资料翻译之三-GI from Wikipedia

最新推荐文章于 2025-02-11 13:27:08 发布

Blnj_J

最新推荐文章于 2025-02-11 13:27:08 发布

阅读量563

点赞数

分类专栏：翻译文章标签： GI Guard Interval

翻译专栏收录该内容

3 篇文章

订阅专栏

本文深入解析了保护间隔(GI)在OFDM和TDMA等通信系统中的关键作用，以及其如何应对传播时延、回声及反射等问题，确保数据安全解码。同时探讨了GI长度对数据传输率的影响。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

做实验时看到一个参数，GI，于是wiki了一下，晚上回宿舍就翻译了下贴在这了。

毕竟是计算机网络的相关内容，只能懂一些表面的东西，大概清楚了GI是什么。

Guard interval

In telecommunications, guard intervals are used to ensure that distinct transmissions do not interfere with one another, or otherwise cause overlapping transmissions. These transmissions may belong to different users (as in TDMA) or to the same user (as in OFDM).

The purpose of the guard interval is to introduce immunity to propagation delays, echoes and reflections, to which digital data is normally very sensitive.

在电信学领域(远程通信)，GI(译作保护间隔)被用来保证有区别的传输不会互相干扰，或者阻止交叠传输。这些传输线路可能来自于不同的用户(时分复用连接)，也可能来自于同一用户(正交频分服用)。

对于数字数据非常敏感的系统而言，引入GI的目的是为了使其获得对传播时延、回声及反射的抵抗力。

Contents

Use in digital communications systems[edit]

In OFDM, the beginning of each symbol is preceded by a guard interval. As long as the echoes fall within this interval, they will not affect the receiver's ability to safely decode the actual data, as data is only interpreted outside the guard interval.

In TDMA, each user's timeslot ends with a guard period, to avoid data loss and to reduce interference to the following user, caused by propagation delay. Thus a user's timeslot is protected from interference from the preceding user, by the guard interval (guard period) at the end of that preceding user's timeslot. It is a common misconception that each TDMA timeslot begins with a guard interval, however the ITU Technical Specifications (such as GSM 05.05) clearly define the guard period as being at the end of each timeslot, thus providing protection against data loss within that timeslot, and protection against interference to the following timeslot.

在OFDM中，每个符号的开始都会被添加一个GI。由于数据是在GI之外被打断的，因此只要失败的反馈发生在这个时间间隔内，有错误的数据就不会影响接收端安全地解码其他的数据。

在TDMA中，每个用户的使用时段结束时都会有一个保护时期，用来避免和减轻有传播实验造成的数据丢失和干扰。因此可以避免一个用户的使用时段被后续用户的使用干扰。一个常见的误解是用户的使用时段开始时的GI是属于本用户的，然而ITU技术说明中很明确的定义每个使用时段的结束时的GI是属于该用户的GI，以用来避免该时段内的数据丢失和接下来的时段造成的干扰。

Longer guard periods allow more distant echoes to be tolerated. However, longer guard intervals reduce the channel efficiency. For example, in DVB-T, four guard intervals are available (given as fractions of a symbol period):

1/32 ; 1/16 ; 1/8 ; 1/4

Hence, 1/32 gives the lowest protection and the highest data rate; 1/4 results in the best protection but the lowest data rate.

Radio waves propagate at the speed of light, 3 µs per 1000 meter (5 μs/mile). Ideally, the guard interval is just longer than the delay spread of the channel.

越长的保护时段可以容忍间隔更大的回声，但会造成信道的效率下降。比如说，在DVB-T有四种GI。在这里，1/32会提供最少的保护但会提供最高的传输速率；1/4会提供最好的保护却会使传输速率降到最低。

无线信号会以光速传播，也就是3us传播1000米。一般而言下，GI需要比信道的时延扩展长。

802.11 guard interval[edit]

The standard symbol guard interval used in 802.11 OFDM is 0.8 μs. To increase data rate, 802.11n added optional support for a 0.4 μs guard interval. This provides an 11% increase in data rate.

The shorter guard interval results in a higher packet error rate when the delay spread of the channel exceed the guard interval and/or if timing synchronization between the transmitter and receiver is not precise. A scheme could be developed to work out whether a short guard interval would be of benefit to a particular link. To reduce complexity, manufacturers typically only implement a short guard interval as a final rate adaptation step when the device is running at its highest data rate.[1]

在802.11的OFDM中使用的标准GI是0.8us。为了提高传输速率，802.11n中额外增加了0.4us的GI支持。这使得无线传输速率提高了11%。

如果信道的时延扩展超过了GI的大小或者RxTx间的时间同步不够精细，较短的GI会导致很高的错包率。可以通过一定的策略来判断一个短的GI是否对一个特定的线路起到了促进作用。为了减少复杂度，对于正在以最高速率传输的设备而言，制造业中往往将GI调整作为最后使用的一种调整速率的步骤。

来自 <https://en.wikipedia.org/wiki/Guard_interval>