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Nano Scientific Research Centre Pvt Ltd
Nano Scientific Research Centre Pvt Ltd


MATLAB - COMMUNICATION IEEE PROJECTS

Specialized on M.Tech/M.E Vlsi Designing (frontend & Backend)

Domains:

  • Processor Architecture
  • Bist Algorithms
  • Signal Processing
  • Image & Video Processing
  • Communication & Bus Protocols
  • Low Power Vlsi
  • Physical Design (250nm-180nm-90nm-45nm-32nm)
  • Fpga Prototyping, Etc. . . ,

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  • Vhdl
  • Verilog Hdl
  • System Verilog
  • H-spice

Softwares :

  • Xilinx Ise
  • Xilinx Platform Studio
  • Tanner Eda
  • Dsch
  • Modelsim Ise
  • Microwind
  • Questasim
  • Pspice

Hardwares :

  • Spartan Series
  • Vertex Series
  • Altera Cyclone Series

Our Training Features :
  • 100% Outputs With Extension
  • Paper Publishing In International Level
  • Project Training Session Are Conducted By Real-time Instructor With Real-time Examples.
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  • State-of-the-art Lab With Required Software For Practicing.

A Blind Fine Synchronization Scheme for SC-FDE Systems

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A Blind Fine Synchronization Scheme for SC-FDE Systems
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This work presents a blind fine synchronization scheme, which estimates and compensates residual carrierfrequency offset (RCFO) and symbol timing offset (STO) , for single-carrier frequency-domain equalization (SC-FDE) systems. Existing fine synchronization schemes for SC-FDE systems rely on time-domain unique words (UW) sequences as reference signals to assure the estimation accuracy, at the cost of decreased system throughput. The proposed technique, named simplified weighted least-square method for single-carrier systems (SWLSSC), combines the decision feedback structure and SWLS estimator for OFDM systems. Together with specifically derived weighting factors, it has much better estimation accuracy than the well-known linear least-square (LLS) method for SC-FDE systems, and its BER performance can approach that of the ideal synchronization condition. The proposed technique is more effective than existing techniques, in terms of both performance and throughput. Theoretical estimation bounds are also derived to verify the effectiveness of the proposed method.

























  • Minimum Order Quantity: 1 student
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    A Multiobjective Optimization Approach for Optimal Link Adap

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    A Multiobjective Optimization Approach for Optimal Link Adap
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    This paper adopts a multiobjective optimization (MOOP) approach to investigate the optimal link adaptation problem of orthogonal frequency division multiplexing (OFDM)- based cognitive radio (CR) systems, where secondary users (SUs) can opportunistically access the spectrum of primary users (PUs). For such a scenario, we solve the problem of jointly maximizing the CR system throughput and minimizing its transmit power, subject to constraints on both SU and PUs. The optimization problem imposes predefined interference thresholds for the PUs, guarantees the SU quality of service in terms of a maximum bit-error-rate (BER), and satisfies a transmit power budget and a maximum number of allocated bits per subcarrier. Unlike most of the work in the literature that considers perfect SU spectrum sensing capabilities, the problem formulation takes into account errors due to imperfect sensing of the PUs bands. Closed-form expressions are obtained for the optimal bit and power allocations per SU subcarrier. Simulation results illustrate the performance of the proposed algorithm and demonstrate the superiority of the MOOP approach when compared to single optimization approaches presented in the literature, without additional complexity. Furthermore, results show that the interference thresholds at the PUs receivers can be severely exceeded due to the perfect spectrum sensing assumption or due to partial channel information on links between the SU and the PUs receivers. Additionally, the results show that the performance of the proposed algorithm approaches that of an exhaustive search for the discrete optimal allocations with a significantly reduced computational effort.

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    Accuracy of Homology Based Coverage Hole Detection

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    Accuracy of Homology Based Coverage Hole Detection
    Approx. Rs 10,000 / student
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    Homology theory has attracted great attention because it can provide novel and powerful solutions to address coverage problems in wireless sensor networks. They usually use an easily computable algebraic object, Rips complex, to detect coverage holes. But Rips complex may miss some coverage holes in some cases. In this paper, we investigate homology-based coverage hole detection for wireless sensor networks on sphere. The case when Rips complex may miss coverage holes is first identified. Then we choose the proportion of the area of coverage holes missed by Rips complex as a metric to evaluate the accuracy of homology-based coverage hole detection approaches. Closed-form expressions for lower and upper bounds of the accuracy are derived. Asymptotic lower and upper bounds are also investigated when the radius of sphere tends to infinity. Simulation results are well consistent with the analytical lower and upper bounds, with maximum differences of 0.5% and 3% respectively. Furthermore, it is shown that the radius of sphere has little impact on the accuracy if it is much larger than communication and sensing radii of each sensor.

























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    Achievable Throughput Optimization

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    Achievable Throughput Optimization
    Approx. Rs 10,000 / student
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    in OFDM Systems in the Pr

    —The aim of this paper is to study the bit-loading and power allocation problem in the presence of interference (Inter-carrier Interference (ICI) and Inter-Symbol Interference (ISI)) in Orthogonal Frequency Division Multiplexing (OFDM) systems. ISI and ICI significantly degrade the performance of OFDM systems and make the resource management optimized without the assumption of interference less efficient. To solve this problem, an initial solution based on the greedy approach is proposed in this paper. Then, several reduced complexity approaches, which yield a little degradation compared to the initial solution, have been developed. Simulation results presented in the context of Power Line Communication (PLC) show that the performance of proposed algorithms is tight with their upper bound. Moreover, these algorithms efficiently improve the system performance as compared to the constant power water- filling allocation algorithm as well as maximum power allocation algorithm.

























