Carrier-to-noise Power Ratio Research Articles

Concurrent Dual-Band Heterodyne Interferometric Receiver for Multistandard and Multifunction Wireless Systems

Radio frequency (RF), microwave, and millimeter-wave (mmW) multiport interferometric receivers present a competitive solution for the front-end reception of low-power multistandard and multifunction wireless applications. The systematic generation of rectified waves in a conventional direct-conversion interferometric receiver is highly related to temporal and power changes and the number of subsignals in the frequency band of interest. It can cause the receiver to saturate and, thus, requires auxiliary power-hungry tunable amplifiers and a data converter for compensation. This work presents a heterodyne detection in an RF/microwave interferometric receiver, the first of its kind, which separates the desired frequency signals from the rectified wave components with two output ports through a frequency offset. This architecture also makes use of the field-effect transistor (FET)-based power detectors to combine the received and reference signals, which reduces a theoretical multiport junction loss of 6 dB to 3 dB. In this way, the proposed receiver is set to support the development of an ultralow-power concurrent dual-band wireless system using a single wave-correlator circuit. A mathematical model of the proposed system is derived and subsequently prototyped using off-the-shelf components to evaluate its carrier-to-noise power ratio (CNR) and error vector magnitude (EVM) performances, which can be extended for integrated circuits (ICs) implementation, such as CMOS and III–V ICs. The power detectors only require a bias voltage at gate terminals with zero direct current (dc) power consumption for optimum voltage responsivity and CNR performances. The demodulation of various modulated digital signals, including QPSK, QAM-16, QAM-32, and QAM-64, has been successfully demonstrated in the 24- and 28-GHz mmW frequency bands at 4 MSps of the symbol rate with a maximum EVM of 11.43% root-mean-square (rms) free from any postprocessing linearization and calibration.

Experiments on FPGA-Implemented Eigenbeam MIMO-OFDM With Transmit Antenna Selection

This paper describes the performance of eigenbeam multiple-input multiple-output (MIMO) with transmit antenna selection using orthogonal frequency-division multiplexing (OFDM), as measured in a testbed implemented using field-programmable gate arrays (FPGAs); it also targets the downlink performance improvement of wireless local area networks (LANs). For this verification, we employ a determinant-based simple transmit antenna selection approach based on the estimated instantaneous MIMO channel matrix. We show extensive experiments on the testbed to confirm the performance of eigenbeam MIMO-OFDM with transmit antenna selection in the three-select-two antenna case. First, the measured packet-error-rate (PER) performance confirms that the eigenbeam scheme with the three-select-two antenna-selection scheme provides a slight degradation in the required carrier-to-noise power ratio (CNR) that is approximately 0.2 dB from the eigenbeam-only scheme with three transmit antennas but with significantly lower computational complexity. Second, to determine the impact of Doppler frequency, both 5 Hz and 20 Hz, we focus on the required CNR performance degradation under various transmission intervals between the channel sounding packet and the data packet. It is experimentally confirmed that the eigenbeam scheme with transmit antenna selection offers improved robustness to MIMO channel fluctuation compared with the eigenbeam-only scheme.

A Burst Modulation/Demodulation Method for Narrowband Ubiquitous Communication Systems

This paper presents a wireless burst modulation/demodulation method for narrowband ubiquitous communication systems. This method especially suits those systems, whose traffic is especially dominated by short frame bursts. The proposed modulation method provides a preamble-less frame structure with training symbols, which improves both transmission efficiency and burst synchronization performance. Moreover, the proposed demodulation method achieves superior burst synchronization performance in low carrier-to-noise power ratio (CNR) environments by applying a synchronization method that includes symbol timing recovery, slot synchronization, carrier frequency correction and channel tracking. In addition, this paper presents the result of experiments on hardware prototypes of the proposed modulator and demodulator. The basic operation and practical performance of the proposed method is confirmed through testbed studies.

