N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 9 - Wireless Systems and Technologies                                                                                   Slide 5 of 80                                                                                                    ________________

    Mobile Radio Concept

                                   Allows Users to Move Physically While Using a Device

                                   Mobile Applications (Phone Services, PC Computing)

                                   Methods of Transmission 

                                   Significant Return on Investment due to Gains in Efficiency

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The wireline networks require a physical link between the user's device and the network resources, which limits the use of other available resources. The wireless networks enable the user freedom of movement when conducting business. Now users can enter, update and access information much faster and make timely decisions. This translates into significant return on investment on the wireless systems.

Mobile Systems typically use one of four methods for transmission: Microwave, Cellular, Packet Radio or Satellite.

Microwave - are high frequency  (2 G Hz to 40 G Hz) radio transmissions and are capable of very high bandwidth. Microwave signals are easily impacted by attenuation, and interference and must be amplified or repeated often, every 1 to 50 miles.

Cellular - is a cell-based telephone system infrastructure to enable transmission of voice and data. A cellular system supports lesser bandwidth than a microwave system.

Packet Radio - is a secure method for data transmission. The information is divided into packets containing address, error control and security codes. Only recipients with the proper decoding code can translate the information.

Satellite - is a form of microwave communication. A satellite receives transmissions from the surface of the earth and passes, or reflects it back down to another earth station.

Early mobile systems had limited coverage and capacity, and used operators for call connection. Sites normally configured to provide coverage for 30-60 Kms. Two channels (30 K Hz) were used for two-way communications.