KR20140104489A

KR20140104489A - Transmitting and receiving station comprising a distributed radio head

Info

Publication number: KR20140104489A
Application number: KR1020147019702A
Authority: KR
Inventors: 까이 마브루; 베르나르 위야르
Original assignee: 앵스띠뛰 미네-뗄레콩
Priority date: 2011-12-16
Filing date: 2012-12-13
Publication date: 2014-08-28
Also published as: FR2984677B1; WO2013087748A1; FR2984677A1; SG11201404093TA; CN104488350A; JP2015510290A; EP2792210A1

Abstract

The claims of the present invention may be applied to a distributed radio head (e. G., &Lt; RTI ID = 0.0 > 303). &Lt; / RTI > The radio head comprises a splitter rig 304, a plurality of distributed access points 308, 309, 310, 311, 312 distributed to the coverage zone, and communication means And the splitter comprises means for transmitting samples of the baseband signal to be transmitted in all of the distributed access points in the coverage zone. The distributed access points may include radio frequency processing means that enable transposition of the signal to a carrier frequency prior to transmitting the signal in the form of radio waves to user terminals (305, 306, 307) .

Description

[0001] TRANSMITTING AND RECEIVING STATION COMPRISING A DISTRIBUTED RADIO HEAD [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transceiver station including a distributed radio head, and particularly to the field of wireless telecommunications.

Current wireless telecommunication 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 the mobility of user terminals. The transmitting / receiving stations used allow access to services within the area corresponding to the coverage area of the base station or base stations.

Other systems manage the mobility of user terminals to ensure continuity of service despite any movement of these users. Especially for second-, third- and fourth-generation mobile radio systems. An example of a second generation system is the GSM system and GSM is the abbreviation of "Global System for Mobile communications ". An example of a third generation system is the UMTS system, and UMTS is the abbreviation of "Universal Mobile Telecommunication system ". An example of the fourth generation is the LTE system, and LTE is the abbreviation of "Long Term Evolution". Transmitting / receiving stations in the GSM system are referred to as base stations and are denoted by the abbreviated BTS (representing "Base Transceiver Station"). The transmitting and receiving stations of the UMTS system are called NodeB and the transmitting and receiving stations of the LTE system are called eNodeB. In the following description, the term "station" refers to a transmitting / receiving station.

In order to ensure continuity of service, it is necessary in the implementation of mobile radio systems to arrange stations sufficient to cover all the areas covered by the operator of the system. Also, in regions with high population density, such as urban areas, the number of stations should be entirely higher because radio resources to be shared among users are limited.

Current architectures of radio access networks are evolving toward architectures that include stations that combine an ever-increasing number of functions. Such stations combine radio frequency processing operations such as, for example, filtering and baseband conversion, but also combine digital processing operations such as channel coding and encryption. Especially for BTS, nodeB and eNodeB stations used in GSM, UMTS and LTE technologies, respectively.

In UMTS, a Node B acts like a gateway with a second device item of a radio access network called an RNC (denoting "Radio Network Controller").

More recently, the LTE standard defines an access network architecture consisting of a single kind of element called eNodeB. Traditionally, most of the functions implemented by the RNC are distributed between the eNodeB and the system core network. The LTE access network therefore consists solely of eNodeBs. The purpose of these trends is to simplify the architecture of the radio access network and simplify the deployment of the radio access network.

This approach, however, presents a number of defects. Stations are so expensive that operators are interested in reducing the number to generate enough revenue. As a result, the area covered by the station should be as wide as possible. In the following description, this area is referred to as the coverage area. Minimizing the number of stations involves relatively high transmission and reception power levels. These levels are needed so that all user terminals in the region can access the system. Thus, the power densities are high in the areas covered by these systems, and the population is concerned about the health impact of life on these power densities. Also, these stations are usually large. Their visibility is a source of problems for their installation because they are even less accommodated by their size, especially because of their size and their visibility.

In addition, because of the high transmit powers, the energy consumption is significant. This means that it is difficult to use solar energy by using a panel located at the station. Indeed, the current power yield at the stations is generally contained by the power amplifier (s) and computation processes in common use.

