November 11, 1999

Mr. Thomas Sugrue

Chief, Wireless Telecommunication

Bureau

Federal Communications Commission

The Portals

445 Twelfth Street, SW, Room 3C252

Washington, DC 20554

**Re: CC Docket No. 94-102**

**E9-1-1/TTY Compatibility**

**Status Report - TTY Forum**

Dear Mr. Sugrue:

Per the Commission\'s request, attached is a status report of the
Wireless TTY Forum\'s on-going efforts to find viable solutions for TTY
access to 9-1-1 over digital wireless systems. The Forum includes
representatives from the four interest groups that have a significant
stake in providing TTY users access to 9-1-1 over digital wireless
systems: wireless telecommunications industry (wireless carriers and
phone manufacturers), manufacturers of TTY equipment, emergency and
relay service providers (9-1-1 and TRS) and consumer organizations that
represent individuals who are deaf and hard of hearing.

If you have any questions or feedback regarding the status report or the
TTY Forum\'s efforts, we are available to meet with you or your staff.
We will contact you early next week to schedule an appointment.

Sincerely,

Ed Hall

Co-chair

Wireless TTY Forum

Todd Lantor

Co-chair

Wireless TTY Forum

Attachment

cc: Ari Fitzgerald

Mark Schneider

Bryan Tramont

Peter Tenhula

Adam Krinsky

Dale Hatfield

Kris Monteith

Elizabeth Lyle

Pam Gregory

Marty Liebman

Jamal Mazrui

TTY Forum

Technical Status Report

11/12/1999

Table of Contents

1 Overview [5](#overview)

2 A Note About U.S. Standards Process and Standards Nomenclature
[6](#a-note-about-u.s.-standards-process-and-standards-nomenclature)

3 Technical Approaches [7](#technical-approaches)

3.1 Voice Based Solutions [7](#voice-based-solutions)

3.1.1 Direct Audio Connection [8](#direct-audio-connection)

3.1.2 Acoustic Solution [9](#acoustic-solution)

3.1.3 RJ-11-type Modular Connection/Jack (Analog Solution)
[10](#rj-11-type-modular-connectionjack-analog-solution)

3.1.4 True RJ-11 Connection [10](#true-rj-11-connection)

3.1.5 Proprietary Solutions [10](#proprietary-solutions)

3.1.6 Recommendation [11](#recommendation)

3.2 Modified Vocoder [11](#modified-vocoder)

3.2.1 Audio Path Solution (Lucent) [11](#audio-path-solution-lucent)

3.2.2 Audio Path Solution (Nokia) [12](#audio-path-solution-nokia)

3.2.3 Audio Path Solution (Motorola) [12](#audio-path-solution-motorola)

3.2.4 Status of Technical Standards Development:
[13](#status-of-technical-standards-development)

4 Data -- Vocoder Bypass: [13](#data-vocoder-bypass)

4.1 Circuit Switched Data / Inter-working Function
[14](#circuit-switched-data-inter-working-function)

4.2 ITU-T Recommendation V.18 Modem Protocol
[15](#itu-t-recommendation-v.18-modem-protocol)

4.3 Standards Support for Data Solution
[15](#standards-support-for-data-solution)

4.4 TTY Forum's Actions to date [15](#tty-forums-actions-to-date)

4.4.1 V.18 [15](#v.18)

4.4.2 IWF [15](#iwf)

5 Performance Testing [15](#performance-testing)

5.1 Uniform Test Plan Development [15](#uniform-test-plan-development)

5.2 Conduct additional tests using Test Procedures and compare new
results
[16](#conduct-additional-tests-using-test-procedures-and-compare-new-results)

6 Consumer Criteria [17](#consumer-criteria)

6.1 Consumer Requirements Document [17](#consumer-requirements-document)

6.2 Notification to Subscribers and Potential Subscribers who use TTYs
[18](#notification-to-subscribers-and-potential-subscribers-who-use-ttys)

