Pilot Configuration for Grant-Free Transmission Overhead
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Solution Overview
Problem
In 5G mobile communications systems, the limited number of pilots in the grant-free transmission mode leads to increased pilot overheads and reduced utilization, resulting in network congestion and pilot collisions, as network devices either reject new terminals or forcibly release existing ones to manage pilot allocation.
Innovation Solution
Configuring terminal devices to use a single pilot for each transmission, with specific configuration modes that include sending the same pilot in initial transmissions and different pilots in subsequent retransmissions, and implementing pilot multiplexing between devices to optimize pilot resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pilots are all allocated by the network device, then receiving reliability is improved, but network device complexity increases and new terminal access is rejected
Solution Approach 1:
The patent segments the pilot allocation process into two parts: network device allocates initial pilots to reduce complexity, while terminal devices autonomously select pilots for repeated transmissions to improve reliability. This segmentation resolves the contradiction by distributing allocation responsibilities.
Solution Approach 2:
Terminal devices perform self-service by autonomously selecting pilots from a pre-configured set for their repeated transmissions without requiring network device intervention. This reduces network device complexity while maintaining receiving reliability through consistent pilot usage across repetitions.
2Adaptability or versatility
If a pilot is randomly selected by the terminal device within a range, then pilot allocation flexibility is improved, but pilot collision probability increases
Solution Approach 1:
The network device pre-configures a set of pilots for terminal devices before transmission begins. Terminal devices select from this predetermined set rather than randomly choosing, which maintains flexibility while reducing collision probability through controlled selection space.
Solution Approach 2:
Different terminal devices are assigned different local pilot sets or different positions within the same pilot set based on their specific conditions (e.g., service type, channel characteristics). This local differentiation reduces overall collision probability while maintaining individual device flexibility.
3Reliability
If the quantity of pilots is increased, then pilot collision probability is reduced, but pilot overhead increases
Solution Approach 1:
A single pilot configured for a terminal device serves multiple functions: it identifies the terminal device, indicates the initial transmission subframe, and enables channel estimation across all K repeated transmissions. This multi-functionality reduces the number of pilots needed while maintaining low collision probability.
Solution Approach 2:
The patent merges the functions of multiple pilots into a single pilot by using it for device identification, timing indication, and channel estimation across repeated transmissions. This consolidation reduces pilot overhead while maintaining system reliability.
4Measurement precision
If different DMRS are used for first transmission and subsequent repeated transmissions, then channel estimation accuracy is improved, but pilot overhead increases
Solution Approach 1:
The patent implements periodic pilot transmission where a single pilot is reused across all K repeated transmissions. The network device performs combined decoding using this periodic pilot, achieving adequate channel estimation accuracy while minimizing pilot overhead through consistent reuse.
Data Source
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AI summary
This application discloses a communication method and a communications apparatus. The method includes: determining, by a terminal device, a configuration mode of one or more pilots used for K repeated transmissions, where in a first configuration mode, the terminal device sends a same pilot in each of first N of the K repeated transmissions, and does not send a pilot in remaining K-N transmissions; in a second configuration mode, the terminal device sends a first pilot in first N of the K repeated transmissions, and sends a second pilot in the remaining K-N transmissions; and in the third configuration mode, the terminal device sends the first pilot in each transmission in a first round of K transmissions, and sends the second pilot in each transmission in a second round of K transmissions; and sending, by the terminal device, the pilots based on the determined configuration mode when performing the K repeated transmissions. A corresponding apparatus is further disclosed. According to the solutions in this application, in the K repeated transmissions, the terminal device needs to configure only one pilot for each terminal device, so that pilot overheads are low and pilot utilization is high.