On generalized optimal scheduling of high data-rate bursts in CDMA systems

In a code-division multiple access (CDMA)-based wireless communication system, forward link is power limited and reverse link is interference limited. With power control and statistical multiplexing, voice services can be supported reasonably well. However, for high data-rate services, a more comprehensive scheduling mechanism is needed in order to achieve a high capacity while satisfying the forward and reverse link constraints. In this paper, we formulate the high data-burst scheduling as a integer programming problem using a generic CDMA system model. We also suggest an optimal algorithm for generating scheduling solutions. With cdma2000 system details plugged in the proposed algorithm, it is found that our algorithm considerably outperforms several fast heuristics, including equal sharing, first-come-first-served, longest delay first, and shortest burst first.published_or_final_versio

System modeling and performance evaluation of rate allocation schemes for packet data services in wideband CDMA systems

To fully exploit the potential of a wideband CDMA-based mobile Internet computing system, an efficient algorithm is needed for judiciously performing rate allocation, so as to orchestrate and allocate bandwidth for voice services and high data rate applications. However, in existing standards (e.g., cdma2000), only a first-come-first-served equal sharing allocation algorithm is used, potentially leading to a low bandwidth utilization and inadequate support of high data rate multimedia mobile applications (e.g., video/audio files swapping, multimedia messaging services, etc.). In this paper, we first analytically model the rate allocation problem that captures realistic system constraints such as downlink power limits and control, uplink Interference effects, physical channel adaptation, and soft handoff. We then suggest six efficient rate allocation schemes that are designed based on different philosophies: rate optimal, fairness-based, and user-oriented. Simulations are performed to evaluate the effectiveness of the rate allocation schemes using realistic system parameters In our model.published_or_final_versio

Optimal admission control algorithms for scheduling burst data in CDMA multimedia systems

3rd generation mobile systems are mostly based on the wideband CDMA platform to support high bit rate packet data services. One important component to offer packet data service in CDMA is a burst admission control algorithm. In this paper, we propose and study a novel jointly adaptive burst admission algorithm, namely the jointly adaptive burst admission-spatial dimension algorithm (JABA-SD) to effectively allocate valuable resources in wideband CDMA systems to burst requests. In the physical layer, we have a variable rate channel-adaptive modulation and coding system which offers variable throughput depending on the instantaneous channel condition. In the MAC layer, we have an optimal multiple-burst admission algorithm. We demonstrate that synergy could be attained by interactions between the adaptive physical layer and the burst admission layer. We formulate the problem as an integer programming problem and derive an optimal scheduling policy for the jointly adaptive design. Both the forward link and the reverse link burst requests are considered and the system is evaluated by dynamic simulations which takes into account of the user mobility, power control and soft-handoff. We found that significant performance improvement, in terms of average packet delay, data user capacity and coverage, could be achieved by our scheme compared to the existing burst assignment algorithms.published_or_final_versio

A quantitative comparison of multiple access control protocols for wireless ATM

The multiple access control (MAC) problem in a wireless network has intrigued researchers for years. For a broad-band wireless network such as wireless ATM, an effective MAC protocol is very much desired because efficient allocation of channel bandwidth is imperative in accommodating a large user population with satisfactory quality of service. Indeed, MAC protocols for a wireless ATM network in which user traffic requirements are highly heterogeneous (classified into CBR, VBR, and ABR), are even more intricate to design. Considerable research efforts expended in tackling the problem have resulted in a myriad of MAC protocols. While each protocol is individually shown to be effective by the respective designers, it is unclear how these different protocols compare against each other on a unified basis. In this paper, we quantitatively compare seven recently proposed TDMA-based MAC protocols for integrated wireless data and voice services. We first propose a taxonomy of TDMA-based protocols, from which we carefully select seven protocols, namely SCAMA, DTDMA/VR, DTDMA/PR, DQRUMA, DPRMA, DSA++, and PRMA/DA, such that they are devised based on rather orthogonal design philosophies. The objective of our comparison is to highlight the merits and demerits of different protocol designs.published_or_final_versio

Synergy between adaptive channel coding and media access control for wireless ATM

In this paper, we propose mechanisms to exploit the synergy between the Media Access Control (MAC) layer and the physical layer for wireless ATM applications. For simplicity, the system considered consists of a single server and a single wireless ATM terminal. A number of virtual circuit connections (VC), with varying Quality of Service (QoS) requirements, are supported. We focus on two components of the wireless ATM system, namely the channel encoder and the ATM scheduler in the MAC layer. The channel encoder is responsible for protecting the ATM cells over the hostile radio channel while the ATM scheduler is responsible for allocating limited resources to the ATM cells for each virtual connection so as to meet the specified QoS requirements. We consider two configurations, namely System-I with isolated adaptive channel encoder and ATM scheduler, and System-II with bi-directional information exchange. It is found that significant performance improvement on the Cell Loss Rate (CLR) and the Mean Cell Delay (MCD) could be achieved for systems exploiting the synergy. © 1999 IEEE.published_or_final_versio

