Posted by : Rohit Hazra Thursday, May 3

Hello Readers,
As I said in the last post I am going to write about the two technologies so here I am with

Multi User MIMO

What's new in MU-MIMO from older SU-MIMO

Multi-User MIMO (MU-MIMO) is the technique which used in the scenarios with a large number of users to be served in one cell, and high capacity gains can be achieved by transmitting independent data streams to different users sharing the same time-frequency resources. Because more than two users share the same time-frequency resources in MU-MIMO systems, there is a big problem for the receiver to cancel the interference of the other users. Inspired by the idea of interference cancellation in CDMA systems, a novel multi-user MIMO scheme is proposed in this paper. It employs spreading in the transmitter and joint detection (SP-JD) in the receiver. Simulation results show that SP-JD scheme could achieve higher sum rates capacity and better bit error rate (BER) performance than Zero-Forcing (ZF) scheme while the receiver is not aware of the precoding vectors applied to the streams transmitted to the other users.
It is a technology that uses the available multiple independent radio terminals to enhance the communication capabilities of each individual terminal. It is also seen as the extended concept of SDMA ( Space Division Multiple Access ).
It can allow multiple users as spatially distributed transmission resources, at the cost of somewhat more expensive signal processing. It's algorithms are developed to enhance MIMO systems when the number of users, or connections, numbers greater than one (admittedly, a useful concept). Multi-user MIMO can be generalized into two categories: MIMO broadcast channels (MIMO BC) and MIMO multiple access channels (MIMO MAC) for downlink and uplink situations, respectively. Single-user MIMO can be represented as point-to-point, pairwise MIMO.
The Image says everything!!!!

To remove ambiguity of the words receiver and transmitter, we can adopt the terms access point (APN; or, base station), and user. An APN is the transmitter and a user is the receiver for downlink environments, whereas an APN is the receiver and a user is the transmitter for uplink environments. Homogeneous networks are somewhat freed from this distinction.

MU-MIMO provides a methodology whereby spatial sharing of channels can be achieved. This can be achieved at the cost of additional hardware - filters and antennas - but the incorporation does not come at the expense of additional bandwidth as is the case when technologies such as FDMA, TDMA or CDMA are used.
16 users connecting to 16 Channels

When using spatial multiplexing, MU-MIMO, the interference between the different users on the same channel is accommodated by the use of additional antennas, and additional processing when enable the spatial separation of the different users.
There are two scenarios associated with MU-MIMO, Multi-user MIMO:
  • Uplink - Multiple Access Channel, MAC:   The development of the MIMO-MAC is based on the known single user MIMO concepts broadened out to account for multiple users.
  • Downlink - Broadcast Channel, BC :   The MIMO-BC is the more challenging scenario. The optimum strategy involves pre-interference cancellation techniques known as "Dirty Paper Coding", DPC. This is complemented by implicit user scheduling and a power loading algorithm
MU-MIMO is very confusing and un-understandable so this is a simple image :  
MU-MIMO in a simpler form
So i wrote about MU-MIMO and DIDO now it is on you to decide Is it Same? or is it not? 

{ 3 comments ... read them below or Comment }

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