CN102223336B - Wireless communication method and equipment - Google Patents
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Abstract
The invention provides wireless communication equipment which relates to the technology of wireless communication, and comprises a receiving antenna and a signal processing module, wherein the receiving antenna is used for receiving wireless signals transmitted by a plurality of wireless channels, the wireless signals respectively carry a plurality of subcarriers to carry out transmission, the signal processing module comprises a channel estimation unit, a channel information counting unit and a detection unit, wherein the channel estimation unit is used for estimating a frequency response value of each subcarrier, the channel information counting unit is used for counting the channel information of the wireless channels and enables the channel information to respectively generate adjustment factors corresponding to the subcarriers, and the detection unit is used for carrying out selective power adjustment to the frequency response values provided by the channel estimation unit and wireless signals of the subcarriers corresponding to the frequency response values according to adjustment factors estimated by the channel information counting unit, so that the signals after the power adjustment are detected. The invention simultaneously provides a wireless communication method.
Description
Technical Field
The present invention relates to wireless communication technologies, and in particular, to a wireless communication method and apparatus based on Orthogonal Frequency Division Multiplexing (OFDM).
Background
In a wireless communication system, a transmission signal at a transmitting end is generally transmitted through a plurality of transmission paths. Since the propagation paths experienced by the various path components of the transmitted signal arriving at the receive antenna are different, the various signal components may have different time delays, which will cause the energy of the received signal to be spread in time.
Assuming that the signal transmitted by the transmitting end is δ (t), the received signal after passing through the multipath channel can be expressed as:wherein alpha islIs the fading factor of the l path, taulIs the propagation delay of the l-th path. Maximum delay spread tau of a multipath channelmaxGenerally defined as the interval length from the time delay of the first signal component received by the receiving end to the time delay of the signal on the last distinguishable path; in practical applications, the coherence bandwidth is defined as the inverse of the maximum delay spread, i.e.: b isc≈1/τmax。
When the system bandwidth of the wireless communication system is greater than the coherence bandwidth, each Frequency component in the bandwidth will experience Frequency Selective Fading (Frequency Selective Fading), that is, for different Frequency components in the bandwidth, the wireless transmission channel will present different random responses, and each Frequency component will experience different degrees of Fading after passing through the wireless channel.
A Long-Term Evolution (LTE) system proposed by 3GPP is an OFDM-based multi-carrier system. Since the OFDM system is a wideband system, its system bandwidth is larger than the channel coherence bandwidth. Therefore, during transmission of the wireless signal in the OFDM system, each frequency component in the bandwidth will experience frequency selective fading, i.e. the data on each subcarrier is subject to different degrees of fading after passing through the channel.
In response to the data fading problem, a receiver of the LTE system usually performs automatic gain control on a wireless signal after receiving the wireless signal to compensate for fading caused by a channel. However, in the prior art, the compensation for the wireless signal is for the entire system bandwidth. Since the fading degree of each subcarrier is different in practice, the compensation is usually not sufficient for some subcarriers with larger fading degree, which may cause the data on the subcarriers to lose effective precision and be detected incorrectly, thereby causing the overall performance of the wireless communication system to be degraded. If some subcarriers with larger fading degree are compensated for, most subcarriers will saturate during a/D (analog-to-digital) conversion, which also causes the overall performance of the wireless communication system to be reduced.
Disclosure of Invention
In view of the above problems, it is desirable to provide a wireless communication method and apparatus for improving the overall performance of a wireless communication system.
The wireless communication device provided by the invention comprises a receiving antenna and a signal processing module, wherein the receiving antenna is used for receiving wireless signals transmitted through a plurality of wireless channels, the wireless signals are respectively carried on a plurality of subcarriers for transmission, the signal processing module comprises a channel estimation unit, a channel information statistic unit and a detection unit, wherein, the channel estimation unit is used for estimating the frequency response value of each subcarrier, the channel information statistic unit is used for carrying out statistics on the channel information of each wireless channel and respectively generating adjustment factors corresponding to the plurality of subcarriers, the detection unit is used for selectively adjusting the power of the frequency response value provided by the channel estimation unit and the wireless signal on the corresponding subcarrier according to the adjustment factor estimated by the channel information statistical unit, so as to detect the signal after power adjustment.
