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WO1997013378A2 - Appareil et procede permettant de determiner et d'utiliser les informations d'etat de canal - Google Patents

Appareil et procede permettant de determiner et d'utiliser les informations d'etat de canal Download PDF

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Publication number
WO1997013378A2
WO1997013378A2 PCT/IL1996/000120 IL9600120W WO9713378A2 WO 1997013378 A2 WO1997013378 A2 WO 1997013378A2 IL 9600120 W IL9600120 W IL 9600120W WO 9713378 A2 WO9713378 A2 WO 9713378A2
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WO
WIPO (PCT)
Prior art keywords
signal
signals
state
channel
received
Prior art date
Application number
PCT/IL1996/000120
Other languages
English (en)
Other versions
WO1997013378A3 (fr
Inventor
Giora Silbershatz
Mordechai Ritz
Valentin Lupu
Amit Priebatch
Yehuda Aizenkot
Ran Gozali
Original Assignee
Geotek Communications, Inc.
Powerspectrum Technology Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Geotek Communications, Inc., Powerspectrum Technology Ltd. filed Critical Geotek Communications, Inc.
Priority to AU69994/96A priority Critical patent/AU6999496A/en
Publication of WO1997013378A2 publication Critical patent/WO1997013378A2/fr
Publication of WO1997013378A3 publication Critical patent/WO1997013378A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/22—Demodulator circuits; Receiver circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector

Definitions

  • the present invention relates to wireless communications. More particularly, it relates to apparatus and methods for determining the state of a frequency channel in a wireless communication channel and for using the channel state information.
  • a frequency channel in a wireless communication channel is subject to many sources of degradation. Thus, communication signals will not always be communicated properly on a frequency channel
  • channel estimators are known in the art, none adequately performs the tasks of determining the state of a frequency channel. Another shortcoming of existing communication systems is found in the usage of channel state information.
  • apparatus and method for determining the state of a frequency channel are needed. Further, apparatus and method for using the channel state information to control the operation of the communication system to achieve improved communication are also needed.
  • channel state information is derived from a set of communication symbols received during an individual time slot, although any set of communication signals or even a single communication signal can be used
  • QPSK modulated symbols are hard detected to determine the actual transmitted signal.
  • the in phase and quadrature components of the received communication symbols in the plane of the modulation points are determined.
  • the channel state is then determined from the ratio of the sum of the in phase components to the sum of the absolute value of the quadrature components.
  • the present invention also contemplates determining the channel state from the phase error of the received signals from the modulation points.
  • the present invention further contemplates determining the channel state from the distance error of received signals from the modulation points
  • method and apparatus for erasing communication signals in accordance with the channel state are provided.
  • the channel state is determined when the communication signal is received and then signals are erased if the channel state is not better than a predetermined level
  • method and apparatus for selecting one of two communication signals for processing when diversity signals are received
  • a first channel state is determined when the first of two diversity communication signals is received and a second channel state is determined when the second of the two diversity communication signals is received. Then, based on the values of the first and the second channel states, one of the two diversity communication signals is selected for further processing
  • FIG. 1 illustrates a wireless communication system in which the apparatus and method ofthe present invention is used
  • FIG. 2 shows the steps used to determine channel state by using the in phase and quadrature components of a received communication signal
  • FIG. 3 illustrate a modulation plane and the determination of channel state by using the in phase and quadrature components of received signals as in FIG. 1 ,
  • FIGS 4 and 5 illustrate an alternate process of determining channel state by using phase error of received signals
  • FIGS. 6 and 7 illustrate a process for determining channel state by using the Euclidean distance error of received signals and the respective modulation points
  • FIG. 8 illustrates the processing apparatus in the subscriber units used to determine channel state in accordance with any of the above processes
  • FIG. 9 illustrates the process in accordance with another aspect of the present invention wherein communication signals from one of two diversity channels are selected for processing
  • FIG. 10 illustrates the process in accordance with one aspect of the present invention wherein communication signals are erased.
  • FIG. 1 1 illustrates a metric decision zone
  • FIG. 1 illustrates a wireless communication system 1 in which the apparatus and method of the present invention can be used.
  • a base station 2 establishes communications with and between a plurality of mobile or portable subscriber units 4 and a plurality of dispatch stations 6.
  • the subscriber units 4 have the ability to communicate with each other and with the dispatch station 6.
  • the communication functions provided preferably include telephony, dispatch, one to one communications, data communications and other communication functions.
  • the communication links are provided between the above described components and over the PSTN.
  • the system of FIG. 1 preferably establishes communications over a plurality of frequency channels and in a plurality of time slots.
  • the communications over the frequency channels are preferably broken into packets which are "hopped" across the frequency channels — thus, a communication is transmitted over more than one frequency channel in accordance with a predetermined sequence, as described in United States Patent No. 5,408,496, which is hereby incorporated by reference.
  • Such a system is commonly referred to as a frequency hopping system.
  • the communications can also be "hopped" across the plurality of time slots.
  • different parts of a communication are transmitted in different time slots, again in accordance with a predetermined sequence.
  • the communication system 1 is shown as a sectorized system having three sectors 8 to 10.
  • the hopping sequences used in the sectors 8 to 10 are preferably orthogonal, as explained in United States Patent No 5,408,496
  • the present invention is not limited to sectorized communication systems or to frequency and/or time hopped communication systems
  • the preferred steps used to determine channel state are illustrated In the first step 100, after the received signals are demodulated, communication signals from one of the plurality of time slots in the time slotted communication system of FIG 1 are detected
  • communication signals received in the time slot consists of thirty-eight QPSK modulated symbols, each symbol falling into one of four quadrants in a modulation plane, the quadrant being specified by two bits
  • FIG. 3 a QPSK modulation plane having four modulation points 102 to 105 in quadrants 0 to 3, respectively, is shown
  • the two bits in the symbol determine which quadrant the symbol belongs in
  • step 100 hard detection -- a well known process -- assigns each symbol to one of the four quadrants This process simply determines the value of the received symbol and makes the quadrant assignment Thus, in FIG 3, symbol Sl, whose bits are 00, is assigned to quadrant 0 Symbol S2, whose bits are 01, is assigned to quadrant 2 Symbol S3, whose bits are 1 1, is assigned to quadrant 3 Symbol S4, whose bits are 10, is assigned to quadrant 1 This process is performed thirty-nine times, one time for each symbol in the time slot
  • each symbol is rotated to a selected one of the four quadrants, preferably quadrant 0
  • quadrant 0 is selected as the quadrant to which all symbols are rotated to, then the symbols are rotated according to the following
  • this process is illustrated with respect to symbols Sl to S4. Since symbol Sl is in quadrant 0, nothing is done and symbol S l remains in quadrant 0. Since symbol S2 is in quadrant 2, 90° is added to rotate symbol S2 to quadrant 0. Since symbol S3 is in quadrant 3, 180° is added to rotate symbol S3 to quadrant 0. Since symbol S4 is in quadrant 1 , 270° is added to rotate symbol S4 to quadrant 0. Again, this process is performed thirty-nine times, one time for each symbol in the time slot.
