Analog Bloom Filter PRACH Reducing Collision Probability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LTE networks face high collision probabilities in physical random access channel (PRACH) due to limited orthogonal Zadoff-Chu sequences, leading to inefficiencies in user equipment (UE) connection initiation, especially as 5G networks are expected to support higher user densities and lower latency.
Innovation Solution
The implementation of a Peak-based Analog Bloom Filter (PABF) scheme, which allows user equipment (UE) to transmit multiple orthogonal sequences instead of a single sequence, reducing collision probability and enabling efficient message decoding with improved latency and error ratio performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple orthogonal Zadoff-Chu sequences are used for PRACH in LTE networks, then the collision probability is reduced, but the device complexity and sequence management become more complex
Solution Approach 1:
The patent divides the PRACH procedure into two independent stages: (1) preamble transmission using a limited set of orthogonal sequences, and (2) message transmission using resource blocks selected from multiple groups. This segmentation allows the system to maintain simple orthogonal sequence transmission while reducing collision probability through diversified resource selection in the second stage.
Solution Approach 2:
The patent extends the random access resource selection from one dimension (sequence selection only) to multiple dimensions by introducing resource block group selection as an additional degree of freedom. UEs randomly select both a preamble sequence and a resource block group, creating a multi-dimensional resource space that exponentially increases the number of possible access combinations without complicating the orthogonal sequence structure.
2Quantity of substance
If more orthogonal sequences are allocated to support higher user density in 5G, then the network capacity increases, but the latency and connection initiation efficiency worsen due to the limited sequence pool
Solution Approach 1:
The patent makes resource blocks serve multiple functions by organizing them into groups that can be dynamically selected for random access. Each resource block group contains multiple resource blocks that can accommodate different UEs, allowing the same physical resources to serve multiple access purposes simultaneously. This multi-functionality increases user density support without requiring proportional increases in orthogonal sequence numbers.
Solution Approach 2:
The patent performs preliminary random selection of resource block groups before actual message transmission. UEs pre-select their resource block groups from available groups and prepare their access messages accordingly. This preliminary action distributes the access load across multiple resource groups in advance, reducing contention and latency when actual transmission occurs.
3Device complexity
If a single orthogonal sequence is used for PRACH transmission, then the device complexity is low, but the collision probability increases significantly
Solution Approach 1:
The patent segments the random access resource space into two independent dimensions: preamble sequences and resource block groups. UEs independently select resources in both dimensions, transforming a single-point collision problem into a multi-dimensional resource allocation problem. This segmentation maintains simple transmission procedures while dramatically reducing collision probability through increased resource diversity.
Solution Approach 2:
The patent implements a nested structure where resource block groups are nested within the overall PRACH framework, and each resource block group contains multiple resource blocks. This nested organization allows UEs to select from multiple hierarchical levels (sequence → group → block), creating a layered resource selection mechanism that reduces collisions without increasing transmission complexity.
Data Source
AI summary
This disclosure describes a novel PRACH scheme based on an Analog Bloom Filter, in which user equipment is allowed to transmit multiple sequences to a base station, instead of only one sequence as is the case with the current LTE. A new decoding algorithm is disclosed, which copes with the unique challenges in the signal generated with ZC sequences, such as peak shifting and multiple peaks. In addition, when CFO can be removed the new scheme allows the UE to piggybacklog27bits of information along with the signal. Evaluation shows that the new scheme outperforms the existing PRACH of LTE by more than an order of magnitude in many cases, and therefore is a good candidate as the PRACH for future wireless networks (e.g., 5G).