WO2007071059A1 - Methode de gestion d'un reseau satellitaire faisant intervenir un budget de reseau - Google Patents

Methode de gestion d'un reseau satellitaire faisant intervenir un budget de reseau Download PDF

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Publication number
WO2007071059A1
WO2007071059A1 PCT/CA2006/002110 CA2006002110W WO2007071059A1 WO 2007071059 A1 WO2007071059 A1 WO 2007071059A1 CA 2006002110 W CA2006002110 W CA 2006002110W WO 2007071059 A1 WO2007071059 A1 WO 2007071059A1
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WO
WIPO (PCT)
Prior art keywords
estimating
power level
satellite
network
downlink
Prior art date
Application number
PCT/CA2006/002110
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English (en)
Inventor
Victor E. Gooding
Original Assignee
Bce Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Publication of WO2007071059A1 publication Critical patent/WO2007071059A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1853—Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service
    • H04B7/18539—Arrangements for managing radio, resources, i.e. for establishing or releasing a connection
    • H04B7/18543—Arrangements for managing radio, resources, i.e. for establishing or releasing a connection for adaptation of transmission parameters, e.g. power control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/373—Predicting channel quality or other radio frequency [RF] parameters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/391—Modelling the propagation channel
    • H04B17/3913—Predictive models, e.g. based on neural network models
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851—Systems using a satellite or space-based relay
    • H04B7/18513—Transmission in a satellite or space-based system
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/30—TPC using constraints in the total amount of available transmission power
    • H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
    • H04W52/346—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading distributing total power among users or channels

