General Electric Company

Ericsson Ge Mobile Communications Inc.

Ericsson Gmbh

George D Rose, Jr

Thomas A Brown

Stephen D Harrison

Richard J Patch

A method and apparatus for determining with high resolution the fidelity of communications over a communications channel is disclosed. Portable/mobile radios freely roaming between multiple trunked RF communications sites calculate the fidelity of communications received over current and alternate channels with comprehensive, high bit error resolution using a weighted average error dispersion procedure. The weighted average error dispersion analysis generates for each group of redundant messages (and in some instances subpreamble bits) received by a roaming radio in each message frame a weighted average error dispersion number whose incrementally increasing magnitude reflects deteriorating signal fidelity. Decisions about switching to alternate communications channels are made by the roaming radio based on the incrementally changing weighted error dispersion number so that communication channels may be selected to achieve optimum signal fidelity and continuity of communication.

Method and apparatus for determining with high resolution the fidelity

Arrangements are disclosed for maintaining time synchronization of simulcast radio frequency communications system transmissions. A circuit continually instructs a modem to use the common system clocking signal, and modems are retrained whenever a channel is taken out of service because of a test call failure.

Self correction of PST simulcast system timing

In a multiple site radio frequency simulcasting RF transmission system, data transmitted from a control point to the RF transmitter sites exhibits random time delay skew because multi-phase modems recover clock signals from an arbitrary one of the multiple phases. The outputs of the modems are temporarily stored at the sites by memory buffers. The control point derives resynchronization signals from a source data clock, this signal containing frequency and timing information. The resynchronization signal is distributed to the various sites via additional phase-stable, delay compensated channels. Each site is provided with a clock recovery circuit that recovers the original source data clocking signal from the resynchronization signal and also extracts read-out timing information from the resynchronization signal. The recovered data clocking signal and the readout timing information are used to synchronize the readout from the FIFO memory buffers--providing approximately simultaneous (coherent) readout of the same data bits from the respective buffers of the different simulcasting transmitter sites.

Public service trunking simulcast system

In a multisite radio frequency simulcasting transmission system involving microwave-multiplex distribution paths to several transmitting sites, each path including manually settable amplitude and time delay devices for equalization of the modulation in signal overlap areas among the various transmitter sites, an automatic simulcast alignment device is included in each distribution path whereby transmissions between a control point and each site transmitter are periodically tested and each path is compensated for amplitude and time delay variations to thus maintain equalized amplitude and time of arrival of the modulation in the transmitter site overlap areas. Thus, the instantaneous distribution of the FM modulation sidebands is maintained to be ideally identical in the signal overlap areas.

Simulcast auto alignment system

A memory device is provided for an integrated injection logic (I.sup.2 L) device in solid state form by a resistor connected at one end to the logic device, and a diode having its cathode connected to the other end of the resistor at a programming junction, and its anode connected to a common point. If the diode conductors are melted or deformed by reverse diode current from the programming junction to the common point, a low impedance path is formed, and the logic portion is provided with a first logic input. If the diode conductors are left unmelted or intact, the logic portion is provided with a second logic input.

Growing community of inventors

Lynchburg, VA, United States of America

George D Rose, Jr