KR100603565B1 - Apparatus and Method for Searching Modem Channel on Cable based Digital Broadcasting - Google Patents

Abstract

According to the present invention, a cable modem channel in cable digital broadcasting can be minimized by excluding a broadcast channel from a search target when searching for channel information of a modem using an exclusive configuration relationship between a broadcast channel and a modem channel. Search apparatus and method, Cable modem channel search apparatus according to an aspect of the present invention, the SI storage unit for storing the broadcast program information received through the network, the broadcast channel of the broadcast program information received from the SI storage unit A broadcast channel processing unit for extracting only information and transmitting it to a broadcast channel storage unit, a broadcast channel storage unit for storing broadcast channel information received from the broadcast channel processing unit, and supplying the broadcast channel information to a modem channel processing unit, and a same channel as the broadcast channel. Perform modem channel discovery only on the remaining channels It includes a modem channel processing unit.

Description

Apparatus and Method for Searching Modem Channel on Cable based Digital Broadcasting}

1 is a block diagram of a cable digital broadcasting system to which the present invention is applied.

Figure 2 is a block diagram of the logical structure of the cable modem channel search apparatus according to the present invention.

* Description of the symbols for the main parts of the drawings *

111: Service Information (SI) Server

112: CA (Conditional Access) server

113: Cable Modem Termination System (CMTS)

121: digital broadcasting server 122: broadcasting head end

130: cable digital broadcasting receiver 131: cable modem

132: MPEG (Host) 133: SI storage unit

20: cable modem channel search apparatus 21: modem channel processing unit

22: broadcasting channel processing unit 23: broadcasting channel storage unit

The present invention relates to an apparatus and method for searching cable modem channels in cable digital broadcasting. More specifically, the apparatus for searching modem channel information in a cable digital broadcasting receiver including a cable modem for processing a plurality of broadcasting channels and a single modem channel. And to a method.

Digital broadcasting includes digital terrestrial broadcasting, digital satellite broadcasting and cable digital broadcasting, depending on the transmission medium. Digital satellite broadcasting is now active worldwide, and digital terrestrial broadcasting is being piloted in some countries in the United States and Europe.

Digital broadcasting efficiently compresses the amount of information of programs for each channel based on the MPEG (Moving Picture Experts Group) coding standard, etc., and efficiently processes programs corresponding to multiple channels based on the digital modulation scheme for each transmission medium. Send multiplexed. Therefore, digital broadcasting can broadcast dozens or hundreds of channels without using a large amount of repeaters as in analog broadcasting.

In general, a broadcasting system for performing cable digital broadcasting includes a head end for receiving and processing data uploaded from a subscriber while transmitting a digital signal related to broadcasting, and a digital signal for receiving a digital signal transmitted from the head end. It includes a set-top box that converts the video signal into an original audio and video signal.

Headend refers to a main coordination center in a cable television system with technical facilities to receive, produce, and retransmit programs from the satellite or elsewhere through the system network. In addition, the set-top box generally means a home communication terminal required when using a multimedia communication service, including video on demand (Video On Demand).

When such a broadcasting system is configured, each cable broadcaster (System Operator, SO) produces a cable TV program, content, and other data or delivers it to the subscriber. The subscriber then sees the desired broadcast by watching the program or other data delivered from the cable TV station.

Video and audio compression technology in cable digital broadcasting is adopted as the Moving Picture Experts Group (MPEG-2) standard worldwide. The modulation method is a QAM method, which is a digital method, which changes amplitude and phase according to a digital data signal to be transmitted, and is suitable for transmitting more efficient data in a limited transmission band. In particular, 64 QAM (64-state Quadrature Amplitude Modulation) digital frequency modulation is primarily used for downlink data transmission over coaxial cable networks, supporting up to 28Mbps on a single 6MHz channel.

Most of the technologies used in cable broadcasting are used in digital TVs. The only difference is that digital TV technology uses a transmission medium called wireless, and cable TV broadcasting uses a transmission medium called wired. Therefore, cable broadcasting has an advantage that it is much better for two-way service than terrestrial broadcasting.

