Today, the mobile communication is becoming more and more popular. You can see lots of people using mobile phones everywhere, in offices, at home and on the way to work. At the year of 2002, the amount of mobile communication user is even more than fixed phone. But have you noticed that there are various kinds of technical being used.
The GSM, which stands for Global System for Mobile communications, is the most common used technology. There are more than 1 billion users from over 200 countries in the America, Europe and Asia etc. However, even in these countries, the frequency range can be very different. In the America and parts of Asia, GSM networks operate in GSM-850 and GSM-1900 bands. Furthermore, most area including P.R.C and UK operator use GSM-800 and GSM-1800 bands. GSM-450 is used by rare countries such as Finland. Although all GSM operators use the same technology, the network is not compatible among some bands.
Besides GSM, there are plenty of technology have been used. For instance, the US and Canada used to use a system known as digital AMPS. Now some other advanced technologies such as GSM have replaced most of the existing networks. Another one is called CDMA, or Code Division Multiple Access. It is first used by the US army. After that, Quslcomm made this technology available for ordinary users. A famous CDMA standard is known as CDMA ONE which is used by the operators from P.R.C and Korea etc. In most area of Asia, another mobile network is market as Personal Access System. It is not commonly used since the weakness on communication. One of the most special standards comes from Japan and is called Personal Digital Cellular. Compared to GSM, this standard has weak connection and lower voice quality.
Everything is developing, the same as mobile communication. All the technologies mentioned above are known as 2G. Today, people are not satisfied with these technologies on account of technical progress. The brilliant scientists have been developing an advanced technology called 3G.
GPRS and EDGE, refer as advanced GSM, is developed at the top of GSM with higher rates and they are mentioned as ?2.5G? and ?2.75G? respectively. It is used by the movable handsets such as GPA and Mobile phones to connect the Internet. The more advanced system UMTS, namely Universal Mobile Telecommunications System, is a 3G standard and is mentioned as 3GSM and is being developing to 4G technologies. UMTS uses other technology as underlying air interface, and the most wildly used one is called W-CDMA.
Now let?s have a look at W-CDMA. W-CDMA comes from the old standard CDMA, and is used as the underlying air interface of UMTS. The operator of Japan runs a network called FOMA which is evolved by W-CDMA with lightly difference.
CDMA-2000, as GPRS, is evolved by older standard with higher rates and is compatible with older system. But CDMA is not compatible with W-CDMA. Another type of 3G is called TD-CDMA, which is being mainly developed by P.R.C and has about 80,000 users now.
Our daily life has changed day by day, so does the mobile communication system. The mobile communications give us so much convenient. Believe it or not, the technical progress happens rapidly. As the 3G technology is being used, our life is bound to become more and more convenient.
Let?s wait 3G era coming!
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Mobile communication system is worldwide used over the world with different model such as GSM, CDMA, D-AMPS and so on. Having a fundamental background of CDMA and its features will give me good start of understanding mobile communication. The target of this project is designing mobile communication, CDMA system, with particular features such as cell size, cell capacity, bandwidth, technique of modulation and demodulation and so on for Orange Island. Orange Island is a distant island with a city, which is Voda. The area of Voda is 1500 km2 within which there is a densely populated centre of approximately area of 100 km2. The density of user in city centre is 1000 people per km2 and in the suburban areas 100 people per km2. The population density in the rest of island is 5 people per km2 averagely. Government of Orange Island want to set up a mobile communication network based on CDMA technology. The available bandwidth in the Island is 890 ? 915MHz for uplink and 935-960 MHz for downlink. The government desire to set up wireless communication and they are considering two options of system. They are:
? A voice only network with a required user data rate of 10 kbps
? A voice and data network with a voice user, data rate of 10 kbps and the data rate of other traffic (e.g. internet data) of 150 kbps.
By considering features of these two options, the answer for question ?which is suitable design for Orange Island?? will be given.
2. CDMA system.
Code division multiple access (CDMA) is a channel access method used by various radio communication technology. The basic concept of CDMA technology is allowing several transmitter send information at the same time over a single communication channels (bandwidth). It also means that user can share a bandwidth frequency with other users. It is so-call multiple access. CDMA also use the technology which is spread spectrum. The spread spectrum technology and using orthogonal coding scheme (idea of orthogonal coding will be cover in part 3.3) are used to allow many user can use the same bandwidth (same channel). the spread spectrum is implemented by doing XOR operation between information data with a pseudo-random bit array which has much higher data generated frequency than information array. (Information of pseudo-random array is provided in part 3.3).
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