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- Journal of Optical Communications and Networking
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Journal of Optical Communications and Networking
Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. The Air Force is becoming a network-enabled paradigm, wherein many of its capabilities will be generated through, and dependent on, the integrated efforts of multiple components.
This approach to operations is expected to result in greater agility and attendant tactical advantages. However, as is the case with any untested concept, there is a need for technology that enables the analysis and execution of the new paradigm. In this case, the scope of change is extremely large, requiring reanalysis of force structures, doctrine, acquisition options, command-and-control systems, training, and long-range planning, not to mention the considerable challenges involved in engineering, constructing, and managing the actual networks.
Much of the planning and analysis will depend on the research described in this chapter, which will provide the necessary conceptual and technical foundation. Network-centric warfare also is critically dependent on software, the subject of Chapter 4 , on the effective distribution and management of information throughout the network, which is the prime topic of Chapter 5 , and on the effective employment of that information, which is considered in Chapter 6.
Figure shows the range of components that will be networked in the future Air Force. The following capabilities are key to achieving the desired functionality, but off-the-shelf technologies are not yet adequate:. Robust dynamic tactical networks support 10, to , communicating devices in theater.
The network must provide robust data and circuit services to tens or hundreds of thousands of fixed and mobile users with different service levels. Some of the service challenges include guaranteed rates, communication over difficult channels, hard time-deadlines, reliable message delivery over unreliable networks, security, and policy-driven resource allocation explained below. Sensors in the networks must be able to relay data while maintaining coherency, and there must be high compression of correlated sensors to reduce communication needs.
Laser communication must be available between satellites and aircraft and to terrestrial sites. Satellite services must be available to mobile and fixed users. Those services must 1 maintain connectivity at all times and track important users, 2 have low probability of detection LPD , low probability of intercept LPI , and antijamming AJ capabilities, 3 be secure, and 4 support very small as well as large terminals.
Wireless radio services must be available in the field without pre-existing infrastructures, and they must be secure, power-efficient, have LPD and LPI, have AJ capabilities, and be able to maintain connectivity with important users. The satellite, radio, and wireless networks must be integrated with a high-bandwidth, affordable, and secure terrestrial fiber network as one supernetwork.
The network must be an integrated one with multilevel security, data delivery within deadlines, and the capability for rapid reconfiguration and adaptation. With the possible exception of power efficiency and some aspects of security, all of these characteristics are primarily driven by defense needs, and they will not be advanced by the commercial sector.
The remainder of this chapter describes some of the technical challenges of future communication modalities planned for the Air Force and the performance of networks when they are connected together in military settings.
It concludes with recommendations of particularly important basic research areas that typically cut across multiple challenges. Defense applications have to contend with communication modalities that are not encountered in commercial and civilian settings.
Radio channels, especially those associated with mobile platforms, have rapidly changing link capacities and connectivities, with disconnections or dropouts that can be on the order of minutes or more. In contrast to this dynamism, traditional layer 3 Network Layer and layer 4 Transport Layer protocols assume fairly stable underlying substrates that change, if at all, over the course of minutes—that is, much more slowly than most transmissions.
Recent applications have shown these traditional protocols often yield low throughputs and poor quality of service when applied to DOD systems. In some cases, these protocols do not work at all despite valiant efforts to provide patches. Thus, the main challenge of Air Force communications is to provide assured connectivity between networks albeit at varying rates under difficult channel conditions, including during adversarial attacks.
A cost-effective investment strategy is to make maximum use of commercial technologies. However, not all the services listed above can be supported by commercial technologies. In many cases, commercial architectures only need to be modified, but in some cases completely new designs are needed. One communications challenge is the need for source compression methods when multiple sensors collect correlated observations, whether or not this was done in a coordinated manner. This is critical in order to fit the large volumes of sensed data in modest network capacities, especially in difficult communication environments.
Particularly challenging is the identification and compression of highly correlated data in the absence of fine coordination among sensing platforms.
