code-division multiple access

code-division multiple access
Name	Code-Division Multiple Access
Abbreviation	CDMA
Purpose	Multiple access protocol
Developer	Qualcomm, IBM, Motorola
Introduced	1989

code-division multiple access is a multiple access protocol used in wireless communication systems, such as cellular networks, satellite communications, and wireless local area networks, developed by Qualcomm, IBM, and Motorola. It allows multiple users to share the same frequency band by assigning a unique pseudorandom noise code to each user, similar to the Global Positioning System used in GPS navigation by NASA and European Space Agency. This technique is also used in spread spectrum communication systems, such as those developed by Hughes Network Systems and ViaSat. The use of code-division multiple access has been standardized by organizations such as the Institute of Electrical and Electronics Engineers and the International Telecommunication Union, with contributions from Bell Labs and MIT Research Laboratory of Electronics.

Introduction to Code-Division Multiple Access

Code-division multiple access is a technique used in telecommunications to allow multiple users to share the same communication channel, such as those used in AT&T and Verizon Communications networks. It is based on the principle of spread spectrum communication, which was first developed by Claude Shannon and John Pierce at Bell Labs. The use of code-division multiple access has been widely adopted in wireless communication systems, including cellular networks developed by Ericsson and Nokia, and satellite communications systems used by Intelsat and Inmarsat. The technique is also used in wireless local area networks, such as those developed by Cisco Systems and Intel Corporation, and has been standardized by organizations such as the Wi-Fi Alliance and the Bluetooth Special Interest Group.

Principles of Operation

The principles of operation of code-division multiple access are based on the use of pseudorandom noise codes to separate the signals of different users, similar to the direct sequence spread spectrum technique used in GPS navigation by Lockheed Martin and Northrop Grumman. Each user is assigned a unique code, which is used to modulate the user's signal, allowing multiple users to share the same frequency band without interfering with each other, as demonstrated by Andrew Viterbi and Irwin Jacobs at Qualcomm. The signals are then transmitted over the communication channel, where they are received by the base station or access point, developed by Alcatel-Lucent and Huawei. The base station or access point uses the unique code assigned to each user to separate the signals and recover the original data, using techniques developed by Shannon and Pierce at Bell Labs.

Types of Code-Division Multiple Access

There are several types of code-division multiple access, including synchronous code-division multiple access and asynchronous code-division multiple access, developed by IBM and Motorola. Synchronous code-division multiple access uses a single clock signal to synchronize the transmission of all users, similar to the synchronous digital hierarchy used in AT&T and Verizon Communications networks. Asynchronous code-division multiple access, on the other hand, uses a separate clock signal for each user, allowing for more flexibility in the transmission of data, as demonstrated by Ericsson and Nokia. Other types of code-division multiple access include multicarrier code-division multiple access and interleaved code-division multiple access, developed by Qualcomm and Intel Corporation.

Applications and Uses

Code-division multiple access has a wide range of applications and uses, including cellular networks developed by Ericsson and Nokia, satellite communications systems used by Intelsat and Inmarsat, and wireless local area networks developed by Cisco Systems and Intel Corporation. It is also used in GPS navigation systems developed by Lockheed Martin and Northrop Grumman, and in military communications systems used by the US Department of Defense and the North Atlantic Treaty Organization. The use of code-division multiple access has been standardized by organizations such as the Institute of Electrical and Electronics Engineers and the International Telecommunication Union, with contributions from Bell Labs and MIT Research Laboratory of Electronics.

Advantages and Limitations

The advantages of code-division multiple access include its ability to allow multiple users to share the same frequency band without interfering with each other, as demonstrated by Andrew Viterbi and Irwin Jacobs at Qualcomm. It also provides a high degree of security, as the signals are spread across a wide frequency band and can only be recovered by the intended recipient, using techniques developed by Shannon and Pierce at Bell Labs. However, code-division multiple access also has some limitations, including the need for complex signal processing algorithms to separate the signals of different users, developed by IBM and Motorola. Additionally, the use of code-division multiple access can be limited by the availability of frequency bands and the need for spectrum allocation by organizations such as the Federal Communications Commission and the European Telecommunications Standards Institute.

Technical Implementation

The technical implementation of code-division multiple access requires a deep understanding of telecommunications and signal processing principles, as demonstrated by Claude Shannon and John Pierce at Bell Labs. The implementation typically involves the use of digital signal processors and software-defined radios developed by Texas Instruments and Analog Devices. The signals are transmitted over the communication channel, where they are received by the base station or access point, developed by Alcatel-Lucent and Huawei. The base station or access point uses the unique code assigned to each user to separate the signals and recover the original data, using techniques developed by Shannon and Pierce at Bell Labs. The recovered data is then transmitted to the intended recipient, using network protocols developed by Internet Engineering Task Force and IEEE Computer Society.

Category:Telecommunications protocols