1. Wireless LAN (WLAN)
Wireless Ethernet
Bluetooth

2. Introduction Demand for wireless device connection has been growing
WLAN is generally used in campus, office as well as in cafe, petrol station etc.
WLAN can also be fixed at home for usage of Internet connection in other mobile devices

3. IEEE
standard define specification that cover physical and data link layer for WLAN
Architecture
Physical layer
Media Access Control Layer (MAC)
Addressing mechanism

4. WLAN architecture: Basic Service Set (BSS)
BSS defined as building block of WLAN
Made of mobile wireless stations and an optional central base station (access point -AP)
BSS without an AP is stand alone network and cannot send data to other BSSs. (called: ad-hoc architecture)
Stations can locate one another and agree to be part of BSS

5. WLAN architecture : Extended Service Set (ESS)

6. WLAN Architecture: Extended Service Set (ESS)
ESS is made of >= 2 BSSs with APs
Generally, BSSs are connected through a distribution system (wired LAN)
Distributed system connects the APs in the BSSs.
IEEE doesn’t restrict the distribution system : It can be any IEEE LAN (such as Ethernet)
Stations in ESS: mobile & stationary
Mobile: normal stations inside a BSS
Stationary: AP stations that are part of a WLAN
When BSSs are connected, this architecture called infrastructure network, and stations in BSS no need AP to communicate one another
However communication between 2 stations from 2 difference BSSs normally occur through 2 APs

7. Stations types
IEEE defines 3 type of stations based on their mobility:
No-transition
Stationary or moving only inside a BSS
BSS-transition
Move from one BSS to another, but the movement is confined inside one ESS
ESS-transition
Move from one ESS to another but IEEE doesn’t guarantee that communication is continuous during the move

8. Physical Layer Specification
IEEE defines specification to convert bit to signal (physical layer)
There are 5 type of specification in radio frequency domain

9. Frequency Hopping Spread Spectrum
Generating signal in 2.4 GHz ISM band
Data transmission using 1 frequency carrier for certain period and hop to another frequency and so on.
After N hops, loop will be repeated.
If initial bandwidth signal is B, spread spectrum bandwidth is : N x B
data rate: 2 Mbps, use FSK modulation at 1M baud/s

10. Direct Sequence Spread Spectrum
Also in 2.4-GHz ISM band (industrial, scientific, medical)
Each bit that sent replaced with bit sequence (chip code)
To prevent the use of buffer, the time to send a chip code should = time to send original bit
If number of bit in each chip code = N, data rate to send code chip = N x original stream bit data rate
Not same as CDMA because this is physical layer implementation
bit sequence use overall band
Data rate 2 Mbps, use PSK modulation at 1Mbaud/s

11. MAC sub-layer in IEEE 802.11 standard
Distributed coordination function(DCF)
Point coordination function (PCF) – more complex for just infrastructure network

12. Acess method: CSMA/CA

13. CSMA/CA and Network Allocation Vector
NAV is CA implementation method
When RTS is sent by 1 station (including time period that needed to use channel)
Other station will start respective NAV– waiting time before checking channel status
Distributed IFS and Short IFS are waiting time between frames

14. MAC sub-layer frame format
The wireless environment is very noisy; a corrupt frame has to be retransmitted
The division of a large frame into smaller ones. (fragmentation)

15. Sub-field in FC field Field Explanation Version
The current version is 0.
Type
Type of information: management (00), control (01), or data (10).
Subtype
Defines the subtype of each type (see ).
To DS
Defined later.
From DS
More flag
When set to 1, means more fragments.
Retry
When set to 1, means retransmitted frame.
Pwr mgt
When set to 1, means station is in power management mode.
More data
When set to 1, means station has more data to send.
WEP
Wired equivalent privacy. When set to 1, means encryption implemented.
Rsvd
Reserved.

16. Control Frame

17. Sub-field value in control frame
Subtype
Meaning
1011
Request to send (RTS)
1100
Clear to send (CTS)
1101
Acknowledgment (ACK)

18. Sub-field in FC field To DS From DS Address 1 Address 2 Address 3
Destination station
Source station
BSS ID
N/A 1
Sending AP
Receiving AP

19. Addressing Mechanism Pengalamatan : kes 1
Addressing in very complex because it involve many APs
Addr 1 : next device
Addr 2 : previous device
Addr 3 : final destination if it is not defined by Addr 1
Addr 4 : original source if it is not the same as Addr 2

20. Figure 15.12 Addressing mechanism: case 2

21. Figure 15.13 Addressing mechanism: case 3

22. Figure 15.14 Addressing mechanism: case 4

23. Bluetooth
WLAN technology designed to connect devices of different functions such as telephone, PDA, camera, printers, mouse, earpiece etc.
It is an ad hoc network– formed spontaneously
Bluetooth devices/gadgets find each other and make a network called a piconet
Bluetooth LAN can even be connected to the Internet if one of the gadgets has this capability
Standard : IEEE that defines wireless personal area network (PAN) operable in an area the size of a room or a hall

24. Network architecture: Piconet
Piconet can have up to 8 station with one of them function as master
The slave devices synchronize their clocks and hopping sequence (hop) with the master
Communication between master-slave can be 1-1 or 1-many
Slave can change from active to parked state and vice versa

25. Network architecture: Scatternet
Piconet 1
Piconet 2

26. Scatternet Piconet can be combined to form scatternet
Station slave in a piconet can be master in another piconet
This Station can receives message from master (first piconet) and acting as master (second piconet ) to deliver them to slave in second piconet

27. Bluetooth device Bluetooth device has short distance radio transmitter
Data rate: 1Mbps with bandwidth 2.4-GHz, therefore may be disruption can happen between WLAN IEEE b and LAN Bluetooth

28. Bluetooth layer
Bluetooth uses layers that do not exactly match TCP/IP model
Radio layer ~ physical layer
Bluetooth devices are lo-power and have a range of 10 m
Band: use 2.4-GHz ISM band divided into 79 channels of 1 MHz each

29. Bluetooth layer
Bluetooth use FHSS method in the physical layer to avoid interference from other devices or networks
Bluetooth hops 1600 per second, which means that each device changes its modulation frequency 1600 times per second
To transform bits to a signal, use GFSK modulation(Gaussian)
Baseband layer: equivalent to MAC sublayer in LAN with access method is Time Divison Duplexing-TDMA (half-duplex communication)
Communication only between master-slave
No direct communication between slave-slave

30. Single-slave communication

31. Multiple-slave communication

32. Frame Format

33. L2CAP Packet Data Format