Showing papers on "Base station published in 1973"

Radio telephone system

Abstract: A portable duplex radio telephone system includes at least one base station transmitter having a predetermined base transmission range, and a plurality of portable or mobile units each having a predetermined portable maximum transmission range predeterminately shorter than the base transmission range. Satellite receivers are deployed about the base station within the base station transmission range for receiving transmissions from the portable units. The base station transmitter transmits signals on a signalling channel and on at least one communications channel. Each transmitter signalling and communications channel has a frequency that is paired or associated with a receiving frequency of the satellite receivers. In a multiple base station system, the portable receiver has means for scanning the base station transmitter signalling frequencies and for tuning the portable transmitter to the signalling frequency associated with the frequency of the strongest signalling signal received from the base transmitter. When communication is initiated, the portable transmitter and receiver are automatically retuned to one of the communications channels as determined by the strongest signalling frequency received by the portable receiver and by channel availability. Means are also provided in the system to continuously locate a portable unit and switch the operating frequency thereof as the portable unit moves between base station transmitter coverage areas. Further means are provided to automatically reduce the output power of each portable transmitter to the minimum level required for satisfactory communications in order to reduce battery drain and the interference caused by the portable transmitters.

Automatic mobile radio telephone system

Abstract: In a multi-channel radio telephone system, each mobile station is assigned a home channel for receiving calls but can initiate calls on any idle channel. Communication is normally in a duplex mode but automatically reverts to semi-duplex when a calling mobile initiates a call to a called mobile on the called mobile''s home channel. Automatic subscriber ticketing is accomplished at the base station, and each channel communicates with the public telephone system via a respective dedicated line. A nonsubscribing mobile attempting to initiate a call on the system is automatically connected to the base station operator for completion of the call, the caller''s I.D. number being automatically displayed for the operator. When called, a mobile automatically returns a decode complete signal to the base station. If the decode complete signal is not received within a predetermined time interval, the call is terminated and the base station automatically proceeds to determine if the called mobile is busy or out-of-service and returns a corresponding signal to the calling party. The mobiles are adapted to operate in other systems wherein the normally assigned home channel is unavailable. In such cases the mobile automatically seeks a channel bearing a predetermined code which identifies that channel as an alternate home channel for the mobile.

A Mobile Radio Single-Frequency "Two-Way" Diversity System Using Adaptive Retransmission from the Base

Abstract: This paper describes an adaptive retransmission system capable of providing a UHF (1 GHz) mobile radio channel with "twoway diversity." The system is unique in that all signal processing associated with the diversity combining is done at the base station. A two-branch prototype of the system, without modulation, was field tested to determine its adaptive retransmission performance. These tests indicate that the statistics of the fading envelope at both the base and mobile stations closely agree with those predicted by theory for an equal gain combiner with correlation between the branches.

Duplexer type radio-telephone data receiver and transmission system

Abstract: A radio-telephone system embodying a duplexer network whereby a request for computerized data may be transmitted to a base station and the data received from the base station through a single antenna. The system includes a scanner to scan incoming signals in conjunction with a decoder. The decoder receives the signals and when they are incorrect, causes the scanner to continue scanning, while, when they are correct, it causes activation of the system to permit it to transmit a request for data and receive the data in return.

Long range marine navigation system

Abstract: In navigation for trans-horizon operation of a mobile station relative to a plurality of base stations, a fractional microsecond high frequency pulse is generated at the mobile station and is expanded with frequency modulation by a surface wave device. The expanded modulated pulse is imposed onto an RF carrier which is amplified and radiated from a transmitter antenna. At each base station, the transmissions are sensed and compressed while reversing the frequency modulation at the mobile station in a mirror image relation to produce a near replica of the pulse. The pulse is synchronously processed for production of a control pulse precisely at the peak of the replica. The control pulse initiates a like transmission from the base station to the mobile station. Thus, the system achieves greatly increased sensitivity and range of operation with increased range resolution by utilizing the full power available in a wide transmission pulse while retaining narrow pulse resolution.

Switching plan for a cellular mobile telephone system

Abstract: Federal Communication Commission Docket 18 262 allocated a 75-MHz band to the common carriers to implement high capacity mobile telephone systems. The Bell System has proposed a cellular arrangement of low-power transmitters/receivers that permits frequency reuse in a coverage area. This method of achieving spectrum efficiency will require extensive centralized coordination and control to properly administer channel assignments and to interconnect the mobiles with each other and with the direct distance dialing (DDD) network. This can be accomplished by means of an electronic switching system (ESS) with special data terminals and trunking arrangements, and a unique program. In the proposed plan the radio sites (base stations) act effectively as remote concentrators in the frequency domain under the control of ESS, which in turn acts primarily as a trunk-to-trunk switcher. In addition to the usual switching, signaling, and supervising functions, the switching office must also perform numerous special functions including paging of mobiles, location of mobiles (signal strength and ranging data analysis), channel reassignment of mobiles, and reswitching of mobiles to various base stations-these last three occurring while customers ate talking.

Communications system and method for transmitting over a limited bandwidth transmission link

Abstract: A communications system, including portable transmitters and several remote receivers connected to a base station by means of a limited bandwidth transmission link (such as a telephone line), wherein the receivers include an encoder for transmitting the information over the transmission link and removing a small band of the information and inserting a carrier frequency, amplitude and frequency modulated by the coded squelch signals and the information signal strength signals, and the base station includes a decoder

Navigation ranging synchronization

Abstract: In radio ranging from a mobile station and a plurality of base stations, different pulse position codes are transmitted from the mobile station in sequence, one code for each base station. Identical reply pulse position codes are transmitted from each base station in response to receipt of one of the unique codes. In response to receipt of each reply code, a plurality of trains of listening intervals, one for each base station, are initiated each being dependent upon the time of receipt of a reply code from a base station. A train of uniformly time spaced ranging pulses is then transmitted after receipt of a reply pulse code from the base stations. The transporting of ranging pulses from each base station is enabled in a sequence between base stations responsive to successive ranging pulses in the train.

Properties of mobile radio propagation above 400 MHz

Abstract: This paper begins with a discussion of multipath interference. The spatial description of the field impinging upon a mobile radio antenna is derived and the power spectrum and other properties of the signal envelope are considered. Next, large scale variations of the average signal are discussed. Measurements of observed attenuation on mobile paths over both smooth and irregular terrain are summarized. The paper concludes with a discussion of methods of predicting the area of coverage from a base station.

A mobile radio single-frequency "Two-way" diversity system using adaptive retransmission from the base

Abstract: This paper describes an adaptive retransmission system capable of providing a UHF (1 GHz) mobile radio channel with "two-way diversity." The system is unique in that all signal processing associated with the diversity combining is done at the base station. A two-branch prototype of the system, without modulation, was field tested to determine its adaptive retransmission performance. These tests indicate that the statistics of the fading envelope at both the base and mobile stations closely agree with those predicted by theory for an equal gain combiner with correlation between the branches.

An approach to estimating land mobile radio coverage

Abstract: This paper reports some propagation and coverage prediction results using various models provided to the Federal Communications Commission, Spectrum Management Task Force.