A QoS-aware Packet Scheduling Scheme in High-speed Downlink Packet Access Networks

We consider modeling the statistical behavior of interactive and streaming traffics in high-speed downlink packet access (HSDPA) networks. Two important applications in these traffic categories are web-browsing (interactive service) and video streaming (streaming service). Web-browsing is characterized by its important sensitivity to delay. Video streaming on the other hand is less sensitive to delay, however, due to its large frame sizes, video traffic is more affected by the packet loss resulting from a limited buffer size at the base station. Taking these characteristics into account, we consider modeling the queuing delay probability density function (PDF) of the Web-browsing traffic, and modeling the queuing buffer size distribution of video streaming traffic. Specifically, we show that the queuing delay of the Web-browsing traffic follows an exponential distribution and that the queuing buffer size of video streaming traffic follows a weighted Weibull distribution. Model fitting based on simulated data is used to provide simple mathematical formulations for the different parameters that characterize the PDFs under consideration. The provided equations could be used, directly, in HSDPA network dimensioning and, as a reference, to satisfy a certain quality of service (QoS).

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

In this paper, we describe the novel concept of broadcast and multicast (BCMC) transmission over high speed downlink packet access (HSDPA), a shared high-speed packet data channel on the downlink defined in the Universal Mobile Telecommunications System (UMTS) standard. We show that the unique features of HSDPA such as link adaptation, channel-sensitive scheduling, and hybrid automatic repeat request (HARQ) can be used to provide performance gains over conventional multimedia broadcast multicast service (MBMS) transmission on the forward access channel (FACH) channel. We address various aspects of system design and performance in the design of a BCMC system over HSDPA, and present a detailed performance analysis using system level simulations. Some of the main objectives of our BCMC design are to enable broadcast and multicast services on HSDPA networks without requiring significant changes to the HSDPA standard in 3rd Generation Partnership Project (3GPP), and to ensure that the solution is backward-compatible with Release 5 HSDPA mobile devices.

In Wideband Code Division Multiple Access (WCDMA) networks the Signaling Radio Bearer (SRB) is transmitted downlink to inform the user i.a. when it needs to make a handover. When transmitting e.g. Voice over IP (VoIP) on High Speed Downlink Packet Access (HSDPA) SRB is mapped on HSDPA user data channel, high-speed downlink shared channel (HS-DSCH) in order to maximize voice capacity. The lack of support for soft handover (SHO) of HS-DSCH may compromise the reception of SRB and thus also a possible incoming serving HSDPA cell change command especially at the cell borders. This can lead to serious VoIP service degradation due to prolonged camping on a poor cell and in the worst case even to call dropping, if the cell change command is not received before VoIP call drop criterion is met. This paper considers the performance of SRB transmission on source cell HS-DSCH during a handover process. Also a strategy of transmitting the serving cell change command from the target cell is analyzed. The study is done by the means of fully dynamic system simulations and they consider both macro-cell and manhattan scenarios. The results show that a relatively low SRB/handover error rate is experienced in a macro cell scenario but in a more challenging manhattan scenario the error rate is higher. Transmitting the serving cell change command from the target cell HS-SCCH results in similar handover failure rates in manhattan scenario than using SRB on HS-DSCH in macro-cell scenario when static power allocation for HS-SCCH is in use.

The provision of data services in 3G systems requires spectral efficiency solutions to increase the capacity of the radio access network as well as support for high data rates. In this context, the 3GPP introduces a new feature in the release 5 specifications denominated high speed downlink packet access (HSDPA). The HSDPA concept appears as an umbrella of features to improve both user and system performance. The concept includes a reduction of the transmission time interval (TTI) to 2 ms, an adaptive modulation and coding (AMC) scheme, and a fast physical layer hybrid ARQ mechanism. In this paper the objective is to analyze the HSDPA performance for streaming, interactive, and background services. Relevant characteristics such as the QoS demands of the different traffic classes, the throughput and delay characteristics has been analyzed and compared with shared channel. We also propose a new packet-scheduling scheme for HSDPA transmission, which improves the overall performance and fairness among the packet users.

