A CDMA wireless packet network for voice-data transmissions

This letter investigates the possibility of integrating voice and data communications in a CDMA wireless packet network to provide access to a base station over a common short-range radio uplink channel for many spatially dispersed voice and data user terminals. Speech activity detection is assumed for voice communications to temporarily devote codes unused by voice user terminals during silence periods to data transmissions. The network proposed exhibits a good performance both in terms of quality of voice communications which is independent of data transmissions and maximum data traffic load supported with bounded delay     

Highly Efficient Voice—Data Integration over Medium and High Capacity Wireless TDMA Channels

A new medium access control (MAC) protocol for mobile wireless communications is presented and investigated. We explore, via an extensive simulation study, the performance of the protocol when integrating voice and data traffic over two wireless channels, one of medium capacity (referring mostly to outdoor microcellular environments) and one of high capacity (referring to an indoor microcellular environment). Data message arrivals are assumed to occur according to a Poisson process and to vary in length according to a geometric distribution. We evaluate the voice packet dropping probability and access delay, as well as the data packet access and data message transmission delays for various voice and data load conditions. By combining two novel ideas of ours with two useful ideas which have been proposed in other MAC schemes, we are able to remarkably improve the efficiency of a previously proposed MAC scheme [5], and obtain very high voice sources multiplexing results along with most satisfactory voice and data performance and quality of service (QoS) requirements servicing. Our two novel ideas are the sharing of certain request slots among voice and data terminals with priority given to voice, and the use of a fully dynamic low-voice-load mechanism.     

IEEE 802.11-saturation throughput analysis

To satisfy the emerging need of wireless data communications, the IEEE is currently standardizing the 802.11 protocol for wireless local area networks. This standard adopts a CSMA/CA medium access control protocol with exponential backoff. We present a simple analytical model to compute the saturation throughput performance in the presence of a finite number of terminals and in the assumption of ideal channel conditions. The model applies to both basic and request-to-send/clear-to-send (RTS/CTS) access mechanisms. Comparison with simulation results shows that the model is extremely accurate in predicting the system throughput     

A portable multimedia terminal

A personal communications system (PCS) that centers on integration of services to provide access to data and communications using a specialized, wireless multimedia terminal is described. The possible applications and support systems for such a terminal are outlined. Several of the major design issues behind portable multimedia terminals, including spectrally efficient picocellular networking, low-power digital design, video data compression, and integrated wireless RF transceivers, are discussed. It is argued that optimizing performance in each of these areas is crucial in meeting the performance requirements of the overall system and providing a small, lightweight terminal for personal communications     

On Multiple Traffic Type Integration over Wireless TDMA Channels with Adjustable Request Bandwidth

A new medium access control (MAC) protocol for mobile wireless communications is presented and investigated. We explore, via an extensive simulation study, the performance of the protocol when integrating voice, video and data packet traffic over a wireless channel of high capacity (referring to an indoor microcellular environment). Depending on the number of video users admitted into the system, our protocol varies: a) the request bandwidth dedicated to resolving the voice users contention, and b) the probability with which the base station grants information slots to voice users, in order to preserve full priority for video traffic. We evaluate the maximum voice capacity and mean access delay, as well as the aggregate channel throughput, for various voice and video load conditions, and the maximum voice capacity, aggregate channel throughput and average data message delays, for various video, voice and data load conditions. As proven by the comparison with a recently introduced efficient MAC scheme (DPRMA), when integrating voice and video traffic our scheme obtains higher voice capacity and aggregate channel throughput. When integrating all three traffic types, our scheme achieves high aggregate channel throughput in all cases of traffic load.     

异构多模终端的接入选择功能架构

不同类型无线网络的融合是宽带无线通信发展的必然趋势。在异构融合网络环境中,无论何种无线网络都能够提供无所不在的最优服务。具有挑战性的问题就是异构多模终端的管理系统和接入选择功能架构的设计。一种异构多模终端管理架构通过与各协议层的有效交互,可以适应多种接入标准与技术的要求,实现多模异构终端的无缝接入和移动。接入选择是核心研究问题之一,接入选择功能架构主要包含3个模块：接入适配、移动管理、用户偏好。     

Services in interworking 3G and WLAN environments

Interworking WLANs and 3G mobile networks are expected to provide ubiquitous wireless communications at high data rates and a large variety of services with variable bandwidth and QoS requirements, across a wide range of propagation environments and mobility conditions, using dual mode terminals. The interworking of the two networks is a major step toward a new generation of wireless networks in which other radio technologies are also be integrated. In this article we present possible architectures that enable the interworking of 3G and WLAN networks. We then address the capabilities of various terminal types and describe future services in the interworking environment. Finally, we present market forecasts on terminal and service demand growth.     

