Grid Cell Location Encoding for ProSe Security
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Solution Overview
Problem
Existing location services, such as ProSe, face inaccuracies and power consumption issues, particularly in indoor and rural areas, and are vulnerable to spatial replay attacks, which compromise the security of device-to-device communication.
Innovation Solution
A method that determines a minimum cell size based on location accuracy and transmits only the least significant bits of counter values in orthogonal directions, optimizing location information transmission to reduce spectrum usage and prevent spatial replay attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full location information (complete counter values) is transmitted, then location accuracy is maintained, but spectrum usage increases and power consumption rises
Solution Approach 1:
The patent extracts only the necessary portion of location information (least significant bits of counter values) for transmission, discarding the more significant bits that consume spectrum and power without providing proportional benefit. This extraction approach maintains sufficient location accuracy for proximity services while dramatically reducing the amount of data transmitted.
Solution Approach 2:
The patent applies different levels of precision to different parts of the location information. Instead of uniformly high precision across all transmitted data, it uses lower precision (fewer bits) for the transmitted portion while maintaining higher precision locally in the device's full counter values, optimizing the trade-off between accuracy and resource consumption.
2Measurement precision
If complete location information is transmitted, then location accuracy is maintained, but spectrum resources are wasted
Solution Approach 1:
The patent extracts only the essential location data (least significant bits) needed for proximity determination, removing redundant high-order bits from transmission. This reduces the quantity of transmitted information while preserving the functional accuracy required for ProSe applications.
Solution Approach 2:
The patent transmits only a partial amount of location information (a subset of the full counter values) that is sufficient for the intended purpose of proximity-based services, avoiding the excessive transmission of complete high-precision location data that would waste spectrum resources.
3Reliability
If location information is included in discovery messages, then spatial replay attacks can be detected, but message size increases
Solution Approach 1:
The patent extracts a compact representation of location information (least significant bits of counter values) that is sufficient for spatial replay attack detection. This extracted subset provides the necessary security verification while keeping the added message overhead minimal.
Solution Approach 2:
The patent changes the parameter of location information representation from full-precision counter values to truncated least significant bits. This parameter transformation maintains the ability to detect spatial replay attacks (by verifying location consistency) while significantly reducing the message size impact.
Data Source
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AI summary
A location information is based on a coordinate grid where different cell sizes could be supported in order to adapt to the accuracy of the available positioning system. The grid is divided into areas of fixed latitude width such that, within each area, and for a fixed minimal cell size, the variation of the geographical area covered by the cells is tolerated with respect to a certain parameter of the service parameter (e.g. the transmission range). Within each area the cells are numbered uniquely along the latitude lines by an x-counter and the longitude line by a y-counter. In order to transmit its location information, the sender uses a positioning method with a certain accuracy, decides on a cell size (among a fixed number of available fixed sizes), determines the x and y counter of the cell where he is located and includes in the message an indication of the chosen cell size and equal numbers of LSBs for each of the counters.