4 g cellular systems l.
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4-G Cellular Systems. What is 4-G?. High data speed: 100 Mbps to 1Gbps anywhere, anytime Enable voice, data and streamed multimedia (enough speed for streaming HDTV, digital video broadcasting, video chat, …) with low latency

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what is 4 g
What is 4-G?
  • High data speed: 100 Mbps to 1Gbps anywhere, anytime
  • Enable voice, data and streamed multimedia (enough speed for streaming HDTV, digital video broadcasting, video chat, …) with low latency
  • Based on TCP/IP (Internet protocol) only (3-G systems use both circuit switched and packet switched networks)
technologies used in 4 g
Technologies used in 4-G
  • It uses OFDMA and other new technologies (Single Carrier FDMA, Interleaved FDMA, Multi-carrier CDMA, …) instead of CDMA, which is used by all 3-G systems. The problem with CDMA is it cannot adjust spectrum allocated to users (all users get the same amount of spectrum). Also, the highest data rate is limited.
  • MIMO (Multiple-Input Multiple-Output) antennas
  • New modulation techniques (64QAM: Quadrature amplitude modulation)
slide4
MIMO
  • Multiple antennas used by the transmitter and the receiver
  • Parallel streams are transmitted simultaneously by those antennas
  • Data rate is increased (if 4 pairs of antennas are used, the data rate can be increased by 4 times)
  • Can also increase reliability
64qam
64QAM
  • The amplitude of two waves, 90 degrees out-of-phase (in quadrature) are changed (modulated) to represent the data signal.
  • Phase modulation is a special case of QAM.
4 g systems
4-G Systems
  • WiMax
  • UMB (Ultra Mobile Broadband)
  • LTE (Long Term Evolution)
slide7
UMB
  • To bring CDMA2000 (US standard) to 4-G
  • Based on Internet (TCP/IP) networking
  • Peak rates of up to 280 Mbps
  • Support handoffs with CDMA2000 and 1xEV-DO
  • Use OFDMA
  • In Novemver 2008, Qualcomm, UMB’s lead sponsor, announced it was ending development of the technolgy, favoring LTE instead.
lte long term evolution
LTE (Long Term Evolution)
  • To bring UMTS (Europe 3G) to 4-G
  • Uses OFDMA for downlink with a maximum of 2048 subchannels
  • Download rate: 326 Mbps for 4x4 antennas for every 20 MHz of bandwidth
  • Uses Single Carrier Frequency Division Multiple Access (SC-FDMA) for uplink. A problem with OFDMA is the high peak-to-average power ratio. SC-FDMA can provide higher power efficiency which is crucial for mobile stations.
  • Uses 64QAM modulation
  • Uses MIMO and beam forming with up to 4 antennas
  • All IP Network
lte cont
LTE (cont.)
  • Downlink peak data rates 300Mbps per 20MHz of spectrum and uplink data rates, 75 Mbps per 20 MHz
  • Supports at least 200 active users per cell in 5MHz
comparison of lte and wimax
Comparison of LTE and WiMax
  • Similar technologies
  • WiMax is already in the market in Pakistan and Sprint Nextel and Clearwire has deployed it in the US (first in Baltimore this year). LTE is still under standardization.
  • LTE is the upgrade for GSM network that accounts for over 85% of all mobile subscribers in the world. The existing GSM/GPRS/EDGE operators can use their current infrastructure (base station towers) with new equipment to upgrade to LTE. A WiMax operator has to start from scratch.
  • AT&T and Verizon will roll out LTE in 2011/2012. Qualcomm supports LTE.