Patent Description:
Wireless communication systems may employ various techniques to increase throughput. For example, wireless communication systems may employ multiple-input and multiple-output (MIMO) for increasing communication capacity by using a plurality of antennas. As techniques for increasing throughput are employed, transmission sides may transmit signals having high complexity and reception sides may process the signals having high complexity.

Interference signals may hinder the reception sides from processing signals received through antennas, and the interference signals may be variously generated. For example, the interference signals may include inter-cell interference, which is a signal received at a boundary of a serving base station from a neighboring base station, intra-cell interference, which corresponds to a radio signal of another terminal within coverage of a serving base station, channel interference, and the like.

In particular, in the situation of weak electric fields, inter-cell interference, intra-cell interference, and channel interference, which may be considered external signals, have reduced signal intensity due to the weak electric fields, whereas self-interference signals experienced by user equipment due to feedback and reception of transmission signals of the same user equipment, from among all interference signals, may rather have increased influence on reception sensitivity. Therefore, there is demand for a method of more efficiently removing such self-interference signals.

The patent literature <CIT> and <CIT> disclose related prior art.

Claim <NUM> defines a wireless communication device. Claim <NUM> defines a method of operating wireless communication device.

Some embodiments may provide an electronic device capable of efficiently removing a self-interference signal by detecting or estimating a phase of a transmission signal, and a method of operating the electronic device.

Example embodiments of the inventive concepts will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:.

Hereinafter, example embodiments of the inventive concepts will be described in detail with reference to the accompanying drawings.

<FIG> each illustrate an example of a self-interference signal according to example embodiments of the inventive concepts.

In particular, <FIG> illustrates a self-interference signal of a wireless communication device <NUM> including multiple antennas, and <FIG> illustrates the self-interference signal of the wireless communication device <NUM> including a single antenna.

Referring to <FIG>, the wireless communication device <NUM> may include a plurality of antennas. At least some of the plurality of antennas may correspond to a transmission antenna(s). The transmission antenna(s) may transmit radio signals to an external device (for example, another user equipment (UE), and/or a base station (BS)) other than the wireless communication device <NUM>. The remaining ones of the plurality of antennas may correspond to a reception antenna(s). The reception antenna(s) may receive radio signals from the external device.

According to example embodiments, the reception antenna(s) may receive radio signals transmitted from the transmission antenna(s) as well as the radio signals transmitted from the external device. For example, when the transmission antenna(s) and the reception antenna(s) respectively correspond to omnidirectional antennas and are arranged adjacent to each other, some of the transmitted radio signals may be fed back through the reception antenna(s). The fed-back radio signals may correspond to self-interference signals.

Referring to <FIG>, the wireless communication device <NUM> may include a single antenna. The single antenna may be connected to both a transmission radio frequency (RF) chain and a reception RF chain via a duplexer. That is, the wireless communication device <NUM> may receive radio signals through the reception RF chain in a receiving mode and may transmit baseband signals to the external device through the transmission RF chain in a transmitting mode.

According to example embodiments, in the case of the wireless communication device <NUM> including the single antenna, feedback of transmission signals based on the transmission antenna and the reception antenna, which are adjacent to each other, may not occur. However, because the duplexer is connected to both the transmission RF chain and the reception RF chain, at least some of the transmission signals may be leaked from the transmission RF chain. When the leaked signals are input to the reception RF chain, the leaked signals may act as self-interference signals.

According to example embodiments, it may be seen that self-interference signals may be generated regardless of the number of antennas included in the wireless communication device <NUM>. Therefore, techniques for removing the self-interference signals may be desirable.

<FIG> is a block diagram of a wireless communication device according to example embodiments of the inventive concepts.

Referring to <FIG>, the wireless communication device <NUM> may include a transmission RF chain <NUM>, a duplexer <NUM>, an antenna <NUM>, a reception RF chain <NUM>, a local oscillator <NUM>, a phase detector <NUM>, and/or an adaptive filter <NUM>. According to example embodiments, the wireless communication device may be a cellular phone, a smart phone, a Personal Digital Assistant (PDA), a wireless modem, a tablet computer, a laptop computer, a personal computer (PC), an Internet of Things (IoT) device, a smart watch, a virtual reality device, etc..

