MXPA00006553A - Antenna system for narrowband communications systems and method of operation - Google Patents

Abstract

There is disclosed an improved base station (411) for communicating with communication units (121, 122) in a wireless messaging system (400). According to an advantageous embodiment, the base station comprises:1) a transmitter (306) that is capable of transmitting messages to the communication units (121, 122) in a forward-channel having a first frequency range;2) a receiver (307) that is capable of receiving messages from the communication units (121, 122) in a reverse-channel having a second frequency range;and 3) an antenna (303) that is capable of transmitting the forward-channel messages (312) at a first angle of electrical downtilt below the horizon and receiving the reverse-channel messages (313) at a second angle of electrical downtilt, wherein the second angle of electrical downtilt is less than the first angle of electrical downtilt.

Description

ANTENNA SYSTEM FOR NARROW BAND COMMUNICATIONS SYSTEMS AND METHOD OF OPERATION CROSS REFERENCE TO RELATED REQUESTS The present invention is related to that described in the US patent application Serial No. 09 / 002,191 (Proxy No. PAGE01 -00115), filed on January 31, 1997, entitled "SYSTEM FOR SCHEDULING REVERSE-CHANNEL MESSAGES IN NARROWBAND" COMMUNICATIONS SYSTEMS AND METHOD OF OPERATION (System for Programming Reverse Channel Messages in Narrowband Communications Systems and Operation Method), which is assigned to the assignee of the present invention Descriptions of this related patent application are incorporated herein by reference for all purposes set forth herein.

TECHNICAL FIELD The present invention is directed, in general, to wireless communication systems and methods for operating them, and, in particular, to narrowband communication systems for transmission in a single direction and in two directions of voice and data messages. .

BACKGROUND OF THE INVENTION The demand for better and cheaper wireless telecommunication services and their equipment continues to develop very quickly. Most of this growth is stimulated by the approval of the Federal Communications Commission ("FCC") of certain frequency bands for the next generation of Personal Communication Service ("PCS") devices that provide telephone service of voice as well as voice and / or data message paging services. A relatively small portion of the available spectrum was set aside for the narrowband PCS, which is more suitable for advanced message paging services, to encourage efficient use of the available spectrum. There are a number of well-known wireless communication techniques that try to maximize the efficiency with which the available spectrum is used. These methods include frequency division multiple access ("FDMA"), time division multiple access ("TDMA"), code division multiple access ("CDMA"), and the like. The term "multiple access" means that simultaneous, multiple users (or "subscribers") are supported in each of these systems. In a FDMA system, for example, the total available radio spectrum is divided into separate frequency bands (or "channels") of, for example, 25-30 KHz for those systems based on "AMPS" or "TACS" standards, or 10 KHz for newer systems, such as advanced narrowband PCS message delivery systems ("NPCS"). In FDMA, only one subscriber at a time is assigned to a channel. No other subscriber can access this channel until the transmission of the message sent by the first subscriber has been completed. In a TDMA system, the total available radio spectrum is again divided into separate frequency bands. Each band afterwards is temporarily subdivided into, for example, three timeslots. Only one subscriber at that time is assigned to each channel, where one channel corresponds to a particular frequency band and to a particular time slot for that band. No other subscriber can access this channel until the transmission of the message sent by the first subscriber has been completed. In a CDMA system, the total available radio spectrum is used by each subscriber. Each subscriber transmits a unique, pseudorandom ("PN") noise code sequence as a spread spectrum signal. The subscriber's transmitter and the receiving base station share the code, which is used to distinguish the subscriber from other subscribers in the system, who uses different PN codes. In this way, a CDMA system uses codes other than the frequency and / or time slots to provide multiple access. The total capacity of a multiple access system in addition it can be improved by dividing a wireless system into cells and, in the case of FDMA and TDMA, using only different frequency channels in junction cells. The organization of message paging and cell phone systems in cells is widely known and understood. The division into cells is achieved by limiting the transmission scale of both the base stations and the mobile communication units. The sequences used in a cell do not interfere with the different frequencies used in the junction cells and are not transmitted far enough to interfere with identical frequencies used in more remote non-junction cells. Frequency "reuse", therefore, is possible by dividing a TDMA or FDMA system into cells. In the case of CDMA, the division of the system into cells does not affect the frequency distribution, since all subscribers use the same amount of spectrum. However, there are fewer subscribers per cell in smaller cells, so there is less interference to distort the signal transmitted by each subscriber. In this way, capacity continues to be improved for the entire system. The structure of a message paging system is a little different than cellular phone systems. In a message paging system, all base station transmitters across a wide coverage area are synchronized and simultaneously broadcast (i.e., simulated) to a paging message in a forward channel to a subscriber pager.

