Cellular & mobile communication

23,591
-1

Published on

Published in: Technology
37 Comments
84 Likes
Statistics
Notes
No Downloads
Views
Total Views
23,591
On Slideshare
0
From Embeds
0
Number of Embeds
5
Actions
Shares
0
Downloads
0
Comments
37
Likes
84
Embeds 0
No embeds

No notes for slide

Cellular & mobile communication

  1. 1. INTRODUCTION TO WIRELESS COMMUNICATION CELLULAR AND MOBILE COMMUNICATIONCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 1 / 303
  2. 2. What is Wireless Communication? Wireless communication is basically transmitting/receiving voice and data using EM waves in open space, basically free from wires.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 2 / 303
  3. 3. What is Wireless Communication? Wireless communication is basically transmitting/receiving voice and data using EM waves in open space, basically free from wires. The information from the sender to the receiver is usually carried over a well defined frequency band. This frequency band also known as bandwidth allocated for wireless communication, is one of the most priced commodity.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 2 / 303
  4. 4. What is Wireless Communication? Wireless communication is basically transmitting/receiving voice and data using EM waves in open space, basically free from wires. The information from the sender to the receiver is usually carried over a well defined frequency band. This frequency band also known as bandwidth allocated for wireless communication, is one of the most priced commodity. The different channels can be formed because wireless communication today is not just between one person and the base station but it is a multiple access scenario, it is a multi user system.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 2 / 303
  5. 5. What is Wireless Communication? Wireless communication is basically transmitting/receiving voice and data using EM waves in open space, basically free from wires. The information from the sender to the receiver is usually carried over a well defined frequency band. This frequency band also known as bandwidth allocated for wireless communication, is one of the most priced commodity. The different channels can be formed because wireless communication today is not just between one person and the base station but it is a multiple access scenario, it is a multi user system. So we need to wisely allocate the frequency channel so that we can accommodate more than one users.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 2 / 303
  6. 6. Example Assume a spectrum of 120 KHz is allocated over a base frequency for communication between station A and BCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 3 / 303
  7. 7. Example Assume a spectrum of 120 KHz is allocated over a base frequency for communication between station A and B Each channel occupies 40 KHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 3 / 303
  8. 8. Example Assume a spectrum of 120 KHz is allocated over a base frequency for communication between station A and B Each channel occupies 40 KHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 3 / 303
  9. 9. Types of Wireless Communication Mobile → Cellular phones (GSM/CDMA 2000.1X)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 4 / 303
  10. 10. Types of Wireless Communication Mobile → Cellular phones (GSM/CDMA 2000.1X) Portable → IEEE 802.11b (Wi-Fi)& IEEE 802.15.3 (UWB)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 4 / 303
  11. 11. Types of Wireless Communication Mobile → Cellular phones (GSM/CDMA 2000.1X) Portable → IEEE 802.11b (Wi-Fi)& IEEE 802.15.3 (UWB) Fixed → IEEE 802.16(Wireless MAN)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 4 / 303
  12. 12. Typical Frequencies FM radio → 88 MHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 5 / 303
  13. 13. Typical Frequencies FM radio → 88 MHz TV Broadcast → 200 MHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 5 / 303
  14. 14. Typical Frequencies FM radio → 88 MHz TV Broadcast → 200 MHz GSM Phones → 900 MHz , 1800 MHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 5 / 303
  15. 15. Typical Frequencies FM radio → 88 MHz TV Broadcast → 200 MHz GSM Phones → 900 MHz , 1800 MHz PCS Phones → 1.8 GHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 5 / 303
  16. 16. Typical Frequencies FM radio → 88 MHz TV Broadcast → 200 MHz GSM Phones → 900 MHz , 1800 MHz PCS Phones → 1.8 GHz Bluetooth → 2.4 GHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 5 / 303
  17. 17. Typical Frequencies FM radio → 88 MHz TV Broadcast → 200 MHz GSM Phones → 900 MHz , 1800 MHz PCS Phones → 1.8 GHz Bluetooth → 2.4 GHz WiFi → 2.4 GHzCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 5 / 303
  18. 18. Typical Frequencies FM radio → 88 MHz TV Broadcast → 200 MHz GSM Phones → 900 MHz , 1800 MHz PCS Phones → 1.8 GHz Bluetooth → 2.4 GHz WiFi → 2.4 GHz 2.4 GHz band is the most favourite band it is a licence free band. Please note that we have put 2.4 as a number, that is not the only frequency at which it works, its a frequency band all the time. We also have frequencies working at 28 GHz, 42 GHz, 60 GHz and trial runs are made at 100 GHz.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 5 / 303
  19. 19. Electromagnetic SpectrumCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 6 / 303
  20. 20. Why Wireless Communication?(1) Freedom from wires: There is no cost of installing wires or rewiring Global Coverage:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 7 / 303
  21. 21. Why Wireless Communication?(1) Freedom from wires: There is no cost of installing wires or rewiring No bunches of wires running here and there Global Coverage:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 7 / 303
  22. 22. Why Wireless Communication?(1) Freedom from wires: There is no cost of installing wires or rewiring No bunches of wires running here and there ”Auto magical” instantaneous communications without physical connection setup, eg; Bluetooth, WiFi Global Coverage:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 7 / 303
  23. 23. Why Wireless Communication?(1) Freedom from wires: There is no cost of installing wires or rewiring No bunches of wires running here and there ”Auto magical” instantaneous communications without physical connection setup, eg; Bluetooth, WiFi Global Coverage: Communications can reach where wiring is infeasible or costly, eg; rural areas, old buildings, battle field, vehicles, outer space(through communication satellites)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 7 / 303
  24. 24. Why Wireless Communication?(2) Stay connected: Roaming allows flexibility to stay connected anywhere and any time. Flexibility:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 8 / 303
  25. 25. Why Wireless Communication?(2) Stay connected: Roaming allows flexibility to stay connected anywhere and any time. Rapidly growing market attests to public need for mobility and uninterrupted access Flexibility:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 8 / 303
  26. 26. Why Wireless Communication?(2) Stay connected: Roaming allows flexibility to stay connected anywhere and any time. Rapidly growing market attests to public need for mobility and uninterrupted access Flexibility: services reach you wherever you go (Mobility). For example you dont have to go to your lab to check your mail.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 8 / 303
  27. 27. Why Wireless Communication?(2) Stay connected: Roaming allows flexibility to stay connected anywhere and any time. Rapidly growing market attests to public need for mobility and uninterrupted access Flexibility: services reach you wherever you go (Mobility). For example you dont have to go to your lab to check your mail. Connect to multiple devices simultaneously(no physical connections required)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 8 / 303
  28. 28. Challenges(1) Efficient Hardware: Low power Transmitters, Receivers Efficient use of finite radio spectrum: Integrated services:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 9 / 303
  29. 29. Challenges(1) Efficient Hardware: Low power Transmitters, Receivers Low power signal processing tools Efficient use of finite radio spectrum: Integrated services:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 9 / 303
  30. 30. Challenges(1) Efficient Hardware: Low power Transmitters, Receivers Low power signal processing tools Efficient use of finite radio spectrum: Cellular frequency reuse, medium access control protocols Integrated services:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 9 / 303
  31. 31. Challenges(1) Efficient Hardware: Low power Transmitters, Receivers Low power signal processing tools Efficient use of finite radio spectrum: Cellular frequency reuse, medium access control protocols Integrated services: voice, data, multimedia over a single network.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 9 / 303
