MXPA97009696A - A two-way communications system providing services for data communication inalambri - Google Patents

Abstract

The present invention relates to a method of operating a communication system for providing wireless omnipresent data communication services between a plurality of remote field units each capable of initiating, by itself, an internal message initiated by field unit a a message operations center (MOC), using a network of widely distributed radio base stations (RBSs) and multiple paging systems (radiolocators), the CHARACTERIZED method comprising the steps of: A. on the MOC website, i. scanning the RBSs to determine radio frequencies that are presently suitable for any of the plurality of field units to send an internal message initiated by field unit to one or more of the RBS sites; determine frequencies and available hours when any of the field units can send an internal message initiated by field unit; format the available frequencies and hours in an output data message iv. send the output data message to each of the paging systems (radiolocators); B. in each of the paging systems (radiolocators), transmit the output data message to the field units; in each of the output units, i. receive the output data message ii. determine if an internal message initiated per unit of field will be sent, and if so, a) select one of the available frequencies and hours from the output data message received, b) encode the data to be sent to the MOC in the form of a short impulse message to minimize the probability of interfering with existing radio stations or other communications at frequencies close to the selected available frequency c) at the selected frequency and time available, transmit the internal message initiated by field unit; . in the RBS sites, i. receive internal messages initiated by field unit from the field units, and ii. send the internal messages initiated by field unit to the M

Description

A Two-Way Communications System Provides Wireless Data Communication Services This invention relates generally to a radio communication system, and in particular, to a technique for transmitting data messages initiated by remote field unit through a wireless HF link to a central communications center. There is a vital and continuing need for wireless communication networks of various types. A particular type of wireless system is focused on the need for reliable two-way data communication. Such networks do not need to support particularly high data exchange rates, but should provide communication over as wide a geographic area as possible, such as the continental United States. Unfortunately, existing and still secure proposed systems, costing many millions of dollars, have failures of one kind or another. Consider, for example, wide-area, wireless data networks that support communication between a mobile field unit and a base station that is land or satellite deployed. Terrestrial systems can also be classified as one-way or two-way. A one-way terrestrial system, such as national-scale paging networks (radioloaders) such as SkyTel, does not provide the capability for a remote user to send data.

Additionally, such networks typically exhibit poor penetration of building structures due to the high carrier frequencies in which they operate. Other existing and proposed two-way terrestrial systems include cellular networks, mobile data networks such as RAM, ARDIS, the national wireless network (NWN), EMBARC, and many others. Although such systems do provide two-way message initiation, although the data rates of these systems are typically quite high, each system requires users to be within a short distance, usually 20 miles or less, of the system's infrastructure. This infrastructure is extremely expensive, requiring hundreds of millions of dollars to build a network on a national scale. It can sometimes be cost-effective to build such infrastructure in areas of high population density, and indeed, approximately 90% of the population of the United States can be supported by such systems. However, this land infrastructure only covers approximately 15-20% of the country, geographically. It is simply not economical for providers of such services to install the required infrastructure in remote areas of low population density.

Several satellite networks, both existing and proposed, have been designed to address the problem of poor geographic coverage. These satellite-based systems typically also require a tremendous investment in infrastructure. The infrastructure is located in orbit where it can not be installed, maintained or replaced without large expenses of space support vehicles. Additionally, the subscriber's mobile devices required to communicate with such relatively expensive systems. In addition, field devices need to be within the satellite line of sight, since they typically have high-range electromagnetic, clearly visible receiving devices, such as dishes or long antennas. Such systems are therefore impractical for certain applications. Consider the problem faced by the manager of a fleet of rental cars. The assets for which the manager is responsible are highly mobile - in truth, they can be located virtually anywhere in the continental United States. The assets are easily stolen and expensive to insure. Assets can also become unproductive when a rental customer fails to return the vehicle to its proper location. Rental cars can "get lost" when there is poor communication between rental points, and valuable time of the rental asset is then wasted. Another important point for fleet managers is the safety of their customers. Car rental drivers, and in fact, all drivers, could benefit from a low cost, highly reliable, wide area system, to request emergency assistance at any time, from any location, without abandoning the vehicle. Similar problems exist in other industries. For example, there is increasing pressure in the rail industry to move toward scheduled service, to facilitate "just in time" delivery in an effort to better compete with the trucking industry. To achieve this goal, the manager of a railroad system should ideally be able to quickly determine the location of each and every rail car on a regular basis, regardless of the location of the rail car. Then the optimal route and delivery time could then be accurately predicted. Other industries, such as the trucking and shipping industries, could also benefit from such capacity, and cheaply and exactly, find the location of shipping containers no matter where they are located.