7 Conclusions [18](#conclusions)

# Overview

Since September 1997, the wireless telecommunications industry (wireless
carriers and wireless phone manufacturers), manufacturers of Text
Telephone Devises (TTYs), emergency and relay service providers (9-1-1
and TRS), and consumer organizations representing individuals who are
deaf and hard-of-hearing ("Stakeholders") have undertaken intensive
collaborative efforts through the Wireless TTY Forum to develop
technically feasible solutions that will enable TTY users to access
9-1-1 over digital wireless systems. The TTY Forum's primary focus has
been on voice-based solutions in an effort to find an acceptable
short-term solution that will meet the FCC's requirement that wireless
carriers be capable of transmitting 911 calls from individuals with
speech or hearing disabilities through means other than mobile radio
handsets, *e.g*, through the use of TTYs. However, the TTY Forum has
also proposed several data-based solutions that will enable TTY users to
access 911 over digital wireless systems in the future. The TTY Forum
has also evaluated a variety of physical connections that will enable
these TTY transmissions to occur. The wireless industry is committed to
continuing intensive collaborative efforts to provide viable and
practical solutions for TTY access over digital wireless systems not
only for 9-1-1 purposes, but also to meet the industry's obligations
under Sections 225 and 255 of the Communications Act of 1934, as
amended.

The wireless industry acknowledges that it must continue to work
cooperatively with TTY manufacturers, appropriate consumer
representatives and organizations representing public safety answering
points ("PSAPs") in order to resolve this issue. The purpose of this
report is to provide a consolidated and concise status update of the
technical discoveries, agreements and advancements made by the Wireless
TTY Forum since its inception, and to provide recommendations that are
in the best interests of all stakeholders.

This report covers every TTY test submitted to the TTY Forum as an
official contribution. Testing conditions included using simulated field
conditions and actual network "real-life" stationary and mobile
operations. The aggregate of all TTY testing conducted by the various
manufacturers includes testing for all digital air-interface
technologies employed in the United States today: CDMA, GSM, iDEN and
TDMA. The goal of the testing was to measure the effectiveness of
passing TTY signals (45.45 baud Baudot) over a digital air interface.
All test result contributions are individually numbered (Forum/
yr.month.day.#) and may be referred to as such in the text of the
report. To measure the success rate of all testing, a Total Character
Error Rate or TCER was used. This is a simple calculation of measuring
the difference (or Delta) of what was received against what was
transmitted. As an example, if 10 out of 100 characters were received
incorrectly, the resulting TCER would be 10%. To create an objective yet
standardized character pattern, a *Throughput Test* was developed. The
*Throughput Test* standardized the testing by specifying an exact amount
of characters, numeric figures, and punctuation. Likewise, a software
program was developed to accurately and uniformly measure the results
and determine the Total Character Error Rate (TCER).

# A Note About U.S. Standards Process and Standards Nomenclature

In the United States, telecommunications standards are created by
industry under a consensus-based process. This process is conducted by
non-governmental standards development organizations (SDOs), such as the
Telecommunications Industry Association (TIA). The American National
Standards Institute (ANSI) accredits SDOs and audits them to ensure that
they comply with ANSI's rules for openness, due process, balance,
appeals process, etc. ANSI also reviews the balloting history and
comment resolution for proposed American National Standards to be issued
by SDOs.

At TIA, standards issued before 1988 have the prefix "EIA" (Electronics
Industries Alliance). In 1988, the EIA Information and
Telecommunications Technology Group merged with the United States
Telecommunications Suppliers Association (USTSA) to form TIA. Standards
issued between 1988 and 1992 have the prefix "EIA/TIA". Standards issued
since 1992 have the prefix "TIA/EIA". All ANSI standards must be
reviewed every five years to ensure that they stay current. At this
review, the standard may be reaffirmed, modified (revised), or
rescinded.

