In this paper, the analog code modulation characteristics of distributed-based transversal filters (DTFs) suitable for use in spectrally encoded CDMA systems are presented. The DTF is verified as an appropriate method to use in high-speed CDMA systems as opposed to previously proposed methods, which are intended for Direct Sequence (DS) CDMA systems. The large degree of freedom of DTF design permits controlling the filter pulse response to generate well specified temporal phase-coded signals. A decoder structure that performs bipolar detection of user subbands giving rise to a Spectral-Amplitude Encoded CDMA system is considered. Practical implementations require truncating the spreading signals by a time window of duration equal to the span time of the tapped delay line. Filter functions are chosen to demodulate the matched channel and achieve improved user interference rejection avoiding the need for transversal filters featuring a large number of taps. As a proof-of-concept of the electronic SAE scheme, practical circuit designs are developed at low speeds (3-dB point at 1 GHz) demonstrating the viability of the proposal.

This paper describes a top-down design methodology to optimize resonant capacitance in a wireless power transfer system with 3-D stacked two receivers. A 1:2 selective wireless power transfer is realized by a frequency/time division multiplexing scheme. The power transfer function is analytically formulated and the optimum tuning capacitance is derived, which is validated by comparing with system simulation results. By using the optimized values, power transfer efficiencies at 6.78MHz and 13.56MHz are simulated to be 80% and 84%, respectively, which are <3% worse than a conventional wireless power transfer system.

To meet the demand for continuous increase in data traffic, full usage of polarization freedom of light is becoming inevitable in the next-generation optical communication and datacenter networks. In particular, Stokes-vector modulation direct-detection (SVM-DD) formats are expected as potentially cost-effective method to transmit multi-level signals without using costly coherent transceivers in the short-reach links. For the SVM-DD formats to be practical, both the transmitter and receiver need to be substantially simpler, smaller, and lower-cost as compared to coherent counterparts. To this end, we have recently proposed and demonstrated novel SV modulator and receiver circuits realized on monolithic InP platforms. With compact non-interferometric configurations, relatively simple fabrication procedures, and compatibility with other active photonic components, the proposed devices should be attractive candidate in realizing low-cost monolithic transceivers for SVM formats. In this paper, we review our approaches as well as recent progresses and provide future prospects.

We numerically investigate a PDM-QPSK multi-rate coherent burst-mode optical receiver capable of receiving 3 different line-rates, suitable for next generation optical networks such as hybrid optical circuit switching (OCS)/optical packet switching (OPS) networks, access networks and datacenter networks. The line-rate detection algorithm relies on a simple-to-generate optical header, it is based on the fast Fourier transform (FFT) which can be efficiently implemented with the Goertzel algorithm, and it is insensitive to polarization rotations and frequency offset. Numerically, we demonstrate that performance in terms of packet detection rate (PER) can be tailored by controlling the sizes of the packet header and the line-rate estimator.

Iterative channel estimation and decoding receivers have evolved over the years, most especially with Turbo and LPDC codes. Nevertheless, few works have determined the performance of symbol level Reed-Solomon (RS) codes in iterative receiver structures. The iterative channel estimation and symbol level RS decoding receiver structure found in literature concentrate on M-QAM systems over flat Rayleigh fading channels. In this paper, attention is focused on the performance of RS codes in iterative channel estimation and decoding receiver structures for Orthogonal Frequency Division Multiplexing (OFDM) systems on frequency-selective Rayleigh fading channels. Firstly, the paper extends the Koetter and Vardy (KV) RS iterative receiver structure over flat Rayleigh fading channels to frequency-selective Rayleigh fading channels. In addition, the paper develops a symbol level RS iterative receiver structure for OFDM systems on frequency-selective Rayleigh fading channels based on the Parity-check matrix Transformation Algorithm (PTA). The performance of the RS-KV and RS-PTA iterative receiver structures for OFDM systems are documented through computer simulation. The simulation results verify that both iterative receiver structures are suitable for real time RS OFDM wireless applications. The results also show that the developed RS-PTA iterative receiver structure is a low complexity and high performance alternative to the RS-KV iterative receiver structure.

