Predictive value of positive lymph node ratio in patients with locally advanced gastric remnant cancer

BACKGROUND Traditional lymph node stage(N stage)has limitations in advanced gastric remnant cancer(GRC)patients;therefore,establishing a new predictive stage is necessary.AIM To explore the predictive value of positive lymph node ratio(LNR)according to clinicopathological characteristics and prognosis of locally advanced GRC.METHODS Seventy-four patients who underwent radical gastrectomy and lymphadenectomy for locally advanced GRC were retrospectively reviewed.The relationship between LNR and clinicopathological characteristics was analyzed.The survival analysis was performed using Kaplan-Meier survival curves and Cox regression model.RESULTS Number of metastatic LNs,tumor diameter,depth of tumor invasion,Borrmann type,serum tumor biomarkers,and tumor-node-metastasis(TNM)stage were correlated with LNR stage and N stage.Univariate analysis revealed that the factors affecting survival included tumor diameter,anemia,serum tumor biomarkers,vascular or neural invasion,combined resection,LNR stage,N stage,and TNM stage(all P<0.05).The median survival time for those with LNR0,LNR1,LNR2 and LNR3 stage were 61,31,23 and 17 mo,respectively,and the differences were significant(P=0.000).Anemia,tumor biomarkers and LNR stage were independent prognostic factors for survival in multivariable analysis(all P<0.05).CONCLUSION The new LNR stage is uniquely based on number of metastatic LNs,with significant prognostic value for locally advanced GRC,and could better differentiate overall survival,compared with N stage.

Advantage of log odds of positive lymph nodes in prognostic evaluation of patients with early-onset colon cancer

BACKGROUND Colon cancer(CC)is one of the most common cancers of the digestive tract,the third most common cancer worldwide,and the second most common cause of cancer-related deaths.Previous studies have demonstrated a higher risk of lymph node metastasis(LNM)in young patients with CC.It might be reasonable to treat patients with early-onset locally advanced CC with extended lymph node dissection.However,few studies have focused on early-onset CC(ECC)patients with LNM.At present,the methods of predicting and evaluating the prognosis of ECC patients with LNM are controversial.From the data of patients with CC obtained from the Surveillance,Epidemiology,and End Results(SEER)database,data of young patients with ECC(≤50 years old)was screened.Patients with unknown data were excluded from the study,while the remaining patients were included.The patients were randomly divided into a training group(train)and a testing group(test)in the ratio of 7:3,while building the model.The model was constructed by the training group and verified by the testing group.Using multiple Cox regression models to compare the prediction efficiency of LNM indicators,nomograms were built based on the best model selected for overall survival(OS)and cause-specific survival(CSS).In the two groups,the performance of the nomogram was evaluated by constructing a calibration plot,time-dependent area under the curve(AUC),and decision curve analysis.Finally,the patients were grouped based on the risk score predicted by the prognosis model,and the survival curve was constructed after comparing the survival status of the high and low-risk groups.RESULTS Records of 26922 ECC patients were screened from the SEER database.N classification,positive lymph nodes(PLN),lymph node ratio(LNR)and log odds of PLN(LODDS)were considered to be independent predictors of OS and CSS.In addition,independent risk factors for OS included gender,race,marital status,primary site,histology,grade,T,and M classification,while the independent prognostic factors for CSS included race,marital status,primary site,grade,T,and M classification.The prediction model including LODDS is composed of minimal Akaike information criterion,maximal concordance indexes,and AUCs.Factors including gender,race,marital status,primary site,histology,grade,T,M classification,and LODDS were integrated into the OS nomogram,while race,marital status,primary site,grade,T,M classification,and LODDS were included into the CSS nomogram.The nomogram representing both cohorts had been successfully verified in terms of prediction accuracy and clinical practicability.CONCLUSION LODDS is superior to N-stage,PLN,and LNR of ECC.The nomogram containing LODDS might be helpful in tumor evaluation and clinical decision-making,since it provides an appropriate prediction of ECC.

Benefit of adjuvant chemoradiotherapy in patients with pathologically lymph node-positive and locally advanced gastric cancer

Objective This study aimed to compare the effectiveness of adjuvant chemoradiotherapy(CRT)and adjuvant chemotherapy(ChT)for T3–4/N+gastric cancer(GC)following D2/R0 dissection,and identify the specific subgroups that could benefit from adjuvant CRT.Methods All eligible patients were divided into the CRT group and ChT group.We assessed the survival outcomes and patterns of recurrence for each group,and determined the prognostic factors for survival by performing Cox proportional risk regression analyses.Results A total of 192 gastric cancer patients were included in the study.The estimated 3-year and 5-year disease-free survival(DFS)probabilities in the CRT and ChT groups were 52.9%vs.36.7%(P=0.024)and 41.2%vs.31.1%(P=0.148),respectively,and the estimated 3-year and 5-year overall survival(OS)probabilities were 82.4%vs.70.0%(P=0.044)and 52.0%vs.35.6%(P=0.022).Patients in the CRT group had a lower risk of locoregional recurrence than those in the ChT group(20.6%vs.34.4%;P=0.031).The subset analyses revealed that patients with stage N1–2 disease were more likely to benefit from adjuvant CRT than from adjuvant ChT(DFS:53.1%vs.36.4%;P=0.039;OS:53.1%vs.38.6%;P=0.036).Conclusion For locally advanced gastric cancer patients with LN+,adjuvant CRT showed superior survival benefits compared with adjuvant ChT alone.Patients with N1–2 achieved better survival from adjuvant CRT.

Effect of the number of positive lymph nodes and lymph node ratio on prognosis of patients after resection of pancreatic adenocarcinoma

BACKGROUND： The prognostic factors related to lymph node involvement [lymph node status, the number of positive lymph nodes, lymph node ratio （LNR）] and the number of nodes evaluated in patients with pancreatic adenocarcinoma after pancreatectomy are poorly defined. METHODS： A total of 167 patients who had undergone resection of pancreatic adenocarcinoma from February 2010 to August 2011 were included in this study. Histological examination was performed to evaluate the tumor differentiation and lymph node involvement. Univariate and multivariate analyses were made to determine the relationship between the variables related to nodal involvement and the number of nodes and survival. RESULTS： The median number of total nodes examined was 10 （range 0-44） for the entire cohort. The median number of total nodes examined in node-negative （pN0） patients was similar to that in node-positive （pN1） patients. Patients with pN1 diseases had significantly worse survival than those with pN0 ones （P=0.000）. Patients with three or more positive nodes had a poorer prognosis compared with those with the negative nodes （P=0.000）. The prognosis of the patients with negative nodes was similar to that of those with one to two positive nodes （P=0.114）. The median survival of patients with an LNR ≥0.4 was shorter than that of patients with an LNR 〈0.4 in the pN1 cohort （P=0.014）. No significance was found between the number of total nodes examined and the prognosis, regardless of the cutoff of 10 or 12 and in the entire cohort or the pN0 and pN1 groups. Based on the multivariate analysis of the entire cohort and the pN1 group, the nodal status, the number of positive nodes and the LNR were all associated with survival. CONCLUSIONS： In addition to the nodal status, the number of positive nodes and the LNR can serve as comprehensive factors for the evaluation of nodal involvement. This approach may be more effective for predicting the survival of patients with pancreatic adenocarcinoma after pancreatectomy.

Axillary lymph node management in breast cancer with positive sentinel lymph node biopsy

The surgical treatment of localized breast cancer has become progressively less aggressive over the years.The management of the axillary lymph nodes has been modified by the introduction of sentinel lymph node biopsy. Axillary dissection can be avoided in patients with sentinel lymph node negative biopsies. Based on randomized trials data, it has been proposed that no lymph node dissection should be carried out even in certain patients with sentinel lymph node positive biopsies. This commentary discusses the basis of such recommendations and cautions against a general omission of lymph node dissection in breast cancer patients with positive sentinel lymph node biopsies. Instead, an individualized approach based on axillary tumor burden and biology of the cancer should be considered.

Development and validation of prognostic nomogram based on log odds of positive lymph nodes for patients with gastric signet ring cell carcinoma

Objective: Our aims were to establish novel nomogram models, which directly targeted patients with signet ring cell carcinoma(SRC), for individualized prediction of overall survival(OS) rate and cancer-specific survival(CSS).Methods: We selected 1,365 SRC patients diagnosed from 2010 to 2015 from Surveillance, Epidemiology and End Results(SEER) database, and then randomly partitioned them into a training cohort and a validation cohort.Independent predicted indicators, which were identified by using univariate testing and multivariate analyses, were used to construct our prognostic nomogram models. Three methods, Harrell concordance index(C-index), receiver operating characteristics(ROC) curve and calibration curve, were used to assess the ability of discrimination and predictive accuracy. Integrated discrimination improvement(IDI), net reclassification improvement(NRI) and decision curve analysis(DCA) were used to assess clinical utility of our nomogram models.Results: Six independent predicted indicators, age, race, log odds of positive lymph nodes(LODDS), T stage, M stage and tumor size, were associated with OS rate. Nevertheless, only five independent predicted indicators were associated with CSS except race. The developed nomograms based on those independent predicted factors showed reliable discrimination. C-index of our nomogram for OS and CSS was 0.760 and 0.763, which were higher than American Joint Committee on Cancer(AJCC) 8 th edition tumor-node-metastasis(TNM) staging system(0.734 and 0.741, respectively). C-index of validation cohort for OS was 0.757 and for CSS was 0.773. The calibration curves also performed good consistency. IDI, NRI and DCA showed the nomograms for both OS and CSS had a comparable clinical utility than the TNM staging system.Conclusions: The novel nomogram models based on LODDS provided satisfying predictive ability of SRC both in OS and CSS than AJCC 8 th edition TNM staging system alone.

CA19-9 level determines therapeutic modality in pancreatic cancer patients with para-aortic lymph node metastasis

Background: In general, para-aortic lymph node(LN16) metastasis has been considered as a contraindication for pancreatic resection. However, some pancreatic cancer patients with LN16 metastasis have been reported to survive for longer than expected after pancreatectomy. The purpose of this study was to determine whether pancreatic cancer patients with LN16 metastasis might benefit from surgery.Methods: We retrospectively reviewed 201 consecutive patients with invasive pancreatic ductal adenocarcinoma who underwent surgery at Osaka National Hospital between April 2003 and December 2012.These patients included 22 patients with LN16 metastasis who underwent an extended lymphadenectomy and 25 patients who underwent a palliative surgical biliary and gastric bypass. The clinicopathological data and outcomes were evaluated using univariate and multivariate analyses.Results: The overall survival of the patients with LN16 metastasis was poorer than that of the LN16-negative patients(P = 0.0014). An overall survival analysis of the LN16-positive patients stratified according to the preoperative CA19-9 level showed a significant difference between patients with a low preoperative CA19-9 level(≤360 U/mL) and those with a high preoperative CA19-9 level(>360 U/mL)(P = 0.0301). No significant difference in overall survival of patients was observed between those with LN16 positivity and those who underwent bypass surgery. However, the overall survival of the LN16-positive patients with a CA19-9 level ≤360 U/mL(n = 11) was significantly higher than that of those who underwent bypass surgery(P = 0.0452).Conclusion: Surgical resection and extended lymphadenectomy remains an option for pancreatic cancer patients with LN16-positivity whose CA19-9 level is ≤360 U/mL.

Lymph node ratio and preoperative CA 19-9 levels predict overall survival and recurrence-free survival in patients with resected pancreatic adenocarcinoma

AIM:Clinicopathologic factors predicting overall survival (OS) would help identify a subset to benefit from adjuvant therapy. METHODS: One hundred and sixty-nine patients patients from 1984 to 2009 with curative resections for pancreatic adenocarcinoma were included. Tumors were staged by American Joint Committee on Cancer 7th edition criteria. Univariate and multivariable analyses were performed using Kaplan-Meier methodology or Cox proportional hazard models. Log-rank tests were performed. Statistical inferences were assessed by two-sided 5% significance level. RESULTS: Median age was 67.1 (57.2-73.0) years with equal gender distribution. Tumors were in the head (89.3%) or body/tail (10.7%). On univariate analysis, adjuvant therapy, lymph node (LN) ratio, histologic grade, negative margin status, absence of peripancreatic extension, and T stage were associated with improved OS. Adjuvant therapy, LN ratio, histologic grade, number of nodes examined, negative LN status, and absence of peripancreatic extension were associated with improved recurrence-free survival (RFS). On multivariable analysis, LN ratio and carbohydrate antigen (CA) 19-9 levels were associated with OS. LN ratio was associated with RFS. CONCLUSION: The LN ratio and CA 19-9 levels are independent prognostic factors following curative resections of pancreatic cancer.