An Interim Standard (denoted by "IS") is a published standard intended
for trial use on a temporary basis. An Interim Standard must be
reaffirmed every year. After three years, the Interim Standard must be
forwarded to ANSI to become an American National Standard or to be
withdrawn. Although they may evolve to American National Standards,
Interim Standards are not approved by the ANSI Board of Standards
Review.

A Telecommunications Systems Bulletin (denoted by "TSB") is a published
document that contains useful information for the industry in the form
of comments about an industry standard or an Interim Standard. A TSB is
not a standard.

# Technical Approaches

In the early stages of the TTY Forum two separate general solutions were
identified. The membership of the Forum agreed early on to pursue both
approaches. The voice based and data based solutions have continued to
represent the only viable solution for all digital technologies
currently known to the TTY Forum. Below is an explanation of each
solution.

## Voice Based Solutions 

The TTY Forum defines voice-based solutions as those that use the audio
path of the digital mobile phone whereby the output of a TTY Device
(Baudot signal) passes through the mobile phones Vocoder[^1]. Proposed
voice-based solutions include physical connection (to the phone and to
the TTY) methods such as:

-   Direct Audio Connection

-   Acoustic Solution

-   RJ-11-type Modular Connection/Jack (Analog Solution)

-   True RJ-11 Connection

-   Proprietary Solutions

    Other proposed voice-based solutions include solutions that may
    require modification of the Vocoder. (See section 3.2)

### Direct Audio Connection

It appears that coupling via a direct audio connection between the TTY
device and a digital wireless handset, *i.e.,* a standard 2.5mm audio
interface (jack) is the preferred voice-based solution. A proposal for a
standard wireless phone 2.5mm audio interface to TTY devices was
submitted to the TTY Forum.[^2] The proposal noted that audio output and
input levels are different for each make and model phone. Thus,
manufacturers of wireless phones would need to provide a special adapter
with standardized levels. Moreover, audio output and input levels of TTY
devices have yet to be defined. The proposal recommended a "common
interface" to resolve the variance in output and input levels.[^3] The
TTY Forum reviewed a draft Technical Information Document (TID), which
was finalized at TTY Forum-9. A Standards Requirements Document (SRD)
for the 2.5mm jack was submitted to TIA\'s TR45 in March 1999. The SRD
was remanded to TIA TR45.1 subcommittee. Completing the effort, TIA
TR45.1 has recommended the use of the audio electrical specifications
set forth in TIA TR45.1.4 vehicle interface standards, which are now
published.

###  {#section .unnumbered}

### Acoustic Solution

Ericsson has indicated that it plans to pursue this option. Due to the
confidential nature of Ericsson's marketing plans for this option, the
TTY Forum recommended that Ericsson meet with the FCC under
confidentiality to discuss specific implementation plans and scheduled
milestones.

Thereafter, Ericsson met with the FCC on various occasions and completed
the design of the acoustic coupler during the 1st quarter of 1999. The
product was first introduced at the June 27, 1999 SHHH exhibitor
conference in New Orleans. This accessory product (T1000), an analog
solution, is available for purchase through the Ericsson Special Needs
Center.

### RJ-11-type Modular Connection/Jack (Analog Solution) 

The TTY Forum has discussed this option and does not consider it to be a
viable short-term solution. Thus, the Forum has not pursued development
or implementation of this option.

### True RJ-11 Connection

The TTY Forum has discussed this option and does not consider it to be a
viable short-term solution. Thus, the Forum has not pursued development
or implementation of this option.

### Proprietary Solutions

Several proprietary solutions such as the Mobility™ TTY, an enhanced TTY
device developed by Lober & Walsh Engineering, the AxCell Interface
Device developed by Sendele Wireless Communications[^4], and RangeStar™
Technology developed by RangeStar International, have been presented to
the TTY Forum for consideration as solutions. Due to the proprietary
nature of these solutions, the TTY Forum has not been privy to how soon
these products will be made commercially available. The TTY Forum
recommends that each company meet with the FCC under confidentiality to
discuss specific implementation plans and scheduled milestones.

