水曜日, 2月 01, 2006

When poor grammer is Good

First take a look at the peaceful side of Tienanmen square.
Now, if you have forgotten what government control is look at this site!

More RFID foo

So if I misspell something, remember, I could be trying to beat the censorship filters. (~/.\0)

NA-TDMA

AMPS system in the americas had some shortcomings that had to be addressed. For instance, security was a serious problem, with an epidemic of cellular phone fraud costing carriers and users millions. Capacity was also an issue in high-use urban areas. Frequency channels where getting used up, and the FCC stated that it would not add any new spectrum for use by cellular companies. In addition, carriers wanted to give their customers similar advanced features in their mobile phones that they were getting with their landline phones, like call waiting, caller ID, and vvoice mail.

In Europe, GSM had been approved and deployement started. GSM solved many of the issues the AMPS networks had raised, such as fraud protection. GSM also had plans for advanced services, such as caller ID, SMS, and in the future high data rates. In America, however, carriers had invested billions in infrastructure and phones, and GSM was a system designed for a newly cleared spectrum band as a complete replacement. GSM was designed for ease of roaming, and it was designed from a clean slate. American engineers felt that a new system needed to fit seamlessly into the already present AMPS networks and architecture and give significant capacity increase.

while Americans decided to come up with their own format, they did borrow much from GSM including the very basic concept of using TDMA. Thus, the NA-TDMA system was born, incorporating the original AMPS with the new TDMA system, where TDMA channels would fit into AMPS channeels. NA-TDMA can also be refered to as Digital Advanced Mobile Phone Service (D-AMPS), American Digital Cellular (ADC) and North American Digital Cellular (NADC), and very often is referred to as the standard that defines it. Originally, the standard created defining NA-TDMA was IS-54. Later, some changes were added, including a digital control channel, support for PCS bands, and some improved services. this new standard was labeled IS-136, essentially an enhanced version of IS-54.

Thus the new NA-TDMA system would encompass the following new features over AMPS, beginning with IS-54 and on to IS-136:
-Digital voice transmission
-DMA and FDMA
-All the original AMPS protocols, including the same frequency channels 30kHz
-Increased capacity (theoretically three times more)
-Authentication for security
-Better power consumption measures such as sleep mode, which allows for longer battery life as well as less need for large cumbersome battery packs
-Improved handoff systems (the MAHO system, where the handset helps make decisions on handoffs
-Dual mode mobile stations (AMPS and TDMA)
-Enhanced special services (such as caller ID and SMS)
-Support for PCS band
-Support for data transmission
-A digital control chasnnel.

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