SUPPORTING FLEXIBLE BANDWIDTH OPERATION IN LTE

Abstract

The invention provides a method for a user equipment, UE, operating in an orthogonal frequency division multiplexed, OFDM, communication system to signal that it is capable of operating at a radio bandwidth other than one predefined according to an OFDM communication standard for the system, the method comprising: the UE sending a capability information message to a base station, the message including an information field which indicates whether the UE supports flexible bandwidth operation or not, wherein the flexible bandwidth operation is at least one of an increase and a decrease in a number of subcarriers to be used by the UE within a frequency band being used concurrently for communication with the base station by other UEs over the bandwidth defined according to the OFDM communication standard.

Claims

1. A method for a user equipment, UE, operating in an orthogonal frequency division multiplexed, OFDM, communication system to signal that it is capable of operating at a radio bandwidth other than one predefined according to an OFDM communication standard for the system, the method comprising: the UE sending a capability information message to a base station, the message including an information field which indicates whether the UE supports flexible bandwidth operation or not, wherein the flexible bandwidth operation is at least one of an increase and a decrease in a number of subcarriers to be used by the UE within a frequency band being used concurrently for communication with the base station by other UEs over a radio bandwidth pre-defined according to the OFDM communication standard.

2. The method according to claim 1, wherein the message includes an information field which indicates whether the UE is able to support at least one of bandwidth compression and bandwidth expansion.

3. The method according to claim 2, wherein the message includes an information field indicating a step size by which the UE is capable of changing the bandwidth.

4. The method according to claim 1, wherein the message includes an information field which indicates whether the UE is capable of changing the bandwidth in a symmetric or asymmetric manner.

5. The method according to claim 4, wherein the message includes an information field which indicates whether the UE is able to shift a DC carrier of a respective frequency band.

6. The method according to claim 1, wherein the message includes a set of flexible bandwidth parameters for each frequency band for which the UE is capable of operating with flexible bandwidth.

7. The method according to claim 1, wherein the OFDM communication standard is a long term evolution, LTE, communication standard.

8. The method according to claim 1, wherein the flexible bandwidth operation is at least one of an increase and a decrease in a number of resource blocks.

9. The method according to claim 1, wherein the capability information message is sent in response to a request from the base station.

10. A user equipment, UE, adapted to transmit an information message to a base station, the information message indicating a capability of the UE to operate in a flexible bandwidth mode when operating in an orthogonal frequency division multiplexed, OFDM, communication system at a bandwidth other than a radio bandwidth pre-defined according to an OFDM communication standard, wherein the flexible bandwidth mode is an operating mode implementing at least one of an increase and a decrease in a number of subcarriers to be used by the UE within a frequency band being used concurrently for communication with the base station by other UEs over the radio bandwidth pre-defined according to the OFDM communication standard.

11. Base station equipment capable of operating according to an orthogonal frequency division multiplexed, OFDM, communication standard, wherein the base station is capable of operating at a frequency band having a radio bandwidth other than a radio bandwidth pre-defined according to the OFDM communication standard and wherein the base station equipment is adapted to store information relating to a capability of connected user equipment, UE, devices to operate with a flexible bandwidth, wherein the flexible bandwidth operation is at least one of an increase and a decrease in a number of subcarriers to be used by the UEs within a frequency band being used concurrently for communication with the base station by other UEs over the radio bandwidth pre-defined according to the OFDM communication standard.

12. A mobile communication system operating according to an orthogonal frequency division multiplexed, OFDM, communication standard, wherein a connected user equipment, UE, device's capabilities pertaining to operation at a radio bandwidth other than one predefined according to the OFDM communication standard are at least partially taken into account for handover decisions.

Description

[0021] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0022] FIG. 1 is a schematic illustration of LTE operation using a flexible bandwidth;

[0023] FIG. 2 is a schematic representation of information exchange between EUTRAN and UE;

[0024] FIG. 3 is an example of an information element of a first embodiment of the invention;

[0025] FIG. 4 is an example of an information element of a second embodiment of the invention; and

[0026] FIG. 5 is an example of an information element of a third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] In the following new fields for inclusion into the UE's list of capabilities are described. In the scope of the present invention the so-called UE-SUTRA-Capability information element, IE, as described in section 6.3.6 of 3GPP TS 36.331 is of relevance. This IE is used to convey the E-UTRA UE Radio Access Capability Parameters (see TS 36.306), and the Feature Group Indicators for mandatory features (see Annexes B.1 and C.1 in TS 36.331) to the network. The UE-EUTRA-Capability IE may be transferred in E-UTRA or in another RAT.

