Patent Publication Number: US-10334535-B2

Title: System and method for power control

Description:
This application is a continuation of U.S. patent application Ser. No. 12/633,657 filed on Dec. 8, 2009, entitled “System and Method for Power Control,” which is incorporated herein by reference as if reproduced in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to wireless communication systems, and more particularly to a system and method for power control. 
     BACKGROUND 
     Wireless communication systems are widely used to provide voice and data services for multiple users using a variety of access terminals such as cellular telephones, laptop computers and various multimedia devices. Such communications systems can encompass local area networks, such as IEEE 801.11 networks, cellular telephone and/or mobile broadband networks. The communication system can use a one or more multiple access techniques, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA) and others. Mobile broadband networks can conform to a number of system types or partnerships such as, General Packet Radio Service (GPRS), 3rd-Generation standards (3G), Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS), the 3rd Generation Partnership Project (3GPP), Evolution-Data Optimized EV-DO, or Long Term Evolution (LTE). 
     An illustration of a conventional mobile broadband system  100  is illustrated in  FIG. 1 . Mobile broadband system is divided into cells  108 ,  110  and  112 , where each cell  108 ,  110  and  112  has corresponding base station  102 ,  104  and  106 . Mobile terminals or user equipment (UE)  116  and  114  access network  100  through one of base stations  102 ,  104  and  106 . Three base stations  108 ,  110  and  112  and two UEs  114  and  116  are used for simplicity of illustration, however, multiple cells and UEs can be used and provided for in real systems. 
     In communication systems such as CDMA and LTE, bandwidth is shared among terminal devices or UEs in the uplink communications channel. Because bandwidth is shared, power control is used in the uplink communications to address the near-far effect. This means that UE  114  at the cell edge with higher path loss PL 2  to base station  102  will generally transmit with a higher power than UE  116  with lower path loss PL 1  so that each respective transmission is received at a reasonable level above noise and interference. 
     The prior art has addressed the power control in a couple of ways. Under the full power control (FPC) scheme, the received signal level of all UEs are about the same at the base station in order to provide equal signal to noise and interference ratio (SNIR) for all users. Under FPC, the UE power is set to fully compensate for the channel loss, thus all users have same received signal level P o  at the base station:
 
 P   0 ={10*log 10( N+I   0 )+SNIR TARG },  (1)
 
where, I 0  is the estimated total interference power at the base station, N is the thermal noise power, and SNIR TARG  is the target SNIR. The transmit power at the UE under FPC is given by:
 
 P   ƒ   ={P   max   ,P   0 +PL},  (2)
 
     Where P max  is a maximum transmit power a UE is allowed to transmit and PL is the path loss. It can be seen that using FPC, all UEs have the same SNIR if the target SNIR is the same for all UEs and if UE power is not limited by P max . When FPC is used, however, the same modulation and coding scheme (MCS) level is typically used by all the UEs, which potentially results in a reduced system throughput because higher MCS levels are not used. 
     The fractional power control (FrPC) scheme proposed in the LTE standard allows users with lower path loss to use a higher power level than would be otherwise required to maintain a minimum SNIR threshold. The allowed margin above the cell edge SNIR is inversely proportional to the path loss of the user, so that a user in closer proximity to the base station can obtain a higher SNIR and a higher MCS level. The transmitter power of a UE under FrPC is expressed as:
 
 P   tx   ={P   max   ,P′   0 +α·PL} and  P′   0   =P   0 +Δ 0 ,
 
where α is a multiplier that is less than 1, and Δ 0  is a power increase factor set such that the cell-edge UEs still achieves the target SNIR. (When α is equal to 1, the system operates as a FPC system.) Under FrPC, UEs that are closer to the base station can boost power above the point that would have been set by FPC, where the increase in power ΔP is given by:
 
Δ P =(1−α)×(PL−PL cell   _   edge ),
 
so that P tx =ΔP+P ƒ .
 
where PL cell   _   edge  is the path loss from the cell edge UE to the base station.
 
