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水下無線傳感網(wǎng)絡(luò)中一種地理-機(jī)會的混合路由
2017年電子技術(shù)應(yīng)用第1期
唐偉萍1,劉桂英2
1.廣西電力職業(yè)技術(shù)學(xué)院 汽車與交通系,廣西 南寧530007;2.廣西師范學(xué)院 職業(yè)技術(shù)教育學(xué)院,廣西 南寧530001
摘要: 為了提高水下無線傳感網(wǎng)絡(luò)(UWSNs)的數(shù)據(jù)采集效率,提出基于地理-機(jī)會的水下無線傳感網(wǎng)的混合路由(GOHR)。當(dāng)源節(jié)點(diǎn)需要轉(zhuǎn)發(fā)數(shù)據(jù)包時,首先計(jì)算候選轉(zhuǎn)發(fā)節(jié)點(diǎn)集,并依據(jù)集內(nèi)節(jié)點(diǎn)的歸一化權(quán)重進(jìn)行排序,形成轉(zhuǎn)發(fā)簇;然后分析每個簇的期望權(quán)重值;最終由最大期望權(quán)重值的簇內(nèi)節(jié)點(diǎn)轉(zhuǎn)發(fā)數(shù)據(jù)包。同時,引用時延機(jī)制,抑制冗余數(shù)據(jù)包。仿真結(jié)果表明,提出的GOHR協(xié)議提高了數(shù)據(jù)包傳遞率,降低了數(shù)據(jù)包傳輸時延。
中圖分類號: TP393
文獻(xiàn)標(biāo)識碼: A
DOI:10.16157/j.issn.0258-7998.2017.01.030
中文引用格式: 唐偉萍,劉桂英. 水下無線傳感網(wǎng)絡(luò)中一種地理-機(jī)會的混合路由[J].電子技術(shù)應(yīng)用,2017,43(1):114-117.
英文引用格式: Tang Weiping,Liu Guiying. A geographic-opportunistic hybrid routing for underwater wireless sensor networks[J].Application of Electronic Technique,2017,43(1):114-117.
A geographic-opportunistic hybrid routing for underwater wireless sensor networks
Tang Weiping1,Liu Guiying2
1.Department of Automotive and Transportation,Guangxi Electric Power Institute of Vocational Training,Nanning 530007,China; 2.Institute of Vocational Education,Guangxi Terchers Education University,Nanning 530001,China
Abstract: To improve the data collection in underwater wireless sensor networks(UWSNs), a geographic and opportunistic hybrid routing(GOHR) is proposed in this paper, which is marked as GOHR. In GOHR, source node determines the neighbors candidate set, which is ordered by normalized advance metric, forming neighbors candidate clustering. Then, it computes the Expected Packet Advanced(EPA) of each cluster, and the cluster with the highest EPA is selected as the next-hop forwarder. In order to void collision in forwarding packet, the time-delay mechanism is adopted. Simulation results show that GOHR protocol has a good performance in terms of packet delivery ratio and end-to-end delay.
Key words : underwater wireless sensor networks;geographic routing;opportunistic routing;acoustic communication;neighbors candidate set;clustering

0 引言

    聲通信已成為水下傳感網(wǎng)絡(luò)(Underwater Wireless Sensor Networks,UWSNs)[1]的唯一有效的通信方式。通過傳感節(jié)點(diǎn)實(shí)時地收集海洋數(shù)據(jù),實(shí)現(xiàn)監(jiān)測海洋目的[2]。據(jù)此,路由協(xié)議已成為UWSNs的研究重點(diǎn)。

    研究人員對UWSNs已進(jìn)行了大量的研究,并提出不同的路由策略。XIE P等[3]提出了DBR(Depth-based routing)路由。DBR路由通過節(jié)點(diǎn)在水下的位置傳輸數(shù)據(jù)包,總是優(yōu)先選擇離水面更近的節(jié)點(diǎn)作為數(shù)據(jù)包轉(zhuǎn)發(fā)節(jié)點(diǎn)。而YAN H等[4]提出了基于虛“路由管”的VAPR路由。一旦接收了數(shù)據(jù)包,就計(jì)算轉(zhuǎn)發(fā)距離[5],若小于門限值就轉(zhuǎn)發(fā),否則丟棄。然而,一旦節(jié)點(diǎn)密度增加,VAPR路由策略加大了網(wǎng)絡(luò)能量消耗。為此,NOH Y等[6]提出VAPR的改進(jìn)協(xié)議,降低能耗,并增強(qiáng)應(yīng)對路由空洞的能力。

    然而,這些路由協(xié)議只在片面地追求路由的某一方面性能,而未能充分利用UWSNs的信道特性。此外,地理位置路由的核心在于下一跳轉(zhuǎn)發(fā)節(jié)點(diǎn)的選擇策略,若能擇優(yōu)選擇轉(zhuǎn)發(fā)節(jié)點(diǎn),就能有效地避開路由空洞。為此,本文提出了新的地理-機(jī)會路由協(xié)議(Geographic and Opportunistic Hybrid Routing,GOHR)。仿真數(shù)值證實(shí),提出的GOHR協(xié)議提高了數(shù)據(jù)包傳遞率,并降低冗余數(shù)據(jù)包。

1 GOHR路由

    假定N表示整個網(wǎng)絡(luò)的節(jié)點(diǎn)集,即N=Nn∪Ns,其中tx2-1-x1.gif為聲納浮標(biāo)(信宿)集。每個節(jié)點(diǎn)的通信半徑為rc,且它們具有低帶寬聲通信能力。而信宿不但具有聲通信能力,還具有射頻通信能力。

1.1 候選轉(zhuǎn)發(fā)節(jié)點(diǎn)集

    一旦源節(jié)點(diǎn)(假定為節(jié)點(diǎn)ni)需要向目的節(jié)點(diǎn)(假定為節(jié)點(diǎn)sθ)傳輸數(shù)據(jù)包,ni就從它的鄰居節(jié)點(diǎn)集Ni(t)搜索離自己最遠(yuǎn)和最近的信宿,即tx2-1-x2.gif則節(jié)點(diǎn)ni的候選轉(zhuǎn)發(fā)節(jié)點(diǎn)集Γi

tx2-gs1.gif

1.2 轉(zhuǎn)發(fā)節(jié)點(diǎn)簇

    為了選擇最優(yōu)的節(jié)點(diǎn)作為數(shù)據(jù)包的轉(zhuǎn)發(fā)節(jié)點(diǎn),節(jié)點(diǎn)ni需進(jìn)一步從Γi中挑選一部分節(jié)點(diǎn)構(gòu)成轉(zhuǎn)發(fā)節(jié)點(diǎn)簇Ψ[7,8]。

    對于節(jié)點(diǎn)nc∈Γi,首先計(jì)算它的歸一化權(quán)重值NADV(nc):

tx2-gs2.gif

1.3 簇期望權(quán)重值

    完成了簇劃分后,再依據(jù)式(3)計(jì)算每個簇的權(quán)重值EPA[9]。最終,選擇最大的EPA簇內(nèi)節(jié)點(diǎn)轉(zhuǎn)發(fā)數(shù)據(jù)包。

    tx2-gs3.gif

1.4 數(shù)據(jù)包傳遞概率

    下面推導(dǎo)對于任意一對相距為d的節(jié)點(diǎn),其傳輸m bit的數(shù)據(jù)包傳遞概率p(m,d)的表達(dá)式。依據(jù)文獻(xiàn)[10,11],水下無障礙物的路徑損耗為:

tx2-gs4-6.gif

其中Ed、Ed分別表示單位比特的平均能量消耗、噪聲功率密度,且均為常數(shù)。

    引用瑞利衰落模型,信噪比SNR的概率分布為:

     tx2-gs7-8.gif

    本文采用BPSK調(diào)制模式,長為d的路徑的比特誤碼概率為可定義為:

     tx2-gs9-10.gif

1.5 定時器設(shè)置

tx2-gs11-12.gif

其中na為接收節(jié)點(diǎn),nb為發(fā)送節(jié)點(diǎn),s為水下聲信號的傳播時間。

    綜上所述,整個GOHR協(xié)議傳輸數(shù)據(jù)包流程如圖1所示。

tx2-t1.gif

2 性能分析

    選擇1 500 m×1 500 m×1 500 m的水下無線傳感網(wǎng)絡(luò)作為研究區(qū)域,借助MATLAB R2012b工具進(jìn)行仿真,并分析仿真數(shù)據(jù)。區(qū)域內(nèi)有45個聲納浮標(biāo),即|Ns|=45。而水下傳感節(jié)點(diǎn)數(shù)從150~450變化,傳感節(jié)點(diǎn)的通信半徑rc=250 m。每個節(jié)點(diǎn)的數(shù)據(jù)包產(chǎn)生率服從泊松分布,且參數(shù)λ=0.15 pkts/min。數(shù)據(jù)率為50 kb/s。每次實(shí)驗(yàn)獨(dú)立重復(fù)進(jìn)行100次,取平均值作為最終的仿真數(shù)據(jù)。

