Optical access network bandwidth allocation method and system

Abstract

The present invention discloses an optical access network bandwidth allocation method and system. The method includes the following steps: 1) before the start of each polling cycle, the OLT checks each ONU to see whether it has an uplink transmission scheduled for the current cycle or the next cycle, records the information, and calculates the expected polling cycle time for the current cycle; 2) in each polling cycle, the next ONU to be polled by the OLT is determined based on the ONU uplink and downlink overlapping working time and channel idle time caused by the polling of each ONU that was not polled in the current cycle; 3) when the OLT polls an ONU, the ONU's uplink transmission corresponding to the allocated bandwidth is scheduled based on the occupied uplink channel, and a sleep time is allocated based on the ONU's scheduled uplink transmission start time or the expected polling cycle time for the current cycle; 4) the ONU performs uplink transmission and sleep according to the OLT's instructions, and reports the required bandwidth at the end of the uplink data transmission. The present invention reduces bandwidth waste and arranges sleep time for the ONU, thereby reducing optical access network latency and improving optical access network energy efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of time division multiplexing passive optical access network, and in particular relates to an optical access network bandwidth resource allocation method and system based on polling sequence scheduling. Background Art

[0002] With the development of an information society, the coverage of optical access networks has extended from urban areas to remote rural areas. At the same time, with the popularization of various delay-sensitive applications, the delay requirements of optical access networks have also been pushed to the 1ms level in the 5G era. However, in sparsely populated rural environments, due to the differences in ONU propagation delays caused by the different distances between different optical network units (ONUs) and optical line terminals (OLTs), achieving low latency often requires adjusting the timing of uplink data transmission of each ONU. As a result, uplink and downlink data transmission of an ONU cannot be carried out simultaneously, which greatly prolongs the ONU's working time and reduces the ONU's energy efficiency.

[0003] Optical access networks are the primary energy consumer in communications networks. With the continued construction and development of communications networks, their energy consumption will become even more prominent. Currently, achieving both low latency and energy efficiency in optical access networks in remote rural and mountainous areas, where ONU propagation delays vary significantly, remains an unresolved issue, and relevant design solutions are urgently needed. Summary of the Invention

[0004] Focusing on optical access networks based on time-division multiplexing passive optical network technology, and aiming at achieving low latency and high energy efficiency in optical access networks with large ONU propagation delay variations, the present invention discloses a method and system for allocating bandwidth resources in optical access networks based on round-robin scheduling, which can effectively achieve low latency and high energy efficiency in optical access networks with large ONU propagation delay variations.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A method for allocating bandwidth of an optical access network comprises the following steps:

[0007] (1) Before the start of each polling cycle, the optical link terminal (OLT) checks whether each optical network unit (ONU) has been scheduled and can correspond to the uplink transmission of the current cycle and records it. At the same time, it checks whether each ONU has been scheduled and can correspond to the uplink transmission of the next cycle and records it. In addition, it calculates the expected polling cycle time of the current cycle.

[0008] (2) In each polling cycle, the next ONU to be polled by the OLT is determined based on the ONU uplink and downlink overlapping working time and channel idle time caused by the polling of each ONU that was not polled in this cycle;

[0009] (3) When the OLT polls an ONU, it arranges the upstream transmission of the ONU corresponding to the allocated bandwidth according to the occupied upstream channels, and allocates sleep time according to the scheduled upstream transmission start time of the ONU or the expected polling cycle time of this cycle.

[0010] (4) After receiving the GATE frame, the ONU performs uplink transmission and sleep according to the instructions, and reports the required bandwidth when the uplink data transmission is completed.

[0011] When the distances between ONUs and OLT vary greatly, the present invention can effectively reduce bandwidth waste caused by ONU propagation delay differences and arrange appropriate sleep time for the ONUs, thereby reducing optical access network delay and improving optical access network energy efficiency.

