In-Flight Entertainment systems play a quintessential role in the airline industry. The success of airline industries,in-fact to a large extent can be attributed to the quality of the IFE systems that they provide. This is evident by the money invested in them by competing airlines. Since, they provide both physical and mental relief to passengers exposed (PAX) to extended flight hours, IFE systems have come a long way since the first inflight movie [2] in 1921. It has therefore become more of a necessity than a luxury given the present day scenario [4]. In consequence to the benefits from these systems, airlines in turn spend billions of dollars trying to constantly upgrade their IFE services, to further boost their profits.The race in trying to build more efficient and reliable IFE systems have given rise to emerging technologies in network topologies, multimedia streaming, peer-to-peer communications and wireless systems to name a few.[1]
The use of infrared in-flight communication to transfer (stream) data (multi-media: images, audio, video, etc.) to provide a complete wireless environment over a peer-to-peer network, is the focus of this paper.
The transition of IFE systems from a wired environment to a wireless world is an important research topic as it is targeted to largely help improve the airline transportation industry. It aids in resource savings, financial savings and more importantly marks out a milestone in communication technology that can aid and help improve other fields of communication as well.
Existing solutions - Currently implemented IFE systems
Switching over to a wireless platform
It is important to note that all present IFE systems are implemented on a server-client architecture and use fixed wires/cables to connect each and every client to the Server. Ergo, these cables run the entire length of the aircraft and affect the design and performance of the aircraft. The advantage of using fixed dedicated lines to each and every console results in very reliable (98%) and efficient services to every passenger. It also reduces congestion to a large extent. However the major disadvantage with this approach is the fact that wires and the server-client hardware add to the aircraft's space and weight. The passenger capacity and fuel efficiency reduce, the heavier an aircraft becomes.This is the main motivation towards building IFE systems that operate wirelessly. Various aspects come into focus in trying to create wireless IFE systems: The cabin environment in an aircraft poses strict rules in terms of signal interference with the aircraft's installed navigation and communication systems. Bandwidth limitations and protocols may change accordingly [2][4].The current Wi-Fi scenario is a good example to illustrate that although a wireless environment can successfully be implemented it still has lot of scope to improve. Many airlines currently provide Wi-Fi by using either a ground to land transmission of data or the satellite. This service is however still in its infancy. Due to the large number of people it caters to, a lot of the bandwidth and distribution issues that arise may cause lack of effective data access and delivery [8].
The switch to wireless can take two paths: the conventional and more popular Bluetooth/Wi-Fi technology or the Infrared technology. In addition it can also be implemented on two common architectures: the client-server architecture or the peer-to-peer architecture.
Why Infrared?
Infrared serves as a relatively clean form of wireless data transfer in that it conforms to air-cabin interference regulations. The requirement of having to cover only a limited area (air-cabin) is also a helping factor. Importantly, Infrared is preferable to regular Wi-Fi/Bluetooth especially when the bandwidth issues are resolved using a peer-peer architecture. It does not interfere with the aircraft's navigation or communication systems as there are no electromagnetic signals used at all. Data communication is solely achieved just by using infrared technology. The use of which reduces the space and weight requirements in order to be implemented. Infrared fall under a large spectrum:Table 1Specifications of selected IR technologies [2]
The infrared technology commonly seen on cell phones, TV remotes, and etc. help exchange data bi-directionally work only when the transmitters and receivers are in each others 'line of sight'. [9] It is referred to as 'Direct' linking. This would not be functional in an air-cabin where individual consoles may not always be in each others line of sight. In most cases the IFE systems are independently integrated into the seats in an aircraft, thus shielding them and creating a hidden field. Alternatively the transmitters and receivers need not rely on the line of sight, in which case they are referred to as 'Diffused'. Diffused linking is made possible by using wide angle transmitters and receivers that catch light reflected by the surrounding walls/boundaries. The following data (media) transfer is achieved by the IrNET protocol which allows for TCP/IP packet transfer and enhanced connectivity as opposed to its predecessor: the IrDA protocol which denied the use of both. Infrared technology is also scalable. [2][9]
Why Peer-to-Peer?
