KR20160113825A - Method for estimating improved toa in fbmc system - Google Patents

Abstract

A TOA estimation method is provided in the FBMC system. This method estimates the TOA using the first path detect algorithm and the High Resolution algorithm.

Description

[0001] METHOD FOR ESTIMATING IMPROVED TOA IN FBMC SYSTEM [0002]

The present invention relates to an FBMC system, and more particularly, to a method for estimating an FBMC system TOA.

FBMC stands for Filter Bank MultiCarrier and is a kind of Multicarrier System. In this method, an appropriate filter is mounted for each carrier to transmit and receive information. As the simplest example, an Orthogonal Frequency Division Multiplexing (OFDM) system can be considered

In an OFDM system without a cyclic prefix (CP), a rectangular filter is used in which the product of the interval T between one symbol and the interval of each carrier frequency is 1, and the value of the filter is 1 in the time axis.

This OFDM system maintains orthogonality in an environment without multipath, so proper transmission and reception is possible, but when there is a multipath, severe degradation of performance occurs due to ISI (Inter Symbol Interference).

In order to prevent this, ISI is prevented by inserting guard time for each symbol in the conventional OFDM system. In addition, since multipath causes interference between adjacent bands in the frequency domain, a guard interval is inserted at both ends of the used frequency band.

These Guard Time and Guard Interval can improve the transmission rate if it is possible to indicate the same Bit Error Rate (BER) performance even if the resource is damaged in time and frequency axis.

To do this, it is necessary to use a filter designed to eliminate ISI and Inter Carrier Interference (ICI) on the doubly dispersed channel on the time and frequency axes.

However, it is known that such an appropriate filter is difficult to configure when the product of the inter symbol spacing T and the inter-carrier frequency spacing is 1.

In order to solve this problem, an FBMC-OQAM (Offset QAM) system which can construct an appropriate filter without adjusting the interval between T and each carrier frequency is suggested as an alternative. This FBMC-OQAM system is proposed as one of candidate technologies for 5G mobile communication.

In order to improve the TOA (Time Of Arrival) performance, the conventional FBMC-OQAM system estimates the TOA based on the synchronization algorithm. When this synchronization algorithm is used, (Or first path) is not suitable for TOA estimation.

Accordingly, an object of the present invention is to provide a TOA estimation method in an FBMC system that can discriminate the first path even if the intensity of the first path is small and reduce a distance error.

According to an aspect of the present invention, there is provided a method for estimating a TOA in an FBMC system, the method comprising: calculating a path having a correlation value exceeding a predetermined threshold for the first time among a plurality of paths having a small correlation value; Estimating a TOA based on a first path detected by the first path and estimating a channel estimated in a frequency axis to improve the accuracy of the estimated TOA; And performing inverse fast Fourier transform using Equations (1) and (2) to estimate a channel on a time axis.

According to the present invention, it can be seen that the case where the algorithms are applied more than the case where the TOA through only the cross correlation is improved significantly in terms of the distance error, and that the High Resolution algorithm shows the improved performance .

1 is a block diagram of an FBMC system according to an embodiment of the present invention.
2 is a graph showing Rayleigh distribution.
3 is a graph illustrating TOA performance simulated according to an FBMC system according to an embodiment of the present invention.
FIG. 4 is a graph showing TOA performance excluding the cross correlation in order to confirm the TOA performance according to the algorithm application situation in detail in FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, advantages and features of the present invention and methods of achieving them will be apparent from the following detailed description of embodiments thereof taken in conjunction with the accompanying drawings.

The present invention may, however, be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, And advantages of the present invention are defined by the description of the claims.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprises "and / or" comprising ", as used herein, unless the recited component, step, operation, and / Or added.

The FBMC system for estimating the TOA according to an embodiment of the present invention includes a transmitter and a receiver as shown in FIG. 1, the transmitter includes a plurality of transmission filters, and the receiver includes a plurality of reception filters.

As shown in FIG. 1, in the FBMC system for estimating the TOA, the difference between the real and imaginary components of the QAM is generated by half the symbol length, and the phase difference is generated to obtain the transmission efficiency. Also, it is possible to overcome ISI and ICI without using CP by using transmission / reception filter and to set transmission efficiency to 1 like OFDM without CP. In FIG. 1, P (t) denotes a filter provided in each of the transmitter and the receiver, and T denotes a transmission time.

