8,297 research outputs found
Second year technical report on-board processing for future satellite communications systems
Advanced baseband and microwave switching techniques for large domestic communications satellites operating in the 30/20 GHz frequency bands are discussed. The nominal baseband processor throughput is one million packets per second (1.6 Gb/s) from one thousand T1 carrier rate customer premises terminals. A frequency reuse factor of sixteen is assumed by using 16 spot antenna beams with the same 100 MHz bandwidth per beam and a modulation with a one b/s per Hz bandwidth efficiency. Eight of the beams are fixed on major metropolitan areas and eight are scanning beams which periodically cover the remainder of the U.S. under dynamic control. User signals are regenerated (demodulated/remodulated) and message packages are reformatted on board. Frequency division multiple access and time division multiplex are employed on the uplinks and downlinks, respectively, for terminals within the coverage area and dwell interval of a scanning beam. Link establishment and packet routing protocols are defined. Also described is a detailed design of a separate 100 x 100 microwave switch capable of handling nonregenerated signals occupying the remaining 2.4 GHz bandwidth with 60 dB of isolation, at an estimated weight and power consumption of approximately 400 kg and 100 W, respectively
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
100\,degrees by 1-2\,degrees. Each CHIME Pathfinder cylinder has a
feedline with 64 dual polarization feeds placed every 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
Proteus II: design and evaluation of an integrated power-efficient underwater sensor node
We describe the design and evaluation of an integrated low-cost underwater sensor node designed for reconfigurability, allowing continuous operation on a relatively small rechargeable battery for one month. The node uses a host CPU for the network protocols and processing sensor data and a separate CPU performs signal processing for the ultrasonic acoustic software-defined Modulator/Demodulator (MODEM). A Frequency Shift Keying- (FSK-) based modulation scheme with configurable symbol rates, Hamming error correction, and Time-of-Arrival (ToA) estimation for underwater positioning is implemented. The onboard sensors, an accelerometer and a temperature sensor, can be used to measure basic environmental parameters; additional internal and external sensors are supported through industry-standard interfaces (I2C, SPI, and RS232) and an Analog to Digital Converter (ADC) for analog peripherals. A 433 MHz radio can be used when the node is deployed at the surface. Tests were performed to validate the low-power operation. Moreover the acoustic communication range and performance and ToA capabilities were evaluated. Results show that the node achieves the one-month lifetime, is able to perform communication in highly reflective environments, and performs ToA estimation with an accuracy of about 1-2 meters
xLED: Covert Data Exfiltration from Air-Gapped Networks via Router LEDs
In this paper we show how attackers can covertly leak data (e.g., encryption
keys, passwords and files) from highly secure or air-gapped networks via the
row of status LEDs that exists in networking equipment such as LAN switches and
routers. Although it is known that some network equipment emanates optical
signals correlated with the information being processed by the device
('side-channel'), intentionally controlling the status LEDs to carry any type
of data ('covert-channel') has never studied before. A malicious code is
executed on the LAN switch or router, allowing full control of the status LEDs.
Sensitive data can be encoded and modulated over the blinking of the LEDs. The
generated signals can then be recorded by various types of remote cameras and
optical sensors. We provide the technical background on the internal
architecture of switches and routers (at both the hardware and software level)
which enables this type of attack. We also present amplitude and frequency
based modulation and encoding schemas, along with a simple transmission
protocol. We implement a prototype of an exfiltration malware and discuss its
design and implementation. We evaluate this method with a few routers and
different types of LEDs. In addition, we tested various receivers including
remote cameras, security cameras, smartphone cameras, and optical sensors, and
also discuss different detection and prevention countermeasures. Our experiment
shows that sensitive data can be covertly leaked via the status LEDs of
switches and routers at a bit rates of 10 bit/sec to more than 1Kbit/sec per
LED
- …