KR100751509B1 - System and method for feedback of channel quality infomation using partially shared bandwidth - Google Patents

Abstract

A method and a system for selective feedback of channel quality information using partial sharing are provided to measure CQI(Channel Quality Information) of each channel and feed back only CQI of a predetermined number of sub-channels having the best quality as satisfying predetermined conditions to a transmission stage, thereby reducing the load of uplink without reducing a data processing rate. A method for selective feedback of channel quality information using partial sharing comprises the following steps of: allocating a first bandwidth and a second bandwidth(S700); measuring quality of each sub-channel having bands divided from the whole frequency band for transmitting data from a transmission stage to a reception stage(S720); selecting a predetermined number of sub-channels satisfying the predetermined reference among the measured sub-channels(S730); and performing feedback of CQI of the selected predetermined number of sub-channels(S740).

Description

System and Method for Feedback of Channel Quality Infomation Using Partially Shared Bandwidth}

1 is a configuration diagram of an entire system to which the present invention is applied;

2 is a detailed block diagram of a channel feedback system using partial sharing according to an embodiment of the present invention;

3 is a graph showing data transmission efficiency according to the number of users in a system using an OFDM scheme;

4 is a graph showing a payload for each feedback method according to a change in the number of users;

5 is a graph showing a change in the probability that the CQI for each channel is actually transmitted as the number of users increases when feeding back the CQI of the five channels having the highest quality.

6 is a conceptual diagram illustrating bandwidth allocated for feedback according to an embodiment of the present invention;

7 is a flowchart of a selective channel feedback method using partial sharing according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

101 cell 200 receiver

201: A / D conversion unit 202: protection section removal unit

203: serial / parallel converter 204: pilot signal extractor

205: Channel quality measuring unit 206: FFT unit

207: equalizer 208: bottle / serial converter

209: demapping unit 210: channel selector

211: feedback unit 300: transmitter

301: mapping unit 302: bottle / serial converter

303: IFFT section 304: Additional protective section

305: bottle / serial converter 306: D / A converter

307: bandwidth allocation

The present invention relates to a wireless mobile communication system and method of orthogonal frequency division multiplexing, and more particularly, to a mobile communication system and method for reducing an uplink load for feeding back channel quality information.

The uplink referred to herein means transmission from the receiving end to the transmitting end, and downlink means transmission from the transmitting end to the receiving end.

Orthogonal Frequency Division Multiplexing (OFDM) method is a digital modulation method for improving transmission rate per bandwidth and preventing multipath interference, and is used for digital audio broadcasting (DAB) in Europe. It was developed as a commercial broadcast from 1996.

The OFDM method is a method of transmitting data using a multi-carrier, in which symbol strings serially input are converted in parallel, and then modulated and transmitted into a plurality of subcarriers having mutual orthogonality.

The OFDM scheme can be regarded as a kind of FDM scheme that transmits data by dividing a frequency band to be used into several small frequency bands (sub-channels). By using subcarriers having orthogonality, The frequency components of each subcarrier may be superimposed on one another, and the frequency utilization efficiency is much higher than that of the conventional FDM method.

In addition, when a plurality of carriers are increased by allocating serially and parallel-converted encoded data to each subcarrier and digitally modulating, the transmission rate per bandwidth can be increased.

On the other hand, in the wireless mobile communication system using the OFDM scheme, the most suitable method for increasing the data transmission efficiency (Throughput) of the entire system has been proposed as adaptive modulation and coding (AMC) )to be.

This technique improves the efficiency of the entire cell managed by the transmitter by changing the modulation scheme and the coding scheme in accordance with the channel state between the transmitter and the receiver. That is, a large amount of data is allocated to a terminal in a good environment that can process a large amount of data, and a small amount of data is allocated to a terminal that is not.

As described above, in order to use the AMC, the receiving end must inform the transmitting end of the cell to which the cell belongs to the downlink channel quality information (CQI).

However, when a plurality of receivers located in the same cell feed back the CQI to the transmitter every predetermined period, there is a problem that uplink overload may occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mobile communication system and method which reduces an uplink load for feeding back channel quality information without reducing data processing efficiency of the system.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the claims.

