WO2005101887A1

WO2005101887A1 - Wireless network controlling the time occurrence of spectrum scanning of a dual mode wireless terminal

Info

Publication number: WO2005101887A1
Application number: PCT/IB2005/051219
Authority: WO
Inventors: Paul Bucknell; Matthew P. J. Baker; David H. Evans; Timothy J. Moulsley
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-04-15
Filing date: 2005-04-13
Publication date: 2005-10-27
Also published as: GB0408417D0

Abstract

A dual mode wireless terminal (100) can obtain service on more than one network. While operating on a first network (200) the terminal scans to determine the availability of a second network (300). The timing of the scanning is controlled by scanning control messages transmitted by the first network (200).

Description

W_IREL_ESS NETWORK CONTROLLING THE TIME OCCURRENCE OF SPECTRUM SCANNING OF A DUAL MODE WIRELESS TERMINAL

DESCRIPTION

The invention relates to a dual mode termi nal operable on a first 5 wireless network and on a second wireless network, to a wireless system comprising such a dual mode terminal, to a method of operating a wireless system comprising such a dual mode terminal, and to a device for operation on a wireless network.

10 The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communications system providing voice and information services to mobile users. UMTS can provide mobile users with high bit rate connections for them to access rich multimedia services. In order to reduce the amount of expensive radio bandwidth used by the UMTS some Public 15 Land Mobile Network (PLMN) operators in the future will make it possible for the user to access services not only through the U IMTS radio network, but through wireless local area network (WLAN) "hot spots" instead. For this, the user will have an UMTS/WLAN dual mode terminal capable of communicating both via the UMTS air interface and via the WLAN air interface. The dual 20 mode terminal may be a stand-alone device or may be implemented as a supplementary device such on a card for use in conjunction with a personal computer. Possible architectures for integrating UMTS and an IEEE802.11 WLAN network are disclosed by Muhammad Jasseemuddin in "An Architecture for 25 Integrating UMTS and 802.11 WLAN Network", Proceedings of IEEE Symposium on Computers and Communications, Antalya, Turkey, pp. 716- 723, 2003, and by A K Salkintzis et al in "WLAN-GP RS Integration for Next- Generation Mobile Data Networks", IEEE Wireless Communications, October 2002, pp112-124. Using these architectures, no user intervention is required 30 to perform the switchover from WLAN to UMTS and the user is not even aware of this handover. Two main ways of interworking have been proposed, "loose coupling" and "tight coupling". With loose coupling the WLAN is complementary to the UMTS network and uses only subscriber information held in the UMTS network. With tight coupling there is a direct connection between the UMTS core network (or even the Radio Network Controller (RNC)) and the WLAN, so that the WLAN is effectively just another radio access network (or even another cell) for the UMTS network. In general, the coverage provided by a WLAN is less extensive that the coverage provided by a UMTS cell. WO2004/002051 addresses inter-working between UMTS and a WLAN, in particular the registration of a WLAN as a UMTS routing area for the purpose of location. WO 2004/006447A2 addresses inter-working between UMTS and a WLAN using an Internet Protocol (IP) with the WLAN handover support provided via the UMTS lur interface between two RNCs. If a dual mode WLAN/UMTS terminal, while operating on the UMTS network, scans all the time for a WLAN connection then rapid switching between networks is possible, but the power consumption of the terminal will be very high. However, if the dual mode terminal scans less often, the handover process will take longer and the effective coverage ares of the WLAN will be reduced as the terminal moves through the actual coverage area. An object of the invention is to enable a reduction in power consumption of a dual mode terminal.

