AUSTRALIA
Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT a a a.
a a a. a-..c a.
*4 a. Applicant(s): SAMSUNG ELECTRONICS CO., LTD.
Invention Title: MODULAR AND DISTRIBUTED ARCHITECTURE FOR A BASE STATION TRANSCEIVER SUBSYSTEM The following statement is a full description of this invention, including the best method of performing it known to me/us: M4ODULAR~ AND DISTRIBUTY.IED
ARCHITECTURE~
**FOR A BASE STATION TR-aXSCEIVER
SUBSYSTM
CROSS REFERENCE TO RELATED
APPLICATIONS
Under Title 35 United States Code _l19(e), this *application claims the benefit of U. S Provisional Application 600828 filed Seteme 9, 1997.
BACKGROUND OF THlE
INVENTION
Field of the nvention The present invention generally relates to wireless comm~funication systems and, more particularly, to base station Mafhs 614579 v 1. 3 3361.00009USCI Docket 33361-00009USCJ STA.WSL.040 transceiver subsystems used in a Code Division Multiple Access (CDMA) network.
Background and Objects of the Present Invention FIGURE 1 (prior art) is a block-flow diagram which graphically represents a wireless communication system. From FIGURE 1 it is seen that a wireless communication system comprises a mobile station 10, a base station 20, a reverse link 30 which represents the electromagnetic wave o communication link transmitted from mobile station 10 to base 10 station 20 and a forward link 40 which represents the electromagnetic wave communication link transmitted from base station 20 to mobile station FIGURE 2 (prior art) shows a cell grid and cell sites.
S"In a wireless communication system based on the cellular principle, a service area 49 is divided geographically, into a number of small areas 50, 52, 54, 56 called "cells." In each S"cell there is a cell site 58, 60, 62, 64 where radio equipment known as a Base Station Transceiver Subsystem (BTS) is installed.
Multiple cell layouts such as macro cells, micro cells, and Pico cells can be provided within a particular geographical area to effect hierarchical coverage (where macro cells provide the largest coverage and Pico cells the smallest). Pico cells may be used to provide coverage inside buildings, to cover a DallWas2 614579 v 1, 33361.00009USCI 2 3 Docket 33361-00009USC1 STA.WSL.040 special area (campus, stadium, airport and shopping mall), to temporarily cover for special events or areas hit by natural disasters, to cover outlying remote locations, to supplement macro or mini cells with hole-filling, or to enhance the capacity of hot spots. FIGURE 3 (prior art) is a block diagram of a wireless system network connected to a land line Public Switched Telephone Network (PSTN) 68. As shown in FIGURE 3, a BTS 66 provides a link to mobile subscribers or (mobile stations) 10. Each BTS 66 typically may include two or more 10 antennas 67, which may be omni antennas or directional antennas.
Omni antenna configurations provide 360 x of coverage, whereas directional antennas provide less than 360x of coverage across an area known as a sector. For example, there may be two or three sectors in a typical directional configuration such that each sector of a two sector configuration generally provides 180 x of coverage and each sector of a three sector configuration generally provides 120 x of coverage. For satisfactory reception and transmission, each sector typically requires at least two antennas for diversity reception.
Continuing with the description of FIGURE 3, each BTS 66 is coupled to a Base Station Controller (BSC) 70 (multiple BTSs 66 may be coupled to a single BSC 70). Likewise, each BSC Dallas2 614579 v I, 33361.00009USCI
&V
Docket 33361-00009USC1 STA.WSL.040 is coupled to a Mobile Switching Center (MSC) 72 and the MSC 72 is in turn coupled to a PSTN 68.
FIGURE 4 (prior art) is a functional block diagram of a BTS. As shown in FIGURE 4, a conventional BTS 66 typically comprises four major functional blocks for each sector of coverage: an RF front-end 74, a plurality of transceivers 76, a plurality of modem processors 78, and a controller Controller 80 interfaces with a BSC 70 over a T1 or El line 81, and the RF front-end 74 is connected to the antennas 67 0 which are typically mounted at the top of a tower or pole 82 as represented in FIGURE 5 (prior art), where FIGURE illustrates an outdoor and ground based BTS coupled to a tower topped mounted antenna.
