GPS is a CDMA system using DSSS, and the length of the C/A cod used by GPS L1 band civil signal is 1023chips. As the Cross-Correlation peak between the C/A codes is not zero, it will degrade the performance of the detection probability. Detection of weak signal is becoming important in many applications like GPS remote sensing etc. Cross-Correlation caused by GPS Gold codes are representing sig...

SUMMARY We propose a novel asynchronous direct-sequence code-division multiple access (DS-CDMA) using feedback-controlled spreading sequences (FCSSs) (FCSS/DS-CDMA). At the receiver of FCSS/DS-CDMA, the code-orthogonalizing filter (COF) produces a spreading sequence , and the receiver returns the spreading sequence to the transmitter. Then the transmitter uses the spreading sequence as its upda...

Iterative joint detection of random CDMA is considered in conjunction with error control coding, in particular using low-density parity-check (LDPC) codes. The spreading sequences are partitioned into sections, called “partitioned spreading (PS)”, creating an artificial repetition code which interfaces the LDPC code with the multiple access channel. A suboptimal, but efficient cancelation proce...

In 1993 some hybrid technics combining OFDM and code division multiple access (CDMA) were proposed [3]. One of that technics is multicarrier code division multiple access (MCCDMA) witch introduce frequency spreading and multiple access. Both, OFDM and MCCDMA, have disadvantage in high peak to average power ratio (PAPR). There are many PAPR reduction schemes are for OFDM and most of them is usef...

Direct sequence code division multiple access (DS-CDMA) is a popular wireless technology. This system suffers from Multiple Access Interference (MAI) caused by Direct Sequence users and Near–Far effect due to different power levels received. Multi-User Detection schemes are used to detect the users’ data in the presence of MAI and Near–Far problem. In this paper, presented comparative study bet...

For every natural number n ≥ 2 and every finite sequence L of natural numbers, we consider the set UDn(L) of all uniquely decodable codes over an n-letter alphabet with the sequence L as the sequence of code word lengths, as well as its subsets PRn(L) and FDn(L) consisting of, respectively, the prefix codes and the codes with finite delay. We derive the estimation for the quotient |UDn(L)|/|PRn...

The Synchronization Variable length codes. The Construction of Variable length codes with good Synchronization Properties. On the Expected codeword Length per Symbol of optimal prefix codes for extended Sources.

Codes Description of C Nonsingular C injective – i.e. ∀x, x′ ∈ X , x 6= x′ =⇒ C(x) = C(x′) Uniquely Decodable The extension the code is nonsingular. Prefix/Instantaneous/Self-punctuating No code word prefixes another: for all distinct x′, x′′ ∈ X , C(x′) does not start with C(x′′) We illustrate this below with the following example for the symbols {a, b, c, d} taken from Chapter 5 in Cover and ...