Mobile TV system architecture for mobile terminals

A mobile TV system architecture for a mobile terminal that reduces the processing required by the main processor during reception of digital broadcasts such as DVB-H. The mobile terminal architecture includes a main processor system and a mobile TV receiver device. The mobile TV receiver device includes units for SI/PSI processing, IP processing and decryption engine. The SI/PSI (service information/program specific information) processing unit receives non-protected transport stream (TS) packets and extracts SI/PSI tables which can be stored in memory local to the receiver device. The IP processing unit receives decrypted error-corrected protected packets containing multimedia content. The receiver device may include an HTTP server for communicating with a browser application running on the main processor system. The browser application presents multimedia content, received via HTTP, corresponding to a URL entered or selected by a user.

FIELD OF INVENTION

This invention relates to mobile wireless terminals and, more particularly, to a system architecture that facilitates integration of mobile TV service into a mobile wireless terminal.

BACKGROUND

For some consumers, it is desirable to “stay connected” at all times. Current mobile phones support some form of non-voice connectivity such as text messaging, allowing users to subscribe to various information services. These services provide periodic content as it becomes available or on demand from the user. Many mobile phones now support some form of Internet browsing, email access, downloading, and other forms of information transfer.

Standards are currently being established for digital TV broadcasts to a variety of wireless mobile terminals, and the availability of such services is expected to increase in the coming years.

Mobile terminals can take the form of a mobile phone, a personal digital assistant (PDA), a portable media platform (PMP), or any similar product that is capable of storing, processing, playing-back, and communicating digital content wirelessly.

FIG. 1is a block diagram of a mobile terminal100P capable of receiving TV signals. Mobile terminal100P includes a mobile TV receiver200P and a main processor system300P. Many mobile terminals include additional functions and interfaces. For example, a mobile phone may include a mobile phone front-end receiver module that allows connectivity to a cellular network such as a GSM, EDGE, or 3G network, a display, a keyboard, headphones, speakers, microphones, a power management system, a camera, an audio/video/image codec and player, and the like.

In the main processor system300P, the functions are divided into four main operational blocks, including, a cellular subsystem302, an A/V subsystem304, a host processor and memory subsystem306, and a human interface308. Other interfaces such as WLAN, Bluetooth, GPS, HDMI and the like, not shown inFIG. 1may also be present.

The mobile TV receiver200P includes a tuner202, an analog-to-digital converter (ADC)204, a demodulator processor and memory206, and an antenna208. Radio frequency (RF) communications are received through the antenna208. The RF signal carries the modulated digital broadcast signal that includes a digital TV signal in addition to other types of broadcast data. The RF signal band, digital modulation scheme, signal bandwidth, and error correction method are specific to the standard utilized by the system. Signal bands between VHF and L band are used, with some systems using higher frequencies. The digital modulation schemes may include QPSK, DQPSK, 16-QAM, 64-QAM and the like. The channel bandwidth to carry TV signals is typically 1.5, 5, 6, 7, or 8 MHz, although other bandwidths are possible. Error correction methods such as convolutional, Reed-Solomon, and Turbo codes may be used to correct multi-byte data packets.

The mobile TV receiver200P handles RF signal tuning and reception, analog-to-digital conversion, and signal demodulation, and provides digital data to the main processor system300P for further processing. Cost, size, and power considerations usually demand that a serial interface110P be used for communication between the receiver and the main processor system. Once the digital data has reached the main processor system300P, additional processing is performed. Additional processing performed by the main processor system300P includes error correction, decryption, decoding, play-back and the like.

Like conventional television, mobile TV is a broadcast system, so data flow is primarily from the mobile TV receiver200P to the main processor system300P. Control information is sent from the main processor system300P to the mobile TV receiver200P to control receiver operation.

One of the standards for mobile TV is DVB-H, or Digital Video Broadcasting-Handheld. DVB-H is an extension of DVB (Digital Video Broadcasting) that addresses the two main issues of broadcasting to a mobile user: power consumption of the terminal and the Doppler Effect—since users may be traveling at relatively high speeds (e.g., in a car or train).

To reduce power consumption, DVB-H utilizes a slicing scheme in which data is sent and received during pre-defined and limited time slots. This allows the receiver to partially shut down outside of the active time slots.

Improved reception quality is achieved by extensive error coding and error correction schemes.

In DVB-H, broadcasts data is sent in the form of fixed size (188 bytes) MPEG-2 (Motion Picture Experts Group) transport stream (TS) packets.FIG. 2shows the structure of an MPEG-2 TS packet400P which includes a header410, a packet identifier (PID)420, and a payload430. Depending on the contents of payload430, packets may be protected packets432or non-protected packets434.

The payload of non-protected packets434carries tables of information about the services (Service Information, SI) and programs (Program Specific Information, PSI) that are being broadcast. SI and PSI tables are a part of the broadcast service delivery and are required to navigate through different types of information available in each MPEG-2 TS packet. They are used to decode the selected audio, video, picture, and/or other digital content.

The payload of protected packets432carries internet protocol (IP) datagrams, i.e., IP packets. The IP packets contain audio, video, image and graphics data related to each program. Additionally, the IP packets can deliver other types of information such as an electronic service guide (ESG), data files, news, traffic data, financial market data, and graphical newspapers, or any other type of multimedia content. Here and throughout, the phrase “multimedia content” refers to any type of content that may be broadcast to a mobile terminal. Mobile terminals supporting Internet Group Management Protocol (IGMP) additionally may receive content associated with groups to which the mobile terminal has privileges.

FIG. 3represents a conventional architecture for mobile terminal100P. The mobile TV receiver200P is partitioned into a physical layer210and a data link layer220.

In the physical layer210, the RF tuner may be tuned to a mobile TV channel which is demodulated and converted to a digital signal. The digital signal is initially in the form of DVB symbols232which are then converted to MPEG-2 TS packets234by DVB-T (Digital Video Broadcasting-Terrestrial) unit214.

In the data link layer220, the MPEG-2 TS packets are sorted into protected packets236and non-protected packets238by MPEG-2 TS unit222. MPE-FEC (multiprotocol encapsulation-forward error correction) is performed on the protected packets to improve carrier-to-noise ratio (C/N) and Doppler performance in MPE-FEC unit224. The IP packets112are extracted and delivered to the IP processing unit312in the main processor system300P. IP processing unit312identifies the IP addresses of the IP packets and filters the packets based on their destination addresses.

Non-protected packets238do not receive MPE-FEC decoding and are passed by Non-MPE-FEC unit226as TS packets114to the SI/PSI processing unit314in the main processor system300P. The SI/PSI tables are extracted from the TS packets by SI/PSI processing unit314.

The IP processing unit312and SI/PSI processing unit314residing on the main processor system300P perform computationally intense tasks. This places a burden on the main processor system.

SUMMARY

A system architecture for a mobile terminal is disclosed that facilitates the integration of mobile TV service into a mobile terminal system.

In one aspect, embodiments relate to a mobile terminal comprising a host device, a receiver device, and an interface. The host device has a media player adapted to receive a multimedia stream and present a multimedia presentation. The receiver device is connected to the host device and comprises a receiver front end and processing unit. The receiver front end has an antenna and a receiver front end output. The receiver front end is adapted to receive a radio frequency (RF) signal via the antenna and output a stream of packets from the receiver front end output. The processing unit has a processor output. The processing unit is adapted to receive internet protocol (IP) packets derived from packets in the stream of packets, identify IP packets corresponding to the multimedia stream, and output the multimedia stream from the processor output. The interface is adapted to connect the host device and the receiver device.

In another aspect, embodiments relate to a method of operating a mobile terminal. The mobile terminal comprises a host device and a receiver device. The receiver device is initially configured to receive packets arriving in a first time slot. The method comprises transmitting from the host device to the receiver device a multimedia content selection, identifying an address corresponding to the multimedia content selection, looking up a packet identifier in a table stored on the receiver device, the packet identifier corresponding to the address, reconfiguring the receiver to a second time slot, and transmitting multimedia content decrypted with a decryption key from the receiver device to the host device.

In another aspect, embodiments relate to a method of processing a broadcast signal by a receiver device for transmission to a host device. The method comprises receiving a RF broadcast signal at the receiver device, converting, in the receiver device, the RF broadcast signal into a baseband signal comprising protected and non-protected packets, sorting protected and non-protected packets in the receiver device, extracting service information and program specific information (SI/PSI) tables from non-protected packets and storing the SI/PSI tables to memory in the receiver device, error correcting protected packets, in the receiver device, wherein the error correcting produces internet protocol (IP) packets, determining, in the receiver device, an IP packet type based on a destination address for each IP packet, and transmitting IP packets having an audio/video (A/V) packet type from the receiver device to the host device, over a serial interface, for playback.

In yet another aspect, embodiments relate to a wireless communications device. The wireless communication device comprises a host processor and a receiver block. The host processor includes a media player and a user interface that permits a user to select a TV channel. The receiver block is connected to the host processor and comprises a receiver front end and a processing unit. The receiver front end is configured to receive an RF signal containing a stream of packets. The processing unit is configured to process at least a portion of the received stream of packets and, in response to a request from the host processor for the user selected TV channel, to provide packets corresponding to the selected TV channel to the host processor for playback by the media player.

DETAILED DESCRIPTION

Mobile terminals are very complex devices that offer a wide variety of functions. Different terminals offer different features, hardware/software capabilities, user interfaces, connection technologies, and available applications for the end user. Because of the diversity, variety, and complexity of mobile terminals, integrating TV and/or other broadcast services into these terminals may be a complicated task.

A system architecture is disclosed that facilitates the integration of the mobile TV service into a mobile terminal system by providing standard-based, well-understood, widely used and ubiquitous networking and programming interfaces. Introduction of such an interface will enable the mobile TV service to be added to the main processor software as a plug-in module, thus reducing the complexity of software integration tasks. The disclosed architecture also reduces the MIPS (Million Instructions Per Second) loading, memory, and timing requirements for the mobile terminal's main processor system. This can lead to an increase in efficiency and throughput of the interface between the mobile TV receiver module and the mobile terminal main processor system.

For convenience, Table 1 lists some of the terms used in this specification.

Description of an Embodiment of Mobile Terminal100

FIG. 4is a block diagram of a mobile terminal100according to some embodiments of the invention. The mobile terminal100is functionally partitioned into a Host/Application main processor system300and a mobile TV receiver device500.

Communication between the mobile TV receiver device500and the main processor system300may be performed over an interface110. While interface110is typically a serial interface, any other type of interface for communicating data between the main processor system300and the mobile TV receiver device500may be used, such as a parallel interface.

In some embodiments, main processor system300is implemented as one or more integrated circuits, such as a digital signal processor, and mobile TV receiver device500is implemented as a separate integrated circuit and/or other hardware. In some embodiments, mobile TV receiver device500and main processor system300may be combined onto the same integrated circuit.

Main Processor System300

Main processor system300is adapted to execute an A/V CODEC and media player360, a user interface330, a mobile TV application340, a service guide350, a browser application370, and may have other components not shown. The A/V codec and media player360may decode the media stream (that is to decompress the compressed media stream) and play back the video and audio contents. For example, the video and audio contents may be played back over an LCD display and a speaker system, respectively. The user interface330may receive input signals from the user and transmit the control signals from such input devices as keyboard, touch sensor screen, buttons, stylus or similar devices to the main processor. The mobile TV application340may be a software that allows the user to select a specific TV channel for viewing. It may also verify that the user has the right privileges for viewing a particular channel. The service guide350may collect all the information about available channels and their schedule in a tabular form. The browser application370may provide the familiar browser graphical user interface on a display screen. It also provides the graphical environment to display the video component of the TV, or the service guide. In some embodiments, the main processor system300may be made of identical or similar hardware as the main processor system300P (FIG. 1) of the prior art.

The main processor system300may present the multimedia content through a stand-alone program or through a browser application similar to Microsoft Internet Explorer, Mozilla Firefox, or any other embedded browser application software. The browser application may provide a familiar look and feel to users.

The receiver device500digitizes received RF communications and performs network layer and additional processing prior to sending multimedia content to the main processor system300. The receiver device500may contain a receiver front end510, a demultiplexer520, an error correction unit530, a protected packet processing unit550containing an IP processing unit540, a non-protected packet processing unit560, an HTTP server570, and a receiver controller580. Each of these units is described below.

Receiver Front End510

The receiver front end510provides the functionality of a receiver unit with a digital signal output. The receiver front end510may be adapted to receive signals of any RF band appropriate for transmission of multimedia content. In some embodiments, tuner512selects the desired signal band, and suppresses unwanted signals. RF communications may be received by an antenna518.

The RF signal received by receiver front end510may be digitized and demodulated. Digitization and demodulation may be performed using hardware, software, or any other suitable means. In some embodiments the RF signal is converted to a digital signal by an analog-to-digital converter (ADC)514, and may then be demodulated by demodulator516.

The receiver front end510outputs a digital signal containing received information to demultiplexer520. In embodiments supporting DVB-H broadcasts, the signal output to demultiplexer520may be in the form of MPEG-2 TS packets. In some embodiments, a signal strength output measurement is provided to receiver controller580.

Demultiplexer520distributes portions of the digital signal received from receiver front end510to various receiver components, such as protected packet processing unit550and non-protected packet processing unit560.

In some embodiments, the digital signal is received as a series of packets. The demultiplexer520sorts the packets based on packet type. In embodiments for receiving DVB-H broadcasts, packets may be sorted into protected packets and non-protected packets.

Error Correction Unit530

Packets requiring error correction (e.g., protected packets, MPEG-2 TS protected packets, MPE-FEC packets) are sent to the error correction unit530by the demultiplexer520. Error correction unit530may perform any suitable error correction method. In embodiments where the receiver device does not send signals back to the transmission station, automatic repeat-request (ARQ) is not practical, and forward error correction (FEC) may be used. In embodiments for receiving a DVB-H broadcast, multiprotocol encapsulation-forward error correction (MPE-FEC) may be performed on protected packets.

Error corrected packets are output from the error correction unit530to the protected packet processing unit550. In embodiments for receiving a DVB-H broadcasts, error correction unit530outputs user datagram protocol (UDP) formatted IP packets to the protected packet processing unit550.

Protected Packet Processing Unit550

The protected packet processing unit550extracts the payload of each packet received from the error correction unit530(e.g., protected packets432,FIG. 2). In some embodiments, the error corrected IP packets are output from the error correction unit530in the UDP format to the IP unit551of the protected packet processing unit550. The IP packet payload and delivery information may be extracted by IP unit551.

In some embodiments supporting IGMP, IP unit551additionally receives information from IGMP unit553for identifying packets pertaining to broadcast data directed to a messaging group with which mobile terminal100is associated.

The payloads extracted by IP unit551are directed to the IP processing unit540. The content of each payload is determined by the IP processing unit540. Payloads may include multimedia content (e.g., A/V packets), information needed for decryption (e.g., electronic service guide files), media session information (e.g., session description protocol files), and any other information necessary for presenting multimedia content. IP processing unit540identifies and directs payloads to the file delivery over unidirectional transport (FLUTE) module544or the real-time transport protocol (RTP) module542based on their packet type as determined by a destination address and UDP port number.

Packet types relevant to DVB-H broadcasts include electronic service guide (ESG) files, session description protocol (SDP) files, and A/V packets. ESG files carry information on how the broadcast A/V data is encrypted. Packets that contain ESG files are delivered to an ESG decoder552through FLUTE module544and an XML (extensible markup language) parser546for extraction of relevant information.

The FLUTE protocol helps in obtaining an error-free delivery of a file over a unidirectional broadcast channel. FLUTE module544may be part of IP processing unit540and is used primarily in dealing with FLUTE protocol packets containing ESG files and SDP files.

The ESG decoder552decrypts the ESG information using standards-based decryption algorithms such as 128-bit AES (advanced encryption standard). The operation that controls the decryption process and manages the decryption keys relies on the extracted information from the ESG files and is called a service purchase and protection (SPP) helper process unit554. The SPP helper process unit554may extract the updated decryption keys from the ESG data and provide the decryption keys to the decryption engine548. The decryption engine uses the decryption keys to decrypt the A/V data before sending it to the main processor system300.

Session description protocol (SDP) module556provides a standard representation of the information required to initiate a streaming media session, such as viewing a broadcast digital TV channel. The standard representation may include information such as bit rate, type of audio/video compression, transport addresses, and other types of media details. Packets that contain SDP files are recognized by their IP destination address and UDP port number and are delivered to the host media player360through FLUTE module544and XML parser546. When the SDP file is extracted from FLUTE data, it can be presented to the A/V CODEC and media player360of the main processor system300.

A/V packets contain actual compressed audio/video tracks for the requested channel or program and are sent from the IP processing unit540via the RTP unit542to the media player360running on the main processor system300via RTP protocols. In some embodiments where decryption is used, the A/V packets are decrypted by the decryption engine548which receives the necessary decryption keys from SPP helper process unit554.

In some embodiments, the multimedia content and session information are sent to the main processor system300using HTTP server570. The HTTP server570transmits multimedia content to the main processor system300using hypertext transfer protocol (HTTP). The multimedia content may be displayed through a browser application370running on the main processor system300.

The HTTP server570may also receive information from the main processor system300. For example, in some embodiments a user may select a TV channel for viewing through a web browser application. The request may be sent to the HTTP server570of device500via HTTP, in the form of a uniform resource locator (URL), over the serial interface110. In such configuration, the list of available programs is presented graphically in the window of the browser application370, and a scroll bar in the browser may allow the user to scroll onto the TV channel to be watched. In some embodiments, simply clicking on the bar (or tapping the screen if a touch sensor is used) will enable the viewing of the TV channel of interest.

Packets not requiring error correction (e.g., non-protected packets) by error correction unit530are directed to the non-protected processing unit560by the demultiplexer520. The non-protected processing unit560may extract and store tables containing information needed to decode the multimedia content. Also extracted in some embodiments is network map information, which provides details on the signal coverage for the surrounding geographic space. In embodiments supporting DVB-H broadcasts, the non-protected processing unit560receives the non-protected packets from the demultiplexer520. The extracted tables are SI/PSI (Service Information/Program Specific Information) tables which are stored in embedded memory564.

