Multi-user symbiotic wireless communication channel estimation and signal detection method

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to a multi-user symbiotic wireless communication channel estimation and signal detection method. According to the designed transmission frame structure, the main system sending symbol is recovered by estimating the combined channel containing the reflection device sending symbol, and then the multiplicative relationship between the main system sending symbol and the reflection device sending symbol is decoupled, so that the error rate performance of main system transmission and reflection device transmission is improved. The scheme provided by the invention is simple to implement and has very high application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wireless communication, and particularly relates to a multi-user coexistence wireless communication channel estimation and signal detection method. BACKGROUND

[0002] As one of the key enabling technologies of 6G communication, passive Internet of Things poses unprecedented challenges to the spectrum efficiency and energy efficiency of wireless networks. Coexistence wireless communication technology, with its high spectrum efficiency and high energy efficiency, has become an important technical solution to support large-scale passive Internet of Things deployment.

[0003] In a coexistence communication system, a passive reflecting device uses the electromagnetic wave sent by the transmitter of the main system as a modulation carrier to transmit information by adjusting the reflection coefficient, and the receiver jointly restores the transmission symbols of the transmitter of the main system and the reflecting device. Since the reflecting device reflects the signal of the main system transmitter, the reflecting device provides multipath gain for the transmission of the main system, thereby improving the transmission performance of the main system.

[0004] For large-scale passive Internet of Things device access scenarios such as smart home, how to design a channel estimation and signal detection scheme for multi-user coexistence wireless communication is a difficult problem that needs to be solved. Specifically, first, the reflecting device signal and the main system transmission signal exhibit a multiplicative coupling relationship at the receiving end, and how to decouple and utilize this multiplicative coupling relationship to improve the transmission of the main system transmitter and the reflecting device is crucial. Second, in a multi-user scenario, how to realize the multipath gain brought by the reflecting device for the transmission of the main system is a key problem. SUMMARY

[0005] To solve the above problems, the present application designs a frame structure for the transmission of the main system and the reflecting device, and proposes a multi-user coexistence wireless communication channel estimation and signal detection method. By estimating the combined channel containing the reflecting device transmission symbol, the main system transmission symbol is restored, and then the multiplicative relationship between the main system transmission symbol and the reflecting device transmission symbol is decoupled, thereby improving the bit error rate performance of the transmission of the main system and the reflecting device.

[0006] The technical scheme of the present application is as follows:

[0007] As shown in Figure 1 , the present application considers a multi-user coexistence wireless communication system, which includes a single-antenna main system transmitter, a receiver configured with a root antenna, and a reflecting device. Let h denote the channel response from the main system transmitter to the receiver, h denote the channel response from the main system transmitter to the first reflecting device, h denote the channel response from the first reflecting device to the receiver, and The receiver receives the channel response from each reflecting device to the receiver. The receiver simultaneously recovers the main system transmitter and... The symbol is transmitted by a reflective device.

[0008] like Figure 2 As shown, this invention designs a frame structure for multi-user co-existing wireless communication primary and secondary system transmission. Specifically, the transmission symbol period of the reflecting device is longer than that of the primary system, and a single symbol transmitted by the reflecting device contains... The main system sends a symbol, causing... Indicates the first The first reflector device in the... The transmitted symbols for each cycle, let Indicates the first The transmitted symbol vector of the main system within the transmission cycle of each reflecting device, then the received signal at the receiver. It can be represented as

[0009]

[0010] in This indicates the power of the main system transmitter; This represents additive white Gaussian noise at the receiver, where each element follows a mean of 0 and a variance of . The complex Gaussian distribution; Indicates the first The cascaded channels experienced by each reflecting device; This refers to the combined channels that the main system signals traverse.

[0011] like Figure 2 As shown, within a coherent block, the channel response remains unchanged, and the master system transmitter first sends... One pilot symbol, sent by each reflecting device. pilot symbols, of which On the other hand, during the duration of each reflector data symbol, the master system transmitter sends... The first pilot symbol, i.e., the first one in the main system's transmitted symbol vector. The element is the sub-pilot, and then... Each element represents the transmitted data. Based on the signal received by the receiver, channel estimation, main system symbol detection, and reflection device symbol detection are performed respectively.

