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In this paper, we deal with channel estimation and intercarrier interference mitigation for very high mobility OFDM systems, the communication is between a BS and a train traveling at a speed of 500km/hr. The scheme proposed here uses piece-wise polynomial expansion to approximate time-variations of multipath channels. Two adjacent symbols are utilized to estimate the first and second-order parameters...
In this paper, we develop a general reduced-rate orthogonal frequency division multiplexing (OFDM) transmission scheme for inter-subchannel interference (ICI) mitigation in a high-mobility environment. By transmit and receive preprocessing, we transform the original N-subcarrier OFDM system into an equivalent K-subcarrier one with significantly reduced ICI. In particular, we develop a general structure...
We study a cyclic prefix (CP) assisted method used for the uplink of code division multiple access (CDMA) systems in which the code despreading is performed in front of the frequency domain equalizer (FDE). The main advantage of the new despreading scheme is that the required points of discrete Fourier transform in the FDE are significantly reduced compared to the conventional CDMA scheme. Although...
In this paper, the blind and semiblind channel estimation and equalization are investigated for zero-padding single-carrier block transmission (ZP-SCBT) systems using second-order statistics. Unlike the conventional channel estimation techniques, the proposed approach focuses on identifying the inverse of the channel impulse response rather than the channel response itself by skillfully exploiting...
This paper presents channel measurements for wireless body area network (WBAN) and provides performance evaluation using the model derived from measurement and the model in the final document of the IEEE802.15.6 channel modeling subcommittee. We measure the radio propagation from 3.0GHz to 5.0GHz which falls in ultra-wideband (UWB) frequency range in an anechoic chamber and give out a static model...
This paper is concerned with the efficient feedback of the channel state information (CSI) in multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. A hybrid transform coding (HTC) scheme is proposed by exploiting the frequency and time correlation of CSI. An upper bound for the overhead-distortion performance of HTC is derived. Numerical results show that,...
Applications for future broadband wireless network should work effectively under highly dynamic wireless channel environment, where strong frequency-selective and time-selective fading and severe multi-path channels will exist. Though some advantage techniques, such as 2-dimensional (2D) block spread, frequency domain equalization (FDE) and antenna diversity techniques, can be applied to the code...
In a multi-relay system, the instantaneous channel state information (CSI) is usually required at relays to achieve the space diversity. In this paper, we propose a delayed noncoherent relaying scheme to achieve space diversity without requiring knowledge of the instantaneous CSI at the relays. Specifically, each relay will non-coherently amplify and forward its received signals with different delays...
Channel-aware assignment of sub-channels to users in the downlink of an OFDMA system demands extensive feedback of channel state information (CSI) to the base station. Since the feedback bandwidth is often very scarce, schemes that limit feedback are necessary. We develop a novel, low feedback splitting-based algorithm for assigning each sub-channel to its best user, i.e., the user with the highest...
In this work, a genetic algorithm (GA) based frequency domain equalization (FDE) scheme referred to as FDE-GA, which does not require any guard interval (GI),is proposed for direct sequence-ultra wideband (DS-UWB) wireless communication systems and is shown to significantly outperform the RAKE receiver. The proposed FDE-GA receiver also has a dramatic complexity reduction over the previous RAKE-GA...
Due to wide coverage and high transmission power of digital television (DTV) transmitters, DTV based wireless positioning is a promising complementary to global positioning system. For Chinese DTV broadcasting network whose key technology is time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM), this paper proposes a time-frequency joint positioning scheme by utilising TDS-OFDM...
Single-carrier block transmission systems with frequency domain equalization (FDE) suffers from power and bandwidth efficiency loss due to the cyclic extension. Conventional schemes to reduce the cyclic extension needed rely heavily on Turbo architecture which has much higher computational complexity. To make good compromise between performance and complexity, we proposed a precoding aided iterative...
For high-speed packet access, hybrid automatic repeat request (HARQ) and multiple-input multiple-output (MIMO) multiplexing are indispensable techniques. As the multiple-access technique, single carrier (SC)-frequency-division multiple-access (FDMA) using transmit filtering is promising. The use of square-root Nyquist transmit filter reduces peak-to-average power ratio (PAPR) of the transmit SC-FDMA...
In this paper, the effect of time difference of arrival (TDoA) is investigated for distributed nodes in OFDMA-based wireless mesh networks (WMNs). In order to minimize the interferences caused by TDoA in WMNs, the optimal starting point of the FFT window at the receiver side of a node is derived by maximizing the effective SINR for each subcarrier. Also, a signal detection technique, called two dimensional...
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 sensing is an essential technique for cognitive radios. This paper addresses the spectrum sensing under uncertain noise power and proposes an adaptive spectrum sensing algorithm. The adaptive decision threshold of energy detection is derived, which is based on the weighted probability of detection and probability of false alarm. By means of estimating noise power and signal power, the decision...
QR decomposition with M-algorithm maximum likelihood detection (QRM-MLD) block signal detection can significantly improve the packet error rate (PER) performance of cyclic prefix-inserted single-carrier (CP-SC) multi-input multi-output (MIMO) spatial multiplexing when compared to the frequency-domain spatial filtering based on the minimum mean square error (MMSE) criterion. However, in order to achieve...
Long Term Evolution (LTE) physical layer identity can be recognized either in frequency domain or time domain. In this paper we serve some comparisons in term of complexity, latency, and recognition probability. As a result, frequency domain detection has superiority on performance for SNR higher than 3dB on all channel models, as well as lower latency than time domain scheme one. However, it requires...
Support of non-contiguous frequency resource allocation (FRA) based on clustered discrete Fourier transform-spread orthogonal frequency division multiplexing (clustered DFT-S-OFDM) is considered a key element of LTE-Advanced uplink to enhance the spectrum efficiency via an enhanced frequency domain scheduling. However, reduction of out-of-band emissions due to multiple clusters is a critical issue...
Multichannel systems can benefit from multiuser diversity by assigning channels to users with best channel conditions in different time instants. In this paper, a two-dimension opportunistic scheme for OFDMA-based in-home PLC systems with random access is presented in order to exploit multiuser diversity over different subchannels and time diversity across different time slots. The proposed scheme...
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