[0012] Preferably, in step (1), before the OLT starts a polling cycle, the OLT uses the time t0 at which it enters the polling cycle as a reference to search for each ONU that has been scheduled and can correspond to the uplink transmission of this cycle, and records it in a 1-dimensional n-item (n is the total number of ONUs in the network) vector A and a 1-dimensional n-item vector AD. The specific method is as follows: i For example, for ONU i , OLT searches for ONU i Is there any scheduled start time greater than t0+TP? i Uplink transmission (where TP i For ONU i If there is a propagation delay), the start time of the earliest uplink transmission is recorded in the i-th item of vector A, and the end time is recorded in the i-th item of vector AD; if there is no such a propagation delay, the i-th item of vector A is recorded as NaN, and the i-th item of vector AD is recorded as NaN.

[0013] Preferably, in step (1), before the OLT starts a polling cycle, the OLT uses the time t0 at which it enters the polling cycle as a reference to check whether each ONU has an uplink transmission that has been scheduled and can correspond to the next cycle, and records it in a 1-dimensional n-item vector B. The specific method is as follows: i For example, for ONU i , OLT searches for ONU i Scheduled and start time greater than t0+TP i If two or more uplink transmissions can be found, the start time of the second uplink transmission is recorded in the i-th item of vector B. Otherwise, the i-th item of vector B is recorded as NaN.

[0014] Preferably, in step (1), before the OLT starts a polling cycle, the OLT calculates the total time BW required to transmit these bandwidths based on the sum of the bandwidth requirements of each ONU in the downstream direction in the previous polling cycle, and calculates the expected polling cycle time TEC of this cycle by the formula n(TG+G)+BW, where G is the protection interval set by the system and TG is the transmission time of the GATE frame.

[0015] Preferably, in step (2), in each polling cycle, the ONU to be polled next by the OLT is determined by the following rule: for each ONU that has not been polled in this cycle, the ONU's downlink transmission start time TDS, downlink transmission end time TDE, matched uplink transmission start time TUS, matched uplink transmission end time TUE, and resulting uplink and downlink channel idle time TI are calculated when the ONU is the next ONU to be polled, and the score of the ONU is calculated by the calculation formula min(TUE, TDE)-max(TUS, TDS)-TI. Afterwards, the OLT selects the ONU with the highest score from the ONUs that have not been polled in this cycle as the next ONU to be polled.

[0016] Preferably, in step (2), an ONU (herein ONU i For example, TDS, TDE, TUS, TUE and TI are calculated as follows: TDS is calculated by the formula FOE+G+TP i Calculation, where FOE is the time when OLT completes the downlink data transmission of the previous polled ONU. At the same time, if OLT finds that ONU i If the TDS value has not yet been restored to normal working state, the ONU will be updated to the value after TDS. i The moment when normal working state is restored. After obtaining TDS, TDE is calculated by the formula TDS+DD, where DD is the OLT transmission ONU i GATE frame and FOE time ONU i The total time required for downlink data. Afterwards, for TUS, if the i-th item of vector A recorded in step (1) is not NaN, then TUS is equal to the value of the i-th item of vector A; otherwise, TUS is calculated by the formula max(ARU+G-TP i ,TDS+TG), where ARU is the time when the OLT completes the last scheduled uplink transmission. For TUE, if the i-th item of the vector AD recorded in step (1) is not NaN, then TUE is equal to the value of the i-th item of the vector AD; otherwise, TUE is calculated by the formula TUS+DU, where DU is the value of the ONU iThe sum of the uplink data transmission time allocated by the latest bandwidth requirement and the REPORT frame transmission time. TI is represented by TDS-TP. i -G-FOE+USW calculation, where if the i-th item of the vector A recorded in step (1) is not NaN, then USW is 0, otherwise USW is calculated by the formula TUS+TP i -G-ARU calculation.

[0017] Preferably, in step (3), poll an ONU (here ONU i For example), the OLT sends a GATE frame to the ONU and transmits the downstream data corresponding to the ONU to the ONU after the GATE frame. At the same time, the OLT allocates its upstream bandwidth according to the latest bandwidth demand of the ONU, arranges the upstream transmission of the ONU, and informs the ONU through the GATE frame and records it for use in the subsequent operation step (1). The specific upstream transmission arrangement rules are as follows: The scheduled upstream transmission start time OAU is given by the formula max(ARU+G-TP i ,SG+TP i +TG) is determined, where SG is when OLT starts sending ONU i The timing of the GATE frame; the upstream bandwidth arranged by the OLT received by the ONU i The OLT determines the latest bandwidth demand information and the duration and end time of the corresponding upstream transmission (including the REPORT frame). After that, the OLT will update its ARU value to the time when the upstream transmission is received and update its FOE value to the time when the downstream data is transmitted.

