JP2812318B2 - Spread spectrum communication method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for spread spectrum communication by frequency hopping, and more particularly, to CDMA (Code Division) between communication stations having uplink and downlink with different line qualities.
A spread spectrum communication method and apparatus suitable for application to on multiple access (on multiple access) communication.

[0002]

2. Description of the Related Art As a spread modulation system of a spread spectrum communication system, a hopping sequence and a direct spread (DS) system for spreading a spectrum over a wide band by directly multiplying an information-modulated signal by a pseudo noise (PN) sequence are supported. There is a frequency hopping (FH) system in which a spectrum is uniformly spread by driving a frequency synthesizer to change (hop) a transmission frequency of an information-modulated signal. In particular, the FH method has the advantage that there is no need to perform transmission power control because there is no perspective problem, and that the FH method is strong against frequency selective fading because of the frequency diversity effect.

Further, in mobile communication and the like, communication is performed between a base station and a mobile station by transmitting and receiving on an uplink and a downlink, and the multiplexing method employs the above-described spread spectrum communication system of the FH system. In particular, a method of separating and multiplexing uplink and downlink frequency bands is generally used.

For example, as shown in the time / frequency matrix of FIG. 6, a total of eight hopping frequencies (fo, f1, f2, f3, f4, f5, f) are used for the uplink and the downlink.
6, f7). In this case, in the downlink, four hopping frequencies (f4, f5, f6, f7)
), Four hopping frequencies (f0, f1)
, F2, f3), the uplink and downlink frequency bands are separated and multiplexed into a high frequency band and a low frequency band. In particular, in FIG. 6, for example, in the uplink between the base station and one mobile station, (f3, f1, f2, f0, f
3) In the downlink, (f5, f6, f4, f7, f5)
The hopping frequency is used in a temporal order.

[0005] Various other methods have been proposed for setting the frequency bands of the uplink and the downlink. For example, FIG. 7 shows a method described in Japanese Patent Application Laid-Open No. 8-181680. In this method, as shown in the time / frequency matrix of FIG. 7, for example, the same frequency band (f0, f1, f2, f3, f4, f5, f6, f6) is used for the uplink and the downlink.
7), and multiplexing using different hopping frequencies such as the frequency band (f1, f3, f5, f7) on the uplink and the frequency band (f0, f2, f4, f6) on the downlink. Is to transmit and receive. Especially FIG.
Then, in the uplink, (f7, f3, f5, f1, f7
), (F2, f4, f0, f6, f2)
The hopping frequency is used in a temporal order.
According to such a method, since the hopping frequencies of the uplink and the downlink are mixed, a frequency diversity effect can be expected even when the wideband frequency band is affected by frequency selective fading or the like.

Japanese Patent Laid-Open Publication No. Hei 6-104865 discloses a code division multiple access system in which communication is performed by time division multiplexing using the same carrier frequency on the uplink and the downlink, and is also effective against fading. It realizes accurate transmission power control. When the line capacity differs between the uplink and the downlink, a technique is disclosed that changes the transmission time of the same carrier frequency to cope with the difference.

[0007]

The conventional spread spectrum communication method based on the frequency hopping method has advantages such as less restrictions imposed by transmission power control and a frequency diversity effect. However, a difference in line quality occurs due to a difference in line quality between the uplink and downlink lines, for example, a difference in antenna size between the base station and the mobile station.

That is, the base station uses a large antenna having a sufficient antenna Gain, while the mobile station is forced to use a small antenna due to a demand for miniaturization.

[0009] Therefore, the downlink from the base station to the mobile station is susceptible to radio propagation, and the bit error rate (BER) of the received signal is likely to deteriorate. On the other hand, the BER is less deteriorated from the mobile station to the base station. In addition, the bit error rate (BE) due to frequency selective fading due to the difference in the frequency band used between the uplink and the downlink.
The degree of deterioration of R) also differs.

There is a problem that the conventional method cannot sufficiently cope with the difference in line quality between the uplink and the downlink.

