Cellular connection

Cellular connection

Cellular connection is one of types of mobile radio contact; a cellular network lies in basis of it. A key feature is that the general area of coverage is divided on cells, which are determined by the areas of coverage of separate base stations. Cells are partly recovered and together form a network. On an ideal (flat and without building) surface an area of base station coverage is a circle, that’s why the network made from them has the form of cells with hexagonal cells.
A network is made by transceivers, spreading in space, working in the same frequency range, and commutating equipment, allowing determining the current location of moving subscribers and providing the continuity of connection during transferring of subscriber from the area of action of one transceiver in the area of action of another.
Speaking about 3G, the radio interface which provides a communication channel between the user and network is meant. Other important aspects of 3G are the backbone network, and methods of creation and grant of services. Till recently the basic factor, determining the development of mobile communications was the traditional transmission of voice. However introduction of new technologies of high-speed data communications, including GPRS and EDGE, and the evolution to UMTS W-CDMA systems will allow the operators of cellular connection to give unlimited wireless multimedia-services, for example, electronic post-cards, viewing of Web-pages, and access to the corporate networks.
Modern 2G networks are the basis upon which the 3G systems inculcated on. UMTS is one of standards in 3G, which is developed under an aegis of the European Telecommunications Standardizations Institute. It was developed on the basis of the most widespread technologies of mobile communication of GSM and has all of prospects to become the indeed global standard of the personal multimedia-connections.
2G was created in the mid-1980s. These systems digitized both the control link and the voice. It made the quality of connection better and made its service more reasonable for the population.
3G provides the improvement of the connection quality, additional services: voice service, fax, the Internet connection, and the seamless roaming. The first 3G network was used in Japan in 2001. 2.5G networks such as GPRS (Global Packet Radio Service) is quite widespread on the territory of Europe.
2G Network.
1. GSM (Global System for Mobile Communications) was the first commercially operated digital cellular system. (Cellular Standards for 1G and 2G, 2008) GSM uses TDMA (Time Division Multiple Access) technology. It is used by all European countries and others continents. This network has become the standard of the cellular system and has about 45% of all worlds’ subscribers of cellular communication.
2. TDMA IS-136 is the digital perfected version of the analog AMPS technology. In 1991 when it was used at first it got the name D-AMPS.
3. CDMA IS-95 increases capacity by using the entire radio band with each using a unique code (CDMA or Code Division Multiple Access)( Cellular Standards for 1G and 2G, 2008). South Korea is the largest and more serious market of CDMA IS-95 in the world.
4. Personal Digital Cellular (PDC) is the second digital mobile standard, which is based upon the he TDMA access technology.
5. Personal Handyphone System (PHS) is more reasonable alternative to cellular systems. It is somewhere in between a cellular and a cordless technology. It has inferior coverage area and limited usage in moving vehicles. (Cellular Standards for 1G and 2G, 2008)
3G Network
IMT-2000, “International Mobile Telecommunications” is known as the third generation system for mobile communications. The range in 400 MHz and 3GHz is technically suitable for the IMT-2000. It offers the opportunity of providing of the additional profitable services on the base of a single standard. IMT-2000 aims to provide the services of the media (satellite, fixed, etc). It is expected that it will also provide the high transmission rates: from 2Mbit/s for stationary or walking users, and 348 kbit/s in a moving vehicle. 2G systems can only provide speeds ranging from 9.6 kbit/s to 28.8 kbit/s.
Besides IMT-2000 has several distinctive features:
1. Flexibility. Taking into account a great number of consolidations in mobile industry and moving into the international markets, operators want to avoid the obligation to supply a wide range of interfaces and technologies. This fact would have hindered the spread and proving of 3G systems. IMT-2000 decides this problem with the help of the flexible system, which is capable to support a lot of services. IMT-2000 also provides five radio interfaces, which based on three different access technologies (FDMA, TDMA and CDMA).
2. Affordability. There was an agreement between creators in a mobile industry that the 3G system will be affordable for the consumers.
3. Compatibility with existing systems. IMT-2000 has to be compatible with existing systems. 2G systems such as GSM will continue its existing and compatibility with this system should be supply with the seamless migration paths.
4. Modular Design. IMT-2000 has to be easy expandable in order to increase the number of subscribers, the area of coverage and new services with the minimal investments.
