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Small-scale fading has its origin in the constructive and destructive superposition of electromagnetic waves. The fading process can be modeled by adding vectors in the complex plane using the so-called phasor model. Simulation results showed that this modeling allows very accurate reproduction of measured fading processes. The parameters of the phasor model can be obtained from measured Doppler power...
This paper investigates the performance of delay diversity with subcarrier-based signal phase rotation in an OFDM system. Delay diversity achieves transmit diversity with channel coding by intentionally ingenerating paths which have different delays at a transmitter side. However, the correlation between subcarriers is not always low. The proposed scheme which combines the delay diversity and the...
For efficient sensor coverage of large industrial and incident areas, fast and flexible strategies for collecting optical sensor data through an autonomous, wirelessly connected swarm of Micro Unmanned Aerial Vehicles (MUAV) is still an emerging challenge. Of particular interest are strategies for spatial coverage optimization of mobile networks and the acquisition of high quality image material targeting...
In this paper, we propose a channel prediction-based user selection algorithm for a single-cell wireless network with multiuser environments. The proposed algorithm focuses on mitigating the degradation of performance due to a feedback process. In particular, by using the Naive Bayes (NB) classifier, the proposed algorithm selects the user who is expected to have the biggest channel gain after feedback...
This paper concerns delay analysis for Fair Power Allocation Strategy (FPAS) in multi antenna Broadcast Channel (BC). It is assumed the transmitter aims at sending individual information to a large number of single-antenna users (n) through a common wireless channel. Assuming there is a total transmit power constraint, the FPAS attempts to select the maximum number of active users in which each can...
This paper presents a novel technique to save the transmitting power of spread-spectrum communication systems based on the application of delay diversity. The core idea of this delay-diversity system is to delay two spreading sequences that carry the same information of a bit with respect to each other in order to statistically separate the influence of fading on the same bit in time domain. The theoretical...
This paper presents a statistical characterization of one Human Body Communication (HBC) channel model based on empirical data. The measurements which were conducted on a considerable amount of people guarantee the precision of the model. An adequate evaluation about the path loss, delay spread is convenience and appropriate to design the advanced wideband HBC system.
This paper considers effective capacity region of two-user opportunistic spectrum access in fading channel under discrete transmission rate policy. Although opportunistic spectrum access has been regarded as a promising solution to the the problem of spectrum inefficiency and scarcity, little attention is given to capacity analysis under QoS constraint. Since discrete transmission rate policy is more...
The high dynamic vehicle, a hotspot in the military research currently, has an important strategic value. TT&C and communication system is the core of information guarantee for the vehicle. To assess the performance and reliability of the communication links, aeronautical channel model in dynamic environment is required. In this paper, a stochastic channel model for the TT&C and communication...
Targeting to the DFM system, which is a digital version of FM and used in the VHF-FM band, the paper proposes a scheme of multimode OFDM-parameters design. The design can not only counteract the multi-path delay and Doppler shift of the DRM-Plus-related wireless channel, but also reduce the implementation complexity. The new diversity techniques CDD help to solve the flat fading problem. Simulations...
Modern communication system is restricted by the underwater communication. the underwater acoustic channel is probably one of the most complex environments for data communication, the main reasons of bit-error-rate in underwater acoustic communication are serious multipath fading and Dopppler shift, the direction of underwater acoustic communication's development is the data transmission with low...
Parameter design of Decision Feedback Equalization (DFE) in high rate DS-UWB system is involved with a challenge in the absence of practical optimized strategy, while the parameter group including the feedforward filter (FFF) length Nf, the feedback filter (FBF) length Nb, and decision delay D greatly affects both performance and complexity. In this paper, an efficient method aiming at achieving quasi-optimum...
This paper examines radio wave propagation in underground and subway environments from the perspective of providing digital radio with multimedia and video enhanced services (DAB/DMB) as a continuity of the same services offered above ground. To this end, a preliminary simulation framework of a DAB/DMB transmission system inside a rectangular subway tunnel is proposed. First, the received power and...
The performance of multi-hop multiple-input, multiple-output (MIMO) communication scenarios is evaluated for space time block coded (STBC) and the proposed distributed cyclic delay diversity (CDD) technique. By increasing the frequency selectivity, multi-stage CDD with low complexity implementation yields significant performance improvement as relaying network. Both diversity techniques based on frequency-correlated...
Communication between two neighboring nodes is the most basic operation in wireless networks. Yet very little research has focused on the local delay, defined as the mean time it takes a node to connect to a nearby neighbor. This problem is non-trivial when link distances are random but static, as is the case when the node distribution of a static network is modeled as a stochastic point process....
Fourth Generation Networks will invariably adopt MIMO-OFDMA techniques, in order to cope with increased data rate demands and improved Quality of Service (QoS) requirements. OFDMA is a popular multiple access candidate, since it facilitates multi-user diversity by enabling two dimensional multiple access, in time and frequency domains. Random Beamforming enables exploitation of spatial multi-user...
In this work, we investigate secret key generation from channel states. We point out, by means of a packet-delay-based attack, that observing its own channel states is not the only way an adversary can learn about the channel states of the legitimate communicating parties. The attack suggests that it is not secure to transmit data via the channel whose states generate secret keys. However, not using...
Orthogonal frequency division multiplexing (OFDM) systems have enjoyed widespread adoption in high data rate wired and wireless networks, due to their ability to efficiently cope with slowly varying dispersive channels. This paper considers the information theoretic secrecy rates that are achievable by an OFDM transmitter/receiver pair in the presence of an eavesdropper that might either use an OFDM...
In this paper, we evaluate the delay experienced by Poisson arriving packets for Cooperative truncated HARQ with opportunistic relaying in the presence of a noisy feedback channel. We derive the theoretical expressions of the expected waiting time and the packet's sojourn time in the queue of truncated opportunistic cooperativeARQ and Hybrid ARQ I, with and without Packet Combining (PC), and Hybrid...
In this paper we analyze the Ricean K-factor for vehicle-to-vehicle (V2V) communications in a typical open sub-urban street crossing. The channel conditions vary from non line-of sight (NLOS) to line-of-sight (LOS). The antenna arrays used for recording the radio channels consist of 4 elements with directional radiation patterns. We measured 16 individual single-input single-output channels, with...
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