Coherent Transmission from Distributed Wireless Transmitters
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Solution Overview
Problem
Conventional wireless networks, such as 802.11 and cellular systems, face limitations in scaling throughput as the number of users increases due to interference between transmitters, which prevents simultaneous concurrent transmissions and limits data throughput.
Innovation Solution
A method that determines channel characteristics between multiple wireless source stations and destination stations using synchronized and unsynchronized radio frequency oscillators, allowing for coherent transmission across multiple access points to emulate a single N-antenna MIMO transmitter, enabling concurrent streams without interference through beamforming and MIMO techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transmitters transmit simultaneously in the same interference region, then throughput can be doubled or tripled, but the system remains limited by the maximum number of antennas on an individual node and cannot continuously scale throughput
Solution Approach 1:
The patent divides the wireless network into multiple interference regions, each served by a coordinated set of transmitters. Instead of requiring all transmitters to have high antenna counts, the system segments the coverage area and coordinates transmissions across segments, allowing throughput to scale with the number of transmitters rather than being limited by individual node antenna capacity.
Solution Approach 2:
The patent embeds multiple levels of coordination within the network architecture, where transmitters are organized in coordinated sets that operate hierarchically. This nested structure allows the system to scale by adding more transmitter sets while maintaining manageable complexity at each level, rather than requiring exponential increases in individual node capability.
2Area of stationary object
If additional transmitters are added to the network, then coverage area increases, but user throughput does not improve because transmitters interfere with each other
Solution Approach 1:
The patent converts the harmful interference between transmitters into a beneficial resource by using it for channel estimation and coordination. Transmitters deliberately transmit known sequences that allow receiving nodes to measure and report channel conditions, which are then used to coordinate future transmissions. This transforms interference from a throughput-limiting factor into a mechanism for enabling scalable coordination across the network.
Solution Approach 2:
The patent implements a feedback mechanism where receiving nodes measure channel conditions from transmitter sequences and report back to transmitters. This feedback loop enables the coordination algorithm to adjust transmission parameters and schedules, allowing the network to maintain high throughput as it scales by dynamically adapting to changing interference patterns and channel conditions.
3Measurement precision
If conventional channel estimation methods are used with unsynchronized oscillators, then channel characteristics cannot be accurately determined, but coherent transmission cannot be achieved
Solution Approach 1:
The patent introduces known transmitter sequences as intermediary signals that mediate between unsynchronized transmitters and receiving nodes. These sequences serve as reference signals that allow receivers to estimate channel characteristics despite oscillator frequency and phase differences. The intermediary sequences enable accurate channel measurement without requiring complex synchronization mechanisms, as the known structure of the sequences provides a stable reference for estimation.
Data Source
AI summary
A distributed wireless communication system includes multiple access points, each with one or more antennas. The access points do not necessarily have synchronized transmitting and receiving radio frequency oscillators. Approaches to channel estimation between the access points and one or more wireless clients account for the lack of synchronization, and do not necessarily require capabilities at the clients that go beyond required or optional features of standard wireless Ethernet (e.g., 802.11n, 802.11g, or 802.11a), thereby supporting “legacy” clients while supporting high data throughput approaches that provide coherent transmission from the multiple antenna of the access points.