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Lately, the proliferation of small portable devices has driven the introduction of a new mobility concept called service mobility. In order to support service mobility, we introduce a new architecture implementing mechanisms to access end user's personalized services regardless of his physical location. The proposed architecture leverages on mobile agent technology to transport and move services to the end user's registered terminals and the Session Initiation Protocol (SIP) for user location signaling. A decentralized approach purely based on mobile agents is compared with a centralized approach. The performance measurement results show that mobile agents are worth being used for realizing service mobility but in specific conditions. Keywords: mobile agents, service mobility, SIP, INTRODUCTION AND BACKGROUND In current generations of mobile networks (1G, 2G and 2.5G), terminal and user mobility are well supported. However, those forms of mobility cannot guaranty a global mobility [...]

The movement-based scheme is a dynamic location management (LM) scheme that is particularly easy to implement. Each mobile simply counts the number of cell-boundary crossings and initiates location update when this number exceeds the predefined movement threshold. Although its LM cost is inferior to that of distance-based schemes, this cost can be decreased by sequential paging methods that take into account mobiles' movement statistics. In this paper, we derive the probability distribution of a mobile's number of cell-boundary crossings during the interval between two location registrations in a movement-based LM scheme for Poisson call arrivals and generally distributed cell residence time. Based on the derived statistics, we obtain the optimal movement threshold and develop an optimal sequential paging scheme. Numeric results are presented to show that the proposed optimal sequential paging scheme outperforms existing sequential paging schemes over a wide range of call-to-mobility ratios. Index Terms--Location management (LM), mobility management, personal communication service (PCS) networks, sequential paging.

There are many asynchronous communication situations for which the prevalent continuous connectivity paradigm is not needed. Communication with a fair delay tolerance may instead be provided by intermittent store-and-forwarding between nodes. This paper proposes a design for an open, receiver-driven broadcasting system that relies on delay-tolerant forwarding of data chunks through mobility of wireless nodes. The system provides public broadcast channels, which may be openly used for both transmission and reception. We show by analysis and simulation under benchmark mobility models that a delay-tolerant broadcast channel has both a sufficiently high throughput and reach to be interesting as a competitive alternative to the regulated wireless broadcast channel. The analysis is based on a queuing model to study the interactions among the mobile nodes in a street. The simulations complement this analysis for mobile nodes moving on a square according to benchmark mobility models. Finally, we present the design of, and experiences with, a proof-of-concept prototype. Index Terms--Broadcasting, communication systems, computer networks, mobile communication, networks, personal communication networks, routing.

For a Personal Communication System (PCS) network to effectively deliver services to the mobile users, it must have an efficient way to keep track of mobile users. Location management fulfills this task through location registration and call delivery procedures. To reduce the signaling traffic, many schemes such as local anchoring, pointer forwarding, and two-level pointer forwarding schemes have been proposed in the past few years. In this paper, we present a novel location management scheme, pointer forwarding based local anchoring scheme, that intends to mitigate the signaling traffic while keeping the tracking delay in check. In this scheme, one visitor location register (VLR) traversed by a user is selected as the mobility agent (MA) for the user at a time, which forms another level of management in order to make some registration traffic localized. The idea is as follows: instead of always carrying out location update to the home location register (HLR), which would become the bottleneck otherwise, many location updates are accomplished by the mobility agent. Moreover, pointers can be set up between VLRs under the coverage of the same MA. When the distance between the MA and the current VLR exceeds a certain threshold, the current VLR will become the new MA, which also updates the HLR (where a user's location information is the identification of the reported MA). The numerical results show that this scheme can significantly reduce the network signaling traffic load without increasing much of the call setup delay. Index Terms--Location management, mobility management, Personal Communication System (PCS) networks, user mobility pattern.

Byline: Andrew H. Kemp (1), Edmund B. Bryant (1) Keywords: delay spread; multipath propagation; irreducible-BER Abstract: The results of channel soundings taken on a selection of six different industrial sites are presented. These results focus on the RMS delay spreads calculated from the channel soundings and the distribution of these results for each site. The distribution of RMS delay spread values is analysed and forms the basis of a statistical description of the multipath propagation on the tested sites. In particular the distribution is used to define the expected propagation delay across the site. The relation between the RMS delay spread and the irreducible-BER is discussed and this is used to link the distribution of RMS delay spread values to bit error rate performance on industrial sites. It is seen that the environment surrounding sites is significant. Author Affiliation: (1) Institute of Integrated Information Systems, School of Electronic and Electrical Engineering, University of Leeds, LS2 9JT, U.K. Article History: Registration Date: 01/01/2004 Article note: Andrew H. Kemp Andrew was born in Portsmouth, UK in 1963. He received a BSc from the University of York in 1984 and PhD from the University of Hull in 1991. His doctoral studies investigated the use of complementary sequences in multi-functional architectures for use in CDMA systems. He spent several years working in Libya and South Africa assisting in seismic exploration and worked at the University of Bradford as a research assistant investigating the use of Blum, Blum and Shub sequences for cryptographically secure 3rd generation systems. More recently he helped develop wireless fieldbus systems for industrial sites and is now lecturing at the University of Leeds, UK in communications. Andrew has over 30 scientific journals and conference papers and a book chapter published. His research interests are in multipath propagation studies to assist system development and wireless broadband connection to computer networks incorporating quality of sevice provision. Edmund B. Bryant Ed Bryant was born in Staffordshire, UK in 1967. After a state education he graduated from Leeds Polytechnic with a BEng in Communication Engineering in 1990. He received a NERC case award for a doctorate at the University of Sheffield in 1991, and achieved a PhD in 1995 entitled 'Radio Tracking of Pinnipeds'. He was subsequently employed by the NERC Sea Mammal Research Unit as a Research Fellow investigating low power radio location systems. In 1997 he spent time in industry designing electronic warfare receivers until he returned to academia at the University of Leeds in 1998. His primary research interests were in channel sounder design and multipath radiowave propagation studies. He left the University of Leeds as a Senior Research Fellow in 2003 to run his own company developing GPS receivers for marine animal research.

