基于LTE-Advanced系统下行共享仿真链路搭建与性能分析
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摘要
随着无线通信技术的发展,人们对信息获取提出了更高的要求,强调了种类的丰富性、渠道的便利性以及时效的敏捷性。第4代移动通信技术标准LTE-Advanced能够有效保证网络传输的高效性,它在LTE长期演进技术的基础上引入了诸如多载波聚合、多点协作、中继技术以及增强MIMO等关键技术从而显著地提高了通信系统的上下行峰值速率和频谱效率,同时有效改善了小区边缘的性能。
作为LTE-Advanced下行物理层最重要的信道之一,下行共享信道承载了传输信道DSCH的数据,并且在物理层实现上采用了许多关键技术以保证数据传输的可靠性与高效性。本文基于LTE-Advanced物理层相关协议研究下行共享信道中的关键技术,分析技术原理以及具体的实施方法,并通过搭建的物理层链路进行仿真分析系统的各项性能指标。本文的总体工作内容归纳如下：
(1)研究下行共享信道发送端处理流程,并搭建发送端浮点仿真算法模型。在此基础上对下行共享信道接收端算法进行探讨,包括解MIMO、解调、解扰、解速率匹配、解信道编码等关键算法,并据此搭建接收端浮点仿真算法模型。和发送端浮点模型进行联合调试验证模型的可行性。
(2)在下行共享信道浮点算法模型基础上研究发送端定点算法处理方案,主要包括其中的调制模块、MIMO模块以及功率补偿模块的处理,在此基础上搭建了下行共享信道定点发送模型。通过浮点与定点模型的波型比较,验证定点方案的可行性。
(3)基于已搭建的链路模型,在不同场景下对不同的调制方式下的性能、不同MIMO配置下的性能以及系统吞吐量进行仿真,验证物理层模型的可靠性同时,测试不同条件下的系统性能。通过链路仿真表明：第一,在低信噪比条件下,高阶调制误码性能非常不理想；第二,不同MIMO配置时,发送分集的可靠性最高,空间复用的可靠性最差,对于开环和闭环空间复用,开环的误码率更高,随着发送天线数的增加,空间复用性能对信道质量更加敏感；第三,在最高配置前提下,LTE-Advanced拥有比LTE更高的频谱利用效率和系统下行吞吐量,且当信道质量较好时,两者性能差异能够达到近10倍。
With the development of wireless communication technology, people put forward higher requrements to information gathering. They emphasize the richness of species, the convenience of the channels and the agility of timing. The4th generation mobile communication technology LTE-Advanced could ensure the efficiency of network transmission reliably. It introduces some technologies like multi-carrier aggregation, multi-point collaboration, relay technology and enhanced MIMO technology based on LTE, significantly improves the communication system uplink and downlink peak rate and spectrum efficiency, and effectively improve the performance of the cell edge.
As one of the most significant physical channel in LTE-Advanced, the physical shared channel (PDSCH) carries the data from downlink shared transport channel, and is introduced in multiple key technologies in physical layer Achievement to ensure the reliability and effiency of data transmission. Based on physical key technologies in LTE-Advanced PDSCH, this article analyses the technical priciples and do some simulation and analysis through building physical layer link on related technologies. This research work is summarized as follows:
(1)Study the processes of PDSCH sender and build the floating-point algorithm simulation model of that. And then probe the receiver algorithm of PDSCH based on sender, including some critical algorithms like MIMO decoder, demodulation, descrambling, rate-matching decoder, channel decoder and so on, and build the floating-point algorithm simulation model of the receiver. Then associate the floating-point model of the sender to make joint simulations and verify its feasibility.
(2)Discuss the fixed-point algorithm process of the sender according to the floating-point algorithm model of PDSCH. Based on that, build the fixed-point algorithm simulation model of PDSCH sender and verify the feasibility of fixed-point plan through comparing the waverform of floating-point model with the waveform of fixed-point model.
(3)Arithmetic simulation based on the channel model built in different scenarios, such as in different modulation types, different MIMO configurations, system throughput to testify the reliability of the physical layer model and system performance.The simulation results shows conclusions as follows:Firstly, the bit-error-rate performance is not satisfactory in the low signal-noise-rate environment with high order modulation. Secondly, between different MIMO configurations, the reliability are much higher in transmit diversity than in spatial multiplexing. At the same time, the BER performance is better in closed-loop spatial multiplexing than in open-loop spatial multiplexing. The sptial multiplexing performance can be more sensitive to the channel quality with the increasing transmit antennas. Thirdly, there could be much higher spectrum efficiency and system downlink throughput of LTE-Advanced than that of LTE under highest configuration. Its performance differences can reach almost ten times when in the circumstances of better channel quality.
