KR100952833B1 - An Allocation Method of Upstream Bandwidth for Guarantee Delay Criteria for EPON - Google Patents

Abstract

The present invention is an uplink in an optical network unit (ONU) that receives a packet from a subscriber station in an EPON (Ethernet Passive Optical Network), stores it in an input queue, moves it to the transmission queue, and transmits it to an optical line terminal (OLT). In the transmission band allocation method, the maximum transmission band (W _MAX ) of the transmission queue allocated from the OLT is a voice traffic-maximum transmission band (W _CBR ) for storing first priority traffic, and second and third priority. Dividing into non-voice traffic-maximum transmission bands (W _NCBR ) for traffic storage; The packet transmitted from the subscriber station is classified into a first priority traffic, a second priority traffic, and a third priority traffic according to priority, and the first priority traffic is classified into voice traffic-maximum transmission band of the transmission queue. Storing the second and third priority traffic in the input queue, respectively; And a third step of storing second and third priority traffic stored in the input queue in a non-voice traffic-maximum transmission band of the transmission queue.

According to the present invention, the voice due to non-voice traffic is preferentially stored in the voice traffic-maximum transmission band of the maximum transmission band of the transmission queue directly without storing the voice / T1 emulation traffic transmitted from the subscriber station in the input queue. There is an effect of preventing the relative uplink transmission delay of the traffic.

EPON, ONU, OLT, Uplink Traffic, Transmission Bandwidth Assignment, Priority Class, 2nd Stage Queue

Description

An Allocation Method of Upstream Bandwidth for Guarantee Delay Criteria for EPON             

1 is a configuration diagram of a general EPON,

2 is a structural diagram of a two-stage queue having N priority buffers in general;

3A is a structural diagram of a two-stage queue having multiple priority classes according to the present invention;

3B is a configuration diagram of an EPON between the OLT and the plurality of ONUs in FIG. 3A;

4 is a flowchart of a method for allocating an uplink transmission band from an ONU to an OLT according to the present invention.

※ Explanation of code about main part of drawing ※

500: Optical Line Terminal (OLT)

600: Optical Network Unit (ONU)

20: input queue,

22: transmission queue,

24: Traffic Classifier                 

26: first virtual buffer,

28: second input buffer,

30: third input buffer.

The present invention relates to an uplink transmission band allocation method in an Ethernet passive optical communication network (EPON), and more particularly, to an uplink transmission band allocation method from an optical subscriber network device (ONU) to an optical fiber termination device (OLT).

The Ethernet Passive Optical Network (EPON) is called passive instead of expensive active components to provide fiber-based high-speed communications services to businesses, SOHOs, and homes. A network constructed using passive components.

1 is a configuration diagram of a general EPON.

The EPON is divided into FTTH (100, Fiber To The Home), FTTB (200, Fiber To The Building), FTTC (300, Fiber To The Corner), and FTTCab (400) according to the location where the terminal is processed. EPON consists of one optical fiber terminal device (500, Optical Line Terminal, hereinafter OLT) and a number of optical subscriber network devices (600, Optical Network Unit, hereinafter, ONU) installed near the subscriber, Typically up to 32 ONUs are connected to one OLT. Packets transmitted from the ONUs 600 are concentrated in the splitter / coupler 700 and then forwarded to the OLT.

The OLT 500 is located in a central office (CO) connected to an end of the Internet, and transmits a packet transmitted from each ONU 600 to another network, to each ONU 600 in a polling manner. Allocates a transmission band.

The ONU 600 is a device for receiving the FTTH (100), FTTB (200), FTTC (300), FTTCab (400) and the like to connect the cable and optical facilities for transmitting the electrical signal of the subscriber station, the subscriber station It provides an interface between the data, video, voice service network and the OLT 500, and is responsible for converting an optical signal into an Ethernet signal, an IP multicast signal, a Plane Old Telephone System (POTS), and a TDM signal.

