Processor Modules. The main components of processor modules are DMS-Core Processor, file processor, Application Processor and LPP. The DMS-core processor supports the call processing, performs control function, down loading DMS super-node software and supports other peripheral controllers. The core processors is a set of central processing units. The file processor provides access to large data files for applications such as SCP and AMA. The application processors are intended for special applications. LPP supports CCS7 and advanced data applications. It is used to support SSP, STP, SCP, ISDN and other services.
Switching Module. The DMS-100 system is equipped with two types of switching matrix. They are dual shelf network (DSN) or enhanced network (ENET). With this arrangement, it takes up less than 16% of the space for the same number of step by step
DMS - Core processor
Line peripheral processor (LPP)
system 20% of cross bar system. DMS offers remote switching with a bunch of remote modules. The use of remote modules extends the advantage like plant floor savings, cost reduction, less maintenance etc. The use of DSN and ENET supports narrow band and wide band services.
Maintenance and Administration Position (MAP) : MAP provides the operation management, administration and maintenance. MAP is a integrated multifunction machine interface that switch maintenance, line and trunk network management and service order changes can be carried out. The billing system supports automatic message accounting (AMA). It records AMA data on tape and disk.
Peripheral Module (PM) : Peripheral modules (PM's) are used as interface between digital carrier spans (DS-1), analog trunks, and subscriber lines. The PM's are used for scanning lines for changes of circuit state, doing timing functions used for call processing, creating dial tones, sending, receiving signalling and controlling information to and from the other modules and checking the network. Before 1984, only four types of PM's gave trunk interfaces (TM, LM, DCM and RLM). Latter many modules are added. All those modules are discussed below :
Trunk Module (TM) and Line Module (LM). The TM changes incoming speech into digital format. TM has the ability to handle 30 analog trunks. The PCM information is combined with trunks supervising and control signals and then transmitted to 2.56 Mb/s over speech links to the network. Each trunk can carry 36 ccs. The TM also uses service circuits such as MF receivers, announcement trunks and test circuits.
LM gives an interface for a maximum of 640 analog lines and condenses the voice and signalling into 2, 3, or 4 DS-30, 32 channel speech links. 4 speech links have the ability to handle 3,700 Average Busy Season Busy Hour (ABSBH) CCS per LM.
Remote Line Module (RLM). It is a LM operating in a remote location from the DMS host. The RLM's can be located up to 150 miles from the host office, depending on the transmission facilities.
Digital carrier Module (DCM). Gives digital interface between the DMS switch and the DS-1 digital carrier. The DS-1 signal consists of 24 voice channels. The DCM takes out and puts in signalling and control information on the DS-1 bit stream which then makes them DS-30, 32 channel speech links. The DCM can interface 5 DS-1 lines, 5 x 24 = 120 voice channels, into 4, 32 channel speech links. The DCM can carry a maximum of 36 CCS of traffic on each trunk.
Digital Trunk Controller (DTC). It provides digital trunk inter-connection between DMS-100 digital switching system and other central offices. It has the ability to interface 20, DS-1 lines. Then the DS-1 lines are linked to the network by a maximum of 16 DS-30 speech links, each trunk is able to handle 36 CCS.
Line Group Controller (LGC). It does medium level processing tasks with the ability to use host and remote subscriber line interfaces. The LGC can interface upto 20 DS-30 speech links from the LCMs or up to 20 DS-1 links with the ability to serve RSCs, RLCMs or OPMs.
Line Trunk Controller (LTC). It combines the function of the LGC and DTC. The LTC has the ability to handle the LCM, RSC, RLCM, OPM and digital trunk interfaces. The LTC has the ability to give interfaces to a maximum of 20 outside ports from DS-30 A speech links or DS-1 links to 16 network side DS-30 speech links.
