Technical field The present invention relates to a device and a method for adaptive power control in a time division duplex (TDD) communication system.

Background In a communication system, such as a wireless communication system, devices communicate with one another while managing various parameters associated with a communication link. For example, a wireless station and user equipment (UE) may communicate with one another while managing various parameters, such as power control, that are associated with a communication link. With respect to TDD communication systems, the same frequency band may be used in both uplink and downlink such that channel reciprocity exists. In this regard, the requirement of providing continuous feedback of channel estimates may be unnecessary. Long Term Evolution (LTE) is one of many communication platforms that support TDD.

Today, power control in 3GPP 's Long-Term Evolution (LTE) system is based on filtered path loss estimations as measured over the entire downlink bandwidth. When an LTE network is run in TDD mode, power control for the Physical Uplink Control Channel (PUCCH) can, in principle, be based on frequency selective path loss as measured on narrow frequency bands in the downlink. This feature is not yet in the standard but it has been seen in simulations that it can improve system performance when user equipment (UE, or UEs) are, in general, moving at low speed. This is because the PUCCH power output as regulated by the power control mechanism then is based on path loss estimates that capture the fast fading in these frequency bands. Since the channel may be assumed to be reciprocal during a non- infinitesimal time span, path loss as measured in this way will be very much more representative for the upcoming transmission than a value averaged over the entire bandwidth (which is what traditional power control uses) . The performance gains on system level come from less interference being induced to other users, which is especially important for the PUCCH since it is based on code-division multiplexing access. This, in its turn, leads to lower bit error rate (BER) . As an example, fast fading capturing power control may increase the multiplexing capacity of the PUCCH by as much as a factor of two as compared to regular open loop power control for slow moving users .

In the section below, techniques are described with which a total power is calculated on path loss measurements based on those frequencies where scheduled uplink transmissions will occur, and then distributed onto those transmissions according to one of several possible algorithms . These techniques have been discussed as a default uplink power control algorithm for the PUCCH in the next release of the LTE standard, R9.

In LTE, the physical uplink control channel (PUCCH) is part of band edges in a frequency spectrum. For example, in a 10 MHz frequency spectrum, only the two outer resource blocks (e.g., 180 kHz frequency bands) are allocated to the PUCCH. One PUCCH message (e.g., ACK/NACK or channel quality indicator (CQI)) may be sent in one slot on one of the resource blocks and then a frequency hop may be made to the other frequency band to the second slot. With respect to the PUCCH, power control consists of a closed loop around an open loop point of operation according to the following expression:

PpuccH(J) = min{PMAX, PO _ PUCCH + PL + AF __ PUCCH(F) + g(i)[dBm] Eq . 1 , where PPUCCH is the total power, PMAX is the maximum allowed power that depends on the UE power class, Po PUCCH is a parameter composed of the sum of a 5-bit cell specific parameter Po_NOMINAL_PUCCH provided by higher layers with 1 db resolution in the range of [-127, -96] dBm and a UE specific component Po_UE_PUCCH configured by Radio Resource Control (RRC) in the range of [-8, 7] dB with 1 dB resolution, PL is the downlink path loss estimate calculated in the UE, AF _PUCCH(F) corresponds to table entries for each PUCCH transport format (TF) given by the RRC (i.e., an offset for the modulation and coding scheme employed) , and g(i) corresponds the current PUCCH power control adjustment. A more detailed description may be found in 3GPP "E-UTRA Physical layer procedures," TS 36.213. The path loss (PL) in Equation 1 is based on the measured path gain of downlink reference symbols. This measurement is typically done over the entire downlink frequency spectrum and is time-filtered, resulting in a slow- fading, frequency averaged gain of which the power control is based.

Prior solutions suggest utilizing the channel reciprocity in TDD-mode where the same frequency band is used in the downlink and the uplink. The open loop shall then be faster to follow multipath fading. It is also suggested that the open loop only be based on measurements on the PUCCH frequencies. The Physical Uplink Shared Channel (PUSCH) in LTE is power controlled in a similar way as PUCCH, as described in 3GPP "E-UTRA Physical layer procedures," TS 36.213, with the same path loss based open loop, according to the following expression:

P puscH (ι) = min {PMAX, 10 log IO(MPUSCH(Ϊ)) + Po _ PUSCH(J) + aPL + AτF(i) + f(i)[dBm] Eq . 2 , where PPUCCH is the total power, PMAX is the maximum allowed power that depends on the UE power class, Mpuscfϊ(i)is the size of the PUSCH resource assignment expressed in number of resource blocks valid for subframe i, PO_PUSCH(J) is a parameter composed of the sum of a 8-bit cell specific nominal component Po_NOMINAL _PUSCH(J) signaled from higher layers for j=-0 and 1 in the range of [-126, 24] dBm with 1 dB resolution and a 4-bit UE specific component Po_UE _PUSCH(J) configured by RRC for j=0 and 1 in the range of [-8, 7] dB with 1 dB resolution, and where the pathloss (PL) is the same wideband downlink pilot measure as for PUCCH. The PUSCH may be transmitted on almost the whole band except the band edges where PUCCH is allocated. However, a UE will often be scheduled on only a fraction of the total band allocated to the PUSCH.

Slow fading gain is only an average value calculated over many frequencies. Therefore, when basing the power output on slow fading gain, this can lead to a coarse power control, as well as slow changes to power output. Additionally, in a closed loop mode (e.g., UE transmits and a base station measures signal-to-noise and transmits back power commands), there exists a delay (e.g., several milliseconds), which in many cases makes it impossible to follow fast fading. In this regard, if the fast open loop power control is based on wideband power, the fast fading will, for most channels, not be captured. Fig. 1 is a diagram illustrating TDD open loop ACK/NACK error rates. As illustrated, if the fast fading can be captured there is a gain (a lower ACK/ NACK error rate) compared to a reference case in an open loop power control mode based on downlink wideband path loss measurements . In an open loop power control mode, the UE may, for example, perform measurements on the downlink, determine the fading environment, and manage its power output. For example, the UE may manage its output power so that it reaches a certain signal-to-noise ratio. These simulations results provide results for both slow fading and fast fading.

However, the technique of using output power based on path loss measured from fast-fading gain on a narrow frequency band works well only if the measurement is accurate and reciprocally or semi-reciprocally reflects the channel for the upcoming uplink transmission. For instance, the fading can change too rapidly to be tracked if the UE moves at high speed.

In the case of power control in a LTE communication system, even if the open loop power control is set based on PUCCH channel bands, the difference between fast fading loss on the two PUCCH resource blocks can be large (e.g., 10 dB or more in case of 10 MHz bandwidths) . Thus, one measure for both slots may not be desirable. In this regard, to set a common power for both slots that performs well for both ACK/NACK and channel quality indicators (CQIs) can be difficult. Accordingly, further improvements are needed in order to obtain a more adaptive power control method and thereby reduce the overall system interference.

Summary

The described embodiments of the invention is directed towards reducing interference on a system level, lowering the bit error rate (BER) and increasing the multiplexing capacity of the UE.

It is an object of the described embodiments to provide a method for adaptive power control based on path loss measured from fast- fading gain on a narrow frequency band, in order to reduce interference on a system level.

This is solved by a method for reducing interference in a wireless network by switching power control modes. The wireless network comprises a User Equipment and an evolved Node B that are communicatively coupled to each other so that channel reciprocity exists. In this method a first fast fading indicator is continuously monitored. When the first fast fading indicator fulfills a first condition, the power control modes are changed, and the User Equipment is being run in a first power control mode. Continuously during this first power control mode, a second fast fading indicator is being monitored. When this second indicator fulfills a second condition, power control modes are changed again, and the UE is being run in a second power control mode.

It is further an object of the invention to provide an improved User Equipment configured for adaptive power control based on path loss measured from fast-fading gain on a narrow frequency band, in order to reduce interference on a system level. This is solved with a User Equipment which is capable of operating in at least two power control modes when in a Time Division Duplex environment.

The User Equipment is configured to monitor a first fading indicator continuously. When a first fast fading indicator fulfills a first condition, the UE changes into a first power control. While maintaining this first power control mode, the User Equipment continuously monitors a second fast fading indicator. When this second indicator fulfills a second condition, the power control modes change again, and the User Equipment now runs in a second power control mode.

