共查询到20条相似文献,搜索用时 15 毫秒
1.
The proportional fair scheduling (PFS) algorithm is implemented in current 3G wireless networks for high data rate delay-tolerant services. Though the algorithm has low implementation complexity, the problem of proportional fairness is NP-hard. An analytical expression is obtained to approximate the throughput of PFS in cellular networks over Rayleigh fading channels. Comparisons against simulation results show that the expression is accurate. 相似文献
2.
In the past years, several signaling protocols were proposed for OBS networks and the most popular one is the Just-Enough-Time
(JET) protocol. JET not only efficiently utilizes the network capacity, but also effectively reduces the end-to-end transmission
delay. However, the most critical defect of JET is its intrinsic deficiency: Fairness. The fairness problem is a traditional
problem common to various kinds of networks. It results in a phenomenon that bursts with a shorter number of hops are generally
favorized and hence deteriorates the network utilization as well. In this article, we investigate this problem and propose
a fair channel scheduling algorithm as a solution. Usually there is a tradeoff between fairness and blocking performance.
Accordingly, the objective of our scheme is to achieve a balance between the two conflicting metrics as much as possible.
In our scheme, each burst is associated with a dynamic priority which is defined by several characteristics of the burst.
When contention occurs, the proposed scheme picks the preferable burst and drops the other one according to their priorities.
From simulation results, we observed that the proposed scheme could improve fairness without causing significant reduction
in dropping performance. Furthermore, it increases the effective link utilization as well.
相似文献
Ching-Fang HsuEmail: |
3.
Pablo Jesus Argibay-Losada Kseniia Nozhnina Andrés Suárez-González Cándido López-García Manuel Fernández-Veiga 《Wireless Networks》2014,20(5):805-816
Proportional fairness is a widely accepted form of allocating transmission resources in communication systems. For wired networks, the combination of a simple probabilistic packet marking strategy together with a scheduling algorithm aware of two packet classes can meet a given proportional vector of n loss probabilities, to an arbitrary degree of approximation, as long as the packet loss gap between the two basic classes is sufficiently large. In contrast, for wireless networks, proportional fairness is a challenging problem because of random channel variations and contention for transmitting. In this paper, we show that under the physical model, i.e., when receivers regard collisions and interference as noise, the same packet marking strategy at the network layer can also yield proportional differentiation and nearly optimal throughput. Thus, random access or interference due to incoherent transmissions do not impair the feasibility of engineering a prescribed end-to-end loss-based proportional fairness vector. We consider explicitly multihop transmission and the cases of Markovian traffic with a two-priority scheduler, as well as orthogonal modulation with power splitting. In both cases, it is shown that sharp differentiation in loss probabilities at the link layer is achievable without the need to coordinate locally the transmission of frames or packets among neighboring nodes. Given this, a novel distributed procedure to adapt the marking probabilities so as to attain exact fairness is also developed. Numerical experiments are used to validate the design. 相似文献
4.
To improve the capacity of multi-hop wireless networks, protocols based on spatial reuse of frequencies with multiple orthogonal channels have been studied earlier. This paper focuses on the design, implementation and analysis of multiple-channel based wireless sensor networks (WSN). The objectives of the paper are two-fold. The first objective is to identify the sensor node bottlenecks in implementing multi-channel MAC protocols. In particular, a control channel based MAC protocol is implemented and analyzed. The analysis shows the gap between reality and simulation models due to system overheads in implementing these protocols. The second objective is to understand the capacity limits of multi-hop paths in a WSN with multiple channels. A generic channel allocation scheme based on k-distance coloring technique is developed. The protocols and mechanisms were implemented on a testbed consisting of Crossbow MicaZ and TelosB motes using IEEE 802.15.4 compliant radios. Throughput and delivery ratio measurements from the testbed are reported. Some of these measurements are incorporated in a discrete-event simulator model, based on OMNET++ 4.0 with Mobility Framework, for more detailed throughput analysis. The results show that it is possible to achieve 90 % delivery ratio over paths consisting of as many as 18 hops, in a 10 × 10 grid topology using 16 channels. 相似文献
5.
