阅读说明：本技术 一种Chirp调制信号的信道估计和均衡方法 (Channel estimation and equalization method for Chirp modulation signal ) 是由 段红光 郑建宏 罗一静 王月 于 2019-09-12 设计创作，主要内容包括：本发明涉及一种Chirp调制信号的信道估计和均衡方法,属于物联网技术领域。在Chirp信号收发过程中,由于Chirp信号的调制特点,接收机接收到的信号幅度是固定的,使用自动增益(AGC)控制即可完成时域均衡处理,但这样不方便对接收到的时域Chirp信号直接进行信道估计和均衡。因此在本发明中,将首先对收到的时域Chirp信号进行快速傅里叶变换,将时域Chirp信号变换到频域进行信道估计和均衡,这有利于解决无线信道中的频率选择性衰落问题。(The invention relates to a channel estimation and equalization method for a Chirp modulation signal, and belongs to the technical field of Internet of things. In the Chirp signal transceiving process, due to the modulation characteristics of the Chirp signal, the amplitude of the signal received by the receiver is fixed, and the time domain equalization processing can be completed by using Automatic Gain Control (AGC), but the channel estimation and equalization can not be directly performed on the received time domain Chirp signal conveniently. Therefore, in the invention, the received time domain Chirp signal is firstly subjected to fast Fourier transform, and the time domain Chirp signal is transformed to the frequency domain for channel estimation and equalization, which is beneficial to solving the problem of frequency selective fading in a wireless channel.)

1. A method for channel estimation and equalization of Chirp modulation signals is characterized in that: the method comprises the following steps:

Firstly, the method comprises the following steps: frequency domain channel estimation process of Chirp signal

If the Chirp signal received by the receiver is a leading Chirp symbol carrying synchronization, locally generating the same Chirp frequency domain data, performing channel estimation by using the locally generated Chirp frequency domain data and the received leading Chirp frequency domain data, and estimating the channel characteristics of each frequency point of the Chirp signal, wherein the channel characteristics are recorded as Hi; wherein i represents the number of each frequency point;

If a plurality of leading Chirp symbols exist, the frequency domain channel characteristics adopt the average value of H obtained by estimating each leading Chirp channel; is marked aswhereinrepresenting the channel characteristics of each frequency point, Hi][j]Representing the channel characteristics of the ith frequency point on the jth leading Chirp symbol;

secondly, the method comprises the following steps: frequency domain channel equalization process for Chirp signals

If a Chirp signal received by a receiver is a Chirp data symbol for carrying a service, and frequency domain data is recorded as data _ Chirp _ F [ i ], wherein the value range of i is 0,1, 2.

wherein ()^*Representing the conjugation operation, and then carrying out Chirp symbol judgment processing on the data _ Chirp _ Eq _ F.

2. The method of claim 1, wherein the method for channel estimation and equalization of a Chirp modulated signal comprises: the frequency domain channel estimation process of the Chirp signal comprises the following steps:

Step 11: after leading data received by the radio frequency module is received, converting an analog Chirp signal into a digital Chirp signal through digital-to-analog conversion (ADC); the modulation time length of each Chirp symbol is fixed, and if the modulation time length is T seconds and the sampling rate of the ADC is R points/second, the length of each digital Chirp symbol is N-TxR points;

The baseband signal processing module carries out N-point FFT (fast Fourier transform) on the received complete Chirp preamble to obtain N-point Chirp frequency domain data, and the N-point Chirp frequency domain data are marked as pilot _ Chirp _ F [ i ], wherein the value range of i is 0,1,2,.

