High Speed Downlink Packet Access System Research Articles

System value-based optimum spreading sequence selection for high-speed downlink packet access (HSDPA) MIMO

This article proposes the use of system value-based optimization with a symbol-level minimum mean square error equalizer and a successive interference cancellation which achieves a system value upper bound (UB) close to the Gaussian UB for the high-speed downlink packet access system without affecting any significant computational cost. It is shown that by removing multi-code channels with low gains, the available energy is more efficiently used, and a higher system throughput is observed close to the system value UB. The performance of this developed method will be comparable to the orthogonal frequency division multiplexing-based long-term evolution scheme, without the need to build any additional infrastructure. Hence, reduce the cost of the system to both operators and consumers without sacrificing quality.

The interference-reduced energy loading for multi-code HSDPA systems

A successive interference cancelation (SIC) method is developed in this article to improve the performance of the downlink transmission throughput for the current high speed downlink packet access (HSDPA) system. The multi-code code division multiplexing spreading sequences are orthogonal at the HSDPA downlink transmitter. However, the spreading sequences loose their orthogonality following transmission through frequency selective multipath channels. The SIC method uses a minimum-mean-square-error (MMSE) equalizer at the receiver to despread multi-code signals to restore the orthogonality of the receiver signature sequences. The SIC scheme is also used as part of the resource allocation schemes at the transmitter and for the purpose of interference and inter-symbol-interference cancelation at the receiver. The article proposes a novel system value based optimization criterion to provide a computationally efficient energy allocation method at the transmitter, when using the SIC interference cancelation and MMSE equalizer methods at the receiver. The performance of the proposed MMSE equalizer based on the SIC receiver is significantly improved compared with the existing schemes tested and is very close to the theoretical upper bound which may be achieved under laboratory conditions.

Service Quality Criteria for Voice Services over a HSDPA System

This paper covers the service quality of packet-based voice service that is provided over a high speed downlink packet access (HSDPA) system. Using the measurement software that has been developed in the course of preparing a advanced service quality management scheme for the packet-based voice service over a wireless network[2][3], a huge scale of experiment is conducted to measure the real quality of the voice service. Based on our analysis of the measurement result, the service quality of the voice service is supposed to be quite good over HSDPA system. In addition, another experiment to investigate the effect of degradation of wireless transmission conditions on the service quality of the voice service shows the values of wireless service metrics in which mean opinion score (MOS) starts to decrease.

An Intelligent HARQ Scheme for HSDPA

In this paper, we propose an intelligent hybrid automatic repeat request (iHARQ) scheme for high-speed downlink packet access (HSDPA) systems. The challenge in the hybrid automatic repeat request (HARQ) control problem of HSDPA is how to choose an appropriate modulation and coding scheme (MCS) for initial transmission in the situation wherein the channel quality indication (CQI) has report delay. The iHARQ scheme will determine the suitable MCS to maximize the system throughput and guarantee the block error rate requirement in such an uncertain environment. By modeling the HARQ behavior as a Markov decision process, we adopt fuzzy logics to determine an appropriate MCS for each initial packet transmission. In addition, a Q-learning algorithm is utilized to update the fuzzy rule base, according to well-designed reinforcement signals fed back from the HSDPA system, such that the iHARQ scheme can adapt to the delayed CQI. Simulation results show that, compared with a conventional adaptive threshold selection method, the proposed iHARQ scheme increases the system throughput by up to 75.2%.