Line Concentrating Module (LCM). LCM when used with the LGC or LTC is just an expanded version of the line module. An LTC provides interface between the subscriber lines and the line group controller. Both of these interfaces provide line concetration. It can serve upto 640 subscriber lines interfaced with two to six DS-30A speech links. Using 6 speech links 5,390 CCS can be handled per LCM.
Outside Plant Module (OPM). It is an outside plant remote unit. The OPM can handle 640 lines over six DS-1 links.
Remote Switching Centre (RSC). It interfaces subscriber lines at a remote location to a DMS-100 host. It consists of (a) LCM similar to LCM of host DMS-100 (b) Remote cluster controller (RCC) when gives DS-1/LCM interface, local switching inside the remote and local intelligence (c) Remote trunking which handles the use of RSC originating or terminating traffic for digital trunking off the RSC. It can give trunking to a CDO co-located with the RSC or within the service range of the RSC, PABXs or Direct inward dialling (DID) trunks. (d) Remote-off-remote which lets the RLCMs and OPMs connect to the RCC through DS-1 interfaces. It lets RLCM and OPM subscribers to use the same lines to the host as the RSC subscribers and (e) Emergency Stand-Alone (ESA) which allows you to call internal to the RSC, if communication with the DMS-100 is lost. It will give station to station and station to trunk calls for DOTS, IBN and electronic business sets.
RSC can handle 16,200 CCS with the use of 16 DS-1 links. RSC had the ability to handle interface for 5,760 lines and is used a replacements for dial offices or PBXs. The Remote line concentrating module (RLCM) is just LCM used in a remote location from the DMS-100 host. The RLCM can handle 640 lines. This is sometimes used as a replacement of CDOs or PBXs.
Subscriber Carrier Module (SCM). It interconnects digital loop carriers to the switching fabric. It gives a direct interface for remote concentrators. Different versions of SCM are SCM-100 R, SCM-1000 U, SCM 100 S and SCM-100. The SCM 100 R can interface upto five Northern Telecom DMS-1 rural remote terminals (RTS). A DMS-1 rural remote terminal can interface upto 256 lines. The SCM-100 U can interface up to three DMS-1 urban RTs. A DMS-1 Urban can interface up to 576 POTS or special service lines. SCM100s can interface upto four mode I (non-concentrated) SLC-96 systems or up to six Mode II (concentrated) systems.
Software Architecture. The DMS 100 is programmed in BNR proprietary PASCAL, in PROTEL and in Assembler (rarely these days). It is upgraded by software loads that take place every six months. The software for the central processor is written in PROTEL, a highlevel PASCAL based language. Peripheral processors use a XMS-PASCAL software language.
The DMS supernode software is arranged in four layers as shown in Fig. 6.12.
The base layer contains DMS super node operating system. The telecom layer supports all basic telecommunication functions. The product layer supports different products that work under this architecture. Some of the products are DMS-100, DMS-250 etc. The customer layer supports customer software and trial services specific to customer.
The evolutionary changes and further demands in telecommunication such as new services for data images and personnel communication demands the switching system for increased processing power, additional line connectivity and open connections to a new generation of multiservice access platform. The siemens EWSD switching system is well ahead of the challenge with a uniquely flexible architecture that anticipates change and adapts easily. EWSD system is an integral part of powerful network solutions. The EWSD switch is designed for incremental expansion in processing power connectivity and services.
The EWSD system meets all of today's service needs in even the largest metropolitan centers. It minimises the investment required to meet each new level of service demand. It makes the convergence of voice and data a reality. Hence, because of its inherent versatility, the EWSD system has become the universal switch, capable of responding to the full range of telecommunication standards and all variety of global service demands. Over 160 million lines of EWSD switch capacity are now in service in more than 100 counties. It was first put into service in 1980.
Features of EWSD system :
1. EWSD system is the leader in the availability of industry standard national ISDN. With national ISDN, telephone companies and carriers can
(i) Offer integrated voice and data to meet the needs of the most businesses and residential professionals.
