WO2012096609A1

WO2012096609A1 - Methods and apparatuses for uplink mimo transmissions

Info

Publication number: WO2012096609A1
Application number: PCT/SE2011/051193
Authority: WO
Inventors: Johan Bergman; Bo Göransson; Johan Hultell
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2011-01-10
Filing date: 2011-10-05
Publication date: 2012-07-19
Anticipated expiration: 2013-07-10

Abstract

The invention relates to methods and apparatuses that facilitate control of radio link quality of uplink MIMO transmissions. A quality difference between different encoded signals is reduced by interleaving the encoded signals over different virtual antennas (17, 18) in a user equipment. The interleaving can be performed on different time-scales and at different stages of the transmission procedure. According to some embodiments encoded transport blocks (103, 4) are interleaved over the virtual antennas (17, 18) to achieve a more even radio link quality between the transport blocks (103, 104). In some embodiments a physical layer transmission of data and a physical layer retransmission of the same data are carried out from different virtual antennas (17, 18) to reduce the quality difference between data transmitted from different virtual antennas.

Description

METHODS AND APPARATUSES FOR UPLINK MIMO TRANSMISSIONS

TECHNICAL FIELD

The embodiments described herein relate to uplink Multiple-Input Multiple- Output, MIMO in a communications system and in particular to transmission and signaling aspects related to uplink MIMO transmissions.

BACKGROUND

Th e re i s a co nt i n uo u s d eve l op m e n t of n ew g en e ratio n s of m ob i l e communications technologies to cope with increasing requirements of higher data rates, improved efficiency and lower costs. High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), together referred to as High Speed Packet Access (HSPA), are mobile communication protocols that were developed to cope with higher data rates than original Wideband Code Division Multiple Access (WCDMA) protocols were capable of. The 3rd Generation Partnersh ip Project (3GPP) is a standards-developing organization that is continuing its work of evolving HSPA and creating new standards that allow for even higher data rates and improved functionality. In a radio access network implementing HSPA, a user equipment (UE) is wirelessly connected to a radio base station (RBS) commonly referred to as a NodeB (NB). A radio base station is a general term for a radio network node capable of transmitting radio signals to a user equipment (UE) and receiving signals transmitted by a user equipment (UE).

3GPP has evaluated the potential benefits of uplink transmit (Tx) diversity in the context of HSUPA. With uplink transmit diversity UEs that are equipped with two o r more transmit antennas are capable of utilizing all of them for uplink transmissions. This is achieved by multiplying a UE output signal with a set of complex pre-coding weights, a so-called pre-coding vector with one pre-coding weight for each transmit antenna. The rationale behind uplink transmit diversity is to adapt the pre-coding weights so that user and network performance is maximized . Depending on UE implementation the antenna weights may be associated with different constraints. Within 3GPP two classes of transmit diversity are considered:

- Switched antenna transmit diversity, where the UE at any given time-instance transmits from one of its antennas only.

- Beamforming where the UE at a given time-instance can transmit from more than one antenna simultaneously. By means of beamforming it is possible to shape an overall antenna beam in the direction of a target receiver.

While switched antenna transmit diversity is possible for UE implementations with a single power amplifier (PA) the beam forming solutions may require one PA for each transmit antenna.

Switched antenna transmit d iversity can be seen as a special case of beamforming where one of the antenna weights is 1 (i.e. switched on) and the antenna weight of any other antenna of the UE is 0 (i.e. switched off).

A fundamental idea behind uplink transmit diversity is to exploit variations in the effective channel to improve user and network performance. The term effective channel here incorporates effects of transmit antenna(s), transmit antenna weights, receiving antenna(s), as well as the wireless channel between transmitting and receiving antennas. Selection of appropriate antenna weights is crucial in order to be able to exploit the variations in the effective channel constructively. During 2009 and 2010 the 3GPP evaluated the merits of open loop beam forming and open loop antenna switching for uplink transmissions in WCDMA HSPA. These techniques are based on that UEs equipped with multiple transmit antennas exploit existing feedback e.g. feedback transmitted on the Fractional Dedicated Physical Channel (F-DPCH) or on the E-DCH HARQ Acknowledgement Indicator Channel (E-HICH) to determine a suitable pre-coding vector in an autonomous fashion. The purpose of pre-coding the signals is to "maximize" the signal to noise plus interference ratio (SIR) at the receiving NodeB. Since the network is unaware of the appl ied pre-coding weights the NodeBs will experience a discontinuity in the measured power whenever a change in pre-coding weights occurs. A summary of the 3GPP studies on open loop transmit diversity techniques can be found in 3GPP's technical report TR 25.863, UTRA: Uplink Transmit Diversity for High Speed Packet Access.

Recently there have been proposals for introducing closed loop transmit diversity for WCDMA HSPA. Closed loop transmit diversity refers to both closed loop beam forming and closed loop antenna switching. At the 3GPP meeting RAN#50 a work item with the purpose of specifying support for closed loop transmit diversity was agreed. Contrary to the open loop techniques where the U E decides pre-coding weights autonomously, closed loop techniques are based on that the network, e.g., the serving NodeB, selects the pre-coding vector with which the signal is multiplied . In order to signal the necessary feedback information from the network to the UE, the NodeB can either rely on one of the existing physical channels, e.g., F-DPCH, or a new feedback channel could be introduced.

Uplink multiple-input-multiple-output (MIMO) transmission is another related technique that has been proposed as a candidate for WCDMA/HSPA in 3GPP standard release 1 1 . A study item on uplink MIMO for WCDMA/HSUPA was started at the 3GPP RAN#50 plenary meeting. For uplink MIMO, different data is transmitted from different virtual antennas, where each virtual antenna corresponds to a different pre-coding vector. Note that closed loop beam forming can be viewed as a special case of uplink MIMO where no data is scheduled on one of two virtual antennas.

MIMO technology is mainly beneficial in situations where the "composite channel" is strong and has high rank. The term composite channel includes the potential effects of transmit antenna(s), PAs, as well as the radio channel between the transmitting and receiving antennas. The rank of the composite channel depends on the number of uncorrelated paths between the transmitter and the receiver. In situations where the rank of the composite channel is low e.g . where there is a l im ited amount of mu lti-path propagation and cross polarized antennas are not used, and/or the path gain between the UE and the NodeB is weak, single-stream transmissions, i.e. beam forming techniques, are generally preferred over MIMO transmissions. This results from a combined effect of that the theoretical gains of MIMO transmissions is marginal at low SIR operating point and that inter-stream interference can be avoided in case of single-stream transmissions.

Currently HSUPA does not allow MIMO transmission since only transmissions from a single virtual antenna are allowed. Inner loop power control (ILPC) and outer loop power control (OLPC) are used to control the quality of the uplink transmission. More specifically, the ILPC is located in the NodeB(s) of an active set. The ILPC is used to ensure that a Dedicated Physical Control Channel (DPCCH) pilot quality target r_target is maintained. The serving NodeB monitors that the received power of the DPCCH pilot fulfills the quality target r_target and based on this monitoring the serving NodeB issues transmit power control (TPC) commands to the UE to raise or lower the transmission power of the DPCCH pilot. Since gain factors for a given transport block size (TBS) in an Enhanced Dedicated Channel Transmission Format Combination (E-TFC) selection process use pre-defined power offsets with respect to the DPCCH transmit power, the ILPC controls the transmit power of all the physical channels. The OLPC is located in the radio network controller (RNC) and it is used to adjust the quality target r_target used by the ILPC. Although not specified in the 3GPP standard the OLPC typically increases the quality target r_target if a too high block error rate (BLER) on E-DCH Dedicated Physical Data Channel (E-DPDCH) transmissions is observed.