作为LTE-Advanced下行物理层最重要的信道之一,下行共享信道承载了传输信道DSCH的数据,并且在物理层实现上采用了许多关键技术以保证数据传输的可靠性与高效性。本文基于LTE-Advanced物理层相关协议研究下行共享信道中的关键技术,分析技术原理以及具体的实施方法,并通过搭建的物理层链路进行仿真分析系统的各项性能指标。本文的总体工作内容归纳如下：
(1)研究下行共享信道发送端处理流程,并搭建发送端浮点仿真算法模型。在此基础上对下行共享信道接收端算法进行探讨,包括解MIMO、解调、解扰、解速率匹配、解信道编码等关键算法,并据此搭建接收端浮点仿真算法模型。和发送端浮点模型进行联合调试验证模型的可行性。
(2)在下行共享信道浮点算法模型基础上研究发送端定点算法处理方案,主要包括其中的调制模块、MIMO模块以及功率补偿模块的处理,在此基础上搭建了下行共享信道定点发送模型。通过浮点与定点模型的波型比较,验证定点方案的可行性。
(3)基于已搭建的链路模型,在不同场景下对不同的调制方式下的性能、不同MIMO配置下的性能以及系统吞吐量进行仿真,验证物理层模型的可靠性同时,测试不同条件下的系统性能。通过链路仿真表明：第一,在低信噪比条件下,高阶调制误码性能非常不理想；第二,不同MIMO配置时,发送分集的可靠性最高,空间复用的可靠性最差,对于开环和闭环空间复用,开环的误码率更高,随着发送天线数的增加,空间复用性能对信道质量更加敏感；第三,在最高配置前提下,LTE-Advanced拥有比LTE更高的频谱利用效率和系统下行吞吐量,且当信道质量较好时,两者性能差异能够达到近10倍。
With the development of wireless communication technology, people put forward higher requrements to information gathering. They emphasize the richness of species, the convenience of the channels and the agility of timing. The4th generation mobile communication technology LTE-Advanced could ensure the efficiency of network transmission reliably. It introduces some technologies like multi-carrier aggregation, multi-point collaboration, relay technology and enhanced MIMO technology based on LTE, significantly improves the communication system uplink and downlink peak rate and spectrum efficiency, and effectively improve the performance of the cell edge.
As one of the most significant physical channel in LTE-Advanced, the physical shared channel (PDSCH) carries the data from downlink shared transport channel, and is introduced in multiple key technologies in physical layer Achievement to ensure the reliability and effiency of data transmission. Based on physical key technologies in LTE-Advanced PDSCH, this article analyses the technical priciples and do some simulation and analysis through building physical layer link on related technologies. This research work is summarized as follows:
(1)Study the processes of PDSCH sender and build the floating-point algorithm simulation model of that. And then probe the receiver algorithm of PDSCH based on sender, including some critical algorithms like MIMO decoder, demodulation, descrambling, rate-matching decoder, channel decoder and so on, and build the floating-point algorithm simulation model of the receiver. Then associate the floating-point model of the sender to make joint simulations and verify its feasibility.
(2)Discuss the fixed-point algorithm process of the sender according to the floating-point algorithm model of PDSCH. Based on that, build the fixed-point algorithm simulation model of PDSCH sender and verify the feasibility of fixed-point plan through comparing the waverform of floating-point model with the waveform of fixed-point model.
(3)Arithmetic simulation based on the channel model built in different scenarios, such as in different modulation types, different MIMO configurations, system throughput to testify the reliability of the physical layer model and system performance.The simulation results shows conclusions as follows:Firstly, the bit-error-rate performance is not satisfactory in the low signal-noise-rate environment with high order modulation. Secondly, between different MIMO configurations, the reliability are much higher in transmit diversity than in spatial multiplexing. At the same time, the BER performance is better in closed-loop spatial multiplexing than in open-loop spatial multiplexing. The sptial multiplexing performance can be more sensitive to the channel quality with the increasing transmit antennas. Thirdly, there could be much higher spectrum efficiency and system downlink throughput of LTE-Advanced than that of LTE under highest configuration. Its performance differences can reach almost ten times when in the circumstances of better channel quality.
