KR20080022663A - Method for measuring performance considering timing jitter of ultra wide band system - Google Patents

Abstract

A performance measurement method of an UWB(Ultra WideBand) system in consideration of a timing jitter is provided to perceive system performance roughly in accordance with the timing jitter under an NMF(Nakagami Multipath Fading) channel by using computer simulation before realizing the UWB system, and to give help for coping with performance reduction. UWB pulse signals are received(S100). A PDF(Probability Density Function) for a signal passing through an NMF channel among the UWB pulse signals is obtained(S110). A power spectral density function for a signal passing through an AWGN(Additional White Gaussian Noise) channel among the UWB pulse signals is obtained(S120). A power spectral density function of a signal including a timing jitter among the UWB pulse signals is obtained(S130). A conditional error probability is obtained by using the power spectral density function of the signal passing through the AWGN channel and the power spectral density function of the signal including the timing jitter(S140). An average error probability is obtained(S150).

Description

Method for measuring performance considering timing jitter of Ultra Wide Band system}

1 is a block diagram illustrating a receiver of a general ultra wide band (UWB) system.

2 is a graph showing attenuation of signal strength due to fading;

3 is a diagram schematically illustrating a method for measuring performance of an ultra wide band (UWB) communication system according to the influence of timing jitter of the present invention.

4 is a flowchart illustrating a method for measuring performance of a UWB system in consideration of the timing jitter of the present invention.

Explanation of symbols on the main parts of the drawings

100: BPF 110: LNA

120: correlator 130: pulse generator

140: ADC 150: signal processing unit

The present invention relates to a method for measuring performance of an ultra wide band (UWB) communication system according to the influence of timing jitter.

Recently, various applications are being developed ahead of the ubiquitous era, and wireless high-speed data communication is attracting attention as the core technology.

When the concept of ubiquitous refers to a situation in which a user can enjoy and utilize information by naturally connecting to a network anytime, anywhere, wireless high-speed data communication as a network access means can be said to be a fundamental technology for realizing this.

In the meantime, if wireless high-speed data communication has been approached as a model for establishing a public network such as wireless communication through mobile phones, WiMAX, WiBro, and implementing services based thereon, the UWB (Ultra Wide Band) can improve the possibility of using high-speed short-range wireless communication in daily life. It is a field of particular interest in the industry.

UWB refers to a radio transmission technology that has a bandwidth of 20% or more of the center frequency or occupies a bandwidth of 500MHz or more. Generally, UWB has a speed over 100Mbps in the 3.1 to 10.6 GHz band, and is low over a very wide band compared to the existing spectrum. It is defined as short-range wireless communication technology that realizes high speed communication with power.

UWB is expected to solve the shortage of frequency slots because of its ability to intermittently transmit data while using ultra-wide bandwidth of several GHz for wireless data transmission.

UWB's biggest feature is that it utilizes ultra-wideband and at the same time, the output is relatively low.UWB has a very high transmission speed of 500Mbps to 1Gbps. It has the advantage that it is only one hundredth of the amount of power required by products such as (WLAN).

As such, UWB is well-received as a connection technology between high-performance portable devices because it is far ahead of conventional WLANs and Bluetooths in terms of high transmission speed and low power consumption. Especially, low power consumption is used to solve battery problems of portable devices. It is expected to help a lot.

In addition, the UWB distributes and transmits signal energy in a spectrum over a few GHz bandwidth to enable communication without interfering with other narrowband signals.

Moreover, since the UWB directly transmits the baseband signal through an antenna without up-modulation and directly demodulates the transmitted signal, the UWB can simplify the transmitter and the receiver.

1 is a block diagram illustrating a receiver of a general ultra wide band (UWB) system. As shown here, a band pass filter (BPF) 100, a low noise amplifier (LNA) 110, a correlator 120, and a pulse generator 130. ), An analog to digital converter (Analog Digital Converter) 140, and a signal processor 150.

The band pass filter (BPF) 100 filters only signals of a desired band by removing unnecessary noise in addition to the band of the UWB pulse signal from the signal received through the antenna.

The low noise amplifier (LNA) 110 receives an analog UWB pulse and amplifies the magnitude of the signal.

That is, the UWB pulse signal component is amplified in the received signal, and the noise component is suppressed as much as possible to increase the size of the UWB pulse signal component.

