14,861 research outputs found
Supporting Read/Write Applications in Embedded Real-time Systems via Suspension-aware Analysis
In many embedded real-time systems, applications often interact with I/O
devices via read/write operations, which may incur considerable suspension
delays. Unfortunately, prior analysis methods for validating timing correctness
in embedded systems become quite pessimistic when suspension delays are
present. In this paper, we consider the problem of supporting two common types
of I/O applications in a multiprocessor system, that is, write-only
applications and read-write applications. For the write-only application model,
we present a much improved analysis technique that results in only O(m)
suspension-related utilization loss, where m is the number of processors. For
the second application model, we present a flexible I/O placement strategy and
a corresponding new scheduling algorithm, which can completely circumvent the
negative impact due to read- and write-induced suspension delays. We illustrate
the feasibility of the proposed I/O-placement-based schedule via a case study
implementation. Furthermore, experiments presented herein show that the
improvement with respect to system utilization over prior methods is often
significant
Efficient Integer Coefficient Search for Compute-and-Forward
Integer coefficient selection is an important decoding step in the
implementation of compute-and-forward (C-F) relaying scheme. Choosing the
optimal integer coefficients in C-F has been shown to be a shortest vector
problem (SVP) which is known to be NP hard in its general form. Exhaustive
search of the integer coefficients is only feasible in complexity for small
number of users while approximation algorithms such as Lenstra-Lenstra-Lovasz
(LLL) lattice reduction algorithm only find a vector within an exponential
factor of the shortest vector. An optimal deterministic algorithm was proposed
for C-F by Sahraei and Gastpar specifically for the real valued channel case.
In this paper, we adapt their idea to the complex valued channel and propose an
efficient search algorithm to find the optimal integer coefficient vectors over
the ring of Gaussian integers and the ring of Eisenstein integers. A second
algorithm is then proposed that generalises our search algorithm to the
Integer-Forcing MIMO C-F receiver. Performance and efficiency of the proposed
algorithms are evaluated through simulations and theoretical analysis.Comment: IEEE Transactions on Wireless Communications, to appear.12 pages, 8
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