Pilot interference cancellation

Pilot frequency interference cancellation

The present invention generally relates to digital communication, and more specifically, relates to interference cancellation techniques for communication receivers.

Wireless communication systems are widely deployed to provide various types of communication such as voice and packet data. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA) or other multiple access that allows multiple devices to share a common communication medium Technology. For example, such systems can follow such as third-generation partner project 2 (3gpp2, or "cdma2000"), third-generation partner (3gpp, or "W-CDMA"), or long-term evolution ("LTE"). standard. When designing such a communication system, it is hoped to maximize the capacity or the number of users that the system can reliably support given the available resources.

One technique used to increase the capacity of the communication system is to apply interference cancellation at the receiver to maximize the received signal-to-interference-to-noise ratio (SINR) of each user. For example, in a CDMA-based communication system, the base station receiver may receive a combination of interference from mobile station traffic signals and traffic signals from other mobile stations, as well as interference from pilot frequency signals from all mobile stations. The conventional interference cancellation technology can initially estimate and cancel the interference of the pilot signal from all users based on the known content of the pilot signal, and then follow the content of such traffic signal, for example, by decoding the traffic signal. Becomes known to estimate and eliminate interference from other users' traffic signals.

When the traffic signal is decoded over time and the reconstructed traffic signal of other users is eliminated from the received signal, the expected pilot frequency estimate can also be improved above its initial value. Hope to use this point to further improve the performance of the communication receiver.

An aspect of the present case provides a method for processing a composite received signal, the composite received signal includes a first channel and a second channel, the method includes: estimating the first channel to generate a first estimate; removing the first estimate from the composite received signal An estimate; decoding the second channel to generate decoded symbols; re-estimating the first channel based at least in part on the decoded symbols to generate a second estimate; and canceling the residual estimate from the composite received signal, the residual estimate including the The difference between the first channel estimate and the second channel estimate.

Another aspect of this case provides a method for processing a composite received signal, the composite received signal includes a first channel and a second channel, and the method includes: successfully decoding the second channel to generate decoded symbols; One channel to estimate the first channel to produce the first estimate; to cancel the first estimate from the composite received signal before successfully decoding the second channel; to estimate the first channel based at least in part on the decoded symbols after decoding the second channel To generate a second estimate; and eliminate the second estimate from the composite received signal.

Another aspect of this case provides a method for processing a composite received signal. The composite received signal includes a first channel and a second channel. The method includes: estimating the first channel to generate a first estimate; and removing from the composite received signal First estimate; decode the second channel to generate decoded symbols; reconstruct the second channel based on the decoded symbols to generate a reconstructed second channel; eliminate the reconstructed second channel from the composite received signal; cancel the reconstructed second After the channel, the first channel is re-estimated to generate a second estimate; and the residual estimate is eliminated from the composite received signal, the residual estimate including the difference between the first channel estimate and the second channel estimate.

Another aspect of this case provides a method for processing a composite received signal. The composite received signal includes a first channel and a second channel. The method includes: estimating the first channel to generate a first estimate; and removing from the composite received signal First estimate; decode the second channel to generate decoded symbols; re-estimate the first channel after eliminating the reconstructed second channel to generate a second estimate, the re-estimation based at least in part on the generated decoded symbols; from Composite received signal cancellation residual estimation, the residual estimation including the difference between the first channel estimation and the second channel estimation; reconstructing the second channel based on the decoded symbols to generate a reconstructed second channel; and The received signal cancels the reconstructed second channel.

Another aspect of the present case provides an apparatus for processing a composite received signal, the composite received signal includes a first channel and a second channel, and the device includes a decoder configured to decode the second channel in advance to generate a decoded signal A channel estimator configured to estimate the first channel based on the first channel to generate a first estimate, the channel estimator is further configured to estimate the first based at least in part on the successfully decoded symbols of the second channel Channel to generate a second estimate; and a canceler configured to cancel the first estimate from the composite received signal before successfully decoding the second channel, and cancel the second estimate from the composite received signal after successfully decoding the second channel.

Another aspect of the present case provides a device for processing a composite received signal, the composite received signal includes a first channel and a second channel, and the device includes: means for pre-decoding the second channel to generate decoded symbols ; Means for estimating the first channel based on the successfully decoded symbols of the second channel to generate a first channel estimate; and means for eliminating the first channel estimate from the composite received signal after successfully decoding the second channel.

Another aspect of the present case provides a computer-readable storage medium storing instructions for the computer to perform the following operations: successfully decode the second channel to generate decoded symbols; estimate the first channel to generate the first channel An estimate; cancel the first estimate from the composite received signal before successfully decoding the second channel; after decoding the second channel, estimate the first channel based at least in part on the decoded symbols to generate a second estimate; and receive from the composite The signal cancels the second estimate.

The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of exemplary embodiments of the present invention, and is not intended to represent the only exemplary embodiments in which the present invention can be practiced. The term "exemplary" used throughout this description means "serving as an example, instance, or illustration," and should not necessarily be interpreted as being superior or superior to other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the present invention. It is obvious to those skilled in the art that the exemplary embodiments of the present invention can be practiced without such specific details. In some instances, well-known structures and devices are illustrated in block diagram form to avoid obscuring the novelty of the exemplary embodiments presented herein.

In this specification and claims, it should be understood that when an element is referred to as being "connected to" or "coupled to" another element, the element can be directly connected or coupled to the other element or an intervening element may be present. In contrast, when an element is referred to as being "directly connected to" or "directly coupled to" another element, there is no intervening element.