  32. 32. Challenges(1) Efficient Hardware: Low power Transmitters, Receivers Low power signal processing tools Efficient use of finite radio spectrum: Cellular frequency reuse, medium access control protocols Integrated services: voice, data, multimedia over a single network. service differentiation, priorities, resource sharingCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 9 / 303
  33. 33. Challenges(2) Network support for user mobility(mobile scenarios)- location identification, handoverCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 10 / 303
  34. 34. Challenges(2) Network support for user mobility(mobile scenarios)- location identification, handover Maintaining quality of service over unreliable linksCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 10 / 303
  35. 35. Challenges(2) Network support for user mobility(mobile scenarios)- location identification, handover Maintaining quality of service over unreliable links Connectivity and coverage (inter-networking)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 10 / 303
  36. 36. Challenges(2) Network support for user mobility(mobile scenarios)- location identification, handover Maintaining quality of service over unreliable links Connectivity and coverage (inter-networking) Cost efficiencyCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 10 / 303
  37. 37. Challenges(3) FadingCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 11 / 303
  38. 38. Challenges(3) Fading MultipathCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 11 / 303
  39. 39. Challenges(3) Fading Multipath Higher probability of data corruptionCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 11 / 303
  40. 40. Challenges(3) Fading Multipath Higher probability of data corruption Need for stronger security mechanismCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 11 / 303
  41. 41. A simplified wireless communication system representationCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 12 / 303
  42. 42. Current Wireless Systems: Now let us look into some of the current wireless systems. Cellular systemsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 13 / 303
  43. 43. Current Wireless Systems: Now let us look into some of the current wireless systems. Cellular systems Wireless LAN’sCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 13 / 303
  44. 44. Current Wireless Systems: Now let us look into some of the current wireless systems. Cellular systems Wireless LAN’s Satellite systemsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 13 / 303
  45. 45. Current Wireless Systems: Now let us look into some of the current wireless systems. Cellular systems Wireless LAN’s Satellite systems Paging systemsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 13 / 303
  46. 46. Current Wireless Systems: Now let us look into some of the current wireless systems. Cellular systems Wireless LAN’s Satellite systems Paging systems PAN’s (Bluetooth)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 13 / 303
  47. 47. UNIT 1 MULTIPLE ACCESS TECHNIQUES AND CELLULAR CONCEPTCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 14 / 303
  48. 48. Unit 1: MULTIPLE ACCESS TECHNIQUES AND CELLULAR CONCEPT Multiple access schemes are generally allowed to use many mobile users share a finite amount of radio spectrum. We know that radio spectrum is a premium resource because most of the cost comes from licensing the spectrum.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 15 / 303
  49. 49. Unit 1: MULTIPLE ACCESS TECHNIQUES AND CELLULAR CONCEPT Multiple access schemes are generally allowed to use many mobile users share a finite amount of radio spectrum. We know that radio spectrum is a premium resource because most of the cost comes from licensing the spectrum. The sharing of spectrum is required to achieve high capacity by simultaneously allocating the bandwidth. There are several ways to do so and hence there are several multiple access schemes. Bandwidth is one of the resource which has to be shared.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 15 / 303
  50. 50. Unit 1: MULTIPLE ACCESS TECHNIQUES AND CELLULAR CONCEPT Multiple access schemes are generally allowed to use many mobile users share a finite amount of radio spectrum. We know that radio spectrum is a premium resource because most of the cost comes from licensing the spectrum. The sharing of spectrum is required to achieve high capacity by simultaneously allocating the bandwidth. There are several ways to do so and hence there are several multiple access schemes. Bandwidth is one of the resource which has to be shared. The constraint in sharing resource is that there should not be severe performance degradation.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 15 / 303
  51. 51. Frequency Division Multiple Access (FDMA) One of the most important multiple access schemes is the Frequency Division Multiple Access (FDMA)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 16 / 303
  52. 52. FDMACellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 17 / 303
  53. 53. TDMACellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 18 / 303
  54. 54. TDMACellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 19 / 303
  55. 55. CDMACellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 20 / 303
  56. 56. CDMACellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 21 / 303
  57. 57. Terminologies Mobile: A radio terminal attached to a high speed mobile platform (eg; a cell phone in a fast moving vehicle.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 22 / 303
  58. 58. Terminologies Mobile: A radio terminal attached to a high speed mobile platform (eg; a cell phone in a fast moving vehicle. Portable: A radio terminal that can be hand held and used by someone at walking speed (eg; a cordless telephone).Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 22 / 303
  59. 59. Terminologies Mobile: A radio terminal attached to a high speed mobile platform (eg; a cell phone in a fast moving vehicle. Portable: A radio terminal that can be hand held and used by someone at walking speed (eg; a cordless telephone). Subscriber: A mobile or portable user.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 22 / 303
  60. 60. Terminologies Mobile: A radio terminal attached to a high speed mobile platform (eg; a cell phone in a fast moving vehicle. Portable: A radio terminal that can be hand held and used by someone at walking speed (eg; a cordless telephone). Subscriber: A mobile or portable user. Base Stations: Fixed antenna units with which the subscribers communicate. Base stations are connected to a commercial power source and a backbone network.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 22 / 303
  61. 61. Terminologies Cells: The area of coverage is divided into cells. Each cell has a base station located at its centre or an edge.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 23 / 303
  62. 62. Terminologies Cells: The area of coverage is divided into cells. Each cell has a base station located at its centre or an edge. Control Channel: Radio channels used for transmission of call set-up, call request and call initiation.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 23 / 303
  63. 63. Terminologies Cells: The area of coverage is divided into cells. Each cell has a base station located at its centre or an edge. Control Channel: Radio channels used for transmission of call set-up, call request and call initiation. Forward channel(downlink):Radio channel used for transmission of information from the base station to the mobile.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 23 / 303
  64. 64. Terminologies Cells: The area of coverage is divided into cells. Each cell has a base station located at its centre or an edge. Control Channel: Radio channels used for transmission of call set-up, call request and call initiation. Forward channel(downlink):Radio channel used for transmission of information from the base station to the mobile. Reverse channels(uplink):Radio channel used for transmission of information from the mobile to the base station.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 23 / 303
  65. 65. Terminologies Full Duplex Systems: Simultaneous two way communication. Transmission and reception on two different channels.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 24 / 303
  66. 66. Terminologies Full Duplex Systems: Simultaneous two way communication. Transmission and reception on two different channels. Hand-off: The process of transferring the mobile station from one channel or base station to another.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 24 / 303
  67. 67. Terminologies Full Duplex Systems: Simultaneous two way communication. Transmission and reception on two different channels. Hand-off: The process of transferring the mobile station from one channel or base station to another. Page: A brief message that is broadcast over the entire service area by many base stations at the same time.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 24 / 303
