【作者】 王亚琛；

【导师】 刘元安；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2009， 博士

【摘要】 无线通信系统的传输技术在通信过程中发挥着至关重要的作用,特别在频带资源越来越紧缺的今天。有效的传输技术能够增加数据传输率,提高带宽的频谱效率。随着多入多出(MIMO)技术和正交频分复用(OFDM)技术在下一代移动通信系统中的应用,无线通信系统的传输技术也由传统的时间域传输扩展到时间域、频率域和空间域的三维联合传输。将MIMO和OFDM各自的优势应用在传输方案中,以建立高速、可靠的通信,成为下一代移动通信技术的发展趋势之一。本论文在国内外相关研究工作的基础上,针对MIMO无线通信系统所涉及的传输技术进行了深入研究,特别是在多小区MIMO广播信道的协作通信、及结合功率分配的优化协作通信,MIMO-OFDM系统的码分多址技术、及空时频正交码设计,分组多载波码分多址(MC-CDMA)的动态资源分配等方面取得了较大研究进展。论文的主要工作和创新之处在于：第一,对基于最大最小速率准则的MIMO广播信道的协作通信进行了研究。分析了迫零(ZF)协作通信和最小均方误差(MMSE)协作通信的和速率范围和基于最大最小速率准则所确定的用户符号功率的表达形式。根据块对角原理,结合MMSE准则,提出了基于MMSE准则的块对角协作通信。块对角协作通信不仅能够有效地抑制小区间干扰,还大大降低了实现复杂度。其在保证频谱效率的情况下提高了实施可行性。第二,研究了MIMO广播信道的优化协作通信。不同于基于最大最小速率准则的协作通信方案,根据用户的信道信息分配不同的功率,以提高数据速率。将用户符号的功率分配与协作通信联合进行优化,大大提高了系统的频谱效率。同时,根据优化协作通信的设计方案,提出了多用户环境下用户选择的准则。第三,研究了MIMO-OFDM系统的码分多址及空时频扩频。介绍了下行MIMO-OFDM系统的空时频扩展方案。基于原有的双正交码,提出了一种扩展双正交扩频码。这种扩频码在保证双正交性能的情况下,打破了原有的双正交码在长度上所受的“2的次方”的限制,能够更加灵活的应用在实际系统中。第四,对用于MIMO-OFDM下行链路中的无约束成对正交码进行了研究。提出了无约束成对正交码的设计方案,它满足无约束成对正交码设计准则,通过平衡用户的性能降低了多用户干扰的影响,保证了系统性能的提高。它充分利用多天线的特点,在发射天线之间实现了完全空间分集增益。同时,它能够构造出长度极为灵活的扩频码矩阵,可在性能得到保证的情况下节约频谱资源,使得其在实际应用中更加广泛。第五,研究了下行分组MC-CDMA系统中的动态资源分配算法。将系统中的子载波分成若干子波段组,并将用户分配至各个子波段组中,能够降低用户干扰,提高系统性能。根据优化理论提出了最优用户分组准则,其包含用户功率的分配,在实际系统中较难加以使用。结合MMSE检测提出了用户等效SINR,并用其作为用户分组的次优准则。根据两种排序方式提出两个用户分组的算法,其能够实现理想的频谱效率和误比特率性能,且实现复杂度较低。更多还原

【Abstract】 Transmission technology plays a very important role in the wireless communication systems, especially when the band resource is becoming more and more limited. Effective transmission is able to increase data rate and improve spectral efficiency. With the development of multiple input multiple output (MIMO) and orthogonal frequency division multiplexing (OFDM), the research on transmission has been extended to frequency domain and space domain besides time domain. It is the tendency to combine the advantages of both MIMO and OFDM, in order to establish high-rate reliable wireless systems.On the basis of international current research works, this thesis investigates some transmission technology in the MIMO wireless communication systems in depth, especially at base coordination in MIMO cellular broadcast channels, power allocation combined optimized coordinated transmission, code division multiplexing access (CDMA) in MIMO-OFDM systems, space-time-frequency spreading code design and dynamic resource allocation in grouped multiple carrier (MC) CDMA. Main work and innovations in this thesis are:Firstly, coordinated transmission based on max-min rate criterion in MIMO broadcast channel (BC) is investigated.The ranges of sum data rate of zero-forcing (ZF) and minimum mean square error (MMSE) coordinated transmissions are given, and the corresponding mathematic forms of power allocation of users’ symbols are presented. Based on block diagonalized (BD) and with MMSE criterions, BD coordinated transmission with MMSE criterion is proposed. BD coordinated transmission with MMSE effectively mitigates co-channel interference and significantly decrease the implemental complexity. Thus it ensures the desirable feasibility with high spectral efficiency.Secondly, optimized coordinated transmission in MIMO broadcast channel is investigated. Different from that based on max-min rate criterion, optimized coordinated transmission allocates users’ symbol power according to their channel information, in order to increase data rate. It has efficiently improved spectral efficiency of the systems to jointly optimize the power allocation of users’ symbol and coordinated transmission. Moreover, in accordance to the optimized coordinated scheme, user selection criterion for multiple user scenarios has been proposed.Thirdly, CDMA and space-time-frequency spreading MIMO-OFDM systems have been investigated. The three-dimensional spreading scheme in downlink MIMO-OFDM systems has been introduced. Motivated by the existing double orthogonal code (DOC), extended double orthogonal spreading code (E-DOSC) has been proposed. E-DOSC breaks the "2 square" limit on spreading length while keeping the double orthogonality. It could be used in the real systems more flexibly.Furthermore, non-limited pair-orthogonal code (NPOC) is investigated in downlink MIMO-OFDM systems.The code design of NPOC has been proposed, which satisfies design criterion of non-limited pair-orthogonality, suppresses multi-user interference (MUI) by balancing users’ performance, ensures the improvement of system performance. It explores the advantages of multiple antennas and realizes full space diversity among transmit antennas.Meanwhile, it has quite flexible code length and can save lots of band resource while performance is ensured.Finally, dynamic resource algorithms in downlink grouped MC-CDMA are investigated. By grouping sub-carriers into several sub-bands and allocating users to different sub-bands, MUI is decreased and performance is improved. The optimal user-grouping criterion is proposed, which is impractical because power allocation is included. With MMSE detection, equivalent SINR is proposed to be used as the grouping criterion. Two user-grouping algorithms are also proposed, which achieve ideal spectral efficiency and bit error rate, with low implemental complexity.更多还原