Communication systems can use single carrier frequency or multi-carrier frequency. 1, in the wireless cellular communication system 100, component symbols 102A to 102G represent cell service areas, component symbols 160A to 160G represent base stations, and component symbols 106A to 106G represent access terminals (ATs). The communication channel includes a forward link (FL) (also called a downlink) for transmission from the base station 160 to an access terminal (AT) 106 and a reverse link for transmission from the AT 106 to the base station 160 Road (RL) (also known as uplink). AT 106 is also called remote station, mobile station or user station. The access terminal (AT) 106 may be mobile or fixed. Each link can incorporate a different number of carrier frequencies. In addition, the access terminal 106 may be any data device that communicates via a wireless channel or via a wired channel (for example, using an optical fiber or a coaxial cable). The access terminal 106 may further be any of several types of equipment including (but not limited to) a PC card, a CF card, an external or built-in modem, or a wireless or wired telephone.

Modern communication systems are designed to allow multiple users to access a shared communication medium. There are many multiple access technologies known in the art, such as time division multiple access (TDMA), frequency division multiple access (FDMA), space division multiple access, division multiple access, code division Multiple access (CDMA) and other similar multiple access technologies. The concept of multiple access is a channel allocation method that allows multiple users to access a shared communication link. Depending on the specific multiple access technology, channel allocation can take various forms. For example, in the FDMA system, the total frequency spectrum is divided into several smaller sub-bands, and each user is given its own sub-band to access the communication link. Alternatively, in the TDMA system, each user is given the entire spectrum during the periodic recurrence of the time slot. In the CDMA system, each user is given the entire spectrum at all times, but distinguishes its own transmission through the use of codes.

Although some exemplary embodiments of this case may be described below based on the operation of the CDMA system, those of ordinary skill in the art will understand that these technologies can be easily applied to other digital communication systems, such as those based on other multiplexed systems. The digital communication system of the access system. Such alternative exemplary embodiments are conceived to fall within the scope of the present case.

Figure 2 illustrates an exemplary channel received on the reverse link 200 of the CDMA communication system at the base station. In FIG. 2, the vertical axis distinguishes channels based on channelization codes (for example, Walsh and/or PN codes), and the horizontal axis represents time. Note that these exemplary channels are illustrated for illustrative purposes only, and are not meant to limit the scope of this case to any specific channel configuration illustrated.

In FIG. 2, the signals received from users #1 to #N are illustrated, in which any user is designated as user #n. In the illustrated implementation, the signal of user #n includes pilot frequency and traffic signal, and the traffic signal can include traffic data bits<i>d</i>_<i>n</i>(<i>t</i>). The traffic of each user can be divided into multiple frames in time. Note that, generally speaking, when received by the receiver, the frame boundaries of a user's traffic signal may not be time aligned with the frame boundaries of other users.

Note that as used in this manual and request, the term "communication" includes data content<i>d</i>_<i>n</i>(<i>t</i>) Is not any channel known a priori by the receiver. Therefore, the term "traffic" can cover not only the data associated with the voice traffic in the cdma2000 system, but also the data associated with the "management burden channel" such as ACK messages and power control messages.

In Figure 2, user#<i>n</i>The pilot frequency is multiplexed to a separate code from the traffic to allow the receiver to separate the pilot frequency from the traffic. In some implementations, other channelization schemes may be used instead of or further multiplexing pilot frequencies. For example, pilot frequencies and traffic may be modulated onto separate quadrature phase (eg, I and Q) carriers. At the receiver, it can handle all users #1 to #<i>N</i>The composite received signal of the sum of the channelized pilot frequency and the traffic signal to restore the traffic associated with each user.

In one implementation, the receiver can implement an early decoding scheme, for example, where it tries to decode the user before receiving the entire frame.#<i>n</i>Data bits of the traffic frame<i>d</i>_<i>n</i>(<i>t</i>). For example, the US patent application No. 12/252,544 with the title "Rate Determination" filed on October 16, 2008 further describes the mechanism for early decoding, and the patent application was assigned to The assignee of the present invention and its disclosure are hereby incorporated by reference in its entirety.

FIG. 3 illustrates that the user # can be used at the access terminal 106 in FIG. 1<i>n</i>Examples of implemented transmitter structures and/or procedures. The functions and components illustrated in FIG. 3 can be implemented by software, hardware, or a combination of software and hardware. Other functions may be added to FIG. 3 as a supplement or replacement of the functions illustrated in FIG. 3.

The data source 300 provides data to the encoder 302<i>d</i>_<i>n</i>(<i>t</i>), the encoder 302 uses one or more encoding schemes to encode data bits to provide encoded symbols. Each coding scheme may include one or more types of coding, such as cyclic redundancy check (CRC), convolutional coding, turbo coding, block coding, other types of coding, or no coding at all. Other coding schemes may include automatic repeat request (ARQ), hybrid ARQ (H-ARQ), and incremental redundancy repeat technology. Different types of data can be encoded with different encoding schemes. The interleaver 304 interleaves the coded data bits to combat fading.

The modulator 306 modulates the coded, interleaved data to generate modulated data. Examples of modulation techniques include binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK). The modulator 306 may also repeat the modulated data sequence, or the symbol puncturing unit may puncture the bits in the symbol. The modulator 306 can also use Walsh overlays (ie, Walsh codes) to spread the modulated data to form a chip stream. The modulator 306 can also use a pseudo random noise (PN) spreader to spread the chip streams with one or more PN codes (for example, short codes, long codes).

The baseband to radio frequency (RF) conversion unit 308 can convert the baseband signal into an RF signal for transmission to one or more base stations 160 via the antenna 310 over the wireless communication link.

FIG. 4 illustrates an exemplary embodiment 400 of a receiver that may be implemented at the base station 160 of FIG. 1. The functions and components illustrated in FIG. 4 can be implemented by software, hardware, or a combination of software and hardware. Other functions may be added to FIG. 4 as a supplement or replacement of the functions illustrated in FIG. 4. Although the interference cancellation at the base station 160 is described below, the concepts herein can be easily applied to the access terminal 106 or any other components of the communication system.

