Abstract
In a 3rd Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-A) uplink, user equipment (UE) has a maximum transmission power limit defined by the UE power class. Generally, the cell edge UE has a higher probability to be constrained by the maximum transmission power level owing to the compensation of the large pathloss. When the UE transmission power is constrained by the maximum level, allocating a higher number of physical resource blocks (PRBs) than the UE power capability can afford will reduce the transmission power to be allocated per PRB, resulting in inefficient use of power resources. To avoid this power inefficiency, the uplink transmission power can be controlled according to the number of PRBs allocated using the power headroom report-based power efficient resource allocation (PHR-PERA) scheme proposed in this paper. Furthermore, adaptive open-loop power control (OL-PC) based on the signal-to-interference-plus-noise ratio (SINR) and the uplink interference is used to improve the cell capacity. By the uplink power control employing the proposed PHR-PERA scheme, the macro and femto UE throughputs were increased by 49.9 and 5 %, respectively, compared to the case of conventional fractional power control (FPC). Additional gains of 21.9 and 4.8 % for macro and femto UE throughputs, respectively, were achieved by adaptive OL-PC. The performance of fast closed-loop power control (CL-PC) based on the received SINR is also evaluated in this paper. The simulation results demonstrate that CL-PC supports OL-PC by compensating the fading effect for the UE uplink SINR to meet the target SINR.
Highlights
In a 3rd Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-A) uplink, the orthogonality provided by single carrier-frequency division multiple access (SC-FDMA) removes intra-cell interference—i.e., the interference between users in the same cell [1]
5.2 Evaluation of the proposed PHR-based uplink power control procedure 5.2.1 Initial parameter setting in conventional open-loop power control the effect of the fractional power control (FPC) scheme and its P0 parameter setting is evaluated in order to determine the initial OL-PC parameters
The separate sets of initial OL-PC parameters are selected for the macro and femtocells, which can maximize the throughputs of the macro user equipment (MUE) and femto user equipments (FUEs) simultaneously
Summary
In a 3rd Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-A) uplink, the orthogonality provided by single carrier-frequency division multiple access (SC-FDMA) removes intra-cell interference—i.e., the interference between users in the same cell [1]. In this paper, all the cells are using the same frequency band to provide spectral efficiency; the uplink power control is used to mitigate the severe interference situation of HetNet. In [8], the cell-specific uplink power control scheme was proposed considering the HetNet environment. In [10], the target received power is controlled based on the interference generated to neighboring cells by exchanging the closed-loop commands under the HetNet environment. The power headroom reportbased power-efficient resource allocation (PHR-PERA) scheme is proposed in order for the base station to consider the UE transmission power state while allocating PRBs. Eventually, the UE transmission power can be controlled by the number of PRBs allocated by using the proposed PHR-PERA scheme.
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