This document discusses various wireless communication techniques used in 4G technologies. It begins by explaining multicarrier modulation (MCM) which uses multiple subchannels to transmit information using fast Fourier transform. It then describes MC-CDMA which combines OFDM and CDMA to allow multiple users to simultaneously access the system. The document also discusses OFDM with TDMA and how it can use higher order modulations. Finally, it introduces smart antenna techniques like MIMO systems which use multiple antennas at the transmitter and receiver to increase wireless channel capacity and examines the cases of SISO, SIMO, MISO, and MIMO configurations.

1. DEPARTMENT OF ECE
EC8004 – WIRELESS NETWORKS
SUBJECT INCHARGE
HEMALATHAR – AssistantProfessor
4G TECHNOLOGIES

2. MULTICARRIER MODULATION
(MCM)

3. MULTICARRIER MODULATION (MCM)
 Multicarrier modulation (MCM) is a derivative of frequency-division
multiplexing
 DSL Modems and Digital Audio/Video Broadcast (DAB/DVB)
 MCM is a baseband process that uses parallel equal bandwidth subchannels to
transmit information and is normally implemented with fast Fourier
transform (FFT) techniques.
 MCM’s advantages are better performance in the inter-symbol-interference
environment, and avoidance of single-frequency interferers

4. MC-CDMA
 MC-CDMA is actually OFDM with a CDMA overlay.
 Similar to single-carrier CDMA systems, the users are
multiplexed with orthogonal codes to distinguish users in
MC-CDMA.
 However, in MC-CDMA, each user can be allocated several
codes, where the data is spread in time or frequency.
 Either way, multiple users simultaneously access the system.

5. OFDM with TDMA
 MC-CDMA uses quadrature phase shift keying
(QPSK) for modulation, while OFDM with TDMA
could use more high-level modulations, such as
multilevel quadrature amplitude modulation
(M-QAM) (where M 4 to 256)
 The task of pulse forming and modulation is
performed by a simple inverse fast Fourier
transform (IFFT) which can be implemented
very efficiently.
 To decode the transmission, a receiver needs
only to implement FFT

6. SMART ANTENNA TECHNIQUES

7. SMART ANTENNA TECHNIQUES
 Smart antenna techniques, such as multiple-input multiple-output
(MIMO) systems, can extend the capabilities of the 3G and 4G systems
to provide customers with increased data throughput for mobile high-
speed data applications.
 MIMO systems use multiple antennas at both the transmitter and
receiver to increase the capacity of the wireless channel

8.  The number of transmitting antennas is M, and the number of receiving
antennas is N, where N ≥ M.
 We examine four cases:
1. Single-Input, Single-Output (SISO)
2. Single-Input, Multiple-Output (SIMO)
3. Multiple-Input, Single-Output (MISO)
4. Multiple-Input, Multiple-Output (MIMO)

9. Single-Input, Single-Output (SISO)
Single-Input, Multiple-Output (SIMO)
Multiple-Input, Single-Output (MISO)
Multiple-Input, Multiple-Output (MIMO)