Browsing by Author "Lin, GJ"

Now showing 1 - 9 of 9

A decision aided CDMA receiver with partially adaptive decorrelating multi-user interference cancellation
(2003-08-01)
Lin, GJ
;
Lee, TS
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電信工程研究所
;
友訊交大聯合研發中心
;
Institute of Communications Engineering
A CDMA receiver with enhanced multiple access interference (MAI) suppression is proposed for a pilot symbols assisted system over multipath channels. The design of the receiver involves the following procedure. First, blind adaptive correlators are constructed at different fingers based on the scheme of generalized sidelobe canceller (GSC) to collect the multipath signals and suppress MAI. A low-complexity partially adaptive (PA) realization of the GSC correlators is proposed which incorporates multi-user information for reduced rank processing. By a judiciously designed decorrelating procedure, a new GSC structure is obtained in which the MAI are decorrelated and suppressed individually. The next step is then a simple coherent combining of the correlator outputs with pilot aided channel estimation. Finally, further performance enhancement is achieved by an iterative scheme in which the signal is reconstructed and subtracted from the GSC correlators input data, leading to faster convergence of the receiver. The proposed low-complexity PA CDMA multi-user receiver is shown to be robust to multipath fading and channel errors, and achieve nearly the same performance of the ideal maximum SINR and MMSE receivers by using a small number of pilot symbols.
A decision feedback CDMA receiver with partially adaptive interference suppression
(2001)
Lin, GJ
;
Lee, TS
;
Tan, CC
;
電信工程研究所
;
Institute of Communications Engineering
A novel CDMA receiver with adaptive multiple access interference (MAI) and narrowband interference (NBI) suppression is proposed for reverse link signal reception over multipath channels. The design of the receiver involves the following procedure. First, adaptive correlators are constructed based on the generalized side-lobe canceller (GSC) scheme to collect the multipath signals and suppress strong MAI and time-varying NBI. In particular, partial adaptivity is incorporated into the GSC for reduced complexity processing. A simple combiner with channel estimation then gives the symbol decisions. In order to enhance the performance of the adaptive correlators, a decision aided scheme is introduced which subtracts the reconstructed signal from the input data of the GSC, leading to improved output SINK and convergence. The proposed CDMA receiver is evaluated through simulations, and the results show that it can outperform the conventional MMSE receiver designed for time-invariant interference.
A low complexity partially adaptive CDMA receiver for downlink mobile satellite communications
(2003-01-01)
Lin, GJ
;
Lee, TS
;
電信工程研究所
;
Institute of Communications Engineering
A novel CDMA receiver with enhanced interference suppression is proposed for pilot symbols assisted mobile satellite systems in the presence of frequency offset. The design of the receiver involves the following procedure. First, adaptive correlators are constructed at different fingers, based on the scheme of generalized sidelobe canceller (GSC), to collect the multipath signals and suppress multi-access interference (MAI). In particular, a partially adaptive (PA) realization of the GSC correlators is proposed based on the Krylov subspace technique, leading to an efficient algorithm without the need of complicated matrix computations. Second, pilot symbols assisted frequency offset estimation, channel estimation and RAKE combining give the estimate of signal symbols. Finally, further performance enhancement is achieved by an iterative scheme in which the signal is reconstructed and subtracted from the GSC correlators input, leading to faster convergence of the receiver. The proposed low complexity PA receiver is suitable or the downlink of mobile satellite CDMA systems, and shown to outperform the conventional fully adaptive MMSE receiver by using a small number of pilot symbols. Copyright (C) 2003 John Wiley Sons, Ltd.
A low-complexity multi-user CDMA receiver with blind channel estimation and partially adaptive MAI suppression
(2003-09-01)
Lin, GJ
;
Lee, TS
;
資訊工程學系
;
電信工程研究所
;
Department of Computer Science
A low complexity multi-user receiver with blind channel estimation and multiple access interference (MAI) suppression is proposed for a CDMA system under multipath fading and frequency offset. The design of the receiver involves the following procedure. First, a method of joint MAI suppression and channel estimation is developed based on the generalized side-lobe canceller (GSC) technique. In particular, channel estimates are obtained blindly in the form of the effective composite signature vectors (CSV) of the users. Second, a low-complexity partially adaptive (PA) realization of the receiver is proposed which incorporates reduced-rank processing based on the information of multi-user CSV's. By a judiciously designed decorrelating procedure, a new PA receiver is obtained with a much lower complexity. Finally, pilot symbols assisted frequency offset estimation and channel gain compensation give the estimate of users' symbols. Further performance enhancement is achieved by a decision aided scheme in which the signal is reconstructed and subtracted from the receiver input data, leading to significantly faster convergence. The proposed receiver is shown to be robust to multipath fading and frequency offset, and achieves nearly the same performance of the optimal maximum SINR and MMSE receivers with a much lower overhead for pilot symbols.
A multistage multi-carrier CDMA receiver with blind adaptive MAI suppression
(2001)
Deng, JH
;
Lin, GJ
;
Lee, TS
;
電信工程研究所
;
Institute of Communications Engineering
A multistage multicarrier CDMA (MSMC-CDMA) receiver with enhanced multiple access interference (MAI) suppression is proposed for a reverse link time-multiplexed pilot symbols assisted system over multipath channels. The design of the receiver involves the following procedure. First, a blind adaptive matched filter is attached to each finger to perform despreading and combat MAI. Second, channel estimation and a RAKE combiner gives the estimate of the signal. Finally, signal reconstruction is accomplished by exploiting the channel estimate, data decisions, and signal's signature. The reconstructed signal is then subtracted from the data sent to the next stage. With signal reconstruction and subtraction as stages proceed, the MSMC-CDMA receiver can achieve nearly the performance of the optimal maximum SINR (MSINR) receiver, as confirmed by simulations.
An OSIC based reduced-rank MIMO equalizer using conjugate gradient algorithm
(2003-09-01)
Ho, CL
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Lin, GJ
;
Lee, TS
;
資訊工程學系
;
電信工程研究所
A reduced complexity multiple-input multiple-output (MIMO) equalizer with ordered successive interference cancellation (OSIC) is proposed for combating intersymbol interference (ISI) and cochannel interference (CCI) over frequency-selective multipath channels. It is developed as a reduced-rank realization of the conventional MMSE decision feedback equalizer (DFE). In particular, the MMSE weight vectors at each stage of OSIC are computed based on the generalized sidelobe canceller (GSC) technique and reduced-rank processing is incorporated by using the conjugate gradient (CG) algorithm for reduced complexity implementation. The CG algorithm leads to a best low-rank representation of the GSC blocking matrix via an iterative procedure, which in turn gives a reduced-rank equalizer weight vector achieving the best compromise between ISI and CCI suppression. With the dominating interference successfully cancelled at each stage of OSIC, the number of iterations required for the convergence of the CG algorithm decreases accordingly for the desired signal. Computer simulations demonstrate that the proposed reduced-rank MIMO DFE can achieve nearly the same performance as the full-rank MIMO MMSE DFE with an effective rank much lower than the dimension of the signal-plus-interference subspace.
Design of a low complexity partially adaptive CDMA receiver using conjugate gradient technique
(2002)
Lin, GJ
;
Lee, TS
;
Tan, CC
;
電信工程研究所
;
Institute of Communications Engineering
A CDMA receiver with enhanced multiple access interference (MAI) suppression is proposed. The design of the receiver involves the following procedure. First, adaptive correlators are constructed at different fingers based on the scheme of generalized side-lobe canceller (GSC) to collect the multipath signals and suppress MAI blindly. In particular, a partially adaptive (PA) realization of the GSC correlators is proposed based on the conjugate gradient (CG) technique. The next step is then a simple coherent combining of the correlator outputs with pilot aided channel estimation. Finally, further performance enhancement is achieved by an iterative scheme in which the signal is reconstructed and subtracted from the GSC correlators input, leading to faster convergence of the receiver. The proposed low complexity PA receiver is suitable for downlink CDMA, and shown to outperform the conventional fully adaptive MMSE receiver by using a small number of pilot symbols.
Design of partially adaptive STBC CDMA receiver using conjugate gradient algorithm
(2004)
Lin, GJ
;
Lin, TT
;
Lee, TS
;
電信工程研究所
;
Institute of Communications Engineering
A novel partially adaptive (PA) receiver with MAI suppression is proposed for an STBC CDMA system under the multipath fading channels. A low-complexity PA realization of the receiver is developed based on the generalized sidelobe canceller (GSC) technique which partial adaptivity is incorporated via the conjugate gradient (CG) algorithm for reduced complexity implementation. The proposed PA receiver is evaluated through simulations, and the results show that it can achieve nearly the same performance of the conventional fully adaptive MMSE receiver by using a small number of pilot symbols.
Space-time partially adaptive pre-equalizer for high rate CDMA systems using conjugate gradient technique
(2002)
Lin, GJ
;
Lee, TS
;
Tan, CC
;
電信工程研究所
;
Institute of Communications Engineering
A novel space-time (ST) pre-equalizer is proposed for the downlink of high data rate CDMA systems over frequency-selective multipath channels. We consider the scenario in which multiple transmit antennas are used at the base station (BS) for downlink transmission, followed by a set of adaptive FIR filters to suppress the multiple access interference (MAI) and possible intersymbol interference (ISI). With the MAI and ISI effectively suppressed, each mobile station (MS) would require only a simple matched filter (MF), leading to a "thin" handsets design suitable for next-generation wireless communications. The tap weights of each adaptive FIR filter are determined based on the generalized sidelobe canceller (GSC) technique, and partial adaptivity is incorporated via the conjugate gradient (CG) algorithm for reduced complexity implementation. The proposed ST pre-equalizer is evaluated through simulations, and the results show that it can achieve better performance compared to the pre-RAKE maximum ratio combining (MRC) method.