A MIMO frequency offset estimation method and system

Abstract

The present invention provides a MIMO frequency offset estimation method and system, including: obtaining frequency domain data where PDSCH-DMRS symbols of two time slots are located, determining whether there is an overlap in the PDSCH frequency domain resource distribution of the two time slots, recording the overlapping part of the frequency domain resources, respectively using the transmission sequences and received data of the DMRS symbols of the two time slots to perform channel estimation on the receiving antennas; calculating the phase difference between two symbols at a preset time interval based on the channel estimation and combining them, and calculating the frequency offset based on the combined phase difference. The present invention uses the phase difference between symbols between SLOTs to estimate FO. Because the selected time interval is relatively large, the accuracy is higher than that of conventional FOE.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and in particular, to a MIMO frequency offset estimation method and system. Background Art

[0002] In a communication system, when there is a frequency offset in a receiver, it will affect the demodulation performance. In a MIMO system, it may cause crosstalk between subcarriers and time-domain interpolation. Especially when using high-order modulation, it is more sensitive to FO (frequency offset). The accuracy of FOE (frequency offset estimation) is related to the time interval between symbols and the number of symbols involved. The larger the time interval and the more the number of symbols, the more accurate the result of FOE. However, in the prior art, when performing frequency offset estimation, the symbol interval used is small, resulting in insufficient accuracy of frequency offset estimation. Summary of the Invention

[0003] Therefore, the present invention provides a MIMO frequency offset estimation method and system to solve the technical problem of insufficient accuracy of frequency offset estimation in the prior art.

[0004] A MIMO frequency offset estimation method includes:

[0005] Step A1: Obtain first frequency-domain data of a first symbol of a demodulation reference signal of a physical downlink shared channel in a first time slot, and second frequency-domain data of a second symbol of a demodulation reference signal of a physical downlink shared channel in a second time slot;

[0006] Step A2: Determine whether there is an overlapping part of the frequency-domain resources of the physical downlink shared channel according to the first frequency-domain data and the second frequency-domain data:

[0007] If so, execute Step A3;

[0008] If not, exit;

[0009] Step A3: Record the overlapping part of the frequency-domain resources;

[0010] Step A4: Obtain first transmitted data and first received data of the first symbol corresponding to the overlapping part, and second transmitted data and second received data of the second symbol;

[0011] Step A5: Obtain a first channel estimation of a receiving antenna for receiving the first symbol according to the first transmitted data and the first received data, and obtain a second channel estimation of a receiving antenna for receiving the second symbol according to the second transmitted data and the second received data;

[0012] Step A6: Obtain symbol pairs composed of a first symbol and a second symbol with a preset time interval, calculate the phase difference between each pair of symbol pairs based on the first channel estimate and the second channel estimate, and combine the phase differences of each pair of symbol pairs.

[0013] Step A7: Calculate the frequency offset based on the combined phase difference.

[0014] Furthermore, it is characterized in that there is a preset number of time slot intervals between the first time slot and the second time slot.

[0015] Furthermore, when the subcarrier spacing in the frequency domain resource is 30 KHz, the preset number is 1 to 4.

[0016] Furthermore, when the subcarrier spacing in the frequency domain resource is 15 KHz, the preset number is 1 to 2.

[0017] Furthermore, in Step A5, the calculation formula for the first channel estimate is as follows:

[0018] H(rx, l0, m) = Y(rx, l0, m) * conj(X(l0, m));

[0019] The calculation formula for the second channel estimate is as follows:

[0020] H(rx, l1, m) = Y(rx, l1, m) * conj(X(l1, m));

[0021] In Step A6, the calculation formula for the combined phase difference is as follows:

[0022]

[0023] Among them,

[0024] l0 is the index of the first symbol with a preset time interval of the symbol;

[0025] l1 is the index of the second symbol with a preset time interval of the symbol;

[0026] rx is the index of the receiving antenna;

[0027] m is the frequency domain resource index of the demodulation reference signal of the physical downlink shared channel;

[0028] τ is the preset time interval;

[0029] Set_idx is the overlapping part of the frequency domain resource;

[0030] is the combined phase difference;

[0031] X(l0, m) is the first transmitted data;

[0032] X(l1, m) is the second transmission data;

[0033] Y(rx, l0, m) is the first received data;

[0034] Y(rx, l1, m) is the second received data.

[0035] Furthermore, in step A7, the calculation formula for the frequency offset is as follows:

[0036] θ = angle(φτ)(2 * π * τ);

[0037] where θ is the frequency offset.

[0038] A MIMO frequency offset estimation system using the aforementioned MIMO frequency offset estimation method includes:

[0039] A first acquisition module for acquiring the first frequency domain data where the first symbol of the demodulation reference signal of the physical downlink shared channel is located in the first time slot, and the second frequency domain data where the second symbol of the demodulation reference signal of the physical downlink shared channel is located in the second time slot;

[0040] A judgment module connected to the first acquisition module for judging whether there is an overlapping part of the physical downlink shared channel frequency domain resources according to the first frequency domain data and the second frequency domain data, and outputting a judgment result;

[0041] A recording module connected to the judgment module for recording the overlapping part of the frequency domain resources;

[0042] A second acquisition module connected to the recording module for acquiring the first transmission data and the first received data of the first symbol corresponding to the overlapping part, and the second transmission data and the second received data of the second symbol;

[0043] A channel estimation module connected to the second acquisition module for obtaining the first channel estimation of the receiving antenna for receiving the first symbol according to the first transmission data and the first received data, and obtaining the second channel estimation of the receiving antenna for receiving the second symbol according to the second transmission data and the second received data;

[0044] A phase calculation module respectively connected to the channel estimation module and the recording module for acquiring symbol pairs composed of the first symbol and the second symbol with a preset time interval, and calculating the phase difference between each pair of symbol pairs according to the first channel estimation and the second channel estimation, and merging the phase differences of each pair of symbol pairs;

[0045] A frequency offset calculation module connected to the phase calculation module for calculating the frequency offset according to the merged phase differences.

[0046] Furthermore, there is a preset number of time slot intervals between the first time slot and the second time slot.

[0047] Further, when the subcarrier spacing in the frequency domain resource is 30 KHz, the preset quantity is 1 to 4.

[0048] Further, when the subcarrier spacing in the frequency domain resource is 15 KHz, the preset quantity is 1 to 2.

[0049] The beneficial technical effect of the present invention is that: by using the phase difference of symbols between time slots SLOT to estimate FO, a larger selected time interval is used, and the FOE accuracy is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a flowchart of the steps of a MIMO frequency offset estimation system according to the present invention;

[0051] Figure 2 is a schematic diagram of the modules of a MIMO frequency offset estimation system according to the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0053] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0054] Next, the present invention will be further described in conjunction with the drawings and specific embodiments, but not as a limitation of the present invention.

[0055] See Figure 1 , the present invention provides a MIMO frequency offset estimation method, including:

[0056] Step A1, obtaining first frequency domain data of the demodulation reference signal of the physical downlink shared channel in the first time slot, and second frequency domain data of the demodulation reference signal of the physical downlink shared channel in the second time slot;

[0057] Step A2, judging whether there is an overlapping part of the physical downlink shared channel frequency domain resource according to the first frequency domain data and the second frequency domain data:

[0058] If so, execute step A3;

[0059] If not, exit;

[0060] Step A3, recording the overlapping part of the frequency domain resource;

[0061] Step A4, obtain the first transmission data and the first reception data of the first symbol corresponding to the overlapping part, and the second transmission data and the second reception data of the second symbol;

[0062] Step A5, obtain the first channel estimation of the receiving antenna for receiving the first symbol based on the first transmission data and the first reception data, and obtain the second channel estimation of the receiving antenna for receiving the second symbol based on the second transmission data and the second reception data;

[0063] Step A6, obtain symbol pairs composed of the first symbol and the second symbol with a preset time interval, calculate the phase difference between each pair of symbol pairs based on the first channel estimation and the second channel estimation, and combine the phase differences of each pair of symbol pairs;

[0064] Step A7, calculate the frequency offset based on the combined phase difference.

[0065] In step A1, the time-domain data of the symbols in the first time slot received from the transmitter is converted into first frequency-domain data, and the time-domain data of the symbols in the second time slot received from the transmitter is converted into second frequency-domain data.

[0066] Furthermore, there is a preset number of time slot intervals between the first time slot and the second time slot.

[0067] Furthermore, when the subcarrier spacing in the frequency-domain resource is 30 KHz, the preset number is 1 to 4.

[0068] Furthermore, when the subcarrier spacing in the frequency-domain resource is 15 KHz, the preset number is 1 to 2.

[0069] In step A1, the first time slot and the second time slot may not be adjacent, and the maximum time length difference is related to the frequency offset range to be estimated. Taking the 5G system as an example,

[0070] When the subcarrier spacing is 30K (30K scs), one SLOT time is 0.5 ms; when the subcarrier spacing is 15K (15K scs), one SLOT time is 1 ms.

[0071] Taking the selected PDSCH-DMRS symbols distributed in the same symbols in 2 SLOTs as an example:

[0072]

[0073]

[0074] For general convergence of the target frequency offset tracking within 100 Hz, when the subcarrier spacing is 30Kscs, the maximum interval between the 2 SLOTs of the selected FOE is 4 SLOTs; when the subcarrier spacing is 15Kscs, the maximum interval is 2 SLOTs.

[0075] Further, in step A5, the calculation formula for the first channel estimation is as follows:

[0076] H(rx, l0, m) = Y(rx, l0, m) * conj(X(l0, m));

[0077] The calculation formula for the second channel estimation is as follows:

[0078] H(rx, l1, m) = Y(rx, l1, m) * conj(X(l1, m));

[0079] In step A6, the calculation formula for the combined phase difference is as follows:

[0080]

[0081] Wherein,

[0082] l0 is the index of the first symbol of the symbol preset time interval;

[0083] l1 is the index of the second symbol of the symbol preset time interval;

[0084] rx is the index of the receiving antenna;

[0085] m is the frequency-domain resource index of the demodulation reference signal of the physical downlink shared channel;

[0086] τ is the preset time interval;

[0087] Set_idx is the overlapping part of the frequency-domain resources;

[0088] is the combined phase difference;

[0089] X(l0, m) is the first transmitted data;

[0090] X(l1, m) is the second transmitted data;

[0091] Y(rx, l0, m) is the first received data;

[0092] Y(rx, l1, m) is the second received data.

[0093] Further, in step A7, the calculation formula for the frequency offset is as follows:

[0094] θ = angle(φτ)(2 * π * τ);

[0095] Wherein, θ is the frequency offset.

[0096] See Figure 2, the present invention also provides a MIMO frequency offset estimation system, which uses the aforementioned MIMO frequency offset estimation method, and includes:

[0097] A first acquisition module (1) for acquiring first frequency domain data of the first symbol of the demodulation reference signal of the physical downlink shared channel in the first time slot, and second frequency domain data of the second symbol of the demodulation reference signal of the physical downlink shared channel in the second time slot;

[0098] A judgment module (2), connected to the first acquisition module (1), for judging whether there is an overlapping part of the physical downlink shared channel frequency domain resources according to the first frequency domain data and the second frequency domain data, and outputting a judgment result;

[0099] A recording module (3), connected to the judgment module (2), for recording the overlapping part of the frequency domain resources;

[0100] A second acquisition module (4), connected to the recording module (3), for acquiring first transmission data and first reception data of the first symbol corresponding to the overlapping part, and second transmission data and second reception data of the second symbol;

[0101] A channel estimation module (5), connected to the second acquisition module (4), for obtaining a first channel estimation of the receiving antenna for receiving the first symbol according to the first transmission data and the first reception data, and obtaining a second channel estimation of the receiving antenna for receiving the second symbol according to the second transmission data and the second reception data;

[0102] A phase calculation module (6), respectively connected to the channel estimation module (5) and the recording module (3), for obtaining symbol pairs composed of the first symbol and the second symbol with a preset time interval, and calculating the phase difference between each pair of symbol pairs according to the first channel estimation and the second channel estimation, and combining the phase differences of each pair of symbol pairs;

[0103] A frequency offset calculation module (7), connected to the phase calculation module (6), for calculating the frequency offset according to the combined phase difference.

[0104] Furthermore, there is a preset number of time slot intervals between the first time slot and the second time slot.

[0105] Furthermore, when the subcarrier spacing in the frequency domain resource is 30 KHz, the preset number is 1 to 4.

[0106] Furthermore, when the subcarrier spacing in the frequency domain resource is 15 KHz, the preset number is 1 to 2.

[0107] The accuracy of the FOE is related to the time interval between symbols and the number of symbols involved. The larger the time interval and the more the number of symbols, the more accurate the result of the FOE. The present invention uses the phase difference between symbols in SLOTs to estimate FO. Since the selected time interval is larger, it has higher accuracy than the conventional FOE.