This simulation increases the probability that the paging message will reach the pager even through obstacles, such as buildings. The paging system does not assign the subscriber to a cell and transmits to the subscriber only in that cell, as in the case of a cellular telephone system. However, even in a paging environment, there is a break in the message paging system in cells. That is, due to the low power of a manual or portable two-way pager, a message transmitted by a user in a reverse channel has a very limited scale compared to the base station transmitters. Therefore, a relatively large number of station receivers must be deployed through the coverage area of the message paging system in order to ensure that the signal transmitted by any pager is received by a base station receiver. As a result, minimizing the number of receivers needed to verify the coverage area of a message paging system becomes an important consideration. By using fewer receivers, the infrastructure cost is reduced and, therefore, the cost of service to subscribers is reduced. There is a need in the art for an improved wireless communication system that minimizes the cost of equipment necessary to operate the system. In particular, there is a need for an improved wireless message delivery system that minimizes the number of base station receivers required to operate the system. Yet another need in the art is for an improved narrowband message sending system capable of providing advanced two-way message sending services that maximize frequency reuse and spectral efficiency with minimum number of station receivers. base.

COMPENDIUM OF THE INVENTION The limitations inherent in the prior art described above are overcome through an improved base station for communicating with mobile communication units (e.g., message pagers, PCS devices, personal data assistants and other processing systems that include a functionality wireless communication) in a wireless messaging system. In an advantageous embodiment, the base station includes: 1) a transmitter that is capable of transmitting messages to the communication units in a forward channel having a first frequency range; 2) a receiver that is capable of receiving messages from the communication units in a reverse channel having a second frequency range; and 3) an antenna that is capable of transmitting the channel messages forward at a first angle of electrical inclination below the horizon and receiving the channel messages in reverse at a second angle of electrical tilt, wherein the second angle of inclination electrical is less than the first angle of electrical inclination. According to an advantageous embodiment, the first electric tilt angle is determined by the first frequency range and the second electric tilt angle is determined by the second frequency range. As will be discussed in detail below, the angle of inclination of a receiving light beam is preferably slightly below the horizon. The use of a relatively small electrical tilt angle in the reverse channel allows the antenna to focus on signals from further communication units, including those beyond the boundaries of the coverage area where the base station resides. This has to increase the probability that the antenna will receive reverse channel signals from communication units in other coverage areas, thereby increasing the total macrodiversity of the antenna in the message sending network.

In an alternative embodiment of the present invention, the base station further comprises an amplifier arranged near the antenna to amplify messages received in the reverse channel before processing in the receiver. In a related embodiment, the antenna is an antenna in sectors operating to transmit a forward message in a selected direction to a higher signal strength in relation to a signal resistor transmitted in an unselected direction. In another related embodiment, the antenna is an antenna in sectors that operates to amplify a received reverse channel message of a selected address and attenuates a reverse channel message received from an unselected address. In another alternative embodiment of the present invention, the second electric tilt angle is approximately zero degrees, so that the antenna is optimized to receive reverse channel messages from remote communication units. The compendium of the above invention summarizes, rather broadly, some advantageous aspects of various embodiments of the present invention, so that those skilled in the art can better understand the detailed description that follows. The additional aspects of the invention that will be described below form the subject matter of the claims of the invention. Those skilled in the art should appreciate that they can readily utilize the described concept and specific embodiments as a basis for designing or modifying other structures to accomplish the same purpose of the present invention. Those skilled in the art should also understand that such equivalent constructions do not deviate from the spirit and scope of the present invention in its broadest form. Before going into the detailed description, it may be advantageous to establish definitions of certain words and phrases used throughout this patent document: the terms "includes" and "includes", as well as their derivatives, mean inclusion without limitation; the term "or" is inclusive, representing and / or; the phrases "associated with" and "associated with it", as well as their derivatives, represent that includes, that is included within, interconnected with, that contains, that is contained within, in relation to or with, coupled to or with, that may be communicated with, that cooperates with, interspersed with, that is a property of, juxtaposition, which is close to, that can be joined to or with, that has, that has a property of, or the like; and the term "controller" represents any device, system or part thereof controlling at least one operation, said device may be implemented in the hardware, firmware or software or some combination of at least two of them. It should be noted that the functionality associated with any particular controller can be centralized or distributed, either locally or remotely. Definitions of certain words and phrases will be provided through this patent document, those skilled in the art should understand that in many, if not in all cases, such definitions apply to prior uses, as well as to future uses. of said defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention, reference will now be made to the following descriptions taken together with the accompanying drawings. Where similar numbers designate similar objects, wherein: Figure 1 illustrates a representative portion of a network of conventional message page according to the prior art; Figure 2 illustrates conventional forward and reverse channels associated with the base station antenna using electric tilt techniques according to the prior art; Figure 3 illustrates forward and reverse channels associated with a base station according to an illustrative embodiment of the present invention; Figure 4 illustrates an improved message delivery network implementing improved base stations and an improved receiver according to an illustrative embodiment of the present invention; Figure 5 illustrates an improved message delivery network implementing improved base stations according to a second embodiment of the present invention. Figure 6 illustrates a flow chart illustrative of an illustrative method for operating the improved base station of Figures 3 to 5 in accordance with the principles of the present invention.

