Random sensory networks: a delay in analysis

A fundamental function performed by a sensory network is the retrieval of data gathered collectively by sensor nodes. The metrics that measure the efficiency of this data collection process are time and energy. In this paper, we study via simple discrete mathematical models, the statistics of the data collection time in sensory networks. Specifically, we analyze the average minimum delay in collecting randomly located/distributed sensors data for networks of various topologies when the number of nodes becomes large. Furthermore, we analyze the impact of various parameters such as size of packet, transmission range, and channel erasure probability on the optimal time performance. Our analysis applies to directional antenna systems as well as omnidirectional ones. This paper focuses on directional antenna systems and briefly presents results on omnidirectional antenna systems. Finally, a simple comparative analysis shows the respective advantages of the two systems

Amplitude and Sign Adjustment for Peak-to-Average-Power Reduction

In this letter, we propose a method to reduce the peak-to-mean-envelope-power ratio (PMEPR) of multicarrier signals by modifying the constellation. For$M$-ary phase-shift keying constellations, we minimize the maximum of the multicarrier signal over the sign and amplitude of each subcarrier. In order to find an efficient solution to the aforementioned nonconvex optimization problem, we present a suboptimal solution by first optimizing over the signs, and then optimizing over the amplitudes given the signs. We prove that the minimization of the maximum of a continuous multicarrier signal over the amplitude of each subcarrier can be written as a convex optimization problem with linear matrix inequality constraints. We also generalize the idea to other constellations such as 16-quadrature amplitude modulation. Simulation results show that by an average power increase of 0.21 dB, and not sending information over the sign of each subcarrier, PMEPR can be decreased by 5.1 dB for a system with 128 subcarriers

Peak to average power reduction using amplitude and sign adjustment

In this paper, we propose a method to reduce the peak to mean envelope power ratio (PMEPR) of multicarrier signals by modifying the constellation. For MPSK constellations, we minimize the maximum of the multicarrier signal over the sign and amplitude of each subcarrier. In order to find an efficient solution to the aforementioned non-convex optimization problem, we present a suboptimal solution by first optimizing over the signs using the result of [1], and then optimizing over the amplitudes given the signs. We prove that the minimization of the maximum of a multicarrier signal over the amplitude of each subcarrier can be written as a convex optimization problem with linear matrix inequality constraints. We also generalize the idea to other constellations such as 16QAM. Simulation results show that by an average power increase of 0.21 db and not sending information over the sign of each subcarrier, PMEPR can be decreased by 5.1 db for a system with 128 subcarriers

ON THROUGHPUT ANALYSIS OF THE MARS IN-SITU ARQ PROTOCOL

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, CaliforniaCombating harsh and unpredictable channel environments is a part of the design of any in-situ communication system (i.e. rover to lander, rover to orbiter, etc.). Channel characteristics can range from simple additive white Gaussian noise (AWGN) channels to more bursty fading channels found in rover to orbiter links (i.e. canyon scenarios and typical orbiter passes around mountain ranges). A combination of forward error correction and automatic repeat request (ARQ) schemes are commonly used to provide a more robust communications link. ARQ enhances the communication link particularly for bursty fading channels. Go-Back-N is a commonly used ARQ scheme and is an option in the newly developed Consultative Committee for Space Data Systems (CCSDS) Proximity-1 Link protocol [7], a data link layer protocol targeted specifically for in-situ applications. Optimization of frame sizes and retransmission persistence of the ARQ scheme require a good analytical model of how the scheme performs over various channel conditions. In this paper, an analytical framework for modeling the COP-1 protocol is presented for both AWGN channels along with bursty fading channels. A Gilbert-Elliot two-state Markov model is used to model a bursty fading channel.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection