US20170163449A1 - Channel estimator, demodulator and method for channel estimation - Google Patents
Channel estimator, demodulator and method for channel estimation Download PDFInfo
- Publication number
- US20170163449A1 US20170163449A1 US14/975,874 US201514975874A US2017163449A1 US 20170163449 A1 US20170163449 A1 US 20170163449A1 US 201514975874 A US201514975874 A US 201514975874A US 2017163449 A1 US2017163449 A1 US 2017163449A1
- Authority
- US
- United States
- Prior art keywords
- channel estimation
- time
- training sequence
- domain training
- estimation value
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims description 27
- 238000004364 calculation method Methods 0.000 claims description 12
- 238000010586 diagram Methods 0.000 description 14
- 230000005540 biological transmission Effects 0.000 description 4
- 230000003044 adaptive effect Effects 0.000 description 3
- 230000001934 delay Effects 0.000 description 3
- 239000000969 carrier Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 1
- 230000015654 memory Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0226—Channel estimation using sounding signals sounding signals per se
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0212—Channel estimation of impulse response
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/024—Channel estimation channel estimation algorithms
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/261—Details of reference signals
- H04L27/2613—Structure of the reference signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2649—Demodulators
- H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2649—Demodulators
- H04L27/26524—Fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators in combination with other circuits for demodulation
- H04L27/26526—Fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators in combination with other circuits for demodulation with inverse FFT [IFFT] or inverse DFT [IDFT] demodulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] receiver or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
Definitions
- the present invention relates to channel estimation, and more particularly, but not limited to a channel estimator, a demodulator and a method for channel estimation.
- Performance of channel estimation determines the performance of a signal demodulator.
- Current Digital Terrestrial Multimedia Broadcast (DTMB) protocol defines three frame structures for channel estimation.
- Conventional channel estimation in DTMB system uses the auto-correlation property of pseudo-random noise code (PN) sequence in the frame header.
- PN pseudo-random noise code
- Conventional channel estimation in DTMB system uses the auto-correlation property of pseudo-random noise code (PN) sequence in the frame header.
- PN pseudo-random noise code
- the performance of conventional channel estimation method in DTMB system is undesirable. Therefore, it is desirable to design a demodulator that may be accurate and applicable to different frame structures.
- An embodiment of the invention discloses a channel estimator, which comprises a receiver, configured to receive a first time-domain training sequence; a first convolution circuit, configured to generate an estimated value for the first time-domain training sequence by convoluting a second time-domain training sequence with a current channel estimation value, wherein the second time-domain training sequence represents a time-domain training sequence generated by the receiver; a first subtractor coupled to both the receiver and the first convolution circuit, and configured to generate an error by subtracting the estimated value for the first time-domain training sequence from a value of the first time-domain training sequence; an updating circuit coupled to both the subtractor and the first convolution circuit and configured to generate an updated channel estimation value by updating the current channel estimation value with the error, and sending the updated channel estimation value to the first convolution circuit; and the receiver iteratively receives a next symbol of the first time-domain training sequence, the first convolution circuit, the subtractor and the updating circuit repeat their operation using the updated channel estimation value until completion of receipt of a last symbol of first time-domain training sequence,
- Another embodiment of the invention discloses a demodulator comprising the channel estimator discussed above.
- Another embodiment of the invention discloses a method of channel estimation, which comprises: receiving, at a receiver, a first time-domain training sequence;
- FIG. 1 is a diagram illustrating a channel convergence circuit 100 according to an embodiment of the invention.
- FIG. 2 a diagram illustrating a received signal of a channel estimator according to an embodiment of the invention.
- FIG. 3A is a diagram 300 A illustrating a combination of the equalizer 310 and a signal re-constructor 320 A in a channel estimator according to an embodiment of the invention.
- FIG. 3B is a diagram illustrating a combination of an equalizer 310 and a signal re-constructor in the channel estimator 300 B with respect to according to an embodiment of the invention.
- FIG. 3C is a diagram illustrating the reconstructed interference signal according to an embodiment of the invention.
- FIG. 4 is a diagram illustrating additional elements in the channel estimator according to an embodiment of the invention.
- FIG. 5 is a block diagram illustrating the structure of the equalizer according to an embodiment of the invention.
- FIG. 6 is a flow chart illustrating a method of performing channel estimation according to an embodiment of the invention.
- FIG. 7 is a flow chart illustrating a method of performing channel estimation according to another embodiment of the invention.
- FIG. 1 is a diagram illustrating a channel convergence circuit according to an embodiment of the invention.
- a channel estimator comprises the channel convergence circuit 100 , as will be discussed in further details with respect to FIG. 4 .
- the channel convergence circuit 100 comprises a receiver 110 , a first convolution circuit 120 , a first subtractor 130 , and an updating circuit 140 .
- the receiver 110 receives a symbol of a first time-domain training sequence.
- the first time-domain sequence may be the sequence 1105 shown in FIG. 1 , or the sequence 1110 also shown in FIG. 1 .
- the sequence 1105 is the time-domain sequence from which the data interference has been cancelled.
- the sequence 1105 includes one part represented with slashes (in a parallelogram shape), which is the sequence from which interference has been cancelled.
- the sequence 1100 is the time-domain sequence which includes the data interference.
- the sequence 1110 includes three parts, a backslash part (in a triangle shape), a slash part (in a parallelogram shape) and a blank part. Unlike sequence 1105 , the sequence 1110 includes interference. Both sequence 1105 and the sequence 1110 will be discussed in detail with respect to following FIG. 2 .
- time-domain training sequence comprises pseudo-random noise code (PN) sequence for DTMB system.
- PN pseudo-random noise code
- the first convolution circuit 120 generates an estimated value for the first time-domain training sequence by convoluting a second time-domain training sequence with a current channel estimation value.
- the second time-domain training sequence represents a time-domain training sequence generated by the receiver 110 .
- the second time-domain training sequence is a locally generated time-domain sequence.
- the second time-domain training sequence may be previously generated and stored in the receiver 110 .
- the second time-domain training sequence may be generated in real-time by a shifting register, which requires fewer hardware resources, such as memories.
- the first subtractor 130 is coupled to both the receiver 110 and the first convolution circuit 120 .
- the first subtractor 130 generates an error by subtracting the estimated value for the first time-domain training sequence generated by the first convolution circuit 120 from the value of the first time-domain training sequence.
- the updating circuit 140 is coupled to both the first subtractor 130 and the first convolution circuit 120 .
- the updating circuit 140 generates an updated channel estimation value by updating the current channel estimation value with the error, and sending the updated channel estimation value to the first convolution circuit 120 .
- the updating circuit 140 further comprises two multipliers 142 and 144 , and a channel estimation update circuit 146 .
- the first multiplier 142 receives both the error output by the first subtractor 130 and step size u.
- the step size u may be a constant, which is a preset value in the receiver.
- the first multiplier 142 is configured to generate an error increment by multiplying the error with the step u.
- the second multiplier 144 receives both the error increment from the first multiplier 142 and the second time-domain training sequence.
- the second multiplier 144 is configured to generate a channel estimation increment by multiplying the error increment with the second time-domain training sequence.
- the channel estimation update circuit 146 is coupled to the second multiplier 144 .
- the channel estimation update circuit 146 comprises a group of registers and a group of adders.
- the set of registers is configured to store a channel estimation value for a previous moment.
- the channel estimation update circuit 146 receives channel estimation increment from the second multiplier 144 , and the group of adders in the channel estimation update circuit 146 generates a current channel estimation value by adding the channel estimation increment to the channel estimation value for the previous moment.
- the arrow on the channel estimation update circuit 146 means that the channel estimation value is updated.
- the updating circuit 140 is further configured to generate an updated channel estimation value by updating the current channel estimation value with the error using least mean squares (LMS) algorithm.
- LMS least mean squares
- the updating circuit 140 is further configured to generate an updated channel estimation value by updating the current channel estimation value with the error using Recurrence Least Square (RLS) algorithm.
- RLS Recurrence Least Square
- the RLS algorithm has a better performance than LMS but has a larger amount of computation than the LMS algorithm.
- the receiver 110 iteratively receives a next symbol of the first time-domain training sequence, the first convolution circuit 120 , the first subtractor 130 and the updating circuit 140 repeat their respective operation using the updated channel estimation value until completion of receipt of a last symbol of the first time-domain training sequence.
- the error generated by the first subtractor 130 reflects the difference between the target channel estimation value and a current channel estimation value.
- the channel estimation value is converged using loop iteration discussed above. By updating the channel estimation value with the error, the updated current channel estimation value is closer to the target channel estimation value.
- the convergence of the channel estimation value is achieved when noise or interference is lower than a threshold, for example, an average of error equals zero.
- the updating circuit 140 outputs the current updated channel estimation value as a channel estimation result upon receipt of a last symbol of the first time-domain training sequence.
- the channel convergence circuit 100 performs the channel estimation in iterations in a symbol-by-symbol manner.
- the first time-domain training sequence includes 140 symbols.
- the receiver 110 receives one symbol of the 140 symbols of the first time-domain training sequence, and the first subtractor 130 , the first convolution circuit 120 and the updating circuit 140 performs their respective operation.
- the error generated by the first subtractor 130 is updated, while the second time-domain training sequence maintains unchanged. Therefore the channel estimation value is updated accordingly.
- the updated channel estimation value in turn is fed back to the first subtractor 130 in the form of the convolution result by convoluting the updated channel estimation value with the second time-domain training sequence.
- the channel estimation is completed when all 140 symbols in the first time-domain training sequence have been treated accordingly. Note the second time-domain training sequence remains unchanged during 140 iterations for channel estimation based on the 140 symbols of the first time-domain training sequence.
- the channel convergence circuit 100 is used in a single carrier mode, and the channel convergence circuit 100 reuses a decision feedback equalizer (DFE).
- DFE decision feedback equalizer
- the channel convergence circuit 100 may replace the system including the first subtractor 130 , the first convolution circuit 120 , the first and second multipliers 142 and 144 with a decision feedback equalizer.
- FIG. 2 is a diagram illustrating a received signal of a channel estimator according to an embodiment of the invention.
- FIG. 2 shows a PN sequence, as an example of the time-domain training sequence.
- a (n ⁇ 1)th frame, a nth frame, and a (n+1)th frame are shown.
- actually received n-th PN signal shown as a rectangle, and represented in arrows
- PN sequence of a n-th frame may include interference signal from previous frame, shown as the backslash triangle and marked as D, and interference signal from current frame, shown as the blank triangle and marked as A, and the received PN sequence, shown as the parallelogram shape.
- FIG. 3A is a diagram illustrating a combination of the equalizer 310 and a signal re-constructor 320 A in a channel estimator according to an embodiment of the invention.
- the channel estimator 300 A further comprises an equalizer 310 , a re-constructor 320 A, and a second subtractor 330 .
- the equalizer 310 generates a pre-equalized signal by pre-equalizing a received signal.
- the signal re-constructor 320 A is coupled to the equalizer 310 and generates a reconstructed interference signal based on the pre-equalized signal.
- the second subtractor 330 is coupled to both the signal re-constructor 320 A and the receiver 110 , and the second subtractor 330 generates the first time-domain training sequence by subtracting the reconstructed interference signal from a received signal for a frame.
- the signal re-constructor 320 A further comprises an IFFT circuit 322 and a second convolution circuit 324 .
