WO2011116659A1 - 一种长期演进先进系统中用户接入服务小区的方法 - Google Patents

一种长期演进先进系统中用户接入服务小区的方法 Download PDF

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Publication number
WO2011116659A1
WO2011116659A1 PCT/CN2011/071766 CN2011071766W WO2011116659A1 WO 2011116659 A1 WO2011116659 A1 WO 2011116659A1 CN 2011071766 W CN2011071766 W CN 2011071766W WO 2011116659 A1 WO2011116659 A1 WO 2011116659A1
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Prior art keywords
relay
enb
serving cell
access
signal strength
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PCT/CN2011/071766
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English (en)
French (fr)
Inventor
张莉莉
潘瑜
高伟东
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普天信息技术研究院有限公司
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Publication of WO2011116659A1 publication Critical patent/WO2011116659A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/02—Access restriction performed under specific conditions
    • H04W48/06—Access restriction performed under specific conditions based on traffic conditions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/042—Public Land Mobile systems, e.g. cellular systems
    • H04W84/047—Public Land Mobile systems, e.g. cellular systems using dedicated repeater stations

Definitions

  • the present invention relates to the field of wireless communication technologies, and in particular, to a method for a user to access a serving cell in a Long Term Evolution Advanced (LTE-Advanced) system.
  • LTE-Advanced Long Term Evolution Advanced
  • the relay is used to implement broadband wireless access in the LTE-advanced system development process.
  • the introduction of relay brings new four different links: eNB to relay downlink, relay to eNB uplink, relay to UE downlink, UE to relay Uplink.
  • eNB to relay downlink
  • eNB uplink relay to UE downlink
  • UE to relay Uplink UE to relay Uplink.
  • the traditional access link that is, the downlink of the eNB to the UE and the uplink of the UE to the eNB still exist.
  • a multi-hop cell is a cell that contains a relay site, and data transmission within the cell may pass through multiple air interfaces.
  • a relay with an independent cell ID is introduced to transmit its own control information and synchronization information.
  • the distributed scheduling relay is used for data transmission between the UE and the eNB, and the eNB and the relay respectively allocate resources for the controlled wireless link.
  • the resources controlled by the relay and the relay link resources of the relay are pre-allocated by the eNB.
  • the relay link is also called the backhaul link.
  • the distributed scheduling mode is adopted, the downlink backhaul link has a bottleneck effect.
  • the relay access link that is, the link resource between the relay and the UE is rich, the throughput that the relay to the UE can provide is greater than the throughput of the eNB to the relay.
  • the downlink backhaul link encounters a bottleneck effect.
  • the uplink and downlink of the UE served by the relay are directly connected to the serving cell of the relay. If the downlink backhaul link encounters a bottleneck effect, the uplink of the UE being relayed is enabled. The downlink and downlink connections are all switched to the serving cell of the eNB. Although the bottleneck effect of the downlink backhaul link can be alleviated, the uplink of the UE to the serving cell of the eNB requires the user to consume a large transmission power for uplink data. transmission.
  • the technical solution for solving the bottleneck effect of the downlink backhaul link is to use the downlink OFDM symbol in the special subframe to transmit data in the backhaul link, but several downlink OFDM symbols in the special subframe are required. Used as a time conversion, it is still not enough to completely solve the bottleneck effect of the downlink backhaul link. For example, as follows: For the TDD time configuration mode 2, set the number of downlink backhaul link subframes to the maximum number of 4, and if it is found that two relay links are scheduled, the downlink backhaul link has a bottleneck effect. The increase in system throughput. Although 8 OFDM symbols in a special subframe can be used as a supplemental downlink backhaul link for data transmission, the bottleneck problem of the downlink backhaul link can still occur when more than two relay links are scheduled.
  • the embodiment of the present invention provides a method for a user to access a serving cell in an LTE-advanced system, so that when the distributed scheduling mode is adopted, the user terminal consumes less transmission power and does not exist.
  • the bottleneck effect of the downlink backhaul link is not limited.
  • a method for a user to access a serving cell in an LTE-advanced system is used for a distributed scheduling manner with a relay relay, and the method includes:
  • the terminal UE is connected to the serving cell according to the cell selection access condition, which specifically includes:
  • the uplink and downlink of the UE are both connected to the serving cell of the relay, which is a fixed value in units of dbm;
  • the signal strength received by the UE from the eNB exceeds the received signal strength from the relay, but when the amount exceeds between the maximum value, the uplink of the UE accesses the serving cell of the relay.
  • the downlink of the UE accessing the serving cell of the eNB is a fixed value in units of dbm;
  • both the uplink and the downlink of the UE access the eNB. Service area.
  • the eNB notifies the relay that the downlink load is biased.
  • the UE accesses the serving cell according to the ' ⁇ , the area selection access condition, specifically, when When the difference between the eNB and the relay signal strength of the UE is less than ⁇ , the uplink and downlink of the UE are both connected to the serving cell of the relay; when the difference between the eNB and the relay signal strength of the UE is greater than
  • the value is equal to less than, that is, the UE is in the intersection area of the eNB and the relay
  • the uplink of the UE accesses the serving cell of the relay
  • the downlink of the UE accesses the serving cell of the eNB
  • the uplink and downlink access addresses are different is called exclusive access;
  • FIG. 1 is a schematic diagram of reference signal strengths of a UE receiving an eNB or a relay according to an embodiment of the present invention.
