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Vector Coding (VC) is a transmission scheme that can obtain path diversity gain while orthogonalizing multiple symbols. It has been shown that VC can provide good bit error rate (BER) performance compared to orthogonal frequency division multiplexing (OFDM). In addition VC has been proven to be the optimal partition of time domain channel. However, In VC, the eigenvectors of the channel matrix must...
To address the security and performance challenges, a novel smart grid communication system based on the frequency-hopping (FH) technology is investigated in this paper. A new FH sequence set with various levels of Hamming cross-correlation values is proposed for this system in order to endow the power users various qualities of services (QoSs). By using the real measurement, we propose a statistic...
Many shortest path routing protocols have been proposed neglecting the effect of lower layers. Here, the Modified Ad-hoc On Demand Distance Vector routing based on Bit Error Rate (MAODV-BER) is proposed, where the route discovery of AODV has been modified to achieve the stable route by obtaining Bit Error Rate (BER) information from physical layer through cross-layer approach. Due to the use of multimedia...
Software-defined radios have received much attention recently, but only little work has targeted the identification of those components that have the highest impact on the quality of the signal transmission and reception. In this paper we therefore have a closer look at the reception path in wireless communication systems. We provide a general overview of those transmit/receive components which play...
The coherent direct-sequence spread spectrum (DSSS) modulation is a very attractive modulation technique for military communication systems, mainly due to its resistance to interference and low probability of detection (LPD). However, the synchronisation to the spreading code phase in the receiver takes time, which makes this technique less interesting for sending very short messages or to combine...
A proposed delay line combination (DLC) receivers have the unique ability to achieve symbol timing synchronization within a single symbol interval [1]. Although DLC receivers do not require channel estimation, the setting of the integration interval affects the performance measured by the mean square error (MSE) and the bit error rate (BER). In this study, we present an adaptive algorithm to determine...
Spectrum is getting more and scarcer with ever expanding wireless application technology. The new generation technologies such as 3G and 4G are causing more spectrum congestion. The solution for this may lie with use of Cognitive Radio (CR) for communication. In this paper, the performance of a new method is analysed. This method increases the channel efficiency and capacity by allowing both the licensed...
In this paper, we do research about Expectation Maximization (EM) Algorithm for MIMO-OFDM systems (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing). The EM algorithm is analyzed and used to channel estimating and channel tracking. It is shown that EM is an efficient iterative algorithm which can adapt to the fading channel for MIMO-OFDM system.
Because of the features of HAPs networks, TCP performance is challenged. In order to solve the TCP problems, optimization of TCP is researched in this paper. An optimized TCP for HAPs network (TCP-HAP) is proposed. It consists of three mechanisms which are rapid congestion notification, reason of packet loss recognition and traffic oriented congestion control. In TCP-HAP, the congestion message is...
Overlap frequency-domain equalization (FDE) requires no cyclic prefix (CP) insertion. In this paper, a new minimum mean square error (MMSE) weight is derived for the overlap FDE. In the previous paper, the MMSE weight for overlap FDE is derived by approximating the IBI as a white Gaussian variable. However, the IBI is an independent colored noise. We derive a new MMSE weight by taking into account...
We demonstrate stabilization of a delay interferometers (DI) for variable bit-rate DPSK receiver from 40 Gbit/s up to 160 Gbit/s using a wavelength tunable CW laser. The phase difference is continuously tunable by tuning the CW laser. The BER of the received 41.25 Gbit/s DPSK signal was successfully stabilized. No noticeable degradation was observed in the eye patterns when the bit rate is 82.5 Gbit/s...
On the basis of analyzing PMA-DCSK scheme, an enhanced PMA-DCSK scheme was proposed in this paper. Plus, we compared the bit error rate between the enhanced and original Scheme in white Gaussian noise channel, and the performance analysis of the enhanced method was also made under the condition of different numbers of clients and delay time. Theory analysis and simulation results both show that the...
This paper presents the studies for the end-to-end QoS of IP over integrated terrestrial and Next Generation Satellite Network (NGSN) using HTTP web application. We compare between Big-LEO and EuroSkyWay like satellites constellations for the QoS parameters (e.g. delay, loss ratio, throughput and connection duration) of request-response HTTP connections from a remote server in London and a remote...
In this paper, the performance of parallel interference cancellation (PIC) multiuser detector in orthogonal frequency division multiple access (OFDMA) mobile communication systems is investigated. In multiuser systems, the multi-user interference (MUI) degraded the system performance, especially in near-far effect environments. The PIC scheme is proposed to reduce the MUIs and to improve the bit error...
In the present literature, the delay line (DL) in transmitted-reference (TR) system is supposed to be ideal. However, it is in fact impossible to design a DL with perfect phase-frequency characteristic. In this paper, based on the statistical model of group delay ripple (GDR) of the non-ideal DL, we investigate the degradation of average bit error rate (BER) for TR UWB communication system. Through...
Owing to the high data rate of IEEE 802.11n, high-definition video transmission becomes one of its major applications. However, it's still difficult for contention-based MAC layer to provide enough QoS guarantee for such latency-sensitive applications. This paper has analyzed the performance on delay, throughput and packet loss rate in error-prone channels based on the frame aggregation mechanism...
To face QoS constraints of multimedia applications, many researches focus on improving the standard MANET routing protocols. Nevertheless, only few works relating to the comparison of enhanced heuristics are available. In those literature, the comparison parameters are measured through simulations performed mainly under unrealistic conditions. In this paper, we compare BER-based enhancements of AODV...
in this paper, a Space-Time-Frequency block code (STFBC) based on Quasi-Orthogonal designs is proposed over a frequency selective Rayleigh fading channel. The proposed code achieves rate-one and full diversity offered by the MIMO-OFDM channel. For quasi-static channel over adjacent OFDM symbol durations, as numerical results demonstrate, the proposed code introduces a significant performance gain...
MIMO-OFDM technology make full use of space and spectrum resources, it can exponentially increase the channel capacity, so it is one of the core technology of next generation mobile communication systems. In order to estimate the time domain (or frequency domain) response of MIMO-OFDM systems fast and accurately, the traditional SVD estimator is modified in this paper. To reduce the time to compute...
Multipath delay profile models for ITS wireless communications are presented. Assuming roadside-to-vehicle communications and vehicle-to-vehicle communications, propagation measurement was carried out using 700MHz spectrum and delay profile models are established based on the measured data. In the paper, the method to extract the delay profile models from the measured data is firstly presented. The...
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