JP3589573B2 - Cell transmission timing control system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cell transmission timing control system in an ATM cell transmission device.
[0002]
[Prior art]
The demand for mobile communication services in recent years is wide, and high-speed digital data communication and variable-speed communication such as packet communication are also required. As an exchange in consideration of high-speed digital communication, packet communication, etc., a network configuration using an ATM having high affinity with high-speed and variable-speed data is more suitable than STM communication in consideration of constant-speed data transmission, In the future, it is conceivable that ATM applications to mobile communication will increase.
[0003]
FIG. 5 is a block diagram showing a configuration example of a conventional system, which constitutes a mobile communication system. The mobile terminal 1 is connected to a plurality of radio base stations 2. The wireless base station 2 is connected to a wired transmission path 3. The wireless base station 2 and the wired transmission path 3 dynamically switch the base station to be used to the one having the best quality between the terminal and the base station by moving the terminal.
[0004]
The plurality of wireless base stations 2 are connected to the mobile switch 4. The mobile switching center 4 selects a base station to be used by a handover trunk or the like. Also, the delay at the egress differs depending on the base station used. The output of the mobile exchange 4 enters the general telephone exchange 6 via the wired transmission line 5. The general telephone exchange 6 is connected to a general subscriber 7.
[0005]
In ATM transmission, each channel is dynamically allocated on a transmission path according to traffic (corresponding to an STM time slot), so that data transmission fluctuates when performing data transmission. When ATM transmission is used for a fixed connection network for mobile communication, the movement of the terminal changes the radio base station, the transmission path delay increases or decreases, and the arrival delay at the fixed network side device further fluctuates. .
[0006]
This delay fluctuation causes a delay in data arrival, data omission, and the like when real-time voice communication or the like is considered, and causes a problem of deterioration in communication quality. In particular, in an apparatus that performs multiplex processing of a plurality of lines on a transmission line, cells may be concentrated at a certain timing, and the degree of delay fluctuation may increase. In order to solve this problem, a method is considered in which a certain number of cells are accumulated in each transmission / relay device on the transmission path and cells are transmitted at the timing designated by the higher-level control unit (each of the transmission paths). The transmission timing of the device is calculated by the host control processor). According to this method, the transmission timing to the transmission path is dispersed, the delay fluctuation is reduced, and the transmission path use efficiency is improved.
[0007]
FIG. 6 is an explanatory diagram of the operation of absorbing delay fluctuation. A cell is transmitted from a cell transmission device (for example, the wireless base station in FIG. 5) 8 and enters the handover trunk 9 via the transmission line 3. The output of the handover trunk 9 enters the cell relay device 10. The cell relay device 10 includes a cell buffer 11 for storing cells, and a transmission timing generator 12 for giving data transmission timing to the cell buffer 11.
[0008]
In the system configured as described above, the amount of delay changes because the transmission path 3 differs depending on the base station used. Therefore, in the cell relay device 10, the reception timing fluctuates depending on the base station used. For this reason, the delay fluctuation is absorbed by temporarily storing the data in the cell buffer 11 and transmitting the data at a fixed time. The management / designation of the transmission timing is performed by the host control processor.
[0009]
FIG. 7 is a block diagram showing a configuration of a main part of the conventional system. The same components as those in FIG. 6 are denoted by the same reference numerals. In the figure, reference numeral 11 denotes a cell buffer, and reference numeral 12 denotes a transmission control unit which supplies a transmission request signal to the cell buffer 11. A storage cell counter 13 receives an input cell and counts the number of arrival cells, and is provided for each line of the multiplexing process. Then, the output of the storage cell counter 13 gives a control signal to the transmission control unit 12.
[0010]
A transmission timing storage unit 14 stores transmission timings set by the host device, and is provided for each line of multiplex processing. Reference numeral 15 denotes a physical timing generator that receives the reference timing signal and generates a physical timing signal. Reference numeral 16 denotes a timing comparison unit that receives the output n of the transmission timing storage unit 14 and the output pt of the physical timing generation unit 15 and compares the respective timings. The output of the timing comparison unit 16 is input to the transmission control unit 12 in the first half. The operation of the circuit thus configured will be described below with reference to the flowchart shown in FIG.
[0011]
FIG. 8 shows a conventional transmission timing control process. First, when a cell is received (S1), it is stored in the cell buffer 11 (S2). Next, the timing comparing section 16 compares whether the higher-order instruction transmission timing n and the physical timing pt match (S3). If they do not match, the process returns to step S1. If they match, the transmission control unit 12 checks whether there is a transmission target cell (S4), and if so, transmits the cell (S5).