According to example embodiments, the transmission RF chain <NUM> may refer to a transmission path for converting a digital signal in a baseband into an analog signal to transmit the analog signal as a radio signal. The digital signal in the baseband may be converted into the analog signal, a frequency in the baseband may be upconverted into a carrier frequency, and the analog signal may be amplified to have sufficient (e.g., a desired) transmission power. According to example embodiments, the wireless communication device <NUM> may generate the digital signal (e.g., by performing signal processing such as encoding, etc.) containing signal data. The signal data may be used by a receiving device to, for example, convert the signal data to sound data (e.g., using a speaker), control a physical device (e.g., using a motor, solenoid, etc.), output visual data (e.g., using a display), etc..

According to example embodiments, the transmission RF chain <NUM> may include a digital-to-analog converter (DAC) <NUM>, a transmission mixer <NUM>, and/or a power amplifier <NUM>. The transmission mixer <NUM> may upconvert a frequency of a baseband signal into a carrier frequency by receiving a reference frequency from the local oscillator <NUM>, and summing up the reference frequency and the frequency of the baseband signal. The power amplifier <NUM> may finally amplify power before transmission through the antenna <NUM>.

According to example embodiments, the duplexer <NUM> may be connected to the transmission RF chain <NUM> and the reception RF chain <NUM>, and may activate one thereof. For example, when the wireless communication device <NUM> is in the transmitting mode, the duplexer <NUM> may activate a connection to the transmission RF chain <NUM>, and when the wireless communication device <NUM> is in the receiving mode, the duplexer <NUM> may activate a connection to the reception RF chain <NUM>. By employing the duplexer <NUM>, the inclusion of respective antennas for a plurality of RF chains may be bypassed.

According to example embodiments, the reception RF chain <NUM> may receive a radio signal with a carrier frequency and downconvert the radio signal into an intermediate frequency or a baseband frequency, and the reception RF chain <NUM> may refer to a reception path for converting a frequency-downconverted analog signal into a digital signal.

According to example embodiments, the reception RF chain <NUM> may include a low noise amplifier (LNA) <NUM>, an analog-to-digital converter (ADC) <NUM>, and/or a reception mixer <NUM>. The LNA <NUM> may correspond to an amplifier that reduces or minimizes noise by amplifying wireless RF signals received by the antenna <NUM>. The ADC <NUM> may convert an analog signal amplified by the LNA <NUM> into a digital signal, and the reception mixer <NUM> may receive the reference frequency from the local oscillator <NUM> and may downconvert the analog signal into a frequency obtained by subtracting the reference frequency from a frequency of the analog signal.

According to example embodiments, the phase detector <NUM> may detect or estimate a phase of an input signal. For example, when the transmission RF chain <NUM> transitions from an inactive state to an active state, a phase of a transmission signal may be changed. The phase detector <NUM> may perform phase detection on the transmission signal having the changed phase and transfer the transmission signal to the adaptive filter <NUM>.

According to example embodiments, the adaptive filter <NUM>, which is a filter adaptively adjustable according to an input signal, may refer to a filter having an adaptively corresponding filter coefficient (or parameter) according to statistical characteristics of the input signal. The adaptive filter <NUM> may perform adaptive filtering on the input signal, based on a least mean square (LSM) algorithm or a recursive least square (RLS) algorithm.

According to example embodiments, the wireless communication device <NUM> may further include a modeling circuit <NUM>. The modeling circuit <NUM> may generate a modeling interference signal from the transmission signal in the baseband, based on the effective channel vector regarding the self-interference, and deliver the generated modeling interference signal to the adaptive filter <NUM>.

According to example embodiments, the adaptive filter <NUM> may receive, from the modeling circuit <NUM>, the modeling interference signal xn generated by modeling a transmission signal tn in the baseband as a self-interference signal, and may regenerate an actual interference signal yn by using the modeling interference signal xn and a digital-converted reception signal rn, thereby removing the interference signal yn from the reception signal rn. An output signal, from which the self-interference signal is removed, may be represented as follows.

In Equation <NUM>, r̃n denotes the output signal from which the self-interference signal is removed, rn denotes the digital-converted reception signal, and yn denotes the interference signal. Here, the interference signal yn may be rewritten as follows.

In Equation <NUM>, w denotes an effective channel vector regarding an interference path, and xn denotes a signal obtained by stacking the interference signal xn modeled from the transmission signal tn according to the effective channel vector by as much as L. That is, it may be represented that <MAT>.

<FIG> illustrates a comparison example of self-interference removal using an adaptive filter.

