CA2673634A1 - Method of determining a channel quality and modem - Google Patents

Method of determining a channel quality and modem Download PDF

Info

Publication number
CA2673634A1
CA2673634A1 CA002673634A CA2673634A CA2673634A1 CA 2673634 A1 CA2673634 A1 CA 2673634A1 CA 002673634 A CA002673634 A CA 002673634A CA 2673634 A CA2673634 A CA 2673634A CA 2673634 A1 CA2673634 A1 CA 2673634A1
Authority
CA
Canada
Prior art keywords
sub
noise
channels
sort
fraction
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.)
Granted
Application number
CA002673634A
Other languages
French (fr)
Other versions
CA2673634C (en
Inventor
Dimitri Korobkov
Patrick Langfeld
Hans Benninger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Technology AG
Original Assignee
Abb Technology Ag
Dimitri Korobkov
Patrick Langfeld
Hans Benninger
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 Abb Technology Ag, Dimitri Korobkov, Patrick Langfeld, Hans Benninger filed Critical Abb Technology Ag
Publication of CA2673634A1 publication Critical patent/CA2673634A1/en
Application granted granted Critical
Publication of CA2673634C publication Critical patent/CA2673634C/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B3/00Line transmission systems
    • H04B3/54Systems for transmission via power distribution lines
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • H04L27/2601Multicarrier modulation systems
    • H04L27/2647Arrangements specific to the receiver only
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0044Arrangements for allocating sub-channels of the transmission path allocation of payload
    • H04L5/0046Determination of how many bits are transmitted on different sub-channels
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058Allocation criteria
    • H04L5/006Quality of the received signal, e.g. BER, SNR, water filling
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B2203/00Indexing scheme relating to line transmission systems
    • H04B2203/54Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5404Methods of transmitting or receiving signals via power distribution lines
    • H04B2203/5416Methods of transmitting or receiving signals via power distribution lines by adding signals to the wave form of the power source
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/0001Arrangements for dividing the transmission path
    • H04L5/0003Two-dimensional division
    • H04L5/0005Time-frequency
    • H04L5/0007Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT

Abstract

The present invention is concerned with an Orthogonal Frequency Division Multiplex (OFDM) data transmission over a transmission channel that is subject to narrowband interferers. An increased overall bit or data transmission rate is achieved by a method of determining a channel capacity of a plurality of sub-channels of the transmission channel based on a net background noise power estimation. The net background noise power comprises only white noise-like contributions and excludes; to a reasonable extent; noise contributions or signal power from narrowband interferers. Hence, the net background noise power is reduced as compared to the conventional case of a background noise power estimated for the totality of sub-channels or a continuous transmission band. Based on this, an OFDM signal code construction or bit allocation scheme is chosen that provides for optimized data transmission at a data rate that approximates or approaches the more realistic channel capacity of the individual sub-channel, resulting in an increased overall bit or data transmission rate.

Description

DESCRIPTION
METHOD OF DETERMINING A CHANNEL QUALITY AND MODEM

FIELD OF THE INVENTION

The invention relates to the field of multi-carrier data transmission, and in particular to Orthogonal Frequency Division Multiplex (OFDM) data transmission. It is concerned with the determination of a channel quality of a plurality of sub-channels of a multi-carrier data transmission subject to narrowband interferers.

BACKGROUND OF THE INVENTION

For the transmission of digital data, multi-channel data transmission based on Orthogonal Frequency Division Multiplex (OFDM), also known as Discrete Multitone (DMT) modulation, is a well-known flexible modulation scheme. OFDM spreads the data to be transmitted over a large number of sub-carriers or sub-channels comprised in a transmission band and separated from each other by a well-defined frequency spacing. The latter ensures orthogonality of the sub-carriers and prevents crosstalk or inter-carrier interference between sub-carriers, i.e. the demodulator for one sub-carrier is not affected by the modulation of the other sub-carriers even though there is no explicit filtering and their spectra overlap. The individual OFDM modulation symbols on each of the carriers represent a number of bits that depends on the choice of the QAM alphabet, i.e. the arrangement of data or constellation points in the quadrature amplitude plain.
For instance, 2 bit/symbol for Quadrature Phase Shift Keying (QPSK), or 4 bit/symbol for 16-QAM
(Quadrature Amplitude Modulation) is commonly used. The complex processes of modulating and demodulating thousands of carriers simultaneously are equivalent to Discrete Fourier Transform operations, for which efficient Fourier transform algorithms exist.

