KR20060088349A - Uwb transmitter and method thereof - Google Patents

Abstract

A UWB transmitter and its transmission method are disclosed. The UWB transmitter according to the present invention reduces the power of the UWB signal with respect to the representative power of the UWB signal in the first subband, and increases the power of the UWB signal with the representative power in the second subband. It includes. Accordingly, the UWB transmitter according to the present invention reduces the transmit power of a subcarrier into which a pilot tone is inserted compared to a subcarrier carrying information among OFDM symbols of a transmitted UWB signal, thereby increasing the transmit power while satisfying FCC regulations on bandwidth. Can be.

 OFDM, FCC, UWB, Power Density Spectrum, Power Regulation, Transmit Power

Description

ＵＷＢ Transmitter and its transmission method {UWB transmitter and method approximately}

1 is a block diagram showing an example of an OFDM transmitter;

2a is a diagram illustrating a power density spectrum output from an OFDM transmitter in the absence of power adjustment;

2b is a diagram illustrating a power density spectrum of a UWB transmitter according to power adjustment according to an embodiment of the present invention;

2c is a diagram illustrating a power density spectrum of a UWB transmitter according to power adjustment according to another embodiment of the present invention;

2d is a diagram illustrating a power density spectrum of a UWB transmitter according to power adjustment according to another embodiment of the present invention;

3A is a block diagram partially illustrating a power adjusted UWB transmitter according to an embodiment of the present invention;

3B is a block diagram partially showing a power adjusted UWB transmitter according to another embodiment of the present invention; and

4 is a flowchart illustrating the operation of a power adjusted UWB transmitter according to the present invention.

Explanation of symbols on the main parts of the drawings

102: MAC interface 104: FEC encoding section

106: symbol modulator 108: IFFT processor

110: preamble insertion unit 112: protection section insertion unit

114: first converter 116: second converter

118: transmitter 120: antenna

The present invention relates to a communication system, and more particularly, to an ultra wideband transmission apparatus and a method thereof.

In a wireless communication system such as an orthogonal frequency division multiplexing (OFDM) system, data is transmitted and received using a plurality of carriers. In particular, an Ultra WideBand (UWB) system such as MultiBand OFDM Alliance (MBOA) or 802.15.3a uses approximately 128 independent OFDM carriers and has a bandwidth of approximately 528 MHz. Thus, data is modulated and transmitted on multiple carriers.

On the other hand, in the case of approximately 10 carriers of a plurality of carriers, unlike other carriers does not necessarily carry information. Such carriers, which carry no general information, are called pilot tones, which may be used to protect the carrier carrying information, to simplify the filtering conditions of the system, or to provide reference phase or amplitude information for demodulation. Can be.

The location of the pilot tone may be defined differently according to communication protocols or according to system users and designers. For example, some pilot tones are located at either end of the frequency spectrum or interspersed within the frequency spectrum. Pilot tones interspersed within the frequency spectrum are referred to as inband pilot tones.

 In general, communication technology is restricted by various aspects of transmission, such as bandwidth and power, according to the regulations of the Federal Communications Commission (FCC). According to current protocol proposals for UWB systems, all carriers, including pilot tones, are transmitted at relatively equal average power.

Accordingly, it is an object of the present invention to provide a UWB transmitter and a method of transmitting the same more efficiently in order to improve the quality of a signal transmitted according to the UWB communication protocol.

The above object of the present invention is to reduce the power of a UWB (Ultra WideBand) signal in a first subband compared to the representative power of the UWB signal, and to represent the power of the UWB signal in a second subband. It is achieved by a UWB signal transmission method comprising increasing relative to power.

Preferably, the bandwidth of the UWB signal is kept equal to or greater than the required bandwidth.

In addition, the bandwidth of the UWB signal is kept equal to or greater than the required bandwidth, the bandwidth is measured in 10dB bandwidth.

Preferably, the accumulated power of the UWB signal does not exceed a predetermined value.

More preferably, the first subband includes a pilot tone.

The first subband also includes a side pilot tone.

Advantageously, said first subband comprises an in-band pilot tone.

In addition, preferably, the power reduction step and the power increase step each include scaling a plurality of modulation symbols.

Here, the power reduction step and the power increase step preferably include filtering a time domain waveform.

Also, it is preferable that the first subband carries no data.

