WO2007081595A2 - Systèmes et procédés de modulation sur demande dans un système de communication à bande étroite - Google Patents

Systèmes et procédés de modulation sur demande dans un système de communication à bande étroite Download PDF

Info

Publication number
WO2007081595A2
WO2007081595A2 PCT/US2006/049704 US2006049704W WO2007081595A2 WO 2007081595 A2 WO2007081595 A2 WO 2007081595A2 US 2006049704 W US2006049704 W US 2006049704W WO 2007081595 A2 WO2007081595 A2 WO 2007081595A2
Authority
WO
WIPO (PCT)
Prior art keywords
signal
samples
look
tables
modulation
Prior art date
Application number
PCT/US2006/049704
Other languages
English (en)
Other versions
WO2007081595A3 (fr
Inventor
Alvin Dale Kluesing
Sai C. Manapragada
Original Assignee
Photron Technologies 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 Photron Technologies Ltd. filed Critical Photron Technologies Ltd.
Publication of WO2007081595A2 publication Critical patent/WO2007081595A2/fr
Publication of WO2007081595A3 publication Critical patent/WO2007081595A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0008—Modulated-carrier systems arrangements for allowing a transmitter or receiver to use more than one type of modulation

Definitions

  • the present invention relates generally to the transmission of information through communication systems.
  • the systems and methods of the present invention provide a user-configurable modulation scheme that may be modified on demand to achieve a given data rate for a given channel bandwidth for the transmission of information through narrowband communications channels.
  • wireless communication system 100 includes: (1) modulator 105; (2) transmitter 110; (3) wireless channel 115; (4) receiver 120; and (5) demodulator 125.
  • Modulator 105 processes the information into a form suitable for transmission over wireless channel 115.
  • the information maybe in the form of voice, data, audio, imagery, video, or any other type of content conveyed in an information signal, also referred to as a message signal.
  • Modulator 105 essentially translates the message signal into a modulated signal suitable for transmission over wireless channel 115 by modifying one or more characteristics of a carrier signal.
  • the modulated signal is passed on to wireless channel 115 by transmitter 110, which usually filters and amplifies the modulated signal prior to its transmission.
  • the function of wireless channel 115 is to provide a wireless link or connection between the information source and destination.
  • the modulated signal is detected and amplified by receiver 120 to take into account any signal attenuations introduced during transmission by wireless channel 115.
  • the transmitted signal is demodulated by demodulator 125 so as to produce a close estimate of the original message signal.
  • the performance of a wireless communications system such as wireless communication system 100 is, in part, dictated by the performance of its modulator, e.g., modulator 105.
  • modulator 105 the modulator that is responsible for converting the message signal into a signal suitable for transmission so as to maximize the use of the overall system resources.
  • a high performance modulator should generate a modulated signal having a frequency spectrum that, when filtered and transmitted by a transmitter such as transmitter 110, would utilize only a small fraction of the total channel bandwidth, thereby enabling many users to share the channel bandwidth simultaneously.
  • a high performance modulator should also work in conjunction with a high performance filter in the transmitter to ensure optimal preservation of the frequency spectrum of the modulated signal.
  • modulation techniques including, but not limited to, amplitude shift keying ("ASK”), frequency shift keying (“FSK”), binary phase shift keying (“BPSK”), quadrature phase shift keying (“QPSK”) and its variations, minimum shift keying (“MSK”), Gaussian minimum shift keying (“GMSK”), and quadrature amplitude modulation (“QAM”), among others.
  • ASK amplitude shift keying
  • FSK frequency shift keying
  • BPSK binary phase shift keying
  • QPSK quadrature phase shift keying
  • MSK minimum shift keying
  • GMSK Gaussian minimum shift keying
  • QAM quadrature amplitude modulation
  • modulation techniques are digital techniques in which the message signal is represented by a sequence of binary symbols. Each symbol may have one or more bits, depending on the modulation technique used.
  • these modulation techniques switch or key the amplitude, frequency, and/or phase of a carrier signal according to the binary symbols in the message signal, e.g., according to binary symbols "0" and "1.”
  • different amplitudes are used to represent both binary symbols in ASK
  • different frequencies are used to represent both binary symbols in FSK
  • different phases are used to represent both binary symbols in BPSK.
  • QPSK is a variation of BPSK in which two bits or more are used per symbol.
  • the phase of the carrier takes on one of four equally spaced values, such as 0, p/2, p, and 3p/2, with each value corresponding to a unique symbol, e.g., 00, 10, 11, and 01.
  • QAM changes the amplitude of two carrier waves that are out of phase.
  • MSK and GMSK are variations of FSK in which the change in carrier frequency from one binary symbol to another is half the bit rate of the message signal.
  • a desirable digital modulation technique provides low bit error rates at low signal-to-noise ratios, occupies a minimum bandwidth, performs well in the presence of multipath and fading conditions, and is cost-effective to implement.
