Communication channel

About: Communication channel is a research topic. Over the lifetime, 137411 publications have been published within this topic receiving 1715077 citations. The topic is also known as: communication channel & communications channel.

A Cognitive MAC Protocol Using Statistical Channel Allocation for Wireless Ad-Hoc Networks

Abstract: The MAC protocol of a cognitive radio (CR) device should allow it to access unused or under-utilized spectrum without (or with minimal) interference to primary users dynamically. To fulfill such a goal, we propose a cognitive MAC protocol using statistical channel allocation and call it SCA-MAC in this work. SCA-MAC is a CSMA/CA-based protocol, which exploits statistics of spectrum usage for decision making on channel access. For each transmission, the sender negotiates with the receiver on transmission parameters through the control channel. A model is developed for CR devices to evaluate the successful rate of transmission. A CR device should pass the threshold of the successful transmission rate via negotiation before it can begin a valid transmission on data channels. The operating range and channel aggregation are two control parameters introduced to maintain the MAC performance. To validate our ideas, we conducted theoretical analysis and simulations to show that SCA-MAC does improve the throughput performance and guarantee the interference to incumbents to be bounded by a predetermined acceptable rate. The proposed MAC protocol does not need a centralized controller, as the negotiation between the sender and the receiver is performed using the CSMA/CA-based algorithm.

Rate control for multi-channel communication systems

Abstract: Techniques to determine a set of rates for a set of data streams to be transmitted in a multi-channel communication system A group of transmission channels to be used for each data stream is initially identified An equivalent system for each group is then defined to have an AWGN (or flat) channel and a spectral efficiency equal to the average spectral efficiency of the transmission channels in the group (216) A metric for each group is then derived based on the associated equivalent system, eg, set to the SNR needed by the equivalent system to support the average spectral efficiency (218) A rate for each data stream is then determined based on the metric associated with the data stream The rate is deemed to be supported by the communication system if the SNR required to support the data rate by the communication system is less than or equal to the metric (226)

Experimental Twin-Field Quantum Key Distribution through Sending or Not Sending.

Abstract: Channel loss seems to be the most severe limitation on the practical application of long distance quantum key distribution. The idea of twin-field quantum key distribution can improve the key rate from the linear scale of channel loss in the traditional decoy-state method to the square root scale of the channel transmittance. However, the technical demands are rather tough because they require single photon level interference of two remote independent lasers. Here, we adopt the technology developed in the frequency and time transfer to lock two independent laser wavelengths and utilize additional phase reference light to estimate and compensate the fiber fluctuation. Further, with a single photon detector with a high detection rate, we demonstrate twin field quantum key distribution through the sending-or-not-sending protocol with a realistic phase drift over 300 km optical fiber spools. We calculate the secure key rates with the finite size effect. The secure key rate at 300 km (1.96×10^{-6}) is higher than that of the repeaterless secret key capacity (8.64×10^{-7}).

MIMO-NOMA Design for Small Packet Transmission in the Internet of Things

Abstract: A feature of the Internet of Things (IoT) is that some users in the system need to be served quickly for small packet transmission. To address this requirement, a new multiple-input multiple-output non-orthogonal multiple access (MIMO-NOMA) scheme is designed in this paper, where one user is served with its quality of service requirement strictly met, and the other user is served opportunistically by using the NOMA concept. The novelty of this new scheme is that it confronts the challenge that the existing MIMO-NOMA schemes rely on the assumption that users’ channel conditions are different, a strong assumption which may not be valid in practice. The developed precoding and detection strategies can effectively create a significant difference between the users’ effective channel gains, and therefore, the potential of NOMA can be realized even if the users’ original channel conditions are similar. Analytical and numerical results are provided to demonstrate the performance of the proposed MIMO-NOMA scheme.

Unidirectional electron flow in a nanometer-scale semiconductor channel: A self-switching device

Abstract: By tailoring the boundary of a narrow semiconductor channel to break its symmetry, we have realized a type of nanometer-scale nonlinear device, which we refer to as self-switching device (SSD). An applied voltage V not only changes the potential profile along the channel direction, but also either widens or narrows the effective channel depending on the sign of V. This results in a diode-like characteristic but without the use of any doping junction or barrier structure. The turn-on voltage can also be widely tuned from virtually zero to more than 10 V, by simply adjusting the channel width. The planar and two-terminal structure of the SSD also allows SSD-based circuits to be realized by only one step of lithography.