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PUSCH Precoding / Transmission Mode (Codebook vs Non-Codebook based)/UL Transmission Scheme

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The technical details of PUSCH (Physical Uplink Shared Channel) precoding, transmission modes, and the UL (Uplink) transmission scheme in the context of wireless communication systems, particularly in LTE (Long-Term Evolution) and NR (5G New Radio) standards.

PUSCH Precoding:

1. Definition:
PUSCH precoding involves manipulating the amplitude and phase of the transmitted signal to optimize its reception at the intended receiver. The goal is to maximize the received signal quality and minimize interference.

2. Codebook-based Precoding:

  • In a codebook-based approach, a predefined set of precoding matrices or vectors (known as a codebook) is used at the transmitter.
  • The codebook contains multiple precoding options, and the transmitter selects the most suitable one based on channel conditions, modulation scheme, and other factors.
  • The advantage of codebook-based precoding is that it adapts to varying channel conditions, providing flexibility and efficiency.

3. Non-Codebook based Precoding:

  • Non-codebook based precoding involves adaptive precoding without relying on a predefined codebook.
  • Channel state information (CSI) is estimated at the transmitter, and precoding is dynamically adjusted based on the real-time channel conditions.
  • This approach is more adaptive but may require more signaling overhead and computational resources.

Transmission Modes:

1. Transmission Modes in LTE:

  • In LTE, there are different transmission modes for uplink communication, such as Single-Input Single-Output (SISO), Multiple-Input Single-Output (MISO), and Multiple-Input Multiple-Output (MIMO).
  • MIMO technology, including precoding, is used to improve spectral efficiency and link reliability.

2. Transmission Modes in 5G NR:

  • 5G NR introduces new transmission modes, such as beamforming and massive MIMO, which leverage advanced antenna technologies.
  • Beamforming allows the concentration of signal energy in specific directions, enhancing coverage and capacity.
  • Massive MIMO employs a large number of antennas to provide significant spatial multiplexing gains.

UL Transmission Scheme:

1. Basic Uplink Transmission:

  • In the uplink, user equipment (UE) transmits data to the base station (eNodeB in LTE, gNodeB in 5G NR).
  • The transmission includes user data, control information, and reference signals for channel estimation.
  • Different transmission schemes, such as SC-FDMA (Single-Carrier Frequency Division Multiple Access) in LTE, are used for efficient uplink communication.

2. Grant-Based and Non-Grant-Based Transmission:

  • Grant-based transmission involves the UE receiving a grant from the base station before transmitting data.
  • Non-grant-based transmission allows the UE to transmit data without explicit permission, suitable for sporadic or low-data-rate transmissions.

3. Multiple Access Schemes:

  • Multiple access schemes like NOMA (Non-Orthogonal Multiple Access) can be employed in the uplink to allow multiple UEs to share the same time-frequency resources.

PUSCH precoding involves manipulating the transmitted signal for optimal reception. Transmission modes vary in complexity and are adapted to different scenarios, and the uplink transmission scheme encompasses various technologies and strategies for efficient communication between the user equipment and the base station.