CN108293031B

CN108293031B - Transmitter for multicarrier communication

Info

Publication number: CN108293031B
Application number: CN201580084565.5A
Authority: CN
Inventors: 多伦·埃兹里; 根纳季·特所迪克; 希米·西隆; 奥德·里德里
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2015-11-19
Filing date: 2015-11-19
Publication date: 2021-01-15
Anticipated expiration: 2035-11-19
Also published as: CN108293031A; WO2017084714A1

Abstract

The invention relates to a transmitter (100) for multicarrier communication. The transmitter (100) comprises a processor (101) for generating a training signal (S), wherein the training signal (S) comprises a first sub-signal (S1) and a second sub-signal (S2). The first sub-signal (S1) and the second sub-signal (S2) are transmitted in time succession, and frequency components of the first sub-signal (S1) are frequency shifted by a predefined frequency shift amount with respect to frequency components of the second sub-signal (S2). The transmitter (100) further comprises a communication interface (103) for transmitting the training signal (S). The invention also relates to a receiver for performing channel distortion correction, in particular Automatic Gain Control (AGC), based on said received training signal (S).

Description

Transmitter for multicarrier communication

Technical Field

The present invention relates to the field of communications technologies, and in particular, to training signal generation and channel distortion correction.

Background

In communication technology, training signals are often used for characterization of the transmission channel between a transmitter and a receiver. Typically, the training signals have a predetermined structure and content, which are known at the transmitter and receiver, thereby enabling the receiver to adapt to different characteristics of the transmission channel, such as scattering, fading, and power attenuation over distance.

The temporal and spectral characteristics of the training signal are important in order to accurately characterize the transmission channel. In particular, in multicarrier communication, the communication symbol length and subcarrier frequency interval of a given total wideband are correlated with each other. For example, an improved representation of the frequency characteristics of the transmission channel can result in an increase in the communication symbol length, thereby resulting in a decrease in the time characteristic representation of the transmission channel.

When channel distortion correction, especially Automatic Gain Control (AGC), is performed at the receiver, an increase in communication symbol length also results in an increase in processing delay, thereby reducing the overall communication efficiency between the transmitter and the receiver. These effects are particularly relevant for multicarrier communications according to the IEEE802.11ax communication standard.

Disclosure of Invention

It is an object of the present invention to improve communication over non-ideal communication channels.

This object is achieved by the features of the independent claims. Further embodiments are apparent from the dependent claims, the description and the drawings.

The present invention is based on the following findings: a training signal can be provided that includes a first sub-signal and a second sub-signal having different frequency components that are transmitted continuously in time. In particular, the frequency components of the first sub-signal are frequency shifted with respect to the frequency components of the second sub-signal by a predefined frequency shift amount. In this way, a finer sampling of the transfer function of the transmission channel between the transmitter and the receiver is achieved, thereby improving the channel distortion correction at the receiver.

The present invention can be applied to any context of multicarrier communication, and particularly, to multicarrier communication based on Orthogonal Frequency-Division Multiplexing (OFDM), Orthogonal Frequency-Division Multiple Access (OFDMA), Filter Bank Multicarrier (FBMC), or Single-Carrier Frequency-Division Multiple Access (SC-FDMA). The invention is particularly applicable to multicarrier communications in accordance with the IEEE802.11ax communications standard.

According to a first aspect, the invention relates to a transmitter for multicarrier communication, comprising a processor for generating a training signal and a communication interface for transmitting the training signal, wherein the training signal comprises a first and a second subsignal, the first and the second subsignal being transmitted consecutively in time and frequency components of the first subsignal being frequency shifted with respect to frequency components of the second subsignal by a predefined frequency shift amount.

By multicarrier communication is meant communication based on OFDM, OFDMA, FBMC or SC-FDMA up to now. The training signal can be used for channel distortion correction at the receiver, in particular Automatic Gain Control (AGC).

In a first implementation form of the transmitter according to the first aspect as described above, the training signal has a predefined length, in particular 4 us. By limiting the training signal to a predefined length, an efficient processing of the training signal at the receiver is achieved.

In a second implementation form of the transmitter according to the first aspect as such or the first implementation form of the first aspect, the first sub-signal comprises a plurality of periods, in particular two periods, of a first type, wherein a period of a first type is a predefined sub-signal, and/or the second sub-signal comprises a plurality of periods, in particular two periods, of a second type, wherein a period of a second type is a predefined sub-signal. In an exemplary implementation, 3 cycles of a first type and two cycles of a second type are used. In another exemplary implementation, two cycles of the first type and 3 cycles of the second type are used.

