On the performance of an ATM switch with multichannel transmissiongroups

A routing architecture applying the concept of multichannel transmission groups (MCTGs) for ATM systems is proposed. A queuing analysis of an internally nonblocking ATM switch employing this MCTG concept with partially shared output buffers is presented. The analysis is based on the discrete-time DA///D/c /B queuing model. Both bulk input traffic bulk-size distribution (A) and deterministic traffic (D₁ +. . .+D_N) are considered. The impact of switch speedup on the performance is also taken into account. It is shown that the MCTG architecture yields better performance in terms of delay and cell loss probability than its single channel counterpart. It is also found that the switch speedup required to closely approximate the optimal performance obtained by having the switch fabric run N times as fast as the input and output channels, where N is the size of the switch, is rather small compared to N. This makes the practical realization of the proposed switch architecture feasible     

Optical switch matrix with simplified N×Ntree structure

Optical switch matrices with compact size and excellent crosstalk characteristics are discussed. Novel architectures for optical switch matrices are obtained by condensing the structure of N× N tree structure. 4×4 switches fabricated on LiNbO₃ substrates are discussed     

Multiwavelength networks and new approaches to packet switching

The author shows how the bandwidth available through the use of multiwavelength optical-fiber technology can be used to achieve novel large-capacity switching systems to address anticipated switching bottlenecks. He does so by describing the features and network applications of a specific multiwavelength network, the Bellcore LAMBDANET packet switch. The discussion is then extended to a number of recent proposals for switching fabrics based on this new multiwavelength technology. The particular technologies he discusses are: the photonic knockout switch, a proposal similar to the concept of the LAMBDANET, but not requiring N receivers at each node; the FOX (fast optical cross-connect), an active wavelength routing approach; the ShuffleNet architecture; the HYPASS and BHYPASS switches; the coherent wavelength division λ switch; and the Bellcore Star-Track multicast switch     

A 2 Gb/s expandable space-division switching LSI and networkarchitecture for gigabit-rate broad-band circuit switching

An expandable space-division (SD) switch architecture and a bipolar circuit design for gigabit-per-second crosspoint-switch LSIs are described. An expandable 2-Gb/s 16×16 crosspoint switch LSI which employs a novel switch structure, a novel circuit design, and a super self-aligned process (SST-1A) is developed. A switching module and partial 1:n nonblock, full 1:1 nonblock switching network architecture are also presented. Using the LSI and the switching network architecture, an experimental 620-Mb/s network system is demonstrated     

A high-resolution multibit ΣΔ ADC with digitalcorrection and relaxed amplifier requirements

A second-order multibit ΣΔ (sigma-delta) analog-to-digital converter (ADC) with a 4-b internal quantizer is described. It uses a simple and fast digital correction scheme. A correlated-double-sampling (CDS) fully differential integrator was used, in which the op amp needed only a low slew rate and moderate bandwidth for a sampling rate of 5.25 MHz. A second-order modulator was fabricated in the standard MOSIS p-well 2-μm CMOS process. The excellent measured linearity and high S/(N+D) ratio (95 dB with an oversampling ratio of only 128) of the corrected converter verified the practical advantages of the proposed architecture     

Delay analysis of a packet voice multiplexer by the ΣDi/D/1 queue

The performance of a statistical multiplexer whose inputs consist of a superposition of voice packet streams is studied. The delay for such a system is analyzed by solving the ΣD_i/ D/1 queue. The analytic method can be used to find the approximate mean delay for an arbitrarily large number of trunks and the approximate delay distribution when the number of trunks is less than 100. An efficient hybrid simulation of the packet voice multiplexer which can be used to find the delay distribution for a large number of trunks is presented. In addition, easily computable error bounds for the present approximation are provided, and the accuracy of the M/ D/1 approximation is investigated     

Extended baseline architecture for nonblocking photonic switching

A new switch architecture called extended baseline networks (EBN) is proposed for nonblocking photonic switching. This switch is a space-division multistage network using 2×2 optical switch elements which may be directional couplers fabricated on titanium diffused lithium niobate (Ti:LiNbO₃) substrates. A recursive definition for the proposed architecture is presented. Some properties including the number of switch elements required, blocking characteristics, number of crossovers, system attenuation, and signal-to-noise ratio (SNR) are derived and analyzed. Most of the characteristics are shown to be better than those of other well-known networks fabricated on single Ti:LiNbO₃ substrates     

