EP0484918A2
Expired / Lapsed
EP
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Improved cellular telephone service using spread spectrum transmission
Assignee: Raytheon Co
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Filing: 1991-11-06
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Granted: —
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Expires: 2011-11-06
Abstract
Abstract A spread spectrum processing system (10) that employs wide bandwidth spread spectrum radio transmissions overlaid over the existing cellular voice signals to simultaneously provide additional cellular services without causing objectionable interference to current users of the cellular voice channels. The spread spectrum radio transmissions also support a large number of low rate digital messages. Both vehicle location and messaging functions are obtained without sacrificing any of the existing voice channel capacity. The cell site processor (40) is designed to share the existing cellular frequencies, real estate, antenna towers, antennas (31), and low noise amplifiers (32) used in the cell site radio frequency receiver chain. The only additional cell site equipment is the spread spectrum signal processor (3240 The processing system provides a means for achieving vehicle location accuracies that are improved by greater than two orders of magnitude over that which is possible by the current transmissions in that band. It provides a means of achieving transmit power control of the vehicle transmitter (11, 12) to combat the extremely large variation (dynamic range) of radio signal path loss to the receiving sites. It also provides a means of excising at the receiver the excessively strong conventional voice cellular signals that are not under power control which ordinarily might interfere with the successful reception of the new broadband signals.
Inventors
- 👤 William E. Sagey
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 08:42
CPC Classifications
H; H04; H04W; H04W88/00; H04W88/08; H04W64/00
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
309 words
In a cellular telephone system (10) having a plurality of cell sites comprising voice communication equipment that is adapted to permit two-way voice communication between mobile and land based telephone systems, and wherein the cellular telephone system (21) comprises a low noise amplifier (32) coupled to a narrowband voice signal transceiver (34) located in each mobile system and at each cell site that includes an antenna (31) adapted to transmit and receive voice communications signals, a vehicle location and digital messaging system characterized by: a vehicle location processor (16) coupled to the cellular telephone system that is adapted to process encoded vehicle location messages transmitted thereto from a plurality of cell sites (13, 20-26), which location messages comprise time of arrival information received by each of the respective cell sites that corresponds to the relative location of a vehicle that has transmitted a vehicle location signal thereto; and a spread spectrum radio transmission system characterized by: a spread spectrum processor (40) coupled to the low noise amplifier (32) of the cellular telephone sites that is adapted to receive and process digital spread spectrum radio transmissions comprising digital messages and vehicle location signals, and which is adapted to transmit the digital message signals to designations identified therein by way of the land based telephone system, and which is adapted to transmit the vehicle location signals to the vehicle location processor for determination of the relative locations of the transmitting vehicles; and a spread spectrum exciter (58) coupled to the transceiver of each mobile system that is adapted to transmit digital spread spectrum radio transmissions using the antenna thereof, which radio transmissions comprise digital message signals and the vehicle location signals that are processed by the land based telephone system and which are simultaneously transmitted with two-way voice communication signals transmitted by the cellular telephone system without adversely affecting voice transmission.
Claim 2
Dependent Claim
86 words
The vehicle location and digital messaging system of Claim 1 which is further characterized by: probe signal transmitting means located at each of the cell sites (13, 20-26) for transmitting a probe signal (29) that has a predetermined stepped configuration and that is adapted to control the transmit power of the transmitters (11, 12) in the vehicles to ensure that the energy density of the digital message signals received at the cell site are below the noise level in each narrowband voice signal transceiver located therein.
Claim 3
Dependent Claim
68 words
The vehicle location and digital messaging system of Claim 2 which is further characterized by: probe signal receiving means disposed in the transceiver (11, 12) of each mobile system for receiving the probe signal (29) transmitted by the probe signal transmitting means and for adjusting the transmit power of the transceiver (11, 12) of the mobile system in accordance with the strength of the probe signal received thereby.
Claim 4
Dependent Claim
29 words
The vehicle location and digital messaging system of Claim 2 wherein the probe signal (29) is characterized by a short duration pulse that is transmitted at predetermined time intervals.
Claim 5
Dependent Claim
27 words
The vehicle location and digital messaging system of Claim 4 wherein the probe signal (29) is characterized by a pulse having a duration of approximately 8 milliseconds.
Claim 6
Dependent Claim
50 words
The vehicle location and digital messaging system of Claim 1 wherein the burst waveform of the spread spectrum location signals transmitted by each of the spread spectrum exciters (58) has a relatively short duration so that they are imperceptible in the normal burst noise background of the cellular telephone system.
Claim 7
Dependent Claim
32 words
The vehicle location and digital messaging system of Claim 1 wherein the burst rate of the spread spectrum signals transmitted by each of the spread spectrum exciters is less than 10 milliseconds.
Claim 8
Dependent Claim
36 words
The vehicle location and digital messaging system of Claim 1 wherein successive spread spectrum tracking signals are sequentially transmitted in successively higher spread spectrum subbands and the process is repeated once the highest subband is reached.
Claim 9
Dependent Claim
89 words
The vehicle location and digital messaging system of Claim 1 wherein the sprad spectrum processor (40) is characterized by: spread spectrum transmitting means for transmitting a location waveform that is not objectionable to users of the voice channel, and that is indicative of an emergency situation at the transmitting vehicle, which waveform is a relatively short spread spectrum pulse that is spread across the entire narrowband voice channel, which pulse is on the order of 10 milliseconds or less in duration, and which is transmitted at predetermined time intervals.
Claim 10
Dependent Claim
22 words
The vehicle location and digital messaging system of Claim 9 wherein the spread spectrum pulse has a duration of approximately 2 milliseconds.
Claim 11
Dependent Claim
89 words
The vehicle location and digital messaging system of Claim 9 that is adapted to transmit a tracking waveform that is not objectionable to users of the voice channel, and that is indicative of the location of the transmitting vehicle, which waveform comprises a full power spread spectrum pulse having a duration of approximately 10 milliseconds, which pulse is transmitted at successive predetermined time intervals, and wherein each succeeding pulse is transmitted in different spread spectrum subband of a plurality of subbands distributed across the full mobile transmit voice band.
Claim 12
Dependent Claim
22 words
The vehicle location and digital messaging system of Claim 11 wherein the spread spectrum pulse has a duration of approximately 2 milliseconds.
Claim 13
Dependent Claim
81 words
The vehicle location and digital messaging system of Claim 1 wherein the sprad spectrum processor (40) is characterized by: spread spectrum transmitting means for transmitting a messaging waveform that is not objectionable to users of the voice channel, and that is suitable for continuous digital message transmission compatible with the voice channel, which waveform is spread across the entire band of voice channels, and which has a signal level that is always below the noise level of the narrowband voice channels.
References Cited (Backward Citations)
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