QoE-Driven Cross-Layer Optimization for High Speed Downlink Packet Access

This paper proposes a Quality of Experience (QoE) based cross-layer design (CLD) framework for High Speed Downlink Packet Access (HSDPA). The proposed scheme aims at maximizing the user satisfaction by taking advantage of the link adaptation mechanism of HSDPA and the rate adaptation capability of multimedia applications. The main contributions of the paper are as follows. First, we describe the multiuser rate region of HSDPA by constructing a long-term radio link layer model. Next, we formulate multimedia QoE by constructing long-term utility functions, describe the multiuser utility space and derive its properties. We show analytically that the maximization of the sum of utility (max-MOS) can be efficiently solved by a fast greedy algorithm which searches only through the boundary of the utility space. We investigate two alternatives to the max-MOS approach, which introduce additional fairness in the system. We compare our proposed QoE-based cross layer optimization schemes to a system that is configured to maximize the overall throughput. For the sake of completeness, we also compare our approaches to a non-optimized HSDPA system. The performance comparison is made by simulation using a software implementation of an actually deployed HSDPA system. Results show that our QoE-based approach leads to significantly improved user perceived quality compared to the other approaches.

Analytical TCP throughput model for high-speed downlink packet access

This study deals with the throughput analysis of data services over high-speed downlink packet access (HSDPA) systems. The achievable throughput is calculated with an approximate analytical method based on the Padhye model that has two input parameters: the packet loss probability and the transmission control protocol (TCP) round trip time. The proposed solution is to calculate these parameters with an equivalent queuing network model of the HSDPA system that takes into account the possible congestion points in the system and the protocol layers that have dominant impact on the delay and packet drop. The modelling considerations and the analysis method are described in detail. Finally, the model is validated with a performance study of the HSDPA system that is executed with detailed NS2- based simulations too. The proposed method is found to be reasonably accurate requiring less computational effort than the simulations.

An enhanced packet scheduling algorithm combined with HARQ for HSDPA system

High speed downlink packet access (HSDPA) is a packet-based data service that supports downlink data rates of up to 14 Mbps in the WCDMA (wideband code division multiple access) system. In HSDPA, the packet scheduler is a key element for high-speed and efficient transmissions. In addition, hybrid automatic request (HARQ) plays a significant role in improving system performance. We propose an enhanced scheduling algorithm combined with HARQ to reduce transfer delay without the degradation of system throughput.

Practical Chip-level Equalizers in HSDPA

High-speed downlink packet access (HSDPA) has been developed to upgrade the current WCDMA system in yerms of providing a higher data rate for mobile users. To ensure a downlink speed of up to 14Mbps, the HSDPA system has three main features: adaptive modulation and coding, a hybrid automatic repeat request, and fast scheduling. Because standard documents describe only the specifications of Node B, various kinds of HSDPA receivers cen be used with different architectures. An ordinary receiver generally has a rake architecture, though a rake receiver is not good at reducing multiple access interference (MAI). The performance of rake receiver is indispensably deteriorated when the number of mobile users in the system increases. Conversely, an equalizer can alleviate the MAI significantly at the expense of complexity and can therefore be an alternative solution for a rake receiver in a HSDPA system. In this paper, the performance of several equalizers of a HSDPA system is compared in terms of several implementation issues. The simulation results provide useful information about proper equalizers for different design purposes with respect to the performance and complexity trade-off.

Research for a Emergency Medical Information Transmission System using High-Speed Downlink Packet Access

Objective: In this research, a full-duplex transmission system was developed in order to send real time medical information(i.e. patient vital signs, real-time patient video/audio data) using HSDPA(High-Speed Downlink Packet Access), a 3.5th generation mobile communication system. Methods: Transmission tests were conducted in an environment simulating that of the inside of a moving ambulance, transporting an emergency patient. The capability of the HSDPA system to transmit emergency medical information has been verified by comparing the prolonged cumulative data, calculating packet loss, and measuring transmission speed. Results: Test results show that the system is capable of transmitting vital signal data, including 12 waveform data, 20 numeric data and 113 events. This provides enough information needed for medical guidance, reading the affected part of the patient, and forwarding 320×420 pixel images at 2fps. Full-duplex voice transmission at 8bit/64kbps is enough to permit reliable communication between emergency medical technicians and hospital professionals. A total of 11.43 kilobytes were lost out of 81.25 megabytes. Therefore, the packet loss was 0.013%. Conclusion: The medical transmission system using HSDPA performs well in data transmission speed and communication quality during emergency medical transportation. It is also expected to further improve emergency medical conditions if supplementary systems such as the standard protocol establishment.