Any shipping container can contain thousands or potentially millions of dollars of valuable goods, and clearly, those responsible for the welfare of goods in transit would like to know where they are at all times. In any of these applications, the fleet manager would very much like to be able to count on the remote field unit initiating the transmission of a message to a central controller indicative of the location and / or status of the field unit. These transmissions may occur, for example, over a certain eventuality (for example, request for emergency assistance), or periodically, such as once every several hours, once a day, etc. Based on the particular application. The same kind of generic problem (that is, requirement of small amounts of data from very remote or highly mobile field units on a rare base at low cost) exists in the areas of remote meters or reading of detectors, monitoring of facilities, security, buoy monitoring, and other applications. While the needs of each of such applications could be met by combining a position detector apparatus such as Global Positioning System (GPS) or Loran receiver in each remote field unit in conjunction with an existing two-way mobile data communication device. such as a cellular or satellite transceiver, each of these systems would be too expensive since the service carries with it relatively high connection time charges, and monthly service fees. Therefore, cellular and satellite transmitter-receiver systems are not feasible solutions due to their prohibitive cost. An object of the present invention is to provide a data communication system in which a very remote or highly mobile field unit can itself initiate the transmission of relatively small amounts of data to a mission operations center (MOC). Another object of the present invention is to provide a data communication system that allows high-range radio data communications between a plurality of field units and the MOC through non-dedicated frequency channels. A further object of this invention is to provide omnipresent coverage over a broad geographic area such as the continental United States, while requiring a minimum of capital expenditures for new infrastructure, and minimum operating costs. The architecture of the system should be such that it uses simple and inexpensive field devices, costing much less than, for example, a comparable satellite data terminal. Field units should not require direct line of sight with a base station unit for communication to be successful and reliable. Field units should also be able to operate on batteries, eliminating the need for external power supply, as typically required by satellite systems. Any data transfer mechanism used should provide highly reliable service, in the same order as that of large radio transmitters. Finally, the use of the system should cost the client much less than existing paging systems (radiolocators), cellular or satellite. Briefly, the invention is a communication system initiated by a field unit that provides an output data message containing information in available radio frequencies to one or more field units that can initiate, by themselves, the transmission of a data message. internal one of the available internal frequencies, to at least one of a plurality of widely distributed radio base stations that carry the internal message to the MOC.

To determine the available internal frequencies and the time gaps during which those frequencies are available, the MOC is regularly updated with information on possible internal frequencies available from each of the radio base stations. From these frequencies, the MOC selects the available internal frequencies that the field units can use to initiate internal messages, and encodes these internal frequencies available in the output data message that is sent to the field units. In one embodiment, the output data message is communicated to all field units using an output message system, such as a paging system (paging) or another wireless network.

The MOC also provides the available frequencies and their corresponding time gaps to the radio base stations, so that each station can tune its receivers to receive any internal message initiated by field unit. Time synchronization between base radio stations and field units can be by any convenient method such as known time sounds, or by time reference signals available from the geographical location or paging receiver (paging devices).

When a field unit wishes to initiate an internal message, it selects one of the available frequencies contained in the output data message and transmits the internal message to the radio base station at the selected available frequency. To facilitate long range communications, the internal frequencies are preferably shortwave radio carrier frequencies within the high frequency radio (HF) band. The internal message is preferably encoded with a wide band coding scheme such as an expanded spectrum modulation, to minimize the likelihood of interfering with existing radio or other communications at close frequencies in the HF band. Upon receipt of an internal data message initiated by a field unit, the base station will take it to the MOC, which in turn can send the message to the appropriate client or act on the message depending on its content. Upon receipt of an internal data message initiated by a field unit, the MOC forms and transmits an acknowledgment output message which is directed via the output message system to the field unit that transmitted the internal data message. The data communications system initiated by the field unit thus consists of four primary subsystems including: From the mission operations center (MOC), 2) the output message system. 3) the remote field units and 4) the internal radio base stations. The MOC provides central control of the radio base stations and periodically (preferably in real time) receives reports of possible frequencies available from the radio base stations, and the time gaps during which the frequencies are estimated to be available. The MOC maintains a database of these frequencies and time gaps. Communications between the MOC and the base stations are generally via modems using appropriate low-cost land-based connections such as PSTN, private or leased telephone circuits, very small aperture wireless (VSAT) wireless networks, or other network connections. cost effective, depending on the number and location of the base stations. Since the internal message transmission initiated by field unit can be in a non-dedicated radio frequency band (that is, the frequency can be under another user's license), the MOC processes the information about each of the possible frequencies to estimate which frequencies have the least chance of interfering with another user, such as an authorized user of the frequency. The MOC selects several of these frequencies, and formulates the output data message with the available frequencies and their respective time gaps as data arguments. The MOC then sends the output data message to an output message system (e.g., a paging network (radiolocators)), requesting that the output data message be sent to all field units. This request to the output message system is typically sent via any convenient ground-based means, such as PSTN, VSAT, or other type of data communication network. The output message system includes a plurality of geographically diverse radio transmission systems in which each receives and transmits the output data message. The output message system can be any convenient low-cost radio transmission system for transmitting data. Although existing paging network infrastructures (radiolocators) are suitably ideal for the output link, it should be understood that other systems may also be used, such as a private radio network, a cellular mobile telephone network (CMT), a satellite network, or any other appropriate system of communication. wireless transmission.

