Browsing by Author "Medjkouh, Said"
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- Channel Charting: Locating Users within the Radio Environment using Channel State Information
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2018-08-23) Studer, Christoph; Medjkouh, Said; Gonultas, Emre; Goldstein, Tom; Tirkkonen, OlavWe propose channel charting (CC), a novel framework in which a multi-antenna network element learns a chart of the radio geometry in its surrounding area. The channel chart captures the local spatial geometry of the area so that points that are close in space will also be close in the channel chart and vice versa. CC works in a fully unsupervised manner, i.e., learning is only based on channel state information (CSI) that is passively collected at a single point in space, but from multiple transmit locations in the area over time. The method then extracts channel features that characterize large-scale fading properties of the wireless channel. Finally, the channel charts are generated with tools from dimensionality reduction, manifold learning, and deep neural networks. The network element performing CC may be, for example, a multi-antenna base-station in a cellular system and the charted area in the served cell. Logical relationships related to the position and movement of a transmitter, e.g., a user equipment (UE), in the cell can then be directly deduced from comparing measured radio channel characteristics to the channel chart. The unsupervised nature of CC enables a range of new applications in UE localization, network planning, user scheduling, multipoint connectivity, hand-over, cell search, user grouping, and other cognitive tasks that rely on CSI and UE movement relative to the base-station, without the need of information from global navigation satellite systems. - Unsupervised Charting of Wireless Channels
A4 Artikkeli konferenssijulkaisussa(2018) Medjkouh, Said; Gönültaş, Emre; Goldstein, Tom; Tirkkonen, Olav; Studer, ChristophFuture wireless communication systems will rely on large antenna arrays at the infrastructure base stations (BSs) to serve multiple users with high data rates in a single cell. We demonstrate that the availability of high-dimensional channel state information (CSI) acquired at such multi-antenna BSs enables one to learn a chart of the radio geometry, which captures the spatial geometry of the users so that points close in space are close in the channel chart, using no other information than wireless channels of users. Specifically, we propose a novel unsupervised framework that first extracts channel features from CSI which characterize large-scale fading effects of the channel, and then uses specialized dimensionality reduction tools to construct the channel chart. The channel chart can, for example, be used to perform (relative) user localization, predict cell hand-overs, or guide scheduling tasks, without accessing location information from global navigation satellite systems.