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Journal of Emerging Technologies in Web Intelligence Contents

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108 JOURNAL OF EMERGING TECHNOLOGIES IN WEB INTELLIGENCE, VOL. 2, NO. 2, MAY 2010B. Integrated CPE Functional DecompositionFigure 2 shows the Open CPE architecture that is<strong>in</strong>tended to fulfill the requirements as listed above and tosupport multiple broadband access technologies andtelephony protocol standards. It is composed <strong>of</strong> a CPEController Module (CCM), LAN Interface Modules(LIM), and WAN Interface Modules (WIM). The CCMconsists <strong>of</strong> a CPE Controller, Flash, ROM, and RAM thatconta<strong>in</strong> a Real-Time Operat<strong>in</strong>g System (RTOS) ands<strong>of</strong>tware to implement telephony call control, networkmanagement, and service logic functions, as well as thirdpartyapplications. The CCM may also <strong>in</strong>clude a DigitalSignal<strong>in</strong>g Processor (DSP) to implement media stream<strong>in</strong>gprocess<strong>in</strong>g functions, such as vocoder, echo cancellation,tone generation and detection. The CCM can be reconfiguredto support different protocols or telephonystandards through s<strong>of</strong>tware download<strong>in</strong>g.Figure 2: Open CPE architectureWIM and LIM conta<strong>in</strong> plug-<strong>in</strong>s to support variousWAN and LAN <strong>in</strong>terfaces. WIM may consist <strong>of</strong> aWireless Modem , a Cable Modem, a DSL Modem, aFiber Modem, and a 10 Gigabit Ethernet module thatprovide <strong>in</strong>terfaces to the broadband access network. LIMmay <strong>in</strong>clude <strong>in</strong>terfaces to analog phones. There are twobuses responsible for the distribution <strong>of</strong> user data, realtimevoice stream<strong>in</strong>g, control signal<strong>in</strong>g, and themanagement data between the CCM Controller and theWIM/LIM. The <strong>in</strong>terface specification should meet therequirements <strong>of</strong> transport<strong>in</strong>g real-time and non-real-timedata. The open CPE architecture as described above isderived from the abstraction <strong>of</strong> multiple CPE platformsthat may use various broadband access technologies andstandards. The goal <strong>of</strong> the abstraction is to f<strong>in</strong>d out whatfunctions are common to all CPEs and therefore shouldbe implemented <strong>in</strong> CCM, and what functions are <strong>in</strong>terfacedependent. and therefore are more appropriatelyimplemented <strong>in</strong> plug-<strong>in</strong> modules. Figure 3 gives anexample <strong>of</strong> the CPE functional decomposition. It depictsthe protocol stacks <strong>of</strong> I-CPE support<strong>in</strong>g cable, xDSL, and10 Gigabit Ethernet broadband <strong>in</strong>terfaces to provide voiceand data convergence services.Figure 3: I-CPE protocol stackThe Cable CPE is <strong>in</strong>tended to provide VoIP services.It uses Network-based Call Signal<strong>in</strong>g (NCS) [4] as thesignal<strong>in</strong>g protocol to perform telephony call controlfunctions, while encapsulat<strong>in</strong>g the voice stream<strong>in</strong>g data <strong>in</strong>the Real-Time Protocol (RTP) packets to be sent to theCable Modem Term<strong>in</strong>ation System (CMTS). xDSL CPEprovides VoIP and Voice over AAL2 (ATM AdaptationLayer type 2) Loop Emulation Services (LES) [5]. It usesH.248 [7] and Channel Associated Signal<strong>in</strong>g (CAS)protocols to implement telephony call control functionsfor VoIP and VoAAL2, respectively. The voice stream<strong>in</strong>gdata are encapsulated <strong>in</strong> either RTP or AAL2 packets tobe sent to the DSL Access Multiplex (DSLAM). In thisexample, the Ethernet CPE acts as a SIP client to provideVoIP services. SIP is used to establish, modify, andterm<strong>in</strong>ate multi-media sessions and calls [10]. The voicestream<strong>in</strong>g is encapsulated <strong>in</strong> the RTP packets transmitt<strong>in</strong>gto the term<strong>in</strong>at<strong>in</strong>g party via the User Datagram Protocol(UDP) connection.In the Time Division Multiplex (TDM) networks,only call control and management functions areimplemented by s<strong>of</strong>tware <strong>in</strong> the processor, leav<strong>in</strong>g thevoice process<strong>in</strong>g to be handled by the hardware, because<strong>of</strong> the latency concern.However, the trend toward packet telephony, alongwith the advancement and <strong>in</strong>creas<strong>in</strong>g performance <strong>of</strong>processors <strong>in</strong> recent years, has made it possible for, andeven demanded that, voice stream<strong>in</strong>g be processed bys<strong>of</strong>tware. Thus, as Figure 3 <strong>in</strong>dicates, it makes good senseto locate the CCM-WIM <strong>in</strong>terface between Layer 2 andLayer 3 <strong>of</strong> the protocol stack. The CCM conta<strong>in</strong>ss<strong>of</strong>tware to implement voice process<strong>in</strong>g, the signal<strong>in</strong>gprotocol, and management functions. WIM shouldimplement Physical layer (PHY), Medium AccessControl (MAC), Logical L<strong>in</strong>k Control (LLC),Asynchronous Transfer Mode (ATM), and ATM.Adaptation Layer (AAL) functions that are closelycoupled with each broadband access <strong>in</strong>terface.IV. CONCLUSIONThe explosion <strong>of</strong> the Internet along with regulationand technology changes are reshap<strong>in</strong>g telecommunicationnetworks <strong>in</strong> many ways. The <strong>in</strong>dustry is mov<strong>in</strong>g towardthe convergence <strong>of</strong> PSTN and the Internet. The© 2010 ACADEMY PUBLISHER

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