1、 1 ATIS-0300084 Network Interconnection Interoperability Forum, (NIIF) Telecommunications Relay Service (TRS) 2 ATIS is a technical planning and standards development organization that is committed to rapidly developing and promoting technical and operations standards for the communications and rela
2、ted information technologies industry worldwide using a pragmatic, flexible and open approach. Over 1,100 participants from more than 350 communications companies are active in ATIS 21 industry committees, and its Incubator Solutions Program. ATIS-0300084, Telecommunications Relay Service (TRS), Jul
3、y 2006, Formerly NIIF-0008 ATIS-0300084, Telecommunications Relay Service (TRS), is an ATIS standard developed by the NIIF under the ATIS OAM&P Functional Group. Published by Alliance for Telecommunications Industry Solutions 1200 G Street, NW, Suite 500 Washington, DC 20005 Copyright 2006 by Allian
4、ce for Telecommunications Industry Solutions All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. For information contact ATIS at 202.628.6380. ATIS is online at . Printe
5、d in the United States of America. 3 Table of Contents 1.0 Background5 1.1 Introduction.5 1.2 Telecommunications Relay Service .5 1.3 Key Regulatory and Legislative Rulings.5 1.4 Carrier of Choice 6 2.0 Needs and Objectives6 2.1 Rating of TRS Calls6 2.2 Efficiency6 3.0 Network Architecture7 3.1 Gene
6、ral.7 3.2 Access to the TRS Platform .8 3.3 Selection of Carrier of Choice 8 3.4 The Use of MF Feature Group D Signaling.8 3.4.1 The Use of Unique ANI II Digit Pairs .8 3.5 The Use of SS7 Feature Group D Signaling .8 3.6 Call Flows9 3.6.1 TRS Call Billed to the Calling Line 9 3.6.2 TRS Call with Alt
7、ernate Billing.10 4.0 Capabilities of the TRS Provider10 5.0 Capabilities of the Transport Carrier 11 6.0 Responsibilities of the LEC 11 7.0 New ANI II Digit Pairs for TRS .11 7.1 TRS II Digit Pair 6012 7.2 TRS II Digit Pair 6712 4 7.3 TRS II Digit Pair 6612 7.4 ANI II Digit Mapping .12 8.0 Addition
8、al Technical Issues13 8.1 Trunking to the LEC Access Tandem Switch .14 8.2 Tollfree Database Access 14 8.3 Inaccessibility of the Designated Carrier 15 8.4 Access to the LEC Operator.15 8.5 Transfer of TRS IntraLATA Calls to the LEC15 8.6 Coin Sent-Paid Calls 15 9.0 Alternate Arrangements .16 5 1.0
9、BACKGROUND 1.1 Introduction This paper presents the current industry understanding regarding network technical issues associated with the implementation of Telecommunications Relay Service (TRS). Of particular concern is the issue of carrier of choice - the ability of the TRS user to specify the car
10、rier the user wishes to transport the call, and the manner in which this feature can be provided. This effort is a result of activity initiated at the Industry Carriers Compatibility Forum (ICCF). It represents the current industry view and may be subject to change. Any such changes, including modif
11、ications or additions to the document will be made under the direction of the Network Interconnection Interoperability Forum (NIIF). Although the technical arrangements described in the document should be considered the product of industry consensus regarding the ultimate network solution to the sta
12、ted issues, there should be no inference relating to the implementation of the proposed architectures by any TRS service provider. That is, the decision to implement these arrangements, and the timetable in which such arrangements should be deployed, is likely to be based on business and regulatory
13、concerns, and will vary accordingly. Moreover, nothing in this document precludes the use of alternative arrangements which may include some or none of the features described. 1.2 Telecommunications Relay Service Telecommunications Relay Service (TRS) is a telephone transmission service that provide
14、s the ability for an individual who has a hearing or speech disability to engage in communication by wire or radio with a hearing individual in a manner that is functionally equivalent to the ability of an individual who does not have a hearing impairment or speech impairment. TRS includes services
15、that enable two-way communication between an individual who uses a Text Telephone (TT) or other non-voice terminal and an individual who does not use such a device. 1.3 Key Regulatory and Legislative Rulings Several regulatory and legislative actions have mandated that TRS be made available. Most si
16、gnificant of these actions is the Americans with Disabilities Act (ADA) which prescribes that “Each common carrier . shall . provide . TRS, individually, through designees, through a competitively selected vendor, or in concert with other carriers.” In addition, the ADA directs the FCC to prescribe
17、regulations that establish functional requirements, guidelines, and operations procedures for TRS. 6 In its Order in Docket 90-571, the Commission provided such regulations. Key among them is a technical standard that prescribes equal or equivalent access to interexchange carriers. Specifically, it