By using a plurality of periods of the first type, the same sub-signal within the first sub-signal can be used. By using a plurality of periods of the second type, the same sub-signal within the second sub-signal can be used. The sub-signals may be communication symbols, such as OFDM symbols. The period may include a communication symbol.

In a third implementation form of the transmitter according to the second implementation form of the first aspect, the periods of the first type have a predefined length, in particular 0.8us, and/or the periods of the second type have a predefined length, in particular 0.8 us. By limiting the periods of the first type and/or the periods of the second type to a predefined length, an efficient processing of the training signal at the receiver is achieved. In an exemplary implementation form, the predefined length is 0.8 us. In another exemplary implementation form, the predefined length is 1.6 us.

In a fourth implementation form of the transmitter according to the first aspect as such or any of the preceding implementation forms, the processor is configured to allocate a first set of sub-carriers to the first sub-signal and/or a second set of sub-carriers to the second sub-signal. By allocating the first set of sub-carriers and/or the second set of sub-carriers, efficient multi-carrier communication is achieved.

By subcarrier is meant up to now a carrier for multi-carrier communication, in particular communication based on OFDM, OFDMA, FBMC or SC-FDMA. The subcarriers may also be referred to as tones. The first set of subcarriers and/or the second set of subcarriers may each include only one subcarrier. The first set of subcarriers and/or the second set of subcarriers may be pre-stored in a memory of the transmitter.

In a fifth implementation form of the transmitter according to the fourth implementation form of the first aspect, 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 assign a second set of beamforming weights associated with the second set of subcarriers to the second subsignal. By allocating the beam forming weight, the purpose that the training signal is transmitted by using the beam forming technology is achieved. The first set of beamforming weights and/or the second set of beamforming weights may be determined by a processor.

In a sixth implementation form of the transmitter according to the fourth implementation form or the fifth implementation form of the first aspect, the subcarrier frequency spacing within the first set of subcarriers is equal and/or the subcarrier frequency spacing within the second set of subcarriers is equal. By using subcarriers with equal frequency spacing, an efficient sampling of the transfer function of the transmission channel is achieved. In addition, this may mean that the time domain signal is a repetition of the same period. The subcarriers within the first set of subcarriers and the subcarriers within the second set of subcarriers may have the same predefined frequency spacing.

In a seventh implementation form of the transmitter according to the first aspect as such or any of the preceding implementation forms, the processor is configured to generate a data packet comprising a training field, wherein the training field comprises the first sub-signal and the second sub-signal, and the communication interface is configured to transmit the data packet. By generating the data packet and arranging the first and second sub-signals within a training field of the data packet, efficient detection and processing of the training signal at the receiver is achieved. The Training Field may be a High Efficiency Short Training Field (HE-STF). The data packet may be an IEEE802.11ax data packet.

According to a second aspect, the invention relates to a receiver for multicarrier communication comprising: a communication interface for receiving 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 sub-signal and a second sub-signal, the first sub-signal and the second sub-signal being transmitted continuously in time, a frequency component of the first sub-signal being frequency shifted by a predefined frequency shift amount with respect to a frequency component of the second sub-signal; and a processor for performing channel distortion correction, in particular Automatic Gain Control (AGC), based on the received training signal, in particular the first and second sub-signals.

Up to this point, channel distortion correction refers to the adaptation of the receiver to the transmission channel characteristics based on the training signal. The channel distortion correction may include Automatic Gain Control (AGC) at the receiver. Channel distortion correction may also include Equalization (EQ) at the receiver.

In a first implementation form of the receiver according to the second aspect as such, the first sub-signal comprises a plurality of periods, in particular two periods, of a first type, wherein a period of the first type is a predefined sub-signal, and/or the second sub-signal comprises a plurality of periods, in particular two periods, of a second type, wherein a period of the second type is a predefined sub-signal, the processor is configured to perform the channel distortion correction based on the plurality of periods, in particular the two periods, of the first type, and/or to perform the channel distortion correction based on the plurality of periods, in particular the two periods, of the second type. By performing channel distortion correction based on a plurality of periods, in particular two periods, of the first type and/or the second type, an efficient channel distortion correction based on sub-signals is achieved. The sub-signals may be detected by a processor.

