2D Antenna Array Space-Frequency Multiplexing
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Solution Overview
Problem
Current LTE-Advanced systems face limitations in simultaneously serving multiple users due to inter-user interference caused by multipath effects, which traditional beamforming methods struggle to address, especially with limited antenna configurations and computationally expensive time-reversal beamforming techniques.
Innovation Solution
A combined space-frequency multiplexing technique that uses a base station with a two-dimensional rectangular antenna array to estimate angular channel coefficients and profiles, discarding interfering beams, and allocating powers to ensure orthogonality, allowing for simultaneous multiplexing of users in the presence of multipath without requiring detailed channel knowledge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional beamforming methods are used to serve multiple users simultaneously, then spatial multiplexing gain is achieved, but inter-user interference increases due to multipath effects
Solution Approach 1:
The patent extends traditional single-dimensional beamforming to two-dimensional beamforming by utilizing both azimuth and elevation angles. This dimensional extension creates more orthogonal spatial dimensions for user separation, reducing inter-user interference while maintaining the ability to serve multiple users simultaneously. The 2D angular domain provides additional degrees of freedom for spatial multiplexing.
Solution Approach 2:
The patent segments the angular domain into discrete azimuth and elevation bins, creating a grid structure in the 2D angular space. This segmentation allows for precise user identification and separation by assigning users to specific angular regions, thereby reducing interference between users in different segments of the spatial domain.
2Reliability
If Time Reversal Beamforming is used to focus energy sharply, then array gain is improved, but computational complexity increases significantly
Solution Approach 1:
The patent replaces the computationally expensive Time Reversal Beamforming algorithm with a simpler, more efficient 2D angular domain processing approach. By using discrete cosine transform (DCT) and straightforward angular binning instead of iterative time-reversal optimization, the system achieves comparable energy focusing capability with significantly reduced computational complexity, making it suitable for practical deployment.
3Productivity
If the number of transmit antennas is limited to eight, then device complexity is controlled, but the number of simultaneously served users is restricted
Solution Approach 1:
The patent transitions from conventional planar antenna arrays to three-dimensional volumetric antenna arrays. This spatial transition adds the elevation dimension to the traditional azimuth plane, creating a 3D spatial multiplexing environment. The additional vertical dimension provides extra orthogonal directions for user separation, enabling more users to be served simultaneously with the same number of physical antennas.
Solution Approach 2:
The patent implements dynamic user scheduling in the 2D angular domain, where users are assigned to time-frequency resources based on their angular positions and channel conditions. This dynamic allocation optimizes the number of simultaneously served users by exploiting temporal and frequency variations in the spatial channel, allowing the system to adaptively maximize user capacity without increasing antenna count.
Data Source
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AI summary
Methods, a base station and computer programs for performing multiple access in wireless OFDM cellular systems over multipath wireless channels considering both space and frequency domains, The base station 100 comprises a large number of antennas 103 in the form of a two-dimensional array and transmits a given number of signals to a number of users 106, so that each one receives its intended signal (or set of intended signals) without interference to/from the other users 106. The base station 100 includes a scheduler in space-time-frequency dimensions 101 as well as an orthogonal space-frequency processing technique 102 for addressing the users 106. The cellular scenario is assumed where the wireless channel 105 presents significant multipath, thereby resulting in multiple signal components being received by each user 106. Orthogonality of the beams is achieved upon transmission by properly discretizing the spatial domain, while inter-user interference is avoided by exciting only those beams that result in multipath components received by one single user 106.