CN1917388B - Distribution type antenna system, and communication method - Google Patents
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Abstract
The antenna system thereof is base on cell architecture; each cell comprises a CPU, multi wireless access units and transmission link; the multi wireless access units are respectively connected to the CPU through their own transmission link. Wherein, the wireless access unit comprises a duplexer and an antenna mounted on it; the CPU comprises a path loss estimator, a resource allotter, a transmission processor, a wireless access unit selector and a RF link group.
Description
Technical Field
The present invention relates to a multi-antenna system and a communication method thereof, and more particularly, to a distributed antenna system and a communication method thereof, which can select an optimal wireless access unit for a user, thereby providing the best system capacity.
Background
Future wireless communication systems need to support very high rate data services such as video conferencing, video on demand, interactive gaming, etc. According to the requirements mentioned in the ITU-R M1645 document: for High speed wireless services (High Mobility), a rate up to 100Mbps needs to be supported; for Low speed (Low Mobility) or Fixed wireless (Fixed wireless) services, a rate of 1Gbps is required. Meanwhile, as a wireless communication system, it must also ensure the coverage of the system, and provide high data rate service for any user anywhere and at any time.
Analysis has found that user coverage is a serious problem for such high link rates. There may be two reasons specifically:
a. the rate to be supported by future systems is very high, even though the prior art can achieve very high spectrum efficiency, a relatively large bandwidth is required for support, and the current experimental system uses bandwidths of 100MHz downstream and 40MHz upstream. In order to be able to accommodate this system, a relatively high frequency band, for example 10GHz, has to be used. The Path Loss (Path Loss, hereinafter abbreviated as P1) of high frequency signals is much larger than that of signals of lower frequency bands (e.g. GSM, 1 GHz; WCDMA, 2GHz), and the transmission distance of high frequency signals is greatly reduced under the same transmission power.
b. As the data rate of the system increases, the signal-to-noise ratio per bit (SNR/bit) that can be achieved with the same transmit power decreases inversely. And the performance of the user has a direct relation to the signal-to-noise ratio per bit. Of course, the same coverage can be satisfied by increasing the transmit power of the system. However, the transmission power of the base station needs to be limited within a certain range in consideration of the health effect of radio waves on human bodies. Thus, the coverage area of the signal can be greatly reduced under the same limited power. In the above situation, the conventional cellular system only achieves the coverage of the system by the cell division method. This results in a large increase in the system infrastructure and thus in increased investment on the one hand, and a trivial cell handover for the user on the move due to the reduced cell area on the other hand.
To solve this problem, two new network architectures have been proposed. One is a network Structure based on a forward and Multi-Hop Structure (Relay and Multi-Hop Structure), and the other is a network Structure based on a Distributed Antenna System (DAS). Here, since the present invention is directed only to a network structure based on a distributed antenna system, a description of a network system based on a forwarding and multi-hop structure will not be made.
For Distributed antenna systems, the earliest one was disclosed in the references [ 1 ], "a.a.m.saleh, a.j.rustako, and r.s.roman". Distributed antenna for antenna Communications, "ieee trans.on Communications, vol.35, pp.1245-1251, dec.1987". Wherein the radio signal is simply transmitted through the coaxial cable to a remote location and then transmitted through one or more antennas, which may be simultaneously connected in series on a coaxial cable. More often, it is possible to lay a coaxial cable and then provide the cable with small openings in the corresponding places for radio signals to leak out, where these openings correspond to small antennas for transmitting radio signals.
In this case, the transmitted signals of the multiple antennas are actually the same signal, and the function of the same signal is mainly to provide indoor signal coverage for the mobile system. Generally, such a distributed antenna system is called a Passive distributed antenna system (Passive DAS), and the system performance gain that can be provided by the Passive antenna system is very limited.
Since the research on Multiple Input Multiple Output (MIMO) systems has been conducted, an Active Distributed Antenna system (Active DAS) was proposed, see reference [ 2 ], "antennas b. sorensen," Intelligent Distributed Antenna system, "ph.d. 2003". In the distributed antenna system, a plurality of antennas at the system end are not collectively installed on a central base station, but are respectively installed on small base stations which are uniformly distributed in different places within a cell. The radio frequency signals to be transmitted/received by each antenna are received/transmitted from the base station signal processing unit through the optical fiber.
