Combined coding and spreading in CDMA systems using maximum free distance convolutional codes

• In CDMA systems maximum theoretical performance can be obtained by spreading with low-rate error control codes. Previously, orthogonal and superorthogonal codes have been proposed for this purpose. We present a family of rate-compatible low-rate convolutional codes with maximum free distance. The performance of these codes for spectrum spreading in a CDMA system is evaluated and shown to outperform that of orthogonal and superorthogonal codes as well as conventional coding/spreading schemes. We also show that our low-rate codes will give simple encoder and decoder implementation. With these codes any 1/n rate can be obtained regardless of the constraint length, resulting in a more flexible and powerful scheme than those proposed up to now.

Ämnesord

NATURVETENSKAP  -- Data- och informationsvetenskap (hsv//swe)

NATURAL SCIENCES  -- Computer and Information Sciences (hsv//eng)

Nyckelord

maximum free distance

low-rate convolutional codes

orthogonal codes

superorthogonal codes

rate-compatible

CDMA

Publikations- och innehållstyp

kon (ämneskategori)

ref (ämneskategori)