WO1999018686A1 - Coding and modulating system - Google Patents

Coding and modulating system Download PDF

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Publication number
WO1999018686A1
WO1999018686A1 PCT/IL1998/000478 IL9800478W WO9918686A1 WO 1999018686 A1 WO1999018686 A1 WO 1999018686A1 IL 9800478 W IL9800478 W IL 9800478W WO 9918686 A1 WO9918686 A1 WO 9918686A1
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WO
WIPO (PCT)
Prior art keywords
output
dynamic table
inverse
signals
walsh function
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PCT/IL1998/000478
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French (fr)
Inventor
Doron Koren
Sergey Toujikov
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Telescicom Ltd.
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Filing date
Publication date
Application filed by Telescicom Ltd. filed Critical Telescicom Ltd.
Priority to AU94563/98A priority Critical patent/AU9456398A/en
Publication of WO1999018686A1 publication Critical patent/WO1999018686A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0007—Code type
    • H04J13/004—Orthogonal
    • H04J13/0048—Walsh
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/10—Code generation

Definitions

  • the present invention relates to coding and modulating systems for telecommunications.
  • conventional CDMA systems include a modulator and a spreading mechanism.
  • the modulator modulates the information and the spreading mechanism is connected to a PN code generator.
  • the spreading mechanism is a simple BPSK (binary shift keying) modulation device, whose efficiency is low.
  • conventional CDMA systems assign a different PN code to each one of the users.
  • the receiver includes a despreader and a demodulator.
  • the despreader must be synchronized first, then the demodulator is synchronized. If the despreader is not synchronized, it is impossible to synchronize the demodulator. This leads to a low efficiency differential modulation scheme in order to permit efficient synchronization.
  • a coding and modulating system including a combined modulator/demodulator and spreading/despreading mechanism (spreadulator).
  • the spreadulator preferably includes an information vector generator (IVG), a dynamic Table coupled to the output of the information vector generator, a multiplication block coupled to the output of the dynamic Table, a Walsh function generator (WFG) coupled to the multiplication block, a summation block coupled to the output of the multiplication block, and a dynamic limiter for limiting the output of the summation block.
  • IVG information vector generator
  • WFG Walsh function generator
  • a coding and modulating system including a transmitting unit including: a spreadulator for modulating and spreading input data including an information vector generator (IVG), a dynamic Table coupled to the output of the information vector generator, a multiplication block coupled to the output of said dynamic Table, a Walsh function generator (WFG) coupled to the multiplication block, a summation block coupled to the output of the multiplication block, and a dynamic limiter for limiting the output of the summation block; a second dynamic table coupled via a bus to the dynamic limiter for converting input signals to I and Q buses including a multiplier where the signals are multiplied by coherent sin and cosin waveforms, a summation element, and an RF front-end.
  • IVG information vector generator
  • WFG Walsh function generator
  • the coding and modulating system further includes a receiving unit including: a front end for receiving transmitted signals, a multiplier for multiplying the received signals by sin and cosine coherent waveforms, an Analog to Digital (A/D) converter, an inverse dynamic table arranged to receive the multiplied digital signals, the inverse dynamic table being the inverse of the second transmitting dynamic table, a TelesciCOM fast transform (TFT) unit for transforming the input signals to a Walsh function spectrum, a management block for synchronizing the output Walsh function spectrum, a second inverse dynamic table which is the inverse of the spreadulator dynamic table, and an inverse information vector generator which is the inverse of the transmitting information generator for generating output signals substantially identical to the input signals in the transmitting unit.
  • a receiving unit including: a front end for receiving transmitted signals, a multiplier for multiplying the received signals by sin and cosine coherent waveforms, an Analog to Digital (A/D) converter, an inverse dynamic table arranged to receive the multiplied digital signals, the inverse
  • the management block includes a threshold detector for dispersed noise of each information block, a comparator for comparing the detected dispersed noise with the average noise dispersion level so as to detect a minimum noise dispersion level, a phase lock loop to integrate several information blocks, and means for providing a synchronization pulse to the fast transform unit.
  • the TFT unit includes a multiple channel butterfly Walsh function correlation block.
  • the management block detects a minimum noise dispersion level according to the formulae: wherein ⁇ is the noise dispersion , ⁇ bar is the average noise level, and ⁇ is the minimum noise dispersion level.
