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Contents
Time Division Multiple Access (TDMA) 2
Frequency Division Multiple Access (FDMA) 2
Code Division Multiple Access (CDMA) 3
Orthogonal Frequency Division Multiplexing (OFDM) 3
RF Characteristics (4)
Frequency (4)
Protocols (5)
References (7)
Time Division Multiple Access (TDMA)
WLANS, personal communications services, and 2G digital cellular use the time division multiple access system. This system uses a combination of TDM and FDM. The numbers of channels using FDM is divided into the available or allocated frequency spectrum. The TDM is applied to carry the multiple users within each channel. Specific time slot for transmission are given to the users. At different moments in time, the users are speaking on the same frequencies. The advantages of this system are the increased capacity, spectral efficiency; the handsets have the capability to scan for a better performance.
Frequency Division Multiple Access (FDMA)
Analog Cellular systems are the main use the frequency division multiple access. In this technique, the users are assigned a different frequency, where the users are using the system at the same time, but the conversations are on a different part of the frequency band. FDMA is a low capacity and has approximately 60 users per cell. The disadvantages to this system are the devices do not search for another frequency with a better transmission quality, which can be expensive to a user but the service providers have to supply more base stations at a high cost. The other disadvantages of this system are it consumes a lot of power versus digital systems. The advantages are it does not need strict clocking devices as the TDMA system does. This type of system is no longer used. Most of analog systems have been decommissioned.
Code Division Multiple Access (CDMA)
WLANs and 3G cellular systems use spread spectrum in this multiple access technique. In a spread spectrum, the users
References: Goleniewski, L., & Jarrett, K. W. (2007). Telecommunications Essentials. The Complete Global Source. Retrieved from https://ecampus.phoenix.edu/content/eBookLibrary2/content/eReader.aspx. http://www.juniper.net/techpubs/software/cable/junosg30/g10-hwguide/html/rf.html http://www.ni.com/white-paper/6934/en/