multiband mobile phone
The earliest construction of China Mobile GSM network is based on the 900MHz digital cellular systems. Afterwards, as the rapid development of mobile communications, network capacity limitations begin to be felt, there will be a lot of the time "network busy, please dial later" prompt and can not connect phone. This situation is now very rare, but when this is a relatively common phenomenon. To solve this problem, cell phone manufacturers to launch a dual-band mobile phone that can GSM900MHz and switch between GSM1800MHz. The busiest in the network can be automatically or manually switch bands. China's first dual-band mobile phone is a Motorola CD928. In fact, CD928 domestic market when the operator does not GSM1800MHz network-building, but only with the concept of dual-band, it makes this mobile phone sales has been amazing.
This is the history of dual-band mobile phone. However, due to a letter GSM1800MHz good penetration poor, the small size of the base station coverage, the cost is relatively high, it is not possible to carry out large-scale large-area network fabric. As a result, China Telecom (now China Mobile) in large and medium-sized cities, densely populated areas, traffic-intensive areas, tourist attractions, airports, railway stations and other local building GSM1800MHz network. With a view to achieving three-dimensional network coverage and enhance network capacity.
However, because the small size of China Unicom's network, network congestion problem is not obvious, therefore, did not start the construction of China Unicom GSM1800MHz network, so that a long time, until now China Unicom's GSM network is still the single frequency network GSM900MHz . Therefore, the dual-band GSM mobile phone network on the use of EDI users do not have any practical meaning.
Now the mobile phone market, sold almost all of them are dual-band mobile phone, and even some tri-band mobile phone can only be used in single-frequency GSM900MHz phone has almost gone. So, what is it tri-band?
This is a GSM cellular telephone system from the start. We know that the GSM (Global System for Mobile Communications, literally translated as Global System for Mobile Communications)
GSM mobile phone in order to achieve true global roaming, mobile phone manufacturers was a tri-band mobile phone launch, which is to support the GSM900MHz, GSM1800MHz and between GSM1900MHz switch automatically or manually, so that GSM mobile phone users in the global GSM network coverage of the can be achieved within the roaming conditions. This is tri-band origins.
Some mobile phone vendors on the phone model marked a significant dual-band, tri-band parameters, such as Ericsson T29SC, which expressed support for C Chinese model, S expressed support for dual-band network; another example of Ericsson T39MC, expressed support for the same C Chinese models, and M expressed support for tri-band network. And most manufacturers did not indicate in the model, but the cell phone will be a detailed written statement of such conditions.
Understanding of dual-band and tri-band concept, will help us to buy mobile phones, for example, if you need to go to a regular national travel GSM1900MHz use, then buy a tri-band phone it is very necessary. For example again, if you used when Unicom's GSM network, then the dual-band mobile phone is for you is do not have any significance, because China Unicom's GSM network does not support dual-band.
http://www.epathchina.com/
http://www.epathchina.com/
Photo:
http://www.prlog.org/
