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1.
《Signal Processing, IEEE Transactions on》2005,53(9):3572-3582
We consider the design of biorthogonal, as opposed to orthonormal, discrete multitone (DMT) systems supporting multiple services in a single antennae setting. The services may have differing quality of service (QoS) requirements, quantified by bit rate and symbol error rate specifications. Different users on the system can be potentially assigned different number of subchannels. Our goal is to minimize the transmitted power given the QoS specifications for the different users, subject to the knowledge of the channel and colored interference at the receiver input of the DMT system. We find an optimum bit loading scheme that distributes the bit rate transmitted across the various subchannels, where the precise subchannels are assigned to each user, and an optimum transceiver. Key conclusions are i) relaxing the orthonormality constraint yields no performance improvement; ii) the optimum transceiver is unaffected by changing service characteristics, and depends only on the channel and interference conditions; iii) the QoS requirements, the number of users, and the number of subchannels assigned to the different users only affect bitloading and subchannel assignment. 相似文献
2.
In this paper we present a computationally efficient, suboptimal integer bit allocation algorithm that maximizes the overall
data rate in multiuser orthogonal frequency division multiplexing (OFDM) systems implemented in wireless networks. Assuming
the complete knowledge of a channel and allowing a subchannel to be simultaneously shared by multiple users we have solved
this data rate maximization problem in two steps. The first step provides subchannel assignment to users considering the users’
requests on quality of service (QoS) expressed as the minimum signal-to-noise ratio (SNR) on each subchannel. The second step
provides transmit power and bit allocation to subchannels in order to maximize the overall data rate. To reduce computational
complexity of the problem we propose a simple method which assigns subchannels to users and distributes power and bits among
them. We have analyzed the performance of our proposed algorithm by simulation in a multiuser frequency selective fading environment
for various signal-to-noise ratios and various numbers of users in the system. We have concluded that our algorithm, unlike
other similar algorithms, is suitable for OFDM wireless networks, especially when signal-to-noise ratio in the channel is
low. Also, the results have shown that the total data rate grows with the number of users in the system. 相似文献
3.
该文研究了无线通信系统保证用户服务质量要求(QoS)的资源分配和调度策略,从信道遍历容量角度出发分析基于Round Robin (RR)和多用户分集/RR思想的调度策略,并提出一种性能更好的部分多用户分集调度策略。该策略将一帧分成若干子帧,子帧的大小以及当前用户集合由无线资源分配算法根据用户的速率要求确定,调度机在每个时刻将各子帧分配给当前用户集合中信道增益最好的用户。仿真结果表明,相比于RR调度和多用户分集/RR调度,部分多用户分集调度能够减少信道占用率并且提高平均信道容量。 相似文献
4.
An adaptive bit allocation algorithm is proposed for multiuser transmission in OFDM/CDMA systems. The proposed scheme takes
advantage of frequency diversity to dynamically allocate a suitable number of bits/per symbol on subcarriers of each user
based on the transmitting objectives such as the required transmission rate and BER. A suboptimal solution to the problem
of the bit allocation on subcarriers for each user is derived by minimizing the interference power from each user. Then an
algorithm for adjusting the number of allocated bits is used to further reduce the interference without changing the total
transmitted data rate. The performance obtained by minimizing the interference resulting from each user is studied in terms
of BER, transmission data rate and the system capacity supporting multiple users. The theoretical analysis and simulation
results show that the proposed algorithm substantially outperforms those reported previously. 相似文献
5.
Kaya O. Ulukus S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(5):1831-1836
We solve for the optimum signature sequence and power allocation policies that maximize the information-theoretic ergodic sum capacity of a code-division multiple-access (CDMA) system subject to fading. We show that at most N users may transmit at any given channel state, where N is the processing gain; and those users who are transmitting should be assigned orthogonal signature sequences. We also show that the power allocation policy that maximizes the capacity together with the choice of these signature sequences is single-user water-filling over sets of channel states that are favorable to each user. That is, the capacity maximizing signaling scheme is shown to dictate that the users allocate their powers and signature sequences in such a way that they always avoid interference from each other. 相似文献
6.
Shaowei Wang Fangjiang Huang Mindi Yuan Sidan Du 《International Journal of Communication Systems》2012,25(2):254-269
In this paper we study the resource allocation problem for the multiuser orthogonal frequency division multiplexing (OFDM)‐based cognitive radio (CR) systems with proportional rate constraints. The mutual interference introduced by primary user (PU) and cognitive radio user (also referred to secondary user, SU) makes the optimization problem of CR systems more complex. Moreover, the interference introduced to PUs must be kept under a given threshold. In this paper, the highest achievable rate of each OFDM subchannel is calculated by jointly considering the channel gain and interference level. First, a subchannel is assigned to the SU with the highest achievable rate. The remaining subchannels are always allocated to the SU that suffers the severest unjustness. Second, an efficient bit allocation algorithm is developed to maximize the sum capacity, which is again based on the highest achievable rate of each subchannel. Finally, an adjustment procedure is designed to maintain proportional fairness. Simulation results show that the proposed algorithm maximizes the sum capacity while keeping the proportional rate constraints satisfied. The algorithm exhibits a good tradeoff between sum capacity maximization and proportional fairness. Furthermore, the proposed algorithm has lower complexity compared with other algorithms, rendering it promising for practical applications. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
7.
Tang Lun Yan Jing-lin Li Qing Chen Qian-bin Wang Huan 《Wireless Personal Communications》2012,65(3):671-687
This paper consider the power allocation strategies in the cognitive radio (CR) system in the presence of channel estimation errors. As the user has different channel condition in CR systems, different amount of power resource is required to meets the QoS request. In order to guarantee the fairness of each CR user, ensure the interference from the primary user and other CR users meet the QoS requirement of the CR user and limit the interference that is caused by CR users on primary user within the range into the level that primary user can tolerate, we proposed some new power allocation schemes. The targets are to minimize the maximum power allocated to CR users, to maximize the minimum signal-to-interference-plus-noise ratio (SINR) among all CR users and to minimize the maximum outage probability over all CR users. The first power allocation scheme can be formulated using Geometric Programming (GP). Since GP problem is equivalent to the convex optimization problem, we can obtain the optimal solutions for the first scheme. The latter two power allocation schemes are not GP problems. We propose iterative algorithms to solve them. Simulation results show that proposed schemes can efficiently guarantee the fairness of CR users under the QoS constraint of the primary user and CR users. 相似文献
8.
在原有动态资源分配算法基础上,提出了一种基于用户速率需求的动态资源分配算法。该算法在满足用户数据速率需求和服务质量要求(QoS)的前提下,以用户公平性为原则,分步执行子载波和比特分配来降低系统总的发射功率。首先,通过比较不同子载波对用户速率的影响,引入速率影响因子,对子载波进行分配;然后为每个用户子载波分配比特,并根据用户速率需求进行比特调整。为了进一步降低系统的复杂度,提出了一种通过子载波分组来完成子载波比特分配的方法。仿真结果表明,该算法能够降低系统功耗、误码率和系统复杂度。 相似文献
9.
Muayad S. Al-Janabi Charalampos C. Tsimenidis Bayan S. Sharif Stéphane Y. Le Goff 《International Journal of Wireless Information Networks》2011,18(3):119-130
A cross-layer scheduling and resource allocation (SRA) strategy for an adaptive modulation and coding (AMC) based orthogonal
frequency multiple access (OFDMA) system is proposed. The objective of this paper is to maximize the system throughput as
a function of the bit error rate (BER) and the spectral efficiency based on the selected modulation and coding schemes (MCSs).
The proposed strategy contains two main algorithms. Firstly, the scheduling algorithm that aims to maximize the average system
throughput by arranging the users in distinct queues according to their priorities and selecting the best user of each queue
individually in order to guarantee a fair user service amongst different priority levels. Secondly, the resource allocation
algorithm that allocates the user, bit and power based on the channel conditions of the scheduling users and the transmission
power constraints. The transmitter of the investigated AMC-OFDMA system at the assigned base station (BS) divides the transmitted
OFDMA frame into sub-channels and assigns each sub-channel to a scheduled user. In this paper, we compare the performance
of the proposed SRA with the conventional first in first out (FIFO) queuing based scheduling and resource allocation strategies
used for an AMC-OFDMA system. The simulation results show that the investigated AMC-OFDMA system based on the proposed SRA
strategy outperforms the conventional approaches. 相似文献
10.