  68. 68. Control and traffic channelsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 25 / 303
  69. 69. Terminologies Half Duplex Systems: Two way communications are done using the same radio channel for both transmission and reception. At a given time the user can either transmit or receive.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 26 / 303
  70. 70. Terminologies Half Duplex Systems: Two way communications are done using the same radio channel for both transmission and reception. At a given time the user can either transmit or receive. Mobile Switching Centre: Switching centre which coordinates the routing of calls in a large service area. In cellular radio system, the MSC connects the cellular base stations to the Public Switched Telephone Network (PSTN).Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 26 / 303
  71. 71. Terminologies Half Duplex Systems: Two way communications are done using the same radio channel for both transmission and reception. At a given time the user can either transmit or receive. Mobile Switching Centre: Switching centre which coordinates the routing of calls in a large service area. In cellular radio system, the MSC connects the cellular base stations to the Public Switched Telephone Network (PSTN). Transceiver: A device capable of transmitting and receiving radio signals.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 26 / 303
  72. 72. Full Duplex Systems Allow simultaneous transmission and reception between the subscriber and the base stationCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 27 / 303
  73. 73. Full Duplex Systems Allow simultaneous transmission and reception between the subscriber and the base station Full duplex is provided either by FDD or TDDCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 27 / 303
  74. 74. Frequency Division Duplex (FDD) Both the base station and the subscriber unit transmit and receive signals simultaneously.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 28 / 303
  75. 75. Frequency Division Duplex (FDD) Both the base station and the subscriber unit transmit and receive signals simultaneously. At the base station two separate transmit and receive antennas are used.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 28 / 303
  76. 76. Frequency Division Duplex (FDD) Both the base station and the subscriber unit transmit and receive signals simultaneously. At the base station two separate transmit and receive antennas are used. At the subscriber unit only a single antenna is used both for transmission and reception. A device called a duplexer is used to enable the same antenna for transmission and reception simultaneously.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 28 / 303
  77. 77. Time Division Duplex (TDD) Uses the fact that it is possible to share a single radio channel in time.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 29 / 303
  78. 78. Time Division Duplex (TDD) Uses the fact that it is possible to share a single radio channel in time. A portion of time is used to transmit from the BS to the MS and the remaining time is used to transmit from the MS tot he BS.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 29 / 303
  79. 79. Time Division Duplex (TDD) Uses the fact that it is possible to share a single radio channel in time. A portion of time is used to transmit from the BS to the MS and the remaining time is used to transmit from the MS tot he BS. Only possible with digital transmission formats and digital modulation (very sensitive to timing)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 29 / 303
  80. 80. Time Division Duplex (TDD) Uses the fact that it is possible to share a single radio channel in time. A portion of time is used to transmit from the BS to the MS and the remaining time is used to transmit from the MS tot he BS. Only possible with digital transmission formats and digital modulation (very sensitive to timing) Used only for indoor or small area applications where the propagation delay are small.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 29 / 303
  81. 81. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(1) High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 30 / 303
  82. 82. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(1) High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell. The same frequencies/time slots or codes are reused by spatially separating the base stations.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 30 / 303
  83. 83. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(1) High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell. The same frequencies/time slots or codes are reused by spatially separating the base stations. A switching technique called handoff enables a call to proceed uninterrupted when one user moves from one cell to another.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 30 / 303
  84. 84. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(1) High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell. The same frequencies/time slots or codes are reused by spatially separating the base stations. A switching technique called handoff enables a call to proceed uninterrupted when one user moves from one cell to another. Resolves the problem of limited radio spectrumCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 30 / 303
  85. 85. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(2) The neighbouring base stations are assigned different group of channels to minimize the interference.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 31 / 303
  86. 86. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(2) The neighbouring base stations are assigned different group of channels to minimize the interference. By systematically spacing base stations and the channel groups may be reused as many number off times as necessary.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 31 / 303
  87. 87. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(2) The neighbouring base stations are assigned different group of channels to minimize the interference. By systematically spacing base stations and the channel groups may be reused as many number off times as necessary. As demand increases the number of base stations get increased, there by providing additional capacity.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 31 / 303
  88. 88. The Cellular Concept:System Design Issues Cellular Systems - Basic Concepts(3) Now let us understand how cellular networks is laid out. Figure: Bandwidth structureCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 32 / 303
  89. 89. The Cellular Concept:System Design Issues Forward and Reverse channels: Forward Voice Channel: It is used for voice transmission from BS to MS.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 33 / 303
  90. 90. The Cellular Concept:System Design Issues Forward and Reverse channels: Forward Voice Channel: It is used for voice transmission from BS to MS. Reverse Voice Channel: It is used for voice transmission from MS to BS.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 33 / 303
  91. 91. The Cellular Concept:System Design Issues Forward and Reverse channels: Forward Voice Channel: It is used for voice transmission from BS to MS. Reverse Voice Channel: It is used for voice transmission from MS to BS. Forward Control Channel: Used for initiating a call from BS to MS.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 33 / 303
  92. 92. The Cellular Concept:System Design Issues Forward and Reverse channels: Forward Voice Channel: It is used for voice transmission from BS to MS. Reverse Voice Channel: It is used for voice transmission from MS to BS. Forward Control Channel: Used for initiating a call from BS to MS. Reverse Control Channel: Used for initiating a call from MS to BS.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 33 / 303
  93. 93. The Cellular Concept:System Design Issues Anatomy of a cellular call: A cell phone when turned on (not yet engaged in a call) scans the group of FCC to determine the one with the strongest signal. Please note that even if we are not making a call we use a battery power and that’s why when we buy a mobile phone we have two kinds of time available, one is the talk time and the other is the standby time.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 34 / 303
  94. 94. The Cellular Concept:System Design Issues Anatomy of a cellular call: A cell phone when turned on (not yet engaged in a call) scans the group of FCC to determine the one with the strongest signal. Please note that even if we are not making a call we use a battery power and that’s why when we buy a mobile phone we have two kinds of time available, one is the talk time and the other is the standby time. The mobile phone monitors the channel and keeps on monitoring because if the strength drops below a certain threshold, it scans for the next strongest.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 34 / 303
