An optimization model with maximum ratio combining (MRC) diversity soft handover is proposed for WCDMA base station location planning with heuristic algorithm, which can calculate the influence of MRC diversity soft handover directly in the process of base station location planning. Experimental results show that the proposed model can get better capacity and coverage performance in the planning results than the traditional optimization model without MRC diversity.

3G must offer high data rates since it should support real-time multimedia services; one performance enhancement, the use of the OVSF code tree, has adopted in 3G WCDMA networks. Unfortunately, this technique allows the link capacity to be set at the base rate times powers of two. This results in wasting bandwidth while the required rate is not powers of two of the basic rate. Several multi-code assignment mechanisms have been proposed to reduce the waste rate, but incur some drawbacks, including high complexity of handling multiple codes and increasing cost of using more rake combiners. Our solution is a dynamic grouping code assignment that allows any rate to be achieved with a single code for any possible rate of traffic. The dynamic grouping approach first forms several calls into a group. It then allocates a subtree to the group and dynamically shares the subtree codes based on time-sharing of slots within a group cycle time. The waste rate and code blocking is thus reduced significantly. Since transmission delay and jitter may occur in such a time-sharing approach, two schemes of cycle interleaving are proposed to minimize delay and jitter. Numerical results demonstrate that the proposed approach reduces the waste rate and increases the system utilization obviously, and the proposed cycle interleaving schemes minimizes delay and jitter significantly.

In this paper, we propose a high speed Preamble Searcher suitable for the RACH (Random Access Channel) structure in WCDMA reverse link receivers. Unlike IS-95, WCDMA system uses the AISMA (Acquisition Indication Sense Multiple Access) scheme. Because of the time limit between RACH preamble transmission and AI (Acquisition Indicators), and the restriction on the number of RACH signatures assigned to RACH preamble, fast acquisition is required for efficient operation. The Preamble Searcher proposed in this paper is designed for 2-antenna systems; it adopts the FHT (Fast Hadamard Transform) algorithm that has the radix-2 16 point FFT (Fast Fourier Transform) structure. The acquisition speed using FHT is 32 times faster than the conventional method that correlates each signature. Based on this fast acquisition scheme, we improved the acquisition performance by calculating correlation up to 4096 chips of the total preamble length.

In wide-band code division multiple access (WCDMA), orthogonal variable spreading factors (OVSF) codes are assigned to different users to preserve the orthogonality between users' physical channels. In this letter, we present the dual OVSF code, which can transmit the variable data rates by suing two different modulated signals without loss of the orthogonality. The bit error rate (BER) performance under a multi-user environment suffering the additive white Gaussian noise (AWGN) channel and correlations of those codes are evaluated. The results demonstrate that the proposed dual OVSF scheme could provide flexible rates and lower correlation values with a slight increase in complexity.

In this paper, we propose an enhanced signal to interference ratio (SIR) measurement algorithm and evaluate the performance of the proposed algorithm in a WCDMA forward link receiver with closed-loop fast transmit power control. The proposed algorithm reduces measured SIR offset by using a pilot channel (CPICH) to compensate for the attenuated signal power in fading channel environment. The proposed SIR measurement algorithm outperforms conventional SIR measurement algorithm with regard to mean SIR values and jitter, especially in high speed mobile channel environment. Also, performance results with closed loop power control show that the proposed algorithm has better performance than the conventional algorithm.

Several multiple-input multiple-output (MIMO) techniques have been proposed for 3GPP WCDMA/HSDPA systems and several performance evaluation for the comparison purpose are in progress. Most MIMO candidates in HSDPA have been generally designed for point-to-point communication, which means that a single-user throughput is of their major concern. However, multiple users and user scheduling need to be considered in wireless packet transmission, so as to maximize system throughput. In this paper we propose an effective user scheduling technique in both space and time domains that offers three main benefits, which are the spatial-beamforming, uplink feedback signaling, and advanced receivers. Furthermore, user scheduling is combined with modified successive interference cancellation (SIC) reception, which allocates all transmit antennas to the best user with SIC or each transmit antenna to different users with minimum mean squared-error (MMSE). Simulation results show that the proposed scheme has higher user diversity gain than other MIMO candidates in terms of achievable throughput.