Meanwhile, an apparatus for transmitting a UWB signal according to the present invention includes an input interface for receiving data, a modulator for modulating the received data into symbols, and a power density spectrum of a UWB (Ultra WideBand) signal connected to the modulator. It includes a power adjustment unit for adjusting.

Here, the power adjustment unit preferably includes a power adjustment controller.

In addition, the power adjustment unit preferably includes an amplitude scaler for adjusting the amplitude of the symbol.

More preferably, the power regulator includes a filter for filtering the time domain waveform.

On the other hand, the UWB signal transmitting apparatus determines whether to adjust the power of the UWB signal, when adjusting the power of the UWB signal, reducing the power of the UWB signal in the first subband compared to the representative power of the UWB signal And maintaining a bandwidth of the UWB signal to be equal to or greater than the required bandwidth, and increasing the power of the UWB signal relative to the representative power in a second subband.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

The invention may be implemented in a variety of ways, such as in a process, apparatus, combination of components, computer recording media, or computer network in which program instructions are transmitted over an optical or electronic communications link. The description herein is merely an example of the above-described implementation manner according to the present invention or all other possible forms of the present invention and the order of steps in the disclosed process can be modified within the scope of the present invention.

According to the present invention, the power density spectrum of the transmission signal is adjusted for higher power efficiency when transmitting the UWB signal.

In particular, in the present embodiment, the power of the carrier carrying data is increased, and the power of the pilot tone can be reduced compared to the normal power of the subband belonging to the pilot tone.

In addition, in the present embodiment, a power adjustment controller is provided to determine whether power adjustment is necessary.

In general, there are several ways to implement power regulation. In this embodiment, the amplitude of the modulated symbol is adjusted. In addition, in the present embodiment, a time domain waveform calculated by applying an inverse fast fourier transform (IFFT) to a symbol is filtered.

1 is a block diagram illustrating an example of an OFDM transmitter.

Referring to the drawings, the transmitter 100 includes a media access controller (MAC) interface 102, a forward error correction (FEC) encoding unit 104, a symbol modulation unit 106, an IFFT processor 108, and a preamble insertion unit. 110, a guard section insertion unit 112, a first converter 114, a second converter 116, a transmitter 118, and an antenna 120.

The MAC interface 102 transmits the signal input to the transmitter 100 to the FEC encoder 104, and the FEC encoder 104 codes the transmitted signal. Meanwhile, the bits encoded by the FEC encoder 104 may be interleaved and repeatedly processed for protection against multipath and interference. In the present embodiment, it is omitted for convenience of description.

The symbol modulator 106 modulates the bits encoded by the FEC encoder 104 to map the symbols. In the OFDM system according to the present embodiment, a quadrature phase shift keying (QPSK) modulation scheme is employed, but other modulation schemes are also applicable. In this case, the pilot tone is inserted at a predetermined position of the symbol modulated signal.

IFFT processor 108 converts consecutive QPSK symbols into a waveform in a time domain called an OFDM symbol. Subsequently, the preamble inserter 110 inserts the preamble into the OFDM symbol.

In addition, the guard interval inserting unit 112 inserts a guard interval and a repetition prefix in the OFDM symbol in which the preamble is inserted. In addition, although interpolation and amplitude clipping may be selectively applied to the OFDM symbol, it is omitted here for convenience of description.

The first converter 114 and the second converter 116 convert the I (Inphase) and Q (Quadrature) components of the OFDM symbol from digital to analog, respectively. The analog signals converted by the first and second converters 114 and 116, respectively, are transmitted to the transmitter 118 and transmitted through the antenna 120.

2A is a diagram illustrating a power density spectrum output from an OFDM transmitter in the absence of power adjustment.

In this embodiment, subcarriers including pilot tones that do not carry information such as pilot tones 200 and 202, for example, have a power level substantially equal to the average power density level X.

Pilot tones are located in subbands 206 and 208, and subcarriers carrying data are located in subbands 210. Hereinafter, the amount of power transmitted in each subband without power adjustment is referred to as the representative power of the signal in the specific subband.

In the UWB transmitter, the total amount of power transmitted over the transmission band 204 (hereinafter, referred to as cumulative power) and the bandwidth of the transmission signal are in accordance with FCC regulations. For convenience of explanation, in the example shown in FIGS. 2A-2D, the bandwidth 204 is assumed to be the minimum bandwidth defined by the FCC.

