Amplify-and-forward Relay Antenna Reduction
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Solution Overview
Problem
Existing two-hop bi-directional communication systems in wireless cellular networks require a large number of antennas at the relay station, making them impractical due to high costs, or necessitate lengthy communication times if MS-BS pairs are served sequentially.
Innovation Solution
The method involves a relay station and base station with substantially the same number of antennas, enabling simultaneous bi-directional communication by receiving and processing signals through at least two antennas, canceling interference, and precoding signals to reduce the number of antennas needed at the relay station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large number of antennas are deployed at the relay station to enable simultaneous bi-directional communication for N MS-BS pairs, then the system capacity and communication efficiency are improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent segments the communication process into two distinct time slots: an uplink time slot for MS-to-BS transmission and a downlink time slot for BS-to-MS transmission. This temporal segmentation allows the relay station to reuse the same antennas for both directions, eliminating the need for separate antenna sets and reducing the total antenna count from 2N to N while maintaining full duplex functionality.
Solution Approach 2:
The system employs periodic time-division multiplexing where communication alternates between uplink and downlink phases. During the uplink phase, MSs transmit to the BS via the relay; during the downlink phase, the BS transmits to MSs via the relay. This periodic switching enables the same physical antennas to serve both directions, resolving the antenna quantity contradiction.
2Device complexity
If MS-BS pairs are served sequentially to reduce the number of antennas at the relay station, then the device complexity is reduced, but the communication time increases significantly
Solution Approach 1:
The patent ensures continuous useful action by organizing communication into two parallel streams that operate simultaneously in different time slots: all MS-BS pairs transmit in the uplink slot, and all MS-BS pairs receive in the downlink slot. This eliminates idle waiting periods between sequential pair servicing, maintaining full system productivity while using fewer antennas.
Solution Approach 2:
By implementing periodic time-division duplexing with synchronized uplink and downlink phases across all pairs, the system achieves continuous throughput. Every time slot is fully utilized with all MS-BS pairs actively communicating, preventing the time loss that would occur with sequential servicing of individual pairs.
3Productivity
If self-interference cancellation or network coding is employed to enable bi-directional relaying, then the communication efficiency is improved, but the difficulty of detecting and measuring increases
Solution Approach 1:
The patent converts the harmful self-interference effect into a beneficial measurement opportunity. By deliberately designing the system so that MSs and BS can predict and calculate their own self-interference components based on known transmit signals and channel estimates, the interference becomes a known quantity that can be subtracted, thereby enabling efficient bi-directional communication with manageable processing complexity.
Data Source
AI summary
Improved amplify-and-forward relaying in a communication network is described, including an example network of multiple single-antenna mobile stations, a multi-antenna relay station, and a multi-antenna base station. Bi-directional communication with improved transmission efficiency is enabled by suitable transmit/receive processing at the relay station without drawbacks of current relaying techniques. Linear transmit and receive processing matrices are disclosed, and it is shown that the numbers of antennas at the relay station and the base station can be substantially the same without reducing network capacity, closely matching the performance for low and high signal to noise ratios of current techniques that require the relay station to have twice as many antennas as the base station.