WO2010062228A1

WO2010062228A1 - A method of providing channel quality information

Info

Publication number: WO2010062228A1
Application number: PCT/SE2008/051357
Authority: WO
Inventors: Qingyu Miao; Huaisong Zhu
Original assignee: Telefonaktiebolaget L M Ericsson (Publ); Du, Jiuhui
Priority date: 2008-11-26
Filing date: 2008-11-26
Publication date: 2010-06-03
Also published as: CN102224749A

Abstract

In a User Equipment a combined CQI, such as an effective SINR, is calculated for multiple timeslots based on a measurement of each of the time slots that the channel is mapped on. Hereby an improved CQI report can be obtained. Thus, an effective SINR for multiple timeslots can be reported to a radio base station NodeB and whereby an improved utilization of radio resources can be obtained.

Description

A METHOD OF PROVIDING CHANNEL QUALITY INFORMATION

TECHNICAL FIELD

The present invention relates to a method and a device for providing channel quality information in a radio system employing time division.

BACKGROUND

Time Division-Synchronous Code Division Multiple Access, or TD-SCDMA, is a 3G mobile telecommunications standard, being pursued in i.a. the People's Republic of China.

TD-SCDMA uses Time Division Duplex (TDD), in contrast to the Frequency Division Duplex FDD scheme used by Wideband Code Division Multiple Access (WCDMA). By dynamically adjusting the number of timeslots used for downlink and uplink, the system can more easily accommodate asymmetric traffic with different data rate requirements on downlink and uplink than FDD schemes. Since it does not require paired spectrum for downlink and uplink, spectrum allocation flexibility is also increased. Also, using the same carrier frequency for uplink and downlink means that the channel condition is the same on both directions, and the base station can deduce the downlink channel information from uplink channel estimates, which is helpful to the application of beamforming techniques. TD-SCDMA also uses Time Division Multiple Access (TDMA) in addition to the CDMA used in WCDMA. This reduces the number of users in each timeslot, which reduces the implementation complexity of multi-user detection and beamforming schemes, but the non- continuous transmission also reduces coverage because of the higher peak power needed, mobility because of lower power control frequency and complicates radio resource management algorithms. In a TD-SCDMA High Speed Downlink Packet Access (HSDPA) (TD-HSDPA) system, The User Equipment (UE) measures physical layer performance on the High Speed-Physical Downlink Shared Channel HS-PDSCH and send CQI (Channel Quality Information) to the radio base station NodeB based on the physical layer measurement result at UE. The CQI can include RTBS (Recommended Transport Block Size) and RMF (Recommended Modulation Format). The CQI is an indication of the current radio link condition. As a result the NodeB will schedule data to send to UE based on the CQI report from UE. In TD- SCDMA, there are 6 traffic time slots in one carrier and there are 16 channelization codes in each timeslot. Further the HS-PDSCH can be setup with more than one traffic time slot.

The UE provides feedback CQI per HS-PDSCH even though the HS-PDSCH is mapped on more than one traffic time slot. The radio link condition and the interference level is different in each timeslot and the RTBS and RMF for each timeslot can differ even much different because the radio link condition in each timeslot is different.

In existing TD-SCDMA systems the UE measure the CQI in the last slot and send feedback to the NodeB based on that measurement. The CQI only contains the radio link condition information in the last slot. The interference in other slots could be totally different due to the beamforming, etc. Hence, if only one set of Recommended Transport Block Size and Recommended Modulation Format (CQI) is feedback to the radio base station NodeB for all timeslots that the HS-PDSCH is mapped on, the NodeB can not get the radio link condition information of each timeslot.

In order to solve this problem the UE can be set to measure HS-PDSCH channel quality in each timeslot that HS-PDCH is mapped on and send CQI per timeslot to the NodeB based on the measurement result as is described in the international application no. PCT/SE2007/050616, which is incorporated herein by reference. Hereby the NodeB can set different Transport Block Size and Modulation Format for each timeslot based on the CQIs of each timeslot. However the solution described in PCT/SE2007/050616 requires an increased amount of signaling and overhead.

Hence, there exist a need for a method and a system that is able to provide feedback on many timeslots that require less signaling and/or overhead and which thereby is more efficient in terms of use of radio resources.

SUMMARY

It is an object of the present invention to overcome or at least reduce some of the problems associated with the generation of channel quality information reports in a radio system relying on time division.

