CN1852275A - Channel correcting method and system - Google Patents

Abstract

The invention discloses a method for channel correction. In the method, different vacant subcarriers are used to carry known signals in different channels; the known signals carried by vacant subcarriers are sent to a coupler and a loop is formed locally through the coupler. ; At the receiving end of the local loop, the spare subcarrier signals passing through different channels are divided according to different channels, and estimated values reflecting the characteristics of different channels are extracted; and channel correction is performed according to the estimated values. The invention also discloses a transmitting channel correction system and a receiving channel correction system. The present invention uses active transmission on the spare orthogonal sub-carriers to automatically complete channel correction. The correction process has no impact on normal business, thus does not affect system capacity, and also does not affect system coverage through local loopback.

Description

Method and system for channel calibration

technical field

The present invention relates to the field of communications, in particular to a channel correction method and system.

Background technique

As a special way of multi-carrier transmission, the concept of Orthogonal Frequency Division Multiplexing (OFDM) appeared as early as the 1950s, and the first patent on OFDM technology was obtained by the US Patent Office in early 1970. Authorized OFDM is a high-speed transmission technology in a wireless environment. The main idea is to divide a given channel into many orthogonal sub-channels in the frequency domain, use a sub-carrier for modulation on each sub-channel, and transmit each sub-carrier in parallel. It not only has strong anti-interference ability, but also improves spectrum utilization. Due to limited processing capacity at that time, OFDM technology was not valued and applied by the industry when it appeared. Until the early 1990s, with the development of processing capability and OFDM technology itself, the conditions for large-scale application of OFDM were fully mature, such as applying it to 802.11a, DAB (Digital Audio Broadcasting), HyperLAN and asymmetric digital users Loop ADSL (Asymmetrical Digital SubscriberLine) and other commercial standards. In an OFDM system, a high-speed data stream is first divided into a series of lower-rate data streams, and these low-speed data streams are correspondingly transmitted in parallel on a series of sub-carriers. These subcarriers are orthogonal to each other, hence the name OFDM Orthogonal Frequency Division Multiplexing. In the OFDM system, the transmitting end and the receiving end can use the fast algorithm of inverse fast Fourier transform IFFT (Orthogonal Frequency Division Multiplexing) and fast Fourier transform FFT (Fast Fourier Transform) respectively, which greatly reduces the complexity of transceiver implementation. Based on the orthogonality between OFDM subcarriers, OFDM can also be used as one of the multiple access methods, called OFDMA, similar to CDMA (Code Division Multiple Access), but in the frequency domain. In an OFDMA system, each user can occupy some orthogonal subcarriers at the same time.

With multi-antenna technology, such as the use of adaptive beamforming technology, the gain of the direction diagram of the user's direction of arrival is improved, and the zero point of the direction diagram is used to reduce the interference of high-power users in space. Smart antenna technology SA (Smart Antenna), multi-input With the wide application of MIMO (Multiple Input Multiple Output) and other technologies, the degree of consistency between multiple channels directly determines the final effect of these technical solutions. Therefore, how to correct multi-channels becomes the first priority in the application of multi-antenna technology. problem to be solved.

A common practice in the industry is to correct multiple channels in the time domain in an OFDMA (Orthogonal Frequency Division Multiplexing Access) system. The system performs calibration at a certain frequency, such as every N frames, and each calibration costs L OFDMA symbol time. During the correction period of this technology, the normal uplink and downlink services need to be closed, thus reducing the system capacity.

Contents of the invention

The present invention provides a channel calibration method and system to solve the problem in the prior art that channel calibration affects system capacity.

The invention provides the following technical solutions:

A method for channel correction, comprising the steps of:

A. Carrying known signals with different vacant subcarriers in different channels;

B. Send the known signal carried by the spare subcarrier to a loop formed locally by the coupler;

C. At the receiving end of the local loop, the spare subcarrier signals passing through different channels are divided according to different channels, and estimated values reflecting the characteristics of different channels are extracted;

D. Correcting the channel using the estimated value.

The step before step A further includes: the control unit collects currently available vacant subcarriers, and then allocates according to the number of channels to be corrected, and allocates different vacant orthogonal subcarriers to different channels.

For the receiving channel, the step B further includes:

B1. The known signal carried by the spare subcarrier is sent to the local coupler through the correction transceiver at the frequency point of the receiving channel, and the coupler mixes the normal service signal from the antenna array with the signal from the correction transceiver After that, it is sent to the normal transceiver for processing, and then sent to the correction calculation unit.