This paper describes a blind frequency offset estimator (FOE) with wide frequency range for coherent quadrature amplitude modulation (QAM) receivers. The FOE combines a spectrum-based frequency offset estimation algorithm as a coarse estimator with a frequency offset estimation algorithm using the periodogram as a fine estimator. To establish our design methodology, each block of the FOE is rigorously analyzed by using formulas and the minimum fast Fourier transform (FFT) size that generates a frequency spectrum for both the coarse and fine estimators is determined. The coarse estimator's main feature is that all estimation processes are carried out in the frequency domain, which yields convergence more than five times faster than that of conventional estimators. The estimation frequency range of the entire FOE is more than 1.8 times wider than that of conventional FOEs. Experiments on coherent optical 64-ary QAM (64-QAM) reveal that frequency offset estimation can be achieved under a frequency offset value greater than the highest value of the conventional estimation range.

This paper proposes an active-RC filter that achieves a wide pseudo-continuous bandwidth-tuning range and a wide gain range with fine steps using a novel switched resistor architecture. A channel-selection filter with the proposed resistor bank is designed for a multi-mode mobile-TV receiver with the 6th order Chebyshev-I topology. The bandwidth, 0.5–6 MHz with 5% steps, supports multiple mobile-TV standards with sufficient margins for process and temperature variations. The filter also accomplishes a 30-dB variable gain range with 6-dB steps, and it relaxes the dynamic range requirement of a succeeding programmable gain amplifier. The power consumption of the filter, 3.4–5.0 mW, is adjustable according to the bandwidth and the signal level. The filter was fabricated with on-chip bandwidth-calibration circuitry in 0.18-µm CMOS and occupied 0.81 mm2.

As a future passive optical network (PON) system, the 10 Gigabit Ethernet PON (10G-EPON) has been standardized in IEEE 802.3av. As conventional Gigabit Ethernet PON (GE-PON) systems have already been widely deployed, 1G/10G co-existence technologies are strongly required for the next system. A gated voltage-controlled-oscillator (G-VCO)-based 10-Gb/s burst-mode clock and data recovery (CDR) circuit is presented for a 1G/10G co-existence PON system. It employs two new circuits to improve jitter transfer and provide tolerance to 1G/10G operation. An injection-controlled jitter-reduction circuit reduces output-clock jitter by 7 dB from 200-MHz input data jitter while keeping a short lock time of 20 ns. A frequency-variation compensation circuit reduces frequency mismatch among the three VCOs on the chip and offers large tolerance to consecutive identical digits. With the compensation, the proposed CDR circuit can employ multi VCOs, which provide tolerance to the 1G/10G co-existence situation. It achieves error-free (bit-error rate < 10-12) operation for 10-G bursts following bursts of other rates, obviously including 1G bursts. It also provides tolerance to a 256-bit sequence without a transition in the data, which is more than enough tolerance for 65-bit CIDs in the 64B/66B code of 10 Gigabit Ethernet.

In this paper, we propose a genetic algorithm (GA) based equalization approach for direct sequence ultra-wideband (DS-UWB) wireless communication systems, where the GA is combined with a RAKE receiver to combat the inter-symbol interference (ISI) due to the frequency selective nature of UWB channels for high data rate transmission. The proposed GA based equalizer outperforms significantly the RAKE and the RAKE-minimum mean square error (MMSE) receivers according to results obtained from intensive simulation work. The RAKE-GA receiver also provides bit-error-rate (BER) performance very close to that of the optimal RAKE-maximum likelihood detection (MLD) approach, while offering a much lower computational complexity.

