US2014101508A1PendingUtilityA1
Hybrid error-control algorithm
Est. expiryAug 30, 2020(expired)· nominal 20-yr term from priority
Inventors:Jack Lee
H04L 1/1809H04L 1/1812H04L 12/1863H04L 1/1819
36
PatentIndex Score
0
Cited by
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References
0
Claims
Abstract
An embodiment of the invention includes an efficient error-control system and method for recovering packet losses, especially losses in distributing multicast video over broadband residential networks. Preferably, unlike most existing error-control algorithms designed for Internet multicast, the system and method does not employ substantial feedback suppression. Preferably, the system and method does not employ substantial multicasted retransmission. Preferably, the system and method does not employ substantial parity retransmission. Preferably, the system and method does not employ substantial local loss recovery. The system and method integrates two existing classes of error-control algorithms: Automatic Repeat Request (ARQ) and Forward Error Correction (FEC), to reduce traffic overhead and achieve scalability.
Claims
exact text as granted — not AI-modified1 . A method for handling communication errors in a communication system for distributing video, the method comprising:
initiating transmission of an intended group of packets of a video signal, the intended group of packets including a set of data and error-correcting information for the set of data; receiving an indication of at least some data, of the set of data, that failed to be correctly received at a receiver among a plurality of receivers; in response to the indication, retransmitting a second group of packets, the second group of packets comprising less than all data, of the set of data, that failed to be correctly received at the receiver; wherein less than all data that failed to be correctly received at the receiver is retransmitted in the retransmitting step, and the receiver will be able to obtain the all data, of the set of data, that failed to be correctly received at the receiver by performing forward error correction with the retransmitted second group of packets, once received, and correctly received portions of the intended group of packets, as received from the transmission that was initiated in the initiating step; and buffering data at a transmission server which transmits the intended group of packets and at each receiver which receives the intended group of packets to support error correction by both retransmission at the transmission server and the forward error correction at the receiver and to allows for continuous play of the video signal at each receiver.
2 . The method according to claim 1 , wherein the communication system comprises a residential broadband network.
3 . The method according to claim 1 , wherein the transmission is a portion of a multicast of the video.
4 . The method according to claim 1 , wherein the transmission of the intended group of packets to the receiver is not over the Internet.
5 . The method according to claim 1 , wherein the retransmitting is a unicasting.
6 . The method according to claim 1 , wherein the indication is received, in the receiving step, via a unicast from the receiver.
7 . The method according to claim 1 , further comprising, at the receiver:
sending the indication, wherein the indication indicates less than all data, of the set of data, that failed to be correctly received at the receiver, wherein the retransmitting step includes retransmitting all data indicated in the indication.
8 . The method according to claim 7 , wherein the sending step is initiated without waiting for all packets of the intended group of packets to either arrive at the receiver or be determined as being lost to the receiver.
9 . The method according to claim 8 , wherein the retransmitting step is initiated before every packet of the intended group of packets has either arrived at the receiver or been lost to the receiver.
10 . The method according to claim 1 , wherein:
some packets of the intended group of packets were not correctly received at the receiver; and the method further comprises identifying a minimally-sized set of packets, of the some packets that were not correctly received at the receiver, that would enable recovery at the receiver of all data, of the set of data, not correctly received at the receiver.
11 . The method according to claim 10 , wherein:
the intended group of packets includes D intended data packets and R intended redundancy packets and no other data packets or redundancy packets, wherein D and R are positive integers; M packets of the intended group of packets were not correctly received at the receiver, wherein M is a positive integer greater than R; and the step of identifying a minimally-sized set of packets comprises identifying a set of M minus R packets, of the M packets that were not correctly received at the receiver.
12 . The method according to claim 11 , further comprising, at the receiver:
initiating sending at least a portion of the indication if at least R plus one packets of the intended group of packets were not correctly received at the receiver, even before every packet of the intended group of packets has either arrived at the receiver or been determined as being lost to the receiver.
13 . The method according to claim 1 , further comprising, at the receiver:
receiving the retransmitted second group of packets; and performing erasure correction on the second group of packets and the correctly received portions of the intended group of packets whose transmission was initiated in the initiating step to thereby obtain the all data, of the set of data, that failed to be correctly received at the receiver.
14 . A method for receiving video content at a receiver, the method comprising:
receiving packets from a multicasted group of packets, wherein the multicasted group of packets include data and error-correction information for the data; if packets received without error in the receiving step include less than all the data, whereby some of the data has been lost, hereinafter referred to as lost data, then: sending a message based on identity of at least some of the lost data; receiving a retransmission triggered by the sent message, wherein the retransmission includes less than all of the lost data; recovering all of the lost data using information from the packets received without error in the receiving packets step and using the received retransmission; and buffering received data at the receiver, including data of retransmission, to allow for continuous play of the video content received at the receiver.