DETAILED DESCRIPTION Now returning initially to Figure 1, a representative portion of a conventional message paging network (generally designated 100, hereinafter referred to as a "message sending network") is illustrated according to the prior art. The message sending network 100 can ii provide, for example, two-way voice and text messages to subscribers. The message sending network 100 is represented by 3 illustrative fixed terrestrial sites, referred to as base stations, for communicating with a plurality of mobile communication units (e.g., message pagers, PCS devices, personal data assistants and other communication systems). processing including wireless communication functionality, etc.), within the message sending network 100. The base stations 111, 112 and 113, each marked "BS" in Figure 1, have coverage areas 101, 102 and 103, respectively, which are determined by the transmitter power in the base stations 111, 112 and 113. For the purposes of illustration and discussion the coverage areas 101, 102 and 103 are shown as circles. In real environments, however, each of the coverage portions 101, 102 and 103 may differ significantly from an idealized circular shape. For purposes of illustration, a plurality of message paging units, each marked "P" in Figure 1, are shown broadcast through the message sending network 100. Paging units 121 and 122 are located within of the coverage area 101 and can couple sending of two-way messages to the base station 111. The paging units 123 and 124 are located in the coverage area 101 and can couple sending of two-way messages to the base station 112. The paging units 126, 127 and 128 are located in the coverage area 103 and can couple the sending of two-way messages to the base station 113. The paging unit 125 is a coverage area 102 and 103 and can couple the sending of two-way messages to the stations base 112 and 113. In a narrowband messaging sending environment, such as FDMA, the base stations 111, 112 and 113 transmit RF signals in a forward channel, such as 939-940 MHz, for example. The base stations 111, 112 and 113 receive RF signals in a reverse channel to, for example, 901-902 MHz. Each base station is effectively a transceiver that contains an RF transmitter and an RF receiver to perform two-way communications . Each paging unit receives forward channel messages directed to it to a selected sequence within the forward channel. Each paging unit also transmits reverse channel messages at a selected frequency within the reverse channel. The message sending network 100 can be, for example, a two-way wireless message delivery system compatible with the MOTOROLA® ReFLEX ™ transport protocol. The ReFLEX® protocol can be used to send a numeric message, such as a conventional 10-digit telephone number, to a paging unit. The paging unit can then transmit on the reverse channel, an automatic recognition message that does not require the action of the subscriber. Alternatively, the ReFLEX® protocol can be used in an improved paging mode to send a more complex alphanumeric message, such as an e-mail text message, to the paging unit. The pager can then transmit, in the reverse channel, an automatic recognition message that does not require the subscriber's action. Shortly thereafter, the subscriber may transmit a "preset" message stored in the paging unit, such as "call later", or a single message composed of the subscriber. In addition, the paging unit can be trained to transmit or receive short duration voice messages recorded by the subscriber or the caller. The base station 111 transmits data and voice messages to paging units in the coverage area 101; the base station 112 transmits voice message data to the paging units in the coverage area 102; and the base station 113 transmits data and voice messages to the paging units in the coverage area 103. The base stations 111, 112 and 113 can be connected together to a central control facility (not shown) through of a structure with wire, such as a proprietary fiber optic network. In alternative embodiments, the base stations 111, 112 and 113 can be connected to each other and to a central control facility via a satellite communications link, such as through a very small aperture terminal ("VSAT") . Voice messages and text paging can be received in the central control facility from a variety of sources. Some messages can be received from the public telephone system in the form of simple call numbers entered by a caller on a DTMF keypad. Alphanumeric messages can be received through the central control installation from an Internet connection. In addition, callers' voice messages may be received from the public telephone system and recorded for subsequent transmission to the subscriber. As is well known, the transmit power of a base station is typically much higher than the transmission power of the paging units in each coverage area. In order to maximize the probability of receiving a reverse channel message from a paging unit, additional reception-only stations, or simply receivers, are frequently arranged through the message sending network 100 in order to decrease the average distance that separates a paging unit from the receiver of the nearest paging system. The extra receivers in this way minimize the effects of multipath fading, delay, and signal blocking with respect to each paging unit. The receivers are also connected to the base stations and the central control facility through a proprietary data link with wire. For example, receivers 131 and 132 are located in coverage area 101 and the delay messages received in the channels in reverse of any of the paging units in the message sending network 100 to the central control facility. Similarly, the receivers 133 and 134, located in the coverage area 102, receive messages on the reverse channel of any of the paging units in the message sending network 100 and retransmit the messages to the central control facility. Finally, receivers 135 and 136 in coverage area 103 retransmit messages received in the reverse channel to the central control facility. Due to the plurality of receivers in each coverage area, including any receiver that may be part of the base station, a message transmitted by a paging unit may be received by more than one receiver. In this way, if the signal received by a receiver experiences multipath fading or is blocked by a structure, such as a building, another receiver can continue to receive the signal and retransmit it to the base station for processing. The receivers are not linked to a particular coverage area. All receivers retransmit the reverse channel signal that is received to the central control facility. For example, paging units 125 and 126 are located near receiver 135 in coverage area 103. Messages transmitted by paging units 125 and 126 can be received by receiver 135, as well as by base stations 112 and 113 in coverage