Transmitter method and apparatus for variable header repetition in a wireless OFDM network

What is this patent about?

’361 is related to the field of wireless OFDM communications, specifically addressing the challenge of ensuring reliable delivery of control information across diverse network environments. In packet-based systems like G.hn or WiMAX, the header contains critical parameters required to decode the subsequent payload. However, varying channel conditions and different bandwidth capabilities among nodes can make a fixed header format either too fragile for narrowband devices or unnecessarily inefficient for wideband devices.

The underlying idea behind ’361 is to implement a flexible header repetition framework that dynamically scales the number of OFDM symbols used to carry header information based on the required level of robustness. By allowing the system to toggle between a standard header and a reinforced version that repeats bit sets across multiple symbols, the invention ensures that even devices operating in noisy or narrow frequency bands can achieve the necessary frequency diversity to decode control data without imposing that same overhead on the entire network.

The claims of ’361 focus on a transceiver and method that generates two distinct packet types: a first type where the header bits are split across two symbols without repetition, and a second type where the header bits are duplicated across four symbols. Specifically, the second packet type maps a first set of bits to both the first and second symbols, and a second set of bits to both the third and fourth symbols. Crucially, the independent claims require that the repeated bits in the second and fourth symbols be transmitted in a different order than their original counterparts in the first and third symbols.

In practice, this bit-reordering mechanism acts as a form of interleaving that protects the header against burst errors or frequency-selective fading. When the receiver processes the second packet type, it can combine the energy from the repeated symbols to improve the signal-to-noise ratio. The system can communicate the repetition factor (D) through a TXOP descriptor in a MAP frame, allowing the receiver to know exactly how many symbols to expect for the header before the payload begins.

This approach differs from prior solutions by moving away from a one-size-fits-all header duration. Instead of a fixed overhead, the invention utilizes a variable repetition scheme that can be adjusted by a domain master or determined dynamically by the transmitter. By integrating the repetition count into the media access plan and employing specific bit-shuffling during repetition, the invention provides a robust fallback for difficult channel conditions while maintaining high throughput for the rest of the domain.