1. What is the local loop?
The local loop is the physical twisted copper pair circuit in the local access network, connecting the terminal equipment in the user’s premises to the network operator infrastructure.
2. What is Local Loop Unbundling (LLU)?
LLU consists of the provision of the local loop by PT Comunicações, S.A., to other licensed operators, so that they may in turn provide users with narrowband and/or broadband services.
3. How do users benefit from LLU?
LLU will enable the promotion of greater competition and dynamisation in the offer of innovative services at the local access level, particularly concerning encouraging the use of e-commerce and information society services, including access to multimedia services and broadband internet. Users will consequently have more choice in terms of services, quality and prices.
Hence, the most varied services may be provided, from the fixed telephone service to broadband internet access, including access to multimedia services (such as VoD – “Video on Demand”), at different transmission speeds, supported by different technologies.
4. What are the main variations in LLU collocation?
LLU can consist of either full unbundling or shared access.
4.1 Full Unbundling Access
In full unbundling access, the operator of your choice has total control over the local loop, in order to provide users with voice and broadband services (Figure 1).
Full unbundling access enables the full frequency spectrum (i.e., the whole available band), of the metallic pair to be used by the operator of choice.
The request for full unbundling access results in cessation of the contract the user maintains with PT Comunicações, S.A. for the local loop in question.
Figure 1: Total Access
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4.2 Shared Access
In shared access, voice and broadband services are respectively made available by PT Comunicações, S.A., and the operator of your choice, even though provided via the same local loop (Figure 2).
Shared access enables frequency spectrum of the local pair to be shared by PT Comunicações, S.A., and the operator of your choice; the highest frequency spectrum band (non-voice frequencies) is used to provide services based on xDSL technologies (Figure 3).
This type of access enables PT Comunicações, S.A., to continue providing the telephone service, while at the same time allowing the operator of your choice to provide high-speed data transmission services using its own xDSL equipment via the same local loop.
The spectrum is split by a filter placed in the end user's premises and a filter at the local exchange.
The request for shared access does not result in cessation of the contract the user maintains with PT Comunicações, S.A. for the local loop in question.
Figure 2: Shared Access
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Figure 3: Frequency spectrum bands for Full Unbundling Access and Shared Access
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5. What are DSL technologies?
The generic designation DSL (Digital Subscriber Line) or xDSL describes a group of digital subscriber line technologies. DSL technologies enable better use of the existing copper network, supporting access services that are more demanding in terms of bandwidth.
Some examples of xDSL technology types follow:
- ADSL (Asymmetric Digital Subscriber Line): Asymmetric broadband transmission technology that enables a high-speed (1.5 to 16 Mbits/s) downstream channel (from the network to the user) and a lower speed (16 Kbits/s to 1,5 Mbit/s) upstream channel (from the user to the network), besides normal telephony service in the low frequency range.
- HDSL (High data rate DSL): Symmetric transmission system that allows transmission of 2 Mbits/s in copper telephone lines over a distance of 3.5 km, without repeater, using at least 2 twisted metallic pair circuit.
- SDSL (Symmetrical Digital Subscriber Line): System for symmetric transmission which enables transmission up to 2.3 Mbit/s, based on a twisted metallic pair circuit. Higher bit-rates and distances are attained using 2 pairs of copper.
- VDSL (Very high bitrate asymmetric Digital Subscriber Line): Evolution of ADSL for short distance data transmission at very high speed. A VDSL connection theoretically enables a maximum downstream channel of 51.84 Mbit/s for 300 metres and an upstream channel of up to 12 Mbit/s.
6. What are the limitations of the DSL technology?
DSL achieves a maximum distance from the local exchange (MDF): up to about 5.5 Km for speeds of 2 Mbit/s, but being reduced up to about 2.5 Km for higher speeds (8 Mbit/s). Apart from the user’s distance, the attainable transmission rates in “downstream” depend on a set of factors, among which are the copper cable diameter and interference between copper pairs. The existence of active systems (repetitors) and reels, for instance, prevents the use of DSL.
7. With what entity should users maintain a commercial relationship regarding the service?
In the case of full unbundling access, the new commercial relationship is established between the operator of choice, with the necessary contacts with PT Comunicações, S.A., undertaken via the licensed operator.
In the case of shared access, the commercial relationship concerning broadband services is established between the user and the operator of choice. The commercial relationship between the user and PT Comunicações, S.A., for voice service is maintained.
The prices for the public depend on the business strategy of each operator interested in providing the service, as well as on the type of service provided.
8. How can users enjoy the benefits of LLU?
Users must have a telephone line, without the limitations referred to in paragraph 6, that belongs to a local exchange eligible for LLU, in which the operator of choice is installed.
9. How can users enjoy the benefits of ADSL?
ADSL may be offered as a service by the network operator of your choice or by currently existing Internet access broadband providers.
