High Data Rate Communication Systems Research Articles

Investigation of the Effect of Building Dielectric Parameters on Indoor Radio Channel Characteristics

The unlicensed industrial, scientific, and medical (ISM) band at 2.4 GHz has gained increased attention recently due to high data rate communication systems developed to operate in this band. In this paper the investigation of the indoor electromagnetic propagation and indoor radio channel characteristics have been performed at this band. Electromagnetic waves propagate by means of reflection, refraction, and diffraction. Reflection mechanisms are dependent on the nature of the surface, dielectric properties, polarization, incidence angle, and material thickness. The effect of the incidence angle and material thickness on the reflection coefficients for both horizontal and vertical polarization has been studied. Two-dimensional ray-tracing simulation has been performed to show the influence of building electromagnetic properties on indoor radio channel parameters, signal level, RMS delay spread, and coherence bandwidth. Results show the influence of the permittivity is more important than the influence of the order of reflection considered for the ray- tracing model. It is shown that, compared with power level, RMS delay spread is more sensitive to the building dielectric parameters. Maximum RMS delay spread is dependent on the dielectric parameters of the surrounded walls. Keywords: Radio propagation, Dielectric parameters, Indoor Channel Parameters

High-Efficiency Angled-Dipole Antennas for Millimeter-Wave Phased Array Applications

A high-efficiency microstrip-fed endfire angled-dipole antenna has been developed for millimeter-wave phased array applications. The antenna is built on both sides of a Teflon substrate (epsivr = 2.2) and this allows a wideband feed from the single-ended microstrip line to the differential dipole. The design results in wide radiation patterns for scanning purposes with a gain of around 2.5 dB at 20-26 GHz and a cross-polarization level of 6 dB at 23.2-24.6 GHz and very low mutual coupling between elements ( 93% when referenced to the microstrip line feed (including mismatch loss). The usefulness of these antennas as phased array radiators is demonstrated by several eight-element linear arrays at 22-24 GHz with scan angle up to 50 degrees. The application areas are in automotive radars and high data-rate communication systems.

Design Considerations for High Performance RF Cores Based on Process Variation Study

RF circuits play a vital role in high data rate communication systems. Although at the design stage several considerations are made to ensure that the designed circuit functions as per desired specifications, the effect of process variations on the circuit's performance is less understood. The parametric variations arising from the various stages of fabrication play a significant role in determining the device characteristics. In this paper, in order to analyze the effect of process variations, we consider a bottom---up approach beginning at the component level for active and passive elements and then move to the circuit level in an RF circuit consisting of both analog and digital components. We take Low Noise Amplifier (LNA) and a Phase Frequency Detector (PFD) which is one of the important building blocks of a Phase Locked Loop (PLL) as case studies for circuit level analysis. In the case of LNA, the performance is analyzed in terms of the S-parameters, gain and Noise Factor on different topologies and for a PFD, an analytical model is developed and the analysis is carried out using the Monte Carlo method to verify the robustness of the circuit elements towards phase noise. Our hierarchical multi-phase analysis technique is shown to provide valuable insights into designing robust RF circuits.

Locally Optimum Detection of Signals in Multiplicative and First-Order Markov Additive Noises

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In most previously reported studies on locally optimum detection of signals, independent observations have been assumed in various noise environments. The use of an independent observation model may cause a considerable performance degradation in detection applications of modern high data-rate communication systems exhibiting dependence among interference components. In this paper, the detection of weak known and random signals is addressed in observations corrupted by multiplicative and first-order Markov additive noises. The asymptotic and finite sample-size performance of several detectors are obtained and compared: it is confirmed that the dependence of noise components need to be taken into account to maintain detection performance appropriately. </para>

무선 센서 네트워크의 주파수 사용 효율성 향상을 위한 OFDM을 사용한 협력적 M-1-1 프로토콜 설계

무선 센서 네트워크는 전력 및 주파수 사용이 매우 제한적이지만, 멀티미디어 센서 기술의 발전에 따라 고용량의 데이터를 전송할 수 있는 통신 시스템 개발이 요구되어진다. 협력 통신 시스템은 노드와 중계 노드의 조력을 통해 공간 다이버시티를 획득하고, 이에 따라 통신 전력을 감소시킬 수 있다는 장점을 가지고 있다. 기존의 협력 통신 시스템은 하나의 중계 노드가 하나의 센서 노드의 데이터 전송을 도와줌에 따라 노드의 동작이 빈번하게 발생한다. 이는 네트워크 수명을 급격히 단축시키는 원인으로 작용한다. 본 논문에서는 하나의 중계 노드가 M개의 센서 노드의 데이터 전송을 돕는 것을 제안한다. 이를 통하여 제안한 시스템은 기존 시스템과 동일한 다이버시티 효과를 획득하고 동시에 주파수 대역, 전력 및 중계 노드의 수를 감소시킨다. 또한, 센서 네트워크의 특성상 주위에 인접한 노드로 인한 신호 간섭이 발생하는데, 이를 직교성을 가진 부반송파를 이용하여 개선한다. 마지막으로 센서 노드들과 중계 노드의 전력 할당에 따른 시스템 성능을 분석하였다. Conventional wireless sensor network(WSN) has limited power and bandwidth. In order to develop multimedia sensor technology, high data rate communication systems are required. Cooperative communication system can help to decrease power consumption through spatial diversity. In cooperative transmission, one partner node assists one sensor node to transmit their data to destination. Instead of using M partners for M sensor nodes, we propose 1 partner for M sensor nodes. Proposed protocol offers similar diversity order as conventional one with much less bandwidth and hardware. It is able to almost reduce scattered nodes interference using orthogonal sub-carriers. In addition, we examined a power allocation between sensor nodes and relay that optimize the system performance.