In order to achieve the above object, the present invention provides a method for feeding back channel quality information from at least one receiving end to a transmitting end, wherein the first bandwidth and other bandwidth are dedicated bandwidths for feeding back the channel quality information to each of the at least one receiving end. A bandwidth allocation step of allocating a second bandwidth, which is a common bandwidth for feeding back the channel quality information together with the channel quality information of a receiver, and a subchannel dividing an entire frequency band for transmitting data from the transmitter to the receiver; A channel quality measuring step of measuring quality for each channel, a channel selecting step of selecting a predetermined number of subchannels satisfying a predetermined criterion among the subchannels whose quality is measured in the channel quality measuring step, and the selected number of subchannels A feedback step of feeding back channel quality information,

The feedback step may include selecting a predetermined number of subchannels in order of good quality among the predetermined number of subchannels, and assigning selected channel information, which is channel quality information of the selected subchannels, in the bandwidth allocation step. Feeding back the selected channel information through a bandwidth, and selecting the non-selected channel information, which is channel quality information of unselected channels, among the predetermined number of subchannels together with the second unselected channel information, which is unselected channel information of another receiver, And feeding back through the second bandwidth allocated in the allocating step.

The present invention also provides a system for feeding back channel quality information from at least one receiving end to a transmitting end, wherein the transmitting end is a dedicated bandwidth for feeding back the channel quality information to each of the one or more receiving ends. And a bandwidth allocation unit for allocating a second bandwidth, which is a common bandwidth for feeding back the channel quality information, together with the channel quality information, wherein the receiving end divides the entire frequency band for transmitting data from the transmitting end to the receiving end. A channel quality measuring unit for measuring quality for each sub-channel, a channel selecting unit for selecting a predetermined number of sub-channels satisfying a predetermined criterion among the sub-channels whose quality is measured by the channel quality measuring unit, and the channel selection Feedback unit for feeding back channel quality information for the predetermined number of subchannels selected by the unit And including,

The feedback unit selects a predetermined number of subchannels from the selected predetermined number of subchannels in order of good quality, and allocates the selected channel information, which is channel quality information of the selected subchannel, to the bandwidth allocation unit. Feedback by one bandwidth, and the non-selected channel information that is the channel quality information of the unselected sub-channel among the predetermined number of channels together with the second unselected channel information that is the non-selected channel information of the other receiving end by the bandwidth allocation unit And feedback through the allocated second bandwidth.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a block diagram of an entire system to which the present invention is applied. As shown in FIG. 1, the entire system 100 to which the present invention is applied includes at least one receiving end 200 and a transmitting end 300.

The transmitter 300 modulates and transmits data to be transmitted to the receiver 200 into an OFDM signal, and transmits the data to the channel selected in the order of excellent quality to one or more receivers 200 through the bandwidth allocator 307. The first bandwidth, which is a dedicated bandwidth capable of feeding back the CQI for the CQI, and the CQI for the unselected channel of another receiver in the same cell 101 managed by the transmitting end 300 to manage the CQI for the unselected channel. Allocates a second bandwidth, which can be a common bandwidth.

In this way, a dedicated bandwidth capable of feeding back the CQI for the channels selected in order of the highest quality to each receiver 200 and the other receivers in the same cell 101 managed by the transmitter 300 for the CQIs for the unselected channels. By allocating a common bandwidth so that it can be fed back with the CQI for the unselected channel of the channel, the uplink load from the channel feedback device 200 to the transmitting end 300 can be further reduced, and more through a limited bandwidth. There is an advantage in that the number of CQI can be fed back.

The receiver 200 is for receiving a signal from the transmitter 300 and transmitting the signal to the user through the OFDM scheme, and may be implemented in various forms such as a general PC, a mobile phone, a notebook, a PDA, and the like.

The receiver 200 measures the CQI for each sub-channel of the signal received from the transmitter 300 through the channel quality measuring unit 205, and predetermined reference among the sub-channels for which the CQI is measured through the channel selector 210. A predetermined number of subchannels having the highest quality satisfying the following are selected.

