SoftModem(tm) Specifications

General Magic has developed software capable of performing a full suite of modem functions in real-time, on general-purpose CPUs. This technology allows licensees to develop products that can be built without separate DSP's or modem chips, thereby reducing overall system cost.

The SoftModem Kits are portable, highly optimized code available for licensing and adaptation. This sheet lists the specifications and requirements for SoftModem development. To date, General Magic has executed the softmodem on both an embedded MIPS platform as well as on an Intel Pentium platform.

Key advantages:

Small code size (150KB RISC code for V.32bis, 250KB RISC code for V.34)
Portable to different processors
Real-time
28.8K and 33.6K bps
V.34 provides fast Internet connections

Specifications

SoftModem 2.0 Technology License 1

V.21 0-300 bps
V.22, V.22bis - automode 1200bps , 2400bps
V.32 - adaptive rate 4800 - 9.6kbps
V.32bis - adaptive rate 4800 - 14.4kbps
V.32terbo - adaptive rate 4800 - 19.2kbps
V.23 - 1200bps/75bps (Minitel)

Fax Modes:

V.29 9600bps
V.29 7200bps
V.27ter 4800bps
V.27ter 2400bps

SoftModem 2.0 Technology License 2

Components as in License 1, plus

V.34 - 2400-33.6K bps including V.8
V.34bis - adaptive rate 2400bps to 33.6kbps plus 200 bps aux. channel
V.17 14.4K bps FAX
Hayes AT-Style command processor

Data Link Layers:

Async and HDLC framers
V.42 LAPM (error-correction) included
MNP error correction optional
V.42bis (compression) -- requires separate license from patent holders to ship
Cellular (AMPS) integration: TX filter, V.42 parameters

Extra Features:

CallerID
Bell212 FSK - 1200bps simplex (CLASS caller-ID)
Tone detection - 2 frequency
Tone generation - 2 frequency
Tone detection - user customizable
Default (US) call-progress detection module
Interface for custom tone/cadence detection including FFT
ADSI 2.0 (1200bps) send/receive modulation
ADSI-compliant tone detection

Modem Performance

For testing and verification of SoftModem, General Magic followed the TSB-38 testing standard which defines a series of TSB-37A line conditions and impairment combinations as line and local-loop models based on US and worldwide telephone surveys. TAS TS837A, PTT 5101, 5102, and 5151A equipment was used for testing.

SoftModem has been tested to meet or exceed all test parameters listed in the Test Parameter Summary, using the specified codec and a suitable DAA, such as the TDK 73M9002 or Xecom XE0055S2. Live outside calls were used for extra testing.

Platform Requirements

SoftModem 1.0 was originally developed using an embedded MIPS ASIC (36 MHz MIPS R3000 RISC core). This ASIC has a single-cycle 16x16 bit on-chip hardware multiply-accumulate module. Existing MIPS multiply instructions have been enhanced; new multiply and add instructions have been added to the R3000 instruction set (officially approved by MIPS Computer Systems). The core has a 4Kb instruction cache and 1Kb data cache.

CPU

License 1: Requires 7 MIPS, with single-cycle 16 bit multiply-accumulate (assuming no cache misses -- this is a theoretical measure, not real world).
Runs in real-time on Dino, 90MHz Pentium or 100MHz SGI Indigo2.

License 2 Requires 14 MIPS with single-cycle 16 bit MAC.

ROM

150 Kb of RISC object code (approx. 100Kb for CISC; 250Kb for License 2).

RAM

64 Kb; less if V.42bis is not used.

Codec

License 1: 14-bit samples, 12-bits linearity; 7200 samples per second. Samples passed in 48-sample frames (normally DMA) from codec. Buffer Half/full interrupts or other double-buffering method required.

License 2: 16-bit samples, 14 bits linearity; 7200, 8400, 8229, 9000, 9600, and 10237 samples per second. Samples passed in 48-sample frames (normally DMA) from codec. Buffer Half/full interrupts or other double-buffering method required.

