineated by a vertical line 501. As can be seen from Figure 4,
data transmitted on the virtual carrier 502 is transmitted across a limited bandwidth. This could be any
suitable bandwidth providing it is smaller than that of the host carrier, which for example is 20MHz. In
the example shown in Figure 4 the virtual carrier is transmitted across a bandwidth comprising
resource blocks and sub-carriers which is equivalent to a 1.4 MHz transmission bandwidth.
Accordingly, a device receiving data transmitted on the virtual carrier need only be equipped with a
receiver capable of receiving and processing data transmitted over a bandwidth of 1.4MHz. This
enables reduced capability devices (for example MTC type devices) to be provided with simplified
receiver units yet still be able to operate within an OFDM type communication network which, as
explained above, conventionally requires devices to be equipped with receivers capable of receiving
and processing an OFDM signal across the entire bandwidth of the signal. In keeping with a
conventional LTE downlink sub-frame, the first n symbols (n is three in Figure 4) form the control
region 300 is reserved for the transmission of downlink control data such as data transmitted on the
PDCCH.
As explained above, the centre frequencies may be an advantageous location to allocate a
virtual carrier within a host carrier. This is because the Primary and Secondary Synchronization
Signals (PSS/SSS) and Physical Broadcast Channel (PBCH) are located in the centre frequency and
therefore can be more easily acquired by MTC communications devices, which can only receive the
virtual carrier and so can reuse these PSS/SSS/PBCH channels. However, if MTC devices can only be
allocated resources from a virtual carrier occupying the centre frequencies, then the resources of those
centre frequencies may become congested. Accordingly the present technique can provide an
arrangement for allocating resources from other parts of the host carrier wireless access interface in
accordance with a capability of the devices. Such MTC devices may still be operating in a virtual
carrier mode, receiving an allocation of resources, which are reserved or predetermined for allocation
to MTC-type devices.
As explained above embodiments of the present technique have been provided to increase the
bandwidth of a shared resource which may be allocated to communications devices which may have a
different capability which may be less than the full capability so that whilst these devices can
communicate within a predetermined frequency range they cannot communicate via the full bandwidth
of the host system. Thus, as illustrated in Figure 5 which corresponds to the diagram shown in Figure
4 a separate frequency range 600 which is less than the host bandwidth of the wireless access interface
is provided for allocation to reduce capability devices for classes of devices which can communicate
within a greater frequency bandwidth than the virtual carrier bandwidth of the virtual carrier 502
shown in Figure 4. Thus, as shown in Figure 5 a virtual carrier control channel VC-PDCCH 602 is
provided with an SS/PBCH 604 which corresponds to the examples shown in Figures 3 and 4 but are
available to communications devices which can communicate in frequencies which are outside the
virtual carrier bandwidth 530 of Figure 4.
Embodiments of the present technique can therefore be viewed, in some examples, as a wider
bandwidth virtual carrier, which is narrower than the host system bandwidth, with supporting
bandwidth altered flexibly per communications devices. Furthermore, the common information that
are intended to all VC UEs such as the broadcast information and control information (VC-PDCCH)
have to be sent at the narrowest possible bandwidth so that all VC UEs are able to receive them.
An example embodiment of the present technique is illustrated in Figure 6 in which a wireless
access interface corresponding to that shown in Figures 4 and 5 is shown but illustrating an operation
in which three classes of communications terminals are operating within the mobile communications
network. As shown in Figure 6, the virtual carrier, shown in Figure 5, 530 is provided by the wireless
access interface with the virtual carrier control channel 602 and the SS/BPCH 604 provided for
communications terminals which can only communicate within the frequency bandwidth of the virtual
carrier. Thus, reduced capability terminals of a first class (Class A) transmit requests for allocations of
resources on the shared channel which are communicated on the downlink to allocate to the
communications devices within the VC-PDCCH 602 and are allocated those shared resources within
the virtual carrier bandwidth 530 in communications resources 702, 704. The central region provides
the lowest available bandwidth which can be supported because this also includes the other control
channels mentioned above (SS/PBCH).
According to the present technique there are other classes of communications terminals other
than class A which can only communicate within the smallest bandwidth of a virtual carrier 530 for
class A. As shown in Figure 6, two other classes, class B and class C are illustrated which are able to
communicate within communications resources within two wider bandwidths 732, 734. Thus, within
the bandwidth 732 of the class B devices, communications resources are allocated to the class B
devices within the second largest bandwidth 732. Accordingly, the class B bandwidth 732 provides a
reserved set of communications resources, for preferable allocation within an extension of the virtual
carrier bandwidth 530 to provide a shared communications resource for the class B devices within a
frequency band 740. Communications devices are therefore capable of communicating within the
second largest bandwidth 732. Similarly, for a class C device which is able to receive signals from
within a bandwidth which is larger than the class B and class A devices 734, a separate band of
communications resources within a section of the wireless access interface 742 is provided which are
allocated to class C communications devices by the mobile communications network. Thus, a class C
device may request downlink communications resources and may be allocated downlink
communications resources by receiving a control channel signal from the virtual carrier downlink
control channel VC-PDCCH 602. The down-link control channel VC-PDCCH 602 may allocate
downlink communications resources within the bandwidth 734 for class C devices which may include
the separate shared communications resources VC-PDSCH for class C devices 742 and may also
include communications resources within the second class B shared channel 740 as well as the class A
channel 530.
