Uplink Resource Allocation for Power Limited Users
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Solution Overview
Problem
In OFDMA systems, power-limited user terminals face challenges in allocating radio resources effectively due to variations in signal-to-interference plus noise ratio (SINR), leading to reduced transmission rates and increased error probabilities, especially when packet sizes and modulation and coding schemes (MCS) are not optimally managed.
Innovation Solution
The method involves fragmenting packets for power-limited user terminals to transmit across multiple time intervals, optimizing MCS selection based on available power and SINR, and scheduling non-delay-sensitive packets to increase spectral efficiency by using fewer resources, particularly during high system loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bandwidth allocated to power-limited user terminals is reduced, then signal to impairment ratio improves, but transmission rate decreases
Solution Approach 1:
The patent segments packets into multiple smaller transport blocks that can be transmitted across multiple subchannels. This allows power-limited terminals to distribute their limited power across more subchannels, improving SINR per subchannel while maintaining overall transmission rate through parallel transmission of multiple blocks.
Solution Approach 2:
The patent introduces the dimension of time by transmitting segmented packets across multiple transmission opportunities. This allows the system to achieve reliable communication at desired rates by utilizing both frequency (subchannels) and time dimensions, transforming a single high-rate unreliable transmission into multiple lower-rate reliable transmissions.
2Productivity
If modulation and coding scheme is optimized for higher transmission rates, then productivity increases, but reliability decreases due to higher SINR requirements
Solution Approach 1:
The patent divides a single high-rate transmission into multiple lower-rate transmissions of segmented packets. Each segmented block uses a more reliable modulation and coding scheme appropriate for the available power and channel conditions, while the overall system achieves high throughput through parallel transmission of multiple blocks across different subchannels and time slots.
3Productivity
If packet fragmentation is implemented, then spectral efficiency improves, but system complexity increases
Solution Approach 1:
The patent implements packet segmentation at the transport block level, which is more efficient than traditional byte-level fragmentation. This approach aligns with the physical layer structure of OFDMA systems, enabling efficient mapping to subchannels and simplifying processing at both transmitter and receiver while improving spectral efficiency.
4Productivity
If more subchannels are assigned to a user terminal, then transmission rate increases, but SINR decreases due to power limitations
Solution Approach 1:
The patent segments the transmission across multiple subchannels, allowing the terminal to distribute its limited power across more subchannels. This results in lower power per subchannel but maintains acceptable SINR through the combined effect of multiple parallel transmissions, achieving both higher overall rate and maintained reliability.
Data Source
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AI summary
A base station in an OFDMA system which determines a modulation and coding scheme to use for a packet of a certain size to be transmitted by a Mobile Station. The base station schedules transmissions by mobile stations and transmits packets. The base station includes a processing unit which determines a number of time-frequency resources required to transmit the packet for a modulation and coding scheme, determines an SINR based on the number of time-frequency resources used and available power at the mobile station, determines a transmission rate as a ratio of the packet size transmitted to the number of time-frequency resources used, sets a rate to zero if the determined SINR is lower than a threshold SINR required for the modulation and coding scheme, and selects the modulation and coding scheme with a highest transmission rate. The base station includes a memory storing modulation and coding schemes.