Abstract
Emergency communication systems play a major role in disaster‐relief environments. In terms of the public safety research, the emergency relief communication system can provide a high system capacity for networks based on the development of Long‐Term Evolution. However, in the event of a disaster, mass traffic information can cause congestion in the core network, and communications between relief workers may be limited. Consequently, spectrum efficiency can be very weak. This paper provides a hybrid traffic offloading mechanism combining Device‐to‐Device (D2D) and Local IP Access (LIPA) modes for the disaster‐resilient network. With receiving power, the distance between relief workers and the distance between relief workers and the vehicular eNodeB (VeNB) as the LIPA/D2D switching criteria, the network can select an appropriate mode to prevent core network congestion. This paper also considers the effects of the mobility models (i.e., random walk and random direction) on the spectrum efficiency of the disaster‐resilient communication system. The proposed hybrid LIPA/D2D traffic offloading mechanism can prevent the local communication traffic from flowing into the core network and significantly improve the system spectrum efficiency when the core network is under congestion. Therefore, the proposed mechanism can effectively improve the quality of the communication between relief workers served by the same VeNB for performing rescue operations. Moreover, the hybrid LIPA/D2D traffic offloading mechanism can be applied to the smart city and smart home in the future.
Highlights
This paper investigated the effect of user mobility on the spectrum efficiency with four traffic offloading modes for disaster-resilient communication networks
The Local IP Access (LIPA) Only mode needs the eNBs surviving in the disaster area or the vehicular eNodeB (VeNB) entering the disaster area to provide communication services for relief workers in the disaster area
The hybrid LIPA/D2D traffic offloading mode can overcome the limitations of both LIPA Only mode and D2D Only mode to provide a more stable emergency communication system. This is because the proposed hybrid LIPA/D2D traffic offloading mechanism can switch LIPA link or D2D link based on the criterion of the received power or reception distance between mobile user equipments (MUEs) of relief workers and the VeNB
Summary
In the framework of the IP-based 4G communication network architecture [1], when a user equipment (UE) communicates with an adjacent receiver within an evolved node B (eNodeB or eNB) service area, data packets shall be transmitted through a radio access network (RAN) to the evolved packet core (EPC) and should be transferred to the receiver along the original path. The disadvantage of such a transmission link is that all data needs to be transmitted by many network devices and Internet service providers (ISPs) during transmission. An increase in transmission traffic may lead to high latency and congestion of the core network
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