Requirements of an OFDMA Pseudolite Indoor Geolocation System

In this paper, the requirements of an Orthogonal Frequency Division Multiple Access (OFDMA) pseudolite indoor geolocation system are proposed. Previously we have proposed an OFDMA pseudolite indoor geolocation system using a direct signal processing approach that operates at −30dB signal to noise ratio (SNR) with no multipath. The requirements of an OFDMA pseudolite indoor geolocation system consists primarily of: 1. OFDMA general system requirements 2. OFDMA pseudolite (or transmitter) requirements 3. OFDMA receiver requirements 4. OFDMA financial, business plan requirements. First, as far as general system requirements are concerned, the geolocation information for each pseudolite consists of the pseudolite’s position and time and the ability of the system to perform distance measurement under severe multipath conditions which is typical indoors. Second, OFDMA pseudolite requirements concern the signal design (or structure), signal modulation, power levels etc. For each pseudolite this information is binary encoded data at a symbol rate of 1 KHz. The encoded geolocation signal is modulated on the corresponding [100 200 300 400] MHz carrier signal via a Frequency Division Multiple Access (FDMA) modulator to mitigate cross-channel interference encountered in an indoor geolocation environment. The Orthogonal Frequency Division Multiplexed (OFDM) signal is then used to provide distance information. Four (4) transmitters are simulated to enable a geolocation estimate on the receiver. Third, the receiver consists of four channels, each one of which is designated to a single transmitter. On each receiving channel the received signal is down-converted, demodulated and decoded. Four distance estimates are used in a Least Squares filter to provide an estimate of the receiver location and time. We have added the ability to perform distance measurement; we have analyzed the effect of the transmitter stability on the position accuracy; we have assessed the effects of the transmitter and receiver oscillator drift (short term stability) on positioning accuracy; we are investigating techniques for detecting an extremely weak LOS signal in the presence of severe multipath; and finally, we are studying techniques for maintaining lock on the LOS signal in the presence of severe multipath; i.e., to enable a high sensitivity receiver. Fourth, we have provided a summary of the financial or business plan requirements which include financial requirements for phase I, II, and III of the analysis, development, and mass production of the system.