WLAN capacity enhancement using SDM

A method for communication over a wireless local area network, comprising:

• prompting a plurality of stations in the WLAN to transmit respective uplink signals such that the stations transmit the uplink signals in a predetermined sequence;
• receiving the uplink signals from the stations in the predetermined sequence;
• responsively to the first uplink signals, determining respective spatial signatures of the stations;
• calculating beamforming weights based on the spatial signatures;
• and
• Communicating with two or more of the stations simultaneously by spatial division multiplexing (SDM) using the beamforming weights,
• wherein prompting the stations comprises causing the stations to transmit the uplink signals at intervals selected so that at least some of the uplink signals overlap in time.

A method for communication over a wireless local area network (WLAN), comprising:

• selecting a set of stations in the WLAN for inclusion in a spatial multiplexing group;
• during a first operating period, permitting the stations in the WLAN to transmit uplink signals subject to a collision-avoidance mechanism provided by a standard applicable to the WLAN;
• transmitting a broadcast message from an access point to the stations in the WLAN so as to disable transmission of the uplink signals, thereby terminating the first operating period;
• and
• during a second operating period immediately following the broadcast message, transmitting downlink signals from the access point simultaneously to the stations in the spatial multiplexing group using spatial division multiplexing (SDM),
• wherein transmitting the broadcast message comprises specifying, in the broadcast message, a duration of the second operating period,
• wherein upon a conclusion of the specified duration, the stations in the WLAN are permitted to resume transmission of the uplink signals.

A method for communication over a wireless local area network (WLAN), comprising:

• receiving uplink signals at an access point from at least one station in the WLAN via multiple antennas that are coupled to the access point;
• finding respective correlations between respective sequences of samples of the uplink signals received by the antennas and a known preamble of a packet carried by the uplink signals;
• tracking respective phases of the uplink signals received by the antennas;
• combining the respective correlations from the plurality of the antennas so as to recover a timing of the uplink signals;
• and
• combining the respective phases from the plurality of the antennas so as to recover a carrier frequency offset and a carrier phase of the uplink signals.

A method for communication over a wireless local area network (WLAN), comprising:

• selecting a number of stations in the WLAN for inclusion in a spatial multiplexing group;
• determining a downlink transmission rate for the spatial multiplexing group responsively to the number of the stations in the group;
• and
• transmitting downlink signals simultaneously to the stations in the spatial multiplexing group using spatial division multiplexing (SDM) at the downlink transmission rate,
• wherein determining the downlink transmission rate comprises measuring a level of uplink signals received from the stations in the spatial multiplexing group, and selecting the downlink transmission rate from a table using an index determined by the level of the uplink signals,
• wherein the table comprises different lists of entries corresponding to different numbers of the stations that may be included in the spatial multiplexing group.

An access point for communication over a wireless local area network (WLAN), comprising:

• a plurality of transceivers, which are coupled to receive uplink signals via respective antennas from stations in the WLAN;
• control circuitry, which is adapted to place data packets in respective queues for downlink transmission to the stations, and which is adapted, responsively to the uplink signals and to a characteristic of the respective queues, to select a set of the stations for inclusion in a spatial multiplexing group;
• and
• spatial division multiplexing (SDM) circuitry, which is coupled to the transceivers so as to transmit downlink signals so as to convey the data packets from the respective queues simultaneously to the set of the stations in the spatial multiplexing group,
• wherein the control circuitry is adapted to process the uplink signals to determine respective spatial signatures of the stations, and to group the stations in the set responsively to the spatial signatures,
• wherein the control circuitry is adapted to calculate respective beamforming weights for the stations in the set responsively to the respective spatial signatures, and wherein the SDM circuitry is coupled to apply the beamforming weights to the downlink signals.

An access point for communication over a wireless local area network (WLAN), comprising:

• a plurality of transceivers, which are coupled to receive first signals via respective antennas from stations in the WLAN;
• control circuitry, which is adapted to prompt the stations to transmit respective first signals such that the stations transmit the first signals in a predetermined sequence and, responsively to receiving the first signals in the sequence, to determine respective spatial signatures of the stations and to calculate beamforming weights based on the spatial signatures;
• and
• spatial division multiplexing (SDM) circuitry, which is coupled to the transceivers so as to communicate with two or more of the stations simultaneously by spatial division multiplexing (SDM) using the beamforming weights,
• wherein the control circuitry is adapted to cause the stations to transmit the uplink signals at intervals selected so that at least some of the uplink signals overlap in time.

