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
  • H04L27/261—Details of reference signals
  • H04L27/2613—Structure of the reference signals
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03G—CONTROL OF AMPLIFICATION
  • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
  • H03G3/005—Control by a pilot signal
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03G—CONTROL OF AMPLIFICATION
  • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
  • H03G3/20—Automatic control
  • H03G3/30—Automatic control in amplifiers having semiconductor devices
  • H03G3/3089—Control of digital or coded signals
• • 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
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
  • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
  • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming

Definitions

• a transmitter for multi-carrier communication A transmitter for multi-carrier communication
• the present invention relates to the field of communication technology, in particular to training signal generation and channel-distortion-correction.
• training signals are commonly used for characterization of a transmission channel between a transmitter and a receiver.
• training signals have a predetermined structure and content which are known at the transmitter and the receiver and thus allow for an adaption of the receiver to varying characteristics of the transmission channel, such as scattering, fading, and power decay over distance.
• the temporal and spectral characteristics of the training signals are of major importance.
• the length of communication symbols and the frequency spacing of subcarriers at a given overall bandwidth are interrelated.
• an improved representation of frequency characteristics of the transmission channel can lead to an increased length of communication symbols and thus to a reduced representation of temporal characteristics of the transmission channel.
• AGC automatic gain control
• a training signal can be provided, which comprises a first subsignal and a second subsignal being transmitted serially in time and differing in frequency components.
• frequency components of the first subsignal are shifted in frequency relative to frequency components of the second subsignal by a pre-defined frequency shift.
• the invention can be applied in any context of multi-carrier communication, in particular multi-carrier communication based on Orthogonal Frequency-Division Multiplexing (OFDM), Orthogonal Frequency-Division Multiple Access (OFDMA), Filter-Bank Multi-Carrier (FBMC), or Single-Carrier Frequency-Division Multiple Access (SC-FDMA).
• OFDM Orthogonal Frequency-Division Multiplexing
• OFDMA Orthogonal Frequency-Division Multiple Access
• FBMC Filter-Bank Multi-Carrier
• SC-FDMA Single-Carrier Frequency-Division Multiple Access
• the invention can particularly be applied for multi-carrier communication according to the IEEE 802.1 1 ax communication standard.
• the invention relates to a transmitter for multi-carrier
• a processor configured to generate a training signal, wherein the training signal comprises a first subsignal and a second subsignal, wherein the first subsignal and the second subsignal are transmitted serially in time, and wherein frequency
• multi-carrier communication refers to OFDM-, OFDMA- , FBMC-, or SC-FDMA- based communication.
• the training signal can be used for channel-distortion-correction, in particular automatic gain control (AGC), at a receiver.
• AGC automatic gain control
• the training signal has a pre-defined length, in particular 4 us.
• a pre-defined length in particular 4 us.
• the first subsignal comprises a plurality, in particular two, periods of a first type, wherein a period of a first type is a pre-defined subsubsignal
• the second subsignal comprises a plurality, in particular two, periods of a second type, wherein a period of a second type is a pre-defined subsubsignal.
• 3 periods of the first type and then 2 periods of the second type are used.
• 2 periods of the first type and then 3 periods of the second type are used.
• identical subsubsignals within the first subsignal can be used.
• a plurality of periods of a second type identical subsubsignals within the second subsignal can be used.
• the subsubsignals can be communication symbols, e.g. OFDM symbols.
• the periods can comprise the communication symbols.
• the period of the first type has a pre-defined length, in particular 0.8 us
• the period of the second type has a pre-defined length, in particular 0.8 us.
• the processor is configured to assign a first set of
• subcarriers to the first subsignal, and/or a second set of subcarriers to the second subsignal.
• a subcarrier refers to a carrier used for multi-carrier communication, in particular OFDM-, OFDMA-, FBMC-, or SC-FDMA-based communication.
• a subcarrier can also be referred to as a tone.
• the first set of subcarriers and/or the second set of subcarriers can comprise only one subcarrier, respectively.
• the first set of subcarriers and/or the second set of subcarriers can be pre-stored in a memory of the transmitter.
• the processor is configured to assign a first set of beamforming weights associated with the first set of subcarriers to the first subsignal, and/or a second set of beamforming weights associated with the second set of subcarriers to the second subsignal.
• a transmission of the training signal using beamforming techniques is realized.
• the first set of beamforming weights and/or the second set of beamforming weights can be determined by the processor.
• the subcarriers within the first set of subcarriers are equally spaced in frequency, and/or the subcarriers within the second set of subcarriers are equally spaced in frequency.
