JP4045448B2 - Terminal apparatus and data transmission method - Google Patents

Description

  The present invention relates to a terminal apparatus and a data transmission method in a transmission system that dynamically allocates a transmission bandwidth of uplink data from a user terminal to a center station.

  Transmission systems that dynamically allocate the transmission bandwidth of uplink data from the user terminal to the center station include a wireless system and a wired system. A representative of the wired system is a PON (passive optical network) using an optical fiber as a transmission path. System.

  The PON system is a star network that branches a plurality of optical fiber transmission lines by providing a passive branching device, so-called optical coupler, in the middle of an optical fiber. The PON system consists of a center station OLT (Optical Line Terminal) and a branching device. The optical fiber in between is shared by each subscriber.

  In the PON system, data transmission (upstream) from an ONU (Optical Network Unit), which is a subscriber terminal device, to an OLT (Optical Line Terminal), which is a subscriber accommodation device of a center station, is dynamically transmitted to the subscriber. A DBA (Dynamic Bandwidth Allocation) method for allocating the data is employed (see, for example, Patent Document 1). That is, the OLT designates a time slot used for uplink transmission to the subscriber, and each subscriber transmits the uplink data to the OLT on the designated time slot. On the optical fiber shared by each subscriber, upstream data from each subscriber is transmitted to the OLT of the center station in different time slots. That is, on the shared optical transmission line, the uplink data of each subscriber is transmitted by TDM (Time Division Multiplexing).

Conventionally, data is transmitted from the user to the center station through the following exchange. The user transmits a predetermined amount of data and a next data transmission request command to the center station. When the OLT receives the data and the transmission request command from the ONU, the OLT transfers the received data to the subsequent network and permits the user to transmit the next data with a possible bandwidth. When the user receives a transmission permission (Grant) signal from the OLT, the user transmits the next data to the OLT within the designated bandwidth.
US Pat. No. 6,546,014

  In TCP, when an acknowledgment (ACK) after data transmission is received, the next data can be transmitted. When the distance between the OLT and the ONU of each subscriber is increased, the time from receiving a data transmission or transmission request until receiving a transmission permission from the OLT is increased, and during this time, the ONU cannot transmit data. That is, an increase in round trip time RTT (Round Trip Time) reduces TCP throughput.

  In the PON system, since the grant period is common to all subscribers, the grant period is set in accordance with the user who is farthest away. Even a user at a short distance can obtain only the same TCP throughput as a user at the longest distance.

  Such a decrease in TCP throughput becomes more conspicuous in faster GE (Gigabit Ethernet) -PON. Ethernet is a registered trademark.

  The TCP throughput can be improved by increasing the TCP window size (WS). However, if the TCP window size (WS) is increased, the probability of packet loss due to buffer overflow increases during congestion, which tends to cause a significant decrease in TCP throughput.

  It is an object of the present invention to provide a terminal device and a data transmission method that improve the data transmission throughput in a dynamic bandwidth allocation system.

A terminal apparatus according to the present invention is a terminal apparatus installed on the user side in a transmission system that dynamically allocates a transmission bandwidth of uplink data from a user to a center station, and a buffer that temporarily stores uplink data; A monitoring device that monitors the amount of stored uplink data in the buffer, a receiving device that receives a grant signal from the center station, and the stored uplink data in the buffer within the transmission bandwidth specified by the grant signal Data transmission means for transmitting to the center station, Bandwidth determination means for determining the required bandwidth in the next permitted transmission cycle in consideration of the amount of data remaining in the buffer after data transmission by the data transmission means, A command for transmitting a command requesting the bandwidth determined by the bandwidth setting means following the data transmission by the data transmitting means. ; And a de transmission means, the bandwidth determination unit, when the uplink data to the buffer after data transmission by the data transmission means remains, the bandwidth obtained by adding a predetermined amount to the previous request bandwidth, the following Determined as the necessary bandwidth in the transmission cycle permitted by the data transmission means, and when the upstream transmission data does not remain in the buffer after the data transmission by the data transmission means and the previous requested bandwidth is not zero, the previous requested bandwidth A bandwidth obtained by reducing the width by a predetermined amount is determined as a necessary bandwidth in the next permitted transmission cycle .

