WO2006111959A2 - Systeme et procede de communication de donnees a diversite de transmission a modulation de phase - Google Patents

Systeme et procede de communication de donnees a diversite de transmission a modulation de phase Download PDF

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Publication number
WO2006111959A2
WO2006111959A2 PCT/IL2006/000464 IL2006000464W WO2006111959A2 WO 2006111959 A2 WO2006111959 A2 WO 2006111959A2 IL 2006000464 W IL2006000464 W IL 2006000464W WO 2006111959 A2 WO2006111959 A2 WO 2006111959A2
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WO
WIPO (PCT)
Prior art keywords
data
transmit signals
transmit
phase
communication system
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PCT/IL2006/000464
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English (en)
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WO2006111959A3 (fr
Inventor
Shmuel Miller
Uzi Timor
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Celletra Ltd.
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Publication date
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Publication of WO2006111959A2 publication Critical patent/WO2006111959A2/fr
Publication of WO2006111959A3 publication Critical patent/WO2006111959A3/fr

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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
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector
    • H04L1/206—Arrangements for detecting or preventing errors in the information received using signal quality detector for modulated signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0212—Channel estimation of impulse response
    • H04L25/0214—Channel estimation of impulse response of a single coefficient
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters

Definitions

  • the present invention relates to improving the data throughput of a phase- modulated transmit diversity (PMTD) data communication system, and, more particularly but not exclusively, to utilizing channel feedback to determine the optimal relative phases of the diversity transmit signals.
  • PMTD phase- modulated transmit diversity
  • the demand for the transmission at high data rates to mobile users drives the search for new technologies and new architectures for third (3G) and fourth (4G) generation wireless systems.
  • Typical technologies are IXEVDO (Evolution Data Optimized) and High-Speed Downlink Packet Access (HSDPA), which are based on CDMA, and Orthogonal Frequency Division Multiple Access (OFDMA).
  • Enhanced throughput is expected by using Multiple-Input Multiple-Output (MIMO) and transmit diversity techniques.
  • MIMO Multiple-Input Multiple-Output
  • Data transmission is tolerant to some delays (in contrast with voice transmission). Resource allocation thus plays an important role in system performance.
  • the transmission is time slotted, where at each slot the transmission is directed to one user (as in IXEVDO and HSDPA) or to several users each with its own defined resources (as in OFDMA).
  • a scheduler determines, for each slot, to which user (or users) the transmission is directed, and at what rate to transmit.
  • Diversity techniques provide an additional powerful means of mitigating gain and phase fluctuations ("fading") of the mobile channel.
  • Diversity is used in cellular and wireless access networks to enhance coverage and capacity.
  • RF diversity techniques such as space diversity and polarization diversity, incorporate two or more antennas, and may be implemented on both the transmit and receive sides of the channel.
  • a diversity-combining system is then applied at the receiver to optimally combine the diversity branches.
  • Data communication systems are often implemented with channel feedback for improved performance.
  • Users constantly monitor the downlink channel conditions, and inform the base station of channel conditions, which are used to determine what resources should be allocated to each user. For example, users may return indications of the C/I (channel to interference) at the receiver, thereby informing the base station of the user's currently achievable data rate.
  • the scheduler can then attempt to balance between conflicting demands of increasing the total throughput of the systems (by transmitting to users with good channel conditions), while being fair to all users (by transmitting some data to users with poor channel conditions).
  • the quality of the channel for each user changes due to fading, and the scheduler takes advantage of this phenomena by scheduling transmission at intervals where the rate is higher than average (for a particular user), thus increasing overall system throughput.
  • the actual physical channel conditions may remain relatively constant over time. This stability is problematic for those low-mobility users who are operating under poor channel conditions, and will therefore suffer from low resource allocation over time.
  • phase modulation transmit diversity (PMTD) to induce artificial channel variations.
  • the main objective is to avoid deep fades by artificially varying the phase between two simultaneous transmissions of the same information.
  • the basic forms of phase modulation that are treated in the published literature are linear phase sweep and non-linear phase modulation.
  • Both linear and non-linear PMTD for high data rate systems were presented in Timor, U.; Miller, S., "Forward-link Throughput Performance of IxEVDO with Phase-modulation Transmit Diversity," 9th CDMA International Conference (CIC2004), Seoul, Korea, Oct. 2004. Celletra Pat. Appl. No. WO 2004/086730 deals with non-linear phase sweep.
  • Another example of PMTD is US Pat. No. 6,694,147 by Park, entitled “Method and Apparatus for Transmitting Information between a Base Station and Multiple Mobile Stations". The contents of each of the above-cited documents are hereby incorporated herein by reference.
  • PMTD are blind transmit diversity systems, where the diversity parameters (amplitude and phase) are changed in a predetermined or random sequence.
  • the base station has feedback information from the users with regards to their channel conditions, but uses the feedback information only to choose the time and the data rate to transmit to the users.
  • the increased data rates which would be possible with optimized diversity parameters are therefore not obtained.
  • a phase transmit diversity wireless communication system which makes use of the feedback information to optimize the diversity parameters and improve system performance, devoid of the above limitations.
  • a method for improving a data rate of a PMTD data communication system which consists of the following steps. First a sequence of test signals is transmitted to a destination. Each test signal consists of a pair of test transmit signal, where each pair in the sequence has a different phase difference between the two test transmit signals. Then a reception quality parameter is obtained from the destination for each of the test signals. Finally, the reception quality parameters are used to determine the required phase difference for a pair of data transmit signals, such that both data transmit signals arrive at the destination in phase.
  • a phase selector for a PMTD data communication system configured to transmit over a channel comprising a first and a second transmit signals, where the two transmit signals have a controllable phase difference and are transmitted in parallel over a first and a second transmit antenna.
  • the data communication system includes a test sequence generator, a reception quality inputter and a phase determiner.
  • the test sequence generator generates a sequence of pairs of test transmit signals. Each of the pairs of test transmit signals includes a first and second test transmit signal having a different phase difference.
  • the reception quality inputter obtains a respective reception quality parameter for each of the pairs of test transmit signals from the destination. Based on the reception quality parameter values, the phase determiner determines a phase difference transmitting a pair of data transmit signals so that the pair of data transmit signals arrive at the destination in phase.
  • the present invention successfully addresses the shortcomings of the presently known configurations by providing a phase transmit diversity wireless communication system which utilizes channel feedback to optimize the relative phases of the transmitted signals to the current channel conditions.
  • the phases of the transmitted signals are adjusted so that the transmitted signals arrive at the receiver in phase.
  • the received signals thus sum at the receiver, without requiring complex processing by the receiver, improving C/I and, consequently, the attainable data rate.
  • all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control, hi addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
  • Implementation of the method and system of the present invention involves performing or completing selected tasks or steps manually, automatically, or a combination thereof.
  • several selected steps could be implemented by hardware or by software on any operating system of any firmware or a combination thereof.
  • selected steps of the invention could be implemented as a chip or a circuit.
  • selected steps of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system, hi any case, selected steps of the method and system of the invention could be described as being performed by a data processor, such as a computing platform for executing a plurality of instructions.
  • Fig. 1 is a phasor diagram of the signals received from two transmit antennas.
  • Fig. 2 is a simplified flowchart of a method for improving a data rate of a data communication system, according to a preferred embodiment of the present invention.
  • Fig. 3 is a graph showing the improvement in C/I obtained using optimum power split between the data transmit signals.
  • Fig. 4 is a simplified block diagram of a phase selector for a PMTD data communication system, according to a preferred embodiment of the present invention.
  • Fig. 5 is a simplified block diagram of a PMTD communication system, according to a preferred embodiment of the present invention.
  • Fig. 6 is a simplified block diagram of an amplification element having a fixed maximum power requirement for each of the amplifiers, according to a preferred embodiment of the present invention.
  • Fig. 7 is a simplified flow chart of an exemplary method of scheduling a user and assigning transmit diversity parameters and allocating communication resources on the dedicated channel, according to a preferred embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • the present embodiments teach a wireless data communication system with phase transmit diversity, which uses channel feedback on the common (or pilot) channel in order to estimate the phase difference of the multiple data signals arriving at the receiver.
  • the diversity parameters are then adapted to the current user, in order to improve the achievable data rate to the user.
  • the present embodiments teach providing the transmitter with information of the C/I at the receiver.
  • the feedback data is used to estimate the phase difference of the various transmission paths from the transmitter to receiver, so that the phase difference may be compensated for during transmission of the data over the dedicated channel.
  • the transmitted data signals thus arrive at the receiver in phase.
  • the in-phase data signals combine at the receiver, thereby increasing the C/I.
  • the channel feedback may be utilized to optimize the power allocated to each transmit antenna.
  • the attainable data rate to each user is thus maximized, yielding an enhanced throughput performance.
  • a system that dynamically compensates for phase changes over the course of transmission, in order to utilize maximum diversity and improve efficiency.
  • a dynamically changing phase offset is provided to one or more of the transmit signals based on the analysis of a test signal.
  • the following describes a built-in or add-on transmit diversity system for high rate data cellular communication systems.
  • the following description focuses on the downlink (Base to mobile) channel, where higher data rates are required, but can also be implemented in the uplink (mobile to Base) channel.
  • the signal is transmitted by the base station over N antennas (N > 2), where at each antenna the signal is multiplied by a complex coefficient (amplitude and phase), and summed at the receiver to yield a single received signal.
  • the transmitted signal includes a common channel, used by all users to monitor channel quality and periodically report it (via the uplink) to the Base Station, and a dedicated channel, for data transmission to each particular user.
  • the transmit parameters (complex coefficients) for the antennas are predetermined for the common channel (chosen to yield good estimation for the channel parameters), and are user dependent (based on measurements performed by the users and transmitted to the Base) for the dedicated channel.
  • the smart diversity system described hereinbelow assigns optimum diversity parameters per user or group of users, yielding increased data rates which result from improved C/I under the optimum diversity parameters. Controlling the diversity parameters per user also yields increased flexibility in slot assignment to users.
  • phase difference and “relative phase” are used interchangeably herein.
  • each slot includes a pilot signal (also denoted herein the test signal) directed to all users over the common channel, and a data signal directed to specific users over the dedicated channel.
  • the pilot signal may be transmitted during specific time intervals within the slot, as in IXEVDO, or over a sub-carrier of the signal. Other embodiments without time slotting are possible.
  • each user measures a reception quality parameter, such as the C/I, of the received pilot signal, and informs the Base Station once per slot.
  • the reception quality parameter may be used to calculate the appropriate data rate which the channel can support.
  • a scheduler assigns slots and rates to users, with the goal of maximizing the total throughput while taking into account other considerations of fairness and priority.
  • Fig. 1 is a simplified illustration of the two received signals propagated from two transmit antennas.
  • the two signals propagate independently and are received as two vectors a and b, with a C/I of a 2 and b 2 respectively.
  • the two vectors are then summed at the receiver to yield a received signal with C/I of c 2 .
  • ⁇ be the angle between the two vectors, resulting from different propagation paths from the two transmit antennas to the receiver's antenna.
  • the resulting C/I at the receiver is:
  • the angle between the two received vectors will be ⁇ + ⁇ .
  • the Base Station receives from each user the corresponding C/I sequence C 1 2 , C 2 2 , C 3 2 ..., and evaluates the resulting shift angles ⁇ i, ⁇ X2 , (X 3 .... If we make the assumption that ⁇ changes very slowly, the Base Station may use a smooth version of the calculated ⁇ . For example, if the (pj sequence is 0, 90°, 180° ... we obtain:
  • a Fig. 2 is a simplified flowchart of a method for improving a data rate of a PMTD data communication system, according to a preferred embodiment of the present invention.
  • transmission is via a pair of transmit signals having a controllable phase difference.
  • the dual-signal embodiment may be expanded to embodiments with N>2 transmit signals.
  • each transmit signal is transmitted from a separate antenna.
  • a sequence of test signals is transmitted to a destination, preferably over a common channel.
  • Each test signal is formed of a pair of test transmit signals having a phase offset between them. The phase difference between the test signal pairs varies over the sequence, which enables the later calculation of ⁇ .
  • a respective reception quality parameter preferably the C/I at the destination, is obtained from the destination for each of the test signals.
  • the reception quality parameter preferably indicates the rate at which the data can be transmitted to the user at the destination.
  • the reception quality parameter generally does not indicate a quality for each transmission path individually, but rather an overall value obtained for the combined signal at the receiver.
  • step 230 the required relative phase of the pair of data transmit signals is determined from the obtained reception quality parameters prior to transmission. The required relative is calculated to compensate for the phase difference ⁇ between the signal vectors a and b.
  • step 240 the phase difference of the pair of data transmit signals is adjusted to equal the required phase difference determined in step 230. For example, the phase of the second transmit signal may be shifted by - ⁇ (with respect to the first signal) before being transmitted.
  • transmission resources such as transmission power, data rate per user and so forth. Allocation may be on a per user basis, per group of users, or per time slot.
  • a total transmit power is split between the data transmit signals in accordance with the relative amplitudes of vectors a and b as follows.
  • the method includes the further step of setting a transmission rate of a data signal in accordance with the calculated equivalent reception quality parameter.
  • the transmission rate may be set per user, per time slot, or per group of users.
  • transmit diversity is implemented over N>2 transmit signals.
  • N >2 For more than two antennas (N > 2), 2N- 1 consecutive C/I reports are needed in order to determine the optimum parameters.
  • the estimation algorithm presented above may be extended straightforwardly to the general N > 2 case.
  • Fig. 4 is a simplified block diagram of a phase selector for a PMTD data communication system, according to a preferred embodiment of the present invention.
  • the system is time-slotted.
  • Phase selector 400 includes test sequence generator 410, reception quality inputter 420, and phase determiner 430.
  • Test sequence generator 410 generates the sequence of pairs of test transmit signals. As discussed above, each of the pairs of the sequence has a different relative phase.
  • Reception quality inputter 420 obtains a sequence of reception quality parameters from the destination (where each reception quality parameter corresponds to a given pair of test transmit signals).
  • Phase determiner 430 determines the required relative phase for the data transmit signals from the reception quality parameters as described above, in order to ensure that the pair of data transmit signals arrive at the destination in phase.
  • phase determiner 430 calculates the phase difference, ⁇ , of the pair of test transmit signals at the destination, and then shifts the phase of one of the data transmit signals by - ⁇ .
  • Fig. 5 is a simplified block diagram of a PMTD communication system, according to a preferred embodiment of the present invention.
  • Communication system 500 incorporates a phase selector essentially as described above.
  • Communication system 500 further includes data transmit signal generator 510, which generates a pair of data transmit signals having the required relative phase, as determined by phase selector 400.
  • the data transmit signals are then transmitted by antennas 520.1 and 520.2.
  • the same antennas commonly serve also for the transmission of the test transmit signal pairs.
  • test transmit signals are transmitted to all users or groups of users over a common channel, whereas the data transmit signals are transmitted to individual users over a dedicated channel.
  • communication system 500 includes at least one signal provider, which includes a splitter, for splitting a single data communication signal into a pair of transmit signals, and a phase shifter, for shifting a phase of one of the transmit signals.
  • the signal provider is capable of transforming an original data signal into a pair of transmit signals having the desired phase.
  • a signal provider may be incorporated into one or both of test sequence generator 410 and data transmit signal generator 510.
  • data transmit signal generator 510 includes signal provider 530, which converts a single data signal into two data transmit signal having the desired phase difference.
  • communication system 500 includes a power allocator 540, which allocates power for the transmission of each of the transmit signals provided to antennas 520.1 to 520.N depending on channel conditions.
  • Power allocator 540 may choose to allocate the total power proportionally to the respective power of the transmit signals received at the destination from each of the channels (see, for example, eqns. 14 and 15). Alternately, power allocator 540 may allocate all power to a single transmit signal or to allocate a fixed power to each of the transmit antennas.
  • communication system 500 preferably includes an adjustable power amplifier prior to each antenna.
  • a first preferred embodiment for implementing the power allocation between the antennas utilizes two power amplifiers (in the case of two transmit antennas) that respectively produce the transmitted signals and feed them into the main and diversity antennas.
  • the optimum power split between the two transmit signals requires each amplifier to be able to produce the maximum required transmit power P.
  • a disadvantage of a system architecture in which both amplifiers are capable of supplying the maximum power P is that usage efficiency is below 100%, since both amplifiers do not deliver the full power simultaneously.
  • a second preferred embodiment of an implementation architecture utilizes a pair of power amplifiers, each capable of producing P/2 output power.
  • the details of the RF network for the present embodiment, as well as the supporting preprocessing are detailed in US Pat. Appl. No. 2003/0162566 by Joseph Shapira et al., which is hereby incorporated by reference within. Fig. 22 of US Pat. Appl. No. 2003/0162566 is provided herein as Fig- 6.
  • the embodiment guarantees a fixed maximum power requirement for each of the amplifiers.
  • the transmit signal is split at low power, one of the signal is phase shifted, and the two equal level signals are then amplified by two power amplifiers with output power of P/2 each.
  • a maximum utilization of the two amplifiers is guaranteed.
  • a phase shifter imposes a 90° shift to align the two signals back before they are applied to the antennas.
  • An advantage of the embodiment of Fig. 6 is that it is possible to use power amplifiers which deliver a power of P/2, rather than power amplifiers with higher capabilities which are not efficiently used. This results in lower heat dissipation requirements, and helps to reduce the costs of the RF network.
  • communication system 500 includes scheduler 550 which allocates communication resources, preferably on a per-user or per-time slot basis.
  • Other communication resources which may be handled by scheduler 550 include time slot allocation and transmission rate.
  • the above-described embodiments are tailored for low mobility users which yield slow changing diversity parameters.
  • Fast changing parameters may indicate a high mobility user or an environment with fast changing interference patterns.
  • the present system and method preferably include a smoothing algorithm, which decides when the low mobility conditions are not valid and refrains from using transmit diversity for the user.
  • the method is applied to a high rate data system, such as OFDMA, which transmits to several users in one slot, assigning distinct radio resources (for example, different subcarriers) to each user.
  • OFDMA a high rate data system
  • each served user with its subcarriers may be assigned a user-specific power ratio and phase difference ⁇ between branches, independently and simultaneously.
  • communication system 500 also utilizes space diversity. In an additional preferred embodiment, communication system 500 also utilizes polarization diversity.
  • Fig. 7 is a simplified flow chart of an exemplary method of asssigning transmit diversity parameters and allocating communication resources on the dedicated channel, according to a preferred embodiment of the present invention.
  • the present embodiment is based on maintaining a table containing current values of key parameters for each user, as shown in Table 1 below (where C eq denotes the equivalent C/I).
  • C eq denotes the equivalent C/I.
  • Cj the value of the reception quality parameter, Cj, is received from each user for each time slot i, and is used to calculate the current parameter values for the user.
  • the table is updated from information received from all users through their uplink reports transmission.
  • the scheduling algorithm need not be changed; any scheduling algorithm can be used.
  • the assignment of slots to users is based on the new diversity parameters, which leads to improved performance in user data rates and total Base Station throughput..
  • the current values of ⁇ , a, b ⁇ for user k at time i are calculated.
  • the values are calculated from the recently received values of the user's C/I (that is, from c 2 i -2 , C 2 I-1 , and c 2 ; ).
  • a smoothing algorithm is applied to the previous m samples. The smoothed values are used to calculate the current values of C eq , P a and P b for user k.
  • table is updated with the current values.
  • step 940 the proper phase shift, -ct k , is obtained from the table for transmission to the current user, as well as C eq , P a and P b . Additionally, communication resources are allocated periodically based on the current table values. Based on the table values, resource allocation may be performed by a scheduler which:
  • any scheduler which bases its assignments on the reported qualitiy of the channel may operate with the optimum diversity parameters and achieve an improved throughput.
  • the embodiments described above utilize phase transmit diversity to obtain improved reception of a data signal. Improving the C/I at the receiver enables transmitting at a higher data rate, resulting in a higher system throughput than is currently achievable. System performance may further be improved by proper transmit power allocation and user scheduling.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Quality & Reliability (AREA)
  • Radio Transmission System (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

L'invention concerne un procédé d'amélioration d'un débit de données d'un système de communication de données PMTD. Ledit procédé est constitué des étapes suivantes. Tout d'abord, une séquence de signaux d'essai est transmise à une destination. Chaque signal d'essai est constitué d'une paire de signaux de transmission d'essai, chaque paire de la séquence présentant une différence de phase différente entre les deux signaux de transmission d'essai. Ensuite, un paramètre de qualité de réception est obtenu à partir de la destination pour chacun des signaux d'essai. Enfin, les paramètres de qualité de réception sont utilisés afin de déterminer la différence de phase requise pour une paire de signaux de transmission de données, de sorte que les deux signaux de transmission de données arrivent à la destination en phase.
PCT/IL2006/000464 2005-04-18 2006-04-11 Systeme et procede de communication de donnees a diversite de transmission a modulation de phase WO2006111959A2 (fr)

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US60/672,098 2005-04-18

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5894496A (en) * 1996-09-16 1999-04-13 Ericsson Inc. Method and apparatus for detecting and compensating for undesired phase shift in a radio transceiver
US6873831B2 (en) * 2002-04-01 2005-03-29 Qualcomm Incorporated Method and apparatus for transmit power modulation in a wireless communications system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5894496A (en) * 1996-09-16 1999-04-13 Ericsson Inc. Method and apparatus for detecting and compensating for undesired phase shift in a radio transceiver
US6873831B2 (en) * 2002-04-01 2005-03-29 Qualcomm Incorporated Method and apparatus for transmit power modulation in a wireless communications system

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