18、is stated that “TRS users shall have access to their chosen interexchange carrier through TRS, and to all other operator services, to the same extent that such access is provided to voice users.” 1.4 Carrier of Choice In each state, TRS is provided, after a selection/certification or competitive bid
19、ding process, by a single carrier, either an interexchange carrier (IC), a local exchange company (LEC), or other (usually non- profit) organization. The regulation prescribing equal access for TRS has been interpreted to require that the TRS provider offer the TRS user the ability to designate the
20、carrier to transport the call. Accordingly, the TRS provider must establish the technical capability and the administrative procedures to route the call to the designated transport carrier. Similarly, the transport carrier must be able to recognize the TRS call, complete the call to its destination,
21、 and obtain sufficient call detail information to accurately rate and bill the call. With such an arrangement, the established connection will link the calling party to the called party, through the TRS platform and the facilities of the transport carrier. The Communications Assistant (CA) of the TR
22、S provider will provide the relay function. 2.0 NEEDS AND OBJECTIVES 2.1 Rating of TRS Calls Several State Commissions have mandated that TRS calls be discounted. Such discounts must be provided not only by the TRS provider, but also by any other carrier that is involved in transporting the TRS call
23、. Accordingly, if a call is routed by the TRS provider to a transport carrier, the transport carrier must be able to identify the call as a TRS call in order that the appropriate discount can be applied. 2.2 Efficiency It is desireable that the TRS provider be able to route the call to the designate
24、d transport carrier in as efficient a manner as possible. The need for such efficiency implies that the transport carrier receive, through available network signaling, all necessary information to complete the call. This information includes the identification of the call as a TRS call, the end user
25、 calling number, and the called number. Moreover, it is desireable that any additional information further describing the nature of the calling line (e.g., hotel/motel, payphone, etc.) be provided. Calls not requiring operator assistance should be routed to the transport carriers non-operator switch
26、. That is, calls where alternate billing (card, collect, third party) is not requested by the calling party should not involve the operator services position of the transport carrier. When 7 alternate billing is requested, the interaction between the CA and the transport carrier operator should be k
27、ept to a minimum. Again, as much information as possible should be provided to the operator services position of the transport carrier through network signaling. Efficient provision of routing to the transport carrier will minimize the call set-up time associated with the TRS call. Minimal call set-
28、up is necessary to better meet the requirement of functional equivalency to non TRS connections. 3.0 NETWORK ARCHITECTURE 3.1 General The suggested network architecture to effect carrier of choice is shown in the figure below. A key feature of the architecture is the capability within the TRS platfo
29、rm which allows the platform to outpulse in an equal access signaling format to a LEC access tandem switch. This capability takes advantage of known access network capabilities and arrangements to effectively provide connectivity to the requested transport carrier. It is recognized that some of the
30、capabilities described as well as the necessary access trunking are not now in place and will have to be deployed to comply with the proposed architecture. Further, it is understood that this network architecture cannot be used for certain calls (see Section 7.5). Finally, as stated in the introduct
31、ion (Section 1.1) the decision to implement these arrangements and the timetable in which these arrangements are deployed, are likely to be based on business and regulatory concerns. 8 3.2 Access to the TRS Platform Connection of the end user (calling party) to the TRS platform is typically provided
32、 through the use of an Toll-free number. The Toll-free service which routes the call to the platform should be configured to deliver to the TRS provider the 10 digit calling number (ANI). In addition to the calling party number, the Toll-free service should deliver to the platform the ANI II digit p
33、air associated with the calling line. 3.3 Selection of Carrier of Choice After connection to the TRS platform, the end user will provide to the CA - either verbally or through use of a TT - the called number, the type alternate billing required, if any, and, if desired, the carrier the caller wishes
