Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-12-17
2003-07-29
Ton, Dang (Department: 2666)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S252000, C370S395520, C370S512000, C375S226000
Reexamination Certificate
active
06600759
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to communication systems and more specifically to an apparatus and method for estimating jitter invoice packets received over a network running the Internet Protocol (IP).
BACKGROUND OF THE INVENTION
The Internet Engineering Task Force (IETF) has developed a standard for transmission of voice traffic over packet data networks running the Internet Protocol. This Real Time Protocol (RTP) is defined in RFC 1889. The Real Time Protocol requires an estimate of the jitter in the arrival time of each received voice packet (referred to herein as the interarrival jitter). A value for the interarrival jitter is required for each voice stream, and the calculation is required to be performed every time that a voice packet is received.
Traditionally, the value for interarrival jitter has been calculated using software algorithms. However, this calculation represents significant processing overhead when many separate voice streams are being received simultaneously.
SUMMARY OF THE INVENTION
According to the present invention, a system is provided for estimating interarrival jitter in real time, using hardware elements. The apparatus of the present invention is capable of processing orders of magnitude more packetized voice streams than prior art software implementations. According to a preferred embodiment of the invention, a plurality of registers and arithmetic units are used to process packet spacing values to generate an estimate of the packet interarrival jitter. The hardware elements are controlled by a state machine whose operation is initiated by the reception of a packet of voice data.
REFERENCES:
patent: 4569042 (1986-02-01), Larson
patent: 4894823 (1990-01-01), Adelmann et al.
patent: 5260978 (1993-11-01), Fleischer et al.
patent: 5640388 (1997-06-01), Woodhead et al.
patent: 5790543 (1998-08-01), Cloutier
IETF RFC 1889, “RTP: A Transport Protocol for Real Time Applications”, Jan. 1996, Schulzrinne et al.
Tomi Yletyinen, et al., “Voice Packet Interarrival Jitter Over IP Switching”, Helsinki University of Technology, ITS'98 Proceedings, SBT/IEEE International Telecommunications Symposium (Cat. No. 98EX202), part vol. 1, p. 16-21.
Hom Shick
Keating & Bennett LLP
Mitel Corporation
Ton Dang
LandOfFree
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