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To fully exploit frequency diversity in cyclic delay diversity orthogonal frequency division multiplexing (CDD-OFDM) system, accurate channel estimation is crucial. Due to the excessive channel delay spread in CDD, traditional in-band pilot assisted channel estimation with limited frequency resolution fails to track the considerable variation in the frequency domain. Alternatively, increasing pilot...
Spectrum awareness is one of the most challenging requirements in cognitive radio (CR). To adequately adapt to the changing radio environment, it is necessary for the CR to be able to perform joint detection and classification of low signal-to-noise ratio (SNR) signals. In this paper we propose a joint detection and classification algorithm for the mobile Worldwide Interoperability for Microwave Access...
Since the IEEE 802.16 first standard was proposed in 2004 to provide broadband wireless service, the standard has not only been widely studied, but also broadly commercialized. The current IEEE 802.16-2009 standard document specifies five Quality of Service classes. As is typical with most standards, IEEE 802.16 does not require the use of a specific scheduler. In this paper, we first evaluate the...
In this paper, we investigate the impact of the a priori channel state information (CSI) on the orthogonal frequency-division multiplexing (OFDM) system performance. A joint iterative channel estimation, detection and decoding receiver involving the dual diagonal linear-minimum-mean-square-error (DD-LMMSE) algorithm is employed. We show that the discrepancy between the a priori CSI and true CSI has...
This paper presents a novel analytical derivation of the false alarm probability (FAP) and detection probability (DP) for non-line-of-sight (NLOS) detection based on LTE signals. Position estimation in indoor or urban area with cellular wireless communication systems is getting more and more important. However, especially in these environments NLOS propagation causes positioning errors in the order...
Based on differential properties of the received preamble, a novel start of packet (SoP) detection and synchronization approach is developed for the IEEE802.11n MIMO-OFDM WLAN system to obtain better mean and variance of timing estimates and lower missing packet and false alarm rates.
The paper describes the transmission of BPSK signals in an OFDM system with 64-point IFFT at transmitter and FFT at receiver. The channel over which transmission will take place is ISI Rayleigh fading channel given by 2 tap channel model with path delay [0, 0.5] μs. The sampling frequency of OFDM is to be kept at 20MHz. Cyclic prefix for OFDM is calculated for improving bandwidth efficiency of the...
In this paper, we propose an area and power efficient pipeline FFT processor for 8×8 MIMO-OFDM systems. The proposed FFT processor is based on mixed-radix multipath delay commutator (MRMDC) architecture in terms of low complexity and high memory utilization. A conventional MRMDC FFT processor increases hardware scale due to delay commutators which are used to change the order of the input sequences...
This paper presents a novel eight-parallel 128/256-point mixed-radix multi-path delay commutator (MRMDC) FFT processor for orthogonal frequency-division multiplexing (OFDM) systems. The proposed FFT architecture can provide a higher throughput rate and low hardware complexity by using an eight-parallel data-path scheme, a multi-path delay commutator structure and an efficient scheduling scheme of...
Wireless OFDM receivers are subject to sample timing errors, causing both sample period and phase errors. Frequency errors lead to loss of orthogonality between subcarriers, resulting in inter-carrier interference (ICI). On the other hand, phase errors lead to erroneous interpretation of the symbols, which degrades the system performance by increasing the BER. In this paper, a time tracking loop is...
The interpolation of complex signals is frequently encountered in the signal processing chains of high performance transmission systems. Linear interpolation might be inappropriate for this kind of situation and, here, geometric interpolation is proposed instead. Specifically, it is proposed, in a Filter Bank-based Multi-Carrier/Offset QAM (FBMC/OQAM) transmission system, to use geometric interpolation...
This paper studies QoS-guaranteed fair resource allocation and packet scheduling for OFDMA networks. We start with non-traffic-aware weighted generalized proportional fair (WGPF) scheduler and make it a delay-fair scheduler. Delay-fair objective is to equalize delay dissatisfaction measures among users. In this paper the focus is on mean queuing delay. We show how the WGPF objectives are connected...
In this paper the joint effects of the inter-cell macrodiversity schemes combined with intra-cell spatial multiplexing are investigated for MIMO-OFDM systems. We compare the SINR and throughput performances of cellular Alamouti, cellular cyclic delay diversity (CDD) schemes and pure macrodiversity at the cell edge. Our simulation results indicate that cellular Alamouti scheme outperforms cellular...
Motivated by the possibility of decreasing the intersymbol interference (ISI) which is due to large delays of a multipath mobile radio channel, orthogonal frequency division multiplexing (OFDM) became very popular. However, the timevariance of the mobile radio channel induces intercarrier interference (ICI) yielding substantial channel estimation errors and thereby tremendous transmission impairments...
Orthogonal frequency division multiplexing (OFDM) communication systems require accurate estimation of timing offset and channel impulse response in order to achieve desirable performance. In this paper, we consider the optimal placement of pilot symbols over the OFDM subcarriers in order to minimize a function of the Cramér-Rao bound on these parameters. Previous work has investigated this problem...
This paper gives an introduction to a generic OFDM based testbed for positioning using time difference of arrival (TDoA) measurements. An overview of the transmitter system and receiver system is given. Furthermore an inital access algorithm with interference mitigation for subsample delay estimation is presented and simulation results are shown. The influence of the geographic base station mapping...
Block transmission of multi-scale orthogonal wavelet division multiplexing (OWDM) is proposed for signaling over wideband linear time-varying channels (LTV). Such channels are best modeled by multi-scale, multi-lag (MSML) models and the proposed OWDM designs are tailored to such channels. Given this signaling, the effective channel matrix for the received signal is banded, allowing for the modification...
For orthogonal frequency division multiplexing (OFDM) systems in multipath channels, the detection of the first path is desirable to avoid inter-symbol-interference (ISI). However, the conventional peak detection of the cyclic prefix (CP) correlation curve can detect the strongest path but not the first path, while the largest slope detection is sensitive to background noise. This paper presents a...
In this paper, the packet combining technique in the downlink OFDMA system is introduced in conjunction with frequency diversity to enhance the reliability of retransmissions and thus reduce the large time delay caused by retransmissions. The novel retransmission technique aims to reduce the maximum number of retransmissions for failed packets, while maximizing the throughput. A suboptimal algorithm...
In this paper we study the performance of a SC-FDMA cellular system when a complete Inter-Cell Interference (ICI) management strategy is implemented. We also introduce a novel sector-and-zone frequency ICI coordination scheme, derived from Fractional Frequency Reuse (FFR), which succeeds on increasing the capacity of an SC-FDMA cellular system. Working together with open-loop Fractional Power Control...
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