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    Achieving Delay Diversity in Asynchronous

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    Achieving Delay Diversity in Asynchronous
    Approx. Rs 10,000 / student
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    In cooperative UWA systems, due to the low speed of sound, a node can experience significant time delays among the signals received from geographically separated nodes. One way to combat the asynchronism issues is to employ orthogonal frequency division multiplexing (OFDM)-based transmissions at the source node by preceding every OFDM block with an extremely long cyclic prefix (CP) which reduces the transmission rates dramatically. One may increase the OFDM block length accordingly to compensate for the rate loss which also degrades the performance due to the significantly time-varying nature of UWA channels. In this paper, we develop a new OFDM-based scheme to combat the asynchronism problem in cooperative UWA systems without adding a long CP (in the order of the long relative delays) at the transmitter. By adding a much more manageable (short) CP at the source, we obtain a delay diversity structure at the destination for effective processing and exploitation of spatial diversity by utilizing a low complexity Viterbi decoder at the destination, e.g., for a binary phase shift keying (BPSK) modulated system, we need a two-state Viterbi decoder. We provide pairwise error probability (PEP) analysis of the system for both time-invariant and block fading channels showing that the system achieves full spatial diversity. We find through extensive simulations that the proposed scheme offers a significantly improved error rate performance for time-varying channels (typical in UWA communications) compared to the existing approaches.

























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    An Efficient Blind Estimation of Carrier Frequency

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    An Efficient Blind Estimation of Carrier Frequency
    Approx. Rs 10,000 / student
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    In this paper, we propose a low-complexity blind carrier frequency offset (CFO) estimation scheme for constant modulus (CM)-signaling-based orthogonal frequency-division multiplexing (OFDM) systems. Provided that the channel can be assumed to be slowly time-varying, subcarriers having the same indexes in two consecutive OFDM symbols will experience nearly the same channel effect. This assumption enables us to derive a cost function that is determined by the sum of the products of the signal amplitudes on each pair of equivalent subcarriers from two successive OFDM symbols. The maximization process of this cost function makes it possible to find an appropriate estimate of the CFO. Over frequency-selective Rayleigh fading channels, the proposed CFO estimation method provides improved performance over existing techniques. Moreover, in the context of narrow-band noise and signal gain variations, the simulations demonstrate the robustness and immunity of our scheme.

























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    Confederation Based RRM with Proportional Fairness

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    Confederation Based RRM with Proportional Fairness
    Approx. Rs 10,000 / student
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    A new radio resource management (RRM) technique for improving the downlink performance in soft-frequencyreuse based long term evolution (LTE) networks is presented. In this RRM the resource is dynamically allocated in distributed and centralized manners such that spectral efficiency is maximized across the whole network. To achieve this a unique interference mapping strategy is implemented to assist in deciding whether a distributed or centralized mode is applicable per basestation. When a distributed approach is granted to a basestation it can use the entire spectrum while when a centralized approach is imposed on a basestation it will only be allocated a subset of the spectrum. The proposed then utilizes the confederation concept in the sense that once the allocation approach is determined the individual basestations can take control of their allocated resource. When combined with proportional fairness scheduling, this RRM can also benefit from multiuser diversity. It will be shown through mathematical analysis and computer simulations that this technique offers significant improvements in terms of sum rate and quality of service by increasing the guaranteed data rate per user.

























  • Minimum Order Quantity: 1 student
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    Cooperative Spectrum Sharing Between Cellular and Ad-Hoc Net

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    Cooperative Spectrum Sharing Between Cellular and Ad-Hoc Net
    Approx. Rs 10,000 / student
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    Spectrum sharing between cellular and ad-hoc networks is studied in this work. Weak signals and strong interferences at the cell-edge area usually cause severe performance degradation. To improve the cell-edge users’ performance quality while keeping high spectrum efficiency, in this paper, we propose a cooperative spectrum sharing scheme. In the proposed scheme, the ad-hoc users can actively employ cooperative diversity techniques to improve the cellular network downlink throughput. As a reward, a fraction of the cellular network spectrum is released to the ad-hoc network for its own data transmission. To determine the optimal spectrum allocation, we maximize the ad-hoc transmission capacity subject to the constraints on the outage probability of the ad-hoc network and on the throughput improvement ratio of the cellular network. Both the transmission capacity of the ad-hoc network and the average throughput of the cellular network are analyzed using the stochastic geometry theory. Numerical and simulation results are provided to validate our analytical results. They demonstrate that our proposed scheme can effectively facilitate ad-hoc transmissions while moderately improving the cellular network performance.

























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    Diversity Relaying for Parallel Use of Power

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    Diversity Relaying for Parallel Use of Power
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    —In this paper, the parallel use of power-line and wireless communication networks with multihop relaying is considered for enhancing the robustness and stability of smart-grid communication. We propose receive and transmit diversity relaying schemes for a unified power-line/wireless relay structure. The performance of the proposed relaying schemes is analyzed in an informationtheoretic framework. Numerical results demonstrate that the proposed schemes provide enhanced performance compared to the separate use of relays in the power-line and wireless channels.

























