JP2013058910A - Distortion compensation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distortion compensation device that implements a delay adjustment precisely reflecting an effective data period compatibly with both FDD and TDD communication modes.SOLUTION: In a distortion compensation device, a distortion compensation section 1 distortion-compensates a transmission signal with the use of a distortion compensation table, a delay adjustment section 2 adjusts a delay of the transmission signal yet to be distortion-compensated relative to a feedback signal of the distortion-compensated transmission signal, and an error computation section 3 updates the distortion compensation table so as to reduce a delay error between the delay-adjusted transmission signal and the feedback signal. An effective data period enable generation section 5 generates a signal indicating a period in which the transmission signal has transmission data (effective data period) with the use of a control signal included in the transmission signal, and the delay adjustment section 2 makes the delay adjustment in the effective data period.

Description

  The present invention provides distortion compensation for performing distortion compensation on a transmission signal by adjusting a delay between a transmission signal before distortion compensation and a feedback signal of the transmission signal after distortion compensation in a section where transmission data is present in the transmission signal. More particularly, the present invention relates to a technique for improving delay adjustment in distortion compensation.

In an apparatus that transmits transmission data by a communication method such as the FDD method or the TDD method, for example, a process for compensating for distortion that occurs when a transmission signal carrying the transmission data is amplified by an amplifier is performed.
For example, in a wired or wireless communication system, when a transmitter amplifies a transmission signal by an amplifier, distortion generated by the amplifier is compensated by a distortion compensator.

As an example of such a distortion compensation apparatus, FIG. 6A shows a distortion compensation apparatus used in the FDD system, and FIG. 6B shows a distortion compensation apparatus used in the TDD system.
A transmission signal in the transmitter is input to the distortion compensation unit 1 and the delay adjustment unit 2.
Based on the content of the distortion compensation table stored in the memory, the distortion compensation unit 1 performs a distortion compensation process (for example, a process that gives a distortion with an inverse characteristic) on the input transmission signal, and after the distortion compensation process The transmission signal is output.

  Here, the distortion compensation table stores, for example, the contents of correspondence between the signal level (for example, amplitude or power) and the distortion compensation mode (for example, a coefficient for distortion compensation), and the distortion compensation table. Based on the contents of the above, the distortion compensation unit 1 performs distortion compensation processing on the transmission signal in a distortion compensation mode corresponding to the detected transmission signal level.

  The distortion-compensated transmission signal output from the distortion compensator 1 is amplified by an amplifier (not shown), the amplified signal is output to the transmission antenna side (not shown), and a part of the amplified signal is also transmitted. The signal is branched by a directional coupler or the like and input to the delay adjustment unit 2 and the error calculation unit 3 as a feedback signal.

The delay adjustment unit 2 inputs a transmission signal and a feedback signal before distortion compensation in the FDD scheme, and inputs a transmission signal and a feedback signal before distortion compensation and a signal from the DL data interval enable generation unit 4 in the TDD scheme. Based on these signals, the delay time of the input transmission signal is adjusted, and the transmission signal after the delay adjustment is output to the error calculator 3.
Here, as a technique for adjusting the delay of the transmission signal, for example, the timings of these signals are matched so that the waveform of the transmission signal and the waveform of the feedback signal are matched (as much as possible or moderately).

The error calculation unit 3 calculates the error between the delay-adjusted transmission signal input from the delay adjustment unit 2 and the input feedback signal, and the distortion compensation table stored in the memory so that the obtained error becomes small. Update the contents of.
By adaptively updating the contents of the distortion compensation table in this way, it is possible to hold the contents of a good distortion compensation table with respect to, for example, aging and temperature changes.

Here, when creating a distortion compensation table to be used in the distortion compensation function, it is essential to match the delay of the transmission signal before distortion compensation and the feedback signal from the amplifier. Therefore, the delay adjusting unit 2 adjusts the delay between the transmission signal before distortion compensation and the feedback signal.
FIG. 7 shows a delay adjustment image of the transmission signal and the feedback signal. FIG. 7A shows before delay adjustment, and FIG. 7B shows after delay adjustment.

Here, when adjusting the delay between the transmission signal before distortion compensation and the feedback signal, if the distortion adjustment is performed in a section where the transmission data does not exist in the transmission signal, the delay adjustment with high accuracy cannot be performed, and accordingly, the distortion compensation table is appropriately set. There is a bug that cannot be updated.
That is, in a section where transmission data exists in the transmission signal, as shown in FIG. 7, delay adjustment with a small error can be performed due to large fluctuations in the signal. On the other hand, in a section where transmission data does not exist in the transmission signal. Since the transmission signal is only transmitted with a control signal, the fluctuation of the signal becomes small and delay adjustment with little error cannot be performed.

Therefore, in the TDD scheme, the delay adjustment by the delay adjustment unit 2 uses a transmission signal section (DL transmission section) as an effective data section, as shown in FIG. The guard interval from the transmission interval to the UL reception interval is regarded as an invalid data interval, and processing for matching the delay between the transmission signal before distortion compensation and the feedback signal is performed only in the effective data interval.
In this specification, DL (Down Link) indicates a signal transmitted from the transmitter to the terminal device or the like, and UL (Up Link) indicates a signal received by the transmitter from the terminal device or the like.

  The LTE (Long Term Evolution: Long Term Evolution) TDD system, which is a new mobile phone communication standard, configures transmission, reception, and guard intervals according to the 3GPP (Third Generation Partnership Project) specification shown in FIG. ing.

Further, in the FDD scheme, the delay adjustment by the delay adjustment unit 2 is based on the enable signal from the DL data interval enable generation unit 4 and the transmission signal (DL signal) in which transmission data exists is an effective data interval. Only in this valid data section, processing for adjusting the delay between the transmission signal before distortion compensation and the feedback signal is performed.
Here, the control signal is always transmitted by being carried on the transmission signal at a predetermined cycle such as a frame or a subframe, but the transmission data to be transmitted depends on the presence or absence of the transmission signal. It becomes a burst transmission state.

In the FDD system, in the continuous transmission state of only the transmission signal (DL signal) in which transmission data exists, as shown in FIG. 8B, the section of the transmission signal (DL signal) is set as an effective data section, and this effective data section. The DL data section enable generation unit 4 outputs the signal as an enable only in FIG. 5, and in response to this, the delay adjustment unit 2 performs a process of matching the delay between the transmission signal before distortion compensation and the feedback signal.
On the other hand, in the burst transmission state in which the transmission signal (DL signal) in which the transmission data exists is intermittent depending on the presence or absence of the transmission data, only the section of the transmission signal (DL signal) is valid as shown in FIG. The DL data interval enable generation unit 4 outputs the signal as an enable signal only in the effective data interval, and the delay adjustment unit 2 adjusts the delay between the transmission signal before the distortion compensation and the feedback signal according to the data interval. Is doing.

As described above, the delay adjustment in the conventional TDD system has been realized by controlling the pattern according to the 3GPP specification and performing the delay adjustment only in the DL transmission section.
On the other hand, delay adjustment in the FDD scheme has been realized by controlling the operation timing of the delay adjustment unit asynchronously with the transmission signal.

International Publication No. 2006/087864 Pamphlet

Communication standard (3GPP TS 36.211 V8.9.0 (2009-12)), Internet (URL: http://www.3gpp.org/ftp/Specs/html-info/36211.htm)

Conventionally, as described above, delay adjustment is realized by control according to the TDD method and the FDD method. However, it is required to realize delay adjustment that can be supported by any communication method.
The present invention provides a distortion compensation apparatus that can cope with any burst signal and can realize delay adjustment that can be handled by any of the FDD and TDD communication systems including a burst transmission state according to a conventional request. The purpose is to provide.

The gist of the present invention is that delay adjustment is performed with an interval in which transmission data exists in a transmission signal as an effective data interval.
Therefore, the present invention can determine the effective data section and adjust the delay regardless of the communication method, and therefore can be applied to both the FDD method and the TDD method.

  The distortion compensation apparatus according to the present invention includes a distortion compensation unit that performs distortion compensation using a distortion compensation table for a transmission signal, and a delay that adjusts a delay between the transmission signal before distortion compensation and the feedback signal of the transmission signal after distortion compensation. An adjustment unit, an error calculation unit that updates a distortion compensation table so that a delay error between the delay-adjusted transmission signal and the feedback signal is reduced, and transmission data in the transmission signal using a control signal included in the transmission signal A valid data section enable generation unit that generates a signal indicating a section in which the data exists.

Then, in the distortion compensation apparatus according to the present invention, the delay adjustment unit, based on the signal generated by the valid data interval enable generation unit, in the interval where transmission data exists in the transmission signal, the transmission signal before distortion compensation and the above-mentioned On the other hand, the delay between the feedback signal and the feedback signal is not adjusted in a section where there is no transmission data in the transmission signal.
Therefore, according to the distortion compensation apparatus according to the present invention, it is possible to accurately reflect the section where the transmission data exists in the transmission signal (effective data section) regardless of the communication method, and to realize delay adjustment by this section. .

Here, in the present invention, the valid data section enable generation unit can generate a signal indicating a section in which transmission data exists in the transmission signal using various control signals according to the communication method. For example, the valid data section enable generation unit can use a BFN signal and other control signals.
The BFN signal is a signal with a period of 10 ms and is a signal located at the head of the data. A control signal (corresponding to PSS, SSS, and PBCH in LTE) is periodically arranged at the head of the data, and a section subsequent to the control signal is a section where transmission data exists even in the case of a burst signal.

