Antenna Subgrouping for Spatial Diversity in MIMO Networks
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Solution Overview
Problem
Existing MIMO techniques in wireless communications networks face limitations such as reduced symbol rate with STC for multiple antennas, potential failure of CDD without proper cyclic delays, and inefficacy of beamforming without channel state information, leading to reduced channel capacity and transmit diversity.
Innovation Solution
The method involves organizing antennas into subgroups to create virtual antennas, using a combination of beamforming, cyclic delay diversity, and pre-coding to achieve spatial diversity without relying on channel state information, by allocating unequal transmitting power to sub-carriers and employing predetermined weighting functions to optimize power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If beamforming is used to create a broadcast beamformed MIMO channel, then channel capacity can be increased, but channel state information acquisition consumes channel resources and reduces available channel capacity
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing beamforming weighting vectors for multiple possible channel conditions before actual transmission. When channel state information is unavailable, the system can directly select pre-computed vectors without real-time resource consumption for channel estimation, thus maintaining channel capacity while preserving available channel resources.
Solution Approach 2:
The system changes parameters by using multiple predetermined beamforming weighting vectors corresponding to different channel conditions. Instead of acquiring channel state information dynamically, the system selects from a set of pre-defined parameter configurations (weighting vectors), allowing beamforming to function without consuming channel resources for information acquisition.
2Reliability
If space-time coding is applied to an antenna array of more than two antennas to increase diversity, then transmit diversity is improved, but the symbol rate is reduced
Solution Approach 1:
The patent segments the antenna array into multiple independent antenna subgroups, where each subgroup processes signals separately with its own beamforming weighting. This segmentation allows each subgroup to maintain higher symbol rates while the overall system achieves diversity through multiple subgroups, resolving the contradiction between diversity and symbol rate.
Solution Approach 2:
Instead of achieving diversity through time-domain spreading (which reduces symbol rate), the patent transitions to spatial-domain diversity by using multiple antenna subgroups with different beamforming weightings. This dimensional shift from time to space allows maintaining high symbol rates while achieving diversity gain.
3Reliability
If cyclic delay diversity is used to achieve transmit diversity with high symbol rate, then performance depends on proper selection of cyclic delays and channel estimation with limited pilot signals
Solution Approach 1:
The patent applies preliminary action by pre-calculating beamforming weighting vectors for multiple antenna subgroups before transmission. This eliminates the need for complex real-time cyclic delay selection and channel estimation with limited pilots, reducing system complexity while maintaining transmit diversity performance.
Solution Approach 2:
The system extracts the complex channel estimation and parameter selection problem by removing the dependency on real-time channel state information. Instead of performing complex estimation and selection operations, the system uses pre-computed weighting vectors, taking out the complexity from the transmission process.
4Power
If multiple MIMO techniques are incorporated to fully utilize multiple antennas, then network performance is improved, but system complexity increases
Solution Approach 1:
The patent merges multiple MIMO techniques (beamforming, spatial diversity, and resource allocation) into a unified antenna subgroup framework. Instead of implementing separate complex systems for each technique, the invention integrates them into a single structured approach where antenna subgroups with predetermined weighting vectors achieve multiple objectives simultaneously, reducing overall system complexity.
Solution Approach 2:
The antenna subgroup structure serves multiple functions simultaneously: it provides beamforming capability, achieves spatial diversity, enables resource allocation, and supports both channel state information available and unavailable scenarios. This multi-functionality reduces the need for separate specialized systems, thereby reducing overall complexity while improving network performance.
Data Source
AI summary
A method and system are provided for achieving spatial diversity of a wireless communications network. The method comprises arranging antennas on a transmitting wireless station into a plurality of antenna subgroups, wherein each of the antenna subgroups forms a virtual antenna, creating a plurality of beamformed MIMO channels using the plurality of virtual antennas, wherein each of the beamformed MIMO channel comprises a plurality of sub-carriers and corresponds to a virtual antenna, dividing sub-carriers in each of the plurality of beamformed MIMO channels into at least a first and second cluster, distributing a first amount of transmitting power to the first cluster and a second amount of transmitting power to the second cluster, wherein the first amount of transmitting power is substantially larger than the second amount of transmitting power.