【无小区大规模MIMO研究现状的文献综述2000字】

导论无小区大规模MIMO研究现状的文献综述2015年Ngo等人首次提出无小区大规模MIMO系统的概念ADDINEN.CITE<EndNote><Cite><Author>Ngo</Author><Year>2015</Year><RecNum>6</RecNum><DisplayText><styleface="superscript">[8]</style></DisplayText><record><rec-number>6</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620483274">6</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>H.Q.Ngo</author><author>A.Ashikhmin</author><author>H.Yang</author><author>E.G.Larsson</author><author>T.L.Marzetta</author></authors></contributors><titles><title>Cell-FreeMassiveMIMO:Uniformlygreatserviceforeveryone</title><secondary-title>2015IEEE16thInternationalWorkshoponSignalProcessingAdvancesinWirelessCommunications(SPAWC)</secondary-title><alt-title>2015IEEE16thInternationalWorkshoponSignalProcessingAdvancesinWirelessCommunications(SPAWC)</alt-title></titles><pages>201-205</pages><dates><year>2015</year><pub-dates><date>28June-1July2015</date></pub-dates></dates><isbn>1948-3252</isbn><urls></urls><electronic-resource-num>10.1109/SPAWC.2015.7227028</electronic-resource-num></record></Cite></EndNote>[8]，该系统在通信覆盖范围内分布式地部署了大量的AP，AP之间相互协作并在同一时频资源下为用户服务，无小区大规模MIMO结合了大规模MIMO与分布式天线的优点，又消除了小区和小区边界的概念，在避免越区切换的同时有效对抗衰落、抑制干扰并且解决了小区边缘用户信号质量差的问题，增强了用户的公平性，能够提供较高的覆盖率和频谱效率ADDINEN.CITEADDINEN.CITE.DATA[18,19]。由于无小区大规模MIMO系统所具备的独特优势，该系统自提出以来便引起了学术界的广泛关注。文献ADDINEN.CITE<EndNote><Cite><Author>Chen</Author><Year>2018</Year><RecNum>8</RecNum><DisplayText><styleface="superscript">[20,21]</style></DisplayText><record><rec-number>8</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620483731">8</key></foreign-keys><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Z.Chen</author><author>E.Björnson</author></authors></contributors><titles><title>ChannelHardeningandFavorablePropagationinCell-FreeMassiveMIMOWithStochasticGeometry</title><secondary-title>IEEETransactionsonCommunications</secondary-title></titles><periodical><full-title>IEEETransactionsonCommunications</full-title></periodical><pages>5205-5219</pages><volume>66</volume><number>11</number><dates><year>2018</year></dates><isbn>1558-0857</isbn><urls></urls><electronic-resource-num>10.1109/TCOMM.2018.2846272</electronic-resource-num></record></Cite><Cite><Author>Chen</Author><Year>2017</Year><RecNum>9</RecNum><record><rec-number>9</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620483861">9</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>Z.Chen</author><author>E.Bjoernson</author></authors></contributors><titles><title>CanWeRelyonChannelHardeninginCell-FreeMassiveMIMO?</title><secondary-title>2017IEEEGlobecomWorkshops(GCWkshps)</secondary-title><alt-title>2017IEEEGlobecomWorkshops(GCWkshps)</alt-title></titles><pages>1-6</pages><dates><year>2017</year><pub-dates><date>4-8Dec.2017</date></pub-dates></dates><urls></urls><electronic-resource-num>10.1109/GLOCOMW.2017.8269162</electronic-resource-num></record></Cite></EndNote>[20,21]研究了无小区大规模MIMO系统中的信道硬化和有利传播特性。研究表明，当无小区大规模MIMO系统的AP配备单根天线时，只有在较小的路径损耗指数情况下，信道硬化现象会随着AP密度的增大而更加明显；当无小区大规模MIMO系统的AP配备多根天线时，保持正常的AP密度和路径衰落，当AP天线增加时，信道硬化显现会变得更明显；另外，随着AP天线数目的增加或AP密度的增大，无小区大规模MIMO系统的有利信道条件也将更加明显。有研究工作比较了无小区大规模MIMO系统与传统蜂窝网络的性能，文献ADDINEN.CITE<EndNote><Cite><Author>Ngo</Author><Year>2017</Year><RecNum>7</RecNum><DisplayText><styleface="superscript">[9]</style></DisplayText><record><rec-number>7</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620483283">7</key></foreign-keys><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>H.Q.Ngo</author><author>A.Ashikhmin</author><author>H.Yang</author><author>E.G.Larsson</author><author>T.L.Marzetta</author></authors></contributors><titles><title>Cell-FreeMassiveMIMOVersusSmallCells</title><secondary-title>IEEETransactionsonWirelessCommunications</secondary-title></titles><periodical><full-title>IEEETransactionsonWirelessCommunications</full-title></periodical><pages>1834-1850</pages><volume>16</volume><number>3</number><dates><year>2017</year></dates><isbn>1558-2248</isbn><urls></urls><electronic-resource-num>10.1109/TWC.2017.2655515</electronic-resource-num></record></Cite></EndNote>[9]分别在相关和非相关阴影衰落模型下推导了采用匹配滤波器接收机的无小区大规模MIMO系统的上行频谱效率以及采用共轭波束赋形的系统下行频谱效率，并与同样条件下的小小区（SmallCell）系统进行了对比，结果表明，与SmallCell系统相比，无小区大规模MIMO系统的平均用户频谱效率提升了5至10倍。