Wireless Overview

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Here is an overview of Cellular Communications I gave back in 2001. It is slightly out of date, but has good info.

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Wireless Overview

  1. 1. Wireless Overview CellularNational Wireless Engineering ConferenceOctober 31, 2000 John Skeffington, Sun Microsystems JFS May, 2001 JFS 10/11/00
  2. 2. Agenda• Historical Perspective• Building a Cellular System• Current Landscape• Future Landscape JFS May, 2001 JFS 10/11/00
  3. 3. Historical Perspective (US)• Evolved from Two-way Radio Systems• Mobile Phone System (MTS) – Operator Interaction Required – 15 - 25 Simultaneous Users on System• Improved Mobile Phone System (IMTS) – Incorporated Direct Dial – Still in Service until Early 1990’s• Advanced Mobile Phone Service (AMPS) – 1st Commercial Phone Call Placed in 1983 JFS May, 2001 JFS 10/11/00
  4. 4. Definitions• Wireless - Large coverage area, high mobility (pedestrian and automotive) usage.• Cellular - A communications system where a small number of radio frequencies are carefully managed and re-used in a geographic area. – Full duplex, two frequencies used for each conversation• PCS - Personal Communications System - A spectrum of frequencies allocated by the FCC for newer cellular type technologies. JFS May, 2001 JFS 10/11/00
  5. 5. Agenda• Historical Perspective• Building a Cellular System• Current Landscape• Future Landscape JFS May, 2001 JFS 10/11/00
  6. 6. Pre Cellular Service Pre-Cellular Scenario - Metropolitan area using seven channels (14 frequencies): seven simultaneous calls JFS May, 2001 JFS 10/11/00
  7. 7. Basic Components• Mobile Switch• Central Switching Office Building• Base Stations• Leased locations for Base Stations• Connections to Landline• Antennas, Cable, Towers, etc.• Mobile Phones• Customers JFS May, 2001 JFS 10/11/00
  8. 8. Basic Analog CellularSystem Billing Base System Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber JFS May, 2001 JFS 10/11/00
  9. 9. Assumptions for “My Mobile”• Mobile Switching Center in place• Base Station (BTS) equipment cost $250,000• Base Station Construction cost $200,000• BTS rental $1000 per month• One T1 line required per BTS, $1200 per month• Subscriber usage is 50 minutes per month• 5% of subscribers use system at any given time• BTS upgrade is $100,000• Very simplistic financial estimating JFS May, 2001 JFS 10/11/00
  10. 10. My Mobile Service Three Cell System3 BTS $3600/mon 3 BTS $ 750,0003 T1 $3000/mon BTS const $ 600,00021 simultaneous calls420 subscribers Total Capital $1,350,000$0.31 per minute JFS May, 2001 JFS 10/11/00
  11. 11. Handoffs• Handoff: Major enabling technology that creates mobile communications, transfer of call from one cell to another – First generation handoffs (AMPS) – MSC initiated, mobile had “passive” role – MSC would query neighboring cells to determine when to handoff based on received power getting lower. – “Intelligence” of handoffs contained to MSC – Hard Handoff: “break before make” connection – Second generation handoff – Mobile initiated, mobile has active role – Database assisted – Soft Handoff: “make before break” connection JFS May, 2001 JFS 10/11/00
  12. 12. Basic Hard Handoff• Caller is active in cell A• Caller is driving on “blue” road• System detects lower signal level in cell A B as caller moves to edge• System checks other cells to determine A which has stronger signal• Cell B is determined C to be stronger signal• System directs mobile to tune to Cell B frequency JFS May, 2001 JFS 10/11/00
