WO2018184696A1

WO2018184696A1 - A network device and method for allocating radio resources to remote devices

Info

Publication number: WO2018184696A1
Application number: PCT/EP2017/058415
Authority: WO
Inventors: Jin Wang; Robert William Young
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2017-04-07
Filing date: 2017-04-07
Publication date: 2018-10-11

Abstract

A network device is provided that comprises a resource allocator. The resource allocator is configured to allocate radio resources to a remote device for a transmission in accordance with a first communication protocol. Those radio resources are comprised in a guard band of a resource block in accordance with a second communication protocol. The network device also comprises a power controller. The power controller is configured to determine a transmit power reduction that is permitted to the remote device for making the transmission using the allocated radio resources, so as to enable the remote device to make the transmission in accordance with the first communication protocol while meeting spectral emission requirements of the second communication protocol. Allowing the remote device to reduce its transmit power in this way enables more of the guard band in accordance with the second communication protocol to become available for transmissions in accordance with the first communication protocol.

Description

A network device and method for allocating radio resources to remote devices

This invention relates to an apparatus and method for allocating radio resources to remote devices.

Mobile Network Operators (MNOs) across the world need an ultra-low cost air interface in licensed spectrum for the rapidly emerging Internet-of-Things (loT) segment. An loT system preferably supports ultra-low cost terminals, is scalable to huge numbers of terminals per node, and yet is secure, easy to access and robust. The system is preferably deployed in licensed spectrum to assure a quality of service. The challenge is to identify bandwidth that is both available and capable of providing the required air interface.

One option is for an loT system to share spectrum that is licensed to another system. It is preferred that this should have minimal impact on the primary licensed system. This can be achieved if the loT system uses parts of the licensed spectrum that are ordinarily not used by the primary licensed system. Such unused spectrum is available in guard bands: spectrum gaps that are left between neighbouring channels. If the loT system is deployed in certain parts of a guard band, it may not be able to meet the spectrum emission mask requirement of the primary licensed system's channel. This may lead the regulator to forbid such a deployment, which would reduce the business opportunities available to network operators.

It is an object of the invention to provide improved concepts for using spectrum in guard bands.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, a network device is provided that comprises a resource allocator. The resource allocator is configured to allocate radio resources to a remote device for a transmission in accordance with a first communication protocol. Those radio resources are comprised in a guard band of a resource block in accordance with a second communication protocol. The network device also comprises a power controller. The power controller is configured to determine a transmit power reduction that is permitted to the remote device for making the transmission using the allocated radio resources, so as to enable the remote device to make the transmission in accordance with the first communication protocol while meeting spectral emission requirements of the second communication protocol. Allowing the remote device to reduce its transmit power in this way enables more of the guard band in accordance with the second communication protocol to become available for transmissions in accordance with the first communication protocol.

In a further implementation form of the first aspect, the resource allocator may be configured to identify one or more frequency locations for a resource block in accordance with the first communication protocol in dependence on spectral emission requirements of the second communication protocol. This enables the resource allocator to identify spectrum that it can use without breaching the spectral emission requirements of the second communication protocol.

In a further implementation form of the first aspect, the resource allocator may be configured to treat the guard band as comprising a series of sub-channels, and the power controller may be configured to associate each sub-channel of the guard band with a respective permitted transmit power reduction. This enables the resource allocator to consider different transmit power reductions for different parts of the guard band.

In a further implementation form of the first aspect, the power controller may be configured to associate each sub-channel of the guard band with a respective permitted transmit power reduction that is dependent on the spectral emission requirements of the second communication protocol. This enables the power controller to consider that the effect of the second communication protocol's spectral emission requirements may not be uniform throughout the guard band.

In a further implementation form of the first aspect, the power controller may be configured to associate each sub-channel of the guard band with a respective permitted transmit power reduction in dependence on a relative position of that sub-channel within the guard band relative to the resource block in accordance with the second communication protocol. This enables the power controller to adapt the permitted transmit power reductions to a common form of spectral emission mask, in which the mask varies in dependence on distance from a boundary of the resource block.

In a further implementation form of the first aspect, the resource allocator may be configured to allocate radio resources to a remote device by allocating that remote device a particular sub-channel of the guard band. The resource allocator is therefore able to allocate specific communication resources to the remote device. In a further implementation form of the first aspect, the network device may comprise a communication unit that is configured to, if the resource allocator has allocated a sub-channel of the guard band that is associated with a permitted transmit power reduction to a remote device, communicate an indication of that permitted transmit power reduction to the remote device. This enables the remote device to meet the performance requirements of the second communication protocol.

