Synchronizing data transmission over wireless networks
View Patent ↗Techniques for providing an uninterrupted data stream to a mobile node are disclosed. In a first technique, a time stamp is inserted at some point in the wireless network and the time stamp is used along with a tolerance value to determine when to transmit a packet in a data stream. By transmitting the packets at the same adjusted time, transmission to mobile nodes is synchronized. A second technique uses duplication of data stream content to avoid an interruption in the data stream at a mobile node. A third technique uses an error correcting code to avoid interruption of the data stream at a mobile node. A fourth technique uses a sequence number inserted into packets in the data stream at the content server to synchronize transmission to mobile nodes.
1. A method of synchronizing transmission to a plurality of mobile nodes comprising:
synchronizing a counter of a packet control function (PCF) with other PCF counters on a wireless network;
selecting a modulo number to calculate a remainder for each sequence number; and
transmitting a packet in a data stream when the counter equals the remainder of the sequence number of the packet in the data stream.
2. The method of claim 1 , wherein a PCF maintains a jitter buffer for buffering the data stream received by the PCF.
3. The method of claim 2 , wherein the size of the jitter buffer is sufficient to store the data received during a maximum expected delay between a content server and the PCF.
4. The method of claim 1 , further comprising inserting a sequence number at a content server to each packet in the data stream.
5. The method of claim 1 , wherein the sequence number is inserted in an IP Header or GRE Header.
6. The method of claim 1 , wherein the sequence number is inserted in a custom packet header.
7. A system for transmitting packets synchronously to mobile nodes comprising:
means for synchronizing a counter of a packet control function (PCF) with other PCF counters on a wireless network;
means for calculating a remainder for a sequence number in a packet; and
means for transmitting a packet in a data stream when the counter equals the remainder of the sequence number of the packet in the data stream.
8. The system of claim 7 , wherein the means for transmitting a packet maintains a jitter buffer for buffering the data stream received by the PCF.
9. The system of claim 8 , wherein the jitter buffer for buffering the data stream is sized according to the rate of incoming packets and the delay experienced on the network.
10. The system of claim 7 , wherein the means for synchronizing a counter involves a network time protocol.
11. The system of claim 7 , wherein the sequence number is stored in a custom generic routing encapsulation (GRE) header.
12. The system of claim 11 , wherein the sequence number is 32 bits long.
13. A system for transmitting packets synchronously to mobile nodes comprising:
a packet control function (PCF) which is coupled to a content server and a base station in a network;
wherein the PCF contains a counter which is synchronized with other PCFs on the network; and
wherein the PCF calculates a remainder for a sequence number in a packet and transmits the packet when the counter equals the remainder of the sequence number.
14. The system of claim 13 , wherein the PCF contains a jitter buffer for buffering the data stream which is sized according to the rate of incoming packets and the delay experienced on the network.
15. The system of claim 13 , wherein the sequence number is placed in the packet at the content server.