Blind Adaptive Decorrelating RAKE (DRAKE) Downlink Receiver for Space-Time Block Coded Multipath CDMA
- PDF / 756,488 Bytes
- 8 Pages / 600 x 792 pts Page_size
- 67 Downloads / 211 Views
Blind Adaptive Decorrelating RAKE (DRAKE) Downlink Receiver for Space-Time Block Coded Multipath CDMA Sudharman K. Jayaweera Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA Email: [email protected]
H. Vincent Poor Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA Email: [email protected] Received 31 January 2002 and in revised form 17 September 2002 A downlink receiver is proposed for space-time block coded CDMA systems operating in multipath channels. By combining the powerful RAKE receiver concept for a frequency selective channel with space-time decoding, it is shown that the performance of mobile receivers operating in the presence of channel fading can be improved significantly. The proposed receiver consists of a bank of decorrelating filters designed to suppress the multiple access interference embedded in the received signal before the space-time decoding. The new receiver performs the space-time decoding along each resolvable multipath component and then the outputs are diversity combined to obtain the final decision statistic. The proposed receiver relies on a key constraint imposed on the output of each filter in the bank of decorrelating filters in order to maintain the space-time block code structure embedded in the signal. The proposed receiver can easily be adapted blindly, requiring only the desired user’s signature sequence, which is also attractive in the context of wireless mobile communications. Simulation results are provided to confirm the effectiveness of the proposed receiver in multipath CDMA systems. Keywords and phrases: multiuser detection, space-time coding, blind adaptive receivers, code division multiple access.
1.
INTRODUCTION
Space-time coding [1, 2, 3], multiuser detection [4], and RAKE combining [5, 6, 7, 8] are powerful techniques that can offer significant performance gains in mobile communications environments and many emerging wireless systems adopt some combination of these techniques. For example, the application of RAKE receivers to multiuser systems has been studied extensively, prompted by the fact that 3G technology is based on the wideband code division multiple access (CDMA) concept and thus it must contend with frequency-selective channels. Of course, RAKE combining allows the receiver to extract the useful signal energy embedded in the signals that arrive via different paths in such channels. Thus, the RAKE receiver provides one way of providing frequency diversity at the receiver [5] in CDMA systems. On the other hand, recent advances in space-time coding exploit the spatial diversity inherent in fading channels [1, 2, 3]. Most space-time coding schemes are based on the assumption of a frequency flat fading channel. Under these conditions, the introduction of space-time coding into multiuser systems seems to provide
significant performance gains just as they do in single-user channels [9, 10, 11, 12, 13, 14]. However, as mentioned above, most next generation wireless systems will be wid
Data Loading...