  • step 108 the in-phase component of each symbol in the x-y plane, which has axes intersecting the modulation points in the modulation plane as shown in FIG. 3, is determined. Since the symbol is a complex number, this is preferably performed by taking the real component of each symbol, Re(Si), where Si are the symbols in a time slot. Then, in step 1 10, the quadrature component of each symbol in the x-y plane is determined. Again, since the symbols are complex numbers, this is preferably done by taking the imaginary component of each symbol in the time slot: Imag(Si). In FIG. 3, the calculation of the in-phase component, Real(Sl), and the quadrature component, Imag(Sl), for one symbol, Sl , is illustrated. It is understood however that this process is preferably performed on each rotated symbol in a time slot.
  • step 112 the channel state of the frequency channel during the time slot that the symbols were received on is determined from the ratio of the sum of the in-phase components to the sum of the absolute value of the quadrature components.
  • the in-phase component from each symbol in the time slot is summed.
  • the absolute value ofthe quadrature component from each symbol is summed
  • the channel state is the ratio ofthe sum of the in-phase components to the sum of the absolute value of the quadrature components.
  • channel state, CS is preferably determined as follows.
  • two points — the nominal modulation point and the received signal point ⁇ are compared to determine channel state.
  • the calculation ofthe in-phase and quadrature components therefore, provides a measure of the variance or error between the received symbol and the actual transmitted symbol as determined by hard detection If the symbols in a time slot show a small deviation, the channel state is "good” since there was not much distortion If, on the other hand, there is a lot of deviation in the received symbols, the channel state is "poor"
  • the processing need not be restricted to the symbols in a time slot — more or less symbols can be used as desired
  • the use of the previously described processing steps is not limited to frequency hopping and time hopping communication systems — they may be used on any type of communication system
  • a plurality of symbols are used, they need not be rotated to one quadrant in the modulation plane as described above; instead the processing can be done within the quadrant that the symbol belongs to and the results averaged accordingly
  • the processing of the present invention can be used with any modulation scheme
  • FIGS 4 and 5 illustrate the determination of the channel state via an alternate embodiment
  • the first two steps 120 and 122 are the same as steps 100 and 106 previously described with respect to FIG 2
  • step 120 hard detection ofthe demodulated received symbols is performed to determine the modulation point ofthe demodulated received signal and, in step 122, all of the received signals from a time slot are rotated to one quadrant in the modulation plane
  • the rotation of four symbols Sl to S4 are illustrated in FIG. 5
  • step 1208 the average phase error of the symbols within a slot is determined using the absolute value ofthe phase error
  • the average phase error of the symbols within a slot can be determined using the square ofthe phase error from each symbol
  • the channel state, CS is determined in accordance with ⁇ (avg).
  • the exact relationship between the channel state and the average phase error i.e. what is "good” and what is “poor" is preferably determined empirically for each communication system, but in general, the greater the average phase error, the worse the channel state and the lower the average phase error, the better the channel state
  • FIGS. 6 and 7 illustrate the determination of the channel state via another alternate embodiment.
  • the first two steps 140 and 142 are the same as steps 100 and 106 previously described with respect to FIG. 2
  • step 140 hard detection of the received symbols is performed to determine the modulation point ofthe received signal and, in step 142, all ofthe received symbols from a time slot are rotated to one quadrant in the modulation plane
  • the rotations of four symbols Sl to S4 are illustrated in FIG. 7.
  • step 144 the Euclidean distance error of each rotated signal is dete ⁇ nined.
  • the Euclidean distance error, El for one received signal, Sl, is the distance between the modulation point of the quadrant that the received signal is in — in this case modulation point 146 ⁇ and the signal S l
  • the absolute value of the Euclidean distance error for each received signal is determined.
  • the channel state, CS is determined from the average distance error Ei of symbols within a time slot
  • step 152 it is further preferred to normalize CS to the average absolute value of the symbols in a time slot
  • the exact relationship between the channel state and the average Euclidean distance error is preferably determined empirically for each communication system, but in general, the greater the average distance error, the worse the channel state and the lower the average distance error, the better the channel state
  • the transmit circuitry which is not important to the present invention, includes a transmitter 200 and a gain control circuit 202 which are controlled, in part, by a frequency synthesizer 204 Signals are transmitted through a duplexer 206 and an antenna 208
  • communication signals are received on the antenna 208 and on a second antenna 210.
  • Two receivers 212 and 214 receive the signals from the antennas 208 and 210, respectively.
  • the frequency channel of reception is programmed into the receivers 212 and 214 by the synthesizer 204.
  • the receivers 212 and 214 are gain and frequency controlled by a circuit 216.
  • the received signals from both antennas 208 and 210 are preferably sent to the modem 218.
  • the modem 218 converts the received signals to digital signals.
  • the modem 218 preferably includes a digital signal processor (DSP), preferably Analog Devices 2111, 2171 or 2181, and a ASIC device 230. These devices process the signals received from both receivers 212 and 214 in accordance with the previously described steps.
  • DSP digital signal processor
  • the processing is controlled by a controller 220.
  • the processed signals are further processed to extract voice and other information by a voice processing package (VPP) 222 and the processed communication signals are provided to a user interface 224 through the interface 226.
  • VPP voice processing package
  • the user interface 224 includes the usual devices found in subscriber units, including a display, speakers and microphones.
  • the circuitry of FIG. 8 can be used to calculate the variation or error associated with received communication signals in accordance with any of the previously described processes.
  • the circuitry of FIG. 8 can calculate in-phase and quadrature components, phase error and/or distance errors associated with the received signals.
