Blind Algorithms for Channel Estimation and Detection in Wireless Handsets
Cavallaro, Joseph R.
code division multiple access (CDMA); frequency-division multiple access (FDMA); time-division multiple access (TDMA); channel estimation; detection
Multiple access is an important consideration in the design and implementation of wireless communications systems. Code division multiple access (CDMA) is one method for providing multiple access in a wireless system. In CDMA, each user is assigned a unique code that identifies the user to the system. This code is used to modulate and demodulate the user's data. CDMA has several advantages over other more traditional multiple access methods like frequency-division multiple access (FDMA) and time-division multiple access (TDMA), one of the most important being its inherent noise-rejection capability. Because of its advantages over other multiple access methods, CDMA is being designed into many current and next-generation wireless systems. Two important functions in a wireless system are channel estimation and detection. Signals transmitted through a wireless channel are attenuated and delayed by the channel, and the purpose of channel estimation is to estimate this attenuation and delay. The purpose of detection is to detect the information symbols contained in the received signal. For reasons of size, power, and cost, the handsets in a wireless system have fewer resources than the base stations in the system and less knowledge than the base stations concerning the other users in the system. Because of this, channel estimation and detection techniques applicable to base stations are not always applicable to handsets, and algorithms that perform these functions on handsets must do so in a manner that is driven more by a need for efficiency and cost effectiveness than by a need for optimal performance. The research presented in this paper is concerned with "blind" algorithms for channel estimation and detection in handsets, where the term "blind" refers to the fact that the handset only has knowledge of the code of its own user. The focus of this research is on algorithmic and architectural improvements to such algorithms that will enable the algorithms to execute more efficiently in a hardware/software environment typifying those used in actual handsets. A goal of this work is to investigate issues related to real-time constraints and fixed-point quantization that would be encountered in the design and implementation of a wireless handset for a CDMA system. Two algorithms for channel estimation and two for detection are considered. One algorithm for channel estimation and one for detection are actually implemented on a Texas Instruments 'C5410 digital signal processor. As of the writing of this paper, these algorithms have only been implemented in floating-point C. It is expected, however, that with little additional effort, the algorithms will be implemented in fixed-point assembly language on the 'C5410.
MetadataShow full item record
- ECE Publications