DSS packet reordering function

Details DSS packet reordering function DSS packet reordering function

2000-08-03

2004-08-24

Chin, Stephen (Department: 2634)

Pulse or digital communications

Systems using alternating or pulsating current

Plural channels for transmission of a single pulse train

C375S130000

Reexamination Certificate

active

06782056

ABSTRACT:

FIELD OF THE INVENTION
The present invention involves a data packet reordering system, and in particular a system for reordering digital spread spectrum (DSS) data packets using a reduced memory buffer.
BACKGROUND OF THE INVENTION
In Direct-TV data protocol, program guides are sent as a collection of data packets.
FIG. 1A
shows a DSS transmitter
101
that transmits DSS data packets that are received by a DSS receiver
102
and routed to a SDRAM
103
. The packets are stored in a random order.
FIG. 1B
shows a typical SDRAM
103
with data packets (P
0
-P
8
)
105
stored at different locations
104
, illustrated as L
0
-L
8
.
FIG. 1B
shows a first set of data packets
106
(packets P
0
-P
4
) stored at memory locations L
4
to L
8
respectively and a second set of data packets (P
5
-P
8
)
107
stored at memory locations L
0
to L
3
respectively.
However for efficient processing, the packets should be stored in the order illustrated in
FIG. 1C
, i.e. packet P
0
should be stored in location L
0
, P
1
in location L
1
and so forth.
Currently a second memory buffer is used to reorder the data packets as they are received.
FIG. 1D
shows a second memory buffer
111
used for reordering data packets. When the first set
106
is received, in step S
101
, packets P
0
-P
4
are moved to memory buffer
111
. In step S
102
, data packets in second set
107
(P
5
-P
8
) are moved to the desired locations, L
5
-L
8
, as shown in FIG.
1
C. Finally, in step S
103
, data packets in set
106
are moved to locations L
0
-L
4
. Currently, the reordering system is expensive and hence increases the overall system cost.
Therefore, what is needed is a system that can efficiently reorder incoming data packets without expensive memory buffer requirements.
SUMMARY
The present invention addresses the foregoing by providing a method and system for reordering digital spread spectrum (DSS) data packets. The process locates the location (Ln) of a last data packet (Pn), and moves Pn to a memory buffer that can at least store a DSS data packet. Thereafter, the process locates a data packet (Px) stored at location Lx, wherein Px should be located at Ln. The process also determines if packet Pn should be located at location Lx, instead of Px. If Pn should not be located at Lx, the process moves Px to Ln.
If Pn should be located at Lx, the process locates the second last packet's (Pn−1) location (Ln−1), and moves Pn−1 to the memory buffer. Thereafter, the process locates a packet (Px′) at location Lx′, that should be located at Ln−1; and also determines if Pn−1 should be located at Lx′. The process then moves Px′ to Ln−1 if Pn−1 should not be located at location Lx′. The process is repeated until all the data packets have been reordered.
By virtue of the foregoing aspects of the present invention, a memory buffer that is smaller than conventional systems is required to reorder numerous data packets. Hence memory cost is reduced and that reduces the overall cost of the system. Furthermore, the present process is more efficient than the conventional prior art systems because data packets are only moved once, unlike conventional systems where data packets are moved more than once.


REFERENCES:
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patent: 5383182 (1995-01-01), Therasse et al.
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patent: 6434148 (2002-08-01), Park
patent: 6529558 (2003-03-01), Fimoff et al.

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