  13. 13. Basic Hard Handoff• Mobile tunes to cell B while still on call• Call is now established in cell B• System detects lower signal level in cell B B as caller moves to edge• System checks other cells to determine A which has stronger signal• Cell C is determined C to be stronger signal• System directs mobile to tune to Cell C frequency JFS May, 2001 JFS 10/11/00
  14. 14. Basic Hard Handoff• Mobile tunes to cell C while still on call• Call is now established in cell C• System detects lower signal level in cell C B as caller moves to edge• System checks other cells to determine A which has stronger signal• Cell A is determined C to be stronger signal• System directs mobile to tune to Cell A frequency JFS May, 2001 JFS 10/11/00
  15. 15. My Mobile Service Eight Cell System1 MSC8 BTS $9600/mon 5 BTS $1,250,0008 T1 $8000/mon BTS const $1,000,00056 simultaneous calls Total Capital $2,250,0001120 subscribers$0.31 per minute JFS May, 2001 JFS 10/11/00
  16. 16. Definitions• Down Link, Forward Link - Radio connection from base station to mobile• Up Link, Reverse Link - Radio connection from mobile to base station• Channel: A physical (or logical) radio frequency(s) – Traffic (voice) channel - A channel dedicated to voice usage – Control (overhead) channel - A channel dedicated to control functions – Access Channel - Channel used for mobile to gain access to system (reverse link) – Paging Channel - Channel used for messaging from system to mobiles (forward link) JFS May, 2001 JFS 10/11/00
  17. 17. Forward / Reverse Links Down Link Down Link Up Link Up Link 0.6 watt portable 3 watt portable JFS May, 2001 JFS 10/11/00
  18. 18. Power Control●System works best when all mobiles appear to besame power at base station●Mobility of mobiles requires power control to bedynamic●Base station tells mobiles whether to power up ordown●Revisions made to original AMPS specs to allowadditional (lower) power levels● CDMA power control happens every 20 msec JFS May, 2001 JFS 10/11/00
  19. 19. Why is Power Control Needed? ● Many Mobiles, many Distances ● Power Level Inversely Proportional to Square of Distance ● Mobile at One Mile = One Watt ● Same Mobile at Two Miles = 1/4 Watt ● Same Mobile at Three Miles = 1/9 Watt 4.5 4 3.5 3 2.5power 2 1.5 1 JFS May, 2001 0.5 JFS 10/11/00 0
  20. 20. Where do I Place Sites?● Site Location Factors● Link Budget ● Method of estimating power levels anywhere within coverage● Technical ● Terrain and Clutter ● Equally spaced “cell centers”● Business ● Lease cost ● Acquisition and Construction cost JFS May, 2001 JFS 10/11/00
  21. 21. System Design Tools • Tools predict propagation of radio signal based on link budget • Creates many different output formats Ideal Cell Locations Predicted Signal Levels JFS May, 2001 JFS 10/11/00
  22. 22. System Manangement JFS May, 2001 JFS 10/11/00
  23. 23. 28 Cell Cellular System1 MSC28 BTS $33600/mon28 T1 $28000/mon 20 BTS $5,000,000196 simultaneous calls BTS const $4,000,0003920 subscribers Total Capital $9,000,000$0.31 per minute JFS May, 2001 JFS 10/11/00
  24. 24. Frequency Re-use Metropolitan area using seven channels: 28 simultaneous calls. Seven cell re-use pattern, same frequency never closer than two cell radii. 5 2 7 7 3 1 2 1 4 7 3 6 6 4 5 1 6 4 5 2 7 5 2 7 3 7 3 1Numbers represent frequency being usedHexagons represent cell coverage areasShading represents frequency grouping JFS May, 2001 JFS 10/11/00