In particular, when trying to realize a code division multiple access communication system in mobile communication or the like, frequency-selective fading becomes a serious problem. The frequency hopping method is said to be strong against frequency selective fading since it originally has a frequency diversity effect. However, in the above-described method of separating and multiplexing the uplink and downlink frequency bands, if one of the frequency bands is affected by frequency selective fading or the like, the reliability of the line decreases. There is.

When code division multiple access is applied to the cellular system, the inter-cell interference on the uplink is the average of the interference from mobile stations uniformly distributed in adjacent cells. However, it is necessary to evaluate the inter-cell interference in the downlink when the mobile station receiving the interference is at the worst position, such as at the edge of a cell. Therefore, the number of channels on the downlink is smaller than the number of channels that can communicate on the uplink. In general,
Since the number of channels of the uplink and the downlink must be equal, there is a problem that the upper limit of the number of channels is limited by the number of channels of the downlink.

The technique disclosed in Japanese Patent Application Laid-Open No. 6-104865 is intended to realize high-precision transmission power control, and performs time division multiplexing in addition to code division multiplexing. In addition, there is a problem that the device becomes complicated.

The present invention has been made in view of the above points, and in a transmission system in which the line quality differs between the uplink and the downlink, the number of hopping frequencies and the number of hops per data symbol are appropriately distributed. It is an object of the present invention to provide a method and apparatus for spread spectrum communication by frequency hopping modulation, which can improve lines with poor line quality and equalize line quality.

Further, the present invention provides a transmission system in which the line quality differs between the uplink and the downlink, by changing the number of hopping frequencies to be allocated and the number of hops, so that the frequency is affected by frequency selective fading or the like. It is an object of the present invention to provide a spread spectrum communication method and apparatus in a code division multiple access communication capable of increasing a diversity effect and enabling highly reliable communication, and capable of equalizing line capacity in consideration of line deterioration. I do.

[0016]

To achieve the above object, a spread spectrum communication method according to the present invention is a spread spectrum communication method using frequency hopping modulation.
Among the uplink and downlink between communication stations, a line with poor line quality is characterized in that at least one of the number of hopping frequencies or the number of hops per data symbol is set higher than a line with good line quality. It is preferable that the hopping frequencies of the uplink and the downlink are mixed and set in the same frequency band.

Also, the spread spectrum communication method includes:
It is suitable for performing code division multiple access communication between communication stations including one base station and a plurality of mobile stations using the hopping frequency and the number of hops per data symbol as codes.

Further, the spread spectrum communication apparatus according to the present invention is a spread spectrum communication apparatus using frequency hopping modulation for performing code division multiple access communication between a communication station including one base station and a plurality of mobile stations. Increasing at least one of the number of hops per data symbol on the line from the base station to the mobile station;
It is characterized in that communication is performed with less communication on a line from a mobile station to a base station.

More specifically, in a code division multiple access communication system between a base station and a mobile station using, for example, a frequency hopping system applicable to a cellular system, the same frequency band is used for uplink and downlink. , And at least one of the number of hopping frequencies to be assigned or the number of hops per data symbol is changed depending on the line quality between the uplink and the downlink, and the uplink and downlink are multiplexed and transmitted and received using different hopping frequencies. It is characterized by having means for communicating by performing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment applied to a method and apparatus for spread spectrum communication by frequency hopping modulation according to the present invention will be described below with reference to the drawings.

