Patent ID: 7292619

Claim:
A method for acquiring a received impulse radio signal in an impulse radio signal channel used by a plurality of users, comprising: receiving a transmitted impulse radio signal represented by S t ⁢ ⁢ r ⁡ ( t ) = ∑ j = - ∞ ∞ ⁢ ⁢ d j ⁢ k ⁢ b ⌊ j / N f ⌋ k ⁢ w t ⁢ ⁢ r ⁡ ( t - j ⁢ ⁢ T f - c j k ⁢ T c ) , where d j are binary random variables, take values of ±1 with a probability of ½, w tr is a transmitted unit-energy pulse, T f is an average pulse repetition time, T c is a chip interval, N f is the number of pulses representing one information symbol, and b is an information symbol transmitted, either zero or one: assigning a pseudo-random sequence [c j ] to each user of the impulse radio signal channel to provide an additional time shift of c j T c seconds to the j th pulse of the impulse radio signal, where T c ≦T f /N c , and a sequence {s j } is defined as s j = { d ⌊ j / N c ⌋ j - N f ⁢ ⌊ jN c ⌋ = c ⌊ j / N c ⌋ 0 otherwise , to express the transmitted impulse radio signal as S tr ⁡ ( t ) = ∑ j = - ∞ ∞ ⁢ ⁢ s j ⁢ b ⌊ j / N f ⁢ N c ⌋ k ⁢ w tr ⁡ ( t - jT c ) when T f /T c =N c , wherein Nc is number of chips so that the received impulse radio signal is expressed as r ⁡ ( t ) = ∑ j = - ∞ ∞ ⁢ ⁢ s j ⁢ w rec ⁡ ( t - jT c - τ ) + σ n ⁢ n ⁡ ( t ) , where w rec (t) is a received pulse, and σ n n(t) is white Gaussian noise with unit power spectral density, and b j k /N j N c =1∀j, and the number cells in the region is N=N f N c , and T c is a minimum resolvable path interval; searching, with respect to time, a region of the received impulse radio signal by correlating the region with a first template signal to locate a block including a signal cell, in which correlations with the first template signal are delayed by a time interval substantially greater than a chip interval, and in which the first template signal is expressed as s m 1 ( b ) ⁡ ( t ) = ∑ i = 0 K - 1 ⁢ ⁢ ∑ n = jN c ( j + m 1 ) ⁢ N c - 1 ⁢ ⁢ s n ⁢ w rec ⁡ ( t - nT c - iT c - ( b - 1 ) ⁢ KT c ) , where m j is the number of pulses over a first correlation interval associated with the region, B is a total number of blocks in the region, each block including K cells, and N=KB; and searching, with respect to time, the block using a second template signal to locate the signal cell to acquire the received impulse radio signal.