TWI446758B - Quadrature modulation rotating training sequence - Google Patents

Description

Orthogonal modulation of the rotation adjustment sequence

The present invention relates generally to modulation of communications, and more particularly to systems and methods for generating quadrature modulation of a rotational tuning signal for adjustment of receiver channel estimates.

Figure 1 is a schematic block diagram of a conventional receiver front end (prior art). A conventional wireless communication receiver includes an antenna that converts a radiation signal into a conductive signal. After some initial filtering, the conduction signal is amplified. Assuming a sufficient power level is given, the carrier frequency of the signal can be converted by mixing the signal with a local oscillator signal (downconverting). Since the received signal is quadrature modulated, the signal is demodulated by separating it before combining the I and Q paths. After frequency conversion, the analog signal can be converted to a digital signal by a analog-to-digital converter (ADC) for baseband processing. The process can include a Fast Fourier Transform (FFT).

There are a large number of errors that can be introduced into the receiver to adversely affect channel estimation and recovery of the intended signal. Errors can be introduced from mixers, filters, and passive components such as capacitors. These errors can deteriorate as they cause an imbalance between the I path and the Q path. In an effort to estimate the channel and thus eliminate some of these errors, the communication system may utilize a message format that includes a calibration sequence that may be a repeating or predetermined data symbol. For example, by utilizing an orthogonal frequency division multiplexing (OFDM) system, the same IQ constellation point can be repeatedly transmitted for each subcarrier.

In an effort to preserve the power of portable battery operating devices, some OFDM systems use only a single modulation symbol for tuning. For example, a unique direction (eg, an I path) in the constellation is excited without exciting the other direction (eg, the Q path). One-way tuning of the same type can also be used with pilot tones. It should be noted that scrambling a single modulated channel ±1 does not rotate the constellation point and does not provide an energy supply for the orthogonal channel.

The power save tuning sequence mentioned above results in a bias channel estimate when quadrature path imbalance occurs, which is more popular in large bandwidth systems. A bias channel estimate can align the IQ constellation in one direction (i.e., the I path) but provide orthogonal unbalance in the orthogonal direction. Preferably, any non-equilibrium can be equally distributed between the two channels.

Figure 2 is a schematic diagram illustrating orthogonal non-equilibrium (prior art) on the receiver side. Although not shown, the transmitter side imbalance is similar. Assume that the Q path is a reference. The impact waveform is cos( wt + θ ), where θ is the channel phase. The Q path is downconverted with -sin( wt ). The I path is downconverted by means of (l+2 ε )cos( wt +2Δ φ ). 2 △ φ and 2 ε are hard unbalanced, which are respectively a phase error and an amplitude error. The low pass filters H _I and H _{Q of} each path are different. These filters introduce additional amplitude and phase distortion. However, these additional distortions move within 2Δ φ and 2 ε . It should be noted that these two filters are practical and affect + w and - w in exactly the same way.

Assume that these errors are small:

The first component cos( wt ) on the right hand side of the equation is a slightly scaled ideal I path. The second component -2 Δ φ .sin( wt ) is a small leak from the Q path. After down-conversion of the impulse waveform: in the I path: (1+2 ε )cos( θ )+2 ε .sin( θ ).

In the Q path: sin( θ ).

These errors lead to misunderstanding of symbol positioning in the quadrature modulation constellation, which in turn leads to incorrect demodulation of the changed data.

Wireless communication receivers are prone to errors due to lack of tolerance in hardware components associated with mixers, amplifiers, and filters. In quadrature demodulator, these errors can also cause an imbalance between the I path and the Q path.

A calibration signal can be used to calibrate the receiver channel error. However, a calibration signal that cannot simultaneously excite both the I path and the Q path cannot solve the imbalance problem between the two paths.

Accordingly, a rotational tuning sequence for transmitting a quadrature modulation is provided. A quadrature modulation transmitter produces a rotational tuning signal. The rotation adjustment signal includes calibration information transmitted via an in-phase (I) calibration path, and calibration information transmitted via a quadrature (Q) modulation path. The quadrature modulated communication data is generated simultaneously with the calibration signal or after the calibration signal. Transmitting the rotation adjustment signal and the orthogonally modulated communication data.

For example, the rotation adjustment signal can be generated by first transmitting the calibration information via the I modulation path and then transmitting the calibration information via the Q modulation path. More specifically, the calibration information transmitted via the I modulation path may include a first symbol (eg, 0∘ or 180∘) having a reference phase. Then, the calibration information transmitted via the Q modulation path will include a second symbol having a phase that is ±90 相 out of phase with the reference phase.

Further details of the above method, a system for generating a rotational tuning signal, and other variations of the invention are provided below.

Various embodiments will now be described with reference to the drawings. In the following, a number of specific details are set forth in order to provide a thorough understanding of one or more embodiments. However, it is apparent that such embodiments may be practiced without such specific details. In other instances, well-known structures and devices are shown in block diagrams in order to illustrate the embodiments.

The terms "component", "system" and similar terms used in this application refer to a computer-related entity that can be a combination of hardware, firmware, hardware and software, software, or implementation. software. For example, a component can be, but is not limited to, a method running on a processor, a processor, an object, an executable file, a thread, a program, and/or a computer. For example, an application running on a computing device and the device itself can be a component. One or more components can reside within a process and/or a thread, and a component can be limited to one computer and/or distributed between two or more computers. In addition, such components can execute from various computer readable media having various data structures stored thereon. The components can communicate by the local and/or remote process, for example, based on a signal having one or more data packets (eg, from one and the other, a decentralized system) Component interaction, and/or information about components that interact with other systems by means of signals across a network (eg, the Internet).

The following will be done by a system that can contain a large number of components, modules, and the like. Various embodiments are provided. It should be understood and appreciated that different systems may include other components, modules, etc., and/or may not include all of the components, modules, etc. discussed in connection with the drawings. You can also use one of these methods to combine.

