JPH11331184A - Spread spectrum radio communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-speed data communication, while holding a carrier sense function. SOLUTION: A spread spectrum radio communication equipment 10 is provided with a correlation calculating part 34 for calculating the correlation of a signal to be received and a spread code and outputting a correlative value signal, an absolute value calculating part 36 for outputting the absolute value signal of the correlative value signal, a carrier detecting circuit 38 for comparing the absolute value signal from the absolute value calculating part 36 with a carrier sense threshold level and outputting a status signal showing whether or not transmission is enabled, a data demodulating circuit 44 for comparing the absolute value signal from the absolute value calculating part 36 with a data demodulation threshold value level and fetching the corresponding correlation value signal as the data, when the absolute value signal is larger than the data demodulation threshold level, and a CPU part 16 for sending a carrier sense request command to the carrier detecting circuit 38 and receiving the status signal from the carrier detecting circuit and the data from the data demodulating circuit 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum wireless communication apparatus for performing wireless communication with another communication apparatus using spread spectrum.

[0002]

2. Description of the Related Art Generally, in an environment in which a communication device communicates with a certain communication device among a plurality of communication devices arranged in a certain space such as a wireless LAN, each communication device has A carrier sense function is provided for sensing whether communication that interferes with each other is performed between the other communication devices before starting communication.

[0003] Carrier sensing is specifically performed by comparing a received signal with a threshold level over a certain period of time. If the received signal is smaller than a certain threshold level, it is determined that transmission is possible, transmission is started, and when a signal returned from another device is received, whether or not the signal is larger than a certain threshold level is compared with noise. A signal larger than a certain threshold level is captured as data.

[0004] The threshold level at the time of performing carrier sensing and the threshold level at the time of capturing data have different levels for the purpose thereof, and the threshold level at the time of capturing data is usually higher than that at the time of performing carrier sensing. It is often set higher than the threshold level. Then, the communication device resets the magnitude of the threshold level between when performing carrier sensing and when capturing data, or two setting units for carrier sensing and data demodulation, A changeover switch connected to the setting device is provided, and the setting device is alternately switched by the changeover switch.

[0005]

However, the setting of these threshold levels or the switching of the changeover switch involves the following.
Since everything is done by instructions from the controller,
It takes time from when a command is issued from the controller until the change is actually completed, during which time data cannot be received. Therefore, there is a problem that high-speed communication cannot be handled.

Also, when it is desired to change the carrier sense threshold level itself or the data demodulation threshold level itself, the same time is required, so that there is a problem that the carrier sense and data cannot be taken in during the change. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a spread spectrum wireless communication apparatus capable of performing high-speed data communication while maintaining a carrier sensing function.

[0007]

According to one aspect of the present invention, there is provided a spread spectrum wireless communication apparatus for performing wireless communication with another communication apparatus using spread spectrum. A correlation calculation unit that calculates a correlation between a received signal and a spread code to be received and outputs a correlation value signal; an absolute value calculation unit that outputs an absolute value signal of the correlation value signal; and the absolute value calculation A carrier detection circuit that outputs a status signal indicating whether transmission is possible by comparing the absolute value signal from the unit and the carrier sense threshold level, and a circuit separate from the carrier detection circuit; The absolute value signal is compared with the data demodulation threshold level, and the data demodulation circuit which takes in the correlation value signal corresponding to the data demodulation threshold level which is larger than the data demodulation threshold level as data and the carrier detection circuit It sends out the Riasensu request command includes a controller that receives data from the status signal and the data demodulation circuit from the carrier detecting circuit.

Since the carrier detection circuit and the data demodulation circuit are individually provided and each circuit compares the carrier sense threshold level or the data demodulation threshold level with the absolute value signal, there is no need to perform switching. This can be dealt with by the controller appropriately selecting the status signal from each carrier detection circuit or the data from the data demodulation circuit.

The invention according to claim 2 is characterized in that the carrier sense threshold level or the data demodulation threshold level is variable by a command from the controller. Since the carrier detection circuit and the data demodulation circuit are separately provided, the data demodulation threshold level is changed during the carrier sense period, and the carrier sense threshold level is changed during the data acquisition period. Can be changed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating an embodiment of a spread spectrum wireless communication apparatus according to the present invention. In the figure, a spread spectrum wireless communication apparatus 10 mainly includes:
Antenna 12, transmitting / receiving unit 14, CP serving as controller
U section 16, spreading section 18, A / D converter 32, demodulation section 2
0, a PN code register 28, an angle ROM 46, and a differential decoding ROM 47. The spreading unit 18 further includes a differential encoding circuit 24 and a PN code spreading unit 26.

The modulated data sent from the CPU section 16 to the spreading section 18 is divided into upper data and lower data and input to the differential encoding circuit 24. Differential encoding circuit 24
Is differential encoding by sequentially adding upper data and lower data as 2-bit data having upper bits and lower bits, respectively. The high-order bit and the low-order bit differentially encoded by the differential encoding circuit 24 correspond to the value of 1 or 0, respectively, and are output by the Ex-OR circuit of the PN code spreading unit 26 to the positive sequence of the PN code Alternatively, an inverse row is allocated and output to the transmission / reception unit 14. At this time, the upper bit side is represented by a COS component (I component).
And the lower bit side is output for the SIN component (Q component).

The transmitting / receiving unit 14 includes a COS component (I component)
The carrier is modulated by the phase information for the SIN component (Q component), and the modulated carrier is transmitted from the antenna 12. The transmission / reception unit 14 obtains a COS component (I component) and a SIN component (Q component) signal of the baseband by orthogonally detecting a signal received from the antenna 12. The COS component (I component) and the SIN component (Q component) are converted by the A / D converter 32 into A
/ D converted, sent to the demodulation unit 20 and digitally processed.

The demodulation section 20 mainly includes a correlation calculation section 34, an absolute value calculation section 36, a carrier detection circuit 38, and a data demodulation circuit 44. The correlation calculator 34 has shift registers for the I side and the Q side, and shifts the PN sequence, which is a prescribed spreading code, and the I component output (and the Q component output) from the A / D converter 32. The correlation value is obtained by multiplying by an I component output sequence (and a Q component output sequence) latched by the register for the PN code length in the system clock cycle. The multiplication inverts the sign of the I component output (and the Q component output) when the PN code is 0,
When the PN code is 1, it is performed by leaving the code as it is, and a signed correlation value signal obtained by adding all the multiplication results of the PN sequence and the latched I component output (and Q component output) sequence. Are output from the I side and the Q side, respectively. The correlation value signals on the I side and the Q side are calculated by an absolute value calculation unit 36.
In the above, when the sign is-, the sign is inverted to +, and the signal on the I side and the signal on the Q side are added to become an absolute value signal.

The absolute value signal from the absolute value calculation section 36 is sent to a carrier detection circuit 38 and a data demodulation circuit 44. The carrier detection circuit 38 includes a carrier sense window setting circuit 50, a comparator 54, a threshold level setting device 56, and a status signal generation circuit 58, as shown in FIG.

As shown in FIG. 3, the carrier sense window setting circuit 50 sets a carrier sense window (FIG. 3B) from a carrier sense request signal (FIG. 3A) from the CPU section 16. . Also, the comparator 54
Then, the absolute value signal and the carrier sense threshold level L
c is being compared (FIG. 3 (c)). The carrier sense threshold level Lc is set by the threshold level setting unit 56. The status signal generation circuit 58
When the absolute value signal exceeds the carrier sense threshold level Lc by a predetermined number of times or more within the carrier sense window, the CPU unit 1 outputs a carrier sense status signal (FIG. 3D).
Send to 6. Note that the carrier sense status signal is
Cleared by a carrier sense request signal outside the carrier sense window.

On the other hand, as shown in FIG. 4, the data demodulation circuit 44 includes a window setting circuit 60, an in-window maximum value detection circuit 61, a comparator 62, a threshold level setting device 66,
A synchronization signal generation circuit 68, a latch circuit 70, an angle data latch circuit 71, and a differential decoded data latch circuit 72 are provided. Since the code length of the PN code for which the correlation calculation is performed is always constant, the peak of the correlation value appears in the code length cycle, and the peaks appearing elsewhere can be considered to be due to some noise (FIG. 6 ( a)). Therefore, the window setting circuit 60 sets a window having a width centered on the peak and having the same cycle as the PN code length, thereby removing noise outside the window. More specifically, as shown in FIG. 5, a window of a short pulse is generated every time the code length elapses after the absolute value signal (FIGS. 5A and 5D) first exceeds the data demodulation threshold level Ld. Is set (FIGS. 5B and 5E). The in-window maximum value detection circuit 61 detects the maximum value of the absolute value signal from the absolute value calculation unit 36 in the set window, and sends the latch timing to the latch circuit 70. The latch circuit 70 latches the absolute value signal from the absolute value calculation unit 36 at the latch timing, and
Represents the latched absolute value signal and the data demodulation threshold level L
Compare with d. The data demodulation threshold level Ld is set by the threshold level setting unit 66.

