1. A method for use in communication systems for transmitting signals from a transmitter having t transmit antennas and a receiver having r receive antennas by forming beams of electromagnetic radiation used to transmit signals from the transmitter to the receiver, the method comprising:
transmitting a test signal from the transmitter to the receiver;
computing a channel matrix by observing the effect of transmission on the test signal;
selecting at least one eigenvector of the channel matrix, to achieve a desired performance level;
selecting a beamforming vector from at least one codebook of predetermined beamforming vectors wherein the selected beamforming vector best approximates the at least one eigenvector;
transmitting information identifying the selected beamforming vector from the receiver to the transmitter; and
using the selected beamforming vector to transmit a signal from the transmitter to the receiver so that the desired performance level is achieved.
2. The method of claim 1 wherein the desired performance level corresponds to a relatively low transmission rate so that transmission along a single eigenvector of the channel is sufficient to achieve the desired performance level, whereby a single eigenvector corresponding to the principal eigenvector of the channel is selected for transmission purposes, and a single beamforming vector providing the best approximation to the principal eigenvector is selected for transmission purposes.
3. The method of claim 1 wherein the desired performance level corresponds to a relatively high transmission rate so that transmission along multiple eigenvectors of the channel is required to achieve the desired performance level, whereby multiple eigenvectors of the channel, beginning with the principal eigenvector, are selected for transmission purposes, and wherein multiple codebook vectors providing the best approximations to the multiple eigenvectors are selected from multiple predetermined beamforming codebooks for use in transmitting signals from the transmitter to the receiver.
4. The method of claim 1 wherein H is the channel matrix, V corresponds to the principal eigenvector of H\u2020H, C1 is a beamformer codebook in t comprising of N1=2b1 vectors wherein the codebook vector in C1 providing the best approximation to the principal eigenvector V is selected by choosing Ci1\u03b5C1 such that \u2225H(Ci1)\u2020\u22252 is maximum for all vectors in C1, wherein Ht refers to complex conjugate transpose of H.
5. The method of claim 4 wherein C11 maximizes the inner product with H among all the vectors in C1.
6. The method of claim 4 wherein V1 corresponds to the principal eigenvector, V2 corresponds to a second active eigenvector of H\u2020H, C2 is a beamformer codebook in t-1 comprising N2=2B2 vectors, wherein the codebook vector providing the best approximation to V2 is selected according to the following additional steps:
constructing a codebook C\u20322 from C2 such that C\u20322 lies in t, wherein by construction C\u20322 is such that the first co-ordinate of all the vectors is set to zero with the result that the vectors in C\u20322 lie in the orthogonal subspace of the axis 1, 0, . . . , 0 of t, and with C\u20322 being in the orthogonal subspace of e1=1, 0, . . . 0 in t;
rotating the vectors in C1 such that C11 coincides with e1;
constructing A as a t\xd7t unitary matrix from C11 such that AC11=e1;
rotating the second vector V2 by the matrix A to give V\u20322=A\u2020V2;
quantizing V2\u2032 in the second beamformer codebook C22\u2032 by selecting the Ck2\u2032 vector in C22\u2032 which maximizes the inner product with V2\u2032;
transmitting the information identifying to Ck2\u2032 to the transmitter;
using A(C2\u2032)T for transmission, wherein the superscript T refers to a matrix transpose operation.
7. A method for use in communication systems comprising a transmitter having t transmit antennas and a receiver having r receive antennas, wherein transmission occurs over a channel mathematically represented by channel matrix H, and wherein signal transmission between the transmitter and receiver occurs according to an approximation of the waterfilling algorithm accomplished by selecting predetermined beamforming codebooks for modifying signals to be transmitted from the transmitter to the receiver, the method comprising:
specifying a desired performance level specification for characterizing the performance of the communications system over a range of operating conditions;
jointly determining a feedback budget and beamforming codebook specification that achieves the performance criteria set forth in the performance level specification, wherein the feedback budget refers, at least in part, to the transmission of bits from the receiver to the transmitter identifying vectors contained in the beamforming codebook specification, wherein the codebook vectors are used to modify signals transmitted by the transmitter to the receiver.