  25. 25. High Usage CellsHigh Usage Cells (hot spot) develops based on statistics from system 1 MSC 28 BTS $33600/mon 28 T1 $28000/mon 196 simultaneous calls 3920 subscribers $0.31 per minute JFS May, 2001 JFS 10/11/00
  26. 26. Increasing Capacity Omni-directional cell● Omni-directional cell transmit equal power inall directions● Cells can be split into sectors using directionalantennas● Requires additional BTS equipment● Very similar to multiple cells in same location Sectorized cell● Careful frequency planning required● Most common is three sector, but six sectorshave been implemented in many cities● Sectorizing and adding “voice channels” veryprofitable to equipment provider JFS May, 2001 JFS 10/11/00
  27. 27. Capacity Increased1 MSC28 BTS $33600/mon34 T1 $34000/mon238 simultaneous calls 3 BTS upgrades $300,0004760 subscribers$0.28 per minute JFS May, 2001 JFS 10/11/00
  28. 28. System Monitoring28 base stations in service 24 x 7●System reports statistics every 10 minutes● ● 40 items each base station ● 6,720 per hour, 161,280 per day ● Each T1 status reported ● 168 per hour, 4,032 per dayLots of data to look at !● JFS May, 2001 JFS 10/11/00
  29. 29. Additional Hot Spot1 MSC28 BTS $33600/mon34 T1 $34000/mon238 simultaneous calls4760 subscribers$0.28 per minute JFS May, 2001 JFS 10/11/00
  30. 30. More Capacity Needed1 MSC28 BTS $33600/mon40 T1 $40000/mon280 simultaneous calls 3 BTS upgrades $300,0005600 subscribers$0.26 per minute JFS May, 2001 JFS 10/11/00
  31. 31. Additional CapacityAdded1 MSC28 BTS $33,600/mon49 T1 $49,000/mon343 simultaneous calls6860 subscribers 3 BTS upgrades $300,000$0.24 per minute JFS May, 2001 JFS 10/11/00
  32. 32. Entire System Sectorized1 MSC28 BTS $33,600/mon93T1 $93,000/mon651 simultaneous calls13020 subscribers 22 BTS upgrades $2,200,000$0.19 per minute JFS May, 2001 JFS 10/11/00
  33. 33. Analog Cellular System Voice Mail System Billing System Base Connection to Transceiver other networks System Base Transceiver Mobile PSTN System Switching Center Customer Care System Base Transceiv Subscriber er System Provisioning System JFS May, 2001 JFS 10/11/00
  34. 34. Network Sizing Voice Mail System Billing• Public Switched System Telephone Base Transceiver Connection to other networks Network is at System Center of Mobile Network Mobile• Interconnect Base Switching Transceiver PSTN Between devices System Center needs to be sized properly Customer Care System Base Transceiv Subscriber er System Provisioning System JFS May, 2001 JFS 10/11/00
  35. 35. Network SizingMost networks sized for 2% blocking●Unit of measure for telco sizing● ● Erlang ● Equivalent to one phone call for 60 minutes ● Used to size a path through the network ● One Erlang: – 1 - 1 hour call – 2 - 30 minute calls – 4 - 15 minute calls – 60 - 1 minute calls JFS May, 2001 JFS 10/11/00
  36. 36. First Generation CellularAdvanced Mobile Phone System (AMPS)● ● American Standard, 824 MHz – 894 MHz ● Initially 666, Later Expanded to 832 Channels ● Split Between Two Carriers ● A Carrier (non- wireline carrier) ● B Carrier (wireline provider) ● 42 Control Channels (21 for each carrier) ● First Commercial Cellular Phone Call Made in 1983 ● Designed as "Higher Power" (3 watt) Car Based System ● Proprietary System for Infrastructure Vendors JFS May, 2001 JFS 10/11/00
  37. 37. Other First GenerationNine Incompatible Standards used in Europe● ● Total Access Communication System (TACS) – UK ● Nordic Mobile Telephone (NMT)Japanese Total Area Cellular System JTACS●Proprietary System for Infrastructure Vendors● JFS May, 2001 JFS 10/11/00