In a typical system, the four major functional blocks of the BTS 66, shown in FIGURE 4, are contained in one physical cabinet or housing which is in close proximity to a pole (or tower) 82 at ground level. Long coaxial cables 84 are then run to the top of the pole 82 where the antennas 67 are mounted.
The cable length typically varies from 50 to 200 feet, depending on various installation scenarios. Cables of these lengths suffer from undesirable power losses. Accordingly, thick coaxial cable diameters of approximately to 1_ inches are used to minimize the cable power loss, which is typically about Dallas2 614579 v 1, 33361.00009USCI 4 Docket 33361-00009USC1 STA.WSL.040 2 to 4 dB. Minimizing these power losses is important because such losses in the cables degrade the receiver sensitivity and reduce transmission power.
FIGURE 5 depicts a prior art BTS unit 66 connected via a long length of cable 84 to an antenna 67 at the top of a supporting structure 82. FIGURE 6 (prior art) is a block diagram of yet another known BTS architecture were a tower top e: mounted RF front-end module consists of a Low Noise Amp (LNA) and a Power Amp (PA) 74 (hereinafter LNA/PA unit 74). The cable 10 power loss in this architecture is not as critical as in the previous mentioned architecture because the power loss can be made up with additional amplification. However, there is still a need to use rather thick cables due to the signals between the LNA/PA unit 74 and the transceiver 76 in the BTS 66 are high frequency radio-frequency (RF) signals. Other problems are associated with transmitted RF signals between the LNA/PA unit 74 and the BTS 66, such as power losses, system noise, and mechanical clutter. Furthermore additional complex circuitry either or both in the RF front-end module and the transceiver may be required to automatically compensate for the wide range of cable losses that arise in different installation scenarios due to varying cable lengths. Such problems get more severe as the operating RF Frequencies are Dallas2 614579 v 1, 33361.00009USCI
U'
Docket 33361-00009USC1 STA.WSL.040 allocating in the increasingly higher frequency bands. This is the case for personal communications systems such as CPCS.
In other words, as the length of a cable 84 increases, or as the frequency transmitted through a cable 84 increases, power losses between the LNA/PA unit 74 and the BTS 66 increase.
Thus, the long cables 84 used to connect the LNA/PA unit 74 to the BTSs 66 (often in excess of 150 feet, sometimes even exceeding 300 feet) introduce large power losses. For example, a 100 W power amplifier in a base station transceiver unit 10 transmits only 50 W of power at the antenna when there is a 3 DB loss in the cable. Power losses in the cable work against reception as well, reducing the ability of the receiver to detect received signals. Also, with Personal Communication Systems (PCS) operating at high frequencies, the power loss in the cable 84 running between the LNA/PA unit 74 and the transceiver 76 in the BTS 66 increases. Thus, RF cable losses "incurred on both the transmit and receive paths result in poorer than desired transmission efficiency and lower than desired receiver sensitivity, making the use of relatively thick (high conductance) coaxial cables necessary to minimize loss.
Noise generated through ground loops, magnetic coupling, or multi-tower units can cause problems. In these applications, there are usually one or more large coaxial cables which carry Dallas2 614579 v 1. 33361.00009USCI 6 I Ii Docket 33361-00009USCl STA.WSL.040 RF signals from the antennas 67 to the base station 66. The RF frequencies associated with such base stations make it difficult to duplex RF signals onto the same coaxial cable, and thus, usually only a single signal is propagated in a single coax cable. Thus, these RF signals are not bundled or duplexes, and therefore require separate cables for each signal and separate connectors for each cable. The RF signal shield of the coax cable 84 is grounded at both ends of the coax cable 84. One end is grounded to the chassis of the BTS, which is 10 grounded to ground 87, whereas the other end of the RF signal shield is grounded through a braid or cable 82 to the chases of the LNA/PA unit 74. This, unfortunately, creates a ground loop. This ground loop may cause noise in the signal path due to common mode currents adding in phase, and may also cause .ooooi magnetic coupling. Also, because each tower-top unit .i generates noise, using multiple tower-top units contributes S"to noise generation.
