N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 7 - LAN, WAN, VPN, WLAN, MAN, FDDI and Optical MANS                                               Slide 15 of 45 _________________                                                                                  __________

                                                Baseband and Broadband LANs

                                               Baseband LANs - Digital Transmission

                                            Broadband LANs - Analogue Transmission

                                            Advantages

                                            Disadvantages

_________________                                                                                  __________

LANs are available as either  baseband or broadband systems.

Baseband LAN - A Baseband system is characterized by the use of digital technology. The data is transmitted without the use of a carrier and with only one channel in the system. A line driver performs voltage shifts onto the channel to represent binary 1s and 0s. The channel acts as a transport mechanism for digital voltage pulses. Baseband LANs can use either coaxial cable, twisted pair or optical fiber. The technology is limited in distance to 1 Km as digital pulses attenuate over longer distances.

A baseband system is configured with the following constraints:
        1. Cable length - 500 m
        2. Distance between two stations - 2.5 m
        3. A maximum of 100 taps per cable
        4. Cable lengths extended by using digital repeaters 

Broadband LAN - A broadband LAN uses an analogue technology for data transmission. It uses a high frequency modem to place carrier signals onto the transmission channel. A wideband coaxial cable is used with frequency division multiplexing to establish multiple channels within a system. The channels are typically 6 M Hz wide. A CATV cable, with bandwidth of 300 to 400 M Hz can carry 50 to 60 separate channels. A broadband LAN is unidirectional and requires two separate channels for two-way operations.

Advantages and Disadvantages: