Farzad Moazzami

An adaptive blind equalizer with signal separation for a MIMO system transmitting QAM signals

In this work we propose a multiple-input multiple-output (MIMO) equalization scheme which uses the CMA+AMA equalizer in a modified multi-stage approach that simultaneously recovers all signal sources. The CMA+AMA equalizer minimizes a linear combination of the constant modulus algorithm (CMA) and alphabet-matched algorithm (AMA) cost functions, and this has been shown to be an effective equalizer for recovering QAM signals in the SISO and SIMO environment. The MIMO equalizer applies individual multiple-input single-output (MISO) equalizers to the received data stream, which is modified during the update process, to simultaneously remove the recovered sources using a channel estimator. By measuring the mean square error (MSE) and symbol error rates (SER) for the recovered sources, we show the effectiveness of this new equalizer in recovering all sources transmitted by the MIMO system.

On the Performance of Equalization Techniques for Aeronautical Telemetry

This paper compares the performance of the zero forcing (ZF), minimum mean-squared error (MMSE), and MMSE-initialized CMA+AMA equalizers using SOQPSK-TG over multipath channels captured during channel sounding experiments at Edwards AFB. The ZF and MMSE equalizers are data-aided and are based on estimates of the channel conditions derived from the preamble and ASM bits included in each iNET packet. The simulated bit error rate results show that MMSE and CMA+AMA achieve similar performance and are both about 1 -- 3 dB better than the ZF equalizer. Comparison with the optimum AWGN detector shows that 4 -- 9 dB of link margin is required to account for the multipath interference.

Application of a blind channel estimator for source separation in MIMO systems

The performance of a blind channel estimator is evaluated in this work. This channel estimator approximates the channel impulse responses in Multiple-Input Multiple-Output (MIMO) communication links without any prior knowledge of either the transmitting channel or the transmitted signals. It uses the autocorrelation of signals at the receiver end.In this paper as a major application of this channel estimation scheme, it is applied to achieve blind source separation (BSS) in a multiple antenna wireless communication system. The performance of the blind channel estimation scheme is compared using an improved version of the CMA equalizer for QAM signals [5] with the training-based Minimum Mean Squared Error (MMSE) and Maximum Likelihood (ML) channel estimators. The frequency and impulse response of the estimated channels are compared to those of the actual channels, and the channel estimation errors are plotted over a range of Signal to Noise Ratio (SNR) for each of the three channel estimators.

Improving and Expanding Engineering Education in the Middle East and Africa Using Mobile Learning Technology and Innovative Pedagogy

Recent innovations in inexpensive and portable laboratory instruments have enabled new pedagogical approaches in the teaching of theoretical concepts and design practices in electrical engineering (EE). Faculty members at six universities in the USA have pioneered the use of these new tools to incorporate hands-on experimental activities into existing lecture courses. This has led to restructured EE courses with a focus on student-centered learning and not instructor-centered lectures. The goal of this effort has been to evaluate whether a more student-centered learning environment can stimulate a deeper understanding of EE principles and increase student engagement. The use of hands-on experiments started with an introductory electric circuits course and has expanded into physics, biology, and higher level EE courses. Several modes of instruction using this technology and pedagogy have been implemented at different institutions. In the blended approach, the classroom experience is a combination of lectures and hands-on activities using the mobile laboratory instruments to reinforce theoretical concepts. For the second instructional model, the inverted or flipped classroom, students are expected to read material at home, prior to their investigation of the concepts via hands-on activities in the classroom. A third model uses the portable laboratory instruments to complete hands-on activities outside of the classroom as homework problems, design projects, and/or a nontraditional laboratory component.

Energy efficient Grid Clustering Hierarchy (GCH) routing protocol for wireless sensor networks

The recent developments in high speed computing electronics and wireless communications have created an opportunity for the advancement in power efficient and low cost Wireless Sensor Networks (WSNs) with diverse areas of applications. But wireless sensor nodes are limited in power. To extend the network lifetime of the nodes in the WSN, efficient power utilization is an important variable to be optimized. In this paper, a routing protocol called Grid Clustering Hierarchy (GCH) that provides an efficient energy management for WSNs is proposed. This protocol divides the network into a variable number of virtual grids based on the current average energy of the network to create optimum clusters in terms of energy consumption. Using a standard radio energy dissipation model that is commonly used for simulation of WSNs, GCH is simulated and its performance is compared with a well-known routing protocol for WSNs named LEACH.

