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Selected Areas in Communications, IEEE Journal on

Issue 4 • Date May 1994

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Displaying Results 1 - 22 of 22
  • Decision feedback equalization for CDMA in indoor wireless communications

    Publication Year: 1994 , Page(s): 698 - 706
    Cited by:  Papers (113)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    Commercial interest in Code Division Multiple Access (CDMA) systems has risen dramatically in the last few years. It yields a potential increase in capacity over other access schemes, because it provides protection against interference, multipath, fading, and jamming. Recently, several interference cancellation schemes for CDMA have been proposed but they require information about all interfering active users or some channel parameters. The authors present an adaptive fractionally spaced decision feedback equalizer (DFE) for a CDMA system in an indoor wireless Rayleigh fading environment. This system only uses information about the desired user's spreading code and a training sequence. An analysis on the optimum performance of the DFE receiver shows the advantages of this system over others in terms of capacity improvements. A simulation of this system is also presented to study the convergence properties and implementation considerations of the DFE receiver. Effects on the performance because of sudden birth and death of users in the CDMA system and bit error rate performance of the DFE receiver is also presented View full abstract»

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  • Performance of DS-CDMA with imperfect power control operating over a low earth orbiting satellite link

    Publication Year: 1994 , Page(s): 560 - 567
    Cited by:  Papers (50)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    The analysis of both the performance and capacity of direct sequence CDMA in terrestrial cellular systems has been addressed in the technical literature. It has been suggested that CDMA be used as a multiple access method for satellite systems as well, in particular for multispot beam low Earth orbit satellites (LEOS). One is tempted to argue that since CDMA works well on terrestrial links, it will nominally work as well on satellite links. However, because there are fundamental differences in the characteristics of the two channels, such as larger time delays from the mobile to the base station and smaller multipath delay spreads on the satellite channels, the performance of CDMA on satellite links cannot always be accurately predicted from its performance on terrestrial channels. In the paper, the authors analytically derive the performance of a CDMA system which operates over a low Earth orbiting satellite channel. They incorporate such effects as imperfect power control and dual-order diversity to obtain the average probability of error of a single user View full abstract»

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  • Effects of filtering on the performance of QPSK and MSK modulation in D-S spread spectrum systems using RAKE receivers

    Publication Year: 1994 , Page(s): 707 - 715
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    Direct-sequence spread spectrum systems utilizing RAKE receivers provide inherent diversity for in-building mobile CDMA radio. A new compact expression for the SNR of the decision variable of a RAKE receiver is derived for generalized offset quadrature carrier modulation in this multipath environment. This expression also applies to BPSK, QPSK, and MSK modulation. The novelty of the derived expression is that it includes the effects of filtering. Filtering must be used to eliminate out-of band radiation and can also be used to shape the in-band spectrum, It is shown that bandlimiting filters have a significant effect on the SNR. A comparison of bandlimited O-QPSK and MSK reveals that, under the same co-user load, MSK has a lower SNR-0.917 times that of O-QPSK. However, MSK has an offsetting advantage of being a constant envelope-type modulation that can be very efficiently generated using direct modulation of a power RF oscillator. It is further shown that the O-QPSK SNR can be increased by a factor of 1.63 by whitening the in-band spectrum View full abstract»

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  • Guest editorial. Code division multiple access networks. I

    Publication Year: 1994 , Page(s): 557 - 559
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    This special issue covers the topics: power control, multiuser receiver and joint detection, network aspects, adaptive equalisation, coding aspects, broadband CDMA systems, and optical systems View full abstract»

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  • A theoretical analysis of the performance of code division multiple access communications over multimode optical fiber channels-part I: transmission and detection

    Publication Year: 1994 , Page(s): 751 - 761
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    This paper presents results of a theoretical investigation to evaluate the performance of code division multiple access communications over multimode optical fiber channels in an asynchronous, multiuser communication network environment. The system is evaluated using Gold sequences for spectral spreading of the baseband signal from each user employing direct-sequence biphase shift keying and intensity modulation techniques. The transmission channel model employed is a lossless linear system approximation of the field transfer function for the α-profile multimode optical fiber. Due to channel model complexity, a correlation receiver model employing a suboptimal receive filter was used in calculating the peak output signal at the ith receiver. The performance measures for the system, i.e., signal-to-noise ratio and bit error probability for the ith receiver, are derived as functions of channel characteristics, spectral spreading, number of active users, and the hit energy to noise (white) spectral density ratio View full abstract»