This will require both lossless and information-lossy compression and new approaches to measuring signal fidelity tailored to battlefield signals. Another challenge lies in creating joint source-network coding: The separation theorem, which for point-to-point communication channels allows one to decouple source and channel coding, does not apply to networks of Air Force interest, where the data volume itself may cause packet loss due to congestion.
It is important to explore the joint consideration of coding for both source compression and network transport from layer 1 to layer 4. A better understanding of capacity limits is needed in order to design the best architectures for Air Force communications systems, which. The open-air satellite, radio, and optical channels planned for the Air Force exhibit fading, dispersion, and interference benign and adversarial not typically encountered in well-known classical channels, especially when the channel is broadband.
For these channels, there are many different ways to design the communication system, and good system design will depend on understanding the channel effects and the fundamental limits of communication performance optimized over the class of possible architectures.
Our current understanding of the fundamental limits of these channels is only rudimentary, and the space of communication designs has yet to be fully characterized and optimized. There are also open questions related to the capacity limits of multiple-access channels with or without coordination.
Multiple-access techniques for open-air channels, such as satellite and battlefield radio channels, are extremely important for good communication performance. Classical techniques must be reconsidered in a context that includes adversarial jamming, interference, coupling, and little or no coordination with some key inputs such as the satellite channel. Classical information theory articulates the limits of communication capacities with no specific attention paid to the transaction delay of the session.
In fact, most results are asymptotic, taken as the delay becomes large. In contrast, some critical Air Force applications are very delay sensitive, and a theory for the fundamental capacity limits of a communication system with delay constraints needs to be developed. In some applications power efficiency is also required.
Classical communication and information theories do not incorporate an element of adversarial attacks, although some results related to LPD, LPI, and AJ communications were developed 40 years ago. The technology assumptions underlying those results have changed, of course, and none of the results were obtained with networking in mind. For instance, networks using open-air interfaces present a new set of vulnerabilities that can be easily exploited by adversaries.
It is important to understand the set of possible technologies and techniques available to adversaries and to design the network with those in mind rather than treating them as an afterthought. Game-theoretic and optimization techniques will likely be relevant approaches, as will methods for authentication and cryptography. Free-space optical communications in space is relatively well developed, though its capabilities for terminal spatial tracking systems and the weight and power demands of the systems can be improved using more.
The current sensitivity of the best receivers direct or heterodyne detection available in prototype form requires received photons per bit. With the advent of solid-state, single-photon detectors, a photon counting receiver can achieve bits per received photon.
A fundamental investigation into the best combination of modulation and coding under technology constraints could lead to large payoffs for Air Force space and aircraft systems. These systems are important for aircraft and ground applications. For supersonic platforms, the bow shock presents even bigger challenges than atmospheric turbulence owing to its speed, which is three orders of magnitude higher.
The current mainstream receiver uses adaptive optics to compensate for phase-front distortion, which gives rise to fading and other undesirable channel effects. While its performance is adequate, the solution is costly and heavy. The Air Force should pursue new system techniques, such as spatial-, temporal-, and frequency-diversity receivers in both coherent and incoherent forms, to mitigate the turbulence effect.
The Air Force needs more energy-efficient communications for two reasons. The second is that some operations may be conducted with ground mobile radios, where battery conservation is very important. The first problem can and should be addressed as part of the research outlined above aimed at developing capabilities for efficient communications for difficult channels and under attack.
The second includes efficient signal processing and higher-layer network protocols, which will be addressed below in the discussion of sensor networks. Recent developments in the new applications of communication networks often require that information be processed in a distributed fashion in real time.
For example, in a sensor network, a relay node often needs to forward a received signal without being able to decode the embedded message reliably; when controlling a dynamic system, decisions often need to be made based on noisy observations. Conventional information theory, which is based on the concept of reliable communications and. The theoretical understanding of how to handle information without the error-free guarantees is therefore important for future developments of highly dynamic and distributed network applications.
The study of communication systems with partial or list decoding using a layered coding structure could be the first concrete step in this direction. The theory of networks has not matured to a point where one can predict how well the protocols developed heuristically in one application setting will perform on a communication network built on radically different communication modalities.