In some cell sites where the capacity required is higher, there is a need to transmit more than one RF carrier signal.
The transmission of multiple RF carriers per sector normally would require a corresponding number of transmit antennas per sector, unless a special effort is made to combine multiple RF carriers prior to RF coupling to the antennas. A single set Dallas2 614579 v 1, 33361.00009USCI 7 t Docket 33361-00009USC1 STA.WSL.040 of antennas, per sector, can be shared on the receive side for multiple RF carrier reception.
The conventional technique for reducing the number of transmit antennas required for multiple RF carrier transmission are shown in FIGURE 7 and FIGURE 8. In FIGURE 7 (prior art) the carriers are combined with a high power combiner.
In FIGURE 8 (prior art) the carriers are combined at low power and then the combined signal is amplified with a multi-carrier.
Neither design is very suitable for use in a compact BTS 10 system. Thus, there is a need for a BTS system which minimizes power loss from the BTS to the antennas and is capable transmitting multiple RF carriers per sector/per antenna.
SUMMARY OF THE INVENTION The present invention provides a BTS having a radio unit (RU) located very near to where antenna are mounted, a main unit (MU) connected to, and remotely located from the RU, and one or more antennas coupled to the RU. There can be multiple RUs connected to one MU, which may operate on the same frequency, or at different frequencies.
Furthermore, an exemplary embodiment of the present invention provides a BTS comprised of: a MU, having a controller module and channel element modules for base band signal processing of CDMA signals, a RU having a transceiver Dallas2 614579 v 1, 33361.00009USCI 8 Docket 33361-00009USC1 STA.WSL.040 module, and a power amplifier electrically coupled to the transceiver module and antenna, and a MU connected to a RU via a length of cable carrying low frequency signals baseband and/or IF signals). The transceiver module in the RU may comprise a transmitter circuit, a receiver circuit and a synthesizer circuit, or a low-noise amplifier (LNA) electrically coupled to the transceiver unit module. The antenna interface module may incorporate a duplexer module, or a power amplifier module and a receiver filter module.
Further, the BTS may comprise: a MU having a channel element module which provides the interface for connectivity to one of the RUs, and a RU having a transceiver module and an antenna interface module.
"i In addition, the main unit module may further comprise a power system assembly (power supply and battery backup), a time and frequency module, and a temperature management "assembly. The RU may also comprise a local controller module and a DC conversion and regulator module. The transceiver module may further comprise transmitter circuitry and two receiver circuits for diversified reception. Furthermore, the RU may incorporate an antenna interface module which may comprise receive filter circuitry and a duplexer circuitry Dallas2 614579 v 1, 33361.00009USC1 Docket 33361-00009USCI STA.WSL.040 comprising a transmit and receive filter circuit(s) combined into a single cavity.
The present invention provides a BTS consisting of up to three RUs and a MU, whereby the RUs can be remotely located from the MU. The RU is primarily comprised of a transceiver and an RF front-end. The transceiver, in turn, comprises an up-converter, down-converter, a synthesizer, a low-noise amplifier and transmit amplifiers. Additionally, the RU e e comprises an antenna interface unit consisting of a duplexer, a receiver filter and a power amplifier. The MU comprises up to four channel cards, an interface card to RUs, a controller card, a time and reference frequency card, a power system assembly, and a heat management assembly.
The architecture of this invention, in essence, separates those of RF elements and dependent elements thereof, which :reside in the RU, where there is one RU per sector, from the *e base band elements and other commonly shared elements thereof, which reside in the MU, supporting up to three RUs.
There are many advantages to this architecture and some of them are as follows: It results in a compact size RU which can be easily mounted close to the antennas, whereby the cable loss is virtually eliminated. Cable losses degrade the receiver sensitivity and Dallas2 614579 v 1, 33361.00009USC! Docket 33361-00009USC1 STA.WSL.040 reduce the transmit power. The present invention, thus, allows a relatively low power PA and provides a transmit power level equivalent to a higher power PA used with a conventional BTS.
