JPH0752884B2 - Power Saving Method for Time Division Multiplexing System - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention is applied to, for example, a coaxial CATV network (wired television network), and a central device and a plurality of network termination devices are connected by an upstream / downstream transmission line, In order to perform time division multiplex communication between a device and a network terminating device and to prevent signals from a plurality of network terminating devices from colliding or interfering with each other in the central device, a central device initiative type The present invention relates to a time division multiplex communication system in which delay measurement control is performed by repeatedly polling each network terminating device.

“Prior Art” For example, as shown in FIG. 3, network terminating devices NT ₁ , NT ₂ ... Are provided for each subscriber's house, and these network terminating devices NT ₁ , NT ₂ ... Signal cable 13 consisting of transmission line 12
Connected to the central unit 14 through the central unit 14
In each subscriber's house, the plurality of terminals 16 are connected by a bus 17 to the network terminator NT in the house.

When performing time-division multiplex communication, network terminating device NT _1, NT ₂ ... is different on the communication cable 13 located between the central unit 14 and a plurality of network terminating device NT _1, NT ₂ ... and in the communication system Therefore, the transmission line length between each network terminating device NT and the central device 14 is different, and each network terminating device NT is connected to the central device.
The transmission delay time of the signal transmitted to 14 differs. Therefore,
When performing signal transmission without considering the difference in transmission delay time, since the signal transmission is performed by the time division multiplexing method, the time slot signal that each network terminating device NT sends to the central device 14. If the interval is not sufficiently set, there occurs a problem that the time slot signals collide with each other on the upstream transmission path 11. In order to solve this problem, the round-trip propagation time between the central device 14 and each network terminating device NT is measured using a dedicated time slot, and each network terminating device NT is time-slotted on the transmission line based on the measurement result. Controls the timing of sending signals. As a result, the time slot signal interval is minimized, the number of time slot signals that can be simultaneously transmitted on the same transmission line is maximized, and at the same time, the collision of time slot signals due to the difference in transmission delay time can be prevented. The procedure of this delay measurement control will be described with reference to FIG.

(1) The central unit 14 sends a delay measurement signal (ASG ₁ ) and at the same time sends its address to the network terminating device NT ₁ for polling.

(2) When the network terminator NT ₁ receives this ASG ₁ signal, 1
After the frame time T _f, the response signal (RSP) is returned to the central unit 14 together with its own address.

(3) The central unit 14 measures the signal delay amount by the RSP signal returned from the network terminator NT ₁ .

(4) The central unit 14 notifies the NT ₁ of the transmission timing control value at the time of polling the network terminating unit NT ₁ by ASG ₁ .

In other words, the central unit 14 sequentially operates the network terminating device for each frame T _f.
NT ₁ , NT ₂ ... are polled and ASG signals are sent out respectively, and response signals RSP sequentially sent from each network terminator NT ₁ , NT ₂ ... cause the respective network terminators NT ₁ , NT ₂ ... Device 14
The signal delay between the network termination device NT ₁ and NT ₂
... determines the transmission timing control value for the network terminator NT _n , polls the network terminators NT ₁ , NT ₂ ... sequentially for each frame T _f from the frame following the transmission of the ASG signal to the last network terminator NT _n . The determined transmission timing control value is transmitted by an ASG signal.

Each network terminator NT ₁ , NT ₂ that received the transmission timing control value
The transmission to each central device 14 is made earlier by the transmission timing control value than the original transmission timing. In FIG. 5A, the central unit 14 sequentially polls the network terminators NT _{1 to} NT _n for each frame T _f and sends an ASG signal.
After that, the network terminating devices NT ₁ to NT _n are sequentially polled to send a sending timing control value to end the initial hunting period and shift to a steady state. As shown in FIG. 5B, each frame is composed of a TDMA (time division multiple access) control unit, an outgoing / incoming call control unit, and a call time slot. At the delay measurement control, the polling address and ASG signal are TDMA controlled. Sent by department. Central device 14 and network terminating device NT
A call assigning time slot used for communication between the first and the second call uses, for example, a demand assign method that is first assigned when a call occurs. These call controls are for example exchanges
Some of the ASG / RSP or call time slots are dedicated to call control in order to be processed on the 15 side and to exchange call control information with the network terminating equipment NT.

