Nicolae Crisan

An Adaptive Combiner-Equalizer for Multiple-Input Receivers

Where multiple-input receivers are concerned diversity combining is one of the most efficient techniques against fading effects. In this paper we propose a multipleinput adaptive combiner-equalizer. The novelty of the solution lies in the unified combining-equalization approach - the two classical operations being performed simultaneously and not sequentially. Our simulations show significant performance in terms of outage probability for both indoor and outdoor conditions, while complexity is lower than for a classical MRC implementation. The concept of unifying certain operations along the transmission chain is feasible today more than ever as it can be easily implemented on SDR (Software Defined Radio) platforms.

The Adaptive Potential of reconfigurable MEMS in MIMO Antenna Technology

Part of a detailed study of adaptive radio techniques, the work presented in this paper focuses on the potential of MEMS (Micro-Electro-Mechanical Systems) in reconfigurable antenna array technology. After identifying the main challenges and benefits of multiple antenna systems, we have analyzed the four mechanisms in which a multiple antenna system can improve upon the throughput of a traditional wireless network: beamforming, beam-steering, transmit and receive diversity, and spatial multiplexing. In this paper we propose a unified technology for both the MEMS and the metallic pixel-patches that form the reconfigurable antenna array, thus aiming at a less expensive one, that can be unitarily controlled, as a single entity. This will in turn reduce the computational complexity of the control module. We have designed, simulated and analyzed reconfigurable MEMS antenna arrays at 40 GHz, 2.4 and 5 GHz. Reconfigurability of the operating frequency and of polarization are discussed. Based on our observations we can set the premises for new adaptive strategies.

Towards Cognitive Antenna Systems based on antenna-channel co-evolution

The paper discusses critical issues and challenges for the present generation of smart antennas, identifying multireconfiguration capabilities that can be addressed by evolutionary computing. A bio-inspired model called Cognitive Antenna System-CAS is proposed. Evolutionary algorithms are pointed at as a means of modelling and implementing cognitive mechanisms in such a system, based on the proposed antennachannel co-evolution concept.

The Impact of Novel RF MEMS and SDCs on Smart Antenna Technologies

This paper evaluates the impact of the newest micro & nanotechnologies on smart antenna systems. After analyzing the key features of the main mobile wireless systems of the present - UMTS, CDMA2000, WiMax 802.16e, and MBWA 802.20, we have identified some common issues, requirements and limitations. Dwelling on the SDC -Software-Defined Component perspectives we have analyzed the impact of novel RF MEMS on reconfigurable circuits, namely on smart antenna systems. This lead us to imagine a software-defined autonomous antenna - SDAA, which includes the RF module. This in turn, integrated on a SDR platform, will prototype the idea of extending the SDR concept over the RF module. This paper introduces our proposed SDR & SDAA architecture and its benefits.

Spectral efficiency improvement for the under-11GHz Broadband Wireless Access

Our evaluation is performed in the context of a study of adaptive radio techniques, in the attempt to improve link availability and transmission quality of BWA (broadband wireless access) systems, and to achieve an efficient use of radio resources. As part of an evaluation of coexistence issues in the under-11 GHz bands, we have analysed several adaptive techniques currently in use in IEEE 802.16 and IEEE 802.11 (a, b, g) standards. This paper is focused on the spectral efficiency and BER performance of the 802.16 FEC block. One of our goals was to study the effect of the interleaving process on the spectrum efficiency for different environments modelled by different radio channels. Another goal was to measure the system throughput and the delay introduced by the interleaver in the presence of noise, these enabling us to investigate from which BER and/or SNR threshold the interleaver can increase the overall spectrum efficiency. In the end, we identify six evaluation criteria for an adaptive FEC (forward error correction) scheme that can improve the performance, in terms of throughput, in an 802.16 SC system. The detailed observations will enable us to set the premour evaluation is performed in the context of a study of adaptive radio techniques, in the attempt to improve link availability and transmission quality of BWA (broadband wireless access) systems, and to achieve an efficient use of radio resources. As part of an evaluation of coexistence issues in the under-11 GHz bands, we have analysed several adaptive techniques currently in use in IEEE 802.16 and IEEE 802.11 (a, b, g) standards. This paper is focused on the spectral efficiency and BER performance of the 802.16 FEC block. One of our goals was to study the effect of the interleaving process on the spectrum efficiency for different environments modelled by different radio channels. Another goal was to measure the system throughput and the delay introduced by the interleaver in the presence of noise, these enabling us to investigate from which BER and/or SNR threshold the interleaver can increase the overall spectrum efficiency. In the end, we identify six evaluation criteria for an adaptive FEC (Forward Error Correction) scheme that can improve the performance, in terms of throughput, in an 802.16 SC system. The detailed observations will enable us to set the premises for new adaptive strategies at the PHY and MAC layer is set for new aadaptivedaptive strategies at the PHY and MAC layer.

