CDMA vs' OFDM in 4G

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CDMA vs. OFDM in 4G

• Manh-Tuan NGUYEN

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CDMA

• Code Division Multiplex Access
• Multiplexing Platform for 3G
• Use in GPS, OmniTRACS

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CDMA

• Frequency reuse

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Introduction of CDMA

• Spread Spectrum characteristic

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CDMA standards

• First IS-95 or cdmaOne by Qualcomm
• IS-2000(CDMA2000) US, CA, AU
• WCDMA supports high speed

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CDMA advantages

• Capacity is CDMA's biggest asset
• CDMA consumes less power and covers large areas
  so cell size in CDMA is larger.
• CDMA uses Soft Handoff, reduces dropped calls,
  increases capacity.
• No frequency planning needed

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CDMA disadvantages

• Patented technology by Qualcomm
• Quality degrades as the number of users in a
  given cell increases
• CDMA towers interfere with themselves

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OFDM

• Orthogonal Frequency-Division Multiplexing
• Divide large amount of data into smaller chunks
• Use in WiFi, WiMax, ASDL

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OFDM Advantages

• Robust to narrow-band co-channel interference
• High spectral efficiency
• Robust to inter-symbol interference and fading
  caused by multipath propagation

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OFDM disadvantages

• Sensitive to Doppler shift
• Sensitive to frequency synchronization problems
• Inefficient transmitter power consumption

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OFDM vs. CDMA in 4G of telephone mobile

• Demands of 4G telephone mobile
• High quality of service for next generation
  multimedia support (real time audio, high speed
  data, HDTV video content, mobile TV, etc)
• Interoperable with the existing wireless
  standards
• Spectrally efficient system (8 bits/s/Hz)
• In summary, the 4G system should dynamically
  share and utilize the network resource to meet
  the minimal requirements of all the 4G enabled
  users

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OFDM vs. CDMA in 4G of telephone mobile

• OFDM is considered robust against multipath
  fading and intersymbol interference because the
  symbol duration increases for the lower-rate
  parallel subcarriers
• OFDM does not require contiguous bandwidth for
  operation.
• Race for the next generation 4G wireless networks
  is on