Scheduled System Maintenance:
On May 6th, system maintenance will take place from 8:00 AM - 12:00 PM ET (12:00 - 16:00 UTC). During this time, there may be intermittent impact on performance. We apologize for the inconvenience.
By Topic

Selected Areas in Communications, IEEE Journal on

Issue 9 • Date Dec. 1996

Filter Results

Displaying Results 1 - 21 of 21
  • Code Division Multiple Access Networks IV [Guest Editorial]

    Publication Year: 1996
    Save to Project icon | Request Permissions | PDF file iconPDF (562 KB)  
    Freely Available from IEEE
  • Adaptive traffic admission for integrated services in CDMA wireless-access networks

    Publication Year: 1996 , Page(s): 1737 - 1747
    Cited by:  Papers (30)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1048 KB)  

    Code-division multiple-access (CDMA) is a serious candidate for personal communication systems at 1.9 GHz in North America. We consider the issue of bandwidth management in a CDMA integrated wireless-access network with heterogeneous services. A framework for adaptive connection admission in the up-link direction is proposed. It is based on estimation of the interference at the base station receivers. The estimation algorithm employs a linear Kalman filter which is driven by a measurement of the interference and by predicted traffic parameters of the admitted connections. We derived several generic variants of the control architecture for the up-link direction to assess the main characteristics of the framework and to determine the trade-offs between complexity and performance. They vary from a fixed strategy with fixed power control to an adaptive strategy with full information about network state and adaptive power control. A numerical study of the proposed framework shows that the estimated value of the average interference adapts well to the real value under nonstationary and nonuniform environment. This feature results in high network utilization for arbitrary traffic conditions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of wireless CDMA with M-ary orthogonal modulation and cell site antenna arrays

    Publication Year: 1996 , Page(s): 1770 - 1783
    Cited by:  Papers (84)  |  Patents (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1144 KB)  

    An antenna array-based base station receiver structure for wireless direct-sequence code-division multiple-access (DS/CDMA) with M-ary orthogonal modulation is proposed. The base station uses an antenna array beamformer-RAKE structure with noncoherent equal gain combining. The receiver consists of a “front end” beamsteering processor feeding a conventional noncoherent RAKE combiner. The performance of the proposed receiver with closed loop power control in multipath fading channels is evaluated. Expressions for the system uncoded bit-error probability (BEP) as a function of the number of users, number of antennas, and the angle spread are derived for different power control scenarios. The system capacity in terms of number of users that can be supported for a given uncoded BEP is also evaluated. Analysis results show a performance improvement in terms of the system capacity due to the use of antenna arrays and the associated signal processing at the base station. In particular, analysis results show an increase in system capacity that is proportional to the number of antennas. They also show an additional performance improvement due to space diversity gain provided by the array for nonzero angle spreads View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A slotted frequency-hopped multiple-access network with packet combining

    Publication Year: 1996 , Page(s): 1859 - 1865
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    A frequency-hopped spread-spectrum (FH/SS) packet radio network is considered. Instead of discarding the received packets which were unsuccessfully decoded, the receiver keeps and combines the different received copies of the same packet to improve the throughput and reduce the delay necessary to transmit a packet successfully. It is shown that the throughput is substantially increased over a similar system where the uncorrectable packets are discarded. This system is equivalent to a fast frequency-hopped system where the diversity level is adapted according to the channel conditions. Reed-Solomon (RS) codes are used for error correction and detection View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive fuzzy proportional integral power control for a cellular CDMA system with time delay

    Publication Year: 1996 , Page(s): 1818 - 1829
    Cited by:  Papers (14)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1104 KB)  