Data transmission method according to the present invention, in a transmission system for dynamically allocating a transmission bandwidth of the uplink data to the center station from a user terminal, a method for transmitting data to the center station from a user terminal, buffering uplink data A temporary storage step for temporarily storing data, a reception step for receiving a grant signal from the center station, and transmitting the stored uplink data of the buffer to the center station within a transmission bandwidth specified by the grant signal. In consideration of the data transmission step, the amount of data remaining in the buffer after data transmission, a bandwidth determination step for determining the required bandwidth in the next permitted transmission cycle, and a command for requesting the determined bandwidth A command transmission step for transmitting to the center station following the data transmission, and the bandwidth determination step. However, when data remains in the buffer after data transmission in the data transmission step, a bandwidth obtained by adding a predetermined amount to the previous request bandwidth is determined as a necessary bandwidth in the next permitted transmission cycle. And when no data remains in the buffer after data transmission by the data transmission step and the previous request bandwidth is not zero, the bandwidth obtained by reducing the previous request bandwidth by a predetermined amount is And determining as a necessary bandwidth in an allowed transmission period.

  According to the present invention, the bandwidth required for the next grant signal is predicted, and the bandwidth is requested from the center station in advance, so that the data transmission efficiency is improved. As a result, the throughput of data transmission is greatly improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention. The center station OLT 10 is connected to the optical coupler 14 via the optical fiber 12. The optical coupler 14 is connected to ONUs 18-1 to 18-n at user's homes via individual optical fibers 16-1 to 16-n. Computers (PC) 20-1 to 20-n are connected to the ONUs 18-1 to 18-n via LAN (Local Area Network), generally Ethernet (registered trademark), respectively.

  The optical coupler 14 divides the downstream optical signal from the OLT 10 into n pieces, and outputs them to the optical fibers 16-1 to 16-n. The ONUs 18-1 to 18-n convert downstream signal light input from the optical fibers 16-1 to 1-n into electrical signals, and transfer only the electrical signals addressed thereto to the computer 20-1. On the other hand, each ONU 18-1 to 18-n outputs upstream signal light to the optical fibers 16-1 to 16-n at a timing specified by the OLT 10. The optical coupler 14 outputs an upstream signal from the optical fibers 16-1 to 1-n to the optical fiber 12. Usually, signal light of different wavelengths is used for upstream and downstream.

  Although only the inside of the ONU 18-1 is illustrated in detail, the internal configuration of the other ONUs 18-2 to 28-n is the same as that of the ONU 18-1.

  First, the flow of uplink data, downlink data, request command, and grant signal in the ONU 18-1 will be described.

  FIG. 2 shows a control flow of uplink data transmission in this embodiment. The computer 20-1 outputs the upstream data to the ONU 18-1. The ONU 18-1 temporarily stores the upstream data in the buffer 22. The ONU 18-1 includes a timer 24 that synchronizes with the OLT 10. The CPU (control circuit) 26 of the ONU 18-1 refers to the timer 24 and controls the entire ONU 18-1. In particular, the CPU 26 is predicted by a buffer amount monitor 28 that monitors the amount of uplink data buffered in the buffer 22, a data amount prediction circuit 30 that predicts the amount of uplink data to be transmitted in the next transmission cycle, and a data amount prediction circuit 30. A command generation circuit 32 that generates a command for requesting transmission of the data amount, and a read control circuit 46 that controls reading of data from the buffer 22.

  When the upstream data from the computer 20-1 is likely to overflow from the buffer 22, the buffer amount monitor 28 transmits a pause frame based on IEEE802.3x to the computer 20-1. Receiving the pause frame, the computer 20-1 stops outputting data for the time specified by the pause frame.

