KR100901669B1 - Method and apparatus for canceling pilot interference in a wireless communication system - Google Patents

Abstract

A method and system for estimating and canceling pilot interference in a wireless (eg, CDMA) communication system. In one method, a received signal consisting of a number of signal instances each containing a pilot is initially processed to provide a data sample. Pilot interference of each signal instance despreads a denter sample into a spreading sequence for the signal instance, channelizes the despread data to provide a pilot symbol, filters the pilot symbol to estimate the channel response of the signal, and estimates It may be estimated by multiplying the spreading sequence by the channel response. The pilot interference estimates due to the plurality of interfering multipaths are accumulated to derive the total pilot interference, and the total pilot interference is subtracted from the data samples to provide pilot-erase data samples. These samples are then processed to derive demodulated data for each one or more (desired) signal instances in the received signal.

Interference, instance, spread.

Description

METHOD AND APPARATUS FOR CANCELING PILOT INTERFERENCE IN A WIRELESS COMMUNICATION SYSTEM}

35 Claims of Priority Under U.S.C §119

This patent application is hereby expressly incorporated by reference and assigned to the assignee herein, and filed June 30, 2004, entitled "Method and Apparatus for Canceling Pilot Interference in a Wireless Communication System" FOR CANCELING PILOT INTERFERENCE IN A WIRELESS COMMUNICATION SYSTEM. "U.S. Provisional Patent Application 60 / 584,527.

background

Field

FIELD OF THE INVENTION The present invention relates generally to data communication, and more particularly to techniques for canceling interference due to pilot in a wireless (eg CDMA) communication system.

background

Wireless communication systems have been widely developed to provide various types of communication such as packet data and the like. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), or some other multiple access technology. CDMA systems may provide certain advantages, including increased system capacity, over other types of systems. CDMA technology is typically all designed to implement one or more standards such as the IS-95, cdma2000, IS-856, W-CDMA, and TS-CDMA standards known in the art.

In some wireless (eg, CDMA) communication systems, a pilot may be transmitted from a transmitter unit (eg, a terminal) to a handwriting unit (eg, a base station) that assists a receiver unit performing multiple functions. . For example, the pilot may be used for estimation of receiver unit, channel response and communication channel quality, coherent demodulation of data transmission, etc., for synchronization with the timing and frequency of the transmitter unit. Pilots are typically based on known data patterns (e.g., all zero sequences) and are generated using known signal processing schemes (e.g., channelized with a particular channelizing code and spread with known spreading sequences).

In the reverse link in cdma2000, a spreading sequence for each terminal is generated based on (1) a complex pseudo-random noise (PN) sequence common to all terminals and (2) a scrambling sequence specific to the terminal. In this method, pilots from different terminals may be identified by different scrambling sequences of terminals. On the forward link in cdma2000 and IS-95 systems, each base station is assigned a specific offset of the PN sequence. In this method, pilots from different base stations may be identified by different assigned PN offsets of the base stations.

At the receiver unit, the rake receiver is often used to recover transmitted pilot, signaling, and traffic data from all transmitter units that have established communication with the receiver unit. The signal transmitted from a particular transmitter unit may be received at the receiver via a multi-signal path, and each received signal instance (or multipath) of sufficient strength may be individually modulated by the rake receiver. Each such multipath is processed in a manner complementary to that performed at the transmitter unit to recover the data and pilot received via this multipath. The recovered pilot represents the channel response to multipath and has the amplitude and phase determined by it. The pilot is typically transmitted with the pilot as well by the channel response and used for coherent demodulation of various types of distorted data. For each transmitter unit, multiple multipath pilots for that transmitter unit are also used to combine the modulated symbols derived from these multipaths to obtain combined symbols with improved quality.

On the reverse link, the pilot from each transmitting terminal acts as interference to the signals from all other terminals. For each terminal, the total interference due to the pilot transmitted by all other terminals may be a large percentage of the total interference experienced by this terminal. This pilot interference can degrade performance (eg, high packet error rate) and also reduce reverse link capacity.

Accordingly, there is a need for a technique for canceling interference due to pilot in a wireless (eg CDMA) communication system.

summary

Aspects of the present invention provide a technique for estimating and canceling pilot interference in a wireless (eg, CDMA) communication system. The received signal typically contains a number of signal instances (ie, multipath). For each multipath that is modulated (ie, each desired multipath), the pilot in every multipath is the interference to the data in the desired multipath. If the pilot is generated based on a known data pattern (e.g., a sequence that is all zeros) and a known channelizing code (e.g., a Walsh code of zero), then the pilot in the interfering multipath is determined by the multipath of the multipath in the receiver unit. It may simply be estimated as a spreading sequence having a phase corresponding to the arrival time. Pilot interference from each interfering multipath may be estimated based on an estimate of the spreading sequence and the channel response of that multipath (which may be estimated by the pilot). The total pilot interference due to the multiple interference multipaths is derived from the received signal and subtracted to provide a pilot-erase signal with pilot interference removed.

In certain embodiments, a method is provided for canceling pilot interference at a receiver unit in a wireless (eg, cdma2000) communication system. According to the method, a received signal consisting of a number of signal instances each comprising a pilot is initially processed to provide a data sample. The data samples are then processed to derive an estimate of pilot interference due to each of the one or more (interfering) signal instances, and the pilot interference estimates are also combined to derive the total pilot interference. The total pilot interference is then subtracted from the data samples to provide pilot-erase data samples, which are further processed to yield modulated data for each of one or more (desired) signal instances of the received signal. .

The pilot interference due to each interfering signal instance is (1) despreading the data samples with a spreading sequence for the signal instance and (2) channelizing the despreading samples with a pilot channelizing code to provide a pilot symbol and (3) a pilot symbol. It may be estimated by filtering to provide the estimated channel response of the signal instance and (4) multiplying the spreading sequence for the signal instance by the estimated channel response to provide the estimated pilot interference. The data demodulation for each desired multipath comprises (1) despreading the pilot erased data samples with the spreading sequence for the signal instance and (2) channelizing the despread samples with the data channelizing code to provide data symbols, (3) may be performed by demodulating data symbols and providing demodulated data to a signal instance. For improved performance, estimation and cancellation may be performed at a sample rate higher than the PN chip rate.

Another system and method for pilot interference cancellation includes determining a multipath channel estimate and a noise estimate, selecting an cancellation factor based on the multipath channel estimate and the noise estimate, and multiplying the channel estimate by the selected cancellation factor. Multiplying the product of the transmit pulse and the receive filter by the product of the step, the channel estimate and the cancellation factor, the spread pilot signal (e.g., a PN sequence) and the weighted filter (i.e. Reconstructing the pilot sample by performing a convolution of a product of the calculated convolution, accumulating the reconstructed pilot sample from the multiple finger processor and subtracting the accumulated reconstructed pilot sample from the data sample to perform data demodulation It may also include a step. The order of these processes may be changed.

Various aspects, embodiments, and features of the invention are described in detail below.

Brief description of the drawings

The features, nature and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the following drawings, wherein like reference numerals correspond equally throughout the specification.

1 is a diagram of a wireless communication system.

2 is a simplified block diagram of an embodiment of a base station and a terminal.

3 is a block diagram of an embodiment of a modulator for the reverse link of cdma2000.

4 is a block diagram of an embodiment of a rake receiver.

5 is a block diagram of a particular embodiment of a finger processor in a rake receiver capable of estimating and canceling pilot interference in addition to performing data demodulation.

6A and 6B are graphs illustrating processing of data samples to derive pilot interference estimates in accordance with one embodiment.

7 is a flow diagram of one embodiment of a process for deriving total pilot interference for multiple multipaths.

8 is a flowchart of an embodiment of a process for data demodulating multiple multipaths with pilot interference cancellation.

9 is a block diagram of another embodiment of a finger processor in a rake receiver such as the sample buffer and the rake receiver of FIG.

10 is an example of a lookup table that may be used by the finger processor of FIG. 9.

FIG. 11 shows an example of a time snapshot for two finger processors similar to the finger processor of FIG. 9.

12A is a flow diagram of another embodiment that derives accumulated pilot interference for multiple multipaths.

12B is a flow diagram of another embodiment of a process for deriving accumulated pilot interference for multiple multipaths.

13A is a block diagram of a receiver having a plurality of antennas and a demodulator having a plurality of interference accumulating buffers.

13B is a block diagram of a receiver having a plurality of antennas and a demodulator having a single interference accumulating buffer.

14 shows an example of the convolution of transmit pulses provided by the transmit filter of FIG. 3 and the receive filter of the receiver of FIG.

details

A single transmission from the terminal may reach the base station via one or more signal paths. These signal paths may include straight paths (eg, signal path 110a) and reflective paths (eg, signal path 110b). When the reflected signal is reflected at the reflection source and reaches the base station via a path different from the line-of-sight path, the reflection path is created. Reflective sources are typically artifacts in the environment in which the terminal operates (e.g., buildings, trees, or some other structure). As a result, the signal received by each antenna at the base station may include multiple signal instances (or multipaths) from one or more terminals.

In system 100, system controller 102 (also sometimes referred to as base station controller (BSC)) is coupled to base station 104, provides coordinates and control to the combined base station, and also provides a terminal (via a combined base station). 106) Control the routing of calls to. In addition, the system controller 102 is coupled to a public switched telephone network (PSTN) via a mobile switching center (MSC) and to a packet data network through a packet data serving node (PDSN), which is not shown in FIG. 1. System 100 may be such as IS-95, CDMA2000, CDMA 2000 1xEV-DV, CDMA 2000 1xEV-DO (IS-856), WCDMA, TD-SCDMA, TS-CDMA, or some other CDMA standard, or a combination thereof. It may be designed to support one or more CDMA standards.

Various aspects and embodiments of the invention may be applied to the forward and reverse links in various wireless communication systems. For clarity, the pilot interference cancellation technique is described in detail for the reverse link in cdma2000.

2 is a simplified block diagram of an embodiment of a base station 104 and a terminal 106. At the terminal 106 on the reverse link, the transmit (TX) data processor 214 receives various types of "traffic" such as user-specific data, messages from the data source 212. TX data processor 214 then formats and codes the different types of traffic based on one or more coding schemes to provide coded data. Each coding scheme may include cyclic redundancy check (CRC), convolution, turbo, block, and other coding, or no coding at all. If error correction codes are used to counter fading, interleaving is commonly applied. Other coding schemes may include automatic retransmission request (ARQ), hybrid ARQ, and incremental redundancy iteration techniques. Typically, different types of traffic are coded using different coding schemes. Modulator (MODL) 216 then receives pilot data and codes the data from TX data processor 214 and further processes the received data to produce modulated data.

3 is a block diagram of one embodiment of a modulator 216a that may be used with the modulator of FIG. On the reverse link in cdma2000, processing by modulator 216a is performed by multiplier 312 for each of a number of code channels (e.g., traffic, sink, paging, and pilot channels) with each Walsh code C _chx . Covering the data to channelize user-specific data (packet data), messages (control data), and pilot data on each code channel. The channelized data for each code channel may be scaled by unit 314 to each gain G _i to control the relative transmit power of the code channel. The scaled data for all code channels for the in-phase (I) path are then summed by summer 316a to provide I-channel data, for all code channels for the quadrature (Q) path. The scaled data is summed by summer 316b to provide Q-channel data.

3 also shows an embodiment of a spreading sequence generator 320 for the reverse link in cdma2000. Within generator 320, long code generator 322 receives the long code mask assigned to the terminal and generates a chair-random noise (PN) sequence having a phase determined by the long code mask. The long PN sequence is then multiplied by the multiplier 326a with the I-channel PN sequence to produce an I spreading sequence. The long PN sequence is delayed by delay element 324, multiplied by Q-channel PN sequence by multiplier 326b, decimated in two factors by element 328, and Walsh code (Cs = +- ) And spread by the multiplier 330 into an I spreading sequence to produce a Q spreading sequence. The I-channel and Q-channel PN sequences form a complex short PN sequence used by all terminals. The I and Q spreading sequences form a complex spreading sequence S _k that is specific to the terminal.

A modulator (216a) within aeseo, I- and Q- channel data channel data (D + jD _{chI chQ)} is spread (S _kI + jS _kQ) to the I and Q spreading sequences via a complex multiplication operation by the multipliers 340 Generate I spread data and Q spread data (D _spI + jD _spQ ). The complex despreading operation is expressed as follows.

I and Q spread data include modulated data provided by modulator 216a.

및

로 업컨버팅하는 단계를 포함한다. 곱셈기 (354a 및 354b) 로부터의 I 및 Q 컴포넌트는 합산기 (356) 에 의해 합산되고 곱셈기 (358) 에 의해 이득 G₀ 로 증폭되어 역방향 링크 변조된 신호를 생성한다.The modulated data is then provided to and adjusted by the transmitter (TMTR) 218a. Transmitter 218a is one embodiment of transmitter 218 of FIG. 2. Signal conditioning includes filtering the I and Q channels with filters 352a and 352b, respectively, and multiplying the filtered I and Q data by multipliers 354a and 354b, respectively.

And

Upconverting to. I and Q components from multipliers 354a and 354b are summed by summer 356 and amplified by gain G ₀ by multiplier 358 to produce a reverse link modulated signal.

Returning to FIG. 2, the reverse link modulated signal is then transmitted via the antenna 220 over the wireless communication link to one or more base stations.

At base station 104, reverse link modulated signals from multiple terminals are received by each of one or more antennas 250. The plurality of antennas 250 may be used to provide spatial diversity against harmful path effects such as fading. For example, for a base station supporting three sectors, two antennas may be used for each sector so that the base station may have six antennas. As a result, any number of antennas may be used at the base station.

Each received signal is provided to a respective receiver (RCVR) 252, where the receiver (RCVR) 252 adjusts (e.g., filters, amplifies, downconverts) the received signal and digitizes the data sample for that received signal. To provide. Each received signal may include one or more signal instances (ie, multipath) for each of the plurality of terminals.

Demodulator (DEMOD) 254 then receives and processes data samples for all received signals to provide recovered symbols. For cdma2000, processing by demodulator 254 to recover data transmissions from a particular terminal may include (1) despreading the data samples with the same spreading sequence used to spread the data at the terminal, (2) despreading samples Channelizing to isolate or channelize the received data and pilot on each code channel, and (3) coherently demodulate the channelized data into the recovered pilot to provide demodulated data. It includes a step. Demodulator 254 may implement a rake receiver capable of processing a plurality of signal instances for each of a plurality of terminals, as described below.

Receive (RX) data processor 256 then receives and decodes the demodulated data for each terminal to recover the user-specific data and messages sent by the terminal on the reverse link. At the terminal, processing by demodulator 254 and RX data processor 256 is complementary to processing by each of modulator 216 and TX data processor 214.

4 is a block diagram of one embodiment of a rake receiver 254a capable of receiving and demodulating reverse link modulated signals from multiple terminals 106. Rake receiver 254a includes one or more (L) sample buffers 408, one or more (M) finger processors 410, a searcher 412, and a symbol combiner 420. The embodiment of FIG. 4 shows all finger processors 410 coupled to the same combiner 420. In some configurations, there may be a significant number of finger processors 410, such as the (256) finger processor.

