**3. Design of networking protocol**

In the prior section, the authors summarized the conventional wireless network technologies. They're, nonetheless, unsatisfactory due to the constraints of the conventional aircrafts.

IEEE 802.11, IEEE 802.15.4, IEEE 802.16 m, and LTE will need the aircrafts to be engineered with freshly installed antennas and are probably jammed by high-speed movement and may experience radio interference since they are acting secondary modulation by OFDM.

As satellite internet utilizing geostationary satellites does not handle the polar regions, it cannot be put on to aircraft traveling near the North Pole. Furthermore, satellite internet utilizing satellite constellations necessitates broadcasting communication among the satellites, which is technically complicated.

Air-based internet and ground-based internet aren't ideal for FIM because the coverage area of theirs is limited.

Long-distance, low-speed networks (excluding LoRa) aren't ideal for FIM, because interaction with mobile vehicles is not taken into consideration in the design of theirs.

Consequently, the authors have created a brand new low-speed (1–10 kbps) wireless communication technology to allow the inter-aircraft flow of information. The authors assume that conventional wireless communications are used by the aircraft in the physical layer and the datalink layer for the best backward compatibility with existing aircrafts.

The authors present the following communication protocol and then verify the effectiveness of the protocol by simulations.

### **3.1 Physical layer**

The authors assume narrowband wireless communication in the physical layer. In order to share the antenna with SSR [31, 32] the authors utilize the UHF band as well as frequency modulation (FM) that is ideal for digital signals, and they have high noise tolerance.

In thought of the practicableness of implementing this specific protocol on typical aircraft, the authors use precisely the same band as SSR (i.e., the UHF band) to enable the potential for diverting the SSR antenna.

As the current SSR uses a straightforward pulse-based communication protocol, the communication band is incredibly narrow. Thus, a bandwidth of roughly 10 kHz with adjacent frequency as being a carrier is available. The authors consider FM for the noise tolerance at this layer. Generally, AM is utilized for the lower selectivity of voice communication channels in aircraft communication, but as this proposal is restricted to digital communication, FM is adopted since it is more reluctant to interference compared to AM.

### **3.2 Datalink layer**

The datalink layer encodes/decodes the data we send/receive with metadata including data sender, time code, etc. These packed data are referred to as the packets.

Permit the size of the packet at the season of exchange from the datalink layer to the physical layer be near 256 [octet]. As the littlest metadata, the authors incorporate a "magic" code up to 4 [octet] specifying the character of the packet, a time code (4 [octet]), and a code of the aircraft (4 [octet]). By considering these headers, 240 [octet] is left inside the datagram. Expecting that 2 kbps is offered as the channel of the datalink layer, it will take 1 s to transmit a solitary packet. The transmission capacity of 2 kbps could be feasible.

In detail, aircraft code (4 [octet]) contains the source aircraft code. A unique number for every aircraft must be allocated. The body (240 [octet]), followed by error-detection code, contains data body. The error-detection code (4 [octet]) contains error detection. CRC-32, which inspects the cyclic redundancy check, is used.

Packets having errors and packets older than a planned threshold are discarded. To scale back the load on the network layer, it manages "time to live" of the packet.

### **3.3 Network layer**

The network layer encodes/decodes the sent/received data by wrapping/ unwrapping the datalink packet. Dropping any irregular data is done in the network layer. If there are not any irregularities, the data is passed to the upper layer, that is, the transport layer. If needed, the received data is retransmitted. A signal body of the transport layer is named a datagram.

The datagram includes a code (up to 4 [octet]) stating the character of the datagram, a destination aircraft code (4 [octet]), a source aircraft code (4 [octet]), and a time code (4 [octet]). The size of the user space of the datagram is 224 [octet].

### **3.4 Transport layer**

In contrast to the internet, it's really hard to assure end-to-end data transmission in aircraft communication. Therefore, the transport layer does not handle the end-to-end connection feature, that's characteristic of TCP, like data retransmission requests. Yet, a comparatively powerful error-correction capability is enforced to the transport layer. The Reed-Solomon (RS) code is thought to be the promising candidate. When three datagrams are transmitted together with error-correction signals distributed in four datagrams, the typical quantity of data per datagram is 168 [octet].

The Reed-Solomon code, which is a more practical error-correction function than the cyclic redundancy check (CRC), is enforced within the transport layer. If three datagrams are coupled with the error-correction signal and, as a result, distributed to four datagrams to be transmitted, 168 [octets] per datagram are allotted to the implementer.

**35**

are arbitrary.

*Design of an Ad Hoc Mesh Network for Aircrafts DOI: http://dx.doi.org/10.5772/intechopen.86510*

. The information received by aircraft *ai*

*cij* = *k*ε<sup>−</sup>*K*|*pi*−*pj*<sup>|</sup>

ing from aircraft *ai* corresponds to *yj*

Assume that *N* aircrafts *ai*

experiment.

position *pj* is defined.

authors denote it as *yij*.

ted by aircraft *ai*

position *pj*

aircraft *ai*

to *aj*

consideration has the form

assume that

*pi*

*ai*

*ai*

**4. Feasibility study of physical, datalink, and network layers**

Let *xij* be the information the authors want to send to aircraft *aj*

In order to confirm the feasibility of the protocol discussed in the prior section,

are existing at positions *pi*

When there's no error in the communication route, the information *xij* originat-

*yj* = *Uixij* (1)

Let us denote the transmission rate of the communication route from aircraft

for some constants *k*, *K*. These parameters may be changed according to the results of experiments. In this report, the authors adopt Eq. (2) as the transmission rate *cij*.

