WO1999021376A1

WO1999021376A1 - Method and apparatus for overlaying a one-way inbound messaging system onto a one-way outbound messaging system

Info

Publication number: WO1999021376A1
Application number: PCT/US1998/000465
Authority: WO
Inventors: Steven Jeffrey Goldberg; Gene Steven Gurley; Michael P. O'brian
Original assignee: Motorola Inc.
Priority date: 1997-10-22
Filing date: 1998-01-07
Publication date: 1999-04-29

Abstract

A two-way messaging system is created by overlaying a one-way inbound messaging system (50) onto a one way outbound messaging system (10) having a subscriber list. The two-way messaging system includes the one-way outbound messaging system and a two-way subscriber unit capable of transmitting an inbound message. The two-way subscriber unit includes a transmitter (206) that transmits the inbound message on an inbound channel without determining a busy/idle status of the inbound channel. A plurality of overlay base receivers (54) receive and decode the inbound message to provide an inbound decoded signal.

Description

METHOD AND APPARATUS FOR OVERLAYING A ONE-WAY INBOUND MESSAGING SYSTEM ONTO A ONE-WAY OUTBOUND

MESSAGING SYSTEM

Related Application

This application is a continuation-in-part of Application Serial No. 08/641,997, filed April 25, 1996 by Goldberg et al., entitled "INBOUND OVERLAY SYSTEM TO AN OUTBOUND PAGING SYSTEM."

Technical Field

This invention relates generally to a messaging system, and in particular, to a method and apparatus for overlaying a one-way inbound messaging system onto a one-way outbound messaging system.

Background

Two-way asymmetrical messaging has benefits in certain communication scenarios. These scenarios are generally characterized by the ability to move data in non real-time and by outbound data greatly exceeding inbound data. A benefit includes the ability to pack data more efficiently since the delivery can be delayed and provided in any sequence, thus increasing channel utilization. Another benefit is power savings in that a subscriber unit only has to "wake up" at known, widely separated times, and in that lower inbound data rates and short transmissions mean the power required is considerably less than would be required for full duplex operation.

One application that can benefit from a two-way system is a campus type system which may require inbound capability on campus, but can revert to a one-way system off campus. For example, a hospital campus would find it very desirable to know who is on campus and can respond to a page.

These reasons make two-way asymmetrical messaging systems attractive and explain why they are being adopted and implemented by many service providers. Unfortunately, the cost to implement these systems with new infrastructure equipment can be a barrier to entry for some in the market place. Thus, a need exists for a lower cost solution that can take advantage of existing one-way messaging infrastructure to provide a two-way asymmetrical messaging system. Additionally, a need exists for a means to cost effectively deploy an inbound message capability in a campus environment, while taking advantage of the inexpensive area wide coverage of an off-campus public messaging system.

U.S. Patent No. 5,526,401, issued June 11, 1996, to Roach, Jr. et al. discloses a method and apparatus for acknowledging a paging message via a cellular network control channel. Roach's technique suffers from several drawbacks. One drawback is that in addition to a paging receiver, the remote communications device incurs the expense and power consumption of a second, cellular receiver for monitoring the busy /idle status bits of the forward control channel transmitted by the mobile switching center. The remote communications device is required to monitor the busy/ idle status bits to determine whether there is a reverse control channel available for transmitting a page acknowledgment message. A further drawback is that when the cellular network control channel is busy handling cellular calls, a page acknowledgment can be delayed, potentially beyond a retransmission time-out, resulting in the page being retransmitted by the outbound paging system, further increasing traffic on both the outbound paging system and the cellular network. Thus, what is needed is a method and apparatus for overlaying a one-way inbound messaging system onto a one-way outbound messaging system, without the drawbacks of the prior art approach. Preferably, the method and apparatus will not require two receivers in the subscriber unit and will not have to check a busy /idle status of the inbound channel before transmitting.

