1. ADSL CPE: INTERIM TELEPERMITTING ARRANGEMENTS
Telecom's proposals for its Fast Internet service were outlined in Newsletter No 109 and the following explains progress towards opening the market for ADSL CPE.
a. Current position
Telecom is continuing with its trial installations using equipment supplied by Nokia and these trials will soon be extended progressively towards full "interim" commercial service. These trials are allowing us to address such matters as service performance under different line conditions, the impact of various customer wiring configurations, the effect on or caused by CPE connected to the same line, the potential for radio interference, and any other sources of service problems,
The ITU has not yet finalised its Recommendation on ADSL and this is why our current service is referred to as "interim". Until the ITU has established the formal standard, there is some doubt about the ongoing compliance of any "pre-standard" proprietary implementations based on either the current ITU draft or the US-originated source document, ANSI T1.413: 1998.
The exchange-end DSLAM's (Digital Subscriber's Line Access Multiplexers) used in the trials are manufactured by Nokia to the above American standard. This same standard is being used as the basis of the draft ITU Recommendation G.992.1, which is expected to be ratified later this year. Unfortunately, the ANSI standard allows for different interpretations, and even the finally agreed ITU Recommendation is expected to provide for quite a large number of options to be adopted by any particular network. As such, it is not expected to be as firm as we would have wished. This is also the position with ANSI T1.413, in that the various chip manufacturers' interpretations mean that full inter-compatibility cannot yet be assured.
The leased modems Telecom is installing in customers' premises are also made by Nokia and incorporate an ADSL chipset manufactured by ADI. One of these modems is mounted external to the customer's PC and provides an Ethernet interface to it. Telecom will soon be introducing network interface cards (NIC's) that are to be sold to customers and installed within their PC's. These are made by Efficient Networks, an associate company of Nokia.
These network interface cards also incorporate the ADI chipset to ensure that there is full compatibility between the customer equipment and the Nokia DSLAM's installed in the local Telecom exchange.
Since Telecom aims to introduce competitive supply of modems, NIC cards, and other ADSL hardware, as soon as the formal standards are in place, Telepermits are being granted to these early Nokia products, based on the arrangements and conditions described below.
b. Nokia certification
Nokia is obligated to ensure that their exchange equipment will support their own customer equipment, all of which complies with ANSI standard T1.413, and are required to certify the compatibility of that equipment. Nokia and Efficient Networks are deploying equipment to the current ANSI standard, because the ADSL standard ITU Recommendation G.992.1 is not fully ratified. It is therefore not possible to test other vendors' equipment for interoperability with G.992.1 at this juncture.
c. Risk?
Even if it works reasonably well with the interim equipment, there is some risk that CPE currently being produced by other suppliers could be non-compliant with the final ITU Recommendation, or that it will no longer interwork with Nokia DSLAM's made to the final standard. It must be remembered that the CPE now going into service has been certified by Nokia as part of their supply contract, not by Telecom. At this stage, Telecom has no way of assessing the potential risk of incompatibility with the final standard. In view of this, PTC specifications capable of guiding other competing suppliers cannot be published yet. To complicate matters, the timing of the standard is still undefined. 3Q99 is possible, but it has been suggested that this could be delayed. It will then be necessary to develop test procedures to ensure compliance with the standard. By the time testing is completed, there will be further delay before products compliant with the new standard are available here.
d. Telepermit assessment
While we are not in a position to publish a PTC Specification at this stage, the basic requirements are as follows:-
1. All "pre-standard" CPE types supplied by Nokia will be certified by them as fully compatible with their present DSLAM. When the ITU Recommendation has been finalised and any Telecom-specific options have been decided, we will move towards independent certification of compliance with ITU Rec. G.992.1;
2. Once independent testing is in place, three samples of each "certified" device submitted for Telepermit shall be provided to Telecom's Technical Evaluation Laboratory, along with evidence of compliance with the published standard. The product's performance under simulated Telecom line conditions will be verified. The Telecom laboratory will provide a brief report to Access Standards advising whether or not the product performs correctly and supports Telecom's service;
If all appears well after these functional tests, one sample will be retained by Telecom's Technical Evaluation Laboratory for follow-up testing in the event of any common service problems being reported. The other two samples will be returned. Should the product exhibit any significant problems during these functional tests, all three samples will be returned to the applicant.