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    Doppler Mitigation in OFDM-Based Aeronautical Communications

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    Doppler Mitigation in OFDM-Based Aeronautical Communications
    Approx. Rs 10,000 / student
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    Doppler spectrum in an aeronautical channel is modeled with dual-Doppler shift instead of classical Jakes model. Orthogonal frequency division multiplexing (OFDM)-based systems are sensitive to Doppler shifts/spread, since the time variation of the channel causes inter-carrier interference (ICI). ICI analysis is provided here for OFDM-based systems in the aeronautical channel. The effect of ICI on the received signal is presented and its power is derived. As compared with terrestrial channels, where ICI is generally overcome by increasing the subcarrier spacing and bounding the normalized Doppler frequency (NDF), we propose to mitigate the effect of Doppler shifts in aeronautical channels, as follows. First, we use parametric spectrum estimation methods to extract the Doppler shifts by exploiting the predictable number of paths. Then, a beamforming-based method is introduced to resolve the incoming rays by separating them individually. Finally, paths are Doppler-compensated and combined using diversity combining techniques. Computer simulations are performed to provide numerical results. It is shown that a mean square error (MSE) performance of 1% is achieved with the parametric estimation methods, and bit error rate (BER) performance approaching the no-Doppler scenario is obtained with the beamforming-based mitigation method

























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    Efficient Exact Regenerating Codes For Byzantine Fault Toler

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    Efficient Exact Regenerating Codes For Byzantine Fault Toler
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    Today’s large-scale distributed storage systems are commonly built using commodity software and hardware. As a result, crash-stop and Byzantine failures in such systems become more and more prevalent. In the literature, regenerating codes have been shown to be a more efficient way to disperse information across multiple storage nodes and recover from crash-stop failures. In this paper, we propose a novel decoding design of product-matrix constructed regenerating codes in conjunction with integrity check that allows exact regeneration of failed nodes and data reconstruction in the presence of Byzantine failures. A progressive decoding mechanism is incorporated in both procedures to leverage computation performed thus far. Unlike previous works, our new regenerating code decoding has the advantage that its building blocks, such as Reed-Solomon codes and standard cryptographic hash functions, are relatively well-understood because of their widespread applications. The fault tolerance and security properties of the proposed schemes are also analyzed. In addition, the performance of the proposed schemes, in terms of the average number of access nodes and the reconstruction failure probability versus the node failure probability, are also evaluated by Monte Carlo simulations.

























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    Energy-Aware Resource Allocation Strategies for LTE Uplink W

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    Energy-Aware Resource Allocation Strategies for LTE Uplink W
    Approx. Rs 10,000 / student
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    In this paper, we propose a framework for energy efficient resource allocation in multiuser localized SC-FDMA with synchronous HARQ constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. The impact of retransmissions on the time-frequency problem segmentation is handled through the use of a novel block scheduling interval specifically designed for synchronous HARQ to ensure uplink users do not experience ARQ blocking. Using this framework, we formulate the optimal margin adaptive allocation problem, and based on its structure, we propose two suboptimal approaches to minimize average power allocation required for resource allocation while attempting to reduce complexity. Results are presented for computational complexity and average power allocation relative to system complexity and data rate, and comparisons are made between the proposed optimal and suboptimal approaches

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    Error-Rate Performance Analysis of Cooperative OFDMA System

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    Error-Rate Performance Analysis of Cooperative OFDMA System
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    In this paper, we investigate the performance of a cooperative orthogonal frequency-division multiple-access (OFDMA) system with decode-and-forward (DaF) relaying. Specifically, we derive a closed-form approximate symbol-error-rate expression and analyze the achievable diversity orders. Depending on the relay location, a diversity order up to (LSkD + 1) + M m=1 min(LSkRm + 1, LRmD + 1) is available, where M is the number of relays, and LSkD + 1, LSkRm + 1, and LRmD + 1 are the lengths of channel impulse responses of source-to-destination, source-to-mth relay, and mth relay-todestination links, respectively. Monte Carlo simulation results are also presented to confirm the analytical findings.






























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    Estimation of Sparse Time Dispersive Channels in Pilot Aided

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    Estimation of Sparse Time Dispersive Channels in Pilot Aided
    Approx. Rs 10,000 / student
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    We propose the use of the atomic norm minimization for the estimation of sparse time dispersive channels. The proposed estimation approach combines the atomic norm minimization, a super resolution method and the least squares (LS) method, and is intended for pilot aided channel estimation in OFDM systems. The combination of the atomic norm minimization and the super resolution method allows for gridless estimation of arbitrary delays of the individual paths in the channel impulse response, and the gains of those paths are then estimated using the LS method. To further improve the performance we also propose a version of the approach with reweighted atomic norm minimization. We compare the performance of the proposed approach with other grid based approaches for sparse channel estimation.

























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    Evolutionary-Algorithm-Assisted Joint Channel Estimation

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    Evolutionary-Algorithm-Assisted Joint Channel Estimation
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    The development of evolutionary algorithms (EAs), such as genetic algorithms (GAs), repeated weighted boosting search (RWBS), particle swarm optimization (PSO), and differential evolution algorithms (DEAs), have stimulated wide interests in the communication research community. However, the quantitative performance-versus-complexity comparison of GA, RWBS, PSO, and DEA techniques applied to the joint channel estimation (CE) and turbo multiuser detection (MUD)/decoding in the context of orthogonal frequency-division multiplexing/space-division multiple-access systems is a challenging problem, which has to consider both the CE problem formulated over a continuous search space and the MUD optimization problem defined over a discrete search space. We investigate the capability of the GA, RWBS, PSO, and DEA to achieve optimal solutions at an affordable complexity in this challenging application. Our study demonstrates that the EA-assisted joint CE and turbo MUD/decoder is capable of approaching both the Cramér–Rao lower bound of the optimal CE and the bit error ratio (BER) performance of the idealized optimal maximum-likelihood (ML) turbo MUD/decoder associated with perfect channel state information, respectively, despite imposing only a fraction of the idealized turbo ML-MUD/decoder’s complexity.

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    Fair Resource Allocation for OFDMA Femtocell Networks

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    Fair Resource Allocation for OFDMA Femtocell Networks
    Approx. Rs 10,000 / student
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    We consider the joint subchannel allocation and power control problem for orthogonal frequency-division multipleaccess (OFDMA) femtocell networks in this paper. Specifically, we are interested in the fair resource-sharing solution for users in each femtocell that maximizes the total minimum spectral efficiency of all femtocells subject to protection constraints for the prioritized macro users. Toward this end, we present the mathematical formulation for the uplink resource-allocation problem and propose an optimal exhaustive search algorithm. Given the exponential complexity of the optimal algorithm, we develop a distributed and low-complexity algorithm to find an efficient solution for the problem. We prove that the proposed algorithm converges and we analyze its complexity. Then, we extend the proposed algorithm in three different directions, namely, downlink context, resource allocation with rate adaption for femto users, and consideration of a hybrid access strategy where some macro users are allowed to connect with nearby femto base stations (FBSs) to improve the performance of the femto tier. Finally, numerical results are presented to demonstrate the desirable performance of the proposed algorithms.

  • Minimum Order Quantity: 1 student
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    Fairness-Adaptive Goodput-Based Resource Allocation in OFDMA

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    Fairness-Adaptive Goodput-Based Resource Allocation in OFDMA
    Approx. Rs 10,000 / student
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    We present a cross-layer resource-allocation (RA) scheme for the downlink in orthogonal frequency-division multiple-access (OFDMA) systems with fairness control among the users, where the resources to be allocated are power, bits per symbol, and subchannels. The use of subchannels, which are defined as group of subcarriers, leads to reducing the complexity of the bandwidth allocation compared with the commonly adopted subcarrier allocation. A goodput-based optimization function, which is derived by combining automatic repeat request (ARQ) and physical (PHY)-layer parameters, is used to perform RA for applications that demand error-free transmissions. Two transmission strategies are considered, with and without concatenation of subchannels, for which two different RA methods are developed, respectively. We also propose an algorithm that improves the complexity associated to both concatenation and nonconcatenation schemes, without appreciable performance loss.

























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    Harnessing Frequency Domain for Cooperative Sensing

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    Harnessing Frequency Domain for Cooperative Sensing
    Approx. Rs 10,000 / student
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    —It is known that current fixed spectrum assignment policy has made the spectrum resource significantly underutilized. As a promising solution, cognitive radio emerges and shows its advantages. It allows the unlicensed users to opportunistically access the spectrum not used by the licensed users. To ensure that the unlicensed users can identify the vacate spectrum fast and accurately without interfering the licensed users, cooperative sensing is explored to improve the sensing performance by leveraging spatial diversity. However, cooperation gain can be compromised dramatically with cooperation overhead. Furthermore, when sensing decisions are made, contention on spectrum access also contributes a lot to the control overhead, especially in the distributed networks. Motivated by this, we propose a novel MAC design, termed Frequency domain Cooperative sensing and Multi-channel contention (FCM) for Cognitive Radio Ad Hoc Networks (CRAHNs). FCM is proposed for OFDM (Orthogonal Frequency Division Multiplexing) modulation based communication systems, which moves cooperative sensing and multi-channel contention from time domain into frequency domain. Therefore, control overhead caused by cooperation and contention can be significantly reduced. Meanwhile, the sensing and access performance can be both guaranteed. Extensive simulation results show that FCM can effectively reduce the control overhead, and improve the average throughput by 220% over Traditional Cooperative MAC for CRAHNs.

























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    In and Out-Degree Distributions of Nodes and Coverage

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    In and Out-Degree Distributions of Nodes and Coverage
    Approx. Rs 10,000 / student
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    —In a random sector graph, the presence of an edge between two nodes depends on their distance and spatial orientation. This kind of graph is widely used for modeling wireless sensor networks where communication among nodes is directional. In particular, it is applied to describe both the radio frequency transmission among nodes equipped with directional antennas and the line-of-sight transmission in optical sensor networks. Important properties of a wireless sensor network, such as connectivity and coverage, can be investigated by studying the degree of the nodes of the corresponding random sector graph. In detail, the in-degree value represents the number of incoming edges, whereas the out-degree considers the outgoing edges. This paper mathematically characterizes the average degree of a random sector graph and the probability distributions of the in-degree and out-degree of the nodes. Furthermore, it derives the coverage probability of the network. All the formulas are validated through extensive simulations, showing an excellent match between theoretical results and experimental data

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    Iterative Cancellation of Non-Linear Distortion Noise In Dig

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    Iterative Cancellation of Non-Linear Distortion Noise In Dig
    Approx. Rs 10,000 / student
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    In this paper, an iterative receiver that performs nonlinear distortion noise cancellation is presented. The performance is assessed for time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA) and single-carrier frequency division multiple access (SC-FDMA) waveforms. Even though a return link setup is considered, the receiver is equally applicable in the forward link, taking into account the differences in the data multiplexing and the channel. Analytical modeling of the received electrical signal-to-noise ratio (SNR) is carried out for OFDMA with one iteration of non-linear distortion noise cancellation. The performance is assessed in terms of power efficiency and spectral efficiency, where the total degradation (TD) of the received SNR in a non-linear channel is minimized. The modulation formats of the DVB-RCS2 satellite return link standard and a respective non-linear channel have been used. OFDMA shows the highest power efficiency gain of 1.1–2.5 dB with 2 iterations of non-linear noise cancellation across the different modulation orders. In SC-FDMA, the gain is in the range of 0.3–1.1 dB, while gains of 0.1–0.8 dB and 0.2–1.9 dB are presented in TDMA with 20% roll-off and 5% roll-off, respectively.

























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    Iterative Synchronization-Assisted Detection Of OFDM Signals

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    Iterative Synchronization-Assisted Detection Of OFDM Signals
    Approx. Rs 10,000 / student
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    Despite many attractive features of an orthogonal frequency-division multiplexing (OFDM) system, the signal detection in an OFDM system over multipath fading channels remains a challenging issue, particularly in a relatively low signalto-noise ratio (SNR) scenario. This paper presents an iterative synchronization-assisted OFDM signal detection scheme for cognitive radio (CR) applications over multipath channels in low-SNR regions. To detect an OFDM signal, a log-likelihood ratio (LLR) test is employed without additional pilot symbols using a cyclic prefix (CP). Analytical results indicate that the LLR of received samples at a low SNR can be approximated by their log-likelihood (LL) functions, thus allowing us to estimate synchronization parameters for signal detection. The LL function is complex and depends on various parameters, including correlation coefficient, carrier frequency offset (CFO), symbol timing offset, and channel length. Decomposing a synchronization problem into several relatively simple parameter estimation subproblems eliminates a multidimensional grid search. An iterative scheme is also devised to implement a synchronization process. Simulation results confirm the effectiveness of the proposed detector.

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    Joint ML Estimation of CFO and Channel, and a Low Complexity

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    Joint ML Estimation of CFO and Channel, and a Low Complexity
    Approx. Rs 10,000 / student
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    In this paper, we propose a pilot aided joint estimation technique for carrier frequency offsets (CFOs) and doubly selective channels (DSCs), and a low complexity turbo equalization (TE) scheme for orthogonal frequency division multiple access (OFDMA) uplink systems with high mobility users. We propose the use of Chebyshev polynomials of the first kind (CPF) for accurately representing the DSCs. As the exact solution to the estimation problem is computationally intensive, we make use of space alternating generalized expectation maximization (SAGE) algorithm, that replaces the complex multidimensional search with many one dimensional searches. We derive the exact Cramer-Rao bound (CRB) of the joint estimation problem and the mean squared error of the proposed estimation technique is shown to be closely comparable to it. The convergence characteristics are also studied and it is proved analytically that the proposed method converges. Additionally, we propose a low complexity turbo equalization method with iterative multiple access interference (MAI) cancellation, which uses the soft feedback symbol estimate for removing the MAI and self inter-carrier interference (ICI) in each iteration. Our proposed estimation and equalization technique can be applied to any type of carrier assignment scheme (CAS) in OFDMA and offers very good performance even at high mobile speeds.

























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    Large-Scale Synthetic Social Mobile Networks with SWIM

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    Large-Scale Synthetic Social Mobile Networks with SWIM
    Approx. Rs 10,000 / student
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    This paper presents small world in motion (SWIM), a new mobility model for ad hoc networking. SWIM is relatively simple, is easily tuned by setting just a few parameters, and generates traces that look real—synthetic traces have the same statistical properties of real traces in terms of intercontact times, contact duration, and frequency among node couples. Furthermore, it generates social behavior among nodes and models networks with complex social communities as the ones observed in the real traces. SWIM shows experimentally and theoretically the presence of the power-law and exponential decay dichotomy of intercontact times, and, most importantly, our experiments show that predicts very accurately the performance of forwarding protocols for PSNs like Epidemic, Delegation, Spray&Wait, and more complex, social-based ones like BUBBLE. Moreover, we propose a methodology to assess protocols on model with a large number of nodes. To the best of our knowledge, this is the first such study. Scaling of mobility models is a fundamental issue, yet never considered in the literature. Thanks to SWIM, here we present the first analysis of the scaling capabilities of Epidemic Forwarding, Delegation Forwarding, Spray&Wait, and BUBBLE

  • Minimum Order Quantity: 1 student
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    MAP Based Iterative Channel Estimation for OFDM Systems

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    MAP Based Iterative Channel Estimation for OFDM Systems
    Approx. Rs 10,000 / student
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    Iterative channel estimation (ICE) usually exploits soft information of unknown data symbols as references to improve estimation performance. This paper investigates ICE for orthogonal frequency division multiplexing (OFDM) over wireless channels. The optimum ICE is derived in terms of maximum a posteriori (MAP) criterion, which can be solved using fixedpoint iteration (FPI). Furthermore, the derived MAP ICE is closely related to the well-known expectation-maximization (EM) estimation. We also demonstrate that the MAP ICE converges within only one step when the signal-to-noise ratio (SNR) is large through analysis and simulation results.

