Optical wireless systems represent one of the most promising approaches for addressing the emerging access market. These robust systems, which establish communications links by transmitting laser beams directly through the atmosphere, have matured to the point that mass-produced models will soon be available. Optical wireless systems offer many features, principal among them being low start-up and operational costs, rapid deployment, and high fiber-like bandwidths. Available systems offer capacities in the range of 100 Mbps to 2.5 Gbps, and demonstration systems report data rates as high as 160 Gbps. This paper presents an overview of the optical wireless industry, including benefits and limitations, and identifies the most advantageous applications.

This paper explores Free Space Optics (FSO) as an access technology in the last mile of metropolitan area networks (MANs). These networks are based in part on fiber-optic telecommunications infrastructure, including network architectures of Synchronous Optical Network (commonly referred to as SONET), the North American standard for synchronous data transmission; and Synchronous Digital Hierarchy (commonly referred to as SDH), the international standard and equivalent of SONET. Several converging forces have moved FSO beyond a niche technology for use only in local area networks (LANs) as a bridge connecting two facilities. FSO now allows service providers to cost effectively provide optical bandwidth for access networks and accelerate the extension of metro optical networks bridging what has been termed by industry experts as the optical dead zone. The optical dead zone refers to both the slowdown in capital investment in the short-term future and the actual connectivity gap that exists today between core metro optical networks and the access optical networks. Service providers have built extensive core and minimal metro networks but have not yet provided optical bandwidth to the access market largely due to the non-compelling economics to bridge the dead zone with fiber. Historically, such infrastructure build-out slowdowns have been blamed on a combination of economics, time-to-market constraints and limited technology options. However, new technology developments and market acceptance of FSO give service providers a new cost-effective alternative to provide high-bandwidth services with optical bandwidth in the access networks. Merrill Lynch predicts FSO will grow into a $2 billion market by 2005. The drivers for this market are a mere 5%- 6% penetration of fiber to business buildings; cost effective solution versus RF or fiber; and significant capacity which can only be matched by a physical fiber link, Merrill Lynch reports. This paper will describe FSO technology, its capabilities and its limitations. The paper will investigate how FSO technology has evolved to its current stage for deployment in MANs, LANs, wireless backhaul and metropolitan network extensions - applications that fall within the category of last mile. The paper will address the market, drivers and the adoption of FSO, plus provide a projection of future FSO technology, based on today's product roadmaps. The paper concludes with a summary of findings and recommendations.

The paper addresses a techno-economic analysis of some key aspects for the network upgrade for the proposed free space optical (FSO) broadband access networks, which include the effect of duct availability and civil works cost, influence of the cost of electronics, optical mesh networks compared to FTTH/U/C/B architecture as a strategic decision, effects on costs of optical network termination customer sharing and timing of the upgrade.

This paper reports on the design considerations and implementations of construction of a receiver system for an infrared communication link using Light-Emitting-Diodes (LEDs). System configuration is non-directed line of sight (LOS) with single element receiver. The speed of the system constructed is 20 MHz (40 Mbps for on-off keying). In our design, the receiver consists of a multi-channel photo-detector array followed by multi-channels transimpedance amplifiers, a summer circuit for combining signals, low-pass filters(LPF) and high pass filters(HPF), and auto-gain control unit(AGC). The spectral match between photodiode and LED, looking angle of photodiode, rise time consideration of the photodiode, trade-off between transit rise time and photodiode effective area, etc, are also be discussed . A receiver module of speed response up to 20 MHz has been successfully constructed and the system is capable of receiving optical signal at a height of 2 m from the ceiling with coverage of a cell of 4 m in diameter.

Laser and LED-based wireless communication systems are currently providing license-free interconnection for broadband voice, data and video transport. These systems allow for the immediate, reliable and low-cost extension of copper and fiber-based networks to any end user, providing efficient First Mile bypass access to high data rate backbone networks at speeds ranging from T-1 voice to full throughput ATM at 155 Mbps and up to Gigabit Ethernet. These wireless optical beams constitute a Virtual Fiber in the air, providing the capabilities of fiber in situations where wired connectivity is unavailable, impractical, expensive or slow-to-implement, while achieving a combination of low cost, speed and reliability that cannot be matched by microwave, mm wave, spread spectrum or other competing (actually complementary) wireless technologies. The carrier frequency of the optical beam is about 10,000 times higher than the highest frequencies used by the millimeter wave technology. By means of Wavelength Division Multiplexing more than 1000 independent data channels can be projected into the air on a single beam thus providing a potential bandwidth ten million times that of any RF solution. The twin barriers of physics and regulatory bureaucracy to this essentially infinite wireless bandwidth are thus eliminated by this Virtual Fiber. As user density and individual bandwidth needs escalate, the optical wireless will be the preferred medium of choice in both network and cellular interconnection. A mesh topology which integrates our optical wireless systems with the latest Optical Access switches and routing equipment will be described using case study examples from Japan to South America. As the Bandwidth Blowout continues to push the limits of electronics and especially in the case of DWDM (Dense Wavelength Division Multiples), the conventional optical wireless solutions are no longer feasible. Instead of using f.o. transceivers to convert photons to electrons and thence back to photons we have designed a series of airlinks whose transmitters and receivers operate without electronics. At the PATX (Photonic Airlink Transmitter), instead of demodulating the fiber optic input signals from a Network Interface Unit (NIU) we project the light from the polished terminated fiber end into the air using appropriate optics. Any signal being carried by the fiber from the NIU is now airborne without any intermediate processing electronics thus realizing the full potential of the optical carrier. At the receiver end (PARX - Photonic Airlink Receiver), the weak optical signals are collected by the appropriate optics (including combiners using large area MMF) and guided to the NIU (switch, PABX, etc.) by compatible fiber. It is necessary to maintain a large field-of-view at the receiver to ensure reliability, stability and ease of alignment. This is achieved by use of high N.A. fiber. In this paper we discuss the design trade off's, construction and field test results of several systems implementing the all- photonic wireless concept including: Transmission of WDM signals through the air at distances up to 1 km. Results with wireless transmission of Gigabit Ethernet using the Optiswitch modules as the NIU. Providing high speed wireless (Fast Ethernet and beyond) to the home at a cost of less than $250 per node. The paper will conclude with a discussion on the role of the all-photonic wireless technology in the emerging field of Passive Optical Networking.

