A method of determining the presence of a loopback in one or more networks comprises storing information related to a test instance; sending a loopback detection beacon (LPDB) containing information related to the test instance from a port on an originating device; monitoring the port for a predetermined time period to detect LPDBs arriving at the port during the predetermined time period; and determining whether a detected LPDB contains information corresponding to the stored information, to detect the presence of a loopback. The method may determine whether a detected loopback is a port loopback, a tunnel loopback or a service loopback. The stored information related to the test instance may be deleted if an LPDB arriving at the port and containing information corresponding to the stored information is not detected within the predetermined time period.

Apparatus and methods for front-end systems with reactive loopback are provided. In certain configurations, a front-end system includes an antenna port, a transmit port, a receive port, an antenna switch configured to selectively provide a transmit signal from the transmit port to the antenna port, a low noise amplifier having an input electrically connected to the antenna port and an output electrically connected to the receive port, and a loopback circuit including a reactive loopback impedance and a back switch electrically connected in series between the antenna switch and the receive port. The reactive loopback impedance includes a plurality of capacitors in series with the back switch and operable to provide a portion of the transmit signal to the receive port when the back switch is activated.

This application relates to the field of communications technologies, and in particular, to a digital predistortion processing method and apparatus. This application provides a digital predistortion processing method and apparatus. Digital predistortion processing of a multichannel power amplifier is supported through deprecoding processing by using one feedback link and one digital predistortion processor. In addition, after being amplified by a power amplifier, a precoded signal is fed back to the feedback link for predistortion parameter calculation, to improve quality of a transmit signal. The digital predistortion processing method and apparatus that are provided in embodiments of this application are intended to improve output linearity and efficiency of a multi-transmit-channel power amplifier while reducing implementation costs and complexity of a transmit device, and further improve overall system performance.

A method of determining the presence of a loopback in one or more networks comprises storing information related to a test instance; sending a loopback detection beacon (LPDB) containing information related to the test instance from a port on an originating device; monitoring the port for a predetermined time period to detect LPDBs arriving at the port during the predetermined time period; and determining whether a detected LPDB contains information corresponding to the stored information, to detect the presence of a loopback. The method may determine whether a detected loopback is a port loopback, a tunnel loopback or a service loopback. The stored information related to the test instance may be deleted if an LPDB arriving at the port and containing information corresponding to the stored information is not detected within the predetermined time period.

Systems and methods are disclosed herein for determining that a diagnostic mode is enabled for a port of a switch, the port being part of a VLAN, and responsively designating a port of the plurality of ports as a loopback port, where a packet transmitted on the loopback port is forwarded according to an entry of a forwarding database. The disclosure further describes generating a layer 2 multicast index comprising an entry for the port and an entry for the loopback port, programming the forwarding database with an entry for a destination address of the switch pointing to the layer 2 multicast index, generating a diagnostic packet, and transmitting the diagnostic packet on the loopback port. Additionally, the disclosure describes determining that the diagnostic packet is received by any port of the plurality of ports, and responsively determining a network problem exists and causing a diagnostic protocol to be executed.

An adapter is configured to connect to a network. The adapter including a controller configured to receive a stream of network communication from a computer system physically connected to the adapter. The controller is further configured to detect a first identifier. The first identifier is related to a first communication unit of the stream of network communication. In response to detecting the first identifier, the controller is further configured to direct the first communication unit away from the network and back toward the controller through a loopback pathway. The controller is further configured to direct the stream of network communication away from the computer system and to the network.

Methods and systems for an optoelectronic built-in self-test (BIST) system for silicon photonics optical transceivers are disclosed and may include, in an optoelectronic transceiver having a transmit (Tx) path and a receive (Rx) path, where the Rx path includes a main Rx path and a BIST loopback path: generating a pseudo-random bit sequence (PRBS) signal, generating an optical signal in the Tx path by applying the PRBS signal to a modulator, communicating the optical signal to the BIST loopback path and converting to an electrical signal utilizing a photodetector, the photodetector being a replica of a photodetector in the main Rx path, and assessing the performance of the Tx and Rx paths by extracting a PRBS signal from the electrical signal. The transceiver may be a single complementary-metal oxide semiconductor (CMOS) die or in two CMOS die, where a first comprises electronic devices and a second comprises optical devices.

Apparatus and methods for front-end systems with reactive loopback are provided. In certain configurations, a front-end system includes an antenna port, a transmit port operable to receive a transmit signal, a receive port, an antenna switch, a back switch, a transmit port DC blocking capacitor coupled between a first end of the antenna switch and the transmit port, an antenna port DC blocking capacitor coupled between a second end of the antenna switch and the antenna port, a receive port DC blocking capacitor coupled between a first end of the back switch and the receive port, and a reactive loopback impedance coupled between a second end of the back switch and the first end of the antenna switch. The reactive loopback impedance provides a portion of the transmit signal to the receive port when the back switch is activated.

One embodiment is a method including configuring a first network element of a fibre channel (FC) network as a generator element, wherein the generator employs a link diagnostic protocol to cause a second network element comprising a peer of the first network element as a reflector element, wherein the first and second elements are connected via a link; entering a first diagnostic phase, wherein in the first diagnostic phase, diagnostic capabilities of the first and second elements are determined; and subsequent to completion of the first diagnostic phase, entering a second diagnostic phase in which a deep loopback test is performed, wherein the deep loopback test comprises a frame level loopback test for exposing an issue in a path between the first and second network elements beyond a Media Access Control (MAC) layer.

Methods and apparatus for operating a communication system comprising three or more communication transceivers. In illustrative embodiments, multiple different cyclic redundancy check (CRC) generation schemes are maintained. Each CRC generation scheme corresponds to a unique CRC residual value. A CRC value generated using one of the CRC generation schemes is placed in a data packet to be transmitted. The chosen CRC generation scheme reflects which one or more transceivers are intended recipients of the data packet. When a data packet is received by a transceiver, a CRC residual value is calculated based on the CRC value contained in the received data packet. The calculated CRC residual value is compared against a list of one or more valid CRC residual values for that particular transceiver. If the calculated CRC value matches one of the listed valid CRC residual values, the data packet is accepted, otherwise it is rejected.