MQAM modulation and RS codes for SS-CDMA communication over Ricianfading channels
Ali, A.A.
Communications, IEE Proceedings-
Volume 145, Issue 6, Dec 1998 Page(s):414 - 418
Digital Object Identifier
Summary:The use of bandwidth efficient high level modulation systems such
as quadrature-amplitude modulation (MQAM) and multiphase (MPSK),
together with Reed-Solomon (RS) codes, provides substantial coding gain
on fading channels. The author derives the optimum modulation and coding
parameters of RS coded MPSK and MQAM schemes. The transmission channel
is subject to flat Rician fading and spread-spectrum code-division
multiple-access (SS-CDMA) interference. For RS codes defined over GF(M
m), the encoded symbols are mapped to the signal points of an
expanded set with cardinality of M such that each RS code symbol
consists of concatenation of m M-ary symbols. It is shown that there is
an optimum selection of m which minimises the bit-error rate. The
Gaussian approximation is used to derive a simple expression of the
probability of error (Pc) using RS codes. Finally, the
optimum modulation and coding parameters which optimise the bit-error
performance are obtained by setting partial derivatives of Pc
to zero and solving the resulting equations. It is shown that the
optimum choice of modulation and coding parameters depends on the
channel interference and fading conditions. Although exact analysis can
be used, the present approach yields a general solution, and optimum
design parameters can be related to channel conditions
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