3 is a schematic block diagram of a wireless communication device 300 having a system for transmitting a rotational tuning sequence. The system 302 includes a radio frequency (RF) transmitter 304 having an input for receiving information, an in-phase (I) modulation path 308, and an orthogonal (Q) modulation path 310 on lines 306a and 306b. And a combiner 312 for combining signals from the I modulation path 308 and the Q modulation path 310, respectively. Although an RF transmitter is used as an illustration of an example of the present invention, it should be appreciated that the present invention is applicable to any communication medium (e.g., wireless, wireline, optical) capable of carrying orthogonally modulated information. The I path and the Q path are alternatively referred to as an I channel and a Q channel. The combined signals are supplied to amplifier 320 on line 318 and ultimately to antenna 322 where they are radiated. Transmitter 304 can be enabled to transmit a message having a rotational tuning signal. A rotational tuning signal (which may also be referred to as a quadrature balanced tuning signal, a balanced tuning signal, a balanced tuning sequence, or a non-deviation tuning signal) includes calibration information transmitted via the I modulation path 308 and Tuning information sent via the Q modulation path. Transmitter 304 also transmits orthogonally modulated (unscheduled) communication material. In one aspect, the orthogonally modulated communication data is transmitted after transmitting the rotational tuning sequence. In another aspect, the calibration signal and the communication data are simultaneously transmitted in the form of a pilot signal. The system is not limited to any particular temporal relationship between the calibration signal and the orthogonally modulated communication material.

4A to 4D illustrate a calibration of communication data having orthogonal modulation Graphical representation of the signal. Considering FIGS. 3 and 4A, in one aspect, the transmitter 304 transmits the rotational tuning signal by first transmitting the calibration information via the I modulation path 308 and then transmitting the calibration information via the Q modulation path 310. That is, the calibration signal contains information, such as a symbol transmitted only via the I modulation path 308 or a series of repeated symbols, followed by transmission of a symbol or series of repeated symbols transmitted only via the Q modulation path 310. As an alternative but not shown, tuning information may be initiated via the Q modulation path 310 and then via the I modulation path 308.

In the case of alternately transmitting a single symbol symbol through the I and Q paths, the transmitter is more likely to transmit a rotational tuning signal with predetermined tuning information via the I and Q modulation paths. For example, the first symbol can always be (1, 0) and the second symbol can always be (0, 1).

The rotation adjustment signal mentioned above (which initially transmits the rotation adjustment signal via the (only) I modulation path) can be supplied to the I modulation path 308 but not to the Q modulation path 310. achieve. Then, after transmitting the calibration information via the I modulation path, the transmitter transmits a rotation adjustment signal via the Q modulation path by supplying energy to the Q modulation path.

5A and 5B are illustrations of rotational adjustment symbols as presented in an orthogonal constellation. Considering FIGS. 3, 4A and 5A, the transmitter 304 generates a rotation adjustment signal by transmitting a first symbol having a reference phase via the I modulation path 308, and transmits a second symbol via the Q modulation path 310. The second symbol has a phase (reference phase + 90 ∘) or (reference phase - 90 ∘) phase. For example, the reference phase of the first symbol can be 0 ∘, in which case the phase of the second symbol can be 90 ∘ (as shown) or -90 ∘ (not shown).

However, it is not necessary to alternate symbol transmission through the modulation path 308/310 as described above to obtain symbol rotation. For example, the first symbol can be transmitted through the (only) I (or Q) modulation path, and the transmitter can simultaneously transmit the calibration information through the I and Q modulation paths, and combine the I and Q modulation signals to Supply the second symbol. As another example, the transmitter can simultaneously transmit the calibration information through the I and Q modulation paths, and combine the I and Q modulation signals to supply the first symbol, and obtain the Q (or I) modulation path by using only the Q (or I) modulation path. The second symbol.

Referring to Figure 4B, the tuned symbols can also be rotated by supplying the symbols by means of I and Q components, respectively, as is typically associated with quadrature modulation. That is, the transmitter 304 can simultaneously transmit the calibration information through the I and Q modulation paths 308/310 and combine the I and Q modulation signals to supply the first symbol on the line 318. For example, the first symbol can occupy a position at 45 该 in the constellation, see FIG. 5B. Similarly, the transmitter will simultaneously transmit tuning information through the I and Q modulation paths 308/310 and combine the I and Q modulation signals to supply the second symbol. For example, the second symbol will be rotated to a position of -45 ,, which is orthogonal to the first symbol (45 ∘).

Thus, in one aspect, a rotational tuning symbol minimally contains a sequence of two symbols having a phase difference of 90 。. However, the system is not limited to a system that uses only two symbols. In general, an even number of symbols is preferred so that one half of the symbols can be generated by using an I modulation path and the other half is generated by using a Q modulation path. However, in a sequence longer than two symbols, there is no need to perform a 90 rotation between each symbol. That is, there is no phase of a particular order between the symbols. In one aspect, half of the symbols are on average 90 degrees from the other half. example For example, an ultra-wideband (UWB) system utilizes six symbols transmitted prior to transmission of communication data or a beacon signal. Therefore, 3 consecutive symbols can be generated on the I modulation path, and then 3 consecutive symbols are generated on the Q modulation path. Using this procedure, it is only necessary to briefly activate the Q channel for 3 symbols before the Q channel returns to sleep.

6 is a diagram showing an exemplary framework for carrying a message having a rotational tuning signal. Considering Figures 3 and 6, in one aspect, the transmitter 304 is operated in accordance with the OSI model. In this typical 7-layer model, the transmitter is associated with a physical layer (PHY). As shown, the transmitter 304 transmits a physical layer (PHY) signal 600 including a preamble 602, a header 604, and a payload 606. The transmitter transmits a rotational tuning signal in the PHY header 604 and transmits the quadrature modulated communication data in the PHY payload 606.