One or more antennas 401 receive reverse link modulated signals from one or more access terminals 106. Multiple antennas can provide space diversity against harmful path effects such as fading. Each received signal is provided to a respective receiver or RF-to-baseband conversion unit 402, which adjusts (eg, filters, amplifies, down-converts) and digitizes the received signal to Generate digital samples.

The demodulator 404 may demodulate the received signal to provide recovered symbols. For cdma2000, demodulation attempts to isolate the received pilot frequency and traffic to their respective code channels by (1) channelizing the de-spread samples, and (2) using the recovered pilot frequency to coherently demodulate the Channelized traffic provides demodulated data to restore data transmission. The demodulator 404 may include a received sample buffer 412 (also known as spliced front-end RAM (FERAM) or sample RAM) for storing samples of the composite received signal for all users/access terminals, and used for de-spreading. The Rake receiver 414 and the demodulated symbol buffer 416 (also called back-end RAM, BERAM, or demodulated symbol RAM) that handle multiple signal instances corresponding to different "multipath" ). There may be a plurality of demodulated symbol buffers 416, each of which corresponds to a specific user/access terminal.

The deinterleaver 406 deinterleaves the data from the demodulator 404.

The decoder 408 can decode the demodulated data to recover the decoded data bits transmitted by the access terminal 106<img file="TW201131997A_D0001.tif" />(<i>t</i>). The decoded data can be provided to the data slot 410.

In Figure 4, the successfully decoded user#<i>n</i>Decoded data bits<img file="TW201131997A_D0002.tif" />(<i>t</i>) Is input to the interference reconstruction unit 460, which includes an encoder 462, an interleaver 464, a modulator 466, and a filter 468. The encoder 462, the interleaver 464, and the modulator 466 may be similar to the encoder 302, the interleaver 304, and the modulator 306 of FIG. 3. The filter 468 forms the decoded user samples with FERAM resolution, for example, at a 2x chip rate. In an exemplary embodiment, the gain of filter 468 may be weighted with channel estimates such as derived from, for example, pilot frequency estimation, data augmentation channel estimation, and/or other channel estimation techniques described further below. Subsequently, in a procedure called traffic interference cancellation (TIC), the traffic cancellation block 461 is used to remove or cancel the decoded user's contribution to the FERAM from the FERAM 412.

A further description of the functions of FERAM 412 and BERAM 416 in TIC receiver 400 is provided below.

In an exemplary embodiment, FERAM 412 and BERAM 416 may be circular buffers. The FERAM 412 stores the received samples (for example, at a 2x chip rate) and is shared by all users. BERAM 416 stores the demodulated symbols of the received bits as produced by the rake receiver 414 of the demodulator. Each user can have a different BERAM, because the demodulated symbol is obtained by using a user-specific PN sequence to de-spread and combine across the fingers. In an exemplary embodiment, in the first-round and residual PIC techniques described below, each finger can estimate its own corresponding pilot frequency, and when the estimated pilot frequency is to be eliminated from FERAM in the PIC, the derivation can be used The offset of the corresponding finger of the estimated pilot frequency is calculated to cancel the estimated pilot frequency. Both TIC receivers and non-TIC receivers can use BERAM 416. The BERAM 416 in the TIC can store the demodulated symbols of the previous frames that are no longer stored in the FERAM 412.

As further illustrated in FIG. 4, a first-round pilot frequency estimation/reconstruction block 470 is provided. At block 470, the first round of pilot frequency interference cancellation (PIC) may be performed on the samples in FERAM 412, so that each user can be affected without interference from pilot frequency signals from the user and other users. The traffic signal is demodulated and decoded.

FIG. 5 illustrates a method 500 of performing the first round of PIC followed by TIC in the receiver 400 of FIG. 4.

At block 502, samples are continuously received and stored in FERAM 412. In an exemplary embodiment, samples can be written to FERAM 412 in real time, that is, samples at 2x chip rate can be<img file="TW201131997A_D0003.tif" />The chip is written. The samples stored in FERAM 412 are denoted as<i>r</i>(<i>t</i>)。

At block 504, the receiver is all users #1 to #<i>N</i>Perform the first round of pilot frequency estimation. Since the pilot frequency pattern for all users is known at the BTS, it is necessary for each user#<i>n</i>Estimate of the received pilot frequency signal<img file="TW201131997A_D0004.tif" />(<i>t</i>) Can be generated by each finger in the rake receiver 414.

At block 506, the pilot frequency estimates obtained at block 504 can be reconstructed and subtracted from the samples stored in FERAM 412.

FIG. 5A illustrates the first round of guide frequency estimation and elimination of user # in boxes 504 and 506<i>n</i>An exemplary embodiment 560 of the first round of guided frequency elimination. In an exemplary embodiment, an example of the block illustrated in 560 may be provided, for example, in each finger demodulator of the rake receiver 414 in FIG. Different multipaths are assigned separate fingers.

In Figure 5A,<i>r</i>(<i>t</i>) Or the signal stored in FERAM 412 is coupled to the pilot frequency<i>n</i>Estimate box 570.<i>n</i>. Boot frequency estimation block 570.<i>n</i>Based on and user#<i>n</i>The associated known pilot frequency pattern is used to calculate the pair and user#<i>n</i>Associated pilot frequency signal<i>p</i>_<i>n</i>(<i>t</i>) Estimate<img file="TW201131997A_D0005.tif" />(<i>t</i>). Eliminate adder 576 from<i>r</i>(<i>t</i>)deduct<img file="TW201131997A_D0006.tif" />(<i>t</i>)To produce<img file="TW201131997A_D0007.tif" />(<i>t</i>)，<img file="TW201131997A_D0008.tif" />(<i>t</i>) Is also referred to herein as the first composite signal. First composite signal<img file="TW201131997A_D0009.tif" />(<i>t</i>) Can be stored back into FERAM 410 as a version of the received signal that is eliminated by the first round of pilot frequency.

