Wireless communications system with detection of foreign radiation sources

A method for use in a wireless LAN-system of the 802.11-type for avoiding interference between radar signals and the signals exchanged between a plurality of wireless broadcasting nodes in the system, the method comprising the steps of:

• enabling one of the nodes in the system to function as a radar controlling node (RCN) and
• letting said RCN carry out measurement on at least one frequency in a frequency band which has been assigned to the system, said measurements being carried out to detect if said at least one frequency is being utilized by a device or a system foreign to said wireless communications system, such as a radar device or system,
• the measurement being enabled to be carried out by means of the RCN transmitting a “quiet” message to other nodes in the system,
• said “quiet” message being a message which prohibits other nodes from transmitting during a certain interval defined in the “quiet” message,
• which method is characterized in that the RCN recognizes radar signals by means of measuring the duration of pulses received during the “quiet” intervals, so that if a received frame has a duration which is shorter than the shortest duration of a frame of the LAN-system, and has a signal strength above a certain predetermined level, radar is assumed, and if the duration of the frame is longer than the longest assumed duration of a radar frame, LAN is assumed.

A method for use in a wireless LAN-system of the 802.11-type for avoiding interference between radar signals and the signals exchanged between a plurality of wireless broadcasting nodes in the system, the method comprising the steps of:

• enabling one of the nodes in the system to function as a radar controlling node (RCN) and
• letting said RCN carry out measurement on at least one frequency in a frequency band which has been assigned to the system, said measurements being carried out to detect if said at least one frequency is being utilized by a device or a system foreign to said wireless communications system, such as a radar device or system,
• the measurement being enabled to be carried out by means of the RCN transmitting a “quiet” message to other nodes in the system,
• said “quiet” message being a message which prohibits other nodes from transmitting during a certain interval defined in the “quiet” message, which method is characterized in that:
• the transmitting of the “quiet” message is triggered by the RCN detecting that it needs a certain amount of time to carry out its measurement, or by the RCN detecting an event which makes the radar detection too uncertain.

A method for use in a wireless LAN-system of the 802.11-type for avoiding interference between radar signals and the signals exchanged between a plurality of wireless broadcasting nodes in the system, the method comprising the steps of:

• enabling one of the nodes in the system to function as a radar controlling node (RCN) and
• letting said RCN carry out measurement on at least one frequency in a frequency band which has been assigned to the system, said measurements being carried out to detect if said at least one frequency is being utilized by a device or a system foreign to said wireless-communication-system, such as a radar device or system,
• characterized in that:
• the RCN tracks the whole LAN traffic without actively controlling the traffic, and,
• at the same time the RCN scans for radar transmissions in time periods without traffic, with said scanning being performed by RSS measurements, which are compared with a predefined radar detection power threshold, and:
• if said threshold is not exceeded it is assumed that no radar is present.
• if said threshold is exceeded, the RCN checks whether this was due to LAN traffic, and if this is the case, the corresponding LAN traffic duration is excluded from the measurement time.

A method for use in a wireless LAN-system of the 802.11-type for avoiding interference between radar signals and the signals exchanged between a plurality of wireless broadcasting nodes in the system, the method comprising the steps of:

• enabling one of the nodes in the system to function as a radar controlling node (RCN) and
• letting said RCN carry out measurement on at least one frequency in a frequency band which has been assigned to the system, said measurements being carried out to detect if said at least one frequency is being utilized by a device or a system foreign to said wireless communications system, such as a radar device or system, characterized in that:
• the RCN schedules measurement periods on its current operating channel, as well as on other channels, including channels which have previously been detected as used by radar devices, and keeps track of the total measurement time (TTOT), said total measurement time being defined as the sum of all measurement intervals (Tmeas) on a specific channel, and,
• the variable TTOT is initially set to a predetermined value once radar has been detected on a specific channel, and
• each time a measurement is made on a channel previously detected as radar-occupied, if radar is detected during a measurement interval, the value of TTOT is unchanged, and if no radar signal is detected during a measurement interval, the total measurement time is increased in a cumulative manner, as TTOT=TTOT+Tmeas, and
• if TTOT satisfies a given requirement on total measurement time, a previously radar-marked channel can be considered as radar-free, and if radar is detected after a number of radar-free measurements, the cumulative total time TTOT will once again be set to its initial predetermined value.