Thereafter, the feedback unit 211 selects a predetermined number of the selected subchannels in order of good quality, and selects the selected subchannels through the first bandwidth allocated by the bandwidth allocator 307 of the transmitter 300. CQI for the feedback, and the unselected subchannels of the selected subchannels are the bandwidth allocation unit 307 of the transmitting end 300 together with the subchannels not selected by other receiving end in the same cell managed by the transmitting end 300. Feedback the CQI through the second bandwidth allocated by &lt; RTI ID = 0.0 &gt;

The predetermined criterion for selecting the subchannel by the channel selector 210 may be equal to or greater than a predetermined Signal to Interference and Noise Ratio (SINR) value or a Receive Signal Strength Indicator (RSSI) value or a standard deviation value.

For example, if the predetermined criterion is three channels with an SINR value of 1.0 or more, the total number of subchannels is five, and the SINR values of each measured channel are 0.8, 0.9, 1.0, 1.1, and 1.2, respectively. Only three channels with SINR values of 1.0, 1.1, and 1.2 will be fed back.

The predetermined criterion and the predetermined number corresponding to the predetermined criterion are reference values that can be set according to the operation policy of the system with parameters of cell location, statistical number of receivers, allocated bandwidth, and traffic increase.

Hereinafter, a detailed configuration and operation of the entire system 100 to which the present invention is applied will be described with reference to FIG. 2.

2 is a detailed block diagram of a selective channel feedback system according to an exemplary embodiment of the present invention. In the description, the same reference numerals as in FIG. 1 refer to the same members performing the same functions.

As shown in FIG. 2, the receiving end 200 of the entire system 100 to which the present invention is applied includes an A / D conversion unit 201, a protection section removing unit 202, a serial / parallel conversion unit 203, Pilot symbol extraction unit 204, channel quality measurement unit 205, FFT unit 206, equalizer 207, bottle / serial conversion unit 208, demapping unit 209, channel selector 210 And a feedback unit 211.

In addition, the transmitter 300 of the entire system 100 to which the present invention is applied includes a mapping unit 301, a serial / parallel conversion unit 302, an IFFT unit 303, a guard interval addition unit 304, and parallel / serial. A converter 305, a D / A converter 306, and a bandwidth allocation unit 307 are included.

First, the signal processing receiving process by the OFDM scheme performed by the receiving end 200 will be described.

First, when an analog signal is received from the transmitter 300, the A / D converter 201 converts the analog signal into a digital signal, and the converted signal is protected from the digital signal converted by the guard interval elimination unit 202. The section is removed.

In this case, the guard interval is to prepare for delay spread that acts as a performance deterioration factor in the wireless environment, and is added by the guard interval adder 304 of the transmitter 300.

The signal in the time domain from which the guard interval is removed is converted into a parallel signal by the serial / parallel conversion unit 203 and then converted into a signal in the frequency domain by the FFT unit 206.

The signal converted into a signal in the frequency domain is compensated for distortion of the channel through the equalizer 207, and is converted into a serial signal by the parallel / serial converter 208, and then de-mapper 209. Demodulated

Here, the pilot symbol extraction unit 204 extracts the pilot symbol from the signal of the frequency domain converted by the FFT unit 206 and transmits the pilot symbol to the channel quality measuring unit 205, and the channel quality measuring unit 205 transmits the pilot symbol. The estimated channel is transmitted to the equalizer 207 and the channel selector 210 by using Equation.

The channel selector 210 measures the CQI for each subchannel based on the estimated channel result, selects only the CQIs of the predetermined number of subchannels having the highest quality satisfying a predetermined criterion among the measured subchannels, and feeds back the feedback. Transfer to section 211.

The feedback unit 211 feeds back the CQI received from the channel selector 210 to the transmitter 300 through the bandwidth allocated by the bandwidth allocator 307 of the transmitter 300.

The reference and the number of the CQI fed back here can be changed as much according to the transmitter 300 or the receiver 200 and other conditions.

Meanwhile, FIG. 3 shows an effect obtained by feeding back only the CQIs of a predetermined number of subchannels whose quality satisfies a predetermined criterion among the subchannels in which the CQIs are measured.

3 is a graph illustrating data transmission efficiency according to the number of users in a system using an OFDM scheme. Here, 'Best-5' in the indicator shown in FIG. 3 means that CQIs for five subchannels satisfying a predetermined criterion are transmitted.

As shown in FIG. 3, even if the number of users increases, the receiver 200 feeds back the CQI for all subchannels, and the present invention in which only the CQIs for the selected five channels are fed back provides data processing efficiency. It can be seen that there is no big difference.

