CDMA Overview and Technical Background

CDMA (Code Division Multiple Access), also known as code division multiple access, is a technology used in wireless communications. CDMA allows all users to simultaneously use the entire frequency band (1.2288 MHz), treating signals from other users as noise, completely eliminating concerns about signal collisions. The voice coding technology provided by CDMA delivers better call quality than current GSM, and can reduce ambient noise during user conversations, making calls clearer. In terms of security, CDMA not only has a robust authentication system, but also, due to its transmission characteristics, uses codes to distinguish users, greatly enhancing protection against eavesdropping. Wideband CDMA (WCDMA), the wideband code division multiple access transmission technology, is an important foundational technology for IMT-2000 and will be one of the standards for third-generation digital wireless communication systems.

Technical Background: CDMA utilizes spread spectrum communication technology, which reduces interference between mobile phones and increases user capacity. Additionally, mobile phone power can be kept relatively low, not only extending usage time but, more importantly, reducing the harm of electromagnetic radiation to humans. CDMA's bandwidth can be expanded significantly and can also transmit video, which is why third-generation mobile phones adopt CDMA.

The emergence of CDMA technology stems from the human demand for higher-quality wireless communications. During World War II, CDMA technology was developed out of wartime necessity, with the original intent of preventing enemy interference with friendly communications. It was widely used in military anti-jamming communications during the war, and was later commercialized into cellular telecommunications technology by Qualcomm in the United States.

In 1995, after the first commercial CDMA system (known as IS-95A) was launched by Qualcomm, the theoretical advantages of CDMA technology were validated in practice, leading to rapid promotion and adoption in North America, South America, and Asia. Many countries and regions worldwide, including Mainland China, Hong Kong, South Korea, Japan, and the United States, have established commercial CDMA networks. In the United States and Japan, CDMA has become the primary mobile communication technology. In the U.S., 7 out of 10 mobile communication operators have adopted CDMA. By April 2006, 60% of South Korea's population were CDMA users. CDMA technology also played a significant role in the 27th Olympic Games hosted in Australia.

China Unicom officially launched its CDMA network and put it into commercial use on January 8, 2002. After October 1, 2008, it was transferred to China Telecom for operation, with mobile number segments 133, 153, 189, and the newly released 180 segment. Actress Hedy Lamarr and her composer husband defined the concept of Spectrum as early as 1942. That patent proposed an important concept — "spread spectrum technology" — and this idea has since brought incredible changes to our world. In the 1950s, Sylvania Corporation in New York State (where TSMC chairman Morris Chang had his first job in the United States, at this semiconductor company) began research and development based on Hedy and George's patent. Later, in the 1960s, related spread spectrum technology emerged, and the U.S. military began using spread spectrum technology in military communication systems. After the Cold War ended in the 1980s, the U.S. military lifted restrictions on spread spectrum technology, allowing its commercialization. Then, in 1985, Qualcomm was founded in California, and based on spread spectrum technology, developed the CDMA (Code Division Multiple Access) system.