JP2000101481A - Frequency hopping method and frequency hopping communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a frequency hopping method where disturbance of a near-by frequency channel is hard to takes place. SOLUTION: Frequency channels are divided into even numbered and add numbered channels. A hopping pattern is assigned in a group of even numbered channels for a first half of one period shown in Figure (a). A hopping pattern is assigned in a group of odd numbered channels for a latter half of one period shown in Figure (b). Connecting each of the hopping patterns for the first half and the latter half of one period, an extended hopping pattern is synthesized. A frequency channel is selected depending on the extended hopping pattern, and modulated transmission data are transmitted through the channel. Thus, there is not period for which frequency channels are adjacent to each other, between frequency hopping systems which adopt different synchronization methods.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a frequency hopping (FH) method and a frequency hopping communication device.

[0002]

2. Description of the Related Art In frequency hopping, which is a type of spread spectrum communication, radio waves output from a plurality of radios are
Sometimes they happen to be on the same frequency channel and are called hits. If there is a hit, the received data at that time becomes an error, so it is desirable that the hit is as small as possible. Generally, frequency hopping is performed asynchronously. In this asynchronous frequency hopping, a user uses a hopping pattern having a random phase relationship between different transmission / reception systems. Therefore, if the hopping pattern is not appropriately selected, the hit probability for receiving radio waves from different transmission / reception systems increases. Therefore, hopping patterns with few hits have been studied, and OCC (One Coincidence) sequences and Reed-Solomon (Reed-Solomon) sequences are known. This OC
The C sequence is an excellent sequence that hits at most once in one cycle when the phases of two patterns are shifted.

FIG. 5 is an explanatory diagram of a conventional asynchronous frequency hopping pattern. In the figure, the multivalued number of 1 to 10 is 1
The number represents the frequency channel number taken during the cycle, and the circled numbers represent the pattern numbers of the hopping patterns. This example is a hopping pattern of 10 types using 10 waves of f ₁ ~f _10. No. 1 is an initial series, and the number of frequency channels taken in one cycle is a value obtained by subtracting 1 from an arbitrary prime number. Sequences from the initial sequence up to No. 10 are sequentially generated according to a predetermined rule. In this figure, the hopping pattern sequences are arranged and numbered so that the first frequency channel number of each sequence is arranged in order.

In contrast to the asynchronous type described above, there is a synchronous type frequency hopping. In the synchronous type, for example, the sequence # 1,
, 9, 10}, the starting phase is shifted, for example, the sequence {2, 3, 4,.
Use a hopping pattern such as 1 °. Therefore,
As long as the phases are synchronized, there is no hit in principle, and the transmission quality is improved. However, in the synchronous type, there is a high probability that different systems use adjacent frequency channels at the same time. The band-pass filter provided on the receiving side for separating the frequency channels cannot sufficiently separate the received signals of the adjacent channels, and thus has a problem that the influence of interference is increased.

FIG. 6 is an explanatory diagram of a frequency channel arrangement in the conventional asynchronous frequency hopping. The horizontal axis is frequency, which indicates each frequency channel number from 1 to 10
The frequencies f _{1 to} f ₁₀ are arranged in correspondence with the multi-valued number of.
The vertical axis represents the gain indicating the pass characteristic of the received signal of each frequency channel by the band pass filter on the receiving side. Band of the transmission signal of one frequency channel centered at each frequency f ₁ ~f ₁₀ is set at a distance from one another. For example, the band of the transmission signal is 700 kHz, and the interval between the frequency channels is 1 MHz. However, the slope of the bandpass filter cannot be cut steeply. For this reason, in the hatched band in the figure, the components of the transmission signal of the adjacent frequency channel are also leaked and received. As a result, adjacent frequency channel interference occurs during periods when adjacent systems simultaneously use adjacent frequency channels. For example, in synchronous frequency hopping, the sequence {1, 2, 3,.
., 9, 10}, if the start phase is shifted by one hopping unit, the frequency channels are always adjacent, and adjacent frequency channel interference always occurs.

