[go: up one dir, main page]

WO2008006930A1 - Procédé, système radio, station de base et terminal utilisateur - Google Patents

Procédé, système radio, station de base et terminal utilisateur Download PDF

Info

Publication number
WO2008006930A1
WO2008006930A1 PCT/FI2006/050332 FI2006050332W WO2008006930A1 WO 2008006930 A1 WO2008006930 A1 WO 2008006930A1 FI 2006050332 W FI2006050332 W FI 2006050332W WO 2008006930 A1 WO2008006930 A1 WO 2008006930A1
Authority
WO
WIPO (PCT)
Prior art keywords
transmit weight
weight vector
noise ratio
signal
base station
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/FI2006/050332
Other languages
English (en)
Inventor
Jyri Hämäläinen
Kari Horneman
Risto Wichman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nokia Inc
Original Assignee
Nokia 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 Nokia Inc filed Critical Nokia Inc
Priority to PCT/FI2006/050332 priority Critical patent/WO2008006930A1/fr
Publication of WO2008006930A1 publication Critical patent/WO2008006930A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

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
    • H04B7/0615—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 weighted versions of same signal
    • H04B7/0617—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 weighted versions of same signal for beam forming
    • 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
    • H04B7/0615—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 weighted versions of same signal
    • H04B7/0619—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 weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content
    • H04B7/0632—Channel quality parameters, e.g. channel quality indicator [CQI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H04W72/21—Control channels or signalling for resource management in the uplink direction of a wireless link, i.e. towards the network
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
    • H04W72/542—Allocation or scheduling criteria for wireless resources based on quality criteria using measured or perceived quality