Evolution in wireless systems management concepts: from composite radio environments to reconfigurability

Wireless communications is witnessing the emergence of the composite radio and reconfigurability concepts. The former assumes that different radio networks can be cooperating components in a heterogeneous wireless access infrastructure, through which network providers can more efficiently achieve the required capacity and QoS levels. Reconfigurability enables terminals and network elements to dynamically select and adapt to the most appropriate radio access technologies for handling conditions encountered in specific service area regions and time zones of the day. Both concepts pose new requirements on the management of wireless systems. This article presents a management system, which has been developed for enabling wireless systems to operate in a CR context. Moreover, the article addresses the necessary extensions to the management system for handling the impact of the reconfigurability context.     

Performance of an exponential backoff scheme for slotted-ALOHAprotocol in local wireless environment

Slotted ALOHA is widely used in local wireless communications not only by itself as a multiple access protocol but also as a component in many reservation protocols. The paper suggests a very simple backoff scheme for slotted ALOHA and evaluates its performance in local wireless environments. The authors analyze the system capacity in full load conditions and the throughput-delay characteristics in underload conditions. They conduct a computer simulation to evaluate the system performance in transient-state. They also give a protocol parameter value which is highly recommendable from the practical viewpoint. As an application example, they examine the packet reservation multiple access (PRMA) system with the suggested backoff scheme and compare its performance with that of the original PRMA system     

Comparison of video protection methods for wireless networks

An experimental comparison of video protection methods targeted for wireless networks is presented. Basic methods are the data partitioning, reversible variable length coding, and macroblock row interleaving as well as macroblock scattering for packet loss protection. An implementation is described, in which scalable video is protected unequally with forward error correcting codes and retransmissions. Comparisons are performed for simulated wideband code division multiple access channel, and measurements are carried out with wireless local area network, Bluetooth as well as with GSM high speed circuit switched data. For the measurements, point-to-point connections are used. The achieved video quality is examined in our real-time wireless video demonstrator. The performance is measured with peak-signal-to-noise-ratio of received video, data overhead, communication delay, number of lost video frames, and decoding frame rate. Results show that the quality of decoded video can be improved by 1 dB with transparent connections compared to connections designed for general packet data. As a conclusion, a video coding subsystem must have access to the error control in a wireless link for the best quality in varying conditions.     

Development of Ka-band 100-W peak power MMPM

Various types of millimeter-wave radio systems are being developed for strong broadband service demands such as fixed wireless access, local multipoint distribution service, as well as satellite communications. In each system, the higher data rate transmission requires more powerful amplification devices. This paper describes the development of a Ka-band 100-W peak power millimeter-wave power module, traveling wave tube-based millimeter-wave amplification module, used for millimeter-wave fixed wireless access base stations and Ka-band satellite Internet terminals.     

An Access Selection Functional Architecture for Heterogeneous Multi-Mode Terminals

The convergence of heterogeneous wireless networks is an inevitable trend in broadband wireless communications development. In heterogeneous networks convergence environment, each wireless network can provide ubiquitous, best Quality of Service (QoS) services. The challenge lies in the design of the management system and access selection architecture for heterogeneous multi-mode terminals. A type of management architecture for heterogeneous multi-mode terminal via effective interaction with all protocol layers is adaptable for multi-access standards and technical requirements to achieve seamless access and mobility for multi-mode heterogeneous terminals. As the core subject for research, access selection functional architecture mainly consists of three modules, namely access adaptation, mobility management, and user preference.     

基于EPON MAC层协议的无线接入研究

光通信与无线通信的融合实现宽带无线接入是将来网络接入最具竞争优势的解决方案之一。为了能应用PON结构的技术优势和实现基于PON的无线接入,提出在EPON MAC层中适当增加WiFi无线接入控制有关的协议帧的技术方案,实现了EPON的宽带无线接入。建立基于该方案的网络模型。通过仿真实验,表明适当修改EPON MAC层协议,可实现EPON与WiFi的无线接入。     

Performance Evaluation of a Variable Frame Multiplexer for Integrated Switched Networks

A scheme which multiplexes long messages and single packets using a time-varying frame is presented. Long messages, generated from a fixed number of terminals, immediately access a main trunk, sharing a dynamically dedicated subchannel in a roundrobin fashion. Fixed size packets arrive with Poisson statistics in a FIFO queue and are served through the same trunk, using the remaining capacity. The two traffic categories share an integrated variable length frame. The frame length is determined by the volume of the increasing traffic at the beginning of the frame and cannot exceed a maximum value. Analysis of the performance of the system is carried out using finite population round-robin processor sharing andM/G/Nqueueing techniques. Simplifying modeling assumptions are checked with simulation. A comparison with fixed frame schemes demonstrates the superiority of the variable frame, in terms of more efficient bandwidth utilization.     

