Turbo soft combining hybrid ARQ techniques: Theory and application to 3G wireless networks

This paper deals with the application of Hybrid Automatic Repeat reQuest (h-arq) techniques to allow reliable data communications in wireless 3G networks. Basically, retransmission of coded data is endowed with soft combining schemes applied, respectively, to packet replicas, or to decoding algorithm outputs. In particular, the proposed coding scheme takes advantage of error correction capabilities of the turbo codes, while the combining algorithm follows the diversity approach. The performance of the proposedh-arq schemes has been derived by means of a suitable analytical approach and numerical simulations in the case of a typical umts environment. The results highlight the good behavior of the proposed scheme in term of error rate, throughput, packet delivery delay and power reduction.     

无线多跳网络的自适应容量感知优化与控制技术

In wireless multimedia communications, it is extremely difficult to derive general end-to-end capacity results because of decentralized packet scheduling and the interference between communi-cating nodes. In this paper, we present a state-based channel capacity perception scheme to provide sta-tistical Quality-of-Service (QoS) guarantees under a medium or high traffic load for IEEE 802.11 wire-less multi-hop networks. The proposed scheme first perceives the state of the wireless link from the MAC retransmission information and extends this information to calculate the wireless channel capaci-ty, particularly under a saturated traffic load, on the basis of the interference among flows and the link state in the wireless multi-hop networks. Finally, the adaptive optimal control algorithm allocates a net-work resource and forwards the data packet by tak-ing into consideration the channel capacity deploy-ments in multi-terminal or multi-hop mesh net-works. Extensive computer simulations demonstrate that the proposed scheme can achieve better per-formance in terms of packet delivery ratio and net-work throughput compared to the existing capacity prediction schemes.     

Cross-Layer MAC Protocol and Holistic Opportunistic Scheduling with Adaptive Power Control for QoS in WiMAX

Providing quality of service (QoS) to different service classes with integrated real-time and non-real-time traffic is an important issue in broadband wireless access networks. Opportunistic MAC (OMAC) is a novel view of communication over spatiotemporally varying wireless link whereby the multi-user diversity is exploited rather than combated to maximize bandwidth efficiency or system throughput. It combines cross-layer design features and opportunistic scheduling scheme to achieve high utilization while providing QoS support to various applications. Channel characteristics, traffic characteristics and queue characteristics are the essential factors in the design of opportunistic scheduling algorithms. In this paper, we propose a cross-layer MAC scheduling framework in WiMAX point-to-multipoint (PMP) systems and a corresponding opportunistic scheduling algorithm with an adaptive power control scheme to provide QoS support to the heterogeneous traffic. Extensive simulation experiments have been carried out to evaluate the performance of our proposal. The simulation results show that our proposed solution can improve the performance of the WiMAX PMP systems in terms of packet loss rate, packet delay and system throughput.     

Idle-signal casting multiple access with data slot reservation(ICMA-DR) for packet radio communications

A population of terminals communicating with a central station over a packet-switched multiple access radio channel is investigated with regard to multiple access control schemes. The authors describe the ICMA-DR, which is an advanced idle-signal casting multiple access (ICMA) scheme characterized by data slot reservation. This improved central controlled multiple-access scheme for packet transmission in terrestrial radio communications is evaluated in terms of throughput traffic, throughput delay characteristics, and handling capacity. It is shown that the throughput characteristics of ICMA-DR are superior than those of ICMA or slotted ALOHA when a packet for data slot reservation is relatively short in comparison to that for upward data. Thus, it is shown that ICMA-DR is suitable for the packet radio multiple-access scheme, especially in the case where fading packet error occurs frequently and ordered traffic is heavy. The ICMA-DR scheme has been utilized for the access control channel of NTT's new 800-MHz-band high-capacity land mobile communication system since the Spring of 1988     

HSDPA中M-LWDF实时业务分组调度算法的改进

HSDPA是UMTS的最新演进。HSDPA采用先进的技术包括AMC、HARQ和快速小区选择以提供更高的数据速率。在HSDPA系统中,无线资源管理功能主要是由分组调度算法来实现,研究先进的分组调度算法是提高数据业务吞吐量、保证用户间的公平性、满足业务QoS的根本。主要介绍了实时业务算法M-LWDF,针对其在公平性方面的缺陷进行了改进,并对上述2种算法在中断率和吞吐量上进行了试验分析。     

