JP2015510290A - Transceiver station with distributed radio head - Google Patents

Abstract

  The subject of the present invention is a distributed radio that allows user terminals (305, 306, 307) residing in a geographical area covered by a radio transceiver station to access services provided by a wireless telecommunications system. This is a wireless transmission / reception station equipped with a head (303). The wireless head includes a distributed frame device (304), a plurality of distributed access points (308, 309, 310, 311, 312) distributed in a coverage area, and communication between the distributed frame device and the distributed access point. The distributed frame comprises means for transmitting a sample of baseband signals to be transmitted in the coverage area to all distributed access points. The distributed access point allows radio frequency processing to convert the signal to a carrier frequency before transmitting the signal in the form of radio waves to user terminals (305, 306, 307) residing in the coverage area Means.

Description

  The present invention relates to a transmission / reception station equipped with a distributed wireless head, and particularly to the field of wireless telecommunications.

  Current wireless telecommunications systems are based on transceiver stations that allow user terminals to access services provided to them by one or more operators.

  Some systems, such as WiFi, do not manage user terminal mobility. The transceiver station used allows access to services in the area corresponding to the coverage area of the station or deployed station.

  Other systems manage the mobility of user terminals to ensure service continuity regardless of any movement of these users. This is especially true for second, third and fourth generation mobile radio systems. One example of a second generation system is the GSM system, which is an acronym for “Global System for Mobile communications”. An example of a third generation system is the UMTS system, which is an acronym for “Universal Mobile Telecommunication System”. An example of the fourth generation system is an LTE system, and LTE is an acronym for “Long Term Evolution”. A GSM system transceiver station is referred to as a base station and is designated by the acronym BTS, which stands for “Base Transceiver Station”. The transmitting and receiving stations in the UMTS system are referred to as NodeB, and those in the LTE system are referred to as eNodeB. In the following detailed description of the invention, the term “station” designates a transmitting and receiving station.

  To ensure service continuity, it will be necessary to deploy enough stations for the mobile radio system implementation to cover all of the areas targeted by the system operator. Furthermore, in high population density areas such as urban areas, the radio resources that are to be shared between users are limited, so the number of stations will need to be increased.

  The current architecture of radio access networks is evolving towards an architecture with stations that combine a growing number of functions. Such stations also combine, for example, radio frequency processing operations such as filtering and baseband conversion, and digital processing operations such as channel coding and encryption. This is especially true for BTS, nodeB and eNodeB stations used in GSM, UMTS and LTE technologies, respectively.

  In UMTS, the NodeB acts as a gateway to a second equipment device in the radio access network called RNC, which represents “Radio Network Controller”.

  More recently, the LTE standard defines an access network architecture composed of a single type of element called eNodeB. Most of the functions previously implemented by the RNC are distributed between the eNodeB and the system core network. Therefore, the LTE access network is composed only of eNodeBs. The purpose of these trends is to simplify the architecture of radio access networks and to simplify the deployment of radio access networks.

  However, this approach poses many drawbacks. As stations become very expensive, operators are interested in reducing their number to generate sufficient revenue. Therefore, the area covered by the station should be as wide as possible. In the following detailed description of the invention, this area is referred to as the coverage area. Minimizing the number of stations involves relatively high transmit and receive power levels. These levels are required so that all user terminals present in this area can access the system. Therefore, power density is high in the areas covered by these systems and people are concerned about the impact of these power densities on human health. In addition, these stations are usually large. As these stations are becoming increasingly unacceptable by people, their prospects are a source of problems in their installation, especially because of their size and hence their visibility.

  Furthermore, energy consumption is significant due to the high transmission power. This means that using solar panels makes it difficult to use solar energy. In practice, the current power output of a station is generally suppressed by the power amplifier used and by the arithmetic processor.

  Another solution is to use a WiFi terminal or “set-top box” installed in the subscriber's home and use them as wireless access points. The energy billing for the operator is effectively reduced in this case, but at the expense of that of the subscriber. In addition, because of the shared use of equipment, subscribers are subject to significant and permanent electromagnetic radiation at home. Furthermore, with this type of solution, the radio coverage outside the building where the set top box is located becomes difficult due to the intrusion loss due to the walls.

  One of the objects of the present invention is in particular to alleviate the drawbacks mentioned above.

