LB1120 MIMO Capable?

[tekuhn]

Can someone please state whether the LB1120 is truly LTE MIMO functional, and if so, at what levels? The documentation simply states there are 2 external antenna connections "for better signal reception". That description leaves a lot to be desired from a technical standpoint. Thanks!

[DarrenM]

You can purchase an external multiple input, multiple output (MIMO) antenna for the modem to extend the mobile broadband signal range indoors or in fringe network areas. The external antenna plugs into the two antenna connectors on the modem to boost speeds and extend coverage in buildings or vehicles, or in remote sites where network coverage is sparse.You could, for example, attach the external antenna on a window with a suction cup

This is localted in the user manual '

DarrenM

[tekuhn]

Hi Darren,

Thank you for responding. I hope you're right, but attaching a MIMO antenna doesn't mean the LB1120 is actually MIMO capable. I am familiar with the manual, however, it (and other LB1120 literature) states the purpose of the external antenna(s) is to increase signal strength, but never state that the product will use two antennas for actual MIMO operation to increase throughput. Here's what I'm hoping to find out - Which of these types of LTE MIMO operation is supported by the LB1120? Thanks!

LTE MIMO modes

There are several ways in which MIMO is implemented in LTE. These vary according to the equipment used, the channel function and the equipment involved in the link.

• Single antenna:   This is the form of wireless transmission used on most basic wireless links. A single data stream is transmitted on one antenna and received by one or more antennas. It may also be referred to as SISO: Single In Single Out or SIMO Single In Multiple Out dependent upon the antennas used. SIMO is also called receive diversity.
• Transmit diversity:   This form of LTE MIMO scheme utilises the transmission of the same information stream from multiple antennas. LTE supports two or four for this technique.. The information is coded differently using Space Frequency Block Codes. This mode provides an improvement in signal quality at reception and does not improve the data rate. Accordingly this form of LTE MIMO is used on the Common Channels as well as the Control and Broadcast channels.
• Open loop spatial multiplexing:   This form of MIMO used within the LTE system involves sending two information streams which can be transmitted over two or more antennas. However there is no feedback from the UE although a TRI, Transmit Rank Indicator transmitted from the UE can be used by the base station to determine the number of spatial layers.
• Close loop spatial multiplexing :   This form of LTE MIMO is similar to the open loop version, but as the name indicates it has feedback incorporated to close the loop. A PMI, Pre-coding Matrix Indicator is fed back from the UE to the base station. This enables the transmitter to pre-code the data to optimise the transmission and enable the receiver to more easily separate the different data streams.
• Closed loop with pre-coding:   This is another form of LTE MIMO, but where a single code word is transmitted over a single spatial layer. This can be sued as a fall-back mode for closed loop spatial multiplexing and it may also be associated with beamforming as well.
• Multi-User MIMO, MU-MIMO:   This form of LTE MIMO enables the system to target different spatial streams to different users.
• Beam-forming:   This is the most complex of the MIMO modes and it is likely to use linear arrays that will enable the antenna to focus on a particular area. This will reduce interference, and increase capacity as the particular UE will have a beam formed in their particular direction. In this a single code word is transmitted over a single spatial layer. A dedicated reference signal is used for an additional port. The terminal estimates the channel quality from the common reference signals on the antennas.

Tom Kuhn