Definitions

  • the present invention relates to the field of satellite communications and more particularly concerns the use of a network budget in the management of a satellite network.
  • satellite delivery offers a unique advantage by increasing the reach of such services to areas that cannot be connected through, or are underserved by, terrestrial means.
  • the supporting satellite networks have become very large and more difficult to build and manage, requiring tools that can handle the large number of complex factors affecting the system design, the on-going quality of service, and the overall economics of the services provided.
  • Link budgets are tools used in the design and running of satellite networks. They are computer programs used to determine power levels and other signal quality indicators in a satellite link, taking into account the various factors affecting signals along communications paths. Link budgets are often built using spreadsheet applications in which well-established operations are performed using appropriate values for each contributing factor. Typically, the considered factors include signal gains and losses from precipitations and other climatic effects, satellite transponders, power amplifiers and antennas, as well as interferences due to atmospheric noise and other signals from the same or another satellite. These values must be skilfully evaluated or estimated, and then manipulated within the link budget, as they will determine the obtained result. Satellite link budget analysis is well established for the links of networks with a small number of beams, such as is typical for satellites operating in the C or Ku frequency bands. These satellite systems are relatively simple, with straightforward satellite and ground systems, a small number of large beams to provide the required coverage, and only minor inter-beam considerations. In these cases, the link budgets pertain to individual links, or to small networks operating within a given beam.
  • satellite systems have introduced more complex payloads operating at higher frequency bands such as the Ka-band and the V-band.
  • the higher frequencies enable the creation of smaller spot beams, which in turn allow the satellite systems to provide higher power levels on the ground by concentrating the available power.
  • the increased power levels ensure that direct- to-user services can be offered with small, affordable user antennas.
  • advanced technologies are incorporated into the satellite payload and the ground equipment to mitigate the higher levels of propagation effects at the higher operating frequencies.
  • a method for building a network budget for a satellite network has a plurality of links, each including an uplink beam transmitted to a satellite of the satellite network and a downlink beam transmitted from this satellite.
  • the method includes, for each of these links: a) estimating an initial power level of the uplink beam ensuring reception thereof at the satellite; b) estimating a power level of the downlink beam at each of a plurality of receiving locations receiving the downlink beam; and c) estimating power variations affecting the downlink beam.
  • a computer readable medium having at least one module for building a network budget for a satellite network recorded thereon.
  • the satellite network has a plurality of links, each including an uplink beam transmitted to a satellite of the satellite network and a downlink beam transmitted from this satellite.
  • the at least one module is operable to: estimate an initial power level of the uplink beam ensuring reception thereof at the satellite; estimate a power level of the downlink beam at each of a plurality of receiving locations receiving this downlink beam; and estimate power variations affecting this downlink beam.
  • a method for managing a satellite network including: a) building a network budget for the satellite network, the network budget including at least one test parameter; b) obtaining a predicted capacity of the satellite network using the network budget; and c) determining at least one set up parameter of the satellite network based on the predicted capacity.
  • a method for optimizing reception of a receiver at a receiving location in a satellite network includes: a) building a network budget for the satellite network; b) determining a target signal-to-noise ratio for the receiving location using the network budget; and c) optimizing a set-up of the receiver in order to obtain an effective signal-to- noise ratio close to the target signal-to-noise ratio.
  • FIG. 1 is a schematic illustration of components of a typical satellite network to which the present invention may be applied.
  • FIG. 2 is a schematic representation of a network budget according to one aspect of the invention.
  • FIG. 3 is a flow chart of a method of building a network budget according to one embodiment of the invention.
  • FIG. 3A represents the power variations taken into account in an embodiment of the method of FIG. 3.
  • FIG. 4 is a flow chart illustrating the steps of a method for managing a satellite network according to one embodiment of the invention.
  • FIG. 5 is a flow chart illustrating the steps of a method for optimizing reception of a receiver at a receiving location in a satellite network, according to another embodiment of the invention.
  • FIGs. 6A and 6B represent link budgets obtained through a network budget according to one embodiment of the invention, respectively for a forward and a return link of a satellite network.
  • a network budget for a satellite network and a method of building such a network budget.
  • the satellite network 10 to which this particular aspect of the invention is directed includes at least one satellite 12 in orbit above a geographical region of interest, which allows the exchange of data between a number of gateways 14 and a plurality of terminals 16. Only one gateway 14 and one terminal 16 are shown in FIG. 1 , for simplicity.
  • Each of the satellite 12, gateways 14 and terminals 16 is provided with at least one antenna for transmitting and/or receiving electromagnetic radiation, typically at microwave frequencies.
  • the gateways 14 may be in terrestrial communication with one or more internet service providers 18 for providing access to a data network 20 such as the internet.
  • Each terminal 16 is located at the premises of a subscriber to such services, and may therefore be connected to a subscriber computer system 22. It will be understood that the provision of internet services is given here as an exemplary purpose of the satellite network, but that the satellite network could equally be used to transmit data in another context such as television services, telephone services, etc.
  • beam A is an uplink beam transmitting data from the gateway 14 to the satellite 12
  • beam B is a downlink beam transmitting data from the satellite 12 to the terminal 16.
  • a beam C transmitting data from the terminal 16 to the satellite 12 and a beam D transmitting data from the satellite 12 to the gateway 14 may also be provided.
  • Each set of uplink and downlink beams allowing the transmission of information between a gateway and a terminal is referred to as a "link".
  • beams A and C form together a forward link
  • beams B and D form together a return link.
  • communications with the satellite 12 need not necessarily be two-way; for example, in the context of internet services provision, the data to be sent back to the internet service provider 18 may be transmitted through phone lines or other terrestrial communication methods.
  • All communications with the satellite are transmitted at frequencies within a frequency band associated with this particular satellite (such as 12).
  • frequency bands are usually standardized. For example, operating frequencies between 4 and 8 GHz are generally associated with the C band, while the Ku band operates in the 12-18 GHz range, the Ka band operates in the 18-30 GHz range, and the V band in the 40-75 GHz range.
  • a given satellite (such as 12) may have more than one dedicated frequency band.
  • the Ka and V bands will therefore generate beams having a smaller spot size, which allows the satellites to provide higher power on the ground.
  • more beams are then required for the same coverage area, necessitating frequency re-use to cover wide areas and provide sufficient bandwidth for the subscribers. It will be understood that this results in potentially significant interference into each beam due to other beams sharing the same frequencies.
