EP2174440A2 - Appareil radio doté d'un nouveau procédé de modulation cifdm - Google Patents

Appareil radio doté d'un nouveau procédé de modulation cifdm

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Publication number
EP2174440A2
EP2174440A2 EP08801511A EP08801511A EP2174440A2 EP 2174440 A2 EP2174440 A2 EP 2174440A2 EP 08801511 A EP08801511 A EP 08801511A EP 08801511 A EP08801511 A EP 08801511A EP 2174440 A2 EP2174440 A2 EP 2174440A2
Authority
EP
European Patent Office
Prior art keywords
transmission
subcarriers
frequency
signal
symbol
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP08801511A
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German (de)
English (en)
Inventor
Olivier Bartels
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Individual
Original Assignee
Individual
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Filing date
Publication date
Priority claimed from DE102007036828A external-priority patent/DE102007036828B4/de
Application filed by Individual filed Critical Individual
Publication of EP2174440A2 publication Critical patent/EP2174440A2/fr
Withdrawn legal-status Critical Current

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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
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • 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
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0015—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the adaptation strategy
    • H04L1/0017—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the adaptation strategy where the mode-switching is based on Quality of Service requirement
    • 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
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1825—Adaptation of specific ARQ protocol parameters according to transmission conditions
    • 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
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1867—Arrangements specially adapted for the transmitter end
    • H04L1/1887—Scheduling and prioritising arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/26035—Maintenance of orthogonality, e.g. for signals exchanged between cells or users, or by using covering codes or sequences
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2697—Multicarrier modulation systems in combination with other modulation techniques
    • H04L27/2698—Multicarrier modulation systems in combination with other modulation techniques double density OFDM/OQAM system, e.g. OFDM/OQAM-IOTA system
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A) or DMT
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058—Allocation criteria
    • H04L5/0062—Avoidance of ingress interference, e.g. ham radio channels