Since the UWB pulse signal is the most sensitive to noise, the low noise amplifier 110 is used to minimize the noise figure.

In the low noise amplifier 110, the noise of the first stage amplifier is transmitted to the system as it is represented by Equation 1 below.

Here, SNR _IN represents an input signal-to-noise power ratio, and SNR _OUT represents an output signal-to-noise power ratio.

The correlator 120 obtains the energy of the received UWB pulse signal. The correlator 120 has a maximum value when the transmitted signal is synchronized with the received signal, thereby obtaining the maximum received power. .

The correlator 120 synchronizes the PN code generated from the receiver and the PN code transmitted from the transmitter. After calculating the added pager delay on the Nakagami multipath channel, the PN code of the receiver compensated for the pager delay is calculated. And integrate the received UWB pulse signal by a certain time and output it.

The pulse generator 130 generates a pulse used as a correlation signal in the correlator 120. The correlation signal is a signal used to calculate a correlation with the received signal.

The analog digital converter 140 converts a band limited analog UWB pulse signal into a sampled and quantized digital signal and outputs the digital signal.

The signal processor 150 processes the signal output from the analog-to-digital converter 140 to restore the signal transmitted from the transmitter, and outputs a control signal for controlling the pulse generator 130.

When using a very short pulse wave like the UWB communication method, since the pulse width of the signal is very short and the size of the signal used is limited, there is a limit in obtaining energy. To be an element.

If the interference or noise is small, it is easy to send a short pulse by using a short pulse, and can transmit a large number of pulses per unit time to increase the transmission speed.

The main causes of noise in UWB transceiver systems are as follows. When the same silicon substrate is used for the analog circuit and the digital circuit, the noise component generated in the mutual circuit affects the generation of noise.

On the other hand, signals are emitted from a clock, an oscillator, an internal line, an antenna, etc. used inside the transceiver to generate crosstalk and noise, and interference of a received signal by a transmission signal also has a significant effect.

As such, a deviation occurs in the timing of data switching due to a state inside the UWB transceiver. This deviation on the time axis is referred to as timing jitter.

If the deviation on the time axis occurs to a certain degree or more, data cannot be latched and a data error occurs.

Therefore, when designing a UWB system, the influence of the timing jitter must be considered, and a method capable of measuring the performance of the UWB system considering the timing jitter is required.

In addition, fading, which is the biggest obstacle in wireless communication, needs to be considered. The fading refers to a phenomenon in which the intensity of the received radio wave is rapidly changed according to the change of the medium through which the received radio wave passes.

 The cause of fading is that the electrical constant of the medium through which the radio waves are transmitted changes over time resulting in loss of propagation, or it may be caused by the bend of the path, which is synthesized when radio waves transmitted from the same transmission point are received through more than one path. The intensity of the radio wave may be generated because the interference wave changes in time with the change in the phase difference in which each radio wave is generated.

2 is a graph showing attenuation of signal strength due to fading. As shown here, it can be seen that the strength of the signal is attenuated by propagation loss and multipath fading due to terrain.

One of the methods for reducing the effects of fading is diversity technology, which utilizes a plurality of antennas to reduce the variation of the received signal-to-noise ratio (SNR).

Many studies to reduce the fading are assumed to follow Rayleigh Fading within urban areas.

However, signals sent from the transmitting side may be passed directly to the receiving side, but may be reflected and reached by buildings, trees, moving cars, and other obstacles. That is, the signal received at the receiving side may be viewed as a combination of signals passing through several channels.

It is more comprehensive to assume that these signals follow the Nakagami Multipath Fading (NMF), which can include not only Rayleigh fading but also Additive White Gaussian Noise (AWGN) environments.

As such, the UWB system needs to measure the performance of the system considering timing jitter under the Nakagami multipath fading environment.

Accordingly, an object of the present invention is to provide a method for measuring the performance of a UWB system that can measure the performance of the system by obtaining the conditional error probability and the average error probability of the signal in consideration of timing jitter.

An embodiment of the method for measuring the performance of a UWB system according to the influence of the timing jitter of the present invention includes receiving an ultra wide band (UWB) pulse signal and Nakagami multipath fading among the received UWB pulse signals. Obtaining a probability density function (PDF) for a signal passing through an NMF channel, and for a signal passing through an additive white Gaussian noise (AWGN) channel among the received UWB pulse signals. Obtaining a power spectral density function, obtaining a power spectral density function of a signal including timing jitter in the received UWB pulse signal, and passing through the additional white Gaussian noise channel. The power spectral density function of the signal and the power spectral density function of the UWB pulse signal containing the timing jitter Obtaining a conditional error probability, and obtaining an average error probability using the conditional error probability and a probability density function of a signal passing through the Nakagami multipath fading channel and a probability density function of timing jitter. It is characterized by.

Hereinafter, a method of measuring performance of a UWB system according to the influence of timing jitter of the present invention will be described in detail with reference to FIGS. 3 and 4. In describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

FIG. 3 is a diagram schematically illustrating a method of measuring performance of an ultra wide band (UWB) communication system according to the influence of timing jitter of the present invention.

As shown here, when a UWB pulse signal signal is first transmitted from a transmitter of a UWB system, the transmitted UWB pulse signal is received by a receiver of the UWB system through a Nakagami multipath channel.

Here, the UWB pulse signal received at the receiver of the UWB system is divided into a signal passing through a Nakagami Multipath Fading (NMF) channel and an additional White Gaussian Noise (AWGN) channel. Can be.

Next, a probability density function (PDF) for a signal passing through the Nakagami multipath fading channel among the received UWB pulse signals is obtained.

In the signal passing through the Nakagami multipath fading channel, a signal-to-noise ratio (SNR) may be represented by Equation 2 below.

는 신호대 잡음비(SNR)를 나타내고,

는 페이딩 크기(Fading Amplitude)를 나타내며,

는 펄스의 에너지를 나타내고,

는 전력 스펙트럼 밀도(Power Spectral Density)를 나타낸다.here,

Represents the signal-to-noise ratio (SNR),

Represents the fading amplitude,

Represents the energy of the pulse,

Denotes the power spectral density.

In addition, the probability density function (PDF) of the signal-to-noise ratio (SNR) of the Nakagami multipath fading in Equation 2 may be expressed by the following Equation 3 according to the Gamma Distribution.

는 신호대 잡음비의 평균값을 의미한다. Here, m means a fading severity parameter, Γ (·) represents a gamma function,

Is the average value of the signal to noise ratio.

Subsequently, a power spectral density function is obtained for a signal passing through an additional white Gaussian noise channel among the received UWB pulse signals.

The power spectral density function of the signal passing through the additional white Gaussian noise channel may be represented by Equation 4 below.

Where σ ² represents the power spectral density function, E represents the average, n (t) represents the Gaussian white noise, and w (t) represents the UWB pulse signal.

The power spectral density of the signal passing through the additional white Gaussian noise channel may be expressed by Equation 5 below.

Where N ₀ represents the power spectral density.

Subsequently, a power spectral density function of a signal in which timing jitter is included in the received UWB pulse signal is obtained.

The power spectral density function of the UWB pulse signal including the timing jitter may be represented by Equation 6 below.

Where G _w (ε) represents the power spectral density function of the UWB pulse signal with timing jitter, ε represents timing jitter, N _p represents the number of pulse repetition, and w (t ) Denotes a UWB pulse signal.

Next, the conditional error probability of the UWB system is calculated using the power spectral density function of the signal passing through the additional white Gaussian noise channel and the power spectral density function of the UWB pulse signal including the timing jitter.

The conditional error probability of the UWB system can be obtained from Equation 7 below.

Here, P (E | ε, α) represents the conditional error probability of the UWB system, Q represents the Q function, and R _w (ε) represents the autocorrelation function.

The Q function is represented by Equation 8 below.

The autocorrelation function R _w (ε) may be represented by the following equation (9).

Next, an average error probability is obtained by using the conditional error probability, a probability density function of a signal passing through the Nakagami multipath fading channel, and a probability density function of timing jitter.

In other words, the average of the conditional error probability is obtained for the probability density function (PDF) of the Nakagami multipath fading and the probability density function (PDF) of the timing jitter.

The average error probability may be expressed by the following equation (10).

는 타이밍 지터의 범위를 나타내고,

는 타이밍 지터의 확률 밀도 함수를 나타내며,

를 나타낸다.here,

Represents the range of timing jitter,

Represents the probability density function of the timing jitter,

Indicates.