This paper proposes the combination of adjustable architecture and parameter optimization software, employing a method based on artificial intelligence (AI), to realize an image rejection mixer (IRM) that can enhance its image rejection ratio within a short period of time. The main components of the IRM are 6 Gilbert-cell multipliers. The tail current of each multiplier is adjusted by the optimization software, and the gain and phase characteristics are optimized. This adjustment is conventionally extremely difficult because the 6 tail currents to be adjusted simultaneously are mutually interdependent. In order to execute this adjustment efficiently, we employed a Genetic Algorithm (GA) that is a robust search algorithm that can find optimal parameter settings in a short time. We have successfully developed an IRM chip that has a performance of 71 dB and is suitable for single-chip integration with WCDMA applications.

A novel mobile assignment method based on transmit power and cell load is proposed for WCDMA base station location planning. Experimental results show that, compared with the currently widely used mobile assignment method based on link attenuation, the proposed mobile assignment method is more reasonable and unnecessary base stations are reduced in the planning results.

This paper studies the optimization of the effective channel capacity of wideband code division multiple access (WCDMA) systems under Rayleigh fading environments. Firstly, the results for Shannon capacity of fading channels with channel side information are reviewed, where the capacity is achieved by using an optimal power control scheme. Secondly, an optimal interference threshold is set for a given system outage probability Pout to minimize total interference. Finally, the effective channel capacity of WCDMA is defined and a target SIR level γ* is derived with the Lagrangian multiplier method to maximize the effective channel capacity. It is shown that is dependent on the power control interference ratio (PCIR) ρ, the number of diversity paths identified by the receiver M, and the outage probability of the system. Simulation results are provided to validate the theoretical deductions. We conclude that the total effective channel capacity will be maximized as long as M4, and ρ0.5 for a proper value of .

A new channel estimator that does not require a separate frequency offset estimator is proposed. The new algorithm has low complexity and low latency compared to the well-known weighted multi-slot averaging algorithm. The simulation results demonstrate the improved resistance to high Doppler frequency and high frequency offset.

This letter describes an efficient architecture for a Software Defined Radio (SDR) Wideband Code Division Multiple Access (WCDMA) receiver using for high performance wireless communication systems. The architecture is composed of a Radio Frequency (RF) front-end, an Analog-to-Digital Converter (ADC), and a Quadrature Amplitude Modulation (QAM) demodulator. A coherent demodulator, with a complete digital synchronization scheme, achieves the bit-error rate (BER) of 10-6 with the implementation loss of 0.5 dB for a raw Quadrature Phase Shift King (QPSK) signal.

In this letter, we propose a new practical architecture of channel estimator that can compensate for the signal distortion due to variable mobile station velocity in WCDMA forward link. The proposed Channel Estimator consists of IIR filter for channel estimation and Velocity Estimator for selection of IIR filter coefficients matched to mobile station velocity. The combination of IIR filter and Velocity Estimator can overcome the divergence problem of IIR filter due to the mobile station velocity. The Velocity Estimator estimates the speed of mobile station velocity by observing power spectrum of the received signal and exhibits stable operation in low SNR environment. To improve the resolution of velocity estimation without additional complexity due to large FFT size, an interpolator is adopted in the velocity estimator. The proposed channel estimation architecture can not only be used for WCDMA forward link but also is applicable for CDMA-2000 system without major modifications. Also, the Velocity Estimator can be applied in the channel quality measurement for the selection of MCS (Modulation and Coding Scheme) level in HSDPA transmission.

This paper defines the maximum available radio resource of a WCDMA downlink in a multiservice context under different wireless conditions. The derived closed-form expression for the maximum available resource, denoted by Rmax, is determined by four important service-independent system parameters: the maximum downlink transmission power, the average propagation loss, the average orthogonality factor, and the average other-to-own-cell interference ratio of the cell. From the Rmax some important radio characteristics of a WCDMA downlink are observed. The application of the Rmax to the link-sharing dimensioning process of WCDMA networks is presented in the paper. Simulation studies are provided to show the accuracy of the analytical model under various urban macro cell conditions.

The uplink performance of WCDMA with voice and World Wide Web (WWW) traffic over Dedicated Channel (DCH)/Common Packet Channel (CPCH) is investigated. The probability of voice packet dropping and average data packet delay are obtained by system level simulation. The system level simulation is conducted based on received Signal-to-Interference Ratio (SIR) with imperfect power control. In addition, we show that the performance of CPCH in terms of probability of data packet dropping is superior to that of DCH for transmitting WWW traffic. Furthermore, we obtain the supportable number of voice users when the target probability of voice packet dropping is set to be 10-2. The supportable number of data users is also found around knee area of average data packet delay.

For three-step cell search in WCDMA, a stepwise serial scheme is conventionally employed, where each step of cell search operates in serial. In order to reduce the cell search time, a stepwise parallel scheme can be considered as a candidate for cell search, where each step operates in pipelined fashion. However, in the parallel scheme where the processing time in every step is equal, excessive accumulations are caused in step (1) and step (3) because the period of a code used for step (2) is much longer than that for the other steps. And it does not provide any gain because the effect becomes easily saturated with the number of accumulations. In this paper, the performance of parallel cell search is analyzed, and compared with that of serial cell search. Finally, it is shown that the performance of parallel cell search can be improved by adjusting the processing time in each step, based on the analytic results.

The linear operation of a HBT with a GaAs/InGaP composite collector structure is demonstrated. The composite collector structure allows for a thin collector design that is suitable for the linear operation of a HBT without critical degradation of the breakdown voltage. The load pull measurements under a 1.95 GHz WCDMA signal have shown that a composite-collector HBT with a 400-nm thick collector layer operates with power-added-efficiency (PAE) as high as 53% at VCE = 3.5 V as a result of improved distortion characteristics. Despite the thin collector design, collector-emitter breakdown voltage of 11 V was achieved even at current density of 10 kA/cm2. The composite-collector HBT has even greater advantage for future low voltage (< 3 V) applications where maintaining PAE and linearity becomes one of the critical issues.

Video telephone service (VTS) is considered one of promising services provided in wideband CDMA (WCDMA) networks. Without a designated call admission policy, VTS calls are expected to suffer from relatively high probability of blocking since they normally have more stringent signal quality requirement than ordinary voice calls. In this letter, we consider a prioritized call admission design in order to reduce the blocking probability of VTS calls, which may encourage the users to access the newly-provided VTS in a more comfortable way. The VTS calls are given a priority by reserving a number of channel-processing equipments. With the reservation, the blocking probability of prioritized VTS calls can be reduced evidently. That of ordinary calls, however, is increasing instead. This letter provides a system model that counts the blocking probabilities of VTS and ordinary calls simultaneously, and numerically examines an adequate level of the prioritization for VTS calls. The results show that the prioritization level should be selected depending on received interference as well as bandwidth required for VTS.

A scheme to evaluate the number of users and cell coverage of a WCDMA supporting multi-rate traffic is newly presented through calculation of the realizable Erlang capacity from a derived blocking probability and the path loss from the COST231 Walfisch-Ikegami (WI) model. Based on this analytical scheme, we evaluate the voice-data Erlang capacities at various data rates of 15 kbps to 480 kbps and the relationship between the cell coverage and the number of active users from them. When the value of Eb/Io is low from 4 dB to 3 dB under voice user capacity of 50 Erlang at 8 kbps, the result shows that the data user capacity is increased to 10 Erlang at low rate of 15 kbps and the cell coverage is enlarged to 100 m, and it is also shown that its capacity is increased to 0.2 Erlang at high rate of 480 kbps and its coverage to 50 m.

This paper presents new High Speed Downlink Shared Channel (HS-DSCH) code management schemes on High Speed Downlink Packet Access (HSDPA) for IP-based multimedia provisioning. The proposed management schemes simplify HS-DSCH code allocation while simultaneously increasing HS-DSCH code utilization. Applying the code management schemes, furthermore, we implement two scheduling algorithms for real-time packets to guarantee the quality-of-service (QoS) requirement. The Real-Time Code Allocation (RTCA) algorithm applies the functionalities of the radio management framework to decide the admission for a new real-time service. Once a new real-time session is established, RTCA allocates HS-DSCH codes to that session such that all real-time packets in the session are scheduled before their related deadlines. Based on the RTCA algorithm, the Real-Time Code Sharing (RTCS) algorithm implements the Early-Deadline-First (EDF) scheme for the schedulability analysis, increasing the schedulable probability for the real-time sessions and thus to improve the utilization of HS-DSCH codes. Experimental results show that RTCS outperforms RTCA in terms of packet drop rates, HS-DSCH code blocking rates and the number of code-domain reassignments.

In this letter, we investigate serially concatenated space-time codes (SC-STs) applying iterative decoding topologies in wideband code division multiple access (WCDMA) communication systems. In the decoding algorithm, an iterative (turbo) process is used, where a priori probability (APP) is exchanged between the symbol-by-symbol space-time (ST) decoder and the bit-by-bit convolutional decoder. The experimental results show that in a Rayleigh fading channel environment the serially concatenated interleaved space-time coding systems show significant error correction capability, and based on the applied system configurations, the nonrecursive ST code outperforms the recursive ST code.