Method of constructing a spreading code associated with one user of a direct sequence code division multiple access digital transmission system and corresponding method of generating a table

Claim 3

A method according to claim 1, wherein the period of said sub-codes is equal to the spreading gain of said transmission system.

Claim 4

A method according to claim 1, wherein said family of basic sub-codes belongs to the group comprising: the family of Gold codes; and the family of Kasami codes.

Claim 5

A method according to claim 1, wherein said spreading code belongs to a family of at least two separate spreading codes, and in that said spreading code can be written: ##EQU8## where: k is the index of said spreading code in said family; Σ signifies concatenation; q is the concatenation index; n is the concatenation factor, i.e. the total number of sub-codes to be concatenated to form said spreading codes; T x is a circular permutation of x elements; a y is a basic sub-code of a family {a y } of basic sub-codes which can be used to construct the sub-codes to be concatenated; c k (q) is the function indicating the basic sub-code to be used to construct the q th sub-code to be concatenated in said k th spreading code; p k (q) is the function indicating the number of permutations to be effected on the basic sub-code a y to be considered, with y=c k (q).

Claim 6

A method according to claim 4, including a step of associating a pair (p k (q), c k (q)) with each value of q.

Claim 7

A method according to claim 5, wherein said step of associating a pair (p k (q), c k (q)) with each value of q is such that the same sub-code cannot have the same concatenation rank in said spreading code and in any other spreading code of said family of spreading codes.

Claim 8

A method according to claim 5, wherein said step of associating a pair (p k (q), c k (q)) with each value of q is such that the same sub-code cannot be present more than once in said spreading code.

Claim 9

A method according to claim 5, wherein said step of associating a pair (p k (q), c k (q)) with each value of q consists of calculating said values p k (q) and c k (q) using a function parameterized by said index k of said spreading code in said family.

Claim 10

A method according to claim 5, wherein said stage of associating a pair (p k (q), c k (q)) with each value of g consists of reading said values p k (q) and c k (q) in a table previously generated using a function parameterized by said index k of said spreading code in said family.

Claim 11

A method of generating a table of the type used in a method according to claim 9, of constructing a spreading code, said table associating, for each of said spreading codes indexed by k, a pair of values (p k (q), c k (q)) with each concatenation index q, said method comprising the following steps: choosing a number K of available basic sub-codes; generating pairs (p k (q), c k (q)) iteratively from the spreading code index k in said family and from the concatenation index q, said iterative generation entailing: * choosing a variable V k (q)=p k (q)*K+c k (q) where V k (q) is the smallest integer such that: V k (q)<K.N where N is the period of the sub-codes; V k (q)≠V k (q') for all q'<q, where q' corresponds to all values of q for which a pair (p k (q), c k (q)) has already been calculated; V k '(q)≠V k (q) for all k'<k, where k' corresponds to all values of k for which a pair (p k (q), c k (q)) has already been calculated; * effecting the integer division of V k (q) by K to obtain the values p k (q) and c k (q).

Claim 22

A method according to claim 15, wherein said generating step comprises generating a plurality of said spreading codes to obtain a family of spreading codes, each spreading code in said family including different sub-codes in accordance with claim 15, and said assigning step comprises assigning a specific one of said family of spreading codes to said specific user.