  • some modulation techniques may prove to be a better fit than others. Consideration must be given to the required data rate, acceptable level of latency, available bandwidth, and target hardware cost, size, and power consumption. For example, in personal communication systems that serve a large subscriber community, the cost and complexity of the receivers must be minimized.
  • the performance of a modulation technique is often measured in terms of its power efficiency and bandwidth efficiency.
  • Power efficiency describes the ability of a modulation technique to preserve the fidelity, i.e., an acceptable bit error probability, of the message signal at low power levels.
  • higher fidelity requires higher signal power.
  • the amount by which the signal power should be increased to obtain a certain level of fidelity depends on the type of modulation employed.
  • the power efficiency of a digital modulation technique is a measure of how favorably this tradeoff between fidelity and signal power is made, and is often expressed as the ratio of the signal energy per bit to noise power spectral density required at the receiver input for a certain probability of error.
  • Bandwidth efficiency describes the ability of a modulation technique to accommodate data within a limited bandwidth.
  • increasing the data rate implies decreasing the pulse- width of a digital symbol, which increases the bandwidth of the signal.
  • Bandwidth efficiency reflects how efficiently the allocated bandwidth is utilized.
  • Bandwidth efficiency is defined as the ratio of the throughput data rate per Hertz in a given bandwidth.
  • the system capacity of a digital modulation technique is directly related to the bandwidth efficiency of the modulation technique, since a modulation technique having a greater bandwidth efficiency will transmit more data in a given spectrum allocation.
  • modulation techniques trade bandwidth efficiency for power efficiency. For example, FSK is power efficient but not as bandwidth efficient and QPSK and GMSK are bandwidth efficient but not as power efficient.
  • Spread spectrum modulation is a technique in which the modulated signal bandwidth is significantly wider than the minimum required signal bandwidth. Bandwidth expansion is achieved by using a function that is independent of the message and known to the receiver. The function is a pseudo-noise ("PN") sequence or PN code, which is a binary sequence that appears random but can be reproduced in a deterministic manner by the receiver. Demodulation at the receiver is accomplished by cross-correlation of the received signal with a synchronously-generated replica of the wide-band PN carrier.
  • PN pseudo-noise
  • PN code pseudo-noise
  • Demodulation at the receiver is accomplished by cross-correlation of the received signal with a synchronously-generated replica of the wide-band PN carrier.
  • spread spectrum modulation enables many users to simultaneously use the same bandwidth without significantly interfering with one another.
  • the use of PN codes allows the receiver to separate each user easily even though all users occupy the same spectrum.
  • spread spectrum systems are very resistant to interference, which tends to affect only a small portion of the spectrum and can be easily removed through filtering without much loss of information.
  • spread spectrum systems perform well in the presence of multipath fading and Doppler spread.
  • 11/171,177 the entire disclosure of which is incorporated herein by reference, comprises a return-to-zero modulation scheme that uses abrupt phase changes to represent incoming binary symbols in a modulated signal that has a double-sideband suppressed carrier ("DSSC") frequency spectrum with two wide spectrum sidebands and no carrier.
  • DSSC double-sideband suppressed carrier
  • narrowband transmission of information maybe accomplished by transmitting only a narrow band of frequencies required for identifying the phase shifts, i.e., by transmitting only a portion of one or both sidebands in the modulated signal within a narrow band of frequencies.
  • the modulated signal may be transmitted by filtering it a with high-Q, low-tolerance sophisticated digital filter that is able to preserve the positions of the phase shifts in a very narrow band of frequencies, as described in commonly-owned, currently pending U.S. Patent Application No. 11/171,592, the entire disclosure of which is incorporated herein by reference.
  • the modulated signal may also be transmitted using a fractal-based table lookup approach in which the modulated signal is transmitted through use of a simple look-up table storing samples extracted from the fractal modeling of the frequency spectrum of a filtered modulated signal. Transmission of a binary symbol may be accomplished by simply encoding the symbol into its corresponding samples stored in the look-up table.
  • the USM scheme may achieve data rates exceeding 5 Mbps to be delivered through frequency channels as narrow as 50 KHz under a variety of channel conditions.
  • use of USM in a communication system can enable wireless service providers to provide broadband wireless services to a large number of users simultaneously by accessing a fully-utilized frequency spectrum that may be divided into various channels of very narrow bandwidths.
  • the USM scheme achieves a given data rate by having pre-determined modulation parameters, such as a pre-determined carrier frequency and a pre-determined number of RF cycles per bit. In one example given, a data rate of 5