     UEs closer to the base station, therefore, have a higher SNIR than UEs farther from the base station. While FrPC shows some improvement over FPC schemes, FrPC chooses UE transmission levels based on a UE path loss and not based on the actual interference level being caused by the UE. Consequently, FrPC power control may not effectively reduce interference in some cases. 
     What is needed are systems and method of power control for multiple access wireless networks that increase throughput and minimize interference. 
     SUMMARY OF THE INVENTION 
     In accordance with an embodiment of the present invention, a method for transmit power control is provided. In this example, the method includes determining a downlink signal to noise ratio (SNIR) between a served user equipment (UE) and a serving base station, computing an uplink transmit power level as a function of the downlink SNIR, and performing an uplink transmission over physical uplink shared channel (PUSCH) resources in accordance with uplink transmit power level. An apparatus for performing this method is also provided. 
     In accordance with another embodiment of the present invention, another method for transmit power control is provided. In this example, the method includes receiving a message indicating target interference levels associated with neighboring base stations, computing an uplink transmit power level as a function of the target interference levels associated with the neighboring base stations, and performing an uplink transmission over the PUSCH resources in accordance with uplink transmit power level. An apparatus for performing this method is also provided. 
     In accordance with yet another embodiment, yet another method for transmit power control is provided. In this example, the method includes receiving a message indicating current interference levels associated with neighboring base stations, computing an uplink transmit power level as a function of the current interference levels associated with the neighboring base stations, and performing an uplink transmission over physical uplink shared channel (PUSCH) resources in accordance with uplink transmit power level. An apparatus for performing this method is also provided. 
     In accordance with yet another embodiment, yet another method for transmit power control is provided. In this example, the method includes receiving an instruction from a serving base station. The instruction instructs a served UE to iteratively reduce an uplink transmit power level of the served UE until an interference level experienced by a neighboring base station has fallen below a threshold. The method further includes iteratively reducing the uplink transmit power level of the served UE over a sequence of time intervals until an instruction to resume a normal power control procedure is received from the serving base station. An apparatus for performing this method is also provided. 
     The foregoing has outlined rather broadly the features of an embodiment of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of embodiments of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  illustrates a diagram of a conventional mobile broadband system; 
         FIG. 2  illustrates a graph showing the relationship between various operating points and an optimal pollution curve; 
         FIG. 3  illustrates a power graph according to an embodiment of the present invention; 
         FIG. 4  illustrates embodiment 0 curves; 
         FIG. 5  illustrates an embodiment power graph; 
         FIG. 6  is an embodiment system parameter chart; 
         FIG. 7  illustrates an embodiment cumulative distribution function; 
         FIG. 8  is a graph illustrating the effect of varying parameters in an embodiment communication system; 
         FIGS. 9 and 10  are graphs illustrating the performance of various embodiment power control methods; 
         FIG. 11  illustrates a block diagram of an embodiment base station; and 
         FIG. 12  illustrates a block diagram of an embodiment user device. 
     
    
    
     Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale. 
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The making and using of various embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention. 
     The present invention will be described with respect to various embodiments in a specific context, namely power control in a broadband wireless networks. The invention may also be applied to power control in other types of networks. 
     In embodiments of the present invention, power control systems and method are implemented that control the uplink transmit power of UEs based on total interference pollution to other cells. The impact of a UE&#39;s interference on the throughput of other cells is taken into account when determining UE transmit power. In embodiments, total interference pollution is calculated by summing UE generated interference to every other cell normalized by the expected mean interference level of the cell receiving the interference. This expected mean interference is used as a loading factor for each cell, which is measured and shared with neighboring cells so that the UEs in the neighbor cells can use that as target interference level for that cell. 
       FIG. 2  illustrates a graph showing the relationship between various operating points with respect to optimal pollution curve  202 . In some embodiments, when the power of a UE is increased, assuming a neighbor cell target mean interference threshold of Ti=T 0 , the resulting interference of each cell would not equal T 0  and it would not be a fixed value either. Rather, the resulting interference would be a value that varies in time depending on interference from other cells. Therefore, not all of the base stations will operate in the optimum point according to some embodiments of the present invention. If the realized mean interference received by a base station is larger than the target, T 0 , an embodiment power adjustment provides a larger power increase than that required to operate in the optimum point. To prevent this from happening, the system increases power some margin Δ 2  below the limit given by the target. Because all UEs are operating using the same algorithm, the actual interference level will also be reduced (point O 1  moves to point O 1 ′, assuming that the system is not power limited at O 1 ), and the system cannot reach the preferred operating point by changing Δ 2 . Similarly, if the actual/experienced total interference level (T 0 ′) is smaller than target T 0 , increasing UE power does not move the operating point close to the optimum pollution curve (point O 2  moves to point O 2 ′). In embodiments of the present invention, the power of different UEs are therefore varied by different amounts to achieve operating points close to optimal pollution curve  202 . As explained later in this disclosure, this is done in some embodiments using a parameter beta so that different UEs have different adjustments than the target, or by making the Δ 2  value dependent on the UE (UE dependent Δ 2  value). As explained herein, this is done based on the interference measurements performed by neighboring base stations in some embodiments. For example, operating point O 1  to shifts to point O 1 ″ and operating point O 2  to shifts to point O 2 ″ by an embodiment method. 
     In an embodiment used for inter-cell interference coordination (ICIC) for different resource blocks (RBs), different interference target levels are derived for different eNB groups and/or different groups of base stations, which are known apriori by the neighboring cells. The ratio of the target interference level for a specific resource block to the nominal reference target interference level in the system is used to normalize the total interference to these different eNB groups. The interference to other cells is to be measured using downlink measurements if the reciprocity of the channel for medium signal level is valid, or using specific uplink sounding signals. 
     In embodiments, the UE uplink power is adjusted so as not to exceed a target interference over thermal noise level (TIOT) in an adjacent sector. In some embodiments that account for multiple sectors having multiple target level, for example multi-TIOT ICIC schemes, embodiment power control systems and methods are used to maximize throughput. 
       FIG. 3  illustrates a power graph  300  according to an embodiment of the present invention. The y-axis of the graph represents transmitted and received power. User equipment UE 0  transmits to Cell 0  with a path loss of PL 0 . The signal received by Cell 0  is S f . The signal from U 0  is also received at neighboring cells Cell 1 , Cell 2  and Cell 3  at power levels q 1 , q 2  and q 3 , respectively, as shown by line  302 . Cell 0  has an interference target of T 0 , Cell 1 , has an interference target of T 1 , Cell 2 , has an interference target of T 2 , and Cell 3 , has an interference target of T 3 . In the illustrated embodiment, each interference target represents the amount of total mean interference each cell that achieves a certain level of performance for that cell&#39;s UEs. In an embodiment, the interference target can also be the measured instantaneous or mean total interference experienced by each neighbor for that resource block, in which case, this information is shared with the neighboring stations. In the illustrated embodiment, Cell 1  receives UE 0 &#39;s signal at a level Δ1+k1 below the target interference level of T 1 , Cell 2  receives the signal at a level Δ2+k2 below the target interference level of T 2 , and Cell 3  receives the signal at a level Δ3+k3 below the target interference level of T 3 . 
     It can be seen that the impact of adding an extra interference (q 0 ) to a base station with a higher interference level T 1 , is smaller than the impact on a base station with a lower interference level, T 2 . This is because, 10*log 10((q 0 +T 1 /T 1 )&lt;10*log 10((q 0 +T 2 )/T 2 ) if T 1 &gt;T 2 . Therefore, in an embodiment, when determining the total interference pollution level, interference is weighted according to the average/target interference level existed/expected before the addition. 
     In an embodiment of the present invention, it is assumed that different base stations have different interference tolerance levels, T 0  in a given RB, which is decided by each base station or dynamically changed under a radio resource management (RRM) scheme, where other neighboring base stations aware of these thresholds. 
     In an embodiment the power of the UE is set to be:
 
 P   ƒ   +ΔP,  
 
where P ƒ  is the FPC transmit level defined in equations (1) and (2) and ΔP is an offset from the FPC transmit level.
 