Therefore, in the synchronous type, the start phase is not simply shifted, but in the same manner as in the asynchronous type, FIG.
It is also conceivable to employ the OCC sequence shown in FIG. However, conventional OCC sequences or Reed-Solomon sequences have not been considered up to such adjacent frequency channel interference. In the case where the OCC sequence shown in FIG. 5 is used, two or more frequency channels are adjacent to each other in one cycle of the hopping pattern even if they are not adjacent in all the cycles. For example, as shown in FIG.
Between the o.2 series, and f ₁ and f _2, f ₁₀ and f ₉ are adjacent.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in the case of synchronous frequency hopping, it is difficult to generate adjacent frequency channel interference including adjacent frequency channel interference. In the case of asynchronous frequency hopping, a frequency hopping method and a frequency hopping communication device, such that when coexisting with a synchronous frequency hopping system using the same hopping pattern sequence, a hit rate due to interference between the systems is reduced. The purpose is to provide.

[0008]

According to a first aspect of the present invention, there is provided a frequency hopping method in which a signal modulated by transmission data is transmitted on a frequency channel corresponding to a hopping pattern. Are assigned to a plurality of groups in the order of frequency magnitude, the hopping patterns are assigned to the respective groups, and the frequency channels are assigned according to the combined hopping patterns to which the hopping patterns of the respective groups are connected. It switches and transmits, receives the transmitted signal, and despreads according to the combined hopping pattern.

Further, in the invention according to claim 2,
In a frequency hopping communication device used for a frequency hopping method in which a signal modulated by transmission data is transmitted on a frequency channel according to a hopping pattern, the frequency channels are allocated to a plurality of groups in order of frequency magnitude, A means for generating a combined hopping pattern in which the hopping patterns are assigned to each group, the hopping patterns of the respective groups being connected, a means for switching the frequency channel according to the combined hopping pattern, and the transmission data Means for transmitting a signal modulated by the above-mentioned frequency channel on the switched frequency channel.

Further, in the invention according to claim 3,
In a frequency hopping communication device used for a frequency hopping method in which a signal modulated by transmission data is transmitted on a frequency channel according to a hopping pattern, the frequency channels are allocated to a plurality of groups in order of magnitude of frequency. Means for receiving the signal, the hopping pattern is assigned to each group, means for generating a combined hopping pattern in which the hopping patterns of each group are connected, and, according to the combined hopping pattern, It has means for despreading the transmitted signal.

Therefore, the frequency hopping method according to the first aspect and the frequency hopping communication apparatus according to the second and third aspects provide the following:
It is difficult to generate adjacent frequency channel interference including adjacent frequency channel interference. Also, in the case of asynchronous frequency hopping, even when there is a synchronous frequency hopping system using the same hopping pattern sequence, the probability of hits due to interference between the systems is reduced.

[0012]

FIG. 1 is a block diagram of a frequency hopping system for explaining an example of a frequency hopping method according to the present invention. In the figure, 1 is an encoder, 2 is 1
Next modulator, 3 is a mixer, 4 is a hopping pattern generator,
5 is a frequency synthesizer, 6 is a high frequency amplifier, 7 is a transmitting antenna, 8 is a receiving antenna, 9 is a high frequency amplifier, 10
Is a mixer, 11 is a hopping pattern generator, 12 is a frequency synthesizer, 13 is a narrow bandpass filter, 1
4 is a primary demodulator and 15 is a decoder.

On the transmission side, transmission data is transmitted to the encoder 1
Is converted into transmission data that can be detected and corrected by an error. The transmission data is subjected to narrowband modulation such as frequency modulation (FSK) in the primary modulator 2 and then frequency-converted in the mixer 3 by the output signal of the frequency synthesizer 5. The frequency synthesizer 5 changes the frequency to be frequency-converted with time according to the hopping pattern output from the hopping pattern generator 4,
Switch the transmission frequency channel. Therefore, the narrow-band modulated signal is transmitted on a frequency channel corresponding to the hopping pattern. As a result, the signal is spread and becomes a spread spectrum signal having a wide frequency band, amplified by the high frequency amplifier 6 and output from the transmission antenna 7.

On the receiving side, the transmitted spread spectrum signal is received by the receiving antenna 8, amplified by the high frequency amplifier 9, input to the mixer 10, and despread. The hopping pattern generator 11 generates the same hopping pattern in synchronization with the hopping pattern generator 4 on the transmission side, and the frequency synthesizer 12 generates a local hopping signal whose frequency changes in the same pattern as that output by the frequency synthesizer 5 on the transmission side. Outputs oscillation signal. The despread signal passes through a narrowband bandpass filter (BPF) 10 through a signal component of a reception frequency band of each frequency channel and is input to a primary demodulator 14. In the primary demodulator 14, corresponding to the primary modulator 2 on the transmission side, for example, FS
Perform K demodulation. The decoder 15 performs error detection and correction on the demodulated reception data corresponding to the encoder 1 on the transmission side, and outputs the error-detected and corrected reception data.