는 다음과 같이 표현된다.Due to the multipath environment, the reverse link modulated signal transmitted from each terminal 106 may reach the base station 104 via multiple signal paths (as shown in FIG. 1), and for each base station antenna The received signal typically includes a combination of different instances of reverse link modulated signals from each of a plurality of terminals. Each signal instance (or multipath) in a received signal is typically associated with a particular magnitude, phase, and arrival time (ie, delay or time offset relative to CDMA system time). The difference in multipath arrival times at the base station is one or more PN chips and the received signal at the input to each receiver 252.

Is expressed as

는 j 번째 단말기에 의해 송신된 j 번째 역방향 링크 변조된 신호이고,

Is a j th reverse link modulated signal transmitted by a j th terminal,

는, j 번째 역방향 링크 변조된 신호

가 송신된 시간에 대한 i 번째 다중경로의 l 번째 안테나에서의 도달 시간이며,

Is the j th reverse link modulated signal.

Is the arrival time at the l th antenna of the i th multipath relative to the transmitted time,

는 l 번째 안테나에서의 j 번째 단말기에 대해 i 번째 다중경로에 대한 채널 이득 및 위상을 나타내고,

Denotes the channel gain and phase for the i th multipath for the j th terminal in the l th antenna,

는 l 번째 신호에서의 모든 역방향 링크 변조된 신호에대한 합이고,

Is the sum of all reverse link modulated signals in the l th signal,

는 l 번째 수신 신호에서의 각 역방향 링크 변조된 신호의 모든 다중경로에 대한 합이고,

Is the sum of all multipaths of each reverse link modulated signal in the l th received signal,

 n (t) represents real channel noise and internal receiver noise in RF.

를 증폭하고 주파수 다운컨버팅하여, 단말기에서 사용된 송신 필터 (예를 들어, 필터 (352)) 에 통상적으로 매칭하는 수신 필터로 신호를 필터링하여 조절된 신호를 제공한다. 그 후, 각 수신기 유닛 (252) 는 조절된 신호를 디지털화하여 데이터 샘플의 각 스트림을 제공하고, 그 후, 데이터 샘플은 각각의 샘플 버퍼 (408) 에 제공된다.Each receiver 252 is each received signal

Amplify and frequency downconvert to filter the signal with a receive filter that typically matches the transmit filter (e.g., filter 352) used in the terminal to provide a regulated signal. Each receiver unit 252 then digitizes the adjusted signal to provide each stream of data samples, after which the data samples are provided to respective sample buffers 408.

Each sample buffer 408 stores the received data sample and provides the appropriate data sample to the appropriate processing unit (eg, finger processor 410 and / or searcher 412) at a suitable time. In one design, each buffer 408 provides a data sample to each set of assigned finger processors to process multipath in the received signal associated with that buffer. In another design, multiple buffers 408 provide data samples to a particular finger processor that has the capacity to process multiple multipaths in a time division multiple manner (eg, in a time division multiple manner). Sample buffers 408a-408l may also be implemented as a single buffer of a suitable size and speed.

Searcher 412 is used to search for strong multipaths in the received signal and provide an indication of the strength and timing of each searched multipath that satisfies a set of criteria. The search for multipath of a particular terminal is typically performed by correlating data samples for each received signal with a spreading sequence of the terminal locally generated at various chip or sub-chip offsets (or phases). Due to the pseudo-noise nature of the spreading sequence, the correlation between the data sample and the spreading signal is except when the phase of the locally generated spreading sequence is time-aligned to the phase of the multipath, where the correlation result is a high value. Should be low.

에 대해, 탐색기 (412) 는 그 역방향 링크 변조된 신호에 대해 탐색된 하나 이상의 다중경로 세트에 하나 이상의 시간 오프셋

세트를 제공할 수도 있다 (각각의 탐색된 다중경로의 신호 강도와 함께일 수 있음). 탐색기 (412) 에 의해 제공된 시간 오프셋

은 기지국 타이밍 또는 CDMA 시스템 시간에 상대적이고, 신호 송신의 시간에 상대적인 수학식 (2) 에 도시된 시간 오프셋

에 관련된다.Each reverse link modulated signal

For, the searcher 412 may include one or more time offsets in one or more multipath sets searched for the reverse link modulated signal.

A set may be provided (which may be with the signal strength of each searched multipath). Time offset provided by the searcher 412

Is the time offset shown in equation (2) relative to the base station timing or CDMA system time and relative to the time of signal transmission.

Is related.

The searcher 412 may be designed with one or more searcher units, and each searcher unit may be designed to search for multipaths through each search window. Each search window includes a range of spreading sequence phases to be searched. The searcher units may be operated in parallel to speed up the search operation. Also or instead, the searcher 412 may be operated at a high clock rate to speed up the search operation. Searchers and searches are described in more detail in US Pat. Nos. 5,805,648, 5,781,543, 5,764,687, and 5,644,591.

또는 시간 오프셋

에 대응하는 위상을 가진 확산 시퀀스

(확산 시퀀스 생성기 (414) 에 의해 생성될 수도 있음) 중 하나, 및 (3) 복구되는 코드 채널에 대한 채널라이징 코드 (예를 들어, 왈시 코드) 를 수신한다. 그 후, 각 핑거 프로세서 (410) 는 수신 데이터 샘플을 프로세싱하여 각 할당된 다중경로에 대한 복조된 데이터를 제공한다. 핑거 프로세서 (410) 에 의한 프로세싱은 이하 더욱 상세히 설명된다.Each finger processor 410 is assigned to each of one or more corresponding multipaths (e.g., multipaths of sufficient strength as determined by the controller 260 based on signal strength information provided by the searcher 412). You can also process sets. Each finger processor 410 then performs, for each assigned multipath, (1) a data sample for the received signal comprising the assigned multipath, and (2) a time offset of the assigned multipath.

Or time offset

Spread sequence with phase corresponding to

One of (which may be generated by spreading sequence generator 414), and (3) a channelizing code (e.g., Walsh code) for the code channel to be recovered. Each finger processor 410 then processes the received data sample to provide demodulated data for each assigned multipath. Processing by the finger processor 410 is described in more detail below.

The symbol combiner 420 receives and combines demodulated data (ie, demodulated symbols) for each terminal. In particular, symbol combiner 420 receives the demodulated symbols for all assigned multipaths for each terminal and, depending on the design of the finger processor, time-aligns (or skews) the symbols to the assigned multipaths. Calculate the difference in time offsets for. The symbol combiner 420 then combines the time-aligned demodulated symbols for each terminal to provide the recovered symbols for the terminal. A plurality of symbol combiners may be provided to combine the symbols for a plurality of terminals simultaneously. The recovered symbols for each terminal are then provided to the RX data processor 256 and decoded.

Multipath processing may be performed based on various demodulation designs. In a first demodulation design, one finger processor is assigned to process multiple multipaths in the received signal. For this design, data samples from the sample buffer may be processed into "segments" covering a specific time duration (ie, a specific number of PN chips) and starting at some defined time boundary. In a second demodulation design, a plurality of finger processors are assigned to process a plurality of multipaths in the received signal. Various aspects and embodiments of the first demodulator design are described.

Pilot interference cancellation may also be performed based on various schemes. In a first pilot interference cancellation scheme based on a first demodulator design, the channel response of a particular multipath is estimated based on the segment of data samples, and then the estimated channel response is used to make this multipath for the same segment. An estimate of the pilot interference due to is derived. This approach may provide improved pilot interference cancellation. However, because the segment of data samples is first processed before data demodulation is performed on the same set to estimate and cancel pilot interference, this approach also introduces additional processing delay in data demodulation for multipath.

In a second pilot interference cancellation scheme based on the first demodulation design, the channel response of a particular multipath is estimated based on the segment of the data sample, and then the estimated channel response is used to make this multipath for the next segment. An estimate of the pilot interference due to is derived. This approach may be used to reduce (or eliminate) additional processing delay in data demodulation resulting from pilot interference estimation and cancellation. However, since the link conditions may change over time, the time delay between the current and the next segment must be kept short enough so that the channel response estimate for the current segment is still accurate for the next segment. For simplicity, pilot interference estimation and cancellation are described below for the second scheme.

5 is a block diagram of a particular embodiment of a finger processor 410x capable of estimating and canceling pilot interference in addition to performing data demodulation. Finger processor 410x may be used for each finger processor 410 in rake receiver 254a shown in FIG. 4. In the following description, FIG. 5 shows the processing elements and FIGS. 6A and 6B graphically show the timing for pilot interference and cancellation.

Finger processor 410x is assigned to demodulate one or more "desired" multipaths in a particular received signal. Sample buffer 408x stores data samples for the received signal including the multipath assigned to finger processor 410x. The buffer 408x requires a finger processor and, as needed, provides data samples (in segments) suitable for the finger processor. In the embodiment shown in FIG. 5, finger processor 410x is a resampler 522, pilot estimate 520 or channel estimator, summer 542, data demodulation unit 550, and pilot interference estimator 530. It is provided.

For the desired multipath demodulated by finger processor 410x, all multipath pilots and all other multipath data in the same received signal act as interference for this multipath. Since the pilot is processed in a known data pattern (e.g., typically all zero sequences) and in a known manner, the "interfering" multipath pilot is estimated and eliminated from the desired multipath to signal quality of the data component of the desired multipath. You can also improve. Finger processor 410x may estimate and cancel pilot interference due to multiple multipaths found in the received signal including the pilot of the desired multipath, as described below.

In one embodiment, pilot interference estimation and cancellation and data demodulation are performed at " burst. &Quot; For each burst (ie, each processing cycle), segments of data samples are processed during a certain number of PN chips to estimate pilot interference due to a particular multipath. In a particular embodiment, for cdma2000, each segment includes a data sample during one symbol period, which may be 64 PN chips. However, other segment sizes may be used (eg, for data symbols of different durations), which is within the scope of the specification. As described below, data demodulation may be performed in a parallel and pipelined manner with pilot interference estimates to increase processing efficiency and reduce overall processing time.

to derive an estimate of pilot interference due to the m th multipath, where m = (i, j, l) and the i th multipath representation for the j th reverse link modulated signal found in the l th received signal The segment of data samples is initially provided from the buffer 408x to the resampler 522 in the finger processor 410x. Resampler 522 then performs decimation and interpolation or a combination thereof to produce a decimated data sample with suitable " fine-grain " at a chip rate. to provide.

6A graphically illustrates one embodiment of the resampling performed by the resampler 522. The received signal is typically oversampled at a sample rate that is a multiple (eg, 2, 4, or 8) times chip rate providing high time resolution. The data sample is stored in sample buffer 408x, and then sample buffer 408x provides a segment of data sample (e.g., 512) during each processing cycle. Resampler 522 then "resamples" the data samples received from buffer 408x to provide the samples with the appropriate timing phase at the chip rate.

은 탐색기 (412) 에 의해 결정되고 제공될 수도 있다. 그러나, 데이터 복조에 대해 할당되지 않은 다중경로로 인한 파일롯 간섭은 또한 각각의 이러한 다중경로의 시간 오프셋이 알려진 한, 추정되고 소거될 수도 있다. 각각의 다중경로의 시간 오프셋

은 기지국 타이밍 또는 CDMA 시스템 시간에 상대적인 심볼 주기의 정수 넘버 및 심볼 주기의 프랙셔널 (fractional) 부분을 포함하는 것으로 (즉,

) 관측될 수도 있고, 여기서 심볼 주기는 채널화 코드의 길이 (예를 들어, cdma2000 에 대한 64 개의 PN 칩) 에 의해 결정된다. 시간 오프셋의 프랙셔널 부분

은 리샘플러 (522) 에 제공하고 데시메이션을 위해 데이터 샘플의 특정 세그멘트를 선택하도록 사용될 수도 있다. 도 6a 에서 도시된 예에서, m 번째 다중경로의 시간 오프셋의 프랙셔널 부분은

=5 이고, 데이터 샘플 세그멘트 (622) 는 버퍼 (408x) 에 의해 제공되며, 리샘플러 (522) 에 의해 제공된 데시메이트된 데이터 샘플은 음영 박스에 의해 표현된다.As shown in FIG. 6A, if the received signal is sufficiently oversampled (eg, at 8 times chip rate), then the resampling for the mth multipath is received each time, eg, from a buffer. It may be done by providing the eighth data sample with the selected data sample aligned closest to the timing of the mth multipath peak. The m-th multipath is typically the multipath allocated for data demodulation and the time offset of the multipath.

May be determined and provided by the searcher 412. However, pilot interference due to unallocated multipath for data demodulation may also be estimated and canceled as long as the time offset of each such multipath is known. The time offset of each multipath

Is an integer number of symbol periods relative to the base station timing or CDMA system time and a fractional portion of the symbol period (ie,

), Where the symbol period is determined by the length of the channelization code (eg, 64 PN chips for cdma2000). Fractional portion of time offset

May be provided to the resampler 522 and used to select a particular segment of the data sample for decimation. In the example shown in FIG. 6A, the fractional portion of the time offset of the m th multipath is

= 5, data sample segment 622 is provided by buffer 408x, and the decimated data sample provided by resampler 522 is represented by a shaded box.

In some other receiver designs where the received signal is sufficiently oversampled, interpolation is instead or additionally performed with decimation to derive a new sample with a suitable timing phase as is known in the art.

에 대응하는 위상을 갖는 (켤레 복소수인) 확산 시퀀스

및 데시메이트된 데이터 샘플을 수신한다. 확산 시퀀스

는 확산 시퀀스 생성기 (414) 에 의해 제공될 수도 있다. cdma2000 에서의 역방향 링크에 대해, 확산 시퀀스

는 도 3 의 확산 시퀀스 생성기 (320) 에 대해 도시된 바와 같이 생성될 수도 있다. 그리고 도 6a 에 도시된 바와 같이, 데이터 샘플 세그멘트와 동일한 길이 및 동일한 타이밍 위상을 갖는 확산 시퀀스

의 세그멘트가 역확산을 위해 사용된다 (즉, 확산 시퀀스

는 데시메이트된 데이터 샘플로 시간-정렬된다). In pilot estimator 520, despreader 524 is a time offset of the m th multipath from which pilot interference is estimated.

Spread sequence (conjugate complex) with phase corresponding to

And receive the decimated data sample. Diffusion sequence

May be provided by the spreading sequence generator 414. Spreading Sequence for Reverse Link on cdma2000

May be generated as shown for the spreading sequence generator 320 of FIG. 3. And a spreading sequence having the same length and the same timing phase as the data sample segment, as shown in FIG. 6A.

Segment of is used for despreading (ie spreading sequence

Is time-aligned with decimated data samples).

로 데시메이트된 데이터 샘플을 역확산시켜 역확산 샘플을 제공한다. 파일롯 채널라이저 (526) 는 단말기에서 파일롯에 대해 사용된 채널화 코드

(예를 들어, cdma2000 에 대한 제로의 왈시 코드) 를 역확산 샘플에 곱한다. 그 후, 복구된 파일롯 샘플은 특정 누산 시간 간격 동안 누산되어 파일롯 심볼을 제공한다. 누산 시간 간격은 통상적으로 파일롯 채널화 코드 길이의 정수배이다. 파일롯 데이터가 제로의 채널화 코드로 커버링되는 경우 (cdma2000 에서와 같음), 채널화 코드

와의 곱셈은 생략될 수도 있고, 파일롯 채널라이저 (526) 는 역확산기 (524) 로부터 역확산 샘플의 누산을 간단히 수행한다. 특정 실시형태에서, 하나의 파일롯 심볼은 하나의 파일롯 주기의 사이즈를 가진 각가의 세그멘트에 제공된다.Despreader 524 (which may be implemented as a complex multiplier, such as multiplier 340 shown in FIG. 3), is a spreading sequence.

