WO2015180026A1 - Methods and devices for transmitting/receiving long term channel state information in wireless communication networks - Google Patents

Methods and devices for transmitting/receiving long term channel state information in wireless communication networks Download PDF

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Publication number
WO2015180026A1
WO2015180026A1 PCT/CN2014/078445 CN2014078445W WO2015180026A1 WO 2015180026 A1 WO2015180026 A1 WO 2015180026A1 CN 2014078445 W CN2014078445 W CN 2014078445W WO 2015180026 A1 WO2015180026 A1 WO 2015180026A1
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WIPO (PCT)
Prior art keywords
csi
long term
groups
dividing
term csi
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PCT/CN2014/078445
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French (fr)
Inventor
Gang Wang
Chuangxin JIANG
Chaofeng LI
Zhennian SUN
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Nec Corporation
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Priority to PCT/CN2014/078445 priority Critical patent/WO2015180026A1/en
Publication of WO2015180026A1 publication Critical patent/WO2015180026A1/en

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Classifications

    • 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
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0027—Scheduling of signalling, e.g. occurrence thereof
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
    • H04L5/0057—Physical resource allocation for CQI
    • 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
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0026—Transmission of channel quality indication
    • 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
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0028—Formatting
    • H04L1/0031—Multiple signaling transmission

Definitions

  • Example embodiments of the present invention relate generally to the wireless communication, and more specifically, to method and device for transmitting/receiving long term channel state information in wireless communication networks.
  • CSI channel state information
  • MU-MIMO multi-user multiple-input- multiple-output
  • the technique of CSI aware scheduling allows scheduling a user in some resource with less fading or interference.
  • the technique of link adaptation allows selecting most proper coding and modulation scheme depending on CSI, and then make full of the resource.
  • the technique of MU-MIMO enables serving multiple users in same time-frequency resource by employing degreed of freedom in spatial domain.
  • One key factor to enable these techniques is the availability of CSI.
  • the channel state information is usually measured at the receiver side.
  • the CSI required for DL scheduling in a cellular network is usually measured by a user equipment (UE), and then transmitted to a base station (e.g., Evolved Node B, eNB).
  • UE user equipment
  • eNB Evolved Node B
  • CSI enables the techniques for spectrum efficiency improvement, such as link adaptation, MU-MIMO, its transmission also consumes both uplink and downlink resources.
  • the base station usually needs to inform UE, via a downlink (DL) channel, about the uplink (UL) resources to be used for the CSI transmission.
  • design of the CSI report scheme has to take into account both the benefit and the cost, to achieve a balance.
  • CSI feedback schemes are designed to support two-dimensional (2D) MIMO, and the CSI could be provided by UE includes rank indicator (RI), precoding matrix index (PMI), and channel quality indicator (CQI), which all represent horizontal characteristic of the wireless communication channel.
  • RI rank indicator
  • PMI precoding matrix index
  • CQI channel quality indicator
  • UE user equipment
  • the feedback process can be implemented in two steps as shown in Figure la, wherein a RI is reported in step 1 and a wideband CQI /PMI is reported in step 2 with a period of Np.
  • the feedback process can be implemented in three steps as shown in Figure lb, wherein a RI is reported in step 1, a wideband CQI /PMI is reported in step 2 and one or more UE selected subband CQI is reported in step 3.
  • LTE release 10 for 8 transmit antenna configuration, dual codebook is introduced where a precoder can be constructed based on multiplication of Wl which is long term or wideband channel information and W2 which is short term or subband channel information.
  • the feedback modes of release 8 are extended to provide the required feedback.
  • the feedback mode 2- 1 is extended via introducing an additional precoding type indicator (PTI), as shown in Figure 2.
  • PTI enables to transmit Wl to eNB only when PTI is set to zero, i.e., when significant variation in Wl has been detected; otherwise, wideband CQI and W2 are reported instead, thereby unnecessary transmission of Wl can be avoided.
  • PTI additional precoding type indicator
  • embodiments of the present invention provide a method for transmitting a long term channel state information (CSI) from a device in a wireless network, the method comprises dividing the long term CSI to be reported into M groups, wherein M is an integer larger thanl, and transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, such that the transmission period of the long term CSI is larger than or equal to M times of the period configured for the second CSI, and a dedicated signaling for configuring resource for the transmission of the long term CSI is avoided.
  • M channel state information
  • dividing the long term CSI to be reported into M groups is performed based on a parameter configuration signaling from a second device, and/or based on predefinition. In another embodiment of the invention, dividing the long term CSI to be reported into M groups is performed based on at least payload size of the second CSI.
  • duplicating each of the L groups for N times comprises duplicating each of the L groups based on a predefined repetition pattern.
  • the long term CSI indicates vertical domain CSI for 3-dimension (3D) multiple-input-multiple-output (MIMO) operation.
  • the second CSI indicates at least one of RI, PMI and CQI specified in current Long Term Evolution (LTE) or LTE-Advanced standard.
  • embodiments of the present invention provide a method for receiving a long term channel state information CSI from a device in a wireless network, wherein the long term CSI is divided into M groups and transmitted in M resources configured for transmission of a second CSI according to a method of the first aspect of the invention, the method for receiving the long term CSI comprises receiving a group of the long term CSI in each of the M resources, and combining the received groups to obtain a complete long term CSI.
  • the method further comprises transmitting a signaling to the device, to configure a parameter required for the operation of dividing the long term CSI into M groups at the device.
  • combining the received groups to obtain a complete long term CSI comprises combining the received groups using a weight vector which is determined based on a predefined repetition pattern.
  • embodiment of the present invention provides a corresponding device which implements the methods described in the first aspect.
  • embodiments of the present invention provide a corresponding device which implements the methods described in the second aspect.
  • FIG. la is a schematic diagram of CSI feedback mode 1-1 in LTE Release 8;
  • FIG. lb is a schematic diagram of CSI feedback mode 2-1 in LTE Release 8;
  • FIG.2 is a schematic diagram of CSI feedback mode 2-1 in LTE Release 10 for 8 transmit antenna scenarios
  • FIG.3 is a schematic diagram of wireless network where an embodiment of the invention can be implemented
  • FIG.4a is a flow chart of a method for transmitting a long term CSI, according to an embodiment of the invention.
  • FIG.4b is a diagram showing distribution of UE geometry in a cellular network
  • FIG.5a-5d are schematic illustration showing examples of a method for transmitting a long term CSI, according to an embodiment of the invention.
  • FIG.6 is a flow chart of a method for receiving a long term CSI, according to an embodiment of the invention.
  • FIG.7 is a block diagram of a device for transmitting a long term CSI, according to an embodiment of the invention.
  • FIG.8 is a block diagram of a device for receiving a long term CSI, according to an embodiment of the invention.
  • Fig.9 illustrates simulation results of the long term CSI using a method according to an embodiment of the invention
  • references in the specification to "one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that the singular forms “a”, “an” and “the” include plural referents unless the context explicitly indicates otherwise.
  • the wireless network 300 comprises one or more network nodes 301, here in the form of evolved Node B, also known as eNode Bs or eNBs.
  • the network nodes 301 could also be in the form of Node Bs, BTSs (Base Transceiver Stations), BS (Base Station) and/or BSSs (Base Station Subsystems), etc.
  • the network nodes 301 provide radio connectivity to a plurality of user equipments (UEs) 302.
  • UEs user equipments
  • the term user equipment is also known as mobile communication terminal, wireless terminal, mobile terminal, user terminal, user agent, machine-to-machine devices etc., and can be, for example, what today is commonly known as a mobile phone or a tablet/laptop with wireless connectivity or fixed mounted terminal.
  • the UEs 2 may, but do not need to, be associated with a particular end user.
  • the wireless network 300 is described to be a 3 GPP LTE network, the embodiments of the present invention are not limited to such network scenarios and the proposed methods and devices can also be applied to other wireless networks, e.g., a non-cellular network, where similar requirement for long term CSI feedback exists and the principles described hereinafter are applicable.
  • the network nodes e.g., eNB 301 will require CSI to perform efficient scheduling.
  • the CSI required for DL scheduling is usually reported by UEs periodically based on configuration, or reported aperiodically based on request from eNB.
