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11-6-2020

Resiliency by Retrograded Communication - the Revival of Shortwave as a Military Communication Channel

Jan Kallberg Army Cyber Institute, [email protected]

Stephen S. Hamilton Army Cyber Institute

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Recommended Citation J. Kallberg and S. S. Hamilton, "Resiliency by Retrograded Communication-the Revival of Shortwave as a Military Communication Channel," in IT Professional, vol. 22, no. 6, pp. 46-51, 1 Nov.-Dec. 2020, doi: 10.1109/MITP.2020.3029944.

This Article is brought to you for free and open access by the Army Cyber Institute at USMA Digital Commons. It has been accepted for inclusion in ACI Journal Articles by an authorized administrator of USMA Digital Commons. For more information, please [email protected]. Resilience and Reliability

Resiliency by Retrograded Communication-the Revival of Shortwave as a Military Communication Channel

Jan Kallberg and Stephen S. Hamilton Military Academy

Abstract—In the last three decades, the great powers have become increasingly dependent on satellite communication (SATCOM), very high (VHF), and ultrahigh frequency providing high line-of-sight communications. These military communication channels lack resilience because an electronic warfare (EW) campaign can affect both VHF and SATCOM simultaneously. The 1940s preferred spectrum, , with its different propagation patterns, offers an opportunity for military communication resiliency in the 21st century. The concept of retrograding could give an operational advantage and create the ability to sustain communication in EW saturated environment.

& DEFENSE FORCES, COAST guard, homeland and reliant on stable communications providing security, and emergency management agencies ample bandwidth to support operations and have, during the last decades, become dependent information flow within the organization. The cur- rent deployed tactical and operational communi- cation networks are highly dependent upon line- of-sight (LOS) communication utilizing very high Digital Object Identifier 10.1109/MITP.2020.3029944 frequency (VHF), ultrahigh frequency (UHF), and Date of current version 6 November 2020. higher . The information grids are

This work is licensed under a Creative Commons Published by the IEEE Computer Society IT Professional Attribution-NonCommercial-NoDerivatives 4.0 46 License. For more information, see https:// creativecommons.org/licenses/bycd/4.0/ tailored by a network of , datastream, radio early 1800s. The U.S. railway system in 1830 links, and satellite communication (SATCOM), all was 40 miles, and by 1860, 28,920 miles of rail- requiring a near to LOS for sufficient propagation, road been laid down.3 The telegraph lines fol- bandwidth, and transmission quality. lowed the railroads, and during the American Meanwhile, the efforts to disrupt and degrade Civil War, 1861–1865. Both sides used the tele- military communications are equally focused on graph to instruct and command units during the VHF/UHF bands that are prevailing for tacti- the engagement. cal and operational radio and data traffic. Within In comparison to landline, the earlier under- the last decade, especially and , sea cables struggled with extremely low band- have made a dedicated effort to radically width down to a word a minute, which increased improve their ability in electronic warfare (EW) over time. The great powers of the time, the and create effects in the electromagnetic spec- , the United States, , Rus- trum (EMS) in the pursuit to deny or degrade tar- sia, and had in the early 1900s estab- geted communication channels. Parallel with lished land-based networks of telegraph this development SATCOM communication risks stations. At the outbreak of World War One, the have increased as several states developed elec- great powers of the day had outfitted their larger tromagnetic, kinetic, and cyber ability to disrupt warships with wireless telegraphs using low fre- these communications. quency, also called , and medium fre- A potential future conflict with a capable quency, known as , providing near-peer adversary; Russia or China are notable communication 80–200 km between warships. in that they have heavily invested in EMS warfare Due to the size and electricity consumption of capacity, and are capable of employing EW the early wireless telegraph, the military wire- throughout their force structure.1 EW elements less equipment for armies had a limited range, deployed within theaters of operation threaten and the early airborne wireless telegraphs had to degrade, disrupt, or deny VHF, UHF, and SAT- ranges that were less than 2 km. COM communication. The introduction of shortwave in the 1920s In this scenario, high frequency (HF) radio is gave governments, companies, and individuals a viable backup mode of communication. The the ability to communicate over unprece- ability retrograde to HF, commonly referred to dented distances at a low cost.4 The innovation as shortwave, creates resilience in an EW-satu- of more efficient also made it pos- rated operational environment. The HF networks sible to design and produce mobile two-way provide satisfying bandwidth if the focus is to radio.4 During World War Two, the Korean transmit operational information, command, War, and the War in Vietnam, HF was a stan- and control. dard way of communicating that was gradually taken over by VHF during the War in Vietnam. The successful launch of Telstar5 in 1962 and HISTORICAL PATH the evolution of satellite communication during The first globally operating military force, with late 1960 changed the flow of communications.6 a presence on all continents, was the British Army In the early 1960s, HF and cable were utilized to and the Royal Navy. They were instrumental in communication to the U.S. or higher com- the growth of the British colonial possessions. mands in theater. Post-Vietnam and the early Once the British Empire was established, there 1980s, tactical VHF, radio link, and SATCOM was a need to communicate with British colonies were utilized for communication to higher com- and direct a British military presence. This paved mands. From the 1980s, this development the way for financing and incentives to rapidly cre- towards VHF/UHF LOS communications has ate a network of undersea cables that linked the accelerated. Since the early 1990s HF is rarely colonies with Great Britain in the 1850s and utilized by ground forces. Even if HF equipment 1860s.2 The , as a form of domestic is fielded it is seldom used. However, HF con- communication, had followed the unprecedented tinues to be used for limited tasks within increase in transportation infrastructure in the navies and air forces.

