MXPA96006390A - Methods to make active channel measurements in a personal base station environment - Google Patents

The present invention relates to a method for operating a wireless communication system having at least one base station and at least one mobile station capable of performing wireless communications with at least one base station, characterized in that it comprises the steps of: deactivating periodically, for a predetermined period of time after a transmission of a synchronization data pattern, a base station transmitter for transmitting an RF signal to at least one mobile station, and for the predetermined period of time, operating a receiver of base station to make a measurement of the strength of the signal received

METHODS FOR MAKING ACTIVE CHANNEL MEASUREMENTS IN A PERSONAL BASE STATION ENVIRONMENT FIELD OF THE INVENTION This invention relates generally to wireless communications and, in particular to the operation of a wireless non-public communication system or network having at least one mobile station (MS) which is coupled to a personal base station (PB ).

BACKGROUND OF THE INVENTION Communications with users of a cellular radiotelephone (also called here mobile station (MS)) are achieved through the use of cellular systems. For example, in the Time Division, Multiple Access System (TDMA) known as IS-136 (IS-136.1, Rev. 0, 5/17/95) the different network systems are classified into three groups: public networks , private and residential. Private and residential networks can also be collectively called as non-public networks. Typically, there are two public cellular systems in a geographic area. Further, REP: 23668 may exist one or more non-public cellular systems available to users within the same geographic area. The two public cellular systems within a geographic area are conventionally known as system A and system B. For example, both in the metropolitan areas of New York and Los Angeles there are two public cellular systems. Each of these systems has its own unique identity, known as SID (System Identification). Generally, the cellular radiotelephone can operate at any given time in one of the two public systems available, and a visual display device of the radiotelephone will typically have indicators (ie, icons A and B) to indicate to the user which system is currently being used. One purpose of non-public systems is to provide specialized telecommunications services to radiotelephone users. The main types of non-public systems include Wireless Business Systems, Limited Service Areas and Residential Cell Phones. In the Wireless Business System (WBS) application, connections for a closed user group are typically switched through an existing PBX or through the public switched telephone network (PSTN). This type of system provides capabilities to offer specific features that can be highly integrated with other telecommunications services used by the group, with the purpose of providing all the capabilities of a desk phone. Examples of those services include: integrated voice mail to an existing wired PBX; centralized speed dialing lists; and simplified private network access. In the limited service area (LSA) application, a closed group of users can receive personalized feature billing considerations and special services while within the private or semi-private system coverage area. Public subscribers who do not belong to the closed group could receive the service at standard billing rates. An LSA can be used in shopping trips, airports, sports facilities, hotels, etc. Full-time staff in such facilities can pay to the LSA service while users or roving subscribers and visitors receive the standard public wireless service over the same network. The Residential Cellular Telephone (RCT) application is intended to be used within a residence, and functions as an augmented wireless telephone device. The RCT application is intended to provide users with a single telephone set, which can be used as a cordless telephone, when operated in conjunction with a home or neighborhood base station (also referred to here as a personal base station ( PB)) within a residential or office environment. The RCT application also aims to provide a standard cellular mobile station when operating within the cellular environment, or as part of a Wireless Business System (WBS). When the telephone set is used as a conventional wireless telephone ', the home base station or the associated neighborhood communicates with the cellular network to ensure that a user's calls are automatically sent to the telephone number of the user's landline. Non-public systems are intended to operate in parallel with public networks and, typically, the sending of signals in non-public systems is in compliance with the sending of signals from the public system. It is also expected that non-public systems use system resources (channels) that are at a particular time of time not used by the public system. That is, non-public systems are adapted in relation to their environment, and reserve and dynamically release resources according to what is required by the public system. So far, the operation of non-public systems is not taken into account in, for example, the IS-136 air interface. However, a body known as the TDMA Forum has defined certain guidelines for the operation in non-public mode. In this regard reference can be made to a document entitled "Forum TDMA, Implementation Guide: Operation and Selection of Non-Public Mode in Flexible Mobile Stations IS-136", Version 2.0, March 9, 1995, where a number of system operators they have described the non-public mode and the selection requirements for mobile stations to adapt to the TIA Interim Standards IS-136 and IS-137. There are, however, certain problems in non-public mode operation that affect the sending of signals between the MS and the base station / mobile switching center / inter-network work function (BMI). For example, one such problem is related to low power, in the construction operation. That is, and as indicated above, many autonomous non-public systems will use dynamic channel allocation to determine the current frequency or operating frequencies. To simplify such systems and reduce their cost, such non-public systems may not operate with a separate scanning device, but may instead make RF signal strength measurements using the same front end and antenna as the PB. This requires the PB of the autonomous system to interrupt or turn off its transmitter for some period of time to make the measurements of the Signal Strength received.

