Showing papers in "IEEE Transactions on Vehicular Technology in 1982"
TL;DR: A new algorithm for frequency channel assignment in mobile radio communication is proposed which enables the calls having all their nominal channels busy to borrow channels from the neighboring cells provided that co-channel interference will not result.
Abstract: A new algorithm for frequency channel assignment in mobile radio communication is proposed. The algorithm uses flexible fixed channel assignment which enables the calls having all their nominal channels busy to borrow channels from the neighboring cells provided that co-channel interference will not result. The borrowed channel cannot be used in three interfering cells; therefore reassignment strategy is used when a call is terminated on a nominal channel to switch a call in progress in a borrowed channel to that nominal one and set free the borrowed channel in the three interfering cells. Thus the traffic carried on borrowed channels is minimized. Also different call switching strategies are proposed to give priority to some channels to be used by the nominal cells and other channels to be borrowed by neighboring cells. These strategies considerably reduce the blocking probability. A simulation study of the algorithm was carried out on 49 hexagonal zones having uniform traffic density. Also a combined telephone and dispatch traffic was included in the simulation study. The results showed that the new algorithm is better than the other channel assignment schemes. This can be applied in high capacity mobile communications systems to utilize the spectrum efficiently.
237 citations
TL;DR: A theory of optimal adjacent channel distance in homogeneous hexagonal cell systems is developed and algorithms generating frequency distributions with best adjacent channel Distance valid for arbitrary co-channel reuse ratios are presented.
Abstract: A theory of optimal adjacent channel distance in homogeneous hexagonal cell systems is developed. Algorithms generating frequency distributions with best adjacent channel distance, valid for arbitrary co-channel reuse ratios, are presented. The theory may be applied to mobile radio telephone systems or broadcast services.
92 citations
TL;DR: In this paper, the use of a side-looking radar in conjunction with a sidewall reflector is one means of obtaining lateral position information for use in vehicle automatic lateral control.
Abstract: The use of a side-looking radar in conjunction with a sidewall reflector is one means of obtaining lateral position information for use in vehicle automatic lateral control. The principle of operation of a two-frequency radar for such use is presented along with a discussion of the reflector design and construction difficulties. Some results of the full-scale testing of this radar using two different types of reflecting surfaces are included. The performance of this radar system is compared with that of the highly accurate wire follower. In general, tracking errors on the order of twice those obtained with the wire follower were achieved. It appears that with some redesign of the radar, performance equal to or better than that of the wire follower should eventually result.
47 citations
TL;DR: A new fixed channel assignment (FCA) scheme, in which a user can be served by any of the nearest k base stations, has been considered and compared with the standard (k = 1) FCA scheme.
Abstract: Schemes for accessing the message channels of base stations in a cellular communication system are considered. Detailed analysis is given for a fixed channel assignment scheme with collision type request channels. The probability P f that a request fails to secure a message channel is considered as a performance criterion. That fraction of bandwidth allocated to request channels, which minimizes the failure probability P f , is determined as well as the optimum P f . Both are plotted as a function of bandwidth utilization S. Sensitivity of system performance to various parameters is considered. A new fixed channel assignment (FCA) scheme, in which a user can be served by any of the nearest k base stations, has been considered and compared with the standard (k = 1) FCA scheme. A mixed scheme with two message types has also been considered. One message type can be served by any of the nearest three base stations but the other type can be served only by the nearest.
43 citations
TL;DR: In this paper, the relation between the prescribed total outage and the necessary margins for thermal noise and co-channel interference is derived, and it is then shown that the respective margins can be calculated separately.
Abstract: A procedure for a radio link design of cellular land mobile radio systems is discussed. The relation between the prescribed total outage and the necessary margins for thermal noise and co-channel interference is first derived. It is then shown that the respective margins can be calculated separately. A simple and useful procedure for determining transmitter power and co-channel reuse distance is presented in concrete flowchart form. Based on this procedure, an example of a radio link design for a digital mobile telephone system is shown.
43 citations
TL;DR: In this paper, various methods of torque measurement which are utilized in the automotive industry are reviewed, starting with the most frequently used types and continuing to less frequently used methods, and performance limitations for each method are summarized.
Abstract: Various methods of torque measurement which are utilized in the automotive industry are reviewed. Seven methods are described in order of usage, starting with the most frequently used types and continuing to less frequently used types of torque measurement. Performance limitations for each method of torque measurement also are summarized.