In the case of the UWB system in the Nakagami multipath fading channel environment, since the average value of the fading severity parameter m is 3.5, the average error probability is calculated using 3.5 as the m value.

The average error probability can be summarized by the following equation (11).

In this way, when the average error probability equation is obtained, the performance of the UWB system according to timing jitter can be measured under the Nakagami multipath fading channel environment.

4 is a flowchart illustrating a method for measuring performance of a UWB system considering timing jitter according to the present invention.

As shown in the figure, when the UWB pulse signal signal is first transmitted from the transmitter of the UWB system, the UWB pulse signal via the Nakagami multipath channel is received by the receiver of the UWB system (step S100).

Next, a probability density function (PDF) for a signal passing through a Nakagami multipath Fading (NMF) channel among the received UWB pulse signals is obtained (step S110).

Subsequently, a power spectral density function is obtained for a signal passing through an additional white Gaussian noise (AWGN) channel among the received UWB pulse signals (step S120).

Subsequently, a power spectral density function of a signal in which timing jitter is included in the received UWB pulse signal is obtained (step S130).

Here, a probability density function for a signal passing through the Nakagami multipath fading channel, a power spectral density function for a signal passing through an additional white Gaussian noise channel, and a power spectral density function for a signal that includes timing jitter in the received UWB pulse signal. Does not matter which one is obtained first and does not depend on the order.

Next, conditional error probability is obtained using the power spectral density function of the signal passing through the additional white Gaussian noise channel and the power spectral density function of the UWB pulse signal including the timing jitter (step S140).

Subsequently, an average error probability is obtained using the conditional error probability, a probability density function of a signal passing through the Nakagami multipath fading channel, and a probability density function of timing jitter (step S150).

Although the present invention has been described in detail with reference to exemplary embodiments above, those skilled in the art to which the present invention pertains can make various modifications to the above-described embodiments without departing from the scope of the present invention. I will understand.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As described above, according to the present invention, before implementing the UWB system, computer simulation can be used to roughly grasp the performance of the system according to timing jitter under the Nakagami multipath fading channel, and performance that may occur in the actual system design. It can help you prepare for a decline.

Claims (7)

Receiving an ultra wide band (UWB) pulse signal: Obtaining a probability density function (PDF) for a signal passing through a Nakagami Multipath Fading (NMF) channel among the received UWB pulse signals; Obtaining a power spectral density function for a signal passing through an additional white Gaussian noise (AWGN) channel among the received UWB pulse signals; Obtaining a power spectral density function of a signal including timing jitter in the received UWB pulse signal; Obtaining a conditional error probability using a power spectral density function of the signal passing through the additional white Gaussian noise channel and a power spectral density function of the UWB pulse signal including the timing jitter; And Determining the average error probability using the conditional error probability and the probability density function of the signal passing through the Nakagami multipath fading channel and the probability density function of the timing jitter. Way. The method of claim 1, The probability density function of the signal passing through the Nakagami multipath fading channel is calculated by the following equation. Equation  3

here,

Is the signal-to-noise ratio (SNR)

Can be represented by

Is the fading amplitude,

Is the energy of the pulse,

Denotes the power spectral density. M is a fading severity parameter, Γ (·) is a gamma function,

Is the average value of the signal to noise ratio. The method of claim 1, The power spectral density function of the signal passing through the additional white Gaussian noise channel is calculated by the following equation. Equation  4

Where σ ² is a power spectral density function, E is an average, n (t) is a Gaussian white noise signal, and w (t) is a UWB pulse signal. The method of claim 1, The power spectral density function of the UWB pulse signal including the timing jitter is calculated by the following equation. Equation  6

Where G _w (ε) is the power spectral density function of the UWB pulse signal with timing jitter, ε is the timing jitter, N _p is the number of pulse repetition, and w (t) is the UWB pulse signal. Indicates. The method of claim 1, The conditional error probability is calculated by the following equation. Equation  7

Where P (E│ε, α) is conditional error probability of UWB system, Q is Q function

Where R _w (ε) is the autocorrelation function

It can be represented as The method of claim 1, The average error probability is calculated by the following equation, the performance measurement method of the UWB system considering the timing jitter. Equation  10

here,

Is the range of timing jitter,

Is the probability density function of timing jitter,

Indicates. 7. The method of claim 6, wherein the average error probability is calculated by using a fading severity parameter m value of 3.5.

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