2G TECHNOLOGY

I. HISTORY OF 2G TECHNOLOGY

It would be heedless to say that we haven’t come a long way as far as mobile technology is concerned. The first cell phones could barely keep a call connected let alone send a text message and now we are streaming content across the wireless spectrum while cruising the web and talking to friends. A long way indeed. Where does it go from here and will the wireless spectrum stand up to the test? We will soon find out.

2G RISES TO THE CHALLENGE

2G, first introduced in 1992, is the second-generation of cellular telephone technology and the first to use digital encryption of conversations. 2G networks were the first to offer data services and SMS text messaging, but their data transfer rates are lower than those of their successors.

When smart phones were first introduced, there was no texting as well as undoubtedly horrible connections. Then came 2G or 2nd Generation networks as well as by having them came the capability to transfer and get information, although the velocities were actually sluggish - 9.6 kb|s - slower than the old, screechy, modems that we used to utilize in the early days of the Internet. Slowly technological innovation strengthened and information rates were raised, by having the latter types of 2G getting to speeds of about 56kb|s and we thought that was fast!

II. HOW 2G NETWORK DOES OPERATES?

2G networks were based on narrow band digital networks. Signals were transmitted in the digital format and this dramatically improved the quality of calls and also reduced the complexity of data transmission. The other advantage of the 2G network came in the form of Semi Global Roaming System, which enabled the connectivity all over the world.

2G (or 2-G) is short for second-generation wireless telephone technology. Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland by Radiolinja (now part of Elisa Oyj) in 1991.[1] Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted; 2G systems were significantly more efficient on the spectrum allowing for far greater mobile phone penetration levels; and 2G introduced data services for mobile, starting with SMS text messages. 2G

technologies enabled the various mobile phone networks to provide the services such as text messages, picture messages and MMS (multi-media messages). All text messages sent over 2G are digitally encrypted, allowing for the transfer of data in such a way that only the intended receiver can receive and read it.

After 2G was launched, the previous mobile telephone systems were retrospectively dubbed 1G. While radio signals on 1G networks are analog, radio signals on 2G networks are digital. Both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.

2G has been superseded by newer technologies such as 2.5G, 2.75G, 3G, and 4G; however, 2G networks are still used in many parts of the world.

III. CAPACITIES OF 2G NETWORK

Using digital signals between the handsets and the towers increases system capacity in two key ways:

Digital voice data can be compressed and multiplexed much more effectively than analog voice encodings through the use of various codecs, allowing more calls to be transmitted in same amount of radio bandwidth.

The digital systems were designed to emit less radio power from the handsets. This meant that cells had to be smaller, so more cells had to be placed in the same amount of space. This was possible because cell towers and related equipment had become less expensive.

2G Data Transmission Capacity:

With GPRS (General Packet Radio Service), you have a theoretical transfer speed of max. 50 kbit/s (40 kbit/s in practice).

With EDGE (Enhanced Data Rates for GSM Evolution), you have a theoretical transfer speed of max. 1 Mbit/s (500 kbit/s in practice).

IV. 2G TECHNOLOGIES and FREQUENCIES USED

There are three different types of technologies in the second generation these are FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access). All types have one common feature of multiple access which means that

many users are able to use the same number of cells. First part of all the technologies makes difference.

Because of different types of technologies utilizes in 2G mobiles, there are different types of mobiles according to the technology incorporate in them. Let see the 2G technologies use in mobiles and their functions as they work.

A. HOW 2G (FDMA) OPERATES?

Frequency Division Multiple Access (FDMA) enables the calls to use different frequency by splitting it into small cells. Each call uses different frequency. The phenomenon is same as in radio where different channels broadcast on separate frequency. So every radio station has been assigned different frequency according to the specific band available. FDMA is best in case of analog transmission but also support digital transmission. No doubt it is accommodating to the digital signals yet with poor service.

B. HOW 2G (TDMA) WORKS?

Different technologies are categorized in second generation’s TDMA standard according to the different time zones indifferent countries in the world. These technologies are

GSM  (Global System for Mobile Communication) nearly used in the whole world.

IDEN (Integrated Digital Enhanced Network) is introduced by Motorola used in US and Canada.

IS-136 (Interim Standard-136) also known as D-AMPS (Digital Advanced Mobile Phone System) prevail in South and North America.

PDC (Personal Digital Cellular) is used in Japan.

TDMA is a narrow band of 30 KHz wide and 6.7 millisecond long. It is divided into three slots of time. Using the CODEC, stands for Compression / Decompression algorithm, compresses the digital information and use less space leaving for the other users. Division of this narrow band into three time slots increases the capacity of frequency band. TDMA supports both frequency bands IS-54 and IS-136. GSM (TDMA) is a different standard and provide basis for IDEN and PCS. Being an international standard, it covers many countries of the world. There is only the need for changing the SIM and you can get connected no need to buy a new phone. Having two different bands

900-1800 MHz band covers Europe and Asia

850-1900 MHz band covers United State   

First band is in sync widely but second is limited to the United State. It is better to go for the first one if you need to go on extensive travelling.