The branching / combining device 700 splits the packet transmitted from the single optical line on the OLT 500 side into a plurality of optical lines downward and delivers the packet to each ONU 600, and from the multiple optical lines on each ONU side. The forwarded packets are combined upward into a single optical line and forwarded to the OLT.

In this EPON, when the ONU transmits a packet to the OLT (uplink traffic transmission), a time division multiple access (TDMA) scheme in which several ONUs share a single uplink wavelength is mainly used. In this time division multiple access scheme, the OLT uses a fixed bandwidth allocation scheme in which the OLT fixedly limits the maximum transmission band of each ONU, or the ONU receiving the grant signal from the OLT receives the next grant signal. An interleaved polling scheme such as Dynamic Bandwidth Allocation is used to notify the ONU of its maximum transmission band.

In the interleaved polling scheme, the OLT alternately transmits a polling message to each ONU. These polling schemes equally distribute the transmission bands to each OLT by preventing a single ONU from monopolizing the entire allocation band and giving polling opportunities to each ONU.

However, if one ONU occupies most of the entire polling period, the remaining ONUs are not allocated a transmission band, so that other ONUs do not have the opportunity to transmit packets. In order to compensate for this, a limited service scheme that limits the maximum transmission band (maximum transmission window) that each ONU can transmit and transmits the packet as much as the maximum transmission band to the OLT during a polling period given to the ONU.

The prior art related to the maximum transmission band of the ONU is a one-step queue method in which traffic transmitted from a subscriber station is directly stored in a transmission queue and transmitted to an OLT, and traffic transmitted from the subscriber station is sequentially transmitted to an input queue and a transmission queue. It is divided into two-step queue method that is stored and transmitted to OLT.

2 is a structural diagram of a two-stage queue having N priority buffers in general. The input queue 20 is a priority queue for storing packets transmitted from the subscriber terminal, and the transmission queue 22 is a first come first service (FCFS) that processes the packets transmitted from the input queue 20. to be.

When the time slot arrives from the OLT 500 to the ONU 600, the packet stored in the transmission queue 22 of the ONU is transmitted to the OLT, and the packet stored in the input queue 20 is empty while the transmission queue is empty. Fill in the empty space of the transmission queue. When the timeslot ends, the ONU reports the occupancy of the transmission queue to the OLT in order to be allocated the corresponding slot size in the next cycle.

In the upstream transmission of traffic from ONU to OLT, OLT adjusts the transmission schedule between each ONU by using adaptive polling. This adaptive polling method, also called dynamic cycle based polling, is a method of adaptively determining a band allocated to each ONU and collecting packets in a predetermined order in order to efficiently use a limited transmission band. When the OLT transmits a grant signal to the ONU to allow data transmission, the ONU transmits to the OLT a packet corresponding to the window size (W _MAX ) of the maximum transmission band of the transmission queue. During this process, the ONU continuously receives new packets from the subscriber station.

This two-step queue method uses the one-step queue method because the ONU does not require the OLT to have a slot larger than the window size of its maximum transmission band, and traffic from the subscriber station must wait in the input queue and the transmission queue. The delay of the traffic is increased.

Therefore, the conventional two-stage queue method has a problem in that the transmission performance of high-priority traffic (voice and video) requiring real time transmission cannot be guaranteed due to such delay of traffic.

An object of the present invention for solving the problems of the prior art as described above, when uplink transmission using the two-step queue method in the ONU, priority traffic such as voice traffic is preferentially stored in the transmission queue without passing through the input queue, The present invention provides an uplink transmission band allocation method for storing non-voice traffic in the remainder of the maximum transmission band of a transmission queue.

In order to achieve the above object, the present invention provides an ONU for receiving a packet from a subscriber station in an EPON (Ethernet Passive Optical Network), storing the packet in an input queue, and then moving the packet to an OLT (Optical Line Terminal). An uplink transmission band allocation method in an optical network unit, comprising: a maximum transmission band (W _MAX ) of the transmission queue allocated from the OLT and a voice traffic-maximum transmission band (W _CBR ) for first priority traffic storage; A first step of dividing into a non-voice traffic-maximum transmission band (W _NCBR ) for storing second and third priority traffics; The packet transmitted from the subscriber station is classified into a first priority traffic, a second priority traffic, and a third priority traffic according to priority, and the first priority traffic is classified into voice traffic-maximum transmission band of the transmission queue. Storing the second and third priority traffic in the input queue, respectively; And a third step of storing second and third priority traffic stored in the input queue in a non-voice traffic-maximum transmission band of the transmission queue.