Many communication systems transmit beacon information at relatively slow orthogonally modulated communication data rates while preserving higher data rates for (non-predetermined) transmission of information. A network operating in accordance with the IEEE 802.11 protocol is an example of such a system. Since many wireless communication devices operate on batteries, it is desirable that such units operate in a "sleep" mode when the information is not actually transmitted. For example, a master unit or access point can broadcast a relatively simple, low data rate beacon signal until a sleep unit responds.

The pilot signal can be considered as one of the tuning signals. Although the calibration signal is typically transmitted before the data using each subcarrier (all N frequencies in the communication bandwidth), the pilot tone is associated with the quadrature modulated communication data in a subset (reserved) Transfer on frequency. In systems utilizing OFDM (e.g., UWB), this reserved set consists of pilot tones. Pilot tone The system is associated with P frequencies, and the data is associated with the remaining N-P frequencies.

The calibration signal is similar to the pilot signal in that the information content of the transmitted data is typically predetermined or "preferred" data that permits the receiver to calibrate and perform channel measurements. When receiving communication (unscheduled) data, there are 3 unknowns: the data itself, the channel, and the noise. The receiver cannot be calibrated for noise, as the noise will change randomly. Channels are typically measured in association with delay and multipath. For relatively short time periods, errors due to multipath can be measured when using predetermined data, such as tuning or pilot signals. Once the channel is known, this measurement can be used to remove errors in the received communication (unscheduled) data. Therefore, some systems supply a calibration signal to measure a channel before data decoding begins.

However, for example, the channel may change as the transmitter or receiver moves in space or clock drifts. As a result, many systems continue to send more "known" and "unknown" data to track slow changes in the channel. For the purposes of illustrating the system, it will be assumed that the pilot signals are a subset of the more general calibrated signals. That is, as used herein, the tuning signal is related to an initial tuning sequence and a tracking adjustment sequence called pilot tones in a UWB or 802.11 system. Another option is that the terms "start tuning" and "tracking tuning" or "pilot tuning" are all types of tuning signals.

Then, in one aspect, after the tuning signal is rotated, the transmitter 304 transmits a message in which the quadrature modulated communication data is a beacon signal at a beacon data rate. That is, beacon signals used by many communication systems can be transmitted with a rotational tuning signal. In addition, a rotation adjustment signal Thereafter, transmitter 304 may alternatively or additionally transmit a message having orthogonally modulated communication data at a communication data rate greater than the beacon data rate.

In one aspect, the transmitter can send a message in combination with a rotating and non-rotating tuning signal. For example, after an unbalanced message, the transmitter 304 can include a multi-cluster message with a balanced message. For the sake of brevity, the phrase "balanced message" is used to describe a message that includes a rotational tuning signal and balanced modulation communication data. An unbalanced message is a message comprising a non-rotating calibration signal, wherein the calibration information is transmitted via the I modulation path but is transmitted, for example, via the Q modulation path. In this aspect, the unbalanced message also includes a message format signal embedded in, for example, a header indicating that a balanced message (having a rotational tuning signal) is sent after the unbalanced message. The unbalanced message contains orthogonally modulated communication material that can be transmitted in the payload after the message format signal. However, the system is not limited to any particular temporal relationship between the calibration signal, the message format signal, and the quadrature modulated data. For example, the unbalanced message can be a beacon signal or an initial calibration message. Alternatively, the unbalanced message can be sent after the balanced message, or the unbalanced message can be dotted with the balanced message.

Considering Figure 4C, many communication systems, such as compliant IEEE 802.11 and UWB, utilize a plurality of simultaneously transmitted subcarriers. In this aspect, the rotational tuning signal can be enabled in the form of a pilot signal. For example, P rotated pilot symbols can be generated, and (N-P) orthogonally modulated communication data symbols. Each rotated pilot symbol contains a calibration information that changes 90 degrees per symbol. because Thus, a balanced message having a rotational tuning signal is transmitted by simultaneously transmitting N symbols. In other aspects, less than P rotated pilot symbols are utilized because some of the pilot symbols are non-rotating symbols.

Considering FIG. 4D, in one of the different subcarrier systems, the rotation calibration signal includes adjusting the subcarriers for the i subcarriers by using the I modulation path instead of the Q modulation path. The symbol produced. In addition, the calibration signal uses calibration information transmitted via the Q modulation path instead of the I modulation path for the j subcarriers. Then, after the calibration information is generated, the IQ modulated communication data is generated for the i and j subcarriers. In one aspect, the subset of subcarriers comprising i "paired subcarrier" or "tone pair", a system which is a frequency of a frequency + f and -f of the tone. Similarly, the tones in subgroup j can also be paired. The pairing of the -f and + f will help to achieve I channel tuning, Q channel tuning and rotational tuning.

If the sequence of tuned symbols through any particular subcarrier is not rotated 90 ∘, then the system will still be considered to generate a rotational tuning signal, since a channel estimation averaging technique can be used at the receiver to be adjacent Subcarrier averaging. Then, the total effect of the adjacent non-rotating I and Q tuning symbols is used to rotate the tuning signal. In one aspect, the calibration signal is designed such that the odd-numbered subcarriers utilize non-rotating calibration symbols transmitted through the I modulation path (channel X), and the even-numbered subcarriers utilize Q modulation paths (channels) X+90∘).

In another aspect of the present invention, the wireless communication device 300 of FIG. 3 can be considered to include a component 308/310 for rotating a calibration signal using the I and Q modulation paths, and a method for generating a positive Intermodulation of the components of communication data 308/310. As mentioned above, the calibration signal can be sent simultaneously with the communication data. The pilot symbol, or the communication data, can be sent after the tuning signal is rotated. In addition, device 300 includes a component 320/322 for transmission as an RF communication.

Similarly, an unbalanced message can be generated, wherein the quadrature modulation component 308/310 is used to generate the following: a non-rotating calibration signal having calibration information transmitted via the I modulation path but not having a Q-modulated path The adjustment information sent; a message format signal indicating that a balanced message (having a rotation adjustment signal) is to be transmitted after the unbalanced message; and the quadrature modulation communication data.

