JPH08228173A - Communication system - Google Patents

Abstract

PURPOSE: To effectively utilize a frequency by changing a channel band width corresponding to the kind of data in a radio LAN system for using a frequency hopping type spread spectrum communication system. CONSTITUTION: In transmission, the data are band-limited in a BPF 218, inputted to a VCO inside a frequency synthesizer 226, FSK modulated, then mixed with carrier signals by an up converter 211, gain-adjusted in a transmission amplifier 209, passed through the BPF 206 and transmitted. At the time, whether the transmission data are a low rate or a high rate is discriminated in a controller 203, and in the case of low-rate data, the frequency division counter value of a hopping PLL 217 is changed, the frequency step of a synthesizer 202 is turned to 1/2, the filter of a 2nd IF is switched to a 221b provided with the passing band of the 1/2 of the BPF 221a, the free channel of a 1/2Fw band is searched and the transmission is performed. Thus, an excessive frequency band is not uselessly assigned to the low-rate data and the frequency is effectively utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bandwidth control method for a channel in a frequency hopping spread spectrum communication (FHSS) communication system.

[0002]

2. Description of the Related Art Conventionally, spread spectrum communication (hereinafter referred to as SS) has been an effective means as a communication technology in a noisy ISM band. And this SS is
There are the following two methods when roughly classified.

(1) Direct sequence method (DS) (2) Frequency hopping method (FH) Of these, the FHSS of (2) moves the frequency (channel) used for communication at high speed to reduce the influence of noise. It is a method.

In this FHSS, a method of switching a channel having a fixed bandwidth at a constant cycle is general.

[0005]

However, in the above-mentioned conventional example, since the step of moving (hopping) the frequency is a constant value (for example, 1 MHz step), the frequency band for one channel is set even for low-speed data. It is difficult to use the frequency band without any gap (and thus effectively) unless it is the maximum data rate that needs to be allocated and is all the same and can be transmitted with the bandwidth of one channel.

It is an object of the present invention to provide a wireless LAN system which can effectively use the frequency band.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a wireless L using a spread spectrum communication system of a frequency hopping system.
The AN system has a determination means for determining low / high speed data type, a notification means for notifying the other party of the data type, and a control means for controlling the frequency bandwidth used in communication, and the data type (data The bandwidth of one channel is changed according to the rate.

[0008]

According to the present invention, by changing the bandwidth of one channel of FHSS according to the data rate, it is possible to eliminate the waste of allocating an excessive frequency band to low-speed data and enable effective use of frequencies. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a wireless LAN according to an embodiment of the present invention.
It is a block diagram which shows the structural example of a system.

As shown, the system of this embodiment is
Audio data (low speed data) terminals 101a and 101b
A facsimile (low speed data) 102, data terminals (high speed data) 103a and 103b, a peripheral device (high speed data) 104 such as a printer, and a composite terminal (high speed / low speed data) 105.

FIG. 2 is a block diagram showing the configuration of the radio section 201 according to the first embodiment of the present invention. This wireless unit 20
1 uses the double conversion method and is provided in each terminal described above.

The wireless unit 201 includes a synthesizer unit 202 for hopping, a controller 203 for controlling the entire wireless unit 201, two antennas 204a and 204b for wireless communication, and antennas 204a, 2a and 2b.
A switch 205 for switching 04b, a band pass filter (hereinafter, referred to as BPF) 206 for removing a signal in an unnecessary band, a switch 207 for switching transmission / reception, and a receiving system amplifier 208. , A transmission system amplifier (with power control) 209, a down converter 210, an up converter 211, and a changeover switch 212.

Further, the synthesizer unit 202 includes a voltage control type oscillator (hereinafter referred to as VCO) 213, a low
A PL including a pass filter (hereinafter referred to as LPF) 214, a charge pump 215, a controller 216 that controls the output voltage of the charge pump 215, a programmable counter, a prescaler, a phase comparator, and the like.
L217 and.

Further, the radio section 201 is a band pass filter 218 for removing an unnecessary band signal from the signal (IF) converted by the down converter 210.
And a down converter 219. The down conversions 210 and 219 form a double conversion system.

Further, the radio section 201 includes a band pass filter 221a having different characteristics such as pass band width,
221b, changeover switches 220a and 220b of the filters 221a and 221b, a 90-degree phase shifter 222,
A quadrature detector 223, a waveform shaping comparator 224, a receiving frequency synthesizer 225, a transmitting synthesizer block 226 having a data modulation (FSK) function, and various synthesizers 202, 225.
It has a reference clock 227 for 226 and a band limiting filter 228 for transmission data (baseband signal).

Next, FIG. 8 is a flow chart showing the operation at the time of transmission in this system, and FIG. 9 is a flow chart showing the operation at the time of reception in this system.