In addition, FIG. 4 illustrates a payload for each feedback method as the number of users increases. As shown in FIG. 4, the present invention that feeds back only CQIs for a predetermined channel is not only much smaller than the conventional method for feeding back CQIs for all subchannels, but also converges to a predetermined value. .

That is, the CQI may be fed back using a given bandwidth regardless of the number of users.

Hereinafter, a signal processing transmission process using the OFDM scheme performed by the transmitter 300 will be described.

First, the mapping unit 301 converts data to be transmitted to the receiver 200 into symbols in a frequency domain using a modulation scheme used in an OFDM subchannel, and converts the converted symbols and pilot symbols into predetermined subchannels. Assign to

These pilot symbols may be used to track and compensate for errors in carrier or sampling frequency as well as channel estimation.

Data and pilot symbols allocated to a predetermined subchannel are converted in parallel through the serial / parallel conversion unit 302 and then converted into signals in the time domain through the IFFT unit 303.

Symbols and pilot signals converted to signals in the time domain are added by a guard interval adding section 304, and serialized again by the parallel / serial conversion section 305.

Thereafter, the D / A converter 306 converts the signal into an analog signal and transmits the signal to the receiver 200.

The bandwidth allocator 307 allocates a bandwidth for feeding back the CQI to each receiver 200 as described above. In this case, a method of allocating a bandwidth will be described with reference to FIGS. 5 and 6.

5 is a graph showing a change in the probability that the CQI for each channel is actually transmitted as the number of users increases when feeding back the CQI of the five channels having the highest quality.

Here, the receiver 200 feeds back only the CQIs related to five channels satisfying a predetermined condition to the transmitter 300, and assumes that the channels 1 to 5 are arranged in order of excellent quality. 'Is the number of users.

Referring to FIG. 5, it can be seen that as the number of users increases when feeding back the CQIs for the five channels, the probability of transmitting the CQIs for the fourth or fifth channels, which are relatively poor in quality, is lowered.

Accordingly, as shown in FIG. 6, a dedicated bandwidth for feeding back the CQI for the channels B1, B2, and B3 that is likely to be fed back to each receiver 200 is allocated, and the channels B4 and B5 that are unlikely to be fed back are allocated. When the common bandwidth for feeding back the CQI for the CB with the CQIs of the channels B4 and B5 that are less likely to be fed back to the other receiver is allocated, more CQIs may be fed back through a given bandwidth. Here, 'Bx' refers to the channel having the superior xth quality.

In addition, the problem of receiving end identification that may occur when a specific CQI is fed back through the shared bandwidth is a separate identification for receiving end identification, such as a predetermined unique identification value for identifying each receiving end 200 given from the transmitting end in the CQI. Can be solved by adding

The predetermined unique identification value is preferably a unique number such as IMSI, SIM card number, ESN, etc. uniquely assigned to each terminal, and using the unique number used to identify the terminal with other terminals. After the repeater (transmitter) in charge of the specific cell region recognizes the unique number, the repeater (transmitter) assigns a temporary unique number such as TMSI to the terminal (receiver) to perform communication.

Hereinafter, a selective channel feedback method using partial sharing according to an exemplary embodiment of the present invention will be described with reference to FIG. 7.

 In the description, the same reference numerals as those in Figs. 1 and 2 refer to the same members performing the same functions.

First, the transmitter 300 allocates one or more of the first bandwidth, which is a dedicated bandwidth for receiving the CQI, and the second bandwidth, which is the common bandwidth for receiving the CQI, with the other receiver, to each of the one or more receivers 200 (S700).

Thereafter, if the data to be transmitted to the receiver 200 is modulated and transmitted to the OFDM signal (S710), the receiver 200 estimates a channel from the received OFDM signal and generates CQI for each subchannel. (S720).

Thereafter, the receiving end 200 selects a predetermined number of subchannels having the highest quality satisfying a predetermined condition among the subchannels in which the CQI is generated (S730), and transmits the CQI for the selected subchannels to the transmitting end 300. Feedback to step (S740).

At this time, the receiving end 200 selects a predetermined number of subchannels in order of good quality among the selected predetermined number of subchannels, and the first terminal in which the transmitting end 300 allocates selection channel information which is channel quality information of the selected channels. A feedback allocated through the bandwidth and allocated by the transmitting end 300 together with the second unselected channel information, which is unselected channel information of another receiving end, unselected channel information which is CQI of unselected subchannels among the predetermined number of subchannels; Feedback through two bandwidths.

