JPH04252541A - Transmission speed setting method for digital transmission link - Google Patents

Abstract

PURPOSE:To facilitate the transmission processing by varying the maximum transmission speed on a transmission medium in matching with the actual transmission link condition. CONSTITUTION:At the start-up of a digital transmission link, a transmission error rate measurement means 9 of a reception signal measures a transmission error rate of a transmission link between communication nodes 1 at a prescribed transmission speed. A transmission speed setting means 10 adjusts the transmission speed depending whether or not the result of measurement satisfies a prescribed transmission error rate. Then the transmission error rate is again measured and the maximum transmission speed of the digital transmission link is set based on the prescribed transmission error rate. That is, the transmission error rate is measured and the transmission speed on the transmission medium in the digital transmission link is subject to variable control. Thus, even when the transmission medium condition such as a transmission medium length differs, uniform transmission quality is obtained and the communication is implemented at the maximum transmission speed available in the transmission link.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for setting the transmission speed of a digital transmission link that interconnects communication nodes using a transmission medium and transmits and receives data in packets, and particularly relates to a method for setting the transmission speed of a signal on the transmission medium. The present invention relates to a transmission rate setting method for a digital transmission link.

0002

BACKGROUND OF THE INVENTION In order to support future communication services, studies on packet-based broadband ISDN (Integrated Services Digital Network) are being conducted mainly by CCITT (International Telegraph and Telephone Consultative Committee). This method breaks down digitized audio, data, and video information from a terminal into fixed-length blocks called packets, attaches a header with the destination to each packet, handles it in a unified manner, and multiplexes these packets. It is transmitted over a transmission medium, and by controlling the number of packets sent per unit time when transmitting information,
Provide any information speed. FIG. 2 is a diagram showing an example of the configuration of a digital transmission link between communicating nodes using packets. In FIG. 2, 1 is a communication node, 2 is a transmission medium,
3 is a terminal; 4 is a packet assembling unit that assembles information from the terminal 3 into packets and controls the number of transmission packets per unit time through negotiation with the terminal 3; 5 forms a transmission frame with the packet and transmission control information; A transmitting unit converts the code into a code suitable for the transmission medium 2 and transmits the code over the transmission medium. 6 is a receiving unit that receives the signal from the transmission medium 2 and extracts a packet from the received frame. 7 is a receiving unit that extracts information from the extracted packet. 8 is a node control unit that controls various parts within the communication node. Further, two opposing communication nodes 1 are interconnected by a transmission medium 2, and a terminal 3 is connected to the communication node 1. Note that a plurality of packet assembling units 4 and packet disassembling units 7 may be provided depending on communication media. Further, other processing units of the communication node 1 are omitted for simplicity. When performing packet communication with such a configuration, the transmission speed on the transmission medium is a predetermined fixed speed. Therefore, when the number of packets transferred per unit time is small, in order to keep the transmission speed on the transmission medium constant, empty packets with no information are inserted on the sending side and discarded on the receiving side. Is going. Furthermore, conventional packet switching technology and broadband IS
Regarding DN, for example, "Journal of the Institute of Electronics, Information and Communication Engineers V
ol. 71, No. 8 (1988),” Journal of the Institute of Electronics, Information and Communication Engineers Vol. 72, No. 5 (1990).
etc. are detailed.

0003

[Problem to be Solved by the Invention] In the above-mentioned conventional technology, the transmission quality such as the transmission error rate in the digital transmission link is greatly influenced by the transmission speed as well as the transmission link conditions such as the characteristics of the transmission medium and externally induced noise. . However, since the transmission speed is fixed, in order to ensure stable transmission quality, it is necessary to strictly define the length of the transmission medium, the core wire diameter, etc. with sufficient margins in mind. For this reason, there has been a problem in that flexibility in building a communication system is lacking, and it is difficult to guarantee uniform transmission quality over the entire communication system. Furthermore, in order to keep the transmission speed of the transmission medium constant,
It was necessary to insert and discard empty packets. An object of the present invention is to make the maximum transmission speed on the transmission medium variable according to the actual transmission link conditions, and to make the transmission speed on the transmission medium variable according to the number of packets transmitted per unit time. To provide a method for setting the transmission speed of a digital transmission link, which can improve the above-mentioned problems, provide flexibility in the construction of a communication system, facilitate transmission processing, and guarantee high transmission quality throughout the system. It is in.