Standardization of 3rd Generation (3G) mobile communication systems has produced the first specification releases and the commercial deployment of the 3G systems has started. Whereas 1G and 2G focused on efficiently providing voice services, in 3G a lot of attention has been devoted to solutions that support both Circuit Switched (CS) and Packet Switched (PS) communication. That has called for very flexible air interface and network solutions. 3G will continue to evolve and there are already on-going standardization activities that will, for example, boost the peak data rates up to 5-10 Mbps and improve spectral efficiency by 2-4 times. In the future, 3G evolution will be going towards 10/100 Mbps peak data rates in wide/local are coverage, respectively. This will take place partly because of technical improvements of 3G radio interface solutions, but also due to network evolution which will allow the integration other radio access methods like radio LANs into the 3G system. In longer term the 3G network evolution will be going towards ALL-IP networks. As 3G evolution seems to be going towards 10 Mbps/100 Mbps peak data rates and ALL-IP networks any beyond 3G air interface or network solution should be clearly better in order to justify its technical and commercial feasibility. Given the long evolution time of 3G and integration of other radio access schemes with 3G radio we may not even see a new, complete beyond 3G system being developed. Maybe we will just witness the emergence of a new, more advanced radio access solution which will then be connected to the evolving 3G network. As 3G evolution will continue for several years to come the research targets for any beyond 3G solutions must be set very high. When it comes to air interface, we should aim at 100 Mbps peak data rates for wide area access with high mobility, and at 1 Gbps for local area access with low mobility. Regarding possible commercial launches of any beyond 3G systems or solutions they could then take place around year 2010 or even later.

In this paper, we propose a cost effective add-drop fiber-optic microcell system for CDMA cellular network. The add-drop microcell is compatible with the existing PCS or digital cellular services (DCS) systems & networks. The proposed fiber-optic add-drop access network is independent of the different channels and gives flexibility in evolution scenarios. This add-drop network provides the optimum solution to cut-down the additional rental fees by sharing the existing fiber-optic cable for cellular/PCS service providers who want to provide third generation services.

UMTS has defined W-CDMA as its main radio interface with data rates up to 2 Mbit/s. However there is a need for faster services. This paper describes the introduction of HIPERLAN/2 into UMTS but also gives an overview on public WLAN operation using 802.11b systems and the options mobile network operators can use to stay competitive.

In UMTS new IP based services with tight delay constraints will be deployed over the W-CDMA air interface such as IP multimedia and interactive services. To integrate the wireline and wireless IP services, 3GPP standard forum adopted the Session Initiation Protocol (SIP) as the call control protocol for the UMTS Release 5, which will implement next generation, all IP networks for real-time QoS services. In the current form the SIP protocol is not suitable for wireless transmission due to its large message size which will need either a big radio pipe for transmission or it will take far much longer to transmit than the current GSM Call Control (CC) message sequence. In this paper we present a novel compression algorithm called Lightweight SIP/SDP Compression Scheme (LSSCS), which acts at the SIP application layer and therefore removes the information redundancy before it is sent to the network and transport layer. A binary octet-aligned header is added to the compressed SIP/SDP message before sending it to the network layer. The receiver uses this binary header as well as the pre-cached information to regenerate the original SIP/SDP message. The key features of the LSSCS compression scheme are presented in this paper along with implementation examples. It is shown that this compression algorithm makes SIP transmission efficient over the radio interface without losing the SIP generality and flexibility.

The needs for more spectrum and for spectrum harmonization are the key factors. The 3G (IMT2000/UMTS) systems will require sufficient spectrum to meet the tremendous traffic demand that is anticipated. Additional 3G bands for different regions were therefore defined at WRC2000 to complement the core bands already allocated at WARC/WRC95. In view of these decisions, ITU-R WP8F is working on the choice of the most appropriate channeling arrangements for these new 3G bands. The main goal is to find a Global Roaming Plan. Present contribution highlights all these activities and aims to find a compromise solution for global roaming.