  • a method of coding and modulating for radio telecommunication including the steps of: modulating input data in an information vector generator in a spreadulator, spreading the input data using a Walsh function generator in the spreadulator, summing the output in a summation block, limiting the output of the summation block in a dynamic limiter, converting the limited signals to I and Q buses in a dynamic table coupled via a bus to the dynamic limiter, multiplying the signals by sin and cosin coherent waveforms, summing the multiplied signals, and transmitting the sum.
  • the method further includes receiving the transmitted signals in a receiving unit, multiplying the received signals by coherent waveforms in a multiplier, converting analog signals to digital signals, converting the limited signals from I and Q buses in an inverse dynamic table, the inverse dynamic table being the inverse of the transmitting dynamic table, transforming the input signals to a Walsh function spectrum in a fast transform unit, synchronizing the output Walsh function spectrum in a management block, and generating output signals substantially identical to the input signals in the transmitting unit in an inverse information vector generator which is the inverse of the transmitting information generator.
  • Fig. 1 is a schematic illustration of a transmitting unit according to one embodiment of the invention.
  • Fig. 2 is a schematic illustration of a receiving unit according to one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION
  • the present invention relates to a multilevel spreading system having very high efficiency which is capable of easily synchronizing in the receiving unit, without losing any energy, even in a noisy environment, unlike conventional systems where resources must be diverted for synchronization.
  • the use of a combined modulator/demodulator and spreading/ despreading mechanism means that we can easily synchronize the receiver and easily recover information. It is a property of the invention that, unlike conventional CDMA, it can reallocate processing gain from unactivated users to activated users.
  • the invention uses a family of Walsh functions in such a way that we first generate the whole set of functions in one block.
  • Fig. 1 there is shown a schematic illustration of a transmitting unit 10 according to the invention including a combined modulator/demodulator and spreader/despreader (spreadulator 12) according to the invention.
  • Input serial bit information is transferred to a symbol by an information vector generator 14 in spreadulator 12, which generates a vector of bits.
  • Each one of the output bits is multiplied by the series of Walsh functions.
  • the information vector generator (IVG) 14 is a block whose input is at least one user serial bit or several users (i.e., multi-channel serial data) and the output is an information vector. In the case of one user, IVG 14 copies each bit to all of the vector.
  • the output of IVG 14 is input to a first dynamic table 18.
  • Dynamic table 18 may be a dynamic permutation table or any other selected table.
  • the data output from the dynamic table 18 is input to a multiplication block 19.
  • the system of the present invention uses a Walsh function generator 16 with series of functions.
  • the data from dynamic table 18 is multiplied by the output of Walsh function generator 16 in multiplication block 19: the first bit XOR with the first Walsh function, the second bit XOR with the second Walsh function, and so on.
  • the level of modulation is unlimited, depending only on the selected set of Walsh functions. Any desired set of Walsh functions can be used, preferably from 16 and above, merely by using more gates and adding more gain.
  • Walsh function generator 16 is coupled to dynamic table 18 and is arranged to produce a high order Walsh function in order to utilize a selected table from among many different tables in dynamic table 18.
  • the information output by multiplication block 19 goes to a summation block 20.
  • the ouput goes to a dynamic limiter 22 which cuts over-shooting and also takes very low signals and stretches them into zero, reducing the dynamic band.
  • the energy above a certain level is not transmitted and lower than certain level is also cut off. While this reduces by a small amount the amount of information transmitted, this information can easily be recovered in the receiver.
  • the system transfers energy from unused levels into the most used levels, thereby increasing average bit energy.
  • the signals go via a bus 24 to a second dynamic table 26, which converts them into I and Q buses. It is a property of dynamic table 26 that is can easily incorporate security codes and differentiate among different users. From the I and Q buses, the signals are multiplied by coherent sin and cosin waveforms, summed in a summation block 28, and transmitted to the air via a conventional RF transmitting front end 30.
  • TFT unit 40 includes a multiple channel butterfly Walsh function correlation block, and serves to transform the input signals to a Walsh function spectrum. In essence, it is a very efficient multilevel/ multichannel correlator.
  • the management block 42 includes a phase lock loop in order to integrate several information blocks so as to achieve better noise immunity.
  • the management block 42 provides a synchronization pulse to TFT 40 and, at the moment of synchronization, the information in TFT 40 is loaded into a second inverse dynamic table 44.
  • Second inverse dynamic table 44 is the inverse of the dynamic table 18 in spreadulator 12 in the transmitting unit. From inverse dynamic table 44, the information is input into an inverse information vector generator 46 which is the inverse of IVG 14 in the transmitter. Inverse IVG 46 in the receiving unit outputs serial information which corresponds to the information as originally input.

