MXPA00000081A - Method of processing a call while switching site affiliation in a radio communication system - Google Patents

Abstract

A subscriber unit handles incoming calls routed through an old server site while in the process of switching site affiliation to a new server site (500). The subscriber unit initiates the switching of site affiliation (510), and during the process, alternates between receiving communication from the new server site (520) and receiving communication from the old server site to monitor for an incoming call (530). When an incoming call routed through the old server site is detected (540), the subscriber unit aborts or suspends the switching process and accepts the incoming call through the old server site (551, 552).

Description

METHOD FOR PROCESSING A CALL WHILE THE MEMBERSHIP OF THE SITE IS CHANGED A RADIOCOMMUNICATION SYSTEM FIELD OF THE INVENTION This invention relates, in general, to radiocommunication systems and, more particularly, to the handling of incoming calls while the affiliation between server sites of a radiocommunication system is switched.

BACKGROUND OF THE INVENTION Geographically dispersed transceiver sites are often employed in two-way radio communication systems to support subscribers operating in a wide coverage area. Normally, the sites are arranged so that each provides coverage for a particular geographic region, which may have some overlap. A subscriber unit is interfaced with a radio communication system through a particular transceiver site, referred to herein as a server site or a cell site. When a subscriber unit moves from one location to another, it may be advantageous to switch the site affiliation, for example with a neighboring site, to ensure a high quality communication link. Before switching the affiliation of P1015 / 00MX site, normally a subscriber unit monitors the communications coming from potential server sites in order to select a suitable site server site. A particular problem may arise when a subscribing unit initiates the switching of affiliation from one site to another, where there is a possibility of losing incoming calls. Consider a subscriber unit that is affiliated with a first site in a radio communication system. The radio system routes the calls destined to the subscribing unit via that site. The subscribing unit can switch affiliation with a second site by obtaining particular information from the second site for establishment or registration purposes, and register affiliation with the second site. After detection of this change in site affiliation, the radio system is alerted to route calls destined to the subscribing unit through the second site. Although the process of switching site affiliation can not take more than a few seconds, there is a problem in previous systems that employ this method in which calls can be lost during the transition from the first site to the second site. It is desired to provide an improved method to change the site affiliation that P1015 / 00MX reduce the potential for missed calls. Therefore, a new method is necessary to process a call while site affiliation is switched in a radio communication system.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a representation of a radio communication system operating in accordance with the present invention. Figure 2 is a block diagram of a subscriber unit, in accordance with the present invention. Figure 3 is a block representation of a timeslot multiple access protocol threshold in accordance with the present invention. Figure 4 is a block diagram of control channels corresponding to the first and second cellular sites, and which highlights the alternating monitoring of the time intervals through the control channels to detect incoming calls, in accordance with the present invention. Figure 5 is a summary of the procedures used by the subscriber unit to monitor incoming calls while site affiliation is switched, in accordance with the present invention. Figure 6 is a block diagram of P1015 / 00MX control channels corresponding to first and second cellular sites that show an alternative to monitor time intervals through the control channels to detect incoming calls, in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODE The present invention provides a method for being used by a subscriber unit when the transition from a first site to a second site is made to avoid the loss of incoming calls routed to the first site during the transition period. In a particular way, when the subscriber unit executes a procedure to effect a transition of cellular affiliation from a first cellular site to a second cellular site, this unit alternates between receiving communication from the second cellular site and receiving communication from the first cellular site to monitor an incoming call during the transition. Preferably, if an incoming call is detected while the site membership is being switched, the subscriber unit aborts or suspends the procedure for switching the site membership, accepts the incoming call through the first site and later transfers that call, if if necessary, to the second site. In the preferred mode, the first site and the second site have P1015 / 00 X first and second control channels synchronized, respectively, and the control channels have broadcast intervals and control data intervals. Incoming calls to the first site are detected by monitoring the control data intervals of the first control channel, in the interval between monitoring broadcast intervals of the second control channel. Figure 1 shows a block diagram of a radio communication system 100, which operates in accordance with the present invention. In the preferred embodiment, the communication system 100 provides a radio network infrastructure that supports telephone, dispatch, data, and other communication services over a wireless network. Wireless communication is presented over the network using a time division multiple access (TDMA) protocol, which is described in more detail below. The system 100 includes a system controller site 110, coupled communication cellular sites 125, 135, 145 and subscriber units 126, 136. The controller 110 includes computer and communication equipment that implement management functions for the radio communication system 100 . For example, the controller 110 manages and coordinates the access of P1015 / 00MX communication to and from, the subscriber unit 126, 136 through the sites 125, 135, 145 and distributes the communication resources in each site. Additionally, the controller 110 coordinates the communication between the participants of the communication system and entities (not shown) external to the system 100, such as, for example, with a public switched telephone network, and the like. The system 100 has a coverage area that includes separate coverage regions 120, 130, 140, which normally overlap (the overlap is not shown). Each 'coverage region is supported by one of the cellular sites 125, 135, 145. The cellular sites 125, 135, 145 preferably comprise radio transceivers that function as base stations. Cell sites 125, 135, 145 are configured to support subscriber communication within their respective coverage regions. The subscriber units 126, 136 are two-way wireless devices, for example portable two-way radio or mobile transceivers, or another electronic device with a wireless communication portion. Generally, a subscriber unit operates within the radio system 100 through an affiliated site using communication resources, such as wireless frequencies, distributed for use by that site. The affiliate site is referred to here as a server site or P1015 / 00 X server cellular site. When a subscriber unit moves from the coverage area of a first site to the coverage area of a second site, the site affiliation can be transferred from the first site to the second site to maintain a communication link. This process is known as handover or transfer when the transfer occurs during a call in process. Transfer protocols for TDMA systems are known in the art as exemplified in U.S. Patent No. 5,159,593 issued to D'Amico, et al. on October 27, 1992 for Channel Acquisition and Hand-Off Method and Apparatus for a TDMA Communication System. The subscribing unit may choose to transfer the site affiliation, even when there is no call in process, since factors such as: received signal strength, signal reception quality, user preference and other parameters, may dictate that a different site be used . Normally, the subscriber unit maintains a monitoring list or a neighbor cell list that contains information necessary to mount neighboring sites to determine potential server sites. When a particular server site is selected as a new server site, the subscribing unit acquires startup information from the new server site and registers the affiliation with that site.

