Abstract: The teachings herein present a method and apparatus that implement and use a factorized precoder structure that is advantageous in terms of performance and efficiency. In particular, the teachings presented herein disclose an underlying precoder structure that allows for certain codebook reuse across different transmission scenarios, including for transmission from a single Uniform Linear Array (ULA) of transmit antennas and transmission from cross-polarized subgroups of such antennas. According to this structure, an overall precoder is constructed from a conversion precoder and a tuning precoder. The conversion precoder includes antenna-subgroup precoders of size NT/2, where NT represents the number of overall antenna ports considered. Correspondingly, the tuning precoder controls the offset of beam phases between the antenna-subgroup precoders, allowing the conversion precoder to be used with cross-polarized arrays of NT/2 antenna elements and with co-polarized arrays of NT antenna elements.

Abstract: A method performed by a base station of enabling a User Equipment (UE) to determine a precoder codebook in a wireless communication system is provided. The base station transmits, to the UE, information regarding precoder parameters enabling the UE to determine the precoder codebook. The precoder parameters are associated with a plurality of antenna ports of the base station. The precoder parameters relate to a first dimension and a second dimension of the precoder codebook. The plurality of antenna ports comprises a number of antenna ports that is a function of a number of antenna ports in the first dimension, and a number of antenna ports in the second dimension.

Abstract: The present invention provides a unified, rank independent mapping between antenna ports and group/code pairs. Each antenna port is uniquely associated with one code division multiplexing (CDM) group and one orthogonal cover code (OCC). The mapping between antenna ports and group/code pairs is chosen such that, for a given antenna port, the CDM group and OCC will be the same for every transmission rank.

Abstract: The present invention relates to a method and arrangement for controlling re-transmission in a user equipment supporting uplink spatial multiplexing. The method comprises the steps of detecting an uplink grant on a physical downlink control channel, the uplink grant being valid for at least one transport block; detecting that at least one transport block is disabled, such that no grant is associated with the at least one transport block; and interpreting the at least one disabled transport block as an acknowledgement, ACK, of previous transmission corresponding to said disabled transport block irrespective of which indication is received on the reception status feedback channel for said previous transmission.

Abstract: A wireless device, a network node and methods performed by the wireless device and the network node for providing a guard interval for transmissions in a communication system are presented. The network node (301, 401) receives a signal (307, 407) transmitted by the wireless device (305, 405) and obtains a series of symbols (311a,b, 411a-g) from the received signal. In one exemplary embodiment, a method by the wireless device in a wireless communication system includes generating (705) the signal comprising the series of symbols, including a pair of consecutive symbols (311a,b, 411e,f, 411f,g) that are to be transmitted at different power levels, with power ramping (316, 416, 418) to occur over a power transition period (315, 415, 417) between the consecutive symbols. Further, the method includes transmitting (707) the transmit signal with a guard interval (313, 413a,b) overlapping at least partly with the power transition period.

Abstract: Systems and methods for providing Channel State Information (CSI) feedback in a cellular communications network are disclosed. In some embodiments, a base station of a cellular communications network disables inter-subframe channel interpolation of CSI-RS estimates across subframes at the wireless device and receives one or more CSI reports from the wireless device that are generated by the wireless device with inter-subframe channel interpolation of CSI-RS estimates across subframes disabled in response to the base station disabling inter-subframe channel interpolation of CSI-RS estimates across subframes at the wireless device. In this manner, CSI feedback is improved particularly in embodiments in which the base station transmits a beamformed CSI-RS resource(s) and reuses the same CSI-RS resource(s) for different beams over time.

Abstract: A network node (10) signals to a wireless communication device (14) which precoders in a codebook are restricted from being used. The network node (10) in this regard generates codebook subset restriction signaling that, for each of one or more groups of precoders, jointly restricts the precoders in the group by restricting a certain component (e.g., a certain beam precoder) that the precoders in the group have in common. This signaling may be for instance rank-agnostic signaling that jointly restricts the precoders in a group without regard to the precoders' transmission rank. Regardless, the network node (10) sends the generated signaling to the wireless communication device (14).

Abstract: A method implemented by a wireless terminal of reporting channel state information to a wireless communication network is disclosed. The wireless terminal receives reference symbols on a set of channel state information reference symbol (CSI-RS) resources, and determines a common transmission rank for the set of CSI-RS resources, based on the reference symbols received on a subset of those CSI-RS resources. The terminal then generates CSI feedback as a function of the common transmission rank, and transmits the CSI feedback to the communication network. The CSI feedback may include the common transmission rank itself, or may include different transmission ranks for different CSI-RS resources each determined as a function of the common transmission rank. A complementary method in which a network node uses such a CSI feedback to perform rank adaptation for the set of CSI-RS resources is also disclosed.

Abstract: A method performed by a base station of enabling a User Equipment, UE, to determine a precoder codebook in a wireless communication system is provided. The base station transmits (303) to the UE, information regarding precoder parameters enabling the UE to determine the precoder codebook. The precoder parameters are associated with a plurality of antenna ports of the base station. The precoder parameters relate to a first dimension and a second dimension of the precoder codebook. The plurality of antenna ports comprises a number NT of antenna ports that is a function of a number Nh of antenna ports in the first dimension, and a number Nv of antenna ports in the second dimension.

Abstract: The present invention relates to a method and arrangement for controlling re-transmission in a user equipment supporting uplink spatial multiplexing. The method comprises the steps of detecting an uplink grant on a physical downlink control channel, the uplink grant being valid for at least one transport block; detecting that at least one transport block is disabled, such that no grant is associated with the at least one transport block; and interpreting the at least one disabled transport block as an acknowledgement, ACK, of previous transmission corresponding to said disabled transport block irrespective of which indication is received on the reception status feedback channel for said previous transmission.

Abstract: A method in a first node for adapting a multi-antenna transmission to a second node over a wireless channel is provided. The wireless channel has at least three inputs and at least one output. The first node and the second node are comprised in a wireless communication system. The method includes obtaining at least one symbol stream, determining a precoding matrix having a product structure created by a block diagonal matrix being multiplied from the left with a block diagonalizing unitary matrix, precoding the at least one symbol stream with the determined precoding matrix, and transmitting the precoded at least one symbol stream over a wireless channel to the second node.

Abstract: Methods and arrangements are described for Multi User Multiple-Input-Multiple-Output (MU-MIMO) signaling via Multiple-Input-Multiple-Output (MIMO) antennas between a base station and one of a plurality of mobile terminals supporting both Single User and Multi User Multiple-Input-Multiple-Output (SU-MIMO and MU-MIMO) signaling modes. Switching between the modes is supported, and the modes have partly shared signaling. SU-MIMO mode signaling which is not needed for MU-MIMO mode signaling is identified. Data bits of the identified signaling is interpreted to comprise signaling information associated with MU-MIMO mode.

Abstract: Systems and methods for providing Channel State Information (CSI) feedback in a cellular communications network are disclosed. In some embodiments, a base station of a cellular communications network disables inter-subframe channel interpolation of CSI-RS estimates across subframes at the wireless device and receives one or more CSI reports from the wireless device that are generated by the wireless device with inter-subframe channel interpolation of CSI-RS estimates across subframes disabled in response to the base station disabling inter-subframe channel interpolation of CSI-RS estimates across subframes at the wireless device. In this manner, CSI feedback is improved particularly in embodiments in which the base station transmits a beamformed CSI-RS resource(s) and reuses the same CSI-RS resource(s) for different beams over time.

Abstract: A base station in a communications network broadcasts a cell-specific instruction to a plurality of mobile terminals in a cell served by the base station. The cell-specific instruction indicates that an uplink symbol in each of multiple subsequent subframes has been semi-statically configured for sounding reference signal (SRS) transmission. The base station determines that a first mobile terminal of the plurality of mobile terminals is to use the uplink symbol in a given one of the multiple subsequent subframes for aperiodic SRS transmission, and in response, signals a terminal-specific instruction to the first mobile terminal. The terminal-specific instruction is distinct from the cell-specific instruction and indicates that the first mobile terminal is to use the uplink symbol in the given subframe for aperiodic SRS transmission and not for data transmission.

