**6. Conclusions and other applications**

*Antarctica - A Key to Global Change*

Antarctic environment and may be able to observe a certain phenomenon, measure its physical properties, quantify this observation, and finally, transmit gathered data. Sensor nodes could also have processing and routing capabilities using either a wireless or a wired medium. In this environment, sensor networks must dynamically provide the necessary QoS depending on the type of information transmitted by sensor nodes in a multihop topology, and then, the information should be transmitted to central station

As the network is composed of an extensive mesh of spread nodes, they must be located in the same link layer domain to communicate among themselves. Therefore, they will use link layer mechanisms instead of network layer techniques such as IP networks or routing protocols. Consequently, communications become

Each type of data may require specific requirements, for example, a critical alarm may demand strict real-time requirements while monitoring reports may not need latency requirements. In order to face these demands, network architecture must deal with several QoS profiles and it should allow discriminating and/or

Taking all the above into account, the ICT requirements identified for the system

• Distributed system: the system itself is to be distributed and it must allow dis-

• Simplicity: the number of protocols and APIs, and the number of different types

• Open system: open to other technologies (future proof) by applying existing standards whenever possible to avoid as much as possible proprietary solutions.

• High interoperability: intertechnology mesh networking between personal area

• Easy configuration: automatic neighbor discovery and plug and play capability.

• Security: security confinement (to avoid the spreading of vulnerabilities).

Due to the large scenario in which the research project is going to be deployed, different technologies will be needed in order to cover all the areas. Some technologies based on IEEE 802.15.4 are presented as wireless communication candidate technologies that work within mesh networks and they are useful for Antarctic local area network coverage. The result has to be able to support large, geographically diverse networks with minimal infrastructure, with potential millions of fixed endpoints. In the upper layers, there may be technologies such as Zigbee or 6LoWPAN. When working at Layer2 (second layer of the open system interconnection protocol stack), the communication between two different technology domains (IEEE 802.15.4 and NVIS) involves a gateway, enabling the communication between two separate IEEE 802.15.4 domains across a NVIS domain. A Layer2 routing multihop algorithm capable of working over the obtained topology database is needed in complex network topologies. The multihop algorithm is in charge of determining the neighbors to reach a destination, and the communication with that destination will be requested from the link layer. It is important to bear in mind that the information used by the multihop algorithm can be filtered by the topology control

through NVIS by implementing a delay tolerant network.

faster and time response turns tighter.

enforcing specific traffic differentiation.

of interfaces are kept to a minimum.

network (PAN) and NVIS backhaul.

algorithm (valid/nonvalid neighbors).

tributed applications.

are as follows:

**34**

In this chapter, we have reviewed all the recent activities around the application of HF communications for the research community in Antarctica. The long-range transequatorial link aims to communicate the Antarctic station directly to the home country as an alternative to satellite communications for low bit rate applications. For a transmission power up to 250 W, two different transmission modes have been developed, the robust mode and the high throughput mode. The robust mode, which uses spread spectrum modulation, is suited for extreme channel conditions and achieves 85 bps for a bandwidth of 16 kHz for the spread signal. The high throughput mode, which uses multicarrier modulation and achieves 370 bps for a bandwidth of 400 Hz, is suited for good channel conditions. Although these bit rates are low, they are enough for most of the current sensors installed around the Antarctic stations.

The NVIS link can provide coverage in a surface of approximately 200–250 km radius without the need of line of sight. The main goal of the proposed system is to extend the influence area of the Antarctic stations with the deployment of a wide-area sensor network. When the sensors are distributed in distant zones, it is a hard work to collect the data regularly, and the data are often accessed once or twice a year. With the NVIS solution, all the researchers may get a report of the sensor data in the SAS every day, with no need of direct vision between the sensor and the SAS. The NVIS node has an internal memory that stores the data until the ionosphere conditions allow the transmission. The nodes are intended to be battery powered so the transmission power is kept to a minimum (below 10 W). For NVIS links, the bit rate ranges from 2.3 to 4.6 kbps, depending on channel conditions. On this basis, digital voice and low-resolution images can be sent apart from data from most of the sensors available on the market.

In addition to the use in the Antarctica or any other remote places, NVIS communications have a straightforward application in case of natural disasters, terrorist acts, and communications for developing countries. During a natural disaster or terrorist attack, all the conventional communication systems such as GPRS, 3G, and 4G can be seriously damaged and the communication systems will stop working properly. Our proposed NVIS system may help sanitary assistants, firefighters, police, and other emergency services to communicate during the event of a disaster. In that case, the ease in putting this system up and not needing direct vision between the nodes would be a good solution to save lives.

On the other hand, some parts of the world do not have any communication infrastructures, either because they are uninhabited areas or simply because people cannot afford the price of a conventional communication system. In places where there is no any telecom operator, the communication can only be made via HF and satellite. The NVIS system, based on a low-cost platform, allows the population of developing countries to have access to primary services, such as e-health and education.

Finally, there is a great deal of applications, which can use the proposed communication protocol architecture. They can be classified in detection (e.g., detection of temperatures exceeding a particular threshold, of unauthorized access), tracking (e.g., the tracking of workers in dangerous work environments), and monitoring (e.g., monitoring of inhospitable environments).

*Antarctica - A Key to Global Change*