  38. 38. Capacity Increases in 1 GNetworksIncrease Spectrum●Cell Splitting (requires● careful frequencyplanning) ● Three Sector ● Six Sector ● Add Additional CellsMove to Digital Standard●● Significant Improvement with similar Infrastructure Investment JFS May, 2001 JFS 10/11/00
  39. 39. Generic Digital System Voice Mail System IWF Base Base Transceiver Transceiver System System Internet Base Mobile Station Connection to Controller Switching other networks Center PSTN Subscriber Base Provisioning Customer Care Transceiver System System System JFS May, 2001 JFS 10/11/00
  40. 40. Second Generation SystemsGSM – Global System for Mobile● ● Channelized, 6 Time Slots / Channel ● Time Division Multiple Access (TDMA) Based ● Most Widely Deployed, Most Predicted Growth ● Common Digital Standard Across Europe, Africa, Middle East, US ● SIM cards widely used ● Defined Interfaces Between Infrastructure Elements ● Multiple Vendors Used in Same Network ● First Commercial Service in 1991 ● Frequency Planning Crucial ● Major Vendors: Ericcson, Nokia, Nortel, Motorola, Lucent JFS May, 2001 JFS 10/11/00
  41. 41. Second Generation SystemsTime Division Multiple Access (TDMA)● ● Channelized, 3 Time Slots/Channel ● Primarily Deployed in US ● AT&T Wireless (Dual Band, Dual Mode Phones, IS-154) ● SBC (Cellular One in Chicago, IS-54) ● Some Markets Will be Transitioned to TDMA from CDMA due to mergers ● Frequency Planning Crucial ● First Commercial Service in 1990 ● Typically One Infrastructure Vendor per Market ● Major Vendors: Ericsson, Lucent JFS May, 2001 JFS 10/11/00
  42. 42. Second Generation SystemsCode Division Multiple Access (CDMA)● ● Spread Spectrum Coded Transmission, Non Channelized ● One Frequency for Entire System ● Primarily Used in US, Canada, Australia, Korea and parts of China ● SprintPCS, Verizon, PrimeCo ● Typically One Infrastructure Vendor per Market (not per Carrier) ● Complex Power Control ● First Commercial Service in Late 1995 ● Major Vendors: Nortel, Lucent, Motorola, Ericsson, Nokia JFS May, 2001 JFS 10/11/00
  43. 43. Mobile Call Origination Flow Mobile Registration MobileCommunication Communication s System Device Control and System Parameters Access Request Phone Call Access Confirmation Dialed Digits Traffic Channel Information Call Setup Information Call Setup Information Call Termination Release Resources JFS May, 2001 JFS 10/11/00
  44. 44. Mobile Call Origination Mobile to Land Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Mobile User Initiates Call JFS May, 2001 JFS 10/11/00
  45. 45. Mobile Call Origination Mobile to Land Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber JFS May, 2001 JFS 10/11/00
  46. 46. Mobile Call Origination Mobile to Land Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Validate Base Transceiver Subscriber System Subscriber JFS May, 2001 JFS 10/11/00
  47. 47. Mobile Call Origination Mobile to Land Call Flow Example Base Transceiver System Valid Subscriber Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber JFS May, 2001 JFS 10/11/00
  48. 48. Mobile Call Origination Mobile to Land Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Phone Rings JFS May, 2001 JFS 10/11/00
  49. 49. Mobile Call Origination Mobile to Land Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Phone Answered JFS May, 2001 JFS 10/11/00
  50. 50. Mobile Call Origination Mobile to Land Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Call Established JFS May, 2001 JFS 10/11/00
