Yinman Lee - Academia.edu (original) (raw)

Papers by Yinman Lee

IEEE Open Journal of Antennas and Propagation

Adaptive antenna array employing phase shifters only can reduce the hardware cost and power consu... more Adaptive antenna array employing phase shifters only can reduce the hardware cost and power consumption, but the related optimization is well understood to be difficult to solve. In this paper, we examine the use of both continuous phase shifters (CPS) and discrete phase shifters (DPS) in antenna array for adaptive interference suppression. First, we formulate the phase-only tuning problem with CPS via quadratically constrained quadratic program (QCQP), which can be approximated through semidefinite relaxation (SDR) and solved by convex-optimization solvers efficiently. We also demonstrate that quantizing such results directly may not necessarily give acceptable performance. Then, we propose to use binary quadratic program (BQP) for the optimization of the adaptive beamformer utilizing DPS with an arbitrary number of control bits to specify the phase-shift levels. The resultant BQP can be relaxed and solved efficiently too. Moreover, due to the similarity between the CPS and DPS formulation, we can mix them in a single beamforming scheme to provide additional compromises between the output signal-to-interference and noise ratio (SINR) performance and implementation cost. Simulations show that in the considered interference-limited environment, our proposed beamformers with CPS, DPS, and hybrid phase shifters (HPS) give desirable results as expected. INDEX TERMS Antenna array, continuous phase shifter (CPS), discrete phase shifter (DPS), conventional beamformer (CB), minimum-variance distortionless response (MVDR) beamformer, adaptive beamformer, quadratically constrained quadratic program (QCQP), binary quadratic program (BQP), convex optimization, semidefinite relaxation (SDR).

2020 International Computer Symposium (ICS), 2020

The dual-hop non-orthogonal multiple access (NOMA)-based diamond relay network can attain a high ... more The dual-hop non-orthogonal multiple access (NOMA)-based diamond relay network can attain a high achievable rate from a source to a destination thanks to the use of the two relays realizing both downlink and uplink NOMA virtually. In this paper, we further enhance its achievable-rate performance through joint power allocation at the source and the two NOMA-functioned relays. Particularly, an efficient algorithm is presented to fulfill this task. Simulation results show that in the considered network, the proposed power-allocation method offers a higher achievable rate than some relevant approaches, especially when the two relays are placed rather asymmetrically, i.e., one is very near the source and another is very near the destination.

2017 IEEE 18th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2017

To enable uplink (UL) multi-user (MU) transmission in 802.11ax, the Access Point (AP) sends a Tri... more To enable uplink (UL) multi-user (MU) transmission in 802.11ax, the Access Point (AP) sends a Trigger Frame to schedule stations (STAs) to send their UL data, and uses the new MU Request to Send (RTS) mechanism to protect large MU transmissions from hidden nodes. This paper addresses the potential problem of having one or more solicited STAs with nonzero Network Allocation Vector (NAV). This would reduce the system efficiency as some allocated resources will not be exploited for the reserved uplink transmission period. Accordingly, this paper proposes a variant of the Trigger operation considering the employment of massive multiple input and multiple output (MIMO) on the AP side, designated as Massive MU RTS (MMU-RTS) mechanism. In the proposed mechanism, some backup STAs not included on the trigger list, but having zero NAV are permitted to respond to the AP together with the solicited STAs. In particular, two user selection algorithms are proposed for the MMU-RTS mechanism. The efficiency of the proposed method is demonstrated through extensive numerical simulations.

IWAT 2005. IEEE International Workshop on Antenna Technology: Small Antennas and Novel Metamaterials, 2005.

The conventional generalized sidelobe canceller (GSC) is sensitive to coherent multipath disturba... more The conventional generalized sidelobe canceller (GSC) is sensitive to coherent multipath disturbance in wireless communication environments. Such disturbance, including coherent interference and local scattering, causes signal cancellation in the GSC. In this paper, we propose a new decision feedback (DF) technique to overcome this problem. The proposed algorithm introduces a feedback filter with one tap weight in the GSC structure. We analyze the robustness of this algorithm and the result shows that the problem of signal cancellation can be avoided. Simulations demonstrate that the DF-GSC has greatly improved robustness as compared to the conventional GSC.