Summary of the Invention

An aspect of the present invention is a method of overlaying a one-way inbound messaging system onto a one-way outbound messaging system having a subscriber list to create a two-way messaging system. The method comprises the steps of providing a plurality of subscriber units, wherein at least one of the plurality of subscriber units is a two-way subscriber unit capable of transmitting an inbound message; and transmitting, by the at least one of the plurality of subscriber units, the inbound message on an inbound channel without determining a busy/idle status of the inbound channel. The method further comprises the steps of receiving the inbound message by at least one of a plurality of overlay base receivers, and decoding the inbound message by the at least one of the plurality of overlay base receivers to provide an inbound decoded signal. In addition, the method includes the steps of receiving the inbound decoded signal at an overlay user access terminal, and managing and correlating at the overlay user access terminal the inbound decoded signal with the subscriber list of the one-way outbound messaging system. Another aspect of the present invention is a two-way messaging system created by overlaying a one-way inbound messaging system onto a one-way outbound messaging system having a subscriber list. The two- way messaging system comprises the one-way outbound messaging system; and a plurality of subscriber units, wherein at least one of the plurality of subscriber units is a two-way subscriber unit capable of transmitting an inbound message. The at least one of the plurality of subscriber units includes a transmitter that transmits the inbound message on an inbound channel without determining a busy/idle status of the inbound channel. The two-way messaging system further comprises a plurality of overlay base receivers for receiving and decoding the inbound message by at least one of the plurality of overlay base receivers to provide an inbound decoded signal, and an overlay user access terminal coupled to the plurality of overlay base receivers for receiving the inbound decoded signal and coupled to the one-way outbound messaging system for managing and correlating the inbound decoded signal with the subscriber list of the one-way outbound messaging system.

Brief Description of the Drawings

FIG. 1 is a block diagram of a two-way asymmetrical messaging system using an inbound overlay messaging system in accordance with the present invention.

FIG. 2 is another block diagram of a two-way asymmetrical messaging system using an inbound overlay messaging system in accordance with the present invention. FIG. 3 is an exemplary timing diagram in accordance with the present invention.

FIG. 4 is an electrical block diagram of a subscriber unit in accordance with the present invention.

Detailed Description of the Preferred Embodiment

The present invention utilizes existing outbound messaging infrastructure and adds the function of an inbound channel as an overlay, thus greatly reducing the initial outlay in infrastructure costs to an existing one-way messaging service provider. Fundamentally, the vast majority of two-way uses can be implemented by generating appropriate blind one-way traffic that in no way requires additional equipment for a traditional outbound carrier.

Referring to FIG. 1, a block diagram for the overlay system is shown in accordance with the present invention. The elements above the demarcation line 100 can be found in an existing outbound-only messaging system 10. The elements below the line 100 belong to the inbound overlay system 50. The outbound-only messaging system typically comprises a user interface 11 which can simply be a conventional phone or preferably an alphanumeric entry device such as Motorola's Alphamate® alpha entry device or a computer having software allowing for a modem or an Internet connection to a messaging terminal such as the user access terminal 12. Messages and data received at the user access terminal 12 are preferably forwarded via link 13 and encoded, queued and batched at a controller 14. Alternatively, these functions or portions of these functions can be done in separate units or within a messaging terminal such as the user access terminal 12. Additionally, the controller can receive data or messages from other sources (21 and 23). Once the functions of queuing and batching are done, the messages can be forwarded to one or more base station transmitters (16) over a plurality of links (15, 25 and /or 27). The base station transmitter 16 can then transmit a selective call message over an RF outbound path 17 to a plurality of subscriber units (18 and 56). The subscriber unit 18 can be a typical one- way unit and the subscriber unit 56 is preferably a two-way unit such as Motorola's Tango™ two-way personal messaging unit.

