Methods, systems, and storage media for vector signal analysis and processing at the uplink signal receiver of a wideband code division multiple access wireless communication system.

Abstract

This invention provides a method, system, and storage medium for vector signal analysis and processing at the uplink signal receiver of a wideband code division multiple access (WCDMA) wireless communication system. It is used to perform frequency domain and modulation domain index measurements, channel decoding, and other processing on the uplink signal of a WCDMA wireless communication system. The beneficial effects of this invention are: by using an R&S cellular test instrument to sample WCDMA uplink signals, the various processes of this invention were debugged. Under conditions of AWGN, DC bias of -39dB, random delay, and random frequency offset, the uplink signal waveform of WCDMA FDD was generated. Simulation processing of various processes, including synchronization, carrier frequency offset estimation and compensation, descrambling, equalization, and despreading, was performed. The DC bias and error vector amplitude (EVM) of the uplink signal were measured, and the downlink physical control channel (DPCCH) and downlink physical dedicated channel (DPDCH) were demodulated and decoded. The CRC check of the DPDCH channel passed, verifying the correctness of each process.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a method, system, and storage medium for vector signal analysis and processing at the uplink signal receiver of a wideband code division multiple access wireless communication system. Background Technology

[0002] The equipment of the Wideband Code Division Multiple Access (WCDMA) standard uses a zero-IF transmitter / receiver. The zero-IF transmitter / receiver does not pass through the intermediate frequency and directly converts the signal from baseband to radio frequency / radio frequency to baseband. The obtained baseband signal is oversampled by an analog-to-digital converter (ADC) and input to a digital signal processor (DSP) module for signal processing to finally obtain useful information. In the downconversion process of zero-IF, due to local oscillator leakage and other reasons, there will be some DC components in the baseband signal. In the subsequent signal processing, these components need to be eliminated to improve the demodulation accuracy [1]. Assuming that the transmission channel is an Additive White Gaussian Noise (AWGN) channel, the receiver first needs to synchronize the sampled digital signal with the radio frame and estimate and compensate for the carrier frequency offset. Since the time accuracy of the oversampled digital signal is low, it also needs to be interpolated and reconstructed to eliminate the inter-symbol interference caused by the low time accuracy of the synchronization.

[0003] For the signal of the Wideband Code Division Multiple Access (WCDMA) standard, the length of the radio frame is 10ms, each radio frame contains 15 time slots, its bandwidth is a unidirectional 5MHz paired frequency band, the chip rate is 3.84M / s, and the multiple access mode of Single Carrier Code Division Multiple Access (DS-CDMA) is adopted. The physical channel is divided into downlink and uplink physical channels. The downlink or uplink physical channels are further divided into public and private types. The public physical channel is shared by multiple UEs, while the private physical channel is exclusively used by each UE. In addition to the physical channel carrying the transmission channel, it also includes physical channels that provide phase reference, cell search information and transmit various indication and control information. The orthogonal variable spreading factor (OVSF) code is used to spread the channel-encoded sequence carried by each physical channel [2], and the Gold code is used to scramble the sequence after the superposition of each spreading sequence [3] to distinguish different cells or users. After the receiver descrambles the received signal, it can perform code domain power monitoring on the received signal based on the OVSF code. After obtaining the code channel number of the activation signal, the signal is despread using the OVSF code of each channel to obtain the gain of the corresponding spreading factor, and equalized using the received pilot channel symbols. The equalized constellation points are then demodulated to obtain the bit data stream.

[0004] In order to extract the data information of the dedicated physical channel DPCH, after equalization and demodulation to obtain the bit data stream carried by the physical channel, it is also necessary to demultiplex the transmission channel and dematch the rate to obtain the coded bit data blocks of each transmission channel, and decode them to obtain the original data blocks. Various different transmission channels mainly adopt three coding schemes: 1 / 2 code rate convolutional code; 1 / 3 code rate convolutional code; 1 / 3 code rate Turbo code [4].

[0005] Convolutional codes, represented by (n, k, L), are error-correcting codes with memory. n is the output codeword, k is the input bit information, and L is the constraint length, also known as the memory depth. The encoding rule is to encode k information bits into n bits. The encoded n codewords are related not only to the currently input k information bits but also to the information from the previous L-1 groups. Taking the 1 / 3 convolutional code encoder used in the WCDMA standard as an example, its generator polynomial is [101 101 111], [110 110 011], [111001001]. This convolutional code encoder has 2^8 states, 2 input symbols, and 8 output symbols. The current input symbol and the current shift register state determine the output symbol and the next shift register state.

[0006] Turbo codes introduce an interleaver in the encoder to give the codewords near-random characteristics. By concatenating component codes in parallel, short codes (component codes) are used to construct long codes (Turbo codes). Although a suboptimal iterative algorithm is used at the receiver, the component codes employ the optimal maximum a posteriori probability decoding algorithm. Through iterative decoding, performance close to maximum likelihood decoding can be achieved. Turbo codes fully consider the conditions assumed in the proof of Shannon's channel coding theorem, thus achieving performance close to Shannon's theoretical limit. Turbo codes also provide the first practical proof of the correctness of the channel coding theorem. In the WCDMA standard, Turbo codes are constructed using two component encoders constructed through interleaving and parallel concatenation (PCCC), with the component encoder being a recursive systematic convolutional code (RSC).