The third generation mobile communication systems are expected to offer a large variety of services and calls for more flexible and efficient admission control strategy. This paper presents an adaptive admission control strategy for uplink transmission in WCDMA systems. The adaptive strategy gives priority to handoff calls and dynamically adjusts the number of guard channels according to the failure rates of the handoff calls. Simulation results demonstrate that the proposed strategy is more robust than fixed strategy under different mobility environment.

The display size and processor capacity of future mobile communicators along with data transmission capacity based on GPRS should provide tools for application builders to make new graphic applications, which are for example based on location data presented by maps, air photos etc. For application designers, service providers, network operators and finally consumers there are several unknown issues in this scenario. The purpose of this study is to present information about this context; especially about the wireless data transmission and its potential possibilities when implemented along the current GSM voice call services.

As very important key technologies of beyond 3G systems, MC- CDMA is the method combined OFDM and CDMA has being received more and more attention recently, because it can provide many advantages, such as larger capacity, high data rate, frequency and time diversity, etc. Multifarious MC-CDMA methods are investigated. In this paper, a new M-ary MC-CDMA method is proposed for transmitting high date rate and employing radio software technique after we investigate and review advanced OFDM, CDMA and MC-CDMA methods. M-ary MC-CDMA proposed is to divide multi parallel branches, each branch is modulated by high rate data using M-ary OFDM and is left each other by CDMA. Then the different user can use different number of parallel branches to transmit multimedia data. Simulation results show that M-ary MC-CDMA method proposed has better performance and high capacity, smart process ability of different multimedia service and resource management.

In this paper, we review the characteristics of a diffuse infrared channel and create a simulation environment for a diffuse infrared wireless network study in the network simulator ns-2. To investigate the performance of Distributed Coordination Function (DFC) access method in IEEE802.11 MAC protocol based on the Diffuse infrared (DFIR) physical layer, we focus on the key mechanisms, RTS/CTS message exchange and backoff algorithm, and evaluate the protocol performance for various network configurations. Our simulations show that the value of RTS_Threshold strongly depends on the network configuration. We also investigate the trade-off between RTS/CTS and backoff schemes. The results are shown in throughput and average MAC delay.

Mobile IPv6 has received tremendous attention from the cellular telephony industry for use in the next generation networks. This paper starts with recent development of Mobile IPv6 technologies and its standards, and explores remaining issues such as fast handover, smooth handover, mobility managements, AAA, QoS, security and scenarios in its deployment, with particular attention to IPv6.

IPv6 has an inherent characteristic of supporting mobility. When a mobile host (MH) undergoes handoff from one link to another, it needs to obtain a new Care-of Address (CoA) at the New Access Router (N.AR) as soon as possible in order to be able to send and receive IP packets. The basic MIPv6 is the case that MH acquired CoA after moving to handoff expected candidate region. MH obtained CoA before handoff, MH have experienced in reduced handoff latencies. The latency involved in forming a new CoA in MIPv6 comes mainly from both Neighbor Discovery (ND) and Duplicate Address Detection (DAD) in stateless auto-configuration scheme. As MH obtained CoA before handoff and P.AR is using a buffer management, our proposed method is fast and lossless. It is expected that DAD check is indispensable to detect the bad guys who use MH's address by stealth.

Mobility support on the network layer is of special importance, as the network layer holds together the huge Internet with common protocol IP. Although based on possibility different wireless or wired technologies, all nodes of the network should be able to communicate. Therefore, mobile IP(an extension of the classical IP) has been designed which enablemobility in the Internet without changing existing wired systems. However, mobile IP leaves some points unsolved. Especially, if it comes to security, efficiency of the packet flow that is called triangular routing. Especially triangular routing can cause unnecessary overhead for the network. Furthermore latency can increase dramatically. This is particularly unfortunate if two communicating hosts are separated by transatlantic links. In order to this problem, many methods like IPv6 and ROMIP are proposed. But these methods have limitation. In other words, they have not compatibility because of needing modification of original IP scheme. Especially ROMIP is very complex and the overhead of control message and processing are serious. The problem of inconsistency of Binding caches may occur too. We therefore propose and analyze the performance of the DRMIP (Direct Routing Mobile IP) which do not modify IP source needed in the sender, is compatible with IP and Mobile IP.

The tremendous demands from social market are pushing the booming development of mobile communications faster than ever before, leading to plenty of new advanced techniques emerging. With the converging of mobile and wireless communications with Internet services, the boundary between mobile personal telecommunications and wireless computer networks is disappearing. Wireless networks of the next generation need the support of all the advances on new architectures, standards, and protocols. Mobility management is an important issue in the area of mobile communications, which can be best solved at the network layer. One of the key features of the next generation wireless networks is all-IP infrastructure. This paper discusses the mobility management schemes for the next generation mobile networks through extending IP's functions with mobility support. A global hierarchical framework model for the mobility management of wireless networks is presented, in which the mobility management is divided into two complementary tasks: macro mobility and micro mobility. As the macro mobility solution, a basic principle of Mobile IP is introduced, together with the optimal schemes and the advances in IPv6. The disadvantages of the Mobile IP on solving the micro mobility problem are analyzed, on the basis of which three main proposals are discussed as the micro mobility solutions for mobile communications, including Hierarchical Mobile IP (HMIP), Cellular IP, and Handoff-Aware Wireless Access Internet Infrastructure (HAWAII). A unified model is also described in which the different micro mobility solutions can coexist simultaneously in mobile networks.