Radio base stations perform several functions. First, to assist in the estimation of the MOC of what frequencies will be available for internal message transmission, each radio base station periodically scans each possible internal link channel to determine if the channel is in use. This can be done, for example, by measuring a power level received on each channel or by sampling subbands on each channel and integrating the detected level of signal power over time, or using other known signal detection algorithms. Second, the radio base stations receive the internal messages from the field units and direct the messages to the MOC. To capture the internal messages from the field units, each of the radio base stations includes several tunable HF receivers. When receiving a command from the MOC to wait for a possible internal message in the frequency and time available, each base station assigns and tunes its HF receivers, and waits for a possible reception of the internal message. If an internal message is received, the radio base station directs the message to the MOC via a modem or other communication channels. Note that the reception of internal messages initiated by field units may be aperiodic, since field units will generally initiate a transmission on an infrequent basis. Upon successful reception of an internal message initiated by field unit, the MOC formats and sends, via the output message system, the output recognition message to the field unit that transmitted the internal message. If the field unit does not receive the acknowledgment message from the MOC, from a certain period of time after transmitting the internal message, the field unit selects another frequency value from the most recent output data message, and retransmits the internal message during the appropriate time gap. The communication system of the present invention provides several advantages. The system allows very remote or highly mobile field units to initiate a transmission, by themselves, of relatively small amounts of data through long-range real-time and relatively low-cost radio links. Omnipresent coverage over a wide geographic area such as the continental United States is possible using existing paging systems (outgoing locators) for outgoing message and a small network of shortwave radio base stations to receive internal messages. The system thus requires a minimum of capital investment for new infrastructure, and significantly lower monthly operating costs.

Additionally, the field units preferably use shortwave HF transmitters that do not require a direct line of sight to communicate reliably with the radio base stations. Therefore, radio base stations can be located up to about 1,000 miles away from a remote field unit. Field units can operate with battery power such as conventional paging receivers (paging devices), since the transmitter of the field unit will be activated only for an internal short duration pulse message. The above and further advantages of the invention can be better understood by referring to the following description in conjunction with the accompanying drawings in which: Figure 1 is a block diagram of a two-way radio communication network; Figure 2A illustrates the format of an output data message sent from the mission operations center (MOC) to a field unit through the paging network (paging); Figure 2B illustrates the format of an internal message initiated per field unit sent by the field unit to a remote base station (RBS) at a particular time and frequency within a shortwave radio band, and as sent from the RBS to the MOC. Figure 2C illustrates the format of the internal message as sent from the MOC to a client; Figure 2D illustrates the format of an output recognition message sent from the MOC to the field unit that transmitted the internal message initiated by field unit illustrated in Figure 2B; Figure 3 is a block diagram of an MOC control unit showing several databases, or tables, maintained by the MOC; Figure 4 is a flow chart of the operations executed by the MOC including the steps executed to generate the output data message; Figure 5 is a flow chart of the operations executed by each of the field units; Figure 6 is a block diagram of an RBS control unit showing several databases maintained by the RBS; Figure 7 is a flow chart illustration of the operations performed by the frequency analysis processor (FAP) of the RBS of Figure 6; and Figure 8 is a flow chart illustration of the operations executed by each RBS to receive internal message initiated by field unit. Turning now to the drawings, Figure 1 illustrates a block diagram of a two-way wireless communication system 10. The system 10 includes a number, S, of call stations 20a, 20b, ..., 20S (collectively, call stations 20), a data communication mechanism 25, a mission operation center 30 (MOC) 30. , a number, p, of geographically dispersed outgoing message subsystems 40a, 40b, ..., 40p covering a wide geographic area, such as the continental United States or Europe, multiple mobile or remote field units 50a, 50b, 50c, 50d,. . .50x, 50y, 50z, and an internal message subsystem that can make use of a number, (for example four) of radio base stations (RBS) 60a, 60b, 60c and 60d, which are also geographically dispersed to provide coverage omnipresent. The data communication mechanism 25 may preferably be a public telephone network (PSTN), as shown. However, private networks, networks (VSAT), Small Aperture Terminal, and other types of communication networks can also be used.

The outgoing message systems 40 provide radio links 45 which are used for communication from the data communication mechanism 25 to the remote field units 50. These radio links are referred to herein as outgoing links 45. In a preferred embodiment , the output links 45 can be provided by multiple paging subsystems (paging devices) 40. However, other systems such as paging systems (national paging), satellite networks, private radio networks, and the like can be used to provide the output links 45. Thus, while the output message system 40 may be referred to here as in some cases as a paging system (paging), it should be understood that other types of outgoing radio links could also be used. Radio communication from the field units 50 sent to the RBS's network are referred to as the internal links 55. The internal links 55 are preferably shortwave radio links, coded in extended spectrum, operating in the high radio band. frequency (HF). The wireless communication system 10 provides two-way data communication on a near real-time basis across a broad geographic area such as can be conveniently covered by a network of only a few short wave radio base stations 60. This architecture eliminates the need for expensive, expensive, specialized and omnipresent infrastructure as now required by the cellular system as well as satellite systems. For example, existing paging subsystems (paging devices) can be used to provide the paging links 45, and network 25 can be the public telephone network. The system is thus much more maintainable and less expensive to support than cellular, paging (radiolocalizers) multi-emission, or satellite systems. Field units can be designed to operate with minimal available power from a solar source or battery, which is ideal in remote locations where access to external power is not readily available, reliable or safe. Because the radio base stations use HF shortwave signaling, a direct line of sight between the radio base stations 60 and the remote field units 50 is not required, and thus the system 10 will operate properly even in situations where the propagation In line of sight is not possible, such as in stacked containers or in densely populated urban areas. System 10 thus exhibits greater availability than competing satellite-based systems.

