Patent Application
20110292868
This invention relates generally to multi-sector, omni sites and particularly to increasing the capacity and coverage of multi-sector, omni sites.
An omni-base station is a base station configured to use an omni-antenna, and a sector base station is a base station configured to use multiple, i.e. two or more, sector antennas.
A base station antenna, whether it be an omni-antenna or a sector antenna, is often mounted in an elevated location, such as on a tower, a pole, on the top or sides of buildings, etc., to enhance coverage and provide better possibilities for direct radio signal propagation paths.
Because omni-base stations use only a single, omni-antenna, they use only a single feeder and a single TMA. They are thus less complex and less expensive than sector base stations, which use, e.g., three sector antennas, three feeder cables, and three TMAs. Yet sector base stations provide more coverage than omni-base stations.
U.S. patent application Ser. No. 11/607,082, which is commonly owned with the present application, discloses a so-called multi-sector, omni-radio base station that provides more coverage than an omni-base station, at a cost less than a sector base station. A multi-sector, omni-radio base station includes an omni-base station coupled to a multi-sector antenna system. Use of a multi-sector antenna system provides increased signal gain (e.g., approximately 7-9 dB for a three-sector antenna system). To reduce the cost associated with use of multiple sector antennas, the multi-sector, omni-radio base station includes a splitter/combiner that permits use of fewer feeders than sector antennas. The splitter/combiner combines uplink signals received from two or more sector antennas onto a single feeder cable. To prevent or mitigate signal loss in the splitter/combiner (which would offset the signal gain achieved from use of the multi-sector antenna system), the uplink signals are converted to different frequencies by a so-called frequency shifting TMA before being combined.
Teachings herein advantageously increase the capacity of a multi-sector, omni-radio base station, and further increase the coverage of such a base station, by sending different transmit signals from a base station unit according to transmit diversity and/or spatial multiplexing. The different transmit signals are sent over different feeders to different splitters, which each split the signal received amongst the sector antennas in a set of sector antennas.
In one embodiment, for example, a base station includes a first set of sector antennas and a second set of sector antennas. The sector antennas in the first set provide coverage for different sectors of a geographic area, and the sector antennas in the second set provide coverage for some of those same sectors. The base station further includes a first splitter and a second splitter. The first splitter is configured to receive a signal sent to it and to then split that signal amongst the sector antennas in the first set. By splitting the signal amongst the sector antennas in the first set, the first splitter provides the signal to each of those sector antennas, but at a fraction of the power. Likewise, the second splitter is configured to receive a signal sent to it and to split that signal amongst the sector antennas in the second set.
With the base station configured in this way, the base station unit sends different transmit signals to the first and second splitters, via first and second feeders, respectively. The base station unit advantageously does so by sending the transmit signals according to transmit diversity, spatial multiplexing, or both.
To advantageously receive signals using this same structure, the base station further includes a first combiner and a second combiner. The first combiner is configured to combine signals received by the sector antennas in the first set and to send the resulting composite signal to the base station unit, via the first feeder. Notably, to prevent or at least mitigate interference between these received signals when they are combined in the first combiner, at least one of those signals is first converted to a frequency different from that at which it was received. In much the same way, the second combiner is configured to combine signals received by the sector antennas in the second set and to send the resulting composite signal to the base station unit, via the second feeder.
The base station unit thus receives two composite signals, one from the first combiner via the first feeder and another from the second combiner via the second feeder. The base station unit in some embodiments is configured to receive these composite signals according to receive diversity, spatial multiplexing, or both.
This embodiment can be also viewed as a multi-sector omni-radio base station that has two transmit branches and two receive branches. The base station in other embodiments may have more than two transmit branches and more than two receive branches, with the number of transmit branches not necessarily being equal to the number of receive branches and not necessarily being equal to the number of sets of sector antennas.
The present invention is therefore not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.
More particularly,
The base station 201 further includes a first splitter 310A and a second splitter 310B. The first splitter 310A is configured to receive a signal sent to it and to then split that signal amongst the sector antennas in the first set {2101A, 2102A, and 2103A}. By splitting the signal amongst the sector antennas in the first set, the first splitter 308A provides the signal to each of those sector antennas, but at a fraction of the power (e.g., at one-third power, where splitting the signal equally amongst three sector antennas). Likewise, the second splitter 310B is configured to receive a signal sent to it and to split that signal amongst the sector antennas in the second set {2101B, 2102B, and 2103B}.
With the base station 201 configured in this way, the base station unit 208 sends different transmit signals to the first and second splitters 310A,B, via first and second feeders 212A,B, respectively. The base station unit 201 advantageously does so by sending the transmit signals according to transmit diversity, spatial multiplexing, or both.
