Nowadays, mobile phone is one of the most essential things of people. It takes much convince for people. The technology of mobile phone is increase rapidly everyday. Form 1^st generation up to now, people want to build up a mobile

1G

1G (First Generation) is the name given to the first generation of mobile telephone networks. These systems used analogue circuit-switched technology, with FDMA (Frequency Division Multiple Access), and worked mainly in the 800-900 MHz frequency bands. The networks had a low traffic capacity, unreliable handover, poor voice quality, and poor security.

1G – First Generation mobile phone networks were the earliest cellular systems to develop, and they relied on a network of distributed transceivers to communicate with the mobile phones. First Generation phones were also analogue, used for voice calls only, and their signals were transmitted by the method of frequency modulation. These systems typically allocated one 25 MHz frequency band for the signals to be sent from the cell base station to the handset, and a second different 25 MHz band for signals being returned from the handset to the base station. These bands were then split into a number of communications channels, each of which would be used by a particular caller.

2G

2G – Second Generation mobile telephone networks were the logical next stage in the development of wireless systems after 1G, and they introduced for the first time a mobile phone system that used purely digital technology. The demands placed on the networks, particularly in the densely populated areas within cities, meant that increasingly sophisticated methods had to be employed to handle the large number of calls, and so avoid the risks of interference and dropped calls at handoffs. Although many of the principles involved in a 1G system also apply to 2G – they both use the same cell structure – there are also differences in the way that the signals are handled, and the 1G network are not capable of providing the more advanced features of the 2G systems, such as caller identity and text messaging.

In GSM 900, for example, two frequency bands of 25 MHz bandwidth are used. The band 890-915 MHz is dedicated to uplink communications from the mobile station to the base station, and the band 935-960 MHz is used for the downlink communications from the base station to the mobile station. Each band is divided into 124 carrier frequencies, spaced 200 kHz apart, in a similar fashion to the FDMA method used in 1G systems. Then, each carrier frequency is further divided using TDMA into eight 577 uS long “time slots”, every one of which represents one communication channel – the total number of possible channels available is therefore 124 x 8, producing a theoretical maximum of 992 simultaneous conversations. In the USA, a different form of TDMA is used in the system known as IS-136 D-AMPS, and there is another US system called IS-95 (CDMAone), which is a spread spectrum code division multiple access (CDMA) system. CDMA is the technique used in 3G systems.

2.5G

2.5G (Second Generation Enhanced) is a generic term used to refer to a standard of wireless mobile telephone networks that lies somewhere between 2G and 3G. The development of 2.5G has been viewed as a stepping-stone towards 3G, which was prompted by the demand for better data services and access to the Internet. In the evolution of mobile communications, each generation provides a higher data rate and additional capabilities, and 2.5G is no exception as it is provides faster services than 2G, but not as fast or as advanced as the newer 3G systems.

Some observers have seen 2.5G as an alternative route to 3G, but this appears to be short-sighted as 2.5G is several times slower than the full 3G service. In technical terms 2.5G extends the capabilities of 2G systems by providing additional features, such as a packet-switched connection (GPRS) in the TDMA-based GSM system, and enhanced data rates (HSCSD and EDGE).

These enhancements in 2.5G systems permit data speeds of 64-144 kbps, which enables these phones to feature web browsing, the use of navigation and navigational maps, voice mail, fax, and the sending and receiving of large email messages.

3G

3G – Third Generation mobile telephone networks are the latest stage in the development of wireless communications technology. Significant features of 3G systems are that they support much higher data transmission rates and offer increased capacity, which makes them suitable for high-speed data applications as well as for the traditional voice calls. In fact, 3G systems are designed to process data, and since voice signals are converted to digital data, these results in speech being dealt with in much the same way as any other form of data. Third Generation systems use packet-switching technology, which is more efficient and faster than the traditional circuit-switched systems, but they do require a somewhat different infrastructure to the 2G systems.