(ii) provide dial-up video conferencing
(iii) offer distance learning services by universities.
(iv) offer medical imaging to health care providers
(v) also guarantee their customers full portability of expensive on-premises terminals and equipment.
2. The AIN 0.1 and AIN 0.2 capabilities on EWSD ststems, enables the network service providers to create their own customer services. The switch offers full SSP access to SCP, allowing services to be deployed across the entire network without changes to individual switching centers.
3. The EWSD switch provides a wide variety, of business and residential services encompassing ISDN, centre and AIN capability. These services are complemented by comprehensive operation, Administration, maintenance and provisioning (OAM and P) capabilities such as user friendly craft machine interface, diagnostics, billing, fault handling, traffic and maintenance measurements.
4. EWSD systems can combine digital and analog lines, allowing full interoperability between digital and analog terminals.
5. With EWSD technology, business customers can have all the conveniences and functionality of EKTS systems without the need to purchase and maintain customer premises switches.
6. EWSD technology allows carriers to deliver ACD services directly from the network. Customers can avoid the cost of on site ACD switching equipment.
7. EWSD system provides a high capacity interface which will prove essential in connecting ISDN, personal communications, video and other advanced services.
8. EWSD also provides Global system for Mobile communication (GSM) based PCS.
9. EWSD systems connect to any of the new generation of multi-service remote digital carrier terminals.
Hardware Architecture. The EWSD switching system is based on a modular hardware platform completely integrated under generic software. Processing is distributed throughout the modular components, and the components can be assembled into a single central office, or they can be distributed to move call processing close subscriber communities. The basic subsystems of the EWSD switch are
• Switching network • Packet handler
• CCS network • Message buffer, central clock
• Digital line unit • Generator and coordination processor.
Fig. 6.13 shows the Siemens Stromberg-Carlson EWSD switch hardware architecture.
The switching network (SN) is the switching fabric of the EWSD. It is time multiplexed and is classified as a TST network. It connects lines trunks and signalling connection between subsystems. This LTG interface multiplexes and controls traffic between line and trunk interfaces and the switching network.
The architectural design provides maximum flexibility. Line types such as single or two party analog, coin, TR-08, basic rate ISDN and XDSL can be varied simply by changing the line card. Connectivity can be increased or relocated by deploying additional digital line units (OLU) or Remote Control Units. DLU interconnects analog subscribers, ISDN basic access and PBX lines to the LTG and also supports SLC access. The channel bank interface connects analog trunks to the LTG.
The services encompassing ISDN, centrex and Advanced Intelligent network capabilities are complemented by comprehensive Operation, Administration and maintenance (OAM and P) capabilities such as user friendly craft machine interface, dignostics, billling fault handling, traffic and maintenance measurements. This subsystem also supports the human mechine interface systems. The CCNC interface supports SS7 signalling between the EWSD switch and SSPs, STPs and SCPs. MB, processes signals between the network and the coordination processor. The CCG provides clock signals for the EWSD switch.
MB - Message buffer, CCG - Central clock generator CP - Coordinator processor, SLC - Subscriber loop carries
Fig. 6.13. Hardware architecture of EWSD.
MB - Message buffer, CCG - Central clock generator CP - Coordinator processor, SLC - Subscriber loop carries
Software Architecture. The software is developed utilizing well defined and loosely coupled functional subsystems. Software additions and changes to one function do not have direct impact on other functions except by design. The structure of the EWSD software is highly modular. The EWSD software can broadly be classified into OAM and P software, exchange software, support software and customer premises software. The exchange software supports call processing, the coordination processor, and all other peripheral processors. All peripheral units such as the MB, DLU, LTG and CCNC are loaded with specific software for their respective function alities. The switching network is also loaded with its specific software.
Because of the quality of manufacturing and exhaustive pre-testing of software releases, the EWSD switch has proven a reliability leader in many countries. EWSD system proved low downtime rates, extemely high reliability and high protection for service providers switching investment.
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