Bidirectional Relay Precoding for Asymmetric Wireless Channels
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Solution Overview
Problem
The existing relay wireless communication systems face limitations in performance due to asymmetric channel quality between hops, leading to inefficient utilization of resources and reduced system capacity, particularly in three-phase bidirectional relaying schemes.
Innovation Solution
The implementation of precoding in a relay wireless communication system, where a relay station determines a precoding matrix and relay power coefficients to optimize the transmission of symbol vectors between the base station and mobile station, enhancing resource utilization by aligning channel capacities and improving data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If three-phase bidirectional relaying is used to reduce transmission time, then resource utilization improves, but system capacity is limited by the poorer channel quality
Solution Approach 1:
The patent changes the parameter of channel capacity by introducing precoding matrices that adapt to asymmetric channel conditions. The relay station determines different precoding matrices for BS and MS based on their respective channel qualities, allowing the system to optimize transmission for each direction independently while maintaining the three-phase bidirectional relaying structure.
Solution Approach 2:
The patent explicitly addresses asymmetric channel quality between BS-RS and MS-RS links by applying different precoding strategies for each direction. The relay station determines relay power coefficients and precoding matrices separately for BS and MS, creating an asymmetric transmission scheme that matches the asymmetric channel conditions rather than treating both directions equally.
2Reliability
If precoding is applied to optimize transmission, then channel capacity utilization improves, but device complexity increases
Solution Approach 1:
The relay station performs preliminary determination of precoding matrices and relay power coefficients before actual data transmission. Channel quality information is obtained in advance, and precoding parameters are calculated beforehand, allowing the system to adapt to channel conditions without adding complexity to the real-time transmission process.
Solution Approach 2:
The patent introduces channel quality information as an intermediary element that mediates between the asymmetric channel conditions and the precoding strategy. The relay station uses this intermediate information to determine appropriate precoding matrices and power coefficients, simplifying the decision-making process while achieving optimal channel utilization.
3Productivity
If relay power coefficients are determined separately for BS and MS, then transmission optimization improves, but calculation complexity increases
Solution Approach 1:
The patent applies local quality by determining relay power coefficients specifically tailored to each direction's channel conditions. Different power coefficients are assigned for BS-to-MS and MS-to-BS transmissions based on their respective channel qualities, allowing localized optimization without requiring complex global optimization algorithms.
Data Source
AI summary
An apparatus for use in a relay wireless communication system is capable of bidirectional relaying with precoding. A Base Station (BS) includes a plurality of antennas. The BS can receive a relay signal that includes a transmit symbol vector of the BS and a transmit symbol vector of a Mobile Station (MS) from a Relay Station. The BS determines power difference values corresponding to all of symbol vectors available as the transmit symbol vector of the MS. The BS further determines the transmit symbol vector of the MS or per bit Log Likelihood Ratios using the power difference values.