    We investigate the use of fuzzy logic control techniques for adaptive power control in a direct-sequence code-division multiple-access (DS/CDMA) cellular system over the mobile fading radio channels with propagation time delay. A fuzzy PI (proportional-plus-integral) control whose input variables are the received power error and error change is introduced to determine each user transmitting power in order to simultaneously equalize all users' signal powers received at the base station and achieve better system stability and control performance. This control strategy can ensure long loop transmission delays without causing the system to become unstable. According to the well-known phase-plane method, the derivation of the fuzzy PI control has been carried out by analyzing the response areas, cross-over, and extreme points of the system step response with apriori knowledge of the dynamics of the CDMA mobile fading channels. For a long time-delay fading process, a methodology is developed to modify the rule base to contain the delay information for reducing the deadtime effects of the process. Moreover, the additional advantages of fuzzy PI control over conventional control theories are: increased robustness in spite of interference and the ability to handle the time-delay process whose parameters are not accurately known. Simulation results show that a good performance can be achieved both in RMS tracking error and traffic capacity by use of fuzzy PI power control, especially in poor interuser interference and long time delay conditions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Congestion relief on power-controlled CDMA networks

    Publication Year: 1996 , Page(s): 1758 - 1761
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A digital cellular radio code-division multiple-access (CDMA) system can only support a finite number of users before the interference plus noise power density, I0, received at the cellular base station causes an unacceptable frame-error rate. Once the maximum interference level is reached, new arrivals should be blocked. In a power-controlled CDMA system, the base station can direct mobiles to reduce their power and data rate to reduce interference and allow more users on the system. This approach is employed in TIA IS-95 with respect to the time-varying voice activity on cellular voice channels. We investigate an alternative technique where we adjust the power and data rate of mobile data users to the time-varying interference level to allow more users on a congested system. This scheme was simulated for various proportions of voice and data users and offered traffic levels. Blocking probabilities are reduced in some cases by two orders of magnitude. Message wait time, now a random variable, may exceed the wait time for a constant rate system at high traffic levels. If the cellular carrier has a maximum blocking requirement, an adaptive rate/power system can increase the capacity. For example, a base station that normally supports 26.4 Erlangs offered traffic with 2% blocking can support 33.5 Erlangs with the same blocking probability if adaptive rates and power control are used. Thus, the adaptive rate system can increase the capacity by 27% View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A medium-access control protocol for a cellular packet CDMA carrying multirate traffic

    Publication Year: 1996 , Page(s): 1728 - 1736
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    We propose and evaluate a medium-access control (MAC) protocol for synchronous cellular packet direct-sequence code-division multiple-access (DS/CDMA). The protocol is designed for handling a variety of multimedia traffic types in an integrated wireless-access network (IWAN). For instance, the protocol is suited for carrying multiple traffic types of different priorities. An analytical model for the equilibrium state has been developed for the proposed protocol. A comparative evaluation of the protocol is done for three different radio frequency bandwidths currently under consideration for personal communication services (PCS), i.e., 1.25 MHz, 5 MHz, and 10 MHz. Our results demonstrate that the proposed protocol is both robust and flexible for the intended IWAN applications. It offers a significant multiplexing gain as the bandwidth increases View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of chip coding in FFH SSMA systems

    Publication Year: 1996 , Page(s): 1841 - 1851
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    This paper proposes chip coding using convolutional codes for fast frequency-hopping spread-spectrum multiple-access (FFH-SSMA) systems. Its performance is evaluated and compared with that of repetition coding which is most commonly used in FFH systems. In our proposal, an information symbol is encoded by a convolutional code of rate 1/n and n chips are transmitted through a frequency hopper. We consider three models when perfect side information (PSI) is available, no side information (NSI) is available, and the ratio threshold test (RTT) is used. The probability density functions (PDFs) of the received signal are derived for asynchronous hopping systems. The performances of convolutional coding with threshold decoding and Viterbi decoding are presented under the constraint of fixed total bandwidth and information bit rate. In comparison with repetition codes, it is found that convolutional codes drastically enhance the system performance. It is identified that Viterbi decoding with RTT offers the most significant performance improvement View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance evaluation of wireless multimedia CDMA networks using adaptive transmission control

