1. Wireless Networks - MAC layer - Bluetooth

2. What is Bluetooth? Cable replacement technology primarily Bluetooth wireless technology is an open specification for a low-cost, low-power, short-range radio technology for ad-hoc wireless communication of voice and data anywhere in the world. Where does the name come from? –To honor a 10th century king Bluetooth in Denmark who united that country and established Christianity

3. Bluetooth Bluetooth Piconet: a polling/TDMA scheme Bluetooth working group history –February 1998: The Bluetooth SIG is formed –promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba –+ 3Com, Lucent, Microsoft, Motorola Bluetooth uses a frequency-hopping scheme in the unlicensed band at 2.4 GHz. The major goal is to allow relatively cheap electronic devices to communicate directly in an ad-hoc fashion, Moreover, the Bluetooth equipped devices can also form networks– such a network of personal devices is often referred to as a personal area network (PAN).

4. Personal Ad-hoc Networks Cable Replacement - Synchronization - Cordless Headset Landline Data/Voice Access Points What does Bluetooth do for you? …and combinations! It is reported that more than two billion Bluetooth-ready devices were shipped during 2012 – over 50 millions every day.

5. Example...

6. Bluetooth Technical Features: 2.4 GHz ISM Open Band –Globally free available frequency –79 channels (2400-2483.5 MHz ISM band) –Frequency Hopping & Time Division Duplex (1600 hops/second typically) 10-100 Meter Range –Class I – 100 meter (300 feet) –Class II – 20 meter (60 feet) –Class III – 10 meter (30 feet) Link Rate : 1 Mbps Simultaneous Voice/Data Capable –SCO (Synchronous connection oriented) for voice –ACL (Asynchronous connectionless link) for data

7. Frequency Hopping 1Mhz 83.5 Mhz 79  Divide Frequency band into 1 MHz hop channels  Radio hops from one channel to another in a pseudo-random manner as dictated by a hop sequence

8. Wireless channel is divided into time slots of 625μs Frequency hopping sequence is defined by a pseudorandom number generator known to both transmitter and receiver Packet transmission is aligned with the start of time slot Frequency Hopping Map

9. PICONET —— Bluetooth LAN Collection of devices connected in an ad hoc fashion One unit acts as master and the others as slaves for the lifetime of the piconet Master – device that initiates a data exchange Slave – device that responds to the master Master determines hopping pattern, slaves have to synchronize –There is one only one pattern in one piconet –1600hops/sec –Devices in a piconet are synchronized to the same clock defined by master Bluetooth Network Topology

10. Point to point link – master - slave relationship – radios can function as masters or slaves ms s s m s Piconet –Master can connect to 7 slaves –hopping pattern is determined by the master Assigning address If (node -> node address==0) If (node -> node address==0) MASTER MASTER else else SLAVE SLAVE

11. Connection Setup Inquiry – scan （查询扫描） –Slave 设备周期地监听来自其他设备的查询消 息，以便自己能被发现, 并在监听到后发送它的 地址和时钟信息。 Inquiry （查询消息） –Master 查找附近的蓝牙设 备，以便通过收集来自从 节点响应查询消息中得到 该节点的设备地址（ 48b ） 和时钟

12. Connection Setup Master Active Slave Parked Slave -Connected -Not in Pico Standby Page （寻呼） –Master 通过在不同的跳频序列发送消息，来激活一个从 节点, 并建立连接。调频序列由 slaver 的地址码计算出 Page – scan （寻呼扫描） –Slaver 周期性地在扫描窗间隔时间内唤醒自己，并监听 自己的访问码， Slaver 节点每隔 1.28s 在这个扫描窗上根 据寻呼跳频序列选择一个扫描频率

13. Physical Link Types Synchronous Connection Oriented (SCO) Link –slot reservation at fixed intervals Asynchronous Connection-less (ACL) Link –Polling access method m s1s1 s2s2 SCO ACL SCO

14. Packet Types Control packets Data/voice packets ID* Null Poll FHS DM1 Voice data HV1 HV2 HV3 DV DM1 DM3 DM5 DH1 DH3 DH5 FHS – Frequency Hop Synchronization DM – Data Medium rate HV – High quality Voice DV – Data Voice DH – Data High rate

15. Packet Format 72 bits 54 bits 0 - 2744 bits Access code Header Payload Data Voice CRC No CRC No retries 625 µs master slave header ARQ FEC (optional) Access code used for timing synchronizatio n, offset compensation, paging, and inquiry

16. Packet Header Addressing (3) Packet type (4) Flow control (1) 1-bit ARQ (1) Sequencing (1) HEC (8) Access code Header Payload 54 bits Purpose Encode with 1/3 FEC to get 54 bits Broadcast packets are not ACKed For filtering retransmitted packets 18 bits total s s m s 16 packet types (some unused) Max 7 active slaves Verify header integrity

17. Inter piconet communication Cell phone Cordless headset Cordless headset Cell phone Cordless headset Cell phone mouse

18. Scatternet - Gateway node participates in more than one piconet on a time-division basis Not implemented in COTS equipment

19. Scatternet, scenario 2 How to schedule presence in two piconets? Forwarding delay ? Missed traffic? Not implemented in COTS equipment

20. Bluetooth Protocol Stack Composed of protocols to allow Bluetooth devices to locate each other and to create, configure and manage both physical and logical links that allow higher layer protocols and applications to pass data through these transport protocols Transport Protocol Group RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications

21. Bluetooth Protocol Stack Additional transport protocols to allow existing and new applications to operate over Bluetooth. Packet based telephony control signaling protocol also present. Also includes Service Discovery Protocol. Middleware Protocol Group RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications

22. Bluetooth Protocol Stack Consists of Bluetooth aware as well as un-aware applications. RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications Application Group

23. Link Manager Protocol Setup and management of Baseband connections Piconet Management Link Configuration Security LMP RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications

24. L2CAP L2CAP - Logical Link Control and Adaptation Protocol L2CAP provides Protocol multiplexing Segmentation and Re-assembly Quality of service negotiation RF Baseband Audio Link Manager L2CAP Data SDP RFCOMM IP Applications

25. RFCOMM (Radio Frequency Communication) -- Serial Port Emulation using RFCOMM Serial Port emulation on top of a packet oriented link Similar to HDLC (High level Data Link Control protocol) RS232 For supporting legacy apps RF Baseband Audio Link Manager L2CAP Data SDP RFCOMM IP Applications Serial Port

26. GOALS IP over Bluetooth V 1.0 Internet access using cell phones Connect PDA devices & laptop computers to the Internet via LAN access points RF Baseband Audio Link Manager L2CAP Data SDP RFCOMM IP Applications

27. Bluetooth Personal Area Networks - Ad Hoc and extend to Mesh PANs extend the Internet to the user personal domain 3G (2.5G) networks will give Internet access to PANs PANs will generate more traffic than a single device Utilize an aggregate of access networks (WLAN, 3G, DSL)

28. IP Bluetooth Networking - Conclusions Bluetooth IP networking opens up new possibilities ---- Mesh networks Enables spontaneous Ad Hoc networking –Between people, –Between machines, Mainly small, short range ad-hoc networks –Solves your “personal problems”... –Limited complexity and security risks –Sharing 3G traffic in current mobile internet???? The enabler for PANs! –Gives a natural extension of Internet into the PAN via 3G –Enables stepwise upgrading of devices -- not tied to one multimedia terminal! –Makes use of the 3G bandwidth immediately QoS ~ Bluetooth ?