LTE MIMO: Multiple Input Multiple Output Tutorial
- MIMO is used within LTE to provide better signal performance and / or higher data rates by the use of the radio path reflections that exist.
3G LTE technology tutorial includes:
• What is LTE :: Introduction
• OFDM and OFDMA / SC-FDMA
• TDD and FDD duplex schemes
• Frame and subframe structure
• Physical logical & transport channels
• Frequency bands and spectrum
• UE category definitions
• SAE system architecture evolution
• LTE self-organising networks
• Voice over LTE, VoLTE
See also: 4G LTE Advanced
MIMO, Multiple Input Multiple Output is another of the LTE major technology innovations used to improve the performance of the system. This technology provides LTE with the ability to further improve its data throughput and spectral efficiency above that obtained by the use of OFDM.
Although MIMO adds complexity to the system in terms of processing and the number of antennas required, it enables far high data rates to be achieved along with much improved spectral efficiency. As a result, MIMO has been included as an integral part of LTE.
LTE MIMO basics
The basic concept of MIMO utilises the multipath signal propagation that is present in all terrestrial communications. Rather than providing interference, these paths can be used to advantage.
Note on MIMO:
Two major limitations in communications channels can be multipath interference, and the data throughput limitations as a result of Shannon's Law. MIMO provides a way of utilising the multiple signal paths that exist between a transmitter and receiver to significantly improve the data throughput available on a given channel with its defined bandwidth. By using multiple antennas at the transmitter and receiver along with some complex digital signal processing, MIMO technology enables the system to set up multiple data streams on the same channel, thereby increasing the data capacity of a channel.
Click on the link for a MIMO tutorial
MIMO is being used increasingly in many high data rate technologies including Wi-Fi and other wireless and cellular technologies to provide improved levels of efficiency. Essentially MIMO employs multiple antennas on the receiver and transmitter to utilise the multi-path effects that always exist to transmit additional data, rather than causing interference.
The schemes employed in LTE again vary slightly between the uplink and downlink. The reason for this is to keep the terminal cost low as there are far more terminals than base stations and as a result terminal works cost price is far more sensitive.
For the downlink, a configuration of two transmit antennas at the base station and two receive antennas on the mobile terminal is used as baseline, although configurations with four antennas are also being considered.
For the uplink from the mobile terminal to the base station, a scheme called MU-MIMO (Multi-User MIMO) is to be employed. Using this, even though the base station requires multiple antennas, the mobiles only have one transmit antenna and this considerably reduces the cost of the mobile. In operation, multiple mobile terminals may transmit simultaneously on the same channel or channels, but they do not cause interference to each other because mutually orthogonal pilot patterns are used. This techniques is also referred to as spatial domain multiple access (SDMA).
Other popular cellular tutorials . . . . .
|• 3G LTE||• LTE Advanced||• UMTS / W-CDMA||• GSM|
|• 3G HSPA||• CDMA2000||• GPRS||• EDGE|
|• Femtocells||• 5G ideas||• HetNets||• SON|
|• Backhaul||• VoLTE|