CN104301258A - Uplink wavelength and bandwidth allocation method in TWDM PON system - Google Patents

Abstract

The invention discloses an uplink wavelength and bandwidth allocation method in a TWDM PON system. For supporting different types of QoS, the TWDM PON system can support four types of traffic containers (T-CONT), wherein T-CONT1 corresponds to fixed bandwidth allocation, wavelength is allocated to optical network units (ONU) in turn; T-CONT2 corresponds to bandwidth allocation guarantee, bandwidth allocation based on prediction is adopted, and the wavelength corresponding to the type of the T-CONT1 is allocated; T-CONT3 does not have any requirement for time delay, and the authorized bandwidth of the T-CONT3 is the required bandwidth, wherein according to the wavelength allocation principle, four wavelengths are divided into a high-load set and a low-load set according to load rates, and the wavelengths belonging to the low-load set are allocated to the T-CONT3; the authorized bandwidth of T-CONT4 is also the required bandwidth, and the wavelength with the lowest load rate is always chosen. According to the uplink wavelength and bandwidth allocation method in the TWDM PON system, the frequency of wavelength modulation of each ONU can be reduced, the bandwidth utilization rate of the wavelengths is increased, and transmission delay is reduced.

Description

Upstream wavelengths band bandwidth allocation method in a kind of TWDM PON system

Technical field

The present invention is a kind of upstream wavelengths band bandwidth allocation method in TWDM PON system, relates to the technical field of broadband access network aspect.

Background technology

The feature of XG-PON technology is that up direction supports that 40Gbps, down direction support 10Gbps, and be considered to Future Access Network technology primary solutions, TWDM PON is the main way of realization of XG-PON.TWDM PON is made up of an optical line terminal (OLT) and multiple optical network unit (ONU), respectively has 4 wavelength to transmit at up-downlink direction.OLT has a reception/transmitter that can receive and send multiple wavelength.ONU have one can be modulated to tunable receiver that the tunable reflector of in up 4 wavelength any 1 and one can receive in descending 4 wavelength any 1.

XG-PON is a kind of bandwidth synthesis Access Network, and in the uplink direction of XG-PON, multiple ONU shares transmission channel.Along with the development of various high bandwidth requirements business, user also will increase bandwidth demand, therefore how according to the type of service of user and demand reasonable distribution channel width particularly important, the effect of dynamic wavelength allocated bandwidth (DWBA) is exactly the control and management to system uplink transfer of data.[M.S.Han, " Performance Evaluation of Dynamic Bandwidth Allocation Algorithm for TWDM PON ", JCIT, vol.8, no.13, pp.282-288,2013.] the TWDM PON system proposed in define only a kind of grade of service.But TWDM PON, in order to support QoS, must can support multiple business grade.

The research of DWBA method has had a lot, document [A.Dixit, B.Lannoo, D.Colle, M.Pickavert, and P.Demeester, " Dynamic Bandwidth Allocation with Optimal Wavelength Switching in TWDM-PONs ", 15th International Conference on Transparent Optical Networks (ICTON), pp.1-4, 2013.] the DWBA method that can reduce Laser Modulation time overhead is proposed, document [Abhishek Dixit, Bart Lannoo, Didier Colle, Mario Pickavet, and Piet Demeester, " Trade-off between End-to-End Reliable and Cost-Effective TDMA/WDM Passive Optical Networks ", 4th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops, pp.691-697, 2012.] propose a kind of protection and be connected the TWDM PON system with reliability.But wherein great majority are based on traditional E PON system.EPON and XG-PON has different in many aspects.First EPON is an asynchronous system, and XG-PON is a synchro system; Secondly, XG-PON can split Frame, and EPON is not all right.Therefore, the TWDM PON system based on XG-PON can not be directly used in based on the DWBA method of the TWDM PON system of EPON.

