Welcome to SSY145 Wireless Networks Lecture 2 By Hani Mehrpouyan, Department of Signals and Systems, Chalmers University of Technology, hani.mehr@ieee.org Office #6317 1 Copy right 2011
Outline History Radio technology today 1G, 2G, and 3G GSM CDMA OFDMA MIMO 2 Copy right 2011
History 1864: James Clark Maxwell predicts the existence of radio waves. 1886: Heinrich Rudolph Hertz demonstrates the existence of radio waves. 1896: Guglielmo Marconi invented the wireless telegraph. Also in 1890s: Nikola Tesla, Alexander Stepanovich Popov, and others demonstrate forms of wireless communications. Marconi gets the credit for attempting wireless communications. 3 Copy right 2011
Cellular Mobile Technology Breakthrough was cellular communications. Frequencies were reused over the cells. Sophisticated hand-offs that would not drop the call. At Bell Labs 1957-1960. The reuse factor was very low. Sectors were created, where 3 cells per tower were created. 4 Copy right 2011
2G Cellular Mobile Technology Leverage digital technology. Speech compression and signal processing Increased the capacity of the overall system. Wide diversity of digital systems: TDMA in the US. PDC in Japan DECT (digitally enhanced cordless communications) and PHS (Personal Handyphone system) in Europe IS-98 CDMA Qualcomm 1989 and first deployed 1994 also USA. GSM (Global system for Mobile) 5 Copy right 2011
CDMA Code division multiple access: All users share the same frequency band. Most success in Korea and USA. Adopted by Verizon and Sprint. Easy migration to 3G since they both use the same modulation. 6 Copy right 2011
GSM Global system for mobile Original called Groupe Special Mobile. Joint European effort which started in 1982. Launched in 1992. Time division multiple access. 900 MHZ band. GSM is the dominant world standard today Well defined interfaces. Many competitors resulting in good prices. 7 Copy right 2011
1G, 2G, 3G Multi-Access Technologies 3.5G and 4G optimize a combination of frequency, time, and code multiplexing. 8 Copy right 2011
1G- Seperate Frequencies 9 Copy right 2011
2G-Time division multiple access (TDMA) 10 Copy right 2011
2G & 3G- Code Division Multple Access Spread spectrum modulation Original developed for the military. Resists jamming and many kinds of interference. Coded modulation is hidden from those without the code All users share the same block of large spectrum. One for one frequency reuse All 3G radio standards based on CDMA CDMA 2000, W-CDMA, and TD-SCDMA 11 Copy right 2011
IMT 2000 Vision Including LAN, WAN, and Satelite Services 12 Copy right 2011
The 3G Vision Universal global Roaming (1 standard and not 7): 3 GSM leads with CDMA 2000 and China TD- SCDMA. Multimedia (voice, data, video). Increase data rates. Increase capacity (more spectral efficiency). Data-centric architecture (ATM at first, and then IP). 13 Copy right 2011
3G Radio Technology Deployed Today EDGE: GSM evolution, i.e., TDMA. CDMA 2000: Multi-Carrier CDMA, Evolution of CDMA. UMTS (Universal mobile telephone service)/3gsm (W-CDMA, HSPA): Direct spread spectrum CDMA. All the above are full-duplex (good for telephony) TD-SCDMA: Time Division Synchronous CDMA (not yet deployed). 14 Copy right 2011
UMTS (3GSM): Market Leader GSM evolution path: 1. W-CDMA, 2. HSPDA, 3. HSPA Leverage GSM s dominant position Legally mandated in Europe and elsewhere Requires substantial BW each way. Slow start but now leading Since it was building on GSM s 80% market share. 15 Copy right 2011
CDMA 2000 Evolution of original Qualcomm CDMA (IS-95). Better migration from 2G to 3G. CDMA operators do not need additional spectrum. Higher data rates than UMTS, at least at first. Could not compete with GSM s critical mass. 16 Copy right 2011
Diverse Mobile Wireless Spectrum 17 Copy right 2011
18 Copy right 2011
LTE Sophisticated multiple access schemes DL: OFDMA with cyclic prefix (CP) UL: single carrier FDMA with CP. Adaptive modulation and coding. QPSK, 16QAM, and 64 QAM. Advanced MIMO spatial multiplexing. Techniques. (2 or 4) (2 or 4) downlink and uplink. 19 Copy right 2011
OFDM and OFDMA OFDM: Orthogonal frequency division multiplexing: Multiple subcarriers that are assigned to a user CP is used to eliminate ISI Vary bits per subcarrier based on instantaneous SNR. 802.11 or WIFI OFDMA: Orthogonal frequency division multiple access The subcarriers are assigned to multiple users. Optimization of frequency, time, and code. 20 Copy right 2011
OFDMA Dynamically allocate user data to sub-carriers based on instantaneous data rates and varying subcarrier capacities. Highly efficient use of spectrum. 21 Copy right 2011
4G Technology-MIMO Multiple input multiple output smart antenna technologies Multiple path improve reliability and increase spectral efficiency. 22 Copy right 2011
bps per hertz per acre per watt 23 Copy right 2011
References http://www.nmscommunications.com/devplatforms/ OpenAccess/Technologies/3G324MandIPVideo/Br oughwirelesstutorial.htm http://williamstallings.com/wireless1e.html Erik Dahlman et al., 3G Evolution: HSPA and LTE for Mobile Broadband, Second edition, Academic Press, 2008, ISBN: 9780123745385. 24 Copy right 2011
Questions What are the advantages and disadvantages of OFDMA? What is spread spectrum and what standard emerged from it? Name the 3 forms of diversity? MIMO systems result in what form of diversity? What is adaptive modulation and what are its advantages? 25 Copy right 2011