• an efficient sampling of the transfer function of the transmission channel is achieved.
• this can mean that the time-domain signal is a repetition of identical periods.
• the subcarriers within the first set of subcarriers and the subcarriers within the second set of subcarriers can have identical pre-defined frequency spacings.
• the processor is configured to generate a data packet comprising a training field, wherein the training field comprises the first subsignal and the second subsignal, wherein the communication interface is configured to transmit the data packet.
• a data packet comprising a training field
• the training field comprises the first subsignal and the second subsignal
• the communication interface is configured to transmit the data packet.
• the invention relates to a receiver for multi-carrier
• the communication comprising a communication interface configured to receive a training signal from a transmitter according to the first aspect as such or any implementation form of the first aspect, wherein the training signal comprises a first subsignal and a second subsignal, wherein the first subsignal and the second subsignal are transmitted serially in time, and wherein frequency components of the first subsignal are shifted in frequency relative to frequency components of the second subsignal by a pre-defined frequency shift, and a processor configured to perform a channel-distortion-correction, in particular an automatic gain control (AGC), based on the received training signal, in particular the first subsignal and the second subsignal.
• AGC automatic gain control
• channel-distortion-correction refers to an adaption of the receiver to
• the channel- distortion-correction can comprise an automatic gain control (AGC) at the receiver.
• the channel-distortion-correction can further comprise an equalization (EQ) at the receiver.
• the first subsignal comprises a plurality, in particular two, periods of a first type, wherein a period of a first type is a pre-defined subsubsignal
• the second subsignal comprises a plurality, in particular two, periods of a second type, wherein a period of a second type is a pre-defined subsubsignal
• the processor is configured to perform the channel-distortion- correction based on the plurality of periods, in particular the second period, of the first type, and/or perform the channel-distortion-correction based on the plurality of periods, in particular the second period, of the second type.
• an efficient channel-distortion-correction based on subsubsignals is realized.
• the subsubsignals can be detected by the processor.
• the communication interface is configured to determine a first energy indicator indicating an energy of the first subsignal, and/or determine a second energy indicator indicating an energy of the second subsignal, wherein the processor is configured to perform the channel-distortion-correction based on the first energy indicator and/or the second energy indicator.
• AGC automatic gain control
• the first energy indicator and/or the second energy indicator can e.g. be indicative of an attenuation of the transmission channel between the transmitter and the receiver.
• the invention relates to a communication system for multi-carrier communication, comprising a transmitter according to the first aspect as such or any implementation form of the first aspect, and a receiver according to the second aspect as such or any implementation form of the second aspect.
• the communication system allows for multi-carrier communication, in particular OFDM-, OFDMA-, FBMC-, or SC-FDMA-based communication, over a transmission channel.
• the communication system can allow for communication according to the IEEE 802.1 1 ax communication standard.
• the invention relates to a transmitting method for multi-carrier communication, comprising generating, by a processor, a training signal, wherein the training signal comprises a first subsignal and a second subsignal, wherein the first subsignal and the second subsignal are transmitted serially in time, and wherein frequency components of the first subsignal are shifted in frequency relative to frequency components of the second subsignal by a pre-defined frequency shift, and transmitting, by a communication interface, the training signal.
• the transmitting method can be performed by the transmitter, in particular the processor and the communication interface. Further features of the transmitting method directly result from the functionality of the transmitter.
• the invention relates to a receiving method for multi-carrier communication, comprising receiving, by a communication interface, a training signal, wherein the training signal comprises a first subsignal and a second subsignal, wherein the first subsignal and the second subsignal are transmitted serially in time, and wherein frequency components of the first subsignal are shifted in frequency relative to frequency components of the second subsignal by a pre-defined frequency shift, and performing, by a processor, a channel-distortion-correction, in particular an automatic gain control (AGC), based on the received training signal, in particular the first subsignal and the second subsignal.
• AGC automatic gain control
• the receiving method can be performed by the receiver, in particular the processor and the communication interface. Further features of the receiving method directly result from the functionality of the receiver.
• the invention relates to a computer program comprising a program code for performing one of the methods of the fourth aspect and/or the fifth aspect when executed on a computer.
• the program code can comprise machine-executable instructions for performing one of the methods.
• the invention can be implemented in hardware and/or software.