The wireless communication method provided by the invention comprises the following steps: receiving wireless signals which are transmitted by a plurality of wireless channels from a transmitting terminal of a wireless communication system, wherein the wireless signals are respectively carried on a plurality of subcarriers; estimating a frequency response value corresponding to each subcarrier according to the wireless signal; counting the channel information of each wireless channel and respectively calculating adjusting factors corresponding to the plurality of subcarriers; and respectively carrying out selective power adjustment on the frequency response value and the wireless signals on the corresponding subcarriers according to the adjustment factor so as to detect the signals after power adjustment.
In the wireless communication method and the wireless communication device provided by the invention, the channel information corresponding to each sub-band is counted by the channel information counting unit and corresponding adjustment factors are respectively generated, so that the detection unit can perform differentiated power adjustment on wireless data carried by each sub-carrier by taking the sub-carrier as a unit, thereby accurately and effectively compensating the influence of frequency selective fading on the data on each sub-carrier, improving the data detection precision and further improving the overall performance of the system.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment of a wireless communication device according to the present invention.
Fig. 2 is a schematic diagram of a connection structure of a channel estimation unit, a channel information statistics unit and a detection unit of the wireless communication device shown in fig. 1.
Fig. 3 is a flowchart of a wireless communication method according to an embodiment of the present invention.
Detailed Description
The invention carries out channel estimation on each wireless channel at the wireless receiving end and carries out power adjustment on each sub-frequency band of the system bandwidth according to the statistical result of the channel estimation, thereby leading each sub-frequency band to carry out differentiated compensation according to the actual fading condition and improving the overall performance of the whole wireless communication system.
Please refer to fig. 1, which is a schematic structural diagram of a wireless communication device according to an embodiment of the present invention. The wireless communication device 100 may be a wireless receiving device that is provided at a receiving end of a wireless communication system. The wireless communication device 100 may be applied in a wireless communication system employing Orthogonal Frequency Division Multiplexing (OFDM), such as a Long Term Evolution (LTE) system, which includes a receiving antenna 110 and a signal processing module 120.
The receiving antenna 110 is used for receiving wireless signals transmitted by a transmitting end of the wireless communication system and transmitted through a wireless network. Wherein the wireless signal may be transmitted over a plurality of wireless channels in a wireless network. In one embodiment, the system effective bandwidth of the wireless communication system may be divided into a plurality of sub-bands, wherein each sub-band corresponds to at least one sub-carrier. The wireless data sent by the transmitting end may be carried on a plurality of subcarriers, and the plurality of subcarriers for carrying the wireless data may further perform transmission of wireless signals in an OFDM manner.
The signal processing module 120 is configured to process the wireless signal received by the receiving antenna 110 to recover the wireless data from the multiple subcarriers. In a specific embodiment, the signal processing module 120 may include: automatic Gain Control (AGC) section 121, a/D conversion section 122, prefix removal section 123, demodulation section 124, channel estimation section 125, channel information statistic section 126, data detection section 127, and channel decoding section 128.
The AGC unit 121 is configured to perform analog AGC processing on the wireless signal received by the receiving antenna 110 to compensate for fading of the wireless signal after being transmitted through the wireless channel. In particular implementations, the AGC unit 121 can perform uniform power adjustment on the wireless signal across the entire system bandwidth.
The a/D conversion unit 122 is configured to perform analog/digital conversion processing on the wireless signal subjected to the uniform power adjustment by the AGC unit 121, so as to quantize the wireless signal into a digital signal for subsequent processing.
The Prefix removing unit 123 may be a Cyclic Prefix (CP) removing functional module, which is configured to perform CP removing processing on the output signal of the a/D conversion unit 122 to remove the CP carried in the signal. Generally, the cyclic prefix is superimposed on the wireless signal before signal transmission in order to overcome multipath interference at the transmitting end of the wireless communication system, and is mainly used for ensuring orthogonality of each subcarrier.
The demodulation unit 124 may be a Fast Fourier Transform (FFT) unit, which is mainly used for OFDM symbol demodulation of the output signal of the prefix removing unit 123.
