Showing papers on "Handover published in 1990"

Mobile assisted handoff

Abstract: The invention relates to a method for communication and handoff in a cellular mobile radio system and a base station and a mobile station for communication and handoff in such a system, in which time slot identifier codes are transmitted in bursts in times slots in frames of radio channels used for time division communication channels, the time slot identifier codes being indicative of burst time slot in a frame but not of transmitter or receiver entity or radio channel, the time slot identifier codes being used for burst synchronization and determining bursts the signal strength of which to be measured for the purpose of possible handoff.

Protocol and transceiver for cordless/cellular telephone service

Abstract: A communications system suitable for use with hand portable radio telephones operating in a cellular mode, the typical cell size being between 500 m and 3 km radius. Each cell comprising at least one primary or base station (10) connected to the PSTN and one or more secondary portable stations (14) which are capable of roaming within the cell. Radio communication between the stations can be initiated by either station. Each primary and secondary station having radio transceiving means for time division duplex communication between the stations, a codec operating at 32 kbits/second or 11.4 kbits/second and means for transmitting digitised speech in accordance with a framed structure comprising 3 full rate or 6 half rate channels per carriers, the carrier being modulated at a carrier bit rate of substantially 270.8333 kbits/second. Provision is made for internal and external handover, if required. Also, if required, the secondary station can be constructed to operate in the DECT system as well as in the above described system.

Control strategy for reuse system assignments and handoff

Abstract: Disclosed is a method of selecting a relatively high reliability signal path between a mobile communication unit and a number of possible base sites.

Method of maintaining an established connection in a mobile radio system comprising both analog and digital radio channels

Abstract: The invention relates to a method in a mobile radio system having both digital and analog radio channels. An object of the invention is that a connection established on a digital radio channel often shall be possible to maintain even when the time dispersion on available digital radio channels exceeds the designed maximum time dispersion of equalizers in receiving stations. According the invention equalizers in the receivers of the system may be designed for a smaller maximum time dispersion than the total time dispersion the whole system shall be capable to handle. Instead handoff is made to an other channel when the time dispersion of a used digital channel tends to become too big. When an other digital radio channel with low time dispersion is available handoff is preferably done to this channel. Alternatively or in the absence of such a digital radio channel handoff is performed to an analog radio channel.

Evaluation of a proposed handover algorithm for the GSM cellular system

Abstract: In the future pan-European cellular mobile telephone system of the 'Groupe Speciale Mobile (GSM)' of CEPT, the decision whether a handover shall happen can be based on a set of variables whose values are measured in the system. Some performance measures for handover algorithms are reported, and a simulation tool for the evaluation of a proposed GSM handover algorithm is described. Some results of the evaluation are included. Special attention is given to the time over which the sampled values are averaged. The evaluation is based on a model of a cellular network, where the radio propagation characteristics are assumed to follow a lognormal law with Rayleigh fading. For given routes of mobiles, measurements of the received signal level are obtained by simulation and fed to the handover algorithm. >

Handover criteria for city microcellular radio systems

Abstract: 1700 MHz attenuation and bit error rate (BER) measurements were conducted at the center of a major urban area in southern England in order to compile a radio propagation and BER database for handover criteria study in city microcellular radio systems. The focus of the experiments was to provide realistic data for handover simulation in typical city microcell environments, thus minimizing inaccuracies due to the inadequacies in propagation modeling. Results revealed the path loss followed the inverse third to fourth power law in majority of the cases using simple regression fitting. The short-term signal fading statistics varied with Rice factors in excess of ten down to zero, as the distance between the mobile unit and the microcellular base station increased. Computer simulation indicated that both RSSI (received signal strength indicator) and BER could be used as handover criteria. The optimal threshold level for handover request, however, differed from location to location. >

Traffic capacity of cellular mobile communications systems

Abstract: In a cellular mobile communication system, the traffic capacity of the system is an important quantity, and depends on the way that channels are allocated to calls. Many channel allocation algorithms have been proposed, and this paper makes a direct comparison of some of them. Specifically, the operating regimes considered are fixed channel assignment, dynamic channel assignment, directed retry, and directed handoff. The main conclusion is that directed handoff gives a strong gain in traffic capacity and traffic adaptability for these systems. The paper also discusses some of the factors affecting the future development of mobile communication systems.

Cellular radio system having reduced handover disruption and method for use in such a system

Abstract: A handover technique in a cellular radio communication system (100) for handing over a radio (102) from a first channel in a first cell to a second channel in a second cell, the technique comprising generating a fill-in message extrapolated from a message of the radio on the first channel and communicating the fill-in message when the radio has ceased communicating on the first channel; and terminating the fill-in message when the radio begins communicating on the second channel, thereby reducing handover disruption. The messages may be digitized audio messages. A timer (110, 118) may be employed to allow the fill-in message to terminate at substantially the same time as the radio begins communicating on the second channel. Alternatively, the fill-in message may be directly terminated (FIG. 2) in response to the radio beginning to communicate on the second channel. If the messages are data messages, no fill-in message is generated and the handover is completed directly (FIG. 2) in response to the radio beginning to communicate on the second channel.

