Performance of Serial, Matched-Filter Packet Acquisition Algorithms with a Preamble-Sequence Acceptance Criterion

In this thesis, we consider two methods to improve the acquisition performance of a packet radio system that uses serial, matched-filter acquisition: an adaptive acquisition threshold, and an acceptance criterion for the system\u27s preamble sequences. Each packet transmission includes a fixed-length acquisition preamble, and the preamble sequence used in packet transmissions is changed at predetermined times based on a sequence-generation algorithm. It is shown that acquisition performance depends largely on the sidelobe energy of the preamble sequence, the acquisition threshold, and the signal-to-noise ratio. The first method uses a threshold-scaling technique to account for the variation in the signal-to-noise ratio. The second method employs preamble sequence-selection based on the preamble\u27s sidelobe energy to reject sequences which are predicted to yield poor acquisition performance. The two techniques are considered individually and in combination, and the range of system parameters for which each is beneficial is investigated. Performance is examined for an additive white Gaussian noise channel and a signal-to-noise ratio that is unknown a priori at the receiver

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Adaptive multilevel quadrature amplitude radio implementation in programmable logic

Emerging broadband wireless packet data networks are increasingly employing spectrally efficient modulation methods like Quadrature Amplitude Modulation (QAM) to increase the channel efficiency and maximize data throughput. Unfortunately, the performance of high level QAM modulations in the wireless channel is sensitive to channel imperfections and throughput is degraded significantly at low signal-to-noise ratios due to bit errors and packet retransmission. To obtain a more “robust” physical layer, broadband systems are employing multilevel QAM (M-QAM) to mitigate this reduction in throughput by adapting the QAM modulation level to maintain acceptable packet error rate (PER) performance in changing channel conditions. This thesis presents an adaptive M-QAM modem hardware architecture, suitable for use as a modem core for programmable software defined radios (SDRs) and broadband wireless applications. The modem operates in “burst” mode, and can reliably synchronize to different QAM constellations “burst-by-burst”. Two main improvements exploit commonality in the M-QAM constellations to minimize the redundant hardware required. First, the burst synchronization functions (carrier, clock, amplitude, and modulation level) operate reliably without prior knowledge of the QAM modulation level used in the burst. Second, a unique bit stuffing and shifting technique is employed which supports variable bit rate operation, while reducing the core signal processing functions to common hardware for all constellations. These features make this architecture especially attractive for implementation with Field Programmable Gate Arrays (FPGAs) and Application-Specific Integrated Circuits (ASICs); both of which are becoming popular for highly integrated, cost-effective wireless transceivers

Canadian Hydrogen Intensity Mapping Experiment (CHIME) Pathfinder

A pathfinder version of CHIME (the Canadian Hydrogen Intensity Mapping Experiment) is currently being commissioned at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC. The instrument is a hybrid cylindrical interferometer designed to measure the large scale neutral hydrogen power spectrum across the redshift range 0.8 to 2.5. The power spectrum will be used to measure the baryon acoustic oscillation (BAO) scale across this poorly probed redshift range where dark energy becomes a significant contributor to the evolution of the Universe. The instrument revives the cylinder design in radio astronomy with a wide field survey as a primary goal. Modern low-noise amplifiers and digital processing remove the necessity for the analog beamforming that characterized previous designs. The Pathfinder consists of two cylinders 37\,m long by 20\,m wide oriented north-south for a total collecting area of 1,500 square meters. The cylinders are stationary with no moving parts, and form a transit instrument with an instantaneous field of view of $\sim$100\,degrees by 1-2\,degrees. Each CHIME Pathfinder cylinder has a feedline with 64 dual polarization feeds placed every $\sim$30\,cm which Nyquist sample the north-south sky over much of the frequency band. The signals from each dual-polarization feed are independently amplified, filtered to 400-800\,MHz, and directly sampled at 800\,MSps using 8 bits. The correlator is an FX design, where the Fourier transform channelization is performed in FPGAs, which are interfaced to a set of GPUs that compute the correlation matrix. The CHIME Pathfinder is a 1/10th scale prototype version of CHIME and is designed to detect the BAO feature and constrain the distance-redshift relation.Comment: 20 pages, 12 figures. submitted to Proc. SPIE, Astronomical Telescopes + Instrumentation (2014

Estudio y diseño de dos placas de intercambio de datos de inclinación y posición entre dos cubesats