The inclusion of the transceiver in the RU allows a lower frequency interface, all the way down to DC, rather than RF interface typically used in prior arts, to the MU. The lower frequency interfaces mean low loss in the cable and this allows the use of inexpensive and small diameter interconnect cables between the RUs and the MU.
10 The separation of RF elements and dependent elements thereof, also, results in easier adaption of the BTS design to support different RF operating environments or conditions, as in different frequency bands and different transmission power levels, as only the RU needs to be modified, while the same MU is used. This also results in a compact size MU for ease of handling and mounting. This is because of less space required without RF elements and, at the same time, less heat load in the MU for cooling.
This architecture also allows the BTS to be configured to support either omni or sector operations, or to upgrade from omni to sector operations as the traffic demand goes up. This is especially important in CDMA systems where softer handoffs need to be supported between the sectors. For an omni Dallas2 614579 v 1, 33361.00009USCI 11 il (I Docket 33361-00009USC1 STA.WSL.040 configuration, only one RU is needed. For two or three sector configurations, two and three RUs are needed, respectively.
The three RUs can be operated on the same frequency in a three sector configuration or at different frequencies in a three carrier omni configuration.
The present invention also allows the connectivity of another set of three RUs connected to its own MU to the same antennas without the use of a combiner.
Some advantages, features and similar features of the 10 present invention are as follows: 1. By locating transceiver module in the RU, close to 9 the low frequency signals can be passed from the transceiver module to the MU. On the receive side, the transceiver module converts a high frequency signal to a low frequency signal, and on the transmit side, the transceiver module converts a low frequency signal from the MU to a high frequency signal for transmission. Thus, only frequency signals are passed between the RU and MU, minimizing power loss in the cables connecting the two units. This results in the ability to use smaller diameter, less costly cables.
2. Because synthesizers are located remotely from the channel processing elements, and grounding loops are Dallas2 614579 v I, 33361.00009USCI Docket 33361-00009USC1 STA.WSL.040 eliminated, the signals being transmitted and received are subject to far less noise than conventional systems.
3. Another advantage to removing the transceiver subsystem from the MU is that the resulting MU is physically much smaller in size and weighs less. This translates into easier installation and maintenance, as well as into flexibility in meeting the technical demands of a challenging operating assignment or challenging environmental considerations. In addition, smaller size and lighter weight 10 BTSs are especially advantageous for Pico-cell applications or micro-cell applications where a greater number of BTSs are required than are needed for macro cell implementations.
4. With the entire transmit functionality contained in the RU, the RU receives only a baseband signal for transmitted eoooo data and does all of the up-conversion and amplification at the RU. This eliminates the need for sending high loss RF 0 signals up to the RU, and allows the RU to operate at a higher efficiency than a unit in which the RF signal must travel the length of the pole.
5. Because up-conversion is done in the RU, direct modulation reduces the complexity of the transmit signal line, and provides a significant cost reduction over systems that run a transmit signal up the pole and then up-convert again Dallas2 614579 v i, 33361.0009USC 13 ;l t Docket 33361-00009USC1 STA.WSL.040 to RF. Far less RF components are required in the present invention than in the prior art.
6. Output power calibration can be done at the factory and the RU can be programmed for usage with any MU. The RU will store full-power settings, as well as reduced power settings, in local memory--thus enabling cell size adjustment from the RU, instead of at the BTS.
7. Wilting and blossoming attenuation can be accomplished in the RU rather than in the BTS.
10 8. Detection of power control is performed in the RU and, more important, can be used to verify the integrity of the entire signal transit path. Previously, in units where the PA is mounted on the pole, the output power attenuation could be detected, but the operator could not determine if the problem was in the PA module or the MU.
9. System upgrades can be accomplished more easily as entire RUs or MUs can be replaced. In addition, because like elements are configured together, board or device level upgrades are also more easily accomplished than with traditional BTS units.
