AnMultiple Input/Multiple Output (MIMO) technology has been used in Wireless Local Area Networks to achieve higher capacity and is now deployed in the Long-Term Evolution (LTE) networks to improve network throughput, capacity and coverage.
MINO schemes are characterised as “MxN” MIMO, where ‘M” indicates the number of transmitting antennas, and N designates the number of antennas receiving the transmitted signals.
For example, the downlink has four (4) transmit antennas at the base station (eNodeB), and two (2) receive antennas in the User Equipment (UE), is referred to as “4×2 MIMO.” The uplink may use one single transmit antenna in the UE and 4 receive antennas at the eNodeB, is referred as a “1×4 SIMO”.
The figure below shows an example of MIMO operations:
There are two major categories of MIMO which improve the throughput, capacity and coverage:
1. Spatial Diversity
In 2×2 MIMO with spatial diversity, each of the two antennas is essentially transmitting and receiving the same data although the data is coded differently. This mode is primarily used to improve signal quality, or to increase the coverage area.
2. Spatial Multiplexing
In 2×2 MIMO with spatial multiplexing, two different streams of data are transmitted over each radio channel, which theoretically doubles the system throughput without the need for additional spectrum resources.
LTE UE Category Definitions
LTE standards define UE in categories, which reduces EnodeB complexity and allow the eNodeB to communicate effectively with all the UEs connected to it. The table below summarises the different categories:
| UE Category | DownLink (Mbps) | UpLink (Mbps) | Maximum number of supported layers for spatial multiplexing in Downlink | Support for 64QAM in Uplink |
| Category 1 | 10 | 2 | 1 | No |
| Category 2 | 50 | 25 | 2 | No |
| Category 3 | 100 | 50 | 2 | No |
| Category 4 | 150 | 50 | 2 | No |
| Category 5 | 300 | 75 | 4 | Yes |
| Category 6 | 300 | 50 | 2 or 4 | No |
| Category 7 | 300 | 100 | 2 or 4 | No |
| Category 8 | 3000 | 1500 | 8 | Yes |
| Category 9 | 450 | 50 | 2 or 4 | No |
| Category 10 | 450 | 100 | 2 or 4 | No |
For a Category 3 UE, the peak downlink with 2×2 MIMO is approximately 100 Mbps and peak uplink data rate of 50 Mbps is achieved using 1×2 SIMO.
This article provides a brief introduction to MIMO and an insight on the deployment of MIMO technologies to achieve LTE full potential. For more information on the topic, contact either Jonathan Stubing or Trevor Williams on +618 6467 0600.