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The motivation behind this study is the essential need for survivability in the telecommunications networks. An optical signal should find its destination even if the network experiences an occasional fiber [...]

We present a liquid level sensing system for cryogenic fluids based on an array of aluminum-coated fiber Bragg gratings written in high-attenuation fibers (HAFs) interrogated by frequency-shifted interferometry (FSI). The sensors are heated up optically through the absorption of light at the core of the HAF sections. The distinct thermal response of sensors in the liquid from that in the gas provides an unambiguous means to detect the liquid level. FSI allows the sensors to have overlapped spectral response, and, therefore, has the potential of accommodating a larger number of sensors in the array. The measurement of liquid nitrogen level using this system was experimentally demonstrated. The successful combination of aluminum-coated HAF Bragg grating sensors and the FSI technique promises a viable solution for liquid level sensor networks at cryogenic temperatures. OCIS codes: 060.2370, 120.3180, 060.3735, 060.4230.

In a random-reference multiplexing scheme, we propose a method of generating different wavefronts without rotating a random pattern-generating element, simply by changing the wavelength of the incident light. A reference pattern with a random wavefront is an important aspect of color recording and readout. The color recording and readout system we propose is simple and compact, and generation of uncorrelated color patterns is easy. An important feature is that simultaneous readout using multiple wavelengths is facilitated. We confirmed the feasibility of this system by simulation and experiment, and we examined color recording and readout using multiple wavelengths. [c] 2010 Optical Society of America OCIS codes: 210.2860, 090.4220.

The resolving power of an imaging system in digital lensless Fourier holographic configuration is mainly limited by the numerical aperture of the experimental setup that is defined by both the restricted CCD size and the presence of a beam splitter cube in front of the CCD. We present a method capable of improving the resolution in such a system configuration based on synthetic aperture (SA) generation by using time-multiplexing tilted illumination onto the input object. Moreover, a priori knowledge about the imaged object allows customized SA shaping by the addition of elementary apertures only in the directions of interest. Experimental results are provided, showing agreement with theoretical predictions and demonstrating a resolution limit corresponding with a synthetic numerical aperture value of 0.45. OCIS codes: 050.1940, 090.1995, 100.2000, 100.6640, 110.0180, 110.1650.

We evaluate numerically the effect of shrinkage of photopolymer on the bit error rate or signal-to-noise ratio in a reflection-type holographic data storage system with angular multiplexing. In the evaluation, we use a simple model where the material is divided into layered structures and then the shrinkage rate is proportional to the intensity in each layer. We present the effectiveness of the proposed model from the experimental results in the recording of the plane waves both in a transmission-type hologram and a reflection-type one. Several kinds of shrinkage rates are used to evaluate the characteristics of angular multiplexing in the reflection-type holographic memory. [c] 2010 Optical Society of America OCIS codes: 210.2860, 160.5470, 090.7330.

We propose a method using phase encryption and hologram multiplexing to encode positional information into the hologram, which can be used during readout to find the correct position of the reference beam. We also include a method to align the position of the phase code in the reference beam during readout, with which we achieved approximately 1/100 hologram size (4.4 [micro]m) precision electronically, without the need of a precise mechanical hologram positioning device. We prove the feasibility of the method with experiments. [c] 2010 Optical Society of America OCIS codes: 090.0090, 090.4220, 210.2860.

As functionality of vehicles increases in complexity, the demand on the in-vehicle networks increases as well. Maximum bus utilization often becomes the communication bottleneck. One way to satisfy the high bandwidth requirement for future vehicles is to use a higher bandwidth bus or multiple buses. However, the use of a higher bandwidth bus increases the cost of the network. Similarly, the use of multiple buses increases the cost as well as the complexity of wiring and network handling. Both options are becoming solutions to high bandwidth demand. An alternative option is the development of a higher layer protocol that uses data-reduction (DR) techniques to reduce the amount of data to be transferred. Its goal is to communicate the same amount of information using less bus bandwidth. It would be acceptable, provided that it does not increase the message latencies significantly so that the safety of the vehicle is not compromised. The cost of the protocol is expected to be marginal because it consists of one-time changes to software. Various DR algorithms are available in the literature, but DR technology has not been introduced in in-vehicle protocol standards. This paper presents a unique DR methodology, along with its comparison with other proposed methodologies. The performance of this new DR algorithm is found to be better than that of the existing DR algorithms for a wide range of signal dynamics. The cost, as well as the impact of this protocol on the end-to-end message latency, has been found to be very marginal. Index Terms--Controller area network (CAN), data reduction (DR), event-triggered bus, in-vehicle network, multiplexing.

