GB2500254A

GB2500254A - Channel Quality Information (CQI) reporting

Info

Publication number: GB2500254A
Application number: GB1204672.8A
Authority: GB
Inventors: Mihai Horatiu Enescu; Tommi Tapani Koivisto; Karl Marko Juhani Lampinen
Original assignee: Renesas Mobile Corp
Current assignee: Renesas Electronics Corp
Priority date: 2012-03-16
Filing date: 2012-03-16
Publication date: 2013-09-18
Anticipated expiration: 2032-03-16
Also published as: GB201204672D0; GB2500254B

Abstract

Apparatus and method for: controlling 704 the measurement of a radio channel to obtain information on Signal to Interference and Noise Ratio (SINR) of a radio channel; calculating 708 a Channel Quality Index (or Channel Quality Information), CQI, on the basis of the information on Signal to Interference and Noise Ratio (SINR), the selection of the channel quality index table the index points to and the indexing method having been made utilising information on radio channel measurements controlled by the apparatus 706; and controlling 712, 714 the transmission of the channel quality index to the communication system. A User Equipment, UE, 116, Figure 1 may perform the SINR measurements and report the associated CQI to a nodeB, 106, Figure 1. The nodeB may indicate 708 to the UE the most appropriate indexing table or indexing method based on an initial radio channel measurement 704, 706, such as a Reference Signal Received Power, RSRP measurement for LTE or Received Signal Code Power on Common Pilot Indicator Channel, CPICH RSCP, or CPICH Ec/N0, Energy per chip to the Spectral Noise Density on Common Pilot Indicator Channel in WCDMA. As is typical the reported CQI information may allow the nodeB to determine the most appropriate Modulation and Coding Scheme, MCS, for the current channel conditions. A continuous subset of indices pointing a channel quality index table may be used. Different channel quality index tables may be used for real or complex valued modulation methods (Figure 6C). Performance differences between different indices of the channel quality index table may be non-uniform.

Description

INTELLECTUAL

PROPERTY OFFICE

Application No. GB1204672.8 RTM ^at6

The following terms are registered trademarks and should be read as such wherever they occur in this document:

UMTS

Java

Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk

1

Apparatus and Method for Communication

Technical Field

The exemplary and non-limiting embodiments of the invention relate generally 5 to wireless communication networks. Embodiments of the invention relate especially to determining channel quality index in wireless communication networks.

Background

Modern communication systems may support the use of more than one 10 modulation method. Example of modulation methods used in communication systems include Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM) and 64QAM to name a few. Continuous developments in research have brought up the possibility of using more and more complex modulation methods which offer greater data rates, for example. In addition, systems using real 15 valued modulations such as pulse amplitude modulations (PAM) are under study because they offer some degrees of freedom for advanced receivers relating to interference cancellation.

In general, the network side of communication systems instruct the mobile units of the system to use a specific modulation and coding scheme (MCS). To be 20 able to select the best suitable MCS for each mobile unit the system may request the mobile units to perform measurements of available radio channels and report the results in some convenient way. As new modulation methods are introduced the signalling related to the new methods should be realized with minimum changes to present solutions.

25

Summary

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical 30 elements of the invention or to delineate the scope of the invention. Its sole purpose is

2

to present some concepts of the invention in a simplified form as a prelude to a more detailed description that is presented later.

According to an aspect of the present invention, there is provided an apparatus in a communication system, comprising a processing system configured to: control 5 the measurement of a radio channel to obtain information on signal to interference and noise ratio (SINR) of a radio channel; calculate a channel quality index on the basis of the information on signal to interference and noise ratio, a selection of the channel quality index table the index points to and/or an indexing method having been made utilising information on radio channel measurements controlled by the apparatus; 10 control the transmission of the channel quality index to the communication system.

According to an aspect of the present invention, there is provided an apparatus in a communication system, comprising a processing system configured to: receive from a transceiver of the communication system radio channel measurements; select a channel quality index table and/or an indexing method to be used when 15 communicating with the transceiver by utilising the received radio channel measurements when making the selection; control the transmission of information on the selected table and/or indexing method to the transceiver.

According to an aspect of the present invention, there is provided an apparatus in a communication system, comprising means for controlling the measurement of a 20 radio channel to obtain information on signal to interference and noise ratio (SINR) of a radio channel; means for calculating a channel quality index on the basis of the information on signal to interference and noise ratio, the selection of a channel quality index table the index points to and/or an indexing method having been made utilising information on radio channel measurements controlled by the apparatus; and means 25 for controlling the transmission of the channel quality index to the communication system.

According to an aspect of the present invention, there is provided an apparatus in a communication system, comprising: means for receiving from a transceiver of the communication system radio channel measurements; means for selecting a channel 30 quality index table and/or an indexing method to be used when communicating with the transceiver by utilising the received radio channel measurements when making the

3

selection; and means for controlling the transmission of information on the selected table and indexing method to the transceiver.

According to another aspect of the present invention, there is provided a method in a communication system, comprising: controlling the measurement of a 5 radio channel to obtain information on signal to interference and noise ratio (SINR) of a radio channel; calculating a channel quality index on the basis of the information on signal to interference and noise ratio (SINR), the selection of a channel quality index table the index points to and/or an indexing method having been made utilising information on radio channel measurements controlled by the apparatus; controlling 10 the transmission of the channel quality index to the communication system.

According to another aspect of the present invention, there is provided a method in a communication system, comprising: receiving from a transceiver of the communication system radio channel measurements; selecting a channel quality index table and/or an indexing method to be used when communicating with the transceiver 15 by utilising the received information when making the selection; controlling the transmission of information on the selected table and indexing method to the transceiver.