    Publication Year: 1996 , Page(s): 1688 - 1697
    Cited by:  Papers (19)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    When multimedia information including speech, image, data etc. are transmitted, the difference in information rates, required quality, and traffic performance should be taken into account. A wireless spread spectrum system can achieve a flexible balance of these differences because of inherent asynchronous code-division multiple-access (CDMA) capability. In order to accomplish wireless multimedia communication, three parameters are investigated: the transmission power, packet length, and time slot. We propose and investigate two methods to accomplish wireless multimedia communication by using these parameters: (1) a method based on control of both transmission power and transmission packet length and (2) a method based on control of both transmission power and adaptive time slot. We derive the optimal transmission packet length and transmission power in (1) and derive optimal adaptive time slot and transmission power in (2) by using traffic of measurement and nonlinear programming. By the comparison, the two proposed methods are compared to the minislotted alternating priority (MSAP). Numerical results demonstrate that the proposed methods, when the priority of each medium is graded, show better performance than other systems in terms of average throughput and delay time of all media View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Known and novel diversity approaches as a powerful means to enhance the performance of cellular mobile radio systems

    Publication Year: 1996 , Page(s): 1784 - 1795
    Cited by:  Papers (17)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1312 KB)  

    The main requirements to be met by third generation mobile radio systems are high cellular spectrum efficiency and high flexibility. The authors focus on high cellular spectrum efficiency, which is difficult to achieve due to the time variance and frequency selectivity of the mobile radio channel and due to interference. It is known that the degrading effects of these adverse characteristics of the mobile radio channel and of interference can be mitigated by diversity. The way how diversity influences cellular spectrum efficiency is derived in general. As a reference point, the types of diversity used in GSM are analyzed. In GSM, the potential for diversity enhancement inherent in code-division multiple-access (CDMA) is not exploited. A joint detection code-division multiple-access (JD-CDMA) system concept aimed at third generation mobile radio systems has been proposed which introduces a CDMA feature into systems based on time-division multiple-access (TDMA) and frequency-division multiple-access (FDMA) like GSM and also advanced TDMA (ATDMA). The gains achievable by different types of diversity in GSM as well as in the JD-CDMA system concept are investigated. It is shown that considerable gains can be achieved by different types of antenna diversity and by exploiting the additional diversity potential of CDMA. Therefore, third generation standards should be flexible in order to allow the use of as many types of diversity as possible to enhance the cellular spectrum efficiency View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of a joint CDMA/PRMA protocol for mixed voice/data transmission for third generation mobile communication

    Publication Year: 1996 , Page(s): 1698 - 1707
    Cited by:  Papers (70)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    A joint code-division multiple-access/packet-reservation multiple-access (CDMA/PRMA) technique is proposed and investigated as a candidate for an uplink protocol for third generation mobile communication systems. Access to the radio channel is controlled such that compared to random access CDMA, interference variance is reduced and throughput increased. Mixed voice/data traffic is investigated for an isolated cell only, whereas voice-only traffic is also investigated in a cellular environment with a regular hexagonal cell structure. Intercell interference is assumed to be Gaussian, and only the average interference level is considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transmit permission control on spread ALOHA packets in LEO satellite systems

    Publication Year: 1996 , Page(s): 1748 - 1757
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1156 KB)  

    A transmit permission control method for improving the throughput characteristics of a low Earth orbit (LEO) satellite communication system employing spread-slotted ALOHA multiple-access scheme is proposed. Both nonfading and fading satellite links are considered. The basic idea of the proposed scheme is to decrease the level of interference at each satellite and, hence, to increase the probability of packet success, by prohibiting the packet transmission from the users with relatively high propagation loss to their connecting satellites. It is shown that the method has the ability to improve the throughput performance in heavy traffic loads and the peak value of the throughput, significantly. It is also shown that the average delay performance of the system employing the proposed scheme is superior to that of the conventional system at heavy traffic loads View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fiber-optic subcarrier multiplexed CDMA local-area networks for subband image transmission

    Publication Year: 1996 , Page(s): 1866 - 1878
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1616 KB)  