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  • Admission policies for integrated voice and data traffic in CDMA packet radio networks

    Publication Year: 1994 , Page(s): 654 - 664
    Cited by:  Papers (54)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    The authors derive optimal admission policies for integrated voice and data traffic in packet radio networks employing code division multiple access (CDMA) with direct-sequence spread spectrum (DS/SS) signaling. The network performance is measured in terms of the average blocking probability of voice calls and the average delay and packet loss probability of data messages. The admission scheme determines the number of newly arrived voice users that are accepted in the network so that the long-term blocking probability of voice calls is minimized. In addition, new data arrivals are rejected if the mean delay or the packet loss probability of data exceeds a desirable prespecified level. A semi-Markov decision process (SMDP) is used to model the system operation. Then, a value iteration algorithm is used to derive the optimal admission control. Two models for the other-user interference of the CDMA system are considered: one based on thresholds and another based on the graceful degradation of the CDMA system performance, and their performance is compared. These admission policies find application in emerging commercial CDMA packet radio networks including cellular networks, personal communication networks, and networks of LEO satellites for global communications View full abstract»

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  • The capacity achievable with a broadband CDMA microcell underlay to an existing cellular macrosystem

    Publication Year: 1994 , Page(s): 744 - 750
    Cited by:  Papers (16)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    Broadband code division multiple access (B-CDMA) using direct sequence spread spectrum can be used as an overlay to an existing analog or narrowband digital cellular system to provide increased capacity and new data services. In order to achieve significant capacity, it has been shown that both transmit and receive notch filters should be used at the base station. This paper addresses whether the B-CDMA overlay concept can be applied to creating a CDMA microcell underlaying an existing analog macrocell. It is shown that indeed high capacity can be achieved in the microcell on both forward and reverse links, largely independently of the separation between microcell and macrocell bases. Furthermore, in the forward link the effect of neighboring base stations is shown to be negligible. In order to achieve maximum capacity, it is found that transmit and receive notch filters at the microcell base station are invaluable at small separations between micro and macrocells. It is also shown that key parameters which must be properly controlled are the powers of the CDMA base and mobile transmitters relative to their analog counterparts View full abstract»

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  • Design study for a CDMA-based third-generation mobile radio system

    Publication Year: 1994 , Page(s): 733 - 743
    Cited by:  Papers (193)  |  Patents (98)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1104 KB)  

    This paper focuses on a CDMA design study for future third-generation mobile and personal communication systems such as FPLMTS and UMTS. In the design study, a rigorous top down approach is adopted starting from the most essential objectives and requirements of universal third-generation mobile systems. Emphasis is laid on high flexibility with respect to the implementation of a wide range of services and service bit rates including variable rate and packet services. Flexibility in frequency and radio resource management, system and service deployment, and easy operation in mixed-cell and multioperator scenarios are further important design goals. The system concept under investigation is centered around an open and flexible radio interface architecture based on asynchronous direct-sequence CDMA with three different chip rates of approximately 1, 5, and 20 Mchip/s. The presented CDMA system concept forms the basis for an experimental test system (testbed) which is currently under development. This experimental system concept has been jointly established by the partners in the European RACE project R2020 (CODIT). The paper describes the radio transmission scheme and appropriate receiver principles and presents first performance results based on simulations View full abstract»

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  • SIR-based call admission control for DS-CDMA cellular systems

    Publication Year: 1994 , Page(s): 638 - 644
    Cited by:  Papers (106)  |  Patents (49)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    Signal-to-interference ratio (SIR)-based call admission control (CAC) algorithms are proposed and studied in a DS-CDMA cellular system. Residual capacity is introduced as the additional number of initial calls a base station can accept such that system-wide outage probability will be guaranteed to remain below a certain level. The residual capacity at each cell is updated dynamically according to the reverse-link SIR measurements at the base station. A 2k factorial experimental design and analysis via computer simulations is used to study the impact of the parameters used in the algorithms. The influence of these parameters on system performance, namely blocking probability and outage probability, is then examined via simulation. The performance of the algorithms is compared together with that of a fixed call admission control scheme (fixed CAC) under both homogeneous and hot spot traffic loading. The results show that SIR-based CAC always outperforms fixed CAC even under overload situations, which is not the case in FDMA/TDMA cellular systems. The primary benefit of SIR-based CAC in DS-CDMA cellular systems, however, lies in improving the system performance under hot spot traffic View full abstract»