Although the system configuration shown in the figure is a simple type of frequency hopping method, in the case of a hybrid system (hybrid frequency hopping / direct spreading system), the primary modulator 2 modulates the signal on the transmitting side. The spread data output from the spread code generator (not shown) directly spreads the transmission data with a relatively small degree of spread, and then outputs the spread data to the mixer 3 to generate a wide frequency band at a relatively wide frequency channel interval. Frequency hopping over a wide range. On the receiving side, the output of the narrowband bandpass filter 13 may be despread with a spreading code output from a spreading code generator (not shown) and then output to the primary demodulator 14.

FIG. 2 is an explanatory diagram of a frequency channel arrangement in the frequency hopping method of the present invention. FIG.
2A shows a frequency channel arrangement in the first half of one cycle of the hopping pattern, and FIG. 2B shows a frequency channel arrangement in the latter half of one cycle of the hopping pattern. The horizontal axis is frequency, which indicates frequency channel numbers 1 to 2
The frequencies f _{1 to} f ₂₀ are arranged in correspondence with the multi-valued number of 0. The vertical axis indicates the gain indicating the pass characteristic of the signal of each frequency channel by the band pass filter on the receiving side. The frequency bands of the transmission signals of the respective frequency channels centered on the frequencies f _{1 to} f ₂₀ are set at intervals, as in the conventional case shown in FIG. The frequency channels are allocated to a plurality of groups in the order of the frequency, and in the example shown in the figure, the channels are allocated to even-numbered channels and odd-numbered channels.

In the first half of one cycle shown in FIG.
A hopping pattern is assigned within the group of the even-numbered channels, and in the latter half of one cycle shown in FIG. 2B, a hopping pattern is assigned within the group of the odd-numbered channels. Therefore, in the first half of one cycle and the second half of one cycle, the frequency channel numbers used for the hopping pattern are every other. And the first half of one cycle and 1
By connecting each hopping pattern in the second half of the cycle,
An extended hopping pattern is synthesized. The frequency channel is switched according to this extended hopping pattern, and the modulated transmission data is transmitted. Therefore, if hopping patterns with different pattern numbers are used between different synchronous frequency hopping systems, there is no period in which frequency channels are adjacent. Therefore, even if the characteristics are the same as those of the conventional bandpass filter, adjacent frequency channel interference due to transmission signals of other frequency channels transmitted by different systems is eliminated.

FIG. 3 is an explanatory diagram of one example of a hopping pattern used in the frequency hopping method of the present invention. In the figure, multivalued numbers 1 to 20 represent frequency channel numbers taken during one cycle, and circled numbers represent pattern numbers of hopping patterns. This example is a hopping pattern of 10 types using 20 waves of f ₁ ~f _20. 10 waves of even frequency channels, 10 waves of odd frequency channels
An OCC sequence is created by allocating one OCC sequence to each group and allocating one OCC sequence to each group. By linking them, a new extended OCC sequence is synthesized.

As a specific method of forming the hopping pattern, the one obtained by doubling each frequency channel number of the conventional OCC sequence shown in FIG. Next, 1 is subtracted from the even frequency channels (the frequency channel is 1).
A hopping pattern composed of an odd number of frequency channels (shifted by the number of channels) is defined as an odd OCC sequence.
A hopping pattern in the latter half of one cycle is used.

For example, in the No. 1 series, the hopping pattern in the first half of one cycle is {2, 4, 6, 8, 10, 1}.
2, 14, 16, 18, 20}, and the hopping pattern in the latter half of one cycle is {1, 3, 5, 7, 9, 11, 13, 15, 17, 1} obtained by subtracting 1 from each frequency channel number.
9 °. By such a hopping pattern creation method, it is possible to obtain the hopping pattern shown in FIG. 2 in which frequency channels are not adjacent in the same period. The hopping pattern generators 4 and 11 shown in FIG. 1 generate one of the series shown in FIG.