These objects and others are obtained by the method, and User Equipment as set out in the appended claims. Thus, by in a User Equipment calculating a combined CQI, such as an effective Symbol Information to Noise Ratio (SINR), for multiple timeslots based on a measurement of each of the time slots that the channel is mapped on, an improved CQI report can be obtained. Thus, an effective SINR for multiple timeslots can be reported to a radio base station NodeB in a single report whereby an improved utilization of radio resources can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which:

- Fig. 1 is a view illustrating a TD-SCDMA system,

- Fig. 2 is a view of a system for calculate the CQI for multiple time slots in a UE, and

- Fig. 3 is a flowchart illustrating steps performed when calculating CQI for multiple time slots in a UE. DETAILED DESCRIPTION

Below an embodiment of the present invention is described in the context of a TD-SCDMA system. The invention is however not limited to a TD-SCDMA system but can be implemented in any radio system employing time division for separating channels into time slots.

In Fig.1 a view illustrating an exemplary cellular radio system 100 utilizing time division multiplexing is depicted. The system 100 can for example be a Time Division Synchronous Code Division Multiple Access TD-SCDMA system. The system 100 comprises a base station (Node B) 101. The base station 101 serves a number of mobile stations, also termed User Equipment (UE) 103, located within the area covered by the base station 101 and or other base stations. The base station 101 is also connected to a radio network controller node (RNC) 105. The UE 103 can further comprise a system 200 for calculating Channel Quality Information (CQI) .

In Fig.2 a view illustrating system 200 for calculate the CQI for multiple time slots in a UE. The system 200 comprises different units 201 for measuring HS-PDSCH channel quality, for example as Symbol Information to Noise Ratio (SINR), in each timeslot that the HS- PDSCH is mapped on. The information thus obtained in the units 201 are fed to a module 203 for converting the information to symbol information (SI) of each slot. Based on the symbol information for each slot, the Received Block Information (RBI) of an entire Transmission Time Interval (TTI) can be calculated in a block 205. The RBI can be converted to the available effective SINR for the whole TTI in a block 207.

In accordance with one embodiment, the UE can be adapted to calculate the effective SINR based on the measured SINR for each slot according to the teachings in Wan Lei, Magnus Almgren, "A link-to-system Interface based on Mutual Information", ETC/WF-04:004_B Based on the available effective SINR as calculated in Block 207 the UE can be adapted to select the RTBS (Recommended Transport Block Size) and RMF (Recommended Modulation Format), which is reported to NodeB.

Assuming one coding block consists of L slots, each of which contains K modulated symbols, RBI expresses the block-level channel capacity, and Received Symbol Information (RSI) expresses the slot-level channel capacity. For the received L slots at the receiver, which experiences multiple channel state ui' %>^{•• •}> Yu _^ the received RBI can be expressed as:

RBI _L = JRSI_n , L ≤ M

(3)

where ^' '" ' is the symbol-level mutual information. Besides the definition of ^' ^m ' in [[ETC/WF Wan Lei, "A Link-to-System Interface Based on Mutual Information", ETC/WF-04:004, A, Mar. 8, 2004.]], there are other approximate expressions see for example [EED/N/RA Udo Wachsmann & Mathias Pauli, "Novel Link Quality Estimation for Coded Transmission on Fading Channels", EED/N/RA-02:055, A, Mar. 04, 2003]] as below.

^o (r,J = l - log₂ (l + ^'^/2 ) , BPSK cutoff rate ₍₆₎

¹ _Gm1Ss CO = ₇ ^log₂0 + ^_n, ) , AWGN capacity, real Gaussian input ^

For a certain codec, the relation between RBI and Block Error Rate (BLER) or any other

D O T quality indicators are known. Therefore, a given quality requirement, ^tmget can be obtained by checking the AWGN performance of the particular codec.

In Fig. 3 a flow chart illustrating procedural steps performed when generating a feedback CQI report in a User equipment to be sent from the User Equipment to a radio base station NodeB. First in a step 301, the channel quality of a particular channel to be measured is measured, for example as Symbol Information to Noise Ratio (SINR), in each timeslot that the channel is mapped on. Next, in a step 303, the information derived in step 301 is converted to symbol information (SI) for each time slot. Thereupon, in a step 305, the symbol information for each time slot is used to calculate the Received Block Information (RBI) of an entire Transmission Time Interval (TTI). Then, in a step 307, a CQI report is generated based on the measurements of all time slots in a TTI. For example an obtained RBI can be used as input to a CQI report to be sent as feedback to the radio base station NodeB. In accordance with one embodiment the RBI can be converted to an effective SINR value for all measured time slots.

