Showing papers in "Wireless Networks in 1996"

Minimizing the average cost of paging and registration: a timer-based method

Abstract: Methods of balancing call registration and paging are developed in this paper. Given that the probability distribution on the user location as a function of time is either known or can be calculated, previous work shows the existence of lower bounds on the average cost of paging. Here these bounds are used in conjunction with a Poisson incoming-call arrival model to formulate the paging/registration optimization problem in terms of timeout parameters, $\tau _m$; the maximum amount of time to wait before registering given the last known location was $\tau _m$. Timer-based methods, as opposed to location-based methods, do not require the user to record and process location information during the time between location updates. This feature might be desirable for minimizing mobile transceiver use during idle periods. We then consider uniform motion processes where a spatial translation of starting location produces an identical spatial translation of the associated time-varying probability distribution. This leads to a universal timeout parameter $\tau $ which may be readily calculated. We study $\tau $ and the minimum cost of paging/registration for a simple model of user motion and compare our results to an earlier method of location-based paging/registration cost minimization.

Gradual removals in cellular PCS with constrained power control and noise

Abstract: In this paper we study the mobile removal problem in a cellular PCS network where transmitter powers are constrained and controlled by a Distributed Constrained Power Control (DCPC) algorithm. Receivers are subject to non-negligible noise, and the DCPC attempts to bring each receiver's CIR above a given target. To evaluate feasibility and computational complexity, we assume a paradigm where radio bandwidth is scarce and inter-base station connection is fast. We show that finding the optimal removal set is an NP-Complete problem, giving rise for heuristic algorithms. We study and compare among three classes of transmitter removal algorithms. Two classes consist of algorithms which are invoked only when reaching a stable power vector under DCPC. The third class consist of algorithms which combine transmitter removals with power control. These are One-by-one Removals, Multiple Removals, and Power Control with Removals Combined. In the class of power control with removals combined, we also consider a distributed algorithm which uses the same local information as DCPC does. All removal algorithms are compared with respect to their outage probabilities and their time to converge to a stable state. Comparisons are made in a hexagonal macro-cellular system, and in two metropolitan micro-cellular systems. The Power Control with Removals Combined algorithm emerges as practically the best approach with respect to both criteria.

Performance evaluation of TCP/RLP protocol stack over CDMA wireless link

Abstract: Due to the high frame error rate in wireless communication channels, an additional link layer protocol, Radio Link Protocol (RLP), has been introduced in the newly approved Data Services Option Standard for Wideband Spread Spectrum Digital Cellular System. In this paper, we investigate performance issues of a typical Cod Division Multiple Access (CDMA) wireless link using the protocol stack given in the standard. In particular, we focus on the dynamics of the TCP and RLP layers of the protocol stack since the fluctuation of systemperformance is largely caused by Automatic Repeat Request (ARQ) mechanisms implemented at these two layers. We compare the network performance of default parameter setting to those of other possible parameter settings. Analytical and simulation results presented in this paper can provide guidance to those attempting to further improve performance of interest.

Dynamic reservation multiple access (DRMA): a new multiple access scheme for personal communication systems (PCS)

Abstract: To improve the spectrum efficiency of integrated voice and data services in Personal Communication System (PCS), several reservation-type multiple access schemes, such as Packet Reservation Multiple Access (PRMA), Dynamic Time Division Multiple Access (D-TDMA), Resource Auction Multiple Access (RAMA), etc., have been proposed. PRMA uses the data packet itself to make a channel reservation, and is inefficient in that each unsuccessful reservation wastes one slot. However, it does not have a fixed reservation overhead and offers shorter access delay. On the other hand, fixed reservation overhead is unavoidable in both RAMA and D-TDMA. Compared to D-TDMA and PRMA, RAMA is superior in the sense that its slot assignment is independent of the traffic load. But its implementation is difficult. With these observations, a new reservation protocol, called Dynamic Reservation Multiple Access (DRMA), is proposed in this paper. With this new protocol, the success probability of channel access is greatly improved at the expense of slightly increased system complexity. It solves the problem of inefficiency in PRMA, but without introducing the fixed reservation overhead as in D-TDMA and RAMA. In addition, it is more suited to the dynamic behavior of the integrated traffic because there is no fixed boundary between voice and data slots (which is mandatory in D-TDMA and RAMA). Our numerical results indicate that its performance is superior to the existing reservation protocols, especially in the integrated traffic scenario. Moreover, the soft capacity feature is exhibited when the traffic load increases.

