Comments on "Analysis of a switch matrix for an SS/TDMA system"

The time slot assignment algorithm presented in the above paper requires some modifications and/or refinements for it to be complete. A few methods to resolve problems in the algorithm are suggested in this letter, and a related theorem in combinatorial theory is also discussed.     

A fast time slot assignment algorithm for TDM hierarchicalswitching systems

A fast (polynomial time) network-flow-based algorithm is presented for time slot assignment in time-division-multiplexing (TDM) hierarchical switching systems. For a nonblocking time-multiplexed central switch the algorithm produces a conflict-free time slot assignment for a given frame (whenever this is possible) on O(M ⁵) time, where M is the system size     

Polynomial time optimal algorithms for time slot assignment ofvariable bandwidth systems

Considers the optimal (i.e., minimum length) time slot assignment problem for variable bandwidth switching systems. Existing algorithms for this problem are known to be pseudo-polynomial. The practical question of finding a fast optimal algorithm, as well as the theoretical question of whether the above problem is NP-complete were left open. The authors present a technique to show polynomial time complexity of some time slot assignment algorithms. Such a technique applies to an algorithm proposed by Chalasani and Varma in 1991 (called the CV algorithm), as well as to a network flow based optimal algorithm, proposed in the present paper for the first time. The CV algorithm and the one proposed are slightly different. Thus, the authors give an answer to both the above questions, by establishing that the problem is in P, and by showing effective algorithms for it     

Wireless Adaptive Framed Pseudo-Bayesian Aloha (AFPBA) Algorithm with Priorities

In this paper, we propose a new priority algorithm to control the access to the wireless ATM MAC uplink frame, for multimedia traffic like wireless ATM, similar to the Pseudo-Bayesian algorithm presented in [1]. The adaptive framed Pseudo-Bayesian Aloha (AFPBA) algorithm ensures minimum access delay for high priority traffic classes with small delay degradation to low priority traffic classes. Control packets are transmitted in each slot according to transmission probabilities based on the history of the channel and in contention with other packets of the same priority class. The number of contention slots assigned for each priority class, on a given frame, changes adaptively according to its priority index and the estimated arrival rate on each frame using an adaptive slot assignment mechanism. Finally, the throughput analysis of the algorithm is presented and the delay performance is evaluated by simulation on a wireless channel in the presence of shadowing, Rayleigh fading and capture. Results show that the wireless channel offers significant delay improvements to all priority packets, especially in the presence of fast fading.     

针对业务变化的TD-SCDMA信道码分配算法探讨

在三代移动通信TD—SCDMA系统信道的分配是载波、时隙、信道码（扩频码）的分配。本文针对用户使用的业务不断变化的TD—SCDMA系统提出一种新的信道码分配算法，对算法的流程进行详细的描述，并且通过仿真证明新算法在呼叫阻塞率方面强与原有信道码分配算法，对于工程的应用有重要的价值。     

一种适用于多信道联合组网的时隙分配新算法

分析了多信道联合组网时隙分配问题的特点,提出分配时隙时应该综合考虑容量需求、负载均衡和分配均匀度三方面因素,并设计了估计该三方面需求满足程度的方法。基于遗传算法,提出了适用于求解该问题的优化算法。仿真试验表明,提出的新算法能够有效求解多信道联合组网环境下的时隙分配问题。     

Bandwidth guaranteed call admission in TDMA/CDMA ad hoc wireless networks

This paper first studied the timeslot assignment problem in time division multiple access/code division multiple access (TDMA/CDMA) wireless ad hoc networks. Given a path P, we prove that a timeslot assignment providing one unit of bandwidth on P can be found in O(P) time if such an assignment exists. The results have been extended to the case that P can provide two units of bandwidth. Based on the timeslot assignment for the special cases, an efficient slot assignment algorithm with O(P²k) is proposed for general cases, where k is the number of slots in a TDMA frame. Then, the timeslot assignment algorithm is integrated into a quality of service (QoS) call admission scheme for QoS call requests. Extensive simulations are conducted and the results have demonstrated the superior performance of our method.     

Admission control in T/CDMA systems supporting voice and dataapplications

This paper analyses the behavior of two hybrid time-code division multiple-access (T/CDMA) architectures on the up-link of a macrocellular mobile radio system. For the examined schemes two categories of users-voice and data-share the domain of available resources, made up of time slots and codewords, through two alternative assignment strategies. Both solutions attribute voice users one single resource pair, i.e., one time slot and a single code to employ on that time slot, but differ in the way data users requests are accommodated: they are either simultaneously granted several codes over the same time slot or are assigned a single code over several distinct time slots. Call admission control is performed by a channel assignment algorithm which dynamically attributes resources only if specified levels of transmission quality are met on the radio channels. The blocking and the outage probability of the two classes of users are determined and compared, showing that one of the proposed schemes exhibits better performance and allows to satisfyingly serve a significant percentage of data users     

