Wireless Service engineering
Bluetooth information sources
- Books:
- Morrow: Bluetooth: Operation and Use
- Bray et al. : Bluetooth Application Developer's Guide
Bluetooth
- Widely supported
- Built-in on many PDA's, mobile phones and some laptops
- Several embedded solutions exist
- keyboards, mouse, head sets, printers, serial line replacement…
- Adding the capability to the device
- PCMCIA cards
- CF cards
- USB dongle
- Current version of Bluetooth is 2.0 with Enhanced data rate (EDR) was released November 8, 2004
- Most devices currently on market use version 1.2
- 2.0 is backward compatible
- Next version of Bluetooth will use UWB in the future on a physical layer?
- Uses 2.4Ghz ISM band
- 79 channels,
- frequency hopping (1600hops/s)
- Gross datarate 1Mbps
- EDR triples this.
- Different links for data and audio
- SCO voice link
- synchronous
- CVSD voiide encoding
- 64 kbps
- ACL data link
- asynchronous
- max data rate
- 433,9 kbps symmetric
- 723/57 kbps asymmetric
- Can be used also to audio.
- Different power classes to support different needs
| Power class | Output power | Range |
| Class 1 | 100 mW | 100 meters |
| Class 2 | 2.5 mW | 10 meters |
| Class 3 | 1 mW | 1 meter |
- Topology
- Star topology
- One master up to 7 slaves
- Initiator of connection is master
- Role switch can be used to switch roles
- Does not affect on application layer client-server roles
- All devices have unique 48bit Bluetooth Device Address (BD ADDR)
- all devices can be identified
- BD ADDR can be rather easily forged
- Access points
- Omnidirectional RF
- Class 1 or 2 radio
- Class 1 devices have ethernet connection to bridge TCP/IP connections
- Many models are running embedded linux
- Possibility to add own applications and services.
- Many brands to choose from
- Low cost
- Do it yourself with PC and Bluetooth dongle?
- Specification is divided in two
- Part 1 the core defines the Bluetooth interfaces and protocols
- Part 2 consists of profiles
- Profiles define what features has to be supported on certain types of applications
- Full protocol stack from link to application layer.
- HCI is the interface used to communicate with Bluetooth hardware
- Newer BNEP protocol can be used instead of RFCOMM and PPP under IP
- The way to use these protocols on different types of products is defined in profiles
- On what layer you should start creating your application?
- Profiles goal is to guarantee interoperability
- Generic access profile has to be followed by all products
- Service discovery application profile defines the service discovery process
- Serial port defines the use of RFCOMM
- Some New profiles
- Extended service discovery to enhance the service discovery process
- PAN profile for use of BNEP
- SIM profile for use of SIM card
- Remote Control Profile, video /audio profiles…
Connectivity with Bluetooth
- The connection forming between two devices consist of 3 steps
1. Device discovery (Inquiry)
- The initiator sends inquiry messages in order to find devices in it's proximity
- Devices in discoverable mode reply with their BD ADDR
- Inquiry in Bluetooth 1.1 takes 10.24 seconds and still might not find all devices on proximity (~90% success)
- shorter time in inquiry adds unreliability
- Enhanced inquiry in Bluetooth 1.2 requires maximum of 5 seconds and is almost 100% reliable
- 10 seconds is often used for inquiry due the compatibility reasons
- Interlaced inquiry scan in Bluetooth 1.2 speeds up the discovery process by 2x to a maximum of 2.5 seconds
- Requires more power
- Is not supported by all devices
2. Connecting devices (paging)
- The initiator pages the device it wants to connect at (BD ADDR)
- BD ADDR can be the one fetched by inquiry or provided by user or fetched from database
- Takea average of 1.28 seconds and maximum of 2.56 seconds
- Interlaced page scan of Bluetooth 1.2 halves the time
- Requires more power
- Is not supported by all devices
3. Service discovery
- Service Discovery protocol is used to discover the capabilities of the device that the basic data connection is formed at.
- More information at the service discovery lecture
- Specification gives no roaming support
- Access point vendors have some own roaming allowing solutions.
- Create your own roaming system?
- Want to create Bluetooth games?
- Contains document and java examples for connection forming
