Mostafa Sayed

Narrowband-PLC/wireless diversity for smart grid communications

Narrowband power line communications (NB-PLC) and unlicensed wireless communications are considered as the two leading two-way communications technologies for the emerging Smart Grid applications. In this paper, we propose exploiting the diversity provided by combining the received signals from the NB-PLC and wireless links, where both carry the same information, to provide robustness against the interference encountered on both links. First, we analyze the performance of each link separately in presence of impulsive noise and interference. Then, we study the performance when combining the output signals from both links and compare it to the performance of each link.

Efficient diversity technique for hybrid narrowband-powerline/wireless smart grid communications

Narrowband powerline communications (NB-PLC) and unlicensed wireless communications are considered as two leading communications technologies for emerging Smart Grid applications. The diversity provided by the simultaneous transmission of the same information over powerline and wireless links can be exploited to enhance the overall system reliability. In this paper, we propose an efficient technique to combine the received signals of the NB-PLC and wireless links considering the impulsive nature of the noise and interference on both links. We derive an expression for the average bit-error-rate of the proposed technique. In addition, we present simulation results that quantify the performance gains achieved by our proposed combining technique compared to conventional techniques.

Interaction of Insulin with Prokinetic Drugs in STZ-induced Diabetic Mice

AIM To study the possible interactions of metoclopramide, domperidone and erythromycin in streptozotocin-induced diabetic mice treated with insulin by various parameters. METHODS Effects of the individual as well as combined drugs were studied in diabetic mice via estimation of the blood glucose and serum insulin levels, small intestinal transit (SIT), gastric emptying (GE), xylose absorption and glucose tolerance tests. Groups were given insulin 2 IU/kg s.c., metoclopramide 20 mg/kg p.o., domperidone 20 mg/kg p.o. and erythromycin 6 mg/kg p.o. individually and in combination. There were also normal and diabetic control groups. The first set of experiments was carried out to investigate the subchronic effect on blood glucose and serum insulin levels in diabetic mice of one week of daily dose administration of the tested drugs individually as well as the combination of insulin with each prokinetic drug. The other five sets of experiments were carried out to investigate the acute effect of a single dose of each drug individually and in combination on blood glucose and serum insulin levels, SIT, GE, oral xylose absorption and glucose tolerance tests. RESULTS The study included the prokinetic drugs metoclopramide (20 mg/kg), domperidone (20 mg/kg) and erythromycin (6 mg/kg), as well as insulin (2 IU/kg), which was individually effective in decreasing SIT, enhancing GE and increasing xylose absorption significantly in diabetic mice. Erythromycin tended to decrease blood glucose level and increase serum insulin level after 1 wk of daily administration in diabetic mice. Erythromycin potentiated the effect of insulin on blood glucose level and serum insulin level whereas other prokinetic agents failed to do so after repeated dose administration in diabetic mice. Metoclopramide or erythromycin in combination with insulin significantly decreased SIT, in diabetic mice, to lower levels than with insulin alone. Administration of prokinetic drugs along with insulin antagonized the action of insulin on xylose absorption. These combinations also increased the rate of glucose absorption from the gut. CONCLUSION The present study suggests that prokinetic drugs could potentially improve glycemic control in diabetic gastroparesis by allowing a more predictable absorption of nutrients, matched to the action of exogenous insulin. The use of prokinetics, such as erythromycin, may be interesting in the clinic in decreasing the need for insulin in diabetic patients. The dose of insulin may be safely decreased with erythromycin in chronic treatments.

Proposed frame and preamble structure for MIMO narrowband power line communications

Narrowband power line communications (NB-PLC) operating in the 3-500 kHz frequency band is proposed as a solution to support the emerging Smart Grid applications that aim to optimize the efficiency and reliability of the power grids. PLC is attractive for Smart Grid communications as it can be deployed over the existing power grids without any additional infrastructure. However, PLC suffers from impulsive noise and frequency-selective channels which degrade the systems reliability and data rate. Multi-Input Multi-Output (MIMO) PLC is a promising technology to increase the data rate and provide robustness against the PLC interference. In this paper, we consider the design of a MIMO frame and preamble structure that can be efficiently used to perform initial receiver synchronization while ensuring backward compatibility with current NB-PLC standards.

Interference mitigation techniques for narrowband powerline smart grid communications

Narrowband cyclostationary interference severely limits the performance of power line communications (PLC) on low-voltage in the [3-500] kHz frequency band. For the IEEE 1901.2 narrowband PLC standard system parameters, this interference is not sparse in the time or the frequency domains making recently-proposed sparse interference mitigation techniques ineffective. In this paper, we investigate other properties of the interference; namely, its cyclostationarity and high spatial correlation across the three output phases to design effective and practical interference mitigation algorithms. The cyclostationarity is exploited to accurately estimate the interferences power spectral density in each of its three temporal regions and use it to enhance the Viterbi and/or Reed-Solomon decoder performance. The high spatial correlation is exploited to mitigate interference effects through cancellation or erasure decoding. Simulation results show considerable performance gains for both techniques.