A suitable OFDM modem architecture comprises an encoder to multiplex, synchronize and encode the data to be transferred, as well as a modulator to form a discrete multitone signal. The encoder translates incoming bit streams into in-phase and quadrature components for each of a multiplicity of sub-channels, i.e. the encoder outputs a number of sub-symbol sequences that are equal to the number of sub-channels available to the system.
A line monitor at the receiver checks the line quality of the sub-channels, e.g. by repeatedly determining the noise-level, gain and phase-shift individually for each of the sub-channels during operation. The background noise power of the totality of sub-channels in the transmission band as well as the bit error rate (BER) and/or the signal-to-noise ratio (SNR) of each individual sub-channel are then used to determine the channel capacity of the sub-channels, i.e. the information density or bit transmission rate that each sub-channel can support. An optimization signal code construction procedure selects an appropriate QAM alphabet or bit allocation scheme that results in a data rate that approximates the sub-channel capacity by considering conditions of limited signal power and maximum bit error rate.

OFDM is suited in particular for Power Line Communication (PLC). Power line data channels at high or medium voltage are affected by interferers, because the cable types that are used for the transmission of electric power are unshielded and therefore vulnerable for electromagnetic ingress. The typical noise scenario on power line channels resulting there from comprises so-called narrowband interferers, i.e. signals with a small bandwidth originating e.g. from radio transmissions and presenting a spectral amplitude rising up to 40 dB above a background noise level deprived of any contribution from narrowband interferers. Likewise, conventional analogue television signals essentially behave like narrow-band interferers to OFDM. Thus, the power line channel does not present an additive white Gaussian noise (AWGN) environment, but in the frequency range from some hundred kilohertz up to 20 MHz is mostly dominated by narrow-band interference caused by ingress of broadcast stations with a received level generally varying with daytime, and impulsive noise from switching power supplies or other transient phenomena.
The international patent application WO 97/40609 is concerned with the reduction of radio-frequency (RF) interference from narrow frequency amateur radio bands between 1 MHz and 12 MHz in a wide-band multi-carrier transmission system. A "drop"
portion of a standard unshielded twisted-pair ADSL subscriber line covering the last 30 m or less up to a remote unit is found to be able to both receive and emit RF signals. In a restricted band comprising the sub-channels prone to interference, no sub-carriers are used for data transmission. In addition, a dummy tone may be used to suppress transmitted power from sidelobe transmissions within that band.
The patent application EP-A 1 137 194 proposes to determine individual SNRs for the sub-channels in a OFDM system and, based there upon, to reallocate data transmission rate and/or signal power to the sub-channels. According to the patent US 6,456,653 the overall SNR in OFDM systems is estimated during regular operation by determining a noise power of inactive sub-carriers and a signal plus noise power of active sub-carriers, and subtracting the former from the latter to obtain a signal power.

DESCRIPTION OF THE INVENTION

It is an objective of the invention to increase the overall bit or data transmission rate of a multi carrier data transmission, and in particular of an Orthogonal Frequency Division Multiplex (OFDM) data transmission, over a transmission channel that is subject to narrowband interferers. This objective is achieved by a method of determining a channel quality, in particular a channel capacity, of a plurality of sub-channels of the transmission channel, as well as by a modem according to the claims 1 and 8, respectively.
Preferred embodiments are evident from the dependent patent claims, wherein the claim dependency shall not be construed as excluding further meaningful claim combinations.

According to the invention, a net background noise power is estimated for the purpose of determining a channel quality, such as a channel capacity, of an individual sub-channel or sub-carrier, based on which the sub-channel may subsequently be assigned an appropriate bit-allocation scheme or even be masked for being affected by narrowband interferers. The net background noise power is based on spectral noise values of at least two selected sub-channels comprising only white noise-like contributions and excludes; to a reasonable extent; noise contributions or signal power from narrowband interferers.
Hence, the net background noise power is reduced as compared to the conventional case of a background noise power estimated for the totality of sub-channels or a continuous transmission band. Accordingly, a channel quality determination for an individual sub-channel yields a higher and more realistic, or less conservative, result than in the latter case. Based on this, a bit allocation scheme or OFDM signal code construction is chosen that provides for optimized data transmission at a data rate that approximates or approaches the more realistic channel quality of the individual sub-channel, resulting in an increased overall bit or data transmission rate.

