Comb-form spectrum communication systems using repeated complementary sequence modulation
View Patent ↗In comb-form spectrum communication systems using repeated complementary sequence modulation, a transmitting signal is constituted by assigning one set of N auto-complementary sequences to each user, where N is an integer equal to or higher than 2, and by transforming the N sequences to N repeated signals which have comb-form spectra without overlapping in frequency with one another with a method of repeating each sequence of the set of auto-complementary sequences a plurality of times, and by assigning the N complementary sequences with auto-complementary sequence characteristics to the N comb-form spectra. Thus, the near-far problem is solved by making the cross-correlation between a signal input to a user's station but addressed to another station and the user's reference code sequence, zero.
1. Comb-form spectrum communication method using repeated complementary sequence modulation, said method comprising:
constituting a transmitting signal by assigning one set of N auto-complementary sequences to each user, where N is an integer equal to or higher than 2,
summing N signals each of which is made by repeating one of said N auto-complementary sequences a plurality of times,
modulating the repeated sequence with an individual carrier frequency so as to have comb-form spectrum without overlapping in frequency with the other said signals, and
arranging said N respective signals having auto-complementary sequence characteristics to N pieces of comb-form spectra.
2. The comb-form spectrum communication method using repeated complementary sequence modulation according to claim 1 , wherein said transmitting signal is constituted by the steps of:
preparing N shift carrier waves so that the K-th frequency is made by adding the inverted value fT of a symbol period T K-times to a reference frequency so as to prevent said N comb-form spectra from overlapping with one another, where K=0, 1, 2, . . . , N−1, and
composing N signals each created by modulating said respective N shift carrier waves with repeated sequences which are made by repeating respective sequences of each set of N complementary sequences which have a relation of auto-complementary sequences.
3. The comb-form spectrum communication method using repeated complementary sequence modulation according to claim 2 , wherein
said set of N auto-complementary sequences assigned to each user are constituted so that said set of N auto-complementary sequences assigned to each user is cross-complementary to a set of N auto-complementary sequences assigned to another user; and
the carrier waves used by all the users are said N shift carrier waves.
4. The comb-form spectrum communication method using repeated complementary sequence modulation according to claim 2 , wherein
for a case where said set of auto-complementary sequences assigned to each user are not cross-complementary to a set of sequences assigned to another user, said transmitting signals are constituted so that the complementary sequences assigned to each user modulate said shift carrier waves whose frequencies are different from those used by the other users.
5. The comb-form spectrum communication method using repeated complementary sequence modulation according to one of claims 1 through 4 , wherein
at a receiver side of the system, N matched filters each matched to a part of a code made by repeating each sequence of said set of N auto-complementary sequences are arranged in parallel in accordance with said set of N auto-complementary sequences, and the transmitted information is detected based on a result obtained by adding the correlation outputs of said N matched filters.
6. The comb-form spectrum communication method using repeated complementary sequence modulation according to one of claims 1 through 4 , wherein
pseudo-periodic sequences, such as obtained by copying the rear and front portions with multiple chips of a finite-length periodic sequence which is made by repeating each sequence of said set of N auto-complementary sequences, and thereby adding the copied portions to the outer front side and the outer rear side of said finite length periodic sequence respectively, are used as codes assigned to respective users; and
matched filters, each matched to said finite length periodic sequence made before extending itself to said pseudo-frequency sequence, are used for demodulation at the receiver side.
7. The comb-form spectrum communication method using repeated complementary sequence modulation wherein correlation outputs we obtained by using convolvers instead of said matched filters recited in claim 5 .
8. The comb-form spectrum communication method using repeated complementary sequence modulation wherein correlation outputs are obtained by using convolvers instead of said matched filters reciten in claim 6 .