Performance analysis of resource sharing policies in CDMA networks

We consider an interference‐limited code division multiple access (CDMA) network, in which some of the service classes are explicit rate controlled. Such rate‐controlled service classes include adaptive ones whose holding time does not depend on the sending rate, while the holding time of elastic services becomes longer when their sending rate is slowed down. We develop a Markov model that allows us to study the impact of employing service differentiation (prioritization) during admission control and rate control on the classwise blocking probabilities and throughputs. The admission control takes into account the interference from adjacent cells as a log‐normally distributed random variable and employs service class and state‐dependent (soft) blocking in addition to hard blocking. The state‐dependent rate control algorithm takes into account the minimum and maximum requested rates of admitted sessions in a fairness policy‐dependent manner. Our conclusion is that work conserving bandwidth sharing policies may have a major impact on the moments of the time spent in the system by elastic services, but only a minor one on the classwise blocking probabilities. When the admission control algorithm takes into account the neighbour cell caused interference, the blocking probability of all classes increases somewhat, but the throughput of the accepted sessions increases. Blocking prioritization in the soft blocking model affects the classwise total blocking probabilities but has little impact on the throughput of adaptive and elastic traffic. Copyright © 2006 John Wiley & Sons, Ltd.     

Common packet data channel (CPDC) for integrated wireless DS-CDMAnetworks

A common packet data channel (CPDC) architecture is proposed to support bursty, packet-based services in direct sequence code-division multiple-access (DS-CDMA) integrated wireless access networks. The architecture employs an asynchronous transfer mode (ATM) strategy in the forward CPDC link and a spread ALOHA-type random access strategy in the reverse CPDC link. A congestion control algorithm using base station broadcast and portable terminal random delay call reattempt is described. A performance analysis of the CPDC architecture and algorithms is carried out, and formulas for the bit error rate, blocking probability, system delay time, transmission time, and waiting time for packet data calls are derived. The interference caused by a CPDC to stream services in the network is determined, and the capacity of a CPDC is evaluated in terms of the number of packet data subscribers that can be served with a specified grade of service (GOS)     

Roaming times of multi‐wireless systems for software defined radio

In this paper, we evaluate the roaming time performance for a reconfigurable multi‐mode mobile station (MS) that experiences possible transition from one kind of wireless system standard to another. In future software defined radio systems (SDR) (IEEE Commun Mag 2000; 138–143, IEE 1998; 1–6, IEEE 1999; 1212–1216, IEEE Commun Mag 1995; 33 ), reconfigurability of the MS is achieved by downloading the system configuration software code over the wireless channel. For evaluation of the roaming times, a generalized state diagram of the multi‐mode MS is presented. We focus on evaluating the times for sensing the universal pilot channel, classic base station pilot channel, association and connection establishment signaling are included. We investigate the effects of packet successful transmission probability over the wireless channel. We also consider the effects of the system resource blocking probability, MS resource blocking probability, and signaling bit rate over the universal base station channel for different cases and design scenarios. Such evaluations are important for prior design of SDR mobile terminal and universal base station in global roaming situations. We include some analysis results from many obtained. These show the feasibility of wireless software download, and switching between different wireless standard as the mobile station roams. Copyright © 2003 John Wiley & Sons, Ltd.     

Multicast contention resolution with single-cycle windowing usingcontent addressable FIFO's

Asynchronous transfer mode (ATM) has been designated as the switching environment for future broadband integrated services digital networks (BISDN) networks and services. Although input-buffered space switches are more economical and simpler to implement than output-buffered space switches, they suffer from external blocking because of destination port contention. We review contention resolution methods used to avoid external blocking, and choose a solution based on ring reservation, resulting in an elegant and efficient mechanism requiring only nearest-neighbor communications. In addition to external blocking, space switches suffer from head-of-line (HOL) blocking, and our technique alleviates HOL blocking without arbitration time overhead. This method makes use of a novel content addressable first in/first out (CAFIFO) to achieve single-cycle windowing, and the CAFIFO design and operation are described in detail. High multicast throughput is achieved by employing call-splitting. Multiple latency priorities can also be supported. Simulation results, for both unicast and multicast switching, and both random and bursty traffic, highlight the versatility and excellent performance of the CAFIFO-based switch     