[0007] For convolutional codes, the Viterbi algorithm is the optimal maximum likelihood decoding algorithm, producing the optimal estimated sequence as the decoded output. However, for Turbo codes, which are concatenated convolutional codes, a modification to the traditional Viterbi algorithm is needed to provide soft information output. This algorithm is called the Soft Output Viterbi algorithm, denoted as SOVA. The decoding process of SOVA is similar to that of the Viterbi algorithm, except that it calculates the reliability of the corresponding path selection along with the branch and path metrics. This reliability becomes extrinsic information, which can be used as prior information input to another component decoder during iterative decoding, thus completing the iterative decoding process of Turbo codes.

[0008] The Viterbi algorithm uses the trellis graph of a convolutional code encoder to calculate path metrics. The algorithm first assigns a partial path metric value to each state node in the trellis graph. This partial path metric value is determined by the path from state S at time 0 to state S at time k. At each state, the branch with the best partial path metric that reaches that state is selected. The best partial path metric can be either the maximum or minimum metric, depending on the definition. Based on the metric used, the partial path that meets the condition is selected as the surviving path, while other branches reaching that state are removed from the trellis graph. The Viterbi algorithm selects the unique surviving path from the start to the end time in the trellis graph as the maximum likelihood path. Following the maximum likelihood path, backtracking from the end time to the start time, the encoded output corresponding to the path traversed is the maximum likelihood decoded output sequence.

[0009] In summary, existing digital signal processing methods for uplink signal receivers in WCDMA wireless communication systems include synchronization, carrier frequency offset estimation and compensation, DC estimation and compensation, code domain parameter estimation and error vector amplitude calculation, and dedicated physical data channel demultiplexing and decoding. Synchronization is based on constructing a reference signal from pilot symbols to calculate correlation peaks; code domain parameters are based on OVSF code tree search; and channel decoding generally employs the optimal maximum likelihood decoding algorithm, Viterbi decoding. Existing methods for measuring frequency and modulation domain parameters and performing channel decoding on uplink signals in WCDMA wireless communication systems suffer from high complexity and low computational efficiency. In actual synchronization processing and carrier frequency offset estimation, the lack of prior information on the pilot symbols in the current time slot makes it impossible to construct the reference signal required for synchronization processing. In the spreading code identification process, there are issues such as high OVSF code tree search complexity and low computational efficiency. In the calculation of the error vector magnitude, the low time precision of the digital signal obtained from oversampling leads to a larger calculated EVM than the actual signal. In the decoding process of the dedicated physical channel DPCH, the different transmission time intervals of multiple transmission channels result in high complexity in demultiplexing transmission channels and derate matching.

[0010] References:

[0011] [1] CN200810116331.6, Ma Jing, A method for eliminating DC bias, 2008.07.08

[0012] [2] CN200580004918.2 Apparatus and method for allocating orthogonal variable spreading factor codes and co-phase / orthogonal phase channels in a wideband code division multiple access system to reduce the peak-to-average power ratio when transmitting data through an enhanced uplink dedicated channel.

[0013] [3] CN200710106782.7 A scrambling generator for WCDMA system and its implementation method [4] 3GPPTS25212-790 Multiplexing and channel coding (FDD), 4.2.3 Channel coding. Summary of the Invention

[0014] This invention provides a method for vector signal analysis and processing at the uplink signal receiver of a wideband code division multiple access wireless communication system, comprising the following steps:

[0015] Step 1: Perform coarse synchronization and fine synchronization on the received WCDMA uplink signal to obtain the slot-level synchronization point and the slot number of the current sequence. A slot is a time slot.

[0016] Step 2: Estimate the carrier frequency offset of the synchronized received signal to obtain the estimated carrier frequency offset value CFO;

[0017] Step 3: Estimate and compensate for the DC bias of the received signal to eliminate the influence of the DC bias on the descrambling and despreading of the received signal;

[0018] Step 4: Compensate the received signal for carrier frequency offset based on the estimated carrier frequency offset CFO to obtain signal SIG1; decimate signal SIG1 at the chip rate according to the start position of the time slot, descramble the decimated signal, despread the DPCCH channel using the spreading code of the DPCCH channel, and obtain the channel estimate Ht from the DPCCH symbol Z_DPCCH, where chip is the code chip and DPCCH is the dedicated physical control channel;

[0019] Step 5: Equalize the chip rate sequence after decimation and descrambling using the channel estimation Ht, and perform code tree search on the equalized sequence to obtain the spreading code and channel power estimation of the active channel. Since the WCDMA uplink signal is fixed to use binary phase shift keying modulation, the reference constellation point RefIQ for calculating the error vector amplitude EVM is constructed from the spreading code, power estimation and scrambling code of the active channel, thereby calculating the error vector amplitude EVM value.

[0020] Step 6: If the active channel has a downlink physical dedicated channel, use the spreading code of the DPDCH channel to despread the DPDCH channel to obtain the DPDCH symbol Z_DPDCH, and then perform subsequent demodulation, dechannel multiplexing, and channel decoding.

