跳频的多样性提高了性能

　　跳频的多样性提高了性能

　　本文介绍了在简单的低功耗无线收发器的典型环境中增强无线链路的方法。它还专注于最大限度地提高无线链路的可靠性，同时保持整体硬件成本下降。对于许多简单的收发器，使用跳频分集的附加开销似乎不值得；然而，本文提出了强大的技术原因，即使是简单的应用程序，也应该考虑这一点。

　　无线信道是一个空间和频率相关的，随时间变化的射频系统。这意味着RF信道的瞬时性能随频率、时间和物理变化而变化。为了获得可靠的无线通信链路，无线系统应该包括使用这三个向量的技术。例如，简单地改变工作频率为频率分集。同样，空间布局的改变也成为空间的多样性，时间成为时间的多样性。

　　Tradeoffs and benefits for each diversity scheme

　　For each diversity scheme there is an increased system cost in the form of extra hardware or more software complexity. Sometimes there can also be a reduced system capacity because of message repetition. When reviewing the different wireless standards most prevalent today， you will find one or more of them currently in use：

　　Space and/or Polarization diversity is used by GSM， DECT and WiFi

　　a. Extra hardware cost in extra transceivers and antennas

　　b. Retains full system data rate

　　Frequency diversity is used by WiFi and Bluetooth

　　a. No hardware cost， however， extra software complexity applies

　　b. Reduced total system data rate because of time spent changing frequency

　　Time diversity （SimpliciTI™）

　　a. No hardware cost， no significant software complexity

　　b. Reduced total system data rate by the number of repetitions of data