The subscriber unit 56 preferably has receive and transmit capabilities and preferably its operation will differ from existing two-way systems in what it expects to receive from the one-way-only infrastructure, and the different means for delivering two-way control data. In other words, the formatting, location, and vehicles used to route control data found in an existing one-way outbound system could be changed so that the overlay system is accommodated without affecting the existing one-way system. For instance, control data typically only found in a header can be imbedded in the message portion of an outbound messaging transmission. In any event, the subscriber unit 56 preferably uses an RF inbound link 57 to transmit to an infrastructure receiver 54 or a plurality of infrastructure receivers (not shown). The subscriber unit 56 can use a variety of modulation techniques for transmitting its inbound messages (i.e., acknowledgment signals, canned responses) including spread spectrum techniques. This receiver 54 may be the same as those used in non-overlay two-way messaging systems and should be able to decode the modulation technique used by the subscriber unit, but it need not be aware of whether this is an overlay or a complete two-way system. The infrastructure receiver 54 is preferably linked to an overlay user access terminal 52 which will provide reconciliation of inbound and outbound messages among other things. Optionally, the infrastructure receiver 54 could have two receivers within the same unit to decode both the inbound messages from the subscriber unit as well as the outbound messages coming from one-way outbound messaging system 10. Alternatively or in addition to the infrastructure receiver 54, a separate infrastructure receiver 69 could be used as a monitor receiver for directly receiving and decoding outbound messages to further add to the integrity of the inbound overlay system. Thus, inbound messages from the subscriber unit 56 will be correctly correlated with the outbound messages from the messaging system 10. The infrastructure receivers that directly receive and decode the outbound messages from the messaging system 10 are particularly useful in cases where the messages do not originate from the overlay user access terminal 52 or the inbound overlay system, but from the user interface 11 for instance. Another option than can eliminate the costs of additional user interfaces and associated phone lines comprises the coding and re-routing of messages designated for the two-way system. For instance, a message that is designated for a known two-way subscriber unit that is initiated through the user interface 11 of the one-way outbound messaging system, could be redirected at the user access terminal 12 to be sent to the overlay user access terminal 52 via link 65. This would allow the overlay user access terminal to act as if the message was initiated at the user interface 58 without requiring the user interface 58. Then, the message could be sent back through link 65 to the user access terminal 12 with the subscriber identification modified such that it is recognized as an outbound-only subscriber unit, or the message could be sent directly to the controller 14 from the overlay user access terminal 52 via link 67. Again, the controller 14 in this instance should view and handle the information from the overlay user access terminal 52 as if the message was initiated from the user access terminal 12 and intended for a typical one-way subscriber unit.

Callers accessing two-way devices such as subscriber unit 56 can reach the overlay user access terminal 52 via a plurality of RF inbound links (53, 59, 61). Alternatively, like the one-way user access terminal 12, another user interface 58 such as a computer with alpha entry messaging software can be linked to the overlay user access terminal 52. The user interface 58 could be used among other things to modify subscriber lists, modify class of service for a particular subscriber, or initiate a page through the overlay user access terminal 52. Initiating an outbound page through the overlay user access terminal 52 would require either a link 65 to the one-way user access terminal 12 or a link 67 to the controller 14 of the outbound messaging system. The link used would depend on the configuration of the service provider's system. The overlay user access terminal 52 is cognizant of the two-way operations and would have access to a data base in memory 55 (or elsewhere) necessary to properly signal the subscriber units. Signals received from the subscriber units are processed and acted on accordingly.

Additionally, a two-way system, including this overlay system can allow for roaming of subscriber units among different messaging systems. Thus, an intraterminal link 60 coupled to the overlay user access terminal 52 as well as to a remote terminal 62 from another system can facilitate the forwarding of messages and location finding of roaming subscriber units. The remote terminal 62 can also be another overlay user access terminal like terminal 52.