P1015 / 00MX Figure 2 is a block diagram of a subscriber unit 200, in accordance with the present invention. The subscriber units 126, 136 of Figure 1 are similar in construction. A controller 201 provides operational control for the subscriber unit 200 by executing well-known instructions that are stored in a coupled memory 210. A transmitter 212 is operably coupled with the controller 201, and with an antenna 216 through a transmit switch 214. / reception (T / R). The T / R switch 214 is selectively coupled to the transmitter 212 by means of the controller 201 to allow the transmission of signals through the antenna 216. For receiving operations, the antenna 216 that is coupled sends signals through the switch T / R 214 to the receiver 204. The receiver 204 decodes the received signals and presents those signals to the controller 201 for processing. A signal strength indicator (RSSI) signal is generated by an RSSI circuit 208, which is based at least in part, on the signal strength corresponding to the received signals. The RSSI circuit 208 uses an analog-to-digital converter 206 to present a digital RSSI to the controller 201. Using the RSSI signal, the controller 201 determines the information concerning the proximity of the site of P1015 / 00MX the subscriber unit 200. In accordance with the present invention, the subscriber unit 200 incorporates a method for switching the site membership 225 which is stored in the memory 210. The method 225 allows to monitor incoming calls routed through the site. old, while start information is received from the new site. As mentioned above, the system operates using a TDMA protocol. In accordance with the TDMA protocol, a communication resource, such as a wireless carrier frequency, is divided into thresholds, and the thresholds are subdivided into time intervals. Figure 3 shows a block representation 300 of a TDMA threshold. At this particular TDMA threshold 301, the first time slot 303 is designated as a control interval wherein the resource management information is communicated. In a typical implementation, there is a frequent communication activity in the control interval 303. The communication in the control interval includes information, identification information and the like. Other intervals 305, 307 are designated as transmission and reception intervals. In some implementations, the transmission and reception intervals are implemented at separate intervals. Different communication units can share a threshold, P1015 / 00MX each with its designated interval for transmission or reception operations. With this arrangement, a subscriber unit can be coupled in communications with another subscriber unit or with other communications during its transmission and reception intervals, but generally, it has time between reception and operation operations (dead time), and during periods of communication inactivity to monitor and for other purposes. In the preferred embodiment, the cellular sites 125, 135, 145 each operate at least one control channel that is organized using TDMA principles. Figure 4 is a timing diagram 400 illustrating the monitoring of TDMA time slots for control channels 420, 410 corresponding to first and second server sites, such as cellular sites 125, 135, in accordance with the present invention. The control channels 420, 410 are operated by the first and second sites, respectively, and have synchronized time intervals, among which are included: synchronized broadcast channel intervals 412, 422 and common control channel intervals 414, 424, 416 , 426 synchronized. The broadcast intervals 412, 422 are used by the serving sites to broadcast cellular data, i.e., to communicate cellular data information required by a subscribing unit for purposes of P1015 / 00MX start and registration. As is typical with TDMA systems, these broadcast intervals 412, 422 are communication intervals temporarily separated from the respective control channels 410, 420. The control intervals 414, 424, 416, 426 are used for subscriber interaction, i.e. the communication of control data between a subscribing unit and its corresponding server site. The control intervals are temporarily separated communication intervals that are interspersed between the diffusion intervals. Figure 5 is a flowchart 500 summarizing the procedure used by the subscriber unit when site affiliation is switched between