In this paper, we study low complexity transceiver for double space time transmit diversity (DSTTD) and orthogonal frequency division multiplexing (OFDM) system with antenna shuffling. Firstly, we propose a novel antenna shuffling method based on the criterion of minimizing the condition number of channel correlation matrix. The condition number is an indicator about the quality of the channel. By selecting the minimum of condition number which has better channel quality, consequently, a linear detector with respect to this new channel may achieve better performance results. A low complexity variant of the condition number calculation is also proposed, and it is shown that this criterion can be reduced to the minimum mean square error (MMSE) based criterion. Furthermore, the weighted soft decision Viterbi decoding is applied to mitigate noise enhancement inherent to zero forcing (ZF) and MMSE linear receivers and improve error rate performance. Next, we propose an algorithm to reduce the amount of feedback by exploiting the fact that the channel frequency responses across OFDM subcarriers are correlated. In the proposed algorithm, subcarriers are clustered in blocks, which are allocated the same shuffling pattern with the largest number of the shuffling patterns in the cluster. This way, the signaling overhead can be reduced in comparison with each subcarrier based feedback. Extensive simulations show that the proposed techniques for DSTTD-OFDM system outperform other existing techniques under both uncorrelated and highly spatial correlated frequency selective MIMO fading channels.

Continuous phase modulation (CPM) is a non-linear modulation technique whose power and bandwidth efficiency make it an attractive choice for mobile communication systems. Current research has focused on devising encoding rules for using CPM over multiple-input multiple-output (MIMO) systems in order to obtain the improved bit error rate (BER) and high data rates promised by MIMO technology. In this paper, optimal and suboptimal non-coherent receivers for a class of CPM signals called orthogonal space-time CPM (OST-CPM) are derived under a quasi-static fading channel assumption. The performance of these receivers is characterized and shown to achieve the same diversity order as that of the corresponding optimal coherent receiver.

The complete subtree (CS) method is widely accepted for the broadcast encryption. A new method for assigning keys in the CS method is proposed in this paper. The essential idea behind the proposed method is to use two trapdoor permutations. Using the trapdoor information, the key management center computes and assigns a key to each terminal so that the terminal can derive all information necessary in the CS method. A terminal has to keep just one key, while log2 N + 1 keys were needed in the original CS method where N is the number of all terminals. The permutations to be used need to satisfy a certain property which is similar to but slightly different from the claw-free property. The needed property, named strongly semi-claw-free property, is formalized in terms of probabilistic polynomial time algorithm, and its relation to the claw-free property is discussed. It is also shown that if the used permutations fulfill the strongly semi-claw-free property, then the proposed method is secure against attacks of malicious users.

In this paper, we consider a mobile system consisting of a single isolated circular cell with K independent users simultaneously sharing the channel using binary DS-CDMA to establish a full duplex channel with the base station. Both coherent and differential detection RAKE receivers with Maximal Ratio Combining (MRC) techniques are considered. The performance of two uplink/downlink receivers in Nakagami wideband fading channel is studied. Our approach relies on the use of total instantaneous interference power calculations instead of the use of average power approximations. We analyzed and derived new exact formulae for bit error probabilities for the considered system, and presented a set of numerical results both for the exact formulae and Gaussian approximation. The performance comparisons suggest that the exact formulae provide superior performance to Gaussian approximation especially at low number of users and either high fading parameters of the desired user or low fading parameters of the MAIs.

The complete subtree (CS) method is one of the most well-known broadcast encryptions which do not enforce the receivers to keep "online." This paper is to reduce the size of secret information which must be stored in a terminal of the method. In the original CS method, the size of the secret information increases as the number of terminals increases. It is shown in this paper that, by making use of a one-way trapdoor permutation, we can make the size constant regardless of the number of terminals. The security of the proposed scheme is investigated, and detailed comparison with other similar schemes is presented. The proposed scheme is suitable for practical implementations of the CS method.

A fully integrated RF front-end for W-CDMA applications including a low noise amplifier, a down conversion mixer, a digitally programmable gain amplifier, an on-chip VCO, and a fractional-N frequency synthesizer is designed using a 0.35-µm CMOS process. A multi-stage ring shaped on-chip LC-VCO exhibiting bandpass characteristics overcomes the limitation of low-Q components in the tank circuits and improves the phase noise performance. The measured phase noise of the on-chip VCO is -134 dBc/Hz at 1 MHz offset. The receiver RF front-end achieves a NF of 3.5 dB, an IIP3 of -16 dBm, and a maximum gain of 80 dB. The receiver consumes 52 mA with a 3-V supply and occupies only 2 mm2 die area with minimal external components.