Lattice-reduction-aided detection for MIMO-OFDM-CDM communication systems

Multiple input multiple output-orthogonal frequency division multiplexing-code division multiplexing (MIMO-OFDM-CDM) techniques are considered to improve the link reliability/spectral efficiency of very high data rate communication systems. In particular, lattice-reduction-aided receivers are proposed for MIMO-OFDM-CDM systems. Simulation results show that the proposed receivers significantly outperform the conventional zero-forcing, minimum mean-squared error, or vertical Bell Labs layered space–time receivers without severely compromising system complexity.

Development of 60 GHz front End circuits for high data rate communication system at Chalmers University

Front‐end circuits such as mixers, amplifiers, frequency multipliers, IF‐amplifiers with gain‐control, and VCOs are presented. Promising results on VCOs based on a coupled Colpitt VCO topology, designed in both HEMT and HBT technologies, have been achieved. A novel balanced 7 ‐ 28 GHz MMIC frequency quadrupler is described and compared with a single ended quadrupler at the same input frequencies. A 3‐stage MHEMT wideband amplifier covering 43–64 GHz with a gain of 24 dB, a minimum noise figure of 2.5 dB and ripple of 2 dB is also described. In order to reduce the manufacturing cost for future 60 GHz products, a higher integration level is necessary. Recently, a multifunctional receiver/transmitter utilizing 60 GHz amplifier, frequency converter, and x8 frequency multiplier was demonstrated based on a commercial pHEMT‐process.

Improved maximum likelihood frequency offset estimation based on likelihood metric design

For emerging high data-rate communication systems in highly dispersive channels such as ultrawideband (UWB) systems, possible frequency offsets could be larger than the estimation range of the existing methods using training signals with identical parts or repetitive training signals (i.e., the training signals are composed of several identical subblocks or are obtained by repeating a training subblock for several times). This paper presents a novel improved maximum likelihood frequency offset estimator which can handle at least twice the estimation range of the existing methods using training signals with identical parts and achieves a better estimation performance. Based on the likelihood metric, a new design metric is introduced which is a pair-wise error probability (PEP) between the correct frequency offset point and a trial frequency offset point. The proposed PEP metric gives more theoretical insights on the performance of practical maximum likelihood estimators. How to design the PEP to achieve both a larger estimation range and a better estimation performance in fading channel environments is also presented and the corresponding estimator implementation is described.

Influence of the Human Activity on Wide-Band Characteristics of the 60 GHz Indoor Radio Channel

This paper presents propagation measurements in the presence of human activity for a 60 GHz channel. Series of 40-min-long measurements of the channel impulse response have been recorded with a sampling period of 1.6 ms, for a total duration of about 20 h. During measurements, the human activity (between zero and 15 persons) was observed with a video camera. The obstruction phenomenon due to the human bodies is characterized in duration and amplitude from the propagation characteristics (attenuation, coherence bandwidth) by means of an appropriate method. The results highlight and quantify the problems due to the human activity for high data rate communication systems. When the direct path is shadowed by a person, the attenuation generally increases by more than 20 dB, for a median duration of about 100 ms for an activity of one to five persons and 300 ms for 11-15 persons. Globally, the channel is "unavailable" for about 1% or 2% of the time in the presence of one to five persons. This channel characterization makes it possible to modelize the temporal variations of the 60 GHz channels. The results also give orientations for the design of high data rate communications systems and networks architectures at 60 GHz.

Linear maximum likelihood decoding of space – time block coded OFDM systems for mobile communications

A new linear decoder for space–time block codes is presented, which enables linear maximum-likelihood decoding in scenarios beyond those described by block-fading models. The new decoder employs linear combinations of received signals with weights designed so as to yield orthogonal estimates for all encoded symbols regardless of channel variations within the block transmission, provided that the channel is known. The combination weights are scalar functions of the channel estimates, obtained through systematic rotations over the decoding matrices of the linear maximum-likelihood decoder for the block-fading case. The proposed decoder yields good performance with low-complexity and is therefore suitable for low-cost portable receivers supporting space–time transmit diversity at the downlink of high data-rate wireless mobile communication systems. Combined with OFDM technology, the technique yields a low-complexity receiver that is effective in combating both time and frequency selectivities, and provides a tool to add flexibility to wireless local area network systems and to offer high data-rate services with support to mobility.