Definitions

  • the invention relates to a method in a radio system supporting opportunistic beamforming, to a radio system, to a base station, to a user termi- nal, and to a computer program product.
  • Multiantenna processing and physical layer scheduling will play an important role in coming broadband wireless access (BWA), 3G LTE (Long Term Evolution) and 4G systems.
  • a celebrated opportunistic beamforming (OBF) provides an attractive tool by which scheduling and multiantenna processing can be combined in packet switched networks.
  • OBF opportunistic beamforming
  • multiple antennas are used in a base station (BS) in order to transmit the same signal with pseudorandomly changing beamforming weights.
  • BS base station
  • Such variation of weights introduces an artificial fading statistics that can be efficiently coupled with channel-aware packet scheduling (PS).
  • PS channel-aware packet scheduling
  • An example of the opportunistic beamforming technique is described in Viswanath P., Tse, D. N.
  • transmit antennas with a low mutual correlation are applied, transmit weights are selected based on feedback from mobiles.
  • transmit antennas with a low mutual correlation are applied, transmit weights are selected based on feedback from mobiles.
  • mode 2 two modes for two transmit antennas are sped- fied of which mode 2 will be optional. Mode 1 applies signal phasing with 2-bit accuracy while mode 2 applies 8-PSK phasing and 1-bit gain adjustment.
  • Figure 3 shows a system model of a basic opportunistic beamforming concept according to prior art.
  • the upper part of Figure 3 marked with dashed lines 360 illustrates the estimation and feedback of signal-to-interference ratio that is executed by all active user terminals during each scheduling time interval.
  • the base station transmitter part for pilots 302 comprises a block for generating M identical pilot signals 306 and multiple antennas 310, 312, 314 that are configured to transmit the same signal from each antenna to a receiver 330 of the user terminal.
  • the transmitter 302 comprises a weight control unit 308 that controls varying the transmit weights in different antennas 310, 312, 314 independently in time but controlled in a pseudorandom fashion.
  • the user terminal comprises a feedback generation unit 330 including a channel estimation unit 336 and a signal-to-noise ratio calculation unit 338 where an overall signal-to-noise ratio is monitored. Feedback 346 about the signal-to-noise ratio is then transmitted back to the base station transmitter for data 304.
  • a scheduling/data buffer unit 316 controls scheduling decisions on the basis of the received feedback 346. If a transmit decision is made, the data streams are transmitted via an encoder/modulator unit 318 to a unit 320 that forms signal replicas for transmission.
  • a weight control unit 322 controls the transmit weights in different antennas 324, 326, 328.
  • the user terminal receiver 332 receives the transmitted data streams and the data is processed in a channel estimation unit 342 and in a demodulation/decoding unit 344.
  • the receiver monitors the overall signal-to-noise ratio and sends feedback to the base station to form a basis for scheduling.
  • the channel monitoring is based on a single pilot signal that is repeated at different transmit an- tennas 310, 312, 314.
  • a large system with several independent fading user terminals is likely to comprise a user terminal whose instantaneous channel gains are close to matching the current powers and phases allocated at the transmit antennas.
  • the transmit weights are randomized and transmission is scheduled to the user terminal which is close being in the optimal beamforming configuration.
  • One of the problems related to the opportunistic beamforming is related to pilot/channel estimation.
  • the receiver estimates the sum channel at a scheduling time interval (STI) that may contain one or more transmit time intervals (TTIs), without knowing the corresponding transmit weight vector.
  • STI scheduling time interval
  • TTIs transmit time intervals
  • the weight vector is changed in a pseudorandom manner and a short time period is needed for channel and SNR estimation before correct feedback can be sent to the base station.
  • scheduling cannot be based on SNR comparisons and thus, the system is not working efficiently. Further, beneficial filtering of consecutive channel gains is difficult due to rapid channel changes.
  • Another problem in the opportunistic beamforming is related to feedback channel.
  • feedback information is sent via a dedicated control channel where accurate power control is applied.
  • control channels are not attractive due to the packet switched nature of the systems.
  • a delay can also become a problem since a receiver may need to wait for a suitable transmit weight and the corresponding coherent channel summation for a long time. This is not acceptable from the services' point of view.
  • An object of the invention is to provide an improved method, an improved radio system, base station, user terminal, and an improved computer program product. According to an aspect of the invention, there is provided a method in a radio system supporting opportunistic beamforming, wherein more than one transmit weight vector sequence is used at the same scheduling time interval.
  • the method comprises: providing information relating to at least two transmit weight vector sequences to one or more user terminals of the radio system, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; calculating, at the one or more user terminals, the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector; sending, by the one or more user terminals, the maximum signal-to-noise ratio of the calcu- lated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio to the base station; and controlling scheduling, by the base station, on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector received from the one or more user terminals.
  • a ra- dio system supporting opportunistic beamforming wherein more than one transmit weight vector sequence is used at the same scheduling time interval, the radio system comprising a base station and one or more user terminals.
  • the base station includes a communication unit for providing information relating to at least two transmit weight vector sequences to one or more user termi- nals of the radio system, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals, the one or more user terminals each include a calculation unit for calculating the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector, and a communication unit for sending the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio to the base station, and the base station further includes a scheduling unit for controlling scheduling on the basis of the maximum signal- to-noise ratio and information relating to the transmit weight vector received from the one or more user terminals.
  • a base station of a radio system supporting opportunistic beamforming wherein more than one transmit weight vector sequence is used at the same scheduling time intervals, the base station communicating with one or more user ter- minals.
  • the base station includes: a communication unit for providing information relating to at least two transmit weight vector sequences to one or more user terminals of the radio system, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; a receiving unit for receiving the maximum signal-to-noise ratio of calculated expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector from the one or more user terminals; a receiving unit for receiving information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio from the one or more user terminals; and a scheduling unit for controlling scheduling on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector received from the one or more user terminals.