引文
[1]崔明.LTE_Advanced中参考信号的设计研究[D].南京：南京邮电大学硕士学位论文.2011
[2]沈嘉,索士强,全海洋等.3GPP长期演进(LTE)技术原理与系统设计[M],北京：人民邮电出版社.2008.11,pp：35-60
[3]Stefania Sesia, Issam Toufik, Matthew Baker. LTE-The UMTS Long Term Evolution: From Theory to Practice[M]. United Kingdom:John Wiley & Sons Ltd,2009:25-61
[4]包东智.LTE的优势及其运营发展[J].电信快报.2008(06),pp：20-23
[5]AMITAVA GHOSH, RAPEEPAT RATASUK. LTE-ADVANCED:NEXT-GENERATION WIRELESS BROADBAND TECHNOLOGY[J]. IEEE Wireless Communications.2010.6,pp:10-22
[6]林辉4G LTE-Advanced技术标准[J].电信网技术.2010.5(05),pp：22-25
[7]熊道琪,黑勇,周玉梅.基于WiMax的OFDM模式的低开销FFT设计[J].半导体技术,2008(09),pp：829-832
[8]Sanghyeon Lee 1, Kyongkuk Cho 1, Kwanghun Kim2. PERFORMANCE ANALYSIS OF LTE-ADVANCED SYSTEM IN THE DOWNLINK SPATIAL CHANNEL MODEL[C]. International Conference on Network Infrastructure and Digital Content.2009
[9]张海滨.正交频分复用的基本原理与关键技术[M].北京：国防工业出版社出版.2006.1,pp：54-58
[10]康弘俊,许从方.基于脉冲成形技术降低OFDM峰均比[J].通信技术.2012(02),pp：35-38
[11]夏树强,戴博,梁春丽LTE-Advanced中的载波聚合中的载波聚合技术研究[J].中兴通讯技术.2011.10(05),pp：30-33
[12]H G Myung, J Lim, D J Goodman. Peak-to-Average Power Ratio of Single Carrier FDMA Signals with Pulse Shaping[C].17th IEEE Personal,Indoor and Mobile Radio Communication.2006, pp:349-355
[13]J. Berkmann, C. Carbonelli, F. Dietrich, et al., "On 3G LTE Terminal Implementation Standard, Algorithms, Complexities and Challenges," [C] Wireless Communications and Mobile Computing Conference,2008,pp:970-975
[14]姚天任,孙洪.现代数字信号处理[M].武汉：华中科技大学出版社.2003,pp：5-8
[15]王知津,王荣瑶.信息的属性和特性：基于Shannon通信模型的理解[J].情报探索.2011(11),pp：1-6
[16]李小文,许虎.LTE系统中Turbo编码的研究与DSP实现[J].集成电路应用.2011(08),pp：59-62
[17]3GPP. TS36.211. V10.3.0 3GPP TSG RAN E-UTRA Physical Channels and Modulation (Release 10) [S].2011.9
[18]王视环,宋荣方.QPP交织器的性能分析[J].吉林大学学报(信息科学版).2010.5(03),pp：219-224
[19]梁广东,高宪军,史彦斌,于海霞.基于MAX-Log-MAP算法和DSP芯片的Turbo译码器[J].电子测量技术,2008(09),pp：129-132
[20]Charls J.Stone. A Course in Probability and StatistiCs[J]. Duxbury Publish.2003.7,pp:76-82
[21]王建新.基于星座图的数字调制方式识别[J].通信学报,2004.6(06),pp：166-173
[22]Tarokh V, Seahadri N, Calderbank A R. Space-time codes for high data rate wireless communication performance criterion and code construction[J]. IEEE Journal on IT,1998, 44(2), pp:744-765
[23]吕锋,王虹,刘皓春等.信息理论与编码[M].北京：人民邮电出版社.2006.7,pp：88-90
[24]康桂华.MIMO无线通信原理及应用[M].北京：电子工业出版社,2009.7,pp：120-131
[25]Matthias Patzold移动衰落信道[M].陈伟译.北京：电子工业出版社,2009.1,pp：3-9
[26]Calcev,G.,Chizhik,D.,Goransson,B.,Howard,S.,Huang,H.,Kogiantis,A.,Molisch,A.F.,Moust akas, A.L.,Reed, D.,Hao Xu. A Wideband Spatial Channel Model for System-Wide Simulations [J]. Vehicular Technology,2007, vol.56, pp:389-403
[27]姜建里.MIMO技术在LTE中的应用[J].电信网技术,2011.4(04),pp：11-15
[28]林雪红,牛凯,贺志强.3GPP LTE系统的预编码码本选择方案[J].2010.2(01),pp：23-26
