Qinqing Zhang

Finite-state Markov model for Rayleigh fading channels

We form a finite-state Markov channel model to represent Rayleigh fading channels. We develop and analyze a methodology to partition the received signal-to-noise ratio (SNR) into a finite number of states according to the time duration of each state. Each state corresponds to a different channel quality indicated by the bit-error rate (BER). The number of states and SNR partitions are determined by the fading speed of the channel. Computer simulations are performed to verify the accuracy of the model.

Hybrid ARQ with selective combining for fading channels

We propose and analyze a hybrid automatic repeat request (ARQ) with a selective combining scheme using rate-compatible punctured convolutional (RCPC) codes for fading channels. A finite-state Markov channel model is used to represent the Rayleigh fading channels. We show that the hybrid ARQ with selective combining yields better performance than the generalized type-II ARQ scheme for fading channels. Furthermore, simulation results of real-time video time division multiple access (TDMA) transmission system are given. Better video quality can be obtained by our proposed scheme, with a bounded delay. Analytical results of throughput and packet error rate (PER) are compared to the simulated results. Our analysis based on a finite-state Markov channel model, is shown to give good agreement with simulations.

An Analysis of VoIP Service Using 1

While voice-over-Internet protocol (VoIP) on wireline network is maturing, VoIP on wireless mobile network is still in its infancy. This disparity is due to the fact that the wireline bandwidth is abundant and can be traded off for delay performance and overhead, whereas bandwidth in wireless mobile network is still a scarce resource. With the deployment of 1

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EV-DO Revision A System

EV-DO revision 0 (DOr0) worldwide, the spectrum efficiency has been significantly improved. However, DOr0 still lacks of features essential for VoIP. For this reason, 1

Performance of UMTS radio link control

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Performance and Capacity of Cellular OFDMA Systems With Voice-Over-IP Traffic

EV-DO revision A (DOrA) has been standardized in the 3GPP2 with many improvements favorable for VoIP implementation. In this paper, we identify challenges and explore the feasibility of implementing VoIP using DOrA. We develop both analytical and simulation models to evaluate the VoIP capacity and delay performance over the air interface.

UMTS air interface voice/data capacity-part 2: forward link analysis

The radio link control (RLC) protocol in Universal Mobile Telecommunication System (UMTS) contains a suite of features and options which make the protocol very flexible and adaptive to operation in different radio environments and for various applications. We analyze the various features and functions associated with the RLC protocol and evaluate the performance over UMTS specific physical link through simulations. Specifically, we examine the detail behavior of the protocol under various conditions and options, including polling, status transmission mechanism, and packet discard functions. We compare different polling mechanisms and examine their impacts on the delay and throughput as well as acknowledgement overhead. We also compare different discard parameters and service rates and evaluate their impacts on the overall performance. Finally we provide quantitative results for web-browsing traffic which is considered as one of the future applications in 3G wireless networks.

UMTS air interface voice/data capacity-part 1: reverse link analysis

We propose a methodology to evaluate the voice-over-IP (VoIP) capacity and performance of orthogonal frequency-division multiple-access (OFDMA)-based systems. The approach combines the queuing and interference analyses to find the delay and power outage. Using this analytical framework, we provide insight into tradeoffs among capacity-limiting factors, including channel dimensions, power, interference threshold and latency, and we identify techniques for capacity optimization. The numerical demonstrations are carried out on the newly standardized ultra mobile broadband (UMB) system. The same methodology can also be applied to Universal Mobile Telecommunications System (UMTS) Long Term Evolution (LTE) and wireless mobile Worldwide Interoperability for Microwave Access (WiMAX) systems.

Connectivity in Selfish, Cooperative Networks

For pt.1 see ibid., p.2725-29. We evaluate the air interface capacity for voice, data, integrated voice and data services in UMTS. We present our analytical and simulation models for the forward link only; the reverse link analysis is presented in part 1. Compared to reverse link the analysis on the forward link is much more challenging because of the forward power allocation problem. We propose a new approach to model the interference distribution based on users locations and shadow fading variables. Furthermore, we apply different approximation methods to calculate capacity based on voice and/or data traffic loading. We derive simple expressions that allow us to calculate the system capacity quickly and effectively. We also develop a static system level simulator to evaluate capacity and coverage for UMTS. By comparing our analytical results with simulations, we show that our analytical approach has a very good match with simulations.