8. The method of claim 7 comprising:
selecting a desired performance level for the communications system;
transmitting a test signal from the transmitter to the receiver;
computing a channel matrix by observing the effect of transmission on the test signal;
selecting sufficient eigenvectors, starting with the principal eigenvector, of the channel matrix, to achieve the desired performance level;
selecting the best approximation from codebooks of predetermined vectors for each of the sufficient eigenvectors, wherein the codebook vectors providing the best approximation to the sufficient eigenvectors are called the selected codebook vectors;
identifying a unique bit code identifying each of the selected codebook vectors;
transmitting information identifying the selected codebook vectors from the transmitter to the receiver; and
using the codebook vectors to transmit signals from the transmitter to the receiver so that the desired performance level is achieved.
9. The method of claim 8 wherein the desired performance level corresponds to a relatively low transmission rate so that transmission along a single eigenvector of the channel is sufficient to achieve the desired performance level, whereby a single eigenvector corresponding to the principal eigenvector of the channel is selected for transmission purposes, and a single codebook vector providing the best approximation to the principal eigenvector is selected for transmission purposes.
10. The method of claim 8 wherein the desired performance level corresponds to a relatively high transmission rate so that transmission along multiple eigenvectors of the channel is required to achieve the desired performance level, whereby multiple eigenvectors of the channel, beginning with the principal eigenvector, are selected for transmission purposes, and wherein multiple codebook vectors providing the best approximations to the multiple eigenvectors are selected for use in transmitting signals from the transmitter to the receiver.
11. The method of claim 8 wherein V corresponds to the principal eigenvector of H\u2020H, C1 is a beamformer codebook in t comprising of N1=2B1 vectors wherein the codebook vector in C1 providing the best approximation to the principal eigenvector V is selected by choosing Ci1 \u03b5C1 such that \u2225H(Ci1)554 \u22252 is maximum for all vectors in C1, wherein Ht refers to complex conjugate transpose of H.
12. The method of claim 11 wherein C11 maximizes the inner product with H among all the vectors in C1.
13. The method of claim 11 wherein V1 corresponds to the principal eigenvector, V2 corresponds to a second active eigenvector of H\u2020H, C2 is a beamformer codebook in t-1 comprising N2=2B2 vectors, wherein the codebook vector providing the best approximation to V2 is selected according to the following additional steps:
constructing a codebook C\u20322 from C2 such that C\u20322 lies in t, wherein by construction C\u20322 is such that the first co-ordinate of all the vectors is set to zero with the result that the vectors in C\u20322 lie in the orthogonal subspace of the axis 1, 0, . . . , 0 of t, and with C\u20322 being in the orthogonal subspace of e1=1, 0, . . . 0 in t;
rotating the vectors in C1 such that Ci1 coincides with e1;
constructing A as a t\xd7t unitary matrix from C11 such that AC11=e1;
rotating the second vector V2 by the matrix A to give V\u20322=A\u2020V2;
quantizing V2\u2032 in the second beamformer codebook C22\u2032 by selecting the Ck2\u2032 vector in C22\u2032 which maximizes the inner product with V2\u2032;
transmitting the bit code corresponding to Ck2\u2032 to the transmitter;
using A(C2\u2032)T for transmission, wherein the superscript T refers to a matrix transpose operation.
14. A beamforming system for use in a telecommunications system comprising at least one base station having t transmit antennas and at least one mobile station having r receive antennas, the beamforming system for use in beamforming of signals transmitted from the base station to the mobile station, the beamforming system comprising:
in the base station:
a test signal generator and transmitter for generating test signals to be transmitted from the base station to the mobile station;
at least one beamforming codebook comprising predetermined beamforming vectors for beamforming of signals transmitted by the base station to the mobile station;
a feedback receiver for receiving codes from the mobile station identifying which beamforming vectors available in the at least one beamforming codebook should be used in beamforming of signals transmitted by the base station to the mobile station; and
a beamformer for using the beamforming vectors selected by the mobile station to beamform signals transmitted from the base station to the mobile station;
in the mobile station:
a test signal receiver for receiving the test signal transmitted by the test signal generator and transmitter of the base station;
a channel matrix calculator for calculating at least the principal eigenvector of a channel matrix describing the state of the transmission channel between the base station and the mobile station by observing the effect of the channel on the test signal;
at least one beamforming codebook comprising predetermined beamforming vectors for beamforming of signals transmitted from the base station to the mobile station, wherein the beamforming vectors comprising the beamforming codebook are identical to those comprising the at least one beamforming codebook located in the base station;
a beamforming vector selector for selecting which beamforming vector in the at least one beamforming codebook best approximates the principal eigenvector of the channel matrix;
a beamforming vector code selector for selecting the unique predetermined code which identifies the beamforming vector which best approximates the principal eigenvector of the channel matrix;
a beamforming vector code transmitter for transmitting the code identifying the beamforming vector which best approximates the principal eigenvector of the channel matrix to the feedback receiver of the base station.
