This paper presents, through simulation experiments, a performance study of both IEEE 802.11n aggregation methods: A-MPDU (Aggregated MAC Protocol Data Unit) and A-MSDU (Aggregated MAC Service Data Unit), considering scenarios of video streaming. The objectives of this article are: (i) investigate the quality of service achieved, (ii) show which of the two methods of aggregation (A-MPDU or A-MSDU) is the more suitable for the application being considered and; (iii) suggest values for the parameters that result in better quality of service.

We develop a simple, yet robust, application-layer adaptation technique based on scalable video codecs. The proposed technique can adapt to the varying capacity available to a connection in order to deliver video with a superior quality. We take advantage of both scalable video properties and the characteristics of the packet dropping random process at the last link's wireless router's queue. By fine-tuning the inter-packet transmission time at the server side, we show that the resulting packet loss pattern yields a superior quality of experience (QoE) without any changes in the wireless router's packet scheduling or drop policies. In other words, by varying the per frame packet inter-spacing time while maintaining a given frame rate (i.e., by varying the transmission burstiness) one can control the QoE. Our proposal is founded on an analytical model to study the loss pattern of individual packets in a n-packet burst.

Admission control algorithms must ensure that, when a new QoS resource reservation is accepted, reservations already present in the system continue having their QoS guarantees honored. In this paper we consider different approaches to compute the aggregated allocated capacity in WiMAX networks and, based on their limitations, propose the E-Diophantine solution. The mathematical foundations for the designed approach are provided along with the performance improvements to be expected, both in accuracy and computational terms, as compared to three alternatives of increasing complexity. Finally, the different solutions considered are evaluated with OPNET's WiMAX simulator in a realistic scenario.

In this paper, we propose a limited feedback scheme to improve outage performance for a wireless cooperative decode-and-forward network. Specifically, based on the instantaneous conditions of the source-destination and relay-destination channels, the destination will allocate the transmission time of the source and relay and feed back the allocation result to the source. Both limited and full (or infinite) rate feedback are considered. Under the practical assumption that only imperfect channel estimation is available at the receiver, we analyze the outage performance by deriving upper bounds on the outage probabilities. It will be demonstrated that, even with only one-bit feedback, the proposed feedback scheme can outperform the no feedback case. Furthermore, the outage performance can approach the optimality by exploiting limited (only a small number of bits) uniformly quantized feedback from the destination.

In this work the behavior of a 3G wireless technology is evaluated. The analysis is done using a simulation tool, based on the Tangram-II platform, which incorporates a detailed propagation model and the relevant features of the cdma20001x EVDO system. Internet access through Web browsers was judged to be the key application to be provided. We are interested in analyzing the throughput, latency and fairness metrics for several scenarios, including cases considering only static users as well as cases where a fraction of terminals has mobility. Our experiments show that the introduction of mobile users severely compromises the fairness in respect to user's goodput and delay. A previous work of ours has shown that even if some parameters of the scheduling algorithm are varied, due to physical layer limitations it is difficult to improve performance of the technology with respect to fairness. In this article we show that the use of directional antennas can play an even more important role in improving EV-DO behavior for the envisioned application when some users are mobile.

In this work the behavior of particular cellular technology for use in a wireless implementation of a bi-directional digital TV return channel is considered. The analysis is done using a simulation tool, based on the Tangram-II platform, that incorporates a detailed propagation model and the relevant features of the cdma2000 EV-DO system. Internet access through Web browsers was judged to be the key application to be provided. This paper presents both throughput and latency results with varying number of terminals in the system. It also identifies variations in the user quality of service due to their geographic position. The results show that even if some parameters of the scheduling algorithm are varied, it is difficult to improve the fairness performance of the technology. A very simple solution is proposed to enhance these fairness characteristics

The increase in subscriber demand and the desire by the operators to provide quality of service guarantee to its customers place a constant demand on the development of efficient radio resource management techniques. This work focus on call admission control and, in particular, in dynamic admission control algorithms that enhance system utilization. There is also a specific concern in meeting the quality of service constraints established by the operators. In this work two QoS-aware dynamic call admission control schemes are proposed and their performance evaluated. These procedures make use of the concept of a probabilistic number of reserved resources. Both methods are fully distributed allowing each sector to independently adapt to its own time variable traffic profile

