Ibrahim S. Raad

A New Spreading Matrix for Block Spread OFDM

This paper presents a new spreading matrix for block spread OFDM (BSOFDM) to improve the performance of the system by increasing the correlation between the symbols. This is achieved by rotating the modulation scheme used at the transmission, say QPSK, into a higher order modulation scheme, for example 16QAM. By this the correlation between the transmitted symbols is increased. The advantage of this new spreading matrix over more traditional spreading matrices is its flexibility in achieving different higher order modulation schemes during transmission depending on the angle alpha. This is compared to other spreading matrices in frequency selective channel environment

Implementation of a turbo codes test bed in the Simulink environment

This paper presents an implementation of turbo codes test bed developed in Matlab’s Simulink which will aid researchers in the field of turbo codes.It discusses the design, implementation and presents the validation results.

A Study of Different Angles for the New Spread Matrix for BSOFDM in UWB Channels

This paper presents a study into different angles for the new spread matrix developed for BSOFDM. It varies the angles for the matrix to develop different constellation schemes which are useful in overcoming the frequency selective channels which are encountered in mobile communication systems. Previously it has been discussed that this new matrix (the rotation matrix) has some advantages over Hadamard and the rotated Hadamard matrix in certain channels. This paper presents a study of varies angles with this new matrix over the UWB channels CM1 to CM4.

New Higher Order Rotation Spreading Matrix for BSOFDM

Previously a new matrix called the rotation spreading matrix was proposed for block spread OFDM which had advantages over other well known spreading matrices such as the Hadamard in frequency selective channels such the UWB channels. Then a new paper discussed a method to expand this Rotation spreading matrix into higher order allowing the system BSOFDM to achieve higher order matrices which still showed excellent orthogonal properties which can be used in these frequency selective channels. This work is continued on the rotation spreading matrix and this paper presents another method to expand the rotation spreading matrix based on complete complementary sets of sequences which the authors have shown to have excellent properties in higher order matrices. This paper discusses the new method and presents a comparison between the two mentioned methods.

Exploiting Time Diversity to Improve Block Spread OFDM in a Multipath Environment

This paper presents a new method to improve on block spread OFDM by exploiting time diversity to ensure that the blocks are independent and uncorrelated in a multipath environment. While BSOFDM utilizes frequency diversity to significantly improve on OFDM in frequency selective channel, this did not improve during flat fading channel which does occur during transmission. Our work has also shown that this improvement is also true in multipath transmission. By exploiting time and frequency diversity, BSOFDM is improved significantly over conventional BSOFDM and conventional OFDM

Space time spreading with modified Walsh-Hadamard sequences

Previous work has shown that the performance of a space time spreading (STS) system using Walsh codes with two transmit antennas at the base station (BS) is degraded in the presence of mutual interference from adjacent sectors in the same cell. We use modified Walsh-Hadamard sequences exhibiting improved cross-correlation performance, which potentially mitigates the effects of MAI (multiple access interference). The presented study also looks at variation of sets of different modified Walsh-Hadamard codes being used by the adjacent interferer, with a hundred randomly selected pairings being chosen, as well as the case where one set of alternate codes is used. It is shown using simulation that significant improvement of the order of 0.5-2 dB is possible using these sequences instead of the standard Walsh code previously proposed.

A new approach to BSOFDM - parallel concatenated spreading matrices OFDM

This paper proposes a new approach to block spread OFDM called parallel concatenated spreading matrices OFDM (PCSM-OFDM). While BSOFDM improved the overall BER performance on OFDM in frequency selective channels, this new approach further improves the BER of BSOFDM by a 3 dB gain. This is achieved through increasing the diversity of the transmitted samples by concatenating two spreading matrices in parallel to BSOFDM.

A Study of Different Angles for Higher Order Rotation Spreading Matrix for BSOFDM in UWB Channels

This paper presents a study into different angles for higher order rotation spreading matrix developed for BSOFDM. It was shown previously that for block size M = 2 that the angle a = pi/3 achieved the best result in terms of BER in UWB channels. It was discovered that this was no longer the case when the higher order rotation spreading matrix was used for larger M sized blocks and that other angles produced better results which proves that the rotation spreading matrix advantage over existing spreading matrices such as the Hadamard is its flexibility to be adapted to different communication systems.

Analytical Study of the Rotation Spreading Matrix of Block Spread OFDM with MMSE Equalization

This paper presents an analytical study on the new spreading matrix for block spread OFDM known as the rotation spreading matrix and simulates the BER performance in the MMSE equation. In (I. Raad et al., 2006) a new spreading matrix was presented for block spread OFDM (BSOFDM) known as the rotation spreading matrix. It was shown to greatly improve on the existing spreading matrices such as the Hadamard and the rotated Hadamard matrices in frequency selective channels such as the ultra wide band and slow fading channels. This paper studies the effect of increasing the block size in BSOFDM using this new matrix.

Soccer RoBot Toy within an Educational Enviro

Many autonomous robotic systems exist which are operated using battery powered subsystems. These systems typically suffer from short battery life, due in some part to the weight of the battery required to power them and the need for regular battery changes or recharges. This makes continuous operation difficult, which is desired for an embedded Internet system. A novel solution proposed here is to use a power cage in lieu of a battery, and limit the area the robot can traverse to the dimension of the cage. A prototype of such a system has been designed and successfully tested. The goal of this prototype system is to play a primitive form of Soccer using two SoccerBots under a remote interface controlled by two humans, a ping pong ball and a suitable sized power cage. Preliminary testing indicates that the system is feasible and relatively inexpensive.