Synchronization of transmitter and receiver frequencies in multiaccess networks

Frequency synchronization of transmitter and receiver in multiple access networks

Technical field

The present invention relates to the combination of a wireless telephone system and a system supporting digital broadband broadcasting.

Background technique

Different wireless network systems that provide different telecommunication services are generally deployed independently of each other. For example, the third generation (3G) wireless system is deployed in the 2GHz International Mobile Telephone (IMT)-2000 frequency allocation according to the International Telecommunication Union (ITU) standard. Wideband Code Division Multiple Access (WCDMA) is an example of third-generation wireless technology. WCDMA has many variants, including direct spread frequency division duplex (in which the uplink and downlink are separated in frequency), direct spread time division duplex (in which the uplink and downlink are separated in time), and multi-carrier CDMA. Direct spread frequency division duplex WCDMA generally uses 5MHz bandwidth or a multiple of 5MHz bandwidth. Third-generation wireless systems can utilize technologies based on different standards, including cdma2000. Cdma2000 is a variant of multi-carrier CDMA technology, compatible with the second-generation wireless systems currently operating in North America. In addition, second-generation (2G) wireless systems are currently in operation all over the world. In Europe, the second-generation wireless system generally complies with the Global System for Mobile Communications (GSM) standard, which is based on time division multiple access technology. In North America and South Korea, the second-generation wireless system operates according to cdmaOne, which is based on code division multiple access technology.

FIG. 1 shows a system supporting base stations 101, 103, 105, 107, and 109 of the Global System for Mobile Communications (GSM) according to the prior art, and these base stations are synchronized by a global positioning system (GPS) reference system 111. Base stations 101-109 serve geographic areas 102, 104, 106, 108, and 110, respectively. The Global Positioning System (GPS) 111 provides a time reference 113 to the base stations 101-109. The time reference 113 can be used to synchronize the base stations 101-109 with a common time base, and to adjust the reference oscillator that controls the center frequency of the radio equipment associated with the base stations 101-109. The time base can be used to establish the timing of the time division multiple access system (TDMA) structure. Frequency adjustment is needed to correct the drift of the center frequency associated with base stations 101-109. In base stations 101-109, frequency shift offsets can cause interference with geographic areas 102-110.

FIG. 2 shows a system of single frequency network (SFN) base stations 201 and 203 synchronized by a global positioning system reference system 111 according to the prior art. The single-frequency network base stations 201 and 203 support the direct extended wideband code division access technology, in which multiple wireless terminals use the same frequency spectrum at the same time. Base stations 201 and 203 support geographic areas 202 and 204, respectively. The global positioning system 111 provides a time reference 113 to synchronize the transmissions from the base stations 201 and 203. The time reference 113 is also used to correct the drift of the local oscillator that controls the center frequency of the radio equipment in the base stations 201 and 203.

Parallel to the deployment of second and third generation wireless systems, digital video broadcasting (DVB) is being deployed in different parts of the world. Digital video broadcasting standards support the broadcasting of digital TV content and other digital information, such as Internet content. For example, terrestrial digital video broadcasting (DVB-T) can utilize very high frequency (VHF) or ultra high frequency (UHF) bands and orthogonal frequency division multiplexing (OFDM) modulation, which is based on multi-carrier modulation. DVB-T is mainly used for unidirectional, broadcast and multicast media transmission, where the frequency bandwidth is large enough to support data rates of up to 32Mbps on the downlink (base station to wireless terminal). Other standards adopted throughout the world are also applicable, including Integrated Services Digital Broadcasting-Terrestrial Transmission (ISDB-T) and Digital Television (DTV).

