WAPS Hybrid Multiplexing for Beacon Cross-Interference Reduction
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Solution Overview
Problem
Conventional positioning systems, such as GPS, experience performance degradation in poor signal conditions due to cross-interference and the need to distinguish multiple concurrent transmissions from geographically spread beacons, particularly in urban and wide area environments, which affects position location accuracy.
Innovation Solution
A wide area positioning system (WAPS) that employs a hybrid multiplexing method combining time division multiplexing (TDMA), code division multiplexing (CDMA), and frequency offset multiplexing (FOM) to distinguish transmissions from multiple beacons, using pseudorandom noise (PN) codes and frequency offsets to reduce cross-interference and improve signal separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positioning systems (GPS) are used in poor signal conditions, then position location accuracy is maintained in open environments, but performance degrades in urban and wide area environments due to cross-interference from multiple concurrent transmissions
Solution Approach 1:
The patent segments the transmission medium by assigning different time slots (TDMA), code sequences (CDMA), and frequency offsets (FOM) to different beacons. This segmentation allows the receiver to separate and process signals from multiple beacons independently, preventing cross-interference from degrading positioning performance in urban and wide area environments.
Solution Approach 2:
The patent introduces multiple dimensions for signal differentiation: time dimension (TDMA time slots), code dimension (CDMA pseudorandom codes), and frequency dimension (FOM offsets). By operating in these multiple dimensions simultaneously, the system can distinguish concurrent transmissions from geographically spread beacons, resolving the cross-interference problem that limits conventional GPS in poor signal conditions.
2Area of stationary object
If multiple concurrent transmissions from geographically spread beacons are used to improve coverage area, then wide area positioning capability is enhanced, but signal separation becomes difficult leading to reduced position location accuracy
Solution Approach 1:
The patent segments the wide coverage area into multiple beacon zones, each transmitting in assigned time slots with unique codes and frequency offsets. This segmentation enables the receiver to isolate and measure signals from individual beacons even when multiple beacons serve the overall wide area, maintaining position location accuracy across the extended coverage.
Solution Approach 2:
The patent changes multiple transmission parameters simultaneously to enable signal separation: time slot assignments (TDMA), code sequence selections (CDMA), and frequency offset values (FOM). By coordinating changes across these parameters, the system achieves both wide area coverage through multiple beacons and precise position location through accurate signal parameter measurement.
3Reliability
If hybrid multiplexing method combining TDMA, CDMA, and FOM is used to distinguish transmissions from multiple beacons, then cross-interference is reduced and signal separation is improved, but system complexity increases
Solution Approach 1:
The patent merges three multiplexing techniques (TDMA, CDMA, FOM) into a unified hybrid framework where time slots, codes, and frequency offsets work together. This merging creates a coordinated system where each dimension reinforces the others: TDMA provides time-based separation, CDMA adds code-based discrimination, and FOM provides frequency-based isolation, achieving superior signal separation while managing complexity through integrated design.
Solution Approach 2:
The patent creates a universal multiplexing framework that can handle multiple concurrent transmissions from geographically spread beacons using a single hybrid TDMA-CDMA-FOM system. This multi-functional approach allows the same set of principles to distinguish all beacon signals simultaneously, rather than requiring separate mechanisms for each beacon, thereby reducing overall system complexity while maintaining reliable signal separation.
Data Source
AI summary
A position location system comprises transmitters that broadcast positioning signals. Each broadcasted positioning signal comprises a pseudorandom ranging signal. The position location system includes a remote receiver that acquires and measures the time of arrival of the positioning signals received at the remote receiver. During an interval of time, at least two positioning signals are transmitted concurrently by the transmitters and received concurrently at the remote receiver. The two positioning signals have carrier frequencies offset from one another by an offset that is less than approximately twenty-five percent of the bandwidth of each positioning signal of the two positioning signals. Cross-interference between the positioning signals is reduced by tuning the remote receiver to a frequency of a selected signal of the two positioning signals and correlating the selected signal with a reference pseudorandom ranging signal matched to a transmitted pseudorandom ranging signal of the selected signal.