Use of Three Dimensional Conformal Radiation Therapy for Node Positive Breast Cancer Does Not Result in Excess Lung and Heart Irradiation

Purpose: This work evaluates the use of target and organs at risk (OAR) dose-volume goals in 3D conformal radiotherapy (3DCRT) planning for node positive breast cancer (NPBC) patients undergoing regional nodal irradiation after lumpectomy/mastectomy. Methods: Dosimetric data for 262 NPBC patients receiving regional nodal and whole breast/chest wall (WB/CW) irradiation from 2000-2009 were analyzed. In all cases, target & OAR volumes were delineated on treatment CT scans for field generation and dose-volume histograms (DVHs) were generated. Cases were analyzed to identify how frequently they met treatment planning institutional dose-volume goals (“institutional guidelines” & standardized in 2005) and how this would affect OAR doses. Results: The incidence of cases from 2000-2009 meeting current institutional guidelines improved over the study period. Target coverage improved from 2005-2009, when guidelines were followed as a part of the plan approval. Those cases from 2000-2004 meeting acceptable target goals were found to be significantly different from those cases from 2005-2009 (p < 0.01). However, no significant difference between cases meeting OAR goals for plans from 2000-2004 versus 2005-2009 was found. Conclusions: The use of institutional guidelines in 3DCRT for WB/CW and regional nodal irradiation for NPBC patients improved target coverage without a statistically significant increase in heart and lung doses.

Log odds of positive lymph nodes is a better prognostic factor for oesophageal signet ring cell carcinoma than N stage

BACKGROUND Signet ring cell carcinoma is a rare type of oesophageal cancer,and we hypothesized that log odds of positive lymph nodes(LODDS)is a better prognostic factor for oesophageal signet ring cell carcinoma.AIM To explore a novel prognostic factor for oesophageal signet ring cell carcinoma by comparing two lymph node-related prognostic factors,log odds of positive LODDS and N stage.METHODS A total of 259 cases of oesophageal signet ring cell carcinoma after oesophagectomy were obtained from the Surveillance,Epidemiology,and End Results database between 2006 and 2016.The prognostic value of LODDS and N stage for oesophageal signet ring cell carcinoma was evaluated by univariate and multivariate analyses.The Akaike information criterion and Harrell’s C-index were used to assess the value of two prediction models based on lymph nodes.External validation was performed to further confirm the conclusion.RESULTS The 5-year cancer-specific survival(CSS)and 5-year overall survival(OS)rates of all the cases were 41.3%and 27.0%,respectively.The Kaplan-Meier method showed that LODDS had a higher score of log rank chi-squared(OS:46.162,CSS:41.178)than N stage(OS:36.215,CSS:31.583).Univariate analyses showed that insurance,race,T stage,M stage,TNM stage,radiation therapy,N stage,and LODDS were potential prognostic factors for OS(P<0.1).The multivariate Cox regression model showed that LODDS was an significant independent prognostic factor for oesophageal signet ring carcinoma patients after surgical resection(P<0.05),while N stage was not considered to be a significant prognostic factor(P=0.122).Model 2(LODDS)had a higher degree of discrimination and fit than Model 1(N stage)(LODDS vs N stage,Harell’s C-index 0.673 vs 0.656,P<0.001;Akaike information criterion 1688.824 vs 1697.519,P<0.001).The results of external validation were consistent with those in the study cohort.CONCLUSION LODDS is a superior prognostic factor to N stage for patients with oesophageal signet ring cell carcinoma after oesophagectomy.

基于多通信半径和改进麻雀搜索算法的DV-HOP节点定位研究

在无线传感器网络中,传统DV-Hop(Distance Vector-Hop)算法因跳数和平均跳距计算存在较大偏差,从而对未知节点定位产生较大误差.针对该问题,设计了基于多通信半径和改进麻雀搜索的DV-Hop定位算法.首先采用多通信半径修正节点间的跳数,使跳数值较真实反映两个节点间的距离.其次采用修正的跳数去修正信标节点的平均跳距,从而获得未知节点到各信标节点修正后的距离.最后采用麻雀搜索算法(Sparrow Search Algorithm,SSA)估算未知节点位置,将节点定位问题转化为函数寻优问题.针对麻雀搜索算法前期容易陷入局部最优解,后期寻优精度不高的问题,提出将Levy飞行策略引入麻雀搜索算法中,提升算法的全局寻优能力.仿真结果表明,与传统DV-Hop算法、SSA DV-Hop算法相比,改进SSA DV-Hop算法的定位精度明显提高.

