Impacts of air interface admission control and user mobility on UTRAN transport simulations

UMTS Terrestrial Radio Access Network (UTRAN) Transport Network Layer dimensioning has been of great interest among network researchers and planners due to the limit of Iub bandwidth. This paper investigates the potential impacts caused by Connection Admission Control (CAC) mechanism of the air interface and User Mobility (UM) on simulations carried out for the UTRAN transport network domain. Independent from the TNL CAC mechanism of the transport network which is in charge of Iub link bandwidth, the Radio CAC function deals with the highly non-linear resources needed for an attempted connection depending on its specific propagation and interference situation. The consideration of the air interface acting as bottleneck results into a less challenging amount of traffic for the transport domain. In addition, mobile user behaviors, e.g. UM, may dynamically change traffic load at the air interface, and in consequence affect Iub load, which has a very close correlation with cell load. In this work, a simulation model with Radio CAC mechanism and Handover strategies is implemented to study this correlation, and evaluate the UTRAN transport network performance given a limited radio capacity. The analysis on the impacts of the Radio CAC and UM are derived from qualitative simulations.     

Enhanced VoIP Support in OFDMA-based Packet Radio Networks

As the first OFDMA-based cellular packet radio network, Evolved UTRAN has already been well studied in 3GPP and semi-persistent scheduling was selected as the most relevant packet scheduling scheme for VoIP traffic. With further evolution of Evolved UTRAN to meet the ambitious goal set by IMT-A, the performance of VoIP needs to be enhanced. In this article, we establish a semi-persistent scheduling centered framework for efficient VoIP support in OFDMA-based packet radio network and evaluate different enhancement methods, such as adaptive transmission bandwidth in persistent resource allocation, dynamic packet bundling, and frequency diversity transmission that can be added into this framework. In addition, we investigate practical constraints, e.g. wideband CQI reporting on real network performance as well as possible corrective measures. The whole system design is verified through large-scale network level simulations in which all the details of various VoIP-specific radio resource management algorithms and enhancement mechanisms as well as interactions between them are explicitly modeled. Simulation results indicate that VoIP in Evolved UTRAN can be well supported using this framework and further improved through different enhancement methods. Compared with fixed transmission bandwidth approach, adaptive transmission bandwidth approach can provide additional capacity gain of 11 and 8% respectively in 3GPP Macro Case 1 and Case 3 deployment scenario. In a highly-loaded network, switching from adaptive transmission bandwidth to dynamic packet bundling can accommodate 18 and 15% more users in Case 1 and 3 respectively. The performance degradation due to wideband CQI reporting can be partly compensated with frequency diversity transmission. It is finally concluded that the enhanced performance of VoIP is sufficient to meet the ambitious target set by IMT-A in all four ITU deployment scenarios.     

Traffic and Interference Adaptive Scheduling for Internet Traffic in UMTS

In this paper we propose a scheduling strategy for the radio resources management when transmitting Internet traffic over third-generation systems. More precisely, we consider the UMTS Terrestrial Radio Access Network (UTRAN) Time Division Duplex (TDD) mode standardized by ETSI. UTRAN TDD uses a hybrid solution of code and time division multiple access, called TD-CDMA. In UMTS systems a key issue in developing access methodologies for the available spectrum is an optimal management of the rare radio resources. In this paper we present a fair and efficient scheduling algorithm that adapts its behavior to traffic and interference conditions. Specifically, our scheduling algorithm is able to manage the radio resources taking into account both the traffic fluctuations in the uplink and downlink direction and the variations of the system interference. The goal of our scheduler is the data-throughput maximization for an efficient utilization of available radio resources. The effectiveness of our scheduling algorithm is shown by exploiting analytical tools.     

A Markovian Approach to Radio Access Technology Selection in Heterogeneous Multiaccess/Multiservice Wireless Networks

This paper addresses the problem of Radio Access Technology (RAT) selection in heterogeneous multi-access/multi-service scenarios. For such purpose, a Markov model is proposed to compare the performance of various RAT selection policies within these scenarios. The novelty of the approach resides in the embedded definition of the aforementioned RAT selection policies within the Markov chain. In addition, the model also considers the constraints imposed by those users with terminals that only support a subset of all the available RATs (i.e. multi-mode terminal capabilities). Furthermore, several performance metrics may be measured to evaluate the behaviour of the proposed RAT selection policies under varying offered traffic conditions. In order to illustrate the validation and suitability of the proposed model, some examples of operative radio access networks are provided, including the GSM/EDGE Radio Access Network (GERAN) and the UMTS Radio Access Network (UTRAN), as well as several service-based, load-balancing and terminal-driven RAT selection strategies. The flexibility exhibited by the presented model enables to extend these RAT selection policies to others responding to diverse criteria. The model is successfully validated by means of comparing the Markov model results with those of system-level simulations.     

