Sun-Ny Chang

QoS-Guaranteed Cross-Layer Transmission Algorithms with Adaptive Frequency Subchannels Allocation in the IEEE 802.16 OFDMA System

In this paper, we analyze the IEEE 802.16 OFDMA system with adaptive allocation of the frequency subchannels to the users. We perform adaptive coding and modulation, allocation of the time-frequency resource, the transmit power, and the frequency subchannels to the downlink and uplink service flows, which are scheduled for transmission in the current frame. Moreover, we consider adaptation of the frame boundary between the downlink and uplink subframes. We minimize the sum time-frequency resource, allocated in both downlink and uplink subframes, under the constraints on the maximum transmit power and the time-frequency resource available in the frame, while satisfying the QoS requirements for all downlink and uplink service flows scheduled for transmission. We propose the cross-layer optimization algorithms, which take into account the MAC and PHY layers processing during the optimization. We also present the results of the proposed algorithms evaluation by system level simulation.

QoS-guaranteed cross-layer adaptive transmission algorithms for the IEEE 802.16 OFDMA system

In this paper, we analyze the IEEE 802.16 OFDMA system with the frequency diversity frame structure. We perform adaptive coding and modulation, allocation of the time-frequency resource and transmit power to the downlink and uplink service flows, which are scheduled for transmission in the current frame. Also, we consider adaptation of the frame boundary between the downlink and uplink subframes. We minimize the sum time-frequency resource, allocated in both downlink and uplink subframes, under the constraints on the maximum transmit power and the time-frequency resource, available in the frame, while satisfying the QoS requirements for all downlink and uplink service flows, scheduled for transmission. We propose the cross-layer optimization algorithms, which take into account the MAC and PHY layers processing during the optimization

Analysis of the Statistical Properties of the SINR in the IEEE 802.16 OFDMA Network

In the IEEE 802.16 network the SINR per subcarrier, the average SINR, and the SINR RMS are stochastic processes. In this paper, we analyze the statistical properties of these stochastic processes using system level simulation. We present the probability density functions for the SINR per subcarrier and the average SINR stochastic processes expressed in both logarithmic and linear scales. We also present the probability density function for the SINR RMS stochastic process, expressed in the logarithmic scale. The results, obtained in this paper, allow using the statistical approach while developing the adaptive transmission algorithms for the IEEE 802.16 network.

Multi-User Water-Filling in Uplink OFDMA Systems

In this paper, we focus on the optimal power allocation problem in the multi-user uplink OFDMA system. For the purpose, based on the KKT conditions of the problem, we design suboptimal algorithms that may be implementable in an iterative and distributive manner. An important feature of our algorithm is that it takes the generated interference to the system into account. Numerical examples show that our algorithms outperform the others, in terms of total throughput, outage probability and energy efficiency.