Patent ID: 8873543
Filing Date: 2014-10-28
Classification: H04L

Abstract:
1. A method for a first Voice over Internet Protocol (VoIP) device to communicate with a second VoIP device over an Internet Protocol (IP) network, comprising: communicating at least one dual-tone multi-frequency (DTMF) code with the second VoIP device over a telephone network to synchronize time between the first and the second VoIP devices; recording a local time at the first VoIP device when the first and the second VoIP devices are synchronized by said communicating as a first synchronization base time; keeping a first synchronization time comprising the local time at the first VoIP device minus the first synchronization base time; transmitting a first voice packet to the second VoIP device over the IP network, the first voice packet including the first synchronization time when the first voice packet was transmitted; receiving a second voice packet from the second VoIP device over the IP network, the second voice packet including a second synchronization time when the second voice packet was transmitted from the second VoIP device, the second synchronization time comprising a local time at the second VoIP device minus a second synchronization base time at the second VoIP device, the second synchronization base time comprising the local time at the second VoIP device when the first and the second VoIP devices are synchronized from said communicating; determining a network delay as a difference between the first and the second synchronization times; determining a missing voice packet from the second VoIP device after placing the second voice packet in a jitter buffer at the first VoIP device; determining an energy level of the missing voice packet from a recent frame energy (RFE) list in the second voice packet; generating a recent lost index (RLI) list identifying the missing voice packet, wherein the missing voice packet is included in the RLI list when the energy level is higher than a threshold; and transmitting a third voice packet to the second VoIP device including the RLI list.