# Cross-Layer Methods for Ad Hoc Networks--Review and Classification
## 3 Cross-Layer Method Publications Review
### One Layer
#### 3.1.3 Network Layer
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Publication** & **Year** & **Citations** & **Layers** & **Goal** \\ \hline
[61] & 2003 & 49 & 2, 3 & route packet error rate \\
[62] & 2004 & 3609 & 1, 2 & route throughput \\
[63] & 2005 & 643 & 1, 2, 3 & route throughput, interference \\
[64] & 2006 & 18 & 1, 2 & route stability \\
[65] & 2008 & 67 & 1, 2, 3 & route packet error rate, energy consumption \\
[66] & 2009 & 64 & 2, 3 & route latency \\
[67] & 2010 & 4 & 1, 2 & route throughput \\
[34] & 2011 & 112 & 1, 2 & route packet error rate \\
[68] & 2012 & 4 & 1, 2 & route throughput, route packet error rate \\
[69] & 2012 & 15 & 2, 3, 5 & route throughput, route stability \\
[70] & 2012 & 22 & 1, 2, 3 & route stability \\
[71] & 2013 & 329 & 2, 5 & route throughput, route latency \\
[72] & 2015 & 8 & 1, 2 & route throughput, energy consumption \\
[73] & 2016 & 32 & 1, 2, 3 & energy consumption \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Cross-layer methods concentrated on network layer routingmetrics..  
[PERSON] et al. [68] propose a metric that takes into account the mobility of nodes, the line load, and the fading of radio lines. This metric is called the network intersection metric. This metric uses the average packet wait time in the queue, the average packet transmission time and the packet loss probability estimate, which is based on the signal-to-noise ratio, packet length, modulation, and error-correcting code. [PERSON] et al. [69] use a metric for line reliability estimation based on queue size, number of hops, distance, and relative speed from the sender node to the receiving node. [PERSON] et al. [70] offer a path stability metric based on queue length, the signal-to-noise ratio, and the probability of packet loss. The queue size assesses the probability of packet drop due to line buffer overflow, the probability of packet loss estimates interference and the signal-to-noise ratio estimates distance and node mobility (if the node moves far away, the signal-to-noise ratio drops). By combining the three metrics into one, one can estimate the stability of the lines and the stability of the routes. [PERSON] et al. [71] present a metric based on delay, bandwidth, and geographic direction. [PERSON] et al. [72] propose a metric based on the residual energy of the node and channel occupancy. [PERSON] et al. [73] have derived a theoretical estimate of route energy consumption based on the probability of packet loss, the number of retransmissions and the number of route hops. The authors have created an algorithm for calculating transmission power for all route nodes in order to minimize the energy spent with a given probability of package delivery. Network layer (routing protocols)The single-layer routing protocol in ad hoc networks, using probing packets, can only receive information about the nodes through which the probing packet passed and the packet travel time that estimates the delay of the found route (Table 7). As a result, the routing protocol can select routes by delay and hop number. Cross-layer routing protocols can use the cross-layer metrics described above or collect information from different layers. [PERSON] et al. [75] offer a routing protocol that uses data about free time slots from the channel layer to reduce interference. When sending a route request packet, it is checked on each hop whether it is possible to reserve non-interfering time slots on previous and next hops; if it's not possible, then the request packet is dropped. [PERSON] et al. [76] propose a modification of the AODV routing protocol, where instead of the hop number metric, the delivery probability is estimated based on the signal-to-noise ratio obtained from the physical layer. [PERSON] et al. [77] suggest an improvement to the AOMDV routing protocol. The new routing protocol uses a weighted function from the queue size of the line buffer and the residual energy of the node to find routes. [PERSON] et al.