Effects of postmastectomy radiotherapy on prognosis in different tumor stages of breast cancer patients with positive axillary lymph nodes

Objective: To explore the effects of postmastectomy radiotherapy(PMRT) on the locoregional failure-free survival(LRFFS) and overall survival(OS) of breast cancer patients under different tumor stages and with one to three positive axillary lymph nodes(ALNs). Methods: We conducted a retrospective review of 527 patients with one to three positive lymph nodes who underwent modified radical or partial mastectomy and axillary dissection from January 2000 to December 2002. The patients were divided into the T1-T2 N1 and T3-T4 N1 groups. The effects of PMRT on the LRFFS and OS of these two patient groups were analyzed using SPSS 19.0, Pearson's χ2-test, Kaplan-Meier method, and Cox proportional hazard model. Results: For T1-T2 N1 patients, no statistical significance was observed in the effects of PMRT on LRFFS [hazard ratio(HR)=0.726; 95% confidence interval(CI): 0.233-2.265; P=0.582] and OS(HR=0.914; 95% CI: 0.478-1.745; P=0.784) of the general patients. Extracapsular extension(ECE) and high histological grade were the risk factors for LRFFS and OS with statistical significance in multivariate analysis. Stratification analysis showed that PMRT statistically improved the clinical outcomes in high-risk patients [ECE(+), LRFFS: P=0.026, OS: P=0.007; histological grade III, LRFFS: P<0.001, OS: P=0.007] but not in low-risk patients [ECE(–), LRFFS: P=0.987, OS: P=0.502; histological grade I-II, LRFFS: P=0.816, OS: P=0.296]. For T3-T4 N1 patients, PMRT effectively improved the local control(HR=0.089; 95% CI: 0.210-0.378; P=0.001) of the general patients, whereas no statistical effect was observed on OS(HR=1.251; 95% CI: 0.597-2.622; P=0.552). Absence of estrogen receptors and progesterone receptors(ER/PR)(–) was an independent risk factor. Further stratification analysis indicated a statistical difference in LRFFS and OS between the high-risk patients with ER/PR(–) receiving PMRT and not receiving PMRT [ER/PR(–), LRFFS: P=0.046, OS: P=0.039]. However, PMRT had a beneficial effect on the reduction of locoregional recurrence(LRR) but not in total mortality [ER/PR(+), LRFFS: P<0.001, OS: P= 0.695] in T3-T4 N1 patients with ER/PR(+) who received endocrine therapy. Conclusion: PMRT could reduce ECE(+), histological grade III-related LRR, and total mortality of T1-T2 N1 patients. T3-T4 N1 patients with ER/PR(–) could benefit from PMRT by improving LRFFS and OS. However, PMRT could only reduce LRR but failed to improve OS for T3-T4 N1 patients with ER/PR(+) who received endocrine therapy.

Different lymph node staging systems for predicting the prognosis of colorectal neuroendocrine neoplasms

BACKGROUND Colorectal neuroendocrine neoplasms(NENs)are a rare malignancy that primarily arises from the diffuse distribution of neuroendocrine cells in the colon and rectum.Previous studies have pointed out that the status of lymph node may be used to predict the prognosis.AIM To investigate the predictive values of lymph node ratio(LNR),positive lymph node(PLN),and log odds of PLNs(LODDS)staging systems on the prognosis of colorectal NENs treated surgically,and compare their predictive values.METHODS This cohort study included 895 patients with colorectal NENs treated surgically from the Surveillance,Epidemiology,and End Results database.The endpoint was mortality of patients with colorectal NENs treated surgically.X-tile software was utilized to identify most suitable thresholds for categorizing the LNR,PLN,and LODDS.Participants were selected in a random manner to form training and testing sets.The prognosis of surgically treating colorectal NENs was examined using multivariate cox analysis to assess the associations of LNR,PLN,and LODDS with the prognosis of colorectal NENs.C-index was used for assessing the predictive effectiveness.We conducted a subgroup analysis to explore the different lymph node staging systems’predictive values.RESULTS After adjusting all confounding factors,PLN,LNR and LODDS staging systems were linked with mortality in patients with colorectal NENs treated surgically(P<0.05).We found that LODDS staging had a higher prognostic value for patients with colorectal NENs treated surgically than PLN and LNR staging systems.Similar results were obtained in the different G staging subgroup analyses.Furthermore,the area under the receiver operating characteristic curve values for LODDS staging system remained consistently higher than those of PLN or LNR,even at the 1-,2-,3-,4-,5-and 6-year follow-up periods.CONCLUSION LNR,PLN,and LODDS were found to significantly predict the prognosis of patients with colorectal NENs treated surgically.