Another solution is to use "set-top boxes" or WiFi terminals installed at the homes of subscribers and use them as radio access points. In this case, energy billing for the operator is effectively reduced, but harms the subscriber. Also, the subscriber receives significant and continuous electromagnetic radiation in his or her home, due to the sharing of his or her device. Also, in this kind of solution, the radio coverage outside the buildings where the set-top boxes are located becomes difficult due to penetration loss due to the walls.

One object of the present invention is to alleviate the above-mentioned defects.

To this end, the claims of the present invention include a distributed radio head that allows user terminals residing in a geographical area covered by a wireless transceiver station to access services provided by a wireless telecommunication system, to be. The radio head comprises a distribution 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 points. The distribution frame includes means for transmitting samples of the baseband signal to be transmitted in all coverage areas to all distributed access points. The distributed access points include radio frequency processing means that enable transposition of the signal to a carrier frequency prior to transmission of the signal in the form of radio waves to user terminals located in the coverage area.

According to one aspect of the invention, the distributed access points include means for transposing radio signals received from user terminals to baseband prior to transmission to the distribution frame device.

The distribution frame device includes, for example, means for combining signals from radio access points.

In one embodiment, the distributed frame device combines the signals from the distributed access points by weighted summing.

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

According to another aspect of the invention, the means of communication between the distributed frame device and the distributed access points correspond to CPRI-type optical links.

The distributed frame device is linked to each distributed access point by optical fibers of the same length, for example, to avoid spreading of delays of signals transmitted and received by the distributed frame device.

The means of communication between the distributed frame device and the distributed access points correspond to wired links or dedicated radio links.

In one embodiment, the distributed access point is off if no user terminal is detected nearby.

As an example, the off-allocated distributed access point periodically wakes up to verify whether the user terminal is located in proximity and if the received power level is greater than a predefined threshold, the presence of the user terminal Is verified.

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

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

Another claim of the invention is a distributed radio head which allows user terminals to access services provided by a wireless telecommunication system, the radio head comprising a distribution frame device, a plurality of distributed access points And means for communicating between the distributed frame device and the distributed access points, wherein the distributed frame device comprises means for transmitting a signal to be transmitted in all of the distributed access points in the coverage area, The points include radio frequency processing means that enable transposition of the signal to a carrier frequency prior to transmission of the signal in the form of radio waves to user terminals located in the coverage area.

According to one aspect of the invention, the distributed access points comprise means for transposing radio signals received from user terminals to baseband prior to transmission to the distribution frame device.

Other features and advantages of the present invention will become apparent from the following description, given by way of example and non-limiting example, in view of the accompanying drawings.
Figures 1A and 1B provide two examples of a transceiver architecture.
Figure 2 shows an example of a wireless telecommunication system using a station with a distributed radio head.
Figure 3 provides an example of an architecture in which distributed radio heads may be implemented.
Figure 4 shows a simplified example of an architecture that may be used in a distributed frame device.
5 shows an example of a distributed access point architecture.

Figures 1A and 1B provide two examples of a transceiver architecture.

Manufacturers of transceiver stations are striving to build architectural standards in the framework of consortia, such as OBSAI (representing "Open Base Station Architecture Initiative"). The purpose of these standards is to reduce the infrastructure costs borne by telecommunications operators. To this end, the base station is composed of a plurality of modules that are standardized and thus commercially available. Thus, an operator may configure his own stations from modules originating from different producers.

For the same reasons, the standardization of the interface protocol between the different modules constituting the station is also of interest. The CPRI (representing the "Common Public Radio Interface") interface is an example of this.

Recent stations are comprised of one or more radio heads 101, 102, 104, 105, 106 and control device items 100, 103. The CPRI interface is an example of a standardized interface that makes it possible to easily link elements that together form a station. In this standard, the radio heads are denoted by the abbreviation RE (denoted "Radio Equipment") and the control device items denoted by the abbreviation REC (denoted "Radio Equipment Control").

