Coordinated optimization of underlay network communication for efficient use of spectrum
View Patent ↗A system and method for selecting an optimal frequency channel to communicate on in a wireless network is disclosed. The optimal frequency is selected from a predefined set of frequencies for all nodes to communicate on based on an exposure calculation. All underlay nodes collect initial SNR information from initial detection of other nodes and adjust their transmit power for an intended receiver such that the signal is received at the lowest allowable underlay-to-overlay power ratio, thus minimizing exposure. The desired underlay-to-overlay ratio is set based on how much we are capable of cancelling the overlay signal and the SINR at which a signal can be recovered such that the data can be successfully received from the underlay node. The optimal channel selected by this algorithm is the one with the least area of undesired exposure, or least probability of interfering with the primary user. The performance increases as a function of number of nodes, or data points.
1. A method for selecting the best frequency channel to communicate on in a wireless network having one or more underlay nodes using one or more predefined set of frequencies comprising:
collecting initial SNR information from initial detection of other underlay nodes by each of the one or more underlay nodes;
using collected SNR information to calculate a minimum transmit power for each of the one or more underlay nodes, wherein the minimum transmit power is calculated by a transmitting underlay node transmitting a signal to each intended receiving underlay node;
using collected SNR information by each of the one or more underlay nodes to calculate a total exposure for each of the predefined set of frequencies, wherein the total exposure on a given frequency of the predefined set of frequencies is the combination of exposure from all transmitting nodes to all possible receiving nodes integrated over all one or more underlay nodes;
adjusting the minimum transmit power by each of the one or more underlay nodes for each of the corresponding intended receiving underlay node such that the signal is received at lowest allowable underlay-to-overlay power ratio, thus minimizing exposure;
setting desired underlay-to-overlay ratio by each of the one or more underlay nodes based on capability of cancelling overlay signal and an allowable SINR such that data is successfully received from each of the one or more underlay nodes; and
selecting a frequency channel by the underlay nodes is based on least total exposure, wherein the selected frequency is
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where (x,y) is a location of one or more underlay nodes, N is the total number of underlay nodes, p i,j (f) is the power of one or more underlay node locations.
2. The method of claim 1 wherein the step of selecting a channel comprises of firstly scanning the available frequency channels and measuring an interference power of the non-cooperative RF transmissions related to each of the one or more underlay nodes by the one or more underlay nodes.
3. The method of claim 2 further comprising detecting the presence of other underlay nodes and measures a signal power received from each of the existing underlay nodes.
4. The method of claim 3 further comprising sharing the SNR information, the minimum transmit power, the total exposure value, and the adjusted transmit power between all of the underlay nodes in the said network.
5. The method of claim 4 wherein a designated underlay node uses the received information to select the frequency channel that minimizes exposure of an underlay network to the other existing networks.
6. The method of claim 5 wherein each underlay node is also assigned a transmit power such that it is received at the intended destination node at a predefined level below the existing interference signals so that the threshold can be user defined but is set based on how much overlay signal interference the receiver can successfully cancel and the SINR where the underlay signal could be recovered.
7. The method of claim 1 wherein the underlay nodes do not require knowledge of geographical location of other underlay nodes, relative location of the overlay nodes and underlays and overlays may transmit at the same time.