Referring to <FIG>, in a first period <NUM>, a state of the wireless communication device <NUM> may correspond to an active state or an ON state. Specifically, during the first period <NUM>, the transmission RF chain <NUM> (may also be referred to herein as an RF Integrated Circuit (RFIC)) of the wireless communication device <NUM> may be activated. The wireless communication device <NUM> may transmit a transmission signal (Tx signal) through the activated transmission RF chain <NUM>. During the first period <NUM>, the reception RF chain <NUM> of the wireless communication device <NUM> may also be activated. During the first period <NUM>, the wireless communication device <NUM> may receive a reception signal (Rx signal) through the activated reception RF chain <NUM>. The reception signal may include a self-interference signal that is based on the transmission signal.

According to example embodiments, the self-interference signal received during the first period <NUM> may have a phase A. The phase of the self-interference signal during the first period <NUM> may flexibly change over time, and hereinafter, the phase A is assumed to be a certain constant of <NUM>° for convenience of description.

According to example embodiments, the adaptive filter <NUM> may perform adaptive filter training on the self-interference signal received during the first period <NUM>. The adaptive filter training may refer to following the phase of the self-interference signal. For example, even when the phase of the self-interference signal changes in real time, the adaptive filter <NUM> may follow a phase change of the self-interference signal by updating a weight vector regarding an n-th sample by using an n-th received sample and a weight vector regarding an n-<NUM>-th sample. That is, the adaptive filter training performed in the first period <NUM> may allow the adaptive filter <NUM> to almost remove the self-interference signal, because weight vectors regarding a plurality of samples have already been updated.

In a second period <NUM>, the state of the wireless communication device <NUM> may correspond to an inactive state or an OFF state. Specifically, the inactive state or the OFF state may indicate that the transmission RF chain <NUM> of the wireless communication device <NUM> is in the inactive state. For example, the transmission mixer <NUM> of the transmission RF chain <NUM> may be changed to the OFF state. That is, because the wireless communication device <NUM> may receive a radio signal at any time, the reception RF chain <NUM> may be continuously maintained in the ON state. On the other hand, when there is no signal to be transmitted by the wireless communication device <NUM>, to reduce power consumption of the wireless communication device <NUM>, the transmission RF chain <NUM> may enter the inactive state for at least some periods. That is, the second period <NUM> may refer to a period in which the transmission RF chain <NUM> is deactivated. Because there is no signal transmitted by the wireless communication device <NUM>, there may also be no self-interference signal. Accordingly, there may be no value of the phase of the self-interference signal.

According to example embodiments, the adaptive filter <NUM> may enter a hold state during the second period <NUM>. The hold state may refer to a state of storing a weight vector tracked until a time point of the end of the first period <NUM>.

In a third period <NUM>, the state of the wireless communication device <NUM> may correspond to the active state or the ON state. That is, after the second period <NUM> is terminated, at the same time as, or a similar time to, the start of the third period <NUM>, the transmission RF chain <NUM> may transition again to the active state or the ON state. For example, in the third period <NUM>, the transmission mixer <NUM> may be changed from the inactive state to the active state.

According to example embodiments, the phase of the self-interference signal in the third period <NUM> may be different from the phase of the self-interference signal in the first period <NUM>. When the transmission RF chain <NUM> is activated again, due to the nature of elements included in the transmission RF chain <NUM>, RF characteristics (for example, phases) may not be identical or similar to those in the first period <NUM>. Accordingly, when the transmission RF chain <NUM> is activated again in the third period <NUM>, the self-interference signal may have a random or different phase. Hereinafter, the phase of the self-interference signal in the third period <NUM> will be referred to as a phase B. For example, the phase B may be <NUM>°.

Specifically, the transmission RF chain <NUM> of the wireless communication device <NUM> may be activated during the first period <NUM>. The wireless communication device <NUM> may transmit the transmission signal (Tx signal) through the activated transmission RF chain <NUM>. The reception RF chain <NUM> of the wireless communication device <NUM> may also be activated during the first period <NUM>. During the first period <NUM>, the wireless communication device <NUM> may receive the reception signal (Rx signal) through the activated reception RF chain <NUM>. The reception signal may include the self-interference signal that is based on the transmission signal.

According to example embodiments, the self-interference signal received during the first period <NUM> may have the phase A. The phase of the self-interference signal during the first period <NUM> may flexibly change over time, and hereinafter, the phase A is assumed to be a certain constant of <NUM>° for convenience of description.

