The Effect of Macrodiversity on the Performance of Maximal Ratio Combining in Flat Rayleigh Fading

The performance of maximal ratio combining (MRC) in Rayleigh channels with co-channel interference (CCI) is well-known for receive arrays which are co-located. Recent work in network MIMO, edge-excited cells and base station collaboration is increasing interest in macrodiversity systems. Hence, in this paper we consider the effect of macrodiversity on MRC performance in Rayleigh fading channels with CCI. We consider the uncoded symbol error rate (SER) as our performance measure of interest and investigate how different macrodiversity power profiles affect SER performance. This is the first analytical work in this area. We derive approximate and exact symbol error rate results for M-QAM/BPSK modulations and use the analysis to provide a simple power metric. Numerical results, verified by simulations, are used in conjunction with the analysis to gain insight into the effects of the link powers on performance.Comment: 10 pages, 5 figures; IEEE Transaction of Communication, 2012 Corrected typo

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals

Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility

MIMO Evolution Beyond 5G Through Reconfigurable Intelligent Surfaces and Fluid Antenna Systems

With massive deployment, multiple-input-multiple-output (MIMO) systems continue to take mobile communications to new heights, but the ever-increasing demands mean that there is a need to look beyond MIMO and pursue the next disruptive wireless technologies. Reconfigurable intelligent surface (RIS) is widely considered a key candidate technology block to provide the next generational leap. The first part of this article provides an updated overview of the conventional reflection-based RIS technology, which complements the existing literature to include active and semiactive RIS, and the synergies with cell-free massive MIMO (CF mMIMO). Then, we widen the scope to discuss the surface-wave-assisted RIS that represents a different design dimension in utilizing metasurface technologies. This goes beyond being a passive reflector and can use the surface as an intelligent propagation medium for superb radio propagation efficiency. The third part of this article turns the attention to the fluid antenna, a novel antenna technology that enables a diverse form of reconfigurability that can combine with RIS for ultrahigh capacity, power efficiency, and scalability. This article concludes with a discussion of the potential synergies that can be exploited between MIMO, RIS, and fluid antennas

The Telecommunications and Data Acquisition Report

This quarterly publication provides archival reports on developments in programs managed by JPL's Telecommunications and Mission Operations Directorate (TMOD), which now includes the former Telecommunications and Data Acquisition (TDA) Office. In space communications, radio navigation, radio science, and ground-based radio and radar astronomy, it reports on activities of the Deep Space Network (DSN) in planning, supporting research and technology, implementation, and operations. Also included are standards activity at JPL for space data and information systems and reimbursable DSN work performed for other space agencies through NASA. The preceding work is all performed for NASA's Office of Space Communications (OSC)

Radar Technology

In this book “Radar Technology”, the chapters are divided into four main topic areas: Topic area 1: “Radar Systems” consists of chapters which treat whole radar systems, environment and target functional chain. Topic area 2: “Radar Applications” shows various applications of radar systems, including meteorological radars, ground penetrating radars and glaciology. Topic area 3: “Radar Functional Chain and Signal Processing” describes several aspects of the radar signal processing. From parameter extraction, target detection over tracking and classification technologies. Topic area 4: “Radar Subsystems and Components” consists of design technology of radar subsystem components like antenna design or waveform design

Secure short-range communications

Analysts predict billions of everyday objects will soon become ``smart’\u27 after designers add wireless communication capabilities. Collectively known as the Internet of Things (IoT), these newly communication-enabled devices are envisioned to collect and share data among themselves, with new devices entering and exiting a particular environment frequently. People and the devices they wear or carry may soon encounter dozens, possibly hundreds, of devices each day. Many of these devices will be encountered for the first time. Additionally, some of the information the devices share may have privacy or security implications. Furthermore, many of these devices will have limited or non-existent user interfaces, making manual configuration cumbersome. This situation suggests that devices that have never met, nor shared a secret, but that are in the same physical area, must have a way to securely communicate that requires minimal manual intervention. In this dissertation we present novel approaches to solve these short-range communication issues. Our techniques are simple to use, secure, and consistent with user intent. We first present a technique called Wanda that uses radio strength as a communication channel to securely impart information onto nearby devices. We focus on using Wanda to introduce new devices into an environment, but Wanda could be used to impart any type of information onto wireless devices, regardless of device type or manufacturer. Next we describe SNAP, a method for a single-antenna wireless device to determine when it is in close physical proximity to another wireless device. Because radio waves are invisible, a user may believe transmissions are coming from a nearby device when in fact the transmissions are coming from a distant adversary attempting to trick the user into accepting a malicious payload. Our approach significantly raises the bar for an adversary attempting such a trick. Finally, we present a solution called JamFi that exploits MIMO antennas and the Inverse-Square Law to securely transfer data between nearby devices while denying more distant adversaries the ability to recover the data. We find JamFi is able to facilitate reliable and secure communication between two devices in close physical proximity, even though they have never met nor shared a key

A Novel Approach to Design an Integrated Antenna-Battery System

In this study, an integrated antenna-battery was explored. Studying the systems separately allowed information to be obtained relating to the materials' performance and feasibility of an integrated system. Conducting polymers are promising in modern day lithium ion batteries. With high electrical conductivity as well as good ionic conductivity, they are now becoming more widely used. Here, we present a study of a co-block polymer (PEDOT-PEG) in which a polymer with high electrical conductivity is linked to a polymer with lithium ion conductivity, using a combination of atomistic simulations and experiments. Simulations showed that the diffusion and ionic conductivity for PEDOT-PEG agreed well with experiments. A trend was identified as a function of lithium salt concentration, in which the ionic conductivity decreased with increasing concentration. This was identified to be down to the significant ion pairing occurring in the system between lithium and the counterion. Requirements for the antenna were the ability to be mounted easily onto a battery substrate without a significant loss in efficiency and bandwidth. Studies were undertaken in which a slot dipole antenna was modified so as to incorporate properties more closely associated with battery materials i.e. permittivity and dielectric loss. An ultra-thin Mylar prototype was also synthesised and mounted onto a variety of surfaces, to assess how the antenna performed in different environments. Results for the antenna showed usable bandwidths and efficiencies when the antenna structure was modified to closely resemble a solid state battery. Despite a reduction seen in certain cases, these losses were not significant, and showed promise with regards to designing an integrated system. The Mylar prototype showed a good match between simulation and experiment in free space and when mounted on surfaces such as polymers, indicating that an ultra-thin antenna-battery is feasible