All the cell phone networks here in the US are are digital spread-spectrum 3G or 4G. While some cell companies still operated analog it was possible to program pre APCO25 800 Mhz. public safety radios into the channels used by the older mobile phones and portable (3kg!) analog "bag phones." We did so with good effect after hurricanes Andrew in Florida and Floyd in VA and NC gate 911 calls into the public safety answering points. There is much less reason to do so now that the telecomm companies have COWs (cellular on wheels) they can rapidly bring in to augment coverage in affected areas.
This link does a good job of explaining the differences between the various types of cellular networks and modes of transmission:
http://confluence.concord.org/display/CC...chnologies
Cell Phone Network Technologies
As in wired networking there has been a trend from circuit-switched to packet-switched network protocols. A circuit-switched network allocates one channel for a transmission from start to end. This is how the telephone system used to work. A packet-switched network can use one channel for many separate transmissions by dividing each transmission up into packets and interleaving the packets from multiple transmissions into one channel. This is how internet-based protocols work.
The terms 1G, 2G, 3G, and 4G are used to broadly classify the technology and capacity of the cellular networks.
1G: Analog networks (towers use digital signaling between towers however there is no digital communication from handset to tower).
2G: Digital network technologies are used for voice and signaling. Shorter range and lower power than analog. Packet-data services can be more easily added. Categorized into two protocols:
TDMA: GSM, iDEN, PDC (only used in Japan), IS-136 (only used in the US). Packet-data protocols include: GPRS and EDGE.
CDMA: IS-95 (US and parts of Asia). Packet-data protocols include: IS-2000 (CDMA2000).
3G: digital networks supporting simultaneous voice and data
3.5G:
4G: predicted to be an IP-based convergence of wired and wireless technologies.
2G to 4G Cellular Technologies
CDMA: Code division multiple access
IS-95 (cdmaOne): This is a technology initially developed and implemented in the US by Qualcomm for 2G networks mainly used by US carriers Verizon and Sprint.
CDMA2000 (IS-2000): There are two versions of CDMA2000 in use:
CDMA2000 1x: Adds digital channels for voice and data compared to IS-95. An add-on to 2G, sometimes described as 2.5G. Data rate: 144 kbps
US Carriers: Verizon, Sprint, MetroPCS, Alltel, Cellular South, U.S. Cellular, and Cricket Communications
CDMA2000 1xEV-DO (IS-856): (EVDO) similar to 1x with High Data Rate (HDR), forward link time-division multiplexed. Some carriers have been closing their EVDO networks in favor of HSDPA in UMTS networks. protocols on UMTS networks. download data rate: 4.9 Mbps x allocated carrier channel upload data rate: 1.8 Mbps x allocated carrier channel US Carriers: Verizon, Sprint
W-CDMA: Wideband Code Division Multiple Access W-CDMA is a 3G competitor to CDMA2000 1xEV-DO.
UMTS: Universal Mobile Telecommunications System: A 3G technology intended to replace GSM (it is sometimes called 3GSM). The UMTS work is coordinated by the 3rd Generation Partnership Project (3GPP). data rate: Deployed rates are limited to 384 kbps for R99 handsets.
HSDPA (High-Speed Downlink Packet Access) is an improved UMTS protocol which supports a 3.6 Mbps download data rate for handsets. Palm states the Treo 750 will support HSDPA in 2007 for Cingular.
[HSUPA (High-Speed Uplink Packet Access) is an improved UMTS Layer 6 protocol for faster uplink speeds ranging from 0.73 to 5.76 Mbps.
FOMA (Freedom of Mobile Multimedia Access) is a 3G technology used only in Japan.
UMTS-TDD is derived from the the UMTS standard and uses Time Division Duplexing to asymmetrically differentiate upload and download bandwidth. Within each time slot the CDMA protocol is used. It is mainly seen as a competitor to WiMAX for 4G networks.
TDMA: Time division multiple access
GSM: Global System for Mobile Communications: The most popular 2G cell network technology across the world. In the US the major carriers are Cingular (owned by AT&T) and T-Mobile. There are three types of data transmission protocols in wide use in GSM networks
Circuit Switched Data: These protocols have low network latency and are usually charged the same as a voice call.
CSD: Circuit Switched Data This older data transmission technology uses a single voice circuit to deliver up to a 9.6 kbps data rate.
HSCSD: High-Speed Circuit Switched Data: This is an incremental improvement based on CSD where up to eight radio channels can be bundled. Combining the extra channels with an improvement in coding leads to a maximum data rate of 144 kbps.
GPRS: is a packet-switched technology usually charged by per kilobyte transferred. Some carriers offer a flat-rate plan.
data rate: 30-40 kbps in real use high latency (6-700 ms)
EDGE (Enhanced Data rates for GSM Evolution) is a higher-speed packet data technology for GSM networks sometimes called E-GPRS.
data rate 236.8 kbps (using four time slots) In the US the major carriers are Cingular (owned by AT&T) and T-Mobile.
OFDM (Orthogonal Frequency Division Multiplexing)
OFDM is the basis for ongoing work towards 4G cellular networks.
HSOPA (High Speed OFDM Packet Access) is intended to be the upgrade path to 4G for UMTS-based networkss being coordinated by 3GPP LTE (Long Term Evolution)
WiMAX (Worldwide Interoperability for Microwave Access). Sprint claims to be planning on rolling this out to 100M customers in the US in 2008.
UMB (Ultra Mobile Broadband) is an extension of the CDMA2000 protocols to 4G networks. This work is being coordinated through the 3rd Generation Partnership Project 2 (3GPP2).
Data Oriented Cellular Services
*Short Message Service (SMS) often called text messaging.
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