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.

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.

Looking back into the initial stages of development the availability of low-cost, low-power CMOS imaging modules helped to charge up the popular craze camera enabled cell phones in today’s world that primitively began in Japan. That proved to be contagious for the rest of the world. From young students to even busy business people avidly annals photos of colleagues and whatever else passes in front of their phones. The popularity has touched sky high and the reason being the good quality that people seek at grass root level endeavors of photography. Americans have the urge to seek betterment in these areas also. They go about to seek cool new digital camera phones that all have VGA resolution 640 x 480 pixels. This is considered a safe bet that this phone is the most expensive model.

Much of a kind of ignorance exists apart from all this regarding the cell phones cameras and it crops from the fact that no benchmarks exist for objectively comparing picture quality in image sensors, camera modules, or end products. The helpless consumers thus have to rely upon advertisements to tell them much. Yet this is not a correct way to knowing a technical device. Considering the technological portion it can be said here that in the cell phone cameras some of the VGA handsets offer fairly good image quality. When you consider that the resolution comes from an imaging module that measures only 6 mm square, its actually pretty amazing quality. That square includes an imaging chip, a digital signal processor (DSP) that supports the VGA format, and a double lens that’s packaged in a light-tight module. Finding room for this module is easy. Plus, power consumption is low because the imaging chip is CMOS.

Considering the further improvements in the cell phone camera technology it can be stated here that some cell phones have incorporated conventional CCD imaging units that are still used in most digital cameras today. These devices require high voltage and a bigger a battery. As a result, CMOS has taken over in VGA-resolution applications. It provides increasingly good image quality. All this discussion shows the various achievements in the technology. However it must be stated here that the cell phone cameras are really good but they are nothing compared to the actual digital cameras. The sole reason being that they are much larger and contain far more features. It must be admitted here that such comparison is irrelevant because they are definitely two separate areas of work in spite of the fact that they are both digital cameras. Yet they are diverse in 100%25 of all their aspects. Hence the comparison is irrelevant.

Considering all the important points discussed in the above lines regarding the various areas of the cell phone digital cameras it comes out to be something that is worth appreciation. Leaving aside all comparisons they cell phone cameras are digital cameras that are certainly good in their areas of applications and mass acceptance and popularity would some day make them as advanced as their pioneer professional digital cameras.