Brief Description of the Drawings

20 Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 illustrates an example of a communication environment;

Figure 2 illustrates the Modulation Coding Scheme (MCS) limitations faced in a pico cell;

25 Figures 3 A and 3B are flowcharts illustrating embodiments of the invention;

Figures 4 and 5 illustrate examples of apparatuses applying embodiments of the invention;

Figures 6A, 6B and 6C illustrate embodiments of the invention; and Figures 7A and 7B are flowcharts illustrating embodiments of the invention.

30

4

Detailed Description

Embodiments are applicable to any base station, user equipment (UE), server, corresponding component, and/or to any communication system or any combination of different communication systems that support required functionality.

5 The protocols used, the specifications of communication systems, servers and user terminals, especially in wireless communication, develop rapidly. Such development may require extra changes to an embodiment. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, embodiments.

10 Many different radio protocols to be used in communications systems exist.

Some examples of different communication systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E-UTRAN), long term evolution (LTE, known also as E-UTRA), long term evolution advanced (LTE-A), Wireless Local Area Network (WLAN) based on IEEE 802.1 lstardard, 15 worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS) and systems using ultra-wideband (UWB) technology. IEEE refers to the Institute of Electrical and Electronics Engineers. LTE and LTE-A are developed by the Third Generation Partnership Project 3GPP.

Figure 1 illustrates a simplified view of a communication environment only 20 showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the systems also comprise other functions and structures. It should be appreciated that the functions, structures, elements and the 25 protocols used in or for communication are irrelevant to the actual invention. Therefore, they need not to be discussed in more detail here.

In the example of Figure 1, a radio system based on LTE/SAE (Long Term Evolution/System Architecture Evolution) network elements is shown. However, the embodiments described in these examples are not limited to the LTE/SAE radio 30 systems but can also be implemented in other corresponding radio systems.

5

The simplified example of a network of Figure 1 comprises a SAE Gateway 100 and an MME 102. The SAE Gateway 100 provides a connection to Internet 104. Figure 1 shows an eNodeB 106 serving a cell 108. In this example, the eNodeB 106 is connected to the SAE Gateway 100 and the MME 102.

5 In the example of Figure 1, user equipment UE 116 is camped on the eNodeB

106.

The eNodeBs (Enhanced node Bs) of a communication system may host the functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic Resource Allocation (scheduling). 10 The MME 102 (Mobility Management Entity) is responsible for the overall UE control in mobility, session/call and state management with assistance of the eNodeBs through which the UEs connect to the network. The SAE GW 100 is an entity configured to act as a gateway between the network and other parts of communication network such as the Internet for example. The SAE GW may be a combination of two 15 gateways, a serving gateway (S-GW) and a packet data network gateway (P-GW).

User equipment UE refers to a portable computing device. Such computing devices include wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: mobile phone, smartphone, personal digital assistant (PDA), tablet 20 computer, laptop computer.

In many communication systems, more than one modulation method is supported. In current LTE based systems, Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM) and 64QAM are supported, in both uplink and downlink.

25 Increased network density is a clear trend in both network deployments of the operators and in 3rd generation standardization, the main driver being the UE density increase and the need to provide better coverage and capacity. Increased network density may be performed through the addition of small cells in forms of pico/femto cells, hence an increase in interference is expected as well. Several ways may be 30 employed to deploy such small cells: on same or on different carrier frequencies, each of these offloading strategies handling the interference in a different way.

6

One method to use small cells is offloading UEs on small cells on same carrier frequency as macro deployment. This leads to increased interference conditions.

One possible way to suppress interference is the use of advanced receivers. Interference cancellation receivers utilising Interference Rejection Combining (IRC) 5 are currently studied in the field. An improvement to IRC receivers is based on real valued modulations which by exploiting information on the transmitted signal covariance in the I/Q domain lead to increased degrees of freedom in terms of interference cancellation. For example, current LTE specifications are supporting complex constellations (M-QAM), hence a UE equipped with 2 Rx antennas can 10 efficiently suppress one inter-cell rank 1 interferer provided that the desired transmission is rank 1 as well. A real valued modulation transmission would enable increasing the degrees of freedom in the receiver as the intended transmission would occupy one dimension out of four available. Such technique could be even more appealing in machine-type communication (MTC) devices where only one receiver 15 chain is envisioned to be utilized in order to decrease UE costs. With one receiver antenna, real value modulation can enable rank 1 desired signal reception and rank 1 inter-cell interference cancellation.

Another possible way to suppress interference is the offloading to a pico cell on an adjacent frequency carrier with the macro cell, hence in easier interference 20 conditions. Figure 2 illustrates the Modulation Coding Scheme (MCS) limitations faced in the pico cell on adjacent frequency. The figure shows the cumulative probability of UE being in a given MCS class for pico cell 200 and macro cell 202. It can be seen that roughly 40% of the UEs connected to in this pico cell are utilizing the highest MCS class. This is an obvious limiting factor in terms of overall system 25 performance, and it becomes desirable to consider introducing higher-order modulations to overcome the MCS limitations. In case of LTE, this would mean introducing 256QAM modulation.

On IEEE side, IEEE 802.1 lac is already being developed and will be extending the modulation support towards 256QAM over 64QAM supported by 30 802.1 In. Thus, it is likely that 256QAM may be introduced also into LTE downlink in future releases of the specifications.

7

In LTE, introducing real valued and higher-order modulations would mean changes to some aspects of the LTE specifications.

The eNodeB's are configured to indicate the MCS to be used in a downlink grant message sent to UE. Adding together the existing modulations, the additional 5 real valued modulations and higher order complex modulation, it results into a quite high number of MCS classes, which might require more bits to be added to the MCS indication in the downlink control information (DCI) formats used for downlink grants. However, since the DCI formats are modified essentially in every new release of the LTE specifications, and since the overhead increase would be only one or two 10 bits, extending the MCS indication to cover new modulation schemes does not seem to be a very big problem.