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    Maximum Likelihood Frequency Estimation and Preamble

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    Maximum Likelihood Frequency Estimation and Preamble
    Approx. Rs 10,000 / student
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    —In multi-cellular WiMAX systems based on orthogonal frequency-division multiple-access (OFDMA), the training preamble is chosen from a set of known sequences so as to univocally identify the transmitting base station. Therefore, in addition to timing and frequency synchronization, preamble index identification is another fundamental task that a mobile terminal must successfully complete before establishing a communication link with the base station. In this work we investigate the joint maximum likelihood (ML) estimation of the carrier frequency offset (CFO) and preamble index in a multicarrier system compliant with the WiMAX specifications, and derive a novel expression of the relevant Cramer-Rao bound (CRB). Since the exact ML solution is prohibitively complex in its general formulation, suboptimal algorithms are developed which can provide a reasonable trade-off between estimation accuracy and processing load. Specifically, we show that the fractional CFO can be recovered by combining the ML estimator with an existing algorithm that attains the CRB in all practical scenarios. The integral CFO and preamble index are subsequently retrieved by a suitable approximation of their joint ML estimator. Compared to existing alternatives, the resulting scheme exhibits improved accuracy and reduced sensitivity to residual timing errors. The price for these advantages is a certain increase of the system complexity.

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    Optimal Windowing and Decision Feedback Equalization

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    Optimal Windowing and Decision Feedback Equalization
    Approx. Rs 10,000 / student
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    Space–frequency block coding with orthogonal frequency-division multiplexing (SFBC-OFDM) suffers from the effect of intercarrier interference (ICI) in doubly selective channels. In this paper, a scheme is proposed in which windowing is applied to the received signal to reduce the effect of ICI to a limited number of neighboring subcarriers. The subcarriers holding the SFBC components of each codeword are separated by a number of subcarriers larger than the ICI range, and hence, they do not interfere with each other. To preserve the structure of the SFBC, the separation between the codeword components is also selected within the coherence bandwidth of the channel. As a result, the diversity gain of the SFBC is preserved. By proper selection of the pilot locations, each OFDM symbol can be divided into subsymbols that can be decoded independently. We show that the proposed windowing technique allows the use of decision feedback equalization to estimate the data transmitted in each subsymbol with low complexity. Simulation results are presented showing the ability of the proposed scheme to significantly improve the performance of SFBC-OFDM and preserve its diversity gain.

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    Outage-Constrained Power Allocation

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    Outage-Constrained Power Allocation
    Approx. Rs 10,000 / student
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    in Spectrum Sharing System

    Due to limited cooperation between the primary users and the secondary users (SUs) in practical spectrum sharing systems, the secondary transmitters and receivers are assumed to have partial channel state information related to the primary receiver. Under such an assumption, this work investigates power allocation strategies for the SUs subject to an outage probability constraint on the primary transmission and a peak transmit power constraint on the secondary transmission. The challenge lies in the non-convexity of the outage probability constraint. Firstly, we prove that strong duality holds and that the Karush-Kuhn-Tucker (KKT) conditions are necessary for optimality. The optimal solution is then derived by addressing the optimality issues of the KKT solutions. Secondly, in order to further reduce the algorithmic complexity, two suboptimal strategies are proposed. The first one is designed based on several simplifications of the optimal strategy. The second one is derived from the convex relaxation of the non-convex primal problem, which corresponds to the problem with the conventional interference temperature constraint. The performance for both suboptimal strategies is derived in closed form. All proposed strategies are shown to outperform non-adaptive power transmission. The near-optimality of the two suboptimal strategies is also validated, in particular for the first one.

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    Outage-Constrained Power Allocation in Spectrum

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    Outage-Constrained Power Allocation in Spectrum
    Approx. Rs 10,000 / student
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    Due to limited cooperation between the primary users and the secondary users (SUs) in practical spectrum sharing systems, the secondary transmitters and receivers are assumed to have partial channel state information related to the primary receiver. Under such an assumption, this work investigates power allocation strategies for the SUs subject to an outage probability constraint on the primary transmission and a peak transmit power constraint on the secondary transmission. The challenge lies in the non-convexity of the outage probability constraint. Firstly, we prove that strong duality holds and that the Karush-Kuhn-Tucker (KKT) conditions are necessary for optimality. The optimal solution is then derived by addressing the optimality issues of the KKT solutions. Secondly, in order to further reduce the algorithmic complexity, two suboptimal strategies are proposed. The first one is designed based on several simplifications of the optimal strategy. The second one is derived from the convex relaxation of the non-convex primal problem, which corresponds to the problem with the conventional interference temperature constraint. The performance for both suboptimal strategies is derived in closed form. All proposed strategies are shown to outperform non-adaptive power transmission. The near-optimality of the two suboptimal strategies is also validated, in particular for the first one.

























