WO2002056542A1

WO2002056542A1 - Radio transmission system

Info

Publication number: WO2002056542A1
Application number: PCT/JP2002/000014
Authority: WO
Inventors: Makoto Fujii; Yoshikazu Kato
Original assignee: Adtec Corporation
Priority date: 2001-01-09
Filing date: 2002-01-08
Publication date: 2002-07-18
Also published as: TW563307B; JPWO2002056542A1; WO2002056542A8

Abstract

A radio transmission system in which a signal can be transmitted/received without any problem even if a large number of radio transmitters near to one another are used. In this system, communication with child devices in a group of one master parent device and one or more slave parent devices and child devices is carried out by sharing a frequency band. The master parent device has an inter-group synchronizing means for controlling the transmission/reception timing in synchronism with the phase of a commercial power supply. Each slave parent device has an intra-group synchronizing means for controlling the transmission/reception timing in synchronism with the master parent device. Data can be transmitted without any problem efficiently since the parent devices synchronously transmits/receives a signal.

Description

Description Wireless transmission

' Technical field

The present invention relates to a wireless transmission system, and more particularly to a wireless transmission system in which a number of wireless transmission devices are used in close proximity, such as a wireless LAN in a building or a connection between a telephone pole and a device in a home.

Background art

Conventionally, in a wireless transmission system in which many wireless transmission devices may be used in close proximity, such as a connection between a building in a building or a wireless LAN or a telephone pole, a nearby wireless transmission device Measures were taken such as using different channels.

In a wireless transmission system in which a large number of wireless transmission devices are used in close proximity, even if the channels used in adjacent wireless transmission devices are different, for example, one wireless transmission device transmits on one channel, and When a wireless transmission device tries to receive on an adjacent channel, the interference wave component of the transmission wave of one device (unwanted wave component that spreads in the frequency band on both sides of the transmission wave) is at a high level and the other device tries to receive it. There was a problem that the signal could not be received, even to the channel.

Disclosure of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless transmission system that solves the above-described problems of the related art and that can transmit and receive signals without hindrance even when a large number of wireless transmission devices are used in close proximity. is there.

The present invention is directed to a wireless transmission system that communicates with slaves in a group by sharing a frequency band in a group formed by one master master unit and one or more slave master units. A master master unit having inter-group synchronization means for controlling transmission / reception timing in synchronization with a master master unit of another group, a data transmission / reception means, and controlling transmission / reception timing in synchronization with the master master unit A slave master unit provided with an intra-group synchronization unit. According to the present invention, even in a wireless transmission system in which a large number of wireless transmission devices are used in close proximity, signal transmission and reception are performed in synchronization, so that data transmission can be performed efficiently without any trouble.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory diagram showing a configuration of a communication system to which the present invention is applied.

FIG. 2 is a block diagram showing a hardware configuration of the wireless transmission device of the present invention. FIG. 3 is an explanatory diagram showing transmission / reception timing between groups in the present invention. FIG. 4 is an explanatory diagram showing the timing of a synchronization cycle between groups in the present invention.

FIG. 5 is an explanatory diagram showing a frequency band used by the system of the present invention.

FIG. 6 is an explanatory diagram showing a flow of data transmission and reception in the present invention.

FIG. 7 is an explanatory diagram showing a flow of a synchronization cycle in the present invention.

FIG. 8 is an explanatory diagram showing a time synchronization method within a group according to the present invention. FIG. 9 is a state transition diagram showing a state change of the priority of the slave unit in the present invention. FIG. 10 is an explanatory diagram showing an example of queue control of the parent device in the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is an explanatory diagram showing the configuration of a communication system including a wireless transmission device to which the present invention has been applied. Within the area of group 1 (for example, radius of about 100 m), there are four subgroup areas, and each subgroup has one master or slave master and multiple slaves. I do.

The master unit and the slave unit are installed close to each other (for example, 10 m), and each is connected to, for example, a server computer via a communication line (not shown), and the server is connected to the Internet. . Each slave unit is connected to, for example, a personal computer (not shown). '

Each subgroup (1 to 4) has its area determined by the directivity and transmission power of the antenna connected to the master master unit or slave master unit. Therefore, it is connected to a predetermined master unit.