Another aspect requiring modifications is the channel quality indication (CQI). For example, when UE report of channel quality indication (CQI) the CQI report should also include states for indicating that 256QAM can be sustained, along with a 15 suitable coding rate.

In LTE, UEs may be requested by the eNodeB to measure the quality of radio channels and report the measurement results back to the eNodeB. The reporting is realised using a Channel Quality Index CQI which points to a CQI mapping table known to both the UE and the eNodeB.

20 However, changing the CQI reports is a problematic issue. Currently LTE

supports both periodic PUCCH-based CQI reports and aperiodic PUSCH-based CQI reports. PUCCH is Physical Uplink Control Channel and PUSCH is Physical Uplink Shared Channel.

Some of the current aperiodic PUSCH-based feedback modes require the UE 25 to report CQI separately for each sub band of N Physical Resource Blocks (PRB) where N depends on bandwidth. Hence in case of sub band CQI reporting, the overhead increase would be multiplied by the number of sub bands. Furthermore in case of MIMO transmission the UE may need to report CQI separately for two code words which would mean that that overhead might increase even further. Finally, LTE 30 supports also carrier aggregation in which case one aperiodic report may contain CQI

8

for multiple carriers. Obviously in such case the overhead increase will be quite significant.

On the other hand, periodic PUCCH reports have typically been able to carry only 11 bits of payload. When supporting MIMO transmissions precoding matrix 5 indicator (PMI) as well as CQIs for possibly two code words need to be included within the 11 bits. Currently the reports use all 11 bits in case of two code words, namely 4 bits for the PMI, 4 bits for the first code word CQI and 3 bits for the second code word CQI. It is obvious that the CQI overhead cannot be increased further.

In an embodiment of the invention, the UE is configured to utilise a 10 predetermined type of CQI reporting and MCS indication which type is selected utilizing information on the radio channel measurements performed by the UE and reported to the communication system. In an embodiment, the measurements are RSRP (Reference Signal Received Power) in LTE or CPICH RSCP (Received Signal Code Power on Common Pilot Indicator Channel) or CPICH Ec/NO (Energy per chip 15 to the Spectral Noise Density on Common Pilot Indicator Channel) in WCDMA. This includes a case where UE is configured into an enhanced interference suppression mode based on measurement reports, i.e. a mode where the UE will be scheduled with real-valued modulations. Also this includes a case where the UE is configured into a high throughput mode utilizing 256QAM, based on measurement reports. 20 Furthermore, this includes cases where a range or subset of CQIs to be reported is selected based on measurement reports.

In an embodiment, the communication system may select channel quality index table and the indexing method by the UE used to access the table on the basis of the channel measurements reported by the UE.

25 In an embodiment, there may be one common CQI table which is used for both for real and complex modulation methods, including higher order MCSs. In an embodiment, the UE is configured to utilise a continuous subset of indices pointing to the channel quality index table. The subset may be selected from a predetermined number of given subsets on the basis of the measurements reported by the UE. The 30 subset may be a predetermined length of indices wherein the index being in the middle of the subset corresponds to the measured radio channel estimate.

9

In an embodiment, separate CQI tables corresponding to real and complex MCS classes are used. The specific CQI table can be utilized based on indication from eNodeB. In an embodiment, the eNodeB selects the CQI table to be utilised based on measurements reported by the UE.

5 Figure 3A is a flowchart illustrating an embodiment of the invention. The process starts at step 300.

In step 302, user equipment is configured to measure a radio channel to obtain information on signal to interference and noise ratio (SINR) of a radio channel.

In step 304, user equipment is configured to calculate a channel quality index 10 on the basis of the information on SINR , the selection of the channel quality index table the index points to and the indexing method utilising information on radio channel measurements made by the user equipment.

In step 306, user equipment is configured to transmit the channel quality index to the communication system.

15 The process ends in step 308.

Figure 4 illustrates an embodiment. The figure illustrates a simplified example of a device in which embodiments of the invention may be applied. In some embodiments, the device may be user equipment UE or a respective device communicating with a base station or an eNodeB of a communications system. 20 It should be understood that the apparatus is depicted herein as an example illustrating some embodiments. It is apparent to a person skilled in the art that the device may also comprise other functions and/or structures and not all described functions and structures are required. Although the device has been depicted as one entity, different modules and memory may be implemented in one or more physical or 25 logical entities.

The device of the example includes a control circuitry or a processing circuit 400 configured to control at least part of the operation of the device.

The device may comprise a memory 402 for storing data. Furthermore the memory may store software 404 executable by the control circuitry 400. The memory 30 may be integrated in the control circuitry.

10

The device comprises a transceiver 406. The transceiver is operationally connected to the control circuitry 400. It may be connected to an antenna arrangement (not shown).

The software 404 may comprise a computer program comprising program code means adapted to cause the control circuitry 400 of the device to control a transceiver 406.

The device may further comprise user interface 410 operationally connected to the control circuitry 400. The user interface may comprise a display which may be touch sensitive, a keyboard or keypad, a microphone and a speaker, for example.

The control circuitry 400 may be configured to control the calculation of a channel quality index on the basis of the SINR of radio channel, where the selection of the channel quality index table the index points to and the indexing method have been utilising information on radio channel measurements made by the apparatus.

In an embodiment, the control circuit is configured to receive from the communication system information on the table the channel quality index points to and the indexing method. Information related to the channel quality index table and the indexing method may be stored in the memory 402.

Furthermore, the control circuitry 400 may be configured to control the transmission of the channel quality index to the communication system.