Fig. 1 shows a schematic diagram of an active distributed antenna system. In order to distinguish from the conventional network structure, the small base station with the antenna module is called a Radio Access Unit (RAU), and the signal processing module is called a Central processing Unit (Central Unit), wherein each Radio Access Unit can be installed with multiple independent antennas. For such a system, the wireless access unit may have only a duplexer, a radio frequency signal photoelectric converter, and a transmission radio frequency signal power amplifier. All other base station units including e.g. up/down converters, encoders, modulators, space-time processors etc. are concentrated in the central processing unit. Research shows that, compared with a Central Antenna System (CAS), a distributed Antenna System can achieve better coverage of System signals and can greatly reduce the transmission power of the signals.
Fig. 1 is a schematic diagram of a cell structure in a distributed antenna system. For such a system, there is a problem to be solved: when a user wants to access the system, it is up to select which radio access units communicate with it.
For the uplink, it is theoretically useful to improve the system performance, as long as the wireless access unit can receive the user's signal, no matter how low the energy of the signal is.
For the downlink, selecting more radio access units to serve a user may not necessarily improve the performance of the system while maintaining the same transmit power. This is because: for a central antenna system, adding transmit antennas may increase the performance of the system, but provided that the path loss to the user is the same for each transmit antenna. However, for the distributed antenna system, since the antennas are distributed at different places, the distance between each wireless access unit and the user is different, and thus the corresponding path loss is different.
Taking fig. 2 as an example, when the distances (e.g., d1 and d2) between the wtrus and the users are relatively large, the efficiency of transmitting power is greatly reduced by adding one of the wtrus while the degree of freedom in the spatial dimension is increased. Increasing the number of radio access units 2 to transmit to the user does not necessarily increase the performance of the system if both the increase in performance due to the increased spatial dimension and the path loss introduced by the radio access unit cannot be compensated. In such a distributed antenna system, the problem is how to select the radio access unit to transmit to the user in order to maximize the performance of the system.
Reference [ 3 ], the "Tao Xiaofeng, Ni Li, Dai zujun, Liu Bao ling, Zhang Ping," Intelligent group handover mode in multicell information structure ", PIMRC 2003, vol.1, sept.7-10, 2003", refers to a concept of group handover, whose basic idea is to set a threshold value, and to select all the radio access units with path loss smaller than this threshold value.
Another method is mentioned in the references [ 4 ], "Wan Choi, Jeffrey g.andrews, and Chaehag Yi," the capacity of multicell distributed antipans networks, "WirelessCom 2005, Jun12-16, 2005", which selects a fixed number of L radio access units each time to transmit data to a user. In this case, L of the radio access units with the smallest path loss are selected.
Both of the above-mentioned methods are actually based on the absolute value of the path loss for the selection of the radio access unit, and neither of them can guarantee the maximization of the system channel capacity. To maximize system capacity, the selection of the radio access units should be related to their relative values of path loss with the user. That is, when the user is close to the radio access unit, the selection of the radio access unit closest to the user can fully maximize the capacity, and it is not necessary to allocate power to other radio access units for data transmission.
Disclosure of Invention
To overcome the above problems, the present invention provides a distributed antenna system and a communication method thereof, which can maximize the system capacity when selecting a wireless access unit for a user.
