Cognitive radio network in vehicular ad hoc network (VANET): a survey

Cognitive radio network and vehicular ad hoc network (VANET) are recent emerging concepts in wireless networking. Cognitive radio network obtains knowledge of its operational geographical environment to manage sharing of spectrum between primary and secondary users, while VANET shares emergency safety messages among vehicles to ensure safety of users on the road. Cognitive radio network is employed in VANET to ensure the efficient use of spectrum, as well as to support VANET’s deployment. Random increase and decrease of spectrum users, unpredictable nature of VANET, high mobility, varying interference, security, packet scheduling, and priority assignment are the challenges encountered in a typical cognitive VANET environment. This paper provides survey and critical analysis on different challenges of cognitive radio VANET, with discussion on the open issues, challenges, and performance metrics for different cognitive radio VANET applications

PGCs expressed SOX10, SOX9 and S100B in the W10.4 human fetal cochlea.

<p>(A–B) Confocal images of the lower basal turn of a W10.4 cochlea immunostained for SOX10 and SOX10 merged with DAPI. (C–D) Confocal images of an adjacent section immunostained for SOX9 and SOX9 merged with DAPI. (E–G) Confocal images of the lower basal turn of a W10.4 cochlea immunostained for S100B (E) and TUBB3 (F) and the merged image with DAPI (G). (H–J) High-magnification view of the center of the spiral ganglion. (K–M) Detail of the peripheral processes at their distal end. Abbreviations: cd, cochlear duct; SG, spiral ganglion. Scale bar = 50 µm (A–G) or 20 µm (H–M).</p

Myelination of spiral ganglion neurons at W22.

<p>(A–E) Confocal images of a spiral ganglion in the middle turn of a cochlea at W22 showing DAPI (A), TUBB3 (B), PRPH (C), MBP (D) and the merged image (E). The spiral ganglion is delineated by the dotted line. (F–J) Confocal images of an axial transection of the cochlear nerve at W22 showing DAPI (F), TUBB3 (G), PRPH (H), MBP (I) and the merged image (J). (K–O) Deconvoluted confocal images of an axial transection of the cochlear nerve at W22 showing DAPI (K), TUBB3 (L), PRPH (M), MBP (N) and the merged image (O). Insets show TUBB3 (left), PRPH (middle) and the merge with MBP and DAPI (right) in high-magnifications examples of PRPH−/TUBB3+/MBP+ cochlear nerve fibers (upper inset) and PRPH+/TUBB3+/MBP+ cochlear nerve fibers (lower inset). Scale bar = 20 µm or 1 µm (insets in O).</p

Terminal differentiation of Schwann cells in the cochlear nerve.

<p>(A–C) Deconvoluted confocal images of the cochlear nerve at W9 showing TUBB3 (A, red), S100B (B, green), and the merged image with DAPI (C). (D–G) Deconvoluted confocal images of an axial transection of the cochlear nerve at W22 showing DAPI (D), TUBB3 (E), S100B (F) and the merged image (G). The upper inset in G shows a high-magnification of TUBB3+ cochlear nerve fibers each enveloped by S100B+ Schwann cells, the lower inset shows a Remak bundle. (H–K) Deconvoluted confocal images of a sagittal transection of the cochlear nerve at W22 showing DAPI (H), TUBB3 (I), MBP (J) and the merged image (K). The inset shows a high-magnification view of a myelinated nerve fiber. Scale bar = 10 µm or 1 µm (insets in G and K).</p

NGFR expression in the cochlear duct epithelium.

