Browsing by Author "Ghasem Pour, Yasaman"

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    Next-Generation Wireless Systems for Joint Communication and Sensing in Millimeter-Wave and Terahertz Spectrum
    (2020-04-24) Ghasem Pour, Yasaman; Knightly, Edward
    The use of mmWave and THz spectrum (30 GHz to 1 THz) for wireless communication is rapidly emerging as one the key paradigms for future (5G and beyond) wireless systems. mmWave/THz communication has the potential to realize an order of magnitude increase in data rates due to the availability of wide spectral bands. However, the increased propagation loss necessitate directional links which brings many challenges including user mobility, blockage, and scaling to dense user populations. This thesis presents design, implementation, and experimental evaluation of novel solutions for mobility adaptation and e cient multi-stream transmissions in mmWave and THz regime. The key idea is to exploit the wireless sensing capabilities of these higher frequencies to enhance directional communication. Namely, the mm-scale wavelength together with wide spectral band can potentially provide high-resolution sensing of user motion. Further, we can pack two order of magnitudes more antennas (i.e., potential \sensors") into the same form factor (compared to legacy 2.4 and 5 GHz bands) or exploit novel high-frequency steering devices that enhance sensing. In particular, in order to scale to dense user populations, I present the first efficient multi-stream beam training protocol for 60 GHz WLANs. I demonstrate how we can leverage channel sparsity, GHz-scale sampling rate, and the knowledge of mm-Wave RF codebook beam patterns to sense a set of beam pattern that can capture diverse or ideally orthogonal paths in order to obtain maximum stream separability. I then present the fi rst single-shot single-antenna motion sensing system in THz wireless networks that allows nodes to proactively adapt their highly directional beams under user mobility or blockage. Combined, these innovations address the key challenges of directional networking in mmWave and THz spectrum. This thesis builds the foundation for uni ed communication and sensing in future wireless technology.
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    Scaling 60 GHz WLANs: Creating and Identifying Opportunities for Multi-User Transmission
    (2016-10-17) Ghasem Pour, Yasaman; Knightly, Edward
    The millimeter scale carrier wavelength of the 60 GHz spectrum makes it feasible to pack two order of magnitudes more antennas into the same form factor compared to legacy bands (i.e. 2.4 and 5 GHz band). Prior works in 60 GHz have exploited this large antenna arrays to enhance the link budget of a single user transmission, which suffers from high path loss in 60 GHz. We are proposing a scalable multi-user scheme in 60 GHz WLANs in order to serve multiple clients with multi-Gbps data rate simultaneously in the same environment using the same frequency channel. To this end, we first propose a scalable beam training protocol, which tracks the users for directional transmissions. Then we have designed and evaluated incremental policies that add clients to a transmission sequentially until the AP's resources are exhausted or client link budgets, including interference, are exceeded. We further target polarization diversity and non-uniform antenna partitioning as mechanisms to dramatically reduce inter-stream interference enabling vastly improved aggregate rate. At lower bands, multi-user aggregation is typically achieved by zero-forcing inter-user interference via sender-side digital pre-coding using channel state information at the source. Unfortunately, such techniques do not scale to 60 GHz since (i) 60 GHz transmission is highly directional and lacks the rich scattering propagation environment assumed for most prior work; (ii) even efficient mechanisms for CSIT collection do not scale to large antenna arrays; (iii) prior techniques employ a large number of radio frequency chains (up to one per antenna) which are not feasible in our scenario. Our experiments through over-the-air testbed built over WARP platform and trace-driven simulations show that our methodology can achieve performance near to that of exhaustive search of all possible client combinations, yet with substantially less overhead.