# Survey on Power-Aware Optimization Solutions for MANETs
## 3 Analysis of Power-Aware Optimization Solutions in MANETs
### Approaches Based on Adaptations of the Radio State Operational Mode
In the WSN environment, achieving maximum possible bandwidth utilization is not as important as in other networks. The design of a MAC protocol that is suitable for MANETs requires smart amendments because various performance parameters in the MANET are acute. These performance parameters are the chances of dynamic changes in link characteristics (i.e., bandwidth, delay, channel error, loss rate, and level of interference), mobility induced topology changes, bursty and highly-loaded traffic, channel error and contention induced losses. We will not only have to think at MAC level design, but we will have to contemplate through every level of the traditional layered structure and bring appropriate changes. A cross-layer-based routing protocol (described extensively in Section 3.8) may trigger sleep mode by sending a command to the MAC layer. The sleep mode mechanism is easy to deploy and can be adapted into well-established routing protocols, such as AODV. For example, the Efficient Power Aware Ad hoc On-Demand Distance Vector (EPAADDV) protocol [90] is a modification of AODV, that uses the \"power-save\" idea to improve the energy efficiency of AODV to extend network lifespan. Other power-save approaches [91; 92] are based on the minimum energy threshold (limit) to decide whether a node should remain in active mode or to be in sleep mode to save energy. [PERSON] et al. [93] designed the Energy-efficientMultipath Routing protocol using Adjustable Sleeping window (EMRAS) by employing two algorithms: (1) Power and Delay Aware Multipath Routing Protocol (PDMRP) and (2) Slow start Exponential and Liner Algorithm (STELA), using a cross-layer design. The STELA algorithm improves the energy efficiency of the network by adjusting the sleeping window if there are no network activities. If there is any network activity, PDMRP selects the path that is energy efficient and that is the shortest. The EMRAS protocol increases the overall residual energy and reduces the total energy consumption without degrading the QoS parameters. In summary, a drawback of the \"power-save\" method is that it increases the end-to-end delay. As nodes in sleep mode cannot transmit and receive any packets, packet retransmission is required. Such retransmission of packets from the source node leads to increased energy consumption. The increased waiting period for the route request or reply for the new routing path provokes the whole situation if the intermediate node in the routing path is in sleep mode. Another drawback is that, in any energy-inefficient routing path, the intermediate nodes cannot be set in sleep mode, as the goal is to improve network capacity and totally reduce energy consumption [79]. Additionally, some low-duty cycle energy-aware MAC designs (S-MAC, T-MAC, X-MAC, R-MAC, DW-MAC, B-MAC, RI-MAC) are highly limited to some applications, where the data generation rate is not very bursty, and mostly these schemes have been evaluated over WSN environment where the nodes are mostly in a sleeping state. Another category of power-aware optimization solutions is routing protocols, based on adaptive load balancing, which consider power consumption.