Low‐jitter slot assignment algorithm for deadline‐aware packet transmission in wireless video surveillance sensor networks

This work presents a distributed time‐slot assignment algorithm which adopts TDMA as Medium Access Control, specially suited to support applications with strict delay, jitter, and throughput requirements characterized by convergecast traffic pattern in sensor networks. (e.g. wireless video surveillance sensor networks). The proposed algorithm has three characteristics: (1) every node is guaranteed a path to the base station for its data delivery. In the path, sufficient resource is reserved and weighted fairness can be achieved. (2) It uses cascading time‐slot assignment and jitter minimization algorithm in each node to minimize jitter and end‐to‐end delay. (3) Nodes are only active during their scheduled slots and sleep otherwise. This offers energy saving by reducing idle listening and avoiding overhearing. The performance of the proposed algorithm is evaluated over simulations and analyzed theoretically in comparison with existing slot assignment algorithm. The results show that our algorithm provides lower end‐to‐end delay, jitter, and higher throughput. Copyright © 2010 John Wiley & Sons, Ltd.     

Forward-link capacity in smart antenna base stations with dynamicslot allocation

We consider a base station, which communicates to a set of portable stations using a smart antenna operating in multibeam, packet-switched, space division multiple access (SDMA) mode. We assume that the system operates using time division duplexing (TDD) and focus on the problem of access to the stations by the base station in the forward-link direction. A polling protocol is used which permits efficient access in this type of system. The operation of the protocol is unique in that it permits dynamic slot allocation and accommodates variations in channel time coherence. In the protocol, dynamic slot assignment is integrated into the forward-link beam scheduling. This allows us to explore the value of dynamic station slot assignment when constructing the SDMA/TDMA frames. The results show the improvements in capacity, which are possible in such systems and give insight into the degradation in protocol performance that occurs when channel coherence times decrease. We find that very large improvements in capacity are possible using dynamic slot allocation, especially under harsh channel conditions. We also investigate various base station queueing issues in this type of system. It is shown that care must be taken in how buffering is performed so that blocking effects do not unnecessarily degrade the forward-link capacity     

Performance evaluation of LIBTA/hybrid time‐slot selection algorithm for cellular systems

This paper studies the performance of radio assignment algorithms for portable access in cellular systems. Several channel access procedures are proposed and simulated using block oriented network simulator (BONeS) simulation of a model 36‐port system. Simulation results exhibit that load‐sharing system with LIBTA algorithm is better than directed retry system with the same algorithm by around 0.9 erlangs while better than quasi‐fixed channel assignment (QFCA) system by around 2 erlangs if the grade of service (GOS) is constrained to less than 10 per cent. Plus, a hybrid time‐slot selection procedure is proposed to enhance the system performance. It is observed that systems with hybrid time‐slot selection perform better than those with LIBTA algorithm in GOS under heavy load. It is also observed that load sharing system with hybrid time‐slot selection algorithm is better than directed retry system with the same algorithm by around 0.7 erlangs and better than QFCA system by around 2 erlangs. Copyright © 2001 John Wiley & Sons, Ltd.     

A demand-based slot assignment algorithm for energy-aware reliable data transmission in wireless sensor networks

This paper proposes a new demand-based slot assignment (DSA) algorithm that allocates time slots based on the bandwidth demand of each node in a tree topology. DSA is basically different from SDA, DAS, or WIRES that assigns one large slot for each sensor node, but is similar to the frame-slot pair assignment (FSA) algorithm used in TreeMAC in that it assigns multiple small size slots for sensor nodes per each data collection round. DSA tackles the shortcomings of FSA in terms of the capability of packet aggregation and filtering, the balance of energy consumption, and bandwidth utilization. In general, nodes at lower tree depths process more packets and consume more energy than ones at higher tree depths, and thus the imbalanced energy consumption shortens network lifetime. The proposed algorithm allocates a sequence of receiving slots and then a sequence of sending slots to each node. This approach not only reduces the power consumption of nodes at lower depths significantly by allowing efficient data aggregation and filtering, but also it improves bandwidth utilization by removing wasted slots. In addition, the RTS and CTS messages are used within a slot for ensuring the reliability of data transmission and updating sync time between a child and its parent. Simulation results show that DSA far outperforms FSA in energy consumption and bandwidth utilization.     

