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.

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.

Now that where to buy has been sorted, and if you have decided to take advantage of the online offers, the next is choosing a plan and a phone that is best for you, a topic dealt with below.

Choosing A Mobile Phone And A Calling Plan:
When you sign a mobile phone contract you are in most cases buying two items, the handset you choose and the network voice and/or data allowance you get with it. The best way to start is to avoid bowing to ’societal’ pressures. Let your personality and needs guide you to choosing the right combination, as any wrong mix will cost you hugely at the long run. Societal pressures may come in the form of a salesman chatting you up on the phone network website, or the one in the stores on commission pushing a particular handset at you. It can also come in the form of a friend, colleague or family member who has a handset model, and with a good intent, feels the same is the best for you.

Results from recent research carried out in the Greater London area of UK show that 79 percent of people polled under-utilize their mobile phones. 82 percent more at some point went over their monthly calling allowance plan and paid out-of-bundle fees as a result. Predominant chain of reasons behind this result was because respondents admit to choosing phones with high functionality – which they rarely used, and got very low calling plans to keep the contracted monthly fees down – a plan which often was never enough. It was therefore almost impossible not to use ‘out-of-bundle’ minutes at some point which eventually end up costing more.

Letting your personality and needs guide your decision requires considering what you do, what and how you communicate, and what phone fits in. There is no need choosing a high speed internet browsing phone with touch screen technology, push email functionality, Satnav, huge GB of memory, etc – you may not need the functions you are paying for, and may compromise on the calling plan you really need to communicate better. Where finance is an issue as with many of us in these troubling economic times, you may be better off with an adequate calling plan that suits how and what you communicate for a monthly fee closest to what you are comfortable to pay today.

Finally, don’t let latest phones be your number one guide. Remember, the latest phones of today won’t be the latest phones 3 months down the line – the technology now changes daily. However, the right and good calling and data plan – like 1000 minutes to be used anytime calling across any mobile network, plus 200 texts with unlimited landline and mobile internet usage – will remain a great deal even up to 24 months down the line.

Contracts To Rebuild Your Credit Rating
If you know you have a poor credit rating and perhaps have been refused by a particular network, do not think you can easily go to the next network and get a contract. In very rare circumstances you may succeed, but while networks are in competition with each other, in most countries they also file in reports of refused applications with credit rating agencies to help alert other networks if a reason of refusal is credit related. I have held conversation with the staff of some mobile phone networks in the UK on this matter and in this circumstance the best the networks can do is extend their services to you, so you can start rebuilding your credit worthiness, but they can only do so where the risk to the network is low

Still using the UK where are based as a case study, all the mobile phone networks here now have short term contracts, some in the form of a one month rolling contract usually SIM only, – no phones involved. With SIM only contracts the network’s risk is limited to the minutes you use and they don’t have to hand you any mobile phone. Some networks may risk signing you up on a 12 or 18 months contract with a phone, so long as the mobile phone set involved is not worth more than £100 – about US$155. An application with high calling plan which enables the phone network to recoup cost of the handset within your first 3 to 6 months on the plan also stand a chance if your credit rating situation is not too poor.

Choosing A Mobile Broadband:
With mobile broadband, it’s quite simple because you are looking at only 3 straightforward issues, coverage, monthly allowance and cost.

Coverage:
Though mobile broadband signals can be received in over 90 percent of UK populated areas at the moment, signal levels vary between the networks. All mobile broadband service providers in the UK have online coverage checker, we strongly advise that you use the online coverage checker of your preferred network before you buy, to check against the signal strength of your preferred network service at your home, office and areas you are likely to use the service

Monthly Allowance:
Depending on how much time you spend online and what you do while on the go. If you intend to use the internet just for emails, and especially if you have a fixed broadband at home, you may go for 1GB monthly allowance, otherwise you are advised not to settle for a 1GB data allowance – it’s rarely enough, even the daily updates of the anti-virus software alone running on your system and other activities rarely under your user control will almost use up your 1GB allowance by the end of the month. A manageable level of data usage will be at least 3GB – an average of 3 hours surfing per day, and the relative cost of the extra 2GB is narrow across all the networks compared to the 1GB monthly cost. Except for mobile broadband contracts with free laptops on offer which generally require a 24 months contract, it is advisable to go for 12 months contract if no laptop offer is included. This is because the sector is very competitive and might yet record lower prices in the near future.

Phone contracts last a long time, and in these days of slow global economic recovery, taking a little more time to research the market and understanding what really matters just before you buy can make a little difference