[0018] Preferably, in step (3), poll an ONU (here ONU i For example), the OLT arranges the sleep start time and sleep duration of the ONU after receiving the downlink data, and informs the ONU through the GATE frame. The specific sleep start time and duration calculation method is as follows: First, the sleep start time and duration corresponding to the ONU calculated in step (2) are calculated as follows: i The value of TUS is recorded in the variable UT, and the value corresponding to ONU calculated in step (2) is recorded in the variable UT. i The TDS value of ONU is recorded in DT. Then, calculate i The uplink transmission end time UE, if the i-th item of the vector AD recorded in step (1) is not NaN, then UE is equal to the value of the i-th item of the vector AD; otherwise, UE is calculated by the formula UT+UD, where UD is the value of the ONU i The sum of the uplink data transmission time allocated by the latest bandwidth requirement and the REPORT frame transmission time. i The end time of downlink transmission DE is determined by DT, TG and sending GATE frame to ONU. iWhen OLT needs to transmit to ONU i Afterwards, if the i-th item of vector B in step (1) is not NaN, the value of the i-th item of vector B is recorded in the variable AS, and the ONU is calculated by the formula AS-max(DE,UE). i At this time, if TOI is greater than the ONU wake-up time OW and UT-DT is less than the expected polling cycle time TEC determined in step (1), the OLT will schedule the ONU i Enter sleep mode from the moment of max(DE,UE), and the sleep duration is TOI-OW; if the i-th item of vector B in step (1) is NaN, and the i-th item of vector A in step (1) is not NaN, then OLT calculates ONU by min(OAU-max(DE,UE),TEC-max(DE,UE)+min(DT,UT)) i The idle time TOI, at this time, if TOI is greater than OW and UT-DT is less than TEC, then OLT will arrange ONU i Entering sleep mode from the moment of max(DE,UE), the sleep duration is TOI-OW; if the i-th item of vector B and vector A in step (1) are both NaN, the OLT calculates ONU by the formula TEC-max(DE,UE)+min(DT,UT) i The idle time TOI, at this time, if TOI is greater than OW, then OLT will arrange ONU i Enters sleep mode from the moment of max(DE,UE) and the sleep duration is TOI-OW. i After receiving the GATE frame, the OLT will record the ONU i Sleep and wake-up time periods, so that the ONU can be extracted in step (2) in the subsequent operation i Time to resume normal working state.

[0019] Preferably, step (4) is as follows: after receiving the GATE frame from the OLT, an ONU will receive subsequent downlink data and, according to the instructions in the GATE frame, perform uplink transmission at the scheduled time and according to the allocated bandwidth. When the uplink data transmission ends, the ONU will count the amount of data that needs to be transmitted in the buffer at this time and send the corresponding bandwidth requirement to the OLT along with the REPORT frame.

[0020] The present invention also discloses an optical access network bandwidth allocation system, based on the above method, comprising the following modules:

[0021] Query and recording module: Before the start of each polling cycle, the optical link terminal OLT checks whether each optical network unit (ONU) has been scheduled and can correspond to the uplink transmission of the current cycle and records it. At the same time, it checks whether each ONU has been scheduled and can correspond to the uplink transmission of the next cycle and records it, and calculates the expected polling cycle time of the current cycle.

[0022] ONU determination module: In each polling cycle, the next ONU to be polled by the OLT is determined based on the ONU uplink and downlink overlapping working time and channel idle time caused by the ONU that was not polled in this cycle.