According to a first aspect of the invention there is provided a method of operating a wireless system comprising a first network and a dual mode terminal operable on the first network and on a second network, the method comprising: at the first network, transmitting a scanning control message; and at the dual mode terminal, whilst operating on the first network, receiving the scanning control message; determining the presence of a second network by spectrum scanning; and controlling a time of occurrence of the spectrum scanning in response to receiving the scanning control message. By means of the scanning control message, the first network, for example a UMTS network, can control the time of occurrence of the spectrum scanning by the dual mode terminal, and hence control the power consumption of the dual mode terminal. Furthermore, the first network can control the speed of switching between networks and the trade-off betw/een power consumption and speed of switching between networks. By controlling the speed of switching between networks, the effective coverage of the second network can be controlled; if a fast switching speed is used, a moving terminal may transfer to the second network as soon as it moves into the coverage area of the second network, whereas if a slow switching speed is used, a moving terminal will remain connected to the first network for some time after entering the coverage area of the second network. The control of the time of occurrence of the spectrum scanning may include controlling the interval between scans, controlling the duration of scanning, and prohibiting scanning for a period of time. Criteria for controlling the time of occurrence of the spectrum scanning may be, for example, the required service, the available capacity on the first or second network, the proximity of the second network, the capabilities of the dual mode terminal, or the location of the dual mode terminal. Using such criteria, the power consumption can be reduced according to whether the required service can be more efficiently provided on the first or the second network, or according to the availability of the second network. Optionally the time of occurrence of the spectrum scanning by the dual mode terminal may be controlled dependent on the location of the dual m ode terminal relative to the location of the second network. In this case, the first network may adapt the content of the scanning control message in response to the location of the dual mode terminal, the location being determined either by the first network, or by the dual mode terminal and reported to the first network. Optionally, if the dual mode terminal determines its own location, it may adapt the time of occurrence of the spectrum scanning according to its location, for example by determining its proximity to the second network using information transmitted by the first network indicating the location of the second network. By using the above options, the amount of scanning may be reduced when the second network is not expected to be within range of the dual mode terminal, thereby reducing power consumption, and the amount of scanning may be increased when the second network is expected to be within range of the dual mode terminal, thereby enabling a fast handover to the second network. Optionally, additional information about the second network may be used to control the time of occurrence of the spectrum scanning. Such additional information may include, for example, data about the services supported by the second network, or data about the capacity available in the second network. Such additional information may be employed by the first network to adapt the content of the scanning control message, or may be transmitted by the first network and used by the dual mode terminal to adapt the time of occurrence of the spectrum scanning. By using such additional information, the power consumption may be reduced when the second network cannot provide the required service, or cannot provide sufficient capacity for the required service. According to a second aspect of the invention there is provided a dual mode terminal operable on a first wireless network and on a second wireless network, comprising: terminal first receiver means adapted to receive a scanning control message from the first network; terminal second receiver means adapted to determine the presence of a second network by spectrum scanning; and terminal control means adapted to control a time of occurrence of the spectrum scanning in response to receiving the scanning control message. According to a third aspect of the invention there is provided a wireless system comprising a dual mode terminal in accordance with the second aspect of the invention and a network device, the network device comprising a device transmitter adapted to transmit the scanning control message. According to a fourth aspect of the invention there is provided a device for operation on a first wireless network, comprising a transmitter adapted to transmit a scanning control message containing a scanning control instruction for controlling a time of occurrence of spectrum scanning by a dual mode terminal when determining the presence of a second network.