The opportunistic beamforming system (OBS) is currently receiving much attention in the field of downlink beamforming due to its simple random beamforming, low feedback complexity, and same throughput scaling obtained with perfect channel-state information using dirty paper coding at the transmitter. In this paper, we focus on its closed-form throughput evaluation over Rayleigh fading channels, based on the asymptotic theory of extreme order statistics. First, the throughput of a single-beam OBS is investigated, and an analytical solution tighter than the previously reported one is derived. Then, the asymptotic throughput bounds on a multibeam OBS are presented, and also, our analytical expression is shown to be very tight with the simulation results even with fewer users. After that, we argue that the reported conclusion that the single-beam OBS is much preferable to the multibeam OBS in the high-signal-to-noise-ratio (SNR) regime is inaccurate, but that, instead, it is satisfied only when the number of users is very small, due to its limited multiuser diversity gain. Finally, we show that four transmit beams is the most preferable in the multibeam OBS with a large number of users and moderate SNR, which arrives at the tradeoff between increasing spatial multiplexing gain and disappearing multiuser diversity gain. Index Terms--Multiple-input single-output (MISO), multiuser diversity, opportunistic beamforming system (OBS), spatial multiplexing, throughput.

In this paper, we propose a novel distributed interleaved random space-time code (IR-STC) designed for multisource cooperation (MSC) employing various relaying techniques, namely, amplify-forward, decode-forward, soft decode-forward, and differential decode-forward. We introduce a two-phase communication regime for our IR-STC-aided MSC and propose a novel structured embedded (SE) random interleaver-generation method. We also characterize the achievable performance of our proposed IR-STC design in conjunction with various relaying techniques communicating over different intersource Nakagami-m fading channels. Index Terms--Cooperative communications, interleaver division multiplexing, relaying, space-time coding.

Tilt error can affect a serious effect to holographic data storage system using angle(polytopic) multiplexing. Because the tolerance about tilt error is very tight it is important to measure the tilt error and compensate it. In this paper, tilt error measurement system with additional red laser and reflection geometry is suggested and servo control experiments are conducted. A servo controller to compensate tilt error is designed using disturbance observer. Amount of tilt is decreased smaller than 0.01 degree and signal-to-noise ratio is increased with the tilt servo controller when 0.216 degree of tilt disturbance is applied. Index Terms--Holographic memories, servosystems.

Generally limited feedback systems that multiplex multiple user signals are noise power limited in the low signal-to-noise-ratio (SNR) regime and interference power limited in the high SNR regime. If the amount of feedback does not grow with SNR, then there is a sum rate ceiling that increasing the transmit power alone cannot surpass. This paper proposes a simple dual mode system where the base station serves either one user or as many users as the number of transmit antennas. The switching mechanism is smooth and is based on instantaneous system conditions. The mobile determines its preferred transmission mode by using a very simple signal-to-interference-and-noise-ratio (SINR) threshold. Based on the mobiles' feedback, the base station chooses the method of signalling accordingly. With a finite number of feedback bits per mobile, it is shown that the proposed system achieves close to the maximum of the sum-rate for single user and multiuser modes. We identify the preferrable mode for an asymptotically large number of users and/or SNR. This proposed architecture is suitable for systems with moderate coherence time, a moderate to large number of users, and a moderate SNR that cannot afford complex processing at the base station or at the mobile. Index Terms--Gaussian broadcast system, dual mode multiuser system, sum-rate ceiling.