According to example embodiments, the adaptive filter <NUM> may perform adaptive filter training on the self-interference signal received during the first period <NUM>. The adaptive filter training may refer to following the phase of the self-interference signal. For example, even when the phase of the self-interference signal changes in real time, the adaptive filter <NUM> may follow the phase change of the self-interference signal by updating the weight vector regarding the n-th sample by using the n-th received sample and the weight vector regarding the n-<NUM>-th sample. That is, the adaptive filter training performed in the first period <NUM> may allow the adaptive filter <NUM> to at least partially remove the self-interference signal, because the weight vectors regarding the plurality of samples have already been updated.

<FIG> illustrates a phase-time graph corresponding to self-interference removal using adaptive filtering.

Referring to <FIG>, the phase of the self-interference signal during the first period <NUM>, and a phase-time graph of the adaptive filter <NUM> that follows the phase of the self-interference signal may be referred to. In the first period <NUM>, the phase of the self-interference signal may be illustrated as having a certain value of a phase, and, for example, the phase of the self-interference signal may correspond to <NUM>° (illustrated as phase A). In example embodiments, the phase of the self-interference signal, which is followed by the adaptive filter <NUM>, may also approximate to <NUM>°. Because the phase of the self-interference signal has been estimated and detected for the plurality of samples before the first period <NUM>, the detected phase by the adaptive filter <NUM> and the phase of the self-interference signal may be locked.

During the second period <NUM>, the adaptive filter <NUM> may enter a hold state. That is, the transmission RF chain <NUM> of the wireless communication device <NUM> may be deactivated during the second period <NUM>. For example, when there is no data to be transmitted, to reduce the power consumption, at least the transmission mixer <NUM> of the transmission RF chain <NUM> may be deactivated. The adaptive filter <NUM> may not perform training regarding the weight vector during the second period <NUM>. The reason is that, because there is no transmission signal due to the deactivation of the transmission RF chain <NUM>, the self-interference signal is not received either. That is, the adaptive filter <NUM> may maintain the value of the phase of the self-interference signal, which is last stored at a time point of the end of the first period <NUM> or the start of the second period <NUM>, without performing an update or training regarding the weight vector.

In the third period <NUM>, the wireless communication device <NUM> may transition the transmission RF chain <NUM> again to the active state. However, due to the nature of an RF device, even when the RF device transitions from the inactive state to the active state again, the RF device may not maintain RF characteristics in the previously inactive state. Accordingly, in the third period <NUM>, the phase of the self-interference signal may be randomly determined or different. For example, although the phase of the self-interference signal in the first period <NUM> is <NUM>°, after the entrance into the inactive state, despite the transition to the active state again, the self-interference signal in the third period <NUM> may not maintain a phase of <NUM>°. In the third period <NUM>, the phase of the self-interference signal after the active state may be changed to, for example, <NUM>° (illustrated as phase B).

In a comparison example in which the phase detector <NUM> is not used, the adaptive filter <NUM> may remove the self-interference signal by using the weight vector that is previously stored. That is, although the weight vector used by the adaptive filter <NUM> is based on the premise that the phase of the self-interference signal is <NUM>°, because the phase of the self-interference signal is abruptly changed to <NUM>° in the third period <NUM>, a significant error may occur and it may fail to efficiently remove the self-interference signal. The adaptive filter <NUM> may adaptively perform update or training regarding the weight vector in the direction of reducing the magnitude of the error. As shown in <FIG>, the adaptive filter <NUM> may reach <NUM>°, which is the phase of the self-interference signal, by measuring the error whenever every sample is received and updating the weight vector in the direction of reducing the error. However, in the case of using the adaptive signal processing technique described above, a large number of samples, corresponding to a lengthy delay, may be acquired before reaching the phase of the self-interference signal, and during this time period, there may be deterioration in reception sensitivity because the self-interference signal is not being efficiently removed.

<FIG> illustrates operations performed by a wireless communication device, according to example embodiments of the inventive concepts.

Referring to <FIG>, in operation S110, the wireless communication device <NUM> may receive new data (e.g., via the reception RF chain <NUM>). The new data (also referred to herein as a new data signal) may refer to, for example, data received after the transmission mixer <NUM> transitions from the inactive state to the active state.

