Adaptive Reference Signal Density for Small Cell Power Savings
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Solution Overview
Problem
Current LTE systems are inefficient in small cell environments like indoor femtocells due to high reference signal power requirements, as they are optimized for macro-cellular systems with longer distances and higher speeds, leading to unnecessary power consumption and potential interference.
Innovation Solution
Adaptive adjustment of reference signal density based on cell size and proximity to other cells, using a network management system to determine and control the density of reference signals, reducing power usage and mitigating interference by dynamically adjusting the pattern in response to signal quality and user terminal mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard LTE reference signal density is used in small cells, then channel estimation reliability is maintained for macro-cellular conditions, but power consumption increases and spectrum efficiency decreases for small cell environments
Solution Approach 1:
The patent changes the density parameter of reference signals dynamically based on cell size and terminal mobility conditions. For small cells with low mobility, the reference signal density is reduced compared to standard LTE configurations, thereby reducing power consumption and spectrum usage while maintaining sufficient channel estimation accuracy for the specific small cell environment.
Solution Approach 2:
The system dynamically adjusts reference signal density according to real-time conditions including cell size, terminal mobility speed, and channel characteristics. This dynamic adaptation allows the base station to optimize power consumption and spectrum efficiency by transmitting fewer reference signals when environmental conditions permit, while maintaining reliability when needed.
2Measurement precision
If standard LTE reference signal density is used in small cells, then channel reconstruction accuracy is maintained for high-speed scenarios, but reference signal pollution increases and spectrum efficiency decreases
Solution Approach 1:
The patent adjusts the density parameter of reference signals based on terminal mobility measurements. For low-speed terminals in small cells, the reference signal density is reduced, which decreases reference signal pollution and improves spectrum efficiency while maintaining sufficient channel reconstruction accuracy for the specific mobility conditions.
Solution Approach 2:
The system dynamically adapts reference signal density in response to terminal mobility conditions and cell characteristics. This dynamic adjustment reduces reference signal pollution in appropriate scenarios while maintaining channel reconstruction accuracy, thereby improving overall spectrum efficiency without compromising measurement precision when needed.
3Use of energy by stationary object
If reference signal density is reduced for power savings, then power consumption and interference are reduced, but difficulty in initial channel acquisition increases
Solution Approach 1:
The patent ensures that sufficient reference signals are transmitted during the initial cell search and acquisition phase, before normal operation begins. This preliminary provision of adequate reference signals enables successful channel acquisition and cell synchronization, after which the system can transition to reduced reference signal density for power savings during steady-state operation.
Solution Approach 2:
The system dynamically adjusts reference signal density based on operational phase and terminal conditions. During initial acquisition and in challenging radio conditions, higher density is maintained to ensure successful detection and measurement. Once acquisition is complete and conditions are favorable, density is reduced to achieve power savings, thus resolving the contradiction between acquisition difficulty and power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significant power savings and efficiency improvements are achieved by optimizing reference signal density for small cell environments, reducing the need for excessive power and spectrum usage while maintaining effective channel estimation and user terminal synchronization.
Implementation Method 1
The frequency domain effect is caused by Doppler shift, whereby the frequency of the received signal at the eNodeB will be shifted down if the UE is moving away from it and shifted up if the UE is moving towards it
Implementation Method 2
The time domain effect is caused by multipath reflections, whereby the reflections cause disturbances in the amplitude and phase of the signals. Such reflections come from surfaces near to the UE and more distant from the UE
Data Source
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Figure 3A
AI summary
A wireless communications network is configured to transmit signals comprising a plurality of data units containing reference signals for use in channel assessment by mobile stations receiving the transmissions. Topological data 220 relating to the relative positions of each base stations 21 in the network is used by a density adjustment function 214, 221 to select a distribution pattern and density of reference signals. A signal is sent to one or more user terminals 20, the signal comprising reference signals arranged in the selected distribution and density of plurality of data units, and including a control signal to indicate to the mobile terminal which density and distribution is in use.