On the Handover Performance of a Tri‐threshold Bandwidth Reservation CAC Scheme

A dynamic tri‐threshold call admission control scheme has been developed. This scheme supports voice, data, and multimedia services and it complies with the universal mobile telecommunications system. The performance of the proposed scheme is evaluated under varying handover rates. The QoS performance–including channel utilization, call dropping probability, and blocking probability–is investigated. The performance of the developed scheme is found to be encouraging.     

Admission control for variable spreading gain CDMA cellular system with imperfect power control and shadowing

Variable spreading gain (VSG) CDMA is the prime transmission scheme for supporting multiple services for the next generation cellular systems. As different services have different quality of service and data rate requirements, admission control is essential in safeguarding the performance of different services in VSG‐CDMA cellular systems in harsh wireless environment. In this paper, we propose an admission control scheme for multiple services VSG‐CDMA cellular system in a practical multi‐cell environment where there exist adverse effects due to imperfect power control and shadowing. Rather than with a fixed bound as in previous studies, the admission bound in our scheme is based on the probability distribution of total intra‐cell power (P_in) and other‐cell interference power (I_other). This is used to estimate the blocking probability by utilizing a simple and accurate approximation that incorporates the random nature of P_in and I_other. Evaluation of the impact of power control error to the mean and standard deviation of P_in and I_other, we performed and compared the blocking probability with fixed admission bound scheme in an integrated voice/data environment. Our work has enabled the calculation of the blocking probability and capacity of different mobility users having different power control errors under shadowing. Copyright © 2006 John Wiley & Sons, Ltd.     

Analysis of hierarchical cellular networks with mobile base stations

In this paper, we develop and evaluate a hierarchical cellular architecture for totally mobile wireless networks (TMWNs). Extensive performance tests were conducted to evaluate the performance of a two‐tier system and compare its throughput, handoff blocking rate and new call success rate with those obtained by a one‐tier model. Our tests have shown that when the total number of channels is kept the same, the two‐tier system outperformed the one‐tier counterpart under all load conditions. Under the constraint of equal power consumption, the two‐tier system still achieved improvement over the one‐tier system, especially at light and medium load levels. The improvement of the two‐tier system over the one‐tier system was observed to diminish as the degree of randomness in the mobility model is reduced; scenarios where the one‐tier system outperforms the two‐tier system are given. Load balancing schemes based on the concept of reversible handoffs are introduced and their performance improvements are analyzed. Comparison results on the percentage of terminal coverage are presented. An analytical model to compute the new call and handoff blocking probabilities in TMWN is given and evaluated. The model extends the Markov chain approach previously used in hierarchical architectures with stationary base stations and uses a corrected derivation for the handoff blocking probability. Copyright © 2002 John Wiley & Sons, Ltd.     

Slot allocation strategies for delay sensitive traffic support in asynchronous ad hoc wireless networks

Supporting real‐time traffic in ad hoc wireless networks is considered as a challenging problem. Existing bandwidth reservation mechanisms assume a TDMA environment where achieving time synchronisation is expensive in terms of resources. Heuristics that exist for slot allocation schemes assume a CDMA over TDMA model in order to alleviate the presence of hidden terminals. Slot allocation strategies in the presence of hidden terminals assume significance in a single channel system for supporting delay sensitive traffic. In this paper, we propose three heuristics for the slot allocation process in asynchronou single channel multihop wireless networks in the presence of hidden terminals. The heuristics we propose are the early fit reservation (EFR), minimum bandwidth‐based reservation (MBR) and position‐based hybrid reservation (PHR). The EFR heuristic assigns bandwidth link‐by‐link in the forward path. The MBR heuristic allocates bandwidth to the links in the increasing order of free conn‐slots. The PHR heuristic assigns bandwidth for every link proportional to its position in the path. Simulation studies show that EFR performs better in terms of delay characteristics. MBR provides better call blocking performance at the cost of high end‐to‐end delay. PHR provides a better delay performance compared to MBR and better call blocking performance comparedto EFR. Copyright © 2004 John Wiley & Sons, Ltd.     

