Source: https://patents.google.com/patent/EP2159933A1/en
Timestamp: 2018-08-16 12:28:12
Document Index: 272365588

Matched Legal Cases: ['art 5', 'art 5', 'art 5', 'art 4', 'arts 4', 'arts 4', 'arts 4', 'art 4', 'art 4']

EP2159933A1 - Levelling amplifiers in a distributed antenna system - Google Patents
Levelling amplifiers in a distributed antenna system Download PDF
EP2159933A1
EP2159933A1 EP20080290805 EP08290805A EP2159933A1 EP 2159933 A1 EP2159933 A1 EP 2159933A1 EP 20080290805 EP20080290805 EP 20080290805 EP 08290805 A EP08290805 A EP 08290805A EP 2159933 A1 EP2159933 A1 EP 2159933A1
EP20080290805
EP2159933B1 (en )
Heniz-Dieter Hettstedt
In known passive systems signals from a centralized source, e.g. Base Transceiver Station (BTS) or Node B or off-air repeater, are combined via a point of interconnection (POI) and fed directly to a coaxial distribution system. The coaxial distribution system can consist of coaxial cables, couplers and RF splitters. Such passive distribution system feeds a distributed antenna system (DAS) consisting of antennas and/or radiating cables. However, the following problems arise from the known passive systems. A coverage area is restricted depending on the output power level of the active equipment and of the high passive losses of the passive distribution network and DAS. That is, the losses of the distribution infrastructure have to be compensated by high output power level of the active equipment, for example the signal source. Furthermore, the extension of such systems to larger coverage areas is complicated, because a second BTS / Node B location has to be installed in confined areas (e.g. in a building) as well as a second independent distribution topology. In addition, a sectorization and capacity optimization has to be chosen carefully during system design. For example, it is not possible to change the sectorization inside a building after the installation. A further problem of known passive systems is that depending on the frequency allocation of the cellular services a high effort for RF filtering is required in case of bordering services. A distribution of overlapping services is only possible if individual infrastructures for uplink (UL) and downlink (DL) bands or a combination thereof is used. That is, in such case two separate networks are used to transmit suitable combinations of UL and DL RF bands.
Basically, the antenna amplifier amplifies uplink and downlink signals. Download signals are amplified in order to provide sufficient coverage for a dedicated coverage area. Furthermore, the antenna amplifier provides for compensation of losses of the wired distribution system in download and low noise amplification of uplink signals. An automatic self-leveling unit of the antenna amplifier provides a limiting function in uplink in order to protect the whole radio frequency network against nonlinear signals resulting from high input power levels. In particular, in uplink the dynamic range is automatically optimized, since incoming power levels from different distributed antenna systems are adjusted to a constant value. Furthermore, low-priced technology can be used in the amplifiers, since the high frequency energy is generated directly at the antennas. In contrast thereto, prior art systems require high-level technology in concentrated amplifiers or base stations at the entry of the network. The line amplifier optimizes the dynamic range of the network and compensates for RF losses resulting from the passive distribution system independently of the distribution. Furthermore, in downlink the line amplifier provides for automatic and independent leveling of the antenna amplifier in order to level the input signals from each path to an equal output power level resulting in a maximized and constant dynamic range. In addition, in downlink the line amplifier increases a power level of an input signal to a constant output power level. The wired distribution system attenuates this power level and the loss is dependent on the network architecture. The automatic level control inside the antenna amplifier compensates for the loss of the distribution system and produces a constant output power level. Thus, in combination with a line amplifier compensating passive losses of the distribution system a plug-and-play system operation is guaranteed.
The present invention enables an easy implementation of additional services. For example, new filter elements can be combined with existing network elements via splitters and all increased RF losses will be compensated automatically. Furthermore, the present invention is applicable to a distribution of single- or multi-band cellular services in confined areas (e.g. in buildings) independently of the frequency allocation. In addition, the wired distribution system preferably comprises broadband elements (e.g. coaxial cables) so that an existing infrastructure can be expanded with future services such as WiMax (FDD and TDD services). Thus, the present invention provides a broadband approach suitable for all frequency combinations between 100 MHz and 3,5 GHz. An extension to 6 GHz is possible by use of high performance coaxial cables.
shows a block diagram of a first embodiment of a radio frequency network according to the present invention;
shows a block diagram of a second embodiment of a radio frequency network according to the present invention; and
shows a flow chart of a method according to the present invention.