  • network budget 24 there is shown an example of a network budget 24 according to one embodiment of the invention.
  • the expression network budget is used herein to refer to an accounting of the relevant factors affecting the transmission of signals throughout the entire satellite network.
  • the network budget is not built for just one link, as with traditional link budgets, but for the entire satellite network, that is, for all the links 26a, 26b, 26c, etc, transmitting data from between the gateways and the terminals.
  • the network budget 24 may therefore be used on a much larger scale compared to standard link budgets.
  • the network budget 24 may be embodied by a computer program including at least one module recorded on a computer readable medium.
  • the computer program embodying the network budget 24 will be described below as a single module, but it will be understood by one skilled in the art that it may in practice include any appropriate number of modules or sub-modules operable to accomplish the functions described below.
  • the module in question is operable to build the network budget 24 according to a method of the present invention, the steps of which will be described with reference to FIGs. 3 and 3A.
  • the method 100 first includes estimating 102 an initial power level of the uplink beam of each link, sufficient to ensure reception of this uplink beam at the satellite.
  • This estimating may for example include calculating a curve fit of the emitted power level of the uplink beam from the ground emitter, that is, the power level of the beam generated at the gateway 14 for a forward link and at the terminal 16 for a return link, as a function of distance from the center of the uplink beam.
  • the curve fit may be performed using a third degree polynomial fit. Power variations affecting this uplink beam are then estimated and taken into account. In this manner, a measure of the necessary power to ensure proper reception of the uplink beam at the satellite 12 may be obtained.
  • the method 100 next includes estimating 104 a power level of each downlink beam at each of a plurality of receiving locations within the corresponding downlink beam. This again may involve performing a curve fit, such as a third degree polynomial fit or other, as a function of distance from the center of each downlink beam. Power variations affecting each downlink beam are then estimated 106.
  • a curve fit such as a third degree polynomial fit or other
  • the power variations affecting either the uplink beams or the downlink beams are based on an estimation of all factors having an impact on the quality of the signal of a given uplink or downlink beam, which include interference factors 42, power gains 28 and power losses 30.
  • the interference factors 42 affecting a given beam along its path for example include thermal noise, equipment noise, and noise from receivers both on the satellite and on the ground. Interference is present when multiple signals are transmitted through a non-linear device, such as a satellite transponder. Interference calculations also include an evaluation of the interference from other beams of the satellite network and from other satellites. Inter-beam interference is particularly relevant when the satellite network involves frequency re-use, that is, that at least two uplinks or two downlinks of the satellite network have a same operating frequency. Such will typically be the case for Ka band satellite networks.
  • Attenuation factors may influence the power losses 30 for a given link.
  • the relevance and impact of each such factors will vary depending on the components of the satellite network, its geographical set up, its operating frequency, etc.
  • Precipitations 36 such as rain or snow, is one factor which creates power losses in an uplink or downlink beam travelling in the affected geographical region. These losses are felt more acutely at higher operating frequencies. Although they can often be ignored for the C and Ku Bands, rain attenuation losses are to be taken into consideration for communications through the Ka and V bands, especially in regions where statistics show that such precipitations are frequent.
  • the network budget 24 may also factor in the use of at least one fade mitigation technique 34, which adds to the power gains 28 by mitigating losses.
  • a number of such techniques are well known in the art for compensating for power losses in a satellite link. For example of fade mitigation techniques, reference may be made to a publication by Athanasio et al.
  • the simulation generally involves modelling the operation of the fade mitigation technique, and calculating its effectiveness with a rain fade model.
  • Available rain fade models for example include Crane Global, ITU-R P618-X and Crane revised 2.
  • Atmospheric losses 38 may also have an impact on the power level of an uplink or downlink beam significant enough to warrant taking them into consideration in building the network budget.
  • Atmospheric losses 38 for example include atmospheric absorption by gases, cloud, fog and smoke, which become more significant at high frequencies.
  • Dispersive losses caused by the accumulation of water droplets from precipitations or dew on antennas may also be taken into consideration. This phenomenon is referred to as antenna wetting 40.
  • Other losses include propagation losses, as is normal for radiation over long distances, antenna pointing error losses, and equipment interconnection cable losses.
  • each of these factors may be taken into consideration in the network budget 24 by the inclusion of a constant loss value.
  • atmospheric absorption 38 of all kinds may be associated with a typical loss of 0.5 dB, or any other appropriate value.
  • Losses due to antenna wetting 38 may be as high as 3 dB for high frequencies, but may be of any other value depending on the particular characteristics of a given system or the presence of shielding or hydrophobic coating on the antenna.
  • the module of the network budget 24 may be further operable to input 44 a query to the network budget 24 and obtain as output 46 information on the satellite network responsive to this query.
  • the query may for example include only the geographical coordinates of an existing or future terminal, and the network budget 24 will be capable of providing any required data relative to service to these particular geographical coordinates. It is not necessary to know in advance which link applies.
  • the data in question may include an identification of the corresponding uplink and downlink beams, and a full link budget for this link.
  • This link budget may for example include the initial power level of the uplink beam of this link, the power level of the downlink beam at the receiving location corresponding to said geographical coordinates, information on the power variations affecting the uplink and downlink beams, etc.
  • the data may further include the operating frequencies of the uplink and downlink beams, an identification of a gateway serving these geographical coordinates, a target signal-to-noise ratio thereat, etc. Exemplary representations of link budgets obtained through an embodiment of the present invention are shown on FIGs. 6A and 6B, respectively for a forward link and a return link.
  • a method 110 for managing a satellite network may be applied to satellite networks such as shown, for example, in FIG. 1.
  • the satellite network may operate at operating frequencies within the C 1 the Ku, the Ka and the V frequency bands, and is particularly advantageous when used for multi- beams, such as Ka or V band, satellite networks.
  • the method 110 for managing a satellite network first includes a step of building 112 a network budget for the satellite network.
  • the network budget may include an accounting of the relevant factors affecting the transmission of signals throughout the entire satellite network.
  • the network budget may be built according to the method described above with reference to FIGs. 3 and 3A.
  • the building of the network budget can involve providing in this network budget at least one test parameter.
  • the test parameter may be embodied by any parameter whose impact on the network budget may be tested.
  • the test parameter is the initial power level of at least one of the beams of the network, such as the uplink and/or downlink beams of a given link, all the uplink and/or downlink beams of the network, or sub-sets thereof.
