Mobile_Communication [Unit-I]_updated.pptx

Mobile communication

1. In-Sem(paper): 30 Marks End-Sem(paper): 70 Marks Unit-I Introduction to Cellular Networks Unit-II Cellular Network Design Unit-III Medium Access Control Unit-IV GSM [Global System for Mobile communication] Unit-V Current 3G and 4G Technologies for GSM and CDMA Unit-VI Advances In Mobile Technologies Elective-II Mobile Communication

2. Unit-I Introduction To Cellular Networks

3. Contents Cell phone generations-1G to 5G Personal Communication System[PCS] PCS architecture Mobile station SIM Base station Base station controller Mobile Switching Center HLR & VLR AUC/EIR/OSS

4. Cellular network It is an underlying technology for mobile phones, personal communication systems, wireless networking etc. The technology is developed for mobile radio telephone to replace high power transmitter/receiver systems. Cellular networks use lower power, shorter range and more transmitters for data transmission.

5. Design approach for early mobile radio systems: a single, high-powered transmitter with an antenna mounted on a tall tower to cover a large service area (e.g., city) Similar to over-the-air radio and television broadcasting Works well from a coverage perspective But system capacity (e.g., number of simultaneous mobile users or voice calls supported) limited by available spectrum, which is scarce and tightly regulated E.g., Bell mobile system in New York City in the 1970s could only support a max. of 12 simultaneous calls over a thousand square miles area

6. Replace a high-power transmitter with many lower power transmitters, each covering only small portion of the service area called a cell Channel allocation and frequency reuse : Each transmitter (base station) is allocated a portion of the available spectrum, specifically a subset of channels from the total number of channels available Neighboring base stations assigned different sets of channels to minimize mutual interference Base stations that are further away can reuse the same set of channels, exploiting signal power falloff with distance

7. Cellular Network Architecture & Terminology

8. Base station Typically located at corner of a cell and area around it divided into multiple sectors, each served by a different sector antenna Cells of different sizes and overlapping cells: Macrocells (coverage up to few kms) Microcells (up to few hundreds of meters) Picocells (up to few tens of meters) Femtocells (cover a few meters across such as a home) Radio Access Network (RAN): the access part of the cellular network that consists of base stations and controllers, and provides connectivity between mobiles and core network Core Network: interconnects RANs and also connects them to external networks, including telephone network and Internet Handover/Handoff : the process of switching connectivity for a mobile from one cell to another (e.g., while moving); can be soft or hard Home network: the cellular network of a mobile’s operator Visited network: a cellular network different from that of a mobile’s operator Roaming: when a mobile connects via a visited network

9. Personal Communication System PCS (personal communications service) is a wireless phone service like cellular telephone. It's sometimes referred to as digital cellular. Technologies used for PCS Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA) Global System for Mobile (GSM) communication. The goals of PCS are to provide a mobile user with voice, data, and multimedia at any place, at any time, and in any format.

10. PCS Architecture PCS technologies have grown rapidly in the telecommunications industry. Two of the most popular are Cellular Telephony Cordless and low tier PCS technology The basic architecture consist of two parts Radio Network Wireline Transport Network

11. Mobile Station: PCS use mobile stations (MSs) to communicate with the base stations. MS is also referred to as handset, mobile phone, subscriber unit Base Station Subsystem (BSS): fundamentally associated with communicating with the mobiles on the network. Base Transceiver Station (BTS): The BTS used in a GSM network comprises the radio transmitter receivers, and their associated antennas that transmit and receive to directly communicate with the mobiles. Base Station Controller(BSC): It controls a group of BTS and is often co-located with one of the BTSs in its group. It manages the radio resources.

12. Network Switching Subsystem (NSS) Mobile Service Switching Centre(MSC): The MSC acts like a normal switching node within a PSTN or ISDN. Provides additional functionality to enable the requirements of a mobile user to be supported. These include registration, authentication, call location, inter-MSC handovers and call routing to a mobile subscriber. Home Location Register (HLR): contains all the administrative information about each subscriber along with their last known location

13. Visitor Location Register(VLR): Database that records the visiting location of each mobile Equipment Identity Register (EIR): The EIR is the entity that decides whether a given mobile equipment may be allowed onto the network. Authentication Centre ( AuC ):  The AuC is a protected database that contains the secret key also contained in the user’s SIM card. It is used for authentication and for ciphering on the radio channel. Operation and Support Subsystem (OSS) The OSS or operation support subsystem is an element within the overall GSM network architecture that is connected to components of the NSS and the BSC. It is used to control and monitor the overall GSM network and it is also used to control the traffic load of the BSS. It must be noted that as the number of BS increases with the scaling of the subscriber population some of the maintenance tasks are transferred to the BTS, allowing savings in the cost of ownership of the system.

