Multicast Broadcast Transmission Repetition and NACK Feedback
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Solution Overview
Problem
Multicast and broadcast transmissions in wireless communication systems face challenges in efficiently conditioning and re-transmitting data to devices with varying power and processing capabilities, particularly for M2M and IoT devices, due to differences in channel conditions and limited feedback mechanisms.
Innovation Solution
A method where a wireless device receives a multicast or broadcast transmission with specified repetitions and uses a negative acknowledgement only feedback scheme to adjust transmission parameters, and a radio network node selects a modulation and coding scheme (MCS) and repetition factor to target different channel conditions, allowing devices to conserve power by stopping unnecessary processing after successful decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multicast or broadcast transmission is used to convey information to a group of wireless devices, then spectral efficiency is improved and delivery time is reduced, but the challenge of conditioning the transmission for reception by different wireless devices with varying power and processing capabilities increases
Solution Approach 1:
The transmission is segmented into multiple repetitions, where each repetition contains the same data. Devices can stop processing after successfully decoding any one repetition, allowing early-exiting devices to conserve power while ensuring reliable delivery to all devices in the group.
Solution Approach 2:
The system changes transmission parameters including the number of repetitions, modulation and coding scheme (MCS), and resource allocation based on channel conditions and device capabilities. This allows the same transmission to be adaptively received by devices with different power and processing capabilities.
2Reliability
If re-transmission is performed to ensure all devices successfully receive the transmission, then reliability is improved, but the complexity of managing different device requirements and processing increases
Solution Approach 1:
A feedback mechanism is implemented where devices that fail to decode the transmission send a negative acknowledgement (NACK). The network node receives this feedback and triggers re-transmission only when necessary, improving reliability while avoiding unnecessary re-transmissions that would increase complexity and resource usage.
Solution Approach 2:
The system dynamically adjusts the number of repetitions and transmission parameters based on real-time feedback from devices. This dynamic adaptation ensures reliable delivery to all devices while optimizing resource usage and reducing overall system complexity compared to static approaches.
3Reliability
If devices with limited power and processing capabilities continuously monitor for transmissions, then reliability of reception is improved, but power consumption increases
Solution Approach 1:
Devices perform partial processing by monitoring only enough repetitions to successfully decode the transmission. Once decoding succeeds, devices stop processing additional repetitions entirely. This partial action approach maintains reliable reception while significantly reducing power consumption compared to continuous monitoring of all repetitions.
Solution Approach 2:
The network node transmits multiple repetitions in advance with the same data content. Devices can successfully decode from any single repetition and stop processing, knowing that sufficient information has been provided. This preliminary provision of redundant information allows devices to conserve power while ensuring reliable reception.
Data Source
AI summary
A wireless device (18) is configured for use in a wireless communication system. The wireless device (18) is configured to receive, from a radio network node (12), a multicast or broadcast transmission (14) and downlink control information indicating a number of repetitions with which the multicast or broadcast transmission (14) is transmitted. The wireless device (18) is also configured to operate according to a negative acknowledgement only feedback scheme in which the wireless device (18) is configured to transmit a negative acknowledgement to the radio network node (12) if decoding of the multicast or broadcast transmission (14) fails using the indicated number of repetitions and to refrain from transmitting a positive acknowledgement to the radio network node (12) if decoding of the multicast or broadcast transmission (14) succeeds.