International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace & Electronic Systems Technology, May 17, 2009
2010 7th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP 2010), 2010
Vehicle-to-infrastructure communication for accident avoidance is an important application define... more Vehicle-to-infrastructure communication for accident avoidance is an important application defined in the IEEE 802.11p. The primary challenge in the current IEEE 802.11p draft standard is the weak performance of channel estimation (CE) in multipath environments due to insufficient pilot density. Therefore, we propose time-domain (TD) CE techniques that can effectively and accurately estimate channel tap-weighting coefficients for solving this problem. Two network traffic types are investigated in this study: periodic transmission and event transmission. In addition, the proposed TD techniques are able to perform remarkably improved CE while completely following the signaling format in the current standard, with the assistance of the symbol prefix.
International Journal of Interdisciplinary Telecommunications and Networking, 2020
Achievable spatial diversity supported by a single transparent amplify-and-forward (AF) relay rel... more Achievable spatial diversity supported by a single transparent amplify-and-forward (AF) relay relies on disintegrated channel state information (CSI) that can be acquired at the destination. This paper studies the impact of the quantization of the source-relay (SR) CSI in terms of the first- and second-order statistics of maximal-ratio combining (MRC) reception with the incomplete SR CSI at the destination. Probability density functions (PDFs) of the upper and lower bounds of the signal-to-noise ratio (SNR) achieved at the destination are derived. Corresponding level-crossing rate (LCR) and average fade-duration (AFD), which are undoubtedly required to choose parameters of forward error correcting (FEC) mechanisms across the transparent AF relay network, are evaluated via Monte Carlo simulations. The simulations show that the SNR PDF, LCR and AFD highly depends not only on the accuracy of SR CSI at the destination but also on the location of the AF relay.
2016 IEEE International Conference on Communications (ICC), 2016
Energy harvesting and wireless energy transfer are capable of relieving the battery limitation of... more Energy harvesting and wireless energy transfer are capable of relieving the battery limitation of wireless devices. In this paper, an amplify-and-forward relay network (AF-RN) is considered, where an energy harvesting source node communicates with a destination node through an energy harvesting relay node. To further improve the performance, the relay is allowed to harvest energy from the radio frequency (RF) signals sent by the source node through a dedicated energy control channel. A joint power control and energy transfer scheme is investigated with the goal of maximizing the achievable sum rate by a deadline subject to energy causality constraints. The problem is challenging in that the objective function is non-convex, and a successive convex approximation approach is proposed to achieve the optimal power control and energy transfer solution. Finally, numerical examples are given to demonstrate the effectiveness of our proposed algorithm.
International Conference on Communications, Jun 26, 2012
Orthogonal frequency-division multiplexing (OFDM) communication is a promising technique for use ... more Orthogonal frequency-division multiplexing (OFDM) communication is a promising technique for use in fourth-generation (4G) mobile communications. Meanwhile, the carrier aggregation technique becomes crucial for raising the transmission rate. The achievable data rate of an OFDM system is generally limited by spectral efficiency and the available bandwidth; the former strongly depends on the adopted modulation techniques, and the latter strongly depends on the spectrum policy. A carrier aggregation method is a feasible and flexible bandwidth utilization technique that facilitates upgrades to transmission throughput by aggregating several contiguous or non-contiguous carriers. Unlike conventional OFDM systems, multiple carrier frequency offsets (CFOs) must be taken into consideration for carrier-aggregated OFDM (CA-OFDM) communications. Several preambles are constructed as pilots for individual component carriers. With knowledge of the preamble property, novel estimation methods for multiple CFOs are proposed and investigated by taking advantage of either a multiple signal classification (MUSIC) or a root-MUSIC algorithm. Simulation results show that the proposed method can achieve good performance in terms of the error rate of detection and the mean-square error (MSE) over time-varying multipath fading channels. With assistance from the accurate multi-CFO estimation and compensation proposed in this paper, the carrier aggregation, which is conventionally accomplished on the medium access control (MAC) layer with a few parallel, ordinary OFDM inner receivers, can be effectively transformed to be a physical-layer (PHY) multiplexing technique by means of a larger-size fast Fourier transform (FFT) demodulation. This transformation can reduce the implementation overhead needed by independently building several parallel ordinary inner receivers. This transformation can also save the header length prefixed on the MAC layer for conducting carrier aggregations.
