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OFDM versus CDMA comparison for
OFDM versus CDMA comparison for
cellular systems
cellular systems
Anand Dabak
DMTS, Manager,
Mobile Wireless Research,
DSPS R&D Center, Texas Instruments
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Standards Comparison
200420062005TBD20052002Deployment
FDDFDD/TDDFDDFDDFDDFDDDuplexing
~ 1 million
gates
~ 1.6 million
gates
~ 1 million
gates
~1.4 million
gates
~1.2 million
gates
~1 million
gates
BB complexity
(incl. memory)
BTSBTSRNC/PDSNRNC/PDSNRNC/PDSNRNC/PDSNIP termination
+ OFDM
+ PHY HARQ
+ IP at BTS
+ OFDM
- MAC HARQ
*
+ IP at BTS
- CDMA
+ PHY HARQ
- IP at RNC
**
- CDMA
+ PHY HARQ
- IP at RNC
**
- CDMA
+ Low latency
- IP at RNC
**
- CDMA
- High latency
- IP at RNC
**
Bandwidth
efficiency features
ProprietaryYesYesYesYesYesStandards
compatibility
Single
company
SharedSharedSharedSingle
company
Single
company
Intellectual
property model
No
153 Kbps
2.4 Mbps
1.25 MHz
DO Rel 0
NoNoYesYesNoCircuit switched
voice support
900 Kbps20 Mbps2 Mbps1.8 Mbps1.8 MbpsUL peak data rate
3.1 Mbps
1.25 MHz
70 Mbps
20 MHz
14.4 Mbps
5 MHz
3.09 Mbps
1.25 MHz
3.07 Mbps
1.25 MHz
DL peak data rate
Bandwidth
F-OFDMWiMax
(802.16(e))
HSDPAEV-DV Rel DDO Rel A
* : 802.16 (d) has MAC level HARQ ** : Most networks are evolving to all IP
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Advantages of OFDM
Advantages of OFDM
• No need for time-domain equalizer:
– CDMA needs chip equalizer even for channels with 1-2 µs delay
spread
• Naturally more robust in frequency selective channels:
– Orthogonality (DFT)
– Cyclic prefix (GI)
• Natural roadmap to achieve higher data rate in the next
releases
– MIMO more natural for OFDM: each tone is flat fading
• Convergence with other wireless technologies. Examples:
– WLAN
– WiMAX
– 4G (VSF-OFCDM)
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