Ee463   cellular comm & cdma - comm 2 presentation - loren schwappach
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  • 1. Introduction to Cellular Communications & CDMA Prepared for Dr. John Santiago CTU EE463 Communications II Loren Karl Schwappach 15 December 2010CTU : EE463 Communications II : Introduction to Cellular Communications & CDMA : Loren K. Schwappach 1
  • 2. Objectives:  Cellular Communications  Brief History of Mobile Phones  The Cellular Concept  Frequency Reuse  Handoffs  G1-G3 Explained  Frequency Division Multiple Access (FDMA)  Time Division Multiple Access (TDMA)  Frequency and Time Division Multiple Access (F/TDMA)  Code Division Multiple Access (CDMA)  G4 and Beyond  Final Conclusions  References  QuestionsNOTE: If you would like to explore any information on this presentation outside of class Ihave used reference blocks “[ ]” throughout this presentation to indicate a recommendedsource (see references slide). CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 2
  • 3. Cellular Communications  Cellular technology:  Fastest growing technology on the planet and utilized by billions of people around the world.  No longer limited to voice: • Cell phones are now capable of providing: Calculators, alarm clocks, contact databases, appointment reminders, day-to-day organizers, Short Message Service (SMS) a.k.a. texting services (used by 74% of all subscribers), games, e-mail, internet browsers, radio, MP3 players, streaming video players, Bluetooth, digital cameras, GPS receivers, and more.  First handheld mobile phone (invented by Martin Cooper) was demonstrated in 1973 by Motorola. [1] • Motorola released the first commercially available mobile phone (DynaTAC 8000x in 1983), by 1990, 12.4 million people worldwide had cellular subscriptions. [3]  There were approximately 4.6 billion worldwide cellular phone subscriptions by the end of 2009. [4] CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 3
  • 4. History  1837 – Samuel Morse patents the electromagnetic telegraph. [5]  1843 - Michal Faraday performs studies to see if space could conduct electricity. [6]  1860s – James Clerk Maxwell predicts the existence of radio waves (Publishes Treatise on Electricity and Magnetism {Maxwell’s Equations} in 1873).  1865 – Dr. Mahlon Loomis becomes the first person to communicate through the atmosphere wirelessly (14-18 miles) using a wireless telegraph (awarded 50,000 for his research). [7]  1876 – Alexander Bell invents the telephone. [5]  1887 – Heinrich Hertz generates radio waves and demonstrates they share the same properties as light. [5]  1896 – Guglielmo Marconi files patents on wireless transmission by radio.  Although the actual inverter of the radio is highly debatable and most historians credit the invention to either Guglielmo Marconi, Nikola Tesla, Alexander Popov, Sir Oliver Lodge, Reginald Fessanden, Heinrich Hertz, Amos Dolbear, Mahlon Loomis, Nathan Stubblefield, and/or James Clerk Maxwell. [8] CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 4
  • 5. History Continued..  1902 – Reginald Fessenden invents AM radio broadcasting. [5]  1919 – Edwin Armstrong invents the super heterodyne radio receiver. [5]  1933 – Edwin Armstrong invents FM for radio transmission. [5]  1938 – H.A. Reeves invents pulse code modulation (PCM). [5]  1940s – Radiotelephones were introduced in the United States. [8]  1973 – Martin Cooper invents the first Mobile phone (previous slide). [5]  1970s – Advanced mobile phone system (AMPS) is launched as a 1G FDMA mobile phone system.  1980s – 2G digital systems are developed. Global System for mobile Communication (GSM) was the first commercially operated 2G system based on TDMA.  2001 – The first 3G network (actually 2.5G network) using TDMA was developed in Japan.  2000s – True 3G networks appear based on advanced CDMA technology.  Today – pre-4G networks are in the market and true 4G networks in development .  Tomorrow – Nearly instant Terabit per second wireless audio/video data transfers changing the world as we know it today. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 5
  • 6. The Cellular Concept  In an analog cell-phone system in the US, the cell- phone carrier receives about 832 frequencies to use across the city. [9]  The carrier chops up the city into a grid of large (10 square mile, 26 square kilometer) hexagonal cells. [9]  Each cell has a base station consisting of a small building and a tower. [9] CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 6