C. HOW 2G (CDMA) WORKS?

Contrary to TDMA, CDMA works in a singular way. Like TDMA, It also converts the information into digital data and sends it. Now the information is extended upon the bandwidth. Incoming calls are spread over the surface of the channel and a code is allocated to them. As the data is spread over the surface of channel it is known as spread spectrum. It compresses the data into small packets and sends it to a separate frequency columns.

Every caller sends out data to a similar spectrum. Every caller’s signals are spread over the channel having a unique code. Reaching at the receiving point, codes are to be matched and hence data delivers. CDMA refers to the GPS standard for marking the time stamp on the broadcast signals. CDMA supports Interim Standard (IS-95) and operational at the frequency bands of 800 MHz and 1900 MHz.

a. CDMA CALL FLOW

CDMA networks increase bandwidth by spreading code, and the codes are specific to each user. This means that many users can

share the same frequency at the same time. Code spreading is accomplished through the use of PN (pseudo-noise) codes, pseudo-random numbers that will sum to zero over time.

The PN code modulates the pilot channel, the first channel a mobile device will acquire when it detects a CDMA network. Once it has acquired the pilot channel, the device identifies a specific carrier’s network and synchronizes its timing.

When initiating a call or data session, the device sends a signal first to the base station. In CDMA2000, the device initiates the session as either a voice session, a packet data session, or both.

D. AVAILABILITY OF INTERNATIONAL EMERGENCY NUMBERS

Another use of this technology is the availability of international emergency numbers, which can be used by international users anytime without having to know the local emergency numbers. PDC or personal digital cellular technology was developed in Japan, and is exclusively used in JAPAN as well. PDC uses 25 KHz frequency. Docomo launched its first digital service of PDC in 1993.integrated digital enhanced network (iDEN) was developed by MOTOROLA, as a major mobile technology. It enabled the mobile users to make use of complex trunked radio and mobile phones. iDEN has a frequency of about 25Khz.i DEN allows three or six user per mobile channel.iS-136 is a second generation cellular phone system. It is also known as digital AMPS. D-AMPS were widely popular in America and Canada. However now it is in the declining phase. This technology is facing a strong competition by GSM technologies.  Now the network carriers have adopted GSM and other CDMA 2000 technologies at large. Interim standard 95 is a first and the foremost CDMA cellular technology. It is most famous by its brand name known as cdmaOne. It makes use of the CDMA to transfer the voice signals and data signals from cellular phones to cell sites (cell sites is cellular network).

V. GSM (GLOBAL SYSTEM FOR MOBILE COMMUNICATION)

GSM or global system for mobile communication is a digital cellular system. It was originated in Finland Europe .however now it is throughout

the world. GSM (Global System for Mobile Communication) accounts for 80% of total mobile phone technologies market. There are over more than 3 billion users of GSM (Global System for Mobile Communication) now. GSM technology got its popularity, when people used it to talk to their friends and relatives. The use of GSM (Global System for Mobile Communication) is possible due to the SIM (subscribers identity module) GSM (Global System for Mobile Communication) is easy to use, affordable and helps you carry your cell phone everywhere. GSM (Global System for Mobile Communication) is a 2G technology. There are many frequency ranges for GSM (Global System for Mobile Communication) however 2G is the most used frequency. GSM (Global System for Mobile Communication) offers moderate security. It allows for encryption between the end user and the service base station. The use of various forms of cryptographic modules is part of GSM technology.

A. APPLICATION OF GSM (GLOBAL SYSTEM FOR MOBILE COMMUNICATION)

Mobile phones connect to the GSM (Global System for Mobile Communication) by locating the cells in the network surroundings. These cells are of five different sizes. These cells include macro, micro, femto, umbrella and Pico cells. Macro cells are the largest cells that cover radio signals. Macro cells are distributed over larger geographical areas. Micro cells cover a small geographical are such as hotels. These cells are supported by powerful cellular stations or in other words tower. Pico cell is a wireless communication scheme. Pico cells also cover a small geographical area. Femto cell is a small base station designed to cater the needs of minor business area. It is connected using DSL technology. Various GSM applications include GSM (Global System for Mobile Communication) modems, GSM terminals, GPRS amalgamation, GSM security, GSM remote monitoring. Application of GSM (Global System for Mobile Communication) is dependent upon its frequency. Some countries in the world use GSM-900 or E-GSM. The frequency in E-GSM is extended to about 920 to 960MHZ.latest mobile phones support E-GSM.GSM technology allows you to use any mobile handset and everywhere. Once you’re connected to the GSM technology you do not have to worry about the network coverage and frequency. GSM technology enables you to use your mobile phone with any connection in more than 212 countries of the world without switching to other network. Your existing GSM has the tendency to connect with the available frequency. All 2G and 3G cell phones have GSM in them. So while you’re traveling you can replace your SIM (Subscriber Identity Module) and still remain connected to the GSM (Global System for Mobile Communication). this 2G mobile technology has

brought a revolution to the mobile technologies. GSM (Global System for Mobile Communication) has provided the base for many advanced 3G technologies like EDGE and UMTS. Thus it is GSM (Global System for Mobile Communication) which has provided us with international roaming and clarity of voice due to its wide infrastructure.