This paper addresses the performance of bit-interleaved coded multiple beamforming (BICMB) [1], [2] with imperfect knowledge of beamforming vectors. Most studies for limited-rate channel state information at the transmitter (CSIT) assume that the precoding matrix has an invariance property under an arbitrary unitary transform. In BICMB, this property does not hold. On the other hand, the optimum precoder and detector for BICMB are invariant under a diagonal unitary transform. In order to design a limited-rate CSIT system for BICMB, we propose a new distortion measure optimum under this invariance. Based on this new distortion measure, we introduce a new set of centroids and employ the generalized Lloyd algorithm for codebook design. We provide simulation results demonstrating the performance improvement achieved with the proposed distortion measure and the codebook design for various receivers with linear detectors. We show that although these receivers have the same performance for perfect CSIT, their performance varies under imperfect CSIT. Index Terms--Beamforming, Bit-interleaved coded modulation, diversity, spatial multiplexing, limited feedback, BICMB.

We show that multiple secure data recording under a wavelength multiplexing technique is possible in a joint transform correlator (JTC) arrangement. We evaluate both the performance of the decrypting procedure and the influence of the input image size when decrypting with a wavelength different from that employed in the encryption step. This analysis reveals that the wavelength is a valid parameter to conduct image multiplexing encoding with the JTC architecture. In addition, we study the influence of the minimum wavelength change that prevents decoding cross talk. Computer simulations confirm the performance of the proposed technique. OCIS codes: 070.0070, 070.4560.

Hadamard multiplexing provides a considerable SNR boost over additive random noise but Poisson noise such as photon noise reduces the boost. We develop the theory for full H-matrix Hadamard transform imaging under additive and Poisson noise effects. We show that H-matrix encoding results in no effect on average on the noise level due to Poisson noise sources while preferentially reducing additive noise. We use this result to explain the wavelength-dependent varying SNR boost in a Hadamard hyperspectral imager and argue that such a preferential boost is useful when the main noise source is indeterminant or varying. OCIS codes: 110.4234, 110.1758, 030.4280, 350.6980.

We propose a spectral imaging method for piecewise 'macropixel' objects, which allows a regular digital camera to be converted into a digital snapshot spectral imager by equipping the camera with only a disperser and a demultiplexing algorithm. The method exploits a 'multiplexed spectrum' intensity pattern, i.e., the superposition of spectra from adjacent different image points, formed on the image sensor of the digital camera. The spatial image resolution is restricted to a macropixel level in order to acquire both spectral and spatial data (i.e., an entire spectral cubet in a single snapshot. Results of laboratory experiments with a special macropixel object image, composed of small, spatially uniform squares, provide to our knowledge a first verification of the proposed spectral imaging method. OCIS codes: 110.4234, 300.6190, 260.2030.

Without interruption or affecting the transmission of ordinary payload channels, we propose a real time polarization mode dispersion (PMD) monitoring system for long-haul, multiple erbium-doped fiber amplifier (EDFA), dense wavelength division multiplexing (DWDM) optical fiber transmission using modulated amplified spontaneous emission (ASE) of one of the EDFAs as the supervisory (SV) signal source. An acousto-optic tunable filter (AOTF) at the receiver side is adopted to scan the spectrum of the transmitted ASE SV signal. Using the fixed-analyzer method, PMDs of different wavelength bands that range from 1545 to 1580 nm of a DWDM fiber-optic communication system can be found by adaptively changing the radio frequency of the AOTF. The resolution and the measuring range of the proposed monitoring system can be significantly improved by cascading the AOTFs at the receiver side. OCIS codes: 060.4510, 230.1040.

We propose and optimize a hybrid erbium-doped fiber amplifier/fiber Raman amplifier (EDFA/FRA). A large number of parameters of a wide-band hybrid amplifier consisting of an erbium-doped fiber amplifier (EDFA) and a fiber Raman amplifier (FRA) have been optimized using an effective and fast global optimization method called particle swarm optimization. Two types of hybrid EDFA/FRA with six- and 10-pumped FRAs have been optimized. A large number of variables affect the hybrid EDFA/FRA performance, thus we need a global optimization method to be able to deal with these variables. Particle swarm optimization helps us to find optimum parameters of a hybrid EDFA/FRA and reduce the gain spectrum variations to 2.91 and 2.03 dB for the six and 10 pumped FRAs, respectively. The optimum design supports the amplification of 60 signal channels in the wavelength range of 1529.2-1627.1 nm for a wavelength-division multiplexing system. OCIS codes: 060.2310, 060.2320.

