Large Array Eigen-based signal combining for deep-space applications
Explore the source record for details and available documents.
relay network planning and scheduling constrained ↗
Engineering topics
Cheung, K. M.
Publications and source records attributed to Cheung, K. M..
Recent results in Mars Relay Network planning and scheduing
At different time periods in the future, Mars missions will overlap and previous studies indicate that during such periods existing deep space communication infrastructure will not be able to handle all Mars communication needs. A plausible solution is to perform optimal resource allocation for the Mars relay communication network; a network consisting of multiple surface units and orbiters on Mars and the Deep Space Stations. Unlike direct-to-earth, a relay communication, either in real-time or store-and-forward, can increase network science data return, reduce surface unit's direct-to-earth communication demands, and enable communication even when the surface unit is not facing Earth. It is the objective of this paper to take advantage of the relay operation to efficiently plan and schedule the network communications.
Relay Network planning and scheduling constrained ↗
Power, data latency, and radio frequnecy interference issues in Mars Realy Network scheduling
At different time periods in the future, missions to Mars will overlap. Previous studies indicate that during such periods, existing deep space communication infrastructure cannot handle all Mars communication needs. A plausible solution is to take into account the end-to-end communication performances of network along with operational constraints, and optimize the resource usage by scheduling communication at highest possible data throughputs. As a result, shorter communication time is required and more missions can be accommodated. This principle is demonstrated in this paper for a Mars relay communication network; a network consisting of multiple surface units and orbiters on Mars and the Deep Space Stations.
power latency RFI Mars Relay Network scheduling↗
Fast Eigen-based signal combining algorithms for large antenna arrays
A Large array of small antennas can be used to enhance signals with very low signal-to-noise ratio and can also be used to replace large apertures. In this paper, a fast combining algorithm is proposed and analyzed to maximize the combined output signal-to-noise ratio.
Eigen signal combining array↗
High-fidelity telecom analysis techniques for spacecraft dynamic events
In this paper, we describe a systematic approach to support telecom planning and analysis for spacecraft dynamic events.
telecom analysis dynamics↗
High-fidelity telecom analysis techniques for spacecraft dynamic events
Explore the source record for details and available documents.
telecom analysis dynamics↗
Deep Space 1 telecom link analysis: enabler of spacecraft mission recovery and ground station performance maintenance
Explore the source record for details and available documents.
Deep Space 1 telecom link telecommunication DS1↗
Design and architecture of the Mars relay network planning and analysis framework
In this paper we describe the design and architecture of the Mars Network planning and analysis framework that supports generation and validation of efficient planning and scheduling strategy. The goals are to minimize the transmitting time, minimize the delaying time, and/or maximize the network throughputs. The proposed framework would require (1) a client-server architecture to support interactive, batch, WEB, and distributed analysis and planning applications for the relay network analysis scheme, (2) a high-fidelity modeling and simulation environment that expresses link capabilities between spacecraft to spacecraft and spacecraft to Earth stations as time-varying resources, and spacecraft activities, link priority, Solar System dynamic events, the laws of orbital mechanics, and other limiting factors as spacecraft power and thermal constraints, (3) an optimization methodology that casts the resource and constraint models into a standard linear and nonlinear constrained optimization problem that lends itself to commercial off-the-shelf (COTS)planning and scheduling algorithms.
Mars relay network planning analysis↗
Channel capacity of an array system for Gaussian channels with applications to combining and noise cancellation
A closed-form expression for the capacity of an array of correlated Gaussian channels is derived. It is shown that when signal and noise are independent, the array of observables can be replaced with a single observable without diminishing the capacity of the array channel. Examples are provided to illustrate the dependence of channel capacity on noise correlation for two- and three-channel arrays.
Cheung, K. M.↗
Locally adaptive vector quantization: Data compression with feature preservation
A study of a locally adaptive vector quantization (LAVQ) algorithm for data compression is presented. This algorithm provides high-speed one-pass compression and is fully adaptable to any data source and does not require a priori knowledge of the source statistics. Therefore, LAVQ is a universal data compression algorithm. The basic algorithm and several modifications to improve performance are discussed. These modifications are nonlinear quantization, coarse quantization of the codebook, and lossless compression of the output. Performance of LAVQ on various images using irreversible (lossy) coding is comparable to that of the Linde-Buzo-Gray algorithm, but LAVQ has a much higher speed; thus this algorithm has potential for real-time video compression. Unlike most other image compression algorithms, LAVQ preserves fine detail in images. LAVQ's performance as a lossless data compression algorithm is comparable to that of Lempel-Ziv-based algorithms, but LAVQ uses far less memory during the coding process.
Cheung, K. M.↗
Further Results On Finite-State Codes
New codes generated and analyzed. Report discusses application of general construction for finite-state (FS) codes to known block codes. Decoding algorithms and results of simulations discussed briefly. First, general construction applied to (24,12) Golay code. Next, general construction applied to (16,8) Nordstrom-Robinson code. Results presented as plots of bit-error probability versus ratio of bit energy to noise energy.
Pollara, F.↗
Efficient multiplication algorithms over the finite fields GF(q sup m), where q equals 3,5
Finite field multiplication is central to coding theory. For this application, there is a need for a multiplication algorithm which can be realized easily on VLSI chips. A new algorithm is developed which is based on the Babylonian multiplication technique utilizing tables of squares. This algorithm is applied to the finite fields GF(q sup m), where q equals 3 and 5. It is also shown that this multiplier can be used to compute complex multiplications defined on the direct sum of two identical copies of such Galois fields.
Truong, T. K.↗