WO2011020243A1 - 用于无线通信系统中协作中继的方法和设备 - Google Patents
用于无线通信系统中协作中继的方法和设备 Download PDFInfo
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- WO2011020243A1 WO2011020243A1 PCT/CN2009/073358 CN2009073358W WO2011020243A1 WO 2011020243 A1 WO2011020243 A1 WO 2011020243A1 CN 2009073358 W CN2009073358 W CN 2009073358W WO 2011020243 A1 WO2011020243 A1 WO 2011020243A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0076—Distributed coding, e.g. network coding, involving channel coding
- H04L1/0077—Cooperative coding
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
- H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
- H04L1/0618—Space-time coding
- H04L1/0637—Properties of the code
- H04L1/0668—Orthogonal systems, e.g. using Alamouti codes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L2001/0092—Error control systems characterised by the topology of the transmission link
- H04L2001/0097—Relays
Definitions
- the present invention generally relates to wireless communication systems and, more particularly, to a method and apparatus for cooperative relaying in a wireless communication system. Background technique
- cooperative relaying is an efficient physical layer technology that achieves diversity gain in a distributed manner.
- the primary idea of cooperative relay is to treat the relay node as a virtual antenna, thereby helping to facilitate wireless communication of a single source-destination pair by implementing two important features of the wireless medium.
- Two important features of the wireless medium are its broadcast properties and the ability to obtain spatial diversity or spatial multiplexing.
- the performance of the wireless communication system can be further improved by introducing cooperative relay technology between the base station (BS) and/or the relay station (RS).
- a cooperative relaying solution commonly found in multi-hop wireless communication systems employs distributed space time block coding (STBC) and distributed spatial multiplexing (SM) in cooperative relaying. Since the distributed STBC and SM transmit data in a fixed format, the receiving end only needs to use channel information (which is obtained by transmitting a known reference signal through the transmitting end) for demodulation, and the transmitting end does not need channel information. Therefore, they do not require feedback channel state information (CSI), which can effectively improve system performance without requiring additional signaling overhead.
- STBC space time block coding
- SM distributed spatial multiplexing
- FIG. 1 depicts an illustrative example of downlink spatial diversity of the cooperative relay described above, wherein the relay stations RS1 and RS2 receive data packets by a relay link via the transmitting device BS to RS1 and RS2 (S 2 , Si), and the receiving device mobile station (MS) receives the data packet respectively via the access link from RS1 and RS2 to the MS
- the relay stations RS1 and RS2 receive data packets by a relay link via the transmitting device BS to RS1 and RS2 (S 2 , Si)
- MS receiving device mobile station
- the path loss exponent is 4
- the difference between the access link power path loss will be 12 dB between the MS and BS separated by two kilometers and the MS and RS separated by one kilometer.
- the spatial diversity gain will be almost completely lost, and even performance may be further deteriorated.
- Figure 2 is a graph showing the effect of power imbalance on throughput performance when the signal-to-noise ratio SN is 4 dB, where throughput is the data rate transmitted at a unit frequency.
- the present invention provides a new solution, which is specifically as follows:
- a method for cooperative relaying in a wireless communication system comprising: receiving a data packet transmitted from a transmitting device via a relay link; Poor power, adaptively adjusted via the access chain a data packet format transmitted to the receiving device to combine data packets received via the direct path power relay station at the receiving device and to achieve spatial diversity between the coordinated relay stations; and to transmit data via the access link
- the packet is sent to the receiving device.
- a relay station for cooperative relay in a wireless communication system
- the relay station comprising: receiving means for receiving a data packet transmitted from a transmitting device via a relay link And an adjusting device, configured to adaptively adjust a data packet group to be transmitted to the receiving device via the access link and a low access link power to cooperate from the access link according to the power difference between the coordinated relay stations
- the data packets received by the relay station are combined, and spatial diversity between the coordinated relay stations is implemented.
- the transmitting device is configured to send the data packet to the receiving device via the access link.
- a method for cooperative relay in a wireless communication system comprising: receiving a data packet transmitted from a transmitting device via a direct link and receiving a coordinated from an access link a data packet transmitted by the relay station; combining the data packet received via the direct link with a data packet received from the coordinated low access link power relay station via the access link, wherein the coordinated relay station Adaptively adjusting data to be transmitted to a receiving device via an access link according to a power difference between each other.
- a receiving device for cooperative relaying in a wireless communication system comprises: receiving means for receiving a data packet transmitted from the transmitting device via the direct link and receiving a data packet transmitted from the coordinated relay station via the access link; combining means for receiving via the direct link The data packet is merged with data packets received from the cooperating low access link power relay station via the access link, where The relay station adaptively adjusts the data packet format to be transmitted to the receiving device via the access link in accordance with the power difference between the two to achieve spatial diversity between the combined and coordinated relay stations.
- a wireless communication system using cooperative relay comprising: a transmitting device, configured to send a data packet to a receiving device via a direct link And transmitting a data packet to the relay station via the relay link; a cooperative relay station for receiving data packets from the transmitting device via the relay link and adaptively adjusting according to a power difference between the coordinated relay stations a data packet format to be transmitted to the receiving device via the access link to enable data packet combining at the receiving device and spatial diversity of the coordinated relay station; a receiving device for receiving the data via the direct link The packets are combined with the digital packets received from the cooperating low access link power relay stations to obtain the same access link power between the access links.