Step 12: locally generating frequency domain data of an upper Chirp and a lower Chirp, wherein the number of frequency domain discrete points is N; generating discrete N-point Chirp symbol data by using a Chirp symbol formula, and then performing N-point FFT (fast Fourier transform) on the N data to generate frequency domain data of a local Chirp symbol, wherein the frequency domain data is marked as local _ Chirp _ F [ i ], and the value range of i is 0,1,2, 1.. and N-1;

Step 13: performing frequency domain channel estimation by using received leading Chirp symbol data, and recording the frequency domain channel estimation as H [ i ], wherein the value range of i is 0,1, 2. The channel characteristic obtained at each frequency domain point is H [ i ] ═ pilot _ Chirp _ F [ i ]/local _ Chirp _ F [ i ];

Step 14: in a scene of a plurality of leading Chirp symbols, respectively calculating the frequency domain channel characteristics corresponding to each leading according to the methods from step 1 to step 3, and marking as H [ i ] [ j ], wherein the frequency domain channel characteristics of the jth Chirp symbol at a frequency point i are represented, and the value range 0,1, 2., the value range 0,1, 2.., of N-1, j, L-1, L is the number of the leading Chirp symbols;

Finally, the channel characteristics of the Chirp signal in the frequency domain are obtained by estimation

3. The method of claim 1, wherein the method for channel estimation and equalization of a Chirp modulated signal comprises: the frequency domain channel equalization process of the Chirp signal comprises the following steps of:

step 21: the method comprises the following steps that a Chirp signal received by a radio frequency module is a data symbol, the Chirp signal is subjected to ADC (analog-to-digital converter) conversion at the radio frequency module, and an analog signal is converted into a digital signal; assuming that the time length of each Chirp symbol is T seconds, and the sampling rate of the ADC is R points/second, the length of each digital Chirp symbol is N ═ TxR points;

Then, performing N-point FFT (fast Fourier transform) on the digital Chirp symbol to obtain Chirp symbol data of a frequency domain, and marking the Chirp symbol data as data _ Chirp _ F [ i ], wherein the value range of i is 0,1, 2.

step 22: and performing channel equalization by using the frequency domain channel characteristics estimated by the Chirp symbols of the preamble, wherein the calculation formula is as follows:

Namely, the frequency domain data of the received Chirp symbol is multiplied by the conjugate of the channel characteristic;

Step 23: and performing Chirp demodulation on the data _ Chirp _ Eq _ F in a baseband signal processing module to obtain data content carried by a Chirp symbol.

Technical Field

The invention belongs to the technical field of Internet of things, and relates to a method for channel estimation and equalization of a Chirp modulation signal.

background

frequency modulated Spread Spectrum (CSS) is an important Spread Spectrum method in Spread Spectrum communications. The Chirp signal has a good autocorrelation characteristic because the instantaneous frequency changes linearly with time in one symbol period, and is a typical spread spectrum signal. Because the Chirp signal pulse compression has strong immunity to frequency offset and Doppler shift, the multipath resolution is high, the peak-to-average power of the transmitted signal is small, and the CSS communication system has the advantages of strong anti-interference capability, insensitivity to frequency offset and Doppler shift, low system complexity and power consumption and the like, the Chirp signal pulse compression is widely applied to various Internet of things systems.

In the conventional CCS communication system, since the wireless bandwidth occupied by the Chirp signal is narrow and is generally only a few hundred hertz, the factors affecting the reception performance of the Chirp signal mainly include signal power and multipath, and thus it can be considered that the problem of frequency selective fading does not exist in the transmission process of the Chirp signal. In a CCS communication system, only a Preamble Chirp symbol and a Chirp symbol for directly modulating data generally exist, where the Preamble Chirp is mainly used for frame synchronization in a data transmission process, so that a receiving end can search for a start position of a data frame without considering channel estimation. In the conventional narrow-band CCS communication system, the Chirp symbol has a small operating bandwidth, and frequency selective fading processing is not required, so that pilot symbols do not need to be inserted when data symbols are transmitted.

due to the development of the communication of the internet of things in recent years, people also put higher requirements on the communication of the internet of things. Due to the development of hardware technology, the Chirp signal processing capability is enhanced. The Chirp symbol bandwidth is developed to several MHz from tens of kHz to hundreds of kHz, and because the CCS communication environment in the Internet of things system is relatively complex, the transmission distance is long, the signal fading is large and the interference is serious, if the frequency selective fading problem in the transmission process is not considered, the advantage of wideband Chirp transmission is difficult to embody.