Figure 3B is a flowchart illustrating an embodiment of the invention. The process starts at step 310.

In step 312, an eNodeB is configured to receive from a transceiver of the communication system radio channel measurements information. The transceiver may be UE of the system connected to the eNodeB.

In step 314, eNodeB is configured to select a channel quality index table and/or the indexing method to be used when communicating with the transceiver and utilising the received radio channel measurement when making the selection. From the radio channel estimate information received from the transceiver the eNodeB obtains information on the MCS which may be used on the radio channels with good enough quality.

11

In step 316, the eNodeB is configured to transmit information on the selected table and indexing method to the transceiver.

The process ends in step 318.

Figure 5 illustrates an embodiment. The figure illustrates a simplified example 5 of a device in which embodiments of the invention may be applied. In some embodiments, the device may be an eNodeB or a base station or a respective device communicating with mobile units of a communications system.

It should be understood that the device is depicted herein as an example illustrating some embodiments. It is apparent to a person skilled in the art that the 10 device may also comprise other functions and/or structures and not all described functions and structures are required. Although the device has been depicted as one entity, different modules and memory may be implemented in one or more physical or logical entities.

The device of the example includes a control circuitry or a processing circuit 15 500 configured to control at least part of the operation of the device.

The device may comprise a memory 502 for storing data. Furthermore the memory may store software 504 executable by the control circuitry or the processing circuit 500. The memory may be integrated in the control circuitry.

The device comprises a transceiver 506. The transceiver is operationally 20 connected to the control circuitry 500. It may be connected to an antenna arrangement (not shown).

The software 504 may comprise a computer program comprising program code means adapted to cause the control circuitry 500 of the device to control a transceiver 506 to communicate with and control user equipment. 25 The device may further comprise interface circuitry 508 configured to connect the device to other devices and network elements of a communication system, for example to core. This applies especially if the device is an eNodeB or a base station or respective network element. The interface may provide a wired or wireless connection to the communication network. The device may be in connection with core network 30 elements, eNodeB's, Home NodeB's and with other respective devices of communication systems.

12

The device may further comprise user interface 510 operationally connected to the control circuitry 500. The user interface may comprise a display, a keyboard or keypad, a microphone and a speaker, for example.

In an embodiment, the control circuitry 500 is configured to control the 5 transceiver 506 to receive from a transceiver of the communication system radio channel measurement information. The control circuitry may be configured to select a channel quality index table and/or the indexing method to be used when communicating with the transceiver and utilising the received radio channel estimate information when making the selection. The circuitry 500 may be further configured 10 to control the transceiver 506 to transmit information on the selected table and indexing method to the transceiver. The memory 502 may be configured to store information on more than one channel quality index tables and indexing methods.

The current LTE CQI mapping table is shown in Table 1. In the mapping table, different index values correspond to different coding and modulation 15 combinations and the modulation methods used include Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), and 64QAM.

The UE is configured to determine SINR in a given radio channel and select a suitable CQI from the table and report it to the eNodeB.

It is known that the SINR measurement accuracy varies depending on the 20 channel conditions. At low SINR situations the measurement accuracy is lower compared to high SINR conditions. However, the mapping table has been designed such that the differences between the SINR levels required for consecutive CQI indices are roughly 2 dB. At low SINR range, this seems even too accurate quantization considering the estimation accuracy.

25

13

CQI

modulation code rate x efficiency index

1024

0

out of range

1

QPSK

78

0.1523

2

QPSK

120

0.2344

3

QPSK

193

0.3770

4

QPSK

308

0.6016

5

QPSK

449

0.8770

6

QPSK

602

1.1758

7

16QAM

378

1.4766

8

16QAM

490

1.9141

9

16QAM

616

2.4063

10

64QAM

466

2.7305

11

64QAM

567

3.3223

12

64QAM

666

3.9023

13

64QAM

772

4.5234

14

64QAM

873

5.1152

15

64QAM

948

5.5547

Table 1

In an embodiment, there may be one common CQI table which is used for 5 both for real and complex modulation methods, including higher order MCSs. The number of indices in the CQI table is thus increased. Having only one table containing all MCS classes would inevitably imply the utilization of more than the existing 4-bit CQI report. This is not easily possible in LTE based systems due to the constraints on uplink coverage for PUCCH/PUSCH reports. In an embodiment, the proposed 10 solution is to divide the table of MCS classes into multiple overlapping (or non-overlapping) CQI intervals, each of the intervals being possible to be reported by the current 4-bit reports. Hence 16 different MCS classes may be contained per CQI interval, while the total number of MCS classes in the CQI table could be higher. In an embodiment, the number of intervals is three.

15 Figure 6A illustrates this embodiment. The figure shows the CQI table 600

which comprises CQI indices for both for real and complex modulation methods, including higher order MCSs such as 256QAM, for example. The number of indices in the table is N+l, where N may be over 16. The eNodeB may instruct the UE to use a continuous subset of indices pointing to a channel quality index table. In the

14

example of Figure 6A, there are three predetermined subsets 602, 604 and 606. The eNodeB may receive a radio channel measurement 608 from the UE. The measurement may be RSRP, for example. The eNodeB may select the subset on the basis of the measurement. In the example of Figure 6A, the first interval 602 is 5 selected because the measurement value is within the channel quality values covered by the first subset.

Figure 6B illustrates another embodiment. The figure shows the CQI table 600 which comprises CQI indices for both for real and complex modulation methods, including higher order MCSs such as 256QAM, for example. The number of indices 10 in the table is N+l, where N may be over 16. As previously described, the eNodeB has received the radio channel measurement made by the UE. In this embodiment, the eNodeB may instruct UE to use a sliding window CQI interval or subset 610, the location of the window being selected on the basis of the measurement. For example, a window or subset may be selected in such a manner that there are an equal number 15 of indices to the left and right of the RSRP measurement 608 of the UE.

