Aerospace and Electronic Systems Magazine April 2017 - 48
DOI. No. 10.1109/MAES.2017.160118
Integration of Reed-Solomon Codes to Licklider
Transmission Protocol (LTP) for Space DTN
Leilei Shi, Soochow University, Jiangsu, China
Jian Jiao, Harbin Institute of Technology (Shenzhen), Guangdong, China
Alaa Sabbagh, Ruhai Wang, Lamar University, Beaumont, TX, USA
Qian Yu, Jianling Hu, Hong Wang, Soochow University, Jiangsu, China
Scott C. Burleigh, Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA, USA
Kanglian Zhao, Nanjing University, Jiangsu, China
Extensive work has been done in developing networking architectures and protocols for satellite/space communications
and interplanetary networks. A variety of solutions have been
proposed [1-9]. Numerous literature surveys [10-14] have also
been conducted on these technologies. Delay/disruption tolerant networking (DTN)  architecture was proposed to enable
automated network communications despite the long link delay
and frequent link disruptions that generally characterize deepspace communications. DTN is presently recognized as the only
candidate protocol that approaches the level of maturity required
to handle the inevitable long link delay, frequent and lengthy
link disconnections, and heavy data loss inherent in space communications .
As the main protocol of DTN protocol stack, bundle protocol
(BP)  was developed to build an overlay network and to provide custody-based data transmission service to DTN. However,
BP does not transmit data directly. Instead, it utilizes the transmission protocols of the underlying networks by invoking the services of an interface called a "convergence layer adapter" (CLA).
A CLA in turn operates the underlying data transport protocol stack
at what is termed the "convergence layer." Licklider transmission
Authors' current addresses: L. Shi, Q.Yu, J. Hu, H. Wang, School
of Electronics and Information Engineering, Soochow University,
Suzhou, Jiangsu 215006, P. R. China; J. Jiao, School of Electronics and Information Engineering, Harbin Institute of Technology
(Shenzhen), Guangdong 518055, P. R. China; A. Sabbagh and R.
Wang, Phillip M. Drayer Department of Electrical Engineering,
Lamar University, Beaumont, TX 77710-1029; Scott C. Burleigh,
Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA 91109; K. Zhao, School of Electronic Science and
Engineering, Nanjing University, Jiangsu 210093, P. R. China. Corresponding author is J. Jiao: E-mail: (firstname.lastname@example.org).
Review handled by M. De Sanctis.
0885/8985/17/$26.00 © 2017 IEEE
protocol (LTP) [17, 18] is developed as DTN's primary "convergence layer" transport protocol for space networks. Similar to the
pervasively used transmission control protocol (TCP), LTP implements an automatic repeat request (ARQ)-based retransmission
scheme. However, LTP operates on multiple concurrent transmissions for efficient data delivery.
While data loss over a space channel may be mitigated by bitlevel forward error correction (FEC) at the link layer, significant
residual loss remains; LTP can recover from this residual data
loss, but only by means of correspondingly heavy retransmission.
However, long link delays and disruptions that characterizes space
communications render ARQ inefficient for data loss recovery,
since additional retransmission rounds increase data delivery latency and thus severely degrade transmission efficiency.
Erasure codes are consistently considered as a complement
to ARQ-based schemes to improve data transmission efficiency.
Because erasure coding is a packet-level FEC technique, it can be
implemented within any layer of the DTN protocol stack that deals
with discrete data units (i.e., packets, frames, etc.). The best layer for
erasure coding in the DTN protocol stack has been a matter of debate.
It is widely recognized that implementation of erasure coding
on an end-to-end basis (i.e., at the bundle layer or at the overlying
application layer) has some clear advantages. First, from a perspective of internetworking, implementing erasure coding in an
upper layer (coding only at the source node and decoding only at
the destination node) allows for efficient handling of any packet
erasures that occur on any network segment and at any layer of
the stack. Second, from a technical point of view, implementing
erasure coding on an end-to-end basis moves complexity towards
the end nodes. This leads to shorter total processing delays of the
communication system since encoding/decoding processes reside
only at the end nodes. In addition, erasure coding in an upper layer
allows applications to signal certain QoS requirements such as delay constraints and packet lengths to the "transport" service below.
On the other hand, efficient end-to-end coding requires information about conditions on all link segments of the end-to-end
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