一种基于部分信道状态信息的稳健性预编码方案 总被引:1,自引:1,他引:0
目前的传输预处理算法都是假设发送端有理想的信道信息.然而,在实际系统中发射端只有来自接收端的部分信道信息.本文首先分析了部分信道状态信息产生的原因.然后提出了一种等效噪声方法,当发射端已知部分信道状态信息时对预编码设计的稳健性进行初步研究.本文的等效方法,即将反馈误差建模为接收端的等效噪声,利用ZF准则对反馈误差、用户间干扰进行统一处理.最后在TD-SCDMA系统应用环境里对该方法进行了仿真分析,结果表明反馈误差对预编码影响较大,采用等效噪声后的预编码相比没有考虑反馈误差的预编码性能很明显提高. 相似文献
6.
Adaptive MIMO-OFDM based on partial channel state information 总被引:11,自引:0,他引:11
Relative to designs assuming no channel knowledge at the transmitter, considerably improved communications become possible when adapting the transmitter to the intended propagation channel. As perfect knowledge is rarely available, transmitter designs based on partial (statistical) channel state information (CSI) are of paramount importance not only because they are more practical but also because they encompass the perfect- and no-knowledge paradigms. In this paper, we first provide a partial CSI model for orthogonal frequency division multiplexed (OFDM) transmissions over multi-input multi-output (MIMO) frequency-selective fading channels. We then develop an adaptive MIMO-OFDM transmitter by applying an adaptive two-dimensional (2-D) coder-beamformer we derived recently on each OFDM subcarrier, along with an adaptive power and bit loading scheme across OFDM subcarriers. Relying on the available partial CSI at the transmitter, our objective is to maximize the transmission rate, while guaranteeing a prescribed error performance, under the constraint of fixed transmit-power. Numerical results confirm that the adaptive 2-D space-time coder-beamformer (with two basis beams as the two "strongest" eigenvectors of the channel's correlation matrix perceived at the transmitter) combined with adaptive OFDM (power and bit loaded with M-ary quadrature amplitude modulated (QAM) constellations) improves the transmission rate considerably. 相似文献
7.
3GPP从R6版本开始,开展了对高速上行分组接入(HSUPA)技术的研究和标准制定工作。基于基站(NodeB)的调度算法是HSUPA的三大技术之一,对它的研究能有效地改善HSUPA系统性能,使系统的上行资源得以更充分的利用。在简述HSUPA中基于NodeB的典型调度算法的基础上,它针对用户的公平性给出了三种改进的正比公平调度算法,并在吞吐量和公平性上与典型调度算法进行仿真对比,仿真验证了当各个信道的衰落特性差别很大时,与正比公平调度算法相比,改进的正比公平调度算法有效地提高了用户的公平度,改善了系统性能。 相似文献
8.
Channel predictive proportional fair scheduling 总被引:2,自引:0,他引:2
Recent work on channel modeling and prediction has shown the feasibility of predicting the mobile radio channel, quite accurately, several milliseconds ahead in time for realistic Doppler spreads. Motivated by these results we consider opportunistic scheduling algorithms that exploit both current and future channel estimates. We demonstrate how this extra channel information can be used to improve the scheduling. Simulations show that the proposed algorithm can improve the inherent tradeoff between throughput, fairness and delay. The current approach builds on proportional fair scheduling but can also be generalized to other criteria. 相似文献
9.
Integration of multicast and unicast data in future radio access networks will be necessary in order to improve the resource
efficiency and provide new services. Such integration requires new and efficient resource sharing mechanisms. These mechanisms
need to be optimized to provide the best possible trade-off between resource efficiency and fairness. In this article, we
consider a case where streaming multicast users are multiplexed together with elastic unicast users on a common time-slotted
channel. We derive a system model to study the performance of various resource allocations strategies under proportional and
resource fairness constraints. Fairness is directly defined in terms of the users’ utilities rather than of the throughputs
they are assigned to. We also describe an extension of the well-known unicast proportional fair scheduler to the multicast
scenario. Through extensive simulations we demonstrate the performance of this scheduler for various traffic loads and multicast
group sizes.
相似文献
Gunnar KarlssonEmail: |
10.
基于M2M终端组的资源分配策略可以有效提高M2M通信中的资源利用率.本文研究了M2M通信系统中基于组的保证不同组间传输速率的比例公平资源分配问题,提出了一种次优的能够保证不同终端组间传输速率比例公平的资源分配算法,并通过仿真对算法的性能进行了验证,给出了速率最大化算法与终端组比例公平算法的性能比较. 相似文献
11.
