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2010-10-26

Network Design and Engineering Guide

21

General Carrier Design

Data and Voice Networking Overview

On the receiving station the whole procedure is reversed:

-

Demodulation and decoding,

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Reassembly of fragments into SLL frames,

-

Replacing of SLL by Ethernet headers (for IP packets),

-

Forwarding of Ethernet (or FR frames) over the Ethernet (or serial) port.

Voice connections

The requirement for data traffic is generally specified in terms of a required data rate. For voice
traffic usually the required number of (bidirectional) voice connections is specified. To translate
that into a data rate requirement it is necessary to know the data rate per voice call. This rate
depends on the codec rate of the used voice codec (typically in the range 6-64 kbps) and the
additional overhead due to the applied network protocol. In

Sky

WAN

®

networks two different

network technologies are used:

-

Voice over IP using IP/UDP/RTP encapsulation of the voice payload (VoIP).

-

Voice over

Sky

WAN

®

FAD using the Frame Relay functionality (VoFR).

The data networking overhead for both options is quite different, leading to a higher bandwidth
consumption for VoIP calls compared to VoFR calls: The VoIP overhead (IP/UDP/RTP) sum-
marizes to 40 Bytes whereas the VoFR overhead is 8 Bytes.

Since the typical voice payload per packet is in the range of 10-40 Byte, the VoIP overhead
represents a large fraction of the required data rate. This may be reduced by the Robust Head-
er Compression (ROHC) technique. A detailed description of this procedure will be given in a
subsequent section of this Guide.

Figure 2-3

Voice over SkyWAN

®

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Содержание SKYWAN IDU 1070

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Страница 3: ...Engineering Guide SkyWAN Indoor Unit IDU 7000 Software Rel 7 11 IDU 2570 Software Rel 7 11 IDU 2070 Software Rel 7 11 Document Number OM2044E_9400711 Document Revision B Revision Date 2010 10 26 IDU 1070 Series IDU 1070 Software Rel 1 11 ...

Страница 4: ...ND SatCom Product GmbH hereafter referred to as ND SatCom which reserves all rights This document or parts of it may not be reproduced duplicated or distributed to third parties Nor may their content be disclosed to third parties without the express written approval of ND SatCom Product GmbH Misuse will be subject to legal action and fines All rights to pat ents and utility models are reserved ...

Страница 5: ... 2 Action objective after finish ing action steps Action Items are used to direct the user to execute the steps in the giv en order for a successful completion of the action fulfilled precondition for successful action comple tion Step 1 perform described action 1 Step 2 perform described action 2 Action objective reached string word number in code formatting Type this word number or string as inp...

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Страница 7: ...e Networking Overview 20 Voice connections 21 Voice Codecs 22 2 3 Essential SkyWAN Satellite Link Layer Features 23 2 3 1 SkyWAN Network Topologies 23 Reception Modes 24 2 3 2 Master and Slave Functionality 25 Control Communication Reference and Request Bursts 25 Active and Backup Master Role 26 2 3 3 SkyWAN MF TDMA functionality 27 TDMA Frame 27 Transmit and Receive Carriers 28 Data Slot Time Fac...

Страница 8: ...al Data Input 57 2 6 1 1 Parameter Summary 58 2 6 2 Section Data Input per Frequency Channel 59 2 6 2 1 Parameter Summary 60 2 6 3 Area General Data Output 62 2 6 3 1 Parameter Summary 62 2 6 4 Area Data output per frequency channel 63 2 6 4 1 Parameter Summary 65 2 6 5 Exporting and Importing TDMA Calculator Values 66 2 7 From Capacity Estimation to TDMA Structure 67 One Carrier Solution 68 Adjus...

Страница 9: ...ata 88 Specify Network Data 88 Output Back Off 89 Stations with 2 Demodulator Boards 90 3 5 4 Tx Amplifier Worksheet 91 3 5 5 Summary Worksheet 92 Input 92 Output 93 Optional Link Filter for Complex Topologies 95 3 5 6 Required Settings for MRB DUB Networks 95 Transponder Data 96 Hub Stations 97 UpLink Area 1 ULA1 97 UpLink Area 2 ULA2 98 Carrier Topology 98 Link Calculations 99 3 6 Link Budget Ex...

Страница 10: ... 4 2 9 Robust Header Compression 122 4 2 10 Transmission Control Protocol Acceleration TCP A 123 4 3 SkyWAN Frame Relay Networking Features 125 4 3 1 Serial port properties 125 4 3 2 Basic Frame Relay Services 126 4 3 3 FR Communication Services and Quality of Service 127 4 3 4 SkyWAN FAD Service 128 FAD Class 7 traffic 128 4 3 5 Traffic Shaping and Congestion Management 128 Realtime Service for I...

Страница 11: ... between Modulation Coding and Carrier PEB 79 Table 3 4 Output Back Off SSPA 90 Table 3 5 Scenarion 1 2 Carrier Solution Requirements 101 Table 3 6 Scenario 1 Carrier Coding and Bandwidth 102 Table 3 7 Scenario 1 Summarized Power Requirements 102 Table 3 8 Scenario 2 Carrier Coding and Bandwidth 104 Table 3 9 Scenario 2 Summarized Power Requirements 104 Table 3 10 Scenario 2 Optimized Carrier Codi...

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Страница 13: ...Slot Assignment with Ranging Subframe 34 Figure 2 18 Slot Assignment Differences 35 Figure 2 19 TDMA Structure of Throughput Example 36 Figure 2 20 Throughput Scenario 1 37 Figure 2 21 Throughput Scenario 2 38 Figure 2 22 Throughput Scenario 3 39 Figure 2 23 Throughput Scenario 4 40 Figure 2 24 Traffic Estimation Scenario IP Traffic 42 Figure 2 25 Traffic Estimation Scenario Fame RelayTraffic 43 F...

Страница 14: ...ions 83 Figure 3 10 Uplink Considerations 84 Figure 3 11 Link Budget Tool Satellite Data Worksheet s 86 Figure 3 12 Link Budget Tool Antenna Data Worksheet s 87 Figure 3 13 Link Budget Tool C Band Antenna Data 87 Figure 3 14 Link Budget Tool Station Worksheet 88 Figure 3 15 Link Budget Tool Define Network 89 Figure 3 16 Link Budget Tool Station with 2 Demodulators 90 Figure 3 17 Link Budget Tool T...