In operation S120, the wireless communication device <NUM> may determine whether phase detection should be performed. For example, the wireless communication device <NUM> may determine that the phase detection of the self-interference signal should be performed, based on the fact that the transmission mixer <NUM> has transitioned from the inactive state to the active state. That is, the wireless communication device <NUM> may consider the transition of the transmission mixer <NUM> to the active state and a total time period for which the transmission mixer <NUM> is in the inactive state. The reason is that the transmission mixer <NUM> may not enter the inactive state during brief pauses in data transmission.

In operation S130, the wireless communication device <NUM> may perform a normal operation on the adaptive filter <NUM>. The normal operation may refer to an operation of removing the self-interference signal, based on the weight vector updated until a time point at which the transmission mixer <NUM> enters the inactive state (e.g., a previous value of the phase). That is, because it has been determined in operation S120 that the phase detection on the self-interference signal should not be performed, the self-interference signal may be removed based on the latest weight vector previously stored. According to example embodiments, the normal operation may include modifying (e.g., updating) the weight vector based on the previous value of the phase.

In operation S140, the wireless communication device <NUM> may detect the phase (e.g., an updated value of the phase) of the self-interference signal by using samples received for a predefined or alternatively, given time period. The predefined or alternatively, given time period may correspond to a time period for receiving a minimum or sufficient number of samples to detect the phase of the self-interference signal.

In operation S150, the wireless communication device <NUM> may determine whether the phase detection is completed. The completion of the phase detection may be based on a magnitude of an error occurring when the self-interference signal is removed according to phases obtained by using the samples received for the predefined or alternatively, given time period in operation S140. According to example embodiments, the error measures an extent to which the new data signal is altered by the self-interference signal.

For example, when the magnitude of the error is greater than a threshold value, the wireless communication device <NUM> may determine that it is still early to terminate the phase detection on the self-interference signal (e.g., the wireless communication device <NUM> may determine that the phase detection on the self-interference signal is not completed). When the magnitude of the error is greater than the threshold value, the wireless communication device <NUM> may directly calculate the phase of the self-interference signal again (operation S140) until the magnitude of the error is detected to be less than the threshold value. As another example, when the magnitude of the error is less than the threshold value, the wireless communication device <NUM> may determine that the wireless communication device <NUM> has successfully followed the random phase changed in the third period <NUM> (e.g., the wireless communication device <NUM> may determine that the phase detection on the self-interference signal is completed).

In operation S160, the wireless communication device <NUM> may modify (e.g., update) the weight vector. In operation S150, when the phase of the self-interference signal has been successfully detected, the weight vector indicating an effective channel regarding the self-interference may be changed based on the detected phase (e.g., the updated value of the phase). According to example embodiments, the wireless communication device <NUM> may filter the new data signal using the modified weight vector and/or the adaptive filter <NUM> to obtain a filtered new data signal. The wireless communication device <NUM> may use the new data included in the filtered new data signal to, e.g., convert the new signal data to sound data (e.g., using a speaker of the wireless communication device <NUM>), control a physical device (e.g., using a motor, solenoid, etc.), convert the new signal data to visual data (e.g., using a display of the wireless communication device <NUM>), etc..

That is, in the case where the wireless communication device <NUM> is based on the adaptive signal processing technique generally used in the related art, the wireless communication device <NUM> may follow the changed phase of the self-interference signal only when performing training by using a large number of samples, and because the wireless communication device <NUM> is not capable of modeling the self-interference signal during the reception of the large number of samples, the wireless communication device <NUM> may not avoid deterioration in reception sensitivity caused by the self-interference signal.

However, according to example embodiments, it is determined that the RF characteristics of the transmission RF chain <NUM> are changed, the phase of the self-interference signal is preemptively detected according thereto, and the self-interference signal is removed by the adaptive filter <NUM> by using the detected phase, whereby a time period for removing the self-interference signal may be reduced as compared with the case of using the adaptive signal processing technique set forth above.

<FIG> illustrates operations for determining whether to perform phase detection, according to example embodiments of the inventive concepts. In particular, <FIG> may correspond to detailed operations of operation S120 in <FIG>.

Referring to <FIG>, in operation S210, the wireless communication device <NUM> may determine whether the transmission RF chain <NUM> has transitioned from the inactive state to the active state. When the transmission RF chain <NUM> has never transitioned, or has not recently transitioned, from the inactive state to the active state, because the self-interference signal may be removed by using the recently updated weight vector, the wireless communication device <NUM> may not perform the phase detection on the self-interference signal.

