Hybrid Full-Duplex and Alternate Multiple Relay Selection and Beamforming in AF Cooperative Networks

In this paper, multiple relay selection and beamforming techniques are applied to a dual-hop full-duplex (FD) amplify-and-forward relaying network. We show that our proposed techniques allow the selection to be adaptive to the residual self-interference (SI) level for each of the available relays in the network. The adaptivity of our selection schemes is manifested through a hybrid system that is based on FD relaying and switching based on the overall channel conditions and the statistics of the residual SI channel for each of the relays. In particular, different proposed techniques are shown to be able to adaptively decide on when and how often the used relays should be switched in the case of overwhelming residual SI. Our results show that allowing such a fusion considerably improves the overall performance of the considered relaying scheme in terms of bit error rate compared with state-of-the-art relay selection schemes.This work was supported by the Qatar National Research Fund (a member of the Qatar Foundation) through GSRA under Grant #2-1-0601-14011.Scopu

A Strategy for Emergency Vehicle Preemption and Route Selection

Emergency vehicle preemption (EVP) aims to give right of way to emergency vehicles (EV) heading toward the incident location through a network of signalized intersections by creating a green wave en-route. The design goals of EVP systems are two folds: first, to avoid any hindrance to the passage of EV along the road and at the intersections and second, to reduce the negative impact of preemption on general traffic. The negative impact of EVP on normal traffic can be minimized by selecting appropriate preemption strategy. The EVP schemes proposed earlier aim to minimize the travel time of the EV with no or little consideration to the negative impact of EVP on the normal traffic. In this study, a joint strategy for optimal path selection and EV preemption is developed. The proposed scheme selects the optimal path for the EV before it departs from its origin and then activates the preemption on each intersection en-route at the right time to clear the intersection before the EV reaches. The proposed EVP scheme also aims to minimize the impact of EVP over normal traffic at both stages (i.e., path selection phase and preemption phase). A major advantage of the proposed method is that once the optimal path is selected, the emergency information can be disseminated to other vehicles using vehicle-to-vehicle and vehicle-to-infrastructure communication in the EV path to clear the entire route or the approaching lane. The strategy was tested using a microscopic simulation environment for a real traffic network. The findings indicated a major reduction in the travel time of the EV while minimizing the impact of preemption on the normal traffic. The proposed strategy and evaluation procedure can be helpful for corresponding agencies and practitioners to assess the impact of implementing preemption on existing or proposed arterials. - 2019, The Author(s).Open access funding provided by the Qatar National Library.Scopu

Sparsity-aware multiple relay selection in large multi-hop decode-and-forward relay networks

In this paper, we propose and investigate two novel techniques to perform multiple relay selection in large multi-hop decode-and-forward relay networks. The two proposed techniques exploit sparse signal recovery theory to select multiple relays using the orthogonal matching pursuit algorithm and outperform state-of-the-art techniques in terms of outage probability and computation complexity. To reduce the amount of collected channel state information (CSI), we propose a limited-feedback scheme where only a limited number of relays feedback their CSI. Furthermore, a detailed performance-complexity tradeoff investigation is conducted for the different studied techniques and verified by Monte Carlo simulations.NPRP grant 6-070-2-024 from the Qatar National Research Fund (a member of Qatar Foundation)Scopu

Sparse Equalizers for OFDM Signals with Insufficient Cyclic Prefix

The cyclic prefix (CP) is appended in orthogonal frequency division multiplexing (OFDM) signals to combat inter-symbol interference (ISI) and inter-carrier interference (ICI) induced by the communication channel, which limits its spectral efficiency. Therefore, inserting an insufficient CP and equalizing the resulting ICI and ISI is a method that has been circulating the literature for a while, aiming at increasing the efficiency of OFDM systems. In this paper, we propose a reduced-complexity sparse linear equalizer and a decision-feedback equalizer for OFDM signals with insufficient CP. A performance-complexity trade-off is highlighted, where we show that it is possible to equalize the received signal with a reduced complexity equalizer while having a limited performance loss. Our proposed equalizer designs are not only less complex to realize, but are shown to provide a higher data rate. The proposed equalizers are further evaluated in terms of the worst-case coherence, a metric determining the effectiveness of our used approach. Numerical results show that we can significantly and reliably reduce the order of the design complexity while performing very close to the conventional complex optimal equalizers. 2013 IEEE.This work was supported by GSRA from the Qatar National Research Fund (a member of Qatar Foundation) under Grant 2-1-0601-14011. The statements made herein are solely the responsibility of the authors.Scopu

The Generalization of the Decomposition of Functions by Energy Operators

This work starts with the introduction of a family of differential energy operators. Energy operators ($Psi_R^+$, $Psi_R^-$) were defined together with a method to decompose the wave equation in a previous work. Here the energy operators are defined following the order of their derivatives ($Psi_k^+$, $Psi_k^-$, k = {0,1,2,..}). The main part of the work is to demonstrate that for any smooth real-valued function f in the Schwartz space ($S^-(R)$), the successive derivatives of the n-th power of f (n in Z and n not equal to 0) can be decomposed using only $Psi_k^+$ (Lemma) or with $Psi_k^+$, $Psi_k^-$ (k in Z) (Theorem) in a unique way (with more restrictive conditions). Some properties of the Kernel and the Image of the energy operators are given along with the development. Finally, the paper ends with the application to the energy function.Comment: The paper was accepted for publication at Acta Applicandae Mathematicae (15/05/2013) based on v3. v4 is very similar to v3 except that we modified slightly Definition 1 to make it more readable when showing the decomposition with the families of energy operator of the derivatives of the n-th power of

