Pseudo-Random Transmit Steering for Legacy OFDM Receivers
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Solution Overview
Problem
Legacy single-antenna devices in OFDM-based wireless communication systems cannot perform special processing required by conventional transmit diversity schemes, limiting their ability to receive data from multi-antenna devices effectively.
Innovation Solution
The implementation of steered mode and pseudo-random transmit steering (PRTS) modes in multi-antenna communication systems, where the transmitting entity performs spatial processing using steering vectors to direct data transmission towards single-antenna receivers, allowing for transmit diversity and spatial spreading without requiring special processing from the receiving entity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transmit diversity schemes are used, then transmit diversity and performance improvement are achieved, but the receiving device must perform special processing that legacy single-antenna devices cannot perform
Solution Approach 1:
The patent introduces pseudo-random sequences as an intermediary element that transforms the multi-antenna transmission into an effective single-antenna channel. The pseudo-random sequences modulate the signals from multiple antennas, creating a composite signal that appears as a random fading channel to the legacy receiver. This allows the receiver to use standard processing while the transmitter achieves diversity through the pseudo-random modulation across multiple antennas.
Solution Approach 2:
The patent changes the parameter of the transmission signal by applying pseudo-random sequence modulation to the multi-antenna signals. This parameter change transforms the deterministic multi-antenna transmission into a stochastic process that mimics random fading channels, enabling legacy receivers to interpret the transmission using conventional single-antenna processing while benefiting from transmit diversity.
2Reliability
If spatial processing is performed to direct transmission toward the receiving entity, then transmission reliability is improved, but the system requires knowledge of the MISO channel response
Solution Approach 1:
The patent performs preliminary action by pre-modulating the transmission signals with pseudo-random sequences before transmission. This preliminary modulation creates an effective channel that randomizes the transmission path, allowing the system to achieve diversity without requiring real-time channel response knowledge. The pseudo-random sequences are generated and applied in advance, enabling the transmitter to create diverse transmission paths without needing to know the actual channel conditions.
Data Source
AI summary
A multi-antenna transmitting entity transmits data to a single- or multi-antenna receiving entity using (1) a steered mode to direct the data transmission toward the receiving entity or (2) a pseudo-random transmit steering (PRTS) mode to randomize the effective channels observed by the data transmission across the subbands. The PRTS mode may be used to achieve transmit diversity or spatial spreading. For transmit diversity, the transmitting entity uses different pseudo-random steering vectors across the subbands but the same steering vector across a packet for each subband. The receiving entity does not need to have knowledge of the pseudo-random steering vectors or perform any special processing. For spatial spreading, the transmitting entity uses different pseudo-random steering vectors across the subbands and different steering vectors across the packet for each subband. Only the transmitting and receiving entities know the steering vectors used for data transmission.