36 citations
TL;DR: A small solid-state radar combined with a microprocessor makes possible collision-mitigation braking and automatic headway control in cars of the future.
Abstract: A small solid-state radar combined with a microprocessor makes possible collision-mitigation braking and automatic headway control in cars of the future. The collision-mitigation function involves the application of antiskid brakes under conditions where, based on radar and other sensor inputs, it is certain that a severe collision will take place. The decision-making algorithm is optimized to prevent the unjustified application of the brakes from false alarms. The automatic headway-control function keeps the car at a safe distance with respect to other vehicles on the road ahead. In the absence of other cars the system operates as a conventional cruise control.
32 citations
TL;DR: Field experiments have been conducted to clarify the feasibility of introducing a newly developed Gaussian filtered minimum shift keying (GMSK) modulation method into 920 MHz mobile radio systems.
Abstract: Field experiments have been conducted to clarify the feasibility of introducing a newly developed Gaussian filtered minimum shift keying (GMSK) modulation method into 920 MHz mobile radio systems, and have been performed in the Tokyo urban, and the Yokosuka suburban areas.
30 citations
TL;DR: In this article, a time and frequency division multiple access (TD/FDMA) scheme, which is a combination scheme of TDMA and FDMA, is proposed as one of the possible solutions for the problems of setting up a large number of base station transceivers and realizing a low-cost highly stabilized local oscillator.
Abstract: Multiple access is an indispensable technique for efficient radio spectrum utilization in mobile radio systems, because a large number of subscribers can be connected only when they require radio channels. Frequency division multiple access (FDMA) scheme using single channel per carrier (SCPC) has been widely used. However, the SCPC-FDMA scheme has some problems, such as difficulty in setting up a large number of base station transceivers and in realizing a low-cost highly stabilized local oscillator. A time and frequency division multiple access (TD/FDMA) scheme, which is a combination scheme of TDMA and FDMA, is proposed as one of the possible solutions for these problems. After explaining the background of the proposal, some of the restrictions of the TD/FDMA scheme resulting from the land mobile radio channel characteristics are described. Basic concept of the digital mobile radio telephone system using TD/ FDMA scheme is then presented. An example of the possible system design is finally shown.
27 citations
TL;DR: Bit error rate (BER) is analyzed theoretically for diversity reception in the quasi-static Rayleigh fading environment with noise and co-channel interference conditions and an approximate BER formula of M-ary (M = 4, 8, 16) angle modulations is derived.
Abstract: Bit error rate (BER) is analyzed theoretically for diversity reception in the quasi-static Rayleigh fading environment with noise and co-channel interference conditions. The analysis is based upon the canonic receiver model with postdetection combining. This model presents exact BER formulas with respect to carrier-to-noise ratio (CNR) and carrier-to-interference ratio (CIR) for both coherent and differential detections (CD and DD) of binary angle modulations. In the case of CD, an exact and explicit BER formula for the maximal-ratio combining diversity (MRC) is obtained. On the other hand, in the case of DD, an explicit BER formula for the equal-gain combining diversity (EGC) is obtained. These results are applied to derive an approximate BER formula of M-ary (M = 4, 8, 16) angle modulations. Phase-shift keying (PSK) and continuous-phase frequency-shift keying (CP-FSK) are demonstrated as examples of angle modulations.
20 citations
TL;DR: The postdetection selection diversity effects on a binary digital FM system are theoretically analyzed in the fast Rayleigh fading signal environment encountered in the typical UHF or microwave land mobile radio channels.
Abstract: The postdetection selection diversity effects on a binary digital FM system are theoretically analyzed in the fast Rayleigh fading signal environment encountered in the typical UHF or microwave land mobile radio channels. Both differential and discriminator detections are considered for demodulation of digital FM signal. The average error rate is presented by a simple closed form including both effects of Rayleigh envelope fading and random FM noise. A few examples of numerical results for minimum shift keying (MSK) are graphically presented.
TL;DR: In this article, a simplified mathematical model for the radiation from helical antennas with a large number of turns is derived, and the near E-field intensity obtained from the theoretical model is compared to the values measured using an accurate Efield probe.
Abstract: The close near field of helical antennas, radiators widely used in connection with two-way portable communication equipment, is investigated theoretically and experimentally. The investigation has been motivated by safety related considerations. A simplified mathematical model for the radiation from helical antennas with a large number of turns is derived. The near E-field intensity obtained from the theoretical model is compared to the values measured using an accurate E-field probe. The agreement between experimental and theoretical values is excellent. The results show that there is a substantial buildup of static-type electric energy in the close vicinity of helical antennas. The intensity of these electric fields in the vicinity of a helical radiator depends essentially on the Q factor of the antenna. For one experimental helix the far-field power density equivalent (|E|2/377) of the electric field at 1-cm distance from the radiator exceeds some proposed safety standards for less than 250-µW radiated power. These values are in complete agreement with the results of previous studies which showed that helical radiators are very ineffective in depositing electromagnetic energy into simulated muscle tissue located in the close vicinity of the antenna. If safety standards of independent or government agencies do not take into account the peculiar nature of the electromagnetic energy in the close vicinity of some radiating devices, it is conceivable that the power of portable two-way communication equipment might be forced down to useless levels.
TL;DR: In this paper, the performance of linear induction motors subject to velocities normal to the track is calculated both by finite element and Fourier analysis techniques, and the response to a step increase in air gap of a high speed vehicle being driven by a linear induction machine supplied with constant current is calculated.
Abstract: The performance of linear induction motors subject to velocities normal to the track are calculated both by finite element and Fourier analysis techniques. Results yielded by the two methods for the case of a small traction linear machine are compared. The response to a step increase in air gap of a high speed vehicle levitated and driven by a linear induction machine supplied with constant current is then calculated. The resulting vertical oscillations have a period of about 2.1 s. Electromagnetic damping effects are found to be small; the time constant of decay of the oscillation is found to be about 35 s.
TL;DR: This work derives upper bounds on the probability of the transmission failure for three different schemes and shows that an efficient scheme for the Rayleigh fading channel is the block-protected one in which a message is transmitted four times, each transmission 4-ms long and spaced 4-MS apart.
Abstract: In a microwave mobile telecommunications system, a digital message must be transmitted several times to overcome the effects of Rayleigh fades that characterize this channel, and thus ensure a high probability that the message is received error-free. Obviously, there are many different transmission schemes that may be suitable for this channel. We present an analytic approach to an evaluation of their comparative performance in terms of the probability of a transmission failure, and provide a basis for the design of an efficient scheme. In the first part, we present some fade statistics that have been used in our analysis. Next, we derive upper bounds on the probability of the transmission failure for three different schemes. The actual failure rates as determined in an experimental simulation are then shown for those schemes that our theoretical study predicts to be acceptable. It is shown that an efficient scheme for the Rayleigh fading channel is the block-protected one in which a message is transmitted four times, each transmission 4-ms long and spaced 4-ms apart. The spacing is obtained by interleaving a similar transmission of another message. The receiver discards a transmission if it fails the parity checks.
TL;DR: The spectrum efficiency of a frequency-hopped multilevel frequency-shift keying (FH-MFSK) spread spectrum modulation technique proposed for use in mobile radio systems is evaluated, and the analysis assumes randomly chosen address vectors, a perfect synchronization at the receiver, and noncoherent detection.
Abstract: The spectrum efficiency of a frequency-hopped multilevel frequency-shift keying (FH-MFSK) spread spectrum modulation technique proposed for use in mobile radio systems is evaluated. The analysis assumes randomly chosen address vectors, a perfect synchronization at the receiver, and noncoherent detection. With perfect transmission where the only degradation is due to mutual interference, the efficiency is 0.262, 0.295, and 0.345 at an average bit error rate of 10-3for 1.64, 3.41, and 20 MHz bandwidth. However, with transmission impairments consisting of additive white Gaussian noise and frequency selective Rayleigh fading, which characterize the mobile radio channel, the efficiency depends on the average signal-to-noise ratio (SNR), and on the average bit error rate.
TL;DR: In this paper, a computer model is described that predicts the reaction forces developed by single-sided linear induction motors (SLIMs) with solid iron secondaries, and the model predictions are compared with test results obtained from three separate SLIM investigations covering a wide range of operating conditions and SLIM design parameters.
Abstract: A computer model is described that predicts the reaction forces developed by single-sided linear induction motors (SLIM's) with solid iron secondaries. The model predictions are compared with test results obtained from three separate SLIM investigations covering a wide range of operating conditions and SLIM design parameters. The results demonstrate the basic validity of the model and its applicability for magnetic levitation (Maglev) optimization and analysis.
TL;DR: A review is given of co-channel interference in small-cell systems and of the means for its avoidance, andPropagation phenomena are described.