###  {#section-1 .unnumbered}

### Recommendation 

> Although all the "Voiced-Based" Solutions offer a great deal of
> promise, the connection that seems to provide the best short term
> solution is the direct connect 2.5mm jack. The ability of the TTY
> Forum to identify both the technical specifications and the consumer
> benefits of a 2.5mm jack solution has been a key motivator for both
> the standards groups and the handset manufacturer community.

## Modified Vocoder

In contrast to the aforementioned solutions, other manufacturers have
found success passing TTY signals over digital wireless phones by using
a modified vocoder. The efforts of these manufacturers are described
below:

### Audio Path Solution (Lucent)

Lucent Technologies has proposed an audio path solution, called the *No
Gain* Solution. By turning the gain down in the adaptive filter in the
vocoder, Lucent has found that it is possible to improve the CER.
Specifically, by turning the filter down to zero when a TTY Baudot
signal is detected, it is possible to send the TTY bits seven times and
use that as a form of correction. Initial tests indicate virtually 0%
CER using this method. Testing of the *No Gain* Solution has been
conducted on CDMA and TDMA vocoders. Lucent indicates that the *No Gain*
Solution is adaptable to other digital technologies, *i.e.,* PCS 1900
and iDEN (digital technologies that use similar vocoders). Lucent has
submitted its contribution to Standards Committee TIA TR45. The
standards process is important in order to provide the interoperability
required to develop a widespread solution.

### Audio Path Solution (Nokia)

> Nokia also has proposed an audio path solution for TDMA. While there
> are similarities between the Nokia and Lucent proposals, a significant
> difference is that the Nokia proposal requires bypassing the vocoder
> to use the TTY decoder. On receipt of the TTY signal, the TTY encoder
> is used. This proposed solution requires a delay of approximately four
> frames for the transmission of the TTY Baudot signal. The delay will
> vary based upon the system. The change to the encoder adds a position
> value to the TTY information. The transmission consists of two bits
> that specify the type of signal present after the specified position.
> The decoder contains an error correction algorithm and TTY signal
> generator. Nokia has indicated that its proposed solution supports
> HCO/VCO.

### Audio Path Solution (Motorola)

> Motorola provided the TTY Forum with a proposed voice-based solution
> for CDMA technology. Motorola proposes that the Baudot signal should
> not be handled by the vocoder. Rather, the Baudot signal should be
> handled in the higher pre-filter and rate selection by a rate
> determination algorithm, which optimizes the frame rate for the
> transmission. TTY tone detector identifies the presence of an
> unmodulated Baudot signal and starts the TTY tone detector. The
> primary channel goes to null traffic and the secondary channel carries
> the TTY character. A history is carried with each character to ensure
> that any lost character will be recovered with the next character as
> history. According to Motorola, up to 100 characters can be contained
> in the secondary channel, all carrying a sequence number to ensure
> sequential transmission and identify any lost characters. Motorola\'s
> proposed solution is independent of the vocoder, because the vocoder
> is turned either on or off. Motorola indicates that the solution is in
> the call processing when the service option is determined upon call
> setup. The TTY option is enabled all the time making the phone capable
> of accepting a TTY or voice call dependent on how the call is set up.
> The proposed solution is currently only applicable to CDMA and would
> require approximately a one-year cycle for development. Motorola
> currently supports the Lucent *No Gain* solution for CDMA and TDMA. An
> iDEN solution is being developed.

