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Proposed Unimodem Extensions for CDMA and TDMA Services

Jim Panian

Ericsson, Inc.

August 2000 PCCA Meeting

Revision 1.0

Introduction

This paper proposes extensions to Unimodem to enable the user to select one of many CDMA or TDMA services when using Windows. Examples of services are Asynchronous Data/Fax, Direct Access Data Services, Packet Data, and Voice Autodialing. TAPI applications such as Dial-up Networking and RAS are used to initiate wireless data connections using these services. The Windows 2000 Unimodem architecture was modified by Microsoft to accommodate a similar issue with GSM multiple services. For GSM, entries can be made into the INF file of a single GSM data modem to enable of one of thirteen GSM services. The GSM service selection can be made programmatically from a TAPI application or manually from the user interface. Refer to Figure 1 on page 2. This proposal introduces similar extensions to TAPI for CDMA and TDMA services.

Advantages

Adoption of this proposal will make installation of CDMA and TDMA wireless modems easy for the user. The user can perform a plug and play installation of a single physical CDMA or TDMA wireless modem that is tethered to the computer’s serial port with a cable.

Today’s Windows Unimodem architecture forces a single physical CDMA or TDMA wireless modem to be presented as many logical modems. This enables the user to select a CDMA or TDMA service by the modem pull down list within specific applications such as Dial-Up Networking or Phone Dialer. Each service must be presented as a separate logical modem with names such as “CDMA Data Fax Modem”, “CDMA Voice Call Dialer” and “CDMA Medium Data Rate Packet Modem”. Only a single logical modem can be installed using Plug and Play. The user must install the remaining logical modems manually.

It is possible for a single physical CDMA or TDMA wireless modem to be installed as a single logical modem with today’s Windows Unimodem architecture. However, the user must enter special AT commands into the Extra Settings box to select services such as Packet Data. It is highly undesirable to force a user to have to enter AT commands. In some cases such as for GPRS, the user performs service selection by entering a well-defined dial string. However, it is rather arcane to require a user to think about associating a well-defined dial string with a particular service.

Microsoft has recommended the use of NDIS miniports for packet switched data services. This model does not work well for TDMA and CDMA mobile terminals that support both circuit switched and packet switched data services. The user must be able to initiate a fax using TAPI as well as access the Internet through the NDIS driver. However, the installation of the NDIS driver blocks other applications such as fax from accessing the serial port. Implementation of this paper’s proposals will enable all data services to be accessed from Unimodem/TAPI/Dial-Up Networking until a time when the Microsoft architecture supports both circuit switched and packet switched data connection requests in a seamless fashion.

Figure 1. Windows 2000 Pull Down Menu for user selection of GSM data protocols (services).

Impact

As shown in Table 1, the quantity of CDMA and TDMA mobile terminals being sold across all manufacturers per year is substantial. The trend is to build tethered mode data capabilities into the mobile terminal with only the need of a serial port data cable accessory to complete the package. Soon Bluetooth will remove the need for a serial port data cable.

1998 / 1999 / 2000
TDMA / 19 / 35 / 62
CDMA / 9 / 28 / [1]57

Table 1. Projected Number of Mobile Terminals Sold (millions). Sources: TDMA-EDGE Web Site, CDG Web Site.

Proposals

The following text is proposed for inclusion into the next revision of the Microsoft Windows 98 and Microsoft Windows 2000 Modem Registry Reference.

Protocol\CDMA

CDMA supports a number of services. The four major classes are:

  1. Asynchronous Data/Fax, using a circuit switched data bearer service. Supports over-the-air data rates of 14,400/9600 bps.
  2. Low Speed Packet Data, connecting to the Internet via a CDMA network provider using a packet switched data bearer service. Supports over-the-air data rates of 14,400/9600 bps.
  3. High Rate Packet Data (1XRTT), connecting to the Internet via a CDMA network provider using a packet switched data bearer service. Supports over-the-air data rates of 144,000 bps.
  4. Voice Autodialing, autodialing voice calls from a computer with applications such as Microsoft Phone Dialer and Outlook.

Windows 2000 allows users and communications applications (e.g. RAS) to select services dynamically. The inclusion of one or more Protocol\CDMA registry keys will enable the corresponding protocols to be selected in the user interface (see Data Connection Preferences), and indicated via TAPI and Unimodem. When a protocol is selected in the user interface, Unimodem will issue the corresponding AT commands prior to originating a call as part of a sequence of commands setting response format and presentation, carrier detect on etc.

Format

CDMA Protocol registry entries have the following form:

HKR, Protocol\CDMA\<protocol_type>, 1,,"command string<cr>”

Sample

HKR, Protocol\CDMA\ASYNC_DF, 1,,"AT+CRM=0<cr>"

Selects the CDMA Async Data/Fax protocol.

The following table lists the CDMA protocols, the entries, sample command strings and notes.

Protocol Type / <protocol
_type> Entry / Sample commands / Notes
Async Data/Fax / ASYNC_DF / AT+CRM=0<cr> / See TIA/EIA IS-707-3 for the definition of standard CDMA AT commands.
+CRM precedes a dial command.
Low Speed Packet Data / LSPD / AT+CRM=1<cr> / <at_string_lspd> sets the mobile terminal to route packet data requests over a packet switched bearer service.
+CRM precedes a dial command.
High Rate Packet Data / 1XRTT / <at_string_1XRTT<cr> / <at_string_1XRTT> sets the mobile terminal to route packet data requests over a 1XRTT packet switched bearer service.

The following registry keys are used to support autodialing voice calls.

