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Automatic And Adaptive System For Efficient Communication In Noisy Communication Line Environments

IP.com Disclosure Number: IPCOM000048534D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 55K

Publishing Venue

IBM

Related People

Woodruff, KR: AUTHOR [+2]

Abstract

The throughput of a communication system using multiphase differential phase shift keying (DPSK) is a function of the bit error rate versus transmission speed for DPSK. The bit error rate is further affected by the signal-to-noise ratio on the transmission lines. By monitoring the block error rate for data transmitted at a specific speed and switching from the normal speed to a lower speed when the block error rate exceeds a predetermined value, the throughput of the transmission link is improved.

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Automatic And Adaptive System For Efficient Communication In Noisy Communication Line Environments

The throughput of a communication system using multiphase differential phase shift keying (DPSK) is a function of the bit error rate versus transmission speed for DPSK. The bit error rate is further affected by the signal-to-noise ratio on the transmission lines. By monitoring the block error rate for data transmitted at a specific speed and switching from the normal speed to a lower speed when the block error rate exceeds a predetermined value, the throughput of the transmission link is improved.

Fig. 1, the relationship between the bit error rates at 2400 bits per second (BPS) and 4800 (BPS) for a given signal-to-noise ratio is shown. For a given line with a fixed signal-to-noise ratio (SNR), the bit error rate at 2400 BPS would be significantly lower than that at 4800 BPS.

Fig. 2 shows the relationship between the effective transmission bit rate and the bit error rate at 2400 BPS and 4800 BPS for a half duplex system sending 1024 bite blocks with SDLC (Synchronous Data Link Control). As is evident from Fig. 2, if the bit error rate at 4800 BPS is greater than 6.2 x 10/-5/, switching to 2400 BPS operation will yield a higher effective bit rate because of the highly improved bit error rate at 2400 BPS. The "cross-over" bit error rate is the decision threshold for deciding which speed of operation to use. It should be noted that the threshold is determined by transmission parameters, such as block size, system modulo, modem turnaround time, line propagation delay, etc. It should also be noted that this approach applies to multi-speed operation as well as single-speed operation, the only difference being that there are decision regions instead of a single threshold, when the idea is applied to a multi-speed module. To make use of this information in an actual transmission system, a means for determining error rate and the ultimate cross-over poi...