Reconfigurable Radio Systems Research Articles

A dual mode circular waveguide cavity resonator based frequency tunable band pass filter using a single tuning element

AbstractIn this letter, we present a tunable band pass filter (BPF) using a dual‐mode circular waveguide cavity resonator using a single tuning element. For the proof of the concept, a 2nd order tunable BPF has been designed and developed over a tuning range from 4.92 to 6.1 GHz (21.4%). The measured bandwidth is 85 ± 10 MHz over the entire tuning range. The peak insertion loss is within 1.3 dB and return loss is better than 15 dB. The tunable filter is proposed to be used in high Q reconfigurable radio systems.

Sensitive readout of implantable microsensors using a wireless system locked to an exceptional point

Exceptional points are degeneracies in physical systems at which both the underlying eigenvalues and eigenvectors of the system coalesce. They originated in theoretical explorations of quantum mechanics, but are of increasing value in photonics, acoustics and electronics because their emergence in physical systems with controlled gain and loss can dramatically alter the response of a system. In particular, systems biased at exceptional points can exhibit an amplified response to a small perturbation, enabling greatly enhanced sensitivity for certain resonant sensors. In biomedicine, implanted electronic sensors based on resonant inductor–capacitor (LC) circuits can be used to monitor internal physiological states, but their capabilities are currently limited by the low sensitivity of existing wireless interrogation techniques. Here we show that a reconfigurable wireless system locked to an exceptional point can be used to interrogate in vivo microsensors with a sensitivity 3.2 times the limit encountered by existing schemes. We use a controller that maximizes the abruptness of a parity–time-symmetry phase transition to operate a reconfigurable circuit at an exceptional point and maintain enhanced sensitivity. With this approach, we demonstrate robust readout of LC microsensors (with diameters of 900 μm) that are subcutaneously implanted in a rat, and show that it can be used for wideband sensor interrogation for measurement of the resonant frequencies of single and multiple sensors. A reconfigurable wireless system locked to an exceptional point can be used to interrogate in vivo inductor–capacitor microsensors with a sensitivity 3.2 times beyond the limit of conventional readout schemes.

Blind Reconstruction of Reed-Solomon Encoder and Interleavers Over Noisy Environment

Blind estimation of code and interleaver parameters is useful in smart storage systems and ubiquitous communication applications such as adaptive modulation and coding, reconfigurable radio systems, non-cooperative radio systems, etc. In this paper, we analyze Reed-Solomon (RS) encoded data stream and propose blind estimation algorithms to identify RS code parameters. We also provide algorithms to estimate block interleaver parameters from RS coded and block interleaved data stream. In addition, synchronization compensation through appropriate bit/symbol positioning is integrated with the proposed code and interleaver parameter estimation algorithms. Simulation results validating the proposed algorithms are given for various test cases involving both erroneous and non-erroneous scenarios. Moreover, the accuracy of estimation of RS code and block interleaver parameters are also given with detailed inferences for different modulation schemes, codeword length, and code dimension values. It has been inferred that the accuracy of parameter estimation improves with decrease in code dimension and codeword length values of RS codes. Further, the accuracy of estimation of lower modulation order schemes is better when compared to higher modulation order schemes as expected. It has also been noted that the proposed code and interleaver parameter estimation algorithms for noisy environment consistently outperform the algorithms proposed in the prior works.

Frequency and polarization reconfigurable microstrip antenna

This paper presents a dual band frequency and polarization reconfigurable microstrip antenna. The simple design consists of two slots and two feeds. In one slot there is a switch. The two feeds are positioned on the right and left diagonal of microstrip antenna. When the switch is ON the electrical size of antenna becomes small and it resonates at higher UMTS 2100 MHz band with circular polarization. Similarly, when the switch is OFF then size of antenna is large and it operates at lower UMTS 1900 MHz band with elliptical polarization. The sense of polarization can be easily changed from right handed to left handed by changing the feed position. The radiation pattern is not disturbed by switch state and gain of proposed antenna is above 5 dBi. This antenna can be used in emerging reconfigurable wireless communication systems.