These and other advantages of the present invention will become apparent to one of ordinary skill in the art after Dallas2 614579 v 1, 33361.00009USCI Docket 33361-00009USC1 STA.WSL.040 consideration of the figures and detailed description which follows hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the method and apparatus of the present invention may be had by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: FIGURE 1 (prior art) depicts a wireless communication 10 system architecture; FIGURE 2 (prior art) is a graphical representation of a *0 S 0. cell grid and cell sites.
4S S FIGURE 3 (prior art) is a block diagram of a base station system (BTS) shown connected to a land-line PSTN; FIGURE 4 (prior art) is a functional block diagram of a
BTS;
FIGURE 5 (prior art) is an illustration of a ground based BTS coupled to a tower top mounted antenna; FIGURE 6 (prior art) is a block diagram of a tower top configuration; FIGURE 7 (prior art) is a block diagram illustrating the combiner method for using one antenna to support multiple transceivers; Dallas2 614579 v 1, 33361.00009USC1 4 A Docket 33361-00009USC1 STA.WSL.040 FIGURE 8 (prior art) is a block diagrams illustrating the combiner/multi-carrier method for using one antenna to support multiple transceivers; FIGURE 9 is a list of Pico-BTS acronyms utilized throughout the present application; FIGURE 10 illustrates a base station system according to an embodiment of the present invention coupled to a pole-mounted antenna; FIGURE 11 is a block diagram illustrating a base station 10 transceiver subsystem architecture according to an embodiment of the present invention for an omni configuration; FIGURE 12 is a block diagram illustrating a base station transceiver subsystem architecture according to an embodiment of the present invention for a three sector configuration; 15 FIGURE 13 is a functional block diagrams of a BTS architecture according to an embodiment of the present invention, with selected subsystems shown; FIGURE 14 is a modular level block diagram of an exemplary BTS; and FIGURE 15 is a block diagram of an alternate embodiment of the present invention of the transceiver/RF front-end module that accommodates two antennas.
Dallas2 614579 v 1, 33361.00009USCI I Docket 33361-00009USC1 STA.WSL.040 DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION In the description which follows, an exemplary preferred embodiment of the invention is described for a Pico base station transceiver subsystem architecture (FIGURE 9 provides a list of Pico-BTS acronyms utilized throughout this application, and which are familiar to those skilled in the art). However, it will be understood that the present invention may be applied to any base station transceiver subsystem architecture in a wireless communication system, including, but not limited to, macro and micro base station transceiver subsystems.
FIGURE 10 illustrates the basic idea underlying a base station transceiver subsystem (BTS) architecture according to 15 an exemplary embodiment of the present invention--the BTS is S"separated into two units, the Pico-BTS Radio Unit 110 and the Pico-BTS Main Unit 105. In the exemplary system illustrated in FIGURE 10, a Pico-BTS comprises the Pico-BTS architecture 100 which is divided into the Pico-BTS Main Unit ("Main Unit System," PMU or MU) 105 which may be located, as shown, at the base of a pole, tower, or other support structure 115, and the Pico-BTS Radio Unit ("Radio Unit System," PRU or RU) 110, which transmits and receives signals through at least one pole- Dallas2 614579 v I, 33361.00009USCI Docket 33361-00009USC1 STA.WSL.040 mounted antenna 120, and communicates with the PMU 105 via a plurality of wires 122 which may include a coax cable.
An embodiment of the present invention is illustrated in a high-level block diagram as an omni configuration in FIGURE 11. PRU 110 can be distally connected to the PMU via the wires or cables 122. The distance or separation between the PRU 110 and the PMU 105 can be from approximately 5 to more than 350 feet (current systems are typically separated by about 150 feet) This is adequate since the PMU 105 is designed to be placed at the bottom of a tower building, pole or other supporting structure 115 and the PRU 110 is to be placed at the top near the antenna(s) To transmit and receive signals, the PRU 110 S" is shown coupled to one, but typically is coupled to at least two, tower top mounted antennas 120.
