MIMO Broadcast Scheduling with Limited Feedback

We consider multiuser scheduling with limited feedback of partial channel state information in MIMO broadcast channels. By using spatial multiplexing at the base station (BS) and antenna selection for each user, we propose a multiuser scheduling method that allocates independent information streams from all M transmit antennas to the M most favorable users with the highest signal-to-interference-plus-noise ratio (SINR). A close approximation of the achievable sum-rate throughput for the proposed method is obtained and shown to match the simulation results very well. Moreover, two reduced feedback scheduling approaches are proposed. In the first approach, which we shall refer to as selected feedback scheduling, the users are selected based on their SINR compared to a predesigned threshold. Only those selected users are allowed to feed back limited information to the BS. The resultant feedback load and achievable throughput are derived. It will then be demonstrated that with a proper choice of the threshold, the feedback load can be greatly reduced with a negligible performance loss. The second reduced feedback scheduling approach employs quantization for each user, in which only few bits of quantized SINR are fed back to the BS. Performance analysis will show that even with only 1-bit quantization, the proposed quantized feedback scheduling approach can exploit the multiuser diversity at the expense of slight decrease of throughput.     

QoS‐Guaranteed Multiuser Scheduling in MIMO Broadcast Channels

This paper proposes a new multiuser scheduling algorithm that can simultaneously support a variety of different quality‐of‐service (QoS) user groups while satisfying fairness among users in the same QoS group in MIMO broadcast channels. Toward this goal, the proposed algorithm consists of two parts: a QoS‐aware fair (QF) scheduling within a QoS group and an antenna trade‐off scheme between different QoS groups. The proposed QF scheduling algorithm finds a user set from a certain QoS group which can satisfy the fairness among users in terms of throughput or delay. The antenna trade‐off scheme can minimize the QoS violations of a higher priority user group by trading off the number of transmit antennas allocated to different QoS groups. Numerical results demonstrate that the proposed QF scheduling method satisfies different types of fairness among users and can adjust the degree of fairness among them. The antenna trade‐off scheme combined with QF scheduling can improve the probability of QoS‐guaranteed transmission when supporting different QoS groups.     

Scheduling Combined Unicast and Multicast Traffic in Broadcast WDM Networks

This paper studies the performance of various strategies for scheduling a combined load of unicast and multicast traffic in a broadcast WDM network. The performance measure of interest is schedule length, which directly affects both aggregate network throughput and average packet delay. Three different scheduling strategies are presented, namely: separate scheduling of unicast and multicast traffic, treating multicast traffic as a number of unicast messages, and treating unicast traffic as multicasts of size one. A lower bound on the schedule length for each strategy is first obtained. Subsequently, the strategies are compared against each other using extensive simulation experiments in order to establish the regions of operation, in terms of a number of relevant system parameters, for which each strategy performs best. Our main conclusions are as follows. Multicast traffic can be treated as unicast traffic, by replicating all multicast packets, under very limited circumstances. On the other hand, treating unicast traffic as a special case of multicast traffic with a group of size 1, produces short schedules in most cases. Alternatively, scheduling and transmitting each traffic component separately is also a good choice.     

Bluetooth Dynamic Scheduling and Interference Mitigation

Bluetooth is a cable replacement technology for Wireless Personal Area Networks. It is designed to support a wide variety of applications such as voice, streamed audio and video, web browsing, printing, and file sharing, each imposing a number of quality of service constraints including packet loss, latency, delay variation, and throughput. In addition to QOS support, another challenge for Bluetooth stems from having to share the 2.4 GHz ISM band with other wireless devices such as IEEE 802.11. The main goal of this paper is to investigate the use of a dynamic scheduling algorithm that guarantees QoS while reducing the impact of interference. We propose a mapping between some common QoS parameters such as latency and bit rate and the parameters used in the algorithm. We study the algorithm's performance and obtain simulation results for selected scenarios and configurations of interest.     

Queue Proportional Scheduling via Geometric Programming in Fading Broadcast Channels

For fading broadcast channels (BC), a throughput optimal scheduling policy called queue proportional scheduling (QPS) is presented via geometric programming (GP). QPS finds a data rate vector such that the expected rate vector over all fading states is proportional to the current queue state vector and is on the boundary of the ergodic capacity region of a fading BC. Utilizing the degradedness of BC for each fading state, QPS is formulated as a geometric program that can be solved with efficient algorithms. The GP formulation of QPS is also extended to orthogonal frequency-division multiplexing (OFDM) systems in a fading BC. The throughput optimality of QPS is proved, and it is shown that QPS can arbitrarily scale the ratio of each user's average queueing delay. Throughput, delay, and fairness properties of QPS are numerically evaluated in a fading BC and compared with other scheduling policies such as the well-known maximum weight matching scheduling (MWMS). Simulation results for Poisson packet arrivals and exponentially distributed packet lengths demonstrate that compared with MWMS, QPS provides a significant decrease in average queueing delay and has more desirable fairness properties.     