  95. 95. The Cellular Concept:System Design Issues Anatomy of a cellular call: A cell phone when turned on (not yet engaged in a call) scans the group of FCC to determine the one with the strongest signal. Please note that even if we are not making a call we use a battery power and that’s why when we buy a mobile phone we have two kinds of time available, one is the talk time and the other is the standby time. The mobile phone monitors the channel and keeps on monitoring because if the strength drops below a certain threshold, it scans for the next strongest. Control channels are defined and standardized over the entire area of service. Typically the control channels use up 5% of the total number of channels.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 34 / 303
  96. 96. A call to a Mobile User:(1) The moment we dial the number the MSC which is connected to the PSTN dispatches the message to all the base stations. The BS and MSC is connected by means of a fibre, point-to-point microwave link. Once the message is broadcast to the base stations the base stations sends a paging message.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 35 / 303
  97. 97. A call to a Mobile User:(1) The moment we dial the number the MSC which is connected to the PSTN dispatches the message to all the base stations. The BS and MSC is connected by means of a fibre, point-to-point microwave link. Once the message is broadcast to the base stations the base stations sends a paging message. The paging message contains the mobile identification number which the characteristic of that mobile station which is being broadcast. It is unique to that mobile. This number may not be same as the phone number. The MS receives the paging message from the BS it is monitoring.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 35 / 303
  98. 98. A call to a Mobile User:(1) The moment we dial the number the MSC which is connected to the PSTN dispatches the message to all the base stations. The BS and MSC is connected by means of a fibre, point-to-point microwave link. Once the message is broadcast to the base stations the base stations sends a paging message. The paging message contains the mobile identification number which the characteristic of that mobile station which is being broadcast. It is unique to that mobile. This number may not be same as the phone number. The MS receives the paging message from the BS it is monitoring. It responds by identifying itself over the RCC. The BS coveys the handshake to the MSC. The MSC instructs the BS to move to an unused voice channel.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 35 / 303
  99. 99. A call to a Mobile User:(2) The BS signals the MS to change over to an unused FVC and RVC.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 36 / 303
  100. 100. A call to a Mobile User:(2) The BS signals the MS to change over to an unused FVC and RVC. A data message (called alert) is transmitted over the FVC to instruct the mobile to ring.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 36 / 303
  101. 101. A call to a Mobile User:(2) The BS signals the MS to change over to an unused FVC and RVC. A data message (called alert) is transmitted over the FVC to instruct the mobile to ring. All of these sequences of events occur in just a few seconds, and a are not noticeable to the user.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 36 / 303
  102. 102. A call to a Mobile User:(2) The BS signals the MS to change over to an unused FVC and RVC. A data message (called alert) is transmitted over the FVC to instruct the mobile to ring. All of these sequences of events occur in just a few seconds, and a are not noticeable to the user. While the call is in progress, the MSC adjusts the transmitted power in order to maintain the call quality.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 36 / 303
  103. 103. A call from a Mobile User:(1) A call initiation request is sent to the RCC.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 37 / 303
  104. 104. A call from a Mobile User:(1) A call initiation request is sent to the RCC. Along with this the MS transmits is MIN, Electronic serial number (ESN) and the phone number of the called party.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 37 / 303
  105. 105. A call from a Mobile User:(1) A call initiation request is sent to the RCC. Along with this the MS transmits is MIN, Electronic serial number (ESN) and the phone number of the called party. The MS also transmits the station class mark (SCM) which indicates the maximum transmit power level for the particular user. This request is send toCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 37 / 303
  106. 106. A call from a Mobile User:(1) A call initiation request is sent to the RCC. Along with this the MS transmits is MIN, Electronic serial number (ESN) and the phone number of the called party. The MS also transmits the station class mark (SCM) which indicates the maximum transmit power level for the particular user. This request is send to The base station which forwards the data to the mobile switching centre which validates the data and makes connection to the called party through the PSTN.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 37 / 303
  107. 107. Frequency Reuse: Need(1) Suppose we have fixed telephone networks and they were running wires to every household.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 38 / 303
  108. 108. Frequency Reuse: Need(1) Suppose we have fixed telephone networks and they were running wires to every household. Suppose we give every household their own allocation of radio spectrum for analog speech of 4 KHz bandwidth. Now we assume that there are 12.5 million households and for every 4 KHz allocation we need to have a 50 GHz of bandwidth.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 38 / 303
  109. 109. Frequency Reuse: Need(1) Suppose we have fixed telephone networks and they were running wires to every household. Suppose we give every household their own allocation of radio spectrum for analog speech of 4 KHz bandwidth. Now we assume that there are 12.5 million households and for every 4 KHz allocation we need to have a 50 GHz of bandwidth. Clearly we cannot allow this kind of outage on a mobile phone network because we cannot reach that 50 GHz bandwidth and no other services possible using the radio transmissionCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 38 / 303
  110. 110. Frequency Reuse: Need(1) Suppose we have fixed telephone networks and they were running wires to every household. Suppose we give every household their own allocation of radio spectrum for analog speech of 4 KHz bandwidth. Now we assume that there are 12.5 million households and for every 4 KHz allocation we need to have a 50 GHz of bandwidth. Clearly we cannot allow this kind of outage on a mobile phone network because we cannot reach that 50 GHz bandwidth and no other services possible using the radio transmission Most of the spectrum unused most of the time. So frequency reuse is very necessary.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 38 / 303
  111. 111. Frequency Reuse: Need(2) Cellular radio systems rely on intelligent allocation and reuse of channels throughout the coverage area.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 39 / 303
  112. 112. Frequency Reuse: Need(2) Cellular radio systems rely on intelligent allocation and reuse of channels throughout the coverage area. Each BS is allocated a group of radio channels to be used within the small geographic area of its cell.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 39 / 303
  113. 113. Frequency Reuse: Need(2) Cellular radio systems rely on intelligent allocation and reuse of channels throughout the coverage area. Each BS is allocated a group of radio channels to be used within the small geographic area of its cell. Neighbouring BS are given different channel allocation from each other.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 39 / 303
  114. 114. Frequency Reuse: Need(2) Cellular radio systems rely on intelligent allocation and reuse of channels throughout the coverage area. Each BS is allocated a group of radio channels to be used within the small geographic area of its cell. Neighbouring BS are given different channel allocation from each other. By designing antennas and regulating the power, the coverage area within the cell is limited and the same group of frequencies are reused to cover another cell separated by a large enough distance to keep co-channel interference within limits. We wish to keep this co-channel interfering cell as far as possible because of the inverse square law that will take place.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 39 / 303
  115. 115. Frequency Reuse: Need(3) On the other way if we put the co-channel interfering cells at a larger distance the less frequently we reuse the frequency, the less capacity we can have. So there is a trade-off between how much capacity we can pack in terms of closely putting the reuse factors and then we can go-ahead and reuse the frequency as and when desired.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 40 / 303