FIG. 7 is a schematic block diagram showing a processing apparatus for transmitting a quadrature modulation rotation tuning sequence. The processing device 700 includes an I path modulation module 702 having an input for receiving information on line 704 and an input for receiving an I control signal on line 706. The I path modulation module 702 has an output on line 708 to supply the I modulated information. A Q path modulation module 710 has an input for receiving information on line 712 and an input for receiving a Q control signal on line 714. The Q path modulation module 710 has an output on line 716 for supplying Q modulated information.

A combiner module 718 has inputs on lines 708 and 716 for receiving the I and Q modulation information, respectively, and an output at line 720 for supplying a quadrature modulated RF signal. A controller module 722 has outputs on lines 706 and 714 to supply I and Q control signals, respectively. The controller module 722 uses the I and Q control signals to generate a message having a rotation adjustment signal, the rotation adjustment signal including the calibration information transmitted via the I modulation path and the calibration information transmitted via the Q modulation path. And orthogonal Change the communication data. The functions performed by the modules mentioned above are similar to those performed by the apparatus shown in FIG. 3 and will not be repeated here for the sake of brevity.

Function Description

As explained above, the rotational tuning signal of the present invention can be used to modify a conventional system for tuning only in the effort of conserving power using an I modulation path. Such a system can be modified by temporarily enabling the Q modulation path during the second portion of the calibration sequence. This solution uses only a little more power, while supplying energy to both the I and Q channels during the tuning sequence.

Alternatively, an unbalanced message with a non-rotating calibration signal can be used for a beacon, and a balanced message with a rotational tuning signal for a high data rate. This solution may require a receiver to be programmed to associate a spin-tuning signal message with a high data rate with a beacon-unbalanced message. To eliminate the need for a receiver to "guess" the type of tuning signal to be received, the information can be embedded in the preamble to inform the receiver of the type of calibration sequence.

In another variation, a conventional unbalanced message can be used as the first burst in a multi-cluster transmission. With multi-cluster transmission, it is easy to inform each transmitter of the type of calibration sequence that will appear in the following bursts in each burst. Then, usually, the first burst can be an unbalanced message, in which all subsequent bursts are balanced messages. Such messages can be initiated as needed, only if, for example, they are supported by both the transmitter and the receiver. In this way, the invention can be made backward compatible with existing devices.

Another solution (which is not backward compatible) is to modify all tuning sequences, Contains the tuning sequence of the beacon so that the tuning sequence is always balanced. In this variation, the receiver does not have to operate on two different types of calibration signals.

For example, an analysis of such improvements is provided below, which can be obtained in a conventional UWB-OFDM system by adding a rotational tuning signal to the balanced message. Typically, the calibration sequence is a repeating OFDM symbol. This means that the same constellation point is repeatedly transmitted for each subcarrier. A unique direction (eg, an I path) in the constellation is excited without exciting the other direction (eg, the Q path). The errors associated with such systems have been presented above in the prior art section.

FIG. 8 is a diagram showing an ideal and unbalanced constellation diagram for two different phases θ of the impulse waveform shown in FIG. This phase unbalanced system 2 Δ φ = 10 ∘ (without amplitude non-equilibrium). It should be noted that the non-equilibrium is the strongest when the angles are 0∘ and 90∘, and almost disappears when the angles are 45∘ and 135∘. This is because the unbalance is self-compensating around 45 在 when the phase of the shock waveform is in the middle between the I and Q paths. The angle of the shock waveform depends on both the data and the channel, and can take any value between 0 and 360 。.

For example, assuming that the angle of the impact waveform is such that all the calibration symbols are aligned with the I direction ( θ = 0), the I direction will be accurately estimated with an error of 0 ∘. However, the Q direction will deviate by 10∘. On average, in the case of Gaussian noise (AWGN), this can result in excessive errors in the constellation points in the Q direction. On the other hand, if the angle of the impact waveform is θ = 45 ∘ (the middle between I and Q), the non-equilibrium almost disappears.

Figure 9 is a graphical representation of phase imbalance as a function of phase on the impact waveform. The solid line on the graph below shows the phase imbalance in the case of a repeating calibration sequence. The dotted line shows the situation of the rotation adjustment sequence. In AWGN, and for uncoded QPSK with a BER of 10 ^-5 , the unbalanced variation between 0 ∘ and 10 具有 has a loss between 0 dB and 1.5 dB (depending on the phase of the impulse waveform).

Analysis can begin with simpler problems of time domain modulation, such as time division multiple access (TDMA) or code division multiple access (CDMA) in AWGN. Assume that all symbols of a tuning sequence are located on the I axis (I channel). After transmission through an AWGN channel, the axis can be rotated in a quadrature 2D plane to a direction X (depending on the channel phase). By aligning all the adjustment symbols with a direction X, the direction X is correctly estimated, and any data symbol in the direction is located on the correct axis (after rotation). However, the sign in the orthogonal direction Y will deviate from the ideal position by 2 Δ φ ∘. It will result in significantly larger errors.

Since all the adjustment symbols are on the X-axis, the channel estimate is H = angle (X).

The error in the X direction is the angle (X) - H = 0.

The error in the Y direction is (Y) - 90 ∘ - H = 2 Δ φ .

This analysis assumes that the calibration sequence is rotated in a constant manner to equally activate the I and Q channels. In this case, the average channel has a phase that is no longer specifically aligned with the X direction. It will also align with the Y direction in half the time.

The channel estimate is now H = [angle (X) + angle (Y) - 90 ∘] / 2.

The error angle in the X direction is (X) - H = -2 Δ φ /2.

The error angle in the Y direction is (Y) - 90 ∘ - H = 2 Δ φ /2.

The dashed curve in the illustration shows the phase imbalance in each direction. Virtual music The line is roughly 0.5 times the solid curve.