The game to play in wireless communications when it comes to increasing spectrum efficiency is to eliminate interference. Currently, all cellular systems use FDD (Frequency Division Duplexing) in an attempt to eliminate the interference from the adjacent cells. Through the use of many technologies only one type of interference remains and that is the adjacent base-tohome mobile interference. TDD (Time Division Duplexing) has not been used for mobile cellular systems, not only because of the adjacent base-to-home mobile interference, but also because of the additional adjacent base-to-home base interference, and adjacent mobile-to-home mobile interference. Therefore, TDD can only be used for small, confined area systems. CDD (Code Division Duplexing) can eliminate all three kinds of interference; the adjacent base-to-home mobile, the adjacent baseto-home base, and the adjacent mobile- to- home in cellular systems. Eliminating each of these interferences makes CDD the most spectrum efficient duplexing system. This talk will elaborate on a set of smart codes, which will make an efficient CDD system a reality.

In this paper, a maximal ratio combining (MRC) and weighted maximal ratio combining (WMRC) diversity receiver are proposed. The MRC receiver makes a decision at each branch based on the minimum distance criterion. The performance of the MRC receiver is analyzed on the frequency-selective Rayleigh and Rician fading channels, in terms of the union bound for bit error probability. In addition, the WMRC receiver, which assigns weighting factors to the decision variable at each branch, based on the optimum decision boundaries, is proposed. The performance of the WMRC is investigated through the computer simulation and compared with those of MRC and equal gain combining (EGC). From the results, it is found that the performances of the WMRC and MRC are better than those of EGC on both the frequency-selective Rayleigh and Rician fading channels and performance improvements over the EGC are noticeable when the number of diversity branches is large as long as the root mean square (rms) delay is smaller than or equal to 10% of the symbol period.

This paper addresses issues in designing OFDM systems with high-density constellations. To achieve high data throughput, many high-speed OFDM systems such as HiperLAN2 and IEEE 802.11a use high-density constellations such as 64QAM to reach up to 54Mbits/s over a 20 MHz frequency bandwidth. Compared with low-density constellation modulations, OFDM systems using M-QAM (M>=64) are very sensitive to analog circuits/components variations causing so-called I-Q imbalances. Moreover, for the purpose of high integration level and low cost, simple front-end radio/analog architectures such as direct conversion and low-IF are desirable but such architectures are even more sensitive to circuitry and component variation. We have developed a patent-pending technology called IQ-Balancing, which removes the adverse effect of I-Q imbalance and enables OFDM systems to have high tolerance to circuitry and component variations. With IQ-Balancing technology, direct conversion and low-IF architectures become very attractive for high-speed OFDM systems. Exploring further with IQ- balancing technology leads to a simple implementation of software Defined Radio (SDR).

In this paper, we present a squaring method to simplify the decoding of orthogonal space-time block codes (OSTBC) in a wireless system with arbitrary number of transmit- and receive-antennas. Using this squaring method, a closed-form expression of signal-to-noise ratio (SNR) after space-time decoding is also derived. It gives the same decoding performance as the maximum likelihood ratio decoding while it shows much lower complexity. On the basis of analyzing the received SNR of OSTBC over Rayleigh fading channel, the expression of capacity for OSTBC is also obtained in this paper. Simulation results show that the capacity increases with the increasing number of receiving antennas if the number of transmitting antennas is invariant, and also increases with the increasing number of transmitting antennas if the number of receiving antennas is constant. The capacity, however, does not increase any more when the number of transmitting antennas is large enough.

Turbo-Codes have attracted great interest in digital mobile radio due to their remarkable error correcting capabilities. In this paper, we present an optimized Turbo decoder for wireless systems following recommended CDMA2000 standard (192 time frames with 8 states per frame). This decoder is implemented using TI's latest C64x digital signal processor. To achieve the maximum parallelism in TI's VLIW architecture, we have specially redesigned the trellis computation algorithm to improve the decoder throughput and reduce the number of computation operations required. In particular, our proposed algorithm transforms a number of add/subtract operations to multiplication operations. In this way, previously unused functional units become available and therefore, more parallel instructions can run simultaneously, leading to throughput increase and latency reduction. To our findings, current TI's compiler (Code Composer V1.2) fails to generate the optimized assembly code when our algorithms are directly implemented in C. To this end, we have illustrated optimized resource binding and timing schedules by applying code motion and loop transformation techniques. The optimized Turbo decoder can finish one decoding stage in 18.1 microseconds for a C64x DSP running at 400 MHz.

