FRACTIONAL POWER CONTROL IN LTE UPLINK CELLULAR NETWORKS

Abstract

3rd Generation Partnership Project (3GPP) has a new standard Long Term Evolution (LTE) for high speed wireless communication which is given in the technology document series (Release 8). LTE is designed to improve the capacity and service performances of cellular phones. It also helps to increases the speed of the data transfer of the system that is built on GSM and HSPA technologies. Single Carrier Frequency Division Multiple Access (SC-FDMA) is the modulation access scheme which is used in the UL UTRAN LTE projects. Peak to Average Power Ratio (PAPR) is lower in SC-FDMA and higher in OFDMA. SC-FDMA provides intracell orthogonality but fails to mitigate the effects in the inter-cell interference. The cellular network uses frequency reuse factor of 1, which accentuated the effects of inter-cell interference. To deal with the above problem Power Control (PC) scheme is an important aspect. The UL power control in LTE networks consist of open-loop power control (called Fractional Power Control (FPC)) and the closed loop power control (CLPC). The open loop power control (OLPC) scheme is used to suppress and compensate the loss occurred by the slow varying path-loss and shadowing. The CLPC scheme is generally specified by the purveyor and this scheme is still resides under development. The CLPC helps to mitigate the loss due to fast variation and is also used in managing the interference in system. In this thesis report, optimisation of compensation factor of FPC is discussed. The path loss compensation factor of FPC is used to enhance the behavior of cell spectral efficiency. Here approximate Signal to Interference plus Noise Ratio (SINR) defined at a given distance from the enode-B, the cell average SINR and the average cell spectral efficiency equations are derived. These help us in finding the optimum compensation factor of fractional power control scheme for different environment and network conditions. The comparative study of cell parameters with the compensation factor of FPC is performed. This work of thesis shows trade-off between cell edge and cell average throughputs. This report provides the relation between optimal compensation factor and half range between enode-B, which shows slight decrement of optimal compensation factor with half range between enode-B. However optimal compensation factor strongly varies with the path loss coefficient and thus affects the cell average spectral efficiency. ii High gain in the cell spectral efficiency of FPC scheme over the full compensated (􀟙 = 􀍳) power control scheme is observed. Gain of FPC scheme over full compensation case is increasing with path loss coefficient. This gain is around 75% at path loss 4. This work is limited to the urban interference environment.