US 5,499,266 A · Low-power frequency-hopped spread spectrum acknowledgement paging system

Abstract

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.

Claims6

Dependent claims

A base receiver for use with a reverse paging system having a base transmitter for transmitting pager uplink messages in one of a plurality of paging channels each corresponding to unique addresses and a plurality of remote units for receiving the messages and transmitting downlink information using frequency-hopped spread-spectrum radio frequency signals synchronized to a repeating pseudo-random code sequence, the base receiver comprising:

clock means for producing a local repeating pseudo-random code sequence in synchrony with the repeating pseudo-random code sequence of the remote units;
radio frequency receiving means connected to the clock means for simultaneously receiving a plurality of downlink frequency-hopped spread-spectrum radio frequency signals from the plurality of remote units;
down converter means connected to the radio frequency receiving means for separating the downlink frequency-hopped spread-spectrum radio frequency signals into a plurality of narrow-band frequencies corresponding to assigned frequency hops and for downconverting the plurality of narrow-band frequencies corresponding to the assigned frequency hops for producing therefrom a plurality of downconverted frequency hops;
decoding means connected to the down converter means and the clock means and operable for decoding information contained in each of the downconverted frequency hops to track the frequency hops of at least one of the plurality of remote units in synchrony with the local repeating pseudo-random code sequence;
and
control means connected to the down converter means, connected to the clock means and connected to the decoding means, the control means operable for selecting the local oscillator frequencies needed for downconverting the plurality of narrow-band frequencies corresponding to the assigned frequency hops.

3 more elements

Dependencies are inferred from the claim text.

Low-power frequency-hopped spread spectrum acknowledgement paging system

Life of this patent

Low-power frequency-hopped spread spectrum acknowledgement paging system

Life of this patent

Abstract

Claims6