Example system of Softmodem 1.0 - low cost configuration using a MIPS embedded processor:

36 MIPS RISC Processor
Slow 32-bit ROM (167 ns), 16-bit DRAM
14-bit (12 linear) codec - Betty ASIC
Uses 52% of the R3000 bandwidth running V.32bis

SoftModem Kit Contents for Initial Evaluation:

SoftModem library for SGI Indigo2, or Sputnik reference hardware (for Magic Cap licensees), or Pentium with DOS. The library will enable the user to control all functionalities of the SoftModem.
Simulation test suite code and data
Real-time constellation plotting code for SGI Indigo2, or MIPS reference hardware, or Pentium with DOS
Schematics and instructions for building an Indigo2 DAA, or a Pentium DAA (available later)
Standalone diagnostic shell with monitor for embedded MIPS target
(Optional, additional cost) embedded MIPS hardware and cables
Documentation of the SoftModem API

Availability:

License 1 kit: now (Released December 1995)
License 2 kit: now (Released June 1996)

SoftModem Kit Contents With Full License:

The above initial evaluation kit
Full C-language source code
GNU compatible makefiles
Some R3000 assembly optimized versions of key C routines
Email support

SoftModem Test Setup - USA Test Parameter Summary

Line types: Flat, TR30-1, TR30-2, TR30-3, TR30-4, TR30-5, TR30-6

For each line type, test parameters randomly varied within ranges specified.

If block error rate is tested, must be better than 1E-3. (corresponds to a bit rate of about 1E-5 or 1E-6, 1000 bit block size)

Fax Modes: Send, Receive

V.29 9600bps
V.29 7200bps
V.27 4800bps
V.27 2400bps

Data Modes: Send, Receive, with full Automoding

V.21 0-300 bps
V.22, V.22bis - automode 1200bps , 2400bps
V.32 - adaptive rate 4800 - 9.6kbps
V.32bis - adaptive rate 4800 - 14.4kbps
V.32terbo - adaptive rate 4800 - 19.2kbps
V.34 - adaptive rate 2400bps - 28.8kbps (SoftModem 2.0)
V.34bis - adaptive rate 2400bps to 33.6kbps (SoftModem 2.0)

Test Parameter

Range

Units

Receive level

-9

-43

dBm

1-way delay

0

0.4

s

Frequency offset

-10

10

Hz

Phase jitter magnitude

0

10

pk-pk °

Phase jitter frequency

20

120

Hz

Far-end echo attenuation

6

18

dB

Near-end echo attenuation

6

18

dB

SNR (3 kHz)

13

35

dB

Test Parameter	Range	Units
Receive level	-9	-43	dBm
1-way delay	0	0.4	s
Frequency offset	-10	10	Hz
Phase jitter magnitude	0	10	pk-pk °
Phase jitter frequency	20	120	Hz
Far-end echo attenuation	6	18	dB
Near-end echo attenuation	6	18	dB
SNR (3 kHz)	13	35	dB

Modulation Thresholds @ -25 dBm receive level, flat line

14,400bps

>= 23.8 dB SNR

12,000 bps

> 20.8 dB

9,600 bps

> 17.8 dB

7,200 bps

> 14.8 dB

4,800 bps

> 11.8 dB

SoftModem 2.0: 28,800 bps

> 30 dB SNR (estimated)

Connect Times Max., after dialing and PSTN connection completed

V.21

0 seconds

V.22

6 seconds (2 seconds if V.25 disabled)

V.22bis

6 seconds (2 seconds if V.25 disabled)

V.32bis

10 seconds

V.34

7 seconds

CPU	License 1: Requires 7 MIPS, with single-cycle 16 bit multiply-accumulate (assuming no cache misses -- this is a theoretical measure, not real world). Runs in real-time on Dino, 90MHz Pentium or 100MHz SGI Indigo2. License 2 Requires 14 MIPS with single-cycle 16 bit MAC.
ROM	150 Kb of RISC object code (approx. 100Kb for CISC; 250Kb for License 2).
RAM	64 Kb; less if V.42bis is not used.
Codec	License 1: 14-bit samples, 12-bits linearity; 7200 samples per second. Samples passed in 48-sample frames (normally DMA) from codec. Buffer Half/full interrupts or other double-buffering method required. License 2: 16-bit samples, 14 bits linearity; 7200, 8400, 8229, 9000, 9600, and 10237 samples per second. Samples passed in 48-sample frames (normally DMA) from codec. Buffer Half/full interrupts or other double-buffering method required.

14,400bps	>= 23.8 dB SNR
12,000 bps	> 20.8 dB
9,600 bps	> 17.8 dB
7,200 bps	> 14.8 dB
4,800 bps	> 11.8 dB

V.21	0 seconds
V.22	6 seconds (2 seconds if V.25 disabled)
V.22bis	6 seconds (2 seconds if V.25 disabled)
V.32bis	10 seconds
V.34	7 seconds