Unit-1:- Introduction

1. Unit-1:- Introduction psathiyamurthi.wordpress.com Mobile Communication

2. Presentation Outline • Syllabus & Course Outcome • What is Mobile Communication? • Transmission Media • Signal Propagation • Antenna • Modulation • Multiplexing • Switching • Standards

3. Course Outcomes At the end of course the student will be able to: • CO1 – Understand the concepts of cellular systems • CO 2 – Identify the various mobile communication technologies • CO3 – Outline the concepts of mobile IP layer and routing algorithms in mobile ADHOC network • CO4 – Compare the Mobile TCP and Traditional TCP • CO5 – Interpret an application on Android platform • Syllabus

4. What is Mobile Communication ? • Entails transmission of data to and from handheld devices • Two or more communicating devices • At least one is handheld or mobile • Location of the device can vary either locally or globally • Communication takes place through a wireless, distributed, or diversified network

5. Transmission media: Categories

6. Guided and Unguided Transmission How should we categorize transmission media? Two broad approaches: By type of path: Communication can follow an exact path (such as a wire) Communication can follow no specific path (such as a radio transmission) By form of energy: electrical energy is used on wires radio transmission is used for wireless light is used for optical fiber We use the terms guided (wired) and unguided (wireless) transmission to distinguish between physical media NOTE: The term wired is used even when the physical medium is an optical fiber 6

7. Fiber and wire-based transmission and their ranges • Guided transmission of electrical signals takes place using four types of cables

8. Guided Transmission Advantages • Transmission along a directed path from one point to another • Practically no interference in transmission from any external source or path • Using multiplexing and coding, a large number of signal-sources simultaneously transmitted along an optical fibre, a coaxial cable, or a twisted-pair cable

9. Guided Transmission Disadvantages • Signal transmitter and receiver fixed (immobile). • No mobility of transmission and reception points. • Number of transmitter and receiver systems limits the total number of interconnections possible

10. Unguided─ Wireless Transmission • Electrical signals transmitted by converting them into electromagnetic radiation • Radiation transmitted via antennae that radiate electromagnetic signals • Various frequency bands within the electromagnetic spectrum • Different transmission requirements • f = c/= (300/ ) MHz [ in meter]

11. Electromagnetic Spectrum

12. Bands

13. VHF and TV-VHF

14. UHF, GSM, DECT, 3G and DAD

15. Unguided Media Electromagnetic spectrum for wireless communication

16. Unguided Media Propagation Methods

17. Wireless PropagationGround Wave

18. Wireless PropagationSky Wave

19. Wireless PropagationLine of Sight

20. Multipath Interference

21. Unguided Media Wireless transmission waves

22. Wireless Transmission Frequencies 2GHz to 40GHz microwave highly directional point to point satellite 30MHz to 1GHz omnidirectional broadcast radio 300 GHz to 400 THz infrared local

23. Broadcast Radio • Radio is 3kHz to 300GHz • Use broadcast radio, 30MHz - 1GHz, for: • FM radio • UHF and VHF television • is omnidirectional • Still need line of sight • Suffers from multipath interference • reflections from land, water, other objects

24. Unguided Media – Radio Waves Omnidirectional Antenna • Frequencies between 3 KHz and 1 GHz. • are used for multicasts communications, such as radio and television, and paging system.

25. Terrestrial Microwave • used for long haul telecommunications • and short point-to-point links • requires fewer repeaters but line of sight • use a parabolic dish to focus a narrow beam onto a receiver antenna • 1-40GHz frequencies • higher frequencies give higher data rates • main source of loss is attenuation • distance, rainfall • also interference

26. Unguided Media – Microwaves • Frequencies between 1 and 300 GHz. • Used for unicast communication such as cellular phones, satellite networks and wireless LANs. Unidirectional Antenna

27. Satellite Microwave • Satellite is relay station • Receives on one frequency, amplifies or repeats signal and transmits on another frequency • eg. uplink 5.925-6.425 GHz & downlink 3.7-4.2 GHz • Typically requires geo-stationary orbit • height of 35,784km • spaced at least 3-4° apart • Typical uses • television • long distance telephone • private business networks • global positioning

28. Unguided Media – Infrared • Frequencies between 300 GHz to 400 THz. • Can not penetrate walls. • Used for short-range communication in a closed area using line-of-sight propagation. • line of sight (or reflection) • no licenses required • typical uses • TV remote control

29. Antennas • Devices that transmit and receive electromagnetic signals • electrical conductor used to radiate or collect electromagnetic energy • transmission antenna • radio frequency energy from transmitter • converted to electromagnetic energy by antenna • radiated into surrounding environment • reception antenna • electromagnetic energy impinging on antenna • converted to radio frequency electrical energy • fed to receiver • Vary from a single piece of wire to a parabolic dish

30. Antennas…..

31. Radiation Pattern • power radiated in all directions • not same performance in all directions • as seen in a radiation pattern diagram • an isotropic antenna is a (theoretical) point in space • radiates in all directions equally • with a spherical radiation pattern

32. Antenna Gain • measure of directionality of antenna • power output in particular direction verses that produced by an isotropic antenna • measured in decibels (dB) • results in loss in power in another direction • effective area relates to size and shape • related to gain

33. Satellite Point to Point Link

34. Satellite Broadcast Link

35. Comparison of Communication Media

36. What is Modulation ? • Modulation = Adding information to a carrier signal • The sine wave on which the characteristics of the information signal are modulated is called a carrier signal

37. Analog modulation

38. Digital modulation and demodulation

39. Signal characteristics that can be modified signal x(t) = A cos(2πft + Φ) • A – amplitude • f – frequency • Φ – phase (initial angle of the sinusoidal function at its origin

40. Modulation

41. Modulation..

42. Digital Modulation Techniques

43. Digital Modulation Techniques • ASK On-off keying (Amplitude Shift Keying) – frequency is kept constant, amplitude has 2 levels (for bit 1 and for bit 0) The binary sequence 0010110010

44. FSK (Frequency shift keyring)

45. PSK (Phase shift keyring)

46. Multiplexing in 4 dimensions space (si) time (t) frequency (f) code (c) Goal: multiple use of a shared medium Important: guard spaces needed! Multiplexing

47. Multiple Access An access network is that part of a communicationsnetwork which connects subscribers to their immediate service provider.

48. Difference between multiplexing & multiple Access Multiplexing is sharing of resources on links inside the network i.e. core network. (The links between the network elements (NEs) of service provider or between two service providers) Multiple Access is sharing of resources on the access part of the network.

49. Difference between multiplexing & multiple Access The main difference between TDM and TDMA (also FDM/FDMA, etc) is that with TDM (also FDM, etc.) the signals multiplexed (i.e. sharing a resource) come from the same node, whereas for TDMA (also FDMA, etc.) the signals multiplexed come from different sources/transmitters.

50. Multiplexing Vs. multiple Access MULTIPLEXING (dial up internet) Multiple Access (satellite internet)