Combined open loop/closed loop method for controlling uplink power of a mobile station

ES 2 592 276 T3

DESCRIPTION

Combined open loop / closed loop procedure to control the uplink power of a mobile station

Technical sector of the invention

The present invention is related to wireless communication systems.

Background

For the Evolved Universal Terrestrial Radio Access (E-UTRA) uplink (UL), several Transmit Power Control (TPC) proposals have been submitted to Working Group 1 ( WG1) of the long term evolution (LTE) of the third generation partnership project (3GPP). These proposals can be broadly divided into open-loop (slow) TPC and TPC based on slow closed-loop or channel quality information (CQI).

Open-loop TPC is based on path loss measurement and system parameters, where path loss measurement is carried out in a wireless transmit / receive unit (WTRU) and the system parameters are provided by the evolved Node B (eNodeB).

Closed-loop TPC is usually based on TPC feedback information (such as a TPC command), which is sent periodically from the eNodeB where the feedback information is generally obtained using a signal-to-noise plus signal-to-interference ratio (SINR). to-interference noise ratio) measured at the eNodeB.

Open-loop TPC can compensate for long-term channel variations (eg path loss and obstacle attenuation), effectively, eg without transmit power history. However, open loop TPC typically results in path loss measurement errors and transmit power tuning errors. On the other hand, the TPC based on slow closed loop or on CQI is less sensitive to errors in the measurement and in the adjustment of the transmission power, because it is based on feedback signaled from the eNodeB. However, CQI or slow closed loop based TPC degrades performance when no feedback is available due to one or more UL transmission pauses in the feedback transmission or channel variations are substantially dynamic.

For UL's E-UTRA, there are several inter-cell PC proposals, which have been submitted to the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Working Group (WG) # 1. These proposals can generally be divided into slow open loop and slow closed loop PC (or CQI based PC). The open-loop PC can compensate for long-term channel variations (e.g. path loss and obstacle attenuation) effectively, e.g. without transmit power history, but it usually suffers from errors in the measurement of the path loss and in the adjustment of the transmission power. On the other hand, the PC based on slow closed loop or CQI is less sensitive to errors in the measurement and in the adjustment of the transmission power, because it is based on feedback signaled from the eNodeB. However, it degrades performance when no feedback is available due to one or more UL transmission pauses in the feedback transmission.

Therefore, there is a need for an improved method of transmit power control.

US 6600772 B1 discloses a method that controls the transmit power of a transmitting communication station in a spread spectrum time division duplex communication system. Combined closed loop / open loop power control controls transmit power levels in spread spectrum time division duplex communication system.

US 2003/002452 A1 discloses a technique for calibrating the open loop transmit power of a wireless communication device. A system dynamically adjusts the transmit power using a feedback loop. The system includes a receiver part and a transmit part implemented using two different gain control factors.

Compendium

A method and apparatus is disclosed in accordance with the independent claims, comprising a combined open loop / closed loop uplink power control scheme for E-UTRA. UL's combined intercell PC open and closed loop procedure controls the transmit power spectral density (PSD), PSDtx, of the wireless transmitting unit (WTRU) (for example, power per RB ).

ES 2 592 276 T3

Brief description of the drawings

A more detailed understanding of the invention can be obtained from the following description of a preferred embodiment, provided by way of example and to be understood in conjunction with the accompanying drawings, in which:

Figure 1 is an example of a wireless communication system;

Figure 2 is an example of a block diagram of a transmitter and receiver configured to implement the disclosed power control (PC) procedure;

Figure 3 shows an example of the timing of the disclosed combined PC procedure;

Figure 4 shows an example of the disclosed combined power control procedure, when interTTI is one (1);

Fig. 5 shows another example of the disclosed combined PC timing, when inter-TTI is two (2);

Figure 6 shows an example of the disclosed combined PC scheme, including discontinuous transmission (DTX);

Figure 7 shows an example of the disclosed PC procedure, for the nth update time; and Figure 8 shows a flow chart of the combined open-loop and closed-loop method of determining TPC.

Detailed description

When mentioned in the following, the term wireless transmission / reception unit (WTRU) includes, but is not limited to, a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a paging device, cell phone, personal digital assistant (PDA), computer, or any other type of user device that can operate in a wireless environment. When mentioned hereinafter, the term base station includes, but is not limited to, a Node B, a site controller, an access point (AP), or any other type of interface device that can operate in an environment. wireless.

Figure 1 shows an example of a wireless communication network (NW) 10 comprising a WTRU 20, one or more Node Bs 30 and one or more cells 40. Each cell 40 comprises one or more Node Bs (NB or eNB) 30 which they include a transceiver 120 configured to implement a disclosed transmit power control (TPC) procedure. The WTRU 20 comprises a transceiver 110 also configured to implement the disclosed TPC procedure.