According to the present invention, the operation timing of the delay adjustment unit is controlled based on the signal generated by the valid data interval enable generation unit, so that the transmission data exists in the transmission signal regardless of the difference between the TDD scheme and the FDD scheme. The delay adjustment can always be operated with.
Thus, since the delay adjustment can be performed with high accuracy, the distortion compensation table is appropriately updated, and the distortion compensation of the transmission signal using the distortion compensation table is realized with high accuracy.

It is a block diagram of the principal part of the distortion compensation apparatus which concerns on one Example of this invention. It is a block diagram of the effective data area enable production | generation part which concerns on one Example of this invention. It is a timing chart explaining operation | movement of the effective data area enable production | generation part which concerns on one Example of this invention. It is a figure explaining arrangement | positioning of the sub-frame which concerns on one Example of this invention. It is a figure explaining the frame structure of 3GPP specification concerning one Example of this invention. It is a block diagram of the principal part of the distortion compensation apparatus which concerns on a prior art example. It is a figure explaining the concept of delay adjustment. It is a figure explaining the delay adjustment concerning a prior art example.

A distortion compensation apparatus according to the present invention will be specifically described based on an embodiment.
Unlike the conventional method in which the DL signal interval is simply set as the effective data interval, the present invention delays and adjusts the interval in which the transmission data exists in the transmission signal as the effective data interval, which will be described below. The embodiment can be applied to any communication method of the FDD method and the TDD method.
In addition, the same code | symbol is attached | subjected to the part similar to said conventional example, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 1, the distortion compensation apparatus according to the present embodiment includes a distortion compensation unit 1, a delay adjustment unit 2, an error calculation unit 3, and an effective data section enable generation unit 5. The transmission signal before compensation, the feedback signal, and the signal from the valid data section enable generation unit 5 are input, and based on these signals, the delay time of the input transmission signal is adjusted, and after the delay adjustment The transmission signal is output to the error calculator 3.

The valid data section enable generation unit 5 generates a signal (valid data section enable) indicating a section (valid data section) in which transmission data exists in the transmission signal, using the control signal included in the transmission signal, and delay adjustment Output to part 2.
In this embodiment, as will be described later, a BFN signal, a CP selection signal, an SPL selection signal, a user configuration (DL effective section) signal, a subframe arrangement selection signal, and a user configuration (subframe arrangement) signal are used as control signals. .

In general, a BFN (node B specific Frame Number) signal is a signal with a period of 10 ms and is located at the beginning of data.
FIG. 4D shows a 3GPP frame configuration used for communication in the present embodiment. The subframe has a 1 ms cycle, and each subframe (# 0 to # 9) has one frame of 10 ms. . In 3GPP, the BFN signal indicates the start timing of subframe number # 0 and is a type of control signal with a period of 10 ms.

  In addition, other control signals (corresponding to PSS, SSS, and PBCH in LTE) are periodically arranged at the head of the data, which is a section in which transmission data exists even at the time of a burst signal. These control signals are composed of a signal for controlling a pattern according to the 3GPP specification in the TDD system and a user configuration setting that allows a user to set a burst waveform independently. By using these control signals, The valid data section enable generator 5 generates a valid data section enable corresponding to any burst signal.

  As shown in FIG. 2, the valid data section enable generation unit 5 includes a subframe counter 11, a sampling counter 12, a DL valid section (SPL) setting unit 13, a subframe arrangement unit 14, a DL valid section comparator 15, an enable selector. 16 and outputs a valid data section enable based on a control signal included in the transmission signal (communication frame).

The subframe counter 11 generates and outputs a subframe number (# 0 to # 9) and a sample counter clear signal using the BFN signal as a trigger.
The subframe number is input to the subframe arrangement unit 14 and is used by the subframe arrangement unit 14 to select a subframe arrangement from the subframe arrangement table (FIG. 4A).
The sample counter clear signal is input to the sampling counter 12 and is used by the sampling counter 12 to clear the count value.

  As shown in FIG. 3A, the subframe number and the sample counter clear signal are signals with a period of 1 ms, and the sample counter clear signal is a signal indicating the head of each subframe.

The sampling counter 12 is a counter function that counts up each subframe in 30720 sections (0 · Ts to 30719 · Ts), and clears the count value with the BFN signal and the sampling clear signal. That is, as shown in FIG. 3 (a), each subframe (# 0 to # 9) with a period of 1 ms is counted up in a section of 0 · Ts to 30719 · Ts, and each frame is received by a BFN signal and a sampling clear signal. And the count value is cleared to 0 · Ts at the end of each subframe.
The count value (sample counter) output from the sample counter 12 is input to the DL effective interval comparator 15 and is used by the DL effective interval comparator 15 for comparison with the DL effective interval setting value.

