Subchannel formation in OFDMA systems

• US 8,665,697 B1
• Filed: 12/23/2009
• Issued: 03/04/2014
• Est. Priority Date: 12/23/2009
• Status: Expired due to Fees

• Current Assignee: ANNA University, KBC Research Foundation Pvt Ltd.
• Original Assignee: ANNA University, KBC Research Foundation Pvt Ltd.
• Inventors: Venugopalan, Sarad Ammanath, Subramanian, Srikanth
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): HALIYUR, VENKATESH N
• Application Number:
  US12/645,709
• Time in Patent Office: 1,532 Days
• Field of Search: 370328-352
• US Class Current: 370/210
• CPC Class Codes: H04J 11/005 of intercell interference
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005

Abstract

Sub-channels in cells of an Orthogonal Frequency Division Multiple Access (OFDMA) network are formed based on random permutations of a set of subcarrier indices. The random permutations are performed for each cell of the network using a pseudo-random number generator (PRNG) and a shuffle technique. Different initial states of the PRNG are used to generate the random permutation of the subcarrier indices for each cell. In an embodiment, sub-carriers represented by a contiguous group of indices in the random permutation obtained for a cell are assigned to form a sub-channel. Interference diversity for the OFDMA network is thereby improved.

Claims

1. A computer-implemented method of forming sub-channels in an OFDMA network comprising:

receiving a plurality of sub-carrier indices representing corresponding sub-carriers to be used for forming sub-channels in a cell of a network;

generating a random permutation of the plurality of sub-carrier indices based on an output of a pseudo-random number generator (PRNG); and

forming a sub-channel in the cell from the sub-carriers represented by a portion of the random permutation,

wherein the receiving, the generating, and the forming are performed in a device including the PRNG and a shuffle block, and

wherein a same intial state value and different offset values of the PRNG are used to generate the random permutation and a second random permutation.

2. The method of claim 1, wherein the generating further comprises:

forming a first sequence of sub-carrier indices representing the sub-carriers;

receiving a random number as the output from the PRNG; and

re-ordering the first sequence based on the random number to form a second sequence of sub-carrier indices.

3. The method of claim 2, wherein the forming a first sequence, the receiving a random number and the re-ordering are performed one or more times to obtain a final sequence of the sub-carrier indices, the final sequence representing the random permutation of the plurality of sub-carrier indices.

4. The method of claim 3, wherein sub-carriers corresponding to a first group of successive sub-carrier indices in the final sequence are assigned to form the sub-channel, and sub-carriers corresponding to a second group of successive sub-carrier indices in the final sequence are assigned to form a second sub-channel,

wherein there are no indices common to the first group and the second group, and

wherein the sub-channel and the second sub-channel are formed for the first cell.

5. The method of claim 4, wherein the re-ordering is performed using a shuffle technique.

6. The method of claim 5, further comprising computing a number representing a measure of interference diversity for the first cell.

7. The method of claim 1, wherein the device containing the PRNG and a shuffle block performs the receiving, the generating, and the forming within a base station corresponding to each one of the plurality of cells.

8. A non-transitory machine readable medium storing one or more sequences of instructions for causing a computing system to form sub-channels in an OFDMA network, wherein execution of the one or more sequences of instructions by one or more processors contained in the computing system causes the computing system to perform operations comprising:

receiving a first sequence of sub-carrier indices representing corresponding sub-carriers to be used for forming sub-channels in cells of the network;

generating a re-ordered sequence of the sub-carrier indices, the generating being performed based on an output of a pseudo-random number generator (PRNG); and

forming a sub-channel in a first cell in the plurality of cells using sub-carriers represented by a first set of successive sub-carrier indices in the re-ordered sequence of the sub-carrier indices;

wherein the computing system is contained in a base station in a cell in the plurality of cells, and performs the receiving, the generating, and the forming to form one or more sub-channels for each of the plurality of cells, the base station containing the PRNG, and

wherein a same initial state value and different offset values of the PRNG are used to generate a random permutation and a second random permutation.

9. The non-transitory machine readable medium of claim 8, wherein the execution of the one or more sequences of instructions by the one or more processors contained in the computing system causes the computing system to further perform operations comprising:

forming a second sub-channel in the first cell using sub-carriers represented by a second set of successive sub-carrier indices in the re-ordered sequence of the sub-carrier indices,

wherein there are no sub-carrier indices common to the first set and the second set, and

wherein the sub-channel and the second sub-channel are formed for the first cell.

10. The non-transitory machine readable medium of claim 8, wherein the execution of said one or more sequences of instructions by one or more processors contained in the computing system further causes the computing system to perform the actions of computing a number representing a measure of interference diversity for the first cell.

11. The non-transitory machine readable medium of claim 8, wherein the PRNG is implemented as Mersenne Twister 19937.

12. The non-transitory machine readable medium of claim 11, wherein the generating the re-ordered sequence is performed using Sattolo'"'"'s shuffle technique.

13. A system comprising:

a pseudo random number generator (PRNG);

a shuffle block configured to receive a first sequence of sub-carrier indices representing corresponding sub-carriers to be used for forming sub-channels in a cell of an OFDMA network, the shuffle block configured to re-order the first sequence of sub-carrier indices based on a random number provided by the PRNG and to generate a final sequence of sub-carrier indices; and

a processor configured to form a sub-channel for the cell using sub-carriers represented by a set of successive sub-carrier indices in the final sequence of sub-carrier indices,

wherein a same initial state value and different offset values of the PRNG are used to generate a random permutation and a second random permutation.

14. The system of claim 13, further comprising:

an OFDM transmitter, wherein the OFDM transmitter receives the set from the processor, and transmits the set.

15. The system of claim 14, wherein the PRNG is implemented as Mersenne Twister 19937.

16. The system of claim 14, wherein the processor computes a number representing a measure of interference diversity for the cell in the OFDMA network.