  • FIG. 2 is a schematic flowchart of a method for a user to access a service and a zone according to a first embodiment of the present invention.
  • FIG. 3 is a schematic flowchart of a method for a user to access a serving cell according to a second embodiment of the present invention. Mode for carrying out the invention
  • the UE accesses the serving cell corresponding to the current network condition, and the reference signal strength of the eNB and the relay received by the UE changes, and the network side
  • the UE may be connected to the serving cell corresponding to the changed reference information strength according to the cell selection access condition.
  • the external access of the UE brings the following technical effects.
  • the UE can access the macro cell and is served by the eNB in view of the bottleneck effect.
  • the UE By narrowing the downlink coverage and expanding the uplink coverage, the UE's access is effectively optimized, thereby reducing the uplink power used by the UE, alleviating the uplink interference condition in the system, and improving the system throughput, and solving the prior art user terminal. It consumes a large transmission power and a bottleneck effect of the downlink backhaul link.
  • FIG. 1 is a schematic diagram of a reference signal strength of a UE receiving an eNB or a relay, indicating a reference signal strength received by the UE from the eNB; RSRP indicating a reference signal strength received by the UE from the relay; and a horizontal axis indicating a distance between the UE and the eNB
  • the vertical axis represents the reference signal strength. That is, the farther the UE is from the eNB, the weaker the reference signal strength of the received eNB is; the closer the UE is to the relay, the stronger the reference signal strength of the received relay.
  • the UE when the UE is closer to the relay and farther away from the eNB, the UE selects to communicate with the relay in order to reduce the transmission power.
  • the signal strength received by the UE from the eNB is less than the signal strength from the relay, or the signal strength received by the UE from the eNB exceeds the received signal strength from the relay, but the amount exceeded exceeds the preset minimum value ⁇ ⁇ , That is, the relay downlink coverage is the interval with the minimum value X i dbm as the offset, ⁇ RSRp eNB _ RSRP ⁇ x i, the UE selects the relay cell as its uplink and downlink serving cell; the signal strength received by the UE from the eNB Exceeding the received signal strength from the relay, but when the excess is between ⁇ and the maximum value, that is, when ⁇ ⁇ - ⁇ ⁇ , the UE selects the relay cell as the uplink serving cell, but selects the macro cell in the downlink.
  • the relay uplink coverage is the interval with the maximum value dbm as the offset.
  • the signal strength received by the UE from the eNB exceeds the received signal strength from the relay, but the excess is not less than the preset ⁇ 2 , ie ⁇ ⁇ - ⁇ ⁇ X 2 , the UE selects the eNB cell as its uplink and downlink serving cell.
  • X1 is determined as follows:
  • ⁇ P and Ptre represent the transmission power of the eNB and the relay, respectively, Pr B and Pr represent the power of receiving the eNB and the relay at the UE, respectively, B and 7 ⁇ . 'representing the transmission path loss of the eNB and the relay , respectively.
  • PteNB - PL eNB P r eNB
  • Pr eNB and the Pr correspond to the RSRP eNB and the RSRP, respectively.
  • the cell selection access conditions are summarized as follows:
  • Mill eNB _KSRP r ⁇ Select the relay cell as the serving cell for the UE. That is, the uplink and downlink data communication of the UE is forwarded through relay;
  • FIG. 2 it is a schematic flowchart of a method for a user to access a serving cell according to the first embodiment of the present invention, which specifically includes the following steps.
  • Step 201 The eNB informs the relay downlink overload by exchanging control information.
  • Steps 202-203 the UE initial access, when satisfied - ⁇ Xl or X 2> RSRP eNB -RSRP relay ⁇ X 1 ⁇ ⁇ UE selecting a relay cell as its serving cell, the selected relay to an access request
  • the reference signal strength of the received eNB and relay is carried in the access request.
  • the UE when R U RP ⁇ x i , the UE selects a serving cell that accesses the eNB.
  • the bottleneck effect of the downlink backhaul link does not occur at this time, and will not be described in detail in this embodiment.
  • Step 204 The relay is determined according to the reference signal strength fed back by the UE, that is, the strength of the reference signal of the eNB and the relay received by the UE.
  • the UE is in the cross coverage range of the relay and the eNB, and the UE may be in the cross coverage range of the relay and the eNB.
  • the downlink data transmission is handed over to the eNB to avoid bottleneck effects on the downlink backhaul link.
  • the UE accesses the eNB in the downlink, but in the uplink direction, the UE still selects the relay that can bring a small path loss to the UE, that is, the relay as its uplink serving cell, thereby minimizing the energy required for the uplink transmission of the UE. Consumption.
  • Steps 210-213 The UE initiates an uplink transmission request to the relay, and the relay authorizes and performs uplink data transmission to the UE, and correspondingly sends the HARQ ACK/NACK message to the UE.