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  • Adaptive receiver structures for asynchronous CDMA systems

    Publication Year: 1994 , Page(s): 685 - 697
    Cited by:  Papers (240)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1176 KB)  

    Adaptive linear and decision feedback receiver structures for coherent demodulation in asynchronous code division multiple access (CDMA) systems are considered. It is assumed that the adaptive receiver has no knowledge of the signature waveforms and timing of other users. The receiver is trained by a known training sequence prior to data transmission and continuously adjusted by an adaptive algorithm during data transmission. The proposed linear receiver is as simple as a standard single-user detector receiver consisting of a matched filter with constant coefficients, but achieves essential advantages with respect to timing recovery, multiple access interference elimination, near/far effect, narrowband and frequency-selective fading interference suppression, and user privacy. An adaptive centralized decision feedback receiver has the same advantages of the linear receiver but, in addition, achieves a further improvement in multiple access interference cancellation at the expense of higher complexity. The proposed receiver structures are tested by simulation over a channel with multipath propagation, multiple access interference, narrowband interference, and additive white Gaussian noise View full abstract»

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  • Novel spatial spread spectrum based fiber optic CDMA networks for image transmission

    Publication Year: 1994 , Page(s): 762 - 772
    Cited by:  Papers (20)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    Novel code division multiple access (CDMA) fiber optic networks based on spatial frequency spread spectrum for image transmissions are proposed. Two key technologies are the parallel fiber optic transmission of spatially encoded images and parallel access to image data through optical spatial encoding and decoding. The temporal signature sequences used in conventional time-domain CDMA are replaced by two-dimensional (2-D) signature patterns to encode and decode binary image pixels. This enables the fully parallel access and transmission of images. The fundamental rules and methodology to construct optical orthogonal signature patterns (OOSP) are presented. Furthermore, it is shown that the all-optical implementation of the proposed system is feasible by utilizing optically addressable spatial light modulators in both the spatial encoder and the decoder along with multicore fibers as the parallel image transmission medium. The predicted overall throughput can reach 10 Tb/s View full abstract»

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  • A novel spread slotted Aloha system with channel load sensing protocol

    Publication Year: 1994 , Page(s): 665 - 672
    Cited by:  Papers (38)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    This paper presents a novel spread slotted Aloha system with channel load sensing protocol (CLSP). CLSP is an effective scheme to improve the throughput performance in spread unslotted Aloha systems. In spread slotted Aloha systems, however, it does not make sense to utilize CLSP because the slot size is usually the same as the packet size. The slot size of the proposed system is set less than the packet size, thereby enabling the authors to apply CLSP and improving the throughput performance. Another feature of the proposed system is that the system is not likely affected by the time difference between channel load sensing and timing of packet access, which they call the access timing delay. Throughput performance of the proposed system is evaluated in the presence of the access timing delay and a significant increase of the throughput is shown compared with that of spread unslotted Aloha with CLSP View full abstract»

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  • Analysis of frequency-hopped packet radio networks with random signal levels-part I: error-only decoding

    Publication Year: 1994 , Page(s): 723 - 732
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    This paper is concerned with the performance analysis of frequency-hopped packet radio networks with random signal levels. The authors assume that a hit from an interfering packet necessitates a symbol error if and only if it brings on enough energy that exceeds the energy received from the wanted signal. The interdependence between symbol errors of an arbitrary packet is taken into consideration through the joint probability generating function of the so-called effective multiple access interference. Slotted networks, with both random and deterministic hopping patterns, are considered in the case of both synchronous and asynchronous hopping. A general closed-form expression is given for packet capture probability, in the case of Reed-Solomon error only decoding. After introducing a general description method, the following examples are worked out in detail: (i) networks with random spatial distribution of stations (a model for mobile packet radio networks), (ii) networks operating in slow fading channels, and (iii) networks with different power levels which are chosen randomly according to either discrete or continuous probability distribution (created captures) View full abstract»