Abstract

A coding and modulating system including a combined modulator/demodulator and spreading/despreading mechanism. In particular, a coding and modulating system wherein the combined modulator/demodulator and spreading/despreading mechanism includes an information vector generator (IVG), a dynamic Table coupled to the output of the information vector generator, a multiplication block for receiving the output of the dynamic Table, a Walsh function generator (WFG) coupled to the multiplication block, a summation block coupled to the output of the multiplication block, and a dynamic limiter for limiting the output of the summation block.

Description

CODING AND MODULATING SYSTEM
FIELD OF THE INVENTION The present invention relates to coding and modulating systems for telecommunications.
BACKGROUND OF THE INVENTION
Many coding and modulating systems are known in the telecommunications art. These include the QAM family, CDMA, the QPSK family, among others.
For example, conventional CDMA systems include a modulator and a spreading mechanism. The modulator modulates the information and the spreading mechanism is connected to a PN code generator. In conventional CDMA systems, the spreading mechanism is a simple BPSK (binary shift keying) modulation device, whose efficiency is low. In order to differentiate between users, conventional CDMA systems assign a different PN code to each one of the users.
The receiver includes a despreader and a demodulator. The despreader must be synchronized first, then the demodulator is synchronized. If the despreader is not synchronized, it is impossible to synchronize the demodulator. This leads to a low efficiency differential modulation scheme in order to permit efficient synchronization.
It is an object of the invention to increase the efficiency of the spreading system. This is accomplished by combining the modulator and spreader into one block (referred to hereinbelow as a spreadulator). This increases the number of bits per second per Hertz so that a larger quantity of information can be transmitted in the same bandwidth.
SUMMARY OF THE INVENTION According to the present invention, there is provided a coding and modulating system including a combined modulator/demodulator and spreading/despreading mechanism (spreadulator). The spreadulator preferably includes an information vector generator (IVG), a dynamic Table coupled to the output of the information vector generator, a multiplication block coupled to the output of the dynamic Table, a Walsh function generator (WFG) coupled to the multiplication block, a summation block coupled to the output of the multiplication block, and a dynamic limiter for limiting the output of the summation block.
According to a preferred embodiment of the invention, there is provided a coding and modulating system including a transmitting unit including: a spreadulator for modulating and spreading input data including an information vector generator (IVG), a dynamic Table coupled to the output of the information vector generator, a multiplication block coupled to the output of said dynamic Table, a Walsh function generator (WFG) coupled to the multiplication block, a summation block coupled to the output of the multiplication block, and a dynamic limiter for limiting the output of the summation block; a second dynamic table coupled via a bus to the dynamic limiter for converting input signals to I and Q buses including a multiplier where the signals are multiplied by coherent sin and cosin waveforms, a summation element, and an RF front-end.
Further according to a preferred embodiment, the coding and modulating system further includes a receiving unit including: a front end for receiving transmitted signals, a multiplier for multiplying the received signals by sin and cosine coherent waveforms, an Analog to Digital (A/D) converter, an inverse dynamic table arranged to receive the multiplied digital signals, the inverse dynamic table being the inverse of the second transmitting dynamic table, a TelesciCOM fast transform (TFT) unit for transforming the input signals to a Walsh function spectrum, a management block for synchronizing the output Walsh function spectrum, a second inverse dynamic table which is the inverse of the spreadulator dynamic table, and an inverse information vector generator which is the inverse of the transmitting information generator for generating output signals substantially identical to the input signals in the transmitting unit.
According to one embodiment of the invention, the management block includes a threshold detector for dispersed noise of each information block, a comparator for comparing the detected dispersed noise with the average noise dispersion level so as to detect a minimum noise dispersion level, a phase lock loop to integrate several information blocks, and means for providing a synchronization pulse to the fast transform unit.
According to one embodiment of the invention the TFT unit includes a multiple channel butterfly Walsh function correlation block.
Further according to an embodiment of the invention, the management block detects a minimum noise dispersion level according to the formulae:
Figure imgf000005_0001
wherein Ν is the noise dispersion , Ν bar is the average noise level, and δ is the minimum noise dispersion level.
There is also provided in accordance with the present invention a method of coding and modulating for radio telecommunication including the steps of: modulating input data in an information vector generator in a spreadulator, spreading the input data using a Walsh function generator in the spreadulator, summing the output in a summation block, limiting the output of the summation block in a dynamic limiter, converting the limited signals to I and Q buses in a dynamic table coupled via a bus to the dynamic limiter, multiplying the signals by sin and cosin coherent waveforms, summing the multiplied signals, and transmitting the sum.
Further according to a preferred embodiment, the method further includes receiving the transmitted signals in a receiving unit, multiplying the received signals by coherent waveforms in a multiplier, converting analog signals to digital signals, converting the limited signals from I and Q buses in an inverse dynamic table, the inverse dynamic table being the inverse of the transmitting dynamic table, transforming the input signals to a Walsh function spectrum in a fast transform unit, synchronizing the output Walsh function spectrum in a management block, and generating output signals substantially identical to the input signals in the transmitting unit in an inverse information vector generator which is the inverse of the transmitting information generator.
BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further understood and appreciated from the following detailed description taken in conjunction with the drawings in which:
Fig. 1 is a schematic illustration of a transmitting unit according to one embodiment of the invention; and
Fig. 2 is a schematic illustration of a receiving unit according to one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a multilevel spreading system having very high efficiency which is capable of easily synchronizing in the receiving unit, without losing any energy, even in a noisy environment, unlike conventional systems where resources must be diverted for synchronization. The use of a combined modulator/demodulator and spreading/ despreading mechanism (spreadulator) means that we can easily synchronize the receiver and easily recover information. It is a property of the invention that, unlike conventional CDMA, it can reallocate processing gain from unactivated users to activated users.
The invention uses a family of Walsh functions in such a way that we first generate the whole set of functions in one block. Looking now at Fig. 1, there is shown a schematic illustration of a transmitting unit 10 according to the invention including a combined modulator/demodulator and spreader/despreader (spreadulator 12) according to the invention. Input serial bit information is transferred to a symbol by an information vector generator 14 in spreadulator 12, which generates a vector of bits. Each one of the output bits is multiplied by the series of Walsh functions. The information vector generator (IVG) 14 is a block whose input is at least one user serial bit or several users (i.e., multi-channel serial data) and the output is an information vector. In the case of one user, IVG 14 copies each bit to all of the vector.
The output of IVG 14 is input to a first dynamic table 18. Dynamic table 18 may be a dynamic permutation table or any other selected table. The data output from the dynamic table 18 is input to a multiplication block 19. The system of the present invention uses a Walsh function generator 16 with series of functions. The data from dynamic table 18 is multiplied by the output of Walsh function generator 16 in multiplication block 19: the first bit XOR with the first Walsh function, the second bit XOR with the second Walsh function, and so on. It will be appreciated that the level of modulation is unlimited, depending only on the selected set of Walsh functions. Any desired set of Walsh functions can be used, preferably from 16 and above, merely by using more gates and adding more gain.
According to one embodiment of the invention, Walsh function generator 16 is coupled to dynamic table 18 and is arranged to produce a high order Walsh function in order to utilize a selected table from among many different tables in dynamic table 18.
The information output by multiplication block 19 goes to a summation block 20. The ouput goes to a dynamic limiter 22 which cuts over-shooting and also takes very low signals and stretches them into zero, reducing the dynamic band. The energy above a certain level is not transmitted and lower than certain level is also cut off. While this reduces by a small amount the amount of information transmitted, this information can easily be recovered in the receiver. The system transfers energy from unused levels into the most used levels, thereby increasing average bit energy.
From the dynamic limiter 22 in spreadulator 12, the signals go via a bus 24 to a second dynamic table 26, which converts them into I and Q buses. It is a property of dynamic table 26 that is can easily incorporate security codes and differentiate among different users. From the I and Q buses, the signals are multiplied by coherent sin and cosin waveforms, summed in a summation block 28, and transmitted to the air via a conventional RF transmitting front end 30.
In the receiver, shown in Fig. 2, is an RF front end 32. The received I and Q signals are multiplied by coherent sin and cosin waveforms in a multiplier 34, then preferably to an A/D converter 36, which can alternatively be located before the multiplier. The resulting digital signals go to an inverse dynamic table 38, which is the inverse of the second dynamic table in the transmitting unit. The inverse dynamic table 38 converts the multiplied digital signals to a symbol stream. The output goes to a TelesciCom fast transform (TFT) unit 40 for fast transformation of the Walsh function. TFT unit 40 includes a multiple channel butterfly Walsh function correlation block, and serves to transform the input signals to a Walsh function spectrum. In essence, it is a very efficient multilevel/ multichannel correlator. The output of TFT 40 goes to a management block 42, which performs synchronization. It is a property of the invention that instead of measuring maximum bit energy, it measures minimum dispersion of noise at each particular time. Thus, management block 42 includes a threshold detector for the dispersed noise for each information block. The system compares the average noise dispersion level with the minimum noise dispersion level. When the minimum dispersed value of the noise is significantly less than the mean energy of the noise, that is the synchronization point. This can be found by using the formulae: Y"-' JML= N
Figure imgf000007_0001
wherein N is the noise dispersion , N bar is the average noise level, and δ is the minimum noise dispersion level. The management block 42 includes a phase lock loop in order to integrate several information blocks so as to achieve better noise immunity.
The management block 42 provides a synchronization pulse to TFT 40 and, at the moment of synchronization, the information in TFT 40 is loaded into a second inverse dynamic table 44. Second inverse dynamic table 44 is the inverse of the dynamic table 18 in spreadulator 12 in the transmitting unit. From inverse dynamic table 44, the information is input into an inverse information vector generator 46 which is the inverse of IVG 14 in the transmitter. Inverse IVG 46 in the receiving unit outputs serial information which corresponds to the information as originally input.
It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims which follow.

