Seamless roaming for wireless local area networks

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit, wherein the message includes a test pattern, the test pattern comprising a string of numbers which is progressively more likely to induce errors upon receipt at the mobile unit;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit, wherein the evaluating comprises determining an error free length of the received data;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit, wherein the message includes a test pattern, the test pattern being transmitted at a lower power level than are other transmissions of data;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit, wherein the transmitting includes transmitting by radio frequency hopping, transmitting at least an identification of the first access point, a current phase of the frequency hopping, and transmitting the number of other mobile units in communication with the first access point, each of which are communicating at a data rate exceeding a threshold, and wherein the message of data is a test pattern;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit, wherein at least a second mobile unit is in communication with the second access point, and wherein the evaluating includes determining a utilization of the second access point by the second mobile unit.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit, wherein even if the quality is above the first threshold value, switching to the second access point to balance a utilization of the first and second access points.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit, wherein the evaluating includes:
• measuring a total data rate at each of the first and second access points from all mobile units in communication with each of the first and second access points;
• and
• counting a number of individual mobile units in communication with each of the first and second access points at a data rate exceeding a third threshold value;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit;
• and
• measuring a total data rate at each of the first and second access points from all mobile units in communication with each of the first and second access points.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit on a first access point to the mobile unit, wherein the transmitting includes transmitting by radio frequency hopping;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit, wherein the switching comprises:
• determining the quality of the communications;
• scanning a plurality of radio frequencies for transmissions from a number of access points;
• and
• storing in the mobile unit a phase of the frequency hopping of each of the number of access points;
• and
• varying a proportion of time spent in the scanning, dependent on the determined current quality of the communications.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• and
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission periodically and at times known to the mobile unit, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit, wherein the times are known in advance by the unit such that the comparing occurs even when the unit does not receive the message.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• and
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit, wherein the stored data pattern is a string of numbers which is progressively more likely to induce errors upon receipt at the mobile unit.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• and
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit, wherein the comparator determines an error free length of the received data pattern.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit;
• means for switching an association of the mobile unit from a first access point to a second access point if the quality of communications with the first access point falls below a first threshold value, wherein at least one other mobile unit is in communication with the second access point, and wherein the means for switching includes means for determining a utilization of the second access point by the at least one other mobile unit.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit;
• means for switching an association of the mobile unit from a first access point to a second access point if the quality of communications with the first access point falls below a first threshold value;
• and
• second means for switching the association to the second access point to balance a utilization of the first and second access points.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit;
• means for switching an association of the mobile unit from a first access point to a second access point if the quality of communications with the first access point falls below a first threshold value;
• and
• means for measuring a total data rate at each of the first and second access points for all mobile units in communication with each of the first and second access points.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a frequency hopping radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit;
• means for scanning a plurality of radio frequencies for transmissions from a number of access points;
• a memory for storing a phase of the frequency hopping of each of the number of access points;
• and
• means for varying a proportion of time spent in scanning, the proportion being dependent on the current quality of the communications.

A method for communicating between a unit and a base using a plurality of communication channels, comprising:

• transmitting a message of data known to the unit on a first communication channel periodically and at times known to the unit from the base to the unit;
• evaluating at the unit a quality of communications on the first channel by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a threshold, switching to a second channel for subsequent communications between the unit and the base, wherein the times are known in advance by the unit such that the evaluating occurs even when the unit does not receive the message.

A method for communicating between a unit and a base using a plurality of communication channels, comprising:

• transmitting a message of data known to the unit on a first communication channel periodically and at times known to the unit from the base to the unit;
• evaluating at the unit a quality of communications on the first channel by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a threshold, switching to a second channel for subsequent communications between the unit and the base, wherein the evaluating occurs at the times known to the unit, even when the unit does not receive the message.

A method for communicating between a mobile unit and a plurality of access points, the access points being in communication with one another on a network, the mobile unit communicating by radio with the access points, the method comprising:

• transmitting a message of data known to the mobile unit periodically and at times known to the mobile unit on a first access point to the mobile unit;
• evaluating at the mobile unit a quality of communications by measuring how much of the known data is received at the mobile unit;
• and
• if the quality falls below a first threshold value, switching to a second access point for subsequent communications with the mobile unit, wherein the evaluating occurs at the times known to the unit, even when the unit does not receive the message.

A mobile unit for being part of a wireless local area network having a plurality of access points, the mobile unit comprising:

• a radio receiver for receiving transmissions from the access points;
• a memory holding a stored data pattern;
• and
• a comparator having a first input terminal connected to the radio receiver and a second input terminal connected to the memory, for comparing the stored data pattern to a data pattern in a received radio transmission periodically and at times known to the mobile unit, thereby providing at an output terminal of the comparator an indication of a quality of communications between each access point and the mobile unit, wherein the comparing occurs at the times known to the unit, even when the unit does not receive the message.