In the above description, one of the existing OCC sequences
One hopping pattern was assigned to each of the even and odd groups, and substantially the same hopping pattern was created for each group. One extended hopping pattern was created by connecting the two. However, the combination of the hopping patterns of the even and odd groups is free as long as the hopping patterns of each group are not used repeatedly. For example, in FIG. 3, the first half of the hopping pattern of No. 1 may be used as the OCC sequence of the even number, and the latter half of the hopping pattern of No. 2 may be used as the OCC sequence of the odd number. That is, $ 2,4
6, 8, 10, 12, 14, 16, 18, 20, 3,
A hopping pattern of 7, 11, 15, 19, 1, 5, 9, 13, 17} may be used.

In the above description, the number of frequency channels of the basic OCC sequence is doubled, and a hopping pattern is created for each of the first half period and the second half period. Instead, the frequency is made three or four times or more, and one cycle of the hopping pattern is divided into three or four periods, and in each period, the frequency channels of different systems are more than twice as large as the adjacent frequency channels. You may make it spread. For example, {1, 2, 3, 4, 5, 6, 7, 8,
From the 9,10} OCC sequence, {3,6,9,12,1
5,18,21,24,27,30}, {2,5,1}
1, 14, 17, 20, 23, 26, 29}, {1,
A sequence of 4, 10, 13, 16, 19, 22, 25, 28} may be created.

In the above description, the number of frequency channels (frequency bands) is increased on the assumption that the total number of hopping patterns (the number of OCC sequences) is the same as that of the conventional OCC sequence. Instead, an OCC sequence in which the number of OCC sequences and the number of frequency channels are less than half the number of conventional OCC sequences is created, and based on this, the number of frequency channels is doubled and May be created for each group. In this case, the number of frequency channels (frequency bands) of the newly created extended OCC sequence can be prevented from being larger than the number of frequency channels (frequency bands) of the conventional OCC sequence.

By using the above-mentioned extended OCC sequence, the interval between frequency channels used in the same period becomes larger than before, so that interference between adjacent frequency channels including adjacent frequency channels is reduced. On the other hand, among the extended frequency channels described above,
For example, only even frequency channels, or
It is also possible to make an OCC sequence using only odd-numbered frequency channels. Also in this case, interference between adjacent frequency channels is reduced. However, since the given frequency band is used only intermittently, the frequency use efficiency is lower than that of the above-described extended OCC sequence,
Also, the spread of the frequency spectrum becomes poor.

In the above description, the case where the extended OCC sequence is applied to the synchronous frequency hopping method has been described. However, the present invention can be applied to the asynchronous frequency hopping method. Since the OCC sequence is used for the frequency hopping pattern, the hit is only once at most in one cycle when the phases of the two patterns are shifted, so the hit probability is small.

FIG. 4 is an explanatory diagram in the case where the synchronous frequency hopping system and the asynchronous frequency hopping system coexist in the same or adjacent areas. In the figure,
21, 22 are first and second synchronous frequency hopping systems, 21a, 21b, 22a, 22b, 22c, 22
d is a radio, 23 is a reference station, 24 is an asynchronous frequency hopping system, and 24a, 24b and 24c are radios. In the illustrated example, one pair of wireless devices or three or more wireless devices exist in one frequency hopping system. Each wireless device may be dedicated to a transmission function, dedicated to a reception function, or one having both transmission and reception functions. Further, a plurality of frequency hopping patterns may be assigned in each system, and multiple access may be made in each system.

The first and second synchronous frequency hopping systems 21 and 22 perform communication within the system using the synchronized extended OCC sequence under the frequency control of the reference station 23, respectively. For example, the first synchronous frequency hopping system 21 uses the No. 1 sequence shown in FIG. 3, and the second synchronous frequency hopping system 22 uses the No. 2 sequence shown in FIG. . Since both are synchronized, for example, in the period during which the frequency channel f ₂ in the first synchronous frequency hopping system 21 is used, the frequency channels are used in the second synchronous frequency hopping system 22 in f ₄ Is done. In the next period in which the frequency is switched, the first synchronous frequency hopping system 21 uses the frequency channel of f ₄ ,
Frequency channel of the second synchronizing frequency hopping system 22 at f ₈ is used.

