CA2331391A1

CA2331391A1 - Mobile radio base station with an adaptive antenna

Info

Publication number: CA2331391A1
Application number: CA002331391A
Authority: CA
Inventors: Armin Splett
Original assignee: Individual
Current assignee: Siemens AG
Priority date: 1998-05-07
Filing date: 1999-05-06
Publication date: 1999-11-11
Also published as: ID26246A; WO1999057919A2; DE19820460C2; BR9910265A; WO1999057919A3; DE19820460A1

Abstract

The invention relates to a mobile radio base station comprising a transmitter (TRX) for each transmission frequency, and a plurality of receivers (RX 1, RX
2, RX 3, RX 0). The outputs of individual antennae (AN 1, AN 2, AN 3) or of a matrix network (BUM) and of at least one omnidirectional antenna (AN 0) are connected to transmitting/receiving switches (SE 1, SE 2, SE 3, SE 0). The receiving branches of the switches are routed to the individual receivers (RX
1, RX 2, RX 3, RX 0). The transmitting branches of the switches are selectively connected to the output of a transmitter (TRX) via a controlled switching device (SWI). A common detector (DET) is provided for processing the output signals of the receiver. Said detector is disposed to deliver a control signal (stw) to the switching device via an antenna control (AST) such that the transmitter is connected to an antenna determined in the detector (DET).

Description

0 c t . O 1 . 2 0 0 0 10 ; 4 6 AM ~ 02331391 2000-11-03 N o . 0 4 3 0 P . 2 (;R 9H P 1672 MOBILE RADII RnRE STATION HAVING AN ADAPTIVE ~ ~T'''ENNA
The invention relates to a mobile radio base atatiorl having a transmitter for each tranamisaion frequency, and havinr.,~ a plurality of receiverR, in whi rh t.-.hp o»t-.p»r. pi final ~a ~ f.r.~m individual antennas are ~upplied directly or via a matrix network, togethe=' wiLti l,tie uul.pul. bie~malb from rat least one omnidirectional antenna, to the receivers, and a common detector is provided for proeeBaing the output signals from the receivers.
base stations of this type have beCOme known for increasing the capdcil.y v1 a ~uvk~ilC wa3i~ ~yaLern and are det~eziLed, applied to a G3M mobile radio system, for example in IEE froc.
Commun., Vol. 143, No. 6, October 1996, p. 304 - 310, M: C.
Wells, ~~Inereasinr~ the Capacity of GSM Cellular Radio Urging Ariapt-.ivP Antennas". In this case, suitable algorithms are used ZO in a weighting and bearing computer to determine the direction in wriich d dpeciric; c~wk~ile earl, V~ L~1C i:ly~l(:4'lll id located. An upgrade for the transmitter end is indicated in the margin in this article but, in any ease, the complexity of the described solution is high since it requires a plurality of transmitting antennae and does not comply with the mobility requirements, since the direction of a mobile station is initially unknown.
Another known tranamisoion/reception arrangement for a base station provides for the transmitting and receiving antenna to be composed of a plurality of elements, which are each connected to their own transmission and reception path. The directional selectivity is achieved by supplying the r~ignal~
to the olementa in the correct phase. IIorrever, ouch a base station ie very costly sinc~ a larg~ number of transmission _i-Received Oct-31-DO 09:32am From- Ta-Smart & BIQQar Paae Ofl2 Oct . O1 . 2000 10 ~ 46AM ~ 02331391 2000-11-03 PJo . 0490 P . 0 and rcecption paths ar~ required and the phaAp relationships between a large number of signals must be maintained correctly over large parts c~f. tr.hp haae station.
A method for mobile radio bare el.a.l:ioiz is known from ~P-A-364190, in which pignnl strengths of the rcaeived signals from a plurality of antcnnap are compared, and the received signal from the antenna having the highPpt signal strength is selected _ The seleot-.~c7 anr_Pnna is then used for the transmitted sigtlalp, in accordance with Lhia selection.
Ome object of the invention is to provide a mobile radio base station which allows the directional selectivity t.c~ hp adjugtad in a cast-effective manner r7»r.ing operation, in order r..o rnmply with the mobility reguirements, so chat this actually ensures an incredr~e in the subscriber density in the network.
This object id achieved by a mobil~ radio base gtatir~n of the type mentioned init.ial7.y in which, according to the invention, the antpnnas~ and the outputs of the matrix network are connected Lo cransmission/recep~lUil auYlexers, in which the reception paths vt l,he duplexers are connected to the individual receiverr~ and the tran~smiopion paths of the duplexers are seleetiv~ly eoanected via a controlJ.pd awir_r_hing device to the output of the transmitter, and the detector is set up to supply a control signal via art antenna controller l.v the switching device such that the transmlLl.or is coiuzected to as duLeimet which is defined in the detector.
The invention allows very good directianal selectivity t.n ha achieved without the ne,mp.~.Pxi t-.y ri jai ng disproportionately and iri which, in particular, only a single tranr~rniar~i~~u chal1l1o1 ie rec3,uirnd. The inventicrr~ also allows rapid direction finding to