Definitions

  • the invention relates to a radio with a novel Comb Interleaved Frequency Division Multiplex (CIFDM) modulation method, which combines the advantages of the known OFDM modulation with the advantages of conventional single-carrier modulations.
  • CIFDM Comb Interleaved Frequency Division Multiplex
  • the data stream to be sent is split into two multicarrier blocks, which are sent into each other with frequency and time offset.
  • a classic modulation with a matched filter system is used; the guard interval is eliminated.
  • the spectral efficiency is significantly increased by introducing an artificial zero crossing in each modulation symbol. During this zero crossing of the other block is transmitted and separated again via a synchronous switch in the receiver.
  • the invention further relates to a modulator for generating a multi-tone signal for the novel Comb Interleaved Frequency Division Multiplex (CIFDM) modulation method in the specific expression of a largely hexagonal arrangement of the subcarriers.
  • the modulator makes it possible to achieve the optimum hexagonal packing density of the subcarrier symbols in order to achieve high spectral efficiency while maintaining extremely high immunity of the multitone signal.
  • the invention also relates to a modem which uses a multitone transmission method with band-limiting Gauss or Matched Filterbänken, with an additional device for measuring and reducing crosstalk interference by using specially modulated especially with pseudo random or gold codes subcarrier for detecting crosstalk.
  • the invention has for its object to transmit a broadband data stream as a radio signal as trouble-free as possible over a greater distance.
  • a broadband data stream as a radio signal as trouble-free as possible over a greater distance.
  • reflections caused by multipath signals can be reconverted undisturbed in the original data stream again.
  • a task comparable to this task consists in the transmission of a broadband data stream via a simple copper cable, such as e.g. a subscriber line, also on this there are reflections on discontinuities such. Terminal blocks.
  • OFDM Orthogonal Frequency Division Multiplex
  • OFDM Orthogonal Frequency Division Multiplex
  • a multicarrier signal with a large number of subcarriers is used, which is generated by means of an orthogonal transformation - generally an inverse Fourier transformation - the transformation takes place in the context of a digital signal processing.
  • the result of the transformation can then be mixed analogously with a main carrier, yet only the subcarriers synthetically generated by mathematical transformation show up in the transmission signal.
  • guard interval protection area
  • OFDM usually uses an orthogonal inverse Fourier transform
  • the transformation is linear and multipath is within the system boundaries is merely a linear superposition of information transported over different paths, and also because the time shift due to the convolution theorem and the design of the guard interval after the return Fourier transform into the frequency plane corresponds to only one scaling, can be achieved by a single complex multiplication per subcarrier a substantial equalization be made.
  • the determination of the coefficients for equalization can be carried out, for example, by means of pilot carriers; likewise, certain subcarriers can preferably be selected, see, for example, DE 19827514Al.
  • the OFDM method impresses with its simplicity and effectiveness and is therefore used today in the state of the art in many modern radio systems such as IEEE 802.11 a / g WLAN, IEEE 802.16d / e WiMAX or wired for ADSL.
  • the data stream is divided according to this method to a plurality of individual carriers, of which modulates in contrast to the OFDM each individual with a low data rate, but still in the sense of a classic single-carrier transmission system conventional and continuous without guard interval becomes.
  • runtime differences due to multipath reception act directly as intersymbol interference on the transmission, but since each carrier operates at a very low data rate, correspondingly large temporal differences are required, so that the intersymbol interference is felt at all, it can also with an adaptive filter with only small coefficients or Trellis encoding with Viterbi evaluation can be easily eliminated.
  • the Nyquist In contrast to the OFDM signal, which provides the orthogonal Fourier transformation for each complex amplitude and phase specification of a single carrier in the frequency plane exactly a complex - corresponding upper and lower sideband - or two real-valued samples in the time plane and thus without guard interval, the Nyquist In the case of multibarrel transmissions with filter banks, a conventional modulation is used per carrier, which concentrates the signal power in certain areas of the spectrum and covers other areas, especially in the sidebands, with far less or almost no power. As a result, there is sub-critical sampling and analysis on the receiver side with the associated loss of spectral efficiency.
  • WO 2004 / 014034A2 likewise discloses an approach for the division of a QPSK signal into at least two sub-channels with mutually offset frequency bands with classical channel filters.
  • this method is therefore primarily economically only for transmission paths such as satellite connections, in which the use of a purely phase-modulated signal due to the special Properties of the transmission path is mandatory.