[29]Xiaolin Hou,Shubo Li'Danpu Liu,Changchuan Yin,Ouangxin Yue.On two-dimensional adaptive charmel estimation in OFDM systems[J].Vehicular Technology Conference,2004 VTC 2004-Fall.2004 IEEE 60th Volume 1.26.29 Sept.2004,pp:498-502
[30]Asad Mehmood, Waqas Aslam Cheema. CHANNEL ESTIMATION FOR LTE DOWNLINK[J]. Blekinge Institute of Technology.2009.9,pp:56-59
[31]焦慧颖LTE-Advanced中的下行8天线码本设计[J].电信网技术,2010.12(12),pp：6-9
[32]刘晋勋LTE-Advanced系统多用户MIMO预编码方法[D].成都：电子科技大学硕十学位论文.2011
[33]TAROKH V, SESHADR1 N, and CALDERBANKA R.Space-Time Block Codes from Orthogonal Designs [J].IEEE Transactions on Information Theory,1999(45),pp:1456-1467
[34]周宁.CRC的算法及计算机编程实现[J].通信与广播电视,1995(01),pp：61-68
[35]3GPP. TS36.212. V10.3.0 3GPP TSG RAN E-UTRA Multiplexing and channel coding (Release 10) [S].2011.9
[36]3GPP. TS36.213. V10.3.0 3GPP TSG RAN E-UTRA Physical layer procedures (Release 10) [S].2011.9
[37]方秋巳.FDD-LTE下行链路MIMO研究[D].武汉：武汉理工大学硕士学位论文.2011
[38]Marvin K.Simon, Ramesh Annavajjala. On the Optimality of Bit Detection of Certain Digital Modulations [J]. IEEE TRANSACTIONS ON COMMUNICATIONS,2005,53(2), pp:299-300
[39]Volker, Kuhn. Wireless Communications over MIMO Channels[J], John Wiley & Sons Inc, 2005, pp:152-159
[40]刘永辉,王芳,黄莎莎等.Wimax系统三阶交调失真对EVM影响的评估[J].通信技术.2011(07),pp：70-71
[41]Jonathan Duplicy, Biljana Badic, Rajarajan Balraj. Research Article:MU-MIMO in LTE System[J]. Hindawi Publishing Corporation,2011,pp:1-14
[42]梁寅明,潘峮,袁超等.TDD-LTE移动通信系统高速铁路场景共存研究[J].广东通信技术.2011.02,pp：45-49
[2]沈嘉,索士强,全海洋等.3GPP长期演进(LTE)技术原理与系统设计[M],北京：人民邮电出版社.2008.11,pp：35-60
[3]Stefania Sesia, Issam Toufik, Matthew Baker. LTE-The UMTS Long Term Evolution: From Theory to Practice[M]. United Kingdom:John Wiley & Sons Ltd,2009:25-61
[4]包东智.LTE的优势及其运营发展[J].电信快报.2008(06),pp：20-23
[5]AMITAVA GHOSH, RAPEEPAT RATASUK. LTE-ADVANCED:NEXT-GENERATION WIRELESS BROADBAND TECHNOLOGY[J]. IEEE Wireless Communications.2010.6,pp:10-22
[6]林辉4G LTE-Advanced技术标准[J].电信网技术.2010.5(05),pp：22-25
[7]熊道琪,黑勇,周玉梅.基于WiMax的OFDM模式的低开销FFT设计[J].半导体技术,2008(09),pp：829-832
[8]Sanghyeon Lee 1, Kyongkuk Cho 1, Kwanghun Kim2. PERFORMANCE ANALYSIS OF LTE-ADVANCED SYSTEM IN THE DOWNLINK SPATIAL CHANNEL MODEL[C]. International Conference on Network Infrastructure and Digital Content.2009
[9]张海滨.正交频分复用的基本原理与关键技术[M].北京：国防工业出版社出版.2006.1,pp：54-58
[10]康弘俊,许从方.基于脉冲成形技术降低OFDM峰均比[J].通信技术.2012(02),pp：35-38
[11]夏树强,戴博,梁春丽LTE-Advanced中的载波聚合中的载波聚合技术研究[J].中兴通讯技术.2011.10(05),pp：30-33
[12]H G Myung, J Lim, D J Goodman. Peak-to-Average Power Ratio of Single Carrier FDMA Signals with Pulse Shaping[C].17th IEEE Personal,Indoor and Mobile Radio Communication.2006, pp:349-355
[13]J. Berkmann, C. Carbonelli, F. Dietrich, et al., "On 3G LTE Terminal Implementation Standard, Algorithms, Complexities and Challenges," [C] Wireless Communications and Mobile Computing Conference,2008,pp:970-975
