Mobile Telephony: 1G, 2G, 3G, 4G and 5G basics

The name Cellular Phone is derived from the partition of a Geographic Region into smaller areas which are called “Cells”. The Voice and data exchanged between the Mobile terminal and phone / internet is transmitted via the Mobile Network which consists of Cellular Operator’s radio access network and core network.

One of the most popular and common application of the radio waves is in the area of mobile telephony. Today, the mobile telephony uses the cellular radio service but in older times the mobile telephone service consisted of bulky mobile telephone radio units. These two way radio units were able to communicate with each other via a single antenna in a particular area. At that time, these radio signals used to interfere with each other and the limit was thus very limited. The service was unreliable and costly.

Development of 1G, 2G and 3G

The development of 1G mobile phones took place in late 1970s. The 1G mobile devices sent only the “analogue voice information” via amplitude modulation (AM), which varies the amplitude of the carrier signal, and frequency modulation (FM), which changes the Frequency of the career signal. In electronics, the analog signal devices were followed by Analog to Digital convertors.

The most important 1G system were

• Advanced Mobile Phone System (AMPS)
• Nordic Mobile Telephone (NMT)
• Total Access Telephone System (TACS).

The devices of the 1G included the Cordless Phone, Paging Systems, Private Mobile Radio, Some primitive mobile systems as mentioned above.

2G

The 2G phase began in the 1990s and much of this technology is still in use. The 2G cell phone features digital voice encoding. Examples include CDMA and GSM. Since its inception, 2G technologies have steadily improved, with increased bandwidth, packet routing, and the introduction of multimedia.

• GSM is most popular standard for mobile telephony systems spread in more than 200 countries / territories. GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity.

The worldwide presence of GSM means that  subscribers can use their phones throughout the world, enabled by international roaming arrangements between mobile network operators.

• GSM networks operate in a number of different carrier frequency ranges and most 2G GSM networks operate in the 900 MHz or 1800 MHz bands.

GSM provides the voice and limited data services and uses the digital modulation for improved audio quality. So this was the beginning of the SMS. The rate was 10 Kbps/user.

2.5G

The GPS was succeeded with GPRS i.e. General Packet Radio Service. This is called 2.5G. This enhanced the data transmission capacity of the GSM and added the packet switched capabilities to the existing mobile telephony. So now the systems were able to send emails and Graphics rich data as a higher speed. 2.5 G or GPRS set the preparatory stage for the 3G

• Applications in 2.5 G are : Digital voice and limited data

3G Technology

3G, 4G and 5 G are the generic names for a set of mobile technologies. These use a host of high-tech infrastructure networks, handsets, base stations, switches and other equipment to allow mobile phones to offer broadband wireless Internet access, data, video, live TV and CD-quality music services. The 3G wireless networks use technologies such as General Packet Radio Service (GPRS); Enhanced Data Rates for Global Evolution (EDGE); UMTS Wideband CDMA (WCDMA) and High Speed Downlink Packet Access. The 3G technology is capable of transferring data at theoretical top speed of just 7.2Mbps.

4G Technology

4G is the short term for fourth-generation; it is a wireless data transmission network. The data transfer speeds here are four time that of 3G making IPTV and interactive gaming a reality on mobile phones. All this will make the mobile phone much like a digital Swiss Knife: a single wireless device for all our needs.  The technology uses Carriers that use orthogonal frequency-division multiplexing (OFDM) instead of time division multiple access (TDMA) or code division multiple access (CDMA).

5G Technology

The term 5G is not used officially and is used in some research papers and projects to denote the next major phase of mobile telecommunications standards beyond the 4G/IMT Advanced standards. Some of the features are lower battery consumption, lower outage probability, better coverage, high bit rates in larger portions of the coverage area, cheaper or no traffic fees due to low infrastructure deployment costs, or higher aggregate capacity for many simultaneous users. Some important other concepts of technology are Cognitive Radio Technology and the WWWW. These two have been discussed here:

WWWW

World Wide Wireless Web (WWWW), is the comprehensive wireless-based web applications that include full multimedia capability beyond 4G speeds and comes under 5G development.

Cognitive Radio Technology

Cognitive Radio Technology or “Smart Radio” or “Intelligent Radio” is a radio that can sense, learn and adapt to the surrounding environment according to its inner and outer stimuli. A primary feature of cognitive radios is the ability to adapt the transmission parameters given a dynamic wireless environment. Please note that Cognitive Radio Technology is based upon the core principles of “Software Defined Radio (SDR)”.

How does it work?

As we know that Electromagnetic Spectrum , particularly the Radio Frequency portion of this Spectrum has become the most valuable natural resource in recent times. So, there is a concern about the efficient use of the spectrum. The answer is Cognitive Radio. It can intelligently detect whether any portion of the spectrum is in use or not, and can temporarily latch into or out of it without interfering with the transmissions of other users thereby efficiently utilizing spectrum.

Thus the main objective of the Cognitive Radio is to “efficiently utilize the spectrum”.

Does GSM allow signals when we travel in aeroplane?

We should not that territory covered with GSM network is divided into hexagonal cells. The covering diameter of each hexagonal cell may be from 400 m up to 50 km, which consists of base station that provides communication-receive and transmission, and antennae. All GSM cellular communication telephone cells are performed via these antennae and stations, which are regulated by switching centre. Switching centre provides communication between city telephone network, base stations and other cellular communication operators. Every time you switch on your cell phone, the communication is performed with the nearest base station. Hence it is also possible to receive signals on cell phone while travelling in an aeroplane, provided the base station range allows.

Cell phone use during flights is still banned by regulations because it disrupts cell service on the ground and has the potential to interfere with an airplane’s navigation and communication instruments.

Advantages and Disadvantages of CDMA

The CDMA Phones don’t have SIM cards. The CDMA phones have phone numbers programmed in the handset just as numbers are programmed in SIM cards by the operator. The latest phones have both options. Since all CDMA phones are network locked, there is no necessity for the SIM card provision. As GSM phones are compatible with any operator, who provides the SIM card which enables connectivity to the network. This makes the phone independent of the operator.

A major difference between the CDMA and GSM networks is the handset. In CDMA, the handsets are provided by the operator and they work only on one network unlike in GSM systems.

One of the major advantages of CDMA is “Soft Handoff’. A handoff occurs in any cellular network where a call switches from one -cell site to another as a person travels: In other technologies this handoff occurs when the network informs the phone of the new channel to which it must switch. The phone then stops receiving and transmitting on the old channel and it commences transmitting and receiving on the new channel. This is known as a “Hard Handoff’. In CDMA, however, every site is on the same frequency. In order to begin listening to a new site, the phone only needs to change the pseudo-random sequence it uses to decode the desired data from the jumble of bits sent for everyone else. While a call is in progress the network chooses two or more alternate sites that it feels are handoff candidates. It simultaneously broadcasts a copy of the call on each of these sites. The phone can then pick and choose between the different sources for the call, and move between them whenever it feels like it. It can even combine the data received from two or more different sites to ease the transition from one to the other.

This puts the phone in almost complete control of the handoff process. Such an arrangement should ensure that there is always a new site ready to take over the call at a moment’s notice.

CDMA has a very high “spectral efficiency”. It can accommodate more users per MHz of bandwidth than any other technology.