  • the object of the invention is therefore to find a modulation method which combines the advantages of the high spectral efficiency of the OFDM method with the robustness of a multicarrier method with conventional modulation of the individual carriers.
  • Figure 1 shows the appropriate signal processing in graphical form, whose individual elements in Figure 1 are referenced below with numbers in parentheses.
  • a microprocessor or digital signal processor according to dependent claim 14 takes over the data to be transmitted from the source and divides them by software into individual data blocks (1).
  • the data blocks are provided with a fail-safe forward error correction code according to dependent claim 8, e.g. a turbo code which adds redundant information to the actual data bits for later error correction in the receiver.
  • the blocks are processed by the processor for modulation (2), this is done, for example, a selection of two bits for a QPSK modulation according to dependent claim 6 per single carrier. From each one bit group, a complex number is selected as the baseband sample corresponding to a table or formula, which is then fed as a transmit sample into the channel filter bank. If this is designed as in the picture for four subcarriers, results in the example, an information amount of two times four bits per data block minus according to dependent claim 10 to be transmitted sub-carrier pilot or spectral zero or backing.
  • the data blocks are prepared for transmission, for this purpose, in each case the even data blocks are given to one and the odd data blocks to another filter bank (3).
  • filter bank (3) According to dependent claim 3 is in a particularly advantageous embodiment of the invention by a multiplexer, reduced FIR filters and inverse fast Fourier transform formed polyphase filter bank, which simultaneously makes the necessary upsampling to the réelleabtastrate and thus the classification of the subcarriers in the spectrum. This allows large filter banks for e.g. 64 to 1024 subcarriers realize.
  • the filter banks have in contrast to a pure inverse Fourier transformation over an arbitrarily adjustable impulse response, according to the dependent claim 4, a matched filter system be formed. This allows an optimization of the system behavior with noise present in the channel or other interference levels while at the same time largely avoiding intersymbol interference.
  • For the correct modulation of the subcarriers it is sufficient to give the individual baseband samples of successive (even or odd depending on the filter bank in the example) data blocks that belong to a subcarrier, as input values in the polyphase filter bank and, if necessary, to adjust the sampling rate in addition
  • the necessary interpolation and signal shaping take over the FIR filters, which also act as Gedumblenis the filter bank.
  • the respective multicarrier signal is now directly in the time plane.
  • one of these signals is first frequency-shifted by half a subcarrier frequency spacing, for example by complex multiplication of the samples with a local oscillator signal (NCO) numerically generated by direct digital synthesis in the complex number space (4).
  • NCO local oscillator signal
  • the latter is obtained by sampling successively taken from a sine or cosine table, since in the specific case usually an integer division ratio is present, the signal generation is limited to a purely sequential cyclic removal without phase accumulator.
  • the output signal of the other filter bank is now offset in time by half a symbol duration (5), this can be done, for example, by means of a ring buffer or a FIFO queue.
  • each output signal before the summation (7) via a for example from a table (6) generated periodic function is scaled so that the output power of one signal is then a maximum, if the other at zero lies.
  • a dynamic selection of the function can be made.
  • PAPR peak to average power ratio
  • a Lokaloszilator (9), vector modulator (10) and (PA) transmission amplifier (11) with existing antenna - transmitter still subjected to a predistortion or another upsampling to an intermediate frequency
  • the scaling functions should also be based on the meaning of the data to be transmitted or on its freedom from error or on the available redundancy.
  • the embodiment according to dependent claim 12 provides for this purpose that, in the case of a packet-oriented (IP) data transmission, either the data packets belonging to a low quality service class are in turn assigned transmit data blocks, which are transmitted via a filter bank, which with reduced power into the transmission signal received. Alternatively, it is possible to timestamp packets which indicate the desired arrival time of the packet at the receiver or to derive these time relationships from the position of the packet in a queue.
  • IP packet-oriented
  • the sender can then attempt to pre-transmit on transmission data blocks with reduced power or transmission quality those packets which are not yet ready for transmission according to the time assignment. If the packet reaches the receiver and the error control code evaluates it as error-free or correctable, this can be communicated to the sender and so a later retransmission via transmit data blocks with full power and high transmission quality are avoided, thereby bandwidth is saved in the case of good radio transmission ratios and the latency shortened.