A new L-band automatic-gain-controlled (AGC) erbium-doped fiber amplifier (EDFA) for dense wavelength-division-multiplexing transmission systems is presented, in which a single 1480 nm laser with an internal thermoelectric cooler is used as a primary pump for stable amplification. All C-band amplified spontaneous emission (ASE) is recycled by the secondary pump to enhance the gain efficiency. A fraction of the output signal is used as an electrical feedback monitor for the AGC to improve the gain-clamped (GC) flatness. Experimental results prove that the AGC EDFA has a gain flatness of better than 0.46 dB/40 nm, i.e., below 1.5%, and a higher gain of approximately 36.5 dB compared to that of approximately 35.3 dB for the conventional GC EDFA at -30 dBm input signal power. The best gain flatness of [+ or -] 0.25 dB can be achieved over the dynamic range greater than 20 dB. The dynamic range of noise figure is between 6.7 and 7.1. The 3 dB down bandwidth is more than 40nm. Overall dynamics measurements for the AGC EDFA feedback stabilization have been carried out. The recorded corresponding rise time of 1.565 ms indicates that the system does not exhibit any overshoot of gain or ASE variation due to the signal at the beginning of the pulse. OCIS codes: 140.3280, 230.4480, 060.4510.

This paper investigates the application of Zipper orthogonal frequency-division multiplexing (OFDM), which is a frequency-domain duplexing technique based on interleaving subcarriers, to multiple-antenna cellular communications. By studying the Cramer-Rao lower bound as well as the performance of a minimum-mean-square-error-based interpolator, we show that the interleaved subcarriers make it possible for the base station to obtain accurate instantaneous downlink channel state information (CSI) from uplink channel measurements. However, the interleaved uplink and downlink subcarriers could introduce interference leakage when the intersubcarrier orthogonality is destroyed in multiple-cell environments. We address this issue by analyzing the uplink-to-downlink power leakage and show that with proper system configuration, such interference only has a marginal effect in typical land mobile radio environments. Finally, by considering maximum ratio transmission as an example, we demonstrate the benefit of knowing instantaneous downlink CSI in multiple-antenna Zipper OFDM systems. Index Terms--Cellular communication, instantaneous channel state information (CSI), interleaved frequency-domain duplexing (FDD), maximum ratio transmission (MRT).

In a time-division duplexing (TDD)/code-division multiple-access (CDMA) cellular network with asymmetric data traffic, dynamic channel allocation (DCA) enhances resource utilization compared with fixed channel allocation (FCA). However, it also induces base-to-base and mobile-to-mobile crossed-slot intercell interference, which can severely degrade system performance. To deal with this problem, a decentralized scheme is proposed, which combines an interference-aware DCA algorithm with space-time linear minimum-mean-square-error (LMMSE) joint detection at the base and mobile stations. The former assigns active links to timeslots in a way that crossed-slot interference is mitigated, while the latter suppresses the remaining intercell interference (along with intersymbol and intracell interference), exploiting its spatio-temporal autocorrelation statistics. The performance of this scheme is evaluated in terms of downlink and uplink signal-to-interference-plus-noise ratio (SINR) outage and average throughput via analytical approximations and Monte Carlo simulations, and it is compared with that of benchmark random DCA (RDCA) and FCA schemes. The cases of single- and dual-antenna reception with perfect and imperfect channel state information are examined. It is shown that the proposed scheme achieves higher average throughput than FCA (particularly for dual-antenna reception) as well as RDCA (for heavy traffic loads). These throughput gains are more significant in uplink than in downlink. Index Terms--Antenna arrays, code-division multiple access (CDMA), land mobile radio cellular systems, resource management, signal detection, time-division duplexing (TDD).

In this paper, we compare the performance of two downlink capacity-improvement schemes based on orthogonal code-hopping multiplexing (OCHM) and multiple scrambling codes (MSCs). Both OCHM and MSC systems have been proposed to overcome a code-limitation problem in a code division multiple access (CDMA) downlink. We mathematically analyze the user capacity in a general form, considering various factors such as user activity, spreading factor, amount of transmission symbol energy that is allocated to common control channels, amount of outer-cell interference, orthogonality factor, and sectorization factor. Numerical examples show that the capacity gain of the OCHM-based system increases as the other-cell interference decreases and the channel activity decreases. Thus, the OCHM-based system is a more effective scheme than the MSC-based system, considering that a code-limited situation more frequently occurs in the case of low other-cell interference and low channel activity. However, the OCHM-based system is more sensitive to the orthogonality factor. Index Terms--Downlink power allocation, multiple scrambling codes (MSCs), orthogonal code hopping multiplexing (OCHM), user capacity.