Figure 1 shows a block diagram of a first embodiment of a radio frequency network 1 according to the present invention. The radio frequency network 1 comprises a distributed antenna system 2 having radiating elements (not shown) and a wired distribution system 3 feeding the distributed antenna system 2. Furthermore, the shown radio frequency network 1 comprises a line amplifier 4 at one end of the wired distribution system 3 and an antenna amplifier 5 at the other end thereof. Signals from a centralized source (not shown), e.g. Base Transceiver Station (BTS) or Node B or off-air repeater, are combined via a point of interconnection 6 (POI) and fed to the wired distribution system 3 via the line amplifier 4. The radio frequency network 1 shown in figure 1 is bidirectional. That is, signals received by the distributed antenna system 2 are transmitted via the antenna amplifier 5, the wired distribution system 3, and the line amplifier 4 to the point of interconnection 6.
The radio frequency network 1 according to the present invention allows for distribution of cellular services independently of the frequency allocation in confined areas.
For example, if the network 1 is used in buildings (in-building mobile communication systems) or tunnels, the wired distribution system 3 exclusively comprises passive components like broadband coaxial cables as transmission lines, splitters (not shown) and combiners (not shown). This allows using the same distribution system independently of the services that are to be transmitted. In case of an upgrade of the radio frequency network 1 to provide modern in-building solutions for cellular services only active network elements have to be exchanged, e.g. band selective filters. This minimizes the effort to upgrade the network in terms of exchanging active elements (e.g. line and antenna amplifiers 4, 5) or at least the filters within these elements.
In uplink, that is, from the distributed antenna system for uplink 2b to the POI 6, the RF path works vice versa. Signals are collected by the distributed antenna system for uplink 2b and fed to the uplink part 5b of the antenna amplifier 5. An automatic level control (not shown) in the uplink part 5b of the antenna amplifier 5 adjusts the signals from mobile terminals (not shown) in order to maximize the system dynamic range and optimizes the system performance. As shown in Figure 1, signals from the distributed antenna system for uplink 2b are combined and transmitted to the uplink part 5b of the antenna amplifier 5. Preferably, the signals from the radiating elements of the distributed antenna system for uplink 2b are passively combined and automatically leveled as well as re-amplified by the antenna amplifier 5. The uplink part 4b of the line amplifier 4 compensates losses of the passive distribution system 3 between antenna and line amplifiers 4, 5 as well as differences in the received power levels, e.g. from individual floors in case that the shown network is an in-building radio frequency network.
The line and antenna amplifiers 4, 5 shown in figure 1 are multi-band amplifiers comprising triplexers 7 and corresponding narrowband amplifiers 8. The architecture of the line and antenna amplifiers 4, 5 as shown in figure 1 is designed for a parallel network. That is, the network comprises separate downlink and uplink paths 9, 10 and the amplifiers 4, 5 comprise separate uplink and downlink parts 4a, 4b, 5a, 5b subdivided into a plurality of frequency bands. Such multi-band amplifiers are applicable for most mobile communication systems where download frequency bands as well as uplink frequency bands can be separated and combined via low cost multiplexers. According to the present invention it is possible to distribute adjacent or overlapping frequency bands for uplink and downlink (e.g. SMR800 and CDMA800) or overlapping frequency bands (e.g. PCS1900 and UMTS21 00), for example in an in-building mobile communication system. In this case, the combining of downlink / uplink frequency bands via filters to a common port is not possible.
Because of the separation of the distributed antenna system 2 (radiating elements) for uplink and downlink 2a, 2b the effort for filtering decreases considerably. Low-cost filter technology (e.g. ceramic filters and duplexers and / or SAW filters) can be used to separate and combine services. That is, separate RF networks are used for uplink and downlink to enable a cost-reduction due to cost-efficient filter technology. Furthermore, the passive network architecture can be adapted to each topology, e.g. in buildings, without reduction of performance.
Figure 2 shows a block diagram of a second embodiment of a radio frequency network according to the present invention. In comparison with figure 1 only the architecture of the line and antenna amplifiers 4, 5 is modified. In case of adjacent or overlapping frequency bands, one uplink and one downlink band are interchanged. Thus, the downlink parts 4a, 5a of the amplifiers 4, 5 of figure 1 comprise two downlink bands and one uplink band in figure 2, whereas the uplink parts 4b, 5b of the amplifiers 4, 5 of figure 1 comprise two uplink bands and one downlink band in figure 2. In other words, one amplifier part 4a, 5a amplifies two downlink bands and one uplink band and vice versa for the second amplifier part 4b, 5b, which transmits two uplink frequency bands and one downlink band over the distribution system 3. This anti-parallel architecture according to the second embodiment of the present invention again allows for the use of low cost filter technology due to the separation of frequency bands that are critical to combine. That is, the anti-parallel architecture allows for distribution of bordering or overlapping frequency bands without the use of high performance filters and multiplexers. In particular, the physical separation of radiating elements (not shown) of the distributed antenna system 2 provides sufficient isolation between adjacent or overlapping frequency bands taken into account at decoupling of radiating elements. The modular design of the active elements as described with respect to figures 1 and 2 allows for an easy network design independently of the frequency spectrum of required mobile services.
Figure 3 shows a flow chart of a method according to the present invention for signal transmission within a radio frequency network. The radio frequency network comprises a distributed antenna system having radiating elements and a wired distribution system feeding the distributed antenna system. In a first step S1 at least one antenna amplifier, arranged between one end of the wired distribution system and the distributed antenna system, amplifies upload and download signals. In a second step S2 at least one line amplifier, arranged at the other end of the wired distribution system than the antenna amplifier, also amplifies the upload and download signals. In a third step S3 self-leveling units included in the antenna and line amplifiers automatically level signals transmitted within the wired distribution system. The order of the steps S1 to S3 is not limited to the above described order. For example, steps S1 and S2 can be exchanged with each other, depending of the respective signal direction (uplink or downlink).
Radio frequency network (1), comprising:
a distributed antenna system (2) having radiating elements,
a wired distribution system (3) feeding the distributed antenna system (2), at least one antenna amplifier (5) between one end of the wired distribution system (3) and the distributed antenna system (2),
at least one line amplifier (4) at the other end of the wired distribution system (3), and
automatic self-leveling units included in the antenna and line amplifiers (4, 5).
Radio frequency network (1) according to claim 1, wherein the automatic self-leveling units are adapted to provide a fixed output signal level for a received signal level range.
Radio frequency network (1) according to claim 1 or 2, wherein the antenna and line amplifiers (4, 5) comprise multiplexers (7) for separating and/or combing upload and download frequency bands.
Radio frequency network (1) according to any of the preceding claims, wherein the wired distribution system (3) comprises broadband coaxial cables, splitters, and combiners.
Radio frequency network (1) according to any of the preceding claims, wherein the distributed antenna system (2) consists of discrete antennas and/or radiating cables.
Method for signal transmission within a radio frequency network (1), the network comprising a distributed antenna system (2) having radiating elements and a wired distribution system (3) feeding the distributed antenna system (2), and the method comprising the steps of:
amplifying (S1) upload and download signals in at least one antenna amplifier (5) arranged between one end of the wired distribution system (3) and the distributed antenna system (2),
amplifying (S2) the upload and download signals in at least one line amplifier (4) arranged at the other end of the wired distribution system (3), and
automatically self-leveling (S3) of signals transmitted within the wired distribution system (3) in the antenna and line amplifiers (4, 5) by means of self-leveling units.
Method according to claim 6, wherein the self-leveling units provide a fixed output signal level for a received signal level range.
Method according to claim 6 or 7, further comprising the step of separating and/or combining of upload and download frequency bands in the antenna and line amplifiers (4, 5) by means of multiplexers (7).
Radio communication system comprising at least one mobile terminal and at least one radio frequency network (1) according to any of claims 1 to 5.
EP20080290805 2008-08-28 2008-08-28 Levelling amplifiers in a distributed antenna system Active EP2159933B1 (en)
US12548899 US8428033B2 (en) 2008-08-28 2009-08-27 Radio frequency network
EP2159933A1 true true EP2159933A1 (en) 2010-03-03
EP2159933B1 EP2159933B1 (en) 2013-03-27
EP20080290805 Active EP2159933B1 (en) 2008-08-28 2008-08-28 Levelling amplifiers in a distributed antenna system
US20100054227A1 (en) 2010-03-04 application
Ref document number: 602008023210
Ipc: H04B 7/26 20060101ALI20120312BHEP
Ipc: H04W 88/08 20090101AFI20120312BHEP
Inventor name: HETTSTEDT, HENIZ-DIETER
Inventor name: KLAUKE, GERD
Inventor name: ZORAD, ROBERT
Inventor name: SCHOMBURG, EKKEHARD
Inventor name: SCHROEDER, AXEL
Ref document number: 604085