US 7,352,796 B1Granted

Multiple data rate complex Walsh codes for CDMA

AssigneeUrbain Alfred von der Embse

InventorUrbain Alfred von der Embse

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Abstract

A method and system using the fast encoding and decoding of hybrid Walsh CDMA and generalized hybrid Walsh CDMA codes for simultaneous transmission of multiple data rate users with the different data rate groups of users separated in the sequency domain of these complex CDMA channelization codes. Sequency is the average rate of phase angle rotations of the code vectors and for hybrid Walsh codes sequency is in a 1-to-1 correspondence with frequency for the discrete Fourier transform codes. Hybrid Walsh codes are derived from lexicographic permutations of the real Walsh and can take values {1, j, −1, −j}. Generalized hybrid Walsh codes are orthogonal and quasi-orthogonal complex codes derived from tensor (Kronecker) product construction, direct product construction, and functional combining of the plurality of codes including the hybrid Walsh and discrete Fourier transform codes.

Claims5

Dependent claims

A method for generating and applying N hybrid Walsh complex orthogonal codes for code division multiple access (CDMA), said method comprising the steps:

generating N Walsh codes W(c) with code index c=0, 1, 2, . . . , N−1, each with N chips where N is a power of 2,
generating said N hybrid Walsh codes {tilde over (W)} (c) by reordering each of said N Walsh codes into a corresponding real component and a corresponding imaginary component of a hybrid Walsh code
as defined by equations
for
⁢
⁢
c
=
⁢
0
,
W
~
⁡
(
c
)
=
W
⁡
(
0
)
+
jW
⁡
(
0
)
for
⁢
⁢
c
=
⁢
1
,
2
,
…
⁢
,
N
⁢
/
⁢
2
-
1
,
W
~
⁡
(
c
)
=
W
⁡
(
2
⁢
c
)
+
jW
⁡
(
2
⁢
c
-
1
)
for
⁢
⁢
c
=
⁢
N
⁢
/
⁢
2
,
W
~
⁡
(
c
)
=
W
⁡
(
N
-
1
)
+
jW
⁡
(
N
-
1
)
)
for
⁢
⁢
c
=
⁢
N
⁢
/
⁢
2
+
1
,
…
⁢
,
N
-
1
,
W
~
⁡
(
c
)
=
W
⁡
(
2
⁢
N
-
2
⁢
c
-
1
)
+
⁢
jW
⁡
(
2
⁢
N
-
2
⁢
c
)
wherein
⁢
⁢
j
=
⁢
√
-
1
,
wherein said N hybrid Walsh codes are generated by reading the N Walsh codes chip values from a Walsh code memory in a digital signal processor and writing the reordered Walsh codes to a hybrid Walsh code memory,
applying said N hybrid Walsh codes in an encoder and in a decoder of a CDMA system by encoding transmitting data and decoding receiving data with said N hybrid Walsh complex codes, and
transmitting data encoded by the encoder and receiving data decoded by the decoder.

173 more elements

Dependencies are inferred from the claim text.