    This paper investigates the application of subcarrier multiplexed code-division-multiple-access (CDMA) techniques to image transmission over fiber-optic local-area networks (LANs). In the hybrid scheme, CDMA is used to suppress the interference caused by the laser nonlinearity in the subcarrier multiplexing (SCM) fiber-optic communication systems. Likewise, the SCM scheme is able to increase the channel data rate of CDMA systems. This hybrid system combines the advantages of both schemes and is particularly well suited to subband coding that divides the image information into multiple parallel data streams using an analysis filter bank, each of which is transmitted via a unique subcarrier-code pair, where the spreading code and subcarrier frequency correspond to the image and one of its subbands, respectively. This hybrid scheme also allows more than one image to be transmitted and be accessed simultaneously at the same channel bandwidth, in which each image is assigned a particular spreading code added to its digital data modulating the subcarrier. After transmission, each received signal is independently recovered at a high-Q surface acoustic wave (SAW) receiver with the matching subcarrier-code pair. Other concurrent signals are rejected by the SAW. Then, all the recovered subbands are reassembled by a synthesis filter bank into a close reproduction to the original image. The image quality of subband image transmission via CDMA/SCM fiber-optic channels is evaluated and examined View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A reservation random-access protocol for voice/data integrated spread-spectrum multiple-access systems

    Publication Year: 1996 , Page(s): 1717 - 1727
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1068 KB)  

    Most code-division multiple-access (CDMA) systems described in the literature provide only one single service (voice or data) and employ the strategy of “one-code-for-one-terminal” for code-assignment. This assignment, though simple, fails to efficiently exploit the limited code resource encountered in practical situations. We present a new protocol called reservation-code multiple-access (RCMA), which allows all terminals to share a group of spreading codes on a contention basis and facilitates introducing voice/data integrated services into spread-spectrum systems. The RCMA protocol can be applied to short-range radio networks, and microcell mobile communications, and can be easily extended to wide area networks if the code-reuse technique is employed. In RCMA, a voice terminal can reserve a spreading code to transmit a multipacket talkspurt while a data terminal has to contend for a code for each packet transmission. The voice terminal will drop a long delayed packet while the data terminal just keeps it in the buffer. Therefore, two performance measures used to assess the proposed protocol are the voice packet dropping probability and the data packet average delay. Theoretical performance is derived by means of equilibrium point analysis (EPA) and is examined by extensive computer simulation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis of soft handoff in CDMA cellular networks

    Publication Year: 1996 , Page(s): 1762 - 1769
    Cited by:  Papers (67)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    The code-division multiple-access (CDMA) scheme has been considered as one possible choice of the future standards for cellular networks because of its various advantages. Since there can be only one carrier frequency being used in CDMA systems, a handoff scheme with diversity, a so-called “soft handoff”, was proposed for higher communication quality and capacity. A mathematical model is developed to analyze the soft handoff process. Markov's concept is applied to describe the system's steady state statistical behavior. System performance such as blocking probability, handoff refused probability, and channel efficiency are also determined. It is concluded that the larger the area the soft handoff region is, the better users in the cellular network will feel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of imperfect power control and user mobility on a CDMA cellular network

    Publication Year: 1996 , Page(s): 1809 - 1817
    Cited by:  Papers (18)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1036 KB)  

    Code-division multiple-access (CDMA) is one of the major candidate access techniques for third generation systems. A great deal of effort has been devoted to the study of the capacity it can support. This paper presents analytical derivations which allow the determination of the link availability in the presence of user mobility and power control imperfections in a CDMA network; moreover, it provides the guidelines which permit the implementation of a simple and flexible simulation tool which is independent of the specific CDMA implementations. As a matter of fact, the reported concepts can be applied to any asynchronous CDMA system, i.e., they hold both for the American Standard IS-95 and for the European Community Standard developed in the framework of the RACE CODIT Project View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Power imbalance effects on packet CDMA

    Publication Year: 1996 , Page(s): 1830 - 1840
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    This paper presents an analysis of packet code-division multiple-access (CDMA) with single user receivers and power level variations. The power level variations are due to imperfect power control. The teletraffic is modeled as an M/G/∞ queueing system. Average error rates and outage probabilities that a user sees are evaluated for a single cell CDMA system. The effects of power level variations are investigated using a combination of an approximation and an upper bound, and the loss in traffic capacity is evaluated. Numerical results for CDMA systems with different processing gains and coding gains are presented. It is shown that imperfect power control reduces significantly the CDMA teletraffic capacity, and much has to be gained by improving the power control schemes. The methods and results of this work could be used for quantifying the required accuracy of power control in CDMA and for evaluation of the capacity loss due to power control errors View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design study for a CDMA-based LEO satellite network: downlink system level parameters

