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如何选择802.11g标准WLAN大功率AP [复制链接]

xiaoq99c3

军衔等级：

新兵

注册：2007-2-13

电梯直达

1^# 大中小

发表于 2007-10-9 17:55:00 |只看该作者 |倒序浏览

<p class="MsoNormal" align="left" style="BACKGROUND: white; MARGIN: 0cm 0cm 0pt; WORD-BREAK: break-all; TEXT-INDENT: 18pt; TEXT-ALIGN: left; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-char-indent-count: 2.0; mso-pagination: widow-orphan;">近年来由于各地运营商新业务的蓬勃开展，运营商急需新的无线网络来承载新业务，然而3G网络并未未实现建设，这时WLAN网络就成了运营商新业务网的首选。与此同时WLAN网络组网设备802.11g<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">大功率AP就越来越被市场所关注。于是乎，各种 “大功率AP”层出不穷，甚至出现了号称功率可达2W、4W的11g大功率AP，一时间市场上大功率AP产品良莠不齐鱼龙混杂。    <p class="MsoNormal" align="left" style="BACKGROUND: white; MARGIN: 0cm 0cm 0pt; WORD-BREAK: break-all; TEXT-INDENT: 18pt; TEXT-ALIGN: left; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-char-indent-count: 2.0; mso-pagination: widow-orphan;">那么真正的符合运营商需求的801.11g<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">大功率AP和市场上大多数所谓的“大功率AP”究竟有何不同呢？下面笔者从3点来进行说明：    <p class="MsoNormal" align="left" style="BACKGROUND: white; MARGIN: 0cm 0cm 0pt; WORD-BREAK: break-all; TEXT-ALIGN: left; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-pagination: widow-orphan; tab-stops: list 45.1pt;">1、   速率不同：   <p class="MsoNormal" align="left" style="BACKGROUND: white; MARGIN: 0cm 0cm 0pt 27.1pt; WORD-BREAK: break-all; TEXT-INDENT: 18pt; TEXT-ALIGN: left; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-char-indent-count: 2.0; mso-pagination: widow-orphan; mso-para-margin-left: 2.58gd;"><span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">从表面产品介绍上来看，每款大功率AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">产品遵守的都是IEEE 802.11g<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">协议，协议速率54M<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">，并且向下兼容802.11b<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">协议，发射功率为500MW<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">或者1W<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">。那么既然协议相同速率就该相差无几啊，为何会速率不同呢？如大家所知，支持802.11g<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">标准的WLAN<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">设备在增加发射功率的同时，因为放大器的线性问题必然会影响其数据传输的净速率，而“伪大功率AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">”恰恰是在“功率”和“净速率”概念上混淆了视听。真正的大功率AP中的放大器线性好、有效保证了其信噪比指标，没有因发射信号功率的加大而影响传输的净速率，以XX通信ET-62XX——WLAN电信级室外大功率AP为例，该设备最大发射功率为500mW，在发射功率为500mW时仍可以802.11g模式（净速率≥20M）提供高速率无线数据传输，而很多号称为400mW、500mW或1W发射功率的大功率AP在它们标称的400mW、500mW或1W满负荷功率下只能以802.11b （净速率≤5M）传输模式工作，只有在发射功率下调为100mW左右时才能以802.11g模式传输，否则就无法保证稳定链接。从此可以看出，这些所谓的大功率AP在产品宣传上割裂了发射功率与净速率的必然联系及必须同时保证的要求，而是将它们分开描述，从而在文字上将用户引向了歧义。    <p class="MsoNormal" align="left" style="BACKGROUND: white; MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-pagination: widow-orphan; tab-stops: list 45.1pt;">2、  功率放大对象不同：<p class="MsoNormal" align="left" style="BACKGROUND: white; MARGIN: 0cm 0cm 0pt 27.1pt; WORD-BREAK: break-all; TEXT-INDENT: 18pt; TEXT-ALIGN: left; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-char-indent-count: 2.0; mso-pagination: widow-orphan; mso-para-margin-left: 2.58gd;"><span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">做为WLAN<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">覆盖网络的骨干设备，大功率AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">在信号放大上的性能是最被人关注的，这个性能决定了大功率AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">设备的有效覆盖范围是否能够满足需要，同时这个能力也决定了设备投入数量和成本的多少。一款真正的大功率AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">产品应该具备“信号双向放大”的功能，即它不仅是放大了自身发射信号，同时放大了客户端向它发来的接收信号。只有这样才能真正扩大WLAN<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">信号的有效覆盖范围，即在相同客户端设备条件下，大幅度扩大WLAN<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">信号覆盖范围后仍保证无线链路的稳定传输。     <p class="MsoNormal" align="left" style="BACKGROUND: white; MARGIN: 0cm 0cm 0pt 27.1pt; WORD-BREAK: break-all; TEXT-INDENT: 18pt; TEXT-ALIGN: left; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-char-indent-count: 2.0; mso-pagination: widow-orphan; mso-para-margin-left: 2.58gd;"><span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">而目前市场上很多大功率AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">由于技术或成本上的原因，采用了在AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">发射支路仅添加一片功放芯片单向放大发射信号的方式，只放大了自身的下行发射信号。表面上看似乎AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">信号覆盖范围有了增加，但网络链接质量并未有改善，与普通功率AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">相比其有效网络覆盖距离几乎没有增加，因而很容易在覆盖的边缘区域产生“信号有去无回”的现象，这样的仅扩大AP<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">自身信号覆盖范围的信号功率放大对WLAN<span style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-bidi-font-family: Arial; mso-font-kerning: 0pt; mso-bidi-font-size: 11.0pt; mso-bidi-font-weight: bold;">覆盖网络建设没有任何意义！

[此贴子已经被zjsunyi于2007-10-10 8:12:45编辑过]