Adaptive energy efficient cellular network
Methods and systems are provided for managing a smart antenna system to maximize energy efficiency while maintaining spectral efficiency and signal integrity. In accordance with certain aspects of a particularly preferred embodiment, antenna beamforming may be optimized at a base station by combining a recursive least squares beamforming technique with Kaiser windowing functions to enable side lobe cancellation in the emitted beam, thus enhancing the capacity and service quality of smart antenna systems. With respect to further aspects of a particularly preferred embodiment, processing methods may be implemented at the base station of a cellular network to cluster mobile stations in a way that improves overall energy efficiency of a base station in the cellular network. More particularly, mobile stations or users may be clustered using a linear radius clustering method and a last user sector based clustering method to direct the beam emitted from the base station antenna to those sectors determined to contain the users having the greatest signal resource need.
1. A method of operating an adaptive antenna array at a base station of a cellular network, comprising:
driving an array propagation vector v the base station, where v =e jn(βdcosθ) , wherein
e is assigned energy,
n is a particular antenna element,
β is a phase constant,
d is a spacing between antenna elements, and
θ is an angle of incident at which a wave front arrives and impinges the antenna array;
initialize a weight value W where W=[0 0 0 . . . 0] T ;
determine an array factor AF initialized to 0 using AF initial =W· v =0;
determine a weight value W in each of K iterations using:
( k )= W ( k− 1)+ g ( k )[ d *( k )− X H ( k ) W ( k− 1)];
update said AF with each weight value using:
AF=AF initial +( k )· v ;
transmit a beam from said adaptive antenna array with said AF;
determine whether said beam includes a side lobe;
upon a determination that said beam has a side lobe, apply a Kaiser side lobe canceller using:
W =Kaiser ( N, α),
wherein N is a Kaiser window size and α is a Kaiser window attenuation factor; and
assign said beam to a user of said cellular network.
2. The method of claim 1 , wherein said cellular network further comprises multiple mobile stations, wherein a beam energy assigned to said beam is defined by:
( BS, ms )=(θ BW /360( d ( BS, ms )* SNIR ) α )+ C 1)+ C 2)
where θ BW is beam width, d is coverage distance (range), C1 is overhead due to a medium access control (MAC) message, C2 is overhead due to energy needed to tune a direction of the beam, BS is a base station, and ms is a mobile station.
3. The method of claim 2 , wherein said beam width comprises an angular distance between half power points of a main lobe of said beam, wherein said half power points from a normalized array factor (AF) are defined by:
HP AF =0.707( AF n ).
4. The method of claim 1 , further comprising the steps of:
establishing a plurality of virtual concentric circles around the base station;
determining a number of mobile stations within said plurality of virtual concentric circles, the radii of said concentric circles, an average density of mobile stations within each said concentric circle, a minimum radius Rmin of said plurality of concentric circles, and a track number Tn between two consecutive concentric circles;
counting a number of mobile stations between Tn and Tn-1;
calculating an area of track Tn;
determine a density of mobile stations in track Tn and compare with the average density; and
adjust a transmit power of the beam in track Tn based on said determined density of mobile stations.
5. The method of claim 1 , further comprising the steps of:
determining a number of mobile stations within a defined circle around the base station;
dividing an area defined by said circle into a number of sectors;
determining a number of mobile stations in each sector;
determining an independent power level at which said beam is to be transmitted for each sector based upon a density of users in each said sector; and
transmitting said beam in each sector at said determined power level.
6. A system for operating an adaptive antenna array at a base station of a cellular network, comprising:
a base station having a cell zooming server; and
an adaptive antenna array;
wherein said cell zooming server further comprises computer executable instructions stored thereon and configured to:
drive an array propagation vector v at the base station, where v =e jn(βdcosθ) , wherein
e is assigned energy,
n is a particular antenna element,
β is a phase constant,
d is a spacing between antenna elements, and
θ is an angle of incident at which a wave front arrives and impinges the antenna array;
initialize a weight value W where W=[0 0 0 . . . 0] T ;
determine an array factor AF initialized to 0 using AF initial =W· v =0;
determine a weight value W in each of K iterations using:
( k )= W ( k− 1)+ g ( k )[ d *( k )− X H ( k ) W ( k− 1)];
update said AF with each weight value using:
AF=AF initial +( k )· v ;
transmit a beam from said adaptive antenna array with said AF;
determine whether said beam includes a side lobe;
upon a determination that said beam has a side lobe, apply a Kaiser side lobe canceller using:
W =Kaiser ( N, α),
wherein N is a Kaiser window size and α is a Kaiser window attenuation factor; and
assign said beam to a user of said cellular network.
7. The system of claim 6 , wherein said cellular network further comprises multiple mobile stations, wherein a beam energy assigned to said beam is defined by:
( BS, ms )=(θ BW /360( d ( BS,ms )* SNIR ) α )+ C 1)+ C 2)
where θ BW is beam width, d is coverage distance (range), C1 is overhead due to a medium access control (MAC) message, C2 is overhead due to energy needed to tune a direction of the beam, BS is a base station, and ms is a mobile station.
8. The system of claim 7 , wherein said beam width comprises an angular distance between half power points of a main lobe of said beam, wherein said half power points from a normalized array factor (AF) are defined by:
HP AF =0.707( AF n ).
9. The system of claim 6 , wherein said computer executable instructions are further configured to:
establish a plurality of virtual concentric circles around the base station;
determine a number of mobile stations within said plurality of virtual concentric circles, the radii of said concentric circles, an average density of mobile stations within each said concentric circle, a minimum radius Rmin of said plurality of concentric circles, and a track number Tn between two consecutive concentric circles;
count a number of mobile stations between Tn and Tn-1;
calculate an area of track Tn;
determine a density of mobile stations in track Tn and compare with the average density; and
adjust a transmit power of the beam in track Tn based on said determined density of mobile stations.
10. The method of claim 6 , wherein said computer executable instructions are further configured to:
determine a number of mobile stations within a defined circle around the base station;
divide an area defined by said circle into a number of sectors;
determine a number of mobile stations in each sector;
determine an independent power level at which said beam is to be transmitted for each sector based upon a density of users in each said sector; and
transmit said beam in each sector at said determined power level.