Applying ATM/AAL2 as a switching technology in third-generationmobile access networks

In this article we focus on the transport and switching part of third-generation mobile access networks and outline some important aspects of applying ATM in these networks. In particular, we argue that in order for the mobile access network to support low-bit-rate delay-sensitive traffic consisting of short packets, the standardization of a new ATM adaptation layer, AAL2, and associated signaling protocol has been necessary. The AAL2 protocol has been designed to support low-bit-rate delay-sensitive services (typically compressed voice) where other adaptation layers fail to deliver the required QoS and maintain efficient resource utilization at the same time. Furthermore, in order to provide mobility and soft handover support in W-CDMA-based mobile networks such as UMTS or IMT-2000, there is also a strong demand for fast connection establishment and release. Therefore, when designing ATM-based cellular access networks some specific architectural and traffic management issues need to be addressed     

Performance study for HARQ–ARQ interaction of LTE

The 3GPP working group proposes the Long‐Term Evolution (LTE) system as the 4G mobile communications technology. To reduce the transmission latency in the radio access network, Evolved Universal Terrestrial Radio Access Network (E‐UTRAN), of LTE, the base station and radio network controller are merged into a single network node, namely eNB. In E‐UTRAN, the Stop‐And‐Wait Hybrid ARQ (SAW‐HARQ) protocol in the Media Access Control (MAC) layer deals with transmission errors without the need to engage the ARQ protocol in the Radio Link Control (RLC) layer. The HARQ and ARQ protocols interact only in case of dealing HARQ residual errors. In this paper, we propose an analytical model to model the behavior of the HARQ–ARQ Interaction. Our analytical model is validated against the simulation experiments that provide more performance metrics (which cannot be obtained through our analytical model). Finally, we investigate the impacts of the HARQ–ARQ Interaction on the Protocol Data Unit (PDU) transmission delay based on our simulation experiments. Copyright © 2009 John Wiley & Sons, Ltd.     

Cost analysis and efficient radio bearer selection for multicasting over UMTS

Along with the widespread deployment of the Third Generation (3G) cellular networks, the fast‐improving capabilities of the mobile devices, content, and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). To this direction, the Third Generation Partnership Project (3GPP) is currently standardizing the Multimedia Broadcast/Multicast Service (MBMS) framework of UMTS. In this paper, we present an overview of the MBMS multicast mode of UMTS. We analytically present the multicast mode of the MBMS and analyze its performance in terms of packet delivery cost under various network topologies, cell types, and multicast users' distributions. Furthermore, for the evaluation of the scheme, we consider different transport channels for the transmission of the multicast data over the UMTS Terrestrial Radio‐Access Network (UTRAN) interfaces. Finally, we propose a scheme for the efficient radio bearer selection that minimizes total packet delivery cost. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysis of Bandwidth Gain Over Various Timer$_$CU of AAL2 for Voice Traffic Multiplexing

An asynchronous transfer mode adaptation layer type 2 (AAL2) transmission scheme commonly is used to deliver the voice and tha data traffic between Node-B and the radio network controller on the universal mobile terrestrial device network. To predict the AAL2 multiplexing performance, we analyzed the bandwidth gain and the cell-packing density using discrete Markov chain model for the voice service and validated these results with simulations. We also performed a detailed simulation for the voice and the data services in a concentrator. Based on the analysis, we proposed an engineering guideline for selecting the optimal Timer$_$CU in a Node-B. We found that there is no major benefit in using the AAL2 multiplexing in a concentrator. The benefit of the AAL2 multiplexing in$ I_ ub$for the data service was much less than that for the voice service. They also depended heavily on the traffic load.     

D-RMA: a dynamic reservation multiple-access protocol for thirdgeneration cellular systems

A dynamic reservation multiple access (D-RMA) protocol for third generation cellular mobile radio systems is proposed and its behavior is investigated under variable multimedia traffic conditions. D-RMA is a protocol which is explicitly designed to support multimedia traffic. Its structure is based on traditional PRMA++ protocol, but in addition to what PRMA++ provides, it introduces a flexible dynamic approach in the choice of the percentage of bandwidth to be used for reservation. Separation between reservation and information channels, along with dynamic adaptation of the percentage of reservation bandwidth within a frame to traffic condition, guarantee the required QoS to multimedia services. Results obtained show that the performance of D-RMA are superior when compared to a traditional “nondynamic” protocol, in terms of both the offered quality of service (QoS) and number of connections which can be activated in a microcell at one time     

Architectures and performance of optical packet switching nodes for IP networks

As new bandwidth-hungry Internet protocol (IP) services are demanding more and more capacity, transport networks are evolving to provide a reconfigurable optical layer in order to allow fast dynamic allocation of wavelength-division-multiplexing (WDM) channels. To achieve this goal, optical packet-switched systems seem to be strong candidates as they allow a high degree of statistical resource sharing, which leads to an efficient bandwidth utilization. In this paper, we propose an architecture for optical packet-switched transport networks, together with an innovative switching node structure based on the concept of per-packet wavelength routing. The traffic performance of such node when loaded by a typical IP traffic is evaluated through computer simulation; packet loss probability and average delay performance are shown for various load conditions.     

