Predictive switched diversity for slow speed mobile terminals

Multipath fading is a difficult problem in many mobile communication applications. Especially, in the applications characterized by low terminal speeds like wireless local loop (WLL) and pedestrian communications the terminal can be in a deep fade for long periods of time. Consequently, the performance of the radio link is seriously degraded. Many techniques having their inherent advantages and disadvantages are available for combatting the multipath fading. One of the most straight-forward methods is antenna diversity. However, in addition to requiring more than one antenna a switching or combination circuitry is needed. The switched antenna diversity is simpler and cheaper solution compared to selecting or combining antenna diversity constructions since only one receiver circuitry is required. Consequently, it is an attractive choice for realizing mobile terminal antenna diversity. Unfortunately, the performance of the switched antenna diversity is worse than selecting and combining methods. A predictive switch-and-examine switching algorithm is presented. In addition, the performance of the developed method is compared to selection and maximal-ratio combining diversity methods by simulations in WLL and GSM/DCS typical urban (TU) channel. According to the results, the developed switching algorithm performed almost as well as selection diversity. Consequently, the predictive switched diversity is an attractive choice for mobile and fixed terminals.