文献ADDINEN.CITE<EndNote><Cite><Author>Nguyen</Author><Year>2017</Year><RecNum>12</RecNum><DisplayText><styleface="superscript">[22]</style></DisplayText><record><rec-number>12</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620484243">12</key></foreign-keys><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>L.D.Nguyen</author><author>T.Q.Duong</author><author>H.Q.Ngo</author><author>K.Tourki</author></authors></contributors><titles><title>EnergyEfficiencyinCell-FreeMassiveMIMOwithZero-ForcingPrecodingDesign</title><secondary-title>IEEECommunicationsLetters</secondary-title></titles><periodical><full-title>IEEECommunicationsLetters</full-title></periodical><pages>1871-1874</pages><volume>21</volume><number>8</number><dates><year>2017</year></dates><isbn>1558-2558</isbn><urls></urls><electronic-resource-num>10.1109/LCOMM.2017.2694431</electronic-resource-num></record></Cite></EndNote>[22]给出了采用迫零预编码的无小区大规模MIMO系统能效表达式，相比于集中式大规模MIMO系统，无小区大规模MIMO系统能量效率得到了显著提升。另外还有更多研究着眼于无小区大规模MIMO系统的信息理论分析，资源管理和信息处理技术ADDINEN.CITE<EndNote><Cite><Author>Ibrahim</Author><Year>2017</Year><RecNum>191</RecNum><DisplayText><styleface="superscript">[23]</style></DisplayText><record><rec-number>191</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620486047">191</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>A.A.I.Ibrahim</author><author>A.Ashikhmin</author><author>T.L.Marzetta</author><author>D.J.Love</author></authors></contributors><titles><title>Cell-freemassiveMIMOsystemsutilizingmulti-antennaaccesspoints</title><secondary-title>201751stAsilomarConferenceonSignals,Systems,andComputers</secondary-title><alt-title>201751stAsilomarConferenceonSignals,Systems,andComputers</alt-title></titles><pages>1517-1521</pages><keywords><keyword>Antennas</keyword><keyword>Resourcemanagement</keyword><keyword>Channelestimation</keyword><keyword>Fadingchannels</keyword><keyword>MIMOcommunication</keyword><keyword>Interference</keyword><keyword>Signaltonoiseratio</keyword></keywords><dates><year>2017</year><pub-dates><date>29Oct.-1Nov.2017</date></pub-dates></dates><isbn>2576-2303</isbn><urls></urls><electronic-resource-num>10.1109/ACSSC.2017.8335610</electronic-resource-num></record></Cite></EndNote>[23]。文献ADDINEN.CITE<EndNote><Cite><Author>Ibrahim</Author><Year>2017</Year><RecNum>191</RecNum><DisplayText><styleface="superscript">[23]</style></DisplayText><record><rec-number>191</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620486047">191</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>A.A.I.Ibrahim</author><author>A.Ashikhmin</author><author>T.L.Marzetta</author><author>D.J.Love</author></authors></contributors><titles><title>Cell-freemassiveMIMOsystemsutilizingmulti-antennaaccesspoints</title><secondary-title>201751stAsilomarConferenceonSignals,Systems,andComputers</secondary-title><alt-title>201751stAsilomarConferenceonSignals,Systems,andComputers</alt-title></titles><pages>1517-1521</pages><keywords><keyword>Antennas</keyword><keyword>Resourcemanagement</keyword><keyword>Channelestimation</keyword><keyword>Fadingchannels</keyword><keyword>MIMOcommunication</keyword><keyword>Interference</keyword><keyword>Signaltonoiseratio</keyword></keywords><dates><year>2017</year><pub-dates><date>29Oct.