1. WIRELESS LANs
BLUETOOTH

2. Topics discussed in this section:
BLUETOOTH
Bluetooth is a wireless LAN technology designed to connect devices of different functions such as telephones, notebooks, computers, cameras, printers, coffee makers, and so on. A Bluetooth LAN is an ad hoc network, which means that the network is formed spontaneously.
Topics discussed in this section:
Architecture Bluetooth Layers Baseband Layer
L2CAP

3. BLUETOOTH
Bluetooth name comes from Danish king Harald Blåtand (Bluetooth),
Credited with uniting the Scandinavian people during the 10th century.
The idea was that Bluetooth wireless technology would unite personal computing devices.

4. Bluetooth
Bluetooth is a trademark owned by the Bluetooth SIG, Inc., USA.
Bluetooth Special Industry Group (SIG) formed in winter of 1998 by Ericsson,IBM, Intel, Nokia, and Toshiba.
Goals
• low cost
• low power
• primarily a cable replacement (to connect mobile phones to headsets)

5. Bluetooth
• There are those who believe it can be used as a Wireless Personal Area Network (WPAN),
hence it was the basis for IEEE
Using:
• short-range radio technology
• ad hoc networking
• dynamic discovery of other Bluetooth devices & the services they offer

6. Figure Piconet

7. PICONET
Can have up to 8 stations:- 1 primary only, the rest are called secondaries (max 7 stations).
Communication between primary and secondary can be one to one or one to many.
All the secondary stations synchronize their clocks and hopping sequence with the primary.

8. PICONET (cont..) Masters vs. Slaves
Each Bluetooth device is a Master or Slave:
• master initiates exchange of data and the slave responds to the master
• in order to communicate devices must use same sequence of
frequency hops, hence slaves synchronize to hop sequence of master

9. PICONET (cont..)
• master assigns an Active Member address (AM_ADDR) to the slaves
participating in active communications within the piconet
Additional devices may be registered with the master and be invited to become
active as necessary -- their state is called “parked”
Devices not currently associated with any piconet are in stand-by mode.

10. Figure Scatternet

11. SCATTERNET Combination of piconet.
A secondary in Piconet can be the primary in another piconet.
This station can receive messages from the primary in the first piconet and acting as a primary, deliver them to secondaries in the second piconet.

12. Figure 14.21 Bluetooth layers

13. BLUETOOTH LAYERS
Radio layer equivalent to physical layer of internet model.
BT devices- low power ;range =10m
Band- 2.4GHz ISM(medical) band,79 channels (1MHzeach).
BT uses FHSS to avoid interference.
Type of modulation used- GFSK.

14. Physical Layer
• Uses 2.4 GHz unlicensed Industrial, Scientific, and Medical (ISM) band
(globally portions of this band are available)
• many other systems using the same spectrum
– interference to other systems
– interference from other systems

15. Physical Layer (cont..)
• GHz, i.e., 83.5 MHz divided into 79 channels with carrier frequencies
f = k MHz, k = 0, … , 78; Channel spacing is 1 MHz
• Gaussian Frequency Shift Keying (GFSK) modulation with one bit per symbol •
• uses fast (1600 hops/s) frequency hopping spread spectrum (FHSS)
• 625 microsecond long time slots
• one hop per packet, but a packet can be 1 slot, 3 slots, or 5 slots long

16. BLUETOOTH LAYERS Baseband layer- equivalent to MAC layer in LANs.
The access method is TDMA. The primary and secondary communicate with each other using time slots.
Single-Secondary Communication (SSC)-
Simple operation, primary uses slots 0,2,4… and secondary uses slots 1,3,5…
Operate in half duplex mode.
Multiple-Secondary communication (MSC)- for more than one secondary in the piconet.
All secondaries listen on even-numbered slots, but only one secondary sends in any odd-numbered slot.

17. Figure 14.22 Single-secondary communication

18. Figure 14.23 Multiple-secondary communication

19. PHYSICAL LINKS 2 types :– a) A sychronous connection oriented (SCO).
Used when avoiding latency is more important than integrity eg: Real time audio
b) An asychronous connectionless link (ACL) .
Used when DATA integrity more important than avoiding latency, eg: ATM

20. Baseband
Baseband controls the radio and is responsible for low level timing, error control,
and management of link during a single data packet transfer
Packet types:
• SCO, ACL - carrying payload
• ID packet consists of access code, used during re-connection
• NULL packet consists of access code and header, used for flow control
or to pass ARQ
• POLL packet same structure as NULL packet, must be acknowledged
• FHS (Frequency Hop Synchronization)

21. L2CAP-logical Link Control and Adaptation Protocol.
Equivalent to LLC sublayer LANs .
Used for data exchange on ACL link.
Specific duties: Muxtiplexing,segmentation and reassembly,QoS and group management.

22. Figure 14.25 L2CAP data packet format

23. Topics discussed in this section:
CONNECTING DEVICES
In this section, we divide connecting devices into five different categories based on the layer in which they operate in a network.
Topics discussed in this section:
Passive Hubs
Active Hubs Bridges
Two-Layer Switches
Routers
Three-Layer Switches
Gateways

24. Figure 15.1 Five categories of connecting devices

25. A repeater connects segments of a LAN.
Note
A repeater connects segments of a LAN.

26. Figure 15.2 A repeater connecting two segments of a LAN

27. A repeater forwards every frame; it has no filtering capability.
Note
A repeater forwards every frame; it has no filtering capability.

28. A repeater is a regenerator, not an amplifier.
Note
A repeater is a regenerator, not an amplifier.

29. Figure 15.3 Function of a repeater

30. Figure 15.4 A hierarchy of hubs

31. A bridge has a table used in filtering decisions.
Note
A bridge has a table used in filtering decisions.

32. Figure 15.5 A bridge connecting two LANs

33. A bridge does not change the physical (MAC) addresses in a frame.
Note
A bridge does not change the physical (MAC) addresses in a frame.

34. Figure 15.6 A learning bridge and the process of learning

35. Figure 15.7 Loop problem in a learning bridge

36. Figure 15.8 A system of connected LANs and its graph representation

37. Figure 15.9 Finding the shortest paths and the spanning tree in a system of bridges

38. Figure 15.10 Forwarding and blocking ports after using spanning tree algorithm

39. Figure 15.11 Routers connecting independent LANs and WANs

40. Topics discussed in this section:
BACKBONE NETWORKS
A backbone network allows several LANs to be connected. In a backbone network, no station is directly connected to the backbone; the stations are part of a LAN, and the backbone connects the LANs.
Topics discussed in this section:
Bus Backbone Star Backbone Connecting Remote LANs

41. In a bus backbone, the topology of the backbone is a bus.
Note
In a bus backbone, the topology of the backbone is a bus.

42. Figure Bus backbone

43. In a star backbone, the topology of the backbone is a star;
Note
In a star backbone, the topology of the backbone is a star;
the backbone is just one switch.

44. Figure Star backbone

45. Figure 15.14 Connecting remote LANs with bridges

46. Note
A point-to-point link acts as a LAN in a remote backbone connected by remote bridges.

47. Topics discussed in this section:
VIRTUAL LANs
We can roughly define a virtual local area network (VLAN) as a local area network configured by software, not by physical wiring.
Topics discussed in this section:
Membership Configuration
Communication between Switches
IEEE Standard
Advantages

48. Figure 15.15 A switch connecting three LANs

49. Figure 15.16 A switch using VLAN software

50. Figure 15.17 Two switches in a backbone using VLAN software

51. VLANs create broadcast domains.
Note
VLANs create broadcast domains.