The power of the transmitted signal can be readjusted to improve the transmission efficiency.

2B is a diagram illustrating a power density spectrum of a UWB transmitter according to power adjustment according to an embodiment of the present invention.

In this embodiment, the power of the pilot tones of the subbands 206 and 208 is reduced compared to the representative power of the signal in each subband, and the power of the subcarriers carrying data in the subband 210 is equal to the representative power of the subband. Increase, but keep the overall required bandwidth 204 intact.

As in the present embodiment, the bandwidth of the UWB signal corresponds to a bandwidth measured by the difference in interval between subcarriers 10 dB below the maximum subcarrier. Accordingly, when the frequency is limited and exceeded, the power density of the signal is 10 dB relative to the maximum power density of the signal. Or even lower. However, in another embodiment, another definition of bandwidth may be applied.

A power regulation technique that increases the link margin of the transmitted signal is sometimes referred to as "bit loading." According to some embodiments, the average power of each transmit symbol is increased to improve the quality of the signal received at the receiver. In addition, according to some embodiments, the transmission power is increased, so that the data can be encoded using a more efficient encoding technique without significantly reducing the signal quality at the receiver. According to the above-described power adjustment, the cumulative output over the transmission band does not exceed the preset limit and the bandwidth of the adjusted signal does not become smaller than the required bandwidth.

2c is a diagram illustrating a power density spectrum of a UWB transmitter according to power adjustment according to another embodiment of the present invention. In this embodiment, the power is adjusted using an analog filter, and a signal having a frequency envelope 220 is generated.

The analog filter is designed to reduce the power of subbands 206 and 208 relative to the representative power, and to increase the power of subcarriers carrying data within subband 210 relative to the representative power. The bandwidth 204 of the filtered signal is approximately equal to the bandwidth of the unadjusted signal shown in FIG. 2A.

2D is a diagram illustrating a power density spectrum according to power adjustment in a UWB transmitter according to another embodiment of the present invention. In this embodiment, the filter adjusts the pilot tone frequencies such that their amplitudes are similar to each other at the power density level of the filtered pilot tones. Bandwidth 204 is maintained in accordance with FCC regulations.

For convenience of description, the pilot tones shown in the figure are shown as side pilot tones located in the subbands at both ends of the transmission band of the signal. Power adjustment also applies to in-band pilot tones located within the transmission band of the signal. In order to further increase the transmit power of the subcarrier carrying the data, the power level of the in-band pilot tone can be reduced. It is desirable to keep the difference between the maximum power of the subcarrier carrying the data and the power of the reduced in-band pilot tone below 10 dB. Otherwise, the bandwidth of the transmitted signal may be less than 10 dB.

According to another embodiment, the power adjustment scheme may be more variously implemented.

3A is a block diagram partially illustrating a UWB transmitter for adjusting power according to an embodiment of the present invention.

In this embodiment, the power adjuster is provided between the symbol modulator 304 and the IFFT processor 310. The power regulator includes a power regulator controller 302, switches 306 and 308, and an amplitude scaler 300. The power power regulation controller 302 controls the switches 306 and 308.

In the switched on state, the amplitude scaler 300 is connected to the output of the modulator 304 and the input of the IFFT processor 310. The amplitude scaler 300 digitally changes the amplitude of the input signal in the frequency domain input to the IFFT processor 310.

After the IFFT processor 310 processes the symbol, the power density of the subcarrier carrying the data is increased, the power density of the pilot tones is reduced and the cumulative power and / or bandwidth is about the same. Also, the adjusted power density spectrum of the transmitter is similar to that shown in FIG. 2B.

When the switch is in the off position, the output of the symbol modulator 304 is directly connected to the input of the IFFT processor 310 and the signal is not adjusted by the amplitude scaler 300.

The power adjustment controller 302 may be controlled according to various variables such as error rate measurements, power consumption, and the like. For example, since the transmitting device may receive feedback from the receiving device indicating a received signal error rate exceeding a threshold, the amplitude scaler 300 is turned on to adjust the shape of the power density spectrum of the transmitting signal and load data. Increase the power density of the subbands. On the other hand, when the power consumption of the transmitter exceeds a predetermined limit, the amplitude scaler 300 is turned off to conserve power.