Figure 6C illustrates another embodiment. In this embodiment, the real and complex MCS classes are arranged in two CQI tables 612, 614. The eNodeB is configured to select the table based on measurement reports, e.g. RSRP, and signal the table to use to the UE.

20 The utilization of real modulations could be for example confined in their own transmission mode which is selected based on RSRP. The efficiency of the real modulation is for low MCSs, hence it is expected that low modulation would be utilized. The existing 4-bit CQI reporting would be sufficient to characterise them, or in fact a potential reduction of number of bits is possible also.

25 If the complex MCS class table includes 256QAM or other high level MCS in addition to currently existing MCSs, 4 bits is not enough for transmitting all indices without modifying the table. In an embodiment, some of the existing states (i.e. indices in Table 1) in the 4-bit CQI report are replaced with new 256QAM states. The states to be replaced are chosen in such a manner that the effective quantization of the 30 CQI is non-uniform. For example, some of the states corresponding to low CQI values may be utilized.

15

In an embodiment, the table is modified by using indices 2, 4, 6 and 8 for 256QAM (with suitably chosen code rates) which would mean effectively that at the low SINR regime the quantization accuracy is 4 dB instead of 2 dB.

Alternatively, the whole table may be redesigned, facilitating introduction of 5 256QAM states within the 4 bits such that at low SINR regime the quantization step may be 3-5 dB while decreasing towards the high SINR, e.g. to 1-2 dB accuracy. In the latter case there would be two tables from which the eNodeB could select which table to use.

Table 2 illustrates an example of a modified LTE CQI mapping table which 10 supports QPSK, 16QAM, 64QAM and 256QAM. Here the indices 2, 4, 6 and 8 are used for 256QAM. The values for code rate and efficiency are not shown as they are system parameters and not relevant regarding the disclosed inventive concept. The efficiency of the 256QAM indices is greater than with the other indices and thus in the example the indices are not in the increasing efficiency order as is the case with Table 15 1. However, this is not any problem for the UE or eNodeB point of view as the mapping is common for both devices.

16

CQI

modulation code rate x efficiency index

1024

0

out of range

1

QPSK

78

0.1523

2

256QAM

###

#.####

3

QPSK

193

0.3770

4

256QAM

###

#.####

5

QPSK

449

0.8770

6

256QAM

###

#.####

7

16QAM

378

1.4766

8

256QAM

###

#.####

9

16QAM

616

2.4063

10

64QAM

466

2.7305

11

64QAM

567

3.3223

12

64QAM

666

3.9023

13

64QAM

772

4.5234

14

64QAM

873

5.1152

15

64QAM

948

5.5547

Table 2

5 Table 3 illustrates another example of a modified LTE CQI mapping table which supports QPSK, 16QAM, 64QAM and 256QAM. Here the indices 2, 4, 6 and 8 of the Table 1 are used for 256QAM. The indices are in the increasing order of efficiency and thus the indices with 256QAM are at the bottom of the table and the original indices have been shifted upwards. The values for code rate and efficiency 10 are not shown as they are system parameters and not relevant regarding the disclosed inventive concept.

17

CQI

modulation code rate x efficiency index

1024

0

out of range

1

QPSK

78

0.1523

2

QPSK

193

0.3770

3

QPSK

449

0.8770

4

16QAM

378

1.4766

5

16QAM

616

2.4063

6

64QAM

466

2.7305

7

64QAM

567

3.3223

8

64QAM

666

3.9023

9

64QAM

772

4.5234

10

64QAM

873

5.1152

11

64QAM

948

5.5547

12

256QAM

###

#.####

13

256QAM

###

#.####

14

256QAM

###

#.####

15

256QAM

###

#.####

Table 3

5 Figure 7A is another flowchart illustrating an embodiment of the invention in user equipment apparatus. The embodiment starts at step 700.

In step 702, an apparatus is configured to receive from an eNodeB a request to perform measurement of one or more radio channels. In an embodiment, this step is not executed as the user equipment performs measurements in a predetermined 10 manner as a standard procedure.

In step 704, user equipment is configured to measure a radio channel. The measurement may be RSRP or some other Radio Resource Management measurement which may aid the eNodeB in CQI selection process.

In step 706, the apparatus is configured to send the measurement result to the 15 eNodeB.

In step 708, the apparatus is configured receive from the eNodeB information on the CQI table to use and/or the indexing method to apply. The indexing method may be the use of a given subset or interval, for example.

In step 710, the apparatus is configured to receive from the eNodeB a request 20 to determine CQI on one or more radio channels. The steps 708 and 710 may be

18

received simultaneously in a single signalling message. Furthermore, if the apparatus has been requested by the eNodeB to periodically report CQI values this step is not necessarily executed.

In step 712, the apparatus is configured to measure a radio channel to obtain 5 information on signal to interference and noise ratio (SINR) of a radio channel and on the basis of the information on SINR determine CQI according to the given table and indexing method.

In step 714, the apparatus is configured to transmit the channel quality index to the communication system.

10 The process ends in step 716.

Figure 7B is another flowchart illustrating an embodiment of the invention in an eNodeB. The embodiment starts at step 720.

In step 722, the eNodeB is configured to store one or more channel quality index tables where different indices correspond to different channel quality values. 15 There may be different tables for real valued and complex modulation methods, for example.

In step 724, the eNodeB is configured to send user equipment a request to perform channel measurements. The measurement may be RSRP or other Radio Resource Management measurement which may aid the eNodeB in CQI selection 20 process. In an embodiment, this step is missing and the UE perform measurements in a predetermined manner as a standard procedure.