0004

[Means for Solving the Problems] In order to achieve the above object, the method of setting the transmission speed of a digital transmission link of the present invention provides a digital transmission link that connects a plurality of communication nodes with a transmission medium and transmits and receives data in packets. In the communication node, a means for setting the transmission rate of the transmitted signal (rate control section), a means for measuring the transmission error rate of the received signal (error rate measuring section), and a means for setting the transmission rate of the transmitted signal (error rate measuring section), It is equipped with means for setting the transmission speed on the medium (speed control section) and means for returning and transmitting the received signal at the same transmission speed (switching section). The transmission error rate of the transmission link between the two is measured, and depending on whether the measurement result satisfies the predetermined transmission error rate, the transmission speed is increased or decreased and the transmission error rate is measured again. It is characterized in that the maximum transmission speed of the digital transmission link is variably controlled by. The device also includes a means (speed control unit) for calculating the required transmission speed based on the number of packets transmitted per unit time from the communication node, and calculates the required transmission speed when transmitting a packet, and Compare the required transmission speed with the maximum transmission speed of the digital transmission link, and if the required transmission speed is smaller, set it to the required transmission speed, and if the required transmission speed is higher, set the number of packets to be sent. A feature is that the transmission speed is variably controlled within the range of the maximum transmission speed of the digital transmission link by regulating and setting the maximum transmission speed.

[0005]

