1、 Rec. ITU-R S.1709-1 1 RECOMMENDATION ITU-R S.1709-1 Technical characteristics of air interfaces for global broadband satellite systems (Question ITU-R 269/4) (2005-2007) Scope This Recommendation proposes air interface characteristics which can be used as guidance by designers of broadband satellit
2、e networks. The substance of the text is divided into four Annexes, the first being a generic description of the network architecture of broadband satellite networks. The remaining Annexes each contain a summary of existing air interface standards that have been approved by various standardization b
3、odies. Annex 2 contains a summary of TIA-1008-A dealing with Internet protocol (IP) over satellite (IPoS). Annex 3 contains a summary of the DVB-RCS standard as described in ETSI Document EN 301 790. Annex 4 contains a summary of the air interface specification for global broadband communications be
4、tween earth stations and regenerative satellites based on ETSI BSM/RSM-A. The ITU Radiocommunication Assembly, considering a) that satellite telecommunications technology has the potential to accelerate the availability of broadband communications both on a global and regional basis; b) that operati
5、onal experience with the deployment of broadband satellite networks has demonstrated the practicality and usefulness of these networks; c) that several different types of architectures are used in broadband satellite systems; d) that these varying uses have led to the development of various air inte
6、rface standards in order to allow seamless transportation of broadband signals over different networks, recommends 1 that when broadband radiocommunications are being designed based on the use of satellites, the generic satellite network architecture and protocol structures defined in Annex 1 may be
7、 used; 2 that when broadband radiocommunications are being provided between earth stations and geostationary satellites, the specifications contained in Annexes 2 to 4 may be used. 2 Rec. ITU-R S.1709-1 Annex 1 Generic network architecture for global broadband satellite systems 1 Introduction The in
8、herent characteristics of satellite communications, that is their wide-coverage, broadcast mode of operation and multicasting, make them capable of providing high-speed Internet connection and multimedia long-distance transmissions. There are many possible implementations of broadband by satellite,
9、however, certain fundamental features such as protocol stacks, satellite dependant and independent functions, user-access to the system and air interface are very similar. This Recommendation addresses three distinct standardization efforts as follows: Telecommunication Industry Association (TIA) IP
10、oS as summarized in Annex 2; European Telecommunication Standards Institute (ETSI) (2000) DVB, interactive channel for satellite distribution systems as summarized in Annex 3; Air interface specifications for global broadband communications between earth stations and regenerative satellites based on
11、 ETSI BSM/RSM-A as summarized in Annex 4. These three standards as summarized in Table 1 could be applied for high-speed Internet access services either for individual households or collective residential services. Satellite interconnectivity with the terrestrial networks in a seamless fashion is ve
12、ry crucial for the broadband satellite service success. The architectures described in the following sections would provide a guidance to the system designers and the evaluators with respect to the system design and deployment. This Annex describes a global broadband network scenario along with comm
13、on applications and services. In addition, the normal network topologies such as star and mesh are described. This Annex provides a basis for the remainder of the Recommendation describing the three standards development for broadband satellite networks. Appendix 1 to Annex 1 provides a list of refe
14、rences for all the specifications described in this Recommendation. TABLE 1 Comparison Table between ETSI EN 301 790 V.1.3.1, TIA-1008-A and ETSI RSM-A Item ETSI EN 301 790 TIA-1008-A ETSI RSM-A Network topology Star or mesh Star Star or mesh Modulation QPSK CE-OQPSK CE-OQPSK Outbound traffic access
15、 method DVB-S DVB-S High rate TDMA Outbound traffic data rate (Mbit/s) 1 to 45 1 to 45 100, 133.33, 400 Inbound traffic access format MF-TDMA MF-TDMA FDMA-TDMA Inbound traffic data rate No restriction 64 kbit/s, 128 kbit/s, 256 kbit/s, 512 kbit/s, 1 024 kbit/s, 2 048 kbit/s 128 kbit/s, 512 kbit/s, 2
16、 Mbit/s, 16 Mbit/s Protocols DVB/MPEG2 TS outbound, AP/AAL5/ATM inbound Multilayered protocol IETF IP Network Protocols Rec. ITU-R S.1709-1 3 2 Global network architecture Figure 1 describes a global broadband satellite network architecture consisting of the following scenarios: Access network: prov
17、iding services to end users. Distribution network: providing content distribution to the edge. Core network: providing trunking services. FIGURE 1 Global broadband satellite network scenarios 2.1 Services Various services being provided by such a network include: Point-to-point Multicast/broadcast C
18、ontent distribution. 2.2 Broadband applications The various broadband applications supported by satellite networks are: Entertainment Video-on-demand TV distribution Interactive games Music applications Streaming. Internet access High-speed Internet access Electronic messaging 4 Rec. ITU-R S.1709-1
19、Multimedia applications Distance learning Telemedicine. Business Videoconferencing Business-to-business Home security. Voice and data trunking IP-transport Voice-over-IP File transfers. 2.3 Topologies The network may use either a mesh or star topology as illustrated in Fig. 2: A star network topolog
20、y is defined by the star arrangement of links between the hub station (or Internet access point) and multiple remote stations. A remote station can only establish a direct link with the hub station and cannot establish a direct link to another remote station. A mesh network is defined by the mesh ar
21、rangement of links between the stations, where any station can link directly to any other station. The star topology can be considered as one special case of the mesh topology. NOTE 1 A star topology can be used to provide mesh connectivity by establishing an indirect link between remote stations vi
22、a the hub station. FIGURE 2 Star and mesh topology Rec. ITU-R S.1709-1 5 A global broadband satellite-system network may use either a non-regenerative or a regenerative satellite architecture: A non-regenerative architecture refers to a single architecture, commonly called a “bent-pipe architecture”
23、. This architecture does not terminate any layers of the air interface protocol stack in the satellite the satellite simply transfers the signals from the user links to the feeder links transparently. A regenerative architecture is the range of other architectures that provide additional functionali
24、ty in the satellite. In these architectures, the satellite functions terminate one or more layers of the air interface protocol stack in the satellite. 2.4 Services architecture Figure 3 illustrates the various services e.g. standard IP services, broadband satellite bearer services, and the underlyi
25、ng radio transmission bearer services. The broadband satellite for multimedia (BSM) working group of ETSI developed a broadband service architecture handling these three types of services. In order to separate the services that are common to all satellite systems from those that are specific to a gi
26、ven satellite technology, the service architecture defines a satellite-independent service access point (SI-SAP) as the interface between these upper and lower layers. This interface corresponds to the ends of the global broadband satellite system bearer services as shown in Fig. 3. FIGURE 3 Global
27、broadband satellite service architecture 6 Rec. ITU-R S.1709-1 2.5 Protocol architecture The global broadband satellite system identifies three groups of protocols: IETF IP network protocols; adapted global broadband satellite system protocols that are satellite system independent; and satellite tec
28、hnology dependent protocols. The global broadband satellite system protocol architecture defines the SI-SAP interface that lies between the IP network layer and the lower layers. Immediately above and below the interface, the architecture defines two new adaptation layers that contain global broadba
29、nd satellite system functions associated with the interface as shown in Fig. 4. Figure 4 shows how the global broadband satellite-system architecture supports multiple alternative families of satellite dependent lower layer protocols. Each family corresponds to a different satellite technology, incl
30、uding both transparent and regenerative satellite and both mesh and star topologies. Each of the families of satellite dependent lower layers can support these generic SI-SAP functions in different ways. Each family defines a satellite dependent adaptation function (SDAF) that is used to provide the
31、 mapping to and from the SI-SAP interface. FIGURE 4 Global broadband satellite-system protocol architecture The concept behind the architecture is a clear separation between functions that are applicable to all satellite systems (satellite independent (SI) and the functions that are specific to a sa
32、tellite technology (satellite dependent (SD) and hence define a satellite independent interface that can be used to provide essentially the same services across all implementations of this architecture. While this should be true for all interworking aspects from layer 2 (i.e. bridging), layer 3 and
33、above, the primary use of this architecture is expected to be the definition of interworking functions for the IP suite of protocols. Rec. ITU-R S.1709-1 7 2.6 IP interworking In the global Internet, a satellite IP-subnetwork should be treated just like any other IP-subnetwork since only a small num
34、ber of hosts will be directly connected to the satellite subnetwork. Consequently, the main interworking guideline for IP services over a satellite subnetwork is that the IP layer protocols on the non-satellite side shall remain unchanged. Any changes to the protocols that are needed for operation o
35、ver a satellite should be provided by a set of IP interworking functions that can be located at the edges of the satellite subnetwork as illustrated in Fig. 5. The SI-SAP architecture then provides a framework for developing a set of common IP interworking standards to ensure transparent interoperab
36、ility between any satellite subnetwork and a non-satellite (e.g. terrestrial) IP-based subnetwork. FIGURE 5 IP interworking Appendix 1 to Annex 1 List of references These reference links describe the characteristics of standard TIA-1008-A as summarized in Annex 2. Document No. Version Status Issued
37、date Location TIA TIA-1008-A Published October 2003 http:/www.itu.int/md/R03-WP6S-C-0191/en 8 Rec. ITU-R S.1709-1 These reference links describe the characteristics of the DVB-RCS standard as summarized in Annex 3 Document No. Version Status Issued date Location ETSI EN 301 790 V1.3.1 Published Marc
38、h 2003 http:/webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=15626 These reference links describe the characteristics of the ETSI-SES/BSM/RSM-A specification as summarized in Annex 4. Document No. Version Status Issued date Location ETSI ETSI TS 102-188-1 V1.1.2 Published July 2004 http:/weba
39、pp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=20888 ETSI ETSI TS 102-188-2 V1.1.2 Published July 2004 http:/webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=20892 ETSI ETSI TS 102-188-3 V1.1.2 Published July 2004 http:/webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=20893 ETSI ETSI
40、 TS 102-188-4 V1.1.2 Published July 2004 http:/webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=20895 ETSI ETSI TS 102-188-5 V1.1.2 Published July 2004 http:/webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=20896 Appendix 2 to Annex 1 Abbreviations For the purposes of this Recommendation
41、, the following abbreviations apply: ACF Access control field ACK-RET Ack-return BoD Bandwidth on demand BPSK Binary phase shift keying BSM Broadband satellite multimedia CoS Class of service CR Constant rate CRC Cyclic redundancy check CRWB Constant rate with burst DLL Data link layer DVB Digital v
42、ideo broadcast Rec. ITU-R S.1709-1 9 EDU Extended data unit FDMA Frequency division multiple access FEC Forward error correction GEO Geosynchronous Earth orbit HPB High priority burst HVUL High volume up-link IP Internet protocol kbit/s Kilobits per second (thousands of bits per second) LAN Local ar
43、ea network LVLL Low volume low latency M however, there are physical requirements involving radio-frequency parameters that are specific for each particular frequency band. The present version of the IPoS physical (PHY) layer interface assumes IPoS services using 14/10-11 GHz satellites with spectru
44、m that is designated for fixed-satellite service (FSS). 3. User segment: In general, the IPoS user segment consists of thousands of user terminals, each of them capable of providing broadband, IP communications to a remote site. User terminals are also referred to in this standard as remote terminal
45、s. The remote terminals support the user hosts, or personal computers (PCs), running the applications. This support of user PCs could be broadly categorized as: Single access point: where the host and the remote terminal are connected, e.g. through a universal serial bus (USB) interface. 12 Rec. ITU
46、-R S.1709-1 Customer premises LAN: where the remote terminals provide access to a multiplicity of PCs. Customer LANs are considered external to the IPoS system. Figure 6 illustrates the highest-level components in the IPoS architecture and identifies the major internal and external interfaces in the
47、 IPoS system. FIGURE 6 IPoS system architecture 2.2 Network interfaces The main interfaces in the IPoS system are: Terminal LAN interface: This is the interface between the user hosts computers, or PCs, and the remote terminals. The terminal LAN interface uses an Ethernet protocol that is not part o
48、f this standard. IPoS satellite interface: This is the interface where remote terminals and the hub exchange user, control, and management information. The IPoS satellite interface, or air interface, is the main focus of this standard. Hub terrestrial interface: This is the interface between the hub
49、 and the backbone connecting the hub to the external packet data networks, public Internet, or private data networks. The hub terrestrial interface uses IP protocols that are not part of this standard. The IPoS satellite interface distinguishes between the two transmissions directions: The outroute direction from the IPoS hub to the user terminals is broadcast over the entire bandwidth allocated to the outroute carrier. Because the IPoS outroute can multiplex a multiplicity of transmissions, it s