11.
Mohsen Ashourian Razieh Salimian Homayoun Mahdavi Nasab 《Wireless Personal Communications》2013,71(1):519-529
In orthogonal frequency division with multiple access (OFDMA) systems dynamic radio resource allocation improves overall performance by exploiting the multiuser diversity gains. A key issue in OFDMA is the allocation of the OFDM subcarriers and power among users sharing the channel. This paper proposes a new rate adaptive resource allocation scheme in the OFDMA downlink transmission system. Our proposed algorithm is based on the users’ sensitivity to the subcarrier allocation which means how frequency selective is the channel from the user’s perspective. As a result of frequency selectivity of the channel, different subchannels of the same user experience different levels of fade. However, how different they undergo fading could be measured by difference between maximum and minimum channel gain of that user. Our proposed method is based on difference between maximum channel gain and minimum channel gain for each user and uniform distribution of power among subcarriers. Simulation results show that the proposed algorithm achieves higher capacity over fixed TDMA method, and reported suboptimal methods with acceptable rate proportionality. 相似文献
12.
In this paper, we propose optimum and sub-optimum resource allocation and opportunistic scheduling solutions for orthogonal frequency division multiple access (OFDMA)-based multicellular systems. The applicability, complexity, and performance of the proposed algorithms are analyzed and numerically evaluated. In the initial setup, the fractional frequency reuse (FFR) technique for inter-cell interference cancellation is applied to classify the users into two groups, namely interior and exterior users. Adaptive modulation is then employed according to the channel state information (CSI) of each user to meet the symbol error rate (SER) requirement. There then, we develop subcarrier-and-bit allocation method, which maximizes the total system throughput subject to the constraints that each user has a minimum data rate requirement. The algorithm to achieve the optimum solution requires high computational complexity which hinders it from practicability. Toward this end, we propose a suboptimum method with the complexity extensively reduced to the order of O(NK), where N and K denote the total number of subcarriers and users, respectively. Numerical results show that the proposed algorithm approaches the optimum solution, yet it enjoys the features of simplicity, dynamic cell configuration, adaptive subcarrier-and-bit allocation, and spectral efficiency. 相似文献
13.
Karakayali M.K. Yates R.D. Razoumov L.V. 《Wireless Communications, IEEE Transactions on》2006,5(12):3492-3500
We investigate optimum rate assignment scheme maximizing network throughput on the downlink of a multirate CDMA wireless network. Systems employing orthogonal variable spreading factor (OVSF) codes as well as systems employing multiple codes have been studied. Our objective is to maximize the network throughput under constraints on total transmit power, total bandwidth and individual QoS requirements specified in terms of minimum rates. First, users are ordered based on their transmit energy per bit requirements to achieve the target received energy per bit to interference power spectral density ratio at the receivers. Based on the initial ordering, we prove that for systems employing multiple codes, greedy rate assignment yields maximum network throughput. For systems employing variable spreading codes, we show that greedy rate assignment is optimal if the minimum rate requirement of a user is larger than or equal to the minimum rate requirement of any other user with a larger transmit energy per bit requirement. Simulation results verify the superiority of the greedy algorithm under various system and channel assumptions 相似文献
14.
In this paper, a performance analysis is presented for user selection schemes in a single‐input multiple‐output spectrum sharing system. In the considered system, multiple secondary users try to use the licensed spectrum of a primary user in an opportunistic manner, in which an interference constraint for the primary user is satisfied. In this paper, we first use 2 conventional user selection schemes for single‐input multiple‐output spectrum sharing system and analyze the system performance for each scheme. We then propose a new user selection scheme that can overcome the limitations of those 2 conventional user selection schemes. As for the performance analysis, the average channel capacity, the outage probability, and the bit error rate performances of the system using the presented user selection schemes are analyzed and mathematical closed‐form expressions for the outage probability are derived. The performances of the system are evaluated using the derived mathematical formulas in different cases. In addition, Monte Carlo simulation results are also provided to show the accuracy and correctness of the performed analysis. 相似文献
15.
受组合投资理论的启发,提出了一种既利用历史信道状态信息,同时又有效保证主用户不受次系统传输所产生干扰的新的资源分配算法.该算法以系统速率的方差作为优化目标,同时通过引入用户间干扰门限来衡量次系统对主用户造成的干扰,并利用二次规划的方法对该问题进行求解.最后,给出经典算法与本算法的性能比较,仿真结果表明该算法在保证次系统传输速率保持在一定的期望速率的条件下,使其方差最小,同时又使主用户所受的干扰限定在所能承受的范围内. 相似文献
16.
Abstract-In a wireless multimedia code division multiple access (CDMA) system, the resources in terms of transmission rate and power should be efficiently distributed to each user to guarantee its quality-of-service (QoS) requirements. In, this paper, a resource allocation algorithm which combines packet scheduling and power assignment is proposed to achieve efficient resource utilization under QoS constraints. The packet scheduling is based on the fair packet loss sharing (FPLS) principle, and the power assignment is determined by the received power limited (RPL) scheme. The basic idea of FPLS is to schedule the transmission of multimedia packets in such a way that, all the users have a fair share of packet loss according to their QoS requirements, which maximizes the number of the served users with QoS satisfaction. The RPL scheme minimizes the received power for each packet. Given the propagation path loss, it in turn minimizes the transmitted power as well. The intercell interference from the scheduled packets is also limited in order to increase the system capacity. 相似文献
17.
18.
This paper proposes a queue-aware resource allocation algorithm which provides quality of service (QoS) guarantees. The proposed solution adopts a cross-layer design approach since it is aware of both users’ queue buffer states (data link layer) and channel quality state (physical layer). Main advantages of the proposed resource allocation algorithm are: the low computational complexity and its capacity of maintaining lower QoS violation probability than other multi-cellular schemes. The proposed solution can also result in enhanced cell-edge data rate and improved fairness performance. User minimum data rate and target bit error rate as considered as QoS parameters. Validation of the proposed algorithm is achieved through various simulation scenarios wherein QoS violation probability, system fairness, user average data rate and cell-edge throughput are investigated. Numerical results and complexity analysis demonstrate the efficiency and the feasibility of the proposed QoS-oriented approach. 相似文献
19.
Scheduling in multimedia CDMA wireless networks 总被引:2,自引:0,他引:2
Wireless systems in the future will have to provide multimedia services where different users have different physical-layer quality of service (QoS) requirements (e.g., bit energy per interference power density, E/sub b//N/sub 0/, or bit error rate and power constraints) and network-layer QoS requirements (e.g., delay bound, delay-jitter, throughput, and loss). We investigate the use of power control, processing gain and/or multiple codes, and scheduling in CDMA systems to accommodate these diverse service requirements. We first show that the instantaneous capacity region, given in terms of the set of user bit rates that can be supported simultaneously subject to peak power and E/sub b//N/sub 0/ constraints, is nonconvex. This suggests that by time-sharing the channel, one may be able to get better system throughput. We define the capacity region as the convex hull of the instantaneous capacity region and we show that it may be obtained by time sharing between operating points, where each user either uses full power or is silent (bang-bang control). We then consider the problem of scheduling so as to meet prespecified delay bounds or minimum service curve requirements for traffic streams, which are specified in terms of a traffic profile such as a sigma-rho constraint (enforced by a leaky bucket) and a guarantee that the system is stable. 相似文献
20.
We propose a simple distributed radio resource allocation algorithm for an OFDMA cellular system, which aims at minimizing the overall transmitted power subject to a rate constraint for each user. In order to reduce the problem complexity we use a single modulation; simulations show that the resulting performance degradation is negligible when the number of users is high enough. Moreover, we propose a simple distributed heuristic that, by reducing the rate constraints, steers the multicell system towards an stable resource allocation. Results show that the proposed system exhibits a great robustness to the destructive effects of multiple access interference. 相似文献