(RSS) to verify a non-interference condition on the RF channels that are currently in operation. However, this mode of operation is currently not adapted to the IS-138, which states in Section 3.2.1.2 that the output power of the base station must be maintained at a constant level throughout the duration of the block when any slot is occupied. It can further be appreciated that a discontinuity of the transmissions of the PB may result in a loss of synchronization of the MS with the transmissions of the PB.

OBJECTS OF THE INVENTION Thus, a first object of this invention is to provide a method for allowing a base station, such as a personal base station, to perform RSS measurements. A second object of this invention is to provide a method for allowing a personal base station to perform RSS measurements when operating with full speed mobile stations.

A third object of this invention is to provide a method for allowing a personal base station to perform RSS measurements when operating with half-speed mobile stations.

BRIEF DESCRIPTION OF THE INVENTION The above and other problems are overcome and the objects of the invention are realized by the methods and apparatuses according to the embodiments of this invention. According to a method of this invention, and a system for implementing the method, a wireless communication system has at least one base station, such as a personal base station, and at least one mobile station capable of performing wireless communications with at least one personal base station. The method includes a step of periodically deactivating, for a predetermined period of time, a transmitter of the base station to transmit an RF signal to at least one mobile station. A next step executed during the predetermined period of time, operates a receiver of the base station to make a measurement of the strength of the received signal (RSS) In the preferred embodiment of this invention, the base station transmits and receives the signals comprising repeated blocks each consisting of a plurality of slots., and the predetermined time period corresponds to a duration of time that is equal to or less than a duration of a slot. In a first embodiment of this invention the deactivation step includes a preliminary step of reserving an inverted slot to be used by the base station, thereby ensuring that a mobile station will not transmit during the reserved inverted slot. In this case the step of making the RSS measurements occurs during the reserved slot. In a second embodiment of this invention the deactivation step includes an initial step of transmitting at least one synchronization data pattern during the predetermined interval before deactivating the transmitter, thereby allowing a mobile station to maintain synchronization with the transmitting station. base even when the transmitter is interrupted or switched off. In this case the RSS measurement is done for a period of time that is less than the duration of the slot.

BRIEF DESCRIPTION OF THE DRAWINGS The features set forth above and the other features of the invention will be more apparent in the following Detailed Description of the Invention when read in conjunction with the accompanying Drawings, in which: Figure 1 is a simplified block diagram of a telecommunications system which includes a PB and a plurality of MS; Figure 2 is a simplified block diagram of one of the MS of Figure 1; Figure 3 illustrates the MS of Figure 2, and also shows a simplified block diagram of the PB of Figure 1; Figure 4 illustrates a block structure of Conventional six-slot TDMA which is suitable for practicing this invention; Figure 5 is a diagram illustrating the structure of a digital control channel time slot (DCCH) in the sending or disconnecting direction of the PB to the MS; Figure 6 illustrates an active channel measurement period according to a first embodiment of this invention, specifically a full speed channel mode; and Figure 7 illustrates an active channel measurement period according to a second embodiment of this invention, specifically a half-speed channel mode.

