wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

7-10 Industrial Communication Systems
for transport layer where the TCP is modified to respond appropriately to unreliable wireless environment
by avoiding retransmission and effective congestion control [KK98]. In addition, power-efficient
strategies are also suggested for the application layer where the operating system (OS) is modified to
handle the hardware and software more efficiently [LS98].
7.4.3 topology and Connectivity
In most of the ad hoc networks, P2P communication topology is required, which means each node in
the network must be able to communicate with any other node in the same network. To attain this,
connectivity between the entire networks must be provided all the times. But the limited resources,
uncontrolled mobility of nodes, and the characteristics of wireless communication channels make it a
challenging issue. Topology and connectivity control can have a significant impact on the performance
of wireless networks. Such algorithms are used to enhance energy efficiency, minimize interference, and
increase effective rate by adjusting transmission power.
Topology control algorithms can be categorized into centralized and distributed [SBC03]. Centralized
approach need to have the global knowledge of the network and works well in static networks. Distributed
approach uses localized information only and works well in mobile networks. There are many issues
with topology control algorithms. Optimal transmit power computation is one of the main challenges.
If high transmit power is used, interference /contention range is increased. If lower power is used, it may
result in a disconnected network. Furthermore, adjusting power level may introduce additional latency.
In centralized approach, where all the information is sent to a central authority, reducing processing and
communication overhead is a challenging task. Efficient topology control algorithms which take node
mobility into account still require a great deal of attention.
7.4.4 Security
Security is required for secure communication and to maintain desired network performance in ad
hoc network [YLYLZ04]. Security issues in ad hoc networks are more challenging than in conventional
networks because of open access mechanism and P2P architecture, no infrastructure, highly
dynamic network topology, publicly known protocols, stringent resource constraints, and unattended
operation.
Security for ad hoc networks entails key establishment and trust setup, secrecy and authentication,
privacy, secure routing, intrusion, and secure data aggregation [PSW04]. Three main goals of security
as discussed in [DPT03] are to maintain confidentiality (data protection), integrity (unauthorized data
tampering), and availability (service availability anywhere and anytime). Common security threats outlined
in [PSS00] and discussed in [DPT03] include “stealing confidential information, tampering information,
resource stealing, and denial-of- service attacks.”
Following is the summary of the open research opportunities and challenges in the security implementation
for ad hoc networks, which are discussed in [ZFZ08,R96,RFLW96]. Because of the wireless
environment and lack of firewall-like devices, the eavesdroppers can spoof the ongoing communication
that compromises confidentiality, privacy, and integrity of data. On the network layer, malicious
nodes can introduce denial-of-service attacks, holes, and tamper information compromising basic
security primitives, for example, availability and integrity of data. Therefore, designing secure routing
protocols is one of the challenging areas in ad hoc networks. [T97] and [SMG97] are a few efforts
in this direction. The major challenge is the authentication of the public keys, which can be solved by
using identity-based cryptography. As the security operations are very frequent in ad hoc networks,
it requires an efficient symmetric key algorithm for authentication and encryption. Key revocation
should happen when a node is declared as malicious or when it is under compromise node attack.
Although different key revocation schemes are working, still there is a demand for universal key
revocation scheme [ZFZ08].
© 2011 by Taylor and Francis Group, LLC