Once all necessary documentation is available, an application is to be made to Access Standards (application forms and other data now available from our website). The applicant is to provide all the usual documentation, as specified on the application form. This, of course, includes an electrical safety test report to AS/NZS 3260, IEC 950, or EN 60950, showing full compliance with one or other of these standards.
NOTE These arrangements do NOT apply to any other xDSL protocols. Telecom is only supporting the Nokia implementation of ADSL at this stage.
3. The Limited Permit scheme will be used initially, so that both the supplier and Telecom can use the trial period as an opportunity to ensure that there are no unforeseen problems. Up to 200 items of any particular type may be connected to Telecom's service during the Limited Permit trial period, on
the condition that further installations must cease if any common service problems arise. This restriction applies even within the first 200 installations.
e. Special conditions
Until we have gained experience with the service and have confidence in the standards, Telepermit grants will have to be subject to some special conditions. We aim to open up the ADSL CPE market to competitive supply at the earliest opportunity, but we must ensure that Telecom staff or contractors are not unnecessarily drawn into customer complaints or called to make service calls due to equipment supplied by third parties. This is especially the situation where network interface cards (NIC's) are fitted into the customer's PC, as a wide range of compatibility and software problems could arise.
4. The Telepermit holder will be required to provide all necessary service and support for the products supplied. The Telepermit holder is also required to inform the customer that Telecom is not responsible for installing, servicing the product or the associated PC, nor for ensuring that existing premises wiring is capable of supporting the service. Should there be any incompatibility with the Telecom network, the risk is on the CPE supplier. Should the Telepermit holder be unwilling to accept this risk, the customer is to be clearly warned of this limitation.
Hopefully, these restrictions can be relaxed after all parties concerned have built up service experience and mutual confidence and the standards have "settled down". We will then be able to revert to the present Telepermitting arrangements applying to other classes of CPE, with independent test laboratories carrying out the full assessment and no limited permit trial stage.
f. Service availability
An important point is that not all Telecom lines can be expected to support ADSL. Telecom is currently working on a scheme to classify lines on the basis of their service capability. This will enable prospective customers and suppliers to call Telecom, give the telephone number of the customer concerned, and be advised whether service is "almost certain", "likely", or "not possible". Part of the present trial is aimed at making these initial assessments more accurate. However, it must be mentioned that line impairments, such as noise from outside sources, are very unpredictable.
g. EMC and wiring requirements
The local importer of any device connected in the customer's premises is required to submit a Declaration of Conformity to the Ministry of Commerce, based on test reports verifying that the product complies with AS/NZS 3548 or EN 55022. This is a legal requirement, not a Telepermit issue.
ADSL operates at line frequencies closely paralleling the AM broadcast radio band. There is some risk of RFI to nearby services should the premises wiring be inadequate in some respect. Telecom's wiring maintenance service covers the customer's wiring only for telephony and voiceband purposes. Telecom is not in a position to provide free wiring replacement to support ADSL services. For example, a high proportion of Telecom customers are still using the earlier 3-wire system, which is not suitable for ADSL. In such cases, ADSL will require the installation of a clean 2-wire run from the splitter to the jackpoint connecting the modem or NIC.
h. Splitter installation
As part of its Fast Internet service installation, Telecom will visit the site to fit a line splitter (this separates the voiceband services from the high frequency ADSL service). The splitter is not being opened to competitive supply at this stage, as it is a fairly critical item. It will generally be fitted within the External Test Point (ETP) and, as such, is regarded as part of the Telecom network. The Telecom contractor will test to ensure that the Fast Internet service is operable to the ETP, using his own lap top computer.
