| Summary: | Technical aspects and general organisation of mobile radio systems are outlined, with particular reference to anticipated overcrowding problems. Various methods for making better use of available frequencies are described, including bandwidth reduction and channel sharing or trunking. A low-cost simulation method is proposed for the investigation and development of mobile radio trunking schemes, whereby an effective demonstration may be made within the confines of a laboratory bench. Trunked radio networks may be implemented by designating a unique calling channel for mobile/base control dialogues. A hardware simulator for such a network is described in detail, using radio frequency cabled links between independent mobiles and a base station control unit. The apparatus brings together techniques in the linear, digital, and microprocessor fields, including a method of programme storage which permits rapid changes in control unit software. Extensive use of microprocessors results in a flexible system which can model a variety of schemes. Operational procedures and typical experimental configurations are described, using a minicomputer interface for simple text display of system status. The introduction of several mobile radio environmental problems - noise, fading, and interference - is discussed, together with methods for their generation. Further experimental procedures are outlined in which the minicomputer provides an interactive graphical display.
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