The invention will now be described, by way of example only, with reference to the accompanying drawings wherein; Figure 1 is a block schematic diagram of a wireless system; Figure 2 is a flow chart of one embodiment of a method of operating a wireless system; and Figure 3 is a flow chart of another embodiment of a method of operating a wireless system. Referring to Figure 1 there is shown a wireless system comprising a dual mode terminal 100, a first wireless network represented by a network device 200, and a second wireless network 300. In general, but for clarity not shown in Figure 1 , the first wireless network may comprise a plurality of network devices 200 and also a plurality of wireless terminals. By way of example, the first wireless network may be a UMTS network and the network device 200 may be a UMTS base station. The network device 200 comprises a transmitter 210 (Tx) and a receiver 220 (Rx). An output of the transmitter 210 and an input of the receiver 220 are coupled to an antenna 230. Coupled to the transmitter 210 and receiver 220 is a control means 250 (μC), which may be for example a processor. Optionally, coupled to the control means 250 is a location means 260 (L) for determining the location of the dual mode terminals 100, and storage means 270 (S) for storing data about one or more second wireless networks 300. The second wireless network 300 comprises a plurality of wireless devices 310, 320; each of these wireless device may be either an access point 310 or a user equipment 320. For example, the wireless network 300 may be a WLAN network operating in accordance with the IEEE 802.11 standard. The dual mode terminal 100 comprises a first transceiver 110 having a first transmitter portion Tx1 and a first receiver portion Rx1, and a second transceiver 120 having a second transmitter portion Tx2 and a second receiver portion Rx2. The first transceiver 110 is coupled to a first antenna 130, and the second transceiver 120 is coupled to a second antenna 140. The first transceiver 110 is adapted to communicate with the network device 200 using the air interface protocol of the first wireless network, for example UMTS. The second transceiver 120 is adapted to communicate with the second wireless network 300 using the air interface protocol of the second wireless network 300, for example IEEE802.11. Although the first transceiver 110 and second transceiver 120 are illustrated as separate transceiver devices, they may be implemented in a common transceiver having at least partial commonality of first and second receiver portions, Rx1 and Rx2, and at least partial commonality of first and second transmitter portions, Tx1 and Tx2. Also, although separate antenna 130, 140 are illustrated for the first and second transceiver 110, 120, a common antenna may be used. Both the first transceiver 110 and the second transceiver 120 are coupled to a control means 150 (μC) which may be, for example, a processor. Optionally, coupled to the control means 150 is a location means 160 (L), such as a GPS (Global Positioning System) receiver, for determining the location of the dual mode terminal 100, and storage means 170 (S) for storing data about one or more second wireless networks 300. The operation of the wireless system illustrated in Figure 1 will now be described with reference to the flow chart of Figure 2 which shows steps performed while the dual mode terminal is in communication with the network device 200 to obtain a desired service from the second wireless network 300. In Figure 2, those steps shown in boxes with a broken line represent variants and the description will omit these initially; they will be described subsequently. Also in Figure 2, the steps on the left hand side of the flow chart relate to steps performed by the network device 200, and the steps on the right hand side of the flow chart relate to steps performed by the dual mode terminal 100. Commencing at step 510, the transmitter 210 of the network device 200 transmits a scanning control message. The scanning control message contains a scanning control instruction for controlling the time of occurrence of spectrum scanning by the dual mode terminal 100. Such an instruction may take various forms, for example, a scan enable/disable indicator, an indication of the time interval between successive scanning periods, an indication of a range of time intervals between successive scanning periods, thereby enabling a degree of flexibility by the dual mode terminal 100 to trade-off power saving against speed of detecting the second network, an indication of the duration of periods of scanning, or any combination of such indications. At step 520 the first receiver portion Rx1 of the first transceiver 110 of the dual mode terminal 100 receives the scanning control message and forwards the message to the control means 150. At step 550 the control means 150 initiates scanning of the wireless spectrum, or adapts any current scanning, by the second receiver portion Rx2 of the second transceiver 120 in accordance with the scanning control message to detect the second network 300. When the second network 300 is detected, flow proceeds to step 590 where the dual mode terminal 100 receives service from the second network 300 by means of the second transceiver 120. The variant steps in Figure 2 will now be described. Optionally, at step 500, the network device 200 may transmit an indication of the location of the second network 300. This indication may be supplied to the network device 200 from an external device (not illustrated), or may be pre-stored in the storage means 270. For transmission, this indication of location may be included in the scanning control message or may be included in a separate message. This indication is received by the dual mode terminal at step 520. At step 530 the dual mode terminal 100 determines its location by means of the location means 160, and reports the location to the control means 150. Also at step 530, the two locations are compared by the control means 150. If the dual mode terminal 100 is within wireless range of the second network 300, according to a predetermined criterion, flow proceeds to step 550. The scanning control message may contain a plurality of alternative scanning control instructions for selection and action by the dual mode terminal 100 according to the outcome of step 530. For example, a short scan period may be specified for use if the dual mode terminal 100 is in close proximity, according to a predetermined criterion, to the second network 300, a short scan period being used in this case to effect the handover to the second network 300 in a short period of time, whereas a longer scan period may be specified for use if the distance is greater, in order to minimise power consumption when there is a low probability of detection of the second network 300. If the dual mode terminal 100 is not within wireless range of the second network 300, the attempt to gain service from the second network 300 may be terminated at step 540. In this latter case, either the service may be provided on the first network by the network device 200, or the process may be repeated to gain service from a further network, or the attempt to gain service may be abandoned. At optional step 560 the control means 150 initiates transmission by the first transmitter portion Tx1 of the first transceiver 1 10 of an indication of the presence of the second network 300. At step 570 the indication of the presence of the second network 300 is received by the receiver 220 of the network device 200 and reported to the control means 250. At step 580 the control means 580 initiates transmission of a service control message by the transmitter 210. Flow then proceeds at step 590 where the dual mode terminal 100 receives service from the second network 300 by means of the second transceiver 120 in response to receiving the service control message via the first receiver portion Rx1 of the first transceiver 1 10. As a further variant, the indication of the location of the second network 300 may be stored in the storage means 170 for use in subsequent comparisons of location. Another embodiment of the invention is illustrated in the flow chart of Figure 3. In Figure 3, the steps on the left hand side of the flow chart relate to steps performed by the network device 200, and the steps on the right hand side of the flow chart relate to steps performed by the dual mode terminal 100. Commencing at step 610, the dual mode terminal 100, determines its location by means of the location means 160 and reports the location to the control means 150. At step 620 the control means 150 initiates transmission by the first transmitter portion Tx1 of the first transceiver 110 of an indication of the location. This indication is received at the network device 200 by the receiver 220 and at step 630 the control means 250 compares the received indication of location of the dual mode terminal 100 with a location of the second network

