多用户OFDM系统的子载波和比特分配算法研究
摘要
OFDM(正交频分复用)最突出的优点是频谱利用率高、抗多径时延能力强,适合未来高速宽带无线通信的应用。在宽带移动OFDM系统中,不同的子信道经受不同的信道衰落,具有不同的传输能力。需要研究更加有效的无线资源分配及管理策略,以便在有限的带宽上达到更高频谱效率、更高的发射功率利用率以及更好的系统性能。因此自适应资源分配得到广泛关注,是当前OFDM研究热点问题之一。
在多径频率选择性衰落信道中,不同的子信道受到不同的衰落,具有不同的传输能力,在多用户OFDM系统中,由于传输路径不同,各用户的信道衰落是相互独立的。各个子信道的衰落情况不一样,对于一个用户呈现出深衰落的子载波不一定对其他用户也呈现深衰落。因此可以考虑一种根据瞬时信道特性来为每一个用户分配子载波的多用户子载波分配方法。这样只有当一个子载波在所有的用户中都处于深衰落时才会被弃用,从而更有效地利用信道资源。
目前,对于多用户系统中的资源分配问题有许多研究方法,这些方法大体上可以分为两类:静态分配方法和动态分配方法。静态分配方法有两种典型的分配策略:OFDM-TDMA和OFDM-FDMA。静态分配算法中,子载波和比特的分配是预先设定的,没有充分地利用瞬时信道增益信息。本文主要分析动态分配算法,从给定总数据速率条件下的总体发射功率最小化问题和给定总发射功率限制条件下的数据速率最大化问题两个角度研究了OFDM系统的资源分配问题。本文在已有算法的基础上研究了一种改进的多用户OFDM系统子载波和比特分配算法。本算法采用分步的思想对系统资源进行动态分配,在给定误码率和用户最小传输速率要求的条件下,使系统总的发送功率最小。仿真结果表明,该算法计算简单,优化效率高。
OFDM (Orthogonal Frequency Division Multiplexing) has outstanding advantages because that it could utilize frequency resource sufficiently and robust against channel delay spread. It's suitable for high speed and broadband wireless communication. In broadband OFDM system over mobile fading channels, each individual sub channel has its own attenuation. So each sub channel has different channel capacity. A more efficient radio resource allocation and management scheme should be proved to transmit with higher spectrum and power efficiency and higher system performance. Adaptive allocation of resource gains more and more attention and becomes one of the focuses in OFDM research.
In multiuser environment, the so-called 'mutiuser diversity' by dynamically allocating subcarriers among the users can be used. Since the subcarriers that appear to be in deep fade for one user may not be in deep fades for others, spectral efficiency can be improved, and equivalently, transmit power can be reduced.
Now, there are many ways to solve how to allocate the resources. Generally, they can be divided into two classes: fixed resource allocation and dynamic resource allocation. Fixed resource allocation schemes, such as time division access (TDMA) and frequency division multiple access (FDMA), assign an independent dimension, e.g. time slot or sub channel, to each user. A fixed resource allocation scheme is rigid regardless of the current channel condition. This paper mostly analyzes dynamic allocation algorithm. From the total data rate to be under the conditions of the overall transmission power to minimize the problems and limitations of transmission power under the condition of maximum data rate of two angles on the issue of OFDM system resource allocation problem. This paper studies on an improved algorithm for subcarrier and bit allocation in multiuser OFDM systems. The algorithm uses the idea of step-by-step for dynamic allocation of resources and tries to minimize the total transmission power with given BER and each user's requirement on minimum rate. Simulation result shows that the proposed algorithm is simple in calculation and high in efficiency.
在多径频率选择性衰落信道中,不同的子信道受到不同的衰落,具有不同的传输能力,在多用户OFDM系统中,由于传输路径不同,各用户的信道衰落是相互独立的。各个子信道的衰落情况不一样,对于一个用户呈现出深衰落的子载波不一定对其他用户也呈现深衰落。因此可以考虑一种根据瞬时信道特性来为每一个用户分配子载波的多用户子载波分配方法。这样只有当一个子载波在所有的用户中都处于深衰落时才会被弃用,从而更有效地利用信道资源。
目前,对于多用户系统中的资源分配问题有许多研究方法,这些方法大体上可以分为两类:静态分配方法和动态分配方法。静态分配方法有两种典型的分配策略:OFDM-TDMA和OFDM-FDMA。静态分配算法中,子载波和比特的分配是预先设定的,没有充分地利用瞬时信道增益信息。本文主要分析动态分配算法,从给定总数据速率条件下的总体发射功率最小化问题和给定总发射功率限制条件下的数据速率最大化问题两个角度研究了OFDM系统的资源分配问题。本文在已有算法的基础上研究了一种改进的多用户OFDM系统子载波和比特分配算法。本算法采用分步的思想对系统资源进行动态分配,在给定误码率和用户最小传输速率要求的条件下,使系统总的发送功率最小。仿真结果表明,该算法计算简单,优化效率高。
OFDM (Orthogonal Frequency Division Multiplexing) has outstanding advantages because that it could utilize frequency resource sufficiently and robust against channel delay spread. It's suitable for high speed and broadband wireless communication. In broadband OFDM system over mobile fading channels, each individual sub channel has its own attenuation. So each sub channel has different channel capacity. A more efficient radio resource allocation and management scheme should be proved to transmit with higher spectrum and power efficiency and higher system performance. Adaptive allocation of resource gains more and more attention and becomes one of the focuses in OFDM research.
