Analysis of Sub-Carrier Multiplexed Radio Over Fiber Link for the Simultaneous Support of WLAN and WCDMA Systems

The present third generation (3G) wireless technology can provide data oriented applications. However, the bit rate is limited to around 2 Mbps with limited mobility. Today, more applications demand high data rate and reasonable mobility. Therefore, by integrating 3G cellular system and wireless local area network (WLAN), there is a potential to push the data rate higher. This integration means 3G cellular users can enjoy high data rate at a location that is within WLAN coverage area. Similarly, WLAN users also can have data services as long as they are under the coverage of the 3G cellular system. The 3G cellular system has a much larger coverage than the WLAN. In this paper, we present the first step toward an integration of the two systems. This paper presents a fiber-wireless architecture that simultaneously supports the wideband code division multiple access (WCDMA) system and the IEEE 802.11b WLAN. Our approach uses sub-carrier multiplexed (SCM) architecture to combine and transmit 2.4 GHz WLAN and 1.9 GHz WCDMA signals through an optical fiber from a central base station (CBS) to a radio access point (RAP, single antenna unit). After the fiber, the signals continue to propagate through the air interface to respective mobile stations. The WLAN access point is also located at the CBS. For the SCM architecture, we investigate three areas: i) the signal to noise ratio of the uplink and the downlink, ii) the cell coverage area for the WCDMA and WLAN systems, and iii) the throughput of the IEEE 802.11b WLAN. Our results show that with up to 2.5 km cell radius, better than 18 dB SNR is possible with 5 km fiber link for WLAN system. Simultaneously, the WCDMA system has at least 18 dB SNR for a cell coverage radius of 8 km. These numbers depend on the relative RF power of each system in the fiber.Roland M.C. Yuen received a Bachelor of Electrical Engineering degree in 2003 from Ryerson University, Toronto, Canada. He is pursuing a Master of Applied Science degree at Ryerson University. He has a conference paper. His research interests are in the area of optical and wireless communications.Currently, he works on unique fiber based architecture to extend the capability of cellular networks and support wireless LANs simultaneously.Xavier N. Fernando () obtained B.Sc. Eng. (First Class Honors) degree from Sri Lanka, where he was first out of 250 students. He got Master’s degree from the Asian Institute of Technology (Bangkok) Ph.D. from the University of Calgary, Canada in affiliation with TRLabs. He has worked for AT&T for three years as an R&D Engineer. Currently he is an Assistant Professor at Ryerson University, Toronto, Canada.Dr. Fernando one US patent and about 38 peer reviewed publications in journals and conference proceedings. His research focuses on signal processing for cost-effective broadband multimedia delivery via optical wireless networks. Dr. Fernando′s work won the best research paper award in the Canadian Conference of Electrical and Computer Engineering for the year 2001. His student projects won both the first and second prize at Opto Canada – the SPIE regional conference in Ottawa in 2002. He is a senior member of IEEE, member of SPIE, Chair of the IEEE Communications Society Toronto Chapter and licensed Professional Engineer in Ontario, Canada. He has many research grants including Canadian Foundation of Innovations (CFI), Ontario Innovations Trust (OIT) and Natural Sciences and Engineering Research Council (NSERC) of Canada.     

The Mobile Broadband WiMAX Standard [Standards in a Nutshell]

Mobile worldwide interoperability for microwave access (WiMAX) is a wireless standard that introduces orthogonal frequency division multiple access (OFDMA) and other key features to enable mobile broadband services at a vehicular speed of up to 120 km/h. WiMAX complements the and competes with wireless local area networks (WLANs) and the third generation (3G) wireless standards on coverage and data rate. More specifically, WiMAX supports a much larger coverage area than WLAN, does not require line of sight for a connection, and is significantly less costly compared to the current 3G cellular standards. Although the WiMAX standard supports both fixed and mobile broadband data services, the latter have a much larger market. Therefore, this article will briefly present the Mobile WiMAX standard, the technologies deployed for the air interface and the network, and the development of the standards to support mobile multihop relays in a WiMAX network.     

