RADIO ACCESS NETWORKS

1 . A communication system comprising:

a plurality baseband units; and

a plurality of remote units communicatively coupled to the baseband units using a switched Ethernet network, the remote units configured to exchange radio frequency signals with user equipment;

wherein each baseband unit is associated with a respective subset of the remote units in order to serve a respective cell in connection with providing wireless service to at least some user equipment;

wherein each baseband unit is configured to communicate baseband data with the respective subset of the remote units associated with that baseband unit over the switched Ethernet network;

wherein each baseband unit is configured to perform at least some baseband processing associated with serving the respective cell;

wherein each remote unit is configured to perform at least some baseband processing associated with serving the respective cell using that remote unit; and

wherein the communication system is configured so that one of the baseband units is a master baseband unit and is configured to transmit time stamp messages with the remote units associated with the master baseband unit and with the remote units associated with the other baseband units of the plurality of baseband units.

2 . The communication system of claim 1 , wherein each baseband unit is configured to advance in time a subframe of baseband data to be delivered to each remote unit associated with that baseband unit to compensate for a time delay between a clock of that remote unit and a clock of that baseband unit.

3 . The communication system of claim 1 , wherein each baseband unit is configured to send information to the user equipment for the user equipment to advance a timing phase of the radio frequency signals to be transmitted to the respective remote units relative to the radio frequency signals received by the user equipment from the remote units.

4 . The communication system of claim 1 , wherein each remote unit uses the time stamp messages to estimate and correct an error of the remote unit clock, and wherein the estimation is based on a priori knowledge about downlink and uplink time stamp delays.

5 . The communication system of claim 4 , wherein the a priori knowledge about the downlink and uplink time stamp delays comprises a ratio of the downlink time stamp delay to the uplink time stamp delay.

6 . The communication system of claim 4 , wherein the a priori knowledge about the downlink and uplink time stamp delays comprises a ratio of an average downlink time stamp delay to an average uplink time stamp delay.

7 . The communication system of claim 4 , wherein the error comprises a timing phase error and each remote unit is configured to estimate the timing phase error by weighting and/or offsetting measured time stamps in the uplink and the downlink according to the a priori knowledge.

8 . The communication system of claim 1 , wherein the time stamp messages are transmitted with high priority according to the IEEE 802.1 q protocol.

9 . The communication system of claim 1 , wherein the time stamp messages and the baseband data are transmitted on different virtual local area networks (VLANs).

10 . The communication system of claim 1 , wherein the time stamp messages and the baseband data are transmitted on the same virtual local area network (VLAN) using different priority markings of the IEEE 802.1 q protocol.

11 . The communication system of claim 1 , wherein the baseband data and the time stamp messages are transmitted using dedicated Ethernet ports and dedicated Ethernet links of the switched Ethernet network.

12 . The communication system of claim 1 , wherein the master baseband unit is in direct coupling with a reference timing source and the remote units are not in direct coupling with the reference timing source.

13 . A method of wirelessly communicating using a communication system that comprises a plurality baseband units and a plurality of remote units communicatively coupled to the baseband units using a switched Ethernet network, wherein the remote units are configured to exchange radio frequency signals with user equipment, the method comprises:

associating each baseband unit with a respective subset of the remote units in order to serve a respective cell in connection with providing wireless service to at least some user equipment;

communicating baseband data over the switched Ethernet network between each baseband unit and the respective subset of the remote units associated with that baseband unit;

performing, by each baseband unit, at least some baseband processing associated with serving the respective cell using that baseband unit;

performing, by each remote unit, at least some baseband processing associated with serving the respective cell using that remote unit;

designating one of the baseband units as a master baseband unit; and

transmitting time stamp messages between the master baseband unit and the remote units associated with the master baseband unit and between the master baseband unit and the remote units associated with the other baseband units of the plurality of baseband units.

14 . The method of claim 13 , the method further comprises advancing in time, by each baseband unit, a subframe of baseband data to be delivered to each remote unit associated with that baseband unit to compensate for a time delay between a clock of that remote unit and a clock of that baseband unit.

15 . The method of claim 13 , the method further comprises sending, by each baseband unit, information to the user equipment for the user equipment to advance a timing phase of the radio frequency signals to be transmitted to the respective remote units relative to the radio frequency signals received by the user equipment from the remote units.

16 . The method of claim 13 , wherein using, by each remote unit, the time stamp messages to estimate and correct an error of the remote unit clock, and wherein the estimation is based on a priori knowledge about downlink and uplink time stamp delays.

17 . The method of claim 13 , wherein the time stamp messages are transmitted with high priority according to the IEEE 802.1 q protocol.

18 . The method of claim 13 , wherein the time stamp messages and the baseband data are transmitted on different virtual local area networks (VLANs).

19 . The method of claim 13 , wherein the time stamp messages and the baseband data are transmitted on the same virtual local area network (VLAN) using different priority markings of the IEEE 802.1 q protocol.

20 . The method of claim 13 , wherein the baseband data and the time stamp messages are transmitted using dedicated Ethernet ports and dedicated Ethernet links of the switched Ethernet network.