  • the channel state CS that is computed from received signals by the processing circuitry of FIG. 8 can be utilized to select between the two signals simultaneously received on the antennas 208 and 210 and by the receivers 212 and 214, respectively. This reception of dual signals is commonly referred to as "diversity" reception.
  • step 300 the channel state for the first receive channel, CS 1 , which is generated by any of the previously described processes or by any other process, from the signals (or signal) received on antenna 208, is determined.
  • step 302 the channel state for the second receive channel, CS2, which is generated as previously described or by any other process, from the signals (or signal) received on antenna 210, is determined.
  • step 304 the channel states from each receive channel are compared. If we assume that the process of FIGS. 2 and 3 are used to calculate the channel state for each receive channel, then the following comparison is made
  • step 306 channel 1 is selected Thus, the signals from antenna 208 are selected for processing
  • step 308 channel 2 is selected so that the signals from the antenna 210 are selected for processing
  • the processing is performed by the circuitry of FIG. 8, in particular, in the digital signal processor in the modem 218
  • the selection of signals from one of two channels for processing is preferably done every time channel states are recalculated
  • the channel states for the diversity channels are calculated for each time slot, it is the signals from the time slot of one of the channels that are selected for processing
  • a new selection is then made for every time slot
  • channel state is determined from another period of signals, by way of example only, from a single signal, then the signals from the period that is used to calculate channel state are the ones selected for processing
  • the channel state CS that is computed from received signals by the processing circuitry of FIG 8 can also be utilized to erase signals which are not received with some minimum confidence level
  • the confidence level is preferably determined in accordance with the channel state
  • the channel state of a receive signal or of a group of receive signals — for example, the signals in a selected time slot — is determined This can either be the channel state of the selected one ofthe two receive channels or it can be the channel state of a single receive channel.
  • the channel state is compared to a threshold, th If the comparison fails, that is, if the channel state is not better than some value represented by the threshold, it is preferred to erase the signal in step 354 If the comparison passes, that is if the channel state is better than some value represented by the threshold, in step 356, the signal is passed on for further processing. Whether “better” means greater or less than the threshold depends on the process used to determine channel state.
  • the number of signals erased preferably coincides with the number of signals used to calculate the channel state.
  • the channel state is calculated from signals in a time slot, it is the signals from the time slot of one of the channels that are erased in step 354.
  • the signals from the period that is used to calculate channel state are the signals that are erased in step 354. So for example only, if channel state were calculate based on a single received signal, then it is prefe ⁇ ed to erase only the single signal in step 354.
  • the prefe ⁇ ed value of the threshold, th depends on the method of calculating channel state. If channel state is calculated via the in-phase and quadrature components of the received signals in a time slot, then the threshold is preferably 3.5 and the erasure is made in step 354 if the channel state of received signals in a time slot falls below that number. If the channel state is calculated via the phase error of the received signals in a time slot, then the threshold th is preferably 0.085 and the erasure is made in step 354 if the channel state o the received signals in the time slot exceeds that number.
  • the erasure is preferably made by setting a metric, which is a number associated with each received signal that represents the confidence level that the received signal was properly received, to a predetermined value, typically the lowest value.
  • a metric which is a number associated with each received signal that represents the confidence level that the received signal was properly received
  • a predetermined value typically the lowest value.
  • a communication device receiving a communication signal performs two measures of channel state and uses one of the channel states to perform diversity selection and the other channel state to perform erasures.
  • the channel state dete ⁇ nined by phase e ⁇ or measurements (FIGS. 4 and 5) is used to perform erasures of poorly received signals while the channel state determined by distance e ⁇ or measurements (FIGS. 6 and 7) is used to select one ofthe two diversity channels.
  • MSD, MHD according to routine Generate metrics, MSD and MHD, for soft and hard decisions, respectively; see the metrics generation routine
  • MET0[i] TABLE 1 (MSD); Apply MSD to Table 1 (see below) which is an example ofthe metrics prefe ⁇ ed for a specific communication system.
  • the table generates a 3 bit metric, MET0[i], where i is the symbol number within the time slot being processed.
  • One bit ofthe metric MET0[i] is I and two bits are the confidence level.
  • METl[i] TABLE2(MSD); Apply MSD to Table 2 (see below).
  • the table generates a 3 bit metric, METl[i], where i is the symbol number within the time slot being processed.
  • One bit ofthe metric METl [i] is Q and two bits are the confidence level.
  • CS_Y: CS_Y +
  • CSmin is the threshold to which
  • I 0 (represented by OXX, i.e. ⁇ 4, where 0 is the bit and XX is the confidence level associated with the bit) erase by setting confidence level to the minimum value, 00, which causes the digital signal processor to erase the bit.
  • MET 0[i] 0.
  • I 1 (represented by 1XX, i.e. > 3, where 1 is the bit and XX is the confidence level associated with the bit) erase by setting confidence level to the minimum value, 00, which causes the digital signal processor to erase the bit.
  • METOfi] 4.
  • A0 : CS X0* CS Yl 0 and 1 indicate the diversity channels
  • channel 0 if AO > Al and select the values from channel 1 if Al > AO.
  • R 3 0 ⁇ ⁇ ⁇ 1.225. IO *3
  • the boundaries should be less than 1; see FIG. 11 for the generated metric decision zones, including the five possible rings.
  • MHD places the signal on one of four quadrants.
  • MET0[1] and MET1 [1] are generated by applying MSD to TABLE 1 and TABLE 2, respectively:
  • Erasures are made, if at all, once all of the symbols in the time slot have been processed. If the channel state falls below a threshold, CS min, then the confidence bits for all symbols in a time slot, Si, are set to "null values", which are of low level of confidence, like 00. The processing then changes the values of the I and the Q bits to null metrics which do not contribute to an e ⁇ oneous decision at the e ⁇ or co ⁇ ecting process. Essentially, the erasure means that the I and Q information content from the time slot is not used. Thus, if an erasure needs to be made, the following occurs:

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Quality & Reliability (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Transmission System (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

La présente invention concerne un appareil et un procédé permettant de calculer l'état de canal correspondant à des signaux reçus, l'état de canal se déduisant des signaux reçus par analyse de ceux-ci. L'invention concerne également un appareil et un procédé permettant, en se référant à l'état de canal, de réaliser des effacements de signaux reçus et de faire une sélection entre signaux de communication à diversité.
PCT/IL1996/000120 1995-10-01 1996-10-01 Appareil et procede permettant de determiner et d'utiliser les informations d'etat de canal WO1997013378A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU69994/96A AU6999496A (en) 1995-10-01 1996-10-01 Apparatus and method for determining and using channel state information

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IL11547695A IL115476A0 (en) 1995-10-01 1995-10-01 Apparatus and method for determining and using channel state information
IL115476 1995-10-01

Publications (2)

Publication Number Publication Date
WO1997013378A2 true WO1997013378A2 (fr) 1997-04-10
WO1997013378A3 WO1997013378A3 (fr) 1997-06-05

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AU (1) AU6999496A (fr)
CA (1) CA2233723A1 (fr)
IL (1) IL115476A0 (fr)
WO (1) WO1997013378A2 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2342546A (en) * 1998-10-01 2000-04-12 British Broadcasting Corp Measuring channel state from a received signal and discriminating digital values from a received signal, suitable for use in COFDM
US6174311B1 (en) 1998-10-28 2001-01-16 Sdgi Holdings, Inc. Interbody fusion grafts and instrumentation
GB2355164A (en) * 1999-10-07 2001-04-11 Oak Technology Inc COFDM demodulator circuit for a digital television receiver
US6371988B1 (en) 1996-10-23 2002-04-16 Sdgi Holdings, Inc. Bone grafts
EP1408621A4 (fr) * 2001-07-13 2006-08-30 Kawasaki Microelectronics Inc Appareil de reception amrc et procede de reception amrc
US7106810B2 (en) 1999-10-07 2006-09-12 Matthew James Collins Method and apparatus for a demodulator circuit
US7221720B2 (en) 2001-05-03 2007-05-22 British Brodcasting Corporation Decoders for many-carrier signals, in particular in DVB-T receivers
US7273498B2 (en) 1997-06-03 2007-09-25 Warsaw Orthopedic, Inc. Open intervertebral spacer
US7276081B1 (en) 1995-10-16 2007-10-02 Warsaw Orthopedic, Inc. Bone grafts

