Channel assignment and call admission control for spatial division multiple access communication systems

A channel assignment method for use in a wireless communication system for establishing an uplink connection between a new subscriber station requesting an uplink connection and a base station, and for reassigning an existing connection to a subscriber station the base station including an array of antenna elements and SDMA processing means, the method comprising:

• (a) computing a first cost for each conventional uplink channel according to a first cost function that is indicative of the uplink interference level that may be realized by assigning the new subscriber station to said each conventional uplink channel, the computing including using spatial properties of the subscriber station for communicating with the base station;
• (b) selecting a subset of conventional uplink channels, the subset consisting of the conventional uplink channels with a first cost that is less than a prescribed first cost level;
• (c) for each conventional uplink channel of the subset, computing a second cost according to a second cost function, the second cost function for a particular conventional channel based on the predicted received signal quality on the particular conventional channel, the received signal quality on a conventional uplink channel predicted using a model of the wireless communication system for predicting signal quality based upon existing connections;
• and
• (d) assigning to the subscriber station one of the conventional uplink channels of the subset that has a second cost that is less than a prescribed second cost level.

A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means enabling the base station to communicate on the downlink with more than one subscriber station on the same conventional channel, each subscriber station on the same conventional channel being communicated to on a different spatial channel of said same conventional channel, the method comprising:

• (a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;
• (b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels;
• and
• (c) assigning, at the base station, the subscriber station to a conventional downlink channel that has a computed cost that is less than a prescribed value,
• the method further comprising the step of assigning a spatial channel to the subscriber station on the assigned conventional downlink channel if the assigned conventional downlink channel is in use by the base station for communicating on the downlink with a second subscriber station on an existing spatial channel.

A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means processing a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, the method comprising:

• (a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;
• (b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels;
• and
• (c) assigning, at the base station, a conventional downlink channel that has a computed cost that is less than a prescribed value,
• wherein step (a) for estimating downlink received interference-plus-noise levels on each downlink channel comprises the following steps:
• (i) adjusting, at the base station, each existing subscriber's downlink multiplexing weights as if the new subscriber was assigned to a given conventional channel;
• (ii) measuring, at the new subscriber station, the downlink received signal level on the given channel after step (i) and reporting the downlink received signal level to the base station;
• (iii) predicting, at the base station, a downlink interference-plus-noise level from the downlink received signal level of step (ii);
• and
• (iv) readjusting, at the base station, each existing subscriber's downlink multiplexing weights as if the new subscriber was not assigned to the given conventional channel.

A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the method comprising:

• (a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;
• (b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels;
• and
• (d) assigning, at the base station, a conventional downlink channel that has a computed cost that is less than a prescribed value,
• wherein step (a) for estimating a downlink received interference-plus-noise level, I.sub.k, for each existing channel k comprises, modeling the downlink received interference-plus-noise level, I.sub.k, as a sum of the noise contribution, N.sub.k, and a predicted second interference signal level that would result if the new subscriber was to be assigned to channel k, estimating the noise contribution N.sub.k as a signal level difference between a measured downlink received signal level, P.sub.k, on channel k and a computed first interference signal level due to all base stations using channel k.

A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the method comprising:

• (a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;
• (b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels;
• and
• (c) assigning, at the base station, a conventional downlink channel that has a computed cost that is less than a prescribed value, and further comprising a step for assigning a selected downlink conventional channel) only if it is expected to result in an acceptable downlink received signal quality for each active subscriber using the selected conventional channel based upon at least one downlink quality factor selected from a group consisting of:
• predicted cost;
• predicted total base station transmitter power;
• predicted intermodulation distortion level;
• predicted interference-plus-noise level;
• and predicted signal to interference-plus-noise ratio.

A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the method comprising:

• (a) estimating, at the base station, the downlink received SINR level that would result for each existing conventional channel if the subscriber station were to be assigned to a given conventional downlink channel, the estimating using spatial information of the new subscriber;
• (b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received SNR level;
• and
• (c) assigning, at the base station, a downlink channel that has a computed cost that is less than a prescribed value,
• the method further comprising the step of assigning a spatial channel to the subscriber station on the assigned conventional downlink channel if the communications system supports and the SDMA processing means enables communication on more than one spatial channel on the same conventional downlink channel, and if the assigned conventional downlink channel is in use by the base station for communicating on the downlink with a second subscriber station on an existing spatial channel.