Estimate block 570 at the boot frequency.<i>n</i>Medium, signal<i>r</i>(<i>t</i>) First by multiplying with the multiplier 590 and accumulating with the addition and dump block 591 to communicate with the user#<i>n</i>The pilot frequency pattern is related. The output of block 591 may be provided to filter 592. Note that, as defined herein, the "correlation" between the first signal and the second signal can encompass multiplying the complex conjugate of the first signal and the second signal (or multiplying the second signal with the Complex conjugate multiplication) and accumulate or filter the result of the multiplication over a period of time.

The filter 592 can, for example, implement any type of filtering operation to improve and user#<i>n</i>The quality of the associated pilot frequency while at the same time attenuating the contribution of noise and other interference. For example, the filter 592 may include a finite impulse response (FIR) filter, an infinite impulse response (IIR) filter, and/or a filter having nonlinear and/or time-varying characteristics as can be deduced by a person skilled in the art. The output of the filter 592 can be "spread", for example by multiplying by the user#<i>n</i>The pilot frequency pattern is reconstructed so that it can be further recovered from the composite signal<i>r</i>(<i>t</i>) To eliminate the pilot frequency estimation block 570.<i>n</i>Output.

Note that the example of the pilot frequency estimation block illustrated in FIG. 5A is provided for illustrative purposes only. Those of ordinary skill in the art will understand that alternative examples of the pilot frequency estimation block illustrated in FIG. 5A can be easily derived by those of ordinary skill in the art, and it is conceived that these alternative examples are combined with the pilot frequency interference cancellation technology of this case. The input receiver is within the scope of this case.

Returning to FIG. 5, after the first round of PIC in blocks 504-506, the undecoded user group G is selected at block 508. In an exemplary embodiment, the user group G may correspond to those users who have received and stored a sufficient amount of data in the FERAM 412. In an exemplary embodiment, G may include a single user, or may include multiple users.

At block 510, demodulation of the traffic channel for users in G is performed, and an attempt is made to decode the traffic based on the received samples. For example, the demodulator 404 demodulates the samples of the frames stored in some or all time segments of the FERAM 412 of the selected user group according to the user's spread spectrum and scramble sequence and its cluster size. In addition, the decoder 408 uses the demodulated FERAM samples and the previously demodulated symbols stored in the BERAM 416 to try to decode the user's traffic. Note that when G includes multiple users, the decoding of each user in G can be performed in parallel or sequentially with the decoding of other users.

At block 512 of FIG. 5, TIC is performed by reconstructing the successfully decoded traffic data (for example, by using the traffic reconstruction block 460) and subtracting the reconstructed traffic from the FERAM 412. In an exemplary embodiment, the successful decoding may be determined by checking whether a cyclic redundancy code (CRC) passes an error check, for example.

At block 514, it is checked whether there are more users to decode. If so, the method returns to block 508 and selects a new user group G to be decoded. If not, the method returns to block 504, where the first round of PIC may be executed for the newly received (ie, before the first round of PIC) sampling in the FERAM 412.

In an exemplary embodiment, for example, in an exemplary embodiment in which the group G includes multiple users, all such users in the group may be decoded together, and then all their interference contributions are deducted. In an alternative exemplary embodiment, for example, in an exemplary embodiment in which the group G first includes one user and is then updated to include the next user at block 514, it may be called Sequential Interference Cancellation (SIC In the procedure of) through the loop from block 514 to block 508, each user is decoded in a sequential manner from one user to the next user and the traffic interference of the user is eliminated. In this embodiment, users with a later decoding order in the same group benefit from elimination of users with an earlier decoding order.

Whenever a user or user group is correctly decoded at block 510, its traffic interference contribution can be deducted from FERAM 412, thereby improving the quality of the samples in FERAM 412 (that is, reducing the number of samples present in these samples). Total interference in). In addition, the knowledge of the decoded data associated with the user or user group can assist in improving the estimation of the channel response, which can lead to more accurate PIC by the receiver. Exemplary embodiments implementing these features are described further below.

Fig. 6 illustrates an alternative exemplary embodiment 600 of the receiver according to the present case. Unless otherwise noted, similarly labeled elements in FIGS. 6 and 4 correspond to blocks with similar functionality. In FIG. 6, the first-round and residual pilot frequency estimation/reconstruction block 620 is provided to replace the first-round pilot frequency estimation/reconstruction block 520 in FIG. 5. The first round and residual estimation/reconstruction block 620 is coupled to the pilot frequency memory 630 for storing the pilot frequency interference samples that have been eliminated from the FERAM 412 for later use in residual pilot frequency processing as described further below. The operation of the receiver 600 can be performed as described in FIG. 7.

FIG. 7 illustrates a method 700 for performing the first round of PIC and the residual PIC in the receiver 600 of FIG. 6.

At block 702, samples are continuously received and stored in FERAM 412.

At block 704, the receiver performs the first round of pilot frequency estimation for all users. In an exemplary embodiment, the first round of pilot frequency estimation may be performed as described with reference to block 504 in FIG. 5, for example.

After block 704, at block 705, the boot frequency estimate is stored in a boot frequency memory such as the boot frequency memory 630 in FIG. 6<img file="TW201131997A_D0010.tif" />(<i>t</i>)arrive<img file="TW201131997A_D0011.tif" />(<i>t</i>) For later use in residual PIC. The guide frequency estimates for users #1 to #N stored in the memory are also expressed as<img file="TW201131997A_D0012.tif" />(<i>t</i>)arrive<img file="TW201131997A_D0013.tif" />(<i>t</i>)。

At block 706, by taking samples stored in FERAM 412<i>r</i>(<i>t</i>) Perform the first round of PIC by subtracting the pilot frequency estimate obtained at block 704.

