Digital radio head system and method
An improved digital radio head system and method for wireless communications is disclosed that simplifies the timing and synchronization between the access network, base station, and radio head. A satellite derived timing source is obtained at one or more of the remote radio heads where it is convenient to obtain and use the timing reference. The reference is transmitted back to the base station, if necessary, to synchronize the two. This is further synchronized at a lower accuracy through the access network.
1 . A wireless communications system, comprising:
a base station receiving communications signals from an access network;
one or more radio heads remotely configured from the base station and coupled for communication to the base station over a wired transmission link, each radio head coupled to one or more antennas to transmit and receive wireless communications signals;
a satellite receiver antenna configured at the radio head location;
a timing generator configured at the radio head location and coupled to the satellite receiver antenna, the timing generator extracting timing information from a satellite signal received at the satellite receiver antenna and providing timing signals to the radio head and to the base station, wherein the base station and radio head employ the timing signals to synchronize transmission of communications signals along the wired transmission link between the base station and radio head.
2 . A wireless communications system as set out in claim 1 , wherein the satellite receiver antenna is a GPS receiver and the satellite signal is a GPS signal.
3 . A wireless communications system as set out in claim 1 , wherein the wired transmission link is a transmission line or an optical fiber.
4 . A wireless communications system as set out in claim 1 , wherein the timing information from the satellite signal comprises a frequency reference and wherein the timing generator comprises a clock filter to filter the frequency reference.
5 . A wireless communications system as set out in claim 4 , wherein the timing information from the satellite signal further comprises a periodic real time reference signal and wherein the timing generator further comprises a framer to provide frames referenced to points in real time derived from the periodic real time reference signal.
6 . A wireless communications system as set out in claim 5 , wherein the timing generator further comprises a time stamper which adds a stamp to the timing signal indicating the precise time for a fixed reference point in each frame.
7 . A wireless communications system as set out in claim 1 , wherein the one or more radio heads comprise a plurality of separate radio heads coupled together through a wired link and wherein one radio head is coupled to the base station through said wired transmission link.
8 . A wireless communications system, comprising:
a transport module receiving communications signals from an access network;
one or more radio heads remotely configured from the transport module, each radio head coupled to one or more antennas to transmit and receive wireless communications signals;
a baseband processing module configured at the radio head location and coupled to the radio head, wherein the baseband processing module is also coupled to the transport module over a wired transmission link and receives and sends user data to and from the transport module also; and
a timing generator configured at the radio head location and providing timing signals to the baseband processing module and radio head.
9 . A wireless communications system as set out in claim 8 , wherein the baseband processing module provides physical layer processing.
10 . A wireless communications system as set out in claim 9 , wherein the baseband processing module provides MAC layer processing.
11 . A wireless communications system as set out in claim 8 , wherein the wired transmission link is a transmission line or an optical fiber.
12 . A wireless communications system as set out in claim 8 , wherein the timing generator also provides timing signals to the transport module.
13 . A wireless communications system as set out in claim 8 , further comprising a satellite receiver antenna configured at the radio head location and wherein the timing generator extracts timing information from a satellite signal received at the satellite receiver antenna to provide said timing signals to the radio head and to the baseband processing module.
14 . A wireless communications system as set out in claim 12 , wherein the satellite signal is a GPS signal.
15 . A wireless communications system as set out in claim 8 , wherein the one or more radio heads comprise a plurality of separate radio heads coupled together through a wired link and wherein one radio head is coupled to the transport module through said wired transmission link via said baseband processing module.
16 . A method for providing a communications signal from a first location at an access-network connection point to a second location adjacent one or more antennas located remotely from said first location for wireless transmission at said second location, comprising:
receiving a communications signal from an access-network connection point at the first location;
transmitting the communications signal in digital form along a wired transmission link to the second location located remotely from said first location;
deriving a timing signal at the second location using an external reference timing source;
performing baseband processing on the digital communications signal at said second location using said timing signal; and
providing the baseband processed signal to a radio head at the second location.
17 . A method as set out in claim 16 , wherein the baseband processing comprises physical layer processing of the digital communications signals.
18 . A method as set out in claim 17 , wherein the baseband processing further comprises MAC layer processing of the digital communications signals.
19 . A method as set out in claim 16 , wherein deriving a timing signal at the second location using an external reference timing source comprises extracting timing information from a satellite signal received at a satellite receiver antenna configured at the second location.
20 . A method as set out in claim 16 , further comprising providing the timing signal derived at the second location to said first location for synchronizing transmitting of the communications signal along the wired transmission link between the first and second locations.