The dedecimated data samples are despread to provide despread samples. Pilot channelizer 526 is the channelization code used for the pilot at the terminal.

(E.g., the zero Walsh code for cdma2000) is multiplied by the despread sample. The recovered pilot sample is then accumulated for a certain accumulation time interval to provide a pilot symbol. The accumulation time interval is typically an integer multiple of the pilot channelization code length. If pilot data is covered with zero channelization code (as in cdma2000), channelization code

Multiplication with may be omitted, and pilot channelizer 526 simply performs accumulation of despread samples from despreader 524. In a particular embodiment, one pilot symbol is provided in each segment having a size of one pilot period.

) 인 파일롯 추정치

를 제공한다. 그 결과, 각 파일롯 추정치

는 복소수 값이다. 파일롯 추정치가 충분한 레이트로 제공되어 다중경로의 채널 응답에서의 무의미하지 않은 변화가 캡처되고 보고된다. 특정 실시형태에서, 하나의 파일롯 추정치나 하나의 심볼 사이즈를 갖는 각 세그멘트에 제공된다.Pilot symbols from pilot channelizer 526 are provided to pilot filter 528 and filtered based on the particular lowpass filter response to remove noise. The pilot filter 528 may be implemented as a finite impulse response filter (FIR), an infinite impulse response (IIR) filter, or other filter structure. Pilot filter 528 is a representation of the channel response of the m th multipath (ie, gain and phase

) In pilot estimate

To provide. As a result, each pilot estimate

Is a complex value. Pilot estimates are provided at a sufficient rate so that insignificant changes in the multipath channel response are captured and reported. In certain embodiments, each segment is provided with one pilot estimate or one symbol size.

는 파일롯 채널라이저 (532) 에 제공되고, 파일롯 채널라이저 (532) 는 파일롯 채널화 코드로 파일롯 데이터를 채널라이징하여 채널라이징된 데이터를 제공한다. 그 후, 확산기 (534) 는 확산 시퀀스

로 채널라이징된 파일롯 데이터를 수신하고 확산하여 확산 파일롯 데이터 (즉, 프로세싱된 파일롯 데이터) 를 생성한다. 확산 시퀀스

는 도 6a 에 도시된 바와 같이, m 번째 간섭 다중경로의 시간 오프셋

에 대응하는 위상을 가지고, 다음 세그멘트에 대해 N 개의 PN 칩 만큼 앞서있다. 파일롯 데이터가 모두 제로의 시퀀스이고 파일롯 채널화 코드가 또한 모두 제로의 시퀀스인 경우, 파일롯 채널라이저 (532) 및 확산기 (534) 는 생략될 수도 있고 확산 파일롯 데이터는 단순히 확산 시퀀스

이다.The pilot interference estimator 530 then estimates the pilot interference due to the m th multipath for the next segment. Pilot data and pilot channelization codes for the m th multipath to estimate pilot interference

Is provided to the pilot channelizer 532, and the pilot channelizer 532 channelizes the pilot data with the pilot channelization code to provide channelized data. Thereafter, spreader 534 is used to spread the sequence.

Receive and spread the channelized pilot data to produce spread pilot data (ie, processed pilot data). Diffusion sequence

Is the time offset of the m th interference multipath, as shown in FIG. 6A

With a phase corresponding to, it is as advanced as N PN chips for the next segment. If the pilot data are all zero sequences and the pilot channelization code is also all zero sequences, the pilot channelizer 532 and spreader 534 may be omitted and the spread pilot data may simply be a spread sequence.

to be.

를 곱하여 다음 세그멘트에 대한 m 번째 다중경로로 인한 파일롯 간섭

의 추정치를 제공한다. 파일롯 추정치

가 현재 세그멘트로부터 도출되고 다음 세그멘트에 대해 추정된 파일롯 간섭을 도출하도록 사용되기 때문에, 예측 기술은 파일롯 추정치에 기초하여 다음 세그멘트에 대한 파일롯 예측치를 도출하도록 사용될 수도 있다. 그 후, 이들 파일롯 예측치는 다음 세그멘트에 대해 추정된 파일롯 간섭을 도출하도록 사용될 수도 있다. The multiplier 536 then receives the spread pilot data and estimates the pilot from the pilot filter 528.

Pilot interference due to m th multipath for the next segment multiplied by

Gives an estimate of. Pilot estimate

Since is derived from the current segment and is used to derive the estimated pilot interference for the next segment, the prediction technique may be used to derive the pilot prediction for the next segment based on the pilot estimate. These pilot predictions may then be used to derive the estimated pilot interference for the next segment.

은 간섭 누산기 (538) 에 제공된다. 도 6a 에 도시된 바와 같이, m 번째 다중경로에 대한 간섭 샘플은 다중경로의 시간 오프셋의 프랙셔널 부분에 의해 결정된 누산기에서의 위치에 저장된다.In one embodiment, multiplier 536 provides the estimated pilot interference with the timing phase of the m th multipath due to the m th multipath at a sample rate (eg, eight times the chip rate). This allows the estimated pilot interference for all multipaths (typically having different time offsets not all aligned to the PN chip timing boundary) to be accumulated at high time resolution. Estimated pilot interference for the m th multipath, including the same number of interference samples, for the data sample segment

Is provided to the interference accumulator 538. As shown in FIG. 6A, the interference samples for the m th multipath are stored at locations in the accumulator determined by the fractional portion of the multipath's time offset.

In order to derive the total pilot interference for all multipaths in a given signal, the above-described processing may be repeated a number of times, and one repetition or processing cycle is performed for each interfering multipath where pilot interference is estimated and canceled from the desired multipath. It is about. Since channel estimates from one antenna are typically not good for the other antenna, pilot interference cancellation is typically performed on multipath received over the same antenna. If the same finger processor hardware is used for multiple iterations, processing may be performed in bursts, with each burst performed on each segment of data samples determined by the multipath fractional time offset.

은 모든 이전-프로세싱된 다중경로에 대해 누산된 파일롯 간섭과 함께 누산된다. 그러나, 도 6a 에 도시된 바와 같이, 추정된 파일롯 간섭

은 현재 다중경로의 시간 오프셋에 의해 결정된 누산기 (538) 의 특정 섹션에서의 샘플과 함께 누산된다. 모든 간섭 다중경로가 프로세싱된 이후에, 누산기 (538) 에서의 누산된 파일롯 간섭은 모든 프로세싱된 다중경로로 인한 총 파일롯 간섭

을 포함한다.Prior to the first iteration, the accumulator 538 is cleared and reset. For each iteration, estimated pilot interference due to current multipath

Is accumulated with accumulated pilot interference for all previously-processed multipaths. However, as shown in FIG. 6A, estimated pilot interference

Is accumulated with samples in a particular section of accumulator 538 determined by the time offset of the current multipath. After all the interference multipaths have been processed, the accumulated pilot interference at accumulator 538 is the total pilot interference due to all processed multipaths.

It includes.

을 이용함), 다음 세그멘트에 대해 m 번째 다중경로로 인한 파일롯 간섭

은 누산기 의 또 다른 섹션에서 추정되고 누산될 수도 있다. 6A illustrates one embodiment of an accumulator 538. Finger processor 410x performs data demodulation on the m th multipath for the current segment (total pilot interference previously derived and stored in accumulator 538).

), The pilot interference due to the m th multipath for the next segment

May be estimated and accumulated in another section of the accumulator.

은 하나의 핑거 프로세서에 의해 동일한 수신 신호에서의 다른 다중경로를 프로세싱하도록 할당된 다른 핑거 프로세서에 제공될 수도 있다. The pilot of the mth multipath is interference for all multipaths in the received signal including the mth multipath. Estimated pilot interference due to the m th multipath, for a demodulator design in which multiple finger processes are assigned to process multiple multipaths in the received signal for a given terminal

May be provided to another finger processor assigned by one finger processor to process another multipath in the same received signal.

를 제공한다. For demodulation to recover data on the m th multipath, data samples for the segments are provided from the buffer 408x to the resampler 522. Resampler 522 then resamples the received data samples to provide decimated data samples having an appropriate timing phase for this multipath at the same rate. The decimated data sample is processed as described above to generate a pilot estimate.

To provide.

에 대한 간섭 샘플은 누산기 (538) 로부터 리샘플러 (540) 에 제공된다. 리샘플러 (540) 는 유사하게 수신 간섭 신호를 리샘플링하여 칩 레이트로 m 번째 다중경로에 대해 적합한 타이밍 위상을 갖는 데시메이트된 간섭을 제공한다. 그 후, 합산기 (542) 는 데시메이트된 데이터 샘프로부터 데시메이트된 간섭 샘플을 수신하고 감산하여 파일롯-소거 데이터 샘플을 제공한다. At the same time, total pilot interference for the same segment

Interference samples for are provided from accumulator 538 to resampler 540. Resampler 540 similarly resamples the received interference signal to provide decimated interference with an appropriate timing phase for the m th multipath at chip rate. Summer 542 then receives and subtracts the decimated interference sample from the decimated data sample to provide a pilot-erase data sample.

로 역확산하여 역확산된 샘플을 제공한다. 확산 시퀀스

는 m 번째 다중경로의 시간 오프셋

에 대응하는 위상을 가진다. 그 후, 채널라이저 (546) 은 역확산된 샘플에 핑거 프로세서에 의해 복구되는 코드 채널에 대해 사용된 채널화 코드

를 곱한다. 그 후, 채널화된 데이터 샘플은 채널화 코드

의 길이 전반에 누산되어 데이터 심볼을 제공한다. In data demodulation unit 550, despreader 544 receives pilot-erase data samples and conjugates (conjugates multiples) a spreading sequence.

Despread to provide a despread sample. Diffusion sequence

Is the time offset of the m-th multipath

Has a phase corresponding to. Channelizer 546 then uses the channelization code used for the code channel recovered by the finger processor to the despread sample.

Multiply by The channelized data sample is then channelized code

Accumulate throughout the length of to provide a data symbol.

로 복조하여 그 후, 심볼 결합기 (420) 로 제공되는 m 번째 다중경로에 대한 복조된 심볼 (즉, 복조된 데이터) 을 제공한다. 데이터 복조 및 심볼 결합은 전술한 미국 특허 제 5,764,687 호에 개시된 바와 같이 획득될 수도 있다. 미국 특허 제 5,764,687 호는 역확산 데이터와 필터링된 파일롯 사이의 도트 (dot) 곱을 수행함으로써 IS-95 에 대한 BPSK 데이터 복조를 설명한다. cdma2000 및 W-CDMA 에서 사용된 QPSK 모듈의 복조는 특허 제 5,764,687 호에 설명된다. 즉, 도트 곱 대신에, 도트 곱 및 크로스-곱이 동위상 및 쿼드러처 스트림을 복구하도록 사용된다. Data demodulator 548 then receives the data symbols and pilot estimates.

Then demodulate to provide the demodulated symbols (i.e., demodulated data) for the m th multipath provided to symbol combiner 420. Data demodulation and symbol combining may be obtained as disclosed in US Pat. No. 5,764,687, described above. U. S. Patent No. 5,764, 687 describes BPSK data demodulation for IS-95 by performing a dot product between the despread data and the filtered pilot. Demodulation of the QPSK module used in cdma2000 and W-CDMA is described in patent 5,764,687. That is, instead of dot products, dot products and cross-products are used to recover in-phase and quadrature streams.

, 및 채널화 코드

를 가짐) 에 대해 파일롯-소거 데이터 샘플을 프로세싱하여 m 번째 다중경로에 대한 데이터 심볼을 제공하고, 역확산기 (524) 및 파일롯 채널라이저 (526) 는 현재 세그멘트 (확산 시퀀스

, 및 파일롯 채널화 코드

를 가짐) 에 대해 데이터 샘플을 프로세싱하여 이 다중경로에 대한 파일롯 심볼을 제공한다. 파일롯 심볼은 파일롯 필터 (528) 에 의해 필터링되어 다중경로에 대한 파일롯 추정치

를 제공한다. 그 후, 파일롯 간섭 추정기 (530) 는 전술한 바와 같이, 다음 세그멘트에 대해 이 다중경로로 인한 추정된 파일롯 간섭

을 도출한다. 이 방식에서, 데이터 복조가 이전의 세그멘트로부터 도출된 총 파일롯 간섭

을 사용하여 현재 세그멘트상에서 수행되는 동안, 다음 세그멘트에 대한 파일롯 간섭이 다음 세그멘트를 위해 사용되도록 추정되고 누산기의 또 다른 섹션에 저장된다. As discussed above, data demodulation for the m th multipath may be performed in a parallel and pipelined manner with pilot interference estimates. Inverter 544 and data channelizer 546 are currently segmented (spreading sequence

, And channelization code

Process the pilot-erase data samples for the < RTI ID = 0.0 > m < / RTI >

, And pilot channelization codes

Data samples are processed to provide a pilot symbol for this multipath. Pilot symbols are filtered by pilot filter 528 to provide pilot estimates for multipath.

To provide. The pilot interference estimator 530 then estimates the pilot interference due to this multipath for the next segment, as described above.

To derive In this way, the total pilot interference where the data demodulation is derived from the previous segment

While being performed on the current segment, the pilot interference for the next segment is estimated to be used for the next segment and stored in another section of the accumulator.

In another embodiment, the pilot for the particular multipath to be demodulated is based on the data sample received from the "raw" (from sample buffer 408x) as described above, and the pilot-erase data sample (accumulator ( Not based) and is estimated. In another embodiment, if the total pilot interference includes some or all of the interference pilot except for the pilot of the multipath to be demodulated, the pilot may be estimated based on pilot-erase data samples (ie, multiple demodulated). The pilot in the path is included in another pilot-erase data sample). This other embodiment may provide an improved estimate of the channel response of the demodulated multipath, and is particularly advantageous for the reverse link where the pilot estimate is typically the limiting factor in handling weak multipath. The same “other erased pilot” data samples used for pilot estimation may also be processed to recover data for multipath, which is advantageous for finger processor architectures that perform both pilot estimation and data demodulation on the same data sample stream. do. The same concept may be used to estimate the channel response of a particular interfering multipath (ie, the estimated channel response may be a raw data sample or a “erased other pilot” data sample with an interference pilot except for the pilot of that particular multipath removed). May be based on either).

및

와 연관된 3 개의 다중 경로를 포함한다. 수신 신호는 8 배의 칩 레이트인 샘플 레이트로 디지털화하여 데이터 샘플을 제공하고, 데이터 샘플은 샘플 버퍼에 저장된다. 이들 다중경로는 다중경로의 피크에서 샘플링될 수도 있고 그렇지 않을 수도 있다.6A and 6B illustrate processing of data samples to derive an estimate of pilot interference, in accordance with an embodiment. In the example shown in Figs. 6A and 6B, the received signal is a time offset

And

It includes three multipaths associated with. The received signal is digitized at a sample rate that is eight times the chip rate to provide data samples, which are stored in the sample buffer. These multipaths may or may not be sampled at the peaks of the multipath.