Byline: Shengli Fu (1), Genyuan Wang (1), Xiang-Gen Xia (1) Keywords: space-time coding; orthogonal design; CPM; iterative decoding Abstract: We present an iterative decoding/demodulation technique for an orthogonal space-time coded continuous-phase modulation (OST-CPM) system. A low-complexity soft input and soft output (SISO) demodulator is developed based on the bidirectional soft output Viterbi algorithm (BSOVA) for the multiple antennas CPM systems. By taking advantage of the orthogonal structure, the complexity of extrinsic information extraction can be significantly reduced at each iteration. Author Affiliation: (1) Department of Electrical and Computer Engineering, University of Delaware, Newark, DE, 19716, U.S.A. Article History: Registration Date: 01/01/2004 Article note: Shengli Fu received the B.S. and M.S. degree in telecommunication engineering from Beijing University of Posts and Telecommunications, Beijing, China, in 1994 and 1997, respectively. In 2000, he enrolled at the Wright State University, Dayton, OH, where he received the M.S. degree in Computer Engineering. He currently pursues his Ph.D. degree in the Department of Electrical and Computer Engineering at the University of Delaware. His research interests include information and coding theory, MIMO wireless communication systems, and acoustic and visual signal processing. Genyuan Wang received B.Sc and MS. degrees in Mathematics from the Shanxi Normal University, Xi'an, China, in 1985 and 1988, respectively, and his Ph.D. degree in Electrical Engineering from Xidian University, Xi'an China, in 1998. From July, 1988 to September 1994, he worked at Shanxi Normal University as an Assistant Professor and then an Associate Professor. From September 1994 to May 1998, he worked at Xidian University as a research assistant. Currently, he is Post-Doctoral Fellow at Department of Electrical and Computer Engineering, University of Delaware. His research interests are radar imaging and radar signal processing, adaptive filter, OFDM system, channel equalization and space-time coding. Xiang-Gen Xia (M'97,S'00) received his B.S. degree in mathematics from Nanjing Normal University, Nanjing, China, and his M.S. degree in mathematics from Nankai University, Tianjin, China, and his Ph.D. degree in Electrical Engineering from the University of Southern California, Los Angeles, in 1983, 1986, and 1992, respectively. He was a Senior/Research Staff Member at Hughes Research Laboratories, Malibu, California, during 1995--1996. In September 1996, he joined the Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware, where he is a Professor. He was a Visiting Professor at the Chinese University of Hong Kong during 2002--2003. Before 1995, he held visiting positions in a few institutions. His current research interests include space-time coding, MIMO and OFDM systems, and SAR and ISAR imaging. Dr. Xia has over 100 refereed journal articles published, and 6 U.S. patents awarded. He is the author of the book Modulated Coding for Intersymbol Interference Channels (New York, Marcel Dekker, 2000). Dr. Xia received the National Science Foundation (NSF) Faculty Early Career Development (CAREER) Program Award in 1997, the Office of Naval Research (ONR) Young Investigator Award in 1998, and the Outstanding Overseas Young Investigator Award from the National Nature Science Foundation of China in 2001. He also received the Outstanding Junior Faculty Award of the Engineering School of the University of Delaware in 2001. He is currently an Associate Editor of the IEEE Transactions on Mobile Computing, the IEEE Signal Processing Letters, the IEEE Transactions on Signal Processing, the International Journal of Signal Processing, and the EURASIP Journal of Applied Signal Processing. He was a guest editor of Space-Time Coding and Its Applications in the EURASIP Journal of Applied Signal Processing in 2002. He is also a Member of the Signal Processing for Communications Technical Committee and the Sensor Array and Multichannel (SAM) Technical Committee in the IEEE Signal Processing Society.

Byline: Emad K. Al-Hussaini (1), Hebat-Allah M. Mourad (1), Fatma A. Newagy (1) Keywords: MC-CDMA; mobile communication; pre-rake combiner; fading channels; transmitter diversity Abstract: In this paper, a multi-carrier code division multiple access (MC-CDMA) downlink mobile communication system employing pre-rake and dual transmit diversity is proposed. It combines high spectral efficiency with an immunity to channel dispersion and fading. It also ensures small size, cost and power consumption of the terminal. Theoretical and simulation results for the system under consideration are obtained. Depicted results show appreciable improvements of the proposed system over those previously known. Author Affiliation: (1) Electronics and Communications Department, Faculty of Engineering, Cairo University, 12613, Giza, Egypt Article History: Registration Date: 01/01/2004 Article note: Emad K. Al-Hussaini received his B.Sc degree in Electrical Communication Engineering from Ain-Shams University, Cairo, Egypt, in 1964 and his M.Sc and Ph.D. degrees from Cairo University, Giza, Egypt, in 1974 and 1977, respectively. From 1964 to 1970, he was with the General Egyptian Aeroorganization. Since 1970, he has been with the Department of Electronics and Communications, Faculty of Engineering, Cairo University, and is currently professor there. He was a research fellow at Imperial College, London, UK, and at the Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA, in the academic years 1976/1977 and 1981/1982, respectively. In 1990, he received the Egyptian national encouragement award for outstanding engineering research. He has written several papers for technical international journals and conferences. His research interests include signal processing, fading channel communication, modulation, and cellular mobile radio systems. Dr Al-Hussaini is a senior member of IEEE. He is listed in Marquis Who's Who in the World and in the IBC (International Biographical Center, Cambridge) for outstanding people of the 20th century. Hebat-Allah M.Mourad received her B.Sc, M.Sc and Ph.D degrees in Electrical Communication Engineering from Cairo University, Egypt, in 1983, 1987 and 1994 respectively. Since 1983 she has been with the Electronics and Communications Department, Faculty of Engineering Cairo University and is currently associate professor there. Her research interests include mobile communications, satellite communications and optical fiber communications. Fatma A. Newagy received her B.Sc and M.Sc degrees in electrical communication engineering from Cairo University, Egypt in 1998 and 2002 respectively. Since 1999, she has been a research assistant with the Department of Electronics and Communications, Faculty of Engineering, Cairo University. She is pursuing her Ph.D. there. Her research interests include mobile communications and modulation techniques for spread spectrum and wireless communications.

