Dynamic Rate Control for CDMA Reverse Link Load Balancing

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

CDMA networks face interference limitations due to simultaneous transmission by mobile stations, leading to fluctuations in reverse link load, which affect system throughput and outage probability, requiring effective rate control mechanisms to maintain signal quality.

Innovation Solution

Implementing a method where base stations periodically estimate reverse link load and broadcast quantized load indications to mobile stations, which dynamically adjust their transmission rates based on calculated rate change probabilities, using mapping functions to determine the likelihood of rate changes, and considering factors like user class and quality of service.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If all mobile stations transmit at maximum power to maintain signal quality, then signal quality is improved, but system interference increases and capacity decreases

Engineering Contradiction:

Improvesignal qualityVSAvoidinterference

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent dynamically changes the transmission rate parameter of mobile stations based on reverse link load conditions. By adjusting the data transmission rate rather than maintaining maximum power, the system maintains signal quality when needed while reducing interference during high load conditions, thus resolving the contradiction between reliability and harmful factors.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If target load is increased to maximize system throughput, then productivity is improved, but outage probability increases

Engineering Contradiction:

Improvesystem throughputVSAvoidoutage probability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements dynamic rate control where mobile stations adjust their transmission rates in response to changing load conditions. This dynamic adaptation allows the system to operate at higher target loads for improved throughput while automatically reducing individual station rates when load exceeds capacity, thereby maintaining reliability and reducing outage probability.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If common rate control commands are broadcast to all mobile stations, then ease of operation is improved, but load fluctuations increase

Engineering Contradiction:

Improverate control managementVSAvoidreverse link load stability

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent allows each mobile station to independently determine its own rate adjustment based on the broadcast command and its local conditions (channel quality, buffer status, power availability). This localized decision-making reduces synchronized rate changes across all stations, thereby dampening load fluctuations while maintaining the simplicity of broadcast-based control.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7599394B2Common rate control method for reverse link channels in CDMA networks

Publication Date: 2009.10.06 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A mobile station dynamically adjusts its data transmission rate based on periodic load indications from a base station. The mobile station calculates a load tracking value based on two or more periodic load indications, and then calculates a rate change probability as a function of the load tracking value. The mobile station selectively changes its transmission rate responsive to a current load indication based on the rate change probability.