WO2013167162A1

WO2013167162A1 - Transmission of primary and secondary data streams

Info

Publication number: WO2013167162A1
Application number: PCT/EP2012/058353
Authority: WO
Inventors: Thomas Chapman; Przemyslaw Czerepinski
Original assignee: Nokia Siemens Networks Oy
Priority date: 2012-05-07
Filing date: 2012-05-07
Publication date: 2013-11-14

Abstract

Primary and secondary data streams are transmitted from a mobile station to a network node. The primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel. A transmission power of the primary control channel is set by the network node. Transmission power of the primary data channel is set by the network node to be equal to a factor of the transmission power of the primary control channel and transmission power of the secondary control channel is either set by the network node such that a received SINR of the secondary control channel is equal to a received SINR of the primary control channel or set by the mobile station based on the data rate on the second channel, which may be in turn set according to a knowledge at the mobile station of the difference in received SINR between the primary and the secondary streams.

Description

TRANSMISSION OF PRIMARY AND SECONDARY DATA STREAMS

FIELD OF THE INVENTION

The invention generally relates to transmission of primary and secondary data streams in a communications network. More particularly, the invention relates to Multiple Input Multiple Output (MIMO) uplink transmission in which primary and secondary streams are transmitted across two antennas.

BACKGROUND OF THE INVENTION

Multiple Input Multiple Output (MIMO) is the use of

multiple antennas at the transmitter and receiver end in a communications network for transmitting and receiving multiple data streams. This type of communication is particularly useful in High Speed Packet Access (HSPA) and Long Term Evolution (LTE) networks, due to the high data throughput provided without the need for additional

bandwidth and increased transmit power.

Uplink UTRAN MIMO is currently under discussion as part of the 3^rd Generation Partnership Project (3GPP) . A proposal is that the channel structure of uplink MIMO should be based on precoding. In this case, a primary data stream is transmitted across two transmit antennas with precoding weights applied at each antenna. A secondary data stream is transmitted across the same two antennas with

"orthogonal" precoding weights applied to the secondary stream at the antennas. Alongside each data stream, a pilot signal is transmitted using the same antenna

precoding weights as are used for the data streams

themselves . However, a problem may arise that received signal on the pilot (control) channel associated with the secondary data stream is too weak for accurate channel estimation, thereby leading to poor link performance.

The invention has been devised with the foregoing in mind.

SUMMARY OF THE INVENTION

Accordingly, an aspect of the invention provides a method, which includes transmitting primary and secondary data streams from a mobile station to a network node. The primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel. A transmission power of the primary control channel is set by the network node and a transmission power of the primary data channel is also set by the network node so that it is equal to a factor of the transmission power of the primary control channel. The network node then sets a transmission power of the secondary control channel .

Both of the control channels include a pilot sequence, which enables the network Node to measure the received power and received Signal to Interference and Noise Ratio (SINR) from the two channels.

In one embodiment, a transmission power of the secondary control channel is set by the network node to be equal to the factor of the transmission power of the primary control channel . In one embodiment, the transmission power of the secondary control channel is set by the network such that a received SINR of the secondary control channel is equal to a

received SINR of the primary control channel.

Since the transmission power of the secondary control channel may be set so that the SINR on both the primary and secondary control channels is equal, this means that a received control channel on the secondary data stream will be high enough for channel estimation, which results in improved link performance. In addition, legacy data format selection procedures used for single stream transmission can be reused for dual stream transmission.

In one embodiment, a transmission power of the secondary data channel is set by the network node to be equal to the factor of the transmission power of the primary control channel .

In another embodiment, a transmission power of the

secondary data channel is set by the network node to be equal to a total transmission power of the primary stream minus the transmission power of the secondary control channel .

The network node may signal to the mobile station the transmission power of the secondary control channel as a factor of the transmission power of the secondary data channel .

The mobile station can select a data transport format combination on the primary stream and may also select a data transport format combination at the mobile station on the secondary stream based on the factor of the

transmission power of the secondary data channel. Preferably, the transmission power of the primary control channel is set using a power control loop. This could be a fast power control scheme, for example.

Another aspect of the invention provides a method, which includes transmitting primary and secondary data streams from a mobile station to a network node, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel, and setting at the mobile station a ratio between a

transmission power of the secondary data channel and a transmission power of the secondary control channel based on a data rate of the secondary stream, which is set according to a knowledge at the mobile station of the difference in received SINR between the primary and the secondary streams.

