Abstract: A communications accounting system is provided wherein the transfer of call detail record information from a remotely located phone may be accomplished in an efficient manner. During non-billable processes or during airtime billed at a reduced rate, the call detail record (CDR) information from the previous registration is simultaneously sent to the collector system for processing to the billing system. More specifically, encrypted and compressed authorization information and call details records (CDRs) from the previous use of the phone are simultaneously communicated from the Cellular Call Computer--Programmable Off-line (C3PO) to the host computer system by modem or other suitable manner. At the validation server, the authorization information is decrypted and uncompressed and stripped away from the CDRs, while the call is live, and sent to an authorization service.

Abstract: There is provided a mechanism for providing data services over a wireless cellular network. It comprises: establishing communications over the cellular network; upon a subscriber designating that it has a data communication, redirecting data traffic to the designated frequency (a shared data channel) on an interconnected wireless data network exhibiting (cellular) reuse of data channel frequencies; and returning the subscriber's transceiver to voice mode upon cessation of data communications. Data service will appear to have been provided by the cellular network.

Abstract: Cell selection and reselection by mobile station in a cellular mobile radio network with a plurality of layers of cells includes, when the station is in a standby state and after selection of a cell by the station, identification of a layer containing the selected cell, reselection of cells in the layer during a predetermined time-delay, cumulative counting of the number of cells reselected in the layer during that time-delay, and comparison of the cumulative number with two thresholds. The reselection, cumulative counting and comparison steps are repeated if the cumulative number is between the thresholds. Otherwise, a change of layer is effected on the basis of the comparison and the previous steps are repeated, starting from the identification step. The mobile station selects the layer most appropriate to the speed at which it is travelling.

Abstract: Several mobile assisted handoff methods for use in the cellular communication system comprising a plurality of cells are disclosed. First, the quality level of a cell a mobile station is presently using is measured to determine whether the quality level is above or below a threshold. If the quality level is below the threshold, a primary list of cells is assigned to the mobile station, whereas if the quality level is above the threshold, a secondary list of cells is assigned to the mobile station. The quality level of each of the assigned cells is then measured by the mobile station and reported to the communication system.

Abstract: A method and system for performing an intersystem handoff of communication with a mobile station between base stations of first and second cellular systems is disclosed herein. At the mobile station, a quantifiable parameter of a signal transmitted by a second base station of the second system is measured. When the measured value of the quantifiable parameter passes through a first predetermined level, the mobile station communicates a signal quality message via a first base station of the first system to a first mobile switching control station. A channel request message is then communicated from the first mobile switching control station to a second mobile switching control station within the second system. At the second base station, a quantifiable parameter of the signal received from the mobile station is also measured. The second base station establishes communication with the mobile station when the measured value of the quantifiable parameter passes through a predetermined level.

Abstract: A method for use in a cellular communication system is disclosed which dynamically assigns a communication device to a cell site and which dynamically assigns transmit power levels to the communication device. The method is based on measurements of interference levels at cell sites and on the path gain between the communication device and the cell site.

Abstract: A cellular communication network (10) includes base stations located in orbiting satellites (12) and any number of subscriber units (26). The satellites (12) monitor the quality of signals received from subscriber units (26) and provide link quality indicator (62) data which subscriber units (26) interpret as instructions to adjust their transmit power levels. Subscriber units (26) evaluate received signal strength and received signal quality to determine whether the signals received at the subscriber units (26) are being interfered with. Subscriber units (26) evaluate the link quality indicator (62) and the quality of signals received at the subscriber units (26) to determine whether the signals received at the satellites (12) are being interfered with. When interference is detected, the subscriber units (26) request a hand-off to another channel (30) within the same cell (28).

Abstract: Modem throughput across a cellular mobile telephone network is increased by controlling the response of the modem to blank and burst orders. In the case of a power control order, the modem may be made aware of the fact that the channel has not changed. Significant performance gain in terms of channel throughput can then be achieved by avoiding a lengthy retraining procedure. The modem operation may be suspended during the blank and burst order and enabled after the blank and burst order, avoiding an unnecessary retrain procedure during the blanking period. In the case of a handoff, the modem may be directed to immediately perform a retrain procedure rather than wait for the long blanking period to be detected by the modem or the link access procedure.

