Articles | Page 20 of 35

Diversity implies two or more independent replicas of the same information

November 2, 2021 Wireless/SDR

Multiple Antenna Techniques

When computing approaches the physical limits of clocking speeds, we turn towards multi-core architectures. When communication approaches the physical limits of transmission speeds, we turn towards multi-antenna systems. What exactly are the benefits that led to scientists and engineers choosing multiple antennas as the foundation of 4G and 5G PHY layers? While having spatial diversity was the original incentive for adding antennas at the base stations, it was discovered in mid 1990s that multiple antennas at Tx and/or Rx sides open up other possibilities not foreseen in single antenna systems. Let us now describe three main techniques in this context.

Average trajectory for squared eye diagrams for a binary PAM sequence of 400 symbols shaped with Raised Cosine pulse with excess bandwidths 0, 0.5 and 1

December 31, 2021 Wireless/SDR

Lock Detectors for Symbol Timing Synchronization

Similar to the carrier lock detectors, timing lock detectors can also be constructed based on some property of the modulated signal. These lock detectors operate in parallel to the timing locked loop and aid the Rx state machine in executing necessary tasks according to each scenario. The expressions for two such timing lock detectors are as follows. The output of a timing lock detector should be at its peak for the correct timing. Therefore, when the matched filter output, denoted by $z(mT_M)$ with $T_M$ being the symbol time, is at its peak, the second sample in a signal oversampled by

Number of goals scored by player 1 in each match

May 13, 2019 DSP

Basic Signals

As we saw here, a signal is any measurable quantity that varies with time (or some other independent variable). Classification of continuous-time and discrete-time signals deals with the type of independent variable. If the signal amplitude is defined for every possible value of time, the signal is called a continuous-time signal. However, if the signal takes values at specific instances of time but not anywhere else, it is called a discrete-time signal. Basically, a discrete-time signal is just a sequence of numbers. Example Consider a football (soccer) player participating in a 20-match tournament. Suppose that his running speed is recorded

Bandwidth, power and DSP correspond to the traditional trio of raw materials, energy and knowledge

October 21, 2020 DSP / Wireless/SDR

Why Building an SDR Requires DSP Expertise

In an introduction to signals, we discussed the idea that the any activities around us, starting from subatomic particles to massive societal networks, are generating signals all the time. Since mathematics is the language of the universe and digital signals are nothing but quantized number sequences, it is fair to say that the workings of the universe can be mapped to an infinitely large set of signals. With these number sequences in hand, an electronic computer can process the signals and either extract the information about the surrounding real world phenomena or even better influence its target environment. We saw

The counter, register and Tx and Rx start events

October 27, 2017 Localization

There and Back Again: Time of Flight Ranging between Two Wireless Nodes

With the growth in the Internet of Things (IoT) products, the number of applications requiring an estimate of range between two wireless nodes in indoor channels is growing very quickly as well. Therefore, localization is becoming a red hot market today and will remain so in the coming years. See the big picture of localization for general solutions to this problem. One question that is perplexing is that many companies now a days are offering cm level accurate solutions using RF signals. The conventional wireless nodes usually implement synchronization techniques which can provide around $\mu s$ level accuracy and if