In a further implementation form of the first aspect, the resource allocator may be configured to allocate a sub-channel of the guard band to a remote device in dependence on a power requirement associated with that device. The resource allocator is therefore able to tailor resource allocations to the specific power requirements of different devices.

In a further implementation form of the first aspect, each sub-channel is associated with a respective transmit power reduction. The resource allocator may be configured to prioritise the allocation of sub-channels that are associated with relatively high permitted transmit power reductions to remote devices that have relatively low power requirements. This improves system performance by increasing the likelihood that remote device transmissions will successfully reach the network for devices that have diverse power requirements. In a further implementation form of the first aspect, the resource allocator may be configured to prioritise the allocation of sub-channels of the guard band that are located relatively close to an edge of the resource block in accordance with the second communication protocol to remote devices having relatively low power requirements. In many examples the resource block will be a channel, so that the resource allocator prioritises the allocation of sub-channels that are located close to the channel edge. In this way, the resource controller can adapt its allocations to common spectral masks that place greater power restrictions on frequencies that are close to a boundary of the resource block.

In a further implementation form of the first aspect, the power controller may be configured to determine a power requirement associated with a remote device in dependence on one or more of: a location associated with that device, a cell associated with that device, a channel quality associated with that device, a power report received from that device, a coverage class associated with the device, and a path loss estimation associated with that device. The power controller is thus able to consider a number of different factors that influence how a transmit power reduction might affect the success of an uplink transmission by the remote device. According to a second aspect, a method is provided that comprises allocating radio resources to a remote device for a transmission in accordance with a first communication protocol. Those radio resources are comprised in a guard band of a resource block in accordance with a second communication protocol. The method also comprises determining a transmit power reduction that is permitted to the remote device for making the transmission using the allocated radio resources, so as to enable the remote device to make the transmission in accordance with the first communication protocol while meeting spectral emission requirements of the second communication protocol.

The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

Figure 1 shows an example of a network device according to an embodiment of the invention;

Figure 2 shows an example of a method according to an embodiment of the invention;

Figure 3 shows the spectrum emission masks of an NB-loT system and an LTE system; and Figure 4 shows a close-up of the masks in Figure 3.

An example of a network device is shown generally at 101 in Figure 1. The network device comprises a resource allocator 102 and a power controller 103. It may also include an optional communication unit 103. The network device could be implemented by any equipment that forms part of a core network and/or a radio access network for managing and controlling the operations of a communication network. The network device could, for example, be implemented by a server or similar. The network device could be configured to perform any role in the network. For example, the network device may be a base station. Resource allocator 102 is configured to allocate radio resources to remote devices. Those remote devices could be any type of device with the ability to communicate wirelessly. The remote devices may be embedded in larger equipment that primarily fulfils a purpose other than wireless communication. For example, the remote device could be a communication chip or similar embedded within a domestic appliance and which serves to connect that appliance to an loT network. The remote device is geographically separate from a core network, whose services it uses to wirelessly exchange data with other pieces of equipment (including other remote devices, servers etc.). The radio resources that the resource allocator 102 allocates to a remote device could be defined by frequency, time and/or transmission codes. The remote device is preferably able to communicate via the wireless network using the first communication protocol. The resource allocator is configured to allocate resources to transmissions in accordance with the first communication protocol. Those resources are comprised in a guard band of a resource block in accordance with a second communication protocol.

The resource block in accordance with the second communication protocol represents a unit of radio resources defined by that protocol. Typically, the resource block will have a frequency dimension and/or a time dimension. For example, the resource block may be a time slot. Thus, for a communication protocol that allocates radio resources using some form of time division multiplexing (TDM) (such as GSM), a resource block could be a single time slot. The resource block may be a channel that is defined by upper and lower boundary frequencies. Thus, for a communication protocol that allocates radio resources using some form of frequency division multiplexing (FDM), a resource block could be a frequency sub-band. The guard band represents a region of radio resources at an upper or lower boundary of the resource block. It provides a gap between one transmission and the next. For example, the guard band may be a gap between a "transmission" bandwidth and a "channel" bandwidth that are defined by the second communication protocol. The result is a narrow, unused frequency band that separates neighbouring transmissions. This region of radio resources is not available for allocation in accordance with the second communication protocol. Its purpose is usually to protect transmissions in one resource block from interference from transmissions in the neighbouring resource block.

