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In this paper, we propose a channel estimation scheme in orthogonal frequency-division multiplexing (OFDM) systems based on the recent methodology of distributed compressed sensing (DCS). The joint sparsity model 2 (JSM-2) in DCS theory and simultaneous orthogonal matching pursuit (SOMP) are both introduced to improve the estimation performance and increase the spectral efficiency. Simulation results...
This paper analyzes the performance of space-time block coded orthogonal frequency division multiplexing (OFDM) systems. In our analysis, we abandon the usually made assumption of quasi-static channel conditions. Instead of this, we consider the more general and realistic case that the channel envelope changes during two consecutive transmission time slots. In addition, we take the spatial correlation...
In this paper, we first investigate two efficient inter-carrier interference (ICI) self-cancellation schemes for orthogonal frequency division multiplexing (OFDM) systems, conjugate cancellation (CC) and phase-rotated conjugate cancellation (PRCC), by examining their system structures and performances. Then, we propose an adaptive receiver design based on conjugate transmission for ICI self-cancellation...
In this paper, for the first time, an Ant Colony Optimization (ACO) based algorithm is used to solve the bit and subcarrier resource allocation problem of single-cell OFDMA systems. It results in a directed multigraph if the vertexes are used to represent the subcarrier and each path corresponds to a possible chosen modulation index of a specific user. Earlier studies which applied evolutionary algorithms...
Orthogonal frequency division multiplexing (OFDM) systems require the knowledge of signal-to-noise ratio (SNR) at the receiver in order to maximize the system performance. In general, the noise variance is required by the SNR estimator and the knowledge of noise variance also improves the performances of carrier frequency offset (CFO) and channel state estimations. This paper first investigates the...
In the next generation wireless systems, it's quite likely that a large number of user terminals are not able to transmit and/or receive over the entire system bandwidth, as much wider system bandwidth, e.g., 100 MHz, is expected to be employed in the future. As a new and challenging problem, user terminal bandwidth limitation is considered in this paper, and multiuser resource allocation for orthogonal...
In this paper, we study resource allocation in a downlink OFDMA system assuming imperfect channel state information (CSI) at the transmitter. To achieve the individual QoS of the users in OFDMA system, adaptive resource allocation is very important, and has therefore been an active area of research. However, in most of the the previous work perfect CSI at the transmitter is assumed which is rarely...
In this paper, we study the resource allocation problem in relay aided two-hop uplink multi-user transmission with a single relay node and a single destination node. The orthogonal frequency division multiple access (OFDMA) is adopted as the main transmission modulation. We investigate the problems of subcarrier allocation, subcarrier coupling, and power allocation. The optimization is formulated...
In this paper, we develop a simple blind channel estimation algorithm for two-way relay network (TWRN) that consists of two terminal nodes and one relay node. We consider the frequency selective channels and adopt the orthogonal frequency-division multiplexing (OFDM) modulation to compensate the inter-symbol interference (ISI). By applying a non-redundant linear precoding at both terminals, we propose...
A time-varying channel estimation method for orthogonal frequency division multiplexing (OFDM) systems is presented. The proposed method makes use of two asymmetric pilot symbols to improve channel estimation performance and meanwhile obtain a reasonable pilot overhead. Complete simulations illustrate that the proposed method can have precise estimation result even under very large normalized Doppler...
Zero-Padding Orthogonal Frequency Division Multiplexing (ZP-OFDM) has been proposed as an alternative solution to coded-OFDM, which often incurs high decoding complexity. Various ZP-OFDM receivers have been proposed in the literature, exchanging performance with complexity. On the contrary, we propose in this paper a novel reduced-complexity minimum mean square error (MMSE)-based receiver for ZP-OFDM...
We consider the robust linear precoding (LP) and Tomlinson-Harashima precoding (THP) schemes for multiuser MIMO-OFDM downlink channels with limited feedback. Benefiting from the correlation of spatial channels, the mobile terminal compresses and feeds back the time-domain channel vectors instead of the corresponding frequency-domain vectors to substantially reduce the feedback signalling overhead...
Envelope elimination and restoration (EER) power amplifier architecture can achieve high efficiency and linearity. However, when used with modern modulation schemes such as orthogonal frequency division multiplexing (OFDM) and wideband code division multiple access (W-CDMA), it suffers from expanded bandwidth problem. This paper shows that, the straightforward bandwidth limitation results in poor...
This paper investigates the impact of carrier frequency offset (CFO) on Single Carrier wireless communication systems with Frequency Domain Equalization (SC-FDE). We show that CFO in SC-FDE systems causes irrecoverable channel estimation error, which leads to inter-symbol-interference (ISI). The impact of CFO on SC-FDE and OFDM is compared in the presence of CFO and channel estimation errors. Closed...
In this paper, we will study the joint problem of power allocation, relay selection and subchannel pairing in OFDM based amplify-and-forward multiple relays system. The optimization problem of maximizing system capacity under joint power constraint at source and relays is firstly formulated. Then, based on Lagrangian dual method, an optimal algorithm to the problem is derived with high SNR assumption...
This paper investigates a novel efficient automatic modulation classification (AMC) algorithm in wireless time division duplex (TDD) orthogonal frequency division multiplexing (OFDM) systems with adaptive modulation (AM). Starting from the well-known maximum-likelihood (ML) classification metric for digital quadrature amplitude modulation (QAM) schemes, partial channel reciprocity in TDD-based adaptive...
In this paper, we report on a mobile broadband wireless access (MBWA) system field trial with Fast Low-latency Access with Seamless Handoff Orthogonal Frequency Division Multiplexing (FLASH-OFDM), which was carried out at Sendai city in Japan. This paper describes coverage estimates of an uplink 16 quadrature amplitude modulation (QAM) signal under the condition of constant terminal output power when...
For Mobile WiMAX, data rate and throughput figures are often presented in literature. However, the used calculation methods and the influence of the packet size on the data rate are often unclear. Therefore, we develop a new method in order to obtain more precise data rate figures at the MAC (Medium Access Control) layer. In this paper the common physical data rate and MAC data rate calculation method...
This paper addresses the sampling jitter estimation and cancellation task in direct RF sub-sampling type radios. The proposed jitter estimation method is based on carefully injecting or superimposing an additional known reference signal to the received signal at the sampler input. Proper digital signal processing methods are then devised and applied to estimate the sampling jitter realizations from...
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