US20090316768A1 - Method and apparatus for generating equalizer filter tap coefficients - Google Patents
Method and apparatus for generating equalizer filter tap coefficients Download PDFInfo
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- US20090316768A1 US20090316768A1 US12/490,614 US49061409A US2009316768A1 US 20090316768 A1 US20090316768 A1 US 20090316768A1 US 49061409 A US49061409 A US 49061409A US 2009316768 A1 US2009316768 A1 US 2009316768A1
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- equalizer
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- sampling
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/30—Time-delay networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
- H04L25/03019—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception
- H04L25/03038—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception with a non-recursive structure
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
- H04L2025/03375—Passband transmission
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03433—Arrangements for removing intersymbol interference characterised by equaliser structure
- H04L2025/03439—Fixed structures
- H04L2025/03445—Time domain
- H04L2025/03471—Tapped delay lines
- H04L2025/03477—Tapped delay lines not time-recursive
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03592—Adaptation methods
- H04L2025/03598—Algorithms
- H04L2025/03611—Iterative algorithms
- H04L2025/03617—Time recursive algorithms
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
- Filters That Use Time-Delay Elements (AREA)
- Dc Digital Transmission (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
A method and apparatus generating an error signal and an update vector signal used to generate filter tap coefficients for an equalizer filter residing in an equalizer. The equalizer filter outputs an equalized signal in response to receiving a sample data stream. The error signal is generated by down-sampling the equalized signal, subtracting the equalized signal from a reference signal, and filtering and down-sampling the resulting signal. Simultaneously, the update vector signal is generated by converting scalar samples of the sample data stream to a data vector signal and descrambling, filtering, and down-sampling the data vector signal. A tap coefficients generator is used to generate the filter tap coefficients for updating the equalizer filter based on the error signal and the update vector signal.
Description
- This application is a continuation of U.S. application Ser. No. 11/216,818, filed Aug. 31, 2005, which claims the benefit of U.S. Provisional Application No. 60/625,627, filed Nov. 5, 2004, which is incorporated by reference as if fully set forth.
- The present invention relates to an equalizer used in a receiver. More particularly, the present invention relates to a method and apparatus for generating tap coefficients for an equalizer filter residing in the equalizer.
- Adaptive equalizers, such as normalized least mean square (NLMS) equalizers which are used in wireless transmit/receive units (WTRUs) and base stations, optimize their associated filter tap weights through an iterative procedure to reach a convergence. In the case of a pilot-directed equalizer, an error signal used to generate an update of the equalizer tap weights is derived by measuring the difference between the locally generated reference signal and the output of the equalizer. For a frequency division duplex (FDD) system, this amounts to supplying a reference signal that corresponds to a scrambled, spread and/or scaled pilot signal such that data symbols have the desired amplitude.
- When operated at a chip rate, the output of a pilot-directed equalizer includes a plurality of signals superimposed on one another whereby only one of which is the pilot signal. Since the pilot signal is small in comparison to the total output signal, the error signal generated for filter coefficient adaptation includes mostly undesired signals.
- The present invention is related to a method and apparatus generating an error signal and an update vector signal used to generate filter tap coefficients for an equalizer filter residing in an equalizer. The equalizer filter outputs an equalized signal in response to receiving a sample data stream. The error signal is generated by down-sampling the equalized signal, subtracting the equalized signal from a reference signal, and filtering and down-sampling the resulting signal. Simultaneously, the update vector signal is generated by converting scalar samples of the sample data stream to a data vector signal and descrambling, filtering, and down-sampling the data vector signal. A tap coefficients generator is used to generate the filter tap coefficients for updating the equalizer filter based on the error signal and the update vector signal.
- A more detailed understanding of the invention may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings wherein:
-
FIG. 1 is a block diagram of an exemplary adaptive equalizer including an equalizer filter in accordance with the present invention; and -
FIG. 2 is a flow diagram of a process for generating tap coefficients for the equalizer filter of the adaptive equalizer ofFIG. 1 . - The preferred embodiments will be described with reference to the drawing figures where like numerals represent like elements throughout.
- Hereafter, the terminology “WTRU” includes but is not limited to a user equipment (UE), a mobile station, a laptop, a personal data assistant (PDA), a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to an access point (AP), a Node-B, a site controller or any other type of interfacing device in a wireless environment.
- The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components.
- The present invention is applicable to both a pilot-directed equalizer and a data-directed equalizer. For simplicity, the present invention will be explained with reference to only the pilot-directed equalizer.