Accordingly, as will be appreciated from the example given in Figure 6, there are various
classes of devices, each class representing a bandwidth which that device can either transmit or receive
communications resources and therefore the mobile network allocates communications resources in
correspondence with the class of device and the ability of the devices within that class to receive
downlink communications from different bandwidths than the virtual carrier. Thus according to the
example shown in Figure 6, a communications device of class A (class A UE) has the minimum
capability and only supports 1.4MHz. When an eNodeB sends data to this device (UE A), it makes
sure that the resource allocated to it is within the centre 1.4MHz. In contrast a device from class B
(UE B) may support a larger bandwidth of 3MHz, in which case, the eNodeB can allocate a 3MHz
wide resource to this device. In one example, the bandwidth of VC-PDCCH 602 needs to be
receivable by all classes of devices operating under the virtual carrier system, and so needs to be
limited to the narrowest maximum bandwidth that the MTC-type devices need to support (which is
1.4MHz in the above case), so all MTC devices can properly receive this common information.
In other example embodiments of the present technique, the down-link control channel for
allocating the communications resources of the shared channel to the communications device is a socalled
enhanced down-link control channel or an ePDCCH-like design, which is applied to the virtual
carrier arrangement (VC-PDCCH). Such embodiments can have an advantage because the common
control information (VC-PDCCH) which needs to be read by all classes of devices is narrow
bandwidth in nature.
A further example is shown in Figure 7. In Figure 7, two classes of devices are identified as
being able to communicate via first and second frequency bands 802, 804. However, unlike the
examples shown in Figure 6 in which the downlink resources are allocated by communicating resource
allocation messages in a VC-PDCCH 602, the example shown in Figure 7 provides a so-called
enhanced downlink control channel ePDCCH which is provided within a separate bandwidth 806 and
extends substantially from the downlink control channel of the host carrier 300, across two example
frames of the wireless access interface 504, 506. This enhanced downlink control channel (ePDCCH)
is provided to allocate communications resources, which is narrow in frequency but wide in time in
contrast to the host PDCCH which is narrow in time but wide in frequency. A second class of
communications devices class B is able to allocate in a wider bandwidth 804 within the host
communications bandwidth 810 and so can be allocated shared channel resources within an extended
region 812 (VC-PDSCH (for UE B)). In contrast the class A devices can only be allocated shared
communications resources within the class A bandwidth 802 within the shared resources provided by
class A devices 818. Accordingly, for the examples shown in Figure 7, downlink control messages are
communicated by the ePDCCH 806 which occupies a narrow bandwidth frequency but an entire
duration of one subframe (two slots) which would otherwise be occupied by shared channel resources
for communicating downlink control channel messages to for both class A and class B
communications devices. In this example, the class A and class B devices can receive downlink
control link messages from the ePDCCH 806 for allocating shared channel communications resources
within the two different bandwidths 802, 804. Thus class A devices receive bandwidth allocations
within the smaller bandwidth 802 that is within the shared resources 818, whereas although class B
devices also receive downlink control channel resource allocation messages from the ePDCCH 806,
these class B devices may be allocated communications resources for downlink communication within
both the class A bandwidth 818 and the class B bandwidth 812.
Communications devices (UEs) operating in accordance with the present technique are
arranged to exchange information with the mobile communications network in order to identify which
class of a plurality of classes of reduced capability devices the communications device belongs. As
illustrated above, with the three classes, class A, class B, class C each class corresponds to a
predetermined bandwidth within which the communications device can receive for example downlink
communications signals within a shared resource. According the present technique therefore, a
communications device exchanges messages with the mobile communications network in order to
identify which class the device belongs. The messages identify at least a bandwidth of the
communications device within which the communications device can receive downlink signals and
therefore can be allocated downlink shared resources within that bandwidth. An example arrangement
in which the communications device sends and receives messages from the mobile network in order to
establish which class the device belongs is shown in Figure 8.
In Figure 8 in step 1 a communications device transmits a request to access the
communications resources of the wireless access interface. For example, the request to access the
communications resources may be an attach procedure in which the communications device first
powers on and attaches to the mobile network by being affiliated with a particular base station which
may be an eNodeB. Thus, in step 1 a request to access the communications resources is sent to the
base station eNodeB. In response, the mobile network communicates a request to identify a capability
of the communications device in step 2. In step 3 the mobile communications device responds by
indicating which class the communications device belongs. For example, this could be a field in a
message sent as part of an attach procedure to the mobile communications network which may include
a field identifying which of the classes the communications device belongs. In response, the eNodeB
grants communications resources in step 4 by communicating the resources which are allocated to the
communications device (UE) in correspondence with a capability of a device from the class of that
device.