Figure 3 shows two different radio networks synchronized by different reference oscillators according to the prior art. The radio network 301 includes a radio device 307 and a reference oscillator 305. The radio network 301 includes radio devices 311, 313, and 315, and a reference oscillator 309. The reference oscillator 305 adjusts the center frequency f1 of the radio equipment 307. The reference oscillator 309 adjusts the center frequencies f2, f3, and f4 of the radio devices 311, 313, and 315, respectively. The radio network 301 can support broadband CDMA technologies such as WCDMA, and the radio network 303 can support different radio technologies and telecommunication services, such as terrestrial digital video broadcasting. Generally speaking, the center frequency f1 is significantly different from the center frequencies f2, f3, and f4 (in the case of WCDMA and DVB-T, as shown in the above example, the radio network 301 can utilize the frequency spectrum of about 2 GHz, while the radio network 303 can The spectrum in the UHF band is used, for example corresponding to channel 40) of approximately 626 MHz. Due to the difference in the center frequency, the radio network 301 and the radio network 303 use independent reference oscillators.

As shown in the example above, from the service provider's point of view, or from the user's point of view, different radio networks are deployed without being integrated. Different radio systems can use different center frequencies and different frequency bandwidths, and at the same time have different symmetrical structures. For example, the WCDMA system is deployed in the 2GHz spectrum, using direct extended CDMA with approximately the same data rate on the uplink (wireless terminal to base station) and downlink (base station to wireless terminal), while the DVB-T system can be deployed on UHF television spectrum using OFDM modulation with a higher data rate on the downlink. In addition, in order to support both DVB-T and WCDMA, the wireless terminal requires two independent radio frequency (RF) front ends. Therefore, providing users with different telecommunication services may be inefficient and complicated.

Integrating different radio network systems can simplify the support of different telecommunication services for users. For example, cellular radio services are almost all over the world. In addition, broadband and multicast services are developing and will soon be widely deployed. Of course, even if the user subscribes to multiple telecommunication services supported by different radio networks, the user wants to hold only a single wireless terminal. Thus, methods and equipment for integrating related radio networks are beneficial to advance the technologies that support these telecommunication services.

Summary of the invention

An aspect of the present invention provides a method and apparatus for integrating operations of multiple radio networks. The multiple radio networks may utilize a common frequency spectrum. Adjust the center frequency of the radio equipment in each radio network in order to reduce the drift with respect to each radio network. In addition, system information about multiple radio networks can be transmitted on one radio channel associated with one of the radio networks.

In an exemplary embodiment of the present invention, a wideband code division multiple access (WCDMA) radio network and a terrestrial digital video broadcasting (DVB-T) radio network are integrated to operate in the IMT-2000 spectrum (corresponding to approximately 2 GHz). The WCDMA radio network includes at least one radio device and a reference oscillator. The WCDMA radio network is coupled to the UMTS Terrestrial Radio Access Network (UTRAN) including a radio network controller. In this embodiment, the oscillator synchronizer synchronizes the first reference oscillator related to the WCDMA radio network and the second reference oscillator related to the DVB-T radio network, so as to adjust the center frequency of the radio equipment. System information about these two radio networks is broadcast to wireless terminals on a broadcast channel (BCCH) through a radio channel, and can be supported by the transmission of system information within UTRAN and the core network. In addition, this embodiment supports the integrated operation of WCDMA and DVB-T services in wireless terminals. In a variant of this embodiment, the reference oscillation located in the WCDMA radio network or the DVB-T radio network adjusts the center frequency of the radio equipment related to another radio network.

Description of the drawings

In conjunction with the accompanying drawings, referring to the following description, the present invention and its advantages can be more fully understood. The same reference numerals in the accompanying drawings indicate the same features, among which: Fig. 1 shows a global positioning system (GPS) according to the prior art. ) A system of base stations synchronized with a reference clock, the base station system supports the Global System for Mobile Communications (GSM); FIG. 2 shows a single frequency network (SFN) base station synchronized by a global positioning system (GPS) reference system according to the prior art System; Figure 3 shows two different radio networks synchronized by different reference oscillators according to the prior art; Figure 4 shows the system architecture of integrating two different radio network systems according to an embodiment of the present invention; 5 shows a common oscillator synchronizer for synchronizing two radio network systems according to an embodiment of the present invention; FIG. 6 shows the architecture of a radio network controller according to an embodiment of the present invention; FIG. 7 shows an embodiment according to the present invention The architecture of the wireless terminal; FIG. 8 shows the message situation of the wireless system integrating two radio network systems according to an embodiment of the present invention.