     In an embodiment, ΔP is set to be. 
                 Δ   ⁢           ⁢   P     =       β   (       S   f     -     10   ⁢           ⁢     log   (       ∑   i     ⁢     (       q   i       λ   i       )       )         )     -     Δ   ⁢           ⁢   2         ,         
where q i  is the respective interference levels caused by the UE, β and Δ2 are parameters to be found using simulations and depend on the environmental conditions and cell planning; λ i  is the ratio between target interference at i th  cell and a reference interference level, T 0 . In an embodiment, if the thermal noise is taken as a reference level, is the target interference power over target thermal power (IOT) of the cell.
 
     A more general expression for ΔP is:
 
Δ P =ƒ(δ P ), where
 
               δ   ⁢           ⁢   P     =       S   f     -     10   ⁢       log   (       ∑   i     ⁢     (       q   i       λ   i       )       )     .               
In an embodiment, ƒ is a monotonic function chosen to keep UE power levels within a specified range and to achieve a desired tradeoff between cell edge performance and cell center throughput. For example, ƒ can be in the form of
 
ƒ( x )=β x   n , so that
 
                 Δ   ⁢           ⁢   P     =       δ   ⁢           ⁢     P     m   ⁢           ⁢   i   ⁢           ⁢   n         +       β   ⁡     (         δ   ⁢           ⁢   P     -     δ   ⁢           ⁢     P     m   ⁢           ⁢   i   ⁢           ⁢   n               δ   ⁢           ⁢     P     ma   ⁢           ⁢   x         -     δ   ⁢           ⁢     P     m   ⁢           ⁢   i   ⁢           ⁢   n             )       n         ,         
where δP min  is the minimum value of δP over all the UEs in the cell and δP max  is the maximum value of δP over all the UEs in the cell. Examples of various curves for ƒ(x)=βx n  is illustrated in  FIG. 4 . Curve A represents the case where β=1 and n=1; curve B represents the case where β=0.7 and n=1. Embodiments employing curve B provide power adjustments for higher margin UEs that are linearly reduced according to the path loss. Curves C, D, E and F correspond to embodiments that non-linearly adjust the power using different functions to treat cell centers differently than cell-edge users as shown below. In embodiments, n and β are found using simulation and optimization techniques known in the art.
 
     In another embodiment, an adaptive algorithm dynamically adjusts the parameter β. Neighboring cells inform the base station when the average interference level over a some period exceeds a margin. Depending on the margin, β is adjusted to increase or decrease the interference to the neighboring cells. This adjustment may be done to the users which generate high levels of interference to particular neighboring cells. 
     In an embodiment an adaptive method uses simulations to achieve a specified fairness. A system throughput is measured, and if the local base station fairness is better/worse than a specified fairness, then beta is increased or decreased by a certain amount. The results of the simulation are used to fix a start value, and the adaptive method is used to adjust the simulation dynamically. The amount by which the simulation is adjusted is determined according to simulation techniques known in the art. 
     In another embodiment, an adaptive method uses simulations that are changed dynamically for a given base station for one value of Δ2. If a neighboring base station wants to change the operating point by changing its interference, only a Δ2 value of a UE is changed that interferes with a neighboring base station. If the neighboring base station wants to reduce or increase interference to it, Δ2 is increased or decreased by a small amount. The amount by which Δ2 is increased or decreased by a small amount is determined according to simulation techniques known in the art. 
     In an embodiment, where target interference levels are the same in adjoining cells, δP can be simplified as:
 
Δ P=S   ƒ −10*log 10(Σ( q   i /λ i ))= S   ƒ −10*log 10(Σ( q   i )+Δ3.
 