In the example shown in FIGS. 6A and 6B, each segment included 512 data samples during the symbol period of 64 PN chips. Pilot interference is estimated for each of the three multipaths and during each symbol period. The symbol timing for each multipath is determined by the time offset of the multipath fraction. If the time offsets of multipath fractions, which are generally true, are not the same, the symbol timing for these multipaths will be different and will be associated with different data sample segments. In one embodiment, multipaths are processed in order based on the time offsets of the multipath fractions, multipaths having the time fractions of the minimum fractions that are first processed, and finally having the time offsets of the maximum fractions processed. . This processing order ensures that when processed, the total pilot interference is derived and available for each multipath.

을 가진 m 번째 다중경로에 대한 n 번째 심볼 주기 동안, 리샘플러 (522) 는 샘플 버퍼 (408) 로부터 샘플 5 내지 516 을 수신하고 역확산기 (524) 에 음영 박스로 표시된 데이터 샘플 5, 13, 21 등 및 509 을 제공한다. 대응하여, 역확산기 (524) 는 동일한 시간 오프셋

에 대응하는 위상을 가진 확산 시퀀스

를 수신하고 확산 시퀀스로 데시메이트된 데이터 샘플을 역확산시킨다. 그 후, 전술한 바와 같이, 파일롯 추정치

는 이 세그멘트에 대해 역확산된 샘플에 기초하여 도출된다.In Figure 6a, the fractional time offset

During the nth symbol period for the mth multipath with, the resampler 522 receives samples 5 to 516 from the sample buffer 408 and the data samples 5, 13, 21 indicated by shaded boxes in the despreader 524. And 509. Correspondingly, despreader 524 is the same time offset

Spread sequence with phase corresponding to

Receive and despread the data sample decimated with the spreading sequence. Then, as described above, the pilot estimate

Is derived based on the despread sample for this segment.

를 수신하고 채널라이징된 파일롯 데이터를 확산한다. 그 후, 곱셈기 (536) 는 확산 파일롯 데이터에 (확산 시퀀스

에 의해 확산됨) 현재 세그멘트로부터 도출된 파일롯 추정치

를 곱하여 다음 세그멘트에 대한 추정된 파일롯 간섭

을 제공한다. 추정된 파일롯 간섭

은 도 6a 에 도시된 바와 같이, 간섭 누산기 (538) 에서 동일한 인덱스들 517 내지 1028 에서의 샘플로 누산된 간섭 샘플 517 내지 1028 을 포함한다. 이 방식에서, m 번째 다중경로의 프랙셔널 시간 오프셋은 총 파일롯 간섭의 도출에서 계산된다. To derive the estimated pilot interference due to the m-th multipath, spreader 534 may spread the spreading sequence corresponding to the next segment.

Receive and spread the channelized pilot data. The multiplier 536 then adds (spread sequence to the spread pilot data)

Spread by) pilot estimate derived from the current segment

Multiply by the estimated pilot interference for the next segment

To provide. Estimated Pilot Interference

6 includes interference samples 517-1028 accumulated in the same indexes 517-1028 in the interference accumulator 538, as shown in FIG. 6A. In this way, the fractional time offset of the mth multipath is calculated in the derivation of the total pilot interference.

For data demodulation of the m th multipath during the n th symbol period, the same segments of interference samples 5 through 516 are provided from accumulator 538 to resampler 540. Resampler 540 is then shown to summer 542 by interference samples 5, 13, 20, and the like corresponding to the same-indexed data samples provided by resampler 522 (also shown by shaded boxes). ). Thereafter, data demodulation of the pilot-erase data samples is performed as described above. Each multipath may be processed in a similar manner. However, because each multipath may be associated with a different time offset, different decimated data and interference samples may be operated.

6B shows three data sample segments, decimated data samples, and three spreading sequences used to derive the estimated pilot interference due to three multipaths.

In another demodulation design, when sufficient processing capacity is provided, pilot interference / erase and data demodulation may be performed in real time (eg, as data samples are received). For example, M finger processors may be assigned simultaneously to process M multipaths in a received signal simultaneously. During each symbol period, each finger processor can derive a pilot estimate for that symbol period, and the pilot estimate is used to derive the estimated pilot interference due to the assigned multipath of the finger processor during the next symbol period. The summer then sums (estimated each time offset) the estimated pilot interference from all finger processors, and the total pilot interference for the next symbol period is stored in the interference accumulator.

Then, if the data sample is received during the symbol period following the interference, the total pilot interference may be subtracted from the data sample, and the same pilot-erase data sample is provided to the M finger processors for data demodulation (also, These finger processors are provided with received data samples that are used to derive a pilot estimate, without pilot cancellation). In this method, data demodulation may be performed in real time on pilot-erase data samples and the sample buffer may be removed. In the manner in which the pilot estimate for the same segment (not the next segment) is used to derive the estimated pilot interference, the data sample may be temporarily stored (eg, one symbol period) while the total pilot interference is derived. During).

For demodulation designs in which the same data sample is processed multiple times (e.g., one finger processor is designed to process multiple multipaths), the sample buffer is designed in such a way as to ensure that the data sample is not inadvertently dropped. May be operated. In one embodiment, the sample buffer is designed to receive incoming data samples while providing stored data samples to the finger processor (s). This is obtained by implementing the sample buffer in such a way that stored data samples may be read from one part of the buffer while new data samples are written to another part of the buffer. The sample buffer may be implemented as a double buffer or a multiple buffer, a multi-port buffer, a circular buffer, or some other buffer design. The interference accumulator may be implemented in a similar manner as the sample buffer (eg, circular buffer).

이 되도록 선택될 수도 있으며, 여기서 N 은 하나의 다중경로에 대한 추정된 파일롯 간섭을 도출하도록 사용된 데이터 샘플의 지속기간이고,

은 데이터 샘플 (칩 레이트를 초과하는 샘플의 비로서 규정됨) 에 대한 오버샘플링 팩터이다. 하나의 심볼 주기 (예를 들어, N=64 개의 PN 칩) 의 세그멘트가 각 다중경로에 대해 프로세싱되는 상기의 예에 대해, 2 개의 심볼 주기의 버퍼는 심볼 주기의 프랙셔널 시간 오프셋에 관계없이 각 다중경로에 대한 데이터 샘플의 하나의 심볼 주기의 세그멘트를 제공할 수 있다. 오버샘플 레이트가

이고, 버퍼의 최대 사이즈는

데이터 샘플이다.For the demodulation design, to prevent overwriting samples that are still being processed, the capacity of the sample buffer may be chosen to be at least twice the time needed to derive the total pilot interference for all M multipaths (time and buffers). The capacity relationship is defined by the sample rate). If different data sample segments may be used for each of the M multipaths, the capacity of the sample buffer should be at least for each received signal assigned to the sample buffer.

May be selected, where N is the duration of the data sample used to derive the estimated pilot interference for one multipath,

Is the oversampling factor for the data sample (defined as the ratio of samples exceeding the chip rate). For the above example where a segment of one symbol period (e.g., N = 64 PN chips) is processed for each multipath, the buffer of two symbol periods may each be independent of the fractional time offset of the symbol period. One symbol period segment of a data sample for multipath may be provided. Oversample rate

The maximum size of the buffer is

Data sample.

가 되도록 선택될 수도 있다. 간섭 누산기에 대한 여분의 심볼 주기 (즉, 2·N 대신 3·N) 는 추정된 파일롯 간섭이 다음 세그멘트에 대해 도출된다는 사실을 고려해야 한다.Similarly, the capacity of the interference accumulator is at least

It may be selected to be. The extra symbol period for the interference accumulator (ie 3 · N instead of 2 · N) must take into account the fact that the estimated pilot interference is derived for the next segment.

As discussed above, the estimated pilot interference derived from one data sample segment may be canceled from a later data sample segment. As a result, for mobile terminals, communication links and channel responses of various multipaths vary continuously. Thus, it is desirable to reduce the delay between data samples for which pilot interference is estimated and data samples for which estimated pilot interference is cancelled. This delay may be as large as 2 N chips.

By selecting a sufficiently small value for N, each multipath channel response may be expected to remain relatively constant over the period of the 2N chip. However, the value of N should be chosen large enough to allow an accurate estimate of the channel response of each multipath being processed.

7 is a flow diagram of a process 700 for deriving total pilot interference for multiple multipaths, in accordance with an embodiment. Process 700 may be implemented by a finger processor shown in FIG. 5.

Initially, the accumulator used to accumulate the estimated pilot interference is cleared at step 712. The unprocessed interference multipath is selected at step 714. Typically, pilot interference is estimated for each multipath assigned for data demodulation. However, pilot interference due to unallocated multipath may also be estimated. In general, any number of interfering multipaths may be processed, and for these multipaths, pilot interference is estimated and accumulated to yield total pilot interference.

At step 716, data samples for signals received in the selected multipath are then processed to derive an estimate of the channel response of the selected multipath. As mentioned above, the channel response may be estimated based on the pilot in the selected multipath. For cdma2000, this processing includes (1) despreading the data sample with a spreading sequence for the multipath (ie, having a suitable phase corresponding to the time offset of the multipath), (2) despreading the data sample Channelizing to provide a pilot symbol (e.g., multiplying the despread sample by a pilot channelization code and accumulating channelized data samples that exceed the pilot channelization code length), and (3) pilot symbols Filtering results in deriving a pilot estimate indicative of the channel response of the selected multipath. In addition, estimation of the channel response using other techniques may be implemented, which is within the scope of the specification.

Then, pilot interference due to the multipath selected in step 718 is estimated. Pilot interference may be estimated by generating processed pilot data and multiplying the data by the estimated channel response derived in step 716. If the pilot data is all zeros and the pilot channelization code is also all zeros, then the processed pilot data is simply the spreading sequence for the selected multipath. In general, the processed pilot data is pilot data after all signal processing at the transmitter unit but prior to filtering and frequency upconverting (eg, output of modulator 216a of FIG. 3 for the reverse link in cdma2000). Data from).

In step 720, the estimated pilot interference for the selected multipath is accumulated in the interference accumulator with the estimated pilot interference for the pre-processed multipath. As mentioned above, the timing phase of the multipath is observed by performing steps 716, 718, and 720.

Then, in step 722 it is determined whether all interfering multipaths have been processed. If the answer is no, the process returns to step 714, and another interfering multipath is selected for processing. Otherwise, the contents of the accumulator represent pilot interference due to all processed multipaths that may be provided to step 724. The process then terminates.

The pilot interference estimate in FIG. 7 may be performed for all multipaths in time division multiplexing using one or more finger processors. In addition, pilot interference estimates for all multipaths may be performed in parallel using multiple finger processors. In this case, if the hardware has sufficient capacity, pilot interference estimates and cancellation may be performed in real time with data demodulation (eg, as data samples are received with minimal or no buffer as described above). ).

8 is a flow diagram of a process 800 for data demodulating multiple multipaths with pilot interference cancellation in accordance with an embodiment. Process 800 may also be implemented by a finger processor shown in FIG. 5.

Initially, in step 812 the total pilot interference due to all of the corresponding multipaths is derived. Step 812 may be implemented using the process 700 shown in FIG. 7. Then, in step 814, the particular multipath is selected for data demodulation. In one embodiment and as described above, in step 816 the total pilot interference is initially canceled from the selected multipath. This may be obtained by subtracting the interference sample (stored in the accumulator) for the total pilot interference from the data sample for the received signal including the selected multipath.

Then, data demodulation is performed on the pilot-erase signal in the normal way. For cdma2000, this includes (1) despreading the pilot-erase data samples, (2) channelizing the despread data to provide data symbols, and (3) demodulating the data symbols into pilot estimates. Entails. The demodulated symbols (ie demodulated data) for the selected multipath are combined with the demodulated symbols for other multipaths for the same transmitter unit (eg, terminal). The demodulated symbols for multipath in a plurality of received signals (eg, when receive diversity is used) may also be combined. Symbol combining may be obtained by the symbol combiner shown in FIG.

Thereafter, it is determined whether the multipath allocated in step 822 has been demodulated. If the answer is no, the process returns to step 814, and another multipath is selected for data demodulation. If not, the process terminates.

As noted above, data demodulation for all assigned multipaths of a given transmitter unit may be performed in a time division multiplexing manner using one or more finger processors. In addition, data demodulation for all assigned multipaths may be performed in parallel using multiple finger processors.

Referring back to FIGS. 4 and 5, the searcher 412 may be designed and operate to search for new multipaths based on pilot-erase data samples (instead of data samples received with from buffer 408). This may provide improved search performance since pilot interference from some or all known multipaths has been eliminated as described above.

Other lake  Receiver and Finger  Processor embodiment

9 is a block diagram of another embodiment of a finger processor 900 and a sample buffer 908 in a rake receiver that may be similar to some aspects of the rake receiver 254a of FIG. 4 described above. The rake receiver may include a large number of individual finger processors 900, such as 256 or 512 finger processors 900, which process several multipaths. The rake receiver may also include a single high speed processor that processes several multipaths in a time division method that simulates the functionality of several finger processors 900. One embodiment of sample buffer 908 may be a cyclic random access memory (RAM) that stores segments of data samples at a sample rate of chip rate x 2 ("chip x 2"). The chip rate is 1 / T _c , where T _c is the chip duration. For example, the chip rate may be 1.2 MHz. Other chip rates may be used.

Finger processor 900 may be used for a CDMA2000 1 × EV-DO system or other system. Finger processor 900 includes a channel estimator 902, a data demodulator unit 904, and a pilot interference estimator 906. Channel estimator 902 includes a despreader 910, a pilot de-channelizer 912, and a pilot filter 914. Data demodulation unit 904 includes a despreader 918, a data de-channelizer 920, and a data demodulator 922. Pilot interference estimator 906 includes cancellation factor calculation unit 924, multipliers 926 and 932, reconstruction filter table 938, pilot reconstruction filtering block 930, pilot interference accumulation block 928, pilot channelizer 934 ) And a diffuser 936.

The channel estimator 902 of FIG. 9 may operate in a similar manner to the pilot estimator 520 described above with reference to FIG. 5 with some exceptions described below. Similarly, the data demodulation unit 904 of FIG. 9 may be performed in a similar manner to the data demodulation unit 550 described above with reference to FIG. 5 with some exceptions described below.

로 전술된 PN 시퀀스인 켤레 복소수 확산 시퀀스

를 수신한다. 일 실시형태에서, 역확산기 (910, 918) 는 우선 시간 오프셋

에 서 시작하는 샘플 버퍼 (908) 로부터의 세그멘트의 데이터 샘플에 확산 시퀀스

를 곱한 후, 역확산된 데이터 샘플을 리샘플링한다. 또 다른 실시형태에서, 역확산기 (910, 918) 는 우선 다중경로의 시간 오프셋

에서 시작하는 샘플 버퍼 (908) 로부터의 세그멘트의 데이터 샘플을 리샘플링한 후, 리샘플링한 데이터 샘플에 확산 시퀀스

를 곱한다.Despreaders 910, 918 are derived from spreading sequence generator 414 (FIG. 4), for example in FIG. 5.