Channel Assignment Strategies for Multiradio Wireless Mesh Networks: Issues and Solutions

Next-generation wireless mobile communications will be driven by converged networks that integrate disparate technologies and services. The wireless mesh network is envisaged to be one of the key components in the converged networks of the future, providing flexible high- bandwidth wireless backhaul over large geographical areas. While single radio mesh nodes operating on a single channel suffer from capacity constraints, equipping mesh routers with multiple radios using multiple nonoverlap- ping channels can significantly alleviate the capacity problem and increase the aggregate bandwidth available to the network. However, the assignment of channels to the radio interfaces poses significant challenges. The goal of channel assignment algorithms in multiradio mesh networks is to minimize interference while improving the aggregate network capacity and maintaining the connectivity of the network. In this article we examine the unique constraints of channel assignment in wireless mesh networks and identify the key factors governing assignment schemes, with particular reference to interference, traffic patterns, and multipath connectivity. After presenting a taxonomy of existing channel assignment algorithms for WMNs, we describe a new channel assignment scheme called MesTiC, which incorporates the mesh traffic pattern together with connectivity issues in order to minimize interference in multi- radio mesh networks.     

End-to-End Adaptive QoS Provisioning over GPRS Wireless Mobile Network

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users over wireless frequency-division duplex links with time division multiple access, and core packet data networks. This paper presents a dynamic adaptive guaranteed Quality-of-Service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain GPRS QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic with peak bandwidth allocation adapted to the current queue length. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests with higher admission priorities over new calls via a dynamic multiple guard channels scheme, which dynamically adapts the capacity reserved for dealing with handoff requests based on the current traffic conditions in the neighboring radio cells. Integrated services (IntServ) QoS provisioning over the IP/ATM-based GPRS core network is realized over a multi-protocol label switching (MPLS) architecture, and mobility is supported over the core network via a novel mobile label-switching tree (MLST) architecture. End-to-end QoS provisioning over the GPRS wireless mobile network is realized by mapping between the IntServ and GPRS QoS requirements, and by extending the AP-CAC protocol from the wireless medium to the core network to provide a unified end-to-end admission control with dynamic adaptive admission priorities.     

Is multiuser detection beneficial to mixed service UMTS networks?

The main objective of this paper is to investigate linear multiuser detection for the uplink of present mixed service UMTS Terrestrial Radio Access Network (UTRAN) Frequency Division Duplex (FDD) networks in terms of system capacity, system coverage as well as power reduction. For the system performance assessments we apply a two-stage power control multiuser detection algorithm where the users are detected by a multiuser block detection. We evaluate the UTRAN FDD load control parameter noise rise and show corresponding system capacity bounds for different service mixes carried over dedicated channels with data rates up to 64 kbit/s. Note that for typical UTRAN FDD services the signal-to-noise operating points of a multiuser detector are very low (less than 0 dB). These low signal-to-interference-plus-noise ratios (SINR) operating points severely limit multiuser detection performance gains. Compared to single-user-matched filtering the minimum mean square error (MMSE) detector leads to fairly modest system capacity gains up to 60% dependent on the service mix assumed while the decorrelator is even worse. With respect to coverage as well as mobile station power, MMSE detection indicates fair to high improvements.     

3G WCDMA网络共享的关键技术

基于3GPP标准中网络共享的最新研究进展,文章介绍了3G WCDMA网络共享的4种解决方案:站点共享、公共共享网络、地理分割网络共享、无线接入网共享,对Release5中的lu-Flex功能、Release5中连接模式下的UTRAN共享机制和Release6中的网络共享支持增强机制等网络共享的关键技术进行了分析.     

A bandwidth reservation protocol for speech/data integration in TDMA-based advanced mobile systems

The traffic performance of third-generation mobile systems is greatly influenced by the multiple access protocols used in the radio access subsystem. The paper introduces an access protocol, SIR (Service Integration Radio Access), which has the potential for accommodating the requirements of speech and bursty data traffic in an efficient way. SIR is evolved from a protocol (PRMA ++) studied in the framework of a TDMA-based version of the European Universal Mobile Telecommunication System (UMTS) and uses dedicated mechanisms for data bandwidth request collection and servicing.     