  • Mbps may be achieved in a 50 kHz channel using a carrier frequency of 20 MHz and four RF cycles per bit. If a total channel bandwidth of, for example, 100 MHz is provided, a total of 2000 modulated signals may be transmitted in channels of 50 kHz each, with each channel operating at a carrier frequency that is 50 kHz apart from its adjacent channels. In this case, as each channel is operating at a different carrier frequency, a different data rate will be achieved in each channel.
  • Achieving a variable data rate for each channel may be desired in several applications, including streaming media applications, video-on-demand applications, Internet traffic, and satellite applications, among others.
  • conventional, spread spectrum and narrowband modulation schemes are currently not capable of achieving variable data rates for different channels having different carrier frequencies without significant modifications to the modulation scheme parameters, channel bandwidth, signal-to-noise ratio ("SNR"), or the communication system itself.
  • SNR signal-to-noise ratio
  • changing the data rate for a streaming media application on a communication system employing QAM may require a change in the modulation constellation, from, say, 16-QAM to 32-QAM, to be able to accommodate the higher data rate with a higher bandwidth efficiency and higher signal-to-noise ratio.
  • changing the data rate may imply a change in the spreading ratio and coding gain.
  • the modulation system should also be able to easily accommodate variable and constant data rates on different channels for a desired reliability and other system constraints. [0030] Thus, there is a need to provide a modulation-on-demand scheme that achieves high bandwidth efficiency for various modulation parameters and channel conditions.
  • a general object of the present invention is to provide a modulation-on-demand scheme that achieves high bandwidth efficiency for various channel conditions and modulation parameters.
  • embodiments of the present invention provides communication systems and methods that implement a modulation-on-demand scheme for achieving a constant bandwidth efficiency with different modulation parameters in different channels without significant degradation of the signal-to-noise ratio in each channel.
  • embodiments of the present invention provides communication systems and methods that promote improved bandwidth utilization when providing wireless services to a large number of users simultaneously under various channel conditions and modulation parameters.
  • Embodiments of the present invention provide a novel modulation-on-demand scheme that achieves high bandwidth efficiency for various channel conditions and modulation parameters, hi one embodiment a modulator for modulating a carrier signal with a message signal to generate a modulated signal is provided, characterized in that: the modulated signal is modified responsive to user-selective modulation parameters, hi other embodiments, the modulation-on-demand scheme comprises a return-to-zero Ultra Spectral Modulation technique, hereinafter referred to as the Ultra Spectral Modulation-On-Demand ("USMoD”) technique, that uses abrupt phase changes to represent incoming binary symbols in a modulated signal.
  • USMoD Ultra Spectral Modulation-On-Demand
  • the USMoD technique also comprises a number of modulation parameters that may be changed on demand, or in real-time, (also referred to as on the fly) in a communication system while maintaining a constant bandwidth efficiency without significant degradation of the signal-to-noise ratio ("SNR") in the channel.
  • modulation parameters may include one or more of the carrier frequency, the number of RF cycles per bit, the number of samples per RF cycle, among others.
  • the present invention provides narrowband communication systems and methods that implement the USMoD scheme for achieving broadband-like services within a narrow frequency spectrum.
  • the communication system may be implemented with a look-up table approach, in which modulated signals are transmitted through use of a simple look-up table storing samples representing a modulated carrier for a given binary symbol, e.g., a "0" or a "1".
  • the samples may be taken directly from a modulated signal, such as a sinusoid modulated with the return-to-zero, abrupt-phase USM technique described in more detail in commonly-owned, currently pending U.S. Patent Application Nos.
  • look-up table samples may be extracted from the fractal modeling of the frequency spectrum of a modulated signal, as described in the above-identified, commonly-owned and currently-pending U.S. Patent
  • transmission of a binary symbol may be accomplished by simply encoding the symbol into its corresponding samples stored in the look-up table.
  • two look-up tables may be used, one for each binary symbol.
  • the look-up tables may be addressed with the use of a simple Finite State Machine (“FSM") that loads the look-up tables with the modulation parameters and the input data samples to be transmitted.
  • FSM Finite State Machine
  • a FIFO buffer may also be used to maintain a uniform data rate — and a constant bandwidth efficiency — in a narrowband communications channel.
  • a system for transmitting information through a narrowband communications channel comprising: a modulator for modulating a carrier signal with a message signal to generate a modulated signal with modulation parameters selected on demand; and one or more look-up tables for storing samples of the modulated signal and selecting a portion of the samples for transmission through the communications channel according to the modulation parameters.