Conjugate complex spreading sequence, which is the PN sequence described above

Receive In one embodiment, despreaders 910, 918 are first time offsets.

Spread sequence to data samples of segments from sample buffer 908, starting at

After multiplying, resample the despread data sample. In yet another embodiment, despreaders 910, 918 are first multipath time offsets.

After resampling a data sample of the segment from the sample buffer 908 starting at, spreading the sample to the resampled data sample

Multiply by

The despreaders 910, 918 of FIG. 9 have a resampler or interpolator that resamples, upsamples, sums, decimates, or interpolates data samples from the sample buffer 908 to obtain a desired rate. It may be. The type of resampling depends on the rate of the received signal sample stored in the sample buffer 908. For example, despreader 910 may upsample a sample from sample buffer 908 to a maximum resolution of a finger time offset at a rate of chip × 2, eg, chip × 8. Despreader 910 may decimate chip × 8 samples into chip × 1 for output to pilot de-channelizer 912.

In general, different rates such as chip × 1, chip × 2, chip × 4 may be used by different components of the finger processor 900. Higher rates, such as chip × 8, may improve the performance and accuracy of the sample. Lower rates, such as chip × 2, may be less accurate, but improve efficiency by reducing computation and processing time.

를 수신하고 (b) 디-채널라이징된 파일롯 심볼을 출력한다. 유사하게, 데이터 디-채널라이저 (920) 는 (a) 애더 (916) 로부터의 역확산된 데이터 샘플 및 데이터 채널화 코드

를 수신하고 (b) 디-채널라이징된 데이터 심볼을 출력한다.Pilot de-channelizer 912 is (a) despread data sample and pilot channelization code from despreader 910

(B) outputs the de-channelized pilot symbol. Similarly, data de-channelizer 920 may (a) despread data samples and data channelization codes from adder 916.

(B) outputs the de-channelized data symbol.

Pilot  filter

및

과 같은 다양한 형태로 파일롯 필터 (914) 로부터 출력될 수도 있는 적어도 2 개의 값

및

을 도출한다.

는 핑거 프로세서 (900) 에 할당될 특정 다중경로의 채널 추정치이다. 채널 추정치

는 채널 계수 (크기, 위상, 및 지연 또는 시간 오프셋) 에 대응한다. 파일롯 필터 (914) 는 하나 이상의 세그멘트, 예를 들어, 현재 세그멘트 "n" 및/또는 과거 또는 미래 세그멘트를 사용하여 채널 추정치

를 제공할 수도 있다. 일 예에서, 파일롯 필터 (914) 는 4 개 내지 6 개의 세그멘트를 사용하여 채널 추정치를 도출한다. 또한, 파일롯 필터 (914) 는 하나 이상의 세그멘트를 사용하여 미래 채널 추정치, 즉, 채널 추정치의 예측을 제공할 수도 있다. 채널 추정치

는 후술하는 바와 같이 파일롯 재구성을 위해 파일롯 간섭 추정기 (906) 에 의해 사용될 것이다. 파일롯 필터 (914) 에 의해 곱셈기 (926) 로의 채널 추정치

출력은 I 및 Q 컴포넌트를 갖는 복소수일 수도 있다.Pilot filter 914

And

At least two values that may be output from the pilot filter 914 in various forms such as

And

To derive

Is a channel estimate of a particular multipath to be assigned to finger processor 900. Channel estimate

Corresponds to the channel coefficient (magnitude, phase, and delay or time offset). Pilot filter 914 can estimate the channel using one or more segments, eg, current segment "n" and / or past or future segments.

May be provided. In one example, pilot filter 914 uses four to six segments to derive a channel estimate. In addition, pilot filter 914 may use one or more segments to provide prediction of future channel estimates, that is, channel estimates. Channel estimate

Will be used by the pilot interference estimator 906 for pilot reconstruction as described below. Channel estimate to pilot multiplier 926 by pilot filter 914

The output may be complex with I and Q components.

는 핑거 프로세서 (900) 에 예측된 간섭 텀 (term) 을 플러스하는 잡음 의 배리언스 (variance) 이다. 채널 추정치

의 배리언스가 높은 경우, 채널은 잡음이다.

은 데이터 복조기 (922) 에 의해 사용되어 데이터를 복조한다.

는 소거 팩터 계산 유닛 (924) 에 의해 사용된다. 파일롯 필터 (914) 는 위상 로테이터 또는 위상 보정기를 구비할 수도 있다.

Is a variation of noise that adds an expected interference term to finger processor 900. Channel estimate

If the variation is high, the channel is noise.

Is used by the data demodulator 922 to demodulate the data.

Is used by the erasure factor calculation unit 924. Pilot filter 914 may have a phase rotator or phase corrector.

elimination Factor  Calculation

If the receiver has complete channel state information, interference cancellation by the plurality of finger processors 900 may improve the capacity of the multiple access channel. In practice, each user's channel is time-varying and may vary to estimate reliable channel state information. Each user's pilot must be canceled from the received signal by using a realistic and reliable pilot-based channel estimate. The use of unreliable estimates leads to over-cancellation of data samples. If the channel estimator 902 detects an unreliable noise pilot-based channel estimate, the channel factor calculation unit 924 reduces or prevents cancellation. As a result, the erasure factor calculation unit 924 minimizes residual energy (noise) after pilot interference cancellation.

For example, three finger processors 900 may process the same received signal at different offsets and detect different SNR or channel estimates. If one finger processor detects a particular noise channel, it may be desirable to reduce the contribution of the finger processor's reconstructed pilot to pilot interference cancellation.

(핑거 프로세서 (900) 에 예측된 간섭 텀을 플러스하는 잡음의 배리언스) 가 높고, 파일롯 신호 강도

가 낮은 경우, 채널 추정치

는 신뢰할 수 없을 수도 있다. 소거 팩터 계산 유닛 (924) 은 0, .1, .2, .5, 등과 같은 낮은 소거 팩터

를 선택할 수도 있다. 이것은 핑거 프로세서 (900) 에 의해 사용된 잡음 채널 추정치의 크기를 감소시켜 파일롯 샘플을 재구성한다.

(Variance of noise that plus predicted interference term to finger processor 900) is high, and pilot signal strength

If is low, the channel estimate

May not be reliable. The erasure factor calculation unit 924 has a low erase factor such as 0, .1, .2, .5, etc.

You can also select. This reduces the magnitude of the noise channel estimate used by finger processor 900 to reconstruct the pilot sample.

가 낮고, 파일롯 신호 강도

가 높은 경우, 채널 추정치

는 신뢰할 수 있고, 간섭 팩터 소거 유닛 (924) 는 .8, .9, 1.0 등과 같은 높은 소거 팩터

를 선택할 수도 있다.

가 높고, 파일롯 신호 강도

또한 높은 경우, 채널 추정치

는 다소 신뢰할 수도 있고, 소거 팩터 계산 유닛 (924) 은 .5, .6, .7, .8 등과 같은 모더레이트 (moderate) 소거 팩터

를 선택할 수도 있다. 소거 팩터

에 대한 값은 파일롯 복조가 어떻게 구현되고, 채널 추정치가 어떻게 도출되는지에 의존할 수도 있다. 일부 경우에, 소거 팩터

는 1 보다 크게 선택될 수도 있다. 예를 들어, 채널의 위상은 소거되는 에너지를 유발하는 파일롯 복조 동안 부적합하게 정렬될 수도 있다. 이 채널은 언더-추정된 신호 크기이거나 바이어스된 채널 추정치를 가진다. 그 결과, 1 보다 큰 소거 팩터

의 선택과 사용은 채널 추정치에 일부 보정 백 (correction back) 을 부가할 것이다. 이하의 수학식은 가우시안 (Gaussian) 잡음을 가진 하나의 세그멘트를 초과하여 지속적인 채널에 최적일 수도 있다.

Low, pilot signal strength

If is high, the channel estimate

Is reliable, and the interference factor cancellation unit 924 has a high cancellation factor such as .8, .9, 1.0, and so on.

You can also select.

High, pilot signal strength

If also high, the channel estimate

May be somewhat reliable, and the erasing factor calculation unit 924 is a modest erasing factor such as .5, .6, .7, .8, etc.

You can also select. Elimination factor

The value for may depend on how pilot demodulation is implemented and how channel estimates are derived. In some cases, the erasure factor

May be chosen to be greater than one. For example, the phase of the channel may be improperly aligned during pilot demodulation causing the energy to be canceled. This channel may be an under-estimated signal magnitude or have a biased channel estimate. As a result, an erase factor greater than 1

The selection and use of will add some correction back to the channel estimate. The equation below may be optimal for a continuous channel beyond one segment with Gaussian noise.

을 사용하여 수학식으로부터 소거 팩터

를 계산한다.In one embodiment, the erasure factor calculation unit 924 is from the pilot filter 914.

Elimination Factor from Equation Using

Calculate

은

에 비례하고,

은 채널 추정기 (902) 에 의해 추정된 칩 당 에너지이며,

는 잡음이고 (

신호 대 잡음비를 나타냄), N 은 채널 추정치의 평균 길이이다. N 은

및

을 추정하도록 사용된 샘플의 개수를 나타낸다. N 은 512, 1024 또는 2048 칩과 같은 세그멘트 길이일 수도 있다.here

silver

Proportional to,

Is the energy per chip estimated by the channel estimator 902,

Is noise (

Signal to noise ratio), N is the average length of the channel estimate. N is

And

Represents the number of samples used to estimate. N may be a segment length such as a 512, 1024 or 2048 chip.

를 사용하여, 룩-업 테이블 (LUT) 로부터의 최적의 소거 팩터

를 선택한다. 룩-업 테이블은

의 소정의 값 또는 범위 및 대응하는 소정의 소거 팩터

를 포함한다.In another embodiment, the erasure factor calculation unit 924 is from the pilot filter 914

, The optimal erasure factor from the look-up table (LUT)

Select. Look-up tables are

A predetermined value or range of and a corresponding predetermined erase factor

It includes.

및 소정의 소거 팩터

에 대한 룩업 테이블의 예이다. 테이블은

을 사용하고, 여기서

는 포화되고 4 비트로 라운딩되어 좌측 열의 0 내지 15 사이의 넘버를 제공한다. 우측 열은 수학식으로부터 도출된 소정의 소거 팩터

를 포함한다.10 is

And a predetermined erase factor

Here is an example of a lookup table for. Table

, Where

Is saturated and rounded into 4 bits to give a number between 0 and 15 in the left column. The right column is a predetermined erase factor derived from the equation

It includes.

이외의 더 많은 정보가 사용되어 소거 팩터를 계산하는 경우, 변할 수도 있다.The size of the table can be any other equation

If more information is used to calculate the erase factor, it may change.

에 소거 팩터 계산 유닛 (924) 으로부터 계산되거나 선택된 소거 팩터

를 곱하여, 즉 스케일링하여 세그멘트 당 (per-segment) 가중 채널 계수를 제공한다.First multiplier 926 is a channel estimate

The erase factor calculated or selected from the erase factor calculation unit 924 at

Multiply, i.e., scale, to provide a per-segment weighted channel coefficient.

Pilot  Reconstruction Filter

이 칩 지속기간 Tc 와 칩 지속기간 Tc 의 프랙션, 즉 하나의 칩 지속기간 Tc 보다 작은 프랙션의 합의 정수배인 경우, 인터-칩 간섭 (ICI) 이 발생한다. 핑거 프로세서 (900) 는 송신기 (218) (도 3) 에 의한 펄스-형상을 설명해줄 재구성 필터링을 수행한다. 도 14 는 도 3 의 송신기 필터 (352a 및 352b) 로부터의 시간 도메인에서의 추정된 (미리-계산된) 송신 펄스

와 수신기 (252; 전술한 바와 같음) 의 수신 필터 함수

의 콘볼루션인

의 예를 도시한다. 구체적으로, 도 9 의 재구성 필터 테이블 (938), 제 2 곱셈기 (932) 및 파일롯 재구성 필터링 블록 (930) 은 송신 펄스의 센터 로브 예컨대, 1402 (즉, 센터 탭 또는 피크값) 뿐만 아니라, 추정된 송신 펄스의 복수의 로브 (lobe) 예컨데, 1402, 1404A, 1404B, 1406A, 1406B (즉, 복수의 탭들) 을 설명해준다. 핑거 프로세서 (900) 에 의해 수행된 필터링은 더욱 신뢰할 수 있는 재구성된 파일롯 샘플을 제공한다. 송신 펄스 및 수신 필터 및 재구성 필터링의 형상을 고려하지 않고, 재구성된 파일롯 신호는 수 신된 샘플에 파일롯의 기여를 정확히 반영할 수 없을 수도 있다. Time delay or offset of multipath received signal

Inter-chip interference (ICI) occurs when the fraction of the chip duration Tc and the fraction of the chip duration Tc, i.e., the sum of fractions less than one chip duration Tc. Finger processor 900 performs reconstruction filtering to account for the pulse-shape by transmitter 218 (FIG. 3). FIG. 14 shows estimated (pre-computed) transmit pulses in the time domain from transmitter filters 352a and 352b of FIG. 3.

And receive filter function of receiver 252 (as described above)

Convolution of

Shows an example. Specifically, the reconstruction filter table 938, the second multiplier 932 and the pilot reconstruction filtering block 930 of FIG. 9 may not only estimate the center lobe of the transmit pulse, eg, 1402 (ie, center tap or peak value), Multiple lobes of transmit pulses are described, for example, 1402, 1404A, 1404B, 1406A, 1406B (ie, multiple taps). The filtering performed by finger processor 900 provides a more reliable reconstructed pilot sample. Without considering the shape of the transmit pulse and receive filter and the reconstruction filtering, the reconstructed pilot signal may not accurately reflect the contribution of the pilot to the received sample.

입력은 8 개의 상이한 가능한 위상 중 하나에 대응하는 필터 계수를 선택한다. 곱셈기 (932) 는 채널 추정치 및 소거 팩터에 의해 필터 계수를 곱한다 (선택된 위상에 따라). 재구성 필터링 블록 (930) 은 필터 계수, 채널 추정치 및 소거 팩터로 칩×8 에서 확산기 (936) 로부터의 확산 파일롯 신호 (의 콘볼루션을 수행함) 를 필터링한다. 콘볼루션이 8 의 데시메이션 이후에, 64 개 (8 개의 샘플의 8 개의 그룹) 샘플을 가진 경우, 재구성 필터링 블록 (930) 은 8-탭 필터이고 단지 8 개의 샘플을 필터링한다. 이 실시형태는 파일롯 간섭 추정기 (906) 의 복잡성을 감소시킬 수도 있다.In one embodiment, pilot reconstruction filtering block 930 is, for example, a polyphase finite impulse response filter (FIR) that combines decimating from chip × 8 to chip × 2 and filtering in a signal process. ). The phase can be given to a polyphase filter, which decimates the filter function and performs filtering according to the given phase. For example, a polyphase filter may use the above-described convolution decimated by eight with eight different possible phases. Time offset into filter table (938)

The input selects filter coefficients corresponding to one of eight different possible phases. Multiplier 932 multiplies the filter coefficients by the channel estimate and the cancellation factor (according to the selected phase). Reconstruction filtering block 930 filters the spread pilot signal (performs convolution of) from spreader 936 at chip × 8 with filter coefficients, channel estimates and cancellation factors. If the convolution has 64 (8 groups of 8 samples) samples after 8 decimations, the reconstruction filtering block 930 is an 8-tap filter and filters only 8 samples. This embodiment may reduce the complexity of the pilot interference estimator 906.