In an advantageous embodiment of the invention, a noise spectral density is recorded.
The spectral noise values constituting the spectrum are sorted, and a first fraction or part of the spectrum comprising the higher spectral noise values is disregarded from a subsequent estimation of the net background noise power. Provided that a suitable criterion for splitting the spectrum is available, this approach is less onerous than an identification of the position of the narrowband interferers, or the affected sub-channels, by repeatedly screening the spectrum for a maximum spectral noise value and eliminating the corresponding sub-channel.

In a first preferred variant, the sorted noise spectrum is normalized with respect to a value at the centre or middle of the spectrum, and not with respect to a mean spectral noise value that would be influenced or biased in an unforeseeable way by a few sub-channels with an exceptionally high spectral noise value. Thus a subsequent comparison of said normalized spectrum with a fixed, pre-determined first threshold represents a first suitable criterion in the aforementioned sense.

In a second preferred variant, the net background noise power is estimated by disregarding the contribution of a first fraction of the sub-channels, defined with the help of a critical normalized derivative as a second threshold or suitable criterion in the above sense. To this end, a smoothing operation is performed beforehand by averaging two or more successive normalized spectral noise values, i.e. values that are adjacent or neighbouring according to the sorted noise spectrum.

In an advantageous embodiment, the statistical confidence of the net background noise power is further improved by disregarding sub-channels at both ends of a second fraction or remaining part of the spectrum, i.e. by eliminating the highest and lowest spectral noise values within the second fraction before estimating the net background noise power.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the invention will be explained in more detail in the following text with reference to preferred exemplary embodiments which are illustrated in the attached drawings, in which:
Fig.l schematically shows the components of an OFDM modem, Fig.2 depicts a flow chart of a net background noise power estimating procedure, and Fig.3 represents a normalized sorted noise spectrum {N'o,soYt(k)} and a derivative {S'(l)}.
The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig.l shows a digital implementation of the orthogonal frequency division multiplexing (OFDM) modulation method. In an OFDM base modulator 10, a QAM-vectoriser 11 5 generates a vector of frequency coefficients in accordance with parallelised digital input bits from the digital input signal D. According to a mapping scheme such as (Quadrature Amplitude Modulation) or, as a special case thereof, 2MDPSK
(Differential Phase Shift Keying) modulation, the frequency coefficients are generally complex 2M-ary symbols Dk. From the vector of frequency coefficients, an Inverse Fast Fourier Transform (IFFT) 12 generates an in-phase component I and an orthogonal quadrature component Q
of a discrete multitone signal. In block 13, each of said components is padded with a cyclic prefix, resulting in two real-valued sequences at sampling rate l/To, i.e. an in-phase component ol (n) and a quadrature component oQ (n) of the modulated digital signal.

In order to prepare the OFDM signal for a frequency shift, the components are upsampled by a factor mlo in upsampler 14, where mlo > (2fo + Bo )To , with Bo being the bandwidth of the OFDM transmission band and fo being its center or frequency offset, must be satisfied to fulfill the sampling theorem. In the next modulation step, in OFDM
modulator frequency shifter 16, the mid-frequencies of the spectrum of ol and oQ are finally moved to fo . The resulting signals are summed up in an adder 16 to build the transmitted signal which is then converted in a modulator D/A converter 17 to an analogue signal Y for amplification and transmission.