Separation of cochannel signals in TDMA mobile radio

We propose a sequential algorithm that separates cochannel time-division multiple-access (TDMA) signals that encounter multipath interference and noise. The receiver employs a multistage architecture where each stage consists of a beamformer and an equalizer that isolates one source, compensates for intersymbol interference (ISI), and demodulates the data. A problem encountered with such bursty sources is that the beamformer/equalizer trained for a particular time slot may not be appropriate for all the data contained in that slot. This occurs because a cochannel source typically overlaps only part of the time slot of interest and may not overlap the training sequence at all. The algorithm presented overcomes this problem by processing the data forward and backward in a sequential noncausal manner. Computer simulations using signals with the IS-54 format are presented to demonstrate the properties of the sequential algorithm     

An Optimal Switching Algorithm for Multibeam Satellite Systems with Variable Bandwidth Beams

In this paper we consider an SS/TDMA system withMuplink beams andNdownlink beams, where uplink beamihas bandwidth βiand downlink beamjhas bandwidth αj. The maximum traffic which can be handled by the satellite (in any given time slot) is assumed to beK. Multiplexing and demuitiplexing are also assumed. An optimal time slot assignment algorithm to minimize the total transmission time for any given traffic demand matrix is proposed and analyzed. Other system configurations of interest are also discussed.     

MR-MC无线传感器网络最小延迟数据聚集调度研究

单radio单信道无线传感器网络的最小延迟聚集调度是一个NPC问题,已提出许多解决方案。在多radio多信道网络中,节点可以同时接收多个不同节点传输的数据,降低延迟。基于上述特点,考虑树结构约束,时槽、信道和radio分配等约束条件,将多radio多信道无线传感器网络最小延迟聚集调度问题定义为一个优化问题,并分解为建立聚集树和节点调度2个子问题,针对这2个子问题分别提出启发式算法。实验结果表明,提出的算法具有良好的性能。     

An Assigned-Slot Listen-Before-Transmission Protocol for a Multiaccess Data Channel

In the multiaccess protocol described in this paper, users are each assigned specific slots of time in which to listen to the channel and determine if the channel is busy or idle. If the channel is idle, a ready user may transmit a fixed length message, or packet; otherwise he must wait a random time and try again. When two or more users transmit simultaneously, none are successful and each must retry after a random time. Though we have considered random slot assignment in general, in this paper we treat only fixed assignment. An interesting special case is when only one user is assigned to each sensing slot. Then there can be no collision and none of the channel capacity is wasted on retransmissions; that is, the channel is conflictfree. Delay-throughput performance curves are presented and compared with some other current multiaccess schemes of interest. Stability considerations are also discussed.     

Performance evaluation of a satellite-switched variable-frame TDMA system

In satellite-switched time-division multiple access (SS/TDMA) systems, the demand assignment control is a suitable scheme for the bursty packets to enhance the capacity efficiency. In the system, by applying the demand assignment scheme, the minimum transmission time could be achieved by the efficient time slot assignment algorithm. According to a given traffic matrix, the minimum transmission time cannot exceed the fixed TDMA frame duration. The spare time may be left at the end of the TDMA frame as the growth space for the future needs. To increase the system efficiency, the spare time could be reduced. In this paper, a demand assignment protocol with a variable frame is proposed for the system. The Markov chain model is applied to analyze the system performance on throughput, balking probability and packet delay. Performance comparison with the previous presented protocol, the proposed protocol could show a simple control technique and the efficient performance results in the system. It is a suitable candidate to be employed in the satellite networks to provide communication between the satellite and earth stations.     

Time slot assignment techniques for TDMA digital cellular systems

In TDMA system each channel may have more than one time slot to serve more than one user. Techniques for the assignment of time slots to users while minimizing co-channel interference are important. The paper presents six time slot assignment techniques. A discrete event stochastic simulation study was performed on 120° and 60° sectored systems. The simulation employs the “blocked calls cleared” traffic model and a log-linear path loss propagation model. Only the down link is considered. The results compare the performance of the six techniques and investigates the effect of the number of time slots per frame and the maximum acceptable interference level     

动态TDMA时隙分配算法在数据链中的仿真

固定TDMA分配算法能够保证节点数据发送的公平性,但不可能针对当前业务和网络状态进行时隙预留分配,很难实现差别服务和提供支持QoS（服务质量）的机制。因此提出一种适用于TTNT（战术瞄准网络技术）数据链通信系统的动态TDMA时隙分配算法,在高负载的网络环境下,这种算法加入了优先级机制并根据业务量轻重对各节点采取不同的发送策略,对时隙有较高利用率,提高了Ad Hoc（自组织网）网络系统吞吐量。在OPNET网络仿真平台上进行了仿真验证,仿真结果表明该算法在吞吐量和时延方面都优于固定TDMA算法。     

Time slot assignment in a heterogeneous environment of a SS/TDMA system

In this paper we consider the time slot assignment for a heterogeneous environment in which circuit-switched traffic and packet-switched traffic share the same satellite. In constructing a single time division multiple access (TDMA) frame for both traffic types, their different characteristics must be taken into account. This problem is known to be NP-complete and a couple of heuristic partial optimization algorithms have been developed. In this paper, we first provide a theoretical result to improve the existing partial optimization algorithms; then a fully optimizing heuristic algorithm is presented. Simulation results show that our algorithm provides a much better solution quality than existing ones. © 1997 John Wiley & Sons, Ltd.