Header compression for real time internet applications

1. A method of compressing a header of a packet for transmission, comprising:

monitoring a sequence of real-time transport protocol, RTP, sequence numbers to identify at least one of missing or out of order packets;

compressing, by a compressor, a RTP header portion of the packet by eliminating the RTP sequence number from the RTP header portion; and

generating radio link control RLC unacknowledged mode UM sequence numbers for packets after the compressing step based on the monitoring step such that a sequence of RLC UM sequence numbers corresponds to the monitored sequence of RTP sequence numbers.

2. The method of claim 1 , further comprising:

performing robust header compression on the packet such that the resulting compressed header includes a compressed RTP header portion, and the compressed RTP header portion includes a number of bits conveying the RTP sequence number; and wherein

the compressing step eliminates the bits conveying the RTP sequence number from the compressed RTP header portion.

3. The method of claim 2 , wherein

the compressed RTP header portion includes a packet type identifier and a number of bits conveying the RTP sequence number; and wherein

the compressing step eliminates the packet type identifier and the bits conveying the RTP sequence number.

4. The method of claim 1 , further comprising:

storing packets in a buffer; and

outputting the stored packet in sequence for compression according to the RTP sequence numbers of the packets.

5. A method of decompressing a header of a received packet, comprising:

reconstructing, by a decompressor, a real-time transport protocol, RTP, sequence number for an RTP header portion of the received packet based on a received radio link control, RLC, unacknowledged mode, UM, sequence number associated with the packet; and

sending, by the decompressor, reconstructed packets to higher layers in a protocol stack even if the reconstructed RTP sequence numbers are not in order,

wherein the reconstructing step combines a previously determined offset with the RLC UM sequence number to obtain the RTP sequence number.

6. The method of claim 5 , wherein the reconstructing step uses the RLC UM sequence number as the RTP sequence number.

7. A method of decompressing a header of a received packet, comprising:

generating, by a decompressor, a user data protocol, UDP, checksum for the received packet;

inserting, by the decompressor, the generated UDP checksum into a UDP header portion of the received packet;

reconstructing, by the decompressor, a real-time transport protocol, RTP, sequence number for an RTP header portion of the received packet based on a received radio link control, RLC, unacknowledged mode, UM, sequence number associated with the packet; and

sending, by the decompressor, reconstructed packets to higher layers in a protocol stack even if the reconstructed RTP sequence numbers are not in order,

wherein the reconstructing step combines a previously determined offset with the RLC UM sequence number to obtain the RTP sequence number.

8. A method of compressing a header of a packet for transmission, comprising:

converting a user data protocol, UDP, portion of the packet to UDP-Lite; and

compressing, by a compressor, the packet according to the robust header compression, RoHC,

wherein the converting step comprises:

overwriting a length in a UDP header portion of the UDP portion with a coverage field according to UDP-Lite;

changing an internet protocol, IP, identifier in an IP header portion of the packet to a value indicating UDP-Lite;

generating a checksum for a coverage indicated by the coverage field; and

replacing a UDP checksum in the UDP header portion with the generated checksum.

9. The method of claim 8 , wherein the coverage field indicates a UDP-Lite header portion and the IP header portion as the coverage.

10. The method of claim 8 , wherein the compressing step further comprises:

compressing a real-time transport protocol, RTP, header portion of the packet by eliminating a RTP sequence number from the RTP header portion.

11. A method of decompressing a header of a received packet, comprising:

converting a user data protocol-Lite, UDP-Lite, portion of the received packet to UDP; and

decompressing, by a decompressor, the received packet according to robust header compression, RoHC,

wherein the converting step comprises:

overwriting a coverage field in a UDP-Lite header portion of the UDP-Lite portion with a length field according to UDP;

changing an internet protocol, IP, identifier in an IP header portion of the packet to a value indicating UDP;

generating a UDP checksum for the received packet; and

replacing a UDP-Lite checksum in the UDP-Lite header portion with generated UDP checksum.

12. The method of claim 11 , wherein

the converting step converts the UDP-Lite portion of the received packet to UDP only if an application to which the received packet is destined does not support UDP-Lite.

13. The method of claim 11 , further comprising:

reconstructing a real-time transport protocol, RTP, sequence number for an RTP header portion of the received packet based on a received radio link control, RLC, unacknowledged mode, UM, sequence number associated with the packet.

14. The method of claim 1 , wherein the RLC UM sequence number for packets uses the same packet order as the RTP sequence number.