  To achieve this object, the subject of the present invention is a distributed radio head that allows a user terminal residing in a geographical area covered by a station to access services provided by a wireless telecommunication system. Is a wireless transmission / reception station. The wireless head includes a distributed frame device, a plurality of distributed access points distributed in a coverage area, and communication means between the distributed frame device and the distributed access point. The distributed frame comprises means for transmitting samples of the baseband signal to be transmitted in the coverage area to all distributed access points. The distributed access point comprises radio frequency processing means that allow the signal to be converted into a carrier frequency before it is transmitted in the form of radio waves to user terminals that are present in the coverage area.

  According to one aspect of the present invention, the distributed access point comprises means for converting baseband signals received from user terminals into them before transmitting them to the distributed frame equipment.

  The distributed frame device includes, for example, means for combining signals from wireless access points.

  In one embodiment, the distributed frame device combines signals from distributed access points with a weighted sum.

  The result of the weighted sum is used to perform digital antenna beamforming, for example.

  According to another aspect of the invention, the communication means between the distributed frame equipment and the distributed access point corresponds to a CPRI type optical link.

  The distributed frame device is linked to each distributed access point by an optical fiber having the same length, for example, to prevent delay spread of signals transmitted and received by the distributed frame device.

  The communication means between the distributed frame device and the distributed access point corresponds to, for example, a wired link or a dedicated wireless link.

  In one embodiment, the distributed access point is turned off when no user terminal is detected in the neighborhood.

  As an example, a distributed access point that is turned off periodically wakes up to check if the user terminal is located in the vicinity, and the presence of the user terminal is pre-defined in received power. It is confirmed when it is larger than the threshold value.

  The location of the user terminal is estimated by, for example, triangulation performed based on a plurality of signals received by different distributed access points, and the estimation is implemented in a distributed frame.

  The system is for example adapted for one or more of the following technologies: GSM, UMTS, LTE.

  Another subject of the present invention is a distributed radio head that allows user terminals to access services provided by a wireless telecommunications system, said radio head being distributed in a distributed frame equipment, coverage area. A plurality of distributed access points, and a communication means between the distributed frame devices and the distributed access points. The distributed frame devices transmit signals to be transmitted in the coverage area to all distributed access points. Radio frequency processing means for enabling the distributed access point to convert the signal into a carrier frequency before transmitting the signal in the form of radio waves to a user terminal residing in a coverage area Is provided.

  According to one aspect of the invention, the distributed access point comprises means for converting baseband radio signals received from the user terminals into the distributed frame equipment before transmitting them.

  Other features and advantages of the present invention will become apparent from the following detailed description of the invention, given by way of illustration and not limitation, with reference to the accompanying drawings.

Two examples of transceiver architecture are provided. 1 shows an example of a wireless telecommunications system using a station having a distributed wireless head. An example of an architecture that can implement a distributed wireless head is provided. A simple example of an architecture that can be used for distributed frame equipment is shown. 2 shows an example of an architecture of a distributed access point.

  1a and 1b provide two examples of transceiver architecture.

  The manufacturer of the transmitting / receiving station tries to establish an architectural standard in a framework of a consortium such as OBSAI, which represents “Open Base Station Architecture Initiative”. The purpose of these standards is to reduce the infrastructure costs borne by telecommunications operators. In contrast, a base station consists of a number of standardized and hence compatible modules. Thus, an operator can configure his station from modules from different manufacturers.

  For the same reason, the standardization of interface protocols between the different modules that make up a station is also of interest. A CPRI interface representing “Common Public Radio Interface” is an example of this.

  A recent station is composed of one or more wireless heads 101, 102, 104, 105, 106 and control equipment 100, 103. The CPRI interface is an example of a standardized interface that allows the elements that together make up a station to be easily linked. In this standard, the wireless head is designated by the acronym RE representing “Radio Equipment” and the control equipment is designated by the acronym REC representing “Radio Equipment Control”. The

  FIG. 1a provides a first example of a base station composed of multiple modules linked together using a standardized interface. In this example, the control equipment 100 is linked to the first wireless head 101 by using the standardized link 107. The wireless head 101 is then also linked to the second wireless head 102 using a second standardized link 108. The standardized link is, for example, a CPRI link. A CPRI type link allows radio control equipment to build a distributed station architecture that is linked remotely to one or more radio heads, eg, via fiber optic links. The use of standardized links has the effect of reducing costs for service providers. In practice, the wireless head often needs to be placed in a place where it is difficult to access, but in particular, the control devices that make up the digital processor can be placed in a more easily accessible remote area. Can be arranged. For a given station, different radio heads RE are allocated some of the radio resources that can be used by the system. In order to reduce interference, a radio head that covers a part of the area covered by the station to which the radio head belongs uses different radio resources. Exemplary FIG. 1a shows an architecture in which wireless heads are linked sequentially. Although a CPRI link is provided as an example, it is a non-limiting example, and other types of standardized links can be implemented within the scope of the present invention.

