In recent years, full-duplex communications in a single frequency channel have become a practical technology. However, existing full-duplex medium access control (MAC) protocols can hardly take full advantages of full-duplex transmission opportunities, because they are not capable of adding one more half-duplex link on an on-going half-duplex link to form a full-duplex link. Besides, the exposed node and hidden node issues in multi-hop wireless networks limit flexible establishment of full-duplex links. Such limitations waste full-duplex transmission opportunities, and thus degrade network performance. In this paper, an efficient full-duplex link establishment protocol called full-duplex opportunity exploitation (FDOE) is developed to exploit full-duplex transmission opportunities in a wireless mesh network. FDOE leverages rateless coding and pseudo-noise (PN) sequences to establish a full-duplex link whenever a full-duplex transmission opportunity is available. Such a distinct feature leads to significant improvement of network performance. FDOE is evaluated through theoretical analysis and extensive simulations. Performance results show that FDOE exploits full-duplex transmission opportunities efficiently in wireless mesh networks, and thus significantly outperforms existing MAC protocols.

This paper is concerned with the phase noise mitigation in millimeter wave (mmW) multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. We first develop a model for phase noise in the mmW MIMO-OFDM system with hybrid precoding. A pilot-assisted estimation and compensation (PEC) scheme is then proposed by jointly estimating the channel response and effective phase noise. Numerical results show that, compared with the available alternative, the PEC scheme can achieve significant performance gain.

We studies the influence of multiple reference signals on different transmit ports for RSTD measurements in small bandwidth scenarios. Because of scalable measurement bandwidth in long term evolution (LTE), the performance of reference signal time difference (RSTD) suffers from small bandwidth. Conventional RSTD scheme is based on positioning reference signals (PRS) which use one transmit antenna and two receive antennas (1x2). In order to reduce the loss of accuracy caused by small bandwidth, three new schemes are proposed. Compared with the conventional scheme, the accuracy of three proposed schemes has been improved in ETU channel. We verify it with our simulation results. The detection probability of one proposal 2x2 scheme which splits PRS symbols on two transmit antennas is decreased by half the number of accumulating symbols on each transmit antenna. Other two schemes which accumulate cell-specific reference signals (CRS) and PRS non-coherently or coherently not only provide better RSTD accuracies but also improve detection probabilities.

Cognitive radios can significantly improve spectrum efficiency by using locally available spectrum. The efficiency, however, depends heavily on their transceiver design. In particular, being able to use non-contiguously aligned spectrum bands simultaneously is a critical requirement. Prior work in this area requires a control channel so that transmitter/receiver pairs can synchronize on their spectrum usage patterns. However, this approach can suffer from high cost and control congestion. In this paper, we propose an in-band solution for informing receivers the spectrum usage patterns. By judiciously designing packet preambles, we embed the spectrum usage patterns in each data packet. Using the legacy 802.11 preamble structure, we focus on choosing the appropriate preamble sequences to maintain reliable packet detection in the presence of noise and interference. We verify our design using simulation and show that it can lead to reliable packet transmissions comparable to those of contiguous spectrum usage. We also identify the impact of interference on our design and propose refinements to choose the preamble sequence using information on the interference.