Synchronization and multipath delay estimation algorithms for digital receivers

This thesis considers the development of synchronization and signal processing techniques for digital communication receivers, which is greatly influenced by the digital revolution of electronic systems. Eventhough synchronization concepts are well studied and established in the literature, there is always a need for new algorithms depending on new system requirements and new trends in receiver architecture design. The new trend of using digital receivers where the sampling of the baseband signal is performed by a free running oscillator reduces the analog components by performing most of the functions digitally, which increases the flexibility, configurability, and integrability of the receiver. Also, this new design approach contributes greatly to the software radio (SWR) concept which is the natural progression of digital radio receivers towards multimode, multistandard terminals where the radio functionalities are defined by software. The first part of this research work introduces a new technique for jointly estimating the symbol timing and carrier phase of digital receivers with non-synchronized sampling clock for both data-aided and non-data-aided systems using a block-based feed-forward architecture. This technique is a practical, rapidly converging, fully digitally implemented synchronization concept based on a low-order polynomial approximation of the likelihood functions using the Farrow-based interpolator. A review of maximum likelihood theory, which is the basis for coherent theory of synchronization, defines first the criteria and general framework for developing near-optimum synchronization schemes for digital communication systems. Then, efficient Farrow-based polynomial approximations of the typical likelihood functions are derived for systematic symbol timing, carrier phase and fine acquisition frequency synchronization algorithms. Another important receiver functionality closely related to synchronization is propagation delay estimation which is the basis of positioning technologies. Mobile phone positioning is becoming unavoidable after the mandate imposed by communications regulatory bodies on emergency call positioning. The second part of this thesis reviews and develops new techniques with subchip resolution capabilities for estimating closely-spaced multipath delays in spread-spectrum CDMA systems. Generally, multipath delays caused by distant reflectors have relatively large delay spread, with more than one chip interval between different paths, that can be resolved using conventional delay-locked-loop techniques. However, shorter excess path delays result in overlapped fading multipath components that introduce significant errors to the line-of-sight path delay and gain estimation. Overlapping fading multipath components are considered as one of the major sources of error that have strong impact on high precision mobile positioning solutions, as well as, on mobile applications of dedicated systems like the Global Positioning System (GPS). An overview of the most promising geolocation positioning techniques for wireless systems that are being standardized is first provided with a survey of fundamental concepts and major problems in positioning. Then, the characteristics of different channel models and conventional multipath delay estimation techniques based on maximum likelihood theory are also discussed. Two new techniques with subchip resolution capabilities are proposed for estimating closely-spaced overlapped multipath components. These techniques are intended to improve the accuracy of location estimates by estimating correctly the delay of the line-of-sight path

Data for: Secondary Users Selection and Sparse Narrow-band Interference Mitigation in Cognitive Radio Networks

Spectrum scarcity is a critical problem that may reduce the effectiveness of wireless technologies and services. To address this problem, different spectrum management techniques have been proposed such as overlay cognitive radio (CR) where the unlicensed users can share the same spectrum with the licensed users. The main challenges in overlay CR networks are the identification and detection of the Primary User (PU) signals in a multi-source narrow-band interference (NBI) scenario. Therefore, in this paper, we investigate the performance of an orthogonal frequency division multiplexing (OFDM) overlay CR network with Secondary Users (SUs) and subcarriers selection schemes. Three approaches for SUs and subcarriers Selection named Direct, Distributed and Incremental selection techniques are proposed in this paper to increase the expected signal to interference and noise ratio based on full or partial knowledge of the channel state information (CSI). We also show that Distributed selection techniques provide all the SUs equal chances to be selected without affecting the selection diversity gain. General as well as simplified outage probability expressions are derived and extensive simulations are conducted to evaluate the performance of the proposed techniques and support the theoretical derivations. To accommodate more SUs, a new approach for asynchronous NBI estimation and mitigation in CR networks is investigated. Without any prior knowledge of the NBI characteristics and based on sparse signal recovery theory, the proposed approach allows the PU to exploit the sparsity of the SUs interference to recover it and approach the interference-free limit over practical ranges of NBI power levels

Performances analysis of SEC based transmit diversity systems with MRC receivers

Switch and Examine combining (SEC) diversity scheme is one of the simplest yet efficient diversity schemes. Earlier in [1] and [2], we proposed sequential power loading algorithm to reduce the average power used at the transmitter in transmit diversity systems. In this paper, we propose the usage of a maximum ratio combining (MRC) receiver on top of sequential power loading, and provide a complete performance analysis of this proposed scheme in terms of average power used, average number of used antennas, average feedback load, and outage probability. Numerical results show that the proposed MRC enhanced scheme provides lower average number of used antennas and average feedback load with better outage performance than post selection and early selection schemes that were proposed earlier. This improved performance comes at the expense of a slightly higher average transmit power used.Scopu

Subchip Multipath Delay Estimation for Downlink WCDMA System Based on Teager-Kaiser Operator

Accurate detection and estimation of overlapping fading multipath components is vital for many communication systems, particularly for positioning technologies. Traditional approaches used for channel estimation generally fail in estimating closely-spaced multipath components in CDMA systems. Here, we present a highly efficient technique for asynchronous downlink WCDMA multipath delay estimation with subchip resolution capability based on nonlinear Teager-Kaiser operator concept. The behaviour of this technique is influenced considerably by the pulse shape waveform. Both rectangular and root raised cosine pulse shaping filters are considered.Peer reviewe