Performance analysis of microcell/macrocell with reuse partitioning in TDMA‐based cellular systems

System capacity and grade of service (GoS) are both important for the rapid growth of cellular communication services. In this paper, we propose a two‐tier TDMA‐based cellular system with macrocell overlaid on microcell clusters by implementing fixed channel assignment (FCA) scheme and fixed reuse partitioning (FRP) scheme in microcell layer and macrocell layer, respectively, named FCA–FRP overlay scheme. Improvement can be achieved in both system capacity and GoS. Theoretical analysis based on the overlay scheme without overflow and with overflow is first presented. It shows that the simulation results are agreed with the analytical results. Then, simulation results, obtained from the overlay scheme with and without overflow, show that the performance in terms of the call blocking probability, the call dropping probability and system capacity of such a system can be greatly improved compared with a conventional one‐tier cellular system deployed with FCA or FRP scheme. Copyright © 2008 John Wiley & Sons, Ltd.     

Advanced Wavelength Reservation Method Based on Deadline-Aware Scheduling for Lambda Grid Networks

A deadline-aware-scheduling scheme for the lambda grid system is proposed to support a huge computer grid system based on an advanced photonic network technology. The assignment of wavelengths to jobs in order to efficiently carry various services is critical in lambda grid networks. Such services have different requirements such as the job-completion deadlines, and wavelength assignment must consider the job deadlines. The conventional job scheduling approach assigns a lot of time slots to a call within a short period in order to finish the job as quickly as possible. This raises the blocking probability of short deadline calls. Our proposal assigns wavelengths in the lambda grid networks to meet quality-of-services guarantees. The proposed scheme assigns time slots to a call over time according to its deadline, which allows it to increase the system performance in handling short deadline calls, for example, lowering their blocking probability. Computer simulations show that the proposed scheme can reduce the blocking probability by a factor of 100 compared with the conventional scheme under the low load condition in which the ratio of long deadline calls is high. The proposed scheduling scheme can realize more efficient lambda grid networks.     

Traffic handling capability of a broadband indoor wireless networkusing CDMA multiple access

CDMA (code division multiple access) may be an attractive technique for wireless access to broadband services because of its multiple access simplicity and other appealing features. In order to investigate the traffic handling capabilities of a future network providing a variety of integrated services, this paper presents a study of a broadband indoor wireless network supporting high-speed traffic using CDMA multiple access. The results are obtained through the simulation of an indoor environment and the traffic capabilities of the wireless access to broadband 155.5 MHz ATM-SONET networks using the mm-wave band. A distributed system architecture is employed and the system performance is measured in terms of call blocking probability and dropping probability, the impacts of the base station density, traffic load, average holding time, and variable traffic sources on the system performance are examined. The improvement of system performance by implementing various techniques such as handoff, admission control, power control and sectorization are also investigated     

PERFORMANCE ANALYSIS OF HETEROGENEOUS TRAFFIC ON AN INTEGRATED NETWORK LINK WITH FINITE WAITING ROOM AND ANTICIPATED-RELEASE RESERVATION POLICY