Primary and Secondary Virtual Carrier Examples
Further example of embodiments of the present technique are illustrated with reference to
Figures 9 to 13 in which a wireless access interface is provided with at least a primary and a secondary
virtual carrier within a host carrier. Figure 9 provides an illustration of such a situation which
corresponds to the example shown in Figure 5. However, from the example shown in Figure 9, two
virtual carriers have been provided within a maximum bandwidth available to communications devices
900. Thus, as shown in Figure 11 alongside the downlink control channel for the host carrier 300, two
virtual carriers are provided 902, 904 in which each is provided with a separate downlink control
channel 906, 908 for communicating resource allocation messages to communications devices
allocating downlink shared resources within a first downlink shared virtual carrier VC-PDSCH 910.
The first downlink shared virtual carrier VC-PDSCH 910 is a primary shared resource with a first set
of communications resources for preferable allocation to reduced capability devices. Also shown for
the example embodiment of Figure 9 is a secondary shared resource 912 within the second virtual
carrier 904. The arrangement shown in Figure 9 therefore provides an example in which two virtual
carriers exist and are hosted by a mobile communications network, which may be supported outside a
centre frequency and configured identically to the primary virtual carrier without the central control
channels PSS/SSS/PBCH, but includes a VC-PDCCH from the primary virtual carrier. Embodiments
of the present technique therefore provide an arrangement for more resource to be allocated for MTCtype
devices, which can therefore reduce congestion on the centre frequency or primary virtual carrier
using virtual carrier aggregation. This is because a communications device which has a maximum
bandwidth 900 can use either of the virtual carriers 902, 904.
Embodiments of the present technique can also provide an advantage by reducing the cost of
the different classes of MTC-type devices compared to conventional full-bandwidth devices, because
the maximum supported bandwidth could be reduced to (highest frequency relevant to a terminal -
lowest frequency relevant to a terminal). This advantage could be particularly applicable where a
network operator and a device manufacturer can collaborate to ensure such bandwidths are allocated.
As will be appreciated although the arrangements shown in Figure 9 provides a separate
downlink control channel for allocating resources within the shared channel for the second virtual
carrier 904, the balance of communications resources to the control channels for communicating
resource allocation message with respect to the shared channel resources means that some capacity can
be underutilised in that the second downlink shared channel 908 of the second virtual carrier 904.
Accordingly, an alternative arrangement is shown in Figure 10 in which the second virtual carrier 904
does not include a separate downlink control channel 908. For this example, therefore, a downlink
control channel of the primary virtual carrier 902 (VC-PDCCH 1006) is arranged to allocate shared
resources to a communications device with an operating bandwidth 900 as illustrated by arrows 950,
952. Thus, in contrast the examples shown in Figure 9 an aggregated arrangement of virtual carriers is
provided in which a downlink control channel 1006 provided on the centre frequencies of the primary
virtual carrier 902 allocates communications resources which are shared in both the primary virtual
carrier 902 and the secondary virtual carrier 904 which forms a combined shared channel resource for
reduced capability devices comprising regions 954, 956. According to the example shown in Figure
10, not only are the PSS/SSS/PBCH control channels provided in the primary virtual carrier but also
the down-link control channel for allocating the shared channel resources (VC-PDCCH). This may
allow for more flexible and efficient resource allocation.
A further example is illustrated in Figure 11 which corresponds to the example shown in
Figure 10 except that the secondary virtual carrier 950, 960 is allocated within a central region close to
or contiguous with the primary virtual carrier. According to this example embodiment
communications resources can be allocated to communications devices with a lower operating
bandwidth 980 compared to that shown in Figure 10. As will be appreciated from the example shown
in Figure 11, a communications device with an operating bandwidth 980 could be allocated shared
channel resources from a secondary bandwidth 950 or a secondary bandwidth 960 which is below that
of the virtual carrier in the centre bandwidth which is the primary virtual carrier 902. Accordingly, the
arrangement shown in Figure 11 provides some additional flexibility. This is because, by providing
this arrangement from the wireless communications bandwidth the location of secondary virtual
carrier resources can reduce a maximum supported bandwidth of a communications devices which is
required to VC Bandwidth x (n+1) where n is the number of contiguously -placed secondary virtual
carriers that the communications device can support.
Further examples of the present technique are illustrated in Figures 12 and 13. In Figures 12
and 13 a first and a secondary virtual carrier is provided 1000, 1001 in which each has a narrow band
but wide duration downlink control channel 1002, 1004 (VC-PDCCH) and shared channel resources
(VC-PDSCH) within a remaining part of the operating bandwidth 1006, 1008, 1010, 1012. Thus, for
the example shown in Figure 12, two separate virtual carriers are provided, each of which has a socalled
enhanced downlink control channel VC-ePDCCH which communicates downlink resource
allocation messages to the communications terminals which are able to communicate within the
primary virtual carrier 1000 or the secondary virtual carrier 1001. However, again from the example
illustrated with reference to Figures 10 and 11, there could be an over-capacity in downlink control
channel resources compared to those of the shared channel resources. Accordingly, in Figure 13, the
secondary virtual carrier 1001 has been adapted to remove a downlink control channel 1004 of the
secondary virtual carrier, so that the secondary virtual carrier 1100 contains only shared channel
resources (VC-PDSCH) whereas the primary virtual carrier 1000 corresponds substantially to the
example shown in Figure 12. Again, according to this example the downlink control channel which is
allocated resource allocation messages for downlink resources in the primary virtual carrier 1000,
1002 allocates resources within the secondary virtual carrier 1100 or the remaining shared channel
resources within the primary virtual carrier 1000 as illustrated by resource allocation indicated as
arrows 1004, 1006. Accordingly, there is an improvement in the efficiency with which the resources
of the wireless access interface are used because there is a relative reduction in the capacity given to
downlink control channel resources and an increase in the shared channel resources by removing the
enhanced downlink shared channel from the secondary virtual carrier from 1100.