When the latched absolute value signal is larger than the data demodulation threshold level Ld as a result of the comparison by the comparator 62, it can be considered that communication synchronization and autocorrelation have been achieved. Conversely, when the latched absolute value signal is smaller than the data demodulation threshold level Ld, it is determined that communication synchronization has not been achieved or autocorrelation has not been achieved. In order to know the communication synchronization state, the synchronization signal generation circuit 68 performs the comparison from the comparator 62 continuously a predetermined number of times (four times in the example of FIG. 5) after the window setting circuit 60 sets the window of the short pulse. The output of the signal is counted (that is, the latched absolute value signal is larger than the data demodulation threshold level Ld). If the signal is counted, it is regarded that synchronization has been achieved, and “H” is output. The synchronization signal of
Output to the PU unit 16 (FIG. 5C). Conversely, FIG.
When the predetermined number of times cannot be counted consecutively, it is considered that synchronization has been lost, and an "L" synchronization signal is output to the CPU section 16 (FIG. 5 (f)).

Since the system clocks of other devices that communicate asynchronously are not exactly the same but always have a difference, the peak value of the correlation calculation also shifts with time. For this reason, the maximum value detection circuit 61 in the window calculates the time difference between the time when the maximum value is detected and the middle of the pulse period of the window, and feeds this time difference back to the window setting circuit 60 as a timing correction signal. The window setting circuit 60 sets the next window based on the time difference. As a result, the position is corrected every cycle (FIG. 6).

The latch circuit 70 also latches the I-side and Q-side signed correlation value signals from the correlation calculator 34 at the latch timing of the maximum value detection circuit 61 in the window.
These signed correlation value signals on the I side and the Q side form an angle RO
It is sent to M46. The angle ROM 46 is schematically shown in FIG.
The horizontal axis indicates the correlation value on the I side and the vertical axis indicates the correlation value on the Q side, and the phase to which each correlation value belongs is represented by 3 bits. Angle R
When the correlation value on the I side and the correlation value on the Q side are input to the OM 46, the corresponding phase is output as 3 bits from these values.

The output phase is sent to the differential decoding ROM 47, latched by the angle data latch circuit 71, and stored for one cycle. The differential decoding ROM 47 is schematically configured as shown in FIG.
The data is demodulated from the current phase sent from.
In the figure, the “−” part indicates a phase difference region that cannot be decoded. However, some decoded data can be applied. Further, by increasing the number of bits more than 3 bits to increase the amount of phase information, it is possible to reliably increase the phase difference area that can be decoded.

As described above, by using a ROM table such as the angle ROM 46 and the differential decoding ROM 47,
Data demodulation can be performed at high speed. Differential decoding R
The demodulated data sent from the OM 47 is latched by the differential decoded data latch circuit 72 and output to the CPU section 16. The latch timing of the angle data latch circuit 71 and the differential decoding data latch circuit 72 is performed by a data latch pulse from the window setting circuit 60. The data latch pulse is a pulse synchronized with the window corrected by the timing correction signal.

As shown in FIG. 9, the carrier sense threshold level Lc used for performing carrier sense and the data demodulation threshold level Ld used for taking in data have different sizes, and although there are exceptions, Normally,
The data demodulation threshold level Ld is larger. In the present embodiment, the carrier detection circuit 38 and the data demodulation circuit 44 are separately provided.
At all times, the comparator 54 compares the carrier sense threshold level Lc set by the threshold level setter 56 with the absolute value signal,
The comparator 62 compares the data demodulation threshold level Ld set by the threshold level setting unit 56 with the absolute value signal. Switching between the level setting unit and the like between carrier sensing and data fetching is not necessary. Instead, the carrier sense status signal from the carrier detection circuit 38 and the synchronization signal and demodulated data from the data demodulation circuit 44 are converted into CPs.
In the U section 16, a carrier sense status signal is captured during a carrier sense period, and a synchronization signal and demodulated data are captured and processed during a data reception period.

