Base Station Synchronization Signal Frequency Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE-Advanced heterogeneous networks, user terminals located at the boundary of low-power base station coverage areas experience uplink interference and synchronization signal cancellation due to transmission power differences between high-power and low-power base stations, leading to communication disruptions and handover failures.
Innovation Solution
A communication control method that involves transmitting synchronization signals on different frequency bands and resource blocks by high-power base stations to allow user terminals to measure and synchronize with low-power base stations, while limiting transmission power only when necessary to prevent interference and ensure seamless handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-power base station limits transmission power at timing and frequency where a low-power base station transmits synchronization signal, then user terminals can perform measurement for the low-power base station, but communication disruption or failure may occur in user terminals that need to perform handover to the high-power base station
Solution Approach 1:
The patent segments the synchronization signal transmission into two distinct frequency bands: center frequency band (6 resource blocks) and non-center frequency band. The high-power base station limits power only in the center frequency band where the low-power base station transmits its synchronization signal, while maintaining normal power in the non-center frequency band. This segmentation allows user terminals to measure the low-power base station in the center band without disrupting handover procedures that utilize the non-center band.
Solution Approach 2:
The patent applies local quality by making the transmission power characteristic frequency-dependent rather than uniform across the entire carrier. Specifically, the high-power base station transmits at reduced power (power limiting) only in the specific frequency region (center 6 resource blocks) where interference would prevent measurement, while transmitting at normal power in other frequency regions. This localized power adjustment resolves the contradiction by applying the restrictive measure only where necessary.
2Productivity
If a high-power base station and a low-power base station use the same carrier, then the heterogeneous network can distribute load, but the low-power base station receives uplink interference from user terminals at coverage boundaries
Solution Approach 1:
The patent changes the frequency parameter of synchronization signal transmission by introducing a frequency shift (frequency offset) from the center frequency. The low-power base station transmits its synchronization signal at a frequency shifted from the center by a predetermined amount (e.g., based on cell ID). This parameter change allows the high-power base station to limit power at the center frequency without affecting the low-power base station's synchronization signal transmission, thereby reducing uplink interference while maintaining load distribution.
3Reliability
If a high-power base station transmits synchronization signal at center frequency, then synchronization can be established, but user terminals cannot receive synchronization signal from low-power base station due to cancellation by downlink signal
Solution Approach 1:
The patent resolves the contradiction by introducing a frequency dimension separation. Instead of having both base stations transmit synchronization signals at the same center frequency (time domain conflict), the low-power base station transmits at a frequency-shifted position (frequency domain separation). This dimensional change in the frequency domain allows both high-power and low-power base stations to provide synchronization signals simultaneously without mutual cancellation, enabling user terminals to receive both signals for proper measurement and handover.
Data Source
AI summary
A communication control method in a mobile communication system, comprises: a step A of transmitting, from a first base station, a first synchronization signal at a first frequency band in the center of a particular carrier, the first synchronization signal being for use to establish synchronization; and a step B of transmitting, from the first base station, a second synchronization signal in a second frequency band different from the first frequency band within the particular carrier, the second synchronization signal being for use to establish synchronization.