178 research outputs found
A Multistage Method for SCMA Codebook Design Based on MDS Codes
Sparse Code Multiple Access (SCMA) has been recently proposed for the future
generation of wireless communication standards. SCMA system design involves
specifying several parameters. In order to simplify the procedure, most works
consider a multistage design approach. Two main stages are usually emphasized
in these methods: sparse signatures design (equivalently, resource allocation)
and codebook design. In this paper, we present a novel SCMA codebook design
method. The proposed method considers SCMA codebooks structured with an
underlying vector space obtained from classical block codes. In particular,
when using maximum distance separable (MDS) codes, our proposed design provides
maximum signal-space diversity with a relatively small alphabet. The use of
small alphabets also helps to maintain desired properties in the codebooks,
such as low peak-to-average power ratio and low-complexity detection.Comment: Submitted to IEEE Wireless Communication Letter
Multishot Codes for Network Coding: Bounds and a Multilevel Construction
The subspace channel was introduced by Koetter and Kschischang as an adequate
model for the communication channel from the source node to a sink node of a
multicast network that performs random linear network coding. So far, attention
has been given to one-shot subspace codes, that is, codes that use the subspace
channel only once. In contrast, this paper explores the idea of using the
subspace channel more than once and investigates the so called multishot
subspace codes. We present definitions for the problem, a motivating example,
lower and upper bounds for the size of codes, and a multilevel construction of
codes based on block-coded modulation.Comment: 5 pages, 2 figures, submitted to ISIT 200
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