We proposes a new adaptive spectral masking method of algebraic vector quantization (AVQ) for non-sparse signals in the modified discreet cosine transform (MDCT) domain. This paper also proposes switching the adaptive spectral masking on and off depending on whether or not the target signal is non-sparse. The switching decision is based on the results of MDCT-domain sparseness analysis. When the target signal is categorized as non-sparse, the masking level of the target MDCT coefficients is adaptively controlled using spectral envelope information. The performance of the proposed method, as a part of ITU-T G.711.1 Annex D, is evaluated in comparison with conventional AVQ. Subjective listening test results showed that the proposed method improves sound quality by more than 0.1 points on a five-point scale on average for speech, music, and mixed content, which indicates significant improvement.

This paper describes non-reference objective quality evaluation for noise-reduced speech. First, a subjective test is conducted in accordance with ITU-T Rec. P.835 to obtain the speech quality, the noise quality, and the overall quality of noise-reduced speech. Based on the results, we then propose an overall quality estimation model. The unique point of the proposed model is that the estimation of the overall quality is done only using the previously estimated speech quality and noise quality, in contrast to conventional models, which utilize the acoustical features extracted. Finally, we propose a non-reference objective quality evaluation method using the proposed model. The results of an experiment with different noise reduction algorithms and noise types confirmed that the proposed method gives more accurate estimates of the overall quality compared with the method described in ITU-T Rec. P.563.

This paper reviews the standardization work that has been done in question 2 of ITU-T study group 15, which is the lead group on optical access transport technology. The major topics covered are the progress in the G-PON series and the new point-to-point fiber access recommendation. Finally, a brief view of the future plan of XG-PON is presented.

The ITU-T J.83 Annex B is a widely adopted standard in North America for digital video and audio transmission over coaxial cable. This paper proposes a new parallel processing architecture of the parity checksum generator and syndrome generator specified in the standard for packet synchronization and error detection. The proposed parallel processing architecture removes the performance bottleneck occurring in the conventional serial processing architecture, leading to significant decrease in processing time for generating a parity checksum in transmitter and a syndrome in receiver. Implementation results show that the proposed parallel processing architecture reduces the processing time by 92% for parity checksum generation and by 81% for syndrome generation over the conventional serial processing architecture.

This paper describes international standardization activities on B-PON, GE-PON, and G-PON. This paper explains their distinctive technologies, and compares them from the technical view. This paper also mentions future PON standards which are discussed in some standardization bodies.

This paper shows the recent standardization activities on Ethernet OAM functions. First, it briefly introduces recent carrier class Ethernet services indicating their characteristics and operational issues. Then, it explains current standardization status on Ethernet OAM functions. Finally it shows the requirements for Ethernet OAM functions and details of the OAM mechanisms currently being standardized by ITU-T SG13, SG15 and IEEE 802.1 WG.

This paper presents a newly developed noise post-processing (NPP) algorithm and the results of several tests demonstrating its subjective performance. This NPP algorithm is designed to improve the subjective performance of low bit-rate code excited linear prediction (CELP) decoding under background noise conditions. The NPP algorithm is based on a stationary noise generator and improves the subjective quality of noisy signal input. A backward adaptive detector defines noisy input signal frames from decoded LSF, energy, and pitch parameters. The noise generator estimates and produces stationary noise signals using past line spectral frequency (LSF) and energy parameters. The stationary noise generator has a frame erasure concealment (FEC) scheme designed for stationary noise signals and therefore improves the speech decoder's robustness for frame erasure under background noise conditions. The algorithm has been applied to the following CELP decoders: 1) a candidate algorithm of the ITU-T 4-kbit/s speech coding standard and 2) existing ITU-T standards, the G.729 and G.723.1 series. In both cases, NPP improved the subjective performance of the baseline decoders. Improvements of approximately 0.25 CMOS (CCR MOS: comparison category rating mean opinion score) and around 0.2-0.8 DMOS (DCR MOS: degradation category rating mean opinion score) were demonstrated in the results of our subjective tests when applied to the 4-kbit/s decoder and G.729/G.723.1 decoders respectively. Other test results show that NPP improves the subjective performance of a G.729 decoder by around 0.45 in DMOS under both error-free and frame-erasure conditions, and a further improvement of around 0.2 DMOS is achieved by the FEC scheme in the noise generator.