To deal with the new and complicated modalities of importance to the Air Force, fundamental tools must be developed to help understand how networks may perform in new environments and to optimize architectures. It is simply too costly to develop these architectures and protocols ad hoc and then experiment with the communication links in the field.
In addition, there are many possible ways to configure a communication system. If a communication system is going to be used as part of a network, it should be designed jointly with the network and not independently.
For example, end-to-end reliable data delivery can be a function of the communication system using diversity receivers and error-correcting codes , or it can be a function of the network using diversity path routing and automatic repeat requests at various layers such as the Data Link Control Layer and the Transport Layer.
The Air Force needs a global broadband fiber network to interconnect its multiple modalities and act as the high-speed backbone. Current networks, such as the Global Information Grid GIG , use commercial technologies with wavelength-division multiplexed optical transport and electronic packet switching.
This technology is both costly it does not scale well to very high data rates and insecure. For terrestrial networks there is a burning need to create economical new optical transport mechanisms such as optical flow switching dynamically set up with short-duration connections on demand with lightweight protocols and also a security architecture for both the Physical Layer the transport mechanisms and the higher layer protocols. Routing over the Internet today is purposely set to change rather slowly to prevent oscillations and overreactions to sudden rate surges.
In contrast, most of the channels used by the Air Force can experience rapid changes in connectivity and link capacities due to random channel effects, mobility, and adversarial attacks. Thus, most routing protocols in use today cannot keep up with such changes nor can they provide effective congestion and flow control.
To create better protocols it is important first to understand the fundamental effects on the Network Layer of these fast dynamics. For example, mobile networks especially those that support high data rates and time-deadline services are not well served by conventional commercial protocols, which are mostly designed for static or quasi-static network topologies.
Many of these dynamics appear first in the Physical Layer and permeate up the protocol stack. The mobility aspect calls for the joint design of the Physical Layer and the higher layers, including routing and the Transport Layer. The development of fundamental mathematical tools is a prerequisite to the understanding and solution of this very important problem. The task of providing error-free, end-to-end delivery of messages in a network is jointly shared by the Data Link Control Layer layer 2 and the Transport Layer layer 4.
For random channels especially those in mobile networks , these two layers interact in ways that are stochastic and not yet well understood; the interactions often result in drastically reduced throughput. Researchers have not yet succeeded in predicting the performance of specific implementations and determining the fundamental limits of these protocols when coupled with random channels. The answer might come from control theory and stochastic system analysis. Current Transport Layer protocols assume a stable Physical Layer communication infrastructure, so packet losses are typically interpreted as buffer overflow at routers due to congestion.
In the random channels with which the Air Force has to deal, packet losses can also be due to path fades or intentional interference by an adversary. Some of these effects can be very fast owing to the mobility and agility of electronic attacks. The Transport Layer Protocol will react poorly to these effects, resulting in very low network throughput. This is plaguing many current DOD programs.
Satellite Communication Network Design and Analysis
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Accordingly, we proposed packet -and-circuit network convergence pac. Network Analysis, Architecture, and Design, Third Edition, uses a systems methodology approach to teaching these concepts, which views the network and the environment it impacts as part of the larger system, looking at interactions and dependencies between the network and its users, applications, and devices. The Network Planning and Optimization enables CSPs to manage telecom network planning, design and optimization processes comprehensively and efficiently. Described are the fundamental concepts of the processes of network analysis, architecture, and design; systems and services; as well as their characteristics and prepares the reader for the analysis process.
Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Satellite Communication Network Design and Analysis Abstract: This authoritative book provides a thorough understanding of the fundamental concepts of satellite communications SATCOM network design and performance assessments. You find discussions on a wide class of SATCOM networks using satellites as core components, as well as coverage key applications in the field. This in-depth resource presents a broad range of critical topics, from geosynchronous Earth orbiting GEO satellites and direct broadcast satellite systems, to low Earth orbiting LEO satellites, radio standards and protocols. This invaluable reference explains the many specific uses of satellite networks, including small-terminal wireless and mobile communications systems.
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