Good execution of seamless handoffs is key to the quality of service perceived by mobile service subscribers. Giving priority to handoff requests is a strategy commonly considered to guarantee low connection loss when performing handoffs. Often, priority systems can be implemented by adopting a pool of reserved (or guard) resources that is available only for calls or transactions being handed over. Most studies published thus far consider that fixed allocation of the guard resources is being employed. This work considers sharing the reserve channels among cells through the use of a particular method of dynamic resource allocation (DRA). It is shown here that the use of DRA on the pool of guard channels affords a great reduction in the probability of handoff failure without affecting the value of the new call blocking probability, thereby improving the quality of service provided by the cellular operator and also increasing system utilization.

In this work, the behavior of resource allocation policies for circuit switched integrated voice and data services is considered. A novel configurable allocation strategy is proposed which anticipates congestion and adjusts to it by gradually reducing the rate allocated to new and handed over data sessions. An elaborate simulation tool was used to evaluate, for two different traffic scenarios, the performance of the new scheme and to compare it to the behavior of existing techniques. One of the measures used in gauging the advantages and disadvantages of each method was a new performance metric, which attempts to properly reflect data customer satisfaction.

In this work, the comparative performance of three resource assignment methods for hierarchal cell structures is evaluated. This performance assessment was done with a complex 3D TDMA simulation tool which attempts to mimic, as much as possible, the conditions in actual deployment. Blocking and forced termination probabilities were computed for a simple speed sensitive strategy as well as for procedures that include overflow and take back capabilities for slow users.

Several alternative strategies for reducing paging and location update costs have been proposed in the literature. This paper compares four well-known strategies, that differ in the manner they approach the problem. The same mobility model and evaluation criteria was used for all strategies analyzed. Users are classified according to the call-to-mobility-ratio (CMR). Results are given weighting in different ways: the signaling cost in the radio interface and in the fixed network part.

A new deterministic packet access method, name D-RAMA, suitable for operation in a wireless multiservice environment is presented. It is shown that the method has excellent fairness properties, while yielding a very low packet loss probability and achieving a statistical multiplexing gain of 2, which is roughly 30% better than the capacity provided by PRMA under equivalent conditions.

Examines the application of simulated annealing to assign indices to the output levels of a vector quantizer (VQ). The quantizer is used for the LSF parameter representation of the short-term predictor of a CELP coder. Three classes of error protection and a 0.1 channel error rate are considered. Simulation results show that the use of the index assignment provides significant gains both in terms of average distortion as well as in terms of reduction of large outliers. The improvements afforded by the index assignment, however, were not significant when the VQ was used inside the structure of a CELP coder.>

A measure is proposed that is based on two key concepts: (1) the congestion caused by a virtual circuit (VC) on the others; and (2) the penalty inflicted by the network on a VC. These two concepts are then combined to define a fairness criterion that uses the principle that a virtual circuit should not be able to congest the network more than it is being penalized by the same network. A suboptimal algorithm to select window sizes according to this fairness criterion was devised and applied to several networks; results are presented for two of these networks. The examples show that the window set produced by the algorithm does not cause any significant degradation in the net overall performance and is superior, in terms of fairness, to other window assignments methods discussed in the literature.>

Noise spectral shaping and performance analysis are considered in the context of Adaptive Delta Modulators (ADM's). The goal pursued is to reduce the in-band distortion by redistributing the noise power over all the frequency band available, in a manner depending upon the feedback network. Since ADM's generally work at a sampling frequency much higher than the Nyquist rate, one could obtain quality improvements by shifting a large amount of quantizing noise outside the base-band. Simulation results reveal that the benefit actually achievable is limited, essentially because the noise shifting causes an increase of slope overload distortion. A suitable ADM scheme with switched narrow-band Noise Shaping filter, permits to mitigate this adverse phenomenon and to achieve a subjective quality improvement.