  FIG. 1b provides a second example of a base station composed of multiple modules linked together using a standardized interface. In this example, the control equipment 103 is linked to the first wireless head 104 by using a standardized link 109. This wireless head 104 is also linked to two other wireless heads 105, 106 by using two standardized links 110, 111. These standardized links 109, 109, 110, 111 are, for example, CPRI links. It appears that wireless heads can be connected together in series, in parallel, or even by a hybrid network.

  FIG. 2 shows an example of a wireless telecommunications system using stations with distributed wireless heads.

  In this example, a mobile radio system is considered, but the invention can be applied to a radio telecommunications system that does not manage the mobility of user terminals.

  Five cells 200, 201, 202, 203, 204 make it possible to cover the areas defined in the deployment phase of the system, and the radio resources of the system are distributed among the cells. Depending on the technology used, these resources may be frequency domain resources, time domain resources, and / or multiple access codes.

  For a given cell, one or more radio heads of the same type as shown with the assistance of FIGS. 1a and 1b can be used, and a subset of radio resources is allocated to each of these radio heads. Assigned to. These wireless heads are referred to as conventional wireless heads. Accordingly, in the first cell 200, four conventional wireless heads 210, 211, 212, 213 are used. In the second cell 201, there are four conventional wireless heads 213, 214, 215, 216, and one conventional wireless head 213 is used for both the first cell 200 and the second cell 201. Is done. In the third cell 202, a conventional wireless head 217 is used. In the fourth cell 203, a conventional wireless head 218 is used. The fifth cell 204 of the system is covered by a distributed radio head. The distributed wireless head is different from the conventional wireless head. It consists of a distributed frame device 209 and a plurality of distributed access points PADs 205, 206, 207, 208, which are distributed in such a way as to cover all of the cells 204. The distributed frame device 209 communicates with the distributed access point by using baseband digital signals. This makes it possible to obtain bandwidth and protect the signal from disturbances.

  Stations are connected either directly or indirectly to control facility equipment 218 to communicate with the core network and / or external networks.

  FIG. 3 provides an example of an architecture that can implement a distributed wireless head.

  The system includes at least one control equipment device 300. This equipment 300 can be linked to one or more wireless heads 301, 302. In addition, the control equipment 300 can be linked to one or more distributed wireless heads 303. As described above, the distributed wireless head includes the equipment called the distributed frame 304 and one or more distributed access points PAD 308, 309, 310, 311, 312. The control equipment 300 can be linked to the distributed frame equipment belonging to the distributed radio head and / or the conventional radio heads 301, 302, for example by using a standardized interface. This standardized interface can be a CPRI type optical link, a wired link, or a dedicated wireless link. The conventional radio heads 301 and 302 and the distributed radio head 303 receive and transmit data to the user terminals 305, 306, and 307 by using radio resources assigned to them. Depending on the radio technology implemented, these radio resources may correspond to a set of carrier frequencies, a set of CDMA codes, and / or a set of time slots.

  In other words, when a conventional wireless head 301, 302 is used to cover a given geographical area, the radio resources available to it are saved in this area thanks to the access point located in the wireless head. Used by user terminals 305, 306, 307. Conventional wireless heads include antennas or multiple antennas that are co-located to form an antenna array when multi-antenna technology is used.

  When the distributed radio head 303 is used, the same radio resources are used throughout all of the areas covered by it. Distributed access points PADs 308, 309, 310, 311, 312 are geographically distributed in this area in such a way that user terminals are always close to the PAD. The geographical distribution of the PAD has the advantage that the power radiated by these equipment is reduced, especially due to the proximity of the user terminals. The manner in which access points are distributed forms part of the general knowledge of wireless engineers who establish link budgets. Due to the proximity of the user terminal and of the distributed access point PAD, the size of the antenna used can be minimized. Advantageously, the reduced size of these distributed access points PAD allows for individual installations that are coordinated and integrated in an environment that facilitates relationships with people during their installation. Since the transmitter power is low, the power amplifier also improves power efficiency. Advantageously, no cooling device is required and power supply to the distributed access point PAD can be expected by using solar panels.

  Another advantage is that the distortion of the signal, which is known to those skilled in the art, is limited so that the signal is less distorted. In practice, since access points RP308, 309, 310, 311 and 312 are distributed throughout all of the coverage area, compared to a system based solely on a conventional wireless head with a single wireless access point, The possibility that the user terminal will be directly visible with the antenna of the distributed access point is improved. The reduction of the bit rate supplied to the user at the cell boundary is a well-known phenomenon due to the reduced power density. Here, this reduction is reduced because the power density is substantially uniform throughout the entire cell as a result of the distributed characteristics of the PAD.