-1Nov.2017</date></pub-dates></dates><isbn>2576-2303</isbn><urls></urls><electronic-resource-num>10.1109/ACSSC.2017.8335610</electronic-resource-num></record></Cite></EndNote>[23]研究了AP装配多根天线时的下行性能表现，并对回程链路造成的网络设施成本进行了简单建模。文献ADDINEN.CITE<EndNote><Cite><Author>Parida</Author><Year>2018</Year><RecNum>95</RecNum><DisplayText><styleface="superscript">[24]</style></DisplayText><record><rec-number>95</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620486013">95</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>P.Parida</author><author>H.S.Dhillon</author><author>A.F.Molisch</author></authors></contributors><titles><title>DownlinkPerformanceAnalysisofCell-FreeMassiveMIMOwithFiniteFronthaulCapacity</title><secondary-title>2018IEEE88thVehicularTechnologyConference(VTC-Fall)</secondary-title><alt-title>2018IEEE88thVehicularTechnologyConference(VTC-Fall)</alt-title></titles><pages>1-6</pages><keywords><keyword>Channelestimation</keyword><keyword>Antennaarrays</keyword><keyword>Downlink</keyword><keyword>MassiveMIMO</keyword><keyword>Arraysignalprocessing</keyword><keyword>Cell-freemassiveMIMO</keyword><keyword>stochasticgeometry</keyword><keyword>fronthaulcapacity</keyword><keyword>binomialpointprocess</keyword></keywords><dates><year>2018</year><pub-dates><date>27-30Aug.2018</date></pub-dates></dates><isbn>2577-2465</isbn><urls></urls><electronic-resource-num>10.1109/VTCFall.2018.8690797</electronic-resource-num></record></Cite></EndNote>[24]给出了前向链路容量受限时无小区大规模MIMO系统的下行用户可达速率，研究表明在此场景下，选择部分AP为单个用户服务能够带来更好的性能。文献ADDINEN.CITE<EndNote><Cite><Author>Nguyen</Author><Year>2018</Year><RecNum>216</RecNum><DisplayText><styleface="superscript">[25]</style></DisplayText><record><rec-number>216</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620486052">216</key></foreign-keys><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>T.H.Nguyen</author><author>T.K.Nguyen</author><author>H.D.Han</author><author>V.D.Nguyen</author></authors></contributors><titles><title>OptimalPowerControlandLoadBalancingforUplinkCell-FreeMulti-UserMassiveMIMO</title><secondary-title>IEEEAccess</secondary-title></titles><periodical><full-title>IEEEAccess</full-title></periodical><pages>14462-14473</pages><volume>6</volume><keywords><keyword>MIMOcommunication</keyword><keyword>Uplink</keyword><keyword>Powercontrol</keyword><keyword>Loadmanagement</keyword><keyword>Receivers</keyword><keyword>Interference</keyword><keyword>Antennas</keyword><keyword>MassiveMIMO</keyword><keyword>powerallocation</keyword><keyword>userassociation</keyword></keywords><dates><year>2018</year></dates><isbn>2169-3536</isbn><urls></urls><electronic-resource-num>10.1109/ACCESS.2018.2797874</electronic-resource-num></record></Cite></EndNote>[25]研究了最小化无小区大规模MIMO上行传输系统功耗的功率控制和AP负载均衡的联合优化问题。文献ADDINEN.CITE<EndNote><Cite><Author>Mosleh</Author><Year>2019</Year><RecNum>20</RecNum><DisplayText><styleface="superscript">[26]</style></DisplayText><record><rec-number>20</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620485982">20</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>S.Mosleh</author><author>H.Almosa</author><author>E.Perrins</author><author>L.Liu</author></authors></contributors><titles><title>DownlinkResourceAllocationinCell-FreeMassiveMIMOSystems</title><secondary-title>2019InternationalConferenceonComputing,NetworkingandCommunications(ICNC)</secondary-title><alt-title>2019InternationalConferenceonComputing,NetworkingandCommunications(ICNC)</alt-title></titles><pages>883-887</pages><dates><year>2019</year><pub-dates><date>18-21Feb.2019</date></pub-dates></dates><isbn>2325-2626</isbn><urls></urls><electronic-resource-num>10.1109/ICCNC.2019.8685542</electronic-resource-num></record></Cite></EndNote>[26]利用上下行对偶性，将下行预编码矢量与功率分配的联合优化问题转变为求解上行瑞利熵问题，来最大化最小用户的可达速率。在用户传输数据之前，需要先通过竞争或分配的方式获得导频资源，由于相干间隔限制了导频数量，因此，在多用户的情况下，部分用户不得不复用相同的正交导频集，造成信道估计干扰，因此导频优化对于提升系统性能具有重要作用。目前，已有的相关研究主要是通过导频分配、AP选择、导频功率优化等角度来优化无小区大规模MIMO系统的导频。首先在导频分配方面，理想情况下是使所有用户使用正交的导频，但这种方式会造成极大的导频资源浪费，同时，考虑到相干块长度的限制，这种正交导频分配的方法也难以实现ADDINEN.CITE<EndNote><Cite><Author>Bashar</Author><Year>2018</Year><RecNum>255</RecNum><DisplayText><styleface="superscript">[33]</style></DisplayText><record><rec-number>255</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620496798">255</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>M.Bashar</author><author>K.Cumanan</author><author>A.G.Burr</author><author>M.Debbah</author><author>H.Q.Ngo</author></authors></contributors><titles><title>EnhancedMax-MinSINRforUplinkCell-FreeMassiveMIMOSystems</title><secondary-title>2018IEEEInternationalConferenceonCommunications(ICC)</secondary-title><alt-title>2018IEEEInternationalConferenceonCommunications(ICC)</alt-title></titles><pages>1-6</pages><keywords><keyword>Resourcemanagement</keyword><keyword>Uplink</keyword><keyword>Receivers</keyword><keyword>Signaltonoiseratio</keyword><keyword>Interference</keyword><keyword>MIMOcommunication</keyword><keyword>Eigenvaluesandeigenfunctions</keyword></keywords><dates><year>2018</year><pub-dates><date>20-24May2018</date></pub-dates></dates><isbn>1938-1883</isbn><urls></urls><electronic-resource-num>10.1109/ICC.2018.8422577</electronic-resource-num></record></Cite></EndNote>[33]。还有一种简单的方式是为用户随机分配导频ADDINEN.CITE<EndNote><Cite><Author>Attarifar</Author><Year>2018</Year><RecNum>235</RecNum><DisplayText><styleface="superscript">[30]</style></DisplayText><record><rec-number>235</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620496552">235</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>M.Attarifar</author><author>A.Abbasfar</author><author>A.Lozano</author></authors></contributors><titles><title>RandomvsStructuredPilotAssignmentinCell-FreeMassiveMIMOWirelessNetworks</title><secondary-title>2018IEEEInternationalConferenceonCommunicationsWorkshops(ICCWorkshops)</secondary-title><alt-title>2018IEEEInternationalConferenceonCommunicationsWorkshops(ICCWorkshops)</alt-title></titles><pages>1-6</pages><keywords><keyword>Signaltonoiseratio</keyword><keyword>MIMOcommunication</keyword><keyword>Interference</keyword><keyword>Contamination</keyword><keyword>Fadingchannels</keyword><keyword>Antennas</keyword><keyword>Channelestimation</keyword></keywords><dates><year>2018</year><pub-dates><date>20-24May2018</date></pub-dates></dates><isbn>2474-9133</isbn><urls></urls><electronic-resource-num>10.1109/ICCW.2018.8403508</electronic-resource-num></record></Cite></EndNote>[30]，这种方式虽然简单快捷，但容易使得两个相邻用户复用相同导频，造成严重的干扰，非常不利于系统性能的提升。同时文献ADDINEN.CITE<EndNote><Cite><Author>Attarifar</Author><Year>2018</Year><RecNum>235</RecNum><DisplayText><styleface="superscript">[30]</style></DisplayText><record><rec-number>235</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620496552">235</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>M.Attarifar</author><author>A.Abbasfar</author><author>A.Lozano</author></authors></contributors><titles><title>RandomvsStructuredPilotAssignmentinCell-FreeMassiveMIMOWirelessNetworks</title><secondary-title>2018IEEEInternationalConferenceonCommunicationsWorkshops(ICCWorkshops)</secondary-title><alt-title>2018IEEEInternationalConferenceonCommunicationsWorkshops(ICCWorkshops)</alt-title></titles><pages>1-6</pages><keywords><keyword>Signaltonoiseratio</keyword><keyword>MIMOcommunication</keyword><keyword>Interference</keyword><keyword>Contamination</keyword><keyword>Fadingchannels</keyword><keyword>Antennas</keyword><keyword>Channelestimation</keyword></keywords><dates><year>2018</year><pub-dates><date>20-24May2018</date></pub-dates></dates><isbn>2474-9133</isbn><urls></urls><electronic-resource-num>10.1109/ICCW.2018.8403508</electronic-resource-num></record></Cite></EndNote>[30]还提出了一种结构化的导频复用的方案，但是也同样对系统性能提升有限。