### Status of Technical Standards Development: 

> **CDMA (TR45.5)** -- Standards based on Lucent's "No Gain" solution
> have been developed. (IS-127-2)
>
> **TDMA (TR45.3)** -- During September 1999, TR 45.3 formally adopted
> the Lucent "No Gain" solution and will continue through the standards
> process. (IS-733)
>
> **GSM** -- Lucent's "No-Gain" solution will be presented in 4Q99.
>
> **iDEN** - Unknown at this time

# Data -- Vocoder Bypass:

> The obstacles associated with passing traditional TTY tones (45.5-Baud
> Baudot) through the vocoder forced the industry to search for
> alternative methods. The most promising approach is the "vocoder
> bypass". When transmitting TTY signals using a "vocoder bypass"
> solution, a couple of fundamental changes in the transmission process
> must take place. First, the conversion of the analog signals to
> digital has to occur prior to transmission through the phone, or the
> signal needs to originate in a digital format. In addition, once the
> signaling is passed through the phone, at some point, (before the
> signal reaches the end point) it needs to be converted back to analog.
> Ultimately, the attention of the TTY Forum turned to Inter-Working
> Function (IWF) solutions. These solutions rely on the development and
> installation of the appropriate IWF software into a wireless carrier's
> network infrastructure. The following sections outline the possible
> IWF solutions.

## Circuit Switched Data / Inter-working Function

> Circuit Switched Data (CSD) is a service that is complementary to the
> existing suite of Voice and Data services including telephone
> interconnect, Short Message Service (SMS) and Packet Data. CSD enables
> subscribers to directly connect a laptop or facsimile device to their
> Multi-Service portable or remote wireless modem and transmit data
> communications to wireline data services.
>
> The Inter-working Function (IWF) contains both the hardware and
> software elements that provide the rate adaptation and protocol
> conversion between a landline destination Public Switched Telephone
> Network (PSTN) and the network for both data and fax services. The IWF
> is required as a network element to support circuit switched data.

## ITU-T Recommendation V.18 Modem Protocol

> Specifies a protocol, which provides for higher speed ASCII[^5] based
> communications while at the same time maintaining compatibility with
> today\'s Baudot TTY devices.

## Standards Support for Data Solution

## TTY Forum's Actions to date

### V.18

> A letter from the TTY Forum to modem manufacturers was sent.

### IWF

> 3Com is scheduled to present their product at the next TTY Forum
> scheduled for November 18, 1999.

# Performance Testing

> The TTY Forum acknowledged the need for a consistent test methodology,
> a uniform method of evaluating the test results ("test plan"), and a
> uniform set of TTY performance standards. The test plan is used to
> determine the minimal level of character error rate that TTY users can
> expect with certain digital technologies used with certain TTY
> devices.

## Uniform Test Plan Development 

> The TTY Forum with the assistance of the wireless digital technology
> groups[^6] developed a uniform test process designed to limit and
> control test variables, establish a test methodology yielding better
> consistency in determining, and compare character error rates (CER)
> across the various digital wireless technologies (CDMA, TDMA, GSM
> 1900, iDEN). Each wireless digital technology group assumed
> responsibility for modifying the test process to accommodate testing
> variances of that technology. Even with the TTY Forum's uniform test
> script and testing procedure, as expected, the test results indicated
> a wide variance in the TCER.

## Conduct additional tests using Test Procedures and compare new results

Each wireless digital technology group identified at least one test
facility and advised the TTY Forum as to the availability of the test
facility in order to commence testing prior to April 1999.[^7] Wireless
manufacturers and carriers conducted tests in accordance with the test
schedules submitted and shared results with the TTY Forum and the FCC.
Concurrently, TTY Forum members continued to research acceptable error
rates, voice-based and data-based solutions during the test schedule.

The TTY Forum provided advance notice to all interested parties of the
test dates, location of the test laboratories, and contact person(s).
Technical representatives of TTY manufacturers, Gallaudet University,
PSAPs and the FCC were encouraged to participate in the testing and to
contact the appropriate manufacturer or carrier conducting the test to
discuss participation.

