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Showing papers on "Cellular network published in 1994"


Journal ArticleDOI
TL;DR: Some information-theoretic considerations used to determine upper bounds on the information rates that can be reliably transmitted over a two-ray propagation path mobile radio channel model, operating in a time division multiplex access (TDMA) regime, under given decoding delay constraints are presented.
Abstract: We present some information-theoretic considerations used to determine upper bounds on the information rates that can be reliably transmitted over a two-ray propagation path mobile radio channel model, operating in a time division multiplex access (TDMA) regime, under given decoding delay constraints. The sense in which reliability is measured is addressed, and in the interesting eases where the decoding delay constraint plays a significant role, the maximal achievable rate (capacity), is specified in terms of capacity versus outage. In this case, no coding capacity in the strict Shannon sense exists. Simple schemes for time and space diversity are examined, and their potential benefits are illuminated from an information-theoretic stand point. In our presentation, we chose to specialize to the TDMA protocol for the sake of clarity and convenience. Our main arguments and results extend directly to certain variants of other multiple access protocols such as code division multiple access (CDMA) and frequency division multiple access (FDMA), provided that no fast feedback from the receiver to the transmitter is available. >

1,216 citations


Journal ArticleDOI
TL;DR: An architecture is presented for a high-speed cellular radio access network based on ATM transport technology which avoids the need to involve the network call processor for every cell handoff attempt and which can readily support a very high rate of handoffs.
Abstract: An architecture is presented for a high-speed cellular radio access network based on ATM transport technology. Central to this approach is a new concept known as the virtual connection tree which avoids the need to involve the network call processor for every cell handoff attempt. Such an approach can readily support a very high rate of handoffs, thereby enabling use of physically small radio cells to provide very high system capacity, but may occasionally cause the volume of traffic to be handled by one cell site to exceed that cell site's capacity. A simple analytical methodology is developed which can be used for admission control, the purpose of which is to limit the number of in-progress calls such that two new quality of service metrics (overload probability and average time in overload) can be kept suitably low. Finally, a general framework is presented for overall system organization and signaling. >

488 citations


Journal ArticleDOI
TL;DR: Optimal pulses designed to minimize multiple-access interference in quasi-synchronous systems are obtained for various bandwidths and are shown to provide a large improvement over the raised cosine pulses.
Abstract: Proposes a multicarrier orthogonal CDMA signaling scheme for a multiple-access communication system, such as the reverse channel of a cellular network, as an alternative to the multi-user interference cancellation approach. The average variance of cross-correlations between sequences is used as a measure for sequence design. The authors search for sets of sequences that minimize the probability of symbol detection error, given that there is imperfect synchronization among the signals, that is, the signals are quasi-synchronous. Orthogonal sequences based on the Sylvester-type Hadamard matrices (Walsh functions) are shown to provide a significant improvement over the case where a Hadamard (orthogonal) matrix is chosen at random. Computer searches suggest that this set of codes is optimal with respect to the above measure. The issue of chip pulse shaping is investigated. Optimal pulses designed to minimize multiple-access interference in quasi-synchronous systems are obtained for various bandwidths and are shown to provide a large improvement over the raised cosine pulses. A multicarrier signaling scheme is introduced in order to reduce chip level synchronization offsets between the users. >

285 citations


Patent
06 Oct 1994
TL;DR: In this paper, a dual mode terminal is provided, in which a mobile station (21) of a mobile radio system and a cordless telephone (22) are combined, and a call re-establishment procedure is utilized for inter-system handovers.
Abstract: A dual mode terminal (20) is provided, in which a mobile station (21) of a mobile radio system and a cordless telephone (22) are combined. This kind of terminal can have a connection with both a base station of the mobile radio system and a base station (fixed part) of the cordless telephone system. Handover in the case of this dual mode terminal implies the transfer of a call from the base station of the mobile radio system to a base station of the cordless telephone system. A call re-establishment procedure is utilized for inter-system handovers between a cordless telephone system having terminal-initiated handovers and the supporting mobile radio system having network-initiated handovers.

174 citations


Patent
02 Jun 1994
TL;DR: In this paper, reference measurements are carried out on relevant traffic routes with the aid of a measuring mobile in order to provide position information related to measured signals, and an adaptive neural network is trained.
Abstract: The invention relates to a method for locating mobile stations in a digital telecommunication network, especially the GSM network. According to the invention, reference measurements are carried out on relevant traffic routes with the aid of a measuring mobile in order to provide position information related to measured signals. With the aid of these reference data and the position information, an adaptive neural network is trained, which network, with the aid of corresponding measurement data which are transmitted from the mobile station to a respective base station, carries out the localisation of the mobile station. Use of the adaptive neural network provides a more accurate position determination than earlier systems which were only based on the TA (timing advance) value.

159 citations


Patent
Paul W. Dent1
04 Apr 1994
TL;DR: In this article, a system and method for minimizing interference between two radio stations, e.g., a mobile radio telephone and a fixed base station, at the initiation of a radio communication is presented.
Abstract: The present invention includes a system and method for minimizing interference between two radio stations, e.g., a mobile radio telephone and a fixed base station, at the initiation of a radio communication. A mobile station initiates a random access at the lowest power level and increases the transmission power level until the base station detects the access signal. Once detected, the power level of the message is maintained at the detected level so that the signal interference is avoided. The present invention also provides a mechanism for synchronizing random access communications between mobile stations and the base station despite variation in distances between the mobile and base stations.

155 citations


Patent
06 Sep 1994
TL;DR: In this article, a wireless communication system combines time and space diversity to reduce fading and simplify receiver design, where a data packet which carries digital telephone traffic, is transmitted at three different times from three different antennas.
Abstract: A wireless communication system combines time and space diversity to reduce fading and simplify receiver design. In particular, a data packet which carries digital telephone traffic, is transmitted at three different times from three different antennas. The mobile subscriber receiver thus receives the same data packet at three different times from three different antennas, and uses the best data packet or combination of the data packets to reduce the effects of fading. A transfer station receives a time division multiplex multiple access (TDMA) signal from a base station carrying telephone data packet traffic to form three data packet repeats at spatially diverse antennas locations. The transfer station further modulates a code division multiple access (CDMA) system using a TDMA signal which links the mobile subscriber receiver to the transfer station. Each data packet received at the transfer station is thus retransmitted at three different times to the mobile subscriber station on a CDMA link. In one embodiment, each transfer station includes the three space diversity antennas. In a second embodiment, three transfer stations, each with one spatially diverse antenna is used. The time division and code division multiplex signals transmitted from space diversity antennas provide the ability to determine subscriber location using the same communication signals which are used for the primary telephone data communication. Specifically, the subscriber station receiver uses the absolute and relative time of arrival of the three repeated data packets to determine the respective distances of the mobile subscriber station to the three transmitting antennas. Since the transmitting antennas are at known fixed locations, receiver location is determined.

149 citations


Patent
12 May 1994
TL;DR: In this paper, a hybrid system combines the high intra-cell capacity of TDMA with the inter-cell and multipath interference rejection capabilities of CDMA, where TDMA is used inside each cell and CDMA signals, having low cross-correlations, are assigned to adjacent cells.
Abstract: In a cellular network, a multiple-access methodology and concomitant circuitry in which TDMA is used inside each cell and CDMA signals, having pulse shapes with low cross-correlations, are assigned to adjacent cells. For example, these pulses could be Direct-Sequence Spread-Spectrum pulses. Such a hybrid system combines the high intra-cell capacity of TDMA with the inter-cell and multipath interference rejection capabilities of CDMA.

142 citations


Journal ArticleDOI
TL;DR: In this paper, 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.
Abstract: 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. >

134 citations



Proceedings ArticleDOI
08 Jun 1994
TL;DR: In this article, the authors proposed a broadband CDMA overlay with agile notch filters at the base station, which can approximately quadruple the nominal capacity of GSM, which is 16 channels per sector, by providing an additional 51 voice channels at 16 kbps each.
Abstract: The author proposes that one can overlay an existing GSM cellular network with a broadband CDMA cellular system utilizing direct-sequence spread spectrum alone with agile notch filters at the base station. Notch filter depths of 35 dB on receive and 20 dB in transmit were found to be adequate. Capacity calculations show that the B-CDMA overlay can approximately quadruple the nominal capacity of GSM, which is 16 channels per sector, by providing an additional 51 voice channels at 16 kbps each. Also, the author has calculated that the B-CDMA mobile transmits on average with 16 dB less power than the GSM mobile, while the CDMA base transmit power per channel would be about 5.5 dB less than the GSM base due to the lower CIR required by the B-CDMA overlay system. >

Patent
15 Apr 1994
TL;DR: In this article, a method of dynamically allocating bandwidth of channels to cells in a communications cellular network according to user demand is proposed, where disjoint groups of cells are formed so as to minimize interference within each group, and a particular channel is assigned to each of the groups.
Abstract: A method of dynamically allocating bandwidth of channels to cells in a communications cellular network according to user demand. Disjoint groups of cells are formed so as to minimize interference within each group, and a particular channel is assigned to each of the groups. The bandwidth of each channel then dynamically allocated by time division to each of the cells in a group according to user demand in each of the cells.

Patent
Eros Gaiani1, Palestini Valerio1
30 Nov 1994
TL;DR: In this paper, power control in a base to mobile link of a mobile radio system is effected by measuring the carrier/interference ratio at each mobile station and transmitting information thereof, usually in terms of the inverse of that ratio, to the base station.
Abstract: Power control in a base to mobile link of a mobile radio system is effected by measuring the carrier/interference ratio at each mobile station and transmitting information thereof, usually in terms of the inverse of that ratio, to the base station. Power is shared between the traffic channels which are active by assigning fractions thereto utilizing a power control factor as the coefficient typical of the channel and depending on the ratios for all of the stations, on the number of active channels, on whether or not there have been variations in the active channels relative to a preceding interval and on the power assigned to the channel in the preceding interval.

Journal ArticleDOI
TL;DR: The mobile user will typically use powerful palmtop or laptop computers that are equipped with wireless communication capability to connect towired networks as discussed by the authors, and this type of computing environment is referred to as mobile computing.
Abstract: munication and wireless LAN technology will make it possible, in the near future, for mobile users to transparently access communication networks from anywhere at any time. The mobile user will typically use powerful palmtop or laptop computers that are equipped with wireless communication capability to connect towired networks. This type of computing environment is referred to as mobile computing. The mobility of the nodes and the small size (in terms of storage space) of the hand-held devices make traditional solutions to network problems such as

Proceedings ArticleDOI
08 Jun 1994
TL;DR: In this paper, a performance analysis in multipath fading radio channels is presented and the average bit error rate (BER) is calculated in dependence of the signal-to-noise ratio for bad urban and hilly terrain channel models, following the COST-207 report.
Abstract: The well known orthogonal frequency division multiplexing (OFDM) multicarrier transmission technique is tailored for a broadband cellular mobile communications system. A performance analysis in multipath fading radio channels is presented and the average bit error rate (BER) is calculated in dependence of the signal-to-noise ratio for bad urban and hilly terrain channel models, following the COST-207 report. Pros and cons for OFDM and code division multiple access (CDMA) techniques are discussed on the basis system robustness, receiver complexity and bandwidth efficiency. >

Journal ArticleDOI
P. Newson1, M. R. Heath1
TL;DR: In this article, the relative capacities of a basic FDMA and CDMA system are examined and 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.
Abstract: 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. >

