KR940002608B1 - Celluler telephone system apparatus for cell locate device - Google Patents

Abstract

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Description

[Name of invention]

Equipment for cellular radiotelephony systems Cell location equipment

[Brief Description of Drawings]

1 is a block diagram of a conventional centrally lit sector wireless telephony system.

FIG. 2 is a detailed block diagram of the cell location facility used by the system shown in FIG. 1 in accordance with the present invention.

3 is a diagram of an RF switch usable in the system shown in FIG. 2 in accordance with the present invention.

4a, b and c contain diagrams of equipment used in sectors in the system shown in FIG. 2 according to the invention.

5 is a flow diagram beneficial for operating the system shown in FIG. 2 in accordance with the present invention.

FIG. 6 is a detailed block diagram of a cell location facility similar to the facility shown in FIG. 2 but modified to apply to a narrow communication area.

Detailed description of the invention

[Field of Invention]

The present invention relates generally to radio frequency (RF) communication systems and, more particularly, to sector-transmitted and sector-received cellular communication systems.

[Description of the Prior Art]

Mobile wireless telephony services have been used early on and have typically been characterized by transmission from a central location to a limited number of mobile or portable units within a wide geographic area at high power. Mobile or portable transmissions are generally received by a network of receivers remote from the central location in the conventional system because of the low transmission power, and the received transmissions are later returned to the central location for processing. Since only a limited number of radio channels were available in a conventional system, wireless telephone calls and numbers throughout the city are limited to a limited number of channels available.

Modern cellular radiotelephone systems divide the radio coverage area into smaller coverage areas (cells) using low power transmitters and limited coverage receivers, thereby allowing a relatively large number to be effectively augmented by channel reuse in metropolitan areas. Has an available wireless channel. Such cellular systems are described in detail in US Pat. Nos. 3,906,166, 4,485,486, and 4,549,311, assigned to the assignee of the present invention.

Some more efficient cellular wireless telephone systems use a central illumination scheme, where each cell is subdivided into sectors. The sectors are illuminated by the directional antenna. Each sector is provided with a number of dedicated voice channels. Such systems are described in US Pat. Nos. 4,128,740, and 4,696,027, which are assigned to the assignee of the present invention. Sectors significantly eliminate interference between adjacent co-channels.

Unfortunately, known patent efficient cellular radiotelephone systems are unable to provide sufficient channel capacity to accommodate the increasing demands of cellular operation. Consider a relatively wide cell where each sector covers a large area. A subscriber population in a given sector can easily occupy all available voice channels available in that sector.

In any case, systems have been developed that attempt to overcome this problem. One particular system, as described in US Pat. No. 4,144,411, subdivides each cell into subcells operating simultaneously on independent, non-intrusive voice channels. While this embodiment is known to be very beneficial for increasing channel capacity in each cell, it is expensive to implement due to the overlap of required base site equipment.

In addition, none of the techniques described above apply to cellular narrow communication paths where cellular communication is required at low cost, for example, over long and narrow areas along highways or train tracks.

Thus, there is a need for a cellular wireless telephone system that overcomes these drawbacks.

[Object and Summary of the Invention]

It is a general object of the present invention to provide a cellular radiotelephone system which overcomes the above mentioned drawbacks.

A more specific object of the present invention is to provide a sector split cellular radiotelephone system that dynamically assigns voice channels within a cell according to communication needs within each sector and optimizes the quality and efficiency of the channels available in the cell.

It is another object of the present invention to provide a system that provides flexible voice channel assignment along narrow and long communication calls.

The present invention is best described through the preferred embodiments, wherein the cellular wireless telephony system uses a base location facility to communicate with subscriber units in a number of areas, including at least two sectored areas. The sectorized area forms at least a portion of the geographic communication area serviced by the base location facility. The operation of the base location facility is controlled by a base location controller, which assigns at least one floating communication channel for communication between the subscriber unit and the base location facility in at least two of the multiple locations.

In another aspect of the invention, the base location facility comprises an omnidirectional antenna for servicing the area surrounding the geographic area, without which access to the subscriber unit becomes impossible. This area is shown in FIG.

Detailed Description of the Preferred Embodiments

Referring now to FIG. 1, there is shown a cellular wireless telephony communication system of the type that would particularly benefit from the invention described herein. Such cellular communication systems include US Pat. Nos. 3,663,762, 3,906,166; Experimental cellular wireless telephone system by Motorola and American Radio-Telephone Services, Inc., supported by the Federal Communications Commission, February 1977; And more recently, a system published by Motorola Inc. of Schaumburg, Illinois, 1982, entitled "Motorola DYNATAC Cellular Radiotelephone System". The cellular systems provide telephony coverage for both mobile and portable wireless telephones located across a wide geographic area. The portable radiotelephone may be of the type described in U.S. Pat.Nos. 4,486,624, 3,962,553, and 3,906,166, assigned to the assignee of the present invention, and the portable radiotelephone is a Motorola service publication in Schaumburg, Illinois. It may be of the type described in Motoro Instruction Manual No. 68P81039E25, published in 1979. Although the present invention has been specifically described for a centrally illuminated sector cell system, it will be apparent to those skilled in the art that the integers of the present invention can be applied to other types of sector split cellular configurations.

As shown in FIG. 1, the geographic area is subdivided into cells 102, 104, and 106 that are illuminated with radio frequency energy from fixed location transceivers 108, 110, and 112, respectively. Fixed position transceivers are controlled by base position controllers 114, 116, and 118 as shown. The base position controllers are coupled to wireless telephone control terminals 120 similar to those described in US Pat. Nos. 3,663,762, 3,764,915, 3,819,872, 3,906,166, and 4,268,722 by data and voice links, respectively. The data and voice links may be provided with dedicated wire lines, pulse code modulated carrier lines, microwave radio channels, or other suitable communication links. The control terminal 120 is coupled to the switched telephone network via a conventional telephone central station 122 to complete the call between mobile and portable wireless and landline telephones.

In order to explain the system of the present invention shown in FIG. 1 in more detail, reference is made to US Pat. No. 4,696,027.

In one embodiment of the present invention for realizing sector-divided cells, as shown in FIG. 2, wireless transceivers are coupled to a sector antenna. Each sector antenna is supplied to a primary transceiver facility (e.g., transceiver 204) dedicated to a particular sector by a multicoupler (e.g., RX multicoupler 202) and bilaterally adjacent sector transceiver facility. (E.g., transceiver 206 for sector 6 and transceiver 208 for sector 2). The transceiver 204, 206 or 208 provides communication for the voice channel dedicated to use in the relevant sector. Each sector antenna is also coupled to a signal processing receiver to allow the signal processing receiver to access all six sector antennas. The transmitter (eg, transmitter 212) of the primary transceiver facility is coupled to the sector antenna via a respective combiner 282 and a duplexer (such as duplexer 210.) The duplexer is an antenna special from Cleveland, Ohio. Similar to Model ACD-2802-AAMO manufactured by Lists Corporation The combiner 282 is made using SRF4006B, available from Motorola, Inc., Arlingter Heights, Weight Sure Drive 1501, Illinois. You can also carry out.

Base position controller 220 is used to control a six-way switch 230 that couples a floating voice channel transceiver 240 to each duplexer 210 via a combiner 282. The transceiver 240 is referred to as a floating voice channel transceiver because, according to the present invention, it provides a voice channel that can float between sectors when a channel request is made in each sector. The receiver portion of transceiver 240 is interconnected with receiver multicoupler 202 in the same manner as described for transceivers 204, 206, and 208 (interconnection not shown).

Implementing in this floating manner is particularly beneficial for rural cellular radiotelephone installations where each geographic area covered by individual sectors can extend beyond the typical coverage area. Consider a cellular system designed to cover large rural areas in accordance with the present invention. Each sector-divided cell includes a number of high-gain sector-divided antennas, each of which can transmit at significantly higher emission power levels than currently implemented, i.e. at 500 watts above the current level, which is approximately 100 watts. . As described above, when the transmission power is increased, the cost is effectively used by using a conventional high gain sector split antenna. The signal processing channel in the system of the present invention uses omni-directional antennas as in conventional sector division cell systems. Since the gain of the omni-directional antenna is lower than that of the sector antenna, a high power amplifier is needed for the signal processing channel to match the effective emission power level for each type of channel.

