Information Theory Sequences with low total squared asynchronous correlation for chip-unaligned CDMA systems

We examine some properties of Chip-unaligned (Cu) CDMA systems with sequences that are obtained by means of an eigen update algorithm. We briefly refer to these systems as ‘Cu systems with low total squared asynchronous correlation (TSAC)’. The notion of TS(A)C, which is well-known for Chip-aligned (Ca) systems, is extended to the Cu case. It is found that the TSAC of Cu systems with low TSAC is a non-sensitive function of the time shift set of the Cu system, but it is strongly dependent on the chip pulse. Similar to the Ca case, for high channel loads, the TSAC of some Cu systems with low TSAC appears to be proportional to the channel load and the number of users in the system, while the equally good property is valid. An examination of the maximum common signal to interference and noise ratio (SINR) target level κmax indicates that particular types of Cu systems with low TSAC allow for a significantly higher value of κmax than achievable in Ca systems. Copyright © 2007 John Wiley & Sons, Ltd.

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