An important feature of the traffic in mobile networks is burstiness. Drawbacks of conventional power control algorithms for time division duplex （TDD）-code division multiple access （CDMA） systems are analyzed. A ...An important feature of the traffic in mobile networks is burstiness. Drawbacks of conventional power control algorithms for time division duplex （TDD）-code division multiple access （CDMA） systems are analyzed. A joint power control algorithm based on service factor is presented to address the TDD-CDMA mobile services in the burst mode according to the Markov modulated Bernoulli process. The joint power control equation is derived. A function model is developed to verify the new algorithm and evaluate its performance. Simulation results show that the new power control algorithm can estimate interference strength more precisely, speed up convergence of power control, and enhance power efficiency and system capacity. It is shown that the proposed algorithm is more robust against link gain changes, and outperforms the reference algorithms.展开更多
WiMAX networks experience sporadic congestion on uplink when applications running at subscriber stations need more bandwidth to transmit than allocated. With the fast proliferation of mobile Internet, the wireless com...WiMAX networks experience sporadic congestion on uplink when applications running at subscriber stations need more bandwidth to transmit than allocated. With the fast proliferation of mobile Internet, the wireless community has been looking for a framework that can address the issue of impediment on uplink. Due to asymmetric behavior of Internet applications downlink sub-frame is expected to have longer duration as compared to uplink. According to IEEE 806.16 standard for WiMAX the segmentation of TDD frame between uplink and downlink can be dynamically redefined even at runtime. Research contributions so far lack in addressing an optimal strategy for readjustment of uplink and downlink sub-frame boundaries;based on traffic statistics. In this paper, we introduce a mechanism that allows uplink sub-frame to grow, borrowing resources from the downlink sub-frame, if the uplink utilization is high and the downlink is being underutilized. We present here, a framework to dynamically demarcate the TDD frame-duration between uplink and downlink. Proposed algorithm takes into account the present utilization of downlink and reallocates a certain quantum of free resources to uplink. This occurs when uplink observes shortage of bandwidth to transmit. We simulate some test scenarios using OPNET Modeler with and without dynamic reallocation capability. The results of our simulation confirm the effectiveness of proposed algorithm which observes a remarkable decrease in end-to-end packet delay. Also, we observe an improvement in throughput at uplink such that, the performance of downlink remains unaffected.展开更多
In this paper, a theoretical analysis of Time Division Duplex-Code Division Multiple Access (TDD-CDMA) uplink capacity constraint is presented when employing the smart antenna techniques. The evaluation formulations o...In this paper, a theoretical analysis of Time Division Duplex-Code Division Multiple Access (TDD-CDMA) uplink capacity constraint is presented when employing the smart antenna techniques. The evaluation formulations of capacity and load for multi-services are proposed. In order to maximize the throughput, the objective of optimization is proposed, and an advanced uplink resource management algo-rithm is developed. The proposed algorithm based on the least interference admission control scheme focuses on the maximum throughput for the circuit switched multi-services. The simulation results show that the pro-posed strategy has a significant improvement in throughput when the optimum admission control threshold is set.展开更多
基金Project supported by the National Science Foundation for Creative Research Groups （Grant No.60521002）, and the National Key Technologies R＆D Program （Grant No.2005BA908B02）
文摘An important feature of the traffic in mobile networks is burstiness. Drawbacks of conventional power control algorithms for time division duplex （TDD）-code division multiple access （CDMA） systems are analyzed. A joint power control algorithm based on service factor is presented to address the TDD-CDMA mobile services in the burst mode according to the Markov modulated Bernoulli process. The joint power control equation is derived. A function model is developed to verify the new algorithm and evaluate its performance. Simulation results show that the new power control algorithm can estimate interference strength more precisely, speed up convergence of power control, and enhance power efficiency and system capacity. It is shown that the proposed algorithm is more robust against link gain changes, and outperforms the reference algorithms.
文摘WiMAX networks experience sporadic congestion on uplink when applications running at subscriber stations need more bandwidth to transmit than allocated. With the fast proliferation of mobile Internet, the wireless community has been looking for a framework that can address the issue of impediment on uplink. Due to asymmetric behavior of Internet applications downlink sub-frame is expected to have longer duration as compared to uplink. According to IEEE 806.16 standard for WiMAX the segmentation of TDD frame between uplink and downlink can be dynamically redefined even at runtime. Research contributions so far lack in addressing an optimal strategy for readjustment of uplink and downlink sub-frame boundaries;based on traffic statistics. In this paper, we introduce a mechanism that allows uplink sub-frame to grow, borrowing resources from the downlink sub-frame, if the uplink utilization is high and the downlink is being underutilized. We present here, a framework to dynamically demarcate the TDD frame-duration between uplink and downlink. Proposed algorithm takes into account the present utilization of downlink and reallocates a certain quantum of free resources to uplink. This occurs when uplink observes shortage of bandwidth to transmit. We simulate some test scenarios using OPNET Modeler with and without dynamic reallocation capability. The results of our simulation confirm the effectiveness of proposed algorithm which observes a remarkable decrease in end-to-end packet delay. Also, we observe an improvement in throughput at uplink such that, the performance of downlink remains unaffected.
基金Sponsored by the National Advanced Technologies Researching and Developing Programs (No.2004AA123160).
文摘In this paper, a theoretical analysis of Time Division Duplex-Code Division Multiple Access (TDD-CDMA) uplink capacity constraint is presented when employing the smart antenna techniques. The evaluation formulations of capacity and load for multi-services are proposed. In order to maximize the throughput, the objective of optimization is proposed, and an advanced uplink resource management algo-rithm is developed. The proposed algorithm based on the least interference admission control scheme focuses on the maximum throughput for the circuit switched multi-services. The simulation results show that the pro-posed strategy has a significant improvement in throughput when the optimum admission control threshold is set.