34、 to route the call. 3.4 The Use of MF Feature Group D Signaling The TRS Platform will route the call to the requested carrier by generating an equal access (FG D) signaling message to an appropriate, originating LEC access tandem switch. Originating FG D signaling through an access tandem uses a two
35、 stage outpulsing sequence with the first stage of the form “OZZ XXX“ where OZZ is used to specify a particular trunk group and XXXX is the carrier code. The calling number (ANI) including the ANI II digits and the called number are provided in the second stage of outpulsing. 3.4.1 The Use of Unique
36、 ANI II Digit Pairs It is necessary that the carrier of choice (the transport carrier) recognize the call incoming to its network as a TRS call. To effect this recognition through network signaling, new ANI II digit pairs must be defined and assigned to identify TRS calls. Because the transport carr
37、ier requires information regarding the nature of the calling line, reflecting, for example, the need for a particular billing treatment, multiple ANI II digit pairs are necessary. Accordingly, the use of these new ANI II digit pairs will identify the incoming call as a TRS call with no billing restr
38、ictions (i.e., bill to the calling number) or a TRS call in which some alternate billing arrangement must be used. Specific definitions of these new ANI II digit pairs are given in Section 6, below. It should be recognized that the ANI II digit pair sent by the TRS platform to the carrier of choice
39、will not be the ANI II digit pair originally associated with the calling line and initially received by the TRS platform. Rather, the TRS Platform must map the ANI II pair of the calling partys line to one of the new ANI II digit pairs assigned for TRS use. 3.5 The Use of SS7 Feature Group D Signali
40、ng The TRS Platform will route the call to the requested carrier by generating an Initial Address Message (IAM) containing the appropriate parameters to enable the originating LEC access 9 tandem to route the call to the appropriate IXC. The 0ZZ XXXX will be sent in the Transit Network Selection (TN
41、S) parameter and, as in the FGD in-band signaling above, the 0ZZ will indicate the trunk group type (Circuit ID) and XXXX will contain the Carrier Identification Code (CIC) of the preferred carrier. The LEC tandem will use the information in the TNS to route the call to the appropriate IXC trunk gro
42、up and to indicate the type of call (1+, 0+, etc.). Since the TNS is not passed from the tandem to the IXC, the NIIF recommends the Carrier Information Parameter (CIP) of the IAM must contain the CIC of the Preferred Inter-exchange Carrier (PIC). The Pre-subscribed or Casual Call status of the call
43、is indicated in the Carrier Selection Parameter (CSP). The NIIF recommends utilizing a CSP value of 7 for TRS calls. CSP value of 7 is defined as “Selected carrier identification pre-subscription unknown (verbal) instructions from the calling party.” Further information on CSP values can be found in
44、 T1.113, Signaling System No. 7 (SS7) - Integrated Services Digital Network (ISDN) User Part. The NIIF recommends that the TRS platform pass the Jurisdiction Information Parameter (JIP). Currently, the TRS platform does not send JIP but TRS providers are willing to have their platforms pass JIP if i
45、t was sent on the inbound call. JIP should not be created by the TRS platform for a call where the originating office was not capable of sending it. The Originating Line Information (OLI) codes are the two-digit codes providing indication of the type of station making the call. These codes are refer
46、red to variously as “ANI II digits”, “Info Digs”, and “II digits”, and are described below for TRS use. The NIIF recommends that the IAM sent by the TRS platform be populated in accordance with T1.113, Signaling System No. 7 (SS7) - Integrated Services Digital Network (ISDN) User Part. 3.6 Call Flow
47、s The following are descriptions of the call processing necessary to establish and complete a TRS call. 3.6.1 TRS Call Billed to the Calling Line Consider a TRS call made from a residence line where the caller wishes to have the call completed over a specific carriers network, and not the network of
48、 the TRS provider. Moreover, the call is to be billed to the calling line. Typically, the calling party would access the TRS Platform by dialing an Tollfree number. The call would be completed and, because of the manner in which the (Tollfree) service was provisioned, the TRS platform would receive
49、the calling party number (ANI) and the associated II digits (in this case 00). The calling party will communicate with the CA, informing the CA of the called number and the choice of carrier. The CA, recognizing (through the II digits) that call is made from an unrestricted line and that no alternate billing (e.g., card, collect) has been requested would assume that the call is to billed to the originating line. The CA would initiate the call to the designated carrier causing an equal access signaling message to be transmitted from the TRS platform to the appropriate LEC access ta