  116. 116. Frequency Reuse: Need(3) On the other way if we put the co-channel interfering cells at a larger distance the less frequently we reuse the frequency, the less capacity we can have. So there is a trade-off between how much capacity we can pack in terms of closely putting the reuse factors and then we can go-ahead and reuse the frequency as and when desired. The design procedure for allocating channel groups for all the cellular BS within a system is called frequency reuse or frequency planning.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 40 / 303
  117. 117. Frequency Reuse: Need(3) On the other way if we put the co-channel interfering cells at a larger distance the less frequently we reuse the frequency, the less capacity we can have. So there is a trade-off between how much capacity we can pack in terms of closely putting the reuse factors and then we can go-ahead and reuse the frequency as and when desired. The design procedure for allocating channel groups for all the cellular BS within a system is called frequency reuse or frequency planning. Frequency planning should not be very complicated because at the end we have to ensure that certain BS are using certain bands and others are using other bands and we cannot come up with a very complicated scheme.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 40 / 303
  118. 118. Example of Frequency ReuseCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 41 / 303
  119. 119. Cell Shape(1)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 42 / 303
  120. 120. Cell Shape(2)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 43 / 303
  121. 121. Cell Shape(3)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 44 / 303
  122. 122. Cell Shape(4)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 45 / 303
  123. 123. Cell Shape(5) Hexagonal cells are conceptualCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 46 / 303
  124. 124. Cell Shape(5) Hexagonal cells are conceptual Theoretically hexagonal models are universally accepted because they have a shape that approximates a circle (for omni-directional radiation) and using hexagon geometry, fewest number of cells can cover the entire geographical region.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 46 / 303
  125. 125. The Geometry of Hexagons(1)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 47 / 303
  126. 126. The Geometry of Hexagons(2) The axes ”u” and ”v” intersect at 60 degrees as we already seen. To find the distance of a point P(u,v) from the origin Use x-y to to u-v coordinate transformation r2 = x2 + y2 x = u + vcos300 r = (v 2 + uv + u 2 )1/2Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 48 / 303
  127. 127. The Geometry of Hexagons(2) The axes ”u” and ”v” intersect at 60 degrees as we already seen. Unit cell is distance between cell centres. To find the distance of a point P(u,v) from the origin Use x-y to to u-v coordinate transformation r2 = x2 + y2 x = u + vcos300 r = (v 2 + uv + u 2 )1/2Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 48 / 303
  128. 128. The Geometry of Hexagons(2) The axes ”u” and ”v” intersect at 60 degrees as we already seen. Unit cell is distance between cell centres. If cell radius to point of a hexagon is R then 2R cos 300 = 1 or 1 R= √ 3 To find the distance of a point P(u,v) from the origin Use x-y to to u-v coordinate transformation r2 = x2 + y2 x = u + vcos300 r = (v 2 + uv + u 2 )1/2Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 48 / 303
  129. 129. The Geometry of Hexagons(3) Using this equation, to locate co-channel cells, we start from a reference cell and move i hexagons along the u axis then j hexagons along the v-axisCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 49 / 303
  130. 130. The Geometry of Hexagons(3) Using this equation, to locate co-channel cells, we start from a reference cell and move i hexagons along the u axis then j hexagons along the v-axis Hence the distance between co-channel cells in adjacent clusters is given by D = (i 2 + ij + j 2 )1/2Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 49 / 303
  131. 131. The Geometry of Hexagons(3) Using this equation, to locate co-channel cells, we start from a reference cell and move i hexagons along the u axis then j hexagons along the v-axis Hence the distance between co-channel cells in adjacent clusters is given by D = (i 2 + ij + j 2 )1/2 The number of cells in a cluster N is given by N = i 2 + ij + j 2 , where i and j are integersCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 49 / 303
  132. 132. The Geometry of Hexagons(3) Using this equation, to locate co-channel cells, we start from a reference cell and move i hexagons along the u axis then j hexagons along the v-axis Hence the distance between co-channel cells in adjacent clusters is given by D = (i 2 + ij + j 2 )1/2 The number of cells in a cluster N is given by N = i 2 + ij + j 2 , where i and j are integers Hence the possible values of N are 1,3,4,7,12.....Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 49 / 303
  133. 133. ExampleCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 50 / 303
  134. 134. In-ValidCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 51 / 303
  135. 135. ValidCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 52 / 303
  136. 136. Co-channel Cell Location(1) Method of locating co-channel cells Figure: Formation of a cluster for N=7 with i=2 and j=1Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 53 / 303
  137. 137. Example Figure: Formation of a cluster for N=28 with i=2 and j=4Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 54 / 303
  138. 138. ExampleCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 55 / 303
  139. 139. Reuse Ratio(1)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 56 / 303
  140. 140. Reuse Ratio(2) √ For hexagonal cells the reuse distance is given by D = 3NR, where R is the cell side and N is the cluster sizeCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 57 / 303
  141. 141. Reuse Ratio(2) √ For hexagonal cells the reuse distance is given by D = 3NR, where R is the cell side and N is the cluster size D √ Reuse factor is q = = 3N RCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 57 / 303
  142. 142. Cell Capacity and Reuse Consider a cellular system with s duplex channelsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 58 / 303
  143. 143. Cell Capacity and Reuse Consider a cellular system with s duplex channels Each cell is allocated k channels. Let these S channels be divided among N cells (cluster). Therefore S = KNCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 58 / 303
  144. 144. Cell Capacity and Reuse Consider a cellular system with s duplex channels Each cell is allocated k channels. Let these S channels be divided among N cells (cluster). Therefore S = KN If a cluster of N cells is replicated M times in the system, total number of duplex channels C can be used as a measure of the system capacity C = MkN = MSCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 58 / 303
  145. 145. Cell Capacity and Reuse Consider a cellular system with s duplex channels Each cell is allocated k channels. Let these S channels be divided among N cells (cluster). Therefore S = KN If a cluster of N cells is replicated M times in the system, total number of duplex channels C can be used as a measure of the system capacity C = MkN = MS If N is reduced, keeping cell size fixed, more clusters are required to cover the entire area. M ↑⇒ C ↑Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 58 / 303
  146. 146. Cell Capacity and Reuse Consider a cellular system with s duplex channels Each cell is allocated k channels. Let these S channels be divided among N cells (cluster). Therefore S = KN If a cluster of N cells is replicated M times in the system, total number of duplex channels C can be used as a measure of the system capacity C = MkN = MS If N is reduced, keeping cell size fixed, more clusters are required to cover the entire area. M ↑⇒ C ↑ Smaller N ⇒ higher capacity ⇒ Larger co-channel interference ⇒ Lower QOSCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 58 / 303
  147. 147. Cell Capacity and Reuse 1 Setup time: The time required to allocate a radio channel to a requesting user.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 59 / 303
  148. 148. Cell Capacity and Reuse 1 Setup time: The time required to allocate a radio channel to a requesting user. 2 Blocked calls: A call that cannot be completed at the time of request due to congestion.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 59 / 303
  149. 149. Cell Capacity and Reuse 1 Setup time: The time required to allocate a radio channel to a requesting user. 2 Blocked calls: A call that cannot be completed at the time of request due to congestion. 3 Holding Time: Average duration of a typical call.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 59 / 303