In various embodiments of the present invention, a UE in TDD mode selectively switches between two or more distinct power control modes for the open loop part of the power control. Either the UE or the serving evolved Node B (eNB) keeps a measure that indicates how fast the frequency-selective fast fading varies for the channel (s) . When this measure indicates that control of the PUCCH no longer gains from using frequency-selective path loss estimates, the UE switches (or is directed to switch) over to, and runs in another power control mode to improve system performance. This may or may not occur in conjunction with re-initialization of fast closed loop power control .

Although the discussion herein focuses on control of the PUCCH, the disclosed techniques can be applied to other channels that reside in known parts of the system bandwidth, in LTE or other communication systems. The emphasis on PUCCH in this document is simply for purposes of explanation and description. Brief Description of the Drawings

The described embodiments, as defined in the claims, can be better understood with reference to the following drawings. The components within the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the described embodiments.

Fig. 1 is a diagram illustrating simulation results for slow fading versus fast fading compensation within an open loop power control mode; Fig. 2A is a diagram illustrating devices communicating with one another via an intermediate device;

Fig. 233 is a diagram illustrating an exemplary implementation of the devices depicted in Fig. 2A; Fig. 3A is a diagram illustrating exemplary components of the User Equipment (UE) depicted in Fig. 2B;

Fig. 3B is a diagram illustrating functional components of the UE that may monitor fast fading variation, switch power control modes, calculate output power and perform power allocation; Fig. 3C is a diagram illustrating an exemplary implementation of the UE that includes a wireless telephone;

Fig. 4A is a flow chart illustrating the method of the present invention; Fig. 4B is a flow diagram related to an exemplary process for calculating and allocating power consistent with concepts describe herein; Fig. 5 is a diagram illustrating an exemplary scenario in which the process described herein may be implemented;

Fig. 6 is a diagram illustrating how frequency bands correspond to resource blocks within spectrum allocations;

Fig. 7 is a diagram illustrating the relation between resource blocks, symbols, sub-carriers illustrated as a physical resource grid where each column corresponds to one OFDM symbol and each row to one OFDM subcarrier;

Fig. 8 is a diagram illustrating the LTE TDD frame structure;

Detailed Description

The following detailed description refers to the accompanying drawings . The same reference numbers in different drawings may identify the same or similar elements. Also, the following description does not limit the described subject matter.

Use of the techniques described herein facilitate improved utilization of the PUCCH, by allowing the UE to adapt its path loss measurement according to how fast the path loss varies.

In LTE 's TDD operating mode, there is an allocation of downlink and uplink frames according to some ratio, for instance 3:2, 7:3, or similar. During the downlink frame cycle, the UE measures the Reference Symbol Received Power (RSRP) on the downlink frequency bands that correspond to PUCCH transmissions in the upcoming uplink frames and transposes this to path loss. As long as some quality measure of the channel - an indicator (as described more fully below) exceeds a threshold value, the PUCCH transmission power is set using this fast-fading power control mode. If/when a predetermined threshold value is reached, the UE changes its measurement process. For instance, in some embodiments the UE changes into a power control mode based on average path loss over more frames. In other embodiments, the UE may fall back onto a power control mode based on traditional path loss measurement, such as a broadband path loss measurement. In still other embodiments, the UE runs in a power control mode that combines the results of the fast-fading path loss measurements and either the measurement filter output or the traditional path loss measurement to get a more reliable path loss estimate when the threshold has been reached. To facilitate a return to pure fast-fading power control mode when it becomes advantageous again, the instantaneous channel variations are continually monitored via an indicator. Thus, a return of the indicator to a level above a predetermined threshold triggers a return to fast fading power control and to using the fast-fading path loss measurements once more.