Channel estimations of many OFDM systems are accomplished by using pilot signals. Two kinds of pilots, frequency-domain pilots and time-domain pilots, are investigated. The performance of these methods in Rayleigh frequency selective channel is simulated. The effects of varying channels on these methods, especially on the time-domain pilot channel estimation technique, are examined. From the results, it can be concluded that when the channel is a slow fading channel time-domain method performs much better than frequency-domain method, but when the channel is a fast fading channel, the performance of time-domain technique is impacted more severely, and is no better than that of frequency-domain technique.

Bluetooth Group Network Profile (GNP) plays a key role in Bluetooth to support an ad-hoc networking and provides the solution of communicating among the Bluetooth devices in a single Piconet. There are several challenges in implementing GNP. The paper provides the related solutions of dynamic IP address assignment, transmission of the broadcast and multicast packets, and profile security architecture. Furthermore, the implementation reduces the code size and increases the portability in the embedded environment.

Bluetooth is a new wireless communication protocol, its background and the structure of Bluetooth Profiles, as well as the concept of data synchronization are introduced first, and then Data Synchronization Algorithm and the implementing models according to Bluetooth Synchronization Specification are provided. Finally, problems of the models are analyzed, and the synchronization solution of combining SyncML protocol and Bluetooth is described.

Bluetooth is a new short-range wireless communication technology developing rapidly in recent years. Bluetooth software architecture consists of stack and profiles. Serial Port Profile (SPP) is an underlying profile that emulates RS232 serial cable connections between two peer devices. Based on SPP, Dial-up Networking (DUN) Profile establishes PPP connection with remote dial-up server, Fax Profile realizes document facsimile function and LAN Access Profile (LAP) provides local area network access service. When it comes to their implementation in embedded systems, there are several challenges such as memory consumption, code efficiency, code reliability, and code portability onto different OS and hardware platforms to be attacked. In this paper, we propose integrated software architecture after discussing the great similarities shared among the three SPP based profiles. Then implementation of the architecture is given, in which OS-dependent and OS-independent parts are clearly separated. Profile interfaces with stack and OS are specified respectively so that the three profiles as a whole can be ported onto various software and hardware platforms easily. As a result, policy of transplanting our implementation onto different platforms is addressed at the end of the paper.

Bluetooth is a promising new technology for short range wireless connectivity between mobile devices. Nevertheless, before the massive products come into the market, reliability of protocol stack and profiles, and interoperability of different Bluetooth products from different vendors are yet to overcome. In this article, we proposed an conformance testing architecture using emulator for different protocol stacks. Our purpose to use emulator instead of hardware is to provide a higher degree of control in testing the system for setting various parameters and test the protocol for a large number of nodes.

This paper describes a formal method to verify the completeness of conformance testing, in which not only Implementation Under Test (IUT) is formalized in SDL, but also conformance tester is described in SDL so that conformance testing can be performed in simulator provided with CASE tool. The protocol set considered is Bluetooth, an open wireless communication technology. Our research results show that Bluetooth conformance test specification is not complete in that it has only limited coverage and many important capabilities defined in Bluetooth core specification are not tested. We also give a detail report on the missing test cases against Bluetooth core specification, and provide a guide on further test case generation in the future.

Developing mobile station (MS) location technologies that meet the U.S. Federal Communications Commission's (FCC) wireless E-911 requirement for emergency location has become an increasingly important topic. The FCC has currently ruled that the carriers begin selling and activating ALI (Automatic Location Identification)-capable handsets no later than October 1, 2001 and has also granted a limited waiver of the accuracy standards to certain carriers. Since location information can potentially be used for other location-dependent applications, there is also an explosive interest in the development of new location-based commercial services. In this paper, we present a summary of the location technologies that could potentially be used as solutions to comply with the E-911 ruling. We also discuss the emergence of location commercial services and explore how mobile location information can be used to (1) improve performance in different layers of the systems, and (2) increase wireless system functionality for location commercial services.

The Enhanced Observed Time Difference (E-OTD) method is one of the emergency positioning technologies that has been standardized for use with GSM systems in the United States. In this paper, we apply the E-OTD approach to a (30 kHz) IS-136 TDMA system in order to study the effect of a linearly increasing BTS clock drift on RMS OTD estimation accuracy. We investigate performance of the OTD estimation algorithm as a function of the SNR, C - I and the magnitude of the BTS clock drift error. Our simulation results indicate that the RMS OTD estimation error can initially be reduced by increasing the observation interval, but that beyond a certain number of measurements (depending on the SNR and C - I), the BTS clock drift becomes the dominant error source and causes the RMS OTD error to rise.

As advertisements are time and location sensitive, a challenge for wireless marketing is to have advertisements delivered when and where they are most convenient. In this paper we introduce a two-stage auction model for location-based wireless targeted advertising. This system extends the notion of location-based service by using location information to target advertising, and does so specifically by enabling advertisers to specify their preferences and bid for advertisement delivery, where those preferences are then used in a subsequent automated auction of actual deliveries to wireless data users. The automated auction in the second stage is especially effective because it can use information about the individual user profile data, including customer relationship management system contents as well as location from the wireless system's location management service, including potentially location history such as current trajectory from recent history and longer-term historical trip records for that user. Through two-stage auction, real-time bidding by advertisers and matching ads contents to mobile users help advertising information reach maximal value.

