The Consultative Committee for Spac

The Consultative Committee for Space Data Systems
CCSDS) has produced over the years a de facto standard

(
for all space-related communication systems. In the latest
versions of the standard [1] there has been an increment in
the foreseen downlink throughput for deep-space
communications, reaching up to tens of megabits per
second. Four channel coding schemes have been described
in [2] and consequently assembled into application-wise
forward-error-correction (FEC) schemes in [3]. Both turbo
[
4] and low-density-parity-check (LDPC) [5] codes are
currently contemplated for deep-space communications
[2]; while the suggested turbo codes target stricter bit error
rate (BER) constraints, LDPC codes have been recently
included in the standard and have higher rate, and they are
currently subject to CCSDS experimentation [6]. Both
turbo and LDPC codes are common in on-Earth wireless
communication systems; however, throughput
requirements are much higher than those for deep-space
communications, while frame error rate (FER) constraints
are more relaxed. In fact, spacecraft-to-Earth
communications are characterized by limited amounts of
available power and long transmission times, and a failed
reception and consequent retransmission are often
unacceptable. Thus, ad hoc powerful FEC schemes must
be devised.
A FEC relying on the serial concatenation of turbo and
LDPC codes has been proposed in [7]; thanks to its very
good error correction capabilities, it has been deemed
suitable for the extremely critical deep-space

communications. To the best of our knowledge, no
implementation solution for the concatenated scheme has
been proposed so far, but decoders for both turbo and
LDPC codes are present in the state of the art, mainly
targeting wireless communications. Multicode and
multistandard decoders that make flexibility their primary
concern have also been introduced recently [8–13]; they
are characterized by different degrees of datapath and
memory sharing.
This work proposes a decoder for concatenated turbo
and LDPC codes targeting deep-space communications.
The usage of the same decoding algorithm for both codes
greatly reduces the area overhead of the concatenated
scheme decoder with respect to a single LDPC or turbo
code decoder. In fact, it allows one to exploit a high degree
of datapath sharing and obtain very low power consumption
and area occupation. In addition to deep-space
communications, the proposed solution could be also
useful in further applications where retransmission of lost
packets is not allowed, such as, for example, broadcasting.
The rest of the paper is organized as follows: Section II
introduces turbo and LDPC code decoding, while
Section III describes the concatenated FEC schemes and
their performance. The hardware structure of the proposed
decoder is explained in Section IV, and Section V gives
the results of the implementation. Finally, conclusions are

drawn in Section VI.

結果 (中文) 1:

空间数据系统咨询委员会CCSDS) 产生了多年来事实上的标准(对于所有与空间有关的通信系统。在最新版本的标准 [1] 那里一直在增量对于深太空预见下行链路的吞吐量通信，达到达几十兆比特每第二次。介绍了四种信道编码方案在 [2]，因此组装成 application-wise[3] 中的前向纠错 (FEC) 计划。这两个涡轮增压[4] 和低密度奇偶校验码 (LDPC) [5] 代码是目前正在考虑为深空通信[2];同时建议的 turbo 码目标严格误比特率率 (BER) 约束，LDPC 码最近一直在在该标准内具有较高的速度，和他们目前受 CCSDS 实验 [6]。两个涡轮增压和 LDPC 码是共同在地球上无线通信系统;然而，吞吐量要求是高于深空间通信，同时帧错误 (FER) 率约束是更轻松。事实上，太空船地球通信的特点是数量有限的可用的电源和长的传输时间，和失败接待和随之而来的重传往往无法接受。因此，特设强大 FEC 方案必须订定。FEC 依靠涡轮串行级联和在 [7]; 提出了 LDPC 码由于对其非常好的错误校正功能，它被认为是suitable for the extremely critical deep-spacecommunications. To the best of our knowledge, noimplementation solution for the concatenated scheme hasbeen proposed so far, but decoders for both turbo andLDPC codes are present in the state of the art, mainlytargeting wireless communications. Multicode andmultistandard decoders that make flexibility their primaryconcern have also been introduced recently [8–13]; theyare characterized by different degrees of datapath andmemory sharing.This work proposes a decoder for concatenated turboand LDPC codes targeting deep-space communications.The usage of the same decoding algorithm for both codesgreatly reduces the area overhead of the concatenatedscheme decoder with respect to a single LDPC or turbocode decoder. In fact, it allows one to exploit a high degreeof datapath sharing and obtain very low power consumptionand area occupation. In addition to deep-spacecommunications, the proposed solution could be alsouseful in further applications where retransmission of lostpackets is not allowed, such as, for example, broadcasting.The rest of the paper is organized as follows: Section IIintroduces turbo and LDPC code decoding, whileSection III describes the concatenated FEC schemes and their performance. The hardware structure of the proposeddecoder is explained in Section IV, and Section V givesthe results of the implementation. Finally, conclusions are第六节绘制。