TechRepublic Resources
- A Comparison of Blind Channel Estimation Schemes for ofdm in Fading Channels
- This paper brings together three recently proposed blind detection schemes which are specific to Orthogonal Frequency Division Multiplexing (OFDM) systems. The aim is to study the performance of these schemes in fading channels and thus give a critical comparison of them in the environment where they are most expected to...
- Tags: Algorithm, Singapore, OFDM, Engineering, Performance Management, Wireless, Human Resources, Workforce Management
- White papers
- The Complex Envelope of a Bandlimited ofdm Signal Converges Weakly to a Gaussian Random Process
- Orthogonal Frequency Division Multiplexing (OFDM) systems have been used extensively in wireless communications applications in recent years; thus, there is significant interest in analyzing the properties of the transmitted signal in such systems. In particular, a large amount of recent work has focused on analyzing the variation of the complex...
- Tags: University Of Massachusetts, OFDM, Wireless
- White papers
- Performance of MIMO ofdm Systems in Fading Channels With Additive TX and RX Impairments
- The performance of OFDM based systems is seriously affected by imperfections in system implementation. To gain a better understanding of the influence of these impairments on the performance of multiple antenna OFDM systems, this paper studies a zero-forcing based MIMO OFDM system with imperfections modeled as additive error sources in...
- Tags: Performance, Impairment, MIMO-OFDM, OFDM, Performance Management, Wireless, Human Resources, Workforce Management
- White papers
- Low-Complexity Channel Estimation for Transmitter Diversity ofdm Systems
- Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed for achieving high-bit rate communication required in wireless systems. Transmitter diversity can be used with OFDM system for performance improvement in a fading environment. For these systems the receiver requires channel state information for decoding. This paper proposes a novel low...
- Tags: Transmitter, OFDM, Wireless
- White papers
- On Cyclic Delay Diversity in ofdm Based Transmission Schemes
- Cyclic Delay Diversity (CDD) is a simple approach to introduce spatial diversity to an Orthogonal Frequency Division Multiplexing (OFDM) based transmission scheme that itself has no built-in diversity. It also can be regarded as a Space-Time Code (STC). But in contrast to that there is no additional effort in the...
- Tags: Diversity, Cyclic Delay Diversity, OFDM, Wireless
- White papers
- PAPR and Other Measures for ofdm Systems With Nonlinearity
- This paper discusses the effects of nonlinearity on the performance in transmission of OFDM signals. Furthermore, the paper studies measures related to nonlinearities, such as PAPR (Peak-to-Average-Power-Ratio), with respect to their ability to correctly predict the effect of a nonlinearity in an OFDM system. The paper also proposes new measures...
- Tags: Measure, OFDM, Wireless
- White papers
- A Reduced Complexity, Improved Frequency Offset Estimation for ofdm-Based WLANs
- This paper presents a reduced complexity frequency offset estimation method as a modification to the nonlinear least square (NLS) method. The complexity reduction is achieved by utilizing the Chirp-Z transform. At similar complexity, the estimation performance gain, de-fined as the mean square error ratio between the NLS method and the...
- Tags: Method, WLAN, University Of Texas, Training, Complexity Reduction, Workforce Management, OFDM, Wireless LANs, Wireless, Human Resources
- White papers
- Downlink Multicell MIMO-ofdm: An Architecture for Next Generation Wireless Networks
- Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier transmission scheme that is well-recognized for it's potential for attaining high rate transmission over frequency selective channels. OFDM is thus a promising candidate for mobile broadband wireless and has already been adopted in many high rate wireless communications standards such as DAB/DVB-T,...
- Tags: Network, University Of Washington, MIMO-OFDM, Wireless Network, OFDM, Wi-Fi, Wireless
- White papers
- Asymptotic Performance Analysis for Redundant Block Precoded ofdm Systems With MMSE Equalization
- A multi-carrier OFDM system using a Cyclic Prefix for preventing inter-block interference is known to be equivalent to multiple flat fading parallel transmission channels in the frequency domain. Linear Precoding consists in multiplying by a N x K matrix a K-dimensional vector obtained by serial to parallel conversion of a...
- Tags: Performance, Motorola Inc., OFDM, Performance Management, Wireless, Human Resources, Workforce Management
- White papers
- A Low Complexity ML Channel Estimator for ofdm
- Orthogonal Frequency-Division Multiplexing (OFDM) with cyclic prefix enables low cost frequency-domain mitigation of multipath distortion. However, to determine the equalizer coefficients, knowledge of the channel frequency response is required. While a straightforward approach is to measure the response to a known pilot symbol sequence, existing literature reports a significant performance...
- Tags: OFDM, Wireless
- White papers
- Design of IRA Codes for Non-Coherent Detection With ofdm
- Irregular Repeat Accumulate (IRA) codes are a special class Of Low-Density Parity-Check (LDPC) codes which perform very close to capacity for memory-less channels with coherent detection. Further, they can be encoded and decoded in linear-time. This paper considers the design of a non-coherent Orthogonal Frequency-Division Multiplexing (OFDM) system for block...
- Tags: Texas A&M University, OFDM, Wireless
- White papers
- A Sub-Optimal Joint Subcarrier and Power Allocation Algorithm for Multiuser ofdm
- This paper investigates subcarrier and power allocation in multiuser OFDM. The aim is to maximize the overall rate while achieving proportional fairness amongst users under a total power constraint. Achieving the optimal solution is computationally demanding thereby necessitating the use of suboptimal techniques. Existing sub-optimal techniques either use fixed power...
- Tags: Algorithm, Allocation, OFDM, Wireless
- White papers
- A Least-/ Mean- Squares Approach to Channel Identification and Equalization in ofdm
- This paper proposes an iterative least-/mean- squares approach to channel identification and equalization in OFDM. This is achieved by exploiting the natural constraints imposed by the channel (sparsity and maximum delay spread) and those imposed by the transmitter (pilots, cyclic prefix, and the finite alphabet constraint). These constraints are used...
- Tags: Constraint, Stanford University, OFDM, Wireless
- White papers
- Modified SMI Techniques for Frequency Selective Channels in ofdm
- The Sample Matrix Inversion (SMI) algorithm has been widely applied in the filed of adaptive antenna arrays. However, in Time Division Multiple Access (TDMA) systems with known data sequences, a low cost solution would imply the computation of the beamformer based exclusively on this data. In some cases, this might...
- Tags: Sample Matrix Inversion Algorithm, OFDM, Wireless
- White papers
- A Low Complexity Antenna Diversity Receiver for ofdm Based Systems
- A low complexity antenna diversity architecture with a new combining technique suitable for Orthogonal Frequency Division (OFDM) based systems is introduced in this paper. For a two branch antenna diversity, this structure requires only one FFT at the receiver and allows optimum maximum ratio combining. For systems with a higher...
- Tags: Technique, OFDM, Productivity, Wireless
- White papers
- Comparison of Iterative Detection Schemes for MIMO Systems With Spreading Based on ofdm
- This paper considers a coded transmission over a time-invariant MIMO channel, where channel state information is present at the receiver but not at the transmitter. As basic modulation technique OFDM is applied. In addition to MC-CDM spreading techniques, the paper introduces a new class of spreading matrices that works both...
- Tags: Technique, MIMO, OFDM, Productivity, Wireless
- White papers
- Optimum Signaling for MIMO-ofdm Systems With Interference
- Optimum signaling is studied for Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems with multiple links which mutually interfere. Numerical results show that using the optimum approach for cases without interference does not always achieve system capacity. In some cases, the overall system performance is improved by forcing users to...
- Tags: Lehigh University, MIMO-OFDM, OFDM, Wireless
- White papers
- Receiver Algorithms for ofdm Systems in Phase Noise and AWGN
- This paper addresses the subject of reducing the impact of phase noise on a QAM-OFDM system transmitting over an AWGN channel. Phase noise is known to have two effects on OFDM systems, rotating each symbol by a different Common Phase Rotation (CPR) and producing an InterCarrier Interference term (ICI) that...
- Tags: Algorithm, Noise, OFDM, Engineering, Wireless
- White papers
- Blind and Semiblind Spatio-Temporal Diversity for ofdm Systems
- Adaptive antenna arrays can be used to improve the performance of Orthogonal Frequency Division Multiplexing systems. They are usually applied in the frequency domain, after the FFT demodulation. In this paper, the selected algorithms are applied in time domain. A blind method is firstly proposed for the maximization of the...
- Tags: Algorithm, Method, Domain, OFDM, Engineering, Wireless
- White papers
- On the Effect of Inband Signaling and Realistic Channel Knowledge on Dynamic ofdm-FDMA Systems
- Dynamically assigning subcarriers of OFDM systems to multiple different terminals in a cell has been shown to be beneficial in terms of different transmission metrics. However, the success of such a scheme depends on the ability of the access point to inform terminals of their newest subcarrier assignments as well...
- Tags: Knowledge, Berlin, OFDM, Wireless
- White papers