In multiuser environment, the so-called 'mutiuser diversity' by dynamically allocating subcarriers among the users can be used. Since the subcarriers that appear to be in deep fade for one user may not be in deep fades for others, spectral efficiency can be improved, and equivalently, transmit power can be reduced.
Now, there are many ways to solve how to allocate the resources. Generally, they can be divided into two classes: fixed resource allocation and dynamic resource allocation. Fixed resource allocation schemes, such as time division access (TDMA) and frequency division multiple access (FDMA), assign an independent dimension, e.g. time slot or sub channel, to each user. A fixed resource allocation scheme is rigid regardless of the current channel condition. This paper mostly analyzes dynamic allocation algorithm. From the total data rate to be under the conditions of the overall transmission power to minimize the problems and limitations of transmission power under the condition of maximum data rate of two angles on the issue of OFDM system resource allocation problem. This paper studies on an improved algorithm for subcarrier and bit allocation in multiuser OFDM systems. The algorithm uses the idea of step-by-step for dynamic allocation of resources and tries to minimize the total transmission power with given BER and each user's requirement on minimum rate. Simulation result shows that the proposed algorithm is simple in calculation and high in efficiency.
引文
[1]佟学俭,罗涛.OFDM移动通信技术原理与应用[M].北京:人民邮电出版社,2003:
[2]黎海涛,张靖.无线OFDM技术[J].通信技术,2002,18(4):9-11.
[3]金旗,装昌幸,张振生.OFDM技术的基本原理[J].通信技术,2002,6:32-36.
[4]Czylwik A.Adaptive OFDM for wideband radio channels[J].IEEE Proc.Globecom'96(S0895-1195),1996,1:713-718.
[5]Fischer R F H,Huber J B.A New Loading algorithm For Discrete Multimode Transmission[C].In Proc.IEEE GLOBECOM London,1996:724-728.
[6]尹长川,罗涛,乐光新.多载波宽带无线通信技术[M].北京:北京邮电大学出版社,2004:
[7]魏克军,益晓新.一种基于OFDM系统的自适应加载算法[J].数字电视与数字视频,2002,246:10-12.
[8]刘培,葛建华,刘刚.多用户自适应调制OFDM系统的高效子载波分配方案[J].电子与信息学报,2004,26(6):871-875.
[9]Wong C Y,Cheng R S,Letaief K B.Multiuser OFDM with adaptive subcarrier bit and power allocation[C].IEEE J.Select.Areas Commun.1999,17:1747-1758.
[10]Zhang Guodong.Subcarrier and Bit Allocation for Real-time Services in Multiuser OFDM Systems[C].2004 IEEE International Conference'on Communications,Paris,2004,5:2985-2989.
[11]Kim Inhyoung,Lee Hae Leem,Kim Beomsup,Lee Yong H.On the Use of Linear Programming for Dynamic Subchannel and Bit Allocation in Multiuser OFDM[C].IEEE 2001,2001:3648-3652.
[12]Zhang Yingjun and Letaief K B.Multiuser Subcarrier and Bit Allocation along with Adaptive Cell Selection for OFDM Transmission[C].IEEE 2002,2002:861-865.
[13]Jang Jiho,Lee Kwang Bok,and Lee Yong-Hwan.Transmit Power and Bit Allocations for OFDM Systems in a Fading Charmel[C].IEEE GLOBECOM 2003,2003:858-862.
[14]王文博,郑侃.宽带无线通信OFDM技术[M].北京:人民邮电出版社,2003:
[15]叶志猛,季卫华.OFDM应用中的关键技术[J].中国移动通信,2003,5(12):79-81.
[16]张贤达,保铮.通信信号处理[M].北京:国防工业出版社,2002:25-150.