Microcellular mobile radio systems

Abstract: The long-term target is a universal system which will provide the man-in-the-street with integrated access to cellular, cordless, wireless PABX, paging and private mobile radio (PMR) type services, perhaps causing the biggest change in social habits and telecommunications service since Alexander Graham Bell's original invention of the telephone. The paper addresses some of the design aspects of microcellular networks, including topics such as cell types, handover issues, cellular infrastructure and interconnection, and radio link management

Method of choosing a base station, a radio channel and a time slot at a mobile station

Abstract: In a cellular mobile radio system a method of choosing at a mobile station an appropriate base station and time slot on a time division multiplexed radio channel for the purpose of call set up or handover, wherein each base station transmits in one time slot of a predetermined control radio channel and, at least once during a multiframe, in each communication radio channel time slot used by the base station for calls, roaming signals comprising in­formation on identity of transmitting base station and communi­cation radio channels available at transmitting base station, the mobile scanning the control and communication channels and when desirous of call set up or handover selecting a base station and a time slot on a communication channel, the mobile desirous of call set up or handover transmitting to the choosen base information on mobile identity and the choosen communication channel time slot.

Adaptive algorithm for variable teletraffic demand in highway microcells

Abstract: An adaptive algorithm is presented which ensures that the probability of a mobile radio call in progress being forced to terminate during handover in highway microcells is always small, even in the presence of high new call request rates.

Experimental digital cellular system for microcellular handoff

Abstract: An experimental digital cellular system composed of a private branch exchange (PBX)-based MSC (mobile switching center), three base stations, two mobile stations, and a radio channel simulator, is developed. The system uses a mobile originated handoff process; i.e. a mobile station requests a handoff to the MSC based on signal strength from surrounding base stations. All control channels are multiplexed on the same carrier so that mobile stations can monitor signal strength quickly. Experimental results show that a handoff decision can be made within a second, even under slow fading (such as walking speed), which agrees with the theoretical calculation very well. It is shown that the whole handoff procedure works reliably under a typical microcell propagation condition. >

Digital European Cordless Telecommunications system blind slot algorithm evaluation results

Abstract: The use of extra system information, which may be available but is not mandatory within the latest specification to aid the system with link establishments and handover procedures, is discussed. A model of the Digital European Cordless Telecommunications (DECT) system, which could be considered a simple cell system in a high-density office environment, is described. Experimental results indicate that the introduction of the fast algorithm in terminal equipment reduces the time taken for a link to be established. The model confirms that the inclusion of blind slot algorithms in the design of DECT portables call considerably reduce link establishment times, compared with the simplest algorithms possible within the CI specifications. >

Method for synchronization in a cellular mobile radio system

Abstract: The invention relates to a method for communication and handoff in a cellular mobile radio system and a base station and a mobile station for communication and handoff in such a system, in which time slot identifier codes are transmitted in bursts in time slots in frames of radio channels used for time division communication channels, the time slot identifier codes being indicative of burst time slot in a frame but not of transmitter or receiver entity or radio channel, the time slot identifier codes being used for burst synchronization and determining bursts the signal strength of which to be measured for the purpose of possible handoff.

Narrowband FM cellular system

Abstract: The voice and data transmission parameters of a spectrally-efficient analog frequency division multiple access (FDMA) cellular system with 12.5 kHz channel assignments are described. Low-speed 100 bit/s Manchester data is transmitted during voice activity and provides channel control. In addition, 200 bit/s baseband data patterns support channel supervision. The use of this subaudible signaling method has yielded improved system operation. Eliminating the high-frequency supervisory audio tone has reduced adjacent-channel interference and has allowed increased voice deviation. Using the low-speed data for control messages does not require interruption of the voice activity. The handoff and disconnect protocols have improved falsing protection over current systems. >

Establishing requirements for homing applications

Abstract: Miss distance performance has generally required a significant simulation effort. Missile simulation models generally require substantial modification to adapt them to a new system concept or to make major changes within the interceptor design. By conducting a sensitivity analysis, an alternate approach is presented to assist the analysis of the the miss and establishing the system level requirements. The analysis section of this paper analyzes each of the three miss components aimpoint determination, measurement accuracy, and interceptor dynamic response. Observation and sample calculations are presented for a maneuvering and a non-maneuvering target. Once the miss requirement has been analytically determined as a function P, then the analytical process can be worked backwards to determine the range and range rate uncertainty requirement at handover, or if at the start of end game engagement, the total angular accuracy (in a r.s.s sense) of the system and required data rate may be determined.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A method for synchronizing a mobile unit and a base station

Abstract: The invention relates to a method for communication and handoff in a cellular mobile radio system and a base station and a mobile station for communication and handoff in such a system, in which time slot identifier codes are transmitted in bursts in times slots in frames of radio channels used for time division communication channels, the time slot identifier codes being indicative of burst time slot in a frame but not of transmitter or receiver entity or radio channel, the time slot identifier codes being used for burst synchronization and determining bursts the signal strength of which to be measured for the purpose of possible handoff.