1. Simple Reference Model
MOBILE COMMUNICATION
Simple Reference Model

2. Simple Reference Model
PDA
Computer
BTS
Inter working unit

3. Simple Reference Model
PDA
Computer
BTS
Inter working unit
Application
Application
Transport
Transport
Network
Network
Network
Network
Data Link
Data Link
Data Link
Data Link
Physical
Physical
Physical
Physical
Medium
Radio
Protocol Stacks

4. Physical Layer
Converts bits into signals at transmitter side and vice-versa at receiver side.
Responsible for frequency selection
Generates carrier frequency
Signal detection
Encryption and decryption of data
Combating Interference, attenuation
Modulation of data into carrier frequency

5. Data Link Layer Media access/control Authentication,
Multiplexing of different data streams
Correction of transmission errors
Synchronizations (detection of data frames
Reliable point to point connection between two devices or point – to – multipoint connection between sender and several receivers.

6. Network Layer
Responsible for routing packets through a network or establishing a connection between two entities over many other intermediate systems.
Addressing
Device location,
Hand-over between different networks

7. Transport Layer
Used for end to end connection
Flow and congestion control
Quality of service

8. Application layer Service location
Support for multimedia applications, new/adaptive applications that can handle the large variations in transmission characteristics
Wireless access to the www using a portable device.
Video (high data rate) and interactive gaming (low jitter, low latency) are very demanding applications.

9. Function of Layers in a Mobile Communication Environment
Service location, multimedia,
new/adaptive applications
End to end connection, congestion/flow control quality of service
addressing, routing, device location,
hand-over between different networks
Media access/control, authentication,
multiplexing, error correction, point to point connection, Synchronizations,
Converts signals in to bits and vice-versa, Encryption, modulation, Frequency selection, Interference, attenuation
Application layer
Transport layer
Network layer
Data link layer
Physical layer

10. Overlay Networks - the global goal
integration of heterogeneous fixed and mobile networks with varying transmission characteristics
regional
vertical
handover
metropolitan area
campus-based
horizontal
handover
in-house

11. FREQUENCIES FOR RADIO TRANSMISSION

12. Electromagnetic Spectrum

13. Frequencies for communication
300 Hz
10 km
30 kHz
100 m
3 MHz
1 m
300 MHz
10 mm
30 GHz
100 m
3 THz
1 m
300 THz
visible light
VLF LF MF HF
VHF
UHF
SHF
EHF
infrared UV
optical transmission
coax cable
twisted pair
Divided into bands which exhibit certain advantages and disadvantages.
VLF = Very Low Frequency UHF = Ultra High Frequency
LF = Low Frequency SHF = Super High Frequency
MF = Medium Frequency EHF = Extra High Frequency
HF = High Frequency UV = Ultraviolet Light
VHF = Very High Frequency
Frequency and wave length  = c/f
 =wave length, c = speed of light  3x108m/s, and f = frequency

14. Frequencies for mobile communication
VHF-/UHF-ranges for mobile radio
simple, small antenna for cars
deterministic propagation characteristics, reliable connections
SHF and higher for directed radio links, satellite communication
small antenna, beam forming
large bandwidth available
Wireless LANs use frequencies in UHF to SHF range
some systems planned up to EHF
limitations due to absorption by water and oxygen molecules (resonance frequencies)
weather dependent fading, signal loss caused by heavy rainfall etc.

15. VLF
LF KHz)
Submarine Comn, Radio ( & KHz in Germany)
MF , HF, VHF
Radio stations. AM ( KHz & SW MHz) FM MHz
VHF( MHz)
TV ( MHz) , DAB ( MHz)
UHF ( MHz)
TV ( MHz), DAB ( MHz)
Mobile phones ( MHz, GSM ( MHz, MHz), DECT( MHz), 3G/UMTS ( MHZ, MHz, MHz)
SHF(3 GHZ-30 GHZ)
Microwaves( 2-40 GHZ), FSS in C, Ku,Ka Bands
EHF(30 GHz-300GHz)
Close to IR.
Note : All radio frequencies are regulated to avoid interference

