Per-User Rate Control for CDMA Reverse Link Capacity
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Solution Overview
Problem
Interference limits the reverse link capacity in CDMA networks, restricting the number of mobile stations that can simultaneously transmit to a base station and affecting data rates, as existing power control methods struggle to efficiently manage interference and optimize network loading.
Innovation Solution
A method and apparatus for controlling reverse link rates in wireless communication networks, where mobile stations indicate desired data rate changes, and the network calculates priority values based on throughput and achievable rates, ranking stations to optimize scheduling and capacity utilization, using techniques like Shannon's Capacity Theorem to determine achievable data rates and adjust transmit power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If closed loop power control is used to reduce interference from each mobile station, then the overall interference is reduced and reverse link capacity is improved, but the system cannot efficiently manage interference and optimize network loading to support higher data rates for more users
Solution Approach 1:
The patent implements dynamic rate control where the base station adjusts the data rate of mobile stations based on real-time interference conditions and network loading. The system dynamically switches between different rate control modes (e.g., mode 1: rate adjustment based on interference; mode 2: rate adjustment based on network loading) to optimize reverse link capacity while managing interference effectively.
Solution Approach 2:
The system changes the data rate parameter of mobile stations dynamically based on measured interference levels and network conditions. By adjusting the data rate parameter in response to changing conditions, the system optimizes the balance between supporting more users at higher rates and maintaining acceptable interference levels.
2Productivity
If more mobile stations are supported simultaneously at higher data rates, then reverse link throughput is improved, but the interference contribution from each station increases and capacity is limited
Solution Approach 1:
The system uses feedback mechanisms where mobile stations report their desired rates and actual throughput, and the base station measures interference levels. Based on this feedback, the base station adjusts the data rates of individual stations and schedules transmissions to optimize overall throughput while controlling interference. The feedback loop enables continuous optimization of the throughput-interference trade-off.
Solution Approach 2:
The system allows mobile stations to request higher rates than would be sustainable under current conditions, and the base station selectively grants these requests based on available capacity and interference constraints. By allowing some stations to operate at higher rates when conditions permit, the system maximizes overall throughput while managing interference through selective scheduling.
3Object-affected harmful factors
If the network schedules users in succession of scheduling intervals to limit simultaneous users, then interference is kept within tolerable levels, but the system cannot efficiently utilize reverse link capacity
Solution Approach 1:
The system dynamically adjusts the scheduling interval and user selection based on real-time interference conditions and network loading. Rather than using fixed scheduling intervals, the base station adapts the scheduling parameters to maximize capacity utilization while keeping interference within acceptable levels, allowing more flexible and efficient use of reverse link capacity.
Data Source
AI summary
A method and apparatus enables a base station to control the reverse link data rates of the mobile stations. Such control may be used to improve reverse link throughput, and such improvements may be balanced against fairness of service interests. Broadly, a radio base station (RBS) makes per-mobile station rate control decisions in each rate control interval based on each mobile station's desired rate and past reverse link throughput. These values may be used to compute a priority value for each mobile station, which values are then used to prioritize the mobile stations in rank order. Rate control decisions are made for the mobile stations in rank order based on their desired rates and remaining reverse link capacity. In one embodiment, the mobile stations provide path loss information to the RBS, and it computes each mobile station's desired rate as the mobile's achievable rate assuming it transmitted at maximum power.