User Equipment Cell Search Using D2D Assistance Signals
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Solution Overview
Problem
User equipment face high power consumption and inefficient cell search when moving out of coverage, particularly at the edge of a cell, due to frequent scanning and battery-saving strategies that prolong search times, leading to battery drain and potential loss of coverage.
Innovation Solution
Utilizing device-to-device synchronization signals from a user equipment in coverage to determine frequencies and times for scanning, limiting the search to specific frequencies and times, and camping on the transmitting user equipment to decode messages and attempt to reconnect to the cell, thereby reducing power consumption and improving search efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the user equipment scans supported frequencies, frequency bands and/or RAT technologies frequently to find a cell to camp on, then the time required to find coverage is reduced, but the power consumption increases
Solution Approach 1:
The patent introduces a base station as an intermediary that provides assistance information to the user equipment. This base station, being in coverage, can guide the out-of-coverage UE to the correct cell by providing frequency, time, and other relevant parameters, thereby reducing the UE's scanning burden and power consumption while maintaining quick coverage acquisition
Solution Approach 2:
The base station performs preliminary actions by pre-calculating and providing assistance information including frequency, time, and other parameters before the UE needs to scan. This preliminary provision of information enables the UE to skip extensive scanning and directly camp on the appropriate cell, reducing both time and power consumption
2Use of energy by moving object
If the user equipment increases the time between searches to preserve battery, then the power consumption is reduced, but the time to find coverage when available increases
Solution Approach 1:
The base station acts as a mediator that provides accurate assistance information, enabling the UE to perform targeted searches rather than exhaustive scanning. This allows the UE to maintain longer intervals between searches (preserving battery) while still finding coverage quickly when needed, because the assistance information directs the search efficiently
3Reliability
If the user equipment scans frequently at the edge of a cell, then the chance to find coverage is increased, but the power consumption increases due to frequent scan timer resets
Solution Approach 1:
The base station provides assistance information that includes accurate timing and frequency parameters, enabling the edge UE to synchronize with the network without frequent scan timer resets. This intermediary guidance maintains reliable coverage acquisition at cell edges while reducing the power consumption associated with repeated scanning
4Reliability
If the user equipment scans all supported frequencies and RAT technologies, then the probability of finding a cell to camp on is increased, but the device complexity and processing load increase
Solution Approach 1:
The patent extracts only the necessary search parameters (frequency, time, RAT type) from the complete set of possible parameters by having the base station provide targeted assistance information. This extraction principle allows the UE to perform a simplified search focusing only on relevant frequencies and RATs rather than scanning all supported options, reducing device complexity while maintaining high success probability
Solution Approach 2:
The base station as an intermediary filters and provides only the relevant assistance information needed for successful cell camping, eliminating the need for the UE to independently evaluate all supported frequencies and RAT technologies. This reduces the search procedure complexity while maintaining high reliability
Data Source
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AI summary
A user equipment (2) comprises a wireless interface for communication with a cellular communication network. The user equipment (2) is configured to detect a device-to-device signal received from a further user equipment (3) consisting of path-loss information from the base station and of its own transmit power to the user equipment (2). The user equipment (2) is configured to measure a further path loss for the device-to-device signal from the further user equipment (3) to the user equipment (2) and to search for a cell (13) of the cellular communication network to camp on based on the device-to-device signal.