WLAN无线接入网络规划及其网络性能优化研究

随着WLAN无线的发展,其覆盖区域、用户量、网络容量不断增加,使其接入网络规划的问题逐渐成为建设公共无线局域网的重要问题.同时,对WLAN无线接入网络性能优化是满足用户需求的关重要手段,网络性能优化主要有覆盖优化、容量优化、设备优化.     

A hierarchical radio resource management framework for integrating WLANs in cellular networking environments

Over the last few years wireless local area networking (WLAN) has become a very important technology that offers high-speed communication services to mobile users in indoor environments. WLAN technology offers some very attractive characteristics such as high data rates, increased QoS capabilities, and low installation costs which has made many professionals claim that it will be the main opponent of IMT-2000, despite the enormous effort needed for the specification and implementation of 3G systems. However, WLANs also present many important constraints related mainly to their restricted coverage capabilities. On the other hand, 3G systems are deployed gradually and carefully since their business prospects have not been validated yet and it is expected that 2G and 2G+ cellular systems will continue to play an important role for at least five more years. Thus, today's wireless networking environment is in fact a conglomeration of all these technologies for which there is a strong need for cooperation. In this article we describe a heterogeneous wireless networking environment together with its features and user requirements. We explain the importance of the existence of WLANs and describe a framework and system architecture that supports seamless integration of WLAN in heterogeneous cellular networking environments, focusing on support for efficient resource provision and management.     

An energy-efficient interface selection for multi-mode terminals by utilizing out-of-band paging channels

With the advent of a number of wireless network technologies such as WCDMA and WLAN, current mobiles are equipped with multiple network interfaces, so called Multi-Mode Terminal (MMT). MMTs are capable to access different kinds of networks by performing a vertical handover between heterogeneous wireless networks, where during the idle state, the MMTs consume a lot of energy since their WLAN interface must wake up for listening to periodical beacons. However, previous studies on the vertical handover did not address how to select the optimal interface taking into account the characteristics of MMTs, especially energy consumption. Therefore, in this paper, we propose an energy-efficient interface selection scheme for MMTs in the integrated WLAN and cellular networks. The proposed interface selection scheme takes advantage of existing out-of-band paging channel of cellular networks, so that the WLAN interface can be completely turned off during the idle state leading to reduction in energy consumption. Simulation results show that the proposed scheme outperforms conventional approaches in terms of energy consumption with reduced signaling overhead and handover delay.     

An outlook on the evolution of mobile terminals: from monolithic to modular multiradio, multiapplication platforms

Terminals, including traditional cellular phones, have historically been optimized for a small number of services over a specific network. With the convergence of consumer electronics and Internet-based services, voice and video are now being offered on a variety of access networks, and many functions are being combined into single devices. In addition to new sophisticated audio/video coding and graphics capabilities, there is a growing demand for cheap and ubiquitous broadband wireless Internet access. This demand is driving the need for multiradio platforms that include new licensed and unlicensed air interface technologies, such as WLAN, UWB and Wimax. The proliferation of new applications and wireless standards has created the need for a dramatic change in the portable/mobile terminal architecture. This paper presents an overview of the evolution of mobile terminal architectures, from monolithic to flexible, modular, and capable of meeting the increasing demand for an ever larger number of features at the right cost and time to market.     