  • Steps 214-215 When the reference signal strength of the eNB and the relay is changed, the network side, including the relay and the eNB, continues to determine the UE to access in the uplink and downlink directions according to the cell selection access condition, and performs The UE is scheduled and notified accordingly.
  • the eNB notifies the bottleneck effect of the backhaul link.
  • the UE initiates the access request, by comparing the reference signal strength, the UE initially selects the access relay as its serving cell, and processes the relay through the relay.
  • the UE is uplinked to the relay, and the relay is still used as its uplink serving cell to avoid a large transmission power, and the downlink access eNB is used as its downlink service', area, thereby avoiding bottleneck effect.
  • FIG. 3 is a schematic flowchart of a method for a user to access a serving cell according to a second embodiment of the present invention, which specifically includes the following steps:
  • Steps 301-32 The eNB informs the relay downlink overload by exchanging control information.
  • the Relay actively notifies the UE of its own downlink overload.
  • the Relay notifies the UE of its own downlink overload.
  • A. Decrease the transmission power of the control signal in the relay, such as the broadcast signal BCH or the synchronization signal SCH.
  • the UE selects a sender that can bring a large control signal strength when initially accessing, such as an eNB as an initial access point of the UE.
  • the UE selects a transmitting end that can bring a large reference signal strength when initially accessing, such as an eNB as an initial access point of the UE.
  • the relay embeds the overload indication information in the control channel message related to itself.
  • the UE selects the sender whose signal strength is greater than a preset threshold and does not overload as the initial access point of the UE when initially accessing.
  • How to preset the threshold is a prior art, and here is not Let me repeat.
  • X 1 ⁇ [0,16dbm) ⁇ X 2 ⁇ 6dbm.
  • X. GlO bm) X 2 9dbm
  • the UE selects a transmitting end that can bring a large control signal strength, such as an eNB as an initial access point of the UE;
  • the UE selects a transmitting end that can bring a large reference signal strength, such as an eNB as an initial access point of the UE;
  • the UE selects a signal whose signal strength is greater than a preset threshold and does not overload, such as an eNB as an initial access point of the UE.
  • Steps 303-307 The UE initiates an access request to the eNB, where the access request carries the strength of the reference signal received from the eNB and the relay, and after performing the downlink resource scheduling, the eNB performs the next For data transmission, the UE transmits an HARQ ACK/NACK message to the eNB accordingly.
  • Steps 308-310 When the UE needs to perform uplink data transmission, the eNB determines the strength of the reference signal sent by the UE according to the following. If relay the uplink load of the UE is allowed to access covers, ⁇ X 2> RSRP eNB - RSRP relay ⁇ X, indicating that the UE is within coverage of the relay and cross e NB and the closer to the relay, the UE may be?
  • the upstream transmission is forwarded to the relay. That is, the downlink still maintains the access eNB, and the uplink selects the relay that can bring the small path loss to the UE, that is, the relay, as the serving cell, thereby minimizing the energy consumption required for the uplink transmission of the UE.
  • the eNB determines whether the relay uplink load is allowed to be accessed through the signaling interaction between the eNB and the eNB. The determining process is a prior art, and details are not described herein.
  • the eNB notifies the relay that covers the UE as the uplink serving cell of the UE, and informs the UE of its uplink serving cell.
  • step 311-314 the UE initiates an uplink transmission request to the relay, and the relay grants an uplink to the UE for uplink data transmission, and correspondingly sends the HARQ ACK/NACK message to the UE.
  • Steps 315-316 the network side, including the relay and the eNB, continue to determine the UE to be accessed in the uplink and downlink directions according to the cell selection access condition, and perform scheduling and notification to the UE accordingly.
  • the value of X1 and the value may be slightly different from those in the first embodiment, but does not affect the technical effect of the present invention.
  • the difference between the second embodiment and the first embodiment is that, when the relay downlink is overloaded, the UE at the edge of the relay coverage area can select the eNB as the initial access point, and can directly communicate with the eNB when initiating downlink data transmission, thereby avoiding An unnecessary transfer and A bottleneck has occurred.
  • the uplink of the UE located at the edge of the relay coverage is connected to the uplink serving cell of the relay.
  • the embodiment of the present invention does not exclude the UE during initial access, on the access conditions are based on cell selection to choose the uplink and downlink access point, the access point, and wherein the ⁇ ⁇ embodiments and ranges The same in the first example.
  • the PUCCH control channel has little influence, and only the PDCCH from the two access points needs to be detected, which adds some blind detection complexity.
  • the processing of the UE in the uplink direction and the downlink direction includes the following cases.
  • the uplink continues to remain in the relay, and the downlink is switched to the eNB for downlink service due to overload, resulting in a half-switching state.
  • the access is denied due to the downlink overload, and all the uplink and downlink are re-accessed to the sub-optimal site eNB.
  • the technical solution in the first embodiment can not only reduce the delay but also improve the throughput, and The suppression of system uplink interference.
  • the downlink is first denied access due to overload and re-accessed to the sub-optimal site eNB.
  • the uplink condition is switched back to the relay according to the cell selection access condition.
  • additional system delays are introduced in the uplink data transmission compared to the original scheme. However, while this delay is incurred, it leads to an increase in throughput and suppression of uplink interference in the system.
  • the processing of the UE in the uplink direction and the downlink direction includes the following cases:
  • the downlink data service When the downlink data service is first used, the rejection of accepting a relay in the prior art is avoided. Re-accessing the eNB, thereby reducing the delay; when there is an uplink data service, the uplink is switched back to the relay according to the cell selection access condition.
  • the uplink data transmission is compared with the prior art. Bring additional system latency. However, while paying this delay, it brings about an increase in throughput and suppression of the uplink interference of the system.

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Description

一种长期演进先进系统中用户接入服务小区的方法
技术领域
本发明涉及无线通信技术领域， 更具体地， 涉及一种长期演进先进 系统 ( Long Term Evolution Advanced, LTE- advanced ) 系统中用户接入 服务小区的方法。 发明背景
现有研究表明， 通过在加强型基站节点 （eNB )与终端 （UE )之间 引入中继节点 （relay ), 组成新型的中继蜂窝通信系统， 可以有效改善 网络覆盖质量、 提升系统容量和提高资源利用率。 因而 relay 在 LTE-advanced系统研发过程中用来实现宽带无线接入。
在 LTE-advanced系统中， relay的引入带来了新的四种不同的链路： eNB到 relay的下行链路、 relay到 eNB的上行链路、 relay到 UE的下行 链路、 UE到 relay的上行链路。 此外， 该系统中必然还存在着一些距离 eNB较近、 与 eNB直接通信的 UE。 对于这些 UE, 传统的接入链路即 eNB到 UE的下行链路和 UE到 eNB的上行链路依然存在。
从调度来讲， 一般存在两种方式， 一种是 eNB负责多跳小区内所有 节点包括 relay和 relay覆盖的 UE的调度， 称为集中调度方式； 另外一 种是 eNB只负责自身所覆盖 UE的调度和中继的调度， 而 relay覆盖的 UE由 relay完成调度，这种方式被称为分布式调度。多跳小区是包含 relay 站点的小区， 该小区内的数据传输可能经过多个空中接口。
LTE-advanced系统中引入具有独立的 cell ID的 relay传输自己的控 制信息及同步信息等。 釆用分布式调度的 relay为了进行 UE与 eNB之 间的数据传输， eNB和 relay分别独立地为所控制的无线链路分配资源。 relay所控制的资源及 relay的中继链路资源由 eNB预先分配。 中继链路 又称回传链路。 当采用分布式调度方式时， 下行回传链路存在瓶颈效应。 当中继接入链路， 即 relay与 UE之间的链路资源丰富时， relay到 UE 能够提供的吞吐量大于 eNB到 relay的吞吐量， 这种情形下下行回传链 路会遭遇瓶颈效应。现有系统中， 被 relay服务的 UE的上行链路和下行 链路都是直接接入到 relay 的服务小区， 如果因下行回传链路遭遇瓶颈 效应而使被中继服务的 UE的上行链路和下行连接全部切换到 eNB的服 务小区， 虽然可以緩解出现的下行回传链路的瓶颈效应， 但 UE的上行 链路切换到 eNB 的服务小区需要用户端耗费较大的传输功率进行上行 数据传输。
