An acknowledgement paging system is described which fits within the existing infrastructure of a paging network and which provides low cost manufacture and low power operation while still enabling the acknowledgement paging over long distances. The acknowledgement paging system consists of a standard paging transmitter and a plurality of remote paging units which respond to a page using frequency-hopped spread-spectrum differential bi-phase shift keying communications. The plurality of pagers are assigned to groups with each group being assigned a separate starting location in a common, repeating pseudo-random noise code which determines the frequency hops. The grouping of pagers minimizes the collisions of acknowledgment transmissions between groups and the enables a large number of paging units to operate within a single geographic area. The pagers include a special double loop PLL synthesizer to produce an accurate narrow band frequency and to change or hop frequencies in a rapid fashion. The base receiving unit employs special algorithms for retrieving very low power acknowledgement paging messages in a noisy environment by using data redundancy, data interleaving, soft decoding and error correction codes to strip the bi-phase-modulated, frequency-hopped spread-spectrum digital data transmitted from the remote pocket pagers. A history of the frequency and phase drift is used during reception of the acknowledgement messages to predict the phase and frequency drift of the encoded digital information to further reduce decoding error. Signal to noise ratios are determined for each frequency hop and relatively noisy hops are discarded or minimized in a soft decoding process based redundancy of data bits.
This is a division of application Ser. No. 08/158,441, filed Nov. 24, 1993, now U.S. Pat. No. 5,430,759, which is a continuation-in-part of U.S. patent application Ser. No. 07/932,610 entitled "REMOTE POSITION DETERMINATION" filed Aug. 20, 1992, now abandoned which in turn is a continuation-in-part of U.S. patent application Ser. No. 07/961,776 entitled "PAGER WITH REVERSE PAGING FACILITY" filed Oct. 15, 1992, now U.S. Pat. No. 5,335,246 both of which are hereby incorporated by reference .
A semiconductor integrated circuit which realizes a reception circuit that can stably detect symbol values even in a case where, in the reception of serial transmission data, the serial transmission data has its phase shifted relative to the sampling clock signals or has its waveform degraded due to the deviation of the delay of a signal in a transmission line. The semiconductor integrated circuit comprises a first clock-signal generating circuit which generates a clock signal of N phases synchronized with an input clock signal, a second clock-signal generating circuit which generates a clock signal of M phases synchronized with one phase selected from among the N-phase clock signal generated by the first clock-signal generating circuit, and in which N.noteq.M holds, and a computation circuit which finds a control value for use in selecting one phase from among the N-phase clock signal, on the basis of the logic value of the serial transmission data sampled using the N-phase clock signal and the M-phase clock signal.
The invention relates to a system for transmitting data according to the frequency hopping method. The digital data, which is transmitted in suddenly changing transmission frequency hops, is encoded according to a woven code consisting of an interlinked external and internal convolution code. The data to be transmitted by hop is preferably distributed over several parallel hops sent with different frequencies.
A method and apparatus improve the user friendliness of messaging systems. A message sender is requested to create a message ID which is used to identify a message being sent by the message sender. At some later time the message sender can query the message center using the sender generated message ID to ask the center to verify whether the message has either been sent to or received by the intended recipient.
A method of reducing computation in spread spectrum signals in which a spread spectrum signal sent by a transmitting station (SS1) includes a group and an individual identity code. A receiver (10, 12) stores the received signals based on their group codes and analyses the stored signals on a group by group basis. This greatly reduces this computation required when recovering individual messages from a number of simultaneously transmitted spread spectrum signals. Optionally the transmitting station may send the group and individual identity code signals simultaneously as quadrature signals.
A receiver of modulated carrier-wave signals equipped with a pseudo-random code time marker, particularly for radio navigation, comprises coincidence modules each of which comprises chronometric memory media which receives a wanted signal, provides storage as data of the time offset of the code offset estimates and the frequency and phase carrier-wave status, and on that basis provides, with a local clock, a local carrier-wave image and that least one local code repeat for the relevant signal and code and carrier-wave slaving control functions providing correlation of the wanted signal and the local code repeat on the basis of a frequency and phase offset signal between the carrier-wave of the wanted signal and the carrier-wave image. It further comprises Fourier transformation media for reception of the offset signal and management/decision-making media which provide invalidation of time offset data where the Fourier transformation indicates the presence of energy outside of the vicinity of a central coincidence line.
