In this paper, we propose a new multistage (iterative) structure where Kalman channel estimation and parallel interference cancellation multiuser detection are conducted in every stage (iteration). The proposed scheme avoids the complexity of the decorrelator in front of Kalman channel estimator, and has better performance than the previous scheme.

A training-based vector channel estimation method has been proposed for single-user code-division multiple access (CDMA) systems in fast-varying correlated multipath fading channels. In this paper, we extend it in an iterative way to multiuser multiple-input multiple-output (MIMO) CDMA systems where both the transmitter and receiver have multiple antennas. In the training period, we propose to add the minimum mean square error (MMSE) front end before channel estimation to suppress multiuser interference (MUI) from substreams with difference spreading codes, so then we can get good initial vector channel estimation for each user. In the data transmission period, we proposed to add MMSE/parallel interference cancellation (PIC) front end to suppress MUI, interference suppression, and vector channel estimation in an iterative way. The perfect channel estimation is assumed in Liu et al., and the inter-play between channel estimation and multiuser detection is not discussed either. On the contrary, the novelty of the proposed method is that we add MMSE/PIC front end (in addition to matched filter) before channel estimation and we repeatedly switch between MMSE/PIC front end and channel estimation.

To improve Digital Audio Broadcasting (DAB) receiver performance, we need to use better signal processing algorithm. However, it is impossible to modify the signal processing algorithm in DAB commercial hardware. In addition, the notebook PC based software radio research platform allows convenient acquisition of the massive radio data at variant environments and online analysis with variable signal processing procedure more easily. We have developed the first prototype portable software radio research platform for DAB which consists of a USB RF receiver module, USB interface and PC based software for device controlling and signal processing. Iterative decoding and ICI cancellation are also added to improve the performance in mobile channels.

Recently, it has been shown that the received signal in the orthogonal frequency-division multiplexing (OFDM) systems can be viewed as the synchronous code-division multiple access (SCDMA) signal in receiver after some mathematical manipulation, and the ICI term in the OFDM system is equivalent to the multiple access interference (MAI) term in SCDMA system. They proposed a successive interference cancellation multicarrier detector and it performs better than the conventional single-carrier detection schemes. To further improve the performance of OFDM systems in the presence of ICI, we propose to use a soft-in soft-out (SISO) multicarrier detector and a SISO convolutional decoder in an iterative (turbo) way. Note that full-complexity turbo multicarrier detector and turbo decoder are not used to strike a balance between performance and complexity of OFDM systems. And the transmitter structure of OFDM systems is unchanged. The simulation results show that the first iteration of the proposed scheme demonstrates 2-3 dB gain compared to the previous multicarrier detection schemes. The second and third iterations improve the performance further.

A new bandwidth-efficient asynchronous multicarrier DS CDMA scheme is proposed for the uplink. In this new scheme, each user employs a set of FIR filters whose impulse responses are a mutually orthogonal (MO) complementary set of sequences. The intentional inter-symbol interference (ISI) and multiple access interference (MAI) are eliminated by the properties of these sequences. We also propose applying this new scheme in a DS CDMA packet network in which slotted ALOHA or pure ALOHA protocol is used. Packet throughput figures are obtained for the new ALOHA/bandwidth-efficient asynchronous MC DS CDMA packet network. Numerical results are given for both slotted and pure ALOHA cases. With the same bandwidth and number of simultaneous users, the throughput is compared favorably to similar figures for single-carrier DS CDMA with random spreading sequences.