300 stored in the storage means 270. If the dual mode terminal 100 is within wireless range of the second network 300, according to a predetermined criterion, flow proceeds to step 510 and to subsequent steps identical to those in the flow chart of Figure 1 having the same reference numerals. However, if the dual mode terminal 100 is not within wireless range of the second network

300, the attempt to gain service from the second network 300 may be terminated, in which case either the service may be provided on the first network by the network device 200, or the dual mode terminal may be commanded to search for a further network, or the attempt to gain service may be abandoned. Optionally, the content of the scanning control message may be adapted by the control means 250 according to the result of the comparison at step 630. For example, if the dual mode terminal 100 is in close proximity, according to a predetermined criterion, to the second network 300, a short scan period may be specified as being sufficient to detect the presence of the second network 300, thereby minimising power consumption, whereas if the distance is greater a longer scan period may be specified in order to ensure reliable detection of the second network 300. In a further variant of the invention, the transmission of the scanning control message, or the adaptation of the content of the scanning control message may be responsive to an indication of the presence of the second network received from a further terminal. In this way information about the availability of the second network may be combined from more than one source, thereby enabling scanning control to be implemented with improved reliability. The indication of the presence of the second network may be transmitted automatically on detection of such a network, or in response to a user requesting a service, for example a user requesting the use of a WLAN. The scanning control message may be transmitted as a broadcast message to all dual mode terminals operating on the first network, or may be addressed to one or more specific dual mode terminals requiring a service, or may be addressed to a sub-set of the dual mode terminals operating on the first network in a particular location or a particular coverage cell. Although the invention has been described with reference to the first network being a UMTS network and the second network 300 being a WLAN, the invention is also applicable to other types of network including GSM (Global System for Mobile Communication), GPRS (Generalised Packet Radio Service, CDMA2000 (Code Division Multiple Access 2000), DECT (Digital European Cordless Telephone), Bluetooth™. The functional elements of the network device 200 are not necessarily co-located but may be distributed within the first network. The order of steps in the flow charts of Figures 2 and 3 may, to some extent, be varied. For example, the determination of location may occur as a background activity such that the locations are already known when the requirement for providing service from the second network 300 arises. In this specification, the term "dual mode" in not intended to exclude terminals which are capable of operating on more than two networks. In the present specification and claims the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Further, the word "comprising" does not exclude the presence of other elements or steps than those listed. The inclusion of reference signs in parentheses in the claims is intended to aid understanding and is not intended to be limiting. , From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the art of wireless networks and apparatus and which may be used instead of or in addition to features already described herein.

