Method and Apparatus for Performing Constellation Scrambling in a Multimedia Home Network

• US 20100098257A1
• Filed: 10/15/2009
• Published: 04/22/2010
• Est. Priority Date: 10/16/2008
• Status: Active Grant

• Current Assignee: Entropic Communications, LLC (SoftBank Group Corp.)
• Original Assignee: Entropic Communications Incorporated (Maxlinear Incorporated)
• Inventors: MUELLER, Arndt
• Granted Patent: US 8,320,566 B2
• Time in Patent Office: Days
• US Class Current: 380/287
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation

Abstract

Systems and methods are provided that allow multiple transmitting network devices to transmit under an orthogonal frequency divisional multiple access (OFDMA) mode to a receiving network device. The multiple transmitting network devices may be configured to perform constellation scrambling on the symbols they will be transmitting using a predetermined scrambling sequence. They may be further configured to synchronize their use of the sequence, for example, by advancing the sequence for each available subcarrier, such that the receiving device may view the payload as if it were sent by a single transmitter. Accordingly, these multiple transmissions may be descrambled using only one instance of a sequence generator.

Claims

1. A method for communications transmission using orthogonal frequency division multiple access on a network comprising:

providing a plurality of transmitting network devices with a set of available subcarriers for orthogonal frequency division multiple access;

providing a corresponding element of a pseudorandom noise sequence for each subcarrier of the set of available subcarriers;

allocating a subset of the set of available subcarriers to each of the transmitting network devices;

a transmitting network device of the plurality of devices mapping a packet onto a plurality of used subcarriers of its allocated subset of available subcarriers, wherein the step of mapping the packet comprises mapping the packet onto a plurality of quadrature amplitude modulated symbols to be transmitted on the used subcarriers;

the transmitting network device performing a predetermined transformation on a quadrature amplitude modulated symbol using the element of the pseudorandom noise sequence corresponding to the used subcarrier;

the transmitting network device transmitting the transformed symbol to a receiving network device.

2. The method of claim 1, wherein the steps of providing a corresponding element of a pseudorandom noise sequence and performing a predetermined transformation comprise:

the transmitting network device receiving an initial pseudorandom noise sequence element from a pseudorandom noise sequence generator, the initial pseudorandom noise sequence element corresponding to a first available subcarrier and transforming the symbol to be transmitted on the first available subcarrier if the first available subcarrier is a used subcarrier; and

the transmitting network device advancing the pseudorandom noise generator to receive a next element of the pseudorandom noise sequence corresponding to a next available subcarrier and transforming the symbol to be transmitted on the next available subcarrier if the next available subcarrier is a used subcarrier.

4. The method of claim 1, wherein the pseudorandom noise sequence comprises a PN-15 sequence.

5. The method of claim 4, wherein the step of performing the predetermined transformation comprises rotating the quadrature amplitude modulated symbol by 180°

if the element of the pseudorandom noise sequence is a ‘

1’ and

not modifying the quadrature amplitude modulated symbol if the element of the pseudorandom noise sequence is a ‘

0’

.

6. The method of claim 4, wherein the receiving network device comprises a network coordinator and wherein the packet comprises a resource reservation request packet.

12. The method of claim 4, wherein the method is performed by a network coordinator and wherein first and second scrambled orthogonal frequency division modulation symbols are contained in a resource reservation request packet.

3. The method of claim 3, wherein the step of the transmitting network device advancing the pseudorandom noise generator is repeated until a symbol to be transmitted on a last used subcarrier is transformed.

7. A method for communications reception using orthogonal frequency division multiple access on a network comprising:

receiving a first scrambled orthogonal frequency division modulation symbol from a first transmitting network device, the first orthogonal frequency division modulation symbol comprising a first plurality of scrambled quadrature amplitude modulation symbols transmitted on a corresponding first plurality of used subcarriers assigned to the first transmitting network device;

receiving a second scrambled orthogonal frequency division modulation symbol from a second transmitting network device, the second orthogonal frequency division modulation symbol comprising a second plurality of scrambled quadrature amplitude modulation symbols transmitted on a corresponding second plurality of used subcarriers assigned to the second transmitting network device;

wherein the first plurality of subcarriers and the second plurality of subcarriers are subsets of a set of available subcarriers, and wherein the subcarriers of the set of available subcarriers have corresponding elements of a pseudorandom noise sequence; and

descrambling the first and second scrambled orthogonal frequency division modulation symbols, the step of descrambling comprising descrambling a scrambled quadrature amplitude modulation symbol transmitted on a used subcarrier using the element of the pseudorandom noise sequence corresponding to the used subcarrier.