The main idea to implement a peer-to-peer architecture over a client-server architecture is to 'de-centralize'. In the traditional client-server architecture a number of clients are connected to a centralized server that supplies information. Data requests (sent by the clients) and data responses(sent back by the server) occur constantly. There are certain problems associated with such a method: Flashcrowds - This occurs when there is a sudden spike in the number of requests for a resource on the server, in which case the server is overloaded and fails to deliver.[3] Other problems include cost, maintenance and etc. [10] Figure 1: Peer-to-Peer architecture and Figure 2: Client-Server architecture [11][12]
Importantly, peer-to-peer architecture overcomes these problems by simply 'distributing' the work load (data sharing load) amongst all its peers. Here, peers refer to each and every IFE system console that act both as a server (transmit/share information) and a client (rece9dataive information). Peers act as a swarm:A cluster of consoles exchanging/sharing the same content(data).Peer-to-peer architecture is categorized into 3 classes namely hybrid, structured and unstructured. Unstructured networks are monitored, structured networks have groups of peers making it relatively easier to search and retrieve data and Hybrid networks bring together the best properties of both the P2P and client-server architecture. Data can be localized by using chord (one of the various applications used in controlling peer-peer activity, that makes each node aware of every other node in the network and also allows for additional new nodes). [2] It can then be transferred by implementing one of the many transmitting techniques such as multicast: Data is sent to a cluster of consoles simultaneously at the same time ensuring to make duplicates only when routes change/split.[7] This divides work and thus, when synchronized with P2P system works smooth.
To illustrate the functioning of a peer-to-peer co-operative data sharing implementation consider BitTorrent (hybrid peer-peer network). [6] BitTorrent is an application that is widely used to download a large variety of data for ex; media files.In essence it breaks down data into chunks (pieces of data) and distributes it over a number of peers attempting to download the whole original file. Data does not reside in a centralized server. The peers eventually download the entire file by exchanging (trade blocks between seeders and leechers) equally prioritized chunks over time. Additionally the peers are monitored by trackerswhich ensure forced yet efficient sharing of data.[6][3]
Given the limited space (air-cabin environment), energy, costs, maintenance, electro-magnetic interference, reliability, weight and data exchange requirements [5], the solution of using an infrared in-flight Entertainment system on a P2P platform shows positive implementation of this idea.
Future Work
Like any other problem, the search for finding and commercialization of an optimal wireless network on board an aircraft has several solutions. Infrared technology, being the highlighted one, in this context.Though a complete wireless technology would be an ideal make over in the IFE industry, the recent future is headed towards a much more heterogeneous approach that allows using certain aspects of the already existing technology in collaboration with the newly evolving wireless technologies. This cushions the high expenses and vast resources that would be required if the entire legacy system is to be changed. [4] Some possibilities include:
Fiber Optics: Fiber optics (though not wireless) can nevertheless bring down weight and occupy lesser space in the aircraft. Since they facilitate multiple wavelength usage, more bandwidth is available for data transfer. The transfer rates are also high. Another useful reason is that fiber optics do not interfere with any of the aircrafts communication or navigation systems as they do not emit Electro-magnetic waves. [5]
WUSB: Refers to wireless USB.As the name suggests it provides matching services as provided by conventional wired USB peripherals. Peers (IFE consoles) conceptualized as a full mesh network (network of radio nodes that can communicate even if one of many nodes fails). In design it is shown to support up to 480Mbps and runs on radio waves. [4]
PLC: Power Line Communication is by far one of the cheaper alternatives proposed in improving IFE systems. Power lines i.e. lines carrying electrical power are used as a means to transport data. This is achieved by installing a modem at the console's end which translates digital into viewable form and back. Although this technique produces Electro-magnetic signals that may cause interference, it can be tweaked to conform to signal regulations. This is a promising alternative as it calls for hardly any expense or space requirements. [4]
A switch from fixed wire IFE systems to a Heterogeneous (Semi-wireless) environment shows immense potential in revolutionizing the overall quality of the airline industry in the near future.
Though a completely autonomous wireless system has not yet been implemented in reality extensive studies continue in this area with a hope to replace the conventional centralized fixed wire systems in the relatively farther future.
"In my opinion, the combination of using diffused infrared communication technology over a hybrid peer-to-peer platform which is oriented towards a multicast style of data exchange [2] integrated with 'some' of the already existing wire/cable structure (legacy systems) forming an altogether hybrid heterogeneous [4] would result in an effective and commercially viable IFE system."
Figures and Table references
Acronym
Name
Range(m)
Data rate(kbps)
Angle
SIR
Slow Infrared
1
9.6-115.2
30
MIR
Medium Infrared
1
576-1,152
30
FIR
Fast Infrared
1
4000
30
VFIR
Very Fast Infrared
1
16000
30
AIR
Advanced Infrared
10+
16000
30
Table 1 [2]: Specifications of selected IR technologies
Figure 1: Peer-to-Peer [11] Figure 2: Client-Server [12]
Figure 3: Mesh Network [13]