The distributed antenna system is based on a cell structure, each cell comprises a central processing unit, a plurality of wireless access units and transmission links, and the wireless access units are respectively connected with the central processing unit through respective transmission links. Each wireless access unit comprises a duplexer, and the duplexer is used for receiving uplink information of users through an antenna on the duplexer and sending downlink information from the central processing unit. The central processing unit includes: a path loss estimator for estimating uplink information from the plurality of radio access units, obtaining path loss between each radio access unit and the user, and correspondingly storing each path loss and the number of the radio access unit; a resource allocator for obtaining resource allocation information according to the stored path loss and the number of the radio access unit, wherein the resource allocation information includes the radio access unit used by the user; a transmitting processor, which performs corresponding transmitting signal processing on the user data of the user according to the resource allocation information, and generates baseband signal flows aiming at each wireless access unit in the wireless access units adopted by the user; a wireless access unit selector, selecting corresponding wireless access unit from all wireless access units connected with the central processing unit according to the resource allocation information, to transmit each baseband signal flow processed by the transmitting processor; and the radio frequency link group is used for respectively carrying out up-conversion processing on the baseband signal streams output by the wireless access unit selector and respectively transmitting the baseband signal streams subjected to up-conversion processing to the corresponding wireless access units as downlink information through transmission links.
The communication method of the present invention includes the steps of:
step one, the wireless access units respectively receive uplink information of the same user and send the uplink information to a central processing unit;
step two, the central processing unit respectively estimates the path loss of the uplink information of the user from each wireless access unit and correspondingly stores the path loss and the number of the wireless access unit;
step three, according to the path loss and the number of the wireless access unit, obtaining resource allocation information, wherein the resource allocation information comprises the wireless access unit adopted by the user;
step four, according to the resource allocation information, the user data of the user is processed correspondingly to send signals, and baseband signal flows of each wireless access unit in the wireless access units adopted by the user are generated;
step five, according to the resource allocation information, selecting a corresponding wireless access unit for transmitting each baseband signal stream to respectively transmit each baseband signal stream; and
step six, respectively carrying out up-conversion processing on each baseband signal stream, and respectively transmitting the baseband signal streams subjected to up-conversion processing to corresponding wireless access units as downlink information; and
and step seven, each wireless access unit sends the downlink information to the same user.
The resource allocation procedure in the above step three includes the following steps:
i) finding out the minimum value of the path loss from the path losses;
ii) finding out the corresponding wireless access unit according to the minimum value, and using the wireless access unit as a wireless access unit for transmitting the user data of the user;
iii) finding the minimum value of the path loss from the rest of the other path losses;
iv) finding out the corresponding wireless access unit according to the minimum value, calculating whether the system capacity is increased by adding the wireless access unit, finishing the resource allocation when the system capacity is reduced by adding the wireless access unit, taking the wireless access unit as the wireless access unit for transmitting the user data when the system capacity is increased by adding the wireless access unit, and repeating the steps iii and iv until the resource allocation is finished.
Compared with the prior art, the distributed antenna system and the communication method can allocate the wireless access unit capable of realizing the maximum system capacity to the same user, and can increase the system capacity while increasing the freedom degree of the space dimension for the user.
Drawings
Fig. 1 is a schematic diagram of an active distributed antenna system.
Fig. 2 is a schematic diagram of a distributed antenna system with path loss differences.
Fig. 3 is a schematic diagram of a distributed antenna system of the present invention.
Fig. 4 is a detailed block diagram of the distributed antenna system of the present invention.
Fig. 5 is a flowchart of a resource allocation procedure of a communication method of the distributed antenna system according to the present invention.
Detailed Description
The distributed antenna system of the present invention will be described in detail below with reference to the accompanying drawings.
Fig. 3 is a schematic diagram of a distributed antenna system of the present invention. In fig. 3 a plurality of cells (indicated by dashed circles) are shown, each cell comprising at least one central processing unit and a plurality of radio access units. For convenience of description, one central processing unit CU and a plurality of radio access units are uniformly disposed in each cell in fig. 3, but in an actual system, the number and distribution of the radio access units may be set according to the cell situation.
In each cell, the wireless access units are connected with the central processing unit, on one hand, each wireless access unit receives uplink information from users in the cell and transmits the uplink information to the central processing unit after processing, and on the other hand, each wireless access unit receives downlink information from the central processing unit and transmits the downlink information to the users in the cell through the transmitting antenna on the wireless access unit after processing.