For example, in the case that the base station unit 208 sends the transmit signals according to transmit diversity, the base station unit 208 sends transmit signals that represent the same data, but that differ in one or more transmission parameters (e.g., time, coding, or the like). That is, the transmit signal sent over the first feeder 212A to the first splitter 310A (and ultimately transmitted by the first set of sector antennas) represents the same data as the transmit signal sent over the second feeder 212B to the second splitter 310A (and ultimately transmitted by the second set of sector antennas), but differs in one or more transmission parameters. This allows the base station 201 to provide better coverage to a mobile terminal 207 by providing the mobile terminal 207 with additional diversity against fading on the radio channel.
Alternatively, in the case that the base station unit 208 sends the transmit signals according to spatial multiplexing, the base station unit 208 sends transmit signals that represent different data. In other words, the transmit signal sent over the first feeder 212A to the first splitter 310A (and ultimately transmitted by the first set of sector antennas) represents different data than the transmit signal sent over the second feeder 212B to the second splitter 310A (and ultimately transmitted by the second set of sector antennas). This allows the base station 201 to provide higher data rates to a mobile terminal 207 by transmitting multiple data streams in parallel.
To advantageously receive signals using this same structure, the base station 201 further includes a first combiner 315A and a second combiner 315B. The first combiner 315A may be associated with, or included in the same physical unit as, the first splitter 310A, and therefore referred to as splitter/combiner 320A. Likewise, the second combiner 315B may be associated with, or included in the same physical unit as, the second splitter 310B, and therefore referred to as splitter/combiner 320B.
Regardless, the first combiner 315A is configured to combine signals received by the sector antennas in the first set {2101A, 2102A, and 2103A} and to send the resulting composite signal to the base station unit 208, via the first feeder 212A. Notably, to prevent or at least mitigate interference between these received signals when they are combined in the first combiner 315A, at least one of those signals is first converted to a frequency different from that at which it was received.
As shown in
In much the same way, the second combiner 315B is configured to combine signals received by the sector antennas in the second set {2101B, 2102B, and 2103B} and to send the resulting composite signal to the base station unit 208, via the second feeder 212B. At least one of these signals is also first converted to a frequency different from that at which it was received (e.g., by frequency converters 3051B, 3052B, and 3053B).
The base station unit 208 thus receives two composite signals, one from the first combiner 315A via the first feeder 212A and another from the second combiner 315B via the second feeder 212B. The base station unit 208 in some embodiments is configured to receive these composite signals according to receive diversity, spatial multiplexing, or both. Where the base station unit 208 is configured to receive the composite signals according to receive diversity, the base station unit 208 receives composite signals that represent the same data, but that differ in one or more transmission parameters. Thus in this case the base station unit 208 is configured to jointly process the composite signals to combat fading of the radio channel (e.g., by dynamically selecting the signal with the best quality, by combining the signals, or the like).
Alternatively where the base station unit 208 is configured to receive the composite signals according to spatial multiplexing (also known as uplink spatial multiplexing), the base station unit 208 receives composite signals that represent different data. In this case therefore the base station unit 208 is configured to achieve higher data rates by receiving multiple data streams in parallel. The base station unit 208 may also receive the composite signals according to any combination of spatial multiplexing and receive diversity, and may further receive signals sent by mobile terminals according to uplink transmit diversity.
Note that the base station 201 may transmit and receive as described above simultaneously by using different transmit and receive frequencies (i.e., frequency division duplexing, FDD). As shown, for example, the sector antennas 210 receive signals at frequency f0 and transmit signals at frequency ft (which is different than f0, f1, f2, or f3), with transmit filters (TX) and receive filters (RX) enabling such transmission and reception to occur simultaneously. Accordingly, at any given time, signals being sent over the feeders 212A,B have different frequencies {ft, f1, f2, f3} and do not interfere with one another. Of course, those skilled in the art will appreciate that in other embodiments time division duplexing may be used such that the sector antennas 210 transmit and receive signals at the same frequency, but at different times.
The above embodiments can be also viewed as including a multi-sector omni-radio base station 201 that has two transmit branches and two receive branches. Consider, for instance,
Those skilled in the art will of course appreciate that the above description and figures represent non-limiting examples of the present invention. Indeed, while the example above described a base station 201 with two transmit branches and two receive branches, the base station 201 may have more than two transmit branches and more than two receive branches, with the number of transmit branches not necessarily being equal to the number of receive branches and not necessarily being equal to the number of sets of sector antennas. In one embodiment, for example, the base station 201 has four receive branches and two transmit branches,
More particularly, the base station unit 208 sends different transmit signals to splitters 310A and 310C, via feeders 212A,B and 212C,D, respectively, according to transmit diversity, spatial multiplexing, or both. Splitter 310A splits the transmit signal sent to it amongst the sector antennas in the first set {2101A, 2102A, and 2103A}, while splitter 310C splits the transmit signal sent to it amongst the sector antennas in the third set {2101C, 2102C, and 2103C}. With transmit signals sent in this way, the base station 201 has two transmit (TX) branches, A and C, as graphically shown in
Signals received by sector antennas in the first set {2101A, 2102A, and 2103A}, and signals received by sector antennas in the second set {2101B, 2102B, and 2103B} are all combined by combiner 315A,B to form one composite signal, which is sent to the base station unit 208 via feeder 212A,B. Before being combined, each of the signals is converted to a different frequency by dual frequency converters 3051A,B, 3052A,B, and 3053A,B. Combiner 315A,B thus combines the received signals to form a composite signal that has six different frequencies {f1, f2, f3, f4, f5, and f6} and sends that composite signal to the base station unit 208 via feeder 212A,B.
