Subscriber Station Seed Position Derivation for GPS Time-to-Fix
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Unassisted GPS-type position determination systems face significant processing challenges due to uncertainties in satellite visibility, timing, frequency, and relative movement, leading to inefficient resource usage and prolonged time-to-fix.
Innovation Solution
A method is introduced where a subscriber station derives a seed position from overhead messages in a wireless communications system, using data structures like lookup tables to reduce search windows and improve efficiency by identifying visible satellites and estimating code phase shifts and Doppler shifts, thereby enhancing the initial time-to-fix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the subscriber station searches for satellite transmissions without using network-provided position information, then the position determination is completely unassisted and independent, but the processing resources required become excessive and the time-to-fix becomes inordinately long
Solution Approach 1:
The patent applies preliminary action by having the wireless communications system provide position information (such as base station location or cell ID) to the subscriber station before the GPS position determination process begins. This preliminary position data allows the subscriber station to initialize its search with a reasonable estimate of its location, thereby reducing the time-to-fix while maintaining unassisted operation. The system prepares and provides assistance data in advance without requiring continuous network support during the actual GPS fixing process.
2Adaptability or versatility
If the subscriber station tests all 32 possible GPS satellites without using network position information, then the position determination is completely independent, but the processing resources consumed become excessive
Solution Approach 1:
The patent applies local quality by using network-provided position information to determine which specific satellites are likely visible to the subscriber station based on its local geographic location. Instead of uniformly testing all 32 satellites, the system narrows the search to a localized subset of satellites that are geographically relevant to the subscriber station's position, thereby reducing processing resources while maintaining independent position determination capability.
Solution Approach 2:
The patent segments the set of 32 GPS satellites into visible and invisible satellites based on the subscriber station's location. By dividing the satellite list into relevant and irrelevant portions, the subscriber station can focus processing resources only on testing transmissions from satellites that are actually visible to it, rather than exhaustively testing all possible satellites.
3Adaptability or versatility
If the subscriber station searches over the full range of possible PN codes and frequencies without using network synchronization, then the position determination is completely unassisted, but the search window size becomes excessively large
Solution Approach 1:
The patent applies parameter changes by using network-provided synchronization information to adjust the search window parameters for PN code phases and frequency offsets. Instead of searching over the full range of possible values, the system narrows the search window based on the synchronization data provided by the wireless communications system, thereby reducing the complexity of the search process while maintaining unassisted operation.
Data Source
Figure 1~2A
Figure 2B
Figure 3A
AI summary
Methods and systems are provided for determining a position of a subscriber station in a wireless communications system. The subscriber station receives an overhead message from the wireless communications system and obtains a parameter value. A data structure stored in memory of the subscriber station is then accessed and a seed position is set to a stored position from an entry of the data structure associated with a value matching the parameter value obtained from the received overhead message. The position of the subscriber station is then determined from a set of signals from a satellite position determination system based on the set seed position.