Gigabit simultaneous Bi-directional signaling using DS-CDMA

Vaishnav Srinivas, Karl J. Bois, Derek Knee, David Ouint, Mau-Chung Chang, Ingrid Verbauwhede

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


This paper proposes the use of orthogonal coding to allow simultaneous communication over a digital link without the use of a modulation scheme. The interconnect consists of a complex, lossy and noisy channel (consistent with designs in a Hewlett-Packard computer system) and a novel transceiver. Code-division multiple access (CDMA) schemes have been used extensively for spread spectrum communications, especially for multiple access in wireless applications. In general, these systems involve spreading the baseband information over a wider bandwidth using a set of codes. These codes are orthogonal to each other and hence provide a means for multiple access. These coded signals are subsequently modulated with a carrier before being sent on the channel [ 1, 2]. This is generally achieved either by a BPSK or a QPSK modulation scheme. The modulation allows for the reduction of the probability of error by optimizing the constellation distances and making the system more robust. If such signals were sent on a wired line it would not be necessary to up-convert the baseband information with a carrier because the resources for frequency allocation are not limited like in air, and baseband transmission is possible. DS-CDMA has been used to design point-to-point wired uni-directional buses [3] but there has been no prior investigation as to its performance on a simultaneous bi-directional channel. This paper provides such an investigation on a potential high-loss interconnect that would connect two CPUs in a Hewlett-Packard computer system. The channel was chosen to demonstrate performance on longer interconnects in computer systems, which often contain high losses and complex discontinuities. Section I of the paper introduces the key concepts used in the design of the link and is a brief overview. Section II describes the channel used. Section III describes the design and implementation of the transceiver. Section IV is a summary of the design and the results.

Original languageEnglish
Title of host publicationElectrical Performance of Electronic Packaging, EPEP 2002
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages4
ISBN (Electronic)0780374517
StatePublished - 1 Jan 2002
Event11th Topical Meeting on Electrical Performance of Electronic Packaging, EPEP 2002 - Monterey, United States
Duration: 21 Oct 200223 Oct 2002

Publication series

NameIEEE Topical Meeting on Electrical Performance of Electronic Packaging


Conference11th Topical Meeting on Electrical Performance of Electronic Packaging, EPEP 2002
CountryUnited States

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