  • a special demultiplexer is used in the receiver according to the particularly advantageous embodiment of dependent claim 2, which is synchronized to the symbol clock. This makes a soft weighting of the incoming samples, which, and this is the crucial trick at this point, simulates a zero crossing in the example QPSK symbol whenever the incoming samples are each destined for the other analysis filter bank.
  • the power drop resulting from a 180 degree transition can also be artificially realized for all other phase jumps, thereby ensuring that at this point the spectrum is available for transmission of the other multicarrier symbol class from the other filter bank.
  • the individual (unmodulated) subcarriers of the one class are placed in the filter edges of the matched filter of the other class by the frequency offset, they contribute little to the interference between two multicarrier symbol classes due to the temporal and frequency offset.
  • the effect can be further enhanced by inserting zero sample values in a subcritical filter bank or by the already described weighting of the output signals of the filter banks according to dependent claim 5.
  • the bandwidth for the guard interval is thus completely available for data transmission, there is also no risk of failure of the transmission method for large propagation time differences in multipath reception and interference on adjacent carriers are easily eliminated by the frequency response of the classical filter, while in the ordinary OFDM as a result the sin (x) / x function of the filter curve of a single carrier, which inherently results from the Fourier transform, can penetrate directly to even more distant carrier.
  • a particular advantage of the invention is the possible choice of differently wide filters for individual subcarriers for the purpose of different symbol rates for data of different service classes according to subclaim 9.
  • a set of high symbol rate carriers may be used for the bandwidth allocation protocol in a point-to-multipoint transmission system, thereby speeding up the allocation of bandwidth and reducing overall latency.
  • Another possibility is the rapid transmission of information for confirmation of successfully transmitted data or for the rapid transmission of repeat requests (ARP / HARP). If necessary, the data sent again if necessary can then be combined with the originally transmitted data for the purpose of error correction; such a soft overlay is particularly suitable for turbo codes.
  • pilot carriers are transmitted according to subclaim 10, they can also be used as an alternative for preamble in packet-oriented transmission or cyclically inserted sync word for exact synchronization of the symbol clock between transmitter and receiver, which for the unit according to dependent claim 2 for separating the input data streams in the receiver necessary is.
  • orthogonal pilot subcarriers can be used in another class, for example, to correct an I / Q imbalance or an I / Q offset.
  • a use of the pilot subcarriers for Doppler correction is also conceivable. Since a pure frequency offset is produced by the Doppler effect, the correction can be carried out directly by reversing the frequency shift of a symbol class in the receiver and the optionally combined transmission of the intermediate frequency into the baseband by means of Digital Down Converter.
  • the use of the pilot subcarrier offers for a correction of the channel impulse response
  • the coefficients of the FIR filter of an analysis filter bank constructed according to dependent claim 3 can also be corrected adaptively.
  • this method does not preclude a subsequent correction of the samples of the individual subcarriers according to complex multiplication as in classical OFDM.
  • differential modulation according to dependent claim 6 can be used so as not to give rise to the need for an absolute phase reference.
  • Radio devices according to the present invention can be combined with single-frequency radio transmission methods, the symbols are simply transmitted by different transmitters synchronously with the same data on the transmitter side, the correction takes place virtually automatically due to the long symbol duration.
  • the procedure according to DE102004013701A1 find use.
  • this transformation can then be optimized mathematically for the respective transmission conditions.
  • the use of the invention is not limited to the wireless transmission, the use for data transmission on copper subscriber lines for a DSL service is just as conceivable as the transmission of data under water by means of ultrasound.
  • the invention further relates to a modulator for CIFDMultiton modulation methods with hexagonal symbol arrangement.
  • the invention relates to a modulator for generating a multi-tone signal for the novel Comb Interleaved Frequency Division Multiplex (CIFDM) modulation method in the specific expression of a largely hexagonal arrangement of subcarriers.
  • the modulator makes it possible to achieve the optimum hexagonal packing density of the subcarrier symbols for the purpose of achieving high spectral efficiency while maintaining an extremely high immunity of the multitone signal.
  • the invention has for its object to transmit a broadband data stream as a radio signal as trouble-free as possible over a greater distance.
  • a broadband data stream as a radio signal as trouble-free as possible over a greater distance.
  • reflections caused by multipath signals can be reconverted undisturbed in the original data stream again.
  • a task comparable to this task consists in the transmission of a broadband data stream via a simple copper cable, such as e.g. a subscriber line, also on this there are reflections on discontinuities such. Terminal blocks.
  • this distance statement refers to units which are related to one another according to the time-bandwidth product and which correspond to corresponding samples in a data stream representing the signal. It is obvious that in this case, unlike a conventional Fourier transform for the known OFDM method, the fixed number of transformed samples results in a symbol duration divided by the number of samples transformed at the block, rather it is indicated by the indicated one Geometry required to adjust the symbol duration to the vertical in the triangles in Figure 4.
  • the object of this invention is to construct a suitable modulator for this, the difficulty is to be considered that the number of samples at the output of the modulator per symbol is a non-integer multiple of the input values of the transformation due to the adaptation of the symbol duration.
  • Figure 5 shows the appropriate signal processing in graphic form, whose individual elements in Figure 5 are referenced below with numbers in parentheses.
  • a microprocessor or digital signal processor takes over the data to be transmitted from the source and divides them by software into individual data blocks (101).
  • the data blocks are provided, if necessary, with a fail-safe code for forward error correction, which adds to the actual data bits redundant information for later error correction in the receiver.
  • the blocks are then prepared by the processor for modulation (102), this being done, for example, a selection of several bits per subcarrier for a QPSK or QAM modulation. From each bit group, a complex number is formed as a baseband sample corresponding to a table or formula. This number is an input value for a subsequent orthogonal transformation, in particular inverse Fourier transformation provided.
  • a phase adaptation of the baseband sample values corresponding to the respective start time of a symbol now takes place.
  • the sub-symbols of the two symbol combs in the example are to be distributed in a hexagonal pattern according to FIG. It follows that the number of samples in the time plane is a non-integer multiple of the number of input values. However, an input value-activated sinusoidal tone of a subcarrier as a result of the inverse Fourier transformation (104) would be disturbed by this time offset in each case discontinuously and thus sensitively.
  • the phase matching provides that the sample at the start time of a symbol corresponds to the phase of the sine wave that would result if the sine tone of the last symbol had continued until then, assuming, of course, a constant input value.
  • phase matching is thus achieved in the example by setting the extension of the symbol duration to the symbol length resulting from the transformation length - where a ratio of one corresponds to a phase angle of 360 degrees -, hence the necessary phase angle for the correction of the fundamental frequency of the Fourier transformation is derived, this multiplied by the index of the input value - with index start value zero for the DC component - and then the 360 degrees modulo is formed.
  • a complex number can now be calculated from the resulting phase value by means of the CORDIC algorithm; the input value for the inverse Fourier transformation is now multiplied by this number in the complex number plane.
  • the CORDIC algorithm which is inherently incremental in nature, can also be integrated into the calculation of the phase adjustment values; the phase adaptation can be carried out both on the basis of absolute and, for example, the previous symbol of relative phases. Furthermore, it is advisable to buffer the phase adjustment values for recurring phases.
  • phase-corrected input values are now supplied to the orthogonal transformation (104), preferably an inverse Fourier transformation in the form of the fast Fourier transformation (FFT) is used here.
  • FFT fast Fourier transformation
  • the FFT configuration of Pease with a fixed permutation is particularly well suited for fast hardware implementation.
  • the optionally statically or dynamically scaled within the inverse FFT arithmetic unit output values are then stored according to the invention in a memory.
  • the storage takes place in each case with a gap of one block spacing, as indicated in FIG. 5 (105), in order to be able to mask the read pointer for the following multiplexed FIR filter according to subclaim 18.
  • the masking causes a repetition of the data, but with the application of new coefficients, with equally progressive coefficients and data pointers of the filter. Only then is it possible to correctly synthesize the number of total output values corresponding to the number of input values and thus also output values of the inverse FFT in a non-integer ratio in the sense of the FIR filter equations.
  • advanced implementations can reuse the resulting memory gap, for example, by adjusting the bits of the read data pointer above the mask by means of a barrel shifter so that when the FFT output data is stored, they can be continuously written.
  • a modulo arithmetic unit can be used to calculate the read pointer.
  • the masking as well as the modulo arithmetic unit further offset values can, for example, be added for different send combs or channels before the read or write memory access, if required.
  • the output values of the FFT thus stored are now fed to a multiplexed complex FIR filter which, according to dependent claim 23, can use the complex coefficients to incorporate the frequency offset of the combs required for this modulation method against each other in one go.
  • the filter receives its coefficients, as shown in FIG. 5, block-by-block from a plurality of data blocks obtained by inverse FFT, one complex sample each comprising one data block with a precisely defined coefficient from the coefficient memory (106). multiplied (107), the sum of these products is formed in an adder (108) and is then available at the modulator output as the output value for digital-to-analog conversion with or without further processing. Further processing, for example, depending on the subsequent analog or high-frequency module, the combination with other symbol combs, frequency offset, global filtering or upsampling or the formation of an analytical signal by delayed Hilbert transformation in question.
  • the Output FIR filter In order to reduce the number of complex multipliers required (107) and to have a high degree of flexibility in the design of the length of the data blocks for a limited number of read ports of the buffer (105) and the coefficient memory (106), it is appropriate for the Output FIR filter to perform necessary calculations sequentially and this to design the FIR adder (108) as an accumulator. This is cleared at the beginning of a FIR arithmetic cycle and returns the previous sum as new summands for the next cycle with each multiplication addition clock. Of course, this calculation can also be made according to the prior art in a pipeline with optional stall. After the required number of cycles, the output value is output and an increment of the base read pointers.
  • the read pointer can be formed for this purpose by means of a bit reversal operation.
  • an index is first formed, which is set to zero with the clearing of the accumulator and increased with each addition cycle.
  • This index is now bit-inverted so that the lowermost bit corresponds to the address offset equal to half the distance of the fixed-distance hardware read pointers.
  • the second lowest bit corresponds to the quarter distance, etc.
  • the value thus formed is added to the offset (base read pointer) corresponding to the position of the current sample or coefficient in the first data block or coefficient block.
  • the computation operations required according to the invention can be implemented both in hardware and by suitable configuration of an FPGA, for example as a result of a VHDL description as well as a computer program which controls a signal processor as part of the modulator.
  • the modulator according to the invention is preferably used in radios, in particular base stations or radio modems or mobile devices of a radio network, but also in radio links.
  • the use in a DSL modem offers, whereby a particularly interference-resistant and long-range signal is generated, which significantly reduces the known crosstalk problems with common leadership with other DSL and non-DSL signals in a wiring harness.
  • an application for the control of optical modulators for fiber optic cables is conceivable to produce a signal which is immune to physically induced dips in the optical transmission spectrum.
  • the FIR filter is then input side, the buffer (105) with the input values of the A / D converter of the receiver (possibly after formation of an analytical signal by delayed Hilbert transformation or by frequency offset and filtering), whose output values are then collected in blocks in a further memory and fed to a Fourier transform or FFT following. This is followed by the phase adjustment of the output values and then the decoding.
  • the demodulation of such a hexagonal symbol pattern is also possible in a classical manner with one or more polyphase feeder banks, the input filters of which receive the data from a ring buffer each with the necessary offset. This does not necessarily have to be a multiple of the transformation block length here, the choice of the sampling time is non-binding in the case of analysis.
  • the invention further relates to a modem with an additional device for measuring and reducing crosstalk attenuation.
  • the invention relates to a modem which uses a multitone transmission method with band-limiting Gauss or Matched Filterbänken, with an additional device for measuring and reducing crosstalk interference by using specially modulated especially with pseudo random or gold codes subcarrier for detecting crosstalk.
  • the invention is based on the object of providing a broadband data stream as a radio signal in a point-to-multipoint system with a central unit, typically in the case of wired transmissions, this is a DSL connection multiplexer (DSLAM), in wireless transmissions the radio base station, and peripheral units, typically the customer modems, if possible trouble-free transmission over a greater distance.
  • DSL connection multiplexer DSL connection multiplexer
  • the capacity-limiting crosstalk between different transmission directions, ie individual cables in a cable bundle or spatial directions, which are served by separate antennas or by phased array beam forming, should be reduced by a suitable choice of transmission parameters.
  • DE 102007036828 introduces the novel modulation method CIFDM, which is distinguished by combining the advantages of the high spectral efficiency of the OFDM method with the robustness of a multicarrier method with conventional modulation of the individual carriers.
