{"id":550,"date":"2025-10-21T14:32:18","date_gmt":"2025-10-21T06:32:18","guid":{"rendered":"https:\/\/hsiang.cc\/?p=550"},"modified":"2025-10-20T14:45:55","modified_gmt":"2025-10-20T06:45:55","slug":"550","status":"publish","type":"post","link":"https:\/\/hsiang.cc\/?p=550","title":{"rendered":"[GNSS\u7b46\u8a18]Cold Start TTFF\uff1a\u6253\u783430\u79d2\u8ff7\u601d"},"content":{"rendered":"<p>\u4e4b\u524d\u4e00\u76f4\u4ee5\u70ba cold start \u7684 TTFF (Time To First Fix) \u81f3\u5c11\u9700\u8981 30 \u79d2\u624d\u80fd\u5b8c\u6210\u5b9a\u4f4d\u3002\u9019\u500b\u8a8d\u77e5\u4f86\u81ea\u65bc\u4e00\u500b\u770b\u4f3c\u5408\u7406\u7684\u908f\u8f2f\uff1aGPS \u885b\u661f\u9700\u8981\u50b3\u8f38\u5b8c\u6574\u7684 5 \u500b subframe \u624d\u80fd\u63d0\u4f9b\u6240\u6709\u5fc5\u8981\u7684\u5c0e\u822a\u8cc7\u8a0a,\u800c\u6bcf\u500b subframe \u9700\u8981 6 \u79d2,\u56e0\u6b64 5 \u00d7 6 = 30 \u79d2\u3002<\/p>\n<p>\u7136\u800c,\u6700\u8fd1\u8207\u6676\u7247\u5ee0\u5546\u5408\u4f5c\u6642,\u4ed6\u5011\u63d0\u4f9b\u7684\u6e2c\u8a66\u6578\u64da\u5fb9\u5e95\u985b\u8986\u4e86\u6211\u7684\u8a8d\u77e5\u2014\u2014<strong>TTFF \u7adf\u7136\u6709\u6642\u5019\u53ef\u4ee5\u9054\u5230 25 \u79d2<\/strong>!<\/p>\n<p><!--more--><\/p>\n<h2>\u521d\u59cb\u7684\u56f0\u60d1<\/h2>\n<p>\u7576\u6211\u7b2c\u4e00\u6b21\u770b\u5230\u9019\u500b\u6578\u64da\u6642,\u5167\u5fc3\u662f\u5145\u6eff\u8cea\u7591\u7684:<\/p>\n<blockquote><p>\n  \"\u9019\u600e\u9ebc\u53ef\u80fd?\u6578\u64da\u9084\u6c92\u50b3\u5b8c\u600e\u9ebc\u5b9a\u4f4d?\"<\/p>\n<p>  \"\u662f\u4e0d\u662f\u6e2c\u8a66\u65b9\u6cd5\u6709\u554f\u984c?\"<\/p>\n<p>  \"\u9084\u662f\u9019\u6839\u672c\u4e0d\u662f\u771f\u6b63\u7684 cold start?\"\n<\/p><\/blockquote>\n<p>\u5e36\u8457\u9019\u4e9b\u7591\u554f,\u6211\u958b\u59cb\u627e\u8cc7\u6599\u7814\u7a76 GPS \u5c0e\u822a\u96fb\u6587\u7684\u7d50\u69cb\u548c\u5b9a\u4f4d\u8a08\u7b97\u7684\u6700\u4f4e\u9700\u6c42\u3002(\u540c\u6642\u4e5f\u53bb\u8a62\u554f\u6676\u7247\u5ee0\u5546\u78ba\u8a8d)<\/p>\n<h2>GPS \u5c0e\u822a\u96fb\u6587\u7d50\u69cb\u56de\u9867<\/h2>\n<p>\u8b93\u6211\u5011\u5148\u56de\u9867\u4e00\u4e0b GPS L1 C\/A \u5c0e\u822a\u96fb\u6587\u7684\u57fa\u672c\u7d50\u69cb:<\/p>\n<ul>\n<li><strong>1 \u500b Frame<\/strong> = 5 \u500b Subframes = 30 \u79d2<\/li>\n<li><strong>1 \u500b Subframe<\/strong> = 10 \u500b Words = 6 \u79d2<\/li>\n<li><strong>\u50b3\u8f38\u901f\u7387<\/strong>: 50 bps<\/li>\n<\/ul>\n<h3>\u5404 Subframe \u7684\u5167\u5bb9<\/h3>\n<table>\n<thead>\n<tr>\n<th>Subframe<\/th>\n<th>\u5167\u5bb9<\/th>\n<th>\u66f4\u65b0\u983b\u7387<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>Subframe 1<\/strong><\/td>\n<td>\u885b\u661f\u6642\u9418\u6821\u6b63\u53c3\u6578\u3001\u885b\u661f\u5065\u5eb7\u72c0\u614b<\/td>\n<td>\u6bcf 30 \u79d2<\/td>\n<\/tr>\n<tr>\n<td><strong>Subframe 2<\/strong><\/td>\n<td>\u885b\u661f\u8ecc\u9053\u53c3\u6578 (\u661f\u66c6) - \u524d\u534a\u90e8<\/td>\n<td>\u6bcf 30 \u79d2<\/td>\n<\/tr>\n<tr>\n<td><strong>Subframe 3<\/strong><\/td>\n<td>\u885b\u661f\u8ecc\u9053\u53c3\u6578 (\u661f\u66c6) - \u5f8c\u534a\u90e8<\/td>\n<td>\u6bcf 30 \u79d2<\/td>\n<\/tr>\n<tr>\n<td><strong>Subframe 4<\/strong><\/td>\n<td>\u96fb\u96e2\u5c64\u6a21\u578b\u3001UTC \u53c3\u6578\u3001Almanac<\/td>\n<td>\u6bcf 12.5 \u5206\u9418<\/td>\n<\/tr>\n<tr>\n<td><strong>Subframe 5<\/strong><\/td>\n<td>\u885b\u661f\u5065\u5eb7\u72c0\u614b\u3001Almanac<\/td>\n<td>\u6bcf 12.5 \u5206\u9418<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>\u771f\u76f8\u5927\u767d\uff1a18 \u79d2\u7684\u53ef\u80fd\u6027<\/h2>\n<p>\u7d93\u904e\u7814\u7a76\u5f8c\u6211\u624d\u604d\u7136\u5927\u609f\uff1a<strong>\u63a5\u6536\u5668\u8981\u5b8c\u6210\u5b9a\u4f4d,\u4e26\u4e0d\u9700\u8981\u7b49\u5f85\u5168\u90e8 5 \u500b subframes!<\/strong><\/p>\n<h3>\u5b9a\u4f4d\u6240\u9700\u7684\u6700\u4f4e\u8cc7\u8a0a<\/h3>\n<p>\u8981\u8a08\u7b97\u51fa\u7b2c\u4e00\u500b\u4f4d\u7f6e\u5ea7\u6a19,\u63a5\u6536\u5668\u5be6\u969b\u4e0a\u53ea\u9700\u8981:<\/p>\n<ol>\n<li>\u2705 <strong>Subframe 1<\/strong>: \u885b\u661f\u6642\u9418\u6821\u6b63\u53c3\u6578 (6 \u79d2)<\/li>\n<li>\u2705 <strong>Subframe 2<\/strong>: \u661f\u66c6\u8cc7\u6599\u524d\u534a\u90e8 (6 \u79d2)<\/li>\n<li>\u2705 <strong>Subframe 3<\/strong>: \u661f\u66c6\u8cc7\u6599\u5f8c\u534a\u90e8 (6 \u79d2)<\/li>\n<\/ol>\n<p>\u4e5f\u5c31\u662f\u8aaa,<strong>\u7406\u8ad6\u4e0a\u6700\u5feb 18 \u79d2\u5f8c\u5c31\u53ef\u4ee5\u958b\u59cb\u8a08\u7b97\u5ea7\u6a19<\/strong>!<\/p>\n<h3>\u70ba\u4ec0\u9ebc\u4e0d\u9700\u8981 Subframe 4 \u548c 5?<\/h3>\n<ul>\n<li><strong>Subframe 4 &amp; 5<\/strong> \u4e3b\u8981\u5305\u542b:\n<ul>\n<li>Almanac (\u7c97\u7565\u7684\u885b\u661f\u8ecc\u9053\u8cc7\u8a0a,\u7528\u65bc\u5feb\u901f\u641c\u5c0b\u885b\u661f)<\/li>\n<li>\u96fb\u96e2\u5c64\u6a21\u578b\u53c3\u6578<\/li>\n<li>UTC \u6642\u9593\u8f49\u63db\u53c3\u6578<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>\u9019\u4e9b\u8cc7\u8a0a\u5c0d\u65bc<strong>\u63d0\u9ad8\u5b9a\u4f4d\u7cbe\u5ea6<\/strong>\u548c<strong>\u52a0\u901f\u5f8c\u7e8c\u5b9a\u4f4d<\/strong>\u5f88\u6709\u5e6b\u52a9,\u4f46\u4e26\u975e\u7b2c\u4e00\u6b21\u5b9a\u4f4d\u7684<strong>\u5fc5\u8981\u689d\u4ef6<\/strong>\u3002<\/p>\n<h2>\u5be6\u969b\u7684 25 \u79d2 TTFF<\/h2>\n<p>\u90a3\u9ebc\u70ba\u4ec0\u9ebc\u5be6\u969b\u6e2c\u5230\u7684\u662f 25 \u79d2\u800c\u4e0d\u662f 18 \u79d2\u5462?<\/p>\n<p>\u9019\u6d89\u53ca\u5230\u5e7e\u500b\u5be6\u969b\u56e0\u7d20:<\/p>\n<h3>1. <strong>\u8a0a\u865f\u6355\u7372\u8207\u8ffd\u8e64\u6642\u9593<\/strong><\/h3>\n<ul>\n<li>\u63a5\u6536\u5668\u9700\u8981\u6642\u9593\u641c\u5c0b\u548c\u9396\u5b9a\u885b\u661f\u8a0a\u865f<\/li>\n<li>\u901a\u5e38\u9700\u8981 2-5 \u79d2<\/li>\n<\/ul>\n<h3>2. <strong>\u8cc7\u6599\u89e3\u78bc\u8207\u9a57\u8b49<\/strong><\/h3>\n<ul>\n<li>\u9700\u8981\u6b63\u78ba\u89e3\u78bc\u5c0e\u822a\u96fb\u6587<\/li>\n<li>\u9032\u884c parity check \u78ba\u4fdd\u8cc7\u6599\u6b63\u78ba\u6027<\/li>\n<li>\u53ef\u80fd\u9700\u8981\u91cd\u50b3\u932f\u8aa4\u7684\u8cc7\u6599<\/li>\n<\/ul>\n<h3>3. <strong>\u591a\u9846\u885b\u661f\u7684\u540c\u6b65\u554f\u984c<\/strong><\/h3>\n<ul>\n<li>\u5b9a\u4f4d\u81f3\u5c11\u9700\u8981 4 \u9846\u885b\u661f<\/li>\n<li>\u4e0d\u540c\u885b\u661f\u7684 subframe \u8d77\u59cb\u6642\u9593\u4e0d\u540c<\/li>\n<li>\u9700\u8981\u7b49\u5f85\u6240\u6709\u5fc5\u8981\u885b\u661f\u90fd\u50b3\u8f38\u5b8c\u524d 3 \u500b subframes<\/li>\n<\/ul>\n<h3>4. <strong>\u4f4d\u7f6e\u8a08\u7b97\u6642\u9593<\/strong><\/h3>\n<ul>\n<li>\u89e3\u7b97\u5c0e\u822a\u65b9\u7a0b\u5f0f<\/li>\n<li>\u8fed\u4ee3\u8a08\u7b97\u6536\u6582<\/li>\n<\/ul>\n<p>\u56e0\u6b64,<strong>25 \u79d2\u7684 TTFF \u662f\u4e00\u500b\u76f8\u7576\u512a\u79c0\u7684\u8868\u73fe<\/strong>,\u4ee3\u8868\u63a5\u6536\u5668\u5728\u6355\u7372\u8a0a\u865f\u5f8c,\u5e78\u904b\u5730\u5728\u8f03\u77ed\u6642\u9593\u5167\u6536\u96c6\u5230\u4e86\u8db3\u5920\u7684\u8cc7\u8a0a\u3002<\/p>\n<h2>\u5be6\u969b\u61c9\u7528\u7684\u8003\u91cf<\/h2>\n<p>\u96d6\u7136\u7406\u8ad6\u4e0a\u53ef\u4ee5\u5728 18-25 \u79d2\u5167\u5b8c\u6210 cold start,\u4f46\u5728\u5be6\u969b\u61c9\u7528\u4e2d:<\/p>\n<h3>\u5927\u90e8\u5206\u60c5\u6cc1 TTFF > 30 \u79d2\u7684\u539f\u56e0<\/h3>\n<ol>\n<li><strong>\u8a0a\u865f\u74b0\u5883\u4e0d\u4f73<\/strong>\n<ul>\n<li>\u90fd\u5e02\u5cfd\u8c37\u6548\u61c9<\/li>\n<li>\u5ba4\u5167\u6216\u906e\u853d\u74b0\u5883<\/li>\n<li>\u591a\u8def\u5f91\u5e72\u64fe<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u53ef\u898b\u885b\u661f\u6578\u91cf\u4e0d\u8db3<\/strong>\n<ul>\n<li>\u9700\u8981\u7b49\u5f85\u66f4\u591a\u885b\u661f\u5347\u8d77<\/li>\n<li>\u67d0\u4e9b\u885b\u661f\u8a0a\u865f\u54c1\u8cea\u4e0d\u4f73<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u63a5\u6536\u5668\u6027\u80fd\u9650\u5236<\/strong>\n<ul>\n<li>\u8a0a\u865f\u8655\u7406\u80fd\u529b<\/li>\n<li>\u5929\u7dda\u9748\u654f\u5ea6<\/li>\n<li>\u6f14\u7b97\u6cd5\u6548\u7387<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u521d\u59cb\u689d\u4ef6\u4e0d\u78ba\u5b9a<\/strong>\n<ul>\n<li>\u5b8c\u5168\u4e0d\u77e5\u9053\u5927\u6982\u4f4d\u7f6e<\/li>\n<li>\u6642\u9593\u8aa4\u5dee\u8f03\u5927<\/li>\n<li>\u9700\u8981\u66f4\u591a\u8cc7\u8a0a\u4f86\u78ba\u4fdd\u5b9a\u4f4d\u53ef\u9760\u6027<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<h2>\u7d50\u8ad6<\/h2>\n<p>\u9019\u6b21\u7d93\u9a57\u8b93\u6211\u5b78\u5230:<\/p>\n<ol>\n<li><strong>\u7406\u8ad6\u6700\u5c0f\u503c<\/strong>: 