The invention also provides a network node, which includes a receiver configured to receive primary and secondary data streams from a mobile station, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel. A power control unit is configured to set a transmission power of the primary control channel using a power control scheme. The power control unit is also configured to set a transmission power of the primary data channel by the network node to be equal to a factor of the transmission power of the primary control channel, and configured to set a transmission power of the secondary control channel by the network node such that a received SINR of the secondary control channel is equal to a received SINR of the primary control channel. The invention further provides a mobile station. The mobile station includes a transmitter unit configured to transmit primary and secondary data streams. The primary stream includes a primary data channel and a primary control channel and the secondary stream includes a

secondary data channel and a secondary control channel. A power control unit is configured to set a ratio between a transmission power of the secondary data channel and a transmission power of the secondary control channel based on a data rate of the secondary stream, which is set according to a knowledge at the mobile station of the difference in received SINR between the primary and the secondary streams.

One aspect of the invention provides a computer program product including a program comprising software code portions being arranged, when run on a processor, to perform transmitting primary and secondary data streams, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel, setting a transmission power of the primary control channel using a power control scheme, and setting a transmission power of the secondary control channel at the network node.

Another aspect of the invention provides a computer program product including a program comprising software code portions being arranged, when run on a processor, to perform transmitting primary and secondary data streams wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel, and setting a ratio between a transmission power of the secondary data channel and a transmission power of the secondary control channel based on a data rate of the secondary stream.

The computer program product may include a computer- readable medium on which the software code portions are stored, and/or wherein the program is directly loadable into a memory of the processor.

The invention will now be described, by way of example onl with reference to specific embodiments and to the

accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

- Figure 1 is a simplified schematic diagram of a wireless communications network;

- Figure 2 is a simplified schematic diagram of a network node of a communications network according to an embodiment of the invention;

- Figure 3 is a simplified schematic diagram of a mobile station according to an embodiment of the invention;

- Figure 4 is a simplified schematic diagram of a

transmit/receive unit of a mobile station according to an embodiment of the invention;

- Figure 5 is a flow diagram illustrating a method

according to an embodiment of the invention;

- Figure 6 is a flow diagram illustrating a method

according to an embodiment of the invention; - Figure 7 is a simplified block diagram illustrating data and control channels of primary and secondary data streams in a MIMO scheme; and

- Figure 8 is a simplified block diagram illustrating data and control channels of primary and secondary data streams in a MIMO scheme.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Figure 1 shows the UTRAN part of a UMTS communications network, which includes a base station or Node B 1 as a node of the network. A mobile station or user equipment (UE) 2 is capable of MIMO operation and may access the network via the Node B 1.

The Node B 1 is shown in Figure 2 and includes a

transmit/receive unit 3, a power control unit 4, and a scheduler 5. During uplink MIMO operation, the

transmit/receive unit 3 may receive an uplink data stream from the UE 2, which includes a primary data stream and a secondary data stream. The power control unit 4 can then set the transmit powers of the primary and secondary data streams .

The UE 2 is shown in Figure 3 and includes a

transmit/receive unit 6 and a power control unit 7. The transmit/receive unit 6 of the UE 2 is shown in more detail in Figure 4. It can be seen that the UE 2 is provided with two antennas Al and A2 in the transmit/receive unit 6, which allow the UE 2 to be capable of MIMO operation. During MIMO operation, uplink data transmitted by the UE 2 includes two data streams; a primary data stream and a secondary data stream. The primary data stream includes a primary data channel, the primary E-DPDCH (or P-EDPDCH) , and a primary pilot or control channel, the primary DPCCH (or P-DPCCH) . Likewise, the secondary data stream includes a secondary data channel, the secondary E-DPDCH (or S- EDPDCH) , and a secondary pilot or control channel, the secondary DPCCH (or S-DPCCH) . The data and control

channels of the primary data stream are multiplexed in the transmit/receive unit 6 by multiplexers Wl and W2 and fed to antennas Al and A2, respectively. The data and control channels of the secondary data stream are multiplied by multipliers Wl* and W2* and fed to antennas Al and A2, respectively. Antennas Al and A2 then transmit the primary and secondary data streams to the Node B 1.

Setting the transmit power for uplink channels may be achieved as described in the examples below and

illustrated in Figures 5-8. Figure 7 illustrates a

situation where the total transmit power on the secondary data stream is less than that on the primary data stream and Figure 8 illustrates a situation where the total transmit power on both the primary and secondary streams is equal .

For the primary stream, the relations defined for single stream HSUPA should be retained; i.e., the primary DPCCH level is adjusted according to fast power control. The TX power for the primary E-DPDCH, E-DPCCH, HS-DPCCH and DPDCH is then set with respect to the primary DPCCH by means of beta factors . However for the secondary stream, a new means of setting the UL TX power is defined, which is dependent on whether the power is set at the Node B 1 or the UE 2.

If the power is set by the Node B 1, the method is as illustrated in the flow chart shown in Figure 5. The UE 2 transmits the primary and secondary data streams in the uplink (Step SI) . The Node B 1 sets the transmit power of the primary DPCCH using fast power control (Step S2) and sets the transmit power of the primary E-DPDCH to be equal to Beta_ed, where Beta_ed is some factor of the transmit power of the primary DPCCH (Step S3) . This also sets the transmit power of the secondary E-DPDCH because the power of the secondary E-DPDCH is also related to the primary DPCCH power by a fixed factor. The Node B 1 then sets the transmit power of the secondary DPCCH such that the

received SINR of the secondary DPCCH is equal to the received SINR of the primary DPCCH (Step S4) .

At the same time, the Node B 1 signals the E-DPDCH grant to the UE 2.

A factor Beta_ed(sec) may then be signalled to the UE 2 by the Node B 1, where Beta_ed(sec) is the factor by which the transmit power of the secondary E-DPCDCH is greater than the transmit power of the secondary DPCCH. Alternatively, beta_ed(sec) may be inferred from the secondary E-DPDCH TX power and the secondary DPCCH TX power. The UE 2 selects the E-TFC on the primary stream. Since the UE 2 knows Beta_ed(sec) and also knows that the received SINR of the secondary DPCCH is as if power control had been applied, the UE 2 can select the E-TFC on the secondary data stream based on the factor Beta_ed ( sec) .

If the power is set at the UE 2, the method is as

illustrated in the flow chart shown in Figure 6. The UE 2 transmits primary and secondary data streams in the uplink in Step Sll, where the TX power for the secondary E-DPDCH is fixed relative to some quantity of the first stream. This quantity could be the primary E-DPDCH power, the primary DPCCH power or the total power on the primary stream. The secondary DPCCH power is then set relative to the power of the secondary E-DPDCH such that the ratio of secondary E-DPDCH power to secondary DPCCH power depends on the data rate applied to the secondary E-DPDCH in Step S12. (secondary DPDCH power/secondary DPCCH power = f (secondary E-DPDCH data rate) ) .

In this manner, it can always be guaranteed that sufficient secondary DPCCH power is available for demodulation of the secondary E-DPDCH.

It may be desirable to maintain equal power on the two streams. In this case, the following procedure could be applied :

The total power on the first stream (E-DPDCH, DPCCH and possibly also HS-DPCCH) is calculated. The same amount of power is then allocated to the secondary stream.

Considering the RX SINR on the secondary stream, a data rate is selected that can be achieved at the SINR and also for which the total E-DPDCH+DPCCH power is equal to the secondary stream power allocation, where the E-DPDCH/DPCCH ratio is set according to the data rate. (This may be performed at the Node B 1 or shared between Node B 1 and the UE 2)

Note that due to the precoding, the power on the antenna branches is always equal and it is not necessary to keep the power equal between the streams. Alternatively, it may be preferable to set the secondary DPCCH transmit power at the Node B 1. If this is the case, then the Node B 1, using its knowledge of the primary DPCCH RX SINR and the eigenmodes of the channel, may set the TX power on the second DPCCH such that the RX SINR is at a level sufficient for channel estimation and demodulation. If the E-DPDCH power on the secondary stream is set equal to that on the primary stream then the E-TFC selection at the UE 2 is able to select an E-TFC such that the beta_ed power offset associated with the E-TFC is equal to the relative power between the secondary E-DPDCH power and the secondary DPCCH power. If the secondary stream power should be set equal to the primary stream power, then the UE 2 subtracts the secondary DPCCH power from the total

secondary stream power in order to calculate the available E-DPDCH power and then select an E-TFC whose beta_ed would correspond to the required E-DPDCH/DPCCH ratio.

Whether the UE 2 or the Node B 1 sets the secondary DPCCH transmit power, it is necessary for the Node B 1 to know the power relationship between the primary and secondary DPCCHs for weight estimation. This is achieved if the Node B 1 sets the power. If the UE 2 sets the secondary DPCCH power, since the Node B 1 knows the fixed relationship between the secondary E-DPDCH power and the primary stream and also the secondary stream E-TFC, the Node B 1 is able to infer the secondary DPCCH power.

The above example illustrated in Figure 8 shows how the power allocation method works for setting the power on the data channels equally. The E-DPDCH on the primary stream is related to the DPCCH by beta_ed, the E-DPCCH/DPCCH is (beta_ec/beta_c) ² and HS-DPCCH/DPCCH is (beta_hs/beta_c) ² in the usual manner. The power ratio of TX power on the secondary stream to the primary DPCCH is (beta_ed/beta_c) ² as for the primary stream in order that the data channels have equal power.

The received SINR of the secondary stream is lower than for the primary stream and the E-TFC selection of the UE 2 is aware of the SINR difference. Therefore, the UE 2 selects a lower data rate for the E-DPDCH on the secondary stream. The S-DPCCH for the secondary stream is set with respect to the S-E-DPDCH by beta_ed (sec) /beta_c, which is dependent on the data rate on the secondary stream. Since the data rate is lower on the secondary stream, beta_ed (sec) is lower than beta_ed for the primary stream and thus the S- DPCCH for the secondary stream is transmitted at a higher power than the primary DPCCH. In this manner, sufficient SINR for channel estimation from the S-DPCCH is guaranteed.

Note that since the primary stream carries also HS-DPCCH and the DPCCH on the secondary stream has a different power level to that of the primary stream, the total TX power levels on the two streams are not equal in general.

In the example shown in Figure 8 and described above, the E-TFC selection assumes equal data power on the two streams. Again, it is assumed that the E-TFC selection is aware of the difference in received SINR between the two streams.

The S-DPCCH transmit power is set according to the S-E- DPDCH transmit power and the data rate on the S-EDPDCH.

An alternative example is one in which the E-TFC selection algorithm selects a data rate for the S-EDPDCH such that the SINR on the S-E-DPDCH is sufficient for detection at the desired BLER and such that the combined power of the secondary channels is equal to the combined power of the primary channels. Note that in this case, there is not a fixed relation between the S-EDPDCH and the P-EDPDCH or DPCCH transmit power.

In the following examples, two methods for system operation of MIMO that maximise reuse of SIMO functionality. The methods differ by how the second stream power is set. In the first method, the E-DPDCH power is set the same for the primary and secondary data streams, whereas in the second method the total stream power is set to be the same between the primary and secondary data streams.

For both methods, the following operation of the scheduler 5 and signalling by the Node B 1 takes place:

The scheduler 5 in the Node B 1 sets a total E-DPDCH power offset. The Node B 1 can also decide on whether transmission should be single stream or dual stream. Alternatively, single/dual stream selection may be based on the value of the allocated E-DPDCH power offset; in this case signalling of whether transmission should be single or dual stream is not required.

The Node B 1 also calculates the difference in post receiver SINR between the primary and secondary DPCCH and on this basis signals an S-DPCCH/DPCCH power offset parameter together with the grant to the UE 2. In principle, the signalled offset is left to implementation, but choosing it such that the post-receiver SINR of both control channels is the same is desirable. The beta parameter associated with the power offset is referred to in the following example as fi_sc .

one embodiment, the procedure at the UE 2 is as follows For dual stream transmission, the maximum TX power (in dB) of the primary E-DPDCH is set equal to primary DPCCH TX power + signalled E-DPDCH power offset less 3dB.

The maximum TX power of the secondary E-DPDCH is equal to the primary E-DPDCH TX power. The secondary DPCCH TX power (in dB) is set equal to the primary DPCCH TX power, plus the offset signalled by the Node B. Then, the maximum secondary E-DPDCH offset at the UE is set as (maximum secondary E-DPDCH TX power - secondary DPCCH TX power) .

Since the received DPCCH SINR and S-DPCCH SINR are the same and hence sufficient to maintain the BLER target on E-DCH, the UE 2 can operate a single stream E-TFC selection algorithm on both of the two streams based on the power offset available for each stream. The selected E-TFC on the second stream is lower than the primary stream due to the lower S-EDPDCH to S-DPCCH offset. However, the correct SINR on both channels to maintain the E-DCH BLER will be achieved. E-DPCCH boosting can operate individually on each stream as required, in the same manner as in single stream HSUPA.

For equal power on both the primary and secondary streams, the procedure at the UE 2 is as follows.