Hereinafter, the processing of the CPU section 16 will be described. Spread spectrum wireless communication apparatus 10 of the present embodiment
Are arranged in a certain space to constitute a wireless communication system, and a case where data is transmitted from one communication device 10 to another certain communication device 10 in the wireless communication system will be described. The CPU section 16 of each communication device 10 is connected to an external controller (not shown).

From the external controller to the CP of the communication device 10
When the U unit 16 receives the transmission data, the CPU 16 packetizes the transmission data. The packet includes a bit synchronization signal, a frame synchronization signal, a call code, an ID, and a CRC, in addition to the data. The ID further includes a packet length, a destination address, a self address, a packet No., a packet data size, and a control code. The packet length is
This is the size of the “ID + data” portion. Packet No.
Is the number of the packet, for example, represents the first packet when the packet No. = 1, and also becomes the packet No. = 1 when there is only one packet. The packet data size indicates the number of bytes of data included in the packet, and the control code indicates the last packet when data is divided into a plurality of packets for communication.

Next, the CPU section 16 executes processing according to the flowchart of FIG. In the transmission process, first, carrier sensing is performed before actual transmission is performed (step 10a). Specifically, the carrier sense is performed by sending a carrier sense request signal to the carrier detection circuit 38. Then, it is determined whether a carrier sense status signal has been received from the carrier detection circuit 38 (step 10b). Packet No. =
When the value is other than 1, if there is no carrier, in other words, if the carrier sense status signal is at the “L” level (No in step 10c), the carrier sense is terminated. On the other hand, when the packet No. is 1, the carrier sense request signal is continuously transmitted until the specified time ends (No in step 10d), and the carrier sense status signal is continuously at the “L” level. Check
After the end of the specified time (Yes in step 10d), the carrier sense ends.

When it is confirmed that there is no carrier, the CP
The transmission data is transmitted from the U unit 16 to the above-described spreading unit 18, and is transmitted from the antenna 12 via the transmission / reception unit 14 to another communication device 10 with which communication is desired (step 10).
e). After the transmission, the transmission NG waiting timer starts (step 10f), and enters a data receiving state, and waits for an ACK from another communication device 10 (step 10f).
g). When the data receiving state is entered, the CPU section 16 determines whether or not a synchronization signal from the data demodulation circuit 44 has been obtained. If the synchronization signal has been obtained, it means that the data has been synchronized and the autocorrelation has been obtained. Therefore, the data latched by the operation decoding data latch circuit 72 is fetched. On the other hand, when a synchronization signal cannot be obtained, no data is taken in because there is no data with which communication is synchronized and autocorrelation is obtained.

If the ACK is not received within the specified time after the transmission NG waiting timer starts,
The transmission process is performed and the packet is retransmitted. If there is no ACK reply even after retransmission for the specified number of times, the communication device 10 notifies the connected external controller of the transmission failure. When it is confirmed that an ACK from another communication device 10 has been received, the process in FIG. 10 is executed again to transmit the next packet. As described above, in the CPU section 16, the carrier sense status signal is captured during the carrier sense period, and the synchronization signal and the demodulated data are captured and processed during the data reception period.

In the above-described embodiment, the carrier sense threshold level and the data demodulation threshold level of the threshold level setting unit 56 and the threshold level setting unit 66 are set to constant values. However, the present invention is not limited to this. The setting values of the threshold level setting device 56 and the threshold level setting device 66 can be changed by a command from the CPU section 16. In this case, the change can be performed by changing the data demodulation threshold level during the period in which the carrier sense is being performed, or by changing the carrier sense threshold level in the period in which the data is being fetched. Therefore, the change can be made in a state where there is sufficient time without interrupting the carrier sense and the data acquisition.

[0029]

As described above, according to the first aspect of the present invention, the carrier detection circuit and the data demodulation circuit are individually provided, and each circuit has a carrier sense threshold level or a data demodulation threshold level. Since the level and the absolute value signal are compared, there is no need to switch the threshold level between when performing carrier sensing and when capturing data, and the controller uses the status signal or data demodulation from each carrier detection circuit. This can be dealt with by appropriately selecting data from the circuit. Therefore, high-speed communication can be performed.

