Sign in Subscribe

lte air interface

Last updated on 

The Long-Term Evolution (LTE) air interface is the wireless communication link between user devices (such as smartphones, tablets, and other LTE-enabled devices) and the LTE network infrastructure. LTE represents a standard for wireless broadband communication and is widely used for 4G (fourth generation) mobile networks. Here's a technical explanation of the LTE air interface:

  1. Frequency Bands:
    • LTE operates in a variety of frequency bands, including the 700 MHz, 800 MHz, 900 MHz, 1800 MHz, 2100 MHz, 2600 MHz, and other frequency ranges. Different bands are used in different regions globally.
  2. Multiple Access Scheme:
    • LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) for the downlink (from the base station to the user device) and Single Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink (from the user device to the base station). OFDMA allows multiple users to share the same frequency band by dividing it into multiple orthogonal subcarriers.
  3. Physical Layer:
    • LTE's physical layer is based on Orthogonal Frequency Division Multiplexing (OFDM) for downlink transmission and SC-FDMA for uplink transmission. OFDM divides the available spectrum into multiple subcarriers, allowing for efficient data transmission. SC-FDMA is chosen for the uplink because of its lower peak-to-average power ratio, which is beneficial for user devices with limited battery power.
  4. Modulation and Coding Schemes:
    • LTE uses various modulation and coding schemes (MCS) to adapt to different channel conditions. The modulation schemes include Quadrature Amplitude Modulation (QAM), with higher-order QAM providing higher data rates but requiring better signal conditions. Error correction coding, such as Turbo coding and Convolutional coding, is applied to enhance the reliability of data transmission.
  5. Multiple Antennas:
    • Multiple Antenna techniques, such as Multiple Input Multiple Output (MIMO), are employed in LTE to improve data rates and system reliability. MIMO uses multiple antennas at both the transmitter and receiver to exploit spatial diversity and multipath propagation.
  6. Channel Access and Scheduling:
    • LTE uses a combination of Frequency Division Duplex (FDD) and Time Division Duplex (TDD) for different duplexing modes. Channel access and scheduling are managed by the LTE scheduler, which allocates resources to users based on factors like channel conditions, priority, and Quality of Service (QoS) requirements.
  7. LTE Frame Structure:
    • The LTE air interface frame structure is based on time and frequency domains. Time is divided into slots, and each slot is further divided into subframes. Frequency is divided into physical resource blocks (PRBs). The combination of time and frequency resources forms the basic unit of data transmission.
  8. Protocols:
    • LTE uses a set of protocols to manage the establishment, maintenance, and termination of communication sessions. The LTE protocol stack includes the Radio Resource Control (RRC), Packet Data Convergence Protocol (PDCP), Radio Link Control (RLC), and Medium Access Control (MAC) layers.
  9. LTE Advanced Features:
    • LTE Advanced introduced additional features such as carrier aggregation, enhanced MIMO, and relay nodes to further improve data rates, spectral efficiency, and coverage.

The LTE air interface employs advanced technologies such as OFDM, MIMO, and various modulation and coding schemes to provide high-speed and reliable wireless communication between user devices and the LTE network infrastructure. The combination of these technologies allows LTE to deliver high data rates, low latency, and efficient use of available spectrum.