The infrastructure required for wireless and mobility services is becoming increasingly complex involving a multitude of different nodes such as smart terminals, base stations, access gateways and application servers and up to tens of millions of concurrent users. For true mobility services, the need to provide seamless access to data - independent of location or device - becomes apparent. But how do you ensure that this data and the corresponding mobile applications are distributed to those network nodes where the data is needed? Whether it's managing subscriber provisioning data of a large farm of access gateways, replicating application servers to allow for system scalability or distributing application software to smart terminals, seamlessness in mobility services requires a distributed data management functionality coupled with advanced multi-user, multi-device synchronization.

iCAR is a new wireless system architecture based on the integration of cellular and modern ad-hoc relaying technologies. It addresses the congestion problem due to limited channel access in a cellular system and provides interoperability for heterogeneous networks. The iCAR system can efficiently balance traffic loads and share channel resource between cells by using ad-hoc relaying stations (ARS) to relay traffic from one cell to another dynamically. The concept of iCAR can be generalized to provide seamless integration of broadband wireless access systems and in particular, realize the vision for having anytime and anywhere ubiquitous wireless access. Analyzing the performance of iCAR is nontrivial as the classic Erlang-B formula no longer applied when relaying is used. In this paper, we build multi-dimensional Markov chains to analyze the performance of the iCAR system in terms of the call blocking probability. In particular, we develop an approximate model as well as an accurate model. While it can be time-consuming and tedious to obtain the solutions of the accurate model, the approximate model yields analytical results that are close to the simulation results we obtained previously. Our results show that with a limited number of ARS's, the call blocking probability in a congested cell as well as the overall system can be reduced.

Mobile, wireless access and networking has emerged in the last few years as one of the most important directions of Internet growth. The popularity of mobile, and, more generally, nomadic Internet access is due to many enabling factors including: (a) emergence of meaningful applications tailored to the individual on the move; (b) small form factor and long battery life; (c) efficient middleware designed to support mobility; and, (d) efficient wireless networking technologies. A key player in the mobile Internet access is the nomad, i.e. the individual equipped with various computing and I/O gadgets (cellular phone, earphones, GPS navigator, palm pilot, beeper, portable scanner, digital camera, etc.). These devices form his/her Personal Area Network or PAN or personal bubble. The connectivity within the bubble is wireless (using for example a low cost, low power wireless LAN such as Bluetooth). The bubble can expand and contract dynamically depending on needs. It may temporarily include sensors and actuators as the nomad walks into a new environment. In this paper, we identify the need for the interconnection of the PAN with other wireless networks in order to achieve costeffective mobile access to the Internet. We will overview some key networking technologies required to support the PAN (eg, Bluetooth). We will also discuss an emerging technology, Ad Hoc wireless networking which is the natural complement of the PAN in sparsely populated areas. Finally, we will identify the need for intelligent routers to assist the mobile user in the selection of the best Internet access strategy.

Multi-Layer Ad Hoc Wireless Networks with UAVs is an ideal infrastructure to establish a rapidly deployable wireless communication system any time any where in the world for military applications. In this paper, we review the research we have done so far for our heterogeneous solution. First of all, we proposed the infrastructure of Multi-level Heterogeneous Ad-Hoc Wireless Network with UAVs. Second, we developed a new MAC layer protocol, Centralized Intelligent Channel Assigned Multiple Access (C-ICAMA), for ground mobile backbone nodes to access UAV. Third, we extended HSR (Hierarchical State Routing) to this Multi-Level Heterogeneous Ad-Hoc Wireless Network. Due to the intrinsic limitations of Extended HSR, we extended the Landmark Ad Hoc Routing (LANMAR) as our forth step. Security is a critical issue for mobile ad-hoc wireless networks, especially for military applications. We developed an embedded distributed security protocol and integrated with this heterogeneous hierarchical ad hoc wireless networks in our fifth step. Therefore, the hierarchical multi-layer approach is the most desirable approach to achieve routing scalability in multi-hop wireless networks.

Recently, it becomes more and more popular that an enterprise builds up a private mobile network. With this wireless network, the enterprise can increase its communication efficiency and productivity. In this paper, we present a private mobile communication system using DECT as the wireless radio technology. The system consists of radio system, Enterprise Service Control Node (ESCN), and PBX. ESCN is the service center of the whole system. It provides functions such as mobility management, call control, and supplementary services. Besides, ESCN is a wireless adjunct to PBX. It integrates the wireless and wired telephone system into one system. In addition, ESCN can connect multiple RE (Radio Exchange) to provide a large number of handsets. The interfaces between ESCN and PBX are T/R and R2/E1. Thus, both line interface and trunk interface are supported. Instead of voice service, it is also important to provide low rate data service in wireless system. In this paper, we describe how to provide short message service in the ESCN. Three different types of short message are supported. They are (1) point-to-point (2) group notification and (3) broadcast. Besides, we also consider how to deliver short message when the short message targets located in multiple campuses. The whole mobile system has been developed, and currently it is under field trial.