  Prior to the transmission of the uplink data, the CPU 24 initializes the loop variable i with 1 (S1), and transmits a transmission start request command to the OLT 10 (S2). At this time, the requested transmission band or transmission data amount may be an appropriate value, or the predicted data amount may be designated as in the process described later. Then, the CPU 24 waits for a grant signal from the OLT 10 (S3).

  The command generation circuit 32 generates the request command at a timing specified by the OLT 10. The request command is applied to the electrical / optical converter 36 via the multiplexer 34. The electrical / optical converter 36 converts the electrical signal from the multiplexer 34 into an optical signal. The electrical / optical converter 36 includes, for example, a laser diode and a drive circuit that drives the laser diode in accordance with an electrical signal output from the multiplexing device 34. The output signal light of the electrical / optical converter 36 is input to the OLT 10 via the WDM (wavelength division multiplexing) optical coupler 38, the optical fiber 16-1, the optical coupler 14, and the optical fiber 12. In response to the transmission request command, the OLT 10 transmits a grant signal designating a band to the request source (here, the ONU 18-1).

  The grant signal is input from the OLT 10 to the WDM coupler 38 of the ONU 18-1 via the optical fiber 12, the optical coupler 14, and the optical fiber 16-1. The WDM coupler 38 supplies an optical signal input from the optical fiber 16-1 to the photoelectric converter 40. The photoelectric converter 40 converts the optical signal from the WDM coupler 38 into an electrical signal and supplies the electrical signal to the separation device 42. The separation device 42 supplies a control signal (for example, the above-mentioned grant signal) for the ONU 18-1 among the electrical signals output from the photoelectric converter 40 to the CPU 26, and other data, generally downstream data and the PC 20 −1 is supplied to the buffer 44.

CPU26 receives a grant signal from the OLT10 from the output of the separation device 42 (S3), determines the amount of transmittable data _{T i} within the range of the bandwidth specified in the grant signal (S4), The data amount prediction circuit 26 predicts the data amount of data T _{i + 1} to be transmitted for the next grant signal (S5). For example, the data T _i of the data amount T _i, the amount of data in the buffer 22 before transmitting the data T _i and Q _i, input from the computer 20-1 before the data transmission for the next grant signal to the buffer 22 Assuming that the amount of uplink data is Q _{i + 1} , the amount of data temporarily stored in the buffer 22 at the start of data transmission for the next grant signal is Q _i −T _i + Q _{i + 1} . That is, T _{i + 1} = Q _i −T _i + Q _{i + 1} . If T _{i + 1} > 0, there is data to be transmitted for the next grant signal, and if not, transmission of the uplink data can be completed by transmitting the data T _i .

If T _{i + 1} > 0 (S6), the command generation circuit 32 generates a transmission request command having a bandwidth capable of transmitting the data T _{i + 1} (S7), and the read control circuit 46 reads the data T _i from the buffer 22. . Multiplexer 34, the uplink data T _i read from the buffer 22 is first supplied to the electric / optical converter 36, then, supplies a transmission request command from the command generating circuit 32 to the electric / optical converter 36. The electrical / optical converter 38 sequentially converts the data _Ti and the transmission request command from the multiplexer 34 into an optical signal. The optical signal is transmitted through the WDM coupler 38, the optical fiber 16-1, the optical coupler 14, and the optical fiber 12, and finally input to the OLT 10. Thus, the data _{T i,} a transmission request command for the next data _{T i + 1} is transmitted to the OLT 10 (S8). The ONU 18-1 increments the loop variable i (S9) and waits for a grant signal from the OLT 10 (S3).

  The OLT 10 outputs the uplink data received from the ONU 18-1 to a network (not shown). Further, when permitting a transmission request from the ONU 18-1, the OLT 10 permits the requested bandwidth to the extent possible and transmits a grant signal indicating the permitted bandwidth to the ONU 18-1.

