AU2003248462B2

AU2003248462B2 - Satellite broadcasting method, and base station and mobile station for use with satellite broadcasting method

Info

Publication number: AU2003248462B2
Application number: AU2003248462A
Authority: AU
Inventors: Toshihiro Shikama; Yoshiko Yamada
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2002-09-30
Filing date: 2003-09-30
Publication date: 2005-05-19
Anticipated expiration: 2023-09-30
Also published as: KR20040029279A; AU2003248462A1; KR100585902B1; JP3743411B2; JP2004128630A

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: MITSUBISHI DENKI KABUSHIKI KAISHA Invention Title: SATELLITE BROADCASTING METHOD, AND BASE STATION AND MOBILE STATION FOR USE WITH SATELLITE BROADCASTING

METHOD

The following statement is a full description of this invention, including the best method of performing it known to us: SATELLITE BROADCASTING METHOD, AND BASE STATION AND MOBILE STATION FOR USE WITH SATELLITE BROADCASTING METHOD BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a satellite broadcasting method of performing broadcasting transmission from a base station to a mobile station by way of a broadcast or communications satellite that forms multiple beams on a ground, and a base station and a mobile station for use with the satellite broadcasting method.

Description of Related Art There have been provided a single-beam method and a multiple-beam method as a method of performing broadcasting transmission to mobile stations on a ground by way of an Earth-orbiting broadcast or communications satellite. In accordance with the single-beam method, though the effective radiation power on the ground is reduced because a wide range on the ground must be covered by a single beam, communication line control within the single beam can be conducted. In contrast, in accordance with the multiple-beam method, though the effective radiation power can be increased, there is a necessity to perform switching between communication lines when a moving object moves between beam areas because a communication line frequency is assigned to each of multiple beams.

For example, Japanese patent application publication (TOKKAIHEI) No.09-214414 discloses a prior art satellite communication method using such a multiple-beam method.

The satellite communication method includes the steps of a mobile station determining whether or not there is a H:\teresab\keep\Specfications\P5087703059.dc 30/09/03 necessity to perform switching between beams based on the Sline qualities of multiple beams or GPS position information, and, when there is a necessity to perform switching between beams, the mobile station transmitting a beam switching request signal to a broadcast or communications satellite.

IND A problem with a prior art multiple-beam satellite 00 communication method is that a mobile station needs a (N receiver in order to measure the line qualities of multiple beams while receiving broadcast data, and therefore there causes a loss of received broadcast data when the mobile station does not have such a receiver. Another problem is that though a mobile station can have a transmission system for transmitting a beam switching request signal, it is difficult to apply such a prior art mobile station to satellite communications intended for broadcasting.

SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided a satellite broadcasting method of transmitting broadcast packets from a base station to a mobile station by way of a broadcast or communications satellite that forms multiple beams on a ground, said method comprising the steps of: transmitting data packets from said base station to said mobile station, and continuously transmitting a switching allowance information packet at predetermined intervals from said base station to said mobile station; in response to the switching allowance information packet, said mobile station, which is staying in a H:\krystalm\keep\Speci\2O3248462 .doc 27/04/05 broadcasting area and is receiving broadcast packets from Ssaid base station via a broadcast line, measuring a quality of another broadcast line associated with another 1 broadcasting area that is adjacent to the broadcasting area in which said mobile station is staying within a transmission ID time period during which the switching allowance information oo 0packet is transmitted to said mobile station; and Sswitching from the broadcast line to the other Sbroadcast line based on a result of the measurement.

According to another aspect of the present invention there is provided a base station comprising: a transmitting unit for carrying out transmission of broadcast packets to a mobile station by way of a broadcast or communications satellite that forms multiple beams on a ground; a data packet generating unit for generating data packets from contents data applied thereto; a packet sending unit for sending, as broadcast packets, either the data packets generated by said data packet generating unit or a series of switching allowance information packet used for instructing said mobile station to carry out switching between beams to said transmitting unit, wherein the mobile station determines whether switching between beams is necessary based on measurement of the broadcast line quality by the mobile station after the switching allowance information packet is received; and a packet controlling unit for instructing said packet sending unit to send the switching allowance information packet at predetermined intervals.