[0021] As a further improvement of the present invention, step 1 includes the following steps:

[0022] Step 1: First, perform matched filtering on the received signal to obtain a digital signal with an oversampling factor of 8. Extract the digital signal with an oversampling factor of 8 into two received sequences with a sampling rate of 3.84M / s. The time deviation between the two received sequences is 1 / 2*Tchip, where Tchip is the chip time of the WCDMA wireless communication system.

[0023] Step 2: Descramble the two received sequences to obtain the index of the symbol start chip (index1) and the index of the OVSF(256,0) spread spectrum symbol (index2);

[0024] Step 3: Based on the symbol starting chip index index1 and the OVSF(256,0) spread spectrum symbol index2 obtained in Step 2, calculate the synchronization point at the slot level and the slot number of the current sequence. Furthermore, by comparing the synchronization energy of the two sequences, obtain the synchronization point with a synchronization accuracy of 1 / 2*Tchip. By comparing the positions of the peak points of the synchronization energy of the two sequences, determine whether the current signal is synchronized correctly.

[0025] Step 4: Fine synchronization employs a method that correlates the received signal with the reference signal SynRefSig. Based on the sign of the DPCCH symbol and the carrier frequency offset CFO, a reference signal SynRefSig is constructed and scrambled. A search is performed at the coarse synchronization starting point, and SIG0 is obtained by decimation at an oversampling factor of 8. Its correlation value with the received signal is then calculated.

[0026] R i =|∑SIG0 i *conj(SynRefSig)| 2

[0027] In the above formula, i represents the starting point of the intercepted signal, and conj(.) represents the conjugate operation. The sampling point corresponding to the correlation peak is the optimal starting point of the signal.

[0028] The present invention also provides a vector signal analysis and processing system for uplink signal receivers in a wideband code division multiple access (WDMA) wireless communication system, comprising: a memory, a processor, and a computer program stored in the memory, wherein the computer program is configured to implement the steps of the vector signal analysis and processing method for uplink signal receivers in the wideband code division multiple access (WDMA) wireless communication system described in the present invention when called by the processor.

[0029] The present invention also provides a computer-readable storage medium, characterized in that: the computer-readable storage medium stores a computer program, the computer program being configured to implement the steps of the vector signal analysis and processing method for the uplink signal receiver of the wideband code division multiple access wireless communication system described in the present invention when called by a processor.

[0030] The beneficial effects of this invention are as follows: By using an R&S cellular comprehensive tester to sample WCDMA uplink signals, the various processes of the practical and efficient VSA processing method for uplink signal receivers in the WCDMA wireless communication system proposed in this invention were debugged. Under the conditions of AWGN, DC offset -39dB, random delay, and random frequency offset, the uplink signal waveform of WCDMA FDD was generated. Simulation processing of various processes such as synchronization, carrier frequency offset estimation and compensation, descrambling, equalization, and despreading was performed. The DC and EVM indicators of the uplink signal were measured, and the Dedicated Physical Control Channel (DPCCH) and Dedicated Physical Data Channel (DPDCH) were demodulated and decoded. The CRC check of the DPDCH channel passed, verifying the correctness of each process. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method of the present invention;

[0032] Figure 2 This is a flowchart of uplink DPDCH demultiplexing and channel decoding.

[0033] Figure 3.1 This is a WCDMA downlink code channel power monitoring graph;

[0034] Figure 3.2 It is a channel amplitude and phase response diagram;

[0035] Figure 3.3 This is a constellation point diagram of the WCDMA downlink DPCH channel;

[0036] Figure 3.4 This is a diagram showing the CRC check result of the WCDMA uplink transmission channel decoding. Detailed Implementation

[0037] The purpose of this invention is to provide a practical and efficient vector signal analysis processing method for uplink signal receivers in Wideband Code Division Multiple Access (WCDMA) wireless communication systems, which is used to perform frequency domain and modulation domain index measurements, channel decoding, and other processing on uplink signals in WCDMA wireless communication systems.

[0038] First, let's explain the following terms: WCDMA refers to Wideband Code Division Multiple Access; DPCCH refers to Dedicated Physical Control Channel; DPDCH refers to Dedicated Physical Data Channel; IQ imbalance is the oscillation amplitude deviation and phase non-orthogonality of the I and Q signals in the receiver mixer; BPSK refers to Binary Phase Shift Keying; and OVSF refers to Orthogonal Variable Spreading Factor.

[0039] For the Wideband Code Division Multiple Access (WCDMA) standard, the radio frame length is 10ms, each radio frame contains 15 time slots, and its bandwidth is a unidirectional 5MHz paired frequency band with a chip rate of 3.84M / s. Physical channels are divided into downlink and uplink physical channels. Downlink and uplink physical channels are further divided into public and dedicated types. Public physical channels are shared by multiple UEs, while dedicated physical channels are used exclusively by each UE. In addition to the physical channels carrying the transmission channels, there are also physical channels that provide phase reference, cell search information, and transmit various indication and control information.

[0040] This invention employs uplink signals conforming to the WCDMA standard. The physical channels include a Q-channel BPSK-modulated DPCCH channel with spreading code OVSF(256,0) and an I-channel BPSK-modulated DPCCH channel with spreading code OVSF(16,4). DPCCH stands for dedicated physical control channel, and DPDCH stands for dedicated physical data channel. At the RF signal receiver, the received RF signal is down-converted to baseband by mixing the I and Q signals and performing low-pass filtering to remove twice the carrier frequency component. Since the carrier frequency is unknown, a certain carrier frequency offset will occur during the down-conversion process.

