High-penetration radiocommunication system using a compact character set

Abstract

A high-penetration transmission method uses a compact character set for encoding an alphanumeric message, in which the signal margin is increased by a combination of bit repetition and a relatively small increase in power. The combination of bit repetition and a relatively small increase in power with a encoding via a compact character set avoids unacceptable delay characteristics. Moreover, the combination of repetition and a relatively small increase in power with the compact character set of the present invention avoids the co-channel interference problems of systems which rely solely on a power increase to increase the signal margin, as less power increase is required to obtain the same increase in signal margin for a given delay time. In one embodiment, a mobile radiocommunication system is provided with a short message service feature for transmitting alphanumeric messages to and from a mobile unit. In order to ensure reliable transmission over channels having severe attenuation, the communication system, a short message is encoded with a compact character set. The message may be further encoded with error detection or correction coding; the message is divided into packets or groups of one or more bits each; each packet is transmitted, at a power level greater than the power level for voice transmission, multiple times over a TDMA communication channel, using the same time slot or slots for each transmission. The transmissions are integrated and checked for errors at the receiver to form a signal having an increased margin.