Patent
20 Jul 1994
TL;DR: In this paper, a method and apparatus for a nation-wide cellular telephone network that controls access to cellular systems is provided in which a cellular system (14) includes a mobile unit (16), transmission towers (18), MTSO (20), and a clearinghouse link (22).
Abstract: A method and apparatus for a nation-wide cellular telephone network that controls access to cellular systems is provided in which a cellular system (14) includes a mobile unit (16), transmission towers (18), MTSO (20), and a clearinghouse link (22). The cellular system (14) is linked to a telecommunications platform (24). The telecommunications platform (24) is linked to central hosts (26 and 28). Calls to or form mobile unit (16) are directed through telecommunications platform (24), thereby reducing opportunities for cellular fraud and reducing cellular air usage charges.

Patent
Je-woo Kim1, Jong-Hyeon Park1
27 Dec 1994
TL;DR: In this article, a DS/SS-CDMA system with a PN code unique to each mobile station is described, where the PN codes are modulated by the data and the identification frequency is shifted by an identification frequency to output a spread spectrum signal.
Abstract: Disclosed is a link access apparatus of a CDMA system using a DS/SS communication method, and more particularly an up-link access apparatus which overcomes a near/far problem occurring when mobile stations and a base station perform multiple access communication using code division. An up-link access apparatus in a DS/SS-CDMA system has a transmitter for mixing data to be transmitted to a base station with a PN code unique to that mobile station to thereby PN code modulate the data. The transmitter then mixes the PN code modulated data with a carrier having a frequency that is shifted by an identification frequency to thereby output a spread spectrum signal. The apparatus further includes a receiver for mixing a demodulation carrier made up of the PN code and the identification frequency with the spread spectrum signal from the transmitter to thereby output a mixed signal. The mixed signal is then integrated according to a period having a reciprocal corresponding to the identification frequency, demodulated and output as a digital signal.

Patent
07 Mar 1994
TL;DR: In this paper, a cellular mobile radio system is arranged to operate in accordance with a packet reservation multiple access protocol, wherein at least one time slot in each frame is designated for the transmission of access contention data which includes a field reserved for data specifying a number of information slots required by a mobile unit.
Abstract: A cellular mobile radio system, which is arranged to operate in accordance with a packet reservation multiple access protocol, wherein at least one time slot in each frame is designated for the transmission of access contention data which includes a field reserved for data specifying a number of information slots required by a mobile unit, and which system includes a base station adapted for operation such that consequent upon receipt of data in the said reserved field the base station is arranged to respond by allocating available slots to satisfy the requirement of the mobile unit.

Patent
12 Oct 1994
TL;DR: In this article, the first mobile telephone roams to the satellite system, and the private branch exchange transfers information of the mobile telephone for roaming to a satellite ground station via the public network before changing communication lines.
Abstract: The mobile communication system comprising a public network, a private system connected to the public network and a satellite system connected to the public network. The private system includes a radio base station which has a communication zone, a first mobile telephone which is able to communicate with the radio base station in the communication zone and is able to communicate with the satellite system, and a private branch exchange connected to both the public network and the radio base station which performs communication processes between the public network and the private system. The radio base station and the first mobile telephone are able to process a private protocol and a public protocol. The satellite system includes a satellite station which relays radio waves on a satellite line, and a satellite ground station which is able to communicate with the satellite station and is connected to the public network. When the first mobile telephone roams to the satellite system, the private branch exchange transfers information of the first mobile telephone for roaming to the satellite ground station via the public network before changing communication lines.

