Home Networking Basis: Transmission Environments and Wired/Wireless Protocols

In this chapter, we will study and construct transmission channel models for twisted pair cables. The first type of twisted cable is the one used in existing in-house telephone wiring. This in-house twisted pair wiring usually extends from the entrance point of a telephone loop to telephone jacks distributed at many different rooms within a residence. For a multiple-pair twisted pair cable, the twist is usually applied to each individual pair with a particular twisting angle. For in-house telephone-wiring twisted pair cable, the twist is normally applied to all wires. Sometimes, flat cable with no twist is also used for in-house telephone wiring. The conventional wiring procedure of this in-house telephone loop extension is called star daisy-chain. At the center of the star is the telephone loop entrance point. From this center, a few branches of twisted pair cables are extended throughout the residence reaching all telephone jacks. Each branch usually connects a few phone jacks along one floor or within a particular region of residence involving multiple floors. Each star daisy-chain branch contains a few cascade twisted pair cable sections sequentially connected at phone jacks along the way. Sometimes, a branch can become multiple branches along the way. For this type of in-house telephone wiring, we will examine commonly used types of twisted pair cables, their transmission and crosstalk characteristics, networking topology, and impedances of telephony devices connected to this star daisy-chain network through telephone jacks. Based on this information, we will calculate transfer function, crosstalk loss, and channel capacity for a broadband communication link established between two phone jacks of the in-house telephone-wiring network.

The second type is the data-grade twisted pair cable. They are typically called Category 3 or Category 5 twisted pair cables. Category 3 and Category 5 twisted pair cables are used as transmission media for 10BaseT and 100BaseT Ethernet. Both require an active hub to connect all Ethernet transceivers together. The wiring topology of a 10BaseT or a 100BaseT Ethernet is a star. A hub with multiple transceivers is at the center of this wiring star. The star topology telephone wiring can often be found at recently completed homes. Data-grade twisted pair cables are often used in conjunction with the star topology telephone wiring. For data-grade twisted pair cables, we will examine their transmission and crosstalk characteristics and calculate the corresponding transfer function, crosstalk loss, and channel capacity for a point-to-point connection of a household dimension.