Fig.2 depicts a flowchart of a preferred embodiment of a net background noise power 6n2 (square of the noise variance 6n) estimating procedure according to the invention. In step 1, an initial estimation of a noise spectral density is performed and a normalized sorted noise spectrum {N'o,soYt(k)} is derived. In step 2, a sequence of derivatives {S'(l)} is calculated there from. In step 3, the extent of narrowband interference is defined and those sub-carriers not affected by narrowband noise are identified and selected according to a certain criterion such as a comparison of the aforementioned derivatives {S'(l)} to a predetermined threshold TwIDTH. Finally, in step 4, a net background noise power 6n2 is determined by averaging spectral noise values No(i) of the selected sub-carriers. The individual steps will be described in detail below.
The inventive procedure of measuring channel conditions or noise scenarios is carried out preferably at start-up of the modem, i.e. before data transmission starts, but may be repeated if e.g. the channel conditions do change significantly. During start-up, a preamble is executed, comprising sending and receiving a sequence of test signals including a mute sequence for measuring the noise scenario as detailed in the following.

The procedure starts with an initial estimation of a raw noise spectrum {N'o(i)} of the transmission channel under consideration, also termed noise spectral density or background power density spectrum. To this end, during the mute sequence mentioned, NEsT OFDM symbols devoid of any signalling information are recorded and subsequently averaged, wherein typically 12 < NEsT < 100. Within an individual OFDM symbol time, a number of N samples of the received signal are obtained, with N being equal to the total number of sub-channels. Then a Fourier transform of length N produces a signal S=(So,...,SN 1) in frequency domain. This is repeated for the NEsT OFDM
symbols and the absolute squared values of Si are summed and averaged by division with the number NEsT
of OFDM symbols:

1 N EST-1 ~
N o IS, (n)I N E S T n-o - , 1. (0.1) The effect of a receiver filter is represented by the complex transfer function HRx(i) that is part of the design of the communication system. The transfer function of the receiver filter might be adaptive and depend on characteristics of the transmission channel, but in any case, HRx(i) is known to the receiver. Its influence on the initially estimated raw noise spectrum {N'o(i) } is then eliminated by the following division:

No (i) = No (i) IHRX (i)12 (0.2) The resulting corrected noise spectrum {No(i)} comprising a plurality of spectral noise values No(i) is then sorted, i.e. the spectral noise values No(i) are re-arranged so as to form a sequence of ascending or descending spectral noise values. The resulting sequence or array is termed sorted noise spectrum {No,soYt(k)}, with a sorting index i=IndexNojse(k) being stored in a sorting table.

A conventional preliminary estimation of the noise variance 6,z7 with the narrowband interferers still present, may then be calculated as follows:
~ Mo-1 6N - - ~ No,so,-r (k) Mo k-o (0.3) with Mo being the number of active sub carriers, wherein Mo < N, N being the total number of sub carriers in the transmission band. The set of active sub carriers comprises all the sub carriers positioned in the pass band of the receiver filter and correspondingly depends on the configurable size of the filter pass band. The set of active sub carriers also comprises sub carriers that are used as pilot signals and that are disregarded in the following, leaving a set of M < Mo sub carriers to be evaluated for narrowband interferers.

In a next step of the procedure, the sorted noise spectrum {No,soYt(k)} is normalized with respect to its value at the centre, i.e. at the (sorting) index k=M/2, yielding a normalized sorted noise spectrum {No,soYt(k) } .

NI (k) = No,sorr (k) o's Y` N (M / 2) o,sorr (0.4) From this normalized sorted noise spectrum {No,soYt(k)}, a first fraction or sub-spectrum consisting of those sub-channels for which a normalized spectral noise value exceeds a first threshold, is identified. The foregoing normalization with respect to a value at the centre, as compared to a mean value, eliminates any unforeseeable influence of a few sub-channels with an exceptionally high spectral noise value. Thus a comparison with a fixed, pre-determined first threshold is justified and provides a reasonable result.
The sub-channels of said first fraction, or their respective spectral noise powers, are considered to be affected by narrowband interferers and consequentially excluded from a subsequent estimation of a net background noise power.

However, and despite the clever normalization introduced above, the reference to a first threshold for the identification of the first fraction still gives rise to some ambiguity as to the determination of said first threshold. A reference to a critical derivative of a continuous noise distribution, or equivalently, a critical difference between two neighbouring values of a discrete sorted noise spectrum, thus presents a viable alternative. In view of the preparation and evaluation of such a derivative as detailed in the following, an averaging or smoothing of the normalized sorted noise spectrum {N'o,soYt(k)} is interposed. To this end, for each sub-channel, an average of a number of successive values, including the one from the sub-channel itself, is calculated. In other words, for a particular sub-channel with index 1, an averaged normalized spectral noise value S(l) is calculated by averaging at least two successive normalized spectral noise values, including the normalized spectral noise value N'o,soYt(k(l)) of the particular sub-channel l itself and at least one normalized spectral noise value N'o,,soYt(k(l) 1) of an adjacent or neighbouring sorted sub-channel.

