Search

EP-4738718-A2 - TRANSMISSION OF REFERENCE SIGNALS FROM A TERMINAL DEVICE

EP4738718A2EP 4738718 A2EP4738718 A2EP 4738718A2EP-4738718-A2

Abstract

The invention relates to a terminal device, a method and a computer program for transmission of reference signals. More specifically, the terminal device comprises at least four physical antenna ports and processing circuitry. The processing circuitry is configured to cause the terminal device to determine a mapping between an uplink reference signal and a physical antenna port, where the determination is based on pairing physical antenna ports which have highest average received signal power. Then the terminal device transmits an uplink reference signal, based on the determined mapping, by using one or more of the at least two paired physical antenna ports with the highest averaged received power.

Inventors

  • PETERSSON, SVEN
  • NILSSON, ANDREAS
  • ATHLEY, FREDRIK
  • TIMO, Roy
  • ZHANG, Xinlin

Assignees

  • Telefonaktiebolaget LM Ericsson (publ)

Dates

Publication Date
20260506
Application Date
20190429

Claims (11)

  1. A terminal device (200) for transmission of reference signals, the terminal device (200) comprising at least four physical antenna ports (250) and processing circuitry (210), the processing circuitry being configured to cause the terminal device (200) to: determine a mapping between an uplink reference signal and a physical antenna port based on pairing physical antenna ports which have highest average received signal power; and based on the determined mapping, transmit an uplink reference signal using one or more of the at least two paired physical antenna ports with the highest averaged received power.
  2. The terminal device according to claim 1, wherein the mapping is for a precoder in a codebook, the at least one precoder defines transmission on at least one spatial layer, and the mapping is determined to select which at least one spatial layer to be transmitted on which physical antenna port (250).
  3. The terminal device according to claim 2, wherein at least one row but less than all rows in each of the at least one precoder consists of all zero-valued coefficients.
  4. The terminal device according to any of the preceding claims, wherein the terminal device (200) is configured to operate in at least two frequency bands, and wherein the mapping is frequency selective such that different mappings are applied in the at least two frequency bands.
  5. The terminal device according to claim 4, wherein the antenna element (260) or array of at least two antenna elements (260) of at least two of the physical antenna ports (250) are arranged at the terminal device (200) to point in at least two mutually different pointing directions (290a, 290b, 290c).
  6. The terminal device according to any of the preceding claims, wherein each physical antenna port (250) is fed by its own power amplifier (270).
  7. The terminal device according to any of the preceding claims, wherein each physical antenna port (250) is operatively connected to only a single antenna element (260) or an array of at least two antenna elements (260).
  8. The terminal device according to any of the preceding claims, wherein the uplink reference signals are sounding reference signals, SRS.
  9. The terminal device according to claim 8, wherein each uplink reference signal defines an SRS port.
  10. A method for transmission of reference signals, the method being performed by a terminal device (200), the terminal device (200) comprising at least four physical antenna ports (250), the method comprising: determining a mapping between an uplink reference signal and a physical antenna port based on pairing physical antenna ports which have the highest average received power; and based on the determined mapping, transmitting an uplink reference signal using one or more of the at least two paired physical antenna ports with the highest averaged received power.
  11. A computer program (820) for transmission of reference signals, the computer program comprising computer code which, when run on processing circuitry (210) of a terminal device (200) comprising at least four physical antenna ports (250), causes the terminal device (200) to: determine a mapping between an uplink reference signal and a physical antenna port based on pairing physical antenna ports which have the highest average received signal power; and based on the determined mapping, transmit an uplink reference signal using one or more of the at least two paired physical antenna ports with the highest averaged received power.

Description

TECHNICAL FIELD Embodiments presented herein relate to a method, a terminal device, a computer program, and a computer program product for transmission of reference signals. BACKGROUND In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed. For example, equipping a terminal device with two or more, or even multiple, transmit antennas (where each such antenna is connected to its own physical antenna port at the terminal device) might enable the uplink performance to be increased through higher spectral efficiency and/or improved link budget than allowed for only one single antenna. Two uplink transmission schemes will be considered next; codebook based (CB) transmission and non-codebook based (NCB) transmission. CB transmission is a feedback based transmission scheme that can be used for frequency division duplex (FDD) and for terminal devices without transmitter-receiver reciprocity. NCB transmission is based on reciprocity and can be used in time division duplex (TDD) for UEs with transmitter-receiver reciprocity. In CB transmission the terminal device first transmits one or two uplink reference signals, such as sounding reference signals (SRS, or SRS ports). The radio access network node serving the terminal device estimates the uplink radio propagation channel based on the received uplink reference signals, where each uplink reference signal is transmitted from a separate physical antenna port, and determines a suitable transmission rank and precoder for the coming uplink data transmission. In general terms, the number of rows of the precoder equals the number of physical antenna ports, and the number of columns of the precoders equals the number of layers. The precoder could be selected from a predetermined set of fixed precoders defined in the 3GPP specifications, a so-called codebook, see 3GPP TS 38.211 "NR; Physical channels and modulation", Version 15.5.0. The radio access network node then signals the transmission rank via a transmit rank indicator (TRI) and an index to the determined precoder in the codebook, a so-called transmit precoder matrix indicator (TPMI). The terminal device shall then use the precoder corresponding to the signaled TRI and TPMI in its upcoming uplink data transmission. Depending on terminal device implementation, it may be possible to maintain the relative phase of the transmit chains of an antenna array (assuming for example one radio chain per antenna element). In this case, the terminal device is enabled to transmit the same modulation symbol over multiple transmit chains with individual gain and/or phase per transmit chain and in this way forming a beam over the corresponding antenna array. This transmission of a common modulation symbol or signal on multiple antenna elements with controlled phase is referred to as coherent transmission. The support for coherent uplink MIMO transmission in Release 10 of the Long Term Evolution (LTE) suite of telecommunication standards is indicated via a feature group indication for relative transmit phase continuity for uplink spatial multiplexing, wherein a terminal device indicates if it can adequately maintain the relative phase of transmit chains over time in order to support coherent transmission. In other terminal device implementations, the relative phase of the transmit chains may not be well controlled, and coherent transmission may not be used. In such implementations, it may still be possible for the terminal device to transmit on one of the transmit chains at a time, or to transmit different modulation symbols on the transmit chains. In the latter case, the modulation symbols on each transmit chain may form a spatially multiplexed, or MIMO, layer. This class of transmission is referred to as non-coherent transmission. In still other terminal device implementations, the relative phase of a subset of the transmit chains is well controlled, but not over all transmit chains. One possible example is described above with respect to multi-panel operation, where phase is well controlled among transmit chains within a panel, but phase between panels is not well controlled. This class of transmission is referred to as partially-coherent. All three of these variants of relative phase control have been agreed to be supported for transmission over the fifth generation (5G) New Radio (NR) air interface, and so terminal device capabilities have been defined for full coherence, partial coherence, and non-coherent transmission. Depending on coherence capability of the terminal device, it is possible to configure the terminal device with three different combinations of codebook subsets. Fig. 1 illustrates three different codebook subsets 10, 20, 30 for rank 1 precoders. Codebook subset 10 is referred to as non-coherent and only consists of antenna selection precoders. Codebook