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Cell Enhancer for Broadband Wireless Access Systems
IEICE TRANSACTIONS on Communications
Publication Date: 2002/05/01
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Wireless Communications Issue)
OFDM, radio repeater, SFN, TDD, broadband wireless access,
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This paper proposes a radio repeater, cell enhancer (CE), that targets 5-GHz broadband wireless access systems to improve the coverage probability without the need to establish a new access point (AP). The CE adopts a non-regenerative repeating scheme to transfer signals and implements two novel approaches, timing control and gain control, to apply to the target systems. By monitoring the control signals broadcast from the AP, the CE behaves as an AP using the same frame timing and transmitting power level, but using a second frequency channel. Thus, the CE can extend the coverage area of one AP. It appears that, however, in the orthogonal frequency division multiplexing (OFDM) system, over two hops with non-regenerative repeating, the additive effect of multipath fading from the two paths results in more violent subcarrier fluctuations and increased delay spread. Computer simulations in multipath fading environments derive the required CNR values for each path, which are required when the CE is installed in the field. In addition, we clarify that multiple CEs can use the same second frequency and provide better coverage with useful macro diversity gain in 5-GHz indoor environments.