In one specific example, the second communication protocol may be LTE. Current LTE standards use the term "resource block" to refer specifically to a frequency-time block that is 180kHz wide in the frequency domain and 0.5ms long in the time domain. An LTE channel contains 6 to 100 LTE resource blocks. For example, a 10MHz LTE channel contains 50 active LTE resource blocks, which occupy 50 x 180kHz = 9MHz. Since the channel bandwidth is 10MHz, this gives a 500kHz guard band at the upper and lower boundaries of the LTE channel. The term "resource block" is used more generally herein than its specific meaning in LTE and refers to any unit of radio resources, as explained above. Hence, the term "resource block" could refer to an LTE resource block or to an LTE channel. In examples below, the term "resource block" is used to refer to an LTE channel that comprises multiple LTE resource blocks and the associated guard bands. Power controller 103 is configured to determine a permitted transmit power reduction. This is a power reduction that is valid when the remote device uses the radio resources that have been allocated to it by the resource allocator. In other words, it represents an amount by which the remote device is allowed to reduce its transmit power when transmitting its data over the allocated radio resources. The power controller may determine the permitted power reduction by way of calculation or via a look-up table. The appropriate calculation might be defined by the first communication protocol. Similarly, the look-up table might be defined by a telecommunications standard, e.g. a standard in accordance with the first or second communication protocol. The communication unit 104 is suitably configured to transmit an indication of a permitted power reduction to the remote device that the power reduction is intended for.

The permitted power reduction suitably gives the remote device permission to reduce its transmit power below a transmit power that the remote device would otherwise be expected to use (as explained in more detail below). The objective of the permitted power reduction is two-fold: (i) to give the remote device permission to reduce its transmit power below the expected amount; and (ii) to place an upper bound on the permitted power reduction. This permitted transmit power reduction is optional: the remote device can choose to use it or not. The remote device might choose to use some of the transmit power reduction but not all of it. The transmit power reduction enables the remote device to make its transmission and still meet the spectral emission requirements of the second communication protocol. The transmission by the remote device can additionally meet the spectral emission requirements of the first communication protocol. The approach described above may enable more guard band spectrum to be made available to the first communication protocol. This is achieved without imposing complicated optimisation burdens on the remote device (for example, it is difficult for a remote device to optimise its power amplifier to achieve better spectral emissions if it is also required to maintain its efficiency). It also enables more guard band spectrum to be made available without increasing the complexity of the remote device, since the remote device is just informed by the network device about the permitted power reduction.

The structures shown in Figure 1 (and all the block apparatus diagrams included herein) are intended to correspond to a number of functional blocks. This is for illustrative purposes only. Figure 1 is not intended to define a strict division between different parts of hardware on a chip or between different programs, procedures or functions in software. In some embodiments, some or all of the techniques described herein may be performed wholly or partly by a processor acting under software control. For example, the power controller and resource allocator might suitably be implemented by a processor acting under software control. In some embodiments, some or all of the techniques described herein are likely to be performed wholly or partly in hardware. For example, the communication unit is likely to incorporate hardware aspects, particularly as part of a transmit or receive chain.

In some implementations, the expected transmit power may be set by the first communication protocol. In other examples, the expected transmit power may be set by the network. The expected transmit power could also be determined by the remote device, perhaps using some parameters set by the network or the protocol. The expected transmit power could be fixed or variable. For example, the expected transmit power might be an absolute value that is set by the protocol, it could be completely determined by circumstance, or it could be selected from a range of predetermined values. In a preferred implementation, the expected transmit power is determined by the remote device within certain parameters that are set by the network. For example, in the NarrowBand Internet of Things (NB loT) protocol, an open-loop power control mechanism is implemented. The network device informs the remote device about an expected receive power. It is then the responsibility of the remote device to decide on an appropriate transmit power. For example, the remote device could estimate the appropriate transmit power by estimating the path loss between it and the base station. This gives:

T_x = mm{P_CMAX, Rx expected + path loss] Where T_x is the appropriate transmit power, R_{x exvec}ted is the expected receive power provided by the network and P_CMAX is the network configured transmit power. T_X is based on the expected receive power and is calculated in accordance with a mechanism set out by the first communication protocol (NB loT in this example). It is therefore a transmit power that the remote device is "expected" to use.

