Correlated shadowing and fading characterization of MIMO off-body channels by means of multiple autonomous on-body nodes

Abstract

Abstract-In off-body communication systems low-cost and compact transceivers are important for realistic applications. An autonomous off-body wireless node was designed and integrated onto a textile antenna. Channel measurements were performed for an indoor non line-off-sight 4x2 MIMO (Multiple-Input Multiple-Output) link using four off-body transmitting nodes and two similar fixed receiving nodes. The channel behavior is characterized as Rayleigh fading with lognormal shadowing and is fitted to a model determining fading and shadowing correlation matrices. The physics of the propagation is captured accurately by the model which is further used to simulate a link using diversity by means of Selection Combining, as implemented on the wireless nodes. The performance of measured and simulated links is compared in terms of outage probability level. The measurements and analysis confirm that the correlated shadowing and fading model is relevant for realistic off-body networks employing diversity by means of Selection Combining.

Synchronous Wearable Wireless Body Sensor Network Composed of Autonomous Textile Nodes

“…In this network protocol, specifically designed for the difficult radio propagation conditions experienced by moving persons in an indoor environment, all data transmitted by each network node are forwarded by all of the other nodes. Data forwarding creates redundancy, resulting in a very reliable data transmission towards the base station, which results in a performance increase comparable to N-th order selection combining diversity for an N-node network, as shown earlier in [ 34 ]. This approach leads to a very significant increase in data reliability and/or communication range.…”

“…We conclude that distributing the nodes over several persons does not compromise the wireless communication between nodes or the network functionality in any way. Node-to-node links on the same body, as well as person-to-person links are always very reliable, thanks to the low packet loss for each link, combined with the redundancy introduced by forwarding packets, leading to a reliability increase of the communication system comparable to N -th order transmit diversity for an N -node network [ 34 ].…”

Analysis of Human Body Shadowing Effect on Wireless Sensor Networks Operating in the 2.4 GHz Band

“…The body-shadowing effect has been investigated by researchers working on wireless systems as well as on body area networks in a very wide range of frequencies [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Statistical analysis is often used to model this effect, including the time variation caused by people in motion and the properties of the indoor environment, which can influence the propagation of the signal [ 13 , 14 , 15 ].…”

“…The 2.4 GHz band is widely used for wireless transmission systems because in most countries, this is an unlicensed band. For this frequency, the study of the body shadowing effect was presented in the literature [ 14 , 21 , 22 , 23 , 24 ]. In [ 21 ], a statistical approach was applied for the analysis and modeling of the impact of path loss on the wireless link that is operating in the 2.4 GHz band.…”

“…Also in [ 22 ], a statistical signal reception model for shadowed body-centric communications was proposed. The parameters of channel models proposed in the literature are extracted from channel measurements and can be used in statistical analysis of wireless system performance [ 23 , 24 ].…”