When T _{i + 1} ≦ 0, that is, when there is no data to be transmitted in the next next transmission cycle (S6), the ONT 18-1 transmits only the uplink data T _i without a transmission request command and ends (S10). . When the next upstream data is input from the computer 20-1, the transmission process shown in FIG. 2 is started.

  In the first embodiment, a bandwidth capable of transmitting the predicted data amount is requested each time. However, each time a transmission request is made, the requested bandwidth is increased or decreased by a predetermined amount depending on the presence or amount of remaining data in the buffer 22. May be. FIG. 3 shows a control flow of the operation thus changed. The flow of the transmission request signal, the grant signal, and the transmission data signal is the same as in the first embodiment.

The CPU 24 initializes a variable Q indicating the amount of data stored in the buffer 22 (S11), initializes an initial value _R0 of the variable R indicating the transmission bandwidth with Q, and initializes a variable Δ indicating the amount of change in the transmission bandwidth. It is initialized to the value Δ ₀ (S12). The CPU 24 further initializes the loop variable i with 1 (S13). Then, the ONU 18-1 transmits a transmission start request command to the OLT 10 and waits for reception of a grant signal. At this time, the requested transmission band or transmission data amount may be an appropriate value, or the predicted data amount may be designated as in the process described later.

Upon receiving a grant signal from OLT 10, and sets the allowed transmission bandwidth _{G i} to the variable G (S14). In the range of allowed transmission bandwidth _{G i,} ONU18-1 transmits uplink data _{T i} stored in the buffer 22 to the OLT 10 (S15). And the amount of data remaining in the buffer 22, the required bandwidth R _i-1 Tokyo in the transmission period of the previous, as follows to determine the required bandwidth R _i for the subsequent data transmission, it requests the OLT 10.

First, the data amount Q _i remaining in the buffer 22 is monitored (S16). When the remaining data amount is 0 (S17), the previous request bandwidth R _i-1 is checked (S18). If the previous required bandwidth R _i-1 is zero (S18), the current required bandwidth R _{i is set} to 0 (S19), otherwise, only Δ from the previous required bandwidth R _i-1 reduce bandwidth for the current required bandwidth _{R i} (S20). When data remains in the buffer 22 (S17), a bandwidth obtained by adding Δ to the previous request bandwidth R _i-1 is set as the current request bandwidth R _i (S20). As described above, when transmission continues and the stored uplink data in the buffer 22 cannot be transmitted at one time (S17), a larger transmission bandwidth is requested (S21). When the stored upstream data in the buffer 22 can be transmitted at one time (S18), a smaller transmission bandwidth is requested (S20).

  The command generation circuit 32 of the CPU 26 generates a transmission request command for requesting the bandwidth determined in steps S19 to S21, and this transmission request command is transmitted to the OLT 10 through the route described in the first embodiment.

  The loop variable i is incremented, and reception of a grant signal from the OLT 10 is waited (S14).

Although from the transmission of the data T _i was determined bandwidth of the next transmission, and transmits after determining the bandwidth of the next transmission, and transmits the data T _i in OLT 10, thereafter, a transmission request command to the OLT 10 It is obvious that the above may be changed.

  In each of the above-described embodiments, uplink data can be transmitted to the center station at a higher speed than before, and the delay time in the ONU can be shortened. That is, the effective transmission rate of upstream data can be improved. Usually, the transmission rate of downlink data is the same regardless of whether or not the present invention is applied, so that the RTT can be improved by the present invention. TCP throughput can also be improved by improving RTT.

  Although the PON system using an optical fiber has been described as an example, the present invention can also be applied to a system that dynamically changes the bandwidth of uplink data between a center station and a subscriber, for example, a wireless system.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

It is a schematic block diagram of one Example of this invention. It is the 1st transmission control flow of the uplink data transmission of a present Example. It is a 2nd transmission control flow of the uplink data transmission of a present Example.