The DL valid section (SPL) setting unit 13 uses a control signal (CP selection signal, SPL selection signal, user configuration signal (DL valid section)) to generate a DwPTS (Downlink Pilot Time) of 3GPP specifications shown in FIG. Slot: Sets the downlink pilot time slot.
The CP selection signal is a signal for selecting “Normal cyclic prefix in downlink” and “Extended cyclic prefix in downlink” in the 3GPP specification shown in FIG.
The SPL selection signal is a signal for selecting “Special subframe configuration” in the 3GPP specification shown in FIG.

The user config (DL valid section) is a control signal for setting a set value other than the 3GPP specifications shown in FIG. Note that a user-specific DL valid section can be set by user configuration (DL valid section).
The DL valid section (SPL) setting unit 13 has a table shown in FIG. 4C, and selects a DL valid section value from the table by the control signal.

The subframe arrangement unit 14 uses the subframe number and the control signal (subframe arrangement selection signal, user configuration (subframe arrangement)) to perform “D” / “U” / in the 3GPP specification shown in FIG. This function selects “S”.
The subframe arrangement selection signal is a signal for selecting “Uplink-downlink configuration” in the 3GPP specification shown in FIG.
The user configuration (subframe arrangement) is a control signal for setting a setting value other than the 3GPP specification shown in FIG. A user-specific subframe arrangement can be set by user configuration (subframe arrangement).

  The subframe arrangement unit 14 has a subframe arrangement table shown in FIG. 4A. As shown in FIG. 3B, the subframe arrangement unit 14 uses the control signal and the subframe number from the subframe counter 11 to A subframe arrangement is selected from the table, and a signal of the subframe arrangement is output to the enable selector 16. Note that the setting values of the subframe arrangement table are as shown in FIG.

The subframe arrangement signals (“0”, “1”, “2”) are 2-bit signals, bit # 1 indicates SPL frame selection, and bit # 0 indicates a DL valid section.
The SPL frame selection of bit # 1 is a signal indicating whether the selected subframe is a special subframe or other, and the DL valid section of bit # 0 is a signal indicating whether the selected subframe is a downlink or other. It is.

The SPL frame selection is performed by the enable selector 16, and the subframe is used as a select signal for DL valid period enable (DL) from a part 14 and DL valid period enable (SPL) from the DL valid period comparator 15.
That is, a subframe DL in which transmission data is loaded and a subframe SPL in which transmission data is present at the head portion are indicated by the subframe arrangement signal.

The DL effective interval comparator 15 generates a DL effective interval enable (SPL) signal using the sample counter from the sampling counter 12 and the DL effective interval setting value from the DL effective interval setting unit 13.
As shown in FIG. 3C, the DL valid section comparator 15 enables the DL valid section enable (SPL) when the sample counter is less than the DL valid section set value (6592 · Ts in the illustrated example). Otherwise, the DL valid period enable (SPL) is disabled.
This DL valid section enable (SPL) is input to the enable selector 16.

As shown in FIG. 3 (d), the enable selector 16 switches between the DL effective interval enable (DL) and the DL effective interval enable (SPL) using the SPL frame selection signal from the subframe arranging unit 14, The valid data section is enabled and output to the delay adjustment unit 2.
That is, the valid data section enable input to the delay adjustment unit 2 is a section obtained by adding the head section of the subframe SPL to all sections of the subframe DL.

Therefore, the delay adjustment unit 2 performs a process of matching the delay between the transmission signal before distortion compensation and the feedback signal only in the effective data section obtained by adding the head section of the subframe SPL to the entire section of the subframe DL.
Thereby, since the delay adjustment can be performed with high accuracy, the distortion compensation table is appropriately updated, and distortion compensation of the transmission signal using the distortion compensation table is realized with high accuracy.

1: distortion compensation unit, 2: delay adjustment unit,
3: error calculation unit, 5: valid data section enable generation unit,

Claims (1)

A distortion compensation unit that performs distortion compensation using a distortion compensation table for a transmission signal;
A delay adjustment unit that adjusts a delay between a transmission signal before distortion compensation and a feedback signal of the transmission signal after distortion compensation;
In a distortion compensation apparatus comprising: an error calculation unit that updates a distortion compensation table so that a delay error between a delay-adjusted transmission signal and the feedback signal is reduced.
Using a control signal included in the transmission signal, an effective data section enable generation unit that generates a signal indicating a section in which transmission data exists in the transmission signal,
The delay adjustment unit adjusts a delay between the transmission signal before distortion compensation and the feedback signal in a section where transmission data exists in the transmission signal based on the signal generated by the valid data section enable generation unit. A characteristic distortion compensation apparatus.

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