In the case of simulating the FBMC system for estimating the TOA according to the embodiment of the present invention, the simulation environment can be implemented as shown in Table 1 below.

Sampling Frequency 4MHz FFTLength 512 PSK System QPSK FBMC-Filter Phydas Filter Overlap Factor 4 Pdb -7dB, -7dB, 0dB Delay 0.275 μs, 1.25 μs, 2 μs

Meanwhile, in the FBMC system according to an embodiment of the present invention, it is necessary to apply a synchronization algorithm, a first path detection algorithm, and a high resolution algorithm in order to accurately estimate the TOA.

In this paper, we propose a new synchronization algorithm called Fusco (Fusco, T.; Petrella, A.; Tanda, M., "Data- aided symbol timing and CFO synchronization for filter multicarrier systems, Hao Chen, and Shaoqian Li, "A Data-aided OFDM / OQAM Synchronization Algorithm", which is proposed by Hao Chen (vol.8, no.5, pp.2705, , Sync was calculated using autocorrelation and cross correlation on the time domain.

In contrast, in the FBMC system according to an embodiment of the present invention, a first path detection algorithm and a High Resolution algorithm are used for accurate estimation of TOA.

First path detect  Algorithm (first algorithm)

The first path detect algorithm is a method to detect a point that exceeds this threshold for the first path after setting the threshold in the interval where the correlation value is small.

In the part where the signal has not yet arrived, the cross correlation is simply the correlation between the noise and the preamble. Therefore, when the Gaussian noise is assumed, the absolute value of this correlation follows the Rayleigh distribution.

We define the Probability of False Detection that this Rayleigh distribution will exceed a certain value, and set this specific value as Threshold, and set this point to the point where the signal first reaches this threshold.

High Resolution  Algorithm (second algorithm)

The High Resolution algorithm is a method of estimating the channel between the sample and the sample to improve the accuracy of the TOA estimation.

Unlike the channel estimation in the existing poly phase in which the auxiliary pilot is inserted to prevent ICI and the like, the High Resolution algorithm applied to the FBMC system according to an embodiment of the present invention performs channel estimation with a simple structure using a preamble .

The estimated channel on the frequency axis is called H _k (k = 0, ... Filter Length-1), and the estimated channel is subjected to Inverse Fast Fourier Transform (IFFT) can do. This IFFT can be expressed by the following equation (1).

Using this, the time between discrete times

, Which is expressed by Equation (2) below. &Quot; (2) "

In the FBMC system that combines the first path detect algorithm and the high resolution algorithm, it can be seen that the accurate TOA can be estimated by calculating a metric measuring how far the received signal constellation is dispersed from the normal signal constellation.

The results of the TOA simulation in the FMBC system according to an embodiment of the present invention are shown in FIG.

In FIGS. 3 and 4, (1) TOA simulation results using the Sync method proposed by Fusco and Hao, (2) TOA simulation results using the first algorithm, and (3) And (4) TOA simulation results obtained by connecting the first algorithm and the second algorithm in series.

As can be seen from FIG. 3, it can be seen that the distance error is significantly improved when algorithms are applied than when the TOA is estimated using only the cross correlation.

Figure 4 shows the performance of the algorithm except for cross correlation in order to check the performance of each situation in detail. From FIG. 4, it can be seen that the High Resolution algorithm shows improved performance.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, .

Claims (2)

A path in which a correlation value exceeding a predetermined threshold for the first time appears is detected in a first path among a plurality of paths in which a correlation value is small and a first path is detected, Estimating a TOA based on the TOA; And
In order to improve the accuracy of the estimated TOA, a step of fast inverse fast Fourier transforming a channel estimated in the frequency domain using Equations 1 and 2 below to estimate a channel on a time axis,
Estimating the channel on the time axis comprises:
If the channel estimated on the frequency axis is _Hk (k = 0, ..., Filter Length-1)
[Equation 1]

&Quot; (2) "

The time between discrete times by

Estimating a channel (h [n + epsilon]) in the FBMC system.
2. The method of claim 1, wherein the threshold value in the step of estimating the TOA includes:
And a probability that the Rayleigh distribution exceeds a specific value (Probability of False Detection) is defined, the specific value is the specific value.

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