  150. 150. Cell Capacity and Reuse 1 Setup time: The time required to allocate a radio channel to a requesting user. 2 Blocked calls: A call that cannot be completed at the time of request due to congestion. 3 Holding Time: Average duration of a typical call. 4 Request Rate: The average number of calls per unit time (λ)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 59 / 303
  151. 151. Cell Capacity and Reuse 1 Setup time: The time required to allocate a radio channel to a requesting user. 2 Blocked calls: A call that cannot be completed at the time of request due to congestion. 3 Holding Time: Average duration of a typical call. 4 Request Rate: The average number of calls per unit time (λ) 5 Traffic Intensity: Measure of channel time utilization (Erlangs ⇒ A channel kept busy for one hour is defined as having a load of one Erlang)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 59 / 303
  152. 152. Cell Capacity and Reuse 1 Setup time: The time required to allocate a radio channel to a requesting user. 2 Blocked calls: A call that cannot be completed at the time of request due to congestion. 3 Holding Time: Average duration of a typical call. 4 Request Rate: The average number of calls per unit time (λ) 5 Traffic Intensity: Measure of channel time utilization (Erlangs ⇒ A channel kept busy for one hour is defined as having a load of one Erlang) 6 Load: Traffic intensity across the entire radio system.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 59 / 303
  153. 153. Cell Capacity and Reuse 1 Setup time: The time required to allocate a radio channel to a requesting user. 2 Blocked calls: A call that cannot be completed at the time of request due to congestion. 3 Holding Time: Average duration of a typical call. 4 Request Rate: The average number of calls per unit time (λ) 5 Traffic Intensity: Measure of channel time utilization (Erlangs ⇒ A channel kept busy for one hour is defined as having a load of one Erlang) 6 Load: Traffic intensity across the entire radio system. 7 Grade of Service: A measure of the congestion which is specified as a probability.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 59 / 303
  154. 154. Traffic Theory The average number of MS requesting service (request/time) is called the average arrival rate (λ)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 60 / 303
  155. 155. Traffic Theory The average number of MS requesting service (request/time) is called the average arrival rate (λ) The average time for the MS requires service is the average holding time (T)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 60 / 303
  156. 156. Traffic Theory The average number of MS requesting service (request/time) is called the average arrival rate (λ) The average time for the MS requires service is the average holding time (T) The offered load is given by a = λ T (Erlangs)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 60 / 303
  157. 157. Example Consider a cell with 100 MS and we assume that on an average 30 requests are generated during an hour (3600 sec) with average holding time t = 360 seconds (6 minutes)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 61 / 303
  158. 158. Example Consider a cell with 100 MS and we assume that on an average 30 requests are generated during an hour (3600 sec) with average holding time t = 360 seconds (6 minutes) 30 Arrival rate λ = request/sec 3600Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 61 / 303
  159. 159. Example Consider a cell with 100 MS and we assume that on an average 30 requests are generated during an hour (3600 sec) with average holding time t = 360 seconds (6 minutes) 30 Arrival rate λ = request/sec 3600 30 Offered load a = λt = × 360 = 3 Erlangs 3600Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 61 / 303
  160. 160. Traffic Theory Average arrival rate during a short interval t is given by λ t (λt)n P(n, t) = × e −λt n! S(t) = 1 − e −µ tCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 62 / 303
  161. 161. Traffic Theory Average arrival rate during a short interval t is given by λ t Assuming Poisson distribution of service requests the probability P(n,t) for n calls to arrive in an interval of length t is given by (λt)n P(n, t) = × e −λt n! S(t) = 1 − e −µ tCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 62 / 303
  162. 162. Traffic Theory Average arrival rate during a short interval t is given by λ t Assuming Poisson distribution of service requests the probability P(n,t) for n calls to arrive in an interval of length t is given by (λt)n P(n, t) = × e −λt n! Assuming µ to be the service rate, probability of each call to terminate during interval t is given by µt. Thus probability of a given call requires service for time t or less is given by S(t) = 1 − e −µ tCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 62 / 303
  163. 163. Erlang B and Erlang C Formulas Erlang B: Probability of an arriving call being blocked is given by Erlang B as 1 B(S, a) = . S S! ak k=0 k! S is the number of channels in the group as (s−a)!(s−a) C (S, a) = S−1 as ai (s−1)!(s−a) + i=0 i!Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 63 / 303
  164. 164. Erlang B and Erlang C Formulas Erlang B: Probability of an arriving call being blocked is given by Erlang B as 1 B(S, a) = . S S! ak k=0 k! S is the number of channels in the group Erlang C: Probability of an arriving call being delayed is given by Erlang C as (s−a)!(s−a) C (S, a) = S−1 as ai (s−1)!(s−a) + i=0 i!Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 63 / 303
  165. 165. Traffic Theory & Example Traffic nonblocked Efficiency = = Capacity Erlangs × Portions of non − routed traffic No. of trunks(channels) Example:Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 64 / 303
  166. 166. Traffic Theory & Example Traffic nonblocked Efficiency = = Capacity Erlangs × Portions of non − routed traffic No. of trunks(channels) Example: Consider a cell with 2 channels and 100 MS which is generating 30 request/hour and the average holding time of each request is 360 seconds(6 min)Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 64 / 303
  167. 167. Traffic Theory & Example Traffic nonblocked Efficiency = = Capacity Erlangs × Portions of non − routed traffic No. of trunks(channels) Example: Consider a cell with 2 channels and 100 MS which is generating 30 request/hour and the average holding time of each request is 360 seconds(6 min) The total load offered is given by a = λt = 3 ErlangsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 64 / 303
  168. 168. Traffic Theory & Example Traffic nonblocked Efficiency = = Capacity Erlangs × Portions of non − routed traffic No. of trunks(channels) Example: Consider a cell with 2 channels and 100 MS which is generating 30 request/hour and the average holding time of each request is 360 seconds(6 min) The total load offered is given by a = λt = 3 Erlangs By applying Erlang B formula the blocking probability B(s,a) = 0.53Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 64 / 303
  169. 169. Traffic Theory & Example Traffic nonblocked Efficiency = = Capacity Erlangs × Portions of non − routed traffic No. of trunks(channels) Example: Consider a cell with 2 channels and 100 MS which is generating 30 request/hour and the average holding time of each request is 360 seconds(6 min) The total load offered is given by a = λt = 3 Erlangs By applying Erlang B formula the blocking probability B(s,a) = 0.53 Rerouted calls is 30 × 0.53 = 16 callsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 64 / 303
  170. 170. Traffic Theory & Example Traffic nonblocked Efficiency = = Capacity Erlangs × Portions of non − routed traffic No. of trunks(channels) Example: Consider a cell with 2 channels and 100 MS which is generating 30 request/hour and the average holding time of each request is 360 seconds(6 min) The total load offered is given by a = λt = 3 Erlangs By applying Erlang B formula the blocking probability B(s,a) = 0.53 Rerouted calls is 30 × 0.53 = 16 calls 3 × (1 − 0.53) ∴ Efficiency = = 0.7 2Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 64 / 303
  171. 171. Erlang B chartCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 65 / 303
  172. 172. Erlang C chartCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 66 / 303
  173. 173. Example Consider a system with 100 cells and each cell having 20 channels which is generating 2 calls/hour and the average holding time of each request is 180 seconds(3 min). How many users will be supported if blocking probability is 2%Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 67 / 303
  174. 174. Example Consider a system with 100 cells and each cell having 20 channels which is generating 2 calls/hour and the average holding time of each request is 180 seconds(3 min). How many users will be supported if blocking probability is 2% From Erlang B chart we get the total traffic is 13 ErlangsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 67 / 303
