Wireless Communications: Networking and …

1 Part IWireless Communications: Networking and Cambridge University PressCambridge University Press978-0-521-51356-2 - Fixed-Mobile Wireless Networks Convergence: Technologies, Solutions, ServicesJoseph GhetieExcerptMore information1 Wireless Communicationsand NetworksCommunications by voice and physical signaling are common means of interactionbetween human beings. In the simplest forms, there is an emitting entity of informationand a receiving entity of information. As the sources move apart the need for telecom-munications appears self-evident. This simple model of communications becomes morecomplex when the information transmitted is not just sound, speech, or music, but fullmotion video images or various forms of data such as text, shared files, facsimile, graph-ics, still images, computer animation or instrumentation measurements.

2 This informa-tion can be transmitted using electrical or optical signals, the native analog informationundergoing numerous conversions and switching to accommodate various communi-cations technologies. Telecommunications can take place over various media be thattwisted copper pairs, coaxial cable, fiber optic, or Wireless radio, microwave, satel-lite, and infrared links. communication can be limited to a small group of people orextended to departments, compounds, or campuses and covering whole metropolitanareas, regions, countries, or continents. Hence, a shared infrastructure is needed, , acommunications networks can be classified in many ways, as there are distinct tech-nologies and network equipment needed for voice communications, data/computer com-munications, and video communications.

3 Among these types of communications, datacommunications, by the virtue of digitization of any type of information, has becomethe convergent system. Classification can also be done corresponding to the kind ofmedia used, wired and Wireless communications or by the underlying technologiessuch as circuit-switched networks (traditional voice communications), packet-switchednetworks (essentially data communications), broadcast networks (direct video broad-cast, cable TV), or message switched networks (store-and-forward electronic mail, voicemail, web serving). Networks classification can go even further, looking at geographicalcoverage, from wide area networks, to metropolitan area, local area, and to personal typical telecommunications network , historically focused on voice processing andvoice communications, is presented in Figure The network , a symmetric infras-tructure that connects Customer Premises Equipment (CPE) as the source and destina-tion of information (telephones), consists of four major systems:access,transmission,switching, andsignaling.

4 The access systems are part of the local loop and consist Cambridge University PressCambridge University Press978-0-521-51356-2 - Fixed-Mobile Wireless Networks Convergence: Technologies, Solutions, ServicesJoseph GhetieExcerptMore information4 Fixed-Mobile Wireless Networks ConvergenceCustomer PremisesEquipment (CPE)(source/destination)Access Systems(media)SwitchingSystemsCustomer PremisesEquipment (CPE)(source/destination)Signaling SystemsAccess Systems(media)SwitchingSystemsTransmissi on Systems(media)Public Telephone NetworkLocal LoopLocal LoopCentral OfficeCentral OfficeInter-Office FacilityFigure network Modelcopper-based twisted pair media or a combination of fiber optic and twisted pairs.

5 Theswitching systems are part of the Central Office equipment connected on one end tothe local loop lines and on the other end to the trunks that are part of the transmissionsystems. Last, but not least, signaling systems provide call control facilities for the wholenetwork through a specialized overlay network . Currently, the same infrastructure is usedto support not only voice but also data communications and other multimedia typical data communications network with clear roots in computer communicationsnetworks is presented in Figure Premises EquipmentInformation Source(sender/receiver)Transmission Systems(media, signals, noise)Customer Premises Equipment Information Destination(receiver/sender)

6 Data - SignalConverterAccessSystemAccessSystemS ignal - DataConverterRouterSwitchesRouterSwitche sRouterSwitchesCircuitLinkPathNodesNodes RouterSwitchesControlInformationPublic Data NetworkFigure Communications network ModelThe data communications network model is a symmetric infrastructure that connectsCustomer Premises Equipment (CPE), as source and destination of information (desk-top computer, laptop, server, fax machine, or instrumentation). It consists of four majorsystems:conversion,access,transmiss ion, andcontrol systems. The conversion sys-tems (modems, coders/decoders, multiplexers) provide data-signal and signal-data con-version to accommodate the existent local loop infrastructure that was initially Cambridge University PressCambridge University Press978-0-521-51356-2 - Fixed-Mobile Wireless Networks Convergence: Technologies, Solutions, ServicesJoseph GhetieExcerptMore informationWireless Communications and Networking5for voice communication .

7 The access systems are mostly part of the same local loop usedin telecommunications and consist of copper-based twisted pair media or a combinationof fiber optic and twisted pairs. Security functions, service access, and billing compo-nents might be built into access systems. In many instances the access and conversionsystems components and functions are bundled in real Networking products. There are nocircuit-switching systems involved since the information is packetized and the packetsare routed as part of the transmission systems, a vast network of interconnected nodes,essentially packet routers. Depending on the transmission procedures adopted, a dedi-cated system may establish, control, and terminate the connection between the senderand receiver of information.

8 Currently, to minimize cost, the same infrastructure is usedto support not only data but also digitized and packetized voice and other voice and data communications networks have evolved as part of the overalltechnical progress in telecommunications with the invention of alternative technologies,implementation of various architectural designs, and multiple service offerings. Theultimate goal of this evolution is the integration of voice and data, a multidimensionalconcept that combines IT infrastructures, networks, applications, user interfaces, andmanagement aimed at supporting all forms of information media on all forms of net-works.

9 A narrower view of this integration is aimed at supporting voice and video overpacket-based Internet Architectures and ProtocolsCommunication between various network components requires a common understandingbetween sender and receiver regarding the transmission procedures, the types of signalscarrying the useful information, and the format of the data transmitted. There are fourmajor aspects involved in communications services: communication interfaces, com-munication protocols, layered communication stacks, and information interfacesare connection points between network components designedaccording to standard or proprietary specifications.

10 An interface is defined by mechan-ical, electrical, and functional characteristics that allow communication to take placebetween adjacent network protocolsare formal descriptionsof data unit formats and transmission rules for message exchange between networkentities. communication protocols are organized in multiplelayered communicationstackswhere each layer provides services to the layer above. Theinformation mod-elsare collections of abstracted managed object definitions and attributes for deviceshaving common characteristics. Currently, there are many communications architecturesand protocols in proceduresused to provide connectivity between network devicesmay include three distinct phases, as indicated in Figure The first is theestablishmentphase which arises as a result of an inquiry about the availability and ability of thecorresponding party to exchange information.