1,216 research outputs found
Throughput Analysis of Primary and Secondary Networks in a Shared IEEE 802.11 System
In this paper, we analyze the coexistence of a primary and a secondary
(cognitive) network when both networks use the IEEE 802.11 based distributed
coordination function for medium access control. Specifically, we consider the
problem of channel capture by a secondary network that uses spectrum sensing to
determine the availability of the channel, and its impact on the primary
throughput. We integrate the notion of transmission slots in Bianchi's Markov
model with the physical time slots, to derive the transmission probability of
the secondary network as a function of its scan duration. This is used to
obtain analytical expressions for the throughput achievable by the primary and
secondary networks. Our analysis considers both saturated and unsaturated
networks. By performing a numerical search, the secondary network parameters
are selected to maximize its throughput for a given level of protection of the
primary network throughput. The theoretical expressions are validated using
extensive simulations carried out in the Network Simulator 2. Our results
provide critical insights into the performance and robustness of different
schemes for medium access by the secondary network. In particular, we find that
the channel captures by the secondary network does not significantly impact the
primary throughput, and that simply increasing the secondary contention window
size is only marginally inferior to silent-period based methods in terms of its
throughput performance.Comment: To appear in IEEE Transactions on Wireless Communication
Distributed MAC Protocol Supporting Physical-Layer Network Coding
Physical-layer network coding (PNC) is a promising approach for wireless
networks. It allows nodes to transmit simultaneously. Due to the difficulties
of scheduling simultaneous transmissions, existing works on PNC are based on
simplified medium access control (MAC) protocols, which are not applicable to
general multi-hop wireless networks, to the best of our knowledge. In this
paper, we propose a distributed MAC protocol that supports PNC in multi-hop
wireless networks. The proposed MAC protocol is based on the carrier sense
multiple access (CSMA) strategy and can be regarded as an extension to the IEEE
802.11 MAC protocol. In the proposed protocol, each node collects information
on the queue status of its neighboring nodes. When a node finds that there is
an opportunity for some of its neighbors to perform PNC, it notifies its
corresponding neighboring nodes and initiates the process of packet exchange
using PNC, with the node itself as a relay. During the packet exchange process,
the relay also works as a coordinator which coordinates the transmission of
source nodes. Meanwhile, the proposed protocol is compatible with conventional
network coding and conventional transmission schemes. Simulation results show
that the proposed protocol is advantageous in various scenarios of wireless
applications.Comment: Final versio
An Energy Efficient MAC Protocol for QoS Provisioning in Cognitive Radio Ad Hoc Networks
The explosive growth in the use of real-time applications on mobile devices has resulted in new challenges to the design of medium access control (MAC) protocols for ad hoc networks. In this paper, we propose an energy efficient cognitive radio (CR) MAC protocol for QoS provisioning called ECRQ-MAC, which integrate the spectrum sensing at physical (PHY) layer and the channel-timeslots allocation at MAC layer. We consider the problem of providing QoS guarantee to CR users as well as to maintain the most efficient use of scarce bandwidth resources. The ECRQ-MAC protocol exploits the advantage of both multiple channels and TDMA, and achieves aggressive power savings by allowing CR users that are not involved in communication to go into sleep mode. The proposed ECRQ-MAC protocol allows CR users to identify and use the unused frequency spectrum of licensed band in a way that constrains the level of interference to the primary users (PUs). Our scheme improves network throughput significantly, especially when the network is highly congested. The simulation results show that our proposed protocol successfully exploits multiple channels and significantly improves network performance by using the licensed spectrum opportunistically and protects QoS provisioning over cognitive radio ad hoc networks
CR-MAC: A multichannel MAC protocol for cognitive radio ad hoc networks
This paper proposes a cross-layer based cognitive radio multichannel medium
access control (MAC) protocol with TDMA, which integrate the spectrum sensing
at physical (PHY) layer and the packet scheduling at MAC layer, for the ad hoc
wireless networks. The IEEE 802.11 standard allows for the use of multiple
channels available at the PHY layer, but its MAC protocol is designed only for
a single channel. A single channel MAC protocol does not work well in a
multichannel environment, because of the multichannel hidden terminal problem.