- the IFFT circuit 322 is configured to generate an IFFT result by performing IFFT calculation on the pre-equalized signal received from the equalizer 310 .
- the second convolution circuit 324 is configured to generate the reconstructed interference signal by convoluting the IFFT result with the channel estimation value of the previous frame (which indicates that the channel estimation value belongs to the previous frame).
- the part 300 A of the channel estimator shown in FIG. 3A performs a time domain operation for generating reconstructed interference signal from the pre-equalized signal by first performing IFFT operation then perform convolution operation.
- the operation may be performed equivalently on the frequency domain instead of time domain.
- FIG. 3B is a diagram illustrating a combination of the equalizer 310 and a signal re-constructor 320 B in a channel estimator according to an embodiment of the invention.
- the signal re-constructor 320 B further comprises a multiplier 326 and an IFFT circuit 328 .
- the multiplier 326 is configured to generate a multiplied signal by multiplying the pre-equalized signal with a channel estimation value of a previous frame.
- the IFFT circuit 328 is configured to generate the reconstructed interference signal by performing IFFT calculation on the multiplied signal.
- FIG. 3C is a diagram illustrating the reconstructed interference signal according to an embodiment of the invention.
- the reconstructed interference signal includes two parts: the front part includes Part D of the n ⁇ 1th frame (interference signal from previous frame, i.e., (n ⁇ 1)th frame) and the rear part includes Part A of the n-th frame (Interference signal from current frame, i.e., nth frame).
- the second subtractor 330 generates the first time-domain training sequence by subtracting Part D of the n ⁇ 1th frame (interference signal from previous frame) and Part A of the n-th frame (Interference signal from current frame) from the received signal (including part D, received PN sequence, and part A).
- the received PN sequence with interference cancelled (denoted as 1105 ) is generated. Note the sequence 1105 is only influenced by noise, while interference is cancelled from sequence 1105 .
- FIG. 4 is a diagram 400 illustrating additional elements with respect to the channel estimator according to an embodiment of the invention.
- the both the signal re-constructor 320 and the second subtractor 330 may be omitted, which are shown in the dashed block, therefore either the first time-domain training sequence 1110 or the first time-domain training sequence 1105 may act as the input of the receiver 110 as shown in FIG. 1 .
- the channel convergence circuit 100 A is similar to the channel convergence circuit 100 discussed with respect to FIG. 1 , and the difference only lies in that the channel convergence circuit 100 A in FIG. 4 does not include the receiver 110 shown in FIG. 1 . Instead, the channel estimator 400 receives the received signal 1110 or 1105 directly.
- FIG. 5 is a block diagram illustrating the structure of the equalizer 310 shown in FIG. 3A and FIG. 3B .
- the equalizer 310 further comprises a FFT circuit 510 , a divider 520 , and a decision circuit 530 .
- the FFT circuit 510 is configured to generate a FFT result by performing FFT calculation on the received signal.
- the divider 520 is coupled to the FFT circuit 510 and is configured to generate a quotient by dividing the FFT result by a channel estimation value of a previous frame.
- the decision circuit 530 coupled to the divider 520 and is configured to retrieve a transmitting signal based on the quotient.
- Embodiments of the invention achieve the advantage of being independent of frame header structures and independent of maximum delays.
- embodiments of the invention are applicable to all frame header structures and various maximum delays.
- the pretreatment of the received signal can improve the accuracy of channel estimation, for example, by interference cancellation and using iteration.
- embodiments of the invention may be applicable to reuse DFE for a single carrier mode defined in DTMB.
- FIG. 6 is a flow chart illustrating a method 600 of performing channel estimation according to an embodiment of the invention.
- the method 600 of channel estimation comprises receiving, in block 610 at a receiver, a first time-domain training sequence; generating, in block 620 , an estimated value for the first time-domain training sequence by convoluting a second time-domain training sequence with a current channel estimation value, wherein the second time-domain training sequence represents a time-domain training sequence generated by the receiver; generating, in block 630 , an error by subtracting the estimated value for the first time-domain training sequence from a value of the first time-domain training sequence; generating, in block 640 , an updated channel estimation value by updating the current channel estimation value with the error; and iteratively receiving a next symbol of the first time-domain training sequence, generating an estimated value for an updated first time-domain training sequence, generating an updated error, and generating an update of the updated channel estimation value, until completion of receipt of a last symbol of the first time-domain training sequence, and outputting,
- the method 600 further comprises generating a pre-equalized signal by pre-equalizing a received signal; generating a reconstructed interference signal based on the pre-equalized signal; and generating the first time-domain training sequence by subtracting the reconstructed interference signal from a received signal for a frame.
- generating a pre-equalized signal by pre-equalizing a received signal is implemented by generating a FFT result by performing FFT calculation on the received signal; generating a quotient by dividing the FFT result by a channel estimation value of a previous frame; and retrieving a transmitting signal based on the quotient.
- generating a reconstructed interference signal is implemented by: generating an IFFT result by performing IFFT calculation on the pre-equalized signal; and generating the reconstructed interference signal by convoluting the IFFT result with a channel estimation value of a previous frame.
- generating a reconstructed interference signal is implemented by: generating a multiplied signal by multiplying the pre-equalized signal with a channel estimation value of a previous frame; and generating the reconstructed interference signal by performing IFFT calculation on the multiplied signal.
- generating an updated channel estimation value by updating the current channel estimation value with the error is implemented by generating an updated channel estimation value by updating the current channel estimation value with the error using least mean squares algorithm.
- FIG. 7 is a flow chart illustrating a method 700 of performing channel estimation according to another embodiment of the invention.
- the method 700 comprises receiving in block 710 , time-domain training sequence.
- the time-domain training sequence is obtained from an input signal using frame synchronization. Due to the multipath effect, the time-domain training sequence is subject to the interference from its previous frame and next frame.