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69103196T2 (de) * 1990-04-27 1995-02-23 Nippon Telegraph & Telephone Antennenauswahl-Diversity-Empfangssystem.
US5214675A (en) * 1991-07-02 1993-05-25 Motorola, Inc. System and method for calculating channel gain and noise variance of a communication channel
US5351274A (en) * 1993-08-20 1994-09-27 General Electric Company Post detection selection combining diversity receivers for mobile and indoor radio channels
US5530926A (en) * 1993-10-04 1996-06-25 Motorola, Inc. Method for operating a switched diversity RF receiver

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7981156B2 (en) 1995-10-16 2011-07-19 Warsaw Orthopedic, Inc. Bone grafts
US7276081B1 (en) 1995-10-16 2007-10-02 Warsaw Orthopedic, Inc. Bone grafts
US6371988B1 (en) 1996-10-23 2002-04-16 Sdgi Holdings, Inc. Bone grafts
US7273498B2 (en) 1997-06-03 2007-09-25 Warsaw Orthopedic, Inc. Open intervertebral spacer
US7993406B2 (en) 1997-06-03 2011-08-09 Warsaw Orthopedic, Inc. Open intervertebral spacer
US7678149B2 (en) 1997-06-03 2010-03-16 Warsaw Orthopedic, Inc. Open intervertebral spacer
US7329283B2 (en) 1997-06-03 2008-02-12 Warsaw Orthopedic, Inc. Open intervertebral spacer
EP0991239A3 (fr) * 1998-10-01 2003-08-20 British Broadcasting Corporation Etablissement de seuils de quantification dans des récepteurs multiporteurs
GB2342546A (en) * 1998-10-01 2000-04-12 British Broadcasting Corp Measuring channel state from a received signal and discriminating digital values from a received signal, suitable for use in COFDM
GB2342546B (en) * 1998-10-01 2003-10-22 British Broadcasting Corp Improvements relating to measuring channel state from a received signal and discriminating digital values from a received signal, suitable for use in cofdm
US7479160B2 (en) 1998-10-28 2009-01-20 Warsaw Orthopedic, Inc. Interbody fusion grafts and instrumentation
US6610065B1 (en) 1998-10-28 2003-08-26 Sdgi Holdings, Inc. Interbody fusion implants and instrumentation
US7625374B2 (en) 1998-10-28 2009-12-01 Warsaw Orthopedic, Inc. Interbody fusion grafts and instrumentation
US7637953B2 (en) 1998-10-28 2009-12-29 Warsaw Orthopedic, Inc. Interbody fusion grafts and instrumentation
US6174311B1 (en) 1998-10-28 2001-01-16 Sdgi Holdings, Inc. Interbody fusion grafts and instrumentation
US7998209B2 (en) 1998-10-28 2011-08-16 Warsaw Orthopedic, Inc Interbody fusion grafts and instrumentation
US7106810B2 (en) 1999-10-07 2006-09-12 Matthew James Collins Method and apparatus for a demodulator circuit
GB2355164B (en) * 1999-10-07 2004-06-09 Oak Technology Inc Demodulator circuit
WO2001026318A3 (fr) * 1999-10-07 2001-12-06 Oak Technology Inc Circuit demodulateur
GB2355164A (en) * 1999-10-07 2001-04-11 Oak Technology Inc COFDM demodulator circuit for a digital television receiver
US7221720B2 (en) 2001-05-03 2007-05-22 British Brodcasting Corporation Decoders for many-carrier signals, in particular in DVB-T receivers
EP1408621A4 (fr) * 2001-07-13 2006-08-30 Kawasaki Microelectronics Inc Appareil de reception amrc et procede de reception amrc

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Publication number Publication date
IL115476A0 (en) 1996-05-14
CA2233723A1 (fr) 1997-04-10
AU6999496A (en) 1997-04-28
WO1997013378A3 (fr) 1997-06-05

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