ISO 20205:2015

INTERNATIONAL ISO
STANDARD 20205
First edition
2015-08-15
Space data and information transfer
systems — Spacecraft Onboard
Interface Systems — Low Data-
Rate Wireless Communications for
Spacecraft Monitoring and Control
Systèmes de transfert des informations et données spatiales —
Services d’interfaces à bord des véhicules spatiaux — Communication
sans fil à faible débit de données pour la surveillance et le contrôle des
véhicules spatiaux
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 20205 was prepared by the Consultative Committee for Space Data Systems (CCSDS) (as
CCSDS 882.0-M-1, May 2013) and was adopted (without modifications except those stated in clause 2 of this
International Standard) by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 13, Space data and information transfer systems.

Recommendation for Space Data System Practices
SPACECRAFT ONBOARD INTERFACE
SYSTEMS—LOW DATA-RATE WIRELESS
COMMUNICATIONS FOR SPACECRAFT
MONITORING AND CONTROL
RECOMMENDED PRACTICE
CCSDS 882.0-M-1
MAGENTA BOOK
May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
AUTHORITY
Issue: Recommended Practice, Issue 1
Date: May 2013
Location: Washington, DC, USA
This document has been approved for publication by the Management Council of the
Consultative Committee for Space Data Systems (CCSDS) and represents the consensus
technical agreement of the participating CCSDS Member Agencies. The procedure for
review and authorization of CCSDS documents is detailed in Organization and Processes for
the Consultative Committee for Space Data Systems (CCSDS A02.1-Y-3), and the record of
Agency participation in the authorization of this document can be obtained from the CCSDS
Secretariat at the address below.

This document is published and maintained by:

CCSDS Secretariat
Space Communications and Navigation Office, 7L70
Space Operations Mission Directorate
NASA Headquarters
Washington, DC 20546-0001, USA
CCSDS 882.0-M-1 Page i May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
STATEMENT OF INTENT
The Consultative Committee for Space Data Systems (CCSDS) is an organization officially
established by the management of its members. The Committee meets periodically to address
data systems problems that are common to all participants, and to formulate sound technical
solutions to these problems. Inasmuch as participation in the CCSDS is completely
voluntary, the results of Committee actions are termed Recommendations and are not in
themselves considered binding on any Agency.
CCSDS Recommendations take two forms: Recommended Standards that are prescriptive
and are the formal vehicles by which CCSDS Agencies create the standards that specify how
elements of their space mission support infrastructure shall operate and interoperate with
others; and Recommended Practices that are more descriptive in nature and are intended to
provide general guidance about how to approach a particular problem associated with space
mission support. This Recommended Practice is issued by, and represents the consensus of,
the CCSDS members. Endorsement of this Recommended Practice is entirely voluntary
and does not imply a commitment by any Agency or organization to implement its
recommendations in a prescriptive sense.
No later than three years from its date of issuance, this Recommended Practice will be
reviewed by the CCSDS to determine whether it should: (1) remain in effect without change;
(2) be changed to reflect the impact of new technologies, new requirements, or new
directions; or (3) be retired or canceled.
In those instances when a new version of a Recommended Practice is issued, existing
CCSDS-related member Practices and implementations are not negated or deemed to be non-
CCSDS compatible. It is the responsibility of each member to determine when such Practices
or implementations are to be modified. Each member is, however, strongly encouraged to
direct planning for its new Practices and implementations towards the later version of the
Recommended Practice.
CCSDS 882.0-M-1 Page ii May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
FOREWORD
This document is a CCSDS Recommended Practice, which is the consensus result as of the
date of publication of the Best Practices for low data-rate communication systems for
spacecraft monitor and control in support of space missions.
Through the process of normal evolution, it is expected that expansion, deletion, or
modification of this document may occur. This Recommended Practice is therefore subject
to CCSDS document management and change control procedures, which are defined in the
Organization and Processes for the Consultative Committee for Space Data Systems
(CCSDS A02.1-Y-3). Current versions of CCSDS documents are maintained at the CCSDS
Web site:
http://www.ccsds.org/
Questions relating to the contents or status of this document should be addressed to the
CCSDS Secretariat at the address indicated on page i.