Analytical Evaluation of Analog Component Effects on AMC Performance in HSDPA System

We analytically evaluated the effects of the analog components on a high-speed downlink packet access (HSDPA) system standardized by 3GPP. We considered the phase noise of synthesizers, the imbalance of demodulators between in-phase and quadrature channels, and the filters. The components are represented by the appropriate equations. We applied adaptive modulation and coding methods for HSDPA systems and base station transmission of adequate data rate signals complying with quality estimated by mobile stations (MSs). The quality represents a data rate indicating that MSs can receive the signals. We estimated the quality using a conventional signal-to-interference measurement of the common pilot channel (CPICH) and found that the phase noise creates a mismatch relationship between the quality and the data rate, while the demodulator imbalance and filters create a suitable relationship. We confirmed this using analytic methods and computer simulation.

Turbo iterative equalization for HSDPA systems

In this paper, a turbo iterative receiver structure with chip equalization is proposed for the 3G high-speed downlink packet access (HSDPA) systems. The receiver equalizes the channel prior to the dispreading and then performs two successive soft-output decisions, achieved by a soft-input soft-output (SISO) multi-code detector and a SISO turbo decoder through an iterative process. At each iteration, extrinsic information is extracted from detection and decoding stages and is then used as a priori information in the next iteration, just as in turbo decoding. Computer simulations show that the turbo iterative receiver structure with chip equalization offers significant performance gain over the traditional receiver structure.

Opportunistic scheduling for streaming multimedia users in high-speed downlink packet access (HSDPA)

High-speed downlink packet access (HSDPA) achieves high data rates and high spectral efficiency by using adaptive modulation and coding schemes and employing multicode CDMA. In this paper, we present opportunistic algorithms for scheduling HSDPA users and selecting modulation/coding and multicode schemes that exploit channel and buffer variations to increase the probability of uninterrupted media play-out. First, we introduce a stochastic discrete event model for a HSDPA system. By employing the discrete event model, we transform the scheduling problem of providing uninterrupted play-out to a feasibility problem that considers two sets of stochastic quality-of-service (QoS) constraints: stability constraints and robustness constraints. A methodology for obtaining a feasible solution is then proposed by starting with a so-called stable algorithm that satisfies the stability QoS constraints. Next, we present stochastic approximation algorithms that adapt the parameters of the stable algorithm in a way that a feasible point for the robustness QoS is reached within the feasibility region of the stability QoS

Channel adaptive CQI reporting schemes for HSDPA systems

HSDPA (high-speed downlink packet access) is an evolved UMTS packet scheme that delivers increased user peak data rates and quality of service. A key technique supporting HSDPA is adaptive modulation and coding (AMC), in which the modulation scheme and the coding rate are changed adaptively according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes channel adaptive CQI reporting schemes in which UEs report the CQI value intelligently by using information about channel quality. With the proposed schemes, the battery capacity of UE can be conserved and the uplink interference can be lowered by filtering off redundant CQI reports or the transmission error rate can be lowered by fast CQI reports

On the Performance of an Indicator-Based Stall Avoidance Mechanism for High-Speed Downlink Packet Access Systems

The stall of delivering medium access control (MAC) layer data to the upper layer is a serious problem when a negative acknowledgement (NACK) control signal becomes an acknowledgement (ACK) signal, especially for a high-speed mobile terminal during handoff. Stall avoidance mechanisms aim to reduce such the transmission delay and keep in-sequence delivery of the MAC layer data to the upper layer. Recently, for providing high-speed downlink packet access (HSDPA) in the wideband code-division multiple access system, an indicator-based stall avoidance (ISA) mechanism was proposed to remove the nonrecoverable gap in the received out-of-sequence packets. In this paper, we derive the closed-form expression for the gap-processing time of the ISA mechanism when applying the multiprocess stop-and-wait (SAW) hybrid automatic repeat request (HARQ) mechanism. The derived analytical formulas can be used to understand performance tradeoffs between the gap-processing time and throughput in terms of various numbers of users and parallel processes when implementing the multiprocess SAW HARQ mechanism in the HSDPA system.