Compared to earlier mobile phones a 3G handset provides many new features, and the possibilities for new services are almost limitless, including many popular applications such as TV streaming, multimedia, videoconferencing, Web browsing, e-mail, paging, fax, and navigational maps.

Japan was the first country to introduce a 3G system, which was largely because the Japanese PDC networks were under severe pressure from the vast appetite in Japan for digital mobile phones. Unlike the GSM systems, which developed various ways to deal with demand for improved services, Japan had no 2.5G enhancement stage to bridge the gap between 2G and 3G, and so the move into the new standard was seen as a solution to their capacity problems.

It is generally accepted that CDMA is a superior transmission technology, when it is compared to the old techniques used in GSM/TDMA. WCDMA systems make more efficient use of the available spectrum, because the CDMA technique enables all base stations to use the same frequency. In the WCDMA system, the data is split into separate packets, which are then transmitted using packet switching technology, and the packets are reassembled in the correct sequence at the receiver end by using the code that is sent with each packet. WCDMA has a potential problem, caused by the fact that, as more users simultaneously communicate with a base station, then a phenomenon known as “cell breathing” can occur. This effect means that the users will compete for the finite power of the base station’s transmitter, which can reduce the cell’s range – W-CDMA and cdma2000 have been designed to alleviate this problem.

The operating frequencies of many 3G systems will typically use parts of the radio spectrum in the region of approximately 2GHz (the IMT-2000 core band), which were not available to operators of 2G systems, and so are away from the crowded frequency bands currently being used for 2G and 2.5G networks. UMTS systems are designed to provide a range of data rates, depending on the user’s circumstances, providing up to 144 kbps for moving vehicles (macrocellular environments), up to 384 kbps for pedestrians (microcellular environments) and up to 2 Mbps for indoor or stationary users (picocellular environments). In contrast, the data rates supported by the basic 2G networks were only 9.6 kbps, such as in GSM, which was inadequate to provide any sophisticated digital services.

4G

As the limitation of the 3G, people are try to make new generation of mobile communication, this is the 4^th generation. This 4G system is more reliable,

Nowadays, some companies have started developing the 4G communication system, this technology can have a high uplink rate up to 200Mbps, and more data can transfer in the mobile phone. So the 4G mobile can have more function such as work as the television. Some telecommunication companies claimed that they would apply this 4G system to the business and it will bring more convenience to people.

In the last decade the cell phone industry has grown thousand fold all around the world. A cell phone is somewhat necessary for an individual to keep up with the busy life of the current era. A few years back, a cell phone was not considered a necessity; it was just a luxury that was being enjoyed by only a small number of individuals. But nowadays, life without a cell phone seems impossible. People all around the world are addicted to the use of a cell phone. This is mainly because the cell phone is no longer just a cell phone; it has evolved into many things like a personal digital assistant (pda), music player, a global positioning system (gps) and a lot more. Everyday different manufacturers around the world are introducing the models with the new features. This is what needs to be taken into consideration when you go for buying a cell phone. You need to be sure about the features you want that suit your lifestyle well.

The Money Matter

Nowadays there is so much choice for an individual to buy a cell phone. Every company is producing the models with state of the art technology and features everyday. Price is the main thing that makes a difference in these different models. An expensive phone is likely to have more features, reliability and a better technology than a cheap one. Everyone wants a best phone in the market for him but high price of the cell phones comes in the way therefore price is a big thing that needs to be kept in mind while buying a cellular phone. But expensive and sophisticated phones are not everyone’s choice; there are people who just want a simple cell phone which is not much expensive but does its job well only as a cell phone. Also the extra features provided in the expensive phones are not everyone’s need.
Therefore the price is a main thing to keep in mind whenever you to buy a cell phone. Do not buy a cell phone just because it is expensive; buy the one that suits your needs.

