Cellular Systems with Multicell Processing and Conferencing Links between Mobile Stations
O. Simeone(1) , O. Somekh(2) , G. Kramer(3) , H. V. Poor(2) and S. Shamai (Shitz)(4)
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CWCSPR, ECE Dept., NJIT, Newark, NJ 07102, osvaldo.simeone@njit.edu Dept. of Electrical Engineering, Princeton University, Princeton, NJ 08544, {orens, poor}@princeton.edu (3) Bell Labs, Alcatel-Lucent, Murray Hill, NJ 07974, gkr@research.bell-labs.com (4) Department of Electrical Engineering, Technion, Haifa, 32000, Israel, sshlomo@ee.technion.ac.il
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Abstract— In this paper, multi-cell processing for the uplink of a cellular system is studied in the presence of orthogonal channels of xed capacity between mobile stations in adjacent cells (conferencing). It is shown that a rate-splitting transmission strategy, where part of the message is exchanged on the conferencing channels and then transmitted cooperatively to the base stations, is capacity-achieving for an asymptotically large conferencing capacity. This strategy can be regarded as able to perform convolutional pre-equalization of the signal encoding the common messages in the spatial domain, where the number of taps of the nite-impulse response equalizer depends on the number of conferencing rounds. Analysis in the low signal-tonoise ratio regime and numerical results validate the advantages of conferencing as a complementary technology to multi-cell processing.
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I. I NTRODUCTION The solution of choice for providing broadband communications is by now considered to include the support of an infrastructure made of base stations (BSs, or access points) connected by a high-capacity backbone. This class of solutions includes: conventional cellular systems, where BSs are regularly placed in the area of interest; distributed antenna systems, which are characterized by a less regular (e.g., random) deployment; and hybrid networks, where infrastructure nodes coexist with multi-hopping. In all these networks, a solution that promises to greatly improve the overall throughput and that is gaining increasing interest in the community is multicell processing. This refers to the class of transmission/ reception technologies that exploit the high-capacity backbone among the BSs to perform joint encoding/ decoding at different cellsites (see [1] [2] for a list of references). In addition to the quickly growing body of work on multicell processing for cellular systems [1] [2] [3], there has recently been some activity around the basic idea of complementing and comparing the advantages of cooperation between BSs with some form of collaboration at the mobile stations (MS) level . In references [4] [5] [6], the basic linear Wyner model for cellular networks [3] was extended by including a layer of dedicated relay terminals, one for each cell, that forward trafc from MSs to BSs (uplink). Another related work is [10], where the linear Wyner model with intra-cell TDMA and single-cell processing was modied by assuming that the active MS in a given cell knows (non-causally) the messages to be sent by a number of its neighbors (as might be the case

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