以最大化无小区大规模MIMO系统上行链路的总频谱效率为目标，文献ADDINEN.CITE<EndNote><Cite><Author>Sabbagh</Author><Year>2018</Year><RecNum>254</RecNum><DisplayText><styleface="superscript">[31]</style></DisplayText><record><rec-number>254</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620496798">254</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>R.Sabbagh</author><author>C.Pan</author><author>J.Wang</author></authors></contributors><titles><title>PilotAllocationandSum-RateAnalysisinCell-FreeMassiveMIMOSystems</title><secondary-title>2018IEEEInternationalConferenceonCommunications(ICC)</secondary-title><alt-title>2018IEEEInternationalConferenceonCommunications(ICC)</alt-title></titles><pages>1-6</pages><keywords><keyword>MIMOcommunication</keyword><keyword>Antennas</keyword><keyword>Uplink</keyword><keyword>Channelestimation</keyword><keyword>Interference</keyword><keyword>Signaltonoiseratio</keyword><keyword>CentralProcessingUnit</keyword></keywords><dates><year>2018</year><pub-dates><date>20-24May2018</date></pub-dates></dates><isbn>1938-1883</isbn><urls></urls><electronic-resource-num>10.1109/ICC.2018.8422575</electronic-resource-num></record></Cite></EndNote>[31]提出了一种动态导频的分配方案。文献ADDINEN.CITE<EndNote><Cite><Author>Li</Author><Year>2018</Year><RecNum>50</RecNum><DisplayText><styleface="superscript">[32]</style></DisplayText><record><rec-number>50</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620485995">50</key></foreign-keys><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Y.Li</author><author>G.A.ArumaBaduge</author></authors></contributors><titles><title>NOMA-AidedCell-FreeMassiveMIMOSystems</title><secondary-title>IEEEWirelessCommunicationsLetters</secondary-title></titles><periodical><full-title>IEEEWirelessCommunicationsLetters</full-title></periodical><pages>950-953</pages><volume>7</volume><number>6</number><dates><year>2018</year></dates><isbn>2162-2345</isbn><urls></urls><electronic-resource-num>10.1109/LWC.2018.2841375</electronic-resource-num></record></Cite></EndNote>[32]综合考虑了导频分配与用户分组方案，先对覆盖范围内的用户进行分组，组内的用户复用同一导频，不同的用户组使用相互正交的导频。这种方案有效避免了用户组之间的信道估计干扰，但是组内用户之间的导频污染仍不可避免。其次在AP选择方面，随机分配AP给用户的方案虽然具有较低的复杂度，但难以体现系统真实的性能ADDINEN.CITE<EndNote><Cite><Author>Ngo</Author><Year>2017</Year><RecNum>7</RecNum><DisplayText><styleface="superscript">[9]</style></DisplayText><record><rec-number>7</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620483283">7</key></foreign-keys><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>H.Q.Ngo</author><author>A.Ashikhmin</author><author>H.Yang</author><author>E.G.Larsson</author><author>T.L.Marzetta</author></authors></contributors><titles><title>Cell-FreeMassiveMIMOVersusSmallCells</title><secondary-title>IEEETransactionsonWirelessCommunications</secondary-title></titles><periodical><full-title>IEEETransactionsonWirelessCommunications</full-title></periodical><pages>1834-1850</pages><volume>16</volume><number>3</number><dates><year>2017</year></dates><isbn>1558-2248</isbn><urls></urls><electronic-resource-num>10.1109/TWC.2017.2655515</electronic-resource-num></record></Cite></EndNote>[9]。