Example Mobile Communications System
Figure 14 provides a schematic diagram showing part of an adapted LTE mobile
communications system. The system includes an adapted enhanced Node B (eNB) 1401 connected to
a core network 1408 which communicates data to a plurality of conventional LTE devices 1402 and
reduced capability devices 1403 within a coverage area (i.e. cell) 1404. Each of the reduced capability
devices 1403 has a transceiver unit 1405 which includes a receiver unit capable of receiving data
across a reduced bandwidth and a transmitter unit capable of transmitting data across a reduced
bandwidth (or full bandwidth of an uplink carrier supported by the eNB 1401) when compared with
the capabilities of the transceiver units 1406 included in the conventional LTE devices 1402.
The adapted eNodeB 1401 is arranged to transmit downlink data using a sub-frame structure
that includes a virtual carrier as described above for example with reference to Figures 4 to 13. A
transmitter and receiver unit 1409 forms a wireless access interface under the control of a controller
1411, which also performs the function of an adapted scheduler. The reduced capability devices 1403
are thus able to receive and transmit data using the uplink and/or downlink virtual carriers as described
above and may be considered as comprising different classes of devices. Each class may have a
different bandwidth capability, which can provide an arrangement for allocating resources outside the
virtual carrier or conceptually an extended virtual carrier.
As has been explained above, because the reduced complexity devices 1403 receive data
across a reduced bandwidth downlink virtual carriers, the complexity, power consumption and cost of
the transceiver unit 1405 needed to receive and decode downlink data and to encode and transmit
uplink data is reduced compared to the transceiver unit 1406 provided in the conventional LTE
devices.
When receiving downlink data from the core network 1408 to be transmitted to one of the
devices within the cell 1404, the adapted eNodeB 1401 is arranged to determine if the data is bound
for a conventional LTE device 1402 or a reduced capability device 1403. This can be achieved using
any suitable technique. For example, data bound for a reduced capability device 1403 may include a
virtual carrier flag indicating that the data must be transmitted on the downlink virtual carrier. If the
adapted eNodeB 1401 detects that downlink data is to be transmitted to a reduced capability device
1403, a controller 1411 included in the adapted eNodeB 1401 ensures that the downlink data is
transmitted to the reduced capability device in question on the downlink virtual carrier. In another
example the network is arranged so that the virtual carrier is logically independent of the eNodeB.
More particularly the virtual carrier can be arranged to appear to the core network as a distinct cell.
From the perspective of the core network it is not known that the virtual carrier is physically colocated
with, or has any interaction with, the host carrier of the cell. Packets are routed to/from the
virtual carrier just as they would be for any normal cell.
The operation of a communications device according to the present technique is summarised
by the flow diagram in Figure 15, which is summarised as follows:
SI: A communications device determines which of a plurality of classes the
communications device belongs. Each class represents at least a different bandwidth capability of a
transmitter or a receiver of the device. The allocation of the class to a device can be determined by the
network during an initial attach procedure or may be predetermined by a network operator and prestored
in the device.
S2: The communications device transmits to the mobile communications network the
relative capability of the communications device to receive data via a wireless access interface
provided by the mobile access network. The relative capability according to the allocated class of
device includes at least an indication of a bandwidth of the communications device.
S4: The communications device receives a resource allocation message from the mobile
communications network which allocates shared communications resources within a bandwidth
corresponding to the predetermined class of the communications device. The allocated resources may
be outside the bandwidth of the virtual carrier or may be an extension of the virtual carrier.
The operation of a network device such as a mobile communications infrastructure equipment
is illustrated by the example provided in Figure 16 and summarised as follows:
S6: A network infrastructure equipment (e.g. eNodeB) provides a wireless access
interface for transmitting data to and receiving data from mobile communications devices using a
transmitter and a receiver. The wireless access interface provides a plurality of communications
resource elements across a host frequency bandwidth, and includes at least onesection of
communications resources for preferable allocation to reduced capability devices within a virtual
carrier bandwidth. The virtual carrier bandwidth is within the host frequency bandwidth, the
communications resources within the virtual carrier bandwidth being provided for preferable
allocation to communications devices to receive signals representing the data transmitted within the
virtual carrier bandwidth so as to form a virtual carrier.
S8: The network infrastructure equipment receives from a communications device a
relative capability of the communications device. The relative capability can be provided as an
indication of a class to which the device belongs and indicates an ability to receive signals
representing the data via the wireless access interface, and indicates at least a bandwidth of the
communications device to receive the signals.
S10: The network infrastructure equipment allocates communications resources outside the
the first virtual carrier, but within the bandwidth of the communications device, in response to the
indication of the relative capability of the communications device.
Various further aspects and features of the present disclosure are defined in the appended
claims. Various combinations of the features of the dependent claims may be made with those of the
independent claims other than the specific combinations recited for the claim dependency.
