Long term Evolution (LTE)
LTE stands for Long-term Evolution. It is considered the fourth generation wireless communication networks. In LTE a user experience the speed up to 100 Mbps download and up to 50 Mbps upload.
LTE Speed & Objectives
- To provide higher performance i.e. 100 Mbps download and 50Mbps upload and 1 Gbps for LTE advanced, to reduce the cell latency to (10 ms) for better user experience. Scalable bandwidth up to 20 MHz
- Compatible with existing 2G/3G/EDGE systems such that with minimal change in hardware and the existing spectrum can be reused.
- To reduce Capital Expenditure and Operational Expenditure with minimal use of hardware.
Different types of Technologies that support LTE
Multi Input Multi Output employs multiple transmit and receive antennas to improve the interface in air. MIMO processing uses spatial multiplexing, allowing different data streams to be transmitted simultaneously from different transmitter antenna. Spatial multiplexing increases the end-user data rate and cell capacity. Also, when knowledge of the radio channel is available at the transmitter, such as through feedback information from the receiver, multiple antennas are also used to transmit the same data stream, thus providing redundancy and improved coverage, especially close to the cell edge.
For the downlink, orthogonal frequency-division multiplexing (OFDM) was selected as the air interface for LTE. OFDM is a particular form of multi-carrier modulation (MCM). In general, MCM is a parallel transmission method that divides a radio frequency channel into several, more narrow-bandwidth sub-carriers and transmits data simultaneously on each sub-carrier. OFDM is well suited for high data rate systems that operate in multipath environments because of its robustness to delay spread. Furthermore, due to its frequency domain nature, OFDM enables flexible bandwidth operation with little complexity. Smart antenna technologies are also easier to support with OFDM because each sub-carrier becomes flat faded and the antenna weights can be optimized on a per-subcarrier or block of sub-carriers basis.
Single-carrier FDMA (SC-FDMA) was chosen to reduce Peak to Average Ratio (PAR), which has been identified as a critical issue for the use of OFDMA in the uplink where power-efficient amplifiers are required in mobile devices. Another important requirement was to maximize the coverage. For each time interval, the base station scheduler assigns a unique time-frequency interval to a terminal for the transmission of user data, thereby ensuring intracell Orthogonality.
- Read it also: Comparison between 1G, 2G, 3G and 4G wireless technologies
- Read it also: Overview of 2G Technology
- High data rates for both Upload (up to 50 Mbps) and Download (up to 100 Mbps).
- 200 Active voice calls simultaneously in every 5 MHz bandwidth.
- The bandwidth is not fixed but can be varied from 5 MHz to 20MHz with 1.5 MHz increment.
- Low latency.
- Usage of existing spectrum.