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MANETs are vulnerable to a number of security threats due to their flexible characteristics such as dynamic topology formation, openness of the wireless medium and resource constraints. Wormhole attack is one of the most sophisticated forms of security threats in MANET wherein two or more colluders silently record packets at one location and then tunnel them to another location in the network. As...
This paper proposes a new blind algorithm for joint carrier offset estimation and data detection, which is based on particle filtering and recursively estimates the joint posterior probability density function of the unknown transmitted data and the unknown carrier offset. We develop new guidelines for resampling of the particles to take into account carrier offset estimation ambiguity at the edges...
TCH (Tomlinson, Cercas and Hughes) sequences have been studied for code-spreading and channel coding, but their true purpose is for synchronization and channel estimation. This is due to their property of being (virtually) orthogonal to all of their sequences obtained via circular shifts, and the use of the FFT (Fast Fourier Transform) for decoding. This property is extremely useful for time-offset...
This work is inspired by the general question of how to choose signaling points from a bounded set such that capacity of the corresponding channel is maximized. Since subject to peak power constraints capacity achieving distributions become discrete, this question is most relevant for practical application. However, a solution seems to be difficult in general. In this paper we confine ourselves to...
This paper investigates LTE-Advanced uplink technologies. In order to support several requirements of LTE-Advanced, we propose new architecture and scheduling grant information. The link performance of LTE-Advanced is evaluated by MMSE in the uplink single user spatial multiplexing with two transmit antennas. Our simulation results show that the target peak data rate of LTE-Advanced uplink exceeds...
The capacity of a millimeter wave propagation channel with multiple antennas is investigated focusing on the minimum antenna spacing required for taking a full advantage of multi-input multi-output (MIMO) systems. Especially, the effect of reflected paths is studied on the required minimum antenna spacing. A signal following a reflected path is assumed not to experience scattering which accompanies...
This paper proposes a new method for classifying Digital Modulations, including the typical PSK (Phase Shift Keying), FSK (Frequency Shift Keying), ASK (Amplitude Shift Keying) as well as the present OFDM (Orthogonal Frequency Division Multiplex) modulation. The method is based on the analysis of the time frequency representation of the digitally modulated signals. At first, some experiments have...
This paper investigates a Slotted ALOHA protocol for a multi-user wireless system operating under partial Line of Sight (LOS) conditions in which both the base station and mobile users are equipped with multiple element antennas. The investigations focus on how physical layer parameters such as spatial correlation, mutual coupling and Rician factor K affect the system capacity. Probability model for...
The estimation of Retransmission Timeout (RTO) in Transmission Control Protocol (TCP) affects the throughput of the transmission link. If the RTO is just a little larger than the Round Trip Time (RTT), retransmissions will occur too often, and this increases congestion in the transmission link. If the RTO is much larger than the RTT, the response to retransmit when a packet is lost will be too slow,...
In this paper, we present the performance of maximum likelihood (ML) estimator for number of multipath and SNR scenarios. Here the multipath acoustic channel output signal is modeled as a superposition of the delayed, attenuated, and filtered version of the stationary Gaussian stochastic input signal. Accuracy percentage (AP) performance measure has been used to characterize the performance of the...
This paper investigates the throughput performance of carrier sense multiple access (CSMA) in Rice fading channels. The approach considered includes the signal capture model with coherent and incoherent addition of interfering signals. The case of uniform attenuation for all terminals (or perfect power control) is studied. Analytical and numerical results are presented.
Self-encoded spread spectrum systems derive spreading codes from the data stream and have been shown to achieve a 3 dB power gain while providing time diversity for robust performance in wireless fading channels. Since the receiver does not knowledge of the initial spreading code, these systems present a unique challenge to code synchronization. In this paper, we present a method to achieve code acquisition...
Real-time Electrocardiogram (ECG) telemonitoring is currently being envisaged to provide improved healthcare services for elderly and chronic care patients. A major challenge that arises in this situation is the need to reliably transmit ECG data over bandwidth constrained communications channels where congestion can lead to loss of ECG data. To overcome this problem, we propose a frequency prioritised...
This paper proposes a new blind algorithm for joint carrier offset estimation and data detection, which is based on particle filtering and recursively estimates the joint posterior probability density function of the unknown transmitted data and the unknown carrier offset. We develop new guidelines for resampling of the particles to take into account carrier offset estimation ambiguity at the edges...
In this paper a novel scheme is introduced to perform the soft input decoding of Reed Solomon Codes using iterative bit flipped decoding based on the LLRs of the received bits. MAP is used as the inner decoder to obtain the LLRs for the decoded bits at the receiver. In case of decoding failure or a decoding error by the outer RS decoder, a combination of bits from the received word are flipped based...
A comparative evaluation of speech enhancement algorithms for robust automatic speech recognition is presented. The evaluation is performed on a core test set of the TIMIT speech corpus. Mean objective speech quality scores as well as ASR correctness scores under two noise conditions are given.
Spectrum sensing plays a vital part in cognitive radio (CR) communication. In this paper, we consider a novel proactive sensing scheme that helps combat the hidden-node problem, while increasing certainty in the decision of spectrum occupancy. We extend this scheme by limiting the power of the probing signal used in carrying out proactive detection, with constraints set based on the interference threshold...
In this paper, we consider a relay system with a number of potential relay nodes. We propose several relay assignment protocols to select a relay node to help transmit source data so that the average outage probability of the system is reduced. These protocols include: Optimal-Position relay assignment, Nearest-Optimal-Position relay assignment, and Left (Right)-Nearest-Optimal-Position relay assignment,...
In multiple-input multiple-output (MIMO) relay network relaying at the relay nodes is performed during two phases: broadcasting phase and cooperative phase known as multiple access phase. The main question is, which is the best receiver able to increase the distributed diversity gain in MIMO relay network for spatial multiplexing (SM) scheme and time division multiple access (TDMA) or multi-carrier...
Multipath fading effects and co-channel interference are the main limitations facing wireless communication systems. The problem to enhance the capacity of a code-division multiple-access (CDMA) in wireless communication system can be solved implementing an interference management. Many techniques controlling or suppressing an interference in CDMA wireless communication systems by transmitter and/or...
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