Sabharwal, Ashutosh2019-05-172019-05-172018-122019-01-02December 2Mylarappa Gowda, Niranjan. "CPLink: Enabling the Reuse of Cyclic Prefix Intervals in OFDM Based Networks." (2019) Diss., Rice University. <a href="https://hdl.handle.net/1911/105924">https://hdl.handle.net/1911/105924</a>.https://hdl.handle.net/1911/105924In this thesis, we propose a method to establish a communication link between any two arbitrary users in an OFDM network by reusing the cyclic-prefix (CP) intervals of the ongoing OFDM link, without degrading the OFDM link performance. We label the link that reuses the CP-intervals as CPLink since they use only the CP-intervals of the ongoing link, which we refer to as MainLink. The commonly used OFDM receivers discard the samples in CP-intervals to mitigate inter-symbol-interference. We leverage this fact and design the CPLink such that the co-channel interference from a CPLink transmitter aligns with the CP intervals at the MainLink receivers. We study two types of CPLinks: (i) Full-duplex CPLink, where a full-duplex base-station is the CPLink receiver, while the CPLink transmitters are half-duplex, and (ii) Half-duplex CPLink, where the CPLink does not involve the base-station and is between two half-duplex user devices. In the thesis, we identify and address several challenges in building a complete framework that supports multiple full and half-duplex CPLinks within a cellular network. First, we consider the case with one CPLink in the cell. We design and study zero-knowledge CPLink, in which the CPLink transmitter ensures below-noise-floor interference at every MainLink-receiver with no knowledge about the locations or the number of MainLink-receivers. We analytically show that the zero-knowledge CPLink capacity is positive. Numerically, we show that the rate achieved by both full and half-duplex CPLink is large enough to support control as well as data communication in the cell. Second, to facilitate full-duplex CPLink in a cell, we propose a full-duplex architecture for massive MIMO base-stations. The proposed architecture, JointNull, jointly optimizes the partial analog cancelation and transmit beamforming. The measurements based evaluation shows that the JointNull can achieve near ideal sum rate with only eight analog cancelers on a 72-antenna array. When the traffic is highly downlink biased, like that of full-duplex CPLink, JointNull achieves 90% of ideal full-duplex gain with no analog cancelers. Third, we present CPNetwork, a framework for supporting multiple half and full-duplex CPLinks within the cell. The main limitation of zero-knowledge CPLink is that it requires the knowledge of transit time of CPLink transmitter. CPNetwork overcomes this limitation and can operate with neither the knowledge of MainLink receiver locations nor the knowledge of transit time of CPLink transmitters. The simulations show that full-duplex CPNetwork with massive MIMO base-station can deliver nearly 40 Mbps uplink rate (on a 20 MHz channel) to several edge CPLink transmitters, simultaneously. The half-duplex CPNetwork is found to support up to a hundred short-range CPLinks with 20-60 Mbps rate for each of the CPLink. The analytical and numerical results in the thesis demonstrate that the full-duplex CPNetwork can support the uplink control as well as data communications in a cellular network. Hence, full-duplex CPNetwork can improve the overall network throughput and more importantly, it can help TDD cellular networks achieve FDD-like latency. The half-duplex CPNetwork can support a network of hundreds of short-range device-to-device links and hence, can host local/personal area networks, small cells etc.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.OFDMWireless Full-DuplexMassive MIMOCyclic-Prefix.Thesis2019-05-17