Abstract: A method of communication handover from a first communication entity (33) to a second communication entity (43) in a communication system (10) where a communication unit (80), communicating with a transceiver (23) associated with the second communication entity, is linked to the first communication entity. The invention provides for establishing a communication link between the communication unit and the second communication entity while maintaining a communication link between the communication unit and the first communication entitiy. Then, communications are substantially simultaneously transfered to the second communication entity while terminated from the first communication entity.

Abstract: A hard-handoff control method for a CDMA mobile switching center includes the steps of detecting an original target switching center number of a switching center for managing a target cell of the handoff request message; converting the speech channel of the mobile station to second switching center areas by determining that the mobile station shifts from the first anchor station in the first switching center to a second anchor station if the target switching center number detected is same as its own switching center number; determining the position of the switching center areas where the mobile station opens a speech path if the target switching center number detected is different from its own switching center original number; converting the speech channel of the mobile station to the second switching center areas if the first switching center is determined as the anchor switching center; comparing the target switching center number with the anchor switching center number if the first switching center is not

Abstract: In a multi-site communication system, a communication may be handed off from a first site to a second site in the following manner. Upon request and when a communication resource is available, a communication resource allocator allocates the communication resource to the requesting communication unit located in the first site. The communication resource allocator also identifies a reserved communication resource in each adjacent site to the first site. When the communication unit relocates to the second site of the adjacent sites, the communication resource allocator allocates the reserved communication resource of the second site to the communication unit without a request from the communication unit.

Abstract: A method and apparatus for providing a reliable means to perform handoff from a code division multiple access (CDMA) system using a pilot signal to an alternative access technique system. Simple pilot box circuitry is added to a set of border base stations. The border base stations are base stations which operate only in the alternative access technique and which have coverage areas which are contiguous with coverage areas of CDMA operation base stations. The mobile unit monitors for the pilot signal from the border base stations in the same manner as it monitors for pilot signals from the CDMA operation base stations. When the mobile unit detects the pilot signal corresponding to a border base station, it notifies a system controller in accordance with standard operation. The system controller is aware that the pilot signal corresponds to a border base station and thus triggers a hard handoff process to the alternative access technique system in response thereto.

Abstract: A cellular telephone system is described of the type wherein a plurality of contiguous cells, each having an assigned set of identification codes, are arranged with means for maintaining continuous communication with mobile telephones moving from cell to cell. The system allows multiple access by including means for assigning at least one of the in the assigned set of identification codes to more than one mobile telephone. A unique identification code is assigned to a mobile telephone located in the cell. A signal having a unique identification code is generated for identifying the mobile telephone. The signal is coupled to the zones. A combiner is also provided for combining signals from all of the zones in the cell. A receiver is coupled to the combiner for retrieving the signals having the code.

Abstract: If a mobile station or a base station considers it necessary to perform a hand-over, a new base station is selected as a hand-over receiving base station and a hand-over supplying base station is defined as a master base station whereas the hand-over receiving base station is defined as a slave base station depending on the master base station. The slave base station receives a signal from the master base station, compares it with a frame timing signal of the master base station, adjusts a frame phase of the slave base station into a frame phase of the master base station, and adjusts a frame phase of a down link line from the slave base station to the mobile station into a frame phase of a down link line from them aster base station to the mobile station.

Abstract: A satellite cellular communication system includes satellites in motion that project cells upon the surface of the Earth. These cells are in motion and pass over individual subscriber units (26) engaged in communications, thus requiring individual subscriber units (26) to perform handoffs as an active current cell (300) currently servicing them advances. Selection of a subsequent servicing cell requires evaluation of active neighboring cells. A pre-computation of candidate cells is performed in advance according to a cell activation schedule. Active neighboring cells of an active current cell (300) are evaluated and prioritized in advance of individual subscriber unit's need for them. A candidate handoff cell list is then delivered to a satellite (12). A candidate handoff cell list is broadcast to all individual subscriber units (26) located within active current cell (300) for use in handoff decisions.

Abstract: An intelligent mobile radio unit is served by one of a network of macrocells and microcells. The unit is arranged to monitor, for example, the signal strength or bit error ratio of signals transmitted from each of a set of candidate base stations of cells surrounding the serving base station based on the assessment of a running average of the rise/fall in signal quality, the unit is arranged to determine from a look-up table of stored templates of conditions for handover whether a handover between base stations and between macro- and microcells is appropriate.