According to the present invention, any remote field unit can initiate, by itself, the transmission of an internal message to the MOC 30 via the radio base stations 60. The MOC periodically sends an output data message containing data fields of available frequencies through which field units can transmit internal messages initiated by field units. The output data message also contains fields defining the time gaps during which the field units 50 can use the available frequencies.

Each of the components of the communication system and its operation will now be discussed at an increased level of technical detail so that one skilled in the art can more easily understand how to build and operate the internal message system initiated by the field unit of the present invention. Figure 2A illustrates the format of an output data message 200 sent from the MOC to all field units through the output links 45 (Figure 1) using the paging network (paging markers) 40 (Figure 1). At a minimum, the message 200 includes at least one data field 200-1 indicating a frequency available for transmission of an internal message initiated per field unit from any of the field units. The data output message 200 also includes a second field 200-2 which indicates the time gap within which the field units can transmit an internal message initiated per field unit. In general, however, the data output message will contain a plurality of available frequencies and time gaps that any of the field units can use to initiate an internal message. Figure 2B shows the format of the internal message 255 initiated by field unit from the field units 50 through the internal links 55, including a field unit ID 255-1, as well as an internal data field 255-2 containing data from field unit 50a. Such internal data 255-2 may, for example, in the case of a mobile field unit 50, include information concerning the position of the field unit in terms of latitude and longitude, together with an emergency code. However, it should be understood that the field unit 50 may also be stationary, and therefore, 255-2 different internal data than position information may be sent, depending on the client's application. Figure 2C illustrates the format of a message 270 sent by the MOC to the calling station 20 in response to reception of the internal message 255 initiated by field unit. Message 270 includes field unit ID 270-1 if necessary, as well as internal data 270-2 returned. Figure 2D illustrates the format of a recognition output message 280 sent from the MOC to the field unit that transmitted the internal message 255 initiated by field unit. This recognition message is sent to the output message system 40 (Figure 1) and passed to the appropriate field unit. It should be understood that the illustration of the message formats in Figures 2A to 2D is not restrictive, and that the various fields may occur in any order in each respective message. Each message 200, 255, 270, and 280 will also typically have additional fields such as header fields, check of sums, itinerary or synchronization information and any other fields as normally required in any message communication system depending on the needs of a particular application / client. Referring to Figure 1, the so-called stations 20a, 20b, ..., 20s provide an interface for the clients to interact with the system 10. A typical unit of the base stations 20a is materialized as a personal computer (PC) 21 having a well-known normal communication apparatus, such as a computer modem 22 that allows the MOC to transmit to the so-called message stations through the PSTN 25. The MOC also has a bank of computer modems 31-1, 31- 2 ... 31-m for communication with multiple calling stations 20. ¥ The MOC 30 includes a computer, referred to as the 32 controller of the mission operation center (MOC), and multiple modems 31-1, 31-2 , ... 31-m and 33-1, 33-2, ... 33-4. The MOC uses the modems 31 for communications through the network 25 with at least the call stations 20 and the network 40 for outgoing messages. The MOC can also use other modems 33-1, 33-2, 33-3, and 33-4 to communicate with base radio stations (RBS's) 60. Because the MOC needs to communicate frequently with the RBS's and because there will generally be only a handful of RBS's, (for example, four), the MOC can connect the modems 33 to dedicated telephone circuits, such as leased lines, connected packet networks, or other cost effective services, high data rate, long line. Figure 3 shows a more detailed block diagram of the MOC controller 32 and several databases 32-5, 32-6, 32-7, 32-9 which it maintains in support of internal messages initiated per field unit. The controller 32 of the MOC includes the usual components of a computer system such as a central processing unit (CPU) 32-1, memory 32-2, storage disk 32-3, interface 32-4 input / output. { 1/0). Because the MOC controller 32 is primarily responsible for coordinating communication between a number of different apparatuses, the architecture of the computer system is preferably an appropriate managed switch or multi-tasking system. To determine the frequencies that the units 50 can use to transmit internal messages initiated per field unit, the MOC controller 32 maintains a first database referred to as a frequency availability table 32-5. This table includes usage information in each frequency channel fn that can be used for internal messages. Each of the RBS's 60 (Figure 1) reports to MOC 30, via a data link, the amount of measurable energy in the RBS location for each frequency fn. As an example, the RBS 60-1 (Figure 1) periodically reports a list of fl, f2, ..., fn possible frequencies available, or open channels, that the RBS 60-1 is presently watching, and the amplitude level of noise Al-1, Al-2, ... Al-n, associated with each such frequency. Similarly, the other RBS's 60-2, 60-3, and 60-4 also periodically report amplitude levels A2-1, A2-2, ... A3-n, and A4-n, measured at their respective locations for channels of frequency fl, f2, ..., fn. The precise manner in which each RBS 60 determines an available frequency is discussed below. Table 32-5 also contains a propagation probability, Pn, for each of the fn values in the table. Pn propagation probability values can be computed by knowing the time of day and atmospheric conditions that allow known ionospheric model algorithms to compute a propagation probability for each frequency fn. However, it is contemplated that more sophisticated propagation prediction algorithms may also be used depending on the geographical configuration of the RBS's 60. For additional details on frequency selection and propagation probability computation, see the co-assignable assignable request in common entitled "Technique to determine propagation and free frequency to be used in wireless data communication network in large area", file number 111045-2 designated Cesari & McKenna, introduced on this same date, and which is incorporated here by reference. The MOC controller 32 may also maintain a field unit location table 32-6 to preserve the track of the last known location of each field unit 50 deployed, each entry in this table consisting of a field unit ID code. , along with position information as reported lately by the field unit, (for example, latitude and longitude). The MOC controller 32 maintains and updates this database 32-6 as the field units 50 are added or removed from service and as internal messages 255 (Figure 2C) are returned by each field unit indicating its latitude and longitude. As mentioned above, in the preferred embodiment, the output links 45 are provided by several paging subsystems (paging devices) 40. A third table 32-7 is thus used to maintain information about the various paging systems (paging devices) 40a, 40b. , ... 40p which together form the output message system 40. This table 32-7 is updated whenever arrangements for the use of multiple paging systems (paging devices) are made by the system operator 10. Table 32-7 may also include details of how the MOC 32 controller can access each different paging system (radiolocators), such as modem telephone numbers, protocol types, and the like. The MOC controller 32 also maintains an available frequency table 32-8 containing data of the available frequencies and time gaps transmitted in the last output data message.