  175. 175. Example Consider a system with 100 cells and each cell having 20 channels which is generating 2 calls/hour and the average holding time of each request is 180 seconds(3 min). How many users will be supported if blocking probability is 2% From Erlang B chart we get the total traffic is 13 Erlangs Traffic intensity per user = λt = 0.1 ErlangsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 67 / 303
  176. 176. Example Consider a system with 100 cells and each cell having 20 channels which is generating 2 calls/hour and the average holding time of each request is 180 seconds(3 min). How many users will be supported if blocking probability is 2% From Erlang B chart we get the total traffic is 13 Erlangs Traffic intensity per user = λt = 0.1 Erlangs 13 Total no.of users that can be supported per cell = = 130 0.1 users/cellCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 67 / 303
  177. 177. Example Consider a system with 100 cells and each cell having 20 channels which is generating 2 calls/hour and the average holding time of each request is 180 seconds(3 min). How many users will be supported if blocking probability is 2% From Erlang B chart we get the total traffic is 13 Erlangs Traffic intensity per user = λt = 0.1 Erlangs 13 Total no.of users that can be supported per cell = = 130 0.1 users/cell ∴ Total number of users that can be supported = 13,000Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 67 / 303
  178. 178. Channel Assignment Strategies A scheme for increasing capacity and minimizing interference is requiredCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 68 / 303
  179. 179. Channel Assignment Strategies A scheme for increasing capacity and minimizing interference is required They can be fixed or dynamic. Fixed assignment requires the advantage of planning and fixing whereas dynamic requires us to be adaptiveCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 68 / 303
  180. 180. Channel Assignment Strategies A scheme for increasing capacity and minimizing interference is required They can be fixed or dynamic. Fixed assignment requires the advantage of planning and fixing whereas dynamic requires us to be adaptive Choice of channel assignment strategy impacts the performance of the system, particularly how a call is managed when a mobile user is handed off from one cell to anotherCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 68 / 303
  181. 181. Channel Assignment Strategies A scheme for increasing capacity and minimizing interference is required They can be fixed or dynamic. Fixed assignment requires the advantage of planning and fixing whereas dynamic requires us to be adaptive Choice of channel assignment strategy impacts the performance of the system, particularly how a call is managed when a mobile user is handed off from one cell to another Capacity and hand-off are the two important requirementsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 68 / 303
  182. 182. Fixed Channel Assignment Each cell is assigned a predetermined set of voice channelsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 69 / 303
  183. 183. Fixed Channel Assignment Each cell is assigned a predetermined set of voice channels Any call requests can be served only by the unused channels in that particular cellCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 69 / 303
  184. 184. Fixed Channel Assignment Each cell is assigned a predetermined set of voice channels Any call requests can be served only by the unused channels in that particular cell If all the channels in the cell are occupied then the call is blockedCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 69 / 303
  185. 185. Fixed Channel Assignment Each cell is assigned a predetermined set of voice channels Any call requests can be served only by the unused channels in that particular cell If all the channels in the cell are occupied then the call is blocked In a variation of the fixed channel assignment, a cell can borrow channels from its neighbouring cell if its own channels are fullCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 69 / 303
  186. 186. Dynamic Channel Assignment Voice channels are not allocated to different users permanentlyCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 70 / 303
  187. 187. Dynamic Channel Assignment Voice channels are not allocated to different users permanently Each time a call request is made, the BS requests a channel from the MSCCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 70 / 303
  188. 188. Dynamic Channel Assignment Voice channels are not allocated to different users permanently Each time a call request is made, the BS requests a channel from the MSC In a more complicated cellular system, there may be more than one MSCCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 70 / 303
  189. 189. Dynamic Channel Assignment Voice channels are not allocated to different users permanently Each time a call request is made, the BS requests a channel from the MSC In a more complicated cellular system, there may be more than one MSC MSC allocates a channel to the requested cell using an algorithm which looks into the following parameters (i) The likelihood of future blocking (ii) The frequency of use of the channel (iii) The reuse distance of the channel (iv) Other cost functionsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 70 / 303
  190. 190. Dynamic Channel Assignment Voice channels are not allocated to different users permanently Each time a call request is made, the BS requests a channel from the MSC In a more complicated cellular system, there may be more than one MSC MSC allocates a channel to the requested cell using an algorithm which looks into the following parameters (i) The likelihood of future blocking (ii) The frequency of use of the channel (iii) The reuse distance of the channel (iv) Other cost functions In the first level of design we are not looking into the variations of the channels. For example some channel may have high priorityCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 70 / 303
  191. 191. Dynamic Channel Assignment To ensure minimum QOS, the MSC only allocates a given frequency if that frequency is not currently in use in the cell, or any other cell which falls within the limiting reuse distance.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 71 / 303
  192. 192. Dynamic Channel Assignment To ensure minimum QOS, the MSC only allocates a given frequency if that frequency is not currently in use in the cell, or any other cell which falls within the limiting reuse distance. DCA reduces the likelihood of blocking, thus increasing the capacity of the systemCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 71 / 303
  193. 193. Dynamic Channel Assignment To ensure minimum QOS, the MSC only allocates a given frequency if that frequency is not currently in use in the cell, or any other cell which falls within the limiting reuse distance. DCA reduces the likelihood of blocking, thus increasing the capacity of the system DCA strategy require the MSC to collect real time data on channel occupancy and traffic distribution on a continuous basisCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 71 / 303
  194. 194. Handoff When a mobile moves into a different cell while the call is in progress, the MSC automatically transfers the call to a new channel belonging to the new BSCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 72 / 303
  195. 195. Handoff When a mobile moves into a different cell while the call is in progress, the MSC automatically transfers the call to a new channel belonging to the new BS The handoff operation involves identifying a new BS and the allocation of voice and control signals associated with the new BS.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 72 / 303
  196. 196. Handoff When a mobile moves into a different cell while the call is in progress, the MSC automatically transfers the call to a new channel belonging to the new BS The handoff operation involves identifying a new BS and the allocation of voice and control signals associated with the new BS. Handoffs must be performed successfully as infrequently as possible and must be imperceptible to the userCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 72 / 303
  197. 197. Handoff When a mobile moves into a different cell while the call is in progress, the MSC automatically transfers the call to a new channel belonging to the new BS The handoff operation involves identifying a new BS and the allocation of voice and control signals associated with the new BS. Handoffs must be performed successfully as infrequently as possible and must be imperceptible to the user by looking at the variation of the signal strength from either BS, it is possible to decide on the optimum area where handoff can take place.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 72 / 303
  198. 198. HandoffCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 73 / 303
  199. 199. Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 74 / 303
