Srikathyayani Srikanteswara

A soft radio architecture for reconfigurable platforms

While many soft/software radio architectures have been suggested and implemented, there remains a lack of a formal design methodology that can be used to design and implement these radios. This article presents a unified architecture for the design of soft radios on a reconfigurable platform called the layered radio architecture. The layered architecture makes it possible to incorporate all of the features of a software radio while minimizing complexity issues. The layered architecture also enables a methodology for incorporating changes and updates into the system. An example implementation of the layered architecture on actual hardware is presented.

An overview of configurable computing machines for software radio handsets

The advent of software radios has brought a paradigm shift to radio design. A multimode handset with dynamic reconfigurability has the promise of integrated services and global roaming capabilities. However, most of the work to date has been focused on software radio base stations, which do not have as tight constraints on area and power as handsets. Base station software radio technology progressed dramatically with advances in system design, adaptive modulation and coding techniques, reconfigurable hardware, A/D converters, RF design, and rapid prototyping systems, and has helped bring software radio handsets a step closer to reality. However, supporting multimode radios on a small handset still remains a design challenge. A configurable computing machine, which is an optimized FPGA with application-specific capabilities, show promise for software radio handsets in optimizing hardware implementations for heterogeneous systems. In this article contemporary CCM architectures that allow dynamic hardware reconfiguration with maximum flexibility are reviewed and assessed. This is followed by design recommendations for CCM architectures for use in software radio handsets.

Power Consumption Minimization for MIMO Systems — A Cognitive Radio Approach

This paper shows how cognitive radio (CR) can help to optimize system power consumption of multiple input multiple output (MIMO) communication systems. Leveraging results from information theory and capabilities of a CR (e.g., the awareness of the component capabilities and characteristics), a theoretical framework is developed to minimize the system power consumption of MIMO systems while still considering radiated power. This paper mathematically formulates the system power consumption minimization problem under a sum rate constraint for MIMO systems. The impact of channel correlation and partial channel state information at the transmitter is considered. Numerical algorithms are developed to solve the constrained optimization problem. The simulation results show that significant power savings (e.g., up to 75% for a 4 × 4 MIMO system with Class A power amplifiers) can be achieved compared to conventional power allocation schemes. The results also show that the more computationally efficient suboptimal heuristic algorithms can achieve power savings comparable to the exhaustive search algorithm.

Minimizing Energy Consumption Using Cognitive Radio

In this paper, we show how cognitive radio can help minimize energy consumption of a wireless mobile communication device. We propose an energy optimization framework using cognitive radio for a given quality of service requirement based on the channel and the radio capabilities. The cognitive radio not only adjusts modulation, coding, and radiated power, as with conventional adaptive modulation, but also adjusts component characteristics (e.g., power amplifier characteristics) so that the radio operates with the highest energy efficient possible way. Simulation results show that significant energy savings (up to 75%) can be achieved compared to conventional adaptive modulation. This framework also can be applied to optimize radio operations to achieve additional goals.

Characterizing Decentralized Wireless Networks with Temporal Correlation in the Low Outage Regime

Communication in decentralized wireless networks is limited by interference. Because transmissions typically last for more than a single contention time slot, interference often exhibits a strong statistical dependence over time that results in temporally correlated communication performance. The temporal dependence in interference increases as user mobility decreases and/or the total transmission time increases. We propose a network model that spans the extremes of temporal independence to long-term temporal dependence. Using the proposed model, closed-form single hop communication performance metrics are derived that are asymptotically exact in the low outage regime. The primary contributions are (i) deriving the joint temporal statistics of network interference and showing that it follows a multivariate symmetric alpha stable distribution; (ii) utilizing the joint interference statistics to derive closed-form expressions for local delay, throughput outage probability, and average network throughput; and (iii) using the joint interference statistics to redefine and analyze the network transmission capacity that captures the throughput-delay-reliability tradeoffs in single hop transmissions. Simulation results verify the closed-form expressions derived in this paper and we demonstrate up to 2× gain in network throughput and reliability by optimizing certain parameters of medium access control layer protocol in view of the temporal correlations.

System power consumption minimization for multichannel communications using cognitive radio

Power consumption has been a significant issue for many mobile and wireless devices, especially those with high rate applications. This paper presents a methodology and framework to minimize system power consumption for multichannel communications using cognitive radio (CR) based on the application quality of service requirement, the channel condition, and the radio capabilities and characteristics. The CR framework enables an adaptation process that is aware of the radio (component) capabilities and characteristics. This paper mathematically formulates a system power consumption minimization problem under a rate constraint for multichannel communications and develops numerical solutions. Simulation results show that the knowledge of the radio capabilities and characteristics can help to reduce system power consumption significantly (e.g., up to 55% for a multichannel system with Class A power amplifiers).

Energy consumption minimization for mobile and wireless devices - a cognitive approach

Energy consumption for mobile and wireless communication device, such as cell phones, has long been an important aspect for both designers and customers. This paper shows how a cognitive radio (CR) framework can help to reduce system energy consumption of a mobile and wireless communication device based on the application quality of service requirement, the channel condition, and the radio capabilities and characteristics. The CR framework enables not only adaptation of modulation, coding rate, coding gain, and radiated power as conventional adaptive modulation (AM) scheme, but also joint adjustment of radio component characteristics (e.g., power amplifier (PA) characteristics) to achieve high energy efficiency. A unified PA efficiency model characterizing theoretical Class A, Class B, and practical PAs is adopted and enables the analysis of the impact of different radio configurations and channel conditions on energy efficiency. Significant energy savings (up to 90%) using the proposed CR framework for systems with theoretical PAs and with a realistic PA can be achieved compared with the conventional AM approach in simulation. This framework can also be used to manage other radio resources.

Channel frame error rate for Bluetooth in the presence of microwave ovens

In this paper, radiation from microwave ovens is measured using PRISM, a custom-built device designed to measure transmissions in the ISM band. The measured signals, treated as a rising noise floor, are then applied to a semi-analytic simulation to determine the probability of frame error rate (FER) per channel for six Bluetooth packet types.

Soft radio implementations for 3G and future high data rate systems

Recent advances in reconfigurable computing have now made it possible to implement the concept of hardware paging which has the potential to greatly advance the design of soft radios. While many soft/software radio architectures have been suggested and implemented, there remains a lack of a formal design methodology that can be used to design and implement these radios on reconfigurable platforms that exploit the latest inventions. A unified architecture, called the layered radio architecture, for design of soft radios on a reconfigurable platform was presented previously by the authors (see IEEE Communications Magazine vol.38, no.2, p.140-7, February 2000). The layered architecture makes it possible to incorporate all of the features of a software radio while keeping complexity issues at a minimal level. The layered architecture also defines the methodology for incorporating changes and updates into the system. In this paper, we implement a RAKE receiver and channel estimation for W-CDMA downlink to show how the architecture combined with the use of the Custom Computing Machine Stallion, can handle 3G and future high data rate systems.

Design and implementation of a completely reconfigurable soft radio

The advances in reconfigurable computing have now made it possible to implement the concept of hardware paging, which has the potential to greatly advance the design of soft radios. While many soft/software radio architectures have been suggested and implemented there remains a lack of a formal design methodology that can be used to design and implement these radios on reconfigurable platforms that exploit the latest inventions. This paper presents a unified architecture, called the layered radio architecture, for design of soft radios on a reconfigurable platform. Using the assumptions of the availability of run-time reconfigurable hardware and the use of stream-based computing, the layered radio architecture defines a soft radio architecture that is scalable in hardware and software, flexible, and capable of supporting multi-mode radios along with over-the-air updates and software validation.