SCMA Congestion Control via Dynamic Slot Allocation
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Solution Overview
Problem
Existing multiple access schemes like TDMA and CDMA face challenges in achieving high channel utilization while maintaining low packet loss and system stability, especially when a large number of access nodes attempt to use the channel, leading to potential congestion and reduced successful decoding rates.
Innovation Solution
The proposed solution involves a telecommunication system that measures error rates and load metrics in real-time to adjust the number of transmission slots and shedding probabilities, allowing access nodes to switch between communication protocols based on error rates, load, and priority determinations to optimize latency and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple access nodes attempt to use the channel simultaneously to increase channel utilization, then channel utilization is improved, but interference increases and successful decoding rate decreases
Solution Approach 1:
The system dynamically adjusts the number of transmission slots allocated to each access node based on real-time error rates and load metrics. When error rates are low, more slots are allocated to increase channel utilization. When error rates increase indicating congestion, slots are reduced to decrease interference. This dynamic adjustment resolves the contradiction by making channel allocation adaptive rather than static.
Solution Approach 2:
The gateway receiver measures error rates and load metrics, then feeds this information back to access nodes to adjust their transmission slot allocation. The feedback loop allows the system to respond to changing channel conditions, increasing utilization when conditions are good and reducing interference when congestion is detected, thus resolving the contradiction between these two parameters.
2Productivity
If the number of transmission slots is increased to improve throughput, then throughput is improved, but packet loss increases due to congestion
Solution Approach 1:
The system dynamically adjusts transmission slot allocation based on real-time error rate measurements. When error rates are low, more slots are allocated to increase throughput. When error rates increase indicating congestion and potential packet loss, slots are reduced to maintain reliability. This dynamic adjustment resolves the contradiction by adapting slot allocation to current channel conditions.
Solution Approach 2:
The system changes the parameter of transmission slot allocation based on measured error rates and load metrics. By adjusting this key parameter in response to channel conditions, the system can optimize throughput when conditions permit while preventing packet loss when congestion is detected, thus resolving the contradiction between throughput and packet loss.
3Reliability
If error rate thresholds are set low to ensure high reliability, then packet loss is reduced, but channel utilization decreases due to excessive shedding
Solution Approach 1:
The system adjusts the error rate threshold parameter based on system load conditions. When load is low, higher thresholds are used to maintain high channel utilization by allowing more transmissions. When load increases, thresholds are lowered to reduce packet loss by shedding more traffic. This dynamic parameter adjustment resolves the contradiction between reliability and utilization.
Solution Approach 2:
The shedding behavior is made dynamic through adaptive threshold adjustment. Instead of using fixed thresholds that would force a trade-off between reliability and utilization, the system dynamically adapts thresholds to current load conditions, achieving both high reliability and high utilization by operating at optimal points under different conditions.
4Productivity
If SCMA is used to allow simultaneous transmissions to improve channel utilization, then channel utilization is improved, but system complexity increases
Solution Approach 1:
The system uses distributed decision-making where each access node autonomously determines its transmission slot allocation based on locally received feedback about error rates and load metrics. This self-service approach allows simultaneous SCMA transmissions to improve utilization while avoiding the need for complex centralized scheduling and coordination, thus managing system complexity.
Data Source
AI summary
A telecommunication system includes a gateway receiver having a processor and a data storage medium. The receiver is programmed to wirelessly communicate with a plurality of terminals, determine an error rate associated with communication with the plurality of terminals, determine an operating probability from the error rate, and transmit the operating probability to the plurality of terminals. A terminal includes a transmitter programmed to transmit signals to the gateway receiver in accordance with a number of transmitting slots. The terminal has a receiver programmed to receive signals transmitted from the gateway receiver, including an operating probability signal representing the operating probability. The terminal also includes processor programmed to select the number of transmitting slots based at least in part on the operating probability.