In operation S220, in response to identifying that the transmission RF chain <NUM> has transitioned from the inactive state to the active state, the wireless communication device <NUM> may determine that the phase detection on the self-interference signal should be performed. Specifically, the wireless communication device <NUM> may determine to perform the phase detection on the self-interference signal, based on whether the transmission mixer <NUM> of the transmission RF chain <NUM> has transitioned from the inactive state to the active state.

<FIG> illustrates an example of self-interference removal according to example embodiments of the inventive concepts. Repeated descriptions given with reference to <FIG> are omitted.

Referring to <FIG>, the wireless communication device <NUM> may perform the phase detection on the self-interference signal first, in response to the entrance into the third period <NUM>. That is, the wireless communication device <NUM> may detect the changed phase of the self-interference signal in the third period <NUM> by using the phase detector <NUM>.

Next, in response to having detected the phase of the self-interference signal, the wireless communication device <NUM> may operate the adaptive filter <NUM> according to the detected phase. For example, when the phase of the self-interference signal in the third period <NUM> is <NUM>° and the phase detected by the phase detector <NUM> is equally, or similarly, <NUM>°, the training of the adaptive filter <NUM> may be terminated after being performed on only one sample. In this case, because the phase detected on the self-interference signal is equal or similar to the actual phase thereof, the error may be output close to <NUM>. Accordingly, the adaptive filter <NUM> may follow the phase of the self-interference signal while continuously updating the weight vector regarding additionally received samples. In comparison with <FIG>, the reception sensitivity deteriorates only during the time taken for the phase detector <NUM> to detect or estimate the phase of the self-interference signal, and after the phase detector <NUM> has detected the phase of the self-interference signal, the weight vector may be updated according to the detected phase, and the self-interference signal may be efficiently removed according to the updated weight vector. That is, the wireless communication device <NUM> according to example embodiments may remove the self-interference signal more quickly by improving the speed at which the weight vector of the adaptive filter <NUM> converges to the phase of the self-interference signal.

<FIG> illustrates a phase-time graph corresponding to an example of self-interference removal, according to example embodiments of the inventive concepts. Repeated descriptions given with reference to <FIG> are omitted.

Referring to <FIG>, the third period <NUM> may include a phase detecting period <NUM> and an adaptive filter training period <NUM>. The phase detecting period <NUM> is a period in which only the phase detector <NUM> operates, and in the phase detecting period <NUM>, the phase detector <NUM> may detect or estimate the phase of the self-interference signal by using a received sample.

The adaptive filter training period <NUM> may be a period in which the adaptive filter <NUM> receives information about the detected phase from the phase detector <NUM> and, based thereon, performs an update of the weight vector regarding the self-interference signal and removal of the self-interference signal.

That is, referring to <FIG>, the wireless communication device <NUM> may detect the phase of the self-interference signal first, and then, may update the weight vector of the adaptive filter <NUM> according to the detected phase. According to example embodiments, the wireless communication device <NUM> may modify the weight vector based on a previous value of the phase by rotating the previous value of the phase by as much as the updated value of the phase (e.g., the wireless communication device <NUM> may rotate the previous value of the phase until the value of the phase becomes equal or similar to the updated value of the phase).

<FIG> illustrates another example of self-interference removal, according to example embodiments of the inventive concepts. Repeated descriptions given with reference to <FIG> are omitted.

Referring to <FIG> and <FIG>, during the third period <NUM>, the wireless communication device <NUM> may perform the phase detection in parallel with the adaptive filter training. That is, while the phase detector <NUM> detects or estimates the phase of the self-interference signal, the adaptive filter <NUM> may simultaneously or contemporaneously perform training regarding the weight vector in the direction of reducing the error.

For example, it may be assumed that the phase of the self-interference signal in the first period <NUM> is <NUM>°, and that the phase of the self-interference signal after the transition to the active state again in the third period <NUM> is <NUM>°. The phase detector <NUM> may detect the phase of the self-interference signal by detecting or estimating the phase of the self-interference signal from the time point of the start of the third period <NUM>. The phase of the self-interference signal, which is detected by the phase detector <NUM>, may correspond to <NUM>°. In parallel therewith, the adaptive filter <NUM> may update the weight vector based on the weight vector lastly updated at the time point of the end of the first period <NUM>. That is, when the third period <NUM> starts, the adaptive filter <NUM> may remove the self-interference signal having a phase of <NUM>° by using the weight vector that is set when the self-interference signal having a phase of <NUM>° is removed. Here, the adaptive filter <NUM> may calculate the error and may estimate the weight vector regarding a self-interference signal in the direction of reducing the calculated error.

