## 7 Cross-Layer Design Schemes
### Tightly Coupled--Multi-Layer Cross-Layer Schemes
\begin{table}
\begin{tabular}{|p{34.1 pt} p{34.1 pt}|} \hline \hline
**Protocol** & \multicolumn{1}{c|}{**Protocol Summary**} \\ \hline CAEM & Allows a node to dynamically adjust data throughput by changing levels of error protection at the node according to quality of the link, estimated bandwidth, and traffic load. Protocol buffers the packet until the channel recovers to the required quality. Performance gains of up to 30\% compared to traditional protocols. \\ \hline CoLaNet & Incorporates the characteristics of the application to make better routing path choices at the network layer and demonstrated energy savings over S-MAC. \\ \hline TICOSS & Based on 802.15.4. Network is divided into time zones where each one takes turn in transmitting. Mitigates the hidden node problem, provides configurable shortest path routing to the BCU and almost doubles node lifetime for high traffic scenarios compared to other standard protocols. \\ \hline SCSP & Dynamically calculates node sleep and data receive periods depending on traffic levels. MAC layer provides the list of neighbor nodes to the network layer, which in turn provides multiple forwarding choices to it. Switches between active and sleep periods by dynamically adapting modes depending on traffic levels. Uses a simple routing protocol that doesn’t need route maintenance or discovery. Extends the network lifetime and connectivity in comparison with 802.15.4. \\ QoS Adaptive Cross-layer Congestion & Incorporates an adaptive cross-layer mechanism to control congestion for real and non-real time data flow to support QoS guarantees at the application layer. Priority given to real time data for delay and available link capacity. Scheme links the QoS requirements at the application layer and packet waiting time, collision resolution, and packet transmission time metrics at the MAC layer. \\ \hline CC-MAC & Cross-layer solution incorporating the application and MAC layers. Exploits the spatial correlation between nodes to reduce energy consumption without compromising reliability at the sink. Delivers improved performance over S-MAC and T-MAC in terms of energy efficiency, packet drop rate, and latency. \\ \hline DQBAN & Incorporates a fuzzy rule scheduler that optimizes the MAC layer to improve overall performance for QoS and energy consumption. Considers node cross-layer constraints such as SNR, waiting time, and battery life to allocate superframe slots. Protocol achieves higher reliabilities compared to 802.15.4 whilst delivering specific latency demands and battery limitations. \\ \hline XLM & Replaces the entire layered architecture by a single protocol where the objective is reliable communication with minimal energy consumption, adaptive communication, and local congestion avoidance. Each node has the freedom to decide on participating in communication. XLM outperforms the traditional layered protocol stack in terms of performance and implementation complexity. \\ \hline XLP & Extends XLM and merges the functionalities of traditional MAC, routing and congestion control into a unified cross-layer module by considering physical layer and channel effects avoiding the need for end-to-end congestion control. \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Low power cross-layer protocols.