areas 102 and 103, respectively. This Development redundancy is known as antenna diversity. Many receiver systems currently comprise a pair of receive paths coupled to two different local antenna systems. In said "microdiversity" system, both receive paths transfer the received signal energy from a reverse channel message to a local receiver circuit system at the base station, which then performs the bit error check to determine if either of the two signals were received well. If both received reverse channel signals contain errors as a result of fading or obstructions, the receiver circuit system can add the energies of both of the received signals to form a composite signal. The composite signal can then be verified for errors to determine the reverse channel message. The base stations and receivers in the message sending network 100 employ a variety of conventional techniques to prevent interference between the signals transmitted by the base stations and the signals transmitted by the paging units. In a narrowband PCS sending system based on FDMA, a level of protection is provided by the frequency filtering that separates the signals according to their transmission frequency. The message sending network 100 may also employ a multiple sector antenna receiver ("SMAR") that focuses transmitted and received signals. For example, the message sending network 100 may employ a SAMR that uses 3 antennas of panel, each of which transmits a signal of complete resistance to a sector of 120 ° in the forward channel, but transmits only one signal attenuated in the remaining 240 ° long. Each panel antenna also amplifies reverse channel signals received from the 10 ° sector and filters signals or noises received from the remaining 240 ° of arc. Prior art paging systems such as the message sending network 100 typically employ an electrical "tilt" in the antennas at base stations and receivers in order to reduce the effective scale of transmitted signals and attenuate received signals of distant paging units or base stations. Figure 2 illustrates the conventional forward and reverse channels associated with antenna 202 of the base station using electric tilt techniques according to the prior art. Although the following discussion of prior art electrical tilt technique centers in the base station 111, it should be noted that this is only by way of illustration, and that the following description applies with equal force to other base stations and receivers in the message sending network 100. The base station 111 comprises a tower 201 for maintaining the antenna 202 in a raised position above the ground 205. The base station 111 also comprises a transmitter 206 for transmitting messages in the channel forward and a receiver 207 to receive messages on the reverse channel. The messages of The forward and reverse channels are appropriately transferred to or from the central control facility. The reference light beam 211 is a horizontal reference axis indicating the relative position of the horizon. The antenna 202 employs electrical tilt to transmit messages in the channel forward along a transmission light beam 212. The transmission light beam 212 represents the direction of travel with respect to the horizon of the main energy lobe transmitted by the antenna 202. As Figure 2 indicates, the transmission light beam 212 is transmitted below the horizon at a transmission angle, T1. The inclination angle 01 is determined by the electrical characteristics of the antenna 202 and depends on the transmission frequency of the forward channel. The antenna 202 employs electrical tilt to receive messages in the reverse channel along a reception light beam 313. The reception light beam 213 represents the direction of travel with respect to the horizon of an incident signal transmitted from a paging unit located at an optimum distance away from the antenna 202. The antenna 202 has been optimized to amplify signals received from the paging units at the optimum distance. The angle of inclination, T2, of! receiving light beam 213 is below the horizon and is also below the inclination angle, T1, of the transmission light beam 212. The main purpose of employing electrical inclination in the transmission beam light 212 is to restrict the size of the coverage areas 101, 102 and 103 in the paging network 100. If the transmission light beam 212 is oriented directly to the horizon without any electrical tilt, much of the energy of the transmitted signal by the antenna it could be transmitted to infinity, and in this way be lost. Furthermore, using only a small electrical tilt angle could direct the main power lobe of the transmission light beam 212 to very distant paging units in other coverage areas resulting in weak forward channel messages that are received in the units. of distant page. The electrical tilt in the forward channel sends a stronger signal to relatively close paging units located at the optimal distance from the antenna 202 (closer to the perimeter of the coverage area), while the signal interference of the signal is minimized. forward channel sent to relatively remote paging units. Similarly, the use of electrical tilt in the reception light beam 213 p allows the antenna 202 to amplify the reverse channel signals from the nearby paging units, while the reverse channel signals of the paging units are attenuated more distant. Since the angle of inclination, T2 of the reception light beam 213 is below the angle of inclination, T1, of the transmission light beam 212, the antenna 202 is optimized to receive signals from reverse channel which are less distant than the paging units activated by the transmission light beam 212. It would seem that the base station 111 may be able to send messages in the forward channel to the paging units, starting from which can not receive messages on the reverse channel. However, it should be remembered that the receiver circuit system in the base station 111 is much more sensitive than the receiver circuit system in the paging units and that a coverage area 111 also contains a plurality of stations only of reception, including receivers 131 and 132, which also receive reverse channel signals. The number and positions of the receivers in the message sending network 100 is selected to ensure sufficient overlap of the receiver coverage areas. A signal from any paging unit in the message sending network 100, therefore, is absolutely assured to be received by one or three nearby receivers. The electrical tilt and antenna diversity techniques described above in relation to the message sending network 100 are very expensive in terms of hardware. A large number of receivers is required to provide effective coverage of reverse channel through the message sending network 100. The present invention provides an improved message sending network that implements a much lower ratio of receivers to transmitters