The means for interconnecting the various blocks are numerous. In general they will be driven by the service provider's existing data networks, the availability within the regions of service, and the costs of the available means. Collocation of the parts, although often a cost advantage, is not necessary to the effective operation as long as the latencies are not severe and the bandwidth adequate for existing traffic. The present invention allows to a varying degree for several full two-way features using inbound control via the outbound infrastructure. For instance, frequency reuse is a feature that creates the ability to locate a subscriber unit to a sufficiently restricted area so a limited number of transmitters can be used for further delivery of data. Other subscriber units which are sufficiently separated from the unit can then also use the same communication resource (same frequency or time slot, etc.) without there being harmful interference at each subscriber unit location. Regional systems have no RF coverage overlap. If a subscriber unit is isolated to a single region, reuse can therefore occur in other regions. Each region may still have its data broadcast in simulcast. The overlay system of the present invention will always be able to provide this level of resolution.

In overlap regions the difficulty is identifying a subset of overlapping transmitter patterns. Using just receiver information may not be viable for single transmitter identification. A set of transmitters would therefore be identified. If the region is sufficiently large, it can be possible to identify non-interfering simulcast sub-regions for bulk data delivery. For example, a system simulcasting from Boston to New York, could identify units in Boston and New York, and simulcast different data around those two cities without worrying about interference occurring in Connecticut.

Full two-way systems can work around this problem by having each transmitter send out a unique identification code. These codes returned by the subscriber unit to the infrastructure allow the identification of one or a few transmitters that are capable of reaching the unit. By simply updating the existing one-way base stations to provide these codes, this capability could also be added to the overlay system's capabilities.

A two-way system allows the elimination of unnecessary transmissions. If the message body is large compared to the size of a minimum page, it is often beneficial to first determine if the pager will be able to receive the bulk transmission. A simple "are you there" page with the appropriate response from the subscriber can be sent to determine if the subscriber is even available to receive a lengthy message. Taking one step further, a page requesting acknowledgment and the memory available at the subscriber unit can further aid in reducing unnecessary transmissions.

On the other hand, a two-way system has the capability to retransmit messages to improve reliability. The two-way system can use a time-out period based on the lack of receipt of an expected inbound response in response to an outbound page which does not acknowledge receipt. Thus, the message can be resubmitted to the outbound messaging system to increase reliability.

As a unit moves to different regions it searches for regional identification codes. These could exist in the normal protocols, or be generated as periodic global pages by the overlay terminal. When a unit detects it has entered a different region, it transmits an unsolicited message. The system receiving this message informs the home system of the unit as to its whereabouts. The home system will now only send pages to the registration area. If the page is not acknowledged in the registration area and if the customer's options are set appropriately, the system may hunt for the unit in other regions, having assumed that registration failed for some reason.

A two-way system facilitates the delivery of subscriber originated information or replies to outbound requests. The delivery of responses, delivery confirmation or failure, or message read indication can be delivered by outdialing, holding the information for caller inquiry, forwarding to another pager, or a variety of other means.