FIG. 2 is a block diagram showing a hardware configuration of the wireless transmission device of the present invention. The master unit and the slave unit have basically the same hardware configuration and different control software. The analog signal processing unit 10 is composed of a known single super heterodyne digital signal transmission / reception circuit, and data can be transmitted / received on an arbitrary frequency channel by two PLL circuits including a frequency synthesizer and a VCO circuit. In the present invention, any known method can be adopted as the transmission / reception circuit method and modulation method.

The first LSI of the digital signal processing unit 20 performs A / D, DZA conversion, direct spreading, despreading, scrambling, preamble processing, frame processing, error detection processing, and correlation signal detection. The second LSI of the digital signal processing unit 20 performs S / P conversion, scramble processing, error detection processing, and the like.

The timer 21 is a timer that is reset and started by a frame detection (flag pattern detection) signal output from the first LSI, and is configured so that the CPU can read a timer value by a program. This timer 21 is used to adjust the clock with the master master unit as described later.

The control unit 30 includes a CPU, a flash ROM storing a program code, a RAM used as a buffer and a work area, a CAM (associative memory), a LAN transceiver, a bus, and the like. The LAN transceiver has a well-known LAN interface function such as the 10BASE-T standard. In the case of a master station, the LAN transceiver is connected to a high-speed line such as an optical fiber through a device such as a line / LAN comparator. In the case of a slave station, it is connected to a personal computer or HUB. The power supply circuit also outputs a zero-cross detection signal along with the power supply.

FIG. 3 is an explanatory diagram showing transmission / reception timing between groups in the wireless transmission system of the present invention. One transmission cycle is basically based on the interval between the zero-cross points of the commercial power supply (timing when the voltage becomes 0). Therefore, if the frequency of the commercial power supply is 50 Hz, the cycle of the transmission cycle is 10 milliseconds. During one transmission cycle, a fixed-length downward window, which is the period during which data is transmitted from the master station to the And a fixed-length upward window that is the reverse of the period.

The zero-crossing point is detected by the master unit in each group, and the transmission / reception timing within the group is controlled based on this timing. Therefore, since the transmission cycle timing is the same between the groups, it is possible to prevent the handset of another group from transmitting and hindering the reception near the handset currently receiving.

When the commercial power for timing detection is supplied from three-phase AC, if the two phases selected as the commercial power are different for each master unit, the zero crossing point will be out of sync and synchronization will not be achieved. Therefore, by setting the timing at which the offset time according to the power supply frequency is added to the zero crossing point as the synchronization timing, the synchronization of the system can be established regardless of which two phases are selected. If the phase shift is known, the offset time can be set manually in each master unit, but if the time information frame from another master unit can be received, the frame can be set. By receiving and making a judgment, the phase shift can be automatically detected and the offset time can be set automatically.

The inter-group synchronization means controls transmission / reception timing based on time information distributed from a standard time distribution server connected via a communication line as well as a commercial power supply, or makes a time inquiry to the standard time server. There is also a method of correcting the internal clock, which is a reference for controlling transmission / reception timing. With these methods, it is possible to synchronize even power supplies that do not guarantee zero-cross timing synchronization between groups.

FIG. 4 is an explanatory diagram showing the timing of a synchronization cycle between groups in the wireless transmission system of the present invention. The master unit executes a “synchronization cycle” once every predetermined number of transmission cycles (for example, 10 times), and adjusts the clock of the master unit and the slave unit. The timing for executing this synchronization cycle is independent for each group, and the phases are different.

FIG. 5 is an explanatory diagram showing a frequency band used by the wireless transmission system of the present invention. FIG. 5 shows a time change of frequency channels (A to D) assigned to four subgroups (# 1 to # 4) in one group. use As a frequency band to be used, for example, a 2.4 GHz band is used, and a band per channel is, for example, about 20 MHz, and a total frequency band of four channels is, for example, about 80 MHz. .

Each master unit and each slave unit store the same frequency transition table, and the phase (address) in the table indicating the next frequency to be used by the slave unit is determined by the phase beacon transmitted from the master station. Be instructed. Therefore, even if reception of the phase beacon fails, communication can be continued by advancing the phase by one after the synchronization cycle.