to through the network of sending messages. Returning now to Figure 3, the channels towards forward and reverse associated with a base station 301 according to an illustrative embodiment of the present invention. The base station 301 comprises a tower 302 for maintaining an antenna 303 in a raised position above ground 205. The base station 301 also comprises a transmitter 306 for transmitting messages in the forward channel and a transmitter 307 for receiving messages in the forward channel. the channel in reverse. The forward and reverse channel messages are appropriately transferred to or from the central control facility (not shown). A tower top amplifier 304 can optionally be included to reinforce signals received on the antenna 303 before retransmitting the received signals to the receiver 307, in order to compensate for line losses occurring in long cables between the antenna and the receiver. Although the remainder of the discussion of the illustrative embodiment focuses on the base station 301, it should be noted that this is only by way of illustration, and that the following discussion applies with equal force to the other base stations and receivers in the improved message delivery network. The reference light beam 311 is a horizontal reference axis indicating the relative position of the horizon. The antenna 303 employs electrical tilt to transmit messages in the forward channel along a transmission light beam 312. The transmission light beam 312 represents the direction of travel with respect to the horizon of the main energy lobe transmitted by antenna 303. As Figure 3 indicates, the transmission light beam 312 is transmitted below the horizon at an inclination angle T1. The angle of inclination, T1, is determined by the electrical characteristics of the antenna 303 and depends on the transmission frequency of the forward channel. The antenna 303 employs electrical tilt to receive messages in the rse channel along a reception light beam 313. The reception light beam 313 represents the direction of travel with respect to the horizon of an incident signal transmitted from a unit Paging located at an optimal distance away from the antenna 303. The antenna 303 has been optimized to amplify signals received from the paging units at the optimum distance. The angle of inclination, T2, is determined by the electrical characteristics of the antenna 303 and depends on the transmission frequency of the rse channel. However, unlike antenna 202 of the prior art, the angle of inclination, T2, of the receiving light beam 313 is now above the inclination angle, T1, of the transmission light beam 312. Further, in a preferred embodiment of the present invention, the inclination angle T2 of the receiving light beam 313 is only slightly below the horizon . In other embodiments of the present invention, the angle of inclination, T2, of the receiving light beam 313 can be oriented directly to the horizon. The use of a smaller angle of electrical tilt in the rse channel in antenna 302 focuses antenna 303 on signals from more distant paging units, including those beyond the boundaries of the coverage area where the base station 301 resides. This type of optimization increases the probability that the antenna 303 will receive rse channel signals from remote paging units in other coverage areas, thus increasing the total macro diversity of the antennas in the paging network. The present invention optimizes the antenna 303 for the amplification of signals from the remote paging units, and thus maximizes the macrodiversity effects of the antenna, under the probability that, although the antenna 303 may occasionally lose signal from a nearby paging unit due to multi-path blocking or fading, at least another less-closely-connected antenna will appropriately receive the lost paging signal since the less-near antenna has also been optimized to amplify the signal from remote paging units. Maximizing the ability of more remote receivers to receive the transmission of the paging unit improves all the performance of the paging network. Returning now to Figure 4, an improved message delivery network (generally designated at 400) is illustrated by implementing improved base stations 411, 412 and 413 and an improved receiver 421 according to an illustrative embodiment of the present invention. Base stations 411, 412 and 413 each marked as "BS" in Figure 4, they have coverage areas 401, 402, and 403, respectively, which are determined by the energy of the transmitters in the base stations 411, 412, and 413. For the purpose of illustration and discussion , coverage areas 401, 402, and 403 are shown as circles. In real environments, however, each of the coverage areas 401, 402 and 403 again can differ significantly from an idealized circular shape. Each of the base stations 411, 412 and 413 communicate with a plurality of paging units generally located within their coverage area. Under ordinary circumstances, the base station 411 transmits data and voice messages to the paging units in the coverage area 401; the base station 402 transmits data and voice messages to the paging units in the coverage area 402; and the base station 413 transmits data and voice messages to the paging units in the coverage area 403. The base stations 411, 412, and 413 are connected to each other and to a central control facility (not shown) through of a wire structure, such as a proprietary fiber optic network or, preferably, through a wireless link, such as a two-way VSAT network. A plurality of paging units is shown broadcast through the message sending network 400. The paging units 121 and 122 are located within the coverage area 401 and may be in two-way communication with so minus the base station 411. The paging units 123, 124 and 125 are located in the coverage area 402 and may be in two-way communication with at least the base station 412. The paging units 126, 127 and 128 are located in the coverage area 403 and can be in two-way communication with at least the base station 413. As in the prior art network, each of the base stations 411, 412 and 413 transmits data and voice messages in a forward channel to the paging units within their associated coverage area. Each base station may also receive messages on a reverse channel from any paging unit in the message sending network 400. Each base station is effectively a transceiver that contains an RF transmitter and an RF receiver to perform communications from two directions. As in the case of the message sending network 100 of the prior art, the two-address message traffic in the message sending network 400 may comprise voice and data messages associated with one of a plurality of information modes or notification, such as numeric and alphanumeric paging and voicemail. In an advantageous embodiment, the message sending network 400 is a system for sending narrowband messages based on FDMA, implementing the MOTOROLA® ReFLEX 25® protocol and employing multiple sector antenna receiver ("SAMR") systems that focus signals transmitted on the channel forward and amplify signals received in the reverse channel. The message sending network 400 also comprises an additional receiving-only station for receiving messages on the reverse channel. The receive-only station, receiver 421, is connected to the base stations and has a central control facility (not shown) through a wire structure, such as a proprietary fiber optic network. Now it can be seen, however, that the total number of receivers required by the message sending network 400, including the receivers in the base stations 401, 402, and 403, is much lower than in the message sending network. 