arXiv subjects

Philip Lundrigan

Publications and source records attributed to Philip Lundrigan.

5 recordsLinked to original sources

arXiv2026

Frequency Lock Encoding

Modern wireless systems are designed with excess synchronization bandwidth to ensure reliable operation under worst-case conditions. This paper presents a protocol-agnostic secondary signaling layer that exploits this unused synchronization margin by intentionally introducing small, controlled frequency offsets into an existing communication signal to embed a parallel stream of information. These offsets are naturally absorbed by the primary receiver's carrier frequency offset (CFO) correction mechanisms, allowing the primary data stream to remain intact while enabling simultaneous secondary communication. The proposed signaling method employs a frequency-shift-keyed overlay engineered to remain within the stable operating region of conventional carrier-synchronization loops, ensuring backward compatibility and transparency for legacy receivers. We analyze the system for single-carrier protocols, characterize the trade-offs between secondary throughput and the impact on the primary link, and validate performance through both simulation and over-the-air experiments using software-defined radios. Results demonstrate reliable secondary communication with negligible degradation to primary performance, making our system well-suited for ad hoc spectrum sharing and decentralized coordination at the tactical edge.

cs.NI↗

arXiv2024

An Information Theoretic Analysis of Ghost Modulation

Side channels have become an essential component of many modern information-theoretic schemes. The emerging field of cross technology communications (CTC) provides practical methods for creating intentional side channels between existing communications technologies. This paper describes a theoretical foundation for one such, recently proposed, CTC scheme: Ghost Modulation (GM). Designed to modulate a low-data-rate message atop an existing network stream, GM is particularly suited for transmitting identification or covert information. The implementation only requires firmware updates to existing hardware, making it a cost-effective solution. However, GM provides an interesting technical challenge due to a highly asymmetric binary crossover erasure channel (BCEC) that results from packet drops and network delays. In this work, we provide a mathematical description of the signal and channel models for GM. A heuristic decision rule based on maximum-likelihood principles for simplified channel models is proposed. We describe an algorithm for GM packet acquisition and timing synchronization, supported by simulation results. Several well known short block codes are applied, and bit error rate (BER) results are presented.

cs.IT↗

arXiv2024

Utilizing Low-Cost Sensors to Monitor Indoor Air Quality in Mongolian Gers

Air quality has important climate and health effects. There is a need, therefore, to monitor air quality both indoors and outdoors. Methods of measuring air quality should be cost-effective if they are to be used widely, and one such method is low-cost sensors (LCS). This study reports on the use of LCSs in Ulaanbaatar, Mongolia, to measure $\mathrm{PM_{2.5}}$ concentrations inside yurts or "gers." Some of these gers were part of a non-government agency (NGO) initiative to improve the insulating properties of these housing structures. The goal of the NGO was to decrease particulate emissions inside the gers; a secondary result was to lower the use of coal and other biomass material. LCSs were installed in gers heated primarily by coal, and interior air quality was measured. Gers that were modified by increasing their insulating capacities showed a 17.5% reduction in $\mathrm{PM_{2.5}}$ concentrations, but these concentrations remained higher than levels recommended by health organizations. Gers that were insulated and used a combination of both coal and electricity showed a 19.1% reduction in $\mathrm{PM_{2.5}}$ concentrations. Insulated gers that used electricity for both heating and cooking showed a 48% reduction in $\mathrm{PM_{2.5}}$, though concentrations were still 6.4 times higher than those recommended by the World Health Organization (WHO). Nighttime and daytime trends followed similar patterns in $\mathrm{PM_{2.5}}$ concentrations with slight variations. It was found that, at nighttime, the outside $\mathrm{PM_{2.5}}$ concentrations were generally higher than the inside concentrations of the gers in this study. This suggests that $\mathrm{PM_{2.5}}$ would flow into the gers whenever the doors were opened, causing spikes in $\mathrm{PM_{2.5}}$ concentrations.

physics.ao-ph↗

arXiv2023

A Versatile Wireless Network Protocol for Spectrum Sharing with Passive Radio Services

With the proliferation of wideband active services in bands shared with passive receivers for remote sensing and radio astronomy, new methods are needed for deconflicting active and passive users. We have developed a technique for active/passive user coordination that is compatible with essentially any existing wireless communications protocol. The passive user transmits an on-off keying modulated signal that can be detected by active radios using simple channel power estimates. Using off-the-shelf WiFi and LoRa hardware and on a software defined radio implementation of LTE, we show that Dynamic Passive to Active Spectrum Sharing (DPASS) is effective on a wide range of frequencies and physical layer implementations. We validate the protocol using these three technologies by demonstrating that each device receives a DPASS packet and dynamically takes an appropriate spectrum coordination action, including shutting off transmissions or switching frequencies.

cs.NI↗

arXiv2017

EpiFi: An In-Home Sensor Network Architecture for Epidemiological Studies

We design and build a system called EpiFi, which allows epidemiologists to easily design and deploy experiments in homes. The focus of EpiFi is reducing the barrier to entry for deploying and using an in-home sensor network. We present a novel architecture for in-home sensor networks configured using a single configuration file and provide: a fast and reliable method for device discovery when installed in the home, a new mechanism for sensors to authenticate over the air using a subject's home WiFi router, and data reliability mechanisms to minimize loss in the network through a long-term deployment. We work collaboratively with pediatric asthma researchers to design three studies and deploy EpiFi in homes.

cs.NI↗