A large number of ATM transmission interfaces are defined for both wide area networks(WAN) and local area networks( LAN). The transmission speeds for the physical media( PM) range from 1.544 Mbps to 622.08 Mbps. The differences between LAN and WAN specifications lie primarily in the transmission medium. While monomode fibers and coaxial cables are primarily used for WAN applications, multimode fibers and STP cables are increasingly used for LAN applications.
Interface cells for SDH and LANs
For the transmission of ATM cells encapsulated in SDH containers in the LAN area, multimode fibers or TP cables have also been specified by the ATM Forum instead of the monomode fibers prescribed in the ITU-T standards.
If STP cables of category 5( Cat 5) are used for transmission speeds of up to 155 Mbit/s, the segment lengths must not exceed 90 m in accordance with the cabling standard and the specification of the ATM Forum, whereby the flexible connection cable must be added with up to 10 m. The RJ45 connector is used as the plug connection. The RJ45 connector is defined as the plug connection. NRZ coding is used when UTP cables are used.
The same coding is used for STP cables. The only difference is the data connector: the IBM data connector or the Sub-D connector are used for the 150 ohm STP cable. For category 3 UTP cables, the ATM Forum defines an interface with 51.84 Mbps. Optionally, this interface can also be operated at 25.92 Mbit/s and 12.96 Mbit/s. At 51.84 Mbit/s, carrierless amplitude-phasemodulation( CAP) with 16 steps, CAP-16, is used; at 25.92 Mbit/s, CAP-4 coding is used, and at 12.96 Mbit/s, CAP-2 coding is used.
Multimode fibers in the LAN
Multimode fibers (62.5/125 µm) are used for direct cell transmission with a transmission rate of 155.520 Mbit/s, as intended for local area networks (LAN). The interface works up to a distance of 2 km. The wavelength of the light is 1310 nm, the ST connector according to IEC 86B is specified as the FOconnector. The coding used is 8B10B coding. For short distances up to 90 m plus 10 m connecting cable, the STP cable with 150 Ohm, corresponding to the IBM cables type 1 and 2, is provided in UNI 3.0. The STP cable also uses 8B/10B coding. The Sub-D connector is defined as the data connector. For the TAXI interface with 100 Mbit/s, the transmission method and the connection correspond to those of FDDI (4B/5B coding, MIC connector).