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  • 1. Duong, Quang Trung
    et al.
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Tsiftsis, Theodoros A.
    Orthogonal Space-Time Block Codes with CSI-Assisted Amplify-and-Forward Relaying in Correlated Nakagami-m Fading Channels2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 3, p. 882-889Article in journal (Refereed)
    Abstract [en]

    In this paper, the performance of multiple-input multiple-output (MIMO) dual-hop amplify-and-forward (AF) relay systems using orthogonal space-time block codes (OSTBCs) over arbitrarily correlated Nakagami-m fading channels is analyzed. In particular, closed-form expressions for the end-to-end outage probability (OP) and the symbol error probability (SEP) with arbitrary number of transceiver antennas and general correlation matrices are derived. Their mathematically tractable forms readily enable us to evaluate the performance of MIMO AF relay systems that utilize OSTBCs. For sufficiently high signal-to-noise ratios, asymptotically tight approximations for the OP and SEP are also attained which reveal insights into the effects of fading parameters and antenna correlation on the system’s performance. Furthermore, we prove that the correlation has no impact on the achievable diversity gain which is equal to the minimum of the sum of fading parameters between the two hops. Selected numerically evaluated results are presented showing an excellent agreement between the proposed analysis and equivalent Monte-Carlo simulations.

  • 2.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Costa, Daniel Benevides da
    Elkashlan, Maged
    Bao, Vo Nguyen Quoc
    Cognitive Amplify-and-Forward Relay Networks over Nakagami-m Fading2012In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 5, p. 2368-2374Article in journal (Refereed)
    Abstract [en]

    In this correspondence, the outage probability (OP) of dual-hop cognitive amplify-and-forward (AF) relay networks subject to independent non-identically distributed (i.n.i.d.) Nakagami-m fading is examined. We assume a spectrum sharing environment, where two different strategies are proposed for determining the transmit powers of the secondary network. Specifically, the transmit power conditions of the proposed spectrum sharing network are governed by either: (i) the combined power constraint of the interference on the primary network and maximum transmission power at the secondary network; or (ii) the single power constraint of the interference on the primary network. Closed-form lower bounds and asymptotic expressions for the OP are derived. Regardless of the transmit power constraint, we reveal that the diversity order is strictly defined by the minimum fading severity between the two hops of the secondary network. This aligns with the well-known result for conventional dual-hop AF relaying without spectrum sharing. Furthermore, the impact of the primary network on the diversity-multiplexing tradeoff is investigated. We confirm that the diversity-multiplexing tradeoff is independent of the primary network.

  • 3. Elkashlan, Maged
    et al.
    Yeoh, Phee Lep
    Yang, Nan
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Leung, Cyril
    A Comparison of Two MIMO Relaying Protocols in Nakagami- m Fading2012In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 3, p. 416-1422Article in journal (Refereed)
    Abstract [en]

    Transmit antenna selection with receive maximal-ratio combining (TAS/MRC) and transmit antenna selection with receive selection combining (TAS/SC) are two attractive multiple-input–multiple-output (MIMO) protocols. In this paper, we present a framework for the comparative analysis of TAS/MRC and TAS/SC in a two-hop amplify-and-forward relay network. In doing so, we derive exact and asymptotic expressions for the symbol error rate (SER) in Nakagami-mfading. Using the asymptotic expressions, the SNR gap between the two protocols is quantified. Given that the two protocols maintain the same diversity order, we show that the SNR gap is entirely dependent on the array gain. Motivated by this, we derive the SNR gap as a simple ratio of the respective array gains of the two protocols. This ratio explicitly takes into account the impact of the number of antennas and the fading severity parameter m. In addition, we address the fundamental question of “How to allocate the total transmit power between the source and the relay in such a way that the SER is minimized?” Our answer is given in the form of new compact expressions for the power allocation factor, which is a practical design tool that optimally distributes the total transmit power in the network.

  • 4. Kim, Kyeong Jin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Poor, H. Vincent
    Lee, Moon Ho
    Performance Analysis of Adaptive Decode-and-Forward Cooperative Single-Carrier Systems2012In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 7Article, review/survey (Refereed)
    Abstract [en]

    A cyclic prefixed single-carrier (CP-SC) relay network incorporating an adaptive decode-and-forward (ADF) protocol is proposed in this paper. For a two-hop ADF protocol, a general expression for the effective end-to-end signal to noise ratio (ESNR) is examined for multiple relays. With the help of a derived probability density function (PDF) for the ESNR, closedform expressions for the outage probability and an asymptotic average symbol error rate (AASER) are obtained. An asymptotic analysis revealing the diversity gain is also performed. Monte Carlo simulations verify these derived analytical results.

  • 5. Ngo, Hien Quoc
    et al.
    Matthaiou, Michail
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Larsson, Erik G.
    Uplink Performance Analysis of Multicell MU-SIMO Systems with ZF receivers2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 9, p. 4471-4483Article in journal (Refereed)
    Abstract [en]

    We consider the uplink of a multicell multiuser single-input multiple-output system, where the channel experiences both small and large-scale fading. The data detection is done by using the linear zero-forcing technique, assuming the base station (BS) has perfect channel state information of all users in its cell. We derive new, exact analytical expressions for the uplink rate, symbol error rate, and outage probability per user, as well as a lower bound on the achievable rate. This bound is very tight and becomes exact in the large-number-of-antennas limit. We further study the asymptotic system performance in the regimes of high signal-to-noise ratio (SNR), large number of antennas, and large number of users per cell. We show that at high SNRs, the system is interference-limited and hence, we cannot improve the system performance by increasing the transmit power of each user. Instead, by increasing the number of BS antennas, the effects of interference and noise can be reduced, thereby improving the system performance. We demonstrate that, with very large antenna arrays at the BS, the transmit power of each user can be made inversely proportional to the number of BS antennas while maintaining a desired quality-of-service. Numerical results are presented to verify our analysis

  • 6. Ngo, Hien Quoc
    et al.
    Matthaiou, Michail
    Duong, Trung Q.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Larsson, Erik G.
    Uplink Performance Analysis of Multicell MU-SIMO Systems With ZF Receivers2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 9, p. 4471-4483Article in journal (Refereed)
    Abstract [en]

    We consider the uplink of a multicell multiuser single-input multiple-output system (MU-SIMO), where the channel experiences both small- and large-scale fading. The data detection is done by using the linear zero-forcing technique, assuming the base station (BS) has perfect channel state information of all users in its cell. We derive new exact analytical expressions for the uplink rate, the symbol error rate (SER), and the outage probability per user, as well as a lower bound on the achievable rate. This bound is very tight and becomes exact in the large-number-of-antenna limit. We further study the asymptotic system performance in the regimes of high signal-to-noise ratio (SNR), large number of antennas, and large number of users per cell. We show that, at high SNRs, the system is interference limited, and hence, we cannot improve the system performance by increasing the transmit power of each user. Instead, by increasing the number of BS antennas, the effects of interference and noise can be reduced, thereby improving system performance. We demonstrate that, with very large antenna arrays at the BS, the transmit power of each user can be made inversely proportional to the number of BS antennas while maintaining a desired quality of service. Numerical results are presented to verify our analysis.

  • 7. Nordberg, Jörgen
    et al.
    Nordholm, Sven
    Grbic, Nedelko
    Mohammed, Abbas
    Claesson, Ingvar
    Performance Improvements for Sector Antennas using Feature Extraction and Spatial Interference Cancellation2002In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 51, no 6, p. 1685-89Article in journal (Refereed)
    Abstract [en]

    Effective utilization of the spatial domain enhances the capacity of a mobile radio network. A common technique is to use sector antennas, where the sectors are formed by weighting the outputs from the antenna elements. This results in spatial domain selectivity, which significantly improves the signal-to-noise and interference ratio in the received signals. However, the operation of the sector antenna will be limited by the sidelobes of the corresponding beam patterns. By introducing a blind spatial interference canceler that combines the fix beamformers in the sector antenna with blind signal separation, a significant improvement in the multi-user interference suppression can be achieved. Thus, it will be able to efficiently handle the near-far problem, where the users are received with different power. The blind signal separation is performed by an independent component analysis algorithm. The convergence rate of the algorithm is significantly improved compared to the standard formulation by taking into account the modulation format. The algorithm is further improved by introducing a forgetting factor on the weight update. The blind spatial interference canceler is evaluated by simulations using the mean square error and the bit error rate as quality measures. The results show that the mean square error obtained from the blind blind spatial interference canceler is within 0.5 dB from the optimum Wiener solution for signal-to noise ratios greather than 0 dB.

  • 8. Nordholm, Sven
    et al.
    Claesson, Ingvar
    Bengtsson, Bengt
    Adaptive Array Noise Suppression of Handsfree Speaker Input in Cars1993In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 42, no 4, p. 514-518Article in journal (Refereed)
    Abstract [en]

    Handsfree speaker input of mobile telephones is most desirable today in order to enable safe operation in cars. This is also a prerequisite for voice control of car devices. This paper presents an ''on the road'' evaluation of the performance of an adaptive microphone array for speech enhancement in cars. The results show a signal-to-noise ratio (SNR) improvement in the range of 10-15 dB over the telephone frequency range with a slight favour for higher frequencies when driving at normal speeds.

  • 9. Ostlin, Erik
    et al.
    Zepernick, Hans-Jürgen
    Suzuki, Hajime
    Macrocell Path Loss Prediction Using Artificial Neural Networks2010In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 59, no 6, p. 2735-2747Article in journal (Refereed)
    Abstract [en]

    This paper presents and evaluates artificial neural network models used for macrocell path loss prediction. Measurement data obtained by utilising the IS-95 pilot signal from a commercial code division multiple access mobile network in rural Australia is used to train and evaluate the models. A simple neuron model and feed-forward networks with different number of hidden layers and neurons are evaluated regarding their training time, prediction accuracy, and generalisation properties. Also, different backpropagation training algorithms, such as gradient descent and LevenbergMarquardt, are evaluated. The artificial neural network inputs are chosen to be distance to base station, parameters easily obtained from terrain path profiles, land usage and vegetation type and density near the receiving antenna. The path loss prediction results obtained by using the artificial neural network models are evaluated against different versions of the semi-terrain based propagation model Recommendation ITU-R P.1546 and the OkumuraHata model. The statistical analysis shows that a non-complex artificial neural network model performs very well compared to traditional propagation models in regards to prediction accuracy, complexity and prediction time. The average ANN prediction results were: 1) maximum error: 22 dB, 2) mean error: 0 dB and 3) standard deviation: 7 dB. A multi-layered feed-forward network trained using the standard backpropagation algorithm was compared with a neuron model trained using the LevenbergMarquardt algorithm. It was found that the training time decreases from 150 , 000 to 10 iterations whilst the prediction accuracy is maintained.

  • 10.
    Tran, Hung
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Sibomana, Louis
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Performance Analysis of a Cognitive Radio Network with a Buffered Relay2015In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, no 2, p. 566-579Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the packet transmission time in a cognitive cooperative radio network (CCRN) where a secondary transmitter (SU-Tx) sends packets to a secondary receiver (SU-Rx) through the help of a secondary relay (SR). In particular, we assume that the SU-Tx and SR are subject to the joint constraint of the timeout probability of the primary user (PU) and the peak transmit powers of the secondary users. On this basis, we investigate the impact of the transmit power of the PUs and channel mean powers on the packet transmission time of the CCRN. Utilizing the concept of timeout, adaptive transmit power allocation policies for the SU-Tx and SR are considered. More importantly, analytical expressions for the endto- end throughput, end-to-end packet transmission time, and stable condition for the SR operation are obtained. Our results indicate that the second hop of the considered CCRN is not a bottleneck if the channel mean powers of the interference links of the networks are small and the SR peak transmit power is set to a high value.

  • 11. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Duong, Trung Q.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Yang, Nan
    da Costa, Daniel Benevides
    Transmit Antenna Selection for Interference Management in Cognitive Relay Networks2014In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 63, no 7, p. 3250-3262Article in journal (Refereed)
    Abstract [en]

    We propose transmit antenna selection (TAS) in decode-and-forward (DF) relaying as an effective approach to reduce the interference in underlay spectrum sharing networks with multiple primary users (PUs) and multiple antennas at the secondary users (SUs). We compare two distinct protocols: 1) TAS with receiver maximal-ratio combining (TAS/MRC) and 2) TAS with receiver selection combining (TAS/SC). For each protocol, we derive new closed-form expressions for the exact and asymptotic outage probability with independent Nakagami-m fading in the primary and secondary networks. Our results are valid for two scenarios related to the maximum SU transmit power, i.e., P, and the peak PU interference temperature, i.e., Q. When P is proportional to Q, our results confirm that TAS/MRC and TAS/SC relaying achieve the same full diversity gain. As such, the signal-to-noise ratio (SNR) advantage of TAS/MRC relaying relative to TAS/SC relaying is characterized as a simple ratio of their respective SNR gains. When P is independent of Q, we find that an outage floor is obtained in the large P regime where the SU transmit power is constrained by a fixed value of Q. This outage floor is accurately characterized by our exact and asymptotic results.

  • 12. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Yang, Nan
    da Costa, Daniel B.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Unified Analysis of Transmit Antenna Selection in MIMO Multi-Relay Networks2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 2Article in journal (Refereed)
    Abstract [en]

    We present a unified asymptotic framework for transmit antenna selection in multiple-input multiple-output (MIMO) multi-relay networks with Rician, Nakagami-m, Weibull, and Generalized-K fading channels. We apply this framework to derive new closed-form expressions for the outage probability and symbol error rate (SER) of amplify-andforward relaying in MIMO multi-relay networks with two distinct protocols: 1) transmit antenna selection with receiver maximalratio combining (TAS/MRC), and 2) transmit antenna selection with receiver selection combining (TAS/SC). Based on these expressions, the diversity order and the array gain with M-ary phase shift keying and M-ary quadrature amplitude modulation are derived.We corroborate that the diversity order only depends on the fading distribution and the number of diversity branches, whereas the array gain depends on the fading distribution, the modulation format, the number of diversity branches, and the average per-hop signal-to-noise ratios (SNRs). We highlight that the diversity order of TAS/MRC is the same as TAS/SC, regardless of the underlying fading distribution. As such, we explicitly characterize the SNR gap between TAS/MRC and TAS/SC as the ratio of their respective array gains. An interesting observation is reached that for equal per-hop SNRs, the SNR gap between the two protocols is independent of the number of relays.

  • 13. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Yang, Nan
    da Costa, Daniel
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Unified Analysis of Transmit Antenna Selection in MIMO Multirelay Networks2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 2, p. 933-939Article in journal (Refereed)
    Abstract [en]

    We present a unified asymptotic framework for transmit antenna selection in multiple-input multiple-output (MIMO) multirelay networks with Rician, Nakagami-m, Weibull, and generalized-K fading channels. We apply this framework to derive new closed-form expressions for the outage probability and symbol error rate (SER) of amplify-and-forward (AF) relaying in MIMO multirelay networks with two distinct protocols: 1) transmit antenna selection with receiver maximal-ratio combining (TAS/MRC) and 2) transmit antenna selection with receiver selection combining (TAS/SC). Based on these expressions, the diversity order and the array gain with M-ary phase-shift keying and M-ary quadrature-amplitude modulation are derived. We corroborate that the diversity order only depends on the fading distribution and the number of diversity branches, whereas the array gain depends on the fading distribution, the modulation format, the number of diversity branches, and the average per-hop signal-to-noise ratios (SNRs). We highlight that the diversity order of TAS/MRC is the same as TAS/SC, regardless of the underlying fading distribution. As such, we explicitly characterize the SNR gap between TAS/MRC and TAS/SC as the ratio of their respective array gains. An interesting observation is reached that for equal per-hop SNRs, the SNR gap between the two protocols is independent of the number of relays.

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