For dual stream transmission, the maximum TX power of t primary E-DPDCH is set equal to primary DPCCH TX power the signalled E-DPDCH power offset less 3dB.

The UE then calculates the primary stream total power as:

¹ P primary = ¹P DPCCH

and sets the secondary stream power equal to the primary stream. The secondary stream E-DPDCH power is then:

S-E-DPDCH

Therefore, the UE 2 can calculate the secondary stream E- DPDCH to S-DPCCH ratio.

Since the RX DPCCH power on both streams maintains the correct SINR to maintain the BLER target, the UE 2 can operate the single-stream E-TFC selection algorithm on both of the two data streams based on the power offset available for each stream. E-DPCCH boosting can operate individually on each stream as required, in the same manner as single stream HSUPA.

It should be noted that the method described above facilitates transmission of S-E-DPCCH on the secondary data stream. Since the S-DPCCH meets the RX SINR, the S-E-DPCCH will meet the SINR required for decoding. Furthermore, since the S-E-DPCCH can be boosted and used for channel estimation, it does not necessarily represent an additional network overhead.

Furthermore, setting the S-DPCCH TX power such that the RX SINR is equivalent to the power control target means that the same E-TFC set, together with the existing E-TFC selection algorithm, can be reused in the UE 2 for both the primary and secondary streams. An alternative approach is to construct an E-TFC set for a separate secondary data stream with an E-TFC dependent S-DPCCH SIR target. In one embodiment, a dual stream uplink MIMO scheme (as described above) is provided in which at least the power ratio between the data and pilot on the second stream is set dependent on the data rate on the second stream, which is set according to a knowledge at the UE 2 of the

difference in received SINR between the primary and the secondary streams.

In another embodiment, a dual stream uplink MIMO scheme (as described above) is provided in which at least the power of the data channel on the second stream is set relative to the primary stream power and then the power of the pilot on the second stream is set relative to the power of the data channel on the second stream and dependent on the data rate on the second stream, which is set according to a knowledge at the UE 2 of the difference in received SINR between the primary and the secondary streams.

In a further embodiment, a dual stream MIMO scheme is provided in which a total amount of power is allocated to the second stream for both data and pilot dependent on the first stream and for which the pilot power is set relative to the data power and dependent on the data rate on the data channel.

In a further embodiment, a single stream MIMO or closed loop beamforming transmission is provided in which at least the power of the data channel on a hypothetical second stream is set relative to the primary stream. The power of the pilot on the hypothetical second stream is set relative to the power of the data channel on the hypothetical second stream and dependent on the data rate on the hypothetical second stream. In one embodiment, a dual stream MIMO or single stream MIMO or closed loop beamforming transmission is provided in which at least the transmit power of the secondary control channel is set relative to the power of the primary pilot (control channel) . The power relationship between the primary control channel and the secondary control channel may be explicitly or implicitly signalled as part of the grant and may be used to compensate for poorer propagation environment on the secondary control channel.

For the purpose of the present invention as described hereinabove, it should be noted that

- method steps likely to be implemented as software code portions and being run using a processor at a network control element or terminal (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or modules therefore), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the embodiments and its modification in terms of the functionality implemented;

- method steps and/or devices, units or means likely to be implemented as hardware components at the above-defined apparatuses, or any module (s) thereof, (e.g., devices carrying out the functions of the apparatuses according to the embodiments as described above) are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor) , CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor- Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components;

devices, units or means (e.g. the above-defined apparatuses and network devices, or any one of their respective units/means) can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, unit or means is preserved;

- an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;

a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.

In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device. Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.

The terms "user equipment (UE) " and "mobile station" described herein may refer to any mobile or stationary device including a mobile telephone, a computer, a mobile broadband adapter, a USB stick for enabling a device to access to a mobile network, etc.

The exemplary embodiments of the invention have been described above with reference to a 3GPP UMTS network. However, the above-described examples may be applied to any wireless communications network.

Although the invention has been described hereinabove with reference to specific embodiments, it is not limited to these embodiments and no doubt further alternatives will occur to the skilled person, which lie within the scope of the invention as claimed.

LIST OF ABBREVIATIONS

3GPP Third Generation Partnership Project

DPCCH Dedicated Physical Control Channel

DPDCH Dedicated Physical Data Channel

E-DPDCH Enhanced Dedicated Physical Control Channel

E-DPDCH Enhanced Dedicated Physical Data Channel

E-TFC Enhanced Transport Format Combination

HS-DPCCH High Speed Dedicated Physical Control Channel

HSPA High Speed Packet Access

HSUPA High Speed Uplink Packet Access

MIMO Multiple Input Multiple Output

RX Receive

P-DPCCH Primary Dedicated Physical Control Channel

P-DPDCH Secondary Dedicated Physical Control Channel

S-DPCCH Secondary Dedicated Physical Control Channel

S-DPDCH Secondary Dedicated Physical Data Channel

SINR Signal to Interference and Noise Ratio

TX Transmit

UE User Equipment

UL Uplink

UMTS Universal Mobile Telecommunications System UTRAN UMTS Terrestrial Radio Access Network

Claims

1. A method, comprising:

transmitting primary and secondary data streams from a mobile station to a network node, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel;

setting a transmission power of the primary control channel at the network node;

setting a transmission power of the primary data channel at the network node to be equal to a factor of the transmission power of the primary control channel; and

setting a transmission power of the secondary control channel at the network node to be equal to a factor of the transmission power of the primary control channel.

2. The method according to claim 1, wherein the

transmission power of the secondary control channel is set so that the factor relating the transmission power of the secondary control channel to the transmission power of the primary control channel is chosen such that a received SINR of the secondary control channel is equal to a received SINR of the primary control channel.

3. The method according to claim 1 or claim 2, further comprising setting a transmission power of the secondary data channel at the network node to be equal to said factor of the transmission power of the primary control channel.

4. The method according to claim 1 or claim 2, further comprising setting a transmission power of the secondary data channel at the network node to be equal to a total transmission power of the primary stream minus the

transmission power of the secondary control channel.

5. The method according to any of claims 1 to 4, further comprising signalling from the network node to the mobile station the transmission power of the secondary control channel as a factor of the transmission power of the secondary data channel.

6. The method according to any of claims 1 to 5, further comprising signalling from the network node to the mobile station the transmission power of the secondary control channel as a factor of the transmission power of the primary control channel.

7. The method according to claim 5, further comprising selecting a data transport format combination at the mobile station on the primary stream.

8. The method according to claim 7, further comprising selecting a data transport format combination at the mobile station on the secondary stream based on said factor of the transmission power of the secondary data channel.

9. The method according to any of claims 1 to 8, wherein the transmission power of the primary control channel is set using a power control loop.

10. The method according to claim 9, wherein the

transmission power of the primary control channel is set using a fast power control scheme.

11. A method, comprising:

transmitting primary and secondary data streams from a mobile station to a network node, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel; and setting at the mobile station a ratio between a transmission power of the secondary data channel and a transmission power of the secondary control channel based on a data rate of the secondary stream.

12. A network node, comprising

a receiver configured to receive primary and secondary data streams from a mobile station, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel; and a power control unit configured to set a

transmission power of the primary control channel using a power control scheme, configured to set a transmission power of the primary data channel by the network node to be equal to a factor of the transmission power of the primary control channel, and configured to set a transmission power of the secondary control channel.

13. The network node according to claim 12, wherein the power control unit is configured to set the transmission power of the secondary control channel by such that a received SINR of the secondary control channel is equal to a received SINR of the primary control channel.

14. A mobile station, comprising:

a transmitter unit configured to transmit primary and secondary data streams, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a

secondary data channel and a secondary control channel; and a power control unit configured to set a ratio between a transmission power of the secondary data channel and a transmission power of the secondary control channel based on a data rate of the secondary stream.

15. A computer program product including a program comprising software code portions being arranged, when run on a processor, to perform:

transmitting primary and secondary data streams, wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel ;

setting a transmission power of the primary control channel using a power control scheme;

setting a transmission power of the primary data channel to be equal to a factor of the transmission power of the primary control channel; and

setting a transmission power of the secondary control channel at the network node.

16. The computer program product according to claim 15, comprising a computer-readable medium on which the

software code portions are stored, and/or wherein the program is directly loadable into a memory of the

processor .

17. A computer program product including a program

comprising software code portions being arranged, when run on a processor, to perform:

transmitting primary and secondary data streams wherein the primary stream includes a primary data channel and a primary control channel and the secondary stream includes a secondary data channel and a secondary control channel; and

setting a ratio between a transmission power of the secondary data channel and a transmission power of the secondary control channel based on a data rate of the secondary stream. The computer program product according to claim 17, comprising a computer-readable medium on which the software code portions are stored, and/or wherein the program is directly loadable into a memory of the

processor .