On soft/hard handoff for packet data services in cellular CDMA mobiles systems

Benefits of macrodiversity operation for packet data services in third generation mobile systems are not obvious. Retransmission procedures to enhance link performance and higher downlink bandwidth requirements could question macrodiversity usage. This paper describes a simple methodology to compare soft and hard handoff performance in terms of transmission delay for packet data services. The handover procedures are based exclusively on power criteria and hysteresis margins.Peer ReviewedPostprint (published version

Soft Handoff and Uplink Capacity in a Two-Tier CDMA System

This paper examines the effect of soft handoff on the uplink user capacity of a CDMA system consisting of a single macrocell in which a single hotspot microcell is embedded. The users of these two base stations operate over the same frequency band. In the soft handoff scenario studied here, both macrocell and microcell base stations serve each system user and the two received copies of a desired user's signal are summed using maximal ratio combining. Exact and approximate analytical methods are developed to compute uplink user capacity. Simulation results demonstrate a 20% increase in user capacity compared to hard handoff. In addition, simple, approximate methods are presented for estimating soft handoff capacity and are shown to be quite accurate.Comment: To appear in IEEE Transactions on Wireless Communication

Performance of Data Services in Cellular CDMA in Presence of Soft Handoff and Packet Combining

Performance analysis of data services is studied in CDMA network in presence of soft handoff (HO) and packet combining. Packet combining in conjunction with soft handoff is found to enhance throughput, reduce delay and packet delay variation (PDV) significantly. A stop and wait automatic repeat request (ARQ) scheme has been assumed. Two different packet combining schemes for packet data service, one based on log likelihood ratio (LLR) and another based on equal gain combining (EGC) have been studied. A cross layer interactions between ARQ and packet combining at link layer and soft HO in physical layer has been shown

A Comparative study on Handoff Algorithms for GSM and CDMA Cellular Networks

The GSM, CDMA cellular systems are most trendy 2G and 3G digital cellular telecommunications systems, which is widely used throughout the world. These systems have many advantages such as high security, higher quality of call transmission over the long distances, low transmitted power, and enhanced capacity with more efficient utilization of the frequency spectrum. With these advantages these cellular systems have attracted more subscribers with more attention in the field of mobile communications. One of the most attractive features of cellular system is handoff which is a continuation of an active call when the mobile is moving from one cell to another without disconnecting the call. Usually, continuous service is achieved by efficiently designed handoff algorithms. So, efficient handoff algorithms are necessary for enhancing the capacity and QoS of cellular system. In this paper, the handoff analysis for GSM, CDMA cellular networks are done under various propagation models. Various handoff algorithms of GSM are described and also a novel received signal strength (RSS) based GSM handoff algorithm with adaptive hysteresis is analyzed. CDMA Soft handoff algorithm is analyzed and effective soft handoff parameters are estimated for better performance. The Comparison of handoff algorithms is studied based on results

Performance analysis of IS-95 CDMA cellular system using noncoherent M-ary orthogonal modulation with other cell interference

The bit error rate (BER) performance of the M-ary DS/CDMA cellular system in the presence of an additive white Gaussian noise (AWGN) and interference from other cells has been investigated. The data frame structure of the IS-95 system was adopted. The system operated in an asynchronous mode with perfect power control and voice activity factor of 3/8. Both the hard handoff and the soft handoff were considered respectively. A close form expression for the BER performance has been derived for the single cell CDMA system whereas numerical integration was employed for the multiple cells CDMA systems instead.published_or_final_versio

Teletraffic Modeling of Cdma Systems

This paper presents teletraffic modeling of Code Division Multiple Access (CDMA) systems that enabled the analysis of such systems capacity. Analytical tools aided by software model that assisted in analysis of the system performance, capacity estimation, dimensioning and design of CDMA networks were achieved. This work, therefore, focused on modeling telephone traffic for analysis of CDMA cellular network capacity. We developed an analytical expression for blocking probability and consequently that for the determination and analysis of the capacity of CDMA networks. The analyses of obtained results showed how interference determined the capacity of CDMA networks and therefore proved that the capacity was not hard limited, but depended on predetermined quality of service for the network. Also, the result showed how the capacity of the network, in terms of number of subscribers, can be estimated for CDMA networks. Graphical results generated from the blocking model showed the effect of variations in interference parameters on CDMA capacity. The Erlang capacity from the model was adapted into Erlang B formula to estimate capacity in terms of channels, and the number of subscribers a typical CDMA sector could accommodate

Capacity and Throughput Optimization in Multi-cell 3G WCDMA Networks

User modeling enables in the computation of the traffic density in a cellular network, which can be used to optimize the placement of base stations and radio network controllers as well as to analyze the performance of resource management algorithms towards meeting the final goal: the calculation and maximization of network capacity and throughput for different data rate services. An analytical model is presented for approximating the user distributions in multi-cell third generation wideband code division multiple access (WCDMA) networks using 2-dimensional Gaussian distributions by determining the means and the standard deviations of the distributions for every cell. This model allows for the calculation of the inter-cell interference and the reverse-link capacity of the network. An analytical model for optimizing capacity in multi-cell WCDMA networks is presented. Capacity is optimized for different spreading factors and for perfect and imperfect power control. Numerical results show that the SIR threshold for the received signals is decreased by 0.5 to 1.5 dB due to the imperfect power control. The results also show that the determined parameters of the 2-dimensional Gaussian model match well with traditional methods for modeling user distribution. A call admission control algorithm is designed that maximizes the throughput in multi-cell WCDMA networks. Numerical results are presented for different spreading factors and for several mobility scenarios. Our methods of optimizing capacity and throughput are computationally efficient, accurate, and can be implemented in large WCDMA networks