Connectivity properties of a packet radio network model

A model of a packet radio network in which transmitters with range R are distributed according to a two-dimensional Poisson point process with density D is examined. To ensure network connectivity, it is shown that πR²D, the expected number of nearest neighbors of a transmitter, must grow logarithmically with the area of the network. For an infinite area there exists an infinite connected component with nonzero probability if π R²D>N₀, for some critical value N₀. It is shown that 2.195<N ₀<10.526     

A note on D-ary Huffman codes

An upper bound on the redundancy of D-ary Huffman codes in terms of the probability p₁ of the most likely source letter is provided. For large values of p₁, the bound improves the one given by R.G. Gallager (1978). Additionally, some results known for the binary case (D=2) are extended to arbitrary D-ary Huffman codes. As a consequence, a tight lower bound that corrects a bound recently proposed by J.D. Golic and M.M. Obradovic (1987) is derived     

Performance analysis of optical heterodyne PSK receivers in thepresence of phase noise and adjacent channel interference

A phase-shift-keying (PSK) optical heterodyne receiver using synchronous detection by means of a Costas phase-locked loop (PLL) is investigated. Taking into account the laser phase noise and adjacent channel interference (ACI), an expression of the phase error variance is derived and error probability calculation is performed. Plots of the error probability versus the number of photons per bit are presented as a function of the optical domain channel spacing (D) and for several linewidth-to-bit-rate ratios (δf/R_b ). Relative sensitivity penalties, based on the performance with and without ACI, are evaluated for several combinations of D and δf/R_b. It is shown that, if lasers with larger linewidths are used, the frequency separation between optical carriers has to be increased in order to allow the same relative sensitivity penalty     

Diffusion and noise in GaAs material and devices

The variation of the diffusion coefficient D(E) versus the electric field strength E is determined at 300 K in n-type GaAs (N_D=3×10^-17 cm^-3 ), using pulsed high-frequency noise measurements. D(E) is found to increase slightly at low field, then to decrease down to one tenth of its ohmic value near the threshold field. Long (⩾4 μm) real n⁺-n-n⁺ Gunn diodes, with an arbitrary doping profile, can be modeled. Comparisons are made, and excellent agreement is found, between experimental and theoretical characteristics of two real diodes, with notch and with gradual doping profiles. The doping profile N_D(x ) is shown to have a considerable influence on the diode behavior, in regard to the electric field profile as well as the noise characteristics. Using the impedance field method, the noise current is modeled and found to by very sensitive in the D(E) variation law, in particular in the range of 2.5-4 kV/cm. The agreement between the experimental noise and the computed noise of real diodes is quite satisfactory when using the D(E) determined     

An 8 mm length nonblocking 4×4 optical switch array

A novel single-mode-single-slip-structure S³ optical switch using carrier-induced refractive index change is proposed as a unit cell for a small polarization-independent nonblocking N×N optical switch array. Sixteen S³ optical switches have been integrated into a nonblocking 4×4 optical switch array on an InP substrate. The 8-mm-length InGaAsP/InP 4×4 optical array has shown satisfactory switching characteristics and is suitable for larger scale integration of optical switch arrays and also for integration with other active optical devices such as laser diodes     

A comparison of three diagonalizers, adaptive crosstalk cancellers,in dual-polarized M-QAM systems

Three different adaptive diagonalizers are compared on a probability of symbol error performance basis for dual-channel M-QAM systems. One diagonalizer (D3) greatly outperforms the other two, and any comparison of the performance of the diagonalizers to that of the minimum mean square error (MMSE) canceller should be based on D3. Receiver structures are also presented     

An InP-based optothyristor for pulsed power-switching applications

A high-power InP-based optothyristor has been fabricated and tested for pulsed power switching. To increase the power handling capability, the device has a 250 μm-thick Fe-doped semi-insulating (SI) InP sandwiched between two p-n junctions grown by MOCVD. The device turn-on is controlled by optical illumination on the SI-InP, which creates a high concentration of electron and hole pairs. The switched current and the di/dt rating have been studied as a function of the switch blocking voltage. It is shown that the optothyristor is capable of switching a current almost four times the current switched by a bulk SI-InP photoconductive switch under the same voltage bias     