The inbound overlay system essentially uses a subscriber unit (56) and infrastructure adjunct (52 &54) to exploit the existence of outbound- only messaging systems without modification. In this way, additional messaging traffic is generated through an existing outbound-only messaging system to, among other things, retransmit an undelivered page, locate a subscriber unit's position, retransmit corrupted or unacceptable data previously sent, or manage the messaging traffic in a more efficient manner. Additionally, the overlay system allows for input and return of two-way traffic via the overlay portion of the system. Many of the benefits described above are equally applicable to the inbound overlay system 501 of FIG. 2. The elements above the demarcation line 100 once again can be found in an existing outbound- only messaging system 10 as described with FIG. 1. Likewise, the elements below demarcation line 100 belong to the inbound overlay system 501, which preferably comprises all the same elements described with respect to the inbound overlay system 50 of FIG. 1 in addition to other elements to be described. The overlay user access terminal 52 of FIG. 2 could be a computer dedicated to the purpose of a terminal or a computer with an application running as a background task. Its basic purpose is to reconcile the inbound response traffic with the outbound messaging traffic. In this case, the overlay user access terminal 52 acts as a control point or as an Intelligent Network Adjunct to a Private Branch Exchange (PBX) system of a local campus style system. It can process a page request, and store the information pertinent to the expected responses from subscriber units. The pages are then sent to a wide area messaging system via a network interface. As seen in FIG. 2, this can be achieved in many ways. Responses and requests from a subscriber unit 56 can be received by an infrastructure receiver 54 as described in FIG. 1 or a receiver coupled to a computer 72 via RF link 57. Responses or requests could also be received by a transceiver coupled to a computer 70. The computer 72 would be linked to the overlay user access terminal 52 via link 59 to reconcile against expected messages. If the computer 72 or computer 70 is not directly coupled to the overlay user access terminal, then the computers (70 or 72) can indirectly forward responses or requests to the overlay user access terminal 52 via a local area network 74. The overlay user access terminal 52 can then forward requests to initiate a page via link 67 to the controller 14 of the outbound messaging system. Alternatively, the local area network 74 can be used to forward requests to either the user access terminal 12 or controller 14 of the outbound messaging system via a network gateway 75 and a wide area network 76 as shown. Use of the network gateway 75 and wide area network 76 depend upon the particular configuration of the campus computer network and the configuration of the outbound messaging service provider. Finally, a local transmitter coupled to a computer 71 could be used within a computer network to transmit local content information to the two-way subscriber unit 56. Preferably the information sent to the subscriber unit contains some possible actions, and the target for the response. The response and target are sent inbound by the subscriber unit 56, and the controller or overlay user access terminal 52 interprets what should be done with it. Both the inbound and outbound traffic are captured. The controller 14 therefore acts on the inbound, based on its decode of the outbound forwarded to it by the overlay system. Regeneration of pages that were not received or received inappropriate responses would be a basic use of such an implementation.

Ideally, the system of the present invention would provide for forwarding for two-way usage. In other words, a wide area network could be given knowledge of the two-way overlay. It would then forward either the page request, or an action option list to the local controller when a suitable page request was received. The local controller would then have the same capabilities as if the input occurred locally.

While the receivers in a local campus style system could use a private link network for their communications, the use of existing computer networks would provide for great cost savings. Computer networks have become ubiquitous in the manufacturing and business buildings of technologically advanced countries. The most predominant of these networks use the protocols referred to mnemonically as TCP/IP. TCP is the Transport Control Protocol (concerned with data integrity and movement), and IP is the Internet Protocol (concerned with unique addresses of entities). The present invention preferably proposes the construction of two ported communication devices. One of the ports preferably consists of a slot for a particular portable communications device type such as a PCMCIA or PCIA receiver device. The other port connects to existing computers or servers by a standard interface such as an RS232 or RS423 or other suitable interface. This interface should be a very generic form suitable for connection to the vast majority of existing computers on a network. If a particular network is made up of numerous computers of the same type, a more cost effective implementation would be cards which directly plug into a computer's bus structure. This eliminates the need for additional power supplies, cabling, housings and so on. An implementation using a PCMCIA or PCIA form factor receiver or transceiver is preferable. While not all fixed computers support this type of physical device, it is generic across computer types. A further variation would involve the slight remoting of the receivers from these ported computers serving as gateways to a computer network. This is desirable to extend the range of the portable devices. This could be accomplished by cables, infrared links, or RF links. The long distance links would continue to be provided by the existing local area network. No matter how the port is attached to the computers, a computer program is required on the host computer. This program preferably performs the task of communicating between the network gateway and the computer's communication network such as the local area network 74. The communication occurs transparent to the user of the computer. Ideally the computer's user would be ignorant of the network gateway transactions being performed.