[0012]
Next, it is checked whether the transmission end timing has come (pt = n + 1) (S6), and if so, the remaining cells at the current transmission timing are discarded (S7). FIG. 9 is a diagram showing conventional cell transmission timing. When the physical timing pt becomes n, the transmission timing specified by the higher-level control unit overlaps, and cell transmission becomes possible. If the cell transmission has not been completed within the cell transmission available time, the remaining cells are discarded.
[0013]
[Problems to be solved by the invention]
In the case of the conventional device described above, it is assumed that the transmission timing specified by the higher-level control unit is uniformly allocated and that the transmission of cells can be completed within the allocation timing. Because they are different, they are not always allocated equally.
[0014]
Therefore, if a cell cannot be transmitted at a certain designated transmission timing due to a problem such as multiplicity, the cell is discarded, and a cell loss occurs. It is desirable that the designation from the higher-level control unit is uniformly assigned. However, if the assignment can be performed without discarding the cells even if the assignment is slightly uneven, the next stage of the transmission path There is also a possibility of being remedied by the device, and the communication quality is improved.
[0015]
The present invention has been made in view of such a problem, and even when transmission cells are concentrated at a certain timing, cells can be reliably transmitted without discarding the cells, and communication quality is improved. It is an object of the present invention to provide a cell transmission timing control system.
[0016]
[Means for Solving the Problems]
(1) FIG. 1 is a principle block diagram of the present invention. The same components as those in FIG. 7 are denoted by the same reference numerals. In the figure, reference numeral 15 denotes a physical timing generation unit that generates a physical timing generated from a reference timing, 20 denotes a logical timing generation unit that generates a logical transmission timing using a cell transmission completion condition,
Reference numeral 16 denotes a timing comparison unit which receives the outputs of the physical timing generation unit 15 and the logical timing generation unit 20 and compares the timings. Reference numeral 11 denotes a cell buffer for storing input cells. And a transmission control unit that supplies a transmission timing signal to the cell buffer 11 upon receiving the transmission timing signal.
[0017]
According to the configuration of the present invention, since the logical timing generation unit 20 generates the logical transmission timing using the condition of the completion of the cell transmission, it is possible to surely transmit the cell without discarding the cell.
[0018]
(2) In this case, transmission is started using the logical timing, the physical timing, and the timing specified by the higher-level control unit.
According to the configuration of the present invention, by starting transmission using the logical timing, the physical timing, and the timing designated by the higher-level control unit, the cell can be transmitted reliably.
[0019]
(3) Further, the logical timing holds a value having a difference corresponding to a certain step value in the transmission timing, and starts transmission when the physical timing and the logical timing are different.
[0020]
According to the configuration of the present invention, the cell transmission is activated only when the logical timing is different from the transmission target timing, so that reliable cell transmission can be achieved.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a block diagram showing one embodiment of the present invention. 1 and 7 are denoted by the same reference numerals. In the figure, reference numeral 13 denotes a storage cell counter that counts the number of input cells upon receiving a cell input, and 12 denotes a transmission control unit that supplies a cell transmission signal to the cell buffer 11. The storage cell counter 13 provides the transmission control unit 12 with information that cells are stored. The transmission completion signal output from the transmission control unit 12 is provided to the logical timing generation unit 20.
[0022]
The logical timing generator 20 stores the transmission timing -1. Reference numeral 21 denotes an adder that adds 1 to the output of the logical timing generator 20. Reference numeral 22 denotes a first timing comparator that compares the output n of the transmission timing storage 14 with the output of the adder 21. Are in the AND circuit 23. The output of the AND circuit 23 enters the transmission control unit 12 as a control signal.
[0023]
Reference numeral 16 denotes a second timing comparison unit that compares the output pt of the physical timing generation unit 15 with the output lt of the logical timing generation unit 20. The AND circuit 23 receives the output of the first and second timing comparison units 16.
[0024]
In the present invention, the received cells are temporarily stored in the cell buffer 11 and wait for activation of transmission from the cell transmission timing generator. The transmission start factor of the stored cells is not only the physical timing generated from the reference timing common to the transmission path, but also the logical timing of counting up upon completion of transmission of the cell and the physical timing comparison result. Start transmission with.
[0025]
Here, as the logical timing, [transmission target timing-1] is held, and in the case of [physical timing 送信 logical timing], transmission is started, and the logical timing is set to +1 upon completion of transmission. According to the comparison method and the method of changing the logical timing, the transmission can be always started in a case other than [logical timing = physical timing] instead of the operation of the conventional example in which the transmission is performed only for a certain fixed time. In this case, the cell can be transmitted without discarding the cell.
[0026]
Hereinafter, the operation of the configured system will be described with reference to the flowchart shown in FIG.