[Operation] In the present invention, by measuring the transmission error rate and variably controlling the transmission speed on the transmission medium in the digital transmission link, uniform transmission quality can be achieved even if the transmission medium conditions such as the transmission medium length are different. and can communicate at the maximum transmission rate that the transmission link can provide. Furthermore, since there is no need to insert or discard empty packets to adjust the transmission speed, and high transmission quality is obtained, communication system construction becomes more flexible, transmission and reception processing becomes easier, and the overall system High transmission quality can be guaranteed over the entire range.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a configuration diagram of a communication node of a digital transmission link in an embodiment of the present invention, FIG. 4 is a detailed diagram of a transmitting section in an embodiment of the present invention, and FIG. 5 is a diagram of a receiving section in an embodiment of the present invention. Detailed diagrams, FIG. 6 is a detailed diagram of the timing supply section in one embodiment of the present invention, FIG. 7 is a detailed diagram of the error rate measurement section in one embodiment of the present invention, and FIG. 8 is a detailed diagram of the speed control in one embodiment of the present invention. FIG. In Figure 3, 1
is a communication node, 2 is a transmission medium, 3 is a terminal, 4 is a packet assembly section, 5 is a transmission section, 6 is a reception section, 7 is a packet disassembly section, 8 is a communication node control section, 9 is a transmission error rate of a received signal 10 is a speed control section that controls the transmission speed on the transmission medium 2. Note that other processing functions of the communication node 1 will be omitted for simplicity. Further, details of the transmitter 5 are shown in FIG. In FIG. 4, 51 is a frame assembling unit that assembles a transmission frame using the packet from the packet assembling unit 4 and transmission control information, 52 is a switching unit that switches the signal source to be transmitted, and 53 is a frame assembly unit that converts the transmission signal into a code suitable for the transmission medium. The transceiver section 54 that converts and sends out onto the transmission medium 2 is a timing supply section that supplies timing signals such as bit synchronization signals and frame synchronization signals to each section. Further, details of the receiving section 6 are shown in FIG. In FIG. 5, 61 is a receiver unit that amplifies and equalizes the waveform of the received signal from the transmission medium 2, and converts it into a code suitable for in-node processing; 62 is a switching unit that distributes the destination of the received signal from the receiver unit 61; and 63 64 is a frame decomposition unit that detects a received frame from a received signal and decomposes it into transmission control information and packets, and 64 is a timing extraction unit that extracts bit timing and frame synchronization signals from the received signal. In this embodiment, the switching sections 52 and 62 of the transmitting section 5 and the receiving section 6 are interlocked with each other, and under the control of the node control section 8, normally, a signal from the frame assembly section 51 is transferred to the transceiver section 53, and the signal is transferred to the transceiver section 53. The received signal from the section 61 is transferred to the frame decomposition section 64, but when a signal of a specific pattern is received, the configuration is such that the received signal is switched from the receiver section 61 to be transferred directly to the transceiver section 53. ing. Further, the timing supply section 5 in the transmitting section 5
The details of 4 are shown in FIG. In FIG. 6, 54a is a reference clock source that generates a reference clock from an oscillator (not shown), 54b is a clock divider that divides the frequency of the reference clock, 54c is a voltage controlled oscillator that changes the oscillation frequency depending on the voltage, and 54d is a signal frequency divider; 54e is a phase difference comparator that compares the phases of the output of the clock frequency divider 54b and the output of the signal frequency divider 54d; and 54f is a phase difference comparator that converts the phase difference between the outputs of the phase difference comparator 54e into a voltage change. These integrators constitute a frequency synthesizer using a PLL (phase locked loop). Further, the output signal of the voltage controlled oscillator 54c is used as a bit timing signal of the transmission signal. Further, the frequency division ratio of the signal frequency divider 54d is specified by the speed control section 10. When the frequency of the output of the clock frequency divider 54b is fc and the frequency division ratio of the signal frequency divider 54d is Ns, the output frequency of the voltage controlled oscillator 54c is fc×Ns. Therefore, by changing the value of Ns, the frequency of the bit timing signal becomes variable, and the transmission speed of the transmission signal can be changed. Furthermore, if the reference clock is switched to the bit timing of the received signal obtained from the timing extractor 64 and the frequency division ratio of the signal frequency divider 54d is made the same as the frequency division ratio of the clock frequency divider 54b, synchronization with the received signal can be achieved. signals can be transmitted. Further, details of the error rate measuring section 9 are shown in FIG. In FIG. 7, 91 is the receiving section 6
A signal bit number counter 92 measures the number of bits of the received signal from
If there is an error bit in the received signal, a signal pattern identifying section 93 outputs an error detection pulse output. Reference numeral 93 is an error bit number counter that measures the pulse output from the signal pattern identifying section 92. In this embodiment, the signal bit number counter 91
The transmission error rate on the transmission link is measured from the count value of the error bit number counter 93. Further, details of the speed control section 10 are shown in FIG. 8. In FIG. 8, 10a is a maximum speed setting unit that calculates the maximum transmission speed on the transmission medium 2 based on the transmission error rate measured from the error rate measuring unit 9, and 10b is the required number of packets transmitted per unit time. The transmission speed setting section 10c that calculates the transmission speed is a frequency division ratio setting section that converts the transmission speed set by these into the frequency division ratio of the signal frequency divider 54d.

Next, a procedure for setting the maximum transmission rate on a link using such a configuration will be described. Figure 1 shows
A flowchart showing a procedure for setting the maximum transmission rate of a transmission link when starting up a transmission link in an embodiment of the present invention. FIG. 9 is a flowchart showing a process for measuring a transmission error rate on a transmission link in an embodiment of the present invention. , Figure 1
0 is a flowchart showing a procedure for setting a transmission rate during packet transfer on a transmission link in an embodiment of the present invention. In this embodiment, when measuring the transmission error rate on a transmission link at a certain transmission speed, the communication node performs processing according to the procedure shown in FIG. As shown in FIG. 9, the transmitter 4 receives an error in the frame assembler 51 based on the control information of the transmission error rate measurement instruction from the node controller 8 and the frequency division ratio No instruction from the speed controller 10 (901). A transmission signal with a specific pattern for rate measurement is generated, and the transmission speed Vo (Vo=f
c×No), transmission begins (902). Note that fc is the frequency of the output of the clock frequency divider 54b. After starting to transmit the transmission signal of the specific pattern in this way, when a return signal of the transmission signal transmitted in step 902 is received from the opposite communication node (903), the error rate measurement unit 9 calculates the number of bits and the number of error bits of the received signal. Measure (904). Then, when the number of bits or the number of error bits of the received signal reaches a predetermined value, the value is notified to the transmission rate setting section 10 and the node control section 8 (905). On the other hand, when the communication node facing the communication node that measures the transmission error rate receives a transmission signal with a specific pattern for transmission error rate measurement,
The reference clock of the timing supply section 65 is switched to the bit timing of the received signal, and the switching sections 52 and 62
By switching, the received signal is sent back. Through such a procedure, a communication node that has transmitted a transmission signal of a specific pattern for error rate measurement can measure a transmission error rate on a round trip transmission link between opposing communication nodes.