For a UE configured in uplink MIMO mode the UE can transmit independent streams, i.e. different data from the different virtual antennas, simultaneously. The data signals transm itted from the different virtual antennas will be associated with different radio link quality. An issue for such settings then becomes how to ensure that the radio link quality associated with all virtual antennas can be controlled. SUMMARY

An object of the present invention is to provide methods and apparatuses that at least to some extent facilitate improved control of radio link quality of uplink MIMO transmissions.

The above stated object is achieved by means of methods and user equipments according to the independent claims.

A first embodiment provides a method in a user equipment configured for uplink Multiple-Input Multiple- Output, MIMO, transmissions using a first virtual antenna and a second virtual antenna. The method comprises a step of interleaving at least one encoded transport block over both the first virtual antenna and the second virtual antenna. A second embodiment provides a method in a user equipment configured for uplink MIMO transmissions using a first virtual antenna and a second virtual antenna. According to the method at least one E-DPDCH is interleaved over both the first virtual antenna and the second virtual antenna. A third embodiment provides a method in a user equipment configured for uplink MIMO transmissions using a first virtual antenna and a second virtual antenna. The method comprises transmitting data through the second virtual antenna. The method further comprises detecting a need for physical layer retransmission of the data and performing physical layer retransmission the data through the first virtual antenna.

A fourth embodiment provides a user equipment comprising digital data processing circuitry configured to implement a first virtual antenna and a second virtual antenna. The user equipment is configured for uplink MIMO transmissions using the first virtual antenna and the second virtual antenna. The digital data processing circuitry is further configured to interleave at least one encoded transport block over both the first virtual antenna and the second virtual antenna. A fifth embodiment provides a user equipment comprising digital data processing circuitry configured to implement a first virtual antenna and a second virtual antenna. The user eq u i pment is config u red for u pl in k M I MO transmissions using the first virtual antenna and the second virtual antenna. The digital data processing circuitry is further configured to interleave at least one E- DPDCH over both the first virtual antenna and the second virtual antenna.

A sixth embodiment provides a user equipment comprising digital data processing circuitry configured to implement a first virtual antenna and a second virtual antenna. The user equipment is configured for uplink MIMO transmissions using the first virtual antenna and the second virtual antenna. The digital data processing circuitry is configured to control that data is transmitted through the second virtual antenna. The digital data processing circuitry is further configured to detect a need for physical layer retransmission of the data and to control that physical layer retransmission is performed of the data through the first virtual antenna.

A seventh embodiment provides a method in a user equipment configured for uplink MIMO transmissions. The method comprises signaling to a network node whether the user equipment is performing uplink transmissions using single or multiple stream transmissions.

An eighth embodiment provides a user equipment configured for uplink MIMO transmissions. The user equipment comprises digital data processing circuitry configured to control the user equipment to signal to a network node whether the user equipment is performing uplink transmissions using single or multiple stream transmissions.

An advantage of some of the embodiments described herein is that a quality difference between different encoded signals is reduced by interleaving the encoded signals over different virtual antennas. The interleaving can be performed on different time-scales and at different stages of the transmission procedure. According to some embodiments encoded transport blocks are interleaved over the virtual antennas to achieve a more even quality between the transport blocks. The interleaving of the encoded transport block is in some embodiments performed prior to physical channel mapping and in other embodiments after physical channel mapping. In some embodiments a physical layer transmission of data and a physical layer retransmission of the same data are carried out from different virtual antennas to reduce the quality difference between data transmitted from different virtual antennas. By keeping radio link quality associated with transmissions from the different virtual antennas at comparable levels may facilitate decoding at the receiver. Accordingly some embodiments of the invention provide for facilitated control of the quality of uplink MIMO transmissions by interleaving transmissions over different virtual antennas.

Another advantage of some of the embodiments described herein is that facilitated control of the quality of uplink MIMO transmissions is achieved by a user equipment signaling to a network node whether the user equipment is performing uplink transmissions using single or multiple stream transmissions. By making the network aware of whether single or multiple stream transmissions are used, it is easier for the network to take appropriate measures to control the radio link quality of the uplink transmissions.

Further advantages and features of embodiments of the present invention will become apparent when reading the following detailed description in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic block diagram illustrating a system in which different embodiments of this disclosure may be implemented.

Fig. 2 is a diagram illustrating fast fading of two different physicalantennas.

Fig. 3 is a schematic block diagram illustrating an embodiment of a user equipment architecture which can support uplink MIMO.

Fig. 4 is a schematic block diagram illustrating an alternative embodiment of a user equipment architecture which can support uplink MIMO.

Figs. 5a and 5b are flow diagrams illustrating embodiments of methods of this disclosure. Fig. 6 is a schematic illustration of retransmission of data from different virtual antennas according to an embodiment.

Fig. 7 is a schematic illustration of retransmission of data from different virtual antennas according to an alternative embodiment.

Fig. 8 is a schematic illustration of an embodiment according to which symbols within a subframe are interleaved over virtual antennas.

Fig. 9 is a schematic illustration of an alternative embodiment according to which symbols within a subframe are interleaved over virtual antennas.

Fig. 10 is a schematic block diagram illustrating an embodiment according to which multiple transport blocks are interleaved over virtual antennas.

Fig . 1 1 is a schematic block diagram illustrating an embodiment according to which different parts of a transport block are interleaved over virtual antennas.

Fig . 12 is a flow diagram illustrating transport channel processing including interleaving over virtual antennas according to an embodiment.

Fig . 1 3 is a schematic block d iagram of a user equ ipment accord ing to an embodiment of this disclosure.

DETAILED DESCRIPTION

The embodiments of this disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which different exemplary embodiments are shown. These exemplary embodiments are provided so that this disclosure will be thorough and complete and not for purposes of limitation. In the drawings, like reference signs refer to like elements. Fig. 1 is a schematic block diagram illustrating a system in which different embodiments of this disclosure may be implemented. Fig. 1 shows a user equipment (UE) 1 1 configured to support uplink MIMO transmissions for communication with a network node 12, which for instance may be a serving NodeB. The exemplary UE 1 1 is illustrated with two physical transmit antennas 13, 14 and the network node is illustrated with two physical receive antennas 15, 16. The composite channel between the UE 1 1 and the network node 15 comprises wireless channels, h1 1 , h12, h21 and h22 between the different transmit antennas 13, 14 and receive antennas 15, 16 as illustrated in Fig. 1 . Using uplink MIMO different data, such as a first signal s1 (t) and a second signal s2(t) as illustrated in Fig. 1 , are transmitted using different virtual antennas 17, 18. Here parts with dashed border are associated with a first virtual antenna 17 and parts with dotted borders are associated with a second virtual antenna 18. Signals associated with the first virtual antenna 1 7 are pre-coded with pre- coding weights w1 and w2 prior to transmission from the different physical antennas 13 and 14. Signals associated with the second virtual antenna 18 are pre-coded with pre-coding weights w3 and w4 prior to transmission from the different physical antennas 13 and 14.