For the transmission channel, the step B further includes: the known signal carried by the vacant subcarrier passes through the normal transceiver together with the normal service signal, and sends it to the local coupler at the frequency point of the transmission channel, and the coupler will The signal is sent to the antenna array and the calibration transceiver, and after being processed by the calibration transceiver, it is sent to the calibration calculation unit.

The step D further includes sending the estimated value to the normal baseband processing unit, and the normal baseband processing unit corrects the corresponding channel according to the estimated value.

The present invention also provides a receiving channel correction system, including a control unit, a correction transceiver, a local coupler, a normal transceiver, a correction calculation unit and a normal baseband processing unit,

The control unit is used to collect currently available vacant subcarriers, allocate them according to the number of channels to be corrected, and allocate different vacant orthogonal subcarriers to different channels;

The correction transceiver is used to receive the known signal carried by the spare subcarrier at the frequency point of the receiving channel, and send it to the local coupler;

The coupler mixes the normal service signal from the antenna array with the known signal carried by the spare subcarrier, and then sends it to the normal transceiver;

The normal transceiver is used to process the known signal carried by the vacant sub-carrier and send it to the correction calculation unit;

The correction calculation unit is used to extract estimated values reflecting different channel characteristics and transmit them to the normal baseband processing unit;

The normal baseband processing unit is used for correcting the corresponding receiving channel according to the estimated value.

The present invention also provides a transmission channel correction system, including a control unit, a correction transceiver, a local coupler, a normal transceiver, a correction calculation unit and a normal baseband processing unit,

The control unit is used to collect currently available vacant subcarriers, allocate them according to the number of channels to be corrected, and allocate different vacant orthogonal subcarriers to different channels;

The correction transceiver is used to accept the mixture of the known signal carried by the spare subcarrier and the service signal, and send it to the local coupler at the frequency point of the transmission channel;

said local coupler for sending said signal to a calibration transceiver;

The correction transceiver is used to process the signal and send the signal carried on the spare subcarrier to the correction calculation unit;

The correction calculation unit is used to extract estimated values reflecting different channel characteristics and transmit them to the normal baseband processing unit;

The normal baseband processing unit is used for correcting the corresponding receiving channel according to the estimated value.

The adaptive antenna system area in the system includes multiple sectors, each sector is configured with a correction transceiver, and each correction transceiver works independently.

The area of the adaptive antenna system in the system includes multiple sectors, and one correction transceiver is configured in some or all of the sectors, and all channels from different sectors use different vacant subcarriers.

The area of the adaptive antenna system in the system includes multiple sectors, some or all of the sectors are equipped with a correction transceiver, and channels from different sectors of different sectors use the unit in a time-division multiplexing manner.

Since the present invention automatically completes channel correction by means of active transmission on the spare orthogonal subcarriers, the correction process has no impact on normal business, thus does not affect the capacity of the system, and also has no impact on the coverage of the system through local loopback .

Description of drawings

Fig. 1 is a schematic diagram of OFDMA subcarrier allocation;

Fig. 2 is the flow chart that the present invention realizes channel correction;

FIG. 3A is a schematic diagram of a system for correcting a receiving channel according to the present invention;

Fig. 3B is a schematic diagram of the system for correcting the transmission channel according to the present invention;

FIG. 4 is a schematic diagram of a system for correcting a receiving channel according to an embodiment of the present invention.

Detailed ways

The way of allocating subcarriers determines the different modes of OFDMA system operation. If at a certain moment, not all of the subcarriers are used, there are idle subcarriers. Due to requirements such as sectorized networking, usually each sector of the OFDMA system reserves idle subcarriers in a dynamic or static manner. Taking the IEEE 802.16 standard as an example, under the PUSC (Partial Usage of SubChannel) mode in IEEE 802.16, three sectors share all subcarriers, so that each sector has a certain number of idle subcarriers, and for example In IEEE 802.16, all sub-channels are used in FUSC (Full Usage of Sub-Channel) mode. In order to reduce the interference between sectors, the load of each sector will not reach 100%, that is, a part of idle sub-carriers will be reserved. Other modes of the IEEE 802.16 standard are similar. The relationship between used subcarriers and idle subcarriers in an OFDMA system is shown in FIG. 1 .

The present invention adopts the mode of active transmission on the unique vacant orthogonal subcarriers of OFDMA system, and uses different vacant subcarriers to carry known signals (such as a bit stream of all 1s, as long as it is a known Bit Pattern) through different channels. ) for channel calibration.

