Apparatus and method for reducing errors in data caused by noise

United States Patent m

Graham et al.

[54] APPARATUS AND METHOD FOR

REDUCING ERRORS IN DATA CAUSED BY
NOISE

[75] Inventors: Martin H. Graham, Berkeley;

Howard W. Johnson, Sunnyvale; Philip H. Sutterlin; Chin-Chen Lee, both of San Jose; Amy O. Hurlbut,

San Francisco, all of Calif.

[73] Assignee: Echelon Corporation, Palo Alto, Calif.

[21] Appl. No.: 698,600

[22] Filed: May 10,1991

[51] Int. CI.* H04M 11/04

[52] U.S. CI 340/310 R; 340/310 A;

340/310 CP; 455/222; 455/223; 375/104

[58] Field of Search 340/310 R, 310 A, 310 CP;

455/223, 222; 375/104

[56] References Cited

U.S. PATENT DOCUMENTS

3,783,387 1/1974 Wernli 455/212

4,030,034 6/1977 Ruegg 455/250.1

4,070,631 1/1978 Nash et al 455/223

4,124,819 11/1978 Hansen 455/223

4,203,072 5/1980 Beningfield et al 455/223

4,783,845 11/1988 McChesney et al 375/104

4,835,517 5/1989 van der Gracht et al 340/310 R

4,845,466 7/1989 Hariton et al 340/310 R

US005210518A

[li] Patent Number: 5,210,518 [45] Date of Patent: May 11,1993

4,922,493 5/1990 Kase .

4,972,510 11/1990 Guizerix et al 455/218

4,988,972 1/1991 Takagi 340/310 R

FOREIGN PATENT DOCUMENTS

2003366 3/1979 United Kingdom 455/223

OTHER PUBLICATIONS

IEEE Transactions on Communications, vol., 38, No., 8, Aug. 1990; Errors-and-Erasures Coding to Combat Impuse Noise on Digital Subscriber Loops, David H. Sargrad and James W. Modestino.

Primary Examiner—Jin F. Ng

Assistant Examiner—Edward Lefkowitz

Attorney, Agent, or Firm—Blakely, Sokoloff, Taylor &

Zafman

[57] ABSTRACT

In a power line communications apparatus an improvement for blanking or snubbing impulse noise. The impulse noise is detected and used to snub the detected signal. The duration of the snubbing pulses is controlled to assure complete blanking of noise including the trailing noise signals following a main noise pulse which may not otherwise be detectable. Also, the number of snubbing pulses which can occur are limited to prevent too much energy from being snubbed during any given baud period.

2 Claims, 13 Drawing Sheets