Today's Internet provides only a single Class of Service (CoS) to all of its services (e.g., Multimedia, Data, Audio), namely the best-effort service. This service does not make any guarantees on the Quality of Service (QoS) an application receives. The continuous demands for QoS guarantees have led to the introduction of various network-layer mechanisms that provide some end-to-end QoS assurance including MPLS, Integrated Service Model (IntServ), and Differentiated Service Model (DiffServ). However, the QoS mapping between the network-layer and the application-layer is still a challenge and needs to be addressed. To guarantee and end-to-end QoS, it is essential to map QoS parameters between these layers. A framework for investigating the mapping of the packet loss rate as an important QoS parameter is presented here. The network QoS performance characteristic for the loss parameter is mapped from lower to upper layer in a quantifiable way.
We address the problem of creating an adaptive source coding algorithm for a genomic encryption protocol using a small alphabet such as the nucleotide bases represented in the genetic code. For codewords derived from an alphabet of N plaintext with probability of occurrence, p, we describe a mapping into a floating point representation of the codewords which are translated into genomic codewords derived from a novel modification of the Shannon-Fano-Elias coding process. Errors in the reverse decoding process are processed through an adaptive, self-correcting codebook to determine the best fit codeword decoding solution. A genetic algorithmic approach to error correction within the source coding is also summarized.
Enhanced Distributed Channel Access (EDCA) is a mandatory part of the IEEE 802.11e standard which provides Medium Access Control (MAC) layer solution for Quality of Service (QoS) provisioning in Wireless Local Area Networks (WLANs). It is a contention based protocol which prioritizes channel access to QoS traffic using four Access Categories (ACs). In this paper, we introduce the performance evaluation of high priority Voice over Internet Protocol (VoIP) traffic over EDCA in multi-rate WLAN. In a multi-rate environment, the channel physical transmission rate is changed by the Access Point (AP) as the stations move towards or away from the AP. The AP performs rate adaptation on each frame according to the channel condition or signal quality that the frame is likely to experience when stations are considered mobile. We implement EDCA at the MAC layer over the physical layer of IEEE 802.11b radios using the network modeling and simulation tool QualNet. We simulate multiple VoIP nodes in a single QoS-enabled Basic Service Set (QBSS) with one QoS-enabled AP (QAP). The performance of each VoIP node is evaluated with three VoIP codecs. We first use codecs without jitter buffer and evaluate jitter with other performance parameters. The simulations are repeated for different codecs with jitter buffer. The effect of jitter buffer on Jitter, Delay and Mean Opinion Score (MOS) for each VoIP node is compared with other codecs in stationary and mobile environments. Simulation results show the effectiveness of using jitter buffer and its limitations in a multi-rate environment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.