TELECOM ACCESS STANDARDS NEWSLETTER NO. 115 JULY/AUGUST 1999 CONTENTS 1. DIGITAL CELLPHONE VOICE ENCODING PROTOCOLS 2. SECOND-HAND AND PARALLEL IMPORTED CELLPHONES 3. ADSL DEVELOPMENTS 4. PLUGS ON APPLIANCES SOLD IN NEW ZEALAND 5. AUDIO CODEC (AC) AND AUDIO MODEM RISER (AMR) CARDS 6. TELEPERMIT SUBMISSION DOCUMENTS 7. DECADIC SIGNALLING: TESTING AND WARNINGS 8. ACCESS STANDARDS RE-LOCATION RETURN TO MAIN INDEX 1. DIGITAL CELLPHONE VOICE ENCODING PROTOCOLS A traditional trade-off in digital cellular transmission is the balance between bit rate and voice quality. In this regard, there is no difference in principle with what goes on with compression technologies used in private networks in the land-based network. In Telecom's cellular network, three types of digital handsets are currently in operation, using two different voice encoding (vocoder) protocols, as defined in the relevant standards: The earlier dual mode analogue/digital cellphones to IS-54B use a VSELP ( Vector Sum Excited Linear Predictive) vocoder, as did the first digital cellphones to IS-136. The more recent digital cellphones to IS-136 use the improved ACELP (Algebraic Code Excited Linear Predictive) vocoder When VSELP is used in medium to low signal strength areas, voice quality tends to deteriorate, so Telecom implemented some local changes at its cellsites. These resulted in some improvement, but the gains were not considered optimum, so Telecom introduced the later ACELP vocoder for both cellsites and cellphones at the end of 1998. This has since resulted in big improvements in call quality and 80% of digital calls are now made via these new generation vocoders. Unfortunately, it is not possible to optimise digital network parameters for both types of vocoders and In view of the improvements that can be achieved for users by increased penetration of ACELP, Telecom would prefer to convert its network fully to ACELP and optimise parameters for this protocol. Since this will impact on VSELP operation to some extent, it is strongly recommended that suppliers promote the use of digital cellphones using the ACELP vocoder. 2. SECOND-HAND AND PARALLEL IMPORTED CELLPHONES There is considerable interest in the pre-paid cellular business at the present time, with numerous enquiries from companies interested in parallel-importing both new and second-hand cellphones. Our present Telepermitting arrangements for cellphones depend very much on the support of the original manufacturer, who has makes available such basic documentation as the FCC test reports, test codes, etc, as explained in Newsletter No. 112. Where a parallel importer cannot gain authorisation to use such information, arrangements will have to be made for re-testing by the parallel importer, such that Telecom receives documentation directly equivalent to that required for new cellphones. With second-hand products, the position is somewhat more complicated, as those products may have been originally made for another market, with different software and features. In some cases, there may be several variants of the same model. If this is the case, we need clear assurance that all variants are compatible with our cellular network. While such products may have been made to the same technical and quality standards as the equivalent new models directly imported into this country, the nature of their previous service life and operating environment is completely unknown. In order to overcome this problem, we will be publishing a supplement to our cellular PTC specifications to introduce a batch sampling and batch acceptance arrangement. Another key issue is compliance with the current FCC requirements and current EIA specifications. We will require all new Telepermit applications to comply with the current standards, not with whatever standards may have applied at the time they were manufactured. 3. ADSL DEVELOPMENTS Telecom's proposals for opening the market for ADSL CPE to support its Fast Internet or "JetStream" service (which was announced on 30 June) were covered in some length in Newsletter No. 114 . I am pleased to report that I have since learnt that the relevant ITU Recommendation, G.992.1, has already been ratified, well ahead of what we had been led to expect. The ITU announced on 5 July that it had approved a set of new world standards providing Multi-Megabit/s network access via ordinary telephone subscriber lines by using ADSL (Asymmetric Digital Subscriber Line) technology. Future PTC specification Although the ITU Recommendation G.992.1 has been finalised, we still need to obtain the actual text, which is expected to be available within a few weeks. We will then need to select appropriate options for our service and negotiate with our supplier for the provision of "ITU standard-compatible" DSLAM's. In the meantime, it is expected that independent testing services will be developed to carry out compliance testing. By the time these measures are in place, we should be in a position to start drawing up the necessary PTC specifications, which will to open the CPE market to other suppliers. However, the actual timing for publication of a draft is not yet known. 