In much the same way, signals received by sector antennas in the third set {2101C, 2102C, and 2103C}, and signals received by sector antennas in the fourth set {2101D, 2102D, and 2103D} are all combined by combiner 315C,D to form one composite signal, which is sent to the base station unit 208 via feeder 212C,D. Before being combined, each of the signals is converted to a different frequency by dual frequency converters 3051C,D, 3052C,D, and 3053C,D. The dual frequency converters each convert two signals to two different frequencies, as opposed to converting just one signal to a different frequency. Thus, combiner 315C,D combines the received signals to form a composite signal that has six different frequencies {f1, f2, f3, f4, f5, and f6} and sends that composite signal to the base station unit 208 via feeder 212C,D. With signals received in this way, the base station 201 has four receive (RX) branches, A, B, C, and D, as graphically shown in
With an appreciation of the above embodiments, those skilled in the art will recognize that the number of transmit branches, not necessarily the number of receive branches, corresponds to the number of splitters 310 and the number of feeders 212. More fundamentally, the number of transmit branches in some embodiments corresponds to the number of power amplifiers included in the base station unit 208. That is, in some embodiments the base station unit 208 includes a plurality of power amplifiers configured to amplify transmit signals, and the base station has as many splitters 310, and as many feeders 212, as there are of those power amplifiers.
Those skilled in the art will also appreciate that while the example above described a three sector omni-radio base station 201, with three sector antennas 210 in each set of sector antennas, the base station 201 may be configured for any number of sectors greater than or equal to two. That is, the number of sectors, and thereby the number of sector antennas 210 per set, may be two or greater.
Similarly, in
Of course,
Although the embodiments described above have included frequency converters 305 for converted each signal received by the sector antennas in a set, in other embodiments fewer frequency converters 305 are included. For example, in the three sector example above, only two frequency converters 305 may be included. The frequency converters 305 may convert two of the signals to different frequencies f1 and f2, while a third signal remains at frequency f0. The combiner 310 combines these signals, and because each of the signals are at different frequencies f0, f1, and f2, no conflict occurs even though one of the signals was not converted. Accordingly, in these embodiments, the base station 201 only includes as many frequency converters 305 as are needed for uplink signals to be combined at different frequencies. In less optimal embodiments, even fewer frequency converters 305 may be used, where some of the uplink signals are combined even though they are at the same frequency.
With the above modifications and variations in mind, those skilled in the art will appreciate that the base station 201 of the present invention generally performs the method illustrated in
The method also includes, not necessarily afterwards in time, at the first combiner 315A, combining signals received by the sector antennas 210 in the first set, with at least one of those signals having first been converted to a different frequency (Block 615). The first combiner 315A then sends the resulting composite signal to the base station unit 208 via the first feeder 212A (Block 620). The method further includes, at the second combiner 315B, combining signals received by the sector antennas 210 in the second set, with at least one of those signals having first been converted to a different frequency (Block 625). The second combiner 315B likewise sends the resulting composite signal to the base station unit 208 via the second feeder 212B (Block 630).
Those skilled in the art will appreciate that the various “circuits” described may refer to a combination of analog and digital circuits, including one or more processors configured with software and/or firmware (e.g., stored in memory) that, when executed by the one or more processors, perform as described above. One or more of these processors, as well as the other digital hardware, may be included in a single application-specific integrated circuit (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).
Those skilled in the art will also appreciate that the mobile terminals discussed herein may comprise a mobile telephone, a Portable Digital Assistant, a laptop computer, or the like. Moreover, those skilled in the art will appreciate that no particular communication interface standard is necessary for practicing the present invention. The mobile communication system discussed, therefore, may be based on any one of a number of standardized communication implementations, including GSM, CDMA (IS-95, IS-2000), TDMA (TIA/EIA-136), wide band CDMA (W-CDMA), GPRS, long term evolution (LTE), or other type of wireless communication system.
Thus, those skilled in the art will recognize that the present invention may be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are thus to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