Advantageously, for a particular sub-channel, a lower average or normalized integral S(l) is derived as the average of all normalized spectral noise values N'o,soYt(k>Z) that are equal to or lower than the normalized spectral noise value N'o,soYt(l) of the particular sub-channel:

S(l) = I No,sorr(k) M-l k_I , 1=0,...,M-1 (0.5) and a derivative or first difference S'(l) of the former is calculated as S'(l)=S(l+l)-S(l) 1=0,...,M-2 (0.6) A typical result of the normalized sorted noise spectrum {N'o,soYt(k)} and a sequence of derivatives {S'(i)} is shown schematically in Fig.3.

The resulting sequence of derivatives {S'(i)} is now evaluated to classify the spectrum and to identify a first fraction or part of the spectrum for which the spectral noise values No(i) are significantly higher than for the remaining part or second fraction of the spectrum. To this end, all indices l with Y(Z) < TwiDTH, wherein TwiDTH
denotes a suitably chosen threshold for the derivative, gradient or first difference, are allocated to the first fraction. The threshold TwiDTH is pre-determined, e.g. empirically, in order to find the start of the more or less flat part of the noise spectrum as a criterion to identify the sub-channels considered to be affected by noise power stemming from narrowband interferers.
A typical value of the threshold TwiDTH is -0.05.

Accordingly, the remaining elements with a sorting index 1> k'io,,, where k'io,, is the smallest sorting index of the second fraction or remaining part of the spectrum, are used to obtain a first estimation of the net background noise variance. In order to further improve the estimation accuracy, a predefined number or percentage, typically 10%, of the highest and lowest spectral noise values of the second fraction are skipped. By doing so, i.e. by disregarding the extreme values both at the low and the high end of the remaining part, the statistical confidence of the estimation is further increased. The estimation of the net background noise power 6N is then performed over a net background noise estimation fraction as indicated by the bracket in Fig.3, and of which the sorting indices are comprised in-between a lower bound kio,, and a higher bound khigh:
1 1 khrgh (7N I Nosorr (k) khigh - klow + 1 k=kr_ (0.7) This estimated net background noise 6N serves as an input for the optimisation procedure of signal code construction as exemplified below.

Finally, Fisher statistics or maximum likelihood principle is applied to generate a spectral mask of narrowband interferers, i.e. to definitely identify the sub-channels that are not to be occupied by the OFDM transmission. To apply Fisher statistic the sorted noise spectrum {No,soYt(k)} is subdivided into two subspaces and the relation of signal energy inside the two subspaces is calculated and compared with a threshold. Subspace A is given by a moving window of size W. Subspace B is equal to the above defined net background noise estimation fraction. The energy 6N in subspace B, the squared value of 6N in (0.7), is already known. The Fisher statistic yields 1: No,soYi (k) FNB(kW)= W k~W 2 N (0.8) For a window of size W = 1 as chosen in the following, the window position index kW
equals the array index k.

Now a subchannel i=IndexNoi,e(k) identified by the channel-index i and the corresponding noise-index k is masked as affected by narrowband interferers, if the following two conditions are true:

1. the result of Fisher statistic exceeds a threshold FNB(k) > TNB
2. the spectral noise value No(i) exceeds a threshold No(i) > TNoi,e As the first condition evaluates the power of narrowband interferers only in relation to the net background noise power, the absolute power of an interferer, i.e. its spectral noise value No(i), could be so small that it would not influence or harm the data transmission quality. Hence the second condition prevents sub-channels with high relative and low absolute noise levels from being excluded from data transmission.

