Packet data transmission with optimum preamble length
In a communication network, a sending node transmits a message with a multi-segment preamble and data to a receiving node. The receiving node calculates characteristics of the sending unit, channel, or transmitted signal by processing preamble segments. Once an unknown characteristic is determined, a segment of the preamble can be eliminated or reduced in length for subsequent messages, which increases efficiency of the message transmissions.
1. A method of transmitting message packets from a sending node to a receiving node comprising the steps of:
a) in a sending node,
i) forming an initial message packet comprising the concatenation of a message packet preamble comprising a plurality of segments and a data field comprising a plurality of data symbols; and
ii) transmitting the initial message packet;
b) in a receiving node:
i) detecting the initial message packet and from the detected initial message packet, determining at least one unknown signal characteristic of the initial message packet; and
ii) transmitting to the sending node an implicit response that an unknown characteristic has been determined;
c) in the sending node, receiving the implicit response that the unknown characteristic has been determined; and
d) in the sending node:
i) in response to receiving the implicit response, forming an optimized message packet by removing at least one segment from the preamble of the initial message packet; and
ii) transmitting the optimized message packet.
2. The method of claim 1 , wherein the receiving node processes a long initial message packet sent by the sending node using an auto-correlation function and processes a shorter initial message using a cross-correlation function.
3. A method of transmitting message packets from a sending node to a receiving node comprising the steps of:
a) in a sending node, forming an initial message packet comprising the concatenation of:
i) a time domain preamble comprising a short training sequence used for coarse setting of automatic gain control, a long training sequence, and a correlator sequence transmitted as a series of quadrature phase shift keyed (QPSK) symbols;
ii) a frequency domain preamble comprising a plurality of orthogonal frequency division multiplex (OFDM) symbols transmitted with a cyclic prefix; and
iii) a data section comprising a plurality of data symbols transmitted as OFDM symbols;
iv) transmitting the initial message packet;
b) in a receiving node, detecting the initial message packet and determining at least one unknown signal characteristic of the initial message packet;
i) transmitting to the sending node an implicit response that an unknown characteristic has been determined;
c) in the sending node, in response to receiving the implicit response, forming an optimized message packet by removing at least one segment from the preamble of the initial message packet; and
d) transmitting the optimized message packet.
4. The method of claim 3 , wherein the long training sequence is used for signal detection, fine frequency offset estimation, and timing synchronization.
5. A method for transmitting message packets from a sending node comprising the steps of:
a) in the sending node, forming an initial message packet comprising the concatenation of a message packet preamble comprising a plurality of segments and a data field comprising a plurality of data symbols;
b) transmitting the initial message packet using signals;
c) in response to the transmission of the initial message packet, receiving an implicit response that a signal characteristic associated with the signals used to transmit the message packet has been determined;
d) in the sending node, in response to receiving the implicit response, forming an optimized message packet by removing at least one segment from the preamble of the initial message packet; and
e) transmitting the optimized message packet.