# Situation-Aware Survivable Network Design for Tactical Environments
## 2 Related Work  
The military quickly adopts WLAN and commercial off-the-shelf (COTS) devices considering their benefits in deploying networks [9, 10, 11, 12]. There have been various studies undertaken to meet the requirements of traffic and guarantee QoS [13, 14, 15]. In particular, researchers have focused on designing a MAC protocol that minimizes the transmission delay of traffic and developing a routing algorithm to ensure network recovery because of the unstable conditions of wireless networks [16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27]. With respect to the MAC protocol, the main approaches consist of optimizing the traffic transmission delay to guarantee QoS. The authors in Ref. [16] present the enhanced collision avoidance (ECA) algorithm to enhance collision avoidance ability in a saturated network. To avoid poor performance of binary exponential backoff (BEB), such as overlapped backoff intervals, backoff interval isolation (BII), and an improved slow decrease (ISD), an algorithm was proposed in ECA. CSMA with enhanced collision avoidance (CSMA/ECA) is proposed in Ref. [17]. A deterministic backoff is defined to traffic differentiation in dense networks without killing the throughput of low priority access categories. They show that CSMA/ECA can construct collision-free periods with improvement of an overall throughput. In Ref. [18], a backoff algorithm based on self-adaptive contention window update factor for IEEE 802.11 distributed coordination function (DCF) is proposed. An optimal contention window update factor is derived based on the theoretical analysis in different situations. The results show that the proposed algorithms outperform BEB, a multiple increase multiple decrease (MIMD) and multi-channel MAC scheme (MMS) algorithm with respect to throughput by reduction of collisions and the number of time slots per contention. To improve the packet loss rate and average delay, the channel-aware contention window adaption (CA-CWA) algorithm that adapts the contention window based on the channel status is proposed [19]. To avoid congestion and reduce the throughput problem, an adaptive virtual backoff algorithm (AVBA) is proposed in Ref. [20]. The access point (AP) generates backoff counts by AVBA, and they are sent to a synchronized centralized random backoff (CRB) node. The AVBA improves the throughput by achieving a collision-free state in comparison to the deterministic backoff algorithm. In Ref. [21], the authors present a differentiated reservation (DR) algorithm in multi-rate WLANs to improve the efficiency and fair sharing of channel resources among the contending nodes. The main contribution of the proposed algorithm is that each node sets its backoff counter as a deterministic value (DRV, deterministic reservation value) to reduce collisions. The simulation results verify that the DR algorithm significantly outperforms the legacy DCF in terms of throughput and airtime fairness. According to the existing research, most of them perform to enhance collision avoidance only without considering QoS requirements for each packet priority. However, the proposed approach is different because it provides different strategies for each priority in hierarchical structure. With respect to routing algorithms, many studies have been conducted aiming to provide trusted link utilization and enhance network lifetime and find the optimal path. [PERSON] and [PERSON] propose an energy efficient zone routing algorithm, called EZone, for the topology control of tactical wireless sensor networks [22]. The EZone algorithm is developed based on the node die out information to increase the network lifetime. The results show that EZone algorithm offers the best opportunity to extend the tactical wireless sensor network service life while maintaining tactical control of the network. In Ref. [23], a distributed split-path routing algorithm is introduced to account for the link utilization between nodes.