In a second implementation form of the receiver according to the second aspect as such or the first implementation form of the second aspect, the communication interface is configured to determine a first energy indicator indicative of an energy of the first sub-signal and/or to determine a second energy indicator indicative of an energy of the second sub-signal; the processor is configured to perform the channel distortion correction based on the first energy indicator and/or the second energy indicator. By determining the first energy indicator and/or the second energy indicator, an efficient channel distortion correction, in particular an Automatic Gain Control (AGC), is achieved. The first energy indicator and/or the second energy indicator may represent an attenuation of a transmission channel between the transmitter and the receiver.

According to a third aspect, the present invention relates to a communication system for multicarrier communication comprising a transmitter according to the first aspect as described above or any implementation form of the first aspect and a receiver according to the second aspect as described above or any implementation form of the second aspect. The communication system allows multi-carrier communication over a communication channel, in particular communication based on OFDM, OFDMA, FBMC or SC-FDMA. The communication system is capable of allowing communication in accordance with the IEEE802.11ax communication standard.

Other features of the communication system are derived directly from the characteristics of the transmitter and receiver.

According to a fourth aspect, the invention relates to a transmission method for multicarrier communication, comprising a processor generating a training signal and a communication interface transmitting the training signal, wherein the training signal comprises a first and a second subsignal, the first and the second subsignal being transmitted consecutively in time, a frequency component of the first subsignal being frequency shifted by a predefined frequency shift amount with respect to a frequency component of the second subsignal.

The transmitting method may be performed by a transmitter, in particular a processor and a communication interface. Other features of the transmission method are derived directly from the functionality of the transmitter.

According to a fifth aspect, the invention relates to a receiving method for multicarrier communication comprising: a communication interface receives a training signal, wherein the training signal comprises a first sub-signal and a second sub-signal, the first sub-signal and the second sub-signal are transmitted continuously in time, and a frequency component of the first sub-signal is frequency-shifted by a predefined frequency shift amount relative to a frequency component of the second sub-signal; and a processor performing a channel distortion correction, in particular an Automatic Gain Control (AGC), based on the received training signal, in particular the first and second subsignals.

The receiving method may be performed by a receiver, in particular a processor and a communication interface. Other features of the receiving method are directly derived from the function of the receiver.

According to a sixth aspect, the invention relates to a computer program comprising program code for performing one of the methods of the fourth and/or fifth aspect when executed on a computer. The program code may comprise machine executable instructions for performing one of the methods.

The present invention may be implemented in hardware and/or software.

Drawings

Embodiments of the invention will be described with reference to the following drawings, in which:

fig. 1 is a diagram of a transmitter for multi-carrier communication;

fig. 2 is a diagram of a receiver for multi-carrier communication;

fig. 3 is a diagram of a communication system for multi-carrier communication;

fig. 4 is a diagram illustrating a transmission method for multi-carrier communication;

fig. 5 is a diagram of a receiving method for multi-carrier communication;

fig. 6 is a diagram illustrating the relationship between frequency components and communication symbols in multicarrier communication;

FIG. 7 is a diagram illustrating the generation of a training signal comprising a first sub-signal and a second sub-signal;

FIG. 8 is a diagram illustrating the generation of a training signal comprising a first sub-signal and a second sub-signal;

fig. 9 is a graph illustrating RSSI estimation performance in multi-carrier communication;

fig. 10 is a graph illustrating RSSI estimation performance in multicarrier communication.

Detailed Description

Fig. 1 is a diagram illustrating a transmitter 100 for multicarrier communication in accordance with an embodiment. The transmitter 100 comprises a processor 101 for generating a training signal S, wherein the training signal S comprises a first subsignal S1 and a second subsignal S2. The first S1 and the second S2 subsignals are transmitted time-sequentially and the frequency components of the first S1 subsignal are frequency shifted by a predefined frequency shift amount with respect to the frequency components of the second S2 subsignal. The transmitter 100 further comprises a communication interface 103 for transmitting the training signal S.

The transmitter 100 may be used to perform multi-carrier communications, particularly communications based on OFDM, OFDMA, FBMC or SC-FDMA.