Abstract: CDMA mobile communication method and system for realizing an autonomous distributed control of radio channel allocation, a synchronization control for a smooth establishment/switching, and a VOX control for a capacity increase are provided. At either one station of each base station and the mobile station, one of a plurality of prescribed short spread codes is selected, and a data sequence to be transmitted is spread by using the selected short spread code and a prescribed long spread code and then transmitted, while at another one station, the data sequence before spreading is reproduced and received by despreading the data sequence from that either one station by using the selected short spread code and the prescribed long spread code.

Abstract: A method, system, and apparatus for communication and handoff in a cellular phone system in which candidate cell units which can support communication with a mobile phone are identified. Neighbor cell units which have recently supported communication with the mobile phone are also identified. Handoff threshold values for each candidate cell are determined based on the existing communication quality and whether the candidate cell is also a neighbor cell such that the handoff threshold is higher when the candidate cell is a neighbor cell. A decision to handoff is made when the improvement offered by candidate cell is greater than the handoff threshold.

Abstract: A frequency hopping synthesizer is constructed from two FET-based multiplier circuits each responsive to a carrier input signal and a modulation signal to produce respective output signals which are in-phase combined to provide a frequency-shifted signal. The multiplier circuits each comprise two dual-gate field effect transistor (FET) amplifiers which are electrically balanced to suppress unmodulated carrier components so that only the modulated carrier signal appears. The respective carrier input signals and modulation signals are in quadrature phase relationship. A direct digital synthesizer controllably generates signal components which serve as the modulation signals for the multiplier circuits.

Abstract: A microcellular communications network includes a plurality of base station units and corresponding antenna units. Each includes either conventional transmitters and receivers or all digital transmitter and receiver equipment, and interface circuitry to a mobile telecommunications switching office. The microcell traffic output is applied to a frame generator/multiplexer. The output of the frame generator/multiplexer is applied to a digitally modulated laser and conveyed by fiber to a remote antenna unit, which demultiplexes the microcell traffic signal, applies it to a digital-to-analog converter, and applies it to a power amplifier and a main antenna. The received signals are filtered, digitized, multiplexed together and transmitted over the optical fiber back to the base station. The strongest signal is selected for use. Deployment of an all digital microcellular communications system occurs in two stages.

Abstract: In a cellular communication system (40) a handoff candidate list is generated for a source sector (51) by eliminating (12) from a list of potential handoff candidates (52-56) any sectors having an interference parameter exceeding a threshold value. The list is further reduced by determining (21) a handoff radius (60) and eliminating any candidate sectors (52-56) that fall outside the handoff radius (60). Candidate sectors (52-56) that do not have overlapping coverage areas are also eliminated (23). In addition, candidate sectors (52-56) having a relative angle of sight to the source sector (51) that exceeds a maximum angle are also eliminated (24). Finally, the list is reduced (15) to a preset number of candidates dependent upon the interference parameter.

Abstract: In a mobile communication system, a method and an apparatus for handing off a mobile station from a first channel on a serving base station to a second channel on a target base station, the mobile station transmitting at a first transmission phase on the first channel, the second channel being ready to take over the communication with the mobile station transmitting at a second transmission phase. A device for determining a time offset is provided in the target base station and is adapted to tune in to the mobile station for determining, prior to a handoff, the time offset between the first transmission phase and the second transmission phase. Also, a device is provided for shifting, upon handoff, the transmission phase of the mobile station by the determined time offset relative to the first transmission phase.

Abstract: A mobile communication system is disclosed which precludes the necessity for mobile station to perform processing for microcell zone switching even when it moves from one microcell zone to another and which permits high-speed microcell zone handover. The service area of mobile communication is split into a plurality of macrocells; the macrocells are each subdivided into a plurality of microcells; a microcell base station equipped with a transmitting and receiving antenna and a power amplifier is installed in each microcell; a different communication channel is assigned to individual mobile station in the macrocell; even when the mobile station moves from one microcell to another, no channel handover takes place; and only when the mobile station moves from one macrocell to another, a mobile network control center which supervises the macrocell base stations effects channel handover.

Abstract: A multi-level layered cellular radio architecture serves mobile subscriber stations moving within the system. Best server selection is performed for the mobile stations by assigning within each cell a preference value to each other one of the cells with which is associated by proximity of service area. The strength of the radio signal received by the mobile from the serving cell as well as the radio channels of associated cells is measured. A decision as to the best serving cell for the mobile station is made based upon both the preference value of the associated cells and the signal strength of their respective radio channels.

Abstract: A method to be used in a Source Routed Bridged LAN by which access points maintain location information of mobile stations, and forward packets destined for mobile stations that have moved to another access point. This method resolves the problem that correspondent stations do not (timely) update the routing information to the mobile stations.

Abstract: A mobile telephone system has in a cell a base station and sub-stations which are connected to a mobile switching center. The mobile telephone system has control channels and frequencies which are time divided to traffic channels. Some of the frequencies are selected as identification frequencies. Each of the sub-stations is assigned a unique set of frequencies from among the identification frequencies and constantly transmit their respective frequency set. A mobile station connected to the base station listens to the identification frequencies and reports the strongest of these frequencies to the mobile switching center. The mobile switching center compares the reported frequencies with the unique set of frequencies, compares the reported signal strength with a threshold value and selects the nearest sub-station for handoff. The mobile switching center switches from the base station to a connection with the sub-section.

Abstract: A method and apparatus for measuring a characteristic of a fading signal received using a two or more branch diversity receiver is presented. This fading characteristic is generally proportional to the speed of the user. In a first embodiment the number of times the antenna branches change in a selection diversity process is counted, and the result is scaled for imbalance between the branches. The output of a fading quality estimator, indicative of the fading and generally proportional to the speed, is thereby obtained.

Abstract: A network hub switching center routes communications from and to a plurality of RTUs. CTSs transmit data to the RTUs dispersed over a predetermined CTS geographic area and the RTUs present multiplexed digital data which is synchronously related to the CTS broadcast signal for communication with identified individual RTUs within designated geographic areas. A number of intermediate receivers are provided with each CTS for receiving messages from low-powered local RTUs. The intermediate receivers are located at a set of cell subdivision sites, which are partitioned from the CTS geographic area and are dispersed over the CTS geographic area. The CTS data processing and transmission facilities provides for synchronizing the transmission facilities with a precision clock signal derived from an independent precision clock source. The clock source is independent of the radio broadcast signals when the interactive radio network operates in conjunction with a source of radio broadcast signals.

Abstract: In a data communication system having a network composed of a central facility, a plurality of relay units, and a plurality of terminal units, traffic information, which may contain information about a number of calls and a total amount of communication time occurred with respect to each relay unit over the predetermined interval, is sent from the relay units to a communication control unit. A ROM stores a threshold value for each relay unit and comparison is made to compare the received traffic information with the corresponding threshold value. Then, the is determined whether the subject relay unit is in a high-load condition. If so, relay units and terminal units that are scheduled to call the high-load relay unit are detected so that those units bypass the high-load relay unit.

Abstract: A mobile-assisted handoff technique for a cellular mobile communications system. A mobile makes measurements of adjacent base stations and reports the measurements to the serving base station. The measurements are adjusted to predict signal measurements that the adjacent base stations would make of the mobile. A full set of adjusted measurements, or a combined set of adjusted measurements and true measurements, made by those base stations with locate receivers, may be used in determining the best cell to hand-off the mobile to.

Abstract: A microcellular communications network includes a plurality of base station units and corresponding antenna units. The base station units are housed in a common location. Each includes either conventional transmitters and receivers or all digital transmitter and receiver equipment, and interface circuitry to a mobile telecommunications switching office. The microcell traffic output is applied to a frame generator/multiplexer. The output of the frame generator/multiplexer is applied to a digitally modulated laser. The laser output is conveyed by fiber to a remote antenna unit, which demultiplexes the microcell traffic signal and applies it to a digital-to-analog converter. The output of the digital-to-analog converter is applied to a power amplifier, which in turn is connected to a main antenna. RF signals from the mobile units are received at both a main and a diversity antenna. The received signals are filtered, digitized, multiplexed together and transmitted over the optical fiber back to the base station.

Abstract: In a frequency hopping cellular communication system (40) having a number of base sites (41-48) and using mobile assisted handoff, a method is offered of providing base site identification signals. The method includes the steps of assigning each base site of the number of base sites to a slot of a intersite control frame; and, periodically transmitting, in the assigned slot of the intersite control frame, the identification signal of the base site.

