1. CDMA2000

2. CDMA2000
400 MHz, 800 MHz, 900 MHz, 1700 MHz, 1800 MHz, 1900 MHz, and 2100 MHz
• Compatible with the cdmaOne standard
A set of 3G communication CDMA2000 standards
CDMA2000 1x (2.5G)
CDMA2000 1xEV-DV (evolution for high speed integrated data and voice) (3G) kbps
CDMA2000 1xEV-DO (evolution for data optimized (3G) 2.05 Mbps
CDMA2000 3x (3G) Three Mbps channels

3. CDMA 2000 Access is random, uses the slotted Aloha protocol
Chipping rate Mchip/s
Short PN code, Long PN code and Walsh code
Multirate transmission
Low data rate signals used for voice and messages
High data rate signals for pictures, videos, and large packets

4. 4G Technologies
100 Mbps for high mobility communication (such as from trains and cars)
1 Gbps for low mobility communication (such as pedestrians and stationary users)
Facilities such as ultra –broadband Internet access, IP Telephony, gaming services, and streamed multimedia may be provided to users.

5. 4G Technologies Pre-4G Technologies such as mobile Wi-Max – 2006.
4G Technologies such as Long Term Evolution (LTE) – 2009.
CDMA radio technology used in 3G is replaced by OFDM

6. OFDM Orthogonal Frequency Division Multiple Access
File transfer at 10 Mbps
• High resolution 1024 × 1920 pixel hi-vision picture transfer at 24 Mb/s
• High resolution video transfer
Mobile multimedia services
Special type of Multi-carrier Modulation

7. Multi-carrier Modulation
It splits the high bit rate stream into many lower bit rate streams, each stream being sent using an independent carrier frequency.
N symbols/S have to transmitted, each subcarrier transmits n/c symbols/S
where c – number of subcarriers
OFDM – orthogonal carriers are used.

8. OFDM
Multiple carriers use mutually orthogonal codes, which enables separation of carriers in case of multi-path transmissions and interference of signals.
• All channel carriers (adjacent channel codes) are using different but mutually orthogonal codes
Each channel carrier has distinct amplitude (power level) and may have a time guard.

9. Three most important characteristics of OFDM
High spectral efficiency
• Strong resiliency to RF inter symbol interferences
• Lower multi-path distortions

10. OFDM
Also called COFDM (code orthogonal frequency division multiplexing)
• Also called spread-spectrum based multicarrier or discrete multi-tone modulation
0s are transmitted as + 1s and 1s are transmitted as –1s for signal mapping as per 3GPP specifications
The codes themselves may be from a different set of orthogonal codes
• The only condition put on them is that they should all be orthogonal with no cross correlation

11. OFDM
Digital Signal Processors are used to perform modulation and demodulation in OFDM systems.

12. Applications
OFDM technology is used in wireless LANs for point-to-point transmission and for multicasting.
OFDM is also used in Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB) which enables users to watch TV on their mobile devices.
OFDM is also used in asymmetric digital subscriber line (ADSL) which is used for broadband Internet over telephone lines.

13. Techniques in OFDM Wideband OFDM (WOFDM)
Flash-OFDM (fast low-latency access with seamless handoff OFDM)
MIMO-OFDM (Multiple Input, Multiple output OFDM)
VOFDM (Vector OFDM)

14. WOFDM
A technique in which spacing between multi-carrier channels is made large
• Therefore, any frequency errors between the transmitter and the receiver do not affect system performance

15. Flash-OFDM
Based on the FHSS spectrum
• Fast-hopped OFDM

16. MIMO-OFDM
A technique in which multiple antennae are used for inputs and outputs
• Provides broadband wireless access (BWA) and performs well in multiple nonline- of-sight multiple-path environments

17. VOFDM
Technique based on MIMO-OFDM
• Developed by Cisco Systems, Inc