Dual Branch Transmit Switch-and-Stay Diversity for Underlay Cognitive Networks

In this paper, we study applying dual branch transmit switch-and-stay combining (SSC) technique for underlay cognitive radio (UCR) networks. In UCR, the secondary user is allowed to share the spectrum with the primary (licensed) user under the condition that interference at the primary receiver is below a predetermined threshold. Assuming binary phase-shift keying (BPSK) modulation and Rayleigh fading channels, we develop a closed form expression for the average bit error rate (BER) of the secondary link as a function of the switching threshold. We then find a closed form expression for the optimal switching threshold in the sense of minimizing the average BER. For the sake of comparison we derive an expression for the average BER of the dual branch transmit selection combining (SC) technique. We finally investigate the effect of correlation between secondary and interference channels on the average BER and the associated optimal switching threshold.

On the Diversity of Hybrid Narrowband-PLC/Wireless Communications for Smart Grids

Narrowband powerline communications (NB-PLC) and unlicensed wireless communications are two leading communications technologies for the emerging smart grid applications. The channel and noise statistics experienced by powerline and wireless transmissions are independent and of a non-identical nature. In this paper, we exploit the diversity provided by the simultaneous transmission of the same information signal over powerline and wireless links to enhance the overall system reliability. In particular, we propose efficient techniques to combine the received signals of the NB-PLC and wireless links for both coherent and differential modulation schemes while considering the impulsive nature of the noise on both links. In addition, we derive closed-form expressions for the average bit-error-rate of the proposed combining techniques. Furthermore, we present simulation results that quantify the performance gains achieved by our proposed receive diversity combining techniques compared with conventional combining techniques.

Joint Opportunistic Beam and Spectrum Selection Schemes for Spectrum Sharing Systems With Limited Feedback

Spectrum sharing systems have been introduced to alleviate the problem of spectrum scarcity by allowing an unlicensed secondary user (SU) to share the spectrum with a licensed primary user (PU) under acceptable interference levels to the primary receiver (PU-Rx). In this paper, we consider a secondary link composed of a secondary transmitter (SU-Tx) equipped with multiple antennas and a single-antenna secondary receiver (SU-Rx). The secondary link is allowed to share the spectrum with a primary network composed of multiple PUs communicating over distinct frequency spectra with a primary base station. We develop a transmission scheme where the SU-Tx initially broadcasts a set of random beams over all the available primary spectra for which the PU-Rx sends back the index of the spectrum with the minimum interference level, as well as information that describes the interference value, for each beam. Based on the feedback information on the PU-Rx, the SU-Tx adapts the transmitted beams and then resends the new beams over the best primary spectrum for each beam to the SU-Rx. The SU-Rx selects the beam that maximizes the received signal-to-interference-plus-noise ratio (SINR) to be used in transmission over the next frame. We consider three cases for the level of feedback information describing the interference level. In the first case, the interference level is described by both its magnitude and phase; in the second case, only the magnitude is considered; and in the third case, we focus on a q-bit description of its magnitude. In the latter case, we propose a technique to find the optimal quantizer thresholds in a mean-square-error sense. We also develop a statistical analysis for the SINR statistics and the capacity and bit error rate of the secondary link and present numerical results that study the impact of the different system parameters.

Joint Switched Multi-Spectrum and Transmit Antenna Diversity for Spectrum Sharing Systems

In spectrum sharing systems, a secondary user (SU) is allowed to share the spectrum with a primary (licensed) network under the condition that the interference observed at the receivers of the primary users (PU-Rxs) is below a predetermined level. In this paper, we consider a secondary network comprised of a secondary transmitter (SU-Tx) equipped with multiple antennas and a single-antenna secondary receiver (SU-Rx) sharing the same spectrum with multiple primary users (PUs), each with a distinct spectrum. We develop transmit antenna diversity schemes at the SU-Tx that exploit the multi-spectrum diversity provided by the existence of multiple PUs so as to optimize the signal-to-noise ratio (SNR) at the SU-Rx. In particular, assuming bounded transmit power at the SU-Tx, we develop switched selection schemes that select the primary spectrum and the SU-Tx transmit antenna that maintain the SNR at the SU-Rx above a specific threshold. Assuming Rayleigh fading channels and binary phase-shift keying (BPSK) transmission, we derive the average bit-error-rate (BER) and average feedback load expressions for the proposed schemes. For the sake of comparison, we also derive a BER expression for the optimal selection scheme that selects the best antenna/spectrum pair that maximizes the SNR at the SU-Rx, in exchange of high feedback load and switching complexity. Finally, we show that our analytical results are in perfect agreement with the simulation results.

Interference-Aware Random Beam Selection for Spectrum Sharing Systems

Spectrum sharing systems have been introduced to alleviate the problem of spectrum scarcity by allowing secondary unlicensed networks to share the spectrum with primary licensed networks under acceptable interference levels to the primary users. In this paper, we develop interference-aware random beam selection schemes that provide enhanced throughput for the secondary link under the condition that the interference observed at the primary link is within a predetermined acceptable value. For a secondary transmitter equipped with multiple antennas, our schemes select a random beam, among a set of power- optimized orthogonal random beams, that maximizes the capacity of the secondary link while satisfying the interference constraint at the primary receiver for different levels of feedback information describing the interference level at the primary receiver. For the proposed schemes, we develop a statistical analysis for the signal-to-noise and interference ratio (SINR) statistics as well as the capacity of the secondary link. Finally, we present numerical results that study the effect of system parameters including number of beams and the maximum transmission power on the capacity of the secondary link attained using the proposed schemes.