μ-law algorithm

Abstract: An all digital system, labeled PCM.RR. is presented, which enables the doubling of traffic capacity of PCM links. This is obtained, although keeping the transmission quality impairment very close to the normal PCM standards, by properly using "Adaptive Quantization" and "Speech Interpolation" performed by means of a "Speech Detector" that works directly on the A -law compressed digital signal.

Abstract: This paper evaluates waveform coding techniques known from low bit-rate communication for their usefulness in low-power digital FIR filtering of speech signals. The encodings considered include linear PCM, PCM with adaptive and logarithmic quantization, and differential PCM, combined with two's-complement and sign-magnitude number representation. Selected implementation aspects for each alternative are discussed. Experimental results are presented to quantify potential power savings subject to statistical signal properties and operating conditions. Guidelines for the choice of encoding in application-specific digital signal processing of speech data are provided.

Abstract: The procedure of first COMpressing and then exPANDing a signal is known as "companding". In pulse code modulation systems, commonly used in telephone switching networks, samples of an analog speech waveform are encoded as binary words and transmitted. Large dynamic range speech is most efficiently encoded and transmitted if the amplitude of the waveform is compressed before transmission and then expanded at the receiver. The paper describes a homomorphic approach to companding. It reviews and illustrates how these signals are processed and used in speech processing and communication networks. >

Abstract: Orthogonal frequency division multiplexing (OFDM) is vastly used in wireless networks. Its superiority relies on the fact that information can be split in large amount of frequencies. Each frequency is called information subcarrier. OFDM exhibits excellent annotation in channel fades and interferers as only a few subcarriers can be affected and consequently a small part of the original data stream can be lost. Orthogonality between frequencies ensures better spectrum management and obviates the danger of intersymbol interference. However, an essential problem exists. OFDM systems have high peak to average power ratio. This implies large fluctuations in signal power, ending up in increasing complexity of ADCs and DACs. Also, power amplifiers must work in a larger linear dynamic region. In this paper we present two new techniques for reducing Peak to Average Power Ratio (PAPR), that can be added in any OFDM system and we compare them with other existing schemes.