와 도 2 의 수신기 (252) 에서의 수신 필터

(예를 들어, 로우 패스 필터) 와의 콘볼루션

을 나타내는 미리-계산된 필터 계수의 세트를 저장한다. 단말기 (106) 의 송신 필터 (352a, 352b) 에 의해 사용된 송 신 펄스

는 기지국 (104) 에서 핑거 프로세서 (900) 에 의해 알려지고 추정될 수도 있다. 송신 펄스

는 이동 전화 제조자 또는 IS-95, CDMA2000 등과 같은 표준에 의해 규정될 수도 있다. 수신 필터 함수는 도 3 의 송신 필터 (352) 와 이상적으로 매칭된 필터 (MF) 가 될 수도 있지만, 실제 수신 필터는 송신 필터 (352) 와 정확히 매칭하지 않을 수도 있다. 기지국 수신기가 제조되는 경우, 수신 필터 함수

는 세트가 될 수도 있다.The reconstruction filter table 938 stores the estimated transmit pulses (from the transmit filters 352a, 352b of FIG. 3).

And the receive filter at the receiver 252 of FIG. 2.

Convolution with (e.g., low pass filter)

Store a set of pre-computed filter coefficients representing < RTI ID = 0.0 > Transmission pulses used by the transmission filters 352a and 352b of the terminal 106

May be known and estimated by finger processor 900 at base station 104. Transmit pulse

May be specified by a mobile phone manufacturer or standards such as IS-95, CDMA2000, and the like. The receive filter function may be a filter MF that ideally matches the transmit filter 352 of FIG. 3, but the actual receive filter may not exactly match the transmit filter 352. Receive filter function when base station receiver is manufactured

May be a set.

의 칩-레벨 샘플에 대응한다. 각 필터 테이블은 2M+1 개의 탭 엔트리를 가질 수도 있고, 각 엔트리는 16 개의 비트를 가질 수도 있다. 일 실시형태에서, M 은 2 와 동일하거나 크도록 선택되어 성능 손실을 감소시킨다 (M=2 인 경우, 2M+1=5 이다). 필터 테이블은 칩×1 에서 5-13 칩 시간 스팬 (여기서 M=2 내지 6 이고, 2M+1=5 내지 13 임), 또는 33-97 칩×8 시간 스팬 (여기서, M=2 내지 6 이고, 2M(8)+1=33 내지 97 임) 이다. 일 실시형태에서, 동일한 필터 테이블 (938) 은 복수의 핑거 프로세서 (900) 에 의해 사용될 수도 있다.In one configuration, the convolution is sampled at the finger processor 900 at the best sample rate, for example, chip × 8, so that the filter table 938 includes a plurality of filter tables, eg, eight filter tables. , Where i ^th filter table is the original chip × 8 correlation function at time offset i (where i = 0, 1, 2, ... 7)

Corresponds to the chip-level sample. Each filter table may have 2M + 1 tap entries, and each entry may have 16 bits. In one embodiment, M is chosen to be equal to or greater than 2 to reduce performance loss (if M = 2, 2M + 1 = 5). The filter table is a 5-13 chip time span at chips × 1 where M = 2 to 6 and 2M + 1 = 5 to 13, or a 33-97 chip × 8 time span where M = 2 to 6 , 2M (8) + 1 = 33 to 97). In one embodiment, the same filter table 938 may be used by multiple finger processors 900.

에 대한 적합 한 시간 오프셋에서 2 개의 이러한 필터 테이블에 접속하고, 하나의 테이블은 짝수 샘플용이고, 하나의 테이블은 홀수 샘플용이다. 제 2 곱셈기 (932) 는 제 1 곱셈기 (956) 로부터의 스케일링된 세그멘트당 채널 추정치

계수에 2 개의 선택된 필터 테이블의 각 필터 탭 (미리-계산된 필터 계수) 을 곱한다. 제 2 곱셈기 (932) 는 파일롯 재구성 필터링 블록 (930) 에 세그멘트당 필터 탭 계수 (예를 들어, 칩×2 에서) 를 출력한다.In one embodiment, the second multiplier 932 of each finger processor 900 (assigned to the finger processor 900) for reconstruction of the chip × 2 pilot samples.

We connect two such filter tables at a suitable time offset for, one table for even samples, and one table for odd samples. The second multiplier 932 is a channel estimate per scaled segment from the first multiplier 956.

Coefficient is multiplied by each filter tap (pre-computed filter coefficients) of the two selected filter tables. The second multiplier 932 outputs a filter tap coefficient per segment (eg, at chip × 2) to the pilot reconstruction filtering block 930.

In one embodiment, if the output of pilot reconstruction filtering block 930 provides a sample at chip × 2, a separate resampler may not be needed for pilot interference estimator 906. Reconstruction filter block 930 may change the chip rate to a sample rate.

를 수신한다. 도 9 의 확산기 (936) 는 현재 세그멘트 "n" 의 확산 시퀀스 Pm 를 수신하고, 다음 세그멘트 "n+1" 가 아닌 현재 세그멘트 "n" 에 대한 확산 파일롯 신호 (예를 들어, 복소 PN 시퀀스 칩) 를 제공한다. 그 결과, 도 9 의 핑거 프로세싱 (900) 은 현재 세그멘트 "n" 의 파일롯 간섭을 재구성한다. 현재 세그멘트 "n" 에 대해 복수의 핑거 프로세서로 부터 파일롯 간섭을 재구성하고 누산하는 단계와 현재 세그멘트 "n" 의 데이터 샘플로부터 현재 세그멘트 "n" 누산된 재구성된 파일롯 간섭을 감산하는 단계 사이에 짧은 지연이 있을 수도 있다. 그러나 이 접근 (현재 세그멘트 "n" 의 데이터 샘플로부터 현재 세그멘트 "n" 의 누산된 재구성된 파일롯 간섭을 소거하는 단계) 은 특히, 높은 시변 채널에 신뢰할 수 있는/정확한 파일롯 간섭 소거를 제공할 수도 있다.The pilot channelizer 934 and spreader 936 of FIG. 9 are the pilot channelizer 532 of FIG. 5 except that the spreader 936 of FIG. 9 receives the spreading sequence P _m of the current segment “n”. And diffuser 534. Conversely, the diffuser 534 of FIG. 5 is a spreading sequence for the next segment, as described above with respect to FIGS. 5 and 6A.

Receive Spreader 936 in FIG. 9 receives the spreading sequence Pm of the current segment "n" and spreads the spread pilot signal for the current segment "n" rather than the next segment "n + 1" (eg, a complex PN sequence chip). To provide. As a result, the finger processing 900 of FIG. 9 reconstructs the pilot interference of the current segment "n". Short delay between reconstructing and accumulating pilot interference from a plurality of finger processors for current segment " n " and subtracting the current segment " n " accumulated reconstructed pilot interference from data samples of current segment " n " There may be this. However, this approach (a step of canceling the accumulated reconstructed pilot interference of current segment "n" from data samples of current segment "n") may provide reliable / accurate pilot interference cancellation, especially for high time-varying channels. .

Pilot channelizer 934 may receive multiple channelization codes having I and Q components. Spreader 936 may receive a complex PN sequence with four possible values +/- 1 or +/- i. Channelizer 934 and spreader 936 generate extra chips on each side of the current segment " n " to assist filtering by pilot reconstruction filtering block 930.

의 곱, 소거 팩터 및 채널 추정치의 콘볼루션을 수행한다. 예를 들어, 파일롯 재구성 필터링 블록 (930) 은 2 개의 5-탭 필터, 9-탭 필터 또는 13-탭 필터를 칩×1 에서 포함할 수도 있다. 각 필터 당 2M+1 개의 탭이 있을 수도 있다. 파일롯 재구성 필터링 블록 (930) 에 의해 제공된 필터링은 ICI (inter-chip interference) 의 효과를 감소시킬 수도 있다.Pilot reconstruction filtering block 930 is used for active filtering, that is, a spread pilot signal (eg, a PN sequence) and filter table coefficients from spreader 936.

Perform convolution of the product, the cancellation factor, and the channel estimate of. For example, pilot reconstruction filtering block 930 may include two 5-tap filters, 9-tap filters, or 13-tap filters at chip × 1. There may be 2M + 1 taps per filter. The filtering provided by pilot reconstruction filtering block 930 may reduce the effect of inter-chip interference (ICI).

에 의존함). 그 후, 샘플은 버퍼 (928) 에 저장된다.Pilot reconstruction filtering block 930 may reconstruct one segment of the user-time aligned pilot signal at chip × 2 resolution and provide a chip × 2 pilot sample. In another embodiment, pilot reconstruction filtering block 930 filters the oversampled PN sequence at chip × 8, and the resampler (between pilot reconstruction filtering block 930 and buffer 928) is a pilot reconstruction filtering block. Decimates chip x 8 from 930 with chip x 2 with a given phase, i.e. starting sample from 0 to 7 (time offset

Depends on). The sample is then stored in buffer 928.

를 출력한다. 파일롯 재구성 필터링 블록 (930) 은 특히, 역확산기 (910) 가 주파수 오프셋을 보상하는 위상 로테이터를 구비하는 경우, 위상 디-로테이터 또는 위상 보정기를 포함할 수도 있다.Pilot reconstruction filtering block 930 is a reconstructed pilot interference signal that includes a multipath estimated pilot sample assigned to finger processor 900.

Outputs The pilot reconstruction filtering block 930 may include a phase de-rotator or phase corrector, especially when the despreader 910 has a phase rotator that compensates for the frequency offset.

Pilot  Interference Accumulation  buffer

Pilot interference accumulation buffer 928 stores and accumulates the reconstructed pilot from pilot reconstruction filtering block 930 at a suitable time offset. By way of example, the pilot interference accumulating buffer 928 may be cyclic random access memory (RAM). In one configuration, there may be a single pilot interference accumulating buffer 928 that stores and accumulates the reconstructed pilot samples at different time offsets from the plurality of pilot reconstruction filtering blocks 930 of the plurality of finger processors 900. A single interference accumulating buffer may use less memory space and other resources than embodiments having a plurality of interference accumulating buffers in multiple finger processors.

The pilot interference accumulating buffer 928 may have the same resolution as the sample buffer 908. For example, pilot interference accumulating buffer 928 may operate at a chip × 2 resolution, ie, a speed of 2 × chip rate. If each segment has a length of 512 chips, the pilot interference accumulating buffer 928 has at least two segments, 512 chips / segments × 2 samples / chip = 1024 generated from the pilot reconstruction filtering block 930. You can also save. With two or more segment lengths, pilot interference accumulating buffer 928 may store an overlap of previous pilot samples. The pilot interference accumulating buffer 928 may be implemented in other sizes. Pilot interference accumulation buffer 928 may use other sample rates, such as 3/2 or 4/3 x chip rate.

After finger processor 900 completes pilot reconstruction, interference accumulation buffer 928 includes an overall pilot interference estimate. Then, the adder 916 of each finger processor 900 subtracts the interference accumulating buffer content sample-wise (from the interference accumulating buffer 928) from the received signal (from the sample buffer 908) to decode the data demodulation unit. Provide a pilot-free data sample at 904.

Reduction in the complexity of using a single interference accumulating buffer may be obtained by generating a reconstructed pilot that is independent of multipath (user) arrival time. For example, the reconstructed pilot may be generated and chip-time-aligned at chip × 2 rate. As a result, the reconstructed pilot is independent of multipath (user) arrival time. The reconstructed pilot provided by the interference accumulating buffer 928 directly from the received signal provided by the sample buffer 908 along the system time, for example via burst subtraction, without taking into account finger or user time, i.e. without resampling. It may be subtracted. This eliminates the need for a resampler such as resampler 540 in finger processor 410 of FIG. 5.

time Snapshot

11 shows an example of a time snapshot for two finger processors 900 (of FIG. 9) with different multipath time offsets t ₁ and t ₂ . The second finger processor has a shorter time offset than the first finger processor. As shown by lines 1112 and 1114, the two finger processors perform pilot demodulation, pilot reconstruction, and data demodulation for the sequences “n-1,” “n-2,” and “n-3,” of the segment. And receiver 252 (FIG. 4) writes the next segment " n + 1 " into sample buffer 908 (FIG. 9) with receiver (RX) write pointer. Bottom line 1116 in FIG. 11 is segment “n-5,” “n-4,” “n-3,” “n-2,” “n-1,” “n,” “n + 1,” and the like. Represents a timeline in real time. Segment " n " represents the current segment. Segment "n-1" represents the previous segment. Segment "n + 1" represents the next segment. Each "segment" may have a time span of 512 chips, for example. Each "chip" may correspond to, for example, 100 clock cycles.

If receiver 252 (FIG. 4) starts writing the next segment “n + 1” into sample buffer 908, one or more previous segments, eg, “n-1” and “n”, are sample buffers. Stored at 908 and available for processing by the two finger processors (by a previous write operation). The time delay offset of each finger processor shifts the start data sample and the end data sample to the right for pilot demodulation of segment "n-1" as shown in FIG. As a result, since segment "n + 1" is written to the sample buffer 908, both the first and second finger processors have some data samples from segment "n-1" and some data samples from segment "n". Demodulate the pilot for segment "n-1". In this embodiment, both finger processors require data samples from segment "n" and segment "n + 1" (due to the time offsets t ₁ and t ₂ of the finger processor), and segment "n + 1" is Since it has not yet been written to the sample buffer 908, the first and second finger processors may not demodulate the pilot for segment "n" while the segment "n + 1" is written to the sample buffer 908.

As described above with reference to FIG. 5, FIG. 11 shows a small delay for data demodulation because the pilot is reconstructed and erased for the current segment “n” in contrast to the estimated pilot interference for the next segment “n + 1”. . However, a finger processor using the timeline of FIG. 11 may obtain more accurate channel estimates and better pilot interference cancellation (PIC) gains.

를 곱한다. 블록 1206 에서, 핑거 프로세서 (900) 는 재구성 필터링을 수행하여 파일롯 샘플을 생성한다. 블록 1208 에서, 단일의 누산 버퍼 (928) 는 예를 들어, 칩×8 또는 칩×2 에서 복수의 핑거 프로세서 (900) 로부터의 재구성된 파일롯 샘플을 저장한다. 블록 1210 에서, 누산된 재구성된 파일롯 샘플은 데이터 복조를 수행하는 복수의 핑거 프로세서에 대한 데이터 샘플로부터 감산된다. 12A is a flow diagram summarizing the process described above in conjunction with FIGS. 9-11 that derive and accumulate pilot interference for a plurality of multipaths. At block 1200, the plurality of finger processors 900 derive a channel signal strength estimate and a noise estimate. In block 1202, the finger processor 900 selects (a) the cancellation factor based on the channel signal strength estimate and the noise estimate and (b) multiplies the channel estimate by the selected cancellation factor. In block 1204, the finger processor 900 may determine the product of the channel estimate and the selected cancellation factor from the reconstruction filter table 930.