LIST OF DESIGNATIONS
10 OFDM modulator 11 QAM vectoriser 12 Inverse Fast Fourier Transform 13 Cyclic Prefix 14 Upsampler Frequency shifter 16 Adder 5 17 D/A converter

Claims (9)

1. A method of determining a channel quality of a plurality of sub-channels of a multi-carrier data transmission subject to narrowband interferers, characterized in that the method comprises - providing a sorted noise spectrum {N0,sort(k)} comprising spectral noise values N0(l) of the plurality of sub-channels in ascending or descending order, - splitting the sorted noise spectrum {N0,sort(k)} into a first fraction with higher spectral noise power from sub-channels that are subject to narrowband interferers and a second fraction with lower spectral noise values, - estimating a net background noise power .sigma.n2 based on the spectral noise values from the second fraction, and - determining the channel quality based on the estimated net background noise power.
2. The method according to claim 1, characterized in that the estimation of the net background noise power .sigma.n2 comprises - calculating a normalized sorted noise spectrum {N'0,sort(k)} from the sorted noise spectrum {N0,sort(k)}, - splitting the sorted noise spectrum {N0,sort(k)} into a first fraction with normalized spectral noise values above and a second fraction with normalized spectral noise values below a first threshold.
3. The method according to claim 1, characterized in that the estimation of the net background noise power .sigma.n2 comprises - calculating a normalized sorted noise spectrum {N'0,sort(k)} from the sorted noise spectrum {N0,sort(k)}, - calculating, for each of the plurality of sub-channels, an averaged normalized spectral noise value S(l) by averaging the normalized spectral noise value of the sub-channel N'0,sort(l) and at least one successive normalized spectral noise value N'0.sort(l~1), - calculating derivatives S'(l) by computing the difference between two successive averaged normalized spectral noise values S(l), S(l+1), and - splitting the sorted noise spectrum {N0,sort(k)} into a first fraction with derivatives S' above and a second fraction with derivatives S' below a second threshold T WIDTH.
4. The method according to claim 3, characterized in that the calculation of the averaged normalized spectral noise value S(l) for each of the plurality of sub-channels comprises - averaging all normalized spectral noise values N'0,sort(k>=1) that are not above the normalized spectral noise value of the sub-channel N'0,sort(l).
5. The method according to one of claims i to 4, characterized in that the estimation of the net background noise power .sigma.n2 comprises - reducing the second fraction by a predefined number of sub-channels at both ends, and calculating the net background noise power .sigma.n2 as the sum of the spectral noise values N0(i) of the sub-channels comprised in the reduced second fraction.
6. The method according to claim 5, characterized in that it comprises - excluding sub-channels from data transmission for which a ratio of the spectral noise value N0(l) to the net background noise power .sigma.n2 exceeds a third threshold T
NB, and for which the spectral noise value N0(i) exceeds a forth threshold T Noise.
7. A modem for multi carrier data transmission comprising means for determining a channel quality of a plurality of sub-channels of a transmission channel subject to narrowband interferers, characterized in that the modem comprises - means for providing a sorted noise spectrum {N0,sort(k)} comprising spectral noise values N0(i) of the plurality of sub-channels in ascending or descending order, - means for splitting the sorted noise spectrum {N0,sort(k)} into a first fraction with higher spectral noise power from sub-channels that are subject to narrowband interferers and a second fraction with lower spectral noise values, - means for estimating a net background noise power .sigma.n2 based on the spectral noise values from the second fraction, and - means for determining the channel quality based on the estimated net background noise power.
8. A use of the method according to one of claims 1 to 6 and/or the modem according to claim 7 in a power line communication data transmission over a high or medium voltage power line.
9. A use of the method according to one of claims 1 to 6 and/or the modem according to claim 7 for Orthogonal Frequency Division Multiplex (OFDM) data transmission.
CA2673634A 2006-12-27 2007-12-21 Method of determining a channel quality and modem Expired - Fee Related CA2673634C (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP06405543A EP1940035B1 (en) 2006-12-27 2006-12-27 Method of determining a channel quality and modem
EP06405543.7 2006-12-27
PCT/EP2007/064498 WO2008077959A1 (en) 2006-12-27 2007-12-21 Method of determining a channel quality and modem

Publications (2)

Publication Number Publication Date
CA2673634A1 true CA2673634A1 (en) 2008-07-03
CA2673634C CA2673634C (en) 2014-04-15