Only best-effort traffic was supported by traditional packet switching networks, but newer applications need network services that allow an end-client to transport data with performance guarantees. The choice of packet-scheduling algorithm used at switching nodes is crucial in providing Quality of Service (QoS). This paper proposes a downlink packet scheduling algorithm for QoS provisioning in High Speed Downlink Packet Access (HSDPA) based UMTS networks. In HSDPA, a single logical channel is shared amongst multiple contending users. Besides better link utilization, scheduling disciplines seek to achieve fair allocation of this shared resource. However, these two criteria can potentially be in conflict. The scheduling algorithm proposed in this paper, Wireless Fair High Speed Scheduling, addresses this conflict. The basic idea is to allocate the wireless channel fairly amongst users, even during short time scales, according to their data rate requirements. Simulation results show that the proposed scheduling algorithm provides better link utilization, as well as long-term and short-term fairness amongst users, even under heavy load conditions.

Future wireless cellular networks such as high speed downlink packet access (HSDPA) and 1x EVolution data optimized (1xEV-DO) promise to revolutionize the mobile user's wireless experience by offering high downlink data rates that are much more beyond what 2.5 G and 3 G cellular systems could offer. In order to support as many users as possible, these systems exploit the bursty nature of the data traffic by utilizing high speed downlink shared channels that are shared among the users according to the packet scheduling scheme being used. However, to support acceptable performance levels especially at peak loads, these systems require much more efficient downlink packet scheduling schemes than ever before. In this paper, we propose a novel generic centralized downlink (GCD) packet scheduling scheme for next generation wireless cellular networks. The proposed scheme utilizes novel utility and opportunity cost functions to satisfy the mobile users as well as the service providers. We show that our scheme converges to two well known schemes, Max CIR and PF. Simulation results are provided to show the effectiveness and strength of the GCD scheme.

This paper provides methods for packet scheduling that designed for VoIP in a mixed traffic scenario over high-speed downlink packet access (HSDPA) in WCDMA. In the interested mixed traffic scenario voice packets are transmitted together with 5 background best-effort (BE) data users. The proposed packet scheduling schemes in such a mixed traffic environment are based on a proportional fair (PF) packet scheduling algorithm, to be more specifically, they are two resource allocation methods for BE data user. The performance is evaluated with a quasi-static system level simulator. Performance with a LMMSE advanced receivers is also addressed. The results indicate that with the proposed scheduling algorithm 2 in this paper the VoIP capacity in a mixed traffic scenario can be up to 106 users with a delay budget 80 ms, which is approximately maintained as that of VoIP single mode. At the same time, a rather good background BE performance can be obtained. With the proposed algorithm 1 the VoIP capacity can reach 101 users per cell. However a better background BE performance than algorithm 2 can be obtained.

In recent years, the growth of smart phone industry drives its users to demand better quality multimedia services while achieving faster internet speeds. With a higher number of subscribers and more data hungry applications, there is a need to improve the current 3G HSDPA data rate until the 4G network is fully implemented globally. Therefore, the aim of this thesis is to improve the downlink data rate of the HSDPA system throughput through both transmitter and receiver optimisations while balancing the complexities of the optimisation algorithms. Initially, improving system throughput through power allocation strategies is investigated in this thesis. Current schemes proposed in the literature that use Equal SINR Equal Rate (ESER) allocation can improve the system throughput for single rate allocation but require a rather high complexity. In this thesis, a System Value (SV) criterion is proposed to decrease the traditional ESER allocation method while achieving similar system throughput performance. To further increase the system throughput, a Successive Interference Cancellation (SIC) receiver is proposed which not only improves the data rate but also has a reduced complexity. The proposed SIC receiver can be used in conjunction with both ESER allocation schemes as well as equal energy allocation schemes. Another transmitter optimisation strategy is to improve the signature sequences. A signature sequence design that minimises correlations between the sequences while reducing the Inter-Symbol Interference (ISI) and noise is proposed. To reduce the amount of channel state information required, a signature sequence selection method which removes the signature sequences that are heavily a ected by interference is also proposed. The proposed optimisation strategies have been veri ed through MATLAB simulations. Moreover, practical measurements using the National Instruments (NI)-PXIe testbed have been carried out for the proposed SIC algorithm which further con rm its e ectiveness in a real world environment.