FIG. 1 is a system block diagram showing a configuration of a bidirectional wireless connection between a base station and a plurality of mobile stations according to the first embodiment of the present invention. In the wireless line shown in the figure, a code division multiple access communication system (CDMA) using a frequency hopping system in which the same frequency band is used for an uplink line and a downlink line and multiplexing is performed using different hopping frequencies. I have. Here, 1 is a base station and 21 to 2N (where N is a natural number) is a mobile station. In FIG. 1, different hopping sequences are allocated to N mobile stations 21 to 2N, and transmission and reception to and from base station 1 are performed by using different hopping frequencies in the same frequency band on the uplink and the downlink respectively. Do. On the downlink, base station 1
The signal modulated by the information modulation / demodulation unit 5 is spread-modulated by changing the hopping frequency in accordance with the hopping sequence 7 by the spread modulation / demodulation unit 6 and transmitted to the mobile station. In the mobile station 21, the received signal is spread-demodulated by using the hopping sequence 91 in the spread modulation / demodulation section 81, and the information is demodulated in the information modulation / demodulation section 101. In the uplink, the signal is similarly transmitted from the mobile station 21 to the base station 1. The other mobile stations 2N have the same configuration.

In the present invention, as shown in FIG. 2, a base station 1 and a mobile station 2 using a frequency hopping method are used.
In the code division multiple access communication system between, for example,
Frequency bands (f0, f1, f2, f3, f4, f5) which are the same for the uplink and the downlink and are composed of nine hopping frequencies
, F6, f7, f8). Then, three hopping frequency bands (f2, f5, f8) on the uplink and six (f0, f1, f3, f4, f6, f7) on the downlink.
Transmission and reception are performed by changing the number of hopping frequencies to be allocated, such as hopping frequency bands, and multiplexing using different hopping frequencies.

FIG. 3 is a diagram showing an embodiment of the relationship between the uplink and downlink times and the hopping frequency between the base station and one mobile station. The vertical axis is used for the uplink and the downlink. The entire frequency band (9 hopping frequencies), and the abscissa indicates 6 chips, 1 data symbol time. Uplinks per data symbol are (f5, f8, f2, f5, f8, f
2), the downlink 1 is (f4, f0, f7, f1, f3,
f6), the downlink 2 is (f1, f3, f6, f4, f0).
, F7) in chronological order.

As described above, in the embodiment of the present invention, the number of hopping frequencies in the downlink is twice as high as that in the uplink, so that an approximately double increase in the channel capacity can be expected. Therefore, even if the line quality of the downlink is about twice as bad as that of the uplink, the line quality of the uplink and the downlink can be made almost equal, and the same line capacity can be expected. Further, even when a wide frequency band is affected by frequency selective fading or the like, a frequency diversity effect can be expected.

Next, a second embodiment of the present invention will be described.

FIG. 4 is a diagram showing a second embodiment of the present invention with respect to the relationship between the time and the hopping frequency in the uplink and downlink between the base station and one mobile station. In the uplink per data symbol (f3, f5, f1),
In the downlink, (f2, f0, f4, f2, f0, f4)
The hopping frequency is used in a temporal order.

As described above, in the second embodiment of the present invention, the number of hops per data symbol in the downlink is larger than that in the uplink, so that the redundancy per data symbol can be increased and both channel qualities can be equalized. , And the line capacity can be increased. Therefore, even if the line quality of the downlink is lower than that of the uplink, it is expected that the uplink and the downlink have the same line capacity. Further, even when a wide frequency band is affected by frequency selective fading or the like, a frequency diversity effect can be expected.

Next, a third embodiment of the present invention will be described.

For the above-mentioned line quality, the bit error rate is measured in advance in the demodulation output of each of the information modulators / demodulators 5, 101 to 10N, and the hopping frequency is fixedly assigned in advance according to the line quality. .

In the first and second embodiments described above, hopping frequency allocation is set in advance based on the difference in line quality between the uplink and the downlink.

However, the present invention is not limited to this. The number of hopping frequencies and the number of hops per data symbol are automatically determined according to the bit error rate of each of the uplink and downlink. Changes can be made to automatically equalize the quality of both lines.

The number of hopping frequencies and 1
The invention for controlling the number of hops per data symbol is the third embodiment of the present invention.

Hereinafter, a third embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 5 is a block diagram showing a configuration of a two-way wireless connection between base station 20 and an arbitrary mobile station 21 among a plurality of mobile stations according to the third embodiment of the present invention.

