In this paper, we present the performance of a multitone code division multiple access (MT-CDMA) system by analyzing the effect of coding. We use convolutionally coded substreams rather than serial-to-parallel converted data to modulate different subcarriers. The bit error rate bound for the decoding metric is derived. The coded and uncoded performance bounds are compared with respect to equal bandwidth, bit rate and other communication resources. We also present the performance trade-off for different coded modulation schemes. Our results indicate that the performance of an MT-CDMA is significantly improved when channel coding is applied.

A robust video transmission technique that protects video signals over wireless channels is proposed in this work. First, we present new packetization and concealment methods for compressed video data. Second, the loss of each packet is quantitatively measured under this normative concealment method. More specifically, the encoder associates each packet with the mean square error between the error-free reconstruction and the concealed reconstruction. Third, a channel code rate is adaptively allocated to protect each packet so that the expected mean square error is minimized subject to a constraint on the overall bit rate. Extensive simulations show that the jointly designed video codec provides acceptable image quality in a high bit error rate environment. Besides, the proposed algorithm can be applied to real time video transmission applications, since its computational complexity is very low.

In this paper, we discuss a pedestrian navigation using cellular phone. In order to offer navigation information intelligible for a user and to solve the problem that cellular phone has a small display area, we provide navigation sentences and landscape images from user's viewpoint. When a pedestrian goes to the destination, landmarks e.g. a building, a crossing, etc. exist on the way. Thus, we provide two navigation sentences at every mark, for example 'Go to the bank at the corner,' and 'Turn to the right at the bank.' At the point which is important or easy to mistake for user, it provide landscape images. Then users can do a check of the direction. Providing a minute information, navigation sentences and landscape images, it is easy for users to go to the destination. Additionary, not having all of navigation data, our system only have a little data to manage it. The navigation data is created by the informer who is the man of the destination, and upload it to their web site. The informer who is knowledgeable about the way to the destination can give the route for users who visit it for the first time. And, it can be created using two or more navigation data which others have been created, which is the difference-use. The data in which information about way guidance from a station to a destination is described by XML (eXtensible Markup Language). Pedestrian navigation system using navigation data with cellular phone is implemented. Proposed system can realize intelligible way guidance for users, and provide the route guide, which are available for a small display area of a cellular phone and for pedestrians.

A call admission control (CAC) scheme and a resource reservation estimation (RRE) method suitable for the wide-band code division multiple access (W-CDMA) systems are proposed in this work. The proposed CAC scheme gives preferential treatment to high priority calls, such as handoff calls, by pre-reserving a certain amount of channel margin against the interference effect. It is called the interference guard margin (IGM) scheme. The amount of guard margin is determined by the measurement performed by the RRE module in base stations. Each RRE module dynamically adjusts the level of guard margin by referencing traffic conditions in neighboring cells based upon users' requests. A comprehensive service model is adopted to accommodate the scenario of multiple services supported in the W-CDMA system. The service model of consideration includes not only mobile terminal's service rate (source rate) but also different levels of priorities, mobility and rate adaptivity characteristics. Simulations are conducted with OPNET to study the performance of the proposed scheme in term of the objective function under different traffic conditions.

Universal Mobile Telecommunications System (UMTS) wireless technologies is a proposed standardization as a part of 3GPP solutions to satisfy IMT-2000 requirements. It is based on wideband CDMA technology. It will provide full coverage and mobility for 144 Kb/s, preferably 384 Kb/s and limited coverage and mobility for 2 Mb/s. It proposes high spectrum efficiency compared to existing systems, handling of different QOS profiles and high flexibility to introduce new service. In this paper, we present our work on modeling of the access stratum (AS) on the User Equipment/Mobile Termination (UE/MT) side of the radio (Uu) interface in accordance with 3GPP UMTS standards. The AS has the following sub-layers: Medium Access Control/Radio Link Control (MAC/RLC), Broadcast Multicast Control (BMC), Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC). We have assumed the number of transport channels interfacing the AS MAC sub layer and the physical layer to be eight. The data rates have been assumed to be 384 Kb/s per transport channel both in uplink and downlink. Processing in each sub-layer with corresponding delays and interaction between adjacent sublayers having timing restrictions or rate restrictions have been analyzed. Interaction of the upper sub-layers with the non-access stratum (NAS) and interaction between peer AS sub-layers in the UE and the UTRAN have also been incorporated. A real time priority based scheduler process has been specified to honor the time restrictions e.g. the Transmission Time Intervals (TTI) of the channels. The system has been simulated on Virtual Silicon, a C based SDL tool and evaluated on CR16C architecture family using CR16C debugger, both developed by National Semi Conductor Corp., U.S.A.

A new power control scheme for downlink CDMA transmission by using an outage probability criterion is proposed in this research. We first analyze the outage probability when data are transmitted over shadowing and Rayleigh fading channels. Then, the power is assigned to each link of the system so that the overall outage probability is minimized subject to three constraints. They are the total transmission power at the base station, the maximum transmission power for each user, and the maximum tolerable outage probability for each user. The Newton-Raphson algorithm is modified to solve the minimization problem under these constraints. Experimental results demonstrate that the proposed algorithm is capable of differentiating QoS requirements for each link in addition to improving the throughput of the system.

In this paper, we analyze the bit error probability of the multistage linear parallel interference canceller in a long- code code division multiple access (CDMA) system. To obtain the bit error probability, we approximate the decision statistic as a Gaussian random variable, and compute its mean and variance. The mean and variance of the decision statistic can be expressed as functions of the moments of (R-I), where R is the correlation matrix of the signature sequences. Since the complexity of calculating the moments increases rapidly with the growth of the stage index, a graphical representation for the moments is developed to alleviate the complexity. Propositions are presented to interpret the calculation of moments as several graph problems that are well known in the literature, i.e., the coloring, graph decomposition and Euler tour problems. It is shown that the graphical representation facilitates the analytic evaluation of the bit error probability, and the analytic results match well with the simulation results.

Multi-carrier technologies are emerging as a considerable force in the wireless world. OFDM charges ahead, with MC-CDMA close behind. However, as this tutorial demonstrates, multi- carrier technologies are not limited to OFDM and MC-CDMA. By application of Carrier Interferometry (CI) principles, we create CI/TDMA and CI/DS-CDMA, multi-carrier implementations of existing TDMA and DS-CDMA technologies. These implementations enable significant improvements in both performance and network capacity. Specifically, we double the network capacity of existing TDMA and DS-CDMA system and simultaneously outperform their traditional implementations. Of course, the benefits of Carrier Interferometry are not limited to TDMA and DS-CDMA: It also significantly improves the existing MC-CDMA and OFDM multi-carrier systems. What emerges is a very powerful technology that creates a common multi-carrier architecture for DS-CDMA, TDMA, OFDM, and MC- CDMA, bridging the hardware gap between the world's most promising technology, all the while enhancing network capacity and probability of error performance.

The optimization of spectrum efficiency will be a major concern for fourth generation wireless systems. In our view, the key principle that holds the promise for ultimate spectrum exploitation is the full-fledged use of diversity techniques. In particular, there is a definite trend towards the adoption of diversity in multiple domains. This trend is justified by the fact that the particular domain whereby diversity is implemented determines the benefit that should be expected in terms of impairments to be counteracted. In this paper we will focus our attention onto Space-Time Coding (STC) techniques, where the domains of antenna diversity and time diversity are joined to yield unprecedented performance gains without increasing bandwidth requirements. The gains can be traded-off for an increase in the data rate, fixing power/interference requirements. Here, we analytically evaluate system performance in the presense of both ideal and realistic propagation conditions: Rice-lognormal and Rayleigh fading channels are considered with ideal and non-ideal channel state recovery. In this framework, a closed-form expression for the average bit error probability for space-time block coding systems has been achieved. In particular, when imperfect channel phase estimation is taking into account, bit error probability has been expressed as a function of the phase error statistical distribution. As a numerical example, the case of the Gaussian phase error model has been considered and the results have been validated through Monte-Carlo simulations.