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BANDWIDTH ADDICTION battlefield with clarity. Without them, many of our The vast majority of the world’s modern most important military advantages evaporate.” armies’ ability to employ HF radio systems has Even if the U.S. is dominant in military atrophied significantly since the as satellite communication, several other countries NATO, and numerous other countries transitioned are quickly building a spaceborne information to counterinsurgency operations. An era of abun- infrastructure, where Russia, China, and India dant and close-to-uninterrupted bandwidth is com- have taken the lead. ing to an end as the future threat landscape, and The knowledge that the high-bandwidth, potential conflicts will likely involve aggressive almost always available, networks will likely be at EW, counter-SATCOM,7 and anti-satellite meas- least degraded in a future conflict should drive a ures.8 Also, satellites can be destroyed by cascad- cultural shift toward a more frugal usage of com- ing events due to debris from kinetic anti-satellite munication that reemphasizes the exchange to attacks on other spaceborne assets9 or space what is mission essential. debris already existing in orbit.10 In the past, the radiotelegraph operators, and After two decades with the uncontested spec- the organizations that utilized the , trum, the U.S. Armed Forces, and a vast majority solved the lack of bandwidth by compressing mes- of the world’s modern armies, have been used to sages. As an example, “2 GERSUB 10 NM SSW GIB” having available bandwidth, communications, transmitted in a few words reads two German sub- and the ability to switch between communication marines are sighted ten nautical miles South- channels with limited interruption and excellent South-West of Gibraltar. During WW I and WW II quality. The counter insurgency operations have trained radiotelegraphists were able to send and provided rear operational areas with a stable receive information that managed ground, air, and energy supply, enabling the ability to set up satel- naval operations over vast spaces. The notion lite and radio links, and reliable communication that current operations need megabits per second channels to higher commands, air assets, medical in available bandwidth is a sign that today’s resources, and the logistics chain. armies, coast guard, homeland security, and Any potential near-peer adversaries are fully emergency management have grown accustomed aware of our dependence on these communica- to having access to high bandwidth and adjusted tions channels and how the loss of these chan- the processes to require these digital streams. nels would severely impact the modern way of The counterinsurgency battlefield, with bases and warfighting. Satellite communications are espe- forward operating bases with a full array of infor- cially vulnerable for several reasons. First, the mation systems and communication infrastruc- satellites transmit at lower power levels, making ture, close to the area of operation, was able to them easier to jam. Second, weather and space deliver high bandwidth close to the actual engage- weather (solar flares) can negatively impact sat- ment. The HF networks give a reduced bandwidth ellite communications. Third, the compact and for data transfer, even if it as limited as a 1990s fragile design of the satellite itself makes them Hayes 9600 baud dialup modem, but that would subject to failure due to space debris or poten- be enough if the exchange is compressed informa- tially an attack from an adversary’s satellite. tion that is mission essential. The Harris PRC-150 Finally, the satellites can be challenging to HF radio operates at 9600 bits per second using upgrade and could, over time, be vulnerable to the STANAG 4539 NATO standard protocol. cyber attacks. William J. Lynn, III, the former U.S. Deputy Secretary of Defense, stated in the summer of REEMERGED OPERATIONAL 2011:11 “The willingness of states to interfere with ENVIRONMENTS satellites in orbit has serious implications for our The recent change from a strategic focus on national security. Space systems enable our mod- counterinsurgency to near-peer and peer-conflicts ern way of war. They allow our warfighters to also extend the areas of operations. The counter- strike with precision, to navigate with accuracy, to insurgency operational environment allowed the communicate with certainty, and to see the establishment of communication hubs in “safe