A large number of phone calls and data services will take place in indoor environments. In Long Term Evolution (LTE), femtocell, as a home base station for indoor coverage extension and wideband data service, has recently gained significant interests from operators and consumers. Since femtocell is frequently turned on and off by a personal owner, not by a network operator, one of the key issues is that femtocell should be identified autonomously without system information to support handover from macrocell to femtocell. In this paper, we propose a dynamic reservation scheme of Physical Cell Identities (PCI) for 3GPP LTE femtocell systems. There are several reserving types, and each type reserves a different number of PCIs for femtocell. The transition among the types depends on the deployed number of femtocells, or the number of PCI confusion events. Accordingly, flexible use of PCIs can decrease PCI confusion. This reduces searching time for femtocell, and it is helpful for the quick handover from macrocell to femtocell. Simulation results show that our proposed scheme re- duces average delay for identifying detected cells, and increases network capacity within equal delay constraints. The 3rd Generation Partnership Project (3GPP) is work- ing on the standardization of asynchronous communication systems. This technology is being enhanced gradually en- suring higher user data rate, bigger system capacity, and lower cost. The wideband CDMA (WCDMA) system is standardized with 3GPP release 99/4 which is being de- ployed in the world. Release 5 is related to High Speed Downlink Packet Access (HSDPA), and it improves the downlink packet transmission speed theoretically up to 14.4 Mbps. High Speed Uplink Packet Access (HSUPA) is enhanced up to 5.76 Mbps in uplink, and it is standardized with the Release 6. We simply mention both HSDPA and HSUPA as High Speed Packet Access (HSPA). In release 7, High Speed Packet Access Evolution (eHSPA, HSPA+) is standardized. eHSPA is based on the HSPA network with a simple upgrade, and it supports more bandwidth efficiency and lower latency. The maximum data rate is 28.8 Mbps in downlink and 11.5 Mbps in uplink (1). How- ever, users still require further system improvements. The technology is dramatically enhanced in release 8, where the standard of Long Term Evolution (LTE) is currently being established. The main objectives of LTE are higher data rates, lower latency, increased capacity, enhanced coverage, and an optimized system for the packet switching network (2). LTE also considers a femtocell, which is referred to as a home base station for an indoor coverage extension and overall network performance enhancement (3). Recently, LTE-Advanced standard targeting of 1Gbps for low mobil- ity is being discussed in release 9. We look into general features and requirements of fem- tocells. Important issues related to access control are de- scribed, followed by our contributions and organization of the paper.

This article investigates the efficient transmission of file download services to several users simultaneously in 3G mobile networks with HSDPA (High-Speed Downlink Packet Access) and MBMS (Multimedia Broadcast Multicast Services). HSDPA supports high speed point-to-point (p-t-p) transmissions (up to several Mb/s), whereas with MBMS the same content can be transmitted with a point-to-multipoint (p-t-m) connection to multiple users in a unidirectional fashion. Multicast delivery can be implemented through only p-t-p transmissions with HSDPA, a single p-t-m transmission with MBMS, or using both jointly in a hybrid approach by employing HSDPA for error repair of the MBMS p-t-m transmission. We investigate the optimum HSDPA and MBMS transmission configuration when they are used separately, and the trade-off between the initial MBMS file p-t-m transmission and the HSDPA error repair for the hybrid delivery. The approach of minimizing the transmission energy (product of the transmit power times the transmission time) to achieve a target file acquisition probability (percentage of users that successfully receive the file) has been adopted.