An access point for communication over a wireless local area network (WLAN), comprising:

• a plurality of transceivers, which are coupled via respective antennas to communicate with stations in the WLAN;
• spatial division multiplexing (SDM) circuitry, which is coupled to the transceivers so as to communicate with a set of the stations simultaneously by spatial division multiplexing (SDM);
• and
• control circuitry, which is configured to permit the stations in the WLAN to transmit uplink signals during a first operating period, subject to a collision-avoidance mechanism provided by a standard applicable to the WLAN, and to transmit a broadcast message to the stations so as to disable transmission of the uplink signals, thereby terminating the first operating period, and to cause the SDM circuitry to transmit downlink signals simultaneously to the stations in the set during a second operating period immediately following the broadcast message,
• wherein the broadcast message specifies a duration of the second operating period,
• wherein the control circuitry is adapted to repeat transmission of the broadcast message periodically, at predetermined intervals, so as to define successive downlink and uplink transmission periods within the WLAN.

An access point for communication over a wireless local area network (WLAN), comprising:

• a plurality of transceivers, which are coupled via respective antennas to receive uplink signals from at least one station in the WLAN;
• and
• control circuitry, which is adapted to find respective correlations between respective sequences of samples of the uplink signals received by the antennas and a known preamble of a packet carried by the uplink signals, and to track respective phases of the uplink signals received by the antennas, and to combine the respective correlations from the plurality of the antennas so as to recover a timing of the uplink signals, and to combine the respective phases from the plurality of the antennas so as to recover a carrier frequency offset and a carrier phase of the uplink signals,
• wherein the control circuitry is adapted to sum the respective phases in order to recover the carrier phase,
• wherein the control circuitry is adapted to measure respective powers of the uplink signals, to weight the respective phases responsively to the respective powers, and to sum the weighted respective phases.

An access point for communication over a wireless local area network (WLAN), comprising:

• a plurality of transceivers, which are coupled via respective antennas to communicate with stations in the WLAN;
• spatial division multiplexing (SDM) circuitry, which is coupled to the transceivers so as to communicate with a number of the stations in a spatial multiplexing group simultaneously by spatial division multiplexing (SDM);
• and
• control circuitry, which is adapted to determine a downlink transmission rate for the spatial multiplexing group responsively to the number of the stations in the group, and to cause the SDM circuitry to transmit downlink signals simultaneously to the stations in the spatial multiplexing group using SDM at the downlink transmission rate,
• wherein the control circuitry is adapted to measure a level of uplink signals received from the stations in the spatial multiplexing group, and to select the downlink transmission rate from a table using an index determined by the level of the uplink signals,
• wherein the table comprises different lists of entries corresponding to different numbers of the stations that may be included in the spatial multiplexing group.

An access point for use in a wireless local area network (WLAN), comprising:

• a plurality of antennas;
• a plurality of transceivers, each comprising:
• a respective receiver, which is coupled to receive uplink radio frequency (RF) signals from a station in the WLAN via a respective one of the antennas;
• a down-converter, which is adapted to down-convert the RF signals to baseband signals having a phase;
• and
• a local oscillator, which is coupled to drive the down-converter, thereby determining the phase of the baseband signals;
• a digital processing circuit, which is coupled to receive and process the baseband signals simultaneously from the plurality of the transceivers;
• and
• a transceiver controller, which is coupled to provide a reference signal to the transceivers so as to synchronize the phase of the baseband signals provided by the plurality of transceivers to the digital processing circuit,
• wherein the transceiver controller is coupled to inject the reference signal into the RF signals, and comprising a phase tracking circuit, which is coupled to measure a phase deviation among the baseband signals by detecting a component of the baseband signals corresponding to the injected reference signal, and to adjust the phase of the baseband signals to compensate for the phase deviation.