With limited available radio frequency spectrum for broadband wireless services, it is essential to explore new bandwidth efficient waveforms with robust error correction code. While the Shannon's theory of high-speed digital communications in the time domain is known, there has been little progress to utilize additional dimensions in the spatial domain as information carriers. In this paper, a true space-time wireless system based on novel ideas in space-time modulation and coding technology is introduced. The advantages of this new technology include enhanced spectral efficiency with more channels to support larger number of subscribers and higher data rate for near real-time multimedia applications. The degree of success in achieving these objectives will not only affect the system performance, but will directly impact the profit of a commercial wireless company.

Adaptive modulation is an effective scheme to observably improve the performance of interactive video data transmission over mobile wireless channels. The effectiveness of adaptive modulation is affected by the accuracy of channel quality estimation. We analyzed in this paper the effect of channel quality estimation error on the performance of the adaptive modulation scheme with four parameters we proposed: Extra BER Cost (EBC), Potential Theoretical Channel Capacity Loss (PTCCL), average system EBC and average system PTCCL. Without considering the details of specific multimedia information to be transmitted, our measurements are simple and direct.

In this paper we propose the use of Turbo Codes for M-ary pulse position modulated pulses over UWB communication channels with multipath. The transmitted power of the UWB pulses is required to be very small as they are used in the existing spectrum designated to other uses. This constraint requires that UWB signals have good performance at low SNR's. Turbo codes have been shown to perform well at low SNRs. We present the simulation results of using rate 1/2 and 1/3 turbo codes. Also, the effects of varying the symbols set size, the SNR of the channel and the interleaver size are presented. It has been shown in this paper that for a fixed SNR (4 dB), the rate 1/3 code shows an improvement of 2 orders of magnitude when M = 2 and 3 orders of magnitude when M = 4 or M = 8. For the same SNR, the rate 1/2 code shows an improvement of 1 to 2 orders of magnitude. To achieve a BER of 10^-5, the rate 1/3 turbo code requires SNR = 6 dB when M = 4 and SNR = 3 dB when M = 8. Increase in the size of the interleaver from 2⁹ to 2¹⁴ results in a decrease in BER from 10^-2 to 10^-3 for SNR = 4 and M = 2.

This paper deals with quadrature demodulators used for Zero Intermediate Frequency (ZIF) and Near Zero Intermediate frequency (NZIF) receivers. ZIF and NZIF receivers are more sensitive to circuitry mismatch, which causes I-Q imbalance. With IQ-Balancing (IQB) technology, any adverse effect of frequency-dependent I-Q imbalance can be removed and quadrature receivers can have high tolerance to the I-Q imbalance. The paper first provides detailed description of the IQB technology for a simple I-Q network. Then the paper shows that any I-Q operations (ideal or non-ideal) can be described by an I-Q network and that the I-Q network can be described by a set of 2-by-2 matrixes, each of which defines the imbalance condition at a given frequency. As a result, the IQB technology can be applied to the I-Q network to remove any adverse effect. The paper then explains how the IQB technology can be used with a quadrature demodulator for ZIF/NZIF receivers for any modulation schemes. Finally, two application examples are included to show how the proposed quadrature demodulator can make ZIF/NZIF receivers have much higher tolerance to I-Q imbalance. System simulation results are provided for a ZIF receiver for OFDM signals and a NZIF receiver for GMSK signals.

Finding the optimal algorithm between an efficient encoding process and the rate distortion is the main research in fractal image compression theory. A new method has been proposed in this paper based on the optimization ofthe LeastSquare Error and the orthogonal projection. A large number ofdomain blocks can be eliminated, in order to speed-up fractal image compression. Moreover, since the rate-distortion performance ofthe most fractal image coders is not satisfactory, a n efficient bit allocation algorithm to improve the rate distortion is also proposed. Some implementation and comparison have been done with the feature extraction method to prove the efficiency ofthe proposed method.

This paper proposes an efficient wavelet-based coding scheme with fine grain scalability, where the base layer is encoded with a novel designed of wavelet-based coder, and the enhancement layer is encoded with progressive fine granularity scalable (PFGS) coding. This algorithm involves multi-frame motion compensation, rate-distortion optimizing strategy with Lagrangian cost function and context-based adaptive arithmetic coding. In order to improve efficiency ofthe enhancement layer coding, an improved motion estimation scheme that uses both information from the base layer and the enhancement layer is also proposed in this paper. The novel designed of wavelet-based coder significantly improves the coding efficiency ofthe base layer compared with MPEG-4 ASP (Advanced Simple Profile) and H.26L TML9. The PFGS coding is a significant improvement over MPEG-4 FGS at the enhancement layer. Experiments show that single layer coding efficiency gain of the proposed scheme is about 2.0-3.0dB and 0.3-1.0dB compared with MPEG-4 ASP and H.26L TML9, respectively. The overall coding efficiency gain of the proposed scheme is about 4.0-5.0dB compared with MPEG-4 FGS.