The network device may also inform the remote device about any additional factors that affect what transmit power it is appropriate for the device to use. For example, transmissions by the remote device should not breach any applicable spectral mask. The remote device may be already aware of the general spectral mask requirements but for implementations where the spectral mask requirements are more stringent than the general case - such as guard band deployment - the network device may inform the remote device about the extra mask requirements in addition to any permitted transmit power reduction. Extra mask requirements will affect the expected transmit power of the remote device. While the permitted transmit power reduction is optional - and the remote device may opt to use some or none of the reduction available - the remote device should ensure that its emissions will be within any spectral mask requirements it knows about. The remote device may thus determine a range of acceptable transmit powers and select its transmit power from within the acceptable range. The range may be initially capped at the upper end by the expected receive power and path loss. This initial limit may be superseded by any spectral mask requirements and/or power limitations inherent to the device if those limitations are lower than that determined via the expected receive power calculation. The range may be capped at the lower end by a combination of an upper end cap and the permitted power reduction.

In setting a permitted transmit power reduction, the network device is essentially accepting a potentially reduced receive power as a trade-off for increasing the amount of bandwidth that is available to allocate to transmissions in accordance with the first communications protocol.

The resource allocator 102 may be configured to identify one or more valid frequency locations for a resource block for the first communication protocol in dependence on the spectral emission requirements of both the first and second communication protocols. This can be explained with reference to the spectral emission masks shown in Figures 3 and 4.

Figures 3 and 4 show examples of the spectral masks for two different protocols. The spectral masks limit out-of-channel emissions. The figures represent the same spectral emission masks, but Figure 4 shows a "close-up" of the relevant section of Figure 3. Figures 3 and 4 relate to an implementation in which the first communication protocol is NB-loT and the second communication protocol is LTE. The figures illustrate the respective spectral masks of those two protocols. The NB-loT network is configured to use unused resource blocks in the LTE guard band. In Figure 3, line 301 represents the spectral mask of a 10 MHz LTE channel 303. The collection of lines denoted 302 represent the spectral masks of NB-loT in the right-hand guard band of the LTE channel. The NB-loT spectral masks are shown at four different frequency offsets relative to the configured LTE resource blocksl. There are four valid frequency locations in the guard band for an NB-loT network according to current NB-loT standards. These give an edge-to-edge distance between the NB-loT resource block and the outer LTE resource block edge of 0, 105, 210 or 300 KHz. Here the outer LTE resource block edges are provided by the first and the last configured LTE resource blocks. So, one resource block edge is provided by the lower frequency limit of the first configured 180kHz LTE resource block in the channel and the other resource block edge is provided by the upper frequency limit of the last configured 180kHz LTE frequency block in the channel. The spectral emission masks at these four different frequency locations are represented by lines 402 to 405 respectively in Figure 4. Without a permitted transmit power reduction, only the first of these frequency locations is able to meet the LTE spectral emission mask. This can be seen in Figure 4, in which line 402 is the only one of the NB-loT spectral emission masks not to impinge on (and exceed) the LTE spectral emission mask 401. By permitting the remote device to reduce its transmit power, the network device can make more frequency locations available for use by the NB-loT protocol (or any other communication protocol, depending on the implementation).

Another factor that the power controller 103 may consider when allowing a transmit power reduction is which radio resource it is allocating. In many implementations, the guard band of the resource block according to the second communication protocol will be divided into sections by resource allocator 102. Each section essentially forms its own resource block, but these resource blocks are now in accordance with the first communication protocol rather than the second. The resource allocator may then allocate each section to a different remote device. For example, the resource allocator may divide the guard band into a plurality of time slots. The resource allocator might also divide the guard band into a plurality of frequency sub- channels. The power controller may then associate each sub-channel with its own respective transmit power reduction.

The power controller 103 may determine an appropriate power reduction for a given subchannel in dependence on the spectral emission requirements of the second communication protocol. In this way, the power controller can free-up more of the guard band for allocating to communications using the first communication protocol. The power controller may also take the relative distance between each sub-channel and the guard band into account when deciding the permitted power reduction. The spectral emission requirements of the spectral mask are usually increasingly restrictive the further away a frequency is to the centre frequency of the second protocol transmission. For example, an LTE spectral mask is most stringent at the LTE channel edges, since the purpose of the spectral mask is to reduce interference to adjacent resource blocks by limiting excessive radiation outside of the resource block. Thus, the power controller may be configured to associate each sub-channel with a respective permitted transmit power reduction in dependence on a relative position of that sub- channel within the guard band relative to the resource block in accordance with the second communication protocol. The table below shows examples of appropriate transmit power reductions that may be allowed for particular sub-channels. These values are applicable to an NB-loT network deployed in the guard band of a 10 MHz LTE channel. The table shows that the transmit power reductions are varied according to the sub-channel, with sub-channels that are located farthest from the configured LTE resource blocks being associated with the largest permitted power reductions.

