Positioningalgorithms Research Based On Radio Frequency Pattern Matching

Location estimation has received a great deal of attention over the last two decades due to the requirements set by the USA Federal Communications Commission (FCC) for Enhanced-911(E-911) safety service. Accuracies of E-911emergency positioning are50(67%) and150m (95%) in the terminal-dependent case and100(67%) and300m (95%) in the network-dependent case. The positioning requirements of mobile services drive companies and universities to look for effective positioning scheme to meet market demand in the cellular network, and wireless operators to develop positioning-based mobile services.The wireless positioning based on radio frequency pattern matching is a useful solution for User Equipment (UE) positioning in the communication system, and it is discussed currently in the3GPP meeting where it’s named as RFPM (Radio Frequency Pattern Matching). The basic principle is as follow:cell in cellular network is separated into a great deal of areas, and pattern database indexed by every separated area can be constructed to store radio measurement vectors between multiple base stations and the centers of every separated areas in advance or real time, and the location of UE can be acquired by matching available measurements of UE with the corresponding data of every separated area. It does not need any additional equipment to existing networks and is not sensitive to the channel states compared with Time of arrival schemes. The measurements can be selected freely and can also be combined with other positioning methods to achieve the ideal time complexity and positioning accuracy.RFPM discussed in the paper will take full advantage of the existing measurements compared with Time of arrival schemes, including Reference Signal Reference Power (RSRP), Reference Signal Time Difference (RSTD), Time of Arrival (TA), Angel of Arrival (AOA). Based on the above measurements, the closed form expressions of Cramer-Rao bound is deduced under the assumption of the two-dimensional positioning for accuracy evaluation and comparison, and Mamimum Likelihood (ML) scheme based on the existing measurements is proposed. RFPM with other positioning methods is simulated in LTE system. From the simulation results, the proposed method has a great advantage over other positioning methods.