Ethernet is the most widely deployed computer oriented communications hardware layer. The present invention would most likely be initially utilized with Ethernet as the communication backbone. The two port gateways which plug into or attach to the computers would in general be ignorant of the actual backbone used. Other possibilities are variations on the IEEE specifications set 802 (Ethernet being 802.3), wireless WANs, Appletalk Network, ATM, or other suitable specifications. The use of TCP as the transport protocol is likewise the predominant transport layer protocol, and therefore preferred. Other protocols such as UDP could be used under appropriate circumstances. Referring to FIG. 3, an exemplary timing diagram in accordance with the present invention depicts a protocol structure 300 preferred for the outbound channel 308 of the outbound messaging system and the inbound channel 310 of the inbound messaging system. The preferred protocol is similar to Motorola's well-known FLEX™ two-way messaging protocol. The outbound channel 308 includes a sync signal 302, followed by a plurality of time slots for message blocks B0-B10. The inbound channel 310 preferably begins at the end of the sync signal 302 and ends before the end of the next subsequent sync signal 302. In this manner, the time slots of the inbound channel are synchronized to the outbound protocol. Preferably, the time slots of the inbound channel 310 are divided into time slots for scheduled messages, such as page acknowledgments, and other time slots for unscheduled (ALOHA) messages, such as registration messages. The boundary 312 separates the scheduled messages B0-B7 from the unscheduled ALOHA messages B8-B10.

Information carried in the outbound message preferably defines which of the time slots B0-B7 of the inbound channel 310 will be used for a scheduled inbound message corresponding to the outbound message. In the case of ALOHA messages, the subscriber unit 56 preferably utilizes a random process to select one of the ALOHA time slots B8-B10 for sending an unscheduled message. It will be appreciated that, alternatively, other numbers of time slots can be utilized for the outbound and inbound channels 308, 310 between the sync signals, and that the two channels 308, 310 are not required to utilize identical numbers of time slots between the sync signals 302. It will be further appreciated that the boundary 312 can be moved to provide for a different mix of scheduled and ALOHA time slots, as required to handle traffic.

The synchronized time slotted technique described above for handling inbound messages minimizes collisions between inbound transmissions from multiple subscriber units 56. As a result, there is advantageously no requirement to check a busy /idle status of the inbound channel before transmitting— a check which would otherwise produce additional system traffic.

As an alternative, instead of utilizing the synchronized time slotted technique for inbound transmissions, a conventional spread spectrum technique can be utilized. The spread spectrum technique also minimizes collisions between inbound transmissions from multiple subscriber units 56, because a large number of chipping sequences can be utilized, thereby reducing the probability of collisions. As a result of using the spread spectrum technique, there also is advantageously no requirement to check a busy/idle status of the inbound channel before transmitting.

FIG. 4 is an electrical block diagram of the subscriber unit 56 in accordance with the present invention. The subscriber unit 56 comprises an antenna 202 for transmitting and receiving radio signals including the inbound and outbound messages. The antenna 202 is coupled to a conventional transmitter 206 for transmitting the inbound message and coupled to a conventional receiver 208 for receiving the outbound message. The receiver 208 and the transmitter 206 are coupled to a processing system 236 for processing the outbound and inbound messages. The processing system 236 is also coupled to a user interface 214 for interfacing with a user of the subscriber unit 56. The user interface 214 comprises a conventional display 216, a conventional alert 218, and conventional user controls 220. The processing system 236 preferably comprises a conventional processor 210 coupled to a conventional memory 212. The memory 212 includes message processing software 222 for processing the inbound and outbound messages in accordance with the present invention. The memory 212 also includes at least one selective call address 224 to which the subscriber unit 56 is responsive.

Thus, it should be clear from the preceding disclosure that the present invention provides a method and apparatus for overlaying a one- way inbound messaging system onto a one-way outbound messaging system, without the drawbacks of the prior art approach. Advantageously, the method and apparatus does not require two receivers in the subscriber unit and does not have to check a busy /idle status of the inbound channel before transmitting. Many modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention can be practiced other than as described herein above for the exemplary embodiments.

What is claimed is:

Claims

1. A method of overlaying a one-way inbound messaging system onto a one-way outbound messaging system having a subscriber list to create a two-way messaging system, the method comprising the steps of: providing a plurality of subscriber units, wherein at least one of the plurality of subscriber units is a two-way subscriber unit capable of transmitting an inbound message; transmitting, by the at least one of the plurality of subscriber units, the inbound message on an inbound channel without determining a busy/idle status of the inbound channel; receiving the inbound message by at least one of a plurality of overlay base receivers; decoding the inbound message by the at least one of the plurality of overlay base receivers to provide an inbound decoded signal; receiving the inbound decoded signal at an overlay user access terminal; and managing and correlating at the overlay user access terminal the inbound decoded signal with the subscriber list of the one-way outbound messaging system.