[17]Wong Cheong Yui,Tsui C Y,Cheng Roger S,Letaief K B.A Real-time Sub-carrier Allocation Scheme for Multiple Access Downlink OFDM Transmission[C].IEEE Vehicular Technology Conference.Amsterdam,1999:1124-1128.
[18]Teng Y,Nagaosa T,Mori K.Proposal of adaptive sub channel and bit allocation method for OFDM access wireless LAN systems[C].IEEE,Proceeding IEEE,VTC'03,2003,2:910-914.
[19]束峰,罗琳,吴乐南.OFDM通信系统中的一种通用的信道估计模型[J].电路与系统学报,2001,6(2):39-43.
[20]Lawrey E.Multiuser OFDM[C].Proceedings of the IEEE international symposium on signal processing and Its applications,Brisbane,Australia,1999:761-764.
[21]Rhee W,Cioffi J M.Increasing in capacity of multiuser OFDM system using dynamic subchannel allocation[C].Proc.IEEE Int.Vehicular Tech.Conf.Tokyo,Japan,May 2000(2):1085-1089.
[22]Jang J,Lee K B.Transmit power adaptation for multiuser OFDM systems[C].IEEE J Sel.Areas Commun,Feb.2003,21(2):171-178.
[23]贺志强,王晓湘,吴伟陵.一种新的时变衰落信道下MIMO系统的功率分配与白适应调制算法[J].电子学报,2004,9(32):1556-1559.
[24]Tu J C,Cioffi J M.A Loading Algorithm for the Concatenation of Codes with Multi-channel Modulation Method[C].IEEE GLOBECOM,1990:1183-1187.
[25]Didem Kivanc,Liu Hui.Subcarrier allocation and power control for OFDMA[C].Proc IEEE VTC'2000.Pacific Grove,CA USA,2000,1:147-151.
[26]Gesbert David,Shaft,Mansoor,Shiu,Da-shan,Smith,Peter.J.and Naguib,Ayman.From Theorv to Practice:An overview of MIMO Space-Time Coded Wireless Systems Selected[J].Aleas.Cornlnun,Apr 2003,21(3):281-302.
[27]李精华,侯春萍,孙山林.多用户OFDM自适应组合调制及比特分配算法的实现[J].桂林电子工业学院学报,2006,2(1):20-23.
[28]Goldsmith A J,Chua S G.Variable-rate variable-power M-QAM for fading channels[C].IEEE VTC'96.Vehicular Technology Conference Proceedings.Atlanta,Georgia,USA,1996:815-819.
[29]赵亚红,张忠培,吴伟陵.一种基于最大容量的多载波系统自适应调制和功率分配算法[J].电子与信急学报,2001,25(7):938-942.
[30]Richard van Nee,Ramjee Prasad.OFDM Wireless Multimedia Communications[C].Artech House,Boston,London,2000.
[31]李晓辉,刘乃安,易克初.多用户OFDM系统中的联合子载波和功率分配算法[J].西安电子科技大学学报(自然科学版),2006,33(3):366-370.
[32]Wong C Y,Cheng R S.Multiuser OFDM with Adaptive Subcarrier,Bit,and Power Allocation[J].IEEE Journal on Selected Areas in Communications.1999,17(10):1747-1758.
[33]D.Hughes-Hartogs.Ensemble Modem Structure for Imperfect Transmission Media[C].U.S.Patent,July,1987.
[34]IEEE Std 802.11a-1999 Supplement to IEEE Std 802.11[S].1999.
[35]Chow P S,Cioffi J M,and J A C Bingham.A practical discrete multitone transceiver loading algorithm for data transmission over spectrally shaped channels[J].IEEE Trans.Commun,Feb.Mar.Apr.1995,43:773-775.
[36]Tellambura C.Computation of the continuous-time PAR of an OFDM signal with BPSK sub-carriers[C].1EEE commu Letters,May.2001,5(5):185-187.
[37]Kuhn H W.The Hungarian Method for the Assignment Problem[J].Naval Research Logistics Quarterly,1995,2(1):83-97.
[38]Louise Min Chuin Hoo.Multiuser transmit optimization for multicarrier modulation systems[C].California in United States:Stanford University,2000.
[39]Campello J.A paractical bit loading for DMT[C].ICC,1999.1999:801-805.
[40]Rohling H,Grunheid R.Performance of an OFDM-TDMA mobile communication system[J].Proc.IEEE Vehicular Technology Conf.(VTC'96),Atlanta,GA,1996:1589-1593.
[41]Lai S K,Cheng R S,Ben K.Adaptive trellis coded MQAM and power optimization for OFDM transmission[C].Proc.IEEE VTC'99,Houston TX,1999.
[42]肖建华,张平.OFDM系统的自适应调制仿真分析[J].无线电工程,2003,第三卷(1):17-19.
[43]杨洁,寇卫东,李晓辉.多用户OFDM系统中改进的动态子载波与功率分配算法[J].电子科技,2005(11):39-42,47.
[44]柯峰,叶梧.多用户OFDM系统中的快速白适应分配策略[J].华南理工大学学报,2005,33(3):40-43.
[45]薛亮,罗汉文,宋文涛.多用户OFDM系统中的快速自适应分配策略[J].电讯技术,2005(3):72-76.
[46]钱学荣,岳殿武,张力军.频率选择型衰落信道中多用户OFDM系统的自适应分配算法[J].电子学报,2002(4):508-511.
[47]付铎如,吴玉成.OFDM中自适应比特及功率分配的分析[J].信号处理,2005,21(1):45-48.
[48]丁玉美,高西全,彭学愚.数字信号处理[M].西安:西安电子科技大学出版社,1995:78-102.
[2]黎海涛,张靖.无线OFDM技术[J].通信技术,2002,18(4):9-11.
[3]金旗,装昌幸,张振生.OFDM技术的基本原理[J].通信技术,2002,6:32-36.
[4]Czylwik A.Adaptive OFDM for wideband radio channels[J].IEEE Proc.Globecom'96(S0895-1195),1996,1:713-718.
[5]Fischer R F H,Huber J B.A New Loading algorithm For Discrete Multimode Transmission[C].In Proc.IEEE GLOBECOM London,1996:724-728.
[6]尹长川,罗涛,乐光新.多载波宽带无线通信技术[M].北京:北京邮电大学出版社,2004:
[7]魏克军,益晓新.一种基于OFDM系统的自适应加载算法[J].数字电视与数字视频,2002,246:10-12.
[8]刘培,葛建华,刘刚.多用户自适应调制OFDM系统的高效子载波分配方案[J].电子与信息学报,2004,26(6):871-875.
[9]Wong C Y,Cheng R S,Letaief K B.Multiuser OFDM with adaptive subcarrier bit and power allocation[C].IEEE J.Select.Areas Commun.1999,17:1747-1758.
[10]Zhang Guodong.Subcarrier and Bit Allocation for Real-time Services in Multiuser OFDM Systems[C].2004 IEEE International Conference'on Communications,Paris,2004,5:2985-2989.
[11]Kim Inhyoung,Lee Hae Leem,Kim Beomsup,Lee Yong H.On the Use of Linear Programming for Dynamic Subchannel and Bit Allocation in Multiuser OFDM[C].IEEE 2001,2001:3648-3652.
[12]Zhang Yingjun and Letaief K B.Multiuser Subcarrier and Bit Allocation along with Adaptive Cell Selection for OFDM Transmission[C].IEEE 2002,2002:861-865.
[13]Jang Jiho,Lee Kwang Bok,and Lee Yong-Hwan.Transmit Power and Bit Allocations for OFDM Systems in a Fading Charmel[C].IEEE GLOBECOM 2003,2003:858-862.
[14]王文博,郑侃.宽带无线通信OFDM技术[M].北京:人民邮电出版社,2003:
[15]叶志猛,季卫华.OFDM应用中的关键技术[J].中国移动通信,2003,5(12):79-81.
[16]张贤达,保铮.通信信号处理[M].北京:国防工业出版社,2002:25-150.
[17]Wong Cheong Yui,Tsui C Y,Cheng Roger S,Letaief K B.A Real-time Sub-carrier Allocation Scheme for Multiple Access Downlink OFDM Transmission[C].IEEE Vehicular Technology Conference.Amsterdam,1999:1124-1128.
[18]Teng Y,Nagaosa T,Mori K.Proposal of adaptive sub channel and bit allocation method for OFDM access wireless LAN systems[C].IEEE,Proceeding IEEE,VTC'03,2003,2:910-914.
[19]束峰,罗琳,吴乐南.OFDM通信系统中的一种通用的信道估计模型[J].电路与系统学报,2001,6(2):39-43.
[20]Lawrey E.Multiuser OFDM[C].Proceedings of the IEEE international symposium on signal processing and Its applications,Brisbane,Australia,1999:761-764.
[21]Rhee W,Cioffi J M.Increasing in capacity of multiuser OFDM system using dynamic subchannel allocation[C].Proc.IEEE Int.Vehicular Tech.Conf.Tokyo,Japan,May 2000(2):1085-1089.
