Conflict Resolution of Elastic Optical Switching Node Based on Inter Modes Crosstalk-avoidance
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摘要: 为了减少业务在少模光纤空分复用弹性光网络全光交换节点内资源冲突的概率,该文在全光分层节点结构中配置共享的有限频谱转换器与资源预留模块(LARSL),提出基于模式间串扰避免的空-频-时域联合资源冲突解决算法(LARSL-CACRA)。在空-频域,为LARSL-CACRA设计基于模式间串扰避免的滑动窗的模式-频谱资源块计算方法,使频谱冲突业务获得负载更均衡的模式-频谱资源块。对于仍然冲突的业务,LARSL-CACRA使用时域资源预留模块,进一步降低业务带宽阻塞率。仿真结果表明,该文设计的LARSL-CACRA可以改善交换节点带宽阻塞率,并减少业务平均时延。Abstract: For addressing the requests conflict in all-optical switching node of space-division multiplexing elastic optical network with few-mode fibers, an all-optical Layered Architecture based on Resource reservation module and Shared Limited-range spectrum converter (LARSL) is studied in the paper. First, a inter modes Crosstalk Avoidance-based on space, frequency and time domain combing resource Conflict Resolution Algorithm for LARSL (LARSL-CACRA) is put forward. Then, a calculation method for crosstalk-avoidance resource block using sliding window is designed to search the more balanced mode-spectrum resource black for the spectrum conflicted requests in the space-frequency domain. Moreover, a time domain resource reservation module is designed to reserve still conflicting requests to next scheduling time for further reducing the bandwidth blocking probability. Simulation result show that the proposed LARSL-CACRA can decrease node’s bandwidth blocking probability and can also reduce the cache delay.
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表 1 业务C冲突转换资源值计算结果
模式 LP01 LP21a LP21a LP11b LP11a 频谱块 [4,5] [6,7] [2,3] [6,7] [2,3] $R_{i,j}^r$ 3/2 3/20 1/5 5/4 6/5 表 2 LARSL-CACRA算法
输入:每个网络节点的LARSL端口数N,模式数M,预留时隙最大值L,串扰阈值TH,业务R(k, i, j),其中,k是业务的传输模式分组,
i和j分别是业务的起始和截止频隙索引值,设Tb=0, Dt=0,业务R的源和目的节点,LRSC的数量NL和转换范围CR,模式-频谱块值MS,
设空闲的模式-频谱块集合为$R_{I,J}^K$=0。输出:输出端口成功传输业务的R(k, i, j)值、业务的预留时隙和失败传输业务的带宽。 (1) 用最短路径算法为业务R计算一条从源节点到目的节点的最短跳数的路径,根据每个网络节点的LARSL上的模式分组和频谱块占用情
况,利用式(1)、式(2)、式(3)构造各路由中转节点输出端口的模式-频谱的串扰辅助图;并用首次适应算法为业务分配初始的空闲模式
和频谱块,使用式(1)、式(2)、式(3)更新串扰辅助图;(2) 若节点的路由表有多个业务争用LARSL中相同目的端口的相同模式-频谱块,或业务的目的端口的模式-频谱块已经被占用,转步骤(4);
否则,转步骤(3);(3) 若该光节点的模式-频谱分配后的串扰值满足式(4),记录节点的R(k, i, j)值,转步骤10;否则,初始的模式-频谱分配不可行,转步骤(4); (4) 若存在频谱冲突节点的LRSC数量NL为0,转步骤(7);否则,转步骤(5); (5) 在所有模式和LRSC的转换频谱范围CR内,分别进行上、下和左、右窗口滑动。若搜索到空闲的模式-频谱块,更新串扰辅助图,计算
将业务R分配该模式-频谱块的串扰值CV,若CV满足式(4),将该空闲的模式-频谱块资源标记为R(k, i, j),放入集合$R_{I,J}^K$中。如果还有
空闲的模式-频谱块没有搜索完,转步骤(5),否则,如果$R_{I,J}^K$为空,说明所有空闲的模式-频谱块的CV不满足式(4),转步骤(7),否则,
转步骤(6);(6) 在$R_{I,J}^K$资源块集合中,利用式(5)计算各模式-频谱资源块的$R_{i,j}^k$值,选择最小$R_{i,j}^k$值对应的空闲的模式-频谱块作为冲突业务R的目的
转换模式-频谱,令LRSC的NL值减1,记录R(k, i, j)信息,转步骤(10);(7) 进入时域资源预留模块,从第1个空闲时隙开始,依次轮询空闲时隙,执行步骤(2)—(7),找到第1个可用的空闲时隙Dt,记录资源R(k,
i, j)的模式-频谱值,根据式(6)更新TN,转步骤(8),否则,转步骤(9);(8) 若TN > L,转步骤9;否则,记录业务的R(k, i, j)和预留时隙Dt,令Tb增加Dt,若路由表中还有频谱冲突的节点,转步骤(2),否则,
转步骤(10);(9) 输出资源分配失败业务R的信息,阻塞该业务,LARSL-CACRA算法结束; (10) 输出成功传输业务R(k, i, j)的路由各节点的模式-频谱值、预留时隙Dt、空闲LRSC数目NL。 -
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