Next, using the transmission error rate measurement procedure shown in FIG. 9, a procedure for setting the maximum transmission speed of the transmission link when starting up the transmission link will be described. As shown in Figure 1, when the transmission speed of the transmission data is V and the frequency division ratio of the signal frequency divider is N, first, a specific transmission speed Vo (when the frequency division ratio of the signal frequency divider is No. , fc×No speed) in Figure 9
The transmission error rate is measured according to the procedure shown in (101), and as a result, it is determined whether or not the transmission link satisfies the expected error rate (102). If you are satisfied with the result,
The transmission error rate is measured again with the transmission rate set to V=V+ΔV (103), and it is determined again whether the result satisfies the expected error rate (104). Note that this ΔV is the amount of change in the transmission speed when the frequency division ratio N is changed, and is a speed that is an integral multiple of fc. In step 104, if the measured transmission error rate does not satisfy the expected error rate, the maximum transmission speed Ve of the transmission link is set as Ve=V-ΔV (105
), the series of settings processing ends. Also, step 104
If the transmission error rate measured in the determination above satisfies the expected transmission error rate, the processing in step 103 and the determination in step 104 are repeated. In addition, if it is determined in step 102 that the measured transmission error rate does not satisfy the expected transmission error rate, the transmission error rate measurement process and the determination of the result are repeated with the transmission rate set to V = V - ΔV ( 106, 107), if the measured transmission error rate satisfies the desired transmission error rate, the maximum transmission speed Ve of the transmission link is set to Ve=V (108), and the series of setting processing is completed. . According to this embodiment, by repeating measurement of the transmission error rate and judgment of the result a plurality of times, it is possible to set the maximum transmission speed Ve on the transmission link that satisfies the desired error rate. Furthermore, by appropriately selecting the initial value Vo of the transmission rate and the amount of change ΔV in the transmission rate, the maximum transmission rate on the transmission link can be set by measuring the transmission error rate at least twice. Also, ΔV
It is also possible to set the maximum transmission speed with high precision by making it coarse at first and gradually making it finer. Furthermore, by changing the intended transmission error rate, it is also possible to set the maximum transmission rate at any transmission error rate. Furthermore, in digital communications, information such as voice is sampled at 8kHz, so if the output frequency fc of the clock frequency divider 54b is set to an integer multiple of 64kHz, the bit timing of the transmission signal can be adjusted to an integer of 64k bits/second. This makes it possible to change the transmission speed in units of octets, which facilitates digital processing of transmitted and received signals.

Next, a procedure for setting the transmission speed of the transmission link at the time of packet transfer in response to a request from the terminal 3 will be described. As shown in FIG. 10, the speed control section 10 calculates the necessary transmission speed Vs based on the information on the number of packets to be transmitted per unit time from the packet assembly section 4 (100
1) Compare the required speed with the maximum speed Vm on the transmission link (1002), and if the required speed is within the maximum transmission speed, set the required speed Vs as the transmission speed of the transmission link (1004) . Further, in step 102, if the required speed exceeds the maximum transmission speed, the maximum number of packets per unit time that can be transferred by the transmission link is notified to the packet assembly section 4, the number of packets to be sent is regulated, and the transmission link Set the speed to the maximum transmission speed (
1003). The transmission speed set in this way is converted into a frequency division ratio (1005), and the process ends. For example, the number of packets sent per unit time is S, and the length of the packet is Bs.
Assuming that the transmission control information in the octet and transmission frame is Bd octet and the transmission frame period is 125 microseconds, the transmission speed Vs required for packet transfer can be found from the following equation. Vs=(8000×Bd+S×B
s) x 8 (bits/second)