Even after shifting to a steady state where communication is possible, each network terminating device NT is periodically polled sequentially and an ASG signal is sent, and the transmission delay time of each network terminating device NT is measured from the response signal RSP, and first. It monitors whether the set sending timing control value is within the specified range, and if it is out of the specified range, resets the sending timing control value or fine-tunes the sending timing control value to communicate. We are trying to stabilize. For example, it is assumed that one signal gable 13 accommodates 500 network terminators NT, and that one of the network terminators NT is
If the polling signal time for each unit is several milliseconds, the period for the central unit 14 to poll a specific network terminating device NT becomes several seconds. In the proposed prior art, the polling cycle was repeatedly performed at the same cycle of several seconds both in the initial hunting period and in the steady state as shown in FIG. 5A. However, in the delay measurement control described above, by using a clock 16 times the transmission rate, the control accuracy is increased to an error range within 1/16 symbols (1 symbol is 2 bits) when it arrives at the central unit 14. Therefore, the code error is prevented from being significantly deteriorated due to the deviation of the data punching tamming at the time of demodulation in the central unit 14.
Currently, semiconductor devices that can operate with a clock 16 times faster than the transmission speed are technically applicable only to high-speed ECL logic ICs, and are used in equipment that requires a time division multiplex communication function. This ECL logic IC has high power consumption. Since the central device 14 polls the network terminating device in a cycle of several seconds even after the completion of the initial hunting, the network terminating device NT must be constantly operated, and the network terminating device NT consumes a lot of power. In a CATV system that integrates broadcasting and communication, maintaining the basic call function is the minimum essential item even in the event of a power failure, so it is also necessary to supply power (back up) from the terminal device NT to the terminal 16. There is a demand for a method of reducing the power consumption of the terminal device NT.

"Problems to be solved by the invention" In a CATV system that fuses broadcasting and communication, ensuring a basic call function is the minimum essential condition even when a power failure occurs. It is necessary to supply power (back up) via. As a power supply at that time, a battery backup may be considered, but if the power consumption of the network termination device NT is large, backup with a battery becomes impossible or a large capacity battery is required, so the network termination device NT The size increases, and the weight of the network terminating device NT also increases, which restricts the installation when installing in a general home. Therefore, the present invention backs up the network terminating device NT with a small-capacity battery and consumes power in a steady state so that the terminal 16 can be supplied with enough power to maintain the basic call function even when the commercial power supply is interrupted. Small quantity,
It is an object of the present invention to provide a power saving method in a time division multiplex communication system which can be a network terminating device with a small amount of heat generation.

[Means for Solving the Problems] According to the present invention, after the initial hunting is completed, the central device repeats polling with respect to each network terminating device until the initial delay measurement control is completed, rather than the polling cycle of the initial hunting period. In the steady state, the polling cycle is lengthened, and each network terminating device is notified that the polling cycle has been lengthened. Receiving the notification that the polling cycle has been lengthened, each network terminating device generates a control signal from the timer circuit only during the period corresponding to the period for receiving the polling addressed to itself, and the control signal causes the upstream signal transmission circuit and the delay measurement control circuit to operate. Only during the period in which the polling addressed to itself is received, the control signal is continuously output from the timer circuit in the communication state due to the incoming / outgoing call, and the upstream signal transmission circuit and the delay measurement control circuit are continuously operated.

[Embodiment] As shown in FIG. 1, in the initial hunting period, the network terminating devices NT _{1 to} NT _n are sequentially polled from the central device for each frame (for example, several milliseconds), that is, the address is issued and the ASG signal is issued. , The response signal RSP from each network termination device NT is received, the transmission delay time is measured, the transmission timing control value is obtained, and the transmission timing at the time of polling each of the next network termination devices NT _{1 to} NT _n . Send the control value.
In this initial hunting period, the cycle in which one network terminating device NT is repeatedly polled is set to be as short as possible, for example, several seconds. In this way, when the initial hunting is performed by the central device without any abnormality, the polling cycle of the delay measurement control for one network terminating device NT in the steady state thereafter is longer than the polling cycle in the initial hunting period, for example, several times. 10 seconds, and AS for each network termination device NT
Use G to indicate that the future polling period will be tens of seconds. So in steady state multiple frames, eg
The network terminators NT _{1 to} NT _n are sequentially polled every 10 frames.