100 of the prior art. This is due to the macrodiversity effect gained through the entire message sending network 400 by optimizing the electrical tilt of the antennas in the improved base stations 411, 412 and 413 and in the improved receiver 421 according to the antenna system described in Figure 3. Returning now to Figure 5, an improved message sending network 500 is illustrated implementing improved base stations 511-514 according to a second illustrative embodiment of the present invention. The electrical tilt of each of the antennas in the enhanced base stations 511-514 is also optimized according to the antenna system described in Figure 3. The illustrative message sending network 500 is optimized for use in an urban area heavy. The outline of a large group of office buildings or a metropolitan area dense is denoted by the perimeter 501. The base stations 511-514 are located around the perimeter 501. The reception-only stations optimized according to the systems described in Figure 3 can also be implemented within the urban core, if the density of paging receivers and the number of signal blocking obstacles so requires. The paging units 521, 522 and 523 are located in the dense urban area and can be in two-way communication with at least one of the base stations 511-514. In the forward channel, base stations 511-514 transmit messages to the dense urban area and take advantage of building reflections to ensure that the forward channel signal reaches the intended paging unit. Similarly, in the reverse channel, the base stations 511-514 can receive reflected signals from buildings to ensure that at least one of the base stations receives a reverse channel message transmitted through any of the paging units. 521, 522 and 523. Returning finally to FIG. 6, a flow diagram of an illustrative method (generally designated at 600) for operating the enhanced base station 411 in accordance with the principles of the present invention. For the purpose of illustration, the message sending network 400 is assumed to be, for example, a two-way wireless message delivery system compatible with the MOTOROLA® ReFLEX ™ transport protocol. In a mode of 2k normal operation, the base station 411 continuously receives from the central control installation, forward channel messages that are to be broadcast (or simulated) to the paging units in the message sending network 400 and synchronization signals, which synchronize the simultaneous transmission of forward channel messages to the appropriate pagers (process step 601). In the illustrated example, the base station 411 receives a message that is to be transmitted to the channel forward to the pager X. Then, at any desired time, the transmitter 306 at the base station 411 transmits the forward channel messages in queue for each pager, including the forward channel message for the X pager (process step 602). All forward channel messages are transmitted by all base stations at an electrical tilt angle of T1. This simulation of each message page through each base station in the message sending network 400 maximizes the probability that each paging message arrives at the targeted paging unit. The forward channel message also includes information that tells a receiving paging unit, such as page pager X, the reverse channel time slot and the frequency at which the receiving pager must transmit any of the messages programmed, such as the automatic acknowledgment message that each paging unit sends after receiving the channel message to ahead. In the reverse channel, the receiver 307 in the base station 411 checks the early time slots 0-17 and the frequency selected in each reverse channel channel to detect the automatic recognition message that the X-page is programmed to send back a receipt of the forward channel message (process step 603). The receiver antenna is optimized at an electric tilt angle of T2 to receive the reverse channel messages transmitted by the relatively remote paging units in the message sending station 400. Next, the receiver 307 in the base section 411 it checks the subsequent time slots 18-22 and the frequency selected in each reverse channel frame to detect unscheduled messages from the X-pager (process step 604). An unscheduled reverse channel message may include the registration request generated by a paging unit when it is first turned on and identifies the message sending network 400. Alternatively, an unscheduled reverse channel message may include a Message Request United, because the pager X informs the message sending network 400 that the subscriber wishes to send a voice or alphanumeric message that the subscriber has composed. Then, the base station 411 sends all reverse channel messages to the central control facility for further processing (process step 605). At this point, the base station 411 can repeat the process described above from the beginning. As is evident from the foregoing, the principles of the present invention are particularly beneficial when applied to wireless communication networks employing simulation message delivery. Those ski in the art should understand that although the message pager has been used to illustrate the principles of the present invention, alternative communication units (or device) can conveniently be used with a message delivery system in accordance with the principles of the present invention. For example, PCS devices, as well as conveniently arranged calculators; pocket microcomputers, battery-powered laptops, notebook-type computers, personal computers or other computers; and any other processing system, including PDAs (ie, devices, or "small and ingenious devices", that perform particular tasks, such as a diary, database, PCS, message paging, multimedia, memo taker, calculator, alarm clock, etc.). Although the principles of the present invention have been described in detail with reference to the system of paging messages and infrastructure modalities, those skilled in the art can understand that they can make various changes, substitutions or alterations in the present without departing from the spirit and scope. of the invention in its broadest form.