Proceedings ArticleDOI
08 Jun 1994
TL;DR: Results of a GSM based case study are given that are applicable to cellular radio systems of the 3rd generation like MBS and UMTS and a hybrid dynamic strategy is proposed for a public MBS.
Abstract: Several location management strategies applicable in cellular networks are presented. Analytical modelling approaches for signalling cost minimisation are discussed. Results of a GSM based case study are given that are applicable to cellular radio systems of the 3rd generation like MBS and UMTS. A hybrid dynamic strategy is proposed for a public MBS. >

Patent
29 Sep 1994
TL;DR: In this article, the authors proposed a power control scheme for a mobile communication system capable of reducing interference among mobile stations and increasing a subscriber capacity of the system. But the scheme requires the base station and the mobile station to share the same power control data, and the power required to adjust the measurement value to a target level according to a number of base stations simultaneously in communication with the mobile stations.
Abstract: A base station and a mobile station in a mobile communication system capable of reducing interference among mobile stations and increasing a subscriber capacity of the system. The base station has a unit for measuring a measurement value for at least one of a receiving level and an interference ratio level of the mobile station transmission signals, and a unit for producing a mobile station transmission power control data specifying a mobile station transmission power required in adjusting the measurement value to a target level according to a number of base stations simultaneously in communication with the mobile station. The mobile station has a unit for measuring a measurement value for at least one of a receiving level and an interference ratio level of the base station transmission signals, and a unit for producing a base station transmission power control data specifying a base station transmission power required in adjusting the measurement value to a target level according to a number of base stations simultaneously in communication with the mobile station.

Patent
Viet Anh Nguyen1
01 Apr 1994
TL;DR: In this article, the local access and transport area identification number (LATAID) of the area within which both the A-party and B-party of a call are located is indicated within all roamer routing messages.
Abstract: The local access and transport area identification number (LATAID) of the area within which both the A- party and B-party of a call are located is indicated within all roamer routing messages. This information enables automatic call setup within a cellular network in the most cost effective manner which still complies with the interLATA carrier regulations.

Patent
02 Dec 1994
TL;DR: In this article, a radio frequency test loop is established between a predetermined downlink channel of a base station transmitter and a predetermined uplink channel of the base station receiver in real time.
Abstract: In a base station of a mobile cellular telephone system of the type having time division multiple access (TDMA) channels, a radio frequency test loop is established between a predetermined downlink channel of a base station transmitter and a predetermined uplink channel of a base station receiver. The test loop is in real time, thereby eliminating the time offset of the radio channels used for communications. The radio frequency test loop includes a circuit for transposing the frequency of the carrier signal from the transmitter to a frequency that can be received by the receiver. The signal having the transposed frequency is used in tests for determining values such as bit error rate (BER), transmission signal level, or reception sensitivity.

Patent
K. Raj Sanmugam1
10 Nov 1994
TL;DR: In this article, a method for detecting fraud in a cellular radio telephone system is proposed, where the system detects a multiple access from a mobile station, when an activity collision occurs, when the system receives a premature registration from the mobile station and when auditing or operator-initiated locating of mobile station reveals the existence of the mobile stations in two locations simultaneously, or tracing of mobile subscriber activity reveals unusual activity.
Abstract: A method for detecting fraud in a cellular radio telephone system. Fraud is suspected when the system detects a multiple access from a mobile station, when an activity collision occurs, when the system receives a premature registration from the mobile station, when auditing or operator-initiated locating of the mobile station reveals the existence of the mobile station in two locations simultaneously, or when tracing of mobile subscriber activity reveals unusual activity.

Patent
Eizenhofer Alfons1
17 Jun 1994
TL;DR: In this paper, a process for locating mobile stations in a cellular mobile radio network with several spatially distributed fixed base stations associated each to several cells and several mobile stations is described.
Abstract: A process is disclosed for locating mobile stations in a cellular mobile radio network with several spatially distributed fixed base stations associated each to several cells and several mobile stations. The network has storage means which contain information about the identity of the mobile stations and about the cells in which the individual mobile stations were last signalled. In order to locate a mobile station in as flexible as possible a manner, but also if required as precisely as possible, the information in the storage means is used for approximately locating the searched-for mobile station and at least one position finding is carried out in order to more precisely locate the mobile station. A cellular mobile radio network for carrying out this process is characterised in that the individual base stations are in communication each with a position finder and that the mobile radio network has a locating central office in communication with all position finders.

Proceedings ArticleDOI
08 Jun 1994
TL;DR: In the paper, a software simulator is described that allows the design of N and H considering the handover occurrence rate and the probability of unnecessary handover, and Rectangular and exponential averaging window shapes have been considered.
Abstract: The event of handing over a call from one base station to another in a cellular mobile radio network requests the cooperation of many system elements, with a consequent load of signalling traffic. Therefore, accurate design of handover procedures must be ensured, to avoid the occurrence of forced terminations and unnecessary handovers. This can be pursued by averaging the received power samples with a window of suitable shape and length, N, and by introducing a hysteresis cycle with margin H (dB). In the paper, a software simulator is described that allows the design of N and H considering the handover occurrence rate and the probability of unnecessary handover. Rectangular and exponential averaging window shapes have been considered. >

Journal ArticleDOI
TL;DR: This paper considers the problem of balancing uniformly the blocking probability throughout the cell offering a fair treatment to the whole area within the cell, by controlling the allocation to the different channel layers.
Abstract: Reuse partitioning is a technique for providing more efficient spectrum reuse in cellular radio systems. A cell in such a system is divided into concentric zones, each associated with an overlaid cell plan. Calls that arise in the periphery of the cell have fewer channels in their availability than those arising close to the base station and therefore they experience higher blocking rates. In this paper we consider the problem of balancing uniformly the blocking probability throughout the cell offering a fair treatment to the whole area within the cell, by controlling the allocation to the different channel layers. A policy that minimizes the maximum blocking probability experienced at any location of the cell is identified and is shown to be of threshold type. The policy satisfies any achievable constraint on the blocking rate uniformly throughout the cell. An adaptive scheme that adjusts the threshold based on estimates of the blocking probabilities in the different zones of the cell is proposed. This scheme tracks the optimal threshold effectively without any knowledge of the traffic parameters. Simulation study shows that substantial capacity improvements are achieved by the application of the optimal channel assignment policy, over the uncontrolled system. >

Patent
Toshifumi Sato1
06 Dec 1994
TL;DR: In this paper, the radio output signal obtained by the TDMA and CDMA is filtered or inversely spread to remove interference and noise from the radio outputs by the use of an adaptive filter which has taps controlled by an adaptive controller.
Abstract: In a communication system from a mobile station to a base station, a transmitter of the mobile station subjects a sequence of transmission signals to both of time division multiple access (TDMA) and code division multiple access (CDMA) to produce a radio output signal located in a time slot of a frame. The radio output signal obtained by the TDMA and CDMA is filtered or inversely spread to remove interference and noise from the radio output signal by the use of an adaptive filter which has taps controlled by an adaptive controller.

Patent
03 Mar 1994
TL;DR: A secure radio personal communication system and method includes a base station which relays cellular verification signals between a wide area cellular network and a cellular terminal via the wire telephone network as discussed by the authors.
Abstract: A secure radio personal communication system and method includes a base station which relays cellular verification signals between a wide area cellular network and a cellular terminal via the wire telephone network. Thus, cellular telephone calls which are routed to a cellular terminal via a base station, when the cellular terminal is within a local region covered by the base station, may be exchanged between the cellular network and cellular terminal over the wire telephone network. Calls from the wide area cellular network which are routed through the base station can thus employ the same security systems and methods which are employed by the wide area cellular network. Signals between the base station and the cellular terminal are preferably exchanged when the cellular terminal is parked in the base station. Verification and encryption signals may be exchanged. The same signals may be used for enhanced security when the base station is relaying wire network calls to the cellular terminal when the cellular terminal is in the local region. Alternatively, separate verification and encryption protocols may be used.