## 3 Possible Use Cases
### SCF Relaying within the Cell  
As briefly introduced in Section 1, via SCF relaying localized transmission are possible when delay on the forwarding information messages can be tolerated. In addition, due to the centralized control offered by the infrastructure units, messages are not replicated at every node encounter and instead forwarding paths are generated with guaranteed deliveries. Within a single cell, the potentials of SCF relaying are considerable. Obviously, allowing mobile relays to carry messages while in transit of their journey reduces the end-to-end communication distance with possible savings in the communication energy consumption. In addition, with reductions in the output transmit power, there is potential to reduce co-channel interference improving even further the system performance. In [21] the authors study the benefits of postponement protocols for the single hop cellular networks. They show that postponing communication could be an effective way for reducing inter-cell interference. Here we extend that previous work for the general multihop scenario where significantly more flexibility on the optimal forwarding policies can be achieved by cooperation between mobile relay nodes.  
In the discussion hereafter, we assume that mobile relay nodes are communication units onboard vehicles. Vehicles, which can be private cars or public transport, travel on a road network and thus their mobility patters are defined by the road structure and the density of nodes within the network. Note that inter-vehicle communication has attracted much attention in the past and successful integration with cellular networks has been demonstrated [22, 23]. With knowledge on location and mobility information, a mobile node can postpone transmission for a later time instance with favorable channel conditions. For the single hop case, a user terminal (UT) onboard a vehicle can refrain communication with the BS such that it moves closer to the cell center. For the general multihop case however, a static UT can transmit to a vehicular relay (VR) which could then carry the message closer to the BS before retransmission. In the same way, a BS can transmit to a VR which could then carry information messages closer to a target user; acting in this way as a message ferry between the two end points. Such an operation is better explained by the topology layout in Figure 2. In this figure we consider the uplink case, however the scenario equally applies to the downlink case as explained above. In the traditional cellular operation, a UT communicates with the BS via the direct link (link 1 in Figure 2). In the basic multihop scheme, a UT could possibly transmit to a relay node (link 2 in Figure 2) which in turn forwards the received data to a relay ahead (link 3 in Figure 2) or to the BS (link 4 in Figure 2). However in the proposed scheme, a relay node can buffer data while in transit (link 5 in Figure 2) allowing for the flexibility to adjust the forwarding strategies depending on the delay sensitivity of message delivery deadlines. Tolerance on message delivery deadlines further allows nodes to buffer information until an effective contact appears for message forwarding. For example, it could be the case that at an instance in time no VRs are present in the vicinity of a target UT. However the BS can inform the UT for future contact opportunities and establish a forwarding path based on both the spatial and temporal dimensions.