[22]Jang J,Lee K B.Transmit power adaptation for multiuser OFDM systems[C].IEEE J Sel.Areas Commun,Feb.2003,21(2):171-178.
[23]贺志强,王晓湘,吴伟陵.一种新的时变衰落信道下MIMO系统的功率分配与白适应调制算法[J].电子学报,2004,9(32):1556-1559.
[24]Tu J C,Cioffi J M.A Loading Algorithm for the Concatenation of Codes with Multi-channel Modulation Method[C].IEEE GLOBECOM,1990:1183-1187.
[25]Didem Kivanc,Liu Hui.Subcarrier allocation and power control for OFDMA[C].Proc IEEE VTC'2000.Pacific Grove,CA USA,2000,1:147-151.
[26]Gesbert David,Shaft,Mansoor,Shiu,Da-shan,Smith,Peter.J.and Naguib,Ayman.From Theorv to Practice:An overview of MIMO Space-Time Coded Wireless Systems Selected[J].Aleas.Cornlnun,Apr 2003,21(3):281-302.
[27]李精华,侯春萍,孙山林.多用户OFDM自适应组合调制及比特分配算法的实现[J].桂林电子工业学院学报,2006,2(1):20-23.
[28]Goldsmith A J,Chua S G.Variable-rate variable-power M-QAM for fading channels[C].IEEE VTC'96.Vehicular Technology Conference Proceedings.Atlanta,Georgia,USA,1996:815-819.
[29]赵亚红,张忠培,吴伟陵.一种基于最大容量的多载波系统自适应调制和功率分配算法[J].电子与信急学报,2001,25(7):938-942.
[30]Richard van Nee,Ramjee Prasad.OFDM Wireless Multimedia Communications[C].Artech House,Boston,London,2000.
[31]李晓辉,刘乃安,易克初.多用户OFDM系统中的联合子载波和功率分配算法[J].西安电子科技大学学报(自然科学版),2006,33(3):366-370.
[32]Wong C Y,Cheng R S.Multiuser OFDM with Adaptive Subcarrier,Bit,and Power Allocation[J].IEEE Journal on Selected Areas in Communications.1999,17(10):1747-1758.
[33]D.Hughes-Hartogs.Ensemble Modem Structure for Imperfect Transmission Media[C].U.S.Patent,July,1987.
[34]IEEE Std 802.11a-1999 Supplement to IEEE Std 802.11[S].1999.
[35]Chow P S,Cioffi J M,and J A C Bingham.A practical discrete multitone transceiver loading algorithm for data transmission over spectrally shaped channels[J].IEEE Trans.Commun,Feb.Mar.Apr.1995,43:773-775.
[36]Tellambura C.Computation of the continuous-time PAR of an OFDM signal with BPSK sub-carriers[C].1EEE commu Letters,May.2001,5(5):185-187.
[37]Kuhn H W.The Hungarian Method for the Assignment Problem[J].Naval Research Logistics Quarterly,1995,2(1):83-97.
[38]Louise Min Chuin Hoo.Multiuser transmit optimization for multicarrier modulation systems[C].California in United States:Stanford University,2000.
[39]Campello J.A paractical bit loading for DMT[C].ICC,1999.1999:801-805.
[40]Rohling H,Grunheid R.Performance of an OFDM-TDMA mobile communication system[J].Proc.IEEE Vehicular Technology Conf.(VTC'96),Atlanta,GA,1996:1589-1593.
[41]Lai S K,Cheng R S,Ben K.Adaptive trellis coded MQAM and power optimization for OFDM transmission[C].Proc.IEEE VTC'99,Houston TX,1999.
[42]肖建华,张平.OFDM系统的自适应调制仿真分析[J].无线电工程,2003,第三卷(1):17-19.
[43]杨洁,寇卫东,李晓辉.多用户OFDM系统中改进的动态子载波与功率分配算法[J].电子科技,2005(11):39-42,47.
[44]柯峰,叶梧.多用户OFDM系统中的快速白适应分配策略[J].华南理工大学学报,2005,33(3):40-43.
[45]薛亮,罗汉文,宋文涛.多用户OFDM系统中的快速自适应分配策略[J].电讯技术,2005(3):72-76.
[46]钱学荣,岳殿武,张力军.频率选择型衰落信道中多用户OFDM系统的自适应分配算法[J].电子学报,2002(4):508-511.
[47]付铎如,吴玉成.OFDM中自适应比特及功率分配的分析[J].信号处理,2005,21(1):45-48.
[48]丁玉美,高西全,彭学愚.数字信号处理[M].西安:西安电子科技大学出版社,1995:78-102.
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