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.
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.