We consider a system where the superposition of two heterogeneous Poisson traffic streams is offered to an integrated network link in synchronous transfer mode, where one stream follows the blocked-and-cleared mode (‘loss’ mode) and the other can wait (finitely) if bandwidth is not available for connection at the time of arrival (‘hold’ mode). We assume that each stream has different bandwidth requirements per call. A reservation scheme, called anticipated-release policy, is introduced where an arrival is accepted into a waiting room only if the amount of time this customer is expected to wait is within acceptable limits. For such a loss/hold system, we provide analytical performance models for exponential service time distributions for both streams as well as for the non-exponential service time distribution case for the traffic stream in ‘hold’ mode. We also present a method on how to model the waiting time distribution of the traffic stream with ‘hold’ mode. From numerical studies, we observe that blocking can be reduced considerably for both services just by introducing a small waiting room for one traffic class compared to ‘loss’ mode for both traffic classes. Furthermore, this holds true for the case when a maximum tolerable time limit is imposed on the waiting. Finally, our results indicate that this loss/hold scenario with limited waiting room appears to be virtually insensitive to the service time distribution of the ‘hold’ mode traffic.     

On the performance of proximity‐based services

Proximity‐based services (PBS) are a subclass of location‐based services that aim to detect the closest point of interest by comparing relative position of a mobile user with a set of entities to be detected. Traditionally, the performances of PBS are measured on the basis of the norm of the estimation error. Although this performance criterion is suitable for location‐based services that aim tracking applications, it does not give enough information about the performance of PBS. This paper provides a novel framework quantifying the system performance of PBS by making use of spatially quantized decision regions that are determined according to service properties. The detection problem in PBS is modeled by an M‐ary hypothesis test, and analytical expressions for correct detection, false alarm, and missed detection rates are derived. A relation between location estimation accuracy requirements that are mandated by regulatory organizations and the performance metrics of PBS is given. Additionally, a flexible cost expression that can be used to design high‐performance PBS is provided. A system deployment scenario is considered to demonstrate the results. By using this framework, PBS designers can improve their command on the services’ behavior and estimate service performance before deployment. Copyright © 2011 John Wiley & Sons, Ltd.     

Using a multiple priority reservation MAC to support differentiated services over HFC systems

The successful commercial deployment of Hybrid Fibre/Coaxial (HFC) access networks in the residential market has so far been driven by demand for faster Internet access and the prospects of a host of new services based on real‐time voice and video. To sustain their growth rates and compete with alternative approaches, such as ADSL, they must be enhanced with the capability to efficiently handle quality‐intensive real‐time services. The new multi‐service paradigm mandates isolation of traffic classes, conditioning of entering traffic and preventive control in addition to traditional closed‐loop control. The differentiated services (DiffServ) architecture with its relevant traffic control tools and the bundling of behaviour aggregates is particularly suited to the H/W‐based MAC of HFC systems. It constitutes a suitable framework enabling the support of proliferating real‐time voice‐ and video‐based services while aligning the system to the emerging Internet strategy of scalable service differentiation. The implementation of such a solution in the ACTS 327AROMA research project is presented in this paper. The performance of the system is evaluated using computer simulation. Copyright © 2002 John Wiley & Sons, Ltd.     

Network dimensioning at the call level for the always‐on network

It is becoming common for the network to provide always‐on access services, where subscribers are guaranteed that their call requests will never be blocked. This paper studies the call‐level link dimensioning for the always‐on network with single‐class traffic. The call‐level QoS requirement is expressed in terms of the probability of a poor‐quality call, which is the probability that a call experiences packet‐level QoS violation at any time during its duration, as opposed to the probability of blocking in the network with call admission control (CAC). The system is modelled as the M/M/infinite system with finite population and an analytic expression for the probability of a poor‐quality call is derived based on performability analysis. The effects of the call‐level traffic characteristics on the required link resources are studied. It is also shown that the call‐level link dimensioning for the always‐on network needs more link resources than the network with CAC, and the call‐level link dimensioning based on the analytic expression can be used to conservatively dimension the always‐on network with arbitrarily distributed call holding time and inter‐call time. The paper also studies the problem of estimating the call‐level traffic characteristics when the knowledge of call boundaries is not available. Copyright © 2004 John Wiley & Sons, Ltd.     