[0012] The specific channel estimation and signal detection methods are as follows:

[0013] Channel estimation: The receiver uses the signal transmitted by the main system... Each pilot symbol, and each reflecting device transmits... One pilot symbol is used to estimate the direct link channel using the linear minimum mean square error algorithm. and reflection link concatenated channel ;

[0014] Master system symbol detection: The receiver uses the duration of each reflecting device's data symbol to detect the master system transmitter's transmission. The combined channel is estimated using a single pilot symbol and a linear minimum mean square error algorithm. ;

[0015] The receiver is based on the estimated combined channel The maximum ratio merging scheme was used to recover the main system's transmitted symbols. ;

[0016] Symbol detection of the reflecting device: The receiver relies on the estimated direct link channel. and reflection link concatenated channel And the recovered main system sent signals The zero-forcing algorithm and the least mean square error algorithm were used to recover the results respectively. The symbol transmitted by the reflecting device .

[0017] The beneficial effects of this invention are as follows: Based on the designed transmission frame structure, a combined channel containing symbols transmitted by the reflecting device is estimated, and the main system transmitted symbols are recovered based on the combined channel. This decouples the multiplicative relationship between the main system transmitted symbols and the reflecting device transmitted symbols, thereby improving the bit error rate performance of both the main system transmission and the reflecting device transmission. The scheme is simple to implement and has strong application value. This scheme focuses on proposing a novel transmission frame structure and receiver channel estimation and channel detection schemes, without being limited to the described minimum mean square error algorithm, maximum ratio combining scheme, and zero-forcing algorithm. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the system composition of the present invention.

[0019] Figure 2 This is the system transmission frame structure in this invention.

[0020] Figure 3 This is a performance diagram of the mean square error of channel estimation in this invention;

[0021] Figure 4 This is a graph showing the bit error rate performance of the main system's transmitted signal and the reflected device's signal in this invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings.

[0023] like Figure 1As shown, the present invention considers a multi-user co-existing wireless communication system, comprising a single-antenna master system transmitter and a configuration The receiver with the root antenna, and A reflective device. (Note) This indicates the channel response from the transmitter to the receiver in the main system. Indicates the main system transmitter to the number Channel response of each reflecting device, Indicates the first The receiver receives the channel response from each reflecting device to the receiver. The receiver simultaneously recovers the main system transmitter and... The symbol is transmitted by a reflective device.

[0024] like Figure 2 As shown, this invention designs a frame structure for primary and secondary system transmission in multi-user co-existing wireless communication. Specifically, the transmission symbol period of the reflecting device is longer than that of the secondary system, and a secondary system transmission symbol contains... The main system sends a symbol, causing... Indicates the first The first reflector device in the... The transmitted symbols for each cycle, let Indicates the first The transmitted symbol vector of the main system within the transmission cycle of each reflecting device, then the received signal at the receiver. It can be represented as

[0025] (1)

[0026] in This indicates the power of the main system transmitter; This represents additive white Gaussian noise at the receiver, where each element follows a mean of 0 and a variance of . The complex Gaussian distribution; Indicates the first The cascaded channels experienced by each reflecting device. Within a coherent block, the channel response remains unchanged, and the master system transmitter transmits first. One pilot symbol, sent by each reflecting device. pilot symbols, of which On the other hand, during the duration of each reflector data symbol, the master system transmitter sends... The first pilot symbol, i.e., the first one in the main system's transmitted symbol vector. The element is the sub-pilot, and then... Each element represents the transmitted data.