[0041] To perform signal measurement and information analysis on the obtained baseband digital signal, signal synchronization and carrier frequency offset estimation and compensation are first required. Since the WCDMA standard uses scrambling codes generated based on cell IDs to scramble the physical channel signal, channel synchronization requires descrambling the signal according to the scrambling codes. After descrambling, pilot information from the DPCCH channel is used for signal synchronization and carrier frequency offset estimation. (See attached...) Figure 1The algorithm flowchart shown illustrates that this invention includes processes such as synchronization of the received signal, carrier frequency offset estimation and compensation, DC estimation and compensation, code domain parameter estimation and error vector amplitude calculation, and demultiplexing and decoding of the dedicated physical data channel. The process includes the following steps:

[0042] Step 1: Perform coarse synchronization and fine synchronization on the received WCDMA uplink signal to obtain the synchronization point at the slot level and the slot number of the current sequence.

[0043] Step 1 includes:

[0044] Step 1: First, the received signal is subjected to matched filtering. A root-raised cosine matched filter with a roll-off factor of 0.22 is used to improve the signal-to-noise ratio of the received signal, resulting in a digital signal with an oversampling factor of 8 for synchronization processing. To improve the accuracy of synchronization and achieve precise synchronization calculation, the digital signal with an oversampling factor of 8 is extracted into two received sequences with a sampling rate of 3.84M / s. The time deviation between the two sequences is 1 / 2*Tchip, where Tchip is the chip time of the WCDMA wireless communication system.

[0045] Step Two: To synchronize the signals, both sequences need to be descrambled first. Since the initial point is unknown within a specific chip timeframe of the radio frame, this invention employs a novel synchronization strategy: despreading the chip-level digital signal sequence based on the fixed spreading code OVSF(256,0) of the DPCCH to achieve a descrambling gain of 256 times. Because the processing method for both sequences is the same, the following explanation uses one sequence as an example. The specific algorithm can be divided into the following steps:

[0046] Step a: Search for 256 chip sampling points for the sequence. These 256 chip sampling points correspond to the 256 starting chip positions of an OVSF(256,0) spread spectrum symbol, thus obtaining the starting point of the OVSF(256,0) spread spectrum symbol.

[0047] Step b: Truncate the spread spectrum to a length equal to multiple OVSF(256,0) spread symbols, where 256 / 3.84M. To descramble the truncated sequence, it is necessary to search for the scrambling codes used when scrambling the 10*15=150 spread spectrum symbols with a spreading factor of OVSF(256,0) in a radio frame. At this point, it is only necessary to use the scrambling codes of 150 symbols from a radio frame to descramble the first 256 chips of the sequence.

[0048] Step c: After descrambling, the absolute values ​​of the calculated symbols from multiple DPCCHs are summed to eliminate the influence of symbol polarity and improve the synchronization signal-to-noise ratio.

[0049]

[0050] In the formula, DescrambleSeq is the descrambled chip rate sequence, where n is the chip number of a DPCCH symbol, i is the cumulative DPCCH symbol number, Nsymbol is the total number of DPCCH symbols, and the spreading factor is 256.

[0051] Step d: Based on the synchronization energy obtained in step c, the index 1 of the starting chip of the symbol in steps a and b and the index 2 of the starting symbol of the 150 symbols of the radio frame can be determined.

[0052] Step 3: Based on the symbol starting chip point index1 and the OVSF(256,0) spreading symbol index2 obtained in Step 2, the slot-level synchronization point and the slot number of the current sequence can be calculated. Furthermore, by comparing the synchronization energy of the two sequences, a synchronization point with a synchronization accuracy of 1 / 2*Tchip can be obtained, where Tchip is the chip time of the WCDMA wireless communication system. By comparing the positions of the peak points of the synchronization energy of the two sequences, it can be determined whether the current signal is correctly synchronized.

[0053] After coarse synchronization of the received signal, a synchronization point with a synchronization accuracy of 1 / 2 * Tchip can be obtained, where Tchip is the chip time of the WCDMA wireless communication system. Fine synchronization of the signal is then required. In this example, since the oversampling factor is 8, the optimal sampling point needs to be searched among 1 / 2 * 8 = 4 sampling points.

[0054] Step 4: Fine synchronization employs a method that correlates the received signal with the reference signal SynRefSig. Based on the sign of the DPCCH symbol and the carrier frequency offset CFO, a reference signal SynRefSig is constructed and scrambled. A search is performed at the coarse synchronization starting point, and SIG0 is obtained by decimation at an oversampling factor of 8. Its correlation value with the received signal is then calculated.

[0055] R i =|∑SIG0 i *conj(SynRefSig)| 2

[0056] In the above formula, i represents the starting point of the intercepted signal, and conj(.) represents the conjugate operation. The sampling point corresponding to the correlation peak is the optimal starting point of the signal.

[0057] Step 2: To construct the reference signal SynRefSig, the carrier frequency offset (CFO) of the synchronized received signal needs to be estimated first. The CFO is estimated based on the phase difference between adjacent symbols. By calculating the phase difference between adjacent symbols and using the time difference of 256 * Tchip, the CFO can be estimated, where Tchip is the chip time of the WCDMA wireless communication system.