Explanation of symbols

10: OLT
12: Optical fiber 14: Optical couplers 16-1 to 16-n: Optical fibers 18-1 to 18-n: ONU
20-1 to 20-n: Computer (PC)
22: Buffer 24: Timer 26: CPU
28: Buffer amount monitor 30: Data amount prediction circuit 32: Command generation circuit 34: Multiplexer 36: Electrical / optical converter 38: WDM coupler 40: Photoelectric converter 42: Separating device 44: Buffer

Claims (7)

In a transmission system that dynamically allocates a transmission bandwidth of uplink data from a user to a center station, a terminal device installed on the user side,
A buffer (22) for temporarily storing upstream data;
A monitor device (28) for monitoring the amount of data stored in the buffer (22);
A receiving device (40, 42) for receiving a grant signal from the center station (10);
Data transmission means (34, 36, 46) for transmitting the stored uplink data of the buffer (22) to the center station (10) within the range of the transmission bandwidth specified by the grant signal;
Considering the amount of data remaining in the buffer (22) after data transmission by the data transmission means, bandwidth determination means (26) for determining a required bandwidth in the next permitted transmission cycle;
Command transmitting means (32, 34, 36) for transmitting a command requesting the bandwidth determined by the bandwidth setting means (26) following data transmission by the data transmitting means.
Provided with a door,
The bandwidth determination means
When uplink data remains in the buffer (22) after data transmission by the data transmission means (S17), a bandwidth obtained by adding a predetermined amount to the previous request bandwidth (R _i ) is permitted next. Determined as the required bandwidth in the period (S21),
If no uplink data remains in the buffer (22) after data transmission by the data transmission means (S17) and the previous requested bandwidth (R _i ) is not zero (S18), the previous requested bandwidth ( The bandwidth obtained by reducing R _i ) by a predetermined amount is determined as the necessary bandwidth in the next permitted transmission cycle (S20).
A terminal device characterized by that. The terminal device according to claim 1 , wherein the transmission system is an optical transmission system that uses an optical fiber as a transmission path. The terminal device, ONU consists (Optical Network Unit), terminal device according to claim 2 in which the center station consists OLT (Optical Line Terminal). The terminal device according to claim 1 , wherein the transmission system is a wireless transmission system using a wireless transmission path. In a transmission system that dynamically allocates a transmission bandwidth of uplink data from a user terminal to a center station, a method for transmitting data from the user terminal to the center station,
A temporary storage step for temporarily storing upstream data in the buffer (22);
A receiving step of receiving a grant signal from the center station (10) (S3, S14);
A data transmission step of transmitting the stored uplink data of the buffer (22) to the center station (10) within the range of the transmission bandwidth specified by the grant signal (S8, S15);
In consideration of the amount of data remaining in the buffer (22) after data transmission, a bandwidth determination step for determining a necessary bandwidth in the next permitted transmission cycle (S5 to S7, S17 to S21),
Command transmission step (S8, S22) for transmitting a command requesting the determined bandwidth to the center station (10) following the data transmission.
And
The bandwidth determination step includes
When uplink data remains in the buffer (22) after the data transmission in the data transmission step (S17), a bandwidth obtained by adding a predetermined amount to the previous requested bandwidth (R _i ) is allowed next. A step (S21) of determining a required bandwidth in a cycle;
If no uplink data remains in the buffer (22) after data transmission in the data transmission step (S17) and the previous requested bandwidth (R _i ) is not zero (S18), the previous requested bandwidth ( A step of determining a bandwidth obtained by reducing R _i ) by a predetermined amount as a necessary bandwidth in the next permitted transmission cycle (S20).
A data transmission method comprising : The data transmission method according to claim 5 , wherein the transmission system is an optical transmission system using an optical fiber as a transmission path. The data transmission method according to claim 5 , wherein the transmission system is a wireless transmission system using a wireless transmission path.

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