- the method 700 further comprises performing pretreatment for the received time-domain training sequence.
- the pretreatment can be performed for example as shown with reference to FIG. 4 .
- the method 700 further comprises performing adaptive channel estimation, for example, using LMS algorithm.
- the method 700 may use RLS algorithm instead of LMS algorithm for performing adaptive channel estimation in block 730 .
- the method further comprises determines whether the transmission system comprises multiple carriers or single carrier.
- the transmitter will transmit system information to the receiver.
- the system information may comprise whether the transmission system comprises single carrier or multiple carrier, the code rate, etc.. Further, the receiver will detect the system information from the transmitter. If the transmission system comprises multiple carriers, then in block 750 A, the method performs multi-carrier equalization. If the transmission system comprises single carrier, then in block 750 B, the method performs single carrier equalization.
- the system may reuse DFE (decision feedback equalizer) for both the adaptive channel estimation in block 730 and the single carrier equalization in block 740 B.
- Another embodiment of the invention discloses a demodulator comprising the above discussed channel estimator.
- single-carrier DFE may be reused so as to reduce the chip areas for demodulators.
- embodiments of the invention use DTMB system as examples, embodiments of the invention may be applicable to any system that use time-domain training sequences.
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Power Engineering (AREA)
- Noise Elimination (AREA)
- Physics & Mathematics (AREA)
- Discrete Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Mathematical Physics (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Abstract
Description
- This application claims priority to Chinese application No. 201510887422.X entitled “Channel Estimator, Demodulator and Method for channel estimation,” filed on Dec. 4, 2015 by Montage Technology (Shanghai) Co., Ltd., which is incorporated herein by reference.
- The present invention relates to channel estimation, and more particularly, but not limited to a channel estimator, a demodulator and a method for channel estimation.
- Performance of channel estimation determines the performance of a signal demodulator. Current Digital Terrestrial Multimedia Broadcast (DTMB) protocol defines three frame structures for channel estimation. Conventional channel estimation in DTMB system uses the auto-correlation property of pseudo-random noise code (PN) sequence in the frame header. However, due to 1) data interference caused by multipath channel, 2) non-ideal auto-correlation property of PN sequence in some frame structures, and/or 3) copied PN that may cause mirrored path in channel estimation when the length of channel estimation is longer than PN length, which may require different channel estimation methods for different time delay paths, the performance of conventional channel estimation method in DTMB system is undesirable. Therefore, it is desirable to design a demodulator that may be accurate and applicable to different frame structures.
- An embodiment of the invention discloses a channel estimator, which comprises a receiver, configured to receive a first time-domain training sequence; a first convolution circuit, configured to generate an estimated value for the first time-domain training sequence by convoluting a second time-domain training sequence with a current channel estimation value, wherein the second time-domain training sequence represents a time-domain training sequence generated by the receiver; a first subtractor coupled to both the receiver and the first convolution circuit, and configured to generate an error by subtracting the estimated value for the first time-domain training sequence from a value of the first time-domain training sequence; an updating circuit coupled to both the subtractor and the first convolution circuit and configured to generate an updated channel estimation value by updating the current channel estimation value with the error, and sending the updated channel estimation value to the first convolution circuit; and the receiver iteratively receives a next symbol of the first time-domain training sequence, the first convolution circuit, the subtractor and the updating circuit repeat their operation using the updated channel estimation value until completion of receipt of a last symbol of first time-domain training sequence, and the updating circuit is configured to output the current updated channel estimation value as a channel estimation result upon receipt of a last symbol of the first time-domain training sequence.
- Another embodiment of the invention discloses a demodulator comprising the channel estimator discussed above.
- Another embodiment of the invention discloses a method of channel estimation, which comprises: receiving, at a receiver, a first time-domain training sequence;
- generating an estimated value for the first time-domain training sequence by convoluting a second time-domain training sequence with a current channel estimation value, wherein the second time-domain training sequence represents a time-domain training sequence generated by the receiver; generating an error by subtracting the estimated value for the first time-domain training sequence from a value of the first time-domain training sequence;
- generating an updated channel estimation value by updating the current channel estimation value with the error; and iteratively receiving a next symbol of the first time-domain training sequence, generating an estimated value for an updated first time-domain training sequence, generating an updated error, and generating an update of the updated channel estimation value, until completion of receipt of a last symbol of the first time-domain training sequence, and outputting the current updated channel estimation value as a channel estimation result upon completion of receipt of a last symbol of the first time-domain training sequence.
- The present invention is illustrated in an exemplary manner by the accompanying drawings. The drawings should be understood as exemplary rather than limiting, as the scope of the invention is defined by the claims. In the drawings, the identical reference signs represent the same elements.
-
FIG. 1 is a diagram illustrating achannel convergence circuit 100 according to an embodiment of the invention. -
FIG. 2 a diagram illustrating a received signal of a channel estimator according to an embodiment of the invention. -
FIG. 3A is a diagram 300A illustrating a combination of theequalizer 310 and asignal re-constructor 320A in a channel estimator according to an embodiment of the invention. -
FIG. 3B is a diagram illustrating a combination of anequalizer 310 and a signal re-constructor in thechannel estimator 300B with respect to according to an embodiment of the invention. -
FIG. 3C is a diagram illustrating the reconstructed interference signal according to an embodiment of the invention. -
FIG. 4 is a diagram illustrating additional elements in the channel estimator according to an embodiment of the invention. -
FIG. 5 is a block diagram illustrating the structure of the equalizer according to an embodiment of the invention. -
FIG. 6 is a flow chart illustrating a method of performing channel estimation according to an embodiment of the invention. -
FIG. 7 is a flow chart illustrating a method of performing channel estimation according to another embodiment of the invention. - Various aspects and examples of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these examples. Those skilled in the art will understand, however, that the invention may be practiced without many of these details. Additionally, some well-known structures or functions may not be shown or described in detail, so as to avoid unnecessarily obscuring the relevant description.