Fig. 2 is a diagram illustrating a receiver 200 for multi-carrier communication according to an embodiment. The receiver 200 comprises a communication interface 201 for receiving a training signal S from the transmitter 100, wherein the training signal S comprises a first sub-signal S1 and a second sub-signal S2. The first S1 and the second S2 subsignals are transmitted time-sequentially and the frequency components of the first S1 subsignal are frequency shifted by a predefined frequency shift amount with respect to the frequency components of the second S2 subsignal. The receiver further comprises a processor 203 for performing channel distortion correction, in particular Automatic Gain Control (AGC), based on the received training signal S, in particular the first and second subsignals S1, S2.

The receiver 200 may be used to perform multi-carrier communications, particularly communications based on OFDM, OFDMA, FBMC or SC-FDMA.

Fig. 3 is a diagram illustrating a communication system 300 for multi-carrier communication in accordance with one embodiment. The communication system 300 includes a transmitter 100 and a receiver 200. The transmitter 100 and the receiver 200 communicate via a transmission channel 301. The transport channel 301 may be a wireless transport channel.

The transmitter 100 comprises a processor 101 for generating a training signal S, wherein the training signal S comprises a first subsignal S1 and a second subsignal S2. The first S1 and the second S2 subsignals are transmitted time-sequentially and the frequency components of the first S1 subsignal are frequency shifted by a predefined frequency shift amount with respect to the frequency components of the second S2 subsignal. The transmitter 100 further comprises a communication interface 103 for transmitting the training signal S. The receiver 200 comprises a communication interface 201 for receiving a training signal S from the transmitter 100, wherein the training signal S comprises a first sub-signal S1 and a second sub-signal S2. The receiver 200 further comprises a processor 203 for performing channel distortion correction, in particular Automatic Gain Control (AGC), based on the received training signal S, in particular the first and second subsignals S1, S2.

Thus, a finer sampling of the transfer function of the transmission channel 301 between the transmitter 100 and the receiver 200 is achieved, thereby improving the channel distortion correction, in particular the Automatic Gain Control (AGC), at the receiver 200.

Communication system 300 may be used to perform multicarrier communications over communication channel 301, and in particular OFDM, OFDMA, FBMC, or SC-FDMA based communications.

Fig. 4 is a diagram illustrating a transmission method 400 for multi-carrier communication according to an embodiment. The transmission method 400 comprises generating 401 a training signal S, wherein the training signal S comprises a first sub-signal S1 and a second sub-signal S2. The first S1 and the second S2 subsignals are transmitted time-sequentially and the frequency components of the first S1 subsignal are frequency shifted by a predefined frequency shift amount with respect to the frequency components of the second S2 subsignal. The transmission method 400 further comprises transmitting 403 a training signal S.

The transmission method 400 may be performed by the transmitter 100.

Fig. 5 is a diagram illustrating a receiving method 500 for multicarrier communication in accordance with one embodiment. The receiving method 500 comprises receiving 501 a training signal S, wherein the training signal S comprises a first sub-signal S1 and a second sub-signal S2. The first S1 and the second S2 subsignals are transmitted time-sequentially and the frequency components of the first S1 subsignal are frequency shifted by a predefined frequency shift amount with respect to the frequency components of the second S2 subsignal. 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 and second subsignals S1, S2.

The receiving method 500 may be performed by the receiver 200.

Further embodiments of the invention are described in more detail below. Further embodiments are described in the context of multicarrier communications according to the IEEE802.11ax communication standard. However, the invention is clearly applicable in the context of any communication standard.

When communicating in accordance with the IEEE802.11ax communication standard, transmitter 100 may generate a data packet, particularly an IEEE802.11ax data packet, that includes a Training Field, particularly a High Efficiency Short Training Field (HE-STF).

The HE-STF within the IEEE802.11ax packets, similar to the HT/VHT-STF in the IEEE802.11 n and IEEE802.11 ac communication standards, may be designed to allow receiver 200 to adjust AGC settings based on data precoding and variable bandwidth at transmitter 100. The AGC adjustments may include gain estimates, gain adjustments, and Direct Current (DC) offset estimates.

In the IEEE802.11 a/g/n/ac communication standard, STFs are typically transmitted every 4 subcarriers. This may produce a copy of 0.8us in duration. In the IEEE802.11 n/ac communications standard, there may be 5 copies of 0.8us duration. However, the IEEE802.11ax communication standard may introduce smaller subcarrier frequency spacing, such as the 1/4 frequency spacing used in IEEE802.11 a/g/n/ac, i.e., 78.125kHz versus 312.5kHz, and thus, the communication symbols may be 4 times longer in time, i.e., 13.2us versus 3.2 us. The spectrum of the STF over a time period of 0.8/1.6/2.4us is further described.

Fig. 6 is a diagram 601 to 607 showing the relationship between frequency components and communication symbols in multicarrier communication. In fig. 601 and 605, subcarriers in the frequency domain are shown. In fig. 603 and 607, a communication symbol in the time domain is shown. Fig. 601 to 607 are associated with each other by Inverse Fast Fourier Transform (IFFT) or fast Fourier transform (IFFT), respectively. F_sRepresenting the sampling frequency in the time domain. Fig. 601 to 607 also show different Cyclic Prefix (CP) requirements.

In the IEEE802.11ax communication standard, it may be intended to use 5 cycles within the HE-STF for AGC processing. If the frequency spacing between the non-zero subcarriers of the HE-STF is preserved, i.e., every 4 subcarriers, the duration is 3.2 us. Thus, the AGC process may last 16us, i.e., 5 × 3.2us. If the frequency spacing or gap between subcarriers in the IEEE802.11 a/g/n/ac communication standard, i.e., 1.25MHz, is preserved, the duration is 0.8us and AGC processing may continue for 4us, i.e., 5 x0.8us. At this time, the frequency interval is every 16 subcarriers.

When OFDMA techniques are typically applied, a single client may be allocated over a very narrow frequency band of a single Resource Unit (RU) or the like, while other broadband may be divided among other clients. The client may be a transmitter and/or a receiver, etc. If beamforming techniques are applied at the transmitter, etc., a single client may see more flat channels at its RUs, while more selective channels may be seen at all RUs not allocated to the single client. This may be due to the use of precoding between other RUs at other clients. At this time, HE-STF with a frequency interval of 1.25MHz, for example, using 16 subcarriers, may not be sufficient to accurately represent the spectrum and may cause erroneous setting of AGC. On the other hand, an HE-STF with a frequency interval of 312.5kHz, for example, using 4 subcarriers, can generate a longer time domain period, and thus can increase the overhead of HE-STF transmission. A trade-off can be made between accurate representation of the spectrum and time overhead.

Fig. 7 shows a diagram 701 to 709 of the generation of a training signal S comprising a first sub-signal S1 and a second sub-signal S2 according to an embodiment. The first S1 and the second S2 subsignals are transmitted time-sequentially and the frequency components of the first S1 subsignal are frequency shifted by a predefined frequency shift amount with respect to the frequency components of the second S2 subsignal.

In diagrams 701 and 705, subcarriers in the frequency domain are shown. In fig. 703, 707, and 709, communication symbols in the time domain are shown. Fig. 701 to 707 are associated with each other by an Inverse Fast Fourier Transform (IFFT) or a fast Fourier transform (IFFT), respectively. F_sRepresenting the sampling frequency in the time domain. Fig. 709 depicts a training signal S comprising a first subsignal S1 and a second subsignal S2. The training signal S may form HE-STF.

The HE-STF may be generated by combining a short duration and an accurate spectral representation. The 1 st and 2 nd copies of the HE-STF, each lasting 0.8us and all being identical, may be generated using a multicarrier signal having a frequency spacing of 1.25 MHz. The 3 rd, 4 th and 5 th copies of the HE-STF, each lasting 0.8us and all being identical, may be generated using a multi-carrier signal with a frequency interval shifted 2 × 312.5khz followed by 1.25MHz, i.e. with a predefined frequency shift of 2 × 312.5 khz.

In each copy, beamforming weights corresponding to the active subcarriers may be used so that the IFFT operation may provide 0.8us long copies in the relevant time domain. These replicas may differ in both frequency components and possibly beamforming weights. Even if the copies are different, they may satisfy the following condition: sampling at 1:4 such that all copies are maintained for an amplitude period of 0.8 us. Since these copies may be 0.8us in duration, compatibility with the AGC mechanism can be achieved.

This approach allows for improved gain estimation based on the HE-STF by modifying the frequency location of the subcarrier in the HE-STF between the copies such that different copies sample the frequency at different locations. By using all the copies, the training signal is more finely frequency-domain sampled and the gain estimation is enhanced.