a first and a second server site of a radio communication system, in accordance with the present invention. Referring to Figure 4 and Figure 5, a subscriber unit affiliated with a first server site initiates a procedure for switching the site membership from the first server site to a second server site, step 510. In the preferred embodiment, the decision of switching the site membership is made when the subscriber unit is in null mode, ie, during a period of time when the subscriber unit is not coupled in a call in process. As part of the switching process, the subscriber unit receives start data P1015 / 00MX from the second cell site at the diffusion intervals 412 of the second control channel 410, step 520. The start data is received at successive 412 diffusion intervals of the second control channel for a period of time until all the necessary information. In accordance with the present invention, the subscriber unit monitors incoming calls routed through the first cellular site during the period of time consumed by the switching process, i.e., the transition period. As such, the subscriber unit monitors the control intervals 424, 426 of the first control channel 420 for communication to detect an incoming call received by the first cellular site during the transition period, step 530. When an incoming call received by the first cellular site is detected during the transition period, step 540, the procedure for switching the site membership, preferably aborted or suspended, step 551, and the incoming call is accepted through communication with the first cell site, step 552 If necessary, the incoming call is transferred from the first cell site to the second site, for continued processing, executing or initiating a handover or other procedure to transfer calls in process, step 553. This transfer can be presented immediately P1015 / 00MX after accepting the call. When no incoming call is detected, the procedure for switching the site membership is completed and the subscribing unit notifies the radiocommunication system of the change in site membership through the registration with the new site, steps 540, 561, 562. The Figure 6 is a timing diagram 600 illustrating an alternative embodiment for monitoring control channels 420, 410 corresponding to first and second cellular sites, in accordance with the present invention. As in the above, the subscriber unit periodically receives start-up data from the second cell site during the procedure for switching the site affiliation via the broadcast intervals 412. However, here the subscriber unit monitors alternately the control intervals 424 of the first control channel 420 and the control intervals 416 of the second control channel 410 to detect whether an incoming call is received in the first cellular site or in the second cellular site. Otherwise, the procedure for switching site affiliation is as described with respect to Figure 4 and Figure 5. Accordingly, in a radio communication system, a procedure is provided for a subscriber unit to handle a call P1015 / 00 X incoming routed through a first cell site during an affiliation switching transition from the first cell site to a second cell site. The subscriber unit receives start data from the second cell site at communication intervals temporarily separated from the second cell site control channel. In particular, the communication intervals corresponding to a control channel of the first cellular site are monitored in the interval of communication intervals temporarily separated from the second control channel, to detect an incoming call received by the first cellular site. In one embodiment, the subscriber unit alternately receives information from a first cell site and from a second cell site, at time intervals of control data that are sandwiched between the successive broadcast time intervals to monitor an incoming call received. for the first cell site or for the second cell site during the transition. The present invention provides significant advantages over the prior art. Using spaces in receiving communication from a new site during a registration process to monitor incoming calls routed through the old site reduces the likelihood of incoming calls. This technique is particularly useful in P1015 / 00 X TDMA systems in which the registration data are communicated using control intervals in synchronous control channels.