The wireless LAN according to the first embodiment will be described below.
The operation of the system will be described. In the following description, low-speed data has a data rate that is 1/2 that of high-speed data.

First, the operation during transmission will be described.

First, the radio unit 201 is in a state of waiting for reception on the control channel (Rx) (S1). FIG. 3 is an explanatory diagram showing a configuration example of channels in this system. As shown in the figure, the channel configuration in this system is composed of a control channel (Tx), a control channel (Rx), and a data channel. These channels all have the same bandwidth.

When a data transmission request is issued from a higher-order means (eg, operator's operation) in S1 (S2), it is discriminated whether the data to be transmitted is low speed data or high speed data (S3).

Then, when the data to be transmitted is low-speed data (here, a data rate of 1/2 of high-speed data) (S
4) Change the value of the reference counter (frequency dividing counter of the reference clock 227) in the hopping PLL 217 to reduce the frequency step of the hopping synthesizer 202 to 1/2. Further, the 2nd IF filter is switched to the BPF 221b (S5). BPF2 here
21b is a B having a pass band that is 1/2 that of the BPF 221a.
It is PF.

After the mode setting is completed, the hopping synthesizer 202 switches the frequency to search the data channel (S6). The data channel searched at this time is
The bandwidth is Fw in the high speed mode and ½ Fw in the low speed mode.

If the data channel is not empty in S7, the transmission is stopped (S8) and the hopping PLL 217 is executed.
Return the value of the reference counter in the
Switch the ndIF filter to the BPF 221a (S
9), transition to S1.

If there is an empty data channel in S7, the transmission / reception changeover switches 207, 212 are switched to transmission, and if the mode is the low speed mode, the transmission request frame is set on the control channel (Tx) as the high speed mode. It is transmitted (S10).

FIG. 4 is an explanatory diagram showing an example of the structure of a transmission request frame used on the control channel in this system.

As shown in the figure, the transmission request frame includes a called address (DA), a calling address (SA), data high speed / low speed information (TYPE ID), and data transmission channel information (Ch. No. ).

After the call setting is completed in S10, if the transmission data is low speed (S11), the mode is switched to the low speed mode (S12), and if it is high speed data (S11), the transmission request frame is kept in the same mode. The frequency is set to the data channel designated in step S3, and the data transmission state is set (S13).

Next, the data flow during transmission will be described.

The serial data (rectangular wave) to be transmitted is band-limited by the baseband filter 228, and then Tx.
It is input to the modulation terminal of the VCO in the frequency synthesizer 226.

The data FSK-modulated by the VCO is
The up converter 211 mixes with the carrier signal from the hopping synthesizer 202, the transmission amplifier 209 performs gain adjustment, and the BPF 206 cuts unnecessary signal / noise in the band, and the antenna 204
It is emitted from a and 204b.

FIG. 5 is an explanatory diagram showing an example of a frequency spectrum at the time of high speed data as described above, and FIG. 6 is an explanatory diagram showing an example of a frequency spectrum at the time of low speed data. FIG. 7 is an explanatory diagram showing an example of a frequency spectrum when high speed data and low speed data are mixed.

Next, the operation at the time of reception will be described.

First, the radio unit 201 is in a state of waiting for reception on the control channel (Rx) (S21).

When the transmission request frame (see FIG. 4) is received in S21 (S22), the TYPE ID is referred to,
Determine the data type (high speed or low speed data) (S
23).

If the data is low in S23 (S24),
The reference counter value in the hopping PLL 217 is changed so that the frequency step of the hopping synthesizer 202 is halved. Furthermore, a BP of 2nd IF filter
F221b is switched to (S25), and the hopping synthesizer 202 is set to Ch. No. Set to the frequency of the channel specified by to enter the receiving state (S
26).

If the data is high speed in S23 (S24), the process directly proceeds to S26.

Next, the data flow during reception will be described.

The radio waves received by the antennas 204a and 204b are level-adjusted by the reception amplifier 208 after removing signals / noise in an unnecessary band by the BPF 206, and input to the down converter 210.

The down converter 210 uses the carrier signal from the hopping synthesizer 202 to remove the carrier signal from the signal from the reception amplifier 208.

The signal from which the carrier signal has been removed is the 1st
A signal / noise in an unnecessary band is removed by the BPF 218 of the IF, and then converted to a frequency of 2ndIF by the down converter 219.

2ndIF signals are BPFs 221a, 2
The signal / noise of the adjacent channel is removed by any of 21b, and the 90-degree phase shifter 222 and the quadrature detector 22 are removed.
Input to 3.