2018 3rd International Conference on Computer and Communication Systems (ICCCS), 2018

Gauss-Seidel (GS) iteration can be used to approximate the minimum mean-squared error (MMSE) resu... more Gauss-Seidel (GS) iteration can be used to approximate the minimum mean-squared error (MMSE) result of signal detection in uplink multiuser massive MIMO systems. In this paper, we first propose to employ decision in GS iteration to enhance the detection performance in various aspects. Specifically, GS iteration with decision (GSID) converges faster than the conventional GS iteration and performs even better than the exact MMSE detection in terms of the resultant error rate. By virtue of the use of decision, interference cancelation can be employed to lower the dimension of the signal model in the detection process, and therefore the computational complexity can be significantly reduced. In addition, grey region is introduced in the signal constellation for decision, which lessens the error-propagation effect and further improves the error-rate performance.

Electronics Letters, 2019

A hybrid Kaczmarz and coordinate-descent (H-KCD) iterative algorithm is proposed for signal detec... more A hybrid Kaczmarz and coordinate-descent (H-KCD) iterative algorithm is proposed for signal detection in massive MIMO systems. Together with the specially-designed orthogonal projection and decision operation during iterations, this approach outperforms the standalone usage of either the Kaczmarz or coordinate-descent iteration, and gives better error-rate performance than the linear minimum mean-squared error detection. Essentially, since the Gram matrix is not required for the proposed H-KCD scheme, it owns lower total computational complexity than some state-of-the-art iterative methods.

2016 International Conference on Networking and Network Applications (NaNA), 2016

Cellular phone networks are often paralyzed after a disaster. However, the infrastructure damage ... more Cellular phone networks are often paralyzed after a disaster. However, the infrastructure damage is difficult to be fixed within a day in the case of the disruptions caused by disasters. This paper addresses the challenges of proximity call communication in emergency and disaster areas. 3GPP Release 12 defines proximity service (ProSe) for public safety. When two users are making proximity call without infrastructure in a diaster, the on-going call is force-terminated as the users move out of the proximity range. In this paper, we propose a method to provide transparent service continuity via extending the ProSe call through a common ProSe neighbor without the need of interacting with the radio access network. Then we propose an analytical model to compute the call completion probability with the assist of common neighbor tunneling.

IET Communications, 2014

In the research of decode-and-forward (DF) cooperative communications, it is often supposed that ... more In the research of decode-and-forward (DF) cooperative communications, it is often supposed that the included relay only transmits correctly decoded signals. This simplifies the analysis of DF cooperation. However, in practical circumstances, erroneous messages may be forwarded which makes the decision at the destination even worst. In this study, the authors formulate a special detection way, named 'detection with erasure', to make certain that the relay-forwarded signals are mostly correct. Specifically, whenever the decoded result at the relay falls into some preset 'erasure regions', the relay will not process and transmit it anymore. This effectively prevents the forwarding of erroneous messages. With general pulse amplitude-modulated or squared quadrature amplitude-modulated signals, the authors demonstrate that these erasure regions can be adjusted to minimise the end-to-end symbol error rate (SER). This detection scheme can be extended to be used in the DF cooperation employing multiple relays as well. Simulations reveal that in terms of the end-to-end SER performance, the proposed detection with erasure can outperform some signal-to-noise ratio threshold-based relaying approaches, and can perform quite similarly as compared with those decoding/combining methods realised at the destination with the advantage of less channel state information exchange.

Proceedings 2011 International Conference on System Science and Engineering, 2011

In wireless communications, the application of cooperation techniques can offer additional spatia... more In wireless communications, the application of cooperation techniques can offer additional spatial diversity. With the decode-and-forward (DF) protocol, it can be shown that the error-rate performance can be much improved in the fading channel environment. However, two strong assumptions are generally required: 1) The included relay can exactly know the correctness of its decision; 2) the destination can also know whether the relay forwards its decoded signal. Obviously, these may not be possible in many cases. In this paper, we utilize some specially-designed methods from detection theory to release these assumptions. Simulations show that through employing the proposed methods, the DF protocol still works well without applying the two assumptions, and the resultant error-rate performance can be quite close to that of the perfect DF scenario.

IEEE International Conference on Communications, 2005. ICC 2005. 2005

Conventional least-mean-square (LMS) based adaptive generalized sidelobe canceller (GSC) suffers ... more Conventional least-mean-square (LMS) based adaptive generalized sidelobe canceller (GSC) suffers from the slow convergence problem. When the environment is fast varying, the conventional GSC cannot perform satisfactorily. In this paper, we propose a new decision feedback (DF) technique to overcome this problem. The proposed algorithm introduces a feedback filter with one tap weight in the GSC structure. The Wiener solution for the proposed structure is derived and the convergence behavior of the adaptive DF-GSC is also analyzed. Simulation results show that the proposed structure can significantly accelerate the convergence and enhance the overall performance.