-2-Raceivad Oct-31-00 08:32am From- To-Smart i Bim~ar Papa 003 Oct.01 . 2000 10:47AM ~ 02331391 2000-11-03 No.0430 F. 4 be carried out using a pmaller number of antennas overall and with leas hardware complexity at the same time, by simultaneous reception of all t:hp antenna signals, high sensitivity by simultaneous reception of all the dml.elma S ~ai.gnals, a reduction in the Raleigh fading as the omriidirecLional dtil.eiunx is set up physically eeparatcly, to be achiev~~i, in the came way ao a power reduction in the bransmit:ter by ppccific connection to a selectsed antPnna_ one advant,agpntm development which provides accurate reaul~s provides for the detector to c;mll.ain a weighting and bearing computer and Lvr useaaages intended for all the mobile pt;atione to be transmitted. Furthermore, it is recommend~d that the antenna controller and/or the detector be set up to supply a control signal to the switching device for t.ranemi arai nn of common messages, such that trio l,wansmitter is connected to the omnidirectivual corona.
Although various criteria con be used for driving the controlled switch, it is particularly simple and al~an expedient if the detector ie ppt »p t:~ supply a control signal for the switching device such that the antenna having the respectively highest reception level ire all~c;al:ed to the l.td.iibL111tter.
Similar advantag~s are offered by an embodiment in which t"hp dWtpr..t-nr 1 a se~t-_ up to supply a control signal for Lhe switching device such that the antenna which ie allocated tv the t=wur~cnll.l.e,c~ ire l.lx~.L which supplies the output signal 3D having the lowest signal-to-noise ratio.
zt ins expedient for the matrix network to be in the to.rm of a Butler matrix, since the unitary nature of this matrix network ensures, in a,daiLivi~ t,v i~a proven design, that sll the

-3-Received Oct-81-00 OAs32am From- To-Smart i BiQ~ar Pope 004 0 c t . O 1 . 2 0 0 0 10 : 4 7 AM ~ 02331391 2000-11-03 N o . 0 4 9 0 F . 6 inf~rmati.on is available for each receiver, as if it were connected directly co one antenna.
The signals are evaluated in an advantageous manner if the adder is followed by a Vitcrbi equalizer oinec thin allowp good freedom from interfer~nee, particularly with regard to intersymbol interference. In principle, the same is true if signals which are weighted via the weighting and bearing computer are supplied to an adder, and thin ire Lvllowed key d Rake receiver.
One preferred variant provides for this to be a base station in a GSM system, but the invention can be applied in quite general form co mobile radio systems in which the problems d~acrib~c~ imit.ia.lly vc;c;ur.
The invention together with further advantagera is explained in mnrP dPt.ail in the fr~llowing text with reference to an exemplary embodiment which is illustrated in thp c7rawing, f-.hi~a 2o uses a simplified block diagram Lo show a mobile radio base station according (,t,7 l,~m iuveml.ivn.
As can be eeen from the drawing, a plurality of individual ant.Pnnag AN 1, AN 2, AN 3 are provided on a base station, and their directional characteristics are designed as a. f..unrtinn of the actual number of antennas. Furthermore, an omnidirectional antenna AN 0 is provlde3 wtticai, dlthvugh it may have a true omnidirectional radiation characteristic, the term omnidirectional ant~nna in the context of the invention shoW.c7 hp ~.mriergt.ood as meanin3 an antenna which covers a radio cell, since radio cell~ are not necessarily circular, the antenna AN 0 could, fU~' exdcaple. also cover 180° or 120°,

