Research Overview
This project aims to enable intelligent and autonomous adaptation of the military mobile communication system to the situational changes at the tactical edge. The driving research methodology is an unique social-aware perspective, which intertwines mobile communication networks and human
social networks at the tactical edge and interprets warfighters' situational response to the heterogeneous battlefield contexts as their social dynamics. We define social dynamics as the temporal and spatial variations of the social relationship among warfighters, and realize adaptivemobile networking through investigation, formulation, and exploitation of these social dynamics.
Current mobile communication systems used by the Army have limited adaptability. These systems operate based on the fixed communication strategies that are configured during the tactical mission planning. It is difficult for them to autonomously maintain warfighters' situational awareness over heterogeneous battlefield contexts. The major factor hindering such adaptability in tactical mobile communication is the practical Disconnected, Intermittent, and Limited (DIL) network environment at the tactical edge. Environmental dynamics and warfighter mobility lead to opportunistic and intermittent network disconnection, and warfighters only communicate when they move into the communication range of others' wireless radios, referred to as contact. Traditional MANET protocols will experience seriously amplified delay or even fail due to these disconnections and unavailability of end-to-end routes.
To deal with the lack of end-to-end network connectivity in DIL environments, existing research adopts the idea of "carry-and-forward", where a node carries data when no route to the destination exists, and later forwards data to a new node (relay) that it contacts. Then, the key networking problem becomes how to design the appropriate relay selection strategy, and researchers have developed different utility metrics for relay selection based on predictions of future contacts. However, current solutions to social-aware tactical mobile networking in DIL environments are not adaptable. They consider the social relationship among warfighters as either pre-defined or fixed over time, and inappropriately exclude the temporal and spatial variations of such social relationship due to the heterogeneous battlefield contexts from relay selection.
The 
goal of this research is to address such tactical communication barriers, and to design adaptive mobile networking strategies by investigating, formulating, and exploiting warfighters' social dynamics from their contact patterns. In the example shown in the right figure, the tactical squads may be reformed and the squad leader may migrate over time. Consideration of social dynamics among warfighters, hence, ensures the network communication strategy to timely adapt to these changes and avoid incorrect aggregation of tactical information or failure of military operations. This research consists of the following three steps: (i) Adaptive Contact Prediction, (ii) Characterization of Social Dynamics, and (iii) Adaptive Networking Framework.
Adaptive Contact Prediction
Precise contact prediction is the cornerstone of efficient relay selection. It builds on appropriate formulation of warfighters' contact patterns, and adapts to transient characteristics of such patterns that could be heterogeneous in both temporal and spatial dimensions. In particular, we notice that the transient contact characteristics discovered by our previous work in civilian mobile scenarios may not hold at the tactical edge. To address this challenge, we adaptively investigate the actual time scale underlying warfighters' contact patterns, and also incorporate the tactical prior knowledge during mission planning into contact prediction.
More specifically, two warfighters are more likely to contact each other in the theater if they are socially correlated, e.g., belonging to the same tactical squad. By the time of initial tactical deployment, warfighters' contact patterns are solely determined by their pre-set social relationship. As time elapses afterwards, social dynamics among warfighters, which are resulted from the situational battlefield changes, become the dominant factor determining warfighters' contact patterns. Our basic idea of incorporating such tactical prior knowledge is to further extend our previous work on contact prediction [TMC13] towards a Bayesian framework, and incorporate the impact of tactical prior knowledge when calculating the posterior probability of contacts between warfighters.
Selected publications:
- Forwarding Redundancy in Opportunistic Mobile Networks: Investigation and Elimination [pdf][ps][slides]
Wei Gao, Qinghua Li, and Guohong Cao, in Proceedings of the 33rd IEEE Conference on Computer Communications (INFOCOM), 2014.
(Acceptance Ratio: 320/1645=19.4%). -
Wakeup Scheduling for Energy-Efficient Communication in Opportunistic Mobile Networks [pdf][ps][slides]
Wei Gao and Qinghua Li, in Proceedings of the 32th IEEE Conference on Computer Communications (INFOCOM), 2013.
