Spreading sequence design and theoretical limits for quasisynchronous CDMA systems
EURASIP Journal on Wireless Communications and Networking - Special issue on innovative signal transmission and detection techniques for next generation cellular CDMA systems
Quasi-orthogonal sequences for code-division multiple-access systems
IEEE Transactions on Information Theory
Design of spreading codes for quasi-synchronous CDMA with intercell interference
IEEE Journal on Selected Areas in Communications
IEEE Transactions on Information Theory
The Assignment of CDMA Spreading Codes Constructed from Hadamard Matrices and Almost Bent Functions
Wireless Personal Communications: An International Journal
Hi-index | 0.07 |
Let V = {1, 2, . . . , M} and let $${\{H_i{:} i \in V\}}$$ be a set of Hadamard matrices with the property that the magnitude of the dot product of any two rows of distinct matrices is bounded above. A Hadamard partition is any partition of the set of all rows of the matrices H i into Hadamard matrices. Such partitions have an application to the security of quasi-synchronous code-division multiple-access radio systems when loosely synchronized (LS) codes are used as spreading codes. A new generation of LS code can be used for each information bit to be spread. For each generation, a Hadamard matrix from some partition is selected for use in the code construction. This code evolution increases security against eavesdropping and jamming. One security aspect requires that the number of Hadamard partitions be large. Thus the number of partitions is studied here. If a Kerdock code construction is used for the set of matrices, the Hadamard partition constructed is shown to be unique. It is also shown here that this is not the case if a Gold (or Gold-like) code construction is used. In this case the number of Hadamard partitions can be enumerated, and is very large.