Coordinated OFDM Scheduling for Intercell Interference Cancellation
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Solution Overview
Problem
Cellular wireless networks experience performance limitations due to intercell interference, particularly at cell edges, leading to reduced data rates and inefficient use of MIMO transmission in low SNIR conditions.
Innovation Solution
A controller adjusts the number of data streams in cellular wireless networks based on channel quality, coordinating base stations to align single-stream transmissions in interfering cells with multi-stream transmissions in serving cells, enabling interference cancellation at the user equipment (UE) receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency reuse of one is used to maximize time/frequency resources, then resource utilization is improved, but intercell interference increases leading to reduced data rates at cell edges
Solution Approach 1:
The system dynamically adjusts the number of MIMO data streams based on channel quality indicators (CQI) and signal-to-interference-plus-noise ratio (SINR). Base stations coordinate to reduce or eliminate multi-stream transmissions in cells interfering with cell-edge users, while maintaining high-order MIMO transmissions in cells with favorable channel conditions. This dynamic adaptation resolves the contradiction by allowing frequency reuse of one to maximize resource utilization while temporarily reducing streams in specific cells to minimize intercell interference at cell edges.
Solution Approach 2:
The invention changes the parameter of the number of data streams (N) in MIMO transmissions based on channel conditions. When a cell-edge user experiences high interference, the system reduces N from multi-stream (e.g., 2 or 4 streams) to single-stream transmission in the interfering cell. This parameter adjustment allows the system to maintain frequency reuse of one for overall resource efficiency while protecting cell-edge users from excessive interference, thereby resolving the contradiction between resource utilization and interference management.
2Productivity
If multiple simultaneous data streams are transmitted over MIMO channels, then data rate is improved, but performance degrades in low SNIR conditions due to interference
Solution Approach 1:
The system dynamically adjusts the number of MIMO data streams based on real-time channel quality indicators (CQI) and SINR measurements. In high SNIR conditions, multiple simultaneous data streams are transmitted to maximize data rate. When SNIR degrades (indicating poor channel conditions or high interference), the system reduces the number of streams to one, ensuring reliable decoding. This dynamic adaptation resolves the contradiction by matching the number of streams to channel conditions, achieving high data rates when possible while maintaining decoding quality when interference is high.
3Area of stationary object
If base stations transmit with maximum power to improve signal strength, then coverage is improved, but intercell interference increases reducing overall network efficiency
Solution Approach 1:
The invention applies local quality by allowing different base stations to use different numbers of MIMO data streams based on their local channel conditions and interference impact on neighbors. Instead of uniform transmission strategies across all cells, each base station adapts its transmission parameters locally. A base station may use multi-stream transmission when its users experience good SINR, while reducing to single-stream when it detects that its transmissions are causing excessive interference to cell-edge users in neighboring cells. This localized adaptation resolves the contradiction between coverage and interference by optimizing each cell's transmission strategy according to its specific situation.
Data Source
AI summary
A user equipment (UE) comprising a receiver, a transmitter, and a processor are configured to simultaneously receive a plurality of orthogonal frequency division multiplex (OFDM) streams from a first base station. The UE is configured to transmit channel condition information to the first base station and to a second base station. The UE is configured to receive, in response to the transmitted channel condition information and corresponding scheduling indicated by the first and second base stations, a first single-stream OFDM transmission from the first base station and a second single-stream OFDM transmission from the second base station, wherein the first and second single-stream transmissions are time-aligned such that their respective arrivals at the UE occur within a cyclic prefix portion of one another.