Synchronizing wireless local area network access points

A system for synchronizing a first wireless access point and a second wireless access point transmitting and receiving data on a common radiofrequency (RF) channel, wherein the RF coverage area of said first wireless access point and the RF coverage area of said second wireless access point overlap in an overlap area, wherein data transmission from said first wireless access point is partitioned into a first contention-free period followed by a first contention period, said first contention-free period having a first start time and a first end time, wherein data transmission from said second wireless access point is partitioned into a second contention-free period followed by a second contention period, said second contention-free period having a second start time and a second end time,

• comprising:
• a monitor station positioned in said overlap area, said monitor station configured to record said first start time and said second start time, wherein the recorded first start time and the recorded second start time are referenced to a clock in said monitor station;
• and,
• a manager communicating with said first access point, said second access point, and said monitor station, said manager configured to receive the recorded first start time and the recorded second start time from said monitor station.

An apparatus for synchronizing a first wireless access point and a second wireless access point transmitting and receiving data on a common radiofrequency (RF) channel, wherein the RF coverage area of said first wireless access point and the RF coverage area of said second wireless access point overlap in an overlap area, wherein data transmission from said first wireless access point is partitioned into a first contention-free period followed by a first contention period, said first contention-free period having a first start time and a first end time, wherein data transmission from said second wireless access point is partitioned into a second contention-free period followed by a second contention period, said second contention-free period having a second start time and a second end time, comprising:

• means for recording by a monitor station positioned in said overlap area said first start time of said first contention-free period, wherein the recorded first start time is referenced to a clock in said monitor station;
• means for recording by said monitor station said second start time of said second contention-free period, wherein the recorded second start time is referenced to said clock;
• means for calculating a retardation interval based on the recorded first start time and the recorded second start time;
• and,
• means for transmitting a control command to said second wireless access point to retard transmission of said second contention-free period by said retardation interval to generate a retarded second contention-free period having a retarded start time.

A method for synchronizing a first wireless access point, a second wireless access point, and a third wireless access point transmitting and receiving data on a common radiofrequency (RF) channel, wherein the RF coverage area of said first wireless access point and the RF coverage area of said second wireless access point overlap in a first overlap area, wherein the RF coverage area of said second wireless access point and the RF coverage area of said third wireless access point overlap in a second overlap area, wherein said first wireless access point transmits a first beacon including a first transmission timestamp and a first contention-free period (CFP) schedule, wherein said second wireless access point transmits a second beacon including a second transmission timestamp and a second CFP schedule, wherein said third wireless access point transmits a third beacon including a third transmission timestamp and a third CFP schedule,

• comprising the steps of:
• receiving first beacon information from a first monitor station positioned in said first overlap area, said first beacon information comprising said first transmission timestamp, said first CFP schedule, a first arrival time recording the time at which said first beacon is received at said first monitor station, said second transmission timestamp, said second CFP schedule, and a second arrival time recording the time at which said second beacon is received at said first monitor station;
• receiving second beacon information from a second monitor station positioned in said second overlap area, said second beacon information comprising said second transmission timestamp, said second CFP schedule, a third arrival time recording the time at which said second beacon is received at said second monitor station, said third transmission timestamp, said third CFP schedule, and a fourth arrival time recording the time at which said third beacon is received at said second monitor station;
• determining a common timebase;
• and,
• transmitting control commands to adjust said first CFP schedule, said second CFP schedule, and said third CFP schedule.

A system for synchronizing a first wireless access point, a second wireless access point, and a third wireless access point transmitting and receiving data on a common radiofrequency (RF) channel, wherein the RF coverage area of said first wireless access point and the RF coverage area of said second wireless access point overlap in a first overlap area, wherein the RF coverage area of said second wireless access point and the RF coverage area of said third wireless access point overlap in a second overlap area, wherein said first wireless access point transmits a first beacon including a first transmission timestamp and a first contention-free period (CFP) schedule, wherein said second wireless access point transmits a second beacon including a second transmission timestamp and a second CFP schedule, wherein said third wireless access point transmits a third beacon including a third transmission timestamp and a third CFP schedule,

• comprising:
• a first monitor station positioned in said first overlap area, said first monitor station configured to receive said first beacon, record a first arrival time at which said first beacon is received at said first monitor station, receive said second beacon, and record a second arrival time at which said second beacon is received at said first monitor station;
• a second monitor station positioned in said second overlap area, said second monitor station configured to receive said second beacon, record a third arrival time at which said second beacon is received at said second monitor station, receive said third beacon, and record a fourth arrival time at which said third beacon is received at said second monitor station;
• and,
• a manager communicating with said first access point, said second access point, said third access point, said first monitor station, and said second monitor station, said manager configured to receive said first transmission timestamp, said second transmission timestamp, said third transmission timestamp, said first CFP schedule, said second CFP schedule, said third CFP schedule, said first arrival time, said second arrival time, said third arrival time, and said fourth arrival time.

A non-transitory computer readable medium storing computer program instructions for synchronizing a first wireless access point and a second wireless access point transmitting and receiving data on a common radiofrequency (RF) channel, wherein the RF coverage area of said first wireless access point and the RF coverage area of said second wireless access point overlap in an overlap area, wherein data transmission from said first wireless access point is partitioned into a first contention-free period followed by a first contention period, said first contention-free period having a first start time and a first end time, wherein data transmission from said second wireless access point is partitioned into a second contention-free period followed by a second contention period, said second contention-free period having a second start time and a second end time, the computer program instructions defining the steps of:

• recording by a monitor station positioned in said overlap area said first start time of said first contention-free period, wherein the recorded first start time is referenced to a clock in said monitor station;
• recording by said monitor station said second start time of said second contention-free period, wherein the recorded second start time is referenced to said clock;
• calculating a retardation interval based on the recorded first start time and the recorded second start time;
• and,
• transmitting a control command to said second wireless access point to retard transmission of said second contention-free period by said retardation interval to generate a retarded second contention-free period having a retarded start time.