-
FIG. 1 is a diagram illustrating a channel convergence circuit according to an embodiment of the invention. A channel estimator comprises thechannel convergence circuit 100, as will be discussed in further details with respect toFIG. 4 . Thechannel convergence circuit 100 comprises areceiver 110, afirst convolution circuit 120, afirst subtractor 130, and anupdating circuit 140. Thereceiver 110 receives a symbol of a first time-domain training sequence. The first time-domain sequence may be thesequence 1105 shown inFIG. 1 , or thesequence 1110 also shown inFIG. 1 . Thesequence 1105 is the time-domain sequence from which the data interference has been cancelled. Thesequence 1105 includes one part represented with slashes (in a parallelogram shape), which is the sequence from which interference has been cancelled. The sequence 1100 is the time-domain sequence which includes the data interference. Thesequence 1110 includes three parts, a backslash part (in a triangle shape), a slash part (in a parallelogram shape) and a blank part. Unlikesequence 1105, thesequence 1110 includes interference. Bothsequence 1105 and thesequence 1110 will be discussed in detail with respect to followingFIG. 2 . For example, time-domain training sequence comprises pseudo-random noise code (PN) sequence for DTMB system. - The
first convolution circuit 120 generates an estimated value for the first time-domain training sequence by convoluting a second time-domain training sequence with a current channel estimation value. The second time-domain training sequence represents a time-domain training sequence generated by thereceiver 110. The second time-domain training sequence is a locally generated time-domain sequence. The second time-domain training sequence may be previously generated and stored in thereceiver 110. Alternatively, the second time-domain training sequence may be generated in real-time by a shifting register, which requires fewer hardware resources, such as memories. - The
first subtractor 130 is coupled to both thereceiver 110 and thefirst convolution circuit 120. Thefirst subtractor 130 generates an error by subtracting the estimated value for the first time-domain training sequence generated by thefirst convolution circuit 120 from the value of the first time-domain training sequence. - The
updating circuit 140 is coupled to both thefirst subtractor 130 and thefirst convolution circuit 120. The updatingcircuit 140 generates an updated channel estimation value by updating the current channel estimation value with the error, and sending the updated channel estimation value to thefirst convolution circuit 120. - As shown in
FIG. 1 , theupdating circuit 140 further comprises twomultipliers estimation update circuit 146. Thefirst multiplier 142 receives both the error output by thefirst subtractor 130 and step size u. The step size u may be a constant, which is a preset value in the receiver. Thefirst multiplier 142 is configured to generate an error increment by multiplying the error with the step u. Thesecond multiplier 144 receives both the error increment from thefirst multiplier 142 and the second time-domain training sequence. Thesecond multiplier 144 is configured to generate a channel estimation increment by multiplying the error increment with the second time-domain training sequence. The channelestimation update circuit 146 is coupled to thesecond multiplier 144. The channelestimation update circuit 146 comprises a group of registers and a group of adders. The set of registers is configured to store a channel estimation value for a previous moment. The channelestimation update circuit 146 receives channel estimation increment from thesecond multiplier 144, and the group of adders in the channelestimation update circuit 146 generates a current channel estimation value by adding the channel estimation increment to the channel estimation value for the previous moment. The arrow on the channelestimation update circuit 146 means that the channel estimation value is updated. - Alternatively, the updating
circuit 140 is further configured to generate an updated channel estimation value by updating the current channel estimation value with the error using least mean squares (LMS) algorithm. - Alternatively, the updating
circuit 140 is further configured to generate an updated channel estimation value by updating the current channel estimation value with the error using Recurrence Least Square (RLS) algorithm. The RLS algorithm has a better performance than LMS but has a larger amount of computation than the LMS algorithm. - The
receiver 110 iteratively receives a next symbol of the first time-domain training sequence, thefirst convolution circuit 120, thefirst subtractor 130 and the updatingcircuit 140 repeat their respective operation using the updated channel estimation value until completion of receipt of a last symbol of the first time-domain training sequence. The error generated by thefirst subtractor 130 reflects the difference between the target channel estimation value and a current channel estimation value. The channel estimation value is converged using loop iteration discussed above. By updating the channel estimation value with the error, the updated current channel estimation value is closer to the target channel estimation value. The convergence of the channel estimation value is achieved when noise or interference is lower than a threshold, for example, an average of error equals zero. - The updating
circuit 140 outputs the current updated channel estimation value as a channel estimation result upon receipt of a last symbol of the first time-domain training sequence. - Note both the first time domain training sequence and the second time domain training sequence has a plurality of symbols. The
channel convergence circuit 100 performs the channel estimation in iterations in a symbol-by-symbol manner. For example, the first time-domain training sequence includes 140 symbols. Each time thereceiver 110 receives one symbol of the 140 symbols of the first time-domain training sequence, and thefirst subtractor 130, thefirst convolution circuit 120 and the updatingcircuit 140 performs their respective operation. During each iteration, the error generated by thefirst subtractor 130 is updated, while the second time-domain training sequence maintains unchanged. Therefore the channel estimation value is updated accordingly. The updated channel estimation value in turn is fed back to thefirst subtractor 130 in the form of the convolution result by convoluting the updated channel estimation value with the second time-domain training sequence. The channel estimation is completed when all 140 symbols in the first time-domain training sequence have been treated accordingly. Note the second time-domain training sequence remains unchanged during 140 iterations for channel estimation based on the 140 symbols of the first time-domain training sequence. - Alternatively, the