现有技术中， 解决下行回传链路的瓶颈效应的技术方案是， 使用特 殊子帧中的下行 OFDM符号传输回传链路中的数据，但特殊子帧中的几 个下行 OFDM符号还需用作时间转换，仍不足以彻底解决下行回传链路 的瓶颈效应。 举例说明如下： 对于 TDD time configuration mode 2, 设置 下行回传链路子帧数目为最大可获得的数目 4, 假如发现调度两个中继 链路时， 下行回传链路已经出现瓶颈效应， 限制了系统吞吐量的提高。 尽管可使用特殊子帧中的 8个 OFDM符号用作增补下行回传链路进行数 据传输， 可当调度两个以上中继链路时， 依然会出现下行回传链路的瓶 颈问题。
综上， 当采用分布式调度方式时， 存在下行回传链路的瓶颈效应和 用户端耗费传输功率较大的问题。 发明内容
本发明实施例提出一种 LTE-advanced 系统中用户接入服务小区的 方法， 从而在采用分布式调度方式时， 用户端耗费传输功率较小且不存 在下行回传链路的瓶颈效应。
本发明实施例的技术方案如下：
一种 LTE-advanced 系统中用户接入服务小区的方法， 用于有中继 relay的分布式调度方式， 该方法包括：
按照小区选择接入条件将终端 UE接入服务小区， 具体包括：
UE接收到的来自 B 节点 eNB 的信号强度小于接收到的来自所述 relay的信号强度时，或 UE接收到的来自所述 eNB的信号强度超过接收 到的来自所述 relay的信号强度， 但超过的量小于预设的最小值 Χι时，
UE 的上行链路和下行链路均接入所述 relay 的服务小区， 是单位为 dbm的固定值；
UE接收到的来自所述 eNB的信号强度超过接收到的来自所述 relay 的信号强度， 但超过的量在 和最大值 之间时， UE的上行链路接入 所述 relay的服务小区， 所述 UE的下行链路接入所述 eNB的服务小区， 是单位为 dbm的固定值；
UE接收到的来自所述 eNB的信号强度超过接收到的来自所述 relay 的信号强度， 且超过的量不小于预设的 时， UE的上行链路和下行链 路均接入所述 eNB的服务小区。
从上述技术方案中可以看出， 在本发明实施例中， eNB 通知 relay 下行负载偏重， 在 UE初次接入时， 根据 '〗、区选择接入条件将 UE接入 服务小区，具体地，当 UE接入的 eNB与 relay信号强度的差值小于 Χι时， UE的上行链路和下行链路均接入所述 relay的服务小区； 当 UE接入的 eNB与 relay信号强度的差值大于等于 小于 时， 即 UE处于 eNB和 relay的交叉区域中， UE的上行链路接入所述 relay的服务小区， 所述 UE的下行链路接入所述 eNB的服务小区； 该 UE的上行与下行分别处 于 relay和 eNB中， 上行与下行的接入地址不同则称为异址接入； 当 UE 接入的 eNB与 relay信号强度的差值大于等于 时，此时接入 eNB的信 号强度超出接入 relay信号强度 X2 dbm,则 UE的上行链路和下行链路均 接入所述 eNB的服务小区；在 UE完成初始接入之后，当 UE接收的 eNB 与 relay信号强度发生变化时， eNB可以根据 '】、区选择接入条件再次确 定 UE的服务小区。 从而， 处于 eNB和 relay的覆盖范围交叉区域内的 UE上行接入 relay使得用户端耗费较小的传输功率， 而该 UE的下行接 入 eNB避免了瓶颈效应。 附图简要说明
图 1为本发明实施例的中用户端接收 eNB或 relay的参考信号强度 示意图。
图 2为本发明第一实施例用户接入服务'】、区的方法流程示意图。 图 3为本发明第二实施例用户接入服务小区的方法流程示意图。 实施本发明的方式
为使本发明的目的、 技术方案和优点表达得更加清楚明白， 下面结 合附图及具体实施例对本发明再作进一步详细的说明。
在本发明实施例中， 在不同的网络情况下，按照小区选择接入条件， UE接入与当前网络情况对应的服务小区， 随着 UE所接收 eNB和 relay 的参考信号强度的变化， 网络侧可以再次按照小区选择接入条件， 将 UE接入与变化后的参考信息强度对应的服务小区。 不论是按照小区选 择接入条件首次接入或是再次接入服务小区 , 用户端的异址接入带来如 下的技术效果，在下行方向，鉴于瓶颈效应， UE可接入宏小区即被 eNB 服务的小区， 从而緩解下行中继链路所遭遇的瓶颈效应； 在上行方向， 考虑 UE接入系统后所需耗费的传输功率大小， UE仍选择接入中继小 区。 通过缩小下行覆盖范围， 扩大上行覆盖范围， 有效地优化了 UE的 接入， 从而降低了 UE使用的上行功率， 緩解系统中的上行干扰状况及 提高系统吞吐量， 解决了现有技术中用户端耗费传输功率较大和下行回 传链路的瓶颈效应。
图 1是用户端接收 eNB或 relay的参考信号强度示意图， 表 示 UE接收到的来自 eNB的参考信号强度； RSRP 表示 UE接收到的来 自 relay的参考信号强度； 横轴表示 UE与 eNB之间的距离； 纵轴表示 参考信号强度。 即 UE距离 eNB越远则接收到 eNB的参考信号强度越 弱； 当 UE距离 relay越近， 则接收到 relay的参考信号强度越强。
