Waveform for use in mobile ad hoc networks

Abstract

A waveform and related devices and methods are disclosed for dynamic use of an air interface in a mobile ad hoc network. The waveform includes a dual preamble sequence enclosing self-discovery data that characterizes modulation for a subsequent data signal. The preamble is designed so that the circular correlation of the preamble sequence with itself is an impulse, and the first preamble sequence is a complex conjugate of the second preamble sequence. The preamble sequence can be used to bound a data packet on both sides so that detection of the impulse yields a window in which a data packet can be located, while the self discovery data provides information to extract the data signal from the wireless waveform. In one aspect, the preamble may be implemented using a CHIRP sequence that is a perfect square for more efficient implementation in a wireless modem. In addition, CHIRP sequences for different nodes can be generated with low cross-correlation to reduce interference among nodes in the MANET. The preamble may also support channel sounding or equalization to reverse amplitude or phase distortion in a channel.

1 . A method of communicating from a node in a mobile ad hoc network comprising:
 identifying a preamble sequence that corresponds to the node, wherein the preamble sequence is constructed to be orthogonal to other preamble sequences corresponding to other nodes of the mobile ad hoc network, wherein the preamble sequence has an ideal auto-correlation property, and wherein the preamble sequence is symmetric in both a real part of the preamble sequence and a complex part of the preamble sequence;   identifying self-discovery data that encodes a signal characteristic with which a data signal will be transmitted to a second node; and   transmitting the preamble sequence followed by the self-discovery data to the second node in an initial transmission.   
     
     
         2 . The method of  claim 1  wherein the signal characteristic includes one or more of a signal format characteristic, a network characteristic, and a content characteristic. 
     
     
         3 . The method of  claim 1  further comprising transmitting a second preamble sequence to the second node after transmitting the self-discovery data and before transmitting the data signal. 
     
     
         4 . The method of  claim 3  wherein the second preamble sequence is a complex conjugate of the preamble sequence. 
     
     
         5 . The method of  claim 1  further comprising transmitting the data signal after the initial transmission. 
     
     
         6 . The method of  claim 5  wherein the preamble sequence is orthogonal to the data signal. 
     
     
         7 . The method of  claim 5  further comprising transmitting the preamble sequence at a higher power level than the data signal. 
     
     
         8 . The method of  claim 5  wherein the initial transmission includes a guard time block and an automatic gain control block. 
     
     
         9 . The method of  claim 8  wherein the initial transmission consists of a plurality of guard time blocks, a plurality of automatic gain control blocks, the preamble sequence, the self-discovery data, and a second preamble sequence. 
     
     
         10 . The method of  claim 5  further comprising:
 transmitting the initial transmission and the data signal on a first frequency segment; 
 transmitting a second initial transmission including a second preamble sequence and second self-discovery data and a second data signal, wherein the second initial transmission and second data signal are each transmitted on a second frequency segment, and wherein both the self-discovery data and the second self-discovery data include instructions for combining the data signal and the second data signal. 
 
     
     
         11 . The method of  claim 1  wherein the preamble sequence includes a generalized chirp-like sequence. 
     
     
         12 . The method of  claim 11  wherein the generalized chirp-like sequence is of the form: S u (k)=exp[−i 2πu k(k+1)/2N G ] for k odd and S u (k)=exp[−i 2πu k 2 /2N G ] for k even, where i 2 =−1, and u, k, and N G  are integers and u and N G  are coprime. 
     
     
         13 . The method of  claim 12  wherein N G  is a perfect square. 
     
     
         14 . A method of communicating from a node in a mobile ad hoc network comprising:
 identifying a preamble sequence that is used at a plurality of nodes of the mobile ad hoc network, wherein the preamble sequence is constructed to be orthogonal to any time-shifted copy of itself, wherein the preamble sequence has an ideal auto-correlation property, and wherein the preamble sequence is symmetric in both a real part of the preamble sequence and a complex part of the preamble sequence;   identifying self-discovery data that encodes a signal characteristic with which a data signal will be transmitted to one of the plurality of nodes; and   transmitting the preamble sequence followed by the self-discovery data in an initial transmission.   
     
     
         15 . A method of receiving a wireless communication comprising:
 receiving an initial transmission at a node in a mobile ad hoc network, the initial transmission including a preamble sequence corresponding to a second node in the mobile ad hoc network, wherein the preamble sequence is constructed to be orthogonal to other preamble sequences that correspond to other nodes of the mobile ad hoc network; wherein the preamble sequence has an ideal auto-correlation property; and wherein the preamble sequence is symmetric in both a real part of the preamble sequence and a complex part of the preamble sequence, the initial transmission further including self-discovery data that encodes a signal characteristic with which a data signal will be transmitted to the node; and   based on the signal characteristic, receiving the data signal.   
     
     
         16 . The method of  claim 15  further comprising using the preamble sequence for a channel equalization. 
     
     
         17 . The method of  claim 16  wherein the channel equalization includes estimating a channel impulse response. 
     
     
         18 . The method of  claim 16  wherein the channel equalization includes computing equalization coefficients. 
     
     
         19 . The method of  claim 15  further comprising detecting packets based upon the preamble sequence. 
     
     
         20 . The method of  claim 15  further comprising channel sounding with the preamble sequence. 
     
     
         21 - 70 . (canceled)