Embodiments described herein may provide a power control mode applicable to a TDD communication system. The power control mode may measure path loss with respect to frequency bands to which the UE intends to transmit. For example, the frequency bands may correspond to scheduled frequency bands (e.g., an uplink data channel) or on an allocated channel (e.g., an uplink control and/or signaling channel) . This is unlike existing techniques in which a path loss may be determined based on the entire (downlink) frequency spectrum. The path loss measurements may also include path loss measurements corresponding to individual frequency bands . The individual path loss measurements may be utilized for power allocation. Based on the power control mode described herein, higher channel capacity in TDD mode, improved signaling (e.g., lower bit error rate), as well as other advantages that necessarily flow therefrom, may be realized. For example, in a LTE TDD system, the power control mode may provide a higher PUCCH capacity in TDD mode for messages transmitted thereon

(e.g., ACK/NACK, CQIs, etc.), as well as a higher PUSCH capacity. Additionally, the power control mode may provide for improved signaling, as well as other advantages that necessarily flow therefrom. For purposes of discussion, the concepts described herein will be described in relation to the LTE TDD system, however, it will be appreciated that these concepts have broader application and may be implemented in other communication systems (e.g., TDD communication systems, such as Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN) ) .

Fig. 2A is a diagram illustrating an exemplary communication system 200 in which the concepts described herein may be implemented. As illustrated, communication system 200 may include a device 205, an intermediate device 210, and a device 215. A device may include, for example, a UE, a gateway, a base station, a relay, a repeater, a combination thereof, or another type of device (e.g., a satellite) . The device may operate at layer 1, layer 2, and/or at a higher layer. As illustrated in Fig. 2A, the devices may be communicatively coupled. For example, the devices may be communicatively coupled via wireless communication links (e.g., radio, microwave, etc.) . Communication system 200 may include a TDD communication system (e.g., a LTE TDD communication system) in which channel reciprocity exists. Since the concepts described herein are applicable to a variety of devices in communication system 200, communication system 200 will be described based on the exemplary devices illustrated in Fig. 2B. Fig. 2B illustrates an exemplary implementation in which device 205 includes a UE, intermediate device 210 includes a base station (e.g., an enhanced Node B (eNodeB) ) , and device 215 includes a UE. Fig. 2B illustrates UE 205, eNodeB 210 and UE 215 as communicatively coupled to form a multi-hop network. UE 205 and 215 may each include a device having communication capability. For example, a UE may include a telephone, a computer, a personal digital assistant (PDA) , a gaming device, a music playing device, a video playing device, a web browser, a personal communication system (PCS) terminal, a pervasive computing device, and/or some other type of communication device.

ENodeB 210 may include a device having communication capability. ENode B 210 may operate in a LTE communication system (not illustrated) . For example, the LTE communication system may include access gateways (AGWs) connected to various types of networks (e.g., Internet Protocol (IP) networks, etc) . Among other things, power control may be implemented between the devices in communication system 200, as illustrated in Fig. 2B. Although Fig. 2B illustrates an exemplary communication system 200, in other implementations, fewer, different, and/or additional devices, arrangements, etc., may be utilized in accordance with the concepts described herein.

Fig. 3A is a diagram illustrating exemplary components of UE 205. UE 215 may be similarly configured. The term component is intended to be broadly interpreted to include, for example, hardware, software and hardware, firmware, software, a combination thereof, and/or some other type of component. As illustrated, UE 205 may include a processing system 300, transceiver 305, antenna 310, a memory 315, an input device 320, and an output device 325.

