Data Chunking in Quasi-Synchronous DS-CDMA

DS-CDMA is a popular multiple access technique used in many mobile networks to efficiently share channel resources between users in a cell. Synchronization between users maximizes the user capacity of these systems. However, it is difficult to perfectly synchronize users in the reverse link due to the geographic diversity of mobile users in the cell. As a result, most commercial DS-CDMA networks utilize an asynchronous reverse link resulting in a reduced user capacity. A possible compromise to increase the user capacity in the reverse link is to implement a quasi-synchronous timing scheme, a timing scheme in which users are allowed to be slightly out of synchronization. This paper suggests a possible way to implement a quasi-synchronous DS-CDMA reverse link using the method of “data chunking”. The basic premise is derived by making a link between TDMA and synchronous DS-CDMA. By considering some basic TDMA limitations, a proposed “data chunked” quasi-synchronous DS-CDMA system is derived from a TDMA system. The effects of such a system are compared to those of a chip interleaved system. MATLAB simulations are performed to analyze the performance of the system in the presence of small synchronization errors between users. Implementation of guard bands is explored to further reduce errors due to imperfect synchronization between users

Energy-Efficient Resource Allocation in Wireless Networks: An Overview of Game-Theoretic Approaches

An overview of game-theoretic approaches to energy-efficient resource allocation in wireless networks is presented. Focusing on multiple-access networks, it is demonstrated that game theory can be used as an effective tool to study resource allocation in wireless networks with quality-of-service (QoS) constraints. A family of non-cooperative (distributed) games is presented in which each user seeks to choose a strategy that maximizes its own utility while satisfying its QoS requirements. The utility function considered here measures the number of reliable bits that are transmitted per joule of energy consumed and, hence, is particulary suitable for energy-constrained networks. The actions available to each user in trying to maximize its own utility are at least the choice of the transmit power and, depending on the situation, the user may also be able to choose its transmission rate, modulation, packet size, multiuser receiver, multi-antenna processing algorithm, or carrier allocation strategy. The best-response strategy and Nash equilibrium for each game is presented. Using this game-theoretic framework, the effects of power control, rate control, modulation, temporal and spatial signal processing, carrier allocation strategy and delay QoS constraints on energy efficiency and network capacity are quantified.Comment: To appear in the IEEE Signal Processing Magazine: Special Issue on Resource-Constrained Signal Processing, Communications and Networking, May 200

Adaptive S-ALOHA CDMA as an alternative way of integrating services in mobile environments

Code-division multiple-access (CDMA) schemes appear to be very promising access techniques for coping with the requirements of third-generation mobile systems, mainly because of their flexibility. This paper proposes an adaptive S-ALOHA DS-CDMA access scheme as a method for integrating nonreal-time (i.e., Internet applications) and real-time (i.e., voice) services in a multicell scenario by exploiting the potentials of CDMA under time-varying channel load conditions. The adaptive component makes data terminals autonomously change their transmission rate according to the total (voice+data) channel occupancy, so that the minimum possible data delay, which can be analytically obtained by defining a birth-death process, is almost always achieved. Moreover, by means of a simplified cellular model, the proposed algorithm revealed the same behavior, i.e., it tries to select the most suitable transmission rate at any time slot, when it is affected by intercell interference and even by power control imperfections. Finally, in order to gain more insight into the potentials of such an access strategy, the adaptive S-ALOHA CDMA scheme is then compared to a reservation time-division multiple-access (TDMA)-based protocol (PRMA++), showing the benefits of the CDMA-based solution in terms of capacity, flexibility, and data delay performance.Peer Reviewe

Final report on the evaluation of RRM/CRRM algorithms

Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin

A study on propagation characteristics and interference of spread spectrum code division multiple access cellular radio systems.

by Kwok Ming Shan.Thesis (M.Phil.)--Chinese University of Hong Kong, 1995.Includes bibliographical references (leaves 102-[109]).Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Cellular Radio Systems --- p.3Chapter 1.2 --- Code Division Multiple Access (CDMA) --- p.7Chapter 1.2.1 --- Direct Sequence CDMA (DS-CDMA) --- p.8Chapter 1.2.2 --- Frequency Hopping CDMA (FH-GDMA) --- p.11Chapter 1.2.3 --- Time Hopping CDMA (TH-CDMA) --- p.12Chapter 1.3 --- Propagation Characteristics --- p.12Chapter 1.3.1 --- Signal Strength Prediction - Path Loss --- p.13Chapter 1.3.2 --- Signal Variability --- p.17Chapter 1.3.3 --- Delay Spread --- p.23Chapter 1.3.4 --- Coherence Bandwidth --- p.23Chapter 1.4 --- Power Control in Cellular Radio Systems --- p.24Chapter 1.4.1 --- Centralized Power Control --- p.24Chapter 1.4.2 --- Distributed Power Control --- p.25Chapter 1.4.3 --- CDMA Power Control --- p.29Chapter 2 --- Contributions --- p.39Chapter 3 --- ACI Analysis of the Reverse-Link --- p.41Chapter 3.1 --- Adjacent Cell Interference --- p.42Chapter 3.2 --- Adjacent Cell Interference Analysis --- p.43Chapter 3.2.1 --- Interference Analysis of Hexagonal Cells --- p.43Chapter 3.2.2 --- Interference Analysis of Circular Cell Structure --- p.47Chapter 3.3 --- Closed-form of Adjacent Cell Interference --- p.51Chapter 3.4 --- Generalization to Irregular Cell Structure --- p.54Chapter 3.5 --- Conclusions --- p.57Chapter 4 --- ACI Analysis of Reverse-Link with Log-normal Shadowing --- p.59Chapter 4.1 --- Interference with Shadowing --- p.59Chapter 4.2 --- Conclusions --- p.66Chapter 5 --- ACI Analysis of Microcell --- p.68Chapter 5.1 --- Propagation Characteristics of Microcellular Radio Systems --- p.69Chapter 5.2 --- CDMA Microcellular Radio Systems --- p.70Chapter 5.3 --- Results and Discussions --- p.74Chapter 5.4 --- Conclusions --- p.76Chapter 6 --- Outage Probability Analysis of Imperfect Power Control --- p.77Chapter 6.1 --- Fast Fading of Signal --- p.78Chapter 6.2 --- Imperfect Power Control in CDMA --- p.81Chapter 6.3 --- Conclusions --- p.85Chapter 7 --- Conclusions --- p.88Chapter 8 --- Examples of CDMA Cellular Radio Systems --- p.91Chapter 8.1 --- Qualcomm CDMA system --- p.91Chapter 8.1.1 --- Forward-link --- p.92Chapter 8.1.2 --- Reverse-link --- p.93Chapter 8.1.3 --- Reverse-Link Open-Loop Power Control --- p.94Chapter 8.1.4 --- Reverse-Link Closed-Loop Power Control --- p.95Chapter 8.1.5 --- Forward-Link Power Control --- p.96Chapter 8.2 --- Interdigital Broadband CDMA System --- p.96Appendix --- p.97Chapter A --- Derivation of the PDF of the fast fading signal power --- p.97Chapter B --- Derivation of the Mean-to-standard deviation ratio --- p.98Chapter C --- Acronyms --- p.100Bibliography --- p.10