According to example embodiments, after the phase detection by the phase detector <NUM> is terminated, the adaptive filter <NUM> may receive a phase output value from the phase detector <NUM>. The adaptive filter <NUM> may determine the weight vector according to the phase output value. The adaptive filter <NUM> may compare the magnitude of the error according to the weight vector, which is determined according to the phase output value (e.g., an updated value of the phase), with the magnitude of the error according to the weight vector updated from the time point of the start of the third period <NUM> (e.g., based on a previous value of the phase). According to example embodiments, the adaptive filter <NUM> may determine a first magnitude of a first weight vector based on the previous value of the phase, and a second magnitude of the error of a second weight vector based on the updated value of the phase. The adaptive filter <NUM> may select one of the weight vectors (e.g., the first weight vector or the second weight vector) according to the phase output value of the phase detector <NUM> and/or the continuously updated weight vector, based on a result of comparing the magnitudes of the errors. According to example embodiments, the adaptive filter <NUM> may set the selected weight vector as the weight vector of the adaptive filter <NUM>.

<FIG> illustrates a phase-time graph corresponding to another example of self-interference removal, according to example embodiments of the inventive concepts. Repeated descriptions given with reference to <FIG> are omitted.

Referring to <FIG>, during the third period <NUM>, the wireless communication device <NUM> may simultaneously or contemporaneously perform the phase detection of the self-interference signal by using the phase detector <NUM> and the update of the weight vector by using the adaptive filter <NUM>.

As shown in the graph, the adaptive filter <NUM> may determine either one of the weight vectors at the time point of the end of the phase detection. One of the weight vectors may be the weight vector according to the phase detected by the phase detector <NUM>, and the other may be the weight vector updated from the time point of the start of the third period <NUM> in the direction of reducing the error.

According to example embodiments, the adaptive filter <NUM> may measure an error on, or corresponding to, newly received data according to each of the weight vectors and may determine the weight vector such that a value of the measured error is smaller.

As an example, when a change in the phase of the self-interference signal between the first period <NUM> and the third period <NUM> is not large (for example, the phase in the first period <NUM> is <NUM>° and the phase in the third period <NUM> is <NUM>°), the magnitude of the error according to the weight vector updated by the adaptive filter <NUM> may be less than the magnitude of the error according to the weight vector that is based on the detected phase.

As another example, when the change in the phase of the self-interference signal between the first period <NUM> and the third period <NUM> is large (for example, the phase in the first period <NUM> is <NUM>° and the phase in the third period <NUM> is <NUM>°), even though the update is performed by the adaptive filter <NUM>, an approximation to the weight vector of the actual interference signal would be achieved only by repeating the update for a sufficiently large number of samples. Accordingly, the adaptive filter <NUM> may select the weight vector according to the phase output value of the phase detector <NUM> such that the magnitude of the error is smaller.

<FIG> illustrates an adaptive filter and a phase detector, according to example embodiments of the inventive concepts.

Referring to <FIG>, the phase detector <NUM> may receive the weight vector from the adaptive filter <NUM>. The weight vector may correspond to, or be, an effective channel vector regarding (e.g., corresponding to or characterizing) the self-interference channel. The phase detector <NUM> may receive the weight vector from the adaptive filter <NUM>, may generate a new weight vector by multiplying the weight vector by the detected phase, and may transfer the generated new weight vector to the adaptive filter <NUM> as an updated weight vector. The adaptive filter <NUM> may remove the self-interference signal from newly input data according to the updated weight vector.

According to example embodiments, the phase detector <NUM> may directly estimate a changed phase of the self-interference signal by using L samples.

In Equation <NUM>, rn denotes an input received by a receiver at an n-th time, woldH denotes a latest weight vector estimated by the adaptive filter <NUM> for interference removal, xn denotes a modeling interference signal generated from the transmission signal tn by nonlinear modeling to make the self-interference signal included in rn, and ejθ denotes a random phase value generated according to RF characteristics when the transmission RF chain <NUM> transitions to the active state in the third period <NUM>. The phase estimation value may be rewritten as follows.

In Equation <NUM>, the matrix X may be defined as [x<NUM> x<NUM> ··· xL-<NUM>].