Processing system 300 may include a component capable of interpreting and/or executing instructions. For example, processing system 300 may include a general- purpose processor, a microprocessor, a data processor, a co-processor, a network processor, an application specific integrated circuit (ASIC) , a controller, a programmable logic device, a chipset, and/or a field programmable gate array (FPGA) . Processing system 300 may control one or more other components of UE 205. Processing system 300 may be capable of performing various communication-related processing (e.g., signal processing, channel estimation, power control, timing control, etc.), as well as other operations associated with the operation and use of UE 205. Transceiver 305 may include a component capable of transmitting and/or receiving information over wireless channels via antennas 310. For example, transceiver 305 may include a transmitter and a receiver. Transceiver 305 may be capable of performing various communication-related processing (e.g., filtering, de/coding, de/modulation, signal measuring, etc.) . Antenna 310 may include a component capable of receiving information and transmitting information via wireless channels. In one implementation, antenna 310 may include a multi-antenna system (e.g., a MIMO antenna system) . Antenna 310 may provide one or more forms of diversity (e.g., spatial, pattern, or polarization) . Memory 315 may include a component capable of storing information (e.g., data and/or instructions) . For example, memory 315 may include a random access memory (RAM) , a dynamic random access memory (DRAM) , a static random access memory (SRAM) , a synchronous dynamic random access memory (SDRAM) , a ferroelectric random access memory (FRAM) , a read only memory (ROM) , a programmable read only memory (PROM) , an erasable programmable read only memory (EPROM) , an electrically erasable programmable read only memory (EEPROM) , and/or a flash memory. Input device 320 may include a component capable of receiving an input from a user and/or another device. For example, input device 320 may include a keyboard, a keypad, a touchpad, a mouse, a button, a switch, a microphone, a display, and/or voice recognition logic. Output device 325 may include a component capable of outputting information to a user and/or another device. For example, output device 325 may include a display, a speaker, one or more light emitting diodes (LEDs), a vibrator, and/or some other type of visual, auditory, and/or tactile output device.

Although Fig. 3A illustrates exemplary components of UE 205, in other implementations, UE 205 may include fewer, additional, and/or different components than those depicted in Fig. 3A. For example, UE 205 may include a hard disk or some other type of computer-readable medium along with a corresponding drive. The term "computer-readable medium," as used herein, is intended to be broadly interpreted to include, for example, a physical or a logical storing device. It will be appreciated that one or more components of UE 205 may be capable of performing one or more other tasks associated with one or more other components of UE 205. Fig. 3B is a diagram illustrating exemplary functional components capable of performing one or more operations associated with the concepts described herein. In one embodiment the exemplary functional component may be implemented in processing system 300 of UE 205. However, it will be appreciated that this functional component may be implemented in connection with, for example, other components (e.g., transceiver 305) of UE 205, in combination with two or more components (e.g., processing system 300, transceiver 305, memory 315) of UE 205, and/or as an additional component (s) to those previously described in Fig. 3A. As illustrated, the functional components may include a power calculator 325 and a power allocator 330.

Power calculator 325 may include a component capable of determining one or more power values and/or power- related values in accordance with the power mode described herein. For example, power calculator 325 may determine one or more power values that may influence the output power of a transmission by UE 205. As will be described in greater detail below, power calculator 325 may determine a power value based on path loss estimates corresponding to frequency bands in which UE 205 intends to transmit. The path loss estimates may include individual path loss estimates that correspond to individual frequency bands .

Power allocator 330 may include a component capable of assigning power output to a transmission based on the power values and/or power-related values determined by power calculator 325. For example, power allocator 330 may assign power values to addressable units (e.g., resource blocks, och carrier frequencies) of a transmission. Power allocator 330 may allocate output power based on the individual path loss estimates.

Although Fig. 3B illustrates exemplary functional components, in other implementations, UE 205 may include fewer, additional, and/or different functional components than those depicted in Fig. 3B. It will be appreciated that one or more functional components of UE 205 may be capable of performing one or more other tasks associated with one or more other functional components of UE 205.

Fig. 3C is a diagram illustrating an exemplary implementation of UE 205, where UE 205 includes a wireless telephone. As illustrated, UE 205 may include a microphone 335 (e.g., of input device 320) for entering audio information, a speaker 340 (e.g., of output device 325) for outputting audio information, a keypad 345 (e.g., of input device 320) for entering information or selecting functions, and a display 350 (e.g., of input device 320 and/or output device 325) for outputting visual information and/or inputting information, selecting functions, etc.

Although Fig. 3C illustrates an exemplary implementation of UE 205, in other implementations, UE 205 may include fewer, additional, or different exemplary components than those depicted in Fig. 3C.

An exemplary first embodiment of the method will now be described in relation to Figure 4A.

In step 600 the UE is in a traditional power control mode, i.e. the UE is using some version of wideband path loss measurements to calculate an appropriate output power level .

During step 600 the UE is monitoring a reference signal's SNR variation. The SNR variation is a good indicator of the behaviour of the fast fading.

In step 602, the UE is waiting for the SNR variation to descend below a predetermined threshold. Alternatively, the decision could here be based on a multitude of parameters indicative of fast fading variation, e.g., by measuring, or obtaining from an advanced eNodeB, the Doppler shift and determining the UE speed to be above a certain threshold, interference measurements, uplink channel variation autocorrelation (possible due to reciprocity) , rank adaptation information, processed channel information, such as DL transmission mode (e.g. closed or open loop spatial multiplexing or other mode that implies slow or fast channel variations), or a suitable combination of said methods . Note that a Doppler shift measurement will probably be available for other purposes in an advanced eNB and an advanced UE. This means that using the Doppler shift as an indicator of channel variations is just a reuse of an existing measurement.

When SNR variation descends below the threshold, because the UE is traveling at low speed, the UE switches to and runs in fast fading power control mode in step 604, This is possible because channel variations are slow, allowing the UE ample time to adjust its output power. It uses path loss measured on narrow frequency bands in the downlink to calculate and allocate an appropriate output power level . A more elaborate description of the preferred power control method used when running in fast fading power control mode will follow below in connection to figure 4A.

In step 606, the UE monitors the SNR variation again, i.e. in this particular embodiment the first and second fast fading indicator are identical. However, where appropriate, a second fast fading indicator, based on one or many parameters indicative of the fast fading variation, such as e.g. the ones above, could be monitored instead.

In step 608, the UE waits for the SNR variation to exceed a predetermined threshold. This will typically happen when the UE increases its speed. This threshold is slightly above the threshold used in step 602, so as to achieve hysteresis in order to avoid flickering between power control modes . In an alternative embodiment the same predetermined threshold is used in steps 602 and 608. It is to be noted though, that the conditions for switching in steps 602 and 608 are different also in this alternative embodiment, since the first condition is to descend below the threshold and the second condition is to exceed the same threshold.

The threshold is set at a level where fast-fading path loss measurements no longer give path loss predictions that are both accurate and timely. This may occur, e.g., if the measurement inaccuracies become too large, or if the power setting cannot be done quickly enough to utilize the measurements, Typically the threshold is exceeded while the UE is increasing its speed. It can also occur due to increased occurrence of moving surrounding objects, such as e.g. cars or buses. When the threshold is exceeded, using one (or more) of several possible decision mechanism, the UE changes its measurement process when switching power control modes in step 610, so that the method of measurement is changed to traditional wideband path loss.

The decision mechanism can be one of several options, such as : a) The UE recognizing by itself that it cannot track the fast fading and thus autonomously adjusts its method of measurement . b) A response to the UE being configured for a specific antenna selection scheme. c) The serving eNB instructing the UE to adjust the measurement to any of the alternative measurements mentioned above. The instruction can be explicit or implicit, through the signaling or another parameter with which the pathloss measurement instruction is coupled.

As a result of switching to a more appropriate path loss measurement technique, the total system performance improves through the reduction of interference on PUCCH transmissions. Meanwhile, fast fading is being monitored, in order to facilitate a quick return back to narrowband measurements .

In some embodiments, the UE changes its measurement filter to average path loss over more frames. In others, the method of measurement is changed to traditional wideband path loss. In still others, fast-fading measurements can be combined with longer-term, frequency-selective measurements or with traditional wideband path loss measurements. In some embodiments, two or more of these approaches may be selectively used, depending on the channel conditions .

In alternative embodiments, the monitoring of the fast fading indicators and the decision mechanisms used in steps 602 and 608 reside in the eNB .

In an alternative embodiment at least one fast fading indicator is a mathematical function of several parameters, and at least one of the parameters is measured in the UE and at least one is measured in the eNB.

In an alternative embodiment at least one fast fading indicator is a mathematical function of several parameters all of which are measured in the eNB.

The power control method used during the fast fading power control mode in a preferred embodiment is described below. An exemplary process is described below, in connection with Fig. 4B, in which UE 205 may perform a power control mode. For purposes of discussion, the exemplary process will be described based on communication system 200 depicted in Fig. 2B. However, it will be appreciated that the exemplary process may be performed in communication system 200 depicted in Fig. 2A, in which different devices may be present.

Fig. 4B is a flow diagram illustrating an exemplary process 400 for calculating and allocating power. The exemplary process 400 of FIG. 4B may be performed by UE 205 for controlling power with respect to a transmission. In addition to Fig. 4B, process 400 will be described in connection with previous figures, as well as Fig. 5. Process 400 may begin with receiving signals in a downlink frequency domain to enable channel estimation (block) . For example, as illustrated in Fig. 5, eNodeB 210 may transmit a downlink signal 505. The received signal may include, for example, a pilot signal or some other reference signal.

Frequency bands in the downlink frequency domain that correspond to uplink frequency bands associated with a channel allocation or a scheduling grant may be selected (block 410) . For example, transceiver 305 may select the frequency bands in downlink signal 505 that correspond to uplink frequency bands associated with the PUCCH or the PUSCH. The frequency bands selected may correspond to the frequency bands in which UE 205 intends to transmit based on its uplink power control 510. For example, with respect to the PUCCH, the frequency bands may correspond to the outer frequency bands in a uplink frequency spectrum. With respect to the PUSCH, the frequency bands may correspond to the frequency bands (e.g.., resource blocks) in which UE 205 received a scheduled grant in the uplink frequency spectrum. In LTE Advanced (the evolution of LTE) where several carrier frequencies can be aggregated (scheduled to and transmitted on from the same UE) the frequency band may correspond to carrier frequencies . The selected frequency bands may be measured (block 415) . For example, transceiver 305 may perform channel measurements on the selected frequency bands. The channel measurements may include fast fading even though this is typically (according to LTE standard) filtered away. Further, if the measurements are performed expediently, such measurements may well match the expected channel of the upcoming PUCCH transmission or PUSCH transmission in TDD. With respect to the PUCCH, for example, downlink pilots in the two corresponding PUCCH frequency bands (typically 18OkHz on the bandwidth edges) may be measured. With respect to the PUSCH, for example, all PUSCH resource blocks may be measured individually. With respect to aggregated carriers in LTE Advanced the carrier frequencies may be measured individually and also the PUSCH resource blocks within each carrier frequency.

Path losses based on the measured selected frequency bands may be estimated (block 420) . For example, power calculator 325 of UE 205 may estimate path losses (PL) based on the pilots in the frequency bands in which UE 205 intends to transmit. For example, with respect to the PUCCH, power calculator 325 may estimate a path loss value (PL) based on the PUCCH measurements. Additionally, power calculator 325 may estimate two individual path loss values, , corresponding to both slots. With respect to the PUSCH, a path loss value (PL) may be estimated by power calculator 325 based on the PUSCH measurements. In one implementation, power calculator 325 may estimate individual path loss values, PLι,P∑2,...,PLx based on the PUSCH measurements. In another implementation, power calculator 325 may not estimate individual path loss values for the PUSCH.

A total power based on the estimated path losses may be calculated (block 425) . For example, power calculator 325 may calculate a total power based on equations 1 and 2, as previously described above. It will be appreciated that, in contradistinction to existing implementations, the path loss value (PL) relates to a path loss corresponding to frequency bands on which UE 205 intends to transmit versus the entire downlink frequency spectrum. With respect to PUCCH, power calculator 325 may also calculate an average power budget for both slots (e.g., PPUCCH_AVG) , where PPUCCH AVG may expressed by the following expression: PPUCCH _ AVG = (PPUCCHI + PPUCCH2) 12 Eq . 3 where PPUCCHI and PPUCCH2 correspond to power values for the two PUCCH slots. This principle may be applicable to the PUSCH also. For example, power calculator 325 may calculate an average power budget with respect to the resource blocks in the PUSCH. In such instances, individual power values may be estimated. For example, the power values PPUCCHI and PPUCCH2 may be calculated according to the standard formula Eq.1 using individual PL values.