EDGE (Enhanced Data rates for GSM Evolution) - digital technology for mobile communication which functions as addition to 2G and 2.5G (GPRS) networks. This technology works in TDMA and GSM networks. For EDGE support in GSM network certain modifications and improvements are required. On the basis of EDGE ECSD (speed-up access to the Internet on the CSD channel), EHSCSD (on the HSCSD channel), and EGPRS (on the GPRS channel) can work. EDGE was first presented in 2003 in North America.
EDGE provides data communications with speed to 474 kbit/s in the mode of package switching (8 time-slots x 59.2 kbit on MCS-9coding scheme) corresponding, thus, to the requirements of ITU to the 3G networks. This technology was accepted by ITU as part of IMT-2000 family of 3G standards. It extends technology of data communications with commutation of HSCSD path, increasing the carrying capacity of this service.
Status of belonging of EDGE to the 2G or 3G networks depends on concrete realization. While EDGE-telephones of the third class and later don’t correspond 3G, telephones of fourth class and higher in theory can provide more high carrying capacity than other technologies, declared as 3G (for example, 1xRTT). Telephones with a maximal carrying capacity on the reception of 237 kbit/s in tenth class, EDGE corresponds both 2G and 3G specifications.
TDMA (Time Division Multiple Access) is a method of the use of radio frequencies, when in one frequency interval there are a few subscribers, different subscribers use different temporal slots (intervals) for a transmission. It is the application of multiplexing path with a division at time (TDM — Time Division Multiplexing) to the radio contact.
Thus, TDMA gives every user the complete access to the interval of frequency during the short period of time (in GSM one frequency interval is divided by 8 temporal). TDMA presently is the dominant technology for mobile cellular networks and used in the standards of GSM, TDMA (ANSI-136), PDC.
Based on above mentioned requirements to the mobile systems, the ITU provided five radio interfaces for IMT-2000 standards (Recommendation 1457). Three of the five standards (CDMA2000®, TD-SCDMA, and WCDMA) are based on CDMA. CDMA2000 is also known by its ITU name, IMT-2000 CDMA Multi-Carrier (MC).
CDMA2000 is based upon the advantages of CDMA and introduced a wide range of improvements such as Orthogonal Frequency Division Multiplexing (OFDM and OFDMA), advanced control and signaling mechanisms, makes better the interference of management techniques, end-to-end Quality of Service (QoS), new antenna techniques such as Multiple Inputs Multiple Outputs (MIMO) and Space Division Multiple Access (SDMA) to increase data rates and quality of service.
W-CDMA transmits on a pair of 5 MHz-wide radio channels, while CDMA2000 transmits on one or several pairs of 1.25 MHz radio channels. (W-CDMA, 2008) Although W-CDMA use the technique of direct sequence CDMA transmission, W-CDMA is not just broadband version of CDMA2000, it is a new design by NTT DoCoMo and it differs from CDMA2000 a lot. From the engineering point of view W-CDMA has provided another kind of balance of interaction between cost, capacity, and density. This system promises to make the profit from the decrease of the prices cost for video phone handsets.
W-CDMA is very suitable for the megapolises in Europe and Asia. It was supplied by a great number of specifications, detailed protocol, which can define the communication between mobile phone and tower, the modulating of a signal, structures of datagrams, and system interfaces, which allows the free competition on the technology elements.
CDMA2000 1xRTT is the central CDMA2000 wireless air interface standard, which is also known as 1x, 1xRTT, and IS-2000. The “1x” means "1 times Radio Transmission Technology”, indicates the same RF bandwidth as IS-95: a duplex pair of 1.25 MHz radio channels. This contrasts with 3xRTT, which uses channels 3 times as wide (3.75 MHz) channels. 1xRTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link, orthogonal to (in quadrature with) the original set of 64. Although capable of higher data rates, most deployments are limited to a peak of 144 kbit/s.(CDMA, 2008)
1xRTT is considered as 3G technology, but it qualifies by some as 2.5G or eve 2.75G system. It allows it to be used in 2G spectrum in some countries, and this can confine the 3G.

References
1. 3G CDMA2000. 2008. CDMA Technology. CDMA Development Group. On-line. Available from Internet, http://www.cdg.org/technology/3g.asp, accessed 8 May 2008.
2. Cellular Standards for 1G and 2G. 2008. All about the Technology. International Communication Union. On-line. Available from Internet, http://www.itu.int/osg/csd/ni/3G/technology/index.html#Access Technologies, accessed 14 May 2008.
3. W-CDMA. 2008. Wikipedia, the Free Encyclopedia. On-line. Available from Internet, http://en.wikipedia.org/wiki/W-CDMA, accessed 7 May 2008.
4. What is EDGE? 2008. GSM World. On-line. Available from Internet, http://www.gsmworld.com/technology/edge/index.shtml, accessed 10 April 2008.
5. CDMA. 2008. Wikipedia, the Free Encyclopedia. On-line. Available from Internet, http://en.wikipedia.org/wiki/CDMA2000