[0027] Next, we will first describe the first step in the receiver design, namely, using the data transmitted by the main system. Each pilot symbol, and each reflecting device transmits... One pilot symbol is used to estimate the direct link channel using the linear minimum mean square error algorithm. and reflection link concatenated channel Specifically, let Indicates the pilot symbol transmitted by the main system transmitter, let Indicates the first The pilot symbols transmitted by a reflecting device, and the corresponding received pilot symbols. It can be represented as

[0028] (2)

[0029] in Indicates that all elements are 1 dimensional vector, , Indicates received noise. To use the linear minimum mean square error algorithm, we first vectorize both sides of the equality in equation (2), which gives us:

[0030] (3)

[0031] in Using the linear minimum mean square error algorithm, we can obtain...

[0032] (4)

[0033] in , The dimension is The unit vector, and .

[0034] Next, the second step in receiver design is to recover the symbols transmitted by the main system, that is, to use the main system transmitter's... The combined channel is estimated using a single pilot symbol and a linear minimum mean square error algorithm. Specifically, let Indicates the first The sub-pilot symbols of the main system transmitter within a symbol period of a reflecting device, making Indicates the first The data symbols of the main system transmitter within a symbol period of a reflecting device are then The received signal in formula (1) can be rewritten as:

[0035] (5)

[0036] Based on sub-pilot symbols and its corresponding received signal The receiver can estimate the combined channel using a linear minimum mean square error algorithm First, vectorize the sub-pilot signals on both sides of equation (5) to obtain

[0037]

[0038] The estimate can be expressed as

[0039] (6)

[0040] where .

[0041] Using the combined channel estimated by equation (6), recover the transmitted data symbols of the primary system

[0042] (7)

[0043] where denotes the set of constellation points of the transmitted symbols of the primary system.

[0044] Finally, the third step of the receiver design is to recover the transmitted symbols of the reflective devices using zero-forcing and minimum mean square error algorithms, respectively, based on the estimated direct link channel and the concatenated channel of the reflective links , and the recovered transmitted symbols of the primary system . Specifically, let denote the vector formed by the transmitted symbols of the reflective devices, then the received signal can be re-expressed as

[0045] (8)

[0046] where denotes the channel matrix formed by all reflective links. To recover , the receiver first removes the direct link signal using the channel estimated in the first step and the recovered transmitted symbols of the primary system , and the processed signal can be expressed as

[0047] (9)

[0048] where characterizes the channel estimation error and the effect of symbol errors in the primary system. Vectorize the above processed signal to obtain

[0049] (10)

[0050] The decision scheme recovered by the zero-forcing algorithm and the minimum mean square error algorithm can be expressed as:

[0051] (11)

[0052] wherein

[0053] (12)

[0054] and .

[0055] Below, the present application shows simulation results to verify the performance of the proposed multi-user coexistence wireless communication channel estimation and signal detection method. Wherein the direct link channel and the reflected link channel are subject to Rayleigh fading, the average intensity ratio of the reflected link to the direct link is -20 dB, the main system transmission signal adopts quadrature phase shift keying modulation, the reflected device signal adopts binary phase shift keying modulation, the period ratio of the reflected device signal to the main system transmission signal is , the number of reflected devices is , the number of receiver antennas is set to , the reflected device pilot length is set to , and the number of main system transmitter sub-pilots is .

[0056] Figure 3 The performance figure of the mean square error of the proposed channel estimation with the change of the signal-to-noise ratio is shown, wherein the calculation method of the mean square error in step one is , and the calculation method of the mean square error in step two is . As can be seen from Figure 3 , the channel estimation algorithm proposed in steps one and two decreases with the improvement of the signal-to-noise ratio. The number of pilots used to estimate the direct link signal and the reflected link channel in step one is , and the number of pilots used to estimate the combined channel in step two is , so step one can achieve better mean square error performance. It is worth noting that although the number of pilots in step one is , the pilot sequence has strong correlation, which is caused by the multiplicative coupling relationship between and .