Embodiments of the present disclosure have been defined largely in terms of reduced capability
devices transmitting data via a virtual carrier inserted in a conventional LTE based host carrier.
However, it will be understood that any suitable device can transmit and receive data using the
described virtual carriers for example devices which have the same capability as a conventional LTE
type device or devices which have enhanced capabilities.
Further examples of the present technique include an infrastructure equipment or network
element for forming part of a mobile communications network comprising a transmitter unit
configured to transmit data to communications devices via a wireless access interface, a receiver unit
configured to receive data transmitted from communications devices via the wireless access interface,
and a controller. The controller is configured to control the transmitter unit and the receiver unit to
form the wireless access interface providing a plurality of communications resource elements across a
host frequency bandwidth, and including, within the host frequency bandwidth, a first section of
communications resource elements within a first frequency bandwidth for allocation preferably to
reduced capability devices to receive signals representing the data transmitted by the transmitter unit
within the first bandwidth forming a first virtual carrier, the reduced capability devices each having a
receiver bandwidth which is greater than or equal to the first frequency bandwidth but less than the
host frequency bandwidth. The controller is configured in combination with the transmitter unit and
the receiver unit to receive from a communications device a relative capability of the communications
device to receive signals representing the data via the wireless access interface, the relative capability
comprising at least an indication of a relative bandwidth of the communications device to receive the
signals within the host frequency range greater than or equal to the first bandwidth, and to allocate
communications resource elements which include communications resource elements which are
outside the first frequency bandwidth, but within the bandwidth of the communications device, in
response to the indication of the relative capability of the communications device.
In one example the infrastructure equipment allocates the communications resource elements
outside the first bandwidth to the communications device in dependence upon a capacity of the first
virtual carrier and a demand on the communications resource elements of the first virtual carrier by the
reduced capability devices. The controller in combination with the transmitter unit and the receiver
unit may be configured to receive signals from and/or transmit signals to communications devices in
accordance with a one of a predetermined set of classes of communications devices, each class
defining a different frequency bandwidth within which the communications device can receive signals
from the infrastructure equipment, and to transmit a resource allocation message to the
communications device which allocates shared communications resource elements to the
communications device within a bandwidth corresponding to one of a predetermined number of
classes of the communications device.
Furthermore the controller may be configured in combination with the receiver unit to receive
from one of the communications devices the class of the communications device from one of the
predetermined classes, each class defining a different frequency bandwidth within which the
communications device can receive signals from the wireless access interface.
The following numbered clauses provide further example aspects and features of the present
technique:
1. An infrastructure equipment for forming part of a mobile communications network,
the infrastructure equipment comprising:
a transmitter unit configured to transmit data to communications devices via a wireless access
interface,
a receiver unit configured to receive data transmitted from communications devices via the
wireless access interface, and a controller configured to control the transmitter unit and the receiver
unit to form the wireless access interface providing a plurality of communications resource elements
across a host frequency bandwidth, and including, within the host frequency bandwidth, a first section
of communications resource elements within a first frequency bandwidth for allocation preferably to
reduced capability devices to receive signals representing the data transmitted by the transmitter unit
within the first bandwidth forming a first virtual carrier, the reduced capability devices each having a
receiver bandwidth which is greater than or equal to the first frequency bandwidth but less than the
host frequency bandwidth, and the controller is configured in combination with the transmitter unit
and the receiver unit
to receive from a communications device a relative capability of the communications device to
receive signals representing the data via the wireless access interface, the relative capability
comprising at least an indication of a relative bandwidth of the communications device to receive the
signals within the host frequency range greater than or equal to the first bandwidth, and
to allocate communications resource elements which include communications resource
elements which are outside the first frequency bandwidth, but within the bandwidth of the
communications device, in response to the indication of the relative capability of the communications
device.
2. An infrastructure equipment according to clause 1, wherein the infrastructure
equipment allocates the communications resource elements outside the first bandwidth to the
communications device in dependence upon a capacity of the first virtual carrier and a demand on the
communications resource elements of the first virtual carrier by the reduced capability devices.
3. An infrastructure equipment according to clause 1 or 2, wherein the controller in
combination with the transmitter unit and the receiver unit are configured
to receive signals from and/or transmit signals to communications devices in accordance with
a one of a predetermined set of classes of communications devices, each class defining a different
frequency bandwidth within which the communications device can receive signals from the
infrastructure equipment, and
to transmit a resource allocation message to the communications device which allocates
shared communications resource elements to the communications device within a bandwidth
corresponding to one of a predetermined number of classes of the communications device.
4. An infrastructure equipment according to clause 3, wherein the controller is
configured in combination with the receiver unit
to receive from one of the communications devices the class of the communications device
from one of the predetermined classes, each class defining a different frequency bandwidth within
which the communications device can receive signals from the wireless access interface.
5. An infrastructure equipment according to clause 4, wherein the controller is
configured in combination with the transmitter unit and the receiver unit
to transmit in response to receiving a request to attach to the mobile communications network
a request to communicate an indication of the class to which the communications device belongs, and
to receive in response to the transmitted request for the class of the communications device an
indication of the class of the communications device.
