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Search Results: 1 - 10 of 218 matches for " Haris Gacanin "
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Throughput of Type II HARQ-OFDM/TDM Using MMSE-FDE in a Multipath Channel
Haris Gacanin,Fumiyuki Adachi
Journal of Electrical and Computer Engineering , 2009, DOI: 10.1155/2009/695620
Abstract: In type II hybrid ARQ (HARQ) schemes, the uncoded information bits are transmitted first, while the error correction parity bits are sent upon request. Consequently, frequency diversity cannot be exploited during the first transmission. In this paper, we present the use of OFDM/TDM with MMSE-FDE and type II HARQ to increase throughput of OFDM due to frequency diversity gain. 1. Introduction Packet services are dominant in future broadband wireless communications, where hybrid automatic repeat request (HARQ) is used for error control [1]. HARQ schemes combine error detection and forward error correction to make more efficient use of the channel. In type I HARQ, all the necessary parity bits are sent with each transmission. However, type II HARQ sends only the error detection parity bits, while the error correction parity bits are retransmitted upon request if the decoder detects errors. Therefore, with type II HARQ scheme a higher throughput can be achieved. Wireless channel is characterized as a multipath propagation environment (i.e., frequency selective fading channel). Orthogonal frequency division multiplexing (OFDM) is attractive due to its robustness against multipath channel, while a drawback is its high peak-to-average power ratio (PAPR) [2]. OFDM with rate compatible punctured turbo (RCPT) coded HARQ [3] gives a good throughput. However, in type II HARQ-OFDM the uncoded packet is send first and consequently, neither coding nor frequency diversity gain is available. In essence, OFDM-based scheme (e.g., multicarrier CDMA) with type II HARQ [4] that efficiently exploits the channel frequency selectivity in the first transmission is preferable. Most of the work in this area preclude the power requirement of multicarrier signaling due to high PAPR. In this paper, we present the use of OFDM combined with time division multiplexing (OFDM/TDM) using minimum mean square error frequency domain equalization (MMSE-FDE) [5] with type II HARQ to exploit the channel frequency selectivity. In type II HARQ OFDM/TDM during the first uncoded transmission the channel frequency selectivity is exploited through MMSE-FDE to increase the throughput of conventional OFDM with a lower PAPR. The paper is organized as follows. Section 2 describes the system model. The performance is presented in Section 3. Section 4 concludes the letter. 2. System Model The OFDM/TDM system model with HARQ is illustrated in Figure 1. At the transmitter, a cyclic redundancy check (CRC) coded sequence is input to the turbo encoder [6]. The parity sequences are punctured before transmission
On Channel Estimation for OFDM/TDM Using MMSE-FDE in a Fast Fading Channel
Haris Gacanin,Fumiyuki Adachi
EURASIP Journal on Wireless Communications and Networking , 2009, DOI: 10.1155/2009/481214
Abstract: MMSE-FDE can improve the transmission performance of OFDM combined with time division multiplexing (OFDM/TDM), but knowledge of the channel state information and the noise variance is required to compute the MMSE weight. In this paper, a performance evaluation of OFDM/TDM using MMSE-FDE with pilot-assisted channel estimation over a fast fading channel is presented. To improve the tracking ability against fast fading a robust pilot-assisted channel estimation is presented that uses time-domain filtering on a slot-by-slot basis and frequency-domain interpolation. We derive the mean square error (MSE) of the channel estimator and then discuss a tradeoff between improving the tracking ability against fading and the noise reduction. The achievable bit error rate (BER) performance is evaluated by computer simulation and compared with conventional OFDM. It is shown that the OFDM/TDM using MMSE-FDE achieves a lower BER and a better tracking ability against fast fading in comparison with conventional OFDM.
The Performance of Network Coding at the Physical Layer with Imperfect Self-Information Removal
Gacanin Haris,Adachi Fumiyuki
EURASIP Journal on Wireless Communications and Networking , 2010,
Abstract: Network capacity for bidirectional communication between pairs of wireless end users assisted by a relay terminal can be improved by network coding at the physical layer (PNC). Narrowband analog network coding (ANC) was introduced as a simpler implementation of PNC in a flat (i.e., frequency-nonselective fading) channel. Recently, broadband ANC has been studied for communication over a frequency-selective fading channel. In ANC, the end user removes its own information from the received signal before detecting the data of the other user. Clearly, the network performance of ANC scheme depends on the self-information removal at the destination terminal. In this paper, we discuss the impact of imperfect self-information removal on the performance of broadband ANC in terms of the bit error rate (BER) and achievable throughput in a frequency-selective fading channel. The theoretical minimum mean square error (MMSE) equalization weight for ANC based on single carrier with frequency domain equalization (SC-FDE) radio access is derived by taking into account the self-interference. We have used analysis and computer simulation to evaluate how the imperfect removal of self-information influences the achievable BER and throughput.
On Channel Estimation for OFDM/TDM Using MMSE-FDE in a Fast Fading Channel
Gacanin Haris,Adachi Fumiyuki
EURASIP Journal on Wireless Communications and Networking , 2009,
Abstract: MMSE-FDE can improve the transmission performance of OFDM combined with time division multiplexing (OFDM/TDM), but knowledge of the channel state information and the noise variance is required to compute the MMSE weight. In this paper, a performance evaluation of OFDM/TDM using MMSE-FDE with pilot-assisted channel estimation over a fast fading channel is presented. To improve the tracking ability against fast fading a robust pilot-assisted channel estimation is presented that uses time-domain filtering on a slot-by-slot basis and frequency-domain interpolation. We derive the mean square error (MSE) of the channel estimator and then discuss a tradeoff between improving the tracking ability against fading and the noise reduction. The achievable bit error rate (BER) performance is evaluated by computer simulation and compared with conventional OFDM. It is shown that the OFDM/TDM using MMSE-FDE achieves a lower BER and a better tracking ability against fast fading in comparison with conventional OFDM.
The Performance of Network Coding at the Physical Layer with Imperfect Self-Information Removal
Haris Gacanin,Fumiyuki Adachi
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/659291
Abstract:
On performance of analog network coding in the presence of phase noise
Amir Ligata, Haris Gacanin and Fumiyuki Adachi
EURASIP Journal on Wireless Communications and Networking , 2013, DOI: 10.1186/1687-1499-2013-2
Abstract: Analog network coding (ANC) as a simple implementation of physical layer network coding based on orthogonal frequency division multiplexing (OFDM) has been proposed to increase the network capacity and reliability of bi-directional link between a pair of users. In ANC protocol, an information between a pair of users is exchanged through two orthogonal time phases (i.e., multiple-access and broadcast phases). On the other hand, the phase noise (PN) introduces phase offset and inter carrier interference (ICI) to the useful signal. Thus, in ANC scheme PN will affect the useful signal during both multiple-access and broadcast phases. In this article, we present a performance analysis of ANC scheme using OFDM in the presence of PN in frequency-selective fading channel. We derive the total composite variance of ANC scheme in the presence of PN to obtain the signal-to-interference-plus-noise ratio (SINR) expression. Then, we evaluate the system’s performance in terms of bit error rate (BER), SINR degradation, and ergodic capacity through both numerical and computer simulations. Computer simulated average BER has been consistent with the numerical results, validating the presented analysis. Our results have shown that the ANC scheme is more sensitive to the PN introduced during the broadcast phase (i.e., at destination) than during the multiple-access phase (i.e., at relay). This is because of the higher ICI to the useful signal and enhanced noise due to the imperfect self-information removal at the destination. In addition, the performance degradation of ANC scheme based on OFDM in the presence of PN is highly expressed for the PN linewidth values up to 20 Hz.
On Channel Estimation for Analog Network Coding in a Frequency-Selective Fading Channel
Gacanin Haris,Sj?din Tomas,Adachi Fumiyuki
EURASIP Journal on Wireless Communications and Networking , 2011,
Abstract: Recently, broadband analog network coding (ANC) was introduced for high-speed transmission over the wireless (frequency-selective fading) channel. However, ANC requires the knowledge of channel state information (CSI) for self-information removal and coherent signal detection. In ANC, the users' pilot signals interfere during the first slot, which renders the relay unable to estimate CSIs of different users, and, consequently, four time-slot pilot-assisted channel estimation (CE) is required to avoid interference. Naturally, this will reduce the capacity of ANC scheme. In this paper, we theoretically analyze the bit error rate (BER) performance of bi-directional broadband ANC communication based on orthogonal frequency division multiplexing (OFDM) radio access. We also theoretically analyze the performance of the channel estimator's mean square error (MSE). The analysis is based on the assumption of perfect timing and frequency synchronization. The achievable BER performance and the estimator's MSE for broadband ANC is evaluated by numerical and computer simulation. We discuss how, and by how much, the imperfect knowledge of CSI affects the BER performance of broadband ANC. It is shown that the CE scheme achieves a slightly higher BER in comparison with ideal CE case for a low and moderate mobile terminal speed in a frequency-selective fading channel.
Multi-Layer Wsn with Power Efficient Buffer Management Policy
Hnin Yu Shwe;Wei Peng;Haris Gacanin;Fumiyuki Adachi
PIER Letters , 2012, DOI: 10.2528/PIERL11121605
Abstract: Power efficiency is a key issue in wireless sensor networks due to limited power supply. Buffer management is also crucially important in the scenario where the incoming traffic is higher than the output link capacity of the network since a buffer overflow causes power waste and information loss if a packet is dropped. There are many available buffer management schemes for traditional wireless networks. However, due to limited memory and power supply of sensor nodes, the existing schemes cannot be directly applied in wireless sensor networks (WSNs). In this work, we propose a multi-layer WSN with power efficient buffer management policy which simultaneously reduces the loss of relevant packets. Unlike the conventional WSNs which consider the whole network as single layer, we divide sensor network topology logically into multiple layers and give a three-layer model as an example. In our proposed scheme, the layers are differentiated by the sensors' information. The buffer can then judge the packets from different layers and then make a decision on which packet to be dropped in case of overflow. We show that our proposed multi-layer WSN can reduce the relevant packet loss and power waste for retransmission of lost packets.
On Channel Estimation for Analog Network Coding in a Frequency-Selective Fading Channel
Haris Gacanin,Tomas Sjödin,Fumiyuki Adachi
EURASIP Journal on Wireless Communications and Networking , 2011, DOI: 10.1155/2011/980430
Abstract:
Bit Error Rate Analysis for an OFDM System with Channel Estimation in a Nonlinear and Frequency-Selective Fading Channel
Ligata Amir,Gacanin Haris,Adachi Fumiyuki,Smolnikar Miha
EURASIP Journal on Wireless Communications and Networking , 2011,
Abstract: Orthogonal frequency division multiplexing (OFDM) is an effective technique for high-speed digital transmission over time-dispersive channels. However, for coherent detection, a reliable channel estimation (CE) is required. OFDM is characterized by its high peak-to-average power ratio (PAPR), which makes it very sensitive to nonlinear distortions that may affect the channel estimation accuracy leading to a bit error rate (BER) performance degradation. In this paper, we present closed-form BER expression for OFDM with a pilot-assisted CE in a nonlinear and frequency-selective fading channel. We discuss how, and to what extent, the nonlinear degradation affects the BER performance with the CE based on a time/frequency division-multiplexed (TDM/FDM) pilot. The analysis is based on a Gaussian approximation of the nonlinear noise due to both HPA amplitude limitation and quantization. We also evaluate the estimator's mean square error (MSE) with both TDM and FDM pilots. Our results show that pilot-assisted CE using FDM pilot is more sensitive to nonlinear distortions than the CE using a TDM pilot, since its pilot subcarriers are affected by nonlinear noise due to both the HPA and the quantization.
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