H\krystalm\keep\Speci\20O3248462.doc 27/04/05 According to another aspect of the present invention there is provided a mobile station comprising: a receiving unit for receiving a broadcasting signal (1 transmitted from a base station by way of a broadcast or communications satellite that forms multiple beams on a O ground; 00 a received signal processing unit for reproducing M contents data from the broadcasting signal received by said Sreceiving unit and outputting the contents data, and for detecting a switching allowance information packet from the received broadcasting signal; and a switching controlling unit, responsive to a notification of a reception of a switching allowance information packet from said received signal processing unit, for instructing said receiving unit to carry out switching from a broadcast line associated with a broadcasting area in which said mobile station is staying to another broadcast line associated with another broadcasting area that is adjacent to the broadcasting area in which said mobile station is staying and to measure a quality of the other broadcast line, and for instructing said receiving unit to select one broadcast line via which said receiving unit receives the broadcasting signal from the two broadcast lines based on a result of the measurement of the quality of the other broadcast line.

According to another aspect of the present invention there is provided a mobile station comprising: a receiving unit for receiving a broadcasting signal transmitted from a base station by way of a broadcast or H\krystalm\keep\Speci\2003248462.doc 27/04/05 communications satellite that forms multiple beams on a Sground; a received signal processing unit for reproducing Cl contents data from the broadcasting signal received by said receiving unit and outputting the contents data, and for NO detecting a switching allowance information packet from the oo 0received broadcasting signal; and Mc, a switching controlling unit for identifying a Sbroadcasting area in which said mobile station is staying from positional information obtained by using a GPS receiver, and for, in response to a notification of a reception of a switching allowance information packet from said received signal processing unit, instructing said receiving unit to carry out switching to a broadcast line associated with the broadcasting area identified thereby.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the structure of an apparatus that uses a satellite broadcasting method in accordance with embodiment 1 of the present invention; Fig. 2 is a schematic diagram showing an example of a track that is formed on a ground by a broadcast or communications satellite for use with the satellite broadcasting method in accordance with embodiment 1 of the H;\krystalm\keep\Speci\2003248462.doc 27/04/05 present invention; Fig. 3 is a schematic diagram showing transmitted and received contents when switching between broadcast lines is carried out in accordance with the satellite broadcasting method of embodiment 1 of the present invention; Fig. 4 is a block diagram showing the structure of a base station for use with the satellite broadcasting method in accordance with embodiment 1 of the present invention; and Fig. 5 is a block diagram showing the structure of a mobile station for use with the satellite broadcasting method in accordance with embodiment 1 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Embodiment i.

A satellite broadcasting method, and a base station and a mobile station for use with the satellite broadcasting method in accordance with embodiment 1 of the present invention will be explained with reference with Figs. 1 to 5. Fig. 1 is a block diagram showing the structure of an apparatus that uses the satellite broadcasting method in accordance with embodiment 1. In Fig. 1, reference numeral 1 denotes a broadcast or communications satellite, reference numerals 2a and 2b denote broadcasting areas formed by multiple beams transmitted from the broadcast or communications satellite 1, respectively, reference numeral 3 denotes a base station, and reference numeral 4 denotes a mobile station.

Furthermore, reference numerals 5a and 5b denote uplinks (having carrier frequencies fl and f2, respectively) that are extending from the base station 3 to the broadcast or H:\teresab\keep\Specifications\P5087703059.dc 30/09/03 communications satellite 1, respectively, reference numeral 6a and 6b denote broadcast lines, downlinks (having carrier frequencies f3 and f4, respectively) that are extending from the broadcast or communications satellite 1 to the broadcasting areas 2a and 2b, respectively. Furthermore, the two uplinks are associated with the two broadcast lines, respectively, so that the uplink 5a pairs up with the broadcast line 6a and the uplink 5b pairs up with the broadcast line 6b. In a variant of this embodiment, the apparatus can include one uplink and a plurality of downlinks. In this case, the broadcast lines 6a and 6b respectively extending from the broadcast or communications satellite 1 to the broadcasting areas are associated with the uplink extending from the base station 3 to the broadcast or communications satellite 1 (in this case, the uplink 5b is replaced by the uplink 5a from here on).