According to example embodiments, the phase detector <NUM> may be bypassed. Specifically, the phase value (e.g., the updated value of the phase) may be directly calculated (e.g., by the wireless communication device) by using L pieces of sample data and may reduce complexity by calculating the phase estimation value only for particular candidates (e.g., a predetermined or alternatively, given number of phase candidates).

For example, the phase estimation value for the candidates may be rewritten as follows.

For example, the candidates for θ may be set to be <NUM>°, <NUM>°, <NUM>°, and <NUM>°. Because a value of y = wHxn may be calculated (e.g., by the wireless communication device <NUM>) only once for each phase included in the candidates, a phase (e.g., a phase candidate) minimizing, or corresponding to a lowest, a Euclidean distance may be selected by rotating a corresponding complex number as follows. In addition, when the candidates are set at intervals of <NUM>°, the complexity of calculations for newly updating the weight vector may also be reduced as follows. According to example embodiments, the wireless communication device <NUM> may rotate a first value of a phase of the weight vector (e.g., the phase of the weight vector maintained in the inactive state) according to a phase candidate minimizing, or corresponding to a lowest, magnitude of error of a reception signal from among the phase candidates.

According to example embodiments, the phase detector <NUM> may also reduce the complexity by mapping the phase estimation value of Equation <NUM> to one of the candidates. According to example embodiments, the detected phase (e.g., the updated value of the phase) may be mapped (e.g., by the wireless communication device <NUM>) to a predefined or alternatively, given number of candidates (e.g., phase candidates) according to a position at which the detected phase is positioned (e.g., plotted) on a complex plane. According to example embodiments, the wireless communication device <NUM> may modify (e.g., rotate) a phase of the weight vector (e.g., based on the previous value of the phase of the self-interference signal and/or one or more of the candidate phases) based on the mapped phase candidates.

In Equation <NUM>, Q(·) denotes a function for quantizing a phase of a complex number. For example, the quantization refers to dividing rTXHw = α + jβ into a real part (Re) and an imaginary part (Im) and may be simplified as follows for a candidate point of a phase change.

Referring to Equation <NUM>, when the phase of the complex number falls within -<NUM>° to <NUM>°, the phase estimation value may be quantized to <NUM>. The phase detector <NUM> may perform training on the adaptive filter <NUM> while reducing the complexity through the quantization.

According to example embodiments, operations described herein as being performed by the wireless communication device <NUM>, the transmission RF chain <NUM>, the duplexer <NUM>, the reception RF chain <NUM>, the local oscillator <NUM>, the phase detector <NUM>, the adaptive filter <NUM> and/or the modeling circuit <NUM> may be performed by processing circuitry. The term 'processing circuitry,' as used in the present disclosure, may refer to, for example, hardware including logic circuits; a hardware/software combination such as a processor executing software; or a combination thereof. For example, the processing circuitry more specifically may include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, application-specific integrated circuit (ASIC), etc..

The various operations of methods described above may be performed by any suitable device capable of performing the operations, such as the processing circuitry discussed above. For example, as discussed above, the operations of methods described above may be performed by various hardware and/or software implemented in some form of hardware (e.g., processor, ASIC, etc.).

The software may comprise an ordered listing of executable instructions for implementing logical functions, and may be embodied in any "processor-readable medium" for use by or in connection with an instruction execution system, apparatus, or device, such as a single or multiple-core processor or processor-containing system.

The blocks or operations of a method or algorithm and functions described in connection with example embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a tangible, non-transitory computer-readable medium. A software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD ROM, or any other form of storage medium known in the art.

Claim 1:
A wireless communication device (<NUM>) comprising:
a transmission radio frequency RF chain (<NUM>) configured to transit from an inactive state to an active state for transmitting a radio signal;
a reception RF chain (<NUM>) configured to receive a radio signal; and
processing circuitry configured to cause the wireless communication device (<NUM>) to:
detect that the transmission RF chain (<NUM>) has transitioned from an inactive state to a first active state,
determine whether to detect an updated value of a phase of a self-interference signal in response to detecting that the transmission RF chain (<NUM>) has transitioned from the inactive state to the first active state,
detect the updated value of the phase, and
modify a weight vector of an adaptive filter (<NUM>) corresponding to the self-interference signal based on the updated value of the phase in response to completing the detection of the updated value of the phase or a previous value of the phase during the detection of the updated value of the phase, the previous value of the phase corresponding to a time point at which the inactive state is entered, the adaptive filter (<NUM>) being configured to receive an input signal and a reception signal.