  • a user terminal of a radio system supporting opportunistic beamforming wherein more than one transmit weight vector sequence is used at the same scheduling time interval, the user terminal communicating with at least one base sta- tion.
  • the user terminal includes: a communication unit for receiving information from a base station relating to at least two transmit weight vector sequences, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; a calculation unit for calculating the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector; a communication unit for sending the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio to the base station for enabling the base station to control scheduling on the basis of the sent maximum signal-to-noise ratio and information relating to the transmit weight vector.
  • a computer program product encoding a computer program of instructions for executing a computer process for data transmission method in a radio system supporting opportunistic beamforming, wherein more than one transmit weight vector sequence is used at the same scheduling time interval, the process comprising: providing information relating to at least two transmit weight vector sequences to one or more user terminals of the radio system, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; receiving the maximum signal- to-noise ratio of calculated expected signal-to-noise ratios of the one or more user terminals and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio of the one or more user terminals; and controlling scheduling on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector received from the one or more user terminals.
  • a computer program product encoding a computer program of instructions for executing a computer process for data transmission method in a radio system supporting opportunistic beamforming, wherein more than one transmit weight vector sequence is used at the same scheduling time interval, the process comprising: receiving information relating to at least two transmit weight vector sequences, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; calculating the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector; and sending the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio to the base station for enabling scheduling control, by the base station, on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector.
  • an integrated circuit that is configured to: provide information relating to at least two transmit weight vector sequences to one or more user terminals of the radio system, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; receive maximum signal-to-noise ratio of calculated expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector from the one or more user terminals; receive information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio from the one or more user terminals; and control scheduling on the basis of the maximum signal-to- noise ratio and information relating to the transmit weight vector received from the one or more user terminals.
  • an integrated circuit that is configured to: receive information from a base station relating to at least two transmit weight vector sequences, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; calculate the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector; send the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maxi- mum signal-to-noise ratio to the base station for enabling the base station to control scheduling on the basis of the sent maximum signal-to-noise ratio and information relating to the transmit weight vector.
  • Multiuser transmission can be taken into account in scheduling and radio system structure where a set of orthogonal weight vector sequences is applied. Transmission resources are saved, and more capacity can be obtained in the radio system. Packet de- lay can be shortened. Embodiments can be easily applied to any antenna configurations.
  • Figure 1 illustrates a radio system to which embodiments of the invention can be applied
  • Figure 2 illustrates another example of a radio system to which embodiments of the invention can be applied
  • Figure 3 illustrates a system model for opportunistic beamforming according to prior art
  • Figure 4 illustrates an example of a system model for opportunistic multiuser beamforming according to an embodiment of the invention.
  • Figure 5 illustrates an example of a method in a radio system sup- porting opportunistic beamforming according to an embodiment.
  • a radio system in Figure 1 represents the third-generation radio systems.
  • the embodiments are, however, not restricted to these systems described by way of example, but a person skilled in the art can apply the instructions to other radio systems containing corresponding characteristics.
  • the embodiments of the invention can be applied, for example, to future Broadband Wireless Access (BWA), 3.9G LTE (Long Term Evolution) and 4G systems.
  • BWA Broadband Wireless Access
  • 3.9G LTE Long Term Evolution
  • 4G systems 4G systems.
  • the user terminal 170 can be, for example, user equipment, a portable communication device, a mobile computer, a mobile phone, or basically any device with a receiver/transmitter in the radio system.
  • the main parts of a radio system are a core network (CN) 100, a radio access network 130 and user equipment (UE) 170.
  • the term UTRAN is short for UMTS Terrestrial Radio Access Network, i.e. the radio access network 130 belongs to the third generation and is implemented by wideband code division multiple access (WCDMA) technology.
  • WCDMA wideband code division multiple access
  • Figure 1 also shows a base station system 160 which belongs to the 2/2.5 generation and is implemented by time division multiple access (TDMA) technology, but it is not fur- ther described here.
  • the radio system can also be defined to comprise user equipment, which is also known as a subscriber terminal and mobile phone, for instance, and a network part, which comprises the fixed infrastructure of the radio system, i.e. the core network, radio access network and base station system.
  • the structure of the core network 100 corresponds to a combined structure of the GSM and GPRS systems.
  • the GSM network elements are responsible for establishing circuit-switched connections, and the GPRS network elements are responsible for establishing packet-switched connections; some of the network elements are, however, in both systems.
  • the base station system 160 comprises a base station controller (BSC) 166 and base transceiver stations (BTS) 162, 164.
  • BSC base station controller
  • BTS base transceiver stations
  • the base station controller 166 controls the base transceiver station 162, 164.
  • the aim is that the devices implementing the radio path and their functions reside in the base transceiver station 162, 164, and control devices reside in the base station controller 166.
  • the base station controller 166 takes care of the following tasks, for instance: radio resource management of the base transceiver station 162, 164, intercell handovers, frequency control, i.e. frequency allocation to the base transceiver stations 162, 164, management of frequency hopping sequences, time delay measurement on the uplink, implementation of the operation and maintenance interface, and power control.
  • the base transceiver station 162, 164 contains at least one transceiver, which provides one carrier, i.e. eight time slots, i.e. eight physical chan- nels. Typically, one base transceiver station 162, 164 serves one cell, but it is also possible to have a solution in which one base transceiver station 162, 164 serves several sectored cells. The diameter of a cell can vary from a few meters to tens of kilometers.
  • the base transceiver station 162, 164 also comprises a transcoder, which converts the speech-coding format used in the radio system to that used in the public switched telephone network and vice versa. In practice, the transcoder is, however, physically located in the mobile services switching center.
  • the tasks of the base transceiver station 162, 164 include: calculation of timing advance (TA), uplink measurements, channel coding, encryption, decryption, and frequency hopping.
  • the radio access network 130 is made up of radio network subsystems 140, 150.
  • Each radio network subsystem 140, 150 is made up of radio network controllers 146, 156 and B nodes 142, 144, 152, 154.
  • a B node is a rather abstract concept, and often the term base transceiver station is used instead.
  • the radio network controller 140, 150 corresponds approximately to the base station controller 166 of the GSM system
  • the B node 142, 144, 152, 154 corresponds approximately to the base transceiver station 162, 164 of the GSM system. Solutions also exist in which the same device is both the base transceiver station and the B node, i.e. said device is capable of implementing both the TDMA and the WCDMA radio interface si- multaneously.
  • the user equipment 170 may comprise mobile equipment (ME) 172 and a UMTS subscriber identity module (USIM) 174.
  • USIM 174 contains information related to the user and information related to information security in particular, for instance, an encryption algorithm.
  • the user equipment 170 can be simultaneously connected with a plurality of base transceiver stations (Node B) in occurrence of soft handover.
  • the most important interfaces between network elements are the Iu interface between the core network and the radio access network, which is divided into the interface IuCS on the circuit-switched side and the interface IuPS on the packet-switched side, and the Uu interface between the radio access network and the user equipment.
  • the most important interfaces are the A interface between the base station controller and the mobile services switching center, the Gb interface between the base station con- trailer and the serving GPRS support node, and the Um interface between the base transceiver station and the user equipment.
  • the interface defines what kind of messages different network elements can use in communicating with each other.
  • the aim is to provide a radio system in which the network elements of different manufacturers interwork well so as to provide an effective radio system. In practice, some of the interfaces are, however, vendor- dependent.
  • the radio system supports opportunistic beamforming wherein more than one transmit weight vector sequence is used at the same scheduling time interval.
  • the radio system of Figure 2 comprises a base station 200 and one or more user terminals 170, 180.
  • the base station includes a communication unit
  • the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals.
  • the one or more user terminals 170, 180 each include a calculation unit 178, 188 for calculating the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector.
  • the signal-to-noise ratios are calculated on the basis of the information relating to the transmit weight vector sequences received from the base station 200.
  • the one or more user terminals 170, 180 each further include a communication unit 176, 186 for sending the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio to the base station 200.
  • the base station 200 further comprises a scheduling unit 206 that is configured to control scheduling on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector received from the one or more user terminals 170, 180.
  • the transmit weight vector sequences are retrieved from a memory of the user terminal 170, 180 when information relating to at least two transmit weight vector sequences is received from the base sta- tion 200.
  • a primary transmit weight vector sequence is stored in a memory of the user terminal 170, 180, and the transmit weight vector sequences can be generated on the basis of the primary transmit weight vector sequence when information relating to at least two transmit weight vector sequences is received from the base station.
  • the calculated expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector are defined as: where SNR n is a signal-to-noise ratio of n's transmit weight vector sequence (n is 1 , 2, ..., K), yt n m ⁇ t) is m's transmit weight vector of M transmit weight vectors of n's transmit weight vector sequence at scheduling time interval t, and h m (t) is m's channel response vector at scheduling time interval t.
  • each user terminal 170, 180 may then calculate signal-to-noise ratios relating to two transmit weight vector sequences: and 2
  • the user terminal 170, 180 may determine the maximum signal-to-noise ratio of the calculated signal-to-noise ratios, and send feedback to the base station 200 accordingly. For example, if 53VR 1 > 53VR 2 , then the feedback to the base station 200 can be: (1 , SNRi). Correspondingly, if 53VR 1 is not greater than 53VR 2 , then the feedback to the base station 200 can be: (2,
  • the better signal-to-noise ratio is signaled to the base station 200 with the information relating to the transmit weight vector corresponding to that signal-to-noise ratio.
  • the scheduling unit 206 may then decide, for example, to select the user terminal 170, 180 with the best signal-to-noise ratio for transmission.
  • the transmit weight vector corresponding to the highest signal-to-noise ratio can be used in transmission.
  • the base station 200 then exe- cutes weight control by using the transmit weight vector corresponding to the maximum signal-to-noise ratio of the selected user terminal 170, 180.
  • the information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio sent to the base station 200 is an index number associated with the transmit weight vector.
  • Figure 4 illustrates an example of a system model for opportunistic beamforming according to an embodiment.
  • the upper part of Figure 4 marked with dashed lines 460 illustrates the estimation of signal-to-noise ratio that is executed by all active user terminals during each scheduling time interval.
  • the exemplary system structure can be applied to both uncorrelated and correlated transmit antennas.
  • the base station transmitter part for pilots 302 comprises multiple antennas 310, 312, 314 that are configured to transmit the same signal from each antenna to a receiver 330 of the user terminal.
  • the base station further comprises a unit for generating orthogonal pilots 410 and common pilot units 412, 414, 416.
  • a common/dedicated pilot structure 412, 414, 416 similar to UTRA FDD (UMTS terrestrial radio access, frequency division duplex) is intra- prised, where a common pilot is transmitted as a cell-wise and dedicated pilot is transmitted as an antenna-wise.
  • UTRA FDD UMTS terrestrial radio access, frequency division duplex
  • the basic difference between the common pilots and the dedicated pilots is that the common pilots are used without transmit weights while the transmit weights are used in the dedi- cated pilot channels.
  • the use of dedicated pilots is, however, optional.
  • the transmit weights are not applied on the common pilot channels but the transmit weights are used on data channels.
  • the antenna weights are changed with a pseudo-random manner using weight sequences.
  • Both the transmitter and the receiver are equipped with the transmit weight information.
  • both ends know the sequence of the transmit weights.
  • the information on the transmit weight sequences can be provided to the user terminals, for example, in the following manner: a user terminal requests a certain service from a base station when a packet connection is being initialized, the numbers or other indicators of the applied transmit weight sequences are send to the user terminal if the service is granted, and the user terminal receiver retrieves the transmit weight vectors corresponding to the sequence numbers from a user terminal memory (alternative weight sequences can be stored in the user terminal memory beforehand).
  • a weight vector sequence controller 420 can control the functions relating to retrieving the transmit weight vectors or calculating them, on the basis of the number or the other indicator of the applied transmit weight sequence.
  • the user terminal may also know the number of the transmit weight in the sequence for a certain scheduling time interval. This information can be made available on some downlink broadcast control channel. Such a number can also be given when initializing the connection.
  • the user terminal is able to begin data detection.
  • orthogonal common pilots are applied on M antennas 310, 312, 314 for enabling the estimation of channels between the user terminal and the M transmit antennas 310, 312, 314.
  • the user terminal can compute the expected signal-to-noise ratios corresponding to any future scheduling time interval by applying the transmit weight sequences.
  • the signal-to noise ratios can be calculated in an SNR calculation unit 338.
  • the receiver can in advance: estimate signal-to-noise ratios corresponding to future transmit time intervals, order or process in some other ways the resulting signal-to-noise ratios and decide - based on service data rate and delay requirements - suitable transmit time interval/signal-to-noise ratio pairs.
  • the channel estimation can be performed on the basis of the common pilots or jointly on the basis of both common and dedicated pilots. Since the mobile receiver knows the transmit weights of the next scheduling time interval in advance, the receiver can estimate the signal-to-noise ratio corresponding to the next scheduling time interval efficiently by using the latest channel information (estimated from common pilots). The base station then has the relevant SNR information at the beginning of each scheduling time interval and the performance of the scheduling procedure remains robust, i.e. the base station can transmit data to those mobile receivers that are in good receiving conditions.
  • the receiver does not have to send SNR feedback during each scheduling time interval if the detected SNR is low.
  • Occasional feedback can be convoyed in uplink packet channels, such as random access channel.
  • the receiver knows the most suitable transmit weights long before they are applied in the base station. The receiver can then be switched off during the waiting times. Further, depending on the signal-to-noise ratio estimations and service needs, the user terminal can suspend the feedback 346 transmission when needed. When a dedicated data transmission arrives, the user terminal can utilize both common and dedicated pilots in joint channel estimation. This enables robust data detection.
  • the signal-to-noise ratios corresponding to the next scheduling time interval can now be reliably estimated. This improves the scheduling performance at the beginning of each scheduling time interval.
  • Channel estimation is more robust since filtering techniques can be utilized better (channel fluctuations due to the changes in transmit weights can be taken into account better).
  • Feedback capacity need is smaller since feedback transmission can be sus- pended from time to time. It is possible to shut off the user terminal receiver from time to time if the channel is stationary or the transmit antennas admit high mutual correlation.
  • a pseudorandom transmit weight sequence may be of the form:
  • w(t) is the transmit weight vector at a scheduling time interval t.
  • This vector contains M components if there are M transmit antennas.
  • T is the length of a sequence time period.
  • the scheduling time interval (STI) can contain one or more transmit time intervals (TTI) and the transmit weight vector is changed after each scheduling time interval.
  • the transmit weight sequence W is known in both the transmitter (here the base station) and the receiver (here the user terminal), and channel estimation is performed from common pilots.
  • SNR is a signal-to-noise ratio
  • w m (f) is a transmit weight vector at a scheduling time interval t
  • h m is a channel response vector of the user terminal.
  • the user terminal then sends the SNR or a corresponding data rate request to the base station scheduler 316.
  • the packet delay can become intolerable and the scheduler 316 may decide to execute the transmission in bad channel conditions.
  • the system efficiency is poor and interference in the network increases.
  • M orthogonal beams can be formed in an M- antenna system.
  • the transmit weight vector is selected according to the index n 0 .
  • the base station does not actually transmit the weight sequences W ⁇ ,...,W M that are used to determined the signal-to-noise values. Instead, the sequences are generated in the user terminals according to a common rule, and the base station only applies the optimum transmit weight vector to the selected user terminal.
  • the system structure of an embodiment where both the base station and the user terminal know the applied transmit weight vectors in advance can be beneficially used especially in broadband wireless access (BWA) systems with nomadic mobility.
  • the user terminal may predict the achievable data rates (or corresponding SNRs) in advance and send this information to the base station scheduler 316.
  • Multiple transmit weight sequences that are known in both ends guarantee a certain minimum performance level and data rate predictions (that are optional) can help the base station to schedule user terminals efficiently from the radio system point of view.
  • the orthogonal common pilots are applied on M antennas for enabling the estimation of channels between the user terminal and M transmit an- tennas.
  • the user terminal can compute the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector (w 1 (t),...,w k ( ⁇ ). Also future signal-to-noise ratios can be computed since the transmit weight vectors (w 1 (t + 5 r ),...,w Jf (t + 5 r )) are known for any time shift s.
  • the resulting signal-to-noise ratios and the index n 0 can be sent to a base station transmitter for data 304 to the scheduler 316 via a feedback channel 346.
  • the index n 0 348 is provided to the weight control unit 322.
  • the data streams are transmitted via an en- coder/modulator unit 318 to a unit 320 that forms signal replicas for transmission.
  • the use of dedicated pilots 400, 402, 404 is optional.
  • a weight control unit 322 controls the transmit weights in different antennas 324, 326, 328.
  • the user terminal receiver 332 receives the transmitted data streams and the data is processed in a channel estimation unit 342 and in a demodula- tion/decoding unit 344.
  • a weight-tracking unit 406 in the receiver 322 knows the applied transmit weight and the channel estimation can therefore be performed from common pilots or jointly from both common and dedicated pilots.
  • Figure 5 illustrates an example of a method in a radio system supporting opportunistic beamforming according to an embodiment.
  • the method starts in 500.
  • information relating to at least two transmit weight vector sequences is provided to one or more user terminals.
  • the transmit weight vectors of the at least two transmit weight vector sequences are orthogonal at the same scheduling time intervals.
  • expected signal-to-noise ratios corresponding to each pos- sible orthogonal transmit weight vector sequence of the at least two transmit weight vector sequences are calculated by the two or more user terminals.
  • the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio is sent to the base station.
  • scheduling is controlled on the basis of the maximum signal- to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio received from the one or more user terminals. The method ends in 510.
  • the scheme of opportunistic closed-loop transmit diversity always gives the same performance as the selection over M orthogo- nal weight vectors.
  • the method according to an embodiment enables avoiding situations where a signal-to-noise ratio of a certain user terminal remains at a low level for a long time. This will also shorten the packet delay.
  • the orthogonal transmit weight vectors there is no waiting time either. Instead, opportunism is used in a tradeoff between a feedback requirement and performance.
  • M transmission antennas and M orthogonal transmit weight vectors the lowest performance corresponds to that of an antenna selection between M antennas. Hence, bad transmission times can be avoided and increased performance can be achieved.
  • the embodiments of the invention may be realized in an electronic device, comprising a controller.
  • the controller may be configured to perform at least some of the steps described in connection with the flowchart of Figure 5 and in connection with Figures 2 and 4.
  • the embodiments may be imple- mented as a computer program comprising instructions for executing a computer process for a method in a radio system supporting opportunistic beam- forming, wherein more than one transmit weight vector sequences at the same scheduling time interval is used.
  • the computer process comprises: providing information relating to at least two transmit weight vector sequences to one or more user terminals of the radio system, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; receiving the maximum signal-to-noise ratio of calculated expected signal-to-noise ratios of the one or more user terminals and information relating to the transmit weight vector corresponding to the maxi- mum signal-to-noise ratio of the one or more user terminals; and controlling scheduling on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector received from the one or more user terminals.
  • the computer process comprises: receiving information relating to at least two transmit weight vector sequences, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; calculating the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector; and sending the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight veo tor corresponding to the maximum signal-to-noise ratio to the base station for enabling scheduling control, by the base station, on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector.
  • the computer program may be stored on a computer program distribution medium readable by a computer or a processor.
  • the computer pro- gram medium may be, for example but not limited to, an electric, magnetic, optical, infrared or semiconductor system, device or transmission medium.
  • the computer program medium may include at least one of the following media: a computer readable medium, a program storage medium, a record medium, a computer readable memory, a random access memory, an erasable program- mable read-only memory, a computer readable software distribution package, a computer readable signal, a computer readable telecommunications signal, computer readable printed matter, and a computer readable compressed software package.
  • the embodiments of the invention may be realized in an integrated circuit that can be included in a base station or in a user terminal. It is also possible that the integrated circuit is included in a separate module outside the base station/user terminal.
  • the integrated circuit is configured to: provide information relating to at least two transmit weight vector sequences to one or more user terminals of the radio system, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; receive maximum signal-to-noise ratio of calculated expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector from the one or more user terminals; receive information relating to the transmit weight vector corresponding to the maxi- mum signal-to-noise ratio from the one or more user terminals; and control scheduling on the basis of the maximum signal-to-noise ratio and information relating to the transmit weight vector received from the one or more user terminals.
  • the integrated circuit is configured to: receive information from a base station relating to at least two transmit weight vector sequences, the transmit weight vectors of the at least two transmit weight vector sequences being orthogonal at the same scheduling time intervals; calculate the expected signal-to-noise ratios corresponding to each possible orthogonal transmit weight vector; send the maximum signal-to-noise ratio of the calculated signal-to-noise ratios and information relating to the transmit weight vector corresponding to the maximum signal-to-noise ratio to the base station for enabling the base station to control scheduling on the basis of the sent maximum signal-to-noise ratio and information relating to the transmit weight vector.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Système radio prenant en charge la formation de faisceaux opportuniste, le système radio comprenant une station de base et un ou plusieurs terminaux utilisateurs. La station de base comprend une unité de communication destinée à fournir des informations relatives à au moins deux séquences vectorielles de pondération de transmission vers un ou plusieurs terminaux utilisateurs du système radio, les un ou plusieurs terminaux utilisateurs comprenant chacun une unité de calcul destinée à calculer les rapports signal/bruit escomptés correspondant à chaque vecteur de pondération de transmission orthogonale possible, et une unité de communication destinée à envoyer vers la station de base le rapport signal/bruit maximal des rapports signal/bruit calculés et des informations relatives au vecteur de pondération de transmission correspondant au rapport signal/bruit maximal. La station de base comprend en outre une unité de programmation destinée à contrôler la programmation sur la base du rapport signal/bruit maximal et des informations relatives au vecteur de pondération de transmission reçu depuis les un ou plusieurs terminaux utilisateurs.
PCT/FI2006/050332 2006-07-11 2006-07-11 Procédé, système radio, station de base et terminal utilisateur Ceased WO2008006930A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/FI2006/050332 WO2008006930A1 (fr) 2006-07-11 2006-07-11 Procédé, système radio, station de base et terminal utilisateur

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/FI2006/050332 WO2008006930A1 (fr) 2006-07-11 2006-07-11 Procédé, système radio, station de base et terminal utilisateur

Publications (1)

Publication Number Publication Date
WO2008006930A1 true WO2008006930A1 (fr) 2008-01-17

Family

ID=38922970

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2006/050332 Ceased WO2008006930A1 (fr) 2006-07-11 2006-07-11 Procédé, système radio, station de base et terminal utilisateur

Country Status (1)

Country Link
WO (1) WO2008006930A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101835191A (zh) * 2010-04-19 2010-09-15 新邮通信设备有限公司 载波聚合通信系统的上行载波调度方法、基站和用户设备
CN104378832A (zh) * 2014-12-09 2015-02-25 江苏省邮电规划设计院有限责任公司 一种lte资源调度方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004036791A1 (fr) * 2002-10-19 2004-04-29 Samsung Electronics Co., Ltd. Appareil et procede de communication mobile comprenant une station de base et une station mobile a antennes multiples
US20050003768A1 (en) * 2003-01-23 2005-01-06 Rajiv Laroia Methods and apparatus of providing transmit diversity in a multiple access wireless communication system
US20050130664A1 (en) * 2003-12-10 2005-06-16 Nec Laboratories America, Inc. Scheduling method with tunable throughput maximization and fairness guarantees in resource allocation
EP1608120A2 (fr) * 2004-06-16 2005-12-21 Samsung Electronics Co., Ltd. Procédé de transmission et réception de données dans un système de communication mobile OFDMA
US20060056451A1 (en) * 2004-08-27 2006-03-16 Takashi Yano Method for allocating subchannel in wireless network

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004036791A1 (fr) * 2002-10-19 2004-04-29 Samsung Electronics Co., Ltd. Appareil et procede de communication mobile comprenant une station de base et une station mobile a antennes multiples
US20050003768A1 (en) * 2003-01-23 2005-01-06 Rajiv Laroia Methods and apparatus of providing transmit diversity in a multiple access wireless communication system
US20050130664A1 (en) * 2003-12-10 2005-06-16 Nec Laboratories America, Inc. Scheduling method with tunable throughput maximization and fairness guarantees in resource allocation
EP1608120A2 (fr) * 2004-06-16 2005-12-21 Samsung Electronics Co., Ltd. Procédé de transmission et réception de données dans un système de communication mobile OFDMA
US20060056451A1 (en) * 2004-08-27 2006-03-16 Takashi Yano Method for allocating subchannel in wireless network

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101835191A (zh) * 2010-04-19 2010-09-15 新邮通信设备有限公司 载波聚合通信系统的上行载波调度方法、基站和用户设备
CN104378832A (zh) * 2014-12-09 2015-02-25 江苏省邮电规划设计院有限责任公司 一种lte资源调度方法
CN104378832B (zh) * 2014-12-09 2017-09-05 江苏省邮电规划设计院有限责任公司 一种lte资源调度方法

Similar Documents

Publication Publication Date Title
JP5542144B2 (ja) Ｍｉｍｏベースの複数基地局協調通信のための方法および装置
CN101411239B (zh) 无线通信系统、无线基站装置和无线终端装置
KR101727016B1 (ko) 상향 링크에서의 다중 사용자 간섭 정렬 시스템 및 방법
EP3926854A1 (fr) Support de signalisation pour la sélection d'antennes au moyen de listes et de masques de sous-ensemble
CN101026405A (zh) 无线通信方法、基站及无线通信系统
CN101002492A (zh) 信号传输时分配传输容量的方法、基站和移动终端设备
KR100957413B1 (ko) 무선 이동 통신 시스템에서 간섭 제거를 위한 장치 및 방법그리고 그 시스템
JP6663256B2 (ja) 無線通信システム及び管理装置
TWI538428B (zh) 在網路中通信的方法、副站台及主站台
KR20140098509A (ko) 무선 통신 시스템에서 스트림 별 채널 이득 피드백을 통한 다중 스트림 mu-cqi 추정 방법 및 장치
JP2010288252A (ja) 無線通信システム、無線基地局装置、制御装置および無線端末装置
KR100929088B1 (ko) 무선 이동 통신 시스템에서 전송 모드 결정 장치 및 방법
CN102724726B (zh) Lte系统中tm8内mimo方式切换的方法及装置
JP6598104B2 (ja) 端末、基地局、無線通信システム及び回線状態情報取得方法
US12250037B2 (en) Beamforming setting selection
JP4677990B2 (ja) 通信制御方法、移動通信システム、基地局及び回線制御局
WO2008006930A1 (fr) Procédé, système radio, station de base et terminal utilisateur
JP7094376B2 (ja) 推定された干渉レベルに従ったアップリンク測定信号および対応するアップリンク送信ビームの信号強度のスケーリング
JP5010730B2 (ja) 無線通信方法
KR101997822B1 (ko) 다중셀 협력통신 시스템에서 협력적 신호 전송 방법
WO2018131335A1 (fr) Terminal, station de base, système de communication sans fil et procédé d'acquisition d'informations d'état de canal
EP2943003A1 (fr) Déploiement de station de base à petites cellules dans des réseaux cellulaires
JP2022080672A (ja) 複数のビーム形成手法を用いて通信する通信装置、通信方法、およびプログラム
WO2008006932A1 (fr) Procédé, système radio, station de base et terminal utilisateur
JP5367870B2 (ja) 無線通信方法、無線通信システム及び無線基地局装置

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 06778522

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

NENP Non-entry into the national phase

Ref country code: RU

122 Ep: pct application non-entry in european phase

Ref document number: 06778522

Country of ref document: EP

Kind code of ref document: A1