On the multiantenna broadcast channel, the spatial degrees of freedom support simultaneous transmission to multiple users. The optimal multiuser transmission, which is known as dirty paper coding, is not directly realizable. Moreover, close-to-optimal solutions such as Tomlinson-Harashima precoding are sensitive to channel state information (CSI) inaccuracy. This paper considers a more practical design called per user unitary and rate control (PU2RC), which has been proposed for emerging cellular standards. PU2RC supports multiuser simultaneous transmission, enables limited feedback, and is capable of exploiting multiuser diversity. Its key feature is an orthogonal beamforming (or precoding) constraint, where each user selects a beamformer (or precoder) from a codebook of multiple orthonormal bases. In this paper, the asymptotic throughput scaling laws for PU2RC with a large user pool are derived for different regimes of the signal-to-noise ratio (SNR). In the multiuser interference-limited regime, the throughput of PU2RC is shown to logarithmically scale with the number of users. In the normal SNR and noise-limited regimes, the throughput is found to scale double logarithmically with the number of users and linearly with the number of antennas at the base station. In addition, numerical results show that PU2RC achieves higher throughput and is more robust against CSI quantization errors than the popular alternative of zero-forcing beamforming if the number of users is sufficiently large. Index Terms--Broadcast channels, feedback communication, multiuser channels, space division multiplexing.

Chromatic dispersion compensation is an essential feature of high speed dense wavelength-division multiplexing (DWDM) systems. We propose a dispersion compensator structure whose characteristics meet the optical DWDM system requirements. The proposed structure is based on Fibonacci quasi-periodic multilayer structures composed of layers with large index differences. Studying the dispersive properties of Fibonacci structures with generation numbers j = 3 and 4, and calculating group delay (GD) and group velocity dispersion (GVD) of their reflection bands, we have demonstrated that to have a smooth GD and almost a constant GVD in each band of a DWDM system, one needs not only to suitably chirp the structure refractive index profile, but also must properly apodize it. We also demonstrate the possibility of achieving high slope GDs and large GVDs by means of high order Fibonacci structures with thicker layers. Finally, by varying the layer dimensions and refractive indices as well as Fibonacci's order, one can design DWDM dispersion compensators suitable for distances as long as 220 km. OCIS codes: 050.1590, 060.4510, 230.2035, 220.1230, 230.4170, 130.2035.

This paper presents a novel generalized transceiver architecture, i.e., Multicarrier Interleave-Division-Multiplexing. aided Interleave Division Multiple Access (MC-IDM-IDMA). A parallel interference cancellation (PIC)-aided iterative multiuser detection (MUD) algorithm, is introduced, and the convergence behavior of the system is evaluated with the aid of EXtrinsic Information Transfer (EXIT) charts under the assumption of an equal-power multiuser scenario. Three interesting design tradeoffs of the MC-IDM-IDMA system are analyzed: 1) the multiplexing versus diversity tradeoffs; 2) the coding versus spreading tradeoffs, where the achievable bandwidth efficiency of both MC-IDM and MC-IDMA are characterized, and a general design rule is provided for low-rate codes; and 3) the complexity versus performance tradeoffs and the EXIT characteristics of two different MUD algorithms are investigated, leading to a reduced-complexity hybrid MUD. Index Terms--EXtrinsic Information Transfer (EXIT) charts, interleave division multiplexing/interleave division multiple access (IDM/IDMA), multicarrier (MC), multiuser detection (MUD).

Aggressive technology scaling raises the need for efficient methods to characterize and model circuit variation at both the front and back end of line, where critical parameters such as threshold voltage and parasitic capacitance must be carefully modeled for accurate circuit performance. In this paper we address this need by contributing a test circuit methodology for the extraction of spatial, layout and size dependent variations at both device and interconnect levels. The test chip uses a scan chain approach combined with low-leakage and low-variation switches, and Kelvin sensing connections, providing access to detailed analog device characteristics in large arrays of test devices. Variation measurement using the designed test chip has proven successful for both device and interconnect test structures. The parameter extraction and variation analyses made possible by the variation test chip enable the identification of likely variation sources, quantification of circuit impact and sensitivity, and specification of layout practices for variation minimization. Index Terms--Design for manufacturability, statistical metrology, statistical modeling, variation.