By circulating the channels as shown in Fig. 5, even if noise occurs in a specific channel and the error rate increases, communication with each slave unit in the group can be continued. Note that the order of the circulation is arbitrary.

FIG. 6 is an explanatory diagram showing a flow of data transmission and reception in the wireless transmission system of the present invention. One transmission (communication) cycle has a fixed-length down window and an up window. In the down window, each master unit sends a beacon signal to the slave unit. The time information of the clock of the master unit is written in this beacon frame, and each slave station adjusts its own clock with the master unit based on this beacon signal by a method described later. Each slave unit transmits at the specified timing according to this clock.

The beacon signal contains information on the child device to which the upstream in the upstream window is allocated, and the child device permitted by the beacon signal transmits data.

Adopts TDMA method. The assignment method will be described later.

There are, for example, four downstream streams in the downstream window, and each can transmit data to any child unit. The base unit allocates downstream as follows based on the order of packets received from the line (LAN).

FIG. 10 is an explanatory diagram showing an example of transmission queue control of the parent device according to the present invention. Figure 1

As shown in 0, a plurality of queues are provided for each slave unit according to the transmission packet type, and when transmitting a bucket to a radio slot, the queue selection control unit selects a queue with a predetermined priority and transmits the packet. . Thus, for example, if the response bucket is prioritized, the response bucket is transmitted earlier, and the timing of sending out the next data bucket in the upper layer protocol is obtained earlier, so that the communication efficiency is improved. If priority is given to packets that require real-time performance, the bandwidth required for transmission of bucketed voice and the like can be secured, and quality can be secured according to the contents of the transfer data.

It is also possible to make the communication priority variable for each slave unit by changing the slot allocation rate to each slave unit depending on the slave unit.

Furthermore, by selecting the destination of the sending slave unit according to the amount of data stored in the queue of each slave unit, it is possible to secure the bandwidth according to the data amount and improve the wireless band utilization rate .

In the first period of the up window, the ACK signal for each downstream in the down window is returned at different timings. If the master unit cannot receive ACK, it resends in the next cycle. However, if the retransmission fails a predetermined number of times, the frame is discarded. In the case of broadcast, retransmission is not performed.

After the ACK period, there are two upstream periods, each of which has been granted permission to transmit. If the master unit fails in reception, specify the same frame number and assign the upstream again. In the case of Internet connection, the downstream has a longer window since the downstream has a larger amount of data on average.

FIG. 7 is an explanatory diagram showing a flow of a synchronization cycle in the wireless transmission system of the present invention. In the synchronization cycle, first, when the master and receiver detects cross-crossing timing in the down window, the master and receiver transmit a master and receiver beacon to each slave master on the currently used channel. The time information of the master master unit's clock is written in the mass evening beacon. Each slave master unit receives the master beacon in the down window of the synchronization cycle, and adjusts the clock of the slave master unit to the clock of the master unit.

After that, each master unit sends out a phase beacon and checks the use channels in each subgroup. Update channels. In the uplink window of the synchronous cycle, the master unit collects request (transmission request) information from all slave units in the sub-loop.

If the slave master unit cannot receive the master beacon continuously for the desired number of times, or if it cannot receive the master beacon continuously for the desired time, it determines that the master master unit has failed. Thereafter, one slave master unit specified according to a predetermined priority order starts an operation corresponding to the master master unit, and starts a substitute operation of the failed master master unit. As a result, the operation of the subgroup belonging to the failed master unit is stopped, and the system is degraded, but there is an effect of preventing all the systems in the group from being stopped.

FIG. 8 is an explanatory diagram showing a time synchronization method within a group according to the present invention. Each wireless transmission device has a clock function by software. For example, the base unit reads the time information (to) from its own clock, and immediately creates and transmits a beacon frame. The beacon frame is composed of a preamble of a predetermined length and a frame having a well-known configuration, and time information (to) is written in a data area of the frame.