  • the network budget is therefore built to represent the state of the network should this test parameter correctly represent reality.
  • the test parameter may be at least one power variation factor affecting at least one of the uplink or downlink beams of the network.
  • This embodiment may for example be used to test estimated value for power gains, power losses or interference effects.
  • the method 110 for managing a satellite network further includes a step of obtaining 114 a predicted capacity of the satellite network, using the network budget built in the previous step.
  • the predicted capacity provided by the network budget may include an estimated power level of one or several of the downlink beams at each of at least one receiving location receiving this particular downlink beam. In this manner, the quality of the received signal at one or more receiving locations, such as the location of a terminal or gateway, can be evaluated for a given test parameter.
  • the obtained estimated power levels may also be compared with a predetermined minimum acceptable power level.
  • the estimated power level available may be an average value or a minimal value.
  • the predicted capacity may be an availability percentage corresponding to the percentage of the time for which the power level is sufficient, at a given receiving location, to provide the services to which the corresponding subscriber is subscribing. This value may further be compared to a minimum acceptable availability. For example, in some circumstances, it has been found that it may be desirable to have an average availability of 99.8% in order to meet the expectations of subscribers as to quality of service in the context of internet services provision.
  • the method 110 for managing a satellite network also includes a step of determining 116 at least one set up parameter of the satellite network based on the obtained predicted capacity.
  • the set up parameter may be an addition of supplementary equipment to the satellite network, or an upgrade of at least one component of the satellite network such as an antenna, a modem or a software application.
  • the equipment added or upgraded may be located at a gateway or terminal of the satellite network. Required satellite configuration changes may also be considered.
  • the obtaining of the predicted capacity of the satellite network gives valuable information as to the requirements necessary to maintain or improve services to subscribers, and allows planning accordingly.
  • the building of the network budget may be performed based on either existing or supposed characteristics of the satellite network.
  • the present method 110 may also be used in a repetitive or iterative manner, for example to obtain a set up parameter such as an equipment upgrade, and then incorporating this upgrade in the network budget to see its effect on the predicted capacity. In this manner, the evolution of the satellite network may be optimized in a well-managed manner instead of blindly.
  • the set up parameter may correspond to a pricing structure for services provided through the satellite network.
  • the method 110 for managing a satellite network could be used prior to the deployment of the satellite network, in a planning phase.
  • the present invention could therefore be used to explore different scenarios for setting up the satellite network and addressing its growth over time.
  • the building of the network budget may be based only on test parameters representing planned or considered characteristics of the future satellite network.
  • this method 120 is used for the optimization of the installation of antennas and related devices of terminals located at subscriber premises, for example in the context of a satellite network as illustrated in FIG. 1.
  • the satellite network may operate at operating frequencies, for example within the C, Ku, Ka and V frequency bands, and is particularly advantageous when used for Ka band satellite networks.
  • the method 120 for optimizing reception first includes a step of building 122 a network budget for the satellite network.
  • the building 122 of the network budget may be similar to the building step 112 already described above.
  • the method 120 for optimizing reception also includes a step of determining 124 a target signal-to-noise ratio for the receiving location, using the network budget built in the previous step.
  • the target signal-to-noise ratio is determined by calculating an estimated power level available in a downlink beam received at a particular receiving location. This may for example involve performing a curve fit of an initial power level available in the downlink beam as a function of the distance of the receiving location from the center of this downlink beam. This curve fit may be performed using a third degree polynomial fit. The impact of power variations affecting this downlink beam on the initial power level available is also estimated. Noise from equipment at the receiving location itself can also be taken into consideration.
  • the target signal-to-noise ratio may be a value automatically outputted by the network budget, as shown in the examples of FIGs. 6A and 6B.
  • a person installing or verifying the installation of a receiver may have access to the network budget from the receiving location, for example through a computer remotely connected to the internet or a private network, and obtain the target signal-to-noise ratio therefrom for this particular receiving location.
  • this person may reach a remote operator via telephone and obtain the target signal-to-noise ratio verbally.
  • the method 120 of optimizing reception also includes a step of optimizing 126 a set-up of the receiver in order to obtain an effective signal-to-noise ratio close to the target signal-to-noise ratio.
  • the effective signal-to-noise ratio corresponds to a value actually measured at the receiver location. By comparing this value to the target one predicted by the network budget, it is possible to make sure that the installation is in fact optimal.
  • optimizing a receiver installation involved measuring the effective signal-to-noise ratio for different orientations of the antenna and identifying a position at which the measured signal was maximal. The antenna was then set to this particular position.
  • This approach leaves a number of uncertainties which may lead to installation problems being overlooked. For example, false maxima may be present in the variation of the effective signal-to-noise ratio as a function of the orientation of the antenna, and the selected orientation may not be the optimal one.
  • the identification of a maximum in the signal-to-noise ratio variation will not bring to light problems in the receiver equipment which may reduce reception evenly for all orientations of the antenna.
  • the method 120 allows the immediate verification of the installation by providing an empirical target value for the signal-to-noise ratio to which the measured effective signal-to-noise ratio may be compared.
  • An error margin may be allowed between the effective signal-to-noise ratio and the target signal-to-noise ratio depending on the degree of precision required in a given installation, on meteorological conditions, etc. This error margin may for example be of the order of 3 dB or less.
  • the orientation of the antenna may be further modified or scanned in order to find the true maximum of the variation of the effective signal-to-noise ratio. Should the problem not be linked to the orientation of the antenna, then the equipment itself may be at fault, and appropriate testing may reveal that a particular piece of equipment may need to be fixed or replaced. In such situations, the source of the problem may simply be a wire which is too long or faulty or wrongly configured software.
  • the method for optimizing reception 120 may be performed during the initial installation of any receiver. It may also be performed subsequently, at least once during a service life of the receiver, at any appropriate point in time. For example, this method 120 may be usefully performed upon report of service difficulties from a subscriber, or at random or periodical service checks.
  • this method 120 may be usefully performed upon report of service difficulties from a subscriber, or at random or periodical service checks.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Astronomy & Astrophysics (AREA)
  • Aviation & Aerospace Engineering (AREA)
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  • Radio Relay Systems (AREA)