Wideband and dynamic characterization of the 60GHZ indoor radio propagation — future homeWLAN architectures

This paper presents some results of a study concerning the radio propagation at 60GHZ in residential environments performed by theIETR (Electronic and Telecommunication Institute of Rennes, France). This study is part of aRNTR project named “COMMINDOR”. This exploratory project concerns the very high data rate (155 Mbit/s) and small range (about 10 m) radio communication systems for future home networks, which will permit multimedia equipment interconnection and control. The study is based on several measurement campaigns realized with a channel sounder based on the sliding correlation technique. This channel sounder has a 500MhZ bandwidth and a 2.3 ns effective time resolution. The measurements have been performed in residential furnished environments. The study of the angles-of-arrival (AOA) emphases the importance of openings (such as doors, staircase, etc.) for the radio propagation between adjacent rooms. A particular attention is paid to the influence of human activity on radio propagation. It is shown that people movements can make the propagation channel unavailable during about one second. From the characterization study of the indoor radio propagation, several recommendations concerning the deployment of the very high data rate 60GHZ wireless networks are derived.

Ka-band multibeam active phased array antenna

The high data rate and global satellite communication systems are expected to be an important technology to the social and economic activities in this century. The experimental high data rate satel...

Indoor 60 GHz radio channel sounding and related T/R module considerations for high data rate communications

The impact of 60 GHz indoor propagation on the definition of T/R modules for high data rate communication systems (155 Mbit/s) is investigated. The influence of the antenna characteristics and the electromagnetic environment is investigated in order to increase the coherent bandwidth of the 60 GHz radio channel and thus optimise the radio interface complexity.

Characterization of the indoor radio propagation channel at 2.4 GHz

The unlicensed industrial, scientific, and medical (ISM) band at 2.4 GHz has gained increased attention recently due to the high data rate communication systems developed to operate in this band. The paper presents measurement results of fading characteristics, multipath parameters and background interference for these frequencies. Some statistical analysis of the measured data is presented. The paper provides information that may be useful in design and deployment of communication systems operating in the 2.4 GHz ISM band, like those compliant with IEEE 802.11 standard and Bluetooth open wireless standard

Development results of partial model of a Ka-band active phased array antenna for gigabit satellite

The high data rate and global satellite communication systems are expected to be an improvement agenda to the social and economic activities in the 21st century. The experimental high data rate (gigabit) communications satellite is required to face the technological challenges of the future growing multi-media applications. For this gigabit communications system, a Ka-band scanning spot beam antenna (SSBA) which realizes multiple beam forming is required. CRL and MELCO have been developing Ka-band active phased array antenna (APAA) for the SSBA as one of the most important and challenging technology. An APAA has been developed mainly for radar systems for many years. CRL and MELCO are investigating and developing the direct radiating APAA for communication satellites which can operate under wide frequency band in Ka-band. This paper describes the preliminary study results of the Ka-band APAA for gigabit satellite and the radiation performances of the partial experimental model of Ka-band APAA with two multiple beams to both transmit and receive signals. The partial model includes the active MMIC device such as HPA (high power amplifier), LNA (low noise amplifier) and PS (phase shifter), and multi-layered BFN (beam forming network) as key components. Performances such as radiation pattern, beam scanning performance and input–output performance have been measured. We also verified that the REV (rotating element electric-field vector) method was effective for pattern calibration. Copyright © 1999 John Wiley & Sons, Ltd.

Compact transmitter and receiver modules with optoelectronic-integrated circuits for optical LAN's

Compact transmitter and receiver modules with monolithic optoelectronic-integrated circuits, i.e., OEIC's, are demonstrated, and 400- and 800-Mbit/s transmission experiments are successfully carried out over up to 4 and 2 km, respectively, with these modules, for the first time. The design of the monolithic-integrated circuits and the compact module structure are presented. The soldering technique based on the use of YAG laser simplifies the packaging procedures, and an efficient and simple scheme for coupling between OEIC's and fibers make the OEIC modules compact. Both modules are attractive for applications in high data-rate communication systems, particularly in local area networks, CATV systems, and intra-office links.

Design and performance analysis of a Digital Acoustic Telemetry System for the short range underwater channel

This paper presents the design and performance description of a microprocessor based Digital Acoustic Telemetry System (DATS). The system was used to transmit data over short range underwater paths and to measure the fading characteristics of a group of CW tones. This work reports on the test results from Woods Hole Harbor. The system has also been used for under-ice propagation experiments in Lake Caanan, NH, and in the Marginal Ice Zone near Svalbard. Geometries chosen for the tests are representative of the short range marine work site paths for which high data rate communications systems are desirable.