Carlos de M. Cordeiro

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In November/2004, we witnessed the formation of the first worldwide effort to define a novel wireless air interface (i.e., MAC and PHY) standard based on Cognitive Radios (CRs): the IEEE 802.22 Working Group (WG). The IEEE 802.22 WG is chartered with the development of a CR-based Wireless Regional Area Network (WRAN) Physical (PHY) and Medium Access Control(More)
In November/2004, we witnessed the formation of the first worldwide effort to define a novel wireless air interface standard based on Cognitive Radios (CRs): the IEEE 802.22 Working Group (WG). The IEEE 802.22 WG is chartered with the development of a CR-based Wireless Regional Area Network (WRAN) Physical (PHY) and Medium Access Control (MAC) layers for(More)
Research in the physical (PHY) and medium access control (MAC) layers for dynamic spectrum access (DSA) and dynamic spectrum sharing (DSS) is still at its infancy. Aspects such as spectrum sensing, coexistence, measurement and spectrum management, network reliability and QoS support in face of the need to avoid causing harmful interference into incumbents,(More)
This paper addresses the issue of deafness and hidden terminal problem in a Mobile Ad Hoc Networks (MANETs) using directional antennas. To minimize these effects, we propose a MAC protocol for directional Antennas (MDA) which employs an enhanced directional network allocation vector (NAV) scheme and, a novel technique of Diametrically Opposite Directions(More)
In this paper we address the issue of spectrum sensing in cognitive radio based wireless networks. Spectrum sensing is the key enabler for dynamic spectrum access as it can allow secondary networks to reuse spectrum without causing harmful interference to primary users. Here we propose a set of integrated medium access control (MAC) and physical layer (PHY)(More)
We explore the price dynamics in a competitive market consisting of spectrum agile network service providers and users. Here, multiple self interested spectrum providers operating with different technologies and costs compete for potential customers. Different buyers or consumers may evaluate the same seller differently depending on their applications,(More)
Most studies on TCP over multi-hop wireless ad hoc networks have only addressed the issue of performance degradation due to temporarily broken routes, which results in TCP inability to distinguish between losses due to link failures or congestion. This problem tends to become more serious as network mobility increases. In this work, we tackle the equally(More)
The popularity of wireless communication systems can be seen almost everywhere in the form of cellular networks, WLANs, and WPANs. In addition, small portable devices have been increasingly equipped with multiple communication interfaces building a heterogeneous environment in terms of access technologies. The desired ubiquitous computing environment of the(More)
This paper addresses the issue of deafness in directional antennas for wireless ad hoc networks. Deafness is caused when a node X repeatedly attempts to communicate with node Y but is unsuccessful, because Y is presently tuned to some other antenna beam. In this paper, we first outline different factors which contribute to such deafness in directional(More)
Several efforts are now underway to develop wireless technologies based on cognitive radios (CR) that can operate in the television (TV) band white space. One such example is the IEEE 802.22 Working Group (WG), which is formulating the first worldwide CR-based standard to operate in the TV bands. A mandatory requirement for any wireless technology operating(More)