[14]姚天任,孙洪.现代数字信号处理[M].武汉：华中科技大学出版社.2003,pp：5-8
[15]王知津,王荣瑶.信息的属性和特性：基于Shannon通信模型的理解[J].情报探索.2011(11),pp：1-6
[16]李小文,许虎.LTE系统中Turbo编码的研究与DSP实现[J].集成电路应用.2011(08),pp：59-62
[17]3GPP. TS36.211. V10.3.0 3GPP TSG RAN E-UTRA Physical Channels and Modulation (Release 10) [S].2011.9
[18]王视环,宋荣方.QPP交织器的性能分析[J].吉林大学学报(信息科学版).2010.5(03),pp：219-224
[19]梁广东,高宪军,史彦斌,于海霞.基于MAX-Log-MAP算法和DSP芯片的Turbo译码器[J].电子测量技术,2008(09),pp：129-132
[20]Charls J.Stone. A Course in Probability and StatistiCs[J]. Duxbury Publish.2003.7,pp:76-82
[21]王建新.基于星座图的数字调制方式识别[J].通信学报,2004.6(06),pp：166-173
[22]Tarokh V, Seahadri N, Calderbank A R. Space-time codes for high data rate wireless communication performance criterion and code construction[J]. IEEE Journal on IT,1998, 44(2), pp:744-765
[23]吕锋,王虹,刘皓春等.信息理论与编码[M].北京：人民邮电出版社.2006.7,pp：88-90
[24]康桂华.MIMO无线通信原理及应用[M].北京：电子工业出版社,2009.7,pp：120-131
[25]Matthias Patzold移动衰落信道[M].陈伟译.北京：电子工业出版社,2009.1,pp：3-9
[26]Calcev,G.,Chizhik,D.,Goransson,B.,Howard,S.,Huang,H.,Kogiantis,A.,Molisch,A.F.,Moust akas, A.L.,Reed, D.,Hao Xu. A Wideband Spatial Channel Model for System-Wide Simulations [J]. Vehicular Technology,2007, vol.56, pp:389-403
[27]姜建里.MIMO技术在LTE中的应用[J].电信网技术,2011.4(04),pp：11-15
[28]林雪红,牛凯,贺志强.3GPP LTE系统的预编码码本选择方案[J].2010.2(01),pp：23-26
[29]Xiaolin Hou,Shubo Li'Danpu Liu,Changchuan Yin,Ouangxin Yue.On two-dimensional adaptive charmel estimation in OFDM systems[J].Vehicular Technology Conference,2004 VTC 2004-Fall.2004 IEEE 60th Volume 1.26.29 Sept.2004,pp:498-502
[30]Asad Mehmood, Waqas Aslam Cheema. CHANNEL ESTIMATION FOR LTE DOWNLINK[J]. Blekinge Institute of Technology.2009.9,pp:56-59
[31]焦慧颖LTE-Advanced中的下行8天线码本设计[J].电信网技术,2010.12(12),pp：6-9
[32]刘晋勋LTE-Advanced系统多用户MIMO预编码方法[D].成都：电子科技大学硕十学位论文.2011
[33]TAROKH V, SESHADR1 N, and CALDERBANKA R.Space-Time Block Codes from Orthogonal Designs [J].IEEE Transactions on Information Theory,1999(45),pp:1456-1467
[34]周宁.CRC的算法及计算机编程实现[J].通信与广播电视,1995(01),pp：61-68
[35]3GPP. TS36.212. V10.3.0 3GPP TSG RAN E-UTRA Multiplexing and channel coding (Release 10) [S].2011.9
[36]3GPP. TS36.213. V10.3.0 3GPP TSG RAN E-UTRA Physical layer procedures (Release 10) [S].2011.9
[37]方秋巳.FDD-LTE下行链路MIMO研究[D].武汉：武汉理工大学硕士学位论文.2011
[38]Marvin K.Simon, Ramesh Annavajjala. On the Optimality of Bit Detection of Certain Digital Modulations [J]. IEEE TRANSACTIONS ON COMMUNICATIONS,2005,53(2), pp:299-300
[39]Volker, Kuhn. Wireless Communications over MIMO Channels[J], John Wiley & Sons Inc, 2005, pp:152-159
[40]刘永辉,王芳,黄莎莎等.Wimax系统三阶交调失真对EVM影响的评估[J].通信技术.2011(07),pp：70-71
[41]Jonathan Duplicy, Biljana Badic, Rajarajan Balraj. Research Article:MU-MIMO in LTE System[J]. Hindawi Publishing Corporation,2011,pp:1-14
[42]梁寅明,潘峮,袁超等.TDD-LTE移动通信系统高速铁路场景共存研究[J].广东通信技术.2011.02,pp：45-49