Byline: Girish Ganesan (1), Petre Stoica (1), Erik G. Larsson (1) Keywords: space-time block codes; orthogonal designs; channel feedback; diversity Abstract: In this paper we consider how Orthogonal Space-Time Block Codes (OSTBC) can be used in the presence of feedback from the receiver to the transmitter. First, we survey how some of the feedback techniques for AWGN channels with fading can be applied to OSTBC. Then we consider a simple scheme with diagonal weighting. The optimal diagonal weighting matrix, which minimizes the probability of error, is derived. The optimal weights depend on the channel and, hence, a feedback becomes necessary. However, the required feedback can be accomplished using log.sub.2 (n .sub.t) bits, where n .sub.t is the number of transmit antennas. Simulations show that relatively significant gains can be achieved with the diagonal weighting scheme. In a practical system it is quite possible that the bits that are fed back to the transmitter are in error. In that case we show that there will be a loss of diversity. To overcome this loss, we develop weighting schemes that are error tolerant and always perform better than the unweighted OSTBC (even in the presence of feedback errors). Author Affiliation: (1) Department of Systems and Control, Uppsala University, P.O. Box 337, SE 751 05, Uppsala, Sweden Article History: Registration Date: 04/10/2004

Byline: Dejan Drajic (1), Kari Hooli (2), Markku Juntti (2) Keywords: WCDMA downlink; turbo coding; equalization; Rake receiver Abstract: In this paper, the performance of turbo coding in WCDMA downlink is considered in conjunction with receivers using two adaptive channel equalizers. Bit error and frame error rates are compared to the performance of the conventional Rake receiver. Special consideration is given to the cases with two receive antennas, the efficiency of the channel interleaver, the number of iterations in decoding, the performance with various numbers of users, the influence of mobile receiver velocity as well as to the effect of power control. The simulation results show that turbo coding, combined with power control and channel equalizers is a very efficient way to implement reliable data transmissions in WCDMA downlink. The results in the paper also verify that the adaptive channel equalizers is a very promising technique to improve the receiver performance and increase the user capacity. Author Affiliation: (1) Ericsson d.o.o., V. Popovica 6, 11070, Belgrade, Yugoslavia (2) Centre of Wireless Communications, University of Oulu, P.O. Box 4500, FIN-g0014, Oulu, Finland Article History: Registration Date: 04/10/2004

Byline: Changjiang Xu (1), Tho Le-Ngoc (1) Keywords: transmit diversity; space-time block coding; constant modulus algorithm; channel estimation; wireless communications Abstract: In this paper, we present channel estimation methods for space-time block coding (STBC) transmissions using constant modulus algorithm (CMA). The channel estimates are directly calculated from the convergence value of the CMA. Two algorithms using the channel-vector-based and channel-gain-based constant modulus (CM) criteria are proposed. An approximation of the CM cost function is introduced to allow the use of the recursive least-square (RLS) technique in designing fast RLS-CMA's. Performance of the proposed schemes is evaluated and compared with others using simulation. Illustrative results show that the proposed scheme outperforms the cross-correlated method and can approach the performance of the training-based method. Author Affiliation: (1) Department of ECE, McGill University, 3480 University Street, Montreal, Quebec, Canada, H3A 2A7 Article History: Registration Date: 04/10/2004

Byline: P.M. Shankar (1) Keywords: fading and shadowing; gamma pdf; generalized fading channels; Rayleigh-lognormal (RL) fading; shadowed fading channels Abstract: Most of the existing models to describe the shadowed fading channels use either the Suzuki or Nakagami-lognormal probability density function (pdf), both based on lognormal shadowing. However, these two density functions do not lead to closed form solutions for the received signal power, making the computations of error rates and outages very cumbersome. A generalized or compound fading model which takes into account both fading and shadowing in wireless systems, is presented here. Starting with the Nakagami model for fading, shadowing is incorporated using a gamma distribution for the average power in the Nakagami fading model. This compound pdf developed here based on a gamma-gamma distribution is analytically simpler than the two pdfs based on lognormal shadowing and is general enough to incorporate most of the fading and shadowing observed in wireless channels. The performance of coherent BPSK is evaluated using this compound fading model. Author Affiliation: (1) Department of Electrical and Computer Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA, 19104, U.S.A. Article History: Registration Date: 04/10/2004

Byline: Aymen I. Zreikat (1), Khalid Al-Begain (2), Kevin Smith (3) Keywords: UMTS networks; interference; power control; propagation models; queueing models; capacity bounds; Hata model Abstract: In the design of cells in mobile communication systems, path loss prediction models play an important role and have been the subject of the study for some time (M.F. Ibrahim and J.D. Parsons, IEE Proceedings, Vol. 130, No. 5, 1983). This paper presents the analysis of two main factors that affect the capacity bounds in a UMTS cell for different propagation models. These are the (i) interference levels at Node B, which increases with the number of active users, and (ii) the limited sending power of the user equipment (UE) which may not be able to send signals with enough power to reach Node B with the required received power level due to path loss. The aim of this paper is to analyse the capacity/coverage of the uplink of UMTS system in different propagation environments (free space, suburban, urban, dense urban, rural) and derive the capacity bounds for the UMTS cell. The capacity bounds have been extracted based on the extended COST-231 Hata model (http://cost.cordis.lu/src/whatiscost.cfm). COST-231 Hata is an extension of the Okumura--Hata model which covers the higher frequencies (G.L. Stuber, 'Principles of Mobile Communications,' Kluwer, 1996) necessary for WCDMA. The basic model describes the propagation loss in an urban environment, but a number of correction factors can be applied to extend its application to a broader range of environments. The analysis takes into account a number of capacity influencing factors such as the CDMA code non-orthogonality, the inter-cell interference, imperfect power control, and different service specific factors. The simulation results show the effect of different system and varying environmental parameters upon the system's capacity in different environments. The results clearly demonstrate that it is too optimistic to rely on studies based on free space assumptions. Author Affiliation: (1) Department of Information Technology, Mutah University, P.O. Box 7, Mutah, Jordan (2) School of Computing, University of Glamorgan, CF37 1DL, Pontypridd, Wales, UK (3) Department of Computing, University of Bradford, BD7 1DP, Bradford, UK Article History: Registration Date: 04/10/2004

Byline: Fan Mo (1), Junghwan Kim (1), Sameep Dave (1), Subhash C. Kwatra (1) Keywords: turbo codes; DS-CDMA; channel estimation; Log-MAP decoder Abstract: Practical implementation of convolutional turbo codec is impeded by the difficulty of real-time execution in high transmission rate communication systems due to high computational complexity, iterative block decoding structure, as well as the requirement of accurate on-line channel reliability estimation for maximum-likelihood decoding. Relying on innovative channel estimation techniques involving DS-CDMA specific noise/interference variance estimation and fading channel variation tracking, this paper provides a low-complexity all-digital design of an iterative SISO log-MAP turbo decoder for DS-CDMA based mobile communication systems. The issues of quantization and data flow in both pre-decoder processing module and iterative trellis decoding module are prudently addressed to ensure highly efficient hardware implementation. The efficient design strategies applied confine the decoding complexity while leading to an excellent performance within 0.2 dB of the software decoder. Author Affiliation: (1) Electrical Engineering and Computer Science Department, The University of Toledo, 2801 W. Bancroft St, Toledo, Ohio, 43606, U.S.A. Article History: Registration Date: 04/10/2004

