Radio resource allocation for cellular networks based on OFDMA with qos guarantees

Abstract

In this paper we address the problem of radio resource allocation for QoS support in the downlink of a cellular OFDMA system. The major impairments considered are cochannel interference (CCI) and frequency selective fading. The allocation problem involves assignment of base stations and subcarriers, bit loading, as well as power control, for multiple users. We propose a three-stage, low-complexity, heuristic algorithm to distribute radio resources among multiple users according to their individual QoS requirements, while at the same time maintaining the QoS of already established links in all the cochannel cells. The allocation objective is to minimize the total transmit power, which adds to reducing CCI. Simulation results show a superior performance of the proposed method when compared to classical radio resource management techniques. Our scheme allows to achieve almost 6 times higher capacity (sum data rate) than the method based on FDMA with power control, at a blocking probability of 0.02.

Performance Evaluation of Bit Loading, Subcarrier Allocation, and Power Control Algorithms for Cellular OFDMA Systems

“…We have proposed a modification of the algorithms described in [12] to solve this allocation problem. The modification includes possibility to perform adaptive cell selection in order to find suitable cell to serve a user.…”

“…Constraint (10) expresses user data rate requirement R u vs. offered data rate oR u , constraint (11) is a limitation of a resulting transmit power oP k , constraint (12) indicates that a subcarrier can be allocated to at most one user within a cell. Problem (9)- (13) is a 3-dimensional allocation problem, in which entries in the cost array P = {P u,n,k } are mutually dependent due to CCI, as can be seen in relations (1)- (2), which is a major difficulty.…”

“…This analysis allows us to better understand applicability of the proposed methods. Moreover, in this paper we propose a modification of the algorithms described in [12] to allow for performing adaptive cell selection (ACS) and we evaluate its performance by simulations. ACS was considered in an OFDMA scenario in [7] but its forms are known in contemporary systems (e.g.…”

“…In [12] we proposed algorithms for appointing a serving base station, allocation of subcarriers, adaptation of modulation levels (bit loading), and finally control of transmit power to satisfy and maintain the users' individual QoS requirements, expressed in terms of bit rate and bit error rate, at the lowest possible cost of resource utilization in OFDMA system. In this paper, in conjunction with the ideas from the companion paper [12] we have focused on performance evaluation of the proposed algorithms under various settings of system parameters. This analysis allows us to better understand applicability of the proposed methods.…”

“…Our previous work in the area of resource allocation for OFDMA in cellular environment includes [11] and [12]. In [12] we proposed algorithms for appointing a serving base station, allocation of subcarriers, adaptation of modulation levels (bit loading), and finally control of transmit power to satisfy and maintain the users' individual QoS requirements, expressed in terms of bit rate and bit error rate, at the lowest possible cost of resource utilization in OFDMA system.…”