Federal Communications Commission Office of Engineering and Technology Laboratory Division

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1 Federal Communications Commission Office of Engineering and Technology Laboratory Division April 26, 2016 GUIDANCE FOR PERFORMING T-COIL TESTS FOR AIR INTERFACES SUPPORTING VOICE OVER IP (E.G., LTE AND WI-FI) TO SUPPORT CMRS BASED TELEPHONE SERVICES 1.0 Introduction The requirements for T-Coil signal tests are defined in Clause 7 of ANSI C This document provides additional guidance to help demonstrate HAC compliance for air interfaces that support Voice over IP (VoIP) transport 2 that are not explicitly identified in Table 7.1 of ANSI C Currently many CMRS providers are supporting both VoLTE and Wi-Fi Calling (VoIP) for their CMRS based Telephone Services. For this document, Wi-Fi Calling means enabling CMRS based Telephone Services over Internet services using Wi-Fi access. Handsets that fall under that also have pre-installed over-the-top (OTT) features are not required to test for HAC; however, a handset manufacturer may test for T-Coil by following this guidance for engineered services such as: Google talk, Yahoo Messenger (Internet Low Bitrate Codec), WebRTC [Opus, Skype (SILK)], IETF RFC 6716, H.263 and H.264, etc Background HAC T-Coil testing is a measurement of the intended magnetic field generated by a telephone handset and is detected by hearing aids that are equipped with T-Coil magnetic pick-up coils. The handset generates a magnetic field in the audio range of the far end telephone conversation directly into the hearing aid, bypassing the hearing aid s acoustic microphone. T-Coil compliance testing includes three measurement parameters: (1) the magnetic field intensity for normal speech level; (2) the frequency response; and (3) the signal quality as a signal to noise ratio of magnetic fields. These measurements are 1 Voice over IP (VoIP) handsets for CMRS are only covered by the measurement procedures in ANSI C Voice over IP is defined in 9.3 of the FCC rules as Interconnected VoIP service. Interconnected Voice over Internet protocol (VoIP) service is a service that: (1) Enables real-time, two-way voice communications; (2) requires a broadband connection from the user's location; (3) requires Internet protocol-compatible customer premises equipment (CPE); and (4) permits users generally to receive calls that originate on the public switched telephone network and to terminate calls to the public switched telephone network (i.e., VoLTE, Wi-Fi Calling and OTT). 3 See: ANSI C _interpretation_T_coil_audio_levels_for_LTE_July_ OTT: Testing T-Coil requires that an engineered service have established standards for voice quality, network average talker reference levels, codec(s) and codec frequency response. Page 1

1 This document provides additional guidance to help demonstrate HAC compliance for air interfaces that support Voice over IP (VoIP) transport 2 that are not explicitly identified in Table 7.

2 typically made using a base station simulator, 5 using defined network reference test signals over supported air interfaces using the appropriate codecs. 6 a) In the HAC Order 7 the Commission recognized the need to permit exemptions air interfaces due to unavailable test equipment and undefined network standards. b) Previous guidance, i.e., KDB Publication D02 v01 and v01r01, provided guidance for this exclusion when testing T-Coil for VoLTE air interfaces and Wi-Fi Calling until such time that OET issues measurement guidance and resolves other pending issues. Initially two issues were identified in the HAC Order: 1) Speech signal level to be used to make the measurement (level of average speech) are not identified in ANSI C ) Base Station simultor test equipment is not available. c) This document KDB Publication D02 v02 updates the previous OET measurement guidance KDB Publication D02 v01 and v01r01 with the following provisions: 1) Handsets supporting VoLTE need not be excluded from T-coil testing because: (A) Average speech levels have been defined. 9 (B) Base station simulators are now available supporting audio call simulation over LTE air interfaces. (C) In addition, handsets tested for VoLTE no longer require Pre-Approval Guidance (PAG) review when tested. (D) Manufacturers are permitted to obtain a HAC rating of handsets without VoLTE T-coil testing under the transition period provided in the Fourth Report and Order (FCC ). 10 Manufacturers electing this exclusion must comply with the filing requirements in Clause 3 of this document. 2) Handsets supporting Wi-Fi Calling can also be tested under this guidance if: (A) Average speech levels are defined. (B) Base station simulators are available. (C) Handsets tested for Wi-Fi Calling will require PAG review. 5 See: 7.1 through of ANSI C Testing T-coil requires establishing the connection and testing the permutations of voice coder, air interface, band, and bit rate as defined by the service. The rating is the worst-case condition associated with an air interface, voice coder, and band and bit rate. 7 Third Report and Order (DA , April 9, 2012) adopted the use of ANSI C for HAC testing became effective August 18, 2012 (HAC Order). 8 See fn. 3, supra. 9 Id. 10 FCC (docket no ) APPENDIX B Final Rules amends 20.19(a)(2), paraphased as follows. Prior to January 1, 2018, hearing aid compatibility requirements permit manufacturers of digital CMRS handsets to exclude T-Coil compliance testing for Voice over IP CMRS operations (i.e., VoLTE, Wi-Fi Calling). After January 1, 2018, T-Coil testing for all Voice over IP, including both interconnected and non-interconnected VoIP services, is required (i.e., VoLTE, Wi-Fi Calling, and OTT features installed by the manufacturer or service provider). Page 2

3 (D) Handsets not tested for Wi-Fi Calling must comply with the filling requirements in Clause 3.0 of this document 3) Handsets pre-installed by the manufacturer or carrier supporting OTT services are not required to test for HAC compliance but have the option to test under Clause 4.0 of this document. (A) Handsets tested will require PAG review. 3.0 Applications excluding T-Coil compliance tests for Voice over IP When excluding T-Coil tests for Voice over IP modes, manufacturers should note this fact in the list of supported air interfaces (for both the T-rating and M-rating test report) and the section demonstrating RF measurement values (for the M rating in the M-rating test report) associated with the same air-interface bands and measurement location that were excluded for T-Coil testing: No associated T-Coil measurement has been made in accordance with the guidance issued by OET in KDB Publication D02 T-Coil Testing for CMRS IP. Grant Note HC is to be used for all CMRS air interfaces tested: (including air interfaces not t-coil tested in accordance with KDB Publication D02 ) HC automatically generates grant comment: This equipment complies with the hearing aid compatibility technical requirements of Section of the rules. Manually add the additional grant comment: Some T-Coil tests have not been performed as permitted by FCC policy. In addition, an appropriate disclosure, as required by the rules, must be included in the user s manual or inserted in accordance with the requirements of 20.19(f)(2)(i). 4.0 Applications including T-Coil compliance tests for Voice over IP 4.1 Instrumentation for T-coil testing for Voice over IP T-Coil testing requires test instrumentation that can (1) establish a connection to the handset under test over the appropriate air-interface; (2) inject a specific set of test audio tones (as defined in the relevant specification for that air interface) to simulate a conversation over the established connection; and (3) have the hand set under test output the audio tones as T-Coil magnetic fields. The magnetic fields are detected by a calibrated probe and analyzed for compliance according to the ANSI C requirements. Base station simulators or adjunct instrumentation must support the appropriate air interfaces. It is necessary (1) for the system to be able to establish an IP call from/to the hand set under test; (2) through an IP Multimedia Subsystem or a simulated protocol (SIP/IP) server; (3) to an analog audio adapter containing the permissible set of codecs used by the device under test; and (4) inject the necessary ANSI C63.19 test tones at the average speech level for the measurement. Page 3

0 of this document. (A) Handsets tested will require PAG review. 3.

Two sets of information are required to successfully test for T-Coil: a) The applied test audio signal representing the average talker as stated in 7.4.2.1 of ANSI C63.19-2011.

4 Two sets of information are required to successfully test for T-Coil: a) The applied test audio signal representing the average talker as stated in of ANSI C For protocols not listed in Table 7.1 of ANSI C , use the normal speech input level as defined in the relevant specification for that air interface (service). b) The set of codecs defined in the relevant specification for that air interface (service). 4.2 T-Coil testing of Voice over IP For testing VoLTE, a PAG is not required. Applied signal levels 11 and codec definition are established by 3GPP standard and supported by a base station simulator. For Wi-Fi Calling and/or OTT features installed by the manufacturer or service provider, a PAG is required if an applicant performs and submits T-Coil tests. The following information is required when submitting the PAG for review: 12 a) The applicant must reference the specific details of the service. The details need to briefly describe the service; the simulated connections used to make the measurement, the set of worst case codecs tested and the engineered normal speech input level specified for the service. b) A description of the T-Coil test set up. c) Specify all the test equipment used, including manufacturer and model numbers. 11 See fn. 3, supra. 12 TCBs reviewing T-Coil test results for IP transport must use the Pre-Approval Guidance (PAG) procedure in KDB Publication Applicants submit a KDB Inquiry for preliminary guidance prior to the TCB submitting the final PAG request. Page 4

b) The set of codecs defined in the relevant specification for that air interface (service). 4.2 T-Coil testing of Voice over IP For testing VoLTE, a PAG is not required.

5 d) Software used to simulate call connection server. e) Voice Codecs tested and how they relate to the targeted telephone service. If certain codecs are not tested, include a justification. Change Notice 10/31/2013: D02 T-Coil testing for CMRS IP v01 has been changed to D02 T-Coil testing for CMRS IP v01r01. Revisions reflect changes to the Permit Bur Ask requirements for 4.2 applicants testing T-Coil for CMRS Voice over IP transport. 04/26/2016: replaces D02 T-Coil testing for CMRS IP v01r01. Revision to remove the exemption for T-coil testing for VoLTE and clarification of the exemption for Wi-Fi Calling. Page 5

Change Notice 10/31/2013: 285076 D02 T-Coil testing for CMRS IP v01 has been changed to 285076 D02 T-Coil testing for CMRS IP v01r01.

SUMMARY: In this document, the Federal Communications Commission (Commission)

SUMMARY: In this document, the Federal Communications Commission (Commission) This document is scheduled to be published in the Federal Register on 01/05/2016 and available online at http://federalregister.gov/a/2015-32757, and on FDsys.gov 6712-01 FEDERAL COMMUNICATIONS COMMISSION