High speed modem suitable for operating with a switched network

Details High speed modem suitable for operating with a switched network High speed modem suitable for operating with a switched network

1978-08-21

1980-06-03

Stewart, David L.

Multiplex communications

Wide area network

Packet switching

179 1555R, 370 19, 375102, H04L 2730

Patent

active

042063205

ABSTRACT:
A modem capable of achieving essentially 9600 bit per second information transfer rate through the switched telephone network. The high bit rate is achieved notwithstanding the variations in the characteristics of the switched telephone network by phase and amplitude modulating a plurality of sub-carriers at a relatively low baud rate. Correlation detection is employed at the receiver to extract or demodulate the information contained in the various sub-carriers. To allow correlation detection with orthogonal signals, each of the sub-carriers is harmonically related to a fundamental which fundamental is, however, slightly higher than the baud rate. This allows the receiver to delay correlation for a "gap" time, which reduces the effect of transients produced by modulation and also provides greater tolerance to inter-symbol distortion. Since the fundamental of all the sub-carriers is higher than the baud rate, the receiver "sees" orthogonal signals during the integration or correlation time which is maintained as the period of the fundamental. In addition to the information sub-carriers, a pair of unmodulated sub-carriers are also transmitted to enable the receiver to maintain the correlation interval in proper synchronization with the transmitter, and to correct for phase distortion and frequency offset.

REFERENCES:
patent: 3522383 (1970-07-01), Chang
patent: 3789149 (1974-01-01), Clark
patent: 4053713 (1977-10-01), Nitadori
patent: 4079202 (1978-03-01), Payne

Affiliated with

Also associated with

Rating

High speed modem suitable for operating with a switched network does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with High speed modem suitable for operating with a switched network, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High speed modem suitable for operating with a switched network will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-716842