Scanning for network connections with variable scan rate

Abstract

A wireless communication terminal includes a radio frequency (RF) transceiver and a baseband processing circuit, which is arranged to detect an indication of a rate of movement of the terminal. The baseband processing circuit is coupled to cause the RF transceiver to scan periodically for access points that are available to communicate with the mobile terminal at a scan rate that is selected responsively to the indication, and upon detecting an available access point, to establish a wireless connection between the terminal and the available access point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, pictorial illustration showing a multi-network system for wireless data communications, in accordance with an embodiment of the present invention;

FIG. 2 is a diagram that schematically illustrates movement of a mobile terminal through coverage areas of WiMAX and WLAN networks, in accordance with an embodiment of the present invention;

FIG. 3 is a block diagram that schematically shows elements of a dual-function mobile terminal, in accordance with an embodiment of the present invention;

FIG. 4 is a block diagram that schematically shows details of baseband processing components in a dual-function mobile terminal, in accordance with an embodiment of the present invention;

FIG. 5 is a state diagram that schematically illustrates a method for dual-function operation of a mobile terminal, in accordance with an embodiment of the present invention;

FIG. 6 is a signal timing diagram that schematically illustrates methods for controlling timing of WiMAX and WLAN transmissions, in accordance with an embodiment of the present invention;

FIG. 7 is a flow chart that schematically illustrates a method for controlling scanning for WLAN availability by a dual-function mobile terminal, in accordance with an embodiment of the present invention;

FIG. 8A is a signal timing diagram that schematically illustrates a method for detecting WLAN availability, in accordance with an embodiment of the present invention; and

FIG. 8B is a flow chart that schematically illustrates a method for detecting and connecting to a WLAN, in accordance with an embodiment of the present invention.

Claims

1. A wireless communication terminal, comprising: a radio frequency (RF) transceiver; anda baseband processing circuit, which is arranged to detect an indication of a rate of movement of the terminal, and is coupled to cause the RF transceiver to scan periodically for access points that are available to communicate with the mobile terminal at a scan rate that is selected responsively to the indication, and upon detecting an available access point, to establish a wireless connection between the terminal and the available access point.

2. The terminal according to claim 1, wherein the indication comprises a change in a geographical position of the mobile terminal.

3. The terminal according to claim 1, wherein the baseband processing circuit is arranged to cause the RF transceiver to exchange data over the air with a base station over a long-range wireless network while scanning periodically for the access points.

4. The terminal according to claim 3, wherein the baseband processing circuit is arranged to assess the rate of movement responsively to a change in signals received by the terminal from the base station over the long-range wireless network.

5. The terminal according to claim 3, wherein the long-range wireless network comprises a WiMAX network, and wherein the wireless connection with the available access point is established over a wireless local area network (WLAN).

6. The terminal according to claim 1, wherein the baseband processing circuit is arranged to scan for the access points at a first scan rate when the terminal is moving at a pedestrian speed, and to scan at a second scan rate, lower than the first scan rate, when the terminal is stationary.

7. The terminal according to claim 1, wherein the baseband processing circuit is arranged to stop the scanning when the rate of movement is indicated to be above a predetermined maximum.

8. Apparatus for communication, comprising: a radio frequency (RF) transceiver; anda baseband processing circuit, which is coupled to cause the RF transceiver to transmit a RF probe signal requesting a response from an access point in a wireless network, and to intermittently switch the RF transceiver on and off during a predetermined time period following the probe signal, and to sample radio signals received while the RF receiver is on, and to determine a probability, responsively to the sampled radio signals, that the radio signals comprise a response to the probe signal transmitted by the access point, and if the probability is equal at least to a threshold value, to operate the RF transceiver continuously so as to receive and demodulate a downlink signal transmitted by the access point.

9. The apparatus according to claim 8, wherein the RF transceiver is intermittently switched so as to operate at a duty cycle less than 50%.

10. The apparatus according to claim 9, wherein the duty cycle is no greater than 10%.

11. The apparatus according to claim 8, wherein the wireless network is a wireless local area network (WLAN).

12. The apparatus according to claim 11, wherein the baseband processing circuit is arranged to maintain a first connection for exchanging data between the wireless terminal and a base station in a long-range wireless data network while attempting to establish a second connection with the access point over the WLAN by transmitting the RF probe signal and sampling the radio signals.

13. A method for communication, comprising: detecting an indication of a rate of movement of a mobile terminal;scanning periodically for access points that are available to communicate with the mobile terminal, at a scan rate that is selected responsively to the indication; andupon detecting an available access point, establishing a wireless connection between the mobile terminal and the available access point.

14. The method according to claim 13, wherein detecting the indication comprises detecting a change in a geographical position of the mobile terminal.

15. The method according to claim 13, and comprising exchanging data over the air between the mobile terminal and a base station over a long-range wireless network while scanning periodically for the access points.

16. The method according to claim 15, wherein exchanging the data comprises receiving at the mobile terminal signals transmitted by the base station, and wherein detecting the indication comprises assessing the rate of movement responsively to a change in the signals.

17. The method according to claim 5, wherein the long-range wireless network comprises a WiMAX network, and wherein establishing the wireless connection comprises connecting the mobile terminal with the available access point over a wireless local area network (WLAN).

18. The method according to claim 13, wherein scanning periodically comprises scanning at a first scan rate when the mobile terminal is moving at a pedestrian speed, and scanning at a second scan rate, lower than the first scan rate, when the mobile terminal is stationary.

19. The method according to claim 13, wherein scanning periodically comprises stopping the scanning when the rate of movement is indicated to be above a predetermined maximum.

20. A method for communication, comprising: transmitting a radio frequency (RF) probe signal from a wireless terminal requesting a response from an access point in a wireless network;during a predetermined time period following the probe signal, intermittently switching a RF receiver of the wireless terminal on and off, and sampling radio signals received while the RF receiver is on;determining a probability, responsively to the sampled radio signals, that the radio signals comprise a response to the probe signal transmitted by the access point; andif the probability is equal at least to a threshold value, operating the RF receiver continuously so as to receive and demodulate a downlink signal transmitted by the access point.

21. The method according to claim 20, wherein intermittently switching comprises operating the RF receiver at a duty cycle less than 50%.

22. The method according to claim 21, wherein the duty cycle is no greater than 10%.

23. The method according to claim 20, wherein the wireless network is a wireless local area network (WLAN).

24. The method according to claim 23, and comprising maintaining a first connection for exchanging data between the wireless terminal and a base station in a long-range wireless data network while attempting to establish a second connection with the access point over the WLAN by transmitting the RF probe signal and sampling the radio signals.