Hybrid ARQ system with a snapshot feedback mechanism for interference prone wireless networks
View Patent ↗An IP packet transmission system is disclosed and more specifically it is a system using a hybrid ARQ method including a sliding purge window and having the transmitter opportunistically piggy-back a snapshot of the transmitter's transmit/send window in data frames. When the receiver receives this snapshot the receiver can compare it with its receive window and if a mismatch is detected, whereby the transmitter has moved on to the next packet, the receiver can now also sync up quicker and not wait for the regular timeout to progress ahead.
1. A sliding purge window and snapshot feedback method to reduce packet losses and synchronization time, and improve transport control protocol throughput in a wireless network between a receiver having a receive window, fed by a fragmentation buffer and a re-assembly buffer to re-assemble fragments of packets received, and a transmitter having a transmission window and that monotonically assigns each packet sent by the transmitter with a packet ID number up to a maximum packet ID number, said wireless network using a Hybrid Automatic Repeat Request transmission scheme having a re-transmission logic that ensures an oldest unacknowledged packet is re-transmitted first wherein the sliding purge window method ensures that the packets in the receive window match the packets in the transmission window such that if there is a transmission error the Hybrid Automatic Repeat Request transmission scheme recovers and the receiver and transmitter remain in synchronization comprising:
said receiver having a sliding purge window;
setting a threshold packet number for said sliding purge window that is less than the maximum packet ID number;
said receiver purging an oldest received packet from said re-assembly buffer and fragmentation buffer each time a fragment is received by said receiver that belongs to a packet having a packet ID number that is greater than the packet ID number of a packet in the fragmentation buffer and re-assembly buffer by said threshold packet number;
said transmitter regularly storing a snapshot of the packets in the transmission window and said transmitter sending said snapshot to said receiver when transmission bandwidth allows; and,
then said receiver receiving and comparing said snapshot to packets in said sliding purge window and when the comparison shows a difference in said snapshot and said sliding purge window nonmatching packets in said sliding purge window are purged by said receiver.
2. The sliding purge window and snapshot feedback method of claim 1 further comprising:
said receiver purging an oldest received packet from said re-assembly buffer and fragmentation buffer each time a new fragment is received by said receiver that belongs to a packet having a packet ID number greater than the packet ID number of a packet in the fragmentation buffer and re-assembly buffer and a difference between the packet ID number of said new fragment and the packet ID number of said packet in the fragmentation buffer and re-assembly buffer is greater than said threshold packet number; and,
said receiver purging an oldest received packet from said re-assembly buffer and fragmentation buffer each time a new fragment is received by said receiver that belongs to a packet having a packet ID number less than the packet ID number of said packet in the fragmentation buffer and re-assembly buffer and a difference between said maximum packet ID number and the packet ID number of said packet in the fragmentation buffer and re-assembly buffer then added to the packet ID number of said new fragment is less than said threshold packet number.