3B is a block diagram partially illustrating a UWB transmitter for adjusting power according to another embodiment of the present invention. In this embodiment the power adjustment module is designed to adjust the output of the IFFT processor 352. The filter 354 is controlled by the power regulation controller 356 as a digital or analog filter. The power adjustment module may be installed at a plurality of other positions in the structure of the transmitter in addition to the output terminal of the IFFT processor 352.

4 is a flowchart illustrating an operation of a UWB transmitter for adjusting power according to the present invention. In the present embodiment, the transmitter receives data from a data source (S400).

The received data is symbol-modulated to generate at least one symbol in the transmitter (S402).

Next, the transmitter determines whether power adjustment is required (S404). Meanwhile, the transmitter may receive feedback from the receiver in relation to the quality of the received signal. That is, if the signal quality is less than the predetermined threshold, the receiver may transmit feedback indicating that power adjustment is required to the transmitter.

In the present embodiment, the transmitter includes a power adjustment controller and an amplitude scaler similarly to that shown in FIG. 3A. If power adjustment is required, the power adjustment controller turns on the amplitude scaler to adjust the symbol to adjust the amplitude of the subcarrier (S406), and transmits the adjusted symbol to the IFFT processor (S408). In this embodiment, a device similar to that shown in FIG. 3B is used as the power adjustment controller and the filter, and the modulated signal is transmitted to the IFFT processor and then filtered.

Accordingly, the transmitter according to the present invention reduces the transmit power of a subcarrier into which a pilot tone is inserted, for example, by 10 dB, compared to a subcarrier carrying information among OFDM symbols, thereby satisfying the FCC bandwidth regulations while satisfying the FCC bandwidth. Since this becomes low, it is possible to increase the transmission power of the transmitter. Thus, the transmission power of the transmitting device can be increased, for example by 0.5 dB, to increase the link margin of the system.

In addition, the present invention can be easily implemented by filtering an analog OFDM signal before transmission using an analog filter or by filtering a OFDM signal by providing a digital filter in front of a digital to analog (DA) converter.

In addition, in an OFDM transmitter including an IFFT processor for converting a frequency domain into a time domain, an amplitude of an input signal in a frequency domain input to an IFFT processor corresponding to a pilot tone according to the present invention is reduced, so that an AD (Analog to Digital) FFT post-time domain filtering may be performed without employing a time domain filter.

According to the present invention, the transmit power of a subcarrier into which a pilot tone is inserted can be reduced compared to a subcarrier carrying information among OFDM symbols, thereby increasing the transmit power of a transmitter while satisfying a bandwidth regulation.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (15)

Reducing the power of an ultra wideband signal in a first subband relative to the representative power of the UWB signal; And And increasing the power of the UWB signal relative to the representative power in a second subband. The method of claim 1, And the bandwidth of the UWB signal is maintained equal to or greater than the required bandwidth. The method of claim 1, The bandwidth of the UWB signal is kept equal to or greater than the required bandwidth, the bandwidth is measured in 10dB bandwidth, UWB signal transmission method. The method of claim 1, The accumulated power of the UWB signal does not exceed a predetermined value. The method of claim 1, The first subband includes a pilot tone. The method of claim 1, The first subband includes a side pilot tone. The method of claim 1, And the first subband comprises an in-band pilot tone. The method of claim 1, And the power decreasing step and the power increasing step each comprise scaling a plurality of modulation symbols. The method of claim 1, And the power decreasing step and the power increasing step include filtering a time domain waveform. The method of claim 1, And the first subband does not carry data. An input interface for receiving data; A modulator for modulating the received data into symbols; And And a power adjuster connected to the modulator and configured to adjust a power density spectrum of a UWB (Ultra WideBand) signal to be transmitted. The method of claim 11, The power adjusting unit, UWB signal transmitting apparatus comprising a power adjusting controller. The method of claim 11, The power control unit, UWB signal transmitting apparatus, characterized in that it comprises an amplitude scaler for adjusting the amplitude of the symbol. The method of claim 11, The power adjuster, UWB signal transmission apparatus comprising a filter for filtering the time domain waveform. Determining whether to adjust power of a UWB signal; Reducing the power of the UWB signal relative to the representative power of the UWB signal in a first subband when adjusting the power of the UWB signal; And Maintaining the bandwidth of the UWB signal to be equal to or larger than the required bandwidth, and increasing the power of the UWB signal relative to the representative power in a second subband. .

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