NexNet is a proprietary two way paging system designed by Nexus Telecommunications Ltd. of Israel. It utilizes spread spectrum technology integrated into their paging receivers to transmit response messages. In its initial implementation, messages are forwarded to pagers through the utilization of the POCSAG protocol. The additional messaging information required for time synchronization of the transmitted messages with the two way pager responses sent at a later time, as well as the transmission of two way paging control data, is imbedded within standard POCSAG output data. NexNet outbound data in support of two way paging is sent in such a way as to be totally transparent to normal POCSAG transmissions so that two way paging may coexist in any preexisting one way paging system.
The Nexus two way paging device, known as the Twager™, sends responses formatted according to the NexNet™ "uplink" protocol specification. In the Spread Spectrum technique, the data is transmitted over a range of different frequencies and is detected by receiving equipment located throughout the coverage region. Each Twager™ utilizes different sets of frequency combinations (frequency hops)when transmitting their data. Complete response messages may be recovered at receivers even though some portions of the response message may have been corrupted. This is because a message segment which is corrupted because of interference from other transmissions or by a simultaneous transmission from another Twager™ at one or more frequencies, has a high probability of being properly received at other frequencies over which this segment is transmitted.
In order to simplify the reception of the spread spectrum frequency hopped signals, the transmissions from the Twagers™ are required to synchronize to a precise clock. This precise time synchronization is achieved through the transmission of precision timing data which is imbedded in the POCSAG output stream. But, this is accomplished in a manner which permits this data to be overlaid into existing paging networks without the need to add any specialized transmission equipment.