21,130 research outputs found
Cooperative Beamforming for Wireless Ad Hoc Networks
Via collaborative beamforming, nodes in a wireless network are able to
transmit a common message over long distances in an energy efficient fashion.
However, the process of making available the same message to all collaborating
nodes introduces delays. In this paper, a MAC-PHY cross-layer scheme is
proposed that enables collaborative beamforming at significantly reduced
collaboration overhead. It consists of two phases. In the first phase, nodes
transmit locally in a random access time-slotted fashion. Simultaneous
transmissions from multiple source nodes are viewed as linear mixtures of all
transmitted packets. In the second phase, a set of collaborating nodes, acting
as a distributed antenna system, beamform the received analog waveform to one
or more faraway destinations. This step requires multiplication of the received
analog waveform by a complex weight, which is independently computed by each
cooperating node, and which allows packets bound to the same destination to add
coherently at the destination node. Assuming that each node has access to
location information, the proposed scheme can achieve high throughput, which in
certain cases exceeds one. An analysis of the symbol error probability
corresponding to the proposed scheme is provided.Comment: 5 pages, 4 figures. To appear in the Proceedings of the IEEE Global
Communications Conference (GLOBECOM), Washington, DC, November 26 - 30, 200
Seamless roaming and guaranteed communication using a synchronized single-hop multi-gateway 802.15.4e TSCH network
Industrial wireless sensor networks (WSNs) are being used to improve the
efficiency, productivity and safety of industrial processes. An open standard
that is commonly used in such cases is IEEE 802.15.4e. Its TSCH mode employs a
time synchronized based MAC scheme together with channel hopping to alleviate
the impact of channel fading. Until now, most of the industrial WSNs have been
designed to only support static nodes and are not able to deal with mobility.
In this paper, we show how a single-hop, multi-gateway IEEE 802.15.4e TSCH
network architecture can tackle the mobility problem. We introduce the Virtual
Grand Master (VGM) concept that moves the synchronization point from separated
Backbone Border Routers (BBRs) towards the backbone network. With time
synchronization of all BBRs, mobile nodes can roam from one BBR to another
without time desynchronization. In addition to time synchronization, we
introduce a mechanism to synchronize the schedules between BBRs to support fast
handover of mobile nodes.Comment: Short paper version of a paper submitted to Ad-Hoc Networks Journal
by Elsevie
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