Browsing by Subject "Adaptive modulation and coding"

Now showing 1 - 3 of 3

Open Access
Analysis of an Adaptive Modulation and Coding scheme with HARQ for TCP traffic
(IEEE, 2015-04) Öztürk, Onur; Akar, Nail
In this paper, we analyze the aggregate TCP throughput performance of a wireless link utilizing Active Queue Management (AQM) and an Adaptive Modulation and Coding (AMC) scheme with Hybrid ARQ (HARQ) based on the probability of failure in the first transmission attempt. We assume packets arriving out-of-order at the wireless receiver due to random retransmissions are resequenced before being released to the network. For this reason, an approximate model for the delay experienced at the resequencing buffer is also presented. In the light of the results obtained from the presented analysis, we propose a threshold for the aforementioned probability of failure making the investigated AMC scheme work at an overall performance close to that of the optimum policy. © 2015 IEEE.
Open Access
A novel queue-aware wireless link adaptation mechanism and its fixed-point analytical model
(SpringerOpen, 2015) Ozturk, O.; Akar, N.
A point-to-point (PTP) wireless link is studied that carries long-lived TCP flows and is controlled with active queue management (AQM). A cross-layer queue-aware adaptive modulation and coding (AMC)-based link adaptation (LA) mechanism is proposed for this wireless link to improve the TCP-level throughput relative to the case where AMC decisions are made based solely on the physical layer (PHY) parameters. The proposed simple-to-implement LA mechanism involves the use of an aggressive modulation and coding scheme (MCS) with high spectral efficiency and high block error rates when the queue occupancy exceeds a certain threshold, but otherwise a relatively conservative MCS with lower spectral efficiency and lower block error rates. A fixed-point analytical model is proposed to obtain the aggregate TCP throughput attained at this wireless link and the model is validated by ns-3 simulations. Numerical experimentation with the proposed analytical model applied to an IEEE 802.16-based wireless link demonstrates the effectiveness of the proposed queue-aware LA (QAWLA) mechanism in a wide variety of scenarios including cases where the channel information is imperfect. The impact of the choice of the queue occupancy threshold of QAWLA is extensively studied with respect to the choice of AQM parameters in order to provide engineering guidelines for the provisioning of the wireless link.
Open Access
Performance modeling and analysis of the interplay among Tcp, active queue management and wireless link adaptation
(2015-09) Öztürk, Onur
We propose a novel workload-dependent queuing model of a wireless router link which employs active queue management and is offered with a number of persistent TCP flows. As opposed to existing work that focus only on the average queue occupancy as the performance metric of interest, the proposed analytical method obtains the more informative steady-state queue occupancy distribution of the wireless link. With the intention of maximizing TCP throughput, this analytical method is used to study traffic agnostic link adaptation schemes with and without hybrid ARQ. Moreover, a novel cross-layer queue-aware link adaptation scheme is proposed to improve the TCP throughput relative to the case where adaptive modulation and coding decisions are made based solely on the physical layer parameters. A fixed-point analytical model is proposed to obtain the aggregate TCP throughput attained at wireless links employing active queue management and queue-aware link adaptation. Allowing packet retransmissions and generalizing the scope from a single link to a network of such links, we propose an energy efficient queue-aware link adaptation scheme with hybrid ARQ which jointly adapts the transmission power and rate of the wireless links based on the queue occupancy levels and the channel conditions. Furthermore, we provide a fixed-point analytical method for such networks.