Antenna-Based Signal Fishing

The paper discusses the possibility of using a short-term, short-range fading characterization to turn a selective channel problem into a flat fading problem. By estimating or measuring the angle of arrival, phase shift, and amplitude of the incoming signal this characterization can be obtained. It is the antenna array that has the main role here. We call this proactive antenna implication, antenna-based signal fishing. We propose a block diagram for the antenna fishing system and we discuss the first experiments which involve the use of a multiple-input adaptive combiner-equalizer.

FEC Performance Analysis for the under-11GHz 802.16 SC Specifications

Our analysis is performed in the context of a study of adaptive radio techniques, in the attempt to improve link availability and transmission quality of broadband wireless systems, and to achieve an efficient use of radio resources. We have implemented and analysed the IEEE 802.16 a WirelessMAN-SCa PHY. The paper is focused on the BER performance of the 802.16 a FEC (forward error correction) block. The implementations, simulation and evaluation have been performed using System View (by Elanix). In the end, we identify six evaluation criteria for an adaptive FEC scheme that would improve the performance in terms of throughput in an 802.16 a system.

Cognitive Antenna System for Sustainable Adaptive Radio Interfaces

Communication systems are usually implemented on a heterogeneous infrastructure and must operate in environments with accelerated dynamics. Adaptation is thus a key feature of such a system. Long-term, sustainable, adaptive solutions did not receive much attention in the design phase of wireless communication systems. With the advent of LTE, which was designed as a highly flexible radio interface—created to evolve—there is room for disruptive solutions to be put in place. A new approach for the receiver is proposed, where the antenna takes an active role in characterising and eventually learning the operation environment. The proposed solution—a Cognitive Antenna System (CAS), is based on two main mechanisms that we called antenna vision (AV) and signal fishing (SF). In the core cognitive cycle ‘observe-decide-act’ we aim to improve the ‘observe’ part, which critically influences the whole decision process. The SF and AV mechanisms bring a set of advantages: higher received SNR, no additional noise, higher AoA estimation accuracy.

Design of multi-antenna diversity system dedicated to sensor interrogation in multi-path environments

In this paper, a new diversity system containing ten planar inverted F antennas (PIFA) placed on a parallelepiped box which combines polarization, radiation pattern and space diversities is presented. The system operates in the [2.4-2.5 GHz] band and exhibits a minimum of 17dB of isolation between all its input ports.

Simulation of a handset MIMO antenna integration in a LTE Tx-Rx chain

A simulation component for a multi-band, handset MIMO antenna is proposed. The new component emulates element coupling and mismatching for a MIMO miniature antenna and enables integration and testing of new antenna designs in an end-to-end Tx-Rx chain. The simulation of a dual-band, two-element antenna integration in an LTE Tx-Rx chain is presented. The entire process is described - from layout design to the final block integration. Simulation results indicate the effectiveness and accuracy of the proposed simulation component.