DETAILED DESCRIPTION OF THE INVENTION Referring first to Figure 1 therein is illustrated a simplified block diagram of a telecommunication system 1 including at least one PB 5 and a plurality of MS 10. System 1 includes a portion of a cellular network comprised of a Data Center. Conventional Mobile Switching (MSC) 2 that has a Home Location Register (HLR) 3. Connected to the MSC / HLR 2, 3 through the PSTN 4 is the PB 5. The PB 5 includes an antenna 6 to communicate with a corresponding antenna 12 of each MS 10, and has an associated set of transmission and receiver frequencies. It is assumed for this discussion that PB 5 is located within and / or adjacent to a building or construction, such as a residence, office or the like, and has a limited area to serve a restricted area. Reference is now made to Figures 2 and 3 to illustrate one of the MS 10 of Figure 1 which is suitable for practicing this invention. The MS 10 includes the antenna 12 for transmitting signals a and for receiving signals from the PB 5. The MS 10 includes a modulator (MOD) 14A, a transmitter 14, a receiver 16, a demodulator (DEMOD) 16A, and a controller 18 that it provides signals to and receives signals from the transmitter 14 and the receiver 16, respectively. These signals include signal sending information in accordance with the applicable cellular system air interface standard, and also the voice frequency of the user and / or the data generated by the user. It was assumed that the air interface standard for this invention includes at least one digital control channel (DCCH). An air interface standard hitherto preferred is that specified by the IS-136 and IS-138. It should be noted, however, that the teaching of this invention is not limited to use with only a particular air interface standard or standards. A user interface of the MS 10 includes a conventional loudspeaker 17, a conventional microphone 19, a display device 20, and a user input device, typically a numeric keypad 22, all of which are coupled to the controller 18. Numeric keypad 22 includes the numeric keys (0-9) and related (#, *) 22a, and also other keys 22b used to operate the MS 10. Those other keys 22b include, for example, a SEND key (send), several menu and programmable function scroll keys and a PWR key. The MS 10 also includes several memories, collectively shown as the memory 24, wherein a plurality of constants and variables are stored which are used by the controller 18 during the operation of the mobile terminal. For example, the memory 24 stores the values of various parars of the cellular system and the number of the allocation module (NAM). An operation program for controlling the operation of the controller of the MS 18 is also stored in the memory 24 (typically in a ROM device). The memory 24 also stores data, including user messages, which are received from the network before presenting the messages to the user. The MS 10 has a battery 26 to energize the different circuits that are required to operate the terminal. PB 5 is comprised of a PB 30 controller that is responsible for implementing the PB related portion of the applicable air interface standard. Attached to the PB 30 controller is a suitable tunable modulation transmitter assembly 32, a tunable demodulation receiver assembly 34, and a memory 36 that stores a list of MS numbers and the corresponding IDs, in addition to any other information that is required during the operation of the PB 30 controller. In particular the memory 36 includes instructions that are executed by the PB 30 controller to implement the applicable air interface standard, such as one based or similar to the IS-136. The PB 5 further includes a suitable PSTN interface unit 38. It is assumed that the receiver assembly 34 includes the circuits for performing an RSS measurement, and for reporting the result to the controller of the PB 30. Figure 4 illustrates a structure conventional six-slot TDMA block that is suitable for practicing this invention, while Figure 5 is a diagram illustrating a Digital Control Channel (DCCH) slot format that is transmitted from PB 5 to MS 10. The reference in this regard can be made based on Figure 4-4 of IS-136.1. Moving from the beginning of the slot to the end of the slot, the DCCH slot consists of a 28-bit synchronization field (SYNC), a first 12-bit shared feedback field (SCF), a first data field. (DATA) of 130 bits, a field of Upper Block Count (CSFP) of data of 12 bits, a second data field (DATA) of 130 bits, a second field SCF of 10 bits, and a reserved field (RSVD) of 2 bits. Three consecutive slots in the block form a TDMA block and, in the environment of the personal base station, the first TDMA block slot is a slot used for the DCCH. As such, slots 1 and 4 are used for the DCCH. The other slots in the block are used for the voice frequency and / or full or average speed data on the digital traffic channels (DTC) carried in the slots 2, 3, 5 and 6. It should be noted that in other embodiments of this invention Any of the slots for the DCCH can be used. According to a first embodiment of this invention, in particular a full speed mode, the PB 5 reserves a DCCH Random Access sub-channel (RACH) connected by block of slots 1 or 4 for its own use, ie to make measurements of active channel. As specified concurrently, it is intended that the RACH subchannels of the DCCH be used only by the inverted link of the MS 10 to the base station. The RACH is used by the MS 10 to request access to the