Time stamp and packet virtual sequence numbering for reconstructing information signals from packets
AssigneeAmerican Telephone and Telegraph Company, AT&T Bell Laboratories
InventorsHarry W. Adelmann, James D. Tomcik
Life of this patent
Estimating the term…
Abstract
Unwanted distortion in signals being reconstructed from packets is substantially eliminated by employing a virtual sequence packet numbering scheme in conjunction with a time stamp value. A virtual sequence number which accompanies the packet identifies the location of the packet in an information spurt. If the packet is the initial packet in the information spurt, the time stamp value is used to "build out" the delay experienced by the packet to a fixed overall value. Subsequent packets in the information spurt are concatenated to the information spurt. A packet following one or more lost packets is also identified by the packet virual sequence number and is also treated as an initial packet.
Claims27
Apparatus for transmitting packets, comprising,
- means for generating a packet including at least a packet header sequence number field,
- means for generating a repeating sequence of numbers,
- means for identifying the first packet in an information spurt, and
- means for inserting one of the numbers of said sequence of numbers into said packet header sequence number field for a packet being generated and for inserting a distinct number in place of said one of the numbers from said sequence of numbers when the packet being generated is identified as the first packet in the information spurt.
Apparatus for reformatting digital samples from packets, each of the packets including an information field and a header having at least a time stamp field, the apparatus comprising,
- means for storing packet information fields,
- means for generating a local time signal,
- means for obtaining a packet originate time value for each received packet, said last named means including means for obtaining the difference between the value of the local time signal upon a packet arriving at the apparatus and a value from the time stamp field from said arriving packet, and
- means responsive to said packet originate time value for each of said received packets and said local time signal for controllably reading out samples from the stored information field for each of said received packets from said means for storing so that a fixed overall delay interval is obtained for each of said received packets.
Apparatus for reformatting digital samples from packets, comprising,
- means for storing packet information fields,
- means for generating a local time signal,
- means for obtaining a packet sequence number for a particular packet,
- means for generating a first time value representative of a local time signal value at which reading out of samples of the particular packet information field from said means for storing is to be initiated,
- means responsive to said packet sequence number for generating an indication signal indicative of whether said particular packet is a scheduled packet, and
- means responsive to said indication signal, said first time value and said local time signal for controlling delay in reading out samples of the information field for said particular packet from said means for storing so that a fixed overall delay is obtained.
Apparatus for reformatting digital samples from packets, comprising,
- means for storing packet information fields,
- means for obtaining a packet sequence number for a particular packet, said sequence number being a number in a predetermined first virtual sequence or a distinct number replacing one of said numbers in said first virtual sequence when said particular packet is an initial packet in an information spurt,
- means responsive to said packet sequence number for generating an indication signal indicative of whether said particular packet is a scheduled packet, said indication signal having a first state when said particular packet is a scheduled packet and a second state when said particular packet is not a scheduled packet, said indication signal generating means being responsive to said distinct number to generate said first state indication signal for the corresponding particular packet, and
- means responsive to said indication signal for controlling delay in reading out samples of the information field for said particular packet from said means for storing so that a fixed overall delay is obtained.
A method for transmitting packets, comprising the steps of,
- generating a packet including at least a packet header sequence number field,
- generating a repeating sequence of numbers,
- inserting one of the numbers of said sequence of numbers into said packet header sequence number field for a packet being generated,
- identifying the first packet in an information spurt, and
- inserting a distinct number in place of said one of the numbers from said sequence of numbers when the packet being generated is identified as the first packet in the information spurt.
A method of reformatting digital samples from packets, each of the packets including an information field and a header having at least a time stamp field, comprising the steps of,
- storing packet information fields,
- generating a local time signal,
- obtaining a packet originate time value for a particular packet, said last step including the step of obtaining the difference between the value of the local time signal upon said particular packet arriving and a value from the time stamp field from said particular arriving packet, and
- utilizing said packet originate time value for said particular packet and said local time signal for controllably reading out samples from the stored information field for said particular packet so that a fixed overall delay interval is obtained.
A method of reformatting digital samples from packets, comprising the steps of,
- storing packet information fields,
- generating a local time signal,
- obtaining a packet sequence number for a particular packet,
- generating in response to said sequence number an indication signal indicative of whether said particular packet is a scheduled packet,
- generating a first time value representative of a local time signal value at which reading out of samples of the stored information field for said particular packet is to be initiated, and
- utilizing said indication signal, said first time value and said local time signal for controlling delay in reading out samples from the stored information field for said particular packet so that a fixed overall delay interval is obtained.
A system including a transmitter for generating packets to be transmitted to a remote receiver where they are reformatted into digital samples, comprising, in the transmitter,
- means for generating a packet including at least a packet header sequence number field,
- means for generating a repeating sequence of numbers,
- means for identifying the first packet in an information spurt, and
- means for inserting one of the numbers of said sequence of numbers into said packet header sequence number field for a packet being generated and for inserting a distinct number in place of said one of the numbers from said sequence of numbers when the packet being generated is identified as the first packet in the information spurt, and in the receiver, apparatus for reformatting digital samples form packets, comprising,
- means for storing packet information fields,
- means for obtaining a packet sequence number for a particular packet from said packet header sequence nubmer field, and
- means responsive to said packet sequence number for controlling delay in reading out samples of the information field for said particular packet from said means for storing so that a fixed overall delay is obtained.
Dependencies are inferred from the claim text.