ofdm Resources

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ZDNet Dictionary Definition

OFDM: Orthogonal Frequency Division Multiplexing A digital transmission technique that uses a large number of carriers spaced apart at slightly different frequencies. Although frequency division multiplexing FDM implies multiple...; Full OFDM Definition >>

ZDNet Resources

Channel Estimation Techniques for OFDM Systems: Channel estimation is an important and necessary function for modern wireless receivers. With even a limited knowledge of the wireless channel properties, a receiver can gain insight into the information that was sent by the transmitter. The goal of channel estimation is to measure the effects of the channel on...; Tags: Technique, Channel Estimation, OFDM, Wi-Fi, Wireless; White papers 2007-03-01
A Broadband Underwater Acoustic Modem Implementation Using Coherent OFDM: Multicarrier modulation in the form of Orthogonal Frequency Division Multiplexing OFDM has prevailed in recent broadband wireless systems over radio channels. In the senior design project discussed in this paper, the authors have implemented an acoustic OFDM modem that transmits digital data through sound propagation. This paper demonstrates OFDM transmission...; Tags: Broadband, OFDM, Modems, Broadband Internet, Telecommunications, Wireless, Hardware, Components; White papers 2007-02-26
Microsoft to launch iPhone rival?: Microsoft to launch iPhone rival?Taking the long view?True, WiMAX hasn't hit it's stride yet but given time I see it being everywhere. Especially once the "mesh" parts get hammered out.Oh god A cell phione that crahesGreat look like microsoft is going to try to ruin the cellular telephine market...; Tags: Telecom & Utilities, Wireless LANs, Microsoft Windows Mobile, phone, Microsoft Corp., Apple iPhone, OFDM; Discussion threads 2007-02-09
Microsoft to launch iPhone rival?: Crunch Gear is reporting that it has confirmed rumors of a Microsoft Zune Phone. Would that be a zPhone? According to Crunch Gears Matt Hickey whose hook was a Microsoft filing with the FCC all cell phone manufacturers must register their devices with the FCC:....it looks like MS is working...; Tags: Crunch Gears Matt Hickey, Entertainment, General, Hollywood On Demand, Microsoft Zune, Mobile, Personal Technology, telephone, Telephony, WiMAX, Wired &, Wireless, Zune Phone; Blog posts 2007-02-09
Approaching MIMO-OFDM Capacity With Closed-Loop V-BLAST: This paper studies schemes for partial channel feedback in Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) block-fading channels. This paper presents a closed-loop extension of the Vertical Bell Labs Layered Space-Time (V-BLAST) architecture for which the transmit power and rate assignments for each transmit antenna at different OFDM tones are...; Tags: IEEE, MIMO-OFDM, OFDM, Wireless; White papers 2007-02-05

Joint Compensation of Transmitter and Receiver Impairments in OFDM Systems: The implementation of OFDM-based systems suffers from impairments such as in-phase and quadrature-phase IQ imbalances in the front-end analog processing. Such imbalances are caused by the analog processing of the Radio Frequency RF signal and can be present at both the transmitter and receiver. The resulting IQ distortion limits the...; Tags: Compensation, Transmitter, Imbalance, OFDM, Wireless; White papers 2007-01-01
Joint Congestion Control and OFDMA Scheduling for Hybrid Wireline-Wireless Networks: This paper considers joint congestion control and multiuser scheduling in a hybrid wireline and wireless network, where the air interface of wireless links is based on Orthogonal Frequency Division Multiplexing OFDM. For static channels, the paper formulates this cross-layer design as a Network Utility Maximization NUM problem with both wireline...; Tags: Congestion, University Of Minnesota, OFDMA, OFDM, Wi-Fi, Wireless; White papers 2006-12-13
Optimal Training and Pilot Pattern Design for OFDM Systems in Rayleigh Fading: This paper deals with two major considerations for Pilot Symbol Assisted Orthogonal Frequency Division Multiplexing (PSA-OFDM) systems when operated over Rayleigh fading channels. One of them is to decide how many pilot symbols should be used and the other is where to place these pilot symbols, i.e. pilot pattern. Incorporating...; Tags: Training, IEEE, OFDM, Workforce Management, Wireless, Human Resources; White papers 2006-12-01
Low-Complexity Time-Domain ICI Equalization for OFDM Communications Over Rapidly Varying Channels: This paper considers wireless OFDM communications over rapidly varying channels as occurring e.g. in high-mobility scenarios. Here, InterCarrier Interference ICI is the major source of impairment that limits the transmission quality. This paper proposes novel equalizers to combat ICI and enable reliable communications even at high Doppler frequencies. In contrast...; Tags: Channel, Vienna University, OFDM, Wireless; White papers 2006-11-28
Will Aussie patents turn Wi-Fi into a house of cards?: Will Aussie patents turn Wi-Fi into a house of cards?WiMax uses OFDMAWiMax also uses Orthogonal Frequency Division Multiple Access technologyhttp://www.intel.com/netcomms/technologies/wimax/OFDMA and OFDMMobile WiMax (802.16-2005)'s OFDMA has a fair amount in common with OFDM, in terms of subdividing frequencies ranges into subchannels, each of which can carry independent data stream. With...; Tags: government, Wi-Fi, OFDMA, OFDM; Discussion threads 2006-11-21
Joint Compensation of IQ Imbalance and Phase Noise in OFDM Systems: The joint effects of IQ imbalance and phase noise on OFDM systems are analyzed, and a compensation scheme is proposed to improve the system performance. The scheme consists of a joint channel estimation algorithm and a joint data symbol estimation algorithm. In the proposed channel estimation algorithm, the channel coefficients...; Tags: Compensation, Benefits, OFDM, Human Resources, Wireless; White papers 2006-11-19
Adaptive OFDM Techniques With One-Bit-Per-Subcarrier Channel-State Feedback: In the Orthogonal Frequency-Division Multiplexing OFDM scheme, some subcarriers may be subject to a deep fading. Adaptive techniques can be applied to mitigate this effect if the Channel-State Information CSI is available at the transmitter. This paper studies the performance of an OFDM-based communication system whose transmitter has only one...; Tags: Feedback, OFDM, Wireless; White papers 2006-11-01
Dynamic Resource Allocation in OFDM Systems: An Overview of Cross-Layer Optimization Principles and Techniques: Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e. policies) potentially provide significant performance gains for various systems. This paper reviews several aspects of cross-layer system optimization regarding wireless OFDM systems. The paper discusses basic optimization models and...; Tags: Technique, Optimization, Allocation, OFDM, Wireless; White papers 2006-10-30
Efficient Detection of Zero-Padded OFDM Signals With Large Blocks: This paper presents a frequency-domain receiver for ZP-OFDM schemes (Zero-Padded Orthogonal Frequency Division Multiplexing) where the duration of the channel impulse response is a significant fraction of the duration of the OFDM block. The proposed receiver has a relatively low complexity, allowing an FFT-based Fast Fourier Transform implementation. The proposed...; Tags: Block, Receiver, OFDM, Wireless; White papers 2006-10-10
Bandwidth Efficient Channel Estimation Using Super-Imposed Pilots in OFDM Systems: This paper proposes a channel estimation algorithm using super-imposed pilots for OFDM systems. The pilot symbols are added linearly to the modulated data symbol at a fraction of the total transmit power, making the method spectrally efficient. This paper presents a series of iterative and non-iterative receivers in which complexity...; Tags: Bandwidth, Complexity, Performance, IEEE, OFDM, Performance Management, Wireless, Human Resources, Workforce Management; White papers 2006-10-05
Optimal Training Signals for MIMO OFDM Channel Estimation in the Presence of Frequency Offset and Phase Noise: The authors develop robust Mean-Square Error MSE-optimal training signal designs for multiple-input multiple-output orthogonal frequency-division multiplexing channel estimation with frequency offset and Phase Noise PN, and present analytical and simulation results for the frequency-offset and PN effects on channel estimation. The proposed designs are more advantageous for moderate-to-high values of...; Tags: Frequency, Training, MIMO-OFDM, Channel Estimation, OFDM, Workforce Management, Wireless, Human Resources; White papers 2006-10-01
Linear Precoding for Multiuser MIMO-OFDM Systems: This paper develops linear precoding schemes for the downlink in multiuser Multiple-Input Multiple-Output MIMO Orthogonal Frequency Division Multiplexing OFDM systems with multiple data streams per user. The authors extend an existing multiuser MIMO algorithm, that jointly optimizes the power allocation and the transmit and receive filters, to MIMOOFDM systems. One...; Tags: MIMO, Allocation, MIMO-OFDM, University Of Toronto, OFDM, Wireless; White papers 2006-09-28
Performance of Space-Time Block Coded OFDM in Time-Selective Macrocell Channel Environments: Space-time coding was first introduced based on the quasi-static fading channel assumption. In this paper, this assumption is not used as it is assumed that the channel is time-selective Rayleigh fading. As such the orthogonality between subcarries in time-selective channel will not hold, resulting in interchannel interference ISI. To combat...; Tags: Channel, Performance, Environment, IEEE, OFDM, Wireless; White papers 2006-09-26
A Low-Complexity Soft Demapper for OFDM Fading Channels With ICI: This paper presents a low-complexity soft demapper that computes bit Log-Likelihood Ratios LLRs while suppressing Orthogonal Frequency Division Multiplexing OFDM Inter-Carrier Interference ICI. The proposed demapper consists of two stages and can be realized in a fully-parallel architecture. This paper examines uncoded and Low-Density Parity-Check LDPC coded performance over frequency-selective...; Tags: Performance, IEEE, OFDM, Performance Management, Wireless, Human Resources, Workforce Management; White papers 2006-09-13
Implementation of OFDM Into Broadband Wireless Networks: In recent time new broadband wireless technologies such as Wifi and WiMAX emerged on the world markets. Due to its many advantages, OFDM has become the modern choice for these systems. This paper describes fundamental principles of OFDM and analyses its advantages and drawbacks. The paper further introduces multiple access...; Tags: Network, Broadband Wireless, Broadband, Wireless Network, OFDM, Broadband Internet, Telecommunications, Wireless; White papers 2006-09-06