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    Performance Investigation Of Pilot

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    Performance Investigation Of Pilot
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    Pilot-subcarrier and pilot-tone aided log-likelihood ratios (PA-LLR, PT-LLR), proposed for LDPC coded coherent optical OFDM (CO-OFDM) system, is reviewed in this paper. The knowledge of common phase error based on pilot-subcarriers or pilot-tone is incorporated into the new PA-LLR or PT-LLR metric, which eliminates the need for prior common phase error estimation and compensation. The formulation of both metrics is presented in a unified way. The performance of both metrics, in their approximate versions, is compared against the approximate conventional LLR (AC-LLR) for different modulation formats using different LDPC codes in a back-to-back case. APA-LLR or APT-LLR outperforms AC-LLR for higher-order QAM, with smaller number of pilot-subcarriers (PSCs) or at smaller pilot-tone-to-signal power ratios (PSRs). A time-domain blind intercarrier interference (BLICI) mitigation algorithm is employed to improve the performance, which eliminates the error floor at large laser linewidth. Furthermore, we examine the tolerance of different LLR metrics to linear fiber impairment (chromatic dispersion) or nonlinear phase noise (self-phase modulation), in which case, our metrics still outperform the conventional one. Iterative demodulation using new tentativedecision-based phasor offers almost 1-dB OSNR improvement for smaller number of PSCs. Finally, we also analytically prove that APA-LLR or APT-LLR converges to AC-LLR as the number of PSCs or PSR value increases. The optimal OSNR for calculating noise power is found to be around 10 dB for actual OSNR values beyond 10 dB in either the back-to-back case or after 13 600- ps/nm/km dispersion with channel compensation. APA-LLR and APT-LLR offer better performance than AC-LLR without any increase in complexity.

























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    Phase Noise in Asynchronous SC-FDMA Systems

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    Phase Noise in Asynchronous SC-FDMA Systems
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    Carrier frequency offset (CFO) and phase noise (PN) are major oscillator impairments in direct-conversion transceivers, and single-carrier frequency-division multiple access (SC-FDMA) is the uplink transmission scheme in the Long-Term Evolution (LTE) standard. We derive a new analytical expression for the normalized mean square error (NMSE) in asynchronous SC-FDMA systems under CFO and joint transmit–receive PN. The derived NMSE expression reveals an interesting cross-layer relationship between the subcarrier mapping scheme at the medium-access-control layer and the immunity to CFO and PN at the physical layer. Furthermore, we propose an iterative reducedcomplexity joint decoding and PN compensation scheme that does not require any pilots in PN tracking and exploits the low-pass nature of the PN process without assuming a specific PN model. Simulation results show the effectiveness of our proposed digital baseband compensation scheme in PN mitigation.

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    Quasi-Orthogonal Space-Frequency Coding in Non-Coherent Coop

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    Quasi-Orthogonal Space-Frequency Coding in Non-Coherent Coop
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    So far, complex valued orthogonal codes have been used differentially in cooperative broadband networks. These codes however achieve less than unitary code rate when utilized in cooperative networks with more than two relays. Therefore, the main challenge is how to construct unitary rate codes for non-coherent cooperative broadband networks with more than two relays while exploiting the achievable spatial and frequency diversity. In this paper, we extend full rate quasi-orthogonal codes to differential cooperative broadband networks where channel information is unavailable. From this, we propose a generalized differential distributed quasi-orthogonal space-frequency coding (DQSFC) protocol for cooperative broadband networks. Our proposed scheme is able to achieve full rate, and full spatial and frequency diversity in cooperative networks with any number of relays. Through pairwise error probability analysis we show that the diversity gain of our scheme can be improved by appropriate code construction and sub-carrier allocation. Based on this, we derive sufficient conditions for the proposed code structure at the source node and relay nodes to achieve full spatial and frequency diversity.

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    Resource Allocation Scheme for Energy Saving in Heterogeneou

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    Resource Allocation Scheme for Energy Saving in Heterogeneou
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    —Energy efficiency in communication networks has received increasing attention in both industry and academia. In this paper, we investigate the energy saving issue in a heterogeneous network (HetNet), which is introduced to cellular radio networks to improve capacity and enhance coverage. A HetNet consists of base stations (BSs) with different transmission powers, resulting in systematic power control that is more complex than that in the conventional cellular networks. The main difficulty is addressing the mutual interference between different kinds of BSs. In this paper, we try to minimize the power consumption of an OFDMbased HetNet while satisfying all users’ rate requirements, as well as considering the inter-cell interference. Our general problem formulation leads to a nonconvex optimization task that is generally hard to tackle. We derive a concave lower bound of user’s achievable rate for a given power allocation, based on which an efficient iterative algorithm is developed to solve the formulated problem efficiently. Numerical results show that our proposed resource allocation scheme works well in different scenarios. The energy consumption of the cellular system is reduced dramatically compared to other schemes. Moreover, our proposed algorithm converges quickly and stably, showing great potential for applications.

