  • the signal / noise ratio of this novel transmission method also suffers from crosstalk disturbances, for example on a cable bundle, due to the signals of other subscribers.
  • a direct measurement and allocation of the subcarrier fails so far on the coupling properties of the commonly used OFDM / DMT method due to the unfavorable sin (x) / x filter form in the frequency domain.
  • DSL transmission system consisting of a DSL connection multiplexer (DSLAM) and the customer modems, which are connected via a cable bundle with single pairs with the DSLAM.
  • DSL connection multiplexer DSL connection multiplexer
  • each modem is requested to send a test signal on one or more dedicated subcarriers, according to the main claim.
  • a test signal is a pseudo random noise signal or gold codes, wherein the polynomial and the initialization data from the DSLAM are specified as a central unit on a control channel.
  • the DSLAM now performs a test measurement on each subcarrier on each incoming pair and makes a correlation with the given codes.
  • the special capability of the invention to combine such a measurement method with such a multi-tone transmission method which works with band-limiting filters or matched filters or filter banks and thus allows continuous transmission of pseudo random noise signal, in contrast to the known OFDM modulation with blockwise transmission:
  • the correlation can also be continuous over long periods of time and thus allows a very high accuracy in the determination of crosstalk, at the same time takes place by the transmission of the test signal no interference other payload channels, as worked here with clear band-limiting Matched or Gauss filters becomes.
  • a transmission can even take place on a useful signal subcarrier, a slow additional modulation of the useful signal with a pseudo random noise signal of low amplitude will hardly affect the useful signal, but is easily through the long continuous transmission time accurate cross-correlation possible.
  • the assignment of the codes is preferably carried out according to the criterion of the subclaim 30 in order to ensure a certain strength of the measurement against reflections.
  • a crosstalk matrix is calculated from the measurement data obtained in this way, or a bipartite graph is calculated to reduce the memory requirement, and the identifiers of the subscriber modems on the one hand and the identifiers of the high over talk as contiguous on the other hand Subcarrier has. For third-party disturbances by third-party modems not included in this system, a further total entry is conceivable.
  • an optimal allocation of the subcarriers and transmission powers with suitable optimization algorithms is now calculated from these data, these are well known from the literature, the optimization can also be based on economic specifications such. the bandwidths booked by the customer, a uniform distribution according to current or predicted data throughput needs is to be striven for.
  • a suitable strategy can be chosen for the occupancy of subcarriers, which are particularly covered by third-party bugs. The use for pilot carriers is conceivable.
  • this calculation and allocation is then transmitted as transmission release to the respective modems from the DSLAM.
  • this calculation and allocation can be made continuously, in particular it makes sense for a newly einbuchendes first modem only to allow the transmission of weak test signals and initially make a very conservative assignment of subcarriers, which does not bother other participants.
  • Another use for the measured values is to introduce them into a forward error correction method according to subclaim 32 as a priori information in order to specify the degree of uncertainty of the soft bits obtained from individual subcarriers.
  • a lowering of the soft bit values from subcarriers affected by high crosstalk towards an undecidable mean value for turbo decoders or LDPC decoders also a more detailed introduction into the correction process, such as the selection of the result which is least dependent on unsafe subcarriers, is conceivable.
  • test signals can also be used simultaneously as an alternative to the modulation on user data carriers as a pure pilot carrier, which at the same time the correction of reflections through an equalizer in the frequency domain.
  • a further possibility of using the crosstalk measurement results is in the control of the line driver, here it is advisable, in addition to the transmission power whose impedance electronically controlled so that the crosstalk or reflections or the operating attenuation are reduced by reflections.
  • a test transmission can be carried out with different configurations of the line driver and the configuration with the best transmission characteristics can be selected.
  • a frequency-dependent setting is also conceivable, for example, by a suitable selection of filters in an analog feedback path for active impedance control. The same applies to the configuration of a line receiver.
  • control and monitoring of the sub-carrier allocations is centralized according to claim 35 via an external computer system with a suitable control software, in this case can be retrieved from a customer database profiles for the confirmed and variable data rates of a customer and incorporated into the decision-making process.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Quality & Reliability (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Time-Division Multiplex Systems (AREA)

