Search results for "OFDM"
showing 10 items of 27 documents
MUSIC-LS Modal Channel Estimation for an OFDM-OQAM System
2008
Orthogonal frequency division multiplexing based on offset quadrature amplitude modulation (OFDM-OQAM) signaling over frequency selective multipath channels shows inter-symbol interference (ISI) and Inter-Channel Interference (ICI) that degrade its performance. Channel equalization and channel estimation are needed to combat these intrinsic interferences. In this paper a novel modal channel estimator based on the MUltiple signal classification (MUSIC) and least squares (LS) algorithms for a wideband passband OFDM-OQAM signaling over static multipath channels is presented. The effects of the frequency selective channel on the received signal are described considering a wideband OFDM-OQAM sys…
MUSIC-based modal channel estimation for wideband OFDM-OQAM
2008
Orthogonal frequency division multiplexing based on offset quadrature amplitude modulation (OFDM-OQAM) over wideband frequency selective multipath channels suffers from inter-symbol interference (ISI) and inter-carrier interference (ICI) that degrade its performance. Channel estimation and equalization are needed to combat these interferences. In this paper a novel channel estimator for passband OFDM-OQAM signaling over wideband multipath channels, which is based on multiple signal classification (MUSIC) with the Spatial Smoothing technique is presented. Numerical simulation results are presented in the low number of subcarriers, i.e. wideband, scenario.
Joint Power Allocation and Link Selection for Multi-Carrier Buffer Aided Relay Network
2019
In this paper, we present a joint power allocation and adaptive link selection protocol for an orthogonal frequency division multiplexing (OFDM)-based network consists of one source node i.e., base station (BS), one destination node i.e., (MU) and a buffer aided decode and forward (DF) relay node. Our objective is to maximize the average throughput of the system via power loading over different subcarriers at source and relay nodes. A separate power budget is assumed at each transmitting node to make the system more practical. In order to form our solution more tractable, a decomposition framework is implemented to solve the mixed integer optimization problem. Further, less complex suboptim…
Energy efficient resource allocation for secure OFDMA relay systems with eavesdropper
2016
In this paper, we address the energy efficient resource allocation problem for a secure orthogonal frequency division multiple access (OFDMA) relay system. In particular, we consider there is a eavesdropper near the base station (BS) which tries to overtake the information sent by BS. We formulate the joint optimization problem with the objective to optimize the energy efficiency of the considered system by considering subcarrier pairing, secret data rate and power allocation. In addition, the system can assign different priority to different users such that the security of information transmission can be guaranteed. The proposed iterative algorithm not only maximizes the system energy effi…
Blind source separation based interference suppression schemes for OFDM and DS-CDMA
2015
In statistical wireless signal processing, extraction of unobserved signals from observed mixtures can be achieved using Blind Source Separation (BSS) algorithms. Orthogonal Frequency Division Multiplexing (OFDM) and Direct Sequence-Code Division Multiple Access (DS-CDMA) can be pronounced as the well established predominant air interface communication techniques. Consequences of an effort taken and counteractive solutions to diminish the undesirable influences encountered within the wireless air interface of those techniques with aid of BSS schemes are disclosed. Filter coefficients for the receiver are ascertained with the support of a set of energy functions and the iterative fixed point…
Architectures and Protocols for Flexible Physical Layers in Wireless Networks
Emerging wireless technologies are characterized by an increasing level of flexibility and programmability, not only in terms of core network functionalities, with the consolidated paradigms of software-defined-networks and function virtualization, but also in terms of radio access functionalities. Although the concept of software-defined PHY and MAC protocols is not new, exploiting flexibility at the lower layers of the protocol stack is not an easy task, because of complexity and performance constraints. Indeed, dealing with software-defined implementations of the radio implies managing complex software routines, often tightly inter-dependent and difficult to reuse, and poses some perform…
Dynamic Adaptations of WiFi Channel Widths Without TX/RX Coordination
2017
Most modern standards for wireless communications support physical layer adaptations, in terms of dynamic selection of channel central frequency, transmission power, modulation format, etc., in order to increase link robustness under time-varying propagation and interference conditions. In this demo, we demonstrate that another powerful solution for extending physical layer flexibility in OFDM-based technologies is the dynamic adaptation of the channel width. Although some standards already define the possibility of utilizing multiple channel widths (e.g. 20MHz, 10MHz, 5MHz forIEEE 802.11a standards), such an utilization is limited to a static configuration of a value defined during the net…
A performance study of LTE MIMO-OFDM systems using the extended one-ring MIMO channel model
2012
In this paper, we consider a long-term evolution (LTE) system for the downlink by using multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) techniques. The downlink channel is modeled by the socalled extended MIMO one-ring model. This model extends the well-known narrowband one-ring model with respect to frequency selectivity. The symbol error rate (SER) performance of the LTE MIMO-OFDM system is investigated for the downlink by employing different kinds of spatial encoders, where it is assumed that the channel state information (CSI) is perfectly known. For comparison, the space-time block coding (STBC) scheme, the vertical Bell Laboratories layered spac…
An Improved Receiver Architecture for Cyclic-Prefixed OFDM
2009
A novel Orthogonal Frequency Division Multiplexing receiver architecture to be employed with standard (e.g. Wireless LAN) transmitters is proposed. It features enhanced error-rate performance with flexible computational complexity and robustness to imperfect channel estimation. It is based on exploitation of the redundancy available in the cyclic prefix after cancellation of interference from the previous block. In order to show the effectiveness of our proposal, a number of comparisons to the standard per-subcarrier receiver and a previously existing method are reported.
Modeling and Performance Analysis of Energy Efficiency Binary Power Control in MIMO-OFDM Wireless Communication Systems
2011
Published version of an article in the journal:International Journal of Distributed Sensor Networks. Also available from Hindawi Publishing: http://dx.doi.org/10.1155/2011/946258 The energy efficiency optimization of the binary power control scheme for MIMO-OFDM wireless communication systems is formulated, and then a global optimization solution of power allocation is derived. Furthermore, a new energy efficiency binary power control (EEBPC) algorithm is designed to improve the energy efficiency of MIMO-OFDM wireless communication systems. Simulation results show that the EEBPC algorithm has better energy efficiency and spectrum efficiency than the average power control algorithm in MIMO-O…