Use of K-means clustering for spectrum efficiency in complex networks

In this work the problem of spectrum efficiency in wireless networks over aeronautical channels is studied and a solution by combining direct communications (LOS) and cooperative networking is proposed. In aeronautical communications due to large scale communication paths and sudden changes in the channel topology, extra measures needs to be taken to accommodate reliable and continuous communication for the flying articles. High ground speed of the mobile nodes is also another factor which needs to be accounted for in the network design. The proposed network management technique is dynamic in all senses and ensures connectivity at any given time.

Multistage blind equalization in time-varying MIMO systems

In this work we evaluate the performance of multistage blind equalization scheme for time-varying MIMO systems. Equalization of the signals is achieved by minimizing a cost function, which is of a linear combination of the constant modulus algorithm (CMA) and the alphabet-matched algorithm (AMA). This has been previously shown to outperform the conventional CMA equalizer in recovery of non-constant modulus signals, such as 16-QAM. The transmitted sources in a MIMO system can be recovered in a multistage fashion using a cascade of CMA-based MISO equalizers. After equalization each captured source is cancelled by estimating its corresponding channel vector and subtracting the contribution of that captured source from the received signal. The modified received signal vector is then used as input to the equalizer at the next stage. A time-varying Gaussian channel model is used to evaluate the effect of time variation on multistage equalization and cancellation.

Energy efficient smart antenna system using Recursive Least Square algorithm and Kaiser side lobe cancellation technique

This work presents an energy efficiency (EE) investigation of a beam generated by the combination of Recursive Least Square (RLS) algorithm and Kaiser side lobe cancellation technique in smart antenna system. The RLS-Kaiser combination is investigated using energy model which is a function of beam width, range and signal to noise plus interference ratio (SNIR). The investigation carried out on linear array geometry with element spacing 0.5 λ. The EE versus range and the EE versus beam width are examined. Finally, we have shown the advantage of using RLS-Kaiser combination during beam formation. And this combination helps for achieving both spectral efficiency (SE) and energy efficiency (EE) at the same time by avoiding interference because of side lobe and by saving the energy that would be wasted as a side lobe respectively. From the result, applying the side lobe attenuation factor in increasing order: 1.3226, 2.1166, 3.3953, and 3.9754 results in decreasing the amount of sidelobe level by 25dB, 30dB, 40dB, and 45dB) respectively with the expense of small increase in beam width. Therefore, even if the main beam width increased due to the saved side lobe energy, on the other hand, the energy efficiency of the generated beam getting improved as the attenuation factor changes from smaller to larger values.

Establishing symmetric pairwise-keys using public-key cryptography in Wireless Sensor Networks (WSN)

Wireless Sensor Networks (WSN) are becoming an increasingly popular technology for data collection. Since data is of significant importance in the current era, security of the data is essentially indispensable. Because the nodes deployed are usually on an unattended environment, security of the data communicated between the wireless sensor nodes is of utmost importance. A secure established connection between two nodes in a WSN promises a number of preventive measures against different threats but the main issue is to establish the secure connection between any two nodes in a wireless sensor network. With limited resources on a wireless sensor node in mind, this research focuses on establishing Symmetric-Pairwise keys between any two WSN nodes using Public-Key Cryptography (pkc) - which in this case is Elliptic Curve Cryptography.

WiFi RSS fingerprinting indoor localization for mobile devices

While WiFi-based indoor localization is attractive, the need for a significant degree of pre-deployment effort is a key challenge. In this paper, indoor localization with no pre-deployment effort in an indoor space, such as an office building corridor, with WiFi coverage but no a priori knowledge of the placement of the access points(APs) is implemented for mobile devices. WiFi Received Signal Strength(RSS) in the considered environment is used to build radio maps using WiFi fingerprinting approach. An offline RSS fingerprint of the environment is compared with an online RSS measurement to estimate the location of a user. Two architectures are developed based on this localization algorithm. The first one involves a client-server approach where the localization algorithm runs on the server whereas the second one is a standalone architecture and the algorithm runs on the SD card of the mobile device. Experimental results in the considered environment validate the approach for both architectures.