The present disclosure discloses a system including a controller and a plurality of radio heads communicatively coupled to the controller. The controller transmits a synchronization signal to each of the radio heads to synchronize the local clocks in the radio heads to a master clock in the controller. The controller also transmits packets to the radio heads. Each of the radio heads includes a deframer. For a radio head, upon detecting that a received packet from the controller includes an error, the deframer alters the received packet to maintain the synchronization between the controller and the radio head and transmits data contained within the altered packet.

A multi-channel and multi-zone audio environment is provided. Various inventions are disclosed that allow playback devices on one or more networks to provide an effective multi-channel and a multi-zone audio environment using timing information. According to one example, timing information is used to coordinate playback devices connected over a low-latency network to provide audio along with a video display. In another example, timing information is used to coordinate playback devices connected over a mesh network to provide audio in one or more zones or zone groups.

A method performs time-synchronization between a master clock and a plurality of slave clocks. The method performs a forward time-synchronization from the master clock to the plurality of slave clocks. Further, the method performs a reverse time-synchronization from the plurality of slave clocks to a corresponding plurality of validator clocks. In addition, the method validates the time-synchronization between the plurality of slave clocks, notably between the master clock and the plurality of slave clocks, based on the plurality of validator clocks.

Embodiments of the present invention provide a synchronization method, user equipment, and a base station. The synchronization method includes: obtaining, by user equipment, synchronization information, where the synchronization information includes at least one of the following information: synchronization source selection parameter information, synchronization source indication information, or synchronization source priority information; receiving, by the user equipment, a first synchronization signal sent by at least one synchronization source; and determining, by the user equipment, a synchronization reference source according to the synchronization information and the first synchronization information. In the embodiments of the present invention, the synchronization information is obtained, and the synchronization reference source is determined according to the synchronization information and the synchronization signal of the at least one synchronization source, so that synchronization can be implemented.

Methods and systems may be used to synchronize time across multiple IoT related entities, such as a network of resource constrained sensor and actuator type devices, IoT gateways, IoT cloud services, or IoT applications.

An example system comprising a first transceiver configured to receive a request airframe from a second transceiver over a wireless link, the request airframe including a first time indication indicating a first time TS1, a second time indication indicating a second time TS2 that the request airframe was received, generate a respond airframe and including a third time indication indicating a third time TS3 that the respond airframe is transmitted to the second transceiver, transmit the respond airframe to the second transceiver, provide a timestamp information request to second transceiver, receive a timestamp information response, the timestamp information response including a fourth time indication indicating a fourth time TS4, calculate a counter offset using the first time, second time, third time and fourth time as follows: $\mathrm{counter}\mathrm{offset}=\frac{\left(\mathrm{TS}1+\mathrm{TS}4-\mathrm{TS}3-\mathrm{TS}2\right)}{2},$
calculate a phase offset based on the counter offset, and correct a phase of the first transceiver.

A building management system and method for sensor time correction is described. The system comprises multiple sensors and an energy manager communicating with the sensors. The sensors, distributed within a particular area, provide multiple time measurements in response to detecting an object traversing among the sensors in which the time measurements are associated with unsynchronized time. The energy manager identifies a predicted time for traversing among the sensors based on one or more distances between pairs of sensors and an average velocity of the object to traverse among the sensors. The energy manager determines a sensor time error for each sensor by cross-correlating the time measurements with the predicted time.

A slave apparatus (300) includes a clock extraction unit (310) and a time-point management unit (350). As long as the slave apparatus (300) receives serial data, the clock extraction unit (310) extracts a communication clock from the serial data being received. The time-point management unit (350) includes a timekeeper (351) driven based on the communication clock.

Systems and methods are provided for master media clock recovery. In various embodiments, recovering a master media clock may comprise receiving clock reference format (CRF) packets carrying timestamps (Ts). Differences of Ts between adjacent CRF packets may be calculated, and an average difference of Ts between adjacent timestamps may be calculated. A recovered frequency of a master clock may be based on the calculated average difference of Ts between adjacent timestamps. The recovered frequency may be used to regulate a timing of, for example, a kernel module and/or a media application.

A system for maintaining a Precision Time Protocol (PTP) hardware clock, the system being operative in conjunction with a network device which is external to the system, the system comprising a controller to receive information characterizing a network peer oscillator frequency, wherein the information was extracted from an RX symbol rate, and to adjust the PTP Hardware Clock's frequency responsive to the information characterizing the network peer oscillator frequency.