This paper introduces a new modulation scheme, dual-amplitude pulse interval modulation (DAPIM) for optical wireless communications. We present the expression for bandwidth requirement, slot and packet error rates, and optical power requirements in a nondispersive channel. We find that DAPIM achieves improved bandwidth and/or power efficiency compared with OOK, PPM, and PIM. DAPIM with 4 bits and 5 bits per symbol is attractive in terms of optical power and bandwidth requirements.

The paper examines, from a carrier's perspective, the viability of free-space optical (FSO) technology as a cost-effective access alternative to fixed point-to-point applications. These include extension of metropolitan area edge networks, network backhaul, temporary deployment while awaiting fiber, disaster recovery, and low cost fiber protection circuits. The paper provides a detailed prognosis of the FSO and its complementing 60GHz RF technology, besides analyses of the total cost of ownership. This leads to some suggestions on how to improve the technical and economical viability of the technology for carriers' applications.

Free space optics (FSO) is attractive for the 'last mile' communication in recent years for many combining advantages of fiber communication and other wireless technologies. FSO can provide high data rate with low power consumption, high immunity to interference, convenient deployment and flexibility. Optical system is an important section in the FSO transceiver terminal. In this paper the design of optical system based on a single Galileo telescope for both transmit and receive is proposed, and a polarization beam splitter is adopted to apart the receiving light from transmitting light. The configuration can avoid interference from the retroreflecting light of the ocular effectively. Some factors that affect the performance of the optical system are analyzed, such as the geometrical spreading loss and the loss increment according to pointing error and telescope maladjustment. Power budget shows that the system can satisfy the need of access for 1km in the light fog, and 2km in the thin fog.

Scintillation and beam drifting are the two main issues, which influence the performance of optical wireless communication system. Multiple propagation paths average effect could be used to alleviate scintillation to these considerations, a 155-622 Mb/s optical wireless communication system was dilation, auto tracking can be used to compensate the beam drifting caused by mirage-like effect. Developed using multiple 800nm laser diode transmitters and auto tracking. Block diagram of design and main elements of the key optics, mechanics, and server control system are presented, and link performances of 155Mb/sand 622 Mb/s digital data transmission by using 3 transmitters over 1 .3 km are illustrated in this paper.

A way to overcome the fading caused by atmosphere is discussed, and the power gain equalization method for the wireless optical communication system is studied, the results for the system are also given. In the scheme of wide-range power-gain equalization, the power gain of the wireless optical system is controlled automatically in accordance with visibility change of propagation channel by means of sampling the propagation channel, which has also been shown.

As infrared transmission has the advantages of wide bandwidth, immunity to radio interference, high security and license-free, it is an attractive alternative to radio for wireless local area networks LAN. The design of an interface between the high-speed optical wireless transceiver (>20Mbps) and the optical wireless LAN is presented in this paper. We transplant the IEEE 802.11 medium access control (MAC) layer protocol to our system, define and implement a new physical (PHY) layer management module. This management module can also provide us an experimental platform to analyze the performance of the modulation schemes, such as L-PPM, PIM, DH-PIM, etc. Due to its characteristics of flexibility, simplicity and low cost, the management module is a good choice for the indoor optical wireless LANs.

This paper investigates the equalized performance of digital pulse interval modulation (DPIM) in the presence of multipath propagation and additive white Gaussian noise. The results for slot error rate (SER) versus electronics SNR with and without equalizer are presented and made by Monte Carlo simulation with a simplified model of the generated received signal, which depends on the impulse response of the channel. Simulation results show that the performance of DPIM system can be improved dramatically by using an equalizer for a severe intersymbol interference (ISI) channel.

The impulse response of the wireless infrared communication channel determines performances of communication system, such as multipath penalty over the maximum baud rate and hidden-station situations. It is significant to correctly describe the impulse response of the working channel for design and performance evaluation of communication systems. In this paper, details of a simulation package that obtains impulse responses for arbitrary wireless infrared indoor channels are presented. Capability of estimating the effects of shapes of room or objects, surface reflection and transmission characteristics on impulse responses is the most important feature of this package. The common simulation models just consider empty cubic rectangular room, with surfaces assumed to be Lambertian reflection pattern. With several examples given in this paper, the conclusions can be drawn that the common simulations models are not adequate to describe the real complicated communication environment and not suitable to the requirement of accurate performance prediction for the communication systems. The results give a demonstration that the use of the common simulation models to approximate the real wireless channels can introduce several decibels in the evaluation of the path loss.