Space--time codes built out of Alamouti components have been adopted in wireless standards such as UMTS, IEEE 802.11n, and IEEE 802.16, where they facilitate higher data rates through multiplexing of parallel data streams and the addition of two or more antennas at the receiver that perform interference cancellation. This correspondence provides new theoretical insight into different algorithms for interference cancellation through a Bayesian analysis that expresses performance as a function of signal-to-noise ratio (SNR) in terms of the "angles" between different space-time coded data streams. Index Terms--Alamouti code, Bayesian analysis, decoding algorithms, interference cancellation, Quaternion arithmetic, space-time block codes.

The problem of resource allocation to maximize the outage exponent over a fading relay channel using the decode-and-forward protocol with quantized channel state feedback (CSF) is studied. Three different scenarios are considered: relay-to-source, destination-to-relay, and destination-to-source-and-relay CSF. In the relay-to-source CSF scenario, it is found that using merely one bit of CSF to control the source transmit power is sufficient to achieve the multiantenna upper bound in a range of multiplexing gains. In the destination-to-relay CSF scenario, the systems slightly outperform dynamic decode-and-forward (DDF) at high multiplexing gains, even with only one bit of feedback. Finally, in the destination-to-source-and-relay CSF scenario, if the source-relay channel gain is unknown to the feedback quantizer at the destination, the diversity gain only grows linearly in the number of feedback levels, in sharp contrast to an exponential growth for multiantenna channels. In this last scenario, a simple scheme is shown to perform close to the corresponding upper bound. Index Terms--Cooperative communications, diversity methods, diversity-multiplexing tradeoff, fading channels, large-deviation analysis, power control, relay channels.

We report high-throughput, nondispersive optical multiplexing of laser beams using a scanning galvanometer. We have utilized this technique for multispecies trace-gas detection using multiple quantum cascade laser photoacoustic spectroscopy. We demonstrate switching from one laser to another in less than 1 s, a performance level needed for a comprehensive multispecies sensor, and a high signal-to-noise ratio detection of five gaseous components, N[H.sub.3], N[O.sub.2], dimethyl methyl phosphonate (DMMP, a simulant for nerve agents), acetone, and ethylene glycol, in a room air gas mixture containing ~3 ppb of N[H.sub.3], ~8 ppb of N[O.sub.2], ~20 ppb of DMMP, ~30 ppb of acetone, and ~40 ppb of ethylene glycol. OCIS codes: 300.1030, 140.3070.

Holographic data pages were multiplexed in different thickness layers of a polyvinyl alcohol/acrylamide photopolymer. This material is formed of acrylamide photopolymers, which are considered interesting materials for recording holographic memories. A liquid crystal device was used to modify the object beam and store the data pages. A peristrophic multiplexing method is used to store a large number of data pages in the same spot in the material. The bit error rate was calculated fitting the histograms of the images to determine what parameters improve the quality of the images. OCIS codes: 090.0090, 090.2900, 090.2870, 100.2960, 210.0210, 210.4810.

Binary coding of multiplexed signals and images has been studied in the context of spectroscopy with models of either purely constant or purely proportional noise, and has been shown to result in improved noise performance under certain conditions. We consider the case of mixed noise in an imaging system consisting of multiple individually-controllable sources (X-ray or near-infrared, for example) shining on a single detector. We develop a mathematical model for the noise in such a system and show that the noise is dependent on the properties of the binary coding matrix and on the average number of sources used for each code. Each binary matrix has a characteristic linear relationship between the ratio of proportional-to-constant noise and the noise level in the decoded image. We introduce a criterion for noise level, which is minimized via a genetic algorithm search. The search procedure results in the discovery of matrices that outperform the Hadamard S-matrices at certain levels of mixed noise. Simulation of a seven-source radiography system demonstrates that the noise model predicts trends and rank order of performance in regions of nonuniform images and in a simple tomosynthesis reconstruction. We conclude that the model developed provides a simple framework for analysis, discovery, and optimization of binary coding patterns used in multiplexed imaging systems. Index Terms--Binary coding, Hadamard spectroscopy, mixed noise, multiplexing.

