This paper proposes an adaptive channel estimation scheme, which uses different moving average length and pilot gain for different mobile environments. It is based on MSE method and extensive simulations under various environments for WCDMA physical layer. The scheme applies a computationally efficient and easily implemented pilot filter on WCDMA forward channel. For different mobile channel environments, the optimal combination of moving average length and pilot gain for low SNR is achieved. The simulation results illustrate that the adaptive scheme can achieve much lower BER compared with two other adaptive schemes, especially when the speed of mobile user is high. And the BER performance of the proposed scheme is insensible to the mobile speed.

The accuracy of channel estimation significantly affects the performance of coherent receiver in a DS-CDMA system. The receiver performance can be improved if an appropriate channel estimation filter is used according to the channel condition. In this paper, we consider the design of channel estimation filters for pilot channel based DS-CDMA systems. When a moving average (MA) FIR filter is used as the channel estimation filter (CEF), the tap size is optimized by minimizing the mean squared error of the estimated channel impulse response. Finally, the analytic design is verified by computer simulation. Numerical results show that the optimum MA FIR CEF provides near optimum performance, i.e., quite similar to that with the use of Wiener filter.

This letter presents a lower bound and approximation for the coverage probability of the pilot channel that can be used for a CDMA downlink design. The approximation of a compound truncated Poisson distribution is used to obtain a closed form equation for the coverage probability of the pilot channel. Computer simulations show that our lower bound curve is truly less than the empirical curve, and our proposed approximation agrees well with the empirical result.

In this paper, we evaluate the performance of pilot channel-aided channel estimation for multicarrier direct-sequence (DS) code division multiple access (CDMA) communication system as proposed by Kondo and Milstein . We consider a multicarrier DS-CDMA system with different number of pilot and data channels. We investigate the optimum number of pilot channels for various coherence bandwidths and different number of subchannels. Keeping the total transmit bandwidth fixed, an optimum number of total subchannels and pilot channels exists under specific channel environment and transmitted energy. As the number of pilot channels increases, more accurate channel estimation is possible but the number of data channels decreases resulting a smaller diversity gain. We show that there is a tradeoff between the number of pilot channels and data subchannels, thereby requiring differing numbers of optimum pilot channels according to channel conditions.

This paper proposes a pilot channel assisted minimum mean square error (MMSE) combining scheme in orthogonal frequency and code division multiplexing (OFCDM) based on actual signal-to-interference power ratio (SIR) estimation, and investigates the throughput performance in a broadband channel with a near 100-MHz bandwidth. In the proposed MMSE combining scheme, the combining weight of each sub-carrier component is accurately estimated from the channel gain, noise power, and transmission power ratio of all the code-multiplexed channels to the desired one, by exploiting the time-multiplexed common pilot channel in addition to the coded data channel. Simulation results elucidate that the required average received signal energy per bit-to-noise spectrum density ratio (Eb/N0) for the average packet error rate (PER) = 10-2 is improved by 0.6 and 1.2 dB by using the proposed MMSE combining instead of the conventional equal gain combining (EGC) in a 24-path Rayleigh fading channel (exponential decay path model, maximum delay time is approximately 1 µsec) in an isolated cell environment, when the number of multiplexed codes = 8 and 32, respectively, with the spreading factor of 32. Furthermore, when the average received Eb/N0 = 10 dB, the achievable throughput, i.e., the number of simultaneously multiplexed codes for the average PER = 10-2 in the proposed MMSE combining, is increased by approximately 1.3 fold that of the conventional EGC.

A novel adaptive algorithm based on pilot channel (PCA) for MMSE multiuser detection in downlink CDMA is proposed in this paper. This algorithm uses the information in pilot channel to compute the desired weight vector directly. Compared with conventional adaptive algorithms and blind algorithms, it does not require training sequences nor channel estimation. Analysis shows that the weight vector obtained by the PCA algorithm converges to the Wiener solution globally and its computational complexity is O(N2). Simulation results show that the PCA algorithm can adapt rapidly to the changing environment. The steady state performance can be enhanced by increasing the transmitted power in pilot channel, but is worse than that of conventional recursive least-square (RLS) algorithm in decision-directed mode. Also, performance of the adaptive MMSE detector is much better than that of conventional RAKE receiver.

Adaptive channel estimation filters are presented for coherent DS-CDMA reverse link using time-multiplexed pilot and parallel pilot structures. Fast transmit power control (TPC) is adopted in the reverse link. Fading statistical properties are not preserved when fast TPC is used. When fading is slow, the channel is similar to non-fading channel, but its starts to vary as fading become faster since fast TPC cannot track fading perfectly. A pragmatic approach is used in this paper to derive adaptive channel estimation filter. The filter coefficients are updated based on the measured autocorrelation function of the instantaneous channel estimate. The bit error rate (BER) performance under frequency selective Rayleigh fading is evaluated by computer simulation to show that the adaptive channel estimation filter provides superior performance to the previously proposed non-adaptive WMSA filter.

This paper compares the BER performance of two types of pilot channel-based coherent Rake combining achievable by the use of weighted multi-slot averaging (WMSA) channel estimation filter in DS-CDMA transmission links. One is for the time-multiplexed pilot channel and the other is for the parallel pilot channel. The WMSA channel estimation filter weights and averages the received pilot over a period of several slots to improve the BER performance. We propose the WMSA channel estimation filters for time-multiplexed pilot and parallel pilot structures. Achievable BER performance under frequency-selective fading environments is computer simulated. The simulation results show that almost same BER performance can be achieved for both pilot channel structures when the same energy is allocated to the pilot.