- Hereafter, the present invention will be explained with reference to an NLMS algorithm. However, it should be noted that any type of adaptive equalization or filtering, such as least mean square (LMS), Griffith's algorithm, recursive least square (RLS), channel estimation based NLMS (CE-NLMS), and other iterative or recursive algorithms using error signal feedback in filter coefficient adaptation may be used.
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FIG. 1 is a block diagram of an exemplaryadaptive equalizer 100 in accordance with the present invention. The adaptive equalizer includes a serial-to-parallel (S→P) tovector converter 104, down-samplers descrambling multipliers vector version unit 118, atap coefficients generator 126, anequalizer filter 130, anadder 144 and anerror filter 150. - An input
sample data stream 102 is input to theequalizer filter 130 and the S→P tovector converter 104. Theequalizer filter 130 is preferably a finite impulse response (FIR) filter. Theequalizer filter 130 processes thesample data stream 102 with filter coefficients which are updated by thetap coefficients generator 126. The sequence of thesample data stream 102 may be generated at any sampling rate, but preferably two times (2×) the chip rate. Theequalizer filter 130 outputs an equalizedsignal 132 which is down-sampled by the down-sampler 134. - If the
sample data stream 102 undergoes over-sampling (OS), the equalizedsignal 132 is down-sampled by a factor of OS, by the down-sampler 134. The down-sampler 134 generates a down-sampledsignal 136 which is then multiplied with a scrambling code conjugatesignal 114, P(n), by thedescrambling multiplier 140 to generate a descrambled equalizedsignal 142 which is always maintained at the chip rate. The descrambled equalizedsignal 142 is then subtracted from areference signal 146 by theadder 144 to generate anerror signal 148 which is input to theerror filter 150. Thereference signal 146 may be a scaled pilot signal, (e.g., a pilot in a common pilot channel (CPICH)). Theerror signal 148 is filtered by theerror filter 150. For example, an N-moving average filter may be used as theerror filter 150, whereby N is a despreading factor that is applied to thereference signal 146. - The equalized
signal 132 includes a plurality of signals superimposed on one another, whereby only one is the pilot signal. Since the pilot signal is small in comparison to the total equalizedsignal 132, the resultingerror signal 148 is substantially an undesired signal. The error filter 150 (e.g., a low pass filter (LPF)) filters the undesired signal components from theerror signal 148 to generate a filterederror signal 152 which is optionally down-sampled by the down-sampler 154 at a desired down-sampling rate M to generate a down-samplederror signal 156. The down-samplederror signal 156 is input to thetap coefficients generator 126. - The S→P to
vector converter 104 converts the scalar samples of thesample data stream 102, x(n), to adata vector signal 106, X(n), such that X(n)={x(n), x(n−1), . . . , x(n−L)}, where L is the length of theequalizer filter 130. The S→P tovector converter 104 is similar to a tapped delay line (TDL) of theequalizer filter 130, whereby thedata vector signal 106 indicates the state of the TDL used to generate the equalizedsignal 132. Thedata vector signal 106 undergoes the same vector version of the processing (i.e., down-sampling, descrambling, filtering, followed by down-sampling) that the equalizedsignal 132 has undergone, such that the down-samplederror signal 156 and thedata vector signal 124 are kept aligned. - The
data vector signal 106 is down-sampled by the down-sampler 108 to generate a down-sampledvector signal 110. If thesample data stream 102 undergoes over sampling (OS), the down-sampledsignal 110 is down-sampled by the down-sampler 108 by a factor of OS and is then multiplied with the scrambling code conjugatesignal 114, P(n), by thedescrambling multiplier 112 to generate a descrambledvector signal 116. The error filtervector version unit 118 is essentially a bank of filters, where each filter in the bank is the substantially identical to theerror filter 150. The number of filters in the bank is equal to the length of the descrambledvector signal 116. Each element of the vector is effectively filtered in the same way as theerror filter 150. The error filtervector version unit 118 generates a filteredupdate vector signal 120 which is optionally down-sampled by the down-sampler 122 at a desired down-sampling rate M to generate a down-sampledupdate vector signal 124. The down-sampledupdate vector signal 124 is input to thetap coefficients generator 126. - The
