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The development of dual polarized digital beamforming techniques shows a bright prospect of high rate Mobile Satellite Communications (MSC). It is a Multi-User Multi-Input Multi-Output (MU-MIMO) network if all user terminals in this network are equipped with dual polarized antennas. The present work focuses on introducing the Proportional Fair (PF) scheduling into this network. The main problem is...
This paper addresses the correlation of fading signal parameters for dual-satellite land mobile satellite (LMS) channels. We use Loo's model to describe the slow and fast variations that occur due to varying shadowing conditions and multipath fading, respectively. Loo's parameters (mean power of direct signal component, standard deviaton of direct signal component, and average multipath power) are...
In this paper, We extended our previous work of QR-RLS based MIMO(Multiple input Multiple output) channel estimation to Mobile Wimax 802.16m system. Mobile wimax system provides high data rate, also fulfills user's requirement like VOD(Video on demand)at very high vehicle speed and also provides better cell coverage area. Channel estimation is crucial part to achieve this goals especially in fast...
This paper describes the signal-to-noise ratio (SNR) estimation based on the preamble in tri-sectored OFDM systems. Several SNR estimators from previous literature suffer degradation in several important fading channel models. This paper proposes an estimation method that takes advantage of the fact that the preamble sequence symbols are assigned to every third subcarrier for each BS sector. Typically...
In this paper, we proposed a new velocity estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems, which is based on the variance of channel frequency response (CFR) of two adjacent OFDM symbols. The proposed algorithm can fast and accurately estimate the velocity in both Rayleigh and Rician fading channels, and is low in computational complexity and memory storage. Simulation...
Virtualization of wireless networks has received more and more research attention. As a means to reduce the investment of mobile network operators and to improve the network performance, LTE (Long Term Evolution) virtualization is one important study cases in the scope of wireless virtualization. To investigate the advantages of virtualization on the LTE air interface, this work starts with an analytical...
Maximum Doppler spread or, equivalently, the vehicle velocity, can be estimated to improve handoff algorithms and tune parameters for systems when channel conditions change. This paper presents a new mobile station velocity estimator based on the normalized auto-covariance of the Rician fading signal and that of the squared envelope respectively of the received signal. The proposed algorithm is based...
In Advanced Long Time Evolution (LTE-A) mobile wireless communication system, the Carrier Aggregation (CA) technique feature was introduced to support large transmission bandwidth. But due to the capacity limit of UE, to measure all component carriers with low latency and cost has been a challenge. In this paper a solution is presented in which only some reference component carriers need to be measured;...
For orthogonal frequency division multiplexing (OFDM) communication systems, the orthogonality among subcarriers is lost in mobile applications due to frequency offset resulting from either transmitter-receiver local oscillator differences or Doppler shift caused by mobility. As a direct result, inter-carrier interference (ICI) is observed on each and every subcarrier, leading to significant performance...
Channel estimation is an important technical issue in mobile communication system, the performance and capacity of mobile communication system are directly influenced by the speed and precision of channel estimation. This paper introduced the definition and the method currently existed of channel estimation firstly, and then proposed a method based on the probability of gain difference by the feature...
Vehicle-to-infrastructure communication for accident avoidance is an important application defined in the IEEE 802.11p. The primary challenge in the current IEEE 802.11p draft standard is the weak performance of channel estimation (CE) in multipath environments due to insufficient pilot density. Therefore, we propose time-domain (TD) CE techniques that can effectively and accurately estimate channel...
With the rapid growth of digital communication in recent years, the need for high speed data transmission is increased. OFDM is a promising solution for achieving high data rates in mobile environment, due to its resistance to ISI, which is a common problem found in high speed data communication. A multiple-input multiple-output (MIMO) communication System combined with the orthogonal frequency division...
Application of second-order statistics of variable fading channels (average level crossing rate and average fade duration) for estimation of time behavior of MIMO-system characteristics is investigated. Mathematical expressions of these statistical parameters for MIMO-system are derived. Verification of the results is conducted using numerical modeling.
The non-symmetric nature of the distortion that NLoS propagation introduces into the measurements when performing location estimation from distance measurements makes standard robust statistical estimation techniques relatively ineffective. In this paper two new window functions obtained by modifying the conventional Huber and Tukey window functions are presented to reduce the error in distance measurements...
Traditional network design may underestimate the dependencies between different layers of the protocol stack and fail to exploit the direct coupling of physical-layer operations to the network topology. In the case of a highly dynamic network, as observed in vehicular communications, the network architecture needs to be able to optimally adapt to the changes brought on by nodes' mobility. In this...
A method for estimating the Doppler spread in mobile orthogonal frequency division multiplexing (OFDM) systems is described. The estimation is based on phase message of time domain channel estimation over several OFDM symbols. In OFDM systems, channel estimation is popularly performed in frequency domain. Channel frequency response estimates are affected by noise and inter-carrier interference (ICI)...
This paper evaluates fixed step algorithm of closed loop power control and investigates an optimum step size for WCDMA communication employing high altitude platforms (HAPs). In CDMA, power control must be used to overcome near-far effect, shadowing and multipath fading. Users who are distributed within HAPs coverage will have different channel characteristic depending on their elevation angle. Therefore,...
We propose and analyze new finger assignment schemes which are applicable for RAKE reception in the soft handover region. These schemes rely on variants of the conventional generalized selection combining (GSC) and the minimum selection GSC schemes in order to choose an acceptable base station and its corresponding paths. Relying on some recently derived results on order statistics, we investigate...
In this paper, an adaptive detection technique for MIMO-OFDM system is proposed. To execute the adaptive detection, existing SMLD technique is considered. The proposed technique selects proper values of V of the SMLD scheme to each subcarrier according to its estimated received power. To estimate the received power, two estimation modes are presented (noise value estimation mode with a preamble and...
In this paper a non-iterative rectangular-type pilot-aided channel estimation algorithm on mobile multiple input-multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is proposed. After minimum mean square error (MMSE) estimation in time direction, channel interpolation must be performed in frequency direction. Recent DFT-based algorithms, in MIMO-OFDM systems, reduce additive...
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