1、 ETSI TS 102 188-7 V1.1.2 (2004-07)Technical Specification Satellite Earth Stations and Systems (SES);Regenerative Satellite Mesh - A (RSM-A) air interface;Physical layer specification;Part 7: SynchronizationETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 2 Reference RTS/SES-00209-7 Keywords air interface,
2、broadband, IP, multimedia, satellite ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice Individual
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6、oing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2004. All rights reserved. DECTTM, PLUGTESTSTM and UMTSTM are Trade Marks of ETSI registered for the benefit of its Members. TIPHONTMand the TIPHON logo are Trade Marks currently being registered by
7、 ETSI for the benefit of its Members. 3GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. ETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 3 Contents Intellectual Property Rights4 Foreword.4 1 Scope 5 2 References 5 3 Definitions and abbreviations
8、.5 3.1 Definitions5 3.2 Abbreviations .5 4 General description of synchronization system6 4.1 System timing structure8 4.2 General requirement .8 4.2.1 Timing and frequency reference point8 4.2.2 ST requirement .8 4.2.3 Network requirement 8 4.2.4 Measurement conditions .8 5 Timing synchronization9
9、5.1 Introduction 9 5.2 Frequency accuracy and stability .9 5.2.1 ST Frequency accuracy and stability 9 5.3 Timing error .9 5.3.1 Initial ST timing error.9 5.3.2 ST Timing error 9 5.4 Time of Day information9 5.4.1 ToD definition 9 5.4.2 ToD format .10 5.4.3 UTC time 11 5.5 Beacon transmission (Satel
10、lite to ST direction) .11 5.5.1 Superframe11 5.5.2 Frame alignment .11 5.5.3 Beacon burst structure 12 5.5.3.1 Beam settling bit pattern .13 5.5.3.2 Unique Word bit pattern14 5.5.3.3 PN sequence bit pattern.14 5.6 Early/Late timing measurement field .15 5.7 Initial timing acquisition 15 5.8 Timing s
11、ynchronization maintenance.15 6 Frequency synchronization.16 6.1 Calculate the Initial Doppler value.16 Annex A (normative): Timing calculations17 A.1 General description.17 A.1.1 Calculation of Path Length.17 A.1.2 GPS accuracy .17 A.2 Calculate the timing offset .17 Annex B (informative): Bibliogr
12、aphy.18 History 19 ETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 4 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members
13、, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/webapp.etsi.org/IPR/home.asp
14、). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the pres
15、ent document. Foreword This Technical Specification (TS) has been produced by ETSI Technical Committee Satellite Earth Stations and Systems (SES). The present document is part 7 of a multi-part deliverable covering the BSM Regenerative Satellite Mesh - A (RSM-A) air interface; Physical layer specifi
16、cation, as identified below: Part 1: “General description“; Part 2: “Frame structure“; Part 3: “Channel coding“; Part 4: “Modulation“; Part 5: “Radio transmission and reception“; Part 6: “Radio link control“; Part 7: “Synchronization“. ETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 5 1 Scope The present do
17、cument presents the requirements for synchronizing timing and frequency between the ST and the satellite network within the TC-SES BSM Regenerative Satellite Mesh - A (RSM-A) air interface family. 2 References The following documents contain provisions which, through reference in this text, constitu
18、te provisions of the present document. References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For a specific reference, subsequent revisions do not apply. For a non-specific reference, the latest version applies. Referenced documen
19、ts which are not found to be publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. 1 ETSI TS 102 189-2: “Satellite Earth Stations and Systems (SES); Regenerative Satellite Mesh - A (RSM-A) air interface; MAC/SLC layer specification; Part 2: MAC layer“. 2 IETF
20、 RFC 1305: “Network Time Protocol (Version 3) Specification, Implementation and Analysis“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: Network Operations Control Centre (NOCC): centre that controls the access of
21、 the satellite terminal to an IP network and also provides element management functions and control of the address resolution and resource management functionality satellite payload: part of the satellite that provides air interface functions NOTE: The satellite payload operates as a packet switch t
22、hat provides direct unicast and multicast communication between STs at the link layer. Satellite Terminal (ST): terminal installed in the user premises terrestrial host: entity on which application level programs are running NOTE: It may be connected directly to the Satellite Terminal or through one
23、 or more networks. 3.2 Abbreviations For the purposes of the present document, the following abbreviations apply: AWGN Additive White Gaussian Noise BPSK Binary Phase Shift Keying ECEF Earth Centred Earth Fixed IP Internet Protocol kbps kilo bits per second (thousands of bits per second) LHCP Left H
24、and Circular Polarization ETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 6 LLA Latitude, Longitude and Altitude LSB Least Significant Bit MIP Management Information Packet MMI Man Machine Interface NOCC Network Operations Control Centre PHY PHYsical PN Pseudo Noise PTP Point-to-PointQPSK Quaternary Phase S
25、hift Keying RHCP Right Hand Circular Polarization RSM Regenerative Satellite Mesh SLC Satellite Link Control ST Satellite Terminal TDMA Time Division Multiple Access TIP Transmission Information Packet ToD Time of Day ULPC UpLink Power Control UTC Universal Coordinated Time UW Unique Word 4 General
26、description of synchronization system BSM RSM-A is a multi-spot beam, multicarrier, synchronous system where the timing and frequency on the satellite serve as the reference to synchronize the TDMA transmissions for the STs, and other network elements. The satellite includes a packet switch designed
27、 to provide single-hop, point to point packet routing between downlink cells. The functions of the physical layer are different for the uplink and downlink. The major functions are illustrated in figure 4. The present document describes the synchronization functions - this group of functions is high
28、lighted in figure 4. ETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 7 UPLINK DOWNLINK Part 3:Channel coding Part 2:Frame structure Part 4:Modulation Part 5:Radio transmission and reception Part 7:Synchronization Block interleaving Inner coding (convolutional) Downlink burst building Downlink modulation (QP
29、SK) ST receiver Scrambling Assemble packets into code blocks Outer coding (Reed - Solomon) No interleaving Inner coding (hamming)Uplink burst building Uplink modulation(OQPSK) Part6:Radio link controlScrambling Assemble packets into code blocks Outer coding (Reed - Solomon) Timing and frequency cont
30、rol ST transmitter Figure 4: Physical layer functions The timing synchronization requirements are described in clause 5, and the frequency synchronization requirements are described in clause 6. Synchronization in the RSM-A system is composed of three major tasks: timing synchronization; frequency s
31、ynchronization; frame synchronization; A master oscillator onboard the RSM-A spacecraft is the primary reference for all synchronization processes. The fundamental goal of synchronization is to have all STs operate such that all bursts arrive at the satellite synchronized in timing and frequency. ET
32、SI ETSI TS 102 188-7 V1.1.2 (2004-07) 8 4.1 System timing structure The RSM-A satellite system is a TDMA system. Timing configuration in the system is composed of superframe, frame, timeslot, symbol and bit. One superframe equals to 768 ms, and is divided into eight uplink frames or 256 downlink fra
33、mes. The downlink frame counter is called the Time of Day (ToD) counter. Each uplink frame has 32 timeslots. The uplink frame duration is 96 ms, one timeslot duration is 3 ms. Each symbol corresponds to 2 bits. The complete uplink and downlink frame structure is defined in BSM RSM-A Physical Layer S
34、pecification, TS 102 188-2. A superframe always starts from the first time slot in a frame that meets ToD mod 256 = 0. An Uplink frame always starts with time slot 0 when ToD mod 32 = 0. 4.2 General requirement 4.2.1 Timing and frequency reference point The satellite is selected to be the reference
35、point for both timing and frequency. 4.2.2 ST requirement The ST timing and frequency requirements are: Both transmitter and receiver timing shall be derived from the same timebase. Both transmitter and receiver frequency shall be derived from the same frequency source. The ST shall use the same sou
