Separated Uplink Downlink Cell Association for Heterogeneous Networks
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Solution Overview
Problem
In heterogeneous cellular networks, the difference in transmission power and antenna gain between macrocell and femtocell base stations leads to signal-to-interference noise ratio (SINR) unfairness and load balancing issues, as terminals often connect to macrocells due to greater coverage, neglecting optimal uplink associations.
Innovation Solution
A method and apparatus that allow separate uplink and downlink connections by determining an uplink base station based on the strength of an uplink reference signal and a bias factor, enabling optimal cell associations for both uplink and downlink communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If terminals connect to base stations based on downlink signal strength, then downlink coverage is improved, but uplink SINR fairness deteriorates
Solution Approach 1:
The patent segments the cell association process into two independent parts: downlink cell association based on downlink reference signal strength, and uplink cell association based on uplink reference signal strength. This allows separate optimization of downlink coverage and uplink SINR fairness by evaluating signals independently in each direction.
Solution Approach 2:
The patent applies different selection criteria for different directions: downlink association uses downlink signal strength metrics while uplink association uses uplink signal strength metrics. This local quality approach ensures each direction optimizes for its specific performance requirements rather than using a single unified criterion.
2Area of stationary object
If macrocell base stations use higher transmission power, then coverage area is improved, but load balancing deteriorates
Solution Approach 1:
The patent separates downlink and uplink connection decisions, allowing femtocell base stations to compete for uplink associations even when macrocells provide stronger downlink signals. This segmentation enables better load distribution by preventing all terminals from concentrating on macrocells.
Solution Approach 2:
The patent introduces an uplink cell association mechanism that changes the connection parameter from downlink signal strength to uplink signal strength for determining uplink base stations. This parameter change allows terminals to connect to femtocells for uplink even when macrocells have larger coverage, improving load balancing.
3Device complexity
If single base station association is used, then system complexity is reduced, but SINR fairness deteriorates
Solution Approach 1:
The patent divides the single base station association into two independent associations: one for downlink and one for uplink. Each association independently selects the optimal base station for its direction, improving SINR fairness while maintaining relatively simple implementation through separate evaluation processes.
Solution Approach 2:
The patent adds a dimensional separation between downlink and uplink associations, transforming the single-dimension problem into a two-dimension problem. This allows independent optimization in each dimension (direction) without significantly increasing overall system complexity.
Data Source
AI summary
Provided is a method and an apparatus for uplink and downlink separated connections, wherein a terminal may establish a downlink cell association with a downlink base station, receive an identifier of an uplink base station providing an uplink from the downlink base station to the terminal through an established downlink, and establish an uplink cell association with the uplink base station using the identifier of the uplink base station, and the downlink base station may select the uplink base station from among base stations in a network based on an uplink reference signal and a bias factor.