LTE Discovery Signal Timing for Dense Small Cell Search
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In densely deployed small cell scenarios, existing synchronization channels in LTE systems struggle to efficiently facilitate cell discovery, power usage, and handover procedures due to increased geographic density of small cells, leading to challenges in identifying and synchronizing with multiple cells.
Innovation Solution
The proposed solution involves generating and transmitting discovery signals in LTE communication systems, which include a pair of synchronization signals and additional signals, with the additional signals transmitted in a symbol separated by no more than half a radio frame from the synchronization signals, allowing for efficient cell search and synchronization in densely populated areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional Synchronization Channels (SCH) are used in LTE systems, then cell search and synchronization procedures can be performed, but the system cannot efficiently handle densely deployed small cell scenarios with high geographic density
Solution Approach 1:
The discovery signal is segmented into multiple components: a first synchronization signal (PSS), a second synchronization signal (SSS), and additional signals (such as PRS or CRS). These segmented components are transmitted in different time slots within the radio frame, allowing the UE to progressively discover and synchronize with cells in dense deployments without overwhelming system complexity.
Solution Approach 2:
The patent introduces preliminary discovery signals that are transmitted before conventional data channels. These discovery signals include synchronization information and cell identification data that are prepared in advance, enabling UEs to quickly identify and synchronize with small cells without having to process full conventional SCH sequences, thus improving cell discovery speed in dense scenarios.
2Area of stationary object
If the number of small cells increases to achieve higher geographic density (40 cells per square kilometre), then network coverage is improved, but the complexity of cell identification and measurement increases significantly
Solution Approach 1:
The patent applies local quality by transmitting discovery signals with specific local characteristics in different geographic areas. Small cells in dense deployments use localized discovery signal patterns and sequences that are distinct from macro cells, allowing UEs to easily differentiate between cell types and identify individual cells based on their local signal properties rather than having to process all cells uniformly.
Solution Approach 2:
The patent uses different signal sequences, frequencies, or time patterns as 'colors' to identify different cells. Each small cell is assigned a unique discovery signal signature (analogous to a color code), enabling UEs to rapidly identify and distinguish between multiple cells in dense deployments through signal recognition rather than complex measurement procedures.
3Reliability
If conventional SCH transmission is used, then synchronization can be achieved, but power consumption increases and handover procedures become slower in dense small cell environments
Solution Approach 1:
The patent implements periodic transmission of discovery signals at optimized intervals within radio frames. Instead of continuous SCH transmission, discovery signals are sent periodically at specific subframe intervals, reducing overall power consumption while maintaining reliable synchronization. The periodic structure allows UEs to efficiently track cell presence and perform handovers by monitoring these periodic signals rather than processing continuous transmissions.
Data Source
AI summary
Communication apparatus is disclosed which is suitable for communicating with a mobile communication device in a communication system which uses a plurality of radio frames wherein each radio frame is subdivided in the time domain into a plurality of subframes, each subframe is subdivided in the time domain into a plurality of slots, and each slot is subdivided in the time domain into a plurality of symbols. The communication apparatus operates a communication cell, generates discovery signals, for use in a cell search procedure, each discovery signal comprising a pair of synchronisation signals and a further signal, and transmits each synchronisation signal and the further signal in a respective symbol of a radio frame. The symbol in which the further signal is transmitted separated, in the time domain, by no more than half a radio frame from at least one of said pair of synchronisation signals.