14. Gateway Mobile Switching Centre(GMSC): The GMSC is the point to which a Mobile Equipment [ME] terminating call is initially routed, without any knowledge of the MS’s location. The GMSC is thus in charge of obtaining the MSRN (Mobile Station Roaming Number) from the HLR based on the MSISDN (Mobile Station ISDN number, the “directory number” of a MS) and routing the call to the correct visited MSC. The “MSC” part of the term GMSC is misleading, since the gateway operation does not require any linking to an MSC.

15. Evolution of Cellular Network Technologies/Standards As different generations: first generation – 1G, second generation – 2G, .. 1G: analogue, voice only, based on FDMA 2G: digital, initially designed for voice but later extended to support data (2.5G) 3G: digital voice and data with greater emphasis on data and higher data rates 4G: same as 3G but focus on even higher data rates + all IP core

16. Using Analog signals Listen to handset It's Speed was upto 2.4kbps. Freq u e n cy typi c ally 150MHz & above 1G Wireless Technology

17. Drawbacks Of 1G Poor battery Poor voice quality Large in size No security Frequency call drop

18. 2G Wireless Technology It enables services such as text messages, picture messages and MMS (multi media message). It’s data speed was upto 64kbps. It provides better quality and capacity .

19. Drawbacks Of 2 G Weaker digital signal These systems are unable to handle complex data such as Videos. Reduce range of sound

20. 2.5 G Wireless Technology 2.5G is a technology between the second (2G) and third (3G) generation of mobile telephony. 2.5G is sometimes described as 2G Cellular Technology combined with GPRS.

21. Features Includes in 2.5 G: Phone Calls Sen d /Rec e ive E -mail Mess a g e s Web Browsing Speed : 64-144 kbps Camera Phones

22. 3G Wireless Technology Data Transmission speed increased from 144kbps- 2Mbps. Providing Faster Communication Send/Receive Large Email Messages High Speed Web / More Security Video Conferencing / 3D Gaming TV Streaming/ Mobile TV/ Phone Calls

23. Drawbacks Of 3 G High Bandwidth Requirement Expensive 3G Phones. Large Cell Phones

24. 4G Wireless Technology “ Any time any where” Capable of providing 100Mbps – 1Gbps speed. More Security High Speed High Capacity Low Cost Per-bit

25. Drawbacks Of 4 G Battery uses is more Hard to implement Need complicated hardware Expensive equipment required to implement next generation network.

26. 5G Wireless Technology The router or switch we are going to use in 5G network would provide high connectivity with wireless device. It is 10 times more faster than 4G. It has a expected speed of 1gbps. Lower cost than the previous version.

27. Featu r es Uploading & Downloading speed of 5G touching the peak (up to 1Gbps) Better & fast solution It is highly supportable to WWWW (Wireless World Wide Web). Large Phone Memory, Dialing Speed, clarity in Audio/Video. 5G technology is going to give tough competition to Computers and Laptops.

28. Comparison

29. comp a rison

30. Radio Spectrum Free space path loss S/N radio Line of sigh transmission Length of antenna Fading in mobile environment

31. Radio Spectrum Radio signals travel in the free space known as spectrum. Distribution of electromagnetic signals over a wide frequency range where all radio emission occur.

32. standard definitions of radio spectrum segments

33. Signal Propagation Effects Free-space path loss Fading Scattering Diffraction R e f r ac t i on Multipath propagation

34. Free-space path loss Free-space path loss (FSPL) is the loss in signal strength of an electromagnetic wave that would result from a line-of-sight path through free space (usually air), with no obstacles nearby to cause reflection or diffraction.

35. F ad i ng In wireless communications, fading is deviation of the attenuation affecting a signal over certain propagation media. The fading may vary with time, geographical position or radio frequency

36. Scattering Scattering is a general physical process where some forms of radiation, such as light, sound,

37. Multipath propagation Multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes atmospheric ducting, ionosphere reflection refraction

38. Free Space Path Loss[FSPL] FSPL – attenuation (weakening) of radio energy between the feed points of two antennas. Loss in signal strength- occurs when an electromagnetic wave travels over a line of sight path in free space. FSPL is used in many areas for predicting radio signal strengths

39. In these circumstances : there are no obstacles that might cause the signal to be reflected ,refracted or that might cause additional attenuation

40. Free space path loss

41. formula d is the distance of the receiver from the transmitter [meters] ƛ is the signal wavelength [meters] f is the signal frequency [Hertz] c is the speed of light in vacuum [meters per second]

42. S/N Ratio Signal to noise ratio – also referred as SNR It is the ratio between the maximum signal strength that a wireless connection can achieve and the noise present in the connection. SNR of a network needs to be as high as possible. Higher the value of SNR, the better will be the signal strength and the quality of transmission

43. S/N Ratio SNR value can decrease due to various reasons like, Rain or fog Dense air High tension electric wiring Too much electronic equipment placed close of the wireless network Frequency emitted by electronic gadgets High powered cell phone handsets Signals may get attenuated(get reduced in strength)

44. Where does noise comes from? Chemical noise Température, pressure, humidity, fumes, etc. Instrumental noise

45. Enhancing signal-to-noise taking precautions to prevent noisy environmental conditions from influencing the signal (such as using shielded cable) using a good electronic architecture  using high quality sensors and electronic devices 

46. Grounding and shielding Surround circuits (most critical conductors) with conducting material that is connected to ground Noise will be picked up by shield and not by circuit

47. Line of Sight Propagation In Mobile Communication In the  line-of-sight communication , as the name implies, the wave travels a minimum distance of sight. Which means it travels to the distance up to which a naked eye can see. Now what happens after that? We need to employ an amplifier cum transmitter here to amplify the signal and transmit again.

48. The figure depicts this mode of propagation very clearly. The line-of-sight propagation will not be smooth if there occurs any obstacle in its transmission path. As the signal can travel only to lesser distances in this mode, this transmission is used for  infrared  or  microwave transmissions .

49. Transmitting and receiving antennas must be within line of sight Satellite communication – signal above 30 MHz not reflected by ionosphere Ground communication – antennas within effective line of sight due to refraction Refraction – bending of microwaves by the atmosphere Velocity of an electromagnetic wave is a function of the density of the medium When wave changes medium, speed changes Wave bends at the boundary between mediums Mobile phone systems, satellite systems, cordless phones, etc.

50. Line of Sight equations Optical line of sight Effective, or radio, line of sight d = distance between antenna and horizon (km) h = antenna height (m) (altitude relative to a receiver at the sea level) K = adjustment factor to account for refraction caused by atmospherics layers;

51. Line of Sight equations Maximum distance between two antennas for LOS propagation: h1=height of antenna one h2=height of antenna two

52. Mobile Antenna   An Antenna converts electromagnetic radiation into electric current, or vice versa. Need of Antenna : For transmission and reception of the radio signal. Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field.

53. Types of Antennas used in Cell Phones Following are some of the antennas used in cellular phones: External Antennas Retractable Monopole (whips) antennas Helical antennas Internal Antennas Microstrip antennas (MSA) Planar inverted-F antennas (PIFA)

54. Retractable Monopole Antenna An antenna that we can retract. Basically a dipole antenna with top loading (looks like a hat)

55. Helical (Stubby) Antenna When we open a cap, we can see a helical antenna. (looks like a spring) We don’t have to retract. → It is convenient for users.

56. Ceramic Helical Antenna High permittivity → Small antenna size

57. Internal antenna[ Intenna]: The antenna is embedded inside the phone which is not visible to us. A phone case is strongly related to an intenna.

58. Intenna for 3G phone A metal strip pattern is served as an antenna.

59. Planner Inverted F Antenna [PIFA] It is also referred to as short circuited microstrip antenna By varying the size of the ground plane, the bandwidth of a PIFA can be adjusted and optimized.

60. PIFA for Notebook

61. Effects of parameter variation in PIFA

62. Comparison Table

63. Fading in Mobile Environment The time variation of received signal power due to changes in transmission medium or paths is known as  fading . In fixed scenario, fading depends on atmospheric conditions such as rainfall, lightening etc. In mobile scenario, fading depends on obstacles over the path which are varying with respect to time. These obstacles create complex transmission effects to the transmitted signal.