Table 1 : Examples of sub-carrier dependent permitted power reductions for an NB-loT system deployed in the guard band of a 10MHz LTE channel, where the term A-MPR refers to the permitted transmit power reduction. As the table shows, to enable the use case of Af = ±105kHz, the remote devices have to fulfil a combined spectral emission mask, which is more stringent than the general NB-loT spectral emission mask. Otherwise, the regulator and/or adjacent operator will object. Hence, the network should signal this extra requirement to all remote devices. By doing this, the network meets its obligations under the regulations that govern use of the first and second protocols (LTE and NB-loT in this example). Furthermore, by allowing a transmit power reduction, the network device aids remote devices to meet the extra spectral emission requirements with relatively low complexity and/or low power consumption.

The resource allocator may advantageously combine the device-by-device power demands and sub-channel specific power reductions to intelligently select appropriate sub-channel allocations for individual devices. In other words, the resource allocator may allocate a subchannel to a remote device in dependence on a power requirement associated with that device. In this way, the resource allocator considers whether a remote device requires maximum transmit power when it allocates radio resources to that device. For example, some devices may not be suitable candidates for a sub-channel associated with a reduced transmit power because a high propagation loss between the remote device and the base station mean that reduced power transmissions by the device are unlikely to be successfully received by the base station. Therefore, to optimise system performance, the resource allocator is preferably configured to prioritise the allocation of sub-channels that are associated with relatively high permitted transmit power reductions to remote devices having relatively low power requirements. For most guard band spectral emission masks, the practical effect of this is that the resource allocator prioritises the allocation of sub-channels that are located relatively close to an edge of the second protocol resource block to remote devices having relatively low power requirements.

Sub-channels can be considered relatively close to the edge of the second protocol resource block if they are closer to the relevant edge of that resource block than other sub-channels in the same guard band. The sub-channels in a guard band may be ranked in terms of their respective position relative to the relevant resource block edge. For example, the sub- channels may be consecutively numbered in order of increasing frequency. The remote devices can be similarly ranked in terms of their power requirements, and the sub-channels allocated by matching the remote devices with the highest power requirements with the sub- channels that are located farthest from the relevant edge of the resource block. Note that in this example, sub-channels that are located in the left-hand guard band and that have low numbers may be allocated to remote devices having the lowest power requirements and vice versa for the right-hand guard band (see e.g. Table 1 above).

The relevant edge of the resource block (for considering how close a particular sub-channel is to the edge of the resource block) is that resource block's appropriate outer limit. This is the outer limit which marks the boundary between the guard band that contains the sub-channels in question and the neighbouring resource block. For example, for the 10MHz LTE channel shown in Figure 3 , the resource block edge is at -5MHz for frequency sub-channels in the left-hand guard band and 5MHz for frequency sub-channels in the right-hand guard band.

A similar approach could be taken if the second protocol guard band represents a gap or spacing in time between one resource block and the next, with sub-channels that are closest in time to the resource block being allocated to remote devices having relatively low power requirements.

Although any remote device can easily meet spectral emission requirements by reducing its transmit power, this can come at the expense of reduced coverage and/or data rate. The aim is to identify devices that can best cope with a reduced transmit power to maximise the number of successful uplink transmissions. In this way, the resource allocator can predict remote device power demand and optimally allocate the sub-channels accordingly. The resource allocator can take a number of factors into account when deciding on an appropriate power back-off/sub-channel allocation for a given device. These include where the device is located, e.g. which cell it is in, the channel quality that the device is experiencing, any information that the network device has on the device's estimated path loss and a coverage class associated with the device. The network device may also consider any power reports received from the device. One example is the power headroom report. As mentioned above, if the resource allocator allocates a remote device a sub-channel that is associated with a permitted transmit power reduction, the network device preferably communicates an indication of that permitted transmit power reduction to the remote device. For example, the message may include an index that the remote device uses to access a pre- stored look up table and identify the permitted power reduction associated with the allocated sub-channel. In some implementations, this communication makes use of an existing message structure in the first communication protocol. For example, if the first communication protocol is an NB-loT protocol, the following steps may be used to assist NB-loT UEs to meet additional spectral mask requirements:

The NB-loT network device can signal additional spectrum emission requirements to the NB-loT UEs by broadcasting new network signalling "NS_XX" messages in system information block type-2 (SIB2). "XX" is a number that is suitably defined in a standard.

