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Mitigating Inter-cell Interference (ICI) and ensuring seamless high-quality communication are two challenging issues for OFDMA systems. Cell-level coordinated resource allocation and handover (HO) are the two key technologies for achieving these goals. They have been investigated intensively, however, mainly separately. In this paper, a novel combined Handover Guarantee and Interference Mitigation...
In multi-cell OFDMA systems, inter-cell interference can severely degrade the system throughput, particularly for cell-edge users. To mitigate the inter-cell interference problem, interference coordination is a promising approach that effectively restricts and allocates certain resources among users in different cells to minimize the effect of inter-cell interference. However, most approaches are...
We study the performance of a two-hop full-duplex OFDM relay link, where the relay, or in-band repeater, amplifies and forwards its input signal on the same channel as the main transmitter. We derive new closed-form expressions for the end-to-end signal-to-interference and noise ratio (SINR) when the multipath channels are modeled with clustered exponential power-delay profiles. Our system model incorporates...
This paper proposes multipath division turbo equalization with block inter-carrier interference cancellation (MD-BIC) for orthogonal frequency division multiplexing (OFDM). When the multipath delay difference exceeds the cyclic prefix (CP) length, the OFDM transmission performance suffers severely due to inter-symbol interference (ISI) and inter-carrier interference (ICI). Cellular systems with amplify-and-forward...
Today, the buzzword is high-data rate wireless connectivity without mobility constraints. The provision of high rates to users, anytime and everywhere is challenged by the time-varying wireless medium and dynamic nature of interference. Primarily, this challenge is directly related to the limited radio resources, spectrum in particular, and energy (i.e., power) to a certain extend. Therefore, a practical...
This paper investigates the sidelobe suppression techniques of orthogonal frequency division multiplexing (OFDM) based cognitive radio (CR) systems. We firstly argue that the existing sidelobe suppression algorithms cannot satisfy the special requirements of CR systems. Then we formulate the interference suppression problem of CR systems into two algorithms from capacity perspective, namely, average...
As a well attractive modulation scheme, minimum-shift keying (MSK) has a fast roll-off side-lobe spectrum. Because of this excellent property, we introduce MSK into the conventional OFDM to form an improved OFDM-MSK system. The new system can effectively overcome the carrier frequency offset (CFO), mitigate the interference among the sub-carriers. And two kinds of OFDM-MSK receiver are discussed in...
In this paper, we present an improved iterative interchannel interference (ICI) cancellation and signal detection technique for orthogonal frequency division multiplexing (OFDM) system on fast time-varying fading channel with nonintegral-delay. As a consequence of the time-varying channel, the orthogonality of subcarriers is destroyed, resulting in interchannel interference (ICI), which increases...
A well-known problem of OFDM signals is their high peak-to-average power ratio, which can cause the clipping of peaks in the transmitted signal due to the limited linear range of high power amplifiers. Operating the amplifier solely in the linear region, i.e., with a large output back-off, results in an undistorted transmitted signal, but at the expense of a low SNR at the receiver. Driving the amplifier...
This paper presents a technique for maintaining good broadband transmission quality in the face of impulsive noise in OFDM-PLC systems. The proposed technique is based on adding one zero between two signal samples in order to estimate the noise power in every transmitted signal sample. Simulation results of complete PLC system highlight good improvement in BER and correction ability performances for...
Soft frequency reuse is a strong tool for co-channel interference mitigation in cellular OFDMA/LTE networks. The performance of such networks significantly depends on the configuration of the power masks that implement the soft frequency reuse patterns. In this paper, we investigate the performance of different power mask configurations against the optimal case, in which a central entity optimally...
Transmission schemes based on orthogonal frequency division multiplexing (OFDM) are promising for underwater acoustic (UWA) communications, thanks to their robustness to large multipath spreads. On the other hand, due to the significant time variations in the UWA channels, the effectiveness of the standard OFDM receivers is impaired by intercarrier interference (ICI). In this paper, we propose two...
In this paper, a low complexity ordered successive interference cancellation (OSIC) equalizer based on minimum-mean squared error (MMSE) criterion is proposed for suppressing intercarrier interference (ICI) caused by time-selective channels in OFDM systems. The proposed scheme exploits a low complexity MMSE equalizer and a partial MMSE-OSIC equalizer appropriately, according to symbol selection algorithm...
In order to avoid inter-cell interference, OFDMA networks are flexible in terms of radio resource management techniques, supporting different frequency reuse schemes (FRSs), which in turn, may decrease inter-cell interference and increase network performance. However, because most of them are based on fix patterns, these FRSs cannot cope with the uneven distribution and dynamic behavior of the traffic...
A precise estimation of SFO (Sampling Frequency Offset) is an important issue in OFDM (Orthogonal Frequency Division Multiplexing) system. However, the conventional method causes serious performance degradation of SFO estimation in low SNR (Signal to Noise Ratio) or large Doppler frequency environment. Therefore, in this paper, we propose a SFO estimation method which can achieve stable operation...
This paper introduces a new method for distributed interference mitigation in full spectral-reuse OFDMA cellular networks. This considers the use of pre-defined frequency-domain power profiles helping make the interference more predictable across the subcarriers. We propose a method for computing the power profiles so as to maximize the capacity of the system in case of maximum throughput scheduling,...
In this paper, a MIMO-OFDM system without cyclic prefix (CP) is considered and a two-step signal detection algorithm is proposed. The algorithm is based on some structural properties derived from shifting the received OFDM symbols. The first step cancels inter-carrier interference (ICI) and inter-symbol interference (ISI) with an equalizer designed using second-order statistics of the shifted received...
Direct-conversion receiver (DCR) architecture has received considerable attention recently owing to its portable architecture and superior performance in terms of power and cost over its super-heterodyne counterpart. Flicker noise is one of the major impairments which severely affects the performance of the system. In this work, we investigate the use of signal processing techniques in the mitigation...
The advanced MIMO (multiple-input multiple-output) system can provide higher capacity gain or higher diversity gain in modern wireless networks. The capacity gain is achieved by interference cancellation technique to fully utilize the spatial degree of freedom. In a multiuser wireless system, the increased degrees of freedom provide the chance to select multiple wireless stations (STAs) to maximize...
Inter-carrier Interference is a severe problem in OFDM systems. Frequency offset is a factor which destroys the orthogonality of subcarriers and causes inter-carrier interference (ICI). In the case of insufficient cyclic prefix (CP), delay dispersion of the channel can also lead to ICI. Time variations of the channel over an OFDM symbol duration can be considered as another factor causing ICI. In...
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