# Location-Based Deferred Broadcast for Ad-Hoc Named Data Networking
## 1 Introduction  
The emerging of connected and autonomous vehicles (CAVs) challenge ad hoc wireless multi-hop communication by mobility induced dynamic topologies (e.g., highways vs urban environments), large-amount of mobile devices (e.g., vehicles and the embedded sensors), and large-scale, in-network data acquisitions and computations (e.g., collaborative platooning, smart transportation systems). Recent research has pointed out that the Named Data Networking (NDN) is suitable for such vehicle ad hoc network scenarios due to its information centric networking approach, where data names are directly used in network architecture. It solves the difficulty in managing the host-based IP addresses and matching the content-centric application needs more naturally [1; 2]. NDN is a reactive communication architecture. In NDN [2], data pieces are named; communications are based on the names of the data instead of host IP addresses. When there is a request for data, a consumer sends an interest packet with the name of the data to the network. The interest packet either follows a routing path to a provider or floods to the network in an exhaustive attempt to find a convenient provider. Any provider who has the name-matching data will return a data packet. For wired Internet, providers run routing protocols to advertise their name prefixes. The features of NDN, such as connection-free, multicast communication nature, and in-path caching can offer great advantages for mobile ad-hoc networks (termed ad-hoc NDN) [1]. The ad-hoc NDN has been further studied for vehicle ad-hoc network (i.e., vehicular named data networking (V-NDN) [3]). Three main modifications to baseline NDN are suggested for V-NDN to tackle the topology dynamics and the dataconsumption pattern, which are that routing protocols are not necessary due to topology dynamics, ubiquitous cache is desired due to ubiquitous data sources, and caching data regardless of network connectivity is helpful due to potential intermittent connectivity. The three modifications apply well to general ad-hoc NDN. Following this line, our work targets at general ad-hoc networking applications. The proposed scheme builds on the software available for vehicular named data networking where the three modifications are implemented but the scheme itself applies to general ad-hoc NDN scenarios. In ad-hoc NDN, flooding interest packets, while being an effective way to spread the interest for a piece of data, suffer from the broadcast storming issue. This issue arises due to the lack of routing information about the data sources (recall that a routing protocol is not used). Thus, when receiving an interest, a node will rebroadcast the pending interest to its neighbors if it does not have the data to satisfy the interest itself. This leads to two issues: first, packet collisions will occur frequently if neighboring nodes rebroadcast the same interest at almost the same time, especially in dense networks; second, blind broadcast will propagate the interest to all directions and flood the network, leading to unnecessary transmissions, further adding to bandwidth overhead and data retrieval latency due to contention. The broadcast storm problem in ad-hoc NDN calls for careful research. [PERSON] et al. proposed a collision avoidance solution by adding a collision avoidance timer with adaptation [PERSON] et al. (2016). Other existing works have proposed broadcast schemes to reach the destination quicker. For example, using the location information to select forwarding nodes either farther away from the original sender, or closer to the data sources [PERSON] et al. (2016); [PERSON] et al. (2016); [PERSON] et al. (2016) but they will either increase the number of redundant interest packets or need global knowledge about data producers. As such, we believe the efficiency and performance of an interest broadcast scheme can be further improved by taking advantage of location information. This paper presents a Location-Based Deferred Broadcast (LBDB) scheme for interest forwarding in ad-hoc NDN.