6. An infrastructure equipment according to any of clauses 1 to 5, wherein the controller
is configured in combination with the transmitter unit and the receiver unit
to form the wireless access interface with a second virtual carrier providing a second section
of communications resource elements for preferable allocation to the reduced capability devices within
a second bandwidth, within the host frequency bandwidth of the wireless access interface,
to transmit signalling information providing the location of the second virtual carrier, and
in accordance with a capability of the communications devices, to transmit signals
representing data to one of the communications devices from communications resource elements of
the second virtual carrier and the first virtual carrier.
7. An infrastructure equipment according to clause 6, wherein the controller is
configured in combination with the transmitter unit and the receiver unit
to form the wireless access interface with the first virtual carrier , which includes a control
channel for communicating messages to the communications device to allocate communications
resource elements of the first and second virtual carriers, and
to transmit a resource allocation message on the control channel to the communications
device, the resource allocation message allocating communications resource elements within the first
and second virtual carriers, and
to transmit signals from the allocated communications resource elements of the first and
second virtual carriers to the reduced capability communications devices.
8. An infrastructure equipment according to any of clauses 1 to 7, wherein the first
virtual carrier is located substantially at centre of the host frequency bandwidth.
9. An infrastructure equipment according to clause 8, wherein the first virtual carrier
bandwidth includes one or more other control channels for providing other control information, and
the controller is configured in combination with the receiver unit to receive other control information
from the other control channels.
10. A method of communicating with a communications device from an infrastructure
equipment for forming part of a mobile communications network, the method comprising:
transmit data to communications devices via a wireless access interface, and
receiving data transmitted from communications devices via the wireless access interface, the
wireless access interface providing a plurality of communications resource elements across a host
frequency bandwidth, and including, within the host frequency bandwidth, a first section of
communications resource elements within a first frequency bandwidth for allocation preferably to
reduced capability devices to receive signals representing the data transmitted by the transmitter unit
within the first bandwidth forming a first virtual carrier, the reduced capability devices each having a
receiver bandwidth which is greater than or equal to the first frequency bandwidth but less than the
host frequency bandwidth, and
receiving from a communications device a relative capability of the communications device to
receive signals representing the data via the wireless access interface, the relative capability
comprising at least an indication of a relative bandwidth of the communications device to receive the
signals within the host frequency range greater than or equal to the first bandwidth, and
allocating communications resource elements which include communications resource
elements which are outside the first frequency bandwidth, but within the bandwidth of the
communications device, in response to the indication of the relative capability of the communications
device.
11. A method according to clause 10, wherein the allocating communications resource
elements outside the first frequency range of the first virtual carrier comprises allocating the
communications resource elements outside the first virtual carrier to the communications device in
dependence upon a capacity of the first virtual carrier and a demand on the communications resource
elements of the first virtual carrier by the reduced capability devices.
12. A method according to clause 10 or 11, wherein the allocating communications
resource elements which include communications resource elements which are outside the first
frequency bandwidth comprises
receiving signals from and/or transmitting signals to communications devices in accordance
with a one of a predetermined set of classes of communications devices, each class defining a different
frequency bandwidth within which the communications device can receive signals from the
infrastructure equipment, and
transmitting a resource allocation message to the communications device which allocates
shared communications resource elements to the communications device within a bandwidth
corresponding to one of a predetermined number of classes of the communications device.
13. A method according to clause 12, wherein the allocating communications resources
outside the first virtual carrier comprises
receiving from one of the communications devices the class of the communications device
from one of the predetermined classes, each class defining a different frequency bandwidth within
which the communications device can receive signals from the wireless access interface.
14. A method according to clause 13, wherein the receiving from one of the
communications devices the class of the communications device from one of the predetermined
classes comprises
transmitting in response to receiving a request to attach to the mobile communications
network a request to communicate an indication of the class to which the communications device
belongs, and
receiving in response to the transmitted request for the class of the communications device an
indication of the class of the communications device.
15. A method according to any of clauses 10 to 14, wherein the allocating
communications resources outside the first virtual carrier comprises
forming the wireless access interface with a second virtual carrier providing a second section
of communications resource elements for preferable allocation to the reduced capability devices within
a second bandwidth, within the host frequency bandwidth of the wireless access interface,
transmitting signalling information providing the location of the second virtual carrier, and
in accordance with a capability of the communications devices, transmitting signals
representing data to one of the communications devices from communications resource elements of
the second virtual carrier and the first virtual carrier.
16. A method according to clause 14 or 15, wherein the forming the wireless access
interface with the first virtual carrier, comprises
forming the wireless access interface with the first virtual carrier, which includes a control
channel for communicating messages to the communications device to allocate communications
resource elements of the first and second virtual carriers,
transmitting a resource allocation message on the control channel to the communications
device, the resource allocation message allocating communications resource elements within the first
and second virtual carriers, and
transmitting signals from the allocated communications resource elements of the first and
second virtual carriers to the reduced capability communications devices.
17. A method according to any of clauses 10 to 16, wherein the first virtual carrier is
located substantially at centre of the host frequency bandwidth.
18. A method according to clause 17, wherein the first virtual carrier includes one or more
other control channels for providing other control information, and the controller is configured in
combination with the receiver unit to receive other control information from the other control
channels.
