跳頻的多樣性提高了性能

　　跳頻的多樣性提高了性能

　　本文介紹了在簡單的低功耗無線收發(fā)器的典型環(huán)境中增強(qiáng)無線鏈路的方法。它還專注于最大限度地提高無線鏈路的可靠性，同時保持整體硬件成本下降。對于許多簡單的收發(fā)器，使用跳頻分集的附加開銷似乎不值得；然而，本文提出了強(qiáng)大的技術(shù)原因，即使是簡單的應(yīng)用程序，也應(yīng)該考慮這一點。

　　無線信道是一個空間和頻率相關(guān)的，隨時間變化的射頻系統(tǒng)。這意味著RF信道的瞬時性能隨頻率、時間和物理變化而變化。為了獲得可靠的無線通信鏈路，無線系統(tǒng)應(yīng)該包括使用這三個向量的技術(shù)。例如，簡單地改變工作頻率為頻率分集。同樣，空間布局的改變也成為空間的多樣性，時間成為時間的多樣性。

　　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