WiSHFUL: Enabling Coordination Solutions for Managing Heterogeneous Wireless Networks

The paradigm shift toward the Internet of Things results in an increasing number of wireless applications being deployed. Since many of these applications contend for the same physical medium (i.e., the unlicensed ISM bands), there is a clear need for beyond-state-of-the-art solutions that coordinate medium access across heterogeneous wireless networks. Such solutions demand fine-grained control of each device and technology, which currently requires a substantial amount of effort given that the control APIs are different on each hardware platform, technology, and operating system. In this article an open architecture is proposed that overcomes this hurdle by providing unified programming interfaces (UPIs) for monitoring and controlling heterogeneous devices and wireless networks. The UPIs enable creation and testing of advanced coordination solutions while minimizing the complexity and implementation overhead. The availability of such interfaces is also crucial for the realization of emerging software-defined networking approaches for heterogeneous wireless networks. To illustrate the use of UPIs, a showcase is presented that simultaneously changes the MAC behavior of multiple wireless technologies in order to mitigate cross-technology interference taking advantage of the enhanced monitoring and control functionality. An open source implementation of the UPIs is available for wireless researchers and developers. It currently supports multiple widely used technologies (IEEE 802.11, IEEE 802.15.4, LTE), operating systems (Linux, Windows, Contiki), and radio platforms (Atheros, Broadcom, CC2520, Xylink Zynq, ), as well as advanced reconfigurable radio systems (IRIS, GNURadio, WMP, TAISC).

ETSI-Standard Reconfigurable Mobile Device for Supporting the Licensed Shared Access

In order for a Mobile Device (MD) to support the Licensed Shared Access (LSA), the MD should be reconfigurable, meaning that the configuration of a MD must be adaptively changed in accordance with the communication standard adopted in a given LSA system. Based on the standard architecture for reconfigurable MD defined in Working Group (WG) 2 of the Technical Committee (TC) Reconfigurable Radio System (RRS) of the European Telecommunications Standards Institute (ETSI), this paper presents a procedure to transfer control signals among the software entities of a reconfigurable MD required for implementing the LSA. This paper also presents an implementation of a reconfigurable MD prototype that realizes the proposed procedure. The modem and Radio Frequency (RF) part of the prototype MD are implemented with the NVIDIA GeForce GTX Titan Graphic Processing Unit (GPU) and the Universal Software Radio Peripheral (USRP) N210, respectively. With a preset scenario that consists of five time slots from different signal environments, we demonstrate superb performance of the reconfigurable MD in comparison to the conventional nonreconfigurable MD in terms of the data receiving rate available in the LSA band at 2.3–2.4 GHz.

Low‐noise tunable filter design by means of active components

A low-noise tunable filter with high dynamic range and minimum power consumption is presented and addressed with circuit details. It is based on an active solution simulating an inductive behaviour that allows improving the filter quality factor without affecting the noise performance. The low-order bandpass filter is realised with minimum number of components and it is suitable to be integrated in integrated circuit or used in hybrid transceiver and modern reconfigurable radio systems. A prototype board with discrete components has been fabricated and tested with good results.

Adaptive Resource Allocation for MC-CDMA and OFDMA in Reconfigurable Radio Systems

This paper studies the uplink resource allocation for multiple radio access (MRA) in reconfigurable radio systems, where multiple-input and multiple-output (MIMO) multicarrier-code division multiple access (MC-CDMA) and MIMO orthogonal frequency-division multiple access (OFDMA) networks coexist. By assuming multi-radio user equipment with network-guided operation, the optimal resource allocation for MRA is analyzed as a cross-layer optimization framework with and without fairness consideration to maximize the uplink sum-rate capacity. Numerical results reveal that parallel MRA, which uses MC-CDMA and OFDMA networks concurrently, outperforms the performance of each MC-CDMA and OFDMA network by exploiting the multiuser selection diversity.

A Reconfigurable Wireless Environment for ECG Monitoring and Encryption

Connected health is the convergence of medical devices, security devices, and communication technologies. It enables patients to be monitored and treated remotely from their home or primary care facility rather than attend outpatient clinics or be admitted to hospital. Patients’ data and medical records within a connected health system should be securely transmitted and saved for further analysis and diagnosis. This paper presents a reconfigurable wireless system for electrocardiogram (ECG) monitoring which can be deployed in a connected health environment. Efficient field programmable gate array (FPGA) implementation for the ECG encryption block has been carried out on the RC10 prototyping board using the advanced encryption standard (AES) algorithm. Results presented have shown that the proposed AES implementation outperforms the existing FPGA-based systems in different key performance metrics and that ECG signals acquired using the VitalSens device can be encrypted/decrypted in real-time. A software based evaluation approach has been also performed to validate the proposed hardware implementation. The proposed solution can be deployed for electronic archiving of health records information systems and health monitoring technologies in personalized medicine.

Future of wireless communication: RadioApps and related security and radio computer framework

This article introduces a novel flexible mobile device reconfiguration classes (MDRCs) framework which is expected to be applicable to future generation mass market radio devices. This framework sets the scene for a vision of a smooth evolution of reconfigurability features in mobile devices, paving the way from current, mainly static implementation choices toward a fully flexible device platform environment. For this flexible mobile device framework, baseband interfaces are introduced as they are currently discussed in ETSI reconfigurable radio systems standardization. Furthermore, this technical solution is positioned with respect to security requirements and the basic regulatory framework which is currently under revision in Europe. Indeed, the future revised Radio Equipment and Telecommunications Terminal Equipment Directive is expected to allow for such advanced reconfiguration, enabling users to acquire and install so-called RadioApps software components which may affect the compliance of a mobile device to the essential requirements of the Directive.

The E3 architecture: enabling future cellular networks with cognitive and self‐x capabilities

AbstractFuture mobile networks are expected to be complex heterogeneous systems. On the one hand this will enable users to take advantage of a number of different access technologies. On the other hand it will seriously affect network management procedures since more extensive operations and decisions will have to be dealt with. To tackle these challenges a number of new dynamic mechanisms need to be designed. It is imperative that certain network management tasks have to be performed without human intervention to reduce the OPEX costs and achieve faster responses in different events. To achieve this goal, the introduction of self‐x functionalities, combined with cognitive mechanisms and the ability to reconfigure network entities and terminals, is required. Moreover, the introduction of a new pilot channel needs to be considered to assist the terminals in selecting the most suitable radio access technology according to their requirements. We present the functional architecture of an evolved network that was designed in the context of the EU‐funded IP project ‘E3: End‐to‐End Efficiency’. This architecture aims to enhance existing procedures usually performed in traditional operation and maintenance systems (e.g. spectrum management, network planning, configuration actions). We explain the rationale of our design and provide specific examples to illustrate the role of the different functional entities and their interfaces. A considerable part of this architecture has recently been approved as a feasibility study by the ETSI Committee Reconfigurable Radio System. Copyright © 2010 John Wiley & Sons, Ltd.

ETSI reconfigurable radio systems: status and future directions on software defined radio and cognitive radio standards

This article details the current work status of the ETSI Reconfigurable Radio Systems Technical Committee, positions the ETSI work with respect to other standards efforts (IEEE 802, IEEE SCC41) as well as the European Regulatory Framework, and gives an outlook on the future evolution. In particular, software defined radio related study results are presented with a focus on SDR architectures for mobile devices such as mobile phones. For MDs, a novel architecture and inherent interfaces are presented enabling the usage of SDR principles in a mass market context. Cognitive radio principles within ETSI RRS are concentrated on two topics, a cognitive pilot channel proposal and a Functional Architecture for Management and control of reconfigurable radio systems, including dynamic self-organizing planning and management, dynamic spectrum management, joint radio resource management. Finally, study results are indicated that are targeting a SDR/CR security framework.

