Sign in Subscribe

What is the function of the Physical Uplink Shared Channel (PUSCH) in LTE?

Last updated on 


The Physical Uplink Shared Channel (PUSCH) in LTE (Long-Term Evolution) is a fundamental component of the physical layer that plays a critical role in transmitting user data from the User Equipment (UE) or mobile device to the base station (eNodeB). The PUSCH is responsible for carrying the actual payload data and is essential for enabling two-way communication in LTE networks. Let's explore the technical details of the function of the PUSCH in LTE:

Data Transmission:

  • The primary function of the PUSCH is to transmit user data from the UE to the eNodeB. This data can include voice, video, web browsing, and other application data generated by the UE.

Resource Allocation:

  • The PUSCH is allocated specific resources within the LTE spectrum by the eNodeB. These resources include a set of subcarriers in the frequency domain and a series of time slots in the time domain.
  • The allocation of resources for the PUSCH is controlled by the eNodeB, which uses the Physical Downlink Control Channel (PDCCH) to instruct the UE on when and where to transmit data.

Modulation and Coding:

  • The PUSCH supports various modulation and coding schemes, including Quadrature Phase Shift Keying (QPSK), 16-QAM (Quadrature Amplitude Modulation), and 64-QAM, depending on the radio conditions and the data rate requirements.
  • The choice of modulation and coding scheme impacts the data rate and the robustness of the transmission.

Transmission Power Control:

  • The UE adjusts its transmission power on the PUSCH based on instructions from the eNodeB. Power control ensures that the UE transmits with just enough power to reach the eNodeB without causing interference to other UEs or degrading network performance.

Multiple Access Scheme:

  • LTE uses a multiple access scheme known as Single Carrier Frequency Division Multiple Access (SC-FDMA) for the PUSCH. SC-FDMA is chosen because it provides better power efficiency and lower peak-to-average power ratios compared to other schemes, making it suitable for uplink transmission where power conservation is crucial for battery-operated UEs.

Error Correction and HARQ:

  • The PUSCH incorporates error correction coding and Hybrid Automatic Repeat Request (HARQ) mechanisms to enhance data reliability. Error correction codes help correct errors that occur during transmission, while HARQ allows for retransmission of data in case of errors, improving the overall reliability of the transmission.

Channel Quality Reporting:

  • The UE periodically reports channel quality measurements to the eNodeB, which helps the eNodeB optimize resource allocation and modulation and coding schemes for the PUSCH. These reports aid in adapting to changing radio conditions and maintaining a stable connection.

Interference Management:

  • Interference from neighboring cells or UEs can affect the quality of the PUSCH transmission. The eNodeB may employ interference management techniques and coordinate interference suppression to ensure a reliable uplink connection.

In summary, the Physical Uplink Shared Channel (PUSCH) in LTE is responsible for transmitting user data from the UE to the eNodeB. It is allocated specific resources, employs modulation and coding schemes, adapts its transmission power, and incorporates error correction and HARQ mechanisms to ensure reliable data transmission. The PUSCH is a critical component for two-way communication in LTE networks, enabling users to send data, make voice calls, and engage in various applications while maintaining efficient and robust connectivity.