CiteULike: dcastros allocation

An efficient multiuser loading algorithm for OFDM-based broadband wireless systems

H Yin — 2008-05-19T18:32:45-00:00

Global Telecommunications Conference, 2000. GLOBECOM '00. IEEE, Vol. 1 (2000), pp. 103-107 vol.1.

In this paper we present a novel loading algorithm for OFDM-based multiuser communication system to maximize the total system throughput while satisfying the total power and users' rate constraints. The new scheme determines the subcarrier, bit, and power allocation by decoupling an NP-hard combinatorial problem into two steps: (1) resource allocation (how much power and how many subcarriers for each user) based on users' average channel gains and their rate requirements; and (2) subcarrier assignment and bit loading based on users' channel profiles across all subcarriers. Compared to existing iterative methods, the two-step approach offers comparable capacity gain with much lower complexity

An efficient waterfilling algorithm for multiple access OFDM

G Munz — 2008-05-19T18:32:42-00:00

Global Telecommunications Conference, 2002. GLOBECOM '02. IEEE, Vol. 1 (2002), pp. 681-685 vol.1.

In this paper we present a novel and computationally efficient waterfilling algorithm for multiuser OFDM. This algorithm is based on the multiuser waterfilling theorem and determines the subcarrier allocation for a multiple access OFDM system. This approach maximizes the total bitrate under the constraints of user-individual power budgets. Once the subcarrier allocation has been established, the bit and power allocation for each user can be determined with a single-user bitloading algorithm, for which several implementations can be found in the literature. The presented iterative algorithm performs well, also with a high number of subchannels.

Subcarrier allocation schemes for multiuser OFDM systems

A Pandharipande — 2008-05-18T14:06:03-00:00

Signal Processing and Communications, 2004. SPCOM '04. 2004 International Conference on (2004), pp. 540-544.

Subcarrier allocation and power control for OFDMA

D Kivanc — 2008-04-15T17:40:52-00:00

Signals, Systems and Computers, 2000. Conference Record of the Thirty-Fourth Asilomar Conference on, Vol. 1 (2000), pp. 147-151 vol.1.

We study the problem of finding an optimal subcarrier and power allocation strategy for downlink communication to multiple users in an OFDM based wireless system. We formulate the problem of minimizing total power consumption with constraints on BER and transmission rate for users requiring different classes of service, and derive simple algorithms which perform well. We divide the larger problem of joint allocation into two steps. In the first step, the number of subcarriers that each user is determined based on the users' average SNR. Numerical results demonstrate that the proposed low complexity algorithms offer comparable performance with an existing iterative algorithm

An adaptive subchannel allocation algorithm for OFDM-based wireless home networks

Jian Zhu — 2008-03-26T08:27:30-00:00

Consumer Communications and Networking Conference, 2004. CCNC 2004. First IEEE (2004), pp. 352-356.

We present a novel, adaptive subchannel allocation algorithm for the downlink channel of a multiuser, OFDM-based wireless home network. Since channel resources are not adaptively allocated in a traditional OFDM system, some of the users with fixed frequency channel allocation may experience deep fading in a frequency-selective multipath environment. This problem can be mitigated using an adaptive algorithm, which can be modeled as an optimization problem that allocates the proper number of subchannels to achieve maximum channel capacity. We employ the classical bipartite matching algorithm to achieve optimal OFDM subchannel allocation. Simulation results show that the total capacity increases remarkably, and that higher channel capacity is achieved when the number of users is increased. In a wireless environment, the reallocation overhead can be large. As such, we propose a hybrid method for subchannel allocation to support more users while reducing the reallocation overhead. We simulated the performance of the hybrid algorithm and compared it with the matching-only algorithm.

Multi-Cell Slots Allocation in OFDMA Systems

David Amzallag — 2008-01-11T08:39:20-00:00

Mobile and Wireless Communications Summit, 2007. 16th IST (2007), pp. 1-5.

OFDMA (Orthogonal Frequency Division Multiple Access) is considered to be the leading technology for the upcoming 4G cellular infrastructure. OFDMA is a multi-user version of the popular OFDM (Orthogonal Frequency Division Multiplexing) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers (subchannels or slots) to individual users. This allows for multiple simultaneous low data rate transmissions to several users. In this paper we describe several optimization problems related to the allocation of radio resources in OFDMA systems. The basic problem we define is a slots assignment task in a multi-cell OFDMA environment. The goal is to assign subchannels to mobile stations such that the demands of all of mobile stations will be satisfied with minimum interferences. We then describe two further optimization problems that generalize the slots assignment problem. A close to optimal solution to these problems will allow providers to better utilize their radio resources and to provide services in a cost efficient way.