1.  Wireless System

2. WHAT IS WIRELESS COMMUNICATION?
Transmitting/receiving voice and data using electromagnetic waves in open space.
The information from sender to receiver is carried over a well defined frequency band(channel).
Each channel has a fixed frequency bandwidth & capacity(bit rate).
Different channels can be used to transmit information in parallel and independently.

3. How communication takes place?
satellite
Received signal
Transmitting signal
Transmitting antenna
Receiving
antenna

4. TYPICAL FREQUENCIES FM RADIO 88 MHZ TV BROADCAST 200 MHZ
GSM PHONES MHZ
GPS GHZ
PCS PHONES GHZ
BLUETOOTH GHZ
Wi-Fi GHZ

5. WHY WIRELESS COMMUNICATION?
Freedom from wires.
No bunch of wires running from here and there.
“Auto Magical” instantaneous communication without physical connection setup e.g.- Bluetooth, Wi-Fi.
Global coverage
Communication can reach where wiring is infeasible or costly
e.g.- rural areas,buildings,battlefield,outerspace.
Stay connected,flexiblity to connect multiple devices.

6. TYPES OF WIRELESS COMMUNICATION?
RADIO TRANSMISSION:- easily generated, Omni-directional , travel long distance , easily penetrates buildings.
PROBLEMS:- frequency dependent , relatively low bandwidth for data communication , tightly licensed by government.
MICROWAVE TRANSMISSION:- widely used for long distance communication , give high S/N ratio , relatively inexpensive.
PROBLEMS:- don’t pass through buildings , whether and frequency dependent.

7. TYPES CONTINUED….
INFRARED AND MILIMETER WAVES:- widely used for short range communication , unable to pass through solid objects , used for indoor wireless LANs , not for outdoors. LIGHT WAVE TRANSMISSION:- unguided optical signal such as laser , unidirectional , easy to install , no license required. PROBLEMS:- unable to penetrate rain or thick fog , laser beam can be easily diverted by air.

8. CURRENT WIRELESS SYSTEMS
CELLULAR SYSTEM
WIRELESS LANs
SATELLITE SYSTEM
PAGING SYSTEM
PANs(BLUETOOTH)

9. What is cellular system?
Definition
Practical
Wireless communication technology in which several small exchanges (called cells) equipped with low-power radio antennas (strategically located over a wide geographical area) are interconnected through a central exchange. As a receiver (cell phone) moves from one place to the next, its identity, location, and radio frequency is handed-over by one cell to another without interrupting a call.

10. Cellular system basic concept?
High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell.
Same frequencies timeslots/codes are reused by spatially separated base stations.
A switching technique called handoff enables a call to proceed uninterrupted when one user moves from one cell to another.
Neighboring base stations are assigned different group of channels so as to minimize the interference.

11. Cellular system basic concept contd…
By systematically spacing base stations and the channel groups may be reuse as many number of times as necessary.
SUBSCRIBER UNIT
Coverage area
BASE STATIONS
CELLS
MSC
PSTN

12. Hand over ? BSC BS1 BS3 BS2 Call ended
Out of BS1 coverage & connect to BS2
Connect to Bs1 & start calling
Out of BS2 coverage & connect to BS3

13. FREQUENCY REUSE THE NEED?
Cellular radio systems rely on intelligent allocation and reuse of channels throughout the coverage area.
Each base station is allocated a group of radio channels to be used within the same geographical area of its cell.
Neighboring base stations are given different channel allocation from each other.
The design procedure of allocating channel groups for all of the cellular BS within a system is called frequency reuse or frequency planning.

14. Example of frequency reuse?
Co channel cells
Co channel cells

15. How to find co -channel cell?
Co channels u v
60 degree D

16. The geometry of hexagon?
Axes u and v intersect at 60 degree.
Unit scale is the distance between center cells.
If cell radius to point of hexagon is R then 2Rcos30=1
Or R = 1/√3. to find the distance of a point P(u , v) from the origin we use x-y to u-v coordinate transformation.
R² = x² + y²
x=ucos30˚
y=u+vsin30˚
r=√(v²+uv+u²)

17. Geometry contd… N = √(i²+ij+j²) where i and j are integers.
Using this equation to locate co-channel cells we start from reference cell and moves i hexagon along u axis then j hexagon along the v axis.
Hence the distance between co-channel cells in adjacent cluster is given by D = √(i²+ij+j²)
The number of cells in a cluster N is given by
N = √(i²+ij+j²) where i and j are integers.
Hence the possible values of N are 1 , 3 , 4 , 7 , 12……