Byline: R. Lojacono (1), M. Re (1), M. Caciotta (2), F. Leccese (2), D. Petri (2), A. Moschitta (3), C. Gennarelli (4), G. Riccio (4), P. Daponte (5), S. Rapuano (5), D. Grimaldi (6), S. Graziani (7), S. Sangiovanni (8) Keywords: QoS; 3G communications systems; TFR; codesign; QoAS Abstract: The UMTS appear to be the communication system of the next future. In thissystem all the communication services will be included. This means that theQuality of Service (QoS) will have a great importance. So is envisaged thatthe management of the system will take in account the momentary systemcapabilities continually determined in real time. Until now, the quality ofthe links is determined by end-to-end in line procedures based on Bit ErrorRate (BER) measurements. It is clear that an end-to-end procedure cannotdetect the worse section of the link. To overcome this inconvenient the morerecent trend of QoS management is to realise a distributed monitoring of thewhole system. Following this last trend this paper proposes a distributedoff-line monitoring of the system based on the analysis of the Quality ofAnalog Signal (QoAS). This proposed analysis implies a high-speed analog todigital conversion of the Intermediate Frequency signal and a very complexprocessing. In this paper, the state-of-the-art researches performed in thisperspective are described. Author Affiliation: (1) University of Rome ``Tor Vergata'', Via del Politecnico 1, 00133, Rome, Italy (2) University of Rome ``RomaTre'', Via della Vasca Navale 84, 00146, Rome, Italy (3) University of Perugia, Via G. Duranti 93, 06125, Perugia, Italy (4) University of Salerno, Via Ponte Don Melillo, 84084, Fisciano (SA), Italy (5) University of Sannio, Piazza Roma, 82100, Benevento, Italy (6) University of Calabria, 87036, Rende (CS), Italy (7) University of Catania, Viale A. Doria, 6, 95125, Catania, Italy (8) University of Rome ``La Sapienza'', Via Eudossiana, 18, 00184, Roma, Italy Article History: Registration Date: 11/10/2004

Byline: J. Farserotu (1), G. Kotrotsios (1), I. Kjelberg (1), A. Prasad (2) Keywords: HAP; DWDM; satellite; SONET; IP; UMTS Abstract: This paper describes a system concept for providing, flexible high capacity multimedia communication that compliments terrestrial cellular communication systems, by supporting end-to-end broadband information services. A key element of the proposed concept is the use of optical HAP-HAP and HAP-satellite links using single color (SONET protocol based) or upon multicolor DWDM technology. The effectiveness of optical communication links is enhanced through the use of advanced optical fine pointing and tracking technology. A concept for a hybrid, optical-RF, HAP based wireless communication is presented and key technologies, capabilities and limitations are described. Author Affiliation: (1) CSEM, Neuchatel, SA, Rue Jacquet-droz 1, Neuchatel, 2007, Switzerland (2) NTT DoCoMo Euro-Labs, Munich, Germany Article History: Registration Date: 11/10/2004

Byline: Lorenzo Favalli (1), Francesco Tarantola (1) Keywords: scalability; adaptive QoS; heterogeneous network Abstract: Mobile networks are becoming nothing but a way to allow ubiquitous access tomultimedia services. To allow efficient use of resources, new systems provideflexible bandwidth and different error protection techniques to match channelbehavior. As the backbone network is increasingly becoming based on packettechniques and in particular on IP and related transport protocols, end toend service quality must be analyzed considering both the fixed andthe mobile part. Source scalability may help in coping with a mixedand heterogeneous environment. In this work we present some results of atransmission chain comprising a scalable MPEG-2 coder, an IP network and aradio access exploiting the availability of satellites. It is shown thatfor a given target rate, differentiated coding can be exploited to achievedecodability and good quality at a channel SNR much lower that single layerstreams. Author Affiliation: (1) University of Pavia, via Ferrata 1, 27100, Pavia, Italy Article History: Registration Date: 11/10/2004

Byline: Matthias Holzbock (1) Keywords: inverse mobile IP; heterogeneous networks; handover management; laboratory demonstrator Abstract: Thinking of future mobile communication from a user acceptance point of view,people are getting more and more used to personalised equipment accommodatedfor their own special needs. On the other hand a number of different accessnetwork (segment) solutions are currently used on local platforms, whichincreases the need of a transparent interworking between the access networks.In order to extend access areas not only beyond segment coverage, but also tocollectively mobile networks like passengers in an aircraft, new networkconcepts are necessary. Especially such collectively mobile networks arelikely to cross coverage areas. Practical user mobility solutions are proposedfor a heterogeneous network, comprising of satellite and terrestrial accessnetworks connected to an IP core network. Different communication scenariosare investigated in support of IPv4 and IPv6 operating on user platforms andover access segments. The paper concludes with a description of a laboratorytestbed, which has been assembeld in order to verify the presented procedures,together with performance measurements of the handover algorithms during anin field vehicular trial. Author Affiliation: (1) DLR, German Aerospace Center, Institute of Communications and Navigation, P.O.B. 1116, 82334, Oberpfaffenhofen, Germany Article History: Registration Date: 11/10/2004

Byline: A. Iera (1), A. Molinaro (2), S. Marano (2) Keywords: soft-QoS; multi-tier coverage; terrestrial-satellite system integration Abstract: In an integrated terrestrial-satellite system exploiting W-CDMA air interfaces, such as the future UMTS, we conduct an in-depth research on radio resource management techniques for the support of multimedia applications with quality guarantees. The multi-bearer transmission coupled with a multitier coverage has the potentiality of allowing the effective exploitation of the radio resources while guaranteeing an adaptive quality to all end-users. Nevertheless, it still remains to be clearly understood how good they cope with typical features of next-generation multimedia cellular systems, such as soft handoff. This paper tries tocontribute to this issue by reporting the lessons learned during a performance assessment study on a simulation platform of a UMTS system. Author Affiliation: (1) Dept. DIMET, University of Reggio Calabria, Via Graziella, Feo di Vito, 89100, Reggio Calabria, Italy (2) Dept. DEIS, University of Calabria, 87036 Arcavacata di Rende (Cosenza), Italy Article History: Registration Date: 11/10/2004