[0023] Polling module: When the OLT polls an ONU, it arranges the upstream transmission of the ONU corresponding to the allocated bandwidth according to the occupied upstream channels, and allocates sleep time according to the scheduled upstream transmission start time of the ONU or the expected polling cycle time of this cycle;

[0024] Report module: After receiving the GATE frame, the ONU performs upstream transmission and sleep according to the instructions, and reports the required bandwidth when the upstream data transmission is completed.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the case where the ONU propagation delay varies greatly, the technical solution of the present invention can effectively reduce the waste of channel resources and maximize the sleep time of the ONU, thereby reducing the network delay and improving the network energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1 is a schematic diagram of a network data flow according to a preferred embodiment of the present invention, including an execution process taking polling cycle k as an example.

[0028] Figure 2 The present invention is a flow chart of a method for allocating bandwidth in an optical access network according to a preferred embodiment of the present invention.

[0029] Figure 3 The present invention is a block diagram of an optical access network bandwidth allocation system according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0030] To more clearly illustrate the embodiments of the present invention, the following specific embodiments of the present invention will be described with reference to the accompanying drawings. Obviously, the following description and drawings are only a preferred embodiment of the present invention, and those skilled in the art can also derive other embodiments based on these descriptions and drawings without inventive effort.

[0031] Example 1:

[0032] See also Figure 1-2This embodiment is a bandwidth allocation method for a time division multiplexing passive optical access network, comprising the following steps:

[0033] Step (1), before the OLT starts a polling cycle, the OLT uses the time t0 at which it enters the polling cycle as a reference to find out the uplink transmissions that have been scheduled for each ONU and can correspond to the current cycle, and records them in a 1-dimensional n-item (n is the total number of ONUs in the network) vector A and a 1-dimensional n-item vector AD. The specific method is as follows: i For example, for ONU i , OLT searches for ONU i Is there any scheduled start time greater than t0+TP? i Uplink transmission (where TP i For ONU i If there is a propagation delay), the start time of the first upstream transmission is recorded in the i-th item of vector A, and the end time is recorded in the i-th item of vector AD. If there is no upstream transmission, the i-th item of vector A is recorded as NaN, and the i-th item of vector AD is recorded as NaN. At the same time, before the OLT starts a polling cycle, the OLT uses the time t0 when it enters the polling cycle as the reference to check whether each ONU has an upstream transmission that has been scheduled and can correspond to the next cycle, and records it in a 1-dimensional n-item vector B. The specific method is as follows: i For example, for ONU i , OLT searches for ONU i Scheduled and start time greater than t0+TP i If two or more upstream transmissions are found, the start time of the second upstream transmission is recorded in the i-th item of vector B. Otherwise, the i-th item of vector B is recorded as NaN. In addition, the OLT calculates the total time (BW) required to transmit this bandwidth based on the sum of the downstream bandwidth requirements of each ONU in the previous polling cycle. It then calculates the expected polling cycle time (TEC) for the current cycle using the formula n(TG + G) + BW, where G is the system-configured guard interval and TG is the transmission time of the GATE frame.

[0034] Step (2), in each polling cycle, the ONU to be polled next by the OLT is determined by the following rules: for each ONU that has not been polled in this cycle, the ONU's downlink transmission start time TDS, downlink transmission end time TDE, matched uplink transmission start time TUS, matched uplink transmission end time TUE, and resulting uplink and downlink channel idle time TI are calculated when the ONU is the next ONU to be polled, and the score of the ONU is calculated by the formula min(TUE, TDE)-max(TUS, TDS)-TI. Afterwards, the OLT selects the ONU with the highest score from the ONUs that have not been polled in this cycle as the next ONU to be polled. An ONU (here ONU i For example, TDS, TDE, TUS, TUE and TI are calculated as follows: TDS is calculated by the formula FOE+G+TP i Calculation, where FOE is the time when OLT completes the downlink data transmission of the previous polled ONU. At the same time, if OLT finds that ONU i If the TDS value has not yet been restored to normal working state, the ONU will be updated to the value after TDS. i The moment when normal working state is restored. After obtaining TDS, TDE is calculated by the formula TDS+DD, where DD is the OLT transmission ONU i GATE frame and FOE time ONU i The total time required for downlink data. Afterwards, for TUS, if the i-th item of vector A recorded in step (1) is not NaN, then TUS is equal to the value of the i-th item of vector A; otherwise, TUS is calculated by the formula max(ARU+G-TP i ,TDS+TG), where ARU is the time when the OLT completes the last scheduled uplink transmission. For TUE, if the i-th item of the vector AD recorded in step (1) is not NaN, then TUE is equal to the value of the i-th item of the vector AD; otherwise, TUE is calculated by the formula TUS+DU, where DU is the value of the ONU i The sum of the uplink data transmission time allocated by the latest bandwidth requirement and the REPORT frame transmission time. TI is represented by TDS-TP. i -G-FOE+USW calculation, where if the i-th item of the vector A recorded in step (1) is not NaN, then USW is 0, otherwise USW is calculated by the formula TUS+TP i -G-ARU calculation.