Summary of the invention

Technical problem to be solved by this invention is to overcome in prior art, ONU in a polling cycle frequent modulation different wave length and the wavelength utilance that causes low, postpone large problem, a kind of wavelength bandwidth distribution method supporting QoS in TWDM PON system is provided, to the different wavelength bandwidth distribution method of data acquisition of every type, reduce the number of times of each ONU modulation wavelength, improve the bandwidth availability ratio of each wavelength, reduce transmission delay.

Specifically there are following steps:

(1) carry out wavelength bandwidth distribution to the T-CONT1 type in each ONU, for T-CONT1, its bandwidth is all fixed allocation at every turn, all ONU ₁, ONU ₂..., ONU _ntake wavelength in turn successively;

(2) distribute the wavelength bandwidth of T-CONT2 in each ONU, T-CONT2 adopts the allocated bandwidth based on prediction, distributes the wavelength the same with the T-CONT1 type of affiliated ONU as far as possible;

(3) wavelength and the bandwidth of the T-CONT3 type in each ONU is distributed, its mandate bandwidth is exactly bandwidth on demand, when distributing wavelength for T-CONT3, the load factor of 4 wavelength is sorted from low to high, lower two wavelength of load belong to low load group, higher two wavelength of load belong to high capacity group, by the Wavelength Assignment of low load group to T-CONT3; When the wavelength that T-CONT1, T-CONT2 of this ONU use belongs to low load group, T-CONT3 preferentially uses this wavelength;

(4) distribute wavelength and the bandwidth of the T-CONT4 type in each ONU, its mandate bandwidth is exactly bandwidth on demand; In order to the load factor of each bar wavelength of equilibrium, select the wavelength that load factor is minimum at every turn.

TWDMPON respectively has 4 wavelength to transmit at up-downlink direction, 4 wavelength of up direction respectively: λ ₀, λ ₁, λ ₂, λ ₃.OLT has a reception/transmitter that can receive and send multiple wavelength.ONU have one can be modulated to tunable receiver that the tunable reflector of in up 4 wavelength any 1 and one can accept in descending 4 wavelength any 1.

In order to support QoS, suppose that TWDM PON system supports the business container (T-CONT) of 4 types.Each ONU has 4 queues to correspond to T-CONT1,2,3,4 respectively.Each queue has one to distribute indications (AllocID).The corresponding fixed-bandwidth of T-CONT1 distributes, and delay requirement is tightly controlled.T-CONT2 correspondence ensures allocated bandwidth, and the bandwidth demand namely in particular range can be met but there is a fixed response time, for VoIP, VOD service.T-CONT3 provides and guarantees that bandwidth sum is non-and guarantee bandwidth, has the constraint with maximum bandwidth of guaranteeing of minimum bandwidth simultaneously, and being applicable to not only needs service guarantees to require simultaneously but also have the business of larger burst flow.The feature of T-CONT4 is without Bandwidth guaranteed, and the congestion condition of system directly affects the distribution of bandwidth, is applicable to the business not high to packet loss, delay time and jitter requirement.

The bandwidth of T-CONT1 is fixed allocation, simultaneously for avoiding the situation of the up wavelength load imbalance of appearance 4, so ONU ₁, ONU ₂..., ONU _ntake wavelength X in turn successively ₀, λ ₁, λ ₂, λ ₃(N is ONU quantity).T-CONT2 correspondence ensures allocated bandwidth, the business of the type has certain requirement to time delay, in order to avoid the risk that the time that the data in same ONU are modulated because frequent modulation produces causes time delay excessive, require that T-CONT2 distributes the wavelength the same with the T-CONT1 type of affiliated ONU as far as possible.And, because the polling mechanism between OLT and ONU can make ONU produce the stand-by period, if when newly having arrived mass data and be not reported to OLT within the ONU stand-by period, these data can only wait until that next polling cycle just can be sent out, therefore also network delay can be increased, so adopt the allocated bandwidth based on prediction for T-CONT2.Because QoS does not have delay requirement for T-CONT3, while the utilization ratio in order to improve every bar wavelength, requiring the wavelength that uses during transmission T-CONT3 as far as possible and transmitting T-CONT1,2 consistent.Therefore, when distributing wavelength to T-CONT3, the load factor of 4 wavelength sorted from low to high, lower two wavelength of load belong to low load group, and higher two wavelength of load belong to high capacity group.When the T-CONT1 of this ONU, the wavelength of 2 uses belong to low load group, T-CONT3 also uses this wavelength; When wavelength belongs to high capacity group, that wavelength that T-CONT3 working load is minimum.T-CONT4 is applicable to the business not high to packet loss, delay time and jitter requirement, and therefore T-CONT4 selects the wavelength that load factor is minimum at every turn, the load factor of balanced each bar wavelength.

