Optical OFDMA network with dynamic sub-carrier allocation
View Patent ↗A system and method for dynamically allocating sub-carriers between the nodes of an optical OFDMA ring network or an OFDMA passive optical network. A carrier allocation system assigns sub-carriers according to a utility function based on real-time measurements of arrival data rates and queue length variance.
1. A system for dynamically allocating sub-carriers to optical transmitters in an optical, Orthogonal Frequency Division Multiple Access (OFDMA) network, comprising:
a dynamic sub-carrier allocation and assignment module configured to dynamically assign sub-carriers to a plurality of optical transmitters according to a utility function, based on measurements of a data arrival rate and a queue length variance for each optical transmitter;
a control module configured to communicate sub-carrier assignments to the plurality of optical transmitters; and
a modulation selection module configured to select a modulation scheme for each sub-carrier based on a measured signal to noise ratio for each optical transmitter.
2. The system of claim 1 , wherein the modulation selection module comprises a table of signal to noise thresholds.
3. The system of claim 1 , wherein the data arrival rate and queue length variance are measured in real-time.
4. The system of claim 1 , wherein the utility function is λ i ( t )/μ(t)×e b i ( t )/ B i , where λ i ( t ) is the measured data arrival rate for node i during a scheduling interval t , μ(t) is the rate at which data is served by node i at time t, b i ( t ) is a measured average queue length for node i during the last scheduling interval t , and B i is a buffer size for node i.
5. The system of claim 1 , wherein the optical transmitters form nodes in a ring network topology.
6. The system of claim 5 , wherein the control module communicates with the nodes via a dedicated, control sub-carrier.
7. The system of claim 5 , wherein the dynamic sub-carrier allocation and assignment module and the control module are components in one or more of the nodes.
8. The system of claim 5 , wherein the dynamic sub-carrier allocation and assignment module and the control module are components in a stand-alone device.
9. The system of claim 1 , wherein the optical transmitters form optical network units in a passive optical network.
10. The system of claim 9 , wherein the optical network units all operate homogeneously according to a single passive optical network standard.
11. The system of claim 9 , wherein the optical network units operate heterogeneously according to a plurality of passive optical network standards.
12. The system of claim 9 , wherein the dynamic sub-carrier allocation and assignment module and the control module are components of an optical line terminal.
13. The system of claim 9 , wherein the dynamic sub-carrier allocation and assignment module and the control module are components in a stand-alone device that communicates with an optical line terminal.
14. A method for assigning sub-carriers in an optical, Orthogonal Frequency Division Multiple Access (OFDMA) network having a plurality of sub-carriers and a plurality of nodes, comprising:
measuring in real-time the data arrival rate and queue length variance for each node;
assigning sub-carriers to nodes based on a utility function based on the nodes' data arrival rates and queue length variance;
measuring the signal to noise ratio for each node; and
selecting a modulation scheme for each sub-carrier after it has been assigned to a node based on the measured signal to noise ratio.
15. The method of claim 14 , wherein said assigning step takes place only when the nodes' queue length variance exceeds a threshold.
16. The method of claim 14 , wherein the data arrival rates and queue length variance are measured in real time.
17. The method of claim 14 , wherein the utility function is λ i ( t )/μ(t)×e b i ( t )/B i , where λ i ( t ) is the measured data arrival rate for node i during a scheduling interval t , μ(t) is the rate at which data is served by node i at time t, b i ( t ) is a measured average queue length for node i during the last scheduling interval t , and B i is a buffer size for node i.
18. The method of claim 14 , wherein the assigning step is conducted periodically.
19. The method of claim 14 , wherein said selecting is accomplished by comparing measured signal to noise ratio to signal to noise thresholds.
20. A non-transitory computer readable medium comprising a computer readable program, wherein the computer readable program when executed on a computer causes the computer to execute the steps of claim 14 .