  • modulation parameters are selected from any one or more of: number of RF cycles used for a binary symbol; number of samples per RF cycle; carrier frequency; fractal bifurcation index; and number of words used to represent each sample in the one or more look-up tables.
  • the modulator is comprised of an encoder for encoding a first binary symbol into a first portion of a carrier signal, the first portion of the carrier signal having an integer number n of cycles and at a first phase, followed by a second portion of the carrier signal, the second portion of the carrier signal having an integer number n of cycles and at a second phase, wherein the second phase is at a phase shift away from the first phase.
  • the encoder may further comprise encoding a second binary symbol into a third portion of the carrier signal, the third portion of the carrier signal having an integer number n of cycles and at the second phase, followed by a fourth portion of the carrier signal, the fourth portion of the carrier signal having an integer number n of cycles and at the first phase.
  • embodiments of the present invention provide a modulator for modulating a carrier signal with a message signal to generate a modulated signal.
  • the modulator comprises one or more look-up tables for storing samples representing the modulated signal; a finite state machine for loading a set of modulation parameters into the one or more look-up tables, the modulation parameters selected on demand; and a multiplexer for selecting a portion of the samples for transmission across a communications channel.
  • the one or more look-up tables comprises a first look-up table for storing a first set of samples corresponding to a first binary symbol in the message signal and a second look-up table for storing a second set of samples corresponding to a second binary symbol in the message signal.
  • methods for transmitting information through a narrowband communications channel comprise the steps of: modulating a carrier signal with a message signal to generate a modulated signal with modulation parameters selected on demand; storing samples of the modulated signal into one or more look-up tables; selecting a portion of the samples for transmission through the communications channel according to the modulation parameters; and transmitting the portion of the samples though the communications channel
  • the systems and methods of the present invention enable designers of a communication system to achieve very high and constant bandwidth efficiency across different channels with different modulation parameters for each channel. Further, the systems and methods of the present invention provide a modulation-on-demand scheme that may be integrated in a narrowband communication system to provide broadband-like services in a very narrow band of frequencies.
  • FIG. 1 shows a general schematic diagram of a conventional wireless communication system
  • FIG. 2 shows a diagram of an exemplary message signal and a modulated signal according to the principles and embodiments of the present invention
  • FIG. 3 shows a schematic diagram of an exemplary communication system for transmitting a message signal modulated according to the principles and embodiments of the present invention
  • FIG. 4 shows a diagram of an exemplary embodiment of a modulator designed according to the principles and embodiments of the present invention
  • FIG. 5 shows an exemplary state diagram of a finite state machine for use in a modulator designed according to the principles and embodiments of the present invention
  • FIG. 6 shows a diagram of another exemplary embodiment of a modulator designed according to the principles and embodiments of the present invention
  • FIG. 7 illustrates exemplary modulation parameters and data rates for an exemplary modulator designed according to FIG. 6.
  • FIG. 8 illustrates other exemplary modulation parameters and data rates for an exemplary modulator designed according to FIG. 6;
  • FIG. 9 illustrates yet other exemplary modulation parameters and data rates for an exemplary modulator designed according to FIG. 6.
  • a modulation-on-demand scheme that achieves high and substantially constant bandwidth efficiencies across different channels with different modulation parameters for each channel.
  • Information may be in the form of voice, data, audio, imagery, video, or any other type of content conveyed in an information signal, also referred to as a message signal.
  • the message signal represents information by means of binary symbols, with each symbol having one or more bits.
  • a modulator for modulating a carrier signal with a message signal to generate a modulated signal is provided, characterized in that: the modulated signal is modified responsive to user-selective modulation parameters.
  • a channel may be any communications channel, including a wired channel, e.g., cable, or a wireless channel.
  • modulation refers to the process by which information conveyed in the message signal is encoded in a carrier signal to generate a modulated signal.
  • the encoding involves modifying one or more characteristics of the carrier signal according to the binary symbols in the message signal.
  • a carrier signal may be any analog signal of a given frequency, for example, a sinusoidal wave at 100 MHz.
  • a modulated signal refers to the carrier signal that has been modified according to the message signal.
  • the modulated signal has a frequency spectrum representation comprising its frequency components.
