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摘要: 針對提高Wi-Fi指紋室內定位技術性能,提出了一種基于卷積神經網絡(Convolutional neural networks,CNN)的信道狀態信息(Channel state information,CSI)指紋室內定位方法。在離線階段聯合定位環境參考點的幅度差和相位差信息,利用CNN進行訓練,保存訓練后的CNN網絡模型作為指紋;在線階段,針對不同實驗場景,對測試數據的幅度差信息和相位差信息進行加權處理,引入改進的基于概率的指紋匹配算法,利用待定位點的CSI信息并通過CNN網絡模型預測待定位點的坐標。此外,為增強算法普適性,針對復雜室內場景,提出了雙節點定位方案來提高定位精度。在廊廳和實驗室室內兩種不同定位場景進行了實驗,信息聯合定位算法分別獲得了24.7 cm和48.1 cm的平均定位誤差,驗證了基于CNN的CSI幅度差和相位差聯合定位算法的有效性。Abstract: To improve the performance of Wi-Fi fingerprint indoor positioning technology, a method based on convolutional neural networks (CNNs) for channel state information (CSI) fingerprint indoor positioning is proposed. This method fully exploits the feature extraction capabilities of CNNs, applies the combination of amplitude difference and phase difference information as training data in the offline phase, and uses the trained CNN network model for an online test. In the online phase, for different experimental scenarios, by analyzing the variance of the amplitude information and phase information, the amplitude difference and phase difference information of the test data are weighted to obtain a certain universal weight factor for a better positioning result. At the same time, considering the characteristics of terminal mobility during real-time positioning, the CSI information sampled twice in succession is adopted as test data to increase the diversity of test data. To address the disadvantage of poor positioning performance of traditional probability-based positioning algorithms, an improved probability-based fingerprint matching algorithm is introduced. By passing the CSI information of the point to be located through the CNN network model, it can output the probability average value corresponding to the reference position with the highest probability in all test data packets and weight it with the reference position coordinate to estimate the point to be located. In addition, to enhance the universality of the algorithm, a dual-node positioning scheme is proposed for complex indoor scenes to improve positioning accuracy. Experiments are conducted in two positioning scenarios in a corridor and laboratory, including the amplitude difference positioning performance, the average positioning error of each positioning method, and the performance comparison of positioning algorithms. The information joint positioning algorithm obtains an average positioning error of 24.7 and 48.1 cm, which verifies the effectiveness of the proposed algorithm.
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表 1 CNN網絡參數
Table 1. CNN network parameters
Layer Parameter Output shape Input Training data (30,30,3,m) Conv2D 1 Conv 2D,fs=5,s=1 (30,30,16,m) Conv2D 2 Conv 2D,fs=5,s=1 (30,30,16,m) Conv2D 3 Conv 2D,fs=2,s=2 (15,15,32,m) Conv2D 4 Conv 2D,fs=5,s=1 (15,15,32,m) Flatten K=7200 (7200,m) FC 1 K=1024 (1024,m) FC 2 K=512 (512,m) Output K=Nrp (N,m) 表 2 廊廳定位誤差和執行時間
Table 2. Corridor positioning error and execution time
Algorithm Mean error/m Standard deviation/m Execution time/s CNNFi combine 0.2473 0.5755 0.3593 CNNFi single 0.7259 1.2447 0.3549 CiFi 1.0845 1.2821 0.4530 DeepFi 0.9939 1.6159 0.1250 表 3 實驗室定位誤差和執行時間
Table 3. Laboratory positioning error and execution time
Algorithm Mean error/m Standard deviation/m Execution time/s CNNFi combine AP=2 0.4806 0.8566 0.5156 CNNFi combine AP=1 0.7159 0.8564 0.3593 CNNFi single 1.1532 1.2243 0.3437 CiFi 1.3559 1.1390 0.4531 DeepFi 1.4523 1.2082 0.1406 www.77susu.com -
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