15 . The method according to claim 14 , wherein the message identifies and requests retransmission of less than all lost data packets of the multicasted group of packets; and wherein the retransmission includes retransmission of the less than all lost data packets of the multicasted group of packets.
16 . The method according to claim 15 , wherein the sending step includes sending at least a portion of the message, even before every packet of the multicasted group of packets has either arrived at the receiver or been determined as lost to the receiver.
17 . The method according to claim 1 , wherein the intended group of packets includes D intended data packets and R intended redundancy packets and no other data packets or redundancy packets, wherein R and D are positive integers, and wherein the receiver has a buffer defined by:
L
hybrid
(
i
)
=
[
(
K
i
-
1
)
(
T
~
S
+
T
tran
+
2
(
T
i
+
T
i
+
)
)
+
(
T
i
+
-
T
i
-
)
T
~
S
]
+
[
T
i
+
-
T
i
-
T
~
S
]
+
D
+
R
+
1
wherein
represents a receiver i of N receivers (0≦i≦N) and N is a positive integer and represents the number of receivers in the system;
K
i
=
[
ln
ρ
max
ln
ɛ
i
]
ɛ
i
=
∑
k
=
R
+
1
D
+
R
(
D
+
R
k
)
ρ
i
k
(
1
-
ρ
i
)
R
+
D
-
k
k
D
+
R
p max is a maximum tolerable packet-loss probability for the data;
p i is a pack loss probability experienced by receiver i; and
ε i is a residual loss probability of a receiver i;
T tran is a transmission time;
{tilde over (T)} S is an inter-packet time; and
T i + and T i − are the maximum delay jitters between a receiver i and the server, and T i ′≧0, T i ″≦0.
18 . The method according to claim 17 , wherein the transmission server has a buffer defined by:
B
hybrid
=
Q
S
(
D
+
R
)
[
r
i
K
i
-
1
DT
S
]
where
r
i
K
i
-
1
=
r
~
i
+
(
T
i
+
T
i
+
)
+
(
K
i
-
2
)
(
T
tran
+
2
(
T
i
+
T
i
+
)
)
and
r
~
i
=
(
D
+
R
-
1
)
T
~
S
+
T
tran
+
T
i
+
T
i
+
wherein Qs is a byte size of one packet and Ts is a period of one packet.
19 . The method according to claim 1 , wherein the intended group of packets includes D intended data packets and R intended redundancy packets and no other data packets or redundancy packets, wherein R and D are positive integers,
wherein a traffic overhead of the system defined as a ratio between traffic at the server incurred in error recovery and traffic at the server for normal delivery of video signals is:
H
hybrid
(
R
)
=
R
D
=
h
(
R
)
where
h
(
R
)
=
1
D
∑
i
=
0
N
-
1
∑
m
=
R
+
1
D
+
R
(
m
-
R
)
h
i
(
D
+
R
m
)
p
i
m
(
1
-
p
i
)
D
+
R
-
m
=
1
D
∑
i
=
0
N
-
1
∑
m
=
R
+
1
D
+
R
∑
j
=
1
K
i
-
1
(
D
+
R
m
)
j
(
m
-
r
)
p
i
m
+
j
-
1
(
1
-
p
i
)
D
+
R
-
m
+
1
and
h
i
=
∑
j
=
1
K
i
-
1
j
(
p
i
j
-
1
(
1
-
p
i
)
)
K
i
=
[
ln
ρ
max
ln
ɛ
i
]
ɛ
i
(
R
)
=
∑
k
=
R
+
1
D
+
R
k
D
+
R
Φ
i
(
k
)
Φ
i
(
k
)
=
∑
m
=
k
D
+
R
(
m
-
R
k
-
R
)
(
p
i
K
i
-
1
)
k
-
R
(
1
-
p
i
K
i
-
1
)
m
-
k
(
D
+
R
m
)
p
i
m
(
1
-
p
i
)
D
+
R
-
m
,
k
≥
R
wherein
H hybrid (R) is the traffic overhead of the system,
N is the number of receivers in the system,
i means the receiver i, and 0≦i≦N,
p max is a maximum tolerable packet-loss probability for the data,
p i is a pack loss probability experienced by receiver I,
ε i is a residual loss probability of a receiver I;
the method further comprising selecting the redundancy R to be a value between 0 and
R FEC =min{ R|ε i ≦ρ max ,∀i}
to minimize H hybrid (R).
20 . A method for delivering video in a broadband network, comprising:
buffering video data, retransmission data for implementing automatic repeat request and redundancy data for implementing forward error correction at a server and each of a plurality of receivers in the network to support error correction by both retransmission under the automatic repeat request and the forward error correction; configuring buffer space at the receiver and each receiver, to allow for continuous play of the video received at the receiver; and performing both retransmission under the automatic repeat request and the forward error correction to correct errors in video data received at each receiver to reduce traffic overhead at the server.
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