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Experiments show that IEEE 802.11 DCF system exhibits unstable behavior in the congestion onset load range where the system starts to become saturated. This phenomenon is not well investigated due to the lack of proper models. In this paper, we propose a two-dimensional (2-D) Markov chain model by combining the well-known saturated model with newly created idle states. Closed-form solution to the...
In vehicular-to-roadside (V2R) communications the bandwidth from roadside units (RSUs) can be shared among the vehicular users in order to improve the resource utilization and reduce the costs of bandwidth reservation. We formulate a coalitional game model to analyze the situation in which multiple vehicular users can cooperate for sharing the bandwidth from serving RSUs. First, we consider a \emph{rational...
VoIP offers cheap voice communication which instigated its quick market growth. IEEE 802.11 WLANs offer cheap wireless coverage which can be used to provide VoIP service in mobile devices. But call capacity of such networks is very low compared to wired networks. To increase voice capacity in WLANs incorporation of power capture, increased data rate, and use of multiple channels are of great importance...
In this paper, we investigate the fairness between two secondary user (SU) groups in an opportunistic spectrum access networks (OSA). First, for a given number of allocated channels the throughput of each SU group is analyzed in terms of its forced termination and blocking probabilities using continuous time Markov model. Based on these calculations, the fairness between two SU groups is discussed...
The newly emerged vehicular ad hoc network adopts the contention based IEEE 802.11 DCF as its MAC. While it has been extensively studied in the stationary indoor environment (e.g., WLAN), the performance of DCF in the highly mobile vehicular environment is still unclear. On addressing this issue, we propose a simple but accurate analytical model to evaluate the throughput performance of DCF in the...
Applications of location estimation have drawn lots of interests in recent years. Many schemes have been developed to estimate the locations of the concerned users. Conventionally, the location of each user is estimated independently by its own observations from the local environment. In this paper, we propose a cooperative location estimation scheme. From the encounter history of a specific user...
High energy consumption at mobile devices is a critical issue for end users to access and enjoy high data-rate multimedia applications and services in Wireless Local Area Networks (WLANs). This paper develops an analytical framework for analyzing and comparing the energy efficiency performance of IEEE 802.11n Medium Access Control (MAC) protocol and a Busy Tone Based Cooperative MAC Protocol(namely...
A Hidden Markov Modeling technique is used to evaluate the exact performance of the Viterbi algorithm for estimating states of a finite state system. This technique is applied to exact calculation of the bit error probability of the Viterbi decoder of a convolutional code in channels with independent errors and in channels with memory. The results are compared with the widely used upper bounds. The...
In mobile multimedia networks, different traffic classes require various levels of quality of service (QoS). In this paper, we propose a cross-layer design to provide diverse QoS provisions for integrated realtime/non-realtime traffic by jointly taking into account the physical layer, data link layer, and application layer. Specifically, at the physical layer, adaptive modulation and coding (AMC)...
The IEEE 802.11 standard offers a cheap and promising solution for small scale wireless networks. Due to the self configuring nature, WLANs do not require large scale infrastructure deployment, and are scalable and easily maintainable which incited its popularity in both literature and industry. In real environment, these networks operate mostly under unsaturated condition. We investigate performance...
Controlled mobile helper nodes called data ferries have recently been proposed to bridge communications between disconnected nodes in a delay-tolerant manner. While existing work has explored various trajectory designs for the data ferry by assuming either static nodes or full observations at the data ferry, the problem remains open when the nodes are mobile and the ferry only has partial observations...
Dynamic spectrum access (DSA) aims to improve spectrum efficiency via spectrum sensing and optimal spectrum access. An essential component in DSA is the joint design of sensing and access strategies. This paper focuses on dynamic spectrum access in the time domain. To maximize channel utilization while limiting interference to primary users, a framework of linear programming is presented based on...
This paper presents two channel aggregation schemes for wideband cognitive radio networks: a constant channel aggregation scheme and a variable channel aggregation scheme. In the variable channel aggregation scheme, the bandwidth of the cognitive user is aggregated with a probability distribution or aggregated on the basis of the number of the residual channels. These channel aggregation schemes are...
In order to ensure fair access and efficiency of bandwidth usage in wireless integrated networks, resource allocation algorithms should be well designed. In this paper, we briefly discuss the complete sharing, complete partitioning and Hybrid resource sharing approaches and their shortcomings in WiMax-WiFi integrated networks. To overcome these shortcomings we propose the Prioritized Resource Sharing...
This paper aims at answering the questions of how to enable cooperative communications in random access networks. And, since cooperation introduces extra transmissions in the channel, what are the benefits and possible tradeoffs associated with cooperation? To achieve this goal, a novel cooperative protocol for wireless networks based on IEEE 802.11 random access protocol is proposed. The proposed...
In cognitive mobile multihop relay (CMMR) network, the mobile user as the primary user is allocated with the channel for transmitting data. Relay station as the secondary user can help primary user to relay transmitted data while in return primary user grants channel access to secondary user. In this paper, credit-based spectrum sharing for primary and secondary user in CMMR network is proposed. With...
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