- relay station By implementing the method, relay station, receiving device and wireless communication system provided by the present invention, it is possible to reduce or eliminate power imbalance on an access link existing in cooperative relay, and to maximize diversity gain, Thereby improving the performance of the wireless communication system.
- FIG. 1 is a diagram schematically showing an example of downlink spatial diversity of cooperative relay
- FIG. 2 is a diagram schematically showing an effect of power imbalance of an access link in cooperative relay on throughput performance ;
- FIG. 3 is a flow chart showing a method for cooperative relaying in a wireless communication system in accordance with one embodiment of the present invention
- FIG. 4 is a block diagram showing a relay station for cooperative relay in a wireless communication system according to an embodiment of the present invention
- FIG. 5 is a flow chart showing a method for cooperative relaying in a wireless communication system according to an embodiment of the present invention
- FIG. 6 is a block diagram showing a receiving device for cooperative relay in a wireless communication system according to an embodiment of the present invention
- FIG. 7 is a detailed flow chart schematically showing adaptive cooperative relay transmission in a downlink according to an embodiment of the present invention.
- FIG. 8 is a diagram showing an adaptive STBC collaboration method and no cooperation according to the present invention.
- FIG. 9 is a diagram showing BLER performance of adaptive spatial frequency block coding (SFBC) and distributed SFBC according to another embodiment of the present invention. Comparative diagram;
- FIG. 10 is a diagram showing a simulation deployment of adaptive spatial frequency block coding according to another embodiment of the present invention.
- Figure 11 is a system performance comparison diagram showing an adaptive cooperative relay method based on the distributed SFBC method and the present invention. detailed description
- step 301 a data packet transmitted from the transmitting device is received via the relay link.
- step 302 the data packet format to be transmitted to the receiving device via the access link is adaptively adjusted according to the power difference between the coordinated relay stations, so as to be received from the transmitting device via the direct link at the receiving device.
- the data packets are combined with data packets received from the cooperating low access link power relay stations via the access link, and spatial multiplexing between the coordinated relay stations is achieved.
- step 303 the data packet is sent to the receiving device via the access link.
- the relay station includes a receiving device 401, an adjusting device 402, and a transmitting device 403.
- the receiving device 401 is configured to receive a data packet sent from the transmitting device via the relay link.
- the adjusting means 402 is configured to adaptively adjust a data packet format to be transmitted to the receiving device via the access link according to the power difference between the coordinated relay stations, so as to be received from the transmitting device via the direct link at the receiving device.
- the data packet rows are merged and spatial diversity between the cooperative repeaters is achieved.
- Transmitting device 403 is configured to transmit data packets to the receiving device via the access link.
- FIG. 5 is a flow chart showing a method for cooperative relay in a wireless communication system according to an embodiment of the present invention.
- step 501 via direct chain
- the road receives the data packet transmitted from the transmitting device and receives the data packet transmitted from the coordinated relay station via the access link.
- step 502 the received data received via the direct link is grouped into a merge.
- the cooperating relay stations adaptively adjust the spatial packet diversity between the relay stations that will transmit the data packet format to be transmitted via the access link to the receiving device in accordance with the mutual power difference.
- the receiving setting includes a receiving device 601 and a merging device 602.
- the receiving device 601 is configured to receive a data packet transmitted from the transmitting device via the direct link and receive the data packet transmitted from the coordinated relay station via the access link.
- the merging device 602 is configured to merge the data received via the direct link.
- the coordinated relay station adaptively adjusts the data packet format to be transmitted to the receiving device via the access link according to the power difference between the two to achieve spatial diversity between the merged and coordinated relay stations.
- the wireless communication system includes: And for transmitting a data packet to the receiving device via the direct link and transmitting the data packet to the relay station via the relay link.
- a cooperative relay station for receiving data packets from the transmitting device via the relay link and adaptively adjusting a data packet format to be transmitted to the receiving device via the access link according to the power difference between the coordinated relay stations , in order to achieve data packet merging at the receiving device and spatial diversity of the coordinated relay station; and receiving means for relaying the data packet received via the direct link with the coordinated low access link power The number of packets received by the station are combined to obtain the same access link power between the access links.
- FIG. 7 is a detailed flow chart schematically showing adaptive cooperative relay transmission in a downlink according to an embodiment of the present invention.
- step 70 the transmitting device BS broadcasts a data packet (S 2 , S! ) to the relay stations RS1 and RS2 involved in the cooperative processing through the relay link and the receiving device MS passes the straight The link receives and stores these data packets from the BS without performing equalization and decoding processing on the data packets.
- the MS respectively transmits channel quality feedback information of the access link between the RS1 and the RS2 to the RS1 and the RS2, and the channel quality feedback information is previously received according to the RS1 and the RS2.
- the signal is estimated.
- the previously received signal refers to the reference signal received by the MS in the previous time slot or the previous frame.
- the channel information estimated by the reference signal can be used as the channel information of the time slot because the communication channel changes slowly. In an environment, adjacent time slots can be considered to be invariant.
- RS1 and RS2 demodulate and decode the data signal received from the BS.
- RS1 and RS2 determine respective channel link quality conditions (ie, respective access link power levels) according to the channel quality feedback information mentioned above, respectively, and adaptively determine that they will The data packet format transmitted to the MS. That is, when there is a power difference between the access links of R_S1 and RS2, the RS of the low access link power transmits to the MS in step 75 or 77 that it has the same data packet as the BS transmits to the MS on the direct link.
- Formatted data packets ie, data packets (S ⁇ S ⁇ o and another RS with high access link power, transmit the same data content to the MS in step 76 or 78, but the data packet format is self-contained Adaptive conversion (symbol and conjugate transformation), ie, data packet (S ⁇ -S ⁇ ).
- the transmitted data packet format from RS1 and RS2 will form a codeword that conforms to the spatial diversity coding. Codewords that conform to the STBC/SFBC encoding rules.
- the MS uses the slightly modified existing STBC/SFBC detection scheme (ie, in equation (7) below) Addition), combining data packets received from RSs with low access link power with data packets previously received from the BS via direct link (preferably, maximum ratio combining), access of lower power RSs
- the power is thereby compensated so that the diversity gain of the STBC/SFBC over the relay link can be maximized, which in turn improves the performance of the wireless communication system.
- the relay RS implements cooperative relaying, which can be extended to cooperation between the BS and the RS, or for cooperation between multiple transmitting stations of the uplink or downlink.
- the transmitting device is an MS
- the receiving device is a switching technology, which also enhances the existing distributed STBC.
- the received signal can be expressed as follows:
- equation (1) can be written as follows:
- the existing Alamouti is based on spatial direction coding for two-antenna STBC coding, that is, the first antenna transmits (S 1 ; -S 2 * ) and the second antenna transmits (S 2 , S ⁇ ), which is different from the spatial direction.
- the existing Alamouti coding method after considering the data format transmitted on the direct link, the improved Alamouti code proposed by the present invention transmits a data packet (SS 2 ) at the first antenna (ie, at RS1) and at the second antenna. (ie at RS2) Send ( ), that is, encoding data packets based on the time direction. It can be seen that it is assumed here that the RS1 access link power is low, thus maintaining the same data packet format as the BS.
- the signal received by the MS from the access link can be written as follows:
- a and are channel state information on the access link from RSI and RS2 to the MS, respectively, assuming that there is a power difference between RS1 and RS2, and the access link power of RS1 to MS is low, so
- the signals are respectively transmitted in two consecutive time slots, and s 2 ) a RS2 to the MS have high access link power, so that they respectively transmit the format-converted signals in two consecutive time slots, correspondingly ( 3) can be expressed as follows:
- Equation (5) can be expressed in the following matrix form:
- the channel state information matrix h reaches the third-order diversity gain, and in the prior system shown in FIG. 1, the distributed STBC can only obtain the two-order diversity gain, which is increased by one.
- the order gain is derived from the data diversity of equation (2) and RS1 transmission, such as maximum ratio combining (MRC).
- MRC maximum ratio combining
- the power of the low access link is improved by increasing this order diversity gain to eliminate power imbalance.
- Similar to the STBC algorithm it is assumed that the channel is invariant between the corresponding two consecutive time slots on the direct link, using the existing STBC detection algorithm, multiplying equation (6) by h*, sending The data packet can be recovered as follows.
- the time diversity gain obtained by maximum ratio combining (MRC) can be used to compensate the RS with low access power, so that the RS reaches equal power or roughly balanced power, thereby Maximize the diversity gain between STBCs on the relay link.
- the RS or BS with low access link power transmits a data packet having the same encoding format as the BS on the direct link. Therefore, when receiving device MS When the channel quality information (eg, signal-to-noise ratio SNR) of the two access links is fed back to the RS, RS1 and RS2 themselves will adaptively determine the STBC encoding format, ie, the RS with low access link power is in the access chain. Another RS transmitted in consecutive time slots of the path with high access link power is transmitted in consecutive time slots of the access link (- ⁇ , ⁇ .
- SNR signal-to-noise ratio
- the performance of the adaptive cooperative relay transmission scheme can be simulated, and for comparison purposes, the non-coordinated multi-hop relay based on the OFDM downlink system and the distributed STBC are also simulated, where In the simulation, cooperation is performed between the BS and the RS.
- Table 1 shows the parameter settings for the simulation.
- Fig. 8 illustrate the comparison of the packet error rate (BLER) performance in the above three cases.
- BLER packet error rate
- the path loss exponent is 4
- the power difference is approximately 13 dB.
- the adaptive cooperation scheme proposed by the present invention can be extended to an SFBC-based cooperative relay wireless communication system. Similar to the description of the implementation of the STBC, the use of the proposed method in SFBC-based cooperative relaying is described below by way of formulation.
- Figure 10 depicts the simulation deployment diagram for the system.
- the network of sectorized cells is formed with 7 cells and each cell includes 3 sectors. In each sector, two repeaters are deployed with a radius of the BS 2/3 cell.
- the simulation parameters are shown in Table 2.
- Figure 11 shows the simulation results.
- SINR signal-to-interference-and-noise ratio
- the present invention can take the form of an entirely hardware implementation, an entirely software implementation, or an implementation comprising both a hardware unit and a software unit.
- the invention is implemented in software including, but not limited to, firmware, resident software, microcode, and the like.
