KR101026141B1 - FHS / TDMA receiving apparatus and method for performing partial cross-correlation during cyclic code transition keying demodulation - Google Patents

Abstract

The present invention relates to an FHSS / TDMA receiver and method for performing partial cross-correlation during cyclic code shift keying demodulation, comprising: a frequency reverse hopping unit for frequency dehopping a received signal, and a frequency reverse hopping signal; An MSK demodulation unit for demodulating a minimum shift keying (MSK) with respect to the MSK, a descrambling unit for descrambling the minimum transition keying demodulated signal using a pseudorandom noise (PN) sequence, and A CCSK demodulator which demodulates a symbol by using a cyclic code shift keying sequence having a predetermined range of a cyclic code shift keying (CCSK) sequence for a descrambled signal, and recovers a symbol; A symbol deinterleaving unit for deinterleaving a signal and a signal-to-noise ratio (SNR) of the deinterleaved symbol To constitute a control section for controlling the CCSK demodulator to determine the range of cyclic shift keying code sequence used in the CCSK demodulation and demodulates the signal of the descrambling in accordance with the scope of the decided cycle sequence code shift keying. As described above, by performing cyclic code transition keying demodulation using only 75% or more chip sequences among chip sequences of cyclic shift keying, there is an effect of reducing inter-symbol interference.

Description

FHS / TDMAA receiving apparatus and method for performing partial cross-correlation during cyclic code shift keying demodulation

The present invention relates to an apparatus and a method for receiving a frequency hopping spread spectrum / time division multiple access (FHSS / TDMA), which performs partial cross-correlation during cyclic code shift keying (CCSK) modulation. And to a method.

A representative military communication system using the FHSS / TDMA communication method is the US military's joint tactical information distribution system / LINK-16 (JTIDS / LINK-16). LINK-16 is a tactical data link system established by the US Air Force but is already in use by the ROK Air Force, such as early warning. The FHSS / TDMA communication method is basically a method of moving a net while performing frequency hopping in every time slot in the TDMA communication method. Here, the net is a network operated at different frequencies.

Therefore, since the units of the small and medium unit communicates while jumping at a different net frequency in every time slot, the units of each small and medium unit use different frequencies to maintain security without interference between frequencies.

By the way, the units of each small and medium size unit must be accurately synchronized in every time slot to make a frequency hopping, but in fact, there is a case of propagation delay. For example, when the transceivers of the system A and the system B communicate on their respective nets, if the distance between the transceivers of the system A is very long, a propagation delay may occur. Then, the boundary of the time slot is broken down and interference between frequencies is inevitably generated.

Hereinafter, the problems of the prior art will be described in more detail with reference to FIG. 1.

1 is a conceptual diagram illustrating inter-symbol interference due to propagation delay of a cyclic code shift keying modulation scheme according to the prior art.

Referring to FIG. 1, the time slots of net i and the time slots of net j are shown. The basic FHSS / TDMA operation is as follows. First, assume that system A operates on net i and system B operates on net j in the same time slot. At the end of the Nth hopping duration, system B frequency hops from net j to net i according to a predetermined frequency hopping period. In system A, when the same N-th hopping period ends, frequency hopping from net i to net k.

However, when the distance between the transmitting and receiving devices of the system A is far, as shown in FIG. 1, a propagation delay section T _D occurs. Thus, system A is not normally synchronized and frequency hopping, but hops to net k at a timing delayed by the propagation delay time. Since system B has already leaped to net i at a normal timing, inter-symbol interference (ISI) is bound to occur as much as a propagation delay period. In most cases, inter-symbol interference exists in FHSS / TDMA systems.

An object of the present invention is to provide an FHSS / TDMA receiving apparatus that performs partial cross-correlation during cyclic code shift keying demodulation.

Another object of the present invention is to provide a method for receiving FHSS / TDMA that performs partial cross-correlation during cyclic code shift keying demodulation.