48 IT Professional zones” close to the battlefield. Even if these some cases, versions of a particular platform can nations, where counterinsurgency operations differ in the ability to communicate using HF. occurred, lacked a national communications infra- Where the older version had the HF capable structure, the military communication infrastruc- delivered from the factory in the 1990s; mean- ture could be established and sustain the while, the updated version had HF radios operation. As General Milley stated,12 “Many of removed. The removal of HF equipment requires the conditions we have grown accustomed to retrofitting HF ability back into the platform. There over the past 18 years will not exist in future bat- are needs to retrograde by adding, modifying, and tles. Control of the air will be contested; Forward updating the HF capacity in these platforms. Even Operating Bases will not provide a safe haven; if the equipment is fielded to the fighting forma- units will be continuously targeted by enemy fires; tions, the ability across the branches will be frag- and communications and systems will mented and not uniform unless a DOD plan is in be intermittent at best.” place to ensure their compatibility. Apart from the Syrian civil war and the con- flict in Eastern , the conflicts the last two RETROGRADE FOR RESILIENCE decades have had an uncontested spectrum and The Russian investment in EW capabilities is access to VHF/UHF with no adversarial EW significant, and EW units are organic to any Rus- assets present. These conditions will likely sian formation from the brigade combat team change, especially in a peer or near-peer conflict. and higher. This can provide a significant strate- The future operations could occur in areas gic advantage in the early stage of a conflict. The with limited satellite coverage to enable military Russian formations can engage cyber and elec- satellite communication over a military space tromagnetic effects already in the “Initial Period information grid or leased channels from a com- of War,” within the grey zone before there is an mercial operator using mobile satellite services. open conflict.13 In that case, even with no present EW or interfer- The U.S. and allied ground forces can offset ini- ence, SATCOM can be unreliable and intermittent. tial strategic inferiority with airpower, naval power, and global strike abilities, but this is dependent on STATE OF HF (SHORTWAVE) communication channels between ground forces COMMUNICATIONS and joint assets.13 The focus of the adversary’s EW Currently, the competency with HF radio sys- is to deny U.S. communications. One alternative is tems within the U.S. Army is limited; however, to retrograde and utilize HF communications, there is a strong case to train and ensure readi- which was the communication channel of World ness for the utilization of HF communication. Even War II and the Korean War. HF radio waves propa- in EMS-denied environments, HF radios can pro- gate by bouncing off the allowing for vide stable, beyond-LOS communication permit- beyond the LOS communications. Due to the sky- ting the ability to initiate a prompt global strike. wave propagation pattern, it is more difficult for While HF radio equipment is also vulnerable to the enemy to perform spectrum denial. Modern HF electronic attack, it can be difficult to target due equipment is approximately the same in weight to near vertical incident signal propaga- and size compared to VHF equipment and does not tion. This propagation method provides the abil- hinder usage by dismounted troops.14 ity to reflect signals off the ionosphere in an EMS- Even in EMS-denied environments, HF radios contested environment, establishing communica- can provide stable, beyond-LOS communication tions beyond the LOS. Due to the signal path, the permitting the ability to initiate a prompt global ability to target an HF is much more strike. While HF (high frequency) radio equipment complicated than transmissions from VHF and is also vulnerable to electronic attack, it can be dif- UHF radios that transmit LOS ground waves. ficult to target due to near vertical incident sky- One concern is the HF capacity, once seen as wave signal propagation. This propagation obsolete and replaced by VHF/UHF, has been method provides the ability to reflect signals off removed to free up space and lower weight in sev- the ionosphere in an EMS-contested environment, eral fixed-wing, helicopter, and vehicle assets. In establishing communications beyond the LOS

