George F. Elmasry

A comparative review of commercial vs. tactical wireless networks

This article presents a comparison between commercial and tactical wireless networks, pointing to their different requirements, expectations, needs, and constraints for information assurance and so on. This comparative study demonstrates why commercial wireless networks have made more technological leaps than tactical wireless networks. The article introduces a model for tactical wireless networks based on the architectures that have been pursued (especially the Joint Tactical Radio System and the Future Force vision) within the last decade or so. The model draws parallels with commercial wireless networks to allow tactical wireless networks a plausible opportunity to achieve similar technological advancements.

Partitioning QoS management for secure tactical wireless ad hoc networks

Addressing quality of service in military wireless ad hoc communication networks involves unique challenges due to imposed tactical requirements and,conditions, such as heterogeneous traffic with stringent-real-time and survivability requirements, mobile wireless nodes in hostile environments, and limited spectrum availability. Encryption adds another layer of complexity because of the partitioning of the network into plain text (unencrypted) and cipher text (encrypted) parts that, by definition, cannot communicate QoS information to one another. A typical communication shelter is composed of unencrypted LANs connected to a packet-encrypted backbone network. This article presents a partitioned QoS approach, focusing on QoS management at the unencrypted LAN that complements QoS management done at the encrypted backbone. Some of the unencrypted LAN QoS techniques being considered for the Warfighter Information Network-Tactical (the future Army tactical backbone network) are outlined.

A measurement-based approach for multilevel admission of heterogeneous traffic in wireless ad-hoc networks

General dynamics C4S has developed a QoS solution for the Armys warfighter information network tactical (WIN-T). This solution is also being applied to other QoS applications in tactical networks. When using an encryption device, any information exchange between the LAN where call admission control (CAC) decisions are made, and the WAN where traffic shaping is made is prevented by the encryptor. This solution was developed and tested using OPNET modeler. The core of this solution is a measurement based admission control (MBAC) type algorithm. This MBAC algorithm regulates the flow of heterogeneous traffic entering a tactical wireless ad-hoc network based on a computed end-to-end congestion level. Traffic can be of different types (voice, video and data) and have multiple levels of importance (survivability) and different real-time requirements. The algorithm prioritizes the admission of calls/sessions (at a source node) based on the QoS attributes of each class of service and the condition of the path to the destination node.

Adaptive RS codes for message delivery over an encrypted mobile network

The authors present a hybrid automatic repeat request technique using adaptive Reed-Solomon (RS) codes with packet erasure. This technique suits the transport layer in tactical mobile wireless networks with type I encryption, where encryption erasures the entire Internet protocol packet. The novelty of the presented technique is the multifaceted optimisation of Reed-Solomon codes at the transport layer for delivery assurance, speed of service (SoS) and network throughput. With this technique, the transport layer in tactical networks can meet the stringent requirements of quality of service imposed by the tactical network user, even under adverse conditions. These requirements define a high level of reliability (delivery assurance), a specific SoS and optimum use of the limited bandwidth (BW) of the wireless network, where the probability of packet erasure can be very high. The provided probabilistic analysis shows that focusing on network throughput alone will result in violating SoS and delivery assurance requirements. On the other hand, focusing on SoS and delivery assurance requirements can result in poor network throughput. The multifaceted optimisation technique, which utilises hybrid ARQ for message delivery, is described using a homogeneous Markov chain.

The progress of tactical radios from legacy systems to cognitive radios

This article gives a tutorial about some critical milestones regarding the journey of tactical radios from legacy systems to cognitive radios. Although tactical radios have been in use for over 100 years, this tutorial focuses on the post- Vietnam War radios and uses examples from the U.S. Department of Defense major acquisition programs. The article considers legacy radios to be the generation of radios that was initiated by the U.S. Department of Defense in the 1970s that had spread-spectrum and frequency-hopping capabilities to resist jamming. The Link-16 system is covered in this article as a benchmark for legacy radios. Two major technological leaps came after these legacy radios. First was the software defined radios initiative, which brought about the ability to develop waveforms entirely in software in the absence of a defined hardware platform. As a result, different waveforms can be ported into the same hardware platform. This article presents the Wideband Networking Waveform, which is a complex waveform developed under a U.S. Department of Defense program, as a software-based waveform that can be downloaded into different hardware platforms. The next technological leap came with cognitive radios, which have the ability to sense their environments and adapt intelligently to the dynamics of the war theatre.

