JPH0879128A - Spread spectrum radio communication system - Google Patents

Abstract

PURPOSE: To improve the communication efficiency of the data requiring a real time property by controlling the interval of retransmission or an access circuit corresponding to the kind of transmission data. CONSTITUTION: When a transmission data string is transferred from a terminal A, a communication control part 2 stores the data string in a memory 4. A CPU 3 transmits a transmission request command to the terminal B through an RF transmission/reception part 12. Corresponding to the response of the terminal B, the CPU 3 reads the data string from the memory 4 and discriminates the kind and then, the data are disassembled into fixed length packets by a packet assembly/disassembly part 10. Then, data packets are transmitted when a radio network is not used by the other terminals and a retransmission processing is started when the radio network is used by the other terminal.

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 system which enables a wireless network to be preferentially used for terminals handling images in which real-time property is important.

[0002]

2. Description of the Related Art In recent years, with the spread of portable and portable computers and portable wireless terminals, there is an increasing need for mobility of terminals connected to a local area network (LAN). In order to meet such needs, there is a demand for a so-called wireless LAN system using a spread spectrum communication system which is one of digital wireless communication systems.
This spread spectrum communication method is a communication method that is excellent in multiple access, confidentiality, and interference resistance, and is divided into a direct spread communication method and a frequency hopping method due to the difference in modulation method.

Direct sequence communication systems include PSK, FM, AM
This is a method of performing secondary modulation by multiplying a carrier wave, which has been primary-modulated by the above method, by a spread code having a wider band than the transmission data. Since the spectrum of the signal after the spread modulation is wider than the spectrum of the signal after the primary modulation, the power density per unit frequency is remarkably reduced, and interference with other communications can be avoided. Further, it is possible to provide a plurality of communication channels by using a plurality of spread codes described above.

On the other hand, the frequency hopping method is a method of spreading transmission data over a wide band by randomly and discretely switching a carrier frequency modulated by the transmission data within a given band. By using a plurality of frequency switching patterns (hopping patterns), it is possible to provide a plurality of communication channels as in the case of the direct spread system. In particular, the low-speed frequency hopping modulation method has a great advantage in that the circuit scale of a frequency synthesizer or the like can be made small, and therefore it is now actively used.

[0005] In addition, access control for sharing a single network efficiently without causing data collision among a plurality of terminals connected to a wireless LAN generally uses CS.
MA / CA (carrier sense multiple access / collis
ion avoidance) method is used. In this method, each terminal checks the usage status of the wireless network (carrier sense) before data transmission and starts data transmission if other terminals are not using it, but other terminals use the wireless network. If it is medium, a specific time (usually determined using a function called a backoff algorithm)
Wait and then make a career sense again. By doing so, it is possible to avoid conflict with other terminals, avoid data collision, and give each terminal equal access rights.

[0006]

However, in the above-mentioned conventional method, when carrier sensing is performed prior to data transmission, if another terminal occupies the wireless network and is performing data transmission, backoff is performed. The transmission operation from carrier sense had to be restarted after waiting for the transmission start for a time calculated by a function called an algorithm.

When there are a plurality of terminals waiting for transmission on the wireless network at the same time, even if the wireless network is released after the packet transmission of the terminal which is currently transmitting packets ends and the wireless network is released. It was not always possible to obtain the right to use the network.

Therefore, for example, when a terminal that handles video data for which real-time property is important tries to use the wireless network, a plurality of terminals are in a waiting state for intensive use of the wireless network, resulting in a decrease in throughput. There has been a problem that the waiting time for acquiring the right to use the wireless network becomes long and the real-time property of the image cannot be compensated.

The present invention has been made to solve the above problems, and controls the retransmitting interval or the number of times of access according to the type of data to be transmitted, thereby communicating data requiring real time. An object of the present invention is to provide a spread spectrum wireless communication system with improved efficiency.

[0010]

[Means for Solving the Problems] and

In order to achieve the above object, the spread spectrum wireless communication system according to the present invention has the following configuration.

[0011] A spread spectrum wireless communication system that enables a wireless network to be preferentially used by a terminal that handles video for which real-time performance is important, and the priority of retransmission is set according to the type of data to be transmitted. It is characterized by comprising setting means for setting and re-transmitting means for re-transmitting according to the priority set by the setting means.

In such a configuration, the retransmission priority is set according to the type of data to be transmitted, and the retransmission is performed with the set priority.

Another spread spectrum wireless communication system of the present invention that achieves the above object has the following configuration.

A spread spectrum wireless communication system that enables a wireless network to be preferentially used by a terminal that handles video for which real-time performance is important. Access to the wireless network is made according to the type of data to be transmitted. It is characterized by having control means for controlling and re-transmitting means for re-transmitting in response to access by the control means.

In such a configuration, the access to the wireless network is controlled according to the type of data to be transmitted, and the retransmission is performed according to the access.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic block diagram showing the internal structure of the radio control unit in the embodiment. In the figure, reference numeral 1 is a data terminal to which a wireless control unit 16 described later is connected. A communication control unit 2 performs data communication with the data terminal 1. A CPU 3 controls the entire wireless control unit 16. A memory 4 stores data to be transmitted and received. Reference numeral 5 is an analog / digital converter (AD converter), which converts transmission / reception data into an analog or digital signal. 6 is a frequency synthesizer, 7 is a frequency filter, 8 is an oscillator, and 9 is a synchronization control unit. 10 is a packet assembling / disassembling unit, which disassembles the packet of the transmission data,
Frame processing, assembly of received packets, etc. are performed. 1
Reference numeral 1 is an IF receiving unit, 12 is an RF transmitting / receiving unit, 13 is an antenna, 14 is a timer, and 15 is a data discriminating unit, which discriminates the type of data (video, image, text, etc.).

FIG. 2 is a diagram showing a packet format of data transmitted and received in the embodiment. As shown, the data packet has a flag 21 and a destination address 2
2, a source address 23, a packet number 24, transmission data 25, a CRC 26, and a flag 27.

FIG. 3 shows an 8-bit register group arranged in the memory 4 at the time of initialization. In the figure, reference numeral 31 denotes a threshold value register, which stores a threshold value of throughput on a wireless network described later. Reference numeral 32 is a control register, which is used in the flow control process described later.
Reference numeral 33 is a counter register, which is used in throughput processing described later. Reference numeral 34 is a priority register, which is used to set the priority depending on the data type such as video and image. Reference numeral 35 is a register for storing a wireless address uniquely given to the wireless control unit 16.

<First Embodiment> In the above configuration, two kinds of back-off algorithms used in the stage of waiting for retransmission are provided, and in the case of data such as video data where real-time property is important, A first embodiment will be described in which the communication efficiency is improved by using an algorithm for starting retransmission in a short period of time, and in the case of data such as text data where real-time property is not important.

FIG. 4 shows a case where the data terminal for transmitting data is terminal A, the data terminal for receiving data is terminal B, and the terminal A is connected to the wireless control unit 16A and the terminal B is connected to the wireless control unit 16B. FIG. 7 is a diagram showing an operation sequence of transmitting data from terminal A to terminal B in FIG. 5 to 7 are
8 is a flowchart showing a transmitting operation of terminal A, and FIG. 8 is a flowchart showing a receiving operation of terminal B.

First, the transmission operation of the terminal A and the radio control unit 16A will be described with reference to FIGS.

A transmission request is generated at terminal A (step S1).
01), when the transmission data sequence is transferred to the wireless control unit 16A via the communication cable, the communication control unit 2 transfers the data sequence to the memory 4. Next, the CPU 3
Whether or not there is communication data on the wireless network is detected via the F transmitter / receiver 12 (hereinafter referred to as carrier sense) (step S102), and the usage status of the wireless network is monitored. Here, if the wireless network is not used by another terminal (step S10)
3), the CPU 3 transmits a transmission request command to the terminal B via the RF transceiver 12 (step S10).
4). When the reception permission command is received from the terminal B (step S105), the packet transmission process is started (step S106).

