Abstract
In some modern communication systems, as it is the case of WiMAX, it has been decided to implement Demand Assignment Multiple Access (DAMA) solutions. End-users request transmission opportunities before accessing the system, which provides an efficient way to share system resources. In this paper, we briefly review the PHY and MAC layers of an OFDMA-based WiMAX system, and we propose to use a Network Utility Maximization (NUM) framework to formulate the DAMA strategy foreseen in the uplink of IEEE 802.16. Utility functions are chosen to achieve fair solutions attaining different degrees of fairness and to further support the QoS requirements of the services in the system. Moreover, since the standard allocates resources in a terminal basis but each terminal may support several services, we develop a new decomposition technique, the coupled-decompositions method, that obtains the optimal service flow allocation with a small number of iterations (the improvement is significant when compared to other known solutions). Furthermore, since the PHY layer in mobile WiMAX has the means to adapt the transport capacities of the links between the Base Station (BS) and the Subscriber Stations (SSs), the proposed PHY-MAC cross-layer design uses this extra degree of freedom in order to enhance the network utility.
Highlights
The wireless community has recently directed much attention on a variety of topics related to Worldwide Interoperability for Microwave Access (WiMAX) technologies as a broadband solution
We fix all requests to 100 kbps and all the minimum granted rates to 1 kbps
We have proposed an algorithm that implements the Demand Assignment Multiple Access (DAMA) mechanism foreseen in the IEEE 802.16 WiMAX standard
Summary
The wireless community has recently directed much attention on a variety of topics related to Worldwide Interoperability for Microwave Access (WiMAX) technologies as a broadband solution. The WirelessMAN Orthogonal Frequency Division Multiplexing (OFDM) uses a 256-point Fast Fourier Transform- (FFT-) based OFDM modulation together with a TDMA scheme to deploy a Point-to-Multipoint (PMP) subnetwork in the frequency range from 2 GHz up to 11 GHz in Non-Line-ofSight (NLOS) propagation conditions This PHY layer has been accepted for fixed WiMAX applications, and it is often termed as fixed WiMAX. Previous works related to Radio Resource Management (RRM) in WiMAX networks address a variety of scenarios, from PMP to mesh, from TDMA to OFDMA access types, and distinguishing single channel or multichannel networks, most of them from a physical (PHY) layer perspective, where the goal is to properly configure the transmission parameters.
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