First and second synchronous frequency hopping systems 21 and 22 and asynchronous frequency hopping system 2
4 coexist in the same or adjacent areas, the radio wave transmitted from the radio 24a of the asynchronous frequency hopping system 24 is transmitted to the first synchronous frequency radio 21b or the second synchronous frequency hopping system. It is also received by the 22 wireless devices 22b to 22d. Or,
Conversely, radio waves transmitted from the wireless devices 21a and 22a are also received by the wireless devices 24b and 24c. At this time, if only the asynchronous frequency hopping system 24 uses a hopping pattern belonging to a different sequence, for example, the conventional OCC sequence shown in FIG. 5, the first and second synchronous frequency hopping systems 21 and 22, different OCC sequences are used. Therefore, when the radios 24b and 24c and the radios 21b and 22b to 22d simultaneously receive radio waves of different OCC sequences, the hit rate increases and the transmission quality deteriorates. Therefore, in the asynchronous frequency hopping system 24 coexisting with the first and second synchronous frequency hopping systems 21 and 22 in the same or adjacent areas, the first and second synchronous OCP sequences shown in FIG. By using a hopping pattern of a pattern number not used by the synchronous frequency hopping systems 21 and 24 of No. 2, the hit rate can be reduced.

In the above description, the OCC sequence has been described as an example. In addition, an extended hopping pattern with little interference of adjacent frequency channels including adjacent frequency channels is similarly used even when m-sequence or Reed-Solomon code is used, which is used as a frequency hopping pattern with a small hit rate in the asynchronous frequency hopping method. Can be created. In the above description, a typical frequency hopping method has been described. However, even in the hybrid system described in the description with reference to FIG. 1, the present invention can be similarly applied because frequency hopping is used. In this sense, the above-described hybrid scheme is also an example of the frequency hopping method of the present invention.

[0030]

As is apparent from the above description, in the present invention, in the case of synchronous frequency hopping, adjacent frequency channel interference is reduced. In the case of asynchronous frequency hopping, the hit rate due to interference between the synchronous system and the asynchronous system can be reduced when used in an environment coexisting with the synchronous frequency hopping system. Therefore, there is an effect that a decrease in transmission quality can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of a frequency hopping system for explaining an example of a frequency hopping method according to the present invention.

FIG. 2 is an explanatory diagram of a frequency channel arrangement in the frequency hopping method of the present invention.

FIG. 3 is an explanatory diagram of one example of a hopping pattern used in the frequency hopping method of the present invention.

FIG. 4 is an explanatory diagram of a case where a synchronous frequency hopping system and an asynchronous frequency hopping system coexist in the same or nearby areas.

FIG. 5 is an explanatory diagram of a conventional asynchronous frequency hopping pattern.

FIG. 6 is an explanatory diagram of a frequency channel arrangement in a conventional asynchronous frequency hopping method.

[Explanation of symbols]

1 encoder, 2 primary modulator, 3 mixer, 4 hopping pattern generator, 5 frequency synthesizer, 6 high frequency amplifier, 7 transmitting antenna, 8 receiving antenna, 9 high frequency amplifier, 10 mixer, 11 hopping pattern generator, 12 frequency Synthesizer, 13 narrow bandpass filter, 14 primary demodulator, 15 decoder, 21
22 first and second synchronous frequency hopping systems,
23 reference stations, 24 asynchronous frequency hopping systems

Claims (3)

[Claims] 1. A frequency hopping method in which a signal modulated by transmission data is transmitted on a frequency channel according to a hopping pattern, wherein the frequency channels are divided into a plurality of groups in order of magnitude of frequency. The hopping pattern is assigned to each group, and the frequency channel is switched and transmitted according to a combined hopping pattern in which the hopping patterns of the respective groups are connected. De-spreading according to the frequency hopping method. 2. A frequency hopping communication device used for a frequency hopping method in which a signal modulated by transmission data is transmitted on a frequency channel according to a hopping pattern, wherein the frequency channels are divided into a plurality of groups in order of frequency magnitude. Means for generating a combined hopping pattern in which the hopping patterns are assigned to each group, and the hopping patterns of the groups are connected; means for switching the frequency channel according to the combined hopping pattern; And a means for transmitting a signal modulated by the transmission data on the switched frequency channel. 3. A frequency hopping communication apparatus for use in a frequency hopping method in which a signal modulated by transmission data is transmitted on a frequency channel according to a hopping pattern, wherein the frequency channels are divided into a plurality of groups in order of frequency magnitude. Means for receiving a transmitted signal, means for assigning the hopping pattern to each group, means for generating a combined hopping pattern in which the hopping patterns of each group are connected, and the combined hopping pattern Means for despreading the transmitted signal according to the frequency hopping communication apparatus.