In addition, the voice traffic-maximum transmission band (W _CBR ) provides an uplink transmission band allocation method, characterized in that for estimating and setting the amount of the first priority traffic to be additionally arrived from the subscriber station.

In the third step, the second and third priority traffics stored in the input queue are sequentially stored in the non-voice traffic-maximum transmission band of the transmission queue in the order of priority and first input. An uplink transmission band allocation method is provided.

Hereinafter, a method of allocating an uplink transmission band in an ONU of an EPON according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3A is a structural diagram of a two-stage queue with multiple priority classes in accordance with the present invention. This two-stage queue includes an input queue 20, a transmission queue 22, and a traffic classifier 24.

The input queue 20 of the ONU 600 includes a first virtual buffer 26, a second input buffer 28, and a third input buffer 30. Among these, the first virtual buffer 26 is a virtual buffer that does not exist, and the second input buffer 28 and the third input buffer 30 are real buffers.

The transmission queue 22 adaptively varies the maximum transmission band (W _MAX ) for each polling period, and the maximum transmission band is the voice traffic-maximum transmission band (W _CBR ) and the non-voice traffic-maximum transmission band (W _NCBR ). Divided by. A method of dividing the maximum transmission band of the transmission queue into a voice traffic-maximum transmission band and a non-voice traffic-maximum transmission band will be described later.

The traffic classifier 24 classifies the packets transmitted from the subscriber station according to the priority. The traffic classifier 24 classifies the three types of traffic according to the priority, so that voice, video, and data traffic can be classified into three classes of services (Cos; Class of Services) of the DiffServ, that is, Expedited Forwarding (EH) and Assured Forwarding (AF). ) And BE (Best-effort) can be easily mapped to the OLT.

In the present invention, the first virtual buffer 26 of the input queue 20 is only shown to help the understanding of the present invention, and is not a substantial input buffer for storing traffic transmitted from the subscriber station. That is, after the traffic classification, the voice traffic having the highest priority P1 and the T1 emulation traffic (T1 Emulation) are the voice traffic-maximum transmission band W of the maximum transmission band of the direct transmission queue 22 after the traffic classification. _CBR ) is stored prior to other traffic.

The second input buffer 28 stores video traffic having a priority P2 following the voice traffic and the T1 emulation traffic, and the data traffic having the lowest priority P3 is stored in the third input buffer 30. Stored. The video traffic and the data traffic stored in the second and third input buffers are sequentially stored in the non-voice traffic-maximum transmission band W _NCBR of the transmission queue 22.

The ONU stores the traffic transmitted from the input queue 20 in the transmission queue 22 and transmits the grant signal to the OLT when a grant signal according to the polling policy of the OLT is applied.

In the transmission queue 22, a maximum transmission band (W _MAX [i]) is set according to the polling policy of the OLT. In the present invention, voice traffic and non-voice traffic are stored in the maximum transmission band, respectively, and then transmitted to the OLT. do. To this end, the maximum transmission band is divided into a voice traffic-maximum transmission band (W _CBR ) and a non-voice traffic-maximum transmission band (W _NCBR ).

Therefore, the relationship W _MAX = W _CBR + W _NCBR is satisfied. The ONU establishes its transmission band by exchanging W _MAX with the OLT and / or neighboring ONUs. The ONU then sets W _CBR by predicting the amount of speech traffic expected to arrive further until the next grant signal is applied. Then, the remaining W _CBR is allocated to W _MAX as W _NCBR . In addition, according to the polling policy of the OLT, the maximum transmission band (W _MAX ) of the ONU is reset at each polling period. Accordingly, the voice traffic-maximum transmission band (W _CBR ) and the non-voice traffic-maximum transmission band (W C) are reset. _NCBR ) is also reset.

