N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 9 - Wireless Systems and Technologies                                                                                 Slide 39 of 80                                                                                                    ________________

Overview of LMDS Architecture

                                    Network Operating Center (NOC) 

                                    Fiber-Based Infrastructure

                                    Base Station

                                    Customer Premise Equipment

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Various network architectures are possible within LMDS system design. The majority of systems operators will be using point-to-multipoint wireless access designs although point-to-point systems and TV distribution systems can be provided within the LMDS system. The LMDS systems support multimedia (voice, video, and data) services. The LMDS network architecture consists of primarily four parts: network operations center (NOC), fiber-based infrastructure, base station, and customer premises equipment.

Network Operations Center (NOC) - The NOC contains the network management system (NMS) equipment that manages large regions of the customer network. Multiple NOCs can be interconnected.

Fiber-based infrastructure - Typically consists of synchronous optical network (SONET) optical carrier (OC)–12, OC–3, and DS–3 links; central-office (CO) equipment; ATM and IP switching systems; and interconnections with the Internet and public switched telephone networks (PSTN).

Base Station - The base station is where the conversion from fibered infrastructure to wireless infrastructure occurs. Base station equipment includes the network interface for fiber termination; modulation and demodulation functions; and microwave transmission and reception equipment typically located atop a roof or a pole. Key functionalities which may not be present in different designs include local switching. This function implies that billing, channel access management, registration, and authentication occur locally within the base station. The customers connected to the base station can communicate with one another without entering the fiber infrastructure.

The alternative base-station architecture simply provides connection to the fiber infrastructure. This forces all traffic to terminate in ATM switches or CO equipment somewhere in the fiber infrastructure. In this scenario, if two customers connected to the same base station wish to communicate with each other, they do so at a centralized location. Billing, authentication, registration, and traffic-management functions are performed centrally.

Customer Premises Equipment - The CPE configurations vary widely from vendor to vendor. Primarily, all configurations will include outdoor mounted microwave equipment and indoor digital equipment providing modulation, demodulation, control, and customer-premises interface functionality. The CPE may attach to the network using time-division multiple access (TDMA), frequency-division multiple access (FDMA), or code-division multiple access (CDMA) methodologies. The customer premises interfaces will run the full range from digital signal, level 0 (DS0), plain old telephone service (POTS), 10BaseT, unstructured DS1, structured DS1, frame relay, ATM25, serial ATM over T1, DS–3, OC–3, and OC–1. The customer premises locations will range from large enterprises (e.g., office buildings, hospitals, campuses), in which the microwave equipment is shared between many users, to mall locations and residences, in which single offices requiring 10BaseT and/or two POTS lines will be connected. Obviously, different customer-premises locations require different equipment configurations and different price points.