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Description
用于无线通信系统中协作中继的方法和设备 支术领域
本发明总体上涉及无线通信系统, 更具体地, 本发明涉及用于 在无线通信系统中协作中继的方法和设备。 背景技术
在多跳无线通信系统中, 协作中继是以分布式方式获得分集增 益的有效物理层技术。 协作中继的主要思想在于将中继节点视为虛 拟天线, 从而通过实施无线介质的两个重要特征来有助于促进单个 源-目的地对的无线通信。 该无线介质的两个重要特征是其广播属性 和获得空间分集或空间复用的能力。 通过在基站(BS )和 /或中继台 ( RS ) 之间引入协作中继技术, 无线通信系统的性能可以得到进一 步改进。
当前, 多跳无线通信系统中常见的协作中继解决方案是在协作 中继中采用分布式空时块编码 (STBC ) 和分布式空间复用 (SM ) 。 由于分布式 STBC和 SM传输固定格式的数据, 接收端只需要利用 信道信息 (该信道信息通过发射端传输已知的参考信号而获得) 来 进行解调, 而发射端是不需要信道信息的, 故它们不需要反馈信道 状态信息(CSI ) , 这样就可以有效地改进系统性能而不需要额外的 信令开销。
为了便于理解, 图 1绘出上述协作中继的下行链路空间分集的 示例性例子, 其中中继台 RS1和 RS2通过经由发送设备 BS到 RS1 和 RS2的中继链路来接收数据分组( S2,Si ) ,而接收设备移动台( MS ) 通过经由从 RS1和 RS2到 MS的接入链路分别接收数据分组
( -S2*,Si ) 和 S2 ) , 从而实现分布式 STBC。 因此, 可以获得 阵列增益和协作接收分集增益, 并由此可以改进接入链路的传输质 量。
然而, 由于基站和中继台所处空间位置的不同, 从基站或多个 中继台发送到移动台的多个信号将经历不同的路径损耗, 这将导致 移动台处接收信号的功率不平衡 (即, 不相等) 。 尽管可以选择合 适的中继台来进行中继传输, 但仍很难避免这样的情况发生。 该接 收信号的功率不平衡将影响到空间分集增益的获得, 尤其当接收信 号的功率不平衡达到一定程度时, 可能无法实现空间分集增益。
例如, 在典型的移动环境中, 当路径损耗指数为 4时, 距离相 隔两公里的 MS和 BS以及距离相隔一公里的 MS和 RS之间, 接入 链路功率路径损耗的差将达到 12dB。当在 BS和 RS之间进行协作处 理时, 空间分集增益将几乎完全丧失, 甚至性能可能会进一步地恶 化。
图 2是仿真当信噪比 SN 为 4dB时, 功率不平衡对吞吐量性能 的影响的示图, 这里吐吞量是指单位频率下传输的数据速率
( bps/Hz )。通过该图可以看出,当两个接入链路上的功率不平衡(也 即功率差)达到 12dB时, 吐吞量损失大约是 83%, 这几乎与没有协 作的多跳中继相同。
为了減小功率不平衡的影响, 根据现有的技术方案必须要选择 合适的中继节点, 即选择具有到 MS相同距离的节点来实现协作处 理, 而这又将极大地限制协作中继技术的应用场景。
因此, 需要一种用于无线通信系统中协作中继的方法和设备, 其能够减小或消除协作中继中所存在的接入链路上的功率不平衡, 并且最大化地实现分集增益, 从而改进无线通信系统的性能。 发明内容
鉴于现有技术存在上述问题, 本发明提供了新的解决方案, 具 体如下:
根据本发明的一个方面,提供一种用于无线通信系统中协作中继 的方法, 所述方法包括: 经由中继链路接收从发送设备发送的数据 分组; 根椐协作的中继台间的功率差, 自适应地调整将经由接入链
路发送到接收设备的数据分组格式, 以便在接收设备处将经由直接 路功率中继台接收的数据分组进行合并, 并实现协作的中继台间的 空间分集; 以及经由接入链路将数据分组发送到接收设备。
根据本发明的另一方面,提供一种用于无线通信系统中协作中继 的中继台, 所述中继台包括: 接收装置, 用于经由中继链路接收从 发送设备发送的数据分组; 调整装置, 用于根据协作的中继台间的 功率差, 自适应地调整将经由接入链路发送到接收设备的数据分组 组与经由接入链路从协作的低接入链路功率中继台接收的数据分组 进行合并, 并实现协作的中继台间的空间分集; 发送装置, 用于经 由接入链路将数据分组发送到接收设备。
根据本发明的另一方面,提供一种用于无线通信系统中协作中继 的方法, 所述方法包括: 经由直接链路接收从发送设备发送的数据 分组和经由接入链路接收从协作的中继台发送的数据分组; 将经由 直接链路接收的所述数据分组与经由接入链路从协作的低接入链路 功率中继台接收的数据分组进行合并, 其中协作的中继台根据相互 间的功率差, 自适应地调整将经由接入链路发送到接收设备的数据 根据本发明的另一方面,提供一种用于无线通信系统中协作中继 的接收设备, 所述接收设备包括: 接收装置, 用于经由直接链路接 收从发送设备发送的数据分组和经由接入链路接收从协作的中继台 发送的数据分组; 合并装置, 用于将经由直接链路接收的所述数据 分组与经由接入链路从协作的低接入链路功率中继台接收的数据分 组进行合并, 其中协作的中继台根据相互间的功率差, 自适应地调 整将经由接入链路发送到接收设备的数据分组格式以便实现所述合 并和协作的中继台间的空间分集。
根据本发明的又一方面, 提供一种使用协作中继的无线通信系 统, 包括: 发送设备, 用于经由直接链路向接收设备发送数据分组
和经由中继链路向中继台发送数据分组; 协作的中继台, 用于经由 中继链路接收来自发送设备的数据分组并且根据协作的中继台间的 功率差, 自适应地调整将经由接入链路发送到接收设备的数据分组 格式, 以便实现在接收设备处的数据分组合并以及协作的中继台的 空间分集; 接收设备, 用于将经由直接链路接收的所述数据分組与 从协作的低接入链路功率中继台接收的数椐分组进行合并以便荻得 接入链路间相同的接入链路功率。
通过实施本发明所提供的方法、 中继台、接收设备和无线通信系 统, 能够减小或消除协作中继中所存在的接入链路上的功率不平衡, 并且最大化地实现分集增益, 从而改进无线通信系统的性能。 附图说明
通过参照附图阅读以下所作的对非限制性实施例的详细描述,本发 明的其它特征、 目的和优点将会变得更明显。 在附图中, 相同和相似 的附图标记代表相同或相似的装置或方法步 , 其中:
图 1是示意性示出协作中继的下行链路空间分集的例子的示图; 图 2是示意性示出协作中继中接入链路的功率不平衡对吞吐量 性能的影响的示图;
图 3是示出根据本发明一个实施方式的用于无线通信系统中协 作中继的方法的流程图;
图 4是示出根据本发明一个实施方式的用于无线通信系统中协 作中继的中继台的框图;
图 5是示出根据本发明一个实施方式的用于无线通信系统中协 作中继的方法的流程图;
图 6是示出根据本发明一个实施方式的用于无线通信系统中协 作中继的接收设备的框图;
图 7是示意性示出根据本发明的一个实施方式的下行链路中自 适应协作中继传输的详细流程图;
图 8是示出根据本发明提出的自适应 STBC协作方法与无协作
多跳中继以及分布式 STBC的误包率 (BLER ) 性能比较的示图; 图 9是示出根据本发明另一实施方式的自适应空间频率块编码 ( SFBC ) 与分布式 SFBC的 BLER性能比较的示图;
图 10是示出根据本发明另一实施方式的自适应空间频率块编码 的仿真部署图; 以及
图 1 1是示出基于分布式 SFBC方法和本发明所提出的自适应协 作中继方法的系统性能比较图。 具体实施方式
下面将结合附图详细描述本发明的实施方式。
首先参考图 3 ,其示出根据本发明一个实施方式的用于无线通信 系统中协作中继的方法的流程图。 如图中所示, 在步骤 301 中, 经 由中继链路接收从发送设备发送的数据分组。 在步骤 302中, 根据 协作的中继台间的功率差, 自适应地调整将经由接入链路发送到接 收设备的数据分组格式, 以便在接收设备处将经由直接链路从发送 设备接收的数据分组与经由接入链路从协作的低接入链路功率中继 台接收的数据分组进行合并, 并实现协作的中继台间的空间分集。 以及在步骤 303中, 经由接入链路将数据分組发送到所述接收设备。
图 4是示出根据本发明一个实施方式的用于无线通信系统中协 作中继的中继台的框图。 该中继台包括接收装置 401、 调整装置 402 和发送装置 403。 其中, 接收装置 401用于经由中继链路接收从发送 设备发送的数据分組。 调整装置 402用于根据协作的中继台间的功 率差, 自适应地调整将经由接入链路发送到接收设备的数据分组格 式, 以便在接收设备处将经由直接链路从发送设备接收的数据分组 行合并, 并实现协作的中继台间的空间分集。 发送装置 403用于经 由接入链路将数据分組发送到所述接收设备。
图 5是示出根据本发明一个实施方式的用于无线通信系统中协 作中继的方法的流程图。 如图中所示, 在步骤 501中, 经由直接链
路接收从发送设备发送的数据分组和经由接入链路接收从协作的中 继台发送的数据分组。 接着, 在步骤 502中, 将经由直接链路接收 收的数据分组进^合并。 '其中, 协作的中继台根据相互间的功率差 , 自适应地调整将经由接入链路发送到接收设备的数据分组格式以便 实现所述合并和协作的中继台间的空间分集。
图 6是示出根据本发明一个实施方式的用于无线通信系统中协 作中继的接收设备的框图。 如图中所示, 该接收设置包括接收装置 601和合并装置 602。 其中, 接收装置 601用于经由直接链路接收从 发送设备发送的数据分组和经由接入链路接收从协作的中继台发送 的数据分组。 合并装置 602用于将经由直接链路接收的所述数据分 进行合并。 其中, 协作的中继台根据相互间的功率差, 自适应地调 整将经由接入链路发送到接收设备的数据分组格式以便实现所述合 并和协作的中继台间的空间分集。
根据本发明的上述多个实施方式,同时提供了一种使用协作中继 的无线通信系统, 其功能框图类似于图 1中所示出的, 故在此省略, 该无线通信系统包括: 发送设备, 用于经由直接链路向接收设备发 送数据分组和经由中继链路向中继台发送数据分组。 协作的中继台, 用于经由中继链路接收来自发送设备的数据分组并且根据协作的中 继台间的功率差, 自适应地调整将经由接入链路发送到接收设备的 数据分组格式, 以便实现在接收设备处的数据分組合并以及协作的 中继台的空间分集; 以及接收设备, 用于将经由直接链路接收的所 述数据分组与从协作的低接入链路功率中继台接收的数椐分组进行 合并以便获得接入链路间相同的接入链路功率。