It represents an index value to look up tables that the remote devices either store or have access to. The index could convey two types of information: (i) that an additional/more stringent spectral emission mask is applicable; and (ii) the permitted power reduction; and

· After receiving a "NS_XX" message, the UE should ensure its spectrum emission meets both the NB-loT spectral mask and the corresponding LTE spectral mask. It may achieve this by, for example, reducing its max transmit power, but by no more than the amount as indicated in the message. The techniques described herein thus allow back-off of the remote device transmit power according to one protocol in order to meet spectral mask requirements of another protocol. The amount of power back-off can vary on a device-by-device basis, depending on the uplink sub-carrier allocation within the guard band of the LTE system. The base station can intelligently select appropriate uplink sub-channel allocations, and therefore the permitted transmit power back-off, in dependence on whether a remote device requires the maximum transmit power. This enables more of the guard band spectrum to be used for first communication protocol transmissions without imposing greater complexity or cost on the remote device. It also minimises system performance loss due to transmit power reduction. In this way, the power controller can give the remote device the flexibility it needs to use its allocated resources and still meet the spectral emission requirements of both protocols.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1 . A network device comprising:

a resource allocator that is configured to allocate radio resources to a remote device for a transmission in accordance with a first communication protocol, said radio resources being comprised in a guard band of a resource block in accordance with a second communication protocol; and

a power controller configured to determine a transmit power reduction that is permitted to the remote device for making the transmission using the allocated radio resources, so as to enable the remote device to make the transmission in accordance with the first communication protocol while meeting spectral emission requirements of the second communication protocol.

2. A network device as claimed in claim 1 , wherein the resource allocator is configured to identify one or more frequency locations for a resource block in accordance with the first communication protocol in dependence on spectral emission requirements of the second communication protocol.

3. A network device as claimed in any preceding claim, wherein the resource allocator is configured to treat the guard band as comprising a series of sub-channels, and the power controller is configured to associate each frequency sub-channel of the guard band with a respective permitted transmit power reduction.

4. A network device as claimed in claim 3, wherein the power controller is configured to associate each sub-channel of the guard band with a respective permitted transmit power reduction that is dependent on the spectral emission requirements of the second communication protocol.

5. A network device as claimed in claim 3 or 4, wherein the power controller is configured to associate each sub-channel of the guard band with a respective permitted transmit power reduction in dependence on a relative position of that sub-channel within the guard band relative to the resource block in accordance with the second communication protocol.

6. A network device as claimed in any of claims 3 to 5, wherein the resource allocator is configured to allocate radio resources to a remote device by allocating that remote device a particular sub-channel of the guard band.

7. A network device as claimed in any of claims 3 to 6, wherein the network device comprises a communication unit that is configured to, if the resource allocator has allocated a sub-channel that is associated with a permitted transmit power reduction to a remote device, communicate an indication of that permitted transmit power reduction to the remote device.

8. A network device as claimed in any of claims 3 to 7, wherein the resource allocator is configured to allocate a sub-channel of the guard band to a remote device in dependence on a power requirement associated with that device.

9. A network device as claimed in any of claims 3 to 8, wherein each sub-channel is associated with a respective transmit power reduction and the resource allocator is configured to prioritise the allocation of sub-channels that are associated with relatively high permitted transmit power reductions to remote devices that have relatively low power requirements.

10. A network device as claimed in any of claims 3 to 9, wherein the resource allocator is configured to prioritise the allocation of sub-channels of the guard band that are located relatively close to an edge of the resource block in accordance with the second communication protocol to remote devices having relatively low power requirements.

1 1 . A network device as claimed in any preceding claim, wherein the power controller is configured to determine a power requirement associated with a remote device in dependence on one or more of: a location associated with that device, a cell associated with that device, a channel quality associated with that device, a power report received from that device, a coverage class associated with the device, and a path loss estimation associated with that device.

12. A method comprising:

allocating radio resources to a remote device for a transmission in accordance with a first communication protocol, said radio resources being comprised in a guard band of a resource block in accordance with a second communication protocol; and

determining a transmit power reduction that is permitted to the remote device for making the transmission using the allocated radio resources, so as to enable the remote device to make the transmission in accordance with the first communication protocol while meeting spectral emission requirements of the second communication protocol.