The continuing liberalization of the world's telecommunications markets and the progressive convergence of voice, data, video and Internet communication are prompting telecommunication service providers to both expand and enhance their service capabilities. As bandwidth-hungry applications proliferate, and the demand for data and data services grows, the requirement for broadband communications appears to be insatiable. To provide the expected level of service in this environment of rapidly increasing demand, telcos and service providers must invest in an expanded network. However, to remain competitive and profitable, they must also continue to leverage their existing infrastructure investment. This paper will examine the current challenges network operators are facing today with the deployment of broadband technologies as they strive to maintain existing infrastructure investments while providing new services to their customers and developing added value network operations. This paper will explore various broadband technologies (optical/wireless) that operate on the primary SDH/SONET standards, their topologies and inherent benefits, which provide operators with solutions to the broadband challenge. New customer demands, such as high-speed Data transmissions (increased Internet use), coupled with operators' continuous need for network optimization, have thrown a wrench into daily operations. Therefore, the need to modernize existing networks has become paramount.

A major challenge in the Asia —Pacificregion, and in every region ofthe world, is satisfying the needs of business, government, and education for high-speed Internet and data access. National telephone companies cannot readily provide the services because their local access infrastructures were engineered for voice, not high-speed data. The "local loop bottleneck" between the customers and the telephone company's switching centers must be replaced to allow high-speed access into the fiber optic Wide Area Network backbone. Fixed broadband wireless access is the logical solution, as P-Com is successfully demonstrating in a number of provinces in China, and in other Asia —Pacific regions and other nations throughout the world.

A multi-user receiver with lower implementation complexity is proposed for IS-2000 up-link which used the group-wise serial interference cancellation (GSIC) with the approximate de-correlating detection within the groups. The bit error rate (BER) performance of the proposed receiver is obtained by simulation in a frequency selective fading channel. It is shown that the proposed receiver is well performing in the IS-2000 up-link.

Space-time spreading (STS) and orthogonal transmit diversity (OTD) are two transmit diversity schemes proposed by CDMA2000 standard. In this paper, performance comparison analysis of the two transmit diversity schemes in multi-path channel are carried out. Link level simulation in forward link CDMA2000 is performed in IMT-2000 channel. Performance analysis and simulation results show that STS outperforms OTD under the same transmitting power.

In this paper, the performance of the two transmit diversity schemes with four antennas proposed in [6] is analyzed by simulation. It is shown that the first scheme outperforms the second one. In addition, we also investigate the effect of the estimate error of the channel gains on the system performance. As an alternative, we consider the pilot signal assisted channel estimate scheme. By simulation, some results on the length of the pilot signal are presented according to the requirement of the quality of service (QOS) in practice.

A novel scheme for channel estimation is proposed in this paper for WCDMA Downlink where a pilot channel is simultaneously transmitted with a dada traffic channel. The proposed scheme exploits channel information in both pilot and data traffic channels by combining channel estimates from these two channels. It is demonstrated by computer simulations that the performance of the Rake receiver is improved obviously.

Both W-CDMA and cdma2000 are strong candidates for third generation mobile communications systems. Based on the physical layer standard of cdma2000, the performance analysis of fixed-point simulations is presented in this paper on cdma2000 1x downlink. The effects of quantization and finite wordlength, which have typically been assumed negligible in floating-point simulations, become significant for fixed-point simulations. The complete fixed-point simulation platform for cdma2000 1x downlink is developed by EDA tool - COSSAP. The structure and performance of the key component in cdma2000 systems, the RAKE receiver, are discussed in details. Comparisons of results between floating-point and fixed-point simulations lead to some important conclusions, which provide certain references for the implementation of practical systems.

Turbo code is widely noticed as a code that can achieve the performance close to Shannon's limit. Turbo code (k=3) and Convolutional code (k=9) are adopted for channel coding units of WCDMA standard. The Turbo code is expected for the system of high rate data transmission in view of performance and hardware complexity. In this paper, the simulation platform of W-CDMA uplink is developed by the EDA tool-COSSAP. Channel model is M.1225 with 6 fingers model estimated by channel estimator on the Base Station using discontinuous pilot channel with different pilot modes. The BER simulation performance of turbo decoder based on Log-MAP algorithm under frequency selective fading channel is presented in comparison with conventional Viterbi decoder. The simulation results show that in the case of enough accurate estimation of channel parameters, Turbo decoder has better BER performance at high E_b/N₀ than conventional Viterbi decoder.

Recently, a new differential detection scheme for transmit diversity was proposed by Tarokh and Jafarkhani, which can achieve full diversity without the requirement to estimate the channel state at the receiver. In this paper, we investigate the effect of the carrier frequency offset on the performance of the transmit diversity with differential encoding scheme and present some results on its maximal tolerable frequency offsets for different MPSK signals. The results have shown that the differential encoding transmit diversity is very robust to the frequency offset and is very feasible in practice.