Multivariate signaling using multiple-in multiple-out (MIMO) configurations, increases the Shannon capacity of communication links, several fold. Among existing schemes that aim at realizing these predicted gains in practical scenarios, e.g., at high transmission rates or when the transmitter lacks channel state information, are orthogonal space-time block codes (STBCs), which are now known to display good performance characteristics, when concatenated with conventional trellis codes. It is shown that the only full-rate orthogonal STBC (for frequency-flat fading channels) achieves the (2,1)- channel capacity for single-sensor reception, and a full-rate block-orthogonal STBC is developed for broadband channels. While this STBC is easily adapted for use in the code division multiaccess down-link, a similar technique is necessary for the uplink, where performance degrades in fading media at high system loads. A simple signature-time transmit diversity paradigm, requiring just a single-sensor transmit-antenna at the mobiles, is shown to counter these degradations, in conjunction with iterative minimum mean square error (MMSE) multiuser decoding, at the base stations. Finally, an efficient layered space-time signaling technique for trellis coded packets, in systems with multisensor transmit- and receive-antennas, as in peer-to-peer communication environments, is proposed. With iterative MMSE decision feedback equalization and multistream decoding, it is observed to deliver significant fractions of the predicted MIMO throughputs.

A smart antenna with a carefully controlled time-varying beam pattern can create a channel with a small coherence time. This small channel coherence time can be used by the mobile station to achieve time diversity benefit, thereby enhancing performance. In this work, the coherence time induced by antenna arrays with time-varying beam-patterns is evaluated using the so-called geometric-based stochastic channel model (GSCM). Here, we assume a circular coverage area in an urban environment and we treat buildings (or parts of buildings) as point scatterers (dimensionless). We demonstrate a relationship between coherence time and antenna array control parameters, and show that 9-fold-time diversity can be created via time-varying beam patterns.

A method to reliably transmit multimedia data over wireless fading channels by using a generalized OFDM technique is presented in this research. Multimedia delivery over wireless links is sensitive to fading effects. It is furthermore characterized by a number of different properties, including unequal error protection needs, time-varying bandwidth requirements, etc. Layered multimedia representation, such as MPEG-4 FGS, has been widely studied to meet these requirements. However, only this component is not sufficient to provide the desired quality of service (QoS). To further improve the overall system performance, we focus on the design of an adaptive modulation scheme, which maintains the ability to adapt to time-varying channel conditions as well as the layered multimedia representation. In particular, we study and analyze the performance of a technique known as Wavelet Packet Modulation (WPM) from the viewpoint of Orthogonal Frequency Division Multiplexing (OFDM), and demonstrate its application to wireless multimedia communication. In our framework, WPM is viewed as a general case of OFDM, which allows flexibility in terms of channel allocation and adaptability with respect to channel conditions. The algorithm demonstrates the flexibility of the new proposed method in transmitting multimedia data over interference-laden channels.

In this paper a review of the Pre-FFT Equalization technique is presented with a particular focus on 4G applications. The essential concepts and motivations for the use of this technique are first presented. Subsequently, previous research of the topic both by the authors and others is reviewed. In particular, methods for implementing the Pre-FFT Equalizer itself and for adapting it are reviewed in detail. The issue of noise amplification and the use of Channel State Information in the COFDM system to mitigate this phenomenon are also discussed. Application of a Pre-FFT Equalizer to a possible, COFDM based, 4G standard is then discussed and software simulations used to demonstrate the benefits that can be achieved by a Pre-FFT Equalizer in a 4G system.

A direct conversion receiver is presented for HiperLAN2 system that uses Orthogonal Frequency Division Multiplexing (OFDM) as its modulation scheme with data rate up to 54 Mbits/second. The direct conversion scheme converts the RF signal directly into a complex low-pass equivalent signal represented by in- phase (I) and quadrature (Q) components or so called I-Q base- band signal without any Intermediate Frequency (IF) stages and expensive Surface-Acoustic-Wave (SAW) filters. However, for a direct conversion receiver there are many key issues to be solved. One of the most important issues is so-called I-Q imbalance caused by the mismatch between I channel and Q channel of the quadrature demodulator. The I-Q imbalance may include gain and group delay difference between the I channel and the Q channel at any frequency within the low-pass signal bandwidth. With the patent-pending IQ-Balancing^TM technology and other proprietary technologies of 4D Connect, inc., the adverse effects of I-Q imbalance on the receiver performance can be removed. Fixed-point simulation results for sensitivity performance and interference performance are presented. Performance comparisons when severe I-Q imbalance is present are also given.