4. PLUGS ON APPLIANCES SOLD IN NEW ZEALAND The question recently arose as to whether a European plug could be used in conjunction with an adapter for some imported equipment in order to avoid the need for an "Australia/New Zealand version" of its plug pack power supply. The matter was raised with the Office of the Chief Electrical Engineer at the Ministry of Commerce and the ruling given was as follows:- "The principle means of compliance with the Electricity Regulations 1997, NZECP 3: 1998, requires that "Supply cords for single-phase portable electrical appliances having a rating not exceeding 10 A shall be fitted with a plug complying with AS/NZS 3112." This office would not consider an electrical appliance fitted with a European style plug, and supplied with an adapter to the NZ supply plug configuration, as meeting the above requirement." I have re-printed this ruling as guidance for test laboratories and any other importers who may be considering the provision of imported equipment with plug connections other than those to AS/NZS 3112. 5. AUDIO CODEC (AC) AND AUDIO MODEM RISER (AMR) CARDS A relatively new concept for modems and audio cards in personal computers is the provision of what is effectively a standardised line interface card that can be associated with computer motherboards having modem and/or audio functions integrated into them. This approach not only avoids the need for separate audio and video peripheral cards, but also simplifies the compliance testing process - especially in the USA and any other countries where FCC requirements apply. The relatively small and simple AMR card provides the necessary line isolation for electrical safety purposes and defines such parameters as ringing and off-hook load, on and off-hook line impedance, impedance balance to earth and line polarity independence. However, there are several other parameters which are defined by software in the associated motherboard modem circuitry and these will still need to be tested. The first such device has turned up at one of our testing laboratories and we have been asked to determine the testing requirements in accordance with PTC 200. The following covers our initial proposals and we are keen to receive industry feedback on these. Technology principles Instead of a complete modem on a card being accessed by the processor via the system bus (ISA, PCI, etc) the data pump function remains on the motherboard with the line interface (Data Access Arrangement or DAA) being implemented on the peripheral card. Communication between the motherboard and peripheral card is via a bi-directional serial PCM link consisting of 12 channels of 20 bits repeated at 48 kHz. The channels are dedicated to: * High fidelity multi-channel audio * Modem functions * General purpose input/output * Control/status information Two standards have been developed - firstly, the Audio Codec (AC), which defines the makeup of the PCM link, and secondly, the Audio/Modem Riser (AMR), which defines an interface to a peripheral card with one AC output data stream and four AC input streams, along with clocks and power supplies on a double sided 50-pin (50 total, with 23 per side and 2 pins removed for keyway) edge connector at 1.27 mm pitch with a 2-pin keyway after pin 11. The driver for the AC technology is that as higher speed processors are becoming commonplace in PCs, these processors are capable of performing more of the functionality of hardware peripherals in software. In the case of modems, AMR technology aims to put most of the telecommunications type approval (Telepermit) parameters onto a card which can be tested once, then used with a number of different motherboards with only minimal re-testing. The AC and AMR specifications have been developed by Intel Corporation and may be found on the web at: AC:http://developer.intel.com/pc-supp/platform/ac97/ AMR:ftp://download.intel.com/pc-supp/platform/ac97/amr101.pdf Brief Specifications for an example of integrated circuits which may be used on the AMR cards can be found on: http://www.silabs.com/products/index.html Compliance Issues A Modem implemented using the AMR technology consists of two parts; the card which contains a DAA and AC interface, and the motherboard which contains the data pump function. At this stage, the following issues are unclear, and the Telepermitting process will necessarily evolve as the technology matures: 1. What will be the likely hardware/firmware/software mix for the data pump function? 2. Will there be a consistent Application Programming Interface? 3. Will Modem Riser Cards be interchangeable with functionality being the only difference (i.e. one card may have a loudspeaking phone interface in addition to a modem interface, and the other just the modem interface, but both would work as modems with the same drivers)? 