Apparatus and method for channel-state-information pilot design for an advanced wireless network

Abstract

A base station and mobile station communicate using a multiple input multiple output (MIMO) communication. The base station includes a two dimensional (2D) antenna array comprising a number n of antenna elements configured in a 2D grid. The 2D antenna array is configured to communicate with at least one subscriber station. The base station also includes a controller configured to transmit n channel-state-information reference-signal (csi-RS) antenna ports (APs) associated with each of the n antenna elements. The subscriber station includes an antenna array configured to communicate with at least one base station. The subscriber station also includes processing circuitry configured receives physical downlink shared channels (PDSCHs) from a 2D active antenna array at the at least one base station. The 2D active antenna array includes a number n antenna elements. The processing circuitry further configured to estimate a full csi associated with the n antenna elements.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY

The present application

TABLE 2
CSI reference signal subframe configuration
	CSI-RS-	CSI-RS periodicity	CSI-RS subframe offset
	SubframeConfig	TCSI-RS	ΔCSI-RS
	ICSI-RS	(subframes)	(subframes)
	0-4	5	ICSI-RS
	5-14	10	ICSI-RS-5
	15-34	20	ICSI-RS-15
	35-74	40	ICSI-RS-35
	75-154	80	ICSI-RS-75

In REF1, CSI-RS sequence generation is explained as in the following section 6.10.5.1-Sequence generation: The reference-signal sequence r_l,ns (m) is defined by Equation 3:

$\begin{array}{cc}{r}_{l,n_s}\left(m\right)=\frac{1}{\sqrt{2}}\left(1-2·c\left(2m\right)\right)+j\frac{1}{\sqrt{2}}\left(1-2·c\left(2m+1\right)\right),m=0,1,\dots ,N_{\mathrm{RB}}^{m\mathrm{ax},\mathrm{DL}}-1& \left(3\right)\end{array}$
where n_s is the slot number within a radio frame and l is the OFDM symbol number within the slot. The pseudo-random sequence c(i) is defined in Section 7.2. The pseudo-random sequence generator is initialized with

$\begin{array}{cc}{c}_{\mathrm{init}}=2^{10}·\left(7·\left(n_s+1\right)+1+1\right)·\left(2·N_{\mathrm{ID}}^{\mathrm{cell}}+1\right)+2·N_{\mathrm{ID}}^{\mathrm{cell}}+N_{\mathrm{CP}}& \left(4\right)\end{array}$
at the start of each OFDM symbol.

Further, for CSI-RS configuration for CoMP: Configuration of multiple non-zero-power CSI-RS resources includes at least:

• • antennaPortsCount, resourceConfig
    • Independently configured among CSI-RS resources
  • subframeConfig
    • Whether common or independent among CSI-RS resources is FFS
  • Configurable parameter to derive the pseudo-random sequence generator initialisation (c_init)
    • c_init is independently configured among CSI-RS resources,
      C_init=2¹⁰·(7·(n_s+1)+1+1)·(2·X+1)+2·X+N_CP  (5)
    • where X is configurable in a UE-specific manner and may take on any value in the range of 0 to 503,
      • FFS whether Rel-10 formula can be used without a change
      • FFS whether beyond 503 are supported
      • FFS whether CSI-RS ports always have the same scrambling or can have different scrambling within a CSI-RS resource
  • P_c
    • Details of signaling is FFS.
      Additional Parameters May be Considered

Quasi Co-location: Two antenna ports are said to be quasi co-located if the large-scale properties of the channel over which a symbol on one antenna port is conveyed can be inferred from the channel over which a symbol on the other antenna port is conveyed. The large-scale properties include one or more of delay spread, Doppler spread, Doppler shift, average gain, and average delay.

CSI Process: UE 116 in transmission mode 10 can be configured with one or more CSI processes per serving cell by higher layers. Each CSI process is associated with a CSI-RS resource (defined in Section 7.2.5) and a CSI-interference measurement (CSI-IM) resource (defined in Section 7.2.6). A CSI reported by UE 116 corresponds to a CSI process configured by higher layers. Each CSI process can be configured with or without PMI/RI reporting by higher layer signalling.

For UE 116 in transmission mode 10, UE 116 derives the interference measurements for computing the CQI value reported in uplink subframe n and corresponding to a CSI process, based on only the zero power CSI-RS (defined in REF3) within the configured CSI-IM resource associated with the CSI process. If UE 116 in transmission mode 10 is configured by higher layers for CSI subframe sets C_CSI,0 and C_CSI,1, the configured CSI-IM resource within the subframe subset belonging to the CSI reference resource is used to derive the interference measurement.

CSI-Process: the IE CSI-Process is the CSI process configuration that E-UTRAN can configure on a serving frequency.

CSI-Process information elements
CSI-Process-r11 ::=	SEQUENCE {
	csi-ProcessIdentity-r11	CSI-ProcessIdentity-r11,
	csi-RS-IdentityNZP-r11	CSI-RS-IdentityNZP-r11,
	csi-IM-Identity-r11	CSI-IM-Identity-r11,
	p-C-AndAntennaInfoDedList-r11 SEQUENCE (SIZE (1..2)) OF P-C-AndAntennaInfoDed-r11,
	cqi-ReportBothPS-r11	CQI-ReportBothPS-r11	OPTIONAL, -- Need OR
	cqi-ReportPeriodicId-r11 INTEGER (0..maxCQI-Ext-r11)	OPTIONAL, -- Need OR
	cqi-ReportAperiodicPS-r11	CQI-ReportAperiodicPS-r11	OPTIONAL, -- Need OR
	...
}
P-C-r11 ::=	INTEGER (−8..15)
P-C-AndAntennaInfoDed-r11::= SEQUENCE {
	p-C-r11	P-C-r11,
	antennaInfoDedConfigId-r11	AntennaInfoConfigDedId-r11
}
CSI-Process field descriptions
antennaInfoDedConfigId
Refers to a dedicated antenna info configuration that is configured for the same frequency as the
CSI process.
csi-IM-Identity
Refers to a CSI-IM configuration that is configured for the same frequency as the CSI process.
csi-RS-IdentityNZP
Refers to a CSI RS configuration that is configured for the same frequency as the CSI process.
cqi-ReportBothPS
Includes CQI configuration parameters applicable for both aperiodic and periodic CSI reporting,
for which CSI process specific values may be configured. E-URAN configures the field if and
only if cqi-ReportPeriodicId is included and/or if cqi-ReportAperiodicPS is included and set to
setup.
cqi-ReportPeriodicId
Refers to a periodic CQI reporting configuration that is configured for the same frequency as the
CSI process. Value 0 refers to the set of parameters defined by the REL-10 CQI reporting
configuration fields, while the other values refer to the additional configurations E-UTRAN
assigns by CQI-ReportPeriodicExt-r11 (and as covered by CQI-ReportPeriodicExtId).
p-C
Parameter: Pc, see TS 36.213 [23, 7.2.5].
p-C-AndAntennaInfoDedList
A p-C-AndAntennaInfoDedList including 2 entries indicates that the subframe patterns configured
for CSI (CQI/PMI/PTI/RI) reporting (i.e. as defined by field csi-MeasSubframeSet1 and csi-
MeasSubframeSet2) are to be used for this CSI process, while a single entry indicates that the
subframe patterns are not to be used for this CSI process. E-UTRAN does not include 2 entries in
p-C-AndAntennaInfoDedList for CSI processes concerning a secondary frequency. E-UTRAN
includes 2 entries in p-C-AndAntennaInfoDedList when configuring both cqi-pmi-ConfigIndex
and cqi-pmi-ConfigIndex2.

CSI-ProcessIdentity: the IE CSI-ProcessIdentity is used to identify a CSI process that is configured by the IE CSI-Process. The identity is unique within the scope of a carrier frequency.

CSI-ProcessIdentity Information Elements

CSI-ProcessIdentity-r11::=INTEGER (1 . . . maxCSI-Proc-r11)

CSI-RS-ConfigNZP: the IE CSI-RS-ConfigNZP is the CSI-RS resource configuration using non-zero power transmission that E-UTRAN may configure on a serving frequency.

CSI-RS-ConfigNZP information elements
CSI-RS-ConfigNZP-r11 ::=	SEQUENCE {
	csi-RS-IdentityNZP-r11	CSI-RS-IdentityNZP-r11,
	antennaPortsCount-r11	ENUMERATED {an1, an2, an4, an8},
	resourceConfig-r11	INTEGER (0..31),
	subframeConfig-r11	INTEGER (0..154),
	scramblingIdentity-r11	INTEGER (0..503),
	qcl-CRS-Info-r11	SEQUENCE {
	qcl-ScramblingIdentity-r11	INTEGER (0..503),
	crs-PortsCount-r11	ENUMERATED {n1, n2, n4, spare1},
	mbsfn-SubframeConfig-r11	MBSFN-SubframeConfig	OPTIONAL,-- Need OR
	}	OPTIONAL,-- Need OR
	...
}

CSI-RS-ConfigZP: the IE CSI-RS-ConfigZP is the CSI-RS resource configuration, for which UE 116 assumes zero transmission power, that E-UTRAN can configure on a serving frequency.

CSI-RS-ConfigZP information elements


CSI-RS-ConfigZP-r11 ::= SEQUENCE {
csi-RS-IdentityZP-r11   CSI-RS-IdentityZP-r11,
resourceConfigList-r11  BIT STRING (SIZE (16)),
subframeConfig-r11      INTEGER (0..154)
}

CSI-RS-ConfigZP field descriptions


resourceConfigList
Parameter: CSI reference signal configuration, see TS 36.211 [21,
table 6.10.5.2-1 and 6.10.5.2-2].
subframeConfig
Parameter: ICSI-RS, see TS 36.211 [21, table 6.10.5.3-1].

CSI-RS-IdentityNZP: the IE CSI-RS-IdentityNZP is used to identify a CSI-RS resource configuration using non-zero transmission power, as configured by the IE CSI-RS-ConfigNZP. The identity is unique within the scope of a carrier frequency.

CSI-RS-IdentityNZP Information Elements

CSI-RS-IdentityNZP-r11::=INTEGER (1 . . . maxCSI-RS-NZP-r11)

CSI-RS-IdentityZP: the IE CSI-RS-IdentityZP is used to identify a CSI-RS resource configuration for which UE assumes zero transmission power, as configured by the IE CSI-RS-ConfigZP. The identity is unique within the scope of a carrier frequency.

CSI-RS-IdentityZP Information Elements

CSI-RS-IdentityZP-r11::=INTEGER (1 . . . maxCSI-RS-ZP-r11)

RRC Multiplicity and Type Constraint Values:

Multiplicity and Type Constraint Definitions

maxCSI-IM-r11	INTEGER ::= 3	-- Maximum number of CSI-IM configurations
		-- (per frequency)
maxCSI-Proc-r11	INTEGER ::= 4	-- Maximum number of CSI RS processes (per frequency)
maxCSI-RS-NZP-r11	INTEGER ::= 3	-- Maximum number of CSI RS resource
		-- configurations using non-zero Tx power
		-- (per frequency)
maxCSI-RS-ZP-r11	INTEGER ::= 4	-- Maximum number of CSI RS resource
		-- configurations using zero Tx power(per frequency)
maxCQI-Ext-r11	INTEGER ::= 3	-- Maximum number of additional periodic CQI
		-- configurations (per frequency)

CSI-IM-CONFIG: the IE CSI-IM-Config is the CSI-IM configuration that E-UTRAN may configure on a serving frequency.

CSI-IM-Config information elements


CSI-IM-Config-r11 ::= SEQUENCE {
csi-im-Identity-r11   CSI-IM-Identity-r11,
resourceConfig-r11    INTEGER (0..15),
subframeConfig-r11    INTEGER (0..154),
...
}

CSI-IM-Config field descriptions

resourceConfig
Parameter: CSI-IM configuration, see TS 36.211 [21,
table 6.10.5.2-1 and 6.10.5.2-2] for 4 REs.
subframeConfig
Parameter: ICSI-RS, see TS 36.211 [21, table 6.10.5.3-1].

CSI-IM-Identity: the IE CSI-IM-Identity is used to identify a CSI-IM configuration that is configured by the IE CSI-IM-Config. The identity is unique within the scope of a carrier frequency.

CSI-IM-Identity Information Elements

CSI-IM-Identity-r11::=INTEGER (1 . . . maxCSI-IM-r11)

Various embodiments of the present disclosure consider pilot transmissions from transmission points equipped with 2-dimensional (2D) active antenna array depicted in FIG. 4. Here, transmission points (TPs) are a network node can transmit downlink signals and receive uplink signals in a cellular network, examples of which include base stations, NodeBs, enhanced NodeBs (eNBs) remote radio heads (RRHs), and so forth. Alternatively, an entity controlling at least one TP is called the controller, the network or eNB. Each active antenna array may have separate base band, which could dynamically control the antenna weights in frequency selective manner.

FIG. 4 illustrates a transmission point equipped with 2D active antenna array according to embodiments of the present disclosure. The embodiment of the transmission point 400 shown in FIG. 4 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

The transmission point 400 includes an antenna array 405 and a controller 410. The Antenna array 405 that includes N (=N_H×N_V) 2D active antenna elements 415, and the N antenna, elements are placed in 2D grid of N_H×N_V. The horizontal spacing between any two closest antenna elements is denoted by d_H 420, and the vertical spacing between any two closest antenna elements is denoted by d_V 425.

FIG. 5 illustrates azimuth and elevation angles to a mobile station from the 2D active antenna array according to embodiments of the present disclosure. The embodiment of the 2D active antenna array 405 shown in FIG. 5 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

A transmission vector between the transmission point 400 equipped with 2D antenna array and UE 116 is transmitted at azimuth and elevation angles. In the example placement shown in FIG. 5, antenna elements 415 are placed in a rectangle on XZ plane in an orthogonal XYZ coordinate system. The origin 505 of the coordinate system is placed at the center of the rectangle. The azimuth (horizontal) angle θ_k 510 for UE 116 is defined as the angle between Y axis 515 and the projection vector 520 of a straight line between the TP and UE 116 to the XY plane. Alternatively, the elevation (vertical) angle θ_k 525 is defined as the angle between Y axis and the projection vector of the straight line to the YZ plane.

In the cellular networks, the network utilizes UEs' channel state information (CSI) to schedule time-frequency resources, to select precoders and modulation and coding schemes (MCS) for each individual UE. To facilitate the UEs' CSI estimation, the network can configure and transmit CSI reference signals (CSI-RS). At the same time, each UE can be configured to feed back estimated precoding matrix information (PMI), channel quality information (CQI) and rank information (RI), by receiving and processing the CSI-RS. Traditionally, the UEs' CSI feedback is designed with mainly targeting horizontal CSI associated with the azimuth angles. For example, PMI/CQI feedback for downlink beamforming in LTE informs the eNB the horizontal direction (or the azimuth angle) along which the UE receives the strongest signal and the associated channel strength. When active antenna array elements are introduced in the vertical domain as well, the necessity of vertical CSI feedback emerges. To facilitate the vertical CSI feedback, the corresponding CSI-RS design is crucial.

Embodiments of the present disclosure illustrate CSI-RS designs and associated configuration methods to be used in the wireless communication networks (e.g., cellular networks) having TPs equipped with 2D active antenna array. It is noted that unless otherwise specified, the CSI-RS disclosed herein refers to NZP CSI-RS.

A new transmission mode (TM), referenced hereinafter as TM X, is defined for helping UEs' reception from the 2D active antenna array 405. When UE 116 is configured with TM X, UE 116 receives PDSCHs from the 2D active antenna array 405, and is configured with a newly designed CSI-RS. The MIMO transmission from the 2D active antenna array 405 is also referenced as full-dimensional MIMO or FD-MIMO.

In one method (method 1), TP 400 is capable of transmitting all the N CSI-RS antenna ports (APs) associated with each of the N antenna elements 415, and the network is capable of configuring all the N CSI-RS APs to each UE using a UE-specific RRC configuration or a broadcast signaling, so that UE 116 can estimate the full CSI associated with the N antenna elements 415.

In another method (method 2), TP 400 is capable of transmitting at least two sets of CSI-RS APs, and the network is capable of configuring the at least two sets of CSI-RS APs to each UE, wherein UE 116 derives and feeds back horizontal CSI (H-CSI) and vertical CSI (V-CSI) estimated by receiving and processing the at least two sets of CSI-RS. Here the total number of CSI-RS APs can be less than N, and hence the CSI-RS transmission overhead is reduced as compared to method 1.

For Horizontal CSI and vertical CSI: the H-CSI of a UE is horizontal CSI estimated at UE 116, which are channel characteristics mainly associated with horizontally placed antenna elements 415 at TP 400. The horizontal CSI includes horizontal CQI (H-CQI), horizontal PMI (H-PMI) and horizontal RI (H-RI). For example, the H-CSI can be the same as the CSI (PMI, CQI and RI) in another LTE system, because the certain LTE systems CSI feedback contents and mechanism are designed considering horizontal antenna array.

The V-CSI of a UE is vertical CSI estimated at UE 116, which are channel characteristics mainly associated with vertically placed antenna elements at TP 400. The vertical CSI includes vertical CQI (V-CQI), vertical PMI (V-PMI) and vertical RI (V-RI).

FIG. 6 illustrates H-PMI and V-PMI according to embodiments of the present disclosure. The embodiment of the H-PMI and V-PMI 600 shown in FIG. 6 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In certain embodiments, UE 1 116, UE 2 115 and UE 3 114 receives the strongest signal when the (H-PMI, V-PMI) pairs are (P1,Q1), (P2,Q2) and (P3,Q3), respectively, according to their respective horizontal directions (or azimuth angles) and vertical directions (or elevation angles). When configured to feed back H-PMIs, UE 1 116, UE 2 115 and UE 3 114 report H-PMIs P1 605, P2 610 and P3 615, respectively. When configured to feed back V-PMIs, UE 1 116, UE 2 115 and UE 3 114 report V-PMIs Q1 620, Q2 625 and Q3 630, respectively.

As for CQI, two feedback methods can be considered: 1) H-CQI and V-CQI are separately derived and are independently fed back to the network; and 2) One joint CQI is derived and is fed back to the network for the N antenna channel. In one design, UE 116 constructs a desired precoding matrix for the N-Tx antenna channel using H-PMI and V-PMI, and calculates a received power under the assumption that the TP transmits signals using the precoding matrix. From the received power, UE 116 derives CQI, where the CQI can be a desired MCS. In one example, the desired precoding matrix is found by taking Kronecker product of H-PMI=[p₁, p₂, . . . , P_NH]^tϵ C^NH×1 and V-PMI=[q₁, q₂, . . . , q_NH]^tϵ CN^NV×1. In this case, when N_H=2, N_V=2, H-RI=1 and V-RI=1, the Kronecker product would be calculated as in the Equations 5 and 6:

$\begin{array}{cc}H-\mathrm{PMI}\otimes V-\mathrm{PMI}=\left[\begin{array}{c}{p}_1\\ p_2\end{array}\right]\otimes \left[\begin{array}{c}{q}_1\\ q_2\end{array}\right]=\left[\begin{array}{c}{p}_1{q}_1\\ p_1{q}_2\\ p_2{q}_1\\ p_2{q}_2\end{array}\right],& \left(5\right)\\ V-\mathrm{PMI}\otimes H-\mathrm{PMI}=\left[\begin{array}{c}{q}_1\\ q_2\end{array}\right]\otimes \left[\begin{array}{c}{p}_1\\ p_2\end{array}\right]=\left[\begin{array}{c}{q}_1{p}_1\\ q_1{p}_2\\ q_2{p}_1\\ q_2{p}_2\end{array}\right].& \left(6\right)\end{array}$

Joint RI is the rank information about the MIMO channels between the N-Tx antenna and a number of receive antennas at the UE.

For ease of illustration, the example shown in FIG. 6 illustrates only line-of-sight channels. However, the non-line-of-sight channels, the V-CSI and H-CSI can be described and defined in a similar way. The example shown in FIG. 6 is for illustration only and it does not prevent other similar constructions and definitions of V-CSI and H-CSI.

FIG. 7 illustrates a first and a second CSI-RS APs according to embodiments of the present disclosure. The embodiment of the transmitter chain 700 including the first and second CSI-RS APs shown in FIG. 7 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

The transmitter chain 700 is configured for multiplexing a first set of CSI-RS 705 (denoted by A-CSI-RS APs) and a second set of CSI-RS APs 710 (denoted by B-CSI-RS APs) for the at least two sets of CSI-RS APs. Here, the multiplexer operation 715 for A-CSI-RS APs 705 and B-CSI-RS APs 710 can be time-domain multiplexing (TDM), CDM (code-domain multiplexing), FDM (frequency-domain multiplexing) and SDM (spatial-domain multiplexing) and any combination of TDM, FDM, CDM and SDM. When TDM multiplexing is applied, A-CSI-RS APs 705 and B-CSI-RS APs 710 transmit their CSI-RS at two different time location, e.g., in two different time slots, or in two different subframes, or in two different sets of OFDM symbols. When FDM multiplexing is applied, A-CSI-RS APs 705 and B-CSI-RS APs 710 transmit their CSI-RS at two different frequency (or subcarrier) location. When CDM multiplexing is applied, A-CSI-RS APs 705 and B-CSI-RS APs 710 transmit their CSI-RS using two different orthogonal codes (e.g., Walsh code, CAZAC code) in the same time-frequency location. When SDM is applied, A-CSI-RS APs 705 and B-CSI-RS APs 710 transmit their CSI-RS in two different spatial beams, and they can be differently scrambled using two different scrambling initializations. Some example combinations of TDM, CDM, FDM and SDM are described below. When FDM/TDM multiplexing is applied, A-CSI-RS APs 705 and B-CSI-RS APs 710 transmit their CSI-RS at two different time-frequency location. Two sets of CSI-RS APs are (quasi) co-located if large-scale propagation properties of the channel over which a symbol on the first antenna port is conveyed can be inferred from the channel over which another symbol on the other antenna port is conveyed.

In certain embodiments, for deriving at least one of joint CQI, joint PMI and joint RI for the N=N_H×N_V antenna channels utilizing the two sets of CSI-RS, UE 116 can assume that the two sets of CSI-RS APs are (quasi) co-located. In certain embodiments, the network can indicate whether UE 116 can assume that the two sets of CSI-RS APs are (quasi) co-located or not for deriving joint CQI, joint PMI and joint RI.

In certain embodiments, (A-CSI-RS, B-CSI-RS) can be (H-CSI-RS, V-CSI-RS), (a first H-CSI-RS, a second H-CSI-RS), (a primary CSI-RS, a secondary CSI-RS), as illustrated in later embodiments.

In certain embodiments, the CSI-RS configurations defined in Rel-10 LTE or Rel-11 LTE is reused for configuring each of A-CSI-RS and B-CSI-RS. When Rel-10 LTE CSI-RS configuration is used, some of the following parameters in the Table 3 are separately configured for each of A-CSI-RS and B-CSI-RS.

TABLE 3

CSI-RS-Config field descriptions


AntennaPortsCount
Parameter represents the number of antenna ports used for
transmission of CSI reference signals where an1 corresponds
to 1, an2 to 2 antenna ports etc. see TS 36.211 [21, 6.10.5].
p-C
Parameter: Pc, see TS 36.213 [23, 7.2.5].
resourceConfig
Parameter: CSI reference signal configuration, see TS
36.211 [21, table 6.10.5.2-1 and 6.10.5.2-2].
subframeConfig
Parameter: ICSI-RS, see TS 36.211 [21, table 6.10.5.3-1].

When Rel-11 LTE NZP CSI-RS configuration is used, some of the parameters defining a CSI-RS-ConfigNZP-r11 (whose fields are copied below and in the background section) are separately configured for each of A-CSI-RS and B-CSI-RS.

CSI-RS-ConfigNZP-r11 ::=	SEQUENCE {
	csi-RS-IdentityNZP-r11	CSI-RS-IdentityNZP-r11,
	antennaPortsCount-r11	ENUMERATED {an1, an2, an4, an8},
	resourceConfig-r11	INTEGER (0..31),
	subframeConfig-r11	INTEGER (0..154),
	scramblingIdentity-r11	INTEGER (0..503),
	qcl-CRS-Info-r11	SEQUENCE {
	qcl-ScramblingIdentity-r11	INTEGER (0..503},
	crs-PortsCount-r11	ENUMERATED {n1, n2, n4, spare1},
	mbsfn-SubframeConfig-r11	MBSFN-SubframeConfig	OPTIONAL,-- Need OR
	}	OPTIONAL,-- Need OR
	...
}

The resource configurations (resourceConfig) and AntennaPortsCount for A-CSI-RS and B-CSI-RS can be independently or jointly configured.

In one example of independent configuration, (A-resourceConfig, A-AntennaPortsCount) and (B-resourceConfig, B-AntennaPortCount) are configured for A-CSI-RS and B-CSI-RS. When these are configured to UE, UE 116 derives each of A-CSI-RS pattern B-CSI-RS pattern with replacing (resourceConfig,AntennaPortCount) by each of (A-resource-Config,A-AntennaPortCount) and (B-resourceConfig, B-AntennaPortCount) according to TABLE 1.

In one example of joint configuration, (resourceConfig, AntennaPortCount) is configured for both A-CSI-RS and B-CSI-RS. When (resourceConfig,AntennaPortCount) is configured to UE 116, UE 116 first derives a CSI-RS pattern according to TABLE 1 with the configured (resourceConfig, AntennaPortCount). Then, the time frequency locations for N₁ A-CSI-RS APs and N₂ B-CSI-RS APs are determined according to a pre-defined way, where AntennaPortCount=N₁+N₂. Note that N₁ and N₂ can be RRC configured or be constants in the standard specification. Some examples of joint configuration are described in FIG. 8 and below.

In a first example (Example 1) When AntennaPortCount=8, N₁=4 and N₂=4, APs 15-18 are assigned for A-CSI-RS, and APs 19-22 are assigned for B-CSI-RS. In other words, A-CSI-RS and B-CSI-RS are FDM-multiplexed; and multiple CSI-RS ports in each of A-CSI-RS and B-CSI-RS are CDM multiplexed.

In a second example (Example 2) When AntennaPortCount=8, N₁=4 and N₂=4, APs (15, 17, 19, 21) are assigned for A-CSI-RS, and APs (16, 18, 20, 22) are assigned for B-CSI-RS. In other words, the 8 CSI-RS are multiplexed in 4 CDM groups of 2 REs each, wherein a first CDM code, e.g., [+1, +1] is assigned for A-CSI-RS; and a second CDM code, e.g., [+1, −1] is assigned for B-CSI-RS.

The resource configurations (resourceConfig) and AntennaPortsCount for A-CSI-RS and B-CSI-RS can be independently or jointly configured.

In one example of independent configuration, (A-resourceConfig, A-AntennaPortsCount) and (B-resourceConfig, B-AntennaPortCount) are configured for A-CSI-RS and B-CSI-RS. When these are configured to UE 116, UE 116 derives each of A-CSI-RS pattern B-CSI-RS pattern with replacing (resourceConfig,AntennaPortCount) by each of (A-resourceConfig,A-AntennaPortCount) and (B-resourceConfig, B-AntennaPortCount) according to TABLE 1.

In one example of joint configuration, (resourceConfig, AntennaPortCount) is configured for both A-CSI-RS and B-CSI-RS. When (resourceConfig,AntennaPortCount) is configured to UE 116, UE 116 first derives a CSI-RS pattern according to TABLE 1 with the configured (resourceConfig, AntennaPortCount). Then, the time frequency locations for N₁ A-CSI-RS APs and N₂ B-CSI-RS APs are determined according to a pre-defined way, where AntennaPortCount=N₁+N₂. Note that N₁ and N₂ can be RRC configured or be constants in the standard specification. Some examples of joint configuration are described in FIGS. 8 and below.

In a first example, (Example 1) When AntennaPortCount=8, N₁=4 and N₂=4, APs 15-18 are assigned for A-CSI-RS, and APs 19-22 are assigned for B-CSI-RS. In other words, A-CSI-RS and B-CSI-RS are FDM-multiplexed; and multiple CSI-RS ports in each of A-CSI-RS and B-CSI-RS are CDM multiplexed.

In a second example (Example 2) When AntennaPortCount=8, N₁=4 and N₂=4, APs (15, 17, 19, 21) are assigned for A-CSI-RS, and APs (16, 18, 20, 22) are assigned for B-CSI-RS. In other words, the 8 CSI-RS are multiplexed in 4 CDM groups of 2 REs each, wherein a first CDM code, e.g., [+1, +1] is assigned for A-CSI-RS; and a second CDM code, e.g., [+1, −1] is assigned for B-CSI-RS.

FIGS. 8A through 8C illustrates joint configuration of A- and B-CSI-RS according to embodiments of the present disclosure. The embodiments of the joint configuration 800, 810, 820 shown in FIGS. 8A through 8C are for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In certain embodiments, a common AntennaPortCount is configured for both A-CSI-RS and B-CSI-RS, and at the same time, A-resourceConfig and B-resourceConfig are separately configured for UE 116. In this case, UE 116 derives A-CSI-RS pattern and B-CSI-RS pattern with (A-resourceConfig, AntennaPortCount) and (B-resourceConfig,AntennaPortCount), respectively.

In addition, the total N number of antenna ports at TP 400 can be additionally signaled from A-AntennaPortCount and B-AntennaPortCount.

The subframe configurations (subframeConfig) for A-CSI-RS and B-CSI-RS can be independently or jointly configured.

In one example of independent configuration, for each of A-CSI-RS and B-CSI-RS, the subframe period and the subframe offset for the occurrence are configured as in the same way as the Rel-10 CSI-RS are configured. In this case, two parameters are configured to UE 116, i.e., A-CSI-RS-SubframeConfig and B-CSI-RS-SubframeConfig and UE 116 derives the subframe period and the subframe offset for the occurrence of each of B-CSI-RS and A-CSI-RS according to TABLE 2, with replacing CSI-RS-SubframeConfig by each of A-CSI-RS-SubframeConfig and B-CSI-RS-SubframeConfig.

In one example of joint configuration, for both A-CSI-RS and B-CSI-RS, the subframe configuration period and the subframe offset for the occurrence are configured as in the same way as the Rel-10 CSI-RS are configured. In this case, one parameter is configured to UE 116 as in Rel-10, i.e., CSI-RS-SubframeConfig and UE 116 derives the subframe period and the subframe offset for the occurrence of both B-CSI-RS and A-CSI-RS according to TABLE 2 with the configured CSI-RS-SubframeConfig.

It is noted that (A-CSI-RS, B-CSI-RS) can be (H-CSI-RS, V-CSI-RS), (a first H-CSI-RS, a second H-CSI-RS), (a primary CSI-RS, a secondary CSI-RS), as illustrated in later embodiments.

For configuration of CSI-RS transmission and CSI feedback for UE 116 configured with TM X, a new CSI process, referenced hereafter as CSI-Process-r12, is defined. To facilitate joint CQI transmission, the new CSI process is associated with two CSI resources, i.e., A-CSI-RS and B-CSI-RS, rather than one CSI-RS and one CSI-IM.

One illustration example construction of CSI-process-r12 is described below, where a common Pc (p-C-AndAntennaInfoDedList-r12) is configured for A-CSI-RS and B-CSI-RS.

CSI-Process-r12 ::=	SEQUENCE {
	csi-ProcessIdentity-r12	CSI-ProcessIdentity-r12,
	a-csi-RS-IdentityNZP-r12	CSI-RS-IdentityNZP-r12,
	b-csi-RS-IdentityNZP-r12	CSI-RS-IdentityNZP-r12,
	p-C-AndAntennaInfoDedList-r12	SEQUENCE (SIZE (1..2)) OF P-C-
AndAntennaInfoDed-r12,
	cqi-ReportBothPS-r12	CQI-ReportBothPS-r12
	OPTIONAL,	-- Need OR
	cqi-ReportPeriodidd-r12	INTEGER (0..maxCQI-Ext-r12)
	OPTIONAL,	-- Need OR
	cqi-ReportAperiodicPS-r12	CQI-ReportAperiodicPS-r12	OPTIONAL,
	-- Need OR
	...}

In certain embodiments, when configuring a set of CSI-RS, a CSI-RS type is signaled in addition to other CSI-RS configuration parameters, e.g., CSI-RS pattern, subframe period, subframe offset, and power. The signaling can be either UE-specific or cell-specific. Depending on the configured CSI-RS type information, UE 116 derives CSI differently with estimating channels using the configured CSI-RS, e.g., based on different PMI codebooks.

In one example, a first CSI-RS type is associated with a first PMI codebook, and a second CSI-RS type is associated with a second PMI codebook.

The first and the second PMI codebooks can be a horizontal PMI codebook and a vertical PMI codebook, respectively. Here, the horizontal PMI codebook can be the same as one of Rel-8 and Rel-10 downlink 2-Tx, 4-Tx and 8-Tx PMI codebooks defined in the LTE specifications; and the vertical PMI codebook can be differently designed from the Rel-8 and Rel-10 downlink 2-Tx, 4-Tx and 8-Tx codebooks.

The first and the second PMI codebooks can have different sizes. That is, the first and the second PMI codebooks are composed of M₁ number of PMI matrices and M₂ number of PMI matrices respectively, wherein M₁ and M₂ can be different.

In one example, the first PMI codebook is a 4-bit codebook, composed of M₁=16 matrices; and the second PMI codebook is a 2-bit codebook, composed of M₂=4 matrices.

In certain embodiments, UE 116 is configured with a first set of CSI-RS of a first CSI-RS type and a second set of CSI-RS of a second CSI-RS type. UE 116 derives a first PMI according to the first PMI codebook with estimating channels using the first set of CSI-RS. UE 116 also derives a second PMI according to the second PMI codebook with estimating channels using the second set of CSI-RS.

The feedback reporting of the first PMI and the second PMI is configured either jointly or independently.

When the feedback reporting is independently (or individually) configured, the first PMI and the second PMI are reported to the eNB 102 according to the respective configurations.

When the feedback reporting is jointly configured, both the first PMI and the second PMI are reported in a single uplink physical channel transmitted in a subframe, e.g., on a PUSCH or a PUCCH.

Similarly, when configuring a set of CSI-RS, a PMI codebook information is signaled in addition to the other CSI-RS configuration parameters. According to the configured PMI codebook, UE 116 derives PMI with estimating channels using the configured CSI-RS. For example, when UE 116 is configured with a first set of CSI-RS and the first PMI codebook; and a second set of CSI-RS and the second PMI codebook, then, UE 116 derives a first PMI according to the first PMI codebook with estimating channels using the first set of CSI-RS. In addition, UE 116 derives a second PMI according to the second PMI codebook with estimating channels using the second set of CSI-RS. In one example, the first PMI codebook and the second PMI codebook are a horizontal PMI codebook and a vertical PMI codebook, respectively.

In certain embodiments, when CSI-process-r12 is newly defined as above, a CSI-RS configuration is implicitly associated with a PMI codebook. In one example, PMI estimated with A-CSI-RS (a-csi-RS-IdentityNZP-r12) is selected from the first codebook; and PMI estimated with B-CSI-RS (a-csi-RS-IdentityNZP-r12) is selected from the second codebook.

FIG. 9 illustrates Vertical CSI-RS APs and horizontal CSI-RS APs according to embodiments of the present disclosure. The embodiment of the transmitter chain 900 including the Vertical CSI-RS APs and horizontal CSI-RS APs shown in FIG. 9 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

Configuration of Vertical and Horizontal CSI-RS APs:

In certain embodiments, two sets of CSI-RS APs 905, 910 out of the at least two sets of CSI-RS APs are separately constructed: one set consists of N_V vertical CSI-RS (V-CSI-RS) APs 905, and the other set consists of N_H horizontal CSI-RS (H-CSI-RS) APs 910. Here, the horizontal CSI-RS APs 910 are used for UEs' horizontal CSI (H-CSI) estimation, and the vertical CSI-RS APs 905 is used for UEs' vertical CSI (V-CSI) estimation.

When UE 116 is configured with N_V V-CSI-RS APs 905 and N_H H-CSI-RS APs 910, UE 116 can assume that the total number of antenna ports at the TP 400 is N=N_H×N_V for deriving at least one of joint CQI and joint PMI for the N antenna channels. In another design the total number of antenna ports at the TP is separately signaled to UE 116.

In certain embodiments, H-CSI-RS is associated with H-PMI codebook and V-CSI-RS is associated with V-PMI codebook. In certain embodiments, H-PMI codebook and V-CSI-RS codebook can be identical.

In one alternative, 3GPP LTE Rel-8 and Rel-10 2-Tx, 4-Tx and 8-Tx DL codebooks are reused for both H-PMI and V-PMI. In certain embodiments, UE 116 derives H-CSI using H-CSI-RS by applying the same procedure used for deriving Rel-10 CQI/PMI/RI based on Rel-10 CSI-RS. In certain embodiments, UE 116 derives V-CSI using V-CSI-RS by applying the same procedure used for deriving Rel-10 CQI/PMI/RI based on Rel-10 CSI-RS.

In another alternative, 3GPP LTE Rel-8 and Rel-10 2-Tx, 4-Tx, and 8-Tx DL codebooks are reused for H-PMI codebook only and V-PMI codebook is newly designed; or both the H-PMI and the V-PMI codebooks are newly designed.

Then, the CSI-RS configuration can include a CSI-RS type field, to indicate whether the configured CSI-RS is H-CSI-RS or V-CSI-RS. When UE 116 is configured with H-CSI-RS, UE 116 derives a PMI (H-PMI) using the H-PMI codebook with estimating channels using H-CSI-RS. Alternatively, when UE 116 is configured with V-CSI-RS, UE 116 derives a PMI (V-PMI) using the V-PMI codebook with estimating channels using V-CSI-RS.

Similarly, the CSI-RS configuration can include a PMI codebook information field, to indicate which PMI codebook should be used for deriving PMI using the configured CSI-RS. When UE 116 receives a configuration signaling of a CSI-RS and a H-PMI codebook, UE 116 derives a PMI (H-PMI) using the H-PMI codebook with estimating channels using the configured CSI-RS; on the other hand when UE 116 receives a configuration signaling of a CSI-RS and a V-PMI codebook, UE 116 derives a PMI (V-PMI) using the V-PMI codebook with estimating channels using the configured CSI-RS.

In another alternative, a PMI codebook information can be separately signaled from the CSI-RS configuration. Then, UE 116 derives H-PMI and V-PMI using either a first PMI codebook or a second PMI codebook, depending on the configured PMI codebook information. In certain embodiments, the first PMI codebook can be 3GPP LTE Rel-8 and Rel-10 2-Tx, 4-Tx, and 8-Tx DL codebooks; and the second PMI codebook can be a newly designed codebook.

In certain embodiments, the codebook sizes of the H-PMI codebook and the V-PMI codebook are different. In one example, for assigning better beam resolution of horizontal beams more than that of vertical beams, a larger size codebook is used for H-PMI than for V-PMI. In one example, for assigning better beam resolution of vertical beams more than that of horizontal beams, a larger size codebook is used for V-PMI than for H-PMI.

FIG. 10 illustrates construction of the horizontal and the vertical CSI-RS APs according to embodiments of the present disclosure. The embodiment of the construction 1000 shown in FIG. 10 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In certain embodiments, in the construction 1000 of the horizontal and the vertical CSI-RS APs (Construction Example 1) includes the N_H horizontal CSI-RS APs (say, H-APs 0, . . . , N_H−1) are transmitted from a row 1005 of the active antenna array, while the N_V vertical CSI-RS APs (say, V-APs 0, . . . , N−1) are transmitted from a column 1010 of the active antenna array. In the example shown in FIG. 10, the horizontal CSI-RS APs are transmitted from the first row 1005 of the antenna array, while the vertical CSI-RS APs are transmitted from the first column 1010 of the antenna array.

When the H-CSI-RS and V-CSI-RS are transmitted in the same subframe, one CSI-RS AP can be shared between the two sets of the CSI-RS APs. For example, only a single CSI-RS signal mapped onto single-port CSI-RS REs is transmitted for H-AP 0 and V-AP 0. Alternatively, the H-CSI-RS and V-CSI-RS can also be orthogonally and independently mapped in the time-frequency grid, even if the two CSI-RS APs are scheduled in the same subframe.

FIG. 11 illustrates construction of the horizontal and the vertical CSI-RS APs according to embodiments of the present disclosure. The embodiment of the construction 1100 shown in FIG. 11 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In certain embodiments, in the construction 1100 of the horizontal and the vertical CSI-RS APs (Construction Example 2), each of the N_H horizontal CSI-RS for the N_H H-CSI-RS APs (say, H-APs 0, . . . , N_H−1) are transmitted from a column 1105 of the active antenna array. Each H-CSI-RS signal is precoded with a precoding vector of [p₁ p₂ . . . p_NV]^t, where the precoding is applied across the antenna elements in each column of the active antenna array.

Alternatively, each of the N_V vertical CSI-RS for the N_V APs (say, V-APs 0, . . . , N_V−1) are transmitted from a row 1110 of the active antenna array. Each H-CSI-RS signal is precoded with a precoding vector of [q₁ q₂ . . . q_NH], where the precoding is applied across the antenna elements in each row of the active antenna array.

The precoding to generate a CSI-RS signal also is referenced as antenna virtualization precoding. As shown in FIG. 11, the construction 1100 can be easily extended to a construction in which different precoding vectors are applied across different rows (or columns) corresponding to the different V-CSI-RS (or H-CSI-RS).

FIG. 12 illustrates first and second sets of horizontal CSI-RS APs according to embodiments of the present disclosure. The embodiment of the transmitter chain 1200 including the first and second sets of horizontal CSI-RS APs shown in FIG. 12 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

Configuration of a First and a Second Horizontal CSI-RS APs:

In certain embodiments, two sets of CSI-RS APs 1205, 1210 out of the at least two sets of CSI-RS APs are separately constructed: each of the two sets consists of N_H H-CSI-RS APs corresponding to a row of antenna elements in the 2D active antenna array 405. Here, the two sets of H-CSI-RS APs 1205, 1210 are used for UEs' horizontal and vertical CSI estimation.

In this case, the total number of antenna ports at the TP N is separately RRC configured from the configurations for the two sets of CSI-RS 1205, 1210. The total number of antenna ports N=N_H×N_V is used for deriving at least one of joint CQI and joint PMI for the N antenna channels

FIG. 13 illustrates construction of two sets of H-CSI-RS APs according to embodiments of the present disclosure. The embodiment of the construction 1300 shown in FIG. 13 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In certain embodiments, in the construction 1300 of the two sets of H-CSI-RS APs (Set Construction Example 1), the two rows of antenna elements corresponding to the two sets of H-CSI-RS APs are the first two rows 1305 in the 2D active antenna array 405. In this case, UE 116 determines the vertical CSI for the entire N_H×N_V antennas in the 2D active antenna array 405 by estimating the phase difference between the two rows, as well as the horizontal CSI by relying on the traditional methods of estimating horizontal CSI. The two rows are configurable by the network, in which case, the network is configured to indicate to each UE at least one of the following: The indices of the two rows corresponding to the two H-CSI-RS APs. For example, when the first two rows 1305, 1310 are corresponding to the two H-CSI-RS APs as in the example shown in FIG. 13, the network configures to each UE two row indices, row index 0 1305 and row index 1 1310.

In certain embodiments, eNB 102 signals to UE 116 the difference of the two indices of the two rows corresponding to the two H-CSI-RS APs. For example, when the first two rows are corresponding to the two H-CSI-RS APs as in the example shown in FIG. 13, the network configures to each UE the difference of the two row indices, i.e., (1−0)=1.

The example shown in FIG. 13 is for illustration only. The same idea can be used for constructing N_V sets of H-CSI-RS APs corresponding to the N_V rows of the 2D antenna array.

In one alternative, CSI-RS configuration includes a CSI-RS type field to indicate whether the configured CSI-RS is the first H-CSI-RS or the second H-CSI-RS.

FIG. 14 illustrates Construction of two sets of H-CSI-RS APs according to embodiments of the present disclosure. The embodiment of the construction 1400 shown in FIG. 14 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In certain embodiments, in the construction 1400 of the two sets of H-CSI-RS APs (Set Construction Example 2), two different virtualization precoding vectors are applied to the two sets of H-CSI-RS APs 1405, 1410. Each H-CSI-RS signal in the first set 1405 is precoded with a precoding vector of [p₁ p₂ . . . p_NV]^t, and each H-CSI-RS in the second set is precoded with a precoding vector of [q₁ q₂ . . . q_NV]^t, where the precoding vector is applied across the antenna elements in each column of the active antenna array in each set of H-CSI-RS APs. UE 116 determines the vertical CSI for the entire N_H×N_V antennas in the 2D active antenna array 405 by estimating the phase difference between the two sets of H-CSI-RS APs 1405, 1410, as well as the horizontal CSI by relying on the traditional methods of estimating horizontal CSI. The two virtualization precoding vectors can be indicated by the network to each UE.

FIG. 15 illustrates primary and secondary CSI-RS APs according to embodiments of the present disclosure. The embodiment of the transmitter chain 1500 including the primary and secondary CSI-RS APs shown in FIG. 15 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

In one alternative, CSI-RS configuration includes a CSI-RS type field, to indicate whether the configured CSI-RS is the primary CSI-RS or the secondary CSI-RS.

Configuration of a First and a Second Horizontal CSI-RS APs:

In certain embodiments, two sets of CSI-RS APs out of the at least two sets of CSI-RS APs are separately constructed and configured (period as well): a set of primary CSI-RS APs 1505 and a set of secondary CSI-RS APs 1510.

Primary CSI-RS APs 1505: in certain embodiments, UE 116 utilizes the set of primary CSI-RS APs 1505 to derive either H-CSI or V-CSI, depending on whether the primary CSI-RS 1505 are corresponding to the (N_H) horizontally placed antenna elements or (N_V) vertically placed antenna elements. Whether UE 116 can derive H-CSI or V-CSI out of the primary CSI-RS 1505 is indicated by the network, or fixed in the standard specification (e.g., pre-stored in memory 360).

Secondary CSI-RS APs 1510: in certain embodiments, UE 116 combines the primary CSI-RS APs 1505 and the secondary CSI-RS APs 1510 to determine either V-CSI-RS or H-CSI-RS. In one example, when the primary CSI-RS APs 1505 correspond to the horizontally placed antenna elements and are used for estimating H-CSI-RS, the secondary CSI-RS APs 1510, together with the primary CSI-RS APs 1505, can be used for estimating the V-CSI-RS. In another example, when the primary CSI-RS APs 1505 correspond to the vertically placed antenna elements and are used for estimating V-CSI-RS, the secondary CSI-RS APs 1510 together with the primary CSI-RS APs 1505 can be used for estimating the H-CSI-RS. The number of secondary APs can be less than the number of the primary APs, and can be separately configured from the number of the primary CSI-RS APs 1505.

In this case, the total number of antenna ports at TP N is separately RRC configured from the configurations for the two sets of CSI-RS. The total number of antenna ports N=N_H×N_V is used for deriving at least one of joint CQI and joint PMI for the N antenna channels.

FIG. 16 illustrates construction of the primary and the secondary CSI-RS according to embodiments of the present disclosure. The embodiment of the construction 1600 shown in FIG. 16 is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In the example construction of the primary and the secondary CSI-RS shown in FIG. 16, the primary CSI-RS 1605 are H-CSI-RS, while only one AP is provided for the secondary CSI-RS 1610, which is the first antenna element 1615 of the second row of the 2D active antenna array 405. When UE 116 is configured with these primary and secondary CSI-RS, UE 116 derives H-CSI utilizing the primary CSI-RS, and UE 116 derives V-CSI utilizing the primary and the secondary CSI-RS, such as, by estimating the phase difference between the two types of CSI-RS. The relative location of the secondary CSI-RS with respect to the primary CSI-RS can be configured by the network.

In another method (method 3), the network is capable of configuring and transmitting at least two sets of CSI-RS APs. A first set of CSI-RS APs is used for horizontal CSI estimation at a first group of UEs, and a second set of CSI-RS APs is used for horizontal CSI estimation at a second group of UEs.

Each of the at least two sets of CSI-RS APs can be targeted to be best received in a certain distance from the TP (or a certain range of elevation angles). For example, a first set of CSI-RS is best received at distance of 0 m to 200 m, while the second set of CSI-RS is best received at distance of 200 m to 400 m. For this operation, the network can tailor antenna virtualization precoding method of each set of CSI-RS accordingly. That is, the first set of CSI-RS is virtualized with a first virtualization precoding so that it is best received at a first range of distances, and the second set of CSI-RS is virtualized with a second virtualization precoding so that it is best received at a second range of distances.

UE 116 can be configured for one set out of the at least two sets of CSI-RS APs by an RRC configuration. Then, UE 116 estimates horizontal CSI based on the configured set of CSI-RS APs.

UE 116 can be re-configured to estimate horizontal CSI based on a first set of CSI-RS APs from a second set of CSI-RS APs, by an RRC configuration.

UE 116 can be configured for the at least two sets of CSI-RS APs. UE 116 can estimate and report RSRPs for the at least two sets of CSI-RS APs, e.g., depending on a configured triggering condition.

Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.

Claims

1. For use in a wireless communication network, a base station comprising:

a two dimensional (2D) antenna array comprising a number n of antenna elements configured in a 2D grid n_H×N_v, the 2D antenna array configured to communicate with at least one subscriber station; and

a controller configured to transmit n channel-state-information reference-signal (csi-RS) antenna ports (APs) associated with each of the n antenna elements, wherein the controller is configured to transmit at least two sets of csi-RS APs and the at least one subscriber station derives and feeds back horizontal csi (H-csi) and vertical csi (V-csi) estimated by the at least one subscriber station receiving and processing the at least two sets of csi-RS APs, and wherein a total number of csi-RS APs is less than n.

2. The base station as set forth in claim 1, wherein the H-csi comprises channel characteristics mainly associated with horizontally placed antenna elements estimated at the at least one subscriber station and includes horizontal channel quality indicator (CQI) (H-CQI), horizontal precoding matrix index (PMI) (H-PMI) and horizontal rank indicator (RI) (H-RI).

3. The base station as set forth in claim 1, wherein the V-csi comprises channel characteristics mainly associated with vertically placed antenna elements estimated at the at least one subscriber station and includes vertical CQI (V-CQI), vertical PMI (V-PMI) and vertical RI (V-RI).

4. The base station as set forth in claim 1, wherein the controller is configured to multiplex a first set of csi-RS APs and a second set of csi-RS APs for the at least two sets of csi-RS APs.

5. The base station as set forth in claim 4, wherein the multiplexer operation comprises one or more of: a time-domain multiplexing (TDM), code-domain multiplexing (CDM), frequency-domain multiplexing (FDM) and spatial-domain multiplexing (SDM) and wherein:

when TDM multiplexing is applied, the controller is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs at two different time locations comprising at least one of: in two different time slots, in two different subframes, in two different sets of OFDM symbols;

when FDM multiplexing is applied, the controller is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs at two different frequency or subcarrier locations;

when CDM multiplexing is applied, the controller is configured to transmit the csi-RS APs corresponding to the at least two sets of csi-RS APs using two different orthogonal codes in the same time-frequency location;

when SDM is applied, the controller is configured to transmit the csi-RS APs corresponding to the at least two sets of csi-RS APs in two different spatial beams and wherein the at least two sets of csi-RS APs are differently scrambled using two different scrambling initializations; and

when FDM/TDM multiplexing is applied, the controller is configured to transmit the csi-RS APs corresponding to the at least two sets of csi-RS APs at two different time-frequency location.

6. The base station as set forth in claim 1, wherein the at least two sets of csi-RS APs comprise one of:

A-csi-RS AP and B-csi-RS AP;

a vertical csi-RS AP and a horizontal csi-RS AP;

two horizontal csi-RS APs; and

a primary csi-RS AP and a secondary csi-RS AP.

7. A subscriber station configured to communicate with at least one base station using a multiple input multiple output (MIMO) communication, the subscriber station comprising:

an antenna array configured to communicate with at least one base station; and

processing circuitry configured to receive physical downlink shared channels (PDSCHs) from a two dimensional (2D) active antenna array at the at least one base station, the 2D active antenna array comprising a number n antenna elements; the processing circuitry further configured to estimate a horizontal channel state information (csi) and vertical csi associated with the n antenna elements, wherein the processing circuitry is configured to receive and process at least two sets of csi-RS antenna ports (APs), and derive and feedback horizontal csi (H-csi) and vertical csi (V-csi) from the at least two sets of csi-RS APs, wherein a total number of csi-RS APs is less than n.

8. The subscriber station as set forth in claim 7, wherein the H-csi comprises channel characteristics mainly associated with horizontally placed antenna elements estimated at the at least one subscriber station and includes horizontal channel quality indicator (CQI) (H-CQI), horizontal precoding matrix index (PMI) (H-PMI) and horizontal rank indicator (RI) (H-RI).

9. The subscriber station as set forth in claim 7, wherein the V-csi comprises channel characteristics mainly associated with vertically placed antenna elements estimated at the at least one subscriber station and includes vertical CQI (V-CQI), vertical PMI (V-PMI) and vertical RI (V-RI).

10. The subscriber station as set forth in claim 7, wherein a first set of csi-RS and a second set of csi-RS APs for the at least two sets of csi-RS APs are multiplexed.

11. The subscriber station as set forth in claim 10, wherein the multiplexer operation comprises one or more of: a time-domain multiplexing (TDM), code-domain multiplexing (CDM), frequency-domain multiplexing (FDM) and spatial-domain multiplexing (SDM) and wherein:

when TDM multiplexing is applied, the controller processing circuitry is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs at two different time locations comprising at least one of: in two different time slots, in two different subframes, in two different sets of OFDM symbols;

when FDM multiplexing is applied, the controller processing circuitry is configured to transmit the csi-RS APs corresponding to the at least two sets of csi-RS APs at two different frequency or subcarrier locations;

when CDM multiplexing is applied, the controller processing circuitry is configured to transmit the csi-RS APs corresponding to the at least two sets of csi-RS APs using two different orthogonal codes in the same time-frequency location;

when SDM is applied, the controller processing circuitry is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs in two different spatial beams and wherein the at least two sets of csi-RS APs are differently scrambled using two different scrambling initializations; and

when FDM/TDM multiplexing is applied, the controller processing circuitry is configured to transmit the csi-RS APs corresponding to the at least two sets of csi-RS APs at two different time-frequency location.

12. The subscriber station as set forth in claim 7, wherein the at least two sets of csi-RS APs comprise one of:

A-csi-RS AP and B-csi-RS AP;

a vertical csi-RS AP and a horizontal csi-RS AP;

two horizontal csi-RS APs; and

a primary csi-RS AP and a secondary csi-RS AP.

13. For use in a wireless communication network, a method comprising:

transmitting, from a two dimensional (2D) antenna array, n channel-state-information reference-signal (csi-RS) antenna ports (APs), the 2D antenna array comprising a number n of antenna elements configured in a 2D grid n_H×N_v, the csi-RS APs associated with each of the n antenna elements, wherein transmitting comprises transmitting at least two sets of csi-RS APs; and

receiving a feedback signal from the at least one subscriber station, the feedback signal comprising horizontal csi (H-csi) and vertical csi (V-csi) estimated by the at least one subscriber station receiving and processing the at least two sets of csi-RS APs, and wherein a total number of csi-RS APs is less than n.

14. The method as set forth in claim 13, wherein the H-csi comprises channel characteristics mainly associated with horizontally placed antenna elements estimated at the at least one subscriber station and includes horizontal CQI (H-CQI), horizontal PMI (H-PMI) and horizontal RI (H-RI).

15. The method as set forth in claim 13, wherein the V-csi comprises channel characteristics mainly associated with vertically placed antenna elements estimated at the at least one subscriber station and includes vertical CQI (V-CQI), vertical PMI (V-PMI) and vertical RI (V-RI).

16. The method as set forth in claim 13, wherein transmitting comprises multiplexing a first set of csi-RS and a second set of csi-RS for the at least two sets of csi-RS.

17. The method as set forth in claim 16, wherein multiplexing comprises one or more of: a time-domain multiplexing (TDM), code-domain multiplexing (CDM), frequency-domain multiplexing (FDM) and spatial-domain multiplexing (SDM) and wherein:

when TDM multiplexing is applied, the controller is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs at two different time locations comprising at least one of: in two different time slots, in two different subframes, in two different sets of OFDM symbols;

when FDM multiplexing is applied, the controller is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs at two different frequency or subcarrier locations;

when CDM multiplexing is applied, the controller is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs using two different orthogonal codes in the same time-frequency location;

when SDM is applied, the controller is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs in two different spatial beams and wherein the at least two sets of csi-RS APs are differently scrambled using two different scrambling initializations; and

when FDM/TDM multiplexing is applied, the controller is configured to transmit the csi-RS corresponding to the at least two sets of csi-RS APs at two different time-frequency location.

18. The method as set forth in claim 13, wherein the at least two sets of csi-RS APs comprise one of:

A-csi-RS and B-csi-RS;

a vertical csi-RS AP and a horizontal csi-RS AP;

two horizontal csi-RS APs; and

a primary csi-RS AP and a secondary csi-RS AP.

19. An apparatus in a base station for transmitting channel state information reference signal (csi-RS), the apparatus comprising:

a controller configured to:

identify a same number of antenna ports associated with aggregation of each of at least two csi-RS configurations, the at least two csi-RS configurations including a first csi-RS configuration and a second csi-RS configuration; and

a transceiver configured to:

transmit information on the same number of antenna ports,

transmit information on the at least two csi-RS configurations, and

transmit a first csi-RS corresponding to the same number of antenna ports and the first csi-RS configuration and a second csi-RS corresponding to the same number of antenna ports and the second csi-RS configuration.

20. The apparatus of claim 19, wherein one subframe configuration is set for the at least two csi-RS configurations, the at least two csi-RS configurations are aggregated in a subframe.

21. The apparatus of claim 19, wherein a resource configuration for each of the at least two csi-RS configurations is set separately.

22. The apparatus of claim 19, wherein the same number of antenna ports is 8.

23. The base station of claim 1, wherein the antenna array is further configured to:

transmit information indicating a codebook for the at least two csi-RS configurations.

24. An apparatus in a mobile station for receiving channel state information reference signal (csi-RS), the apparatus comprising:

a transceiver configured to:

receive information on a same number of antenna ports, and

receive information on at least two csi-RS configurations, wherein the same number of antenna ports is associated with aggregation of the at least two csi-RS configurations and the at least two csi-RS configurations include a first csi-RS configuration and a second csi-RS configuration; and

a controller configured to identify the same number of antenna ports associated with the aggregation of the at least two csi-RS configurations,

wherein the transceiver is configured to receive a first csi-RS corresponding to the same number of antenna ports and the first csi-RS configuration and a second csi-RS corresponding to the same number of antenna ports and the second csi-RS configurations.

25. The apparatus of claim 24, wherein one subframe configuration is set for the at least two csi-RS configurations, the at least two csi-RS configurations are aggregated in a subframe.

26. The apparatus of claim 24, wherein a resource configuration for each of the at least two csi-RS configurations is set separately.

27. The apparatus of claim 24, wherein the same number of antenna ports is 8.

28. The apparatus of claim 24, wherein the transceiver is further configured to:

receive information indicating a codebook for the at least two csi-RS configurations.

29. A method for transmitting channel state information reference signal (csi-RS) by a base station, the method comprising:

identifying a same number of antenna ports associated with aggregation of each of at least two csi-RS configurations, the at least two csi-RS configurations including a first csi-RS configuration and a second csi-RS configuration;

transmitting information on the same number of antenna ports;

transmitting information on the at least two csi-RS configurations; and

transmitting a first csi-RS corresponding to the same number of antenna ports and the first csi-RS configuration and a second csi-RS corresponding to the same number of antenna ports and the second csi-RS configurations.

30. The method of claim 29, wherein one subframe configuration is set for the at least two csi-RS configurations, the at least two csi-RS configurations are aggregated in a subframe.

31. The method of claim 29, wherein a resource configuration for each of the at least two csi-RS configurations is set separately.

32. The method of claim 29, wherein the same number of antenna ports is 8.

33. The method of claim 29, further comprising:

transmitting information indicating a codebook for the at least two csi-RS configurations.

34. A method for receiving channel state information reference signal (csi-RS), comprising:

receiving information on a same number of antenna ports;

receiving information on at least two csi-RS configurations, wherein the same number of antenna ports is associated with aggregation of the at least two csi-RS configurations and the at least two csi-RS configurations include a first csi-RS configuration and a second csi-RS configuration;

identifying the same number of antenna ports associated with the aggregation of the at least two csi-RS configurations; and

receiving a first csi-RS corresponding to the same number of antenna ports and the first csi-RS configuration and a second csi-RS corresponding to the same number of antenna ports and the second csi-RS configurations.

35. The method of claim 34, wherein one subframe configuration is set for the at least two csi-RS configurations, and the at least two csi-RS configurations are aggregated in a subframe.

36. The method of claim 34, wherein a resource configuration for each of the at least two csi-RS configurations is set separately.

37. The method of claim 34, wherein the same number of antenna ports is 8.

38. The method of claim 34, further comprising:

receiving information indicating a codebook for the at least two csi-RS configurations.

39. An apparatus in a base station for transmitting channel state information reference signal (csi-RS), the apparatus comprising:

a controller configured to:

identify a total number of antenna ports associated with aggregation of at least two csi-RS configurations; and

a transceiver configured to:

transmit information on the at least two csi-RS configurations, and

transmit csi-RSs corresponding to the total number of antenna ports and the at least two csi-RS configurations,

wherein the antenna ports associated with aggregation of at least two csi-RS configurations comprise, for a two dimensional (2D) antenna array, channel state information reference signal (csi-RS) antenna ports (APs) corresponding to two rows of antenna elements including a first row of n antenna elements and a second row of n antenna elements for a total of 2N antenna elements, and wherein the csi-RS APs are each mapped 1:1 with one of the 2N antenna elements.

40. An apparatus in a mobile station for receiving channel state information reference signal (csi-RS), the apparatus comprising:

a transceiver configured to:

receive information on at least two csi-RS configurations, and

receive csi-RSs corresponding to a total number of antenna ports and the at least two csi-RS configurations; and

a controller configured to:

identify the total number of antenna ports associated with aggregation of the at least two csi-RS configurations,

wherein the antenna ports associated with aggregation of at least two csi-RS configurations comprise, for a two dimensional (2D) antenna array, channel state information reference signal (csi-RS) antenna ports (APs) corresponding to two rows of antenna elements including a first row of n antenna elements and a second row of n antenna elements for a total of 2N antenna elements, and wherein the csi-RS APs are each mapped 1:1 with one of the 2N antenna elements.

41. A method for transmitting channel state information reference signal (csi-RS) by a base station, the method comprising:

identifying a total number of antenna ports associated with aggregation of at least two csi-RS configurations; and

transmitting information on the at least two csi-RS configurations;

transmitting csi-RSs corresponding to the total number of antenna ports and the at least two csi-RS configurations,

wherein the antenna ports associated with aggregation of at least two csi-RS configurations comprise, for a two dimensional (2D) antenna array, channel state information reference signal (csi-RS) antenna ports (APs) corresponding to two rows of antenna elements including a first row of n antenna elements and a second row of n antenna elements for a total of 2N antenna elements, and wherein the csi-RS APs are each mapped 1:1 with one of the 2N antenna elements.

42. A method for receiving channel state information reference signal (csi-RS), comprising:

receiving information on at least two csi-RS configurations;

identifying a total number of antenna ports associated with aggregation of the at least two csi-RS configurations;

receiving csi-RSs corresponding to the total number of antenna ports and the at least two csi-RS configurations,

wherein the antenna ports associated with aggregation of at least two csi-RS configurations comprise, for a two dimensional (2D) antenna array, channel state information reference signal (csi-RS) antenna ports (APs) corresponding to two rows of antenna elements including a first row of n antenna elements and a second row of n antenna elements for a total of 2N antenna elements, and wherein the csi-RS APs are each mapped 1:1 with one of the 2N antenna elements.