Neeraj Sharma- Panjab University
Neeraj Sharma
- Panjab University
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Introduction
Current institution
Publications
Publications (4)
Conventional multiple-input multiple-output (MIMO) systems operating at sub-6 GHz frequencies generally employ fully digital precoding which requires dedicated radio frequency (RF) chain for each antenna element. However, this architecture is infeasible for the millimeter wave (mmWave) massive MIMO systems due to excessive power consumption and spa...
Questions
Questions (7)
In the attached paper titled, "Approximate expressions for BER performance in downlink mmWave MU-MIMO hybrid systems with different data detection approaches", mathematical operator ℝ{.} is used with minus sign in Equation (14). Can anybody help explain the meaning of this operator? Why minus sign is used?
Can anyone suggest some papers on the current status of implementation of practical Massive MIMO (both sub-6 GHz and millimeter wave) and issues faced by it?
Any reply will be highly appreciated.
It is common practice to represent a poor scattering channel like millimter wave MIMO channel with a clustered channel model consisting of few clusters of rays. I have also seen in a few papers that poor scattering nature is also captured in terms of a Finite Dimensional channel.
1. Can anyone clarify the difference between the two channel models?
2. As per my knowledge, both channel models are used to reflect the poor scattering property of practical MIMIO channel. Which one to use under what channel conditions?
I shall be highly obliged if someone could spare time and share his/her knowledge.
The channel model for mmWave frequencies is often depicted as consisting of finite number of clusters with finite number of rays per cluster. How same channel is applicable for the whole frequency range from 30 to 300 GHz? Is there one-to-one corresponding between the number of propagation paths and the frequency of millimeter waves?
Can anybody help in understanding how in a MIMO system with large (ideally infinite) number of transmit/receive antennas and poor scattering (e.g at mmWave), the transmit/receive array response vectors form an orthogonal vector set?
In the attached paper, for a uniform linear antenna array (ULA), the same is proved at page 104. I request to please help me understand how (b) is arrived in section 7.1? How poor scattering (small L) is considered in the result?
Consider a single user massive MIMO system working at mmWave frequency, whose precoders and combiners have been estimated. See the attached paper for reference. Can anybody tell how to determine energy efficiency of this system? Can anybody provide MATLAB code for the same?
Regards
It is said that Massive MIMO working at microwave frequencies have rich scattering (weak LOS) channel, whereas same system working at mm wave frequencies have sparse channels (strong LOS).
1. How dose rich scattering/sparse channels affect the performance the of MIMO?
2. Does it mean that mm Wave system has low channel rank and hence not suitable for spatial multiplexing? If yes, how can this system be used for multi user scenario?
