RF and Baseband of BT

RF(無線電)：

• 採用2.4GHz的ISM公用頻段 - 頻段從2400MHz 到 2483,5MHz，劃分為79個頻道，每個頻道1MHz (f=2402+k MHz, k=0,…,78)
• 採用跳頻式展頻技術（Frequency Hopping Spread spectrum）- 每秒跳動1600次(在正常操作的情況下)1Mhz的頻道間距
  
• 採用GFSK（Gaussian Frequency Shift Key）調變 - 數位FM模式，容許的峰值頻率偏差為175kHz
  
• 最低功率的傳輸距離為10公尺，加大功率最多可達100公尺

Baseband(基頻)：

• BT device address: 每個bt device有一個48 bits的IEEE MAC, it's like an unique id of the device. MAC分成 -- Lower address(24 bits), Upper address(8 bits) and Non-significant address(16 bits)

• BT clock: Every Bluetooth device shall have a native clock that shall be derived from a free running system clock. The clock determines critical periods and triggers the events in the device. Four periods are important in the Bluetooth system: 312.5 μs, 625 μs, 1.25 ms, and 1.28 s.
  

• Piconet and Scatternet: a) single-slave piconet, b) multi-slave piconet and c) scatternet (master is also slave, many piconets form a scatternet)

• 封包結構: access code, header, payload (this is the standard basic rate packet format)

• Logical transport:
  
• Synchronous Connection-Oriented (SCO) logical transport
• Extended Synchronous Connection-Oriented (eSCO) logical transport
• Asynchronous Connection-Oriented (ACL) logical transport
• Active Slave Broadcast (ASB) logical transport
• Parked Slave Broadcast (PSB) logical transport
  

SCO : Circuit-switched - 較適合語音（Voice）服務的傳輸方式，它有點像是在溝通的兩方之間設立一條專 用道路，這條專用道路在通話過程中不會有別人來Share。
ACL : Packet-switched - 大家共享一條高速公路，人少的時候，你可以開快一 點。塞車的時候，就會慢一點，通常較適合資料（Data）的傳輸。