An FHSS / TDMA receiver for performing partial cross-correlation during cyclic code shift keying demodulation according to the above-described object of the present invention comprises: a frequency reverse hopping unit for frequency dehopping a received signal; An MSK demodulation unit for demodulating minimum shift keying (MSK) for a signal, a descrambling unit for descrambling the minimum transition keying demodulated signal using a pseudorandom noise (PN) sequence; A CCSK demodulator for demodulating the descrambled signal by using a cyclic code shift keying sequence having a predetermined length and recovering a symbol from a cyclic code shift keying (CCSK) sequence of a predetermined length; A symbol deinterleaving unit for deinterleaving a symbol and measuring a signal-to-noise ratio (SNR) of the deinterleaved symbol; And determining a range of a cyclic code transition keying sequence to be used by the CCSK demodulator and controlling the CCSK demodulator to demodulate the descrambled signal according to the determined range of the cyclic code transition keying sequence. Herein, a cyclic code shift keying sequence of a predetermined range among the cyclic code shift keying (CCSK) sequences is a cyclic code shift keying sequence of 75% or more and 100% or less of all cyclic code shift keying sequences. Characterized by the cyclic code transition keying demodulation may be configured to perform partial cross-correlation. A 75% or more and 100% or less cyclic code transition keying sequence of the entire cyclic code transition keying sequence may be 75% or more and 100% or more from a chip sequence in the range of 75% or more and 100% or less from the beginning of the entire cyclic code transition keying sequence. It is preferable that it is a chip sequence of the following range. And, when the measured signal-to-noise ratio is lowered below a predetermined threshold, it is preferable to determine to gradually reduce the range of the cyclic code transition keying sequence to be used among the entire cyclic code transition keying sequences.

In the FHSS / TDMA reception method for performing partial cross-correlation when performing cyclic code shift keying demodulation according to the object of the present invention, a predetermined signal is selected from among cyclic code shift keying (CCSK) sequences having a predetermined length. Demodulating using a range of cyclic code transition keying sequences to recover a symbol, measuring a signal-to-noise ratio for the recovered symbol, and cyclic code transition keying of the predetermined length according to the measured signal-to-noise ratio Determining a range of cyclic code transition keying sequences to use among the sequences, and demodulating the received signal using the determined range of cyclic code transition keying sequences to recover symbols. The determining of the range of the cyclic code transition keying sequence to be used among the cyclic code transition keying sequences of the predetermined length according to the measured signal-to-noise ratio may include a range of cyclic code transition keying sequences to be used among all cyclic code transition keying sequences. Is preferably in the range of 75% or more and 100% or less. In addition, it is preferable to determine the range of 75% or more and 100% or less from the front or 75% or more and 100% or less from the rear part of the entire cyclic code transition keying sequence. And when the measured signal-to-noise ratio is lowered below a predetermined threshold, it is desirable to determine to gradually reduce the range of cyclic code transition keying sequences to be used among the entire cyclic code transition keying sequences.

According to the above-described FHSS / TDMA receiving apparatus and method, cyclic code transition keying demodulation is performed using only 75% or more chip sequences of the cyclic code transition keying chip sequence, thereby reducing inter-symbol interference due to propagation delay. In addition, it has the effect of obtaining almost the same signal-to-noise ratio as when demodulating using a 100% chip sequence.

1 is a conceptual diagram illustrating inter-symbol interference due to propagation delay of a cyclic code shift keying modulation scheme according to the prior art.
2 is a block diagram of an FHSS / TDMA transmission apparatus of JTIDS / LINK-16.
3 is a block diagram of an FHSS / TDMA receiver for performing partial cross-correlation when performing cyclic code shift keying demodulation according to an embodiment of the present invention.
4 is a graph showing the bit error rate according to the degree of overlap between symbols of the FHSS / TDMA receiver of JTIDS / LINK-16.
5 is a graph illustrating a bit error rate according to a range of partial cross-correlation during cyclic code shift keying demodulation in an FHSS / TDMA receiver according to an embodiment of the present invention.
6 is a block diagram of a FHSS / TDMA transmission method of JTIDS / LINK-16.
7 is a flowchart illustrating an FHSS / TDMA receiving method for performing partial cross-correlation when performing cyclic code shift keying demodulation according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5.

2 is a block diagram of an FHSS / TDMA transmission apparatus of JTIDS / LINK-16.

Referring to FIG. 2, the FHSS / TDMA transmitter 100 (hereinafter, referred to as an 'FHSS / TDMA transmitter') of the JTIDS / LINK-16 includes an RS encoder 110, a symbol interleaving unit 120, and CCSK modulation. The unit 130, the scrambling unit 140, the MSK modulator 150, and the frequency hopping unit 160 are configured to be included. The FHSS / TMDA transmitter 100 of FIG. 2 is a conventional transmitter corresponding to the FHSS / TDMA receiver 200 of the present invention. The detailed configuration will be briefly described below.

First, the RS encoder 110 performs channel encoding on a bit string of an input signal using a Reed-Solomon code. The symbol interleaving unit 120 interleaves the channel coded signal and outputs a 5-bit symbol. The CCSK modulator 130 performs cyclic code shift keying modulation on the interleaved symbols. Cyclic code transition keying consists of a sequence of 32 chips, consisting of one base sequence and a total of 32 sequences generated by shifting chips one by one with respect to the base sequence. The cyclic code transition keying sequence of Table 1 below is an example of a code used in LINK-16.

