Bit-to-Bit Error Dependence in Direct-Sequence Spread-Spectrum Multiple- Access Packet Radio Systems
Abstract
Slotted direct-sequence spread-spectrum multiple-access (DS/SSMA) packet broadcasting systems with random signature sequences are analyzed within the framework of the lower three layers of the International Standards Organization Reference Model of Open Systems Interconnection. At the physical layer, we show that a widely-used Gaussian approximation (which we call the Standard Gaussian Approximation) for the probability of data bit error in a chip and phase asynchronous system is accurate only when there are a large number of simultaneous users on the channel; otherwise, this approximation can be optimistic by several orders of magnitude. For interfering signals with fixed delays and phases relative to the desired signal, however, the Standard Gaussian Approximation is quite accurate for any number of simultaneous users. To obtain a closer approximation to the probability of data bit error for an asynchronous system, we introduce the Improved Gaussian Approximation, which involves finding the distribution of the multiple-access interference variance over all possible delay and phase values and then taking a Gaussian approximation over the support of the distribution and averaging the results. To accurately analyze packet performance at the data link layer, we first use the theory of moment spaces to gain insight on the effect of bit-to-bit error dependence caused by the constant relative delays and (possibly) phases of the interfering signals over the duration of a desired packet.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1988
- Accession Number
- ADA196384
Entities
People
- Robert K. Morrow Jr
Organizations
- Air Force Institute of Technology