Subcarrier Allocation Algorithm Research Articles

Subcarrier and power allocation algorithm based on inter-cell interference mitigation for OFDMA system

This article proposes a dynamic subcarrier and power allocation algorithm for multicell orthogonal frequency division multiple access (OFDMA) downlink system, based on inter-cell interference (ICI) mitigation. Different from other ICI mitigation schemes, which pay little attention to power allocation in the system, the proposed algorithm assigns channels to each user, based on proportional-fair (PF) scheduling and ICI coordination, whereas allocating power is based on link gain distribution and the loading bit based on adaptive modulation and coding (AMC) in base transceiver station (BTS). Simulation results show that the algorithm yields better performance for data services under fast fading.

A Subcarrier Allocation Algorithm for Efficiently Reducing Power in Multiuser OFDM Systems

Resource allocation in multiuser OFDM systems is a complex nonlinear optimization problem. In order to avoid direct solution, based on the analytical results of the problem of minimizing the total transmit power, a two-step subcarrier allocation algorithm is presented. The algorithm reduces the total transmit power by reducing the achievable minimum transmit power value required by each user. Subcarriers are allocated in the algorithm according to the data rate required by users and the channel characteristics. The required number of subcarriers allocated to users does not need to be known in advance. The allocation process consists of two steps: basic subcarrier allocation and residual subcarrier allocation. Numerical results demonstrate that the proposed algorithm can reduce the total transmit power effectively.

A multicarrier interleave-division uwb system

We propose a multicarrier interleave-division multiple-access scheme for ultra-wideband wireless communications. For the uplink, a chip-level interleaving method at the transmitter with a simple turbo receiver is proposed to effectively suppress the frequency-selective fading and multiple-access interference. Both hard and soft frequency notching methods are suggested to suppress the narrowband interference. For the downlink, a two-layer interleaving scheme is proposed, in which data from different users are separated in the frequency-domain while the different data streams for the same user are separated in the interleaver-domain. A joint power and subcarrier allocation algorithm is developed to exploit the multiuser diversity and thereby improve the system performance. The performance of the proposed system is evaluated by both theoretic analysis and simulations. It is seen that within a few iterations, the proposed system exhibits single-user performance even under over-loaded conditions

Subcarrier allocation and bit loading algorithms for OFDMA-based wireless networks

Orthogonal Frequency Division Multiple Access (OFDMA) is an emerging multiple access technology. In this paper, we consider OFDMA in the context of fixed wireless networks. This paper addresses the problem of assigning subcarriers and bits to point-to-point wireless links in the presence of cochannel interference and Rayleigh fading. The objective is to minimize the total transmitted power over the entire network while satisfying the data rate requirement of each link. We formulate this problem as a constrained optimization problem and present centralized algorithms. The simulation results show that our approach results in an efficient assignment of subcarriers and transmitter power levels in terms of the energy required for transmitting each bit of information. However, centralized algorithms require knowledge of the entire network topology and channel characteristics of every link. In a practical scenario, that would not be the situation and there is a need for distributed rate allocation algorithms. To address this need, we also present a distributed algorithm for allocating subcarriers and bits in order to satisfy the rate requirements of the links.

Downlink resource management for packet transmission in OFDM wireless communication systems

In this paper, an optimal downlink resource management scheme for heterogeneous packet transmission in orthogonal frequency-division multiplexing (OFDM) wireless communication systems is proposed. By making use of the channel impulse response and the properties of the OFDM physical layer, a resource management scheme is developed by integrating power distribution, subcarrier allocation, and the generalized processor sharing (GPS) scheduling. The scheme can: 1) maximize system throughput; 2) guarantee the required signal-to-noise ratio for heterogeneous traffic; 3) provide fairness to all the traffic admitted in the system; and 4) satisfy the total transmission power constraint. For practical implementation, a simplified power and subcarrier allocation algorithm, a robust H/sub /spl infin// channel estimation algorithm, and a truncated GPS (TGPS) scheduling scheme are introduced. Simulation results show that the proposed resource management scheme exhibits good throughput performance.

Block adaptive subcarrier allocation for wireless multiuser OFDM system

In this paper, a blockwise adaptive subcarrier allocation algorithm for multiuser Orthogonal Frequency Division Multiplexing (OFDM) system is introduced. Assuming the knowledge of channel information for all users, the algorithm minimizes the total transmit power while satisfying the total power and users’ rate constraints. The result of simulation shows that the proposed algorithm reduces the average bit Signal-to-Noise Ratio (SNR) by approximately 4 dB compared with OFDM-Frequency Division Multiple Access (OFDM-FDMA), and supports more users in a multiuser Rayleigh fading channel. As assigning subcarriers in block, the computational complexity of the algorithm is much lower than that of the derivation of “water-filling” algorithm.

Capacity enhancement of a multi-user ofdm system using dynamic frequency allocation

A dynamic subcarrier allocation algorithm is developed and studied in order to improve the capacity of a multi-user OFDM system in the downlink environment. The proposed algorithm uses a decentralized approach and considers the instantaneous channel response of each user in parallel. In order to reduce the complexity of the system, the available subcarriers are divided into a number of partitions and the algorithm attempts to allocate the partition with the highest average channel gain to each user. However, situations may arise whereby two or more users attempt to select the same partition. As such, an important aspect of the algorithm is to resolve such conflicts. Based on the above allocation plan, adaptive modulation is employed for each user on the allocated partitions. The results obtained show that the proposed dynamic allocation scheme outperforms a static allocation scheme in terms of a lower BER and a higher system capacity for the same SNR. In addition, it is possible to obtain performance improvements at the expense of an increase in the system complexity by dividing the subcarriers into a larger number of partitions.

Analytical study of the pointwise availability of a parallel redundant [formula omitted] system under head-of-line repair echelon : P. P. Gupta and Sunil Kumar Mittal. QR J. 55 (May 1984)

In future wireless network, one user will require multiple homogeneous or heterogeneous services simultaneously. Then, the scheduling algorithm is not only responsible for assigning a resource block to different users but also sharing the assigned resource block among multiple services for one user. Most of the traditional scheduling algorithms are designed to serve one service per user, and cannot be applied directly to this scenario because of the fairness criterion. This article focuses on adaptive resource allocation for multiple services per user at the downlink of orthogonal frequency division multiplexing (OFDM) based system. This article addresses this integrative resource scheduling problem based on utility function. First, the optimal algorithm for dynamic subcarrier allocation and share is deduced for homogeneous best-effort service system. Then the algorithm is extended to heterogeneous services system by classifying the delay sensitive service according to the head-of-line packet delay. The design goal is to maximize aggregate utility function to exploit multiuser diversity gain to the greatest extent even as guaranteeing quality of service (QoS) for delay sensitive service.