Claims

1. A method of operating a wireless system comprising a first network and a dual mode terminal (100) operable on the first network and on a second network, the method comprising: at the first network, transmitting (510) a scanning control message; and at the dual mode terminal (100), whilst operating on the first network, receiving the scanning control message; determining (550) the presence of a second network (300) by spectrum scanning; and controlling (550) a time of occurrence of the spectrum scanning in response to receiving the scanning control message.

2. A method as claimed in claim 1 , further comprising, at the dual mode terminal (100), determining (610) the location of the dual mode terminal

(100) and transmitting (620) an indication of said location, and at the first network, receiving the indication of said location, comparing (530) the locations, and transmitting (630, 510) the scanning control message only if said location matches the location of the second network according to a predetermined criterion.

3. A method as claimed in claim 1 , further comprising, at the dual mode terminal (100), determining (610) the location of the dual mode terminal and transmitting (620) an indication of said location, and at the first network (200), receiving the indication of said location, comparing (630) the location of the dual mode terminal with the location of the second network, and adapting (630) the content of the scanning control message according to the result of the comparison.

4. A method as claimed in claim 1 , further comprising, at the first network, transmitting (500) an indication of location of the second network, and, at the dual mode terminal (100), receiving (520) said indication of location, determining (530) the location of the dual mode terminal (100), comparing (530) the locations, and performing (550) the spectrum scanning only if the location of the dual mode terminal (100) and the location of the second network (300) match according to a predetermined criterion.

5. A method as claimed in claim 1 , wherein the scanning control message comprises a plurality of scanning control instructions, the method further comprising, at the first network, transmitting (500) an indication of location of the second network (300), and, at the dual mode terminal (100), receiving (520) said indication of location, determining (530) the location of the dual mode terminal (100), comparing (530) the locations, selecting, dependent on the outcome of the comparison, one of the plurality of scanning control instructions, and controlling (550) the time of occurrence of the spectrum scanning in accordance with the selected scanning control instruction.

6. A method as claimed in any of claims 1 to 5, wherein the transmission of the scanning control message is responsive to an indication of the presence of the second network received by the first network from a further terminal.

7. A method as claimed in any of claims 1 to 6, wherein the scanning control message comprises an indication of a time interval between successive scans.

8. A method as claimed in any of claims 1 to 6, wherein the scanning control message comprises an indication of a range of time intervals between successive scans.

9. A method as claimed in any of claims 1 to 8, wherein the scanning control message comprises an indication of a time duration for which an individual scan is to be performed.

10. A method as claimed in any of claims 1 to 9, wherein the scanning control message transmitted by the first network is a broadcast message.

11. A method as claimed in any of claims 1 to 9, wherein the scanning control message transmitted by the first network is addressed to the dual mode terminal.

12. A dual mode terminal (100) operable on an first wireless network (200) and on a second wireless network (300), comprising: terminal first receiver means (Rx1) adapted to receive a scanning control message from the first wireless network (200); terminal second receiver means (Rx2) adapted to determine the presence of a second network (300) by spectrum scanning; and terminal control means (150) adapted to control a time of occurrence of the spectrum scanning in response to receiving the scanning control message.

13. A dual mode terminal (100) as claimed in claim 12, comprising location determining means (160) for determining the location of the dual mode terminal (100), wherein the terminal first receiver means (Rx1) is adapted to receive an indication of location of the second network, and wherein the terminal control means (150) is further adapted to compare the locations and to permit the spectrum scanning only if the location of the dual mode terminal (100) and the location of the second network (300) match according to a predetermined criterion.

14. A dual mode terminal (100) as claimed in claim 12, comprising location determining means (160) for determining the location of the dual mode terminal (100), wherein the terminal first receiver means (Rx1) is adapted to receive a scanning control message containing a plurality of scanning control instructions, wherein the terminal first receiver means (Rx1) is adapted to receive an indication of location of the second network, and wherein the terminal control means (1 50) is further adapted to compare the locations and to select, dependent on the outcome of the comparison, one of the plurality of scanning control instructions, and to control the time of occurrence of the spectrum scanning in accordance with the selected scanning control instruction.

15. A wireless system comprising a dual mode terminal (100) as claimed in claim 12 and a network device (200), the network device comprising a device transmitter (210) adapted to transmit the scanning control message.

16. A wireless system as claimed in claim 15, wherein: the dual mode terminal (100) further comprises location determining means (160) for determining the location of the dual mode terminal (100) and terminal first transmitter means (Tx1) adapted to transmit an indication of the location of the dual mode terminal (100); the network device (200) comprise a device receiver (220) adapted to receive said indication of the location of the dual mode terminal (100), storage means (270) for storing an indication of location of the second network (300); and comparison means (250) for comparing the location of the dual mode terminal (100) with the location of the second network (300); and wherein the device transmitter (21 0) is adapted to transmit the scanning control message only if said locations match according to a predetermined criterion.

17. A wireless system as claimed in claim 15, wherein: the dual mode terminal (100) further comprises location determining means (160) for determining the location of the dual mode terminal (100) and terminal first transmitter means (Tx1) adapted to transmit an indication of the location of the dual mode terminal; and the network device (200) further comprises a device receiver (220) adapted to receive said indication of the location of the dual mode terminal, storage means (270) for storing an indication of location of the second network (300), comparison means (250) for comparing the locations, and device control means (250) for adapting the content of the scanning control message according to the result of the comparison.

18. A wireless system as claimed in claim 15, wherein: the device transmitter (210) is adapted to transmit an indication of location of the second network (300); the dual mode terminal (100) comprises location determining means (160) for determining the location of the dual mode terminal (100); the terminal first receiver means (Rx1) is adapted to receive the indication of location of the second network (300); and the terminal control means (150) is further adapted to compare the locations and to permit the spectrum scanning only if the location of the dual mode terminal (100) and the location of the second network (300) match according to a predetermined criterion.

19. A wireless system as claimed in claim 15, wherein: the scanning control message comprises a plurality of scanning control instructions; the device transmitter (210) is adapted to transmit an indication of location of the second network (300); the dual mode terminal (100) comprises location determining means (160) for determining the location of the dual mode terminal (100); the terminal first receiver means (Rx1) is adapted to receive the indication of location of the second network (300); and the terminal control means (150) is further adapted to compare the locations and to select, dependent on the outcome of the comparison, one of the plurality of scanning instructions, and to control the time of occurrence of the spectrum scanning in accordance with the selected scanning instruction.

20. A device (200) for operation on a first wireless network, comprising a transmitter (210) adapted to transmit a scanning control message containing a scanning control instruction for controlling a time of occurrence of spectrum scanning by a dual mode terminal (100) when determining the presence of a second network (300).

21. A device (200) as claimed in claim 20, wherein the scanning control message contains a plurality of scanning control instructions and the transmitter (210) is adapted to transmit an indication of location of the second network (300).