    Publication Year: 1996 , Page(s): 1796 - 1808
    Cited by:  Papers (15)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1152 KB)  

    The performance analysis of a new concept of a code-division multiple-access (CDMA) based low Earth orbit (LEO) satellite network for mobile satellite communications is presented and discussed. The starting point was to analyze the feasibility of implementing multisatellite and multipath diversity reception in a CDMA network for LEO satellites. The results are used to specify the design parameters for a system experimental test bed. Due to the extremely high Doppler, which is characteristic of LEO satellites, code acquisition is significantly simplified by using a continuous wave (CW) pilot carrier for Doppler estimation and compensation. The basic elements for the analysis presented are: the channel model, the pilot carrier frequency estimation for Doppler compensation, and multipath and multisatellite diversity combining View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Direct-detection optical synchronous CDMA systems with double optical hard-limiters using modified prime sequence codes

    Publication Year: 1996 , Page(s): 1879 - 1887
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (780 KB)  

    An optical code-division multiple-access (CDMA) system with double optical hard-limiters is proposed where the optical hard-limiters are placed before and after an optical correlator. Moreover, the-effect of the optical hard-limiter on the performance of the optical synchronous CDMA systems using modified prime sequence codes as signature codes is analyzed under the assumption of a Poisson shot noise model for the receiver photodetector where the noise due to the detector dark currents exists. We evaluate the performance under average power and bit rate constraints. Our results show that using the single optical hard-limiter slightly degrades the performance of the optical CDMA systems under the assumption of Poisson shot noise model for the receiver photodetector where the noise due to the detector dark currents exists. Moreover, we show that the optical CDMA systems with double optical hard-limiters have better performance than other conventional CDMA systems with and without the optical hard-limiter when the number of simultaneous users is not so large View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis of a fully-connected, full-duplex CDMA ALOHA network with channel sensing and collision detection

    Publication Year: 1996 , Page(s): 1708 - 1716
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    In cases where machines having bursty data are equally likely to transmit to one another, code-division multiple-access (CDMA) ALOHA which allows for an individual “virtual channel” for each receiving station may be a better multiple-access protocol than simple ALOHA. With the use of a “receiver-based code” multiple-access protocol, it is also possible for a station to listen to the channel of the intended receiver before transmission, and also abort transmission when it detects others transmitting on the same channel. This paper describes a model for a fully-connected, full duplex, and slotted CDMA ALOHA network where channel sensing and collision detection are used. The model is analyzed using a discrete time Markov chain and some numerical results are presented. For a system with a large number of users, where Markov analysis is impractical, equilibrium point analysis is used to predict the stability of the system, and estimate the throughput as well as the delay performance of the system when it is stable. Finally, a comparison is made with a simple channel sense multiple-access with collision detection (CSMA-CD) network, showing that a substantial improvement in the performance is achieved by the proposed network View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multicarrier CDMA with adaptive frequency hopping for mobile radio systems

    Publication Year: 1996 , Page(s): 1852 - 1858
    Cited by:  Papers (45)  |  Patents (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    A modified multicarrier (MC) direct-sequence code-division multiple-access (DS-CDMA) system has been proposed for use over slow multipath fading channels with frequency selectivity in the reverse link transmission of a cellular network. Instead of transmitting data substreams uniformly through subchannels, data substreams hop over subchannels with the hopping patterns adaptively adjusted to the channel fading characteristics. The problem of determining the optimal hopping pattern is formulated as a multiobjective optimization problem, for which an efficient algorithm, based on the water-filling (WF) principle, is designed to solve the problem practically. Simulation results show that the performance in terms of the average bit-error probability (BEP) (over all users) is better than that of single carrier RAKE receiver systems, conventional MC CDMA systems applying moderate error protection, or diversity systems with different combining techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Muriel Médard
MIT