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WO2000011806A1 - Systeme de radiocommunications a transmission en diversite selective, procede d'activation de ce type de transmission, et reseau de radiocommunications faisant appel auxdits systeme et procede - Google Patents

Systeme de radiocommunications a transmission en diversite selective, procede d'activation de ce type de transmission, et reseau de radiocommunications faisant appel auxdits systeme et procede Download PDF

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Publication number
WO2000011806A1
WO2000011806A1 PCT/US1999/018952 US9918952W WO0011806A1 WO 2000011806 A1 WO2000011806 A1 WO 2000011806A1 US 9918952 W US9918952 W US 9918952W WO 0011806 A1 WO0011806 A1 WO 0011806A1
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WO
WIPO (PCT)
Prior art keywords
transmitter
radio frequency
recited
characteristic
network
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1999/018952
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English (en)
Inventor
William Eric Bird
Alan Triggs
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Ericsson Inc
Original Assignee
Ericsson Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ericsson Inc filed Critical Ericsson Inc
Priority to AU56810/99A priority Critical patent/AU5681099A/en
Publication of WO2000011806A1 publication Critical patent/WO2000011806A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0667—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal
    • H04B7/0671—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal using different delays between antennas
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0602—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using antenna switching
    • H04B7/0608—Antenna selection according to transmission parameters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0602—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using antenna switching
    • H04B7/0608—Antenna selection according to transmission parameters
    • H04B7/061—Antenna selection according to transmission parameters using feedback from receiving side
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
    • H04B7/0691—Hybrid systems, i.e. switching and simultaneous transmission using subgroups of transmit antennas
    • H04B7/0693—Hybrid systems, i.e. switching and simultaneous transmission using subgroups of transmit antennas switching off a diversity branch, e.g. to save power

Definitions

  • the present invention is directed, in general, to wireless communications systems and, more specifically, to a wireless communications system employing selective diversity transmission, a method of enabling selective diversity transmission, and a wireless telecommunications network that employs the system or the method.
  • radio communication occurs between fixed equipment at a base station, or "cell site,” and mobile units, or “remote receivers,” travelling within the cell.
  • the signal path from the cell site to the remote receivers is typically referred to as the "forward” path, while the signal path from a remote receiver to the cell site is typically referred to as the "reverse” path.
  • One of the limitations of cellular system performance is the capability of remote receivers to receive information in the presence of interference that affects the forward path signal.
  • the key performance measure is the minimum ratio of signal power to interference power, or "signal-to-noise ratio,” that permits acceptable communication quality.
  • bit error rate (BER) associated with the information contained in a received signal increases; as the bit error rate (BER) associated with the forward path increases, and/or the signal strength decreases, the quality of the communications system from the perspective of a remote receiver becomes degraded.
  • an equalizer is required to be integrated into the circuitry of a remote receiver.
  • the equalizer must be capable of operating well when receiving signals through two distinct paths separated in time by up to a symbol duration.
  • the purpose of the equalizer is to mitigate the effects of delay spread as it arises in the transmission environment of cellular telephones; delay spread is the period over which a signal transmitted at an instant is spread over time by the communication channel.
  • a conventional equalizer will perform very well when the channel appears to have consisted of two paths of equal average power, separated in time by a symbol duration.
  • This improved performance results from a combination of two factors: the diversity between the two paths (i.e., the low probability that the two signal paths will fade simultaneously relative to the individual probabilities of fading), and the minimal level of Inter-Symbol Interference (ISI) that occurs when the paths are separated by exactly a symbol duration.
  • ISI Inter-Symbol Interference
  • Improved receiver performance can be achieved, however, by transmitting two forward path signals, delayed in time by up to a symbol duration, to simulate the effect of delay spread; this transmission technique is known as "diversity transmission.”
  • the present invention relates to a wireless communications system employing selective diversity transmission, a method of enabling selective diversity transmission, and a wireless telecommunications network that employs the system or the method.
  • a wireless communications system employing the principles of the invention includes: a first transmitter that receives an input signal and generates a first radio frequency signal; a second transmitter having a delay associated therewith; and a diversity transmission mode controller that selectively couples the input signal to the second transmitter as a function of at least one characteristic of the system.
  • the second transmitter generates a second radio frequency signal that is delayed relative to the first radio frequency signal.
  • a remote receiver is preferably capable of simultaneously receiving and processing the first and second radio frequency signals whereby the transmission quality of the system is enhanced.
  • BER transmission bit error rate
  • RSS received signal strength
  • the present invention therefore provides a selectively-enabled diversity transmission mode in a wireless communications system.
  • the present invention enables diversity transmission as a function of one or more system characteristics, such as the BER associated with a radio frequency signal received by a remote receiver; e.g., if the BER associated with only transmitting a single signal exceeds a predetermined value, then the diversity transmission mode controller preferably enables the diversity transmission mode to decrease the BER.
  • the RSS at the remote receiver can be used to trigger the enablement of diversity transmission; e.g., if the RSS associated with only transmitting a single signal is less than a predetermined value, then the diversity transmission mode controller preferably enables the diversity transmission mode.
  • a timing advance parameter of the remote receiver, the system load, and/or a subscriber class of the remote receiver can also be used to trigger the enablement of diversity transmission.
  • Any system characteristic, or parameter can be used, individually or in combination with one or more other system characteristics, to trigger the enablement of diversity transmission; e.g., if the BER exceeds a predetermined value and the system load is less than a predetermined threshold, then the diversity transmission mode controller preferably enables the diversity transmission mode.
  • FIGURE 1 illustrates a simplified block diagram of a diversity transmission system
  • FIGURE 2 illustrates a simplified block diagram of a remote receiver capable of receiving and processing signals transmitted by the diversity transmission system illustrated in FIGURE 1 ;
  • FIGURE 3 illustrates exemplary plots of bit error rate (BER) versus signal-to-noise ratio (SNR) for normal and diversity transmission modes;
  • BER bit error rate
  • SNR signal-to-noise ratio
  • FIGURE 4 illustrates a functional schematic of an exemplary wireless communications system employing the selective diversity transmission principles of the present invention
  • FIGURE 5 illustrates an exemplary method for selectively enabling diversity transmission in a wireless communications system
  • FIGURE 6 illustrates an exemplary telecommunications network in which the selective diversity transmission principles of the present invention may be employed to advantage.
  • FIGURE 1 illustrated is a simplified block diagram of an exemplary diversity transmission system
  • the diversity transmission system 100 is based on the system and method of employing base station diversity transmission to enhance the forward path performance of a cellular system as described in United States Patent No. 5,574,989 to Watson, et al., ("Watson"); a diversity transmission scheme, however, can be employed to advantage in other cellular, or non- cellular, wireless communications systems.
  • an input signal 110 is selected for transmission and, at a desired point in the transmission circuitry, is directed into two paths.
  • the input signal division is done while the signal is at low frequencies, while in other systems signal division can be performed at an upconverted frequency level, such as the radio frequency level.
  • the input signal 110 is coupled to first radio frequency hardware 120 for upconversion to radio frequency, power amplification and transmission from an antenna 125.
  • the input signal 110 is applied to second radio frequency hardware 130, having a time delay circuit 131 associated therewith, for upconversion to radio frequency, power amplification and transmission from an antenna 135.
  • the time delay circuit 131 can operate with a fixed time delay or with a selectable variable time delay up to the symbol duration corresponding to symbols to be transmitted by the system 100.
  • the total delay spread may exceed the capabilities of an equalizer in a remote receiver, described with reference to FIGURE 2, in areas where significant "natural" delay spread exists.
  • control over the extent of the introduced delay spread may be employed; e.g., a cell site may be configured with a time delay specifically selected for local conditions.
  • the antenna 135 can be suitably located in spaced relation on the same tower as the antenna 125; alternatively, separate towers can be provided for the antennas 125 and 135.
  • time spaced signals 126 and 136 are transmitted to achieve relatively good independence between the signal transmission paths; i.e., to achieve relatively good signal diversity based on transmitted signals with preselected time separation and transmission path independence.
  • the signals 126 and 136 are transmitted to traverse different paths to a remote receiver.
  • Path independence can be achieved by transmitting the signals 126 and 136 through physically separated antennas 125 and 135, as described above, or by an appropriate electronic, or other, technique, such as polarization variation.
  • the signal 126 and the signal 136 which is delayed relative to signal 126, are transmitted as diversity signals with intentionally structured time separation to a remote receiver, described with reference to FIGURE 2, in the station reception area.
  • FIGURE 2 illustrated is a simplified block diagram of a remote receiver 200 capable of receiving and processing signals 126 and 136 transmitted by the diversity transmission system 100 illustrated in FIGURE 1.
  • the transmitted signals 126 and 136 are both received by an antenna 210 as received signals 226 and 236, which are typically slightly different from the transmitted signals 126 and 136 due to channel conditions.
  • the received signals 226 and 236 are directed to receiver hardware 220.
  • the receiver hardware 220 conventionally includes radio frequency (RF) circuitry 221 to separate and downconvert the received signals 226 and 236 for application to intermediate frequency (IF) hardware 222, which demodulates the signals.
  • IF intermediate frequency
  • the demodulated signals are coupled to an equalizer 230.
  • the equalizer 230 can be, for example, a maximum likelihood sequential estimator that conventionally operates on diversity signals that are delayed by natural channel conditions. Equalizer performance improves the quality of reception through reduction of error rates when there are two uncorrelated, time-separated fading paths, and especially when the delay between the paths is a symbol duration. In accordance with the principles of diversity transmission, the equalizer 230 also is intended to operate on diversity signals that are intentionally time separated (i.e., separated by an artificially imposed delay spread) relative to each other prior to transmission, as described with reference to FIGURE 1. The equalizer 230 resolves the artificially imposed delay spread by first separating the two independent fading signals summed at the receiving antenna 210 and then optimally combining the signals in a manner like that applied to diversity signals that are delayed by natural channel conditions.
  • conventional signal processing circuitry can be used to decode the equalized, received signals 226 and 236.
  • a decoder 240 such as a forward error correcting (FEC) decoder
  • a vocoder 250 can be used to decode and convert the signal to an analog signal that is coupled to an audio speaker 260.
  • FEC forward error correcting
  • other conventional signal processing circuitry can be used to decode the data for use by a digital system coupled to the equalizer 230.
  • diversity transmission can be used for the transmission of both voice and data, whereby remote receiver performance is improved through an artificial creation of two time-separated signal paths from a transmitting station.
  • FIGURE 3 illustrated are exemplary plots of bit error rate (BER) versus signal-to-noise ratio (SNR) for normal and diversity transmission modes 310 and 320, respectively. As can be seen from the plots
  • the BER is always less when diversity transmission is used.
  • voice quality is acceptable when the channel BER is less than or equal to about 3%.
  • the gain associated with using diversity transmission is about 3 dB at a channel BER of 3%.
  • a system using diversity transmission can achieve the same BER performance as a system using only a conventional, or "normal,” transmission scheme.
  • the performance advantage of using diversity transmission becomes even greater, as shown by the greater decrease in BER for the diversity transmission mode 320.
  • FIGURE 4 illustrated is an functional schematic of an exemplary wireless communications system 400 employing the selective diversity transmission principles of the present invention.
  • the system 400 includes first radio frequency hardware 420, and second radio frequency hardware 430 having a time delay circuit 431 associated therewith.
  • the radio frequency hardware 420 and 430 each include multiple "channels" for receiving multiple input signals for upconversion to radio frequency, power amplification and transmission from antennas 425 and 435, respectively.
  • the time delay circuit 431 can operate with a fixed time delay or with a selectable variable time delay up to the symbol duration corresponding to symbols to be transmitted by the system 400.
  • the antenna 435 can be suitably located in spaced relation on the same tower as the antenna 425; alternatively, separate towers can be provided for the antennas 425 and 435.
  • time spaced signals 426 and 436 are transmitted to achieve relatively good independence between the signal transmission paths; i.e., to achieve relatively good signal diversity based on transmitted signals with preselected time separation and transmission path independence.
  • the system 400 further includes a multiplexer circuit 440 for receiving multiple input signals, for example input signals 410a, 410b and 41 Ox, and coupling each signal to one or both of the first and second radio frequency hardware 420, 430. If diversity transmission is not enabled, a signal is only coupled to one of the radio frequency hardware 420, 430. It should be noted that an input signal can be transmitted using only radio frequency hardware 430, which includes time delay circuit 431 ; in such case, a remote receiver will receive and process the time-delayed signal as a normal signal without the benefits of diversity transmission. When it is desired for a signal to be transmitted using diversity transmission, however, the signal must be coupled to both the first and second radio frequency hardware 420, 430.
  • Selecting a signal for diversity transmission reduces the channel capacity of the system 400. For example, if it is assumed that radio frequency hardware 420 and 430 each have three channels, then there are a total of six transmission channels. Because the diversity transmission of one signal requires one channel from each of the radio frequency hardware 420, 430, then a maximum of three input signals could be selected for diversity transmission. If only one input signal is selected for diversity transmission, however, the system can transmit an additional four input signals using conventional (i.e., non-diversity) transmission.
  • the system 400 further includes a controller 450.
  • the controller 450 includes a system characteristic(s) monitor 451 that determines one or more "characteristics" of the system 400; as used herein, a system “characteristic” is defined to include any measurable parameter related to the transmission performance of the system 400, a capability of a remote receiver, or a class of service associated with a remote receiver or system user.
  • the controller 450 is coupled to the multiplexer 440 and directs the multiplexer to couple an input signal to one or both of the radio frequency hardware 420, 430 as a function of one or more characteristics associated with the system 400 or the remote receiver (or system user) to which the input signal is to be transmitted.
  • a system employing the principles of the present invention will enable diversity transmission for each input signal as a function of one or more system characteristics, such as an average transmission bit error rate (BER); e.g., if the BER associated with only transmitting a single signal exceeds a predetermined value, then the diversity transmission mode controller preferably dynamically couples the input signal to both of the radio frequency hardware 420, 430.
  • the received signal strength (RSS) at a remote receiver can be used to trigger the enablement of diversity transmission; e.g., if the RSS associated with only transmitting a single signal is less than a predetermined value, then the diversity transmission mode controller preferably dynamically enables the diversity transmission mode for the input signal to be transmitted to that remote receiver.
  • RSS received signal strength
  • a timing advance parameter of a remote receiver, the system load, and/or a subscriber class of the remote receiver can also be used to trigger the enablement of diversity transmission.
  • Any system characteristic can be used, individually or in combination with one or more other system characteristics, to trigger the enablement of diversity transmission; e.g., if the BER exceeds a predetermined value and the system load is less than a predetermined threshold, then the diversity transmission mode controller preferably enables the diversity transmission mode.
  • FIGURE 5 illustrated is an exemplary method 500 for selectively enabling diversity transmission in a wireless communications system.
  • the exemplary method 500 is preferably implemented as a software- definable process executable within the hardware of a general, or special, purpose computer; alternatively, the process 500 can be implemented in hardware, including embedded software (i.e., firmware).
  • the method 500 is initiated in a first Step 510, which may include receiving input from a system operator as to which system characteristic(s) are to be monitored and the algorithms or threshold values to be used in determining whether to enable the diversity transmission mode.
  • a Step 520 one or more system characteristics, such as BER or RSS, are monitored.
  • Step 530 it is determined whether the one or more system characteristics are, for example, less than, greater than, or equal to some predetermined value(s); this step may include one or more algorithms, such as Boolean functions, that receive the value of one or more system characteristics as input.
  • the result of Step 530 is preferably a "yes” or “no;” e.g., a "yes” result indicates that diversity transmission mode should be enabled in a Step 540.
  • the method 500 continues in a closed-loop fashion, continually monitoring one or more system characteristic(s) in Step 520 and enabling diversity transmission mode in Step 540 as a function of a result produced in Step 530.
  • L_Threshold is a value for the load (e.g., the number of simultaneous users) on the cell site
  • Q_Threshold is a BER value which represents the average call quality in the cell.
  • At least one transceiver (TRX) in the cell is deemed to be available for diversity transmission; similarly, the value of Q_Threshold can be used trigger diversity transmission if the call quality in the cell is deemed unsatisfactory.
  • the load and call quality criteria can be used in combination to trigger the activation of diversity transmission; e.g., using Boolean AND or OR functions. In order to avoid rapid changes in transmission modes, it may also be desirable to employ timing filters or hysteresis parameters to control the selective enabling, and disabling, of diversity transmission.
  • the L_Threshold is set to 50%
  • the Q_Threshold is set to 3%
  • a logical OR operation is selected.
  • the channel resource usage during peak hours is averaged over a short filter length and found to be high
  • the average BER in the cell is determined to be relatively good (e.g., 2%). Because the channel resource usage is high, it is undesirable to enable diversity transmission, which would reduce the number of users that could simultaneous receive service from the cell. During off-peak hours, however, the channel resource usage drops below 50%, while the BER remains the same. Because the load has dropped below L_Threshold, and because an OR operation was selected, diversity transmission is enabled, which will most likely result in a reduction in the average BER.
  • the L_Threshold is set to 60%
  • the Q_Threshold is set to 4%
  • a logical AND operation is selected.
  • the channel resource usage during peak hours is averaged over a short filter length and found to be high (e.g., 80%) and the average BER in the ceil is determined to be relatively poor (e.g., 6%).
  • the use of diversity transmission is desirable to improve the poor BER, it will not be enabled because the channel usage is greater than L_Threshold and, thus, the result of the logical AND operation is
  • FIGURE 6 illustrates an exemplary telecommunications network 600 in which the selective diversity transmission principles of the present invention may be employed to advantage.
  • the architecture of network 600 is functionally equivalent to the conventional architecture defined by standards for the Global System for Mobile (GSM) Communications; see, for example, General Description of a GSM Public Land Mobile Network (PLMN); GSM 01.02, Oct. 1993, Version 4.02.
  • the network 600 includes a Mobile-services Switching Center (MSC)
  • the MSC is coupled to a Base Station Controller (BSC) 650, which manages the radio interfaces in a plurality of Base Transceiver Stations (BTSs), generally designated 620, through the allocation, release and handover of radio channels.
  • BSC Base Station Controller
  • the network 600 also includes a Home Location Resource 670 that stores information related to each remote receiver 200, such as subscriber class information.
  • Each BTS 620 includes a Distribution Unit (DXU) 640, analogous to the multiplexer 440 described with reference to FIGURE 4, and multiple transceivers (TRXs), generally designated 630, which are each coupled to an antenna, generally designated 635.
  • the TRXs 630 each include a delay circuit (not shown), analogous to the delay circuit 431 described with reference to FIGURE 4.
  • the interface between the BSC 650 and each BTS 620 is typically a T-1 line that includes multiple voice channels as well as a control channel.
  • the control channel routes control signals to a BTS 620 to configure the DXU 640 and TRXs 630.
  • a conventional BSC 650 includes computer resources that execute software processes to control the operation of BSs 620; the same computer resources can be programmed to execute the method 500, described above, to provide selective diversity transmission.
  • the control channel of the T-1 interface between the BSC 650 and BS 620 can be used to send appropriate configuration information to the DXU 640 to couple one or more voice channels to two TRXs 630, as well as sending a signal to each TRX 630 to enable or disable its delay circuitry and adjust the amount of delay to be applied to a particular signal.
  • the system characteristics used to control the enablement of diversity transmission are acquired by the BSC 650 from various sources.
  • a remote receiver 200 periodically transmits measurement reports 201 to a BTS 620; conventional measurement reports include parameters such as the transmission BER and RSS.
  • the information contained in the measurement reports 201 is combined with BTS statistics and transmitted in a result report 621 to the BSC 650.
  • the BSC 650 can receive subscriber class information from the HLR 670 via the MSC 610; subscriber class information may indicate, for example, that a user has subscribed to "premium" service.
  • a subscription to "premium" service may include, for example, a preference for diversity transmission; such preferential service could temporarily exclude network access to other subscribers, if necessary, in order to provide network resources for diversity transmission to the premium subscriber. If the average BER is within an acceptable level, however, it is preferable that diversity transmission not be provided, even for premium subscribers, in order to maximize the availability of system resources.
  • the present invention provides significant advantages to wireless communications systems, in general, and the invention is particularly advantageous in cellular communications networks.
  • the principles of selective diversity transmission disclosed herein can optimize the transmission quality of cellular communications networks while increasing the utilization of network resources.
  • the transmitter i.e., TRX 630
  • the remote receiver is typically "mobile”
  • the foregoing generally described the use of the present invention to improve wireless communications between a "transmitter” and a "remote receiver.”
  • a selective diversity transmission scheme according to the principles of the present invention can be employed to improve transmission quality from a base to a mobile receiver and from a mobile receiver to a base station.
  • a mobile station e.g., a "cell phone”
  • a cell phone which conventionally includes only one transmitter
  • the second transmitter would preferably not be used, in order to reduce power consumption, but could be dynamically enabled if necessary to improve the transmission quality of the "reverse" path.
  • the principles of selective diversity transmission disclosed herein can be adapted to all forms of wireless communications systems.

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  • Computer Networks & Wireless Communication (AREA)
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  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un système de radiocommunications permettant de transmettre un signal d'entrée à un récepteur distant, qui comprend les élément suivants: premier émetteur transmettant le signal d'entrée et fournissant un premier signal radioélectrique, second émetteur auquel est associé un retard, et unité de commande de mode de transmission en diversité qui couple sélectivement le signal d'entrée au second émetteur au moins en fonction d'une caractéristique du système, le second émetteur fournissant un second signal radioélectrique retardé par rapport au premier signal radioélectrique. De préférence, le récepteur distant est capable de recevoir et de traiter simultanément les premier et second signaux, ce qui permet d'améliorer la qualité de transmission du système. On peut utiliser diverses caractéristiques du système, isolément ou en combinaison, pour déclencher l'activation sélective du mode de transmission en diversité, à savoir: taux d'erreur sur les bits à la transmission associé au premier signal, puissance du signal reçu au récepteur distant associé au premier signal, paramètre d'avance de synchronisation du récepteur distant, nombre de récepteurs distants qui reçoivent simultanément le service du système, et classe d'abonné du récepteur distant.
PCT/US1999/018952 1998-08-25 1999-08-24 Systeme de radiocommunications a transmission en diversite selective, procede d'activation de ce type de transmission, et reseau de radiocommunications faisant appel auxdits systeme et procede Ceased WO2000011806A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU56810/99A AU5681099A (en) 1998-08-25 1999-08-24 Wireless communications system employing selective diversity transmission, method for selectively enabling diversity transmission, and a wireless telecommunications network employing the system or the method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US13937098A 1998-08-25 1998-08-25
US09/139,370 1998-08-25

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WO2000011806A1 true WO2000011806A1 (fr) 2000-03-02

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US6542556B1 (en) 2000-03-31 2003-04-01 Nokia Mobile Phones Ltd. Space-time code for multiple antenna transmission
EP1292049A3 (fr) * 2001-09-06 2003-07-02 NTT DoCoMo, Inc. Station de base et procédé de commande de communications radio avec de l'émission en diversité
EP1315312A3 (fr) * 2001-10-25 2003-08-13 NTT DoCoMo, Inc. Station de base radio et procédé de commande de communications radio
WO2003047123A3 (fr) * 2001-11-28 2004-02-26 Arraycomm Inc Emission en diversite variable dans un systeme de radiocommunications basee sur des caracteristiques de signal recu
US6748024B2 (en) 2001-03-28 2004-06-08 Nokia Corporation Non-zero complex weighted space-time code for multiple antenna transmission
KR100442833B1 (ko) * 2002-07-12 2004-08-02 삼성전자주식회사 이동통신시스템에 있어서 다중대역 무선주파수 수신방법및 장치
US6865237B1 (en) 2000-02-22 2005-03-08 Nokia Mobile Phones Limited Method and system for digital signal transmission
EP1530317A1 (fr) * 2003-11-10 2005-05-11 Mitsubishi Electric Information Technology Centre Europe B.V. Gestion d'accès à un support de transmission partage pour plusieurs connexions
US7046737B2 (en) 1997-12-23 2006-05-16 Cingular Wireless Ii, Llc Near-optimal low-complexity decoding of space-time codes for wireless applications
US7120200B2 (en) 1997-09-16 2006-10-10 Cingular Wireless Ii, Llc Transmitter diversity technique for wireless communications
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WO2014187893A1 (fr) * 2013-05-24 2014-11-27 Hirschmann Automation And Control Gmbh Boîtier de redondance (redbox) sans fil à diviseur temporel
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