This paper provides a scheme to reduce the cost to distribute multimedia content to a set of nearby mobile peers, which we call chums. One peer, called the proxy, downloads multimedia content via a telecommunication link, and distributes it (which we call chumcast) to the ad hoc network formed from the set of nearby peers. Each peer in the ad hoc network takes turns serving as a proxy. Every peer is associated with a server that resides in the internet. The server for the proxy, called the active server, manages peer information, schedules the next proxy, selects a set of rebroadcasting peers, and detects partitioning of the ad hoc network. With support from the servers in the internet, peers receive benefits of reduced telecommunication bandwidth, computation power, as well as several security features. Simulation results show that 80% of the telecommunication cost is saved with as few as six peers. Copyright © 2005 John Wiley & Sons, Ltd.

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This paper proposes a coupled-feed structure accompanied by cavity walls for an extremely small four-element array with an aperture size of less than 0.4λ. The feeding loop of the proposed structure is connected to two output ports of a hybrid chip coupler, and the radiating loop is coupled to the feeding loop through near electromagnetic fields confined within the substrates. This structure allows to increasing the effective dielectric constant of the antenna, which helps to miniaturize the aperture size of the antenna. Another advantage of the proposed structure is that the effective dielectric constant can be adjusted by varying the height of the cavity walls. To verify the operating principles, an equivalent circuit is built, and variations of magnetic field distributions are also observed. Furthermore, performances on interference mitigation are evaluated based on the power inversion algorithm. The results confirm that the proposed structure is suitable to replace current single-antenna systems for an additional capability of effective interference mitigation in such a restricted area. INDEX TERMS Small antenna array, microstrip antenna, coupled feed, anti-jamming, controlled reception pattern antenna.

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