Review of Key Points from Yesterday

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Review of Key Points from Yesterday
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Wireless Overview

• Cellular market converging with WiMAX on
• OFDM/MIMO
• IP network
• Hybrid ARQ
• WiMAX may be 3G AND 4G
• More intelligence and flexibility
• New technologies being grafted onto old standards
• MIMO for WCDMA
• Adaptive modulation
• Proliferation of standards
• Movement to OFDM/MIMO
• Indicate movement to SDR?

Source http//www.wimaxforum.org/technology/downl
oads/ WiMAX_and_ IMT_2000.pdf
http//www.wisoa.net/members_logos/mobile_internet
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TD-SCDMA

• Similar to WCDMA
• Synchronous Time-slotted CDMA (OVSF)
• Asymmetric UL/DL TDD
• Significant opportunities to exploit multi-user
  diversity
• Short term evolution will adopt 3GPP advances
• Evolving to exploit OFDM and MIMO long term
• Significantly delayed roll-out
• Nationwide may miss the Olympics, though fall
  back to just test systems is viable

B. Li, D. Xie, S.Cheng, J. Chen, P. Zhang, W.Zhu,
B. Li Recent advances on TD-SCDMA in China,
IEEE Comm. Mag, vol 43, pp 30-37, Jan 2005
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OFDM / MIMO

• Cyclic prefix FFT allow OFDM systems to
  overcome delay spread limitations
• Amenable to adaptive modulation
• Lower complexity than equivalent single carrier
  system
• Flat fading per subcarrier simplifies MIMO
  implementation
• For high SNR, spatial multiplexing can provide
  significant gains in capacity, growing linearly
  with rank of H, (approximately minNt, Nr)
• For low SNR, diversity (e.g., STBC) can
  significantly improve reliability
• When H is not full rank, beamforming can still
  provide significant benefits
• Closed loop adaptations perform significantly
  better than open-loop

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WiFi
Millions of WiFi Chipset Shipped

• Hugely popular standard
• Applications growing
• Variety of different PHY and MAC protocols
• Expanding into different bands, providing new
  services
• 802.11n (OFDM/MIMO) significantly increases
  throughput without exponentially increasing
  complexity
• 802.11n seeing more use for range extension

Wi-Fi Alliance, Introducing Wi-Fi Protected
Setup, January 3, 2007