In a wireless communication system, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, a method for assignment of a full-duplex channel in which a duplex channel is selected from a set of duplex channels wherein each duplex channel of the set provides acceptable quality uplink communications, and the downlink channel assignment is made in accordance with existing rules of the system, the method comprising:

• (a) computing a cost for each conventional uplink channel according to a cost function that is indicative of a lack of communications quality expected interference level that may be realized by assigning the subscriber station to the conventional uplink channel, the cost function being a function of spatial properties of the subscriber station for communicating with the base station;
• (b) assigning a conventional uplink channel by selecting a conventional uplink channel with a cost less than a prescribed cost level;
• and
• (c) selecting a downlink channel in accordance with existing rules of the communication system.

In a wireless communication system, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means enabling the base station to communicate on the downlink with more than one subscriber station on the same conventional channel, each subscriber station on the same conventional channel being communicated to by the base station on a different spatial channel of said same conventional channel, a method for assignment of a full-duplex channel in which a duplex channel is selected from a set of duplex channels wherein each duplex channel of the set provides acceptable quality downlink communications, and the uplink channel assignment is made in accordance with existing rules of the system, the method comprising:

• (a) computing a cost for each conventional downlink channel according to a cost function that estimates a lack of communications quality expected from existing connections on each conventional downlink channel, if a given conventional downlink channel was assigned;
• (b) assigning a conventional downlink channel by selecting a conventional downlink channel with a cost less than a prescribed cost level;
• and
• (c) selecting a uplink channel in accordance with existing rules of the communication system.

A call admission control method, based on an interference cost function, for use in a wireless communication system for controlling admission of a connection for a new subscriber station, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, the method comprising:

• (a) evaluating a cost for a selected conventional channel according to a cost function that is indicative of the interference-plus-noise on the selected conventional channel if the selected conventional channel were to be assigned, the evaluation using spatial properties of the subscriber station for communicating with the base station;
• (b) comparing the cost with a prescribed channel assignment cost level;
• and
• (c) admitting the call if the cost is less than the prescribed channel assignment cost level.

A call admission control method for use in a wireless communication system for controlling admission of a connection for a new subscriber station, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, the method comprising:

• (a) predicting the received signal level and interference-plus-noise level on each conventional channel based upon a model of the wireless communication system for predicting a received signal level and interference-plus-noise level on each conventional channel based upon existing connections, if a given conventional channel was assigned for the new subscriber station;
• (b) selecting a conventional channel for the new subscriber station that has an acceptably high predicted signal-to-interference-plus-noise ratio (SINR) determined according to predicting step (a);
• and
• (c) admitting the call if the SINR is greater than a prescribed admission level SINR threshold value,
• the method further comprising the step of assigning a spatial channel for the call on the selected conventional channel if the communications system supports and the SDMA processing means enables communication on more than one spatial channel on the same conventional channel, and if the assigned conventional channel is in use by the base station for communicating with a second subscriber station on an existing spatial channel.

A call admission control method for use in a wireless communication system for controlling admission of a connection of a new subscriber station, the method, based on an estimate of existing system call load, comprising:

• (a) estimating the existing call load for indicating how much of the system capacity is being utilized;
• (b) prescribing a call load threshold that is indicative of a maximal call load allowed for the system;
• and
• (c) comparing the existing call load with the call load threshold;
• and
• (d) admitting a new call if the estimated existing call load is less than the call load threshold,
• wherein estimating step (a) further comprises monitoring the rate at which intracell handoffs occur, and estimating the existing call load from the rate at which intracell handoffs occur.

A call admission control method for use in a wireless communication system for controlling admission of a connection of a new subscriber station, the method, based on an estimate of existing system call load, comprising:

• (a) estimating the existing call load for indicating how much of the system capacity is being utilized;
• (b) prescribing a call load threshold that is indicative of a maximal call load allowed for the system;
• and
• (c) comparing the existing call load with the call load threshold;
• and
• (e) admitting a new call if the estimated existing call load is less than the call load threshold,
• wherein estimating step (a) further comprises estimating the existing call load by monitoring the rate of channel reassignments.