图 7是示意性示出根据本发明的一个实施方式的下行链路中自 适应协作中继传输的详细流程图;
在步驟 70中, 发送设备 BS通过中继链路向涉及协作处理中的 中继台 RS1和 RS2广播数据分组 ( S2,S! ) 并且接收设备 MS通过直
接链路接收和存储来自于 BS的这些数据分组而不对这些数据分组 进亍均衡和解码处理。
接着, 在步骤 71和 72中, MS分别将其与 RS1和 RS2之间的 接入链路的信道质量反馈信息发送给 RS1和 RS2, 该信道质量反馈 信息是根据从 RS1和 RS2先前所接收到的信号来估计的。 这里先前 所接收到的信号是指 MS在前一个时隙或前一帧所接收到的参考信 号, 通过谅参考信号估计出的信道信息可以作为本时隙的信道信息, 因为在通信信道緩慢变化的环境中, 相邻时隙可以认为是不变的。 同时在上述步骤中, RS1和 RS2对从 BS接收的数据信号进行解调 和解码。
在步骤 73和 74中, RS1和 RS2分别根据上面所提到的信道质 量反馈信息确定各自的信道链路质量状况 (即各自的接入链路功率 水平) , 并将如下自适应地确定其将向 MS传送的数据分組格式。 即, 当 R_S1和 RS2的接入链路之间存在功率差时, 低接入链路功率 的 RS在步骤 75或 77中向 MS传送具有与 BS在直接链路上传送到 MS的数据分组相同格式的数据分組, 即, 数据分组(S^S^ o 而另 一个具有高接入链路功率的 RS在步骤 76或 78中向 MS传送相同的 数据内容, 但对该数据分组格式进行了自适应地转换 (符号和共轭 变换) , 即, 数据分組( S^-S^ ) 。 从而, 来自 RS1和 RS2的传送 的数据分组格式将形成符合空间分集编码娩则的码字。 优选地, 符 合 STBC/SFBC编码规则的码字。
最后, 在步骤 79处, MS在从接入链路接收到发自 RS1和 RS2 的数据分组后, 通过使用经略微改动的现有 STBC/SFBC检测方案 (即, 在下面的公式 (7 ) 中加入 项) , 将从接入链路功率低的 RS接收到的数据分组与先前经直接链路从 BS接收的数据分组进行 合并(优选地, 最大比合并) , 功率较低的 RS的接入功率由此得到 补偿, 从而可以最大化地获取中继链路上的 STBC/SFBC的分集增 益, 继而改进无线通信系统的性能。
这里需是指出的是本发明上面所提出的方法不限于使用两个中
继台 RS来实现协作中继, 其可以被扩展到 BS和 RS之间的协作 , 或者用于上行链路或下行链路的多个发射台之间的协作。 例如, 当 在上行链路方向上进行协作中继时, 发送设备是 MS, 而接收设备是 换技术, 也使现有分布式 STBC得到增强。
下面将以公式化表达的方式来进一步描述图 7的实施方式。 由 于 Alamouti码是无线通信系统中广泛使用的 STBC, 因此在 RS1和 RS2之间执行 Alamouti码。
根据图 7, 当 BS将其数据分组经由直接链路传送到 MS后, 所 接收到的信号可以如下表示:
1 1 1 (1)
y2 = h2s2 + n2
其中 A和 是发送的连续两个时隙中的数据分组, 和 A2是从 B S 到 MS的相应信道状态信息, 并且 ^和 是两次接收的加性高斯白噪 声。 不失一般性, 等式 ( 1 ) 可以写成如下:
V Λ
+ (2)
、 0 —h2*入一 S. 2 n2
这里" *"表示共轭变换。 当选择 RS1和 RS2或 BS和一个 RS来 协同发送数据分组以便获得分集增益时,将使用改进的 Alamouti码,
Alamouti码。 现有的 Alamouti对于两天线 STBC编码来说是基于空 间方向的编码,即第 1天线发送(S1 ;-S2* )而第 2天线发送(S2, S^ ) , 不同于基于空间方向的现有 Alamouti编码方法, 在考虑了直接链路 上发送的数据格式后, 本发明所提出的改进的 Alamouti码在第 1天 线 (即 RS1处)发送数据分组 ( S S2 ) 而在第 2天线 (即 RS2处) 发送 (
) , 即基于时间方向来编码数据分组。 可以看出, 此 处假设 RS1接入链路功率较低, 因而保持了与 BS相同的数据分组 格式。 从而, MS从接入链路所接收到的信号可以写成如下:
(3)
其中 A„和 分别是从 RSI和 RS2到 MS的接入链路上的信道状 态信息, 这里假设 RS1和 RS2二者之间存在功率差, 并且 RS1到 MS的接入链路功率低, 因此其在连续的两个时隙内分别发送信号 ,s2 ) a RS2到 MS的接入链路功率高, 因此其在连续的两个时隙内 分别发送经过格式变换的信号 相应地, 等式 (3 ) 可以如下 表示:
合并等式 (2 ) 和 (4 ) , 可以得到
等式 (5 ) 可以以如下的矩阵形式来表示:
y =hs+n (6)
从等式(5 ) 可以看出, 信道状态信息矩阵 h达到三阶的分集增 益, 而在图 1所示的现有系统中, 分布式 STBC仅能获得两阶的分 集增益, 这增加的一阶增益来自于等式(2 )与 RS1传输的数据分集 合并,如最大比合并(MRC ) 。 通过增加这一阶分集增益改善低接入 链路的功率以消除功率不平衡。 类似于 STBC算法中所提到的, 假 设信道在直接链路上的相应两个连续时隙间是不变的, 利 用现有的 STBC检测算法, 对等式(6 )乘上 h*,发送的数据分组可以 如下恢复。
