The air interface is the radio-based communication link between the mobile station and the active base station. LTE air interface supports high data rates. LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) for downlink transmission to achieve high peak data rates in high spectrum bandwidth. LTE uses Single Carrier Frequency Division Multiple Access (SC-FDMA) for uplink transmission, a technology that provides advantages in power efficiency.
LTE air interface characteristics
LTE air interface characteristics are:
Downlink (DL) based on OFDMA. OFDMA offers improved spectral efficiency capacity using OFDMA technology.
Uplink (UL) based on SC-FDMA. SC-FDMA is similar to OFDMA for uplink from hand-held devices such as mobile phones which require better battery power conservation.
Supports both FDD and TDD modes:
- Provides deployment flexibility in spectrum allocation.
- With FDD, DL and UL transmissions are performed simultaneously in two different frequency bands.
- With TDD, DL and UL transmissions are performed at different time intervals within the same frequency band.
Significant reductions in delay over air interface and idle to active mode transition.
Suitable for real-time applications, for example, VoIP, PoC, gaming, and so on.
Large improvement in uplink spectral efficiency.
Advanced adaptive MIMO support. Balance average/peak throughput, coverage/cell-edge bit rate.
LTE channel
Channels are used to transport and segregate different types of data across the LTE radio access network interface.
The various data channels are grouped into three categories:
- Physical channels – The physical channels are transmission channels that carry user data and control messages.
- Transport channels – The physical layer transport channels offer information transfer to Medium Access Control (MAC) and higher layers.
- Logical channels – The logical channels provide services for the Medium Access Control (MAC) layer within the LTE protocol stack.
LTE Air Interface Characteristics & LTE Channel Function
The LTE air interface is designed to deliver high-speed data and low latency while supporting a large number of users. It uses Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink to efficiently use the available spectrum and minimize interference. The air interface is optimized for flexibility, allowing LTE to adapt to various bandwidths and use cases, from urban areas to rural coverage.
Key Characteristics of LTE Air Interface:
- High Data Rates: LTE supports peak data rates of up to 300 Mbps in the downlink and 75 Mbps in the uplink, making it ideal for high-bandwidth applications like video streaming and gaming.
- Low Latency: The air interface minimizes delay, ensuring near-real-time services like VoIP and video calls work seamlessly.
- Efficient Spectrum Usage: By using OFDMA in the downlink and SC-FDMA in the uplink, LTE optimizes spectrum use and reduces interference, ensuring reliable service in diverse conditions.
- Scalable Bandwidth: LTE can operate in different frequency bands and bandwidths, allowing flexible deployment in various regions and spectrum availability.
LTE Channel Functions:
- Physical Channels: These are responsible for the transmission of actual data over the air interface. Examples include the Physical Downlink Shared Channel (PDSCH) and Physical Uplink Shared Channel (PUSCH), which carry user data.
- Control Channels: These handle control information required for managing communication. Examples include the Physical Downlink Control Channel (PDCCH), which carries downlink scheduling information, and the Physical Uplink Control Channel (PUCCH), which carries control information in the uplink.
- Reference Signals: These are used for cell identification, channel estimation, and synchronization. Examples include the Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS) in the downlink.
- Signaling Channels: These channels are used for network management and signaling between the UE and the eNodeB, such as the Random Access Channel (RACH) for initial access.
These characteristics and channels work together to ensure LTE can deliver high-speed, low-latency, and efficient communication for both mobile and fixed wireless applications.