Abstract The most recent revisions of the IS‐2000 standards are being designed with the view of maximizing the achievable throughput while maintaining an acceptable Quality‐of‐Service (QoS) for the supported voice and data sessions. Revision C of the IS‐2000 standard is specifically geared towards maximizing the throughput on the forward link. However, this increase in forward link capacity requires adding new reverse link overhead channels thereby decreasing reverse link capacity. This paper describes the Control‐Hold mode designed to reduce the resource usage of reverse link overhead channels. In particular, the focus is on the DV‐control‐hold (DVCH) mode jointly proposed by Ericsson and Nortel for the 1xEVDV standard and adopted as an optional feature in the IS‐2000 standard as part of its Revision C 5 . The DV‐control‐hold mode is an intermediary state between the active and dormant modes of a mobile. In this state, a mobile station uses less resources than when active and can also be quickly reactivated (typically in 20 ms). The QoS achieved for mobile stations (MSs) that use the Active‐DVCH‐Dormant state machine is compared to the performance of MSs with regular Active‐Dormant state machines. Simulation results show that the introduction of the DVCH mode increases both, the achievable forward link throughput and the number of admissible mobiles per sector. When the DVCH mode is introduced and for the typical ‘Active‐to‐Dormant’ timer values of 3 and 6 s, the number of admissible sessions per sector increases by 35% and 66% respectively, while the corresponding throughput increases by 14% and 50%. Copyright © 2003 John Wiley & Sons, Ltd.

In this paper, we investigate the code allocation problem of forward link channelization, i.e., allocation of Walsh codes and quasi-orthogonal functions (QOF's) in cdma2000 systems. Given multipath power profiles, geometry factors, and allocated codes of mobile stations (MSs), we propose a simple solution for the total sector transmit power. It is shown that the sector transmit power can be expressed in terms of a single variable, namely, the lumped geometry factor (LGF), which accounts for MS geometry factors, code channel activities, and cross-correlations among all the allocated codes. The formula is used to devise a code allocation algorithm that is proven optimum in the sense of maximizing capacity, under the condition of single-path channels.

Soft handoff (SHO) is one of the critical components that determine the performance of a CDMA cellular system. The mobile station in 3G systems send power control commands to the base stations to adjust their powers. These power control commands can be received in error by on of the base stations in the active set serving the mobile. This results in the base stations transmitted powers deviating. Reducing the deviation in the base stations transmitted powers helps to achieve the desired diversity gain from SHO. We propose to change the way the base stations respond to power control commands. This does not require changing the way the mobile issues the power control commands. From the simulation results we see that at a speed of 5 km/h, the probability that the difference in the two base stations transmitted powers being greater than 5 dB is about 25% using the conventional scheme while it is only 8% for the proposed scheme (majority voting over two commands). We notice also that the base stations average transmitted power is reduced by employing the majority voting scheme.

Requirements for CDMA high-speed data (HSD) services make one of the distinguish marks between second generation and third generation (3G) wireless systems. cdma2000 provides 3G capacity, high data rates of up to 2 Mb/s and services. This paper describes a generalized frame structure for the support of sub-frames within cdma2000. This structure is parameterized such that it can be configured for efficient operation, depending on the radio environment and mobile station complexity, in order to provide several degrees of freedom. Impact on both convolutional code and turbo-code physical layer implementation is investigated. The results show the benefits of using the sub-frames technique.

Turbo codes have enjoyed a great attention. Among different soft-output decoding algorithms of turbo codes only maximum a posteriori (MAP) decoding as an iterative soft-output decoder (BCJR) allows for achieving an acceptable BER performance at Eb/No levels within only 1 dB of the value corresponding to the Shannon capacity. The drawback of the MAP algorithm is the excessive memory required. Here, we investigate the so-called symbol-based turbo codes. These codes allow for a reduced required memory by 30% for the BCJR method.

A new correlator receiver architecture based on a modified version of unipolar-bipolar correlation is proposed for noncoherent optical fiber code-division multiple-access (CDMA) networks. For this architecture, the receiver average bit-error rate (BER) performance is numerically evaluated as a function of the received optical power for noncoherent transmission and direct detection with the number of simultaneous users as a parameter. The BER performance is also evaluated by a closed-form formula that is developed in this paper. Comparison of the results from the latter with numerical results show that, the formula provides a good approximation to the system performance. Furthermore, the closed form solution suggests that the system can achieve the same capacity as a CDMA system using coherent detection.

A hybrid scheme is proposed for the purpose of suppressing the effects of external modulation and/or laser nonlinearities in subcarrier multiplexing (SCM) fiber optic communications systems. Hybrid CDMA/FDMA combines two schemes in such a way that the resulting hybrid network is robust against interference and is much more spectrally efficient than a CDMA system. Several possible architectures are introduced for the hybrid CDMA/FDMA subcarrier fiber optic local area network (LAN). The networks utilize CDMA and SCM, an asynchronous multiple access scheme. Direct sequence spread spectrum multiple access (DS/SSMA), the most common form of CDMA is employed. It is shown that by using the code sequence sets for which the shift-and-add property holds, intermodulation products (IMPs) and harmonics have a similar interference-like effect as nonmatching sequences do. Owing to the fact that the shift-and-add property holds for conventional spreading sequences, suppression of nonlinear distortions is examined. An average error probability performance evaluation of the selected configuration is presented for a transceiver pair. In analysis of the system, the authors assume the interference term arising from other users is Gaussian distributed. The results are compared to that obtained by exact evaluation of interference distribution using Gauss quadrature rule integration method. The authors compare the performance of this scheme for two different code sequence lengths. They also present some preliminary experimental results on the proposed LAN implementation as well as its measured transmission performance.>