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Medium access in ad-hoc wireless networks must be performed in a distributed fashion due to lack of coordination between nodes. Specifically, when nodes are capable of receiving more than one transmission simultaneously, the design of distributed medium-access mechanisms that efficiently exploit the receiver's capability becomes more challenging. Adaptive probabilistic medium access for ad-hoc wireless...
With demands increasing in lunar and Mars explorations, the need for a new space communication standard protocol is becoming more and more critical. The DTN Research Group (DTNRG) is developing a series of communication protocols with new architecture, generally called DTN protocols, to tolerate highly stressed communication environments with long propagation delays and frequent link disruptions....
In this paper, we propose a new channel access protocol for transmission over cooperative ad-hoc networks. The proposed protocol, which aims at minimizing the number of blocked nodes and consequently improving the system throughput, employs directional antennas at both source and relay stations. The network performance under the proposed settings is modelled using continues Markov chains. Steady state...
In this paper we introduce a new MAC protocol called Continuous Contention-Assisted Transmission (CAT) for wireless Ad-hoc network. This proposed protocol is based on Carrier sense multiple access with collision avoidance (CSMA/CA) but we have modified the ACK packet and re-designed mobile stations behavior so that they could continuously transmit data without contention. Our proposed algorithm tries...
We study the scaling laws for wireless ad hoc network in which the distribution of nodes in the network is homogeneous but the traffic is heterogeneous. More specifically, we consider the case in which a node is the sink to k sources sending different information, while the rest of the nodes are part of unicast communications with a uniform assignment of source-destination pairs. We prove that the...
We consider the effect of network throughput on the convergence of a specific class of distributed averaging algorithms, called consensus algorithms. These algorithms rely on iterative computation of the desired average by message passing among the nodes. It is thus assumed that the rate of convergence should benefit from greater network connectivity. However, one must also account for the additional...
Packet acquisition for a time-frequency hopped asynchronous random multiple access (RMA) system is investigated. A novel analytical approach to performance evaluation is provided, which enables the waveform designer to quickly evaluate the network performance as various waveform design and RMA protocol parameters and are chosen. The results show that the network throughput is estimated and upper-bounded...
A number of multi-channel assignment schemes have recently been proposed to improve the throughput of IEEE 802.11-based multi-hop wireless mesh networks (WMNs). In these schemes, channel coordination is done either through time synchronization across all the hosts, or through the use of a dedicated channel for the transmission of necessary control messages. Either way, excessive system overhead and/or...
In this paper, we present a collision-free asynchronous multi-channel access protocol for Ad Hoc wireless networks using a single transceiver. Our protocol, dubbed AMMAC for Asynchronous Multi-channel Medium Access Control, targets low-cost and low-power deployments where nodes are equipped with a single transceiver. Other distinguishing features of AM-MAC include its simplicity and the fact that...
This paper analyzes TCP fairness in IEEE 802.11-based wireless mesh networks (WMNs). Fairness of bandwidth sharing is important for equitable network access by various users. With our Indoor WMN testbed, we observe that even though TCP flows have similar round trip time and loss probability, they encounter an unfairness problem. Especially, when TCP flows experience high TCP ACK losses (around 20%),...
Cognitive networks are becoming extremely popular in the network domain. This paper proposes a novel concept in cognitive network management and protocol configuration, where any protocol of the TCP/IP protocol reference model can be extended to dynamically tune its configuration parameters based on "immediate past" performance. The approach is focused on inter-node cognitive adaptation...
Available network information is an important factor in determining network performance. In this paper, we study the basic limits on the amount of network information that should be transmitted in the network to achieve a given level of network performance. From the perspective of information theory, network information is an information source, and the lower bound on network information is the minimum...
Cooperative relaying methods can improve wireless links, but introduce overhead due to relay selection and resource reservation compared to non-cooperative transmission. In order to be competitive, a cooperative relaying protocol must avoid or compensate for this overhead. In this paper, we present a MAC protocol for relay selection and cooperative communication as an extension to CSMA/CA which addresses...
In IEEE 802.11 Distributed Coordination Function (DCF), the multi-rate Basic Service Set (BSS) suffers from the performance anomaly issue, which brings unfairness in terms of channel occupancy time. To solve the issue, this paper presents a rate control scheme for TCP Friendly Rate Control (TFRC) in IEEE 802.11 DCF mode. The proposed scheme controls the sending rate so that each station can use the...
In cognitive radio (CR) networks, the multichannel access problem is an important problem, which may directly affect user applications. However, most of previous work on this problem focuses on maximizing physical layer throughput, rather than the end-to-end transmission control protocol (TCP) performance. In this paper, we propose an optimal TCP throughput based channel access scheme in CR networks,...
In this paper, we consider the problem of transmission delay in terms of finite coding length derived from the random coding bound for different cooperative protocols. Specifically, we first study the impact of cooperative transmission on the routing decision for wireless ad-hoc networks, where a routing optimization problem is formulated to minimize the end-to-end delay that ensures a satisfactory...
Consider a wireless network of two tiers with different priorities: a primary tier and a secondary tier, which is an emerging network scenario with the advancement of cognitive radio technologies. The primary tier is constructed over static nodes of density n, which are randomly distributed and have an absolute priority to access the spectrum. The secondary tier contains mobile nodes of density m...
Transmission Control Protocol (TCP) is the most commonly used transport protocol on the Internet. All indications assure that it will be an integral part of the future internetworks. In this paper, we present how regular TCP which was designed for wired networks is not suitable for dynamic spectrum access networks. We develop an analytical model to estimate the TCP throughput of Dynamic spectrum access...
A key technology in cooperative communications is distributed space-time coding (DSTC) which achieves spatial diversity gain from multiple relays. A novel DSTC, called randomized distributed space-time coding (R-DSTC), shows considerable advantages over a regular DSTC in terms of system complexity. In this paper, we exploit the benefits of R-DSTC physical (PHY) layer and develop a distributed and...
In network layer based mobility protocols, such as mobile IP, the correspondent node is not aware of handovers and therefore continues to send data at the same rate as before the handover which may exhibit network unfriendliness, especially when the capacities of the two subnets differ significantly. On the contrary, transport layer based mobility protocols, such as SIGMA, do not show such phenomena...
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