Figure 4 is a flow chart of a process routine 400 executed by the MOC controller 32. The controller executes a first step 401 to receive the data of possible frequencies available from the RBS's 60 and update the table 32-5 (Figure 3), including probabilities of propagation Pn. The frequencies to be used for the internal messages initiated per unit of field are then selected in step 402 based on the Pn values of propagation probability and frequency utilization as measured at the various radio base station sites. In general, the frequency values selected in step 402 represent the most available frequencies. That is, each frequency has a high probability of propagation Pn and a relatively low level of noise An. The time gaps for transmission at the available frequencies are then determined in step 404 by adaptively estimating when each of the available frequencies will be available. By selecting the frequency, f, to be used, the MOC controller 32 attempts to minimize the noise and interference power at the frequencies in use by all the RBS's. Thus, for example, since other users appear as noise and interference, and since the exact location of the field unit is not known, the MOC preferably chooses a frequency that is the lowest noise power An through all the RBS's 60 and is estimated as remaining low for the time it takes to complement an internal message. This minimizes the possibility of interference with another user of the HF spectrum. Other techniques can be used to refine the frequency selection process. For example, the MOC controller 32 may selectively exclude, from the frequency selection process, designated portions of the radio spectrum HF known to contain known transmitters or fixed transmitters. Additionally, the propagation probability factor, Pn, can be used to further refine the selection of a frequency f. For example, if a frequency is clean, that is, each of the four RBS's reported low noise amplitudes Al, A2, A3, A4 for that frequency, but the successful propagation probability Pn is low, then another frequency is selected from Table 32-5. Additionally, minimizing the time between observation of a clean frequency and then selecting it for transmission in step 402 is also key to successful communication, and is the reason why the RBS's are requested to update table 32-5 of frequency availability in time. close to real. The system 10 is thus designed so that the MOC controller 32 uses the selected frequencies within several seconds, and then abandons them. When determining the feasibility of system design 10, a computational model was made of the probability of occurrence of conflicting use in the European environment. The European environment is typically much more demanding than the average environment in the United States. Table 1 below shows the probability that a frequency will be used by another conflicting user after the MOC controller 32 has identified it as clean but before the transmission of the message has been completed.

Time elapsed since Probability of interference frequency selection 3 seconds 0.01 10 seconds 0.03 30 seconds 0.10 1 minute 0.15 6 minutes 0.63 The information in Table 1 can thus be used to determine how often the frequency availability table 32-5 should be updated, depending on an acceptable probability of interference with the internal link. In step 406, the output data message 200 (FIG. 2A) is formed containing data fields for the available frequencies, and time gaps. The output data message 200 is then sent in step 408 to the output message network 40 which transmits the output data message to all remote field units 50. A list of available frequencies and time gaps for each one it is maintained by the MOC controller 32 in table 32-9 (Figure 3). The next task for the MOC controller 32 is step 410 to determine if some remote field units 50 have sent in internal message (or messages), initiated by field unit to MOC 30 via the RBS's 60. If so, the The message is withdrawn and implemented or sent as necessary in step 412 to a customer call station 20. Since the internal message will also preferably contain a field specifying the last position of the remote field units, step 414 updates table 32-6 field unit locator. The MOC will then form and send an exit acknowledgment message in step 416 through the exit message network 40 to the field unit that initiated the internal message.

