【AT研发专区】模组网络通用丨蜂窝网络基本知识介绍
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">在物联网的时代，蜂窝网络<span style="color: black;">作为</span>了连接<span style="color: black;">各样</span>智能设备的重要<span style="color: black;">基本</span>。而在蜂窝网络中，蜂窝模组则是实现物联网连接的关键组件。<span style="color: black;">做为</span>物联网<span style="color: black;">研发</span>人员，<span style="color: black;">认识</span>蜂窝网络的<span style="color: black;">基本</span>知识是非常重要的。本文<span style="color: black;">仔细</span>解答了6个在<span style="color: black;">研发</span>过程的<span style="color: black;">平常</span>问题，<span style="color: black;">帮忙</span>客户更好地理解蜂窝模组在物联网<span style="color: black;">研发</span>中的应用和<span style="color: black;">功效</span>。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-axegupay5k/f50b88395b14490fb904d1b6522681b3~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1725628440&x-signature=eumUkof3gMOj089YwRZyPJ5cphE%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">1．什么是2G、4G、5G、NB-IoT网络？</span></strong></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(1) 2G网络：全<span style="color: black;">叫作</span>第二代移动通信系统，移动的2G技术<span style="color: black;">叫作</span>之为GSM（Global System for Mobile Communication），是一种典型的蜂窝网络。传统的GSM网络以数字语音传输技术为核心，是一种电路交互技术，<span style="color: black;">无</span>分组域功能；GSM网络辅以GPRS分组交换技术<span style="color: black;">才可</span>实现数据业务功能。所有2G物联网模组均<span style="color: black;">运用</span>GPRS网络进行数据收发；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(2) 4G网络：全<span style="color: black;">叫作</span>第四代移动通信系统，该技术<span style="color: black;">包括</span>TDD-LTE和FDD-LTE，<span style="color: black;">亦</span>是蜂窝网络中的一种，是基于UMTS网络技术的<span style="color: black;">长时间</span>演进（LTE, Long Time Evolution）。相比于2G网络，4G网络<span style="color: black;">拥有</span>更简化的网络构架和更精简的信令开销，使得4G网络的速率和时延相比2G网络有本质上的<span style="color: black;">提高</span>；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(3) 5G网络：<span style="color: black;">所说</span>5G网络所指的<span style="color: black;">便是</span>在移动通信网络发展中的第五代网络。与之前的四代移动网络相比较而言，5G网络在<span style="color: black;">实质</span>应用过程中表现出更加强大的功能，并且理论上其传输速度每秒钟能够达到数十GB，是4G移动网络的几百倍。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(4) NB-IoT网络：全<span style="color: black;">叫作</span>窄带物联网（Narrow Band Internet of Things），该技术是一种基于LTE网络构架的、3GPP协议标准LPWA（低功耗广域网）<span style="color: black;">处理</span><span style="color: black;">方法</span>。<span style="color: black;">经过</span>其上下行重传、<span style="color: black;">提高</span>功率谱密度等<span style="color: black;">方法</span><span style="color: black;">供给</span>比LTE高达20dB的增益，并且<span style="color: black;">经过</span>协议中的PSM模式，使模组达到uA级的休眠态功耗，这使其能广泛地应用于<span style="color: black;">各样</span>低速率、对时延不<span style="color: black;">敏锐</span>、对移动性<span style="color: black;">需求</span>不强的场景。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">2．什么是APN？<span style="color: black;">为何</span>要设置APN信息？</span></strong></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(1) APN（Access Point Name）是一种网络接入技术，终端模组在接入到网络时必须配置该参数，该参数决定了模组以何种方式接入网络；用户在上网时，针对<span style="color: black;">区别</span>的APN，GGSN/P-GW会把用户转接代理到<span style="color: black;">区别</span>的网络，<span style="color: black;">因此</span><span style="color: black;">一般</span><span style="color: black;">状况</span>下，都<span style="color: black;">运用</span>运营商<span style="color: black;">供给</span>的公用APN节点；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(2)中国移动2G公用APN为CMMTM和CMNET；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(3)中国移动4G公用APN为CMNET，4G物联网卡APN为CMIOT；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(4)中国移动NB-IoT正式商用网络公用APN为CMNBIOT，NB-IoT<span style="color: black;">区别</span>的APN还承载着<span style="color: black;">区别</span>的PSM和eDRX功能差异；非商用NB网络的APN以各地区网络侧<span style="color: black;">实质</span>设置为准。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">表1为中国移动公网常用NB-IoT APN及其对应的PSM和eDRX支持<span style="color: black;">状况</span>。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/4e5426e7ad3a473e8b73adca26e17c43~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1725628440&x-signature=WkGM4IHG8JjpNRWVC2XqNCLsbkQ%3D" style="width: 50%; margin-bottom: 20px;">
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;">表1 中国移动NB-IoT网络常用 APN</p>
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<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">3．小区<span style="color: black;">选取</span>、小区重选和小区切换有何区别？</span></strong></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(1)小区<span style="color: black;">选取</span>是当终端模组开机或者从盲区进入覆盖区时，将会<span style="color: black;">按照</span>SIM卡信息，寻找PLMN<span style="color: black;">准许</span>的所有频点，并<span style="color: black;">选取</span>合适的小区驻留这一<span style="color: black;">全部</span>流程；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(2)小区重选/小区切换均<span style="color: black;">指的是</span>终端模组驻留在当前小区，<span style="color: black;">因为</span>网络环境<span style="color: black;">出现</span>变更，需要离开本小区，驻留到其他小区上的过程，但小区重选必须在idle态进行，小区切换必须在连接态进行；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(3)小区切换又分为硬切换和软切换:</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">所说</span>硬切换，<span style="color: black;">便是</span>指终端采用先断开与原小区的连接、再与新小区<span style="color: black;">创立</span>连接的方式进行切换，这种切换会<span style="color: black;">引起</span>业务中断；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">所说</span>软切换，<span style="color: black;">便是</span>指终端采用保持与原基站连接<span style="color: black;">持续</span>的前提下，切换到新小区，最后再断开与原小区之前的连接的方式进行切换；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">需要<span style="color: black;">重视</span>的是NB-IoT网络协议中<span style="color: black;">无</span>定义切换概念，只支持小区重选，4G网络和5G网络<span style="color: black;">运用</span>的都是软切换方式。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">4．终端进行数据业务激活，<span style="color: black;">怎样</span>确认模组本地IP<span style="color: black;">位置</span>及IP<span style="color: black;">位置</span>变化？</span></strong></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(1) 2G、4G、NB-IoT终端均可<span style="color: black;">经过</span>AT+CGPADDR指令读取模组当前的业务IP，<span style="color: black;">通常</span><span style="color: black;">状况</span><span style="color: black;">来讲</span>，该IP都是浮动的；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(2)模组终端断开当前PDP连接，重新执行PDP激活之后，该IP将会<span style="color: black;">出现</span>变化。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">5．<span style="color: black;">为么</span><span style="color: black;">查找</span>网络质量结果会<span style="color: black;">显现</span>变动？</span></strong></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">因为</span>网络信号受基站发射功率、无线环境和干扰等影响，会<span style="color: black;">显现</span>不可预知的信号质量波动，<span style="color: black;">引起</span>模组收到的信号质量是一个变换的状态，而不是一个恒定值，这<span style="color: black;">亦</span>是无线网络的特点之一。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">6．TCP和UDP数据传输方式有何区别？</span></strong></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(1) TCP面向连接，采用数据流方式通信；UDP面向无连接，采用数据包方式通信；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(2) TCP方式存在握手和应答机制，能<span style="color: black;">保准</span>数据的<span style="color: black;">靠谱</span>性，并且能<span style="color: black;">保准</span>数据的<span style="color: black;">次序</span>性；而UDP方式不存在这种握手和应答机制，在传输中可能存在丢包的问题，<span style="color: black;">因为</span>面向无连接，<span style="color: black;">不可</span><span style="color: black;">保准</span>数据报的<span style="color: black;">次序</span>，可能<span style="color: black;">显现</span>后发的UDP包先上报的<span style="color: black;">状况</span>，但正是<span style="color: black;">因为</span>UDP传输这种特性，使得传输数据减少，传输速率<span style="color: black;">升高</span>；</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">(3)如想<span style="color: black;">保准</span>UDP传输<span style="color: black;">靠谱</span>性，可在应用层设计握手应答机制实现数据传输的<span style="color: black;">靠谱</span>性和<span style="color: black;">次序</span>型。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/4b8da7c8a2b54432af35795cff3bb8ac~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1725628440&x-signature=1QSf5PEvLSnrJB7skgC433O1EAY%3D" style="width: 50%; margin-bottom: 20px;">
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;">表2 TCP和UDP协议对比</p>
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<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><a style="color: black;">#通信模组#</a><a style="color: black;">#模组<span style="color: black;">研发</span>#</a><a style="color: black;">#<span style="color: black;">研发</span>指南#</a><a style="color: black;">#物联网模组#</a></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><a style="color: black;">#蜂窝网络#</a></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">转载自中移物联网，仅供模组品牌对应于中移物联网模组体系参考。</span></p>
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