Now, each direction X and Y share half of the orthogonal unbalanced load. The loss corresponds to a maximum unbalance of 5 每一 on each axis and is 0 to 0.5 dB. The gain varies from 0 to 1 dB. It should be noted that in the presence of a LOS channel (AWGN), most carriers can be aligned at the same phase and degraded by 1.5 dB for repeated tuning sequence situations. In the same situation, the rotation tuning sequence is degraded only 0.5 dB with a gain of 1 dB. However, since the phase noise and/or frequency offset remaining will change the phase of the impulse waveform, the phase imbalance will vary from 0 to 10 。. Smooth the error portion. However, for high data rates, the diversity may not be sufficient to compensate for the excessive error of the rules hitting the subcarriers. The impact on high data rates is more important.

An implementation of a rotational tuning sequence does not necessarily imply any large hardware complexity in a receiver or transmitter. At the receiver, rotating 90 turns before accumulation is performed by exchanging the I and Q channels and signing one of them. This operation can be done in the time domain (if all frequencies are rotated in the same way) or in the Fourier domain (which is more general).

Utilizing the "Compensation of IQ imbalance in OFDM systems" by Jan Tubbax et al. in the 2003 IEEE publication, the authors refer to the imbalance between the I and Q channels in order to Instead of having an unbalanced 2Δ φ and 2 ε on the I channel, each of I and Q obtains an unbalanced Δφ and ε .

In the absence of any channel and noise, the signal received by the orthogonal unbalanced distortion can be expressed as y = αx + βx ^* where x is a composite transmission signal, x ^* is its complex conjugate, y is Composite received signal, and α 1 and β 0 is a complex of characterization of orthogonal unbalanced distortion. Which is given by α = cos △ φ + jε .sin △ φ β = ε .cos △ φ - j sin △ φ consistent respectively equal to 0 and 1, the received signal to the transmitted signal.

A more formal description will be used to review the time domain modulation scenarios in AWGN. But does not appear in the noise occurs where c is a coefficient having the AWGN channel, the received signal based cx prior to non-equilibrium and non-equilibrium after it is y = αcx + βc ^* x ^*

If the deviation over the training sequence transmitted by a training sequence of symbols composed of a ± u, i.e. 2D plane is always aligned with the unique direction of u, it is possible to obtain the two received symbols y = αcu + βc ^* u ^{* y = - αcu - βc *} u * for simplicity without loss of generality, it is assumed unitary vector u system to estimate the channel, respectively, and + u ^* - u ^* a numerical solution applied spin frequency estimates to obtain Cc + βc ^* u ^*2

On the left hand side of the addition, the channel (or approximation) is obtained, but a noise or deviation occurs on the right hand side. This noise does not disappear as more and more tuning symbols are averaged: it remains as if only white noise disappeared. Therefore, if a calibration sequence that is substantially aligned with the symbol u is transmitted, the estimated value of the channel deviates.

When the transmission of the data x begins, the metric value entering a Viterbi decoder is obtained by multiplying the complex conjugate of the channel (the matched filter of the channel) by the received signal. Therefore, the metric = [ α c + β c ^* u ^*2 ] ^* y = [α c + β c ^* u ^*2 ] ^* [α cx + β c ^* x ^* ] and after eliminating some secondary terms Measure =| α | ² | c | ² x + αβ | c | ² x ^* + αβ ^* c ² u ² x

The first component of the above metric is ideally a positive real scalar proportional to the channel energy, which increases the original constellation point. However, the second and third components of the formula are undesired noises created by the deviation. The noise variance is consistent and equal to | α | ² | β | ² | c | ⁴ | x | ² , without any other noise sources, the signal-to-noise ratio (SNR)

This noise is not distributed with white Gaussian noise, but if different symbols are obtained from different independent channels c _i (multipath in CDMA, or interlaced, etc.), after combining the symbols, the white Gaussian is obtained. The news is slowly gathering. This SNR may be approximately 10 to 20 dB. For additional data rates running at low SNR, this additional noise may not be a problem. However, for high data rates operating at high SNR, this additional noise has a significant impact.

The non-perpendicular to the alignment direction of the deviation of the training sequence In terms of the direction u (denoted v) half the transmission symbols, instead of sending the entire training sequence is aligned with the unique direction of u, an average value is obtained for the channel estimated value : αc + βc ^* ( u ^{* 2} + v ^{* 2} ) = αc Since u ^{* 2} + v ^{* 2} =0 when the two simplex vectors are orthogonal, the right-hand side deviation disappears. Now, the metric is metric =| α | ² | c | ² x + αβ | c | ² x ^{* One of the} orthogonal unbalanced noises has disappeared. This SNR (when no noise is present) improves by 3 dB.

OFDM In OFDM, the formula of the received symbol is slightly changed, but the entire OFDM symbol must be treated as a symbol vector, y = FFT { α IFFT(c·x) + β[IFFT(c·x)] ^* } where vector Indicated in bold, and where the (.) operation is the element-level product between the two vectors. Channel C is the Fourier domain version of the channel. This equation can be rewritten as y=αc. x+ β (c·x) _m ^* = αc·x+ β (c _m ^* · x _m ^* ) where index m denotes a vector mirrored on the subcarrier. Only a frequency of + f + f contributors based equalization and the frequency of the received symbols - symbol at f and the channels. Balancing two subcarriers and + f - f can be isolated, and the sub-carriers of the received symbol + f is written _{^{y = αcx + βc m * x}} m * where the index m is designated frequency - f of the channel or symbols. The main difference between this formula and the formula for TDMA or CDMA is that the distortion is now created by channels and signals at different frequencies (ie, frequency -f ). If the equalization frequency has a much larger channel or a much stronger signal, this can have a significant impact on a particular received symbol. Therefore, it may be more problematic in OFDM.

The deviation adjustment sequence assumes that the pilot tone system u transmitted at frequency +f and the pilot tone system u _m transmitted at frequency one f, then a deviation adjustment sequence does not correctly rotate the pilot tones, thus A deviation is introduced in the channel estimate.