Referring again to Figure 1, all outbound links 45 preferably use licensed FCC communication means, such as existing paging network infrastructure (paging devices). However, such output links 45 can also be provided by public or private carriers such as paging network systems (radiolocators), frequency modulated subcarriers (FM) using special radio networks, high frequency radio networks (HF). , or other types of suitable output links, depending on the nature of the field units 50. For example, if the field units 50 are expected to be located in stacked containers, output links 45 should not be implemented using a communication methodology that requires line of sight. The internal links 55 make use of high frequency (HF) radio stations 60 that operate with carrier frequencies in the radio spectrum from about 3 to 30 MHz. There are two critical elements in establishing reliable communication in the internal HF links from the field units 50 to the RBS network 60. First, a remote field unit 50 must be instructed about which frequencies in the HF band are propagating between itself and the RBS's network 60. Due to the multiple atmospheric phenomena in HF communication , which occur over long distances mainly by ionospheric reflection, different portions of the spectrum from 3 to 30 MHz spread in different directions at different times of the day, and depending on sunspot activity. Second, of those frequencies that are spreading, it must be known which channels are clean, that is, which channels are not being used presently. Referring to Figure 1, an exemplary output message subsystem may be a paging system (paging devices) 40a which is a normal paging system (paging) that can accept a paging request (paging) through the network. As is known in the art, such paging systems 40a include a modem 41 for accepting paging requests (paging), a paging control center (paging) 42 that is typically a computer of some type and a number of paging devices. paging system transmitters (radiolocators) 43, 43-1 ... 43-n. When the output data message 200 (Figure 2a) is sent from the MOC 30, the paging subsystem (radioloaders) 40a formats and then sends the output data message 200 in the conventional manner. The paging system (paging devices) 40a need not be a two-way system or require any acknowledgment of paging reception (paging) from the field units 50. As illustrated in Figure 1 an exemplary field unit includes a message receiver output such as a paging receiver (paging) 51, a tunable transmitter HF 52, a field unit controller 53, and data collection apparatus such as a geo-location receiver 54. The receiver 54 of the geo-location system can be any of the known types, such as global positional system (GPS) or Loran receiver. Figure 5 is a flow chart illustration of a routine 500 executed for each field unit. At routine input 500, step 502 receives the output data message 200 (FIG. 2A) containing the available frequency channels, f, and time gaps, t, which field units can use to transmit an internal message. initiated by field unit. Step 504 then determines whether the field unit wishes to initiate, by itself, the transmission of an internal message. If the field unit wishes to initiate an internal message, step 508 selects, from the most recent output data message 200, a frequency and time gap available to be transmitted therein. Step 510 is then executed to form the internal message 255 initiated by field unit (Figure 2B) containing the data that the field unit wishes to transmit. As an example, if the field unit is located in a shipping container, an alarm can trigger the unit to initiate the data transfer indicating that someone has opened the container without authorization and the location of the container. Additionally, an internal message can also be initiated by a rented car driver by pressing an emergency button to transmit the location of the vehicle to the MOC. One of ordinary skill will appreciate that there are many applications that the low cost message system initiated by the field unit of the present invention may find useful. Once the internal message has been formed, step 512 is executed to transmit the internal message on the selected frequency and at the appropriate time. In general, this involves tuning the transmitter 52 of the field unit (Figure 1) and waiting for the appropriate time as specified in the output data message, before executing the current transmission through the internal radio link 55 (Figure 1). ). The transmission time gaps in the internal communication links 55 can be synchronized using normal universal time data, as may be available from a GPS receiver 54 or other normal time radio broadcast transmitters. Unique non-interfering characteristics of the internal HF links 55 are thus possible because the remote field 50 units already know, before transmitting, which frequencies are not in use at particular times. The frequency is then quickly unoccupied after a single use by the MOC controller 32 thus making it available for other uses, such as its regularly authorized use. Additionally, field units transmit on only one of the open frequencies for a short period of time. In particular, field units 50 use a low power extended spectrum HF waveform having a duration of about one (1) to ten (10) seconds to transmit an internal message initiated per field unit. The waveform can, for example, be a waveform of direct deployment, phase 8 key offset (PSK) with a bandwidth of 3 KHz and a chip rate of around 2400. This provides a data rate about 75 bits per second for internal messages 255. The HF transmitter 52 in the remote field unit can thus be instructed by the controller 53 to jump to any 3 KHz channel in the 3-30 MHz HF spectrum.