Bottleneck discovery in large-scale networks based on the expected value of per-hop delay

To relieve congestion in a large-scale network, it is crucial to identify the links, which contribute most to the congestion and then take action to relieve it. This paper presents an algorithm for detecting bottlenecks in a congested large-scale packet-switched network. The strongest bottleneck candidate for a congested session is not necessarily the session link with highest percent utilization or the link with the lowest capacity, but rather the session link with the highest expected value of delay - provided that this links expected value of delay is significantly greater than the average delay for all links in the session. The approach is based on estimating the per-link expected value of delay (transmission plus queuing) and turning this expected value to a per-link weight. Based on this per-link weight and information collected from an end-to-end QoS monitoring mechanism, the algorithm points to the bottleneck hop where congestion likely occurred. To alleviate congestion, the following actions may be taken: redirect traffic, increase the bottleneck link bandwidth (if possible), implement aggressive traffic shaping, and/ or throttle low priority calls/sessions using the congested link.

ECN-Based MBAC algorithm for use over HAIPE

This work addresses the development of an ECN-based MBAC algorithm for use over HAIPE. The proposed MBAC resides at the red enclaves, but leverages the ECN, which is defined in RFC 3168 and can be activated at the existing black routers. With these MBAC capabilities, ad-mission control policies are generated at the red enclaves to react to the black core congestion without the need to pass information from the black core to the red enclave, which would violate HAIPE requirements. The presented technique adheres to HAIPE 3.1 specifications and creates no extra overhead traffic or breaks the red-black boundaries defined by the HAIPE standards. The advantages of the capability are demonstrated through a hardware test-bed.

Partitioned QoS solution for tactical networks - addressing the of encryption

This paper presents a QoS solution for tactical networks with security consideration. Since encryption prevents the exchange of QoS information between the cipher text side and the plain text side, a partitioned QoS approach is presented. We present measurement based admission control (MBAC) as part of the plain text side QoS solution. MBAC uses real time measurements to regulate the flow of traffic entering a tactical core network based on a computed end-to-end congestion level. This paper discusses the benefits of using MBAC and the possible challenges of such an approach. The paper shows how the measurements can be used to create a Markov chain indicating the severity of path congestion. The paper also presents some simulation results from implementing MBAC in an OPNET model of the warfighter information network-tactical (WIN-T) network

Enhancing TCP and CAC Performance Through Detecting Radio Blockage at the Plain Text Side

Encryption partitions tactical networks into plain text and cipher text sides, and information exchange between these two sides is severely restricted. This paper presents a QoS edge technique, on the plain text side, for detecting radio blockage due to foliage and terrain. Detected blockage can be used to enhance Call Admission Control (CAC) policies by distinguishing between blockage and congestion. Similarly, by distinguishing between blockage and satellite or Link Layer induced delay, this technique can aid decision making as regards the use of a TCP proxy. This detection technique does not preclude but rather complements other blockage mitigation techniques on the cipher text side (e.g., link layer ARQ).

Capacity analysis for large-scale packet-switched wireless networks based on expected value of delay

This paper describes a capacity analysis and planning tool developed for large-scale packet-switched wireless on the move (OTM) tactical networks. The tool uses a novel technique to analyze and evaluate the different phases of the network topology in a rapid and robust matter. Analysis of the network topology identifies links where congestion is likely to occur and links that are underutilized. Well-optimized links can also be identified. Based on these analyses, statistics can be collected to reflect the utilization state of a planned topology and traffic scenario at different phases of its deployment.