Coverage and Interference for Second-Adjacent Channel FM Broadcast Stations

The coverage and interference of seven Los Angeles area FM broadcast stations are analyzed. The area and population coverages predicted by the FCC methods described in the rules are compared with a method that considers the intervening terrain in some detail. We also show that the criteria for deciding second-adjacent-channel interference threshold of -50 dB (rather than the present -20 dB) adequately protects modern receivers, based on data available in FCC filings and on the performance of these stations. We believe the techniques used in this analysis could be widely applied, and would result in more efficient spectrun use.     

Simulation Models for Investigation of Multiuser Scheduling in MIMO Broadcast Channels

Spatial correlation is a result of insufficient antenna spacing among multiple antenna elements, while temporal correlation is caused by Doppler spread. This paper compares the effect of spatial and temporal correlation in order to investigate the performance of multiuser scheduling algorithms in multiple‐input multiple‐output (MIMO) broadcast channels. This comparison includes the effect on the ergodic capacity, on fairness among users, and on the sum‐rate capacity of a multiuser scheduling algorithm utilizing statistical channel state information in spatio‐temporally correlated MIMO broadcast channels. Numerical results demonstrate that temporal correlation is more meaningful than spatial correlation in view of the multiuser scheduling algorithm in MIMO broadcast channels. Indeed, the multiuser scheduling algorithm can reduce the effect of the Doppler spread if it exploits the information of temporal correlation appropriately. However, the effect of spatial correlation can be minimized if the antenna spacing is sufficient in rich scattering MIMO channels regardless of the multiuser scheduling algorithm used.     

A Sequential Approach for Optimal Broadcast Scheduling in Packet Radio Networks

An important problem that arises in the design of packet radio networks is that of scheduling access to the high speed communications channel in such a way as to avoid interference while keeping the frame length to a minimum. The broadcast scheduling problem is known to be NP-hard and to date, this problem has been formulated as a nonlinear discrete optimization problem for a given frame length, and solved via heuristic approaches by parametrically varying the length of the frame. This paper presents a linear integer programming formulation for the composite problem of maximizing channel utilization while minimizing the length of the frame. It then introduces a solution approach based on solving two relatively easier (though still NP-complete) integer programs in succession. Computational experiments are conducted on a set of benchmark cases and additional randomly generated problem instances. Results show that this sequential integer programming approach is very effective, solving all the problems optimally within a few seconds. These results imply that optimal solutions can be identified in very little time for problems of realistic size, and that heuristic approaches will be needed only when problems get much larger than those considered in the literature to date.     

MIMO广播信道中联合多用户速率和延迟约束调度的研究

该文给出了一种多入多出高斯广播信道中具有延迟约束的多用户无线数据包的传输方案。首先,在信道的QR分解及脏纸编码基础上,通过贪婪算法获取多用户分集与包延迟约束之间的有效结合。其次,将包到达速率、可达服务速率、用户数以及传输天线数构成一优化问题,得到最佳的用户组合及调度周期。最后,在不同用户数及发射天线数情况下对该方案进行了性能仿真,仿真结果表明：在满足包传递最小延迟等待要求的同时,得到了传输容量的最大化。     

数字播出机房的环境建设

广电行业新技术的不断发展,带来了新产品新设备,如何保证这些设备良好地运行,对播出环境有严格的要求。通过广州有线数字播出机房的设计施工,结合相关的国标要求,对播出环境的建设进行探索,很有实践意义。     

Scheduling Constraints and Interference Graph Properties for Graph-based Interference Coordination in Cellular OFDMA Networks

The currently emerging 802.16e (WiMAX) and 3GPP Long Term Evolution (LTE) cellular systems are based on Orthogonal Frequency Division Multiple Access (OFDMA). OFDMA suffers from heavy inter-cell interference if neighboring base stations use the same frequency range. One approach to solve this issue is the application of beamforming antennas in combination with interference coordination (IFCO) mechanisms between base stations. In this paper, we trace the problem of IFCO back to the graph coloring problem and investigate the achievable resource utilization of the interference coordinated system. We develop a heuristic that allows the combination of arbitrary scheduling algorithms with the IFCO mechanism. This allows an efficient utilization of the radio system’s frequency resources while still obeying scheduling constraints, such as Quality of Service requirements. Finally, we study the tradeoff between fairness and the total system throughput.

Spatial Scheduling With Interference Cancellation in Multiuser MIMO Systems

This paper proposes a novel downlink spatial scheduling algorithm in multiuser multiple-input-multiple-output (MIMO) systems, which selects a good combination of terminals and base station's (BS's) transmit beams so that the BS's beams nullify interstream interference at the selected terminals. In the derivation process, we reveal the new property that the optimization problem of downlink spatial scheduling is equivalent to that of uplink scheduling under the BS's zero-forcing beamforming. Using this property, an efficient downlink scheduling algorithm is presented, applying the principle of an uplink scheduling algorithm. Numerical results show that the presented spatial scheduling achieves a much higher system throughput than a multiuser MIMO system without spatial scheduling or with conventional spatial scheduling by linear processing. We also present a realistic control structure to achieve the uplink and downlink spatial scheduling in time-division duplex systems.     

动力环境监测系统在广播电视监测中的应用探讨

本文根据广播电视监测系统运维过程中出现的实际问题,设计了所需的动力环境监测系统的理论框架结构,并探讨了动力环境监测系统在实际应用中可能面对的问题.本文的研究工作实现了对监测系统的实时巡检,显著降低了巡检人员的工作量,提高了工作效率.     

广播电视安全播出指挥调度平台管理系统

安全播出工作是广播电视的生命,随着广播电视和现代科技的发展,广电局的监管能力和应急指挥调度需要更新更便捷的技术系统,来保证安全播出日常管理工作和应急处置工作的顺利进行。从应用前景、发展趋势、主要功能及技术难点、技术关键等方面简要介绍了广播电视安全播出指挥调度平台管理系统。     

LTE同频干扰环境下干扰抑制检测算法的研究

基于上行干扰抑制合并技术（IRC）提出了两种干扰检测算法。第一种改进方案需要预先知道目标小区和干扰小区信道状态信息,第二种改进方案在不知道目标小区和干扰小区信道状态信息的情况下,通过盲估的方法进行计算。这两种算法都能有效抵御同频干扰,并减少误码率。     

基于递归算法的应急广播资源调度机制研究

本文首先简要介绍了国家级应急广播体系建设的必要性和紧迫性,概述了建模所需的广播电视资源、应急信息发布和公共事件要素以及递归算法函数定义与分析;在此基础上建立了资源调度递归算法模型,并针对执行顺序、区域等级、输入参数和调度冲突情况方面对模型进行了扩展.     

Traffic and Interference Adaptive Scheduling for Internet Traffic in UMTS

In this paper we propose a scheduling strategy for the radio resources management when transmitting Internet traffic over third-generation systems. More precisely, we consider the UMTS Terrestrial Radio Access Network (UTRAN) Time Division Duplex (TDD) mode standardized by ETSI. UTRAN TDD uses a hybrid solution of code and time division multiple access, called TD-CDMA. In UMTS systems a key issue in developing access methodologies for the available spectrum is an optimal management of the rare radio resources. In this paper we present a fair and efficient scheduling algorithm that adapts its behavior to traffic and interference conditions. Specifically, our scheduling algorithm is able to manage the radio resources taking into account both the traffic fluctuations in the uplink and downlink direction and the variations of the system interference. The goal of our scheduler is the data-throughput maximization for an efficient utilization of available radio resources. The effectiveness of our scheduling algorithm is shown by exploiting analytical tools.     

Collision-Free and Low-Latency Scheduling Algorithm for Broadcast Operation in Wireless Ad Hoc Networks

It is desirable for broadcast operation in wireless ad hoc network to prevent collision and achieve low latency at the same time. In this letter, we propose a greedy broadcast scheduling algorithm based on the graph theory of Maximum Weight Independent Set (MWIS) problem. During each broadcast wave cycle, MWIS is able to find the optimal selection of forwarders so that maximum number of untouched nodes is covered without incurring collision. Numerical results show that this algorithm could produce better performance results than recent 2-step approach.     

Reduction of Adjacent Channel Interference in the Standard (AM) Broadcast Band

Side channel interference has been a problem in the standard (AM) broadcast band since the advent of radio broadcasting. The two major contributing factors are: 1) radiation of audio-frequency components greater than 5 kHz, and 2) receivers having poor selectivity characteristics. Other more or less controllable factors are overmodulation of the carrier and inherent distortion in the transmitter.     

Enhanced Multi-mode Transmission by User Scheduling in MISO Broadcast Channels with Finite-Rate Feedback

This paper investigates the user selection strategy in multiuser downlinks using zero-forcing beamforming (ZFBF) and finite-rate feedback (FRF). In order to mitigate the interference-limited effect in ZFBF-FRF systems, we propose an efficient user scheduling scheme combined with adaptive transmission mode selection strategy. In this scheme, each user first evaluates its preferred transmission mode and the corresponding achievable rate according to a derived tight lower bound of the rate. Given such information on the users through feedback, the BS then determines the global transmission mode of the system and selects users for simultaneous transmission. Asymptotic analysis shows that limited feedback beamforming to a single user is the best choice at both low and high SNR regimes. Simulation results demonstrate individual effects of different system parameters on the sum rate performance by the proposed scheme.