We fabricated a 1.55-µm polarization insensitive Michelson interferometric wavelength converter (MI-WC). The MI-WC consists of a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA) on a planar lightwave circuit (PLC) platform. Clear eye opening and no power penalty in the back-to-back condition were obtained at 10 Gb/s modulation. We also confirmed the polarization insensitive operation on the input signal. Moreover, for an application of the MI-WC to DWDM networks, we demonstrated the selective wavelength conversion of 2.5 G/s optical packets from Fabry-Perot laser diode (FP-LD) light to four ITU-T grid wavelengths. We confirmed the good feasibility of this technique for use in DWDM networks. The wavelength conversion we describe here is indispensable for future all-optical networks, in which optical signal sources without wavelength control will be used at user-end terminals.

We fabricated a 1.55-µm polarization insensitive Michelson interferometric wavelength converter (MI-WC). The MI-WC consists of a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA) on a planar lightwave circuit (PLC) platform. Clear eye opening and no power penalty in the back-to-back condition were obtained at 10 Gb/s modulation. We also confirmed the polarization insensitive operation on the input signal. Moreover, for an application of the MI-WC to DWDM networks, we demonstrated the selective wavelength conversion of 2.5 G/s optical packets from Fabry-Perot laser diode (FP-LD) light to four ITU-T grid wavelengths. We confirmed the good feasibility of this technique for use in DWDM networks. The wavelength conversion we describe here is indispensable for future all-optical networks, in which optical signal sources without wavelength control will be used at user-end terminals.

This paper proposes three MAC protocols over APON to provide residential and small business customers with multimedia services. The proposed protocols support the frame structure of ITU-T recommendation G.983.1 and also provide diverse ATM service classes such as CBR, rtVBR, nrtVBR, ABR, and UBR traffics. Each service is allocated on the basis of priority. Especially, for allocating CBR and rtVBR services, each protocol uses different cell arrival timing information which is achieved with specific coding and ranging procedure. Focusing the difference of cell arrival timing information, we will investigate the performance of proposed protocols. For the proposed MAC protocols, we present grant field format, minislot format, and bandwidth allocation algorithm. Computer simulation shows the performance of the proposed protocols in terms of CDV and delay, comparing with the normal FIFO protocol.

This paper describes recent standardization activities on optical networking and relevant issues which are conducted in ITU-T. The organization is first described, then, several recommendations both which are already recommended and expected to be completed in a couple of years.

We have developed a low bit-rate video coding using a video digital signal processor (DSP) called VDSP1χ, which performs real-time encoding and decoding for discrete cosine transform-(DCT-) based algorithms, such as ITU-T H. 261, H. 263 and wavelet-based subband encoding algorithms. This LSI features a processing unit which implements wavelet filters at high speeds, a compact DCT circuit, and a fast, flexible DRAM interface for low-cost systems. This system is capable of processing quarter common intermediate format (QCIF)(176144 pixels) size pictures at a rate greater than 15 frames/s.

This paper describes an oversampling analog-to-digital converter (ADC) suitable for PCM codes. Non-linear 5-level quantizer is implemented to noise-shaping modulator. This ADC meets the specifications of ITU-T G.712, in spite of using first order delta-sigma modulator, and realizes low power operation. This chip is fabricated in 0.8 µm double-poly and double-metal CMOS process and occupies a chip area of 15 mm2. Maximum power consumption is 12.8 mW with a single +3 V power supply including DAC and TONE generator.