Data rate change algorithms for efficient HF communications

There has been a re-newed interest for frequency adaptive HF systems due to the reliable and fully automatic cost-effective voice link and message transfer they can provide. An important requirement for general market acceptance is the existence of a standardised platform, though. This is available in the form of the U.S. MIL-STD-188-141A/FED-STD-1045A standard, popularly referred to as the Automatic Link Establishment (ALE) standard. However, as can be seen from the build-up of other information transfer system (e.g. the Intemet), it is difficult to estimate the sufficient throughput capacity needed to be provided. When store-and-forward type traffic, such as e-mail, became a regular means of communication the overall traffic load broke (and still does) every capacity increase plan made. Therefore it is important to take such (expandability) effects into account when designing automated HF networks. This paper proposes a synchronous scanning scheme which would still enable full compatibility with the current (asynchronously scanning) ALE standard. The proposed scheme makes it possible to use more frequencies which can be dynamically exchanged, thus providing increased resilience to interference and varying propagation conditions. The proposed scheme ought also to be comparably easy to implement since it does not impose any higher performance or implementation requirements than the asynchronous scheme. In fact, a network may consist of both asynchronous stations and synchronous stations.

The author describes an attempt to use HF automatic link establishment (ALE) radio equipment as a ship-shore sounder in the Mediterranean Sea. The method selected as potentially most effective for HF channel selection purposes was a state-of-the-art HF ALE radio system. This system consists of fully automatic microprocessor-controlled HF radio transceivers incorporating the ALE control protocols and waveform specified in MIL-STD-188-141A. The primary result of the test was that the use of the HF ALE radio system as a sounder to support VFCT (voice frequency carrier telegraph) HF terminations provided no operating advantage in the Mediterranean operating areas. It is concluded that, in spite of the inability to find a ready solution for HF communications in the Mediterranean, this was a very successful test. The ALE radio system performance data obtained provides a first real-world glimpse at how MIL-STD-188-141A might serve the navy in future automated HF communications system. >

Internet based applications are mostly based on a reliable transport service. TCP (transmission control protocol) is one of the protocols responsible for applications performance. Mobile users access to Internet services through 2.5 and 3 Generation networks, which have a significant latency due to error mechanisms introduced at the link layer, as well as transmission delays in the radio access networks. High latency produces interaction with timers of upper protocols. Data rate is other limiting characteristic on these networks. Moreover, data rate changes during a TCP connection due to mobility. TCP can adapt its rate when slow data rate changes thanks to its self-clocking propriety. In case of a sudden change, TCP performance is degraded due to spurious retransmission, and the activation of its congestion control mechanisms. This paper will show the effects and optimization of some TCP parameters over GPRS (general packet radio service) and 802.11b real networks.

In order to solve the high bit error rate (BER) caused by rate oscillation in traditional Data Rate Change (DRC) algorithm, an improved DRC algorithm based on Adaptive Frame Length (AFL) was proposed. Firstly, the frame length and transmission rate of the initial transmission were determined by the parameters of the current channel and the information of previous empirical values. Then, if two frames with the same length were successively sent in the transmission process, the frame length would be accordingly increased. If the retransmission failed twice in a row, the frame length would be halved in the next transmission. Finally, the frame error rate was calculated based on the current frame length. The data rate would be updated If the value was less than the present threshold. Compared with RapidM DRC, the average bit error rate of the link decreased by 4.8 percentage points, and the link availability increased by 10 percentage points. The experimental results show that the proposed algorithm can eliminate the rate oscillation and improve the communication capability of the HF communication system.

The phase 1 upgrade of the ATLAS [1] pixel detector will be done by inserting a fourth pixel layer together with a new beampipe into the recent three layer detector. This new detector, the Insertable B-Layer (IBL) should be integrated into the recent pixel system with as few changes in services as possible, but deliver some advantages over the recent system. One of those advantages will be a new data transmission link from the detector modules to the off-detector electronics, requiring a re-design of the electro-optical converters on the off-detector side. First ideas of how to implement those, together with some ideas to reduce cost by increasing the systems throughput are discussed.