In step 726, the eNodeB is configured to receive measurement results from the

UE.

In step 728, the eNodeB is configured to select a channel quality index table 25 and the indexing method to be used when communicating with the UE and utilise the received estimation information when making the selection.

The eNodeB may select to use a given CQI table depending on the modulation method chosen for the UE. The eNodeB may use a single CQI table and select a suitable indexing method to use. The indexing method may be the use of a given 30 subset or interval, for example.

19

The eNodeB select as the indexing method a continuous subset of indices pointing to a channel quality index table. The subset may be one from a predetermined number of given subsets, as illustrated in connection with Figure 6A. The subset may be of predetermined length of indices wherein the index being in the middle of the subset corresponds to the radio channel estimate received from the UE, as illustrated in connection with Figure 6B.

In step 730, the eNodeB is configured to send user equipment information on which CQI table and/or indexing method to use.

In step 732, the eNodeB is configured to send user equipment a request to determine CQI according to the given table and indexing method. In an embodiment, the steps 730 and 732 are combined simultaneously in a single signalling message. In an embodiment, the eNodeB indicates the UE to report the estimation results in either periodic or aperiodic way. If the eNodeB has previously requested UE to periodically report CQI values this step is not necessarily executed.

In step 734, eNodeB is configured to receive a channel quality index transmitted by UE.

The process ends in step 736.

The steps and related functions described in the above and attached figures are in no absolute chronological order, and some of the steps may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps or within the steps. Some of the steps can also be left out or replaced with a corresponding step.

The apparatuses or controllers able to perform the above-described steps may be implemented as an electronic digital computer, processing system or a circuitry which may comprise a working memory (RAM), a central processing unit (CPU), and a system clock. The CPU may comprise a set of registers, an arithmetic logic unit, and a controller. The processing system, controller or the circuitry is controlled by a sequence of program instructions transferred to the CPU from the RAM. The controller may contain a number of microinstructions for basic operations. The implementation of microinstructions may vary depending on the CPU design. The program instructions may be coded by a programming language, which may be a

20

high-level programming language, such as C, Java, etc., or a low-level programming language, such as a machine language, or an assembler. The electronic digital computer may also have an operating system, which may provide system services to a computer program written with the program instructions.

5 As used in this application, the term 'circuitry' refers to all of the following:

(a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and software (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software including digital signal processor(s), software, and memory(ies) 10 that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of 'circuitry' applies to all uses of this term in this application. As a further example, as used in this application, the term 'circuitry' would also cover 15 an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and/or firmware. The term 'circuitry' would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another 20 network device.

An embodiment provides a computer program embodied on a distribution medium, comprising program instructions which, when loaded into an electronic apparatus, are configured to control the apparatus to execute the embodiments described above.

25 The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, and a software distribution package, for example. Depending on the processing power needed, the computer program may 30 be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

21

The apparatus may also be implemented as one or more integrated circuits, such as application-specific integrated circuits ASIC. Other hardware embodiments are also feasible, such as a circuit built of separate logic components. A hybrid of these different implementations is also feasible. When selecting the method of 5 implementation, a person skilled in the art will consider the requirements set for the size and power consumption of the apparatus, the necessary processing capacity, production costs, and production volumes, for example.

It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its 10 embodiments are not limited to the examples described above but may vary within the scope of the claim.

22

Claims

Claims

1. An apparatus in a communication system, comprising a processing system configured to:

5 control the measurement of a radio channel to obtain information on signal to interference and noise ratio (SINR) of a radio channel;

calculate a channel quality index on the basis of the information on signal to interference and noise ratio, a selection of the channel quality index table the index points to and/or an indexing method having been made utilising information on radio 10 channel measurements controlled by the apparatus;

control the transmission of the channel quality index to the communication system.

2. The apparatus of claim 1, the apparatus configured to receive from the 15 communication system information on the table the channel quality index points to and/or the indexing method.

3. The apparatus of claim 1 or 2, the apparatus configured to utilise a continuous subset of indices pointing to a channel quality index table.

20

4. The apparatus of claim 3, the apparatus configured to use a subset selected from a predetermined number of given subsets on the basis of the radio channel measurements.

25 5. The apparatus of claim 3, the apparatus configured to utilise a subset determined on the basis of the radio channel measurements, the subset being of predetermined length of indices wherein the starting and ending indices being selected on the basis of the measured radio channel estimate.

23

6. The apparatus of any preceding claim, the apparatus configured to utilise a different channel quality index table for real valued modulation methods and complex modulation methods.

5 7. The apparatus of any preceding claim, wherein performance differences between different indices of the channel quality index table are nonuniform.

8. The apparatus of any preceding claim, wherein the processing system 10 is arranged to configure the apparatus to operate in a Universal Mobile

Telecommunication System Long-Term Evolution network and/or in a Universal Mobile Telecommunication System Long-Term Evolution Advanced network.

9. An apparatus in a communication system, comprising a processing 15 system configured to:

receive from a transceiver of the communication system radio channel measurements;

select a channel quality index table and/or an indexing method to be used when communicating with the transceiver by utilising the received radio channel 20 measurements when making the selection;

control the transmission of information on the selected table and/or indexing method to the transceiver.

10. The apparatus of claim 9, the apparatus configured to send the 25 transceiver information on the selected table the channel quality index points to and/or the indexing method.

11. The apparatus of claim 9 or 10, the apparatus configured to send the transceiver a command to calculate a channel quality index utilising the selected table

30 and/or indexing method and to transmit the channel quality index.

24

12. The apparatus of claim 9, 10 or 11, the apparatus configured to select as the indexing method a continuous subset of indices pointing to a channel quality index table.