The network terminating device NT has, for example, the configuration shown in FIG. 2, and a downstream signal from the central device 14 to the network terminating device NT passes through a downstream transmission line in the signal cable 13 and is a duplexer of the network terminating device NT. Added to 21. The demultiplexer 21 passes the signal only in the downlink frequency band, and the signal is input to the demodulator 22. The demodulator 22 extracts and generates the delay measurement signal clock and frame synchronization signal from the received signal, adds the control signal to the delay measurement control circuit 23, and the ASG extraction / error check circuit 24 extracts the ASG included in the downlink signal and CRC. Performs an error check of (check bit for error correction). This extracted ASG information is CPU
25, and CPU 25 performs information analysis. On the other hand, for the upstream signal, the CPU 25 outputs the RSP information generated based on the ASG to the RSP generation / CRC addition circuit 26. CRC is added based on this information to generate an RSP signal, which is input to the modulator 27. Duplexer 21
Then, only the signal in the upstream frequency band is passed, and the signal is transmitted to the central unit 14 via the upstream transmission line in the signal cable 13.

In this embodiment, during the initial hunting period, the operation of the time slot extraction / generation and speed conversion circuit 28 unrelated to the initial hunting operation is stopped from the CPU 25 through the TDM control line 29. For example, the operating power supply of the circuit 28 is turned off.
The transmission timing control value from the central unit 14 is demodulated by the demodulator 22 and set in the delay measurement control circuit 23, and the time slot signal input from the time slot extraction / generation and speed conversion circuit 28 through the line 30 is set. It is supplied to the RSP generation CRC adding circuit 26 at a timing earlier than the transmission timing control value.

The central unit 14 gives an instruction to set the polling cycle to several tens of seconds.
When it is sent using G, the CPU 25 controls the timer circuit 31 so that the control signal that was always output from the timer circuit 31 until the polling addressed to itself is slightly lengthened forward or backward. A control signal is generated, and this control signal is given to the delay measurement control circuit 23 and the modulator 27 so that the delay measurement control circuit 23 and the modulator 27 operate only during the period of receiving the polling addressed to itself and slightly before and after that. To be in a state. For example, in the case of the network terminating device NT ₁ , as shown in FIG. 1B, the control signal 32 is transmitted only for a frame (several milliseconds) of the period for receiving the polling from the central device 14 to the network terminating device NT _{1 and} a few times before and after the frame. Is generated. Since the cycle of the control signal 32 is several tens of seconds, the delay measurement control circuit 23 and the modulator 27 intermittently operate for several milliseconds every tens of seconds. Further, in this example, when the instruction to set the polling cycle to several tens of seconds is received, the CPU 25 operates the time slot extraction / generation and speed conversion circuit 28 by giving the control signal 33 to the TDMA control line 29 as shown in FIG. 1C. State.

Since the demodulator 22 is always operating even in the steady state,
When it is polled from the central unit 14, it is received and the timing of the polling is delayed by the delay measurement control circuit 23 and the modulator 27.
Since it is in the operating state, it is possible to transmit the response RSP to the ASG, and it is possible to set the received transmission timing control value in the delay measurement control circuit 23, and to set the number of each network in the cycle of several tens of seconds. Delay measurement control can be sequentially performed on the end devices NT _{1 to} NT _n . Call from terminal 16 or converter 15
When an incoming call from the CPU 25 occurs, the CPU 25 controls the timer circuit 31 to continuously output the control signal 32, and the delay measurement control circuit
23 and the modulator 27 are continuously operated. Therefore, the upstream signal from the terminal 16 is a time slot extraction / generation and speed conversion circuit 28-delay measurement control circuit 23-RSP generation CPC addition circuit 26-
Modulator 27-Demultiplexer 21-Sent to the central unit 14 through the upstream transmission line, and the downlink signal from the central unit 14 is the downstream transmission line-Splitter 21-Demodulator 22-Time slot extraction / generation and speed conversion circuit 28-Sent to the terminal 16 through the bus 17 and mutual communication is performed. During this period, the polling cycle for delay measurement control is several tens of seconds. When the mutual communication is completed, the CP
The U25 controls the timer circuit 31 to intermittently generate the control signal 32, and returns the delay measurement control circuit 23 and the modulator 27 to the intermittent operation state of a cycle of several tens of seconds.