Preferred embodiments of the floating voice channel system are described with reference to FIGS. 3, 4a, 4b and 4c. 3 includes a flow diagram of a floating voice channel targeting one of six sectors of a cell. FIG. 3 also includes a conventional internally terminated RF coaxial switch 310, such as 6-IT-2L31, available from DB Product, Pasadena, CA, which switches with switch 230 of FIG. Used in a similar way. This preferred embodiment differs from the embodiment of FIG. 2 in that the system uses multiple floating voice channels instead of just one floating voice channel. Switch 310 of FIG. 3 is a representative switch for one voice channel (one switch is used for each floating voice channel) and allows the base position controller to dynamically switch the voice channel as long as it is associated with any particular sector. A representative switch for one voice channel (one switch is used for each floating voice channel).

Such dynamic switching is beneficial, for example, when a subscriber moves from one sector to another. In this case, the base position controller only needs to switch the floating voice channel assigned to the subscriber to the next sector. More importantly, as discussed above, the dynamic switching provides a significant improvement to the system in that each available floating voice channel can be switched to any sector to service the rush of subscribers requiring service. The availability of a single floating channel provides an increase in channel capacity for all sectors in the cell. At least in part, effective channel capacity is achieved by adding an additional fixed channel to each sector, since the communication system can be designed so that wireless telephone calls are relatively simple and there are no requests for additional communication channels in a particular region. It's a huge improvement over what you can do. For example, by comparing two cells with virtually identical traffic density characteristics (eg, using conventional Erlang unit measurements), an effective channel capacity improvement will be described. The first cell is a conventional cell with six sectors with three dedicated channels per sector, without floating channels, and the second cell is a cell designed according to the invention, with one dedicated channel per sector. It has six floating channels with six sectors and can be used in a cell. It will be readily appreciated that 18 channels are required in a typical embodiment, while only 11 channels are required in an embodiment of the present invention.

For a statistical analysis of the viability of "over flow" channels in a typical telecommunications system, Business Communications, 7-8, 1983, by Michael T. Hills, "Practical Traffic Engineering-Part of the Minimum Cost Routing System 5, 'Packet' traffic: what is it and when is it problematic? '

Those skilled in the art will appreciate the need to avoid co-channel interference between sectorized regions. For example, it is beneficial to avoid the interference using floating channels with a wide reuse distance. The orientation of the dedicated channel is suitably designed as shown and described in US Pat. No. 4,128,740, assigned to the assignee of the present invention.

Those skilled in the art will appreciate that any number of dedicated channels per sector may be used and any number of floating channels per cell may be used without departing from the scope of the present invention. For example, it may be desirable to use zero dedicated channels per sector and multiple floating channels per cell.

4A shows a general block diagram of a floating voice channel interconnection for sector 1 of an exemplary cell. Voice channel transmitter 450 is shown to couple a sector-only (or fixed) voice channel, i.e., a non-floating voice channel, to a conventional channel combiner 455. Also coupled to combiner 455 are signal paths 460, 462, 464, and 466 for carrying four floating voice channels, respectively, from RF coaxial switch 310. The combiner 455 typically operates to couple the voice channel (path) to the antenna 458 of the sector.

FIG. 4B shows a general block diagram of a facility for sector 2 of an exemplary cell, which is essentially the same as the facility shown in FIG. 4A. In FIG. 4B, the voice channel transmitter 470 is shown as coupling another sector dedicated voice channel to a similar channel combiner 475. Signal paths 480, 482, 484, and 486, respectively, for carrying the same four floating voice channels from another RF coaxial switch 310 dedicated to sector 2 of the exemplary cell, via combiner 475 and antenna 478 Is coupled to.

More detailed than the block diagrams of FIGS. 3A and 3B and consistent with the second installation, FIG. 4C shows a block diagram of a representative sector installation for the system of the present invention described above. This includes the base position controller 220, the (voice channel) transceiver 240, the switch 230, the transceiver 204, the duplexer 210, the receiver multicoupler 202, and the five-channel comb shown in FIG. Included are the bins 282 and blocks representing the combiners 455 or 475 shown in FIGS. 4A and 4B. The combiner 282 is shown to couple the outputs of the switch 230, other switches (not shown) and the output of the transceiver (transmitter) 204 to the duplexer 210. Other interconnections correspond to the illustration of FIG.