The channel estimation unit 125 is configured to estimate a frequency response of a wireless channel from a transmitting end to the receiving antenna 110 in the wireless communication system, i.e., a specific frequency response value on each subcarrier, according to the signal output by the demodulation unit 124. For example, the channel estimation unit 125 may obtain, according to the received radio signal sequence, amplitude and phase distortions generated in channel transmission of the radio signal and superimposed white gaussian noise, and further identify a time domain transmission characteristic and/or a frequency domain transmission characteristic of the radio transmission channel, so as to obtain a specific frequency response value of each subcarrier. Further, the channel estimation unit 125 may also provide the frequency response values of the subcarriers estimated by the channel estimation unit to the detection unit 127. In a specific embodiment, the channel estimation unit 125 may include an LS channel estimation sub-module 201 for performing LS channel estimation processing on a wireless channel, and a time/frequency domain interpolation sub-module 202 for performing time domain or frequency domain interpolation processing on an LS channel estimation result.
The channel information statistic unit 126 is connected to the output end of the LS channel estimation sub-module 201, and further connected to the data detection unit 127, and is capable of performing statistics on each wireless channel in the frequency domain by using the LS channel estimation result at the RS, and providing a corresponding adjustment factor for the detection module 127 according to the statistical result. Functionally, the channel information statistic unit 126 can correspond to a digital AGC block. In this embodiment, since the channel information statistics of the channel information statistics unit 126 is performed in the frequency domain (after the FFT module), it is possible to perform statistics on each sub-band in the system bandwidth and then provide an adjustment factor in each frequency band, which also makes up for the disadvantage of the analog AGC in time domain adjustment, and can better compensate for the frequency selective fading caused by the wireless channel.
The data detecting unit 127 may be a multiple-input multiple-output (MIMO) detecting unit, and is configured to perform selective power adjustment on the frequency response value provided by the channel estimating unit 125 and the wireless data on the subcarrier corresponding to the frequency response value according to the adjustment factor provided by the channel information counting unit 126, so as to detect the data after power adjustment, so as to recover the wireless data transmitted by the transmitting end of the wireless communication system. In a specific embodiment, the power adjustment of the wireless data may be performed in units of subcarriers.
The channel decoding unit 128 is used for performing signal decoding to remove redundant information in the signal output by the data detecting unit 127, where the redundant information may be redundant bit information added by the transmitting end to improve transmission reliability.
The wireless communication device 100 provided in this embodiment is provided with the channel information statistics unit 126, and the channel information statistics unit 126 performs statistics on the channel information corresponding to each sub-band and generates corresponding adjustment factors, respectively, so that the detection module 127 can selectively perform power adjustment in units of sub-carriers. Thus, the wireless communication device 100 can effectively compensate for the influence of frequency selective fading on data on each subcarrier, thereby improving data detection accuracy and improving overall performance of the system.
For a better understanding of the present invention, an alternative implementation of the channel information statistics unit 126 in the wireless communication device 100 is described in detail below.
Specifically, in N, over the entire system bandwidthfThe whole system bandwidth is divided into M sub-bands by taking the sub-carriers as a unit, whereinN is the number of effective subcarriers in the system bandwidth. In the time domain, N is selectedtThe OFDM symbols are used as a unit, and the time-frequency domain cross part is used as a statistical unit.
The channel information statistics unit 126 may extract a part of REs from the statistics unit for statistics when performing channel information statistics, and the statistics result of the part of REs may be used to represent the channel statistics information of the whole statistics unit. For example, the channel information statistics unit 126 may select the channel estimation result at the RS for channel information statistics, and may count the average power, the average channel strength, and the like. With the statistical information, the channel information statistics unit 126 can further obtain an adjustment factor for the data detection unit 127 to detect the data in the statistics unit.
Within the whole system bandwidth, can be NRBPRB pairs (Physical Resource Block Pair, Physical Resource data Block Pair)) Performing channel average power statistics for each unit, wherein the average power is used to obtain an adjustment factor for the NRBAnd the data in each PRB pair is detected. Wherein the system bandwidth of the wireless communication system is divided into
Sub-band, NRB DLIs the number of PRBs within the system bandwidth. In addition, the PRB pair may be a cross portion that spans 12 subcarriers in the frequency domain and one subframe in the time domain, and may correspond to two PRBs (N) adjacent in the time domainf＝12·NRB，
). In specific implementation, the channel information statistic unit 126 can utilize the LS channel estimation result at RS
r is equal to {0, 1}, p is equal to {0, 1, 2, 3} to NRBAnd counting the channel power of each PRB pair, wherein r represents a receiving antenna number, and p represents a transmitting antenna number. Because the statistical characteristics of the LS channel estimation result are not changed by the time/frequency domain interpolation, that is, the channel information obtained by the time/frequency domain interpolation has the same statistical characteristics as the channel information obtained by the LS channel estimation, the calculation amount can be greatly reduced.