  In 4th generation systems such as LTE, the use of relays is provided to counter the effects of shadow areas and improves the available bit rate at the cell boundaries. The relay receives signals from different channels of the cell, amplifies them, and retransmits them. These transmissions can have glare and degradation problems due to noise factors. In a system that implements a distributed radio head, the shadow area is covered by a PAD linked to a distributed frame, for example by a fiber type dedicated link.

  A solution belonging to the prior art proposes to implement a picocell, ie a conventional wireless head that covers a small coverage area. In this type of solution, the user terminal is also as close as possible to the pico cell. However, neighboring pico cells use radio resources specific to them. These resources are potentially different from the resources assigned to their neighbors. The conclusion is that the mobility of user terminals moving from one to another from one pico cell needs to be managed. Therefore, it is necessary to introduce means to guarantee communication continuity during their movement, which is usually implemented using so-called “handover” techniques.

  In the system illustrated by FIG. 3, the same radio resource is used throughout all of the area covered by the distributed radio head by using N distributed access points PAD. Therefore, it is not necessary to introduce these “handover” techniques when the user terminal is moving around in the area covered by the distributed radio head.

  In a preferred embodiment, the distributed access point PAD is turned off when no user terminal is detected in the neighborhood. As an example, a distributed access point that is off can wake up periodically to see if the user terminal is located in the vicinity. In contrast, it can ascertain the received power level in the frequency band of the system and compare it to a threshold. The distributed access point PAD wakes up every P seconds for 20 milliseconds, for example.

  Once set up, the distributed access point PAD has a known location. Because of their proximity, terminals are often in radio visibility with multiple wireless access points. This wireless line-of-sight is reflected in the presence of a direct route. Thus, the location of the terminal can be estimated by triangulation performed based on multiple signals received by different distributed access points. Instead, the location of the terminal can be estimated by using the identifier ID assigned to each of the distributed access points PAD, and the knowledge of the identifier ID of the PAD with which the terminal communicates allows this estimation. .

  Such location estimation can be implemented in distributed frames.

  FIG. 4 shows a simple example of an architecture that can be used for distributed frame equipment.

  In this example, the distributed frame device comprises means for connecting to one or more distributed access points PAD. These means correspond to, for example, the input ports 400, 401, 402, and 403 to which the data management module 404 is linked. The function of this module is to format and synchronize the data received on ports 400, 401, 402, 403 and the data that will be transmitted on these same ports.

  Each port 400, 401, 402, 403 is linked to a distributed access point PAD, for example, by an optical fiber of the same length to generate delay spread of signals transmitted and received by distributed frame equipment. To prevent. This link makes it possible to transmit digital samples of the signal in baseband.

ここで、ｘ_ｉ［ｋ］は、ｉ番目のポート上で受信された信号のｋ番目のサンプルを表す。ａ_ｉは、ｉ番目のポートによって受信された信号に適用される重み付け係数を表す。ｙ［ｋ］は、加重和の結果である信号を表す。Ｍは、使用される入力／出力ポート、ゆえに、分散型アクセスポイントＰＡＤからの信号の総数を表す。 The device also includes a digital signal processing module 405. This primary function is to combine digital signals received from different input / output ports 400, 401, 402, 403 by using a single weighted sum given by the following equation.

Here, x _i [k] represents the k th sample of the signal received on the i th port. a _i represents the weighting factor applied to the signal received by the i-th port. y [k] represents a signal that is the result of the weighted sum. M represents the total number of signals from the input / output ports used and hence from the distributed access point PAD.

  The signal processing module also comprises, for example, channel coding and decoding, source coding and decoding, and interference prevention filtering and processing functions. The selection of functions to be implemented depends on the transmission technology used. A system according to the invention can be implemented, for example, for UMTS or LTE.

  The distributed frame equipment also comprises means for connecting one or more control equipment equipment. These means correspond to, for example, a CPRI optical type interface management means. Thus, the device comprises an optical input / output port 407, followed by a first data management module 406. The purpose of this module is to format the received packet and transmit it over the optical interface. Module 406 combines functions corresponding to “Open System Interconnect”, layers 1 and 2 of the OSI reference model.

