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The wireless communication system used by an Unmanned Aerial Vehicle has special requirements. Two separate data streams are used, one for telemetry and control of the vehicle, and one for payload. The first stream is of relatively low data rate, but must be very robust. The second stream requires high data rate, but a best effort approach is acceptable. Real-time remote control usage mandates low...
OFDM system suffers from inter-carrier interference due to frequency offset produced by the movement of terminals. Several schemes have been proposed to mitigate this type of interference. In this paper, an unscented Kalman filter (UKF) based methodology is addressed to estimate the carrier frequency offset (CFO).We have compared the BER performance of UKF with other schemes and also analyzed the...
In this paper, the problem of adaptive bit and power allocation for coded OFDM systems is considered. With emphasis on low feedback overhead and low complexity, we present a simple adaptive allocation technique, where data are transmitted only using the strongest subcarriers with uniform power and uniform constellation size. Due to the reduced number of used subcarriers, a fraction of coded bits are...
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 consider channel estimation with the use of dedicated pilot signal in multiple-input multiple-output orthogonal frequency division multiplexing wireless systems. The dedicated pilot signal is transmitted through a channel virtually transformed by means of beam weighting. We consider the use of a minimum mean squared error (MMSE)-type estimator that fully exploits the statistics of...
In this paper, the packet combining technique in the downlink OFDMA system is introduced in conjunction with frequency diversity to enhance the reliability of retransmissions and thus reduce the large time delay caused by retransmissions. The novel retransmission technique aims to reduce the maximum number of retransmissions for failed packets, while maximizing the throughput. A suboptimal algorithm...
Low Density Signature-Orthogonal Frequency Division Multiplexing (LDS-OFDM) has been introduced recently as an efficient multiple access technique. In this paper, we focus on the subcarrier and power allocation scheme for uplink LDS-OFDM system. Since the resource allocation problem is not convex due to the discrete nature of subcarrier allocation, the complexity of finding the optimal solutions is...
We investigate an outage optimal adaptive resource allocation scheme for the upstream of two-hop OFDMA based decode-and-forward cooperative relay systems. The objective of this work is to design resource allocation strategy, which addresses the needs of the users minimizing their outage probability. This scheme utilizes the subchannel-pairing and proportional fairness in two-hop multiuser multirelay...
Dynamic OFDMA has been recognized as a promising technique for improving the performance of future wireless cellular systems. However, this potential performance improvement comes at the cost of additional signaling overhead, which can have a non-negligible effect on the system efficiency. In this paper, we propose a new method for optimizing the frame length for the downlink in OFDMA systems. The...
Network coding at the physical layer (PNC) can be used to improve the network capacity in a wireless channel. Broadband analog network coding (ANC) was introduced as a simpler implementation of PNC. The coherent detection and self-information removal in ANC require accurate channel state information (CSI). In this paper, we theoretically investigate an impact of the channel time-selectivity on the...
InterCell Interference Coordination (ICIC) is a major RRM (Radio Resource Management) feature recently included in wireless OFDMA networks. This paper studies OFDMA/ICIC algorithms. The model of networks considered is based on the LTE and WiMAX physical layers. After a state-of-the-art, we compare the simulation results of some of the proposed ICIC algorithms. We propose some adjustments to these...
In this paper, an enhanced orthogonal frequency division multiplexing (OFDM) with offset quadrature amplitude modulation (OQAM) system utilising Walsh- Hadamard transform (WHT) is presented. This system demonstrates high resistance to the multipath transmission. The simulation results over standard ITU channels for pedestrian and vehicular confirm the improvement of the proposed system over the conventional...
In this paper we present the closed form expression of bit-error-rate (BER) of a convolution coded MB-OFDM Ultra-Wideband (UWB) system. The analysis considers the log-normal fading statistics of UWB channels and captures the estimation error variances of timing and carrier frequency offset (CFO) estimation by our already published synchronizers ATS [1] and MBAFS [2] respectively. The derivation invokes...
The linear minimum mean square error (LMMSE) channel estimation has better performance than the least square (LS) channel estimation. However, it requires channel statistics which are often difficult to obtain. In addition, the computational complexity of the LMMSE channel estimation is high because of the inverse matrix computation. In order to overcome these implementation issues, a vector quantization...
A cross-correlation function (CCF) based timing synchronization algorithm of low complexity, applicable for single-band transmission is presented. Novelty of the synchronizer lies in utilization of specific preamble structure of the Multi-band OFDM frame format. This threshold based algorithm also takes care of the fact that stronger multipath components frequently appear on the later clusters. Performance...
The concept of small cells such as femtocell has been regarded as a promising solution to achieve green communication and deal with the coverage hole and growth of traffic within macrocells. However, the unpredictable deployment pattern of such nodes makes static network planing impractical and the overlaying macrocell and femtocell tiers may suffer significant cross-tier interference from each other...
Abstract - High-speed mobility has been a central issue to telecommunication in both theory and practice. Each generation of technology presents unique design and engineering challenges in products and deployments. It is especially critical to a class of upcoming 4G (4th-Generation) mobile broadband systems because of broader spectrum usage, aggressive modulation schemes, and sophisticated adaptation...
In this paper, a new handover technique for OFDM-based mobile mesh networks (MMNs) is proposed to reduce the handover overhead by distinguishing an inter-cluster handover event from an intra-cluster handover event using a hierarchical design concept of a preamble. The proposed handover procedure can simplify scanning procedure and skip/simplify network entry procedure, resulting in a significant reduction...
In this paper we study the performance of a SC-FDMA cellular system when a complete Inter-Cell Interference (ICI) management strategy is implemented. We also introduce a novel sector-and-zone frequency ICI coordination scheme, derived from Fractional Frequency Reuse (FFR), which succeeds on increasing the capacity of an SC-FDMA cellular system. Working together with open-loop Fractional Power Control...
Algebraic Space-Time Codes (ASTC) for MIMO systems are based on quaternion algebras. Thanks to their algebraic construction, the ASTC codes are full-rank, full-rate and have the non-vanishing determinant property. These codes have been proposed for MIMO flat fading channels in order to increase the spectral efficiency and to maximize the coding gain. The purpose of this work is to analyze the performance...
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