  • Modulated signals according to the USMoD technique of the present invention have frequency spectrums comprising no carrier and two bands or "sidebands" of frequencies, one above (the “upper sideband” or “USB”) and one below (the “lower sideband” or “LSB”) the carrier frequency. Transmission of one of the sidebands is referred to as single-sideband suppressed-carrier ("SSSC”) transmission and transmission of both sidebands is referred to as double-sideband suppressed carrier (“DSSC”) transmission.
  • SSSC single-sideband suppressed-carrier
  • DSSC double-sideband suppressed carrier
  • Transmission of the modulated signal through a communications channel may be accomplished by using one or more look-up tables that store samples representing a binary symbol, e.g., a "0" or a "1".
  • the samples may be taken directly from a modulated signal.
  • the samples may be extracted from the fractal modeling of the frequency spectrum of a modulated signal, as described in the above-identified, commonly-owned and currently-pending U.S. Patent
  • transmission of a binary symbol may be accomplished by simply encoding the symbol into its corresponding samples stored in the one or more look-up tables.
  • Aspects of the invention further provide for the one or more look-up tables to be loaded with USMoD parameters that may be changed on the fly.
  • modulation parameters may include, but are not limited to, the carrier frequency, the number of RF cycles per bit, the number of samples per RF cycle, among others.
  • the modulation parameters are loaded into the look-up tables via a Finite State Machine (“FSM”), which, as used herein, generally refers to a behavioral model composed of states, transitions, and actions.
  • FSM Finite State Machine
  • the USMoD technique of the present invention may be used to transmit information through a narrowband communications channel at very high data rates for various different configurations of modulation parameters. For example, data rates of 5-10 Mbits/sec (and even higher) may be achieved on 50 kHz channels with carrier frequencies that are 50 kHz apart and with different number of RF cycles per binary symbol or bit. For example, a data rate of 5 Mbits/sec may be achieved on a 50 kHz channel with a 20 MHz carrier having 4 RF cycles per bit and the same data rate may be achieved on a 50 kHz channel with a 70 MHz carrier having 15 RF cycles per bit.
  • the width of a narrowband channel will vary depending upon the application.
  • a channel having a bandwidth of about 200 KHz and below may be generally characterized as a narrowband channel, and more typically a bandwidth of about 100 KHz and below. It should be appreciated that while embodiments of the present invention describe application of the invention in a narrowband communications channel and system, the system and methods of the present invention may be employed in other communication systems as well.
  • a channel bandwidth generally refers to the band of frequencies allocated for transmission of one or more modulated signals.
  • a channel having a bandwidth of 100 MHz may support the transmission of one or more modulated signals within a frequency spectrum of 100 MHz. If, for example, each modulated signal occupies a bandwidth of 10 kHz, then the channel is able to support the transmission of 10,000 such signals.
  • the amount of data that can be transferred in a channel having a given bandwidth may be generally referred to herein as the channel's data rate (expressed in bits per second).
  • the maximum data rate supported by a channel for a given bandwidth, noise level, and other channel assumptions may be generally referred to as the channel capacity.
  • the Ultra Spectral Modulation (“USM”) technique described in commonly- owned, currently-pending U.S. Patent Application Nos. 11/171,177 and 11/171,592, the entire disclosures of which are incorporated by reference herein, comprises a return-to-zero modulation technique that uses abrupt phase changes in a carrier signal to represent incoming binary symbols.
  • the abrupt phase changes occur mid-pulse, i.e., in the middle of a bit period, after an integer number of cycles of the carrier signal, or at a bit boundary.
  • a binary symbol e.g., "0" or "1" is represented with an integer number of cycles, e.g., n cycles, of a carrier signal, of which n/2 cycles are used at a given phase and the other n/2 cycles are used at a phase shift, with the abrupt phase shift occurring mid-pulse.
  • the modulated carrier signal is referred to herein as the "modulated signal.”
  • Message signal 200 is a signal represented by the following binary sequence:
  • Message signal 200 is modulated using the USM technique into a sinusoidal carrier having a given carrier frequency, which in this case is four cycles per binary symbol or bit. For example, if the carrier frequency is set at 20 MHz and the number of RF cycles per bit is set at 4, a data rate of 5 Mbps may be achieved with the USM technique. [0066] Using USM to modulate message signal 200 with a sinusoidal carrier having a carrier frequency at least twice the data rate produces modulated signal 205. Modulated signal 205 is a sinusoidal wave having abrupt phase shifts every mid-pulse.
  • Each bit is represented with two sinusoidal patterns, a "data bit” pattern lasting for the first half of the pulse-width, e.g., for the first two cycles of the carrier frequency, and a "datum bit” pattern lasting for the second half of the pulse- width, e.g., for the last two cycles of the carrier frequency.
  • a data bit pattern for a given binary digit e.g., "0" or "1,” has a phase that is 180° degrees away from the phase of the datum bit pattern. Additionally, a data bit pattern for a given binary digit has a phase that is 180° degrees away from the phase of the data bit pattern of the other binary digit. For example, as illustrated, a data bit pattern for a "0" bit has a phase of q while the datum bit pattern for the "0" bit has a phase of q - p. Conversely, a data bit pattern for a "1" bit has a phase of q - p while the datum bit pattern for the "1" bit has a phase of q.
  • each data bit pattern and datum bit pattern have two RF cycles, resulting in four RF cycles being used to represent each binary symbol.
  • the main characteristic of the USM technique lies in the abrupt phase shifts occurring mid-pulse.
  • the abrupt phase shifts may be viewed as another layer of phase reversals occurring on top of traditional BPSK modulation techniques, in which phase shifts occur only at the bit transitions, i.e., at the edge of each pulse. Having the datum bit pattern inserted in each pulse ensures a return-to-zero modulation technique with a DSSC frequency spectrum.
  • USM technique may have parameters specified on demand.
  • the USM technique may have various values of carrier frequency, number of RF cycles per bit, and number of samples per RF cycle, all selected on demand as desired.
  • a USM technique having modulation parameters that are selected on demand is hereinafter referred to as a Ultra Spectral Modulation-on-Demand technique, or "USMoD" for short.
  • Sample USMoD parameters are shown below in Table I. The illustrated parameters are provided for illustration only and are not intended to limit the invention in any way. Other parameters may be selected according to the teaching of the present invention.
  • Modulation parameters that may be selected and modified on the fly include the number of RF cycles used for each binary symbol, the number of samples per RF cycles, the carrier frequency, and the number of 12-bit words used to represent each sample in the look-up tables. It is appreciated that the values shown below in Table I are exemplary values only and other values may be selected without deviating from the principles and embodiments of the present invention. It will also be appreciated that other modulation parameters may be selected on demand, including, for example, the type of carrier signal used, e.g., a sinusoid, a square wave, etc.
  • Communication system 300 includes USMoD modulator 305 for modulating a message signal according to user- configurable modulation parameters that may be selected on demand. USMoD modulator may modulate the message signal according to the USM technique as described above with the modulation parameters selected by the user.
  • Communication system 100 also includes one or more look-up tables
  • LUTs 310 for storing samples of a modulated signal generated by USMoD modulator 305.
  • LUTs 310 may have these samples already stored therein, and depending on the modulation parameters that are selected by the user, a portion of these samples may be selected for transmission across the communications channel.
  • LUTs 310 may have its samples loaded in real-time or on the fly. The samples may be extracted from the modulated signal itself, or from a multiresolution-based decomposition of the signal using signal primitives, such as fractal bifurcations or wavelets, as described in more detail in currently-pending U.S. Patent Application Nos.
  • signal primitives such as fractals
  • fractals may be bifurcated a number of times to generate smaller, self similar primitives at different scales or levels of detail. The number of bifurcations is given by a bifurcation index.
  • the fractals may be generated for example by a fractal pattern generator capable of generating fractals, such as various fractal pattern generators implemented as software routines.
  • a Moire or Mandelbrot fractal pattern generator as implemented in the art with Java® or Matlab® may be used to generate fractal primitives.
  • Other programs are available to be used to generate wavelet primitives.
  • a simple finite state machine may be used to control the loading of the modulation parameters into LUTs 310.
  • a data buffer may also be used to guarantee a given bandwidth efficiency for the modulation parameters selected by the user.
  • USMoD modulator 400 includes input line 405 to load modulation parameters into look-up tables 420-425.
  • Input line 405 may load the parameters serially, i.e., one bit at a time.
  • Modulation parameters that may be loaded into look-up tables 420-425 may include the parameters shown above in Table I.
  • the modulation parameters that are loaded via input line 405 are loaded into look-up tables 420-425 via finite state machine (“FSM”) 415.
  • FSM 415 controls the loading sequence of the modulation parameters into look-up tables 420-425.
  • FSM 415 may be implemented with two states, "wait" state 500 and "load” state 505.
  • “wait” state 500 FSM 415 waits to receive a load signal that indicates that modulation parameters are to be loaded into look-up tables 420-425.
  • FSM 415 determines the number of samples that are to be loaded for each binary symbol based on the USMoD modulation parameters, i.e., by multiplying the number of RF cycles to be used to represent a binary symbol by the number of samples per RF cycle.
  • FSM 415 then enters "load” state 505 and starts loading look-up tables 420-425 with samples corresponding to the modulated representation of the given binary symbol.
  • the samples may be taken directly from a modulated signal, such as modulated signal 205 shown in FIG. 2, based on the modulation parameters selected by the user, including the number of RF cycles per binary symbol and the number of samples that need to be extracted per RF cycle.