Family

ID=38080885

Family Applications (1)

Application Number Title Priority Date Filing Date
CA2673634A Expired - Fee Related CA2673634C (en) 2006-12-27 2007-12-21 Method of determining a channel quality and modem

Country Status (11)

Country Link
US (1) US8811504B2 (en)
EP (1) EP1940035B1 (en)
CN (1) CN101573875B (en)
AT (1) ATE427589T1 (en)
BR (1) BRPI0722080A2 (en)
CA (1) CA2673634C (en)
DE (1) DE602006006081D1 (en)
ES (1) ES2323477T3 (en)
RU (1) RU2432672C2 (en)
SI (1) SI1940035T1 (en)
WO (1) WO2008077959A1 (en)

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102195679B (en) * 2010-03-10 2013-10-16 青岛东软载波科技股份有限公司 Power line carrier modulation method, demodulation method, circuit and chip
US8848521B1 (en) * 2011-12-22 2014-09-30 Landis+Gyr Technologies, Llc Channel allocation and device configuration
US9667315B2 (en) * 2012-09-05 2017-05-30 Landis+Gyr Technologies, Llc Power distribution line communications with compensation for post modulation
CN104242964A (en) * 2013-06-20 2014-12-24 中兴通讯股份有限公司 Method and device for restraining impulse interference in communication system
RU2545102C1 (en) * 2014-01-09 2015-03-27 Дмитрий Владимирович Григоренко Method of optimising modem operation
US9722650B2 (en) * 2014-12-15 2017-08-01 Intel Corporation Method for noise power estimation
CA2971853A1 (en) * 2014-12-23 2016-06-30 Abraham Hasarchi Harmonizing noise aggregation and noise management in distributed antenna system
US9306624B1 (en) 2015-03-31 2016-04-05 Landis+Gyr Technologies, Llc Initialization of endpoint devices joining a power-line communication network
US9461707B1 (en) 2015-05-21 2016-10-04 Landis+Gyr Technologies, Llc Power-line network with multi-scheme communication
WO2017058169A1 (en) * 2015-09-29 2017-04-06 Aruba Networks Inc. Air-time capacities
CN108111249B (en) * 2016-11-24 2021-03-30 富士通株式会社 Method and device for bit number distribution and power distribution of subcarriers and electronic equipment
US10608786B2 (en) * 2017-02-24 2020-03-31 Huawei Technologies Co., Ltd. Apparatus and methods of specifying ordered sequences of coding sub-channels
TWI646842B (en) * 2017-09-11 2019-01-01 晨星半導體股份有限公司 Circuit applied to display device and related signal processing method
CN114095967B (en) * 2021-11-19 2023-03-31 电子科技大学 Method for evaluating out-of-band interference of ultra-wideband signal
CN114124161B (en) * 2021-12-07 2022-10-18 国网湖南省电力有限公司 Method and device for separating narrow-band noise of communication channel of high-speed power line carrier

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3484757B2 (en) * 1994-05-13 2004-01-06 ソニー株式会社 Noise reduction method and noise section detection method for voice signal
US6035000A (en) 1996-04-19 2000-03-07 Amati Communications Corporation Mitigating radio frequency interference in multi-carrier transmission systems
EP0923824B1 (en) * 1996-09-02 2003-05-28 STMicroelectronics N.V. Improvements in, or relating to, control channels for telecommunications transmission systems
JP3454190B2 (en) * 1999-06-09 2003-10-06 三菱電機株式会社 Noise suppression apparatus and method
US6456653B1 (en) * 1999-08-25 2002-09-24 Lucent Technologies Inc. Fast and accurate signal-to-noise ratio estimation technique for OFDM systems
US7415061B2 (en) * 1999-08-31 2008-08-19 Broadcom Corporation Cancellation of burst noise in a communication system with application to S-CDMA
GB2355145B (en) * 1999-10-08 2003-12-31 Nokia Mobile Phones Ltd A portable device
US6807145B1 (en) * 1999-12-06 2004-10-19 Lucent Technologies Inc. Diversity in orthogonal frequency division multiplexing systems
DE10014676C2 (en) * 2000-03-24 2002-02-07 Polytrax Inf Technology Ag Data transmission over a power supply network
US6763061B1 (en) * 2000-07-31 2004-07-13 3Com Corporation Frequency domain technique for narrowband noise cancellation in DMT receivers
US7804772B2 (en) * 2001-06-08 2010-09-28 Broadcom Corporation Receiver having integrated spectral analysis capability
US7773699B2 (en) * 2001-10-17 2010-08-10 Nortel Networks Limited Method and apparatus for channel quality measurements
US20040218519A1 (en) * 2003-05-01 2004-11-04 Rong-Liang Chiou Apparatus and method for estimation of channel state information in OFDM receivers
US7809067B2 (en) * 2003-10-01 2010-10-05 Nxp B.V. Multi-carrier OFDM UWB communications systems
JP4552635B2 (en) * 2004-12-07 2010-09-29 日本電気株式会社 Multi-carrier transmission apparatus and multi-carrier transmission method
US7526015B2 (en) * 2005-09-15 2009-04-28 02Micro International Ltd. Parallel correlator implementation using hybrid correlation in spread-spectrum communication

