In wireless communication, the magnitudes of certain parameters such as power and voltage vary over several orders- for example; the received signal power level in mobile communications can vary between tenths of a milli-watt to about a few hundred of a milli-watt. For certain wireless communication systems, the received power can vary between a few tens of a watt up to few tenths of a microwatt! This is due to the wireless channel conditions in the form of noise, fading and so on.The following equations represent the voltage and power gains with reference to 1 V and 1 W respectively.$$Voltage\:gain(dBV)=20log_{10}(\frac{Voltage\:Value}{1V})$$$$Power\:gain(dBV)=10log_{10}(\frac{Power\:Value}{1W})$$Since ... Read More

dBW, dBV, dBmW, dBµW, dBmV and dBµVLet us see some commonly used decibel based representation units in wireless communications. The difference between these entities lies in the type of ratio and the reference levels of the quantities. We can have power ratio, voltage ratio, current ratio, and so on. Reference levels can be 1 W, 1 V, 1 mW (milli-watt), 1 mV (milli-volt), 1 µW (microwatt), 1 µV (microvolt), and so on.Voltage based dB representation unitsThe ratio of two voltages will be mapped on to the decibel scale. Often, one of the two quantities of the ratio is a reference ... Read More

Valid and Invalid Operations on dBSome of the valid operations that can be performed with ‘dB' is discussed in this article. When we add ‘dB’ to a quantity, we are increasing its value and when we are subtracting ‘dB’ from a quantity, we are reducing its value.We can add ‘dB’ to ‘dBm’ but not ‘dBm’ to ‘dBm’.37 dBW + 3 dB gives 40 dBW. However, 37 dBm + 37 dBm doesn’t yield 74 dBm. This is an invalid operation.$$37\:dBm=10log_{10}(\frac{P_{out}}{1mW})$$$$log_{10}(\frac{P_{out}}{1mW})=3.7;\:P_{out}\sim\:10^{3.7}mW\sim\:5W$$Also, 74 dBm ≈ 25 MW. When we add 37 dBm to 37 dBm, all we get is around 10 kW, which ... Read More

Introduction to dB OperationsThe ‘decibel’ is a form of representing ratios on a logarithmic scale instead of linear scale. They are used across several disciplines of STEM. In this article, we will see how to perform calculations using decibels with examples pertaining to electrical engineering. We know that the ‘decibel’ represents the ratio of two quantities on the logarithmic scale. While comparing two quantities, one of them will be considered as a reference. This article discusses the basic operations that could be performed on decibels with some examples.Basic operations based on logarithmsLogarithmic MultiplicationThe logarithm of the product of two numbers ... Read More

What are the applications of decibel (dB) representations?For convenient representation of data for analysis, the decibel representation is used for various parameters such as amplifier gain, return loss, path loss, signal-to-noise ratio (SNR) and so on. Some of such representations are presented here.Quantity in decibel (dB) = log10(Compared Quantity)/(Reference Quantity)Amplifier GainRF (Radio Frequency) power amplifier gains are also usually expressed in ‘dB’. It is a practice to arrange amplifiers in series to achieve high gain at the output. This form of arrangement is called cascading. In a cascaded amplifier system, the output of one amplifier is fed as input to ... Read More

1. What is dB Representation?‘Decibel’ is a very common representation used across several disciplines of STEM (Science, Technology, Engineering and Mathematics). An electronic engineering student might have never missed coming across the terms‘amplifier gain’, signal-tonoise ratio’, ‘antenna gain’, ‘return loss’, ‘path loss, and so on. One thing common in all of them is that they are all expressed in ‘decibels’(dB). The decibel representation (dB) is to express magnitudes that vary over large range of levels, in a single plot.2. What is the Definition of decibel (dB)?The dB representation maps the ratio of two comparable quantities in the linear scale onto ... Read More

Latency is common in both wired and wireless systems. It is a quality of service (QoS) parameter – it acts as one of the performances determining factors of the wired or wireless communication link of interest. Different applications require different levels of latency. In simpler terms, latency refers to how quick the data is transferred from the source (or the sender) to the destination (or the receiver). Latency takes the unit of time. Link speeds are often specified in milliseconds (ms), microseconds (µs), nanoseconds (ns) and so on.Latency Is a Quality-of-Service ParameterNumeric example of latencyLet us look into an example ... Read More

Overview of Modulation in Wireless CommunicationsLike bidding in auction, telecom service providers also auction frequency bands. Huge investments are made while bidding even smaller bands- say a few megahertz. Bands in the very basic sense mean the 'air' around us. Air is a wireless ‘channel’/ ‘transmission medium’ that carries our data confined the electric and magnetic fields of the electromagnetic waves.Therefore, bands mean the frequency ranges over which each service provider renders services to its subscribers. Since a huge amount of money is invested, effective utilization needs to be ensured. Technically, we need to use 'effective modulation techniques' for this ... Read More

Definition of spectrumSpectrum refers to the entire range of frequencies right from the starting frequency (the lowest frequency) to the ending frequency (the highest frequency). Spectrum basically refers to the entire group of frequencies.Example of spectrum- Electromagnetic SpectrumThe electromagnetic spectrum is one good example. The electromagnetic (EM) spectrum covers frequencies right from zero (DC) to gamma band frequencies. This spectrum includes the human voice frequency band (audio band), ISM (Industrial Scientific Medical) band and optical frequency bands.Numeric example- Microwave radiation spectrumMicrowave radiations span in frequency from 300 MHz to 300 GHz. What is the spectrum of microwave radiation?Spectrum refers to ... Read More

A wireless communication link is specified or characterized in terms of some performance metrics. We call these performance metrics as 'Quality of Service' (QoS) metrics or parameters. Some of the major QoS parameters include bandwidth, throughput, jitter, latency and bit error rate.Bandwidth and Throughput – Key TermsBandwidth is a popular term used in the context of both networking and communications. In networking, the bandwidth is specified using bps (bits per second), kbps (kilobits per second), Mbps (Megabits per second) and so on.In communications, bandwidth is measured in the unit kHz (kilo Hertz), MHz (Mega Hertz), GHz (Giga Hertz) and so ... Read More