5-bit symbol CCSK code word 00000
00001
00010
00011
00100
.
.
.
11111 S0 = 01111100111010010000101011101100
S1 = 11111001110100100001010111011000
S2 = 11110011101001000010101110110001
S3 = 11100111010010000101011101100011
S4 = 11001110100100001010111011000111
.
.
.
S31 = 00111110011101001000010101110110

Meanwhile, the scrambling unit 140 performs an XOR operation on the CCSK-modulated signal using a 32 chip PN code, and the MSK modulation unit 150 pulses shaping using a minimum transition keying modulation method. . The frequency hopping unit 160 frequency hops the pulse-shaped signal according to a predetermined hopping period and transmits it on one of 51 carriers through an antenna.

3 is a block diagram of an FHSS / TDMA receiver for performing partial cross-correlation when performing cyclic code shift keying demodulation according to an embodiment of the present invention.

Referring to FIG. 3, an FHSS / TDMA receiver 200 (hereinafter referred to as an 'FHSS / TDMA receiver') that performs partial cross-correlation when performing cyclic code shift keying demodulation according to an embodiment of the present invention is a frequency power factor. It is configured to include the weak unit 210, the MSK demodulator 220, the descrambling unit 230, the CCSK demodulator 240, the symbol deinterleaving unit 250, the control unit 260 and the RS decoding unit 270. .

The FHSS / TDMA receiving apparatus 200 has a feature of reducing symbol interference due to propagation delay by partially correlating the CCSK demodulation using only a part of the cyclic code shift keying sequence instead of using the whole. The FHSS / TDMA receiving apparatus 200 uses the fact that the signal-to-noise ratio is not deteriorated when demodulating using only a sequence of about 75% or more of the total sequence. That is, if demodulation is performed using only the first 75% sequence or the latter 75% sequence of the entire sequence, discarding the symbols interfered by the propagation delay has a good effect on the overall signal-to-noise ratio. Hereinafter, the detailed structure is demonstrated.

The frequency reverse hopping unit 210 performs frequency reverse hopping on the received signal in synchronization with the same frequency hopping period as the frequency hopping unit 110.

The MKS demodulator 220 demodulates the frequency reverse-hopped signal with the same minimum transition keying code as the MSK modulator 150.

Next, the descrambling unit 230 descrambles the demodulated signal with the same PN code as the PN code of the scrambling unit 140.

The CCSK demodulator 240 performs CCSK demodulation in the same sequence as the cyclic code shift keying sequence of the CCSK modulator 130. At this time, in the related art, CCSK demodulation is performed using the cyclic code transition keying sequence as a whole. However, in the present invention, the scrambled signal is demodulated using a cyclic code transition keying sequence of a predetermined range among cyclic code transition keying sequences having a predetermined length. It is configured to restore.

When inter-symbol interference occurs due to propagation delay, the overall signal-to-noise ratio is worsened by the interference symbol. Inter-symbol interference always occurs to some extent. By removing the inter-symbol interference and performing CCSK demodulation, the overall signal-to-noise ratio can be increased. On the other hand, the signal-to-noise ratio has little effect on the signal-to-noise ratio when the CCSK demodulation is about 75% or more of the total length of the cyclic shift keying sequence. 4 shows these experimental results.

4 is a graph showing the bit error rate according to the degree of overlap between symbols of the FHSS / TDMA receiver of JTIDS / LINK-16.

As shown in FIG. 4, it can be seen that the signal-to-noise ratio has almost the same signal ratio up to about 7 bit error rate, and the signal-to-noise ratio significantly decreases at the bit error rate higher than that. Accordingly, approximately 7 bits (25%) of all 32 bits constituting one symbol reconstructed by CCSK demodulation are not largely affected even if they are not CCSK demodulated. Therefore, it is more advantageous not to perform CCSK demodulation on bits in which intersymbol interference has occurred.

Accordingly, the CCSK demodulator 240 is preferably configured to demodulate using only a cyclic code transition keying sequence of 75% or more or 100% or less of the total cyclic code transition keying sequences.

However, since it is not known at which bits inter-symbol interference occurs, it is basically a chip sequence in the range of 75% or more and 100% or less in the front of the entire cyclic code transition keying sequence or a chip sequence in the range of 75% or more and 100% or less from the back. It is preferable to demodulate using. This is because the symbol interference due to the propagation delay is likely to occur in the front part or the rear part of the entire chip sequence. 5 shows the bit error rate according to such partial cross-correlation.