Αc + βc _m ^* u _m ^* u ^* Then, the received metric at the frequency +f can be written as a metric (+ f ) = | α | ² | c | ² x + α ^* βc ^* c _m ^* x _m ^* + Ββ ^* cuc _m u _m x +| β | ² | c _m | ² u _m ux _m ^* The fourth (with noise) term in the above formula can no longer be ignored, because channel | c _m | ² may be extremely Strong. The noise-bearing item may now be dependent on the strength of the channel with a frequency of -f and may be significant. The frequency -f acts as a jammer that can confuse the Viterbi decoder, which can sometimes interpret a weak metric with sufficient interference as a good metric.

Non-deviation tuning sequence For a non-deviation tuning sequence, the channel estimate is α c and two noise terms are removed from the equation to obtain the metric (+ f )=| α | ² | c | ² x The improvement of + α ^* βc ^* c _m ^* x _m ^* is obvious. However, it is difficult to assess the benefits of a 480 megabit per second (Mbps) data rate in UWB-OFDM prior to simulation in an actual channel model. It should be noted that for such high data rates, it is desirable for such devices to have a LOS or an approximate LOS, and therefore the channel variations at frequencies of + f and -f are not expected to be too large. However, a difference of 3 dB or more in the channel strength is extremely possible.

Transverse Unbalanced Transmitter Orthogonal unbalance also appears on the transmitter side and is added to distortion. If α' and β' are labeled as the unbalanced coefficients on the transmitter side, the output of the transmitter can be written as z = α'x + β'x ^*

And c after channel distortion and α, β, receiver obtains ^{y = αcz + βc * z *} = (αα'c + ββ '* c *) x + (αβ'c + α' * βc *) x * = a(c,c ^* )x + b(c,c ^* )x ^{* The} above analysis applies to TDMA/CDMA, but if c _m ^{* is} substituted for c ^* and x _m ^{* is} substituted for x ^* (that is, frequency - f The value is also applicable to OFDM.

The orthogonal imbalance problem at both the transmitter and the receiver remains the same as in previous studies, but has different values for the unbalanced coefficients as a function of the channel. If the secondary quantity is ignored, and assuming that c _m ^* is not excessively stronger or weaker than c , then Increase noise from distortion. Utilizing non-deviation tuning sequences will help eliminate certain items that are beneficial to noise in metrics, as explained above.

Transmitting a non-deviation tuning sequence can be accomplished in a conventional UWB system by transmitting the first portion of the tuning sequence using the I path and transmitting the second portion using the Q path. Even if a non-biased (no rotation tuning signal) is used for the beacon to save power by turning off the Q channel, a special embedded in the preamble The fixed signal can also inform the receiver of the type of calibration sequence. Alternatively, the receiver can automatically detect the transmitted calibration sequence. This is not a difficult task, as it is sufficient to look at a small number of strong subcarriers to determine whether the transmission is consistent or rotated by 90 。.

As mentioned previously, pilot tones are considered a particular case of tuning signals, as many conventional systems use pilots that are transmitted in a complex plane in a complex direction. When tracking the pilot tones, a deviation is constantly directed in the direction of the pilot. Better by rotating the pilots by 90 turns per OFDM symbol, or by rotating some pairs of (±f) subcarriers by 90 参照 with reference to other pairs of subcarriers (on different frequencies) in the same OFDM symbol. Pilot. This pilot tone change is simple and almost zero cost. Depending on the clock drift between the transmitter and the receiver, the pilot tones may have the potential to compensate for certain deviations that are introduced by the initial offset adjustment sequence when an unbalanced calibration signal is used. In other words, generating a spin-only pilot tone while maintaining a bias (non-rotation) tuning sequence will reduce the bias in most cases.

The simulation has been run to measure the effects of orthogonal unbalance with and without a balanced calibration sequence. For an unbalanced amplitude of 10% (0.4 dB) on the TX side with a phase of 10 ,, and for an equal amount of unbalance on the receiver side, the maximum data rate (480 Mbps) gain is close to 1 dB. If more types of losses are introduced, which results in a higher SNR, an even larger gain can be expected. The higher the SNR, the greater the gain that can be obtained with a balanced calibration sequence.

Figure 10 is a flow chart illustrating a method for transmitting a communication tuning sequence. Although the method is illustrated in the figures as a series of numbered steps for clarity, this numbering does not necessarily specify the order of the steps. It will be appreciated that some of these steps may be skipped, performed in parallel, or there may be no need to maintain a strict sequence when implementing some of the steps. The method begins in step 1000.

Step 1002 generates a rotational tuning signal in a quadrature modulation transmitter. Typically, predetermined or conventional information is sent as a calibration signal. Step 1002a sends the calibration information via an I modulation path, and step 1002b sends the calibration information via a Q modulation path. Step 1004 produces orthogonally modulated communication data. Step 1004 can be performed after step 1002 or concurrently with the performance of step 1002. In one aspect, step 1004 generates a beacon signal at a beacon data rate. Alternatively, step 1004 generates information at a communication data rate greater than the beacon data rate. Step 1006 transmits the rotation adjustment signal and the orthogonally modulated communication data. Usually, the generation and transmission of symbols or information occurs almost simultaneously.

In one aspect, transmitting the rotational tuning signal in step 1006 includes first transmitting the calibration information via the I modulation path, and then transmitting the calibration information via the Q modulation path. For example, first generating the calibration information via the I modulation path (step 1002a) may include supplying energy to the I modulation path, but not supplying energy to the Q modulation path. Then, after the calibration information is generated via the I modulation path, the calibration information generated via the Q modulation path includes the energy supply to the Q modulation path. Alternatively, the calibration information can be sent in reverse order. More precisely, generating the calibration information via the I modulation path in step 1002a can include generating a first symbol having a reference phase. Then, generating the calibration information via the Q modulation path in step 1002b includes generating a second symbol having a phase of reference phase +90 ∘ or a reference phase of -90 。.