Beyond 3G: wideband wireless data access based on OFDM and dynamicpacket assignment

The rapid growth of wireless voice subscribers, the growth of the Internet, and the increasing use of portable computing devices suggest that wireless Internet access will rise rapidly over the next few years. Rapid progress in digital and RF technology is making possible highly compact and integrated terminal devices, and the introduction of sophisticated wireless data software is making wireless Internet access more user-friendly and providing more value. Transmission rates are currently only about 10 kb/s for large cell systems. Third-generation wireless access such as WCDMA and the evolution of second-generation systems such as TDMA IS-136+, EDGE, and CDMA IS-95 will provide nominal bit rates of 50-384 kb/s in macrocellular systems. This article discusses packet data transmission rates of 2-5 Mb/s in macrocellular environments and up to 10 Mb/s in microcellular and indoor environments as a complementary service to evolving second- and third-generation wireless systems. Dynamic packet assignment for high-efficiency resource management and packet admission; OFDM at the physical layer with interference suppression, space-time coding, and frequency diversity; as well as smart antennas to obtain good power and spectral efficiency are discussed in this proposal. Flexible allocation of both large and small resources also permits provisioning of services for different delay and throughput requirements     

WLAN-GPRS integration for next-generation mobile data networks

The ongoing wireless LAN standardization and R&D activities worldwide, which target bit rates higher than 100 Mb/s, combined with the successful deployment of WLANs in numerous hotspots justify the fact that WLAN technology will play a key role in wireless data transmission. Cellular network operators have recognized this fact, and strive to exploit WLAN technology and integrate this technology into their cellular data networks. For this reason, there is currently a strong need for interworking mechanisms between WLANs and cellular data networks. We focus on these interworking mechanisms, which effectively combine WLANs and cellular data networks into integrated wireless data environments capable of ubiquitous data services and very high data rates in hotspot locations. We discuss the general aspects of integrated WLANs and cellular data networks, and we examine the generic interworking architectures that have been proposed in the technical literature. In addition, we review the current standardization activities in the area of WLAN-cellular data network integration. Moreover, we propose and explain two different interworking architectures, which feature different coupling mechanisms. Finally, we compare the proposed interworking architectures, and discuss their advantages and drawbacks.     

The Effect of On-Off Scheduling to the Required Transmit Power in Systems with Fast Power Control

Physical layer channel-aware scheduling may significantly improve coverage and throughput of IP based services in wireless cellular networks, and the feasibility of such schedulers is actively studied within 3G and 4G systems. A channel-aware scheduler requires access to instantaneous channel state information in order to direct transmission to users with favorable channel conditions. In frequency division duplex (FDD) systems, this requires a fast feedback channel between mobile and base stations, and the overhead of the feedback control channel should be kept as low as possible.In this paper, we study the effect of control channel overhead to on-off scheduling (OOS) when fast transmit power control is applied in data and control channels. On-off scheduling is a simple channel-aware scheduling algorithm, where transmission to a user is suspended if the transmit power exceeds a given threshold. On-off scheduling is applied on the data channel while control channel is always on so that the scheduler is able to obtain channel state information from active users. The gain of OOS strongly depends on the power ratio between control and data channels, and increased interference due to control signaling and decreased interference due to channel-aware scheduling should be jointly considered in system design. Gains in the required transmit power are translated into gains in coverage and capacity assuming WCDMA parameters, and the results can be applied, e.g., when designing scheduling algorithms and corresponding signaling formats for WCDMA uplink.     

高校WLAN覆盖方案及安全策略研究

高校由于人流密集,用户资源优良,场景丰富,数据业务需求突出,成为了WLAN覆盖的重点区域。本文提出一种普遍可行的高校WLAN建设方案和多种安全策略。     

Design and implementation of a WLAN/cdma2000 interworking architecture

The combination of 3G and WLAN wireless technologies offers the possibility of achieving anywhere, anytime Internet access, bringing benefits to both end users and service providers. We discuss interworking architectures for providing integrated service capability across widely deployed 3G cdma2000-based and IEEE 802.11-based networks. Specifically, we present two design choices for integration: tightly coupled and loosely coupled, and recommend the latter as a preferred option. We describe in detail the implementation of a loosely coupled integrated network which provides two kinds of roaming services, a SimpleIP service and a Mobile-IP service. We present, in detail, two new components used to build these services: a network element called a WLAN integration gateway deployed in WLAN networks; a client software on the mobile device. For a mobile device with interfaces to both technologies, our system supports seamless handoff in the presence of overlapping radio coverage.     