Abstract: An off-load cellular system controls cellular service between a main cellular system and the off-load cellular system and provides off-load cellular service to a mobile telephone. The off-load cellular system includes a receiver circuit, monitoring and receiving an origination message broadcast from the mobile telephone located in the off-load cellular system, and a system controller, for receiving the origination message output from the receiver circuit, and for outputting a connect signal indicating whether the off-load cellular service is to be provided to the mobile telephone responsive to the origination message.

Abstract: A technique for handing over between PCS networks that are connected to the ISDN/AIN switches wherein the PCS networks have source-centric hand over and the ISDN/AIN switching infrastructure has target-centric hand over by using AM components.

Abstract: For preventing a mobile radio terminal station from causing an interruption of communication on changing of a communication system, a receiving apparatus receives a main and a supplementary modulated signal at a boundary area which is between a main and a supplementary service area. The main and the supplementary modulated signals are modulated in a main and a supplementary modulation system, respectively. A first processing circuit (23) processes the main and the supplementary modulated signals into a first processed signal under control by a control circuit (28). A second processing circuit. (24) processes the main and the supplementary modulated signals into a second processed signal under control by the control circuit. In accordance with the first and the second processed signals, a signal producing circuit (25) produces a local signal. A switch circuit (26) selects one of the first processed, the second processed, and the local signals under control by the control circuit.

Abstract: A method for a non-registered communication unit to access a communication system consists of sending a service request. Upon receiving a service request, the communication resource allocator assigns an entry in the communication system database to the non-registered unit and assigns system default features to the entry such that the unit has default access to the communication system. Thus allowing a communication unit that has subscribed to system services and has not been recognized by the system manager to access the system utilizing default parameters until the system manages properly registers the unit.

Abstract: In a method of handing off traffic in a low orbit satellite communication system serving terminals, a terminal being connected to a terrestrial communication network by means of a connection station, handing off of the satellite-terminal and satellite-connection station links is possible only within a particular area. The decision to hand off the traffic is based on deterioration of the quality of service and of the radio environment for a group of terminals of said area. The system for implementing this method includes transmit/receive terminals and terrestrial connection stations.

Abstract: Each mobile unit in a cellular communications system accumulates at least one mobility or communications traffic (teletraffic) statistic representative of "typical" operation of the mobile unit within the cellular communications system. The mobile units process or collect the statistics and then transmit the aggregate statistics to a microcell or macrocell base station at time of origination of a call to or from the mobile, request for a handoff of a call by the mobile unit or the registration process. Included within the characteristics which can be monitored in accordance with the present invention are the following: cell sojourn time; area sojourn time; call holding times; call throughput; number of previous handoffs in an ongoing call; time periods between two consecutive failed handoffs for the mobile unit; and, the ratio of calls originating from a mobile unit to the number of calls terminating to a mobile unit.

Abstract: A passive handoff cellular communication system includes a cell divided into a plurality of zones. A base station is connected by transmission apparatus to a plurality of antenna units. The base station includes analog RF signal generation circuitry for generating a plurality of RF signals on different channels and a first switch responsive to a first control signal for switching and combining the RF signals to form a composite RF signal for each zone. Analog-to-digital conversion circuitry converts the composite signal for each zone to a digitized stream of samples and applies the samples to the transmission apparatus for transmission to each corresponding antenna unit.

Abstract: A method and an arrangement for subscriber location management among a group of radio networks comprising at least two radio networks (101, PMR1, PMR2) in which at least some of the subscribers (SBR1, SBR2, SBR3) may roam away from the home network and register in another radio network over the radio path. To enable centralized subscriber location management, the subscriber database (HLR) of one radio network (101) is arranged to maintain in a centralized manner the location data of all subscribers (SBR1) that have roamed outside their home networks and registered in another radio network (PMR2) at least with an accuracy of a radio network.

Abstract: A cellular mobile telephone exchange system comprises a switch which allows optional setting of the connecting conditions between a plurality of radio base-station transmitter-receivers and a plurality of base-station controllers.

Abstract: An IC memory card type radio modem includes a connecting portion, a radio section, a radio interface unit section, a channel selection circuit section, a terminal interface unit section, and a control section. The connecting portion can be connected to a PC card portion of a portable information processing device. The radio section is adaptable to at least one type of radio infrastructure. The radio interface unit section is adapted to the radio section. The channel selection circuit section is connected to the radio interface unit section. The terminal interface unit section is connected to the channel selection circuit section. The control section controls the plurality of radio sections. The radio interface unit section is controlled to always switch to a radio infrastructure which can perform communication.