0010

According to the present invention, since the maximum transmission speed on the transmission link between communication nodes is set while measuring the transmission error rate on the transmission link, transmission link conditions such as transmission medium characteristics and external induced noise can be set. Even if the values differ, the maximum transmission rate that satisfies the desired transmission error rate can be set, and the maximum transmission capacity is guaranteed with stable transmission quality. Furthermore, there are no restrictions on the length of the medium, the diameter of the core wire, etc., and flexibility in system construction is increased. Furthermore, by making the transmission speed during packet transfer variable according to the number of packets transferred per unit time within the range of the maximum transmission speed, there is no need to insert or discard empty packets to adjust the speed, making processing easier. As well as becoming easier,
Reliability is improved by lowering the transmission speed, and more stable transmission can be guaranteed. Furthermore, since it is possible to arbitrarily change the transmission speed and the intended transmission error rate, it is possible to provide the most efficient transmission form for each communication medium.

[0011]

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a procedure for setting the maximum transmission speed of a transmission link when starting up a transmission link in an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a digital transmission link between communicating nodes using packets.

FIG. 3 is a configuration diagram of a communication node of a digital transmission link in an embodiment of the present invention.

FIG. 4 is a detailed diagram of a transmitter in an embodiment of the present invention.

FIG. 5 is a detailed diagram of a receiving section in an embodiment of the present invention.

FIG. 6 is a detailed diagram of a timing supply section in an embodiment of the present invention.

FIG. 7 is a detailed diagram of an error rate measuring section in an embodiment of the present invention.

FIG. 8 is a detailed diagram of a speed control section in an embodiment of the present invention.

FIG. 9 is a flowchart showing a process for measuring a transmission error rate on a transmission link in an embodiment of the present invention.

FIG. 10 is a flowchart showing a procedure for setting a transmission rate during packet transfer on a transmission link in an embodiment of the present invention.

[Explanation of symbols]

1 Communication node 2 Transmission medium 3 Terminal 4 Packet assembly department 5 Transmission section 6 Receiving section 7 Packet disassembly section 8 Node control unit 9 Error rate measurement section 10 Speed control section 10a Maximum speed setting section 10b Transmission speed setting section 10c Division ratio setting section 51 Frame assembly section 52 Switching section 53 Transceiver section 54 Timing supply section 54a Reference clock source 54b Clock divider 54c voltage controlled oscillator 54d Signal divider 54e Phase difference comparator 54f Integrator 61 Receiver section 62 Switching section 63 Frame disassembly part 64 Timing extraction section 91 Signal bit number counter 92 Signal pattern identification section 93 Error bit number counter

Claims (2)

[Claims] Claim 1. In a method for setting the transmission speed of a digital transmission link that connects a plurality of communication nodes via a transmission medium and transmits and receives data in packets, the communication nodes include:
means for setting the transmission rate of the transmitted signal; means for measuring the transmission error rate of the received signal; means for setting the transmission rate on the transmission medium based on the transmission error rate; when the digital transmission link is started up, measures the transmission error rate of the transmission link between communication nodes at a predetermined transmission speed, and checks whether the measurement result satisfies the predetermined transmission error rate. A method for setting a transmission speed of a digital transmission link, comprising increasing or decreasing the transmission speed, measuring the transmission error rate again, and setting the maximum transmission speed of the digital transmission link under a predetermined transmission error rate. 2. When transmitting a packet from the communication node, the communication node comprises means for calculating a required transmission rate based on the number of packets per unit time, and when transmitting a packet, the required transmission rate and the maximum of the transmission link are calculated. 2. The method for setting a transmission speed of a digital transmission link according to claim 1, wherein the transmission speed is compared with the transmission speed, and the transmission speed is arbitrarily set within the range of the maximum transmission speed based on the comparison result.