18. Co-channel location Formation of cluster for N=7
Suppose i=2 and j=1 will give co channel cell
Same color showing co-channel cells.
j-=1
i=2
Co channel cells

19. What is GSM?
Global system for mobile communication is a set of ETSI standards specifying the infrastructure for a digital cellular services.
GSM networks are structured hierarchically it consist of one administrative region which is assigned to a MSC.
Each administrative region is made up of at least one location area (LA). LA is also called the visited area.
An LA consists of several cell groups.
Each cell group is assigned to a base station controller (BSC)

20. GSM system hierarchy? LA LA GSM NETWORK MSC REGION MSC REGION CELL
LOCATION AREA (LA) LA
BS CONTROLLER
BS CONTROLLER
BS CONTR-OLLER
CELL
CELL LA
MSC REGION

21. OPENED VIEW OF GSM ARCHITECHTURE?
NSS
NMS
HLR
VLR
AUC
ISDN
MSC
EIR
PSTN
BSC
OTHER NETWORKS
BSS
Mobile station

22. Mobile station? Consist of two main elements. 1. The mobile equipment
2. Subscriber identity module(SIM).

23. The Base Station Subsystem?
BSS = BSC BTS
SPEECH PROCESSING
MODULATION/DEMODULATION
TRANSCODER
MINIMIZE TRANSMISSION PROBLEM
AIR INTERFACE MANAGEMENT
CENTRAL N/W ELEMENT OF BSS
CALL ESTABLISHMENT
MOBILITY MGMT
STATISTICAL RAW DATA COLLECTION
RADIO PATH CONTROL
AIR INTERFACE SIGNALLING

24. THE N/W SWITCHING SUBSYSTEM?
NSS = MSC HLR VLR + AUC EIR
MANAGE
COMMUNICATION
B/W USERS
INCLUDE
DATABASE TO STORE INFORMATION OF USER
CALL CONTROL
MOBILITY
MGMT
SUBSCRIBER
DATA HANDLING
CHECK IDENTITY OF USER
PERMANENT STORAGE OF USER INFORMATION
STORE A COPY OF HLR
CHECK ROAMING
PROVIDE AUTHENTICATION
SECURITY
CHECK IMEI NUMBER OF MOBILE

25. N/W MANAGEMENT SUBSYSTEM?
1. MONITORING
MANAGE
OPERATION
4. MAINTANENCE
NMS

26. GSM TECHNOLOGY ?
USE TDMA + FDMA MODULATION USED = GMSK(Gaussian minimum shift keying) UPLINK FREQUENCY = 890 – 915 MHZ DOWNLINK FREQUENCY = 935 – 960 MHZ

27. Wireless local area network(WLAN)
WLAN connect local computers
Range (100 m) confined region
Break data into packets
Channel access is shared
Backbone internet provides best service
Poor performance in some application like videos
Low mobility

28. Satellite system ? Global coverage Different orbit height
Optimized for good transmission
Expensive base stations.
Voice and data transmission
Telecommunication application
GPS , global telephone connection
TV broadcasting , military , whether broadcasting

29. Paging system ? Pager system Broad coverage for short messages
Message broadcast from all base stations
Simple terminals
Optimized for one way transmission
Answer back hard
Overtaken by cellular
Pager system

30. Wide area paging system ?
Base station
City 1
Paging terminal
Terrestrial link
Base station
City 2
Paging terminal
Terrestrial link
Paging control center
PSTN
Base station
City N
Paging terminal
Satellite link

31. Personal area network ? Bluetooth Cable replacement RF technology
Short range(10m)
2.4 GHz band
TDD duplex scheme
1 Mbps data rate shared b/w 7 devices
Polling based multiple access
Work on frequency hopping spread spectrum technology

32. Ad-hoc network ? Peer to peer communication No backbone infrastructure
Routing can be multihop
Topology is dynamic
Fully connected with different link SINRs.

33. Ad-hoc network contd….
Ad-hoc network provides a flexible network infrastructure for many emerging applications.
The capacity of such networks is generally unknown.
Transmission , access and routing strategies for these networks are generally ad-hoc.
Cross layer design is very critical and challenging.
Energy constraints impose interesting design for trade offs communication and networking.

34. Thank U