At block 708, the undecoded user group G is selected.

At block 710, demodulation of the traffic channel is performed, and based on the received samples, an attempt is made to decode the traffic about the user in G.

At block 712, a residual PIC based on Data Amplification Channel Estimation (DACE) is performed for the successfully decoded user. In DACE, the successfully decoded traffic is used to amplify the pilot frequency pattern to obtain a better channel estimation than the channel estimation possible with only the pilot frequency pattern. DACE is achieved by coherently combining the pilot frequency pattern with the decoded data and can be advantageously used to improve the quality of the PIC, as described further below. Use channel estimates derived from DACE to perform residual PIC for users who have successfully decoded. In an exemplary embodiment, the residual PIC may be configured to account for the pilot frequency estimates stored in the pilot frequency memory 630 at block 705 earlier that have been eliminated from the samples of the FERAM 412<img file="TW201131997A_D0014.tif" />(<i>t</i>)。

At block 714, it is checked whether there are more users to decode. If so, the method returns to block 708 and selects a new user group G to be decoded. If not, the method returns to block 704, where the first round of PIC may be performed for the newly received samples in FERAM 412.

Figure 7A illustrates an exemplary embodiment 760 of operations performed by the DACE-based residual PIC block 712. An example of the block illustrated in 760 can be provided in each finger demodulator of the rake receiver 414 in FIG. 6, for example, with each user#<i>n</i>The associated disparate multipath assigns separate fingers.

In Figure 7A,<img file="TW201131997A_D0015.tif" />(<i>t</i>) Or the signal stored in FERAM 412 after the first round of PIC is coupled to the channel<i>n</i>Estimate box 770.<i>n</i>. At channel estimation block 770.<i>n</i>In the adder 771.<i>n</i>First of all, about the user#<i>n</i>For example, the pilot frequency signal previously stored in the pilot frequency memory 630 at step 705<img file="TW201131997A_D0016.tif" />(<i>t</i>) Add back to<img file="TW201131997A_D0017.tif" />(<i>t</i>). DACE cube 772.<i>n</i>Then based on the known pilot frequency pattern and the user#<i>n</i>The associated successfully decoded traffic is used to calculate the pair and user#<i>n</i>Associated pilot frequency signal<i>p</i>_<i>n</i>(<i>t</i>) Estimate<img file="TW201131997A_D0018.tif" />(<i>t</i>). Subsequently, the elimination adder 774 is used.<i>n</i>Come from block 772.<i>n</i>The output is subtracted from the stored pilot frequency signal that has been eliminated<img file="TW201131997A_D0019.tif" />(<i>t</i>) To derive the pilot frequency estimate that has been eliminated<img file="TW201131997A_D0020.tif" />(<i>t</i>) And DACE-based pilot frequency estimation<img file="TW201131997A_D0021.tif" />(<i>t</i>) Residuals. Use elimination adder 776 to remove the signal<img file="TW201131997A_D0022.tif" />(<i>t</i>) Deduct 774.<i>n</i>Output to generate the second composite signal<img file="TW201131997A_D0023.tif" />(<i>t</i>). Second composite signal<img file="TW201131997A_D0024.tif" />(<i>t</i>) Can be written back to FERAM 412 to replace the signal<img file="TW201131997A_D0025.tif" />(<i>t</i>)。

Figure 7B illustrates block 772 by DACE.<i>n</i>Exemplary operations performed. In Figure 7B, for the user<i>n</i>, Use the multiplier 790 and the addition and dump block 791 to correlate the incoming signal with the known pilot frequency pattern and the successfully decoded traffic. Those skilled in the art will understand that by correlating the incoming signal with both the pilot frequency and the successfully decoded traffic data, it is important for users<i>n</i>The associated channel can obtain a better estimate than that possible with only the pilot frequency.

Those of ordinary skill in the art will further understand that in an alternative exemplary embodiment (not shown), the correlation performed by block 790 and block 791 may use separate multiplication and accumulation blocks (for example, a multiplication and accumulation block is used The complex conjugate of the pilot frequency pattern and a multiplication and accumulation block is used for the complex conjugate of the successfully decoded traffic) and the results are added together to implement. In yet another exemplary embodiment, instead, the incoming signal may be related only to the successfully decoded traffic data (not related to the pilot frequency) in a procedure called data-based channel estimation (DBCE) . It is contemplated that such alternative exemplary embodiments fall within the scope of the present case.

In FIG. 7B, the output of block 791 is provided to filter 792. The output of the filter 792 is used to communicate with the user by using the multiplier 793<i>n</i>The pilot frequency pattern is multiplied and re-synthesized to be used from<img file="TW201131997A_D0026.tif" />(<i>t</i>) Eliminated pilot frequency signal.

In the method 700 of FIG. 7, since the DACE-based PIC at block 712 is performed on the received sampling of the first round of PIC that has been performed (at block 704), the PIC at block 712 is also referred to as "backward" or "Remaining" DACE-based PIC.

FIG. 7C illustrates an alternative exemplary embodiment 761 of the operations performed by the DACE 712 and the residual PIC block 713. In FIG. 7C, an SNR weighting block 778 is provided to estimate the pilot frequency before being eliminated from the FERAM 412 by the elimination adder 776 (DACE block 770.<i>n</i>The output) is weighted. In the illustrated exemplary embodiment, the pilot frequency estimate can be scaled as a function of the SNR of the pilot frequency estimate in order to minimize the residual cancellation error. Ideally, cancellation only removes the desired signal; however, actual implementation may include estimation errors that add pilot noise to the effect due to estimation errors. SNR-based scaling can be used to minimize the mean square power of the pilot frequency with the residuals eliminated, thereby making a trade-off between the elimination of the original pilot frequency and the addition of pilot frequency noise due to estimation errors. Those of ordinary skill in the art will understand that such weighting techniques can be applied to any of the PIC schemes described herein, and it is contemplated that such alternative exemplary embodiments fall within the scope of this case.