In the figure, the transmitting side of the base station 20 modulates data to be transmitted to the mobile station 21 by the information modulator 51, spread-modulates the data by the spread modulator 61, and transmits as a radio signal.

On the other hand, the receiving side is despread by the spread demodulator 62 and then demodulated by the information demodulator 52 and output as received data. Here, the hopping frequencies of the spread modulator 61 and the spread demodulator 62 are controlled by a hopping frequency control unit (HOPPING CONT) 13.

The hopping frequency control section 13 controls the hopping frequency as follows. That is, the bit error rate of the output data of the information demodulator 52 on the uplink (BE
R1) is detected by the BER detector 11. The BER value (BER1) and the BER detector 1 of the mobile station 21
1 is compared with the BER value (BER2) detected by the BER comparator 12, and the difference ΔBER = BER1−BER
Find the value of 2.

If ΔBER is larger than the predetermined value ε, it is determined that the uplink has lower line quality than the downlink.

Therefore, in this case, control is performed so that the number of hopping frequencies assigned to the uplink is greater than the number of hopping frequencies assigned to the downlink.

On the other hand, when ΔBER is equal to or smaller than the predetermined value ε, it is determined that the uplink has better line quality than the downlink. Therefore, control is performed such that the number of hopping frequencies assigned to the uplink is smaller than the number of hopping frequencies assigned to the downlink.

If the difference between BER1 and BER2 is within a predetermined value ε, it is determined that the uplink and downlink qualities are almost equal. So, in this case,
The hopping frequency will not change. In this way, the number of hopping frequencies of the uplink and the downlink is automatically controlled according to the difference in the channel quality between the uplink and the downlink.

Next, for the mobile station 21, the output data of the information demodulator 52 is input to the BER detector 11, and the bit error rate (BER2) of the downlink is obtained. This value is input to the information modulator 51 and transmitted to the base station 20 as a part of the transmission data from the mobile station 21.

Finally, as described above, the number of hopping frequencies for the uplink and downlink determined by the hopping frequency controller 13 of the base station 20 is set as follows.

That is, the base station 20 transmits the number of hopping frequencies of the uplink and downlink to each mobile station using a control data line different from a plurality of spread signals. Then, each mobile station receives the control data line, and the base station 20 and each mobile station operate at the same number of hopping frequencies.

As another method, the spreading process is stopped for a part (for example, the head of data) of the spread signal transmitted from the base station 20, and after each mobile station normally receives as non-spread data, It operates at a given number of hopping frequencies.

Further, as another method, before changing the number of hopping frequencies, the base station 20 transmits the number of hopping frequencies set next to each mobile station in advance, and operates at a predetermined hopping frequency. To do it.

In the third embodiment described above, the method of automatically changing the hopping frequency between the uplink and the downlink according to the line quality has been described, but as described in the second embodiment, A method of changing the number of hops per data symbol as well as changing the number of hopping frequencies can be similarly applied.

As described above, the present invention has been described with respect to a code division multiple access communication system as an embodiment. It is based on a spread spectrum communication system based on frequency hopping, which enables the securing.

In one embodiment of the code division multiple access communication system, one of the number of hopping frequencies of a line with poor line quality or the number of hops per data symbol is increased for a line with good line quality. In the example described above, both the hopping frequency and the number of hops may be relatively increased or decreased between lines. In this case, the effect of the quality improvement or the like is obtained by the combination of the two. Can be significantly improved. Furthermore,
Adjustment of the hopping frequency or the number of hops mutually equalizes the quality within a predetermined quality range, and allocates between the uplink and downlink to equalize the line capacity of the upper and lower lines and secure the maximum. You may make it distribute.

[0050]

According to the present invention, in spread spectrum communication by frequency hopping modulation between communication stations, even in a transmission system in which the line quality differs in the line direction, the line quality can be improved and the quality of both lines can be equalized. Is possible.

When multiplexing the uplink and downlink with different line qualities, the numbers of hopping frequencies of the uplink and downlink are made different, mixed in the same frequency band, and hopped over a wide band. In addition, it is possible to equalize the line capacities of the uplink and the downlink and realize a frequency diversity effect with respect to frequency selective fading which affects a wide frequency band.