This paper presents a novel Call Admission Control (CAC) algorithm based on the statistical multiplexing of VBR traffic. The proposed algorithm is called Statistical Multiplexing based on Discrete Bandwidth levels of GOP rate (SMDB) because the solution is based on the discretization of the GOP rate in a set of bandwidth levels and on the time characteristics of discrete bandwidth levels of MPEG sources. SMDB is compared with another statistical CAC based on the Normal/Lognormal distribution of the GOP rate (SMND). SMDB outperforms SMND in many situations such as high variance around the average video traffic GOP rate of sources and heavy traffic load. The new CAC has been tested in the new generation satellite platform called Digital Video Broadcasting via Return Channel Satellite (DVB-RCS). A high system utilization and multiplexing gain with respect to QoS constraints is obtained. Index Terms--Call admission control, DVB-RCS, MPEG traffic sources, statistical multiplexing.

In this paper, a local optimization framework is proposed, which is able to include system constraints including channel availability, receiver availability and tuning overhead by linear mathematical formulations so that it is sufficient to obtain the optimal performance in terms of message delay. A mixed integer linear programming (MILP) based scheme for passive star coupled WDM optical networks is presented. Based on the new solution, the wavelength assignment and message sequence that guarantee the delivery of the given traffic request, while minimizing the average delay can be achieved. Moreover, the negative effect of the tuning overhead has been incorporated into the new algorithm, which has been ignored in most of the previous work. Numerical results obtained suggest that the proposed scheme is a promising approach for optimizing the network performance in terms of average message delay. Index Terms--Optical fiber networks, packet switching, wavelength division multiplexing, scheduling.

Constructions of multiblock space-time coding schemes that are optimal with respect to diversity-multiplexing (D-M) tradeoff when coding is applied over any number of fading blocks are presented in this correspondence. The constructions are based on a left-regular representation of elements in some cyclic division algebra. In particular, the main construction applies to the case when the quasi-static fading interval equals the number of transmit antennas, hence the resulting scheme is termed a minimal delay multiblock space-time coding scheme. Constructions corresponding to the cases of nonminimal delay are also provided. As the number of coded blocks approaches infinity, coding schemes derived from the proposed constructions can be used to provide a reliable multiple-input multiple-output (MIMO) communication with vanishing error probability. Index Terms--Cyclic-division algebras, diversity-multiplexing (D-M) tradeoff, fading channels, multiblock space-time codes, multiple-input multiple-output (MIMO) channels, number fields, space-time codes.

This correspondence demonstrates the significant gains that multiple-access users can achieve from sharing a single amplify--forward relay in slow-fading environments. The proposed protocol, namely, multiple-access amplify-forward (MAF), allows for a low-complexity relay and achieves the optimal diversity--multiplexing tradeoff (DMT) at high multiplexing gains. Analysis of the protocol further reveals that it outperforms both the compress-forward strategy at low multiplexing gains and the dynamic decode-forward protocol at high multiplexing gains. An interesting feature of the proposed protocol is that, at high multiplexing gains, it resembles a multiple-input single-output (MISO) system, and at low multiplexing gains, it provides each user with the same DMT as if there were no contention for the relay from the other users. Index Terms--Amplify-forward, block-fading channel, cooperative diversity, diversity--multiplexing tradeoff (DMT), multiple-access relay channel (MARK), wireless networks.

For the fully connected K user wireless interference channel where the channel coefficients are time-varying and are drawn from a continuous distribution, the sum capacity is characterized as C(SNR) = K/2 log(SNR) + o(log(SNR)). Thus, the K user time-varying interference channel almost surely has K/2 degrees of freedom. Achievability is based on the idea of interference alignment. Examples are also provided of fully connected K user interference channels with constant (not time-varying) coefficients where the capacity is exactly achieved by interference alignment at all SNR values. Index Terms--Capacity, degrees of freedom, interference alignment, interference channel, multiple-input-multiple-output (MIMO), multiplexing.