5G Antennas in a Nutshell
5G takes advantage of sophisticated SDMA (Spatial Diversity Multiplexing Access) technique to reuse the time/frequency resources available in the communication channel.
In the following you can have a fast look at some antenna technologies adopted for SDMA in 5G. More information are available in the other Sections of this site
In few words....
... what is a beam-steering antenna?
A beam-steering, antenna in an antenna whose main beam can be electronically controlled so that it points toward the end user during data transmission.
SIM_MOV_v0.aviIn this simulation the base station (placed in (0,0) in Fig (a)) is connected to three users (circles in Fig (a)) in time division by mean of a beam-steering antenna. Fig (b) shows the power of the Resource Elements in the subcarrier-OFDM symbol grid (fig (b)). Fig (c) shows the power channel in a 1MHz bandwidth centred on the central frequency of the six SS/PDCH. Fig(d) shows the incident field on the moving user. Note how the field of the moving user changes depending on its position with respect to the the the other users. When it enters on the main lobe of the beams of the other users, an increase of the incident field is observed.
(More information in the "Papers-5G safety" section.)
... what is a MIMO antenna?
Basically, a MIMO antenna is a 'standard' antenna whose pattern is modulated by data.
Loosely speaking, information transmission is based on 'surprise'. Every time we receive something unexpected, we gain information.
The field radiated by a "standard" antenna has a known spatial configuration in far-field. The standard far-field antenna parameters, as Directivity, Gain, radiation pattern and so on, are a direct consequence of the single spatial configuration of the field.
In MIMO antenna using spatial multiplexing we have more than one possible pattern. Consequently, the receiver does not know which 'pattern' will be used. Only when the incident field impinges on the receiving antenna, the specific pattern is identified. Each pattern is associated to a different piece of information. Consequently, transmission on N bits requires a set a 2^N patterns. In 5G, the set of pattern is used to transmit more symbol.
Simple, smart, intriguing...
MIMO_QPSK_a.aviIn this movie you can see and example of how the pattern is modified according to the transmitted information in case of a QPSK constellation using 2 MIMO channels.
(more information in the "Paper-Information and Electromagnetic" section on the site.)
... what is a Multi-User MIMO (MU-MIMO) antenna ?
A Multi-user MIMO (MU-MIMO) antenna connects more than one user at the same time and using the same frequency band. So, instead of having only one beam, the antenna has multiple beams.
MU_MIMO_v1.aviThe field radiated by a MU-MIMO antenna connecting four users (circles) in a scattering environment (rhombs)
(more information in the "Paper-Information and Electromagnetic" section on the site.)
... what is a Massive MIMO antenna ?
Massive MIMO antennas are antenna with a lot of radiating elements. The ability to concentrate the radiated energy in the space depends on the number of elements of the antenna: more elements, larger the antenna in terms of wavelengths. The use of larger antennas reduces the probability of 'overlapping' of the beams associate to different users, allowing to transmit information using same frequency bands and time slots with low interference.
MU_MIMO_v2.avi... concluding
The above examples are simple simulations in free space chosen in order to give an intuitive idea of the basic concepts; precise analysis, in particular in case of scattering environments, requires a lot of maths. Anyway, maths does not change (and sometimes hides) the basic concepts.
For more information please see the section Papers - 5G safety of this website