FIG. 1A provides a first example of a base station comprising a plurality of modules linked together using a standardized interface. In this example, the control device item 100 is linked to the first radio head 101 by using the standardized link 107. [ The radio head 101 is then linked to the second radio head 102 using a second normalized link 108. Standardized links are, for example, CPRI links. The CPRI-type links enable, for example, to configure a distributed station architecture in which radio control device items are remotely linked to one or more radio heads via fiber optic links. The use of standardized links has the effect of reducing costs for service providers. In fact, while radio heads are often located in places that are difficult to access, control devices, especially digital processors, may be located in more accessible remote areas. In the case of given stations, some of the radio resources that can be used by the system are assigned to different radio heads RE. To reduce interference, the radio heads that cover parts of the area covered by the stations they belong to use distinct radio resources. 1a shows an architecture in which radio heads are linked in series. CPRI links are provided by way of example, but are non-limiting examples, and other kinds of standardized links may be implemented within the scope of the present invention.

FIG. 1B provides a second example of a base station comprising a plurality of modules linked together using a standardized interface. In this example, the control device item 103 is linked to the first radio head 104 by using the standardized link 109. The radio head 104 is also linked to two other radio heads 105, 106 by using two standardized links 110, 111. These standardized links 109, 109, 110, 111 are, for example, CPRI links. It is evident that the radio heads can be connected together in series, in parallel, or even into a hybrid network.

Figure 2 shows an example of a wireless telecommunication system using a station with a distributed radio head.

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

The five cells 200, 201, 202, 203, 204 enable covering the defined area in the arrangement 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 kind as those described with the aid of FIGS. 1A and 1B may be used, and a subset of the radio resources is allocated for each of these radio heads. These radio heads are referred to as conventional radio heads. Thereby, in the first cell 200, four conventional radio heads 210, 211, 212, and 213 are used. Four conventional radio heads 213,214 and 215 and 216 are used and one conventional radio head 213 is used in the first cell 200 and the second cell 201. In the second cell 201, Lt; / RTI > In the third cell 202, a conventional radio head 217 is used. In the fourth cell 203, a conventional radio head 218 is used. The fifth cell 204 of the system is covered by the distributed radio head. The distributed radio head is different from a conventional radio head. It consists of a distribution 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 points by using baseband digitized signals. This makes it possible to obtain bandwidth and safeguard the signal from disturbances.

In order to communicate with the core network and / or the external network, the stations are connected directly or indirectly to the control device item 218.

Figure 3 provides an example of an architecture in which distributed radio heads may be implemented.

The system includes at least one control device item (300). The device item 300 may be linked to one or more radio heads 301, 302. The control device item 300 may also be linked to one or more distributed radio heads 303. As previously mentioned, the distributed radio head is comprised of a device item called a distribution frame 304 and one or more distributed access points PAD 308, 309, 310, 311, 312. The control device item 300 may be linked to a distributed frame device and / or conventional radio heads 301, 302 belonging to a distributed radio head, for example, by using a standardized interface. This standardized interface may be an optical link of the CPRI type, a wired link, or a dedicated radio link. The conventional radio heads 301 and 302 and the distributed radio heads 303 receive and transmit data to the user terminals 305, 306 and 307 by using radio resources allocated to them. Depending on the radio technology being 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 conventional radio heads 301 and 302 are used to cover a given geographical area, the radio resources available to them can be used by user terminals (e.g., 305, 306, 307). A typical radio head includes an antenna, or a plurality of antennas co-located to form an antenna array when multiple antenna technologies are used.

When a distributed radio head 303 is used, the same radio resources are used throughout all areas covered by the distributed radio head. The distributed access points PAD 308, 309, 310, 311, 312 are geographically distributed in this area in such a manner that the user terminal is always in close proximity to the PAD. The geographic distribution of PADs has the advantage, among other things, that the power emitted by these device items is reduced due to the proximity of the user terminals. The way in which the access points are distributed forms part of the general knowledge of the radio engineer to build the link budgets. Due to the proximity of the user terminals and the distributed access points PAD, the dimensions of the antennas used can be minimized. Advantageously, the reduced size of these distributed access points PAD allows for discrete installations that are harmoniously integrated within the environment, which facilitates relationships with residents during its installation. Because the power of the transmitter is low, the power efficiency of the power amplifiers is improved. Advantageously, no cooling device is required, and the power supply to the distributed access points PAD can be visualized by using a solar panel.