Furthermore, the CQI fed back through the shared bandwidth preferably includes separate information for receiving end identification, such as a unique identification value, to identify each receiving end assigned from the transmitting end for the problem of receiving end identification. Do.

As mentioned above, although this invention was demonstrated by the limited embodiment and drawing, this invention is not limited by this, The person of ordinary skill in the art to which this invention belongs, Of course, various modifications and variations are possible within the scope of equivalent claims.

The present invention as described above, by measuring the CQI for each sub-channel, by feeding back only the CQI for a predetermined number of sub-channels with the highest quality satisfying a predetermined condition among the sub-channels CQI is measured, In addition to reducing the load on the uplink that feeds back channel quality information without reducing data processing efficiency,

Allocate bandwidth so that one or more receivers can feed back CQIs for the best-selected channels in order of quality, and CQIs for non-selected channels are for unselected channels of other receivers in the same cell managed by the transmitter. By allocating the bandwidth to be fed back with the CQI, there is an advantage that can be fed back more CQI through the given bandwidth.

Claims (8)

delete A method for feeding back channel quality information from at least one receiving end to a transmitting end, A bandwidth allocation step of allocating a second bandwidth which is a common bandwidth for feeding back the channel quality information together with the first bandwidth which is a dedicated bandwidth for feeding back the channel quality information to each of the at least one receiving end and the channel quality information of another receiving end; A channel quality measuring step of measuring quality for each sub-channel dividing an entire frequency band for transmitting data from the transmitter to the receiver; A channel selection step of selecting a predetermined number of subchannels satisfying a predetermined criterion among the subchannels whose quality is measured in the channel quality measuring step; And A feedback step of feeding back channel quality information on the selected predetermined number of subchannels; The feedback step selects a predetermined number of subchannels in order of good quality among the predetermined number of subchannels, and selects channel information, which is channel quality information of the selected subchannels, in the bandwidth allocation step. Feedbacking the selected channel information through the channel allocation and assigning the unselected channel information, which is channel quality information of unselected channels, among the predetermined number of subchannels together with the second unselected channel information, which is unselected channel information of another receiver; Feedback through the second bandwidth allocated in step And the predetermined criterion of the channel selection step is a predetermined SINR value. The method of claim 2, wherein the unselected channel information, And selective identification information for identifying a receiving end corresponding to the unselected channel information. The method of claim 3, wherein the predetermined identification information, And a unique identification value for distinguishing each receiving end from the transmitting end. delete A system for feeding back channel quality information from at least one receiving end to a transmitting end, The transmitting end allocates a second bandwidth, which is a common bandwidth for feeding back the channel quality information, with the first bandwidth, which is a dedicated bandwidth for feeding back the channel quality information, and the channel quality information of another receiving end, to each of the at least one receiving end. Including bandwidth allocation, The receiving end includes a channel quality measuring unit for measuring quality for each sub-channel dividing an entire frequency band for transmitting data from the transmitting end to the receiving end; A channel selector for selecting a predetermined number of subchannels satisfying a predetermined criterion among the subchannels whose quality is measured by the channel quality measuring unit; And A feedback unit for feeding back channel quality information for the predetermined number of subchannels selected by the channel selector, The feedback unit selects a predetermined number of subchannels in order of good quality among the selected predetermined number of subchannels, and allocates the selected channel information, which is channel quality information of the selected subchannels, to the bandwidth allocator. Feedback through the bandwidth, and allocates the unselected channel information, which is channel quality information of unselected subchannels, out of the predetermined number of channels together with the second unselected channel information, which is unselected channel information of another receiver, by the bandwidth allocation unit. Feedback through the second bandwidth, The predetermined criterion of the channel selector is a selective channel feedback system using partial sharing, characterized in that more than a predetermined SINR value. The method of claim 6, wherein the unselected channel information, Optional channel feedback system using partial sharing, characterized in that it further comprises a predetermined identification information for identifying each receiving end. The method of claim 7, wherein the predetermined identification information, And a unique identification value for distinguishing each receiving end provided from the transmitting end.

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