The development of a hardware technology improves the performance of a Chirp receiver, and the receiving processing of a Chirp signal can be divided into a radio frequency receiving part and a baseband signal processing part, so that favorable conditions are provided for the Chirp signal to carry out channel equalization. The invention provides a solution for the problem of frequency selective fading of a broadband Chirp signal in the application of the Internet of things.

Disclosure of Invention

in view of the above, the present invention is directed to a method for channel estimation and equalization of a Chirp modulated signal. The receiver consists of a radio frequency receiving module and a baseband signal processing module. The radio frequency module receives a wireless Chirp signal, then down-converts the wireless Chirp signal to a Chirp analog baseband signal, then performs analog-to-digital conversion (ADC for short), converts the analog signal into a digital signal to form baseband data (IQ data for short) with orthogonal phases, and sends the baseband data to the baseband signal processing module.

in order to achieve the purpose, the invention provides the following technical scheme:

A method for channel estimation and equalization of Chirp modulated signals comprises the following steps:

Firstly, the method comprises the following steps: frequency domain channel estimation process of Chirp signal

If the Chirp signal received by the receiver is a leading Chirp symbol carrying synchronization, locally generating the same Chirp frequency domain data, performing channel estimation by using the locally generated Chirp frequency domain data and the received leading Chirp frequency domain data, and estimating the channel characteristics of each frequency point of the Chirp signal, wherein the channel characteristics are recorded as Hi; wherein i represents the number of each frequency point;

If a plurality of leading Chirp symbols exist, the frequency domain channel characteristics adopt the average value of H obtained by estimating each leading Chirp channel; is marked asWhereinRepresenting the channel characteristics of each frequency point, Hi][j]Representing the channel characteristics of the ith frequency point on the jth leading Chirp symbol;

Secondly, the method comprises the following steps: frequency domain channel equalization process for Chirp signals

If a Chirp signal received by a receiver is a Chirp data symbol for carrying a service, and frequency domain data is recorded as data _ Chirp _ F [ i ], wherein the value range of i is 0,1, 2.

Wherein ()^*Representing the conjugation operation, and then carrying out Chirp symbol judgment processing on the data _ Chirp _ Eq _ F.

Optionally, the frequency domain channel estimation process of the Chirp signal includes the following steps:

Step 11: after leading data received by the radio frequency module is received, converting an analog Chirp signal into a digital Chirp signal through digital-to-analog conversion (ADC); the modulation time length of each Chirp symbol is fixed, and if the modulation time length is T seconds and the sampling rate of the ADC is R points/second, the length of each digital Chirp symbol is N-TxR points;

the baseband signal processing module carries out N-point FFT (fast Fourier transform) on the received complete Chirp preamble to obtain N-point Chirp frequency domain data, and the N-point Chirp frequency domain data are marked as pilot _ Chirp _ F [ i ], wherein the value range of i is 0,1,2,.

Step 12: locally generating frequency domain data of an upper Chirp and a lower Chirp, wherein the number of frequency domain discrete points is N; generating discrete N-point Chirp symbol data by using a Chirp symbol formula, and then performing N-point FFT (fast Fourier transform) on the N data to generate frequency domain data of a local Chirp symbol, wherein the frequency domain data is marked as local _ Chirp _ F [ i ], and the value range of i is 0,1,2, 1.. and N-1;

Step 13: performing frequency domain channel estimation by using received leading Chirp symbol data, and recording the frequency domain channel estimation as H [ i ], wherein the value range of i is 0,1, 2. The channel characteristic obtained at each frequency domain point is H [ i ] ═ pilot _ Chirp _ F [ i ]/local _ Chirp _ F [ i ];

