面向地電極電流場透地通信的兩階段長相關(guān)信號捕獲方法
doi: 10.11999/JEIT240399 cstr: 32379.14.JEIT240399
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1.
北京信息科技大學現(xiàn)代測控技術(shù)教育部重點實驗室 北京 102206
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2.
北京信息科技大學信息與通信工程學院 北京 102206
基金項目: 國家重點研發(fā)項目(2020YFC1511701)，北京市教育委員會科學研究計劃(KM202211232006)，北京信息科技大學促進高校分類發(fā)展-重點研究培育基金(2121YJPY222)
Two-stage Long-correlation Signal Acquisition Method for Through-the-earth Communication of the Ground Electrode Current Field
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1.
Key Laboratory of Modern Measurement and Control Technology of the Ministry of Education, Beijing Information Science and Technology University, Beijing 102206, China
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2.
Institute of Information and Communication Engineering, Beijing Information Science and Technology University, Beijing 102206, China
Funds: The National Key Research and Development Program (2020YFC1511701), The Scientific Research Program of Beijing Municipal Education Commission (KM202211232006), Beijing University of Information Science and Technology promotes the classified development of universities - Key Research and Cultivation Fund (2121YJPY222)
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摘要: 地電極電流場透地通信可以為地下強遮蔽空間信息傳輸提供解決方案。針對接收的電流場信號信噪比(SNR)低、易畸變且受載波頻偏影響大導致捕獲困難的問題，該文設(shè)計一種長同步信號幀結(jié)構(gòu)，在此基礎(chǔ)上提出一種聯(lián)合頻偏粗估計和精估計的兩階段長相關(guān)信號捕獲算法。該算法第1階段利用接收時域信號中的訓練符號，依據(jù)最大似然算法進行采樣間隔偏差粗估計，并計算采樣點補償間隔粗估計值。第2階段結(jié)合粗估計值和接收信噪比，確定采樣點補償間隔精估計值的遍歷范圍，進而設(shè)計本地補償后的長相關(guān)模板信號，實現(xiàn)電流場信號的精確捕獲。本研究在距離地面30.26 m的地下強遮蔽空間中進行了算法性能驗證。實驗結(jié)果表明，與傳統(tǒng)的滑動相關(guān)算法相比，該文所提算法具有更高的捕獲成功概率。
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關(guān)鍵詞:
- 強遮蔽空間 /
- 透地通信 /
- 地電極電流場 /
- 長相關(guān)模板信號 /
- 捕獲算法
Abstract: Wireless through-the-earth communication provides a solution for information transmission in heavily shielded space. The received current field signal has low Signal-to-Noise Ratio (SNR), is easily distorted, and is greatly affected by carrier frequency offset, making signal acquisition difficult. In this paper, a long synchronization signal frame structure is designed and a two-stage long correlation signal acquisition algorithm is proposed that combines coarse and fine frequency offset estimation. In the first stage, the training symbols in the received time-domain signal are used for coarse estimation of sampling interval deviation based on the maximum likelihood algorithm, and the coarse estimation value of the sampling point compensation interval is calculated. In the second stage, the coarse estimation value and the received SNR are combined to determine the traversal range of the fine estimation value of the sampling point compensation interval. A long correlation template signal with local compensation is designed to achieve accurate acquisition of the current field signal. The algorithm’s performance is verified in a heavily shielded space located 30.26 m below the ground. Experimental results show that compared to traditional sliding correlation algorithms, the proposed algorithm has a higher acquisition success probability. -
1 基于粗估計值$ \text{N} $遍歷計算頻偏修正后本地長同步信號
輸入：$ {{\mathrm{Sync}}\_L} $ //本地長同步信號 輸出：$ {{\mathrm{Sync}}\_L}{'} $ //頻偏修正后本地長同步信號 (1) for $ {N'} $ = $ {N}{-}{x} $ to $ {N}{+}{x} $ do // $ {N'} $在范圍內(nèi)遍歷 (2) $ {i} $ = $ {i} $ +1 // $ {i} $的初始值為0 (3) if $\vartheta < 0$ $ {{\mathrm{Sync}}\_L}{'}{(}{i}{)} $ = interpolation ($ {{\mathrm{Sync}}\_L} $, $ {N'}{(}{i}{)} $) //在本地長同步信號信號上每隔$ {N'}{(}{i}{)} $個點插入1個樣值，生
成第$ {i} $個頻偏修正后本地長同步信號(4) else $ {{\mathrm{Sync}}\_L}{'}{(}{i}{)} $ = decline ($ {{\mathrm{Syn}}{\mathrm{c}}\_L} $, $ {N'}{(}{i}{)} $) //在本地長同步信號信號上每隔$ {N'}{(}{i}{)} $個點去除1個采樣點 (5) end (6) end (7) return $ {{\mathrm{Sync}}\_L}{'}{(}{i}{)} $ 
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2 采樣點補償間隔精估計值計算
輸入：$ \text{Sync\_L}{'} $ // 頻偏修正后本地長同步信號 $ {R} $// 接收信號 輸出：$ {N'} $// $ \text{Sync\_L}{'} $與$ {R} $滑動相關(guān)峰值最大時對應的采樣點補
償間隔精估計值(1) for $ {i} $ = 1 To $ {{l}}_{{1}}{-}{{l}}_{{2}}{-1} $ do // 相關(guān)滑動窗口，共有$ {{l}}_{{1}}{-}{{l}}_{{2}}{-1} $個。 (2) $ {g}{(}{i}{)} $ = corr($ {R} $, $ \text{Sync\_L}{'}{(}{i}{)} $) // $ {R} $與 $ \text{Sync\_L}{'}{(}{i}{)} $進行滑動相關(guān) (3) $ {{K}}_{{i}} $ = max($ q7j3ldu95{(}{i}{)} $) //獲取相關(guān)峰值 (4) end (5) $ {N'} $=find(max($ {{K}}_{{i}}{} $)) //獲取相關(guān)峰值最大時對應的采樣點補償間隔精估計值 (6) return $ {N'} $
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表 1 仿真參數(shù)
參數(shù)名稱 參數(shù)值 發(fā)送信號載波頻率(Hz) 10 發(fā)射機時鐘頻率(MHz) 10 收發(fā)機時鐘頻率偏差(PPM) 0.1 [16] 收發(fā)機采樣頻率(Hz) 500 信道類型 加性高斯白噪聲信道 信噪比(dB) –3～6 同步信號長度 30～70符號
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表 2 不同算法捕獲成功概率在不同同步信號點數(shù)下達到95%所需信噪比(dB)
接收同步信號
點數(shù)滑動相關(guān)
捕獲算法粗估計捕獲
算法長相關(guān)捕獲
算法1 500 6 4 3 2 000 5 2 0 2 500 – 0 –2 3 000 – –1 –2 3 500 – –2 –4
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