channel convergence circuit 100 is used in a single carrier mode, and thechannel convergence circuit 100 reuses a decision feedback equalizer (DFE). For example, thechannel convergence circuit 100 may replace the system including thefirst subtractor 130, thefirst convolution circuit 120, the first andsecond multipliers -
FIG. 2 is a diagram illustrating a received signal of a channel estimator according to an embodiment of the invention.FIG. 2 shows a PN sequence, as an example of the time-domain training sequence. InFIG. 2 , a (n−1)th frame, a nth frame, and a (n+1)th frame are shown. Due to the multi-path effect, actually received n-th PN signal (shown as a rectangle, and represented in arrows) that includes PN sequence of a n-th frame may include interference signal from previous frame, shown as the backslash triangle and marked as D, and interference signal from current frame, shown as the blank triangle and marked as A, and the received PN sequence, shown as the parallelogram shape. -
FIG. 3A is a diagram illustrating a combination of theequalizer 310 and asignal re-constructor 320A in a channel estimator according to an embodiment of the invention. Thechannel estimator 300A further comprises anequalizer 310, a re-constructor 320A, and asecond subtractor 330. Theequalizer 310 generates a pre-equalized signal by pre-equalizing a received signal. The signal re-constructor 320A is coupled to theequalizer 310 and generates a reconstructed interference signal based on the pre-equalized signal. - The
second subtractor 330 is coupled to both thesignal re-constructor 320A and thereceiver 110, and thesecond subtractor 330 generates the first time-domain training sequence by subtracting the reconstructed interference signal from a received signal for a frame. - In
FIG. 3A , thesignal re-constructor 320A further comprises an IFFT circuit 322 and asecond convolution circuit 324. The IFFT circuit 322 is configured to generate an IFFT result by performing IFFT calculation on the pre-equalized signal received from theequalizer 310. Thesecond convolution circuit 324 is configured to generate the reconstructed interference signal by convoluting the IFFT result with the channel estimation value of the previous frame (which indicates that the channel estimation value belongs to the previous frame). - The
part 300A of the channel estimator shown inFIG. 3A performs a time domain operation for generating reconstructed interference signal from the pre-equalized signal by first performing IFFT operation then perform convolution operation. Alternatively, the operation may be performed equivalently on the frequency domain instead of time domain. - Accordingly,
FIG. 3B is a diagram illustrating a combination of theequalizer 310 and a signal re-constructor 320B in a channel estimator according to an embodiment of the invention. Thesignal re-constructor 320B further comprises amultiplier 326 and anIFFT circuit 328. Themultiplier 326 is configured to generate a multiplied signal by multiplying the pre-equalized signal with a channel estimation value of a previous frame. TheIFFT circuit 328 is configured to generate the reconstructed interference signal by performing IFFT calculation on the multiplied signal. -
FIG. 3C is a diagram illustrating the reconstructed interference signal according to an embodiment of the invention. As shown inFIG. 3C , the reconstructed interference signal includes two parts: the front part includes Part D of the n−1th frame (interference signal from previous frame, i.e., (n−1)th frame) and the rear part includes Part A of the n-th frame (Interference signal from current frame, i.e., nth frame). - Referring back to
FIG. 2 , for example, thesecond subtractor 330 generates the first time-domain training sequence by subtracting Part D of the n−1th frame (interference signal from previous frame) and Part A of the n-th frame (Interference signal from current frame) from the received signal (including part D, received PN sequence, and part A). As a result, the received PN sequence with interference cancelled (denoted as 1105) is generated. Note thesequence 1105 is only influenced by noise, while interference is cancelled fromsequence 1105. -
FIG. 4 is a diagram 400 illustrating additional elements with respect to the channel estimator according to an embodiment of the invention. As thesecond subtractor 330 and thesignal re-constructor 320 have already been discussed with reference toFIG. 3A andFIG. 3B , they are not discussed here for simplicity. Note in an embodiment, the both thesignal re-constructor 320 and thesecond subtractor 330 may be omitted, which are shown in the dashed block, therefore either the first time-domain training sequence 1110 or the first time-domain training sequence 1105 may act as the input of thereceiver 110 as shown inFIG. 1 . Further thechannel convergence circuit 100A is similar to thechannel convergence circuit 100 discussed with respect toFIG. 1 , and the difference only lies in that thechannel convergence circuit 100A inFIG. 4 does not include thereceiver 110 shown inFIG. 1 . Instead, thechannel estimator 400 receives the receivedsignal -
FIG. 5 is a block diagram illustrating the structure of theequalizer 310 shown inFIG. 3A andFIG. 3B . As shown inFIG. 5 , theequalizer 310 further comprises aFFT circuit 510, adivider 520, and adecision circuit 530. TheFFT circuit 510 is configured to generate a FFT result by performing FFT calculation on the received signal. Thedivider 520 is coupled to theFFT circuit 510 and is configured to generate a quotient by dividing the FFT result by a channel estimation value of a previous frame. Thedecision circuit 530, coupled to thedivider 520 and is configured to retrieve a transmitting signal based on the quotient. - Embodiments of the invention achieve the advantage of being independent of frame header structures and independent of maximum delays. In other words, embodiments of the invention are applicable to all frame header structures and various maximum delays. Further, the pretreatment of the received signal can improve the accuracy of channel estimation, for example, by interference cancellation and using iteration. Further, embodiments of the invention may be applicable to reuse DFE for a single carrier mode defined in DTMB.
