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Open Systems Interconnect Reference Model

See OSI (Open System Interconnection) Model.

Orthogonal Frequency Division Multiplexing (OFDM)

A special method of multi-carrier modulation for encoding data onto a radio frequency signal. A single high-frequency carrier is replaced by multiple subcarriers, each operating at a significantly lower frequency. OFDM works by transmitting multiple high data rate signals concurrently on different frequencies. The channel spectrum is passed into a number of independent non-selective frequency sub-channels and these subchannels are used for one transmission link between the access point and mobile terminals. OFDM is the modulation method of choice for both 802.11a and 802.11g.

OSI (Open System Interconnection) Model

Introduced in 1984 to be an abstract model for internetworking, the OSI model defines internetworking in terms of a vertical stack of layers. The upper layers of OSI represent software that implements network services like encryption and connection management. The lower layers of OSI implement more primitive functions like routing, addressing, and flow control. Although the OSI model was designed to be an abstract model, the model remains a practical framework that many of today's key network technologies fit into, as such the OSI model provides a conceptual understanding of LAN/WAN internetworking and is an essential aspect of computer networking theory and practice.

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