Each network termination device the central unit 14 in the steady state NT ₁
~ NT When the signal from _n is analyzed, that is, when an abnormality is detected by monitoring, the subsequent delay measurement control polling is performed in the cycle of the initial hunting period, in this example, a few seconds. The network terminating device that has received this notification controls the timer circuit 31 to continuously send the control signal 32 and stops the operation of the time slot extraction / generation and speed conversion circuit 28 through the TDMA control line 29. . When the abnormality is recovered, the polling cycle is returned to several tens of seconds, the control signal is intermittently output from the timer circuit 31, the delay measurement control circuit 23 and the modulator 27 are brought into the intermittent operation state, and the time slot extraction / generation and speed conversion circuit. 28 is activated.

As described above, according to the present invention, the polling cycle for delay measurement control in the steady state after the end of the initial hunting period is made longer than the polling cycle at the time of initial hunting, and in the network termination device. In the steady state, the delay measurement control circuit and the modulator (upstream signal transmission circuit) are operated only during the period when the polling addressed to itself is received, and the other periods are inoperative, that is, the intermittent operation is performed.
The power consumption of the delay measurement control circuit and modulator can be significantly reduced compared to the case of continuous operation.Therefore, it is possible to use the high-speed operation ECL circuit that consumes a large amount of power and accurately control the timing. Therefore, the interval between time slots can be minimized, and even if a small-capacity, small-sized battery is used, the terminal can be backed up and the basic call function can be maintained in the event of a power failure. Even if the polling cycle is increased in this way, the transmission state, that is, each transmission time between the central device and each network terminating device does not suddenly change, so that time-division multiplex communication can be stably maintained. In addition, since the polling cycle is shortened in the initial hunting period or in the abnormal state, the transmission timing control value can be determined in a short time, and the communication-enabled state can be set quickly. When an outgoing / incoming call occurs in the steady state, the delay measurement control circuit and the modulator are continuously operated, so that mutual communication can be performed without any trouble.

[Brief description of drawings]

FIG. 1A is a diagram showing polling for delay measurement control from a central unit in the system of the present invention, and FIG. 1B is a diagram showing operation control signals for a delay measurement control circuit and a modulator in a network terminator NT ₁ . FIG. 1C is a diagram showing operation control signals for the time slot extraction / generation and speed conversion circuit 28 in the network terminator NT ₁ , and FIG. 2 is a block diagram showing an example of the network terminator used in the system of the present invention. 3 is a block diagram showing an example of a communication system to which the present invention is applied, and FIG.
FIG. 5 is a time chart showing a procedure of delay measurement control, FIG. 5A is a view showing polling for delay measurement control from a central device in the conventional system, and FIG. 5B is a view showing an example of a frame structure. .

Claims (1)

[Claims] 1. A central device and a plurality of network terminating devices to which terminals are connected are connected via an upstream / downstream transmission path, and a communication time slot signal from the network terminating device to the central device is transmitted. Time-divisionally transmitted via an up transmission line, a communication time slot signal from the central device to the network terminating device is transmitted in a time division manner via the down transmission line, and an upward transmission from the plurality of network terminating devices is performed. In order to avoid collision and interference of signals with each other, a time division multiplex communication system in which the central device initiative type performs delay measurement control by repeatedly polling the network terminating device, and the initial delay measurement control is The polling period in the initial hunting period in which the central device repeatedly polls each network terminating device until the end is completed is longer than the polling period in the steady state after the initial handing is completed. The network terminating device is notified that the polling period has been lengthened and the polling period has been lengthened, and each network terminating device that has received the notification that the polling period has been lengthened corresponds to the period for receiving the polling addressed to itself. Control signal is generated from the timer circuit only during the period of time during which the control circuit outputs the upstream signal transmission circuit and delay measurement control circuit only during the period in which polling addressed to itself is received. A power saving method in a time division multiplex communication system, characterized in that a control signal is continuously output to continuously operate the upstream signal transmission circuit and the delay measurement control circuit.