In FIG. 709, the generation of 5 replicas is shown. The 3 rd, 4 th and 5 th copies are shifted in frequency by 2 × 312.5kHz to 625kHz with respect to the 1 st and 2 nd copies. The 2 nd copy can be used for gain estimation without performance degradation. The standard method performs the same as the method when energy or power is collected only on the 2 nd copy in the HE-STF. This means that the method does not degrade the energy or power estimation performance. When other copies in the HE-STF are used for energy or power estimation, e.g., the 4 th copy, the energy or power estimation may be enhanced because each copy may be sampled at a different subcarrier. In practice, this will sample the frequency more frequently.

Accordingly, a chipset vendor wishing to enhance energy or power estimation at the receiver is able to operate with minor changes to the AGC mechanism. The AGC adjustment may be made on the basis of an energy or power indicator indicative of 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 sub-signal S1 and a second sub-signal S2 according to an embodiment. The first S1 and the second S2 subsignals are transmitted time-sequentially and the frequency components of the first S1 subsignal are frequency shifted by a predefined frequency shift amount with respect to the frequency components of the second S2 subsignal.

In diagram 801, a communication symbol in the time domain is shown. So far, diagram 801 corresponds to diagram 709 in fig. 7. The training signal S may form a HE-STF.

Of course, the number of identical copies may differ between the first sub-signal S1 and the second sub-signal S2 within the HE-STF. For example, as shown in FIG. 801, 3 identical copies are used initially, followed by 2 identical copies. This design may enable improved initial gain estimation, for example by averaging two consecutive copies.

Fig. 9 shows a graph 901 illustrating RSSI estimation performance in multicarrier communication. Graph 901 depicts a Cumulative Distribution Function (CDF) that depends on the estimation error.

Fig. 10 shows a graph 1001 illustrating RSSI estimation performance in multicarrier communication. The graph 1001 describes a Cumulative Distribution Function (CDF) that depends on an estimation error.

In fig. 901 and 1001, exemplary simulation results for two HE-STF designs are shown. Both designs use a frequency spacing of 1.25MHz between the pilot subcarriers in the HE-STF. In the legend, "identical periods" refers to 5 periods each having a duration of 0.8us, where all periods are identical; "proposed solution" refers to 5 cycles each of 0.8us in duration, wherein the design is as previously described. In the considered case, 2 identical periods of the first type are used, then 3 identical periods of the second type are used.

The energy estimation error, i.e. the Received Signal Strength Indication (RSSI), is compared between each design and a reference design with 1X symbol duration, i.e. sub-pilot carriers of every 4 sub-carriers.

The following parameters are assumed to exist with reference to the simulation:

-20MHz bandwidth

-9 clients, each client being assigned a single Resource Unit (RU)

-2 transmitting antennas (Tx)

-random beamforming weights per carrier outside of client Resource Units (RUs)

Urban Micro (UMi) channel

In graph 901, the RSSI estimation error is compared between the two schemes for the UMi channel model when the RSSI estimation is only performed on the second cycle in the HE-STF. As shown, the performance of the proposed scheme is the same as the performance of the existing scheme in this example.

In diagram 1001, the RSSI estimation error is compared between the two schemes for the UMi channel model when the RSSI estimation is performed on the 2 nd and 4 th periods in the HE-STF. As shown, in this example, the proposed scheme has superior performance to the "same period" scheme, up to 1 dB.

In summary, a design for a training signal, in particular for HE-STF, is presented, wherein a period of 0.8us for both sets is provided. This design yields improved RSSI estimation performance over 5 identical 0.8us cycles because sampling is more frequent using the proposed design frequency. The proposed design does not incur any additional overhead.

By proposing a design, the energy or power difference between each cycle may be small enough that only a Variable Gain Amplifier (VGA) is able to modify the reference energy or power. The Low Noise Amplifier (LNA) is not modified, so the implementation is simple. Because the transmitted training signal is modified, it may be simple to receive the transmitted training signal and analyze the frequency content of each copy. The training signal S may be detected if some of the copies are frequency shifted relative to others.

While the invention has been described with reference to specific features and implementations thereof, it will be apparent that various modifications and combinations of the invention can be made without departing from the spirit and scope of the invention. The specification and figures are to be regarded only as illustrative of the invention as defined in the appended claims and any and all modifications, variations, combinations, or equivalents that fall within the scope of the specification are contemplated.