Here, referring to FIG. 6, step S1
The packet transmission processing in 06 will be described below.

First, the data string transferred from the terminal A is read from the memory 4, and the data discrimination section 15 discriminates the data type (step S201). At this time, if the data type is video data (step S202),
"1" is set in the priority register 34 (step S
203). However, other than that, for example, if it is a still image or text data, "0" is set in the priority register 34 (step S204).

Next, the packet assembling / disassembling unit 10 decomposes the above-mentioned data into fixed length packets. At this time, as shown in FIG. 2, a flag 21, a destination address 22, a source address 23, a packet number 24, and
A frame process in which the CRC 26 for error detection is added is performed to form a data packet (step S205). Then, the CPU 3 starts carrier sense again (step S206). As a result of the carrier sense, if the wireless network is not used by another terminal (step S207), the above-mentioned data packet transmission is started (step S208).

After that, the above-mentioned data packet transmission is repeated, and when all the data packets have been transmitted (step S209), this transmission process is terminated. On the other hand, if the wireless network is being used by another terminal in step S207, the retransmission process is started.

FIG. 7 is a flowchart showing this retransmission processing, and this retransmission processing will be described below with reference to the drawings.

As described above, if the carrier sense is performed and the wireless network is in use, the CPU 3 reads the value of the priority register 34 (step S301). If the value of the priority register 34 is "1" (step S302), the timer 14 is started (step S30).
3) Until the value of the timer 14 becomes equal to X1 (step S304), the start of retransmission is awaited.

If the value of the priority register 34 is "0" in the above step S302, the timer 14 is started (step S305), and the value of the timer 14 is X2 (X1 ≧ 1).
X2) is waited for until the start of retransmission (step S306).

The above X1 and X2 are times calculated by a function called a backoff algorithm,
The number of retransmissions is also taken into consideration.

Here, returning to FIG. 5, when the packet transmission processing is completed, the reception response command from the terminal B is waited, and if the reception response command from the terminal B is received (step S107), the transmission processing is terminated. . Also, step S
In 107, if there is no reception response from the terminal B even after waiting for a fixed time, that is, if the timer 14 times out before receiving the reception response command (step S108),
The CPU 3 issues an abnormal end command to the terminal A (step S109) and ends the transmission process.

Next, the receiving operation at the terminal B will be described below with reference to FIG.

First, the RF transmission / reception unit 12 that has received the transmission request command from the terminal A (step S401) notifies the CPU 3 via the filter and IF reception unit 11. On the other hand, if the wireless control unit 16B is in a receivable state, the CPU 3 that has received the transmission request command starts carrier sense (step S402), and as a result of carrier sense, the wireless network must not be used by another terminal. If so (step S403), the reception permission command is transmitted to the terminal A (step S404).

Next, when the RF transmitting / receiving unit 12 receives the data packet (step S405), the data packet is converted into digital data via the filter and IF receiving unit 11. Then, the CPU 3 reads the destination address 22 in the data packet, and the destination address is the wireless address 3 given to the wireless controller 16B.
5 and the CRC check result shows that there is no error in the received packet, the data packet is stored in the memory 4 as normal reception.

Then, the processing of the above step S405 is repeated to continue receiving the data packets, and when the final packet is received (step S406), the reception response command is transmitted to the terminal A (step S407), and all the packets are received. The reception operation ends. If the timer 14 times out without receiving the data packet in step S405 (step S408), the abnormal termination command is transmitted to the terminal A (step S409).

As described above, according to the first embodiment, in the retransmission process performed when the wireless network is used by another terminal, it is highly necessary to attach importance to real-time transmission of data. By setting the difference in the re-transmission interval between the low data transmission and the low data transmission, the re-transmission process can be started earlier than other competing terminals when the radio network is released, so that the wireless network is given priority. It can be used, and thus it is easy to ensure the quality of real-time video.