Design and evaluation of an optimization based approach to multiple burst admission control for cdma2000

In our recent study, we have formulated the burst admission control problem for wideband CDMA systems as an integer programming problem. In this paper, we propose and analyze the performance of a novel burst admission technique, called the multiple-burst admission-spatial dimension algorithm (MBA-SD) to judiciously allocate the previous channels in wideband CDMA systems to burst requests. Both the forward link and the reverse link burst requests are considered and the system is simulated by dynamic simulations which takes into account of the user mobility, power control and soft hand-off. We found that significant performance improvement, in terms of data user capacity, coverage, and admission and outage probabilities, could be achieved by our scheme compared to the existing burst assignment algorithms.published_or_final_versio

Enabling Wireless Power Transfer in Cellular Networks: Architecture, Modeling and Deployment

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A novel channel-adaptive uplink access control protocol for nomadic computing

We consider the uplink access control problem in a mobile nomadic computing system, which is based on a cellular phone network in that a user can use the mobile device to transmit voice or file data. This resource management problem is important because an efficient solution to uplink access control is critical for supporting a large user population with a reasonable level of quality of service (QoS). While there are a number of recently proposed protocols for uplink access control, these protocols possess a common drawback in that they do not adapt well to the burst error properties, which are inevitable in using wireless communication channels. In this paper, we propose a novel TDMA-based uplink access protocol, which employs a channel state dependent allocation strategy. Our protocol is motivated by two observations: 1) when channel state is bad, the throughput is low due to the large amount of FEC (forward error correction) or excessive ARQ (automatic repeated request) that is needed and 2) because of item 1, much of the mobile device's energy is wasted. The proposed protocol works closely with the underlying physical layer in that, through observing the channel state information (CSI) of each mobile device, the MAC protocol first segregates a set of users with good CSI from requests gathered in the request contention phase of an uplink frame. The protocol then judiciously allocates channel bandwidth to contending users based on their channel conditions. Simulation results indicate that the proposed protocol considerably outperforms five state-of-the-art protocols in terms of packet loss, delay, and throughput.published_or_final_versio

Performance analysis of SIMO space-time scheduling with convex utility function: Zero-forcing linear processing

In a multiple-antenna system, an optimized design across the link and scheduling layers is crucial toward fully exploiting the temporal and spatial dimensions of the communication channel. In this paper, based on discrete optimization techniques, we derive a novel analytical framework for designing optimal space-time scheduling algorithms with respect to general convex utility functions. We focus on the reverse link (i.e., client to base station) and assume that the mobile terminal has a single transmit antenna while the base station has nR receive antennas. In order that our proposed framework is practicable and can be implemented with a reasonable cost in a real environment, we further assume that the physical layer involves only linear-processing complexity in separating signals from different users. As an illustration of the efficacy of our proposed analytical design framework, we apply the framework to two commonly used system utility functions, namely maximal throughput and proportional fair. We then devise an optimal scheduling algorithm based on our design framework. However, in view of the formidable time complexity of the optimal algorithm, we propose two fast practical scheduling techniques, namely the greedy algorithm and the genetic algorithm (GA). The greedy algorithm, which is similar to the one widely used in 3G1X and Qualcomm high-data-rate (HDR) systems (optimal when nR = 1), exhibits significantly inferior performance when nR > 1 as compared with the optimal approach. On the other hand, the GA is quite promising in terms of performance complexity tradeoff, especially for a system with a large number of users with even a moderately large nR. As a case in point, for a system with 20 users and nR = 4, the GA is more than 36 times faster than the optimal while the performance degradation is less than 10%, making it an attractive choice in the practical implementation for real-time link scheduling.published_or_final_versio

On channel-adaptive multiple burst admission control for mobile computing based on wideband CDMA

Mobile computing systems built using third generation wireless standards are mostly based on the wideband CDMA platform to support high bit rate packet data services. One important component offering packet data service in CDMA is a burst admission control algorithm. We formulate the multiple-burst admission control problem as an integer programming problem, which induces our novel jointly adaptive burst admission algorithm, called the jointly adaptive burst admission-spatial dimension algorithm (JABA-SD), which is designed to effectively allocate valuable resources in wideband CDMA systems to burst requests. Both the forward link and the reverse link burst requests are considered and the system is evaluated by dynamic simulations which takes into account user mobility, power control, and soft hand-off.published_or_final_versio