Modern mobile communications require optimum bandwidth utilization with minimum loss, delay and good quality of speech transmission This triggered the usage of low bit rate voice codecs, among which CELP codecs inherit the merits of both waveform and source codecs, like toll quality, low bit rate etc In this paper several hardware and software optimization techniques are presented for efficient implementation of ITU G729 standard (CS-ACELP, conjugate structure algebraic code excited linear prediction) of 8 Kbit/s bit rate on a real time digital signal processor (DSP), with the aim of overcoming the limitation of computational burden and also scaling this application for enhanced speed to process more channels These techniques are in general applicable to any speech codec and DSP processor platform

Optimizations of ITU G.729 speech codec

Performance evaluation, in a complete speech analysis-synthesis system, has been carried out for a wavelet-based pitch detection scheme that has been reported earlier. Speech quality, time for computation and memory consumption (for real-time implementation) are the parameters that have been considered while comparing this system with analysis-synthesis systems that use pitch detection based on autocorrelation and cepstral analysis. Results for different speech signals show that autocorrelation-based pitch detection scheme is the best in terms of speech quality and memory consumption while wavelet-based pitch detection stands in between the other two methods.

Performance evaluation of a wavelet-based pitch detection scheme

Long propagation delays and high bit error rates in heterogeneous networks with geostationary earth orbit (GEO) satellite links have negative impact on the performance of Transmission Control Protocol (TCP). In this paper, we propose modifications to TCP by introducing adaptive delay and loss response (TCP-ADaLR) to mitigate the adverse effects of satellite link characteristics. The proposed modifications incorporate delayed acknowledgment (ACK) recommended for Internet hosts. TCP-ADaLR introduces adaptive window increase and loss recovery mechanisms to address TCP performance degradation in satellite networks. We evaluate and compare the performance of TCP-ADaLR, TCP SACK, and TCP NewReno, with delayed ACK enabled and disabled. In the absence of losses, TCP-ADaLR exhibits the shortest user-perceived latency for HTTP and FTP applications. In the presence of only congestion losses, TCP-ADaLR shows comparable performance to TCP SACK and TCP NewReno. In the presence of only error losses, TCP-ADaLR exhibits improvements up to 61% and 76% in throughput and utilization, respectively. In the presence of both congestion and error losses, TCP-ADaLR exhibits goodput and throughput improvements up to 43%. TCP-ADaLR exhibits the best performance in the absence of losses and in the presence of losses due to both congestion and errors. It also friendly to TCP NewReno, exhibits better fairness, and maintains TCP end-to-end semantics.

TCP with Adaptive Delay and Loss Response for Heterogeneous Networks

Voice-over Internet Protocol (VoIP) telephony which is the transmission of real-time voice over an
Internet Protocol (IP) data network, is increasingly becoming a variant telecommunication technology that
one day may surpass the old analog and digital telephone systems. The Quality-of-Service (QoS) factor is
an important parameter to be considered when measuring the performance of a VoIP system. Algorithmic
delay (latency) may influence the QoS of a VoIP system. This paper presents the hardware implementation
of the Linear Prediction (LP) Analysis and Quantization component of the Conjugate-Structure
Algebraic-Code-Excited Linear-Prediction (CS-ACELP) speech compression algorithms. The LP Analysis and
Quantization units were implemented in hardware using Xilinx 11.1 ISE, after which ITU-T test vectors
were used to determine whether they were equivalent implementations of the LP Analysis and Quantization.
The algorithmic delays of hardware-implementations were obtained via simulation using Modelsim XE 6.4b
while the algorithmic delays of the software-implemented speech compression algorithms were obtained by
software profiling using the GPROF profiler.
After comparison the algorithmic delays of the hardware-implementations of the LP Analysis and
Quantization was found to be shorter than the algorithmic delays of their software-implemented and
hardware-implemented counterparts.

Linear Prediction Analysis and Quantization for the Conjugate-Structure Algebraic-Code-Excited Linear-Prediction Speech Compression Algorithm

TCP with adaptive delay and loss response for heterogeneous networks

Spectral efficiency is the most important aspect in wireless communication systems and cellular mobile radio As speech transmissions are the most used form of communications in the personal communication systems, the low bit speech codecs play an important role in determining the system's spectral efficiency A toll quality low bit rate speech codec that was proposed to meet the personal communication system's requirement is the CS-ACELP speech codec The speech codec has high robustness to withstand high-bit error rates and performs well in tandeming conditions, hence leading to efficient bandwidth utilization and increased channel capacity In this paper several optimization techniques are presented for efficient implementation of ITU G729 standard (CS-ACELP, conjugate structure algebraic code excited linear prediction) of 8 Kbit/s bit rate on a real time digital signal processor (DSP), with the aim of overcoming the limitation of computational burden and also scaling this application for enhanced speed to process more channels These techniques are in general applicable to any speech codec and DSP processor platform

Optimal real time DSP implementation of ITU G.729 speech codec

Space Communication Protocol Standards - Transport Protocol (SCPS-TP) is a set of extensions to the Transmission Control Protocol (TCP) aimed at improving TCP performance in the space environment. Some work has been done on performance comparison between SCPS-TP and the widely used TCP. It is expected to have an experimental evaluation of the link delay impact on SCPS-TP, especially by comparing it with standard TCP. The paper describes an experimental study of link delay impact on throughput performance of TCP and SCPS-TP. It has been found that the SCPS protocol implementation is less sensitive to link delay variations than the TCP implementation. TCP is highly sensitive, SCPS-VJ is moderately sensitive, and SCPS-Vegas is less sensitive, to the change of link delay.

http://ieeexplore.ieee.org/iel5/9623/30415/01404841.pdf

An experimental evaluation of link delay impact on throughput performance of TCP and SCPS-TP in space communications

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Optimal real time DSP implementation of ITU G.729 speech codec

Optimizations of ITU G.729 speech codec

An experimental evaluation of link delay impact on throughput performance of TCP and SCPS-TP in space communications