Abstract

L'invention concerne un budget de réseau destiné à un réseau satellitaire, ainsi qu'une méthode de création d'un tel budget de réseau. On calcule des niveaux de puissance estimés, pour chaque liaison du réseau satellitaire, en évaluant les niveaux de puissance initiaux de chaque faisceau de liaison montante et de liaison descendante, et en évaluant les variations de puissance qu'ils subissent. L'invention concerne également des méthodes visant à gérer le réseau satellitaire et à optimiser l'installation d'un récepteur, à l'aide d'un budget de réseau.
PCT/CA2006/002110 2005-12-23 2006-12-22 Methode de gestion d'un reseau satellitaire faisant intervenir un budget de reseau WO2007071059A1 (fr)

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CA 2531551 CA2531551A1 (fr) 2005-12-23 2005-12-23 Gestion d'un reseau satellitaire au moyen d'un budget de reseau
CA2,531,551 2005-12-23

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CN114650085A (zh) * 2020-12-21 2022-06-21 诺基亚技术有限公司 改进的上行链路操作

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009033155A1 (fr) * 2007-09-06 2009-03-12 Vt Idirect, Inc. Appareil et procédé de configuration de microstation terrienne (vsat) hautement intégrée
US8379563B2 (en) 2007-09-06 2013-02-19 Vt Idirect, Inc. Highly integrated very small aperture terminal (VSAT) apparatus and method
US9083429B2 (en) 2007-09-06 2015-07-14 Vt Idirect, Inc. Highly integrated very small aperture terminal (VSAT) apparatus and method
US9413425B2 (en) 2007-09-06 2016-08-09 Vt Idirect, Inc. Highly integrated very small aperture terminal (VSAT) apparatus and method
US10587333B2 (en) 2016-12-13 2020-03-10 Inmarsat Global Limited Forward link power control
CN114650085A (zh) * 2020-12-21 2022-06-21 诺基亚技术有限公司 改进的上行链路操作
US12009872B2 (en) 2020-12-21 2024-06-11 Nokia Technologies Oy Uplink operation

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