# LTE MIMO - Multiple Input Multiple Output

Multi-antenna scheme - 2x2 MIMO:

MIMO techniques are multi-antenna techniques used in wireless devices to support higher data rates into radio links or RF. MIMO stands for Multiple Input Multiple Output antenna system. A set of mathematical equations are used to determine performance improvements. We will be discussing the 2x2 MIMO antenna architecture below.

MIMO is discussed below for 2x2 antennas: Before we discuss the mathematical equations for MIMO, lets first discuss the theoretical setup of a 2X2 MIMO.

LTE - 4G Wireless Technology

Digital fundamentals.

Interview Questions. From the setup of 4G LTE 2x2 MIMO, we can observe that each receiver is getting two streams of data one from Transmitter 1 and other from transmitter 2. The straight line is a direct path whereas angle path is an indirect path. The direct connections are always denoted with same numbers like h11 or h22. The indirect components are denoted with combinations of different transmitters, like h12 or h21.

When we combine all the components in one matrix we get Matrix channel or transmission matrix H. Can also be extended for 4x4 LTE MIMO

If we characterize the Transmitters as x and Receiver components as Y, we can get our equation for MIMO as

Y = Hx
Adding Guassian Noise and G we will get our final equation.
Y = Hx +G

Tutorials `@fullchipdesign.com`

Verilog Tutorial.

LTE Tutorial.

Memory Tutorial.

This technique supports high data rates. This approach of combining signals allows better resistance against interferers like - multipath, channel fading etc.
Mathematical formula for the theoretically equivalent of channel capacity is referred from Shannon- Hartley theorem, discussed below.

Capacity = BW x log2 (1 + SNR)

For MIMO the same equation is going to allow the Capacity to be multiplied by a factor equal to the number of transmitters in the MIMO system.

Capacity = N x BW x log2 (1 + SNR)

LTE supports data rates upto 100 Mbps for downloads and 50 Mbps for uploads. The the high throughput needs to be transmitted over the air  without causing packet corruption or packet loss. This is also used in WiMax antenna as an option

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