Choices in Different Vendors and their Models

Lucky for the customers that nowadays there are a huge number of cell phone manufacturers who have a vast number of models for customers to choose from. Every vendor holds certain advantages that the other lacks in. This creates a great competition which is very healthy for the cell phone industry. Also this competition results in the reduction of the price which is beneficial for the end user.
Some people have liking for a certain brand but they still have a lot of choice in the models offered by the same brand. Every other day a new model is launched by a company, this is a strategy of companies to keep a customer stick to their brand and attract more.

Research is Always Better

It is always better to research about the phone you are going to buy before you set out to actually buy it. There are number of ways to know about that phone, the best one is internet. You can read the product reviews on the internet for that phone and know if there are any issues with it. You can also know the people’s view about the certain features offered by that particular device on internet. Also try to read the review by some critic about that phone; it will further clarify its view in your mind.
Hence it is to be said that in order to get the desired satisfaction, the above things should be kept in mind before buying a cell phone.

When considering purchasing a phone card one of the things to consider is the total cost per minute. Are there any other fees in addition to the rate per minute quoted? If there are, what are they and how much are they adding to the usage rate? Unusually low per minute rates are usually offset in some way by other charges. You want to be aware of this.

There may be times when people want to buy a phone card for just a few weeks usage. They may be going on an overseas vacation or a cruise where the convenience of a phone card is desired. They will be able to find a phone card for this purpose. Shop around for the best rates and overall deals. They can check with their own carrier or they can look on the internet at all of the different companies and plans. People can also buy a pre-paid cellular phone for use when they travel. The phone only works with the pre-paid phone card. The units on the phone card begin at thirty minutes and go up, depending on the number you want to buy. When the number of minutes is expired, the phone stops working. If the user wants to keep using the cellular phone, he has to purchase another phone card or more minutes for the existing phone card. The pre-paid cellular phone will not function without pre-paid minutes.

Phone cards make both domestic and international calls easier for people when they cannot use their own phone. They don’t have to pay other people for the use of their private phones because they aren’t incurring charges on them. They dial the phone card number, give their pin number and the phone number they want to call, whether it is domestic or international. The phone call is already paid for.

First do this little test to see if you have noise on the phone line. Get a regular phone, unplug your modem and plug in the phone. It is important to use that line to make sure you test the phone line leading to your computer. Pick up the receiver, dial “1″ and then listen. It should be absolutely silent. If you hear noise, you know there is a problem. Make sure the phone you use for that does not make noise itself!

Next, go outside and find your phone line box. You should be able to plug your phone directly into that box. This will let you do the same test directly on the phone line before it enters your house. If you do not have any noise on that, you know the problem is your inside wiring. In that case you can either redo the wiring yourself or pay someone else to do it. Some phone companies offer a wiring plan where you pay a few bucks a month, but in exchange the phone company will do and pay for all inside wiring work. Make sure to ask about all details before signing up for that! Especially ask about any waiting period before you can use that service or any long-term commitments that might come with that. Know exactly what you have to pay, for how long you have to pay and what you get for that.

If you also hear noise on the outside phone box, chances are you really have noise on your phone line. Be sure to test your phone at a friend’s place! If you call the phone company and it turns out your phone is causing the noise, you might be charged a hefty service charge. If your phone is silent at your friend’s place you can be absolutely sure that there is in fact noise on the phone line coming from the phone company before it enters your house.

Now, when you call the phone company and report noise on the phone line, do not mention anything about your Internet Access! Your phone company will blame your ISP and tell you to contact your Internet Service Provider. Instead, say that you have noise while making phone calls. If you have noise on the phone line while making phone calls, the phone company is required by law to check your phone line. They are not required to trouble shoot your Internet Connection! That is why you should not mention the Internet at all, even if your phone company is also your ISP!

Your phone company will then either send a technician or they will just do tests and let you know what they find. Try to be home when the technician comes to your house. Talking to the local technician will be more helpful that talking to some phone operator. Remember to be nice and friendly to your local technician! They will be the ones fixing things! In many cases this has helped people to get rid of noise in their phone line.