2012 International Conference on Communications and Information Technology (ICCIT), 2012
In this paper, a hybrid Cramér-Rao bound (HCRB) for the channel estimation of non-orthogonal, di... more In this paper, a hybrid Cramér-Rao bound (HCRB) for the channel estimation of non-orthogonal, disintegrated, amplify-and-forward (NAF) relaying systems is derived. The HCRB is an effective benchmark for examining channel estimation performance. Several conventional frequency-domain channel estimations, such as the least-squares (LS), minimum-mean-square-error (MMSE) channel estimators are simulated and compared with the derived HCRB.
Next-generation telematics solutions are driven by the mature and recently employed intelligent t... more Next-generation telematics solutions are driven by the mature and recently employed intelligent transportation systems (ITSs), which are assisted by integration and rapid collaboration with information communication technology (ICT) markets as well as the automotive industry. ITSs are a rising technology and include many aspects. For ITSs, smart vehicles and wireless communications are promising technologies that may improve driving safety, reduce traffic congestion, and support information services in vehicles; further, green life for a blue planet is our ultimate goal. Despite the recent global economic downturn that has negatively affected the automobile industry, active research continues in these areas, and new technical challenges have emerged that demand research and development. Dedicated short-range communication (DSRC) exemplifies these challenges because wireless communication techniques have become significant and relevant for vehicular environments. The direct link between clean mobility and ITSs includes less gasoline consumption and toxic gas emission. Thus, to maximize ITS efficiency, the population that adopts ITSs for daily transportation should increase as much as possible. To achieve this goal, the ITS design should not be limited by technique; the "user-centric" notion is the most important requirement and should be considered.
2015 IEEE 26th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2015
In this paper, we focus on designing energy-efficient power allocation schemes to improve the ene... more In this paper, we focus on designing energy-efficient power allocation schemes to improve the energy efficiency (EE) in multiuser multi-carrier two-way relay networks which are able to not only balance the EE of the two-way links but also ensure the quality-of-service (QoS). Specifically, the proposed design framework attempts to maximize a ratio of the spectral efficiency (SE) over the total network power consumption under a total power constraint as well as a signal-to-interference plus noise power ratio (SINR) constraint. The original problem is indeed non-convex, and we prove the convexity of the problem after a series of convex transformation. An iterative approach is proposed to find the local optimal solution of the original problem for achieving the maximum EE. Simulation results are provided to demonstrate the tradeoff between the EE and the SE.
IEEE Transactions on Wireless Communications, 2016
This paper proposes an initial synchronization architecture for the sector search process in thir... more This paper proposes an initial synchronization architecture for the sector search process in third-generation partnership project (3GPP) long-term evolution (LTE) communications. The proposed system, consisting of three techniques, takes intercell interference, intercarrier interference and multipath fading into consideration with assistance from inherent diversity. The outage and detection probabilities are derived by taking multisector diversity into account in the coarse timing alignment. The long-lag differential correlator can achieve approximately 4.7-dB signal-to-noise ratio (SNR) gain in primary synchronization sequence (PSS) acquisition probability. Joint estimation of the residual timing error and the fractional frequency offset is achieved by evaluating the short-lag autocorrelation at an orthogonal frequency division multiplexing (OFDM) symbol duration. Mean-square errors obtained via simulations are compared with the modified Cramér-Rao lower bounds derived here. The proposed technique can achieve approximately 6.9-dB SNR gain when it is compared with that assisted from the synchronization signalling. Joint detection of the integral frequency offset (IFO) and the sector identification (SID) is achieved by exploiting a frequency-domain (FD) matched filter (MF) to deal with frequency selectivity. Differential detection on a segmental FD MF is considered in frequency-selective environments. Computer simulations are conducted to verify that the proposed technique can achieve high IFO and SID detection probabilities.
International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace & Electronic Systems Technology, May 17, 2009
2010 7th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP 2010), 2010
Vehicle-to-infrastructure communication for accident avoidance is an important application define... more Vehicle-to-infrastructure communication for accident avoidance is an important application defined in the IEEE 802.11p. The primary challenge in the current IEEE 802.11p draft standard is the weak performance of channel estimation (CE) in multipath environments due to insufficient pilot density. Therefore, we propose time-domain (TD) CE techniques that can effectively and accurately estimate channel tap-weighting coefficients for solving this problem. Two network traffic types are investigated in this study: periodic transmission and event transmission. In addition, the proposed TD techniques are able to perform remarkably improved CE while completely following the signaling format in the current standard, with the assistance of the symbol prefix.
International Journal of Interdisciplinary Telecommunications and Networking, 2020
Achievable spatial diversity supported by a single transparent amplify-and-forward (AF) relay rel... more Achievable spatial diversity supported by a single transparent amplify-and-forward (AF) relay relies on disintegrated channel state information (CSI) that can be acquired at the destination. This paper studies the impact of the quantization of the source-relay (SR) CSI in terms of the first- and second-order statistics of maximal-ratio combining (MRC) reception with the incomplete SR CSI at the destination. Probability density functions (PDFs) of the upper and lower bounds of the signal-to-noise ratio (SNR) achieved at the destination are derived. Corresponding level-crossing rate (LCR) and average fade-duration (AFD), which are undoubtedly required to choose parameters of forward error correcting (FEC) mechanisms across the transparent AF relay network, are evaluated via Monte Carlo simulations. The simulations show that the SNR PDF, LCR and AFD highly depends not only on the accuracy of SR CSI at the destination but also on the location of the AF relay.
2016 IEEE International Conference on Communications (ICC), 2016
Energy harvesting and wireless energy transfer are capable of relieving the battery limitation of... more Energy harvesting and wireless energy transfer are capable of relieving the battery limitation of wireless devices. In this paper, an amplify-and-forward relay network (AF-RN) is considered, where an energy harvesting source node communicates with a destination node through an energy harvesting relay node. To further improve the performance, the relay is allowed to harvest energy from the radio frequency (RF) signals sent by the source node through a dedicated energy control channel. A joint power control and energy transfer scheme is investigated with the goal of maximizing the achievable sum rate by a deadline subject to energy causality constraints. The problem is challenging in that the objective function is non-convex, and a successive convex approximation approach is proposed to achieve the optimal power control and energy transfer solution. Finally, numerical examples are given to demonstrate the effectiveness of our proposed algorithm.
International Conference on Communications, Jun 26, 2012
Orthogonal frequency-division multiplexing (OFDM) communication is a promising technique for use ... more Orthogonal frequency-division multiplexing (OFDM) communication is a promising technique for use in fourth-generation (4G) mobile communications. Meanwhile, the carrier aggregation technique becomes crucial for raising the transmission rate. The achievable data rate of an OFDM system is generally limited by spectral efficiency and the available bandwidth; the former strongly depends on the adopted modulation techniques, and the latter strongly depends on the spectrum policy. A carrier aggregation method is a feasible and flexible bandwidth utilization technique that facilitates upgrades to transmission throughput by aggregating several contiguous or non-contiguous carriers. Unlike conventional OFDM systems, multiple carrier frequency offsets (CFOs) must be taken into consideration for carrier-aggregated OFDM (CA-OFDM) communications. Several preambles are constructed as pilots for individual component carriers. With knowledge of the preamble property, novel estimation methods for multiple CFOs are proposed and investigated by taking advantage of either a multiple signal classification (MUSIC) or a root-MUSIC algorithm. Simulation results show that the proposed method can achieve good performance in terms of the error rate of detection and the mean-square error (MSE) over time-varying multipath fading channels. With assistance from the accurate multi-CFO estimation and compensation proposed in this paper, the carrier aggregation, which is conventionally accomplished on the medium access control (MAC) layer with a few parallel, ordinary OFDM inner receivers, can be effectively transformed to be a physical-layer (PHY) multiplexing technique by means of a larger-size fast Fourier transform (FFT) demodulation. This transformation can reduce the implementation overhead needed by independently building several parallel ordinary inner receivers. This transformation can also save the header length prefixed on the MAC layer for conducting carrier aggregations.
2012 International Conference on Communications and Information Technology (ICCIT), 2012
In this paper, a hybrid Cramér-Rao bound (HCRB) for the channel estimation of non-orthogonal, di... more In this paper, a hybrid Cramér-Rao bound (HCRB) for the channel estimation of non-orthogonal, disintegrated, amplify-and-forward (NAF) relaying systems is derived. The HCRB is an effective benchmark for examining channel estimation performance. Several conventional frequency-domain channel estimations, such as the least-squares (LS), minimum-mean-square-error (MMSE) channel estimators are simulated and compared with the derived HCRB.
Next-generation telematics solutions are driven by the mature and recently employed intelligent t... more Next-generation telematics solutions are driven by the mature and recently employed intelligent transportation systems (ITSs), which are assisted by integration and rapid collaboration with information communication technology (ICT) markets as well as the automotive industry. ITSs are a rising technology and include many aspects. For ITSs, smart vehicles and wireless communications are promising technologies that may improve driving safety, reduce traffic congestion, and support information services in vehicles; further, green life for a blue planet is our ultimate goal. Despite the recent global economic downturn that has negatively affected the automobile industry, active research continues in these areas, and new technical challenges have emerged that demand research and development. Dedicated short-range communication (DSRC) exemplifies these challenges because wireless communication techniques have become significant and relevant for vehicular environments. The direct link between clean mobility and ITSs includes less gasoline consumption and toxic gas emission. Thus, to maximize ITS efficiency, the population that adopts ITSs for daily transportation should increase as much as possible. To achieve this goal, the ITS design should not be limited by technique; the "user-centric" notion is the most important requirement and should be considered.
2015 IEEE 26th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2015
In this paper, we focus on designing energy-efficient power allocation schemes to improve the ene... more In this paper, we focus on designing energy-efficient power allocation schemes to improve the energy efficiency (EE) in multiuser multi-carrier two-way relay networks which are able to not only balance the EE of the two-way links but also ensure the quality-of-service (QoS). Specifically, the proposed design framework attempts to maximize a ratio of the spectral efficiency (SE) over the total network power consumption under a total power constraint as well as a signal-to-interference plus noise power ratio (SINR) constraint. The original problem is indeed non-convex, and we prove the convexity of the problem after a series of convex transformation. An iterative approach is proposed to find the local optimal solution of the original problem for achieving the maximum EE. Simulation results are provided to demonstrate the tradeoff between the EE and the SE.
IEEE Transactions on Wireless Communications, 2016
This paper proposes an initial synchronization architecture for the sector search process in thir... more This paper proposes an initial synchronization architecture for the sector search process in third-generation partnership project (3GPP) long-term evolution (LTE) communications. The proposed system, consisting of three techniques, takes intercell interference, intercarrier interference and multipath fading into consideration with assistance from inherent diversity. The outage and detection probabilities are derived by taking multisector diversity into account in the coarse timing alignment. The long-lag differential correlator can achieve approximately 4.7-dB signal-to-noise ratio (SNR) gain in primary synchronization sequence (PSS) acquisition probability. Joint estimation of the residual timing error and the fractional frequency offset is achieved by evaluating the short-lag autocorrelation at an orthogonal frequency division multiplexing (OFDM) symbol duration. Mean-square errors obtained via simulations are compared with the modified Cramér-Rao lower bounds derived here. The proposed technique can achieve approximately 6.9-dB SNR gain when it is compared with that assisted from the synchronization signalling. Joint detection of the integral frequency offset (IFO) and the sector identification (SID) is achieved by exploiting a frequency-domain (FD) matched filter (MF) to deal with frequency selectivity. Differential detection on a segmental FD MF is considered in frequency-selective environments. Computer simulations are conducted to verify that the proposed technique can achieve high IFO and SID detection probabilities.
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