-4-Received Oct-31-00 09:32am From- To-Smart & Biaaar Page 005 0 c t . O 1 , 2 0 0 0 10 : 4 7 AM ~ 02331391 2000-11-03 p~ o , 0 4 g 0 P . 6 Each of the antenna~ AiV 1., AN 2, AN 3 and AN o is allocated its own reception secCivti RX 1, RX 2, RX 3 a~zd RX 0, in which the iupu~r~ uL l,heae s~ec;epl.i~ii asc:l,ic~ma car receivers ate connected to the reception paths of transmiseion/reception duplcxcro, SE 1, SE 2, SE 3 and SE 0.
Thp i ndi vi c7m1 anr.Pnnar~ A1U ~, AN z , A1V 3 which are arranged to form an antenna array are connected to the associated transmission/reception duplexera 8E 1, 9E 2, sE 3 via a matrix network, in the present e:~smple via a butler matrix DUM. Euch a matrix allows a specific linear phase of the individual antennae to be allocated to each input_ Further details relating to matrix networks and the »utler matrix can be found in relevant literature in which, by way of example, reference is made to Meinke-Grundlach, Taschenbuch der Hochfrcqucnztcchnils [Radio-frequency engineering handbook), 5Ln edition, Section 15.4, "Speisenetzwerk" [Supply network], page N H~ - N f5, T~pN ~-54O-5471 f-9 anc~ t-.hp 1 i 1-Rrat»rR r.i tpc~
there, and to: ltudolf c3rabau, ~~~~unkpeiltechnik" [kadio c~ltwc:l.lUil-.rlllC~,111~] , FL'dtlG:ktl' k3 (ale V~wldc~stmudluly 1989, ISBN

440-05991-X. Transmission/reception duplexers are described in the 4°n edition of thip work, on pagco R 34, R 35.
The procesr~ing of the output. signals from those of the receivers FZX 1, kx 2, xx 3 which are allocated to the iuc~.iYidua,l antennas AN 1, AN Z, AN 3 is carried out in a known manner using s signal processor, in thin case referred to na the weighting and bearing computer CrR. This computer users the individual air~nals, whose phases of the amplitude9 differ, to aU c!a1c~.»lar.e? a weighting vPCt:or, and it. wPight.s the signals in multipliers ML 1. ML 2. ML 3, before supplying them to an adder 9tJM and, finally, to a Viterbi edualizer VEQ or to a rake receiver. Such a rcccptioa structure is described in more detail in the article mentioned initially by M. C. Wells. The

-5-Recemed Oct-31-00 08:32am From- To-Smart i By~ar Pale 006 Oct,0l. 2000 10:47AM ~ 02331391 2000-11-03 Pdo~0490 P. 7 weightir~.g and b~aaring computer GPR can hp provided as software, by a cr~mmnn algorithm, together wlLh the Yiterbi Rr~,~alizPr VEQ. A Rake receiver can also be provided insteda of the viterbi equalizer.
The reception path of the transmiooion/reception duplexer SE
0, which is allocated in the omzzidir~ctional antenna AN 0, ire also connected to the ingot. of a rpr_Piver or receptiolz section RX 0, and t-hp output signal of Lhis receiver is r~up~lierl to lU Lhe Viterbi equalizer VEQ or tv a Rake receiver, but it can also be subjected to weighting assessment.
If the individual antennae AN 1, AN 2, AN 3 a.rr antennae with a pronounced directional charar.tRristic, they can be collr~.eCted directly, that is to say without using a Butler matrix, l.~ the Lransmission/rec:epl.ivm cluplexera SE 1, 9E 2, SE 3. This is Indicated by dashed lines in the drawing. On the other hand, a butler matrix makeo it possible to use conventional individual antennas to simulat~ a number of directir~nal ant.Pnna~r in which ease, of co~arr~r~, i t ma.y also not be iriexpedienL ror Lhe individual antennas to have a specific directional characteristic whets ubimg a Butler matrix.
In contrast to the reception paths, the transmission paths of ~5 th~ transmission/reception duplexPrr~ SR 9, ~F 2, SE 3 and 5E U
are supplied t.~ a awitahing device, in this case a Controlled switch SWI. This switch ie driven via a drive AST from the weiqht:inq and bedriu~ c;~« ~puLcr GPR so that, depending on the drive, the output of a tranamittcr TRX, in this oase indicated by a modulator MOD, and RF section I-IFT and an output stage LEV, can be applied to the t.ranamiApinn path of one of the t.ranr~mi aai nn/rRr_r~pr_icn duplexere SE 1, SE 2, SE 3 and SL 0, and Chus Lo one of the arutetmar~ AN 1, AN 2 , AN 3 and AN 0 .

-6-Recoived Oct-31-00 08:32am From- To-Smart i Bi~~ar Pa~~ OOl 0 c t , 01 . 2 0 0 0 10 : 4 O AM ~ 02331391 2000-11-03 N o ~ 0 4 9 0 P . 0 Uwlng Lo Lhe uuiLdry nature of the Sutler matrix HUM, all fihe info=~cnation is available for the receivers RX 7, RX 2 and Rx 3 ad if it were dirECtly available at each ~f i-.he individual antcnnao, so that appropriately adaptive reception is possible using a plurality of receivers. 'fhe direction Cf a mobile paxt can hp determined rapidly by mec~~la of suitable algorithms, which are executed pz-i~uarily in the weighting and bearing Computer GPR, in conjunction with the multipliers MT. 1., ML Z
and ML 3 arid, possibly, with the adder SUM anrl the Viterbi cgualizer vEQ, and which are described, for example, irl the article by M. C. Wells, so that the reception direction is always optimally aligned with l,hls mobile station, and high directional r~elactivity is achieved, The combination of thR
rnull,i-element antenna with the Hutler matrix HUM provi.e~es a 1~ number of directional antennas for the transmission direction, which makes it possible tn use the controlled switch SWI to point. the transmission beam in the chcaen direction in a coat--Pffeetive manner. In Llm process, correct allocation between Lhe transmibsic:~n and reception directions always means that the transmission 0ignal is allocated to the outp»fi of the Hutler matrix HUM having the highest re.r..~ption level. Phase relationships need bP maintained oilly between Lhe mulLl-element ant.Rnnas AN 1 LO AN 3 arid Lhe Butler ~uaLrix HUM.
As f~hVwn in the exemplary embodiments, the receiver RX 0 in this case i~ also included together with the omnidirpational antenna 1~N 0 in the signal proce~asing, as a result of which, in many cases, direct.ionc~ can be determined even more arrarately arid deciHions can be made om the choice of the respective direCGional drn.e~ma, and/or signal lose due to Raleigh fading can be avoided. In any cas~, the omnidirectional antenna AN 0, ae shown hero, can also be used to transmit common mRar~agps to all the mobile parts in l,tm radio cell, in Ghe sense of a "brodc7,c;a~wt channel" . For this Received Oct-31-00 09:3Eam From- To-Smart i BIQQaf Papa 008 ~ C t ~ ~ I ~ L ~ ~ ~ I ~ ~ 4 0 AM CA 02331391 2000-11-03 ~ 0 ~ 0 4 9 0 P ~ 9 purpose, the computer GPR (to whirh - ae indicated by dadhed lines - furt.her s~i finale can, of course, be supplied) dr~ivcd trp awit~~h sWI appropriately via the drive AST.
Received Oct-31-00 09:32am From- To-Smart i Bi~~ar Page 009

Claims

1. A mobile radio base station - having a transmitter (TRX) for each transmission frequency, - a plurality of receivers (RX 1, RX 2, RX 3), in which output signals from a plurality of individual antennas (AN 1, AN 2, AN 3) are supplied via transmission/reception duplexers (SE 1, SE 2, SE 3) to the receivers (RX 1, RX 2, RX 3), and - having a common detector (DET) for processing the output signals of the receivers (RX 1, RX 2, RX 3, RX 0) characterized in that - the detector (DHT) has a weighting and bearing computer (GPR) via which the output signals of the receivers (RX 1, RX
2, RX 3) are weighted and are supplied to an adder (SUM), and which drives a switching device (SWI) via an antenna controller (AST) in such a manner that the transmitter (TRX) is selectively connected to an antenna (AN 1, AN 2, AN 3) which is defined in the weighting and bearing computer (GPR).

2. Mobile radii base station as claimed in claim 1, characterized in that the individual antennas (AN 1, AN 2, AN
3) are connected via a matrix network (BUM) to the transmission/reception duplexers (SE 1, SE 2, SE 3).

3. The mobile radio base station as claimed in claim 1 or 2.
characterized in that said mobile radio base station also has at least one omnidirectional antenna (AN 0) which is connected via a transmission/reception duplexer (SE 0) and a receiver (RX 0) to the detector (DET), and in which the transmitter (TRX) can be connected to the omnidirectional antenna (AN 0) by means of the switching devise (SWT).

4. The mobile radio base station as claimed in the preceding claim, characterized in that the transmitter (TRX) is connected to the omnidirectional antenna (AN 0) in order to transmit common messages.

5. A mobile radio base station as claimed in a preceding claim, characterized in that the antenna controller (AST) drives the switching devise (SWI) such that the antenna (AN 1, AN 2, AN 3, AN 0) having the respectively highest reception level is allocated to the transmitter (TRX).

6. The mobile radio base station as claimed in one of claims 1 to 5, characterized in that the antenna controller (AST) drives the switching device (SWI) such that the antenna (AN 1, AN 2, AN
3, AN 0) which is allocated to the transmitter (TRX) is that which supplies the output signal having the lowest signal-to-noise ratio.

7. The mobile radio base station as claimed in one of claims 2 to 6, characterized in chat the matrix network ie in the form of a butler matrix (BUM).

8. The mobile radio base station as claimed in a preceding claim, characterized in that the weight and bearing computer(GBR) is followed by a Viterbi equalizer (VEQ).

9. The mobile radio bane station ae claimed in one of claims 1 to 7, characterized in that the weight and bearing computer (GBR) is followed by a Rake receiver.
The mobile radio base station as claimed in a preceding claim, characterized in that said mobile radio base station is a base station in a GSM system,