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The service provider protects the network to access nodes such as telecommunications exchanges
using a synchronous digital hierarchy (SDH) ring. In the access network, wireless networks such as
3G/4G and Wireless LAN may be used to provide an alternative path to the fixed network.
It is not clear how the sensor layer network should be provided with resilience to a single point of
failure close to and including the sensor (or actuator). For critical applications duplication of sensors
may be required. This could be using a protected ring or on separate but interleaved networks.

The resilience of wireless sensor networks including protection against intrusion or deliberate
jamming is the subject of research.

3.2 Growth, Maintenance and Upgrade in New Build Situations

3.2.1 Growth and flexibility for upgrade

Growth and flexibility for upgrade is required in all infrastructures. Provision of utility tunnels or
accessible duct can save cost.
Fibre infrastructure for ICT services could be laid in easily‐accessible covered trenches sharing
conduits for optical fibre, electricity, fresh water, and possibly storm water sewerage if gravity flow
can be maintained. There would be removable covers along the entire route length to ensure easy
access for installation and maintenance. These covers could have a surface suitable for pedestrians
or cyclists.
Retrofitting utility cables is costly. Blown fibre microducts should be considered to allow for addition
or replacement of fibre as demand for services increases [b‐11].

Figure 19 – Air Blown Fibre Tubing
[Brand‐Rex Ltd, b‐12]

3.2.2 Provision for Branching

No branching is allowed in the utility tunnel according to [b‐1].
Even so branching is essential for services involving gravity such as storm water run‐off.

3.2.3 Identification and Location of nodes/plant

Provision is needed for identification and location of underground ICT infrastructure. Examples
include barcodes and radio frequency identification tags.
As the sensor layer network evolves the precise geographic location of "a thing" will be critical. For
example, wireless devices containing a battery will need locating to replace the battery.

ITU‐T's Technical Reports and Specifications 409