In this paper, a general model of wireless channels is established based on the physics of wave propagation. Then the problems of inverse scattering and channel prediction are formulated as nonlinear filtering problems. The solutions to the nonlinear filtering problems are given in the form of dynamic evolution equations of the estimated quantities. Finally, examples are provided to illustrate the practical applications of the proposed theory.

The main purpose of this paper is to assess the performance limits of an analog optical link for 3GPP W-CDMA systems by using a combination of simple two-tone test and analytic simulation results. ACLR of the transmitted IS-95 CDMA and 3GPP W-CDMA signals have been measured and analyzed for multiple frequency assignments (FAs). In 3GPP specifications the required ACLR is ?5 dBc, and the downlink total power dynamic range shall be 18 dB or greater. The required IIP3 and slope efficiency of a DFB laser diode at an optical loss of 10 dB are presented to realize four W-CDMA FAs (20 MHz bandwidth) transmission. Performance limits of a dual-band fiber-optic link to transmit both of IS-95 CDMA and W-CDMA signals are estimated and presented.

Following the development of MEMS fabrication technique, novel patch antennas are developed to become reality using surface micromachining process. In this paper, surface micromachined patch antennas are investigated and fabricated to have an excellent RF performance. The square patch antenna is designed to operate in its dominant mode with the broad radiation pattern of approximately 6.5dB in directivity. The impedance bandwidth is approximately 1.5% and the radiation efficiency is approximately 53%. The radiation patterns of micromachined patch antennas are broad in nature, when operating from 13 to 22GHz. Since the radiation efficiency and directivity (gain) of the individual element is rather weak, arrays are designed to obtain better overall the radiation efficiency and directivity.

With the recent growth of microelectromechanical systems (MEMS), RF capacitive microswitches are becoming popular. As such there is a need to accurately characterize the performance of the RF capacitive microswitches. To realize this goal, the paper proposes both electrical and static mechanical models to precisely extract the performance parameters of the RF capacitive microswitches. The electrical model proposed in this paper provides a means to represent the RF capacitive microswitches for use to determine the resistance, capacitance, and inductance. The static mechanical model predicts the effective stiffness constant and the pull-in voltage. Deformation of the bridge and its contact behavior with the dielectric layer are also precisely analyzed using Finite Element Method. Finally this paper discusses the fabrication of the RF capacitive microswitches.

Full coverage in mobile service region will elate mobile telephone customers. Limited frequency resources make mobile system capacity poor. High capacity and full coverage are two main key problems for system design. CDMA system has advantage of customer capacity, and Antenna array brings its coverage ability and intelligence into full play. Smart antenna combined with code division multiple access will improve mobile telecom system performance. Increasing system performance and capacity appear through enhancing desired signal and suppressing interference signals. Several kinds of antenna array techniques including beam forming, diversity, switched-beam antenna array and sectorization were discussed here in detail. The small antenna applications in TDMA mobile telecommunication systems are also discussed.

This thesis introduces the background knowledge and characteristics of Bluetooth technology. Then it summarizes the architecture and working principle of Bluetooth software. After carefully studying the characteristics of embedded operating system and Bluetooth software, this thesis declared two sets of module about Bluetooth software. Corresponding to these module's characteristics, this thesis introduces the design and implementation of LAN Access and Bluetooth headset. The Headset part introduces a developing method corresponding to the particularity of Bluetooth control software. Although these control software are application entity, the control signaling exchanged between them are regulations according to former definitions and they functions through the interaction of data and control information. These data and control information construct the protocol data unit (PDU), and the former definition can be seen as protocol in fact. This thesis uses the advanced development flow on communication protocol development as reference, a formal method - SDL (Specification and Description Language) - describing, validating and coding manually to C. This method not only reserved the efficiency of manually coded code, but also it ensures the quality of codes. The introduction also involves finite state machine theory while introduces the practical developing method on protocol development with the aid of SDL.

Low light level (LLL) image communication has received more and more attentions in the night vision field along with the advance of the importance of image communication. LLL image compression technique is the key of LLL image wireless transmission. LLL image, which is different from the common visible light image, has its special characteristics. As still image compression, we propose in this paper a wavelet-based image compression algorithm suitable for LLL image. Because the information in the LLL image is significant, near lossless data compression is required. The LLL image is compressed based on improved EZW (Embedded Zerotree Wavelet) algorithm. We encode the lowest frequency subband data using DPCM (Differential Pulse Code Modulation). All the information in the lowest frequency is kept. Considering the HVS (Human Visual System) characteristics and the LLL image characteristics, we detect the edge contour in the high frequency subband image first using templet and then encode the high frequency subband data using EZW algorithm. And two guiding matrix is set to avoid redundant scanning and replicate encoding of significant wavelet coefficients in the above coding. The experiment results show that the decoded image quality is good and the encoding time is shorter than that of the original EZW algorithm.

In this paper, we firstly analyze the requirements of RFCOMM protocol. Then we explain our primary experience in validation and implementation of this protocol in order to make our software stable, easy to port into embedded system and well interoperable. At last, we summarize all the experience and show the importance of validated SDL model and efficient testing techniques.