LTE/LTE-A网络层关键技术
摘要
为了满足IMT-A的需求,LTE物理层技术以MIMO-OFDM为基础,采用多天线技术,把空间域作为了另一个新资源,可以达到更高的频谱效率；并且其延伸技术--多用户MIMO,又进一步提高了系统的性能。通过采用OFDM技术,LTE系统可以有效的控制小区内干扰,但是如果邻小区采用相同时频资源则会带来小区间干扰,严重影响系统性能,特别是在异构场景中,因此需要采用小区间干扰协调技术来改善小区边缘用户的性能。论文的研究内容如下：
本文通过LTE系统的典型场景,搭建LTE系统级仿真平台,验证了LTE系统各个场景下的系统性能。每种场景都是以MIMO、调度、链路自适应等技术为基础,包括针对提高小区容量的单用户和多用户场景,抑制小区间干扰提升小区边缘频谱效率的多点协作场景,以及在业务分布不均匀的条件下的异构网络场景。
本文重点研究了LTE多用户MIMO的预编码算法和用户选择算法。基于半静态用户选择,本文提出了一种考虑潜在用户干扰的起始用户选择准则,与传统的选择最佳的单用户为起始用户选择准则相比,这种算法能够提升半静态用户选择的性能而不带来任何复杂度的增加,在用户数量较大的情况下,性能提升更为明显。另外,为了改善一次半静态用户选择在用户数较大的情况下性能的损失较大,本文提出了一种多次半静态用户选择算法,是一种算法性能和复杂度的折中。
在异构场景下通过范围扩展技术增大了接入低功率节点的用户数,能够更好的分担宏基站的负载,但是在小区边缘带来了很强的宏基站的干扰,通过几乎空子帧(ABS)方案,能够缓解小区边缘的强干扰,但是会造成宏小区用户的调度次数的减少,通过低功率几乎空子帧技术(LP-ABS),能够适当提高宏小区用户的吞吐量,也能适当的降低对低功率节点边缘用户的干扰。本文提出的一种通过小区间交换CQI和RSRP的小区间协作调度算法,能够很好的提高小区的平均谱效率和小区边缘用户谱效率,而且能够适应小区用户分布的变化。
To meet the requirements of the IMT-A, LTE physical layer technology is based on MIMO-OFDM. Through the Multi-antenna technology, spatial being regard as another new resources, achieving higher spectral efficiency. Beside, multi-user MIMO technology further improve the performance of the system. By Orthogonal Frequency Division Multiplexing, LTE system has a good control of the intra-cell interference, but if the adjacent cell using the same frequency resources, it will bring the inter-cell interference seriously affect system performance, especially in heterogeneous scenario, inter-cell interference coordination is required to improve the performance of the cell-edge users. The contents are as follows:
System level simulation platform is built to verify the performance of several typical scenarios in the LTE system involving single-user, multi-user as well as heterogeneous network scenario. Each scenario is a combination of MIMO techniques, scheduling, link adaptation techniques and so on.
This paper focuses on the LTE multi-user MIMO precoding and scheduling algorithm. Selection criteria of starting user based on semi-static scheme considering the potential user's interference present in this paper is compared with the traditional selection of the best single-user. It's proved that this algorithm can improve the performance of the semi-static users selection without cause any increase in the complexity, and the performance increase is more pronounced when the number of users is large. In addition, semi-static users selection will loss the performance when the number of user is large, this paper presents an algorithm named several times semi-static user selection have a tradeoff of performance and complexity
To share the load of the macro basestation, users belong to macro basestation access to the low power node through range extension technique in heterogeneous scenario, but this brings a strong interference of the macro base station in the cell edge. By almost blanks subframe (ABS) scheme, it is possible to alleviate the strong interference of the cell edge, but it will cause a decrease the schedule opportunity of macrocell. Low power almost blank subframe (LP-ABS) can appropriately improve the throughput of the macrocell user, and also reduce the interference on the edge of the low-power node user. An inter-cell interference coordination scheduling algorithm by exchanging CQI and RSRP information is presented, which can improve the average cell spectral efficiency and cell edge user spectral efficiency, and able to adapt to changes in the distribution of users and business.