FIG. 6 shows a location facility that is substantially the same as FIG. 2 but has been modified to apply, for example, to a narrow communication area along a highway. Facilities common to both FIGS. 2 and 6 will be apparent from the common terminology used herein. The difference between FIG. 2 and FIG. 6 is that the cell positioning equipment associated with antenna sectors 2, 3, 5 and 6 has been omitted, the conventional omni-directional antenna 612 has been added, and the omni-directional antenna zone 614 (for A dashed line with respect to the directional antenna 612).

The apparatus of FIG. 6 is preferably used in a manner substantially similar to the operation of the cell location equipment of FIG. At least one floating voice channel is provided through switch 230 to communicate in one of three regions, one of two sectored regions or one of the omnidirectional antenna zones. Upon request, the floating voice channel is switched to the area requesting service. This method of operation is particularly beneficial on rural highways or railway lines where the sectored areas are arranged to cover the longest possible route of travel.

In either case, the moving subscriber enters the communication system coverage area in one of the two sectored regions and is designated as either a fixed channel or a floating channel. If a floating channel is designated, it is appropriate that the floating channel be used through the movement path, for example through the omnidirectional zone from antenna sector area 1 and again through antenna sector area 4. If a fixed channel was originally specified, then the floating channel is only used when the subscriber enters the omnidirectional zone, and then it is appropriate to be used through the mobile.

The apparatus of FIG. 6 provides significant advantages. The omnidirectional zone prevents the call from being disconnected as the subscriber quickly crosses the sector-divided area. The omnidirectional zone allows communication to be maintained while the subscriber is physically under the channel of the sector antenna. Incidentally, the device provides a cost effective implementation for this type of application. Floating channel technology reduces costs by eliminating the need for equipment to be applied to unused channels.

FIG. 5 shows a flow chart that is beneficial for channel assignment operation in a particular cell for the system shown in FIG. 2 in accordance with the present invention. This flowchart applies to the designated operation for both the fixed (dedicated) voice channel and the floating voice channel for a cell. It will be readily appreciated to modify the flow chart for the operation of the facility arranged in FIG. The flowchart begins at block 510 where the base position controller is described as monitoring a signal processing channel for a subscriber radio telephone call request. Flow proceeds from block 510 to block 515 where a test is performed by the base position controller to determine if the subscriber station has requested the use of the voice channel in the sector. Otherwise, flow proceeds to block 510.

If the subscriber station requested a voice channel in a particular sector, flow proceeds from block 515 to block 520, where another test is performed to determine if a fixed channel is available in that particular sector. If a fixed channel is available, flow proceeds to block 525 where channel assignment to the available voice channel is made. Flow from block 525 returns to block 510.

If a fixed channel is not available in a particular sector, flow proceeds from block 520 to block 530 where a test is performed to determine if a floating channel is available in that particular sector. If a floating channel is available, flow proceeds to block 535 where the base position controller (BSC) controls the sector's RF coaxial switch to connect the available floating channel to the subscriber station request. Flow from block 535 proceeds to block 540 where actual channel assignment is made. As described at block 545, once the wireless telephone call terminates on the floating channel, the base position controller disconnects the floating channel for the particular setter, as described at block 550. Flow from block 550 returns to block 51.

From block 530, if the floating channel is not available in a particular sector, flow proceeds to block 560 where a test is performed to determine if a fixed channel is available in a sector adjacent to the particular sector for which the subscriber station requests the channel. Proceed. The test described at block 560 is typical (sometimes referred to as sector sharing) in a typical sector split telephony system when no voice channel is available in the sector for which the channel is requested. Thus, if a fixed channel is available in the neighboring sector, flow proceeds to block 565 where the subscriber station request is directed to the channel from the neighboring sector. Flow returns from block 565 to block 510.

If no fixed channel is available in the neighboring sector, then the flow is determined at block 560 by the base position controller to determine if a subscriber request can be directed to the channel in the neighboring cell, suitably the closest in the cell closest to the subscriber unit. Proceeds to block 570, which determines if a sector can be assigned. This is typically accomplished by determining whether the designation of a channel from an adjacent cell causes excessive co-channel interference in another cell. More specifically, if the subscriber signal strength in the target cell exceeds the co-channel interference threshold of the system, the flow proceeds to block 580 where the call request is rejected (blocked). If the subscriber signal strength does not exceed the threshold, flow proceeds to block 575 where the call is directed to the adjacent cell. Flow from block 575 returns to block 510.

