Optimized Scheduling Technique of Null Subcarriers for Peak Power Control in 3GPP LTE Downlink

Abstract

Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system.

A Novel Scheduling Algorithm Based on Game Theory and Multicriteria Decision Making in LTE Network

“…Step 2 (construct the normalized decision matrix). To make a decision over multicriteria using TOPSIS algorithm, each attribute is transferred from dimensions into dimensionless by finding the normalized value of criteria related to user as it is shown in (6). The matrix in ( 7) contains the normalized attribute values of all users.…”

“…The resource block is the basic 2 International Journal of Distributed Sensor Networks time-frequency unit in the scheduler, spanning 180 kHz in the frequency domain. The scheduler assigns resource blocks to a user each 1 ms of scheduling interval [6].…”