  200. 200. Handoff Hand-off is made when the received signal at the BS falls below a pre-specified thresholdCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 74 / 303
  201. 201. Handoff Hand-off is made when the received signal at the BS falls below a pre-specified threshold In deciding when to hand-off, it is important to ensure that the drop in the signal level is not due to momentary fadingCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 74 / 303
  202. 202. Handoff Hand-off is made when the received signal at the BS falls below a pre-specified threshold In deciding when to hand-off, it is important to ensure that the drop in the signal level is not due to momentary fading Inorder to ensure this, the BS monitors the signal for a certain period of time before initiating hand-offCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 74 / 303
  203. 203. Handoff Hand-off is made when the received signal at the BS falls below a pre-specified threshold In deciding when to hand-off, it is important to ensure that the drop in the signal level is not due to momentary fading Inorder to ensure this, the BS monitors the signal for a certain period of time before initiating hand-off The length of the time needed to decide if hand-off is necessary depends on the speed at which the MS is movingCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 74 / 303
  204. 204. Interference and system capacity Major limiting factor in the performance of cellular radio systemsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 75 / 303
  205. 205. Interference and system capacity Major limiting factor in the performance of cellular radio systems It limits capacity and increases the number of dropped calls and has a direct correlation with the QOSCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 75 / 303
  206. 206. Interference and system capacity Major limiting factor in the performance of cellular radio systems It limits capacity and increases the number of dropped calls and has a direct correlation with the QOS Sources of interference include (i) Another mobile in the same cell (ii) A call progressing in a neighbouring cell (iii) Other BS operating in the same frequency bandCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 75 / 303
  207. 207. Interference and system capacity Major limiting factor in the performance of cellular radio systems It limits capacity and increases the number of dropped calls and has a direct correlation with the QOS Sources of interference include (i) Another mobile in the same cell (ii) A call progressing in a neighbouring cell (iii) Other BS operating in the same frequency band Very severe in urban areas due to greater RF noise and more number of MS and BSCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 75 / 303
  208. 208. Interference and system capacity Major limiting factor in the performance of cellular radio systems It limits capacity and increases the number of dropped calls and has a direct correlation with the QOS Sources of interference include (i) Another mobile in the same cell (ii) A call progressing in a neighbouring cell (iii) Other BS operating in the same frequency band Very severe in urban areas due to greater RF noise and more number of MS and BS urban areas have an advantage, i.e the path loss exponent is high which leads to decreased interference levels.Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 75 / 303
  209. 209. Effects of Interference Voice Channels Cross talks Control channelsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 76 / 303
  210. 210. Effects of Interference Voice Channels Cross talks Noise in the background Control channelsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 76 / 303
  211. 211. Effects of Interference Voice Channels Cross talks Noise in the background Control channels Missed callsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 76 / 303
  212. 212. Effects of Interference Voice Channels Cross talks Noise in the background Control channels Missed calls Blocked callsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 76 / 303
  213. 213. Effects of Interference Voice Channels Cross talks Noise in the background Control channels Missed calls Blocked calls Dropped callsCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 76 / 303
  214. 214. Types of Interference Co-channel Interference: It is due to the cells that use the same set of frequenciesCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 77 / 303
  215. 215. Types of Interference Co-channel Interference: It is due to the cells that use the same set of frequencies Adjacent channel Interference: It is due to the signals that are adjacent in frequencyCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 77 / 303
  216. 216. Co-channel InterferenceCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 78 / 303
  217. 217. Co-channel Interference Unlike thermal noise CCI cannot be overcome by increasing the carrier power of the transmitterCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 79 / 303
  218. 218. Co-channel Interference Unlike thermal noise CCI cannot be overcome by increasing the carrier power of the transmitter For similar sized cells the CCI is independent of the transmitted power and depends on the cell radius R and the distance to the nearest co-channel cell DCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 79 / 303
  219. 219. Co-channel Interference Unlike thermal noise CCI cannot be overcome by increasing the carrier power of the transmitter For similar sized cells the CCI is independent of the transmitted power and depends on the cell radius R and the distance to the nearest co-channel cell D To reduce CCI the co-channel cells must be physically separatedCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 79 / 303
  220. 220. Co-channel Interference Unlike thermal noise CCI cannot be overcome by increasing the carrier power of the transmitter For similar sized cells the CCI is independent of the transmitted power and depends on the cell radius R and the distance to the nearest co-channel cell D To reduce CCI the co-channel cells must be physically separated D The co-channel reuse ratio Q = where D ⇒ distance between R co-channel BS and R ⇒ cell RadiusCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 79 / 303
  221. 221. Co-channel Interference Unlike thermal noise CCI cannot be overcome by increasing the carrier power of the transmitter For similar sized cells the CCI is independent of the transmitted power and depends on the cell radius R and the distance to the nearest co-channel cell D To reduce CCI the co-channel cells must be physically separated D The co-channel reuse ratio Q = where D ⇒ distance between R co-channel BS and R ⇒ cell Radius It determines the spatial separation relative to the coverage distance of the cellCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 79 / 303
  222. 222. Co-channel Interference Unlike thermal noise CCI cannot be overcome by increasing the carrier power of the transmitter For similar sized cells the CCI is independent of the transmitted power and depends on the cell radius R and the distance to the nearest co-channel cell D To reduce CCI the co-channel cells must be physically separated D The co-channel reuse ratio Q = where D ⇒ distance between R co-channel BS and R ⇒ cell Radius It determines the spatial separation relative to the coverage distance of the cell D √ For a hexagonal cell pattern, Q = = 3N RCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 79 / 303
  223. 223. Co-channel Interference Unlike thermal noise CCI cannot be overcome by increasing the carrier power of the transmitter For similar sized cells the CCI is independent of the transmitted power and depends on the cell radius R and the distance to the nearest co-channel cell D To reduce CCI the co-channel cells must be physically separated D The co-channel reuse ratio Q = where D ⇒ distance between R co-channel BS and R ⇒ cell Radius It determines the spatial separation relative to the coverage distance of the cell D √ For a hexagonal cell pattern, Q = = 3N R Thus a smaller value of Q provides a larger capacity but higher CCI and hence there is a trade-off between capacity and interferenceCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 79 / 303
  224. 224. Calculation of signal to interference ratio S/I The signal-to-interference ratio for a mobile is given by S S = m Where S is the desired signal strength and Ii is the I Ii i=1 interference caused by the i th co-channel cellCellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 80 / 303
  225. 225. Calculation of signal to interference ratio S/I The signal-to-interference ratio for a mobile is given by S S = m Where S is the desired signal strength and Ii is the I Ii i=1 interference caused by the i th co-channel cell The average received power at a distance d is given by −n d Pr = P0 d0Cellular and Mobile Communication () Chettinad Tech, Karur January 25, 2013 80 / 303

×