  • 7. Frequency Reuse  A single Analog cell-phone system  Uses one-seventh of the available duplex (2-way) voice channels for a unique set of frequencies without collisions. [9]  As mentioned a cell-phone carrier typically gets 832 radio frequencies. [9] • Since each cell phone uses two frequencies per call there are typically 395 voice channels per carrier (42 are used as control channels). • Therefore each cell has about 56 channels in an analog system. • Common 2G TDMA based systems can carry approximately three times as many channels per cell. Newer 3G CDMA based systems carry even more.  Cell phones have low-power transmitters in them and typically have two signal strengths (0.6W and 3W). [9]  The Base Station performs power balancing and also transmits at low power allowing frequency reuse. [9] • This cellular approach requires a large number of bases (hundreds in most cities).  Each Base Station also has communication with the Mobile Telephone Switching Office (MTSO). [9] CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 7
  • 8. Handoffs  All Cell phones have special codes associated to them. These codes are used to identify the phone, the phones owner and the service provider. [10]  System Identification Code (SID) – A unique 5-digit number assigned to each carrier by the FCC (Programmed into the phone). [10]  Mobile Identification Number (MIN) – A 10-digit number derived from you phone’s number. [10]  Electronic Serial Number (ESN) – A unique 32-bit number programmed into the phone when it is manufactured. [10] CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 8
  • 9. Handoffs  When you power up the phone it begins listening for a SID using a control channel (freq used by phone and base station to communicate). [10]  If no control channels are available you receive a “no service” indication.  When the phone receives a SID, the phone compares it to the SID programmed into the phone. [10]  If correct it begins communication with the base station.  If not correct then the phone knows it is roaming (using another carrier) and you may be subject to large roaming fees.  Along with the SID the phone transmits a registration request (consisting of the SID, MIN, and ESN) to the connected base station. [10]  This lets the MTSO keep track of your phone in it’s database. This allows the MTSO to know which cell you are in. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 9
  • 10. Handoffs Continued..  Now the MTSO picks a frequency pair for your phone to use and communicates it to your phone from the base station over the control channel. [10]  Now that your phone and base station are using the frequency pair your call is connected and the base station keeps track of the signal strengths of your frequency pair. [10]  As you move toward the edge of your cell, you cell’s base station reports to the MTSO that your signal strength is diminishing. Meanwhile the base station you are approaching detects your signal strength increase and both stations report to the MTSO to coordinate a new frequency pair for your phone and the approaching base station. [10] CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 10
  • 11. Handoffs Continued..  After some time your phone gets a signal on a control channel informing your phone to change frequencies. [10]  This process is called Handoff and attempts to keep you connection intact while traversing through cells. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 11
  • 12. G1 – G3 Explained  1G – 1st Generation Wireless Telephone Technology  Unencrypted analog system for mobile communications.  1970s technology using Frequency Division Multiple Access (FDMA) technology.  2G – 2nd Generation Wireless Telephone Technology  Digitally encrypted phone conversations.  Initially launched in 1991 on the GSM standard using TDMA technology.  GSM (TDMA based) accounts for approximately 80% of worldwide subscribers.  IS-95 (CDMA based) a newer standard than GSM accounts for the majority of US subscribers and approximately 17% of worldwide subscribers.  2.5G standards using GPRS (uses a modified form of TDMA) for up to 115 Kbps.  2.75G standards using EDGE supports data rates up to 236.8Kbps using 8PSK encoding.  3G – 3rd Generation Wireless Telephone Technology [11]  Digital Standards launched initially by Japan in 2001.  Provides mobile broadband access of several Mbps.  CDMA2000 (CDMA based) supports up to 14.7Mbps.  Uses 1.8 – 2.5GHz Frequency Band.  4G – 4th Generation Wireless Telephone Technology  I’ll talk about this later. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 12