Another advantage is that the signals will be less distorted because the transient spreading of the signals known to those skilled in the art is limited. In fact, since the distributed access points RP 308, 309, 310, 311, 312 are distributed across all of the coverage areas, the probability that the user terminal is in direct visibility with the antenna of the distributed access point, Points compared to systems based only on conventional radio heads. The decrease in bit rate provided to users at cell boundaries is a phenomenon known due to the reduced power density. This degradation will be reduced here because of the virtually uniform power density across the entire cell due to the distributed nature of the PADs.

In fourth generation systems such as LTE, the use of repeaters is provided to combat the effects of regions of the shadow and to improve the available bit rate at the cell boundary. The repeater receives signals from the different channels of the cell, amplifies them, and retransmits them. These transmissions may suffer from glare and degradation due to the noise factor. In a system that implements distributed radio heads, the shadow area will be covered by a PAD linked to the distribution frame by, for example, a dedicated link of fiber type.

The prior art solutions propose the implementation of conventional radio heads that cover pico cells, i.e., coverage areas of small sizes. In this kind of solution, user terminals are also as close as possible to the picocells. However, side by side picocells use radio resources that are specific to them. These resources are potentially different from those assigned to their neighbors. The result is that the mobility of user terminals moving from one picocell to another picocell should be managed. It is therefore necessary to implement means for ensuring continuity of communications during these moves, and this continuity is usually implemented using so-called "handover" techniques.

In the system shown in Fig. 3, the same radio resources are used over all of the areas covered by the distributed radio head by using the N distributed access points PAD. Thus, there is no need to perform these "handover" techniques when the user terminal moves around in the area covered by the distributed radio head.

In a preferred embodiment, if no user terminal is detected in close proximity, the distributed access point PAD is off. As an example, an off-point distributed access point may periodically wake up to verify whether the user terminal is located in proximity. For this purpose, it is possible to verify the received power level in the frequency band of the system and compare it with the threshold value. The distributed access point PAD wakes up every P seconds for a period of, for example, 20 ms.

Once deployed, the distributed access points PAD have a known position. Because of its proximity, terminals are often in radio visibility with multiple radio access points. This radio visibility is reflected in the extension of direct paths. As such, the position of the terminal can be estimated by triangulation performed based on the plurality of signals received by the different distributed access points. Alternatively, the position of the terminal can be estimated by using the identifiers ID assigned to each of the distributed access points PAD, and the knowledge of the identifier (s) ID of the PAD (s) Allow estimation.

This position estimate can be implemented in a distribution frame.

Figure 4 shows a simplified example of an architecture that can be used in a distributed frame device.

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

Each port 400,401, 402,403 may be provided with a plurality of ports 400,402, 403,403 which are distributed by optical fibers of the same length, for example, to avoid the occurrence of spreads in delays of signals transmitted and received by the distributed frame device Linked to point PAD. This link enables the transmission of digital samples of the signal in the baseband.

The device also includes a digital signal processing module (405). The main function of this is to combine the digitized signals received from the different input / output ports 400, 401, 402, 403 by using a simple 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;

_i represents the weighting factor applied to the signal received by the i < _th > port;

y [k] represents the signal resulting from the weighted sum.

M represents the total number of signals coming from the input / output ports used and hence the distributed access point PAD.

The signal processing module also includes, for example, channel coding and decoding, source coding and decoding, and anti-interference filtering and processing functions. The choice of functions to be implemented depends on the transmission technology used. The system according to the present invention may be implemented for UMTS or LTE, for example.

The distribution frame device also includes means for connecting one or more control device items. These means correspond, for example, to the management means of the CPRI optical type interface. As such, the device includes a first data management module 406 that is in line with the optical input / output port 407. The purpose of this module is to format the received packets and transmit them via the optical interface. It combines functions corresponding to layers 1 and 2 of the Open Systems Interconnection (OSI) reference model.

5 shows an example of a distributed access point architecture. The distributed access point RP is connected to a data management module (e. G., &Lt; RTI ID = 0.0 > 501). The purpose of the module 501 is to format the packets transmitted and the packets received via the optical interface. It combines functions corresponding to, for example, layers 1 and 2 of the OSI reference model.