  • the samples may be extracted from the fractal modeling of the frequency spectrum of a modulated signal, as described in the above-identified, commonly-owned and currently-pending U.S. Patent Application Nos. 11/171,177 and 11/171,592.
  • transmission of a binary symbol may be accomplished by simply encoding the symbol into its corresponding samples stored in look-up tables 420-425.
  • the samples stored in look-up tables 420-425 are independent of the message signal, that is, the same samples are stored therein regardless of the modulation parameters selected by the user.
  • the modulation parameters may be used to control the number of samples to be extracted for each RF cycle and which samples out of look-up tables 420-425 to be transmitted across the communications channel.
  • USMoD modulator 400 may be implemented with two look-up tables, i.e., look-up tables 420-425, with each table storing samples for a given binary symbol. For example, look-up table 420 may be used to store samples for a "0" and look-up table 425 may be used to store samples for a "1.”
  • Samples from each table are selected by the message signal to be modulated, which is input into multiplexer 430 via input line 410.
  • Multiplexer 430 uses each binary symbol in the message signal as a selector for the modulated signal samples stored in look-up tables 420-425. For example, if the message signal has the sequence "010,” multiplexer 430 outputs samples from look-up table 320, then samples from look-up table 425 and again from look-up table 420.
  • the samples from look-up tables 420-425 are the modulated samples that are eventually transmitted in a communications channel; they are output by multiplexer 430 in output line 435.
  • USMoD modulator 400 shown in FIG. 4 outputs samples as they come into the system without any data rate control to provide a constant data rate or constant bandwidth efficiency.
  • data synchronization approaches may be necessary. Such approaches may be used to synchronize a clock with the input data and minimize the amount of null data that may be needed to guarantee a given data rate.
  • USMoD modulator 600 has FIFO data buffer 605 to ensure that the input data is synchronized with a clock to provide a constant bandwidth efficiency across a communications channel.
  • FIFO data buffer 605 takes the message signal as input and outputs the message signal at the clock rate provided by clock 610. Null data is provided in the output to guarantee a given data rate.
  • data coming into the buffer could be either synchronized or non-synchronized with clock 610.
  • the data rate of message signals being input into FIFO data buffer 605 could also be greater than, equal to, or less than the output data rate generated by USMoD modulator 600.
  • the message signal may be synchronized with the clock signal provided by clock 610 in input data sync 615.
  • the buffer will synchronize the input data to the output, by either storing data or sending null data.
  • Input data sync 615 takes the data output by FIFO buffer 605 and outputs the data at a desired clock rate, computed from the USMoD parameters loaded into FSM 620.
  • the desired clock rate may be given by the clock signal from clock 610 divided by the total number of samples for a given binary symbol in the message signal, that is, divided by the number of RF cycles per binary symbol and the number of samples in each RF cycle.
  • the synchronized data may then be used to select the samples stored in lookup tables 630-635 via multiplexer 640. It is appreciated that doing so ensures that the message signal is modulated to guarantee a given data rate across a communications channel of fixed bandwidth, thereby guaranteeing a constant bandwidth efficiency.
  • the modulation parameters of USMoD modulator 400 may be easily modified on demand. For example, if the input data traffic is bursty or has increased, such that FIFO buffer 605 may be filled up, then the number of RF cycles per binary symbol may be reduced to increase the channel bandwidth.
  • the required bandwidth may be reduced by increasing the fractal bifurcation index, as described in the above-identified, commonly-owned and currently-pending U.S. Patent Application Nos. 11/171,177 and 11/171,592.
  • the number of RF cycles per symbol could be increased to reduce the amount of null data sent.
  • the data rate and the required bandwidth may change if the number of RF cycles per binary symbol remains the same.
  • the number of RF cycles per binary symbol or the fractal bifurcation index may then be changed to keep the message signal within the preset limits of the new channel, i.e., F2.
  • Table 700 shows data rates that may be achieved with different USMoD parameters in three adjacent channels. Each channel may have a bandwidth of 50 kHz, with a carrier frequency at the center frequency. The carrier frequencies may then be 50 kHz apart, ranging from 149,950 kHz to 150 MHz and 150,050 kHz. Table 700 shows that a data rate of at least 10 Mbits/sec may be achieved with a carrier frequency of 150 MHz by using 15 RF cycles to represent each binary symbol and a total of 8 samples per RF cycle.
  • lowering the number of RF cycles from 15 to 14 in the channel having a carrier frequency of 149,950 kHz results in a data rate slightly higher than 10 Mbits/sec (720).
  • Similar performance results may be achieved for a different set of carrier frequencies, as shown in FIG. 8 for carrier frequencies ranging from 69,950 kHz to 70,050 kHz and as shown in FIG. 9 for carrier frequencies ranging from 19,950 kHz to 20,050 kHz.
  • These sets of carrier frequencies may be used to achieve data rates of up to 5 Mbits/sec in narrowband communications channels of only 50 kHz of bandwidth.