本文通过LTE系统的典型场景,搭建LTE系统级仿真平台,验证了LTE系统各个场景下的系统性能。每种场景都是以MIMO、调度、链路自适应等技术为基础,包括针对提高小区容量的单用户和多用户场景,抑制小区间干扰提升小区边缘频谱效率的多点协作场景,以及在业务分布不均匀的条件下的异构网络场景。
本文重点研究了LTE多用户MIMO的预编码算法和用户选择算法。基于半静态用户选择,本文提出了一种考虑潜在用户干扰的起始用户选择准则,与传统的选择最佳的单用户为起始用户选择准则相比,这种算法能够提升半静态用户选择的性能而不带来任何复杂度的增加,在用户数量较大的情况下,性能提升更为明显。另外,为了改善一次半静态用户选择在用户数较大的情况下性能的损失较大,本文提出了一种多次半静态用户选择算法,是一种算法性能和复杂度的折中。
在异构场景下通过范围扩展技术增大了接入低功率节点的用户数,能够更好的分担宏基站的负载,但是在小区边缘带来了很强的宏基站的干扰,通过几乎空子帧(ABS)方案,能够缓解小区边缘的强干扰,但是会造成宏小区用户的调度次数的减少,通过低功率几乎空子帧技术(LP-ABS),能够适当提高宏小区用户的吞吐量,也能适当的降低对低功率节点边缘用户的干扰。本文提出的一种通过小区间交换CQI和RSRP的小区间协作调度算法,能够很好的提高小区的平均谱效率和小区边缘用户谱效率,而且能够适应小区用户分布的变化。
To meet the requirements of the IMT-A, LTE physical layer technology is based on MIMO-OFDM. Through the Multi-antenna technology, spatial being regard as another new resources, achieving higher spectral efficiency. Beside, multi-user MIMO technology further improve the performance of the system. By Orthogonal Frequency Division Multiplexing, LTE system has a good control of the intra-cell interference, but if the adjacent cell using the same frequency resources, it will bring the inter-cell interference seriously affect system performance, especially in heterogeneous scenario, inter-cell interference coordination is required to improve the performance of the cell-edge users. The contents are as follows:
System level simulation platform is built to verify the performance of several typical scenarios in the LTE system involving single-user, multi-user as well as heterogeneous network scenario. Each scenario is a combination of MIMO techniques, scheduling, link adaptation techniques and so on.
This paper focuses on the LTE multi-user MIMO precoding and scheduling algorithm. Selection criteria of starting user based on semi-static scheme considering the potential user's interference present in this paper is compared with the traditional selection of the best single-user. It's proved that this algorithm can improve the performance of the semi-static users selection without cause any increase in the complexity, and the performance increase is more pronounced when the number of users is large. In addition, semi-static users selection will loss the performance when the number of user is large, this paper presents an algorithm named several times semi-static user selection have a tradeoff of performance and complexity
To share the load of the macro basestation, users belong to macro basestation access to the low power node through range extension technique in heterogeneous scenario, but this brings a strong interference of the macro base station in the cell edge. By almost blanks subframe (ABS) scheme, it is possible to alleviate the strong interference of the cell edge, but it will cause a decrease the schedule opportunity of macrocell. Low power almost blank subframe (LP-ABS) can appropriately improve the throughput of the macrocell user, and also reduce the interference on the edge of the low-power node user. An inter-cell interference coordination scheduling algorithm by exchanging CQI and RSRP information is presented, which can improve the average cell spectral efficiency and cell edge user spectral efficiency, and able to adapt to changes in the distribution of users and business.
引文
[1]Erik Dahlman, Stefan Parkvall and Johan Skold. "4G LTE/LTE-Advance for Mobile Broadband," Academic Press,2011
[2]3GPP, TR 36.814 Further advancements for E-UTRA physical layer aspects, 2012.
[3]3GPP, TS 36.213 Physical layer procedures,2012.
[4]Volker Pauli, Juan Diego Naranjo, Eiko Seidel "Heterogeneous LTE Networks and Inter-Cell Interference Coordination", Nomor Research GmbH, Munich, Germany, December,2010
[5]3GPP, TS 36.211 Physical channels and modulation,2010
[6]沈嘉,3GPP长期演进(LTE)技术原理与系统设计,人民邮电出版社,2008：1-231
[7]John G. Proakis, Digital Communications,电子工业出版社,2009.
[8]R. Srinivasan, J. Zhuang, L. Jalloul, R. Novak, and J. Park, "IEEE 802.16m Evaluation Methodology Document," IEEE 802.16 Broadband Wireless Access Working Group, Tech. Rep.,2008.
[9]Xin He; Kai Niu; Zhiqiang He; Jiaru Lin;, "Link Layer Abstraction in MIMO-OFDM System," Cross Layer Design,2007. IWCLD'07. International Workshop on, vol., no., pp.41-44,20-21 Sept.2007
[10]ITU-R.2135,Guidelines for evaluation of radio interface technologies for IMT-Advanced,2009.
[11]3GPP, TR 25.996, Spatial channel model for Multiple Input Multiple Output (MIMO) simulations,2012.
[12]R1-093996, " Consideration on MU-MIMO and Related Signaling Support in1 LTE-A", Texas Instruments,3GPP TSG RAN WG1 58 bis, October,2009
[13]Q. H. Spencer, A. L. Swindlehurst, and M. Haardt, "Zero-Forcing Methods for Downlink Spatial Multiplexing in Multiuser MIMO Channels," IEEE Transactions on Signal Processing, vol.52, no.2, pp.461-470,February 2004.