Figure 2 is a functional block diagram of transceivers 110, 120 configured to carry out the disclosed procedure. In addition to the components included in a typical transceiver / receiver, i.e. a WTRU or Node B, transceivers 110, 120 include processors 115, 125, receivers 116, 126 in communication with processors 115, 125, transmitters 117, 127 in communication with processors 115, 125 and antennas 118, 128 in communication with receivers 116, 126 and transmitters 117, 127 to facilitate wireless data transmission and reception. Additionally, receiver 126, transmitter 127, and antenna 128 may be a single receiver, transmitter, and antenna, or may include a series of individual receivers, transmitters, and antennas, respectively. Transmitter 110 may be located on a WTRU or multiple transmission circuits 110 may be located on a base station. Receiver 120 can be located at either the WTRU, Node B, or both.

The disclosed TPC method comprises a combined open loop and closed loop scheme for power control between uplink cells (UL). The method comprises controlling the spectral density of the transmit power (PSD), or transmit PSD (PSDtx), of the WTRU, for example, the power per resource block (RB), or the transmit power of the WTRU using Aperiodic open-loop and closed-loop (PC) power control for both UL data channel control channels and Sound Reference Symbols (SRS). The UL Channel Quality Indicator (CQI) (or Modulation Coding Set / Grant Information (MCS)) is used in the WTRU to correct open loop and / or measurement errors, assuming the UL grant / MCS represents signal-to-interference plus noise ratio (SINR) received at node B. If no CQI is available, then only open loop is performed. Implicit command signaling can be used, for example without signaling overhead, for the closed-loop component. Alternatively, an exploit of TPC command signaling on the DL control channel can be used for the closed-loop component. Additionally, the disclosed method can quickly correct open loop errors, resulting in good performance.

ES 2 592 276 T3

The disclosed method, as indicated above, comprises controlling the spectral density of the transmit power (PSD) of the WTRU or transmit PSD (PSDtx), for example, the power per resource block (RB) or transmission power. It should be noted that although the disclosed method includes controlling the transmit PSD, this is equivalent to controlling the transmit power. The PSDtx is defined as:

<img file="ES2592276T3_D0001.tif" />

Equation (1) where PSD_tobuert represents path loss based open loop PSD, in dBm; Acerrado is a power correction factor that is determined based on the closed-loop component, which will be disclosed in detail later; Amos is MCS power offset granted; is already a weighting factor to activate (ct = 1) or deactivate (a = 0) the closed loop component, depending on the availability of the downlink control channel (DL), which incorporates signaling of (correction of ) Closed-loop PC (explicitly or implicitly). The weighting factor can be determined by the WTRU 20 by autonomously detecting the presence of closed-loop PC command signaling. Alternatively, the WTRU 20 is informed by overhead signaling from the eNodeB 30 as to whether there is command signaling. The transmit PSD should not exceed the maximum transmit PSD, PSD_max, where PSD_max is obtained based on the maximum allowed power, P_max, which depends on the UE power class, by PSD_max = P_max / M, where M is the size of the UL channel resource allocation expressed in number of valid resource blocks for a given subframe.

The intra-cell PC scheme proposed in equation (1) can use an absolute power correction factor compared to open-loop based PSD. From equation (1), the WTRU Tx PSD in the nth update case can be expressed as:

PSD_li(n) = PSD_EU^ n) ₊ a ^ closed ^ ^ MCS («);

= PSD_Tx («-!) + (PS ^_erto (n) - PSD ^ Jn -!)) + «· (\_errad0{n) - \_wrong(n -1)) + \_MCS (n)

Equation (2) where Ρ Β_Τχ(η 1) represents the (nl) -th PSD of Tx without the granted MCS power offset, which is given by (^{n _} 9 ⁼ (”-1) - &amp; mcs (ⁿ ~ D

Typically, the power offsets for individual granted MCSs are known to both the WTRU and the eNodeB.

The WTRU 20 processor 115 combines path loss-based open-loop and closed-loop PCs to determine PSDtx. According to the disclosed method, the WTRU 20 first performs an open loop PC based on path loss measurement and system parameters (PSD_tob¡erto) PSD_tob_andrto is calculated as follows:

<img file="ES2592276T3_D0002.tif" />

Equation (3) where • Target PSD is a target PSD received at the serving eNodeB 30, which is preferably a specific parameter of a WTRU (or a subgroup of WTRUs). The target PSD can be adjusted by means of an outer loop mechanism according to the Quality of Service (QoS) (for example, the Target Block Error Rate (BLER)), and also a function of the path loss measurement, to compensate for a fraction of the path loss. Target PSD target signaling is accomplished by higher layer signaling from Node B 30 to WTRU 20 after adjustment to a reduced rate scheme; and • L is the filtered path loss in dB, including obstacle attenuation, from the serving eNodeB 30 to the WTRU 20, where the WTRU 20 first measures the instantaneous path loss based on the reference signal. (RS, reference signal) of DL whose transmission power is known. The WTRU 20 then applies a path loss filtering procedure. For example, the filtered path loss in the kth case, Lk, can be calculated as

<img file="ES2592276T3_D0003.tif" />

Equation (4) where Lk-i and Lk represent the filtered path loss in the (kl) -th case and the instantaneous path loss in the k-th case; P is a filter coefficient, 0 &lt;p &lt;1, which is generally determined by the WTRU 20, as a function of the variation of the loss per path, of the fast fading rate, of the time of the

ES 2 592 276 T3 transmission of UL and others, for example. Filtering for path loss can be done on the PHY layer and / or on the L 2/3 layer.

Once the WTRU 20 determines the open-loop component, the processor 115 calculates the closed-loop component. As those skilled in the art know, there are errors related to open loop, including path loss estimation error due to non-perfect reciprocity in UL and DL in FDD and Tx deterioration in WTRU due to a non-linear power amplifier. To compensate for these errors and keep the power channel quality controlled along with the target quality, the WTRU applies an open-loop-based PSD correction in the form of a closed-loop PC, such as in equation (1) ( or equation (2))

The serving eNodeB 30 determines a WTRU-specific (absolute and / or accumulated) PC correction command for each UL-scheduled WTRU (or a subset of scheduled WTRUs). Preferably, the eNodeB 30 uses the power controlled data channel as a reference for the correction command. The resulting correction command is signaled to the WTRU 20 (or a subset of the scheduled WTRUs) via the UL grant, and / or the DL scheduling channel, sent on the Layer 1 or Layer control channels. DL layer 2. The correction command can be signaled only in the UL grant associated with a particular (predefined) HARQ process, such as in each HARQ 1 process.

Upon receiving the correction command (s) at the WTRU 20, the WTRU 20 processor 115 determines the correction factor, A_closesdo, based on the correction command (or accumulated correction commands) expressed as:

TO_tight= f (Pe correction command (s)) · Equation (5) where Acerrado can adopt a set of multiple stepped levels, for example, {+/- 4, +/- 1 dB} using 3 bits of the command.

Alternatively, the eNodeB 30 sends to each scheduled WTRU 20 (or subset of scheduled WTRUs) a power correction factor using multiple bits of the command, such as 3 bits, in the UL grant and possibly in the DL schedule on the channel. DL control, where the correction command is preferably determined based on the link quality (such as SINR or received PSD) of the UL power controlled data channel (and possibly the UL probe reference symbol, if available) . For example, assuming that a set of power correction factor values ​​is {-7, +/- 5, +/- 3, +/- 1.0 dB} with 3 bits, the correction factor can be determined as go on

Δ__λ= [ESINR_to - J; Equation (6) where ESINR_{its T} and SINR_ORTarget indicates the estimate of the effective SINR (ESINR) at the receiver and the target SINR, respectively, of the controlled power channel or channels, in dB. [x] indicates, in the set of corrections, the correction value that is closest to x. The samples observed at the eNodeB for ESINR estimation include (part or all of) the SC-FDMA symbols of the power controlled UL channel (s), which have been received since the last DL correction command signaling.

To reduce command signaling overhead, the correct command is not required on every UL grant (and on every DL schedule, if used). That is, the correction command can be sent at a pre-configured signaling time (for example, on each grant channel N or on each Transmission Time Interval (TTI) N, where N is a configurable parameter that is less than or equal to UL's minimum PC update period).

A correction command signaling timing is configured at eNodeB 30 (or at an RRC level) for each WTRU, and is then known to both eNodeB 30 and WTRU 20 by higher layer signaling.

When the correction command is signaled on the UL grant, assuming the UL HARQ is synchronous, the signaling timing configuration can be simplified such that the command signaling is performed on particular UL grants, such as the UL grant associated with a predefined HARQ process, for example HARQ process # 1. But, even in this case, correction commands do not need to be signaled on all associated UL grant channels. For example, signaling can occur on each associated grant channel N for N&gt; = 1, which could be equivalent to one command signaling in every period of N HARQ cycles. The signaling timing (or associated parameters) can be reconfigured to a semi-static frequency.

Figure 3 shows an example of the disclosed PC procedure, when the PC correction command is carried in the UL grant associated with the HARQ process # 1 and N is set to 2. In this example, the update rate of the PC is 8 ms, assuming that the number of HARQ processes is 4 and the transmission interval (TTI) is equal to 1.

ES 2 592 276 T3

When the WTRU 20 receives a correction command from the serving eNodeB 30 in a UL grant (or possibly, correction commands accumulated in multiple UL grants) since the last PSD adjustment of Tx, it shall obtain a correction factor, A_cerrado, from the received correction command (or after combining multiple correction commands if more than one command is received) for the next PSD adjustment.

The WTRU 20 then adjusts the data channel transmit PSD in accordance with equation (1) (or equation (2)) using the obtained correction factor, the most recent open-loop PSD, and an associated power offset. with MCS granted. The resulting Tx PSD should be applied from the start (the first SC-FDMA symbol) of the next UL TTI for the data channel and remain constant until the next PSD setting, as shown in Figure 3.

Figure 4 shows an example of the timing of the disclosed combined PC procedure, assuming that UL HARQ is a synchronous scheme with 4 HARQ processes and that the WTRU 20 is scheduled to send a data packet (e.g. a process HARQ) each TTI (for example, inter-TTI = 1). In addition, the eNodeB 30 sends a PC correction command only on the UL grant associated with the HARQ process 1. In this case, the Tx power update period of the WTRU is 4 TTIs (eg, 4 ms).

As shown in Figure 4, in the initial UL transmission, since there may be no correct PC command available, the WTRU 20 adjusts its transmit power based only on the open-loop component (i.e., the factor weighting, a, is zero in equation (1)). Before the next HARQ transmission time (a HARQ cycle time), the eNodeB 30 sends a correction command on the grant channel in HARQ process 1 associated with the DL control channel, where the command has been determined based on to the link quality (power or SINR) of the first two HARQ processes. If the WTRU 20 correctly receives the correction command, the WTRU 20 then calculates its transmit PSDtx based on the combined open-loop and closed-loop scheme, and applies the PSDtx to subsequent HARQ processes.

Figure 5 shows another example of the disclosed combined PC timing, where inter-TTI is two. In this case, the update period of the UL PC is 8 TTIs (8 ms).

When there is no recent closed loop correction command (for example, due to a recent scheduled UL data transmission, say UL DTX), the WTRU 20 can adjust its Tx PSD based on the open loop. In this case, the weighting factor, a, in equation (1) is set to zero as in the case of initial Tx PSD setting.

Alternatively, the WTRU 20 may adjust the Tx PSD based on the variation in path loss between the time before DTX and the time before the UL transmission resumes. If the UL DTX is short, the WTRU can use equation (2) by setting a to zero, so that

PSD_n(n) = PSD,. (n -1) + (PSD ^ Jn) -PSD_m(n-1)) + Δ „_Ω(»)

Equation (7) where n is the Tx PSD setting time before resuming UL transmission and (n-1) is the PSD setting time before DTX. An example of the timing in this case is shown in Figure 6.

In another alternative, the WTRU 20 may apply a power offset relative to the most recent PSD for the Physical Uplink Control Channel (PUCCH), if available. Although there is no UL data transmission, there may be UL control signaling (such as CQI and ACK / NACK) for DL. In this case, since the UL control channel is also power controlled based on equation (1) (but using different parameters and update rate), the Tx PSD of the UL control channel can be used to the Tx PSD of the data channel, as follows:

PSD_Tx (data) = PSD_Tx (control) + k_eontrü¡ ((¡Atos, control)

Equation (8) where PSDtx (control) is the most recent PSD (or PSD averaged over recent updates) for the UL and A control channel_COntroi (data, control) represents the power offset of the control channel with respect to the Tx PSD for data.

If the DTX period is long, then the PSDtx of the WTRU 20 can be determined immediately following the DTX based only on the open loop, as is the case with the initial PSDtx setting.

Figure 7 shows an example of the proposed combined PC scheme, including DTX.

Typically, the UL grant assignment (eg MCS and TBS assigned) on the DL control channel is tied to the link quality (such as received PSD or SINR) of the UL data transmission. Is given to

ES 2 592 276 T3 know another procedure in which the processor 125 of the eNodeB 30 can assign the UL grant (MCS and TBS) for the WTRU 20 in such a way that the grant assignment represents the link quality (for example, SINR ) received at the eNodeB 30. In this case, the WTRU 20 can obtain its PSD from Tx as follows:

^PSDTx = ^$^ open^{+ a} 'f (^asl9^nation UL grant_} WITHOUT R_T) + Á_MCS (dBm);

Equation (9) where PSD_toBerto, A and Amos are, respectively, the same as defined above. f (UL grant assignment, SINRt) is a correction factor in dB that substitutes for the power correction factor, Acerrado, in equation (1). SINRt is the target SINR in dB. The grant-based correction factor, f (UL grant assignment, SINRt), can be expressed as follows:

f (UL grant assignment, SINT_T ) = SINR_T - E {SINR_at (Uí concession assignment)};

Equation (10) where SINR_{it is}t (UL grant assignment) represents the SINR estimate received at the eNodeB, which the WTRU 20 derives from the UL grant assignment. E {SINR_{it is}t} indicates the average over time of the estimated SINR, such as

E \ SINR_esl (grant)} = p · E \ siNR_esl (grant ')} + (1 - /?) E \ SINR_esl (concession)}

Equation (11)

Where concession¹* represents the k-th received UL grant assignment and p is the average filter coefficient, 0 &lt;p &lt;1. The SINR estimate_{it is}t (UL grant assignment) in the WTRU can be based on a grant mapping table (MCS, TBS), which is configurable by the network via higher layer signaling, semi-statically.

Similar to equation (1), the correction factor in equation (8) can be used to compensate for open loop errors. The main advantage of using equation (8) is that it does not require explicit signaling of correction commands in the UL grant on DL's L1 / L2 control channel (resulting in reduced signaling overhead), whereas Equation (1) (and Equation (2)) require that the explicit command be signaled in the UL grant (and / or DL ​​scheduling). Using equation (3), the closed-loop component can be based on the UL grant assignment (e.g. MCS and / or TBS), without explicit signaling of correction commands in the UL grant on the channel. DL L1 / L2 control.

However, equation (9) may not be applicable for some cases, such as persistent scheduling and grant mismatch (eg MCS) (ie, the assigned MCS does not accurately represent the received SINR). Accordingly, the Tx WTRU PSD setting can be switched between equation (1) and equation (8).

By means of correction factor type signaling in higher layers, where the eNodeB 30 (or network 10) signals to the WTRU 20 which (equation (1) or equation (8)) should be used for the Tx power adjustment of the WTRU. In this case, it is preferable that the correction factor type signal is configurable by the network 10 semi-statically and by each WTRU.

Alternatively, a one-bit MCS misadjustment flag may be inserted into the DL L1 / 2 control signaling. For example, bit 1 can indicate to use equation (1), and bit 0 can be used to indicate equation (8).

In another alternative, one of the explicit correction command levels can be used to indicate the use of equation (8). This alternative assumes that equation (1) is the default PC procedure. Thus, the eNodeB 30 adjusts one of the correction command levels in the UL grant to indicate the use of equation (8). For example, when the correction command in equation (8) is three bits long, one of the 8 levels of the command, for example '000', is configured for the WTRU 20 to use equation (8).

A flow chart of the combined open-loop and closed-loop procedure for determining TPC is shown in Figure 8. WTRU 20 processor 115 performs open loop power control based on path loss measurement, determining a target power spectral density, target PSD (step 800), and a filtered path loss (L) ( step 801). The WTRU 20 then determines a closed loop component using a power control correction command received at receiver 116 through the UL grant channel (step 802). Upon receiving the correction command, receiver 116 transmits the correction command to processor 115 to determine a correction factor A_cerrado (step 803). The

ES 2 592 276 T3 processor 115 then calculates an Acerrado correction factor. (Step 804). Processor 115 then combines the open-loop PC with the closed-loop component to determine transmit power control. (Step 805).

In a disclosed TPC procedure for unplanned data (e.g. VolP), there are several options for the WTRU to adjust its Tx PSD: i) based only on the open loop PSD, i) for the part of closed loop, the eNodeB transmits UL grants at particular instants (in time), where the UL grant carries the correction command. In this case, the format of the UL grant (and / or the format of the correction command) may be different than for the scheduled data; oi¡¡) apply a power offset from the most recent PSD (or PSD averaged over recent updates) for the PUCCH, if available.

^psdtx = ^por + ^{WITHOUT R}objective⁺ PL + a Ace; rado + L_mcs (dBm); Equation (12)^PSDopen where P_or it is a specific parameter per cell (in dBm) that includes the UL interference level, etc., which is signaled by the eNodeB using higher layer signaling.

• SINRtarget is a specific parameter of the WTRU (or a subset of WTRUs) (in dB), which allows the eNodeB to adjust classes of service for the UE (or for a subset of UEs). SINR objective can be a function of path loss to the serving cell and some neighboring cells. SINR can be configured by the serving eNodeB semi-statically and then signaled to the UE (or to a subset of UEs) by means of higher layer signaling;

• PL is the downlink path loss (in dB);

• λ is a cell-specific path loss compensation factor for fractional power control, where 0 &lt;λ &lt;= 1. λ can be configured by the eNodeB in a semi-static way and signaled by means of higher layer signaling;

• Acerrado is a power correction factor in dB, which is determined based on a closed loop mechanism;

• α is a weighting factor to activate (a = 1) or deactivate (a = 0) the closed-loop component, depending on the availability of the DL control channel that carries the closed-loop correction command. The weighting factor is determined autonomously by the WTRU by detecting the presence of the PC correction command. The WTRU is supposed to be informed via higher layer signaling from the eNodeB regarding where and when command signaling exists. For example, in the initial UL transmission, since there may be no correct command available from the eNodeB, the WTRU sets it to = 0;

• Amos is a MCS power offset granted. Typically, the power offsets for individual granted MCSs are known to both the WTRU and the eNodeB.

Since the eNodeB 30 knows the Amos in use in a given case, the eNodeB 30 can extract the MCS value from the received PSD when it determines a correction command, comparing a resulting received PSD (or SINR) with a given target level. over the network 10.

As discussed above, this disclosed method uses an absolute power correction factor compared to open loop based PSD. Therefore, from equation (12), the WTRU Tx PSD in the nth update case is expressed as follows:

PSD_Tl{n) = PSD_Bertha(n) + a A ^ Jn) + A_wcs(n).

= PSD_Tx(n -1) + (PSZ&gt;_bíerfo(«) - ^pSQ_b,_ertÁn -1)) + «(A_J) - A_cefratto(fl “D) + ¿mcsW '

Equation (13) where ^ρ$^ρτχ (^η~ 1) represents the (nl) -th PSD of Tx without the granted MCS power offset, which is given by ^ρ$^ρτχ (^{n _} 9 ^{= ρ}$^ρτχ (^{n _} 1) ~ &amp;_MC$ (ⁿ ~ 9 ·

Since the transmit power of the WTRU is limited by the maximum transmit power level, indicated by P_max, from the WTRU, the total transmit power of the WTRU, indicated by Ptx, is expressed as:

P_Tx= min {P_max, (lO- \ og_lQ(M) + PSD_Tx)} (dBm); Equation (14)

ES 2 592 276 T3 where M is the number of assigned RBs.

Therefore, the transmit PSD of the actual WTRU can be represented as:

PSD ™¹ = P_Tx-W- log₁₀(M) (dBm)

Equation (15)

It should be noted that the UL PC in equation (15) is implemented by the processor 115 of the WTRU 20.

In accordance with the disclosed PC procedure for unplanned data, the WTRU 20 calculates the open loop PSD as follows:

PSD = P₀+ SINR + A-PL (dBm) open Target

Equation (16) where • The target SINR, SINR_ORobjectively, it can be adjusted by means of an outer loop mechanism in the service eNodeB 30 according to the quality of service (QoS) (such as the target BLER) and also be a function of path loss measurements to the service cell and neighboring cells; and • PL is the filtered path loss, in dB, including obstacle attenuation, from the serving eNodeB to the WTRU. The WTRU continuously (or periodically) measures the instantaneous path loss based on the RS of DL whose transmit power is known in the WTRU. A filtering procedure is then applied to path loss measurements, such as

PL_k= p-PL_k__x + (1 -p) PL_k Equation (17) where PLk and PLr-i represent the filtered path loss in the k-th case and at the (kl) -th time, respectively. Lk is the instantaneous path loss at the k-th time. p is a filter coefficient, 0 &lt;p &lt;1, which is generally determined by the WTRU 20 as a function of variation in path loss, fast fading rate, UL transmission time, etc. Alternatively, a moving average procedure can be considered for filtering path loss.

The closed-loop component is determined by processor 115 in a manner similar to that disclosed above.

^TOcemd0 = [^ESINRis ~ ^{WITHOUT R}objected_{V &lt;}\ Equation (18) where ESINR_{its T} and SINR_ORTarget indicates the estimate of the effective SINR (ESINR) at the receiver and the target SINR, respectively, of the controlled power channel or channels, in dB. [x] indicates, in the set of corrections, the correction value that is closest to x.

Similar to the procedures described above, when the correction command is signaled in the UL grant, assuming the UL HARQ is synchronous, the setting of signaling timers can be simplified such that command signaling is performed in particular UL grants, such as the UL grant associated with a predefined HARQ process.

For unplanned data (e.g. VolP), when there is no recent closed loop correction command (e.g. due to recent scheduled UL data transmission, say UL DTX), the WTRU 20 can adjust its Tx PSD based on open loop: in this case, the weighting factor, a, in equation (13), is set to zero as in the case of initial Tx PSD adjustment. Alternatively, the WTRU 20 may adjust its Tx PSD based on the variation in path loss between the time before the DTX and the time before the UL transmission resumes: if the UL DTX is short, the WTRU can use equation (2) by setting a to zero such that

PSD_n(n) = PSD_r, (n -1) + (PSDJO - PSD ^ n -1)) + Δ_Μα(_Π);

Equation (19) where n is the Tx PSD setting time before resuming UL transmission and (n-1) is the PSD setting time before DTX. An example of this case is shown in Figure 4.

ES 2 592 276 T3

Alternatively, the WTRU 20 may apply a power offset relative to the most recent PSD for PUCCH, if available. Although there is no UL data transmission, there may be UL control signaling (such as CQI and ACK / NACK) for DL. In this case, since the UL control channel (PUCCH) is also power-controlled based on equation (12) (but using different parameters and update rate), the Tx PSD of the control channel can be used. of UL (PUCCH) for the Tx PSD of the data channel (PUSCH), as follows:

PSD_Tx (PUSCH) = PSD_Tx (PUCCH) + A_control (PUSCH, PUCCH);

Equation (20) where PSD_Tx (PUCCH) is the most recent PSD (or PSD averaged over recent updates) for the UL control channel (PUCCH) and A_withtroi (PUSCH, PUSCH) represents the power offset of the control channel (PUCCH) with respect to the PSD of Tx for PUSCH.

For a sounding pilot signal, its Tx PSD, PSDtx (pilot signal), may be offset by a pilot signal power offset relative to the data Tx PSD, PSD_Tx (data), such as

PSD_Tx(pilot) = PSD_Tx (data) + A ^^ data, piloted) Equation (21) where A_{I know}ñai pilot (data, pilot signal) represents the power offset of the pilot signal, which can be a specific parameter of the WTRU configured by the eNodeB in a semi-static way.

For UL control signaling, it is preferable to use different parameters (such as the target PSD) and a faster refresh rate than for data. Furthermore, it is preferred that the reference channel measured by the correction commands for control signaling is the control channel itself and that the correction command for the control is carried in the DL schedule. The number of bits for the correction command for control can be different than for data, where the number of bits in the command can be a semi-static configurable parameter for each WTRU. However, a relative average power offset is maintained between the data and control channels, such as

E (PSD_Tx (data)) = E (PSD_Tx (control)) + k_{c &lt;Mrol} (data, control)

Equation (22) where * E (PSDT_X(data)) represents the average PSD for the data channel, in dBm;

* E (PSD_Tx(control)) represents the average PSD for the control channel in dBm; Y

TO_COntroi (data, control) is a power offset between the data channel and the control channel.

In another disclosed UL PC method, a combined open loop / closed loop UL PC with reduced interference is used for shared data channel. According to this procedure, the WTRU 20 controls its transmitted PSD for UL channels. If the bandwidth allocation (eg, RB allocation) of the WTRU 20 varies, then the total transmit power of the WTRU varies such that the PSD remains constant.

As described in the previously disclosed procedures, the WTRU 20 performs open loop PC based on path loss measurement and system parameters. The WTRU 20 then corrects its PSD using some kind of closed-loop PC to compensate for open-loop errors. It should be noted that for each WTRU scheduled in UL, the CQI information is periodically signaled from the eNodeB 30 for AMC and scheduling. Therefore, the closed-loop PC component of this disclosed method does not require any additional PC commands signaled by the eNodeB. To reduce interference between cells, in the neighboring cell or cells, the WTRU 20 incorporates an interference charge indicator from the stronger neighboring cell.

According to this procedure, for the UL shared data channel, in the initial transmission phase, the WTRU 20 obtains its transmitted PSD, PSD_Tx, based on the DL reference signal (RS), as follows:

PSD_Tx = SINRj. + PL + IN₀ + K + A (loT_s) -10 log 10 (BW_RU -N_KU);

Equation (23) where SINR_T is the target SINR in dB at serving eNodeB 30. PL is the path loss in dB, including obstacle attenuation, from serving eNodeB 30 to WTRU 20, where WTRU 20 measures 10

ES 2 592 276 T3 path loss based on the RS of DL whose transmit power is known in the WTRU 20 by means of DL layer 2 / layer 3 signaling, IN₀ is the interference power plus UL noise in dBm, measured at the serving eNodeB 30. K is a power control margin established by the serving eNodeB 30.

It is preferable that the target SINR for WTRU 20 (or for a subset of WTRUs) is adjustable using an outer loop PC scheme, according to a link quality metric (such as BLER) at the serving eNodeB 30. Furthermore, in the case of UL Multiple In Multiple Out (MIMO), the target SINR also depends on the selected MIMO mode, which takes into account the fact that different MIMO modes require different SINRs for quality. determined link. A (loTs) represents the size of the UL load control stage, which is a function of the indicator of the UL interference load (e.g. thermal interference) from the strongest neighboring cell, loTs, where the neighboring cell is the most Strong is determined at the WTRU 20, based on path loss measurements from each individual neighboring cell to the WTRU 20. Each cell 40 is supposed to periodically broadcast a UL interference payload bit (similar to the relative grant in HSUPA), such that the WTRU 20 can decode the indicator bit from the selected strongest neighbor cell.

For example, A (loTs) can have the following values:

δ &lt;0, when IoT_s -1 or "command down"

0, when IoT_s = 0, "DTX", or "raise command" where δ is a predefined system parameter, for example, δ = -1 or -2 dB. With the use of A (loT_s), inter-cell interference can be reduced in neighboring cells.

Since WTRUs in the center of the cell inject less interference into other cells than those at the edge of the cell, a fraction of the size of the load control stage is considered as follows:

δ, for WTRUs at the edge of the cell δ = «δ - _tfor WTRUs inside the cell where x&gt; 1. X

The WTRU 20 may make a decision as to whether it is at the edge of the cell or inside the cell based on the ratio of path loss between its serving cell and the strongest neighboring cell, for example.

If (serving cell path loss - strongest neighbor cell path loss) &lt;R (dB), x = 4;

where R represents the virtual boundary layer between the interior area of ​​the cell and the border area of ​​the cell. The R parameter can be broadcast by the eNodeB 30 semi-statically.

After the initial transmission phase, the PSD-rx of the WTRU 20 is calculated as follows:

PSD_Tx = SINR_T + PL + IN₀ + K + &amp; (loT_s) + af (CQI, SINR_T) -10 log 10 (BW_RU N_RU)

Equation (24) where f (CQI, SINRt) is a correction factor based on the UL CQI and the corresponding target SINR, where both the CQI and the target SINR are signaled from the serving eNodeB 30; a, where 0 &lt;a &lt;1, is a weighting factor that can be determined according to the channel conditions and the availability of CQI (or UL transmission pause). For example, in case there is no UL CQI (UL MCS or Grant Information) available from the eNodeB 30 due to no planned UL data transmission, the weighting factor, a, is set to zero , which means that the WTRU 20 depends only on the open-loop PC (such as the PC for the random access channel (RACH)); otherwise, it is set to be less than or equal to one (1).

The correction factor, f (CQI, SINRt), in equation 24, is used to compensate for errors related to open-loop PC, including path loss measurement error due to imperfect reciprocity in UL and DL in FDD. , and deterioration of the WTRU transmitter 20 due to non-linear power amplification of the WTRU transmitter. In addition, the correction factor is used to compensate for the target quality mismatch due to different channel conditions. Therefore, the quality of the power controlled channel (s) is maintained along with a certain target quality (such as the target SINR).

