Multi-Mode Wireless Transmitter for High-Rate Payload Modulation
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Solution Overview
Problem
Direct sequence spread spectrum communications systems, such as those used in the IEEE 802.15.4 standard, face reduced data throughput due to spread spectrum coding, limiting their capacity and usability, especially in applications requiring higher data rates.
Innovation Solution
Implementing a multi-mode transmitter that uses non-spread spectrum modulation for the payload portion of data packets in addition to the standard spread spectrum modulation for the preamble and start of frame delimiter, allowing for increased data rate throughput by encoding user data bits directly into channel symbols without spreading, thereby bypassing the O-QPSK to MSK encoding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct sequence spread spectrum modulation is used for all packet data transmission, then interference rejection capability is improved, but data throughput is reduced
Solution Approach 1:
The packet is segmented into different portions with different modulation schemes: the preamble and SFD use spread spectrum modulation for reliable synchronization and frame detection, while the payload data uses non-spread spectrum modulation for high data throughput. This segmentation allows each portion to be optimized for its specific function.
Solution Approach 2:
Different quality characteristics are applied to different parts of the packet: spread spectrum modulation provides robust interference rejection for the preamble and SFD where reliability is critical, while non-spread spectrum modulation provides high data rate for the payload where throughput is the priority. Each local region of the packet has the appropriate modulation quality for its function.
2Length of moving object
If spread spectrum coding is applied to increase communication range, then extended range communication is achieved, but data rate capacity of hardware is reduced
Solution Approach 1:
The transmission is segmented into a preamble portion using spread spectrum for extended range and reliable detection, and a payload portion using non-spread spectrum for high data rate. This allows the system to achieve both extended range communication and high data rate capacity within the same hardware.
Solution Approach 2:
The system dynamically switches modulation schemes based on the packet portion being transmitted. The preamble uses spread spectrum for reliable long-range detection, then transitions to non-spread spectrum for the payload to maximize data rate capacity. This dynamic adaptation optimizes both range and throughput.
3Productivity
If non-spread spectrum modulation is used for payload data, then data rate throughput is increased, but interference rejection capability may be compromised
Solution Approach 1:
The packet is divided so that the preamble and SFD use spread spectrum modulation to establish reliable communication and detect interference conditions, while the payload uses non-spread spectrum modulation for high throughput. The spread spectrum preamble ensures that interference rejection is established before the high-rate payload transmission begins.
Solution Approach 2:
Spread spectrum modulation is applied preliminarily to the preamble and SFD to establish reliable signal detection and synchronization before the high data rate payload transmission. This preliminary use of spread spectrum ensures interference rejection capabilities are validated before switching to the higher throughput non-spread spectrum mode for the payload.
Data Source
AI summary
A multi-mode transmitter (301) is adapted to modulate a data packet (200) communicated by a wireless communications signal. The data packet includes a packet header comprising a preamble (201) and a start of frame delimiter (202), and a data payload comprising a payload data length portion (203) and a payload portion (204). The packet header is modulated with a spread spectrum technique. When transmitting a data payload in one mode, the data payload is also modulated with the spread spectrum technique. When transmitting a data payload in another mode, the data payload is modulated with a non-spread spectrum technique.