In digital broadcasting, a digital broadcasting receiver (Settop-Box) decodes digitized broadcasting and management information transmitted from a head-end installed in a local cable TV company for cable TV or cable modem service to subscribers. It is a device whose main purpose is to transmit analog signals. The digital broadcast receiver receives broadcast and management information from a headend such as a digital broadcast server (Audio / Video Server), a service information server for transmitting broadcast channel information, and a conditional access server.

Cable digital broadcasting receivers of cable digital broadcasting based on cable networks often include a cable modem. A cable modem is a device that converts analog signals into digital signals for high-speed Internet access through a cable network. The name modem is because the cable network is an analog network such as a telephone network. The telephone network is copper, and the cable network consists of coaxial and optical cables, so the bandwidth of the cable network is much wider. However, cable networks also require modulation and demodulation techniques that convert digital to analog and back to digital when transmitting data. The cable modem was developed to support this.

In cable digital broadcasting, a cable digital broadcasting receiver including a cable modem basically consists of a plurality of broadcasting channels and a single modem channel. Broadcast channels and modem channels are divided into physical frequencies and cannot be duplicated, thus forming mutually exclusive relationships. The broadcast channel information is managed by information called SI (Service Information), but the channel information of the modem is to find its own channel through its own search process. In this case, the cable modem is structured to search not only the modem channel but also the broadcast channel as a search target, thus wasting excessive time searching for a wide range of broadcast channels.

In order to solve the above problems, a cable capable of minimizing a modem channel search time by excluding a broadcast channel from the search target when searching for channel information of a modem using an exclusive configuration relationship between a broadcast channel and a modem channel is provided. An object of the present invention is to provide an apparatus and method for searching a modem channel in digital broadcasting.

An apparatus for searching a cable modem channel according to an aspect of the present invention includes an SI storage unit for storing broadcast program information received through a network, and extracts only broadcast channel information among broadcast program information received from the SI storage unit to a broadcast channel storage unit. A broadcast channel processing unit for transmitting, a broadcast channel storage unit for storing broadcast channel information received from the broadcast channel processing unit, and supplying the broadcast channel information to the modem channel processing unit, and the modem channel only for the other channels except the same channel as the broadcast channel. Modem channel processing unit for performing the search.

The broadcast channel storage unit may include a nonvolatile RAM. When the broadcast channel transmitted from the broadcast channel storage unit matches the search target channel, the modem channel processor skips the channel frequency of the search target. Search for the next channel to be searched.

In the modem channel search step, when the stored broadcast channel and the search target channel match, the channel frequency of the search target is skipped and the next search target channel is searched.

According to another aspect of the present invention, a cable modem channel search method includes an SI storage step of storing broadcast program information received through a cable network, a broadcast channel processing step of extracting only broadcast channel information from the stored broadcast program information, and the extracted broadcast. A broadcast channel storage step of storing channel information and a modem channel search step of performing a modem channel search for only the remaining channels except for the same channel as the stored broadcast channel.

According to another aspect of the present invention, a cable digital broadcasting system includes: a service information server transmitting broadcast channel information to a cable digital broadcasting receiver; And receiving broadcast channel information from the service information server, and if the received broadcast channel and the search target channel match, the channel frequency of the search target is skipped and the next search target channel is searched for and cabled. It includes a cable digital broadcast receiver for searching modem channels.

Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the drawings.

1 shows a configuration of a cable digital broadcasting system to which the present invention is applied.

The cable digital broadcasting system has a structure in which a cable network connects a local cable broadcasting station and a subscriber. The subscriber's equipment includes a cable digital broadcasting receiver 130 including a cable modem, a TV receiver, and the like. The local cable broadcasting station includes an SI server 111, a CA server 112, a CMTS 113, and the like. Devices such as the digital broadcasting server 121 and the broadcasting headend 122 are located.

The data transmitted from the local cable broadcasting station to the subscriber side device includes additional information such as broadcast program information in addition to the video signal and the audio signal and is transmitted in packet units. Upon receiving this information, the cable digital broadcasting receiver 130 processes the broadcast signal received from the television receiver and the cable broadcasting station and converts the broadcast signal into an analog signal that can be recognized by the television receiver.

First, the device located in the local cable broadcasting station will be described.

Examples of devices related to the Internet signal may include a CMTS 113, a CA (Conditional Access) server 112, and an SI (Service Information: User Information) server 111, and among these devices, IP (Internet Protocol). ) Are interconnected by a network.

The CMTS (Cable Modem Termination System) 113 is a cable modem head-end, and is a device that converts the cable modem 131 data into Internet data packets. The CMTS 113 provides several functions, including routing to contain local data in the cable system, filtering to protect cable operators from unwanted hacking, and traffic shaping to ensure the quality of service to subscribers.

The SI (Service Information) server 111 transmits channel information, program map, event information, etc. of the cable broadcast to the subscriber side, and the CA (Conditional Access: Restriction of Access) server 112 provides a specific service. Or controls the ability to allow only users who are allowed to access the content.

On the other hand, the equipment associated with the broadcast signal includes a digital broadcast server 121 and the broadcast head end 122.

The digital broadcasting (Audio / Video) server 121 compresses the MPEG audio / video signal, digitizes it, and transmits it to the subscriber's MPEG (Host) 132 through the broadcasting headend 122.

The broadcast head end 122 refers to a main control center having technical facilities for receiving, producing, and retransmitting a program from the digital broadcasting server 121 through a network.

The local broadcasting station composed of the above components communicates with the cable digital broadcasting receiver 130 located in the home, using the CMTS 113 and the broadcasting headend 122 as end points in contact with the network.

In the communication between the cable modem termination system (CMTS) 113 and the subscriber side, there is a signal flow in the CMTS 113 toward the subscriber and a signal flow in the opposite direction. That is, the CMTS 113 and the subscriber side are bidirectional communication.

On the other hand, in the case of the broadcast headend 122, there is a signal flow from the broadcast headend 122 to the subscriber, but there is no signal flow in the opposite direction, characterized in that the one-way communication.

The equipment necessary for watching cable digital broadcasting in the home is the cable digital broadcasting receiver 130.

The cable digital broadcasting receiver 130 is a main component of the cable modem 131, the MPEG (Host) 132, the SI storage unit 133, and the like.

The cable modem 131 is a device that connects a PC to a cable TV line and receives data at speeds of up to 10 Mbps. If the cable modem 131 is installed together with the set-top box, the TV can be viewed. All cable modems 131 must be connected to the coaxial cable of the cable TV company in order to communicate with the CMTS 113 in the cable stations in each region. All cable modems 131 can only exchange data with the CMTS 113 and cannot exchange signals with other cable modems connected to the same line. The actual bandwidth of a cable TV line for Internet service is up to 27 Mbps down (downstream from the subscriber side) and up to 2.5 Mbps upstream (from the subscriber side towards the station).

The cable modem function of the cable digital broadcasting receiver 130 is connected to a user PC (Personal Computer) to enable the Internet service of the PC, and is used as a return path of the reception restriction device of the cable digital broadcasting receiver 130 to receive the data. Used as a communication path with a restriction server. When the data broadcasting application is embedded in the digital broadcasting receiver, it is used as a communication path for bidirectional data broadcasting. For example, a case such as a stock broadcast may be mentioned.

Originally, the cable modem 131 standard was made to provide an Internet service using an already equipped cable TV network. Cable carriers installed by each carrier support up to 750MHz, where uplink and downlink channels are used. In addition, the frequency band uses 6 MHz per channel.

The uplink signal uses a method called quadrature phase shift keying (QPSK), and the downlink signal mainly uses a quadrature amplitude modulation (QAM) method. Downlink signals can use up to about 30 Mbps using the commonly used 64 QAM scheme. In the case of the uplink speed, 10Mbps can be used by using all 6MHz bandwidths, but because of noise or other effects, it is not using all 6MHz and uses about 2.4Mbps. The cable modem's upward speed is slower than the downward speed because of noise. To protect the network equipment from the noise from devices installed in each generation, it uses a method called QPSK that can reduce the noise even a little. Downward, on the other hand, uses QAM because speed is important.

Moving Picture Experts Group (MPEG) (Host) 132 demodulates video / audio data among received MPEG data to be processed by a video / audio processing unit (not shown), and broadcast program information, which is additional information among MPEG data, is demodulated. To the CPU (not shown).

The SI (Service Information) storage unit 133 is a means for processing and finally storing the program information received from the CPU. The broadcast program information includes a broadcast channel, a broadcast time, a program length, a program title / type, a program grade, a transmission time, event information, and the like.

The search for a modem channel in the cable digital broadcasting receiver 130 having the above components is performed around the cable modem 131.

Looking at the overall operation of the cable modem 131 step by step as follows.

First, scan the frequency of the channel used for downloading. When the cable modem 131 is powered on, first of all, the cable modem automatically finds the frequency used for upload and download. This frequency is different for every cable modem operator. If a channel is found, the channel is locked. In the channel search step, the present invention is applied, and a means for more quickly and effectively performing the channel search process will be the core of the present invention.

After the cable modem 131 detects / fixes the corresponding frequency, the cable modem 131 receives data including an upstream channel descriptor for the channel used for upload, and the cable modem 131 uses this information to provide an external information. Communicate with the network.

Next, the cable modem 131 searches for the strength of the upload (which is referred to as 'level') when uploading. After all the settings related to the channel used for uploading and downloading are completed, the cable modem 131 connects to a Dynamic Host Configuration Protocol (DHCP) server and receives an IP (Internet Protocol) address and a gateway address. The cable modem 131 stores the received address and delivers it to the LAN card of the PC.

The cable modem 131 assigned an IP receives a configuration file, which contains various information necessary for the cable modem to operate in addition to the frequency information, from the server. In this case, the cable modem 131 uses a protocol called TFTP (Trivial File Transfer Protocol). This configuration file varies by cable modem, and cable modem operators can use this configuration file to limit upload / download speeds.

The DHCP server leases IP to the cable modem at fixed intervals (24 hours, 12 hours, 1 hour, etc.). And if your cable modem is still in use after a certain amount of time, it will allow you to use the same IP that your cable modem lent. To do this time calculation, the cable modem is fed the current time from the server. In this case, the server is often a server such as a DHCP server.

Through the above-described series of processes, an environment in which users can normally use the Internet is set.

In the discovery method according to the present invention, the modem channel processing unit selects a discovery method and excludes the broadcast channel secured in advance from the search target channel, and this series of processes is performed using the cable digital broadcasting receiver 130 of FIG. It is made centered. FIG. 2 illustrates only the main logical blocks that are the core of the cable modem channel search within the cable digital broadcasting receiver 130.

2 shows a logical block configuration of a cable modem channel search apparatus according to the present invention.

The cable modem channel search is centered on the cable modem channel search device 20 located in the cable digital broadcasting receiver 130. The cable modem channel searching apparatus 20 includes a modem channel processor 21, a broadcast channel processor 22, a broadcast channel storage 23, and an SI storage unit 133 described with reference to FIG. 1. Include.

When the SI storage unit 133 receives / stores broadcast program information through a network, and transmits the corresponding information to the broadcast channel processor 22, the broadcast channel processor 22 extracts only broadcast channel information from the broadcast program information and broadcast channel. Supply to the storage unit 23. The broadcast channel storage unit 23 stores the received broadcast channel information and provides the data for channel search of the modem channel processing unit 21. The modem channel processor 21 receiving the broadcast channel information performs the modem channel search only for the remaining channels except for the same channel as the broadcast channel.

If you look at this in more detail as described below.

The broadcast channel processing unit 22 receives a broadcast signal of various channels received through the digital broadcasting server 121 and the broadcasting headend 122 located at a local cable broadcasting station, searches for a broadcast channel selected by a user, and then searches the TV receiver. It is in charge of outputting to. The broadcast channel processor 22 extracts only broadcast channel information from the broadcast program information received from the SI storage unit 133 and stores the broadcast channel information in the broadcast channel storage unit 23.

The broadcast channel storage unit 23 stores the broadcast channel information input from the broadcast channel processing unit 22 and transmits the information to the modem channel processing unit 21, and according to an exemplary embodiment of the broadcast channel storage unit 23. An example is NVRAM.

Non-Volatile Random Access Memory (NVRAM) is RAM whose contents are retained even when the computer's external power is turned off or lost. NVRAM can be implemented by providing SRAM (Static RAM) with a backup battery, or by storing and restoring the contents in electrically erased and programmable read-only memory (EEPROM). Can be.

The modem channel processing unit 21 searches for a channel assigned to the cable modem among the wireless channels provided by the local cable broadcasting station to provide an Internet service on the corresponding channel.

To this end, the modem channel processing unit 21 must first search for a modem channel. In general, the channel search process is performed in a fast mode and a low speed mode search for a Harmonic Related Carrier (HRC) band, and an incremental related carrier (IRC) band. The high speed mode and the low speed mode are searched for.

The channel search may proceed sequentially from the low frequency to the high frequency in the allocated frequency band, or may skip while skipping in several channel units. Of course, if the search direction is reversed, it can be considered sufficiently.

In the present invention, regardless of the search progress method, a scanning method for excluding broadcast channel information acquired from the broadcast channel storage unit 23 from the search process in advance is applied.

For example, suppose that a total of 127 channels are allocated from 93 MHz to 855 MHz in the frequency band allocated to the local cable station. Suppose that 645 MHz is assigned to the modem channel, 155 MHz is set for channel 1, 161 MHz for channel 2, 699 MHz for channel 50, and 699 MHz is set for channel 50. The total number of channels to be searched by the cable modem channel search apparatus is 127 channels in total.

On the other hand, when the cable modem channel searching method according to the present invention is followed, the modem channel processing unit 21 secures the information about the broadcasting channel in advance and then excludes it from the search target. Is bound to decrease.

If the search method selected in the present embodiment is a method of sequentially searching from low frequencies, the modem channel processing unit 21 will start searching from 93 MHz of the allocated band and continue searching while increasing the frequency. In the meantime, when a time point to search for 155MHz, which is the first channel allocated to a broadcast channel, comes, the corresponding channel is skipped without being searched. Subsequently, channel search continues and when another broadcast channel is encountered, it is also skipped, resulting in omitting the search for the 50 channels allocated to the broadcast channel.

This means that the search for the modem channel can be completed only by searching for 77 channels except for 50 broadcasting channels among the 127 channels allocated to the corresponding local broadcasting station. The omission of the search for the broadcast channel leads to the omission of 50 channels out of the 127 channels and a short time for the modem channel search by about 40%.

The present invention eliminates the insignificant time for searching a large amount of broadcast channels by excluding a broadcast channel in advance in a modem channel search process of a digital broadcast receiver including a cable modem, thereby reducing the overall modem channel search time of the cable modem. Brings effect.

Claims (6)

A cable modem channel searching apparatus in a cable digital broadcasting receiver, A service information (SI) storage unit for storing broadcast program information received through a cable network; A broadcast channel processor extracting only broadcast channel information among broadcast program information received from the SI storage unit and transmitting the extracted broadcast channel information to a broadcast channel storage unit; A broadcast channel storage unit for storing broadcast channel information received from the broadcast channel processor and supplying the stored broadcast channel information to a modem channel processor; And And a modem channel processing unit configured to perform modem channel searching only for the remaining channels except for the same channel as the broadcast channel. The method of claim 1, The broadcast channel storage unit, A cable modem channel search device comprising a nonvolatile RAM. The method of claim 1, The modem channel processing unit, When the broadcast channel transmitted from the broadcast channel storage unit and the search target channel match, the channel frequency of the search target is skipped and the cable modem channel search is performed for the next search target channel. Device. In the cable modem channel search method of a cable digital broadcasting receiver, A service information (SI) storing step of storing broadcast program information received through a cable network; A broadcast channel processing step of extracting only broadcast channel information from the stored broadcast program information; A broadcast channel storage step of storing the extracted broadcast channel information; And And a modem channel search step of performing a modem channel search only for the remaining channels except for the same channel as the stored broadcast channel. The method of claim 4, wherein The modem channel discovery step, And if the stored broadcast channel matches the search target channel, the channel frequency of the search target is skipped and the search for the next search target channel is performed. In cable digital broadcasting system, A service information server for transmitting broadcast channel information to a cable digital broadcasting receiver; And When the broadcast channel information is received from the service information server, and the received broadcast channel and the search target channel match, the channel frequency of the search target is skipped and the search for the next search target channel is performed. Cable digital broadcasting system comprising a digital broadcasting receiver for searching channels.

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