2.1 數(shù)據(jù)包傳遞率

    首先,分析數(shù)據(jù)包傳遞率隨節(jié)點(diǎn)數(shù)變化情況,如圖2所示。從圖2可知,節(jié)點(diǎn)數(shù)越多,數(shù)據(jù)包傳遞率越高。原因在于:節(jié)點(diǎn)數(shù)越多,參與路由的節(jié)點(diǎn)就越多,相應(yīng)地,路由也就越穩(wěn)定。

tx2-t2.gif

    此外,相比于DBR和VAPR,GOHR路由的數(shù)據(jù)包傳遞率得到有效地提升。這主要是因?yàn)镚OHR路由建立穩(wěn)定的轉(zhuǎn)發(fā)節(jié)點(diǎn)簇,并使得簇內(nèi)節(jié)點(diǎn)能夠彼此監(jiān)聽各自的行為。例如,當(dāng)節(jié)點(diǎn)數(shù)為450時,GOHR路由的數(shù)據(jù)包傳遞率為0.82,而DBR和VAPR路由只有0.6和0.65。

2.2 冗余數(shù)據(jù)包數(shù)

    接下來,分析冗余數(shù)據(jù)包數(shù)隨節(jié)點(diǎn)數(shù)的變化情況,如圖3所示。相比于DBR和VAPR路由,GOHR具有最低的冗余數(shù)據(jù)包數(shù)。從圖3可知,當(dāng)節(jié)點(diǎn)數(shù)為300時,GOHR路由只產(chǎn)生了2個冗余包,而DBR和VAPR分別產(chǎn)生了8個、6個。原因在于:DBR采用了多徑傳輸策略,又沒有引用抑制冗余數(shù)據(jù)包機(jī)制;而VAPR未能實(shí)現(xiàn)低權(quán)重值節(jié)點(diǎn)監(jiān)聽高權(quán)重值的節(jié)點(diǎn)的功能,這必然增加冗余數(shù)據(jù)包數(shù)。

tx2-t3.gif

2.3 端到端傳輸時延

    最后,分析了端到端傳輸時延隨節(jié)點(diǎn)數(shù)的變化情況,如圖4所示。GOHR和VAPR的平均時延高于DBR。結(jié)合圖2、3可知,GOHR和VAPR路由是高的傳輸時延換取了高的數(shù)據(jù)包傳遞率和低冗余數(shù)據(jù)包數(shù)。即通過機(jī)會路由提高了數(shù)據(jù)包傳輸率,增加了傳輸時延。而與VAPR相比,GOHR路由的時延得到有效的下降。

tx2-t4.gif

3 結(jié)束語

    本文針對水下無線傳感網(wǎng)絡(luò)的數(shù)據(jù)傳輸問題,提出基于地理-機(jī)會的混合路由GOHR。GOHR在轉(zhuǎn)發(fā)數(shù)據(jù)包時,不是選擇一個轉(zhuǎn)發(fā)節(jié)點(diǎn),而是選擇一個簇,即轉(zhuǎn)發(fā)節(jié)點(diǎn)簇。GOHR通過先將節(jié)點(diǎn)劃分簇,再計(jì)算每個簇的權(quán)重值,最后將具有最大權(quán)重值的簇作為轉(zhuǎn)發(fā)節(jié)點(diǎn)簇。同時,GOHR考慮了冗余數(shù)據(jù)包問題,因此引用時延機(jī)制抑制數(shù)據(jù)包冗余問題。實(shí)驗(yàn)數(shù)據(jù)證明,提出的GOHR路由提高了數(shù)據(jù)傳輸能力。

參考文獻(xiàn)

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作者信息:

唐偉萍1,劉桂英2

(1.廣西電力職業(yè)技術(shù)學(xué)院 汽車與

交通系,廣西 南寧530007;2.廣西師范學(xué)院 職業(yè)技術(shù)教育學(xué)院,廣西 南寧530001)

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