Ali Al-Shaikhi

Erasure rate analysis and tighter upper bound for binary product codes

Product codes are powerful codes that can be used to correct errors and/or recover erasures. Judging the erasure recovery performance of a product code based on its minimum distance is pessimistic because the code is actually capable of recovering many erasure patterns beyond those with the number of erasures determined by the minimum distance. By analyzing the non-recoverable erasure patterns, this letter develops a tighter upper bound on the post-decoding erasure rate for any binary product code. The analytical derivations are verified through computer simulations using Hamming and single parity check (SPC) product codes.

Design of packet-based block codes with shift operators

This paper introduces packet-oriented block codes for the recovery of lost packets and the correction of an erroneous single packet. Specifically, a family of systematic codes is proposed, based on a Vandermonde matrix applied to a group of information packets to construct redundant packets, where the elements of the Vandermonde matrix are bit-level right arithmetic shift operators. The code design is applicable to packets of any size, provided that the packets within a block of information packets are of uniform length. In order to decrease the overhead associated with packet padding using shift operators, non-Vandermonde matrices are also proposed for designing packet-oriented block codes. An efficient matrix inversion procedure for the off-line design of the decoding algorithm is presented to recover lost packets. The error correction capability of the design is investigated as well. The decoding algorithm, based on syndrome decoding, to correct a single erroneous packet in a group of received packets is presented. The paper is equipped with examples of codes using different parameters. The code designs and their performance are tested using Monte Carlo simulations; the results obtained exhibit good agreement with the corresponding theoretical results.

Time-sensitive, sensor-based, joint planning and control of mobile robots in cluttered spaces: A harmonic potential approach

This paper suggests an integrated navigation control system for time critical missions. The navigation control is derived from a harmonic potential field. It is designed to enable a mobile agent to proceed to a target point in an unknown environment without the need for a dedicated exploration and map-building stage. The agent, en route to the target, collects and processes only the necessary and sufficient sensory data needed to successfully execute the mission. Sensing, processing and all related activities needed to generate mobility are carried-out in real-time at the servo-level. The structure of the navigation control is described in details. Experimental results are provided as a proof of principle.

Seeding undergraduate research experience: From Georgia Tech to KFUPM case study

In this paper, implementation and outcomes of an undergraduate research course are presented. The associated gains and learning outcomes of the course are evaluated and benchmarked with other international undergraduate research experiences. The course was offered to undergraduate students at King Fahd University of Petroleum and Minerals (KFUPM). The research group structure adopts Georgia Tech model. The paper summarizes the course structure, content, and best practices. In addition, the results of undergraduate research experience survey are presented and analyzed. The students reported significant gains in understanding of the research process and significant improvements in writing and oral presentation skills.

Efficient, Single Hop Time Synchronization Protocol for Randomly Connected WSNs

This letter develops a single-hop fast accurate and energy-efficient time synchronization protocol for wireless sensor networks. The protocol is designed to operate in harsh environments and is based on a resistive electrical network metaphor. It treats the nodes’ times as the states of a discrete decentralized unconditionally stable dynamical system. The synchronizer monitors the evolution of these states during the transient phase to determine the instant at which the time encoded by a state is close to the master node time. The procedure can yield high quality time estimates with accuracies that are fractions of the communication cycle. The synchronization method is developed and its capabilities are demonstrated by simulation and physical experiments on the MICA-Z wireless sensor network.

Joint order identification and estimation of the discrete relaxation spectrum for ground penetrating radars

This paper suggests a novel procedure to jointly identify the order of a GPR discrete relaxation spectrum and estimate its parameters (relaxation frequencies and their strengths). These quantities are important for interpreting the contents of the subsurface layers. The suggested method turns the estimator into a nonlinear control system that can convert an initial guess of the number and parameters of the relaxation modes into the correct one. Blindly identifying the number of relaxation modes and estimating their values and strengths is guaranteed if the number of assumed modes is higher than the number of actual modes. The procedure is hardware-friendly and exhibit high resistance to noise.

Servo-level, sensor-based navigation using harmonic potential fields

This paper suggests an integrated navigation control system for time critical missions. The navigation control is derived from a harmonic potential field. It is designed to enable a mobile agent to proceed to a target point in an unknown environment without the need for a dedicated exploration and map-building stage. The agent, en route to the target, collects and processes only the necessary and sufficient sensory data needed to successfully execute the mission. Sensing, processing and all related activities needed to generate mobility are carried-out in real-time at the servo-level. The structure of the navigation control is described in details. Experimental results are provided as a proof of principle.

Self-contained, ultrasonic sensor-based mobility generation for differential drive UGVs

This paper suggests a self-contained, mobility system for velocity controlled, differential drive robots in unknown cluttered environments. The system tackles the use of ultrasonic sensing at the servo-level to generate motion. It can, in real-time, convert the raw measurements from the onboard ultrasonic sensors to a control signal that safely propels the robot to its target. The structure uses a safety-based, subjective representation of the environment to synthesize the control signal. This significantly relaxes the burden of having to accurately localize the components of the environment. Moreover, the structure can decouple the computational burden from the size of the environment representation, hence enabling real-time servo-level navigation. The structure is implemented and thoroughly tested on the X80 mobile robot platform using only one out of the six ultrasonic sensors the robot has (the front sensor). The test consistently demonstrated that the robot can safely reach its target, from the first attempt, along a well-behaved trajectory using well-behaved control signals.

Constellation compaction design to reduce both PAPR and average power in OFDM systems

This paper proposes a novel way to compact the constellation points in QAM modulation schemes and exploits this compaction to reduce the peak to average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. The compaction is accomplished using one dimensional product code (PC). Significant PAPR reduction is achieved by carefully mapping the points in the compact version of the constellation to their radial symmetric points and choosing for transmission signalling points which result in lower PAPRs. Specifically, the complementary cumulative distribution function (CCDF) of the modified OFDM signal shows about five dB improvement in PAPR at a clipping probability of 10−4 over the original OFDM signal. This performance is comparable to that in similar PAPR reduction schemes; however, it is achieved using simple single parity check (SPC) product code and at lower average power.