Our proposed protocol enables secondary users (SUs) to utilize multiple
channels by switching channels dynamically, thus increasing network throughput.
In our proposed protocol, each SU is equipped with only one spectrum agile
transceiver, but solves the multichannel hidden terminal problem using temporal
synchronization. The proposed cognitive radio MAC (CR-MAC) protocol allows SUs
to identify and use the unused frequency spectrum in a way that constrains the
level of interference to the primary users (PUs). Our scheme improves network
throughput significantly, especially when the network is highly congested. The
simulation results show that our proposed CR-MAC protocol successfully exploits
multiple channels and significantly improves network performance by using the
licensed spectrum band opportunistically and protects PUs from interference,
even in hidden terminal situations.Comment: 14 Pages, International Journa
An Energy Efficient Multichannel MAC Protocol for Cognitive Radio Ad Hoc Networks
This paper presents a TDMA based energy efficient cognitive radio
multichannel medium access control (MAC) protocol called ECR-MAC for wireless
Ad Hoc Networks. ECR-MAC requires only a single half-duplex radio transceiver
on each node that integrates the spectrum sensing at physical (PHY) layer and
the packet scheduling at MAC layer. In addition to explicit frequency
negotiation which is adopted by conventional multichannel MAC protocols,
ECR-MAC introduces lightweight explicit time negotiation. This two-dimensional
negotiation enables ECR-MAC to exploit the advantage of both multiple channels
and TDMA, and achieve aggressive power savings by allowing nodes that are not
involved in communication to go into doze mode. The IEEE 802.11 standard allows
for the use of multiple channels available at the PHY layer, but its MAC
protocol is designed only for a single channel. A single channel MAC protocol
does not work well in a multichannel environment, because of the multichannel
hidden terminal problem. The proposed energy efficient ECR-MAC protocol allows
SUs to identify and use the unused frequency spectrum in a way that constrains
the level of interference to the primary users (PUs). Extensive simulation
results show that our proposed ECR-MAC protocol successfully exploits multiple
channels and significantly improves network performance by using the licensed
spectrum band opportunistically and protects QoS provisioning over cognitive
radio ad hoc networks.Comment: 8 Pages, International Journa
Cooperative medium access control based on spectrum leasing
Based on cooperative spectrum leasing, a distributed “win–win” (WW) cooperative framework is designed to encourage the licensed source node (SN) to lease some part of its spectral resources to the unlicensed relay node (RN) for the sake of simultaneously improving the SN’s achievable rate and for reducing the energy consumption (EC). The potential candidate RNs carry out autonomous decisions concerning whether to contend for a cooperative transmission opportunity, which could dissipate some of their battery power, while conveying their traffic in light of their individual service requirements. Furthermore, a WW cooperative medium-access-control (MAC) protocol is designed to implement the proposed distributed WW cooperative framework. Simulation results demonstrate that our WW cooperative MAC protocol is capable of providing both substantial rate improvements and considerable energy savings for the cooperative spectrum leasing system
Multi-Round Contention in Wireless LANs with Multipacket Reception
Multi-packet reception (MPR) has been recognized as a powerful
capacity-enhancement technique for random-access wireless local area networks
(WLANs). As is common with all random access protocols, the wireless channel is
often under-utilized in MPR WLANs. In this paper, we propose a novel
multi-round contention random-access protocol to address this problem. This
work complements the existing random-access methods that are based on
single-round contention. In the proposed scheme, stations are given multiple
chances to contend for the channel until there are a sufficient number of
``winning" stations that can share the MPR channel for data packet
transmission. The key issue here is the identification of the optimal time to
stop the contention process and start data transmission. The solution
corresponds to finding a desired tradeoff between channel utilization and
contention overhead. In this paper, we conduct a rigorous analysis to
characterize the optimal strategy using the theory of optimal stopping. An
interesting result is that the optimal stopping strategy is a simple
threshold-based rule, which stops the contention process as soon as the total
number of winning stations exceeds a certain threshold. Compared with the
conventional single-round contention protocol, the multi-round contention
scheme significantly enhances channel utilization when the MPR capability of
the channel is small to medium. Meanwhile, the scheme automatically falls back
to single-round contention when the MPR capability is very large, in which case
the throughput penalty due to random access is already small even with
single-round contention
- …