16. REGULATIONS RF are scarce resource
Nations find it difficult for common word wide regulation due to their national / economic interest
ITU , sub org of UN, at Geneva; is responsible for world wide coordination of telecommunication activities (wired & wireless)
ITU-R (formerly CCIR) handles
(a) Standardisation in the wireless (b) Freq planning
Three regions – for world wide coordination and to reflect national interest
Region 1 – Europe, Africa , Middle East and Countries of erstwhile Soviet Union
Region 2 – North and South America and Green Land
Region 3 – Far East, India, Australia and New Zealand

17. - Systems are operating at different frequencies
REGULATIONS
National agencies are responsible within these regions e.g. FCC in USA, CEPT in Europe, WPC in India
Harmonisation. ITU-R holds the world wide conference (WRC) to discuss and decide freq allocation for the three regions – a difficult task
- Systems are operating at different frequencies
- Satl Freq – generally cross national boundaries
- ISM band , 5, 17.2, 24 & 61 GHz
433 & 686 MHz – for car locks, wireless hand sets, RFIDs

18. Frequencies and regulations
Universität Karlsruhe
Institut für Telematik
Frequencies and regulations
Mobilkommunikation
SS 1998
ITU-R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences)
Examples
Europe
USA
Japan
Cellular phones
GSM , , ,
UMTS ,
AMPS, TDMA, CDMA, GSM ,
TDMA, CDMA, GSM, UMTS ,
PDC, FOMA ,
PDC ,
FOMA ,
Cordless phones
CT , CT
DECT
PACS ,
PACS-UB
PHS
JCT
Wireless LANs
802.11b/g
802.11b/g
802.11b
802.11g
Other RF systems
27, 128, 418, 433, 868
315, 915
426, 868
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller 18

19. ASSIGNMENT NO 1
Q1. Differentiate between user mobility and device portability.
Q2. Write short history of mobile communication.
Q3. What are the two different approaches in regulation regarding mobile phone systems ? What are its consequences?
Q4. Draw the simplified reference model and explain the functions of each layer.
Q5. Differentiate between mobile and wireless.

20. Assignment No. 1
Q1. Differentiate between user mobility and device portability (PP 21)
Q2. Differentiate between mobile and wireless. (PP 21-22)
Q3.). Write short history of mobile communication. (pp 29-34).
Q4. Draw the simplified reference model and explain the functions of each layer. (pp 39)

21. Q3. What are the two different approaches in regulation regarding mobile phone systems ? What are its consequences?
Ans
The classical European approach was based on standardisation and regulation before any products were available. The EU governments founded ETSI to harmonize all national regulations. ETSI created the standards, all countries had to follow.
2.In the US companies develop systems and try to standardize them or the market forces decide upon success. The FCC, e.g., only regulates the fairness among different systems but does not stipulate a certain system.
The effects of the two different approaches are different. Many “governmental” standards in Europe failed completely, e.g., HIPERLAN 1, some succeeded only in Europe, e.g., ISDN, and however, some soon became a worldwide success story, e.g., GSM. For most systems the US approach worked better, first some initial products, then standards. One good example is the wireless LAN family , a good counter example is the mobile phone market: several different, incompatible systems try to succeed, many features, well established in Europe since many years, are not even known in the US (free roaming, MMS, GPRS roaming, no charges for being called etc.).

22. SIGNALS

23. SIGNALS Physical representation of data
Layer 1 of OSI model is for conversion of data into signals & vice versa
Signals are functions of time and location
g(t) = At sin(2πft +φt)
Classification
continuous time/discrete time signals
continuous values/discrete values signals
analog signal = continuous time and continuous values
digital signal = discrete time and discrete values
signal parameters of periodic signals: period T, frequency f=1/T, amplitude A, phase shift 
signal parameters: parameters representing the value of data