相应的， 当 UE距离 relay较近且距离 eNB较远时， UE为了减少传 输功率，会选择与 relay通信。 UE接收到的来自 eNB的信号强度小于来 自 relay的信号强度时， 或 UE接收到的来自 eNB的信号强度超过接收 到的来自 relay的信号强度， 但超过的量小于预设的最小值 Χι， 即 relay 下行覆盖范围是以最小值 Xi dbm 为偏移的区间， ^ RSRp eNB _ RSRP < xi 时 , UE选择中继小区作为其上行和下行服务小区； UE接收到的来自 eNB 的信号强度超过接收到的来自 relay的信号强度， 但超过的量在 Χι和最 大值 之间时， 即当 Χ ^ - ^^^≥ 时， UE选择中继小区作为 上行服务小区， 但下行选择宏小区作为其下行服务小区， 其中 χ2 > 。 relay上行覆盖范围是以最大值 ^ dbm为偏移的区间， UE接收到的来自 eNB的信号强度超过接收到的来自 relay的信号强度， 但超过的量不小 于预设的 χ2 , 即^^ ^ - ^^ ≥X2时， UE选择 eNB小区作为其上行 和下行服务小区。 在本发明中 Xl和 按照如下方法确定：
Ρ ΝΒ和 Ptre"分别代表 eNB和 relay的传输功率， Pr B和 Pr 分别代 表在 UE处接收 eNB和 relay的功率， B和7^。'分别代表 eNB和 relay 的传输路损。
可知， Pt =Pr +PL
则有 PteNB - PLeNB = Pr eNB , P elay - ^^relay = ^^elay 将两式相减 , 有 Ρ ― - Ρ ΝΒ + PLrelay = Pr eNB - Prrday
一般来说， ptcm =46dbm, 但由于 3gpp定义的两种中继的传输功率 值即 '· =3( ^ U dbm 。 那么针对不同的 取值 是不同的。
当 V =30i¾m时， 有 若 PL <PLeNB , 有 Prreiay+i6dbm>PreNB , 其中 PreNB与 Pr '分别对应 RSRPe 与 RSRPrday ,
则 X2 -\6dbm 本发明中，
Figure imgf000008_0001
。
当 Pt = ^dbm , 有 若
Figure imgf000008_0002
, 有 + 9dbm > Ρκ^，
其中 PreNB与 Pr 分别对应 RSRPeNB与 RSRP ,
则 X2 = 9dbm 本发明中， 因此^ ^，^ ）。
小区选择接入条件总结如下：
1、 磨 eNB_KSRPr < 为 UE选择中继小区作为其服务小区， 即 UE的上下行数据通信都是通过 relay转发；
2、 当 PLw < PLeNB即 > RSRPeNB - RSRPrelay ≥ X1 ^ 为 UE选择中继小区 作为其上行服务小区， 即 UE的上行数据通信通过中继转发； 为 UE选 择宏小区作为其下行服务小区， 即 UE的下行数据传输直接与 eNB进行 交互；
3、 pLr ≥ PL eNB ^> RSRp eNB - RSRP ≥ x 2 , 为 UE选择宏小区作为其 服务小区， 即 UE的上下行数据通信都是直接与 eNB进行交互。
实施例一
参见附图 2， 是本发明第一实施例用户接入服务小区的方法流程示 意图， 具体包括以下步骤。
步骤 201、 eNB通过交换控制信息告知 relay下行链路过载。
步驟 202-203、 UE 初次接入时， 当满足 ― < Xl或 X2 > RSRPeNB -RSRPrelay≥X1 ^ ^ UE选择中继小区作为其服务小区， 并向所 选择的 relay发起接入请求，在接入请求中携带接收到的 eNB和 relay的 参考信号强度。
在本实施例中， 当 RU RP ≥ xi 时， UE选择接入 eNB的服 务小区。 此时不会出现下行回传链路的瓶颈效应， 在本实施例中不作详 细描述。
步骤 204、 relay根据 UE反馈的参考信号强度判断， 即 UE接收到 的 eNB和 relay的参考信号的强度， 当 X2 > 对, 该 UE处于 relay和 eNB的交叉覆盖范围内，可以将该 UE的下行数据传输 转交给 eNB, 即可以避免下行回传链路出现瓶颈效应。 该 UE的下行接 入 eNB， 但在上行方向， 该 UE仍选择能给该 UE带来较小路损的发送 端即 relay作为其上行服务小区，从而最小化 UE上行传输所需要的能量 消耗。
实施例一中的 和 是根据上文中的计算方法得到的，针对不同的 取值是不同的。当 Pt = 30dbm时， Xi e [0'16 , χ2 = ^dbm . 当 ρ = yidbm χι e [0, 9dbm) Χ2 = 9dbm 步骤 205-209、 relay将该 UE的下行链路切换到 eNB， eNB作为 UE 的下行服务小区， 然后通知 UE其所在的下行服务小区。 eNB进行下行 资源调度后， 进行下行数据传输， UE 相应地向 eNB 发送 HARQ 的 ACK/NACK消息。
步骤 210-213、 UE向 relay发起上行传输请求， relay向该 UE授权 并进行上行数据传输， 并相应地将 HARQ 的 ACK/NACK 消息发送至 UE。
步骤 214-215、当 UE接收 eNB和 relay的参考信号强度发生变化时， 网络侧， 包括 relay 和 eNB , 依据小区选择接入条件继续， 再次确定 UE 在上下行方向上要接入的小区， 并进行相应地调度及通知 UE。
应用附图 2中所示技术方案 , eNB通知出现回传链路的瓶颈效应 , 当 UE发起接入请求时，通过比较参考信号强度， UE初始选择接入 relay 作为其服务小区， 通过 relay的处理， 使该 UE上行接入 relay, relay仍 作为其上行服务小区以避免耗费较大传输功率，下行接入 eNB作为其下 行服务'〗、区， 从而避免出现瓶颈效应。
