Abstract: According to a handoff method for a cellular digital mobile communication system, a communication test of a new channel is performed by utilizing a free time of a time-divisionally multiplexed channel. A mobile station of this invention includes a communication circuit for performing communication by using a time-divisionally multiplexed channel, a switching circuit for connecting a new channel during a free time of the time-divisionally multiplexed channel, and a communication test circuit for performing a communication test when the switching circuit is connected to the new channel.

Abstract: An improved cellular telephone communication system is described having operational steps which prevent a call from being dropped due to a radiotelephone (130) not receiving a handoff instruction from its host base site (115). The system includes a switch controller (122) for determining that the radiotelephone requires a handoff from a first base site coverage area (110) to a second base site coverage area (112) and for communicating a handoff message to the associated first (115) and second base site equipment (119). The first base site equipment then transmits the handoff message to the radiotelephone. If the radiotelephone does not receive the message, it determines that the call has been lost, siezes a signalling channel from the second base site, and requests, via the second base site a call reconnection by transmitting a special message. The second base site then informs the radiotelephone of the handoff instruction and the handoff is completed with a successful reconnection of the call.

Abstract: Simulations show that adaptive channel allocation significantly increases the capacity of a system as compared to traditional fixed channel allocation. With 90 channels it is possible to carry 10 erlangs per cell, with a blocking of 2.4% at initial access, and with a neglectable number of calls lost during handover. This is estimated to be almost twice the capacity of a system with fixed channel allocation. Two different algorithms are studied. In the first algorithm all channels can be used both at call setup and after a handover, while in the second algorithm 10% of the channels are reserved for hand-over only, in order to minimize the number of lost calls. >

Abstract: A handoff control process, which can handle frequent cell-boundary crossings by mobile radio users in microcellular systems, is presented. Handoff determination criteria are investigated under microcellular propagation models. As a result, it is shown that relative field strength measurement should be applied because of its almost twice higher spectrum efficiency than that of relative distance measurement. In application, measurement frequency greatly increases due to not only cell size reduction but also microcellular propagation characteristics. In order to solve this problem, a mobile-station-originated handoff process is proposed. This process becomes feasible in a TDMA (time-division multiple-access) system because mobile stations can be easily equipped with a measurement function. >

Abstract: The network functions of the GSM (CEPT's Groupe Special Mobile) system are discussed. They can be divided into four broad categories: network functions required for basic service provision (call handling, subscriber authentication, emergency call, and supplementary services); network functions required for cellular operation (location registration and handover); additional network functions for call handling (queueing, off air call setup, security-related services); and operation and maintenance-oriented network functions. Several of these functions are unique for mobile networks, e.g., all the functions related to cellular operation. Most of the other functions require different or additional implementation in mobile networks as compared to fixed networks. >

Abstract: Consideration is given to the hand-over rate in future cellular radio communications systems in which a much higher number of subscribers and smaller cell sizes than in currently operating systems are to be expected. Three models are used to estimate future hand-over rates. The first is valid for simple roads, the second works with the area of a cell, and the third is a simulation in which information about the road net in the cell and the traffic behaviour of the vehicles is taken into account. The results obtained using all three models show that mobile subscribers will cross cell boundaries more often, so the number of hand-overs per second that a base station of the fixed network has to handle will be much higher than in current mobile telephone systems. >

Abstract: Digital switching controls for integrated-services digital mobile radio communications are discussed. The digital radio networks controls radio terminals by way of the radio multiaccess subscriber line. The network also handles tracking switching for call setup and handover for voice and data communications. The basic concepts of the signal reference model, layer configuration, and protocol structure of the user/network interface are described. >

Abstract: The author proposes a mobile ISDN (integrated services digital network) protocol architecture, which is capable of supporting packet communication services Connections in layers two and three for transporting user packet data are defined between a mobile terminal and a packet handler (PH) by means of a cell site and a switching function, which is installed between the cell site and the PH This architecture enables packet data loss, which has occurred during handoff, can be recovered after the mobile terminal retunes to a radio channel, using the existing layer two-packet recovery procedure No matter how many times communication path changeovers are required, the mobile terminal can continuously communicate with the originally connected PH It is shown that handoff does not affect the existing layer two and higher layer protocols and that the same handoff procedure can be used for both packet- and circuit-switched communications >