<Second Embodiment> Next, the second embodiment of the present invention will be described.
Embodiments will be described below with reference to the drawings.

In the second embodiment, a data terminal that transmits data such as text data that does not need to attach importance to real-time property reduces the number of times of access to the wireless network per unit time, thereby realizing real-time video data. It is possible to preferentially use the data terminal that is trying to transmit the data and prevent deterioration of the real-time video quality.

The structure of the apparatus is the same as that of the first embodiment described above, and the description thereof is omitted.

Similar to the first embodiment, terminal A to terminal B
The operation of transmitting data to will be described below with reference to FIGS. 9 to 11.

9 and 10 are flow charts showing the transmission processing in the second embodiment, and FIG. 11 is a flow chart showing the throughput processing.

First, the throughput process executed when there is no transmission request in step S501 shown in FIG. 9 will be described.

The counter register 33 of FIG. 3 is cleared to zero (step S701), carrier sense is started (step S702), and it is confirmed whether communication data exists on the wireless network. Here, if there is data to be transmitted by another terminal on the wireless network (step S
703), "1" is added to the counter register 33 (step S704). Then, carrier sensing is performed for a certain period of time (step S705), and the counter register 3
The value of 3 is read (step S706).

From the value of the counter register 33, the throughput (usage rate) of the wireless network is calculated (step S707), and the calculated value Q and the value set in the threshold value register 31 are compared, whereby the flow control is performed. It is determined whether or not is necessary (step S708). Here, if the calculated value Q is larger, that is, the wireless network is so crowded as to deteriorate the quality of the real-time video data,
If it is necessary to reduce the usage rate by flow control (step S708), "1" is set in the control register 32 (step S709). On the contrary, if the threshold value is larger and flow control is not necessary, "0" is set in the control register 32 (step S710).

Here, returning to FIG. 9, when a transmission request is generated in the terminal A (step S501) and the transmission data string is transferred to the wireless control unit 16A via the communication cable, the communication control unit 2 Transfers the data string to the memory 4. Next, the CPU 3 carries out carrier sense through the RF transmission / reception unit 12 (step S502), and monitors the usage status of the wireless network. Here, if the wireless network is not used by another terminal (step S50)
3), the CPU 3 transmits a transmission request command to the terminal B via the RF transceiver 12 (step S50).
4). When the reception permission command is received from the terminal B (step S505), the packet transmission process described later is started (step S506).

Now, referring to FIG. 10, step S
The packet transmission processing at 506 will be described below.

First, the CPU 3 reads the data transferred from the terminal A from the memory 4, and the data discrimination section 15 discriminates the data type. If the data type is video data, "1" is set in the priority register 34.
Set. However, in other cases, for example, if it is a still image or text data, "0" is set in the priority register 34 (step S601).

Next, the packet assembling / disassembling unit 10 decomposes the above-mentioned data into fixed length packets (step S6).
02). Here, in this data, a flag 21, a destination address 22, a source address 23, a packet number 24,
A frame process in which the CRC 26 for error detection is added is performed to form a data packet (step S603). Then, the CPU 3 starts carrier sense (step S
604), if the wireless network is not in use (step S605), the priority register 34 is read. If the value of the priority register 34 is "0" (step S606), it is determined that the priority is low, and the control register 32 is read. If the value of the control register 32 is "1", it is determined that the flow control is necessary (step S607), and the CPU 3 uses the timer 14 to delay the start of transmission for a certain time (step S608).

After that, the transmission of the data packet is started (step S609). Also, step S606 described above.
If the priority is high (the value of the priority register is "1"),
Alternatively, if the flow control is not necessary in step S607 (the value of the control register is “0”), the data packet transmission process is started as it is. Then, the processing from step S603 above is repeated until the transmission of all the data packets is completed (step S610), and when the transmission is completed, the packet transmission processing is terminated.