Remote positioning system based on GPS/GPRS

Considering the need of target positioning,a remote positioning system is designed based on global positioning system(GPS)and general packet radio service(GPRS);The data collection terminal is based on microcontroller unit(MCU)PIC24FV301.It uses GPRS network to create wireless link and transmits GPS source information which is collected by LEA-5H board to monitor center on the Internet.The monitor center obtains the target information through processing and analysis of the calculated data.Actual operation results indicate that the designed system has excellent performance and achieves the goal of the remote location.

k-Means++算法下的无线局域传感网络凸包质心定位

为了提高无线局域传感网络凸包质心定位的准确性,利用k-Means++聚类算法计算传感器节点的接收信号强度和路径损耗,筛选出具有代表性和稳定性的节点作为凸包质心,再使用加权算法计算凸包质心定位权值,选择出更准确地质心。在此基础上,通过分析无线传感器信号的间隔时间以及比较周边凸包质心和未知节点的接收信号实际条件,确定凸包质心之间的连通性关系。根据设定的凸包质心定位判断阈值,进一步确定凸包质心的定位结果,提高定位的准确性和可靠性。仿真结果表明,所提方法最大定位误差为0.167 m,在不同凸包质心数量下通信半径为40 m时的定位误差小于0.35 m。证明了所提方法能有效地实现无线局域传感网络中的质心定位,定位误差小。

基于GA-TS搜索算法的工业无线传感网节点定位研究

为了解决工业无线传感网覆盖过程中通信半径跳距离产生偏差过大的问题,设计了一种基于GA-TS搜索算法的节点定位方法,并开展仿真分析。研究结果表明,当通信半径不断增大后,算法误差产生不同程度的减少。与传统最大似然估计定位算法相比,GA-TS搜索算法的优化效果更佳,误差大概缩减30%;与移动锚节点算法相比,误差大概降低至15%。相比较之下GA-TS搜索算法定位精度误差最小,具有很大的应用准确性和适应范围。该研究有助于工业无线传感网定位精度,对保证网络信号的传输效率具有一定的意义。

无线传感器网络DV-HOP定位算法的改进

节点定位在无线传感器网络的应用中起着重要作用,一直备受学术界和工业界的关注。在深入研究分析无线传感器网络DV-Hop定位算法和部分已有改进算法的基础上,提出了一种新的改进算法。针对DV-Hop算法在未知节点到信标节点距离计算中的不足,该算法对信标节点的平均每跳距离做出改进;并对可参考信标节点数小于3的未知节点进行估计定位,消除了因拓扑结构而造成的不可定位节点。仿真结果表明,改进算法比原算法及部分现有改进算法的定位精度有所提高。

无线传感器网络DV-Hop定位算法的改进

DV-Hop定位算法利用跳数乘以平均每跳跳距估算节点间距离,针对算法过程存在缺陷导致定位误差较大的问题,在不改变原算法的步骤,也不需要额外增加硬件设备的条件下,从两个方面对传统DV-Hop定位算法进行了改进：一是基于节点的通信半径对节点间的跳数进行修正;二是借助信标节点间的估计距离与实际距离的偏差对平均每跳跳距进行修正。仿真实验表明,在相同的网络环境下,改进后的算法与传统算法相比定位误差减少了15%左右;与另外一种利用估算出的理想跳数值对信标节点间的实际跳数值进行修正的改进算法相比,定位误差也有5%~7%的降低。实验结果表明所提出的改进算法能更有效地降低节点间的距离估算误差,提高定位精度。

基于跳数修正的DV-Hop改进算法

针对无线传感器网络DV-Hop定位算法在实际应用中定位误差较大的问题,提出一种基于跳数修正的改进算法。在引入限跳机制的条件下,按未知节点与信标节点间的跳数值分类估算,对1跳区域内的节点采用RSSI测距技术,对于节点间跳数值大于1跳的节点,则利用信标节点间实际距离与估计距离的误差值修正平均每跳距离。仿真实验表明,在相同的网络条件下,与原DV-Hop定位算法和其他改进算法相比,改进后的算法能更有效地减少跳距估算带来的定位误差,提高平均定位精度并保持较好的算法稳定性。

基于加权质心和DV-Hop混合算法WSN定位方法研究

为了提高无线传感器网络中节点定位的精确度,分析了DV-Hop(distance vector—hop,距离向量-跳段)定位算法和质心算法的优缺点,提出基于加权质心和DV-Hop混合算法,并用MATLAB进行了仿真实验。实验结果表明,在基准节点密度相同的条件下,混合算法的定位精度比DV-Hop平均提高了20%,比质心算法平均提高了15%。该混合算法在提高无线传感器节点精确度上是有效的。