Also Published As

Publication number Publication date
WO2008077959A1 (en) 2008-07-03
ATE427589T1 (en) 2009-04-15
CA2673634C (en) 2014-04-15
SI1940035T1 (en) 2009-08-31
EP1940035A1 (en) 2008-07-02
US20090316766A1 (en) 2009-12-24
CN101573875B (en) 2013-04-03
ES2323477T3 (en) 2009-07-16
CN101573875A (en) 2009-11-04
EP1940035B1 (en) 2009-04-01
RU2009128701A (en) 2011-02-10
DE602006006081D1 (en) 2009-05-14
US8811504B2 (en) 2014-08-19
BRPI0722080A2 (en) 2014-04-01
RU2432672C2 (en) 2011-10-27

Similar Documents

Publication Publication Date Title
CA2673634C (en) Method of determining a channel quality and modem
KR100777314B1 (en) Signal constellations for multi-carrier systems
US8457226B2 (en) Crest factor reduction for OFDM communications systems by transmitting phase shifted resource blocks
KR101161382B1 (en) Radio transmitter apparatus and modulation scheme selecting method
US20100124293A1 (en) Method to Reduce Peak to Average Power Ratio in Multi-Carrier Modulation Receivers
CN101115036A (en) Apparatus and method for channel estimation for data demodulation in broadband wireless access system
EP2321941A1 (en) Iterative channel estimation method and apparatus for ici cancellation in multi-carrier systems
US20100061474A1 (en) Fft spreading among selected ofdm sub-carriers
TW201515413A (en) Transmitters and receivers for transmitting and receiving signals
CN111600826A (en) Non-orthogonal access-transmission communication method in communication network
Rajbanshi et al. OFDM-based cognitive radios for dynamic spectrum access networks
Okano et al. Overlap-windowed-DFTs-OFDM with overlap FFT filter-bank for flexible uplink access in 5G and beyond
KR101042774B1 (en) Method and apparatus for transmitting/receiving a signal in a fast frequency hopping - orthogonal frequency division multiplexing communication system
KR100889984B1 (en) Method For Channel Estimation In Virtual Subcarrier Environment
WO2014091198A1 (en) Data processing apparatus and method for reduction of papr in multi-carrier transmission systems
KR100551553B1 (en) Interference Minimized OFDM Based Wireless Communication System and Method Therefor
KR20050119053A (en) The system and method for cinr estimation using puncturing pattern in ofdm
Raosaheb et al. Adaptive OFDM Modulation Used For SDR
EP1914898A1 (en) Method and apparatus for detecting narrowband interferences within a multi-carrier signal, in particular an OFDM modulated UWB signal
KR101112699B1 (en) Apparatus for estimating cinr in wireless communication system and method thereof
KR20050119592A (en) Apparatus and method for channel estimation in a mobile communication system using an frequency hopping - orthogonal frequency division multipl access scheme
KR20110097021A (en) Method and apparatus for transmitting and receiving pilot in wireless telecommunications system
Akilandeswari Reduced Bit Error Rate Over Multiple Fading Channels

Legal Events

Date Code Title Description
EEER Examination request
MKLA Lapsed

Effective date: 20171221