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  • Delay and throughput characteristics of TH, CDMA, TDMA, and hybrid networks for multipath faded data transmission channels

    Publication Year: 1994 , Page(s): 622 - 637
    Cited by:  Papers (10)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB)  

    The new concepts of adaptive time hopping and variable frame code division (CDMA) multiple access are introduced. By a unified analysis, the probabilities of bit and packet errors in multipath fading environment for five time division (TDMA), code division, and time hopping (TH) related multiaccess networks are obtained; namely, TDMA, CDMA, CDMA/TDMA, Adaptive CDMA/TH, and variable frame CDMA/TDMA networks. The delay and useful throughputs of the five systems are also evaluated for data and voice traffic. All systems compared have the same channel power and bandwidth and support the same traffic. Though implementation issues are not covered, CDMA systems are put at a disadvantage (compared to cellular-type FDMA networks, for example) by ignoring such inherent advantages as voice silence utilizations and automatic frequency reuse. Nontheless, two CDMA systems outperform TDMA systems at low and medium input traffics View full abstract»

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  • The capacity of a spread spectrum CDMA system for cellular mobile radio with consideration of system imperfections

    Publication Year: 1994 , Page(s): 673 - 684
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB)  

    There has been much interest in the use of spread spectrum code division multiple access (CDMA) techniques for cellular mobile radio. To date, spread spectrum has been used mainly for military applications, in which the inherent transmission security and immunity to deliberate jamming are important. Spread spectrum systems, however, possess various other features such as multiple access and multipath rejection capability, which make their use attractive within the mobile radio environment. However, the current interest has been principally motivated by the work of Gilhousen et al. (see IEEE Trans. Vehic. Technol., vol.VT-40, no.2, p.303, 1991) in which it is claimed that the CDMA option may offer capacity improvement over more conventional frequency and time division multiple access, FDMA and TDMA, techniques. Within this paper, the relative capacities of a basic FDMA and CDMA system are examined. It is shown that, in the absence of capacity-enhancing features such as voice activity detection and cell sectorization, the capacity of each system is comparable. The paper then assesses the sensitivity of the CDMA system to typical propagation conditions, power control errors, and realistic antenna patterns and shows that the capacity of a CDMA system may be significantly reduced under nonideal conditions View full abstract»

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  • DS/SSMA communication system with trellis coding and CPM

    Publication Year: 1994 , Page(s): 716 - 722
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    A direct-sequence spread spectrum multiple access (DS/SSMA) communication system employing continuous phase modulation (CPM) and trellis coding is described and analyzed to obtain an estimate of the error probability. The trellis code provides significant coding gain while the CPM signal format gives desirable spectral properties. The analysis shows that significant improvement in error probability over the standard binary DS/SSMA system can be achieved with relatively simple codes View full abstract»

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  • Traffic handling capability of a broadband indoor wireless network using CDMA multiple access

    Publication Year: 1994 , Page(s): 645 - 653
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

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

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  • Multiuser detection scheme based on canceling cochannel interference for MFSK/FH-SSMA system

    Publication Year: 1994 , Page(s): 593 - 604
    Cited by:  Papers (32)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1004 KB)  

    The paper proposes and investigates a multiuser detection scheme based on canceling cochannel interference (CCI) to improve spectral efficiency or to increase user capacity in an MFSK (multilevel frequency shift keying)/FH-SSMA (frequency hopping-spread spectrum multiple access) system. In the MFSK/FH-SSMA system, an address code is employed as a hopping sequence to hop the carrier frequency in MFSK. In the proposed scheme, it is assumed that the address codes of all users in MFSK/FH-SSMA are known. Then, candidates of the transmitted vector which are regenerated from the time-frequency matrices decoded by all the users' address codes are added with logical OR operation to produce candidates of the received matrix. The candidates of the received matrix are utilized in order to estimate a pattern of all users' data symbols which has the most number of coincident entries with the received matrix. Its BER (bit error rate) performance is evaluated by theoretical analysis and computer simulation in order to show the improvement of user capacity. Moreover, the authors investigate a hybrid scheme combining a multiuser detection scheme and the decoding scheme of an error-correcting code for the coded MFSK/FH-SSMA system View full abstract»

