MIMO Broadcast Precoding With Interference-Compensating Filters
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Solution Overview
Problem
Current Multiple Input Multiple Output Broadcast Channel (MIMO-BC) schemes fail to achieve maximum theoretical sum-rate capacity due to heuristic approaches that do not account for optimal channel conditions and interference compensation.
Innovation Solution
A transmitter with multiple antennas estimates channel conditions, uses feedbackward and feedforward filters to compensate for co-signal interference, and allocates power to achieve maximum sum-rate capacity, allowing receivers to extract intended signals independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If heuristic precoding schemes (linear or non-linear) are used at the transmitter, then signal transmission is simplified, but the maximum theoretical sum-rate capacity of the MIMO-BC channel cannot be achieved
Solution Approach 1:
The transmitter performs preliminary channel condition estimation and determines optimal precoding matrices and power allocation before signal transmission. This advance preparation enables the system to achieve maximum sum-rate capacity by pre-optimizing the transmission parameters based on current channel states, rather than using heuristic approaches during transmission.
Solution Approach 2:
The system dynamically adjusts transmission parameters including precoding matrices, power allocation coefficients, and modulation schemes based on estimated channel conditions. By changing these parameters optimally according to channel state, the system achieves maximum sum-rate capacity while maintaining manageable complexity through structured parameter optimization.
2Ease of operation
If receivers extract signals independently without cooperation, then receiver independence is maintained, but signal extraction becomes non-trivial due to co-signal interference
Solution Approach 1:
The transmitter applies precoding matrices that pre-compensate for co-signal interference before transmission. This preliminary anti-action creates orthogonal or near-orthogonal signal spaces for different receivers, allowing each receiver to extract its intended signal independently without needing to know or process signals intended for other receivers, thus maintaining receiver independence while eliminating interference.
Solution Approach 2:
The transmitted signal space is segmented into orthogonal subspaces, each dedicated to a specific receiver. Through precoding, the system divides the multiple antenna resources such that each receiver receives signals in a dedicated subspace, enabling independent signal extraction without inter-receiver interference and eliminating the need for receiver cooperation.
3Productivity
If power is allocated to maximize sum-rate capacity, then channel utilization is optimized, but the complexity of determining optimal power allocation increases
Solution Approach 1:
The system uses channel condition estimation feedback to determine optimal power allocation. Receivers provide feedback about channel states to the transmitter, which then uses this information to calculate optimal power allocation coefficients that maximize sum-rate capacity. This feedback mechanism enables optimized channel utilization while managing complexity through iterative optimization based on actual channel measurements.
Data Source
AI summary
A Multiple Input Multiple Output (MIMO) communication system 1 has a transmitter for transmitting signals over a MIMO Broadcast Channel (MIMO-BC) 6. Data for communication to respective receivers 41, 4K-1, 4K is encoded by encoding stages 101, . . . , 10K-1, 10K in a selected order by selecting codewords c1, . . . cK-1, cK from codebooks C1, . . . CK-1, CK of a nested lattice code. Dither adders 111, . . . , 11K-1, 11K are arranged to add a respective dither d1 . . . , dK-1, dk to the selected codewords c1, . . . cK-1, cK. Quantising stages 121, . . . , 12K-1, 12K each perform respective quantising operations mod ΛS,1, . . . , mod ΛS, K-1, mod ΛS, K using the shaping lattice ΛS of the nested lattice code. Quantised signals u1, . . . , uK-1, uK of data encoded earlier in the selected order are output to feedbackward filter stages 141, . . . , 14K-1 for filtering the codewords c1, . . . cK-1, cK of data encoded later in the selected order before they are quantised by the quantising stages 121, . . . , 12K-1 using a feedbackward filter Fb. At the receivers 41, 4K-1, 4K feedforward filter stages 151, . . . , 15K-1, 15K filter received signals y1, . . . , yK-1, yK by applying a feedforward filter Ff. A combination of the feedbackward and feedforward filters Fb, Ff is substantially equivalent to a single filter for extracting the signals representing the data intended to be communicated to the receivers 41, 4K-1, 4K with a minimum mean squared error, but the feedforward filter Ff can be applied by each of the receivers 41, . . . , 4K-1, 4K without knowledge of signals y1, . . . , yK-1, yK received by the other receivers 41, . . . , 4K-1, 4K.