tap coefficients generator 126 generatestap coefficients 128 for use by theequalizer filter 130 based on the down-sampledupdate vector signal 124 and the down-samplederror signal 156. The tap update may be performed using any type of adaptive equalization or filtering, such as LMS, Griffith's algorithm, RLS, CE-NLMS, or any other iterative or recursive algorithms using error signal feedback in filter coefficient adaptation. For example, the equation for the NLMS would be -
- where the down-sampled
update vector signal 124 is x, e is down-samplederror signal 156, parameters α, μ are optional leakage and step size parameters, respectively, and w is theupdated tap coefficients 128. The subscripts n and n−1 indicate that the previous value of w is used to compute the current value of w. The parameter ε is used to optionally prevent division by zero. - In accordance with the present invention, the
tap coefficients generator 126 operates with a cleaner error signal and provides better performance in terms of convergence speed and miss-adjustment. Down-sampling also permits lower complexity operation in very slow moving channels. - The present invention may be applied to diversity structures. For example, the outputs of two
equalizer filters 130 operating on two receive diversity antennas may be combined. The combined signal may then be descrambled and subtracted from a reference signal. The resulting error signal may be used to drive atap coefficients generator 126 associated with each antenna. -
FIG. 2 is a flow diagram of aprocess 200 including method steps for generatingtap coefficients 128 for theequalizer filter 130 ofFIG. 1 . Instep 205, theequalizer filter 130 is used to process an inputsample data stream 102 with filter coefficients to generate an equalizedsignal 132. Instep 210, the equalizedsignal 132 is down-sampled (by a factor of OS if the sample data stream undergoes over-sampling). Instep 215, a scramblingcode conjugate signal 114 is multiplied with the down-sampled equalizedsignal 136 to generate a descrambled equalizedsignal 142. Instep 220, anerror signal 148 is generated by subtracting the descrambled equalized signal 142 from areference signal 146. Instep 225, theerror signal 148 is filtered to generate a filterederror signal 152. Instep 230, the filterederror signal 152 is down-sampled at a desired down-sampling rate to generate a down-sampledfiltered error signal 156. Instep 235, scalar samples of thesample data stream 102, x(n), are converted to adata vector signal 106, X(n), such that X(n)={(x(n), x(n−1), . . . , x(n−L)}, wherein L is the length of theequalizer filter 130. Instep 240, thedata vector signal 106 is down-sampled (by a factor of OS if the sample data stream undergoes over-sampling). Instep 245, the scramblingcode conjugate signal 114 is multiplied with the down-sampled data vector signal to generate a descrambleddata vector signal 116. Instep 250, a filteredupdate vector signal 120 is generated based on the descrambleddata vector signal 116. Instep 255, the filteredupdate vector signal 120 is down-sampled at the desired down-sampling rate. Instep 260, tap coefficients are generated for theequalizer filter 130 based on the down-sampledfiltered error signal 156 ofstep 230 and the down-sampled filteredupdate vector signal 124 ofstep 255. - While the present invention has been described in terms of the preferred embodiment, other variations which are within the scope of the invention as outlined in the claims below will be apparent to those skilled in the art.
Claims (16)
1. An equalizer comprising:
at least one equalizer filter for processing at least one input sample data stream with filter coefficients from at least one antenna to generate at least one equalized signal;
a first multiplier configured to multiply a scrambling code conjugate signal with the at least one equalized signal to generate at least one descrambled equalized signal;
an adder configured to generate at least one error signal by subtracting the at least one descrambled equalized signal from a reference signal;
an error filter configured to filter the at least one error signal to generate at least one filtered error signal;
a tap coefficients generator configured to generate tap coefficients based on the at least one filtered error signal for updating the filter coefficients of the at least one equalizer filter; and
a first down-sampler inserted between the at least one equalizer filter and the first multiplier, the first down-sampler configured to down-sampling the at least one equalized signal, wherein the at least one equalized signal is down-sampled by the first down-sampler by a factor of over-sampling on a condition that the at least one sample data stream undergoes over-sampling.
2. The equalizer of claim 1 further comprising:
a second down-sampler inserted between the error filter and the tap coefficients generator, the second down-sampler configured to down-sampling the at least one filtered error signal at a desired down-sampling rate.
3. The equalizer of claim 1 wherein the at least one equalizer filter is a finite impulse response filter.
4. An equalizer comprising:
at least one equalizer filter configured to process at least one input sample data stream with filter coefficients from at least one antenna to generate at least one equalized signal;
a first multiplier configured to multiply a scrambling code conjugate signal with the at least one equalized signal to generate at least one descrambled equalized signal;
an adder configured to generate at least one error signal by subtracting the at least one descrambled equalized signal from a reference signal;
an error filter configured to filter the at least one error signal to generate at least one filtered error signal;
a tap coefficients generator configured to generate tap coefficients based on the at least one filtered error signal for updating the filter coefficients of the equalizer filter;
a serial-to-parallel to vector converter configured to convert scalar samples of the at least one sample data stream to at least one data vector signal;
a second multiplier configured to multiply the scrambling code conjugate signal with the at least one data vector signal to generate at least one descrambled data vector signal; and
an error filter vector version unit configured to generate at least one filtered update vector signal based on the at least one descrambled data vector signal, wherein the tap coefficients generated by the tap coefficients generator are also based on the at least one filtered update vector signal.
5. The equalizer of claim 4 further comprising:
a third down-sampler inserted between the serial-to-parallel to vector converter and the second multiplier for down-sampling the at least one data vector signal, wherein if the at least one sample data stream undergoes over-sampling, the at least one data vector signal is down-sampled by the third down-sampler by a factor of over-sampling.
6. The equalizer of claim 5 further comprising:
a fourth down-sampler inserted between the error filter vector version unit and the tap coefficients generator for down-sampling the at least one filtered update vector signal at a desired down-sampling rate.
7. The equalizer of claim 1 wherein the tap coefficients generator generates the tap coefficients based on a normalized least mean square algorithm.
8. An equalizer comprising:
an equalizer filter for processing at least one input sample data stream with filter coefficients from at least one antenna to generate at least one equalized signal;
a serial-to-parallel to vector converter which converts scalar samples of the at least one sample data stream to a data vector signal;
a first multiplier for multiplying the scrambling code conjugate signal with the at least one data vector signal to generate at least one descrambled data vector signal;
an error filter vector version unit for generating at least one filtered update vector signal based on the at least one descrambled data vector signal; and
a tap coefficients generator for generating tap coefficients based on the at least one filtered update vector signal for updating the filter coefficients of the at least one equalizer filter.
9. The equalizer of claim 8 further comprising:
a first down-sampler inserted between the serial-to-parallel to vector converter and the first multiplier for down-sampling the at least one data vector signal, wherein if the at least one sample data stream undergoes over-sampling, the at least one data vector signal is down-sampled by the first down-sampler by a factor of over-sampling.
10. The equalizer of claim 9 further comprising:
a second down-sampler inserted between the error filter vector version unit and the tap coefficients generator for down-sampling the at least one filtered update vector signal at a desired down-sampling rate.
11. The equalizer of claim 8 wherein the equalizer filter is a finite impulse response filter.
12. The equalizer of claim 8 further comprising:
a second multiplier for multiplying a scrambling code conjugate signal with the at least one equalized signal to generate at least one descrambled equalized signal;
an adder for generating at least one equalizer error signal by subtracting the at least one descrambled equalized signal from a reference signal; and
an equalized signal error filter for filtering the at least one equalizer error signal to generate at least one filtered equalizer error signal, wherein the tap coefficients generated by the tap coefficients generator are also based on the at least one filtered equalizer error signal.
13. The equalizer of claim 10 further comprising:
a second multiplier for multiplying a scrambling code conjugate signal with the at least one equalized signal to generate a descrambled equalized signal;
an adder for generating at least one equalizer error signal by subtracting the at least one descrambled equalized signal from a reference signal; and
an equalized signal error filter for filtering the at least one equalizer error signal to generate at least one filtered equalizer error signal, wherein the tap coefficients generated by the tap coefficients generator are also based on the at least one filtered equalizer error signal.
14. The equalizer of claim 10 further comprising:
a third down-sampler inserted between the at least one equalizer filter and the second multiplier for down-sampling the equalized signal, wherein if the at least one sample data stream undergoes over-sampling, the at least one equalized signal is down-sampled by the third down-sampler by a factor of over-sampling.
15. The equalizer of claim 14 further comprising:
a fourth down-sampler inserted between the second error filter and the tap coefficients generator for down-sampling the at least one filtered equalizer error signal at the desired down-sampling rate.
16. The equalizer of claim 8 wherein the tap coefficients generator generates the tap coefficients based on a normalized least mean square algorithm.