Order to
The channel information statistics unit 126 may first calculate P by the following formula, where P represents the number of OFDM symbols carrying RS transmitted by an antenna port P in one subframeLS，m：
Wherein,
is largest for mth sub-bandPRB number; Δ N ═ 2 (N)max，m-m·NRB)。
Further, the track information statistic unit 126 can be represented by a formula
The corresponding adjustment factor delta can be calculatedLS，m。
And, the channel information statistic unit 126 may convert δLS，mThe channel information and data in the module are adjusted by transmitting to the detection unit 127, so that the purpose of correct detection is achieved, and the system performance is improved.
Through the above description, when the wireless communication device provided in the embodiment of the present invention performs channel information statistics, according to the division of the statistical units, the following two limit situations may occur:
(1) the channel information statistics can be carried out by taking the whole system bandwidth as a statistical unit to obtain an adjustment factor, which is equivalent to carrying out power adjustment on AGC adjusted data once again, and the method is still favorable for improving the effective precision of data entering a detection module and improving the system performance.
(2) If data adjustment is required in RE units, it can be made small according to the supply to the detection unit 127.
It can be seen that, in the present embodiment, the smaller the channel information statistical unit division, the larger the calculation amount. Suitable statistical units can thus be divided according to simulations in combination with the maximum delay spread and doppler shift of the system. Available coherent bandwidth B due to channel variation in frequency domaincDescribing how fast and slow the change in the time domain is the available coherence time TcDescription of the coherence bandwidth BcRefers to a specific frequency range in which any two frequency components have strong amplitude correlation and are proportional to the inverse of the maximum delay spread, Bc≈1/τmax(ii) a Coherent time refers to the statistical average of the time interval over which the channel impulse response remains constant, TcProportional to maximum DopplerInverse of the frequency shift, Tc≈1/fmWherein f ismIs the maximum doppler shift. The variation speed of the channel in the time domain and the frequency domain also determines the division condition of the statistical unit in the time domain and the frequency domain, namely determines NtAnd NfThe size of (2). N is a radical oftIs taken to be the inverse of the maximum doppler shift (coherence time T)c) Proportional ratio, NfIs taken to be the inverse of the maximum delay spread (coherence bandwidth B)c) Is in direct proportion. In practical application, comprehensive consideration can be carried out between performance and calculation amount to determine the size of a statistical unit, namely to determine NtAnd NfThe value of (a).
Based on the above wireless communication device 100, the present invention further provides a wireless communication method. Please refer to fig. 3, which is a flowchart illustrating a wireless communication method according to an embodiment of the present invention. The wireless communication method may include: step S1, receiving a wireless signal from a transmitting end of the wireless communication system and transmitted through a plurality of wireless channels, wherein the wireless signal is respectively carried on a plurality of subcarriers; step S2, estimating a frequency response value corresponding to each subcarrier according to the wireless signal; step S3, counting channel information of each wireless channel and calculating adjustment factors corresponding to the plurality of subcarriers, respectively; step S4, detecting the data carried by each subcarrier according to the frequency response value, and performing differential power adjustment on the data carried by each subcarrier in the frequency domain according to the adjustment factor.
It should be understood that the wireless communication method provided by this embodiment may be implemented in the wireless communication device 100 of the previous embodiment, and correspondingly, the specific implementation process of each step of the wireless communication method provided by this embodiment may refer to the description of the above embodiment.
In particular, in an alternative, the step of counting the channel information of each wireless channel in step S3 may include: according to a specific number of OFDM symbols selected in a time domain, taking the intersection part of the time domain and a frequency domain corresponding to the selected OFDM symbols as a statistical unit; counting the extracted partial RE from the counting unit to calculate corresponding channel statistical information; and calculating the adjustment factor corresponding to each subcarrier according to the channel statistical information.
Or, in another alternative, the step of counting the channel information of each wireless channel may also include: determining a statistical unit of the channel information statistics according to the maximum delay spread and the Doppler frequency shift of the system; performing incomplete statistics on the channel information in the statistical unit, and taking a statistical result obtained by the incomplete statistics as statistical information of a corresponding channel; and calculating the adjustment factor corresponding to each subcarrier according to the channel statistical information.