Fig. 4 is a detailed block diagram of the distributed antenna system of the present invention, in which the central processing unit and the radio access unit in only one cell are shown. For the sake of generality of the description, it is therefore assumed here that the number of radio access units within the cell is nT. Meanwhile, for convenience of description, only one central processing unit is taken as an example, and an example of using a plurality of central processing units in the same cell can be derived therefrom.
For each wireless access unit, it includes a duplexer 11, an antenna 12 located on the duplexer 11, a reception power amplifier 13, an electro-optical converter 14, a transmission power amplifier 15, and an electro-optical converter 16. Here, the reception power amplifier 13 and the transmission power amplifier 15 belong to selectable units. It may also be omitted in case the power of the distributed antenna system is large and the signal to noise ratio is good.
Meanwhile, for the central processing unit CU, it includes an optical-to-electrical converter 21, a path loss estimator 22, a resource allocator 23, a transmission processor 24, a radio access unit selector 25, a radio frequency link group 26, and an electrical-to-optical converter 27.
Before establishing communication between a user and the distributed antenna system, the user determines a cell to be accessed according to downlink channel information received by the user. For example, for a GSM system, a user decides an accessed cell according to the energy on the frequency of each cell channel, and for a WCDMA system, the user decides the accessed cell according to the energy on the scrambling code of each cell.
After determining the cell to access, the user will send a communication request to the cell.
In the uplink direction in the distributed antenna system of the present invention, for each radio access unit, the duplexer 11 receives uplink information (radio frequency signal, which may be the above-mentioned communication request, or other information) from the user by using the antenna 12 thereon, and performs power amplification on the received radio frequency signal by using the receiving power amplifier 13, which may be a low noise power amplifier. The electrical-to-optical converter 14 performs electrical-to-optical conversion on the amplified radio frequency signal to obtain a corresponding optical signal, and sends the optical signal to the central processing unit CU through an optical fiber link between the wireless access unit and the central processing unit CU.
For the central processing unit, the optical-to-electrical converter 21 receives optical signals from all nT wireless access units in the cell via the optical fiber link, and converts the optical signals from each wireless access unit into corresponding radio frequency signals, respectively. The path loss estimator 22 estimates the path loss between the user and each radio access unit in the cell according to the radio frequency signal, and stores the obtained path loss and the radio access unit corresponding to the obtained path loss. For example, the path loss and corresponding radio access units may be stored in order of decreasing order, e.g., in the manner shown in table 1, assuming { Pl1，Pl2，Pl3，...PlnTWhere Pl1Representing the minimum path loss value. Table 1 is only a storage method, and the present invention is not limited to this, and the storage may be performed in an order from large to small or in an unordered manner, and only the corresponding relationship between the path loss and the corresponding radio access unit needs to be established.
TABLE 1
| RAU1 | RAU2 | RAU3 | ... | RAUnT |
| Pl1 | Pl2 | Pl3 | ... | PlnT |
The resource allocator 23 allocates resources according to the path loss estimated by the path estimator 22 and the corresponding radio access unit. As shown in fig. 5, the resource allocation process of the resource allocator is as follows:
step one, finding out the minimum value of the path loss from the path losses estimated by the path estimator 22;
step two, finding out the corresponding wireless access unit according to the minimum value, and using the wireless access unit as a wireless access unit for transmitting the user data of the user;
finding out the minimum value of the path loss from the rest other path losses;
and step four, finding out the corresponding wireless access unit according to the minimum value, and calculating whether the addition of the wireless access unit increases the system capacity. When the system capacity is reduced by the addition of the radio access unit, the resource allocation is ended. When the wireless access unit is added to increase the system capacity, the wireless access unit is taken as the wireless access unit for transmitting the user data, and then the third step and the fourth step are repeated until the resource allocation is finished.
In the above resource allocation procedure of the resource allocator 23, the selection of the radio access unit that realizes the maximum system capacity can be performed by equation (1).
Where Ce represents the expected value of the channel capacity, E represents the calculation for obtaining the expected value, InRIs an identity matrix of dimension nR by nR, nR represents the number of antennas of the user, H and H*Respectively channel matrix and its transpose, QLA correlation matrix for transmitting signals, and L represents the number of radio access units selected from the nT radio access units when the system capacity is maximum.