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within a regional area. Due to the signal path, the There is limited competency with HF radio sys- ability to target an HF transmitter is more compli- tems within all the branches; however, there is a cated than transmissions from VHF and UHF radios strong case to train and ensure readiness for the that transmit LOS ground waves. Also, modern dig- utilization of HF communication. Even in EMS ital transmission modes allow for communications denied environments, HF radios can provide sta- to occur at low power levels making it more diffi- ble, beyond-LOS communication permitting the cult for the adversary to detect these signals. ability to initiate a prompt global strike. While HF Alarmingly, as hostile near-peer adversaries radio equipment is also vulnerable to electronic reemerge, it is necessary to re-establish HF alter- attack, it can be difficult to target when configured natives should very-HF, UHF, or SATCOM come to use near vertical incident skywave signal propa- under attack and no longer remain viable options gation. This high-angle take-off propagation for battlefield communications. HF communica- method provides the ability to refract signals off tion has its inherent weaknesses and challenges. the ionosphere in an EMS-contested environment, Common challenges are size and configu- establishing communications beyond the LOS out ration and propagation changes throughout the to 400 miles. Due to the high-angle signal path, the day and night due to changes in the ionosphere. ability to direction find and target an HF transmit- Still, it does not remove the fact that it can provide ter is more complicated than transmissions from communications beyond the LOS, which can serve VHF and UHF radios that transmit LOS ground as an alternative in critical junctures. By stepping waves. Also, Russian listening posts located out- back and being able to retrograde to HF as a resil- side of the 400-mile radius cannot intercept the iency measure, the U.S. is increasing communica- communications. The recent digital modes utilizing tion redundancy. This also adds an asymmetric 3G Automatic Link Establishment (ALE) technology advantage when the adversary has to divert EW allows for digital communication at lower power assets with a different set of requirements to levels than what was previously required for voice. address the HF ability. In addition, this mode simplifies operation by auto- HF radio signals propagate by bouncing off matically selecting the optimal frequency for com- the ionosphere and require more resources to munication to other HF nodes in the network. This disrupt and degrade. The HF propagation pat- technology allows for tac chat messaging along terns would send signals to broader areas, which with digital voice within a 3G ALE network. Using allows for the adversary to hear the signal and lower power is a crucial advantage when trying to direct countermeasures. Still, it also will enable prevent direction finding, and adding encryption to parts of the propagation to pass through enough the digital signal helps prevent signal interception. to get communication established even in a high The HF spectrum offers low-cost opportuni- saturated EW environment. HF jamming equip- ties to increase unit survivability and increase ment requires more energy and has a significant battlefield effectiveness by achieving a stealthier signature, which enables U.S. and NATO neutral- communication channel that potential adversar- izing attacks with stand-off weaponry and anti- ies will have difficulties to find the source of the radiation missiles to be successful. The Russian transmission. HF should be included in any uni- Armed Forces utilize HF communications as t’s communication PACE (Primary Alternate Con- well, and a broad and unrestricted HF jamming tingency Emergency) plan as the emergency can degrade and disrupt their own communica- method at a minimum. The expense to attain an tions. There is also a possibility that the HF improved HF-readiness level is low compared to transmission propagates in a way it cannot be other defense initiatives, yet with a high return heard by the adversary providing undisrupted on investment. In the U.S., the equipment (Harris communication when utilizing low probability of AN/PRC-150) has already been fielded to maneu- intercept and low probability of detection tech- ver units, and foreign forces have similar equip- niques. On the other hand, LOS communications ment already purchased, which enables these have a more narrow propagation channel, which forces to be retrograde to generate resiliency. allows the EW attacker higher certainty that After almost three decades of limited interest communications are denied or degraded. in ground forces’ HF communications, there are