# Consumer Criteria

## Consumer Requirements Document

> The purpose of the document was to stimulate discussion and solicit
> the views of the wireless carriers and manufacturers participating in
> the TTY Forum.[^8] On September 10, 1998, representatives of the
> consumer groups circulated a document to members of the TTY Forum
> outlining a new set of criteria to address only functional
> characteristics of any proposed solution for TTY access to digital
> wireless systems.[^9] In accordance with the FCC's Extension Order,
> the TTY Forum considered whether the criteria set forth in the
> September 1998 Consumer Memo is supported in the proposed voice-based
> and data-based solutions set forth in this report. Consumers indicated
> that the less than 1% CER is the viable and acceptable target. They do
> not intend to revisit or change the CER target.[^10]

## Notification to Subscribers and Potential Subscribers who use TTYs

> In compliance with the FCC's rules, wireless carriers have notified
> subscribers and potential subscribers that they may not be able to use
> TTYs to access 9-1-1 over digital wireless systems. Wireless carriers,
> with the support of the wireless trade associations, the consumer
> advocacy groups, TTY manufacturers and wireless handset manufacturers,
> will continue to notify subscribers and potential subscribers at
> appropriate intervals until a product is commercially available.

# Conclusions

The information, test data, test results and findings contained in this
report indicate that the wireless industry has diligently attempted to
resolve the issue of sending 45.5 Baud Baudot tones over digital air
interfaces. Following two years of collaborative research, consumer
input and guidance it is concluded that:

The Lucent "No-Gain" solution is the most reasonable voice based
solution, not only for CDMA but possibly for all digital technology that
use code-excited linear predictive (CELP) vocoders.

Furthermore, it can be concluded that although the "No-Gain" approach
may be the most reasonable, there may be other solutions sought by
vendors / carriers that may be more practical and timely to implement.
This is acceptable as long as the consumer needs and requirements are
met. Furthermore, the TTY Forum concludes that the data based solution
using Interworking Function (IWF) that exploits the full potential of
the V.18 protocol should be developed to support future data
capabilities with backward compatibility to existing TTY devices using
45.5 Baud Baudot.

The TTY Forum does not support any one solution over others.

[^1]: A voice compression technique that employs algorithms so that only
    some of the digitally encoded voice signal is actually transmitted.

[^2]: [See]{.underline} Proposed - Wireless Phone 2.5mm Audio Interface
    to TTY/TDD ("2.5mm Audio Interface Proposal"). Attached to October
    Quarterly Status Report as Appendix K.

[^3]: [See]{.underline} 2.5mm Audio Interface Proposal at 3-4. Attached
    to October Quarterly Status Report as Appendix K.

    .

[^4]: Sendele Wireless has informed the TTY Forum that it has a CDMA
    product and testing is being done in analog.

[^5]: American National Standard Code for Information Interchange

[^6]: For purposes of this report, wireless digital technology groups
    refers to the CDMA Development Group ("CDG"), GSM North America
    (GSMNA), Universal Wireless Communications Consortium (UWCC) and
    Motorola (iDEN).

[^7]: GSM NA commenced testing in January 1999 to provide test results
    to the TTY Forum and the FCC, subject to the following
    conditions: 1) the test specification with modifications suggested
    by the GSM NA is approved and released by October 30, 1998; 2) lab
    based testing with real world conditions is accepted; 3) the test
    specification does not change dramatically; 4) manufacturers can
    assist the test facilities to set up the test; and 5) no unforeseen
    restrictions are placed on the testing.

[^8]: The FCC's Wireless Telecommunications Bureau has elevated the new
    list of criteria by attaching it to the Extension Order as an
    appendix and holding it out as an example of what consumer groups
    would like to have incorporated into any solution implemented by the
    Forum, and therefore the Workplan. [See]{.underline} Extension Order
    at 4.

[^9]: ^?^ Memorandum from Consumer Representatives to TTY Forum, Sept.
    10, 1998. Attached to October Quarterly Status Report as Appendix R.

[^10]: CTIA and consumer groups have initiated an on-going dialogue to
    address accessibility issues. They plan to meet every four to six
    months to discuss such issues.