<p>(A–C) Confocal images of the cochlear duct epithelium in the upper middle turn of a cochlea at W12 showing TUBB3 (A, red), S100B (B, green) and the merged image with DAPI (C). The arrow points to penetrating TUBB3+ peripheral processes. (D–F) Confocal images of the cochlear duct epithelium in the lower basal turn showing TUBB3 (D, red), S100B (E, green) and the merged image with DAPI (F). The arrowhead points to the first developing (inner) hair cell. (G–H) Confocal images of the cochlear duct epithelium of the lower basal turn of a cochlea at W12 showing NGFR (G, green) and the merged image with DAPI (H) and MYO7A (red). The bold arrows point to the NGFR+ Schwann cells. The thin arrows outline the epithelial cells that weakly express NGFR. (I–J) Upper middle turn of a cochlea at W14 showing NGFR (I, green) and the merged image (J) with DAPI (blue) and MYO7A (red). The bold arrows point to the NGFR+ Schwann cells. (K–L) Lower middle turn of a W14 cochlea immunostained for NGFR (K, green) and the merged image with DAPI (blue) and MYO7A (red). The bold arrow points to the NGFR+ Schwann cells. The thin arrow points to a bright band of NGFR. (M–N) Lower basal turn of a W14 cochlea immunostained for NGFR (M, green) and the merged image (N) with DAPI (blue) and MYO7A (red). The bold arrows point to the NGFR+ Schwann cells. The thin arrow points to a band brightly immunostained for NGFR. (O–Q) Confocal images of the spiral ganglion in the lower basal turn of a cochlea at W18 showing TUBB3 (O), NGFR (P, green) and the merged image with DAPI (Q). (R–S) Confocal images of the organ of Corti of a cochlea at W18 showing NGFR (R, green) and the merged image with DAPI (S). Abbreviations: cd, cochlear duct; m, mesenchyme; B1, lower basal turn; M1, lower middle turn; M2, upper middle turn; SG, spiral ganglion; PPs, peripheral processes. * = autofluorescence of erythrocytes. Scale bar = 20 µm (A–N, R–S) or 50 µm (O–Q).</p

Immature Schwann cells along the peripheral processes express NGFR.

<p>(A–D) Confocal images of the lower basal turn of a cochlea at W9 showing DAPI (A), TUBB3 (B) and NGFR (C) and the merged image (D). The spiral ganglion is delineated by the dotted line. The asterisk marks two NGFR+ cells in the center of the spiral ganglion. (E–I) Confocal images of the lower basal turn of a cochlea at W10.4 showing DAPI (E), TUBB3 (F), SOX10 (G) and NGFR (H) and the merged image (I). The spiral ganglion is delineated by the dotted line. The inset shows a deconvoluted, high-magnification view of TUBB3 and NGFR at the distal tips of the peripheral processes. Abbreviations: SG, spiral ganglion. Scale bar = 50 µm or 5 µm (inset in I).</p

Capturing PGCs in the human cochlea.

<p>(A) Schematic model of PGC development in the human fetal cochlea. Neural crest cells differentiate via a Schwann cell precursor stage into S100+ immature Schwann cells. The immature Schwann cells subsequently maturate into myelinating and non-myelinating Schwann cells, and (presumably) satellite glial cells. (B) Schematic illustration of a mid-modiolar cut of the adult human cochlea, showing the lower basal turn (B1), upper basal turn (B2), lower middle turn (M1), upper middle turn (M2) and the apex (A). (C) Schematic illustration of the PGCs in the adult human cochlea. Satellite glial cells (green) envelop all SGN cell bodies. Non-myelinating Schwann cells (light blue) ensheath both the central and peripheral processes of the type II SGNs (yellow) that innervate the outer hair cells (OHC). Myelinating Schwann cells (dark blue) ensheath and myelinate both processes of the type I SGNs (red) that innervate the inner hair cells (IHC). Beyond the habenula perforata, in the organ of Corti, neither Schwann cell types ensheath the most distal part of the peripheral processes of type I and type II SGNs.</p

PGCs expressed SOX10, SOX9 and S100B in the W9 human fetal cochlea.

<p>(A–E) Confocal images of a cochlea at W9 showing DAPI (A), TUBB3 (B), SOX10 (C), and S100B (D) and the merged image (E). The spiral ganglion is delineated by the dotted line. (F–H) Confocal images of a cochlea at W9 showing the cochlear nerve (F), the spiral ganglion in the upper basal turn (G), and the spiral ganglion in the lower basal turn (H), delineated with dotted lines and immunostained with antibodies against SOX9 and TUBB3. Cell nuclei were visualized with DAPI. Abbreviations: B1, lower basal turn; B2, upper basal turn; SG, spiral ganglion. Scale bar = 100 µm.</p