Method for reducing peak-to-average power ratio in combination with THP precoding

Abstract

The invention discloses a method for reducing a peak-to-average ratio in combination with THP precoding, which is characterized in that a prefilter is added between a modulus in a THP precoding filter and a feedback filter for coding, so that the peak-to-average ratio of a signal is reduced based on a dynamic range output by the filter on the THP precoding, and the dynamic range reaching a transmission drive is reduced. The invention provides a method for reducing the peak-to-average power ratio in combination with THP precoding, which is used for reducing the peak-to-average power ratio of a transmitted signal so as to reduce the design requirement on transmission drive.

Description

Technical Field

[0001] The present invention relates to the field of mobile communications, and more specifically, to a method for reducing a peak-to-average ratio by combining THP precoding. Background Art

[0002] The line transmit driver is used to amplify the transmission signal. In a symmetrical twisted pair transmission system, since the data transmission in the uplink and downlink directions is transmitted in the same frequency band, echo cancellation is required in the receiver. This requires the line driver to have high linearity. The peak-to-average ratio (PARR) defines the ratio of the peak voltage to the root mean square voltage, mainly in decibels (dB).

[0003] Generally speaking, for a fixed output power, the higher the peak-to-average ratio, the lower the high linearity range of the transmit driver. Therefore, reducing the peak-to-average ratio of the transmitted data helps to improve the dynamic range of the transmit driver, thereby improving the overall performance of the system. THP precoding filter (Tomlinson-Harashima precoding) technology is widely used in twisted pair transmission systems. By performing nonlinear precoding at the transmitting end, a pre-equalization effect can be achieved, avoiding the use of decision feedback equalization at the receiving end.

[0004] Conventional THP precoding filters such as Figure 2 As shown, the data source generates source data symbols to the THP precoding filter, and after being processed by the adder, modulo and digital filtering, the data is sent to the downstream module.

[0005] like Figure 3 As shown, the data generated by the data source is usually processed in the digital domain by the THP precoding filter and the digital shaping filter, converted into an analog signal by the DAC, and then sent to the transmission driver after removing the image by the analog transmission filter. Due to the existence of the modulo algorithm in the THP module, the dynamic range of the THP precoding filter output is between -1 and +1, but the dynamic range of the digital shaping filter is between -1.7 and +1.7, and the dynamic range of the analog transmission filter is usually between -1.3 and +1.3. Compared with the output of the THP precoding filter, the signal reaching the transmission driver has a larger dynamic range, resulting in a higher peak-to-average ratio, so the requirements for the line driver circuit are also high. Summary of the invention

[0006] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0007] In order to achieve these objectives and other advantages of the present invention, a method for reducing the peak-to-average ratio in combination with THP precoding is provided, by adding a prefilter encoding between the modulus and feedback filter in the THP precoding filter (Tomlinson-Harashima precoding) to reduce the peak-to-average ratio of the signal based on the dynamic range of the filter output on the THP precoding, thereby reducing the dynamic range reaching the transmit drive.

[0008] Preferably, the encoding of the pre-filter is performed by adding a positive modulo taker and a negative modulo taker to the modulo, thereby performing positive modulo, normal modulo and negative modulo to form three types of transmission signal estimation modules. The modulo control module receives three groups of signals, takes the smallest signal among them, and transmits it to the feedback filter.

[0009] Preferably, the method specifically comprises the following steps:

[0010] Step 1: The data source generates source data symbols to the THP precoding filter, passes through the adder, and reaches the pre-filter on the modulus;

[0011] Step 2: The pre-filter can perform three operations of positive modulus, normal modulus and negative modulus according to the control signal through the added positive modulus taker and negative modulus taker. The signal output by the positive modulus taker is sent to the first transmission signal estimation module, the signal output by the normal modulus taker is sent to the second transmission signal estimation module, and the signal output by the negative modulus taker is sent to the third transmission signal estimation module;

[0012] Step 3: The data estimated by the first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module are sent to the modulo control module for size comparison, and the one with the smallest peak-to-average ratio is selected. At this time, the pre-filter outputs a control signal according to the comparison situation, controls the modulo 2 to perform the corresponding modulo operation, and transmits it to the feedback filter. The new data source enters and repeats steps 1 to 3. This is an iterative operation, and each iteration has a corresponding output result;

[0013] Step 4: The data generated by the THP precoding filter is processed in the digital domain by the digital shaping filter, converted into an analog signal by the DAC, and then passed through the analog transmit filter to remove the image and sent to the transmit driver.

