Jan 31, 2013

What is Local Loop Unbundling?

Local Loop Unbundling (LLU) is the process where the incumbent operators (BT and Kingston in the UK) makes its local network (the copper cables that run from customers premises to the telephone exchange) available to other companies. Operators are then able to upgrade individual lines using DSL technology to offer services such as always on high speed Internet access, direct to the customer.

Types of access

For LLU, operators have the choice of a number of options for gaining access to the local loop.

1. Physical space within the incumbent's site

BT offers operators two options for co-location within its exchanges. The location of an operator's equipment in a site can either be within a hostel, a room that is built to a standard design to house a number of operators, or in a bespoke arrangement. The basic unit of capacity of a hostel is the "equipment bay". In the standard hostel arrangement the unit of space is a three rack bay which has a footprint of 1.8m x 0.8m and a total area, including circulation space, of 10m2. This area is separate from the incumbent's operations.

If an operator does not wish to be located within a hostel (e.g. where they have non-standard requirements) they have the option of requesting a bespoke arrangement.

Each pair of copper wires run from the customer's home to the primary connection point (PCP). The PCP's are the cabinets that are located at the side of the road. The PCP connects the wires from the customer's home to a pair of wires from the exchange. Inside the exchange the wires in the external cable are terminated on the main distribution frame (MDF) and then are connected to the internal exchange equipment.

The wires connected to the MDF are then connected via an internal tie cable from the MDF to the handover distribution frame (HDF) which is adjacent to the OLO's equipment. The HDF (Handover Distribution Frame) is used to terminate the cable from the exchange and to make the pairs available to the operator.

2. Distant co-location

One of the options available to operators is distant location. This is where an operator houses its equipment away from the incumbent's building and uses a tie cable to connect the incumbent's exchange with this remote site. The remote site can be a building or a green cabinet on the side of a road.

A tie cable is used to connect the MDF at the local exchange to the HDF at the distant site, but in this case an external tie cable is used.

3. Line Sharing

The EU Regulation on LLU requires incumbents to offer shared access (or line sharing). Line sharing enable operators and the incumbent to share the same line. Consumers can acquire data services from an operator while retaining the voice services of the incumbent. Some operators may choose to offer data services only, so with line sharing consumers can retain their BT service for voice calls while getting higher bandwidth services from another operator without needing to install a second line.

From the MDF the wires are connected to a splitter (which separates the frequencies for voice telephony and those for higher bandwidth services). The incumbent provides voice telephony over the lower frequency portion of the line, while another operator provides DSL services over the high frequency portion of the same line.

4. Sub-loop unbundling

The EU Regulation also requires that other operators can interconnect with the local access network at a point between the incumbent's site and the end user. This arrangement is referred to as sub-loop unbundling.

In sub loop unbundling the connection point is the primary connection points (PCP's), which are the green street cabinets. Sub-loop unbundling can be used for emerging technologies such as VDSL where the equipment needs to be much closer to the home to deliver very high bandwidth services. An optical fibre would deliver the high-speed services to the local green cabinet and VDSL used to send them along the copper pair to the consumer's premises.

The equipment that transfers the incumbent's line to the other operator is adjacent to the PCP (the cabinet by the side of the road) rather than the telephone exchange. This arrangement will be used for distributing very high bandwidth services, which can only be sent a short distance on the copper pair.

History of LLU

In November 1999, Oftel issued a statement, Access to Bandwidth: Delivering Competition for the Information Age, which set out its decision to require BT to make its local loop available to other operators.

The Statement set out Oftel's conclusion that the opening up of the local loop was necessary to introduce competition into the provision of higher bandwidth services such as high speed always on Internet access and video on demand.

The statement also concluded that local loops should be available at cost based prices (which Oftel would determine). The requirement for BT to provide loops would be through a licence condition to be inserted in BT's licence (see Annex C). The statement also set out Oftel's approach to BT's wholesale DSL service.

To take this work forward, four industry groups were set up. These activities have been co-ordinated by a Focus Group, chaired by Oftel since September 2000. The groups focussed on Trials, Products and Processes, Commercial Issues and Contracts. - source


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