[0058]

[0059] In the formula, Δθ represents the phase difference between adjacent DPCCH symbols, in radians. Since the time interval between adjacent pilot symbols of the DPCCH is 1 / 15 ms, the maximum frequency deviation of the received signal should be less than 3750 Hz. Then, it is also necessary to know the sign of the DPCCH symbols obtained by descrambling and despreading the received signal. Since the symbol modulation type of the DPCCH channel is BPSK, the bit values ​​between adjacent symbols can be determined by comparing the phase difference between them, using the first symbol as a reference.

[0060] Step 3: Since the receiver uses a zero-IF receiver, there may be DC leakage. Therefore, the DC bias of the received signal is estimated and compensated first to eliminate the impact of DC bias on the descrambling and despreading of the received signal. The DC bias estimation uses a two-step estimation. First, the average value of the I and Q signals is calculated to perform a coarse estimate of the I and Q signals, that is, to obtain the coarse estimate of the DC bias value DC1. Then, coarse DC compensation is performed.

[0061] DC1 = mean(y R (n))+j·mean(y I (n))

[0062] In the above formula, y R (n) and y I (n) represent the real and imaginary parts of the received sequence y(n), respectively, j represents the imaginary unit, and mean(.) represents the mean. After estimating the spreading code and channel power for the active channel, and constructing the reference constellation point RefIQ for the error vector amplitude using the scrambling code, the DC bias is precisely estimated based on the constructed reference constellation point RefIQ to obtain DC2, i.e.:

[0063] DC2 = mean(y(n) - IdealSeq)

[0064] In the above formula, IdealSeq represents the ideal received sequence after hard decision based on the constructed reference constellation points, and mean(.) represents the mean value. The result of the two-step estimation, DC = DC1 + DC2, is then used to perform DC compensation on the subsequent signal.

[0065] Step 4: Based on the carrier frequency offset estimate CFO, the received signal SIG1 is compensated for the carrier frequency offset. According to the start position of the time slot, the chip rate sequence Seq1 is obtained by decimating the chip rate of signal SIG1. The decimated signal Seq1 is then descrambled, and the DPCCH channel is despread using the spreading code of the DPCCH channel. Assuming the channel is a Gaussian white noise (AWGN) channel, the least squares (LS) estimate Ht of the Gaussian white noise (AWGN) channel is obtained from the DPCCH symbol Z_DPCCH and the known pilot symbol Pilot_DPCCH.

[0066]

[0067] Step 5: Equalize the descrambled chip rate sequence using the channel estimation Ht, and perform a code tree search on the equalized sequence to obtain the spreading code of the active channel and the channel power estimate. Since the spreading factor used in WCDMA signals is 4 to 512, when performing code tree search on each spreading factor, in order to simplify the search, the search can start from the leaf node of the OVSF code tree. If the current leaf node is the active channel code, then all the root nodes corresponding to it cannot be activated again, and there is no need to repeat the search.

[0068] In step 5, since the WCDMA uplink signal always uses BPSK modulation, the reference constellation point RefIQ for calculating the error vector magnitude EVM can be constructed from the spreading code, power estimation, and scrambling code of the active channel. The method is as follows:

[0069] Because WCDMA uplink signals use IQ multiplexing, multiple physical channels with different spreading codes exist on both the I and Q paths. Taking the I path as an example, for a certain physical channel, since the spreading code OVSF is a sequence of 1 or -1, the spread chip rate sequence is either 1 or -1. For the dedicated physical data channel DPDCH, since the maximum rate of the DPDCH channel in WCDMA is 6*960kbps, there are at most 3 physical channels with a spreading factor of 4 on the I path. The corresponding sequence after superimposing the spread chip rate sequences is as follows:

[0070] {α|α∈[-2 0 2]}, 2 DPDCHs or {α|α∈[-3 -1 1 3]}, 3 DPDCHs

[0071] The spread sequence {α} of each physical channel n}, n∈0~2559, multiply by the power estimated by each physical channel, and superimpose all activated physical channels. Finally, multiply all the obtained constellation points by 1+j, 1-j, -1+j, and -1-j respectively to obtain the scrambled reference constellation points RefIQ.

[0072] In step 5, to calculate the error vector magnitude (EVM), the received sequence is first inlined using Lagrange interpolation, and then decimated by a factor of 8 to obtain the decimated chip rate sequence Seq2. This example uses four Lagrange interpolation inlining functions:

[0073]

[0074] The optimal weighted sum is obtained by calculating the modulation domain EVM (Error Vector Magnitude) of the sequence at a synchronization accuracy of 1 / 32 * Tchip, using a weighted sum of four consecutive points of an 8x oversampled sequence. This yields a better weighted value compared to the original sequence, as it eliminates ISI (Inter-symbol Interference) more effectively. Tchip represents the chip time of the WCDMA wireless communication system. The minimum distance, minDIST, is calculated by subtracting the scrambled reference constellation point RefIQ from Seq2 to obtain the reference point's position IdealSeq(n), where n ∈ 0~2559. The Error Vector Magnitude (EVM) value is calculated using the following formula:

[0075]

[0076] Thus, the error vector magnitude EVM value is calculated; and the second estimate of the DC bias DC2 can be obtained from the reference sequence IdealSeq of the received signal obtained from the reference point.

[0077] Step 6: If a DPDCH channel exists in the active channel, despread the DPDCH channel using the spreading code to obtain the DPDCH symbol Z_DPDCH, and then perform subsequent demodulation, de-channel multiplexing, and channel decoding. Assuming the transmission channel is a Gaussian white noise (AWGN) channel, only initial phase compensation is needed on the demodulated symbol Z_DPDCH to obtain the constellation points after equalization of the symbol Z_DPDCH, thus enabling correct 2-bit phase shift keying (BPSK) demodulation to obtain the physical bit sequence carried by the DPDCH channel.

[0078] Combined with appendix Figure 2The flowchart shown illustrates the uplink DPDCH demultiplexing and channel decoding process. In step 6, after descrambling, equalizing, and demodulating the input data, the physical bit sequence carried by the DPDCH channel in a WCDMA wireless communication system is a multiplexing of multiple transmission channels. The demodulated bit sequence must first be demultiplexed before subsequent rate matching and transmission channel decoding can be performed to obtain the transport block for each transmission channel. Specifically, the number of physical channel bits TB1 and the number of encoded bits TB2 for each transmission channel should be calculated based on the rate matching parameters. Then, according to the rate matching algorithm provided by the WCDMA protocol, the puncture positions or repetition positions of the bit sequence carried by the physical channel are obtained, leading to the encoded bit sequence of the transmission channel. To demultiplex the DPDCH channel, rate matching must first be performed based on the DPDCH rate matching parameters. The number of bits carried by the physical channel and the number of physical channel bits TB1 and the number of encoded bits TB2 for each transmission channel are calculated using the formula. After obtaining the number of coded bits for a single transmission channel, Viterbi decoding is performed based on the channel coding type of that transmission channel. A CRC check is then performed on the decoded output to verify the correctness of the decoded transport block (TB). Since the transmission channel sends information at a transmission time interval (TTI), the TTI of the dedicated physical data channel (DPDCH) is typically multiple radio frames. The rate matching and channel multiplexing of the uplink DPDCH are processed in units of one radio frame (10ms), while the Viterbi decoding process requires the collection of data for a full TTI before it can proceed, thus obtaining the TB transport block.

[0079] In step 6, the transmission channel of the WCDMA wireless communication system encodes the data source using convolutional codes or Turbo codes. In the WCDMA standard, the generator polynomial of the 1 / 3 rate convolutional code is [101 101 111], [110 110011], [111 001 001]. This convolutional code encoder has 2^8 states, 2 input symbols, and 8 output symbols. The current input symbol and the current shift register state determine the output symbol and the next shift register state. The Turbo code is constructed using two component encoders interleaved and concatenated in parallel (PCCC). The component encoder is a recursive systematic convolutional code (RSC) with the following generator polynomial:

[0080]

[0081] in:

[0082] g0(D)=1+D 2 +D3 ,

[0083] g1(D) = 1 + D + D 3 .

[0084] Since the encoder of a traditional convolutional code consists of shift registers and does not contain feedback, it can be equivalent to a finite impulse response (FIR) filter. A recursive systematic convolutional code, due to the presence of feedback, can be equivalent to an infinite impulse response (IIR) filter. Because the matrix transformations during the systematization of convolutional codes do not change the rank of the generator matrix, the minimum distance of this systematic convolutional code is the same as the minimum distance of its corresponding non-systematic convolutional code.

[0085] For convolutional codes, the Viterbi algorithm is the optimal maximum likelihood decoding algorithm, and the decoded output is the optimal estimated sequence. The Viterbi algorithm uses the trellis graph of the convolutional code encoder to calculate the path metric. The algorithm first assigns a partial path metric value to each state node in the trellis graph. This partial path metric value is determined by the state S from the start time 0 to the current time k. At each state, the branch with the best partial path metric that reaches that state is selected. The best partial path metric can be a maximum or minimum metric, depending on the definition. Based on the metric used, the partial path that meets the condition is selected as the surviving path, while other branches that reach that state are removed from the trellis graph. The Viterbi algorithm selects the unique surviving path from the start time to the end time in the trellis graph as the maximum likelihood path. Following the maximum likelihood path, traversing back from the end time to the start time, the encoded output corresponding to the path traversed is the maximum likelihood decoded output sequence. The transmitted codeword sequence y is estimated according to the maximum likelihood estimation criterion, and the log-likelihood function is:

[0086]

[0087] In the above formula, n0 represents the length of the codeword, L+m-1 represents the total number of received codewords, and m represents the m zero symbols added to the input to obtain the final codeword. For Turbo codes, which belong to concatenated convolutional codes, the traditional Viterbi algorithm has two drawbacks: First, burst errors in the output of one component decoder can affect the decoding performance of another component decoder, thus degrading the performance of the concatenated code. Second, whether it's a soft-decision or hard-decision Viterbi algorithm, the decoding output is hard-decision information. Therefore, if one component decoder uses the Viterbi algorithm, the other component decoder can only use the hard-decision result as input and cannot achieve soft-input decoding, thus degrading its performance. However, if the Viterbi decoder can provide soft information output, these two drawbacks can be overcome, and the decoding performance of the concatenated code can be greatly improved by exchanging soft information between component decoders. Therefore, it is necessary to modify the traditional Viterbi algorithm to provide soft information output. The corresponding algorithm is called the SoftOutput Viterbi Algorithm (SOVA).

