999 research outputs found
Joint Adaptive Modulation-Coding and Cooperative ARQ for Wireless Relay Networks
This paper presents a cross-layer approach to jointly design adaptive
modulation and coding (AMC) at the physical layer and cooperative truncated
automatic repeat request (ARQ) protocol at the data link layer. We first derive
an exact closed form expression for the spectral efficiency of the proposed
joint AMC-cooperative ARQ scheme. Aiming at maximizing this system performance
measure, we then optimize an AMC scheme which directly satisfies a prescribed
packet loss rate constraint at the data-link layer. The results indicate that
utilizing cooperative ARQ as a retransmission strategy, noticeably enhances the
spectral efficiency compared with the system that employs AMC alone at the
physical layer. Moreover, the proposed adaptive rate cooperative ARQ scheme
outperforms the fixed rate counterpart when the transmission modes at the
source and relay are chosen based on the channel statistics. This in turn
quantifies the possible gain achieved by joint design of AMC and ARQ in
wireless relay networks.Comment: 5 pages, 4 figures, To appear in the Proceedings of the 2008 IEEE
International Symposium on Wireless Communication Systems (ISWCS), Rykevick,
Island, Oct 200
RECOMAC: a cross-layer cooperative network protocol for wireless ad hoc networks
A novel decentralized cross-layer multi-hop cooperative protocol, namely, Routing Enabled Cooperative Medium Access Control (RECOMAC) is proposed for wireless ad hoc networks. The protocol architecture makes use of cooperative
forwarding methods, in which coded packets are forwarded via opportunistically formed cooperative sets within a region, as RECOMAC spans the physical, medium access control (MAC) and routing layers. Randomized coding is exploited at the physical layer to realize cooperative transmissions, and cooperative forwarding is implemented for routing functionality, which is submerged into the MAC layer, while the overhead for MAC and route set up is minimized. RECOMAC is shown to provide dramatic performance improvements of eight times higher throughput and one tenth of end-to-end delay than that of the conventional architecture in practical wireless mesh networks
Wireless industrial monitoring and control networks: the journey so far and the road ahead
While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks
Cooperative Relaying in Wireless Networks under Spatially and Temporally Correlated Interference
We analyze the performance of an interference-limited, decode-and-forward,
cooperative relaying system that comprises a source, a destination, and
relays, placed arbitrarily on the plane and suffering from interference by a
set of interferers placed according to a spatial Poisson process. In each
transmission attempt, first the transmitter sends a packet; subsequently, a
single one of the relays that received the packet correctly, if such a relay
exists, retransmits it. We consider both selection combining and maximal ratio
combining at the destination, Rayleigh fading, and interferer mobility.
We derive expressions for the probability that a single transmission attempt
is successful, as well as for the distribution of the transmission attempts
until a packet is transmitted successfully. Results provide design guidelines
applicable to a wide range of systems. Overall, the temporal and spatial
characteristics of the interference play a significant role in shaping the
system performance. Maximal ratio combining is only helpful when relays are
close to the destination; in harsh environments, having many relays is
especially helpful, and relay placement is critical; the performance improves
when interferer mobility increases; and a tradeoff exists between energy
efficiency and throughput
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