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Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. In a subscriber unit of a radio communication system having first and second cellular sites that operate in first and second control channels, respectively, a method to handle an incoming call while affiliating is switched from the first cellular site to the second cellular site, the method comprising the steps of: receiving start data from the second site cell in communication intervals temporarily separated from the second control channel, as part of a process for switching the affiliation of the first cell site to the second cell site; and monitoring the communication from the first cell site at communication intervals of the first control channel, in the interval between the communication intervals temporarily separated from the second control channel, to detect an incoming call received by the first cell site. The method according to claim 1, wherein the first and second control channels each comprise diffusion channel intervals and common control channel intervals interspersed between the P1O15 / 00MX diffusion channel ranges, and wherein the alternately receiving and monitoring steps further comprise the steps of: receiving start data in the diffusion channel ranges of the second cell site; and monitoring incoming call data in the common control channel intervals of the first cell site. The method according to claim 2, wherein the receiving and monitoring steps further comprise the steps of; alternately monitor incoming call data in the common control channel range of the first cellular site and in the common control channel range of the second cellular site. 4. In a subscriber unit of a radio communication system having first and second cellular sites, a method comprising the steps of: executing a method for effecting a transition of site affiliation from a first cell site to a second cell site; and alternate between receiving communication from the second cell site and receiving communication from the first cell site to monitor an incoming call during the transition. 5. The method according to claim 4, which P1015 / 00MX further comprises the steps of: detecting an incoming call at the first cellular site during the transition, and following detection: communicating with the first cellular site to accept the incoming call; and initiating the transfer of the incoming call from the first cell site to the second cell site to continue the processing of the incoming call immediately after accepting the incoming call. The method according to claim 4, wherein the first and second cell sites have diffusion time intervals synchronized with one or more synchronized control data time slots that are sandwiched between the diffusion time slots, and in wherein the step of alternating comprises the steps of: receiving information from the second cell site in successive broadcast time intervals; and receiving information from the first cell site at time intervals of control data that are sandwiched between successive broadcast time intervals to monitor an incoming call received by the first cell site during the transition. 7. The method according to claim 4, in P1015 / 00MX wherein the first and second cellular sites have broadcast time intervals synchronized with one or more time slots of synchronized control data that are sandwiched between the broadcast time slots, and wherein the alternating step comprises the steps of: receiving information from the second cell site in successive intervals of diffusion time; and alternatively receive information from the first cell site and from the second cell site in time intervals of control data that are interspersed between the successive intervals of broadcast time to monitor an incoming call received by the first cell site or by the second site cellular during the transition. A method for processing a call between serving sites in a radio communication system, comprising the steps of: initiating a procedure for switching the site membership from a first cell site to a second cell site; receive periodically, starting data from the second cell site during the procedure; monitor the first cell site during the spaces in the reception of start data P1015 / 00MX from the second cell site to detect an incoming call routed through the first cell site; when an incoming call is detected: reverse towards the first cell site to accept the call; and transfer the handling of the call from the first cell site to the second cell site to continue the processing of the call. The method according to claim 8, wherein the step of monitoring comprises the step of alternately monitoring the first cell site and the second cell site to detect an incoming call routed through the first cell site or through the second cell site. 10. In a time division multiple access (TDMA) radio communication system having first and second cellular sites operating a first and second control channels, respectively, the first and second control channels have synchronous time slots including time intervals. diffusion for disseminating cellular data, and control intervals for interaction with the subscriber, a method in a subscriber unit affiliated with the first cellular site, the method comprising the steps of: executing, during a transition period, a procedure for switching the affiliation of site P1015 / 00MX to the second cell site at a particular time when the subscriber unit is not coupled in a call; receive data from the second cell site at successive diffusion intervals of the second control channel; monitoring the control intervals of the first control channel, in the interval of reception of data from the second cellular site, to detect an incoming call received by the first cellular site during the transition period; when an incoming call received by the first cell site is detected during the transition period: abort the procedure for switching the site membership; and accept the incoming call through the first cell site; and when no incoming call is detected during the transition period, complete the procedure to switch the site affiliation with the second site. 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