Over the air synchronization of network nodes

Abstract

The described technology is generally directed towards over the air synchronization of network nodes. In general, the techniques disclosed herein can be implemented by a first base station node device and a second base station node device. A wireless backhaul connection between the base station node devices allows the first base station node device to connect to a core network via the second base station node device. The techniques disclosed herein can be implemented as a protocol including communications back and forth between the base station node devices, which enables measurement of communication delays such as propagation delays and processing delays. The base station node devices can then use the measured communication delays to better synchronize clocks used to time radio frequency transmissions.

What is claimed is: 
     
         1 . A method, comprising:
 facilitating, by a first base station node comprising a processor, sending a delay test communication to a second base station node via a backhaul connection between the first base station node and the second base station node;   facilitating, by the first base station node, receiving a delay measurement communication comprising at least a measurement of propagation delay associated with the backhaul connection, wherein the measurement of propagation delay is based on the delay test communication; and   using, by the first base station node, the propagation delay to synchronize timing of transmissions via the backhaul connection between the first base station node and the second base station node.   
     
     
         2 . The method of  claim 1 , further comprising facilitating, by the first base station node, sending an offset correction communication to the second base station node via the backhaul connection. 
     
     
         3 . The method of  claim 2 , wherein the offset correction communication comprises a physical uplink shared channel transmission. 
     
     
         4 . The method of  claim 1 , further comprising facilitating, by the first base station node, receiving a delay test trigger communication from the second base station node, wherein sending the delay test communication is in response to receiving the delay test trigger communication. 
     
     
         5 . The method of  claim 4 , wherein sending the delay test communication comprises sending the delay test communication at a time indicated in the delay test trigger communication. 
     
     
         6 . The method of  claim 1 , wherein the delay test communication comprises a physical random access channel communication. 
     
     
         7 . The method of  claim 1 , further comprising:
 tracking, by the first base station node, reference signal transmissions from the second base station node;   using, by the first base station node, the reference signal transmissions to determine additional propagation delays; and   using, by the first base station node, the additional propagation delays to synchronize the timing of the transmissions via the backhaul connection between the first base station node and the second base station node.   
     
     
         8 . The method of  claim 1 , further comprising using, by the first base station node, in addition to the propagation delay, a processing delay at the first base station node to synchronize the timing of the transmissions via the backhaul connection between the first base station node and the second base station node. 
     
     
         9 . Base station equipment, comprising:
 a processor; and   a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations, comprising:   receiving, from a first base station equipment, a delay test communication;   using the delay test communication to measure at least a propagation delay associated with a backhaul connection between the first base station equipment and the base station equipment; and   sending, to the first base station node device, a delay measurement communication comprising at least the propagation delay, wherein the propagation delay is applicable at the first base station equipment to synchronize timing of transmissions via the backhaul connection between the first base station equipment and the base station equipment.   
     
     
         10 . The base station equipment of  claim 9 , wherein the operations further comprise receiving an offset correction communication from the first base station equipment via the backhaul connection, and sending a delay test trigger communication to the first base station equipment in response to receiving the offset correction communication. 
     
     
         11 . The base station equipment of  claim 10 , wherein the delay test trigger communication comprises a contention free physical random access channel trigger communication. 
     
     
         12 . The base station equipment of  claim 11 , wherein the contention free physical random access channel trigger communication is sent as a physical downlink control channel or as a physical downlink shared channel transmission. 
     
     
         13 . The base station equipment of  claim 10 , wherein the operations further comprise sending the delay test trigger communication to different base station equipment of a group of base station equipment. 
     
     
         14 . The base station equipment of  claim 10 , wherein using the delay test communication to measure at least the propagation delay associated with the backhaul connection between the first base station equipment and the base station equipment comprises determining a time difference between sending the delay test trigger communication and receiving the delay test communication. 
     
     
         15 . The base station equipment of  claim 10 , wherein using the delay test communication to measure at least the propagation delay associated with the backhaul connection between the first base station equipment and the base station equipment comprises determining a time difference between a first time indicated in the delay test trigger communication and a second time associated with the receiving the delay test communication. 
     
     
         16 . The base station equipment of  claim 9 , wherein using the delay test communication to measure at least the propagation delay associated with the backhaul connection between the first base station equipment and the base station equipment comprises translating between a baseband time reference at the base station equipment and a radio frequency time reference at the base station equipment to account for a processing delay at the base station equipment. 
     
     
         17 . The base station equipment of  claim 10 , wherein the operations further comprise:
 tracking reference signal transmissions from the first base station equipment;   using the reference signal transmissions to determine additional propagation delays; and   sending additional delay measurement trigger communications to the first base station equipment to correct for the additional propagation delays.   
     
     
         18 . A non-transitory machine-readable medium, comprising executable instructions that, when executed by a processor of a first base station, facilitate performance of operations, comprising:
 transmitting a delay test communication via a wireless backhaul connection between the first base station and a second base station;   receiving a delay measurement communication comprising at least a measurement of propagation delay associated with the wireless backhaul connection between the first base station and the second base station; and   using, by the first base station, the propagation delay to synchronize timing of wireless transmissions via the wireless backhaul connection.   
     
     
         19 . The non-transitory machine-readable medium of  claim 18 , wherein the operations further comprise receiving a delay test trigger communication from the second base station, and wherein transmitting the delay test communication is in response to receiving the delay test trigger communication. 
     
     
         20 . The non-transitory machine-readable medium of  claim 19 , wherein using the delay test communication to measure the propagation delay comprises at least one of:
 determining a time difference between the delay test trigger communication and the delay test communication;   determining a time difference between a time indicated in the delay test trigger communication and a time associated with the delay test communication; or   translating between a baseband time reference at a base station of the base stations and a radio frequency time reference at the base station.