Hello, everyone!
Today, I would like to share with you an article about Cellular Network Standards and Generations.
Digital cellular service uses several different competing standards that do not interoperate with each other. This means that digital cellular handsets cannot work on networks that use another wireless standard.
In Europe and much of the rest of the world outside the United States, the standard is GSM, short for Global System for Mobile Communication. Three out of four of the world’s estimated 2 billion cell phones are GSM, including most of China, the world’s largest cell phone market. The system’s strength is its international roaming capability. Users have seamless same-number roaming in more than 170 countries. Most GSM systems outside North America operate in the 900-MHz and 1.8-GHz frequency bands. (In North America they operate in the 1.9-GHz band.) The bandwidth is divided among users based on time division multiple access (TDMA) in which each user is allocated a portion of time on the frequency.
In the United States, GSM is not the standard because the Federal Communications Commission (FCC) permitted open competition in cell phone technology, resulting in multiple incompatible standards. This situation limits roaming and contributes to the high prices of U.S. cell phones.
There are GSM cell phone systems in the United States, including T-Mobile, VoiceStream, Cingular, and AT&T. However, the major standard in the United States is Code Division Multiple Access (CDMA), which is the system used by Verizon, MCI, and Sprint. CDMA was developed by the military during World War II. It transmits over several frequencies, occupies the entire spectrum, and randomly assigns users to a range of frequencies over time. In general, CDMA is cheaper to implement, is more efficient in the use of spectrum, and provides higher quality throughput of voice and data than GSM. Because of its inherent efficiency, implementing CDMA and a standard called wide-band CDMA (WCDMA) is the long-term objective even of existing GSM systems.
CELLULAR GENERATIONS
Wireless phone systems throughout the world are gradually moving toward much higher speeds and capacities. This transition involves over $200 billion in worldwide investment in what is called 3G networks (third-generation cellular networks).
The first generation (1G) of cellular networks originating in the early 1980s was analog-based. They supported voice communication and could only be used for data transfer with a proper modem. Second-generation (2G) cellular networks appeared about 10 years later using digital networks. 2G systems provide better voice quality and global roaming capabilities and can support simple data services such as SMS. Although 2G systems are used primarily for voice, they can support data transmission at rates ranging from 9.6 to 14.4 kilobits per second (Kbps). This transmission speed is still too slow for comfortable Internet access.
Third-generation (3G) cellular networks are based on packet-switched technology that achieves greater efficiencies and higher transmission speeds. 3G networks have speeds ranging from 144 Kbps for mobile users in, say, a car, to over 2 Mbps for stationary users. This is sufficient transmission capacity for video, graphics, and other rich media, in addition to voice, making 3G networks suitable for wireless broadband Internet access and always-on data transmission. If 3G networks live up to their promise, they will be able to handle e-mail, instant messaging, and Web browsing as effortlessly as current wired technologies.
Although wireless carriers have invested in 3G technology, it is still not in wide use. In the meantime, those interested in high-speed Internet access and data transmission are turning to an interim solution called 2.5G networks. These networks are packet-switched, use many existing infrastructure elements, and have data transmission rates ranging from 50 to 144 Kbps. A 2.5G service called General Packet Radio Service (GPRS) transports data over GSM wireless networks and improves wireless Internet access. 2.5G also improves data transmission rates for CDMA.
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