The various link adaptation techniques employed by High Speed Downlink Packet Access (HSDPA) in the third generation (3G) networks augment the bandwidth oscillation, which is identified as one of the most important factors resulting in the throughput deterioration of Transmission Control Protocol (TCP). In this paper, we firstly explain why the bandwidth oscillation degrades the TCP performance through a special simulation experiment. Subsequently, a split connection Window Adaptation TCP Proxy is proposed to improve the TCP throughput over HSDPA networks. In this solution, the built-in attributes of HSDAP system are sufficiently utilized. In order to effectively use the precious cellular link resources, the length of the queue connected with it is intentionally kept around the reference value through adjusting the sending window size of TCP proxy based on the dynamic values of varying bandwidth. A discrete-time stochastic state space model is formulated to analyze the system stability. The validity of enhanced scheme is verified through simulation experiments. The performance of TCP proxy is compared with the standard TCP protocol. The numerical results show that our TCP proxy is able to keep the cellular link utilization over 90%, and to improve TCP throughput by 100% under most conditions.

TCP-based data flows generate packets and ACKs in two directions, be it in the wireline or wireless networks. In the latter case, packets are typically found in the downlink whereas ACKs are in the uplink. Those two links are asymmetric in the case of CDMA-based High Data Rate (HDR)/High-Speed Downlink Packet Access (HSDPA) systems, the uplink being much slower than the downlink and thus, in some cases, restrictive in terms of the achievable throughput of the TCP flow. The aim of this work is to evaluate the performance of such a setting, in the presence of both streaming and elastic traffic, under a dynamic scenario where users arrive to the system and leave it after completion of their service. We specifically quantify the impact of the uplink on the overall performance of TCP and study the model variations according to several parameters such as load, file size and radio conditions.

TCP-based data flows generate packets and ACKs in two directions, be it in the wireline or wireless networks. In the latter case, packets are typically found in the downlink whereas ACKs are in the uplink. Those two links are asymmetric in the case of CDMA-based High Data Rate (HDR)/High-Speed Downlink Packet Access (HSDPA) systems, the uplink being much slower than the downlink and thus, in some cases, restrictive in terms of the achievable throughput of the TCP flow. The aim of this work is to evaluate the performance of such a setting, in the presence of both streaming and elastic traffic, under a dynamic scenario where users arrive to the system and leave it after completion of their service. We specifically quantify the impact of the uplink on the overall performance of TCP and study the model variations according to several parameters such as load, file size and radio conditions.

In order to improve support for higher speed data, 3GPP has developed an evolution of UNTS based on WCDMA known as HSDPA(high speed downlink packet access). The target of HSDPA is to provide service for not only voice user but also higher speed data users. For HSDPA, there are two important parameters, which are the rate ratio and the power ratio between higher speed data signal and voice data signal. In this article, we deduced two useful conclusions, which are based on the research of the relationship between the rate ratio and the power ratio. One of the two conclusions is that the transmission power is in positive proportional to data rate when the user numbers of higher speed data is high, which would result in dramatic interference of multi-user. The other is that the same capacity can be achieved by only using half transmission power when there is one higher speed data user over one transmission time interval. Based on the two conclusions, the feasibility of HSDPA is studied. We found that it is impossible for HSDPA to provide simultaneously service for multiple high-speed data users and voice users. A feasible CDMA/TDMA reform scheme is proposed, which can achieve the design goal of WCDMA HSDPA. The reform scheme employs the method of time domain multiplexing(TDM) to realize the transmission of high speed data over a special CDMA channel. The reform scheme can increase dramatically downlink capacity, improve spectral efficiency, and also reduce system cost by employing simple interference eliminator.