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Top1. Introduction
When telephone was invented, people were thrilled to know that it was possible to verbally communicate with near and dear ones over long distances. Telephone services were widespread across the world through a technology which is later termed as circuit switching networks. The speaker and the listener were connected through a pair of two wires. For extending the distance of connection modulation was used. This arrangement was found to be convenient for a very long time from the beginning of 20th century. However, people felt some amount of mobility would be better. Limited mobility was provided through wireless extension handsets. Soon the requirement for more mobility was sensed. Different generations of mobile communication standards are developed over the years.
With the pace of development, the telephone which was mainly used for voice communication has now found many more uses than just voice communication. Smartphones are currently in use by billions of people all over the globe. The uses of Smartphones are mind boggling. For many, Smartphones constitute the hand held computer. It can be used for the age-old voice communication as the basic service. Additionally, it can be used for recording photos / videos and transmitting them from any corner of the world to any other place. It can be used to browse the Internet for any information and down load any content from anywhere. Currently 4G and 5G technologies are in the forefront being used by many customers. The data being exchanged through Smartphones is phenomenal. As per the estimates offered by Ericsson, the data traffic through Smartphones is 51 Exabites (EB) per month by the end of 2020 and is expected to grow exponentially to 220 EB per month by the year 2026.
Though 4 G and 5 G services are on offer for some time now, the ready upgrade from 3G has not taken place. There is some hesitancy shown by some customers to switch to higher generation services. As on 2016, it is reported (Opensignal, 2016) that in many countries sizable number of customers is not enthusiastic to switch over from 3G due to costs involved in changeover. However, due to requirements from different users who still use 2G or 3G and with the service providers having to offer 4G and 5G services to their customers, it becomes necessary for service providers to offer 3G, 4G and 5G services to their customers.
There are cellular phones that work on different frequency bands. GSM is the popular mode of operation for cellular phones and GSM operates in four possible bands, namely, 800, 900, 1800 and 1900 MHz bands. Some mobile phones operate in all these bands of frequencies. With multitude of Smartphones and the different services being offered in 3G, 4G and 5G networks, the data transfer is taking place at a phenomenal rate. The data transfer grows day by day due to the use of social networks such as Whatsapp, Facebook etc. To cater to the ever growing needs of the users, the service providers are expanding the networks exponentially. However, there is a Shannon limit that defines the maximum data rate through the medium. Another major limitation of cellular phones is the limited battery life. So, for better communication and with longer distance between the base station and the mobile phone it will not be possible to increase the transmitting power from the mobile phone beyond certain limits. Channel coding is an option to trade off between power and bandwidth in digital communication systems. That is, channel coding increases bandwidth but helps the receiver to detect errors due to weak received signals and correct them.