Qasim Chaudhari Blog on DSPRelated.com

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

Qasim Chaudhari — Mon, 23 Oct 2017 12:28:10 +0000

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.

One question that is perplexing is that many companies now a days are offering cm level accurate...

A Beginner's Guide to OFDM

Qasim Chaudhari — Mon, 01 May 2017 07:02:27 +0000

In the recent past, high data rate wireless communications is often considered synonymous to an Orthogonal Frequency Division Multiplexing (OFDM) system. OFDM is a special case of multi-carrier communication as opposed to a conventional single-carrier system.

The concepts on which OFDM is based are so simple that almost everyone in the wireless community is a technical expert in this...

Minimum Shift Keying (MSK) - A Tutorial

Qasim Chaudhari — Wed, 25 Jan 2017 06:38:24 +0000

Minimum Shift Keying (MSK) is one of the most spectrally efficient modulation schemes available. Due to its constant envelope, it is resilient to non-linear distortion and was therefore chosen as the modulation technique for the GSM cell phone standard.

MSK is a special case of Continuous-Phase Frequency Shift Keying (CPFSK) which is a special case of a general class of modulation schemes...

Some Thoughts on Sampling

Qasim Chaudhari — Tue, 15 Nov 2016 11:48:56 +0000

Some time ago, I came across an interesting problem. In the explanation of sampling process, a representation of impulse sampling shown in Figure 1 below is illustrated in almost every textbook on DSP and communications. The question is: how is it possible that during sampling, the frequency axis gets scaled by $1/T_s$ -- a very large number? For an ADC operating at 10 MHz for example, the...