文献ADDINEN.CITE<EndNote><Cite><Author>Nguyen</Author><Year>2018</Year><RecNum>216</RecNum><DisplayText><styleface="superscript">[25]</style></DisplayText><record><rec-number>216</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620486052">216</key></foreign-keys><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>T.H.Nguyen</author><author>T.K.Nguyen</author><author>H.D.Han</author><author>V.D.Nguyen</author></authors></contributors><titles><title>OptimalPowerControlandLoadBalancingforUplinkCell-FreeMulti-UserMassiveMIMO</title><secondary-title>IEEEAccess</secondary-title></titles><periodical><full-title>IEEEAccess</full-title></periodical><pages>14462-14473</pages><volume>6</volume><keywords><keyword>MIMOcommunication</keyword><keyword>Uplink</keyword><keyword>Powercontrol</keyword><keyword>Loadmanagement</keyword><keyword>Receivers</keyword><keyword>Interference</keyword><keyword>Antennas</keyword><keyword>MassiveMIMO</keyword><keyword>powerallocation</keyword><keyword>userassociation</keyword></keywords><dates><year>2018</year></dates><isbn>2169-3536</isbn><urls></urls><electronic-resource-num>10.1109/ACCESS.2018.2797874</electronic-resource-num></record></Cite></EndNote>[25]以最小化发送功率为目标，提出了一种基于负载平衡的AP选择算法。文献ADDINEN.CITEADDINEN.CITE.DATA[28,29]分析了AP选择与大尺度衰落、接收功率以及信噪比之间的关系，提出了一种最大化系统和速率的AP选择算法。文献ADDINEN.CITE<EndNote><Cite><Author>Boroujerdi</Author><Year>2017</Year><RecNum>221</RecNum><DisplayText><styleface="superscript">[27]</style></DisplayText><record><rec-number>221</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620486052">221</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>M.N.Boroujerdi</author><author>A.Abbasfar</author><author>M.Ghanbari</author></authors></contributors><titles><title>AntennaassignmentinCellFreeMassiveMIMOsystems</title><secondary-title>2017IranianConferenceonElectricalEngineering(ICEE)</secondary-title><alt-title>2017IranianConferenceonElectricalEngineering(ICEE)</alt-title></titles><pages>1747-1751</pages><keywords><keyword>Antennas</keyword><keyword>Wirelesscommunication</keyword><keyword>Noisemeasurement</keyword><keyword>MassiveMIMO</keyword><keyword>distributedantennasystems</keyword><keyword>precoding</keyword><keyword>resourceallocation</keyword><keyword>user-antennaassociation</keyword><keyword>antennaassignment</keyword><keyword>cellularsystems</keyword></keywords><dates><year>2017</year><pub-dates><date>2-4May2017</date></pub-dates></dates><urls></urls><electronic-resource-num>10.1109/IranianCEE.2017.7985333</electronic-resource-num></record></Cite></EndNote>[27]以用户为中心，提出了一种AP选择算法，该算法根据AP与用户之间的信道质量，在系统频谱效率的约束下以最小化系统链路能量消耗为目的，为用户分配AP。最后，在优化导频功率方面，文献ADDINEN.CITE<EndNote><Cite><Author>Nguyen</Author><Year>2018</Year><RecNum>224</RecNum><DisplayText><styleface="superscript">[34]</style></DisplayText><record><rec-number>224</rec-number><foreign-keys><keyapp="EN"db-id="5w5xwx9ro9rdf4ef0xk52wpj2rx9v9p2ttxt"timestamp="1620486052">224</key></foreign-keys><ref-typename="ConferenceProceedings">10</ref-type><contributors><authors><author>T.K.Nguyen</author><author>T.H.Nguyen</author></authors></contributors><titles><title>PerformanceofAssigningPilotSequencesinCellFreeMassiveMIMOunderSINRConstraints</title><secondary-title>2018IEEESeventhInternationalConferenceonCommunicationsandElectronics(ICCE)</secondary-title><alt-title>2018IEEESeventhInternationalConferenceonCommunicationsandElectronics(ICCE)</alt-title></titles><pages>121-126</pages><keywords><keyword>MIMOcommunication</keyword><keyword>Interference</keyword><keyword>Qualityofservice</keyword><keyword>Signaltonoiseratio</keyword><keyword>Uplink</keyword><keyword>Antennaarrays</keyword><keyword>Resourcemanagement</keyword></keywords><dates><year>2018</year><pub-dates><date>18-20July2018</date></pub-dates></dates><urls></urls><electronic-resource-num>10.1109/CCE.2018.8465748</electronic-resource-num></record></Cite></EndNote>[34]采用迭代逼近的思想，提出了一种导频功率控制策略，该方案具有较高的复杂度，当无小区大规模MIMO系统中AP和用户数量较多时，该方案就难以适用。另外还有文献研究了一种最小化最大的信道估计误差均方值的导频功率优化