5 13. The apparatus of claim 12, the apparatus configured to select the subset on the basis of the radio channel measurements from a predetermined number of given subsets.

14. The apparatus of claim 12, the apparatus being configured to determine 10 the subset on the basis of the radio channel measurements, the subset being of predetermined length of indices wherein the starting and ending indices being selected on the basis of the radio channel measurements.

15. The apparatus of any of claims 9 to 14, the apparatus configured to 15 select a different channel quality index table for real valued modulation methods and complex modulation methods.

16. The apparatus of any of claims 9 to 15, wherein performance differences between different indices of the channel quality index table are non-

20 uniform.

17. The apparatus of any of claims 9 to 16, the apparatus configured to command the transceiver to report channel quality index periodically or aperiodically.

25 18. The apparatus of any preceding claim 9 to 17, wherein the processing system is arranged to configure the apparatus to operate in a Universal Mobile Telecommunication System Long-Term Evolution network and/or in a Universal Mobile Telecommunication System Long-Term Evolution Advanced network.

30

19.

An apparatus in a communication system, comprising:

25

means for controlling the measurement of a radio channel to obtain information on signal to interference and noise ratio (SINR) of a radio channel;

means for calculating a channel quality index on the basis of the information on signal to interference and noise ratio, a selection of the channel quality index table 5 the index points to and/or an indexing method having been made utilising information on radio channel measurements controlled by the apparatus; and means for controlling the transmission of the channel quality index to the communication system.

10 20. An apparatus in a communication system, comprising:

means for receiving from a transceiver of the communication system radio channel measurements;

means for selecting a channel quality index table and/or an indexing method to be used when communicating with the transceiver by utilising the received radio 15 channel measurements when making the selection; and means for controlling the transmission of information on the selected table and indexing method to the transceiver.

21. A method in a communication system, comprising: 20 controlling the measurement of a radio channel to obtain information on signal to interference and noise ratio (SINR) of a radio channel;

calculating a channel quality index on the basis of the information on signal to interference and noise ratio (SINR), the selection of a channel quality index table the index points to and/or an indexing method having been made utilising information on 25 radio channel measurements controlled by the apparatus;

controlling the transmission of the channel quality index to the communication system.

30

22. The method of claim 21, further comprising:

receiving from the communication system information on the table the channel quality index points to and/or the indexing method.

26

23. The method of claim 21, further comprising: utilising a continuous subset of indices pointing to a channel quality index table.

5 24. The method of claim 21, further comprising: using a subset selected from a predetermined number of given subsets on the basis of the radio channel measurements.

25. The method of claim 23, further comprising: utilising a subset 10 determined on the basis of the radio channel measurements, the subset being of predetermined length of indices wherein the starting and ending indices being selected on the basis of the measured radio channel estimate.

26. The method of claim 23, further comprising: utilising a different 15 channel quality index table for real valued modulation methods and complex modulation methods.

27. The method of any of claims 21 to 26, wherein performance differences between different indices of the channel quality index table are non-

20 uniform.

28. A method in a communication system, comprising:

receiving from a transceiver of the communication system radio channel measurements;

25 selecting a channel quality index table and/or an indexing method to be used when communicating with the transceiver by utilising the received information when making the selection;

controlling the transmission of information on the selected table and/or indexing method to the transceiver.

30

27

29. The method of claim 28, further comprising: sending the transceiver information on the selected table the channel quality index points to and/or the indexing method.

5 30. The method of claim 28, further comprising: sending the transceiver a command to calculate a channel quality index utilising the selected table and/or indexing method and to transmit the channel quality index.

31. The method of claim 28, further comprising: selecting as the indexing

10 method a continuous subset of indices pointing to a channel quality index table.

32. The method of claim 31, further comprising: selecting the subset on the basis of the radio channel estimate from a predetermined number of given subsets.

15 33. The method of claim 31, further comprising: determining the subset on the basis of the radio channel estimate, the subset being of predetermined length of indices wherein the starting and ending indices being selected on the basis of the measured radio channel measurements.

20 34. The method of any of claims 28 to 33, further comprising: selecting a different channel quality index table for real valued modulation methods and complex modulation methods.

35. The method of any of claims 28 to 34, wherein performance

25 differences between different indices of the channel quality index table are nonuniform.

36. The method of any of claims 28 to 35, further comprising: commanding the transceiver to report channel quality index periodically or

30 aperiodically.

28

37. A computer readable medium comprising a set of instructions, when executed on a processing system causes the processing system to perform the steps of any of claims 21 to 36.

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS

29

Claims

1. An apparatus in a communications network comprising a network element, the apparatus comprising a processing system configured to:

control a measurement of a radio channel to obtain information on signal to interference and noise ratio (SINR) of the radio channel;

receive an indication from the network element of a subset of channel quality indices from a channel quality index table, the indication of the subset for use by the apparatus for reporting a channel quality index to the network element, wherein the subset has been selected by the communications network on the basis of a radio channel measurement received by the communications network;

calculate a channel quality index of the radio channel on the basis of the subset indicated by the network element and the SINR information; and control the transmission of the calculated channel quality index to the network element.

2. The apparatus of claim 1, the apparatus configured to use a subset that is selected from a predetermined number of given subsets on the basis of the radio channel measurement.

3. The apparatus of claim 1, the apparatus configured to use a subset that is determined on the basis of the radio channel measurement, the subset having a predetermined number of indices, wherein the starting and ending indices are determined on the basis of a measured radio channel estimate.

4. The apparatus of any preceding claim, the apparatus configured to utilise different channel quality index tables for real valued modulation methods and complex modulation methods.

5. The apparatus of any preceding claim, wherein performance differences between different indices of the channel quality index table are non-uniform.