15. A base station having t transmit antennas for use in a telecommunications system comprising the base station and mobile stations having r receive antennas, the base station comprising:
test signal generator and transmitter for generating test signals to be transmitted from the base station to a mobile station;
at least one beamforming codebook comprising predetermined beamforming vectors for beamforming of signals transmitted by the base station to the mobile station;
a feedback receiver for receiving codes from the mobile station identifying which beamforming vectors available in the at least one beamforming codebook should be used in beamforming of signals transmitted by the base station to the mobile station; and
a beamformer for using the beamforming vectors selected by the mobile station to beamform signals transmitted from the base station to the mobile station.
16. A mobile station having r receive antennas for use in a telecommunications system comprising the mobile station and base stations having t transmit antennas, the mobile station comprising:
a test signal receiver for receiving a test signal transmitted by a base station;
a channel matrix calculator for calculating at least the principal eigenvector of a channel matrix describing the state of the transmission channel between the base station and the mobile station by observing the effect of the channel on the test signal;
at least one beamforming codebook comprising predetermined beamforming vectors for beamforming of signals transmitted from the base station to the mobile station, wherein the beamforming vectors comprising the beamforming codebook are identical to those comprising the at least one beamforming codebook located in the base station;
a beamforming vector selector for selecting which beamforming vector in the at least one beamforming codebook best approximates the principal eigenvector of the channel matrix;
a beamforming vector code selector for selecting the unique predetermined code which identifies the beamforming vector which best approximates the principal eigenvector of the channel matrix; and
a beamforming vector code transmitter for transmitting the code identifying the beamforming vector which best approximates the principal eigenvector of the channel matrix to a base station.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A modular battery control apparatus, comprising:
a first stationary contact adapted for electrical communication with coach loads and a battery charger;
a second stationary contact adapted for electrical communication with a coach battery;
a third stationary contact adapted for electrical communication with a chassis battery;
a fourth stationary contact adapted for electrical communication with chassis loads and an alternator;
a first solenoid;
a first movable contact attached to said first solenoid, said first movable contact adapted to abuttingly engage and disengage said first and second stationary contacts;
a second solenoid;
a second movable contact attached to said second solenoid, said second movable contact adapted to abuttingly engage and disengage said second and third stationary contacts;
a third solenoid;
a third movable contact attached to said third solenoid, said third movable contact adapted to abuttingly engage and disengage said third and fourth stationary contacts;
sense and control means for selectively activating and deactivating said first, second, and third solenoids; and
a user-controlled switch panel adapted to communicate with said sense and control means.
2. The modular battery control apparatus of claim 1, further comprising:
said first, second, and third solenoids being latching solenoids so that no energy is required to hold said solenoids in their respective engaged or disengaged positions.
3. The modular battery control apparatus of claim 1, further comprising:
a protective enclosure for housing said first, second, and third solenoids and said sense and control means.
4. The modular battery control apparatus of claim 3, further comprising:
said first, second, third, and fourth stationary contacts disposed in penetrating relation to said protective enclosure so that first respective parts thereof are disposed within said protective enclosure and second respective parts thereof are positioned externally of said protective enclosure.
5. The modular battery control apparatus of claim 1, further comprising:
a memory means included in said sense and control means;
said sense and control means being unable to determine a polarity of each solenoid when each solenoid is energized for a first time;
said sense and control means being operative to determine whether a solenoid latched by entering into engagement with its associated stationary contacts or unlatched by disengaging from its associated stationary contacts when said solenoid is energized for a first time;
said solenoid adapted to send a first signal to said memory means when a determination is made that said solenoid latched when initially energized, thereby indicating a first polarity, and said solenoid adapted to send a second signal to said memory means when a determination is made that said solenoid unlatched when initially energized, thereby indicating a second polarity, so that said sense and control means accesses said memory means before sending subsequent signals to said solenoid so that said subsequent signals will be of the correct polarity.
6. The modular battery control apparatus of claim 1, further comprising:
said sense and control means adapted to monitor a charge on said coach battery and said chassis battery;
said sense and control means adapted to generate and send a disconnect signal to prevent complete discharge if the charge on a monitored battery drops below a predetermined threshold.