In another aspect, step 1002b utilizes the following sub-steps (not shown) to generate tuning information via the Q modulation path. Step 1002b1 simultaneously generates calibration information through the I and Q modulation paths, and step 1002b2 combines the I and Q modulation signals to supply the second symbol. Alternatively or additionally, generating the tuning information via the I modulation path may include sub-steps (not shown). Step 1002a1 simultaneously generates calibration information through the I and Q modulation paths, and step 1002a2 combines the I and Q modulation signals to supply the first symbol.

In a different aspect, the transmission (step 1006) includes sub-steps. Step 1006a organizes a physical layer (PHY) signal containing a preamble, a header, and a payload. It should be noted that this organization typically occurs as a response to receiving information that will be transmitted in a corresponding MAC format. Step 1006b transmits a rotational tuning signal in the PHY header, and step 1006c transmits the IQ modulated communication data in the PHY subcarrier.

In another aspect, step 1001a transmits a multi-plex transmission having an unbalanced message (step 1001b) followed by a rotation adjustment signal (step 1006). The unbalanced or unbalanced message includes a non-rotational calibration signal having calibration information transmitted via the I modulation path (step 1001b1), but without calibration information transmitted via the Q modulation path ( Step 1001b2). The unbalanced message includes a generated message format signal (step 1001b3) indicating that a rotational tuning signal is transmitted after the unbalanced message. The quadrature modulated communication data is generated in step 1001b4. In a different aspect, generating a rotational tuning signal in step 1002 includes generating P rotating pilot symbols, and generating quadrature modulated communication data in step 1004 includes generating (N-P) communication data. symbol. Then, at the step Transmitting in 1006 involves transmitting N symbols simultaneously.

In another variation, generating a rotational tuning signal in step 1002 includes simultaneously generating symbols for a plurality of subcarriers. More specifically, step 1002a uses tuning information transmitted via the I modulation path instead of via the Q modulation path for the i subcarriers. Step 1002b uses calibration information transmitted via the Q modulation path instead of the I modulation path for the j -subcarrier. Then, generating the quadrature modulated communication data in step 1004 includes generating quadrature modulated communication data for the i and j subcarriers after the calibration information is generated. In one aspect, each i subcarrier is adjacent to a j subcarrier.

More formally, the sub-carrier i of the channel estimation based _{^{αc + βc m * u m *}} u * (1) by means of adjacent subcarriers j αc + βc _m ^* ju _m 90∘ a rotating pilots to estimate the channel is almost the same ^* Ju ^* = αc - βc _m ^* u _m ^* u ^* (2) It should be noted that the sign for the complex number j in the equation should not be confused with the subgroup j . Then, after averaging the subcarriers, that is, after averaging the results of (1) and (2), the deviation is automatically cleared.

The above flow diagram can also be interpreted as an expression of a machine readable medium having stored therein instructions for transmitting a quadrature modulated rotational tuning sequence. The instructions for transmitting a rotational tuning signal should correspond to steps 1000 through 1006, as explained above.

Systems, methods, apparatus, and processors have been provided herein to effect the transmission of a quadrature modulated rotational tuning signal in a wireless communication device transmitter. Examples of specific communication protocols and formats have been given to illustrate the invention. However, the invention is not limited to these examples. Those who are familiar with this technology will conceive of this issue. Other variations and embodiments of the invention.

300‧‧‧Wireless communication device

302‧‧‧System

304‧‧‧RF (RF) transmitter

306a‧‧‧ lines

306b‧‧‧ lines

308‧‧‧In-phase (I) modulation path

310‧‧‧Orthogonal (Q) modulation path

312‧‧‧ combiner

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320‧‧‧Amplifier

322‧‧‧Antenna

600‧‧‧ Physical layer (PHY) signal

602‧‧‧Previous items

604‧‧‧ Header

606‧‧‧ payload

700‧‧‧Processing device

702‧‧1 Path Modulation Module

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706‧‧‧ lines

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710‧‧‧Q path modulation module

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718‧‧‧ combiner module

720‧‧‧ lines

722‧‧‧Controller Module

Figure 1 is a schematic block diagram of a conventional receiver front end (prior art).

Figure 2 is a schematic diagram illustrating orthogonal non-equilibrium (prior art) on the receiver side.

3 is a schematic block diagram of a wireless communication device having a system for transmitting a rotational tuning sequence.

4A to 4D are diagrams showing a calibration signal having orthogonally modulated communication data.

5A and 5B are diagrams of rotational adjustment symbols as shown in an orthogonal constellation diagram.

6 is a diagram showing an exemplary framework for carrying a message having a rotational tuning signal.

FIG. 7 is a schematic block diagram showing a processing apparatus for transmitting a quadrature modulation rotation tuning sequence.

FIG. 8 is a diagram showing an ideal and non-equilibrium constellation diagram of two different phases θ of the impulse waveform shown in FIG.

Figure 9 is a graphical representation of phase imbalance as a function of phase on a shock waveform.

Figure 10 is a flow chart illustrating a method for transmitting a communication tuning sequence.