Compared to existing technology, the present invention has following beneficial effect:

(1) Wavelength allocation method that the present invention proposes have employed the way that Static and dynamic combines, and not only reduces the number of times of wavelength-modulated in an ONU, reduces propagation delay time, and makes each wavelength can load balancing.

(2) the present invention is for the data of T-CONT2, adopts the method for predicting based on history, the buffered data of ONU is reflected in claim frame in real time, reduces propagation delay time.

Accompanying drawing explanation

Fig. 1 is the wavelength bandwidth distribution method that each data type of the present invention adopts.

Fig. 2 is the predictive bandwidth allocation method for T-CONT2 based on polling mechanism definition of the present invention.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in detail:

Step 1: wavelength bandwidth distribution is carried out to the T-CONT1 type in each ONU.Data bandwidth due to the type is fixed distribution, therefore only need consider Wavelength Assignment.In order to avoid there is the situation of wavelength load imbalance, up 4 wavelength distribute to each ONU in turn, and 4 wavelength are numbered m=0,1,2,3, represent when cycle n, ONU _it-CONT1 be assigned to wavelength numbering.

Step 2: the wavelength bandwidth of distribution T-CONT2.Because T-CONT2 is defined as guarantee bandwidth, do not distribute fixed-bandwidth, and have strict restriction to delay requirement.As shown in Figure 2, large quantities of data can wait for during this period of time in arrival, in order to ensure that claim frame can reflect the buffered data in ONU in real time, need to predict T-CONT2.

$M_{i,n-k}=\frac{1}{k}\underset{n-k}{\overset{n-1}{\mathrm{\Σ}}}{Q}_{i,n}^{T-\mathrm{CONT}2},n=\mathrm{1,2},...,k=\mathrm{1,2},...---\left(1\right)$

${\mathrm{\ΔQ}}_{i,n}^{T-\mathrm{CONT}2}=Q_{i,n}^{T-\mathrm{CONT}2}-Q_{i,n-1}^{T-\mathrm{CONT}2}---\left(2\right)$

$P_{i,n}^{T-\mathrm{CONT}2}=M_{i,n-k}+{\mathrm{\α}}_1{\mathrm{\ΔQ}}_{i,n-1}^{T-\mathrm{CONT}2}+{\mathrm{\α}}_2{\mathrm{\ΔQ}}_{i,n-2}^{T-\mathrm{CONT}2}+...+{\mathrm{\α}}_k{\mathrm{\ΔQ}}_{i,n-k}^{T-\mathrm{CONT}2}---\left(3\right)$

in cycle n, ONU _ithe data received within the stand-by period, M _{i, n-k}oNU in k the cycle before cycle n _ithe mean value of the data received within the stand-by period, be with difference, be prediction in cycle n, ONU _ithe data received within the stand-by period, α ₁, α ₂... α _kit is weight.[Zhang Qi-yu, Li Bin, Wu Run-ze, " A Dynamic Bandwidth Allocation Scheme for GPON Based on Traffic Prediction ", 9th International Conference on Fuzzy Systems and Knowledge Discovery (FSKD2012), pp.2043-2046,2012.] through experimental verification in, k=4, weight is respectively 0.4,0.3,0.2,0.1 has good predictability.Therefore the bandwidth licensing to the T-CONT2 of this ONU is at cycle n, ONU _ithe T-CONT2 data in buffer are stored in.