Wiring from the ETP to the computer jackpoint (the service delivery point) can be carried out by Telecom staff or contractors, but a charge will apply for this work. Independent contractors will be required to comply with Telecom's Codes of Practice.
i. Future PTC specification
Despite the potential risks outlined above, some suppliers will no doubt be keen to get into this sector of the CPE market at the earliest opportunity and the above arrangements will cater for this. The pre-requisites for an open market are that:-
* The ITU Recommendation is finalised;
* Specific options have been selected by Telecom;
* Telecom has firm specifications of the production "ITU standard-compatible" Nokia DSLAM;
* Telecom has more experience of the service under its own network conditions, and
* Independent testing services are available to carry out compliance testing.
By the time these measures are in place, we should be in a position to publish the necessary PTC specification and overcome the present uncertainties.
j. Independent testing
We will probably be relying on overseas test laboratories with the necessary specialised knowledge and test gear to carry out the first independent compliance testing. In due course, it is expected that local functional testing will be carried out by any accredited laboratory, as for other PTC testing.
k. Scope of Telepermit for ADSL CPE
The PTC 27x-series will be allocated to ADSL CPE to clearly differentiate it from PSTN and ISDN products. The PTC 271 number series will apply to the initial pre-standard CPE, with the PTC 272-series used for those products that comply with the published ITU recommendation.
As explained in Newsletter No. 108, Telecom's leased analogue lines are restricted to voiceband frequencies (300 Hz - 3400 Hz) and shall not be used for high frequency services.
Any grant of a Telepermit for ADSL CPE is restricted to the connection of that CPE to Telecom customers' telephone lines supporting Telecom's Fast Internet service. The grant of a Telepermit does NOT indicate that the equipment may be connected to leased analogue lines, such as A1, A2, A3, V1 or L1.
All parties should note that the grant of a Telepermit denotes Telecom's "permission to connect" another company's product. It is neither a warranty nor a guarantee of that product's performance".
l. Industry comment
As is our usual practice, industry comment is invited on the above matters. ADSL technology and DSL technology in general is expected to provide the initial customer access to the "brave new world" of Internet Protocol (IP) based network multi-media services. As such, it will form a significant sector of the CPE industry and, probably, this will happen within the next few months.
Telecom is committed to opening the CPE market at the earliest opportunity and if there is some way of achieving this before the ITU recommendations are formally published, we will be interested to hear of any proposals. A primary requirement is that we and our customers must be assured that early (and probably expensive) CPE products will not become "orphans" with perhaps well under a year of actual service life.
2. ADSL wiring Code of Practice
In time, we will either advance PTC 103 or publish a brief ADSL wiring Code of Practice to cover connection to the splitter (provided by Telecom) and the 2-wiring to a jackpoint adjacent to the customer's PC location.
The key recommendation at this stage is that a "clean" 2-wire cable (meeting PTC 222 requirements) should start at the splitter and run to the designated 2-wire jackpoint, and that there be no stubs or loops to other jackpoints on this "high frequency" cable run. This will provide the best possible service. We also require that the second pair of our standard 2-pair cable (Orange and Orange/White or White) be used for ADSL service. This helps to ensure that this pair will not be cut into for line grabbing devices or tees to other jackpoints at some later date, as is often the case with the Blue and Blue/White or White pair used for the POTS-based services.
The remaining jackpoints in the customer's premises will continue to serve the POTS-based services. These may remain "looped" or "starred", as already installed. However, all jackpoints should be converted to 2-wire if this has not already been done, because 3-wiring introduces imbalance to earth and potential radio interference. The main point is that the splitter is provided by Telecom at the entry point and as part of the network. The splitter is thus able to fully separate the two lots of internal cabling and so avoid mutual interference between the high and low frequency services.
Wiring the jackpoint for the ADSL modem or PC network card via a spare pair in existing 3-pair (PTC 204) cable is NOT a practicable option. Even if the selected pair is jointed through at intermediate jackpoints and there are no stubs or multiples on the cable run, quite high levels of noise can be injected into the POTS service and there is increased risk of radio frequency interference.