VTC Spring 2008 - IEEE Vehicular Technology Conference, 2008

... Multiplexing over Time-Varying MIMO Channels Kai-Jian Lin Graduate Institute of Communication... more ... Multiplexing over Time-Varying MIMO Channels Kai-Jian Lin Graduate Institute of Communication Engineering National Chi Nan University Puli, Taiwan, ROC Email: s95325532@ncnu.edu.tw ... Q = I − 2(vv H)/(v H v) (15) where v = Sign{u1}ue1 +u, e1 = [1 0 ··· 0]T , u is the ...

2014 19th International Conference on Digital Signal Processing, 2014

For multiple-input multiple-output (MIMO) spatial multiplexing systems, it is known that the maxi... more For multiple-input multiple-output (MIMO) spatial multiplexing systems, it is known that the maximum likelihood (ML) detector can achieve the optimal error-rate performance at the cost of high computational complexity, while the zero-forcing (ZF) detector and its variation with successive interference cancelation (SIC) attain low complexity with degraded performance. In this paper, we propose a new low-complexity MIMO detector which smartly includes ZF, ML and SIC for processing. The required computational complexity of this special mixture can be lower than that of the ordered SIC-ZF method in many cases. Importantly, simulation results show that this proposed low-complexity detector can significantly outperform the ordered SIC-ZF method in terms of the bit-error rate (BER), and own a diversity gain quite similar to that of the ML detector.

2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013

In a drive-thru Internet vehicular network, vehicles can communicate with access points (APs) for... more In a drive-thru Internet vehicular network, vehicles can communicate with access points (APs) for the Internet services. When a vehicle leaves the AP's transmission range, it encounters intermittent connectivity and unreliable connection. Using vehicle-to-vehicle (V2V) relay can loosen the limitation of transmission coverage. However, the harsh conditions of wireless channel and the rapid change of vehicle topology remain the challenge for relay selection. The relay candidate with a better channel quality can forward the packet with a higher data rate. Therefore, the MAC layer mechanisms are needed to exploit the multi-rate capability in the PHY layer. This paper utilizes the channel state information to exploit good channel quality for the relay link between the sender and the receiver. The objective is to increase the opportunity of channel access for the relay candidate with better channel quality. Considering various issues, such as the collision probability, packet delivery ratio, and delivery delay, we propose an analytical model to dynamically configure the window size for channel contention. Numerical results show that the proposed method outperforms the basic DCF and distance-based DCF.

2012 IEEE 75th Vehicular Technology Conference (VTC Spring), 2012

To take on challenges of communication in sparse VANET, we propose a Store-Carry-Broadcast (SCB) ... more To take on challenges of communication in sparse VANET, we propose a Store-Carry-Broadcast (SCB) scheme to assist message dissemination by broadcasting over a specific road segment instead of a single vehicle. In the SCB scheme, an opposite vehicle helps to disseminate the safety messages to oncoming vehicles traveling on the reverse lane by broadcasting. Compare with the well-known store-carry-forward broadcasting in VANET, the SCB scheme consumes much less network bandwidth in terms of the number of broadcasting performed. Extensive simulation results are presented to demonstrate that when the traffic density is low or when the DSCR penetration rate is low, our proposed SCB scheme significantly reduced both broadcast overhead as well as delivery delay in sparse VANET.

IET Communications, 2011

For cooperative communications, the decode-and-forward (DF) protocol can give promising error-rat... more For cooperative communications, the decode-and-forward (DF) protocol can give promising error-rate performance provided that the relay node has the decoding capability. In this study, the authors consider the DF cooperation for cellular uplink communications, in which the source node is equipped with a single antenna, and both the relay and destination nodes are equipped with multiple antennas. For this case, the authors analyse the exact symbol-error-rate (SER) for M-quadrature amplitude modulation (QAM) signals over Nakagami-m fading channels. To avoid the cumbersome integral calculation, the authors derive an asymptotic approximation for the SER, which lets them not only gain fast understanding of the improvement from cooperative diversity, but also have more insight into how the channel characteristics and the number of antennas affect the SER performance. Specifically, to reduce the SER, the authors find that: first, good condition of the relay-destination channels is more critical than good condition of the source-relay channels; second, large number of antennas at the relay node is more critical than large number of antennas at the destination node. All these results are not exploited and discussed before. Simulations are finally presented to demonstrate the correctness of the authors' analysis and perception for the considered cooperation scenario.

IEE Proceedings - Communications, 2006

Error propagation can seriously affect the performance of an adaptive decision feedback equaliser... more Error propagation can seriously affect the performance of an adaptive decision feedback equaliser (DFE), especially when operated in time-varying channel environments. Error propagation not only affects DFE decisions, but also disturbs the DFE adaptation. The paper focuses on improving the robustness against error propagation for the least-mean-square (LMS) based minimum mean-squared-error DFE (MMSE-DFE). A specifically designed channel estimator is introduced to help the DFE adaptation in the decision-directed (DD) mode. Unlike the conventional DFE, the proposed adaptive channel-aided DFE (ACA-DFE) only adapts the feedforward filter with the LMS algorithm. The feedback filter, however, is obtained from the postcursors of the estimated channel convolved with the feedforward filter. As a result, the proposed ACA-DFE can reduce the error propagation effect and perform better than the conventional adaptive DFE. We also demonstrate that the ACA-DFE can be extended to multipleinput multiple-out (MIMO) systems improving the performance of the conventional MIMO DFE.

IEEE Transactions on Wireless Communications, 2008

Adaptive parallel interference cancellation (PIC) has been recently proposed for the signal detec... more Adaptive parallel interference cancellation (PIC) has been recently proposed for the signal detection in multipleinput multiple-output (MIMO) systems. However, it suffers from error propagation when operated in time-varying channels. In this letter, an adaptive two-stage PIC with the minimum variance (MV) criterion is proposed to solve the problem. Adaptation with the MV criterion is realized with a decision feedback generalized sidelobe canceller (DFGSC). In the first-stage cancellation, a special structure involving dual DFGSCs is developed. All adaptation operations are implemented with the least-mean-square (LMS) algorithm. Simulations show that the proposed adaptive PIC detection can significantly outperform the conventional adaptive PIC detection in time-varying MIMO channel environments.

IEEE Transactions on Vehicular Technology, 2013

It is known that the achievement of the decode-and-forward (DF) protocol for cooperative communic... more It is known that the achievement of the decode-and-forward (DF) protocol for cooperative communications is critically based on the prerequisite that the relay forwards the source transmitted signals as faithfully as possible. This implies that the relay can mostly know the correctness of its decoded results. In this paper, we employ the idea of detection with erasure in relay to approach this prerequisite. An erasure region is set to minimize the cost function that is formulated based on a specially designed bit-error-rate (BER) expression for the cooperation network. Whenever the received signals fall into this region, the relay will not perform DF. Power allocation can be simultaneously optimized as well. Simulations show that its resultant BER can be quite close to that of the perfect DF scenario and better than the BER of most previously presented signal-to-noise ratio (SNR) threshold-based relaying schemes.

IEEE Communications Letters, 2009

Recently, symbol-based beamforming/combining has been introduced for OFDM systems with multiple t... more Recently, symbol-based beamforming/combining has been introduced for OFDM systems with multiple transmit and receive antennas. Despite the complexity reduction, the resultant SNR values of different subcarriers are often not balanced, and it limits the system performance. In this letter, we propose to use the max-min criterion to overcome the problem. Simulation results show that the error-rate performance of the proposed symbol-based processing scheme can be improved as compared with that of the conventional one.

IEEE Communications Letters, 2013

Incremental relaying (IR) was previously proposed to mitigate the spectral-efficiency loss in coo... more Incremental relaying (IR) was previously proposed to mitigate the spectral-efficiency loss in cooperative communications. In this letter, based on the amplify-and-forward (AF) protocol with M-ary phase-shift keying (M-PSK) signals, we propose a new way to implement IR with better spectral efficiency. Specifically, based on the end-to-end symbol error rate (e2e SER), an uncertainty region for detection is defined. Only if the processed signal at the destination falls into this region, the included relays will perform AF relaying. Simulations reveal that in terms of the e2e SER performance, the proposed IR-AF scheme performs quite well as compared with the conventional signal-to-noise ratio (SNR)-based IR-AF method, and, importantly, with significantly lower average relay usage.