Claims

1. A coding and modulating system comprising a combined modulator/demodulator and spreading/despreading mechanism.
2. The coding and modulating system according to claim 1, wherein said combined modulator/demodulator and spreading/despreading mechanism includes: an information vector generator (IVG); a dynamic Table coupled to the output of said information vector generator; a multiplication block for receiving the output of said dynamic Table; a Walsh function generator (WFG) coupled to said multiplication block; a summation block coupled to the output of said multiplication block; and a dynamic limiter for limiting the output of the summation block.
3. A coding and modulating system comprising a transmitting unit including: a spreadulator including: an information vector generator; a dynamic Table coupled to the output of said information vector generator for preparing data for multiplication; a Walsh function generator (WFG); a multiplication block coupled to said dynamic Table and to said Walsh function generator; a summation block coupled to the output of said multiplication block; and a dynamic limiter for limiting the output of said summation block; a second dynamic table coupled via a bus to the dynamic limiter for converting input signals to I and Q buses including a multiplier where the signals are multiplied by coherent sin and cosin waveforms; a summation element; and an RF front-end.
4. The coding and modulating system according to claim 3, further comprising a receiving unit comprising: a front end for receiving transmitted signals, a multiplier for multiplying the received signals by coherent sin and cosin waveforms; an Analog to Digital (A/D) converter; an inverse dynamic table arranged to receive the multiplied digital signals and convert them to a symbol stream, the inverse dynamic table being the inverse of the second transmitting dynamic table; a fast transform unit for transforming the signals from said dynamic table to a Walsh function spectrum; a management block for synchronizing the output Walsh function spectrum; a second inverse dynamic table, the inverse of the spreadulator dynamic table in the transmitting unit, for converting the output Walsh function spectrum; and an inverse information vector generator which is the inverse of the transmitting information generator for generating output signals substantially identical to the original input signals in the transmitting unit.
5. The coding and modulating system of claim 4, wherein said management block includes: a threshold detector for dispersed noise of each information block; a comparator for comparing the detected dispersed noise with the average noise dispersion level so as to detect a minimum noise dispersion level; a phase lock loop to integrate several information blocks; and means for providing a synchronization pulse to said fast transform unit.
6. The coding and modulating system of either of claims 4 and 5, wherein said management block detects a minimum noise dispersion level according to the formulae:
Σ"~' IM' N
Figure imgf000010_0001
wherein N is the noise dispersion , N bar is the average noise level, and ╬┤ is the minimum noise dispersion level.
7. The coding and modulating system of any of claims 4 to 6, wherein said fast transform unit includes a multiple channel butterfly Walsh function correlation block.
8. The coding and modulating system of any of claims 2 to 7, wherein said Walsh function generator is coupled to said spreadulator dynamic table and is arranged to produce a high order Walsh function in order to selectably utilize any selected table in said dynamic table.