PIANO: A power saving strategy for cellular/VoWLAN dual-mode mobiles

The integration of cellular and VoIP over WLAN (VoWLAN) systems recently has attracted considerable interest from both academia and industry. A cellular/VoWLAN dual-mode system enables users to access a low-cost VoIP service in a WLAN hotspot and switch to a wide-area cellular system without WLANs. Unfortunately, cellular/VoWLAN dual-mode mobiles suffer the power consumption problem that becomes one of the major concerns for commercial deployment of the dual-mode service. In this study, we present a novel power saving mechanism, called PIANO (paging via another radio), for the integration of heterogeneous wireless networks, and further apply the proposed methods to implement a cellular/VoWLAN dual-mode system. Based on the proposed mechanisms, a dual-mode mobile can completely switch off its WLAN interface, only leaving the cellular interface awake to listen to paging messages. When a mobile receives a paging message from its cellular interface, it wakes up the WLAN interface and responds to connection requests via WLAN networks. Therefore, a dual-mode mobile reduces the power consumption by turning off the WLAN interface during idle, and can also receive VoWLAN services. Measurement results based on the prototype system demonstrate that the proposed methods significantly extend the standby hours of a dual-mode mobile.     

Secure Service and Network Framework for Mobile Ethernet

Secure cellular data services have become more popular in the Japanese market. These services are based on 2G/3G cellular networks and are expected to move into the next-generation wireless networks, called Beyond 3G. In the Beyond 3G, wireless communication available at a user's location is selected based on the type of the service. The user downloads an application from one wireless network and executes it on another. Beyond 3G expects core and wireless operators and allows to plug-in new wireless access. A security model that can accommodate these requirements needs to be sufficiently flexible for end users to utilize with ease. In this paper, we explain the Mobile Ethernet architecture for all IP networks in terms of the Beyond 3G. We discuss usage scenario/operator models and identify entities for the security model. We separate a mobile device into a personal identity card (PIC) containing cryptographic information and a wireless communications device that offers security and flexibility. We propose a self-delegation protocol for device authentication and use a delegated credential for unified network- and service-level authentication. We also propose proactive handover authentication using the security context between different types of wireless access, such as Third Generation Partnership Project (3GPP) and WLAN, so that the secure end-to-end communication channels established by service software on the TCP/IP are not terminated. Lastly, we raise security issues regarding the next-generation platform.     

A MIMO-OFDM prototype for next-generation wireless WANs

Coupled with a robust and efficient OFDM air interface, MIMO technologies lead to a very compelling high-speed data downlink solution for future wireless systems. This article presents Nortel Networks' MIMO-OFDM concept prototype and measured performance results. This prototype has been developed in the framework of a Nortel Networks system concept for 3G evolution systems and next-generation wide area wireless networks. The prototype is based on a shared access MIMO-OFDM physical layer in the downlink, supporting adaptive modulation and coding, with peak rates up to 37 Mb/s. The uplink is based on an enhanced UMTS WCDMA physical layer. Performance for the high-speed downlink has been measured under various emulated fading conditions. The measured performance illustrates the robustness of OFDM in frequency-selective channels and high-speed mobility channels, supporting speeds as high as 200 km/h. The prototype can also be used for over-the-air assessment of the technology.     