FIG. 8 illustrates a method of using (only) channel estimation based on pilot frequency to perform the first round of PIC before successful traffic decoding in the receiver 600 of FIG. 6 and performing the first round of PIC based on DACE after successful traffic decoding 800.

At block 802, samples are continuously received and stored in FERAM 412.

At block 804, before successfully performing traffic decoding for the user, the channel for the user is estimated based only on the known pilot frequency pattern. In an exemplary embodiment, such pilot frequency estimation may be performed as described with reference to block 504 in FIG. 5, for example.

At block 806, the first round of PIC is performed using the channel estimation based on the pilot frequency obtained at block 804.

At block 808-block 810, the user group G is selected and decoded.

At block 812, data augmentation channel estimation (DACE) is performed, and the resulting channel estimation is used to perform the first round of PIC for the remaining part of the user's frame for which traffic was successfully decoded at block 810. In an exemplary embodiment, this type of first round of DACE-based PIC is a sample of FERAM 412 received after successful traffic decoding<i>r</i>(<i>t</i>), such as sampling for the first round of PIC based on the pilot frequency that has not been performed<i>r</i>(<i>t</i>) To execute. Those of ordinary skill in the art will understand that performing DACE on samples received after successful decoding of the traffic may, for example, include re-encoding the successfully decoded symbols to generate information about the signals to be received on the remaining part of the frame. The expected transmission pattern of the service signal; and by comparing the expected transmission pattern and/or pilot frequency signal of the traffic signal with the composite received signal to estimate the pilot frequency signal for the remaining part of the frame.

At block 814, it is checked whether there are more users to decode. If so, the method returns to block 808 and selects a new user group G to be decoded. If not, the method returns to block 804.

FIG. 8A illustrates how to provide the user according to the method 800#<i>n</i>The timing diagram 800A of the executed PIC. In FIG. 8A, the horizontal axis represents time as illustrated, and the vertical axis represents an idealized measurement of the power of the corresponding signal. Note that these timings and signals are illustrated for illustrative purposes only, and are not meant to limit the scope of the case in any way.

In Figure 8A, receiving at the receiver includes corresponding to user#<i>n</i>The RX pilot frequency 810A and the RX signal 820A of the RX traffic. The RX traffic is formatted into a frame, where the frame boundaries are marked. The estimated pilot frequency 830A corresponds to the receiver's estimation of the RX pilot frequency 810A present in the RX signal.

The first part 830A.1 of the estimated pilot frequency 830A corresponds to the estimation of the RX pilot frequency 810A by the receiver using the pilot frequency-based estimate obtained, for example, from the operation performed at block 804 of FIG. 8. The second part 830A.2 of the estimated pilot frequency 830A, which starts after the successful traffic decoding at 825A, corresponds to what the receiver uses for the RX pilot frequency 810A using, for example, the DACE obtained from the estimation operation performed at block 812 in FIG. 8 estimate.

The RX pilot frequency 840A after the PIC corresponds to the result of eliminating the estimated pilot frequency 830A from the RX pilot frequency 810A. The first part 840A.1 of the RX pilot frequency 840A after the PIC corresponds to elimination using, for example, the channel estimation based on the pilot frequency obtained from the operation performed at block 806 of FIG. 8. The second part 840A.2 of the RX pilot frequency 840A after the PIC corresponds to erasure using, for example, the DACE obtained from the erasure operation performed at block 812 in FIG. 8.

In the method 800 of FIG. 8, since the DACE-based PIC at block 812 is performed on the samples received after successful traffic decoding, the PIC at block 813 is also referred to as the "forward" PIC based on DACE. .

Fig. 9 illustrates an alternative exemplary embodiment 900 of the receiver according to the present case. The receiver 900 combines the first round and residual pilot frequency estimation/reconstruction block 620 with the traffic cancellation block 461 to further improve the performance of the PIC. In an exemplary embodiment, the operation of the receiver 900 may be performed as described in FIG. 10 or FIG. 11.

FIG. 10 illustrates a method 1000 for performing the first round of PIC, DACE-based residual PIC, and TIC in the receiver 900 of FIG. 9.

At block 1002, samples are continuously received and stored in FERAM 412.

At block 1004, the first round of pilot frequency estimation is performed for all users. In an exemplary embodiment, the operations performed may be similar to those performed at block 504 in FIG. 5. Guide frequency estimate obtained at this box<img file="TW201131997A_D0027.tif" />(<i>t</i>)arrive<img file="TW201131997A_D0028.tif" />(<i>t</i>) Is stored in the boot frequency memory 630 at block 1005, and the boot frequency estimates stored in the memory are expressed as<img file="TW201131997A_D0029.tif" />(<i>t</i>)arrive<img file="TW201131997A_D0030.tif" />(<i>t</i>)。

At block 1006, the pilot frequency estimate obtained at block 1004 is used to perform the first round of PIC for all users.

At blocks 1008-1010, user group G is selected and decoded.

At block 1012, DACE-based residual pilot frequency estimation is performed on the samples in FERAM 412. In an exemplary embodiment, the operations performed at block 1012 may be similar to those performed by block 760 in FIG. 7A, where channel estimation is performed using both pilot frequency and successfully decoded traffic (DACE). implemented. In an alternative exemplary embodiment, only successfully decoded traffic (DBCE) may be used to perform channel estimation. Can sample from FERAM 412<i>r</i>(<i>t</i>) Eliminate the difference between the DACE (or DBCE)-based pilot frequency estimation and the first round of pilot frequency estimation.

At block 1013, by reconstructing the traffic signal based on the decoded data, and sampling from the FERAM 412<i>r</i>(<i>t</i>) Eliminate the reconstructed signal to perform TIC for the user who is successfully decoded.