Further, the wireless communication method provided in the embodiment of the present invention may further include: before channel information statistics, analog AGC, A/D conversion, prefix removal processing and demodulation processing are carried out on a received wireless signal. The specific processes of analog AGC, a/D conversion, prefix removal processing, and demodulation processing may refer to the above embodiments, and are not described in detail below.
Although the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention.
Claims (8)
1. A wireless communication device comprises a receiving antenna and a signal processing module, wherein the receiving antenna is used for receiving wireless signals transmitted through a plurality of wireless channels, and the wireless signals are respectively carried on a plurality of subcarriers for transmission; the channel information statistical unit is used for counting the channel information of each wireless channel and respectively generating adjusting factors corresponding to the plurality of subcarriers, and when the channel information statistical unit is used for carrying out channel information statistics, according to a specific number of OFDM symbols selected in a time domain, the cross part of the corresponding time domain and frequency domain is taken as a statistical unit, and part of REs are extracted from the statistical unit for statistics so as to calculate the corresponding channel statistical information; the detection unit is used for selectively adjusting the power of the frequency response value provided by the channel estimation unit and the wireless signal on the corresponding subcarrier according to the adjustment factor estimated by the channel information statistical unit, so as to detect the signal after power adjustment.
2. The wireless communication device as claimed in claim 1, wherein the channel estimation unit comprises an LS channel estimation sub-module for performing LS channel estimation processing on each channel, and a time/frequency domain interpolation sub-module for performing time domain or frequency domain interpolation processing on the LS channel estimation result.
3. The wireless communication device as claimed in claim 2, wherein the channel information statistic unit is connected between the output of the LS channel estimation sub-module and the detection unit.
4. The wireless communication device of claim 1, further comprising: and the automatic gain control unit is connected to the receiving antenna and is used for uniformly performing analog automatic gain control processing on the wireless signals received by the receiving antenna in the whole system bandwidth.
5. The wireless communication device of claim 4, further comprising: a demodulation unit, arranged at the front end of the channel estimation unit, for performing OFDM symbol demodulation on the wireless signal received by the receiving antenna before the wireless signal is input to the channel estimation unit.
6. A method of wireless communication, comprising:
receiving wireless signals which are transmitted by a plurality of wireless channels from a transmitting terminal of a wireless communication system, wherein the wireless signals are respectively carried on a plurality of subcarriers;
estimating a frequency response value corresponding to each subcarrier according to the wireless signal;
counting the channel information of each wireless channel and respectively calculating adjusting factors corresponding to the plurality of subcarriers;
selectively adjusting the power of the wireless signals on the frequency response value and the corresponding subcarriers according to the adjustment factor, so as to detect the signals after power adjustment;
the step of counting the channel information of each wireless channel comprises the following steps:
according to a specific number of OFDM symbols selected in a time domain, taking the intersection part of the time domain and a frequency domain corresponding to the selected OFDM symbols as a statistical unit;
extracting part of REs from the statistical unit to carry out statistics so as to calculate corresponding channel statistical information;
and calculating the adjustment factor corresponding to each subcarrier according to the channel statistical information.
7. The wireless communication method of claim 6, wherein the step of counting channel information of each wireless channel comprises:
determining a statistical unit of the channel information statistics according to the maximum delay spread and the Doppler frequency shift of the system;
performing incomplete statistics on the channel information in the statistical unit, and taking a statistical result obtained by the incomplete statistics as statistical information of a corresponding channel;
and calculating the adjustment factor corresponding to each subcarrier according to the channel statistical information.
8. The wireless communication method of claim 7, further comprising: before channel information statistics, analog automatic gain control, A/D conversion, prefix removal processing and demodulation processing are carried out on a received wireless signal.
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| CN101502029A (en) * | 2006-11-30 | 2009-08-05 | 松下电器产业株式会社 | Radio transmission device, radio reception device, radio transmission method, and radio reception method |
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| CN1708999A (en) * | 2002-10-29 | 2005-12-14 | 高通股份有限公司 | Uplink pilot and signaling transmission in wireless communication systems |
| CN1956352A (en) * | 2005-10-28 | 2007-05-02 | Ut斯达康通讯有限公司 | Distribution method of transmitting antenna speed, power in V-BLAST system |
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