For multi-antenna transmission techniques it is important that the network, e.g. a serving NodeB, has the ability to acquire knowledge about the channel. This is because for a UE 1 1 configured in uplink MIMO mode, knowledge about the channel characteristics are needed both to determine the rank of the channel and to determine suitable pre-coding vector(s).

In the following we assume that the UE 1 1 transmits a primary pilot signal on a primary dedicated physical control channel (P-DPCCH) and a secondary pilot signal on a secondary dedicated physical control channel (S-DPCCH). It is further assumed that the transmit power associated with the P-DPCCH is Pp. DPccH and the transmit power associated with the S-DPCCH is PS-DPCCH = δ-Ρρ. DPccH, where δ D is a relative power difference between P-DPCCH and S- DPCCH. We furthermore let h "l l h "12

H (Eq. 1 )

h_2l h₂₂ denote the channel matrix of the wireless channel between the UE 1 1 and the network node 1 2. Here h_l2 denotes the wireless channel between a second transmit antenna 14 of the UE 1 1 and a first receive antenna 15 of the network node 12. We also let a

Ω (Eq. 2)

0 be a matrix summarizing inaccuracies of power amplifiers (PAs) associated with the different physical antennas 13, 14. Note that a is a random variable that describes the inaccuracy associated with the first (upper) transmit branch, while ε is a random variable describing the inaccuracy of the PA associated with the second (lower) transmit branch illustrated in Fig. 1 . Finally we also let w_l w,

W (Eq. 3)

represent a pre-coding matrix. Here [w_x w₂ ] are the pre-coding weights applied to the P-DPCCH and other signals associated with the first virtual antenna 17 and [w₃ w₄] are the pre-coding weights applied to the S-DPCCH and other signals associated with the second virtual antenna 18. With these notations a received signal at the NodeB r= [r_x r₂ ]can be written as r = H-n-W diag([1 d])-s (Eq. 4) where s = [^ (t) s₂(t)]^J are two pilot signals. In a case where the DPCCH pilots are not pre-coded, as will be explained further below in connection with Fig. 4, W corresponds to the identity matrix.

As mentioned above an issue in case of uplink MIMO is how to ensure that the radio link quality associated with all virtual antennas can be controlled. One solution would be to introduce additional ILPCs and OLPCs so that each virtual antenna has its individual ILPC and OLPC. However, this solution presents several drawbacks and problems. For instance the signaling load on the serving RNC (S-RNC) will increase due to that the S-RNC needs control two or more OLPCs. Another drawback is that additional Fractional Dedicated Physical Channel (F-DPCH) resources need to be allocated to UEs configured in MIMO mode since each ILPC will require F-DPCH resources. Yet another drawback is that channel estimation for the purpose of channel sounding will become increasingly difficult. The later is because the NodeB(s) need to be aware of the relative power difference δ between the DPCCH pilots in order to estimate the channel as can be seen from Equation 4 above. The channel is in turn necessary for performing the channel sounding in which suitable pre-coding vectors and the number of streams that should be scheduled is determined.

Apart from increasing downlink overhead, an architecture relying on multiple ILPC and OLPC loops thus require that the relative power difference between the DPCCHs are signaled by the UE. Due to the large dynamic that can be expected in terms of DPCCH transmission power, in case similar SIR targets are used for all virtual antennas, several bits would have to be allocated on existing control channels. In addition to a difference in fast fading a difference in required transmit power would also lead to that the virtual different antennas will be associated with different far-field antenna pattern. Characteristics of the far- field antenna characteristics were studied in 3GPP's technical report TR 25.863, UTRA: Uplink Transmit Diversity for High Speed Packet Access, where it was shown that the difference often could be in the order of 5 dB. To avoid such redesigns a solution relying on one ILPC and one OLPC may be desirable.

To ensure that the serving and any non-serving NodeB are aware of the power difference δ, it can either be signaled by the UE 1 1 or kept constant. The latter could be achieved with a single ILPC that adjust the transmit power of both the P-DPCCH and the S-DPCCH.

In the following we will focus on a context where there only exists a single ILPC that controls the transmit power of both the P-DPCCH and the S-DPCCH.

A problem with an architecture that relies on one ILPC and one OLPC is however that the DPCCH pilots may experience highly varying radio quality e.g. link capacity or block error rate (BLER) given a certain transport block size (TBS). As the transmission power associated with the transmissions of data other than the DPCCH pilots is determined by multiplying the DPCCH power with a power offset, sometimes also referred to as gain factors, the radio link quality associated with the transmissions from the virtual antenna(s) that are not power controlled by the ILPC and OLPC will be exhibit large variations in quality. In the prolonging, having an asymmetric radio link quality associated with the transmissions from the different virtual antennas can result in that:

- The ILPC and/or OLPC will increase the DPCCH transmit power associated with all virtual antennas until the weakest DPCCH fulfills the quality target "on average". This can be achieved by e.g. having the ILPC operating on the DPCCH associated with weakest received power. Alternatively, If the ILPC only operates on one of the streams and the OLPC operate on both streams the OLPC will increase the quality target used by the ILPC(s) so that the qual ity associated with the stream on wh ich the I LPC(s) does not consider, on average meets the DPCCH quality level. This will cause additional overhead since the transmit power of all physical channels is decided by the link that is weakest.

- There will be increased jitter on radio link control (RLC) and media access control (MAC) layer. Increased jitter will increase the risk of window stalling thus harming higher layer performance.

Increased jitter will increase the required buffer sizes at the NodeB. Additionally, a problem associated with an architecture where only one ILPC exists and a second virtual antenna is not power controlled, is that the transmit power used for the transmissions of the signals, except the S-DPCCH, from the second virtual antenna initially needs to be based on some open-loop estimate when the network has been scheduling single-stream transmissions and then schedules dual-stream transmissions.

Hence, there are good reasons for introducing techniques through which the radio link quality associated with the transmissions from the different virtual antennas can be kept at comparable levels and moreover controlled also when a single ILPC and OLPC is employed.

In the following description we will assume, unless otherwise stated, that a transport block is mapped to a single E-DPDCH. Thus the terms E-DPDCH and transport block will in many cases be used in an interchangeable manner as will be explained further below. It is however also possible to map a transport block to multiple E-DPDCHs.

Furthermore, as mentioned above we will focus on scenarios in which there are fewer ILPC available for power control than there are virtual antennas, such as a scenario with a single ILPC loop for controlling the radio quality of the transmissions from two virtual antennas. Since there only is one ILPC available for controlling the radio link performance of the transmissions from both virtual antennas there is an issue of how the quality of the transmissions can be controlled in an efficient manner. For example, if the ILPC always ensures that the transmissions associated with worst DPCCH have sufficient quality then the transmissions from the other virtual antenna will have unnecessarily good performance; thus a resource wastage will occur. Another alternative could be to always associate the single ILPC loop with a selected one of the virtual antennas, i.e. having the ILPC loop operate on the DPCCH associated with said selected virtual antenna so that transmissions through that virtual antenna is subject to ILPC power control. For both these alternatives, transmissions through the other virtual antenna is not subject to ILPC but the transmission power used for transmissions on the other virtual antenna is rather set to the same transmission power as used for transmissions on the virtual antenna whose DPCCH is accounted for in the single ILPC loop.

The embodiments described below are particularly useful in scenarios where there is an issue of how the radio link quality of the transmissions can be controlled in an efficient manner. Therefore the embodiments described herein are particularly useful in scenarios with fewer ILPC loops than there are virtual antennas. However, even if there is an ILPC available for each virtual antenna, some of the embodiments described herein may still be used, even though the benefits are more limited when there are other means available for controlling the quality and transmission power of each individual virtual antenna.

In the following we will describe and illustrate exemplary settings where transmissions can take place from two virtual antennas simultaneously and where the link quality associated with the transmissions from the different virtual antennas are different. The varying quality levels could be a consequence of an architecture where there are fewer ILPC(s) and OLPC(s) than streams (in other words fewer ILPC(s) and OLPC(s) than virtual antennas). To exemplify, Fig. 2 depicts two realizations of fast fading associated with two physical antennas by illustrating the instantaneous link quality in dB as a function of time of the two physical antennas. From Fig. 2 it is evident that the effective radio link quality for each virtual antenna can differ significantly. The effective radio link quality for each virtual antenna includes the combined effect of pre-coding vectors and the link quality associated with each physical antenna. In addition to the fast fading, realistic transmit antennas will typically be associated with different far-field antenna radiation patterns, see e.g. the 3GPP technical report TR 25.863, UTRA: Uplink Transmit Diversity for High Speed Packet Access for more information. The difference in far-field antenna radiation patterns can often be in order of 3-5 dB and it will cause additional link quality asymmetry. Due to these effects, it follows that a solution in which only one of the two DPCCHs is power controlled, e.g., the P-DPCCH, will result in that the link quality associated with the transmissions from the other virtual antenna can be highly different. As noted above, varying physical layer qual ity amongst different streams is detrimental for the overall performance.

Fig . 3 and Fig. 4 illustrate two possible physical channel layouts for a UE configured in uplink MIMO mode comprising two physical antennas 13 and 14 and two virtual antennas 17 and 18. The term physical channel encompass existing legacy channels, e.g. Fractional Dedicated Physical Channel (F-DPCH), E-DCH Dedicated Physical Control Channel (E-DPCCH), E-DCH Dedicated Physical Data Channel (E-DPDCH), etc. For uplink MIMO transmissions, a UE can transmit two of certain physical channels; one from each virtual antenna as illustrated in Figs. 3 and 4. For demodulation purposes at least one DPCCH pilot needs to be transmitted for each virtual antenna. In Fig. 6 the primary DPCCH (P-DPCCH) pilot and the secondary DPCCH (S-DPCCH) pilot are pre-coded with the same pre-coding vectors as used for pre-coding the other physical channels transmitted from each virtual antenna. In Figure 7 the P-DPCCH and S-DPCCH are not pre-coded. Note that the E-DPCCH used to describe the modulation used for the transmitted data signals can be transmitted from different or the same virtual antennas. If the radio link quality associated with the transmissions from the different virtual antennas 17, 18 is different and parallel transmissions of transport blocks of different sizes are to be supported from the different virtual antennas 17, 18, different E-DPCCH(s) needs to be transmitted, e.g., since different E-DCH Transport Format Combination Identifiers (E-TFCIs) are used for the transport blocks. In other words, if two unique TBSs can be transmitted in parallel, then two signals characterized by different coding and modulation needs to be transmitted. Note that when referring to transport blocks here we mean encoded transport blocks as will be explained in further detail below.

In a first embodiment, transmissions of some or all encoded signals are interleaved over the virtual antennas. This will reduce the quality difference of the signals that are interleaved. For example if a transport block associated with a first stream is mapped to one E-DPDCH and a transport block associated with a second stream is mapped to another E-DPDCH, the two E-DPDCHs can be interleaved over the virtual antennas. It is also possible to interleave the transport blocks over the virtual antennas prior to physical channel mapping but after encoding. Therefore, when referring herein to "interleaving of encoded transport block(s) over virtual antennas" the expression is intended to encompass both interleaving of the encoded transport block(s) prior to physical channel mapping as well as interleaving of the encoded transport block(s) after physical channel mapping, wherein the latter case corresponds to interleaving of the physical channel(s) to which the encoded transport block(s) was mapped. Note that it is possible to extend this to scenarios where multi-code E-DPDCHs are required for carrying the transport block. Furthermore, it is also possible that the data is encoded into one transport block and then the symbols in the transport block are mapped to the different virtual antennas. This will be explained further below.

Fig. 5a is a flow diagram illustrating a method in accordance with the above described first embodiment. The method is performed in a user equipment configured for uplink MIMO transmissions using at least a first virtual antenna 17 and a second virtual antenna 1 8. The method comprises a step 51 of interleaving at least one encoded transport block over both the first virtual antenna 17 and the second virtual antenna 18.

In different embodiments the interleaving can occur on different time-scales. According to a second embodiment, physical layer retransmissions of data are retransmitted from another virtual antenna than the data originally was transmitted from. Thus physical layer retransmissions of data that originally was transmitted through a virtual antenna whose link is not power controlled may be retransmitted from a virtual antenna that is power controlled. This can be beneficial because the performance associated with the transmissions from the virtual antenna that is not power controlled will be unpredictable, i.e. the physical layer can be both better as well as worse when compared to the quality associated with the power controlled link. However, assuming that the BLER target towards which the ILPC and OLPC is adjusted is moderate an unsuccessful reception of a transport block transmitted on a link that is not power controlled can be used as an indicator that the physical layer performance associated with that link is inferior. Thus, as long as the channel coherence time is sufficiently long an additional diversity gain can be achieved by retransmitting the transport block from the other virtual antenna that is power controlled.

Fig. 5 b is a flow diagram illustrating a method according to the above described second embodiment. The method is performed in a UE configured for uplink MIMO transmissions using at least a first virtual antenna 17 and a second virtual antenna 18. The method comprises transmitting data through one of the virtual antennas, e.g. the second virtual antenna 18, in a step 52. In a step 53 of the method the UE detects a need for physical layer retransmission of the data. Thereafter the UE performs physical layer retransmission in a step 54 of the data through the other virtual antenna, i.e. through the first virtual antenna 17 assuming that the data first was transmitted through the second virtual antenna 18.

Fig. 6 and Fig. 7 illustrate schematically two examples of how retransmission according to the second embodiment can be carried out. Fig. 6 illustrates that in a first subframe t1 both a transmission of a first packet 61 of data from a first virtual antenna 17, and a transmission of a second packet 62 of d ata from a second virtual antenna 18 are unsuccessful. After a retransmission of both the first packet 61 and the second packet 62 from different virtual antennas, the first packet 61 which was originally transmitted from the first virtual antenna 17 can be successfully in received in a subframe t2 whereas the second packet 62 still is erroneous. In a subsequent subframe t3, the second packet 62 is again transmitted from the second virtual antenna 1 8 whereas a new packet 63 is transmitted from the first virtual antenna 17.

Fig. 7 illustrates a similar scenario as in Fig. 6. The difference with respect to the scenario in Fig. 6 is that there is only one E-HICH configured to MIMO users in the scenario in Fig . 7. Consequently both the first packet 61 and the second packet 62 need to be successfully receive before a new transmission can take place from any of the virtual antennas.

In the embodiments described above only the subsets of the signals associated with the virtual antennas are interleaved. For example, either

- the encoded transport blocks (E-DPDCH(s)) are retransmitted on a different virtual antenna, or

the encoded transport blocks (E-DPDCH(s)) and some other signals, e.g., the E-DPCCHs, are retransmitted from another virtual antenna. According to a third exemplary embodiment the symbols of two signals associated with the different streams that are to be transmitted within one sub- frame are interleaved over the virtual antennas. This results in that part of the symbols in, e.g. an encoded transport block, is transmitted from one virtual antenna and part of the symbols is transmitted from the other virtual antenna. By time-multiplexing the symbols from signals over multiple virtual antennas the difference in physical layer quality of the signals that are time-interleaved will be reduced. Note that according to the third exemplary embodiment, only the encoded transport block (E-DPDCH(s)) or the encoded transport blocks (E- DPDCH(s)) as wel l as some other sig nals, such as e .g . , E-DPCCH are interleaved across the virtual antennas.

Figs. 8 and 9 illustrate two different examples in accordance with the above mentioned third exemplary embodiment.

Fig. 8 illustrates an embodiment in which symbols within a sub frame are time interleaved. Fig. 8 schematically illustrates a first packet 81 associated with a first stream and a second packet 82 associated with a second stream that are to be transmitted within one subframe. The symbols of the first and second packets 81 , 82 are time-interleaved over the first virtual antenna 17 and second virtual antenna 18, such that a first subset 83 of symbols of the first packet 81 is transmitted from the first virtual antenna 17 and a second subset 85 of symbols of the first packet 81 is transmitted from the second virtual antenna 18. Correspondingly a first subset 84 of symbols of the second packet 82 is transmitted from the first virtual antenna 17 and a second subset 86 of symbols of the second packet 82 is transmitted from the second virtual antenna 18. When transmitted from the first virtual antenna 17, symbols in the first subset 83 of symbols of the first packet 81 are time multiplexed with symbols in the first subset 84 of symbols of the second packet 82. Correspondingly, when transmitted from the second virtual antenna 18, symbols in the second subset 85 of symbols of the first packet 81 are time multiplexed with symbols in the second subset 86 of symbols of the second packet 82. Thanks to the time interleaving the quality difference associated with the transmissions from the two virtual antennas will be reduced. In the example illustrated in Fig. 8 there is only one common E HICH shared for both streams. Thus transmissions of new data can only take place once both packets have been successfully received. Accordingly, as illustrated in Fig. 8, when the second packet 82 is unsuccessfully received in a subframe t1 , both the first and second packet 81 , 82 are retransmitted in a subsequent subframe t2.

Fig. 9 illustrates a similar scenario as in Fig. 8 with the only difference that there are two E-H ICHs in the scenario in Fig . 9. Thus, transmission of new packets can take place as soon as one of the packets has been successfully received. In Fig. 9 it is illustrated that symbols of a third packet 83 are interleaved over the virtual antennas 17, 18 and time multiplexed with symbols of the second packet 82 after the first packet has been successfully received in the subframe t1 . Fig. 10 is a schematic block diagram illustrating an embodiment according to which multiple transport blocks are interleaved over virtual antennas 17, 18. Fig. 10 illustrates that data 100 is encoded in two separate transport blocks 103, 104 associated with different streams 101 , 102 respectively. A functional block, an interleaver 105, interleaves symbols of the transport blocks 103 and 104 over both of the virtual antennas 17, 18.

In yet another embodiment illustrated in Fig. 1 1 symbols associated with one encoded signal in a certain sub-frame is partitioned across the two virtual antennas 17, 18 so that part of the symbols are transmitted from one virtual antenna and part of the symbols are transmitted from the other virtual antenna. Note that the difference between this embodiment and the embodiment described in connection with Fig. 10 above is that data 1 1 1 here first is encoded in to one transport block 1 12 independently on whether single or dual stream transmission is used. Then, if dual stream transmission occurs, the transport block 1 12 is partitioned into two parts 1 13, 1 14 and each part is transmitted from a separate virtual antenna 17, 18. Numerous ways for partitioning the data are possible. One example would be to transmit even symbols (symbol 0, 2,...) from one virtual antenna and odd symbols (symbol 1 , 3, 5, ... ) from the other virtual antenna. This approach is illustrated in Figure 1 1 . At the receiver the two segments (parts 1 13 and 1 14) need to be combined before they are decoded, i.e. the data transmitted from one virtual antenna cannot be decoded without the information transmitted from the other virtual antenna.

As indicated above there are different variants of the embodiments described above. For example the transport block size (TBS) of the transport blocks could either be different or identical for different streams. If the TBS for some of the streams is required to be identical, the uplink overhead can furthermore be reduced since it is sufficient to transmit a single E-DPCCH. To maximize the probability that the E-DPCCH is successfully decoded by the NodeB(s) in the active set it could be transmitted from a virtual antenna that is power controlled and/or with an additional power offset in case of dual stream transmissions. Furthermore, the data transmissions of the different streams could either have one common or HARQ processes or separate HARQ processes. For the case where there is a common HARQ process for all streams it is sufficient to have one E-HICH as in the scenarios illustrated in Figs. 7 and 8. Note also that in the case where there is a common HARQ the layer 1 (L1 ) encoding could be performed over the data associated with both streams jointly. If there are separate HARQ processes multiple E-HICH(s) are required as in the scenarios illustrated in Figs. 6 and 9.

In different variants of embodiments interleaving of one or several transport blocks over virtual antennas can be carried out in different stages of the transmission procedure. Fig. 12 is a flow diagram illustrating E-DCH transport channel processing including interleaving over virtual antennas according to an embodiment. Fig. 12 illustrates steps 121 -126 which correspond to the coding steps described for single stream transmission described in section 4.8 of the 3GPP standard specification TS 25. 212 V. 10.0.0. Fig. 12 however illustrates a dual stream transmission scenario, where two transport blocks 1 19, associated with different streams, arrive from the MAC layer to L1 . In the step 121 , a Cyclic Redundancy Check (CRC) is attached to each transport block 1 19, respectively. In the step 122, code block segmentation is carried out separately for the different transport blocks 1 19. Channel coding is performed on the transport blocks 1 19 respectively in the step 123, resulting in encoded transport blocks 120. Thereafter follows physical layer HARQ functionality and rate matching in a step 124 and physical channel segmentation in a step 125. Bits of one encoded transport block 120 may be mapped to one or several physical channels in the step 125 depending on whether one or several E-DPDCHs are used per stream. In the step 126 bit interleaving and physical channel mapping is performed. It is to be noted that the bit interleaving in the step 126 is interleaving of bits separately within each physical channel. Accordingly, the bit interleaving in the step 126 is not an interleaving over different virtual antennas. The step 126 results in the physical channels in the form of E-DPDCHs 127. The E-DPDCHs 127 are then interleaved over the virtual antennas in a step 51 , corresponding to the step 51 illustrated in Fig. 5a, which was described above. In variants of the embodiment illustrated in Fig. 12, the step 51 may instead be carried out at another stage of the E-DCH transport channel processing after the step 123. The step 51 may e.g. be carried out on the encoded transport blocks 1 20 after the step 1 23 and prior to the step 1 24 or alternatively in connection with bit interleaving in the step 1 26, such that bit interleaving and interleaving over virtual antennas are combined.

In some embodiments the UE additionally informs the network, e.g., NodeB(s) in the active set, when it performs dual-stream transmission by reusing bits in the P-DPCCH or (one of) the E-DPCCH transmitted from the first virtual antenna 17. In this case, the physical channels conveying the information regarding whether there is single or dual stream transmission is not time-interleaved. To simplify network operation it is beneficial if the UE can signal whether or not it transmits two streams in a certain subframe. For single-stream transmissions interleaving across the virtual antennas is undesirable.

It may be argued that the Node-B will be aware of whether the UE will transmit one or two streams if the standard stipulates that the UE always should transmit two streams if the network requests dual stream transmission. However, in WCDMA/HSUPA the UE can be in soft handover. Hence there always exist situations where some of the Node-B(s) in the active set is unaware of whether the UE will transmit one or two streams.

If the TBS associated with the two streams can be different the UE will have to transm it two E-DPCCHs. Hence there will be two so-called "happy bits" available whenever dual-stream transmissions take place. The UE uses a happy bit to signal to the network whether or not the UE is satisfied (happy) with the current serving grant. However, for scheduling one of the two happy bits will be sufficient. Consequently one of the two happy bits can be reused for signaling to the network whether single or dual-stream transmission is used. To exemplify, if the happy bit associated with the E-DPCCH transmission of the primary stream is set to "unhappy" and the used E-TFCI in the sub-frame is lower than the one that has been scheduled by the network, this can be viewed as an indication that dual-stream transmissions may have taken place during the sub-frame. Assuming that this condition is fulfilled the NodeB(s) could try to detect the other E-DPCCH . If both E-DPCCHs are detected and decoded successfully, the NodeB(s) can perform the E-DPDCH decoding under the assumption that dual- stream transmission has taken place. Note that this approach requires that two E-DPCCHs are transmitted in case of dual-stream transmissions and that this approach only can be interpreted by the serving NodeB since this is the only NodeB that is aware of the grants. Non-serving NodeBs would have to perform blind detection given that the happy bit associated with the transmissions from the virtual antenna associated with the primary stream is set to "unhappy".

An alternative way for the UE to signal whether or not it transmits two streams in a certain sub-frame would be to reduce the granularity and/or range of the supported E-TFCIs supported for UEs configured in uplink MIMO mode. By reducing the granularity and/or range of the supported E-TFCIs sufficiently one or several of the bits currently allocated to signaling the E-TFCIs can be reused for signaling whether there is single or dual-stream transmissions. Note that this approach is applicable independently on whether the one or two E-DPCCHs are transmitted by UEs configured in uplink MIMO mode.

Yet an alternative approach would be to introduce a new DPCCH format and include information on whether there is a single or dual stream transmission in the P-DPCCH.

Although the embodiments have been described in the context of a single uplink with focus on scenarios where the UE can transmit at most two independent streams, all concepts presented here can be extended to multi-carrier uplink transmission settings and/or settings in which M IMO techniques supporting transmissions on more than two streams simultaneously are supported.

Fig. 13 is a schematic block diagram of an exemplary embodiment of the UE 1 1 in Fig. 1 . As illustrated in Fig. 13, the UE 1 1 comprises the physical antennas 13 and 14, but the UE 1 1 may also comprise further physical antennas. The UE includes transceiver circuitry 132. Alternatively the transceiver circuitry may be arranged in a separate receiver and a transmitter. The UE 1 1 further comprises digital data processing circuitry 131 which may be embodied as one or more processors, application-specific integrated circu its (ASICs), d ig ital sig nal processors (DSPs) or a combination thereof. The digital data processing circuitry may be adapted to perform processing according to any of the embodiments described above. The digital data processing circuitry 131 is inter alia configured to implement the first and second virtual antennas 1 7, 1 8. In order to perform processing i n accordance with any of the descri bed embodiments the digital data processing circuitry 131 may be configured with d ifferent modu les . I n fig . 1 3, two exem plary mod u les 1 33 and 1 35 are ill ustrated . The modu le 1 33 is a module for virtual antenna interleaving according to one or several of the embodiments described above. The module 1 35 is a module for inner loop power control of one or several of the virtual antennas 17, 1 8. The modules 1 33 and 135 are merely some examples and other modules may be used in alternative embodiments, such as a module for controlling signaling to a network node to inform the network node whether the UE 1 1 uses single or multiple stream transmission. The modules 133 and 135 would generally be program modules implemented in software, although implementations completely or partly in firmware, hardware or combinations thereof are also feasible. Program modules may be comprised in one or several computer program products embodied in the form of a volatile or nonvolatile memory, e.g . a RAM, an EEPROM, a flash memory or a disc drive. The UE 1 1 in Fig . 13 also includes a memory 1 34. In case the modules 133 and 135 are program modules, these may be stored by the memory 134 and executed by the digital data processing circuitry 131 .

From the description above it is apparent that some of the embodiments of this disclosure enables improved network control of quality of the packet transmissions for uplink MIMO transmissions.

In the drawings and specification, there have been disclosed typical embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of linnitation, the scope of the invention being set forth in the following claims.

Claims

1 . A method in a user equipment (1 1 ) configured for uplink Multiple-

Input Multiple-Output, MIMO, transmissions using at least a first virtual antenna (17) and a second virtual antenna (18), the method comprising:

interleaving (51 ) at least one encoded transport block (103, 104, 1 1 2, 120, 127) over both the first virtual antenna (17) and the second virtual antenna (18).

2. The method according to claim 1 , wherein symbols (83, 84, 85, 86) generated for said at least one encoded transport block (103, 104, 1 12, 120, 127) for transmission within a sub-frame are interleaved over both the first and second virtual antennas (17, 18).

3. The method according to claim 2, wherein said symbols (83, 84, 85,

86) include first symbols (83, 85) generated for a first encoded transport block (103) and wherein a first subset (83) of said first symbols (83, 85) are transmitted through the first virtual antenna (17) and a second subset (85) of said first symbols (83, 85) are transmitted through the second virtual antenna (18).

4. The method according to claim 3, wherein said symbols (83, 84, 85, 86) include second symbols (84, 86) generated for a second encoded transport block (104) and wherein a first subset (84) of said second symbols (84, 86) are transmitted through the first virtual antenna (17) and a second subset (86) of said second symbols are transmitted through the second virtual antenna (18).