At block 1014, it is checked whether there are more users to decode. If so, the method returns to block 1008 and selects a new user group G to be decoded. If not, the method returns to block 1004.

FIG. 11 illustrates a method 1100 for performing the first round of PIC, TIC, and residual PIC in the receiver 900 of FIG. 9.

At block 1102, samples are continuously received and stored in FERAM 412.

At block 1104, the first round of pilot frequency estimation is performed for all users.

At block 1106, the pilot frequency estimate obtained at block 1104 is used to perform the first round of PIC.

At blocks 1108-1110, user group G is selected and decoded.

At block 1112, by reconstructing the traffic signal based on the decoded data, and sampling from the FERAM 412<i>r</i>(<i>t</i>) Eliminate the reconstructed signal to perform TIC for the user who is successfully decoded.

At block 1113, a residual PIC is performed on the samples in FERAM 412 for all users. The residual pilot frequency estimation performed at this block benefits from FERAM 412 sampling<i>r</i>(<i>t</i>) Due to the TIC performed at block 1112 in the current round of iterations and also due to the TIC performed at block 1112 in the previous rounds of iterations from block 1108 to block 1114 to a lower degree of interference. In an exemplary embodiment, the operation performed at block 1113 may be based only on the pilot frequency, and the residual PIC block 1160 illustrated in FIG. 11A may be utilized. In view of the technique disclosed above, the operation of the residual PIC block 1160 It will be clear to those skilled in the art.

At block 1114, it is checked whether there are more users to decode. If so, the method returns to block 1108 and selects a new user group G to be decoded. If not, the method returns to block 1104.

In certain alternative exemplary embodiments, block 1008, block 1108, block 1014, block 1114 may be configured to execute PIC and TIC more than once for the same user or the same user group successively. The PIC and TIC are called "iterative" PIC and TIC, and can improve decoding performance, because subsequent rounds through the decoder can benefit from the cumulative elimination of interference to other users. In such exemplary embodiments, the boot frequency memory 630 may be further configured to store the most recently erased pilot frequency estimate instead of just the first erased pilot frequency estimate, so that, for example, in block 712 of method 700 Subsequent rounds of residual PIC executed at FERAM 412 can correctly account for the pilot frequency estimates that have been eliminated from the samples in FERAM 412. It is contemplated that such alternative exemplary embodiments fall within the scope of the present case.

Those of ordinary skill in the art will understand that the various techniques described above can be combined to arrive at alternative exemplary embodiments that are not explicitly illustrated or described. For example, in an alternative exemplary embodiment, the forward PIC technology described with reference to FIGS. 8 and 8A may be combined with the residual PIC and/or TIC technology described with reference to other drawings. It is contemplated that such alternative exemplary embodiments fall within the scope of the present case.

Those skilled in the art will understand that information and signals can be expressed using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that may be mentioned throughout the above description can be made by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof. Express.

Those skilled in the art will further understand that the various illustrative logical blocks, modules, circuits, and algorithm steps described in conjunction with the exemplary embodiments disclosed herein can be implemented as electronic hardware, computer software, or both The combination. To clearly illustrate the interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above based on their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and design constraints imposed on the overall system. The skilled person may implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as causing a departure from the scope of the exemplary embodiments of the present invention.

Various illustrative logic blocks, modules, and circuits described in conjunction with the exemplary embodiments disclosed herein can be used with general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays ( FPGA) or other programmable logic devices, individual gates or transistor logic, individual hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors cooperating with a DSP core, or any other such configuration.

The steps of the method or algorithm described in combination with the exemplary embodiments disclosed herein can be directly implemented in hardware, in a software module executed by a processor, or in a combination of the two. The software module can reside in random access memory (RAM), flash memory, read-only memory (ROM), electronically programmable ROM (EPROM), electronically erasable programmable ROM (EEPROM), temporary storage In a storage medium, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from the storage medium and write information to the storage medium. In the alternative, the storage medium may be integrated into the processor. The processor and storage medium may reside in the ASIC. The ASIC can be resident in the user terminal. In the alternative, the processor and the storage medium may reside in the user terminal as separate components.

In one or more exemplary embodiments, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, each function can be stored as one or more instructions or codes on a computer readable medium or transmitted through it. Computer readable media include both computer storage media and communication media. Communication media includes any media that facilitates the transfer of computer programs from one location to another. The storage medium can be any available medium that can be accessed by a computer. For example (but not limiting), such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices or can be used to carry or store instructions or Any other media that can be accessed by the computer in the form of the desired code in the form of a data structure. In addition, any connection is appropriately referred to as a computer readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave Coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of media. Disks and discs as used herein include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVD), floppy discs and Blu-ray discs, where disks are usually magnetically Reproduce the data, and the disc (disc) uses laser to optically reproduce the data. The above-mentioned combinations can also be included in the scope of computer readable media.

The previous description of the disclosed exemplary embodiments is provided to enable anyone skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be obvious to those skilled in the art, and the general principles defined herein can be applied to other exemplary embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the exemplary embodiments shown herein, but should be granted the widest scope consistent with the principles and novel features disclosed herein.