This paper presents a methodology for SOC designusing soft IP cores with application to W-CDMA.

Digital IF is the current solution of software radio terminal. Digital IF expands the digital signal processing towards the IF section of terminal. It requires the "softly" reconfigurable IF hardware platform, thereby operating the different mobile standards on the given terminal. Due to the high reconfiguration of FPGA, it is the very approach to digital IF. Starting with considerations of the digital IF, we discuss the implementation of digital IF on FPGA.

A scenario and its experimental results of hybrid DS/FH SS (Spread Spectrum) receiver based code-spread-spectrum (CSS) is presented in the paper.CSS is an efficient spread spectrum technology.The transmission efficiency is improved when PN code rate isn¡¯t changed.It suits to the situations which are rigorous for the bandwidth.The hybrid DS/FH receiver presented by the paper uses TMS320C33 as the processor,and uses FPGA to implement correlator,digital down-convertor,PN code generator and matched filters.Frequency-synthesizer is implemented by DDSAD9854.Method which transmits pilot PN code captured by using serial/parallel technology to synchronize rapidly is brought forward.DPLL and SCAFCT(signed cross automatic frequency track) is used respectively to track code and carrier.The optimum noncoherent demodulation (Max SNR Output ) which utilizes orthogonality of PN code can be the same with high dynamic environment.Finally,the figures including PN code synchronization and frame synchronization and demodulation are demonstrated.We can conclude that performance of the receiver is approving.

Structure of the software radio system and basic theory are discussed and analyzed in this paper. Point out necessity of research the software radio and it's develop foreground, accentuate status of wireless system development, condition of software programmable technology and software develop. The paper introduced application diapason of the software radio and high-tech result of current headway in the international, such as the soft interface, the software BUS and the radio frequency synthesis and so on. To need develop tools and debugging work for software radios, the article given some recommendation. For the moment, also pay attention especially to exist some problems when research to the software radio. In the paper author take notice of application of communication and network; cordially put forward a series of suggestion and appreciation, too. The software radio is a system that it is used of the software to control, digit signal processing mode, to complete simulate wireless signal work state. So, work principle of the software radio and simulate mode consult each other, further give prominence to software programming, it and simulate mode have a lot of difference. Software radio using, it can meet information and culture all of requirement. It has obvious characteristics: It can be programmable completely. Used software to program realizes wireless a lot of advanced and complicated function that software work processes incarnate out full digital format. It is used of the network interface and to easy use program application to extend that work environment of more frequency paragraph and more systems, and encode unification. It has unification secrecy property; equipment upgrade and change type is easy, because it is software main, if change an applying the software, the equipment is renovated immediately.

Advances in information technologies have made it possible to have Personal Information Service, i.e., personalized multimedia information available anywhere, anytime. Such ubiquitous access requires that a portion of the underlying network infrastructure be wireless. This prompts the debate on what the next-generation wireless network will look like. In this paper, we attempt to shed some light on this debate. To help us in this task, we give an overview of the challenges and some solutions associated with operating a wireless multimedia network.

This paper proposes an enterprise-oriented WLAN/3G network integration solution, called the Internet Roaming system. Differing from other operator-oriented WLAN/3G network integration solutions, the Internet Roaming system is a practical IP-based corporate network architecture that provides seamless internetworking across office WLAN, home WLAN, public WLAN, and 2.5G/3G cellular network for corporate wireless data users. An Internet Roaming system may have four building blocks. They are IRC (Internet Roaming Client), SMG (secure mobility gateway), SIA (Secure IP Access) gateway, and VSA (virtual single account) server. The IRC is a special client tool (software or hardware) installed on a wireless data device. It provides a secure mobile IP connection from the wireless data device to the corporate network transparent to the operating system of the wireless data devices. The SMG is a mobile IPsec gateway installed on the corporate core network facing the Internet. It works with the IRC to maintain a secure mobile IP connection when the wireless data device is connected on the Internet through a home WLAN, a public WLAN, or a cellular network. The SIA server is a special IPsec gateway installed on the corporate intranet where office WLAN is installed. It works with the IRC to assure the security of office WLAN while improving the routing efficiency for users computers. The VSA server manages the IRC, SMG, and SIA servers.