[0035] Step (3), poll an ONU (here ONU iFor example), the OLT sends a GATE frame to the ONU and transmits the downstream data corresponding to the ONU to the ONU after the GATE frame. At the same time, the OLT allocates its upstream bandwidth according to the latest bandwidth demand of the ONU, arranges the upstream transmission of the ONU, informs the ONU through the GATE frame, and records it for use in the subsequent operation step (1). The specific upstream transmission arrangement rules are as follows: The scheduled upstream transmission start time OAU is given by the formula max(ARU+G-TP i ,SG+TP i +TG) is determined, where SG is when OLT starts sending ONU i The timing of the GATE frame; the upstream bandwidth arranged by the OLT received by the ONU i The OLT determines the latest bandwidth demand information of the ONU, and thereby determines the duration and end time of the corresponding upstream transmission (including the REPORT frame). Afterwards, the OLT will update its ARU value to the time when the upstream transmission is received, and update its FOE value to the time when the downstream data is transmitted. In addition, the OLT arranges the sleep start time and sleep duration of the ONU after receiving the downstream data, and informs the ONU through the GATE frame. The specific sleep start time and duration calculation method is as follows: First, the corresponding ONU calculated in step (2) i The value of TUS is recorded in the variable UT, and the value corresponding to ONU calculated in step (2) is recorded in the variable UT. i The TDS value of ONU is recorded in DT. Then, calculate i The uplink transmission end time UE, if the i-th item of the vector AD recorded in step (1) is not NaN, then UE is equal to the value of the i-th item of the vector AD; otherwise, UE is calculated by the formula UT+UD, where UD is the value of the ONU i The sum of the uplink data transmission time allocated by the latest bandwidth requirement and the REPORT frame transmission time. i The end time of downlink transmission DE is determined by DT, TG and sending GATE frame to ONU. i When OLT needs to transmit to ONU i Afterwards, if the i-th item of vector B in step (1) is not NaN, the value of the i-th item of vector B is recorded in the variable AS, and the ONU is calculated by the formula AS-max(DE,UE). i At this time, if TOI is greater than the ONU wake-up time OW and UT-DT is less than the expected polling cycle time TEC determined in step (1), the OLT will schedule the ONU iEnter sleep mode from the moment of max(DE,UE), and the sleep duration is TOI-OW; if the i-th item of vector B in step (1) is NaN, and the i-th item of vector A in step (1) is not NaN, then OLT calculates ONU by min(OAU-max(DE,UE),TEC-max(DE,UE)+min(DT,UT)) i The idle time TOI, at this time, if TOI is greater than OW and UT-DT is less than TEC, then OLT will arrange ONU i Entering sleep mode from the moment of max(DE,UE), the sleep duration is TOI-OW; if the i-th item of vector B and vector A in step (1) are both NaN, the OLT calculates ONU by the formula TEC-max(DE,UE)+min(DT,UT) i The idle time TOI, at this time, if TOI is greater than OW, then OLT will arrange ONU i Enters sleep mode from the moment of max(DE,UE) and the sleep duration is TOI-OW. i After receiving the GATE frame, the OLT will record the ONU i Sleep and wake-up time periods, so that the ONU can be extracted in step (2) in the subsequent operation i Time to resume normal working state.