4. Assuming "yes" to question 2, which end parameters would be determined by application software, and which would be determined by motherboard hardware/firmware? To meet the aim of reducing testing to an absolute minimum, question 1 should be irrelevant, the answers to questions 2 & 3 should be "yes", and to question 4 "that all parameters (except those fixed in hardware on the line side of the modem riser card) will be determined by the application software". Given these answers, overall network compatibility will be independent of the motherboard, which will only determine functionality. On the other hand, should compatibility be dependent on the specific combination of Riser Card, Motherboard and application software, there would be little chance of the technology meeting its aim of reducing testing to an absolute minimum. Telecom Telepermit Requirements Taking the optimistic view, Access Standards initially proposes to Telepermit a combination of the Modem Riser Card and the Application Software with testing being performed on a typical generic motherboard. Should the software require the additional functionality of a particular motherboard, this shall also be supplied to the Test Laboratory for Testing. The Modem Riser Card shall be tested once for the following clauses of PTC 200 which are expected to be specific to the card, and unlikely to be affected by the application software: Clause 2.8 Electrical Safety Clause 4.5.2 On-hook line impedance Clause 4.8 Impedance balance ratio to earth Clause 6.2 Polarity independence Clause 6.7 On-hook line current Clause 7.5.3 Ringer Loading Some parameters such as off-hook return loss, and ringer sensitivity, which are normally fixed in hardware, are known to be software controlled in some implementations. As long as these parameters are fixed in a particular implementation, it should not be necessary to test them more than once. All other relevant PTC 200 clauses shall be tested with the combination of the modem riser card and application software in a suitable motherboard. Telepermit holders will have to ensure that any modem driver software changes are tested before release, and that that users are advised to download only those software releases which are either available from local websites or specifically intended for the Telecom network. The overall aim is to minimise any risk of customers obtaining software designed for different local markets from overseas sites and ending up with network compatibility problems. Further information will be published in this Newsletter, as and when reports are received from our testing laboratories. In the meantime, we would be pleased to hear from any suppliers who can shed more light on the network compatibility testing principles of AMR systems. 6. TELEPERMIT SUBMISSION DOCUMENTS Applicants are again reminded of the need to include their application reference number (the number allocated in the format "CP AS 99/xxx" when the application is first received and registered into our records) when sending in additional documentation for a Telepermit application. We seem to be getting a lot of partial applications lately and it can be confusing to receive documents for similarly named products when they are sent separate from the main application. Parallel importing is causing further confusion, as we find that documentation for exactly the same product may be sent to us at roughly the same time. Needless to say, we are anxious to avoid getting involved in disputes about the use of intellectual property on behalf of the "wrong party". Also, please address documents and correspondence to "Access Standards", rather than to an individual. This allows Sonali or Janine (who is expected to be returning soon) to associate the new information with the main application documents and one of the team can then deal with the complete package without the risk of any subsequent documents being overlooked. 7. DECADIC SIGNALLING: TESTING AND WARNINGS The question of testing decadic signalling has been raised with us in the context of products that support only "international" decadic, as distinct from the Telecom "reverse" decadic operation. Needless to say, whether or not the signalling timing is correct for a product that sends the wrong numbers of pulses is somewhat immaterial, as it is very unlikely that a customer will attempt to use such a product with all the digits reversed. Modems are a good example of this situation. All can be set up for decadic or DTMF, but few if any customers will set them up for decadic signalling when DTMF is available. The only real risk is where the wrong type of signalling is set up in error and it will soon become clear that things are not going properly. In the circumstances, it has been agreed that products should support DTMF signalling primarily. Those that also support Telecom "reverse" decadic operation will need to be tested in accordance with PTC 200. Those which also support "international" decadic will not require testing, but will require the addition of a clear warning in the user instructions along the lines: "WARNING This product is to be set up for tone (DTMF) dialling only. Decadic (Pulse) signalling will result in wrong numbers and is NOT to be used". Products which support only "international" decadic (not DTMF-capable) are not eligible for the grant of a Telepermit. 8. ACCESS STANDARDS RE-LOCATION We have now re-located to:- Level 7, Hewlett Packard House, 186 - 190 Willis Street, Wellington. Our current postal address of P O BOX 570 will remain unchanged, but our telephone and fax numbers are now as follows:- Doug Burrus +64-4-382 5345 Richard Brent +64-4-382 5344 Paul Armstrong +64-4-382 5313 Sonali Gooneratne (and, soon, Janine Jackson)   +64-4-382 5358 Our new fax number is: +64-4-384 5920 Our email addresses are, of course, unchanged. DOUG BURRUS Manager Access Standards