The paper is related to TCP performance enhancement in Buffer Management of Mobile IPv6 where transmission control protocol is used as transport layer protocol. A mechanism that improves TCP performance in buffer management for Mobile IPv6 is proposed when handovers are normally taken place. By this mechanism, MB-aware routers can send

Wireless mobile connections have some well known disadvantages, like slow data rate, high and variable error-rate. In addition to that there are possible (and probable) inefficiencies when connecting different types of protocols stacks, like running TCP over GPRS. On the other hand mobile and portable devices have some limitations, which are based on their size and cannot therefore be removed totally. Potential users are so-called common people and they would like to have very simple-to-use applications solving their daily problems, not causing new ones. One approach to make this situation better is to use agents. They could operate on many different levels, like connecting different physical servers to produce the service needed, connecting different services together, optimizing for different types of user devices, connecting different message types (like audio, animation etc.) to produce the service, making transformations (like reading e-mails as voice mail etc.). This paper will discuss these various aspects of agent technology in the context of mobile services provided to consumers. Discussion and conclusions are partly based on the ZanderMail project. Although it is a mail agent project its results can easily be extended to various message types and various other services, like those based on the location of mobile device. The paper will cover widely these different ideas and ZanderMail is just used as an example and a tool for testing various issues. The idea is to utilize agents many ways to fade away at least partly those known problems mentioned in the beginning. An agent could operate in the network quite near the mobile device to overcome the problem caused by different protocol stacks. It could make logical decisions based on location and other local information, like weather, and it could handle priority issues on various levels of application(s).

Handoff rate is a fundamental index to evaluate the handoffperformance and as a result it afftcts the overall performance of cellular mobile communication system. Meanwhile, moving patterns of mobiles are critical to the handoff rate. In this paper the relation between user's mobility and system handoff rate is studied The analytic result shows the soft handoff rate increases with the mobile speed Furthermore, with a little simplijication of the analytical model, the handoffrate and the mobile speed display linear relation, which is confirmed by the simulation results. Based on it, the effect about combinations of users 'multiple velocities on the handoff rate is investigated. It turns out that the handoffrate ofa system with several user mobility patterns can be estimated with the handoff rates ofcorresponding single user mobility pattern systems.

It is well know that soft handover extends the coverage and increases uplink capacity in CDMA systems. Triggered by the asymmetric features of 3G Internet and multimedia services, in this paper, we analysed the soft handover effects on both downlink capacity and coverage. The relationship between the capacity and the coverage is also investigated. Results show that when the soft handover overhead is beyond a certain value, there is a trade-off between the capacity and coverage. We quantified and compared the soft handover effects on the capacity and the coverage with three different soft handover algorithms: distance-based, IS-95A, and UTRA algorithms. It is shown that, the performance of soft handover is closely related to the algorithm and parameters setting. Distance-based algorithm is not accurate for analysing coverage.

We have recently witnessed a phenomenal growth in the development and deployment of wireless services, evident from the proliferation of the cellular data services and the emerging wireless multimedia applications. This opens up a new avenue for research, and calls for the re-examination of some of the fundamental issues in wireless cellular networks. With the cell size being systematically reduced into micro-cell and pico-cell systems, in order to increase the overall network capacity, one of the key challenges is the design of effective call admission control (CAC) policies, which have to guarantee potentially different quality of service (QoS) requirements from diverse traffic types while at the same time maintaining high utilization of the scarce wireless bandwidth. The objectives of this article are to review the key issues involved in the design of call admission control policies based on some of the recent proposals, and to discuss the challenges associated to offer effective support for multi-services

The future 3G/4G wireless communication systems will provide internet access for mobile users. Packet scheduling algorithms are essential for QoS of diversified data traffics and efficient utilization of radio spectrum.This paper firstly presents a new packet scheduling algorithm DSTTF under the assumption of continuous transmission rates and scheduling intervals for CDMA data networks . Then considering the constraints of discrete transmission rates and fixed scheduling intervals imposed by the practical system, P-DSTTF, a modified version of DSTTF, is brought forward. Both scheduling algorithms take into consideration of channel condition, packet size and traffic delay bounds. The extensive simulation results demonstrate that the proposed scheduling algorithms are superior to some typical ones in current research. In addition, both static and dynamic wireless channel model of multi-level link capacity are established. These channel models sketch better the characterizations of wireless channel than two state Markov model widely adopted by the current literature.

