A definition of CDMA
The Allies in World War II developed Code Division Multiple Access (CDMA) to prevent Nazis from jamming radio transmissions. With CDMA, the Allies transmitted information over several frequencies, making it difficult for the Germans to get the figure out the signal. Over the decades, CDMA has grown to be one of the two major radio systems used in cell phones; the other is Global System for Mobiles, or GSM. Both CDMA and GSM signals keep networks and carriers divided. For example, in the United States, Sprint, Verizon, and U.S. Cellular use CDMA, but AT&T and T-Mobile use GSM.
Code Division Multiple Access networks layer digitalized calls on top of one another and assign them unique codes to distinguish between them. Each call encrypts data with encoded keys, which are then transmitted simultaneously on the network. CDMA receivers also sport a unique key, resulting in the combined signal splitting into multiple individual calls.
Disadvantages of CDMA
There are a few notable disadvantages of CDMA. The most notable disadvantage, Code Division Multiple Access networks make it difficult to swap phones. Whereas, GSM carriers include customer information on removable SIM cards, so swapping phones is as simple as switching cards. Unfortunately because of this benefit, GSM carriers must accept any GSM-compliant device with a GSM SIM card. Code Division Multiple Access carriers, on the other hand, use network-based white lists to verify subscribers. The result is that switching phones isn't as easy - these carriers don't have to accept phones onto their networks. Although many Sprint and Verizon phones feature SIM cards, (for 4G LTE network purposes) they still use Code Division Multiple Access to authenticate phones to their specific networks.
- International roaming is not available.
- GSM offers better coverage in foreign countries.
- Channel pollution may occur when signals from too many cell phones are present. You can see this happening when the quality of the audio decreases.
Advantages of CDMA
There are several advantages. For one, CDMA gives users complete access to the entire spectrum of bands, so users can connect at any given time. It also encodes each user's conversation using a pseudo-randomized digital sequence. When this happens, the voice data inside the digital sequence is protected only the participants in the phone call will receive the data.
This network also is a global standard for cell communication. When used in conjunction with a leading, reliable carrier, it delivers superior call quality. These networks also handle a greater number of users, so the capacity for communication handily beats that of GSM networks. CDMA also is known for quality infrastructure, so calls and data are better supported by it. In fact, CDMA consistently provides higher-quality capacity for voice and data than other mobile technologies, and that is why it is the most common platform for 3G technologies.
Rural cell users benefit from CDMA, especially. Because CDMA deployed before GSM, it boasts more bases throughout North American rural areas. By some accounts, dropouts occur twice as frequently with GSM networks than with CDMA networks. Thus, GSM can't reliably cover many of the rural areas that CDMA networks can.
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