For the Wavelength Assignment of T-CONT2, the wavelength identical with T-CONT1 should be used, unless the remaining bandwidth of this wavelength is not enough to the bandwidth requirement ensureing T-CONT2 as far as possible.Suppose that F (m) represents at this cycle medium wavelength λ _mthe bandwidth that residue can be distributed.After distributing T-CONT1 type, if then ${\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}2}={\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}1},$ Otherwise ${\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}2}=\max \{F\left(0\right),F\left(1\right),F\left(2\right),F\left(3\right)\}.$

Step 3: the wavelength of distribution T-CONT3 type and bandwidth.T-CONT3 provides and guarantees that bandwidth sum is non-and guarantee bandwidth, have the constraint with maximum bandwidth of guaranteeing of minimum bandwidth simultaneously, not only need service guarantees to require simultaneously but also have the business of larger burst flow, the therefore inapplicable flux prediction model of T-CONT3 type, the bandwidth of mandate $G_{i,n}^{T-\mathrm{CONT}3}=R_{i,n}^{T-\mathrm{CONT}3}.$

For the Wavelength Assignment of T-CONT3 type, the present invention proposes 4 wavelength to be divided into two groups, G by load factor height _lfor two wavelength that load is lower, G _hfor two wavelength that load factor is higher.After distributing T-CONT1,2 types, in order to the load factor of the every bar wavelength of equilibrium, if and then ${\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}3}={\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}2},$ If $G_{i,n}^{T-\mathrm{CONT}3}\≤F\left({\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}2}\right)$ But ${\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}2}\∈G_H,$ In order to make wavelength load balancing, ${\mathrm{\λ}}_{i,n}^{T-\mathrm{CONT}3}=\max \{F\left(0\right),F\left(1\right),F\left(2\right),F\left(3\right)\}.$

Step 4: bandwidth Wavelength Assignment is carried out to T-CONT4 type.The feature of T-CONT4 is without Bandwidth guaranteed, and the congestion condition of system directly affects the distribution of bandwidth.The bandwidth authorizing of T-CONT4 type directly according to request, therefore $G_{i,n}^{T-\mathrm{CONT}4}=R_{i,n}^{T-\mathrm{CONT}4}.$

For the Wavelength Assignment of T-CONT4 type, more consideration wavelength utilance problem.Therefore, the wavelength at every turn distributing to T-CONT4 is all the wavelength that present load rate is minimum,

From above wavelength bandwidth assigning process, the dynamic wavelength bandwidth allocation methods with QoS support of the present invention's proposition effectively can reduce delay, under the prerequisite of each wavelength load balancing, improves the bandwidth availability ratio of wavelength.

Claims (1)

1. the upstream wavelengths band bandwidth allocation method in TWDM PON system, is characterized in that there are following steps:

(1) carry out wavelength bandwidth distribution to the T-CONT1 type in each ONU, for T-CONT1, its bandwidth is all fixed allocation at every turn, all ONU ₁, ONU ₂..., ONU _ntake wavelength in turn successively;

(2) distribute the wavelength bandwidth of T-CONT2 type in each ONU, T-CONT2 adopts the allocated bandwidth based on prediction, distributes the wavelength the same with the T-CONT1 type of affiliated ONU as far as possible;

(3) wavelength and the bandwidth of the T-CONT3 type in each ONU is distributed, its mandate bandwidth is exactly bandwidth on demand, when distributing wavelength for T-CONT3, the load factor of 4 wavelength is sorted from low to high, lower two wavelength of load belong to low load group, higher two wavelength of load belong to high capacity group, by the Wavelength Assignment of low load group to T-CONT3; When the wavelength that T-CONT1, T-CONT2 of this ONU use belongs to low load group, T-CONT3 preferentially uses this wavelength;

(4) distribute wavelength and the bandwidth of the T-CONT4 type in each ONU, its mandate bandwidth is exactly bandwidth on demand; In order to the load factor of each bar wavelength of equilibrium, select the wavelength that load factor is minimum at every turn.