Страница 15: ...ocol Stack IDU 7000 series 109 Figure 4 2 SkyWAN IP Protocol Stack IDU 1070 110 Figure 4 3 SkyWAN Meshed IP Data and Management Network 111 Figure 4 4 SkyWAN Hybrid IP Data and Management Network 112 Figure 4 5 Static Routing in a Star Network 113 Figure 4 6 OSPF Cost Metric 116 Figure 4 7 Mapping of Forwarding Behaviours to Transmit Queues 119 Figure 4 8 RoHC Feature Overview 123 Figure 4 9 TCP A...

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Страница 17: ...ineered for customer premisses Figure 1 1 Overview VSAT Station 1 2 Manual Content This SkyWAN Network Design and Engineering Guide provides information about how to de sign and engineer a SkyWAN Satellite Network based on the SkyWAN IDU modem series Some typical network design scenarios will be discussed starting from customer traffic require ments an optimized SkyWAN Carrier and Outdoor Unit Des...

Страница 18: ...res A detailed description of the SkyWAN support of Data Networking Protocols TCP IP and Frame Relay will be given Implication for typical applications and services will be dis cussed Information for installation line up network commissioning and system overview is covered in the SkyWAN manuals suite refer to chapter 1 5 1 2 1 Who should read this document This document is intended for engineers d...

Страница 19: ...on via Frame Relay and or IP GSM backhaul solutions SNMP based network management system L Band transmit and receive interface between indoor unit IDU and outdoor unit ODU SkyWAN Technology offers the following advantages over competing satellite communication technologies Flexibility By allowing meshed star and hybrid topologies SkyWAN networks can be ideally adapted to diverse customer requireme...

Страница 20: ...tions a new design phase is required Customer Input which is required as a starting point for the design typically consists of the fol lowing information Description of applications and utilisation scenarios Descripton of the customer network environment Satellite transponder data Station locations General SkyWAN requirements Specific requirements for IP based applications Specific requirements fo...

Страница 21: ...n effi cient setup of configuration to install and commission a SkyWAN IDU station SkyWAN IDU 7000 1070 Series Station Com missioning Manual Describes how to assemble in stall and commission a Sky WAN IDU to transfer data over a SkyWAN Satellite Network After initial configuration the sta tion is able to join the SkyWAN Satellite Network and get in con tact with the active master sta tion to setup...

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Страница 23: ... help of the ND SatCom TDMA Calculator tool Consider the resulting effects of the design approach to network efficiency network behavior and future expansions The original plain requirements refer to section A1 in figure 2 1 represent the customer input In general such requirements have to be adapted in order to make them suitable as input for the satellite communication design The first task in s...

Страница 24: ...e ethernet port interface 1 SkyWAN supports the Internet Protocol IP routing functionality On the serial ports 2 5 interfaces 2 5 the Frame Relay FR switch ing functionality is supported a Both types of data packet protocols are transported over the satellite link layer interfaces mod ulator port Tx Out and demodulator port s Rx In using an efficient proprietary Satellite Link Layer SLL encapsulat...

Страница 25: ...e of the used voice codec typically in the range 6 64 kbps and the additional overhead due to the applied network protocol In SkyWAN networks two different network technologies are used Voice over IP using IP UDP RTP encapsulation of the voice payload VoIP Voice over SkyWAN FAD using the Frame Relay functionality VoFR The data networking overhead for both options is quite different leading to a hi...

Страница 26: ...le 2 1 IP Voice Call Data Rates Table 2 2 Frame Relay Voice Call Data Rates Codec Codec Bit Rate bps Voice Payload byte Bit Rate Ethernet bps IP Bit Rate w o RoHC bps IP Bit Rate incl SLL encaps bps RoHC Bit Rate bps RoHC Bit Rate incl SLL encaps bps G 711 64 000 160 87 200 80 000 83 200 65 600 68 800 G 722 32 000 80 55 200 48 000 51 200 33 600 36 800 G 723 6 300 24 21 525 16 773 18 885 7 269 9 38...

Страница 27: ...ybrid topologies In a hy brid topology a part of the network may be fully meshed while some stations may only have star connectivity Or a multi star topology may be configured where the star terminals have connec tivity to multiple hub stations The optimal choice of topologies depends on the required network connectivity A network where data and voice connections can go from any to any station are...

Страница 28: ...esented in the figure would need an RDR license whereas the star terminals could run with the default Limited Data Re ception LDR license The LDR license would still be sufficient if the star terminals have to communicate with two hub stations i The restriction imposed by the LDR mode does not apply to node manage ment via IP based protocols SNMP FTP Telnet It is therefore possible to manage the s...

Страница 29: ...generator FPG board Satellite link requirement The master station must be able to reach each other station in the network over a satellite link with sufficient quality In a star or hybrid network this means that only peer or hub stations may perform the master role RDR license is required for a master station Control Communication Reference and Request Bursts The following figure 2 6 presents an o...

Страница 30: ...mmended to configure two stations to be potential master stations Both sta tions have to fulfil the master station requirements mentioned before The station which enters the network first will become active master the other station backup master If the backup mas ter detects an outage of the active master it will take over the master role within 2 seconds This ensures a seamless transition which d...

Страница 31: ...arrier channel 1 The TDMA frame starts with a time slot furthermore notated as slot which is allocated to the active mas ter to transmit the reference burst The following slot is assigned to slave stations for transmis sion of their request bursts The rest of the TDMA frame consists of time slots for user traffic data bursts which are allocated on demand to various stations indicated by color in t...

Страница 32: ...onfiguration and are referred to as Home Channel One and Home Channel Two SkyWAN stations can transmit data on any active carrier in the network frequency or carrier hopping By configuration the possible transmit carriers can be allocated restricted for each station A TDMA frame plan for a SkyWAN network with 8 carriers is displayed in figure 2 9 In this example carrier 1 and 2 carry a reference b...

Страница 33: ...Request capacity on the home channel s of the receiving station if it is not already allocat ed Use the allocated time slot to transfer the data to the destination Data Slot Time Factors Base time slot durations are identical for every carrier used in the network That does not mean however that the payload data is identical because symbol rate modulation and coding may be configured differently on...

Страница 34: ...eeded for the request bursts 2 3 4 Downlink and Uplink Populations SkyWAN stations within a network can be grouped according to the carrier on which they re ceive the reference burst from the master and on the carrier on which they transmit request bursts to the master Downlink Population N Set of all stations which receive the reference burst on carrier number N i e all stations with Home Channel...

Страница 35: ...on carrier 1 only Symbolrate mod ulation and coding may be set differently on each carrier A graphical representation of the frame structure has been given in the section MF TDMA Functionality refer to figure 2 9 MRB DUB Mode For a network with N downlink populations carrier 1 and 3 N 1 carry a reference burst There is no reference burst on carrier 2 The number of downlink populations can range fr...

