Low-power frequency-hopped spread spectrum reverse paging system
First Claim
1. A reverse paging system, comprising:
- a local paging terminal having a telephone connection means for receiving a telephone call with a paging message, and encoding the paging message;
a paging antenna connected to the local paging terminal operable for transmission of the paging message corresponding to a unique address;
a plurality of reverse pagers divided into a plurality of groups, each pager corresponding to the unique address and having a transmitter for transmitting an acknowledgement signal on a frequency-hopped spread spectrum carrier the frequencies being selected by a repeating pseudo-random code sequence, each of said groups being assigned to a different non-overlapping sequence segment on the code sequence where the pagers of each of said groups use orthogonal frequencies;
at least one reverse paging terminal having a receiving antenna for receiving the acknowledgement signal on a frequency-hopped spread spectrum carrier.
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Accused Products
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.
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Citations
24 Claims
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1. A reverse paging system, comprising:
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a local paging terminal having a telephone connection means for receiving a telephone call with a paging message, and encoding the paging message; a paging antenna connected to the local paging terminal operable for transmission of the paging message corresponding to a unique address; a plurality of reverse pagers divided into a plurality of groups, each pager corresponding to the unique address and having a transmitter for transmitting an acknowledgement signal on a frequency-hopped spread spectrum carrier the frequencies being selected by a repeating pseudo-random code sequence, each of said groups being assigned to a different non-overlapping sequence segment on the code sequence where the pagers of each of said groups use orthogonal frequencies; at least one reverse paging terminal having a receiving antenna for receiving the acknowledgement signal on a frequency-hopped spread spectrum carrier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A reverse paging system for use with a base transmitter for transmitting messages each corresponding to unique addresses, comprising:
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a plurality of remote units each corresponding to one of the unique addresses, each remote unit including; a radio receiver connected to an antenna for receiving the messages; input means for receiving information to be transmitted; remote unit control means connected to the radio receiver and the input means, and operable for continually monitoring a repeating pseudo-random random code sequence, for selecting a frequency hopping sequence based upon the repeating pseudo-random code sequence, and for encoding the information to be transmitted and producing therefrom encoded information; carrier generator means connected to the remote unit control means for producing a series of narrow-band carrier frequencies selected in response to the repeating pseudo-random code sequence; modulation means connected to the carrier generating means and the remote unit control means for modulating the encoded information onto the series of narrow-band carrier frequencies to produce a modulated frequency-hopped carrier; transmitter means for transmitting the modulated frequency-hopped carrier; and a base receiver for receiving the modulated frequency-hopped carrier and for demodulating the information. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A two-way paging system for use in an existing licensed paging frequency allocation, comprising:
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a base station having a conventional paging transmitter operating within predetemined bandwidth and power limitations and including means for sending time-of-day synchronization information as part of the paging data stream and having a frequency-hopping spread spectrum receiver for receiving and decoding a plurality of frequency-hopped spread spectrum signals; a plurality of remote units, each being a member of only one of a plurality of unique groups, each remote unit comprising; means for receiving standard paging signals containing a unique address of the remote unit, a message to be conveyed and the time-of-day synchronization information; means for comparing the time-of-day synchronization information to a local calendar-clock; means for storing an adjustment to the local calendar clock; means for selecting a transmission code from a look-up table based on the synchronization information and the adjustment to the local calendar clock, the transmission code being used to select a unique pattern of frequencies used in a unique sequence used only within the group to which this remote unit corresponds; and means for transmitting a frequency-hopped spread spectrum signal back to the base station in response to an operator command, the signal being transmitted at a power level of less that one watt and the signal including the unique pattern of frequencies transmitted in the unique sequence such that collisions between other remote units of other groups is avoided through the use of an orthogonal set of selected frequencies and patterns.
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Specification