Hereinafter, a method of allocating the maximum transmission band, voice traffic-maximum transmission band, and non-voice traffic-maximum transmission band of the transmission queue will be described in detail.

FIG. 3B is a configuration diagram of an EPON between the OLT and the plurality of ONUs in FIG. 3A.

If the maximum transmission band (W _MAX [i], maximum transmission window) of the transmission queue 22 accommodates all voice traffic transmitted from the subscriber station, it is sufficient to set a large voice traffic-maximum transmission band of the maximum transmission band. In this case, the ONU increases the number of voice traffic transmitted to the timeslot as long as the OLT is applied. However, the polling period becomes longer according to the timeslot processing. Therefore, the waiting time for the next polling period becomes longer and the delay limit is exceeded. Occurs. Therefore, it is necessary to set this maximum transmission band appropriately.

In the kth transmission transmission cycle of the OLT, ONU sets the maximum transmission band (W _MAX [i] [k]) and the maximum voice traffic-maximum transmission band (W _CBR [i] [k]) and the non-voice traffic-maximum of the transmission queue. A method of determining the transmission band W _NCBR [i] [k] will be described in detail.

C [k] is the total length of the kth cycle time, that is, the transmission time and guardband time from ONU _i to ONU _N , and W [i] [k] and C [i] [k] are k respectively. It is called the required window size of ONU _i and the corresponding transmission time in the first cycle, and _WNCBR [i] [k] is the ONU in the kth cycle for traffic (P2, P3) excluding the highest priority traffic (P1). _{Let i} be the window size you need to request.

We _assume that the maximum required window for this non-voice traffic transmission is W _NCBR (W _NCBR [i] [k] ≤ W _NCBR ), assuming that the same applies to all ONUs and cycles to maintain fairness, B [ i] is the interframe gap between ONU _i and ONU _{i + 1} , i.e. the guardband. Then kth cycle time C [k] is C [k] = (C [1] [k] + B [1]) + (C [2] [k] + B [2]) +... It satisfies the relationship + (C [N] [k] + B [N]).

W _CBR [i] [k] is the ranging time T = [(B [i] + C [i + 1] [k-1]) + (B [i + 1] + C [i + 2) ] [k-1]) +… + (B [N] + C [1] [k]) + (B [1] + C [2] [k]) +... + (B [i-1] + C [i] [k])] for CBR traffic, which is the voice traffic P1 expected to arrive at the input queue 20 of ONU _i . That is, voice traffic-maximum transmission band for voice traffic that is expected to arrive in its input queue during the ranging time that combines the total transmission time of ONUs transmitting traffic to the same OLT and the guard band time between each ONU. It can be set.

Then, W _NCBR [i] [k] _arrives at the second input buffer 28 and the third input buffer 30 during this ranging time T after the k-1th polling of ONU _i is completed. It is the amount of packets, and this amount is transmitted to the transmission queue 22 of ONU _i according to the priority until the maximum W _NCBR . During this time, the highest priority traffic P1 is stored in the transmission queue as soon as it arrives at the input queue 20.

Traffic stored in the transmission queue is transmitted to the OLT according to the polling scheduling of the OLT.

4 is a flowchart of a method for allocating an uplink transmission band from an ONU to an OLT according to the present invention.

First, an input buffer for storing a packet transmitted from a subscriber station is configured in the input queue 20 (S400). A first priority traffic (voice traffic, T1 emulation traffic) has a video traffic having a priority P2 following. A second input buffer 28 to be stored and a third input buffer 30 to store data traffic having the lowest priority P3 are configured.

The ONU 600 sets the maximum transmission band W _{MAX of the} transmission queue 22 by exchanging information with the OLT 500 and / or neighboring other ONUs. Then, the maximum transmission band (W _MAX) voice traffic - the maximum transmission band (W _CBR) and non-voice traffic. This sets the maximum transmission band (W _NCBR) (S402) end groups one weeks of polling in accordance with the scheduling of the OLT, The maximum transmission band of the transmission queue is reset, and thus the voice traffic-maximum transmission band and the non-voice traffic-maximum transmission band are also reset.