Abstract: A method (100) in a network node serving a User Equipment (UE) capable of network assisted interference cancellation is disclosed. The method involves a signaling (104) of an indication to the UE indicating whether the UE should enable or disable (108) the network assisted interference cancellation, or whether the UE should autonomously choose (110) to enable or disable the network assisted interference cancellation. The enabling or disabling is done for at least one of demodulating the downlink channel or computing the channel state information. The method further involves a receiving (106) of information from the UE about whether the network assisted interference cancellation has been used by the UE for at least one of demodulating the downlink channel and computing the channel state information. A related method in a UE is also disclosed, together with the network node and the UE as such.

Abstract: The present invention uses user-specific resources, as allocated on the uplink, for conveying one or more antenna-specific sounding reference signals (SRSs). This technique advantageously permits, for example, a user equipment (UE) configured for uplink Multiple-Input-Multiple-Output (MIMO) operation to send antenna-specific SRSs within the granted resources allocated to the UE via one or more scheduled uplink grants. That is, within the granted resources allocated by a given uplink grant, a UE uses at least a portion of those resources for sending antenna-specific SRSs, rather than for sending uplink data (user traffic). Thus, in one or more embodiments, the present invention comprises a method at a UE of transmitting antenna-specific SRSs for two or more uplink transmit antennas. The method comprises transmitting an antenna-specific sounding reference signal for at least one of the uplink transmit antennas within a granted resource allocated to the user equipment for a scheduled uplink data transmission.

Abstract: A method and an arrangement in a user equipment for reporting Channel State Information, CSI, and a method and an arrangement in a base station for obtaining CSI are provided. The user equipment is in connection with the base station in a cellular communication network. After receiving a receiving a grant in a subframe n to be used for CSI reporting, from the base station, the user equipment determines subframe type of a subframe n+p. The user equipment then reports to the base station, CSI reflecting channel conditions in the subframe type of subframe n+p. p is a variable value.

Abstract: According to some embodiments, a wireless device receives (1020) a discovery burst from a network node (115). The same discovery burst includes multiple signals within at least one subframe, each of the multiple signals having one or more associated measurement functions. At least one of the multiple signals is received with multiple repetitions within the same discovery burst and two or more repetitions of the same type of signal can be combined by the wireless device. The wireless device performs (1024) at least one radio measurement based at least in part on a particular one of the signals of the discovery burst. The performed at least one radio measurement corresponds to a measurement function associated with the particular signal of the discovery burst.

Abstract: Method performed by a network node (210) to indicate a first and a second set of antenna ports. The network node (210) indicates (803) to a wireless device (250) at least one of: a) a first indication of a first set (M?) of antenna ports for first measurements on first radio signals, the first measurements associated with periodic reporting, and b) a second indication of a second set (M) of antenna ports for second measurements on second radio signals, the second measurements associated with aperiodic reporting. The first set is different than the second set. The periodic and the aperiodic reporting are by the wireless device (250) and correspond to a same Channel State Information, CSI, process. The network node (210) also transmits (804), to the wireless device (250), the first radio signals, periodically, over the first set and the second radio signals over the second set.

Abstract: One aspect of the teachings herein relates to signaling codebook restrictions, to restrict the precoder recommendations being fed back from a remote transceiver, so that precoder selections made by the remote receiver are restricted to permitted subsets of overall precoders within a defined set of overall precoders, or to permitted subsets within larger sets of conversion precoders and tuning precoders, for the case where the overall precoders are represented in factorized form by conversion and tuning precoders. As a non-limiting example, these teachings advantageously provide for precoder restrictions in LTE or LTE-Advanced networks, where ongoing development targets the use of larger, richer sets of precoders, and where the disclosed mechanisms for determining, signaling, and responding to subset restrictions provide significant operational advantages.