WSN定位誤差分析及精度控制方法
發(fā)布時間：2018-08-17 17:16
【摘要】：近年來,對于小型無線移動設(shè)備的定位得到了越來越多的關(guān)注。對WSN(Wireless Sensor Networks,無線傳感器網(wǎng)絡(luò))的定位是其中一個分支。在WSN中,通常都存在一些為位置已知的節(jié)點,被稱為錨節(jié)點,其他節(jié)點為位置未知的普通節(jié)點。未知節(jié)點通過測量自身與通信范圍內(nèi)錨節(jié)點的距離或到達角等信息來得到自身位置。事實上,利用信號強度傳播模型,可以通過RSS(Received Signal Strength,接收信號強度)來估計出收發(fā)端的距離�；赗SS的測距方法得到了廣泛的關(guān)注和研究,因為它不需要額外的硬件支持,且算法很簡單。但該系統(tǒng)存在兩個很大的問題。1)由于無線信道快衰落和慢衰落的影響,基于RSS的測距精度很低。慢衰落即陰影衰落,它對于測距精度的影響已經(jīng)得到了廣泛的研究。而快衰落由多徑效應(yīng)引起,一般認為可以通過多次測量取平均的方法來予以消除,所以很少有相應(yīng)的研究。但是,當(dāng)所要求的精度給定時,所需的測量次數(shù)依舊懸而未決。2)該定位系統(tǒng)的定位精度不止受到測距精度的影響,還與錨節(jié)點相對于未知節(jié)點的分布狀況有關(guān)。這就使得不同的節(jié)點的定位精度不同,有時甚至相差很大。一些節(jié)點的定位精度很高,而另外一些可能很低。這就使得整個系統(tǒng)可靠性很差、很不穩(wěn)定。針對以上問題,本文主要完成了以下方面的工作:1)對于測距問題,很重要的一個問題就是如何得到無線信道的參數(shù)。通過測量少數(shù)幾個點的RSS值,再利用最小二乘法來估計所需參數(shù)。本文在實際環(huán)境下進行了實驗,證明了該方法的有效性和準(zhǔn)確性。2)從理論上詳細地分析了快衰落對測距精度的影響。首先假設(shè)快衰落服從對數(shù)正態(tài)分布,推導(dǎo)出了原有的測距方法的誤差分布函數(shù)。理論分析表明該方法存在固有偏差,但通過一個很簡單的修正即可以變?yōu)闊o偏估計。為了證明該方法的性能,進一步推導(dǎo)了基于RSS測距的CRLB(Cram′er-Rao Lower Bound,克拉美羅下限),即測距誤差的方差所能達到的最低程度。各個方面的論證都表明,測距誤差的方差與收發(fā)端距離的平方成正比。3)測距后即得到了一系列的方程組,本文通過線性迭代的方法進行求解。通常使用最小二乘法,但在基于RSS測距的背景下,該方法可以被證明并非最優(yōu)。本文進一步給出了最優(yōu)的迭代矩陣,以達到最小化定位誤差的目的。4)為了解決系統(tǒng)的不穩(wěn)定性問題,本文定義了GDOP(Geographical Dilution of Precision,幾何精度因子),并基于此概念提出了APC(Automatic Precision Control,自動精度控制)算法。該算法通過迭代動態(tài)地調(diào)節(jié)測量次數(shù),從而使定位精度穩(wěn)定在給定的限制附近。
[Abstract]:In recent years, more and more attention has been paid to the positioning of small wireless mobile devices. Location of WSN (Wireless Sensor Networks, wireless sensor networks is one of the branches. In WSN, there are usually some known nodes, called anchor nodes, and other nodes are common nodes with unknown location. Unknown nodes obtain their position by measuring the distance or angle of arrival between themselves and the anchor nodes in the communication range. In fact, using the signal intensity propagation model, the distance between the transceiver and receiver can be estimated by RSS (Received Signal Strength,. The ranging method based on RSS has been widely studied because it does not require additional hardware support and the algorithm is very simple. However, there are two big problems in this system. 1) because of the influence of fast fading and slow fading in wireless channel, the ranging accuracy based on RSS is very low. Slow fading is shadow fading, and its influence on ranging accuracy has been widely studied. However, fast fading is caused by multipath effect, which is generally considered to be eliminated by multiple measurements, so there is little research on it. However, when the required precision is timed, the required number of measurements is still unresolved (.2). The positioning accuracy of the positioning system is affected not only by the ranging accuracy, but also by the distribution of the anchor nodes relative to the unknown nodes. This makes the positioning accuracy of different nodes different, sometimes even very different. Some nodes have high positioning accuracy, while others may be very low. This makes the whole system very poor reliability, very unstable. Aiming at the above problems, this paper mainly completes the following work: 1) for the ranging problem, one of the most important problems is how to get the parameters of the wireless channel. By measuring the RSS values of a few points, the least square method is used to estimate the required parameters. In this paper, experiments are carried out in a practical environment, and the effectiveness and accuracy of this method are proved. 2) the influence of fast fading on ranging accuracy is analyzed in detail theoretically. First, the error distribution function of the original ranging method is derived from the logarithmic normal distribution of fast fading suit. Theoretical analysis shows that the method has inherent deviation, but it can be changed into unbiased estimation by a simple correction. In order to prove the performance of the method, the CRLB (Cram'er-Rao Lower Boundary) based on RSS ranging is further derived, that is, the minimum degree of variance of ranging error. It is shown from all aspects that the variance of ranging error is proportional to the square of the distance between the transceiver and the receiver) and a series of equations are obtained after ranging. The method of linear iteration is used to solve the problem in this paper. The least square method is usually used, but in the context of RSS ranging, the method can be proved not to be optimal. In order to solve the instability problem of the system, the optimal iterative matrix is given to minimize the positioning error. In this paper, GDOP (Geographical Dilution of Precision, geometric precision factor is defined, and based on this concept, APC (Automatic Precision Control, automatic precision control algorithm is proposed. The algorithm dynamically adjusts the number of times of measurement by iterating so that the positioning accuracy is stable near the given limit.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN929.5;TP212.9
本文編號：2188340
[Abstract]:In recent years, more and more attention has been paid to the positioning of small wireless mobile devices. Location of WSN (Wireless Sensor Networks, wireless sensor networks is one of the branches. In WSN, there are usually some known nodes, called anchor nodes, and other nodes are common nodes with unknown location. Unknown nodes obtain their position by measuring the distance or angle of arrival between themselves and the anchor nodes in the communication range. In fact, using the signal intensity propagation model, the distance between the transceiver and receiver can be estimated by RSS (Received Signal Strength,. The ranging method based on RSS has been widely studied because it does not require additional hardware support and the algorithm is very simple. However, there are two big problems in this system. 1) because of the influence of fast fading and slow fading in wireless channel, the ranging accuracy based on RSS is very low. Slow fading is shadow fading, and its influence on ranging accuracy has been widely studied. However, fast fading is caused by multipath effect, which is generally considered to be eliminated by multiple measurements, so there is little research on it. However, when the required precision is timed, the required number of measurements is still unresolved (.2). The positioning accuracy of the positioning system is affected not only by the ranging accuracy, but also by the distribution of the anchor nodes relative to the unknown nodes. This makes the positioning accuracy of different nodes different, sometimes even very different. Some nodes have high positioning accuracy, while others may be very low. This makes the whole system very poor reliability, very unstable. Aiming at the above problems, this paper mainly completes the following work: 1) for the ranging problem, one of the most important problems is how to get the parameters of the wireless channel. By measuring the RSS values of a few points, the least square method is used to estimate the required parameters. In this paper, experiments are carried out in a practical environment, and the effectiveness and accuracy of this method are proved. 2) the influence of fast fading on ranging accuracy is analyzed in detail theoretically. First, the error distribution function of the original ranging method is derived from the logarithmic normal distribution of fast fading suit. Theoretical analysis shows that the method has inherent deviation, but it can be changed into unbiased estimation by a simple correction. In order to prove the performance of the method, the CRLB (Cram'er-Rao Lower Boundary) based on RSS ranging is further derived, that is, the minimum degree of variance of ranging error. It is shown from all aspects that the variance of ranging error is proportional to the square of the distance between the transceiver and the receiver) and a series of equations are obtained after ranging. The method of linear iteration is used to solve the problem in this paper. The least square method is usually used, but in the context of RSS ranging, the method can be proved not to be optimal. In order to solve the instability problem of the system, the optimal iterative matrix is given to minimize the positioning error. In this paper, GDOP (Geographical Dilution of Precision, geometric precision factor is defined, and based on this concept, APC (Automatic Precision Control, automatic precision control algorithm is proposed. The algorithm dynamically adjusts the number of times of measurement by iterating so that the positioning accuracy is stable near the given limit.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN929.5;TP212.9
【參考文獻】
相關(guān)碩士學(xué)位論文 前1條
1 劉文娟;基于RSSI測距的WSN定位系統(tǒng)設(shè)計[D];大連理工大學(xué);2010年
，本文編號：2188340
本文鏈接：http://sikaile.net/kejilunwen/wltx/2188340.html
最近更新
教材專著