The application of the automatic link establishment (ALE) procedures of MIL-STD-188-141A, combined with improved signal processing technology found in advanced modems, provides the basic elements to create adaptive high frequency (HF) radio networks. Dynamic changes in ionospheric conditions and noise fluctuations make the HF network a hostile one, where links between nodes are subject to frequent failure. The addition of adaptive routing and information management enhances network robustness in this environment. This suggests the use of a distributed routing algorithm in which convergence to the shortest path is of primary concern. However, routing decisions derived from such distributed processes exhibit an inherent uncertainty due to the randomness of link failures and the latency of network performance information. The authors describe predictions of a computer simulation of a wide area HF radio network that invokes ALE procedures, adaptive routing, and information management protocols. Aspects include the impact of modem interleaver delay time, encryption synchronization delay, management overhead, and message handling on throughput and network latency. Recommendations are presented with respect to the application of statistical neural processing to improve network management in this environment. >

It is difficult to recognize Automatic Link Establishment (ALE) behaviors of a short-wave radio station, if we do not acquire the radio station's communication protocol standard. A method is proposed to recognize different ALE behaviors by using an improved unidimensional DenseNet. In this work, we directly recognize ALE signals in physical layer without the radio station's communication protocol standard. Hence, we can avoid difficulties in demodulation, decryption and so on. Actually, the original DenseNet is used extensively in the field of computer vision, so the original DenseNet is firstly adapted for the unidimensional input. And then, two parallel dense blocks are used in our improved unidimensional DenseNet, which could improve the capability of network to extract ALE signals' deep features. The experimental results show that the proposed method is able to recognize different ALE behaviors of a short-wave radio station. And improved DenseNet has better recognition performance than simple DenseNet. The simple DenseNet only contains one dense block. Finally, the results of comparison experiments also show that some classic networks have worse performance in ALE behaviors recognition, such as LeNet-5, ResNet-34, and DenseNet-121.

The US Navy has all but ceased to use high frequency (HF) radio for long-haul ship-shore communications. Satellite systems have rightfully assumed this role, but the antiquated nature of the Navy HF system has soured planners on even considering HF for supplementary uses or other roles. In an attempt to dispel this undeserved reputation and gain operating experience for application of automation to new shipboard HF systems, an HF radio communications system incorporating automatic link establishment (ALE), single-tone serial modems and 500-watt transceivers was deployed on USS TARAWA (LHA-1) and to serving Navy shore communications stations during her recent deployment to the Indian Ocean and Persian Gulf. The authors describe the use of this system for bidirectional 600 baud message traffic. This is the first application of the combination of MIL-STD-188-141A ALE and MIL-STD-188-100A single tone serial modem technology in a US Navy operational environment. The ALE radio system was used to automatically test and select the best channel from among several assigned frequencies and establish a link between ship and shore. Accumulated message traffic was then passed over the single-tone serial modem to the distant end. Technical details of the installation and operational techniques are presented along with a discussion of how automation greatly reduced the level of skill and experience needed to successfully operate this HF system. Test results are presented which illustrate the success enjoyed in maintaining communications over paths which had long been considered unworkable with existing shipboard HF equipment and techniques. The potential for application of automated HF to short-range over-the-horizon (OTH) communication needs for littoral warfare is also discussed. >

Traditionally, high frequency (HF) communications have been difficult to manage efficiently, mainly due to the variable nature of the propagating conditions. An automatic radio control system (ARCS) consisting of automatic channel selection (ACS), automatic link establishment (ALE), and automatic link maintenance (ALM) will provide an automated system which will alleviate operator workload and improve communications availability at HF. Effective network management is fundamental to such a system. Computer modelling and simulation is a powerful method for testing the suitability of parameter values and how they affect the operation of a communications systems. Various networks can be simulated highlighting the shortcomings and also the positive aspects of each configuration. This paper describes the current status and capabilities of a computer based ARCS network simulation designed to be used as an aid to developing the ARCS specification. It also presents some initial results.