Страница 36: ...er 2 for ranging and request bursts If only one uplink population exists in the network carrier 2 will not be defined The following restrictions apply Only one master station is possible no backup master functionality Pure star topology with the master station serving as a hub No satellite link between slave stations If two uplink populations are used carrier 1 and 2 must have the same symbol rate...

Страница 37: ...rovides transmit queues With these queues data to be send via satellite is treated differently regarding priority measures 1 Highest priority Real Time RT user data 2 Less priority Control data internal station messaging and network management data 3 Lowest priority Non Real Time NRT user data The queueing principle is shown in figure 2 15 The differentiation is more precise and will be shown in m...

Страница 38: ...gned for this purpose If there are no unregistered stations in the network ranging slots can be allocated as dynamic data slots The size of the ranging section depends on the timeslot duration typically it is in the range of 1 5 base slots Figure 2 17 Slot Assignment with Ranging Subframe Stream Slots Stream Slots are triggered from data stored in the Real Time Transmit Queues Usage for a real tim...

Страница 39: ...ion This makes sense if one wants to avoid the situation that high priority real time traffic is occupying 100 of the available slots on a carrier thus disrupting non real time application for an indefinite time The system limitation for the number of stream slots is equal to the number of data slots minus one because one time slot is needed for potential key exchange for link encryption on carrie...

Страница 40: ...ng slots from the common pool if its private pool is already exhausted Oversubscription with guaranteed throughput definitions is not allowed That means that for every carrier the sum of guaranteed slots for all stations and the common streaming slot pool must be smaller or equal to the number of data slots on this carrier The master is free to allo cate any unrequested data slot as dynamic slot t...

Страница 41: ...kyWAN FAD real time service should be ac tive between the stations Figure 2 20 Throughput Scenario 1 Effect Due to the defined guarantee for both stations the 6 dynamic slots needed for the PC applica tion will always be available irrespective of the general congestion state of the network For the voice calls each station would need 3 streaming slots As long as there are enough free slots availabl...

Страница 42: ...s used for the PC application 10 out of 12 available stream slots are already consumed by this application If there are in addition two parallel voice calls between IDU1 and IDU2 all available stream slots would be allocated Now any additional stream request would be blocked even if there are still unrequested slots outside the common stream pool In this scenario the current traffic is not guarant...

Страница 43: ...ecause the required 5 slots for each station are still available in the private pool If how ever an additional voice call is set up between the stations the additional streaming slot again must be taken out of the private pool leaving only four slots for other services Note that real time services have always priority over non real time services As long as the network is not congested the PC appli...

Страница 44: ...ny additional streaming slot request from these stations would be rejected by the master even if there are still available slots in the common streaming pool Other stations could use this capacity for real time services but IDU1 and IDU2 are limited to their private pools concerning real time bandwidth Additional non real time services however might still be possible for these stations if there ar...

Страница 45: ...traffic IP or Frame Relay Voice traffic served by analog or digital SkyWAN FAD interfaces or VoIP systems For the purpose of traffic estimation it makes no difference if the traffic is based on the IP or Frame Relay functionality Estimations for non real time and real time traffic however have to be done in a different way Non real time traffic for example file downloads are flexible concerning th...

Страница 46: ... consisting of 50 stations Four different station groups station types are defined head offices big sites medium sites and small sites In figure 2 24 the non real time traffic flow between stations of specific types is sketched Keep in mind that the numbers here do not represent maximum but committed data rates for individual flows For example a small site will typically be able to send more non r...

Страница 47: ...ample account for only a small fraction of the network traffic they can be neglected in the estimation of the network traffic The next step is to summarize the traffic requirements to derive the user traffic capacity for each station of a specific type To sum up the capacity needed by one station on its receive carrier Home Channel we consider all traffic flows to a specific station in receive dir...

Страница 48: ...elds in this spreadsheet are indicated by a grey background The following picture presents a work sheet filled with data from the example presented in this section Figure 2 26 Traffic Calculation Example Capacity Worksheet The main results in this worksheet are Network traffic requirement per traffic type voice real time FR non real time IP non real time Total network traffic requirement Voice tra...

Страница 49: ... real time capacity for the type 4 stations not to individual stations but to the whole network as it is displayed in the following picture Figure 2 27 Per Network Traffic Erlang B Calculation Worksheet The second work sheet includes formulas for an estimation of required voice circuits using the Erlang B distribution This statistical method allows the calculation of the blocking probability i e r...

Страница 50: ...out header compression are already predefined in the sheet If an other codec should be used the data rate for a Custom Codec may be defined in the lookup table Note that the data rate must include the network layer overhead up to the IP or Frame Relay level The estimation for the total network traffic would be sufficient for a single carrier SkyWAN net work If a multi carrier network is designed t...

Страница 51: ...stations of a specific type The following picture represents that sheet filled with data from our network example Figure 2 29 Traffic Calculation Example Voice Traffic Flow Worksheet The input values in this sheet are the fractions of voice calls switched within or between stations of a specific type the output values the amount of voice traffic for one station of a specific type Note that these f...

Страница 52: ...rative reasons the master stations must be located at the head offices There fore both stations of type 1 must be assigned to carrier 1 To create a 2 carrier solution with almost equally sized carriers only the head offices one big and one medium size office are assigned to carrier 1 and all other stations to carrier 2 For the 3 carrier solution the assignment for carrier 1 cannot be changed as th...

Страница 53: ...by 256 kbps In that situation it may be more optimal to leave all small sites on one common carrier even if this leads to larger differences in data rates The last worksheet TDMA Calc Input is used to simplify TDMA structure optimization with the TDMA Calculator tool and will therefore be discussed together with this tool in chapter 2 7 2 4 2 Limitations of the Traffic Estimation Approach The netw...

Страница 54: ...ps If the hub station could not support the additional bandwidth due to power limitations one might be tempted to increase the network capacity by adding an additional carrier instead i e having a carrier configuration like Carrier 2 1000 kbps Carrier 3 1000 kbps If the additional 10 stations are assigned to the new carrier 3 such a solution would formally fulfill the capacity requirements of the ...

Страница 55: ...ng a LAN packet over satellite 1 On reception of an Ethernet packet on the LAN port the SkyWAN IDU will first strip the Ethernet header The SkyWAN IDU operates as an IP router therefore Ethernet infor mation will not be transported over the satellite link After inspection of the IP destination address the IDU will perform the routing procedure to decide if the packet has to be for warded over one ...

Страница 56: ...quirement for the carrier Figure 2 34 Add Turbo Phi Coding 4 The result of step 3 is a coded gross container which includes the error correction bits This information is transported over the satellite link by modulating the carrier using phase shift keying SkyWAN IDU 7000 supports quadrature QPSK and 8 8PSK phase shift keying Generally the number of PSK symbols relates to the number of coded bits ...

Страница 57: ... a brief period after a network restart once all stations are registered again at the active master these slots may be allocated as user traffic slots Figure 2 36 Signalling Time Slots 7 At this point we have constructed a TDMA carrier which has enough capacity to carry the required user traffic data rate as well as the necessary signaling information The band width of the carrier is specified by ...

Страница 58: ... For each step the additional overhead is specified explicitly Note the two different defini tions of data rates User data rate The data rate of user traffic received on the terrestrial interfaces LAN se rial ports Note that the LAN data does not include the Ethernet header and CRC check sum as this will be stripped before forwarding to the satellite link Modem data rate The data rate of all infor...

Страница 59: ...be exported and copied into the relevant configuration profile parameter A menu bar is available for exiting the application export and import to from a file and to show via and About entry the toolrelease version A status line is provided where output mes sages are displayed The stand alone version is a software application that does not need a login TDMA Calculator as tool integrated in the SkyN...

Страница 60: ...and on the right the section Data Input per Frequency Channel Detailed descriptions for the particular fields are given in chapter 2 6 1 and chapter 2 6 2 For each channel input data can be specified separately When starting the SkyNMS integrated TDMA Calculator input fields are pre defined either with values requested from SkyNMS for the corresponding configuration profile or with default values ...

Страница 61: ...is selected to 2 a DUB mode is specified In this case additional input fields will appear refer to figure 2 40 The input field Size of UL population 1 defines the number of stations in the network Figure 2 40 TDMA Calculator two Uplink Populations specified If Number of uplink populations is specified to 2 the following input fields will appear addi tionally In the select box Masterstation with se...

Страница 62: ...ct 2 if a cross strapped satellite transponder is used Dual Uplink Mode DUB a second ULP has to be defined using carrier 2 Masterstation with self recep tion MRB and MRB DUB mode both require a master able to receive its own reference burst If this self reception is not possible NFB DUB mode has to be configured YES MRB DUB mode 2 Uplink Populations 2 to 7 Downlink Populations No NFB_DUB mode max ...

Страница 63: ...e specified There are 6 different traffic types possible 1 FR Voice Frame Relay Voice Voice over SkyWAN FAD Select the appropiate Codec or protocol used 2 FR Realtime Frame Relay Real time 3 FR Non Realtime Frame Relay Non Real time 4 VoIP Voice over IP 5 IP Realtime IP Real time 6 IP Non Realtime IP Non Real time For each traffic type the Average packet length byte and the fraction of the total u...

Страница 64: ...lot sizes In combo box Time slot sizing ruled by choose 1 for slot size optimization depending on Frame Relay Voice traffic type 1 FR Voice If this option is selected the TDMA calculator defines the base gross container size and slot time factor in such a way that the resulting data rate per slot assignment will support the transport of one or multiple Frame Relay voice calls per slot The data rat...

Страница 65: ...Type in the average packet size in byte of Real time Frame Relay traffic 2 FR Realtime of user data rate Type in the fraction of the user data traffic used for Frame Relay Real time traffic 3 FR Non Realtime Average packet length byte Type in the average packet size in byte of Non Real time Frame Re lay traffic 3 FR Non Realtime of user data rate Type in the fraction of the user data traffic used ...

Страница 66: ...sulting data rate per slot assignment will support the transport of one or multiple Frame Relay voice calls per slot Select 2 3 5 or 6 The base gross container size and slot time factor is defined in that way that the resulting time slot container will transport one or multiple packets of the selected traffic type including the satellite link layer framing and fragment descriptor The packet size i...

Страница 67: ... length 1 optimized for the specified traffic Traffic is sent over satellite in coded gross container packages A base gross container holds the traffic data plus some overhead e g TDMA header SLL header signalling bursts before adding the For ward Error Correction FEC bits Time base slot Displays optimized TDMA base slot time of the network in microsec onds Number request slots per base slot Displ...

Страница 68: ...alculator For the definition of the user data refer to chapter 2 5 The spectral efficiency is represented by two definitions Efficiency per symbol user data rate symbol rate Efficiency per Hz user data rate frequency bandwidth The difference between these definitions is given by the carrier spacing factor ...

Страница 69: ...how many base slots are contained in one data slot for this channel Time slots per TDMA frame Displays how many time slots are contained in one TDMA frame for this channel Attention If the given number exceeds the allowed maximum see note above the solution is invalid Length ref slot time slots Displays how many data slots are configured as reference slot for this channel Length rqst frame time sl...

Страница 70: ... values manually Saved customer sheets can be imported in the TDMA Calculator using the Import function of the menu SkyNMS integrated TDMA Calculator after calculation click the button Apply to Configu ration Profile at the bottom of the window The calculated parameters are imported in the SkyNMS Network Configurator for the corresponding configuration profile and stored in the SkyNMS database The...

Страница 71: ...alculation Tool The following results are important for the TDMA calculation The composition of the user traffic according to the different traffic types These numbers are used to define the corresponding channel input parameters in the TDMA Calculator The user data rate per carrier for the single and multiple carrier solutions The user data rates calculated by the TDMA Calculator shown in area Da...

Страница 72: ...ent and Optimization Considerations 1 Evaluating the channel data output one notices that the number of time slots per TDMA frame larger than the maximum supported by SkyWAN networks Adjusting the time slot optimization rule to 3 calls per slot reduces this number to an allowed value 107 2 A further optimization can be achieved by reducing the number of data slots required for request bursts Start...

Страница 73: ...e estimated by the Capacity Calculation presented at the beginning of this section All the assumptions made so far are still valid however we must now find a solution which provides sufficient user data rates for all 3 carriers The proposed optimized solution is presented in the following screenshots Adjustment and Optimization Considerations 1 For the 3 carrier solution we have selected smaller t...

Страница 74: ...eeded in the case of big time slots If this extra capacity cannot be used for additional traffic on this carrier it will be wasted 3 Since the same optimization criterion 2 voice calls per slot has been selected for all chan nels the TDMA Calculator uses a data slot length factor of 2 for the small carriers to cre ate slots which can also carry 2 voice calls for these carriers If we want an even f...

Страница 75: ...which will be explained in the following section of this guide Only after that calculation the proper value for Eb No can be inserted for each channel leading to a new selection of modulation and error correction factors This change will hardly affect the user data rate but will have a profound influence on the symbol rate and the required frequency bandwidth The input and output values of the TDM...

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Страница 77: ...th stations The next steps in the engineering process are the choice of a suitable satellite rsp satellite transponder s and an optimized outdoor unit design 3 1 Introduction The general principle of the satellite link and outdoor unit design may be summarized by the following steps as shown in figure 3 1 Figure 3 1 Steps for Outdoor Unit and Satellite Link Design Select Satellite Transponder Star...

Страница 78: ...s the area where the earth stations are located Typically two types of beams are available Wide beams global or hemispherical which cover a wide geographical area potentially including multiple continents Spot beams which cover a restricted geographical area with a diameter of typically 2000 3000 km Wide beams are typically available in the C Band frequency band uplink frequency 5 GHz The advantag...

Страница 79: ...ca and Africa The NSS 7 global beam would cover the entire area If the stations would be located in Europe and Africa the east hemisphere beam would be more suitable because the beam intensity is typ ically 5 dB higher compared to the global beam Finally let s consider a network with stations in Brazil and Angola Both areas are served by a high power Ku Band spot beam If cross strapping between th...

Страница 80: ...nection represents the signal propagation from the transmitting earth station to the satellite whereas the downlink part represents the signal path from the sat ellite to the receiving earth station Equivalent Isotropic Radiated Power EIRP and Antenna Gain The signal intensity signal power per area of the earth station or satellite signal in the main beam direction of the antenna is determined by ...

Страница 81: ...ature which is defined by the formula where kB is Boltzmann s constant and B the signal bandwidth The noise production by both the satellite and the earth station is usually combined with the antenna gain to the system s fig ure of merit G T The resulting signal received at the earth station s demodulator will have both a signal carrier power C and a noise power N The signal quality will be determ...

Страница 82: ...is to use the highest possible value for modulation and FEC to save bandwidth costs without exceeding the maximum power available on both the satellite transponder and the earth stations Power Equivalent Bandwidth As already mentioned the available power on a satellite transponder is limited The available power is determined by the transponder s saturation EIRP reduced by the necessary output back...

Страница 83: ...d PEB are identical Any further increase in modulation and coding will increase again the space segment cost as the PEB increases even though the carrier bandwidth would still decrease So the optimal mod ulation and coding for this downlink would be QPSK 6 7 Rain fade In Ku Band strong rain falls can attenuate the signal substantially resulting in a temporary drop of the Eb No levels below the min...

Страница 84: ...rain fade in the link budget calculation increases the power requirements on the earth stations and on the satellite transponder As an example we assume a situation where according to the required availability and the rain zones of the earth stations a necessary rain margin of 5 dB for the uplink and 4 dB for the down link is determined The difference between up and downlink could result from diff...

Страница 85: ... rain fade has disappeared refer to figure 3 7 Figure 3 7 Power Conditions with constant Power Level At clear sky condition the satellite transponder would operate at a power level which is 5 dB higher than under maximum rain fade and actually 9 dB higher than necessary for clear sky conditions That leads to an unnecessary high power requirement for the satellite transponder which may even exceed ...

Страница 86: ...but is always given by EIRPT EIRPT clear Sky Downlink rain fade Uplink rain fade 3 4 Considerations for SkyWAN Link Budget Calcu lations 3 4 1 Network Topology So far we have considered satellite links which include a transmitting and a receiving earth sta tion using a specific satellite transponder Most widely used link budget tools actually are de signed for such point to point links where each ...

Страница 87: ...is used 3 4 2 Downlink Optimization Figure 3 9 Downlink Considerations The performance of the satellite downlink is given by the maximum available EIRP of the sat ellite the earth stations figure of merit and their location within the satellite beam footprint The maximum EIRP is only available in the center of the beam stations located at the beam edge will receive a weaker signal The difference i...

Страница 88: ...downlink optimization discussion it was assumed that the satellite transmits with the max imum available EIRP to the earth stations This is however only true if the signal intensity re ceived from the earth stations reaches the maximum Input Power Flux Density IPFD The IPFD is given by the transponder Saturation Flux Density SFD reduced by the Input Back Off IBO which is necessary to prevent exces...

Страница 89: ... for each network Result Power requirement for every SkyWAN earth station in the network The link budget tool is a Microsoft Excel spreadsheet which consists of the following work sheets Summary Input Carrier parameters for up to 8 SkyWAN carriers required bit error rate level and rain availability Output Earth station power requirements power equivalent bandwidth Stations Earth station data link ...

Страница 90: ...low to specify signal degradation due to intermodulation on the up and downlink The default settings 300 200 dBW Hz describe a situation without intermodulation effects If no detailed information about transponder intermodulation is available a typical way to estimate this effect is Increase I0 up until the power requirement for the earth stations is increased by 20 Increase I0 down until the powe...

Страница 91: ... angles 0 90 have to be inserted refer to figure 3 12 The antenna name for each data set has to be unique This name is used to link earth station properties to the antenna data In the case of C Band antenna data sets for linear and circular polarization may be specified Here the link from earth stations to antennas is done via a common antenna name for both po larization types which is specified a...

Страница 92: ...isplayed in the Active Calculation box blue background Specify Network Data Step 1 Specify each network by a Calculation Name Goto lower section Stored Calcu lations and enter network identifier heading field with grey background in column B Step 2 For each individual network 3 network parameters have to be defined using the pull down menu at the top of each Stored Calculations box Please define t...

Страница 93: ...have a disadvantage of 0 dB for other sta tions the difference between maximum and actual G T or EIRP has to be entered Antenna type according to the defined frequency band of the network the pull down menu allows the selection of any antenna type defined in the Ku or C Band antenna sheet before Output Backoff The difference between saturation power and maximum usable output power of the station s...

Страница 94: ...an additional back off has to be added which is defined on the summary work sheet refer to figure 3 18 If more than one IDU is connected to the same ODU besides an additional back off the power requirement for the amplifier is multiplied by the number of IDUs Stations with 2 Demodulator Boards If a station is equipped with a second demodulator board a second entry with the same station parameter s...

Страница 95: ... specify the maximum power class available for SSPA amplifier types for Ku and C Band input field markde in figure 3 18 If the power requirement is higher than the available SSPA power class the additional TWTA back off is added to the station s power requirement Add the TWTA back off value in the Sum mary sheet in the marked field shown in figure 3 18 The tool will propose after the link calculat...

Страница 96: ...mbol rate have to be taken from the TDMA Calculator Additionally the following link quality parameters must be defined Maximum Bit Error Rate Two Way Rain Availability Step 2 For each carrier the network topology may be selected from a pull down menu Mesh mandatory for carrier 1 or Star Star topology for all stations which use a Star Carrier as their home channel only links to the hub stations the...

Страница 97: ...ation input box No input means that the power require ment for a station loop is calculated The last line states the required amplifier power including the station output back off Figure 3 20 Link Budget Tool Summary Worksheet Downlinks The second part represents the power requirement considering all downlinks to reachable sta tions For fully meshed stations this includes all stations in the netwo...

Страница 98: ...ion with and without UPC are stated in terms of a power equivalent bandwidth and are compared to the carrier bandwidth of the station s home channel If the PEB with UPC is higher than the carrier bandwidth an indication Power Limited will appear in the output field For informational purposes the results for the individual links are also displayed on the Sum mary sheet This can be used to identify ...

Страница 99: ...links between stations located in these areas carriers on up to four different transponders may be required Carrier 1 must be located on a looped transponder for ULA1 This carrier is used by the master and backup master station to send reference bursts and to receive request bursts from stations located in ULA1 and for the master synchronization which requires self re ception of the master station...

Страница 100: ...urope and Africa ULA1 and America ULA2 is presented The transponders used for this network are served by the hemispherical beams on the SES World Skies Satellite NSS 7 cf chapter 3 2 for foot print diagrams of that satellite Transponder Data For each beam of a cross strapped transponders additional entries in the satellite sheet are necessary Figure 3 24 MRB DUB Network Satellite Data Figure 3 25 ...

Страница 101: ...B Network Hub Stations UpLink Area 1 ULA1 The slave stations of ULA1 use carrier 1 for the primary demodulator Any ULA1 station which should be able to communicate directly with a station in ULA2 must have a second demodulator using carrier 2 as its home channel In this example the stations in Rome and Johannesburg have no direct link to the stations in America whereas Casablanca has a direct link...

Страница 102: ...is mesh com munication within ULA2 Figure 3 28 MRB DUB Network ULA2 Stations Carrier Topology The definition of the carrier parameter topology in the summary sheet has to be done in the following way Carrier 1 Mesh in ULA1 Carrier 2 ULA2 ULA1 All Carrier 3 ULA1 All ULA2 Carrier 4 ULA2 ULA2 Note that modem data rate modulation and coding on carrier 1 and 2 must be identical For the other carriers t...

Страница 103: ...LA2 links to the master stations and to stations in ULA1 with a sec ond reception channel on carrier 2 will be calculated Additionally for slave stations in ULA2 with a second reception channel on carrier 4 meshed links to other stations in ULA2 with second reception channel will be calculated In the following pictures the results for the link calculations in the lower section of the Summary sheet...

Страница 104: ...ios and typ ical optimization steps 3 6 1 Scenario 1 Ku Band 5 Stations Fully Meshed The first scenario is a fully meshed 5 station network located in a Ku Band spot beam over Eu rope and North Africa Possible amplifier types should be ND Satcom RFT 5000 Ku Band with 8 20 or 30 Watt Master stations should be located in Berlin and Madrid Figure 3 32 Scenario 1 Uplink Footprint Figure 3 33 Scenario ...

Страница 105: ... requirement of 8625 kbps Preliminary link calculation showed that a single carrier solution would lead to a very high power requirement for the earth stations Therefore it was decided to split the capacity into two carriers the master stations using carrier 1 and the slave stations carrier 2 The following requirements were defined Table 3 5 Scenarion 1 2 Carrier Solution Requirements Carrier 1 Ca...

Страница 106: ...ulting bandwidths Table 3 6 Scenario 1 Carrier Coding and Bandwidth The power requirements for the individual earth stations can be summarized in following table Table 3 7 Scenario 1 Summarized Power Requirements Meshed Network Carrier 1 Carrier 2 Total bandwidth re quired carrier spac ing 1 2 KHz Modulation 8PSK QPSK FEC 2 3 2 3 7096 Estimated Symbol Rate ksps 2713 3200 Meshed Network Madrid Berl...

Страница 107: ... station power requirement would be to split the network capacity into more than 2 carriers For small networks this may however cause inefficiencies if too few stations are sharing a carrier leading to a smaller statistical multiplexing gain The applications may also prevent further splitting of the bandwidth If an application requires a high bandwidth data stream e g high quality video streaming ...

Страница 108: ...that there is really only negligible communica tion need between the remote stations Optimization There is still potential room for optimization Whereas on carrier 2 PEB and carrier bandwidth is almost equilibrated on carrier 1 the network still uses only 1 3 of the available transponder power The limitation is given by the Casablanca earth station which is located at the edge of the satellite foo...

Страница 109: ...ated for both carriers The bandwidth saving should again compensate the higher antenna and installation cost in Casablanca within a short time provided that the site in Casablanca allows the installation of a 3 8 m antenna Further carrier optimization is not possible because we have reached on both carriers maxi mum modulation and FEC Putting bigger antennas on other sites than Casablanca would re...

Страница 110: ...filter matrix is used Network topology on carrier 2 is set to Meshed in ULA1 but the calculation of the satellite link loops for Casablanca and Tunis as well as the links between these two stations are suppressed by entering 0 for these links in the link filter matrix cf corresponding picture in chapter 3 6 If all other network parameters are unchanged the link budget calculation result is similar...

Страница 111: ...s one for user data one dedicated for man agement data The access to this interfaces is provided by 4 LAN ports refer to tables below 4 logical IP over Satellite interfaces for user traffic 1 IP over Satellite interface for management data 1 service interface for local management access Interfaces may belong to the IP User or Management Plane i e they are responsible for for warding user traffic o...

Страница 112: ...rface Sat UT1 SatOne is used data on this interface may be received by the primary or the secondary demodulator IP based management functions are e g uploading configuration files via FTP or querying sys tem parameters using SNMP commands Two SkyWAN IP features which will be discussed in more detail later in this guide extend the IP functionality beyond packet forwarding TCP acceleration TCP A whi...

Страница 113: ...gure 4 1 SkyWAN IP Protocol Stack IDU 7000 series Table 4 1 IP Interface Usage of IDU 7000 series Interface Number Interface Name User or Management Plane 1 LAN User Management 8 Sat UT1 SatOne User Management 9 Sat UT2 SatTwo User Management 10 Sat UT3 SatThree User Management 11 Sat UT4 SatFour User Management 12 Sat MT Management dynamic Service Port Management For local management only no pack...

Страница 114: ...nter face Number Port Number Interface Name User or Management Plane 5 1 LAN1 User Traffic 5 2 LAN2 User Traffic 5 3 LAN2 User Traffic 5 4 LAN4 Management 9 Sat UT1 SatOne User Management 10 Sat UT2 SatTwo User Management 11 Sat UT3 SatThree User Management 12 Sat UT4 SatFour User Management 13 Sat MT Management dynamic Service Port Management For local management only no packet for warding over s...

Страница 115: ...ted via its Sat MT interface to a common Manage ment IP network This management network is used to perform remote management of the en tire network via satellite using a SkyNMS PC which can be connected to the LAN MT interface of any station This management network is defined on the master station Note that it must not overlap with any user IP subnetwork including networks which are not directly c...

Страница 116: ... to the same satellite management network like the meshed stations To ensure network management connectivity the station to which the SkyNMS PC is connected must have direct satellite link connectivity to every station This condition is always fulfilled for the master and backup master station but may be possible also for other meshed stations 4 2 3 Static Routing IP packet forwarding to remote ne...

Страница 117: ... a star network may be enabled by defining static routes via the hub station Typical configuration is to define a default route on each star terminal with the hub station as a next hop and to define explicit static routes to each terminal s LAN network on the hub To prevent that the hub station informs the terminals that they can reach each other via a direct hop generation of ICMP redirect messag...

Страница 118: ...aphic router identification is not supported Satellite interfaces may not belong to different OSPF areas The following OSPF features are available on SkyWAN stations Ethernet and satellite IP interfaces may be defined as broadcast OSPF interfaces Single or multiple OSPF Areas Up to 6 OSPF neighbors are possible on the Ethernet interface Up to 200 OSPF neighbors are possible on the satellite interf...

Страница 119: ...ical minimal path costs This mode works for both static routing and OSPF Non Equal Cost Multi Path Load balancing will be performed over all paths to a destina tion irrespective of the path cost This mode only works for static routing Load balancing is only performed over the satellite link If there are two alternative paths with identical cost one over the Ethernet interface and the other over th...

Страница 120: ...is has a summary cost metric of 2 compared to a cost metric summary of 3 for the path R 2 via IDU 5 As long as IDU 4 and its Ethernet interface is up all IP unicast traffic will be routed via IDU 4 using the frequency channel 2 which is the home channel of IDU 4 Only in case of failure of this station traffic will be rerouted via IDU 5 using then frequency channel 3 This situation may lead to an u...

Страница 121: ...allocate sufficient capacity on all channels to perform the packet forwarding on eve ry channel IGMP Querier Role SkyWAN IDU supports the Internet Group Management Protocol IGMP version 2 This al lows hosts connected to the local LAN to register for specific multicast addresses Forwarding to ethernet can be made dependent on the existence of at least one host which is currently reg istered to this...

Страница 122: ... SkyWAN IDU If enabled each IP microflow which should be forwarded to the satellite interface may be classified using protocol header information and rules defined in the station s for ward aggregate table into a forwarding behavior may be preallocated for real time forwarding behaviors according to the forwarding be havior stream slot capacity The traffic flow will be enqueued to a transmit queue...

Страница 123: ...ld Silver Bronze and Default normal priority non real time traffic The high priority traffic is mapped to the IP Control 2 queue the normal priority traffic to the IP Non Real Time queue Capacity for this traffic type is allocated as dynamic slots Management Plane IP traffic Management plane IP traffic generated internally in the IDU e g OSPF routing messages responses to SNMP queries is mapped to...

Страница 124: ... a maximum data rate for each Titanium aggregate Traffic ex ceeding this limit will be discarded Platinum Platinum forwarding aggregates define a permanent real time traffic flow When the aggregate is activated the IDU will request sufficient streaming bandwidth to serve the aggregate s con figured data rate When this capacity is allocated by the master the aggregate becomes operational and packet...

Страница 125: ...teways in our network multiple calls between these gateways would use IP flows with iden tical source and destination addresses Setting the flow detection parameter to flow would consider the streams generated by all the calls as a single IP flow Choosing microflow or mi croflowevenport would correctly identify each voice call as an individual Platinum Dynamic flow It is sufficient to define a sin...

Страница 126: ...e to compression will be released This capacity reduction works only for the audio codecs not for video codecs For data rate requirement for the above mentioned voice codecs with and without header com pression please refer to table 2 1 in chapter 2 2 Data and Voice Networking Overview As an example a typical VoIP connection is assumed using G 729 voice codec packets with an RTP payload size of 20...

Страница 127: ...red at each station 4 2 10 Transmission Control Protocol Acceleration TCP A The throughput of an individual TCP connection over long delay links is limited by the fact that the sender has to wait a long time for acknowledgment from the receiver before it can resume sending further data To overcome this limitation SkyWAN IDU supports a TCP acceleration functionality Theoretically the maximum throug...

Страница 128: ...ting system or applications are necessary The TCP acknowledgments will be sent by the local IDU with low delay thus the satellite delay has no impact on the TCP throughput Up to 32 TCP connections can be accelerated by any IDU Connections exceeding this limit will be supported as transparent TCP connection without acceleration An IP flow to which TCP acceleration should be applied must have a defi...

Страница 129: ...n the software license The following table 4 5 displays the possible port types Table 4 5 UIM Board FR Serial Port Types The interface standard is defined by the selected cable type Note that there are special cable types available for a SkyWAN IDU FAD connection Each port type supports port speeds 2 4 4 8 9 6 19 2 and 38 4 Kbit s The port types X 21 EIA 232 and V 35 support additionally port spee...

Страница 130: ...s a direct single hop connection be tween the IDUs Double hop connectivity via an intermediate IDU is not supported for Frame Relay services Besides connections across the satellite network SkyWAN IDUs support also local switching i e PVCs connecting two serial ports on the same IDU In addition to unicast connections also multicast connections are possible For a multicast PVC a remote multicast gr...

Страница 131: ...ved on the individual PVCs are forward ed to the satellite link The following figure 4 10 describes the mapping of communication serv ice to Frame Relay transmit queue on the IDU Figure 4 10 Mapping of FR Services to Transmit Queues There are two transmit queues for Frame Relay user traffic for each satellite carrier on the IDU FR Realtime FR Non Realtime The FR Control queue is reserved for the i...

Страница 132: ...the same PVC If a voice call setup is signaled by a FAD the SkyWAN IDU will automatically request suf ficient streaming slot bandwidth for the signaled voice codec If a call disconnect is signaled the streaming capacity is automatically released In addition to voice traffic transparent data traffic between FAD serial ports may also be trans ported as realtime traffic In this case the configured se...

Страница 133: ...ervice for Isochronous FRAD Ports An exception to these rules is the realtime service for isochronous FRAD ports Here the con figured serial port speed defines the required amount of streaming bandwidth and automatical ly limits the user traffic to this value Hence no traffic policy parameters must be defined and traffic shaping should be disabled Congestion Management of Non Realtime FR Packets C...

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Страница 135: ...uration SkyWAN satellite link master and network parameters according to TDMA calcu lation result SkyWAN home channel settings SkyWAN satellite link station parameters according to used ODU hardware Tx and Rx path local oscillator frequency and spectrum inversion Monitoring and Control protocol parameter Additional input may be required from the satellite operator especially carrier frequencies fo...

Страница 136: ...ay device Permanent virtual circuits PVCs have to be defined with a DLCI numbering scheme which may have to be adjusted to the customer s PVC topology The final result of the engineering process should be documented in a Detailed Network De sign document This should contain all necessary information for the SkyWAN network com missioning procedure i Some of the IDU s data networking features may on...

Страница 137: ...about new features in this release Table 6 1 What s new in the Engineering Manual Table 6 2 What s new in Rev B Number Item Description 1 TDMA calculation New TDMA Calculator introduced Number Item Description 1 TDMA Calculator standalone tool Appendix added with hard and software re quirements for installation of TDMA Calculator standalone tool 2 TDMA Calculator integrated tool Output parameter o...

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Страница 139: ...it Error Rate Test CCR Convolutional Code Rate C N Signal to Noise Ration CRC Cyclic Redundancy Check CW Continuous Wave DC Direct Current DCE Data Communication Equipment DIAG Diagnostic DL Downlink DLCI Data Link Connection Identifier DR Designated Router DSCP Differentiated Services Code Point DTE Data Terminal Equipment DUB Dual Uplink Beam ECMP Equal Cost Multi Path EIRP Equivalent Isotropic ...

Страница 140: ... Frame Relay Access Devcice FRF Frame Relay Forum FTP File Transfer Protocol GSM Global System for Mobile communications GUI Graphical User Interface G T Gain to Noise Temperature HU Height Unit IBO Input Back Off ICMP Internet Control Message Protocol IDU Indoor Unit IGMP Internet Group Management Protocol IP Internet Protocol IPFD Input Power Flux Density ISDN Integrated Services Digital Network...

Страница 141: ... MIB Management Information Base MOD Modulator MRB Multiple Reference Burst MRB DUB Multiple Reference Burst Dual Uplink Beam NFB DUB No direct Feedback for Active Master Dual Uplink Beam NMS Network Management System noECMP Non Equal Cost Multi Path NRT Non Real Time NVRAM Non Volatile Random Access Memory ODU Outdoor Unit OP Operation OSPF Open Shortest Path First PC Personal Computer PN Pseudo ...

Страница 142: ...Real Time Transport Protocol RTT Round Trip Time Rx Receive SAS Satellite Access Subsystem Sat MT Satellite Port Management Traffic Sat UT 1 4 Satellite Port User Traffic 1 to 4 synonym to SatOne SatTwo SatThree SatFour SIC Satellite Interface Controller SIM Satellite Interface Module SFD Saturation Flux Density SLL Satellite Link Layer SkyNMS SkyWAN Network Management System SMCP SkyWAN Monitor a...

Страница 143: ...wer Control TOS Type of Service TTL Time to Live Tx Transmit TWTA Travelling Wave Tube Amplifier UDP User Datagram Protocol UFC Uplink Frequency Control UIM User Interface Module UL Uplink ULA Uplink Area VoFR Voice over Frame Relay VoIP Voice over IP V2oIP Voice and Video over IP VSAT Very Small Aperture Terminal WAN Wide Area Network 8PSK 8 Phase Shift Keying Abbreviation Meaning ...

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Страница 145: ... using a fixed os cillator frequency Burst A short transmission over the satellite link The burst time is smaller than the time slot Carrier to Noise Ratio C N The ratio of the received carrier power and the noise power in a given bandwidth expressed in dB The higher the C N the better the quality C band Frequency band with uplink 5 925 to 6 425 GHz downlink 3 7 to 4 2 GHz Container Part of a data...

Страница 146: ...rbit GEO Geostationary Earth Orbit satellites orbit at 35 786 km 22 282 mi above the equator in the same direction and speed as the earth rotates on its axis making them appear as fixed in the sky G T The figure of merit of an earth station or satellite transponder expressed in dB K G is the antenna gain and T the system noise temperature The higher the G T the better the system Guard Band Transmi...

Страница 147: ...ombination of propagation queuing and processing delays is usually named network latency profile See also Propagation Delay and Processing Delay Low Noise Block Down Converter LNB Combination of Low Noise Amplifier and down converter built into one device attached to the feed It is used for the downlink satellite transmission by converting a band from a higher fre quency to a lower frequency L Ban...

Страница 148: ...ions Cent er NOC Centralized location where control over operation of a network is managed and monitored remotely Network Management System NMS Hardware and software used for monitoring and controlling a satellite network See also SKYNMS Node From a networking perspective a SkyWAN IDU acts as a net work node Hence in the context of communication services the term node for aSkyWAN IDU is preferred ...

Страница 149: ...o rainfall Reference Burst Burst sent from the SkyWAN master IDU containing TDMA network management information like the frame plan Request Burst Burst sent from the SkyWAN slave stations to the master to request network resources Satellite Communications satellites orbit the earth in geostationary orbit and transmit and receive radio frequency signals from VSAT earth stations Satellite news gathe...

Страница 150: ...n by routing through a hub Symbol Rate Also known as baud or modulation rate is the number of sym bol changes signalling events made to the transmission me dium per second using a digitally modulated signal or a line code Often used modulation techniques in VSAT communica tions are QPSK and 8PSK Time Division Multiple Ac cess TDMA Channel access method that allows applications or users to share th...

Страница 151: ...higher 250 MByte of available hard disk space XGA 1024 x 768 or higher resolution video adapter and monitor CD ROM or DVD drive Keyboard and Microsoft Mouse or compatible pointing device Ethernet network interface card and ethernet cable Serial port and serial cable 9 2 Software Requirements SkyWAN TDMA Calculator uses the commercial operating system Microsoft Windows XP Professional or Windows 7 ...

Страница 152: ... on the installation CD A wizard will guide you through the installation process 4 If the correct Sun Java Runtime Environment JRE is not available on the PC hardware plat form it can be installed during the installation 9 4 Run TDMA Calculator Standalone Tool The SkyWAN TDMA Calculator Standalone Tool is started without login procedure Start TDAM Calculator either from the windows start menu Star...

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