(Acceptance Ratio: 280/1613=17.4%) - On Exploiting Transient Social Contact Patterns for Data Forwarding in Delay Tolerant Networks [pdf]
Wei Gao, Guohong Cao, Thomas F. La Porta, and Jiawei Han, IEEE Transactions on Mobile Computing, vol. 12(1), 2013, pp. 151-165.
Characterization of Social Dynamics
Built on the results of contact prediction, we quantitatively characterize the social dynamics among warfighters by aggregating the transient characteristics of multiple opportunistic communication links and exploring the correspondence of various sociological concepts in tactical DIL environments. These concepts include: i) centrality: the social importance of warfighters' facilitating communication among others, and ii) community: warfighters are formed into groups according to their social relations. These concepts are formulated into specific sociological metrics with respect to the transient contact patterns that depict warfighters' regular tactical routines, as well as their irregular tactical behaviors in sporadic events that deviate from their regular contact patterns.
More specifically, We first developed a centrality metric that incorporates the transient contact characteristics between a warfighter and its k-hop contacted neighbors, so as to quantitatively characterize the social dynamics within the warfighter's k-hop contacted neighborhood [INFOCOM11]. Afterwards, we investigated the impact of transient contact patterns on the social community structure among warfighters, and further propose methods to analytically characterize such transient communities [TON12]. Such metrics are then exploited to investigate the interoperability between social-aware routing and traditional link-state-based MANET routing protocols in tactical environments [MILCOM14].
Selected publications:
-
Towards Interoperability of Adaptive Social-Aware Routing at the Tactical Edge [pdf]
Wei Gao and Mitesh Patel, in Proceedings of the 33rd Military Communications Conference (MILCOM), 2014. - Social-Aware Multicast in Disruption Tolerant Networks [pdf]
Wei Gao, Qinghua Li, Bo Zhao, and Guohong Cao, IEEE/ACM Transactions on Networking, vol. 20(5), 2012, pp. 1553-1566. -
User-Centric Data Dissemination in Disruption Tolerant Networks [pdf][ps][slides]
Wei Gao and Guohong Cao, in Proceedings of the 30th IEEE Conference on Computer Communications (INFOCOM), 2011.
(Acceptance Ratio: 291/1823=15.9%)
Adaptive Networking Framework
The formulations and metrics of social dynamics among warfighters are further exploited to develop a social-aware networking framework which autonomously adapts the relay selection strategies to warfighters' social dynamics. First, we actively select relays and disseminate data to the appropriate transient communities according to their distinct data interests [INFOCOM11]. Second, within each community, data access is alternatively provided through cooperative caching, which responds to warfighters' data queries in an on-demand manner and hence improves the data access efficiency [ICDCS11, ICDCS12].
Selected publications:
- Distributed Maintenance of Cache Freshness in Opportunistic Mobile Networks [pdf][ps][slides]
Wei Gao, Guohong Cao, Mudhakar Srivatsa, and Arun Iyengar, in Proceedings of the 32nd Int'l Conference on Distributed Computing Systems (ICDCS), 2012.
(Acceptance Ratio: 71/515=13.7%) -
Supporting Cooperative Caching in Disruption Tolerant Networks [pdf][ps][slides]
Wei Gao, Guohong Cao, Arun Iyengar, and Mudhakar Srivatsa, in Proceedings of the 31st Int'l Conference on Distributed Computing Systems (ICDCS), 2011.
(Acceptance Ratio: 15%) -
User-Centric Data Dissemination in Disruption Tolerant Networks [pdf][ps][slides]
Wei Gao and Guohong Cao, in Proceedings of the 30th IEEE Conference on Computer Communications (INFOCOM), 2011.
(Acceptance Ratio: 291/1823=15.9%)
Acknowledgement
This project is supported in part by the U.S. Army Research Office (ARO) under the grants W911NF-14-1-0262 and W911NF-15-1-0221. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the ARO.