Nowadays, vehicles are not only merely used as a transportation medium, but also as a highly mobile Internet of Things (IoT) node, collecting data from all types of sources. The delivery of aggregated vehicle sensor data into the cloud for further analysis is very fragile, as vehicles move fast in their environment and channel conditions vary heavily. Next to mastering possible packet loss, communication protocols need to quickly adapt to the frequent data rate changes. Random Linear Network Coding (RLNC) has been proven as an efficient and robust mechanism for reliable data transfer especially on lossy channels. In this paper, the authors extend the Scalable Network Coding (ScalaNC) framework with the novel congestion control Bottleneck, Bandwidth and Round-Trip Time (BBR) in order to quickly adapt to the frequent changes in data rate and allow effective transfer of high amounts of data from vehicles and into the cloud. ScalaNC is validated in a Hardware-in-the-Loop field test consisting of a Long Term Evolution (LTE) base station and channel emulator.

The complexity and variability of streaming data have brought a great challenge to the elasticity of the data processing systems. Streaming systems, such as Flink and Storm, need to adapt to the changes of workload with auto-scaling to meet the QoS requirements while saving resources. However, the accuracy of classical models (such as a queueing model) for QoS prediction decreases with the increase of the complexity and variability of streaming data and the resource interference. On the other hand, the indirect metrics used to optimize QoS may not accurately guide resource adjustment. Those problems can easily lead to waste of resources or QoS violation in practice. To solve the above problems, we propose AuTraScale, an automated and transfer learning auto-scaling solution, to determine the appropriate parallelism and resource allocation that meet the latency and throughput targets. AuTraScale uses Bayesian optimization to adapt to the complex relationship between resources and QoS, minimizing the impact of resource interference on the prediction accuracy, and a new metric that measures the performance of operators for accurate optimization. Even when the input data rate changes, it can quickly adjust the parallelism of each operator in response, with a transfer learning algorithm. We have implemented and evaluated AuTraScale on a Flink platform. The experimental results show that, compared with the state-of-the-art method like DRS and DS2, AuTraScale can reduce 66.6% and 36.7% resource consumption respectively in the scale-down and scale-up scenarios while ensuring QoS requirements, and save 13.5% resource on average when the input data rate changes.

The author explains the various features and capabilities within the PropMan system that enable quick and comprehensive personal computer (PC)/laptop HF frequency-management analysis and tradeoffs. The evolving propagation resource manager PropMan provides a comprehensive, quick, and user-friendly process for making HF channel allocations. It is noted that PropMan can encompass the expertise necessary to eliminate many of the blatant errors typical of HF misuse. This expertise can be applied at two levels: frequency assignments and in-the-field operator support. Applying PropMan to the communications mission to generate an ALE (automatic link establishment) scan list and using ALE automation significantly enhance HF communications and facilitate effective utilization of frequency assets. >

This paper examines existing automatic link establishment (ALE) techniques for high frequency (HF) radio systems, identifying areas of improvement in calling techniques and protocols for ALE. Automated HF radio systems improved in these areas have been implemented, and results of these implementations are presented. Compromises between link establishment time and reliability are also considered.

The SoDark cipher is used to protect transmitted frames in the second and third generation automatic link establishment (ALE) standards for high frequency (HF) radios. The cipher is primarily meant to prevent unauthorized linking and attacks on the availability of HF radio networks. This paper represents the first known security analysis of the cipher used by the second generation ALE protocol—the de facto world standard—and presents a related-tweak attack on the full eight round version of the algorithm. Under certain conditions, collisions of intermediate states several rounds into the cipher can be detected from the ciphertext with high probability. This enables testing against the intermediate states using only parts of the key. The best attack is a chosen-ciphertext attack which can recover the secret key in about an hour with 100% probability, using 29 chosen ciphertexts.

The future wireless communication systems ought to offer high spectral efficiency and flexibility to carry multimedia services with variable rate requirements. The data rate change should be made scalable, continuous and real‐time based to match exactly to what required in different content for conservation of precious bandwidth. The rate change in multiples of two, as implemented in the UMTS W‐CDMA standard, is clearly undesirable. In particular, the multiple access technique itself should support asymmetrical traffic in up‐ and down‐links to fit different connection modes of Internet‐based applications. This paper is to propose an innovative CDMA architecture based on complete complementary (CC) codes, which can address all above concerns. The architecture makes use of ‘offset‐stacked’ spreading modulation, based on which both high spectral efficiency and flexible rate matching are guaranteed. The proposed CC–CDMA system can support continuously alterable data rates, which can match exactly to the user demand without the need of complex ‘rate‐matching’ algorithms. Copyright © 2003 John Wiley & Sons, Ltd.