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    Resource Allocation for Delay-Sensitive Traffic Over LTE-A

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    Resource Allocation for Delay-Sensitive Traffic Over LTE-A
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    Future wireless networks will face the dual challenge of supporting large traffic volumes while providing reliable service for delay-sensitive traffic. To meet the challenge, relay network has been introduced as a new network architecture for the fourth generation (4G) LTE-Advanced (LTE-A) networks. In this paper, we investigate resource allocation including subcarrier and power allocation for LTE-A relay networks under statistical quality of service (QoS) constraints. By dual decomposition, we derive the optimal subcarrier and power allocation strategies to maximize the effective capacity (EC) of the underlying LTE-A relay systems. Characteristics of optimal resource allocation strategies are identified, and a low-complexity suboptimal scheme is developed through optimizing the subcarrier and power allocation individually. Our result suggests that the optimal subcarrier and power allocation strategies depend heavily on the underlying QoS constraint. For example, in the low signal-to-interference-plus-noise (SINR) regime, when there are less stringent QoS constraints, base stations and relay stations tend to allocate all the power to the best available subcarrier. However, as QoS requirements become more stringent, both base stations and relay stations will spread their power over available subcarriers. On the other hand, in the high SINR regime, regardless of the QoS constraints, base stations and relay stations tend to equally allocate power among available subcarriers.

























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    Sequence Designs for Interference Mitigation in Multi-Cell

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    Sequence Designs for Interference Mitigation in Multi-Cell
    Approx. Rs 10,000 / student
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    We propose a training sequence that can be used at the handshaking stage for multi-cell networks. The proposed sequence is theoretically proved to enjoy several nice properties including constant amplitude, zero autocorrelation, and orthogonality in multipath channels. Moreover, the analytical results show that the proposed sequence can greatly reduce the multi-cell interference (MCI) induced by carrier frequency offset (CFO) to a negligible level. Therefore, the CFO estimation algorithms designed for single-user or single-cell environments can be slightly modified, and applied in multi-cell environments; an example is given for showing how to modify the estimation algorithms. Consequently, the computational complexity can be dramatically reduced. Simulation results show that the proposed sequences and the CFO estimation algorithms outperform conventional schemes in multi-cell environments.

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    Shot Interference Detection and Mitigation for Heterogeneous

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    Shot Interference Detection and Mitigation for Heterogeneous
    Approx. Rs 10,000 / student
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    Heterogeneous networking is a promising solution for improving wireless coverage, relieving overcrowded bandwidth, and enhancing system throughput for next-generation wireless networks. However, one of the main concerns to put through heterogeneous networks is the interference among overlaid cells. In this paper, we consider femtocell uplink transmissions with dynamic and short-period interference (also called shot interference) from macrocell users. It is shown that, without the information on interferer channels between femtocells and macrocells at any base station, femtocell networks suffer from severe performance degradation when they adopt orthogonal frequency-division multiple access (OFDMA) or single-carrier FDMA (SC-FDMA) techniques. To mitigate the stringent shot interference, we propose a precoded FDMA (P-FDMA) transmission with novel detectors. Our results show that the proposed designs collect multipath diversity in the presence of interference without the knowledge of interferer channels, and our designs are robust to the power levels of shot interference. Simulation results validate our theoretical findings.
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    Spectrum Monitoring Using Energy Ratio Algorithm for OFDM-BA

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    Spectrum Monitoring Using Energy Ratio Algorithm for OFDM-BA
    Approx. Rs 10,000 / student
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    This paper presents a spectrum monitoring algorithm for Orthogonal Frequency Division Multiplexing (OFDM) based cognitive radios by which the primary user reappearance can be detected during the secondary user transmission. The proposed technique reduces the frequency with which spectrum sensing must be performed and greatly decreases the elapsed time between the start of a primary transmission and its detection by the secondary network. This is done by sensing the change in signal strength over a number of reserved OFDM sub-carriers so that the reappearance of the primary user is quickly detected. Moreover, the OFDM impairments such as power leakage, Narrow Band Interference (NBI), and Inter-Carrier Interference (ICI) are investigated and their impact on the proposed technique is studied. Both analysis and simulation show that the energy ratio algorithm can effectively and accurately detect the appearance of the primary user. Furthermore, our method achieves high immunity to frequency-selective fading channels for both single and multiple receive antenna systems, with a complexity that is approximately twice that of a conventional energy detector.

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    Stochastic Guard-Band-Aware Channel Assignment with Bonding

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    Stochastic Guard-Band-Aware Channel Assignment with Bonding
    Approx. Rs 10,000 / student
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    —Fading and shadowing along with the primary user dynamics make channel quality in dynamic spectrum access networks uncertain. Furthermore, the imperfect design of filters and amplifiers in wireless devices motivates the need for guard-bands (GBs) to prevent adjacent-channel interference. In this paper, we develop novel stochastic GB-aware sequential and batch channel assignment schemes that aim at maximizing the spectrum efficiency. In line with recent IEEE 802.11 and LTE standards, our schemes support bonding and aggregation. We propose two assignment models for each of the sequential and batch schemes: a static single-stage and an adaptive two-stage. In the static model, channel assignment is performed once such that the rate demands are probabilistically met. The adaptive model is a two-stage model, where the initial assignment may be corrected once uncertainties are partially revealed. We refer to our formulations of the sequential and batch static assignments as chance-constrained stochastic subset-sum problem (CSSP) and chance-constrained stochastic multiple subset-sum problem (CMSSP), respectively. Moreover, we develop stochastic formulations for the sequential and batch adaptive assignments, which we refer to as two-stage CSSP with recourse (CSSPR) and two-stage CMSSP with recourse (CMSSPR), respectively. Finally, we present computationally efficient simpli- fied versions of CSSP and CSSPR with near-optimal performance.

























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