  • the periodic CSI feedback utilizes physical uplink control channel (PUCCH) resources, and UEs are assigned PUCCH resources via configuration signaling which indicates, for example, periodicity, time offset, etc., for each type of CSI report including precoding matrix index(PMI), rank indicator (RI), channel quality indicator (CQI). Due to different time-varying characteristic of long term PMI, short term PMI, RI and CQI, the periodicity configured for each CSI report type can be different to save signaling overhead.
  • PMI precoding matrix index
  • RI rank indicator
  • CQI channel quality indicator
  • CSIs may be required to support these new features, e.g., vertical domain CSI may be required to enable 3D-MIMO. It can be contemplated that if the base station need to configure UEs on feedback resources and periodicity, etc., for a newly introduced CSI, the signaling overhead and the required resource for such signaling may increase significantly, moreover, if UEs need to report the new CSI in additional feedback resources, the consumed resources will be further increased.
  • channel state information has very slow time-varying characteristic, i.e., no significant change may occur in a related short time duration. For example, it may be unnecessary to report vertical domain PMI with a period shorter than that configured for any existing CSI in LTE/LTE-A, e.g. RI,PMI or CQI.
  • each physical channel has its transmission capacity, which can be represented by a payload size that can be transmitted with satisfying performance.
  • the PUCCH type II channel used for periodic CSI feedback can convey 5 bits without introducing obvious reliability loss, thus the payload size of 5 bits can be considered as the capacity of the PUCCH type II channel.
  • the RI feedback only has a payload of 2 or 3 bits depending on the number of antenna ports.
  • the payload size is 4 bits which is still 1 bit less than the capacity can be supported by PUCCH channel. Then it will be beneficial if the remaining capacity of a PUCCH channel configured for a CSI feedback can be reused for carrying another CSI, such that avoiding dedicated resource configuration for the another CSI.
  • FIG. 4a illustrates a flow chart for an example method 400, performed by a device, e.g., a UE 302 in Figure 3, for transmitting long term channel state information CSI from a device in a wireless network.
  • the method 400 comprises a step 401 for dividing a long term CSI into M groups, wherein M is an integer larger than 1; and a step 402 for transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, by reusing the remaining capacity of this resource, such that the transmission period of the long term CSI is larger than or equal to M times of the second CSI's period.
  • the parameter(s), e.g., the value of M, or the number of bits per group, required for performing the dividing operation in step 401 is determined based on configuration signaling from a second device, and/or predefinition.
  • the value of M, or, the number of bits per group can be determined based on configuration signaling from eNB.
  • the method 400 may further comprise an additional step 411 for receiving the parameter configuration signaling, related to the dividing operation in step 401, from eNB.
  • the value of M, or, the number of bits per group is predefined, e.g., specified in a communication standard.
  • the parameter of M or, the number of bits per group can be determined by a combination of the signaling and the predefinition, e.g., a set of values for M is predefined, then based on the position of a UE, an eNB can evaluate the maximum payload that can be supported by a feedback channel, then configure the value of M by selecting a proper value from the set, to guarantee satisfying transmission performance.
  • the eNB may also configure total payload size of long term CSI, in some embodiments. It should be noted that such configuration can be common among UEs or can be UE-specific.
  • the parameter(s), e.g., the value of M, or the number of bits per group, required for performing the dividing operation in step 401 is determined based on at least the payload size of the second CSI which is transmitted jointly with the long term CSI in step 402.
  • the value of M can be determined by taking into account total payload which can be supported by the feedback channel (i.e., the resources configured for transmission of the second CSI), and the payload already occupied by the second CSI.
  • the second CSI (e.g., RI in 8Tx feedback submode 2 of mode 1-1 ) includes 3 bits, there are still 2 bits can be transmitted together with the second CSI in the same feedback channel.
  • the second CSI e.g., RI in 8Tx feedback submode 2 of mode 1-1
  • it can be divided into 2 groups with 2 bits per group, as shown in an example of Figure 5a.
  • the total payload can be supported is 5 bits and the second CSI includes 4 bits (e.g., RI+PTI), then there is only 1 bit can be transmitted together with the second CSI in the same feedback channel.
  • the 4 bits long term CSI can be divided into 4 groups, leaving only 1 bit per group, as shown in an example of Figure 5b.
  • 5 bits are assumed to be the total payload can be supported due to the observation a PUCCH channel can carry 5bits without introducing obvious reliability loss, however, it would be understood by those skilled in the art that other suitable values can also be used depending on the performance requirement and/or the channel utilized for transmission.
  • the second CSI can also be any other suitable CSI type than what has been shows here as examples, e.g., it can be CQI and/or PMI.
  • the distributed transmission of a single long term CSI in multiple groups may increase the feedback error probability for UEs with low signal to interference plus noise power ratio (SINR), since only when every group is received correctly, the complete long term CSI can be detected properly.
  • SINR signal to interference plus noise power ratio
  • error rate of a long term CSI transmitted according to some of the embodiments of the invention described above may be high.
  • the number of UEs with very low SINR is very small, as can be seen from the UE geometry distribution in Figure 4b.
  • the long term CSI can be fedback according to another embodiment of the invention described in the following.
  • L is an integer larger than equal to 1
  • N is an integer equal to or larger than 2.
  • the first group is transmitted, then repeated, and followed by the second group and its repetition, and so on.
  • Such implementation is based on the observation that feedback period of some long term CSI, e.g., a vertical domain CSI, can be much larger than that of horizontal domain CSI, then each vertical domain CSI can be repeated for multiple times in one vertical CSI period to increase feedback reliability.
  • the period of vertical domain CSI can be equal or larger than T_p*L*N with L and N defined as above.
  • Such implementation enables the long term CSI to be transmitted with repetition in each period, thereby improves transmission performance by employing diversity gain.
  • duplicating the L groups of the long term CSI to obtain totally M groups comprises duplicating each of the L groups based on a predefined repetition pattern.
  • the repetition pattern may have a length of N and indicate a weight to be applied to each of the N times of repetition.
  • a repletion pattern of "1 1 1 1” may indicate repeating of 4 times and each repetition equals the original information
  • a repetition pattern of "1 -1” may represent repeating of 2 times with a weight of -1 applied to the second repetition.
  • the parameter e.g., parameter of L or N
  • the parameter required for performing the duplication can be determined based on configuration signaling from a base station, predefinition, or a combination thereof.
  • the long term CSI indicates vertical domain CSI for 3D-MIMO operation.
  • the long term CSI may indicate other CSI types which may be required in current or future communication system.
  • the second CSI may indicate any suitable CSI, for example but not limited to, RI, PMI and CQI specified in current 3GPP LTE/LTE-A standard.
  • transmitting each of the M groups jointly with a second CSI in step 402 means encoding and modulating the long term CSI jointly with the second CSI, then the resulting symbols are transmitted together in a resource configured for the second CSI.
  • the long term CSI and the second CSI are encoded and modulated separately, and then transmitted together using same resource configured for the second CSI.
  • the resource configured for the second CSI can be a physical uplink control channel (PUCCH) in LTE, but the embodiments are not limited to this.
  • FIG. 6 illustrates a flow chart for an example method 600, performed by a device, e.g., a base station 301 in Figure 3, for receiving a long term channel state information CSI from a second device in a wireless network, wherein the long term CSI is transmitted according to a method described with reference to Figures 4 and 5a-5d and method 400.
  • the method 600 comprises a step 601 for receiving a group of the long term CSI in each of the M resources, and a step 602 for combining the received groups to obtain a complete long term CSI.
  • the method 600 further comprises the step 611 for transmitting parameter configuration signaling to the second device which is the transmitter of the long term CSI, to configure, for example, the value of M, or number of bits per group of the long term CSI, and/or the total payload of long term CSI.
  • the signaling can be a common control signal, for example a signaling broadcast to all or a group of UEs, or a UE-specific dedicated signaling which enables specific configuration per UE.
  • step 602 the received groups of the long term CSI are combined using a weight vector which is determined based on a predefined repetition pattern. For example, if a repetition pattern of "1 -1" is used in step 401 of the transmission method 400, then in the step 602 of the method 600, same pattern can be used to obtain a weight vector of [1 -1] for combining the 2 repetitions.
  • the method 600 may further comprise a step 604 for adaptive configuration based on the detection results of the long term CSI. For example, if the repetition pattern is known to be "1 1 1 1", but the detected signals for the repeated transmissions before combination are "A A A B", then it can be determined that at least one repetition are not detected correctly, which means the second CSI transmitted together with it in last transmission may also be corrupted. Once such transmission failure is detected, in step 604, some actions may be taken to improve the feedback performance of the second CSI, e.g., trigger an aperiodic CSI feedback
  • example method 400 and example method 600 are described in the context of LTE/LTEA system, the embodiments of the present invention are not limited to such network scenarios and similar methods can also be applied to other wireless networks, e.g., a non-cellular network, or device-to-device communication network, as long as similar requirement for long term CSI feedback exists.
  • wireless networks e.g., a non-cellular network, or device-to-device communication network
  • FIG. 7 illustrates a block diagram of a device 700 according to an embodiment of the present invention.
  • the device 700 according to Figure 7 can be a UE 302 in Figure 3, and may perform the example methods described with reference to Figures 4 and 5a-5b but is not limited to these methods. Then any feature presented above, e.g., in the description with reference to Figures 4 and 5a-5d and method 400, if appropriate, can be applied to the device 700 presented below. It is to be noted that the methods described with reference to Figures 4 and 5a-5d may be performed by the device of Figure 7 but is not limited to being performed by this device 700.
  • the device 700 may be any wireless devices, for example a mobile phone, a laptop computer, etc.
  • the device 700 comprises at least a dividing unit 701 and a transmitting unit 702; the dividing unit 701 is configured for dividing a long term CSI to be reported into M groups, wherein M is an integer larger than 1, and the transmitting unit 702 is configured for transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, such that the transmission period of the long term CSI is larger than or equal to M times of the second CSI's period.
  • the dividing unit 701 is further configured for determining parameter(s), e.g., the value of M or the number of bits per group, based on configuration signaling from a second device, and/or predefinition.
  • the dividing unit 701 can determine the value of M, or, the number of bits per group based on configuration signaling from base station, and the configuration signaling can be received by the dividing unit 701, or another separate unit 711 not shown in Figure 7.
  • the value of M, or, the number of bits per group is predefined, e.g., specified in a communication standard, and the dividing unit 701 can determine the value based on the predefinition.
  • the dividing unit 701 can determine the parameter(s), e.g., M or, the number of bits per group based on a combination of the signaling and the predefinition. For example, a set of values for M is predefined, then based on the position of a UE, a base station can evaluate the maximum payload that can be supported by a feedback channel, then configure the value of M by selecting a proper value from the set to guarantee satisfying transmission performance. In such case, the dividing unit 701 can determine the parameter(s) based on the predefined set and a configuration signaling which indicate which value in the set should be used.
  • M the parameter(s)
  • the configuration signaling may also indicate other parameters, like report periodicity, totally payload size of the long term CSI, etc., and the configuration signaling can be common for all or a group of UEs, or UE- specific.
  • the dividing unit 701 can determine the parameter(s) based on at least the payload size of the second CSI which is transmitted jointly with the long term CSI by the transmitting unit 702. For example, the dividing unit 701 can determine the parameter(s) by taking into account total payload which can be supported by the feedback channel (i.e., the resources configured for transmission of the second CSI), and the payload already occupied by the second CSI. Assuming the total payload can be supported is 5 bits and the second CSI (e.g., RI) includes 3 bits, then there are still 2 bits can be transmitted together with the second CSI in the same feedback channel.
  • the feedback channel i.e., the resources configured for transmission of the second CSI
  • the payload already occupied by the second CSI Assuming the total payload can be supported is 5 bits and the second CSI (e.g., RI) includes 3 bits, then there are still 2 bits can be transmitted together with the second CSI in the same feedback channel.
  • the total payload can be supported is 5 bits and the second CSI includes 4 bits (e.g., RI+PTI), then there is only 1 bit can be transmitted together with the second CSI in the same feedback channel.
  • L is an integer equal to or larger than 1
  • N is an integer equal to or larger than 2.
  • the repetition operation in the dividing unit 701 also enables to detect at the receiver side some transmission failure in the second CSI which may trigger the receiver to take some actions to improve the feedback performance, e.g., can configure open-loop transmission scheme, for example, spatial frequency block coding (SFBC), to avoid feedback, or can configure additional PUCCH resources for the long term CSI feedback.
  • SFBC spatial frequency block coding
  • the dividing unit 701 is further configured to duplicate each of the L groups based on a predefined repetition pattern.
  • the repetition pattern may have a length of N and indicate a weight vector to be applied to each of the N times of repetition as discussed with reference to method 400, and then details will be omitted here.
  • the parameter required for the dividing unit 701 to perform duplicating it can be determined similarly as discussed above with reference to the parameter M, i.e., it can be determined based on configuration signaling from a base station, predefinition, or a combination thereof.
  • the long term CSI divided by the dividing unit 701 and transmitted by the transmitting unit 702 indicates vertical domain CSI to support 3D-MIMO operation.
  • the long term CSI can indicate other CSI which may be required in current or future communication system.
  • the transmitting unit 702 is configured to encode and modulate the long term CSI jointly with the second CSI, and to transmit the resulting symbols in a resource configured for the second CSI.
  • the transmitting unit 702 is configured to encode and modulate the long term CSI and the second CSI separately, then transmit them together using same resource configured for the second CSI.
  • the resource configured for the second CSI and used for transmission of the long term CSI can be a physical uplink control channel (PUCCH) in LTE, but the embodiments are not limited to this.
  • PUCCH physical uplink control channel
  • the methods can be applied to other wireless networks, e.g., a non-cellular network or a device-to-device communication, and the resources configured for the second CSI can also be other channels than the PUCCH channel mentioned above.
  • FIG 8 illustrates a block diagram of a device 800 according to an embodiment of the present invention.
  • the device 800 according to Figure 8 can be a base station 301 in Figure 3, and may perform the example methods described with reference to Figure 6 but is not limited to these methods. Then any feature presented above, e.g., in the description with reference to Figure 6, if appropriate, can be applied to the device 800 presented below. It is to be noted that the methods described with reference to Figure 6 may be performed by the device of Figure 8 but is not limited to being performed by this device 800.
  • the device 800 may be, for example, a macro base station, eNB, a small cell base station, a relay node, an access point (AP), etc.
  • AP access point
  • the device 800 comprises at least a receiving unit 801 and a combination unit 802.
  • the receiving unit 801 is configured for receiving a group of the long term CSI in each of the M resources from a second device
  • the combination unit 802 is configured for combining the received groups to obtain a complete long term CSI.
  • the long term CSI can be transmitted using a method described with reference to Figure 4a and method 400.
  • the device 800 further comprises configuration unit 803 for transmitting signaling to the second device, i.e., the transmitter of the long term CSI, to configure the parameter required for dividing/repetition operation (e.g., a value of M, or a number of bits per group) of the long term CSI.
  • the parameter required for dividing/repetition operation e.g., a value of M, or a number of bits per group
  • the combination unit 802 is configured to combine the received groups of the long term CSI using a weight vector which is determined based on a predefined repetition pattern. For example, if a repetition pattern of "1 -1" is used in step 401 of the transmission method 400, then the combination unit 802 can be configured to use a weight vector of [1 -1] for combining the 2 repetitions.
  • the device 800 may further comprise an adaptation unit 804, configured to perform adaptive configuration based on the detection results of the long term CSI. For example, if some transmission failure is detected by the receiving unit 801, or combination unit 801, e.g., based on the knowledge of repetition pattern, the adaptation unit 804 can be configured to take actions to improve the performance, e.g., to trigger an aperiodic CSI feedback.
  • Scheme 4 4 bits divided into 4 groups and each group transmitted jointly with a 4 bits CSI;
  • Scheme 5 4 bits divided into 2 groups and each group transmitted jointly with a 3 bits CSI;
  • Scheme 6 4 bits divided into 4 groups and each group repeated for 3 times to get totally 12 groups, then each group is transmitted jointly with a 4 bits CSI;
  • Scheme 7 4 bits divided into 4 groups and each group repeated for 4 times to get totally 16 groups, then each group is transmitted jointly with a 4 bits CSI.
  • each of the seven curves indicate performance of one of schemes respectively.
  • schemes 1 to 3 are prior art feedback solutions used for comparison, while the schemes 4 to 7 are methods according to some embodiments of the invention.
  • the schemes 4 and 5 can achieve better performance than that of scheme 3, which is a transmission with the maximum payload(ll bits) supported by PUCCH according to current LTE specification.
  • scheme 1 which is 4 bits CSI transmission according to current LTE specification.
  • the embodiments of the invention enables to transmit additional long term CSI with satisfying performance by utilizing remaining capacity of current CSI feedback resource, and avoid dedicated resource for the additional long term feedback.
  • each block in the flow charts or block diagrams could represent a part of a module, a program segment, or code, where the part of the module, program segment, or code comprises one or more executable instructions for implementing a prescribed logic function.
  • each block in a block diagram and/or a flow chart, and a combination of the blocks in the block diagram and/or flow chart could be implemented by software, hardware, firmware, or any of their combinations.
  • function of a block can also be implemented by multiple blocks, and functions of multiple blocks shown in Figures 7-8 may also be implemented by a single block in other embodiments.
  • the example embodiments can store information relating to various processes described herein, e.g., store the measured CSI, the received indicator etc.
  • the components of the example embodiments can include computer readable storage medium or memories according to the teachings of the present inventions and for holding data structures, tables, records, and/or other data described herein, or the program codes for implementing any of the methods according to the embodiments of the invention.

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Abstract

Embodiments of the present invention provide methods and devices for transmitting a long term channel state information CSI to support 3-dimension (3D) multiple-input-multiple-output (MIMO) operation in a wireless network. The method comprising dividing the long term CSI to be reported into M groups, wherein M is an integer larger than1, and transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, such that the transmission period of the long term CSI is larger than or equal to M times of the period configured for the second CSI, and a dedicated signaling for configuring resource for the transmission of the long term CSI is avoided. Corresponding methods and devices for receiving the long term CSI which is transmitted using above method are also disclosed.

Description

METHODS AND DEVICES FOR TRANSMITTING/RECEIVING LONG TERM CHANNEL STATE INFORMATION IN WIRELESS COMMUNICATION NETWORKS
FIELD OF THE INVENTION
[0001] Example embodiments of the present invention relate generally to the wireless communication, and more specifically, to method and device for transmitting/receiving long term channel state information in wireless communication networks.
BACKGROUND OF THE INVENTION
[0002] In wireless communication, the demand for data rate keeps increasing but the time-frequency resources are limited, thus it is always an important object in wireless communication to increase spectrum efficiency (SE). There are many well-known techniques proposed for this purpose, including channel state information (CSI) aware scheduling, link adaptation and multi-user multiple-input- multiple-output (MU-MIMO). The technique of CSI aware scheduling allows scheduling a user in some resource with less fading or interference. The technique of link adaptation allows selecting most proper coding and modulation scheme depending on CSI, and then make full of the resource. The technique of MU-MIMO enables serving multiple users in same time-frequency resource by employing degreed of freedom in spatial domain. One key factor to enable these techniques is the availability of CSI.
[0003] The channel state information is usually measured at the receiver side. For example, the CSI required for DL scheduling in a cellular network is usually measured by a user equipment (UE), and then transmitted to a base station (e.g., Evolved Node B, eNB). Though CSI enables the techniques for spectrum efficiency improvement, such as link adaptation, MU-MIMO, its transmission also consumes both uplink and downlink resources. For example, to obtain a CSI report, the base station usually needs to inform UE, via a downlink (DL) channel, about the uplink (UL) resources to be used for the CSI transmission. Thus, design of the CSI report scheme has to take into account both the benefit and the cost, to achieve a balance.
[0004] In current specification of the third generation project partnership (3GPP) Long Term Evolution (LTE), for example, 36.213 cOO, CSI feedback schemes are designed to support two-dimensional (2D) MIMO, and the CSI could be provided by UE includes rank indicator (RI), precoding matrix index (PMI), and channel quality indicator (CQI), which all represent horizontal characteristic of the wireless communication channel. Moreover, to enable frequency selective scheduling, a user equipment (UE) in LTE can be requested to report wideband CSI and/or sub-band CSI via specific CSI feedback mode configuration. For example, in LTE release 8, for feedback model-1, the feedback process can be implemented in two steps as shown in Figure la, wherein a RI is reported in step 1 and a wideband CQI /PMI is reported in step 2 with a period of Np. For feedback mode 2-1, the feedback process can be implemented in three steps as shown in Figure lb, wherein a RI is reported in step 1, a wideband CQI /PMI is reported in step 2 and one or more UE selected subband CQI is reported in step 3.
[0005] In LTE release 10, for 8 transmit antenna configuration, dual codebook is introduced where a precoder can be constructed based on multiplication of Wl which is long term or wideband channel information and W2 which is short term or subband channel information. Correspondingly, to support the dual codebook precoding operation, the feedback modes of release 8 are extended to provide the required feedback. For example, the feedback mode 2- 1 is extended via introducing an additional precoding type indicator (PTI), as shown in Figure 2. The PTI enables to transmit Wl to eNB only when PTI is set to zero, i.e., when significant variation in Wl has been detected; otherwise, wideband CQI and W2 are reported instead, thereby unnecessary transmission of Wl can be avoided. Thus to avoid unnecessary updating of the long term Wl. However, there are some problems in such design. First, when PTI=0, no subband CQI and W2 can be reported, then frequency-selective scheduling gain will be reduced. Second, when PTI=0, one transmission of wideband CQI and wideband W2 is replaced with transmission of Wl, then wideband CQI and W2 can not be updated timely in some case, and it may result in improper precoding or cause interference.
[0006] In the embodiments of the present invention, methods and devices which can solve the above problems and enable efficient transmission of long term CSI are provided. Moreover, in future wireless networks, e.g., in later release of 3GPP LTE, more advanced features may be adopted and more CSI may be required to be reported. For example, to enable 3-dimension (3D) MIMO operation, vertical domain CSI may need to be transmitted to the base station. The methods and devices provided herein can be applied to the future CSI reporting as long as similar problems occur.
SUMMARY OF THE INVENTION
[0007] Various embodiments of the invention aim at addressing at least part of the above problems and disadvantages. Other features and advantages of embodiments of the invention will also be understood from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the invention.
[0008] Various aspects of embodiments of the invention are set forth in the appended claims and summarized in this section. It shall be noted that the protection scope of the invention is only limited by the appended claims.
[0009] According to a first aspect of the invention, embodiments of the present invention provide a method for transmitting a long term channel state information (CSI) from a device in a wireless network, the method comprises dividing the long term CSI to be reported into M groups, wherein M is an integer larger thanl, and transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, such that the transmission period of the long term CSI is larger than or equal to M times of the period configured for the second CSI, and a dedicated signaling for configuring resource for the transmission of the long term CSI is avoided.
[0010] In accordance with some embodiments of the invention, dividing the long term CSI to be reported into M groups is performed based on a parameter configuration signaling from a second device, and/or based on predefinition. In another embodiment of the invention, dividing the long term CSI to be reported into M groups is performed based on at least payload size of the second CSI.
[0011] According to an embodiment of the invention, dividing a long term CSI to be reported into M groups further comprises dividing the long term CSI to be reported into L groups, and duplicating each of the L groups for N times, to obtain totally M groups, wherein M=LxN, and L is an integer equal to or larger than 1, and N is an integer equal to or larger than 2. In a further embodiment of the invention, duplicating each of the L groups for N times comprises duplicating each of the L groups based on a predefined repetition pattern.
[0012] In an embodiment of the invention, the long term CSI indicates vertical domain CSI for 3-dimension (3D) multiple-input-multiple-output (MIMO) operation.
[0013] In an embodiment of the invention, the second CSI indicates at least one of RI, PMI and CQI specified in current Long Term Evolution (LTE) or LTE-Advanced standard.
[0014] According to a second aspect of the invention, embodiments of the present invention provide a method for receiving a long term channel state information CSI from a device in a wireless network, wherein the long term CSI is divided into M groups and transmitted in M resources configured for transmission of a second CSI according to a method of the first aspect of the invention, the method for receiving the long term CSI comprises receiving a group of the long term CSI in each of the M resources, and combining the received groups to obtain a complete long term CSI.
[0015] In some embodiments of the invention, the method further comprises transmitting a signaling to the device, to configure a parameter required for the operation of dividing the long term CSI into M groups at the device.
[0016] In an further embodiment of the invention, combining the received groups to obtain a complete long term CSI comprises combining the received groups using a weight vector which is determined based on a predefined repetition pattern.
[0017] According to a third aspect, embodiment of the present invention provides a corresponding device which implements the methods described in the first aspect.
[0018] According to a fourth aspect, embodiments of the present invention provide a corresponding device which implements the methods described in the second aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other aspects, features, and benefits of various embodiments of the invention will become more fully apparent, by way of example, from the following detailed description and the accompanying drawings, in which like reference numerals refer to the same or similar elements:
[0020] FIG. la is a schematic diagram of CSI feedback mode 1-1 in LTE Release 8;
[0021] FIG. lb is a schematic diagram of CSI feedback mode 2-1 in LTE Release 8;
[0022] FIG.2 is a schematic diagram of CSI feedback mode 2-1 in LTE Release 10 for 8 transmit antenna scenarios;
[0023] FIG.3 is a schematic diagram of wireless network where an embodiment of the invention can be implemented;
[0024] FIG.4a is a flow chart of a method for transmitting a long term CSI, according to an embodiment of the invention;
[0025] Fig.4b is a diagram showing distribution of UE geometry in a cellular network;
[0026] FIG.5a-5d are schematic illustration showing examples of a method for transmitting a long term CSI, according to an embodiment of the invention;
[0027] FIG.6 is a flow chart of a method for receiving a long term CSI, according to an embodiment of the invention;
[0028] FIG.7 is a block diagram of a device for transmitting a long term CSI, according to an embodiment of the invention; and
[0029] FIG.8 is a block diagram of a device for receiving a long term CSI, according to an embodiment of the invention.
[0030] Fig.9 illustrates simulation results of the long term CSI using a method according to an embodiment of the invention
DETAILED DESCRIPTION OF EMBODIMENTS
[0031] Some preferred embodiments will be described in more detail with reference to the accompanying drawings, in which the preferred embodiments of the present disclosure have been illustrated. However, the present disclosure can be implemented in various manners, and thus should not be construed to be limited to the embodiments disclosed herein. On the contrary, those embodiments are provided for thorough and complete understanding of the present disclosure, and completely conveying the scope of the present disclosure to those skilled in the art.
[0032] In the following description, numerous specific details of embodiments of the present invention are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. Those of ordinary skills in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation.
[0033] References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that the singular forms "a", "an" and "the" include plural referents unless the context explicitly indicates otherwise. [0034] Reference is now made to Figure 3 which is a diagram of an example wireless network scenario where a method according to an embodiment of the present invention can be applied. The wireless network 300 comprises one or more network nodes 301, here in the form of evolved Node B, also known as eNode Bs or eNBs. The network nodes 301 could also be in the form of Node Bs, BTSs (Base Transceiver Stations), BS (Base Station) and/or BSSs (Base Station Subsystems), etc. The network nodes 301 provide radio connectivity to a plurality of user equipments (UEs) 302. The term user equipment is also known as mobile communication terminal, wireless terminal, mobile terminal, user terminal, user agent, machine-to-machine devices etc., and can be, for example, what today is commonly known as a mobile phone or a tablet/laptop with wireless connectivity or fixed mounted terminal. Moreover, the UEs 2 may, but do not need to, be associated with a particular end user. Though for illustrative purpose, the wireless network 300 is described to be a 3 GPP LTE network, the embodiments of the present invention are not limited to such network scenarios and the proposed methods and devices can also be applied to other wireless networks, e.g., a non-cellular network, where similar requirement for long term CSI feedback exists and the principles described hereinafter are applicable.
[0035] In the network 300 depicted in Figure 3, the network nodes, e.g., eNB 301 will require CSI to perform efficient scheduling. The CSI required for DL scheduling is usually reported by UEs periodically based on configuration, or reported aperiodically based on request from eNB. In LTE/LTEA, the periodic CSI feedback utilizes physical uplink control channel (PUCCH) resources, and UEs are assigned PUCCH resources via configuration signaling which indicates, for example, periodicity, time offset, etc., for each type of CSI report including precoding matrix index(PMI), rank indicator (RI), channel quality indicator (CQI). Due to different time-varying characteristic of long term PMI, short term PMI, RI and CQI, the periodicity configured for each CSI report type can be different to save signaling overhead.
[0036] With the advance of wireless communication, more and more new features may be adopted, and more CSIs may be required to support these new features, e.g., vertical domain CSI may be required to enable 3D-MIMO. It can be contemplated that if the base station need to configure UEs on feedback resources and periodicity, etc., for a newly introduced CSI, the signaling overhead and the required resource for such signaling may increase significantly, moreover, if UEs need to report the new CSI in additional feedback resources, the consumed resources will be further increased.
[0037] It has been observed that some channel state information has very slow time-varying characteristic, i.e., no significant change may occur in a related short time duration. For example, it may be unnecessary to report vertical domain PMI with a period shorter than that configured for any existing CSI in LTE/LTE-A, e.g. RI,PMI or CQI.
[0038] Furthermore, it should be noted that each physical channel has its transmission capacity, which can be represented by a payload size that can be transmitted with satisfying performance. For example, in LTE/LTE-A, the PUCCH type II channel used for periodic CSI feedback can convey 5 bits without introducing obvious reliability loss, thus the payload size of 5 bits can be considered as the capacity of the PUCCH type II channel. It has been observed that in current LTE-A specification (36.213 v.cOO), many CSI feedback type does not reach the PUCCH capacity. For example, the RI feedback only has a payload of 2 or 3 bits depending on the number of antenna ports. Taking subband feedback of 8ports in LTE-A as an example, the payload size is 4 bits which is still 1 bit less than the capacity can be supported by PUCCH channel. Then it will be beneficial if the remaining capacity of a PUCCH channel configured for a CSI feedback can be reused for carrying another CSI, such that avoiding dedicated resource configuration for the another CSI.
[0039] Based on such observations, in present invention, methods and devices are provided to transmit/receive long term CSI in an efficient manner, which can minimize the configuration signaling overhead, resource consumption and impact on existing short term CSI report.
[0040] Reference is not made to Figure 4a, which illustrates a flow chart for an example method 400, performed by a device, e.g., a UE 302 in Figure 3, for transmitting long term channel state information CSI from a device in a wireless network. The method 400 comprises a step 401 for dividing a long term CSI into M groups, wherein M is an integer larger than 1; and a step 402 for transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, by reusing the remaining capacity of this resource, such that the transmission period of the long term CSI is larger than or equal to M times of the second CSI's period.
[0041] In accordance with some embodiments of the invention, the parameter(s), e.g., the value of M, or the number of bits per group, required for performing the dividing operation in step 401, is determined based on configuration signaling from a second device, and/or predefinition. As one example, the value of M, or, the number of bits per group can be determined based on configuration signaling from eNB. In such an example, the method 400 may further comprise an additional step 411 for receiving the parameter configuration signaling, related to the dividing operation in step 401, from eNB. As another example, the value of M, or, the number of bits per group is predefined, e.g., specified in a communication standard. Alternatively, the parameter of M or, the number of bits per group can be determined by a combination of the signaling and the predefinition, e.g., a set of values for M is predefined, then based on the position of a UE, an eNB can evaluate the maximum payload that can be supported by a feedback channel, then configure the value of M by selecting a proper value from the set, to guarantee satisfying transmission performance. Besides the value for M, the eNB may also configure total payload size of long term CSI, in some embodiments. It should be noted that such configuration can be common among UEs or can be UE-specific.
[0042] According to another embodiment of the invention, the parameter(s), e.g., the value of M, or the number of bits per group, required for performing the dividing operation in step 401, is determined based on at least the payload size of the second CSI which is transmitted jointly with the long term CSI in step 402. For example, the value of M can be determined by taking into account total payload which can be supported by the feedback channel (i.e., the resources configured for transmission of the second CSI), and the payload already occupied by the second CSI. Assuming the total payload can be supported is 5 bits and the second CSI (e.g., RI in 8Tx feedback submode 2 of mode 1-1 ) includes 3 bits, there are still 2 bits can be transmitted together with the second CSI in the same feedback channel. In such case, for a long term CSI with 4 bits, it can be divided into 2 groups with 2 bits per group, as shown in an example of Figure 5a. As another example, if the total payload can be supported is 5 bits and the second CSI includes 4 bits (e.g., RI+PTI), then there is only 1 bit can be transmitted together with the second CSI in the same feedback channel. In such case, the 4 bits long term CSI can be divided into 4 groups, leaving only 1 bit per group, as shown in an example of Figure 5b. Here, 5 bits are assumed to be the total payload can be supported due to the observation a PUCCH channel can carry 5bits without introducing obvious reliability loss, however, it would be understood by those skilled in the art that other suitable values can also be used depending on the performance requirement and/or the channel utilized for transmission. It should also be noted that the second CSI can also be any other suitable CSI type than what has been shows here as examples, e.g., it can be CQI and/or PMI.
[0043] In the example embodiments described above, by dividing the long term CSI into groups and transmitting each part jointly with another existing CSI which has shorter reporting period, dedicated resource for transmitting of the long term CSI, as well as the corresponding signaling for configuring the dedicated resource, can be avoided. Moreover, since only part of the long term CSI is transmitted together with an existing CSI, the payload to be transmitted can be kept low and the impact on transmission performance of the existing CSI, i.e., the second CSI, can be minimized. However, it should be noted that the distributed transmission of a single long term CSI in multiple groups may increase the feedback error probability for UEs with low signal to interference plus noise power ratio (SINR), since only when every group is received correctly, the complete long term CSI can be detected properly. For UEs which have very low SINR, error rate of a long term CSI transmitted according to some of the embodiments of the invention described above may be high. Fortunately, the number of UEs with very low SINR is very small, as can be seen from the UE geometry distribution in Figure 4b. For UEs with very low SINR, the long term CSI can be fedback according to another embodiment of the invention described in the following.
[0044] In one embodiment of the invention, to support UEs with low SINR, in step 401, the long term CSI is divided into M groups by dividing the long term CSI to be reported into L groups and then duplicating each of the L groups for N times to obtain totally M=LxN groups, wherein L is an integer larger than equal to 1 and N is an integer equal to or larger than 2. In Figures 5c-5d, two examples of duplicating are illustrated. In both examples, L=4 and N=2. In Figure 5c, the L=4 groups are transmitted in order, and then the 4 groups are repeated. In Figure 5d, the first group is transmitted, then repeated, and followed by the second group and its repetition, and so on.
[0045] Such implementation is based on the observation that feedback period of some long term CSI, e.g., a vertical domain CSI, can be much larger than that of horizontal domain CSI, then each vertical domain CSI can be repeated for multiple times in one vertical CSI period to increase feedback reliability. In such case, the period of vertical domain CSI can be equal or larger than T_p*L*N with L and N defined as above.
[0046] Such implementation enables the long term CSI to be transmitted with repetition in each period, thereby improves transmission performance by employing diversity gain. Besides this, the above repetition method also enables to detect at the receiver side some transmission failure in the second CSI which is transmitted jointly with the long term CSI in step 402. For example, assuming N=4, i.e., each group of information will be transmitted for 4 times, then if the receiver detects significant difference in the four transmissions before combination, for example, the four received signals are "A A A B", then the receiver (e.g., the eNB) can judge that at least one repetition is not detected correctly, which means the second CSI transmitted together with it in the last transmission may also be corrupted. Once such transmission failure is detected, it may trigger the receiver to take some actions, e.g., in an additional step 412, to improve the feedback performance of the second CSI, e.g., trigger an aperiodic CSI feedback. [0047] In one further embodiment, duplicating the L groups of the long term CSI to obtain totally M groups comprises duplicating each of the L groups based on a predefined repetition pattern. The repetition pattern may have a length of N and indicate a weight to be applied to each of the N times of repetition. For example, a repletion pattern of "1 1 1 1" may indicate repeating of 4 times and each repetition equals the original information, and a repetition pattern of "1 -1" may represent repeating of 2 times with a weight of -1 applied to the second repetition. Similar as what discussion above on determining a value for M, the parameter (e.g., parameter of L or N) required for performing the duplication can be determined based on configuration signaling from a base station, predefinition, or a combination thereof.
[0048] In some embodiments of the invention, the long term CSI indicates vertical domain CSI for 3D-MIMO operation. In some other embodiments, the long term CSI may indicate other CSI types which may be required in current or future communication system. Similarly, the second CSI may indicate any suitable CSI, for example but not limited to, RI, PMI and CQI specified in current 3GPP LTE/LTE-A standard.
[0049] In accordance with one embodiment of the invention, transmitting each of the M groups jointly with a second CSI in step 402 means encoding and modulating the long term CSI jointly with the second CSI, then the resulting symbols are transmitted together in a resource configured for the second CSI. In other embodiments, the long term CSI and the second CSI are encoded and modulated separately, and then transmitted together using same resource configured for the second CSI. According to an embodiment of the invention, the resource configured for the second CSI can be a physical uplink control channel (PUCCH) in LTE, but the embodiments are not limited to this.
[0050] It should also be noted that though in above examples, some embodiments are described in a LTE/LTEA environment, but the embodiments of the present invention are not limited to this. For example, the methods can be applied to other wireless networks, and the resources configured for the second CSI can also be other channels than the PUCCH channel mentioned above.
[0051] Reference is now made to Figure 6, which illustrates a flow chart for an example method 600, performed by a device, e.g., a base station 301 in Figure 3, for receiving a long term channel state information CSI from a second device in a wireless network, wherein the long term CSI is transmitted according to a method described with reference to Figures 4 and 5a-5d and method 400. The method 600 comprises a step 601 for receiving a group of the long term CSI in each of the M resources, and a step 602 for combining the received groups to obtain a complete long term CSI.
[0052] In some embodiments of the invention, to achieve a common understanding on the division parameters of the long term CSI (for example, on how many groups the long term CSI should be divided before transmission), the method 600 further comprises the step 611 for transmitting parameter configuration signaling to the second device which is the transmitter of the long term CSI, to configure, for example, the value of M, or number of bits per group of the long term CSI, and/or the total payload of long term CSI. It should be noted that the signaling can be a common control signal, for example a signaling broadcast to all or a group of UEs, or a UE-specific dedicated signaling which enables specific configuration per UE.
[0053] According to an embodiment of the invention, in step 602, the received groups of the long term CSI are combined using a weight vector which is determined based on a predefined repetition pattern. For example, if a repetition pattern of "1 -1" is used in step 401 of the transmission method 400, then in the step 602 of the method 600, same pattern can be used to obtain a weight vector of [1 -1] for combining the 2 repetitions.
[0054] In another embodiment of the invention, the method 600 may further comprise a step 604 for adaptive configuration based on the detection results of the long term CSI. For example, if the repetition pattern is known to be "1 1 1 1", but the detected signals for the repeated transmissions before combination are "A A A B", then it can be determined that at least one repetition are not detected correctly, which means the second CSI transmitted together with it in last transmission may also be corrupted. Once such transmission failure is detected, in step 604, some actions may be taken to improve the feedback performance of the second CSI, e.g., trigger an aperiodic CSI feedback
[0055] It can be understand by those skilled in the art that though the example method 400 and example method 600 are described in the context of LTE/LTEA system, the embodiments of the present invention are not limited to such network scenarios and similar methods can also be applied to other wireless networks, e.g., a non-cellular network, or device-to-device communication network, as long as similar requirement for long term CSI feedback exists.
[0056] To be noted that in some alternative implementations, the functions indicated in the block diagrams could also occur in a sequence different from what is indicated in the figures. For example, two sequentially indicated blocks could be executed substantially in parallel or sometimes in an inversed order, depending on the functions as involved.
[0057] It is also to be understood that methods described with reference to Figures.4, 5a-5b and 6 can be implemented in various ways, by software, hardware, firmware, or any of their combinations, e.g., a processor, computer programming code stored in a computer readable storage media, etc.
[0058] Reference is now made to Figure 7, which illustrates a block diagram of a device 700 according to an embodiment of the present invention. The device 700 according to Figure 7 can be a UE 302 in Figure 3, and may perform the example methods described with reference to Figures 4 and 5a-5b but is not limited to these methods. Then any feature presented above, e.g., in the description with reference to Figures 4 and 5a-5d and method 400, if appropriate, can be applied to the device 700 presented below. It is to be noted that the methods described with reference to Figures 4 and 5a-5d may be performed by the device of Figure 7 but is not limited to being performed by this device 700. The device 700 may be any wireless devices, for example a mobile phone, a laptop computer, etc.
[0059] As shown in Figure 7, the device 700 comprises at least a dividing unit 701 and a transmitting unit 702; the dividing unit 701 is configured for dividing a long term CSI to be reported into M groups, wherein M is an integer larger than 1, and the transmitting unit 702 is configured for transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, such that the transmission period of the long term CSI is larger than or equal to M times of the second CSI's period.
[0060] In accordance with some embodiments of the invention, the dividing unit 701 is further configured for determining parameter(s), e.g., the value of M or the number of bits per group, based on configuration signaling from a second device, and/or predefinition. As one example, the dividing unit 701 can determine the value of M, or, the number of bits per group based on configuration signaling from base station, and the configuration signaling can be received by the dividing unit 701, or another separate unit 711 not shown in Figure 7. As another example, the value of M, or, the number of bits per group is predefined, e.g., specified in a communication standard, and the dividing unit 701 can determine the value based on the predefinition. Alternatively, the dividing unit 701 can determine the parameter(s), e.g., M or, the number of bits per group based on a combination of the signaling and the predefinition. For example, a set of values for M is predefined, then based on the position of a UE, a base station can evaluate the maximum payload that can be supported by a feedback channel, then configure the value of M by selecting a proper value from the set to guarantee satisfying transmission performance. In such case, the dividing unit 701 can determine the parameter(s) based on the predefined set and a configuration signaling which indicate which value in the set should be used. It should be noted that besides the parameter M, the configuration signaling may also indicate other parameters, like report periodicity, totally payload size of the long term CSI, etc., and the configuration signaling can be common for all or a group of UEs, or UE- specific.
[0061] According to another embodiment of the invention, the dividing unit 701 can determine the parameter(s) based on at least the payload size of the second CSI which is transmitted jointly with the long term CSI by the transmitting unit 702. For example, the dividing unit 701 can determine the parameter(s) by taking into account total payload which can be supported by the feedback channel (i.e., the resources configured for transmission of the second CSI), and the payload already occupied by the second CSI. Assuming the total payload can be supported is 5 bits and the second CSI (e.g., RI) includes 3 bits, then there are still 2 bits can be transmitted together with the second CSI in the same feedback channel. In such case, for a long term CSI with 4 bits, the dividing unit 701 can determine to use M=2 groups, and 2 bits per group, as shown in the example of Figure 5a. As another example, if the total payload can be supported is 5 bits and the second CSI includes 4 bits (e.g., RI+PTI), then there is only 1 bit can be transmitted together with the second CSI in the same feedback channel. In such case, the dividing unit 701 can determine to use M=4, leaving only 1 bit per group, as shown in the example of Figure 5b.
[0062] In one embodiment of the invention, the dividing unit 701 is configured to divide the long term CSI into M groups by dividing the long term CSI into L groups and then duplicating each of the L groups for N times to obtain totally M=LxN groups, wherein L is an integer equal to or larger than 1 and N is an integer equal to or larger than 2. Such implementation enables the long term CSI to be transmitted with repetition in each period, thereby improves transmission performance by employing diversity gain. Two examples of sue duplicating operation can be found in Figures 5c-5d. As described with reference to Figure 4a, besides transmission performance improvement of the vertical domain CSI, the repetition operation in the dividing unit 701 also enables to detect at the receiver side some transmission failure in the second CSI which may trigger the receiver to take some actions to improve the feedback performance, e.g., can configure open-loop transmission scheme, for example, spatial frequency block coding (SFBC), to avoid feedback, or can configure additional PUCCH resources for the long term CSI feedback.
[0063] In one further embodiment, the dividing unit 701 is further configured to duplicate each of the L groups based on a predefined repetition pattern. The repetition pattern may have a length of N and indicate a weight vector to be applied to each of the N times of repetition as discussed with reference to method 400, and then details will be omitted here. Regarding the parameter required for the dividing unit 701 to perform duplicating, it can be determined similarly as discussed above with reference to the parameter M, i.e., it can be determined based on configuration signaling from a base station, predefinition, or a combination thereof.
[0064] In some embodiments of the invention, the long term CSI divided by the dividing unit 701 and transmitted by the transmitting unit 702 indicates vertical domain CSI to support 3D-MIMO operation. In some other embodiments, the long term CSI can indicate other CSI which may be required in current or future communication system.
[0065] In accordance with one embodiment of the invention, the transmitting unit 702 is configured to encode and modulate the long term CSI jointly with the second CSI, and to transmit the resulting symbols in a resource configured for the second CSI. In other embodiments, the transmitting unit 702 is configured to encode and modulate the long term CSI and the second CSI separately, then transmit them together using same resource configured for the second CSI. According to an embodiment of the invention, the resource configured for the second CSI and used for transmission of the long term CSI can be a physical uplink control channel (PUCCH) in LTE, but the embodiments are not limited to this.
[0066] It should also be noted that though in above examples, some embodiments are described in a LTE environment, but the embodiments of the present invention are not limited to this. For example, the methods can be applied to other wireless networks, e.g., a non-cellular network or a device-to-device communication, and the resources configured for the second CSI can also be other channels than the PUCCH channel mentioned above.
[0067] Reference is now made to Figure 8, which illustrates a block diagram of a device 800 according to an embodiment of the present invention. The device 800 according to Figure 8 can be a base station 301 in Figure 3, and may perform the example methods described with reference to Figure 6 but is not limited to these methods. Then any feature presented above, e.g., in the description with reference to Figure 6, if appropriate, can be applied to the device 800 presented below. It is to be noted that the methods described with reference to Figure 6 may be performed by the device of Figure 8 but is not limited to being performed by this device 800. The device 800 may be, for example, a macro base station, eNB, a small cell base station, a relay node, an access point (AP), etc.
[0068] As shown in Figure 8, the device 800 comprises at least a receiving unit 801 and a combination unit 802. The receiving unit 801 is configured for receiving a group of the long term CSI in each of the M resources from a second device, and the combination unit 802 is configured for combining the received groups to obtain a complete long term CSI. The long term CSI can be transmitted using a method described with reference to Figure 4a and method 400.
[0069] In some embodiments of the invention, to achieve a common understanding on how many groups the long term CSI should be divided before transmission, the device 800 further comprises configuration unit 803 for transmitting signaling to the second device, i.e., the transmitter of the long term CSI, to configure the parameter required for dividing/repetition operation (e.g., a value of M, or a number of bits per group) of the long term CSI.
[0070] According to an embodiment of the invention, the combination unit 802 is configured to combine the received groups of the long term CSI using a weight vector which is determined based on a predefined repetition pattern. For example, if a repetition pattern of "1 -1" is used in step 401 of the transmission method 400, then the combination unit 802 can be configured to use a weight vector of [1 -1] for combining the 2 repetitions.
[0071] In another embodiment of the invention, the device 800 may further comprise an adaptation unit 804, configured to perform adaptive configuration based on the detection results of the long term CSI. For example, if some transmission failure is detected by the receiving unit 801, or combination unit 801, e.g., based on the knowledge of repetition pattern, the adaptation unit 804 can be configured to take actions to improve the performance, e.g., to trigger an aperiodic CSI feedback.
[0072] In Figure 9, some results obtained via computer simulation are presented to show performance can be obtained by using some embodiments of the invention, and the simulation parameters are listed blow in Table I.
Figure imgf000016_0001
Table I. Simulation parameters [0073] In Figure 9, results for the following 7 schemes are presented: [0074] Scheme 1 : 4 bits CSI, [0075] Scheme 2: 5 bits CSI, [0076] Scheme 3: 11 bits CQI,
[0077] Scheme 4: 4 bits divided into 4 groups and each group transmitted jointly with a 4 bits CSI;
[0078] Scheme 5: 4 bits divided into 2 groups and each group transmitted jointly with a 3 bits CSI;
[0079] Scheme 6: 4 bits divided into 4 groups and each group repeated for 3 times to get totally 12 groups, then each group is transmitted jointly with a 4 bits CSI;
[0080] Scheme 7: 4 bits divided into 4 groups and each group repeated for 4 times to get totally 16 groups, then each group is transmitted jointly with a 4 bits CSI.
[0081] Each of the seven curves indicate performance of one of schemes respectively. Among these schemes, schemes 1 to 3 are prior art feedback solutions used for comparison, while the schemes 4 to 7 are methods according to some embodiments of the invention. As can be observed, even without repetition, the schemes 4 and 5 can achieve better performance than that of scheme 3, which is a transmission with the maximum payload(ll bits) supported by PUCCH according to current LTE specification. With repetition introduced, the performance of 4 bits long term CSI is further improved, and error rate is even much lower than that of scheme 1, which is 4 bits CSI transmission according to current LTE specification. Thus, the embodiments of the invention enables to transmit additional long term CSI with satisfying performance by utilizing remaining capacity of current CSI feedback resource, and avoid dedicated resource for the additional long term feedback.
[0082] It should be noted that the flow charts and block diagrams in the figures illustrate the likely implemented architecture, functions, and operations of the system, method, and apparatus according to various embodiments of the present invention. In this point, each block in the flow charts or block diagrams could represent a part of a module, a program segment, or code, where the part of the module, program segment, or code comprises one or more executable instructions for implementing a prescribed logic function. It should also be noted that each block in a block diagram and/or a flow chart, and a combination of the blocks in the block diagram and/or flow chart could be implemented by software, hardware, firmware, or any of their combinations. Furthermore, it should be understood that in some embodiments, function of a block can also be implemented by multiple blocks, and functions of multiple blocks shown in Figures 7-8 may also be implemented by a single block in other embodiments.
[0083] The example embodiments can store information relating to various processes described herein, e.g., store the measured CSI, the received indicator etc. The components of the example embodiments can include computer readable storage medium or memories according to the teachings of the present inventions and for holding data structures, tables, records, and/or other data described herein, or the program codes for implementing any of the methods according to the embodiments of the invention.
[0084] While the present inventions have been described in connection with a number of example embodiments, and implementations, the present inventions are not so limited, but rather cover various modifications, and equivalent arrangements, which fall within the purview of prospective claims. It is also obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

Claims

WHAT IS CLAIMED IS:
1. A method for transmitting a long term channel state information (CSI) from a device in a wireless network, the method comprising:
- dividing the long term CSI to be reported into M groups, wherein M is an integer larger than 1; and
- transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, by reusing the remaining capacity of the one of the resources configured for transmission of the second CSI, such that the transmission period of the long term CSI is larger than or equal to M times of the period configured for the second CSI.
2. A method of Claim 1, wherein dividing the long term CSI to be reported into M groups is performed based on a parameter configuration signaling from a second device, and/or based on predefinition.
3. A method of Claim 1, wherein dividing the long term CSI to be reported into M groups is performed based on at least payload size of the second CSI.
4. A method of Claim 1, wherein dividing a long term CSI to be reported into M groups further comprising:
- dividing the long term CSI to be reported into L groups; and
- duplicating each of the L groups for N times, to obtain totally M groups, wherein M=LxN, and L is an integer equal to or larger than 1 and N is an integer equal to or larger than 2.
5. A method of Claim 4, wherein duplicating each of the L groups for N times comprising:
- duplicating each of the L groups based on a predefined repetition pattern.
6. A method of Claim 1, wherein the long term CSI indicates vertical domain CSI for 3-dimension (3D) multiple-input-multiple-output (MIMO) operation.
7. A method of any of Claims 1 to 6, wherein the second CSI indicates at least one of RI, PMI and CQI specified in current Long Term Evolution (LTE) or LTE- Advanced standard.
8. A method for receiving a long term channel state information CSI from a device in a wireless network, wherein the long term CSI is divided into M groups and transmitted in M resources configured for transmission of a second CSI by reusing the remaining capacity of the M resources according to a method of any of the Claims 1 to 7, the method for receiving the long term CSI comprising:
- receiving a group of the long term CSI in each of the M resources; and
- combining the received groups to obtain a complete long term CSI.
9. A method of Claim 8, further comprising:
- transmitting a signaling to the device, to configure a parameter required for the operation of dividing the long term CSI into M groups at the device.
10. A method of Claim 8 or 9, wherein combining the received groups to obtain a complete long term CSI comprising:
- combining the received groups using a weight vector which is determined based on a predefined repetition pattern.
11. A device for transmitting long term channel state information CSI in a wireless network, the device comprising:
- dividing unit, configured for dividing a long term CSI to be reported into M groups, wherein M is an integer larger than 1, and
- transmitting unit, configured for transmitting each of the M groups jointly with a second CSI, in one of the resources configured for transmission of the second CSI, by reusing the remaining capacity of the one of the resources configured for transmission of the second CSI, such that the transmission period of the long term CSI is larger than or equal to M times of the second CSI's period.
12. A device of Claim 11, wherein the dividing unit is further configured for:
- dividing the long term CSI to be reported into M groups based on a parameter configuration signaling from a second device, and/or based on predefinition.
13. A device of Claim 11, wherein the dividing unit is further configured for: - dividing the long term CSI to be reported into M groups based on at least payload size of the second CSI.
14. A device of Claim 11, wherein the dividing unit is further configured for:
- dividing the long term CSI to be reported into L groups, and
- duplicating each of the L groups for N times, to obtain totally M groups, wherein M=LxN, and L is an integer larger than or equal to 1 and N is an integer equal to or larger than 2.
15. A device of Claim 14, wherein the dividing unit is further configured for:
- duplicating each of the L groups based on a predefined repetition pattern.
16. A device of Claim 11, wherein the long term CSI indicates vertical domain CSI for 3-dimension (3D) multiple-input-multiple-output (MIMO) operation.
17. A device of any of Claims 11 to 16, wherein the second CSI indicates at least one of RI, PMI and CQI specified in current Long Term Evolution (LTE) or LTE- Advanced standard.
18. A device for receiving long term channel state information CSI from a second device in a wireless network, wherein the long term CSI is divided into M groups and transmitted in M resources configured for transmission of a second CSI by reusing the remaining capacity of the M resources according to a method of any of the Claims 1 to 7, the device for receiving the long term CSI comprising:
- receiving unit, configured for receiving a group of the long term CSI in each of the M resources; and
- combination unit, configured for combining the received groups to obtain a complete long term CSI.
19. A device of Claim 18, further comprising:
- configuration unit, configured for transmitting parameter configuration signaling to the second device, to inform the parameter required for the operation of dividing the long term CSI into M groups.
20. A device of Claim 18 or 19, wherein the combination unit is further configured for:
- combining the received groups using a weight vector which is determined based on a predefined repetition pattern.
PCT/CN2014/078445 2014-05-26 2014-05-26 Methods and devices for transmitting/receiving long term channel state information in wireless communication networks WO2015180026A1 (en)

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CN103427938A (en) * 2012-05-18 2013-12-04 电信科学技术研究院 Method, system and device for measurement of configuring channel and DLCSI feedback
WO2014015811A1 (en) * 2012-07-26 2014-01-30 中兴通讯股份有限公司 Channel state information sending method and device
CN103812545A (en) * 2012-11-06 2014-05-21 上海贝尔股份有限公司 Feedback method and device for channel state information

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102971998A (en) * 2010-07-07 2013-03-13 高通股份有限公司 Channel state information (csi) feedback protocol for multiuser multiple input, multiple output (mu-mimo)
CN103427938A (en) * 2012-05-18 2013-12-04 电信科学技术研究院 Method, system and device for measurement of configuring channel and DLCSI feedback
WO2014015811A1 (en) * 2012-07-26 2014-01-30 中兴通讯股份有限公司 Channel state information sending method and device
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