Without loss of generality, Δ3 can be set to be 0. Therefore,
 
Δ P =β·( S   ƒ −10*log 10(Σ( q   i ))−Δ2,
 
where Σ(q i ) is the total mean interference a UE causes to all the other cells. The above adjustment, ΔP can be directly estimated from a mean downlink SNIR:
 
                 SNIR   DL     =             p   DL     ⁢     I   d             ∑   i     ⁢       p   DL     ⁢     I   i         +     N   0         ≈       l   d         ∑   i     ⁢     l   i           =           p   tx     ⁢     l   d           ∑   i     ⁢       p   tx     ⁢     l   i           ≈         s   f     ⁡     (     =     UL   ⁢           ⁢   received   ⁢           ⁢   power   ⁢           ⁢   at   ⁢           ⁢   serving   ⁢           ⁢   cell       )           ∑   i     ⁢       q   i     ⁡     (     =     UL   ⁢           ⁢   total   ⁢           ⁢   interference   ⁢           ⁢   to   ⁢           ⁢   neighbours       )                 ,         
where P DL  is the downlink transmit power of the base stations, l d  is the downlink path loss from the serving cell l i  is downlink path loss from the ith neighbor base station, and N 0  is the thermal noise. Therefore, δP=SNIR DL  (in dB). When n=1, the power transmitted at the UE is:
 
 P   tx   =P   ƒ +βSNIR DL −Δ2.
 
This will be referred to an embodiment Geometry Based Power Control (GPC) scheme.
 
     In alternative embodiments, GPC schemes can be modified. For example, in order to increase the cell-edge throughput with minimal impact to overall system throughput, the UE transmit power can be adjusted when ΔP is positive (i.e. δP=max(δP,0). In an embodiment, the total UE transmit power is determined according to:
 
 P   tx   =P   ƒ +βSINR DL −β2,β·SNIR DL ≥Δ2
 
 P   tx   =P   ƒ ,β·SNIR DL ≥Δ2.
 
This will be referred to as an embodiment capped Geometry Based Power Control (GPC-Cap) scheme. In a further embodiment, a MTPC-cap scheme can be defined as a method where if the overall power adjustment factor ΔP is negative, ΔP is set to zero.
 
     In an embodiment, there are several groups of base stations, each group of which share a common interference threshold level. For a system with three base station groups:
 
δ P=S   ƒ −10*log 10((Σ( q   1j )/λ 1 )+Σ( q   2j )/λ 2 )+Σ( q   3j )/λ 3 )),
 
where λ1, λ2, and λ3 are the relative TIOT levels associated with each BS group, and (Σ(q 1j )λ 1 ), (Σ(q 2j )/λ 2 ) and (Σ(q 3j )/λ 3 ) represent the impact of the total interference a UE causes to each base station group weighted by their target interference levels. In an embodiment, these interferences can be evaluated using downlink pilot power measurements or special pilot arrangements (e.g. introducing common pilots to each base station group). This will be referred to as an embodiment Multi-Target Power Control (MTPC) scheme.
 
     In an embodiment, at least one of the neighboring base stations adjusts its pilot power level according to a mean interference over threshold level IOT of another one of the neighboring base stations. The expression 
               ∑   i     ⁢     (       q   i       λ   i       )           
is then evaluated using the downlink SNIR of the pilot signal.
 
     In an embodiment, neighboring base stations use a common pilot signal, and the UE measures a total power of the common pilot signal I, and a desired signal level S from the serving base station. The downlink SNIR is then evaluated according to the expression, SNIR=S/(I−S). 
     In another embodiment, an iterative scheme is used to follow the interference pollution based scheme in a way that makes less assumptions for all UEs. For example, an optimum power level at which the increase in power of a UE would cause decrease in total throughput is found such that increase in throughput is lower than the decrease of throughput in the other cells. The total throughput of all the cells is determined as: 
             Q   =         log   2     ⁡     (     1   +     p   ·       L   0     /     q   0           )       +       ∑   i     ⁢     [         log   2     ⁡     (     1   +       S   i     /     (     Ti   +     p   ·     L   i         )         )       ,                 
where p is the UE uplink transmit power, L 0  is the uplink path loss to the serving station, q 0  is total interference plus noise received by the serving base station from the UEs in the neighbor base stations, L i  is uplink path loss to the i th  neighboring base station S i  is the expected received signal level for a UE served by the i th  neighboring station, and T i  is the total interference plus noise power, received by the i th  neighboring base station.
 