24. Signals Parameters of signal may change with time.
Universität Karlsruhe
Institut für Telematik
Signals
Mobilkommunikation
SS 1998
Parameters of signal may change with time.
Phase shift determines the shift of the signal relative to the same signal without shift. See fig below
(a) (b) (c)
Different representations of signals
(a) amplitude (Time domain)
(b) frequency spectrum (frequency domain)
(c) phase state diagram (amplitude M and phase  in polar coordinates)
A [V]
Q = M sin 
A [V]
t[s] 
I= M cos  
f [Hz]
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller 24

25. Fourier representation of periodic signals
Universität Karlsruhe
Institut für Telematik
Signals
Mobilkommunikation
SS 1998
sine wave is a special periodic signal for a carrier: g(t) = At sin(2  ft t + t)
Fourier representation of periodic signals 1 1 t
Ideal periodic signal t
real composition
(based on harmonics)
Prof. Dr. Dr. h.c. G. Krüger
E. Dorner / Dr. J. Schiller 25

26. Composed signals transferred into frequency domain using Fourier transformation
Digital signals need
- infinite frequencies for perfect transmission
- modulation with a carrier frequency for transmission (analog signal!)

27. ANTENNA

28. ANTENNA
Couples the EM energy to and from space from and to a wire or coaxial cable
Isotropic antenna-- a reference antenna – a point radiating equal power in all directions. The radiation pattern is symmetric in all directions
Radiation pattern- measurement of radiation around an antenna Y Z X
Fig. Radiation pattern of an isotropic antenna
However such antenna does not exist in reality

29. ANTENNA
Real Antennas are not isotropic radiators but exhibit directive effects.
Simplest real antenna is a thin, centre-fed dipole also called Hertzian dipole
dipole with length /4 on car roof
 shape of antenna proportional to wavelength
λ/2
Dipole is made of two collinear conductors of equal length, separated by a small gap
Dipole
λ/4
Marconi antenna

30. Antennas: Simple Dipoles
Example: Radiation pattern of a simple Hertzian dipole
side view (xy-plane) x y
side view (yz-plane) z
top view (xz-plane)
simple
dipole
Gain: maximum power in the direction of the main lobe compared to the power of an isotropic radiator (with the same average power)
This type of antenna can only overcome environmental challenges by boosting power level of the signals. Challenges could be mountains, valleys, buildings, etc.

31. Directional Antennas Sectorized Antennas Multi element antenna arrays.
Smart Antennas

32. Directed Antennas : Radiation Pattern
Often used for microwave connections or base stations for mobile phones (e.g., radio coverage of a valley) y y z
Directed
antenna x z x
side view (xy-plane)
side view (yz-plane)
top view (xz-plane) z
Sectorized antenna – several antennas combined on single pole
- Enables freq reuse z x x
top view, 3 sector
top view, 6 sector

33. Antennas: diversity Diversity combining
Grouping of 2 or more antennas to improve reception
Also called multi-element antenna arrays
Antenna diversity
switched diversity or selection diversity
receiver chooses antenna with largest output
Diversity combining
combine output power to produce gain
Co-phasing needed to avoid cancellation +
/4
/2
ground plane

34. Smart Antennas : Salient Features
Combine multiple antenna elements( also called antenna array) with signal processing to optimise the radiation / reception pattern.
Can adapt to changes in received power, transmission conditions and many signal propagation effects.
Can be used for beam forming. This would be an extreme case of directed antenna which can follow a single user thus using SDM.
Today's hand set antenna are omni directional as integration of smart antenna into mobile is difficult.

35. ASSIGNMENT NO 1
Q1. Is it possible to transmit a digital signal, e.g., coded as square wave as used inside a computer, using radio transmission without any loss? Why?
Q2. Is a directional antenna useful for mobile phones? Why? How can the gain of an antenna be improved?
Q3. What are the main problems of signal propagation? Why do radio waves not always follow a straight line? Why is reflection both useful and harmful?
Q4. Why, typically, is digital modulation not enough for radio transmission? What are general goals for digital modulation? What are typical schemes?

36. Q.5 Discuss various types of antennas briefly? (MDU May 09)