EP0817308B1 - Method for the automatic selection of one beam among those formed by a multibeam antenna, in particular for radiomobile systems - Google Patents

Method for the automatic selection of one beam among those formed by a multibeam antenna, in particular for radiomobile systems Download PDF

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Publication number
EP0817308B1
EP0817308B1 EP97111319A EP97111319A EP0817308B1 EP 0817308 B1 EP0817308 B1 EP 0817308B1 EP 97111319 A EP97111319 A EP 97111319A EP 97111319 A EP97111319 A EP 97111319A EP 0817308 B1 EP0817308 B1 EP 0817308B1
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EP
European Patent Office
Prior art keywords
estimation
radiomobile
selection
minimum
received
Prior art date
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EP97111319A
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German (de)
English (en)
French (fr)
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EP0817308A3 (en
EP0817308A2 (en
Inventor
Fulvio Margherita
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Siemens Holding SpA
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Siemens Mobile Communications SpA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/24—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture

Definitions

  • the present invention relates to a method for the automatic choice of one beam among those set up by a multibeam antenna, in particular for radiomobile systems.
  • the invention relates to a method to select a beam among those set up by a multibeam antenna, in particular for radiomobile base stations systems comprising a radio receiver set and a directional antenna with steerable beam consisting of a beamformer connected downstream of an array and a device, for the selection of an optimal beam, connected to the beam former.
  • a radiomobile telephone system provides for a plurality of portable phone sets, so called cellular phones, in communication with a base station provided with a receiving and transmitting antenna.
  • the different cellular phones are moving and the antenna of the base station must be able to receive and transmit radio frequency signals from and towards such mobile sets.
  • switched beams antennas are able to receive and transmit with a plurality of radiation diagrams with maximum intensity in different directions, and for which the power assigned by the base stations to a single user is concentrated in a very reduced angular width, even of 20° only, called hereafter beam.
  • the smart antenna is composed by a multibeam antenna and a system selecting continuously the best beam for the reception and transmission A possible structure is schematically illustrated in figure 1.
  • the signals 1, 2, 3 and 4 received by the different radiant elements differ only for a phase factor and they are coupled among them by a beam shaper 5 or beam former.
  • the beam former 5 is a device receiving, as input, signals arriving from the various radiant elements of the array and processing them to supply, as output, the received signals on different beams.
  • Such device may be realised with analog components operating in radio frequency (e.g. the Butler matrix) as well as with a simple digital realisation operating in base band. More particularly the beam former 5 carries out a plurality of linear combinations of the input signals using suitable coefficients. Multiple output gates are provided which may be connected to a receiver by means of a switching unit.
  • the array 10 radiation diagram is steered in a predetermined direction ⁇ i.
  • the functioning of the beam former 5 must be considered in a conceptional way as bi-directional i.e. that through a switch block 8 it is also possible to couple the output gates to a transmitter 7 TX in order to be able to transmit signals on a predetermined beam.
  • the selection of a beam on which to transmit or receive to and from a predetermined radiomobile is carried out by a selection device 9 which elaborates the signal received on different beams and controls the switching block to connect the receiver 6 or the transmitter 7 to the beam which guarantees the best possible communication with that given radiomobile.
  • the present invention concerns specifically a new method for the selection of the beam to be implemented in said selection device 9.
  • the presence of echoes reaching the receiver with predetermined delays cause further interferences which for instance one could try to overcome in the GSM receiver using a suitable filtering algorithm known as the Viterbi algorithm.
  • a channel comprising a plurality of echoes with significant delays among them may turn out to be very distorting, even if the signal is received with a high level.
  • US 5,303,240, Borras et al. discloses the structure of a communication system using a multi-beam antenna. The quality over different beams is detected on the basis of the best Signal Strength, on the bases of the best signal-to-noise ratio (S/N) or on the bases of signal-to-interference ratio (S/I). However, apart from Signal Strength which can be straightforwardly measured, the patent does not disclose any algorithm adapted to measure the S/N ratio, the S/l ratio or BER.
  • the beam is seleceted on the basis of Signal Strength. Besides the BER estimated from the receiver is feedbacked to the beam selector so that when the beam with the highest power level has a bad quality (due to a strong interference) a different beam is selected.
  • Channel selection is done measuring the overall interference power over all free channels (Equation 5 in the patent specification) and calculating the wanted user pathloss through the assigned traffic channel or a control channel .
  • the demodulation quality is continuously measured over each traffic channel and channel reselection procedure (hand-off) is started when detected quality is not good (column 5 line 8-19).
  • Quality is measured calculating the Euclidean distance between the received signal (corrupted by noise or interference) and the desired signal.
  • the technical problem at the basis of the present invention is that to excogitate a method for the selection of an optimum signal beam, in particular for radiomobile systems having the characteristics to making it possible to upgrade the performances of the antennas receiving the signals of the mobiles overcoming the limitations still existing in the solutions according to the background art.
  • the idea of a solution as the basis of the present invention is that of identifying an optimum transmission beam reducing to a minimum an estimation of the decoding error probability of the received signals. Based on this idea of a solution the technical problem has been resolved by a method, of the previously mentioned type, characterised in that the selection of the optimum beam is carried out by selecting a beam having the maximum value of a parameter d min , defined as the minimum distance between received signals related to all combinations of two different transmitted symbols sequences.
  • the parameter d min is the minimum distance between the received signals corresponding to any possible couple of transmitted symbol sequences. This minimum distance d min depends only on the overall system impulse response and not on the actual transmitted symbol sequence.
  • LNA low noise amplifiers
  • analog filters for channel selection.
  • Such components are schematically shown by the block 11 of figure 2.
  • the automatic control of the gain will be carried out in a block 12 AGC by measuring the level of the signal during a burst (packet of bits).
  • the gain supplied is a whole multiple of 2 dB.
  • the analog digital converter is a high speed one with a precision of 8 bits (included the sign).
  • the striking signal is a square wave which spectrum is set up by the fundamental frequency (IF) and by the third harmonic.
  • a filter 15 downstream of the block 13 is used to eliminate the noise components centred on the third harmonic which would otherwise be in base band and in output of the following mixer 16.
  • a low pass filter 17 is inserted downstream of the mixer 16 and before a decimation block 18. This filter 17 is used to eliminate the noise of the multiple frequencies of the decimation rate which would be again in base band after the decimation and to eliminate the second and fourth harmonic frequencies present at the output of mixer 16.
  • the signals arriving from the elements of the antenna array must have undergone the same amplification, even if the automatic control of the gain has been carried out in an independent way on the signal of each element, of the array.
  • a device 14 compensating the gain of the AGC equalises the gain of the different radiant elements.
  • the beam former 5 combines them in a linear way in order to form the different beams.
  • the signals 1, 2, 3, 4 set up in this way are then sent to the selection device 9 which is prepared to carry out the selection of the best beam identifying the one for which the estimation of the decoding error probability of the received signals is at the minimum.
  • the operations carried out by this device for each beam are:
  • the selection device 9 After having calculated the minimum distance for each one of the beams the selection device 9 commands a pair of multiplexers which supply the parameters of the filter and the input signal to a circuit realising a matched filter 23.
  • the output of the matched fitter 23 is therefore sampled in a decimation block 24 with a rate equal to the symbol frequency and the samples obtained in this way are sent to a Viterbi demodulator 25.
  • the received signal may be defined as a temporary function r(t) obtained as a summation of a sequence of symbols to be transmitted a k : where T is the duration of a given symbol and h(t) is the impulsive response of the transmission system.
  • transmission system is understood the set of filters in transmission, of the transmission channel (supposed to be linear and stationary) and of filters in reception.
  • the optimum demodulator In case of white Gaussian noise the optimum demodulator must be able to calculate for all possible transmitted sequences b k the distance between the signal really received r(t) and the signal r b (t) that would have been received in case of transmission of sequence b k : and to choose the sequence b k to which corresponds the minimum value of this distance.
  • the decoding error probability of the received signals is very sensible to the minimum value of this distance, we define d min and which turns out, for what said, a function of the impulsive response h(t).
  • a n and b n are supposed to be two possible sequences of transmitted symbols, a ( t ) and b ( t ) the complex envelopes of the corresponding received signals, and d a-b the distance between these signals. All these elements are defined in the following way: where h(t) is the complex envelopes of the impulsive response of the transmission system and N is the number of transmitted symbols.
  • a multibeam array 10 allowing to receive with n different radiation diagrams makes n different channels available with the same number of impulsive responses h l (t)...h n (t). Therefore the selection of the best beam may be made (if all impulsive responses h(t) are known) choosing the one representing the maximum value of the parameter d min .
  • the GSM transmission standard foresees the transmission, at the centre of every burst, of a training sequence enabling the receiver to estimate precisely the impulsive response h(t).
  • the method foresees to carry out this estimation upstream the receiver and to use it both for the selection of the beam and inside of the receiver to implement the matched filter.
  • a training sequence c n is introduced, known at the receiver.
  • this training sequence c n is inserted at the centre of the burst.
  • the training sequence has a duration L tr equal to 26 bits and is periodical with a period P tr equal to sixteen bits, as illustrated in figure 3.
  • the impulsive response may be estimated correlating the received signal samples with the symbols c k
  • the required computational load for the estimation is absolutely not heavy for the receiver set.
  • N c is the number of samples per symbol (four for the proposed realisation) and T c is the sampling period.
  • the here described method may be extended to other radiomobile standards using at the receiver an estimate of the transmission system impulsive response h(t).
EP97111319A 1996-07-04 1997-07-04 Method for the automatic selection of one beam among those formed by a multibeam antenna, in particular for radiomobile systems Expired - Lifetime EP0817308B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI961369 1996-07-04
IT96MI001369A IT1285217B1 (it) 1996-07-04 1996-07-04 Metodo per la selezione automatica di un fascio tra quelli formati da un'antenna multifascio,in particolare per sistemi radiomobili

Publications (3)

Publication Number Publication Date
EP0817308A2 EP0817308A2 (en) 1998-01-07
EP0817308A3 EP0817308A3 (en) 1998-04-08
EP0817308B1 true EP0817308B1 (en) 2002-11-27

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EP97111319A Expired - Lifetime EP0817308B1 (en) 1996-07-04 1997-07-04 Method for the automatic selection of one beam among those formed by a multibeam antenna, in particular for radiomobile systems

Country Status (3)

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EP (1) EP0817308B1 (it)
DE (1) DE69717354T2 (it)
IT (1) IT1285217B1 (it)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6470192B1 (en) * 1999-08-16 2002-10-22 Telefonaktiebolaget Lm Ericcson (Publ) Method of an apparatus for beam reduction and combining in a radio communications system
DE10025987C2 (de) * 2000-05-25 2002-04-04 Siemens Ag Verfahren zum Steuern der Downlink-Strahlformung
WO2009080101A1 (en) * 2007-12-20 2009-07-02 Telefonaktiebolaget Lm Ericsson (Publ) An improved antenna arrangement in an electronic device

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5303240A (en) * 1991-07-08 1994-04-12 Motorola, Inc. Telecommunications system using directional antennas
US5684491A (en) * 1995-01-27 1997-11-04 Hazeltine Corporation High gain antenna systems for cellular use
US5590399A (en) * 1995-02-23 1996-12-31 Nextel Communications Up-link channel assignment scheme for cellular mobile communications systems employing multi-beam antennas with beam selection
FI107851B (fi) * 1996-05-22 2001-10-15 Nokia Networks Oy Menetelmä antennikeilan valitsemiseksi, tukiasema ja solukkoradiojärjestelmä

Also Published As

Publication number Publication date
ITMI961369A0 (it) 1996-07-04
ITMI961369A1 (it) 1998-01-04
DE69717354D1 (de) 2003-01-09
EP0817308A3 (en) 1998-04-08
EP0817308A2 (en) 1998-01-07
DE69717354T2 (de) 2003-09-18
IT1285217B1 (it) 1998-06-03

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