Multiply by In block 1206, the finger processor 900 performs reconstruction filtering to generate a pilot sample. At block 1208, a single accumulation buffer 928 stores the reconstructed pilot samples from the plurality of finger processors 900, for example at chip × 8 or chip × 2. At block 1210, the accumulated reconstructed pilot sample is subtracted from the data samples for the plurality of finger processors that perform data demodulation.

에 의해 누산 버퍼 (928) 로부터의 파일롯 샘플을 필터링한다. 블록 1260 에서, 누산된 재구성된 파일롯 샘플은 데이터 복조를 수행하는 복수의 핑거 프로세서에 대한 데이터 샘플로부터 감산된다.12B is a flowchart of another embodiment of a process for deriving accumulated pilot interference for multiple multipaths, in which filtering and pilot interference accumulation are switched in the order compared to FIG. 12A. At block 1250, the plurality of finger processors 900 derive a channel signal strength and noise estimate. At block 1252, finger processor 900 (a) selects an cancellation factor based on the channel signal strength estimate and the noise estimate and (b) multiplies the channel estimate by the selected cancellation factor. In block 1254, the finger processor 900 reconstructs the pilot sample using the channel estimate and the selected erase factor. At block 1256, a single accumulation buffer 928 stores the reconstructed pilot samples from the plurality of finger processors 900, for example, at chip × 8 or chip × 2. In block 1258, a single reconstruction filtering block is

Filter the pilot samples from the accumulation buffer 928 by using a. At block 1260, the accumulated reconstructed pilot sample is subtracted from the data samples for the plurality of finger processors that perform data demodulation.

In FIG. 12B, filtering is performed after accumulating the reconstructed pilot interference samples from the plurality of finger processors 900 and before subtracting the pilot interference from the data samples. Each finger processor 900 may not need to perform filtering. This may reduce the complexity of each finger processor 900.

Equation

(복소수 값) 는 다음과 같이 표현된다.Actual total pilot interference signal of the received reverse link (RL) signal

(Complex value) is expressed as follows.

Where n represents a segment of the received signal (eg, n may have a sample rate equal to chip rate × 2);

K is the total number of users or terminals that contribute to segment n of the received signal;

L is the total number of multipaths that contribute to segment n of the received signal;

i refers to the time index;

는 K^th 사용자의 1^th 경로의 추정된 복수 채널 계수이며;

Is an estimated multi-channel coefficient of 1 ^th path of K ^th user;

는 k^th 사용자의 복소 PN-시퀀스 p 및 파일롯 채널화 코드

의 곱과 동일하고; 파일롯 채널화 코드

는 CDMA 2000 과 같은 일부 CDMA 시스템에서의 하나의 시리즈이기 때문에,

는 k^th 사용자의 복소 PN-시퀀스 p 와 동일하다;

K ^th user's complex PN-sequence p and pilot channelization codes

Equal to the product of; Pilot channelization code

Is a series in some CDMA systems, such as CDMA 2000,

Is equal to the complex PN-sequence p of k ^th users;

는 예를 들어, 로우 패스 필터와 같이, 수신기 필터

(도 2 의 수신기 252 에서) 와 송신 펄스

(도 3 의 필터 (352a, 352b) 로부터의) 의 콘볼루션 (도 14) 이고, 전술한 바와 같이, 콘볼루션은 일 실시형태에서, 칩×8 해상도에서일 수도 있다.

Receiver filter, for example, low pass filter

(At receiver 252 in FIG. 2) and transmit pulse

Convolution (from FIG. 14) of filters 352a and 352b of FIG. 3, and as described above, the convolution may be at chip × 8 resolution, in one embodiment.

는 샘플링 주기이고;

Is a sampling period;

는 칩 당 샘플의 수이며;

Is the number of samples per chip;

는 k^th 사용자의 1^th 경로의 경로 지연이다.

Is the path delay of k ^th user's 1 ^th path.

A rake receiver with a plurality of M finger processors 900 (FIG. 9) will yield a total reconstructed pilot interference signal (also referred to as a pilot interference "replica" or "estimation" represented as follows. It may be.

Where M is the total number of finger processors processing the multipath;

는 m^th 핑거 프로세서의 추정된 복소 채널 계수이며;

Is an estimated complex channel coefficient of the m ^th finger processor;

는 m^th 핑거 프로세서에 의해 사용된 복소 PN-시퀀스이고;

Is the complex PN-sequence used by the m ^th finger processor;

는 m^th 핑거의 추정된 경로 지연이다.

Is the estimated path delay of the m ^th finger.

는 각 핑거 프로세서 (900) 에 의해 도출된 각 재구성된 파일롯 간섭 신호

의 합으로서 표현될 수도 있다.Total Reconstructed Pilot Interference Signal

Is each reconstructed pilot interference signal derived by each finger processor 900.

It can also be expressed as the sum of.

Each reconstructed pilot interference signal derived by the finger processor 900 is represented as follows.

가 하나의 세그멘트에 대해 미리 합산된 상수인 경우, 상기 수학식은 다음과 같이 재기록될 수도 있다.Estimated Complex Channel Coefficient

If is a constant previously summed for one segment, the equation may be rewritten as follows.

는 m^th 핑거의 복소 재구성된 MF (매칭된 필터) 샘플이다. 추정된 복소 채널 계수

는 도 9 의 곱셈기 (926) 에 의해 제공될 수도 있고,

는 도 9 의 필터 테이블 (938), 곱셈기 (932), 파일롯 채널라이저 (934), 확산기 (936) 및 파일롯 재구성 필터링 블록 (930) 에 의해 제공될 수도 있다.here,

Is a complex reconstructed MF (matched filter) sample of the m ^th finger. Estimated Complex Channel Coefficient

May be provided by multiplier 926 of FIG. 9,

9 may be provided by filter table 938, multiplier 932, pilot channelizer 934, spreader 936, and pilot reconstruction filtering block 930.

의 펄스 형상 및 I 및 Q PN 시퀀스 p 를 프로세싱하여 I 및 Q 재구성된 샘플

을 생성할 수도 있다. I 재구성된 샘플

은 복소 채널 추정치

의 I 및 Q 컴포넌트에 의해 곱해진다. 유사하게, Q 재구성된 샘플

은 복소 채널 추정치

의 I 및 Q 컴포넌트에 의해 곱해진다. 옵션적 위상 로테이션은 I 및 Q

샘플상에서 수행될 수도 있다. 그 후, I 및 Q

샘플은 선택된 소거 팩터

에 의해 곱해지고 누산 버퍼 (928) 에 누산될 수도 있다. 그 결과, 소거 팩터

는 필터링 (도 9) 이전 대신 필터링 (필터링 블록 (930) 의 출력상에) 이후에 구현될 수도 있다.The order of the processes in FIG. 9 may be changed in other embodiments. One variation of FIG. 9 is

I and Q reconstructed samples by processing the pulse shape of and the I and Q PN sequences p

You can also create I reconstructed sample

Is a complex channel estimate

Multiplied by the I and Q components. Similarly, Q reconstructed sample

Is a complex channel estimate

Multiplied by the I and Q components. Optional phase rotation is I and Q

It may also be performed on a sample. After that, I and Q

Sample is selected erase factor

May be multiplied by and accumulated in the accumulation buffer 928. As a result, the erasure factor

May be implemented after filtering (on the output of filtering block 930) instead of before filtering (FIG. 9).

Multiple antennas

13A shows a receiver 252 (FIG. 2) having a plurality of antennas 250A to 250L, for example, 12 antennas, and a plurality of interference accumulating buffers 928A to 928L, for example, 12 interference accumulating buffers. Is a block diagram of a demodulator 254 having a. Each interference accumulation buffer 928 stores the reconstructed pilot for the different antenna 250.

FIG. 13B illustrates a single unit that stores reconstructed pilots for some or all of receiver 252 (FIG. 2) and antennas 250A-250L with a plurality of antennas 250A-250L, for example, 12 antennas. Is a block diagram of a demodulator 254 having an interference accumulating buffer 928. In this embodiment, finger processor 900 reconstructs the reconstructed pilot interference for one antenna 250 and stores the pilot interference in interference accumulation buffer 928. The finger processor 900 then reconstructs all the pilots for another antenna by shifting the PN sequence (and may do some additional processing) and stores the pilot interference in the interference accumulation buffer 928. Finger processor 900 continues until all pilots from some or all of antenna 250 are reconstructed and stored in interference accumulating buffer 928. The reconstructed pilot is aligned at system time and stored in a single interference accumulating buffer 928. By using a single interference accumulating buffer 928, this embodiment may reduce memory requirements by 6-12 times.

과 유사한 방법으로 총 채널 간섭

에 기여한다.모든 단말기로부터 송신된 파일롯은 모든 단말기 및 기지국에 의해 나타난 총 간섭 레벨의 실질적인 부분을 나타낼 수도 있다. 이것은 각 개별 단말기에 대한 더 낮은 SNR (lower signal-to-total-noise-plus-interference) 를 유발한다. 사실, 용량 근처에서 동작하는 cdma2000 (역방향 링크상의 파일롯을 지원함) 에서, 기지국에서 나타난 간섭의 대략 1/2 이 송신 단말기로부터의 파일롯으로 인할 것일 수도 있다는 것이 추정된다. 다중-단말기 및 다중-경로 파일롯 간섭의 소거 또는 감소는 각 개별 단말기의 SNR 을 개선하여, 각 단말기가 낮은 전력 레벨로 송신하고 여전히 바람직한 디코딩 성능을 획득하게 한다. 그 결과, 파일롯 간섭 소거 (PIC) 는 역방향 링크 용량을 증가시켜, 존재하는 단말기로부터 더 높은 데이터 레이트, 예를 들어, 30-35% 데이터 레이트 용량 증가를 허용하거나, 더 많은 단말기 또는 사용자, 예를 들어, 10-15% 더 많은 사용자가 무선 통신 시스템, 예를 들어, 기지국 서비스 영역에 추가될 수 있게 한다.The pilot interference cancellation technique described herein may provide a notable improvement in performance. As mentioned above, the pilot transmitted by each terminal on the reverse link is subject to background noise.

Total channel interference in a similar way to

The pilot transmitted from all terminals may represent a substantial portion of the total interference level exhibited by all terminals and base stations. This results in lower signal-to-total-noise-plus-interference (SNR) for each individual terminal. In fact, it is estimated that in cdma2000 operating near capacity (supporting the pilot on the reverse link), approximately half of the interference seen at the base station may be due to the pilot from the transmitting terminal. The cancellation or reduction of multi-terminal and multi-path pilot interference improves the SNR of each individual terminal, allowing each terminal to transmit at a lower power level and still obtain the desired decoding performance. As a result, pilot interference cancellation (PIC) increases reverse link capacity, allowing higher data rates, eg, 30-35% data rate capacity increase, from existing terminals, or allowing more terminals or users, e.g. For example, 10-15% more users can be added to a wireless communication system, eg, base station service area.

Techniques for estimating and canceling pilot interference described herein may be used in various wireless communication systems for transmitting pilot with data. For example, this technology can be used in various CDMA systems (e.g., IS-95, CDMA2000, CDMA 2000 1xEV-DV, CDMA 2000 1xEV-DO, WCDMA, TD-SCDMA, TS-CDMA, etc.), personal communication services (PCS). ) Systems (eg, ANSI J-STD-008), and other wireless communication systems. The technique described herein is a pilot when a plurality of instances of each of the one or more transmission signals are received and processed (eg, by a rake receiver or other demodulator), and also when the plurality of received signals are received and processed. It may be used to estimate and cancel the interference.

For clarity, various aspects and embodiments have been described with respect to a reverse link in cdma2000. The pilot interference cancellation technique described herein may also be used for the forward link from the base station to the terminal. Processing by the demodulator is determined by whether the particular CDMA standard and creative techniques supported are used for the forward and reverse links. For example, "despreading" into a spreading sequence in IS-95 and cdma2000 is equivalent to "descramble" in a scrambled sequence in W-CDMA, and Walsh code or QOF (quasi- in IS-95 and cdma2000). channelization is equal to "despreading" with OVSF in W-CDMA. In general, the processing performed by the demodulator in the receiver is complementary to that performed by the modulator in the transmitter unit.

For the forward link, the techniques described herein may also be used to approximately cancel other pilots that may be transmitted in addition to or instead of the “common” pilots transmitted to all terminals in the cell. For example, cdma2000 supports a "transmit diversity" pilot and a "auxiliary" pilot. These other pilots use different Walsh codes (ie different channelization codes, which may be QOF functions). Different data patterns may also be used for the pilot. To process any of these pilots, the despread sample is recovered to the same Walsh code used to channelize the pilot at the base station and further correlated to the same pilot data pattern used at the base station for the pilot (ie, multiply and accumulate). do). The transmit diversity pilot and / or the reserve pilot may be estimated and canceled in addition to the common pilot.

Similarly, W-CDMA supports many different pilot channels. First, a common pilot channel (CPICH) may be transmitted on the primary base station antenna. Second, diversity CPICH may be generated based on non-zero pilot data and transmitted on the diversity antenna of the base station. Third, one or more second CPICHs may be transmitted in a limited portion of the cell, and each second CPICH is generated using a non-zero channelization code. Fourth, the base station may transmit a dedicated pilot to a specific user using the same channelization code as the user data channel. In this case, the pilot symbols are time-multiplexed with data symbols for the user. Thus, those skilled in the art will appreciate that the techniques described herein are applicable to the above different types of pilot channels and other pilot channels that may be transmitted in a wireless communication system.

Demodulator 254 (FIG. 2) and other processing units that may be used to implement various aspects and embodiments may be implemented in hardware, software, firmware, or a combination thereof. For hardware design, demodulators (including data demodulation units and elements used for pilot interference estimation and cancellation, such as pilot estimators and pilot interference estimators), and other processing units may include one or more application specific integrated circuits (ASICs), digital signals. Implemented as a processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microcontroller, a microprocessor, another electronic unit, or a combination thereof May be

For software implementations, elements used for pilot interference estimation and cancellation and data demodulation may be implemented as modules (eg, transitions, functions, etc.) that perform the functions described herein. The software code may be stored in a memory unit (eg, memory 262 of FIG. 2) and executed by a processor (eg, controller 260). The memory unit may be implemented within the processor or external to the processor, in which case the memory unit can be communicatively coupled to the processor via various means known in the art.

An element used to implement the pilot interference estimation and cancellation described herein may be a receiver unit that may be integrated into a terminal (eg, handset, handheld unit, stand-alone unit, etc.), base station, or other communication device or unit, or It may also be integrated into the demodulator. The receiver unit or demodulator may be implemented in one or more integrated circuits.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit and scope of the invention. As a result, the present invention is not limited to the embodiments described herein, but corresponds to the widest scope consistent with the principles and novel features disclosed herein.