[14]M. Sadek, A. Tarighat, and A. H. Sayed, "A Leakage-Based Precoding Scheme for Downlink Multi-User MIMO channels," IEEE Transactions on Wireless Communications, vol.6, no.5, pp.1711-1721, May 2007.
[15]Boccardi, F.; Huang, H.; Trivellato, M.;, "Multiuser eigenmode transmission for mimo broadcast channels with limited feedback," Signal Processing Advances in Wireless Communications,2007. SPAWC 2007. IEEE 8th Workshop on, vol., no., pp.1-5,17-20 June 2007
[16]Z. Shen, R. Chen, J. G. Andrews, R. W. Heath, and B. L. Evans, "Low Complexity User Selection Algorithms for Multiuser MIMO Systems With Block Diagonalization," IEEE Transactions on Signal Processing, vol.54, no.9, pp. 3658-3664, September 2006.
[17]L. Liu, R. Chen, S. Geirhofer, K. Sayana, Z. Shi, and Y. Zhou. "Downlink MIMO in LTE-Advanced SU-MIMO vs MU-MIMO," IEEE Communications Magazine, February 2012.
[18]L. Liu, Y.-H. Nam, and J. Zhang, "Proportional Fair Scheduling for Multi-Cell Multi-User MIMO systems," Information Sciences and Systems (CISS) 44th Annual Conference on,2010.
[19]T. Yoo and A. Goldsmith, "On the Optimality of Multiantenna Broadcast Scheduling Using Zero-Forcing Beamforming," IEEE Journal on Selection Areas in Communications, vol.24, no.3, pp.528-541, March 2006.
[20]R1-103831, "Results for MU-MIMO under 4 TX Evaluation Assumptions," NEC Group,3GPP TSG-RAN WG1 #61, June 2010.
[21]R1-100117, "Further Discussions on Feedback Framework for SU/MU MIMO,' Samsung,3GPP TSG RAN WG1 Meeting #59, January 2010.
[22]R1-101218,"Performance of DL MU-MIMO Based on Implicit Feedback Scheme in LTE-Advanced", NTT DOCOMO,3GPP TSG RAN WG1 Meeting #60, February,2010.
[23]R1-094845, "MU-MIMO Performance Comparison of Two Feedback Assumptions:Rel-8 Codebook and Spatial Covariance," Motorola,3GPP. TSG RAN1 #59, November 2009.
[24]R1-122085," Discussion on the features and signaling support for non-zero transmit power ABS", Fujitsu,3GPP TSG-RAN1 #69, May,2012
[25]R1-122127," On signalling support for reduced power ABS", ZTE,3GPP TSG-RAN1 #69, May,2012
[26]R1-122403," Performance Evaluation of Non-zero Transmit Power ABS for FeICIC", Nokia Siemens Networks, Nokia,3GPP TSG-RAN1 #69, May,2012
[27]R1-122474," On Signalling Support for Non-zero Transmit Power ABS" Alcatel-Lucent Shanghai Bell, Alcatel-Lucent,3GPP TSG-RAN1 #69, May,2012
[28]Rl-122531," Discussion on the signalling support for non-zero transmit power ABS". KDDI,3GPP TSG-RAN1 #69, May,2012
[29]Chiang, M.; Chee Wei Tan; Palomar, D.P.; O'Neill, D.; Julian, D.;, "Power Control By Geometric Programming," Wireless Communications, IEEE Transactions on, vol.6, no.7, pp.2640-2651, July 2007
[30]Gjendemsj, A.; Gesbert, D.; Oien, G.E.; Kiani, S.G.;, "Binary Power Control for Sum Rate Maximization over Multiple Interfering Links," Wireless Communications, IEEE Transactions on, vol.7, no.8, pp.3164-3173, August 2008
[2]3GPP, TR 36.814 Further advancements for E-UTRA physical layer aspects, 2012.
[3]3GPP, TS 36.213 Physical layer procedures,2012.
[4]Volker Pauli, Juan Diego Naranjo, Eiko Seidel "Heterogeneous LTE Networks and Inter-Cell Interference Coordination", Nomor Research GmbH, Munich, Germany, December,2010
[5]3GPP, TS 36.211 Physical channels and modulation,2010
[6]沈嘉,3GPP长期演进(LTE)技术原理与系统设计,人民邮电出版社,2008：1-231
[7]John G. Proakis, Digital Communications,电子工业出版社,2009.
[8]R. Srinivasan, J. Zhuang, L. Jalloul, R. Novak, and J. Park, "IEEE 802.16m Evaluation Methodology Document," IEEE 802.16 Broadband Wireless Access Working Group, Tech. Rep.,2008.
