Low Rate Wireless Personal Area Networks
What is WPAN?
- Wireless personal area network
- Group of technologies that are designed for short-range comminications
- Eliminates the need for wires or cables to interconnect multiple devices
- Applications for WPAN technology include:
- Synchronizing PDA's, cellular, and Smartphones
- Home control systems (smart home)
- Cordless telephones
- Portable device data exchange
- Industrial control systems
- Location- smart tags used to locate people at home or the office
- security systems
- interactive toys
- inventory tracking
- Advantages
- WPAN devices use very little power
- short range helps maintain security and privacy
- Data Link layer
- Logical link control (LLC)
- Media access control (MAC)
- PHY layer
- physical layer
- j;
Infrared WPANs (IrDA)
- most common infrared connection today
- based on the irDA specifications
- IrDA specifications
- define both physical devices and network protocols
- IrDA devices characteristics
- provide walk-up connectivity
- provide point to point method of data transfer
- between only two points at a time
IrDA considerations
- Factors to consider:
- half duplex transmission
- deflection angle
- ambient light
- ease of use
- security
- distance limitations
Uhoh! Digressions!
IEEE and Bluetooth
- Bluetooth RF layer
- defines how the basic hardware that controls the radio transmissions functions
- data bits are converted into radio signals and transmitted
- Modulation technique
- Bluetooth uses a variation of FSK
- two-level gaussian frequency shift keying (2-GFSK)
- uses two different frequencies
- to indicate whether a 1 or 0 is being transmitted
- modulation index
- amount that the frequency varies
- between 280 KHz and 350 KHz
- Baseband layer
- lies on top of the RF layer
- manages physical channels and links
- handles packets, and does paging and inquiry
- to locate other bluetooth devices in the area
- Radio frequency
- 2.4GHz ISM band (industrial, scientific, medical)
- devides frequency into 79 different channels
- spaced 1 MHz apart
- bluetooth uses FHSS
- uses the same frequency as IEEE 802.11b WLANs
- they can interfear with each other
- Bluetooth V 1.2 added a feature called adaptive FH
- which further improves compatibility with 802.11b
- Network topologies
- piconet and scatternet
- bluetooth devices
- master controls all of the wireless traffic (phone)
- slave takes commands from the master (earpeice)
- piconet
- bluetooth network that contains one master and at least one slave and that uses the same channel
- Each bluetooth device is preconfigured with an address
- needed when participating or not participating in the piconet