B. GSM CALL FLOW

A GSM mobile phone uses a Random Access Channel (RACH) to request a dedicated channel from the base station. The base station responds with a Radio Resource Assignment on the Access Grant Channel (AGCH).

Then the device sends a service request to the base station on the Stand Alone Dedicated Control Channel. But the base station will not grant service until the device authenticates itself, so it sends an authentication request to the user’s SIM card in the form of a random 128-bit number (RAND). The mobile device uses the RAND to generate a 32-bit number, called the Signed Response. Once the base station gets this response, the user is authenticated.

Then the device sends to the base station the ISDN (integrated service digital network) number of the phone that it is trying to call, and the base station assigns a traffic channel. The base station then sends the call to the mobile switching center (MSC) via the base station controller (BSC).

The mobile switching center (MSC) sends an initial address message to the network via the GSMC (Global System for Telecommunication), and the call is routed to the correct switching center, often via the landline network. The network generates an address complete message (ACM) when the correct switching center is found. When the MSC receives this message it alerts the base station, which in turn alerts the mobile phone of the caller to generate a ringing sound in the earpiece. If the called party answers, the MSC alerts the caller’s mobile device to transmit voice on the assigned traffic channel

VI. ADVANTAGES AND DISADVANTAGES OF 2G NETWORK

A. ADVANTAGES OF 2G TECHNOLOGY

While digital calls tend to be free of static and background noise, the lossy compression they use reduces their quality, meaning that the range of sound that they convey is reduced. Talking on a digital cell phone, a caller hears less of the tonality of someone's voice.

Digital signals require consume less battery power, so it helps mobile batteries to last long. Digital coding improves the voice clarity and reduces noise in the line. Digital signals are considered environment friendly. The use of digital data service assists mobile network operators to introduce short message service over the cellular phones. Digital encryption has provided secrecy and safety to the data and voice calls. The use of 2G technology requires strong digital signals to help mobile phones work. If there is no network coverage in any specific area, digital signals would be weak.

B. DISADVANTAGES OF 2G TECHNOLOGY

`In less populous areas, the weaker digital signal transmitted by a cellular phone may not be sufficient to reach a cell tower. This tends to be a particular problem on 2G systems deployed on higher frequencies, but is mostly not a problem on 2G systems deployed on lower frequencies. National regulations differ greatly among countries which dictate where 2G can be deployed.

Analog has a smooth decay curve, but digital has a jagged steppy one. This can be both an advantage and a disadvantage. Under good conditions, digital will sound better. Under slightly worse conditions, analog will experience static, while digital has occasional dropouts. As conditions worsen, though, digital will start to completely fail, by dropping calls or being unintelligible, while analog slowly gets worse, generally holding a call longer and allowing at least some of the audio transmitted to be understood.

VII. Evolution of 2G Technology

2G networks were built mainly for voice services and slow data transmission (defined in IMT-2000 specification documents), but are considered by the general public to be 2.5G or 2.75G services because they are several times slower than present-day 3G service.

2.5G (GPRS)

2.5G ("second and a half generation") is used to describe 2G-systems that have implemented a packet-switched domain in addition to the circuit-switched domain. It does not necessarily provide faster services because bundling of timeslots is used for circuit-switched data services (HSCSD) as well. The first major step in the evolution of GSM networks to 3G occurred with the introduction of General Packet Radio Service (GPRS). CDMA2000 networks similarly evolved through the introduction of 2.5G

2.75G (EDGE)

GPRS networks evolved to EDGE networks with the introduction of 8PSK encoding. Enhanced Data rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE was deployed on GSM networks beginning in 2003—initially by AT&T in the United States.

EDGE is standardized by 3GPP as part of the GSM family and it is an upgrade that provides a potential three-fold increase in capacity of GSM/GPRS networks. The 2G digital service provided very useful features, such as caller ID, call forwarding and short messaging.

Pamantasan ng Lungsod ng Maynila

(University of the City of Manila)

Intramuros, Manila

College of Engineering and Technology

Computer Engineering Department

Principles of Communication

2G TECHNOLOGY

Submitted by:

YAMSON, Eirry Rose Anne R.

BS CpE 4

2012-10707

Submitted to:

Engr. Wencie Nidea

September 19, 2015

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