5 is a graph illustrating a bit error rate according to a range of partial cross-correlation during cyclic code shift keying demodulation in an FHSS / TDMA receiver according to an embodiment of the present invention.

As shown in FIG. 5, it can be seen that in the case of an error between symbols, partial cross-correlation using only some of them has a good effect on the overall signal-to-noise ratio rather than using the entire cyclic code transition keying sequence.

Referring back to FIG. 3, the symbol deinterleaving unit 250 is configured to deinterleave the symbols reconstructed by the CCSK demodulation unit 240.

Next, the controller 260 monitors the change in the signal-to-noise ratio by measuring the signal-to-noise ratio of the deinterleaved symbol. The length ratio of the cyclic code transition keying sequence used in the CCSK demodulator 240 is determined within a predetermined range. However, when 100% is the initial value, the signal-to-noise ratio is lowered while the signal-to-noise ratio is gradually worsened. It may be configured to increase. That is, the controller 260 determines the range of the cyclic code transition keying sequence to be used by the CCSK demodulator 240 by measuring the signal-to-noise ratio of the deinterleaved symbol, and descrambled according to the determined range of the cyclic code transition keying sequence. The control may be configured to control the CCSK demodulation 240 to demodulate the signal. Of course, since the signal-to-noise ratio is not necessarily lower than the charge of the signal-to-noise ratio due to inter-symbol interference, the operation of the controller 260 can be regarded as one of the components for increasing the signal-to-noise ratio. On the other hand, the signal measured by the controller 260 is not an output symbol of the symbol deinterleaving unit 250 may be a symbol that has been RS decoded by the RS decoder 260.

Next, the RS decoder 270 decodes the same code as the RS coded by the RS encoder 110.

Hereinafter, another preferred embodiment of the present invention will be described in detail with reference to FIGS. 6 and 7.

6 is a block diagram of a FHSS / TDMA transmission method of JTIDS / LINK-16. The FHSS / TMDA transmission method of FIG. 6 is a conventional transmission method corresponding to the FHSS / TDMA reception method of the present invention. The detailed configuration will be briefly described below.

First, the RS encoder 110 performs channel encoding on a signal according to an RS code (S110). The symbol interleaving unit 120 interleaves the channel coded signal to output a 5-bit symbol (S120). Next, the CCSK modulator 130 performs cyclic code shift keying modulation on the interleaved symbol (S130). Then, the scrambling unit 140 performs an XOR operation on the CCSK-modulated signal using a 32 chip PN code (S140), and the MSK modulation unit 150 performs pulse shaping using a minimum transition keying modulation scheme. pulse shaping) (S150). The frequency hopping unit 160 frequency hops the pulse-shaped signal according to a predetermined hopping period and loads one of the 51 carriers through the antenna (S170).

7 is a flowchart illustrating an FHSS / TDMA receiving method for performing partial cross-correlation when performing cyclic code shift keying demodulation according to an embodiment of the present invention. Hereinafter, the detailed structure is demonstrated.

First, the signal is received through the antenna (S210), and the frequency reverse hop unit 210 frequency-hops the received signal (S220). The reverse hop is performed according to the same frequency hopping period as in the frequency hopping unit 160. The MSK demodulator 220 demodulates the MSK demodulated signal (S230), and the descrambler 230 descrambles the MSK demodulated signal (S240).

Next, the CCSK demodulator 240 demodulates the descrambled signal using a cyclic code transition keying sequence of a predetermined range among cyclic code transition keying sequences of a predetermined length to recover a symbol (S250). At this time, the predetermined range is a length range of 75% or more and 100% binomial of the entire length.

Meanwhile, the symbol deinterleaving unit 250 deinterleaves the CCSK demodulated symbol (S260).

Then, the controller 260 measures the signal-to-noise ratio for the deinterleaved symbol (S270). In operation S280, it is determined whether the signal-to-noise ratio is decreasing.

If the signal-to-noise ratio is not lowered, the RS decoder 270 normally performs channel decoding using the RS code (S290).