A system of multiple services with guaranteed QoS requires resource allocation. A novel algorithm on bandwidth allocation together with associate class-unit application model is proposed in this article. Bandwidth is allocated to flows in unit of class due to different QoS-bandwidth functions. Applications within one class achieve the same bandwidth and the allocation among classes based on QoS-Based MAX-MIN fairness. Simulations confirm that the proposed scheme simplifies the calculation of the so-called host station, and flows achieve satisfying QoS based on QoS-bandwidth functions.

In this paper, based on the derivation of the comprehensive factor (Coupling Factor) which is used to characterize the system interference condition, a new CF-DCA is proposed and applied to TD-SCDMA system to evaluate the system capacity in the indoor environment. Performance evaluation has been carried out in both speech-only and mixed services and the simulation results show that increased system capacity and power saving can be achieved compared with the traditional methods.

This paper investigates the power control mechanism in the context of third generation multimedia multirate wideband CDMA (WCDMA) mobile communications. We first present the system model and get the sufficient condition for the existence of feasible power assignment. Under this constraint, we reformulate the power control problem as a non-cooperative game in allocating the normalized QoS products, and propose a new call admission control (CAC) algorithm based on uniform-price auction (UPA) to control the power. Properties of UPA Nash equilibrium, especially its efficiency, are also discussed in wireless system environment. The results of comparison show that our scheme charging users on the QoS products has the enormous advantage over other pricing schemes charging users directly on the transmit powers. Numerical results which demonstrate the viability of the proposed algorithm are presented.

This paper proposes a novel flooding algorithm based on an existing IEEE 802.11 MAC protocol in wireless ad hoc networks. Currently when we use the multi-hop routing algorithm, such as the Ad hoc On-demand Distance Vector (AODV) algorithm, the Cluster-Based Routing Protocol (CBRP) and so on, we frequently use the broadcast packet in order to get the topology information. At this time all nodes receiving the packet try to forward the received packet to other nodes. If a number of nodes are located in the sender's coverage, the channel is busy due to the delivery of the received packet. With respect to the coverage of the IEEE 802.11, the utilization factor of the wireless network is decreased because of occupying the channel to distribute the received packet. Thus we propose the new algorithm to resolve this problem. In this algorithm, each node maintains a table of immediate neighbors as well as each neighbor's neighbors. When each node receiving broadcast packets in the sender's coverage forwards the packets, it decides whether to forward them or not by comparing the neighbor list of receiver with that of sender. The proposed algorithm can increase the network efficiency due to the decrease in frequency of broadcast packets in the multi-hop routing protocol. Finally, we evaluate the improved performance through the simulation.

Wireless power transmission (WPT) has been proposed for many years and is expected to be one of the most promising power transmission style in the near future, especially in space power supply and emergency power recovery. The long distance WPT often enrolls the relay procedures and forms a power transmission network. In this paper, we talk about the wireless power transmission based on Ad Hoc networks. Meanwhile, the adaptive architecture and flexible deployment of WPT Ad Hoc networks have been given a special further discussion. We also bring along a novel multi-trace power routing concept and analyze the major challenges of WPT Ad Hoc networks.

The wireless ad hoc network technology provides a flexible infrastructure for next generation mobile telecommunication. In this paper, the performances of the networks based on IEEE802.11a standard, including packets successful delivery rate, average end-to-end delay and system throughput, have been studied with different routing protocols (AODV, WRP, and FISHEYE) using GloMoSim to evaluate the effects of various factors, such as node mobility, node density, and node radio transmission range. The simulation results show that adaptive routing protocol will be more suitable for the variation ad hoc network and the results are helpful for the optimum design and deployment of an actual network.

End-to-End (ETE) Quality of Service (QoS) is critical for next generation wireless multimedia communication systems. To meet the ETE QoS requirements, Universal Mobile Telecommunication System (UMTS) requires not only meeting the 3GPP QoS requirements [1-2] but also mapping external network QoS classes to UMTS QoS classes. There are four Quality of Services (QoS) classes in UMTS; they are Conversational, Streaming, Interactive and Background. There are eight QoS classes for LAN in IEEE 802.1 (one reserved). ATM has four QoS categories. They are Constant Bit Rate (CBR) - highest priority, short queue for strict Cell Delay Variation (CDV), Variable Bit Rate (VBR) - second highest priority, short queues for real time, longer queues for non-real time, Guaranteed Frame Rate (GFR)/ Unspecified Bit Rate (UBR) with Minimum Desired Cell Rate (MDCR) - intermediate priority, dependent on service provider UBR/ Available Bit Rate (ABR) - lowest priority, long queues, large delay variation. DiffServ (DS) has six-bit DS codepoint (DSCP) available to determine the datagram's priority relative to other datagrams and therefore, up to 64 QoS classes are available from the IPv4 and IPv6 DSCP. Different organisations have tried to solve the QoS issues from their own perspective. However, none of them has a full picture for end-to-end QoS classes and how to map them among all QoS classes. Therefore, a universal QoS needs to be created and a new set of QoS classes to enable end-to-end (ETE) QoS provisioning is required. In this paper, a new set of ETE QoS classes is proposed and a mappings algorithm for different QoS classes that are proposed by different organisations is given. With our proposal, ETE QoS mapping and control can be implemented.

With the development of Internet technology, especially the conditions of wireless and mobility be migrated, more user's tasks with different QoS requirement will be implemented in Internet. However, user will front a network which state changes from the static to the dynamic, the QoS requirement will changes from the one for single network condition to the other for several heterogeneous. In the face of the complexity of the next generation network, traditional QoS concept model will not suit for this condition. In this paper, we propose a new QoS concept model QoSw for the next generation network. In QoSw, we define Network-space N and User-space U conceptions and analyze the mapping relations between N and U. We enlarge the scales of network QoS guarantee from the network-level for user's physical resource needs plus both the application-level for the application characteristics and the user-level characteristic for the user characteristics. Finally, the policy format of the QoS requirement can express better the semantics for user's needs, this will better adapt to the next generation network conditions and have a better expression for use's personality.

Supporting end-to-end QoS of media streaming applications over wireless Internet has received tremendous interest recently. In this paper we propose a new architecture for transmitting real-time multimedia streams over Bluetooth wireless Internet integrated with Differentiated Services (DiffServ) mechanism. IP support over Bluetooth is discussed in details to take advantage of the DiffServ framework. In our proposed architecture, the Bluetooth wireless users are connected to the Bluetooth LAN Access Point to acquire the capability of Internet access. Different media streams are classified at edge routers of the DiffServ core network, mapped to different priorities and delivered according to the dynamically negotiated Service Level Agreement (SLA). QoS monitoring agents deployed in network nodes and endsystems can monitor network QoS conditions and provide reports to the concerned nodes. Implementation details of the prototype of the proposed architecture are given in this paper. Specially, the Bluetooth communication is implemented as a virtual network card that supports IP protocol in order to provide consistent access to the DiffServ Internet. Experimental results show that enhanced end-to-end QoS can be achieved based on our architecture.

In this paper we consider service differentiation in wireless networks using pricing policy. The pricing methodology examined is based on "auctioning" pricing. In the present work, it is applied on IEEE 802.11-based wireless networks. The uplink traffic in an IEEE 802.11 wireless network operating in the PCF mode is considered to be "thin" as the mobile users in the network are subject to power limitations and the biggest volume of traffic occurs on the downlink - from the Base Station to the mobile users. The Base station advertises different levels of Quality of Service (QoS) and the Mobile Users are competing for channel resources by bid requests. Based on the variability of the wireless channel, the amount of the available bandwidth shared between the mobile users changes, the price of the QoS changes as well and the users might change the bids they are offering or change the QoS they request from the Base Station. In the present bidding and pricing scheme, an analytical model for price determination is provided and the results of OPNET based simulations for prove of concept are presented.

Because of unbalanced inbound and outbound bit rate in PDCP buffer, the congestion may happen in 3G RNC. In this paper, one mechanism, called Dynamic buffer Management (DBM), is proposed to enhance the performance while TCP traffic is transmitted from the server in Internet to the mobile user. The simulation model aiming at the current PDCP buffer management is introduced first, the DBM mechanism is described in detail then. The performance comparison between the existing method and the DBM proves the efficiency of the DBM.

Headers of IP packets are growing and the bandwidth required for transmitting headers is increasing. To overcome such limitations, current protocol mechanisms need to be improved. This paper addresses this important issue - Header Compression Scheme. Our compression scheme is presented and compared with some other previous methods. We can show how to reduce the size ofUDP/IP headers down to several limited bytes to efficiently use the bandwidth. In order to efficiently transfer data over lossy links, the congestion control module in our scheme is also discussed. With the information from congestion control, the size of the window mentioned above can be changed according to the congestion situation. When severe congestion is probed, the decrease of window size can obviously increase the stability of the system. This is another key error avoidance step in our system. Finally, we analyze our system under windows 2000 and Ns2 framework. The experimental data are given to testify the validity and performance of our scheme.

Existing cordless keyboard and mouse products that utilize proprietary RF interfaces and protocols, are not interoperable, have no security, and have only one-way operation. Bluetooth will bring the wireless keyboard and mouse application into real life by providing standard RF frequency and protocols, having good protection against interference, providing two-way communication, reliable links and secure data transmission. This paper discusses the benefits of wireless keyboard and mouse based on the bluetooth technology and presents how the prototyping of bluetooth wireless keyboard and mouse was done at Motorola Suzhou Design Center, focusing on the system architecture and S/W stacks designed and implemented on the embedded device. All the protocol stacks are designed and implemented above the HCI UART layer on the Motorola 8 bit HC08 micro-controller. Several key issues for prototyping wireless keyboard/mouse such as security and power management are also discussed here.

This paper describes the hardware design of a high speed Viterbi decoder for the IEEE 802.11a Wireless Local Area Networks (WLAN) application. A fully parallel Add-Compare-Select (ACS) and trace-back architecture is presented to achieve the decoding rate up to 54Mbps. Modulation scheme and coding rate dependent quntaization accuracy for soft decision Viterbi decoding is explored and a hardware implementation scheme with run-time configurable bit-length for soft decision is then proposed to reduce the system power consumption.

In this paper we present a deterministic approach of modeling wideband MIMO (multiple-input multiple-output) radio fading channel for wireless multicarrier systems. Implementation problem of downlink MIMO model for mobile station (MS) was first investigated, while space-time coding or downlink beam-forming is taken into count at base station (BS). The MIMO channel are determined by both power azimuth profile (PAP) at MS and various configuration of multiple antennas at BS. Based on tap-delay-line structure and deterministic fading channel modeling method, SIMO fading model, corresponding to any one transmitter antenna, is formed by generating doppler phase difference between two receiver antenna aided by PAP at MS. The von Mises probability density function was adopted to characterize phenomenon of nonisotropic scattering components around MS. The ultimate MIMO channel simulation model is sum of all SIMO channel with all transmitter antennas. Finally, we predicted MIMO channel capacity based on proposed simulation model with parameters of wireless multicarrier systems under specified 'Vehicular A channel' of ITU-R M.1225.

In this paper, different frequency offset estimation schemes and their combinations are investigated for IEEE 802.11a based Wireless LAN. Their performance has been compared in terms of deviation and required hardware implementation complexity. Our simulation results show that, by using the short sequences alone, the estimation error can be less than 2% of the sub-carrier spacing for a given SNR of 15 dB. Two-stage frequency offset compensation by using short sequences for coarse estimation followed by long sequences for fine estimation may not give significant improvement due to some independent estimation error effects.

Whether exploring in the Empty Quarter, drilling offshore in the Gulf of Mexico, or monitoring gas pipelines or oil wells in the deserts, communications is a key element to the success of oil and gas operations. Secure, efficient communications is required between remote, isolated locations and head offices to report on work status, dispatch supplies and repairs, report on-site emergencies, transfer geophysical surveys and real-time drilling data. Drilling and exploration firms have traditionally used land-based terrestrial networks that rely on radio transmissions for voice and data communications to offshore platforms and remote deep desert drilling rigs. But these systems are inefficient and have proven inflexible with today's drilling and exploration communications demands, which include high-speed data access, telephone and video conferencing. In response, numerous oil and gas exploration entities working in deep waters and remote deep deserts have all tapped into what is an ideal solution for these needs: Very Small Aperture Terminal Systems (VSAT) for broadband access services. This led to the use of Satellite Communication Systems for a wide range of applications that were difficult to achieve in the past, such as real-time applications transmission of drilling data and seismic information. This paper provides a thorough analysis of opportunities for satellite technology solutions in support of oil and gas operations. Technologies, architecture, service, networking and application developments are discussed based upon real field experience. More specifically, the report addresses: VSAT Opportunities for the Oil and Gas Operations, Corporate Satellite Business Model Findings, Satellite Market Forecasts

Traditionally, blind channel identification/equalization techniques have been based on higher-order statistics, which are known to suffer from many drawbacks. Later some methods using only second order statistics have been proposed, and it's a major breakthrough. The main methods based on second order statistics include linear prediction algorithm (LPA)[ 1][2], outer product decomposition algorithm (OPDA)[3]{4], multi-step linear prediction algorithm (MSLP)[5], least square smoothing algorithm (LSS)[7], and constrained minimum output energy algorithm (CMOE)[6]. But the simulations ofthese algorithms show that the channel couldn't be identified because there still needs other condition, which couldn't be got for knowing nothing about the channel in the whole blind condition. This paper will analyze these algorithms and point out the reason that results in the failure of channel identification.

