OFDM Transmitter Antenna Diversity via Data Permutation
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Solution Overview
Problem
Existing radio communication systems using OFDM with multiple antennas face limitations in achieving efficient data transmission due to the need for complex demodulators and restricted modulation methods, particularly with the Alamouti method, and lack of flexibility in using any number of antennas.
Innovation Solution
A method and transmitter that divide data into elements and assign them to subcarriers using a cyclic shift pattern before or after OFDM modulation, allowing each antenna to transmit different elements on different subcarriers, with antenna-specific and element-specific factors for efficient space diversity, enabling flexible antenna usage and simplified receiver structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Alamouti method is used for OFDM transmission with multiple antennas, then transmit diversity is achieved, but the receiver requires an expensive modified demodulator and the choice of modulation method is restricted
Solution Approach 1:
Instead of applying complex signal processing at the receiver side (Alamouti method), the patent applies the diversity technique at the transmitter side by permuting data elements before transmission. Each antenna transmits permuted versions of the data elements on different subcarriers, achieving diversity without requiring complex receiver demodulation.
Solution Approach 2:
The patent changes the arrangement parameters of data elements across antennas and subcarriers using permutation patterns. By systematically varying the position parameters of data elements in the frequency domain before transmission, transmit diversity is achieved while keeping the receiver simple.
2Reliability
If CDD (Cyclic Delay Diversity) method is used with multiple antennas, then space diversity is introduced, but it can only be viably used in combination with channel encoding to reduce transmission errors
Solution Approach 1:
Instead of introducing diversity through time delays in the time domain (CDD method), the patent introduces diversity through permutation in the frequency domain. Data elements are rearranged across different subcarriers and antennas, achieving space diversity without requiring additional channel encoding.
3Productivity
If data is divided into elements and assigned to subcarriers with antenna-specific factors before OFDM modulation, then spectral efficiency is improved and flexibility in antenna deployment is increased, but the transmission requires coordinated processing across multiple antennas
Solution Approach 1:
The patent segments data into multiple elements that are independently permuted and assigned to different subcarriers and antennas. This segmentation allows parallel processing at the transmitter and improves spectral efficiency by utilizing multiple spatial and frequency dimensions simultaneously.
Solution Approach 2:
The permutation and assignment of data elements to antennas and subcarriers is performed in advance before OFDM modulation. This preliminary arrangement optimizes the transmission structure and enables efficient utilization of multiple antennas without requiring complex real-time coordination during transmission.
Data Source
AI summary
A method transmits data by radio during which a frequency band is split into a plurality of subcarriers, and a plurality of antennas are used for transmitting. The data are split into a number of elements, which are to be respectively transmitted by each antenna, said number of elements corresponding to the number of subcarriers, whereby for each antenna, each element is respectively assigned to a subcarrier for transmitting, and at least two antennas on at least one subcarrier transmit different elements. Before an OFDM modulation for each antenna, each element is multiplied by an antenna-specific and element-specific factor. Alternatively, after an OFDM modulation for at least one antenna, the time sequence of the time-dependent signal generated on the basis of the OFDM modulation is reordered. A transmitter carries out the method.