detailed description

In the following description of the various embodiments, reference is made to the accompanying drawings, which constitute a part of the description, and exemplify various embodiments in which the present invention can be practiced. Obviously, other embodiments can also be used, and structural and functional modifications can be made without departing from the scope of the present invention.

FIG. 4 shows the system architecture of a wireless system 400 that integrates two different radio network systems according to an embodiment of the present invention. The radio network 403 includes a UMTS (Universal Mobile Telecommunications Service) terrestrial radio access network (UTRAN), and the radio network 409 includes a terrestrial video broadcasting network 409. The radio network 403 generally includes a plurality of radio network subsystems (RNS), such as RNS 407. The radio network system 407 includes a Node B 411 and a Node B 413. Node Bs 411 and 413 function as base stations in the UMTS architecture, and provide radio communication to wireless terminals 401 and 402 through a radio channel 459 (designated by Uu interface 459). The radio network controller 415 owns and controls radio resources within its range (for example, Node Bs 411 and 413). The radio network controller 415 is a service access point for all services provided by the UTRAN 403 to the core network (CN) 405. The core network 405 includes a mobile service switching center/visitor location register (MSC/VLR) 423 and a serving GPRS (General Packet Radio Service) support node (SGSN) 425. MSC/VLR 423 is a telecommunication exchange and database serving wireless terminals 401 and 402. The function of SGSN 425 is similar to MSC/VLR 424 function, but generally used for packet switching services. The corresponding part of the core network 405 is generally referred to as the packet switched domain. The Iu-CS interface 451 connects the UTRAN 403 and the MSC/VLR 423 to support circuit switching services. The Iu-PS interface 453 connects the UTRAN 403 and the SGSN 425 to support packet switching services.

The radio network 409 includes DVB radio equipment 417, which provides digital content to wireless terminals 401 and 402 through a broadcast radio channel 461. The radio channel 461 is configured to provide wide bandwidth capacity on the downlink (ie, from the DVB radio 407 to the wireless terminals 401 and 402). The content delivery of the digital multimedia content is broadcast or multicast, wherein the delivery contents to the wireless terminals 401 and 402 are the same. The radio network 409 receives digital multimedia content from the core network 405 through the interface 457. The interface 457 can be connected to an entity of the core network 405, such as the SGSN 425, or the gateway GPRS support node (GGSN) not shown in the figure, or another entity. Connectivity gateway to receive content from the Internet (not shown in Figure 4).

In this embodiment, the radio networks 403 and 409 utilize the frequency spectrum allocated to the third generation mobile system by the International Telecommunication Union (ITU). In Europe and most places in Asia, the IMT-2000 frequency band ranges from 1920MHz to 2170MHz. In the United States, no new spectrum is allocated, but the existing spectrum (approximately 1850MHz to 2000MHz) for the second-generation mobile system can be used. The wireless terminals 401 and 402 can be notified of the frequency configuration through messages transmitted on the broadcast channel (BCCH) according to the Uu interface. The messaging on the broadcast channel is discussed in more detail in the context of Figure 8.

In this embodiment, the radio networks 403 and 409 use different radio transmission schemes (for example, different modulation techniques), and in addition, can support different telecommunication services for wireless users. However, the radio system 400 can realize the integrated operation of the radio networks 403 and 409, as described in the context of FIGS. 5-8.