[0014] Preferably, wherein

[0015] It is known that the filter parameter settings of the first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module need to satisfy the transmission function:

[0016] H etx (f) = H dtx (f)*H atx (f)

[0017] The transfer function of the digital shaping filter is H dtx (f), the transfer function of the analog link composed of DAC and analog transmit filter is H atx (f);

[0018] Furthermore, the first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module are three completely identical digital filters.

[0019] Preferably, wherein H dtx (f) is the transfer function of the digital shaping filter, passing through the first step of the most unfavorable sampling time:

[0020]

[0021] in,

[0022] i represents the signal number; t represents the sampling time;

[0023] y(t) represents the signal output by the digital shaping filter;

[0024] x i represents the ith filter input signal; h represents the transfer function of the digital shaping filter;

[0025] T is the sampling period;

[0026] The second step is sampling time t:

[0027]

[0028] in,

[0029] i represents the signal number; t represents the sampling time;

[0030] y(t) represents the signal output by the digital shaping filter;

[0031] h represents the transfer function of the digital shaping filter; T is the sampling period;

[0032] After determining the most unfavorable sampling time t in the third step, we can get:

[0033] h dtx (t) = h(t max +i·T)i=0,1,...,N;

[0034] in,

[0035] i represents the signal number;

[0036] t max It is the sampling time when the filter output amplitude is the largest (the most unfavorable sampling time);

[0037] y(t) represents the signal output by the digital shaping filter;

[0038] h dtx It represents the transfer function of the digital shaping filter at the most unfavorable sampling time;

[0039] T is the sampling period;

[0040] The fourth step is to normalize the sampling value at the most unfavorable sampling time to obtain the corresponding H dtx (f) Filter transfer function.

[0041] Preferably, the normalization selects maximum normalization, dividing all coefficients by the largest coefficient through linear transformation.

[0042] Preferably, after each round of symbol data processing is completed, the data registers of the first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module need to be updated to the currently selected data values ​​to prepare for the next symbol data reference.

[0043] The present invention has at least the following beneficial effects:

[0044] The present invention provides a method for reducing the peak-to-average ratio by combining THP precoding, which can be well combined with the THP precoding system and will not reduce the system transmission performance. The peak compensation filter can estimate the line transmission signal and generate a corresponding modulus control signal according to the estimated signal.

[0045] The purpose of the present invention is to design a pre-filter and method in combination with a THP precoding filter, so as to reduce the peak-to-average ratio of a transmitted signal, thereby reducing the design requirements for a transmit driver.

[0046] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of a method for reducing the peak-to-average ratio by combining THP precoding according to the present invention;

[0048] Figure 2 It is the operating principle diagram of the conventional THP precoding filter;

[0049] Figure 3 The diagram is a schematic diagram of the operation of a data source entering a sending driver in the prior art. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0051] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0052] It should be noted that in the description of the present invention, the orientation or positional relationship indicated by the term is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0053] In the description of the present invention, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] In addition, in the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0055] In order to solve the problem that the output signal of the THP module is transmitted to the transmitting driver with a higher dynamic range and a higher peak-to-average ratio, the present invention reduces the peak-to-average ratio of the transmitting signal by setting a pre-filter, thereby reducing the design requirements for the transmitting driver. The specific solution ideas are as follows:

[0056] Figure 1-3 A method of reducing the peak-to-average ratio by combining THP precoding according to the present invention is shown, comprising:

[0057] By adding a pre-filter encoding between the modulus 2 and the feedback filter 3 in the THP pre-coding filter, the peak-to-average ratio of the signal is reduced based on the dynamic range of the filter output on the THP pre-coding, so that the dynamic range reaching the transmission drive is reduced. Specifically,

[0058] The encoding of the pre-filter is performed by adding a positive modulo 7 and a negative modulo 8 to the modulo 2, thereby performing positive modulo, normal modulo and negative modulo to form three types of transmission signal estimation modules. The modulo control module 9 receives three groups of signals, takes the smallest signal among them, and transmits it to the feedback filter 3.

[0059] As in the above scheme, the identification test method of the method of reducing the peak-to-average ratio by combining THP precoding specifically includes the following steps:

[0060] Step 1: The data source generates source data symbols to the THP precoding filter, passes through adder 1, and reaches the pre-filter on modulus 2;

[0061] Step 2: The pre-filter can perform three operations of positive modulus, normal modulus and negative modulus according to the control signal through the added positive modulus taker and negative modulus taker. The signal output by the positive modulus taker is sent to the first transmission signal estimation module 4, the signal output by the normal modulus taker is sent to the second transmission signal estimation module 5, and the signal output by the negative modulus taker is sent to the third transmission signal estimation module 6;

[0062] Specifically:

[0063] ① The signal passes through the forward modulo 7, adds an offset 2N to the modulo 2 output signal, and outputs the first transmission signal to the first transmission signal estimation module 4;

[0064] ② The signal is not assisted by any modulus taker, and directly enters the second transmission signal estimation module 5 as the original signal (recorded as the second transmission signal);

[0065] ③ The signal passes through the negative modulo 8, adds a bias of -2N to the modulo 2 output signal, and outputs the third transmission signal to the third transmission signal estimation module 6;

[0066] Step 3: The data estimated by the first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module are sent to the modulus control module 9 for size comparison, and the one with the smallest peak-to-average ratio is selected. At this time, the pre-filter outputs a control signal according to the comparison situation, controls the modulus 2 to perform the corresponding modulus operation, and transmits it to the feedback filter 3, and then infinitely iterates steps 1 to 3 until the signal meets the output result;

[0067] By comparing the first transmission signal, the second transmission signal and the third transmission signal in the modulo control module 9, intercepting the smallest one among them, outputting the control signal, the modulo 2 performs the corresponding modulo operation and then transmits the signal to the feedback filter 3, the new data source enters and repeats steps 1 to 3, this is an iterative operation, and each iteration has a corresponding output result;

[0068] Step 4: The data generated by the THP precoding filter is processed in the digital domain by the digital shaping filter, converted into an analog signal by the DAC, and then passed through the analog transmit filter to remove the image and sent to the transmit driver.

[0069] The present invention has reduced the peak-to-average ratio of the transmission signal through the pre-filter. When the signal is transmitted to the transmission driver, the dynamic range tends to the normal range, thereby reducing the design requirements for the transmission driver.

[0070] As in the above scheme,

[0071] It is known that the filter parameter settings of the first transmission signal estimation module 4, the second transmission signal estimation module 5 and the third transmission signal estimation module 6 need to satisfy the transmission function:

[0072] H etx (f) = H dtx (f)*H atx (f)

[0073] The transfer function of the digital shaping filter is H dtx (f), the transfer function of the analog link composed of DAC and analog transmit filter is H atx (f);

[0074] The first transmission signal estimation module 4, the second transmission signal estimation module 5, and the third transmission signal estimation module 6 are three completely identical digital filters, which ensure that the signal output by the modulo 2 is input and the deviation is reduced. At this time, the transmission signal estimation module outputs the estimated transmission signal under the corresponding input signal;

[0075] Among them, H atx (f) can be obtained by testing means in combination with a specific circuit, and the present invention will not elaborate on this. dtx (f) The specific steps for determining the function are:

[0076] Through the first step, the most unfavorable sampling time (that is, the sampling time when the output signal has the maximum value):

[0077]

[0078] in,

[0079] i represents the signal number; t represents the sampling time;

[0080] y(t) represents the signal output by the digital shaping filter;

[0081] x i represents the ith filter input signal; h represents the transfer function of the digital shaping filter;

[0082] T is the sampling period;

[0083] The second step is sampling time t:

[0084]

[0085] in,

[0086] i represents the signal number; t represents the sampling time;

[0087] y(t) represents the signal output by the digital shaping filter;

[0088] h represents the transfer function of the digital shaping filter; T is the sampling period;

[0089] After determining the most unfavorable sampling time t in the third step, we can get:

[0090] h dtx (t) = h(t max +i·T)i=0,1,...,N;

[0091] in,

[0092] i represents the signal number;

[0093] t max It is the sampling time when the filter output amplitude is the largest (the most unfavorable sampling time);

[0094] y(t) represents the signal output by the digital shaping filter;

[0095] h dtx It represents the transfer function of the digital shaping filter at the most unfavorable sampling time;

[0096] T is the sampling period;

[0097] The fourth step is to normalize the sampling value of the worst sampling phase to obtain the corresponding filter coefficient (the filter coefficient is a fixed coefficient that has been tested and calculated in advance, and the coefficient is related to the filter parameters). dtx (f) Filter transfer function.

[0098] As in the above scheme, the normalization (normalization, also known as data normalization, is a common data preprocessing technology, which helps to improve the convergence speed of the model, avoid weight imbalance, minimize the precision loss of fixed-point operations, and improve calculation accuracy) selects normalization processing to find the most suitable filter coefficients to obtain the corresponding H dtx (f) Filter transfer function.