[0088] The decoding process of SOVA is similar to that of the Viterbi algorithm, except that while calculating the branch metric and path metric, it also calculates the reliability of the corresponding path selection, which also becomes external information. During the iterative decoding process, it can be used as the prior information input of another component decoder, thereby completing the iterative decoding process of Turbo code.

[0089] Define the branch metric at time t:

[0090]

[0091] And some path metrics:

[0092]

[0093] The k-th branch metric represents the cost of selecting this branch at time t in the trellis diagram, while the k-th partial path metric represents the cost of selecting a partial decoded symbol sequence from the initial time t=0 to the current time k.

[0094] Using an R&S cellular test instrument to sample WCDMA uplink signals, the various processes of the proposed practical and efficient VSA processing method for the uplink signal receiver in a WCDMA wireless communication system were debugged. Under conditions of AWGN, DC offset -39dB, random delay, and random frequency offset, the uplink signal waveform of WCDMA FDD was generated. Simulations were performed on various processes, including synchronization, carrier frequency offset estimation and compensation, descrambling, equalization, and despreading. The DC and EVM indicators of the uplink signal were measured, and the Dedicated Physical Control Channel (DPCCH) and Dedicated Physical Data Channel (DPDCH) were demodulated and decoded. The CRC check of the DPDCH channel passed, verifying the correctness of each process. Figures 3.1-3.4 As shown.

[0095] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for vector signal analysis and processing at the uplink signal receiver of a wideband code division multiple access wireless communication system, characterized in that, Includes the following steps: Step 1: Perform coarse synchronization and fine synchronization on the received WCDMA uplink signal to obtain the slot-level synchronization point and the slot number of the current sequence. A slot is a time slot. Step 2: Estimate the carrier frequency offset of the synchronized received signal to obtain the estimated carrier frequency offset value CFO; Step 3: Estimate and compensate for the DC bias of the received signal to eliminate the influence of the DC bias on the descrambling and despreading of the received signal; Step 4: Compensate the received signal for carrier frequency offset based on the estimated carrier frequency offset CFO to obtain signal SIG1; decimate signal SIG1 at the chip rate according to the start position of the time slot, descramble the decimated signal, despread the DPCCH channel using the spreading code of the DPCCH channel, and obtain the channel estimate Ht from the DPCCH symbol Z_DPCCH, where chip is the code chip and DPCCH is the dedicated physical control channel; Step 5: Equalize the chip rate sequence after decimation and descrambling using the channel estimation Ht, and perform code tree search on the equalized sequence to obtain the spreading code and channel power estimation of the active channel. Since the WCDMA uplink signal is fixed to use binary phase shift keying modulation, the reference constellation point RefIQ for calculating the error vector amplitude EVM is constructed from the spreading code, power estimation and scrambling code of the active channel, thereby calculating the error vector amplitude EVM value. Step 6: If the active channel has a downlink physical dedicated channel, use the spreading code of the DPDCH channel to despread the DPDCH channel to obtain the DPDCH symbol Z_DPDCH, and then perform subsequent demodulation, dechannel multiplexing, and channel decoding.

2. The vector signal analysis and processing method for the uplink signal receiver in a wideband code division multiple access wireless communication system according to claim 1, characterized in that, Step 1 includes the following steps: Step 1: First, perform matched filtering on the received signal to obtain a digital signal with an oversampling factor of 8. Extract the digital signal with an oversampling factor of 8 into two received sequences with a sampling rate of 3.84M / s. The time deviation between the two received sequences is 1 / 2*Tchip, where Tchip is the chip time of the WCDMA wireless communication system. Step 2: Descramble the two received sequences to obtain the index of the symbol start chip (index1) and the index of the OVSF(256,0) spread spectrum symbol (index2); Step 3: Based on the symbol starting chip index index1 and the OVSF(256,0) spread spectrum symbol index2 obtained in Step 2, calculate the synchronization point at the slot level and the slot number of the current sequence. Furthermore, by comparing the synchronization energy of the two sequences, obtain the synchronization point with a synchronization accuracy of 1 / 2*Tchip. By comparing the positions of the peak points of the synchronization energy of the two sequences, determine whether the current signal is synchronized correctly. Step 4: Fine synchronization employs a method that correlates the received signal with the reference signal SynRefSig. Based on the sign of the DPCCH symbol and the carrier frequency offset CFO, a reference signal SynRefSig is constructed and scrambled. A search is performed at the coarse synchronization starting point, and SIG0 is obtained by decimation at an oversampling factor of 8. Its correlation value with the received signal is then calculated. R i =|∑SIG0 i *conj(SynRefSig)| 2 In the above formula, i represents the starting point of the intercepted signal, conj(.) represents the conjugate operation, and the sampling point corresponding to the correlation peak is the optimal starting point of the signal:

3. The vector signal analysis and processing method for the uplink signal receiver in a wideband code division multiple access wireless communication system according to claim 2, characterized in that, In step one, the matched filter is a root-raised cosine matched filter with a roll-off factor of 0.22; In step 2, In the formula, Δθ is the phase difference between adjacent DPCCH symbols, in radians; In step 4, Pilot_DPCCH is the pilot symbol.

