13 research outputs found
Effects of the Generation Size and Overlap on Throughput and Complexity in Randomized Linear Network Coding
To reduce computational complexity and delay in randomized network coded
content distribution, and for some other practical reasons, coding is not
performed simultaneously over all content blocks, but over much smaller,
possibly overlapping subsets of these blocks, known as generations. A penalty
of this strategy is throughput reduction. To analyze the throughput loss, we
model coding over generations with random generation scheduling as a coupon
collector's brotherhood problem. This model enables us to derive the expected
number of coded packets needed for successful decoding of the entire content as
well as the probability of decoding failure (the latter only when generations
do not overlap) and further, to quantify the tradeoff between computational
complexity and throughput. Interestingly, with a moderate increase in the
generation size, throughput quickly approaches link capacity. Overlaps between
generations can further improve throughput substantially for relatively small
generation sizes.Comment: To appear in IEEE Transactions on Information Theory Special Issue:
Facets of Coding Theory: From Algorithms to Networks, Feb 201
Random Linear Fountain Code with Improved Decoding Success Probability
In this paper we study the problem of increasing the decoding success
probability of random linear fountain code over GF(2) for small packet lengths
used in delay-intolerant applications such as multimedia streaming. Such code
over GF(2) are attractive as they have lower decoding complexity than codes
over larger field size, but suffer from high transmission redundancy. In our
proposed coding scheme we construct a codeword which is not a linear
combination of any codewords previously transmitted to mitigate such
transmission redundancy. We then note the observation that the probability of
receiving a linearly dependent codeword is highest when the receiver has
received k-1 linearly independent codewords. We propose using the BlockACK
frame so that the codeword received after k-1 linearly independent codeword is
always linearly independent, this reduces the expected redundancy by a factor
of three.Comment: This paper appears in: Communications (APCC), 2016 22nd Asia-Pacific
Conference o
Expander Chunked Codes
Chunked codes are efficient random linear network coding (RLNC) schemes with
low computational cost, where the input packets are encoded into small chunks
(i.e., subsets of the coded packets). During the network transmission, RLNC is
performed within each chunk. In this paper, we first introduce a simple
transfer matrix model to characterize the transmission of chunks, and derive
some basic properties of the model to facilitate the performance analysis. We
then focus on the design of overlapped chunked codes, a class of chunked codes
whose chunks are non-disjoint subsets of input packets, which are of special
interest since they can be encoded with negligible computational cost and in a
causal fashion. We propose expander chunked (EC) codes, the first class of
overlapped chunked codes that have an analyzable performance,where the
construction of the chunks makes use of regular graphs. Numerical and
simulation results show that in some practical settings, EC codes can achieve
rates within 91 to 97 percent of the optimum and outperform the
state-of-the-art overlapped chunked codes significantly.Comment: 26 pages, 3 figures, submitted for journal publicatio
Network-coded NOMA with antenna selection for the support of two heterogeneous groups of users
The combination of Non-Orthogonal Multiple Access (NOMA) and Transmit Antenna Selection (TAS) techniques
has recently attracted significant attention due to the low cost,
low complexity and high diversity gains. Meanwhile, Random
Linear Coding (RLC) is considered to be a promising technique
for achieving high reliability and low latency in multicast
communications. In this paper, we consider a downlink system
with a multi-antenna base station and two multicast groups of
single-antenna users, where one group can afford to be served
opportunistically, while the other group consists of comparatively
low power devices with limited processing capabilities that have
strict Quality of Service (QoS) requirements. In order to boost
reliability and satisfy the QoS requirements of the multicast
groups, we propose a cross-layer framework including NOMAbased TAS at the physical layer and RLC at the application
layer. In particular, two low complexity TAS protocols for NOMA
are studied in order to exploit the diversity gain and meet the
QoS requirements. In addition, RLC analysis aims to facilitate
heterogeneous users, such that, sliding window based sparse RLC
is employed for computational restricted users, and conventional
RLC is considered for others. Theoretical expressions that
characterize the performance of the proposed framework are
derived and verified through simulation results