Interference to voice users in the HF spectrum is thus minimal since the noise pulse from system 10, even if there is some interference, would be similar to a typical HF channel fading. Other users of HF spectrum data are also typically equipped to handle second-time channel fades and have typically implemented ARQ or coded leaf patterns to avoid fading difficulties. Thus, other data users in the HF band should not notice the existence of the system 10. Once the internal message 255 (FIG. 2B) has been transmitted, a test 514 is executed to determine if an acknowledgment message has been output. received from the MOC, via the output message system, within a predetermined period of time. The acknowledgment indicates that the MOC has successfully received the internal message initiated by field unit. If the acknowledgment is not received in time, the field unit assumes that the transmission of the internal message was interfered with by another user, and therefore, unsuccessful. The field unit will then retransmit the internal message, but this time in different frequency and time gap. Step 516 selects a different available frequency and time gap from the output data message. Step 512 is then executed to retransmit the internal message, but this time, in the new frequency and time gap. The process is repeated until the transmission of the internal message is finally successful, or until the internally constructed test logic (not shown) determines that there is a major fault and that the transmission recognition message can not be expected. Once the recognition message has been received, or it was determined that the field unit did not wish to initiate an internal message (test 504), the execution returns. Fig. 6 is a block diagram of a typical base radio station (RBS) 60-1, consisting of a RBS controller 61, a modem 62, a modem battery HF 63, HF 64 receivers, and an analyzer processor. frequency 65. The RBS controller 61 can be a similar conventional controller 32 of the MOC. The RBS controller 61 uses the modem 62 to exchange messages with the MOC controller 32. The RBS controller 61 maintains a real-time database 66 of available frequency channels. Each entry in the table 66 includes a frequency HF, f, and an A measurement of the observed noise power amplitude level. The frequency table 66 can be maintained by a frequency analysis processor (FAP) 65 which periodically determines the identity of clean operating HF frequencies, on a regular basis. The FAP 65 can do this using a sweep receiver, or it can walk one or more of the tunable HF receivers 64 through the frequency band (e.g. 3-30 MHz). The FAP 65 typically also includes a computer or microcomputer. The frequency table 66 may also contain reports of power measurements of signals received from its own remote devices or known probes to further assist the MOC controller in predicting available frequencies. In most cases, the FAP has a good chance of finding frequencies that are not occupied by another user, assuming a worst case of time of day, such as at dawn, about 2 MHz of radio spectrum HF spreads in any given location. Given a 30% assumption of channel occupation, which is based on empirical observations, the system 10 will typically have at least 466 available channels of the required 3 KHz bandwidth, available in the 3-30 MHz. of the HF modems 63 and associated HF receivers 64 is handled by the RBS controller 61 to receive internal messages initiated by field units at the frequencies and times specified in the output data message. To help in this process, a table 67 for displaying HF receivers is maintained. Each entry in this table 67 contains an HF receiver ID, associated HF modem ID, serving the channel, and a busy field B, indicating whether the receiver / modem HF pair is presently assigned. If the busy field indicates active status, the input also contains a frequency, F, and time, t, in which an internal message initiated by field unit can be received by the HF, receiver / modem pair. The HF receivers 64 are adapted to receive the extended spectrum waveform generated by the field units 50, as already described. Figure 7 is a flow chart of operations 700 executed by a control processor in FAP 65. After entering routine 700, in step 701 the FAP determines the identity of a possible next available HF channel. In step 702, the FAP then measures the received power level, and in step 703, if the power level is sufficiently lower than a threshold amount, the FAP updates its internal table 66 (Figure 6). In step 704, the process is repeated until all channels are reviewed. Finally, in step 705, the FAP sends the updated table information to the MOC controller 32 through the PSTN 25. Figure 8 is a flow chart illustration of the operations 800 executed by each RBS to receive an internal message 255 initiated by field unit. The first step is a test 802 to determine whether a new output data message 200 (FIG. 2A) has been received. If it has been, HF receivers are assigned and tuned in step 804 to the frequency values, f, specified in the output data message. The HF receiver deployment table is also updated to indicate that newly assigned HF receivers and modems are now occupied. In step 806, the receivers are then activated at the appropriate time t, to listen for any internal messages initiated per unit of field. The next step is an 808 test to verify if some internal messages initiated per field unit have been received. If none was received, the routine returns. Otherwise, step 810 is executed to send the internal message initiated by field unit to the MOC. Once the MOC receives the message initiated by field unit, it can either act on the message itself, or pass the information to a client call station 20.

Although the present invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that various other changes, omissions and additions may be made to the embodiments described herein, without departing from the spirit of rank. of the present invention.

Claims (20)