Claims

1. A transmitter (100) for multicarrier communication, comprising:

a processor (101) for generating a training signal (S),

wherein the training signal (S) comprises:

a first subsignal (S1);

a second sub-signal (S2);

-the first sub-signal (S1) comprises a plurality of periods of a first type, in particular two periods, wherein a period of the first type is a predefined sub-signal; and/or

-the second sub-signal (S2) comprises a plurality of periods of a second type, in particular two periods, wherein a period of the second type is a predefined sub-signal;

the period of the first type has a predefined length, in particular 0.8 us; and/or

The period of the second type has a predefined length, in particular 0.8 us;

the first sub-signal (S1) and the second sub-signal (S2) are transmitted consecutively in time, and frequency components of the first sub-signal (S1) are frequency shifted by a predefined amount of frequency shift relative to frequency components of the second sub-signal (S2);

the processor (101) is further configured to send

Assigning a first set of beamforming weights associated with a first set of subcarriers to the first subsignal (S1); and/or

Assigning a second set of beamforming weights associated with a second set of subcarriers to the second subsignal (S2);

a communication interface (103) for transmitting the training signal (S).

2. The transmitter (100) of claim 1,

the training signal (S) has a predefined length, in particular 4 us.

3. The transmitter (100) of claim 1 or 2,

the processor (101) is used for connecting

Allocating a first group of subcarriers to the first subsignal (S1); and/or a second group of subcarriers to the second subsignal (S2).

4. The transmitter (100) of claim 3,

the subcarrier frequencies in the first group of subcarriers are equally spaced; and/or

The subcarrier frequencies within the second set of subcarriers are equally spaced.

5. The transmitter (100) of claim 1 or 2,

the processor (101) is used for

Generating a data packet comprising a training field, wherein the training field comprises the first subsignal (S1) and the second subsignal (S2);

the communication interface (103) is used for

And sending the data packet.

6. A receiver (200) for multi-carrier communication, comprising:

communication interface (201) for receiving a training signal (S) from a transmitter (100) according to one of the preceding claims,

wherein the training signal (S) comprises:

a first sub-signal (S1), the first sub-signal (S1) having a first set of beamforming weights associated with the first set of subcarriers;

a second sub-signal (S2), the second sub-signal (S2) having a second set of beamforming weights associated with the second set of subcarriers;

The period of the second type has a predefined length, in particular 0.8 us;

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).

7. The receiver (200) of claim 6,

the processor (203) is configured to:

performing the channel distortion correction based on the plurality of periods of the first type, in particular the two periods; and/or

Performing the channel distortion correction based on the plurality of periods of the second type, in particular the two periods.

8. The receiver (200) of claim 6 or 7,

the communication interface (201) is configured to:

determining a first energy indicator indicative of the energy of the first sub-signal (S1); and/or

Determining a second energy indicator indicative of the energy of the second sub-signal (S2); the processor (203) is configured to:

performing the channel distortion correction based on the first energy indicator and/or the second energy indicator.

9. A communication system (300) for multi-carrier communication, comprising:

the transmitter (100) of one of claims 1 to 5; and

receiver (200) according to one of the claims 6 to 8.

10. A transmission method (400) for multi-carrier communication, comprising:

generating (401) a training signal (S),

wherein the training signal (S) comprises:

a first subsignal (S1);

a second sub-signal (S2);

The period of the second type has a predefined length, in particular 0.8 us;

assigning a first set of beamforming weights associated with a first set of subcarriers to the first subsignal (S1); and/or a second set of beamforming weights associated with a second set of subcarriers is assigned to the second subsignal (S2);

-transmitting (403) the training signal (S).

11. A receiving method (500) for multicarrier communication, comprising:

-receiving (501) a training signal (S),

wherein the training signal (S) comprises:

a first sub-signal (S1), the first sub-signal (S1) having a first set of beamforming weights associated with a first set of subcarriers;

a second sub-signal (S2), the second sub-signal (S2) having a second set of beamforming weights associated with a second set of subcarriers;

The period of the second type has a predefined length, in particular 0.8 us;

-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).

12. A storage medium comprising computer program code, characterized in that the program code is adapted to perform one of the methods (400, 500) according to claim 10 or 11 when executed on a computer.