[0036] In step (4), after receiving the GATE frame from the OLT, an ONU will receive the subsequent downstream data and, according to the instructions in the GATE frame, perform upstream transmission at the scheduled time and according to the allocated bandwidth. At the end of the upstream data transmission, the ONU will count the amount of data that needs to be transmitted in the buffer at this time and send the corresponding bandwidth requirement to the OLT along with the REPORT frame.

[0037] Example 2:

[0038] like Figure 3 As shown, this embodiment discloses an optical access network bandwidth allocation system, based on the method described in Example 1, which includes the following modules:

[0039] Query and recording module: Before the start of each polling cycle, the optical link terminal OLT checks whether each optical network unit (ONU) has been scheduled and can correspond to the uplink transmission of the current cycle and records it. At the same time, it checks whether each ONU has been scheduled and can correspond to the uplink transmission of the next cycle and records it, and calculates the expected polling cycle time of the current cycle.

[0040] ONU determination module: In each polling cycle, the next ONU to be polled by the OLT is determined based on the ONU uplink and downlink overlapping working time and channel idle time caused by the ONU that was not polled in this cycle.

[0041] Polling module: When the OLT polls an ONU, it arranges the upstream transmission of the ONU corresponding to the allocated bandwidth according to the occupied upstream channels, and allocates sleep time according to the scheduled upstream transmission start time of the ONU or the expected polling cycle time of this cycle;

[0042] Report module: After receiving the GATE frame, the ONU performs upstream transmission and sleep according to the instructions, and reports the required bandwidth when the upstream data transmission is completed.

[0043] For other contents of this embodiment, please refer to Example 1.

[0044] The present invention provides a method and system for allocating bandwidth resources in an optical access network based on ONU polling sequential scheduling, which is applied to a time-division multiplexed passive optical access network consisting of an optical line terminal (OLT) and multiple optical network units (ONUs). In the technical solution of the present invention, before the start of each polling cycle, the OLT checks and records whether each ONU has an upstream transmission scheduled for the current cycle and can transmit it. It also checks and records whether each ONU has an upstream transmission scheduled for the next cycle and can transmit it. Furthermore, it calculates the expected polling cycle time for the current cycle. Subsequently, during a polling cycle, the next ONU to be polled by the OLT is determined based on the ONU's upstream and downstream overlapping operating time and channel idle time caused by the polling of each ONU that was not polled during the current cycle. Then, when the OLT polls an ONU, it schedules the ONU's upstream transmission corresponding to the allocated bandwidth based on the occupied upstream channels and allocates a sleep time based on the start time of the ONU's scheduled upstream transmission or the expected polling cycle time for the current cycle. By adopting the above technical solution, the present invention reduces the waste of channel resources and maximizes the sleep time of the ONU, and can effectively achieve low delay and high energy efficiency in a time-division multiplexing passive optical access network with large ONU propagation delay differences.

[0045] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, based on the ideas provided by the present invention, there may be changes in the specific implementation methods, and these changes should also be considered as the scope of protection of the present invention.