The non-protected packet processing unit560includes the SI/PSI processing unit562and memory564. The SI/PSI processing unit562navigates through the received TS packets, extracts the relevant SI/PSI tables and stores them in memory564. The SI/PSI tables may contain information about the available frequency bands, networks, channels, and programs. The tables also include the IP addresses of those IP packets containing compressed audio/video data for broadcast programs and packets containing ESG.

The receiver controller580may control the receiver front end510. At start up, the receiver controller may configure the receiver front end and instruct it to scan for available content bands. Signal strength measurements provided from the receiver front end510may be used to determine if the receiver should be reconfigured to receive content from a different transmitter.

In embodiments where handover from one transmitter to another requires a change in tuner configuration, the receiver controller580enables the seamless reconfiguration of the receiver front end without perceptible interruption of content.

Receiver controller580may include a frequency scan unit582and a handover unit584. In Multi-Frequency Networks (MFNs), a handover takes place when a mobile terminal100leaves a coverage area of a first cell and enters a coverage area of a second cell. In MFNs, transmitters of neighboring cells operate at different frequencies. In some embodiments, handover is managed by the mobile TV receiver device500without involvement of the main processor system300. In DVB-H systems, handover may involve a change in frequency and/or change in the transport stream that carries the desired signal. The time slicing feature of DVB-H allows for the seamless handover from the first cell to the second without interruption of service.

Radio signal strength may be monitored by receiver controller580. The SI/PSI tables stored in memory564contain network map information and how the area is covered by multiple antennas. This information is provided to handover unit584. When the signal strength of the tuned frequency band decreases below a threshold, the handover unit may cause the tuner512, via frequency scan unit582, to tune to a different frequency band based on the network map data.

In some embodiments, the broadcasts from adjacent cells may be monitored during the off-time in DVB-H systems. The signal strength for the neighboring cells is measured. The handover unit584may cause the frequency scan unit582to tune to the cell of the same network with the strongest signal. By synchronizing to the new frequency, the transport stream of the same IP stream is found in the new cell and the relevant content is sent to the main processor system300without interruption of service.

The frequency scan unit582may control tuner512. If no frequency band is preset, frequency scan unit582starts a scanning process by configuring tuner512for the proper mode and registers all the available bands. This list is stored in memory564and is available to the main processor system300upon invocation of an appropriate API (application programming interface) such as mobile TV application340. In some embodiments, a GUI (graphical user interface) may present this list to the user. A graphical presentation may also be made by the browser application370.

Method of Operating a Mobile Terminal100

In some embodiments, a user may select a channel for viewing from a list of channels provided by user interface330. An embodiment of a selection process is shown inFIG. 5. The list of channels may be stored in the main processor system300and is derived from the ESG and SI/PSI data processed by the mobile TV receiver device500. In embodiments where the main processor system300is running a browser application, the user directly or indirectly selects the URL of the desired channel (step602). The URL, which may reference the TV station or channel, e.g. www.bbc.co.uk/mobiletv, is sent from the browser application on the main processor system300over the serial interface to the HTTP server570running on the mobile TV receiver device500(step604).

The received URL is decoded into an IP address by the HTTP server570. HTTP server570relies on the information stored in the SI/PSI tables by non-protected packet processing unit560on the mobile TV receiver device500as well as the information decoded and stored by the ESG decoder552(step606).

At step608, the IP address is accessed from a table in memory564that is regularly updated by the SI/PSI processing unit562and the ESG decoder552.

The result of the access is reported in step610. The result may be a list of packet identifiers (PID's) for the TS packets that contain the desired A/V stream. The list of PIDs for a channel is extracted for the non-protected packets by the SI/PSI processing unit560.

Once the PIDs for a specific TV channel are known, a search is conducted to determine if the TS packets with that PID are already being received and if they are being corrected into IP datagram, and if they are further processed by the RTP module542, and sent to the main processor system300(step612) for decode and play back. If so, the channel is displayed using the user interface.

If the desired PID is not being received, the mobile TV receiver device500switches to the time slot where the PID is being sent (step614). The appropriate time slot information is extracted by the SI/PSI processing unit562.

The RF signal band, digital modulation scheme, signal bandwidth, and error correction method are specific to the standard utilized by the system.

It should be appreciated that components of a mobile terminal may be implemented as hardware, software, or a combination of both. Having thus described at least one illustrative embodiment of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention is limited only as defined in the following claims and the equivalents thereto.