On blocking time in multi‐class optical burst switching nodes

Recently, there has been an increasing research interest being directed to optical burst switching (OBS) networks because of its mature electronic processing capability and high‐capacity optical transport capability. The blocking time for an OBS node, representing the time duration in which a certain channel is occupied by some class of bursts, plays an important role in characterizing the performance of an OBS network. In this paper, we analyze this important metric for an OBS node with a horizonal and a single channel theoretically and numerically. On the basis of that, the burst arrivals are assumed to follow the Poisson process and the burst lengths have a phase‐type distribution, we are able to formulate a working mechanism of an OBS node into a multilayer stochastic fluid model. Using a level crossing arguments method, we are able to obtain the Laplace–Stieltjes transforms of the blocking time, from which n ‐order moments and the probability density functions of the blocking time can be further derived. We provide a numerical example to illustrate the theoretical analyses, and we further discuss the effects of the offset time and the arrival density on the blocking time through this numerical example. Copyright © 2016 John Wiley & Sons, Ltd.     

Development for 4th generation mobile communications

The great success of the i‐mode service shows that data communication services are becoming accepted in the mobile communication world. Multimedia mobile communication services will be provided by 3rd generation IMT‐2000 systems next year in Japan. Thus, the time has come to begin the research and development for 4th generation (4G) mobile communication systems. There exist many difficult issues for 4G systems, such as frequency resources, additional investment, higher speed wireless transmission technology and so on. Furthermore, a new concept must be discussed for 4G before solving these issues. This paper briefly presents current conditions of cellular systems and the development of IMT‐2000 in Japan. The concept and problems of the 4G system are then described along with new technologies that will be useful in solving technical problems. Copyright © 2001 John Wiley & Sons, Ltd.     

Relay Performance Analysis of TTR and STR Relay Modes in IEEE 802.16j MMR System

The IEEE802.16j standard uses non‐transparent relay stations to extend coverage. There are two types of non‐transparent relay modes, that is, the time‐division transmit and receive (TTR) relay mode which can operate with one of two types of frame structures, a single‐frame and multiframe structure, and the simultaneous transmit and receive (STR) relay mode. In this paper, we analyze the relay performance of TTR and STR relay modes in IEEE 802.16j MMR system. We also propose a fair resource allocation scheme for the downlink relay frame. Numerical results show that relay performance of the TTR with a single‐frame or a multiframe structure and that of the STR relay modes are almost the same in a two‐hop system. However, in a three‐hop system, the TTR mode with a single‐frame structure outperforms other relay modes.     

A queueing model with time‐varying QoS and call dropping for evaluating the performance of CDMA cellular systems

In this paper, we present a queueing model to evaluate the performance of CDMA reverse link in a multiple cell environment. Since CDMA capacity is interference limited, both the communication quality of ongoing calls and the admission condition of new arriving calls for each cell depend on the time‐varying signal‐to‐interference ratio (SIR). We use a quasi‐birth‐and‐death process to capture the variation of traffic loads in cells. After obtaining the stationary distribution of the system, we study some important performance indices such as the outage probability of existing calls, the blocking probability of new calls, the average carried traffic in a cell and the dropping frequency of ongoing calls. Numerical results reveal the effects of system parameters on its performance. Copyright © 2004 John Wiley & Sons, Ltd.     

On the performance of TCP over a TDD‐TD/CDMA architecture

This paper determines the performance of TCP when it is employed over a TDD‐TD/CDMA architecture which supports different classes of subscribers and adopts an interference‐driven admission control policy. The blocking and the outage probability of the system users are evaluated under various traffic conditions as well as the TCP throughput that data users experience. Call blocking and TCP throughput are determined by means of a semi‐analytical approach. This work shows that when TCP is taken into account, many options come out for the system design in order to optimize radio resources. Resource assignment in the TDD‐TD/CDMA system can then be done as a function of the actual radio link quality with the goal both to serve as many users as possible and to keep the TCP throughput as high as possible. Copyright © 2003 John Wiley & Sons, Ltd.