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  • Optimum diversity combiner based multiuser detection for time-dispersive Rician fading CDMA channels

    Publication Year: 1994 , Page(s): 580 - 592
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1100 KB)  

    Multiuser detection for asynchronous code division multiple access (CDMA) data transmission over the time-dispersive two-path Rician fading channel is considered. The multiuser maximum likelihood sequence detector (MLSD) is derived, and an equivalence of the fading channel to an asynchronous Gaussian intersymbol interference (AGISI) CDMA channel is established. However, the MLSD is found to be implementationally infeasible and this motivates the derivation of the optimum linear detector with near/far resistance as the performance criterion. The optimally near/far resistant linear time-invariant K-user detector is shown to consist of a cascade of a 2 K input/K output linear multiuser diversity combining filter followed by a K input/K output decorrelator that is designed for the equivalent AGISI/CDMA channel. This detector solves the near/far problem and also supports significantly higher bandwidth efficiencies for CDMA communication over the fading channel than does the conventional near/far limited single-user diversity combiner. The performance penalties incurred by multiuser detectors designed for the Gaussian channel when used over the Rician fading channel are also analytically characterized. It is shown that these penalties can be significant, making the case for the use of multiuser detectors optimized for this fading channel, particularly the optimum linear detector due to its relative implementational simplicity View full abstract»

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  • Performance of a cellular hybrid C/TDMA mobile radio system applying joint detection and coherent receiver antenna diversity

    Publication Year: 1994 , Page(s): 568 - 579
    Cited by:  Papers (69)  |  Patents (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1116 KB)  

    For future mobile radio systems, an appropriately chosen multiple access technique is a critical issue. Multiple access techniques presently under discussion are code division multiple access (CDMA), time division multiple access (TDMA), and hybrids of both. In the paper, a hybrid C/TDMA system using joint detection (JD-C/TDMA) with coherent receiver antenna diversity (CRAD) at the base station (BS) receiver is proposed. Some attractive features of the JD-C/TDMA system are the possibility to flexibly offer voice and data services with different bit rates, soft capacity, inherent frequency and interferer diversity, and high system capacity due to JD. Furthermore, due to JD, a cluster size equal to 1 can be realized without needing soft handover. The single cell Eb/N0 performance and the interference situation in a cellular environment of the uplink of a JD-C/TDMA mobile radio system with CRAD is investigated in detail. It is shown that the cellular spectrum efficiency is remarkably high, taking values up to 0.2 bit/s/Hz/BS in the uplink, depending on the actual transmission conditions View full abstract»

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  • Network protocols for frequency-hop packet radios with decoder side information

    Publication Year: 1994 , Page(s): 612 - 621
    Cited by:  Papers (36)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    Reliable data distribution within spread-spectrum packet radio networks requires high performance from the network protocols. This paper describes research in forwarding and routing protocols that are designed specifically for slow-frequency hop (SFH) packet radio networks in which some of the radios are subjected to excessive interference. It is shown that information extracted from the decoder can be used to aid the network protocols. New metrics are introduced that use this information to give a quantitative assessment of the interference environment experienced by the receiver in an SFH radio. Forwarding protocols are developed that can react quickly to local sources of interference, and the metrics that are introduced permit the routing algorithm to react to changes in the interference conditions in the network View full abstract»

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  • Microcellular CDMA system with a linear multiuser interference canceler

    Publication Year: 1994 , Page(s): 605 - 611
    Cited by:  Papers (23)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    In the paper, the authors suggest an asynchronous microcellular CDMA system with a matrix-based multiuser interference canceler for the reverse link, in which multiuser interference is completely removed on a symbol-by-symbol basis. The linear interference cancellation scheme, whose matrix order is equal to the number of active users, does not require knowledge of their received power levels, thereby resulting in high capacity and near/far resistance. In the paper, the influence of surrounding cell interference on a given base station receiver for various propagation path loss models is also analyzed and then the system performance is investigated theoretically. Provided the normalized capacity is defined by a required SNR (=Eb/N0 ) of 7 dB at the binary DPSK detector, the CDMA system can provide capacity per cell of 46~54% View full abstract»

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Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

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Editor-in-Chief
Muriel Médard
MIT