Browsing by Author "Tan, CC"

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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.
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.
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.
Termination detection protocols for mobile distributed systems
(2001-06-01)
Tseng, YC
;
Tan, CC
;
資訊工程學系
;
Department of Computer Science
This paper studies a fundamental problem, the termination defection problem, in distributed systems. Under a wireless network environment, we show how to handle the host mobility and disconnection problems. in particular, when some distributed processes are temporarily disconnected, we show how to capture a weakly terminated state where silence has been reached only by those currently connected processes. A user may desire to know such a state to tell whether the mobile distributed system is still running or is silent because some processes are disconnected. Our protocol tries to exploit the network hierarchy by combining two existing protocols together. It employs the weight-throwing scheme [9], [16], [21] on the wired network side, and the diffusion-based scheme [5], [13] on each wireless cell. Such a hybrid protocol can better pave the gaps of computation and communication capability between static and mobile hosts, thus more scalable to larger distributed systems. Analysis and simulation results are also presented.