First, a cell is received (S1), and the cell is stored in the cell buffer 11 (S2). Next, the timing comparing unit 16 checks whether the physical timing pt and the logical timing lt are not equal (S3). If they are equal, the process returns to step S1. If not equal, the timing comparing section 22 checks whether or not the higher-order instruction transmission timing is equal to the logical timing +1 (S4). That is, it is checked whether n = lt + 1.
[0027]
When the physical timing and the logical timing are not equal and the higher-order instruction transmission timing is equal to the logical timing + 1, the AND circuit 23 performs cell transmission when there is a cell to be transmitted (S5) (S6). Whether or not there is a cell is given from the storage cell counter 13. If the higher-order instruction transmission timing is not equal to the logical timing +1 in step S4, and if there is no transmission target cell, the logical timing is set to +1 and the process returns to step S1.
[0028]
FIG. 4 is an explanatory diagram of the cell transmission timing of the present invention. In the comparison between the physical timing pt and the logical timing lt, a cell is transmitted when the physical timing pt is n and the logical timing lt is n-1. The period when the physical timing is n is the designated transmission timing from the upper control unit, and the period when the logical timing is n-1 is the cell transmission available time. The cell is transmitted during the period when the logical timing is n-1, and lt is counted by 1 at the end of the cell transmission. As described above, according to the present invention, when two or three cells are shifted, it cannot be determined that they are equal. Therefore, it is necessary to store a value of -1 in order to determine that they are not equal. To perform the comparison operation.
[0029]
According to the present invention, when transmission cells are concentrated at a certain timing by starting transmission of cells not only at physical transmission timing but also at logical transmission timing in the device in consideration of the end of cell transmission However, cells are reliably transmitted without discarding the cells. Therefore, the frequency of cell loss is reduced and communication quality is improved.
[0030]
【The invention's effect】
As described above, according to the present invention,
(1) A physical timing generation unit that generates a physical timing generated from a reference timing, a logical timing generation unit that generates a logical transmission timing using a cell transmission completion condition, a physical timing generation unit, and a logical timing A timing comparison unit that receives the output of the generation unit and compares the timings, a cell buffer that stores the input cells, and a transmission control unit that receives the output of the timing comparison unit and provides a transmission timing signal to the cell buffer. With this configuration, the logical timing generation unit generates the logical transmission timing using the condition of the completion of the cell transmission, so that the cell can be reliably transmitted without discarding the cell.
[0031]
(2) In this case, by starting transmission using the logical timing, the physical timing, and the timing specified by the higher-level control unit, the transmission is started using the logical timing, the physical timing, and the timing specified by the higher-level control unit. By starting, cells can be transmitted reliably.
[0032]
(3) Further, the logical timing holds a value having a difference corresponding to a certain step value in the transmission timing, and starts transmission when the physical timing and the logical timing are different, so that the transmission timing is changed to the logical timing. By activating cell transmission only at different times, reliable cell transmission becomes possible.
[0033]
As described above, according to the present invention, even when transmission cells are concentrated at a certain timing, a cell transmission timing control system that can reliably transmit cells without discarding the cells and improves communication quality is provided. Can be provided.
[Brief description of the drawings]
FIG. 1 is a principle block diagram of the present invention.
FIG. 2 is a block diagram showing an embodiment of the present invention.
FIG. 3 is a flowchart showing the operation of the present invention.
FIG. 4 is an explanatory diagram of cell transmission timing of the present invention.
FIG. 5 is a block diagram illustrating a configuration example of a conventional system.
FIG. 6 is an explanatory diagram of an operation of absorbing delay fluctuation.
FIG. 7 is a block diagram showing a configuration of a main part of a conventional system.
FIG. 8 is a flowchart showing a conventional delay fluctuation absorbing operation.
FIG. 9 is a diagram showing conventional cell transmission timing.
[Explanation of symbols]
Reference Signs List 11 Cell buffer 12 Transmission control unit 13 Storage cell counter 14 Transmission timing storage unit 15 Physical timing generation unit 16 Timing comparison unit 20 Logical timing generation unit 21 Addition unit 22 Timing comparison unit 23 AND circuit

Claims (3)

A physical timing generation unit that generates a physical timing generated from the reference timing;
A logical timing generation unit that generates a logical transmission timing using a cell transmission completion condition;
A timing comparison unit that receives the output of the physical timing generation unit and compares the timings by receiving outputs of the logical timing generation unit;
A cell buffer for storing input cells;
A cell transmission timing control system comprising: a transmission control unit that receives an output of the timing comparison unit and supplies a transmission timing signal to the cell buffer. 2. The cell transmission timing control system according to claim 1, wherein the transmission is started using the logical timing, the physical timing, and the timing specified by the higher-level control unit. 3. The cell transmission timing control system according to claim 2, wherein the logical timing holds a value obtained by giving a difference by a certain step value to the transmission timing, and starts transmission when the physical timing and the logical timing are different.

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