QoS provisioning in micro-cellular networks supporting multiple classes of traffic

Abstract: We introduce an adaptive call admission control mechanism for wireless/mobile networks supporting multiple classes of traffic, and discuss a number of resource sharing schemes which can be used to allocate wireless bandwidth to different classes of traffic. The adaptive call admission control reacts to changing new call arrival rates, and the resource sharing mechanism reacts to rapidly changing traffic conditions in every radio cell due to mobility of mobile users. In addition, we have provided an analytical methodology which shows that the combination of the call admission control and the resource sharing schemes guarantees a predefined quality-of-service to each class of traffic. One major advantage of our approach is that it can be performed in a distributed fashion removing any bottlenecks that might arise due to frequent invocation of network call control functions.

Channel access and interference issues in multi-code DS-CDMA wireless packet (ATM) networks

Abstract: Multi-Code Direct-Sequence Code-Division-Multiple-Access (MC-CDMA) has been proposed as a flexible multiple access scheme for wireless packet networks that support a large variety of mobiles with different and even time-varying rates. Using MC-CDMA, traffic streams with significantly different transmission rates can be easily integrated into a unified architecture, with all the transmissions occupying the same bandwidth and having the same spread spectrum processing gain. In this paper, we address medium-access and interference issues in MC-CDMA wireless packet networks. For medium access, we propose and study Multi-Code CDMA (MC-CDMA) with Distributed-Queueing Request Update Multiple Access (DQRUMA) to form a unified bandwidth-on-demand fair-sharing platform for multi-rate wireless services. DQRUMA is an efficient demand-assignment multiple access protocol for wireless access and scheduling. Pseudo-Noise (PN) codes (primary codes) and optimal power levels are allocated to the mobiles on a slot-by-slot basis, and a Maximum Capacity Power Allocation (MCPA) criterion exploits the sub-code concatenation property of the MC-CDMA transmission. Simulation results show that the system provides close to ideal-access performance for multi-rate mobiles, both with homogeneous traffic characteristics and with a mix of heterogeneous traffic characteristics. Finally, we analyze the effects of MC-CDMA intercell interference on the reverse link (i.e., mobile to cell site) and investigate interference reduction by using the Maximum Capacity Power Allocation (MCPA) criterion. Our results show significant reduction in reverse-link MC-CDMA intercell interference is possible using the MCPA criterion.

Predicting RF coverage in large environments using ray-beam tracing and partitioning tree represented geometry

Abstract: We present a system for efficient prediction of RF power distribution in site specific environments using a variation of ray tracing, which we called ray-beam tracing. The simulation results were validated against measured data for a number of large environments with good statistical correlation between the two. We represent geometric environments in full 3D which facilitates rooftop deployment along with any other 3D locations. We use broadcast mode of propagation, whose cost increases more slowly with an increase in the number of receiving bins. The scheme works well both for indoor and outdoor environments. Simple ray tracing has a major disadvantage in that adjacent rays from a transmitter diverge greatly after large path lengths due to multiple reflections, such that arbitrarily large geometric entities could fall in between these rays. This results in a sampling error problem. The error increases arbitrarily as the incident angle approaches $90^\circ $. The problem is addressed by introducing the notion of beams while retaining the simplicity of rays for intersection calculations. A beam is adaptively split into child beams to limit the error. A major challenge for computational efficiency is to quickly determine the closest ray-surface intersection. We achieve this by using partitioning trees which allows representation of arbitrarily oriented polygonal environments. We also use partitioning trees for our full 3D interactive visualization along with interactive placement of transmitters, receiving bins, and querying of power.

The SpectrumWare approach to wireless signal processing

Abstract: The SpectrumWare project is applying a software oriented approach to wireless communication and distributed signal processing. Advances in processor and analog-to-digital conversion technology have made it possible to implement virtual radios that directly sample wide bands of the RF spectrum and process these samples in application software. The elimination of dedicated hardware introduces tremendous flexibility into a wireless communication system. Our approach goes further than the software implementation of traditional signal processing functions. We use processor and network memory to temporally decouple the sample streams from the software modules so that the bulk of the processing can be realized within virtual time programming environments. Decoupling relaxes the temporal constraints on the processing algorithms and their execution. This paper describes the SpectrumWare concept, our experimental approach, and the implications that this approach has for wireless signal processing algorithms.

Wireless ATM: an enabling technology for multimedia personal communication

Abstract: An ATM-based wireless network capable of supporting integrated voice, video and data services with Quality-of-Service (QoS) control is proposed as a key element of the future distributed multimedia computing scenario. A specific architecture for “wireless ATM” is described, and design issues are briefly discussed for each major functional layer of the network. The system approach is based on the incorporation of wireless channel specific medium access, data link and wireless control layers into a mobility-enhanced ATM protocol stack. Selected software emulation results are given for applicable Medium access Control (MAC) and Data Link Control (DLC) protocols. The paper concludes with a brief view of related ongoing prototyping activities aimed at demonstrating a seamless wired plus wireless multimedia networking environment.

Loss profiles: a quality of service measure in mobile computing

Abstract: With rapid technological advances being made in the area of wireless communications it is expected that, in the near future, mobile users will be able to access a wide variety of services that will be made available over future high-speed networks. The quality of these services in the high-speed network domain can be specified in terms of several QOS parameters. In this paper we identify a new QOS parameter for the mobile environment, called loss profiles, that ensures graceful degradation of service (for applications that can tolerate loss) in situations where user demands exceed the network's capacity to satisfy them. A new transport sub-layer is proposed that efficiently implements this new QOS parameter. We also show how this protocol can be easily incorporated into existing proposals for high-speed network transport layer protocols and into the MPEG-2 Transport System.

Transport and control issues in multimedia wireless networks

Abstract: It is not an easy task in the UMTS environment to effectively design the transport and the management of traffic belonging to multimedia teleservices among those defined by ITURecommendations, due to the hard communication requirements which this kind of application can call for. In this paper the results of an overall research work, dealing with an effective management of “multimedia” and “multi-requirement” services in enhanced third-generation mobile radio systems, are presented. The contemporary use of several bearers, one for each traffic component of the service, is proposed as a reference scenario for the transport of multimedia services in future mobile radio environments. The effectiveness of this choice is guaranteed by providing for innovative control techniques, on top of a PRMA-based access protocol, ad-hoc developed to recognise and jointly manage the different parts of a unique multimedia traffic. For this aim, a two-level priority (static and dynamic priorities) mechanism is proposed to be adopted by the higher protocol levels of UMTS for the adaptation of call set-up, channel access, handover, and admission control procedures to the nature of multimedia services and for optimising the sharing of radio channel resources and the management of the reservation buffer. Achieved results demonstrate that the priority-based mechanism shows good performance especially during periods in which the system traffic load is high and well reacts to the worsening of multimedia service quality, both in terms of information loss and synchronisation of its different traffic components.

Supporting mobile multimedia in integrated services networks

Abstract: Owing to widespread user mobility, limited radio resources, and changing network characteristics, supporting multimedia communications in a mobile internetworking environment is a challenging problem. In this paper, we present an `adaptive reserved service' framework for use in integrated services networks to support mobile connections carrying multimedia traffic. Integrated in the framework are an anticipatory handoff control mechanism which enables fast handoff, and an adaptive link partitioning scheme which enhances handoff success. Besides, bandwidth reservations in the wireline network are dynamically adjusted based on resource availability in the wireless networks. An accompanying reservation protocol not only facilitates distributed control of mobile connections but also provides network feedback to mobile hosts.

Worst-case performance of cellular channel assignment policies

Abstract: Many cellular channel assignment policies have been proposed to improve efficiency beyond that resulting from fixed channel allocation The performance of these policies, however, has rarely been compared due to a lack of formal metrics, particularly under nonhomogeneous call distributions In this paper, we introduce two such metrics: the worst-case number of channels required to accommodate all possible configurations of N calls in a cell cluster, and the set of cell states that can be accommodated with M channels We first measure two extreme policies, fixed channel allocation and maximum packing, under these metrics We then prove a new lower bound, under the first metric, on any channel assignment policy Next, we introduce three intermediate channel assignment policies, based on commonly used ideas of channel ordering, hybrid assignment, and partitioning Finally, these policies are used to demonstrate the tradeoff between the performance and the complexity of a channel allocation policy

Optimal transmission ranges for mobile communication in linear multihop packet radio networks

Abstract: The analysis of multihop radio transmission for randomly distributed terminals in the plane has drawn a lot of attention in the literature. Several routing strategies have been investigated concerning throughput and normalized expected progress. Because of mathematically intractable problems all analyses use simulation studies as part of the derivation. In this paper we present a one-dimensional model to investigate the performance of multihop networks. This model seems to be more adequate for applications in road traffic information systems. Three routing strategies 'most forward with fixed transmission range', 'positively most forward with fixed transmission range', and 'positively most forward with variable transmission range' are analyzed on the basis of a complete mathematical description. We also consider directional antennas. The results are presented in closed formulae which are evaluated numerically and depicted in corresponding diagrams. It turns out that adjusted transmission ranges enlarge network performance. Furthermore, some interesting differences to the usual two-dimensional random model occur.

Throughput of selective-repeat ARQ with time diversity in Markov channels with unreliable feedback

Abstract: In this paper, a modified form of the ARQ selective repeat protocol with timer control is studied. Transmissions on both the forward and the reverse channels are assumed to experience Markovian errors and therefore the feedback is unreliable. Feedback error recovery is made possible through the use of time diversity.Using results from renewal theory, exact results for the throughput of the protocol are evaluated. In order to overcome the complexity of the exact analytical technique, lower and upper bounds are developed. Simulation results, that confirm the analysis and document the tightness of the bounds are also shown, and a number of implementation issues are discussed. An application to mobile radio is also presented.It is shown that the use of an appropriate degree of time diversity makes it possible to approach the ideal protocol performance obtained with perfect feedback.

A comprehensive model for voice activity in conversational speech—development and application to performance analysis of new-generation wireless communication systems

Abstract: Proposed new wireless communication systems such as third generation cellular and PCN will utilize speech interpolation, disconnecting the user from the spectral resource during pauses in speech in order to reduce radiated emissions and improve spectral efficiency. An accurate model of the on-off characteristics of conversational speech is thus necessary to analyze system performance, particularly if the system utilizes a time and/or frequency division multiple access technique. Previously developed speech activity models are deficient because they either do not reproduce short silent pauses of less than 200 ms. (representative of the silence gaps between syllables or words) or else they do not replicate the dynamics between the two conversing parties. Starting with the P.T. Brady model and developing appropriate modifications, this paper formulates a simple, accurate, comprehensive 8-state Markov model for voice activity in conversational speech. The new model can easily be incorporated into simulations or analyses assessing the performance of various new-generation wireless networks, thus improving the accuracy of the performance assessments.

Transmission of video telephony images over wireless channels

Abstract: In this paper, the effects of digital transmission errors on H.263 codecs are analyzed and the transmission of H.263 coded video over a TDMAradio link is investigated. The impact of channel coding and interleaving on video transmission quality is simulated for different channel conditions. Fading on radio channels causes significant transmission errors and H.263 coded bit streams are very vulnerable to errors. Powerful Forward Error Correction (FEC) codes are therefore necessary to protect the data so that it can be successfully transmitted at acceptable signal power levels. FEC, however, imposes a high bandwidth overhead. In order to make best use of the available channel bandwidth and to alleviate the overall impact of errors on the video sequence, a two-layer data partitioning and unequal error protection scheme based on H.263 is also studied. The scheme can tolerate more transmission errors and leads to more graceful degradation in quality when the channel SNR decreases. In lossy environments, it can improve the video transmission quality at no extra bandwidth cost.

A generic multicast transport service to support disconnected operation

Abstract: Many mobile computing applications can profit from process groups and reliable multicast communication to maintain replicated data, but most operating systems available today fail in providing the primitive operations needed by such applications. In this paper we describe a highly configurable, Generic Multicast Transport Service (GTS), which supports the implementation of group-based applications in wide-area settings. GTS is unique in that it offers fault-tolerant, order-preserving multicast on arbitrary communication protocols, including e-mail. As another distinguishing mark, messages can be sent to processes even when they are temporarily unavailable, which permits disconnected operation and mobility. We further propose an object-oriented system design consisting of adaptor objects interconnected to form a protocol tree. Adaptor objects offer a common interface to dissimilar communication protocols, and make it easy to incorporate new protocols into GTS. Currently, GTS is being used in a cooperative software engineering environment and in other projects. GTS is available for anonymous ftp.

Handover in a micro-cell packet switched mobile network

Abstract: This paper proposes a distributed handover protocol for a micro-cell packet switched mobile network. In such a network, users move from one cell to another very often, and each change of location may result in misrouted and lost packets. The purpose of the new protocol is to minimize these consequences of location changes: as long as a mobile moves from one cell to another but stays in the same region, the protocol avoids loss of packets and preserves order of transmission. Thus it increases the performance of the transport layer protocol by minimizing the need to retransmit packets.

A wireless local area network employing distributed radio bridges

Abstract: This paper presents a novel distributed wireless local area network (WLAN) architecture, where each wireless terminal (WT) accesses a backbone local area network (LAN) segment via multiple radio bridges (RB's). We introduce a self-learning routing algorithm for the RB's, which automatically adapts to changes in terminal locations, and prevents multiple copies of each data frame from being forwarded over the backbone LAN segment. The distributed WLAN architecture eases the management of network topological changes and terminal mobility, compared to centralized cellular architectures. We consider the use of direct-sequence spread-spectrum (DS/SS) signaling and the slotted Aloha medium access control (MAC) protocol over the wireless links, with multiple uplink receivers and downlink transmitters at the RB's for each MAC frame. Simulation results for the uplink show that the multi-receiver site diversity and the capture effect of DS/SS signaling effectively combat multipath and multiaccess interference, resulting in high throughput capacity and stable operation for the channel. Under overload traffic, the system is able to maintain a high level of throughput with bounded delays. It is shown that the use of multiple receiver reduces the access fairness problem for WT's at different locations caused by the near-far effect.

A mobile virtual-distributed system architecture for supporting wireless mobile computing and communications

Abstract: This paper describes a novel mobile virtual-distributed system architecture for supporting global mobile computing and communications. The principal contribution of this paper is to innovatively apply virtual memory concepts to mobile systems by deploying mobile-floating agents to de-couple services and resources from the underlying network and allow them to move around following their mobile users. The mobile-floating agents maintain data structures associated with a mobile user. By combining the mobile-floating agent functions with a predictive mobility management algorithm and location-aware caching and prefetching, services and user data structure are pre-connected and pre-assigned at the locations to which the user is moving. Thus, the users can maintain their data structures or immediately receive service with virtually the same efficiency as at the previous location.

A cache approach for supporting life-time UPT number

Abstract: A life-time Universal Personal Telecommunication (UPT) number allows a user to change the Personal Communications service provider without changing his/her UPT number. Since a translation from the life-time UPT number to a routing address must be done for every call placed, it is essential to make this process efficient. Two general approaches are the table lookup method and the database query method. The life-time UPT number can be easily implemented in the database query method. However, the UPT-routing address translation cost in the database query method is much higher than in the table lookup method. Address translation can be done efficiently in the table lookup method, but pointer forwarding is required to support a life-time UPT number. To reduce the pointer forwarding cost, we modify the table lookup method by adding a cache at each cellular switch (in Taiwan, the number of cellular switches that need to equip with the caches is 8 for AMPS and 7 for GSM). We show that the cache scheme can remove most pointer forwarding operations for an originating switch if some PCS users are accessed more frequently than others.

Fade margins for soft and hard handoffs

Abstract: A particularly attractive feature of CDMA wireless systems proposed in the Telecommunication Industry Association's standard IS-95 [1] is their ability to get into what is known as ”soft handoff”. A mobile in soft handoff maintains simultaneous radio links with multiple base-stations which enables it to make use of the best quality leg most of the time. This is believed to result in a reduction of the fade margin that is needed to provide the desired coverage in a given geographical area in the presence of log-normal shadow fading. This paper presents an analysis of fade margins for systems allowing soft handoffs (e.g. CDMA) and those where only hard handoffs are possible (e.g. FDMA, TDMA). The analysis is based on a model for hard handoffs with hysteresis and connection delay and confirms the belief that soft handoffs result in smaller fade margins.

Probability models of microcell coverage

Abstract: Once a subscriber unit served by a microcell initiates a call, it must remain in the coverage area of the microcell long enough to complete call set up and hand-off functions. This restricts the minimum size attainable by a microcell. This paper derives the relationship between the microcell size, the call processing time, and the probability that a subscriber unit, initiating a call, will remain inside the microcell coverage area for at least the duration of call processing. Under simple assumptions, time spent in the coverage area of the microcell before and after call initiation have the same cumulative density function, which is derived in this paper for traffic conditions encountered in highway and metropolitan settings.

DS/CDMA M -ary orthogonal signalling in a shadowed Rayleigh channel for mobile communications

Abstract: In this paper a modified RAKE receiver is studied for a frequency selective mobile radio channel. The reverse link (mobile to base station) is analysed, assuming lognormal shadowing and Rayleigh fading and K asynchronous users, with M orthogonal sequences per user. The analysis is based on the consideration of the quadrature components of the signal and noise, taking advantage of the multipath effects. The performance evaluation is carried out in terms of both the bit error rate and outage probability in order to qualify completely the proposed receiver. The positive results assure the possibility of applying this system in a microcellular mobile radio environment.

Near-optimality of distributed load-adaptive dynamic channel allocation strategies for cellular mobile networks

Abstract: In this paper we focus on the so-called load-adaptive Dynamic Channel Allocation (DCA) strategies for cellular mobile networks. Such strategies envisage the dynamic assignment of radio resources with the constraint that the outage probability (i.e. the probability that the carrier-to-interference power ratio be less than a given threshold) be less than a specified value, even in the worst foreseen propagation scenario. We identify a set of constraints to be satisfied in order that a DCA strategy belongs to the load-adaptive class. This provides a tight lower bound on traffic blocking and dropping performance such that: (i) it implies a dramatically lower computational effort than the known optimum strategy (based on the Maximum Packing algorithm); (ii) it is much tighter than the bound provided by the simple Erlang-B formula. A performance evaluation is carried out to compare the call blocking and dropping probabilities resulting from the tight bound above with those relevant to the Fixed Channel Allocation and to some recently proposed DCA strategies, including the Geometric DCA. The simulations exploit a mobility model that provides different degrees of offered traffic peakedness. It emerges that the Geometric DCA yields a practical way to attain near optimal performance in the load-adaptive class, leading a viable pathway to enhance the capacity of nowadays 2nd generation cellular networks in the short-medium term.

Data-delay evaluation in integrated wireless networks based on local product-form solutions for voice occupancy

Abstract: In this paper we consider the evaluation of data-packet delay in wireless integrated voice/data networks. In networks that support voice in the classical circuit-switched fashion, the voice occupancy process satisfies a product-form solution under reasonable modeling assumptions. Although this product-form solution provides an accurate characterization of equilibrium voice-traffic behavior, it does not directly provide a method to evaluate data-packet delay. However, examination of each link separately in a manner that incorporates interaction with the rest of the network permits us to take advantage of the wireless nature of the network and obtain a three-flow characterization of each link, which also satisfies a product-form solution and is hence termed a ”mini-product-form” solution. By matching the values of these flows to the average values obtained from the product-form solution of the entire network, we obtain a three-dimensional Markov chain characterization of the voice occupancy state on the link, which permits a simpler evaluation of data-packet delay. A further reduction is possible by converting the three-dimensional chain to a single-dimensional one. Performance results demonstrate that these models provide satisfactory delay estimates that also appear to be upper bounds on delay.

Optimal strategies for admitting voice and data traffic in networks of LEO satellites using CDMA

Abstract: Efficient policies are derived for admitting voice and data traffic into networks of low-earth-orbit (LEO) satellites using code-division multiple-access (CDMA) with direct-sequence spread-spectrum (DS/SS) signaling. The satellites act as bent-pipes; no on-board processing or intersatellite links are present. Dual satellite diversity is used to mitigate the effects of shadowing. The policies assume a movable boundary form, allocate optimally the CDMA capacity (PN codes) to voice and data users, and can increase significantly the number of users served while satisfying their bit error rate (BER) requirements. In contrast to direct admission policies that do not take into consideration the statistical features of the traffic, the new policies do account for the different nature of voice and data traffic and the history of prior transmissions/admissions. Two priority schemes are considered: voice users have higher priority than data users, or voice and data users have the same priority. A modified version of our policies can handle two classes of data users: one with high priority which requires real-time delivery and another with low priority that can be queued; the BER requirements of the two data types may differ. Optimal policies have lower voice blocking rates and data packet error rates than direct admission policies.

Smooth migration from the GSM system to UMTS for multimedia services

Abstract: Third generation of mobile systems is now entering the operational phase; European Community ACTS (RACE follow-on) programme just aims at finalizing the plenty of solutions resulting from the European Community RACE programme as well as from several other studies and researches. European manufactures, also deeply involved in the ACTS programme, seem to show a preference for solutions which gradually upgrade the present pan-European GSMsuccessful standard. The underlying concept is the one of a smooth migration from the GSM network to the third generation system, in order to reuse, at least in the first phases of the transition, most of the existing technologies and infrastructures already implemented for the GSM network. In this respect, this paper, by referring to radio interface aspects, proposes a two step evolution: in the first step, a Dynamic Channel Allocation (DCA) strategy with distributed control should be implemented for coping with the high variance of traffic entailed by the reduction of cell dimensions; in the second step, a gradual upgrading of the GSMBase Stations should allow a smooth transition towards the third generation Packet Reservation Multiple Access (PRMA) technique and the provision of broadband services. The paper is partly based upon the work performed by the author in the framework of the RACE project “Satellite Integration in the Future Mobile Network (SAINT)” and of the European Community ACTS Projects MEDIAN. The opinions herewith reported are not necessarily those of the European Community.