For example, the broadcast or communications satellite 1 is a non-stationary broadcast or communications satellite that can fly in about the zenith direction of a specific region, and forms multiple beams on a communication area including this specific region.

For example, this broadcast or communications satellite 1 can be one broadcast or communications satellite included in a group of three broadcast or communications satellites. In this case, the three broadcast or communications satellites stay one after another in a range having a predetermined elevation angle within a specific region for eight hours, and provide communication services one after another. As a result, the three broadcast or communications satellites can ensure communications between base stations and mobile stations at all times. The above-mentioned range having a H:\teresab\keep\Specications\P5087703059.doc 30/09/03 predetermined elevation angle can be an elevation angle range having elevation angles of 70 to 90 degrees (zenith), for example, and is set depending upon an individual communication satellite system. Furthermore, the broadcast or communications satellite 1 that is roughly flying in about the zenith direction can be an elliptic orbit satellite having a periodicity of 24 hours, an orbit tilt angle of 45 degrees, an eccentricity of 0.139, an apogee altitude of 41,650 km, and a perigee altitude of 29,930 km, for example. Fig. 2 shows an example of a track which is formed on the ground by a point located directly under the satellite that is flying in such an orbit, and the satellite might be called a semi-zenith satellite. The number of broadcast or communications satellites included in an individual communication satellite system can be determined independently.

In Fig. 1, the base station 3 can broadcast data about voice, video, and so on to the mobile station 4 by way of the broadcast or communications satellite 1.

Above-mentioned broadcasting can include transmission for simultaneous reception of music, video, and so on, and communications that are conducted in such a manner that contents are widely unidirectionally transmitted. The mobile station 4 can move freely within either of the broadcasting areas 2a and 2b formed by the broadcast or communications satellite i, and the satellite broadcasting method in accordance with the present invention supports switching between broadcast lines, which is caused by a movement of the mobile station 4. Fig. 3 is a schematic diagram showing contents being transmitted through each pair of one uplink and one downlink and contents being receiving by the mobile station when switching between the H:\teresab\keep\Spedfications\P50877_03059.dc 30/09/03 two broadcast lines is carried out. In Fig. 3, reference numeral 7 denotes a data packet including data about video, voice, and so on. The base station 3 transmits data packets P1, P2, P3, and to the mobile station in order of P1, P2, P3,and Reference numeral 8 denotes a switching allowance information packet used for instructing the earth station 4 that is a receiver to switch between communication lines.

The base station 3 transmits the data packets P1, P2, and P3 to the broadcast or communications satellite 1 by way of the uplink 5a (having a frequency of fl), and the broadcast or communications satellite 1 then transmits the received data packets P1, P2, and P3 to the broadcasting area 2a by way of the broadcast line 6a (having a frequency of f3). Similarly, the base station 3 transmits the data packets P1, P2, and P3 to the broadcast or communications satellite 1 by way of the uplink 5b (having a frequency of f2), and the broadcast or communications satellite 1 then transmits the received data packets P1, P2, and P3 to the broadcasting area 2b by way of the broadcast line 6b (having a frequency of f4). The base station 3 continuously transmits a switching allowance information packet 8 that instructs the mobile station 4 to switch between the two broadcast lines at predetermined intervals. The mobile station 4 receives the data packets 7 by way of the broadcast line 6a when it is staying in the broadcasting area 2a, and further receives the series of switching allowance information packets 8. When receiving the series of switching allowance information packets 8, the mobile station 4 temporarily changes the receive frequency thereof to f4 and then receives a signal broadcasted to the other broadcasting area 2b (simply referred to as an adjacent broadcasting area in this H:\teresab\keep\Specifiations\P508773059.doc 30/09/03 specification) to which the mobile station 4 is moving and which is adjacent to the broadcasting area in which the mobile station 4 is staying. The mobile station 4 then measures the quality of the broadcast line 6b having the frequency of f4, which is associated with the other broadcasting area 2b, such as a received signal strength or a bit error rate. The mobile station 4 compares the line qualities of the broadcast lines 6a and 6b with each other, and performs a switching operation when necessary.

For example, when the broadcast line 6a has a better quality than the broadcast line 6b, the mobile station 4 returns the receive frequency thereof to f3. In contrast, when the broadcast line 6b has a better quality than the broadcast line 6a, the mobile station 4 holds the receive frequency thereof at f4. Within a time period T during which the switching allowance information packet 8 is continuously transmitted to the mobile station 4, the mobile station 4 carries out the measurement of the qualities of the two broadcast lines 6a and 6b, the comparison between them, and switching between the two broadcast lines when necessary. As an alternative, the mobile station 4 can carry out the measurement of the qualities of the two broadcast lines within a time period T during which it continuously receives the switching allowance information packet for the first time, after that, carry out the comparison between the qualities of the two broadcast lines while receiving the next data packets P4 and P5 when staying in the broadcasting area 2a, switch the receive frequency thereof from f3 to f4 when continuously receiving a switching allowance information packet for the next time, and receive the subsequent data packets by way of the broadcast line 6b associated with the broadcasting area 2b. Because the H:\teresab\keep\Specifications\P087703059.doc 30/09/03 mobile station 4 thus carries out switching between the two broadcast lines (switching between the two receive frequencies) within a time period T during which it continuously receives a switching allowance information packet 8 from the base station 3, the mobile station 4 can receive data packets 7 that are significant data without any loss of them. Each switching allowance information packet 8 includes, as packet data, an identifier indicating that the packet transmitted from the base station 3 is not a data packet 7. In other words, the mobile station 4 only has to determine the arrival of a time period during which the mobile station 4 can carry out switching between the two broadcast lines with such a thing as a symbol included in each switching allowance information packet 8.

Next, the structure of the base station will be explained. Fig. 4 is a block diagram showing the structure of the base station. In Fig. 4, reference numeral 9 denotes a transmitting antenna, reference numeral 10 denotes a transmitting unit that carries out uplink transmission of packets to the broadcast or communications satellite 1 by way of the transmitting antenna 9, reference numeral 11 denotes a packet sending unit that sends out data packets to the transmitting unit 10, reference numeral 12 denotes a packet controlling unit that instructs the packet sending unit 11 to send out a series of switching allowance information packets, and reference numeral 13 denotes a data packet generating unit that generates data packets from contents data.

Next, an operation of the base station 3 will be explained with reference to Fig. 4. Contents data about music, video, and so on are input to the data packet generating unit 13. The data packet generating unit 13 H:\teresab\keep\Specifications\P50877_03059.doc 30/09/03 generates data packets 7 from the received contents data and delivers them to the packet sending unit 11. At that time, the data packet generating unit 13 generates data packets 7 after time-based compressing stream data or the like when necessary. The packet sending unit 11 delivers the data packets 7 from the data packet generating unit 13 to the transmitting unit 10 within a time period during which the base station 3 carries out transmission of data packets. The packet controlling unit 12 measures the length of the interval from when the data packets 7 start being transmitted or a series of switching allowance information packets 8 is previously transmitted so as to determine the next timing at which the packet sending unit 11 transmits a series of switching allowance information packets 8 to the transmitting unit 10. The packet controlling unit 12 instructs the packet sending unit 11 to send out a series of switching allowance information packets 8 when the next timing comes. The packet sending unit 11 that has received this instruction stops sending data packets 7 and continuously sends the switching allowance information packet 8 to the transmitting unit throughout a time period T. When the length of predetermined intervals at which the packet sending unit 11 transmits a series of switching allowance information packets 8 is too long, the mobile station 4 may move to another broadcasting area without receiving the series of switching allowance information packets 8 when the mobile station 4 is moving rapidly and there may cause a loss of broadcast packet data received by the mobile station. In contrast, when the length of predetermined intervals at which the packet sending unit 11 transmits a series of switching allowance information packets 8 is too short, the amount of data packets included in data carried by the H:\teresab\keep\Specifications\P5087703059.doc 30/09/03 broadcasting signal decreases, and therefore the timebased compression rate of data increases. Therefore, the timing the length of predetermined intervals) at which the packet sending unit 11 transmits a series of switching allowance information packets 8 is predetermined according to the transmitted contents data and the type of the mobile station 4 to which the contents data are to be transmitted. For example, the packet controlling unit can change the timing at which the packet sending unit 11 transmits a series of switching allowance information packets 8 according to the volume of the contents data.

By referring to a prepared lookup table, the packet controlling unit can set the timing at which the packet sending unit 11 transmits a series of switching allowance information packets 8 according to the volume of the contents data.

Next, the structure of the mobile station 4 will be explained. Fig. 5 is a block diagram showing the structure of the mobile station 4. In Fig. 5, reference numeral 14 denotes a receiving antenna, reference numeral denotes a receiving unit that receives a signal broadcasted from the broadcast or communications satellite 1 by way of the receiving antenna 14, and reference numeral 16 denotes a received signal processing unit that reproduces contents data from the received signal and outputs them, and, when receiving a series of switching allowance information packets 8, notifies the reception of the switching allowance information packets 8 to a line switching controlling unit 17. The received signal processing unit 16 can time-based expand stream data or the like when necessary so as to reproduce contents data from the expanded data. The line switching controlling unit 17 controls switching between two broadcast lines in H:\teresab\keep\Spefications\P50877_359.dc 30/09/03 the mobile station 3 within a time period T during which the mobile station receives the series of switching allowance information packets transmitted thereto.

The received signal process unit 16 detects the reception of a series of switching allowance information packets with an identifier included in each of the switching allowance information packets, and notifies the switching controlling unit 17 that it has received a series of switching allowance information packets. In response to this notification, the switching controlling unit 17 instructs the receiving unit 15 to change the receive frequency thereof to the one associated with an adjacent broadcasting area, which is adjacent to the broadcasting area in which the mobile station is staying.

The receiving unit 15 switches between the two receive frequencies successively so as to measure the quality of each of the two broadcast lines, such as the strength of a signal received by way of each of the two broadcast lines or the bit error rate of each of the two broadcast lines, and delivers the measurement result to the switching controlling unit 17. The switching controlling unit 17 compares the quality of the other broadcast line associated with the other broadcasting area with that of the broadcast line associated with the broadcasting area in which the mobile station is staying now, and determines whether switching from the broadcast line currently being used to the other broadcast line is necessary from the comparison between the quality of the broadcast line currently being used and that of the other broadcast line.

When the measured quality of the other broadcast line associated with the other broadcasting area is better than that of the broadcast line currently being used, the switching controlling unit 17 instructs the transmitting H:\teresab\keep\Specications\P5087703059.dc 30/09/03 unit 15 to switch to the other broadcast line.

Immediately after determining that the measured quality of the other broadcast line associated with the other broadcasting area is better than that of the broadcast line currently being used, the switching controlling unit 17 can instruct the transmitting unit 15 to switch to the other broadcast line. As an alternative, after waiting for a reception of the next series of switching allowance information packets, the switching controlling unit 17 can instruct the transmitting unit 15 to switch to the other broadcast line.

In accordance with embodiment 1 of the present invention, the satellite broadcasting method makes it possible to perform a beam switching process without any loss of broadcast data received by the mobile station while the mobile station is performing a measurement of the qualities of two broadcast lines, a comparison between them, and switching between the two broadcast lines.

Embodiment 2.

The satellite broadcasting method in accordance with embodiment 1 includes the steps of measuring the quality of a broadcast line associated with an adjacent broadcasting area to which a mobile station 4 is moving, and determining whether or not there is a necessity to carry out switching from another broadcast line currently being used to the above-mentioned broadcast line. In contras, a satellite broadcasting method in accordance with embodiment 2 includes the steps of disposing a GPS receiver in a mobile station 4, calculating the position of the mobile station 4, and switching between two broadcast lines respectively associated with two broadcasting areas according to a relationship between the H:\teresab\keep\Specifications\P50877_03059.doc 30/09/03 coverages of the two broadcasting areas.

In this case, a switching controlling unit 17 identifies a broadcasting area in which the mobile station is staying based on the positional information calculated by using the GPS receiver without measuring the quality of any broadcast line. The identification is done assuming that in the mobile station 4, all broadcasting areas are already known or are updated as appropriate. When a received signal processing unit 16 recognizes a reception of a series of switching allowance information packets 8 and notifies the reception to the switching controlling unit 17, the switching controlling unit 17 instructs a transmitting unit 15 to carry out switching to a broadcast line associated with a broadcasting area in which the mobile station is staying at that time. When the mobile station is staying in an area where two broadcasting areas overlap each other, the mobile station can measure the qualities of the broadcast lines respectively associated with the two broadcasting areas that overlap each other after receiving a series of switching allowance information packets, and carry out a switching operation so as to select one of the two broadcast lines that has a better quality.

In accordance with embodiment 2 of the present invention, the mobile station can perform a beam switching process in a short time without measurement of the quality of a broadcast line associated with an adjacent broadcasting area.

Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, H:\teresab\keep\Specifications\P5087703059.doc 30/09/03 except as defined in the appended claims.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

H:\teresab\keep\Spefications\P50877_3059.doc 30/09/03

Claims

1. A satellite broadcasting method of transmitting broadcast packets from a base station to a mobile station by way of a broadcast or communications satellite that forms multiple beams on a ground, said method comprising the steps of: transmitting data packets from said base station to said mobile station, and continuously transmitting a switching allowance information packet at predetermined intervals from said base station to said mobile station; in response to the switching allowance information packet, said mobile station, which is staying in a broadcasting area and is receiving broadcast packets from said base station via a broadcast line, measuring a quality of another broadcast line associated with another broadcasting area that is adjacent to the broadcasting area in which said mobile station is staying within a transmission time period during which the switching allowance information packet is transmitted to said mobile station; and switching from the broadcast line to the other broadcast line based on a result of the measurement.

2. A base station comprising: a transmitting unit for carrying out transmission of broadcast packets to a mobile station by way of a broadcast or communications satellite that forms multiple beams on a ground; a data packet generating unit for generating data packets from contents data applied thereto; a packet sending unit for sending, as broadcast packets, either the data packets generated by said data H:\teresab\keep\Specfications\P5087703059.doc 30/09/03 1 packet generating unit or a series of switching allowance Sinformation packet used for instructing said mobile station to carry out switching between beams to said transmitting (1 unit, wherein the mobile station determines whether switching between beams is necessary based on measurement of the IND broadcast line quality by the mobile station after the oo 0switching allowance information packet is received; and M a packet controlling unit for instructing said packet Ssending unit to send the switching allowance information packet at predetermined intervals.

3. A mobile station comprising: a receiving unit for receiving a broadcasting signal transmitted from a base station by way of a broadcast or communications satellite that forms multiple beams on a ground; a received signal processing unit for reproducing contents data from the broadcasting signal received by said receiving unit and outputting the contents data, and for detecting a switching allowance information packet from the received broadcasting signal; and a switching controlling unit, responsive to a notification of a reception of a switching allowance information packet from said received signal processing unit, for instructing said receiving unit to carry out switching from a broadcast line associated with a broadcasting area in which said mobile station is staying to another broadcast line associated with another broadcasting area that is adjacent to the broadcasting area in which said mobile H:\krystalm\keep\Speci\2003248462.doc 27/04/05 station is staying and to measure a quality of the other Sbroadcast line, and for instructing said receiving unit to select one broadcast line via which said receiving unit receives the broadcasting signal from the two broadcast lines based on a result of the measurement of the quality of the O other broadcast line. 00 (N

4. A mobile station comprising: a receiving unit for receiving a broadcasting signal transmitted from a base station by way of a broadcast or communications satellite that forms multiple beams on a ground; a received signal processing unit for reproducing contents data from the broadcasting signal received by said receiving unit and outputting the contents data, and for detecting a switching allowance information packet from the received broadcasting signal; and a switching controlling unit for identifying a broadcasting area in which said mobile station is staying from positional information obtained by using a GPS receiver, and for, in response to a notification of a reception of a switching allowance information packet from said received signal processing unit, instructing said receiving unit to carry out switching to a broadcast line associated with the broadcasting area identified thereby.

A method as claimed in claim i, and substantially as herein described with reference to the accompanying drawings. h:\krystalm\keep\Speci\2003248462.doc 27/04/05 I

6. A base station as claimed in claim 2, and Ssubstantially as herein described with reference to the accompanying drawings.

7. A mobile station as claimed in claim 3 or claim 4, INO and substantially as herein described with reference to the oo accompanying drawings. O Dated this 2 7 t h day of April 2005 MITSUBISHI DENKI KABUSHIKI KAISHA By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia Hi\krystalm\keep\Speci\2003248462.doc 27/04/05