  51. 51. Mobile Call Termination Flow Mobile Registration Mobile Communication Communication s Control and System Parameters System Device Page for Mobile Phone Call Page Response Call Setup Information Call Setup Information Call Termination Release Resources JFS May, 2001 JFS 10/11/00
  52. 52. Mobile Call Termination Land to Mobile Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Land Line User Initiates Call JFS May, 2001 JFS 10/11/00
  53. 53. Mobile Call Termination Land to Mobile Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Validate Base Subscriber Transceiver System Subscriber JFS May, 2001 JFS 10/11/00
  54. 54. Mobile Call Termination Land to Mobile Call Flow Example Base Transceiver System Valid Subscriber Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber JFS May, 2001 JFS 10/11/00
  55. 55. Mobile Call Termination Land to Mobile Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Page Mobile JFS May, 2001 JFS 10/11/00
  56. 56. Mobile Call Termination Land to Mobile Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Page Response JFS May, 2001 JFS 10/11/00
  57. 57. Mobile Call Termination Land to Mobile Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Update Subscriber Database Base Transceiver System Subscriber Page Response JFS May, 2001 JFS 10/11/00
  58. 58. Mobile Call Termination Land to Mobile Call Flow Example Base Transceiver System Base Transceiver Mobile PSTN System Switching Center Base Transceiver System Subscriber Page Response Call Established JFS May, 2001 JFS 10/11/00
  59. 59. Spectrum Comparison30 kHz AMPS no time slots 180 kHz30 kHz TDMA 3 time slots 180 kHz GSM 8 time slots (6 voice, 2 control) 200 kHz CDMA 1.23 MHz JFS May, 2001 JFS 10/11/00
  60. 60. Comparison of CurrentSystems AMPS GSM TDMA CDMAPhysical Channels per Carrier 1 8 3 VariableChannel Spacing (kHz) 30 200 30 1,230Cellular Efficiency (conversations 2.3 5.0 – 6.6 7.0 12.1 – 45.1 /cell/MHz) Capacity Compared to - 2.1 – 2.8 3 5.2 – 19.6 AMPS CapacityCompared to GSM - - 1 - 1.4 1.8 – 6.8 Capacity Compared to - - - 1.7 – 6.4 TDMAReference David J. Goodman, Wireless Personal Communications Systems, 1997 Addison Wesley Longman, Inc. JFS May, 2001 JFS 10/11/00
  61. 61. Agenda• Historical Perspective• Cellular Overview• Current Landscape• Future Landscape JFS May, 2001 JFS 10/11/00
  62. 62. Chicago Wireless Market• Seven Carriers now in service – Cingular - TDMA (AMPS & IS-54) – Verizon - CDMA(AMPS, IS-95A/B, Jstd-8) – Nextel - TDMA based – PrimeCo - CDMA(Jstd-8) – Sprint PCS - CDMA (Jstd-8) – AT&T Wireless - TDMA(IS-136) – VoiceStream -GSM JFS May, 2001 JFS 10/11/00
  63. 63. Issues Facing Today’sCarriers• Network Sizing – Coverage vs. Capacity – Quality of Service• Hot Spots – Concentrated areas of usage – Special Events, Sporting Events, Trade Shows – Emergency Requirements• E911 JFS May, 2001 JFS 10/11/00
  64. 64. Network Sizing (14.4 kbpsTerminals)14.4 kbps Base Transceiver Base System Transceiver IWF System Internet Base Mobile Station Controller Switching Center 2-3 Voice Channels One T1 per 64 PSTN per DS0 Channel Base (64/3=21DS0) Station Base Subscriber Transceiver System64 Voice Channels JFS May, 2001 JFS 10/11/00
  65. 65. Current Situation• Short Message Service (SMS) – Currently Deployed Across All Standards – 180 - 240 Characters per Message• Wireless Internet Access – Wireless Application Protocol (WAP) – In Service now – Designed for Low Bandwidth – Compatibility Problems JFS May, 2001 JFS 10/11/00
  66. 66. Agenda• Historical Perspective• Cellular Overview• Current Landscape• Future Landscape JFS May, 2001 JFS 10/11/00