300‧‧‧Wireless communication device

302‧‧‧System

304‧‧‧RF (RF) transmitter

306a‧‧‧ lines

306b‧‧‧ lines

308‧‧‧In-phase (I) modulation path

310‧‧‧Orthogonal (Q) modulation path

312‧‧‧ combiner

318‧‧‧ lines

320‧‧‧Amplifier

322‧‧‧Antenna

Claims (18)

A method for transmitting a communication adjustment sequence, the method comprising: generating a calibration sequence in an orthogonal modulation transmitter, the calibration sequence representing at least one first symbol representing a first complex value, tight One of the following represents a second sign of the second complex value, and the next one represents a third sign of the third complex value, wherein the first complex value and the second complex value define a first angle Wherein the second complex value and the third complex value define a second angle, and wherein the first angle is equal to the second angle and less than 180 degrees; providing energy to an in-phase (I) at a first time Modulating the path but not supplying energy to an orthogonal (Q) modulation path, and supplying energy to the Q modulation path at a second time different from the first time but not supplying energy to the I modulation path Transmitting the calibration sequence; generating an unbalanced message containing data; transmitting the unbalanced message before, after, or simultaneously transmitting the calibration sequence, the unbalanced message including a message format signal indicating the calibration sequence How is the unbalanced message sent? . The method of claim 1, wherein transmitting the calibration sequence comprises transmitting the calibration information via the in-phase modulation path at different times and transmitting the calibration information via the orthogonal modulation path. The method of claim 1, further comprising generating the orthogonally modulated communication data and transmitting the orthogonally modulated communication data, wherein generating the orthogonally modulated communication data comprises generating a component selected from the group consisting of Group information: a beacon signal generated at a beacon data rate, and a large Communication data generated at a communication data rate of the beacon data rate. The method of claim 1, wherein generating a calibration sequence comprises generating symbols for the plurality of subcarriers. The method of claim 1, wherein generating a calibration sequence comprises: generating calibration information for both in-phase and quadrature modulation paths; and combining the calibration information for both the equivalent phase and the quadrature modulation path to generate The calibration sequence. The method of claim 1, further comprising: generating the orthogonally modulated communication data and transmitting the orthogonally modulated communication data, wherein transmitting the calibration signal and the orthogonally modulated communication data comprises: organization one a physical layer (PHY) signal including a preamble, a header, and a payload; transmitting the calibration signal in the PHY header; and transmitting the quadrature modulated communication data in the PHY payload. The method of claim 1, wherein the calibration sequence has an even number of symbols. The method of claim 1, wherein the first angle is 90 degrees. A processing apparatus for transmitting a communication adjustment sequence, the processing apparatus comprising: a generation module configured to generate a calibration sequence, the calibration sequence representing at least one representing a first complex value The symbol, one of the following represents a second symbol of the second complex value, and the next one represents a third symbol of the third complex value, wherein the first complex value and the second complex value define a a first angle, wherein the second complex value and the third complex value define a second angle, and wherein the first angle and the second angle Equal and less than 180 degrees; a transmission module for supplying energy to an in-phase (I) modulation path at a first time but not supplying energy to an orthogonal (Q) modulation path, and different from Transmitting the calibration sequence in a manner that one of the first time supplies energy to the Q modulation path but does not supply energy to the I modulation path; wherein the generation module is configured to generate one of the contained data Unbalanced message; and wherein the unbalanced message is transmitted before, after, or simultaneously with the adjustment sequence, the unbalanced message including a message format signal indicating how the calibration sequence is transmitted relative to the unbalanced message system . A system for transmitting a communication adjustment sequence, the system comprising: a processor configured to generate a calibration sequence, the calibration sequence representing at least one first symbol representing a first complex value, tight One of the following represents a second sign of the second complex value, and the next one represents a third sign of the third complex value, wherein the first complex value and the second complex value define a first angle Wherein the second complex value and the third complex value define a second angle, and wherein the first angle is equal to the second angle and less than 180 degrees; and a transmitter configured to be in the first The time supply energy to an in-phase (I) modulation path but does not supply energy to an orthogonal (Q) modulation path, and provides energy to the Q modulation path at a second time different from the first time but not Transmitting the calibration sequence in a manner that energizes the I modulation path; wherein the generator is configured to generate an imbalance message containing data; Wherein the transmitter is configured to transmit the unbalanced message before, after, or simultaneously with transmitting the calibration sequence, the unbalanced message including a message format signal indicating the adjustment sequence relative to the unbalanced message system How to be sent. The system of claim 10, wherein the transmitter transmits the calibration sequence by transmitting the calibration information via the in-phase modulation path at different times and transmitting the calibration information via the quadrature modulation path. The system of claim 10, wherein the processor is further configured to generate quadrature modulated communication data, wherein the transmitter is further configured to transmit the quadrature modulated communication data, and wherein the The orthogonally modulated communication data includes generating data selected from the group consisting of: a beacon signal generated at a beacon data rate, and a communication data generated at a communication data rate greater than the beacon data rate . The system of claim 10, wherein the processor is further configured to generate a rotational tuning signal by generating symbols for the plurality of subcarriers. The system of claim 10, wherein the processor is configured to generate calibration information for both in-phase and quadrature modulation paths and to combine the calibration information for both the equivalent phase and the quadrature modulation path. This tuning sequence is generated. The system of claim 10, wherein the processor is further configured to generate quadrature modulated communication data, wherein the transmitter is further configured to transmit the quadrature modulated communication data, and wherein the modulation The calibration sequence and the orthogonally modulated communication data are transmitted via a physical layer (PHY) signal, the physical layer (PHY) signal including a preamble, a header, and a payload having a standard at the PHY The adjustment sequence in the head and the The quadrature modulated communication data in the payload of the PHY. The system of claim 10, wherein the tuning sequence has an even number of symbols. The system of claim 10, wherein the first angle is 90 degrees. A non-transition machine readable medium having stored thereon instructions for transmitting a communication tuning sequence, the instructions comprising: generating a tuning sequence in an orthogonal modulation transmitter, the tuning sequence representing at least one representative a first symbol of a first complex value, a second symbol followed by a second complex value, and a third symbol immediately following a third complex value, wherein the first complex value And the second complex value defines a first angle, wherein the second complex value and the third complex value define a second angle, and wherein the first angle is equal to the second angle and less than 180 degrees; The first time supplies energy to an in-phase (I) modulation path but does not supply energy to an orthogonal (Q) modulation path, and supplies energy to the Q modulation path at a second time different from the first time. But transmitting the calibration sequence without supplying energy to the I modulation path; generating an unbalanced message containing the data; and transmitting the unbalanced message before, after, or simultaneously transmitting the calibration sequence, the unbalanced message Contains a message format signal indicating the tone Sequences relative to how the system is unbalanced message sent.