[0108] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all the equivalent replacements and obvious changes made by using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A MIMO frequency offset estimation method, characterized in that, it includes: Step A1, obtaining first frequency domain data of the first symbol of the demodulation reference signal of the physical downlink shared channel in the first time slot, and second frequency domain data of the second symbol of the demodulation reference signal of the physical downlink shared channel in the second time slot; Step A2, judging whether there is an overlapping part of the physical downlink shared channel frequency domain resources according to the first frequency domain data and the second frequency domain data: If so, execute Step A3; If not, exit; Step A3, recording the overlapping part of the frequency domain resources; Step A4, obtaining first transmission data and first reception data of the first symbol corresponding to the overlapping part, and second transmission data and second reception data of the second symbol; Step A5, obtaining a first channel estimate of the receiving antenna for receiving the first symbol according to the first transmission data and the first reception data, and obtaining a second channel estimate of the receiving antenna for the second symbol according to the second transmission data and the second reception data; Step A6, obtaining symbol pairs composed of the first symbol and the second symbol with a preset time interval, and calculating the phase difference between each pair of the symbol pairs according to the first channel estimate and the second channel estimate, and combining the phase differences of each pair of the symbol pairs; Step A7, calculating the frequency offset according to the combined phase difference; In the step A5, the calculation formula of the first channel estimate is as follows: H(rx, l0, m) = Y(rx, l0, m) * conj(X(l0, m)); The calculation formula of the second channel estimate is as follows: H(rx, l1, m) = Y(rx, l1, m) * conj(X(l1, m)); In the step A6, the calculation formula of the combined phase difference is as follows: Wherein, l0 is the index of the first symbol of the preset time interval; l1 is the index of the second symbol of the preset time interval; rx is the index of the receiving antenna; m is the frequency domain resource index of the demodulation reference signal of the physical downlink shared channel; τ is the preset time interval; Set_idx is the overlapping part of the frequency domain resources; is the combined phase difference; X(l0, m) is the first transmission data; X(l1, m) is the second transmission data; Y(rx, l0, m) is the first reception data; Y(rx, l1, m) is the second reception data.

2. A MIMO frequency offset estimation method according to claim 1, characterized in that, there is a preset number of time slot intervals between the first time slot and the second time slot.

3. A MIMO frequency offset estimation method according to claim 2, characterized in that, when the subcarrier spacing in the frequency domain resources is 30 KHz, the preset number is 1 to 4.

4. A MIMO frequency offset estimation method according to claim 2, characterized in that, when the subcarrier spacing in the frequency domain resources is 15 KHz, the preset number is 1 to 2.

5. A MIMO frequency offset estimation method according to claim 1, characterized in that, in the step A7, the calculation formula of the frequency offset is as follows: θ = angle(φτ)(2 * π * τ) ； where θ is the frequency offset.

6. A MIMO frequency offset estimation system, characterized in that it uses a MIMO frequency offset estimation method as described in any one of claims 1-5, including: A first acquisition module, configured to acquire first frequency-domain data where a first symbol of a demodulation reference signal of a physical downlink shared channel is located in a first time slot, and second frequency-domain data where a second symbol of a demodulation reference signal of a physical downlink shared channel is located in a second time slot; A judgment module, connected to the first acquisition module, configured to judge whether there is an overlapping part of the physical downlink shared channel frequency-domain resources according to the first frequency-domain data and the second frequency-domain data, and output a judgment result; A recording module, connected to the judgment module, configured to record the overlapping part of the frequency-domain resources; A second acquisition module, connected to the recording module, configured to acquire first transmission data and first reception data of the first symbol corresponding to the overlapping part, and second transmission data and second reception data of the second symbol; A channel estimation module, connected to the second acquisition module, configured to obtain a first channel estimation of a receiving antenna that receives the first symbol according to the first transmission data and the first reception data, and obtain a second channel estimation of the receiving antenna of the second symbol according to the second transmission data and the second reception data; A phase calculation module, respectively connected to the channel estimation module and the recording module, configured to obtain symbol pairs composed of the first symbol and the second symbol with a preset time interval, and calculate a phase difference between each pair of the symbol pairs according to the first channel estimation and the second channel estimation, and merge the phase differences of each pair of the symbol pairs; A frequency offset calculation module, connected to the phase calculation module, configured to calculate a frequency offset according to the merged phase differences.

7. A MIMO frequency offset estimation system as described in claim 6, characterized in that there is a preset number of time slot intervals between the first time slot and the second time slot.

8. A MIMO frequency offset estimation system as described in claim 7, characterized in that when the subcarrier spacing in the frequency-domain resources is 30 KHz, the preset number is 1 to 4.

9. A MIMO frequency offset estimation system as described in claim 7, characterized in that when the subcarrier spacing in the frequency-domain resources is 15 KHz, the preset number is 1 to 2.

Images