Segmented RACH Access for LTE Cell Edge Collision Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current 3GPP LTE systems face challenges in efficiently reusing random access channel (RACH) sequences due to varying distances between user equipment and the base station, leading to excessive sequence requirements for user equipment close to the base station and inadequate sequence allocation for those farther away, resulting in reduced success probability and increased collision probability.
Innovation Solution
A segmented access scheme is implemented, where user equipment selects a channel configuration based on its location within the cell, allocating different sequences with varying lengths and zero correlation zones (ZCZ) to optimize resource usage and reduce collisions, by determining the region of the user equipment and using resources such as time, frequency, or both, proportionally to the cell radius, and redefining sequences for each region to meet specific requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a uniform RACH sequence allocation is used for all user equipment, then the system structure is simple, but user equipment close to the base station experience excessive sequence requirements and collision probability increases
Solution Approach 1:
The patent divides the cell into multiple regions (first region and second region) based on distance from the base station. Different RACH sequence allocation strategies are applied to each region: the first region (closer to base station) uses a first allocation strategy with fewer sequences, while the second region (farther from base station) uses a second allocation strategy with more sequences. This segmentation resolves the contradiction by tailoring sequence allocation to local conditions rather than using a uniform approach.
Solution Approach 2:
The patent implements local quality by assigning different RACH configuration parameters to different spatial regions. User equipment in the first region receives different sequence sets and allocation rules compared to user equipment in the second region. This allows each region to have optimized local characteristics for its specific distance requirements from the base station, reducing collisions near the base station while maintaining adequate access opportunities farther away.
2Reliability
If RACH sequence length is increased to support user equipment far from base station, then detection performance improves for edge users, but resource efficiency decreases due to excessive sequences for nearby users
Solution Approach 1:
The patent segments the user equipment population into two groups based on their location relative to the base station. The first region (nearby users) uses shorter sequences with optimized detection parameters, while the second region (edge users) uses longer sequences that provide adequate detection performance for their distance. This segmentation prevents the system from unnecessarily allocating resources for the maximum possible sequence length across all users.
Solution Approach 2:
The patent applies local quality by configuring different sequence lengths and detection parameters according to the specific needs of each region. Edge users in the second region receive longer sequences that compensate for path loss and maintain detection performance, while nearby users in the first region use shorter sequences that are sufficient for their closer proximity, thereby optimizing resource efficiency.
3Adaptability or versatility
If guard time is increased to accommodate maximum round-trip delay, then all user equipment can access the channel, but time resources are wasted for user equipment close to the base station
Solution Approach 1:
The patent divides the cell into regions based on round-trip delay characteristics. The first region contains users with shorter delay requirements (closer to base station), while the second region contains users with longer delay requirements (farther from base station). Different guard time values are assigned to each region, allowing the system to accommodate the maximum delay for edge users while avoiding excessive guard time for nearby users, thus improving time resource efficiency.
Solution Approach 2:
The patent implements local quality by assigning different guard time parameters to different spatial regions. Users in the first region experience shorter guard times appropriate for their proximity to the base station, while users in the second region receive longer guard times that ensure adequate time for signal transmission and reception at the cell edge. This localized approach optimizes time resource utilization across the entire cell.
Data Source
AI summary
A method and apparatus of transmitting signals for segmented access in a communication system is disclosed. The method for transmitting signals from a user equipment in a communication system includes the steps of selecting a predetermined channel structure depending on location of the user equipment among available channels defined differently depending on the location of the user equipment within a cell, and transmitting signals using the selected channel structure. Also, a method for transmitting signals using sequences allocated differently depending on location of a user equipment within a cell is disclosed.