The quadrature detector 223 performs detection / demodulation using the original signal and the signal whose phase is shifted by the 90-degree phase shifter 222. And the demodulated signal is
The waveform is shaped by the comparator 224 and output as received data (rectangular wave).

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

FIG. 10 is a block diagram showing the structure of a radio section using the single conversion system according to the second embodiment. Note that the system configuration is the same as that in FIG. 1 described above, and the radio unit 901 shown in FIG. 10 is assumed to be provided in each of the above-mentioned terminals.

The radio unit 901 includes a synthesizer unit 902 for hopping, a controller 903 for controlling the entire radio unit 901, antennas 904a and 904b,
A changeover switch 905 of the antenna 904, a BPF 906 for removing a signal in an unnecessary band, a transmission / reception changeover switch 907, a reception system amplifier 908, a transmission system amplifier (with power control) 909, and a down converter 910. And an up converter 911 and a changeover switch 912.

Further, the synthesizer section 902 has a VCO 9
13, a LPF 914, a charge pump 915, a controller 916 that controls the output voltage of the charge pump 915, and a PLL 917 including a programmable counter, a prescaler, a phase comparator, and the like.

Further, radio section 901 has different characteristics such as pass band width for removing the signal / noise of the unnecessary band and the signal / noise of the adjacent channel from the signal (IF) converted by down converter 910. BPF919
a and 919b, changeover switches 918a and 918b of BPFs 919a and 919b, and a 90-degree phase shifter 920.
A quadrature detector 921, a waveform shaping comparator 922, a transmission system synthesizer block 923 having a data modulation (FSK) function, reference clocks 924 for various synthesizers 902 and 923,
And a band limiting filter 925 for transmitting data (baseband signal).

Next, in the operation during transmission in the second embodiment, S5, S9 and S12 of the first embodiment (FIG. 8) described above.
In the above, filters 919a and 919b are switched when the low speed / high speed mode is set.

Next, the data flow during transmission will be described.

The transmission serial data (rectangular wave) is band-limited by the baseband filter 925, and then Tx.
It is input to the modulation terminal of the VCO in the frequency synthesizer 923.

The data FSK-modulated by the VCO is
The up converter 911 mixes with the carrier signal from the hopping synthesizer 902, the gain is adjusted by the transmission amplifier 909, and then the BPF 906 cuts unnecessary signal / noise in the band, and the antenna 904
a, 904b.

Further, in the operation at the time of reception in the second embodiment, in S25 of the first embodiment (FIG. 9), the filters to be switched when the low speed mode is set are 919a and 91.
9b.

Next, the data flow upon reception will be described.

The radio waves received by the antennas 904a and 904b are level-adjusted by the reception amplifier 908 and are input to the down converter 910 after removing signals / noise in an unnecessary band by the BPF 206.

Down converter 910 removes the carrier signal from the signal from receiving amplifier 908 using the carrier signal from hopping synthesizer 902.

The signal from which the carrier signal has been removed is the BPF.
Unwanted band signal / noise and adjacent channel signal / noise are removed by either 919a or 919b, and the signals are input to the 90-degree phase shifter 920 and the quadrature detector 921.

The quadrature detector 921 detects and demodulates the original signal and the signal whose phase is shifted by the 90-degree phase shifter 920. Then, the demodulated signal is waveform-shaped by the comparator 922 and received data (rectangular wave)
Is output as

[0058]

As described above, according to the present invention,
The frequency can be effectively used by changing the bandwidth of one channel of FHSS according to the data rate.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a wireless LAN system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a wireless unit according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a configuration example of channels in the above embodiment.

FIG. 4 is an explanatory diagram showing a configuration example of a transmission request frame used on a control channel in the above embodiment.

FIG. 5 is an explanatory diagram showing an example of a frequency spectrum during high-speed data in the above embodiment.

FIG. 6 is an explanatory diagram showing an example of a frequency spectrum during low-speed data in the above embodiment.

FIG. 7 is an explanatory diagram showing an example of a frequency spectrum when high speed data and low speed data are mixed in the above embodiment.

FIG. 8 is a flowchart showing an operation at the time of transmission in the first embodiment.

FIG. 9 is a flowchart showing an operation at the time of reception in the first embodiment.

FIG. 10 is a block diagram showing a configuration of a wireless unit according to a second embodiment of the present invention.

[Explanation of symbols]

 101a, 101b ... Voice data terminal, 102 ... Facsimile, 103a, 103b ... Data terminal, 104 ... Peripheral device, 105 ... Combined terminal.

Claims (1)

[Claims] 1. In a spread spectrum communication system of a frequency hopping system, a judging means for judging low / high speed data type, a notifying means for notifying a data type to a partner, and a frequency bandwidth used for communication are controlled. A communication system comprising a control means and changing the bandwidth of one channel according to the data type.