Abstract
In the last few years, the increasing use of LEDs in illumination systems has been conducted due to the emergence of Visible Light Communication (VLC) technologies, in which data communication is performed by transmitting through the visible band of the electromagnetic spectrum. In 2011, the Institute of Electrical and Electronics Engineers (IEEE) published the IEEE 802.15.7 standard for Wireless Personal Area Networks based on VLC. Due to limitations in the coverage of the transmitted signal, wireless networks can suffer from the hidden node problems, when there are nodes in the network whose transmissions are not detected by other nodes. This problem can cause an important degradation in communications when they are made by means of the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) access control method, which is used in IEEE 802.15.7 This research work evaluates the effects of the hidden node problem in the performance of the IEEE 802.15.7 standard We implement a simulator and analyze VLC performance in terms of parameters like end-to-end goodput and message loss rate. As part of this research work, a solution to the hidden node problem is proposed, based on the use of idle patterns defined in the standard. Idle patterns are sent by the network coordinator node to communicate to the other nodes that there is an ongoing transmission. The validity of the proposed solution is demonstrated with simulation results.
Highlights
Optical wireless communications based on visible light [1], named Visible LightCommunications (VLCs), use visible light to transmit data by modulating intensity in light emitting diodes (LED), employing faster switching rates than the persistence of the human eye to avoid flickering in data/light sources
We present an evaluation of the effects of the hidden node problem in the performance of uplink communications when using the slotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) random access procedure defined in the Institute of Electrical and Electronics Engineers (IEEE) 802.15.7 standard
IEEE 802.15.7 Medium Access Control (MAC) layer defines a medium access control procedure based on the CSMA/CA method; uplink transmissions made according to this procedure are susceptible to be affected by the hidden node problem
Summary
Communications (VLCs), use visible light to transmit data by modulating intensity in light emitting diodes (LED), employing faster switching rates than the persistence of the human eye to avoid flickering in data/light sources. The hidden node problem is a well known problem in wireless networks based on radio frequency using CSMA/CA channel access mechanisms [5,6] This problem is caused by signal coverage constraints, resulting in network nodes not being able to detect transmissions performed by other nodes. We present an evaluation of the effects of the hidden node problem in the performance of uplink communications when using the slotted CSMA/CA random access procedure defined in the IEEE 802.15.7 standard.
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