由于使用直接链路上发送的信号, 通过最大比合并 (MRC ) 所 获得的时间分集增益可以用于补偿具有低接入功率的 RS, 从而 RS 到达相等的功率或大致平衡的功率, 由此可以最大化地获得中继链 路上的 STBC间的分集增益。
由于考虑到 MRC,具有低接入链路功率的 RS或 BS发送具有与 直接链路上的 BS相同编码格式的数据分组。 因此, 当接收设备 MS
向 RS反馈两个接入链路的信道质量信息 (例如信噪比 SNR ) 时, RS1和 RS2 自身将自适应地确定 STBC编码格式, 即, 具有低接入 链路功率的 RS在接入链路的连续时隙内发送 而具有高接入 链路功率的另一个 RS在接入链路的连续时隙内发送 (—^,^。
使用上面的分析, 可以对自适应协作中继传输方案的性能做出 仿真, 并且为了比较的目的, 对基于 OFDM下行链路系统无协作多 跳中继以及分布式 STBC也进行仿真, 其中在该仿真中, 协作是在 BS和 RS之间执行的。 表 1给出了仿真的参数设定。
图 8的仿真结果图示出在上述三种情况下, 误包率 (BLER ) 性 能的比较。 正如所预期的, 当路径损耗指数是 4时, 功率差大约是 13dB。 由于从 BS到 MS的差的直接链路, 分布式 STBC将恶化低 SNR区域中的性能, 但在高的 SNR区域中, 分布式 STBC可以获得 部分分集增益, 因此相比较于当 BLER=l x l 0-3时的多跳中继, 其性能 可以被提高大约 ldB。 由于通过使用时间分集增益来自适应地补偿 不平衡功率, 功率差被减小。 因此, 相比较于当 BLER=l x l(T3时的分 布式 STBC的性能,本发明所提出的方法的性能可以提高大约 3.8dB。
本发明所提出的自适应协作方案可以被扩展到基于 SFBC的协 作中继无线通信系统中。
类似于针对 STBC的实施方式的描述,下面通过公式化表达的方 式来描述本发明所提出的方法在基于 SFBC的协作中继中的使用。 同样地, 当 BS在直接链路上发送其数据分组后, MS接收到的数据 分组可以如下表示为: γ^ + \) = + \)3^ + ή + η^ + ί) (8) 其中 k表示 OFDM系统中的子载波, 和 s2 t+l)是两个连续的 子载波 k和 k+1 中发送的数据分组, ;^^和^^+)是从 BS到 MS的 直接链路的相应信道状态信息, 并且
次接收的加性 高斯白噪声。 不失一般性, 等式 (8) 可以写成如下:
其中" *"表示共轭变换。 当两个 RS或 BS和一个 RS被选择以协 同发送数据分组, 从而获得分集增益时。 类似于前面分布式 STBC 中的描述, 也可以使用改进的 Alamouti码, 即所提出的方法基于频 率方向而非空间方向来编码数据分组, 即, MS从协作的接入链路的 两个子载波上所接收到的信号是
y3(k) = hll(k)sl(k)-hl2(k 2(k+l)+n}(k)
(10) 其中 ku(k)和 W分别是协作的接入链路中子载波 k上从两个协 作的中继台到 MS的信道状态信息。 假设连续两个子载波的信道状 态信息是不变的, 即, hl(k) = h2(k+l),hu(k)=hl](k + i),hl2(k) = hll(k + l), 则等式
同样地,将接入链路上发送的 SFBC数据合并直接链路上接收的 数据,
类似于上面所推导的, 等式 ( 12) 可以表示成如下的矩阵形式:
y = hs + n (13)
对基于 SFBC的协作中继进行仿真。仿真的参数设定如表 1中所 给出的。 从图 9看出, 当 BLER=2xl(T3时, 通过补偿功率不平衡, 相比较于分布式 SFBC, 性能大约改进 4.0dB。
为了验证所提出的方案, 对系统性能也进行了仿真。 图 10绘出 了系统的仿真部署图。 扇区化小区的网络以 7个小区形成并且每个 小区包括 3个扇区。 在每个扇区中, 部署有距离 BS 2/3小区半径的 两个中继台。 在表 2中示出仿真参数。
表 2
图 11示出了仿真结果。 从图中可以看出, 在分布式 SFBC系统 中 40 %的 MS的信干噪比( SINR )为 15dB, 而本发明所提出的方法 40 %的 MS的 SINR达到 18dB, 这说明性能增益约为 3dB , 这是因 为移动用户位于不同的位置处, 路径损耗差静态地变化, 但在每个 位置中, 自适应地功率补偿提供了改进的 SINR增益, 因此系统的性 能仍将被增强。
以上结合附图对本发明的多个实施方式进行了描述。 应当注意, 为了使本发明更容易理解, 上面的描述省略了对于本领域的技术人 员来说是公知的、 并且对于本发明的实现可能是必需的更具体的一 些技术细节。
本发明可以采取完全硬件实现、 完全软件实现或者同时包含硬 件单元和软件单元的实现的形式。 在优选的实施例中, 本发明是以 软件实现的, 该软件包括但不限于固件、 驻留软件、 微代码等。
提供本发明的说明书的目的是为了说明和描述, 而不是用来穷 举或将本发明限制为所公开的形式。 对本领域的普通技术人员而言, 许多修改和变更都是显而易见的。