Abstract: In a digital half-duplex frequency division multiple access radio system a mobile station is either sending or receiving. For each call between a mobile station and a base station, a first frequency is allocated for the up link direction (from the mobile station to the base station) and a second frequency is allocated for the down link direction (from the base station to the mobile station). The signals exchanged by the stations are organized in frames of predetermined fixed duration grouped into multiframes comprising a predetermined number of frames including at least one control frame. At least some of the control frames are listening frames during which the sending mobile station interrupts sending, switches to receive mode and (if appropriate) reverts to send mode.

Abstract: A two-way paging system utilizes four local frequencies for transmissions between pager units (22) and a central control station (20). A first local frequency (f.sub.1) carries a local clock; a second local frequency (f.sub.2) carries communications packets from the central control station to paging units; a third local frequency (f.sub.3) carries communication packets from the pager units to the central control station; and a fourth local frequency (f.sub.4) carries a status or request signal from the paging units (22) to the central control station (20). Transmissions on the fourth local frequency (f.sub.4) are in accordance with a time divided slot allocation among pager units accessing the central control station (20). For a two-way paging system having a plurality of central control stations (420.sub.x) servicing a corresponding plurality of cells, a total of eight frequencies are utilized within any one cell. Four of the utilized frequencies are the local frequencies (f.sub.1 -f.sub.

Abstract: In a method for handover between old and new cells of a time-division multiple access (TDMA) cellular mobile radio system a call between a mobile station and the system, initially effected via the old cell on a first channel defined by a first on air timeslot and a first set of frequencies comprising at least one frequency, is effected via the new cell on a new channel defined by a second on air timeslot and a second set of frequencies comprising at least one frequency. The first and second on air timeslots are identical, the first and second sets of frequencies are separate, and the method consists in transmitting, after verifying that the second on air timeslot identical to the first on air timeslot is available in the new cell, a frequency indication message indicating to the mobile station the second set of frequencies so that the mobile station continues the call using the same on air timeslot and the second set of frequencies.

Abstract: A communication system (100) has automatic selection of talkgroups based on geographically defined areas. The system (100)includes wireless two-way communication units (120) capable of communicating with each other within a coverage area 205. A particular communication unit 120 is automatically caused to operate as a member of a particular talkgroup when that particular communication unit (120) is within a particular area of operation (207), which particular area of operation (207) is smaller than, and contained within, the coverage area (205).

Abstract: A mobile terminal locator for locating a mobile terminal in a cellular telecommunication system having a plurality of base stations and associated cells. The mobile terminal locator identifies a plurality of candidate handoff cells having sufficient signal strength to maintain a call with the mobile terminal, and forces sequential handoffs of the mobile terminal from its serving cell to the plurality of candidate handoff cells. The locator then measures signal strength and propagation delay between the mobile terminal and each base station associated with each of the plurality of candidate handoff cells and between the mobile terminal and the serving base station. Either the signal strength, the propagation delay, or both are then used to calculate a distance between the mobile terminal and each base station associated with each of the plurality of candidate handoff cells and between the mobile terminal and its serving base station.

Abstract: A cellular telephone system is upgraded by modifying subscriber units for selective service provider acquisition-during roaming. Priority of acquisition is given to those service providers associated with the home service provider. These preferred service providers are identified by System Identification (SIDs) numbers. A roaming subscriber unit will tune to a single broadcast frequency to identify available system providers operating in a physical area to which the subscriber has roamed.

Abstract: A wireless communication system for servicing personal communicators is connected to a a digital switch of a landline telephone network. The communication system includes a plurality of wireless communication base units, each having wireless circuitry enabling it to extract channel and setup information other from nearby wireless communication base units. Each unit measures the RSSI of channels of neighboring wireless communication base units and makes channel assignments to a base unit in response to RSSI measurements being compared to a threshold.

Abstract: A system for facilitating global cellular/trunked mobile communication is disclosed. This system permits communication with hand held and mobile mounted cellular telephones. The system permits two-way communications anywhere on or above the earth up to a particular height above the earth of several hundred nautical miles. The system employs a number of low-earth orbiting satellites moving about the earth in orbit. Links are provided from the satellites directly to the users and via the public switched telephone network to other users. The satellites are interconnected via links in a ring structure surrounding the earth. Switching is performed by each of the satellites. In addition, each of the satellites hands off a call as it moves out of the range of a particular user.