30

CO

o

CD

6. The apparatus of any preceding claim, wherein the processing system is arranged to configure the apparatus to operate in a Universal Mobile Telecommunication System Long-Term Evolution network and/or in a Universal

5 Mobile Telecommunication System Long-Term Evolution Advanced network.

7. The apparatus of any preceding claim, wherein the subset of channel quality indices is associated with sixteen modulation coding scheme classes.

10 8. An apparatus in a communications network comprising a transceiver,

the apparatus comprising a processing system configured to:

receive from the transceiver a radio channel measurement;

determine a continuous subset of indices from a channel quality index table for 1^- 15 use in determining a channel to be used for communications with the transceiver, the determination of the subset being based on the received radio channel measurement; and control the transmission of data indicative of the determined subset to the transceiver.

20

9. The apparatus of claim 8, the apparatus configured to send the transceiver a command to calculate a channel quality index utilising the subset and to transmit the channel quality index.

25 10. The apparatus of claim 8 or 9, the apparatus configured to select the subset on the basis of the radio channel measurement from a predetermined number of given subsets.

11. The apparatus of claim 8 or 9, the apparatus being configured to 30 determine the subset on the basis of the radio channel measurement, the subset having

31

a predetermined number of indices wherein the starting and ending indices are selected on the basis of a radio channel estimate.

12. The apparatus of any of claims 8 to 11, the apparatus configured to 5 determine different channel quality index tables for real valued modulation methods and complex modulation methods.

CO

o

CD

10

13. The apparatus of any of claims 8 to 12, wherein performance differences between different indices of the channel quality index table are non-uniform.

14. The apparatus of any of claims 8 to 13, the apparatus configured to command the transceiver to report channel quality index periodically or aperiodically.

15. The apparatus of any of claims 8 to 14, wherein the processing system 1^- 15 is arranged to configure the apparatus to operate in a Universal Mobile

Telecommunication System Long-Term Evolution network and/or in a Universal Mobile Telecommunication System Long-Term Evolution Advanced network.

16. The apparatus of any of claims 8 to 15, wherein the subset of channel 20 quality indices is associated with sixteen modulation coding scheme classes.

17. An apparatus in a communications network comprising a network element, the apparatus comprising:

means for controlling a measurement of a radio channel to obtain information 25 on signal to interference and noise ratio (SINR) of the radio channel;

means for receiving an indication from the network element of a subset of channel quality indices from a channel quality index table, the indication of the subset for use by the apparatus for reporting a channel quality index to the network element, wherein the subset has been selected by the communications network on the basis of a 30 radio channel measurement received by the communications network;

32

means for calculating a channel quality index of the radio channel on the basis of the subset indicated by the network element and the SINR information; and means for controlling the transmission of the calculated channel quality index to the network element.

18. An apparatus in a communications network comprising a transceiver, comprising:

means for receiving from the transceiver a radio channel measurement;

means for determining a continuous subset of indices from a channel quality index table for use in determining a channel to be used for communications with the transceiver, the determination of the subset being based on the received radio channel measurement; and means for controlling the transmission of data indicative of the determined subset to the transceiver.

19. A method in a communications network, comprising:

controlling a measurement of a radio channel to obtain information on signal to interference and noise ratio (SINR) of the radio channel;

receiving an indication of a subset of channel quality indices from a channel quality index table, the indication of the subset for use by the apparatus for reporting a channel quality index in the communications network, wherein the subset has been selected on the basis of a radio channel measurement received by the communications network;

calculating a channel quality index of the radio channel on the basis of the indicated subset and the SINR information;

controlling the transmission of the calculated channel quality index to the communications network.

20. The method of claim 19, further comprising: using a subset that is selected from a predetermined number of given subsets on the basis of the radio channel measurement.

33

21. The method of claim 19, further comprising: utilising a subset that is determined on the basis of the radio channel measurement, the subset having a predetermined number of indices, wherein the starting and ending indices are determined on the basis of a measured radio channel estimate.

22. The method of any of claims 19 to 21, further comprising: utilising different channel quality index tables for real valued modulation methods and complex modulation methods.

23. The method of any of claims 19 to 22, wherein performance differences between different indices of the channel quality index table are non-uniform.

24. The method of any of claims 19 to 23, wherein the subset of channel quality indices is associated with sixteen modulation coding scheme classes.

25. A method in a communications network, comprising:

receiving from a transceiver of the communications network a radio channel measurement;

determine a continuous subset of indices from a channel quality index table for use in determining a channel to be used for communications with the transceiver, the determination of the subset being based on the received radio channel measurement; and controlling the transmission of data indicative of the determined subset to the transceiver.

26. The method of claim 25, further comprising: sending the transceiver a command to calculate a channel quality index utilising the subset and to transmit the channel quality index.

34

27. The method of claim 25 or 26, further comprising: selecting the subset on the basis of the radio channel measurement from a predetermined number of given subsets.

28. The method of claim 25 or 26, further comprising: determining the subset on the basis of the radio channel measurement, the subset having a predetermined number of indices wherein the starting and ending indices are selected on the basis of a measured radio channel estimate.

29. The method of any of claims 25 to 28, further comprising: selecting different channel quality index tables for real valued modulation methods and complex modulation methods.

30. The method of any of claims 25 to 29, wherein performance differences between different indices of the channel quality index table are non-uniform.

31. The method of any of claims 25 to 30, further comprising: commanding the transceiver to report channel quality index periodically or aperiodically.

32. The method of any of claims 25 to 31, wherein the subset of channel quality indices is associated with sixteen modulation coding scheme classes.

33. A computer readable medium comprising a set of instructions, when executed on a processing system causes the processing system to perform the steps of any of claims 19 to 32.