Signal Constellation Multiple Access for OFDMA Throughput
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Solution Overview
Problem
Current OFDMA systems, such as LTE and WiFi, face inefficiencies in downlink data transmission due to varying channel qualities among mobile units, leading to suboptimal throughput and spectral efficiency, especially when some units have weak channels assigned lower bit loading, limiting overall system performance.
Innovation Solution
The implementation of Signal Constellation Multiple Access (SCMA) using tiled-building-block trellis codes allows different mobile units with varying channel qualities to decode shared multi-resolution signal constellations, enabling additional bits to be encoded and decoded from resource blocks originally assigned to weak channels, thereby enhancing data throughput and spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different mobile units are assigned different bit loading levels based on channel quality, then channel reliability is maintained, but overall system throughput is reduced
Solution Approach 1:
The patent merges the resource blocks of weak channel users with strong channel users to form shared resource blocks. Strong channel users decode additional bits from these shared blocks that were originally intended for weak channel users, thereby combining the throughput contributions of multiple users into a single resource block transmission.
Solution Approach 2:
The shared resource blocks serve multiple functions: they maintain reliable communication for weak channel users while simultaneously enabling additional data transmission for strong channel users. The same physical resource block performs both protective and productivity-enhancing roles.
2Adaptability or versatility
If resource blocks are allocated to mobile units with weak channels, then coverage is extended, but spectral efficiency is reduced
Solution Approach 1:
The patent combines resource blocks assigned to weak channel users with those assigned to strong channel users, creating shared resource blocks that are decoded by both user types. This merging allows the system to maintain coverage for weak channel users while recovering spectral efficiency through the contributions of strong channel users.
Solution Approach 2:
Different portions of the shared resource block are decoded at different levels of resolution according to local channel quality. Weak channel users decode at a lower resolution level while strong channel users decode at a higher resolution level, allowing each user to utilize the resource block according to their local channel conditions.
3Productivity
If higher bit loading is used for all resource blocks, then system throughput increases, but error rates increase for weak channel users
Solution Approach 1:
The patent applies different decoding resolution levels to different users based on their local channel quality. Strong channel users benefit from higher bit loading and higher resolution decoding, while weak channel users maintain lower bit loading and lower resolution decoding for their portion of the shared resource block.
Solution Approach 2:
The patent segments the bit streams into different levels of resolution, allowing strong channel users to decode additional higher-resolution bits while weak channel users decode only the base-level bits. This segmentation prevents error propagation and maintains reliability for vulnerable users while enabling throughput enhancement for robust users.
Data Source
AI summary
The present invention provides methods, apparatus and systems for improving a systems-level data rate on a communications link such as the orthogonal frequency division multiplexed multiple access (OFDMA) downlink used in WiFi and LTE cellular/wireless mobile data applications. The present invention preferably uses a form of multilevel coding and decoding known as tiled-building-block encoding/decoding. With the present invention, different receivers coupled to different parallel downlink channels with different channel qualities decode different received signal constellations at different levels of resolution. This allows the downlink of the OFDMA system to operate with a significantly higher data rate, thus eliminating existing inefficiencies in the downlink and significantly increasing system level bandwidth efficiency.