Claims

1. A method for allocating bandwidth of an optical access network, characterized in that Follow these steps: (1) Before the start of each polling cycle, the optical link terminal (OLT) checks whether each optical network unit (ONU) has been scheduled and can correspond to the uplink transmission of the current cycle and records it. At the same time, it checks whether each ONU has been scheduled and can correspond to the uplink transmission of the next cycle and records it, and calculates the expected polling cycle time of the current cycle. (2) In each polling cycle, the next ONU to be polled by the OLT is determined based on the ONU uplink and downlink overlapping working time and channel idle time caused by the ONU that was not polled in this cycle. (3) When the OLT polls an ONU, it arranges the upstream transmission of the ONU corresponding to the allocated bandwidth according to the occupied upstream channels, and allocates sleep time according to the scheduled upstream transmission start time of the ONU or the expected polling cycle time of this cycle; (4) After receiving the GATE frame, the ONU performs uplink transmission and sleep according to the instructions, and reports the required bandwidth when the uplink data transmission is completed; In step (1), before the OLT starts a polling cycle, the OLT uses the time t0 of entering the polling cycle as a reference to find out the uplink transmissions that have been scheduled for each ONU and can correspond to the current cycle, and records them in a 1-dimensional n-item vector A and a 1-dimensional n-item vector AD, where n is the total number of ONUs in the network, as follows: i , OLT searches for ONU i Is there any scheduled start time greater than t0+TP? i Uplink transmission, TP i For ONU i If there is a propagation delay, the start time of the earliest uplink transmission is recorded in the i-th item of vector A, and the end time is recorded in the i-th item of vector AD. If there is no propagation delay, the i-th item of vector A is recorded as NaN, and the i-th item of vector AD is recorded as NaN; In step (1), before the OLT starts a polling cycle, the OLT uses the time t0 of entering the polling cycle as a reference to check whether each ONU has an upstream transmission that has been scheduled and can correspond to the next cycle, and records it in a 1-dimensional n-item vector B, where n is the total number of ONUs in the network, as follows: i , OLT searches for ONU i Scheduled and start time greater than t0+TP i If two or more uplink transmissions can be found, the start time of the second uplink transmission is recorded in the i-th item of vector B. Otherwise, the i-th item of vector B is recorded as NaN. In step (1), before the OLT starts a polling cycle, the OLT calculates the total time BW required to transmit these bandwidths based on the sum of the bandwidth requirements of each ONU in the downstream direction in the previous polling cycle, and calculates the expected polling cycle time TEC of this cycle by the formula n(TG+G)+BW, where n is the total number of ONUs in the network, G is the set protection interval, and TG is the transmission time of the GATE frame; In step (2), in each polling cycle, the ONU to be polled next by the OLT is determined by the following rules: for each ONU that has not been polled in this cycle, the downstream transmission start time TDS, the downstream transmission end time TDE, the matched upstream transmission start time TUS, the matched upstream transmission end time TUE, and the resulting upstream and downstream channel idle time TI of the ONU are calculated respectively if the ONU is the next ONU to be polled, and the score of the ONU is calculated by the calculation formula min(TUE, TDE)-max(TUS, TDS)-TI; then, the OLT selects the ONU with the highest score from the ONUs that have not been polled in this cycle as the next ONU to be polled; In step (2), the TDS, TDE, TUS, TUE and TI of an ONU are calculated as follows: TDS is calculated by the formula FOE+G+TP i Calculated, where FOE is the time it takes for the OLT to complete the downlink data transmission of the previous polled ONU. At the same time, if the OLT finds that the ONU i If the TDS value has not yet been restored to normal working state, the ONU will be updated to the value after TDS. i The moment of resuming normal working state; after obtaining TDS, TDE is calculated by the formula TDS+DD, where DD is the OLT transmission ONU i GATE frame and FOE time ONU i The total time required for downlink data; for TUS, if the i-th item of vector A recorded in step (1) is not NaN, then TUS is equal to the value of the i-th item of vector A; otherwise, TUS is given by max(ARU+G-TP i , TDS+TG), where ARU is the time it takes for the OLT to receive the last scheduled uplink transmission. For TUE, if the i-th item of the vector AD recorded in step (1) is not NaN, then TUE is equal to the value of the i-th item of the vector AD. Otherwise, TUE is calculated by the formula TUS+DU, where DU is the value of the ONU i The sum of the uplink data transmission time allocated by the latest bandwidth demand and the REPORT frame transmission time; TI is represented by TDS-TP i -G-FOE+USW calculation, where if the i-th item of the vector A recorded in step (1) is not NaN, then USW is 0, otherwise USW is calculated by the formula TUS+TP i -G-ARU calculation; In step (3), when polling an ONU, the OLT sends a GATE frame to the ONU and transmits the downstream data corresponding to the ONU to the ONU after the GATE frame. At the same time, the OLT allocates its upstream bandwidth according to the latest bandwidth demand of the ONU, arranges the upstream transmission of the ONU, and informs the ONU through the GATE frame and records it. The specific upstream transmission arrangement rules are as follows: The scheduled upstream transmission start time OAU is given by the formula max(ARU+G-TP i ,SG+TP i +TG) is determined, where SG is when OLT starts sending ONU i The timing of the GATE frame; the upstream bandwidth arranged by the OLT received by the ONU i The latest bandwidth demand information is determined, and the corresponding upstream transmission duration and end time are determined accordingly; then, the OLT will update the ARU value to equal the time when the upstream transmission is received, and update the FOE value to equal the time when the downstream data is transmitted; In step (3), when polling an ONU, the OLT arranges the sleep start time and sleep duration of the ONU after receiving the downlink data, and informs the ONU through the GATE frame. The specific sleep start time and sleep duration are calculated as follows: First, the ONU corresponding to the ONU calculated in step (2) i The value of TUS is recorded in the variable UT, and the value corresponding to ONU calculated in step (2) is recorded in the variable UT. i The TDS value is recorded in DT; Then, calculate ONU i The uplink transmission end time UE, if the i-th item of the vector AD recorded in step (1) is not NaN, then UE is equal to the value of the i-th item of the vector AD; otherwise, UE is calculated by the formula UT+UD, where UD is the sum of the uplink data transmission time allocated according to the latest bandwidth requirement of ONUi and the REPORT frame transmission time; Next, calculate ONU i The end time of downlink transmission DE is determined by DT, TG and sending GATE frame to ONU. i When OLT needs to transmit to ONU i The sum of the downlink data transmission time is determined; Afterwards, if the i-th item of vector B in step (1) is not NaN, the value of the i-th item of vector B is recorded in variable AS, and ONU is calculated by the formula AS-max(DE,UE) i At this time, if TOI is greater than the ONU wake-up time OW and UT-DT is less than the expected polling cycle time TEC determined in step (1), the OLT will schedule the ONU i Enter sleep mode from the moment of max(DE,UE), and the sleep duration is TOI-OW; if the i-th item of vector B in step (1) is NaN, and the i-th item of vector A in step (1) is not NaN, then OLT calculates ONU by min(OAU-max(DE,UE),TEC-max(DE,UE)+min(DT,UT)) i The idle time TOI, at this time, if TOI is greater than OW and UT-DT is less than TEC, then OLT will arrange ONU i Entering sleep mode from the moment of max(DE,UE), the sleep duration is TOI-OW; if the i-th item of vector B and vector A in step (1) are both NaN, the OLT calculates ONU by the formula TEC-max(DE,UE)+min(DT,UT) i The idle time TOI, at this time, if TOI is greater than OW, then OLT will arrange ONU i Enter sleep mode from the moment of max(DE,UE), and the sleep duration is TOI-OW; After sending ONU i After receiving the GATE frame, the OLT records the ONU i Sleep and wake-up time periods, so that the ONU can be extracted in step (2) in the subsequent operation i Time to resume normal working state.