19. A mobile communications network comprising
one or more infrastructure equipment configured to form a wireless access interface for
transmitting data to or receiving data from communications devices, the wireless access interface
providing a plurality of communications resource elements across a host frequency bandwidth, and
including within the host frequency bandwidth, a first section of communications resource elements
within a first frequency bandwidth for allocation preferably to reduced capability devices to receive
signals representing the data transmitted by the transmitter unit within the first bandwidth forming a
first virtual carrier, the reduced capability devices each having a receiver bandwidth which is greater
than or equal to the first frequency bandwidth but less than the host frequency bandwidth, and the
infrastructure equipment is configured
to receive from a communications device a relative capability of the communications device to
receive signals representing the data via the wireless access interface, the relative capability
comprising at least an indication of a relative bandwidth of the communications device to receive the
signals within the host frequency range greater than or equal to the first bandwidth, and
to allocate communications resources elements which include communications resource
elements which are outside the first frequency bandwidth, but within the bandwidth of the
communications device, in response to the indication of the relative capability of the communications
device.
20. A mobile communications network according to clause 19, wherein the infrastructure
equipment is configured
to receive signals from and/or transmit signals to communications devices in accordance with
a one of a predetermined set of classes of communications devices, each class defining a different
frequency bandwidth within which the communications device can receive signals from the
infrastructure equipment, and
to transmit a resource allocation message to the communications device which allocates
shared communications resource elements to the communications device within a bandwidth
corresponding to one of a predetermined number of classes of the communications device.
21. A mobile communications network according to clause 20, wherein the infrastructure
equipment is configured
to receive from one of the communications devices the class of the communications device
from one of the predetermined classes, each class defining a different frequency bandwidth within
which the communications device can receive signals from the wireless access interface.
22. A mobile communications system comprising a mobile communications network and
a communications device,
the mobile communications network comprising one or more infrastructure equipment
configured to form a wireless access interface for transmitting data to or receiving data from
communications devices, the wireless access interface providing a plurality of communications
resource elements across a host frequency bandwidth, and including, within the host frequency
bandwidth, a first section of communications resource elements within a first frequency bandwidth for
allocation preferably to reduced capability devices to receive signals representing the data transmitted
by the transmitter unit within the first bandwidth forming a first virtual carrier, the reduced capability
devices each having a receiver bandwidth which is greater than or equal to the first frequency
bandwidth but less than the host frequency bandwidth, and the communications device is configured
to transmit to the mobile communications network a relative capability of the communications
device to receive data via the wireless access interface, the relative capability comprising at least an
indication of a relative bandwidth of the receiver unit within the host frequency range greater than or
equal to the first bandwidth, and
the infrastructure equipment is configured
to receive from the communications device the relative capability of the communications
device and in response to allocate communications resource elements which are outside the first
frequency bandwidth to the communications device, but within the bandwidth of the communications
device, in response to the indication of the relative capability of the communications device.

CLAIMS
1. A communications device for receiving data from a mobile communications network,
the mobile communications network including one or more network elements providing a wireless
access interface for the communications device, the communications device comprising:
a transmitter unit configured to transmit data to the mobile communications network via the
wireless access interface provided by the one or more network elements of the mobile communications
network, and
a receiver unit configured to receive data from the mobile communications network via the
wireless access interface provided by the one or more network elements of the mobile communications
network, the wireless access interface providing a plurality of communications resource elements
across a host frequency bandwidth, and including, within the host frequency bandwidth a first section
of communications resource elements within a first frequency bandwidth for allocation preferably to
reduced capability devices forming a first virtual carrier, the reduced capability devices each having a
receiver bandwidth which is greater than or equal to the first frequency bandwidth but less than the
host frequency bandwidth, and
a controller configured in combination with the transmitter unit and the receiver unit
to transmit to the mobile communications network a relative capability of the communications
device to receive data via the wireless access interface, the relative capability comprising at least an
indication of a relative bandwidth of the receiver unit to receive signals within the host frequency
range greater than or equal to the first bandwidth, and
to receive an allocation of communications resource elements which include communications
resource elements which are outside the first frequency bandwidth, but within the bandwidth of the
receiver unit, in response to the indication of the relative capability of the communications device.
2. A communications device as claimed in Claim 1, wherein the mobile communications
network allocates the communications resource elements outside the first frequency bandwidth of the
first virtual carrier to the communications device in dependence upon a capacity of the first virtual
carrier and a demand on the communications resource elements of the first virtual carrier by the
reduced capability devices.
3. A communications device as claimed in Claim 1, wherein the transmitter unit and or
the receiver unit are configured to transmit and/or receive signals in accordance with a bandwidth
corresponding to one of a predetermined set of classes of communications devices, and the controller
in combination with the receiver unit is configured to receive from the mobile communications
network the resource allocation message which allocates communications resource elements within a
bandwidth corresponding to the predetermined class of the communications device.
4. A communications device as claimed in Claim 3, wherein the controller is configured
in combination with the transmitter unit to communicate to the mobile communications network the
class of the device from one of a predetermined set of classes, each class defining a different
frequency bandwidth within which the communications device can receive signals from the wireless
access interface, which is greater than or equal to the first bandwidth.
