01-01-2013, 03:03 PM
corDECT Wireless Local Loop
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Introduction:
The traditional wired local loop used to connect each telephone subscriber to the nearest exchange is expensive and unreliable. Wireless Local Loop (WLL) systems largely eliminate these copper wires using wireless technologies and could provide a cost effective solution. corDECT is a technology based on DECT(Digital Enhanced Cordless Technology), corDECT is an advanced, field proven, wireless Access system developed by Midas Communication & The Indian Institute of Technology, Madras in association with Analog devices Inc .U.S.A. corDECt is a wireless Local Loop System And it is used to connect each subscriber to its nearest exchange. It uses Multi-carrier time division multiple access. With corDECT we can achieved the better quality of voice and data capability at a cost bellow that of wired local loop. This technology uses Micro cells and dynamic channel selection (DCS).And it can handle the high subscriber density without frequency planning. By using the 1,000-line corDECT technology it achieve the Busy Hour Call Attempt (BHCA) is about 36,000 call/hr. Which is far greater than the wired local loop which achieves 20,000hr.and by using 10,000-line the BHCA is about 2,10,0000 call/hr. corDECT technology uses the high SWITCH MIPS processor.
This technology gives the data transfer rate of 30-70kbps.The main features of the corDECT is Toll Quality Voice, Simultaneous Voice and Data Internet up to 70 Kbps, For both urban and rural networks, Lost cost effective access technology. And after some more years the corDECT will give rise to new technology that will give the top quality of voice and better Internet up to 1Mbps. The DECT standard proposed by the European Telecommunication Standards Institute (ETSI) is meant for providing wireless access to networks of various types, from the PSTN to LAN’s. It deals only with the task of defining the air interface between subscriber terminal and Base Station. The mode of connecting the DECT-based Wireless Local Loop system to the PSTN and Internet is left to the service provider.
Conceptual Access System:
In this conceptual model, there is a Subscriber Unit (SU) located at the subscriber premises. The SU has a standard two-wire interface to connect a telephone, cordless phone, or modem. It also provides direct (without modem) Internet connectivity to a standard PC, using either a serial port (RS-232 or USB) or Ethernet. The access system allows simultaneous telephone and Internet connectivity. The SU’s are connected to an Access Centre (AC) using any convenient technology like wireless, plain old copper, coaxial cable, optical fiber, or even power lines. The AC is thus a shared system catering to multiple subscribers. The voice and Internet traffic to and from subscribers can be concentrated here and then carried on any appropriate backhaul transport network to the telephone and Internet networks respectively. At the AC, the telephone and Internet traffic is separated. The telephone traffic carried to the telephone network on E1 links using access protocols such as V5.2. the Internet traffic from multiple subscribers is statically multiplexed, taking advantage of the burst nature of the Internet traffic, and carried to the Internet network.
Working of corDECT WLL
With its micro-cellular architecture, each corDECT system has many base stations distributed throughout the coverage area. All these base stations cannot be located at the exchange (DIU). In the corDECT system, the local loop consists of a wired connection from the DIU to the base station and a wireless connection from the base station to the subscriber. The wired connection between base station and the DIU employs N-ISDN physical interface for communication (Fig. 2). The DIU consists of an OMC (Operation and Maintenance Control), SWITCH and Base Station Interface Modules (BIMs). The OMC platform is a standard Personal Computer (PC). It provides a user interface to the operator and performs the system operation, maintenance, remote fault monitoring, subscriber registration and billing. The OMC PC runs the DECT NWK software. The OMC is connected to the SWITCH through a 128 kbps signaling link. The SWITCH is responsible for switching the voice between the subscribers and runs the DECT DLC Layer. For connecting each CBS to the DIU, only three pairs of wire are required in order to serve 30–70 subscribers with each CBS supporting 12 simultaneous duplex connections. Each link connecting CBS and DIU provides 16 kbps signaling bandwidth. The CBSs are connected to the DIU at the BIM and each BIM supports two CBS. The BIMs are connected to the SWITCH through 64 kbps signaling link. The SWITCH monitors the health of the BIMs and CBSs connected to them. The CBS provides wireless access to subscribers and runs the DECT PHL, MAC layers and a part of DECT DLC layer. The portable runs the entire DECT protocol stack.
Base Station Distributor :
The BSD is a compact, remotely located, locally powered, rack-mountable unit that supports up to 4 CBS’s. The E1 interface between a DIU and the BSD can be on copper, fiber, or radio and link distance depends only on the link design. The BSD is designed to extend corDECT coverage to packets of subscribers located far away from the DIU.
Conclusion:
The corDECT development team will continue to make available new products to take corDECT to ever higher levels of performance. At the same time, existing versions will be maintained and upgraded. This will ensure that corDECT remains the most versatile and cost-effective WLL system with the best suite of features and services.