Step 14: in a scene of a plurality of leading Chirp symbols, respectively calculating the frequency domain channel characteristics corresponding to each leading according to the methods from step 1 to step 3, and marking as H [ i ] [ j ], wherein the frequency domain channel characteristics of the jth Chirp symbol at a frequency point i are represented, and the value range 0,1, 2., the value range 0,1, 2.., of N-1, j, L-1, L is the number of the leading Chirp symbols;

finally, the channel characteristics of the Chirp signal in the frequency domain are obtained by estimation

Optionally, the frequency domain channel equalization process of the Chirp signal includes the following steps:

step 21: the method comprises the following steps that a Chirp signal received by a radio frequency module is a data symbol, the Chirp signal is subjected to ADC (analog-to-digital converter) conversion at the radio frequency module, and an analog signal is converted into a digital signal; assuming that the time length of each Chirp symbol is T seconds, and the sampling rate of the ADC is R points/second, the length of each digital Chirp symbol is N ═ TxR points;

Then, performing N-point FFT (fast Fourier transform) on the digital Chirp symbol to obtain Chirp symbol data of a frequency domain, and marking the Chirp symbol data as data _ Chirp _ F [ i ], wherein the value range of i is 0,1, 2.

step 22: and performing channel equalization by using the frequency domain channel characteristics estimated by the Chirp symbols of the preamble, wherein the calculation formula is as follows:

Namely, the frequency domain data of the received Chirp symbol is multiplied by the conjugate of the channel characteristic;

Step 23: and performing Chirp demodulation on the data _ Chirp _ Eq _ F in a baseband signal processing module to obtain data content carried by a Chirp symbol.

The invention has the beneficial effects that:

Firstly, the method comprises the following steps: in the conventional CCS communication system, since the Chirp modulation bandwidth ratio is small, and is only several tens khz to several hundreds khz, the frequency selective fading problem existing in the Chirp communication system is not basically considered. However, in practical application, the occupied bandwidth of the Chirp symbol is larger and larger, which reaches several mhz, and the influence of frequency selective fading on the demodulation of the Chirp signal is larger and larger. The invention provides a method for performing frequency domain channel estimation and equalization on a wideband Chirp signal.

Secondly, the method comprises the following steps: in the Chirp signal transceiving process, due to the modulation characteristics of the Chirp signal, the amplitude of the signal received by the receiver is fixed, and the time domain equalization processing can be completed by using Automatic Gain Control (AGC), but the channel estimation and equalization can not be directly performed on the received time domain Chirp signal conveniently. Therefore, in the invention, the received time domain Chirp signal is firstly subjected to fast Fourier transform, and the time domain Chirp signal is transformed to the frequency domain for channel estimation and equalization, which is beneficial to solving the problem of frequency selective fading in a wireless channel.

Thirdly, the method comprises the following steps: in a CCS communication system, transmissions are made in a frame burst format, with each frame divided into a preamble portion and a data portion. The invention uses the front part not only for frame synchronous search, but also for frequency domain channel estimation, if there are several front sequences, then uses all front parts to estimate channel, to improve the accuracy of frequency domain channel estimation.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a block diagram of a Chirp signal receiver in a CCS communication system according to the present invention;

Fig. 2 is a frequency domain channel characteristic estimation process of preamble symbols;

FIG. 3 is a process of frequency domain channel equalization of data symbols;

Fig. 4 is a time domain waveform of instantaneous frequencies and real parts of upper and lower Chirp;

fig. 5 is a frame format of a Chirp modulation scheme in an internet of things system;

fig. 6 is a schematic diagram of a Chirp signal receiver;

FIG. 7 is a frame synchronization and channel estimation process;

Fig. 8 is a service data reception process.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

the same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.

In a CCS communication system, particularly in the application of the Internet of things, Chirp modulation and demodulation are processed in an analog mode, and the method is simple and low in cost. In recent years, due to the development of integrated circuits, the Chirp signal processing is mainstream by adopting a digital mode, and the receiver and the transmitter can be realized by adopting a combined mode of a radio frequency module and a baseband signal processing module, so that the method is favorable for performing FFT conversion on a Chirp symbol to a frequency domain for processing.

Before describing the specific embodiment of the present invention, first, the characteristics of the Chirp signal are described, and the Chirp signal in one symbol period can be expressed as follows:

Wherein a represents the signal amplitude; f. of₀Is a signal center frequency point; μ is the chirp slope; theta₀Is the initial phase; t represents the period of the symbol, the bandwidth of the signal is represented as B ═ μ T, and the instantaneous expression of the Chirp signal can be obtained according to the above formula

When mu is greater than 0, the instantaneous frequency of the Chirp signal is continuously increased, and s (t) is called as an up-sweep signal. When mu is less than 0, the instantaneous frequency of the Chirp signal is continuously reduced, and s (t) is called as a lower sweep frequency signal. As shown in fig. 4.

In the invention, the length of a Chirp signal in a time domain is T, and the bandwidth is B. And obtaining a continuous analog Chirp signal of the T time length by using an s (T) calculation formula. For convenience of processing, s (t) may be sampled to obtain digital Chirp symbol data. Assuming that N-point sampling is performed on a Chirp time-domain signal within one symbol period T, N-point FFT transformation is performed on time-domain data to obtain N-point frequency-domain data. The time domain Chirp signal processing problem can be handled by converting to the frequency domain.

specifically processing a Chirp signal in a frequency domain, wherein a baseband signal processing module performs Fast Fourier Transform (FFT) on a received Chirp digital signal, converts the received Chirp digital signal from a time domain into a frequency domain, and then performs frequency domain processing on the Chirp digital signal.

a schematic diagram of a Chirp receiver is shown in fig. 1.

In the present embodiment, the baseband signal processing is mainly divided into two processes. I.e. frequency domain channel estimation and equalization of the Chirp signal.

Firstly, the method comprises the following steps: frequency domain channel estimation process of Chirp signal

And if the Chirp signal received by the receiver is a synchronous leading Chirp symbol, locally generating the same Chirp frequency domain data, performing channel estimation by using the locally generated Chirp frequency domain data and the received leading Chirp frequency domain data, and estimating the channel characteristics of each frequency point of the Chirp signal, wherein the channel characteristics are recorded as H [ i ]. Where i denotes the number of each frequency bin.

And if a plurality of leading Chirp symbols exist, the frequency domain channel characteristics adopt the average value of H obtained by estimating each leading Chirp channel. Is marked asWhereinrepresenting the channel characteristics of each frequency point, Hi][j]And the channel characteristics of the ith frequency point on the jth leading Chirp symbol are shown. The specific steps are shown in fig. 2.

step 1: after the leading data is received by the radio frequency module, the analog Chirp signal is converted into a digital Chirp signal through digital-to-analog conversion (ADC). The modulation time length of each Chirp symbol is fixed, and assuming that T seconds, and the sampling rate of the ADC is R points/second, the length of each digital Chirp symbol is N-TxR points.

and the baseband signal processing module performs N-point FFT (fast Fourier transform) on the received complete Chirp preamble to obtain N-point Chirp frequency domain data, and the N-point Chirp frequency domain data is marked as pilot _ Chirp _ F [ i ], wherein the value range of i is 0,1, 2. As in step 1 of figure 2.

Step 2: and locally generating frequency domain data of an upper Chirp and a lower Chirp, wherein the number of frequency domain discrete points is N. Generating discrete N-point Chirp symbol data by using a Chirp symbol formula, and then performing N-point FFT (fast Fourier transform) on the N data to generate frequency domain data of a local Chirp symbol, wherein the frequency domain data is marked as local _ Chirp _ F [ i ], and the value range of i is 0,1, 2. As in step 2 of figure 2.

And step 3: and performing frequency domain channel estimation by using the received Chirp symbol data of the preamble, wherein the frequency domain channel estimation is recorded as H [ i ], and the value range of i is 0,1, 2. The channel characteristic obtained at each frequency domain point is H [ i ] ═ pilot _ Chirp _ F [ i ]/local _ Chirp _ F [ i ]. As in step 3 of figure 2.

And 4, step 4: in a scene of a plurality of leading Chirp symbols, according to the methods from the step 1 to the step 3, respectively calculating the frequency domain channel characteristics corresponding to each leading, and marking as H [ i ] [ j ], representing the channel characteristics of the jth Chirp symbol at a frequency point i, wherein the value range of i is 0,1, 2.

Finally, the channel characteristics of the Chirp signal in the frequency domain are obtained by estimationas shown in steps 4 and 5 of fig. 2.

secondly, the method comprises the following steps: frequency domain channel equalization process for Chirp signals

If a Chirp signal received by a receiver is a Chirp data symbol for carrying a service, which is denoted as data _ Chirp _ F [ i ], wherein the value range of i is 0,1, 2.

Wherein ()^*Representing the conjugation operation, and then carrying out Chirp symbol judgment processing on the data _ Chirp _ Eq _ F. The specific steps are shown in fig. 3.

Step 1: the Chirp signal received by the radio frequency module is a data symbol, and the Chirp signal is firstly subjected to ADC (analog-to-digital converter) conversion in the radio frequency module, and an analog signal is converted into a digital signal. Assuming that the time length of each Chirp symbol is T seconds, and the sampling rate of the ADC is R points/second, the length of each digital Chirp symbol is N — TxR points.

And then carrying out N-point FFT (fast Fourier transform) on the digital Chirp symbol to obtain Chirp symbol data of a frequency domain, and marking the Chirp symbol data as data _ Chirp _ F [ i ], wherein the value range of i is 0,1, 2. As in step 1 of fig. 3.

step 2: and performing channel equalization by using the frequency domain channel characteristics estimated by the Chirp symbols of the preamble, wherein the calculation formula is as follows:

i.e. the frequency domain data received with the Chirp symbol is multiplied by the conjugate of the channel characteristics. As in step 2 of fig. 3.

And step 3: and performing Chirp demodulation on the data _ Chirp _ Eq _ F in a baseband signal processing module to obtain data content carried by a Chirp symbol.

In this embodiment, in an actual scene of the internet of things, data transmission is generally performed by sending one burst, where one burst is also referred to as a send data packet, and each data packet has a fixed frame format, as shown in fig. 5. A frame format consists of two parts, one part for synchronization indication of packet reception, called preamble symbols, and the other part for carrying traffic data, called data symbols.

In this embodiment, it is assumed that the time length of the Chirp symbol is T seconds, the signal bandwidth is B, and the number of preamble symbols is K. The schematic diagram of the Chirp signal receiver is shown in fig. 6, and mainly comprises two parts, wherein the front end is a radio frequency part, and the rear end is a Chirp baseband signal processing part.

In this embodiment, the signal processing flow of the Chirp receiver is divided into a frame synchronization and channel estimation and a traffic data receiving process.

Chirp receiver signal processing procedure 1: frame synchronization and channel estimation procedure

Step 1: the method comprises the steps that a Chirp signal receiver starts to be powered on, the initialization task of the receiver is completed firstly, the initialization process comprises the step of generating frequency domain data of a local preamble symbol, the upper Chirp symbol is marked as local _ upChirp _ F [ i ], the lower Chirp symbol is marked as local _ dwChirp _ F [ i ], and the value of i is 0,1, 2. In the following description, if it is the upper Chirp symbol, local _ Chirp _ F is local _ upChirp _ F, otherwise local _ Chirp _ F is local _ dwChirp _ F.

The synchronous search state is then entered. In a CCS communication system, data is generally transmitted in a burst frame structure, and a receiver cannot know when a burst data frame arrives, so that the receiver must monitor and search for a preamble symbol of the frame in real time.

since the receiver does not know the start time of the preamble symbol when it starts receiving the frame data, the unsynchronized FFT data is not necessarily the complete Chirp symbol data. As shown in steps 1 and 2 in fig. 7.

Step 2: performing Chirp leading symbol search on Chirp frequency domain data after FFT, firstly determining whether the received data is frequency domain data of a leading Chirp symbol, if the received data is the frequency domain data of the leading Chirp signal, finding a frequency domain starting position of the Chirp symbol, finally converting the frequency domain starting position into a corresponding time domain starting position, and adjusting the starting position calculated by FFT, thereby ensuring that the output of each FFT is complete Chirp symbol data. As shown in step 3 of fig. 7.

And step 3: and receiving frequency domain data of the complete lead Chirp signal, and recording the frequency domain data as pilot _ Chirp _ F [ i ], wherein the value of i is 0,1, 2. Then, the frequency domain channel characteristic H [ i ] of the Chirp symbol is pilot _ Chirp _ F [ i ]/local _ Chirp _ F [ i ], where i is 0,1, 2. As shown in step 4 of fig. 7.

And 4, step 4: in the present embodiment, it is assumed that the preamble in the data frame has K Chirp symbols in total, but the receiver can correctly detect only L preamble symbols and has searched for the end of the preamble symbol.

estimating the channel characteristic of each pilot symbol by adopting the method of step 3, and recording the channel characteristic as H [ i][j]And the channel characteristics of the jth Chirp symbol at the frequency point i are represented, wherein the value range of i is 0,1, 2. Then the channel characteristics of the Chirp symbol in the frequency domain are finally obtained as

In this step, if the end symbol of the preamble symbol is searched, the Chirp preamble symbol sequence searching submodule immediately notifies the Chirp data receiving and equalization processing submodule that the data symbol processing of the frame has started.

As shown in the 5 th and 6 th steps in fig. 7

chirp receiver signal processing process 2: service data receiving process

step 1: according to the frame structure characteristics, a burstThe frame structure comprises leading symbols and data symbols, and a Chirp leading symbol sequence searching submodule sends data initial position indication and frequency domain channel estimationAfter receiving the data start position indication, the Chirp data receiving and equalizing processing submodule starts to receive symbol data in a frame, namely Chirp frequency domain data after FFT. As in step 1 of fig. 8.

Step 2: after receiving a complete frequency domain data of Chirp symbol, marking as data _ Chirp _ F [ i ]]Wherein the value range of i is 0,1, 2. Frequency domain equalization using frequency domain channel characteristics from Chirp preamble symbol search submoduleThe frequency domain equalization of the Chirp symbol results in

wherein the value range of i is 0,1, 2. As shown in step 2 of fig. 8.

and step 3: and performing data judgment on the frequency domain Chirp symbol data _ Chirp _ Eq _ F, performing convolution calculation on the received Chirp symbol data and the local upper Chirp symbol and lower Chirp symbol in the time domain according to a Chirp signal demodulation principle, if the convolution result of the upper Chirp is greater than that of the lower Chirp, judging that the received Chirp symbol is the lower Chirp symbol, and if not, judging that the received Chirp symbol is the upper Chirp symbol.

According to the principle of signal processing, performing convolution calculation in the time domain is equivalent to performing dot product calculation in the frequency domain. In the embodiment of the invention, as the FFT hardware accelerator is adopted, only the frequency domain calculation method of the Chirp symbol is considered in the Chirp baseband signal processing.

The frequency domain Chirp signal demodulation sub-module performs dot product using the frequency domain data from the Chirp data reception and equalization processing sub-module and local _ Chirp _ F. And if the dot product result obtained by the dot product of the local upper Chirp symbol frequency domain data and the local upper Chirp symbol frequency domain data is larger than the dot product result of the lower Chirp symbol frequency domain data, judging that the received Chirp symbol is the lower Chirp symbol, and otherwise, judging that the received Chirp symbol is the upper Chirp symbol.

In a CCS communication system, the above steps 1,2 and 3 are repeated for a plurality of data symbols included in a data frame until all the data symbols in the frame are received.

finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.