5. A communications device as claimed in Claim 4, wherein the controller is configured
in combination with the transmitter unit and the receiver unit
to attach to the mobile communications network, and
to receive in response to attaching to the mobile communications network a request to
communicate an indication of the class to which the communications device belongs, and
to transmit in response to the received request for the class of the communications device an
indication of the class of the communications device.
6. A communications device as claimed in Claim 1, wherein the communications device
is configured to receive signalling information providing a location of a second virtual carrier
providing within a second section of communications resource elements for preferable allocation to
the reduced capability devices within a second virtual carrier bandwidth, within the host frequency
bandwidth of the wireless access interface, and in accordance with a capability of the communications
device, the communications device is configured to receive signals allocating communications
resource elements from the second virtual carrier and the first virtual carrier.
7. A communications device as claimed in Claim 6, wherein one or both of the first and
second virtual carriers include a control channel for communicating messages to the communications
device to allocate communications resource elements of the first and second virtual carriers, and the
communications device is configured
to receive the resource allocation message on the control channel,
to determine from the control channel message that the communications device has been
allocated communications resource elements within the first and second virtual carriers, and
to receive signals from the mobile communications network from the allocated
communications resource elements of the first and second virtual carriers.
8. A communications device as claimed in Claim 1, wherein the first bandwidth of the
first virtual carrier is located substantially at the centre frequency of the host frequency bandwidth.
9. A communications device as claimed in Claim 8, wherein the first virtual carrier
includes one or more other control channels for providing other control information, and the controller
is configured in combination with the receiver unit to receive other control information from the other
control channels.
10. A method of receiving data from a mobile communications network using a
communications device, the mobile communications network including one or more network elements
providing a wireless access interface, the wireless access interface providing a plurality of
communications resource elements across a host frequency bandwidth, and including, within the host
frequency bandwidth, a first section of communications resource elements within a first frequency
bandwidth for allocation preferably to reduced capability devices, to form a first virtual carrier, the
reduced capability devices each having a receiver bandwidth which is greater than or equal to the first
frequency bandwidth but less than the host frequency bandwidth, the method comprising
transmitting to the mobile communications network a relative capability of the
communications device to receive data via the wireless access interface, the relative capability
comprising at least an indication of a relative bandwidth of the communications device to receive
signals within the host frequency range greater than or equal to the first bandwidth, and
receiving an allocation of communications resources which include communications resource
elements which are outside the first frequency bandwidth, but within the bandwidth of the
communications device, in response to the indication of the relative capability of the communications
device.
11. A method as claimed in Claim 10, wherein the receiving the allocation of
communications resources outside the first bandwidth includes
receiving the allocation of the communications resources outside the first bandwidth in
dependence upon a capacity of the first bandwidth and a demand on the communications resources of
the first virtual carrier by other communications devices.
12. A method as claimed in Claim 10 , wherein the communications device transmits
and/or receives signals in accordance with a bandwidth corresponding to one of a predetermined set of
classes of communications devices, and the receiving the allocation of communications resources
outside the first bandwidth includes receiving the resource allocation message from the mobile
communications network which allocates shared communications resources within a bandwidth
corresponding to the predetermined class of the communications device.
13. A method as claimed in Claim 12, wherein the transmitting to the mobile
communications network a relative capability of the communications device to receive data via the
wireless access interface includes
communicating to the mobile communications network a class of the device from one of a
predetermined set of classes, each class defining a different frequency bandwidth within which the
communications device can receive signals from the wireless access interface, each class having a
minimum bandwidth of the virtual carrier.
14. A method as claimed in Claim 13, wherein the communicating to the mobile
communications network a class of the device from one of a predetermined set of classes includes
attaching by the communications device to the mobile communications network,
receiving in response to attaching to the communications network a request to communicate
an indication of the class to which the communications device belongs, and
transmitting in response to the received request for the class of the communications device an
indication of the class of the communications device.
15. A method as claimed in Claim 10, the method comprising
receiving at the communications device signalling information providing a location of a
second virtual carrier providing in a second section communications resource elements for preferable
allocation to reduced capability devices from a second frequency bandwidth, which is outside the first
virtual carrier bandwidth, within the host frequency bandwidth of the wireless access interface, and in
accordance with a capability of the communications device, receiving signals representing data at the
communications device from the second virtual carrier.
16. A method as claimed in Claim 15, wherein one or both of the first virtual carrier and
the second virtual carrier includes a control channel for communicating messages to the
communications device to allocate communications resource elements from either of the first or the
second virtual carriers, and the method comprises
receiving, at the communications device, a resource allocation message on the control channel,
determining, at the communications device, from the resource allocation message that the
communications device has been allocated communications resources within the first virtual carrier
and the second virtual carrier, and
receiving signals from the mobile communications network, at the communications device,
from the allocated communications resources from the first and the second virtual carriers.
17. A method as claimed in Claim 10, wherein the first virtual carrier is located
substantially at centre of the host frequency bandwidth.
18. A method as claimed in Claim 17, wherein the first virtual carrier includes one or
more other control channels for providing other control information, and the method comprises
receiving other control information from the other control channels.
19. A mobile communications device substantially as hereinbefore described with
reference to the drawings.
20. A method of communicating data to and/or from mobile communications devices
substantially as hereinbefore described with reference to the drawings.