Further, since the number of hops per data symbol in the uplink and the downlink is changed and mixed in the same frequency band and the hop is performed in a wide band, the line capacities of the uplink and the downlink are equalized, The frequency diversity effect can be realized with respect to the frequency selective fading affecting the frequency band.

[Brief description of the drawings]

FIG. 1 shows a system block diagram according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of changing the number of hopping frequencies for uplink and downlink in the configuration of FIG.

FIG. 3 is a diagram illustrating a method of setting a hopping frequency per data symbol in the uplink and downlinks 1 and 2 in the configuration of FIG. 1;

FIG. 4 is a diagram showing a second embodiment of the present invention;
FIG. 6 is a diagram illustrating a method of setting a hopping frequency when changing a hopping frequency per data symbol.

FIG. 5 is a diagram showing a system block diagram according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a method of setting a hopping frequency in a conventional spread spectrum communication system, in which uplink and downlink are separated.

FIG. 7 is a diagram showing another setting method of the hopping frequency of the conventional spread spectrum communication system, in which the uplink and the downlink are set alternately.

[Explanation of symbols]

 Reference Signs List 1 base station 21-2N mobile station 3 hopping frequency band used in downlink 4 hopping frequency band used in uplink 5 information modulation / demodulation unit 6 spreading modulation / demodulation unit 7 hopping sequence 81-8N spreading modulation / demodulation unit 91-9N hopping sequence 101- Reference Signs List 10N information modulation / demodulation unit 11 bit error rate (BER) detector 12 bit error rate (BER) comparator 13 hopping frequency control unit

Continuation of the front page (56) References JP-A-5-219008 (JP, A) JP-A 64-86638 (JP, A) JP-A 4-334222 (JP, A) JP-A 7-177059 (JP) , A) JP-A-8-139641 (JP, A) JP-A-8-168075 (JP, A) JP-A-4-344729 (JP, A) JP-A-8-181680 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H04B 1/713 H04B 1/04 H04B 7/12 H04B 7/26

Claims (6)

(57) [Claims] In a spread spectrum communication method based on frequency hopping modulation, a difference between the line qualities of uplink and downlink between opposing communication stations is detected, and if the difference is larger than a predetermined value, the uplink is detected. Divided into
Hopping frequency or one data symbol
If the difference is smaller than a predetermined value , the number of hops is reduced.
Hopping frequency or one data symbol
So that the number of hops increases.
A spread spectrum communication method characterized by controlling respective hopping frequency controllers . 2. The spread spectrum communication method according to claim 1, wherein the hopping frequencies of the uplink and the downlink are mixed and set in the same frequency band. 3. A code division multiple access communication is performed between a communication station consisting of one base station and a plurality of mobile stations by using the hopping frequency and the number of hops per data symbol as codes. Or the spread spectrum communication method according to 2. 4. The spread spectrum communication method according to claim 1, wherein said channel quality is determined based on a bit error rate of said communication station. 5. A spread spectrum communication apparatus using frequency hopping modulation for performing code division multiple access communication between a communication station comprising one base station and a plurality of mobile stations, wherein the hopping frequencies of the uplink and downlink are the same. Means for mixing with each other in a frequency band, means for detecting a difference in line quality between the uplink and downlink in the base station and the mobile station, respectively, if the difference is larger than a predetermined value, the uplink Divided into
Hopping frequency or one data symbol
If the difference is smaller than a predetermined value , the number of hops is reduced.
Hopping frequency or one data symbol
Base station and mobile station so as to increase the number of hops
A spread spectrum communication apparatus comprising: means for controlling each hopping frequency control unit; and means for multiplexing and transmitting and receiving the uplink and downlink using different hopping frequencies. 6. The spread spectrum communication apparatus according to claim 5 , wherein said channel quality is determined based on a bit error rate detected at a receiving side of said base station or mobile station.