Priority Applications (1)
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US12/490,614 US20090316768A1 (en) | 2004-11-05 | 2009-06-24 | Method and apparatus for generating equalizer filter tap coefficients |
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US62562704P | 2004-11-05 | 2004-11-05 | |
US11/216,818 US7555040B2 (en) | 2004-11-05 | 2005-08-31 | Method and apparatus for generating equalizer filter tap coefficients |
US12/490,614 US20090316768A1 (en) | 2004-11-05 | 2009-06-24 | Method and apparatus for generating equalizer filter tap coefficients |
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US11/216,818 Continuation US7555040B2 (en) | 2004-11-05 | 2005-08-31 | Method and apparatus for generating equalizer filter tap coefficients |
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US12/490,614 Abandoned US20090316768A1 (en) | 2004-11-05 | 2009-06-24 | Method and apparatus for generating equalizer filter tap coefficients |
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US11/216,818 Expired - Fee Related US7555040B2 (en) | 2004-11-05 | 2005-08-31 | Method and apparatus for generating equalizer filter tap coefficients |
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EP (1) | EP1810399A4 (en) |
JP (1) | JP2008519558A (en) |
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CN (1) | CN101057400B (en) |
CA (1) | CA2585618A1 (en) |
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NO (1) | NO20072860L (en) |
TW (2) | TWI379514B (en) |
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Cited By (1)
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WO2011153414A1 (en) * | 2010-06-04 | 2011-12-08 | Research In Motion Limited | Message decoding for discretized signal transmissions |
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US20080063041A1 (en) * | 2006-09-08 | 2008-03-13 | Noam Galperin | Fast training equalization of a signal |
US8073046B2 (en) * | 2007-06-14 | 2011-12-06 | Zoran Corporation | Fast training equalization of a signal by using adaptive-iterative algorithm with main path phase correction |
TWI425765B (en) * | 2010-06-01 | 2014-02-01 | Etron Technology Inc | Equalizer and method of equalizing signals |
CN104038181B (en) * | 2014-06-05 | 2017-05-17 | 北京航空航天大学 | Self-adapting filter construction method based on NLMS algorithm |
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2005
- 2005-08-31 US US11/216,818 patent/US7555040B2/en not_active Expired - Fee Related
- 2005-10-18 KR KR1020077012224A patent/KR100867398B1/en not_active IP Right Cessation
- 2005-10-18 CA CA002585618A patent/CA2585618A1/en not_active Abandoned
- 2005-10-18 MX MX2007005454A patent/MX2007005454A/en not_active Application Discontinuation
- 2005-10-18 WO PCT/US2005/037654 patent/WO2006052406A2/en active Application Filing
- 2005-10-18 CN CN2005800382132A patent/CN101057400B/en not_active Expired - Fee Related
- 2005-10-18 JP JP2007540331A patent/JP2008519558A/en active Pending
- 2005-10-18 KR KR1020077014792A patent/KR20070086764A/en not_active Application Discontinuation
- 2005-10-18 EP EP05809794A patent/EP1810399A4/en not_active Withdrawn
- 2005-10-18 KR KR1020087026068A patent/KR20080102319A/en not_active Application Discontinuation
- 2005-10-19 TW TW095115808A patent/TWI379514B/en not_active IP Right Cessation
- 2005-10-19 TW TW094136620A patent/TWI326545B/en not_active IP Right Cessation
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- 2007-06-05 NO NO20072860A patent/NO20072860L/en not_active Application Discontinuation
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US8744015B2 (en) | 2010-06-04 | 2014-06-03 | Blackberry Limited | Message decoding for discretized signal transmissions |
Also Published As
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JP2008519558A (en) | 2008-06-05 |
WO2006052406A3 (en) | 2007-03-15 |
US7555040B2 (en) | 2009-06-30 |
EP1810399A2 (en) | 2007-07-25 |
KR100867398B1 (en) | 2008-11-06 |
CN101057400A (en) | 2007-10-17 |
KR20070086764A (en) | 2007-08-27 |
TW200713812A (en) | 2007-04-01 |
US20070189373A1 (en) | 2007-08-16 |
TWI326545B (en) | 2010-06-21 |
CA2585618A1 (en) | 2006-05-18 |
KR20070065919A (en) | 2007-06-25 |
TWI379514B (en) | 2012-12-11 |
KR20080102319A (en) | 2008-11-24 |
TW200625887A (en) | 2006-07-16 |
NO20072860L (en) | 2007-08-03 |
MX2007005454A (en) | 2007-05-21 |
EP1810399A4 (en) | 2007-12-05 |
WO2006052406A2 (en) | 2006-05-18 |
CN101057400B (en) | 2010-08-04 |
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