H and Q as described aboveLRespectively shown in formulas (2) and (3):
Hwis a random equation of dimension nT by nR, each element of which is a gaussian random variable of zero mean, unit variance. Wherein,representing the channel gain between the user and the nT-th radio access unit.
After the above resource allocation procedure, it is assumed that the resource allocator 23 selects L radio access units at this time, and these radio access units are used for transmitting the user data of the user and can meet the maximum system capacity. Meanwhile, it can be concluded that the user data of the user should be divided into L paths for transmission. That is, the resource allocation information generated by the resource allocation procedure includes: the radio access unit employed by the user.
In the downlink direction, the transmit processor 24 performs transmit signal processing on the user data of the user according to the resource allocation information to generate an L-baseband signal, where the processing includes spatial signal processing, coding, modulation, and the like, which may be determined by a communication request issued by the user during communication.
The radio access unit selector 25 selects L radio access units for transmitting the user data according to the resource allocation information to transmit L paths of user data. In the figure, L indicates the number of selected radio access units, nT indicates a total of nT radio access units, and the user data of the user is not transmitted to the unselected radio access units.
The transmitting rf link group 26 performs up-conversion on the nT baseband signals (only the baseband signals corresponding to the selected L wireless access units transmit the user data of the user) output from the wireless access unit selector 25 to obtain corresponding rf signals.
The electro-optical converter 27 performs electro-optical conversion on the nT channels of radio frequency signals output by the transmission radio frequency link group 26, so as to obtain corresponding nT channels of optical signals, and transmits the corresponding nT channels of optical signals to corresponding wireless access units through optical fiber links.
The optical-to-electrical converter 16 receives the optical signal from the central processing unit CU through an optical fiber link and converts the optical signal into a corresponding radio frequency signal. The radio frequency signal is amplified by a transmission power amplifier 15 and then transmitted from an antenna 12 to a user via a duplexer 11.
As can be seen from the above, by assigning the radio access unit capable of achieving the maximum system capacity to the user at the central processing unit, it is possible to increase the system capacity while increasing the degree of freedom in the spatial dimension for the user.
The above is only one preferred embodiment for implementing the present invention, which mainly aims at the case that the wireless access unit is far away from the central processing unit, so that the optical fiber link is adopted to transmit signals between the wireless access unit and the central processing unit. For this purpose, they require respective optical-to-electrical and electrical-to-optical converters on the wireless access unit and on the central processing unit to achieve interconversion between optical and electrical signals (radio frequency signals).
However, in the case where the wireless access unit is located close to the central processing unit, a cable link may be used instead of the optical fiber link, so that the processes of converting electrical signals into optical signals and converting optical signals into electrical signals may be omitted, and further, the distributed antenna system may not need to use an electrical-to-optical converter and an optical-to-electrical converter.
Further, since the distance between the wireless access unit and the central processing unit can be set according to actual conditions, a cable link can be used for transmitting signals when the distance is short, and an optical fiber link can be used for transmitting signals when the distance is long.
It is noted that although only one antenna is shown on each radio access unit in fig. 4, for an actual distributed antenna system, it may be multiple antennas, and in the case of meeting the maximum system capacity, the central processing unit may allocate these antennas to the same user at the same time (all or part of them), and the user also has multiple antennas. At this time, the rf link group multiplexes user data transmitted from different antennas on the same radio access unit using a multiplexer, and transmits the multiplexed user data to the radio access unit via an optical fiber link or a cable link. At the same time, the radio access unit also needs multiple sets of units in fig. 4 as well as a multiplexer (uplink direction) and a demultiplexer (downlink direction) to realize transmission and reception of the multiplexed signals. That is, each radio access unit corresponds to a plurality of radio access units, and shares one transmission link by using a multiplexer and a demultiplexer.