18 \u79d2 (\u63a5\u6536\u5b8c Subframe 1-3)<\/li>\n<li><strong>\u512a\u79c0\u8868\u73fe<\/strong>: 25 \u79d2\u5de6\u53f3<\/li>\n<li><strong>\u5178\u578b\u8868\u73fe<\/strong>: 30-60 \u79d2<\/li>\n<li><strong>\u56f0\u96e3\u74b0\u5883<\/strong>: \u53ef\u80fd\u8d85\u904e 2 \u5206\u9418<\/li>\n<\/ol>\n<p>GNSS \u5b9a\u4f4d\u662f\u4e00\u500b\u7406\u8ad6\u8207\u5be6\u8e10\u7d50\u5408\u7684\u9818\u57df,\u5f88\u591a\u6642\u5019\u6211\u5011\u7fd2\u4ee5\u70ba\u5e38\u7684\"\u5e38\u8b58\"\u80cc\u5f8c,\u5176\u5be6\u9084\u6709\u66f4\u6df1\u5c64\u7684\u539f\u7406\u503c\u5f97\u63a2\u8a0e\u3002\u9019\u6b21\u5c0d TTFF \u7684\u91cd\u65b0\u8a8d\u8b58,\u4e5f\u63d0\u9192\u6211\u8981\u6301\u7e8c\u4fdd\u6301\u597d\u5947\u5fc3\u548c\u5b78\u7fd2\u614b\u5ea6\u3002<\/p>\n<hr \/>\n<p><strong>\u9577\u77e5\u8b58\u4e86!<\/strong> \u539f\u4f86 cold start \u4e0d\u4e00\u5b9a\u8981\u7b49 30 \u79d2,\u4f46\u5be6\u969b\u4e0a\u5927\u90e8\u5206\u6642\u5019\u9084\u662f\u6703\u8d85\u904e 30 \u79d2\u3002\u9019\u5c31\u662f\u7406\u8ad6\u8207\u5be6\u52d9\u7684\u5dee\u8ddd\u554a! \ud83d\udce1\ud83d\udef0\ufe0f<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e4b\u524d\u4e00\u76f4\u4ee5\u70ba cold start \u7684 TTFF (Time To First  &hellip; <a href=\"https:\/\/hsiang.cc\/?p=550\">\u95b1\u8b80\u5168\u6587 <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[497,396],"tags":[551,99,68,550,549,553,552],"class_list":["post-550","post","type-post","status-publish","format-standard","hentry","category-iot","category-tech","tag-cold-start","tag-gnss","tag-gps","tag-time-to-first-fix","tag-ttff","tag-553","tag-552"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/hsiang.cc\/index.php?rest_route=\/wp\/v2\/posts\/550","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hsiang.cc\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hsiang.cc\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hsiang.cc\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/hsiang.cc\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=550"}],"version-history":[{"count":4,"href":"https:\/\/hsiang.cc\/index.php?rest_route=\/wp\/v2\/posts\/550\/revisions"}],"predecessor-version":[{"id":554,"href":"https:\/\/hsiang.cc\/index.php?rest_route=\/wp\/v2\/posts\/550\/revisions\/554"}],"wp:attachment":[{"href":"https:\/\/hsiang.cc\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=550"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hsiang.cc\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=550"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hsiang.cc\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=550"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}