Claims (36)

51 REIVINDI &ATIONS

1. - For use in a wireless message sending system, a base station communicating with communication units located in said wireless message delivery system, said base station comprises: a transmitter that is capable of transmitting messages to said units communication in a forward channel having a first frequency range; a receiver that is capable of receiving messages from said communication units in a reverse channel having a second frequency range; and an antenna that is capable of transmitting said channel messages forward at a first angle of electrical inclination below the horizon and receiving said channel messages in reverse at a second angle of electrical tilt, wherein said second angle of electrical tilt is smaller than said first angle of electric inclination.

2. The base station according to claim 1, wherein the first angle of electrical inclination is determined by the first frequency range.

3. The base station according to claim 1, wherein the second electric tilt angle is determined by the second frequency range.

4. The base station according to claim 1, which further comprises an amplifier arranged near said antenna that is capable of amplifying messages received in the reverse channel before processing in said receiver.

5. The base station according to claim 1, wherein the antenna is an antenna in sectors that is capable of operating to transmit a forward channel message in a selected direction to a higher signal strength in relation to a signal strength transmitted in an unselected direction.

6. The base station according to claim 5, wherein the antenna is an antenna in sectors operating to amplify a reverse channel message received from a selected address and attenuates a reverse channel message received from an address not selected

7. The base station according to claim 1, wherein the second electric tilt angle is approximately zero degrees, so that the antenna is optimized to receive reverse channel messages from units of 'remote communication.

8. A wireless message sending system that communicates with communication units, comprising: a plurality of transmission stations, each of said plurality of transmission stations comprising: a transmitter that is capable of transmitting messages to said units of communication in a forward channel having a first frequency range; and an antenna that is capable of transmitting said channel messages forward at a first angle of electrical inclination below the horizon; and a plurality of receiving stations, each of said plurality of receiving stations comprising: a receiver that is capable of receiving messages from said communication units in a reverse channel having a second frequency range; and an antenna that is capable of receiving said reverse channel messages at a second electrical tilt angle, wherein said second electrical tilt angle is smaller than the first electrical tilt angle.