5. The method according to claim 4, wherein symbols in said first subset (83) of said first symbols (83, 85) are time-multiplexed with symbols in said first subset (84) of said second symbols (84, 86) in the transmissions through the first virtual antenna (17) and wherein symbols in said second subset (85) of said first symbols (83, 85) are time multiplexed with symbols in said second subset (86) of said second symbols (84, 86) in the transmissions through the second virtual antenna (18).

6. The method according to any one of claims 4 and 5, wherein the first encoded transport block (1 03) is mapped to a first Enhanced Dedicated Channel Dedicated Physical Data Channel, E-DPDCH, (127) while the second encoded transport block (104) is mapped to a second E-DPDCH (127).

7. The method according to any one of claims 2- 5, wherein a first part (1 13) of the first encoded transport block (1 12) is mapped to a first E-DPDCH (127) and a second part of the first encoded transport block (1 14) is mapped to a second E-DPDCH (127).

8. The method according to any one of claims 1 -7, further comprising interleaving symbols generated for an Enhanced Dedicated Channel Dedicated Physical Control Channel, E-DPCCH, over both the first virtual antenna (17) and the second virtual antenna (18).

9. A method in a user equipment (1 1 ) configured for uplink MIMO transmissions using at least a first virtual antenna (1 7) and a second virtual antenna (18), the method comprising:

interleaving (51 ) at least one E-DPDCH (127) over both the first virtual antenna (17) and the second virtual antenna (18).

10. The method according to claim 9, wherein symbols generated for said at least one E-DPDCH (127) within a sub-frame are interleaved over both the first and second virtual antennas (17, 18).

1 1 . The method according to claim 10, wherein said symbols (83, 84, 85, 86) include first symbols (83, 85) generated for a first E-DPDCH (127) and wherein a first part (83) of said first symbols (83, 85) are transmitted through the first virtual antenna (17) and a second part (85) of said first symbols (83, 85) are transmitted through the second virtual antenna (18).

12. The method according to claim 1 1 , wherein said symbols (83, 84,

85, 86) include second symbols (84, 86) generated for a second E-DPDCH (127) and wherein a first part (84) of said second symbols (84, 86) are transmitted through the first virtual antenna (17) and a second part (86) of said second symbols (84, 86) are transmitted through the second virtual antenna (18).

13. The method according to claim 12, wherein symbols in said first part (83) of said first symbols (83, 85) are time-multiplexed with symbols in said first part (84) of said second symbols (84, 86) in the transmissions through the first virtual antenna (17) and wherein symbols in said second part (85) of said first symbols (83, 85) are time multiplexed with symbols in said second part (86) of said second symbols (84, 86) in the transmissions through the second virtual antenna (18).

14. The method according to any one of claims 12 and 13, wherein the first E-DPDCH (127) is used for transmission of a first transport block (103) while the second E-DPDCH (127) is used for transmission of a second transport block (104).

15. The method according to any one of claims 12 and 13, wherein the first E-DPDCH and the second E-DPDCH are used for transmission of different parts of the same transport block.

16. The method according to any one of claims 1 1 , 12, 13, 14 and 15, wherein symbols generated for an E-DPCCH associated with the first E-DPDCH (127) are interleaved over both the first virtual antenna (17) and the second virtual antenna (18).

17. The method according to any one of claims 1 1 , 12, 13, 14 and 15, wherein symbols generated for an E-DPCCH associated with the first E-DPDCH (127) are transmitted through the first virtual antenna (17).

18. The method according to any one of 1 1 , 12, 13, 14 and 15, wherein symbols generated for an E-DPCCH associated with the first E-DPDCH are transmitted through the second virtual antenna (18).

19. A method in a user equipment (1 1 ) configured for uplink MIMO transmissions using at least a first virtual antenna (17) and a second virtual antenna (18), the method comprising:

transmitting (52) data through the second virtual antenna (18);

detecting (53) a need for physical layer retransmission of said data; and performing (54) physical layer retransmission of said data through the first virtual antenna (17).

20. The method according to claim 19, wherein said data is at least one transport block (120) generated for a first E-DPDCH (127).

21 . The method according to any one of claims 1 -20, wherein a single Inner Loop Power Control loop (135) is used for controlling transmission power of transmissions through both the first virtual antenna (17) and the second virtual antenna (18).

22. The method according to claim 21 , wherein the single Inner Loop Power Control loop (135) operates based on a DPCCH associated with the worst uplink radio transmission quality.

23. The method accord ing to an y o n e of cl a i m s 1 -20, wherein transmission through the first virtual antenna (17) is subject to Inner Loop Power Control while transmissions through the second virtual antenna (1 8) is not subject to Inner Loop Power Control.

24. The method according to any one of claims 1 -23, wherein the user equipment (1 1 ) transmits a control signal to a network node (12) indicating whether the user equipment (1 1 ) is performing uplink transmissions using single or multiple stream transmissions.

25. A user equipment (1 1 ) comprising digital data processing circuitry (131 ) configured to implement a first virtual antenna (17) and a second virtual antenna (18), wherein the user equipment (1 1 ) is configured for uplink Multiple- Input Multiple-Output, M IMO, transm issions using at least the first virtual antenna (17) and the second virtual antenna (18), and wherein the digital data processing circuitry (131 ) is further configured to interleave at least one encoded transport block (103, 104, 1 12, 120, 127) over both the first virtual antenna (17) and the second virtual antenna (18).

26. The user equipment (1 1 ) according to claim 25, wherein the digital data processing circuitry (131 ) is configured to interleave symbols generated for said at least one encoded transport block (103, 104, 1 12, 120, 127) for transmission within a sub-frame over both the first and second virtual antennas (17, 18).

27. The user equipment (1 1 ) accord ing to claim 26, wherein said symbols include first symbols (83, 85) generated for a first encoded transport block (103) and wherein the digital data processing circuitry (131 ) is configured to control that a first subset (83) of said first symbols (83, 85) are transmitted through the first virtual antenna (1 7) and a second subset (85) of said first symbols (83, 85) are transmitted through the second virtual antenna (18).

28. The user equipment (1 1 ) according to claim 27, wherein said symbols include second symbols (84, 86) generated for a second encoded transport block (104) and the digital data processing circuitry (131 ) is configured to control that a first subset (84) of said second symbols (84, 86) are transmitted through the first virtual antenna (17) and a second subset (86) of said second symbols (84, 86) are transmitted through the second virtual antenna (18).

29. The user equipment (1 1 ) according to claim 28, wherein the digital data processing circuitry (131 ) is configured to time-multiplex symbols in said first subset (83) of said first symbols (83, 85) with symbols in said first subset (84) of said second symbols (84, 86) in the transmissions through the first virtual antenna (17) and wherein the digital data processing circuitry (131 ) is further configured to time-multiplex symbols in said second subset (85) of said first symbols (83, 85) with symbols in said second subset (86) of said second symbols (84, 86) in the transmissions through the second virtual antenna (18).