Referring to Figure 2, the main process is as follows:

Step 100, collecting currently available vacant subcarriers, and then allocating according to the number of channels to be corrected, and allocating different vacant subcarriers to different channels.

Step 110, use the assigned vacant subcarriers to carry known signals on the channels that need to be corrected.

Step 120, sending the known signal carried by the spare sub-carrier to a loop formed locally by the coupler.

Step 130: Using a predetermined algorithm at the receiving end of the loop, the known signals carried by the spare subcarriers passing through different channels are divided according to channels, and estimated values reflecting the characteristics of different channels are extracted. Estimated values of information such as phase difference, time delay, and amplitude gain.

Step 140, use the estimated value of each channel to correct the communication.

Since the vacant sub-carrier is used, it has no impact on the normal business, so it does not affect the capacity of the system. In addition, the local loopback basically has no impact on the coverage of the system. According to the different directions of the calibration channels, the present invention can be used to calibrate the transmitting channel and the receiving channel respectively.

FIG. 3A is a schematic diagram of a system for calibrating a receiving channel. First, the control unit CU collects the currently available vacant subcarriers, and then allocates them according to the number of channels that need to be corrected, and assigns different vacant orthogonal subcarriers to different channels; The frequency point is sent to the local coupler after being corrected by the transceiver. The coupler mixes the normal service signal from the antenna array with the signal from the calibration transceiver and sends it to the normal transceiver; processed by the normal transceiver After (such as modulation, demodulation, encoding, decoding, etc.), the signal on the vacant subcarrier is sent to the correction calculation unit, and the calculation unit is based on a certain algorithm (a known estimation method can be used, such as maximum likelihood estimation) etc.) estimate the characteristics of different channels, pass these estimated values to the normal baseband processing unit, and then the normal baseband processing unit corrects different receiving channels according to these estimated values (phase difference, time delay difference, amplitude difference, etc. of the main correction channel, these properties are used in a similar manner.). The invention can be used for channel correction of smart antenna or MIMO.

FIG. 3B shows a schematic diagram of the system when the present invention corrects the transmission channel. First, the control unit CU collects the currently available vacant subcarriers, and then allocates them according to the number of channels to be corrected, and assigns different vacant orthogonal subcarriers to different channels; then these vacant subcarriers carry known signals and are compared with normal The service signals are sent to the local coupler at the frequency point of the transmission channel through the transceiver. The coupler not only sends the signal to the antenna array, but also sends the signal to the correction transceiver. After being processed by the correction transceiver, the The signal on the spare sub-carrier is sent to the correction calculation unit, which estimates the characteristics of different channels according to a certain algorithm, and transmits these estimated values to the normal baseband processing unit, and then the normal baseband processing unit corrects the different transmissions according to these estimated values. aisle.

Taking the IEEE802.16e base station as an example, the area of the adaptive antenna system in this type of base station is divided into three sectors, and each sector consists of multiple antennas to form an antenna array. The base station operates in PUSC mode and adaptive antenna system AAS mode for all sub-channels, and different sub-carrier clusters are used in different sectors. The structural diagram of the system for correction using the uplink receiving channel of the present invention is shown in FIG. 4 . Wherein, a correction transceiver is configured in each sector of the base station system, and each transceiver works independently. First, the control unit CU collects the vacant subcarriers currently available in each sector, and then allocates the vacant subcarriers available in each sector according to the number of channels to be corrected, and allocates different vacant orthogonal subcarriers to different channels; then the known signals are carried by these vacant sub-carriers, and together with the normal service signals, they are sent to the local coupler of the sector at the frequency of the transmission channel through the transceiver of the sector. The signal is sent to the outside of the antenna array of the sector, and the signal is also sent to the correction transceiver of the sector, and the signal on the spare subcarrier is sent to the correction calculation unit after being processed by the correction transceiver. The calculation unit estimates the characteristics of different channels according to a certain algorithm, and transmits these estimated values to the normal baseband processing unit, and then the normal baseband processing unit corrects the different transmission channels according to these estimated values.