8. The method of claim 7, wherein the step of descrambling the first and second scrambled orthogonal frequency division modulation symbols comprises receiving an initial pseudorandom noise sequence element from a pseudorandom noise sequence generator, the initial pseudorandom noise sequence element corresponding to a first available subcarrier and descrambling the symbol received on the first available subcarrier if the first available subcarrier is a used subcarrier;

and

advancing the pseudorandom noise generator to receive a next element of the pseudorandom noise sequence corresponding to a next available subcarrier and descrambling the symbol received on the next available subcarrier if the next available subcarrier is a used subcarrier.

9. The method of claim 8, wherein the step of advancing the pseudorandom noise generator is repeated until a symbol to be transmitted on a last used subcarrier is descrambled.

10. The method of claim 7, wherein the pseudorandom noise sequence comprises a 15th order pseudorandom noise sequence.

11. The method of claim 10, wherein the step of descrambling the scrambled quadrature amplitude modulated symbol comprises rotating the scrambled quadrature amplitude modulated symbol by 180°

if the element of the pseudorandom noise sequence is a ‘

1’ and

not modifying the scrambled quadrature amplitude modulated symbol if the element of the pseudorandom noise sequence is a ‘

0’

.

13. A communications network system, comprising:

a network device configured to transmit a quadrature amplitude modulated symbol on a subcarrier of a set of subcarriers available for orthogonal frequency division multiple access;

wherein the network device is configured to perform a constellation scrambling operation on the quadrature amplitude modulated symbol, the constellation scrambling operation comprising;

initializing a sequence generator with a predetermined seed; and

,

while proceeding through the set of available subcarriers in a predetermined order, advancing the sequence generator for each subcarrier preceding the subcarrier, and using an element of a sequence generated by the sequence generator to scramble the quadrature amplitude modulated symbol.

14. The system of claim 13, further comprising:

a second network device configured to transmit a second quadrature amplitude modulated symbol on a second subcarrier of the set of available subcarriers;

wherein the second network device is configured to perform a second constellation scrambling operation on the second quadrature amplitude modulated symbol, the second constellation scrambling operation comprising;

initializing a second sequence generator with the predetermined seed; and

,

while proceeding through the set of available subcarriers in the predetermined order, advancing the second sequence generator for each subcarrier preceding the second subcarrier, and using a second element of a second sequence generated by the second sequence generator to scramble the second quadrature amplitude modulated symbol.

15. The system of claim 14, further comprising:

a receiving network device configured to receive the first and second scrambled quadrature amplitude modulated symbols;

wherein the receiving network device is configured to perform a constellation descrambling operation on the first and second scrambled quadrature amplitude modulated symbols, comprising;

initializing a third sequence generator with the predetermined seed; and

,

while proceeding through the set of available subcarriers in the predetermined order, advancing the third sequence generator for each subcarrier preceding the first subcarrier, and using the first element to descramble the first quadrature amplitude modulated symbol, advancing the third sequence generator for each subcarrier preceding the second subcarrier, and the using the second element to descramble the second quadrature amplitude modulated symbol.

16. A network device configured to transmit a quadrature amplitude modulated symbol on a subcarrier of a set of subcarriers available for orthogonal frequency division multiple access, the network device comprising a computer readable medium having a computer executable program code embodied on the computer readable medium, wherein the computer executable code is configured to cause the network device to perform the steps of:

performing a constellation scrambling operation on the quadrature amplitude modulated symbol to form a scrambled quadrature amplitude modulated symbol, the constellation scrambling operation comprising;

initializing a sequence generator with a predetermined seed; and

,

while proceeding through the set of available subcarriers in a predetermined order, advancing the sequence generator for each subcarrier preceding the subcarrier, and using an element of a sequence generated by the sequence generator to scramble the quadrature amplitude modulated symbol.

17. The network device of claim 16, wherein the computer executable program code is further configured to cause the device to transmit the scrambled quadrature amplitude modulated symbol to a receiving network device.

18. The network device of claim 17, wherein the receiving network device comprises a network coordinator, the sequence comprises a 15th order pseudorandom sequence, and the quadrature amplitude modulated symbol comprises an encoded symbol of a resource reservation request.