因此, 选择并描述实施例是为了更好地解释本发明的原理及其 实际应用, 并使本领域普通技术人员明白, 在不脱离本发明实质的 前提下, 所有修改和变更均落入由权利要求所限定的本发明的保护 范围之内。
Claims
1. 一种用于无线通信系统中协作中继的方法, 所述方法包括: 经由中继链路接收从发送设备发送的数据分组;
根据协作的中继台间的功率差,自适应地调整将经由接入链路发 送到接收设备的数据分组格式, 以便在接收设备处将经由所述直接 链路从发送设备接收的数据分组与经由所述接入链路从协作的低接 入链路功率中继台接收的数据分组进行合并, 并实现协作的中继台 间的空间分集; 以及
经由接入链路将数据分組发送到所述接收设备。
2. 根据权利要求 1所述的方法, 其中根据从接收设备接收到的 信道质量反馈信息确定存在功率差的高接入链路功率中继台和低接 入链路功率中继台。
3. 根据权利要求 1所述的方法, 其中所述自适应地调整包括保 持所述低接入链路功率中继台经由中继链路从所述发送设备接收的 数据分组格式不变, 而自适应地改变高接入链路功率中继台经由中 继链路从所述发送设备接收的数据分组格式, 以便从协作的中继台 发送到所述接收设备的数据分组格式符合空间分集编码的准则。
4. 根据权利要求 3所述的方法, 其中所述空间分集编码是空时 块编码或空频块编码。
5. 根据权利要求 4所述的方法, 其中所述空时块编码或所述空 频块编码是满足经由接入链路发送的数据分组格式的要求的
Alamouti码。
6. 一种用于无线通信系统中协作中继的中继台, 所述中继台包 括:
接收装置, 用于经由中继链路接收从发送设备发送的数据分组; 调整装置, 用于根据协作的中继台间的功率差, 自适应地调整将 经由接入链路发送到接收设备的数据分组格式, 以便在接收设备处
的低接入链路功率中继台接收的数据分组进行合并, 并实现协作的 中继台间的空间分集; 以及
发送装置, 用于经由接入链路将数据分组发送到所述接收设备。
7. 根据权利要求 6所述的中继台, 其中所述调整装置根据从接 收设备接收到的信道质量反馈信息确定存在功率差的高接入链路功 率中继台和低接入链路功率中继台。
8. 根据权利要求 6所述的中继台, 其中所述调整装置用于保持 所述低接入链路功率中继台经由中继链路从所述发送设备接收的数 据分组格式不变, 而自适应地改变高接入链路功率中继台经由中继 链路从所述发送设备接收的数据分组格式, 以便从协作的中继台发 送到所述接收设备的数据分组格式符合空间分集编码的准则。
9. 根据权利要求 8所述的中继台, 其中所述空间分集编码是空 时块编码或空频块编码。
10. 根据权利要求 9所述的中继台, 其中所述空时块编码或所述 空频块编码是满足经由接入链路发送的数据分组格式的要求的
Alamouti码。
1 1. 一种用于无线通信系统中协作中继的方法, 所述方法包括: 接收从协作的中继台发送的数据分组;
将经由直接链路接收的所述数据分组与经由接入链路从协作的 低接入链路功率中继台接收的数据分组进行合并, 其中协作的中继 台根据相互间的功率差, 自适应地调整将经由接入链路发送到接收 设备的凝
12. 根据权利要求 11所述的方法, 其中从发送设备接收的数据 分组与从低接入链路功率中继台接收的数据分組具有相同的数椐分 组格式, 而从高接入链路功率中继台接收的数据分组具有经该中继 台自适应地改变以便符合协作的中继台的空间分集编码准则的数据 格式。
13. 根据权利要求 11所述的方法, 其中所述合并使用最大比合 并对经由直接链路接收的数据分組和经由低功率接入链路接收的数 据分组进行合并。
14. 一种用于无线通信系统中协作中继的接收设备, 所述接收设 备包括:
接收装置,用于经由直接链路接收从发送设备发送的数据分組和 经由接入链路接收从协作的中继台发送的数据分组;
合并装置,用于将经由直接链路接收的所述数据分组与经由接入 链路从协作的低接入链路功率中继台接收的数据分组进行合并, 其 中协作的中继台根据相互间的功率差, 自适应地调整将经由接入链 台间的空间分集。
15. 根据权利要求 14所述的接收设备, 其中所述接收装置从发 送设备接收的数据分组与从低接入链路功率中继台接收的数据分組 具有相同的数据分组格式, 而从高接入链路功率中继台接收的数据 分组具有经该中继台自适应地改变以便符合协作的中继台的空间分 集编码准则的数据格式。
16. 根据权利要求 14所述的接收设备, 其中所述合并装置使用 最大比合并对经由直接链路接收的数据分组和经由低功率接入链路 接收的数据分组进行合并。
17. 一种使用协作中继的无线通信系统, 包括:
发送设备,用于经由直接链路向接收设备发送数据分组和经由中 继链路向中继台发送数据分组;
协作的中继台,用于经由中继链路接收来自发送设备的数据分组 并且根据协作的中继台间的功率差, 自适应地调整将经由接入链路 发送到接收设备的数据分組格式, 以便实现在接收设备处的数据分 组合并以及协作的中继台的空间分集; 以及
接收设备,用于将经由直接链路接收的所述数据分组与从协作的
间相同的接入链路功率。
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