Wireless Networks - In practical communication systems, there are always multiple subscribers competing for limited resources, such as time and frequency, hence effective user scheduling is... 相似文献
12.
In this paper, we study the resource allocation problem in multiuser Orthogonal Frequency Division Multiplexing (OFDM)-based cognitive radio networks. The interference introduced to Primary Users (PUs) is fully considered, as well as a set of proportional rate constraints to ensure fairness among Secondary Users (SUs). Since it is extremely computationally complex to obtain the optimal solution because of integer constraints, we adopt a two-step method to address the formulated problem. Firstly, a heuristic subchannel assignment is developed based on the normalized capacity of each OFDM subchannel by jointly considering channel gain and the interference to PUs, which approaches a rough proportional fairness and removes the intractable integer constraints. Secondly, for a given subchannel assignment, we derive a fast optimal power distribution algorithm that has a complexity of O(L 2 N) by exploiting the problem’s structure, which is much lower than standard convex optimization techniques that generally have a complexity of O((N + K)3), where N, L and K are the number of subchannels, PUs and SUs, respectively. We also develop a simple power distribution algorithm with complexity of only O(L + N), while achieving above 90 % sum capacity of the upper bound. Experiments show that our proposed algorithms work quite well in practical wireless scenarios. A significant capacity gain is obtained and the proportional fairness is satisfied perfectly. 相似文献
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《Vehicular Technology, IEEE Transactions on》1984,33(3):98-102
We consider the use of error correction codes of rate r on top of pseudonoise (PN) sequence coding for code division multiple accessing of the spread spectrum channel. The channel is found to have a maximum throughput of 0.72 and 0.36 based on the evaluation of channel capacity and cutoff rate, respectively. More generally, these two values are derived for given bandwidth expanding n/r versus n/N where n is the length of the PN sequence and N is the number of Simultaneous users. It is found that to achieve the maximum throughput, n should be small. This implies that coding schemes with short PN sequences and low rate codes are superior in terms of throughput or antijam capability. The extreme case of n = 1 corresponds to using a very low rate code with no PN sequence coding. Convolutional codes are recommended and analyzed for their error rate and decoding complexity. 相似文献
16.
Round-robin scheduling for max-min fairness in data networks 总被引:3,自引:0,他引:3
The author studies a simple strategy, proposed independently by E.L. Hahne and R.G. Gallager (1986) and M.G.H. Katevenis (1987), for fairly allocating link capacity in a point-to-point packet network with virtual circuit routing. Each link offers its packet transmission slots to its user sessions by polling them in round-robin order. In addition, window flow control is used to prevent excessive packet queues at the network nodes. As the window size increases, the session throughput rates are shown to approach limits that are perfectly fair in the max-min sense. If each session has periodic input (perhaps with jitter) or has such heavy demand that packets are always waiting to enter the network, then a finite window size suffices to produce perfectly fair throughput rates. The results suggest that the transmission capacity not used by the small window session will be approximately fairly divided among the large window sessions. The focus is on the worst-case performance of round-robin scheduling with windows 相似文献
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本文基于单信道系统中时间公平机会调度的研究,提出了3种推广到多用户下行OFDM多载波系统中的方案.这3种方案均以子载波为单位进行调度,充分利用信道的时变和频率选择特性:方案1对每个子载波单独调度,控制参数以时隙为单位更新;方案2将时频二维的子载波串在一起调度,控制参数以子载波为单位更新;方案3同方案2,但控制参数以时隙为单位更新.仿真结果表明,这3种方案均能够在保证时间公平性的前提下,相对非机会调度较大程度地提高系统性能.并且,这3种方案对子载波数和用户数没有限制,简单高效地使用有限的无线资源. 相似文献
20.
Hoon Kim Youngnam Han 《Communications Letters, IEEE》2005,9(3):210-212
This letter extends the proportional fair (PF) scheduling proposed in the high data rate (HDR) system to multicarrier transmission systems. It is known that the PF allocation (F. P. Kelly et al. (1998)) results in the maximization of the sum of logarithmic average user rates. We propose a PF scheduling that assigns users to each carrier while maximizing the sum of logarithmic average user rates. 相似文献