30. The user equipment (1 1 ) according to any one of claims 28 and 29, wherein the digital data processing circuitry (131 ) is configured to map the first encoded transport block (103, 104, 1 12, 120, 127) to a first Enhanced Dedicated Channel Dedicated Physical Data Channel, E-DPDCH, (127) and to map the second encoded transport block (1 03, 1 04, 1 1 2, 1 20, 1 27) to a second E- DPDCH (127).

31 . The user equipment (1 1 ) according to any one of claims 26-29, wherein the digital data processing circuitry (131 ) is configured to map a first part (1 13) of the first encoded transport block (1 12) to a first E-DPDCH (127) and to map a second part (1 14) of the first encoded transport block (1 12) to a second E-DPDCH (127).

32. The user equipment (1 1 ) according to any one of claims 25-31 , wherein the dig ital data processing circuitry (1 31 ) is further configured to interleave symbols generated for an Enhanced Dedicated Channel Dedicated Physical Control Channel, E-DPCCH, over both the first virtual antenna (17) and the second virtual antenna (18).

33. A user equipment (1 1 ) comprising digital data processing circuitry (131 ) configured to implement a first virtual antenna (17) and a second virtual antenna (18), wherein the user equipment (1 1 ) is configured for uplink Multiple- Input Multiple-Output, M IMO, transm issions using at least the first virtual antenna (17) and the second virtual antenna (18), and wherein the digital data processing circuitry (131 ) is further configured to interleave at least one E- DPDCH (127) over both the first virtual antenna (17) and the second virtual antenna (18).

34. The user equipment (1 1 ) according to claim 33, wherein the digital data processing circuitry (131 ) is configured to interleave symbols (83, 84, 85, 86) generated for said at least one E-DPDCH (127) within a sub-frame over both the first and second virtual antennas (17, 18).

35. The user equipment (1 1 ) accord ing to claim 34, wherein said symbols (83, 84, 85, 86) include first symbols (83, 85) generated for a first E- DPDCH (127) and wherein the digital data processing circuitry (131 ) is configured to control that a first part (83) of said first symbols (83, 85) are transmitted through the first virtual antenna (17) and a second part (85) of said first symbols (83, 85) are transmitted through the second virtual antenna (18).

36. The user equipment (1 1 ) according to claim 35, wherein said symbols (83, 84, 85, 86) include second symbols (84, 86) generated for a second E-DPDCH (127) and the digital data processing circuitry (131 ) is configured to control that a first part (84) of said second symbols (84, 86) are transmitted through the first virtual antenna (17) and a second part (86) of said second symbols (84, 86) are transmitted through the second virtual antenna (18).

37. The user equipment (1 1 ) according to claim 36, wherein the digital data processing circuitry (131 ) is configured to time-multiplex symbols in said first part (83) of said first symbols (83, 85) with symbols in said first part (84) of said second symbols (84, 86) in the transmissions through the first virtual antenna (17) and wherein the digital data processing circuitry (131 ) is further configured to time-multiplex symbols in said second part (85) of said first symbols (83, 85) with symbols in said second part (86) of said second symbols (84, 86) in the transmissions through the second virtual antenna (18).

38. The user equipment (1 1 ) according to any one of claims 36 and 37, wherein the digital data processing circuitry (131 ) is configured to use the first E- DPDCH (127) for transmission of a first transport block (103) and to use the second E-DPDCH (127) for transmission of a second transport block (104).

39. The user equipment (1 1 ) according to any one of claims 36 and 37, wherein the digital data processing circuitry (131 ) is configured to use the first E- DPDCH and the second E-DPDCH for transmission of different parts (1 13, 1 14) of the same transport block (1 12).

40. The user equipment (1 1 ) according to any one of claims 35-39, wherein the digital data processing circuitry (1 31 ) is configured to interleave symbols generated for an E-DPCCH associated with the first E-DPDCH over both the first virtual antenna (17) and the second virtual antenna (18).

41 . The user equipment (1 1 ) according to any one of claims 35-39, wherein the digital data processing circuitry (1 31 ) is configured to transmit symbols generated for an E-DPCCH associated with the first E-DPDCH (127) through the first virtual antenna (17).

42. The user equipment (1 1 ) according to any one of claims 35-39, wherein the digital data processing circuitry (1 31 ) is configured to transmit symbols generated for an E-DPCCH associated with the first E-DPDCH (127) through the second virtual antenna (18).

43. A user equipment (1 1 ) comprising digital data processing circuitry (131 ) configured to implement a first virtual antenna (17) and a second virtual antenna (18), wherein the user equipment (1 1 ) is configured for uplink Multiple- Input Multiple-Output, M IMO, transm issions using at least the first virtual antenna (17) and the second virtual antenna (18), and wherein the digital data processing circuitry (131 ) is further configured to:

control that data is transmitted through the second virtual antenna

(18);

detect a need for physical layer retransmission of said data;

control that physical layer retransmission is performed of said data through the first virtual antenna (17).

44. The user equipment (1 1 ) according to claim 43, wherein said data is at least one transport block (103, 104, 1 12) generated for a first E-DPDCH (127).

45. The user equipment (1 1 ) method according to any one of claims 25-44, wherein the digital data processing circuitry (1 31 ) is configured with a single Inner Loop Power Control loop (135) for controlling transmission power of transmissions through both the first virtual antenna (17) and the second virtual antenna (18).

46. The user equipment (1 1 ) according to claim 45, wherein the single Inner Loop Power Control loop (135) is configured to operate based on a

DPCCH associated with the worst uplink radio transmission quality.

47. The user equipment (1 1 ) according to any one of claims 25-44, wherein the digital data control circuitry is configured such that transmission through the first virtual antenna (17) is subject to Inner Loop Power Control while transmissions through the second virtual antenna (18) is not subject to Inner Loop Power Control.

48. The user equipment (1 1 ) according to any one of claims 25-47, wherein the digital data processing circuitry (131 ) is configured to control that the user equipment (1 1 ) transmits a control signal to a network node (12) indicating whether the user equipment (1 1 ) is performing uplink transmissions using single or multiple stream transmissions.

49. A method in a user equipment (1 1 ) configured for uplink Multiple-

Input Multiple-Output, MIMO, transmissions, the method comprising signaling to a network node (12) whether the user equipment (1 1 ) is performing uplink transmissions using single or multiple stream transmissions.

50. The method according to claim 49, comprising transmitting two E-

DPCCHs, wherein a happy bit of one of said two E-DPCCHs is used to signal to the network node (12) whether the user equipment (1 1 ) is performing uplink transmissions using single or multiple stream transmissions.

51 . A user equipment (1 1 ) configured for uplink Multiple-Input Multiple-

Output, MIMO, transmissions, the user equipment comprising digital data processing circuitry configured to control the user equipment (1 1 ) to signal to a network node (12) whether the user equipment (1 1 ) is performing uplink transmissions using single or multiple stream transmissions.

52. The user equipment (1 1 ) according to claim 51 , wherein the user equipment (1 1 ) is configured to transmit two E-DPCCHs, and wherein said digital data processing circuitry is configured to control that a happy bit of one of said two E-DPCCHs is used to signal to the network node (12) whether the user equipment (1 1 ) is performing uplink transmissions using single or multiple stream transmissions.