Claims (7)
1. A distributed antenna system is based on a cell structure, each cell comprises a central processing unit, a plurality of wireless access units and transmission links, the wireless access units are respectively connected with the central processing unit through respective transmission links, wherein,
each wireless access unit comprises a duplexer, the duplexers of the plurality of wireless access units receive uplink information of the same user through an antenna on the duplexer and transmit downlink information from the central processing unit to the user,
the central processing unit includes:
a path loss estimator for estimating uplink information from the plurality of radio access units, obtaining path loss between each radio access unit and the user, and correspondingly storing each path loss and the number of the radio access unit;
a resource allocator for obtaining resource allocation information according to the stored path loss and the number of the radio access unit, wherein the resource allocation information includes the radio access unit used by the user;
a transmitting processor, which performs corresponding transmitting signal processing on the user data of the user according to the resource allocation information, and generates baseband signal flows aiming at each wireless access unit in the wireless access units adopted by the user;
a wireless access unit selector, selecting corresponding wireless access unit from all wireless access units connected with the central processing unit according to the resource allocation information, to transmit each baseband signal flow processed by the transmitting processor; and
and the radio frequency link group is used for respectively carrying out up-conversion processing on the baseband signal streams output by the wireless access unit selector, and respectively transmitting the baseband signal streams subjected to up-conversion processing to the corresponding wireless access units as downlink information through the transmission links.
2. The distributed antenna system of claim 1, wherein the wireless access unit further comprises:
the transmitting power amplifier is used for carrying out power amplification on the downlink information from the central processing unit and transmitting the downlink information after power amplification to the duplexer; and
and the receiving power amplifier is used for carrying out power amplification on the uplink information received by the duplexer and transmitting the uplink information after power amplification to the central processing unit through a transmission link.
3. The distributed antenna system of claim 1,
the wireless access unit further comprises:
the electro-optical converter (14) is used for converting the uplink information received by the duplexer into a corresponding optical signal and transmitting the optical signal to the central processing unit through the transmission link; and
an opto-electric converter (16) for converting the downstream information from the central processing unit into a corresponding electric signal and transmitting the electric signal through the antenna on the duplexer and,
the central processing unit further comprises:
an optical-to-electrical converter (21) for converting the optical signals from each transmission link into corresponding electrical signals and transmitting them to the path loss estimator, respectively; and
and the electro-optical converter (27) is used for converting each path of downlink information from the radio frequency link group into a corresponding optical signal and transmitting the corresponding optical signal to the corresponding wireless access unit through a corresponding transmission link.
4. The distributed antenna system of claim 2,
the wireless access unit further comprises:
an electro-optical converter (14) for converting the uplink information power-amplified by the receiving power amplifier into a corresponding optical signal and transmitting the optical signal to the central processing unit through the transmission link; and
an opto-electric converter (16) for converting downstream information from the central processing unit into a corresponding electrical signal and transmitting the electrical signal to the transmit power amplifier, and,
the central processing unit further comprises:
an optical-to-electrical converter (21) for converting the optical signals from each transmission link into corresponding electrical signals and transmitting them to the path loss estimator, respectively; and
and the electro-optical converter (27) is used for converting each path of downlink information from the radio frequency link group into a corresponding optical signal and transmitting the corresponding optical signal to the corresponding wireless access unit through a corresponding transmission link.
5. The distributed antenna system of claim 2 or 4, wherein the receive power amplifier is a low noise power amplifier.
6. A communication method for a distributed antenna system having a central processing unit, a plurality of radio access units, and transmission links, the method comprising the steps of:
step one, the wireless access units respectively receive uplink information of the same user and send the uplink information to a central processing unit;
step two, the central processing unit respectively estimates the path loss of the uplink information of the user from each wireless access unit and correspondingly stores the path loss and the number of the wireless access unit;
step three, according to the path loss and the number of the wireless access unit, obtaining resource allocation information, wherein the resource allocation information comprises the wireless access unit adopted by the user;
step four, according to the resource allocation information, the user data of the user is processed correspondingly to send signals, and baseband signal flows of each wireless access unit in the wireless access units adopted by the user are generated;
step five, according to the resource allocation information, selecting a corresponding wireless access unit for transmitting each baseband signal stream to respectively transmit each baseband signal stream; and
step six, respectively carrying out up-conversion processing on each baseband signal stream, and respectively transmitting the baseband signal streams subjected to up-conversion processing to corresponding wireless access units as downlink information; and
and step seven, each wireless access unit sends the downlink information to the same user.