  FIG. 5 shows an example of a distributed access point architecture. The distributed access point RP manages data transmission and reception of digital data from the distributed access point PAD to the distributed frame device via the input / output port 500 and, for example, the optical interface 505. A module 501 is provided. The purpose of module 501 is to format received packets and packets that are to be transmitted over an optical interface. Module 501 combines functions corresponding to layers 1 and 2 of the OSI reference model, for example.

  The digital signal processing module 502 can be used to implement one or more digital filters. A conversion module 503 is used and comprises an analog-to-digital converter ADC and a digital-to-analog converter DAC to perform the required conversion of the received signal and the signal to be transmitted from the access point RP to the user terminal. To do. The radio frequency module 504 is then used in particular for baseband conversion of analog signals from user terminals and for conversion of signals to be transmitted to the terminals into carrier frequencies.

  In an alternative embodiment, the distributed access point does not include a conversion module, and signals are exchanged between these two pieces of equipment in analog form.

Claims (14)

  A distributed radio that allows a user terminal (305, 306, 307) residing in a geographical area covered by the station to access services provided by a wireless telecommunications system. The wireless head (303) includes a distributed frame device (209, 304), a plurality of distributed access points (205, 206, 207, 208, 308, 309, 310) distributed in a coverage area. 311 and 312), and communication means between the distributed frame device and the distributed access point, and the distributed frame (209) is a sample of a baseband signal to be transmitted in the coverage area. Means for transmitting to all of the distributed access points The distributed access point allows radio frequency processing to convert the signal to a carrier frequency before transmission in the form of radio waves to the user terminals (305, 306, 307) residing in the coverage area A transmitting / receiving station comprising means.   The distributed access point comprises means for converting a baseband signal received from a user terminal (305, 306, 307) into the baseband signal before transmitting it to the distributed frame device (209, 304). Item 2. The transmitting / receiving station according to item 1.   The transceiver station according to claim 2, wherein the distributed frame device (209, 304) comprises means for combining the signals from wireless access points.   The distributed frame device (209, 304) combines the signals from distributed access points (205, 206, 207, 208, 308, 309, 310, 311, 312) by a weighted sum. Transmit / receive station.   The transmission / reception station according to claim 4, wherein the result of the weighted sum is used to perform digital antenna beamforming.   The communication means between the distributed frame equipment (209, 304) and the distributed access point (205, 206, 207, 208, 308, 309, 310, 311, 312) supports CPRI type optical links. The transmitting / receiving station according to any one of claims 1 to 5.   The distributed frame equipment (209, 304) is linked to each distributed access point (205, 206, 207, 208, 308, 309, 310, 311, 312) by optical fibers of the same length, The transmission / reception station according to claim 6, which prevents delay spread of the signal transmitted and received by a distributed frame device from occurring.   The communication means between the distributed frame device (209, 304) and the distributed access point (205, 206, 207, 208, 308, 309, 310, 311, 312) can be a wired link or a dedicated wireless link. The transmitting / receiving station according to any one of claims 1 to 7.   Decentralized access point (205, 206, 207, 208, 308, 309, 310, 311, 312) according to any one of claims 1 to 8, which is turned off when no user terminal is detected in the neighborhood. Transmit / receive station.   Distributed access points (205, 206, 207, 208, 308, 309, 310, 311, 312) that are off periodically wake up to see if the user terminal is located in the neighborhood, The transmitting / receiving station according to claim 9, wherein the presence of the user terminal is confirmed when the received power level exceeds a predefined threshold.   The location of the user terminal (305, 306, 307) is estimated by triangulation performed based on a plurality of signals received by different distributed access points, the estimation being implemented in the distributed frame Item 11. The transceiver station according to any one of Items 1 to 10.   The transceiver station according to any one of claims 1 to 11, adapted for one or more of GSM, UMTS, LTE.   A distributed wireless head (303) that allows user terminals (305, 306, 307) to access services provided by a wireless telecommunications system, wherein the wireless head (303) is a distributed frame device. (209, 304), a plurality of distributed access points (205, 206, 207, 208, 308, 309, 310, 311, 312) distributed in the coverage area, and the distributed frame device and the distributed access point The distributed frame device (209) comprises means for transmitting a signal to be transmitted in the coverage area to all of the distributed access points, the distributed access point comprising: Before the signal is present in the coverage area in the form of radio waves Before sending to the user terminal (305, 306), distributed wireless head comprising a radio frequency processing means making it possible to convert the signal to the carrier frequency. The distributed access point converts a baseband radio signal received from a user terminal (305, 306, 307) into the baseband radio signal before transmitting the baseband radio signal to the distributed frame device (209, 304). The distributed wireless head according to claim 12, comprising:

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