# A Novel Self-Forming Virtual Sub-Nets Based Cross-Layer MAC Protocol for Multihop Tactical Network
## 2 Related Work  
Few research studies based on cross-layer schemes have been carried out to support distributed communication in multihop ad hoc and tactical networks. A cross-layer framework CL-TDMA for tactical SDRs that provides self-forming and self-healing features was proposed in [13]. The design uses TDMA as the MAC layer and ad-hoc on-demand distance vector(AODV) on network layer. control messages for multihop network routing and finds slots for collision-free data transmission. It performs better in throughput, call setup delay, and latency than traditional TDMA. A cross-layer scheme that offers decision-based routing is proposed in [14], designed for unmanned flying ad hoc networks (UFANETs). The method uses cross-layer metrics such as signal-to-noise ratio (SNR), received signal strength indication (RSSI), and AODV routing packets to establish data transmission routes. It overcomes issues of latency, unsuccessful data transmission ratio, and high usage of AODV protocol messages. A cross-layer cognitive system designed by the authors of [15] operates with distributed coordination and local information exchange among SDRs. The system integrates dynamic spectrum sensing (DSA), routing, and network coding for a multihop cognitive radio network. It also optimizes spectrum utility by joining the backpressure algorithm with network coding to support unicast and multicast traffic. A selective cross-layer-based routing scheme based on probabilistic technique combined with AODV to resolve route selection issues such as relay node selection and optimal route establishment based on energy and distance was proposed in [16]. The scheme uses a population-based stochastic optimization technique to schedule slot assignment during data transmission. A cross-layer routing protocol for visible light ad hoc networks (LANETs) was proposed in [17]; it interacts closely with the MAC layer to maximize network throughput with the focus on the reliability of routes. The design uses route reliability scores (RSS), a utility-based three-way handshaking process computed on immediate neighbors' information to reach the sink node and mitigate the effects of link and transmission failures. A link-adaptive multihop routing protocol for tactical combat radios was presented in [18]. It adapts link state changes and selects a stable route to perform video streaming over TDMA. The design is compared with link adaptation protocols, AODV and optimized link state routing (OLSR) with carrier-sense multiple access/collision avoidance (CSMA/CA) structures. An application-centric network architecture for tactical communication systems that can applicably respond to the dynamic network topology, link quality at the link layer, and provide a solution to the limitations of conventional single-cost function-based routing protocols at the network layer was proposed in [19]. The designed architecture offers better QoS and dynamic traffic distribution to all available paths. A robust cross-layer routing and resource allocation algorithm for orthogonal frequency-division multiplexing (OFDM) based wireless ad hoc networks was proposed in [20]. The algorithm uses limited knowledge such as maximum transmit power and total bandwidth at the transmitting node to perform joint resource allocation and routing. Another cross-layer autonomous route discovery mechanism was proposed in [21] for vehicular networks (VANETs). The mechanism incorporates a cross-layer cluster-based routing protocol to set stable clusters up that improve routing path lifetime and decrease link breaks for multimedia data transmission. The design uses mobility metrics and the relative distance among nodes to find reliable relay nodes to the destination and improves reliability, throughput, and energy consumption depending on nodes velocity and density. A cross-layer neighbor discovery algorithm based on hexagonal clustering and GPS is proposed by [22]. The algorithm uses hello messages at the MAC layer, sent in TDMA method combined with hexagonal clustering algorithm and GPS.