Optimized Paraunitary Filter Banks for Time-Frequency Channel Diagonalization

We adopt the concept of channel diagonalization to time-frequency signal expansions obtained by DFT filter banks. As a generalization of the frequency domain channel representation used by conventional orthogonal frequency-division multiplexing receivers, the time-frequency domain channel diagonalization can be applied to time-variant channels and aperiodic signals. An inherent error in the case of doubly dispersive channels can be limited by choosing adequate windows underlying the filter banks. We derive a formula for the mean-squared sample error in the case of wide-sense stationary uncorrelated scattering (WSSUS) channels, which serves as objective function in the window optimization. Furthermore, an enhanced scheme for the parameterization of tight Gabor frames enables us to constrain the window in order to define paraunitary filter banks. We show that the design of windows optimized for WSSUS channels with known statistical properties can be formulated as a convex optimization problem. The performance of the resulting windows is investigated under different channel conditions, for different oversampling factors, and compared against the performance of alternative windows. Finally, a generic matched filter receiver incorporating the proposed channel diagonalization is discussed which may be essential for future reconfigurable radio systems.

Functional architecture

In this article, we propose and describe a functional architecture (FA) for the efficient radio and spectrum resource management of the anticipated future compound communication systems. This work comprises an advancement of the FA that has been initially proposed within end-to-end reconfigurability - phase 2 (E2R II) project and has been enhanced to incorporate cognitive and self-x capabilities to address the newly born B3G challenges. Furthermore, the proposed FA is currently being elaborated within the Working Group 3 (WG3) of the Reconfigurable Radio Systems Technical Committee (RRS TC). This committee was created by European Standards Telecommunication Institute (ETSI) Board with the aim to study the feasibility of standardization activities related to reconfigurable radio systems (including software defined and cognitive radios). It should be also mentioned that a relevant functional architecture for optimized radio resource usage in heterogeneous wireless networks is currently under standardization within IEEE.

Green Reconfigurable Radio Systems

The wireless standards scene and its evolution strengthens the need for functional flexibility in future radios. Multimode terminals supporting an increasingly large variety of standards (cellular, WLANs, WMANs, WPANs) are subject to a cost increase that is addressed by more flexible radio interfaces. Energy efficiency, however, is the main obstacle to successfully deploying such reconfigurable radios. To address this, it is essential to design energy-scalable SDRs, both for the radio front-end and the digital baseband platform. Complementing this, an essential ingredient is an intelligent controller that optimally exploits this scalability and the run-time dynamics to translate potential energy scalability to actual low-power operation. To realize this goal, an energy-aware cross-layer radio management framework is introduced. It was instantiated in different case studies, showing the applicability of this approach in realistic setups. Results have shown that substantial gains can be achieved through effective cross-layer optimization and problem partitioning. Next, it was shown that SDRs will play a crucial role in enabling CRs, which will enable saving on both the scarce radio spectrum and battery lifetime. A key building block for the design of such CRs, i.e., the appropriate control intelligence to make the SDR platform cognitive, can be derived by incrementally building on the proposed framework. As a result, green (or environment friendly) reconfigurable radio systems will emerge, which offer a wide variety and ubiquitous availability of wireless services, while overcoming energy and spectrum scarcity

Software-Defined Radio—Basics and Evolution to Cognitive Radio

We provide a brief overview over the development of software-defined or reconfigurable radio systems. The need for software-defined radios is underlined and the most important notions used for such reconfigurable transceivers are thoroughly defined. The role of standards in radio development is emphasized and the usage of transmission mode parameters in the construction of software-defined radios is described. The software communications architecture is introduced as an example for a framework that allows an object-oriented development of software-defined radios. Cognitive radios are introduced as the next step in radio systems' evolution. The need for cognitive radios is exemplified by a comparison of present and advanced spectrum management strategies.

Dynamic spectrum allocation in composite reconfigurable wireless networks

Future wireless systems are expected to be characterized by increasing convergence between networks and further development of reconfigurable radio systems. In parallel with this, demand for radio spectrum from these systems will increase, as users take advantage of high quality multimedia services. This article aims to investigate and review the possibilities for the dynamic allocation of spectrum to different radio networks operating in a composite reconfigurable wireless system. The article first looks into the current interest of regulators in this area, before describing some possible schemes to implement dynamic spectrum allocation and showing some example performance results. Following this, the technical requirements that a DSA system would have, in terms of reconfigurable system implementation, are discussed.