36、rce for both RF frequency generation and the timebase generator. All return link signals (control and user data) transmitted from the STs shall achieve frame/timeslot alignment on the satellite timing reference point, i.e. input of satellite antenna. In various operation modes, synchronization shall
37、 be maintained under the worst case timing and frequency drift rate due to ST-satellite relative motion and ST master oscillator stability. The ST oscillator short-term stability shall maintain all timing offset, frequency offset and symbol rate requirement specified in BSM RSM-A physical layer spec
38、ification, TS 102 188-5. 4.2.3 Network requirement The Network timing and frequency requirements are: The network should make multiple rate and volume timeslot assignments on the same uplink frequency or with the same carrier designator (see BSM RSM-A physical layer specification, TS 102 188-5) as f
39、ar as possible. When assigning timeslots on different carrier designators the network shall provide at least 3 ms guard time for the ST to switch between the two different transmit frequencies. An ST may ignore assignments which it cannot use. At ST initialization, the network shall be able to estim
40、ate the slotted aloha signal arrival to the accuracy better than 15 Hz 1-sigma in frequency, 2,6 s 1-sigma in timing, under the condition of AWGN channel. 4.2.4 Measurement conditions In the present document, all timing and frequency related parameters are defined under the condition of AWGN channel
41、, when the Beacon is received at a C/No = 78 dB-Hz minimum. Unless specified otherwise, all timing and frequency related parameters are defined as 1-sigma value. ETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 9 5 Timing synchronization 5.1 Introduction The BSM RSM-A synchronization function is to align sat
42、ellite and ST frequencies and timing to allow uplink and downlink communications. The Satellite is in geosynchronous orbit with a very small inclination; however, there are still range changes that give rise to frequency offsets (Doppler) and a varying time delay that would put signals outside the r
43、equired limit if they were not corrected. Satellite and ST receivers have a dynamic but limited capability to acquire and demodulate the signal within a single burst in the presence of time and frequency errors. Two key elements are implemented to provide the necessary accuracy. First, a full covera
44、ge synchronization beacon signal is transmitted from the satellite. It contains frequency and time references to allow the STs to synchronize to the satellite. Propagation effects and receiver noise corrupt the transfer. Second, the Satellite ephemeris is disseminated to the STs so that they may eac
45、h independently compute their range to the satellite and the Doppler frequency offsets. The ST uplink timing is refined and tracked by using early/late replies from the satellite. 5.2 Frequency accuracy and stability The satellite reference consists of a reference oscillator and a reference timing s
46、ection. All transmitted uplink signal frequencies and clock rates as well as all transmitted downlink signal frequencies and clock rates, including PTP, shaped beams, and beacons are derived from the same source. 5.2.1 ST Frequency accuracy and stability The ST shall modify its transmitter frequency
47、 to compensate for Doppler variations of up to 300 Hz referred to the nominal uplink transmit frequency. 5.3 Timing error 5.3.1 Initial ST timing error At installation, the ST shall have a mechanism whereby the uplink bursts are timed to arrive within 4 s relative to the transmitted downlink LHCP be
48、acon superframe at the satellite. In order to achieve this accuracy, an ST shall have a mechanism to know its position with an accuracy of 1 000 m. See also, BSM RSM-A, Physical Layer Specifications, TS 102 188-6. 5.3.2 ST Timing error The maximum ST timing error for all uplink transmissions relativ
49、e to the ideal uplink timing, shall not exceed 2,6 s, except during installation. 5.4 Time of Day information 5.4.1 ToD definition The Time of Day (ToD) counter on board the satellite is a master timing reference for the BSM RSM-A system. The ToD counter on board the satellite shall be initialized such that all-zeroes correspond to January 1, 2000 at 00:00:00 UTC. The ToD counter then continues to increment. ETSI ETSI TS 102 188-7 V1.1.2 (2004-07) 100 1 23 4 56 7 PAY LOAD STPAYLOAD SUPERFRAME N PAYLOAD SUPERFRAME N+1 ST