WLAN与WCDMA网络及业务融合初探

在介绍WLAN业务组网网络结构和WLAN与3G融合的必要性的基础上,分析了WLAN和WCDMA融合形成综合性的移动数据网,实现不同终端过渡或无缝连接的业务分配及共享的无线宽带网络。     

Authentications and Key Management in 3G-WLAN Interworking

The successful deployment of WLAN for high speed data transmission and 3G cellular systems for wide coverage and global roaming has emerged to be a complementary platform for wireless data communications. But security in the 3G-WLAN interworking, especially the efficient authentication and valid key management, has been remaining a challenging issue. What’s more, some emerging security challenges are neglected by 3GPP specifications as well as the previous studies. This paper first analyzes and evaluates the current contributions in this field, and then puts forward some design issues. Thereafter, by modifying the EAP-AKA keying framework we propose an improved authentication scheme which enables a WLAN user to efficiently access packet switch services through the 3G networks. What’s more, through the new keying framework the user can efficiently realize the future re-authentications and handover authentications. The proposed authentication scheme, the corresponding re-authentications and handover authentications are simulated, and results indicate that our scheme can reduce authentication latency significantly.     

Signal processing advances for 3G WCDMA: From rake receivers to blind techniques

As already deployed and proven technology, code-division multiple access has evolved to support competitive high-data-rate low-latency multimedia services over wireless cellular networks. In this article we introduce advanced signal processing techniques to enhance CDMA receiver performance further. In particular, we consider the possibility of optimal joint multiuser detection for long code WCDMA using fast inversion based on a state-space approach with reasonable complexity, and semi-blind channel estimation techniques to realize rate-efficient transmission for the latest 3G standards.     

Enhancing IP service provision over heterogeneous wirelessnetworks: a path toward 4G

Second-generation mobile radio systems have been deployed successfully worldwide and have evolved to higher data rates and services. Third-generation mobile radio systems are currently starting to be developed in different regions of the world. Today, the open question is how the third-generation systems will evolve. It is very likely that fourth-generation systems will not be a single standardized air interface, but a set of different technologies and standards. In particular, wireless LAN/wireless PAN type systems are designed for high/medium-data-rate access, low range, and, in general, low mobility. They are applicable to corporate networks and public access as a complement to cellular mobile radio systems for hot spot applications such as airports, hotels, and campuses. In this specific WLAN/WPAN framework and to guarantee an agreed QoS provision over such infrastructures, we propose a solution based on the wireless adaptation layer approach. In particular, aspects related to wireless link impairments and traffic requirements are approached by the implementation of configurable, modular software that is adapted to the specific conditions and needs of the particular wireless infrastructures     

Radio interfaces make the difference in 3G cellular systems

Third-generation cellular telephony is on its way-not, unfortunately, as a single worldwide system, but as three incompatible ones. The main difference between the three lies in their choice of radio interface technology. This fact is crucial for several reasons, since the radio interface determines not only the fundamental capacity of a mobile radio network, but also how it deals with such issues as interference, multipath distortion, and handing off calls from one base station to another as users move around. Consequently, as might be expected, the choice of radio interface has a dramatic effect on the complexity of the system and its cost. Also, global travellers will need more than one phone with which to communicate, at least until trimode phones reach the market. To understand what is being developed, and why, the author begins with one of the stated goals of third-generation (3G) systems, namely to support variable user data rates as high as 2 Mb/s. In one way or another, all three approaches provide for adaptive bandwidth-on-demand. Two of the systems use wideband code-division multiple access (WCDMA) for the radio interface. The other uses two variations of time-division multiple access (TDMA)     

Analysis of TCP performance under joint rate and power adaptation in cellular WCDMA networks

To improve the spectral efficiency while meeting the radio link level quality of service requirements such as the bit-error-rate (BER) requirements for the different wireless services, transmission rate and power corresponding to the different mobile users can be dynamically varied in a cellular wideband code-division multiple-access (WCDMA) network depending on the variations in channel interference and fading conditions. This paper models and analyzes the performance of transmission control protocol (TCP) under joint rate and power adaptation with constrained BER requirements for downlink data transmission in a cellular variable spreading factor (VSF) WCDMA network. The aim of this multilayer modeling of the WCDMA radio interface is to better understand the interlayer protocol interactions and identify suitable transport and radio link layer mechanisms to improve TCP performance in a wide-area cellular WCDMA network.