2. The method of claim 1, wherein the transmitting step comprises the step of transmitting the inbound message in a scheduled time slot defined by an outbound message and synchronized to an outbound protocol from the one-way outbound messaging system.

3. The method of claim 1, wherein the transmitting step comprises the step of transmitting the inbound message in an unscheduled ALOHA time slot synchronized to an outbound protocol from the one-way outbound messaging system.

4. The method of claim 1, wherein the step of managing and correlating comprises the step of directing the one-way outbound messaging system to retransmit a page to one of the plurality of subscriber units when one of the plurality of overlay base receivers detects that the one of the plurality of subscriber units did not receive the page.

5. The method of claim 1, wherein the step of managing and correlating comprises the step of the overlay user access terminal sending location information of at least one of the plurality of subscriber units to the one-way outbound messaging system once an inbound message is received from the at least one of the plurality of subscriber units.

6. The method of claim 1, wherein the step of managing and correlating comprises the step of directing the one-way outbound messaging system to retransmit a portion of a message to one of the plurality of subscriber units when the one of the plurality of subscriber units receives the message with a corrupted portion.

7. The method of claim 1, wherein the transmitting step comprises the step of transmitting the inbound message as a spread spectrum signal.

8. The method of claim 1, wherein at least one of the step of receiving the inbound decoded signal and the step of managing and correlating comprises the step of communicating through a computer network.

9. A two-way messaging system created by overlaying a one-way inbound messaging system onto a one-way outbound messaging system having a subscriber list, the two-way messaging system comprising: the one-way outbound messaging system; a plurality of subscriber units, wherein at least one of the plurality of subscriber units is a two-way subscriber unit capable of transmitting an inbound message, the at least one of the plurality of subscriber units including a transmitter for transmitting the inbound message on an inbound channel without determining a busy /idle status of the inbound channel; a plurality of overlay base receivers for receiving and decoding the inbound message by at least one of the plurality of overlay base receivers to provide an inbound decoded signal; and an overlay user access terminal coupled to the plurality of overlay base receivers for receiving the inbound decoded signal and coupled to the one-way outbound messaging system for managing and correlating the inbound decoded signal with the subscriber list of the oneway outbound messaging system.

10. The two-way messaging system of claim 9, wherein the transmitter is arranged to transmit the inbound message in a scheduled time slot defined by an outbound message and synchronized to an outbound protocol from the one-way outbound messaging system.

11. The two-way messaging system of claim 9, wherein the transmitter is arranged to transmit the inbound message in an unscheduled ALOHA time slot synchronized to an outbound protocol from the one-way outbound messaging system.

12. The two-way messaging system of claim 9, wherein the overlay user access terminal is programmed to direct the one-way outbound messaging system to retransmit a page to one of the plurality of subscriber units when one of the plurality of overlay base receivers detects that the one of the plurality of subscriber units did not receive the page.

13. The two-way messaging system of claim 9, wherein the overlay user access terminal is programmed to send location information of at least one of the plurality of subscriber units to the one-way outbound messaging system once an inbound message is received from the at least one of the plurality of subscriber units.

14. The two-way messaging system of claim 9, wherein the overlay user access terminal is programmed to direct the one-way outbound messaging system to retransmit a portion of a message to one of the plurality of subscriber units when the one of the plurality of subscriber units receives the message with a corrupted portion.

15. The two-way messaging system of claim 9, wherein the transmitter is arranged to transmit the inbound message as a spread spectrum signal.

16. The two-way messaging system of claim 9, wherein at least one of the plurality of overlay base receivers and the overlay user access terminal are arranged to communicate through a computer network.