• Fig. 1 shows a diagram of a transmitter for multi-carrier communication
• Fig. 2 shows a diagram of a receiver for multi-carrier communication
• Fig. 3 shows a diagram of a communication system for multi-carrier communication
• Fig 4 shows a diagram of a transmitting method for multi-carrier communication
• Fig 5 shows a diagram of a receiving method for multi-carrier communication
• Fig. 6 shows diagrams illustrating relations between frequency components and communication symbols in multi-carrier communication
• Fig. 7 shows diagrams illustrating the generation of a training signal comprising a first subsignal and a second subsignal
• Fig. 8 shows a diagram illustrating the generation of a training signal comprising a first subsignal and a second subsignal
• Fig. 9 shows a diagram illustrating an RSSI estimation performance in multi-carrier communication.
• Fig. 10 shows a diagram illustrating an RSSI estimation performance in multi-carrier communication.
• Fig. 1 shows a diagram of a transmitter 100 for multi-carrier communication according to an embodiment.
• the transmitter 100 comprises a processor 101 configured to generate a training signal S, wherein the training signal S comprises a first subsignal S1 and a second subsignal S2.
• the first subsignal S1 and the second subsignal S2 are transmitted serially in time, and frequency components of the first subsignal S1 are shifted in frequency relative to frequency components of the second subsignal S2 by a pre-defined frequency shift.
• the transmitter 100 further comprises a communication interface 103 configured to transmit the training signal S.
• the transmitter 100 can be configured to perform multi-carrier communication, in particular OFDM-, OFDMA-, FBMC-, or SC-FDMA-based communication.
• Fig. 2 shows a diagram of a receiver 200 for multi-carrier communication according to an embodiment.
• the receiver 200 comprises a communication interface 201 configured to receive a training signal S from a transmitter 100, wherein the training signal S comprises a first subsignal S1 and a second subsignal S2.
• the first subsignal S1 and the second subsignal S2 are transmitted serially in time, and frequency components of the first subsignal S1 are shifted in frequency relative to frequency components of the second subsignal S2 by a pre-defined frequency shift.
• the receiver further comprises a processor 203 configured to perform a channel-distortion-correction, in particular an automatic gain control (AGC), based on the received training signal S, in particular the first subsignal S1 and the second subsignal S2.
• AGC automatic gain control
• the receiver 200 can be configured to perform multi-carrier communication, in particular OFDM-, OFDMA-, FBMC-, or SC-FDMA-based communication.
• Fig. 3 shows a diagram of a communication system 300 for multi-carrier communication according to an embodiment.
• the communication system 300 comprises a transmitter 100 and a receiver 200.
• the transmitter 100 and the receiver 200 communicate over a
• the transmission channel 301 can be a wireless transmission channel.
• the transmitter 100 comprises a processor 101 configured to generate a training signal S, wherein the training signal S comprises a first subsignal S1 and a second subsignal S2.
• the first subsignal S1 and the second subsignal S2 are transmitted serially in time, and frequency components of the first subsignal S1 are shifted in frequency relative to frequency
• the transmitter 100 further comprises a communication interface 103 configured to transmit the training signal S.
• the receiver 200 comprises a communication interface 201 configured to receive the training signal S from the transmitter 100, wherein the training signal S comprises the first subsignal S1 and the second subsignal S2.
• the receiver 200 further comprises a processor 203 configured to perform a channel-distortion-correction, in particular an automatic gain control (AGC), based on the received training signal S, in particular the first subsignal S1 and the second subsignal S2.
• AGC automatic gain control
• the communication system 300 can be configured to perform multi-carrier communication, in particular OFDM-, OFDMA-, FBMC-, or SC-FDMA-based communication, over the transmission channel 301.
• Fig. 4 shows a diagram of a transmitting method 400 for multi-carrier communication according to an embodiment.
• the transmitting method 400 comprises generating 401 a training signal S, wherein the training signal S comprises a first subsignal S1 and a second subsignal S2.
• the first subsignal S1 and the second subsignal S2 are transmitted serially in time, and frequency components of the first subsignal S1 are shifted in frequency relative to frequency components of the second subsignal S2 by a pre-defined frequency shift.
• the transmitting method 400 further comprises transmitting 403 the training signal S.
• the transmitting method 400 can be performed by the transmitter 100.
• Fig. 5 shows a diagram of a receiving method 500 for multi-carrier communication according to an embodiment.
• the receiving method 500 comprises receiving 501 a training signal S, wherein the training signal S comprises a first subsignal S1 and a second subsignal S2.
• the first subsignal S1 and the second subsignal S2 are transmitted serially in time, and frequency components of the first subsignal S1 are shifted in frequency relative to frequency
• the receiving method 500 further comprises performing 503 a channel-distortion-correction, in particular an automatic gain control (AGC), based on the received training signal S, in particular the first subsignal S1 and the second subsignal S2.
• AGC automatic gain control
• the receiving method 500 can be performed by the receiver 200.
• transmitter 100 can generate a data packet, in particular an IEEE 802.1 1 ax data packet, which comprises a training field, in particular a High Efficiency Short Training Field (HE-STF).
• a data packet in particular an IEEE 802.1 1 ax data packet, which comprises a training field, in particular a High Efficiency Short Training Field (HE-STF).
• HE-STF High Efficiency Short Training Field
• the HE-STF within the IEEE 802.1 1 ax data packet like the HTA HT-STF in the IEEE
• 802.1 1 ⁇ and IEEE 802.1 1 ac communication standards can be designed to allow a receiver 200 to adjust the settings of an AGC according to data pre-coding and/or variable bandwidth at the transmitter 100.
• the adjustment of the AGC can include gain estimation, gain settling and direct current (DC) offset estimation.
• the STF is usually transmitted on every 4-th subcarrier. This can result in replicas of 0.8 us duration. In the IEEE 802.1 1 n/ac communication standard, there can be 5 replicas of 0.8 us duration.
• the IEEE 802.1 1 ax communication standard may introduce a smaller frequency spacing of the subcarriers, e.g. 1/4 of the frequency spacing as used in IEEE 802.1 1 a/g/n/ac, i.e. 78.125 kHz vs. 312.5 kHz, and therefore a communication symbol may be 4x longer in time, i.e. 13.2 us vs. 3.2 us. Spectral patterns of the STF with a periodicity in time of 0.8/1 .6/2.4 us are further intended.
• Fig. 6 shows diagrams 601 -607 illustrating relations between frequency components and communication symbols in multi-carrier communication.
• diagram 601 and diagram 605 subcarriers are shown in frequency domain.
• diagram 603 and diagram 607 shows diagrams 601 -607 illustrating relations between frequency components and communication symbols in multi-carrier communication.
• the diagrams 601 -607 are interrelated by an inverse fast Fourier transform (IFFT) or a fast Fourier transform (FFT), respectively.
• F s denotes a sampling frequency in time domain.
• the diagrams 601 -607 further illustrate different cyclic prefix (CP) requirements.
• the IEEE 802.1 1 ax communication standard it may be intended to use 5 periods within the HE-STF for AGC processing. If the frequency spacing between the non-zero subcarriers of HE-STF is preserved, i.e. every 4th subcarrier, then the duration in time is 3.2 us; thus AGC processing may last 16 us, i.e. 5 x 3.2 us. If the frequency spacing or gap between the subcarriers of the IEEE 802.1 1 a/g/n/ac communication standard is preserved, i.e. 1.25 MHz, then the duration in time is 0.8 us and AGC processing may last 4 us, i.e. 5 x 0.8 us. In this case, the frequency spacing is every 16 th subcarrier.
• a single client may be allocated on a very narrow band, e.g. a single resource unit (RU), while the rest of the bandwidth may be divided between other clients.
• the clients can e.g. be transmitters and/or receivers. If beamforming techniques are e.g. applied at the transmitters, a single client may see a more flat channel at its RU, whereas it may see a more selective channel at all the RUs that are not allocated to it. This can be due to pre-coding being used across other RUs for other clients.
• a HE-STF with frequency spacing of 1.25 MHz e.g.
• HE-STF with frequency spacing of 312.5 kHz e.g. using 4 subcarriers
• the trade-off can be between accurate representation of spectrum and overhead in time.
• Fig. 7 shows diagrams 701 -709 illustrating the generation of a training signal S comprising a first subsignal S1 and a second subsignal S2 according to an embodiment.
• the first subsignal S1 and the second subsignal S2 are transmitted serially in time, and frequency components of the first subsignal S1 are shifted in frequency relative to frequency components of the second subsignal S2 by a pre-defined frequency shift.
• subcarriers are shown in frequency domain.
• diagram 703, diagram 707 and diagram 709 communication symbols are shown in time domain.
• the diagrams 701 -707 are interrelated by an inverse fast Fourier transform (IFFT) or a fast Fourier transform (FFT), respectively.
• IFFT inverse fast Fourier transform
• FFT fast Fourier transform
• the diagram 709 depicts the training signal S comprising the first subsignal S1 and the second subsignal S2.
• the training signal S can form an HE-STF.
• the HE-STF can be generated by combining a short time duration and an accurate spectrum representation.
• the 1 st and 2nd replicas of HE-STF, each lasting 0.8 us and both being identical, can be generated using a multi-carrier signal with frequency spacing of 1 .25 MHz.
• the 3rd, 4th and 5th replicas of HE-STF, each lasting 0.8 us and all being identical, can be generated using a multi-carrier signal with frequency spacing of 1.25 MHz shifted by 2 x 312.5 kHz, i.e. having a pre-defined frequency shift of 2 x 312.5 kHz.
• beamforming weights corresponding to active subcarriers can be employed such that an IFFT operation can provide relevant time domain 0.8 us duration replicas.
• the replicas can be different both in their frequency components and possibly beamforming weights. Although replicas can be different, they may satisfy the condition that they are sampled 1 :4 such that an amplitude periodicity of 0.8 us is maintained for all. Since these replicas may be of 0.8 us duration, compatibility with AGC mechanisms can be achieved.
• This approach allows for improving HE-STF based gain estimation by modifying the frequency location of subcarriers in the HE-STF between replicas, so that different replicas sample the frequency at different locations.
• a finer sampling in frequency domain by the training signal is performed and gain estimation is enhanced.
• diagram 709 the generation of 5 replicas is shown.
• the 2nd replica can be used for gain estimation without any performance degradation.
• energy or power is collected only over the 2nd replica in the HE-STF, the performance of standard approaches and this approach may be identical. This means that this approach may not degrade energy or power estimation performance.
• additional replicas in the HE-STF are used for energy or power estimation, such as for example the 4th replica, the energy or power estimation can be enhanced since each replica can sample at different subcarriers. In effect, this will sample more densely in frequency.
• Chipset vendors wishing to enhance energy or power estimation at receivers can consequently do so with minor changes to the AGC mechanism.
• the adjustment of the AGC can be performed upon the basis of energy or power indicators indicating the energy or power of the first subsignal S1 and/or the second subsignal S2.
• Fig. 8 shows a diagram 801 illustrating the generation of a training signal S comprising a first subsignal S1 and a second subsignal S2 according to an embodiment.
• the first subsignal S1 and the second subsignal S2 are transmitted serially in time, and frequency components of the first subsignal S1 are shifted in frequency relative to frequency components of the second subsignal S2 by a pre-defined frequency shift.
• communication symbols are shown in time domain.
• diagram 801 corresponds to diagram 709 in Fig. 7.
• the training signal S can form an HE-STF.
• the number of identical replicas may differ between the first subsignal S1 and the second subsignal S2 within the HE-STF.
• the number of identical replicas may differ between the first subsignal S1 and the second subsignal S2 within the HE-STF.
• 3 identical replicas at the beginning and afterwards 2 identical replicas can be used.
• Such design can allow improved initial gain estimation, e.g. by averaging over two consecutive replicas.
• Fig. 9 shows a diagram 901 illustrating an RSSI estimation performance in multi-carrier communication.
• the diagram 901 depicts a cumulative distribution function (CDF) in dependence of an estimation error.
• CDF cumulative distribution function
• Fig. 10 shows a diagram 1001 illustrating an RSSI estimation performance in multi-carrier communication.
• the diagram 1001 depicts a cumulative distribution function (CDF) in dependence of an estimation error.
• CDF cumulative distribution function
• the error in energy estimation i.e. received signal strength indication (RSSI)
• RSSI received signal strength indication
• the RSSI estimation error between the two schemes for the UMi channel model is compared, when the RSSI estimation is carried out over the 2nd and 4th periods in the HE-STF.
• the suggested scheme outperforms the "Identical Periods" scheme by up to 1 dB in this example.
• a design for a training signal in particular for an HE-STF, is presented, wherein two groups of identical 0.8 us periods are provided.
• the design yields an improved RSSI estimation performance compared to 5 identical 0.8 us periods, because frequency sampling is denser using the suggested design.
• the suggested design may not incur any additional overhead.
• the difference in energy or power between each period may be small enough for only the variable gain amplifier (VGA) to modify the reference energy or power.
• VGA variable gain amplifier
• LNA low noise amplifier

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• Computer Networks & Wireless Communication (AREA)
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• Circuits Of Receivers In General (AREA)

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• 2015
  • 2015-11-19 WO PCT/EP2015/077121 patent/WO2017084714A1/en active Application Filing
  • 2015-11-19 CN CN201580084565.5A patent/CN108293031B/zh active Active

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