Figure 5 shows a common oscillator synchronizer 517 for synchronizing radio network systems 501 and 503 according to an embodiment of the present invention. In this embodiment, the radio network 501 may correspond to the DVB-T access point 409, and the radio network 503 may correspond to the Node B 411 in FIG. 4. The radio network 501 includes a reference oscillator 505 and a radio device 507. The radio network 503 includes a reference oscillator 509 and radio equipment (radio) 511, 513, and 515. The reference oscillator 505 adjusts the center frequency f1 associated with the radio equipment 507. The reference oscillator 509 adjusts the center frequencies f2, f3, and f4 associated with the radio devices 511, 513, and 515, respectively. The oscillator synchronizer 517 synchronizes the reference oscillators 505 and 509 in order to provide the frequency and time stability required for simultaneous operation of the radio network 501 and the radio network 503 using the IMT-2000 spectrum. The oscillator synchronizer 517 can be implemented in a variety of ways. For example, the oscillator synchronizer 517 may include the Epsilon Clock 2S RB type high performance standard manufactured by Tekelec Systemes (www.temex-telecom.com).

Without synchronizing the oscillators 505 and 509, the center frequencies of the radio devices 507, 511, 513, and 515 will drift with each other, which may cause the performance of the radio networks 501 and 503 (for example, adjacent channel interference) to not meet the performance specifications .

Although FIG. 5 illustrates that the radio network 501 and the radio network 503 are extremely close, as if the radio networks 501 and 503 are located at the same location, the variation of this embodiment can support a configuration in which the radio networks 501 and 503 are physically separated by a certain distance, The distance is limited by the time delay between the oscillator synchronizer 517 and the reference oscillator 509, and the time delay between the oscillator synchronizer 517 and the reference oscillator 505. In addition, with the present embodiment of the present invention, the oscillator synchronizer 517 may be physically associated with the radio network 501 or the radio network 503, or be associated with the networks 501 and 503 remotely.

In a variant of the present invention, the reference oscillator 509 adjusts the center frequency of the radio device 507 through the connection 519, so that the reference oscillator 505 and the oscillator synchronizer 517 are not required. With regard to other variations of this embodiment, the reference oscillator 505 adjusts the radio devices 511, 513, and 515 through connections (not shown), so that the reference oscillator 509 is not required.

Although Figure 5 shows two radio networks 501 and 503, other embodiments of the present invention may support more than two radio networks. In this case, the oscillator synchronizer 517 can synchronize the reference oscillators in each radio network. On the other hand, the reference oscillator in one of the radio networks can adjust the radio equipment in the other radio network.

Fig. 6 shows the architecture of a radio network controller (as shown in Fig. 4) according to an embodiment of the present invention. The radio network controller 415 includes a processor 601 and a data structure 603 containing system information about the radio network 403 and the radio network 409. The system information includes the center frequencies associated with the radio devices 507, 511, 513, and 515. The data port 605 supports communication between the radio network controller 415 and the core network 405 so as to support the Iu-CS interface 451 and the Iu-PS interface 453. The data port 607 supports communication between the radio network controller 415 and the Node Bs 411 and 413. The data port 609 supports communication between the radio network controller 415 and a control center (not shown), which enables the service provider to configure the radio network controller 415, including the system information contained in the data structure 603.

FIG. 7 shows the architecture of a wireless terminal 401 (as shown in FIG. 4) according to an embodiment of the present invention. The wireless terminal 701 includes a processor 703, a radio frequency (RF) front end 705, a WCDMA module 709, a DVB-T module 707, a user interface 711 and a memory 713. The RF front-end 705 receives RF signals on radio channel 459 (related to WCDMA) and radio channel 461 (related to DVB-T). The RF front end 705 filters, amplifies, and demodulates the RF signals received on the radio channel 459 (corresponding to WCDMA) and the broadcast radio channel 461 (corresponding to DVB-T) into corresponding intermediate signals. The WCDMA intermediate signal is transmitted to the WCDMA module 709, and the DVB-T intermediate signal is transmitted to the DVB-T module 707. The WCDMA module 709 completes the further conversion of the WCDMA intermediate signal, which may include message framing and error detection or correction, resulting in the WCDMA data signal processed by the processor 703. The DVB-T module 707 completes the further conversion of the DVB-T intermediate signal, resulting in a DVB-T data signal that is also processed by the processor 703. In this embodiment, the WCDMA module 709 and the DVB-T module 707 and the radio subsystem (radio subsystem) is logically related. In other embodiments of the present invention, all or part of the WCDMA module 709 and the DVB-T module 707 may physically reside in the radio subsystem, or physically reside in the processor 703.