9. The wireless message sending system according to claim 8, wherein the first electric tilt angle is determined by the first frequency range.

10. The wireless message sending system according to claim 8, wherein the second electric tilt angle is determined by the second frequency range.

11. The wireless message sending system according to claim 8, further comprising an amplifier arranged near said antenna that is capable of amplifying messages received in the reverse channel before processing in the receiver. 12.- The wireless message sending system in accordance with claim 8, wherein the antenna is an antenna in sectors operating to transmit a forward channel message in a selected direction to a higher signal resistor relative to a signal resistor transmitted in an unselected direction. 13. The wireless message sending system according to claim 12, wherein the antenna is an antenna in sectors operating to amplify a reverse channel message received from a selected address and attenuates a received reverse channel message. from an unselected address. 14. The wireless message sending system according to claim 8, wherein the second electric tilt angle is approximately zero degrees, so that the antenna is optimized to receive reverse channel messages from remote communication units. . 15. A method for operating a wireless message sending system for communicating messages with communication units located in said wireless message delivery system, said method comprises the steps of: transmitting messages to the communication units in a channel towards forward having a first frequency range and at a first angle of electrical inclination below the horizon; and receiving messages from the communication units in a reverse channel having a second frequency range and at a second electric tilt angle, wherein the second angle of Electrical tilt is less than the first electric tilt angle. 16. The method according to claim 15, wherein the first electric tilt angle is determined by the first frequency range. 17. The method according to claim 15, wherein the second electric tilt angle is determined by the second frequency range. 18. The method according to claim 15, wherein the step of transmitting further includes the step of transmitting channel messages forward in a selected direction to a signal strength greater than forward channel messages transmitted in one direction. not selected 19. The method according to claim 15, wherein the receiving step further includes the step of amplifying a reverse channel message received from a selected address. 20. The method according to claim 15, wherein the receiving step further includes the step of attenuating a reverse channel message received from an unselected address. 21. A wireless communication system that includes a plurality of associated base stations capable of simulating messages to the communication units in a forward channel and receiving messages from one of the communication units in a reverse channel, said messages of forward channel simulate at a first angle of electrical tilt and said messages from Reverse channel received at a second angle of electrical inclination, said second angle of electrical inclination being less than the first angle of electrical inclination. 22. The wireless message sending system according to claim 21, wherein the first electric tilt angle is determined by the first frequency range. 23. The wireless message sending system according to claim 21, wherein the second electric tilt angle is determined by the second frequency range. 24. The wireless message sending system according to claim 21, wherein one of the base stations includes an amplifier that is capable of amplifying messages received in the reverse channel. 25. The wireless message sending system according to claim 21, wherein one of the base stations includes an antenna in sectors operating to transmit a forward channel message in a selected direction to a higher signal strength. in relation to a signal resistance transmitted in a non-direction. selected 26. The wireless message sending system according to claim 25, wherein the antenna in sectors operates to amplify a reverse channel message received from a selected address and attenuates a reverse channel message received from a non-directed address. selected 27.- The wireless message sending system in accordance with claim 21, wherein the second electric tilt angle is approximately zero degrees, so that an antenna is optimized to receive reverse channel messages from remote communication units. 28. The wireless message sending system according to claim 21, wherein said base stations are associated with a perimeter of an urban area. 29. A method for operating a wireless communication system that includes a plurality of associated base stations capable of simulating messages to communication units in a forward channel and receiving messages from one of the communication units in a reverse channel, the method comprises the cooperative steps of: simulating said forward channel messages at a first electric tilt angle, and receiving the reverse channel messages at a second electrical tilt angle, wherein the second electric tilt angle is less than the first angle of electric inclination. 30. The method of operation according to claim 29, wherein the first angle of electrical inclination is determined by a first frequency range. 31. The method of operation according to claim 29, wherein the second angle of electrical inclination is determined by a second frequency range. 32.- The method of operation according to the claim 29, which further comprises the step of amplifying messages received in the reverse channel. The method of operation according to claim 29, further comprising the step of using an antenna in sectors to transmit a forward channel message in a selected direction to a higher signal strength in relation to a signal resistance transmitted in an unselected direction. The method of operation according to claim 33, further comprising the step of further amplifying a reverse channel message received from a selected address and attenuating a reverse channel message received from an unselected address. The method of operation according to claim 29, wherein the second electric tilt angle is approximately zero degrees, so that an antenna is optimized to receive reverse channel messages from remote communication units. 36. The method of operation according to claim 29, further comprising the step of associating said base stations with a perimeter of an urban area.