  67. 67. JFS May, 2001 JFS 10/11/00
  68. 68. 3G Challenges• Network Capacity – Current Networks Sized to Provide 9.6 - 14.4 kbps – Future Networks to Provide 1+ Mbps – Capacity Planning (Where will it be needed?) – Ubiquitous Coverage (in-building, in-residence) – Cell Site Development Costs (alternatives to traditional cells?)• Is 3G Viable - Auction Costs• What is 3G? – Current Standards Define Technical Aspects – Is There a “Killer App”? – Video (one and two way)? – Instant Messaging? JFS May, 2001 JFS 10/11/00
  69. 69. Evolving Wireless StandardsNo Clear Winner - Yet! 2G 2G+ 3G (up to 14.4 kbps) (up to 384 kbps) (up to 2 mbps) GSM GPRS EDGE W-CDMA TDMA IS-136+ ? (64 kbps) IS-136HS CDMA IS-95B 1X-EV CDMA-2000 (64 kbps) JFS May, 2001 JFS 10/11/00
  70. 70. Basic Soft/Softer Handoff• Caller is driving on “blue” road• Caller is active in cell A sector 1 and cell B sector 3• Phone is constantly checking for 3 1 neighbor cells 2• Phone communicates with network B and adds sectors as they exceed B power threshold 3 1• Phone detects lower signal level in 2 cell A S1 as caller moves to edge A• Cell A S1 is dropped from call• Cell B S2 is added to call 3 1 C 2 C JFS May, 2001 JFS 10/11/00
  71. 71. Basic Soft/Softer Handoff• Caller is active in cell B sector 3 and cell B sector 2• Phone is constantly checking for neighbor cells 3 1• Phone detects cell C S1 as 2 exceeding threshold, adds to call B• Phone detects lower signal level in cell B S3 as caller moves to edge 3 1• Cell B S3 is dropped from call 2 A 3 1 C 2 C JFS May, 2001 JFS 10/11/00
  72. 72. Basic Soft/Softer Handoff• Caller is active in cell B sector 2 and cell C sector 1• Phone is constantly checking for neighbor cells 3 1• Phone detects cell C sector 2 as 2 exceeding threshold, adds to call B• Phone detects lower signal level in cell B sector 2 as caller moves to 3 1 edge, cell B sector 3 is dropped 2 from call A• Phone detects cell C sector 3 as exceeding threshold, adds to call 1 3 C 2 C JFS May, 2001 JFS 10/11/00
  73. 73. Basic Soft/Softer Handoff• Caller is active in cell C sectors 1, 2 and 3 - softer handoff• Phone is constantly checking for neighbor cells 3 1• Phone detects lower signal level in 2 cell C sector 1 as caller moves to B edge, cell C sector 1 is dropped B from call 1 3• Phone detects cell A sector 2 as 2 exceeding threshold, adds to call A• Phone detects lower signal level in cell C sector 2,cell C sector 2 is 1 3 dropped from call C 2 C JFS May, 2001 JFS 10/11/00
  74. 74. Basic Soft/Softer Handoff• Caller is active in cell C sector 3 and cell A sector 2• Phone is constantly checking for neighbor cells 3 1• Phone detects lower signal level in 2 cell C sector 3 as caller moves to B edge, cell C sector 3 is dropped B from call 1 3• Phone detects cell A sector 3 as 2 exceeding threshold, adds to call A• Phone detects cell A sector 1 as exceeding threshold, adds to call 1 3 C 2 C JFS May, 2001 JFS 10/11/00
  75. 75. Basic Soft/Softer Handoff• Caller is active in cell A sectors 1, 2 and 3 - softer handoff• Phone is constantly checking for neighbor cells 3 1• Phone detects lower signal level in 2 cell A sector 2 as caller moves to B edge, cell A sector 2 is dropped B from call 1 3 2 A 3 1 C 2 C JFS May, 2001 JFS 10/11/00
  76. 76. Basic Soft/Softer Handoff• Caller is active in cell A sectors 1 and 3 - softer handoff• Phone is constantly checking for neighbor cell 3 1 2 B B 3 1 2 A 3 1 C 2 C JFS May, 2001 JFS 10/11/00

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