<p>100. . . Wireless cellular communication system</p><p>102A. . . Cell Service Area</p><p>102B. . . Cell Service Area</p><p>102C. . . Cell Service Area</p><p>102D. . . Cell Service Area</p><p>102E. . . Cell Service Area</p><p>102F. . . Cell Service Area</p><p>102G. . . Cell Service Area</p><p>106A. . . Access terminal</p><p>106B. . . Access terminal</p><p>106C. . . Access terminal</p><p>106D. . . Access terminal</p><p>106E. . . Access terminal</p><p>106F. . . Access terminal</p><p>106G. . . Access terminal</p><p>160A. . . Base station</p><p>160B. . . Base station</p><p>160C. . . Base station</p><p>160D. . . Base station</p><p>160E. . . Base station</p><p>160F. . . Base station</p><p>160G. . . Base station</p><p>200. . . Reverse link</p><p>300. . . Data source</p><p>302. . . Encoder</p><p>304. . . Interleaver</p><p>306. . . Modulator</p><p>308. . . Fundamental frequency to radio frequency (RF) conversion unit</p><p>310. . . antenna</p><p>400. . . Embodiment/TIC receiver/receiver</p><p>401. . . antenna</p><p>402. . . RF to fundamental frequency conversion unit</p><p>404. . . Demodulator</p><p>406. . . Deinterleaver</p><p>408. . . decoder</p><p>410. . . Data slot</p><p>412. . . Sample buffer</p><p>414. . . Rake receiver</p><p>416. . . Symbol buffer</p><p>460. . . Interference reconstruction unit</p><p>461. . . Traffic elimination box</p><p>462. . . Encoder</p><p>464. . . Interleaver</p><p>466. . . Modulator</p><p>468. . . filter</p><p>470. . . First round of pilot frequency estimation/reconstruction block</p><p>500. . . method</p><p>502. . . Cube</p><p>504. . . Cube</p><p>506. . . Cube</p><p>508. . . Cube</p><p>510. . . Cube</p><p>512. . . Cube</p><p>514. . . Cube</p><p>560. . . Example</p><p>570.n. . . Pilot frequency estimation block</p><p>576. . . Elimination adder</p><p>590. . . Multiplier</p><p>591. . . Adding and dumping blocks</p><p>592. . . filter</p><p>600. . . Embodiment/receiver</p><p>620. . . First round and residual pilot frequency estimation/reconstruction block</p><p>630. . . Boot frequency memory</p><p>700. . . method</p><p>702. . . Cube</p><p>704. . . Cube</p><p>705. . . Cube</p><p>706. . . Cube</p><p>708. . . Cube</p><p>710. . . Cube</p><p>712. . . Cube</p><p>714. . . Cube</p><p>760. . . Example/Block</p><p>761. . . Example</p><p>770.n. . . Channel estimation block</p><p>771.n. . . Adder</p><p>772.n. . . DACE cube</p><p>774.n. . . Elimination adder</p><p>776. . . Elimination adder</p><p>778. . . SNR weighted block</p><p>790. . . Multiplier</p><p>791. . . Addition and dump box</p><p>792. . . filter</p><p>793. . . Multiplier</p><p>800. . . method</p><p>802. . . Cube</p><p>804. . . Cube</p><p>806. . . Cube</p><p>808. . . Cube</p><p>810. . . Cube</p><p>810A. . . RX pilot frequency</p><p>812. . . Cube</p><p>814. . . Cube</p><p>820A. . . RX Communications</p><p>825A. . . step</p><p>830A. . . Estimated pilot frequency</p><p>830A.1. . . The first part of the estimated pilot frequency 830A</p><p>840A. . . RX pilot frequency</p><p>840A.1. . . The first part of the RX boot frequency 840A after PIC</p><p>900. . . Embodiment/receiver</p><p>1000. . . method</p><p>1002. . . Cube</p><p>1004. . . Cube</p><p>1005. . . Cube</p><p>1006. . . Cube</p><p>1008. . . Cube</p><p>1010. . . Cube</p><p>1012. . . Cube</p><p>1013. . . Cube</p><p>1014. . . Cube</p><p>1100. . . method</p><p>1102. . . Cube</p><p>1104. . . Cube</p><p>1106. . . Cube</p><p>1108. . . Cube</p><p>1110. . . Cube</p><p>1112. . . Cube</p><p>1113. . . Cube</p><p>1114. . . Cube</p><p>1160. . . Residual PIC block</p>

Figure 1 illustrates a wireless cellular communication system.

Figure 2 illustrates an exemplary channel received on the reverse link of the CDMA communication system at the base station.

FIG. 3 illustrates an example of a transmitter structure and/or program that can be implemented at the access terminal of FIG. 1.

FIG. 4 illustrates an exemplary embodiment of a receiver that may be implemented at the base station of FIG. 1. FIG.

FIG. 5 illustrates a method of performing the first round of PIC (Pilot Frequency Interference Cancellation) followed by TIC in the receiver of FIG. 4.

FIG. 5A illustrates the first round of guidance frequency estimation and elimination of the user# in the box illustrated in FIG. 5<i>n</i>An exemplary embodiment of the first round of guided frequency elimination.

Fig. 6 illustrates an alternative exemplary embodiment of the receiver according to the present case.

FIG. 7 illustrates a method of performing the first round PIC and the residual PIC in the receiver of FIG. 6.

FIG. 7A illustrates an exemplary embodiment of operations performed by the DACE block and the residual PIC block in FIG. 7.

FIG. 7B illustrates an exemplary operation performed by the DACE block in FIG. 7A.

FIG. 7C illustrates an alternative exemplary embodiment of operations performed by the DACE block and the residual PIC block in FIG. 7.

FIG. 8 illustrates a method of performing the first round of PIC using (only) channel estimation based on pilot frequency before successful traffic decoding in the receiver of FIG. 6 and performing the first round of PIC based on DACE after successful traffic decoding.

Figure 8A illustrates the method according to Figure 8 for the user#<i>n</i>Timing diagram of the executed PIC.

Fig. 9 illustrates an alternative exemplary embodiment of the receiver according to the present case.

FIG. 10 illustrates a method of performing the first round of PIC, DACE-based residual PIC and TIC in the receiver of FIG. 9.

FIG. 11 illustrates a method of performing the first round of PIC, TIC, and residual PIC in the receiver of FIG. 9.

FIG. 11A illustrates an exemplary embodiment of operations performed at the residual PIC block of the method of FIG. 11.