Low complexity subcarrier and power allocation algorithm for uplink OFDMA systems

Abstract

In this article, we consider the joint subcarrier and power allocation problem for uplink orthogonal frequency division multiple access system with the objective of weighted sum-rate maximization. Since the resource allocation problem is not convex due to the discrete nature of subcarrier allocation, the complexity of finding the optimal solution is extremely high. We use the optimality conditions for this problem to propose a suboptimal allocation algorithm. A simplified implementation of the proposed algorithm has been provided, which significantly reduced the algorithm complexity. Numerical results show that the presented algorithm outperforms the existing algorithms and achieves performance very close to the optimal solution.

Electromagnetic Emission-Aware Scheduling for the Uplink of Multicell OFDM Wireless Systems

“…We compare our scheme against a state of the art uplink multicell (MC) SE maximization scheme of [16] and two single cell (SC) schemes, i.e., our EM emission reduction scheme of [14] and a classic SE maximization scheme [11], where each sector uses different frequency bands i.e., the number of subcarriers is split amongst the M sectors, to avoid interference. In the following, the results of three different versions of our scheme are presented, where "proposed-PA1" denotes the version of our proposed scheme using PA1 power allocation, while "proposed-PA2 scheme (approx.)"…”

“…• Simulation results demonstrate that our proposed scheme significantly outperforms the single cell EM emission minimization scheme of [14] (i.e., without intercell interference) by up to 70%, and by over 3 and 4 orders of magnitude when compared to the multicell SE maximization scheme of [16] and the single cell SE maximization scheme of [11], respectively. Furthermore, the results show that the uplink EM emission in the network is proportional to the number of users and their QoS requirements.…”

“…A sub-optimal, but practical, way of simplifying this problem is to perform subcarrier and power allocations in a sequential manner as, for instance, in [11] or [12]; at first subcarrier allocation is performed to obtain α m k,n (t) values, then powers are allocated based on the knowledge of α m k,n (t) ∀k, n, t, m.…”

“…Knowing r m k,n (t) ∀k, n, m, t, the optimal per-subcarrier transmit powers can then be obtained from (11).…”

“…Thus, in [9], we proposed a user scheduling algorithm to minimize the EM emission of users in the uplink of TDMA, which reduces the EM emission by up to 45% in comparison with traditional TDMA system. In the single cell scenario, subcarrier and power allocation in the uplink of OFDM systems have been very well investigated but mainly for SE improvement [10], [11] and, recently, EE [12], [13]. In the context of EM emission reduction, in [14], we proposed a scheduler for the uplink of OFDM systems to minimize EM emissions and maintain QoS, based on the assumption that the channel state information (CSI) of all the users can be predicted over a certain transmission window (i.e., spanning several time slots).…”