[0028] The names and encoding variants of the novel fields and parameters discussed here shall be understood to serve merely as examples. There are many other options to get the information from the mobile device across the air to the base station. This invention is by no means restricted to the encoding examples disclosed.

[0029] Furthermore, the newly proposed parameters to be used by a UE to signal its Bandwidth Flexibility capabilities may be arranged in more than one way, for example they may be collated in a new or already existing hierarchical structure, or grouped together with other fields for instance in a list of mandatory features, optional features, conditionally mandatory features, or be assigned to a particular feature group. In the latter case only a Feature Group Indicator (FGI) would have to be signalled (as part of the UE-EUTRA-Capability IE) from the UE to the infrastructure side instead of a list of distinct parameters.

[0030] In the following, the new fields to be included in the UE-EUTRA-Capability IE are highlighted in bold letters and encircled with a box.

Embodiment 1

[0031] This embodiment reproduced in FIG. 3 represents the simplest embodiment of the present invention. The UE is enabled to signal general support for the Bandwidth Flexibility concept. The new field is labelled FlexibleBandwidthSupport and is a simple flag of category Boolean used to indicate whether a UE supports the Flexible Bandwidth concept or not.

Embodiment 2

[0032] This embodiment is reproduced in FIG. 4. In this example, a new field is specified FlexBandwidth which is used to specify a UE's flexible bandwidth characteristics. The field contains two new sub-fields, FlexType and Granularity. FlexType is a parameter used to indicate whether the UE is able to either expand or compress E-UTRA frequency bands, or both while granularity is a parameter used to inform the infrastructure side about the granularity supported by the UE. In FIG. 4, two different step sizes are defined: the value 1 RB indicates a step size of one resource block (which corresponds to 180 kHz); the value 5 RB indicates a step size of five resource blocks (which corresponds to 900 kHz). In the LTE resource lattice there are always 180 kHz per Resource Block regardless of the sub carrier spacing configuration, because 12 sub carriers are used in case of 15 kHz spacing and 24 sub carriers are used in case of 7.5 kHz spacing.

Embodiment 3

[0033] This embodiment is reproduced in FIG. 5 and is the most complex of the three. It offers maximum adaptability for the signalling of capabilities pertaining to the bandwidth flexibility concept. It allows for different flexibility per E-UTRA frequency band.

[0034] The embodiment provides the field FlexBwSupportList with up to max entries (one for each E-UTRA frequency band) used to specify a UE's flexible bandwidth capabilities. A further field FlexBwSupport comprises a set of flexible bandwidth parameters per E-UTRA frequency band. The field bandEUTRA may be used to specify the E-UTRA frequency band in question. The field Expansion is a parameter used to indicate whether the UE is able to expand the respective E-UTRA frequency band in order to form non-standard spectrum block sizes while the field Compression is a parameter used to indicate whether the UE is able to shrink the respective E-UTRA frequency band in order to form non-standard block sizes. Field Direction is a parameter used to indicate whether the UE is able to expand or compress the respective E-UTRA frequency band symmetrically or asymmetrically (and in the latter case at what end).

[0035] The field Granularity as previously is a parameter used to inform the infrastructure side about the granularity supported by the UE (step size) when an E-UTRA frequency band is expanded or compressed. The value SubCarrier indicates sub carrier level (i.e. the step size is 15 kHz (or 7 kHz depending on the configuration of sub carrier spacing)); the value ResourceBlock indicates resource block level (i.e. the step size is one Resource Block which corresponds to 180 kHz); the value 1 MHzBlock indicates units of 1 MHz; the value of 500 kHzBlock indicates units of 500 kHz; and so on.

[0036] The field DcCarrierOffset is a parameter used to indicate whether the UE is able to shift the DC Carrier of the respective E-UTRA frequency band (for example, to move the resource block alignment of the entire frequency band in question about half the bandwidth of one resource block (i.e. 6 or 12 sub carriers, depending on the configuration of sub carrier spacing, up or down). This may be necessary when the initial standardized frequency band comprises an even (odd) number of resource blocks and the target non-standardized frequency band comprises an odd (even) number of resource blocks.