Enabling Technologies and Techniques for Floor Identification

Location information has initiated a multitude of applications such as location-based services, health care, emergency response and rescue operations, and assets tracking. A plethora of techniques and technologies have been presented to ensure enhanced location accuracy, both horizontal and vertical. Despite many surveys covering horizontal localization technologies, the literature lacks a comprehensive survey incorporating up-to-data vertical localization approaches. This paper provides a detailed survey of different vertical localization techniques such as path loss models, time of arrival, received signal strength, reference signal received power, and fingerprinting utilized by WiFi, radio frequency identification (RFID), global system for mobile communications (GSM), long term evolution (LTE), barometer, inertial measurement unit (IMU) sensors, and geomagnetic field. The paper primarily aims at human localization in indoor environments using smartphones in essence. Besides the localization accuracy, the presented approaches are evaluated in terms of cost, infrastructure dependence, deployment complexity, and sensitivity. We highlight the pros and cons of these approaches and outline future research directions to enhance the accuracy to meet the future needs of floor identification standards set by the Federal Communications Commission.