Switching converters with wide DC conversion range

Compared to basic converter topologies (buck, boost, buck-boost, Cuk, etc.), pulse-width modulation (PWM) converters with quadratic DC conversion ratios, M(D)=D², M (D)=D²/(1-D) or M(D)=D²/(1-D)² , offer a significantly wider conversion range. For a given minimum ON-time and, consequently, for a given minimum duty ratio D _min, D² in the numerator of M (D) yields a much lower limit on the minimum attainable conversion ratio. By applying a systematic synthesis procedure, six novel single-transistor converter configurations with quadratic DC conversion ratios are found. The simpler, single-transistor realization is the most important advantage over the straightforward cascade of two basic converters. As far as conversion efficiency is concerned, it is clear that a single-stage converter is usually a better choice than a two-stage converter. The quadratic converters proposed are intended for applications where conventional single-stage converters are inadequate-for high-frequency applications where the specified range of input voltages and the specified range of output voltages call for an extremely large range of conversion ratios     

1/f noise in hot-carrier damaged MOSFET's: effects ofoxide charge and interface traps

The 1/f noise in the drain current of hot-carrier damaged MOSFETs biased in weak inversion has been studied. By the use of a biased annealing treatment to simultaneously decrease the density of oxide trapped charge (N_ot) and increase the density of interface traps (D_it), the authors have separated the contributions of these two kinds of defects. The results clearly indicate that, while the low-frequency 1/f noise is correlated with N_ot, the high-frequency 1/f noise is correlated with D_it     

When are two geometric Goppa codes equal?

Sufficient and necessary conditions are obtained for which the geometric Goppa codes C(D,G) and C( D,H) are equal for two divisors G and H . In particular, it is proven that if G and H are two effective divisors of the same degree smaller than n-1, then C(D,G) and C(D,H ) are equal, if and only if G=H     

Rearrangeable Nonblocking 8 × 8 Matrix Optical Switch Based on Silica Waveguide and Extended Banyan Network

Based on the crossbar network and the Banyan network (BN), a new rearrangeable nonblocking structure of extended Banyan network (EBN) was proposed for implementing an 8 times 8 optical matrix switch. The interconnection characteristics of the rearrangeable nonblocking EBN were studied, and the diagram of the logic program for driving the operation of switching units was provided. A silica waveguide 8 times 8 matrix optical switch was designed and fabricated according to the calculated results. The silica waveguide propagation loss of 0.1 dB/cm and waveguide-fiber coupling loss of 0.5 dB/facet were measured. With the fabricated 8 times 8 matrix optical switch, the insertion loss of 4.6 dB, the crosstalk of -38 dB, the polarization-dependent loss of 0.4 dB, the averaged switching power of 1.6 W, and the switching time of 1 ms were achieved. A basic agreement between experimental results and theoretical calculated values was achieved     

Scanning properties of large dual-shaped offset and symmetricreflector antennas

The scanning properties of shaped reflectors, both offset and circularly symmetric, are examined and compared to conic section scanning characteristics. Scanning of the pencil beam is obtained by lateral and axial translation of a single point source feed. The feed is kept pointed toward the center of the subreflector. The effects of power spillover and aperture phase error as a function beam scanning are examined for several different types of large reflector design including dual-offset, circularly symmetric large f/D, and smaller f/D dual reflector antenna system. It is shown that the Abbe-sine condition for improved scanning of an optical system cannot, inherently, be satisfied in a dual-shaped reflector system that is shaped for high gain and low feed spillover. The gain loss, with scanning, of a high-gain shaped reflector pair is demonstrated to be due to both aperture phase error loss and power spillover loss     

A fast topology maintenance algorithm for high-bandwidth networks

A fast time-driven algorithm for topology maintenance in high-speed networks is presented. The algorithm uses only four time units for each broadcast by each computer. The best previous algorithm required O(log m) time units for each broadcast by each computer, where m is the number of currently operational computers in the network. In addition to its speed, the presented algorithm makes several significant contributions. I. Cidon et al. (1988) have shown that Ω(log m) time units are necessary for time-driven topology maintenance algorithms of high-speed networks that do not allow a packet to traverse the same edge in both directions. The proposed algorithm shows that this lower bound does not hold for networks that do allow a packet to traverse the same edge in both directions. The O(log m) algorithm assumed that it takes each computer at most one time unit to simultaneously broadcast messages to all neighbors of the computer. In contrast, a node in the proposed algorithm can send at most, one message per time unit. As in the O(log m) algorithm, the algorithm requires O (D) broadcasts per node before all nodes know the correct topology of the network, where D is the diameter of the currently operational portion of the network