7. The communication method according to claim 6, wherein the resource allocation procedure in the third step comprises the steps of:
i) finding out the minimum value of the path loss from the path losses;
ii) finding out the corresponding wireless access unit according to the minimum value, and using the wireless access unit as a wireless access unit for transmitting the user data of the user;
iii) finding the minimum value of the path loss from the rest of the other path losses;
iv) finding out the corresponding wireless access unit according to the minimum value, calculating whether the system capacity is increased by adding the wireless access unit, finishing the resource allocation when the system capacity is reduced by adding the wireless access unit, taking the wireless access unit as the wireless access unit for transmitting the user data when the system capacity is increased by adding the wireless access unit, and repeating the steps iii and iv until the resource allocation is finished.
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| US9112547B2 (en) | 2007-08-31 | 2015-08-18 | Adc Telecommunications, Inc. | System for and method of configuring distributed antenna communications system |
| US9049601B2 (en) | 2007-09-04 | 2015-06-02 | Sharp Kabushiki Kaisha | Base station apparatus, mobile station apparatus, distributed antenna wireless communications system, pilot channel generation method, synchronization channel generation method, and antenna selection method |
| CN101277140B (en) * | 2008-05-09 | 2011-11-09 | 清华大学 | Method for receiving uplink of multiuser distributed antenna system |
| CN101272629B (en) * | 2008-05-09 | 2011-05-11 | 清华大学 | Reliable communication method for terminal moving in large range |
| JP5278110B2 (en) * | 2009-03-30 | 2013-09-04 | Ｋｄｄｉ株式会社 | Wireless signal transmission system and method |
| JP2011041001A (en) * | 2009-08-11 | 2011-02-24 | Samsung Yokohama Research Institute Co Ltd | Radio base station, and radio communication method |
| JP5445152B2 (en) | 2010-01-14 | 2014-03-19 | 富士通株式会社 | Wireless communication device, remote station device, base station device |
| JP5476552B2 (en) * | 2010-06-08 | 2014-04-23 | 日本電信電話株式会社 | Peak transmission power limiting method and radio communication system |
| JP5270648B2 (en) | 2010-12-08 | 2013-08-21 | 株式会社日立製作所 | Distributed antenna system, base station apparatus, and antenna selection control method |
| CN102332944B (en) * | 2011-11-04 | 2014-07-30 | 上海电机学院 | Method and device for selecting downlink beam-forming base stations of distributed multiple-input multiple-output (MIMO) system |
| WO2012167584A1 (en) * | 2011-12-05 | 2012-12-13 | 华为技术有限公司 | Detection system and device for distributed antenna system |
| JP5510576B2 (en) * | 2013-03-07 | 2014-06-04 | 富士通株式会社 | Pilot control method |
| WO2015197101A1 (en) * | 2014-06-23 | 2015-12-30 | Telecom Italia S.P.A. | Method for dynamically reducing fronthaul load between a base station and multiple remote radio units |
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| WO2005018181A1 (en) * | 2003-08-06 | 2005-02-24 | Qualcomm Incorporated | Cooperative autonomous and scheduled resource allocation for a distributed communication system |
| WO2005039214A1 (en) * | 2003-10-20 | 2005-04-28 | Telefonaktiebolaget Lm Ericsson (Publ) | Radio resource-sharing cells |
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| JP3645140B2 (en) * | 1999-12-28 | 2005-05-11 | 株式会社エヌ・ティ・ティ・ドコモ | Mobile communication system |
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| WO2005018181A1 (en) * | 2003-08-06 | 2005-02-24 | Qualcomm Incorporated | Cooperative autonomous and scheduled resource allocation for a distributed communication system |
| WO2005039214A1 (en) * | 2003-10-20 | 2005-04-28 | Telefonaktiebolaget Lm Ericsson (Publ) | Radio resource-sharing cells |
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