In this paper, the average bit error probability of uplink and downlink Multicarrier Code Division Multiple Access (MC-CDMA) system using coherent Maximal-Ratio Combining (MRC) and Equal Gain Combining (EGC) receivers is evaluated for frequency selective Nakagami fading channels. The analysis assumes that different subcarriers experience independent fading channels, but not necessary identically distributed. The analysis is based on Gaussian approximation of the multiple access interference. Generalized bit error probability (BEP) expressions for both uplink and downlink with MRC and EGC receivers were derived. The analytical results are supported with simulation results. The effect of fading parameters, number of users, and number of subcarriers were presented. The BEP performance of the EGC receiver in the uplink is highly influenced by the fading parameter compared with the MRC receiver. The EGC receiver outperforms the MRC receiver in the downlink, but the MRC receiver gives almost the same performance as the EGC in the uplink.

In this paper, we describe the design, optimization and fabrication of high-speed InP/InGaAs heterojunction bipolar phototransistors (photo-HBTs) with both optical cut-off frequency (Fc) and optical gain (Gopt) higher than 100 GHz and 30 dB, respectively. Small- and large-signal models of the photo-HBT have been developed in order to design optoelectronic monolithically integrated circuits (OEIC) using this device. Integrated circuits such as optoelectronic narrow-band amplifiers at 28 GHz with a transimpedance gain of 50 dBΩ and optoelectronic upconverting mixers at 28 and 42 GHz with a mixer conversion gain of 17.8 dB and 9.2 dB respectively, were fabricated. The performances of the mixer circuits were superior to those of individual photo-HBT mixer. These optoelectronic integrated circuits based on InP photo-HBTs are attractive building blocks for realizing compact and cost-effective photoreceivers for millimeter-wave radio-over-fiber links.

This article addresses the problem of designing and implementing multigigabit post-detection filters for application in optical communication systems using optical soliton pulses. The designed filters have the main advantages of full integration, electrically adjustable frequency response and active input and output impedance match.

10-Gbit/s monolithic receiver OEIC's for 1.55-µm optical transmission systems were fabricated using a stacked layer structure of p-i-n photodiodes and HEMT's grown on InP substrates by single-step MOVPE. A receiver OEIC with a large O/E conversion factor was obtained by adding a three-stage differential amplifier to a conventional feedback amplifier monolithically integrated with a surface-illuminated p-i-n photodiode. The circuit configuration gave a preamplifier a transimpedance of 60 dBΩ. The receiver OEIC achieved error-free operation at 10 Gbit/s without a postamplifier even with the optical input as low as -10.3 dBm because of its large O/E conversion factor of 890 V/W. A two-channel receiver OEIC array for use in a 10-Gbit/s parallel photoreceiver module based on a PLC platform was made by monolithically integrating multimode WGPD's with HEMT preamplifiers. The side-illuminated structure of the WGPD is suitable for integration with other waveguide-type optical devices. The receiver OEIC arrays were fabricated on a 2-inch wafer with achieving excellent uniformity and a yield over 90%: average transimpedance and average 3-dB-down bandwidth were 43.8 dBΩ and 8.0 GHz. The two channels in the receiver OEIC array also showed sensitivities of -16.1 dBm and -15.3 dBm at 10 Gbit/s. The two-channel photoreceiver module was constructed by assembling the OEIC array on a PLC platform. The frequency response of the module was almost the same as that of the OEIC chip and the crosstalk between channels in the module was better than -27 dB in the frequency range below 6 GHz. These results demonstrate the feasibility of using our receiver OEIC's in various types of optical receiver systems.

Silicon-based monolithic microwave integrated circuits (MMICs) present an interesting option for low-cost consumer wireless systems. SiGe/Si heterojunction bipolar transistors (HBTs) are a major driving force behind Si-based MMICs, because they offer excellent microwave performance without aggressive lateral scaling. This article reviews opportunities for receiver frontend components (low-noise amplifiers and mixers) using SiGe HBTs.