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Multicast/broadcast is an important service primitive in networks. It is supported by all IEEE 802.x standards, including 802.11. The IEEE 802.11 multicast/broadcast protocol is based on the basic access procedure of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). This protocol does not provide any media access control (MAC) layer recovery on multicast/broadcast frames. As a result, the reliability of the multicast/broadcast service is reduced owing to the increased probability of lost frames resulting from interference or collisions. Recently, a few MAC protocols have been proposed to enhance the reliability and the efficiency of the 802.11 multicast/broadcast protocol. In this paper, we observe that these protocols are still unreliable or inefficient. To redress the problems of reliability and efficiency, we propose a reliable Batch Mode Multicast MAC protocol (BMMM), which in most cases reduces the number of contention phases from n to 1, where n is the number of intended receivers in the multicast/broadcast. This considerably reduces the time required for a multicast/broadcast. We then propose a Location Aware Multicast MAC protocol (LAMM), which uses station location information to further improve upon BMMM. Extensive analysis and simulation results validate the reliability and efficiency of our multicast MAC protocols. Copyright © 2003 John Wiley & Sons, Ltd.

3D thick electrode design is a promising strategy to increase the energy density of lithium-ion batteries but faces challenges such as poor rate and limited cycle life. Herein, a coassembly method is employed to construct low-tortuosity, mechanically robust 3D thick electrodes. LiFe 0.7 Mn 0.3 PO 4 nanoplates (LFMP NPs) and graphene are aligned along the growth direction of ice crystals during freezing and assembled into sandwich frameworks with vertical channels, which prompts fast ion transfer within the entire electrode and reveals a 2.5-fold increase in ion transfer performance as opposed to that of random structured electrodes. In the sandwich framework, LFMP NPs are entrapped in the graphene wall in a "plate-on-sheet" contact mode, which avoids the detachment of NPs during cycling and also constitutes electron transfer highways for the thick electrode. Such vertical-channel sandwich electrodes with mass loading of 21.2 mg cm −2 exhibit a superior rate capability (0.2C-20C) and ultralong cycle life (1000 cycles). Even under an ultrahigh mass loading of 72 mg cm −2 , the electrode still delivers an areal capacity up to 9.4 mAh cm −2 , ≈2.4 times higher than that of conventional electrodes. This study provides a novel strategy for designing thick electrodes toward high performance batteries.

A novel PEDOT/S@aPG composite with good cycling stability and excellent rate capability is prepared.

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