Adaptive QoS scheduling in wireless cellular networks

Quality of service (QoS) has been always controversial in resource shared networks. Scheduling as a packet prioritizing mechanism at Data Link Layer (DLL) contributes to QoS guarantee provisioning significantly. In this paper, a novel packet scheduler is developed in wireless cellular networks. The proposed scheme provides QoS-guaranteed service for the applications running on the sensor nodes in all the three aspects of QoS, i.e. data rate, packet loss and packet delay with regard to jitter simultaneously. We establish a three-dimensional space with certain basis vectors for QoS and introduce the efficient point of performance in terms of QoS provisioning in that space. Then we develop a generalized metric, the QoS-deviation, which is the Euclidean distance between the QoS work point of flows and the QoS efficient point in the proposed space. Based on this metric, a novel scheduling approach, namely AQDC, is designed which makes it possible to tune the trade-off between QoS provisioning and throughput optimization in an adaptive manner depending on the current Cell QoS-deviation level (CDL). Furthermore, we also develop another scheduler, namely ARTC, which is the residual-time version of the AQDC scheduler. Finally, a QoS-deviation-based CAC policy will be introduced which can be applied to all schedulers without any consideration about their structure and can be employed in cellular packet switched networks.     

Power controlled H-ARQ in cdma2000 1/spl times/EV-DV

The newly applied H-ARQ technique in the reverse link of a cdma2000/spl reg/ 1/spl times/EV-DV system is shown to be similar in nature to the fast power control technique such that the two techniques both reduce interference to other users. In order to balance the H-ARQ gain and packet delay time, four modes of operation are defined: normal, reduction, boost, and boost reduction. The four modes are defined according to the way the channel gain is set for the H-ARQ operation. Simulation results show that the reduction modes have better performance in terms of both PER and packet delay time. It is also shown that the boost modes have lower PER and packet delay time than the non-boost modes, but at the expense of more energy.     

Joint Power-Frequency-Time Resource Allocation in Clustered Wireless Mesh Networks

Wireless mesh networking is an emerging technology for future broadband wireless access. Future wireless networking can benefit from a robust and reliable wireless mesh backbone rendered by mesh routers, providing an all-wireless ambience. Due to the requisite multichannel communications for high-speed data transmissions, power allocation for opportunistically exploiting fading wireless channels, and packet scheduling for QoS provisioning, joint power-frequency-time resource allocation is indispensable. In this article we propose a low-complexity intracluster resource allocation algorithm, taking power allocation, subcarrier allocation, and packet scheduling into consideration. Numerical results demonstrate that our scheme is near optimal, and that our optimality-driven resource allocation approach outperforms a greedy algorithm, working out a better performance compromise among throughput, packet dropping rate, and packet delay.     

Cross-layer resource allocation for QoS guarantee with finite queue constraint in multirate OFDMA wireless networks

Efficient radio resource allocation is essential to provide quality of service （QoS） for wireless networks. In this article, a cross-layer resource allocation scheme is presented with the objective of maximizing system throughput, while providing guaranteed QoS for users. With the assumption of a finite queue for arrival packets, the proposed scheme dynamically a/locates radio resources based on user＇s channel characteristic and QoS metrics derived from a queuing model, which considers a packet arrival process modeled by discrete Markov modulated Poisson process （dMMPP）, and a multirate transmission scheme achieved through adaptive modulation. The cross-layer resource allocation scheme operates over two steps. Specifically, the amount of bandwidth allocated to each user is first derived from a queuing analytical model, and then the algorithm finds the best subcarrier assignment for users. Simulation results show that the proposed scheme maximizes the system throughput while guaranteeing QoS for users.     

自适应调制与编码系统及其在WCDMA中的应用

本文主要讨论自适应调制与编码系统(Adaptive Modulation and Coding system）的原理，介绍AMCS实现的几个关键技术，包括RCPT（速率适配凿孔turbo）码、高阶调制、H-ARQ和MIMO（多输入多输出）系统。介绍了在WCDMA的高速下行分组接入业务（HSDPA）中使用的自适应调制编码机制，并讨论了可能增加的设备复杂度。     

System Throughput Analysis of Rate Adaptive TDMA System Supporting Two Class Services

In this paper, an adaptive transmission scheme is proposed to improve the spectral efficiency of TDMA systems. Services accommodated in such systems are classified as QoS services and BE services. Unlike conventional adaptive TDMA systems where the time slot duration is fixed for each user, our proposed system employs transmission slots with adaptive duration. For QoS services, rate adaptive modulation is adopted to make use of the instantaneous channel conditions of individual user. For BE services, a media access control strategy (MAC) that takes the instantaneous transmission conditions of all physical links of all BE services into consideration is employed. A framework to study the proposed system in terms of the average packet loss and the average system throughput is presented. The maximum number of QoS services that can be supported in the system while a predefined requirement on the average packet loss is still satisfied is investigated. A comparison study shows that our proposed scheme has higher system throughput over both conventional fixed and adaptive TDMA systems. Ronghong Mo received her B.Sc. and M. Sc. Degree from Zhongshan University, Guangzhou, China, both in Physics. From July 1999 to July 2003, she was a research scholar in the department of Electrical and Computer Engineering in National University of Singapore (NUS), toward her PhD degree. She is currently working as a research engineer in NUS. Her research interests include adaptive modulation, synchronization and channel estimation in wireless communications. Yong Huat Chew received the B.Eng, M.Eng and Ph.D. degrees in Electrical Engineering from National University of Singapore, Singapore. Since 1996, he has been with the Institute for Infocomm Research (formerly also known as Center for Wireless Communications and Institute for Communications Research), an institute under Agency for Science, Technology and Research, where he is presently a lead Scientist. His research interests are in wireless communications, transmission over HFC, DSL and all-optical networks.     