Here, returning to FIG. 9, when the packet transmission processing is completed, the reception response command from the terminal B is waited, and if the reception response command from the terminal B is received (step S507), the transmission processing is completed. . Also, step S
At 507, if there is no reception response from the terminal B even after waiting for a certain time, that is, if the timer 14 times out before receiving the reception response command (step S508),
The CPU 3 issues an abnormal termination command to the terminal A (step S509) and terminates the transmission process.

As described above, according to the second embodiment, when the utilization rate (throughput) of the wireless network determined by the carrier sense is so high that the real-time property of the video cannot be ensured, the real-time processing is performed on the wireless network. Other terminals in the process of transmitting data with less necessity to place importance on wireless communication reduce the number of access to the wireless network per unit time, and preset the throughput of the wireless network (the usage rate of the network per unit time). Flow control is performed autonomously so as not to drop below the threshold value.

Therefore, it becomes possible to preferentially use the terminal which is trying to transmit the real-time video data, and prevent the deterioration of the real-time video quality.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device.

It is needless to say that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0056]

As described above, according to the present invention,
By controlling the retransmission interval or the number of accesses according to the type of data to be transmitted, it is possible to improve the communication efficiency of data that requires real-time property.

[0057]

[Brief description of drawings]

FIG. 1 is a schematic block diagram illustrating a configuration of a wireless control unit according to an embodiment.

FIG. 2 is a diagram showing a format of a data packet in the embodiment.

FIG. 3 is a diagram showing a register format in the embodiment.

FIG. 4 is a diagram showing an operation sequence in the embodiment.

FIG. 5 is a flowchart showing a transmission process according to the first embodiment.

FIG. 6 is a flowchart showing a packet transmission process of FIG.

FIG. 7 is a flowchart showing the retransmission processing of FIG.

FIG. 8 is a flowchart showing a receiving process in the embodiment.

FIG. 9 is a flowchart showing a transmission process according to the second embodiment.

10 is a flowchart showing a packet transmission process of FIG.

FIG. 11 is a flowchart showing the throughput processing of FIG.

[Explanation of symbols]

 1 data terminal 2 communication control unit 3 CPU 4 memory 5 analog / digital conversion unit 6 frequency synthesizer 7 filter 8 transmitter 9 synchronization control unit 10 packet assembling / disassembling unit 11 IF receiving unit 12 RF transmitting / receiving unit 13 antenna 14 timer 15 data discrimination Section 16 Wireless control section

Claims (6)

[Claims] 1. A spread spectrum wireless communication system capable of preferentially using a wireless network for a terminal that handles video for which real-time performance is important, and prioritizes retransmission according to the type of data to be transmitted. A spread spectrum wireless communication system, comprising: setting means for setting a degree, and re-transmitting means for re-transmitting according to the priority set by the setting means. 2. The spread spectrum wireless communication system according to claim 1, wherein said setting means sets a high priority for retransmission in the case of data requiring real-time property. 3. The spread spectrum wireless communication system according to claim 2, wherein the retransmitting unit retransmits at a short interval when the priority is set high by the setting unit. 4. A spread spectrum wireless communication system that enables a wireless network to be preferentially used by a terminal that handles video for which real-time performance is important, wherein the wireless network is connected to the wireless network according to the type of data to be transmitted. A spread spectrum wireless communication system comprising: a control unit for controlling access; and a retransmitting unit for retransmitting data according to the access by the control unit. 5. The control means includes a calculation means for calculating a utilization rate of the wireless network, and a result of the calculation means,
5. The spread spectrum wireless communication system according to claim 4, wherein when the data is highly utilized and does not require real-time data, control is performed so as to reduce the number of accesses to the wireless network. 6. The spread spectrum wireless communication system according to claim 5, wherein the re-transmitting unit waits for a predetermined time and then re-transmits when the control unit reduces the number of accesses.