Cable Modem Upstream Scheduling for Low-Latency Bandwidth Grants
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Solution Overview
Problem
Conventional cable modem communication networks face issues with latency in best-effort upstream bandwidth allocation techniques and inefficiencies in proactive grant services due to inefficient bandwidth allocation when service flows stop using allocated bandwidth.
Innovation Solution
A new technique that combines best-effort and proactive grant services by using a scheduler processing method to allocate upstream bandwidth based on requested, guaranteed, and proactive bandwidth needs, predicting future bandwidth requirements, and ensuring equitable distribution among service flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional best-effort technique is used for upstream bandwidth allocation, then bandwidth is allocated based on actual requests from modems, but latency increases due to one-to-one relationship between requests and grant responses
Solution Approach 1:
The CMTS performs preliminary actions by proactively allocating bandwidth to service flows before actual data transmission occurs. The system predicts future bandwidth requirements and pre-allocates timeslots, eliminating the need for modems to send individual requests for each data packet and thereby reducing latency while maintaining allocation accuracy.
Solution Approach 2:
The patent segments the bandwidth allocation process into different components: guaranteed bandwidth allocation for predictable traffic patterns and proactive grant service for predictive bandwidth assignment. This segmentation allows the system to handle different traffic types differently, reducing overall latency while maintaining reliability.
2Loss of time
If conventional proactive grant services are used for upstream bandwidth allocation, then latency is reduced by reducing the number of requests, but bandwidth allocation efficiency deteriorates when service flows stop using allocated bandwidth
Solution Approach 1:
The system incorporates feedback mechanisms where the CMTS monitors actual bandwidth usage by service flows and adjusts allocations accordingly. When a service flow stops using allocated bandwidth, the feedback loop detects this and reallocates the bandwidth to other active flows, maintaining efficiency while preserving the low-latency benefits of proactive allocation.
Solution Approach 2:
The patent implements dynamic bandwidth allocation where the CMTS continuously adjusts proactive grants based on real-time usage patterns. The system transitions from static pre-allocation to dynamic adjustment, allowing it to maintain low latency for active flows while efficiently reallocating bandwidth when usage patterns change, thus solving the efficiency deterioration problem.
3Loss of time
If more proactive bandwidth allocation is implemented, then latency is reduced, but device complexity increases due to additional scheduling processing requirements
Solution Approach 1:
The system manages complexity by changing key parameters such as prediction accuracy thresholds and allocation granularity. By adjusting these parameters, the CMTS can implement proactive allocation to reduce latency while keeping the scheduling processing within acceptable complexity limits, avoiding excessive computational overhead.
Data Source
AI summary
In a cable modem network, upstream bandwidth is allocated to service flows by receiving requests from modems, wherein each request identifies an amount of requested bandwidth for a corresponding requesting service flow; determining how much best-effort bandwidth to allocate for each requesting service flow; determining how much remaining bandwidth is available after taking into account all of the best-effort bandwidth for the requesting service flows; determining how much of the remaining bandwidth to allocate as proactive grant service (PGS) upstream bandwidth to PGS service flows; determining, for each requesting service flow, a summed bandwidth as a sum of any corresponding best-effort bandwidth and any corresponding PGS bandwidth; determining, for each requesting service flow, an amount of allocated bandwidth as a minimum of the summed bandwidth and a maximum allowable bandwidth; and transmitting grants to the modems identifying the amounts of allocated upstream bandwidth for the corresponding service flows.