# Enhancing the 3 GPP V2X Architecture with Information-Centric Networking
## 5 3 GPP V2X-NDN Forwarding Strategy
### Interest and Data Processing at the eNodeB  
Resource allocation in the legacy eNodeB is typically _data-agnostic_: there is no way for the eNodeB to know whether grant requests by different UEs are for the transmission of the same packets. Our proposal, instead, is to make resource allocation at the eNodeB _name-aware_ by embedding the NDN packets processing in the resource allocation procedures. To this aim, we extend the scope of the grant request so that it carries information about the packet to be transmitted. More in detail, a portion of such a packet's header, i.e., only the content name and the NDN packet type (Interest or Data), is conveyed in the BSR sent by the UE.  
When receiving a grant request for an Interest packet by a consumer UE, the eNodeB acts as follows (see Figure 3). First, it checks its CS to verify if it caches a copy of the named content requested by the Interest. If the check succeeds, it directly replies with the related Data to the UE. If the CS matching fails, it checks the PIT. In the case of a matching, the eNodeB rejects the request, because it infers that it has already allocated resources for the same named Interest, and notifies the consumer. If the PIT matching fails, it allocates resources to the requesting UE for the Interest transmission and updates the PIT accordingly. The Interest packet will then be transmitted over the corresponding interface on the resource blocks (RBs) allocated by the eNodeB. If the Interest is transmitted over the LTE-Uu interface, the eNodeB has also to enforce its treatment over the downlink direction, selecting unicast or multicast transmission. Multicast can efficiently disseminate the Interest in a large area. In particular, according to rules in the FIB, depending on their turn on the content name, the eNodeB decides to which and how many cells the Interest should be forwarded. It is the V2X AS that fills in the FIB of the eNodeB.  
A slightly different processing holds if the eNodeB receives a grant request for a Data packet by a provider UE. First, the eNodeB checks the PIT. In the case of matching, the eNodeB allocates resources to the requesting UE and deletes the corresponding PIT entry. Conversely, if there is no matching in the PIT, the grant request for the Data packet is discarded, being considered as an unsolicited transmission.  
If the Data is transmitted over the LTE-Uu interface in UL, the eNodeB has to decide how to forward it in DL, according to the number of received requests for the same Data. An approach similar to the one proposed in [17] for mobile ad hoc environments can be pursued. In this approach, if a provider realizes that the same content is simultaneously requested by a number of consumers (appropriately tracked) greater than a given threshold, then it switches from unicast to broadcast. Here, the decision is whether sending Data through (multiple) unicast connections or to save radio resources by leveraging eMBMS facilities. Smarter strategies may also account for the position in the cell of requesting UE(s) and their advertised channel quality indicators (CQIs).