15 The wires or cables 122 can include optical cabling between the PMU 105 and the PRU 110. Optical cabling will increase the distance allowable between the PMU and RMU because an optical signal will be less lossy than an electric signal in, for example, a coaxial cable.
FIGURE 12 illustrates a BTS architecture according to an exemplary embodiment of the present invention for a three sector configuration. Note that the hardware systems which are required to be duplicated are only duplicated in the PRU 110.
Dallas 614579 v 1,33361.00009USCI 18 Docket 33361-00009USC1 STA.WSL.040 Thus, the PMU is capable of interfacing with 1, 2, 3 or potentially more PRU's.
FIGURE 13 is a block diagram illustrating exemplary elements of the PRU 110 and the PMU 105. As seen the PRU 110 is composed of transceiver module 155 which is coupled to the antenna interface assembly 160. The antenna interface assembly 160 is coupled to the antennas 120.
The PRU 110 is coupled to the PMU 105 through a set of cables 122 which terminate in the PMU 105 at the Transmit and Receive interface 135 (T/R interface) which is coupled to the channel elements 130. The channel elements 130 are where the CDMA signal is modulated and demodulated. The PMU 105 may also "contain a global positioning receiver 140 which provides accurate clock and frequency signals to a main controller module 15 125, the channel elements 130, the T/R interface 135, and the PRU(s). Also within the PMU 105 is a power system 145, and a temperature control subsystem 150. Figure 14 provides additional detail of the PRU 110 and PMU 105 subsystems. As shown in FIGURE 14, each PRU 110 essentially comprises two modules: a transceiver module 155 (XCVR) and antenna interface module 160 (AIF). These modules, however, can be combined into one or more then one module. Accordingly, the antenna interface module 160 may include a transmit power amplifier Dallas2 614579 v 1, 33361.00009USC 19 Docket 33361-00009USC1 STA.WSL.040 (PA) which amplifies the signal to a level required for desired cell coverage, two low-noise amplifiers (LNA--not shown) for amplifying received signals to maximize receiver sensitivity, a duplexer module for transmitting and receiving signals to and from a single antenna, and a receiver filter The transceiver module 155 may include synthesizer circuitry, transmitter circuitry, and two receiver circuits (it is common to refer to a system's transmitter and receiver circuitry collectively as a "transceiver").
The PRU 110 also includes a microprocessor and nonvolatile memory (not shown) to store calibration data and provide real-time temperature operating parameter compensation to the transceiver. Thus, a mobile station or mobile simulator is not needed for calibration, and system 15 calibration in the field is also no longer needed.
PRU 110 preferably houses the duplexer and the receive filter in a common cavity. This is essentially three filters (two receive and one transmit) combined into one aluminum cavity.
By combining the prior art duplexer cavity with the prior art diversity receive cavity, valuable space inside the unit may be used for other circuitry and cost is further reduced.
In the preferred exemplary embodiment, the duplexer/receiver filter cavity of PRU 110 is designed so that Dallas2 614579 v 1, 33361.00009USCI Docket 33361-00009USC1 STA.WSL.040 the connectors on the filter protrude directly through the cover of the unit, eliminating any coaxial cable bulkhead connectors.
This approach requires fewer parts in the unit, again saving valuable space and reducing cost.
As illustrated in FIGURE 14, the PMU 105 includes six functional subsystems: a Pico-BTS main controller card 125 (PMCC), a Pico-BTS channel card 130 (PCC), a transmit and receive interface card 135 (TRIC), a time and frequency card 140 (TFC), and a power supply assembly 145 (PSA) for converting AC to DC and for distributing the DC power throughout the PMU 105 and the PRU 110. The temperature management subsystem 150 is not shown in FIGURE 14 to simplify the Figure.
In operation, the PMCC 125, which includes an external S. interface module and a communications controller module, often 15 called a packet engine, monitors all of the cards in the BTS architecture 100 and routes traffic and signaling packets between a Base Station Controller (BSC, see FIG. 3) shown) and the PCCs 130. Likewise, the TRIC 135 provides the interfaces between the transceiver module 155 and the PCCs 130. The TRIC provides the connectivity to the PRU 110 through interconnect cables 122.
Base-band analog signals and intermediate frequency (IF) signals in the frequency range of about 1 KHz to about 700 MHz Dallas2 614579 v 1, 33361.00009USCI 21 Docket 33361-00009USC1 STA.WSL.040 are propagated in cables 122 connecting PMU 105 with PRU 110.
The preferred IF frequency range is 239 MHz with a 1.26 MHz bandwidth and a signal strength of between -50 dBm and -70 dBm.
The advantage of this approach is that the modulated signals can be duplexed and sent through a standard, inexpensive RG-58 coaxial cable. Other signals to be carried between the units include 48Vpower, a 10 MHz reference, and RS-422 control lines.
o. The separation of the PRU 110 and the PMU 105 allows the PRU 110 to be installed close to the antennas 120. Since in 10 practice power losses in the antenna cable degrade receiver sensitivity and reduce the transmit power at a 1:1 ratio (dB per dB) locating the PRU 110 in close proximity to the antenna 120 maximizes the performance of the BTS 100. The location of the PRU also reduces power and signal losses through a cable 15 and thereby may save energy.
It is worth noting that all wires and coaxial cables may be bundled into a single polymer jacket. Thus, a single multi-wire/coaxial connector is used at both ends of the cable.
The resulting cable is typically built as a unitary item which provides ease of installation and repair in the field. Thus, the cable diameter may easily be kept under 0.75 inches, providing easy installation in the field, as well as in an indoor applications (which require turning corners).
Dallas2 614579 v 1, 33361.00009USC 22 Docket 33361-00009USC1 STA.WSL.040 Coaxial cables coming into PRU 110 are transformer coupled to the transceiver, which eliminates the possibility of ground loops (and their corresponding ground noise), and ensures that the PRU 110 can be placed up to and in excess of 150 feet away from PMU 105. In addition, if the PRU 110 is connected to a pole or other conductive structure which is grounded, there will be no system performance degradation due to noise coupling.
Power, at 24 or 48 VDC or an AC voltage, is sent to the tower top with a separate return. This provides less power loss in 10 the power wires, making the system more efficient.
The signals carried by the cable 122 between PMU 105 and PRU 110 operate most efficiently over a range of about 1 KHz to 240 MHz. This results in low signal attenuation, even when using thin, low cost cables.
FIGURE 15 depicts an exemplary embodiment whereby two PRUs 110 provide an additional means of connectivity such that only two antennas are required with two PRUs for dual frequency carrier operation. As shown, both antennas are connected to the duplexer (DX) ports of the PRUs. In a single RF carrier operation, antenna 1 (Ant-1) would transmit and receive one diversity signal and the other antenna would receive only the other diversity signal In a dual carrier operation in either omni or sector configuration, both antennas Dallas2 614579 v 1, 33361.00009USC1 23 Docket 33361-00009USC1 STAjWSL. 040 transmit, Ant-1 transmits Freq. A from PRU-1 and Ant-2 transmits Freq. B from PRU-2, and at the same time both antennas receive one diversity signal each. One receive PRU transmit signal and the other receive diversity signal comes from the other antenna indirect through the other PRU after it has been pre-amplified to maintain the receive sensitivity to maximum.
This diagram does not necessarily reflect the actual implementation, as they can be many different possibilities with different advantages and disadvantages. This technique 10 thus allows the addition of a second RF carrier for higher capacity operation without requiring additional antennas.
While the invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various 15 changes in form and detail may be made thereto, and that other embodiments of the present invention, beyond embodiments specifically described herein, may be made or practiced without departing from the spirit and scope of the present invention as limited solely by the appended claims.
For the purposes of this specification it will be clearly understood that the word "comprising" means "including but not limited to", and that the word "comprises" has a corresponding meaning.
Dallas2 614579 v 1, 33361.00009USCI