According to the second aspect of the present invention, since the carrier detection circuit and the data demodulation circuit are separately provided, it is possible to change the data demodulation threshold level during the period of performing carrier sensing. The carrier sense threshold level can be changed while data is being read or data is being captured. Therefore, the change can be made in a state where there is sufficient time without interrupting the carrier sense and the data acquisition.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a spread spectrum wireless communication apparatus according to the present invention.

FIG. 2 is a block diagram of a carrier detection circuit of FIG. 1;

FIG. 3 is an explanatory timing chart illustrating an operation of a carrier detection circuit.

FIG. 4 is a block diagram of the data demodulation circuit of FIG. 1;

FIG. 5 is an explanatory timing chart illustrating the operation of the data demodulation circuit.

FIG. 6 is an explanatory timing chart illustrating the operation of the data demodulation circuit.

FIG. 7 is an explanatory diagram of an angle ROM table.

FIG. 8 is an explanatory diagram of a differential decoding ROM table.

FIG. 9 is an explanatory timing chart illustrating a relationship between each signal and a threshold level when performing carrier sense and receiving data.

FIG. 10 is a flowchart illustrating a transmission process of a CPU unit of FIG. 1;

[Explanation of symbols]

 Reference Signs List 10 spread spectrum wireless communication apparatus 16 CPU unit (controller) 34 correlation calculation unit 36 absolute value calculation unit 38 carrier sense detection circuit 44 data demodulation circuit

[Procedure amendment]

[Submission date] June 14, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007]

According to one aspect of the present invention, there is provided a spread spectrum wireless communication apparatus for performing wireless communication with another communication apparatus using spread spectrum. A correlation calculation unit that calculates a correlation between a received signal and a spread code to be received and outputs a correlation value signal; an absolute value calculation unit that outputs an absolute value signal of the correlation value signal; a controller; and a carrier. Carrier sense threshold to set sense threshold level
Before having communication with other communication devices with a value level setting device
In response to a carrier sense request command from the controller,
The absolute value signal from the absolute value calculation unit is compared with the carrier sense threshold level, and another signal is output according to the comparison result.
Control status signal whether it can send to the communication apparatus
And a carrier detection circuit that outputs the data demodulation threshold to a data demodulation threshold.
Has a data demodulation threshold level setting device to set the value level
Status signal indicating that transmission is possible from the carrier detection circuit
Is output, the absolute value signal from the absolute value calculator for the received signal is compared with a data demodulation threshold level, and a correlation value signal corresponding to a case where the data is larger than the data demodulation threshold level is taken as data. write-controller
And a data demodulation circuit that outputs the data to the data demodulation circuit.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009] The carrier sense threshold level or the data demodulation threshold level is individually variable according to a command from the controller. Since the carrier detection circuit and the data demodulation circuit are separately provided, the data demodulation threshold level is changed during the carrier sense period, and the carrier sense threshold level is changed during the data acquisition period. Can be changed.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichiro Yamada 2-16-46 Minami Kamata, Ota-ku, Tokyo Inside Tokimec Co., Ltd. (72) Inventor Uhiko 2-16-46 Minami Kamata, Ota-ku, Tokyo Inside Tokimec Co., Ltd.

Claims (2)

[Claims] 1. A spread spectrum wireless communication apparatus for performing wireless communication with another communication apparatus using spread spectrum, comprising calculating a correlation between a received signal and a spread code to output a correlation value signal. A correlation calculation unit, an absolute value calculation unit that outputs an absolute value signal of the correlation value signal, a status signal indicating whether transmission is possible by comparing the absolute value signal from the absolute value calculation unit with a carrier sense threshold level And a carrier detection circuit, which is different from the carrier detection circuit, and compares the absolute value signal from the absolute value calculation unit with the data demodulation threshold level to handle a case where the absolute value signal is larger than the data demodulation threshold level. A data demodulation circuit that captures the correlation value signal to be transmitted as data, sends a carrier sense request command to the carrier detection circuit, and outputs the status from the carrier detection circuit. A controller for receiving the data from the item and the data demodulation circuit,
A spread spectrum wireless communication device comprising: 2. The spread spectrum wireless communication apparatus according to claim 1, wherein the carrier sense threshold level or the data demodulation threshold level is variable according to a command from the controller.