Coordinated Wireless Downlink Transmission for Intercell Interference
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Solution Overview
Problem
Intercell interference in wireless networks limits RF efficiency and capacity due to RF interference from adjacent cells, which affects the number of concurrent users and data throughput.
Innovation Solution
A method of coherently coordinated downlink transmission among base stations in a wireless network, using zero-forcing operations and dirty paper coding to cancel interference, ensuring signals constructively add at intended receivers while canceling out at interfering locations, and optimizing transmission rates based on power constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If base stations transmit signals independently without coordination, then each base station can operate with simple transmission schemes, but intercell interference increases and reduces network capacity
Solution Approach 1:
The patent merges the transmission operations of multiple base stations by coordinating their signal transmissions coherently. Base stations jointly process signals for users in their coverage areas, combining their transmission capabilities to serve users simultaneously while eliminating mutual interference, thereby increasing overall network capacity
Solution Approach 2:
The patent converts the harmful intercell interference into a beneficial effect by using coordinated coherent transmission. The same multiple base stations that previously caused interference are now coordinated to make their signals constructively combine at user receivers, transforming the interference problem into enhanced signal strength and capacity
2Productivity
If base stations coordinate transmissions coherently to reduce interference, then spectral efficiency improves, but system complexity increases due to coordinated signal processing
Solution Approach 1:
The patent introduces a coordination mechanism that acts as an intermediary between base stations. This coordination system manages the joint signal processing and coherent transmission scheduling, allowing base stations to operate in a coordinated manner while centralizing the complexity in the coordination function rather than in each individual base station
Solution Approach 2:
The patent segments the coordinated transmission process into distinct functional components: signal generation at each base station, coordination processing for coherent combining, and joint transmission scheduling. This segmentation allows the complex coordinated transmission to be implemented through modular, manageable steps
3Productivity
If signals are transmitted at high rates to increase throughput, then data capacity increases, but interference to other users increases and reduces fairness
Solution Approach 1:
The patent merges the signal transmissions from multiple base stations so that they constructively combine at the intended user receiver. This coherent combining allows the system to transmit at higher rates while the coordinated signals reinforce each other rather than interfere, and simultaneously eliminates interference to other users through zero-forcing beamforming
4Area of stationary object
If base stations are spaced closely to increase network coverage density, then coverage area increases, but intercell interference increases due to shorter distances between transmitters
Solution Approach 1:
The patent merges the transmission operations of closely spaced base stations through coherent coordination. By treating the closely spaced base stations as a unified collaborative system rather than independent transmitters, the patent enables them to serve users in their combined coverage area while their coordinated signals eliminate the interference that would normally result from their close proximity
Data Source
AI summary
To reduce intercell interference, a method of coherently coordinated downlink transmission in a wireless network involves coordinating transmissions from a plurality of base stations to a plurality of wireless units, for coherent, reinforced reception of the transmitted signals at the wireless units. Thus, transmissions from the base stations are coordinated such that signals received at each wireless unit's particular location constructively add, but cancel out at other locations. The signals are generated based on a zero-forcing operation, e.g., by applying zero-forcing complex antenna weight vectors to data symbols designated for transmission to the wireless units. For fairness, the signals are transmitted at no less than a guaranteed common rate. A convex optimization problem (which incorporates a per-base station power constraint or a per-transmission antenna power constraint) is solved to maximize the guaranteed common rate. Dirty paper coding may also be employed.