Synchronous data transmission system

• US 20010053147A1
• Filed: 08/02/2001
• Published: 12/20/2001
• Est. Priority Date: 08/04/2000
• Status: Active Grant

• Current Assignee: Lenovo Innovations Ltd Hong Kong (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Namiki, Hideo
• Granted Patent: US 7,359,319 B2
• Time in Patent Office: Days
• US Class Current: 370/386
• CPC Class Codes: H04L 2012/5674 Synchronisation, timing recovery or alignment
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A first and a second terminals 100 and 200 are connected to an asynchronous transmission line 300. Microphones 101 and 201 and loudspeakers 102 and 202, or image input units (i.e., cameras) 111 and 211 and image output units (i.e., displays) 112 and 212, are connected to the first and second terminals 100 and 200, respectively. The terminals 100 and 200 comprise sampling clock generators 103 and 203, data generators 104 and 204, data reproducers 105 and 205, transmission buffers 106 and 206 and n- (or plural) stage reception buffers 107 and 207. Thus, it can prevent data quality deterioration due to an overflow or an underflow when transmitting such data as voice or image data between the first and the second terminals via an asynchronous transmission line.

Claims

1. A synchronous data transmission system for transmitting such data as voice or image data between a first and a second terminals via an asynchronous transmission line, wherein:

the first and second terminals each comprise a data generator and a data reproducer operable under control of a clock from a sampling clock generator, and a transmission buffer and a plurality of reception buffer stages connected to the data generator and the data reproducer, respectively.

3. The synchronous data transmission system according to

claim 1

or

2

, wherein which further comprises a clock synchronizing means for synchronizing clocks generated in the sampling clock generators in the first and second terminals.

4. The synchronous data transmission system according to

claim 1

or

2

, which further comprises a frequency difference eliminating means for eliminating the frequency difference between the clocks generated in the sampling clock generators in the first and second terminals.

5. The synchronous data transmission system according to

claim 1

or

2

, wherein a synchronous data transmission line is connected to the data generators and the data reproducers in the first and second terminals.

2. A synchronous data transmission system for transmitting such data as voice or image data between a first and a second terminals via an asynchronous transmission line, wherein:

the first and second terminals each comprise a data generator and a data reproducer operable under control of a clock from a sampling clock generator, and a transmission buffer and a plurality of reception buffer stages connected to the data generator and the data reproducer, respectively, and the first and second terminals each further comprise an asynchronous transmission line interface connected to the asynchronous transmission line.

6. The synchronous data transmission system according to

claim 2

, wherein the sampling clock generators in the first and second terminals are controlled on the basis of the received data from the asynchronous transmission line interface.

7. A synchronous data transmission system comprising a first and a second terminals and a synchronous transmission line connected between first and a second terminals for voice or image communication with each other, each terminal including a voice or image input means, a sampling clock generator, an A/D converter for digitalizing the output of the voice input means, a data generator, operable with the output of the sampling clock generator, for generating data on the basis of the output of the A/D converter, a transmission buffer receiving the generated data, a plurality of reception buffer stages supplied with the received data via a asynchronous transmission line, a data reproducer operable with the output of the sampling clock generator, for reproducing data from the plurality of reception buffer stages, a D/A converter for converting the reproduced data to an analog signal, a voice or image output means for outputting voice based on the D/A converter output, the data stored in the transmission buffer having been packeted in certain time units (t) and being outputted via asynchronous transmission line interface to the asynchronous transmission line for the time unit (t), the data received from the asynchronous transmission line being stored via the asynchronous transmission line interface in the reception buffer, the data stored in the reception buffer being transmitted to the data reproducer, the reception buffer being capable of storing data received from the asynchronous transmission line for a plurality of times (n×

t) in every unit time (t), and the data reproducer reproducing data when data for the plurality of times (n×

t) has been stored.

8. The synchronous data transmission system according to

claim 7

, further comprising a sampling clock synchronizing means for synchronizing the sampling clocks of the sampling clock generators in the first and second terminals by inputting the output of the sampling clock generator in one terminal to the sampling clock generator in another terminal.

9. The synchronous data transmission system according to

claim 7

, wherein the frequency difference between the sampling clocks generated in the sampling clock generators in the first and second terminals is eliminated by inputting the clock from the sampling clock generator in one terminal to the sampling clock generator in another terminal.

10. The synchronous data transmission system according to

claim 7

, wherein the sampling clock frequency of one terminal is made closer to the sampling clock frequency of another terminal by estimating the sampling clock on the basis of the data received from the asynchronous transmission line.