ERCIM News No.48, January 2002 [contents]

Home ambient network for the whole family.
Home ambient network for the whole family.

Ambient Network

by Philippe Jacquet

At home or outdoors, wireless networks are different. Mobile or ad hoc, Hiperlan or Bluetooth communications must be merged into an ambient network, transparent to the user.

Scenario: Arthur, a student, is leaving his school and walking home with his friends. During the day, the wireless network of the school campus has provided all the multimedia support needed by his teachers for their lectures. The mobile network from school to home allows Arthur to exchange data via his portable device as he is walking home; generally games and jokes, and sometimes information about lectures. Once at home, Arthur enters the home network, which is connected to the residential network. His portable device exchanges data with the home computers. Arthur knows exactly where all the other members of his family are (cat included, thanks to a low-power positioning implant). His sister Sabrina is not at home; she has exported her homework next door to her friend Marina’s place, and will stay there for a couple of hours. The oven informs Arthur via his portable device that there are cookies ready, but his mother has left instructions that Arthur should not eat more than two before his sister is back. When his homework is completed (with some multimedia support reviews on the home TV screen) and the results acknowledged by the teacher e-mail system, Arthur can play soccer with his friends. No need of a referee, since the ball contains a low-power wireless chip and a complete description of the ground that enables it to automatically detect offside play, goals, and some other extra rules specifically invented by the team. The video surveillance of the playground can provide an automatic replay on the portable device in case of arguments. When dinner is ready, Arthur is called back home through the residential network via his portable device.

As described in this scenario, an ambient network refers to the presence of a digital environment that is sensitive, adaptive, and responsive to the presence of people. An ambient network can thus be characterised by the following basic elements: ubiquity, transparency, and intelligence. For an ambient network to succeed it must address many challenges, and as a consequence, the relevant research covers several areas:

  • hardware must become adaptable, scalable and stream-efficient to provide computational resources that are both energy-efficient and powerful for a variety of computational tasks
  • software and protocols must become adaptable to provide flexibility and spontaneity, eg, by supporting smooth vertical hand-offs among communication technologies. Services and software objects must be named by intent, for example, ‘the nearest printer’, rather than by address.

There is no universal radio technology that suffices for all Arthur’s communicating devices as they are described above. Indeed it has been theoretically proven that capacity is inversely proportional to range. For example, the 100 kbps of a single GSM frequency can cover up to 10km, OK for a call for dinner. But the 10 Mbps needed for video transmission (IEEE802.11, Hiperlan) is limited to 100m. The causes of the limitation have long been known. In 1948 Shannon proved that the number of bits per Hertz was bounded by the logarithm of the ratio of signal to noise. This naturally limits the capacity of low-power portable devices compared with more highly powered versions. The very limitation of wireless capacity lies in the digital signal processing (DSP) ability, ie, the algorithms used to extract the data from the signal. Since surrounding buildings, walls and other obstacles significantly distort this signal, the DSP becomes crucial at high throughput when close to Shannon limit. The stronger the DSP, the more power it consumes.

There is therefore a need to maintain the co-existence of various wireless standards. Thanks to reprogrammable DSP or multiple interface devices, Arthur’s portable device switches from Hiperlan to GSM when exiting campus. It switches to IEEE 802.11 when Arthur gets home and during his homework. It switches to Bluetooth on the playground, to IEEE 802.11 again for game replay and finally to mobile phone for the call to dinner.

INRIA is working on wireless network algorithms that manage such protocols within the best performance and quality of services. In particular, ad hoc networking offers the possibility of considerably augmenting the range of high-speed networks by relaying from host to host, or of adding flexibility with multiple interface routers.

Moreover, these algorithms mean that heterogeneous traffic can be efficiently routed in response to application demands, through nodes that differ in connectivity, computational power, and resources. Other research subjects concerning ambient networks cover security and service location protocols.
In the near future, thanks to this promising research, our homes will have a distributed network of intelligent devices providing us with information, communication, and entertainment. Of course, Arthur shouldn’t even be aware of all this, since he has plenty of homework to do.

Please contact:
Eric Fleury, INRIA
or Philippe Jacquet, INRIA
or Gerardo Rubino, INRIA