Hierarchical Modulation Coding for IoT Multicast Energy Efficiency
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Solution Overview
Problem
Current methods for transmitting data packets to devices with varying channel conditions, such as in IoT applications, face challenges in optimizing modulation and coding schemes, leading to inefficient energy use and prolonged device wake times, especially in multicast and broadcast transmissions.
Innovation Solution
A method that selects a hierarchy of modulation and coding schemes to create multiple layers of data packets, where the most robust bits are used for devices with poor channel conditions and less robust bits for those with good conditions, allowing receivers to selectively demodulate and decode layers based on their conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transmitted signal uses a high modulation and coding scheme (MCS) to obtain good spectrum efficiency, then spectrum efficiency is improved, but devices with poor receiver conditions will not be able to correctly receive the packet
Solution Approach 1:
The data packet is segmented into multiple layers with different robustness levels. The first layer contains robustly encoded data that can be decoded by devices with poor receiver conditions, while additional layers contain less robustly encoded data for devices with better conditions. This segmentation allows the same transmission to serve multiple device types simultaneously.
Solution Approach 2:
Different portions of the data packet are assigned different quality levels through hierarchical modulation. The most critical data bits are encoded with higher robustness (lower modulation order) while less critical bits use lower robustness (higher modulation order), allowing receivers to decode according to their specific channel conditions.
2Reliability
If a packet is sent with low MCS, which is robust, in order to ensure that as many devices as possible are able to decode the packet, then packet reception reliability is improved, but those receivers that have favorable channel conditions will need to be receiving for an unnecessarily long time, resulting in unnecessarily high power consumption
Solution Approach 1:
The packet structure is divided into layers where devices can selectively decode only the layers appropriate to their channel conditions. Devices with favorable conditions can decode the first layer quickly and wake up earlier, reducing their receiving time and power consumption, while devices with poor conditions decode additional layers at their own pace.
Solution Approach 2:
The system enables dynamic adaptation of receiving behavior based on channel conditions. Receivers can adjust their wake time and decoding depth according to their specific SNR levels, allowing favorable receivers to exit early while poor receivers continue decoding additional layers, optimizing overall system energy efficiency.
3Reliability
If the MCS is determined by the link requirements of the device with the lowest SNR, then reliability for the weakest link is improved, but the devices with much better SNR will need to be receiving for a longer time than the channel conditions actually allow
Solution Approach 1:
The transmission is divided into hierarchical layers where the first layer is optimized for the weakest link (lowest SNR devices) and additional layers provide incremental improvements for stronger links. This allows weakest-link devices to decode the essential first layer while stronger link devices can optionally decode additional layers if time permits, eliminating the need for all devices to wait for the full transmission duration.
Solution Approach 2:
The most robustly encoded first layer is prepared in advance and can be decoded independently by any receiver. This preliminary layer ensures that even devices with the worst channel conditions can obtain essential data, while devices with better conditions have the option to decode additional layers without delaying the basic transmission completion.
Data Source
AI summary
A method for modulating and coding a data packet comprising digitally encoded information. The method comprises selecting a hierarchy of modulation and coding schemes to use for modulation and coding of the digitally encoded information. The method also comprises identifying, among the bits in the digitally encoded information and based on the selected hierarchy of modulation and coding schemes, two sets of data, a first set of data and a second set of data, the second set of data being a sub-set of the first set of data and comprising bits different from the most robust bits of the first set of data. The method further comprises performing modulation and coding of the first set of data using a modulation and coding scheme with high order modulation in order to create a first layer of the data packet.