system, and the RACH is divided into three or six subchannels to support three or six MS 10. Referring to Figure 6, it can be noted that there is a deviation of approximately two slots between the two. blocks of the PB of transmission (transmission) and investment (reception) . When a full speed TDMA carrier has a DCCH channel in slots 1 and 4, and the DTC carriers of slot 2 (and 5) and 3 (and 6), there is no opportunity for PB 5 to perform an RSSI measurement to detect possible interference. This is because PB 5 must be either sending or receiving at all times, even if there is a call in progress. To overcome this problem the PB 5 reserves for itself at least one RACH subchannel in one of the reverse link slots 1 or 4 that could normally be used by one of the MS 10. As a result of the reservation of the RACH sub-channel, the PB 5 ensures that there is at least one time slot where the transmitter 32 and the receiver 34 of the PB are not required, as long as there is no traffic currently allocated to the corresponding sending DTC slot (for example, the slot 3) . As seen in the example of Figure 6, the slot of the DCCH 1 in the receiver block can thus be used to perform a RSS measurement (i.e., that the DCCH slot 1 defines a measurement period (MP)) , as long as there is no call assigned to the DTC slot (transition) 3 (ie, the transmitter 32 can be idle), and the corresponding RACH sub-channel is reserved by the PB 5 (ie, the receiver 34 does not it is required to receive MS transmissions since no MS will be transmitting over the reserved RACH subchannel). Since PB 5 does not require the use of transmitter 32 to make a DTC slot transmission, receiver? 4 can be used to make at least one measurement of at least RSS during the slot. If interference is detected with a public system, the controller of the PB 30 is therefore activated to reassign the frequency channels to avoid contention with, for example, the frequency channels in use by the public system. Reference can be made to IS-136.1, Sections 4.4.2 and 4.11 for a hitherto preferred technique for reserving an RACH sub-channel. In general, this is achieved by placing SCF indicators in the DCCH in an appropriate manner. In particular, the SCF field includes a Busy / Reserved / Unoccupied (BRI) 6-bit field that is plotted in the sending DCCH slots as shown in Figure 4-5 of the IS-136.1. As defined in Section 5.3.2.1.1", a BRI indicator was used to indicate whether the corresponding inverted DCCH RACH slot is occupied, reserved or unoccupied, Section 4.11 of IS-136.1 describes in detail the RACH sub-channeling and the use of the SCF indicators In accordance with this aspect of the invention, by self-preservation of a DCCH RACH sub-channel setting one of the bits of the BRI SCF indicator, the PB 5 is able to measure if the active channel that is transmitting over any of the corresponding DTC slots 3 and 6 is unoccupied (without traffic), that is, when the transmission does not take place during the DTC slot the transmitter 32 can be interrupted for the duration of the slot, and the receiver 34 used to make RSS measurements during the DCCH slot (RACH subchannel) aligned with the corresponding reserved time It is assumed, of course, that the MS 18 controller responds to the fixing of the The BRI bits in the DCCH are sent not to transmit on any RACH sub-channel that is designated as reserved. This method can also be used by the medium speed channels. However, and referring to Figure 7, a second embodiment of this invention is preferred instead for use with the medium speed channels. In this mode PB 5 optionally interrupts the transmissions during a single active slot per block. For this type of operation, the PB 5 interrupts the transmission during a DCCH slot after transmitting at least the portion of the synchronization word (SYNC). That is, the word SYNC is transmitted, thus allowing any MS to verify the transmission of the slot to maintain synchronization., after which the transmitter 32 is interrupted or turned off. For the remainder of the slot, or measurement period (MP), the receiver 34 is used to make at least one RSS measurement for the active transmission channel. It is preferred that when the PB operates in this manner that some descending interval of the transmitter is provided after the transmission of the synchronization word, as is an ascending interval of the transmitter going before starting the transmission in the next slot. As such, the duration of the measurement period (MP) is reduced by an amount at least equal to the duration of the descending and ascending intervals of the transmitter. Although described in the context of a TDMA system that was based on or similar to IS-136, the teaching of this invention can also be used with other types of TDMA systems, as well as with certain types of Code Division Systems, Multiple Access, such as that specified by, for example, IS-95. It should further be understood that the two modes can be combined to reserve an inverted inverted slot b for use by the base station, and also transmit at least the synchronization data portion of the corresponding send slot. Thus, although the invention has been particularly shown and described with respect to the preferred embodiments thereof, it should be understood by those skilled in the art that changes can be made in the form and details thereof without departing from the scope and spirit. of the invention. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property: