eNodeB Spatial Resolution for LTE Random Access Collisions
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Solution Overview
Problem
In LTE networks, the Random Access procedure is hindered by collisions between user equipment (UEs) using the same preamble, leading to increased delay and resource costs, particularly in high-load scenarios, as the eNodeB cannot distinguish between UEs with identical random UE IDs, resulting in failed access attempts and limited RA capacity.
Innovation Solution
The method involves an eNodeB receiving multiple instances of uplink Random Access messages, spatially resolving the signals to identify directions or locations of transmission, and transmitting distinct downlink Random Access messages to each UE, thereby granting different resources and reducing collisions by using directional and power-based separation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple UEs use the same preamble for random access, then the RA procedure can be initiated, but collisions occur and access attempts fail due to inability to distinguish between users
Solution Approach 1:
The patent introduces spatial dimension (direction of arrival) as an additional parameter to distinguish between UEs using the same preamble. By resolving the direction from which uplink signals are received, the eNodeB can differentiate between multiple users on the same time-frequency resources, effectively adding a spatial layer to the random access procedure.
Solution Approach 2:
The patent segments the random access responses by transmitting distinct downlink Random Access messages in different spatial directions corresponding to the identified directions of uplink messages. This segmentation allows each UE to receive a dedicated response tailored to its spatial location, resolving collisions without requiring complex signal processing at the UE side.
2Productivity
If contention-based RA procedure is used to handle multiple UEs, then access requests can be processed, but increased delay and resource costs occur due to collision resolution requirements
Solution Approach 1:
The patent performs preliminary spatial resolution of uplink Random Access messages before transmitting downlink responses. By identifying the directions of incoming signals in advance, the eNodeB can prepare and transmit distinct responses in the appropriate directions simultaneously, avoiding sequential collision resolution and reducing overall access delay.
Solution Approach 2:
The patent replaces the traditional time-based sequential contention resolution mechanism with a spatial-parallel mechanism. Instead of resolving collisions through multiple time slots and retransmissions, the system uses spatial direction information to handle multiple UEs simultaneously, substituting temporal multiplexing with spatial multiplexing.
3Reliability
If spatial resolution is implemented to identify directions of uplink messages, then collisions can be reduced, but the processing complexity at eNodeB increases
Solution Approach 1:
The patent leverages the existing antenna system and signal processing capabilities of the eNodeB, which are already designed for spatial operations in LTE networks. The same hardware infrastructure supports both traditional communications and the enhanced spatial resolution functionality, avoiding the need for dedicated complex processing equipment.
4Productivity
If distinct downlink messages are transmitted in multiple directions, then resource allocation efficiency improves, but transmission complexity increases
Solution Approach 1:
The patent changes the spatial parameter (transmission direction) of downlink Random Access messages based on the identified directions of corresponding uplink messages. By adjusting the beam direction parameter, the eNodeB can efficiently allocate resources to multiple UEs without requiring complex resource scheduling algorithms or additional time-frequency resources.
Data Source
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AI summary
Methods and apparatus for providing a Random Access procedure used by a communications device and an access node, for example the UE (user equipment) and eNodeB (the LTE radio basestation) in an LTE network, to e.g. establish a Radio Resource Control (RRC) connection. An example of a method according to the invention for use in an access node comprises: receiving (42) signals comprising multiple instances of an uplink Random Access message; spatially resolving (44) the received signals to identify (46) directions from which the uplink Random Access message was received; and transmitting (48) distinct downlink Random Access messages in the identified directions from which the uplink Random Access message was received.