4. The vector signal analysis and processing method for the uplink signal receiver in a wideband code division multiple access wireless communication system according to claim 2, characterized in that, Step two includes the following steps: Step a: Search for 256 chip sampling points in the sequence. These 256 chip sampling points correspond to the 256 starting chip positions of an OVSF(256,0) spread spectrum symbol, thus obtaining the starting point of the OVSF(256,0) spread spectrum symbol. Step b: Extract multiple OVSF(256,0) spreading symbol lengths of 256 / 3.84M. Search for the scrambling codes used when scrambling the 150 spreading symbols of a radio frame with OVSF(256,0) spreading factors. That is, use the scrambling codes that may be used by the 150 pilot symbols of a radio frame to descramble the first 256 chips of the sequence. OVSF is an orthogonal variable spreading factor. Step c: After the truncated sequence is descrambled, the absolute values ​​of the symbols of the calculated multiple DPCCHs are summed to eliminate the influence of the polarity of each symbol and improve the synchronization signal-to-noise ratio. Step d: Determine the symbol starting chip point and a specific symbol of the 150 symbols in the radio frame based on the synchronization energy obtained in step c.

5. The vector signal analysis and processing method for the uplink signal receiver in a wideband code division multiple access wireless communication system according to claim 4, characterized in that, In step c, In the formula, DescrambleSeq is the descrambled chip rate sequence, where n is the chip number of a DPCCH symbol, i is the cumulative DPCCH symbol number, Nsymbol is the total cumulative number of DPCCH symbols, and the spreading factor is 256.

6. The vector signal analysis and processing method for the uplink signal receiver in a wideband code division multiple access wireless communication system according to claim 1, characterized in that, In step 3, the DC bias is estimated using a two-step estimation method. First, a coarse estimate of the I and Q signals is obtained by calculating the average value of the I and Q signals, thus yielding a coarse estimate of the DC bias. DC1=mean(y R (n))+j·mean(y I (n)) And perform coarse DC compensation, y R (n) and y I (n) represent the real and imaginary parts of the received sequence y(n), respectively, j represents the imaginary unit, and mean(.) represents the mean value; after estimating the spreading code and channel power of the active channel, and constructing the reference constellation point RefIQ for the error vector amplitude in combination with the scrambling code, the DC bias is then precisely estimated based on the constructed reference constellation point RefIQ to obtain DC2, i.e.: DC2 = mean(y(n) - IdealSeq) The results of the two-step estimation, DC = DC1 + DC2, are combined to perform DC compensation on the subsequent signal. IdealSeq represents the ideal received sequence after hard decision based on the constructed reference constellation points.

7. The vector signal analysis and processing method for the uplink signal receiver in a wideband code division multiple access wireless communication system according to claim 1, characterized in that, In step 5, the spreading code used by the active channel of the received signal is identified based on the OVSF code tree search, and the power of the active channel is estimated. Since the spreading factor used by WCDMA signals is 4 to 512, in order to identify the spreading code, a code tree search is performed on each spreading factor. The search starts from the leaf node of the OVSF code tree. If the current leaf node is the active channel code, then all the root nodes corresponding to it cannot be activated again, so there is no need to repeat the search. In step 5, the received sequence is first inlined using Lagrange interpolation, and then decimated by 8 times. The optimal weighting value is obtained by calculating the EVM of the modulation domain of the sequence with a synchronization accuracy of 1 / 32*Tchip. Tchip is the chip time of the WCDMA wireless communication system. The reference constellation point RefIQ is constructed by using BPSK modulation, the spreading code of the active channel, power estimation, and scrambling code to calculate the error vector amplitude of the WCDMA uplink signal.

8. The vector signal analysis and processing method for the uplink signal receiver in a wideband code division multiple access wireless communication system according to claim 1, characterized in that, In step 6, Z_DPDCH is demodulated using the symbol modulation type BPSK of the DPDCH channel. To demultiplex the DPDCH channel, rate matching is first performed based on the rate matching parameters of the DPDCH. The number of bits carried by the physical channel and the number of physical channel bits TB1 and the number of encoded bits TB2 of each transmission channel are calculated. After obtaining the number of encoded bits of a single transmission channel, Viterbi decoding is performed using the channel coding type of that transmission channel. In step 6, the 1 / 3 rate convolutional code and 1 / 3 rate Turbo code used in the WCDMA standard are respectively subjected to Viterbi decoding, and the decoding output is checked by CRC to verify the correctness of the decoded output transport block TB. In step 6, the rate matching and channel multiplexing of the uplink dedicated physical data channel DPDCH are processed on a per radio frame basis, while the Viterbi decoding process can only be performed after a full TTI of data has been collected, thus obtaining a TB transport block.

9. A vector signal analysis and processing system for the uplink signal receiver of a wideband code division multiple access wireless communication system, characterized in that, include: The memory, the processor, and the computer program stored in the memory, the computer program being configured to, when invoked by the processor, implement the steps of the vector signal analysis and processing method for the uplink signal receiver of any one of claims 1-8 in a wideband code division multiple access wireless communication system.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program configured to, when invoked by a processor, implement the steps of the vector signal analysis and processing method for the uplink signal receiver of the wideband code division multiple access wireless communication system according to any one of claims 1-8.

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