[0099] As in the above scheme, after each round of symbol data processing is completed, the data registers of the first transmission signal estimation module 4, the second transmission signal estimation module 5, and the third transmission signal estimation module 6 need to be updated to the currently selected data values ​​to prepare for the next symbol data reference;

[0100] The purpose of register update is to accurately estimate the size of the transmitted signal next time. The selected value needs to be updated to the filter to provide a pre-basis for effective estimation of the next transmitted signal.

[0101] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for reducing peak-to-average ratio by combining THP precoding, characterized in that: By adding a pre-filter encoding between the modulus and the feedback filter in the THP pre-coding filter, the peak-to-average ratio of the signal is reduced based on the dynamic range of the filter output on the THP pre-coding, so that the dynamic range reaching the transmission drive is reduced.

2. The method for reducing peak-to-average ratio by combining THP precoding according to claim 1, characterized in that: The encoding of the pre-filter is performed by adding a positive modulo taker and a negative modulo taker to the modulo, thereby performing positive modulo taker, normal modulo taker and negative modulo taker to form three types of transmission signal estimation modules. The modulo control module receives three groups of signals, takes the smallest signal among them, and transmits it to the feedback filter.

3. The method for reducing peak-to-average ratio by combining THP precoding according to claim 1, characterized in that: The specific steps include: Step 1: The data source generates source data symbols to the THP precoding filter, passes through the adder, and reaches the pre-filter on the modulus; Step 2: The pre-filter can perform three operations of positive modulus, normal modulus and negative modulus according to the control signal through the added positive modulus taker and negative modulus taker. The signal output by the positive modulus taker is sent to the first transmission signal estimation module, the signal output by the normal modulus taker is sent to the second transmission signal estimation module, and the signal output by the negative modulus taker is sent to the third transmission signal estimation module; Step 3: The data estimated by the first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module are sent to the modulo control module for size comparison, and the one with the smallest peak-to-average ratio is selected. At this time, the pre-filter outputs a control signal according to the comparison situation, controls the modulo 2 to perform the corresponding modulo operation, and transmits it to the feedback filter. The new data source enters and repeats steps 1 to 3. This is an iterative operation, and each iteration has a corresponding output result; Step 4: The data generated by the THP precoding filter is processed in the digital domain by the digital shaping filter, converted into an analog signal by the DAC, and then passed through the analog transmit filter to remove the image and sent to the transmit driver.

4. The method for reducing peak-to-average ratio by combining THP precoding according to claim 3, characterized in that: It is known that the filter parameter settings of the first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module need to satisfy the transmission function: H etx (f)=H dtx (f)*H atx (f) The transfer function of the digital shaping filter is H dtx (f), the transfer function of the analog link composed of DAC and analog transmit filter is H atx (f); The first transmission signal estimation module, the second transmission signal estimation module and the third transmission signal estimation module are three completely identical digital filters.

5. The method for reducing peak-to-average ratio by combining THP precoding according to claim 4, characterized in that: The H dtx (f) is the transfer function of the digital shaping filter, passing through the first step of the most unfavorable sampling time: in, i represents the signal number; t represents the sampling time; y(t) represents the signal output by the digital shaping filter; x i represents the ith filter input signal; h represents the transfer function of the digital shaping filter; T is the sampling period; The second step is sampling time t: in, i represents the signal number; t represents the sampling time; y(t) represents the signal output by the digital shaping filter; h represents the transfer function of the digital shaping filter; T is the sampling period; After determining the most unfavorable sampling time t in the third step, we can get: h dtx (t)=h(t max +i·T)i=0,1,...,N; in, i represents the signal number; t max It is the sampling time when the filter output amplitude is the largest (the most unfavorable sampling time); y(t) represents the signal output by the digital shaping filter; h dtx It represents the transfer function of the digital shaping filter at the most unfavorable sampling time; T is the sampling period; The fourth step is to normalize the sampling value at the most unfavorable sampling time to obtain the corresponding H dtx (f) Filter transfer function.

6. The method for reducing peak-to-average ratio by combining THP precoding according to claim 5, characterized in that: The normalization selects maximum normalization, and divides all coefficients by the largest coefficient through linear transformation.

7. The method for reducing peak-to-average ratio by combining THP precoding according to claim 3, characterized in that: After each round of symbol data processing is completed, the data registers of the first transmission signal estimation module, the second transmission signal estimation module, and the third transmission signal estimation module need to be updated to the currently selected data values ​​to prepare for the next symbol data reference.

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