  • 13. Frequency Division Multiple Access (FDMA)  Used by Analog mobile phones.  Band of Frequencies is broken up into smaller bands.  Each transmitter transmits using radio waves in its own sub-band.  AMPS the first 1G implementation used 30KHz for each user.  Pros:  Simple Design  No Inter-symbol Interference (ISI)  No interference among users in a cell.  Cons:  Narrowband interference  Static spectrum allocation (less secure)  Freq. reuse problems  Requires High Q analog filters or large guard bands. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 13
  • 14. Frequency Division Multiple Access(FDMA) CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 14
  • 15. Time Division Multiple Access (TDMA)  In pure TDMA, the base station does not split up its allocated frequency band into smaller sub-bands.  Communicates with users one at a time through time partitioning.  Pros:  Suited for digital.  Higher capacity than FDMA.  High Q filters are not required.  Cons:  Very susceptible to jamming, and other-cell interference.  Requires equalizers. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 15
  • 16. Time Division Multiple Access (TDMA) CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 16
  • 17. Frequency and Time Division Multiple Access(F/TDMA)  F/TDMA is the real TDMA implemented by most providers (2G technology).  IS-54 (2G) used 30 KHz channels with three users sharing them (3 slots).  GSM (2G) uses 270KHz channels with eight users sharing them (8 slots).  Pros:  Better suited for digital.  Higher capacity than FDMA and TDMA alone.  High Q filters are not required.  Cons:  Strict synchronization and guard time needed.  Still susceptible to jamming, and other-cell interference.  Requires equalizers. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 17
  • 18. Frequency and Time Division MultipleAccess (F/TDMA) CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 18
  • 19. Code Division Multiple Access (CDMA)  All users communicate with the receiver at the same time and using the same set of frequencies.  This means all users interfere with each other.  How would you separate the users from interfering with each other?...  CDMA controls this interference by assigning each user a unique code. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 19
  • 20. Code Division Multiple Access CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 20
  • 21. Code Division Multiple AccessWhy use CDMA?  Higher capacity than TDMA and FDMA.  CDMA systems can reuse frequencies in every cell.  No guard bands or guard times are typically required.  No equalizer is typically required.  Improved performance due to diversity. [12]  Lower mobile transmit power . [12]  Longer battery life.  Variable transmission rate with voice activity detection. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 21
  • 22. Code Division Multiple AccessWhy use CDMA?  Allows soft handoff. [15 ]  Combats user interference. [12] & [13]  If a user doesn’t have anything to send, it causes less interference to other users of the system.  Is a form of Spread-Spectrum technology making it usable for military use.  Cells can use directional antennas to “sectorize” the cell. [14]  120 degree antennas can create 3-sector cells which is very common (triples capacity).  All 3G Systems use CDMA! CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 22
  • 23. Code Division Multiple AccessWhy use CDMA?  Cons:  Requires tight synchronization to use orthogonal codes.  Quasi-orthogonal codes cause self-interference.  Near-far problem is a serious hindrance, requiring fast and accurate power control measures.  Near-far Problem:  Users near the base receive high power  Users far from the base receive low power CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 23
  • 24. Code Division Multiple Access CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 24
  • 25. Code Division Multiple Access Low-Bandwidth Signal: High-Bandwidth Spreading Code: Mix is a simple multiply … and transmit. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 25
  • 26. Code Division Multiple Access To Decode / Receive, take the signal: Multiply by the same Spreading Code: … to get ... CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 26
  • 27. Code Division Multiple Access CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 27
  • 28. Code Division Multiple Access Don’t ask me to explain this: However, this ones for Dr. Santiago.. It uses the Welsh coding scheme. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 28