If the subscriber station request exceeds the co-channel interference threshold, flow proceeds from block 570 to block 580 where the base position controller informs the subscriber station that the call request cannot be serviced. From block 580, flow proceeds to block 510.

The above-described sequence shown in the flowchart of FIG. 5 describes a good sequence of channel availability checks. The base position controller first proceeds to check if a fixed channel is available in a particular sector, otherwise checks whether a floating channel is available. After the base position controller determines that neither fixed or floating channels are movable in a particular sector, the base position controller only checks for channel availability in an adjacent sector. Sequence is important for the efficiency of channel use. It is best to use a fixed channel in each sector before any floating channel is used.

Those skilled in the art will appreciate that various modifications may be made to the above described systems without departing from the spirit or scope of the invention.

Claims (9)

First and second signals, each having a radio frequency transmitter 240 operating as one signal frequency source and resonant cavity means for separating one signal frequency source from another signal frequency source. 17. An apparatus for cellular radiotelephone system cell location equipment having first and second signal combiner devices 282 tuned in frequency, the apparatus comprising: coupling means for coupling the separated signal frequency source to a common transmitter output, respectively; Operatively coupled to a signal combiner device 282 having a 210, and to the radio frequency transmitter 240, a first signal combiner device 282, and a second signal combiner device 282. And radio frequency switching means 230 for coupling the radio frequency transmitter 240 to either one of the first and second signal combiner devices 282. Cellular wireless telephony system cell positioning equipment. The radio frequency transmitter (240) of claim 1 operatively coupled to the radio frequency transmitter (240) and radio frequency switching means (230) to designate the radio frequency transmitter (240) for one of the first and second signal frequency sources. And control means for dynamically switching said radio frequency transmitter (240) to a corresponding signal combiner device (282) tuned for said signal frequency source. 2. The antenna of claim 1, wherein the common transmitter output is from a group consisting of a sector-divided antenna (antenna sector 1), an omni-antenna 614, a direct coupled optical fiber link, and an indirect coupled communication link via a frequency conversion mechanism. Device for a cellular wireless telephony system cell location facility, characterized in that it is selected. 10. The apparatus of claim 1, wherein the common transmitter output serves a geographic area selected from the group consisting of a sector partitioned antenna area and an omni-antenna zone. First and second signal combiners tuned to the same signal frequency with radio frequency transmitter 240 operating as one signal frequency source and resonant cavity means for separating one signal frequency source from another signal frequency source. 10. An apparatus for cellular positioning system cell location equipment having a device 282, comprising: coupling separate signal frequency sources of the first and second signal combiner devices to first and second common transmitter outputs, respectively. A signal having a coupling means 210 is operatively coupled to the combiner device 282, the radio frequency transmitter 240, and the first and second signal combiner devices 282 to provide the first and second signals. Cellular radio, characterized in that it comprises radio frequency switching means (230) for coupling said radio frequency transmitter (240) to one of said second signal combiner devices (282). Communications system equipment device for cell location. The radio frequency transmitter (240) of claim 5, operatively coupled to the radio frequency transmitter (240) and the radio frequency switching means (230) to maintain the radio frequency transmitter (240) at the same signal frequency. And a control means for dynamically switching said radio frequency transmitter (240) to one of said binor devices (282). 6. A group according to claim 5, wherein each common transmitter output comprises a sector divided antenna (antenna sector 1), an omni-antenna 614, a direct coupled optical fiber link and an indirect coupled communication link via a frequency conversion mechanism. Device for a cellular wireless telephony system cell location equipment, characterized in that is selected from. 6. The apparatus of claim 5, wherein the first common transmitter output serves a geographic area that is different from a geographic area serviced by the second common transmitter output. 9. The first common transmitter output of claim 8, wherein the first and second common transmitter outputs serve one sector divided antenna region (antenna sector 1) in one cell and another sector divided antenna region of the same cell. Service a second transmitter output serving antenna sector 2) and a first common transmitter output serving one sector divided antenna region (antenna sector 1) in a cell; A second transmitter output, a first common transmitter output for serving one sector-divided antenna region in one cell (antenna sector 1) and a second transmitter output for serving a sector-divided antenna region of another cell, and one cell It consists of a first common transmitter output serving one sectored antenna region (antenna sector 1) within and a second transmitter output serving an omni-antenna zone of another cell. Cellular radiotelephone communication system cell location for the facility device, characterized in that serving the geographic area is selected from the.