9. A method of coding and modulating for radio telecommunication comprising the steps of: modulating input data in an information vector generator in a spreadulator; spreading the input data using a Walsh function generator in the spreadulator; summing the output of the information vector generator multiplied by a set of Walsh function ouput from said Walsh function generator in a summation block; limiting the output of said summation block in a dynamic limiter; converting the limited signals to I and Q buses in a second dynamic table coupled via a bus to said dynamic limiter; multiplying the signals by coherent sin and cosin waveforms; summing the multiplied signals; and transmitting the sum.
10. The method according to claim 9, and further comprising the steps of: receiving the transmitted signals in a receiving unit; multiplying the received signals by coherent sin and cosin waveforms in a multiplier; converting analog signals to digital signals; receiving the multiplied digital signals in an inverse dynamic table, the inverse dynamic table being the inverse of the second transmitting dynamic table; transforming the input signals to a Walsh function spectrum in a fast transform unit; synchronizing the output Walsh function spectrum in a management block; converting said output Walsh function spectrum to symbols in a second inverse dynamic table, said second inverse dynamic table being the inverse of the dynamic table in the combined modulator/demodulator and spreading/despreading mechanism in said transmitting unit; and generating output signals substantially identical to the input signals in the transmitting unit in an inverse information vector generator which is the inverse of the transmitting information generator.
1 1. The method according to claim 10, wherein said management block synchronizes the output Walsh function spectrum in accordance with the following formulae: y-╬╣ "╬╣=-ΓÇ₧0' J n L= N
Figure imgf000012_0001
wherein Ν is the noise dispersion , Ν bar is the average noise level, and δ is the minimum noise dispersion level.
PCT/IL1998/000478 1997-10-06 1998-09-29 Coding and modulating system WO1999018686A1 (en)

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IL12189297A IL121892A0 (en) 1997-10-06 1997-10-06 CDMA system

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Cited By (11)

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WO2001031823A1 (en) * 1998-01-23 2001-05-03 Nortel Networks Corporation Broadband wireless access based on code division parallel access
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US6434135B1 (en) 1999-08-31 2002-08-13 Interdigital Technology Corporation Adaptive RF amplifier prelimiter
EP1388937A2 (en) * 1999-08-31 2004-02-11 Interdigital Technology Corporation Adaptive RF amplifier prelimiter
US6904292B2 (en) 1999-08-31 2005-06-07 Interdigital Technology Corporation Base station having an adaptive RF amplifier prelimiter
US6920127B2 (en) 1999-08-31 2005-07-19 Interdigital Technology Corporation User equipment (UE) having an adaptive RF amplifier prelimiter
US6968202B2 (en) 1999-08-31 2005-11-22 Interdigital Technology Corporation Method for operating a user equipment by prelimiting an output signal
EP1388937A3 (en) * 1999-08-31 2006-10-18 Interdigital Technology Corporation Adaptive RF amplifier prelimiter
US7164931B2 (en) 1999-08-31 2007-01-16 Interdigital Technology Corporation Method for operating a base station by prelimiting an output signal
EP2045917A3 (en) * 1999-08-31 2009-04-22 Interdigital Technology Corporation Adaptive RF amplifier prelimiter
US7912505B2 (en) 1999-08-31 2011-03-22 Interdigital Technology Corporation Method for operating a base station by prelimiting an output signal station

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