El grupo de investigación DISEN con sede en el Campus de Terrassa de la UPC está intentando impulsar el proyecto de la implementación de una infraestructura de comunicaciones basada en el enlace óptico de CubeSats. Mediante este tipo de comunicación, se podría obtener un mayor data-rate y un menor consumo de potencia que en los actuales sistemas de radiofrecuencia. Para poder realizar este enlace óptico, es necesario que el rayo láser proveniente de uno de los satélites se centre de forma muy precisa en el foto-detector del otro satélite. Para realizar dicho centrado, ambos satélites deberán conocer a priori la posición e inclinación de ambos, información que deberán intercambiarse mediante radiofrecuencia. El presente TFG versa sobre el diseño del subsistema de intercambio de datos de posición e inclinación entre dos CubeSats. Concretamente, el diseño de dos placas PCB formadas por un módulo GPS, para obtener la posición de los CubeSats; un módulo IMU, para obtener sus actitudes; un módulo de radio UHF, para enviar datos entre los dos CubeSats por radiofrecuencia; y un módulo Bluetooth para poder enlazar el sistema con el ordenador de base. Además, las placas cuentan con un microcontrolador para procesar y almacenar la información de dichos módulos

THE APPLICATION OF REAL-TIME SOFTWARE IN THE IMPLEMENTATION OF LOW-COST SATELLITE RETURN LINKS

Digital Signal Processors (DSPs) have evolved to a level where it is feasible for digital modems with relatively low data rates to be implemented entirely with software algorithms. With current technology it is still necessary for analogue processing between the RF input and a low frequency IF but, as DSP technology advances, it will become possible to shift the interface between analogue and digital domains ever closer towards the RF input. The software radio concept is a long-term goal which aims to realise software-based digital modems which are completely flexible in terms of operating frequency, bandwidth, modulation format and source coding. The ideal software radio cannot be realised until DSP, Analogue to Digital (A/D) and Digital to Analogue (D/A) technology has advanced sufficiently. Until these advances have been made, it is often necessary to sacrifice optimum performance in order to achieve real-time operation. This Thesis investigates practical real-time algorithms for carrier frequency synchronisation, symbol timing synchronisation, modulation, demodulation and FEC. Included in this work are novel software-based transceivers for continuous-mode transmission, burst-mode transmission, frequency modulation, phase modulation and orthogonal frequency division multiplexing (OFDM). Ideal applications for this work combine the requirement for flexible baseband signal processing and a relatively low data rate. Suitable applications for this work were identified in low-cost satellite return links, and specifically in asymmetric satellite Internet delivery systems. These systems employ a high-speed (>>2Mbps) DVB channel from service provider to customer and a low-cost, low-speed (32-128 kbps) return channel. This Thesis also discusses asymmetric satellite Internet delivery systems, practical considerations for their implementation and the techniques that are required to map TCP/IP traffic to low-cost satellite return links

Automatic Circuit Recloser (ACR) communications using P25 RMU (Radio Modem Unit)

The current Ergon Energy telecommunications in the field for remote smart grid operations to its Automatic Circuit Reclosers (ACRs) uses public carriers such as Telstra mobile data services and Immarsat BGN network (Satellite). The operational cost of using Immarsat BGN network is very costly ($8 per Megabyte) so there is financial incentive to investigate the use of the P25 Radio Modem Unit (RMU) to provide communications to ACR using existing the Ergon Energy P25 Radio Network. This project aims to assess the capabilities of the P25 devices in the context of Ergon Energy’s operational requirements through both research and practical experimentation. The results will be used to identify and quantify (where possible) potential issues and make recommendations about any implementation. The main aim is to use P25 RMUs over the Ergon Energy P25 Radio Network for communications to ACRs by benchmarking against the existing NextG modems in use. Communications must be implemented for two serial ports on the ACR, one for SCADA and the other for engineering configuration access. The data and packet formats of the P25 communications protocol for both the SCADA DNP3 and engineering access connections have been documented. The operational requirements of the ACR SCADA and Remote Engineering connections have been identified. Following this a testbed was established and used to evaluate performance across a range of parameters. These were compared to the identified requirements. The P25 RMU testbed assessed performance against the benchmarks established for the existing NextG modem application used on ACR. The P25 RMU worked with limitations which are to be outlined in the report on findings and hence recommendations to further improve the performance