Hybrid ARQ with Cross-Packet Channel Coding

We describe hybrid automatic repeat request/forward error correction (H-ARQ) with cross-packet channel coding which extends current H-ARQ schemes for point-to-point communications. In contrast to current H-ARQ schemes, the transmission of two consecutive packets of information bits is considered jointly. If a retransmission for the first packet is necessary, we encode the first and a second packet jointly. For fading channels, this allows diversity gain from retransmissions without decreasing the total code rate. We describe an encoder and a decoder which can be decoded iteratively for a system with H-ARQ with cross-packet channel coding     

Routing protocol development for quality of service optimization of video‐on‐demand system over mobile ad hoc networks

A video‐on‐demand (VoD) application system over mobile ad hoc networks typically requires particular quality of service (QoS) parameters to be achieved. In this paper, we have proposed a novel QoS‐based routing protocol called as mobile VoD protocol. This protocol has been developed for improving the QoS of the mobile VoD system (normal Mobi_VoD approach). The protocol uses customer caching scheme for storing the first fragment of the entire video in the mobile customers and thereafter broadcast them when the new mobile customers missed the portion of the already transmitted first fragment for reducing the service delay of the customer, consequently optimizing QoS parameters. Various scenarios have been studied, and the efficacy of simulation results proves that the proposed system architecture in which the mobile customers use an ad hoc network caching scheme (mobile VoD protocol) is more efficient and performs better than the existing system (ad hoc on‐demand distance vector protocol) when compared in terms of QoS parameters such as the end‐to‐end delay, energy consumption, packet delivery ratio, throughput, and overhead.     

Quality-of-service driven power and rate adaptation for multichannel communications over wireless links

We propose a quality-of-service (QoS) driven power and rate adaptation scheme for multichannel communications systems over wireless links. In particular, we use multichannel communications to model the conceptual architectures for either diversity or multiplexing systems, which play a fundamental role in physical-layer evolutions of mobile wireless networks. By integrating information theory with the concept of effective capacity, our proposed scheme aims at maximizing the multichannel-systems throughput subject to a given delay-QoS constraint. Under the framework of convex optimization, we develop the optimal adaptation algorithms. Our analyses show that when the QoS constraint becomes loose, the optimal power-control policy converges to the well-known water-filling scheme, where the Shannon (or ergodic) capacity can be achieved. On the other hand, when the QoS constraint gets stringent, the optimal policy converges to the scheme operating at a constant-rate (i.e., the zero-outage capacity), which, by using only a limited number of subchannels, approaches the Shannon capacity. This observation implies that the optimal effective capacity function decreases from the ergodic capacity to the zero-outage capacity as the QoS constraint becomes more stringent. Furthermore, unlike the single-channel communications, which have to trade off the throughput for QoS provisioning, the multichannel communications can achieve both high throughput and stringent QoS at the same.     

Buffered fixed routing: a routing protocol for real-time transportin grid networks

We propose a new routing protocol called buffered fixed routing (BFR) for real-time applications on grid networks. While previous routing protocols for grid networks have been designed to improve network throughput, the BFR scheme is proposed to guarantee the end-to-end packet delay and sequencing without loss by using finite buffers at each node. Thus the proposed scheme can satisfy quality-of-service (QoS) requirements of real-time applications. The BFR scheme uses the token on the row ring to provide QoS guarantees. The performance of the BFR scheme is analyzed by using the Geom/Geom/1 queueing system under uniform traffic. In the simulation, the BFR scheme shows the zero-loss, high-throughput performance with the minimum delay variation compared to other routing protocols such as store and forward routing, deflection routing and vertical routing. In addition, it has shown the smallest average delay at intermediate and heavy loads     

