Packet Format 및 Advertising 방법
Preamble
- Receiver에서 Frequency 동기화
- Symbol timing estimation
- AGC(Automatic Gain Control)
- 10101010b, 01010101b로 구성
- Access Address의 LSB Address가 1이면 01010101b, 이외에는 모두 10101010b
Access Address
- Advertising Packet은 10001110100010011011111011010110b (0x8E89BED6)
- Data Packet은 두 Device의 Link layer connection에 따라서 변경
PDU
CRC
Advertising Packet Size :
- Header : Advertising Header 1Byte, Payload Length 1 Byte
- Payload: Advertiser Address : 6Byte, Advertising Data : 0-31Byte
Data Packet Size :
- Header : Data Header 1Byte, Payload Length 1Byte
- Payload : L2CAP Length 2Byte, L2CAP CID 2Byte, Data 0-21Byte, MIC(Message Integrity Check) 3Byte
- Data Payload Size는 암호화 여부에 따라서 차이 발생
- 암호화를 진행하면 MIC를 포함, 암호화하지 않으면 MIC를 포함하지 않음
- 암호화하지 않는 경우 Data Payload size : 0-27Byte
- 암호화하는 경우 Data Payload size : 0-31Byte
Advertising 작동 방식
Advertising Interver예
- Advertising Interval Min : 20ms
- Advertising Interval Max : 80ms
Passive Scan : Central Device에서 Slave에서 보내는 기본 Advertising Packet을 수신하고 추가적인 정보를 요청 하지 않음.
Active Scan : Central Device에서 Slave에서 보내는 기본 Advertising Packet을 수신하고 추가적인 정보를 요청.
Advertisement packet 포함 정보
- Device 상태 정보 : Discoverability and connectability mode
- Advertiser Address
- TX Power level
- Support Service
- Application data
Scan Response packet 포함 정보
- Device name
- Support service(Profiles)
Advertising PDU 종류
- ADV_IND : connectable undirected advertising event
- ADV_DIRECT_IND : connectable directed advertising event
- ADV_NONCONN_IND : non-connectable undirected advertising event
- ADV_SCAN_IND : scannable undirected advertising event
- SCAN_REQ
- SCAN_RSP
- CONNECT_REQ
Data PDU 종류
- LL Data PDU
LL Control PDU
- LL_CONNECTION_UPDATE_REQ
- LL_CHANNEL_MAP_REQ
- LL_TERMINATE_IND
- LL_ENC_REQ
- LL_ENC_RSP
- LL_START_ENC_REQ
- LL_START_ENC_RSP
- LL_UNKNOWN_RSP
- LL_FEATURE_REQ
- LL_FEATURE_RSP
- LL_PAUSE_ENC_REQ
- LL_PAUSE_ENC_RSP
- LL_VERSION_IND
- LL_REJECT_IND
Bluetooth Specification Version 4.0 Volume 6 Part B 2.4 참조
Connection Process
