A simple and effective precoding scheme for noise whitening onintersymbol interference channels

A precoding scheme for noise whitening on intersymbol interference (ISI) channels is presented. This scheme is compatible with trellis-coded modulation and, unlike Tomlinson precoding, allows constellation shaping. It can be used with almost any shaping scheme, including the optimal SVQ shaping, as opposed to trellis precoding, which can only be used with trellis shaping. The implementation complexity of this scheme is minimal-only three times that of the noise prediction filter, hence effective noise whitening can be achieved by using a high-order predictor     

Growth of polysilicon and silicide films for MOS-VLSI application

Doped and undoped polycrystalline silicon films were grown byapcvd and thermal evaporation techniques. The effect of growth and annealing conditions on the crystalline nature of the films and their properties were studied by electrical, optical, x-ray diffraction andsem techniques. Metal silicides such as TiSi₂ and PtSi₂ were prepared by co-evaporation technique over polysilicon layers to study their suitability in microelectronic applications. Some of the properties of polysilicon and silicides are discussed.     

Trellis-based scalar-vector quantizer for memoryless sources

The paper describes a structured vector quantization approach for stationary memoryless sources that combines the scalar-vector quantizer (SVQ) ideas (Laroia and Farvardin, 1993) with trellis coded quantization (Marcellin and Fischer, 1990). The resulting quantizer is called the trellis-based scalar-vector quantizer (TB-SVQ). The SVQ structure allows the TB-SVQ to realize a large boundary gain while the underlying trellis code enables it to achieve a significant portion of the total granular gain. For large block-lengths and powerful (possibly complex) trellis codes the TB-SVQ can, in principle, achieve the rate-distortion bound. As indicated by the results obtained, even for reasonable block-lengths and relatively simple trellis codes, the TB-SVQ outperforms all other fixed-rate quantizers at reasonable complexity     

Designing a mobile broadband wireless access network

In this paper, a new OFDM-based air interface technology for a mobile broadband wireless system is described. The technology leverages the standard Internet protocol (IP) network elements to build the system and deploys a new air interface technology based on OFDMA. Cross-layer optimization played a major role in the design where the choices made in the physical, MAC, and link layers are also driven by the goal of extending the Internet to the wireless space. A major physical layer benefit of this air interface comes from the orthogonality property that the results in the elimination of in-cell interference are averaged and a worst-case interferer does not limit the system performance. The physical layer features not only result in high capacity but also provide very fine granularity of allocating air link resources, which improves the MAC and link-layer efficiency. The MAC and link layer provide contention-free, fast control channels between the RAR and the WTs. These channels are used to ferry a variety of signaling such as assignments of traffic channel, acknowledgements, channel quality, and traffic request reports. This holistic approach allows for a scheduler that could not only achieve high spectral efficiency but also allow for a fine control over QoS attributes such as latency, reliability, and service differentiation.     

Coding for intersymbol interference channels-combined coding andprecoding

This paper describes a new coding scheme for transmission over intersymbol interference (ISI) channels. This scheme, called ISI coding, combines trellis coding with precoding (used to combat ISI). Like the recently introduced precoding scheme of Laroia, Tretter, and Farvardin (LTF), the ISI coder makes it possible to achieve both shaping and coding gains over ISI channels. By combining coding and precoding, however, the ISI coder makes the “precoding loss” independent of the number of coset partitions used to generate the trellis code. At high rates (large signal-to-noise ratio (SNR)), this makes it possible to approach the Shannon capacity of an ISI channel. The V.34 (formerly V.fast) international modem standard for high-speed (up to 28.8 kb/s) communication over voice-band telephone lines uses the version of the ISI coder described in Section IV of this paper     

Flavor and texture characteristics of low fat ground beef patties formulated with whey protein concentrate

Low fat ground beef patties (10-11% fat), formulated with 10% water, 0.5% salt and 1-4% whey protein concentrate (WPC), were evaluated for cooking characteristics and compared with controls of higher fat content. A reduction in the fat level from 22 to 11% improved all cooking parameters with respect to better cooking yield (p < 0.01) and fat retention (p < 0.05), increased cooked moisture content (p < 0.05) as well as reduced shrinkage (p < 0.05). Texture profile analysis (TPA) showed an increase in chewiness for low fat samples over the high fat control, while hardness and springiness remained unaffected. Adding 10% water to the low fat meat did not change the cooking characteristics, except for a further increase in cooked moisture content (p < 0.05) and an increase in the value for springiness (p < 0.05). Addition of increasing levels of WPC with 10% water to low fat meat resulted in a linear increase (p < 0.05) in cooked yield with a linear decrease (p < 0.05) in shrinkage. The 4% WPC level produced the highest cooking yield (125% of the high fat control) and the least shrinkage (49% of the high fat control). Sensory analysis showed the 4% WPC level to be preferred over lower levels with respect to juiciness and overall acceptability. Addition of 0.3% of texture-modifying additives showed that calcium chloride and hydroxypropylmethylcellulose had a detrimental effect on yield and shrinkage, whereas the effect of tripolyphosphate (TPP) was positive (p < 0.05). Perception of juiciness and overall acceptability of formulated low fat products was significantly better (p < 0.05) with the addition of TPP (0.3%) and lactose (1.2%) to the WPC formulations. Fat levels (11, 18 and 22%) and lactose levels (0.24 and 1.2%) affected volatile components of the beef patties as measured by dynamic head space analysis. Ketones, i.e. 2-butanone, 2-pentanone and 3-hydroxy-2-butanone increased with an increase in fat content from 11 to 22% fat. Addition of WPC and lactose decreased the relative concentrations of pentane, hexane and heptane. The increase of lactose level in meat was accompanied by an increase in 4,4 diethyl-2-oxetanone and 2-methyl-butanal, two compounds that may originate from non-enzymatic browning of lactose.     

