Tag: MIMO

A view of time-frequency-space grid in a communication system
Wireless/SDR

How Multiple Antennas Sample the Signal

Once upon a time, an antenna was viewed as a simple device to transmit and receive an electromagnetic wave, much like a battery the sole purpose of which is to provide electrical power. A set of antennas, however, can be viewed from a new angle as follows. Sampling in Time Domain An Analog-to-Digital Converter (ADC) is a device that samples an analog signal in time domain to create a corresponding sequence of numbers. Similarly, a Digital-to-Analog Converter (DAC) gets a sequence of numbers as an input to generate a reconstructed analog signal. As an example, a rectangular pulse shape is

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Wireless/SDR

Converting Spatial Diversity into Time and Frequency Diversity

We have seen before that diversity implies using two or more statistically independent replicas for the transfer of the same information. This improves the reliability of the received message because nothing can recover the data signal in a deep fade except getting more copies of the same message. Spatial diversity has also been discussed in the context of multiple antenna systems. In this article, we describe how this diversity arising from the presence of multiple antennas can be converted into time or frequency diversity. Delay diversity converts spatial diversity into frequency diversity Phase-roll diversity converts spatial diversity into time diversity

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Channel hardening implies the channel flutucations due to small-scale fading smooth out
Wireless/SDR

On Massive MIMO, Channel Hardening and Favorable Propagation

Imagine an alien race looking at our planet from outside the solar system through a lens of time. They will notice one unmistakable direction. Our pursuit of MORE in everything. This tendency might be ingrained in the fundamental idea of life itself. To live is to grow. While our dreams for faster transportation face mechanical roadblocks from the laws of physics, technologies for faster communication are only bound by the laws of electromagnetics. Ever since we linked digital electronics to information exchange from one point to another without any physical medium, on-demand reception and transmission of data at any place

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Earth lies in the Goldilocks Zone of our solar system
Wireless/SDR

Diversity in Wireless Communication Systems

Diversity is one of those few ideas that are extremely dumb and extremely clever at the same time. It can be explained in one sentence as well as in a whole book. The basic idea, nevertheless, is quite simple. What is Diversity? Consider the following two different cases. Many phenomena in the world need a series of outcomes to succeed. For instance, for life to exist in the cold and dark universe, we need a star to provide energy as heat. A planet is also required as a home. Furthermore, this planet must reside in the Goldilocks Zone of that

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Frequency domain beamforming implements a procedure for broadband signals that resembles the conventional narrowband beamformers
Wireless/SDR

Beamforming for Broadband Signals

Recall that classical or physical beamforming is based on calculating the differences in wave arrival times of a signal between antenna array elements and compensating for these delays through signal processing techniques that steer the beams in any desired direction. There are two main candidates for this purpose: Phase shifting and True Time Delays (TTD). We saw in that article on beamforming that phase shifts implemented through a set of complex multipliers are incapable of beamforming over the entire bandwidth of a signal. Why? The intuitive reason is clear from a signal level view. In the narrowband scenario, the same

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