Abstract

La présente invention se rapporte à des systèmes et à des procédés de modulation sur demande dans un système de communication à bande étroite. La modulation sur demande est assurée par une nouvelle technique de modulation qui permet d'obtenir une efficacité de largeur de bande élevée pour divers états de canaux et paramètres de modulation. De tels paramètres de modulation peuvent comprendre entre autres la fréquence porteuse, le nombre de cycles RF par bit et le nombre d'échantillons par cycle RF. Un système de communication faisant appel à une technique de modulation sur demande émet un signal de message via une ou plusieurs tables de recherche dans lesquelles sont stockés des échantillons représentant le signal de message modulé.
PCT/US2006/049704 2005-12-30 2006-12-29 Systèmes et procédés de modulation sur demande dans un système de communication à bande étroite WO2007081595A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US75535305P 2005-12-30 2005-12-30
US60/755,353 2005-12-30

Publications (2)

Publication Number Publication Date
WO2007081595A2 true WO2007081595A2 (fr) 2007-07-19
WO2007081595A3 WO2007081595A3 (fr) 2008-03-06

Family

ID=38256820

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2006/049704 WO2007081595A2 (fr) 2005-12-30 2006-12-29 Systèmes et procédés de modulation sur demande dans un système de communication à bande étroite

Country Status (2)

Country Link
TW (1) TW200742362A (fr)
WO (1) WO2007081595A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115037356A (zh) * 2022-06-08 2022-09-09 中山大学 一种用于北斗三号rdss链路的数据分包方法及系统

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5528621A (en) * 1989-06-29 1996-06-18 Symbol Technologies, Inc. Packet data communication system
US20020102937A1 (en) * 1995-02-06 2002-08-01 Mark J. Dapper Communication system with multicarrier telephony transport
US20030180053A1 (en) * 2002-03-05 2003-09-25 Teh Fa Technology Co., Ltd. System and a method for handling laser communication multiplexing in chaotic secure communications

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5528621A (en) * 1989-06-29 1996-06-18 Symbol Technologies, Inc. Packet data communication system
US20020102937A1 (en) * 1995-02-06 2002-08-01 Mark J. Dapper Communication system with multicarrier telephony transport
US20030180053A1 (en) * 2002-03-05 2003-09-25 Teh Fa Technology Co., Ltd. System and a method for handling laser communication multiplexing in chaotic secure communications

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
LO T. ET AL.: 'A Vehicle to Roadside Communications Architecture for ITS Applications' A UNIVERSITY OF CALIFORNIA BERKELEY INSTITUTE OF TRANSPORTATION STUDY, REF# UCB-ITS-PRR-2003-3, [Online] Retrieved from the Internet: <URL:http://www.path.berkeley.edu/PATH/Publications/PDF/PRR/2000/PRR-2000-03.pdf> *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115037356A (zh) * 2022-06-08 2022-09-09 中山大学 一种用于北斗三号rdss链路的数据分包方法及系统

Also Published As

Publication number Publication date
WO2007081595A3 (fr) 2008-03-06
TW200742362A (en) 2007-11-01

Similar Documents

Publication Publication Date Title
CN105531975B (zh) 用于发送具有恒定包络的信号的方法和装置
US6992973B2 (en) Transmitting apparatus, receiving apparatus, communication system, transmission method, reception method, and communication method
US6888789B1 (en) Transmitting apparatus, receiving apparatus, communication system, transmission method, reception method, and communication method
JP3589992B2 (ja) 通信装置及び伝送方式選択方法
Ibrahim et al. The potential of FBMC over OFDM for the future 5G mobile communication technology
US7471743B2 (en) Systems and methods for high-efficiency transmission of information through narrowband channels
JPH10308717A (ja) 受信装置および受信方法
JP2002164866A (ja) Ｏｆｄｍ変調方式を用いた放送装置
WO2008041160A2 (fr) Procédé et appareil pour générer des paquets de données à transmettre dans un système de communication ofdm
KR20120071951A (ko) 송수신 장치 및 방법
KR20130022286A (ko) 오프셋 위상 로테이션 쉬프트 키잉 변조 장치 및 방법, 위상 사일런스 로테이션 쉬프트 키잉 변조 장치 및 방법, 및 위상 사일런스 로테이션 쉬프트 키잉 복조 장치 및 방법
WO2007081595A2 (fr) Systèmes et procédés de modulation sur demande dans un système de communication à bande étroite
US7359452B2 (en) Systems and methods for designing a high-precision narrowband digital filter for use in a communications system with high spectral efficiency
JP4409722B2 (ja) 無線送信装置及び無線送信方法
CN112600781A (zh) 一种变包络频移键控调制、解调方法及设备
US7269230B2 (en) Systems and methods for designing a high-precision narrowband digital filter for use in a communications system with high spectral efficiency
JP2005027177A (ja) 無線送信機
JP2003244091A (ja) マルチキャリア信号の生成方法、及びマルチキャリア信号の受信方法
US20060233282A1 (en) Modulation method, modulation apparatus, demodulation apparatus, and radio communication system
JP4150284B2 (ja) 直交周波数分割多重送信装置、直交周波数分割多重送信方法、直交周波数分割多重送信プログラムおよび直交周波数分割多重受信装置、直交周波数分割多重受信方法、直交周波数分割多重受信プログラム
WO2007133651A9 (fr) Systèmes et procédés de communication de transmission à haute efficacité d&#39;information par des voies à bande étroite à base de modulation ultra spectrale
JPH08274752A (ja) 符号多重通信装置
WO2002093861A1 (fr) Procede d&#39;application d&#39;une modulation d&#39;amplitude en quadrature sur un systeme de radiocommunication
KR19990046587A (ko) 반송파변조신호가상관관계를갖는직교주파수분할다중화방식및장치
WO2009035256A1 (fr) Appareil de communication zigbee, et procédé d&#39;émission et de réception à haute vitesse

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application
NENP Non-entry into the national phase in:

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 06849233

Country of ref document: EP

Kind code of ref document: A2