  • 29. Code Division Multiple Access  Direct Sequence CDMA (DS-CDMA) [16]  Classical DS-CDMA uses binary pseudo-noise (PN) codes. • Synchronization problem solved using an acquisition search by searching all phase delays (accomplished with a delay lock loop (DLL)), and a  Chaotic signals can offer very attractive properties such as the security of transmission and low probability of interception .  Chaos-based DS-CDMA with additive pilot signals (ACAS-A)  1 2 x 2  Uses chaotic generator function, for example: k 1 k x  Uses Gold sequence codes. Sounds cool right? See referenced IEEE paper for more. [16] CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 29
  • 30. G4 and Beyond  4G – 4th Generation Wireless Telephone Technology  Must meet speed requirements of 100s of Mbps.  Pre-4G technologies include: mobile WiMAX, and LTE  4G standards in development: IEEE 802.16m (1 Gbps), Flash- OFDM (uses OFDM system, remember a presentation on OFDM this November?)  iBurst and MBWA (uses High Capacity Spatial Division Multiple Access (HC-SDMA) a technology beyond my current level of understanding)  5G – 5th Generation Wireless Telephone Technology  Standard beyond the 4G standard expected to be finalized by 2013.  Implementation expected around 2020  Who knows what kind of throughputs and technologies the new standard will introduce.. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 30
  • 31. Final Conclusions  TODAY WE LEARNED LOTS ABOUT:  The History of Mobile Phones  The Cellular Concept  Frequency Reuse  Handoffs  G1-G3 Technologies  Frequency Division Multiple Access (FDMA)  Time Division Multiple Access (TDMA)  Frequency and Time Division Access (F/TDMA)  Code Division Multiple Access (CDMA)  Chaos Based DS-CDMA  G4 and Beyond CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 31
  • 32. References  [1] Teixeira, Tania. “Meet Marty Cooper – the inventor of the mobile phone." BBC News. 23 April 2010. Retrieved 15 December 2010. Website: http://news.bbc.co.uk/2/hi/programmes/click_online/8639590.stm  [2] Teixeira, Tania. Photograph of Martin Cooper, Inventor of the mobile phone. BBC News. 23 April 2010. Retrieved 15 December 2010. Website: http://news.bbc.co.uk/2/hi/programmes/click_online/8639590.stm  [3] “Cellular Subscribers 1990“. Worldmapper the world as you’ve never seen it before. WorldMapper. 23 April 2010. Retrieved 15 December 2010. http://www.worldmapper.org/display.php?selected=333  [4] “Number of Cell Phones Worldwide Hits 4.6B”. CBS News. GENEVA. 15 February 2010. Retrieved 15 December 2010. Website: http://www.cbsnews.com/stories/2010/02/15/business/main6209772.shtml  [5] Ulaby, F., “Fundamentals of Electromagnetics Fifth Edition”. Pearson Prentice Hall, Upper Saddle River, NJ, 2007.  [6] “The History of Cell Phones”. ORACLE ThinkQuest Projects by Students for Students. Retrieved 15 December 2010. Website: http://library.thinkquest.org/04oct/00047/historycell.htm  [7] “Mahlon Loomis”. CBS News. GENEVA. 15 February 2010. Retrieved 15 December 2010. Website: http://www.smecc.org/mhlon_loomis.htm  [8] Burande, Abhay. “History of the Radio – Who Invented the Radio”. Buzzle.com Retrieved 15 December 2010. Website: http://www.buzzle.com/articles/history-of-radio-who-invented-the- radio.html CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 32
  • 33. References:  [9] “HowStuffWorks Cell Phone Frequencies”. HowStuffWorks.com Retrieved 15 December 2010. Website: http://electronics.howstuffworks.com/cell-phone1.htm  [10] “HowStuffWorks Cell Phone Codes”. HowStuffWorks.com Retrieved 15 December 2010. Website: http://electronics.howstuffworks.com/cell-phone3.htm  [11] Degada A., Channel Estimation and Rake Reception for 3G Air Interface Wideband Coded Division Multiple Access. IEEE (2009). Accessed 15 Dec 2010.  [12] Brown T., Ghazi-Moghadam V., Kaveh M., Detection of Code Division Multiple Access Signals in a Multiuser Environment Using Antenna Arrays. IEEE (1995). Accessed 15 Dec 2010.  [13] Jeng W., Su T., Hsieh W., Using Code Division Technique to Improve the Performance of Ad Hoc Wireless Network. IEEE (2005). Accessed 15 Dec 2010.  [14] Haghighi S., Varadharajan K., Varadharajan V., Mohammadi-Nodooshan V., Overhearing Gain Analysis in Low-Traffic CDMA Wireless Sensor Networks. IEEE (2010). Accessed 15 Dec 2010.  [15] He Z., Ye F., Wang C., Junyao M., Li W., Tao Z. Huang D. A Quick Distributed Soft Handoff Method in CDMA System Based on Mobile Agent. IEEE (2010). Accessed 15 Dec 2010.  [16] Kaddoum G., Roviras D., Charge P., Fournier-Prunaret D., Signal Processing 89. ScienceDirect Journal (2008). Accessed 15 Dec 2010. CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 33
  • 34. Questions CTU : EE463 Communications 2 : Cellular Communications & Introduction to CDMA : Loren K. Schwappach 34