64. The figure depicts amplitude versus distance chart for slow fading and fast fading 

65. Fading Types

66. Large Scale Fading: It includes path loss and shadowing effects. Small Scale Fading: It is divided into two main categories viz. multipath delay spread and doppler spread. The multipath delay spread is further divided into flat fading and frequency selective fading. Doppler spread is divided into fast fading and slow fading. ➤Fading models: Above fading types are implemented in various models or distributions which include Rayleigh, Rician, Nakagami , Weibull etc. As we know, fading signals occur due to reflections from ground and surrounding buildings as well as scattered signals from trees, people and towers present in the large area. There are two types of fading viz. large scale fading and small scale fading.

67. 1. Large Scale Fading Large scale fading occurs when an obstacle comes in between transmitter and receiver. This interference type causes significant amount of signal strength reduction. This is because EM wave is shadowed or blocked by the obstacle. It is related to large fluctuations of the signal over distance.

68. A) PATH LOSS The free space path loss can be expressed as follows. Pt/ Pr = {(4 * π * d) 2 / λ 2 } = (4*π*f*d) 2 /c 2 Where, Pt = Transmit power Pr = Receive power λ = wavelength d = distance between transmitting and receiving antenna c = speed of light i.e. 3 x 10 8 From the equation it implies that transmitted signal weakens over distance as the signal is being spread over larger and larger area from transmit end towards receive end.

69. B) SHADOWING EFFECT It is observed in wireless communication. Shadowing is deviation of received power of EM signal from average value. It is result of obstacles over the path between transmitter and receiver. It depends on geographical position as well as radio frequency of EM (Electromagnetic) waves.

70. 2. Small Scale Fading Small scale fading is concerned with rapid fluctuations of received signal strength over very short distance and short time period. Based on  multipath delay spread  there are two types of small scale fading viz. flat fading and frequency selective fading. These multipath fading types depend on propagation environment.

71. 2. A) FLAT FADING The wireless channel is said to be flat fading if it has constant gain and linear phase response over a bandwidth which is greater than the bandwidth of the transmitted signal. In this type of fading all the frequency components of the received signal fluctuate in same proportions simultaneously. It is also known as non-selective fading. Signal BW << Channel BW Symbol period >> Delay Spread The effect of flat fading is seen as decrease in SNR. These flat fading channels are known as amplitude varying channels or narrowband channels.

72. 2.B) FREQUENCY SELECTIVE FADING It affects different spectral components of a radio signal with different amplitudes. Hence the name selective fading. • Signal BW > Channel BW • Symbol period < Delay Spread Based on  doppler spread  there are two types of fading viz. fast fading and slow fading. These doppler spread fading types depend on mobile speed i.e. speed of receiver with respect to transmitter.

73. 2.C) FAST FADING The phenomenon of fast fading is represented by rapid fluctuations of signal over small areas (i.e. bandwidth). When the signals arrive from all the directions in the plane, fast fading will be observed for all directions of motion. Fast fading occurs when channel impulse response changes very rapidly within the symbol duration. • High doppler spread • Symbol period > Coherence time • Signal Variation < Channel variation

74. Fast fading is result of reflections of local objects and motion of his parameters result into frequency dispersion or time selective fading objects relative to those objects. In fast fading, receive signal is sum of numerous signals which are reflected from various surfaces. This signal is sum or difference of multiple signals which can be constructive or destructive based on relative phase shift between them. Phase relationships depend on speed of motion, frequency of transmission and relative path lengths.

75. 2.D) SLOW FADING Slow fading is result of shadowing by buildings, hills, mountains and other objects over the path. • Low Doppler Spread • Symbol period <<Coherence Time • Signal Variation >> Channel Variation Slow fading results in a loss of SNR. Error correction coding and receiver diversity techniques are used to overcome effects of slow fading.

76. 1) Which of the following usually stores all user-related data that is also relevant to GSM mobile systems? VLR HMR CMR SIM

77. 6) In a Cellular network, which of the following is used to use the same frequency for others? Frequency hopping Frequency reuse Frequency planning None of the above

78. Which of the following is a fundamental principle of wireless communication? Electromagnetic waves Microwaves Both A and B None of the above

79. The term "HLR" stands for the ______ Home Location Register House Location Register Home Live Register None of the above