The traffic classifier 24 classifies the packets transmitted from the subscriber station into the three classes, and transmits the non-voice traffic to the second input buffer 28 and the third input buffer 30 of the input queue 20, respectively. (S404)

First, the ONU stores the voice traffic having the highest priority P1 and the T1 emulation traffic in the voice traffic-maximum transmission band of the maximum transmission band of the transmission queue (S406).

Then, the video traffic stored in the second input buffer 28 is stored in the non-voice traffic-maximum transmission band of the maximum transmission band of the transmission queue (S408). If the traffic-maximum transmission band stores all the video traffic of the second input buffer and there is extra space, the data traffic of the third input buffer 30 is stored (S410, S412).

If, in step S410, the video traffic of the second input buffer cannot be stored in the non-voice traffic-maximum transmission band of the maximum transmission band of the transmission queue, the remaining video traffic is transmitted from the subscriber station in the current polling period. The video traffic is temporarily stored in the second input buffer and then stored in the non-voice traffic-maximum transmission band of the transmission queue in the next polling period (S414).

In addition, after storing the video traffic in the non-voice traffic-maximum transmission band of the maximum transmission band of the transmission queue in step S412, if all of the data traffic of the third input buffer cannot be stored, the remaining data traffic and the current data are stored. The data traffic transmitted from the subscriber station is temporarily stored in the third input buffer in the polling period, and then stored in the non-voice traffic-maximum transmission band of the transmission queue in the next polling period (S416 and S418).

The above process is performed during the polling period of the ONU according to the polling policy of the OLT. The voice, video, and data traffic stored in the voice traffic-maximum transmission band and the non-voice traffic-maximum transmission band of the maximum transmission band of the transmission queue are respectively Upon receiving a grant signal from the OLT, the ONU sends the traffic to the OLT.

While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all such changes, modifications or adjustments.

 As described above, according to the present invention, the voice / T1 emulation traffic transmitted from the subscriber station is stored in the voice traffic-maximum transmission band of the maximum transmission band of the transmission queue directly, without storing the voice / T1 emulation traffic in the input queue. There is an effect of preventing the relative uplink transmission delay of the voice traffic.

In addition, by setting the non-voice traffic-maximum transmission band of the maximum transmission band of the transmission queue and sequentially storing the video traffic and the data traffic, there is an effect of reducing the unfairness of the non-voice traffic according to the priority.

Claims (5)

Uplink bandwidth allocation in the Optical Network Unit (ONU), which receives packets from subscriber terminals in EPON (Ethernet Passive Optical Network), stores them in the input queue, moves them to the transmission queue, and transmits them to the optical line terminal (OLT). In the method, The maximum transmission band (W _MAX ) of the transmission queue allocated from the OLT is set to a voice traffic-maximum transmission band (W _CBR ) for storing first priority traffic, and a non-voice traffic for storing second and third priority traffic. A first step of dividing by the maximum transmission band (W _NCBR ); The packet transmitted from the subscriber station is classified into a first priority traffic, a second priority traffic, and a third priority traffic according to priority, and the first priority traffic is classified into voice traffic-maximum transmission band of the transmission queue. Storing the second and third priority traffic in the input queue, respectively; And A third step of storing second and third priority traffic stored in the input queue in a non-voice traffic-maximum transmission band of the transmission queue; Uplink bandwidth allocation method comprising a. The method of claim 1, The voice traffic-maximum transmission band (W _CBR ) is configured to estimate and set the amount of the first priority traffic to be additionally arrived from the subscriber station. The method of claim 1, The third step, And sequentially storing the second and third priority traffic stored in the input queue in a non-voice traffic-maximum transmission band of the transmission queue in order of priority and first input. The method of claim 1, And the first priority traffic is voice traffic and T1 emulation traffic, the second priority traffic is video traffic, and the third priority traffic is data traffic. delete

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