- What is IMT2000?
Mobile telecommunication progressed from analogue type FDMA, the first generation, to the second generation digital type. Digital type can be generally divided by the wireless connection method in two major trend: TDMA (Europe, China and some part of the U.S.) and CDMA (Asia-Pacific region including the U.S., Korea, Australia). As PCS (Personal Communication Services) also became commercial all over the world, mobile telecommunication market showed a rapid growth.
However, because of the technological similarity with the conventional cellular mobile system, PCS is distinctive from other mobile services regarding high-speed data transmission and mobility of phones and users.
Because different wireless telecommunication connection standards make impossible to use a mobile phone in other areas, international roaming service is impossible for PCS. PCS's data transmission speed is only 8-13Kbps, limiting high-speed transmission needed for multimedia service.
To overcome these shortcomings, the need of a new communication concept of IMT-2000 (International Mobile Telecommunication) wan considered. Therefore, ITU (International Telecommunication Union) adopted international frequency (1885~1980㎒, 2010~2025㎒, 2110~2170 ㎒) to realize a seamless global roaming service only to be failed by the U.S. government's allocation of a part of the suggested IMT-2000 frequency band to its domestic second generation PCS provider.
After that, two mainstreams, Europe/Japan leading asynchronous type (W-CDMA) and the U.S. leading synchronous type (cdma2000), are progressing technology standardization and development, respectively. When the service is available, among the region under the same type, global roaming service will become available.
When IMT-2000 is fully serviceable, through a super high-speed wired and wireless integrated network, internet and multimedia services can become mobile. In the future, a seamless true global roaming service will become available.
- IMT-2000: Synchronous versus Asynchronous
Synchronous (CDMA2000) and asynchronous (W-CDMA), the two next generation mobile telecommunication system, types have fundamental differences in signal connection and processing methods.
Synchronous type receives time signal from satellites in synchronizing to enable real-time conversation regardless of their locations. But, asynchronous type, without a help from satellites, induce real-time conversation using chips.
Asynchronous type, lead by Europe and Japan, is now takes about 70% of the world telecommunication market. This type is based on GSM and has an advantage in international roaming. Synchronous type, lead by the U.S., is a few steps behind of Asynchronous type in coverage, communication capacity and transmission speed.
When compared to synchronous type, WCDMA type is, along with its core GSM standards, more efficient in frequency usage. This type attracts businesses with an increase of data transmission speed, probability of a price drop, cost-efficiency of operation and maintenance, and convenient user network connection features. This is proven by the fact that over 70% of new IMT-2000 service providers adopted WCDMA. WCDMA is the most suitable one for international roaming, an essential IMT-2000 feature, and has other strong points of providing intelligent network services and stable other services.
Since both types, synchronous and asynchronous, need a new investment, there seems not a big difference in cost. However, market forecast, progression of network system, applications, roaming partners and region, and customer needs should be considered before deciding which type to adopt.
- Comparison with Conventional systems
The first distinctive fact about IMT-2000 is its 2GHz frequency spectrum which was suggested by ITU for a seamless global roaming service.
Bandwidth per channel decides data transmission speed. IMT-2000 uses from 5㎒ to 20㎒ for multimedia services while the conventional digital mobile phones and PCS adopted 1.23㎒ which transmits data up to 14.4Kbps. As the result, compared to the conventional, IMT-2000 can pull the speed up to 2Mbps, enabling not only voice but also large video data transmission. This capability comes form its higher frequency spectrum than PCS's.
IMT-2000's frequency band is 1.9~2.2GHz, and its allocated valid bandwidth is 230㎒. Conventional PCS's frequency band is 1.7~1.8GHz, and its valid bandwidth is 60㎒. The higher the band, the wider is the valid bandwidth. It is like a truck with a large tare has a bigger loading capacity.
-CDMA2000 1x & GPRS
CDMA2000 1x, capable to compress data for a high-speed wireless transmission, is one type of communication connection methods between mobile phones and base stations. According to its transmission speed, CDMA2000 1x has been progressed to IS-95A~C today.
Today's mobile phones, applying IS―95B technology, can transmit data up to 64kbps, while the early phase A could transmit data up to 9.6~14.4kbps. CDMA2000-1x, belonged to IS-95C, is capable of wireless transmission at the speed of 144kbps, twice times faster than IS―95B. CDMA2000-1x is now can transmit 100 A4 pages of characters in 6 seconds. So, it is capable of sending video data, not to mention character data and still images.
Additionally strong point of CDMA2000-1x is that it provides backward compatibility to IS-95A or B. It has been developed on the current mobile telecommunication network, and the existing mobile phones and numbers can be used without a change.
CDMA2000-1x uses the same bandwidth (800㎒, 1.8GHZ) with the second generation mobile telecommunication technology (cellular and PCS) , while providing some features of IMT-2000, the third generation technology. With this implication, CDMA2000 1X is called 2.5G.
GPRS (General Packet Radio Service) concept is one step ahead of GSM. It is comparable to cdma2000 1x of CDMA type. This system is called 2.5 generation GSM type. GPRS performs transmission using packet-switching technology on GSM networks, increasing the transmission speed from 9,600bps to 14,400bps or up to 115,000bps through data compression technologies.