[0057] Figure 4 ​The graph shows the performance of the bit error rate (BER) of the main system signal and the reflecting device signal as a function of the direct link signal-to-noise ratio (SNR). It can be seen that as the SNR of the direct link increases, the BER of both the main system signal and the reflecting device signal decreases, with no BER plateau. Furthermore, the performance of estimating the reflecting device signal using the minimum mean square error (MMS) algorithm is superior to that using the zero-forcing algorithm, because the MMS algorithm considers the impact of noise. In addition, the graph compares the performance of signal detection based on the channels estimated in steps one and two with the performance of signal detection under known channel information. It shows that for the BER performance of the main system and reflecting device signals, the channel estimation error will result in a performance difference of 2-3 dB. The graph also compares the BER performance under a perfectly known channel scenario without a reflecting device. It shows that the proposed detection scheme can realize the multipath gain brought by the reflecting device, and as the ratio of the average strength of the reflecting link to the direct link increases (from -20 dB to -10 dB in the last curve), the multipath gain obtained by the main system increases.

Claims

1. A method for channel estimation and signal detection in multi-user co-existing wireless communication, wherein the multi-user co-existing wireless communication system has one antenna master system transmitter and one configuration The receiver with the root antenna, and A reflector device, the receiver simultaneously restores the main system transmitter and... The symbol transmitted by a reflecting device is characterized by: The symbol period of the reflecting device is set to be longer than that of the main system, and a symbol transmitted by the reflecting device contains [number of symbols]. Each master system transmits symbols; within a coherent block, the channel response remains unchanged; the master system transmitter transmits... One pilot symbol, sent by each reflecting device. pilot symbols, of which During the duration of each reflector data symbol, the master system transmitter sends... The first pilot symbol, i.e., the first one in the main system's transmitted symbol vector. The element is the sub-pilot, and then... Each element represents the transmitted data. It is the length of the symbol vector transmitted by the main system; defined in the... Within the symbol period of the reflecting device, the first The transmitted symbol of each reflecting device is The main system's transmitted symbol vector is ,in Indicates the first Sub-pilot symbols of the main system transmitter within one symbol period of the reflecting device symbol. Indicates the first The data symbols transmitted by the main system transmitter within a symbol period of the reflecting device, and the received signals at the receiver. for: ， in, This indicates the power of the main system transmitter. This represents the channel response from the transmitter to the receiver in the main system. Indicates the main system transmitter to the number Channel response of a reflecting device Indicates the first Channel response from a reflecting device to a receiver. Indicates the main system transmitter to the number The cascaded channel response from the reflecting device to the receiver To receive noise, where the matrix Each element follows a mean of zero variance. The signal follows a complex Gaussian distribution. Based on the received signal, channel estimation, main system transmitted symbol detection, and reflection device transmitted symbol detection are performed respectively. The channel estimation method is as follows: definition This indicates the pilot symbols transmitted by the main system transmitter. Indicates the first The pilot symbols transmitted by a reflecting device, and the corresponding received pilot symbols. Represented as: ， in, To receive noise, For elements all equal to 1 dimensional vector, Represented as , Vectorization yields: ， in, The solution is obtained using the linear minimum mean square error algorithm. The estimated value : ， in, , The dimension is The unit vector, and ,in yes The estimated value, It is all indivual The estimated value; The main system sends a symbol detection method as follows: Based on the main system's transmitted symbol vector The received signal from the receiver is: ， in, Sub-pilot symbol The corresponding received signal, Indicates main system data symbols The corresponding received signal, For combined channels, It is the additive white Gaussian noise at the receiver, which is vectorized to obtain: ， The solution is obtained using the linear minimum mean square error algorithm. The estimated value : ， in, ; use Restore the data symbols sent by the main system : ， in, This represents the set of constellation points for the symbols transmitted by the master system; therefore, the master system transmits signals. The estimated value is ; The method for detecting symbols transmitted by the reflecting device is as follows: definition express If a vector is formed by symbols transmitted by a reflecting device, then the received signal is represented as: ， in, This represents the channel matrix formed by all reflection links; Using the estimated In and the main system sending symbols for recovery Remove direct link signals: ， in, The vectorized result is used to characterize the impact of channel estimation error and main system symbol errors. ， The symbols transmitted by the reflecting device were recovered using the zero-forcing algorithm and the least mean square error algorithm. ， ， in, , by estimation The conclusion is as follows.

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