-
FIG. 6 is a flow chart illustrating amethod 600 of performing channel estimation according to an embodiment of the invention. Themethod 600 of channel estimation, comprises receiving, inblock 610 at a receiver, a first time-domain training sequence; generating, inblock 620, an estimated value for the first time-domain training sequence by convoluting a second time-domain training sequence with a current channel estimation value, wherein the second time-domain training sequence represents a time-domain training sequence generated by the receiver; generating, inblock 630, an error by subtracting the estimated value for the first time-domain training sequence from a value of the first time-domain training sequence; generating, inblock 640, an updated channel estimation value by updating the current channel estimation value with the error; and iteratively receiving a next symbol of the first time-domain training sequence, generating an estimated value for an updated first time-domain training sequence, generating an updated error, and generating an update of the updated channel estimation value, until completion of receipt of a last symbol of the first time-domain training sequence, and outputting, inblock 650, the current updated channel estimation value as a channel estimation result upon completion of receipt of a last symbol of the first time-domain training sequence. - Alternatively, although not shown in the drawings, the
method 600 further comprises generating a pre-equalized signal by pre-equalizing a received signal; generating a reconstructed interference signal based on the pre-equalized signal; and generating the first time-domain training sequence by subtracting the reconstructed interference signal from a received signal for a frame. - Alternatively, although not shown in the drawings, generating a pre-equalized signal by pre-equalizing a received signal is implemented by generating a FFT result by performing FFT calculation on the received signal; generating a quotient by dividing the FFT result by a channel estimation value of a previous frame; and retrieving a transmitting signal based on the quotient.
- Alternatively, although not shown in the drawings, generating a reconstructed interference signal is implemented by: generating an IFFT result by performing IFFT calculation on the pre-equalized signal; and generating the reconstructed interference signal by convoluting the IFFT result with a channel estimation value of a previous frame.
- Alternatively, although not shown in the drawings, generating a reconstructed interference signal is implemented by: generating a multiplied signal by multiplying the pre-equalized signal with a channel estimation value of a previous frame; and generating the reconstructed interference signal by performing IFFT calculation on the multiplied signal.
- Alternatively, although not shown in the drawings, generating an updated channel estimation value by updating the current channel estimation value with the error is implemented by generating an updated channel estimation value by updating the current channel estimation value with the error using least mean squares algorithm.
-
FIG. 7 is a flow chart illustrating amethod 700 of performing channel estimation according to another embodiment of the invention. Themethod 700 comprises receiving inblock 710, time-domain training sequence. The time-domain training sequence is obtained from an input signal using frame synchronization. Due to the multipath effect, the time-domain training sequence is subject to the interference from its previous frame and next frame. Then, inblock 720, themethod 700 further comprises performing pretreatment for the received time-domain training sequence. The pretreatment can be performed for example as shown with reference toFIG. 4 . Then, inblock 730, themethod 700 further comprises performing adaptive channel estimation, for example, using LMS algorithm. Alternatively, themethod 700 may use RLS algorithm instead of LMS algorithm for performing adaptive channel estimation inblock 730. Then inblock 740, the method further comprises determines whether the transmission system comprises multiple carriers or single carrier. Note the transmitter will transmit system information to the receiver. The system information may comprise whether the transmission system comprises single carrier or multiple carrier, the code rate, etc.. Further, the receiver will detect the system information from the transmitter. If the transmission system comprises multiple carriers, then inblock 750A, the method performs multi-carrier equalization. If the transmission system comprises single carrier, then inblock 750B, the method performs single carrier equalization. The system may reuse DFE (decision feedback equalizer) for both the adaptive channel estimation inblock 730 and the single carrier equalization in block 740B. - Another embodiment of the invention discloses a demodulator comprising the above discussed channel estimator.
- Embodiments of the invention may further have the following advantages:
- 1. Uniformly use LMS algorithm for channel estimations for all channels with different frame header structure and different channel delays, which is a unified method;
- 2. Cancel the impact of data interference on the channel estimator via equalizer, which, in some embodiments, are more precise and accurate.
- 3. In single carrier mode, single-carrier DFE may be reused so as to reduce the chip areas for demodulators.
- Note although embodiments of the invention use DTMB system as examples, embodiments of the invention may be applicable to any system that use time-domain training sequences.
- Features and aspects of various embodiments may be integrated into other embodiments, and embodiments illustrated in this document may be implemented without all of the features or aspects illustrated or described. One skilled in the art will appreciate that although specific examples and embodiments of the system and methods have been described for purposes of illustration, various modifications can be made without deviating from the spirit and scope of the present invention. Moreover, features of one embodiment may be incorporated into other embodiments, even where those features are not described together in a single embodiment within the present document. Accordingly, the invention is described by the appended claims.