实施例二
附图 3为本发明第二实施例用户接入服务小区的方法流程示意图， 具体包括以下步驟：
步骤 301-302、 eNB通过交换控制信息告知 relay下行链路过载。 在 本实施例中， Relay主动通知 UE自身的下行链路过载。 Relay通知 UE自身的下行链路过载的方式有以下几种。
A、 减小 relay中控制信号， 诸如广播信号 BCH或同步信号 SCH的 发射功率。 这样一来， UE在初次接入时选择能带来较大控制信号强度 的发送端， 如 eNB作为 UE初始接入点。
B、 减小 relay中参考信号的发射功率。 这样一来， UE在初次接入 时选择能带来较大参考信号强度的发送端，如 eNB作为 UE初始接入点。
在 A 和 B 的两种情况下， 因为减小 relay 的发射功率， 则有
Ptrelay <30dbm 或 Ptrday < dbm , 那 么 [0， — , =κ )气
C, relay在与自身相关的控制信道消息中嵌入过载指示信息。 这样 一来， UE 在初次接入时选择信号强度大于某一预设的门限值并且不过 载的发送端作为 UE初始接入点， 如何预设门限值是现有技术， 在此就 不再赘述。 当 二30 ^"时， X1 ^[0,16dbm) ^ X2 =\6dbm. 当 =37c¾m , X. GlO bm) X2 = 9dbm 针对 A、 B、 C不同的过载通知方式， UE在初次接入时分别作 a、 b、 c: ^下处理：
a、 UE选择能带来较大控制信号强度的发送端， 如 eNB作为 UE初 始接入点；
b、 UE选择能带来较大参考信号强度的发送端， 如 eNB作为 UE初 始接入点；
c、 UE选择信号强度大于某一预设的门限值并且不过载的发送端如 eNB作为 UE初始接入点。
步骤 303-307、 UE向 eNB发起接入请求，该接入请求中携带从 eNB 和 relay接收到的参考信号的强度， eNB进行下行资源调度后， 进行下 行数据传输， UE相应地向 eNB发送 HARQ的 ACK/NACK消息。
步骤 308-310、 当 UE需要作上行数据传输时， eNB根据 UE发送的 参考信号的强度作如下判断。如果覆盖该 UE的 relay上行负载允许接入， ^ X2 > RSRPeNB - RSRPrelay≥ X, ? 说明该 UE处于 relay与 eNB的交叉覆盖范 围之内并且距离 relay更近， 则可将该 UE的上行传输转交给 relay。 即 下行仍保持接入 eNB , 上行选择能给该 UE 带来较小路损的发送端即 relay作为其服务小区 ,从而最小化 UE上行传输所需要的能量消耗。 eNB 通过 relay与 eNB之间进行信令交互判断 relay上行负载是否允许接入， 该判断过程是现有技术， 在此就不再赘述。
eNB通知覆盖该 UE的 relay作为该 UE的上行服务小区， 告知该 UE其上行服务小区。
步驟 311-314、 该 UE向 relay发起上行传输请求， relay向该 UE上 行授权并进行上行数据传输， 并相应地将 HARQ的 ACK/NACK消息发 送至 UE。
步骤 315-316、 网络侧， 包括 relay 和 eNB依据小区选择接入条件 继续判决 UE的在上下行方向上要接入的小区， 并进行相应地调度及通 知 UE。
实施例二中的 χι和 是根据上文中的计算方法得到的，针对不同的 Ρ , χι、 取值是不同的。 由于在步骤 302中有可能对 relay的发射 功率进行调整， 则 Xl、 取值会稍不同于实施例一中的取值， 但并不影 响本发明的技术效果。
实施例二与实施例一的区别在于， 当 relay下行过载时， 可以使一个 位于 relay覆盖范围边缘的 UE选择 eNB作为初始接入点， 进而在发起 下行数据传输时可以直接与 eNB进行通信，避免了一次不必要的转交和 出现瓶颈问题。 考虑到避免耗费较大传输功率， 将位于 relay覆盖范围 边缘的 UE的上行接入 relay的上行服务小区。
当然， 在本发明实施例中并不排除 UE在初始接入时， 就依据小区 选择接入条件分别做下行接入点和上行接入点的选择，其中 χι和 的取 值范围是和实施例一中相同的。
本发明实施例中， 对于异址接入的 UE, 对 PUCCH控制信道影响不 大， 只是需要检测来自两个接入点的 PDCCH, 增加了一些盲检复杂度。
在实施例一中， 当初始选择 relay作为接入点时， UE在上行方向和 下行方向的处理包括以下情况。
1 )、 当只有下行数据时， 或只有上行数据时， 实施例一中的技术方 案同现有技术相同， 即正常进行下行数据或上行数据的传输。
2 )、 当先有上行数据后有下行数据时， 根据小区选择接入条件， 上 行链路继续保留在 relay, 而下行链路因过载选择切换到 eNB 以作下行 服务， 造成一种半切换状态。 比较现有技术中， 因下行过载被拒绝接入， 并重新将上下行全部接入次优站点 eNB， 实施例一中的技术方案不仅能 够减小时延， 而且带来吞吐量的提升， 及对系统上行干扰的抑制。