CCSDS 882.0-M-1 Page iii May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
At time of publication, the active Member and Observer Agencies of the CCSDS were:
Member Agencies
– Agenzia Spaziale Italiana (ASI)/Italy.
– Canadian Space Agency (CSA)/Canada.
– Centre National d’Etudes Spatiales (CNES)/France.
– China National Space Administration (CNSA)/People’s Republic of China.
– Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Federal Space Agency (FSA)/Russian Federation.
– Instituto Nacional de Pesquisas Espaciais (INPE)/Brazil.
– Japan Aerospace Exploration Agency (JAXA)/Japan.
– National Aeronautics and Space Administration (NASA)/USA.
– UK Space Agency/United Kingdom.
Observer Agencies
– Austrian Space Agency (ASA)/Austria.
– Belgian Federal Science Policy Office (BFSPO)/Belgium.
– Central Research Institute of Machine Building (TsNIIMash)/Russian Federation.
– China Satellite Launch and Tracking Control General, Beijing Institute of Tracking
and Telecommunications Technology (CLTC/BITTT)/China.
– Chinese Academy of Sciences (CAS)/China.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– CSIR Satellite Applications Centre (CSIR)/Republic of South Africa.
– Danish National Space Center (DNSC)/Denmark.
– Departamento de Ciência e Tecnologia Aeroespacial (DCTA)/Brazil.
– European Organization for the Exploitation of Meteorological Satellites
(EUMETSAT)/Europe.
– European Telecommunications Satellite Organization (EUTELSAT)/Europe.
– Geo-Informatics and Space Technology Development Agency (GISTDA)/Thailand.
– Hellenic National Space Committee (HNSC)/Greece.
– Indian Space Research Organization (ISRO)/India.
– Institute of Space Research (IKI)/Russian Federation.
– KFKI Research Institute for Particle & Nuclear Physics (KFKI)/Hungary.
– Korea Aerospace Research Institute (KARI)/Korea.
– Ministry of Communications (MOC)/Israel.
– National Institute of Information and Communications Technology (NICT)/Japan.
– National Oceanic and Atmospheric Administration (NOAA)/USA.
– National Space Agency of the Republic of Kazakhstan (NSARK)/Kazakhstan.
– National Space Organization (NSPO)/Chinese Taipei.
– Naval Center for Space Technology (NCST)/USA.
– Scientific and Technological Research Council of Turkey (TUBITAK)/Turkey.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
– United States Geological Survey (USGS)/USA.
CCSDS 882.0-M-1 Page iv May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
DOCUMENT CONTROL
Document Title Date Status
CCSDS Spacecraft Onboard Interface May 2013 Current issue
882.0-M-1 Systems—Low Data-Rate Wireless
Communications for Spacecraft
Monitoring and Control,
Recommended Practice, Issue 1
CCSDS 882.0-M-1 Page v May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
CONTENTS
Section Page
1 INTRODUCTION. 1-1

1.1 PURPOSE . 1-1
1.2 SCOPE . 1-1
1.3 APPLICABILITY . 1-1
1.4 RATIONALE. 1-1
1.5 DOCUMENT STRUCTURE . 1-1
1.6 DEFINITIONS . 1-2
1.7 CONVENTIONS . 1-2
1.8 REFERENCES . 1-3

2 OVERVIEW . 2-1

2.1 RATIONALE AND BENEFITS . 2-1
2.2 SCOPE OF INTEROPERABILITY . 2-1
2.3 EVOLUTION OF THE BOOK . 2-2
2.4 DIFFERENTIATING CONTENTION-BASED AND
SCHEDULED CHANNEL ACCESS . 2-3
2.5 SECURITY PROVISIONING . 2-4
2.6 QUALITY OF SERVICE PROVISIONING . 2-4

3 RECOMMENDED PRACTICES FOR LOW DATA-RATE
WIRELESS COMMUNICATIONS FOR SPACECRAFT
MONITORING AND CONTROL . 3-1

3.1 OVERVIEW . 3-1
3.2 RECOMMENDED PRACTICES. 3-1

ANNEX A JUSTIFYING THE SCHEDULED MEDIUM ACCESS
RECOMMENDATION (INFORMATIVE) . A-1
ANNEX B SECURITY CONCERNS FOR WIRELESS SYSTEMS
(INFORMATIVE) .B-1
ANNEX C DISCUSSION ON LOW DATA-RATE WIRELESS
COMMUNICATIONS FOR SPACECRAFT MONITORING
AND CONTROL (INFORMATIVE) . C-1
ANNEX D JUSTIFICATIONS FOR THE 2.4 GHZ BAND PREFERENCE
(INFORMATIVE) . D-1
ANNEX E ABBREVIATIONS AND ACRONYMS (INFORMATIVE) .E-1
ANNEX F INFORMATIVE REFERENCES (INFORMATIVE) . F-1
CCSDS 882.0-M-1 Page vi May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
CONTENTS (continued)
Figure Page
2-1 IEEE 802.15.4 Superframe . 2-5

Table
2-1 PHY/MAC Security Service Provisioning . 2-4
C-1 Application Profile Quick Look-Up Table .C-4
C-2 Quick-Look Table for Scenarios That Can Utilize Low Data-Rate Wireless
Communications .C-4
C-3 Typical Operating Parameters for the Single-Hop, Periodic Data Aggregation
Application Profile .C-6
C-4 Typical Operating Parameters for the Single-Hop Triggered, Event-Driven Data
Acquisition Application Profile .C-7
C-5 Typical Operating Parameters for the Single-Hop Command and Control Application
Profile.C-9
D-1 Power Regulations . D-2

CCSDS 882.0-M-1 Page vii May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
1 INTRODUCTION
1.1 PURPOSE
This document presents the recommended practices for the utilization of low data-rate
wireless communication technologies in support of spacecraft ground testing and flight
monitoring and control applications. Relevant technical background information can be
found in reference [3].
The recommended practices contained in this document enable member agencies to select the
best option(s) available for interoperable wireless communications in the support of
spacecraft monitoring and control applications. The specification of a Recommended
Practice facilitates interoperable communications and forms the foundation for cross-support
of communication systems between separate member space agencies.
1.2 SCOPE
This Recommended Practice is targeted towards monitoring and control systems, typically
low data-rate and low-power wireless-based applications.
1.3 APPLICABILITY
This Recommended Practice specifies protocols (including at least the Physical [PHY] layer
and Medium Access Control [MAC] sublayer of the Open Systems Interconnection [OSI]
Model—see reference [F1]) that enable a basic interoperable wireless communication system
to support low data-rate spacecraft monitoring and control applications.
1.4 RATIONALE
From an engineering standpoint, mission managers, along with engineers and developers, are
faced with a plethora of wireless communication choices, both standards-based and
proprietary. This Recommended Practice provides guidance in the selection of systems
necessary to achieve interoperable communications in support of wireless, low data-rate
monitoring and control.
1.5 DOCUMENT STRUCTURE
This document is composed from a top-down (technology) perspective, first defining the
technology as a recommended practice, then providing informative material supporting specific
application profiles. (For more information on space mission use cases addressed by wireless
technologies, see reference [3]).
Section 2 provides an informational overview of the rationale and benefits of spacecraft
onboard wireless technologies for use in spacecraft monitoring and control operations.
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Section 3 provides recommended practices and applicable standards relating to low data-rate
wireless communication systems.
Annex A justifies the choice of an alternative, scheduled medium access scheme.
Annex B discusses security considerations related to the specifications in this document.
Annex C provides an informative description of the recommended practices, through an
overview of the technologies, and a set of application profiles where the recommendations
are applicable.
Annex D provides justification for selection of the 2.4 GHz band.
Annex E lists abbreviations used in this document along with their expanded forms.
Annex F provides a list of informative references.
1.6 DEFINITIONS
low data-rate: 250 kbps or less.
NOTE – In general the definition of low data-rate is somewhat ambiguous; for this
Recommended Practice it is specified as 250 kbps.
low power: 10 mW or less (typical).
quality of service, QoS: The ability to provide different priority to different applications,
users, or data flows, or to guarantee a certain level of performance to a data flow.
1.7 CONVENTIONS
1.7.1 NOMENCLATURE
The following conventions apply for the normative specifications in this Recommended
Practice:
a) the words ‘shall’ and ‘must’ imply a binding and verifiable specification;
b) the word ‘should’ implies an optional, but desirable, specification;
c) the word ‘may’ implies an optional specification;
d) the words ‘is’, ‘are’, and ‘will’ imply statements of fact.
NOTE – These conventions do not imply constraints on diction in text that is clearly
informative in nature.
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RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
1.7.2 INFORMATIVE TEXT
In the normative section of this document, informative text is set off from the normative
specifications either in notes or under one of the following subsection headings:
– Overview;
– Background;
– Rationale;
– Discussion.
1.8 REFERENCES
The following publications contain provisions, which through reference in this text,
constitute provisions of this document. At the time of publication, the editions indicated
were valid. All publications are subject to revision, and users of this document are
encouraged to investigate the possibility of applying the most recent editions of the
publications indicated below. The CCSDS Secretariat maintains a register of currently valid
CCSDS publications.
[1] IEEE Standard for Local and Metropolitan Area Networks—Part 15.4: Low-Rate
Wireless Personal Area Networks (LR-WPANs). IEEE Std 802.15.4a™-2011. New
York: IEEE, 2011.
[2] Wireless Systems for Industrial Automation: Process Control and Related Applications.
ISA-100.11a-2011. Durham, North Carolina: ISA, 2011.
[3] Wireless Network Communications Overview for Space Mission Operations. Report
Concerning Space Data System Standards, CCSDS 880.0-G-1. Green Book. Issue 1.
Washington, D.C.: CCSDS, December 2010.

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2 OVERVIEW
2.1 RATIONALE AND BENEFITS
Monitoring and controlling the behavior of a spacecraft and launch systems, during testing
phases on ground or during nominal operations in orbit, is the key to ensuring the correct
functioning of various onboard systems and structures, the responses of these systems in their
operational working environments, and the long-term reliability of the spacecraft. These data
are also highly significant when compiling lessons learned that will be applied to building
better space systems and increasing the reliability of future space components. (Refer to
reference [3] for a comprehensive overview of application domains and for a detailed
summary of RF communications and restrictions in differing operational environments.)
The quantity of acquired spacecraft functional data depends on the ability to monitor required
parameters at precise locations within a given project time and cost envelope. Hundreds and
often thousands of data measurement locations are required, steadily increasing the mass
(acquisition systems, cables, and harnesses) and the project costs and time (installation and
verification of each new sensor).
The use of wireless technologies is foreseen to reduce the integration effort, cost, and time
typically required to instrument a high number of physical measurement points on a space
structure. Technicians should need less time to integrate and verify their installations, while
the risk of mechanically damaging interfaces during the process should be reduced. Large
structures should see health monitoring equipment mass reduced, while last-minute changes
in the instrumentation (e.g., addition/removal of sensing nodes at measurement points)
should be easier to accept at project level. One of the byproducts of using wireless
technologies in space systems is the extra flexibility introduced when implementing wireless
fault-tolerance and redundancy schemes.
An overriding consideration in this document is the desire to provide recommendations that
utilize wireless technology to augment the overall networking infrastructure in a spacecraft
rather than to provide dedicated data transport to particular end-to-end application-specific
subsystems. That is, although the recommendations specified in this document are related to
relatively small-scale Personal Area Networks (PANs) rather the more familiar Local Area
Networks (LANs) such as Ethernet, the desire is for wireless PANs to function as natural
extensions of the backbone LAN. This implies in particular that the recommendations
specified herein focus on providing wireless data transport across the lower levels of the OSI
model (PHY and MAC) and not on achieving higher-level application-specific behavior.
2.2 SCOPE OF INTEROPERABILITY
The intent of the recommended practices promulgated in this book is to provide a framework
for establishing a scalable wireless infrastructure for low-rate data transport that will (1)
support traffic generated by diverse sensor types, multiple application-specific devices, and
devices supplied by multiple different vendors and (2) facilitate operation of multiple
wireless networks in the same bandwidth with minimal interference. The recommended
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RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
practices will ensure interoperability of low data-rate wireless devices on a common network
at the PHY layer and MAC sublayer so that data packets generated by new devices entering
the network will be transported by the existing network devices without regard to the sensor
or application that generated the data in the packet payload. In its current form, the book’s
recommendations should allow new nodes to enter a star topology network and begin
communicating with a gateway. Should future revisions augment the current
recommendations to allow for transport mechanisms such as peer-to-peer communication and
multi-hop relaying, new nodes entering the network will not only be able to transmit their
own data to a gateway, but they may also be able to communicate with other nodes and to
transport data for other network devices.
Adherence to these recommended practices will promote interoperability of the low data-rate
wireless networks addressed in this document with other wireless networks using the same
bandwidth via the interference mitigation techniques encompassed by the recommendations.
2.3 EVOLUTION OF THE BOOK
The current version of this document specifies two recommended practices for low data-rate
spacecraft monitoring and control. Functionally, the current recommendations can be
regarded as pertaining only to the behavior of the network at the PHY layer and MAC
sublayer of the OSI network stack, not at the Logical Link sublayer or higher. This level of
detail in the recommendations is in line with the philosophy discussed in 2.1 above, that the
recommended behavior of wireless networks should be specified only at the lower layers of
the network stack (similar to the behavior specified for the backbone network in the
spacecraft), leaving higher-layer behavior at the discretion of system designers.
Furthermore, the two recommended practices specified in the current version of the
document are restricted to a subset of the network functionality generally supported by the
PHY and MAC layers of the OSI stack: one for single-hop contention-based access within a
star topology and one for single-hop scheduled access within a star topology. Hence, both
recommendations provide a mechanism for data packets to be exchanged between a network
coordinator or gateway and individual nodes on the wireless network, but they do not address
a mechanism for data packets to be exchanged between two non-coordinator nodes in the
network or for communication between any two nodes via intermediary nodes in a multi-hop
fashion. The evolution of this document is foreseen to propose additional recommended
practices for anticipated application profiles, such as recommended practices for peer-to-peer
communication in both mesh and star topologies and for multi-hop data transport in mesh
topologies.
The current recommendations also do not address a mechanism for exchanging data packets
between a node on the network and a device outside of the wireless network. It is assumed
that the network coordinator or gateway will somehow be able to communicate with the
backbone network of the spacecraft, but the mechanisms for that, which are typically
implemented at the Network (NWK) Layer of the stack, are beyond the scope of the current
document and are not discussed. Similarly, the recommendations do not discuss or provide
mechanisms for end-to-end acknowledgement or re-transmission of data packets sent
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RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
between user applications. The mechanisms for that behavior are typically implemented at
the Transport or the Application (APP) Layer of the stack and once again are beyond the
scope of the current document. While it is anticipated that future recommendations may
address some functionality at the NWK layer, such as routing of Internet Protocol (IP)
packets within the wireless network, it is not anticipated that protocol behavior above the
NWK layer (such as any APP-layer functionality) will be addressed by future
recommendations.
2.4 DIFFERENTIATING CONTENTION-BASED AND SCHEDULED CHANNEL
ACCESS
There are two predominant types of medium-access schemes currently utilized in wireless
sensor networks: random or contention-based access and scheduled access (see
reference [F2]). Contention-based schemes require no centralized control of network access
and are thus well suited for ad-hoc network architectures as well as other situations where it
is desirable to minimize network administration overhead and operational complexity. Nodes
are allowed to attempt channel access at arbitrary times in an ad-hoc fashion as dictated by
local data traffic flow and must therefore contend with one another for access in a fairly
random manner. The most common contention-based access technique utilized in sensor
networks is Carrier-Sense Multiple Access (CSMA) with Collision Avoidance (CA),
generally abbreviated as CSMA-CA or simply CSMA. In contrast, scheduled access schemes
require some type of (generally centralized) control mechanism for coordinating network
access for all nodes in the network in a synchronized fashion. Typically, this will be based on
predetermined or anticipated traffic flow so that bandwidth is available in a predictable
manner that precludes contention among the nodes. This approach increases network
administrative overhead and operational complexity but facilitates QoS guarantees and
deterministic network behavior. The most common scheduled access technique utilized in
sensor networks is Time-Division Multiple Access (TDMA).
In terms of application support, CSMA is best suited for situations where tight bounds on
packet latency and packet jitter are not required but nodes may sometimes require relatively
large amounts of available channel bandwidth for relatively short periods of time in a
relatively unpredictable manner. CSMA does not readily support deterministic network
behavior but does readily support bursty and aperiodic traffic flow. In contrast, TDMA is
well suited for applications requiring much tighter bounds on packet latency and jitter but for
which the traffic flow from the nodes is more uniform and predictable. TDMA readily
supports deterministic network behavior but is generally better suited for applications with
less bursty and more periodic traffic flow. In addition, interference avoidance schemes such
as frequency hopping are far more easily implemented in a scheduled TDMA MAC sublayer
than in a contention-based CSMA MAC sublayer. The same applies to maintaining
connectivity in a mesh network topology that supports multi-hop relay traffic with battery
powered nodes on a low duty cycle (long sleep period, short active period), although multi-
hop transport is beyond the scope of the current Recommended Practice.
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2.5 SECURITY PROVISIONING
Wireless networks suffer the maladies of both active tampering and passive eavesdropping
due to the inherent nature of wireless communications where access to the transmission
media is not a physical constraint as within wired communications. In addition, wireless
sensors have severely limited computational processing power and may have no available
onboard data storage. Because of the computational complexity of cryptographic algorithms,
coupled with the limited battery-based lifetime of a wireless sensor node, security
provisioning in these types of devices is a pragmatic engineering balance.
The cryptographic mechanism in this standard is based on symmetric-key cryptography and
uses keys that are provided by higher-layer processes; the mechanism assumes a secure
implementation of cryptographic operations and secure and authentic storage of keying
material (reference [1]). For the recommended practice contained in this document, the
PHY/MAC layer provides services that support data confidentiality, data integrity
(authenticity), and replay protection:
Table 2-1: PHY/MAC Security Service Provisioning
Security service Description
Data confidentiality Transmitted information is disclosed only to
parties for which it is intended
Data integrity Assurance of the source of transmitted
information (and, hereby, that information
was not modified in transit)
Replay protection Assurance that duplicate information is
detected
NOTE – Per annex B some of the required security architectural elements may be
implemented at higher layers (e.g., key management) in the OSI stack and are not
strictly defined, or implemented, at the PHY/MAC layer.
2.6 QUALITY OF SERVICE PROVISIONING
Both of the recommended practices prescribed in 3.2 provide support for implementing QoS
provisioning so that system designers can implement their QoS policies over the wireless
network.
In the 802.15.4 CSMA-CA operational mode, QoS primitive operations are achieved
utilizing Guaranteed Time Slots (GTS) as shown in figure 2-1. Briefly, the active portion of
the superframe is composed of a beaconing period, a Contention Access Period (CAP) and a
CCSDS 882.0-M-1 Page 2-4 May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
Contention Free Period (CFP); the slotted CSMA scheme is utilized during the CAP, and the
GTS scheme is utilized during the CFP period.

Beacon
Beacon
Active portion
Inactive portion
CAP CFP
GTS GTS
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
superframe duration
beacon interval
Figure 2-1: IEEE 802.15.4 Superframe
The GTS scheme enables bandwidth reservation between an 802.15.4 PAN coordinator and a
PAN device. Notably, more sophisticated QoS schemes that attempt to enforce either some
type of fairness for all nodes in the network and/or to handle nodes entering and leaving the
network are advanced functionality that is typically implemented at the higher Network
(NWK) Layer of the communications stack.
In the 802.15.4 scheduled medium-access operational mode, which is TDMA-based, the
available TDMA slots are analogous to CSMA GTS slots during the CFP. Integrated
communication stacks based on 802.15.4 (e.g., ZigBee, ISA100, 6LoWPAN, 802.15.4e—see
reference [F7]) all enable deployment-wide QoS at the NWK layer. (Refer to annex A for
additional QoS provisioning provided in the ISA100.11a recommendation.)

CCSDS 882.0-M-1 Page 2-5 May 2013
RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
3 RECOMMENDED PRACTICES FOR LOW DATA-RATE
WIRELESS COMMUNICATIONS FOR SPACECRAFT
MONITORING AND CONTROL
3.1 OVERVIEW
This section presents the recommended practices for spacecraft monitoring and control
applications using low data-rate wireless communication technologies. (See table C-2 for a
non-exhaustive set of example use-cases that may benefit from using low data-rate wireless
communications.)
As discussed in section 2, in order to ensure the most basic interoperability between low
data-rate wireless communication devices, the current recommendations are focused on
specification of functionality at the air interface PHY layer and the MAC sublayer of the OSI
model. Following this guideline, two different compliant systems would thus be able to share
the medium and potentially join the same wireless network.
3.2 RECOMMENDED PRACTICES
3.2.1 APPLICATIONS SUITED FOR SINGLE-HOP CONTENTION-BASED
COMMUNICATIONS
For spacecraft monitoring and control activities employing low data-rate contention-based
wireless communications in single-hop configurations, both the air interface PHY layer and
the MAC sublayer shall comply with the IEEE 802.15.4-2011 specification (reference [1]).
Single-hop contention-based communication networks and devices should utilize the 2.4
GHz frequency band. (See annex D for rationale pertaining to 2.4 GHz band preferences; see
reference [3] for Electromagnetic Interference (EMI) considerations of the 2.4 GHz
frequency band.)
3.2.2 APPLICATIONS SUITED FOR SINGLE-HOP SCHEDULED MEDIUM-
ACCESS COMMUNICATIONS
For spacecraft monitoring and control activities employing low data-rate communications
utilizing a scheduled medium-access scheme in a single-hop configuration, both the air
interface PHY layer and the MAC sublayer shall comply with the ISA100.11a-2011 PHY-
layer and MAC-sublayer specifications (reference [2]).
3.2.3 RESTRICTIONS/HAZARDS
When selecting a wireless technology for application in a spacecraft environment, the risks
associated with the selected radio frequency band, transmission power level, and physical
location should be taken into account for the following governing environmental factors:
a) Operation in explosive environments;
b) RF exposure levels in excess of governmental limits (see annex D);
c) Electromagnetic Compatibility (EMC).
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RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
ANNEX A
JUSTIFYING THE SCHEDULED MEDIUM ACCESS
RECOMMENDATION
(INFORMATIVE)
A1 BACKGROUND
From its introduction 2003, application of IEEE 802.15.4 to embedded sensing tasks has
been steadily increasing. Use has been largely limited to home and office automation,
however, since it has been found that 802.15.4 reliability suffers as the RF complexity of the
environment in which it is deployed increases. Specifically, industrial deployments of
802.15.4 are often observed to exhibit unacceptably low reliability and high latencies.
Amendments incorporated in the IEEE 802.15.4-2006 revision recommended, and even those
subsequently incorporated in the 802.15.4-2011 revision, have failed to address these
concerns adequately, leading to native IEEE 802.15.4’s being widely considered a poor
solution for process monitoring and control in harsh industrial environments.
This discrepancy is documented in the IEEE 802.15.4e-2012 amendment, which incorporates
a scheduled MAC layer very similar to the ISA100.11a MAC recommended in this Magenta
Book. In justifying the update to 802.15.4-2011 provided by the 802.15.4e amendment, the
IEEE states that “this amendment to IEEE Std 802.15.4-2011 specifies additional media
access control (MAC) behaviors and frame formats that allow IEEE 802.15.4 devices to
support a wide range of industrial and commercial applications that were not adequately
supported prior to the release of this amendment.”  It goes on to observe “industrial
applications (and some commercial applications) have critical requirements such as low
latency, robustness in the harsh industrial RF environment, and determinism that are not
adequately addressed by IEEE Std 802.15.4-2011” (reference [F7]).
Given that many spaceflight applications have constraints on reliability and latency similar to
those in industrial process control, it was determined that this Magenta Book required a
recommendation that rectifies many of the shortcomings in IEEE 802.15.4-2006 (and later,
802.15.4-2011) that the IEEE itself recognizes. Unfortunately, IEEE 802.14.4e-2012 is new
enough that there are not sufficient commercial parts available for testing to justify its
inclusion in the present edition of this Magenta book, although future editions may adopt it as
the scheduled MAC recommendation.
Instead, the ISA100.11a MAC, which along with the WirelessHART standard inspired the
IEEE 802.15.4e-2012 recommendation, is adopted here due to the availability of radios for
testing. Indeed, testing by the authors of this Magenta Book has confirmed the relative
robustness of ISA100.11a and the relative weakness of IEEE 802.15.4 in the presence of Wi-
Fi interference (reference [F8]). ISA100.11a is chosen over WirelessHART since it is
capable of supporting a greater variety of application layers and is in general more
customizable. (For a detailed comparison of the two, see reference [F9].)
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RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
A2 MECHANISMS FOR INCREASED ROBUSTNESS
ISA100.11a provides a number of mechanisms for increasing the overall quality of service.
As mentioned in 2.4, the scheduled ISA100.11a MAC provides greater determinism for
channel access. Time in an ISA100.11a network is divided into slots, and a time distribution
mechanism embedded in packet acknowledgements ensures that radios keep slot boundaries
synchronized with respect to neighboring radios to ensure coordinated transmission/reception
between communicating pairs.
A Network Manager overseeing operation of the ISA100.11a network allocates
communication opportunities to radios requesting bandwidth, thereby ensuring time diversity
within the ISA100.11a network. That is, an individual radio within the network will only
attempt to use the wireless medium in a time slot assigned to that radio for transmission. If
the attempt fails for any reason (e.g., excessive RF interference), the transmission will be
retried at the radio’s next scheduled opportunity. Furthermore, frequency diversity is added
by the Network Manager, assigning one of the up to 16 channels available under the 802.15.4
2.4 GHz DSSS PHY employed by ISA100.11a to the communication attempt. Should a
retransmission be required, the next scheduled attempt will be on a different channel, drawn
from a predetermined channel-hopping sequence. Time synchronization between radios
allows the Network Manager to configure the receiving radio to have its receiver tuned to the
channel of the transmitter for the scheduled transaction. ISA100.11a supports adaptive
blacklisting, so that channels on which communication attempts repeatedly fail can be
removed from sending and receiving radios’ channel hopping sequences. For multi-hop
topologies, spatial diversity is also added through the use of routing graphs with redundant
next-hop paths, although that is outside the scope of this Magenta Book’s current
recommendation for single-hop communication.
These diversity features, taken together, enhance the ability of ISA100.11a to coexist with
other RF systems that are acting as interferers. It should also be noted that, since ISA100.11a
uses the 2.4 GHz DSSS PHY specified in IEEE 802.15.4-2006, it inherits the benefits of the
Clear Channel Assessment (CCA) service used by the CSMA MAC of 802.15.4, which in
particular promotes non-interference of the ISA100.11a radios with other systems operating
in the same RF band.
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RECOMMENDED PRACTICE FOR LOW DATA-RATE WIRELESS COMMUNICATIONS
ANNEX B
SECURITY CONCERNS FOR WIRELESS SYSTEMS

(INFORMATIVE)
B1 INTRODUCTION
The 802.15.4 and ISA100.11a specifications recommended in this book describes RF
wireless PHY-layer and MAC-sublayer protocols for low-power and relatively low data-rate
networked communications. These specifications support a diverse application domain;
wireless applications for space operations can benefit from the security features provided in
these PHY-layer/MAC-sublayer protocol specifications.
Communications security attempts to ensure the
...