Taking into account the fact that the UL CQI (UL MCS or Grant Information) represents the SINR received at the eNodeB 30, the correction factor can be calculated as, f (CQI, SINT_T) = SINR_T - E {SINR_{&amp; I} (CQl)} (dB); Equation (25)

ES 2 592 276 T3 where SINR_{it is}t (CQI) represents the SINR estimate received at the eNodeB, which the WTRU obtains from the UL CQI feedback. E {SINR_{it is}t (CQI)} indicates the time average of the estimated SINR, as follows:

E {siNR_{it is}(CQI^k)} = p (1 - /&gt;) Equation (26) where CQI^k represents the k-th received CQI and p is the average filter coefficient, 0 &lt;p &lt;1.

The correction factor, provided above in equation 25 by the difference between the target SINR and the estimated SINR (obtained from the reported CQIs), represents the open-loop PC relative errors that need to be compensated for.

The total transmit power of the WTRU should be within the maximum power level, P_max, y of the minimum power level, P_m¡_n, in dBm, respectively, where the maximum and minimum power levels are determined based on the WTRU class.

The eNodeB 30 preferably signals parameters, including a target SINR level, SINRt, which is a specific parameter of a WTRU (or a group of WTRUs), where the target SIR can be adjusted by means of an outer loop mechanism based in QoS, such as the target BLER. The target SINR may also be a function of the path loss measurement. The signaling of the target SIR is performed by means of in-band L1 / 2 control signaling, after adjustment. A power control margin, K, which is a specific parameter of the eNodeB, is also signaled by the eNodeB 30. K is preferably semi-static and is signaled via the broadcast channel (BCH). It should be noted that although K is supposed to be signaled independently along with the other parameters, it can be incorporated into the target SINR, ie SINRt (after incorporation) = SINRt + K (dB). In this case, explicit Kala WTRU 20 signaling is not required.

The eNodeB 30 also signals a total noise and interference level of UL, INo, which is averaged across all subcarriers (or RBs) in use, or subcarriers as a whole. This parameter is preferably obtained by the serving eNodeB 30 (and possibly signaled by BCH). The refresh rate for this signaling is generally relatively slow. The maximum and minimum UL power level, P_max and Pm¡n, ​​is also signaled by the eNodeB 30. Each of these can be a parameter dependent on the capacity of the WTRU, or it can be expressly signaled by the eNodeB 30.

A UL Channel Quality Indicator, CQI (e.g. UL MCS or Grant Information), which is originally signaled for the purpose of UL AMC (with a maximum signaling frequency of once per TTI (e.g. , 1000 Hz).

A CQI mapping rule (or bias between the CQI and the measured SINR), which the eNodeB uses for CQI feedback generation. This rule or parameter can be combined into the target SINR. In this case, explicit signaling of the rule (or parameter) is not required.

A UL interference charge indicator from each eNodeB.

The semi-static parameter R that represents the virtual boundary layer between the inner area of ​​the cell and the border area of ​​the cell.

The disclosed PC procedure does not require any other feedback PC commands in addition to the system parameters listed above, including the target SINR, the cell interference / noise level, and the reference signal transmit power. and a constant value, which can be broadcast (or directly signaled) to the WTRUs with a low frequency.

It is designed to be flexible and adaptable to dynamic system / link parameters (target SINR and inter-cell interference state of charge) and channel conditions (path loss and obstacle attenuation), to achieve E-UTRA requirements. .

Furthermore, this disclosed method is compatible with other link adaptation schemes such as AMC, HARQ and adaptive MIMO.

In an alternative method of reducing inter-cell interference, instead of broadcasting the interference charge indicator from each eNodeB, the serving eNodeB 30 can coordinate inter-cell interference levels with other cells 40 and incorporate them by adjusting accordingly. target SIR, power control margin K, or possibly P_max.

Although features and elements in particular combinations have been described above, each feature or element may be used separately without the other features and elements, or in various combinations with or without other features and elements, within the scope of the invention as defined. by independent claims. The procedures or flowcharts disclosed herein may be implemented in computer program, software, or embedded firmware.

ES 2 592 276 T3 on a computer-readable storage medium, for execution by a general-purpose computer or a processor. Examples of computer-readable storage media include read only memory (ROM), random access memory (RAM), register, cache, semiconductor memory devices, magnetic media such such as internal hard drives and removable disks, magneto-optical media, and optical media such as CD-ROMs and digital versatile disks (DVDs).

Suitable processors include, by way of example, a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), a series of microprocessors, one or more microprocessors in association. with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), any other type of integrated circuit (IC) and / or a state machine.

A processor may be used in association with software, to implement a radio frequency transceiver for use in a wireless reception transmission unit (WTRU), a user equipment (UE), a terminal, a base station, a radio network controller ( RNC, radio network controller) or any host computer. The WTRU can be used together with modules, implemented in hardware and / or software, such as a camera, a video camera module, a videophone, a hands-free phone, a vibrating device, a loudspeaker, a microphone, a television transceiver, a hands-free headset, a keyboard, a Bluetooth module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an internet browser and / or any wireless area network module local (WLAN, wireless local area network) or ultra-wide band (UWB, Ultra Wide Band).