I have studied in a paper that "Massive MIMO offeres many excess degree of freedom that can be used to cancel the interference and signals from intentional jammers" Please explain What is meaning of degee of freedom and how it is useful.
Thanks.
Do you have access to IEEE Xplore?
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6798744
Seems like if the number of antennas at the base station tends to infinity, while the user equipment only has a single antenna, the base station is able to direct the signal so precisely that each user can be estimated like a single SISO user on that channel, with no interference from the others.
Degrees of freedom refers to the flexibility of this base station antenna array in directing the beams. The worst case being where the base station has line of sight to the user equipment, because massive MIMO makes use of scatterers along the path. Without them, processing gains diminish dramatically.
Degrees of freedom means different things in different research topics.
In massive MIMO, you have M degrees of freedom if you have M antennas at the base station. In the downlink, this means that you choose a precoding vector in 1 out of M dimensions. If you have K precoding vectors (= K users), then you do the precoding in a subspace of dimension K in a larger space of dimension M. These precoding vectors are selected based on your channel estimates.
Having excess degrees of freedom means that M>>K. This means that the K true channel vectors will be spread out in the M-dimensional space such that they "far" from each other. Even if you misestimate one of the channels, the estimate is likely to be far from another channel vector.
Thanks a lot Emil Sir for very nice explanation....
Thanks to Albert and Omid...
DF is the number of independent pieces of information that went into calculation.
A massive Mimo system is said to have degree of freedom in excess if for example its BS has 100 antennas to serve 10 terminals. The 10 terminals are showing presence while the remaining 90 degree of freedom are still available. These available degree of freedom can be exploited by using them for signal shaping.
I don't know the topic but with the explanation of Sir, Emil Björnson gave me an understanding of what is all about.
Nice topic, following this page, and kind regards to all.
Degree of Freedom (DoF) represents the maximum number of beams can be transmitted by the base station which is equal to the number of active antennas.
High DoF means that the number of active antennas is much higher the number of served users. Hence, there is a high possibility to change the beams between the base station and served user and do the beamforming to reduce the interference.
- Badges
- Science topic
- Similar topics
- Filing