Designed a set of the network system of data information management in this paper It is this conception that base on Client/server to take synthesis layout and data information exchange manage. And it researched the interface LAN and WAIS. It also is dissertated as network structure and function of system and integrated array of system. Selection of these devices, colligation of wiring and configure of Software/Hardware also are expatiated. This system has best function and property such as the database management, data on the safe side, man-machine conversation interface and local keep secret. This development environment of system adopts popular structure of present computer applied management system, namely Client/Sever structure. It is mainly composed of database server and customer application program as well as network. Data information management system of police base on Client/Server mode overcomes above-mentioned shortcomings. In the heterogeneous distribution environment, this system achieves information col lector and integrated processing. And the network connection about general station and branch as well as different local police station is accomplished, so it meet the needs on the fastness and accuracy and safety of the data information management and data information transmission.

Nowadays Internet can be considered has the cne of most instrument of communication. They are two important exigencies that are strongly been demanded by the digital imaging market: progressiveness, which is requested by the tremendous market of the world wide web, and resolution independence, which is a key requirement for desktop publishing. A hybrid fractal wavelet Trellis -Code Quantization (TCQ) method is proposed for transmission of compression image to satisfy these two requirements. The high compression and the resolution independency are assured the Hybrid Fractal-Wavelet method, and the TCQ the progressiveness in transmission, by quantize the residual error in the encoding. The efficiency of our method has been proved comparison with the common Fractal-Wavelet method.

This paper investigates the power control mechanism in the context ofthird generation multimedia multirate wideband CDMA (WCDMA) mobile communications. We first present the system model and get the sufficient condition for the existence of feasible power assignment. Under this constraint, we reformulate the power control problem as a non-cooperative game in allocating the normalized QoS products, and propose a new call admission control (CAC) algorithm based on uniform-price auction (UPA) to control the power. Properties ofUPA's Nash equilibrium, especially its efficiency, are also discussed in wireless system environment. The results of comparison show that our scheme charging users on the QoS products has the enormous advantage over other pricing schemes charging users directly on the transmit powers. Numerical results which demonstrate the viability ofthe proposed algorithm are presented.

There is a trend towards satellite laser communication using advanced laser technology including developing a network based on microsatellite laser communication. But the advantage of small laser beam divergence creates a complex problem for acquisition, pointing and tracking. Microsatellite laser communication networks require research in systems and algorithms for acquisition. The purpose of the acquisition system is to compensate for large pointing errors at the beginning of the process and to achieve the minimal desired errors that will provide the beginning of the tracking and optical communication phase. In this process the requirement is to detect the optical signal with a given probability within a given time. The paper will describe several acquisition methods and compare their probability of acquisition and the acquisition time. These acquisition methods include Stare/Stare Method Scan/Stare Methoth Scan/Scan MethodS Stare/Scan Method. In the process we mainly discuss two kinds of scanning patterns. They are raster scanning and spiral scanning. Furthermore, we will examine influences of satellite vibrations on the acquisition scanning because this is the major difficulty in this process. We will give the integrate stimulation and suggest a correction algorithm.

Distributed Multi-sensor Detection System is a wide field distributed wireless detection system, which is composed of Command Center and varieties of Detection Units. The Command Center acquires a lot of real-time information from the area that has been monitored by means of bi-directional communication between it and each unit. Communication mode that has been adopted in this detection system will determine the validity and reliability greatly. So the system should adopt appropriate communication mode and information processing mode to realize the real-time transmission of information in the wide area. According to the particular characteristic of this Multi-sensor Detection System, we go deep into discussing all kinds of communication modes that can be used in the system and also compare their work modules and practicability. Based on the comparison, we offer a more suited communication mode, Code Division Multiple Access (CDMA) mode for this detection system. We also built a multi-sensor test platform based on the communication mode. By means of a mass of experiments and on site testing, we arrive at a conclusion that the higher operational reliability can be gained by choosing this communication mode in this detection system. It is adaptive to work under the condition of complexity.

The design proposals of active alignment system suitable for different transmission ranges are presented. Influence of light power distribution on the focal plane ofthe receiver on complexity of a alignment system is analyzed, The optical system ofthe lasercom system is not used in imaging, but transmitting signals, and so the optical design method of the suitable power distribution of the light spot on the focal plane of the receiver should be adopted in the design of whole optical system from transmitter to receiver in order to reduce the bad influence due to the spot shifting on signal transmitting.