FPGA Implementation of Eigenbeam MIMO-OFDM for Wireless LAN and Its Experimental Performance

This paper describes the experimental performance of eigenbeam multi-input multi-output with orthogonal frequency division multiplexing (MIMO-OFDM) systems as measured in a testbed implemented with field programmable gate arrays (FPGAs). The FPGA-testbed, characterized by the software-defined radio (SDR) technique, offers 1/5-scale real time signal processing. Extensive experiments on the testbed confirm the basic operation and performance of eigenbeam MIMO-OFDM with quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (QAM). From the packet error rate (PER) performance, we confirm that the eigenbeam 16QAM/MIMO-OFDM scheme with permutation matrix and three transmit antennas (M t = 3) drastically improves the required carrier-to-noise power ratio (CNR) by approximately 5.6 dB over the scheme without eigenbeam with M t = 2. Furthermore, to determine the impact of Doppler frequency f d , we focus on the transmission interval between the MIMO channel estimation and data transmission. To suppress the required CNR degradation to within 1.5 dB, it is found that the eigenbeam 16QAM/MIMO-OFDM scheme with permutation matrix and M, = 3 permits a transmission interval of approximately 68.5 ms when f d = 1 Hz for a 1/5-scale model.

BER performance of MLSE demodulator for digital SSB with partial response signaling

AbstractIn this paper, we propose a demodulation method using maximum likelihood sequence estimation (MLSE) after coherent detection for partial response signaling single sideband (SSB) signals and present the bit error rate performance achieved by this configuration. Coherent detection is implemented by a pilot carrier method. The power of the pilot carrier inserted in the SSB modulated wave and the noise bandwidth of the phase locked loop (PLL) that extracts the base carrier cause the degradation in the power efficiency of the SSB signal. We then evaluate the equivalent carrier‐to‐noise power ratio (CNR) degradation of the pilot carrier method. The partial response demodulated signal can be MLSE decoded since the signal is time correlated. From the characteristics of an SSB demodulated signal, first‐order MLSE decoding using only the in‐phase channel generally results. Here, we also study a complex MLSE decoding method that considers the quadrature channel. Based on this configuration, we show that the SSB signal power efficiency was improved by about 5 dB compared to the conventional coherent detection and instantaneous identification and demodulation method. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(4): 44–53, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20167

Detection of Optical FM-SCM Signal through Coherent Carrier Reconstruction

This paper proposes a scheme for optical FM-SCM signal demodulation utilizing coherent carrier reconstruction in a high-Q injection-locked Fabry-Perot laser diode. This scheme can eliminate the composite second order (CSO) distortion of the baseband-modulated subcarrier at the output of the photodiode. Carrier-to-noise power ratio (CNR) in a given channel for the proposed coherent carrier demodulator is much greater than that calculated for the quadrature-biased Mach-Zehnder interferometric discriminator. Typical value of CNR with a received power of -10 dBm and FM index per channel of 3%, is 34 dB for 100 channels. Calculated CNR and CTB levels for 100 channels are found to be within the prescribed limits of a CATV receiver for good quality picture reproduction.

Analysis of the Optical Limiter-Discriminator Demodulating the Optical FM-SCM Signals

This paper analyzes the demodulation performance of an optical limiter-discriminator, in response to an optical FM-SCM signal. The carrier-to-noise power ratio (CNR) as well as composite second order (CSO) and composite triple beat (CTB) distortions have been calculated at the output of the optical limiter-discriminator. The analysis predicts that to achieve a CTB level of less than -39 dB with the constituent laser diode power of 1 mW each, the effective optical FM index should be less than (.03) for 100 subcarrier channels. The system can operate with a low level of received optical power. The proposed limiter-discriminator meets the requirement of a FM CATV receiver.