*yj* = *Uicijxij* (3)

Until now, the authors have dealt with only one-to-one communication from

described by *xij*. When the information that aircraft *ak* receives and retransmits is *zk*, where *zk* = *ijcikxij*, there would be an explosive increase in the amount of data if

*zk* = *Uijcikdijkxij*. (4)

Here, the attenuation term *dijk* denotes the probability of intentionally discarding the packet during the packet relay. Finally, the equation that takes the relay into

*yj* = *Uicij*(*xij* ∪ *zij*). (5)

In this report, to statistically investigate the arrival rate of data based on Eqs. (4) and (5), the authors performed computer simulation with the following parameters: **Airspace.** Three-dimensional orthonormal space. It is a cube whose vertexes are (0, 0, 0)-(0, 0, 1)-(0, 1, 0)-(0, 1, 1)-(1, 0, 0)-(1, 0, 1)-(1, 1, 0)-(1, 1, 1). The units

**Time.** The simulation is performed between 0 and 100 s with a time step of 1 s.

to aircraft *aj* by *cij*. The transmission rate *cij* refers to the packet data transmit-

that is actually received by aircraft *aj*

of correct information transmission. Let *cij* be a function of position *pi*

Taking the transmission rate into account, Eq. (1) is modified to

the authors do not use an artificial attenuation (decay) term *dijk*, as in

received by aircraft *aj*

. That is, *cij* = *e*(*pi*, *pj*). In wireless communication, we can reasonably

2

, but we can consider another aircraft *ak* relaying the communication

 may or may not be a three-dimensional orthonormal coordinate system. The primary point in this discussion is that the distance *pi* − *pj* ∨ between position *pi*

, respectively. Position

is, nonetheless, different from *xij*—the

and

from aircraft

. This can be described as

, that is, the probability

and

(2)

the authors developed the model described below and conducted a simulation

*Wireless Mesh Networks - Security, Architectures and Protocols*

transmission capacity of 2 kbps could be feasible.

the transport layer is named a datagram.

interference compared to AM.

**3.2 Datalink layer**

**3.3 Network layer**

**3.4 Transport layer**

packets.

As the current SSR uses a straightforward pulse-based communication protocol, the communication band is incredibly narrow. Thus, a bandwidth of roughly 10 kHz with adjacent frequency as being a carrier is available. The authors consider FM for the noise tolerance at this layer. Generally, AM is utilized for the lower selectivity of voice communication channels in aircraft communication, but as this proposal is restricted to digital communication, FM is adopted since it is more reluctant to

The datalink layer encodes/decodes the data we send/receive with metadata including data sender, time code, etc. These packed data are referred to as the

Permit the size of the packet at the season of exchange from the datalink layer

In detail, aircraft code (4 [octet]) contains the source aircraft code. A unique number for every aircraft must be allocated. The body (240 [octet]), followed by error-detection code, contains data body. The error-detection code (4 [octet]) contains error detection. CRC-32, which inspects the cyclic redundancy check, is used. Packets having errors and packets older than a planned threshold are discarded. To scale back the load on the network layer, it manages "time to live" of the packet.

The network layer encodes/decodes the sent/received data by wrapping/ unwrapping the datalink packet. Dropping any irregular data is done in the network layer. If there are not any irregularities, the data is passed to the upper layer, that is, the transport layer. If needed, the received data is retransmitted. A signal body of

The datagram includes a code (up to 4 [octet]) stating the character of the datagram, a destination aircraft code (4 [octet]), a source aircraft code (4 [octet]), and a time code (4 [octet]). The size of the user space of the datagram is 224 [octet].

In contrast to the internet, it's really hard to assure end-to-end data transmission in aircraft communication. Therefore, the transport layer does not handle the end-to-end connection feature, that's characteristic of TCP, like data retransmission requests. Yet, a comparatively powerful error-correction capability is enforced to the transport layer. The Reed-Solomon (RS) code is thought to be the promising candidate. When three datagrams are transmitted together with error-correction signals distributed in four datagrams, the typical quantity of data per datagram is

The Reed-Solomon code, which is a more practical error-correction function than the cyclic redundancy check (CRC), is enforced within the transport layer. If three datagrams are coupled with the error-correction signal and, as a result, distributed to four datagrams to be transmitted, 168 [octets] per datagram are allotted

to the physical layer be near 256 [octet]. As the littlest metadata, the authors incorporate a "magic" code up to 4 [octet] specifying the character of the packet, a time code (4 [octet]), and a code of the aircraft (4 [octet]). By considering these headers, 240 [octet] is left inside the datagram. Expecting that 2 kbps is offered as the channel of the datalink layer, it will take 1 s to transmit a solitary packet. The

**34**

168 [octet].

to the implementer.