The processor 703 processes the WCDMA data signal and the DVB-T data signal, so that the data output can be provided to the user at the user interface 711. The DVB-T output signal can correspond to the video image on the video display, and the WCDMA output signal can correspond to the audio signal played by the audio output device. This embodiment also enables the processor 703 to save the processed signal in the memory 713 for later access.

In this embodiment, the processor 703 receives system information from the Node B 411 (as shown in FIG. 4) through the RF front end 705 and the WCDMA module 709. The system information may be included in the system information message (as described in the context of FIG. 8). The processor 703 processes system information, and configures the WCDMA module 709 and the DVB-T module 707 according to the system information.

FIG. 8 shows the message situation of the wireless system integrating the radio network 403 and the radio network 409 according to an embodiment of the present invention. The system information 809 is stored in the data structure 603 of the radio network controller 415 (the system information 809 may originate from the core network 405, the radio network controller 415, or the Node Bs 411 and 413). With the aid of the system information request message 811 sent from the radio network controller 415 to the node B 411 through the Iub interface 455, the radio network controller 415 initiates the system information update procedure. The Node B 411 receives updated system information 809 containing information related to the current configuration of the DVB-T access point 409. If the updated system information is successfully broadcast on the Uu interface 459, the Node B 411 returns a system information response message 813 to the radio network controller 415.

In FIG. 8, the Node B 411 sends a system information message 815 to the wireless terminals 701, 803, 805, and 807 on the broadcast channel (BCCH). The broadcast channel (BCCH) is a logical channel supported by the Uu interface 459. The system information message 815 carries a system information block (SIB), and the system information block gathers together system information elements of the same nature. The system information message 815 may carry several system information blocks or only a part of one system information block, depending on the size of the system information block to be transmitted. In this embodiment, information about the DVB-T access point 409 (for example, the center frequency of the radio device 511) is included in one or more system information blocks transmitted to the wireless terminals 701, 803, 805, and 807. This embodiment may use the system information block specified in the third generation partnership project (3GPP) specification TS 25.331 (RRC protocol specification).

The Node B 411 may receive the system information contained in the data structure 603 from the radio network controller 415, the system information including the center frequencies related to the radio devices 507, 511, 513, and 515. As a variant of this embodiment, the radio network 403 and the radio network 409 can exchange configuration information of a certain geographic area (for example, the number of configured radio devices, related frequency bandwidth and guard band requirements). One of the radio networks can use the configuration information to calculate the frequency allocation and notify the other radio network of the frequency allocation (by adding up the spectrum requirements of the configured radio devices and minimizing the interference between the configured radio devices, The center frequency of each configured radio device can be determined. Generally, the center frequency is selected to maintain the maximum frequency separation between adjacent frequency spectrums of the configured radio device).

Those skilled in the art will understand that a computer system having a relevant computer-readable medium containing instructions for controlling the computer system can be used to implement the exemplary embodiments disclosed herein. The computer system may include at least one computer, such as a microprocessor, data signal processing, and related peripheral electronic circuits.

Although the present invention has been described with respect to specific examples including preferred modes for implementing the present invention, those skilled in the art will recognize that there are various changes in the above-mentioned systems and technologies that fall within the spirit and scope of the present invention as defined by the appended claims. And change.