Lightweight Hierarchical Error Control Codes for Multi-Bit Differential Channels

In this thesis we describe a new class of error control codes that is designed to be used over " Multi-Bit Differential Signaling (MBDS), " a new off-chip signaling technology. This new class of codes, called " Lightweight Hierarchical Error Control Codes (LHECC), " takes advantage of inherent structural properties of MBDS's channel encoding mechanism, called " N choose M (nCm) " encoding. These properties are used to make LHECC codes extremely lightweight by offsetting much of the overhead cost normally required to add error control support to a channel. Lightweight Hierarchical Error Control Codes exploit both the inherent error detection characteristics and extra code words offered by nCm encoding. High-performance signaling technology for chip-to-chip links is an increasingly important area of research in computer system design. The growing gap between on-chip and off-chip signaling speeds is creating a potential bottleneck and future system design. This phenomenon is caused by the inherent challenges in transmitting high-speed signals through off-chip signaling paths. These challenges stem from additional vulnerability to noise and a larger amount of conductive material associated with off-chip signaling paths relative to on-chip signaling paths. For any given signaling technology there are various parameters that affect its maximum achievable signaling speed. Many of these parameters are influenced by the way in which data is encoded prior to transmission. In this work, we build an additional layer of data encoding on top of a newly developed high-performance off-chip signaling technology. This technology utilizes a base channel encoding mechanism to achieve high code density while offering noise rejection. The additional encoding further improves signal integrity and allows for higher total throughput. In addition to developing LHECC codes, we present simulation experiments from a prototype MBDS system. These preliminary results demonstrate that the error correction and detection capabilities of LHECC codes are well suited to recover from the types of signaling errors that are likely to occur in an MBDS link. Signal errors are caused by various noise sources that are intrinsic to any signaling technology. The increased signal integrity that is gained from LHECC codes allow MBDS links to cope with noise and operate at higher speeds that can otherwise be achieved without an additional level of data encoding for error control.