In the slave unit, when a beacon is received within the reception window, synchronization is established at an arbitrary timing in the preamble section of the beacon, and the frame (the first flag pattern of the beacon) is detected. When a frame is detected, the hard timer 21 shown in Figure 2 is set and activated, and starts counting.

When the slave unit has successfully received a frame, processing by the program starts and the count value of timer 21 is read. The program calculates the current time (t 3) by adding the delay time tp from the reading of the clock time to the detection of the frame and the count time tt of the timer 21 to the time information (to) written in the frame to the time information (to) written in the frame. Update your watch to t3.

Since the times tp and tt are predetermined times depending on hardware or software, the above method is used to adjust the clock of the master unit and the clock of the slave unit with higher accuracy than the detection of the cross-point of the mouth. Is possible.

With the above method, the master beacon from the master The clock of the master unit is synchronized with the master unit, and the beacon from each master unit to the slave unit adjusts the clock of each slave unit with each master unit. By accurately synchronizing the clocks of each device, it is possible to reduce the idle time (margin) of transmission and increase the transmission efficiency.

FIG. 9 is a state transition diagram showing a state change of the priority of the slave unit in the present invention. In the system of the present invention, the master unit collects transmission requests from slave units only in the synchronization cycle, and does not collect transmission requests in other cycles. Also, since there are only two upstreams in the upstream window, for example, the master unit controls the priority of the slave units in order to efficiently assign them to the slave units, and assigns the transmission right to the slave units with higher priority. To control.

In the embodiment, there are four levels of priority, "high", "medium", "low", and "not connected", as shown in the figure. If the request bucket has not been received a predetermined number of times continuously due to power-off, etc., the slave unit will be in the "disconnected" state, and if the power is turned on and a request packet has been received from the slave unit, it will be in the "low" level. Move to

When a transmission request is received at the “Low” or “Medium” level, the state shifts to the “High” level, and when a transmission request is received at the “High” level, or when there is a transmitted packet or received packet. Remains at the “high” level. If a transmission request is not received at the “high” level, there is no transmission packet and no reception packet, and the up slot is continuous for 1 second, the transition to the “medium” level is made and the empty slot is set for 1 second. If consecutive, move to the "low" level.

If there are multiple slave units of the same level, assign slots in order. In addition, if there is a “medium” level handset, a slot is also allocated to the “medium” level handset at least 20% even if there is a “high” level handset. Assignment to a “Low” level slave unit is only made when there are no “High” and “Middle” level slave units.

Industrial applicability

The present invention includes inter-group synchronization means for controlling transmission / reception timing in a group formed by one master master unit and one or more slave master units in synchronization with a master master unit of another group. Master master unit, same as master master unit And a slave master unit having intra-group synchronization means for controlling transmission / reception timing in anticipation. Therefore, according to the present invention, the transmission and reception of signals are performed synchronously, so that even in a wireless transmission system in which a large number of wireless transmission devices are used in close proximity, data transmission can be efficiently performed without hindrance. This has the effect.

Claims

The scope of the claims

1. In a wireless transmission system that communicates with slaves in a group by sharing a frequency band within a group formed by one master and one or more slave masters,

A master / slave master unit comprising: a master / slave transmission / reception means;

A slave master unit having data transmission / reception means and an intra-group synchronization means for controlling transmission / reception timing in synchronization with the master master unit;

A wireless transmission system comprising:

2. In addition, a plurality of child units having data transmission / reception means with the master master unit or the slave master unit, and intra-group synchronization means for controlling transmission / reception timing in synchronization with the master master unit or the slave master unit. 2. The radio transmission system according to claim 1, further comprising a device.

3. The inter-group synchronization means detects a phase of a commercial power supply and controls transmission / reception timing in synchronization with the phase signal or a timing offset from the phase signal by a predetermined time. Item 1. The wireless transmission system according to item 1.

4. The intra-group synchronization means synchronizes the master master unit's clock with the slave master unit's clock by the slave master unit receiving a frame including the time information transmitted from the master master unit. 2. The wireless transmission system according to claim 1, wherein:

5. The master unit determines priority of the slave unit based on the past communication status of the slave unit, and has priority control means for assigning a transmission right to the slave unit based on the priority. Wireless transmission according to claim 1: