Structured cabling systems

General

Structured cabling systems are generally intended to serve for a long period of time. However, it is likely that transmission system requirements will change during the life of the cabling system. For this reason it is important that the cabling system is designed to be flexible and scalable to accommodate future increased bandwidth requirements. This is particularly important where cabling is installed underground or in other locations where upgrades to plant can be expensive and disruptive.

Background

The communications cabling system plays a critical role in telecommunications systems, providing the physical link between sources and destinations of information. Data, voice, video and control signals are transmitted over this infrastructure linking devices across the room or throughout the building.

The cabling system provides the physical link between active network equipment such as routers and switches, and the terminal equipment such as computers and telephones. Structured cabling systems (SCS) are typically comprised of unshielded twisted pair (UTP) copper cable and optical fibre cable.

To facilitate the day-to-day operations of a normal office environment, the cabling system must enable the user to make additions, moves and changes, wherever and whenever necessary. Furthermore, the SCS must also be flexible and provide the capability to carry a wide variety of applications, from high speed local area network (LAN) applications to voice and video, and low speed data.

As data through-put and transmission speeds continue to grow, greater demands are being placed on the UTP and optical fibre cabling plant. Emerging network applications, such as Gigabit Ethernet, use “parallel transmission schemes” to transmit signals simultaneously over multiple copper pairs instead of one pair.  Delivery of these new services requires increased performance from cabling plant.

Other factors to be considered in relation to cabling system design and performance include:

• Convergence of data and voice applications including IP Telephony
• Video delivery using the Internet Protocol (IP)
• Wireless LAN technology

Structured Cabling System Description

A Structured Cabling System is a set of cabling and connectivity products that are constructed according to standardised rules to facilitate integration of voice, data, video and other signals. Use of such a system provides benefits in terms of rationalisation of infrastructure costs and facilitating predictable performance.

For the purpose of this document a SCS is defined as the cabling, connecting hardware, terminations, patch cords and work area cords. Equipment enclosures and associated pathways and spaces are considered as ancillary items.

The cabling, connecting hardware, termination and interconnecting cords comprising the SCS shall be a single matched solution from a certified vendor. The two major advantages to this approach are:

• Manufacturer’s Warranty: Cabling equipment manufacturers offer a total end-to-end “system performance” channel warranty of 20 to 25 years if the installation is a “Single Brand Solution” that is installed by a contractor certified or accredited by the manufacturer. Uncertified installers using mixed brand products to construct cabling systems are likely to offer doubtful warranties of no better than one to five years.
• Performance Improvements: Independent testing has revealed that mixing cabling products from a number of manufacturers can have significant impact upon the performance of the cabling system thereby limiting the useful life of the installation.

In the case of work undertaken to change or expand an existing cabling installation the following requirements shall be applied: 

The new equipment shall be specified to ensure all existing warranties and system performance are maintained.

The new equipment should be matched as closely as possible to the existing equipment unless a more up-to-date and cost effective solution is available or such matching would conflict with occupational health and safety requirements or mandatory standards.

The number of differing types of equipment installed throughout a site should be kept to a minimum.

In the case of cabling for new buildings added to an ECE Service, the cabling system shall comply with the requirements of this document unless such compliance would create compatibility or performance issues.

Applications and Cabling Performance

The Ministry’s minimum standard for new horizontal cabling installations is based on using Category 6 cabling components to provide a Class E infrastructure performance which is guaranteed to transport Gigabit Ethernet (GbE) and allow for emerging technologies as they develop.

For the small installations considered in this document it is unlikely that backbone cabling, whether copper or optical fibre, will be necessary. In the event that backbone cabling is required, refer to the Ministry’s document: “Information Technology Infrastructure Cabling – Policy and Guidelines for Schools”.

ECE Service cabling systems shall be constructed to conform to AS/NZS 3080 – Telecommunications installations – Generic cabling for commercial premises.

AS/NZS 3080 specifies six performance classes (A, B, C, D, E and F) for balanced cabling channels. Only Class D and Class E performance is considered in this document.

The cable and components used within balanced cabling systems are classified according to Category. Category 5 components provide Class D performance while Category 6 components provide Class E performance.

Cabling System Architecture

The Structured Cabling System within an ECE Service will typically combine the Building Distributor (BD) and Floor Distributor (FD) functions in a single enclosure. A conceptual layout of an ECE Service is illustrated below.

The components of the SCS pertinent to ECE Services are described in the following sections.

Horizontal Cabling

The horizontal cabling subsystem extends from a floor distributor to the telecommunications outlet(s) connected to it. It includes distributor patch cords but does not include work area cords between the terminal equipment and the telecommunications outlet.

The horizontal cabling shall be a star topology connecting each workplace telecommunications outlet to a patch point at a distributor. Please refer to the downloadable diagram on this page for Figure 1 - Horizontal Cabling.

Horizontal cabling for new installations shall be Category 6 4 pair 100ohm UTP balanced cable.

Horizontal Cabling Variations

Horizontal cabling for new installations shall be continuous 4 pair UTP cables between the telecommunications outlets and the distributor as shown above.  Variations to this arrangement may be permitted for changes to existing installations – these being the use of consolidation points (CP) and multi-user telecommunications outlets (MUTO). These are primarily intended to reduce the effort associated with rearrangements occurring in open office style environments.  The CP or MUTO is installed within close proximity to a cluster of telecommunications outlets as shown below. In the event of rearrangement, the cabling between the distributor and the CP/MUTO can be retained. Please refer to the downloadable diagram on this page for Figure 2 - CP and MUTO Arrangment.

CPs are used with solid copper UTP and are constructed using insulation displacement punch down termination blocks.

MUTOs provide a number of RJ45 outlets and are designed to accommodate the flexible work area cords.

CP and MUTO arrangements shall not be used in new installations.

Wireless LAN Interfaces

Wireless LAN (WLAN) equipment conforming to the IEEE 802.11 standards is progressively being deployed. WLAN equipment is not considered to form part of the cabling system.  However, WLAN access may provide an effective alternative to wired network access for educators in an ECE environment and horizontal cabling is necessary to connect the wireless access points to the network infrastructure and this aspect is briefly discussed below.

The following aspects shall be considered in the placement of telecommunications outlets used to connect WLAN access points to the network infrastructure:

WLAN antennas shall be located at elevated positions in accordance with the manufacturer’s specification to provide optimum coverage and to minimise potential for exposure to radiation.

• Multiple access points may be required to cover large or irregularly shaped spaces.  Outlet spacing needs to be designed with due consideration of coverage, building construction materials, and interference.
• Proximity of electrical power outlets to provide power to the WLAN access point will be necessary if the access point does not support Power-over Ethernet (PoE) technology.
• WLAN access points should not be located near to microwave ovens or other sources of interference.
• Telecommunications and power outlets for access points must be internal to buildings with provision, if required, for external antennas which shall be located in secure positions with a low risk of vandalism.

Copper Terminations

The means of terminating balanced copper cabling shall be the modular 8 pin sockets (commonly known as RJ45) and plugs using the T568A standard.

The method of termination at the RJ45 sockets will be by punch down Insulation Displacement Connection (IDC). The punch down blocks will be fitted to 19” rack mount frames at the floor distributor and to flush plates, selected to match other electrical fittings in style and colour, at the telecommunications outlet.

Cable Utilisation Guidelines

Introduction

The optimum cable arrangement will depend on the circumstances of the particular installation. Factors to be considered in determining the composition of the SCS include:

• Distances between distributors and outlets
• Compatibility with existing cabling and equipment
• The equipment that will use the cabling system and constraints that such equipment may introduce with regard to supported interfaces
• Environmental factors such as salt atmosphere and prevalence of lightning

Guidelines for utilisation of the various cabling alternatives with respect to distance and locations are included in the following subsections.

General Cable Utilisation Guidelines

External (outdoor) cable routes are not covered in this document.  In the unlikely event that an ECE Service requires external cabling, reference shall be made to the Ministry’s Policy and Guidelines for Schools, the latest version of which may be obtained from the Ministry of Education website.

Similarly, guidelines for cabling selection for campus and building backbones are not covered in this document and reference shall be made to the Ministry’s Policy and Guidelines for Schools as above.

Cable Utilisation

Guidelines for cabling selection for horizontal cabling are included below.

• Category 6 for new works
• Category 5 for additions to existing Category 5 installations

Capacity and Dimensioning

General Dimensioning Requirements

General dimensioning requirements are as below:

• The total number of outlets at ECE Services should not exceed the total number of students plus staff.
• Each main indoor activity space should have at least three dual telecommunications outlets.  Each dual outlet should have two adjacent dual power outlets so as not to create any potential occupational, health and safety issues with multi-way power boxes and extension leads.

Work area cords should be provided on the following basis:

• Category 6
• Immediate requirements plus 10% for spares
• 2.0m in length

Patch cords should be provided on the following basis:

• Category 6
• Immediate requirements plus 10% for spares
• 1.0m in length (or as required)

Specific Dimensioning Requirements

Unless otherwise specified the minimum distribution of data outlets for ECE Services should be as follows: