Patent Application
20080263614
This application claims priority under 35 U.S.C. § 119(a) to a Korean Patent Application filed in the Korean Intellectual Property Office on Apr. 16, 2007 and assigned Serial No. 2007-37170, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to a method and apparatus for transmitting and receiving broadcast service data in a digital broadcasting system, and in particular, to an apparatus and method for transmitting and receiving broadcast service data depending on the coverage where broadcast service data is provided in a digital broadcasting system. Further, the present invention provides an apparatus and method for indicating national services for Mobility Support in a Digital Video Broadcasting-Satellite services to Handheld (DVB-SH) system.
2. Description of the Related Art
Referring to
The DVB-SH standard is generally classified into two types of modes: a DVB-SH-A system supporting an Orthogonal Frequency Division Multiplexing (OFDM)-based satellite transmitter mode and a DVB-SH-B system supporting an OFDM-based terrestrial transmitter mode and a Time Division Multiplexing (TDM)-based satellite transmitter mode.
The conventional DVB-SH-A system and the conventional DVB-SH-B system, the satellite supports only national services. In the DVB-SH-A system, the service provider generates and provides different Transport Streams (TSs) for national services and local services, and in the DVB-SH-B system, the service provider generates one common TS for national services and local services, and transmits it to satellite and terrestrial transmitters after removing the services that the corresponding transmitters do not support, thereby enabling the transmitters to support different services. The term ‘national services’ refer to broadcast services provided nationwide in common, and the term ‘local services’ refer to broadcast services provided uniquely in corresponding areas. That is, in the DVB-SH-B system, a satellite transmitter removes from the common TS the services, which are not supported by the satellite, before transmission, and a terrestrial transmitter removes from the common TS the services, which are provided in the corresponding area, before transmission to the terminal.
The DVB-SH system has a problem that it should support the handover caused by simultaneous transmission of the same national services to the satellite and the terrestrial transmitters. That is, in both the DVB-SH-A and DVB-SH-B systems, only the national services are supported by the satellite. However, the supported services vary depending on through which path (formed by satellite and/or terrestrial transmitter) the DVB-SH services are received.
As illustrated in
Therefore, the DVB-SH system should determine how to distinguish the national services from the local services. In addition, the user terminal needs to determine when it will consider mobility, and to this end, the user terminal should know TS available in several areas, and should also known which broadcast services among the national services and local services are carried by the TS.
Particularly, for the national services, a user terminal needs a particular mechanism to seamlessly receive the currently received national services both when the user terminal moves to a satellite cell area where only the satellite signals are received and when it moves to the terrestrial cell.
That is, when a terminal considers handover as it leaves the current cell and moves to the satellite cell or another terrestrial cell, the services presently being provided through Program Specific Information/Service Information (PSI/SI) information may not be provided in the cell to which the terminal moves. However, in light of the current configuration of the DVB-SH system, it is possible that the terminal cannot know that the currently received services are national services. Particularly, in the DVB-SH-A system and DVB-SH-B system where the satellite generates a common TS, removes corresponding local services from the common TS, and transmits only the national services, since TS_id of the common TS is maintained even when the actual contents of the TS have changed due to the removal of the services, it is not then possible to determine which services in the corresponding TS are national services. Therefore, there is a need for a system and method capable of identifying the national services.
The present invention has been designed to address at least the problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an apparatus and method providing seamless broadcast services during handover of a terminal in a digital broadcasting system.
Another aspect of the present invention is to provide an apparatus and method for transmitting and receiving broadcast service data according to a coverage area in which broadcast service data is provided, in a digital broadcasting system.
Another aspect of the present invention is to provide an apparatus and method for seamlessly providing national services in a digital broadcasting system.
Another aspect of the present invention is to provide an apparatus and method for transmitting and receiving broadcast service information indicating if broadcast services included in a transport stream are national services, in a digital broadcasting system.
Another aspect of the present invention is to provide an apparatus and method for transmitting and receiving broadcast service data according to a flag indicating that broadcast services included in a transport stream are national services, in a digital broadcasting system.
In accordance with an aspect of the present invention, there is provided a method for transmitting broadcast service data in a transmission system of a digital broadcasting system. The method includes setting a flag indicating a service area representative of coverage where broadcast service data is provided, for each broadcast service; and transmitting broadcast service information including the flag and a Transport Stream (TS) including the broadcast service data.
In accordance with another aspect of the present invention, there is provided a method for transmitting broadcast service data in a broadcasting system providing a broadcast service in the form of a Transport Stream (TS), wherein broadcast service information of the TS includes information used for identifying each broadcast service. The method includes, when all broadcast service data included in the TS is provided nationwide, generating information indicating that all the broadcast service data included in the TS is broadcast service data provided nationwide; including the generated information in broadcast service information of the TS; and transmitting the broadcast service information along with each broadcast service data.
In accordance with another aspect of the present invention, there is provided a method for receiving broadcast service data in a terminal of a digital broadcasting system. The method includes, when there is a need for handover while receiving broadcast service data, checking if a flag is set in broadcast service information, which indicates if the currently received broadcast service data is for a national service, and performing handover according to the check result; and when broadcast service data previously received before the handover is for a national service, receiving a Transport Stream (TS) carrying each broadcast service data, and demodulating the broadcast service data previously received before the handover in the received TS.
In accordance with another aspect of the present invention, there is provided a method for receiving broadcast service data in a broadcasting system providing a broadcast service in the form of a Transport Stream (TS), wherein broadcast service information of the TS includes information used for distinguishing each broadcast service. The method includes, when there is a need for handover while receiving broadcast service data, checking if information is set, which indicates if all broadcast service data included in the currently received TS is for a national service provided nationwide, and performing handover according to the check result; and when all broadcast service data included in the TS previously received before the handover is for a national service, receiving a TS carrying each broadcast service data and demodulating the broadcast service data previously received before the handover in the received TS.
In accordance with another aspect of the present invention, there is provided an apparatus for transmitting broadcast service data to a user terminal in a digital broadcasting system. The apparatus includes a flag generator for setting a flag indicating a service area where broadcast service data to be transmitted to the user terminal is provided, for each broadcast service; and a transmission unit for multiplexing broadcast service information including the flag and a Transport Stream (TS) including the broadcast service data, and transmitting the multiplexed TS.
In accordance with another aspect of the present invention, there is provided a terminal apparatus for receiving broadcast service data in a digital broadcasting system. The terminal apparatus includes a reception unit for receiving a Transport Stream (TS), and demodulating broadcast service data and broadcast service information included in the TS; a demultiplexer for demultiplexing broadcast service information necessary for receiving the demodulated broadcast service data, and broadcast service data to be provided to a user; a flag checker for checking if a flag indicating that the received broadcast service data is for a national service is inserted into the demultiplexed broadcast service information; and a controller for controlling the reception unit so as to perform handover when there is a need for handover, and if the flag is inserted, to demodulate broadcast service data previously received before the handover in a TS received after the handover.
The above and other aspects, features, and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:
Preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for clarity and conciseness.
However, before a description of the present invention is given, a brief description will be made of DVB-SH-A and DVB-SH-B, which are two standards of the DVB-SH system.
In the DVB-SH-A system, national services are transmitted by the satellite and terrestrial transmitters, and the local services unique to a corresponding area are transmitted by the terrestrial transmitters.
A filtering unit 220 and an OFDM modulator 230 filter and modulate the received National TS, respectively, thereby filtering the services specific to the corresponding area from the National TS. As a result, a local service of Service i (where i is one of 1 to 10) and a national service, i.e., Service 11, are transmitted in area 240, and the same services are transmitted in area 250. Such services are transmitted to a user terminal through associated terrestrial transmitters. In area 260, all local services are filtered from the National TS by filtering unit 270 and modulator 280, such that only the national service (Service 11) is transmitted. Service 11 is transmitted to the terminal via the satellite.
In
For the TS_(national+local) 330, before it is transmitted to a satellite 315, local services are filtered from it as shown by reference numeral 317 and only the national service is transmitted to the satellite 315. The satellite 315 directly transmits the received national service to a user terminal 318. A ground-based fixed transmitter TR(a) 316 provides the user terminal 318 located in the local service area, with the local service TS_local 340 and a TS_(national+local) 350, which is a common TS including the national service and the local service.
Embodiments of the present invention insert a predetermined flag (national flag) into broadcast service information or Program Specific Information/Service Information (PSI/SI) before transmission in order to notify that the service currently being provided to a user terminal is a national service. That is, in embodiments of the present invention, a transmitter sets a flag to a predetermined value, indicating whether the coverage where each broadcast service data included in a transmission TS is provided corresponds to a national area or a local area, and inserts the flag into the PSI/SI of the TS before transmission, and the user terminal checks during handover if there is a flag inserted into PSI/SI of the received TS and if the flag is set to a predetermined value to thereby determine whether the currently received broadcast service is a national service or a local service, and performs the corresponding procedure. That is, when the currently received broadcast service is a national service, the user terminal can receive the same service even after moving, as it can perform handover without a separate procedure. When the currently received broadcast service is a local service, the user terminal should perform a separate procedure, such as sending a request to a server in order to continuously receive the same service as the service previously received before handover. Because the separate procedure for the service continuity of the local service departs from the scope of the present invention, a description thereof will be omitted herein. When the user terminal is receiving the local service, if there is no information on the flag, because the corresponding service is interrupted when the user terminal leaves the corresponding local cell, it is efficient to insert the flag so as to give the opportunity that the user terminal can perform a procedure for receiving the corresponding service.
Embodiments of the present invention, described below, are divided according to the method of inserting the national flag into the broadcast service information.
The term ‘scenario’ is used herein as a handover operation of a user terminal regardless of the embodiments. That is, embodiments of the present invention are divided according to the method of inserting the flag into PSI/SI, thereby indicating the inclusion of a national service in TS.
The national flag is a 1-bit indicator, and when it is set to a predetermined value ‘1’ or ‘0’ indicating a national service, this indicates that the broadcast service corresponding to the national flag is a national service. When the national flag is set to a predetermined value indicating the national service, it is possible to indicate that a particular service among the services included in a TS is a national service (Embodiment 1-1), and it is also possible to indicate that all services in the corresponding TS are national services, according to the position of the flag (Embodiment 1-2). For example, it is preferable for the DVB-SH-A system to indicate that all services in the TS are national services, and it is preferable for the DVB-SH-B system to indicate if each broadcast service included in the TS is a national service. For example, if the national flag is set to ‘1’, it may mean that the TS including broadcast service information is for a national service.
Therefore, embodiments of the present invention, by setting the national flag to a predetermined value, can indicate the coverage where the broadcast service is provided, i.e., indicate whether the broadcast service is a broadcast service provided nationwide or a broadcast service provided separately in each area.
Table 1 shows an example of a national flag inserted into an NIT table according to Embodiment 1-1 of the present invention. As shown in Table 1, a ‘national flag’ is inserted into an NIT table according to Embodiment 1-1 of the present invention. In Table 1 to Table 3, the remaining elements except for ‘national flag’ are defined in ETSI EN 300468 (DVB: Specification for service information in DVB systems), so a description thereof will be omitted.
As shown in Table 1, a TS transmission side, by setting National_flag to a predetermined value, can indicate whether a broadcast service corresponding to Service_id is a national service provided nationwide or a local service provided separately in each area, and a terminal receiving the TS can determine whether the broadcast service corresponding to Service_id is a national service or a local service according to the value to which National_flag is set.
There are two methods for indicating whether broadcast services included in the TS are national services or local services with the use of National_flag. A first method inserts the flag into the PSI/SI of the TS only for the broadcast service of a national service, and a second method sets the flag to a value of ‘0’ or ‘1’ to distinguish the broadcast service of a national service from the broadcast service of a local service, and inserts the set flag into the PSI/SI. The two methods are both available in the present invention.
Embodiment 1-2, unlike Embodiment 1-1, notifies that the broadcast service included in the corresponding TS is a national service by using a global descriptor. That is, Embodiment 1-2 notifies that all services in the corresponding TS are national services, and Embodiment 1-1 is different in that it attaches a flag separately for each service in the NIT table. That is, in Embodiment 1-1, since some services include a national flag and some services include no flag, it is different from the global descriptor indicating that all broadcast services included in the TS are national services. Embodiment 1-2 of the present invention is a scheme for inserting into the NIT table a global descriptor Global_descriptor( ) indicating that all services in the TS transmitted to the user terminal are national services. Table 2 shows an example of Global_descriptor( ) according to Embodiment 1-2 of the present invention.
In Table 2, Descriptor_tag is a value of a particular number assigned to recognize the corresponding descriptor. For example, for Service_list_descriptor, because its tag has a value ‘0x41’, it is possible to distinguish each descriptor. Descriptor_length is a field indicating a length of a data part of the corresponding descriptor. Global_flag is a flag indicating if the broadcast service transmitted by the corresponding TS is a national service.
Table 3 shows an example of an NIT table into which a global descriptor of the present invention is inserted.
Embodiment 2, which is another embodiment for a method of inserting a national flag separately for each broadcast service, inserts a national flag into an SDT table, and the SDT table is as shown in Table 4. Table 4 shows an example of an SDT table into which a national flag for each broadcast service is inserted according to Embodiment 2 of the present invention. In Table 4, the remaining elements, except for the ‘national flag’ indicating whether a corresponding service is a national service separately for each broadcast service included in the TS, are defined in ETSI EN 300468 (DVB: specification for service information in DVB systems).
By setting National_flag to a predetermined value as shown in Table 4, a TS transmission side can indicate that the broadcast service corresponding to Service_id is a national service, and a terminal receiving the TS can determine that the broadcast service corresponding to Service_id is a national service.
Embodiment 3 of the present invention inserts a national flag into an INT table separately for each broadcast service, and the INT table is shown in Table 5. In Table 5, ‘national flag’ indicates if the corresponding broadcast service is a national service separately for each service included in the TS according to Embodiment 3 of the present invention, and the remaining elements, except for the ‘national flag’, are defined in ETSI EN 300468 (DVB: specification for service information in DVB systems).
By setting National_flag to a predetermined value before transmission as shown in Table 5, a TS transmission side can indicate that the broadcast service corresponding to Service_id is a national service.
A definition of the existing field values of the INT and SDT tables in Embodiment 2 and Embodiment 3 of the present invention follows the definition of ETSI EN 300468 and its associated specifications, so a description of the existing field values will be omitted herein.
As presented in the above-described embodiments, the present invention inserts a national flag into PSI/SI information and transmits it to a user terminal, thereby enabling the user terminal to determine which broadcast service among the broadcast services transmitted in the TS is a national service. This information is utilized by the user terminal when it moves to another cell while receiving the broadcast service.
The present invention insets a flag or a global descriptor into the PSI/SI in order to indicate that a broadcast service included in TS is a national service, before transmission. Consequently, a user terminal can determine if the received broadcast service is a national service.
Therefore, if the previously received broadcast service is a national service, because the user terminal knows that the previously received broadcast service is provided even after performing handover, the user terminal, when it is receiving a national service, has no need to search PSI/SI to determine if a TS received after handover includes an identifier of the broadcast service received before handover even though the user terminal moves to another cell as illustrated in
If the service the user terminal was receiving is a local service, the user terminal can receive the corresponding local service in another area over a communication network by sending a request to a server before moving to another cell. The user terminal cannot continuously receive the corresponding local service in another cell unless it receives additional information indicating that a service having a certain service ID in another cell is the same as the currently received service. Therefore, with the use of the national flag or global descriptor of the present invention, the terminal is notified that the corresponding service is a local service, enabling the terminal to perform the foregoing additional procedure before handover. The foregoing additional procedure for continuing the local service is not described herein.
Next, a description will be made of an operation of a user terminal according to an embodiment of the present invention.
Scenarios 1 and 2 described below are used regardless of embodiments of the present invention as described above. That is, embodiments of the present invention can be applied to the following handover scenarios according to the actual network configuration.
Scenario 1 corresponds to the case in which PSI/SI of a satellite cell is different from PSI/SI of a terrestrial cell, and in this case, PSI/SI information is updated when the user terminal moves from the terrestrial cell area to the satellite cell area.
Scenario 2 corresponds to the case in which PSI/SI of the satellite cell is the same as PSI/SI of the terrestrial cell, and in this case, PSI/SI information is not updated when the user terminal moves from the terrestrial cell area to the satellite cell area.
Herein, the term ‘terrestrial cell’ is an area in which TS is transmitted by a terrestrial transmitter, and the term ‘satellite cell’ is an area in which TS is transmitted by the satellite. Generally, the satellite cell area has a broader coverage than the terrestrial cell area.
Scenario 1: In this scenario, the user terminal is receiving a DVB-SH service via a terrestrial transmitter. The user terminal can receive only the satellite service as it leaves the terrestrial cell area and enters the satellite cell area. This means that though the user terminal can no longer receive the local service as it leaves the local service area, the user terminal moves to the national service area where it can receive only the satellite service.
Herein, the term ‘satellite service’ is a broadcast service provided from the satellite, and the term ‘terrestrial service’ is a broadcast service provided via the terrestrial transmitter. It is assumed in Scenario 1 that a PSI/SI signal transmitted in the terrestrial cell is different from a PSI/SI signal transmitted in the satellite cell.
However, in Scenario 2, a PSI/SI signal is not updated when the user terminal moves from the terrestrial cell area to the satellite cell area. That is, in Scenario 2, PSI/SI used in the terrestrial cell matches PSI/SI used in the satellite cell. The scenarios are divided herein according to whether PSI/SI update is performed or not because the handover now defined in Convergence of Broadcasting and Mobile Service (DVB-CBMS) Workgroup is described as an operation performed in an IP platform. That is, one or several networks can exist in one UP platform.
When user terminal inter-cell movement is made within one network, there is no need for PSI/SI update, and when the inter-cell movement is inter-network movement, there is a need for PSI/SI update. That is, in operation, there are two possible cases, on in which PSI/SI is updated and one in which PSI/SI is not updated. Therefore, a description thereof will be made separately for each scenario.
In step 410, a user terminal is receiving a broadcast service from a terrestrial transmitter of a local cell where it is currently located. In step 415, when the user terminal leaves a local service area which is a cell area where the broadcast service is provided, a quality of the signal received from the terrestrial transmitter is reduced, raising the need for handover to the satellite or another terrestrial transmitter. The user terminal searches in step 420 at least one of the NIT, SDT, and INT tables proposed above by the present invention, and checks a national flag or a global descriptor in step 425. The user terminal performs the following operation according to a set value (‘0’ or ‘1’) of the national flag or the presence/absence of the global descriptor in PSI/SI.
In step 425, the user terminal can previously determine whether the currently received broadcast service is a local service or a national service using the national flag. If it is determined in step 425 that the currently received broadcast service is a national service, the user terminal can continuously receive the same service as the broadcast service previously received from the previous terrestrial transmitter by changing the path through which the broadcast service is received to the satellite or another terrestrial transmitter after handover.
If it is determined in step 425 that the national flag is set to ‘1’ or the global descriptor exists in PSI/SI, the user terminal, perceiving that the received broadcast service is a national service, acquires frequency information of the broadcast service it will receive after handover, by means of Cell_list_descriptor and Cell_frequency_link_descriptor of NIT in PSI/SI or by means of scanning in step 430. Step 430 is an operation needed to receive a broadcast service for the national service provided from the satellite when the terminal moves to and accesses the national service network while receiving the broadcast service corresponding to the local service, or to receive a broadcast service for the national service when the terminal performs handover to another local service area.
In step 435, the terminal checks a quality of the signal from the satellite or another terrestrial network using the frequency information acquired in step 430. In step 435, if the signal quality is greater than or equal to a predetermined value, the user terminal changes its reception path to the satellite or the terrestrial transmitter in step 440. In step 445, the user terminal continuously receives the broadcast service, and updates PSI/SI information necessary for receiving the previous broadcast service, with PSI/SI of the TS received through a new reception path. Further, in step 445, the user terminal performs handover to the satellite or another terrestrial transmitter, and continuously receives the previously received national service using the updated PSI/SI. However, the user terminal has no need to search PSI/SI of the newly received TS to determine whether the broadcast service previously received before handover is included in the newly received TS. Therefore, the user terminal, when receiving the national service, can seamlessly receive the broadcast service.
However, if it is determined in step 425 that the corresponding service is a local service, in step 450, the terminal attempts another handover procedure or ends the operation of receiving the broadcast service from the previous terrestrial transmitter. That is, by using the information indicating that the corresponding service is a local service, the user terminal can attempt another handover procedure before the reception of the corresponding local service is interrupted due to the inter-cell movement.
In step 540, the user terminal checks a service list descriptor of an NIT table in the PSI/SI newly received in step 535 or a service IP address of an INT table, and determines from acquired information whether the broadcast service is receivable.
In step 545, the user terminal determines if a desired broadcast service (broadcast service previously received before handover) exists in the TS received from the satellite or another terrestrial transmitter, and if the desired broadcast service exists, the user terminal receives the corresponding broadcast service from the satellite or another terrestrial transmitter in step 550. However, if the desired service does not exist in step 545, the user terminal ends handover or performs another handover procedure in step 555. Because step 555 departs from the main concept of the present invention, a description thereof is briefly given.
According to DVB-H implementation guideline (ETSI TR 102 377), 10 sec or 30 sec is required for the minimum transmission period of the NIT table and the INT table. This means that in the worst case, the user terminal should wait 30 sec or longer to determine whether the broadcast service previously received before handover exists in the TS transmitted from the cell to which it performed handover. When the service is a national service, the service continuity is possible after a lapse of an update time for the PSI/SI as handover is possible. However, when the service is a local service, the user terminal wastes time determining the possibility of the service continuity, and the corresponding local service is already unreceivable after inter-cell movement. That is, for the continuous reception of the local service, information indicating that the corresponding service is a local service should be provided to the terminal before the inter-cell movement is made.
A comparison between the flowcharts of
As a national flag is inserted in
In step 610, the transmission system determines whether each broadcast service provided to user terminals is a national service or a local service. If it is determined that the broadcast service is a national service, the transmission system sets in step 615 a national flag to a predetermined value and inserts it into an NIT, SDT, or INT table for each national service, or inserts a global descriptor into the NIT table. In step 620, the transmission system sets other PSI/SI parameters corresponding to each transmitter, and PSI/SI corresponding to each transmitter is not identical. In step 625, the transmission system transmits TS including the set national flag or the global descriptor-inserted PSI/SI.
Scenario 2 corresponds to the case in which PSI/SI is not updated when the terminal enters the satellite cell's area. As stated above, all embodiments of the present invention can be applied to each scenario.
The TS transmitted by the satellite and the TS transmitted by the terrestrial transmitter have the same PSI/SI. Therefore, unless a common TS including a local service and a national service together is assigned a new TS_id at the time the local service is removed from the common TS, the INT and NIT tables should have information related to a list of all services in the TS even though the local services are not provided by the satellite. However, even in this case, the terminal cannot determine which one of the services is a national service, and thus cannot determine which service is available in the national service area and can simply distinguish only the service available in a certain local service area. In the case where the satellite TS and the terrestrial TS have different TS_ids, even though services having the same Service_id are found in the satellite TS and the terrestrial TS, the terminal cannot recognize that they are the same services since Service_id is unique only in one TS.
In step 725, the user terminal acquires frequency information of the path through which the broadcast service it should continuously receive even after handover is transmitted, by means of Cell_list_descriptor and Cell_frequency_link_descriptor of PSI/SI or by scanning. In step 730, the user terminal measures a signal quality of the satellite or another terrestrial transmitter that provides the national service, using the frequency information acquired in step 725.
If the signal quality measured in step 730 is good (high), the user terminal performs handover to change the reception path of the broadcast service to the satellite or another terrestrial transmitter in step 735, and continuously receives the national service in step 740. At this point, the user terminal has no need to check if a desired broadcast service identifier exists in PSI/SI of the TS transmitted from the cell to which it will perform handover, in order to continuously receive the broadcast service even after handover.
However, if it is determined in step 720 that the national flag is set to ‘0’, the user terminal, identifying that the currently received service is a local service, performs another handover procedure or closes the corresponding service in step 745.