3 )、 当先有下行数据服务后有上行数据服务时， 首先下行链路因过 载被拒绝接入，并重新接入次优站点 eNB。在此之后的上行数据服务中， 可根据小区选择接入条件，上行链路会切换回 relay。在这种实施方案中， 相比原有方案在上行数据传输中会带来额外的系统时延。 但付出这种时 延的同时却带来吞吐量的提升及对系统上行干扰的抑制。
在实施例二中， 当得到 relay发出的下行链路过载的通知， UE初始 选择 eNB作为接入点时， UE在上行方向和下行方向的处理包括以下情 况：
当先有下行数据服务时，避免了现有技术中的接受一次中继的拒绝， 重新接入 eNB， 从而减小了时延； 当先有上行数据服务时， 根据小区选 择接入条件上行链路切换回 relay, 在这种实施方案中， 相比现有技术在 上行数据传输中会带来额外的系统时延。 但付出这种时延的同时却带来 吞吐量的提升及对系统上行干扰的压制。
以上所述， 仅为本发明的较佳实施例而已， 并非用于限定本发明的 保护范围。 凡在本发明的精神和原则之内， 所作的任何修改、等同替换、 改进等， 均应包含在本发明的保护范围之内。

Claims

权利要求书
1、 一种 LTE-advanced系统中用户接入服务小区的方法， 用于有中 继 relay的分布式调度方式， 其特征在于， 该方法包括：
按照小区选择接入条件将终端 UE接入服务小区， 具体包括： UE接收到的来自 B 节点 eNB 的信号强度小于接收到的来自所述 relay的信号强度时，或 UE接收到的来自所述 eNB的信号强度超过接收 到的来自所述 relay的信号强度， 但超过的量小于预设的最小值 时，
UE 的上行链路和下行链路均接入所述 relay 的服务小区， 是单位为 dbm的固定值；
UE接收到的来自所述 eNB的信号强度超过接收到的来自所述 relay 的信号强度， 但超过的量在 χι和最大值 之间时， UE的上行链路接入 所述 relay的服务小区， 所述 UE的下行链路接入所述 eNB的服务小区，
^是单位为 dbm的固定值；
UE接收到的来自所述 eNB的信号强度超过接收到的来自所述 relay 的信号强度， 且超过的量不小于预设的 时， UE的上行链路和下行链 路均接入所述 eNB的服务小区。
2、 根据权利要求 1所述 LTE-advanced系统中用户接入服务小区的 方法， 其特征在于：
所述 UE接收到的来自所述 eNB的信号强度超过接收到的来自所述 relay 的信号强度， 但超过的量小于预设的最小值 包括： - RSRP < Xl , 是所述 UE接收到的来自所述 eNB的参考 信号强度， 所述 是所述 UE接收到的来自所述 relay的参考信号 强度； 所述 UE接收到的来自所述 eNB的信号强度超过接收到的来自所述 relay 的信号强度， 但超过的量在 和最大值 之间 包括
X2 > RSRPeNB - RSRPrelay≥X1 ;
UE接收到的来自所述 eNB的信号强度超过接收到的来自所述 relay 的信号强度，且超过的量不小于预设的 之外包括
Figure imgf000016_0001
- RSRP ≥ X2。
3、 根据权利要求 1所述 LTE-advanced系统中用户接入服务小区的 方法， 其特征在于， 所述按照小区选择接入条件将所述 UE接入服务小 区之前进一步包括， 初次按照小区选择接入条件将所述 UE接入服务小 区时， 所述 relay通知 UE所述 relay的下行链路过载。
4、 根据权利要求 1所述 LTE-advanced系统中用户接入服务小区的 方法， 其特征在于， 所述按照小区选择接入条件接入服务小区后进一步 包括， eNB或者 relay再次按照小区选择接入条件将 UE接入服务小区。
5、 根据权利要求 3所述 LTE-advanced系统中用户接入服务小区的 方法， 其特征在于， 所述 relay通知 UE所述 relay的下行链路过载包括： 所述 relay减小发送给所述 UE的控制信号的发射功率。
6、 根据权利要求 3所述 LTE-advanced系统中用户接入服务小区的 方法， 其特征在于， 所述 relay通知 UE所述 relay的下行链路过载包括： 所述 relay减小发送给所述 UE的参考信号发射功率。
7、 根据权利要求 3所述 LTE-advanced系统中用户接入服务小区的 方法， 其特征在于， 所述 relay通知 UE所述 relay的下行链路过载包括： 所述 relay在发送给所述 UE的控制信道消息中嵌入过载指示信息。
8、 根据权利要求 1、 2、 3、 4或 7任一所述 LTE-advanced系统中用 户接入服务小区的方法， 其特征在于， 当 relay的传输功率 ^ 二3^^" 时， 所述 Xl的取值范围是 Q < Xl < 16， 所述 χ2 = 1 6。
9、 根据权利要求 1、 2、 3、 4或 7任一所述 LTE-advanced系统中用 户接入服务小区的方法， 其特征在于， 当 relay的传输功率 =37i¾m 时， 所述 的取值范围是 0 < χι < 9， 所述 χ2 = 9。
10、根据权利要求 5或 6所述 LTE-advanced系统中用户接入服务小 区的方法， 其特征在于， 所述 的取值范围是 ， 所 述 ， Pt^是所述 eNB的传输功率， 是所述 relay的传 输功率。
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