Image Processing Reference
In-Depth Information
Coverage of BS/AP
Central control of BS/AP
Service of BS/AP
Central control of BS/AP
Service of BS/AP
Service of BS/AP
802.11
Infrastructure mode
PCF
GSM
802.11
Ad hoc mode
Cellular
Ad hoc
ZigBee
DECT
UMTS
WCDMA
Piconet
bluetooth
scatternet
ZigBee
beacon
ODMA
UMTS/TDD
MANET
ODMA
parrot
PRnet
stationless
PRnet
FIGURE .
Classification of wireless technologies between cellular and ad hoc; MANET stands for Mobile (or
Multihop [JIC]) Ad hoc NETwork (designed for Internet applications [IET]), PRnet stands for Public Radio network
[Mal], ODMA for opportunity driven multiple access [rd,RBM]; a Bluetooth scatternet means that several
Bluetooth piconets are interlinked; BS
=
base station, AP
=
access point.
is—because of the licensing regulations and costs for extensive infrastructure—often not economic.
WWANs are thus excluded from further investigations.
For the discussion of the radio network performance, most important differences between ad hoc
andcellularsystemsarediscussedinthefollowing:
•
As cellular networks are systematically laid out, the minimum distance to the next co-
channel interferer (i.e., the next uncoordinated user transmitting at the same time on
the same frequency) is generally controllable, known, and fixed. In contrast, in ad hoc
networks the next co-channel interferer can be very close from one moment to the next,
without any possibility to influence the situation (see Figure .).
•
Centralized control in cellular networks allows for effective and fair distribution of
resources, because of the accurate knowledge of the overall traffic demand and the possi-
bility of a more global resource management. For ad hoc networks or several coexisting
WPANs, knowledge of overall traffic demand is generally not available and the systems
compete for the resources.
25.3 Bluetooth Technology
25.3.1 Technical Background
Bluetoothtechnology(BT)isirstofallacablereplacementtechnologyaimingatefortlesswireless
connectivity in an ad hoc fashion. It supports voice as well as data transmission [Haa,BS,Bis,
Blu,Blu]. Its desired key associations are easy to use, low in power consumption, and low in cost,
with the aim that the Bluetooth functionality is integrated in as many devices as possible.
To meet these goals, the BT special interest group placed the technology in the unlicensed
ISM-band at . GHz. This allows close to worldwide deployment without needing to pay fees