Abstract

L'invention concerne un appareil radio doté d'un nouveau procédé de modulation "Comb Interleaved Frequency Division Multiplex" (Multiplexage par division de fréquence et entrelacement en peigne - CIFDM), qui combine les avantages de la modulation OFDM connue et les avantages des modulations classiques sur une seule porteuse. Le flux de données à envoyer est divisé en deux blocs de porteuses multiples qui sont envoyés en étant entrelacés l'un dans l'autre avec décalage de fréquence et décalage temporel. Pour chaque sous-porteuse séparée d'un bloc, on utilise ainsi une modulation classique avec un système de filtre adapté, et l'intervalle de garde disparaît. Le rendement spectral est ainsi considérablement accru par le fait que l'on insère un passage artificiel par zéro pour chaque symbole de modulation. Pendant ce passage par zéro, l'autre bloc est transmis et est séparé dans le récepteur par un inverseur synchrone.
EP08801511A 2007-08-03 2008-08-01 Appareil radio doté d'un nouveau procédé de modulation cifdm Withdrawn EP2174440A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE102007036828A DE102007036828B4 (de) 2007-08-03 2007-08-03 Funkgerät mit neuartigem CIFDM Modulationsverfahren
DE102008015513 2008-03-24
DE102008030179A DE102008030179A1 (de) 2007-08-03 2008-06-28 Modem mit Zusatzeinrichtung zur Messung und Reduzierung der Übersprechdämpfung
PCT/EP2008/006382 WO2009018980A2 (fr) 2007-08-03 2008-08-01 Appareil radio doté d'un nouveau procédé de modulation cifdm

Publications (1)

Publication Number Publication Date
EP2174440A2 true EP2174440A2 (fr) 2010-04-14

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EP08801511A Withdrawn EP2174440A2 (fr) 2007-08-03 2008-08-01 Appareil radio doté d'un nouveau procédé de modulation cifdm

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Country Link
EP (1) EP2174440A2 (fr)
WO (1) WO2009018980A2 (fr)

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CA3076552C (fr) * 2017-09-20 2023-03-14 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Synchronisation temporelle adaptative pour la reception de signaux en rafale et en continu
DE102022113117B3 (de) 2022-05-24 2023-10-05 Oliver Bartels Besonders sicheres Mehrträger-Kommunikationsgerät für hohe Datenraten
CN115278859B (zh) * 2022-08-03 2024-10-29 易事特储能科技有限公司 无线载波同步方法、装置、设备及可读存储介质
CN116708112B (zh) * 2023-08-07 2023-10-03 中国电子科技集团公司第二十九研究所 降低fmt系统papr的传输与检测方法、介质及装置
CN120044443B (zh) * 2025-04-15 2025-06-20 济宁市海富电子科技有限公司 一种手机数据线电性能测试方法

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CA2064758C (fr) * 1990-06-12 1996-11-12 Steven Charles Jasper Signal de communication a composante pilote temporelle
IT1261364B (it) * 1993-12-01 1996-05-20 Sisvel Spa Sistema di ricetrasmissione di dati a multiplazione ortogonale con modulatore unico per l'allocazione in frequenza dei sottocanali
ATE259129T1 (de) * 1996-11-08 2004-02-15 France Telecom Erzeugung von prototypsignalen für mehrträgerübertragung
FR2765757B1 (fr) * 1997-07-01 1999-09-17 France Telecom Procede et dispositif de modulation d'un signal multiporteuse de type ofdm/oqam, et procede et dispositif de demodulation correspondants

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Title
See references of WO2009018980A2 *

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WO2009018980A2 (fr) 2009-02-12

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