[9]Xin He; Kai Niu; Zhiqiang He; Jiaru Lin;, "Link Layer Abstraction in MIMO-OFDM System," Cross Layer Design,2007. IWCLD'07. International Workshop on, vol., no., pp.41-44,20-21 Sept.2007
[10]ITU-R.2135,Guidelines for evaluation of radio interface technologies for IMT-Advanced,2009.
[11]3GPP, TR 25.996, Spatial channel model for Multiple Input Multiple Output (MIMO) simulations,2012.
[12]R1-093996, " Consideration on MU-MIMO and Related Signaling Support in1 LTE-A", Texas Instruments,3GPP TSG RAN WG1 58 bis, October,2009
[13]Q. H. Spencer, A. L. Swindlehurst, and M. Haardt, "Zero-Forcing Methods for Downlink Spatial Multiplexing in Multiuser MIMO Channels," IEEE Transactions on Signal Processing, vol.52, no.2, pp.461-470,February 2004.
[14]M. Sadek, A. Tarighat, and A. H. Sayed, "A Leakage-Based Precoding Scheme for Downlink Multi-User MIMO channels," IEEE Transactions on Wireless Communications, vol.6, no.5, pp.1711-1721, May 2007.
[15]Boccardi, F.; Huang, H.; Trivellato, M.;, "Multiuser eigenmode transmission for mimo broadcast channels with limited feedback," Signal Processing Advances in Wireless Communications,2007. SPAWC 2007. IEEE 8th Workshop on, vol., no., pp.1-5,17-20 June 2007
[16]Z. Shen, R. Chen, J. G. Andrews, R. W. Heath, and B. L. Evans, "Low Complexity User Selection Algorithms for Multiuser MIMO Systems With Block Diagonalization," IEEE Transactions on Signal Processing, vol.54, no.9, pp. 3658-3664, September 2006.
[17]L. Liu, R. Chen, S. Geirhofer, K. Sayana, Z. Shi, and Y. Zhou. "Downlink MIMO in LTE-Advanced SU-MIMO vs MU-MIMO," IEEE Communications Magazine, February 2012.
[18]L. Liu, Y.-H. Nam, and J. Zhang, "Proportional Fair Scheduling for Multi-Cell Multi-User MIMO systems," Information Sciences and Systems (CISS) 44th Annual Conference on,2010.
[19]T. Yoo and A. Goldsmith, "On the Optimality of Multiantenna Broadcast Scheduling Using Zero-Forcing Beamforming," IEEE Journal on Selection Areas in Communications, vol.24, no.3, pp.528-541, March 2006.
[20]R1-103831, "Results for MU-MIMO under 4 TX Evaluation Assumptions," NEC Group,3GPP TSG-RAN WG1 #61, June 2010.
[21]R1-100117, "Further Discussions on Feedback Framework for SU/MU MIMO,' Samsung,3GPP TSG RAN WG1 Meeting #59, January 2010.
[22]R1-101218,"Performance of DL MU-MIMO Based on Implicit Feedback Scheme in LTE-Advanced", NTT DOCOMO,3GPP TSG RAN WG1 Meeting #60, February,2010.
[23]R1-094845, "MU-MIMO Performance Comparison of Two Feedback Assumptions:Rel-8 Codebook and Spatial Covariance," Motorola,3GPP. TSG RAN1 #59, November 2009.
[24]R1-122085," Discussion on the features and signaling support for non-zero transmit power ABS", Fujitsu,3GPP TSG-RAN1 #69, May,2012
[25]R1-122127," On signalling support for reduced power ABS", ZTE,3GPP TSG-RAN1 #69, May,2012
[26]R1-122403," Performance Evaluation of Non-zero Transmit Power ABS for FeICIC", Nokia Siemens Networks, Nokia,3GPP TSG-RAN1 #69, May,2012
[27]R1-122474," On Signalling Support for Non-zero Transmit Power ABS" Alcatel-Lucent Shanghai Bell, Alcatel-Lucent,3GPP TSG-RAN1 #69, May,2012
[28]Rl-122531," Discussion on the signalling support for non-zero transmit power ABS". KDDI,3GPP TSG-RAN1 #69, May,2012
[29]Chiang, M.; Chee Wei Tan; Palomar, D.P.; O'Neill, D.; Julian, D.;, "Power Control By Geometric Programming," Wireless Communications, IEEE Transactions on, vol.6, no.7, pp.2640-2651, July 2007
[30]Gjendemsj, A.; Gesbert, D.; Oien, G.E.; Kiani, S.G.;, "Binary Power Control for Sum Rate Maximization over Multiple Interfering Links," Wireless Communications, IEEE Transactions on, vol.7, no.8, pp.3164-3173, August 2008