Let,
 
                 δ   ⁢           ⁢   Q       δ   ⁢           ⁢   p       =       0   ==   &gt;         L   0     /     q   0         1   +     p   ·       L   0     /     q   0               =       ∑   i     ⁢       1     1   +       S   i       Ti   +     p   ·     L   i               ·           S   i     ·     L   i             (     Ti   +     p   ·     L   i         )     ⋀     ⁢   2       .                 
Therefore,
 
               p   ⁡     (   n   )       =       1       ∑   i     ⁢         S   i     ·     L   i           (     Ti   +       p   ⁡     (     n   -   1     )       ·     L   i       +     S   i       )     ·     (     Ti   +       p   ⁡     (     n   -   1     )       ·     L   i         )             -         q   0       L   0       .             
An iterative scheme is then used to find the optimum power for each UE assuming fixed target Si and known Ti&#39;s for all the other cells.
 
     In an embodiment, each UE (or eNB) starts the above iteration with initial value (n=1) of p(n−1)=p(0)=pƒ (transmit power under full power control). Then, p(n=2) is evaluated. Similarly p(n) is found for larger values of n until the change is small. A fixed target Si and known Ti&#39;s are assumed for the other cells. 
     In an iterative embodiment, a fairness requirement is not considered when the optimum power level is determined through iteration. It considered in the case when throughput gain of the desired cell is greater than the sum of the throughput losses in other cells, or 
                   ∑   i     ⁢     log   ⁢           ⁢     C   ⁡     (   i   )           &gt;   0     ,         
where C(i) is the throughput for the UE in cell i. Instead, when a fairness requirement is considered,
 
                 ∑   i     ⁢       w   ⁡     (   i   )       ⁢   log   ⁢           ⁢     C   ⁡     (   i   )           &gt;   0         
is used for the iterative scheme, where w(i) is a weighting factor for the i th  cell.
 
       FIG. 5  illustrates a power graph showing the relationship between the transmit power of UE 2  with the received power from UE 0  at a serving cell and at cell i. Assume at a given UE transmit power level P, the received signals at different BSs are qi, where i=[1 . . . n]. Let S 0  represent the serving base station received signal. Ti is the sum of all the other cell interference in cell I (without this test terminal UE 0 ). When P is very large, the interference to other cells are well above the total interference they receive from other UEs. At this point, if the UE power is increased by a small amount, the cost of interference pollution (i.e. throughput loss) from that increase is higher than the corresponding gain (throughput) in the desired cell. In an embodiment, an optimal threshold is found, over which the increase of UE power provides lower performance solution to the system. When p is increased by Δp, assume qi is increased by Δqi, Ti by ΔTi, and Si by ΔSi: 
     
       
         
           
             