A power allocation based on the calculated total power may be determined (block 430) . With respect to the PUCCH, a number of different power allocation schemes associated with the slots may be implemented by power allocator 330 of UE 205. For example, the total power may be allocated on the two PUCCH slots based on the individual path losses, where [ ] = F( PLi, PL2, PPUCCH _ AVG ) , and the function F( ) may utilize individual path losses and/or an average power budget for power allocation. In one implementation, all of the power (e.g., 2 * PPUCCH_AVG) may be allocated to the best slot. The criterion for determining the best slot may be based on the slot that has the minimum path loss. In another implementation, all of the power may be allocated to the best slot if the absolute value of the difference in path losses, PLi,PLi , is larger than a specified threshold. In the event that the difference in path losses is less than the threshold, the total power may be distributed between both slots. The threshold may be any value (e.g., one to infinity) . In still another implementation, all of the power may be allocated in a manner that provides that both PUCCH slots are received by eNodeB 210 at equal strength. For example, the power allocation of each slot may be determined based on the following expression:

Set the power of slot k to p(A) = signal-to-noise- target*measured noise/ PLK Eq. 3.

In yet another implementation, allocation of power per slot p(A-) may be distributed based on a water filling principle, which may be expressed according to the following expression: p(A) = max (A - 1/ PLKO) , with the constraint that sum(p(A;)) is less than the maximum available output power. The variable A is a parameter that is used to tune the water filling algorithm..

It will be appreciated that the power allocation may be different for ACK/NACK and CQI transmissions. For example, for ACK/NACK transmissions, all of the power may be allocated to the slot that has the minimum path loss since the same information is transmitted on both slots. On the other hand, for example, for CQI transmissions, all of the power may be allocated in a manner that provides that both slots are received by eNodeB 210 at equal strength since different information may be transmitted in each slot.

With respect to the PUSCH, the total power may be allocated to the frequency bands associated with the uplink grant. For example, power allocator 330 may a power allocation scheme based on the schemes described for the PUCCH .

An uplink transmission based on the determined power allocation may be transmitted (block 435) . For example, as illustrated in Fig. 5, UE 205 may transmit an uplink transmission 515 based on the determined power allocation. As described, a device, such as UE 205, may employ a power scheme that includes calculating power values and/or power-related values based on path losses that correspond to frequency bands in which UE 205 intends to transmit. In the case of a LTE communication system, application of these concepts has been described in connection with the PUCCH and the PUSCH. The device, such as UE 205, may also manage power allocation based on individual path losses. Power allocation schemes may be tailored to the particular information being transmitted. For example, as previously described, different power allocation schemes may be used between ACK/NACK and CQI transmissions.

It should be noted that as far as this application goes, a change of measurement modes signifies a change of power control modes .

The foregoing description of implementations provides illustration, but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the teachings. For example, the individual path losses may be incorporated into equations 1 and/or 2. The closed loop parameters may be the same for both PUCCH slots or individually controlled for each PUCCH slot. These principles may equally apply for the PUSCH. Additionally, it will be appreciated that the concepts described herein may be applied to communication systems, other than LTE. For example, the concepts described may be applied to WiMAX, such as, for example sub-channel scheduling on the Partial Usage of Subchannels (PUSC) , and to WiMAX carrier frequencies . In addition, while a series of blocks has been described with regard to the process illustrated in Fig. 4B, the order of the blocks may be modified in other implementations. Further, non-dependent blocks may be performed in parallel. Further one or more blocks may be omitted. It will be appreciated that one or more of the processes described herein may be implemented as a computer program. The computer program may be stored on a computer- readable medium or represented in some other type of medium (e.g., a transmission medium) .

It will be apparent that aspects described herein may be implemented in many different forms of software, firmware, and hardware in the implementations illustrated in the figures. The actual software code or specialized control hardware used to implement aspects does not limit the invention. Thus, the operation and behavior of the aspects were described without reference to the specific software code - it being understood that software and control hardware can be designed to implement the aspects based on the description herein.

As discussed above, the utilization of channel reciprocity is an important way to improve PUCCH capacity, which can be further improved by fast-fading power control. The controllability described herein is vital if the fast- fading tracking becomes infeasible, since trying to track fast fading in that case will cause a performance loss when compared to using traditional path loss estimates.

The preceding descriptions of various techniques for carrying out uplink power control operations in a TDD communication system are given for purposes of illustration and example.