Of course, in the present invention, the correction transceivers can be configured in different ways. In addition to configuring one for each sector mentioned above, all sectors can also share the same correction transceiver, or some sectors can share the same correction transceiver. letter machine. When multiple sectors share the same calibration transceiver, the channels of different sectors can use this unit in a time-division multiplexing manner, or use this unit in a frequency-division multiplexing manner.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (13)

1, a method for channel correction, is characterized in that, comprises the steps: A. Carrying known signals with different vacant subcarriers in different channels; B. Send the known signal carried by the spare subcarrier to a loop formed locally by the coupler; C. At the receiving end of the loop, the known signals carried by the spare subcarriers passing through different channels are divided according to different channels, and estimated values reflecting the characteristics of different channels are extracted; D. Correcting the channel using the estimated value. 2. The method according to claim 1, wherein the step before step A further comprises: collecting currently available vacant subcarriers, and then assigning different vacant subcarriers to different channels according to the number of channels to be corrected. aisle. 3. The method according to claim 1, characterized in that, for the receiving channel, the step B further comprises: B1. The known signal carried by the spare subcarrier is sent to the local coupler through the correction transceiver at the frequency point of the receiving channel, and the coupler mixes the normal service signal from the antenna array with the signal from the correction transceiver After that, it is sent to the normal transceiver for processing, and then sent to the correction calculation unit. 4. The method according to claim 1, characterized in that, for the transmission channel, the step B further comprises: the known signal carried by the vacant sub-carrier passes through the normal transceiver together with the normal service signal, The frequency point of the transmission channel is sent to the local coupler, and the coupler sends the signal to the antenna array and the calibration transceiver, and after being processed by the calibration transceiver, it is sent to the calibration calculation unit. 5. The method according to any one of claims 1 to 4, wherein said step D further comprises transmitting the estimated value to the normal baseband processing unit, and the normal baseband processing unit corrects the corresponding channel according to the estimated value . 6. A receiving channel correction system, characterized in that it includes a control unit, a correction transceiver, a local coupler, a normal transceiver, a correction calculation unit and a normal baseband processing unit; The control unit is used to collect currently available vacant subcarriers, allocate them according to the number of channels to be corrected, and allocate different vacant orthogonal subcarriers to different channels; The correction transceiver is used to receive the known signal carried by the spare subcarrier at the frequency point of the receiving channel, and send it to the local coupler; The coupler mixes the normal service signal from the antenna array with the known signal carried by the spare subcarrier, and then sends it to the normal transceiver; The normal transceiver is used to process the known signal carried by the vacant sub-carrier and send it to the correction calculation unit; The correction calculation unit is used to extract estimated values reflecting different channel characteristics and transmit them to the normal baseband processing unit; The normal baseband processing unit is used for correcting the corresponding receiving channel according to the estimated value. 7. The system according to claim 6, wherein the adaptive antenna system area in the system includes multiple sectors, each sector is equipped with a correction transceiver, and each correction transceiver works independently. 8. The system according to claim 6, wherein the adaptive antenna system area in the system includes multiple sectors, and one calibration transceiver is configured in some or all of the sectors, and all channels from different sectors are Spare subcarriers different from each other are used. 9. The system according to claim 6, characterized in that the adaptive antenna system area in the system includes multiple sectors, some or all of the sectors are equipped with a correction transceiver, and different sectors from different sectors The channel uses this unit in the way of time division multiplexing or frequency division multiplexing. 10. A transmission channel correction system, characterized in that it includes a control unit, a correction transceiver, a local coupler, a normal transceiver, a correction calculation unit, and a normal baseband processing unit; The control unit is used to collect currently available vacant subcarriers, allocate them according to the number of channels to be corrected, and allocate different vacant orthogonal subcarriers to different channels; The correction transceiver is used to accept the mixture of the known signal carried by the spare subcarrier and the service signal, and send it to the local coupler at the frequency point of the transmission channel; said local coupler for sending said signal to a calibration transceiver; The correction transceiver is used to process the signal and send the signal carried on the spare subcarrier to the correction calculation unit; The correction calculation unit is used to extract estimated values reflecting different channel characteristics and transmit them to the normal baseband processing unit; The normal baseband processing unit is used for correcting the corresponding receiving channel according to the estimated value. 11. The system according to claim 10, wherein the adaptive antenna system area in the system includes multiple sectors, each sector is equipped with a correction transceiver, and each correction transceiver works independently. 12. The system according to claim 10, characterized in that the adaptive antenna system area in the system includes multiple sectors, some or all sectors are equipped with a correction transceiver, and all channels from different sectors are Spare subcarriers different from each other are used. 13. The system according to claim 10, characterized in that the adaptive antenna system area in the system includes multiple sectors, some or all of the sectors are equipped with a correction transceiver, and different sectors from different sectors The channel uses the correction transceiver in the way of time division multiplexing or frequency division multiplexing.

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