Claims (56)

A receiver unit configured to receive a wireless signal comprising at least a first and a second signal instance each comprising a data and pilot signal, The receiver unit, Determine a first channel estimate for the first signal instance, Estimate a first pilot of the first signal instance using the first channel estimate and a spread pilot signal associated with the first signal instance, Determine a second channel estimate for the second signal instance, A processor configured to estimate a second pilot of the second signal instance using the second channel estimate and a spread pilot signal associated with the second signal instance; And A buffer configured to accumulate the estimated first and second pilots, The processor is configured to subtract the estimated and accumulated first and second pilots from the received signal to estimate a pilot-erase received signal and use the estimated pilot-erase received signal to obtain data of the first signal instance. Is configured to demodulate, The processor, Determine a first noise estimate of the first signal instance, An cancellation factor based on the first channel estimate and the first noise estimate

To derive Multiplying the first channel estimate by the cancellation factor to produce a weighted channel estimate, And further estimate the first pilot of the first signal instance using the weighted channel estimate and the spread pilot signal associated with the first signal instance. The method of claim 1, And the radio signal is a code division multiple access (CDMA) signal. The method of claim 1, A receiver unit, configured to receive the first and second signal instances from first and second remote terminals, respectively. The method of claim 1, And the first and second signal instances are multipath components of a signal from one remote terminal. The method of claim 1, The buffer accumulates (a) a first pilot estimated according to a first estimated time offset of the first signal instance and (b) a second pilot estimated according to a second estimated time offset of the second signal instance. A receiver unit, further configured to. The method of claim 1, And a sample buffer configured to store the wireless signal at a sample rate equal to a multiple of the chip rate of the wireless signal. The method of claim 6, The sample rate of the sample buffer is equal to the sample rate of the buffer accumulating the estimated pilot. The method of claim 1, Each spread pilot signal comprises a pilot signal spread by a pseudo-noise (PN) sequence. The method of claim 1, The first channel estimate, a spread pilot signal associated with the first signal instance, and the first estimated pilot correspond to a segment of the received signal, the segment comprising data samples for a time period of the received signal. Receiver unit. delete The method of claim 1, The erasure factor

Is,

Derived from Where h is the first channel estimate, N _t is the first noise estimate, and N is the number of samples used to estimate h and N _t of the first signal instance. The method of claim 1, And the cancellation factor is in the range of 0 to 1.0. The method of claim 1, And the cancellation factor is a value greater than 1.0. The method of claim 1, And a look-up table having a set of channel estimates and noise estimates corresponding to the cancellation factor. The method of claim 1, The processor, Multiplying the first channel estimate by a convolution of a predetermined transmit pulse and a receive filter function, performing a convolution of (a) a spread pilot signal associated with the first signal instance and (b) the product of the first channel estimate, the predetermined transmission pulse and the convolution of the receive filter function, thereby performing the first signal instance And further configured to estimate a first pilot of the receiver unit. The method of claim 15, And the predetermined transmission pulse is defined by a Code Division Multiple Access (CDMA) standard. The method of claim 15, The processor, (c) convolution of the predetermined transmit pulse and the receive filter function, and (d) (i) a spread pilot signal associated with the first signal instance, (ii) the first channel estimate, the predetermined transmit pulse, and the A receiver unit configured to downsample a rate of at least one convolution of the product of the convolution of a receive filter function to match the rate of the buffer. The method of claim 15, The processor, (c) convolution of a predetermined transmit pulse with the receive filter function, and (d) (i) a spread pilot signal associated with the first signal instance, (ii) the first channel estimate, the predetermined transmit pulse, and the And upsample a rate of at least one of the convolutions of a product of the convolution of a receive filter function to match the rate of the buffer. The method of claim 15, The processor, Decimates a sample of the convolution of the predetermined transmit pulse and the receive filter function according to a phase associated with an estimated time offset of the first signal instance, Multiplying the first channel estimate by a decimated sample of the convolution of the predetermined transmit pulse and the receive filter function, And perform a convolution of a spread pilot signal associated with the first signal instance and the product of the first channel estimate and the decimated sample to estimate a first pilot of the first signal instance. The method of claim 15, Decimates a sample of the convolution of the predetermined transmit pulse and the receive filter function according to a phase associated with an estimated time offset of the first signal instance, Multiplying the first channel estimate by a decimated sample of the convolution of the predetermined transmit pulse and the receive filter function, A polyphase finite impulse that estimates a first pilot of the first signal instance by performing a convolution of a product of a spread pilot signal associated with the first signal instance and the first channel estimate and the decimated sample A receiver unit, further comprising a response filter (FIR). The method of claim 15, Further comprising a filter table of predetermined filter coefficients corresponding to a plurality of different phases, The processor is configured to select a phase and corresponding filter coefficients based on an estimated time offset of the first signal instance. The method of claim 1, The processor is further configured to filter the estimated pilot-erase received signal by convolution of a predetermined transmit pulse and a receive filter function. The method of claim 1, The processor, Substantially in parallel with determining the first channel estimate and estimating a first pilot of the first signal instance using the first channel estimate and a spread pilot signal associated with the first signal instance, Determine the second channel estimate and estimate a second pilot of the second signal instance using the second channel estimate and a spread pilot signal associated with the second signal instance. The method of claim 1, And the processor is configured to estimate pilots for the plurality of signal instances in a time division multiplexing method. A base station configured to receive a radio signal comprising at least a first and a second signal instance each comprising a data and pilot signal, The base station, Determine a first channel estimate for the first signal instance, Estimate a first pilot of the first signal instance using the first channel estimate and a spread pilot signal associated with the first signal instance, Determine a second channel estimate for the second signal instance, A processor configured to estimate a second pilot of the second signal instance using the second channel estimate and a spread pilot signal associated with the second signal instance; And A memory configured to accumulate the estimated first and second pilots, The processor is configured to subtract the estimated and accumulated first and second pilots from the received signal to estimate a pilot-erase received signal and use the estimated pilot-erase received signal to extract data of the first signal instance. Configured to demodulate, The processor, Determine a first noise estimate of the first signal instance, An cancellation factor based on the first channel estimate and the first noise estimate

To derive Multiplying the first channel estimate by the cancellation factor to produce a weighted channel estimate, And estimate a first pilot of the first signal instance using the weighted channel estimate and a spread pilot signal associated with the first signal instance. The method of claim 25, The processor, Multiplying the first channel estimate by a convolution of a predetermined transmit pulse and a receive filter function, performing a convolution of (a) a spread pilot signal associated with the first signal instance and (b) the product of the first channel estimate, the predetermined transmission pulse and the convolution of the receive filter function, thereby performing the first signal instance And estimate the first pilot of the communication system. The method of claim 25, The base station includes a plurality of antennas and a plurality of buffers in the memory, Each buffer is configured to accumulate the estimated pilot of a signal instance received by one of the antennas. The method of claim 25, The base station includes a plurality of antennas, and the memory is configured to accumulate the estimated pilot of signal instances received by the plurality of antennas. The method of claim 25, The base station includes X antennas and Y buffers in the memory, X is greater than Y, One or more buffers configured to accumulate an estimated pilot of signal instances received by two or more antennas. Means for receiving a wireless signal comprising at least a first and a second signal instance each comprising a data and pilot signal; Means for determining a first channel estimate for the first signal instance; Means for deriving a convolution of a predetermined transmit pulse and a receive filter function and the product of the first channel estimate; Means for estimating a first pilot of the first signal instance using the product of the convolution and the first channel estimate; Means for determining a second channel estimate for the second signal instance; Means for deriving a product of the predetermined transmit pulse and the convolution of a receive filter function and the second channel estimate; Means for estimating a second pilot of the second signal instance using the product of the convolution and the second channel estimate; Means for accumulating the estimated first and second pilots; And A receiver unit having means for subtracting the estimated and accumulated first and second pilots from the received signal to derive an estimated pilot-erase received signal, The receiver unit, Means for determining a noise estimate of the first signal instance; Means for deriving an erasure factor based on the first channel estimate and the noise estimate of the first signal instance; Means for multiplying the first channel estimate by the cancellation factor to produce a weighted channel estimate; And Means for estimating a first pilot of the first signal instance using the weighted channel estimate and a spread pilot signal associated with the first signal instance. Receiving a wireless signal comprising at least a first and a second signal instance each comprising a data and pilot signal; Determining a first channel estimate for the first signal instance; Deriving a convolution of a predetermined transmit pulse and a receive filter function and the first channel estimate; Estimating a first pilot of the first signal instance using the product of the convolution and the first channel estimate; Determining a second channel estimate for the second signal instance; Deriving a product of the convolution of the predetermined transmit pulse and the receive filter function and the second channel estimate; Estimating a second pilot of the second signal instance using the product of the convolution and the second channel estimate; Accumulating the estimated first and second pilots; And Subtracting the estimated and accumulated first and second pilots from the received signal to derive an estimated pilot-erase received signal, the method comprising: The method, Determining a noise estimate of the first signal instance; Deriving an cancellation factor based on the first channel estimate and the noise estimate of the first signal instance; Generating a weighted channel estimate by multiplying the first channel estimate by the cancellation factor; And Estimating a first pilot of the first signal instance using the weighted channel estimate and a spread pilot signal associated with the first signal instance. The method of claim 31, wherein Receiving the wireless signal comprises receiving the first and second signal instance from a first and a second terminal. The method of claim 31, wherein Each signal instance has an estimated time offset due to the transmission path of the signal instance. The method of claim 31, wherein The wireless signal comprises a code division multiple access (CDMA) signal. The method of claim 31, wherein The wireless signal is transmitted from a terminal to a base station. The method of claim 31, wherein The wireless signal is transmitted from a base station to a terminal. The method of claim 31, wherein Buffering the received wireless signal at a sample rate equal to the plurality of chip rates. The method of claim 31, wherein Determining a first channel estimate for the first signal instance comprises: Despreading a sample derived from the received signal into a spreading sequence associated with the first signal instance to provide a despread sample; De-channelizing the despread sample with a pilot channelization code to provide a pilot symbol; And Filtering the pilot symbol to provide the first channel estimate. The method of claim 31, wherein Determining a first channel estimate for the first signal instance uses a first segment of data samples from the received signal and the first estimated pilot corresponds to the first segment of data samples. The method of claim 39, Wherein the first segment comprises a data sample for a time period of the received signal. delete The method of claim 31, wherein The erasure factor

Deriving the step,

Using, Wherein h is the first channel estimate, N _t is the noise estimate, and N is the number of samples used to estimate h and N _t for the first signal instance. The method of claim 31, wherein Decimating a sample of the convolution of the predetermined transmit pulse and the receive filter function according to a phase associated with an estimated time offset of the first signal instance; Multiplying the first channel estimate by a decimated sample of a convolution of the predetermined transmit pulse and the receive filter function; Performing a convolution of a spread pilot signal and the product of the first channel estimate and the decimated sample to estimate a first pilot of the first signal instance. The method of claim 31, wherein Selecting a phase based on the estimated time offset of the first signal instance; Retrieving a predetermined filter coefficient corresponding to the convolution of the predetermined transmit pulse and the receive filter function using the selected phase; And multiplying the retrieved filter coefficients by the first channel estimate. The method of claim 31, wherein Estimating a first pilot of the first signal instance using the product of the convolution and the first channel estimate, performing a convolution of (a) a product of the convolution and the first channel estimate and (b) a spread pilot signal associated with the first signal instance. The method of claim 45, The first channel estimate, a spread pilot signal associated with the first signal instance, and the first estimated pilot correspond to a first segment of the received signal, wherein the first segment is data for a time period of the received signal. A method comprising a sample. The method of claim 45, And a spread pilot signal associated with the first signal instance has a phase corresponding to the arrival time of the first signal instance. The method of claim 31, wherein Demodulating data of the first signal instance using the estimated pilot-erase received signal. 49. The method of claim 48 wherein Demodulating the data of the first signal instance using the estimated pilot-erase received signal, Despreading the sample of the estimated pilot-erase received signal into a spreading sequence associated with the first signal instance to provide a despread sample; De-channelizing the despread sample with a data channelization code to provide a data symbol; And Demodulating the data symbol into a first channel estimate for the first signal instance to provide demodulated data for the first signal instance. The method of claim 31, wherein Determining the first channel estimate, deriving the product of the convolution and the first channel estimate, and estimating a first pilot of the first signal instance using the product of the convolution and the first channel estimate The steps are Determining the second channel estimate, deriving the product of the convolution and the second channel estimate, and estimating a second pilot of the second signal instance using the product of the convolution and the second channel estimate Occurring substantially in parallel with the step of doing so. The method of claim 31, wherein Determining the first channel estimate, deriving the product of the convolution and the first channel estimate, and estimating a first pilot of the first signal instance using the product of the convolution and the first channel estimate The steps are Determining the second channel estimate, deriving the product of the convolution and the second channel estimate, and estimating a second pilot of the second signal instance using the product of the convolution and the second channel estimate A method of generating a time division multiplexing method. The method of claim 31, wherein Accumulating the estimated first and second pilots, (a) accumulating a first pilot estimated according to a first estimated time offset of the first signal instance and (b) a second pilot estimated according to a second estimated time offset of the second signal instance. Including, method. The method of claim 31, wherein Accumulating the estimated first and second pilots occurs at a predetermined sample rate equal to the sample rate of the received signal. The method of claim 53 wherein And the sample rate is a multiple of the chip rate. Receiving a wireless signal comprising at least a first and a second signal instance each comprising a data and pilot signal; Determining a first channel estimate for the first signal instance; Estimating a first pilot of the first signal instance using the first channel estimate; Determining a second channel estimate for the second signal instance; Estimating a second pilot of the second signal instance using the second channel estimate; Accumulating the estimated first and second pilots; Filtering the accumulated estimated first and second pilots with a convolution of a predetermined transmit pulse and a receive filter function: and A method comprising: subtracting the estimated, accumulated, filtered first and second pilots from the received signal to derive an estimated pilot-erase received signal, the method comprising: The method, Determining a noise estimate of the first signal instance; Deriving an cancellation factor based on the first channel estimate and the noise estimate of the first signal instance; Generating a weighted channel estimate by multiplying the first channel estimate by the cancellation factor; And Estimating a first pilot of the first signal instance using the weighted channel estimate and a spread pilot signal associated with the first signal instance. Receiving a wireless signal comprising at least a first and a second signal instance each comprising a data and pilot signal; (a) processing a convolution of a predetermined transmit pulse and a receive filter function, and (b) processing a spread pilot signal associated with the first signal instance to generate a reconstructed pilot sample of the first signal instance; Determining a first channel estimate for the first signal instance; Multiplying the reconstructed pilot sample by the first channel estimate to derive a first pilot estimate of the first signal instance; (a) processing a convolution of the predetermined transmit pulse and the receive filter function and (c) a spread pilot signal associated with the second signal instance to generate a reconstructed pilot sample of the second signal instance; Determining a second channel estimate for the second signal instance; Multiplying the reconstructed pilot sample by the second channel estimate to derive a second pilot estimate of the second signal instance; Accumulating the first and second pilot estimates; And A method comprising: subtracting the accumulated first and second pilot estimates from the received signal to derive an estimated pilot-erase received signal; The method, Determining a noise estimate of the first signal instance; Deriving an cancellation factor based on the first channel estimate and the noise estimate of the first signal instance; Generating a weighted channel estimate by multiplying the first channel estimate by the cancellation factor; And Estimating a first pilot of the first signal instance using the weighted channel estimate and a spread pilot signal associated with the first signal instance.

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