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The performance of an echo canceller is measured in echo return loss enhancement (ERLE), [3] [9] which is the amount of additional signal loss applied by the echo canceller. Most echo cancellers are able to apply 18 to 35 dB ERLE. The total signal loss of the echo (ACOM) is the sum of the ERL and ERLE. [9] [10]
Long-latency connections also benefit; in the case of satellites orbiting distant planets, retransmission due to errors would create a delay of several hours. FEC is also widely used in modems and in cellular networks. FEC processing in a receiver may be applied to a digital bit stream or in the demodulation of a digitally modulated carrier.
It specifies the latency for a bit of data to travel across the network from one communication endpoint to another. [1] [2]: 5 It is typically measured in multiples or fractions of a second. Delay may differ slightly, depending on the location of the specific pair of communicating endpoints.
The actual maximum code rate allowed depends on the error-correcting code used, and may be lower. This is because Shannon's proof was only of existential nature, and did not show how to construct codes that are both optimal and have efficient encoding and decoding algorithms.
A natural concept for a decoding algorithm for concatenated codes is to first decode the inner code and then the outer code. For the algorithm to be practical it must be polynomial-time in the final block length. Consider that there is a polynomial-time unique decoding algorithm for the outer code.
Mac OS X 10.5 and 10.6 implement ECN support for TCP. It is controlled using the Boolean sysctl variables net.inet.tcp.ecn_negotiate_in and net.inet.tcp.ecn_initiate_out . [ 20 ] The first variable enables ECN on incoming connections that already have ECN flags set; the second one tries to initiate outgoing connections with ECN enabled.
The first class of turbo code was the parallel concatenated convolutional code (PCCC). Since the introduction of the original parallel turbo codes in 1993, many other classes of turbo code have been discovered, including serial concatenated convolutional codes and repeat-accumulate codes. Iterative turbo decoding methods have also been applied ...
The speed of light imposes a minimum propagation time on all electromagnetic signals. It is not possible to reduce the latency below = / where s is the distance and c m is the speed of light in the medium (roughly 200,000 km/s for most fiber or electrical media, depending on their velocity factor).