Presentation

Wireless Networks that can See

Dennis Prather

10:00 - 11:00 | Monday 14 December 2015 | Emerald

Summary

By offering enhanced frequency re-use, "small cells" have been proposed to address the need for increased capacity in future wireless networks. However, while a more-dense cellular topology is indeed attractive, their deployment is challenging due to the need for additional real estate, permits, and access to back-haul. As an alternative, dense sectoring is being proposed, wherein RF beam forming is used to "sectorize" the Tx/Rx capabilities of a base station into smaller angular regions, which also allows for enhanced frequency re-use. However, dense sectoring is challenged by co-channel and adjacent-channel interference (CCI and ACI), which inevitably arises due to nonlinear operations that result in signal intermixing and intermodulation as the Rx aperture receives all sectors simultaneously. In short, present beam-forming Rx arrays do not adequately discriminate between the multitude of spatial and spectral signals that are simultaneously received at a base station.To address these challenges, we present a Tx/Rx array that first "images" the spatial and spectral signals and subsequently "detects" them, thereby eliminating intermixing and intermodulation and thereby allows for full spatial/spectral discrimination and hence full frequency re-use in each sector. By analogy, visible imaging systems inherently perform such spatial/spectral discrimination by first performing a spatial mapping of the scene with a lens and then subsequently performing a spectral analysis of the signal to determine color. As an example consider a Christmas tree with multi-colored lights. From a signal detection perspective, each light is first spatially mapped, or imaged, onto the retina, which effectively renders a spatially orthogonal signal plane, i.e., each point of origin in the source plane is focused to a separate and distinct point in the image plane that does not overlap with any adjacent points. Subsequently, the inherently non-linear process of detection is performed to determine the spectral nature of the imaged point, however, because each point is spatially separated from every other point, i.e., non-overlapping, signal intermixing does not take place due to the orthogonal nature of the imaging process and the inherent isolation it provides.In the context of wireless networks, the various colors represent frequency re-use and the various spatial locations correspond to the sectors within a wireless cell. In this talk, we present such an imaging/receiver system that operates in the wireless spectrum. In so doing, it provides inherent CCI and ACI suppression over many spatial sectors and thereby enables ultra dense frequency reuse. Moreover, this approach allows for massive MIMO capability as all spatial sectors are imaged simultaneously with latencies limited only by the propagation delay of the wireless signals themselves. This talk will also present an efficient and high capacity Tx system that complements the "imaging-receiver" in terms of spatial/spectral signal exploitation.