2. The optical access network bandwidth allocation method according to claim 1, wherein: In step (4), after receiving the GATE frame from the OLT, an ONU receives subsequent downstream data and, according to the instructions of the GATE frame, performs upstream transmission at the scheduled time according to the allocated bandwidth; at the end of the upstream data transmission, the ONU counts the amount of data that needs to be transmitted in the cache at this time, and sends the corresponding bandwidth requirement along with the REPORT frame to the OLT.

3. An optical access network bandwidth allocation system, based on the method according to any one of claims 1-2, characterized in that Includes the following modules: Query and recording module: Before the start of each polling cycle, the optical link terminal OLT checks whether each optical network unit (ONU) has been scheduled and can correspond to the uplink transmission of the current cycle and records it. At the same time, it checks whether each ONU has been scheduled and can correspond to the uplink transmission of the next cycle and records it, and calculates the expected polling cycle time of the current cycle. ONU determination module: In each polling cycle, the next ONU to be polled by the OLT is determined based on the ONU uplink and downlink overlapping working time and channel idle time caused by the ONU that was not polled in this cycle. Polling module: When the OLT polls an ONU, it arranges the upstream transmission of the ONU corresponding to the allocated bandwidth according to the occupied upstream channels, and allocates sleep time according to the scheduled upstream transmission start time of the ONU or the expected polling cycle time of this cycle; Report module: After receiving the GATE frame, the ONU performs upstream transmission and sleep according to the instructions, and reports the required bandwidth when the upstream data transmission is completed.

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