Cross-Layer design in HSDPA system to reduce the TCP effect

This paper focuses on the interaction between the transport control protocol (TCP) layer and the radio interface in the high-speed downlink packet access (HSDPA) wireless system. In the literature, studies of the interaction between TCP and wireless networks are focused on the evaluation of user bit rate in the case of dedicated channels. In this paper, the interaction between TCP, hybrid automatic repeat request (HARQ), and scheduling techniques (especially, proportional fair scheduling) is conducted. Analytical models to evaluate HSDPA cell capacity, user bit rate, and interaction with TCP layer are presented. Even if as expected the bit rate per flow decreases strongly with the congestion frequency in the wired network, it is shown that the overall capacity achieved by HSDPA is not as affected by the TCP layer. Using this result, a method to reduce the effect of TCP on wireless network without losing much cell capacity is proposed. This method has the advantage of modifying the scheduling algorithm only and of not requiring any change to the TCP protocol.

An enhanced channel-quality indication (CQI) reporting scheme for HSDPA systems

A major evolution of UMTS standard is the high speed downlink packet access (HSDPA). One of key techniques supporting HSDPA is the adaptive modulation and coding (AMC) in which the modulation scheme and the coding rate are adaptively changed according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes an enhanced CQI reporting scheme that can be used when a proportional fair scheduling algorithm (PFA) is used as a packet scheduling algorithm. The proposed scheme uses a dynamic threshold to filter off redundant CQI reports. With the proposed scheme, the battery capacity of UK can be conserved, maintaining the performance of traditional CQI reporting scheme.

A genetic approach for downlink packet scheduling in HSDPA system

High speed downlink packet access (HSDPA) system currently under development in 3rd generation partnership project (3GPP) [1] employs number of parallel shared channels and adaptive modulation and coding scheme (MCS) to enable a high rate packet data transfer from base station (Node-B) to user equipment (UE). To decide how to share the available radio channel capacity amongst the active UEs, a packet scheduling and channel assignment algorithms are employed at Node B. Packet scheduling techniques such as max carrier to interference ratio (C/I) or round robin (RR) fails to take into account all the aspects of the quality of service (QoS) provisioning. In this paper, the fundamentals genetic algorithms and conventional wireless scheduling techniques are combined and the weaknesses of the existing known techniques are exploited to propose a novel hybrid genetic packet scheduler (HGPS) for the HSDPA system. A combination of random and intelligent diversity of population and comparative nature of the selection process of genetic engine contribute to its robustness. The proposed HGPS outperforms Max C/I packet scheduler in terms of total delivered throughput within low delay thresholds. Unlike conventional packet scheduling technique HGPS does not rely only on the current or past status of the scheduling process. By treating the possible solutions as points in a search space, the proposed HGPS through a genetically guided search visits and examines the possible solutions and estimates the impact of each these solution on overall performance of system in terms of fairness, throughput or QoS without actually performing a transmission. Subsequently, the solution that achieves the best estimated overall performance is chosen for the actual transmission. By means of computer simulation, performance of the HGPS algorithm is characterized in Rayleigh fading and shadowing radio channel conditions. The impact of imperfect reporting on the performance of HSDPA system is evaluated. We examine the joint impact of reporting latency, imperfect channel estimation and the corruption of reports in the feedback channel on the performance. It is shown that the proposed class of intelligent parallel random schedulers is highly robust against the imperfect reports from UEs.