Abstract: A review is given of co-channel interference in small-cell systems and of the means for its avoidance. Propagation phenomena are described. A table is given for the separation of base stations having both the same channel and the same supervisory tone, for up to 16 cells per block and zero to seven tones. Curves are given versus distance for the probability of interference from one station and from one or more stations in a seven-cell arrangement. Means for avoiding such interference are reviewed.
TL;DR: In this paper, the stability of loran C signals in a nonurban area was carried out to determine the suitability of these signals for land vehicle location, and the root mean square (rms) time difference prediction errors were on the order of 200 ns or less.
Abstract: Measurements of the stability of loran C signals in a nonurban area were carried out to determine the suitability of these signals for land vehicle location. Measurements were made at a 25- point grid within a 400 square mile area in central Indiana and extended over a ten month period. It was found that root mean square (rms) time difference prediction errors were on the order of 200 ns or less and the rms position errors computed from three time-difference measurements were on the order of 45 m over the ten month test period. Methods of improving position estimates using least-squares and maximum likelihood procedures are discussed.
TL;DR: An extensive study of digitized speech transmission over existing VHF FM mobile radio sets is presented and Objective criteria expressed in terms of bit error rate (BER) are determined for the performance evaluation of analog FM radios when transmitting digital voice.
Abstract: An extensive study of digitized speech transmission over existing VHF FM mobile radio sets is presented. Objective criteria expressed in terms of bit error rate (BER) are determined for the performance evaluation of analog FM radios when transmitting digital voice. These criteria are used to define the technical characteristics such as the receiver sensitivity, co-channel rejection, and adjacent channel selectivity in the case of digital FM transmission. The concept of performance measurements of existing sets in the digital mode of operation is suggested. The results of performance measurements reported here include the following: 1) radiated FM spectra, 2) bit error rate curves, 3) receiver sensitivity, 4) BER performance in the presence of analog or digital FM interference on the same or adjacent channel, 5) signal plus noise plus distortion to noise plus distortion ratio (SINAD) performance in the presence of co-channel or adjacent channel interference for both types of interfering signals, 6) co-channel rejection and adjacent channel selectivity for various combinations of the wanted and interfering signals, 7) receiver selectivity for both modes of operation, and 8) adjacent-signal selectivity for various combinations of the desired and undesired signals. Optimum values of design parameters of digital voice radio system are deduced from the obtained results. Finally, the implications of digitized speech transmission on the technical characteristics, operating range, channel reuse distance, and adjacent channel interference performance of analog FM radios are discussed.
TL;DR: It is shown that for mobile radio, DCDM, as expected, is the better of the two coders because it does not sacrifice its overload performance for the sake of error resistance.
Abstract: A characteristic of a mobile radio channel is the occurrence of correlated signal fading that results in burst errors. The use of adaptive delta modulation (ADM) based on explicit transmission of the quantizer step size was proposed earlier for speech communication over such a channel. Two other variable step-size delta modulation (VSDM) schemes are presented, and their performance in a mobile radio environment is discussed. One of them is the constant factor delta modulation that uses one-bit memory and produces fast and instantaneous step-size changes. The other is the digitally controlled delta modulation (DCDM) that incorporates a new step-size adaptation strategy using seven bits of memory. In some cases, bit scrambling has been used. This is equivalent to scrambling (spreading out in time) the, clustered errors. Computer simulations providing values of coder parameters for satisfactory signal-to-noise ratios for band-limited speech signals and Gaussian noise are described. New hardware realizations are given that allow those parameters to vary smoothly for a wide range of sampling frequencies. Results of informal listening tests obtained with a mobile radio channel simulator are included. It is shown that for mobile radio, DCDM, as expected, is the better of the two coders. This is because it does not sacrifice its overload performance for the sake of error resistance.
TL;DR: In this article, the Doppler spectrum from an extended object illuminated by a finite beam is analyzed theoretically, and the long-time spectrum is the product of an antenna spectrum and an object spectrum, which may lead to significant systematic errors in determination of velocity.
Abstract: The Doppler spectrum from an extended object illuminated by a finite beam is analyzed theoretically. The long-time spectrum is the product of an antenna spectrum and an object spectrum, which may lead to significant systematic errors in determination of velocity. The error probability is larger for short-time spectra. Experimental results on automobiles also indicate the existence of a very wide spectrum, which may be multipeaked with incorrect dominating peaks for short periods of time. Physically the errors may be interpreted as a result of moving phase centers.