Two methods are used to transmit signals between nodes: baseband and broadband. The Baseband and Broadband Signals Diagram illustrates these two methods. For LANs, broadband refers to analog transmission of computer information, and baseband refers to digital transmission of computer information.

Baseband is analogous to a telegraph. Voltage levels are modulated onto a constant carrier signal. Transitions from one level to the other indicate a 0 or 1. The Baseband Transmission Diagram illustrates bi-directional digital waves.

Broadband is analogous to TV cable transmission. Just as many different TV channels can broadcast different programs simultaneously, a broadband link can support many independent communications channels. These channels can be used as independent links between nodes, or in parallel to increase the effective throughput of the link. The signals still represent 1s and 0s, only in a different manner. The Broadband Transmission Diagram illustrates unidirectional analog wave.

Baseband is relatively simple, less costly than broadband, and yet still very fast. It is far more widely used than broadband. Although potentially much faster and able to span longer distances than baseband, broadband requires a modem at each end of a link, which increases the cost of every device attached to a LAN.

By far, the predominant signal type in computer networks is baseband. Broadband is typically associated with the cable TV industry, but is also found in computer networks.

   Activities

See the Activities and Extended Activities section in Unit 2 Lesson 1 in your textbook Introduction to Networking to test what you have learned so far.

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