Type / Entry / Sample commands / Notes
Cellular Voice Dial / Voice_Dial_Prefix / +CDV / See TIA IS-707-3 for the definition of standard CDMA AT commands.
Cellular Voice Hang-up / Voice_Hangup / AT+CHV0<cr> / See TIA IS-707-3 for the definition of standard CDMA AT commands.

Protocol\TDMA

TDMA supports a number of logical services. The four major classes are:

  1. Asynchronous Data/Fax, using a circuit switched data bearer service. Supports over-the-air data rates of 9600 to 28,800 with highly compressed data.
  2. Direct Access Data Services, connecting to the Internet via a TDMA network provider using a circuit switched data bearer service. Supports over-the-air data rates of 9600 to 28,800 with highly compressed data.
  3. EDGE – Generalized Packet Radio Service (GPRS), connecting to the Internet via a TDMA network provider using a packet switched data bearer service. A mobile may support up to 8 timeslots for a maximum theoretical data rate of approximately 480 Kbps.
  4. Voice Autodialing, autodialing voice calls from a computer with applications such as Microsoft Phone Dialer and Outlook.

Windows 2000 allows users and communications applications (e.g. RAS) to select services dynamically. The inclusion of one or more Protocol\TDMA registry keys will enable the corresponding protocols to be selected in the user interface (see Data Connection Preferences), and indicated via TAPI and Unimodem. When a protocol is selected in the user interface, Unimodem will issue the corresponding AT commands prior to originating a call as part of a sequence of commands setting response format and presentation, carrier detect on etc.

Format

TDMA Protocol registry entries have the following form:

HKR, Protocol\TDMA\<protocol_type>, 1,,"command string<cr>”

Sample

HKR, Protocol\TDMA\ASYNC_DF, 1,,"AT+COS=4<cr>"

Selects the TDMA Async Data/Fax protocol.

The following table lists the TDMA protocols, the entries, sample command strings and notes.

Protocol Type / <protocol
_type> Entry / Sample commands / Notes
Async Data/Fax / ASYNC_DF / AT+COS=4<cr> / See TIA/EIA-136-350 for the definition of standard TDMA AT commands.
+COS precedes a dial command.
Direct Access Data Services / DADS / AT+COS=8<cr> / See TIA/EIA-136-350 for the definition of standard TDMA AT commands.
+COS precedes a dial command.
EDGE-GPRS / EGPRS / AT+CGDATA=”PPP”<cr> / See TIA/EIA-136-351 for the definition of standard TDMA AT commands.
Note. +CGDATA is issued instead of a dial command.

The following registry keys are used to support autodialing voice calls.

Type / Entry / Sample commands / Notes
Cellular Voice Dial / Voice_Dial_Prefix / +COS=3;D / See TIA/EIA-136-350 for the definition of standard TDMA AT commands.
Cellular Voice Hang-up / Voice_Hangup / ATH<cr> / See TIA/EIA-136-350 for the definition of standard TDMA AT commands.

Protocol\CDPD

CDMA and TDMA mobile terminals may support CDPD packet data when roaming onto an AMPS network.

Format

CDPD Protocol registry entries have the following form:

HKR, Protocol\CDPD\<protocol_type>, 1,,"command string<cr>”

Sample

HKR, Protocol\CDPD\PACKET, 1,,"AT+WS46=4<cr>"

Selects the CDPD protocol.

The following table lists the CDPD protocols, the entries, sample command strings and notes.

Protocol Type / <protocol
_type> Entry / Sample commands / Notes
Packet / PACKET / AT+WS46=4<cr>
<at_string_cdpd<cr> / See PCCA STD 101 Annex L for the definition of standard CDPD AT commands.
<at_string_cdpd> contains other CDPD setup commands from the PCCA STD 101 Annex L.

Bluetooth

Microsoft has stated that a digital cellular mobile terminal (GSM, TDMA, CDMA) that supports Bluetooth will appear as a “Modem Bluetooth Cell Phone” to the user. See Figure 2. Therefore, the Microsoft standard Bluetooth INF file must also support the TDMA/CDMA extensions.

Figure 2. GSM, CDMA, TDMA mobile terminals that support Bluetooth appear as a “Modem Bluetooth Cell Phone” to the user. Source: Microsoft Bluetooth Design Review, June 5, 2000; Microsoft Web Site.

Alternatives

Another alternative for mobile terminal manufacturers is to follow the current Microsoft recommendation to relegate all circuit switched services to Unimodem/Dial-Up Networking and all packet switched services to NDIS miniports. However, it must be recognized that there will be CDMA/TDMA mobile terminals that support circuit switched data and packet data within the same device. The user or application must still be able to select the services as described in this paper. The Microsoft architecture must be modified to enable a seamless user experience. For example, the user must not be burdened with shutting down an NDIS driver to make a circuit switched data call using Dial-Up Networking.

References

  1. Using the Microsoft Windows 98 and Windows 2000 Modem Development Kit (MDK), Version 1.5.0. January 1999.
  1. Microsoft Windows 98 and Microsoft Windows 2000 Modem Registry Reference, Version 1.5.0. February 1999.
  1. TIA/EIA IS-707-3, Data Service Options for Wideband Spread Spectrum Systems: AT Command Processing and the Rm Interface, November 19, 1997.
  1. TIA/EIA-136-350, TDMA Third Generation Wireless – Data-Service Control. Arlington: Telecommunications Industry Association, 2000.
  1. TIA/EIA-136-351, Telecommunications Industry Association, 2000.
  1. PCCA Standard Command Set Extensions for CDPD Modems PCCA ANX-101 L Revision 2.0 Official Standard, March, 1998.
  1. Microsoft Bluetooth Design Review, June 5, 2000.

[1] As of March 2000.