               
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       FIG. 6  lists the parameters of an example embodiment.  FIG. 7  illustrates a cumulative distribution function of SNIR for the case of a Single TIOT under additive white Gaussian noise (AWGN) comparing the performance of various power control schemes according to the system parameters of  FIG. 6 . Curve  712  represents a system in which no power control is provided; and curve  702  represents a system in which a full power control scheme (FPC) is used. Curve  704  represents a system where fractional power control (FrPC) is used with α=0.8, which results in s=2.8 dB, where s is the standard deviation of IOT variation at the base stations. Curve  710  represents a system in which an embodiment GPC-cap power control method is used with β=1.0 and Δ2=−3, which results in s=2.1 dB. Curve  709  represents a system in which an embodiment FrGPC-cap power control method is used where α=0.9, β=0.7, Δ2=0. FrGPC-cap is a power control scheme in which the GPC-cap power adjustment is implemented on top of FrPC scheme instead of the FPC scheme, which results in s=2.4 dB. Curve  709  represents a system in which an embodiment FrGPC-cap power control method is used where α=0.9, β=0.7, Δ2=0, thereby resulting in s=2.4 dB. Curve  706  represents a system in which an embodiment FrGPC-cap power control method is used where α=0.9, β=0.7, Δ2=1, thereby resulting in s=2.6 dB). Finally, curve  708  represents a system in which an embodiment FrGPC-cap power control method is used where α=0.9, β=0.7, Δ2=3, resulting in s=2.5 dB. It can be seen that the percent of users having SNIRs less than 3 dB to 4 dB is significantly reduced for the FrGPC-cap method compared to having no power control. The GPC cap (curve  710 ) and FrGPC-Cap method (curves  706 ,  708  and  709 ) has a higher percentage of users having SNIRs greater than 6 dB compared to full power control (curve  702 ) and fractional power control (curve  704 ). In summary, embodiment methods allow higher throughput for higher throughput users, as well as allowing for more throughput for low throughput (i.e., cell-edge) users. 
       FIG. 8  illustrates the effect of varying β and Δ2 on embodiment power control methods for a single TIOT case under AWGN. It can be seen that decreasing β from 1.0 to 0.8 improves fairness and cell-edge performance by lowering the percentage of users with SNIRs of less than 2 dB. (See curves  806  and  816 .) It can be further seen that varying Δ2 from 0 to 2 improves fairness and sharply enhances cell edge performance. (See curves  802 ,  804  and  806 .) 
       FIG. 9  illustrates a comparison of cell-edge throughput v. aggregate throughput for different power control methods for a single TIOT case under AWGN. Curve  902  represents a fractional power control system with different α values; curve  904  represents a GPC-cap system with β varied from 0.6 to 1.0; and curve  906  represents a GPC-cap systems with Δ2 varied form 0 dB to 2 dB. 
       FIG. 10  illustrates a comparison of fairness index v. aggregate cell throughput for different power control methods for multiple target interference over thermal noise level (MULTi-TIOT) cases. The fairness index represents is scaled such that a fairness index of 1 means that all users have the same throughput. Curve  950  represents a fractional power control. Curves  952 ,  954  and  956  represent GPC power control methods with different intercell interference control (ICIC) scheduling algorithms (single TIOT case), which shows that embodiment schemes provide larger gain when used in combination with different interference control schemes. Curve  958  represents a MTPC power control method applied to a multi-TIOT ICIC scheme. It can be seen that higher average throughputs are achievable using embodiment power control methods. 
     A block diagram of an embodiment base station  1100  is illustrated in  FIG. 11 . Base station  1100  has a base station processor  1104  coupled to transmitter  1106  and receiver  1108 , and network interface  1102 . Transmitter  1106  and receiver  1108  are coupled to antenna  1112  via coupler  1110 . Base station processor  1104  executes embodiment algorithms. In embodiments of the present invention, base station  1100  is configured to operate in a LTE network using an OFDMA downlink channel divided into multiple subbands and using single carrier FDMA in the uplink. In alternative embodiments, other systems, network types and transmission schemes can be used, for example, Wimax, and 1×EV-DO. 
     A block diagram of an embodiment user device  1200  is illustrated in  FIG. 12 . User device  1200  can be implemented, for example, as a cellular telephone, or other mobile communication device, such as a computer or network enabled peripheral. Alternatively, user device  1200  can be a non-mobile device, such as a desktop computer with wireless network connectivity. User device  1200  has mobile processor  1204 , transmitter  1206  and receiver  1208 , which are coupled to antenna  1212  via coupler  1210 . User interface  1202  is coupled to mobile processor  1204  and provides interfaces to loudspeaker  1214 , microphone  1216  and display  1218 , for example. Alternatively, user device  1200  may have a different configuration with respect to user interface  1202 , or user interface  1202  may be omitted entirely. In an embodiment, user device  1200  is configured to determine a downlink SNIR by evaluating the expression 
               ∑   i     ⁢       (       q   i       λ   i       )     .           
User device  1200  can be further configured to emit a sounding signal.
 
     Although present embodiments and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, many of the features and functions discussed above can be implemented in software, hardware, or firmware, or a combination thereof. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.