Blind estimation of modulation schemes according to noise powers in the presence of carrier frequency offset

AbstractA method for identifying modulation schemes is a vital elemental technology of adaptive software‐defined radio that switches its software in response to the environment and the application objective. The problems faced in conventional modulation scheme estimation are synchronization and robustness in a fading environment. In this paper, we address the problem of the degradation in the accuracy of modulation scheme estimation due to the presence of carrier offsets and the fluctuations in the carrier‐to‐noise power ratio (CNR). The former is addressed by implementing offset cancellation that uses the temporal phase difference information in one symbol. The latter is addressed by using the estimates found by a blind noise power estimation algorithm to implement modulation scheme estimation that exhibits excellent estimation accuracy even with a fluctuating CNR. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(12): 76–88, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10001

Millimeter-wave remote self-heterodyne system for extremely stable and low-cost broad-band signal transmission

We have developed a millimeter-wave remote self-heterodyne transmission system that enables extremely stable and low-cost broad-band transmission in the millimeter-wave band. The system was applied to a 60-GHz-band transmission system for the first time. The transmitter of the developed system transmits RF modulated signals and a local oscillation signal simultaneously, and the receiver detects these signals by using a square-law-type detection technique, thus creating a very stable and low phase-noise millimeter-wave transmission link without the use of an expensive and more advanced frequency-stabilization technology. Since the receiver no longer requires a millimeter-wave oscillator for frequency conversion, the devices used in this system can be miniaturized and the cost of the system can be reduced. This paper discusses the performance of the developed system in terms of its phase-noise degradation and carrier-to-noise power ratio (CNR). We also discuss the optimal transmitter design to obtain the maximum CNR. Using our miniaturized monolithic millimeter-wave integrated-circuit-based 60-GHz-band experimental system, we demonstrate that our millimeter-wave transmission link is completely free of phase-noise and frequency-offset degradation due to the use of a millimeterwave local oscillator. We show that equal transmission-power distribution between the RF signal and local carrier gives the maximum CNR under the transmission-power-limited conditions. Also, we demonstrate that QPSK-modulated satellite broadcast multichannel video signals with a 300-MHz bandwidth, in total, can be successfully transferred over a distance of 8 m.

Theoretical analysis of propagation characteristics in millimeter-wave intervehicle communication system

The paper presents an analysis of the multipath propagation characteristics of an intervehicle high-speed radio communication system using the ray-tracing method. A model of the millimeter-wave intervehicle propagation path accounting for vehicle traffic was developed and used to study the delay profile, while varying the distribution of the reception power and other multipath propagation characteristics. In the case of digital signal transmission between the vehicles, the probability density function of the carrier-to-noise power ratio (CNR) was determined and a theoretical analysis of the average bit error rate was performed by modeling the intervehicle propagation path using a Rice fading channel. By performing a numerical simulation, close relationships were established between the transmission power necessary to provide the required average bit error rate, the maximum transmission rate, the vehicle traffic, and the size of the antenna. A study of the improved signal propagation characteristics obtained by using diversity reception was also performed. It was found that by reducing the fading effect, an improvement in signal propagation characteristics can be expected. © 2000 Scripta Technica, Electron Comm Jpn Pt 2, 83(11): 33–43, 2000

A multiaccess coherent optical communication system using common optical carrier with star configuration

AbstractA variety of multiaccess optical communication systems with common carrier have been reported recently. This paper proposes a new type of multiaccess coherent optical communication system with star configuration in which a common optical carrier from a single source is distributed by a star coupler. In this system, the carrier is phase‐modulated at each user by an external modulator through a subcarrier signal and the signal is received by an optical heterodyne receiver. A feature of the system is that the distributed optical carrier and the modulated light are directional‐division multiplexed.Theoretical analysis of the carrier‐to‐noise power ratio (CNR) of the system is carried out in this paper taking into account the effect of interference light caused by reflections, backscattering, or insufficient isolation of a circulator used in the system, followed by discussions on the allowable value of the signal‐to‐interference light power ratio and on the relation between transmitter power and maximum user numbers.