The intersymbol interference channel: lower bounds on capacity andchannel precoding loss

The discrete-time additive Gaussian intersymbol interference (ISI) channel with i.i.d. (not necessarily Gaussian) input signals is considered. Several new and old lower bounds on the capacity are derived in a unified manner by assuming different front-end receiver filters, in particular the sampled whitened matched filter (SWMF) and the minimum mean-squared error-decision feedback equalizer (MMSE-DFE) filter. The features of the bounds are demonstrated and compared in several examples with binary and quaternary input signals. It is also shown that the effect of an ideal post-cursor or tail cancellation, in an information-preserving context, depends primarily on the front-end filter. While, as is well known, ideal post-cursor cancellation at the output of the SWMF decreases the information, the opposite trend is seen when an MMSE-DFE front filter is considered. This observation reflects the basic theoretical obstacles in precoding, i.e., ideal post-cursor cancellation in the presence of a pre-cursor. It is used to assess the inherent loss (in terms of information rates as compared to the rates achievable with the hypothetical ideal post-cursor cancellation) associated with any post-cursor cancellation technique such as precoding, DFE, or other variants, when operating in synergy with the MMSE-DFE front-end filter. The effect of the front-end filter on an ideally interleaved, precoded coded-modulation system is also addressed     

Opportunistic beamforming using dumb antennas

Multiuser diversity is a form of diversity inherent in a wireless network, provided by independent time-varying channels across the different users. The diversity benefit is exploited by tracking the channel fluctuations of the users and scheduling transmissions to users when their instantaneous channel quality is near the peak. The diversity gain increases with the dynamic range of the fluctuations and is thus limited in environments with little scattering and/or slow fading. In such environments, we propose the use of multiple transmit antennas to induce large and fast channel fluctuations so that multiuser diversity can still be exploited. The scheme can be interpreted as opportunistic beamforming and we show that true beamforming gains can be achieved when there are sufficient users, even though very limited channel feedback is needed. Furthermore, in a cellular system, the scheme plays an additional role of opportunistic nulling of the interference created on users of adjacent cells. We discuss the design implications of implementing. this scheme in a complete wireless system     

Curie temperatures and 0°K magnetic moments of zinc-substituted lithium ferrites

Because of their several attractive features including relatively high Curie temperatures, substituted lithium ferrites have become important for applications at microwave frequencies. Néel collinear arrangement of spins onA andB sublattices is unable to satisfactorily explain the 0°K saturation moments and the observed Curie temperatures of the zinc-substituted lithium ferrites, especially at concentrations of zincz>0·3 in the formula Li_0·5−z/2Zn_zFe_2·5−z/2O₄. Rosencaig’s localized canting model has been extended and used to compute 0°K magnetic moments and Curie temperatures of these ferrites with substitution levels up toz=0·7. Reasonably good agreement between the calculated and experimental values, both for the 0°K magnetic moments and the Curie temperatures, has been obtained using exchange parameters ratios based on the valuesJ _aa=−20°K,J _bb=−8°K andJ _ab=J _ba=−29°K.     

Trellis-based scalar vector quantization of sources with memory

The trellis-based scalar-vector quantizer (TB-SVQ) can achieve the rate-distortion performance bound for memoryless sources. This paper extends the scope of this quantizer to coding of sources with memory. First considered is a simple extension, called the predictive TB-SVQ, which applies a closed-loop predictive coding operation in each survivor path of the Viterbi codebook search algorithm. Although the predictive TB-SVQ outperforms all other known structured fixed-rate vector quantizers, due to practical reasons, it may not approach the rate-distortion limit. A new quantization scheme motivated by the precoding idea of Laroia et al. (1993), called the precoded TB-SVQ, is also considered; the granular gain is realized by the underlying trellis code while the combination of the precoder and the SVQ structure provides the boundary gain. This new quantization scheme is asymptotically optimal and can, in principle, approach the rate-distortion bound for Markov sources