Claims (14)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201510887422 | 2015-12-04 | ||
CN201510887422.XA CN106850467B (en) | 2015-12-04 | 2015-12-04 | Channel estimator, demodulator and channel estimation methods |
CN201510887422.X | 2015-12-04 |
Publications (2)
Publication Number | Publication Date |
---|---|
US9667449B1 US9667449B1 (en) | 2017-05-30 |
US20170163449A1 true US20170163449A1 (en) | 2017-06-08 |
Family
ID=58738045
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/975,874 Active US9667449B1 (en) | 2015-12-04 | 2015-12-21 | Channel estimator, demodulator and method for channel estimation |
Country Status (2)
Country | Link |
---|---|
US (1) | US9667449B1 (en) |
CN (1) | CN106850467B (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN108123906B (en) * | 2017-12-26 | 2020-09-11 | 中国科学院微电子研究所 | Channel estimation method |
EP3534580B1 (en) * | 2018-02-28 | 2021-04-28 | Nxp B.V. | Method and apparatus to reduce delays in channel estimation |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6314147B1 (en) * | 1997-11-04 | 2001-11-06 | The Board Of Trustees Of The Leland Stanford Junior University | Two-stage CCI/ISI reduction with space-time processing in TDMA cellular networks |
SG120921A1 (en) * | 2002-03-13 | 2006-04-26 | Ntt Docomo Inc | Mimo receiver and method of reception therefor |
US7852915B2 (en) * | 2007-03-21 | 2010-12-14 | Freescale Semiconductor, Inc. | Adaptive equalizer for communication channels |
CN100562002C (en) * | 2007-12-24 | 2009-11-18 | 清华大学 | Protection fill method and communication system thereof at interval in a kind of orthogonal FDM modulation system |
US9338031B2 (en) * | 2009-08-17 | 2016-05-10 | Qualcomm Incorporated | Methods and apparatus for interference decrease/cancellation on downlink acquisition signals |
WO2011093779A1 (en) * | 2010-01-28 | 2011-08-04 | Telefonaktiebolaget L M Ericsson (Publ) | Block decoding using overlapping and add |
CN101808056B (en) * | 2010-04-06 | 2013-01-30 | 清华大学 | Training sequence reconstruction-based channel estimation method and system |
US9118377B2 (en) * | 2012-07-05 | 2015-08-25 | Telefonaktiebolaget L M Ericsson (Publ) | Method for interference and carrier power estimation and its application to automatic gain control and signal-to-interference-and-noise-ratio computation |
KR102007804B1 (en) * | 2013-03-19 | 2019-10-21 | 삼성전자주식회사 | Apparatus and method for channel estimation in wireless communication system |
-
2015
- 2015-12-04 CN CN201510887422.XA patent/CN106850467B/en active Active
- 2015-12-21 US US14/975,874 patent/US9667449B1/en active Active
Also Published As
Publication number | Publication date |
---|---|
CN106850467A (en) | 2017-06-13 |
US9667449B1 (en) | 2017-05-30 |
CN106850467B (en) | 2019-11-08 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA2560497C (en) | Hybrid domain block equalizer | |
CN1193563C (en) | Multicarrier receiver with channel estimator | |
US6912258B2 (en) | Frequency-domain equalizer for terrestrial digital TV reception | |
US8711918B2 (en) | Adaptive known signal canceller | |
US20060159196A1 (en) | Apparatus and method for channel estimation and cyclic prefix reconstruction in an OFDM-STBC mobile communication system | |
US8000417B1 (en) | Methods and OFDM receivers providing inter-carrier interference cancellation with guard interval reuse scheme | |
US10659260B2 (en) | Decision feedback equalization processing device and method | |
JP2006050253A (en) | Receiver in ofdm system | |
WO2011111583A1 (en) | Receiving device, receiving method, receiving program, and processor | |
JP4545209B2 (en) | Orthogonal frequency division multiplexed signal receiving apparatus and receiving method thereof | |
CN102164110B (en) | Method and system for balancing frequency domain | |
JP2003218826A (en) | Method for receiving orthogonal frequency division multiplexed signal and receiver using the same | |
Wang et al. | On interference suppression in doubly-dispersive channels with hybrid single-multi carrier modulation and an MMSE iterative equalizer | |
US9667449B1 (en) | Channel estimator, demodulator and method for channel estimation | |
EP3090519B1 (en) | Methods and devices for doppler shift compensation in a mobile communication system | |
Wang et al. | Hybrid carrier modulation with time-domain windows and iterative equalization over underwater acoustic channels | |
JP4133587B2 (en) | Receiver | |
Xie et al. | MMSE‐NP‐RISIC‐Based Channel Equalization for MIMO‐SC‐FDE Troposcatter Communication Systems | |
US7864901B2 (en) | System, apparatus, and method for cancelling interferences of received signals | |
US9794008B2 (en) | Noise power estimator, receiver and method for noise power estimation | |
D'Agostini et al. | Adaptive concurrent equalization applied to multicarrier OFDM systems | |
KR100809017B1 (en) | Method for low-complexity equalization reducing intercarrier interference caused by doppler spread | |
JP5287846B2 (en) | High performance transmission system, transmission method, receiver, and transmitter | |
Alayyan et al. | Blind equalization in OFDM systems exploiting guard interval redundancy | |
Takahashi et al. | Iterative Reception Employing Sparse Channel Estimation for OFDM Systems |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: MONTAGE TECHNOLOGY (SHANGHAI) CO., LTD., CHINA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LU, ZHEN;REEL/FRAME:037336/0185 Effective date: 20151215 |
|
AS | Assignment |
Owner name: MONTAGE TECHNOLOGY (SHANGHAI) CO., LTD., CHINA Free format text: CORRECTIVE ASSIGNMENT TO CORRECT THE ADDRESS OF THE ASSIGNEE PREVIOUSLY RECORDED ON REEL 037336 FRAME 0185. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT;ASSIGNOR:LU, ZHEN;REEL/FRAME:039862/0861 Effective date: 20160816 |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
AS | Assignment |
Owner name: MONTAGE LZ SEMICONDUCTOR (SHANGHAI) CO., LTD., CHI Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MONTAGE TECHNOLOGY (SHANGHAI) CO., LTD.;REEL/FRAME:044033/0131 Effective date: 20171013 Owner name: MONTAGE LZ TECHNOLOGIES (CHENGDU) CO., LTD., CHINA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MONTAGE TECHNOLOGY (SHANGHAI) CO., LTD.;REEL/FRAME:044033/0131 Effective date: 20171013 |
|
FEPP | Fee payment procedure |
Free format text: ENTITY STATUS SET TO SMALL (ORIGINAL EVENT CODE: SMAL); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YR, SMALL ENTITY (ORIGINAL EVENT CODE: M2551); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY Year of fee payment: 4 |
|
AS | Assignment |
Owner name: RENLAI ELECTRONIC TECHNOLOGIES (SHANGHAI) CO., LTD., CHINA Free format text: SECURITY INTEREST;ASSIGNORS:MONTAGE LZ SEMICONDUCTOR (SHANGHAI) CO., LTD.;MONTAGE LZ TECHNOLOGIES (CHENGDU) CO., LTD.;REEL/FRAME:067200/0638 Effective date: 20240321 |