Byline: Y.P. Zhang (1), J.T. Ong (1) Keywords: leaky feeder; indoor radio propagation channel; personal communication systems Abstract: This paper presents the results of narrowband and wideband propagation measurements carried out at 2.0 GHz in a large enclosed area using a coaxial cable with leaky sections as the transmitting antenna. The narrowband measurements were devised to measure attenuation of radio signals and the wideband techniques to measure multipath impulse responses and their associated root mean square delay spread. Analysis of the narrowband data files shows that the received signal levels in the direction parallel to the cable generally decay and display peaks in front of leaky sections due to the specific attenuation and special structure of the cable. The received signal levels in the direction radial to the cable decrease slowly and the distance-power law exponent is found to be slightly larger than one. The slow and fast variations of the received signal levels are also examined. The results reveal that the slow variations do not follow the lognormal distribution, while the fast variations fit the Rayleigh distribution in both parallel and radial directions. Analysis of the wideband data files yields that the maximum value of the root mean square delay spread is 86.1 ns and the root mean square delay spread values are less than 55 ns 50% of the time. One therefore can conclude that the enclosed area channel excited by the coaxial cable with leaky sections has a broad coherent bandwidth and can support the data rate up to 2.3 Mb/s without equalization. Author Affiliation: (1) School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore Article History: Registration Date: 11/10/2004

Byline: Chyi-Ren Dow (1), Jong-Shin Chen (1) Keywords: cellular networks; resource planning; fault-tolerant; traffic-adaptation; distributed algorithm Abstract: Efficient management of wireless channels is critical for the performance of cellular systems. Resource planning represents the allocations of system channels into cells. Accordingly, channel assignment strategies respond for using the allocated channels of cells to provide communication services in cells. However, a cellular system that experiences the varying of traffic distributions and the mobile service stations (MSSs) failing to provide communication services or recovered from failures will lessen the utilization of channels to provide communication services. In this paper, we present a distributed fault-tolerant resource planning scheme that can adaptively allocate channels to cells according to above variations in cellular systems. When the MSS of a cell fails to provide communications, its allocated channels can be reallocated to other non-failed MSSs. Our scheme has the advantages of low message overhead and low time delay. Moreover, freedom from deadlock is ensured. Simulation results, which are observed from reducing the overall average call blocking probability and the message overhead with and without applying our resource planning scheme to various channel assignment strategies, demonstrate that our algorithm is very efficient. Author Affiliation: (1) Department of Information Engineering and Computer Science, Feng Chia University, Taichung, Taiwan Article History: Registration Date: 11/10/2004

Byline: Ben Lu (1), Xiaodong Wang (1) Keywords: space-time trellis codes; orthogonal frequency-division multiplexing (OFDM); trellis-coded modulation (TCM); frequency-selective fading diversity; spatial diversity Abstract: We introduce a new design method for space-time trelliscodes (STTC's) in orthogonal frequency-division multiplexing(OFDM) systems with frequency-selective fading. First, byanalyzing the pairwise error probability (PEP), we conclude thatlarge effective length and random interleaving are twocritical principles in designing robust space-time codes (STC's)for OFDM systems. Then, based on the analogy between the proposedSTC design principles for multiple-antenna OFDM systems and thetrellis-coded modulation (TCM) code design criteria forsingle-antenna flat-fading channels, we develop a new STTC designmethod. At each trellis stage, this method converts the singleoutput code symbol of a traditional TCM code into several STTCcode symbols, which are to be simultaneously transmitted frommultiple transmitter-antennas, and hence results in a new class ofSTTC's. In this way, the effective lengths that have beenoptimized for traditional TCM codes are preserved in the resultingSTTC's together with a random interleaver, the proposed new classof STTC's can robustly and efficiently exploit both the spatialand the frequency-selective fading diversity resources inmultiple-antenna OFDM systems. Finally, the excellent performanceof the proposed STTC's are demonstrated through computersimulations. Author Affiliation: (1) NEC USA, C&amp C Research Laboratories, Princeton, NJ, 08540, U.S.A Article History: Registration Date: 11/10/2004

Byline: Qing Zhang (1), Tho Le-Ngoc (1) Keywords: turbo codes; turbo product codes; BCH codes Abstract: This paper presents an iterative soft-input/soft-output (SISO) decoderfor product code using optimality test and amplitude clipping. A modifiedexpression for computing the soft-output of SISO decoder is proposed.The correlation discrepancy is employed to provide an optimality teston the decision codeword. The optimality test is performed in rowand column decoding to evaluate the reliability of row and columndecision codewords. Based on the optimality test, the variable reliabilityfactor is introduced for optimization of turbo decoding. A stoppingcriterion with very little performance degradation is also designedfor turbo decoding of product codes by using the optimality test.Besides, the amplitude clipping is employed to improve the performanceof turbo product code. Simulation results on the performance of theintroduced SISO decoder are presented. Author Affiliation: (1) Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec, Canada Article History: Registration Date: 11/10/2004

Byline: R. Sanz (1), L. Munoz (1), P. Mahonen (2) Keywords: TDMA; wireless ATM; service policy; resource assignment Abstract: This paper describes an analytical model for performance estimation of a mobile communications system based on a TDMA/TDD access scheme. In accordance with the ATM classification of services and its terminology, three types of traffic have been taken into account: CBR for voice connections, VBR for real-time data applications and ABR for non real-time data services. Both voice and data traffic is modeled following Poisson processes. Moreover, three different policies for data resource assignment are evaluated: FCFS, NPPS and silence exploitation (SAD). Theoretical versus simulated results show the suitability of the model when the real-time traffic load is relatively low compared to non real-time traffic. Author Affiliation: (1) Department of Communications Engineering, University of Cantabria, Spain (2) Department of Electrical Engineering, University of Oulu, Finland Article History: Registration Date: 11/10/2004

Byline: Kimmo Kettunen (1), Jorma Lilleberg (2) Keywords: CDMA; downlink; RAKE receiver; bit metric Abstract: In this paper we propose a soft-output RAKE receiver for CDMA mobile terminals using low spreading factor and/or high-order modulation constellations for high data rates. Based on the outputs of theRAKE correlator fingers, the receiver produces symbol or bit metrics for soft decision decoding. The formulation of these metrics is derived analytically taking into account the multipath propagation, interfering users and channel estimation errors. Simulations show thata performance gain is achieved when low spreading factors or high-order modulation constellations are used. Author Affiliation: (1) Signal Processing Laboratory, Helsinki University of Technology, Finland (2) Nokia Mobile Phones, Finland Article History: Registration Date: 11/10/2004

Byline: J. Y. Pan (1), C. B. Soh (1), E. Gunawan (1) Keywords: iterative multiuser detection; CDMA; MMSE filtering; soft-interference cancellation; polynomial-expansion detector Abstract: We propose to simplify the inverse matrix computation of the iterative MMSE multiuser detector by using a low-complexity polynomial-expansion matrix approximation. This approximation is an application of the polynomial-expansion multiuser detector. The number of stages is set to the number of users to obtain a linear complexity. Simulations under AWGN and asynchronous multipath channels show that the approximation performs as well as the exact inverse implementation for iterative MMSE multiuser detector. Author Affiliation: (1) School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798, Singapore Article History: Registration Date: 11/10/2004

Byline: Jesper Adum Nielsen (1), Valentine Afanassiev (2), JArgen Bach Andersen (1) Keywords: wide band model; time-varying PDP; ray clustering; channel measurements; indoor channel modeling Abstract: This paper proposes a new approach to modeling the radio channel experienced by transceivers moving in an indoor environment. For modeling the time-varying impulse response (IR) a randomly time-varyingpower-delay profile (PDP) is used, which enables the use of PDPs specific to local environments while widely different environments still can be included in the model. The PDPs are expanded in terms of so-called cluster functions modeling ray scattering on major physical objects in the environment. By using random weighting of the cluster functions, transceiver movements in some imaginary environment is modeled. In addition to the new model, the paper also presents results obtained from measurements of the indoor channel. A good agreement is found between measurement and model data, and thus the concepts applied in the new model seem to be useful in practice. Author Affiliation: (1) Center for PersonKommunikation, Aalborg University, Fredrik Bajers Vej 7A, 9220, Aalborg A, Denmark (2) Institute for Problems of Information Transmission, Bolshoj Karetnyj 19, Moscow, Russia Article History: Registration Date: 04/10/2004

Byline: Guoqiang Xue (1), Jianfeng Weng (1), Tho Le-Ngoc (1) Keywords: CDMA; multiuser detection; power control; channel estimation Abstract: Simulation performance comparison of various linear multiuser and parallel interference cancellation (PIC) detectors in the presence of imperfect power control and channel estimation is presented. Results show that imperfect power control degrades even the performance of a single-user detector. Therefore, tight power control is highly indispensable for suboptimal detectors to maintain a good performance. When power control is not perfect, interference cancellation detectors can outperform linear multiuser detectors. Among cancellation detectors, the conventional [1] and partial PIC [2] detectors are fairly sensitive to channel estimation error, while the LMS PIC [3] is quite robust in this regard. Author Affiliation: (1) Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, Quebec, Canada, H3A 2A7 Article History: Registration Date: 04/10/2004

Byline: Hui Huang (1), Danny H.K. Tsang (1), Tsz-Mei Ko (1) Keywords: fuzzy adaptive control; switched diversity combining; fuzzy systems; antenna selection diversity Abstract: Diversity combining techniques, due to their extreme effectiveness incounteracting fading effects in wireless environment, have been extensivelystudied in recent years. In this paper, we propose an improved switchedcombining scheme using fuzzy adaptive control, namely, fuzzy adaptive switcheddiversity (FASD), which is applicable for implementation at mobile units.Specifically, the fuzzy adaptive control dynamically adjusts the thresholdlevel, at which switching is performed, based on the present varying channelconditions. By incorporating the statistics of mobile fading channels andextensive simulations, we have achieved an effective system design of FASDwhich has a significant improvement in system performance in terms of both thediversity gain and BER (bit error rate), while maintaining reasonablesimplicity in implementation. Author Affiliation: (1) Department of Electrical and Electronic Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Article History: Registration Date: 04/10/2004

Byline: Z. Baranski (1), A.M. Haimovich (2) Keywords: digital modulations Abstract: A digital modulation recently proposed and referred to as variablephase-shift-keyeing is analyzed. The autocorrelation function, powerspectral density, and probability of error are computed. Our results showthat claims of very high spectral efficiency are unjustified. Author Affiliation: (1) Automatic Switch Co., Florham Park, NJ, 07932, U.S.A (2) Center for Communications and Signal Processing Research, Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ, 07102, U.S.A Article History: Registration Date: 04/10/2004

Byline: Fernando J. Velez (1,2), Luis M. Correia (2), Jose M. Brazio (2) Keywords: Mobile Broadband System; millimetre wavebands; line-of-sight propagation; frequency reuse; system capacity Abstract: This paper addresses the comparison of characteristics between the bands of40 and 60 GHz, prospectively allocated for Mobile Broadband CommunicationSystems. The key difference between the two bands is the oxygen absorption,which is negligible at 40 GHz, but presents high values at 60 GHz, decreasingfrom 14 dB/km (at 62 GHz) down to approximately 1 dB/km (at 66 GHz). Theimpact of this excess absorption is two-fold: on one hand it reduces thereceived signal power but on the other hand it also reduces the co-channelinterference. These two quantities may not suffer the same amount ofreduction, and hence differences in the reuse pattern may result. The resultsshow that for the regular coverage geometries the difference in the reusepattern obtained in both bands is not relevant, a value of 3 being achieved.Differences however exist in the range of maximum coverage distances valuesat 43.5 GHz being up to 20% larger than at 66 GHz. For irregular urbangeometries the results obtained from specific cellular layouts, show that thereuse pattern is the same for both bands (in the range 5--7)for the the range of coverage distances where the system operationinterference limited (say, for coverage distances less than 124 m).Again, larger coverage lengths can be achieved at 40 GHz, although with ahigher associated reuse pattern. Author Affiliation: (1) Department of Electromechanical Engineering, University of Beira Interior, 6200, Covilha, Portugal (2) Instituto de TelecomunicacAues, Instituto Superior Tecnico, Technical University of Lisbon, 1049-001, Lisboa, Portugal Article History: Registration Date: 04/10/2004

Byline: R. Berangi (1), P. Leung (1) Keywords: co-channel interference; cancelling; constant modulus; mobile communications; cellular communications Abstract: This paper describes a blind cochannel interference cancelling technique, indirect cochannel interference cancelling (ICIC), that cancels a constant envelope modulated interferer in cellular mobile radio communication channels. ICIC exploits the constant envelope property of the interfering signal to simplify the receiver structure. The basic concept of ICIC and the possible receiver structures are discussed. The performance of a ICIC receiver in practical channels as well as its sensitivities to the channel parameters are investigated by simulation. Author Affiliation: (1) School of Communications and Informatics, Victoria University of Technology, P.O. Box 14428 MCMC, Melbourne, 8001, Australia Article History: Registration Date: 04/10/2004

Byline: Anand R. Prasad (1), Neeli R. Prasad (2), Ad Kamerman (2), Henri Moelard (2), Albert Eikelenboom (2) Keywords: wireless LANs; wireless networks; IEEE 802.11; security; deployment Abstract: This paper presents a system design technique for the IEEE 802.11 Wireless Local Area Network (WLAN) considering the significant parameters namely coverage, cell/frequency planning, interference, power management and data rate. The effect of the parameters on the performance of IEEE 802.11 in terms of throughput has been discussed using measurement and numerical results.These results and concepts are extremely important not only for the system design and deployment of IEEE 802.11 WLANs but also for other indoor wireless communications systems. Author Affiliation: (1) Genista Corporation, Aoyama Nozue Bld. 301, 2-11-10 Kita Aoyama, Minato-ku, Tokyo, 197-0061, Japan (2) Wireless Communications &amp Networking Division, Agere Systems, 3431 JZ, Nieuwegein, The Netherlands Article History: Registration Date: 04/10/2004

Byline: Pablo Garcia Escalle (1), Vicente Casares Giner (1) Keywords: mobility tracking; location update; registration; interrogation; paging Abstract: Mobility tracking operations in Personal Communication Services Networks (PCS) are signal-consuming. Several strategies have been proposed in the literature to reduce both the location update (LU) and the paging (PG) costs. In this paper, we use a Three Location Area (TrLA) Location Tracking Algorithm. In the TrLA, the Mobile Terminal (MT) is located in three Location Areas (LAs) with a common perimeter between them. They form the Big Location Area (BLA). Each time the MT exits the BLA, and thus enters a new LA, it triggers an LU message towards the Fixed Network (FN) and updates its cache memory. In this article, we evaluate the impact of the TrLA Location Tracking Algorithm in the FN and provide the Registration (RG) and Interrogation (IG) costs in order to estimate the load per MT in the FN devices. These devices are the Home Location Register (HLR) and the Visitor Location Registers (VLRs), and they form the System DataBase (SDB). Our study is based on an analytical model of a semi-Markov process. Author Affiliation: (1) Departamento de Comunicaciones, UPV, Camino de Vera s/n, 46022, Valencia, Spain Article History: Registration Date: 04/10/2004

Byline: Ser W. Oh (1), Kwok H. Li (1) Keywords: cellular CDMA; forward link; Nakagami fading; frequency-selective channels Abstract: The bit-error rate (BER) for a forward-link cellulardirect-sequence code-division multiple-access (DS-CDMA) systemis evaluated. This analysis takes into account the effects ofmulti-cell interference resulting from Nakagami multipath fading,frequency selectivity, path loss and mobile user spatialdistribution. Exponentially decaying multipath intensityprofile (MIP) is adopted in the model to investigate itssignificance on the overall performance. In order to evaluatethe BER performance efficiently, saddlepoint integration (SPI)is applied in the analysis. By fixing the number of resolvablemultipaths and varying the number of fingers for the RAKEreceiver, it can be shown that the capacity of a DS-CDMAcellular system increases almost linearly with the number ofRAKE fingers. Author Affiliation: (1) School of Electrical and Electronic Engineering, Nanyang Technological University, S1, Singapore, 639798, Republic of Singapore Article History: Registration Date: 04/10/2004

Location update interval for mobility database failure restoration in personal communications services is examined.

Byline: Lixin Wang (1), Mounir Hamdi (2) Keywords: multiple access protocols; multimedia wireless networks; performance evaluation Abstract: This paper proposes a new medium access protocol (MAC) protocol for futurewireless multimedia personal communication systems, denoted hybrid andadaptive multiple access control (HAMAC) protocol. The HAMAC protocolintegrates fixed assignment TDMA protocol, reservation-based protocols, andcontention-based protocols into a single wireless network so as tosimultaneously and efficiently support various classes of traffic such asconstant-bit-rate (CBR), variable-bit-rate (VBR), and available-bit-rate (ABR)traffic. In particular, the HAMAC protocol uses a novel preservationslot technique to overcome the packet contention overhead in packetreservation multiple access (PRMA) like protocols, while keeping mostisochronous service features of TDMA protocols to serve voice and CBR trafficstreams. A preservation slot is a very short slot which is used torepresent a CBR connection when the traffic in the CBR connection is in asilent period in which there is no meaningful data to transmit. Due to thevery short length of the preservation slot, it only takes minimalportion of the bandwidth pre-allocated to the CBR connection, so that theremaining bandwidth can be freed for other connections to use. When the CBRsource becomes active again, the preservation slot is replaced bynormal data slots without any reservation operation, extra delay, orsignificant bandwidth loss. Consequently, the guaranteed service andsimplified signaling features of TDMA protocols, together with the adaptivebandwidth allocation features of PRMA-like protocols, are both realized in theHAMAC protocol. We have analyzed the performance of the HAMAC protocol usingextensive simulations. The results show that the HAMAC protocol can achievevery low loss rates for various multimedia traffic with stringent quality ofservice (QoS) requirements and outperforms state-of-the-art PRMA-likeprotocols. As a result, the HAMAC protocol appears to be a good candidate forfuture generation multimedia personal communication systems. Author Affiliation: (1) The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (2) The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong E-mail Article History: Registration Date: 24/09/2004

The history and probable future direction of wireless communications is examined, with a focus on contributions by Bell Labs. Selected enabling technologies that are being developed are described, together with Bell Labs research in these areas.

The transmission of wireless standard (IS-95) code-division multiple-access (CDMA) signals from a remote antenna to a centralized base station over an analog optical fiber link has been examined. The results showed that two uncooled unisolated lasers met the requirements to transport CDMA signals from a remote antenna to a centralized base station. These were a 1.3-micrometer Fabry-Perot laser and a 1.55-micrometer distributed-feedback laser.

Byline: Filippo Giannetti (1), Marco Luise (1), Ruggero Reggiannini (1) Keywords: 60 GHz communications; millimeter-wave communications; mobile radio communications; radio propagation Abstract: This paper intends to present a summary of the technical issues arising in the exploitation of the 60 GHz mm-wave band for mobile and personal communications. The most significant applications proposed so far are surveyed, with particular emphasis placed on recent experimentation about millimeter-wave propagation for road/railway transportation as well as indoor scenarios. As a case study, the capacity of a (micro-)cellular Code Division Multiple Access (CDMA) network in the 60-GHz band is also evaluated in detail. Author Affiliation: (1) Dipartimento di Ingegneria dell'Informazione, Universita di Pisa --, Via Diotisalvi, 2--I-56126, Pisa, Italy Article History: Registration Date: 14/10/2004

Byline: Eloise Tse (1), Subbarayan Pasupathy (1) Keywords: blind equalization; differential detection; ISI; fading; decision feedback Abstract: Schemes which combine differential detection and blind equalization, to eliminate the need for phase recovery and training sequence, are studied. Decision feedback is also added in an attempt to equalize null and fading channels. Using Godard and Modified Constant Modulus Algorithms (MCMA) new systems are proposed by combining coherent and noncoherent detection with these two algorithms. For MCMA, as it can track the carrier, neither differential detection nor a PLL is required. Contrarily, Godard Algorithm needs either differential detection or a PLL to correct phase error. While the proposed system combining differential detection, blind equalization and decision feedback can indeed, in principle, equalize different channels, the robustness of the system is compromised. Author Affiliation: (1) Department of Electrical and Computer Engineering, University of Toronto, Toronto, Canada, M5S 3G4 Article History: Registration Date: 14/10/2004

In a macrodiversity cellular system, switching radio links between base stations cannot be done instantaneously. Thus, branch selection is usually based on the measurement of the slowly varying local-mean power rather than the rapidly varying instantaneous signal power. In this paper, we offer an exact mathematical model to analyze the performance of a local-mean-based macrodiversity cellular system in a shadowed-Rician (desired)/shadowed-Rayleigh (interfering) channel. We investigate the impact of both fading (Rician or Rayleigh) and shadowing in terms of cochannel interference (CCI) probability. We also present an analytical model to incorporate the effects of branch correlation on macrodiversity systems. Index Terms - Cellular radio system, cochannel interference, macrodiversity, Nakagami fading, Rician fading, shadowing.

The frequency bands currently used by existing narrow-band users might be shared with a code-division multiple-access (CDMA) spread-spectrum (SS) overlay system. Thus, the spectral efficiency is improved, providing more capacity for future personal communications services. Since both narrow- and wide-band signals interfere with each other, an SS modulation scheme with a good resistance to narrow-band interference results in an increased number of acceptable overlay users. We study a frequency-diversity SS modulation scheme for which optimal detection in the presence of narrow-band interference is easy to implement. The acceptable number of overlay users is evaluated and compared to that of conventional direct-sequence SS (DS-SS) modulation schemes with and without interference rejection filters. The proposed system also presents the following advantage: by suppressing transmission of replicas where narrow-band signals (NBS's) are present, the mutual interference can be avoided completely. Index Terms - Broad-band overlay, code-division multiple access, interference suppression, spread-spectrum communications.

Byline: Xing Zhang (1), Weihua Zhuang (2) Keywords: channel assignment; neighbor cell channel sharing; cellular mobile communications Abstract: This paper presents a channel sharing scheme, Neighbor Cell Channel Sharing (NCCS) , based on region partitioning of cell coverage for wireless cellular networks. Each cell is divided into an inner-cell region and an outer-cell region. Cochannel interference is suppressed by limiting the usage of sharing channels in the inner-cell region. The channel sharing scheme achieves a traffic-adaptive channel assignment and does not require any channel locking. Performance analysis shows that using the NCCS scheme leads to a lower call blocking probability and a better channel utilization as compared with other previously proposed channel assignment schemes. Author Affiliation: (1) AMPS/PCS Business Leadership Group, Lucent Technologies, Rm. 14H-405, 67 Whippany Rd., P.O. Box 903, Whippany, New Jersey, 07981-0903, U.S.A (2) Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada Article History: Registration Date: 14/10/2004

Byline: Elyes B. Bdira (1), Paul Mermelstein (1) Keywords: CDMA; integrated wireless access networks; distributed antenna diversity; personal communication systems Abstract: We consider the use of distributed antennas to increase the capacity and peak data rate achievable in a microcellular CDMA system with limited bandwidth. In additon to the diversity against Rayleigh fading achievable by use of microdiversity among nearly co-located transmit or receive antennas, we exploit macrodiversity against shadow fading that more widely separated antennas permit. We report on antenna configurations for both directional and omni-directional antennas that provide the most uniform signal-to-interference ratio coverage, averaged over a large number of position vectors drawn from a spatially uniform distribution of mobiles. Call capacities and peak transmission rates are determined for an integrated system carrying traffic at different constant rates, where processing gain and the transmission rate are selected to satisfy a common chip rate. For the downlink a 5.5 dB capacity gain can be achieved for 64 kb/s calls using four antennas located on the diagonals of each square cell. A bandwidth of 5 MHz allows two or more calls to be simultaneously supported at data rates up to 512 kb/s, as opposed to only 128 kb/s for three co-located antennas. On the uplink we distinguish between the computationally simpler equal-gain combining of the antenna signals and the possibly more complex maximum-ratio combining. With equal gain combining we achieve a peak data rate of 128 kb/s and a capacity gain of 2.5 dB relative to equal gain combining of three nearly co-located antenna signals. With maximum ratio combining the peak uplink rate can be as high as 512 kb/s and the capacity is increased by 2.0 dB relative to the maximum-ratio combining of three co-located antennas. Author Affiliation: (1) INRS Telecommunications, Universite de Quebec, 16 Place du Commerce, Ile-Des-Soeurs, Verdun, PQ H3E-1H6, Canada Phone Article History: Registration Date: 14/10/2004

Byline: Andreas F. Molisch (1) Keywords: bit error rate; time dispersion; AWGN; error floor; two-delay channel; line-of-sight component; Gaussian Minimum Shift Keying Abstract: We show a new approach to analytically compute the error probability BER in mobile radio channels. The method is applicable to a variety of differentially detected modulation formats here we use minimum shift keying (MSK) as an example. We include the following effects: (i) fading and (ii) time dispersion of the mobile radio channel (iii) noise, and (iv) filtering both of the data sequence and the received signal. Sampling is at a fixed but arbitrary instant. We develop a new mathematical formalism, which we call the two-path equivalent-matrix (TPEM) method. In this method, we reduce the general channel (including noise) exactly to a two-path fading channel without noise, whose BER can be easily computed. With this method, we can find analytically the BER for both filtered and unfiltered (G)MSK if the BER is small for large BER a single well-behaved integral must be solved numerically. Asymptotic equations for unfiltered MSK and small BERs are also given. To a first approximation, the BER is 0.5* [(S/T).sup.2+1/SNR] for pure MSK, where S/T is the delay spread normalized to the bit duration and SNR is the signal-to-noise ratio. The BER is increased by less than 50% for Gaussian filtering of the data sequence and receiver filtering with a time-bandwidth product larger than 0.3. Author Affiliation: (1) Institut fur Nachrichtentechnik und Hochfrequenztechnik, Technische Universitat Wien, Gusshausstrasse 25/389, A-1040 Vienna, Austria Fax Article History: Registration Date: 14/10/2004