Further, in the radio base station NodeB, the effective SINR can be calculated in the corresponding manner for the Transport Format combination TFC selection or power/code allocation.

Using the method and system as described herein will provide for calculation of the CQI for multiple time slots in a UE accurately and in an efficient manner.

Claims

1. A method in a User Equipment, UE, for generating a channel quality information report, the method comprising the steps of:

- receiving information on a channel mapped on at least two time slots in a time division radio system,

- measuring each time slot of the channel in a Transmission Time Interval,

- generating a Channel Quality Indicator, CQI, report based on the measuring of each time slot of the channel.

2. The method according to claim 1 , wherein the step of measuring each time slot comprises determining the Symbol Information to Noise Ratio for each time slot.

3. The method according to any of claims 1 or 2, further comprising determining a Received Block Information of an entire Transmission Time Interval based on the measuring of each time slot.

4. The method according to claim 3, further comprising the step of converting the Received Block Information to an effective Symbol Information to Noise Ratio for the Transmission Time Interval.

5. The method according to any of claims 1 - 4 wherein the channel quality information report is generated for a Time Division Synchronous Code Division Multiple Access, TD- SCDMA, radio system.

6. A method in a radio base station for generating an effective Symbol Information to Noise Ratio SINR value, the method comprising the steps of:

- measuring each time slot of the channel in a Transmission Time Interval, - generating a Symbol Information to Noise Ratio based on the measuring of each time slot of the channel.

7. The method according to claims 6, further comprising determining a Received Block Information of an entire Transmission Time Interval based on the measuring of each time slot.

8. The method according to claim 7, further comprising the step of converting the Received Block Information to an effective Symbol Information to Noise Ratio for the Transmission Time Interval.

9. The method according to any of claims 6 - 8 wherein the Symbol Information to Noise Ratio is generated for a Time Division Synchronous Code Division Multiple Access, TD- SCDMA, radio system

10. The method according to any of claims 6 - 9, wherein the effective Symbol Information to Noise Ratio is used in Transport Format combination TFC selection or power/code allocation.

11. A User Equipment, UE comprising means for generating channel quality information, the UE further comprising:

-means for receiving information on a channel mapped on at least two time slots in a time division radio system,

- means for measuring each time slot of the channel in a Transmission Time Interval, and - means for generating a Channel Quality Indicator, CQI, report based on the measuring of each time slot of the channel.

12. The User Equipment according to claim 11, further comprising means for determining the Symbol Information to Noise Ratio for each time slot.

13. The User Equipment according to any of claims 11 or 12, further comprising means for determining a Received Block Information of an entire Transmission Time Interval based on a measuring of each time slot.

14. The User Equipment according to claim 13, further comprising means for converting Received Block Information to an effective Symbol Information to Noise Ratio for the Transmission Time Interval.

15. The User Equipment according to any of claims 11 - 14 wherein the UE is adapted to connect to a Time Division Synchronous Code Division Multiple Access, TD-SCDMA, radio system.

16. A radio base station adapted to generate an effective Symbol Information to Noise Ratio SINR value, the radio base station comprising:

- means for receiving information on a channel mapped on at least two time slots in a time division radio system,

- means for measuring each time slot of the channel in a Transmission Time Interval, and

- means for generating a Symbol Information to Noise Ratio based on the measuring of each time slot of the channel.

17. The radio base station according to claims 16, further comprising means for determining a Received Block Information of an entire Transmission Time Interval based on a measuring of each time slot.

18. The radio base station according to claim 17, further comprising means for converting the Received Block Information to an effective Symbol Information to Noise Ratio for the Transmission Time Interval.

19. The radio base station according to any of claims 16 - 18 wherein the radio base station base station is a Time Division Synchronous Code Division Multiple Access, TD-SCDMA, radio system radio base station.

20. The radio base station according to any of claims 16 - 19, wherein further comprising means for performing Transport Format combination TFC selection or power/code allocation based on the effective Symbol Information.