CDMA2000 1xEV-DO中的分组调度算法

移动通信系统需要更好地支持分组数据业务，并满足高速分组数据业务的服务质置要求。这可以通过采用好的调度算法提高平均业务速率和系统整体稳定性实现。针对CDMA2000 1x EV-DO系统的有代表性的调度算法有3种：正比公平算法、速率受限的最大载干比算法、加权公平排队-正比公平（WFQ-PF）联合算法。正比公平调度算法是一种算法简单实用的调度方案，但不能满足用户的服务质景保证；速率受限的最大载干比算法具有比正比公平算法更高的平均吞吐量，可方便地在吞吐量和公平性之间获得很好的折衷；WFQ-PF联合算法具有良好的综合性能，但算法较复杂。     

一种改善IP网络中基于类的数据服务QoS的调度方法

IP网络中基于类的数据服务QoS支持一般包括包的延时、吞吐量和丢失率,目前的研究成果大都集中于对其中某一个指标的确保或支持。该文提出一种在IP网络中一个网络路由器节点上同时考虑类间流量带宽、包丢失和延时区分的队列管理调度算法,称为动态比例自适应算法(Dynamic Proportional Adaptive Algorithm,DPAA)。该算法是针对比例区分服务PDS(Proportional Differentiated Services)中流量负载频繁变化的情况提出的。仿真实验通过与前人提出的基于比例区分服务模型的调度算法比较,证明了DPAA 算法的有效性。     

Interference Mitigation Based on Radio Aware Channel Assignment for Wireless Mesh Networks

An intricate network deployment for high demand users leads to simultaneous transmission in wireless mesh networks. Multiple radios are adapted to individual nodes for improving network performance and Quality of Service (QoS). However, whenever multiple radios are assigned to the same channel, co-located radio interference occurs, which poses a major drawback. This paper proposes a Radio aware Channel Assignment (Ra-CA) mechanism based on a direct graphical model for mitigation of interference in multi-radio multi-channel networks. Initially, the co-located radio interference is identified by classifying non-interfering links for simultaneous transmission in the network. Proposed channel assignment mechanism helps in allocating the minimal number of channels to the network that mitigate co-located radio interference. Performance analysis of the proposed Ra-CA strategy is carried out compared with other existing techniques, like Breadth First Search-Channel Assignment (BFS-CA) and Maximal Independent Set Channel Assignment (MaIS-CA), in multi-radio networks. Simulation results demonstrate that the proposed channel assignment scheme is more efficient compared to the existing ones, in terms of QoS parameters like, packet drop rate, packet delivery ratio, transmission delay and throughput.     

Uplink resource allocation and power control for D2D communications underlaying multi-cell mobile networks

Proximity user equipments (UEs) in mobile networks may be communicated directly without passing their traffic through the base station by using device-to-device (D2D) communications. This can be done using the underlaying approach in which the D2D-UEs (DEs) are allowed to use the same resources allocated for cellular UEs (CEs), which can enhance the spectral efficiency. However, if the resource allocation for DEs is not designed appropriately, it would generate harmful interference on CEs communications. Therefore, this paper addresses a resource allocation and power control problems for D2D communications underlaying multi-cell mobile networks with the consideration of the inter-cell and intra-cell interferences. The problem is formulated to maximise the network performance in terms of achieved throughput while ensuring the quality-of-service (QoS) constraints for CEs and DEs. A two-step algorithm is proposed in which the admission control is performed firstly to determine the set of possible D2D connections and their CE partners that achieve the minimum QoS demands. Then, the optimal power for each permissible DE and its possible partners in different cells are allocated to maximise the network throughput. Simulation results illustrate that the suggested algorithm can remarkably enhance the performance of the network in terms of throughput gain and access rate.     

Wireless Access Method to Ensure Each User's QoS in Unpredictable and Various QoS Requirements

With the fast growth of Internet services, the demand for wireless high speed and advanced multimedia communications is rapidly increasing. Initial multimedia services have already been offered in the second generation systems (2-G). Currently, the third generation systems (3-G) are being deployed and it will support up to 2 Mbps packet oriented data services. But it is expected that the demand for higher data rate and large variety of high quality services will increase further more. Therefore, it is mandatory for the fourth generation systems (4-G) to take each user's quality of service (QoS) control into account.In this paper, we firstly describe an overview on requirements and technical issues for the 4-G systems, and wireless QoS control issues considering End-to-End QoS control in the IP network. Next, we propose broadband wireless access method for the fourth generation mobile communication systems. The proposed method for downlink is based on MC-CDMA (Multi-Carrier Code Division Multiple Access) with Multi-Timeslot, in which total downlink resources are split into three aggregates according to the QoS classes in time domain. It is considered that one of the typical advantages for the MC-CDMA is the effect of frequency diversity. We evaluated the effect by computer simulation using ray-traced propagation model. Simulation results show that short-term fading can be relaxed. Furthermore, we propose Multi-Level (ML) ARQ as one of the link adaptation methods. Simulation results show that the proposed scheme has a good performance with throughput and average retransmission power.