The digital signal processing module 502 may be used to implement one or more digital filters. A conversion module 503 is used and includes an analog-to-digital converter ADC and a digital-to-analog converter DAC for performing the necessary conversions of the signals transmitted to the user terminals from the access point RP and the received signals. The radio frequency module 504 is then used for baseband conversion of analog signals, particularly from user terminals, and transposition to carrier frequencies of signals to be transmitted to the terminals.

In an alternative embodiment, the distributed access points do not include a conversion module, and signals are exchanged in analog form between the two device items.

Claims

A distributed radio head 303 that allows user terminals (305, 306, 307) in geographical areas covered by a wireless transceiver station to access services provided by a wireless telecommunication system The wireless transceiver station comprising:
The distributed radio head 303 includes a distributed frame device 209, 304, a plurality of distributed access points 205, 206, 207, 208, 308, 309, 310, 311, 312 distributed in a coverage area, (209) for transmitting samples of a baseband signal to be transmitted in the coverage area to all of the distributed access points, wherein the distribution frame (209) comprises means for communicating between the distributed frame device and the distributed access points And wherein the distributed access points enable transposition of the signal to a carrier frequency prior to transmission in the form of radio waves to the user terminals (305, 306, 307) residing in the coverage area Radio frequency processing means.

The method according to claim 1,
Wherein said distributed access points comprise means for transposing radio signals received from user terminals (305, 306, 307) to baseband prior to transmission to said distribution frame device (209, 304) soup.

3. The method of claim 2,
The distribution frame device (209, 304) comprises means for combining signals from radio access points.

The method of claim 3,
The distribution frame device (209, 304) combines the signals from the distributed access points (205, 206, 207, 208, 308, 309, 310, 311, 312) by weighted summing.

5. The method of claim 4,
The result of the weighted sum is used to perform digital antenna beamforming.

6. The method according to any one of claims 1 to 5,
Wherein the communication means between the distributed frame devices (209, 304) and the distributed access points (205, 206, 207, 208, 308, 309, 310, 311, 312) , A wireless transceiver station.

The method according to claim 6,
The distributed frame devices 209 and 304 are connected to respective distributed access points 205, 206, 207 and 208 by optical fibers of the same length to avoid spreading of delays of signals transmitted and received by the distributed frame device , 308, 309, 310, 311, 312).

8. The method according to any one of claims 1 to 7,
The communication means between the distributed frame devices 209 and 304 and the distributed access points 205, 206, 207, 208, 308, 309, 310, 311 and 312 are connected to wired links or dedicated radio links Corresponding, wireless transceiver station.

9. The method according to any one of claims 1 to 8,
The distributed access point (205, 206, 207, 208, 308, 309, 310, 311, 312) is off when no user terminal is detected in proximity.

10. The method of claim 9,
The distributed access points 205, 206, 207, 208, 308, 309, 310, 311, 312 that are off and on periodically wake up to verify whether the user terminal is located in proximity, Wherein the presence of the user terminal is verified if the power level is greater than a predefined threshold.

11. The method according to any one of claims 1 to 10,
The location of the user terminals 305, 306, 307 is estimated by triangulation performed based on the plurality of signals received by the different distributed access points and the estimation is implemented in the distribution frame , A wireless transceiver station.

12. The method according to any one of claims 1 to 11,
The following technologies are configured for one or more of: GSM, UMTS, LTE.

A distributed radio head (303) that allows user terminals (305, 306, 307) to access services provided by a wireless telecommunication system,
The distributed radio head 303 includes a distributed frame device 209, 304, a plurality of distributed access points 205, 206, 207, 208, 308, 309, 310, 311, 312 distributed in a coverage area, Wherein the distribution frame device comprises means for communicating between the distributed frame device and the distributed access points, the distributed frame device comprising means for transmitting a signal to be transmitted in the coverage area to all of the distributed access points And the distributed access points enable transposition of the signal to a carrier frequency prior to transmitting the signal in the form of radio waves to the user terminals (305, 306, 307) residing in the coverage area A distributed radio head comprising radio frequency processing means.

13. The method of claim 12,
Wherein the distributed access points comprise means for transposing radio signals received from user terminals (305, 306, 307) to baseband prior to transmission to the distribution frame device (209, 304) Radiohead.