Voice over ATM using AAL2 and bit dropping: performance and calladmission control

Asynchronous transfer mode (ATM) adaptation layer 2 (AAL2) has been designed for efficient transport of voice, fax, and voiceband data (VBD) traffic over an ATM virtual circuit. The protocol helps achieve low latency and high bandwidth efficiency while applying suitable compression methods on voice/VBD/fax calls and silence elimination on voice calls. We analyze the performance and capacity of an ATM multiplexer based on AAL2 adaptation. We assume that embedded adaptive differential pulse code modulation (ADPCM) is used to compress voice, and silence elimination is used to achieve statistical multiplexing gain. The embedded ADPCM coding scheme allows selective dropping of less significant bits of voice during congestion in the ATM/AAL2 multiplexer. We compare the call capacities of voice multiplexers with and without bit dropping (BD). The performance models and results presented are based on fairly general assumptions and can be used for traffic engineering and call admission control in land-line or wireless ATM systems for a variety of voice/voiceband compression algorithms. A generalized algorithm for call admission control is also described     

Internet connection with UMTS

Mobile telecommunication new services are based on data networks specially Internet. These services include http, telnet, ftp, Simple Mail Transfer Protocol, etc. Besides, we recognize a mobile network as a multiuser network. Transmission Control Protocol (TCP)/Internet Protocol which is sensitive to link congestion in wireline data links is also used in wireless networks. In order to improve the system performance, the TCP layer uses flow control and congestion control. Besides, radio link control (RLC) and medium access control sublayers have been introduced to compensate the deficiency of TCP layer in wireless environment. RLC has an important role in quality of service enhancement of the Universal Mobile Telecommunications System (UMTS). In this paper, we review the protocol stack of UMTS Terrestrial Radio Access Network which is based on Third-Generation Partnership Project. Then, we evaluate its layer 2 error control mechanisms and verify TCP over automatic repeat request error control mechanism and finally quality of service improvement results from it in fading channels.     

Soft‐State Bandwidth Reservation Mechanism for Slotted Optical Burst Switching Networks

This paper proposes a novel transport network architecture for the next generation network (NGN) based on the optical burst switching technology. The proposed architecture aims to provide efficient delivery of various types of network traffic by satisfying their quality‐of‐service constraints. To this end, we have developed a soft‐state bandwidth reservation mechanism, which enables NGN transport nodes to dynamically reserve bandwidth needed for active data burst flows. The performance of the proposed mechanism is evaluated by means of numerical analysis and NS2 simulation. Our results show that the packet delay is kept within the constraint for each traffic flow and the burst loss rate is remarkably improved.     

End-to-end bandwidth allocation scheme for voice traffic support over MANETs

Multimedia and real-time applications require bandwidth guarantees, which can be achieved by resource reservation. However, bandwidth reservation in ad-hoc networks is a very challenging task due to the instability of radio channels, node mobility and lack of coordination between mobile nodes. Most proposed reservation protocols focus on point-to-point reservations, and only a few work has been done to propose an efficient end-to-end reservation scheme. In this paper, we propose a reservation scheme called End-to-end reservation scheme for voice and data traffic support (EERV). The basic component of our protocol is a handshake mechanism which has the role to establish point-to-point reservations, and to ensure consistency of reservations between neighbor nodes. Both data and voice sources are allowed to establish reservations with priority given to voice sources. This reservation scheme is extended to support the reservation and release of resources along a path in cooperation with the routing layer. Our reservation scheme is based on DSR, a well-known reactive routing protocol. Mobility of nodes and node failure cause frequent reservation breakages resulting in significant performance degradation. In order to resolve this issue we propose a reservation loss detection and reservation recovery mechanisms. We achieved intensive simulations to evaluate the performance of our protocol. Simulation results show the effectiveness of this protocol.     

Mobile packet radio networks: State-of-the-art

MUCH WORK HAS been done in the areas of packet switching, packet radio, and random communication channels. However, efforts combining these areas are not as plentiful. There are several reasons for this. One reason is, the packet communications area is relatively young. Much of the research into packet communications has been accomplished by computer scientists rather then communications engineers, with a resulting emphasis on architecture, protocols, software, and so on. Even the development of packet radio has not fostered extensive examination of link effects on system performances. The UHF line-of-sight links and SHF satellite links have been assumed to be perfect with packet collisions as the dominant error source, which is a good assumption under normal circumstances. However, abnormal circumstances including ionospheric scintillations and multipath fading are another source of error on degraded packet radio links, which characterize Mobile Packet Radio Networks (MPRNET). In this paper we define and discuss Mobile Packet Radio Networks and presend their channel characteristics. The performance avaluation of some channel access protocols for a Mobile Packet Radio Network link, which is a typical example of a degraded packet radio channel, is descirbed.