Approaches – 4G

Principal technologies

• Physical layer transmission techniques are as follows:
• MIMO: To attain ultra high spectral efficiency by means of spatial processing including multi-antenna and multi-user MIMO
• Frequency-domain-equalization, for example Multi-carrier modulation (OFDM) in the downlink or single-carrier frequency-domain-equalization (SC-FDE) in the uplink: To exploit the frequency selective channel property without complex equalization.
• Frequency-domain statistical multiplexing, for example (OFDMA) or (Single-carrier FDMA) (SC-FDMA, a.k.a. Linearly precoded OFDMA, LP-OFDMA) in the uplink: Variable bit rate by assigning different sub-channels to different users based on the channel conditions
• Turbo principle error-correcting codes: To minimize the required SNR at the reception side

1. Channel-dependent scheduling: To utilize the time-varying channel.
2. Link adaptation: Adaptive modulation and error-correcting codes
3. Relaying, including fixed relay networks (FRNs), and the cooperative relaying concept, known as multi-mode protocol

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