However, when the signal-to-noise ratio is lowered below a certain level, the controller 260 controls the CCSK demodulator 240 to change the cross correlation ratio (S285). That is, the controller 260 determines a range of cyclic code transition keying sequences to be used among cyclic code transition keying sequences having a predetermined length according to the measured signal-to-noise ratio. At this time, it is configured to determine a range of 75% or more and 100% or less of the cyclic code transition keying sequence to be used among all cyclic code transition keying sequences. Further, it is desirable to determine the range of 75% or more and 100% or less from the front or 75% or more and 100% or less from the beginning of the entire cyclic code transition keying sequence. On the other hand, when the measured signal-to-noise ratio is lowered below a predetermined threshold, it is desirable to determine to gradually reduce the range of cyclic code transition keying sequences to be used among the entire cyclic code transition keying sequences.

According to this series of processes, the CCSK demodulator 240 demodulates the received signal by using the cyclic code transition keying sequence in the range determined by the controller 260 to restore the symbol.

Although described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (8)

A frequency reverse hopping unit for frequency dehopping the received signal;
An MSK demodulator for demodulating minimum shift keying (MSK) on the frequency de-hopped signal;
A descrambling unit for descrambling the minimum transition keying demodulated signal using a pseudorandom noise (PN) sequence;
A CCSK demodulator for demodulating the descrambled signal using a cyclic code shift keying sequence of a predetermined length from a cyclic code shift keying (CCSK) sequence to recover a symbol;
A symbol deinterleaving unit for deinterleaving the recovered symbols;
Measuring a signal-to-noise ratio (SNR) of the deinterleaved symbol to determine a range of cyclic code transition keying sequences to be used by the CCSK demodulator, and to demodulate the descrambled signal according to the determined cyclic code transition keying sequence range An apparatus for receiving frequency hopping spread spectrum / time division multiple access (FHSS / TDMA) when performing partial cross-correlation during cyclic code shift keying demodulation comprising a control unit for controlling the CCSK demodulator. The cyclic code shift keying sequence of the cyclic code shift keying (CCSK) sequence of the predetermined range,
An FHSS / TDMA receiver for performing partial cross-correlation during cyclic code transition keying demodulation, wherein the cyclic code transition keying sequence is 75% or more and 100% or less of the entire cyclic code transition keying sequences. The cyclic code transition keying sequence of claim 2, wherein 75% or more and 100% or less of cyclic code transition keying sequences include:
Partial cross-correlation during cyclic code transition keying demodulation, characterized in that the chip sequence in the range of 75% or more and 100% or less from the front or the chip sequence in the range of 75% or more and 100% or less from the rear of the entire cyclic code transition keying sequence. FHSS / TDMA Receiver. The method of claim 3, wherein the control unit,
When the measured signal-to-noise ratio drops below a predetermined threshold, determining to reduce the range of cyclic code transition keying sequences to use among the entire cyclic code transition keying sequences until the signal-to-noise ratio rises above the threshold. A FHSS / TDMA receiver for performing partial cross-correlation during cyclic code shift keying demodulation. Recovering a symbol by demodulating the received signal using a predetermined range of a cyclic code shift keying (CCSK) sequence of a predetermined length;
Measuring a signal-to-noise ratio for the recovered symbols;
Determining a range of cyclic code transition keying sequences to use among the cyclic code transition keying sequences of the predetermined length according to the measured signal to noise ratio; and
Frequency hopping spread spectrum / time division multiple (FHSS / TDMA) performing partial cross-correlation during cyclic code transition keying demodulation, comprising: demodulating a received signal using the determined range of cyclic shift keying sequence access) How to receive. The method of claim 5, wherein the determining of the range of the cyclic code transition keying sequence to use among the cyclic code transition keying sequences of the predetermined length according to the measured signal to noise ratio comprises:
A FHSS / TDMA reception method for performing partial cross-correlation during cyclic code transition keying demodulation, wherein the range of cyclic code transition keying sequences to be used among all cyclic code transition keying sequences is determined to be 75% or more and 100% or less. The method of claim 6, wherein the determining of the range of the cyclic code transition keying sequence to use among the cyclic code transition keying sequences of the predetermined length according to the measured signal to noise ratio comprises:
FHSS / TDMA reception for performing partial cross-correlation during cyclic code transition keying demodulation, characterized in that it is determined within the range of 75% or more and 100% or less from the front or 75% or more and 100% or less from the rear of the entire cyclic code transition keying sequence Way. 8. The method of claim 7, wherein determining a range of cyclic code transition keying sequences to use among the cyclic code transition keying sequences of the predetermined length according to the measured signal to noise ratio,
When the measured signal-to-noise ratio drops below a predetermined threshold, determining to reduce the range of cyclic code transition keying sequences to use among the entire cyclic code transition keying sequences until the signal-to-noise ratio rises above the threshold. FHSS / TDMA receiving method for performing partial cross-correlation during cyclic code shift keying demodulation.

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