New concepts and technologies for achieving highly reliable andhigh-capacity multimedia wireless communications systems

The rapid growth of multimedia wireless communications services forces the development of advanced digital wireless systems with high reliability and high speed as well as flexibility for varying traffic conditions. To achieve such advanced wireless systems. New system design concepts different from the conventional ones aiming at increasing system capacity for voice transmission would be required. Since multimedia wireless communications require high quality, high speed, and high flexibility as well as temporary and spatial control of traffic under severe fading environments, the so-called conventional system design concept will be insufficient. New system design concepts and techniques for achieving highly reliable and high-capacity multimedia wireless communications are discussed using both time division multiple access (TDMA) and code division multiple access (CDMA) systems. The demands for high-speed and high-reliability mobile, personal, and multimedia wireless communications services strongly require matching with the trunk network constructed by a broadband optical fiber system or wired system     

Technological developments and socio-economic issues of wireless mobile communications

During the last 10 years, wireless communications can be considered as the fastest growing segment of telecommunications. In fact, mobile telephones have become an everyday accessory for hundreds of million people, and they are increasingly being used in the most developed and many developing countries in the world. Current forecasts indicate that demands for wireless access will exceed the number of fixed access lines by year 2010. This paper examines the technological developments, as well as the worldwide social-economic impacts of wireless mobile communications. More specifically, it gives an overview on the technological developments of wireless mobile communications, describes the evolution towards the next-generation systems, analyzes the reasons for the growth rate of subscribers, and the related social development. As a conclusion, it suggests several solutions in response to dangerous behaviour generated by wireless terminals.     

Performance analysis of dynamic OFDMA systems with inband signaling

Within the last decade, the orthogonal frequency- division multiplexing (OFDM) transmission scheme has become part of several standards for wireless systems. Today, OFDM is even a candidate for fourth-generation wireless systems. It is well known that dynamic OFDMA systems potentially increase the spectral efficiency. They exploit diversity effects in time, space, and frequency by assigning system resources periodically to terminals. Informing the terminals about new assignments creates a signaling overhead. Up to now, this overhead has not been taken into account in studies on dynamic orthogonal frequency-division multiplexing access (OFDMA) systems. Yet this is crucial for a realistic notion of the performance achieved by dynamic approaches. In this paper, we close this gap. We introduce two forms of representing the signaling information and discuss how these affect system performance. The study of the signaling impact on the performance is conducted for an exemplary dynamic approach. We find that the throughput behavior of dynamic OFDMA systems is significantly influenced by the signaling overhead. In many situations, neglecting the overhead leads to wrong performance conclusions. Also, the performance difference between dynamic and static schemes is now much more sensible to the specific parameter set of the transmission scenario (e.g., frame length, subcarrier number, etc.). This leads to the proposal of access points which should adapt certain system parameters in order to provide optimal performance.     

Comparison of maximum-likelihood-based detection for two multirateaccess schemes for CDMA signals

Future wireless systems will need to accommodate information sources with different data rates. Direct-sequence code-division multiple-access (DS/CDMA) is a multiple access technique that is well suited to provide multirate access. Thus, in this paper, multirate communication systems are considered for the transmission of DS/CDMA wireless signals. Performance for maximum-likelihood-based detection is studied in the context of two multirate access methodologies: multicode access, where high data rate users multiplex their information streams onto multiple codes; and variable spreading length access where signature sequences of different lengths are assigned to users with different data rates. Various maximum-likelihood-based detection schemes for the variable spreading length system are considered as they can achieve near-optimal performance and thus provide reference points for comparison with suboptimal schemes. In addition, asymptotic multiuser performance measures are calculated and bounded to compare performance of the two systems     

Guaranteed quality-of-service wireless access to ATM networks

We study the problem of wireless access to asynchronous transfer modes (ATMs). We consider three classes of ATM sources: constant bit rate (CBR), variable bit rate (VBR), and available bit rate (ABR). We propose a polling scheme with nonpreemptive priority. Under such a scheme, we derive sufficient conditions such that all the CBR sources satisfy their jitter constraints and all the VBR sources satisfy their delay constraints. The remaining bandwidth is used by the ABR sources, for which we adapt a random access scheme proposed by Chen and Lee (1994). For this random access scheme, we derive the throughput-offer load characteristic, and thus the capacity. Based on this, we propose adaptive random access schemes that track the offer load to its optimal value. Our simulations show that our adaptive schemes maintain a high throughput with respect to the whole range of system load