1. Claims 1. A method of operating a communication system for providing wireless communication services ubiquitous data between a plurality of remote units each field able to start by itself, an internal message initiated by field unit to a center message operations (MOC) using a network of widely distributed base radius (RBSs) stations and multiple paging systems (pagers), the method characterized by comprising the steps of: A. in the MOC site, i. scanning the RBSs to determine radio frequencies that are presently suitable for any of the plurality of field units to send an internal message initiated by field unit to one or more of the RBS sites; ii. determine frequencies and available times when any of the field units can send an internal message initiated by field unit; iii. format the available frequencies and hours in an output data message; iv. send the output data message to each of the paging systems (radiolocators);
2. B. in each of the paging systems (radiolocators), transmitting the output data message to the field units; C. in each of the output units, i. receive the output data message; ii. determine if an internal message initiated by field unit will be sent, and if so, a) select one of the available frequencies and hours from the received output data message, b) encode the data to be sent to the MOC in the form of a short duration pulse message to minimize the likelihood of interfering with existing radio stations or other communications at frequencies close to the selected available frequency; c) at the selected frequency and time available, transmit the internal message initiated by the field unit; D. in the RBS sites, i. receive internal messages initiated per field unit from the field units; and ii. send the internal messages initiated by field unit to the MOC. 2. A method as in claim 1, characterized in that the MOC is connected to the paging systems (radiolocators) through a terrestrial base public telephone network (PSTN).
3. 3. A method as in claim 1, wherein the MOC communicates with the RBSs through a terrestrial base connection such as the public connection telephone network.
4. 4. A method as in claim 1, wherein the MOC communicates with the RBSs through a terrestrial base connection such as leased private telephone circuits.
5. 5. A method as in claim 1, wherein the MOC further executes the step of alerting each RBSs a message initiated by field unit may be received from any of the units field in any of the frequencies and available hours.
6. 6. A method as in claim 5, wherein each RBS performs the step of periodically measuring a received power level in each available internal frequency channel.
7. 7. A method as in claim 6, CHARACTERIZED by further comprising the step of, in each field unit collecting data that can be reported in the internal message initiated by field unit including information indicative of the location of the field unit .
8. 8. A method as in claim 2, characterized in that the short duration internal message is encoded using extended spectrum modulation.
9. 9. The method of claim 1, CHARACTERIZED by further comprising the steps executed in each RBS of: receiving the output data message from the MOC; and tuning the tuneable receivers to the frequencies available in the output message in the selected time gaps.
10. 10. The method of claim 7, characterized in that each of the available frequencies is a short wave carrier frequency with the HF band.
11. 11. A two-way wireless data communication system CHARACTERIZED by understanding: a subsystem of outgoing messages to send outgoing data messages; an internal message subsystem consisting of a network of at least two radio frequency base stations to receive internal messages, the radio frequency base stations also continuously sampling, at their respective locations, a set of frequency channels in an internal radio band frequency, to determine a level of frequency availability observed for the set of frequency channels by each base station; at least one field unit having an output message receiver and a tunable internal message transmitter; and a central control unit, where the central control unit uses the output message subsystem as an output link to send an output data message to the field unit, and uses the input message subsystem as a link internal to receive an internal message from the field unit, and where the output message includes data fields indicating available frequencies and times in which the field units can initiate, by themselves, the transmission of an internal message and where the unit Central control receives reports of the observed availability and frequency levels from the radio base station network and the central control unit selects the available frequencies, so that internal messages will be received at the base stations without interference from other communication systems .
12. 12. A system as in claim 11, CHARACTERIZED that the internal message subsystem uses the high frequency radio frequency (HF) band as the internal radio frequency band.
13. 13. A system as in claim 12, wherein the output message subsystem is a paging subsystem (paging).
14. 14. A system as in claim 13, characterized in that the central control unit further comprises means for selecting the available frequencies by estimating a probability of radio energy in the internal frequency will propagate.
15. 15. A system as in claim 13, CHARACTERIZED by comprising multiple internal links implemented by multiple radio base station receivers and where the control unit determines the available frequencies depending on the observed frequency availability in each of the station receivers radio base.
16. 16. A system as in claim 13, characterized in that each of the field units comprises a geographical position detector that determines the location of the field unit and provides a signal value indicative of the position that is encoded in the message internal to provide the MOC with the location of the field unit.
17. 17. A two-way wireless data communication system for communications between a plurality of field units that initiate by themselves, data transmissions to a mission operations center, CHARACTERIZED by comprising: a paging subsystem (paging) to send messages output to the plurality of remote field units; an internal message subsystem consisting of at least one radio base station for receiving internal messages from the remote field units, the radio base station also continuously sampling at its respective location, a set of frequency channels in a radio frequency band , to determine a level of frequency availability observed for the frequency set for the base station; a central control unit, which sends an output data message to the paging subsystem (paging) for transmission to all field units, and uses an internal message subsystem as an internal link to receive internal messages from any of the units field where the output data message includes data fields indicating available frequencies and times at which any of the field units can send an internal message and where the central control unit receives reports of the levels of frequency availability observed from Each of the radio base stations selects the internal available frequencies, so that each internal message will be received by one or more of the radio base stations without interference from other communication systems.
18. 18. A system as in claim 17, characterized in that the internal message subsystem uses the high frequency radio frequency band HF as the internal radio frequency band.
19. 19. A system as in claim 17, CHARACTERIZED by comprising multiple internal links implemented by multiple radio base station receivers, and wherein the control unit allocates the carrier frequency depending on the observed availability of that carrier frequency in a plurality of the receivers of radio base station.
20. 20. A system as in claim 17, characterized in that the control unit dislodges the selected available frequency after transmission of the internal message, to minimize interference with other communication systems that make use of that available frequency. Summary A two-way communications system provides ubiquitous wireless data communication services such as through the continental United States, using a network of only a few widely distributed radio base station (RBS) sites and the paging network infrastructure (radiolocalizers) existing. A network hub or mission operations center (MOC) coordinates 1 operation of the paging systems (paging devices) and RBSs of a central location. The paging network infrastructure (radiolocators) is used as an output link through which each of the field units is regularly provided with an output data message containing information about the available frequencies and time gaps that the field units can use to transmit messages internal data to the RBSs. If any of the field units wishes to transmit data to the MOC, the field unit selects an available frequency from the output data message and transmits its data at the selected frequency and time available. At least one of the RBSs will receive the internal message and direct it to the MOC which then sends a message of acknowledgment output, via the paging network (radiolocators), to the field unit that sent the internal message.