Signal‐detection characteristics in trellis‐coded modulation system under impulsive noise environment and its optimum reception

AbstractThis paper investigates the performances of the trellis‐coded modulation (TCM) systems under impulsive noise environment. Conventionally, receivers for a TCM system have been designed based on Euclidean distances between signal sequences assuming their use under Gaussian noise environments. These receivers are not suitable for impulsive noise environments having statistics significantly different from Gaussian noise and thus designs based on the statistics of impulsive noise are needed. The error event probability characteristics of TCM signals received by conventional‐type receivers have been obtained, and it has been clarified that coding gain is obtained even under impulsive noise when the carrier‐to‐noise power ratio (CNR) is sufficiently large, and there is a range of CNR at which the error event probability characteristics of TCM signals become worse than those of uncoded signals.Next, it is shown that the error event probability characteristics of TCM signals are inferior to those of the case in which uncoded signals are received by optimum receivers designed by considering impulsive radio noise. In addition, it has been shown that optimum receivers for TCM systems under impulsive radio noise can simply be constructed by adding a number of circuits to conventional‐type TCM receivers, and their performances exceed those of the case in which uncoded signals are received by optimum receivers at any CNR and great coding gain is obtained.

Performance of high level QAM in the presence of impulsive noise and co-channel interference in multipath fading environment

An analysis is presented for the performance of a high-level (e.g. 16, 64 and 256-QAM) QAM (quadrature amplitude modulation) system in the presence of Gaussian thermal noise combined with a non-Gaussian impulsive noise and cochannel continuous wave interference in the multipath fading environment. The system performance is evaluated in terms of CNR (carrier-to-noise power ratio), CIR (carrier-to-interference ratio), impulsive index of the noise, power ratio of the Gaussian noise-to-impulsive noise, and fading figure. >

Exact radio link design in cellular mobile communication systems

AbstractIn the design of a radio link for terrestrial mobile communication, the transmitter power and the cluster size are determined based on the specification derived from the quality requirement and the outage. In the traditional design, the required quality and the outage are allocated according to the two degrading factors, i.e., the noise and the co‐channel interference, and the transmitter power and the cluster size are determined independently. The method is employed widely because of its simplicity, even though there is a certain error in the designed values. By contrast, this paper proposes an exact design for the radio link, where the reliability of the designed value is emphasized, aiming at a more efficient utilization of the frequencies. The concept of the prescribed quality transmission curve which considers simultaneously the two degrading factors, is newly introduced. The expression for the outage is derived from the prescribed transmission quality curve and the joint probability of the carrier‐to‐noise power ratio (CNR) and the carrier‐to‐interference power ratio (CIR). The relations among the outage, transmitter power and the cluster size are determined. As a precise method of calculation, a method is presented which gives the graphical relation between the transmitter power and the outage, with the cluster size as the parameter. Using a design example, it is shown that the minimum cluster size, which has been 12 in the traditional method, is now 9 by the proposed method. Thus, the usefulness of the method in the frequency utilization is indicated.

Transmission Characteristics of an M-ary Coherent PSK Signal Via a Cascade of N Bandpass Hard Limiters

This paper provides a general analysis of the transmission characteristics of a coherent PSK signal, where an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</tex> -ary coherent signal is transmitted via a repeater system composed of a cascade of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> bandpass hard limiters. The probability density function of a composite phase of the signal and noise over the system is newly derived to obtain an error probability. In addition, the comparison with the repeater system composed of a cascade of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> linear amplifiers is made to clarify the features of the transmission characteristics. It is found that the probability density function of the composite phase over the system is symmetric about each input carrier-to-noise power ratio (CNR), and it reduces to some well-known results. It is also shown that for a reasonably large input CNR in each stage, the presence of the bandpass hard limiter (BPHL) provides some improvement, but that for small input CNR it causes degradation in performance.

Distribution of Click Amplitudes

The amplitude of a click is defined as the output of an ideal FM demodulator at the time of occurrence of the click. It is shown that the amplitude of a click (when the carrier is unmodulated) is a function of two random variables whose join distribution function is derived under the condition that a positive click has occurred. The distribution of positive click amplitudes is derived with the carrier-to-noise power ratio (CNR) at the output of the intermediate frequency (IF) filter as a parameter The results are extended to include negative clicks. The probability density and distribution functions of click amplitudes are plotted for the special case of a rectangular IF and CNRs of 4 and 9 The effect of modulation on the distribution of click amplitudes is determined. Results are given for the special case of a sinusoidal modulating signal fully deviating the carrier and a rectangular IF