3. PTC 103: AMENDMENT No. 1
a. Segregation between telecommunications and 230 v mains wiring and hardware
PTC 103: 1998, clause 2.3.3(1), requires "a permanent separation of at least 50 mm from mains power cables in all locations, except where the cables are separately enclosed". This is the traditional NZPO/Telecom requirement which meets electrical safety requirements and minimises the risk of noise being caused by induction. With current wiring practices, it is inevitable that telecommunications and 230 V mains/Low Voltage TPS (Toughened Plastic Sheath) cable sheaths will touch in some places where the wiring is inaccessible and not clipped, such as in wall cavities. Further, even where the wiring is visible and clipped, maintenance of the full 50 mm clearance is not always reasonably achievable at cross-over points or over short distances.
Cable contact is not considered an electrical hazard where both cables are sheathed, but this situation is not specifically provided for in the Electricity Regulations: 1997. In view of this, Telecom has discussed the matter with the Office of the Chief Electrical Engineer of the Ministry of Commerce, which is of the opinion "that if a telephone cable has both insulated and sheathed conductors it could be installed in close proximity to the sheath of a TPS cable without being a hazard." Clause 2.3.3 (1) of PTC 103 is therefore being amended to read: -
"2.3.3(1) Telecommunications cables should be installed at least 50 mm clear of Low Voltage (usually 230 V mains) TPS cables wherever practicable. Where the 50 mm clearance is not easily achievable, fully sheathed cables may touch at cable crossings, in wall cavities, and over short distances."
A minor change in wording of sub-clause (2) will also be made. To align with the Electricity Regulations, the term "mains power" will be amended to "Low Voltage". This also makes it quite clear
that we are not just referring to cables supplying 230 V mains power outlets, but to all cables carrying Low Voltage, as defined in the regulations.
There are still potential risks where one or other cable sheath has been removed to allow termination at fittings. Desirably, all unsheathed wires will be fully contained within a substantially enclosed box. This may not always be so, especially where a simple mounting bracket has been used instead of a flush box to mount the 230 V/Low Voltage fitting. PTC 103 addresses this particular issue in clauses 2.3.3 (2) and (3),
which require a minimum 200 mm horizontal separation between 230 V/Low Voltage fittings and telecommunications sockets unless all unsheathed wires are fully contained within substantially enclosed boxes, or separated by a rigidly fixed barrier such as timber framing. Note that this applies to BOTH sides of the wall. Having the required separation on one side of an internal wall, but not on the other, would
defeat the aims of this safety requirement. Wall board is an acceptable barrier in those cases where exposed telecommunications wiring is clipped to the wall and the jackpoint is surface mounted.
A separate safety requirement is that all unsheathed wires of the telecommunications cabling shall be fully contained within the jackpoint mounting box or, with some flush-mounted units, within the plastic shroud provided with the jackpoint.
b. External telephone cable: pair colours
Clause 2.3.2(3) indicates an alternative colour scheme of blue/blue-white for pair 1 and orange/orange-white for pair 2 in 2-pair "external telephone cable" for wiring outdoors. Unfortunately there are manufacturing difficulties in striping the foamed polyethylene insulant. This alternative colour scheme has therefore now been changed to blue/white for pair 1 and red/black for pair 2.
The above points and some minor editorial and drawing amendments will soon be published on our website so that any downloaded copies of PTC 103 will incorporate the changes.
4. PUBLICATION OF PTC 222: RESIDENTIAL TYPE TELECOMMUNICATIONS CABLE
The 1997 draft of PTC 222 has now been replaced by the published version, PTC 222: 1999. This version will be supplied free of charge to those who purchased the draft version. Other readers wishing to purchase a copy may fax or email their requests to Access Standards. The price per copy is $25, inclusive of postage and GST.
A few editorial changes have been made in addition to the changes announced in Newsletters 110 and 111.
5. ACCESS STANDARDS RE-LOCATION DELAYED
Our projected shifting date of mid-June has been delayed. I will advise the expected timing, new telephone numbers, etc, when this information is available. In the meantime, please continue to communicate with us using the present numbers, street address, etc, as shown on the letterhead.
DOUG BURRUS
Manager
Access Standards