In step 825, if the quality of the signal received from the satellite or another terrestrial transmitter is good (high), the user terminal changes the path through which it will continuously receive the broadcast service, to a path of the satellite or a path of another terrestrial transmitter. In step 830, the user terminal determines if an identifier of the previously received broadcast service exists in PSI/SI of the currently received TS. However, the user terminal cannot assuredly determine if it can continuously receive the broadcast service it was receiving before its movement, because it cannot certainly determine whether the currently received broadcast service is a national service or a local service. Also, because the PSI/SI is identical, the user terminal cannot determine whether the broadcast service received before its movement and the broadcast service received after its movement are a local service or a national service by checking the PSI/SI.
If it is determined in step 835 that a broadcast service the user terminal desires to receive exists in the TS received after its movement, the user terminal receives the desired broadcast service from the satellite or another terrestrial transmitter in step 840. However, if the desired broadcast service does not exist, the user terminal performs another handover procedure or closes the broadcast service received before its movement in step 845. In this case, when the currently received service is a local service, the reception of the corresponding service is already interrupted after inter-cell movement. Therefore, it can be understood that in order to continue the reception, it is necessary to provide the terminal with information indicating whether it can continue the corresponding service before the inter-cell movement.
Referring to
The PSI/SI storage 1030 stores the PSI/SI including the national flag value and other information. A multiplexer 1040 multiplexes the PSI/SI with the broadcast service data read from the IP service storage 1010 and the PSI/SI storage 1030, and a modulator & transmitter 1050 encodes and modulates the multiplexed signal, and transmits the modulated signal.
At this point, the national flag generator 1020, inserts a national flag indicating IF the broadcast service is a national service, into an NIT, SDT, or INT table of PSI/SI information, or inserts a global descriptor into the NIT table before transmission. More specifically, the national flag generator 1020 sets a national flag to a predetermined value according to the service area where the broadcast service is provided, and inserts it into a PSI/SI. That is, the national flag generator 1020 sets the national flag to a predetermined value according to whether the broadcast service is for a national service or for a local service, and inserts it into the PSI/SI stored in the PSI/SI storage 1030.
However, although not illustrated, a PSI/SI generator can combine the PSI/SI with the national flag output from the national flag generator 1020, and output the result to the multiplexer 1040. A combination of the multiplexer 1040 and the modulator & transmitter 1050 will be referred to herein as a transmission unit. The IP service is provided from a content provider (not shown), and the multiplexer 1040 multiplexes broadcast service data, national flag, and PSI/SI, and can be included in service & network head-ends 302 and 312. The multiplexed broadcast service, national flag, and PSI/SI are transmitted after undergoing modulation in the modulator & transmitter 1050. The modulator & transmitter 1050 can be included in broadcast distribution networks 306 and 313, and DVB-SH broadcast head-ends 304 and 314.
More specifically, the national flag checker 1125 determines whether the corresponding broadcast service is for a national service or for a local service according to a specific one of the predetermined values, to which the national flag is set, and provides the information acquired in this way to a controller 1140.
When the national flag checker 1125 identifies from the national flag or the global descriptor that the currently received service is a national service, it provides the corresponding information to the controller 1140, and the controller 1140 forwards this information to the demodulator & receiver 1110 in order to adjust hardware parameters so that the user terminal can receive even in the new cell the same broadcast service as the broadcast service previously received in the old cell. In addition, the controller 1140 measures strength of the signal that the demodulator & receiver 1110 has received, and determines to perform handover to another cell if the measured signal strength is lower than a predetermined value. Because this process is well known in the art, a detailed description thereof will be omitted.
When the user terminal needs to handover while receiving the broadcast service data, the controller 1140 determines if the national flag included in a PSI/SI of the currently received TS indicates a national service. If the broadcast service data previously received before handover corresponds to a national service, the controller 1140 controls the demodulator & receiver 1110 in order to receive the TS carrying each broadcast service data after handover and demodulate the broadcast service data previously received before handover in the TS received after handover. The demodulator & receiver 1110 will be referred to herein as a reception unit. Although the controller 1140 and the national flag checker 1125 are separately illustrated in
As is apparent from the foregoing description, the present invention inserts flag or descriptor information indicating if the broadcast service provided to the user terminal is a national service, into the PSI/SI signal before transmission, so that the user terminal can continuously receive the corresponding service. As a result, the user terminal can reduce the time and power required for determining the continuity of the corresponding service during its handover.
While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 37170/2007 | Apr 2007 | KR | national |