50 IT Professional knowledge gaps to fill to ensure the optimal tech- 5. D. Prouse, “Telstar—The birth of transatlantic satellite niques, tactics, and procedures. Science and tech- communications,” Institution of Engineering and nology have during these decades advanced, Technology Seminar on the Story of Transatlantic therefore there multiple opportunities to cost- Communications 2008, Manchester, 2008, pp. 85–85. effectively enhance and improve the HF communi- 6. D. H. Martin, Communication Satellites. Reston, VA, cation ability, especially pushing targeting data USA: AIAA, 2000. through HF communications. The revival of HF 7. J. C. Wright, Deep Space Warfare: Military Strategy communications as a resilience measure will pos- Beyond Orbit. Jefferson, NC, USA: McFarland, 2019. ture the Joint Force, and its branches, in a state of 8. J. Kallberg, “Designer satellite collisions from covert higher readiness for future conflicts. cyberwar,” Strategic Stud. Quart., vol. 6, pp. 124–136, Spring 2012. CONCLUSION 9. D. J. Kessler, N. L. Johnson, J. C. Liou, and M. Matney, In the last three decades, the great powers “The Kessler syndrome: Implications to future space have become increasingly dependent on satellite operations,” Adv. Astronaut. Sci., vol. 137, no. 8, communication (SATCOM),15 VHF, and UHF, pro- pp. 47–61, 2010. viding high bandwidth LOS communications. 10. J. C. Liou and N. L. Johnson, “Risks in space from These military communication channels lack resil- orbiting debris,” Science, vol. 311, no. 5759, ience because an EW campaign can affect both pp. 340–341, 2006. VHF and SATCOM simultaneously. The 1940s pre- 11. W. J. Lynn, III, “A military strategy for the new space ferred spectrum, HF, with its different propagation environment,” Washington Quart., vol. 34, no. 3, pattern, offers an opportunity for military commu- pp. 7–16, 2011. nication resiliency in the 21st century. 12. Department of the Army, A message to the Force from the Secretary of the Army, Chief of Staff of the Army, and Sergeant Major of the Army, “Army senior leaders ACKNOWLEDGMENTS send - lessons from D-Day,” Jun. 6, 2019. We acknowledge the generous support of 13. J. Kallberg, S. S. Hamilton, and M. G. Sherburne, insights, technical, and operational knowledge “Electronic warfare in the suwalki gap: Facing the of HF, shared by Major Matthew G. Sherburne, Russian “accompli attack”,” Joint Forces Quart., U.S. Army, 1st Cyber Battalion, Cyber Protection vol. 97, pp. 30–38, Second Quarter, 2020. Brigade, Fort Gordon, . The views 14. R. L. Edmonson et al., “Tactical employment expressed are those of the authors and do not considerations of HF radios in the cavalry squadron,” reflect the official policy or position of the Army Cyber Defense Rev., vol. 4, no. 1, pp. 23–32, Spring 2019. Cyber Institute at West Point, the U.S. Military 15. P. J. Nicholas, J. C. Tkacheff, and C. M. Kuhns, Academy, or the Department of Defense. “Measuring the operational impact of military SATCOM degradation,” in Proc. IEEE Winter Simul. Conf., 2016, & REFERENCES pp. 3087–3097. 1. Department of the Army, TRADOC Pamphlet 525-3-3, Military Operations—The US Army in multi-domain operations 2028”, US Army, Nov. 27, 2018. Jan Kallberg, Ph.D., is currently a Research 2. D. Lindley, Degrees Kelvin: A Tale of Genius, Scientist with the Army Cyber Institute at West Invention, and Tragedy. Washington, DC, USA: Point and an Assistant Professor with the U.S. Mili- Joseph Henry Press, 2004, p. 114. tary Academy, West Point, NY, USA. Contact him 3. H. C. Adams, Report on Transportation Business in the at [email protected]. United States at the Eleventh Census: 1890, vol. 2. Washington, DC, USA: GPO, 1894. Stephen S. Hamilton, Ph.D., is currently the Chief 4. P. M. Hawkins, “The development of of Staff with the Army Cyber Institute at West Point in the 1920’s and 30’s,” in Proc. and an Academy Professor with the U.S. Military Acad- Int. Conf. 100 Years Radio, 1995, pp. 147–152, emy, West Point, NY, USA. Contact him at stephen. doi: 10.1049/cp:19950805. [email protected].

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